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FLUID-ABSORBENT ARTICLE

20200121521 ยท 2020-04-23

    Inventors

    Cpc classification

    International classification

    Abstract

    Provided herein are fluid-absorbent articles, fluid absorbent cores, and fluid-absorbent mixtures with improved properties, especially rewet performance and liquid acquisition. The fluid-absorbent article includes (A) an upper liquid-pervious sheet, (B) a lower liquid-impervious sheet, (C) a fluid-absorbent core including from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles, (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material, (D) an optional acquisition-distribution layer (D) between (A) and (C), (F) other optional components, wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    Claims

    1. A fluid absorbent article, comprising (A) an upper liquid-pervious sheet; (B) a lower liquid-impervious sheet; (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; (D) an optional acquisition-distribution layer (D) between (A) and (C); and (F) other optional components, wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    2. A fluid-absorbent article according to claim 1, wherein the fluid-absorbing core (C) comprises at least two layers (K, L), wherein one of the layers (K) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the first type of water-absorbent polymer particles (G) based on the sum of water-absorbent polymer particles and fibrous material, and the second layer (L) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material.

    3. A fluid-absorbent article according to claim 2, wherein in the fluid-absorbent core (C), the layer (K) comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer (L) comprising the second type of water-absorbent polymer particles (H).

    4. A fluid absorbent article according to claim 1, wherein the fluid-absorbent core (C) comprises from 60 to 20% by weight fibrous material and from 40 to 80% by weight of a mixture of the first type of water-absorbent polymer particles (G) and the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material.

    5. A fluid-absorbent article according to claim 1, wherein the second type of water-absorbent polymer particles (H) of the fluid-absorbent core (C) have a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    6. A fluid-absorbent article according to claim 1, wherein the second type of water-absorbent polymer particles (H) of the fluid-absorbent core (C) have a SFC at maximum of 510.sup.7 cm.sup.3.Math.s/g.

    7. A fluid absorbent article according to claim 1, wherein a production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    8. A fluid-absorbent article according to claim 1, wherein the water absorbent polymer particles (G, H) are surface-postcrosslinked.

    9. A fluid-absorbent article according to claim 1, wherein the first type of water-absorbent polymer particles (G) is present of at least 30% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    10. A fluid-absorbent article according to claim 1, wherein the first type of water-absorbent polymer particles (G) is present of at least 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    11. A fluid-absorbent article according to claim 1, wherein the first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    12. A fluid-absorbent article according to claim 1, wherein the first type of water-absorbent polymer particles (G) and the second type of water-absorbent polymer particles (H) are present within the fluid-absorbent core (C) in equal amounts by weight.

    13. A fluid-absorbent article, according to claim 1, wherein for the fluid absorbent core (C the rewet under load (RUL) for the 4th insult is reduced by at least 20% compared to a second fluid absorbent core of a second fluid-absorbent article, wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type of water-absorbent polymer particles (G).

    14. A fluid-absorbent article according to claim 1, wherein for the fluid absorbent core (C), the liquid acquisition time for the 4th insult is reduced by at least 5% compared to a third fluid absorbent core of a third fluid-absorbent absorbent article, wherein the total amount of water-absorbent polymer particles (G and H) are replaced by the same amount by weight of the second type of water-absorbent polymer particles (H).

    15. A fluid absorbent article according to claim 1, wherein the second type of water-absorbent polymer particles (H) have an AUHL of at least 15 g/g.

    16. A fluid-absorbent core (C), comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material, wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the second type of water-absorbent polymer particles (H) of the fluid-absorbent core (C have a sphericity of at least 0.80.

    17. A fluid-absorbent core (C) according to claim 16, wherein the second type of water-absorbent polymer particles (H) of the fluid-absorbent core (C) has a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    18. A fluid absorbent core according to claim 16, wherein a production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    19. A fluid-absorbent mixture comprising a first type of water-absorbent polymer particles (G) with a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and a second type of water-absorbent polymer particles (H) with a sphericity of at least 0.80, wherein the second type of water-absorbent polymer particles (H) has a SFC at maximum of 1510.sup.7 cm.sup.3 s/g.

    20. A fluid-absorbent mixture according to claim 19, wherein a production process of the first type of water absorbent polymer particles (G) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    Description

    [0234] Preferred embodiments are depicted in FIGS. 1 to 15.

    [0235] FIG. 1: Process scheme

    [0236] FIG. 2: Process scheme using dry air

    [0237] FIG. 3: Arrangement of the T_outlet measurement

    [0238] FIG. 4: Arrangement of the dropletizer units with 3 droplet plates

    [0239] FIG. 5: Arrangement of the dropletizer units with 9 droplet plates

    [0240] FIG. 6: Arrangement of the dropletizer units with 9 droplet plates

    [0241] FIG. 7: Dropletizer unit (longitudinal cut)

    [0242] FIG. 8: Dropletizer unit (cross sectional view)

    [0243] FIG. 9: Bottom of the internal fluidized bed (top view)

    [0244] FIG. 10: openings in the bottom of the internal fluidized bed

    [0245] FIG. 11: Rake stirrer for the intern fluidized bed (top view)

    [0246] FIG. 12: Rake stirrer for the intern fluidized bed (cross sectional view)

    [0247] FIG. 13: Process scheme (surface-postcrosslinking)

    [0248] FIG. 14: Process scheme (surface-postcrosslinking and coating)

    [0249] FIG. 15: Contact dryer for surface-postcrosslinking

    [0250] The reference numerals have the following meanings: [0251] 1 Drying gas inlet pipe [0252] 2 Drying gas amount measurement [0253] 3 Gas distributor [0254] 4 Dropletizer unit(s) [0255] 4a Dropletizer unit [0256] 4b Dropletizer unit [0257] 4c Dropletizer unit [0258] 5 Reaction zone (cylindrical part of the spray dryer) [0259] 6 Cone [0260] 7 T_outlet measurement [0261] 8 Tower offgas pipe [0262] 9 Dust separation unit [0263] 10 Ventilator [0264] 11 Quench nozzles [0265] 12 Condenser column, counter current cooling [0266] 13 Heat exchanger [0267] 14 Pump [0268] 15 Pump [0269] 16 Water outlet [0270] 17 Ventilator [0271] 18 Offgas outlet [0272] 19 Nitrogen inlet [0273] 20 Heat exchanger [0274] 21 Ventilator [0275] 22 Heat exchanger [0276] 24 Water loading measurement [0277] 25 Conditioned internal fluidized bed gas [0278] 26 Internal fluidized bed product temperature measurement [0279] 27 Internal fluidized bed [0280] 28 Rotary valve [0281] 29 Sieve [0282] 30 End product [0283] 31 Static mixer [0284] 32 Static mixer [0285] 33 Initiator feed [0286] 34 Initiator feed [0287] 35 Monomer feed [0288] 36 Fine particle fraction outlet to rework [0289] 37 Gas drying unit [0290] 38 Monomer separator unit [0291] 39 Gas inlet pipe [0292] 40 Gas outlet pipe [0293] 41 Water outlet from the gas drying unit to condenser column [0294] 42 Waste water outlet [0295] 43 T_outlet measurement (average temperature out of 3 measurements around tower circumference) [0296] 45 Monomer premixed with initiator feed [0297] 46 Spray dryer tower wall [0298] 47 Dropletizer unit outer pipe [0299] 48 Dropletizer unit inner pipe [0300] 49 Dropletizer cassette [0301] 50 Teflon block [0302] 51 Valve [0303] 52 Monomer premixed with initiator feed inlet pipe connector [0304] 53 Droplet plate [0305] 54 Counter plate [0306] 55 Flow channels for temperature control water [0307] 56 Dead volume free flow channel for monomer solution [0308] 57 Dropletizer cassette stainless steel block [0309] 58 Bottom of the internal fluidized bed with four segments [0310] 59 Split openings of the segments [0311] 60 Rake stirrer [0312] 61 Prongs of the rake stirrer [0313] 62 Mixer [0314] 63 Optional coating feed [0315] 64 Postcrosslinker feed [0316] 65 Thermal dryer (surface-postcrosslinking) [0317] 66 Cooler [0318] 67 Optional coating/water feed [0319] 68 Coater [0320] 69 Coating/water feed [0321] 70 Base polymer feed [0322] 71 Discharge zone [0323] 72 Weir opening [0324] 73 Weir plate [0325] 74 Weir height 100% [0326] 75 Weir height 50% [0327] 76 Shaft [0328] 77 Discharge cone [0329] 78 Inclination angle [0330] 79 Temperature sensors (T.sub.1 to T.sub.6) [0331] 80 Paddle (shaft offset 90)

    [0332] The drying gas is fed via a gas distributor (3) at the top of the spray dryer as shown in FIG. 1.

    [0333] The drying gas is partly recycled (drying gas loop) via a baghouse filter or cyclone unit (9) and a condenser column (12). The pressure inside the spray dryer is below ambient pressure.

    [0334] The spray dryer outlet temperature is preferably measured at three points around the circumference at the end of the cylindrical part as shown in FIG. 3. The single measurements (43) are used to calculate the average cylindrical spray dryer outlet temperature.

    [0335] In one preferred embodiment a monomer separator unit (38) is used for recycling of the monomers from the condenser column (12) into the monomer feed (35). This monomer separator unit is for example especially a combination of micro-, ultra-, nanofiltration and osmose membrane units, to separate the monomer from water and polymer particles. Suitable membrane separator systems are described, for example, in the monograph Membranen: Grundlagen, Verfahren und Industrielle Anwendungen, K. Ohlrogge and K. Ebert, Wiley-VCH, 2012 (ISBN: 978-3-527-66033-9).

    [0336] The product accumulated in the internal fluidized bed (27). Conditioned internal fluidized bed gas is fed to the internal fluidized bed (27) via line (25). The relative humidity of the internal fluidized bed gas is preferably controlled by the temperature in the condensor column (12) and using the Mollier diagram.

    [0337] The spray dryer offgas is filtered in a dust separation unit (9) and sent to a condenser column (12) for quenching/cooling. After dust separation (9) a recuperation heat exchanger system for preheating the gas after the condenser column (12) can be used. The dust separation unit (9) may be heat-traced on a temperature of preferably from 80 to 180 C., more preferably from 90 to 150 C., most preferably from 100 to 140 C.

    [0338] Example for the dust separation unit are baghouse filter, membranes, cyclones, dust compactors and for examples described, for example, in the monographs Staubabscheiden, F. Lffler, Georg Thieme Verlag, Stuttgart, 1988 (ISBN 978-3137122012) and Staubabscheidung mit Schlauchfiltern und Taschenfiltern, F. Lffler, H. Dietrich and W. Flatt, Vieweg, Braunschweig, 1991 (ISBN 978-3540670629).

    [0339] Most preferable are cyclones, for example, cyclones/centrifugal separators of the types ZSA/ZSB/ZSC from LTG Aktiengesellschaft and cyclone separators from Ventilatorenfabrik Oelde GmbH, Camfil Farr International and MikroPul GmbH.

    [0340] Excess water is pumped out of the condenser column (12) by controlling the (constant) filling level in the condenser column (12). The water in the condenser column (12) is pumped counter-current to the gas via quench nozzles (11) and cooled by a heat exchanger (13) so that the temperature in the condenser column (12) is preferably from 40 to 71 C., more preferably from 46 to 69 C., most preferably from 49 to 65 C. and more even preferably from 51 to 60 C. The water in the condenser column (12) is set to an alkaline pH by dosing a neutralizing agent to wash out vapors of monomer a). Aqueous solution from the condenser column (12) can be sent back for preparation of the monomer solution.

    [0341] The condenser column offgas may be split to the gas drying unit (37) and the conditioned internal fluidized bed gas (27).

    [0342] The principle of a gas drying unit is described in the monograph Leitfaden for Lftungsund KlimaanlagenGrundlagen der Thermodynamik Komponenten einer Vollklimaanlage Normen und Vorschriften, L. Keller, Oldenbourg Industrieverlag, 2009 (ISBN 978-3835631656).

    [0343] As gas drying unit can be used, for example, an air gas cooling system in combination with a gas mist eliminators or droplet separator (demister), for examples, droplet vane type separator for horizontal flow (e.g. type DH 5000 from Munters AB, Sweden) or vertical flow (e.g. type DV 270 from Munters AB, Sweden). Vane type demisters remove liquid droplets from continuous gas flows by inertial impaction. As the gas carrying entrained liquid droplets moves through the sinusoidal path of a vane, the higher density liquid droplets cannot follow and as a result, at every turn of the vane blades, these liquid droplets impinge on the vane surface.

    [0344] Most of the droplets adhere to the vane wall. When a droplet impinges on the vane blade at the same location, coalescence occurs. The coalesced droplets then drain down due to gravity.

    [0345] As air gas cooling system, any gas/gas or gas/liquid heat exchanger can be used. Preferred are sealed plate heat exchangers.

    [0346] In one embodiment dry air can be used as feed for the gas distributor (3). If air used as gas, then air can be transported via air inlet pipe (39) and can be dried in the gas drying unit (37), as described before. After the condenser column (12), the air, which not used for the internal fluidized bed is transported via the outlet pipe outside (40) of the plant as shown in FIG. 2.

    [0347] The water, which is condensed in the gas drying unit (37) can be partially used as wash water for the condenser column (12) or disposed.

    [0348] The gas temperatures are controlled via heat exchangers (20) and (22). The hot drying gas is fed to the cocurrent spray dryer via gas distributor (3). The gas distributor (3) consists preferably of a set of plates providing a pressure drop of preferably 1 to 100 mbar, more preferably 2 to 30 mbar, most preferably 4 to 20 mbar, depending on the drying gas amount. Turbulences and/or a centrifugal velocity can also be introduced into the drying gas if desired by using gas nozzles or baffle plates.

    [0349] Conditioned internal fluidized bed gas is fed to the internal fluidized bed (27) via line (25). The steam content of the fluidized bed gas can be controlled by the temperature in the condenser column (12). The product holdup in the internal fluidized bed (27) can be controlled via rotational speed of the rotary valve (28).

    [0350] The amount of gas in the internal fluidized bed (27) is selected so that the particles move free and turbulent in the internal fluidized bed (27). The product height in the internal fluidized bed (27) is with gas preferably at least 10%, more preferably at least 20%, more preferably at least 30%, even more preferably at least 40% higher than without gas.

    [0351] The product is discharged from the internal fluidized bed (27) via rotary valve (28). The product holdup in the internal fluidized bed (27) can be controlled via rotational speed of the rotary valve (28). The sieve (29) is used for sieving off overs/lumps.

    [0352] The monomer solution is preferably prepared by mixing first monomer a) with a neutralization agent and secondly with crosslinker b). The temperature during neutralization is controlled to preferably from 5 to 60 C., more preferably from 8 to 40 C., most preferably from 10 to 30 C., by using a heat exchanger and pumping in a loop. A filter unit is preferably used in the loop after the pump. The initiators are metered into the monomer solution upstream of the dropletizer by means of static mixers (31) and (32) via lines (33) and (34) as shown in FIG. 1 and FIG. 2. Preferably a peroxide solution having a temperature of preferably from 5 to 60 C., more preferably from 10 to 50 C., most preferably from 15 to 40 C., is added via line (33) and preferably an azo initiator solution having a temperature of preferably from 2 to 30 C., more preferably from 3 to 15 C., most preferably from 4 to 8 C., is added via line (34). Each initiator is preferably pumped in a loop and dosed via control valves to each dropletizer unit. A second filter unit is preferably used after the static mixer (32). The mean residence time of the monomer solution admixed with the full initiator package in the piping before dropletization is preferably less than 60 s, more preferably less than 30 s, most preferably less than 10 s.

    [0353] For dosing the monomer solution into the top of the spray dryer preferably three dropletizer units are used as shown in FIG. 4. However, any number of dropletizers can be used that is required to optimize the throughput of the process and the quality of the product. Hence, in the present invention at least one dropletizer is employed, and as many dropletizers as geometrically allowed may be used.

    [0354] A dropletizer unit consists of an outer pipe (47) having an opening for the dropletizer cassette (49) as shown in FIG. 7. The dropletizer cassette (49) is connected with an inner pipe (48). The inner pipe (48) having a PTFE block (50) at the end as sealing can be pushed in and out of the outer pipe (51) during operation of the process for maintenance purposes.

    [0355] The temperature of the dropletizer cassette (57) is controlled to preferably 5 to 80 C., more preferably 10 to 70 C., most preferably 30 to 60 C., by water in flow channels (55) as shown in FIG. 8.

    [0356] The dropletizer cassette has preferably from 10 to 2000 bores, more preferably from 50 to 1500 bores, most preferably from 100 to 1000 bores. The diameter of the bores size area is 1900 to 22300 m.sup.2, more preferably from 7800 to 20100 m.sup.2, most preferably from 11300 to 17700 m.sup.2. The bores can be of circular, rectangular, triangular or any other shape. Circular bores are preferred with a bore size from 50 to 170 m, more preferably from 100 to 160 m, most preferably from 120 to 150 m. The ratio of bore length to bore diameter is preferably from 0.5 to 10, more preferably from 0.8 to 5, most preferably from 1 to 3. The droplet plate (53) can have a greater thickness than the bore length when using an inlet bore channel. The droplet plate (53) is preferably long and narrow as disclosed in WO 2008/086976 A1. Multiple rows of bores per droplet plate can be used, preferably from 1 to 20 rows, more preferably from 2 to 5 rows.

    [0357] The dropletizer cassette (57) consists of a flow channel (56) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and two droplet plates (53). The droplet plates (53) have an angled configuration with an angle of preferably from 1 to 90, more preferably from 3 to 45, most preferably from 5 to 20. Each droplet plate (53) is preferably made of a heat and/or chemically resistant material, such as stainless steel, polyether ether ketone, polycarbonate, polyarylsulfone, such as polysulfone, or polyphenylsulfone, or fluorous polymers, such as perfluoroalkoxyethylene, polytetrafluoroethylene, polyvinylidenfluorid, ethylene-chlorotrifluoroethylene copolymers, ethylene-tetrafluoroethylene copolymers and fluorinated polyethylene. Coated droplet plates as disclosed in WO 2007/031441 A1 can also be used. The choice of material for the droplet plate is not limited except that droplet formation must work and it is preferable to use materials which do not catalyze the start of polymerization on its surface.

    [0358] The arrangement of dropletizer cassettes is preferably rotationally symmetric or evenly distributed in the spray dryer (for example see FIG. 3 to 5).

    [0359] In a preferred embodiment the angle configuration of the droplet plate (53) is in the middle lower then outside, for example: 4a=3, 4b=5 and 4c=8 (FIG. 5).

    [0360] The throughput of monomer including initiator solutions per dropletizer unit is preferably from 10 to 4000 kg/h, more preferably from 100 to 1000 kg/h, most preferably from 200 to 600 kg/h. The throughput per bore is preferably from 0.1 to 10 kg/h, more preferably from 0.5 to 5 kg/h, most preferably from 0.7 to 2 kg/h.

    [0361] The start-up of the cocurrent spray dryer (5) can be done in the following sequence: [0362] starting the condenser column (12), [0363] starting the ventilators (10) and (17), [0364] starting the heat exchanger (20), [0365] heating up the drying gas loop up to 95 C., [0366] starting the nitrogen feed via the nitrogen inlet (19), [0367] waiting until the residual oxygen is below 4% by weight, [0368] heating up the drying gas loop, [0369] at a temperature of 105 C. starting the water feed (not shown) and [0370] at target temperature stopping the water feed and starting the monomer feed via dropletizer unit (4)

    [0371] The shut-down of the cocurrent spray dryer (5) can be done in the following sequence: [0372] stopping the monomer feed and starting the water feed (not shown), [0373] shut-down of the heat exchanger (20), [0374] cooling the drying gas loop via heat exchanger (13), [0375] at a temperature of 105 C. stopping the water feed, [0376] at a temperature of 60 C. stopping the nitrogen feed via the nitrogen inlet (19) and [0377] feeding air into the drying gas loop (not shown)

    [0378] To prevent damages the cocurrent spray dryer (5) must be heated up and cooled down very carefully. Any quick temperature change must be avoided.

    [0379] The openings in the bottom of the internal fluidized bed may be arranged in a way that the water-absorbent polymer particles flow in a cycle as shown in FIG. 9. The bottom shown in FIG. 9 comprises of four segments (58). The openings (59) in the segments (58) are in the shape of slits that guides the passing gas stream into the direction of the next segment (58). FIG. 10 shows an enlarged view of the openings (59).

    [0380] The opening may have the shape of holes or slits. The diameter of the holes is preferred from 0.1 to 10 mm, more preferred from 0.2 to 5 mm, most preferred from 0.5 to 2 mm. The slits have a length of preferred from 1 to 100 mm, more preferred from 2 to 20 mm, most preferred from 5 to 10 mm, and a width of preferred from 0.5 to 20 mm, more preferred from 1 to 10 mm, most preferred from 2 to 5 mm.

    [0381] FIG. 11 and FIG. 12 show a rake stirrer (60) that may be used in the internal fluidized bed. The prongs (61) of the rake have a staggered arrangement. The speed of rake stirrer is preferably from 0.5 to 20 rpm, more preferably from 1 to 10 rpm most preferably from 2 to 5 rpm.

    [0382] For start-up the internal fluidized bed may be filled with a layer of water-absorbent polymer particles, preferably 5 to 50 cm, more preferably from 10 to 40 cm, most preferably from 15 to 30 cm.

    [0383] The surface-postcrosslinked water-absorbent polymer particles obtained by droplet polymerization preferably having a mean sphericity or roundness from 0.80 to 0.95, preferably from 0.82 to 0.93, more preferably from 0.84 to 0.91, most preferably from 0.85 to 0.90. The sphericity (SPHT) is defined as

    [00001] SPHT = 4 .Math. .Math. .Math. A U 2 ,

    [0384] where A is the cross-sectional area and U is the cross-sectional circumference of the polymer particles. The mean sphericity is the volume-average sphericity.

    [0385] The mean sphericity can be determined, for example, with the Camsizer image analysis system (Retsch Technolgy GmbH; Haan; Germany): For the measurement, the product is introduced through a funnel and conveyed to the falling shaft with a metering channel. While the particles fall past a light wall, they are recorded selectively by a camera. The images recorded are evaluated by the software in accordance with the parameters selected.

    [0386] To characterize the roundness, the parameters designated as sphericity in the program are employed. The parameters reported are the mean volume-weighted sphericities, the volume of the particles being determined via the equivalent diameter xc.sub.min. To determine the equivalent diameter xc.sub.min, the longest chord diameter for a total of 32 different spatial directions is measured in each case. The equivalent diameter xc.sub.min is the shortest of these 32 chord diameters. To record the particles, the so-called CCD-zoom camera (CAM-Z) is used. To control the metering channel, a surface coverage fraction in the detection window of the camera (transmission) of 0.5% is predefined.

    [0387] In the context of this invention sphericity means mean sphericity or in particular mean volume-weighted sphericity Fluid-absorbent particles suitable for the first type (G) of fluid-absorbent particles useful for present invention preferably have a centrifuge retention capacity of at least 25 g/g, preferably at least 30 g/g and a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, preferably at least 3010.sup.7-cm.sup.3.Math.s/g.

    [0388] As the centrifuge retention capacity (CRC) is the maximum liquid retention capacity of the surface-postcrosslinked water-absorbent polymer particles it is of interest to maximize this parameter. However the absorption under high load (AUHL) is important to allow the fiber-matrix in a hygiene article to open up pores during swelling to allow further liquid to pass easily through the article structure to enable rapid uptake of this liquid.

    [0389] The SFC is a measure of the permeability. Increased permeability usually results in a loss of absorption capacity of the fluid-absorbent polymers.

    [0390] Fluid-absorbent particles suitable for the second type (H) of fluid-absorbent particles useful for present invention preferably have a centrifuge retention capacity of at least 30 g/g, preferably 35 g/g, more preferably 40 g/g.

    [0391] Fluid-absorbent particles also suitable for the second type (H) of water-absorbent polymer particles (H) having a sphericity of at least 0.80, preferably of at least 0.85, particularly preferred of at least 0.90.

    [0392] The SFC of the first type of water-absorbent polymer particles (G) is at least 2010.sup.7 cm.sup.3.Math.s/g, more preferably at least 2510.sup.7 cm.sup.3.Math.s/g, particularly preferred at least 3010.sup.7 cm.sup.3.Math.s/g, preferentially at least 4010.sup.7 cm.sup.3.Math.s/g, more preferably at least 6010.sup.7 cm.sup.3.Math.s/g, most preferably at least 8010.sup.7 cm.sup.3.Math.s/g, further most preferably of at least 10010.sup.7 cm.sup.3.Math.s/g, but not above 20010.sup.7 cm.sup.3.Math.s/g

    [0393] The SFC of the second type of fluid-absorbent polymer particles (H) is at maximum of 1510.sup.7 cm.sup.3.Math.s/g, preferably of at maximum of 1010.sup.7 cm.sup.3.Math.s/g, particularly preferred of at maximum of 510.sup.7 cm.sup.3.Math.s/g, more preferably of 310.sup.7 cm.sup.3.Math.s/g, most preferably of 010.sup.7 cm.sup.3.Math.s/g.

    [0394] The bulk density of the fluid-absorbent polymer particles is preferably from 0.6 to 0.75 g/cm.sup.3 for the first type (G) of fluid-absorbent polymer particles, preferably from 0.62 to 0.68 g/cm.sup.3, Preferably 0.62 to 1 g/cm.sup.3, more preferably from 0.7 to 0.9 g/cm.sup.3 for the second type (H) of fluid absorbent polymer particles.

    [0395] Generally the suited water-absorbent polymer particles have an absorbency under high load (AUHL) of at least 10 g/g, preferably of at least 15 g/g.

    [0396] For the second type of water-absorbent polymer particles (H) it is preferred having an AUHL of at least 15 g/g.

    [0397] Furthermore the water-absorbent polymer particles have a level of extractable constituents of less than 10% by weight, preferably less than 9% by weight, more preferably less than 8% by weight, most preferably less than 6% by weight.

    [0398] The average particle diameter of the water-absorbent particles useful for the present invention is preferably from 200 to 550 m, more preferably from 250 to 500 m, most preferably from 350 to 450 m.

    [0399] According to one embodiment of the invention at least two types of water-absorbent polymer particles are mixed.

    [0400] According to the invention the mixture of water-absorbent polymer particles comprises at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H);

    [0401] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0402] An embodiment of the inventive mixture, wherein the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0403] Another embodiment of the inventive mixture, wherein the at least first type of water-absorbent polymer particles (G) is present of at least 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0404] An embodiment of the inventive mixture, wherein the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H) According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) comprises at least 30% by weight, preferably least 33% by weight of the first type of water-absorbent polymer particles (G) and at maximum 66% by weight, preferably at maximum 70% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0405] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) comprises at least 50% by weight of the first type of water-absorbent polymer particles (G) and at maximum 50% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0406] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) comprises at maximum 66% by weight, preferably at maximum 70% by weight of the first type of water-absorbent polymer particles (G) and at least 30% by weight, preferably at least 33% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0407] The mixture according to the invention, wherein the first type of water-absorbent polymer particles (G) preferably have an SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, preferably of at least 2510.sup.7 cm.sup.3.Math.s/g, more preferably of at least 3010.sup.7 cm.sup.3.Math.s/g, preferentially of at least 4010.sup.7 cm.sup.3.Math.s/g, more preferably of at least 6010.sup.7 cm.sup.3.Math.s/g, most preferably of at least 8010.sup.7 cm.sup.3.Math.s/g, further most preferably of at least 10010.sup.7 cm.sup.3.Math.s/g, but not above 20010.sup.7 cm.sup.3.Math.s/g According to the invention the second type of water-absorbent polymer particles (H) having a sphericity of at least 0.80, preferably of at least 0.85, particularly preferred of at least 0.90.

    [0408] The second type of water-absorbent polymer particles (H) furthermore preferably have an SFC of at maximum of 1510.sup.7 cm.sup.3.Math.s/g, preferably of at maximum of 1010.sup.7 cm.sup.3.Math.s/g, particularly preferred of at maximum of 510.sup.7 cm.sup.3.Math.s/g, more preferably of 310.sup.7 cm.sup.3.Math.s/g, most preferably of 010.sup.7 cm.sup.3.Math.s/g.

    [0409] Preferably the first type of water-absorbent polymer particles (G) of the inventive mixture having a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and the second type of water-absorbent polymer particles (H) having a sphericity of at least 0.80 and an SFC of at maximum 510.sup.7 cm.sup.3.Math.s/g.

    [0410] The production process of the first type of water-absorbent polymer particles (G) of the inventive fluid-absorbent mixture comprise the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    [0411] According to one embodiment the inventive mixture of water absorbent polymer particles comprising at least a first type of water-absorbent polymer particles (G) having a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and at least a second type of water-absorbent polymer particles (H) having a sphericity of at least 0.80 and an SFC of at maximum 1510.sup.7 cm.sup.3.Math.s/g, whereas the mixture of equal amounts of the at least a first type of water-absorbent polymer particles (G) and the at least second type of water-absorbent polymer particles (H) has an SFC of at maximum 2510.sup.7 cm.sup.3.Math.s/g, preferably an SFC of at maximum 2310.sup.7 cm.sup.3.Math.s/g, more preferably an SFC of at maximum 2010.sup.7 cm.sup.3.Math.s/g.

    [0412] The inventive mixture of at least a first type of water-absorbent polymer particles (G) having a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, and at least a second type of water-absorbent polymer (H) having a sphericity of at least 0.80 and an SFC of at maximum 1510.sup.7 cm.sup.3.Math.s/g present in the absorbent core of an absorbent article ensures compared to the same amount of at least one of the first type (G) and/or the second type (H) of water-absorbent polymer particles an improved performance of the core and/or the absorbent-article especially in respect to rewet under load and/or liquid acquisition time.

    C. Fluid-Absorbent Articles

    [0413] A fluid absorbent article, comprising [0414] (A) an upper liquid-pervious sheet, [0415] (B) a lower liquid-impervious sheet, [0416] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of water-absorbent polymer particles (G, H) based on the sum of water-absorbent polymer particles and fibrous material; preferably 50 to 30% by weight of fibrous material and from 50 to 70% by weight of water-absorbent polymer particles (G, H), [0417] more preferably 40 to 35% by weight of fibrous material and from 60 to 65% by weight of water-absorbent polymer particles (G, H), [0418] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0419] (F) other optional components. [0420] According to one embodiment of the invention the fluid-absorbent article, furthermore comprising [0421] (A) an upper liquid-pervious sheet, [0422] (B) a lower liquid-impervious sheet, [0423] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0424] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0425] (F) other optional components, wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80. [0426] According to another embodiment of the invention the fluid-absorbent article, furthermore comprising [0427] (A) an upper liquid-pervious sheet, [0428] (B) a lower liquid-impervious sheet, [0429] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of a mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0430] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0431] (F) other optional components, [0432] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0433] The inventive fluid-absorbent article shows improved rewet and fluid acquisition properties. Fluid-absorbent articles are understood to mean, for example, incontinence pads and incontinence briefs for adults or diapers and training pants for babies. Suitable fluid-absorbent articles including fluid-absorbent compositions comprising fibrous materials and optionally water-absorbent polymer particles to form fibrous webs or matrices for the substrates, layers, sheets and/or the fluid-absorbent core.

    [0434] Suitable fluid-absorbent articles are composed of several layers whose individual elements must show preferably definite functional parameter such as dryness for the upper liquid-pervious layer (A), vapor permeability without wetting through for the lower liquid-impervious layer (B), a flexible, vapor permeable and thin fluid-absorbent core (C), showing fast absorption rates and being able to retain highest quantities of body fluids, and an optional acquisition-distribution layer (D) between the upper layer (A) and the core (C), acting as transport and distribution layer of the discharged body fluids. These individual elements are combined such that the resultant fluid-absorbent article meets overall criteria such as flexibility, water vapour breathability, dryness, wearing comfort and protection on the user facing side, and concerning liquid retention, rewet and prevention of wet through on the garment side. The specific combination of these layers provides a fluid-absorbent article delivering both high protection levels as well as high comfort to the consumer.

    [0435] For fluid-absorbent articles it is advantageous especially in respect to fluid distribution to have acquisition-distribution layers. The acquisition-distribution layer (D) acts as transport and distribution layer of the discharged body fluids and is typically optimized to affect efficient liquid distribution with the underlying fluid-absorbent core. Hence, for quick temporary liquid retention it provides the necessary void space while its area coverage of the underlying fluid-absorbent core must affect the necessary liquid distribution and is adopted to the ability of the fluid-absorbent core to quickly dewater the acquisition-distribution layer.

    [0436] Methods to make fluid absorbent articles are for example described in the following publications and literature cited therein and are expressly incorporated into the present invention: EP 2 301 499 A1, EP 2 314 264 A1, EP 2 387 981 A1, EP 2 486 901 A1, EP 2 524 679 A1, EP 2 524 679 A1, EP 2 524 680 A1, EP 2 565 031 A1, U.S. Pat. No. 6,972,011, US 2011/0162989, US 2011/0270204, WO 2010/004894 A1, WO 2010/004895 A1, WO 2010/076857 A1, WO 2010/082373 A1, WO 2010/118409 A1, WO 2010/133529 A2, WO 2010/143635 A1, WO 2011/084981 A1, WO 2011/086841 A1, WO 2011/086842 A1, WO 2011/086843 A1, WO 2011/086844 A1, WO 2011/117997 A1, WO 2011/136087 A1, WO 2012/048879 A1, WO 2012/052173 A1 und WO 2012/052172 A1.

    [0437] Typically fluid-absorbent articles according to the invention comprising, [0438] (A) an upper liquid-pervious sheet, [0439] (B) a lower liquid-impervious sheet, [0440] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles [0441] (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0442] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0443] (F) other optional components, [0444] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0445] According to the invention the second type of water-absorbent polymer particles has a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    [0446] According to another embodiment of the invention the SFC of the second type of water-absorbent polymer particles is more preferably at maximum of 510.sup.7 cm.sup.3.Math.s/g.

    [0447] According to the invention the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    [0448] The fluid-absorbing core (C) according to the inventive fluid-absorbent article may comprise at least two layers (K, L), wherein one of the layers (K) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the first type of water-absorbent polymer particles (G) based on the sum of water-absorbent polymer particles and fibrous material and the second layer (L) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the at least second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material.

    [0449] According to a preferred embodiment, in the fluid-absorbent core (C) of the fluid-absorbent article the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H).

    [0450] Whereas it is preferred that the at least first type of water-absorbent polymer particles (G) and the at least second type of water-absorbent polymer particles (H) are present within the fluid-absorbent core (C) in equal amounts by weight.

    [0451] It is furthermore preferred that the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight and the second type of water-absorbent polymer particles (H) are present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0452] According to another embodiment of the invention, in the fluid absorbent article the at least first type of water-absorbent polymer particles (G) is present in an amount of at least 50% by weight and the second type of water-absorbent polymer particles (H) are present of at maximum 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0453] It could be preferred that the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight and the second type of water-absorbent polymer particles (H) are present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0454] According to another embodiment of the invention in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H). According to the invention for this embodiment the rewet under load (RUL) for the 4th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles. Furthermore for this embodiment it is preferred that the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0455] For an embodiment providing equal amounts of the respective water-absorbent polymer particles (G, H) in each layer (K, L) of the fluid-absorbent core and wherein in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H), it is preferred that its rewet under load (RUL) for the 4th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50%, at maximum up to 80% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0456] For this embodiment providing equal amounts of the respective water-absorbent polymer particles (G, H) in each layer (K, L) of the fluid-absorbent core and wherein in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H), it could be preferred that the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0457] FIG. 16 is a schematic view of a fluid absorbent article according to the invention

    [0458] An absorbent article according to the invention preferably comprise as shown in FIG. 16 an upper liquid-pervious layer (A), a lower liquid-impervious layer (B) at least one fluid absorbent core (C) comprising one (FIG. 16 A) or two layers (K, L) (FIG. 16 B) of water-absorbent polymer particles (G, H), which are mixed with fibrous material (M), between (A) and (B); and an acquisition-distribution layer (D) between (A) and (C), an optional tissue layer disposed immediately above and/or below (C) or wrapped fully or partially around (C). The layers may optionally be connected to each other by binder (N) e. g. by adhesive, ultrasonic bonding or any other suitable method.

    [0459] According to the invention the two layers of water-absorbent polymer particles (K, L), are positioned adjacent to one another in direct connection or connected by a binder (N). According to the invention each layer (K, L) of water-absorbent polymer particles (G, H) could be wrapped with an optional tissue layer. An airthrough bonded layer is not present between layers (K, L).

    [0460] According to another embodiment the fluid-absorbent articles according to the invention comprising, [0461] (A) an upper liquid-pervious sheet, [0462] (B) a lower liquid-impervious sheet, [0463] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of a mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0464] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0465] (F) other optional components, [0466] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0467] According to the invention the second type of water-absorbent polymer particles has a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    [0468] According to another embodiment of the invention the SFC of the second type of water-absorbent polymer particles is more preferably at maximum of 510.sup.7 cm.sup.3.Math.s/g.

    [0469] According to the invention, the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    [0470] According to the inventive fluid-absorbent article the mixture comprises at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H) and fibrous material;

    [0471] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0472] According to an embodiment of the inventive fluid-absorbent article, the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0473] According to an embodiment of the inventive fluid-absorbent article the at least first type of water-absorbent polymer particles (G) is present of at least 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0474] According to another embodiment of the inventive fluid-absorbent article the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0475] According to further embodiment of the inventive fluid-absorbent article the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at least 30% by weight, preferably least 33% by weight of the first type of water-absorbent polymer particles (G) and at maximum 66% by weight, preferably at maximum 70% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0476] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at least 50% by weight of the first type of water-absorbent polymer particles (G) and at maximum 50% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0477] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at maximum 66% by weight, preferably at maximum 70% by weight of the first type of water-absorbent polymer particles (G) and at least 30% by weight, preferably at least 33% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0478] For an embodiment of the inventive fluid-absorbent article the rewet under load (RUL) for the 4th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0479] Furthermore it is preferred that the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults for the inventive absorbent article is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0480] Preferably for an embodiment of the inventive fluid-absorbent article providing equal amounts of the first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) in the fluid-absorbent core (C) it is preferred that for the fluid-absorbent core (C) rewet under load (RUL) for the 4.sup.th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50%, at maximum up to 80% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0481] For this embodiment providing equal amounts by weight of the first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) in the fluid-absorbent core (C), it is preferred that for the fluid-absorbent core (C) the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0482] According to the invention the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer. The resulting water absorbent polymer particles are therefore irregularly shaped.

    [0483] According to the invention the at least first type of water-absorbent polymer particles (G) and the at least second type of water-absorbent polymer particles (H) are present within the fluid-absorbent core (C) of the fluid-absorbent article in equal amounts by weight.

    [0484] Liquid-Pervious Sheet or Liquid Pervious Layer (A)

    [0485] The liquid-pervious sheet (A) is the layer which is in direct contact with the skin. Thus, the liquid-pervious sheet is preferably compliant, soft feeling and non-irritating to the consumer's skin. Generally, the term liquid-pervious is understood thus permitting liquids, i.e. body fluids such as urine, menses and/or vaginal fluids to readily penetrate through its thickness. The principle function of the liquid-pervious sheet is the acquisition and transport of body fluids from the wearer towards the fluid-absorbent core. Typically liquid-pervious layers are formed from any materials known in the art such as nonwoven material, films or combinations thereof. Suitable liquid-pervious sheets (A) consist of customary synthetic or semisynthetic fibers or bicomponent fibers or films of polyester, polyolefins, rayon or natural fibers or any combinations thereof. In the case of nonwoven materials, the fibers should generally be bound by binders such as polyacrylates. Additionally the liquid-pervious sheet may contain elastic compositions thus showing elastic characteristics allowing to be stretched in one or two directions.

    [0486] Suitable synthetic fibers are made from polyvinyl chloride, polyvinyl fluoride, polytetrafluorethylene, polyvinylidene chloride, polyacrylics, polyvinyl acetate, polyethylvinyl acetate, non-soluble or soluble polyvinyl alcohol, polyolefins such as polyethylene, polypropylene, polyamides, polyesters, polyurethanes, polystyrenes and the like.

    [0487] Examples for films are apertured formed thermoplastic films, apertured plastic films, hydro-formed thermoplastic films, reticulated thermoplastic films, porous foams, reticulated foams, and thermoplastic scrims.

    [0488] Examples of suitable modified or unmodified natural fibers include cotton, bagasse, kemp, flax, silk, wool, wood pulp, chemically modified wood pulp, jute, rayon, ethyl cellulose, and cellulose acetate.

    [0489] The fibrous material may comprise only natural fibers or synthetic fibers or any combination thereof. Preferred materials are polyester, rayon and blends thereof, polyethylene, and polypropylene. The fibrous material as a component of the fluid-absorbent compositions may be hydrophilic, hydrophobic or can be a combination of both hydrophilic and hydrophobic fibers. The definition of hydrophilic is given in the section definitions in the chapter above. The selection of the ratio hydrophilic/hydrophobic and accordingly the amount of hydrophilic and hydrophobic fibers within fluid-absorbent composition will depend upon fluid handling properties and the amount of water-absorbent polymer particles of the resulting fluid-absorbent composition. Such, the use of hydrophobic fibers is preferred if the fluid-absorbent composition is adjacent to the wearer of the fluid-absorbent article, that is to be used to replace partially or completely the upper liquid-pervious layer, preferably formed from hydrophobic nonwoven materials. Hydrophobic fibers can also be member of the lower breathable, but fluid-impervious layer, acting there as a fluid-impervious barrier.

    [0490] Examples for hydrophilic fibers are cellulosic fibers, modified cellulosic fibers, rayon, polyester fibers such as polyethylen terephthalate, hydrophilic nylon and the like. Hydrophilic fibers can also be obtained from hydrophobic fibers which are hydrophilized by e. g. surfactant-treating or silica-treating. Thus, hydrophilic thermoplastic fibers derived from polyolefins such as polypropylene, polyamides, polystyrenes or the like by surfactant-treating or silica-treating.

    [0491] To increase the strength and the integrity of the upper-layer, the fibers should generally show bonding sites, which act as crosslinks between the fibers within the layer.

    [0492] Technologies for consolidating fibers in a web are mechanical bonding, thermal bonding and chemical bonding. In the process of mechanical bonding the fibers are entangled mechanically, e.g., by water jets (spunlace) to give integrity to the web. Thermal bonding is carried out by means of raising the temperature in the presence of low-melting polymers. Examples for thermal bonding processes are spunbonding, through-air bonding and resin bonding.

    [0493] Preferred means of increasing the integrity are thermal bonding, spunbonding, resin bonding, through-air bonding and/or spunlace.

    [0494] In the case of thermal bonding, thermoplastic material is added to the fibers. Upon thermal treatment at least a portion of this thermoplastic material is melting and migrates to intersections of the fibers caused by capillary effects. These intersections solidify to bond sites after cooling and increase the integrity of the fibrous matrix. Moreover, in the case of chemically stiffened cellulosic fibers, melting and migration of the thermoplastic material has the effect of increasing the pore size of the resultant fibrous layer while maintaining its density and basis weight. Upon wetting, the structure and integrity of the layer remains stable. In summary, the addition of thermoplastic material leads to improved fluid permeability of discharged body fluids and thus to improved acquisition properties.

    [0495] Suitable thermoplastic materials including polyolefins such as polyethylene and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyethylvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides, copolyamides, polystyrenes, polyurethanes and copolymers of any of the mentioned polymers.

    [0496] Suitable thermoplastic fibers can be made from a single polymer that is a monocomponent fiber. Alternatively, they can be made from more than one polymer, e.g., bi-component or multicomponent fibers. The term bicomponent fibers refers to thermoplastic fibers that comprise a core fiber made from a different fiber material than the shell. Typically, both fiber materials have different melting points, wherein generally the sheath melts at lower temperatures. Bi-component fibers can be concentric or eccentric depending whether the sheath has a thickness that is even or uneven through the cross-sectional area of the bi-component fiber. Advantage is given for eccentric bi-component fibers showing a higher compressive strength at lower fiber thickness. Further bi-component fibers can show the feature uncrimped (unbent) or crimped (bent), further bi-component fibers can demonstrate differing aspects of surface lubricity.

    [0497] Examples of bi-component fibers include the following polymer combinations: polyethylene/polypropylene, polyethylvinyl acetate/polypropylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester and the like.

    [0498] Suitable thermoplastic materials have a melting point of lower temperatures that will damage the fibers of the layer; but not lower than temperatures, where usually the fluid-absorbent articles are stored. Preferably the melting point is between about 75 C. and 175 C. The typical length of thermoplastic fibers is from about 0.4 to 6 cm, preferably from about 0.5 to 1 cm. The diameter of thermoplastic fibers is defined in terms of either denier (grams per 9000 meters) or dtex (grams per 10 000 meters). Typical thermoplastic fibers have a dtex in the range from about 1.2 to 20, preferably from about 1.4 to 10.

    [0499] A further mean of increasing the integrity of the fluid-absorbent composition is the spunbonding technology. The nature of the production of fibrous layers by means of spunbonding is based on the direct spinning of polymeric granulates into continuous filaments and subsequently manufacturing the fibrous layer.

    [0500] Spunbond fabrics are produced by depositing extruded, spun fibers onto a moving belt in a uniform random manner followed by thermal bonding the fibers. The fibers are separated during the web laying process by air jets. Fiber bonds are generated by applying heated rolls or hot needles to partially melt the polymer and fuse the fibers together. Since molecular orientation increases the melting point, fibers that are not highly drawn can be used as thermal binding fibers. Polyethylene or random ethylene/propylene copolymers are used as low melting bonding sites.

    [0501] Besides spunbonding, the technology of resin bonding also belongs to thermal bonding subjects. Using this technology to generate bonding sites, specific adhesives, based on e.g. epoxy, polyurethane and acrylic are added to the fibrous material and the resulting matrix is thermically treated. Thus the web is bonded with resin and/or thermal plastic resins dispersed within the fibrous material.

    [0502] As a further thermal bonding technology through-air bonding involves the application of hot air to the surface of the fibrous fabric. The hot air is circulated just above the fibrous fabric, but does not push through the fibrous fabric. Bonding sites are generated by the addition of binders. Suitable binders used in through-air thermal bonding include crystalline binder fibers, bi-component binder fibers, and powders. When using crystalline binder fibers or powders, the binder melts entirely and forms molten droplets throughout the nonwoven's cross-section. Bonding occurs at these points upon cooling. In the case of sheath/core binder fibers, the sheath is the binder and the core is the carrier fiber. Products manufactured using through-air ovens tend to be bulky, open, soft, strong, extensible, breathable and absorbent. Through-air bonding followed by immediate cold calendering results in a thickness between a hot roll calendered product and one that has been though-air bonded without compression. Even after cold calendering, this product is softer, more flexible and more extensible than area-bond hot-calendered material.

    [0503] Spunlacing (hydroentanglement) is a further method of increasing the integrity of a web. The formed web of loose fibers (usually air-laid or wet-laid) is first compacted and prewetted to eliminate air pockets. The technology of spunlacing uses multiple rows of fine high-speed 30 jets of water to strike the web on a porous belt or moving perforated or patterned screen so that the fibers knot about one another. The water pressure generally increases from the first to the last injectors. Pressures as high as 150 bar are used to direct the water jets onto the web. This pressure is sufficient for most of the nonwoven fibers, although higher pressures are used in specialized applications.

    [0504] The spunlace process is a nonwovens manufacturing system that employs jets of water to entangle fibers and thereby provide fabric integrity. Softness, drape, conformability, and relatively high strength are the major characteristics of spunlace nonwoven.

    [0505] In newest researches benefits are found in some structural features of the resulting liquid-pervious layers. For example, the thickness of the layer is very important and influences together with its x-y dimension the acquisition-distribution behaviour of the layer. If there is further some profiled structure integrated, the acquisition-distribution behaviour can be directed depending on the three-dimensional structure of the layer. Thus 3D-polyethylene in the function of liquid-pervious layer is preferred.

    [0506] Thus, suitable liquid-pervious sheets (A) are nonwoven layers formed from the fibers above by thermal bonding, spunbonding, resin bonding or through-air bonding. Further suitable liquid-pervious layers are 3D-polyethylene layers and spunlace.

    [0507] Preferably the 3D-polyethylene layers and spunlace show basis weights from 12 to 22 gsm.

    [0508] Typically liquid-pervious sheets (A) extend partially or wholly across the fluid-absorbent structure and can extend into and/or form part of all the preferred sideflaps, side wrapping elements, wings and ears.

    [0509] Liquid-Impervious Sheet or Liquid Impervious Layer (B)

    [0510] The liquid-impervious sheet (B) prevents the exudates absorbed and retained by the fluid-absorbent core from wetting articles which are in contact with the fluid-absorbent article, as for example bedsheets, pants, pajamas and undergarments. The liquid-impervious sheet (B) may thus comprise a woven or a nonwoven material, polymeric films such as thermoplastic film of polyethylene or polypropylene, or composite materials such as film-coated nonwoven material.

    [0511] Suitable liquid-impervious sheets include nonwoven, plastics and/or laminates of plastic and nonwoven. Both, the plastics and/or laminates of plastic and nonwoven may appropriately be breathable, that is, the liquid-impervious layer (B) can permit vapors to escape from the fluid-absorbent material. Thus the liquid-impervious sheet has to have a definite water vapor transmission rate and at the same time the level of impermeability. To combine these features, suitable liquid-impervious layers including at least two layers, e.g. laminates from fibrous nonwoven having a specified basis weight and pore size, and a continuous three-dimensional film of e.g. polyvinylalcohol as the second layer having a specified thickness and optionally having pore structure. Such laminates acting as a barrier and showing no liquid transport or wet through. Thus, suitable liquid-impervious layers comprising at least a first breathable layer of a porous web which is a fibrous nonwoven, e.g. a composite web of a meltblown nonwoven layer or of a spunbonded nonwoven layer made from synthetic fibers and at least a second layer of a resilient three dimensional web consisting of a liquid-impervious polymeric film, e.g. plastics optionally having pores acting as capillaries, which are preferably not perpendicular to the plane of the film but are disposed at an angle of less than 90 relative to the plane of the film.

    [0512] Suitable liquid-impervious sheets are permeable for vapor. Preferably the liquid-impervious sheet is constructed from vapor permeable material showing a water vapor transmission rate (WVTR) of at least about 100 gsm per 24 hours, preferably at least about 250 gsm per 24 hours and most preferred at least about 500 gsm per 24 hours.

    [0513] Preferably the liquid-impervious sheet (B) is made of nonwoven comprising hydrophobic materials, e.g. synthetic fibers or a liquid-impervious polymeric film comprising plastics e.g. polyethylene. The thickness of the liquid-impervious sheet is preferably 15 to 30 m.

    [0514] Further, the liquid-impervious sheet (B) is preferably made of a laminate of nonwoven and plastics comprising a nonwoven having a density of 12 to 15 gsm and a polyethylene layer having a thickness of about 10 to 20 m.

    [0515] The typically liquid-impervious sheet (B) extends partially or wholly across the fluid-absorbent structure and can extend into and/or form part of all the preferred sideflaps, side wrapping elements, wings and ears.

    [0516] Fluid-Absorbent Core (C)

    [0517] The fluid-absorbent core (C) is disposed between the upper liquid-pervious sheet (A) and the lower liquid-impervious sheet (B).

    [0518] According to the present invention the fluid-absorbent core can include the following components: [0519] 1. an optional core cover [0520] 2. a fluid storage layer [0521] 3. an optional dusting layer

    [0522] 1. Optional Core Cover

    [0523] In order to increase the integrity of the fluid-absorbent core, the core is provided with a cover. This cover may be at the top and/or at the bottom of the fluid-absorbent core with bonding at lateral juncture and/or bonding at the distal juncture by hot-melt, ultrasonic bonding, thermal bonding or combination of bonding techniques know to persons skilled in the art. Further, this cover may include the whole fluid-absorbent core with a unitary sheet of material and thus function as a wrap. Wrapping is possible as a full wrap, a partial wrap or as a C-Wrap.

    [0524] The material of the core cover may comprise any known type of substrate, including nonwovens, webs, garments, textiles, films, tissues and laminates of two or more substrates or webs. The core cover material may comprise natural fibers, such as cellulose, cotton, flax, linen, hemp, wool, silk, fur, hair and naturally occurring mineral fibers. The core cover material may also comprise synthetic fibers such as rayon and lyocell (derived from cellulose), polysaccharides (starch), polyolefin fibers (polypropylene, polyethylene), polyamides, polyester, butadiene-styrene block copolymers, polyurethane and combinations thereof. Preferably, the core cover comprises synthetic fibers or tissue.

    [0525] The fibers may be mono- or multicomponent. Multicomponent fibers may comprise a homopolymer, a copolymer or blends thereof.

    [0526] 2. Fluid-Storage Layer

    [0527] According to the invention the fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H) and fibrous material; [0528] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80

    [0529] According to the invention the SFC of the second type of water-absorbent polymer particles is at maximum of 1510.sup.7 cm.sup.3.Math.s/g, preferably of at maximum of 1010.sup.7 cm.sup.3.Math.s/g, particularly preferred of at maximum of 510.sup.7 cm.sup.3.Math.s/g, more preferably of 310.sup.7 cm.sup.3.Math.s/g, most preferably of 010.sup.7 cm.sup.3.Math.s/g.

    [0530] According to the invention the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    [0531] The water absorbent polymer particles (G, H) present are preferably surface-postcrosslinked. An embodiment of the fluid-absorbing core (C) according to the invention comprising at least two layers (K, L). as illustrated in FIG. 16 B. One of the layers (K) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the first type of water-absorbent polymer particles (G) based on the sum of water-absorbent polymer particles and fibrous material and the second layer (L) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the at least second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material.

    [0532] To ensure a low rewet and a fast liquid acquisition it is preferred in the fluid-absorbent core according to the invention to arrange the layer comprising the first type of water-absorbent polymer particles (G) in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H).

    [0533] It is preferred that the amount of the at least first type of water-absorbent polymer particles (G) in one layer and the amount of the at least second type of water-absorbent polymer particles (H) in the second layer are equal by weight.

    [0534] According to an embodiment of the inventive fluid-absorbent core, the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0535] According to an embodiment of the inventive fluid-absorbent core the at least first type of water-absorbent polymer particles (G) is present of at least 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0536] According to another embodiment of the inventive fluid-absorbent core the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0537] It is furthermore preferred that the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight and the second type of water-absorbent polymer particles (H) are present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0538] According to another embodiment of the invention the at least first type of water-absorbent polymer particles (G) is present in an amount of at least 50% by weight and the second type of water-absorbent polymer particles (H) are present of at maximum 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0539] It is also preferred that the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight and the second type of water-absorbent polymer particles (H) are present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0540] For the embodiment of the invention in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H). For this embodiment it could be preferred that its rewet under load (RUL) for the 4th insult is reduced by at least 20%, preferably at least 50% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0541] Furthermore it is preferred that the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults for the inventive absorbent core is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0542] For an embodiment providing equal amounts of the respective water-absorbent polymer particles (G, H) in each layer (K, L) of the fluid-absorbent core (C) and wherein in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H), it could be preferred that its rewet under load (RUL) for the 4th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50%, at maximum up to 80% compared to a fluid-absorbent article and/or fluid absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles. For this embodiment it is preferred that equal amounts of the respective water-absorbent polymer particles (G, H) in each layer (K, L) of the fluid-absorbent core are provided.

    [0543] For an embodiment providing equal amounts of the respective water-absorbent polymer particles (G, H) in each layer (K, L) of the fluid-absorbent core (C) and wherein the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H), it could be preferred that the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article and/or fluid absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0544] Especially the layered core comprising both water-absorbent polymer particles in equal amount by weight, surprisingly shows a synergistic effect in the fluid-absorbent article.

    [0545] But the direct mixture of the first type (G) and the second type (H) of fluid-absorbent polymer particles is preferred.

    [0546] According to another embodiment of the invention the fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of a mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H) and fibrous material;

    [0547] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0548] According to an embodiment of the inventive fluid-absorbent core, the at least first type of water-absorbent polymer particles (G) is present of at least 30% by weight, preferably of at least 33% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0549] According to an embodiment of the inventive fluid-absorbent core the at least first type of water-absorbent polymer particles (G) is present of at least 50% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0550] According to another embodiment of the inventive fluid-absorbent core the at least first type of water-absorbent polymer particles (G) is present of at maximum 66% by weight, preferably of at maximum 70% by weight within the fluid-absorbent core (C) based on the sum of water-absorbent polymer particles (G, H).

    [0551] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at least 30% by weight, preferably least 33% by weight of the first type of water-absorbent polymer particles (G) and at maximum 66% by weight, preferably at maximum 70% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0552] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at least 50% by weight of the first type of water-absorbent polymer particles (G) and at maximum 50% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0553] According to the invention the mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) within the absorbent core comprises at maximum 66% by weight, preferably at maximum 70% by weight of the first type of water-absorbent polymer particles (G) and at least 30% by weight, preferably at least 33% by weight of the second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles (G, H).

    [0554] According to the invention the absorbent core the first type of fluid-absorbent polymer particles (G) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g, preferably of at least 2510.sup.7 cm.sup.3.Math.s/g, particularly preferred of at least 3010.sup.7 cm.sup.3.Math.s/g, preferentially of at least 4010.sup.7 cm.sup.3.Math.s/g, more preferably of at least 6010.sup.7 cm.sup.3.Math.s/g, most preferably of at least 8010.sup.7 cm.sup.3.Math.s/g, further most preferably of at least 10010.sup.7 cm.sup.3.Math.s/g, but not above 20010.sup.7 cm.sup.3.Math.s/g.

    [0555] According to a further embodiment of the inventive absorbent core the second type of water-absorbent polymer particles (H) have an SFC of at maximum of 1510.sup.7 cm.sup.3.Math.s/g, preferably of at maximum of 1010.sup.7 cm.sup.3.Math.s/g, particularly preferred of at maximum of 510.sup.7 cm.sup.3.Math.s/g, more preferably of 310.sup.7 cm.sup.3.Math.s/g, most preferably of 010.sup.7 cm.sup.3.Math.s/g.

    [0556] According to another embodiment the second type of water-absorbent polymer particles (H) of the inventive absorbent core have a sphericity of at least 0.80, preferably of at least 0.85, particularly preferred of at least 0.90.

    [0557] According to the invention the absorbent core the second type of water-absorbent polymer particles (H) have a sphericity of at least 0.80 and a SFC of at maximum 510.sup.7 cm.sup.3.Math.s/g.

    [0558] According to the inventive absorbent core the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer.

    [0559] According to the invention the second type of water absorbent polymer particles (H) of the fluid-absorbent core (C) are produced by polymerizing droplets of a monomer solution in a surrounding heated gas phase.

    [0560] The water absorbent polymer particles (G, H) of the fluid-absorbent article or absorbent core respectively according to one embodiment of the invention are surface-postcrosslinked.

    [0561] For an embodiment according to the invention it is preferred that its rewet under load (RUL) for the 4th insult is reduced by at least 20%, preferably at least 50% compared to a fluid-absorbent article wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0562] Furthermore according to the invention the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults for the inventive absorbent core is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0563] For an embodiment providing a mixture of equal amounts by weight of the first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) in the fluid-absorbent core (C) it is preferred that for the fluid-absorbent core (C) rewet under load (RUL) for the 4.sup.th insult and/or the sum of rewet under load for 4 succeeding insults is reduced by at least 20%, preferably at least 50%, at maximum up to 80% compared to a fluid-absorbent article and/or fluid absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the first type (G) of water-absorbent polymer particles.

    [0564] For an absorbent core according to the invention comprising a mixture of equal amounts by weight of the first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) in the fluid-absorbent core (C), it is preferred that for the fluid-absorbent core (C) the acquisition time for the 4th insult and/or the sum of acquisition times for 4 succeeding insults is reduced by at least 5%, preferably at least 10%, at maximum up to 20% compared to a fluid-absorbent article and/or fluid absorbent core wherein the total amount of water-absorbent polymer particles (G and H) in the fluid-absorbent core (C) are replaced by the same amount by weight of the second type (H) of water-absorbent polymer particles.

    [0565] The direct mixture of the first type and the second type of fluid-absorbent polymer particles, preferred a homogeneous mixture, preferably in equal amounts by weight in the absorbent core results in a reduction of rewet under load and liquid acquisition time measurements compared to cores containing the same amount of only one of the respective fluid-absorbent polymer particles. Surprisingly the mixture ensures better values in respect to rewet under load and liquid acquisition time. The mixture is synergistic in respect to rewet under load and liquid acquisition time.

    [0566] Fibers useful in the absorbent core according to the present invention include natural fibers and synthetic fibers. Examples of suitable modified or unmodified natural fibers are given in the chapter Liquid-pervious Layer (A) above. From those, wood pulp fibers are preferred.

    [0567] Examples of suitable synthetic fibers are given in the chapter Liquid-pervious Layer (A) above. The fibrous material may comprise only natural fibers or synthetic fibers or any combination thereof.

    [0568] The fibrous material as a component of the fluid-absorbent compositions may be hydrophilic, hydrophobic or can be a combination of both hydrophilic and hydrophobic fibers.

    [0569] Generally for the use in a fluid-absorbent core, which is the embedded between the upper layer (A) and the lower layer (B), hydrophilic fibers are preferred. This is especially the case for fluid-absorbent compositions that are desired to quickly acquire, transfer and distribute discharged body fluids to other regions of the fluid-absorbent composition or fluid-absorbent core. The use of hydrophilic fibers is especially preferred for fluid-absorbent compositions comprising water-absorbent polymer particles.

    [0570] Examples for hydrophilic fibers are given in the chapter Liquid-pervious Layer (A) above. Preferably, the fluid-absorbent core is made from viscose acetate, polyester and/or polypropylene.

    [0571] The fibrous material of the fluid-absorbent core may be uniformly mixed to generate a homogenous or in-homogenous fluid-absorbent core. Alternatively the fibrous material may be concentrated or laid in separate layers optionally comprising water-absorbent polymer material. Suitable storage layers of the fluid-absorbent core comprising homogenous mixtures of fibrous materials comprising water-absorbent polymer material. Suitable storage layers of the fluid-absorbent core including a layered core-system comprise homogenous mixtures of fibrous materials and comprise water-absorbent polymer material, whereby each of the layers may be built from any fibrous material by means known in the art. The sequence of the layers may be directed such that a desired fluid acquisition, distribution and transfer results, depending on the amount and distribution of the inserted fluid-absorbent material, e.g. water-absorbent polymer particles. Preferably there are discrete zones of highest absorption rate or retention within the storage layer of the fluid-absorbent core, formed of layers or in-homogenous mixtures of the fibrous material, acting as a matrix for the incorporation of water-absorbent polymer particles. The zones may extend over the full area or may form only parts of the fluid-absorbent core.

    [0572] Suitable fluid-absorbent cores comprise fibrous material and fluid-absorbent material. Suitable is any fluid-absorbent material that is capable of absorbing and retaining body fluids or body exudates such as cellulose wadding, modified and unmodified cellulose, crosslinked cellulose, laminates, composites, fluid-absorbent foams, materials described as in the chapter Liquid-pervious Layer (A) above, water-absorbent polymer particles and combinations thereof.

    [0573] Techniques of application of the water-absorbent polymer materials into the absorbent core are known to persons skilled in the art and may be volumetric, loss-in-weight or gravimetric. Known techniques include the application by vibrating systems, single and multiple auger systems, dosing roll, weigh belt, fluid bed volumetric systems and gravitational sprinkle and/or spray systems. Further techniques of insertion are falling dosage systems consensus and contradictory pneumatic application or vacuum printing method of applying the fluid absorbent polymer materials.

    [0574] As suitable fluid-absorbent cores may also include layers, which are formed by the process of manufacturing the fluid-absorbent article. The layered structure may be formed by subsequently generating the different layers in z-direction.

    [0575] Alternatively a core-structure can be formed from two or more preformed layers to get a layered fluid-absorbent core.

    [0576] Alternatively layers of other materials can be added, e.g. layers of opened or closed celled foams or perforated films. Included are also laminates of at least two layers comprising said water-absorbent polymer material.

    [0577] According to the invention it is preferred that the fluid-absorbent core (C) comprises not more than 20% by weight of an adhesive. The quantity of water-absorbent polymer particles within the fluid-absorbent core is from 3 to 20 g, preferably from 4 to 18, more preferably from 6 to 16 g, and from 8 to 13 g in the case of maxi-diapers, and in the case of incontinence products up to about 50 g.

    [0578] The fluid-absorbent core (C) typically has a uniform size or profile. Suitable fluid-absorbent cores can also have profiled structures, concerning the shape of the core and/or the content of water-absorbent polymer particles and/or the distribution of the water-absorbent polymer particles and/or the dimensions of the different layers if a layered fluid-absorbent core is present.

    [0579] The shape of the core in view from above (x-y dimension) can be rectangular, anatomical shaped with a narrower crotch area or any other shapes.

    [0580] The top view area of the fluid-absorbent core (C) is preferably at least 200 cm.sup.2, more preferably at least 250 cm.sup.2, most preferably at least 300 cm.sup.2. The top view area is the part of the core that is face-to-face to the upper liquid-pervious layer (A).

    [0581] The fluid-absorbent core may comprise additional additives typically present in fluid-absorbent articles known in the art. Exemplary additives are fibers for reinforcing and stabilizing the fluid-absorbent core. Preferably polyethylene is used for reinforcing the fluid-absorbent core.

    [0582] Further suitable stabilizer for reinforcing the fluid-absorbent core are materials acting as binder.

    [0583] In varying the kind of binder material or the amount of binder used in different regions of the fluid-absorbent core it is possible to get a profiled stabilization. For example, different binder materials exhibiting different melting temperatures may be used in regions of the fluid-absorbent core, e.g. the lower melting one in the central region of the core, and the higher melting in the distal regions. Suitable binder materials may be adhesive or non-adhesive fibers, continuously or discontinuously extruded fibers, bi-component staple fibers, non-elastomeric fibers and sprayed liquid binder or any combination of these binder materials.

    [0584] Further, thermoplastic compositions usually are added to increase the integrity of the core layer. Thermoplastic compositions may comprise a single type of thermoplastic polymers or a blend of thermoplastic polymers. Alternatively, the thermoplastic composition may comprise hot melt adhesives comprising at least one thermoplastic polymer together with thermoplastic diluents such as tackifiers, plasticizers or other additives, e.g. antioxidants. The thermoplastic composition may further comprise pressure sensitive hot melt adhesives comprising e.g. crystalline polypropylene and an amorphous polyalphaolefin or styrene block copolymer and mixture of waxes.

    [0585] Suitable thermoplastic polymers are styrenic block copolymers including A-B-A triblock segments, A-B diblock segments and (A-B).sub.n radial block copolymer segments. The letter A designs non-elastomeric polymer segments, e.g. polystyrene, and B stands for unsaturated conjugated diene or their (partly) hydrogenated form. Preferably B comprises isoprene, butadiene, ethylene/butylene (hydrogenated butadiene), ethylene/propylene (hydrogenated isoprene) and mixtures thereof.

    [0586] Other suitable thermoplastic polymers are amorphous polyolefins, amorphous polyalphaolefins and metallocene polyolefins.

    [0587] Concerning odor control, perfumes and/or odor control additives are optionally added. Suitable odor control additives are all substances of reducing odor developed in carrying fluid-absorbent articles over time known in the art. Thus, suitable odor control additives are inorganic materials, such as zeolites, activated carbon, bentonite, silica, aerosile, kieselguhr, clay; chelants such as ethylenediamine tetraacetic acid (EDTA), cyclodextrins, aminopolycarbonic acids, ethylenediamine tetramethylene phosphonic acid, aminophosphate, polyfunctional aromates, N,N-disuccinic acid. Suitable odor control additives are further antimicrobial agents such as quaternary ammonium, phenolic, amide and nitro compounds and mixtures thereof; bactericides such as silver salts, zinc salts, cetylpyridinium chloride and/or triclosan as well as surfactants having an HLB value of less than 12.

    [0588] Suitable odor control additives are further compounds with anhydride groups such as maleic-, itaconic-, polymaleic- or polyitaconic anhydride, copolymers of maleic acid with C.sub.2-C.sub.8 olefins or styrene, polymaleic anhydride or copolymers of maleic anhydride with isobutene, di-isobutene or styrene, compounds with acid groups such as ascorbic, benzoic, citric, salicylic or sorbic acid and fluid-soluble polymers of monomers with acid groups, homo- or co-polymers of C.sub.3-C.sub.5 mono-unsaturated carboxylic acids.

    [0589] Suitable odor control additives are further perfumes such as allyl caproate, allyl cyclohexaneacetate, allyl cyclohexanepropionate, allyl heptanoate, amyl acetate, amyl propionate, anethol, anixic aldehyde, anisole, benzaldehyde, benzyl acetete, benzyl acetone, benzyl alcohole, benzyl butyrate, benzyl formate, camphene, camphor gum, laevo-carveol, cinnamyl formate, cis-jasmone, citral, citronellol and its derivatives, cuminic alcohol and its derivatives, cyclal C, dimethyl benzyl carbinol and its derivatives, dimethyl octanol and its derivatives, eucalyptol, geranyl derivatives, lavandulyl acetete, ligustral, d-limonene, linalool, linalyl derivatives, menthone and its derivatives, myrcene and its derivatives, neral, nerol, p-cresol, p-cymene, orange terpenes, alpha-ponene, 4-terpineol, thymol etc.

    [0590] Optional Dusting Layer

    [0591] An optional component for inclusion into the absorbent core is a dusting layer adjacent to. The dusting layer is a fibrous layer and may be placed on the top and/or the bottom of the absorbent core. Typically, the dusting layer is underlying the storage layer. This underlying layer is referred to as a dusting layer, since it serves as carrier for deposited water-absorbent polymer particles during the manufacturing process of the fluid-absorbent core. If the water-absorbent polymer material is in the form of macrostructures, films or flakes, the insertion of a dusting layer is not necessary. In the case of water-absorbent polymer particles derived from dropletization polymerization, the particles have a smooth surface with no edges. Also in this case, the addition of a dusting layer to the fluid-absorbent core is not necessary. On the other side, as a great advantage the dusting layer provides some additional fluid-handling properties such as wicking performance and may offer reduced incidence of pin-holing and or pock marking of the liquid impervious layer (B).

    [0592] Preferably, the dusting layer is a fibrous layer comprising fluff (cellulose fibers).

    [0593] Acquisition-Distribution Layer (D)

    [0594] An optional acquisition-distribution layer (D) is located between the upper layer (A) and the fluid-absorbent core (C) and is preferably constructed to efficiently acquire discharged body fluids and to transfer and distribute them to other regions of the fluid-absorbent composition or to other layers, where the body fluids are immobilized and stored. Thus, the upper layer transfers the discharged liquid to the acquisition-distribution layer (D) for distributing it to the fluid-absorbent core.

    [0595] The acquisition-distribution layer (D) comprises fibrous material.

    [0596] Preferred acquisition-distribution layers may be hydrophilic, hydrophobic or can be a combination of both hydrophilic and hydrophobic fibers. It may be derived from natural fibers, synthetic fibers or a combination of both.

    [0597] Suitable acquisition-distribution layers are formed from cellulosic fibers and/or modified cellulosic fibers and/or synthetics or combinations thereof. Thus, suitable acquisition-distribution layers may contain cellulosic fibers, in particular wood pulp fluff. Examples of further suitable hydrophilic, hydrophobic fibers, as well as modified or unmodified natural fibers are given in the chapter Liquid-pervious sheet or liquid pervious layer (A) above.

    [0598] Especially for providing both fluid acquisition and distribution properties, the use of modified cellulosic fibers is preferred. Examples for modified cellulosic fibers are chemically treated cellulosic fibers, especially chemically stiffened cellulosic fibers. The term chemically stiffened cellulosic fibers means cellulosic fibers that have been stiffened by chemical means to increase the stiffness of the fibers. Such means include the addition of chemical stiffening agent in the form of surface coatings, surface cross-linking and impregnates. Suitable polymeric stiffening agents can include: cationic modified starches having nitrogen-containing groups, latexes, wet strength resins such as polyamide-epichlorohydrin resin, polyacrylamide, urea formaldehyde and melamine formaldehyde resins and polyethylenimine resins.

    [0599] Stiffening may also include altering the chemical structure, e.g. by crosslinking polymer chains. Thus crosslinking agents can be applied to the fibers that are caused to chemically form intrafiber crosslink bonds. Further cellulosic fibers may be stiffened by crosslink bonds in individualized form. Suitable chemical stiffening agents are typically monomeric crosslinking agents including C.sub.2-C.sub.8 dialdehyde, C.sub.2-C.sub.8 monoaldehyde having an acid functionality, and especially C.sub.2-C.sub.9 polycarboxylic acids.

    [0600] Preferably the modified cellulosic fibers are chemically treated cellulosic fibers. Especially preferred are curly fibers which can be obtained by treating cellulosic fibers with citric acid. Preferably the basis weight of cellulosic fibers and modified cellulosic fibers is from 50 to 200 gsm.

    [0601] Suitable acquisition-distribution layers further include synthetic fibers. Known examples of synthetic fibers are found in the Chapter Liquid-pervious sheet or liquid pervious layer (A) above. Another possibility available is 3D-polyethylene film with dual function as a liquid-pervious layer (A) and acquisition-distribution layer.

    [0602] Further, as in the case of cellulosic fibers, hydrophilic synthetic fibers are preferred. Hydrophilic synthetic fibers may be obtained by chemical modification of hydrophobic fibers. Preferably, hydrophilization is carried out by surfactant treatment of hydrophobic fibers. Thus the surface of the hydrophobic fiber can be rendered hydrophilic by treatment with a nonionic or ionic surfactant, e.g., by spraying the fiber with a surfactant or by dipping the fiber into a surfactant. Further preferred are permanent hydrophilic synthetic fibers.

    [0603] The fibrous material of the acquisition-distribution layer may be fixed to increase the strength and the integrity of the layer. Technologies for consolidating fibers in a web are mechanical bonding, thermal bonding and chemical bonding. Detailed description of the different methods of increasing the integrity of the web is given in the Chapter Liquid-pervious sheet or liquid pervious layer(A) above.

    [0604] Thus, suitable acquisition-distribution layers comprising from 80 to 100% by weight a fibrous material and from 0 to 20% by weight water-absorbent polymer particles;

    [0605] Preferred acquisition-distribution layers show basis weights in the range from 20 to 200 gsm, most preferred in the range from 40 to 60 gsm.

    [0606] Alternatively a liquid-impervious layer (D) comprising a synthetic resin film between (A) and (C) acting as an distribution layer and quickly transporting the supplied urine along the surface to the upper lateral portion of the fluid-absorbent core (C). Preferably, the upper liquid-impervious layer (D) is smaller than the under-laying fluid-absorbent core (C) (80). There is no limit in particular to the material of the liquid-impervious layer (D). Such a film made of a resin such as polyethylene, polypropylene, polyethylene therephthalate, polyurethane, or crosslinked polyvinyl alcohol and an air-permeable, but liquid-impervious, so-called: breathable film made of above described resin, may be used.

    [0607] Preferably, the upper liquid-impervious layer (D) comprises a porous polyethylene film for both quick acquisition and distribution of fluid.

    [0608] Alternatively a bundle of synthetic fibers acting as acquisition-distribution layer loosely distributed on top of the fluid-absorbent core may be used. Suitable synthetic fibers are of copolyester, polyamide, copolyamide, polylactic acid, polypropylene or polyethylene, viscose or blends thereof. Further bicomponent fibers can be used. The synthetic fiber component may be composed of either a single fiber type with a circular cross-section or a blend of two fibre types with different cross-sectional shapes. Synthetic fibers arranged in that way ensuring a very fast liquid transport and canalisation. Preferrably bundles of polyethylene fibers are used.

    [0609] An optional tissue layer is disposed immediately above and/or below (C).

    [0610] The material of the tissue layer may comprise any known type of substrate, including webs, garments, textiles and films. The tissue layer may comprise natural fibers, such as cellulose, cotton, flax, linen, hemp, wool, silk, fur, hair and naturally occurring mineral fibers. The tissue layer may also comprise synthetic fibers such as rayon and lyocell (derived from cellulose), polysaccharides (starch), polyolefin fibers (polypropylene, polyethylene), polyamides, polyester, butadiene-styrene block copolymers, polyurethane and combinations thereof. Preferably, the tissue layer comprises cellulose fibers.

    [0611] Other Optional Components (F)

    [0612] 1. Leg Cuff

    [0613] Typical leg cuffs comprising nonwoven materials which can be formed by direct extrusion processes during which the fibers and the nonwoven materials are formed at the same time, or by laying processes of preformed fibers which can be laid into nonwoven materials at a later point of time. Examples for direct extrusion processes include spunbonding, meltblowing, solvent spinning, electrospinning and combinations thereof. Examples of laying processes include wet-laying and dry-laying (e.g. air-laying, carding) methods. Combinations of the processes above include spunbond-meltblown-spunbond (sms), spunbond-meltblow-meltblown-spunbond (smms), spunbond-carded (sc), spunbond-airlaid (sa), meltblown-airlaid (ma) and combinations thereof. The combinations including direct extrusion can be combined at the same point in time or at a subsequent point in time. In the examples above, one or more individual layers can be produced by each process. Thus, sms means a three layer nonwoven material, smsms or ssmms means a five layer nonwoven material. Usually, small type letters (sms) designate individual layers, whereas capital letters (SMS) designate the compilation of similar adjacent layers.

    [0614] Further, suitable leg cuffs are provided with elastic strands.

    [0615] Preferred are leg cuffs from synthetic fibers showing the layer combinations sms, smms or smsms. Preferred are nonwovens with the density of 13 to 17 gsm. Preferably leg cuffs are provided with two elastic strands.

    [0616] 2. Elastics

    [0617] The elastics are used for securely holding and flexibly closing the fluid-absorbent article around the wearers' body, e.g. the waist and the legs to improve containment and fit. Leg elastics are placed between the outer and inner layers or the fluid-absorbent article, or between the outer garment facing cover and the user facing bodyside liner. Suitable elastics comprising sheets, ribbons or strands of thermoplastic polyurethane, elastomeric materials, poly(ether-amide) block copolymers, thermoplastic rubbers, styrene-butadiene copolymers, silicon rubbers, natural rubbers, synthetic rubbers, styrene isoprene copolymers, styrene ethylene butylene copolymers, nylon copolymers, spandex fibers comprising segmented polyurethane and/or ethylene-vinyl acetate copolymer. The elastics may be secured to a substrate after being stretched, or secured to a stretched substrate. Otherwise, the elastics may be secured to a substrate and then elastisized or shrunk, e.g. by the application of heat.

    [0618] 3. Closing System

    [0619] The closing system can include tape tabs, landing zone, elastomerics, pull ups and the belt system or combinations thereof

    [0620] At least a part of the first waist region is attached to a part of the second waist region by the closing system to hold the fluid-absorbent article in place and to form leg openings and the waist of the fluid-absorbent article. Preferably the fluid-absorbent article is provided with a reclosable closing system.

    [0621] The closing system is either re-sealable or permanent, including any material suitable for such a use, e.g. plastics, elastics, films, foams, nonwoven substrates, woven substrates, paper, tissue, laminates, fiber reinforced plastics and the like, or combinations thereof. Preferably the closing system includes flexible materials and works smooth and softly without irritating the wearer's skin.

    [0622] One part of the closing elements is an adhesive tape, or comprises a pair of laterally extending tabs disposed on the lateral edges of the first waist region. Tape tabs are typically attached to the front body panel and extend laterally from each corner of the first waistband. These tape tabs include an adhesive inwardly facing surface which is typically protected prior to use by a thin, removable cover sheet.

    [0623] Suitable tape tabs may be formed of thermoplastic polymers such as polyethylene, polyurethane, polystyrene, polycarbonate, polyester, ethylene vinyl acetate, ethylene vinyl alcohol, ethylene vinyl acetate acrylate or ethylene acrylic acid copolymers.

    [0624] Suitable closing systems comprise further a hook portion of a hook and loop fastener and the target devices comprise the loop portion of a hook and loop fastener.

    [0625] Suitable mechanical closing systems including a landing zone. Mechanical closing systems may fasten directly into the outer cover. The landing zone may act as an area of the fluid-absorbent article into which it is desirable to engage the tape tabs. The landing zone may include a base material and a plurality of tape tabs. The tape tabs may be embedded in the base material of the landing zone. The base material may include a loop material. The loop material may include a backing material and a layer of a nonwoven spunbond web attached to the backing material.

    [0626] Thus suitable landing zones can be made by spunbonding. Spunbonded nonwoven are made from melt-spun fibers formed by extruding molten thermoplastic material. Preferred is bi-oriented polypropylene (BOPP), or brushed/closed loop in the case of mechanical closing systems.

    [0627] Further, suitable mechanical closing systems including elasticomeric units serving as a flexible abdominal and/or dorsal discrete waist band, flexible abdomen and/or dorsal zones located at distal edge for fluid-absorbents articles, such as pants or pull-ups. The elasticomeric units enable the fluid-absorbent article to be pulled down by the wearer as e.g. a training pant.

    [0628] Suitable pants-shaped fluid-absorbent article has front abdominal section, rear dorsal section, crotch section, side sections for connecting the front and rear sections in lateral direction, hip section, elastic waist region and liquid-tight outer layer. The hip section is arranged around the waist of the user. The disposable pants-shaped fluid-absorbent article (pull-up) has favorable flexibility, stretchability, leak-proof property and fit property, hence imparts excellent comfort to the wearer and offers improved mobility and discretion.

    [0629] Suitable pull-ups comprising thermoplastic films, sheets and laminates having a low modulus, good tear strength and high elastic recovery.

    [0630] Suitable closing systems may further comprise elastomerics for the production of elastic areas within the fastening devices of the fluid-absorbent article. Elastomerics provide a conformable fit of the fluid-absorbent article to the wearer at the waist and leg openings, while maintaining adequate performance against leakage.

    [0631] Suitable elastomerics are elastomeric polymers or elastic adhesive materials showing vapor permeability and liquid barrier properties. Preferred elastomerics are retractable after elongation to a length equivalent to its original length.

    [0632] Suitable closing systems further comprise a belt system, comprising waist-belt and leg-belts for flexibly securing the fluid-absorbent article on the body of the wearer and to provide an improved fit on the wearer. Suitable waist-belts comprising two elastic belts, a left elastic belt, and a right elastic belt. The left elastic belt is associated with each of the left angular edges. The right elastic belt associated with each of the right angular edges. The left and right side belts are elastically extended when the absorbent garment is laid flat. Each belt is connected to and extends between the front and rear of the fluid-absorbent article to form a waist hole and leg holes.

    [0633] Preferably the belt system is made of elastomerics, thus providing a conformable fit of the fluid-absorbent article and maintaining adequate performance against leakage.

    [0634] Preferred closing systems are so-called elastic ears attached with one side of the ear to the longitudinal side edges located at the rear dorsal longitudinal edge of the chassis of the fluid-absorbent article. Commercially available fluid-absorbent articles include stretchable ears or side panels which are made from a stretchable laminate e.g. nonwoven webs made of mono- or bi-component fibers. Especially preferred closing systems are stretchable laminates comprising a core of several layers each of different fibrous materials, e.g. meltblown fibers, spunbond fibers, containing multicomponent fibers having a core comprising a first polymer having a first melt temperature and a sheath comprising a second polymer having a second melt temperature; and a web of an elastomeric material as top and bottom surfaces to form said laminate.

    D. Fluid-Absorbent Article Construction

    [0635] The present invention further relates to the joining of the components and layers, films, sheets, tissues or substrates mentioned above to provide the fluid-absorbent article. At least two, preferably all layers, films, sheets, tissues or substrates are joined.

    [0636] In order to immobilize the water-absorbent polymer particles, the adjacent layers are fixed by the means of thermoplastic materials, thereby building connections throughout the whole surface or alternatively in discrete areas of junction. For the latter case, cavities or pockets are built carrying the water-absorbent particles. The areas of junction may have a regular or irregular pattern, e.g. aligned with the longitudinal axis of the fluid-absorbent core or in a pattern of polygons, e.g. pentagons or hexagons. The areas of junction itself may be of rectangular, circular or squared shape with diameters between about 0.5 mm and 2 mm. Fluid-absorbent articles comprising areas of junction show a better wet strength.

    [0637] The construction of the products chassis and the components contained therein is made and controlled by the discrete application of hotmelt adhesives as known to people skilled in the art. Examples would be e.g. Dispomelt 505B, Dispomelt Cool 1101, as well as other specific function adhesives manufactured by Bostik, Henkel or Fuller.

    [0638] In order to ensure wicking of applied body fluids, preferred fluid-absorbent article show channels for better transport. Channels are formed by compressional forces of e.g. the top sheet against the fluid-absorbent core. Compressive forces may be applied e.g. by heat-treatment between two heated calendar rollers. As an effect of compression both on top sheet and fluid-absorbent core deform such that a channel is created. Body fluids are flowing along this channel to places where they are absorbed and leakage is prevented. Otherwise, compression leads to higher density; this is the second effect of the channel to canalize insulted fluids. Additionally, compressive forces on diaper construction improve the structural integrity of the fluid-absorbent article.

    [0639] Typically fluid-absorbent articles according to the invention comprising, [0640] (A) an upper liquid-pervious sheet, [0641] (B) a lower liquid-impervious sheet, [0642] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0643] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0644] (F) other optional components, [0645] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010.sup.7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a sphericity of at least 0.80.

    [0646] According to the invention the second type of water-absorbent polymer particles has a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    [0647] The fluid-absorbing core (C) according to the invention may comprise at least two layers (K, L), wherein one of the layers (K) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the first type of water-absorbent polymer particles (G) based on the sum of water-absorbent polymer particles and fibrous material and the second layer (L) comprises from 60 to 20% by weight fibrous material and 40 to 80% by weight of the at least second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material.

    [0648] According to a preferred embodiment, in the fluid-absorbent core (C) the layer comprising the first type of water-absorbent polymer particles (G) is arranged in z-direction above the layer comprising the at least second type of water-absorbent polymer particles (H).

    [0649] According to another embodiment the fluid-absorbent articles according to the invention comprising, [0650] (A) an upper liquid-pervious sheet, [0651] (B) a lower liquid-impervious sheet, [0652] (C) a fluid-absorbent core comprising from 60 to 20% by weight fibrous material and from 40 to 80% by weight of a mixture of at least a first type of water-absorbent polymer particles (G) and at least a second type of water-absorbent polymer particles (H) based on the sum of water-absorbent polymer particles and fibrous material; [0653] (D) an optional acquisition-distribution layer (D) between (A) and (C), [0654] (F) other optional components, [0655] wherein the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) have a SFC of at least 2010-7 cm.sup.3.Math.s/g and wherein the at least second type of water-absorbent polymer particles (H) of the fluid-absorbent core have a mean sphericity of at least 0.80.

    [0656] According to the invention the second type of water-absorbent polymer particles has a SFC at maximum of 1510.sup.7 cm.sup.3.Math.s/g.

    [0657] The inventive fluid-absorbent article shows improved rewet and fluid acquisition properties. According to the invention the production process of the first type of water absorbent polymer particles (G) of the fluid-absorbent core (C) comprises the steps of polymerization of the monomer solution, forming and comminuting a polymer gel, drying and grinding of the polymer. The resulting water absorbent polymer particles are therefore irregularly shaped.

    [0658] According to a preferred embodiment of the invention the at least first type of water-absorbent polymer particles (G) and the at least second type of water-absorbent polymer particles (H) are present within the fluid-absorbent core (C) in equal amounts by weight.

    [0659] Methods:

    [0660] The measurements should, unless stated otherwise, be carried out at an ambient temperature of 232 C. and a relative atmospheric humidity of 5010%. The water-absorbent polymers are mixed thoroughly before the measurement.

    [0661] The WSP standard test methods are described in: Standard Test Methods for the Nonwovens Industry, jointly issued by the Worldwide Strategic Partners EDANA (European Disposables and Nonwovens Association, Avenue Eugene Plasky, 157, 1030 Brussels, Belgium, www.edana.org) and INDA (Association of the Nonwoven Fabrics Industry, 1100 Crescent Green, Suite 115, Cary, N.C. 27518, U.S.A., www.inda.org). This publication is available both from EDANA and INDA.

    [0662] Accelerated Aging Test

    [0663] Measurement 1 (Initial color): A plastic dish with an inner diameter of 9 cm is overfilled with superabsorbent polymer particles. The surface is flattened at the height of the petri dish lip by means of a knife and the CIE color values and the HC 60 value are determined.

    [0664] Measurement 2 (after aging): A plastic dish with an inner diameter of 9 cm is overfilled with superabsorbent polymer particles. The surface is flattened at the height of the petri dish lip by means of a knife. The plastic dish (without a cover) is then placed in a humidity chamber at 60 C. and a relative humidity of 86%. The plastic dish is removed from the humidity chamber after 7, and 14 days, cooled down to room temperature and the CIE color values are determined.

    [0665] Absorbency Under No Load (AUNL)

    [0666] The absorbency under no load of the water-absorbent polymer particles is determined analogously to the EDANA recommended test method No. WSP 242.3 (11) Gravimetric Determination of Absorption Under Pressure, except using a weight of 0.0 g/cm.sup.2 instead of a weight of 21.0 g/cm.sup.2.

    [0667] Absorbency Under Load (AUL)

    [0668] The absorbency under load of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 242.3 (11) Gravimetric Determination of Absorption Under Pressure

    [0669] Absorbency Under High Load (AUHL)

    [0670] The absorbency under high load of the water-absorbent polymer particles is determined analogously to the EDANA recommended test method No. WSP 242.3 (11) Gravimetric Determination of Absorption Under Pressure, except using a weight of 49.2 g/cm.sup.2 instead of a weight of 21.0 g/cm.sup.2.

    [0671] Bulk Density

    [0672] The bulk density of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 250.3 (11) Gravimetric Determination of Density.

    [0673] Centrifuge Retention Capacity (CRC)

    [0674] The centrifuge retention capacity of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 241.3 (11) Fluid Retention Capacity in Saline, After Centrifugation, wherein for higher values of the centrifuge retention capacity larger tea bags have to be used.

    [0675] Color Value (CIE Color Numbers [L, a, b])

    [0676] Measurement of the color value is done by means of a colorimeter model LabScan XE S/N LX17309 (HunterLab; Reston; U.S.A.) according to the CIELAB procedure (Hunterlab, Volume 8, 1996, Issue 7, pages 1 to 4). Colors are described by the coordinates L, a, and b of a three-dimensional system. L characterizes the brightness, whereby L=0 is black and L=100 is white. The values for a and b describe the position of the color on the color axis red/green resp. yellow/blue, whereby positive a values stand for red colors, negative a values for green colors, positive b values for yellow colors, and negative b values for blue colors.

    [0677] The measurement of the color value is in agreement with the tristimulus method according to DIN 5033-6.

    [0678] Extractables

    [0679] The level of extractable constituents in the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 270.3 (11) Extractables.

    [0680] Free Swell Capacity (FSC)

    [0681] The free swell capacity of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 240.3 (11) Free Swell Capacity in Saline, Gravimetric Determination, wherein for higher values of the free swell capacity larger tea bags have to be used.

    [0682] Free Swell Rate (FSR) 1.00 g (=W1) of the dry water-absorbent polymer particles is weighed into a 25 ml glass beaker and is uniformly distributed on the base of the glass beaker. 20 ml of a 0.9% by weight sodium chloride solution are then dispensed into a second glass beaker, the content of this beaker is rapidly added to the first beaker and a stopwatch is started. As soon as the last drop of salt solution is absorbed, confirmed by the disappearance of the reflection on the liquid surface, the stopwatch is stopped. The exact amount of liquid poured from the second beaker and absorbed by the polymer in the first beaker is accurately determined by weighing back the second beaker (=W2). The time needed for the absorption, which was measured with the stopwatch, is denoted t. The disappearance of the last drop of liquid on the surface is defined as time t.

    [0683] The free swell rate (FSR) is calculated as follows:


    FSR [g/gs]=W2/(W1t)

    When the moisture content of the hydrogel-forming polymer is more than 3% by weight, however, the weight W1 must be corrected for this moisture content.

    [0684] Gel Bed Permeability

    [0685] The gel bed permeability (GBP) of a swollen gel layer under a pressure of 0.3 psi (2070 Pa) is, as described in US 2005/0256757 (paragraphs [0061] and [0075]), determined as the gel bed permeability of a swollen gel layer of water-absorbing polymer particles.

    [0686] Sphericity or Roundness

    [0687] The roundness is determined with the PartAn 3001 L Particle Analysator (Microtrac Europe GmbH; Meerbusch; Germany)

    [0688] or with the Camsizer image analysis system (Retsch Technolgy GmbH; Haan; Germany): For the measurement, the product is introduced through a funnel and conveyed to the falling shaft with a metering channel. While the particles fall past a light wall, they are recorded selectively by a camera. The images recorded are evaluated by the software in accordance with the parameters selected.

    [0689] The parameters reported are the mean volume-weighted sphericities.

    [0690] Moisture Content

    [0691] The moisture content of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 430.2-05 Moisture Content.

    [0692] Particle Size Distribution

    [0693] The particle size distribution of the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 220.3 (11) Particle Size Distribution.

    [0694] The average particle diameter (d.sub.50) here is the value of the mesh size which gives rise to a cumulative 50% by weight.

    [0695] The degree of polydispersity of the particle size particle is calculated by


    (=(d.sub.84.13d.sub.15.87)/(2d.sub.50)

    wherein d.sub.15.87 and d.sub.84.13 is the value of the mesh size which gives rise to a cumulative 15.87% respective 84.13% by weight.

    [0696] Rewet Under Load (RUL) and Acquisition Time

    [0697] The test determines the amount of fluid a fluid-absorbent article will release after being maintained at a pressure of 0.7 psi (49.2 g/cm.sup.2) for 5 min following multiple separate insults. The rewet under load is measured by the amount of fluid the fluid-absorbent article releases under pressure. The rewet under load is measured after each insult.

    [0698] The fluid-absorbent article is clamped nonwoven side upward onto the inspection table. The insult point (pee point) is marked accordingly with regard to the type and gender of the diaper to be tested (i.e. in the centre of the core for girl, 2.5 cm towards the front for unisex and 5 cm towards the front for boy). A 3.64 kg circular weight (10 cm diameter) having a central opening (2.3 cm diameter) with perspex tube is placed with on the previously marked insult point.

    [0699] To measure the RUL for absorbent pads with an ADL on top, the pad is clamped ADL side upward onto the inspection table. The insult point (pee point) is marked accordingly with regard to the type and gender of the diaper to be tested (i.e. in the center of the core for girl, 2.5 cm towards the front for unisex and 5 cm towards the front for boy) For the primary insult 75 g of aqueous saline solution (0.9% by weight) is poured into the perspex tube in one shot. Amount of time needed for the fluid to be fully absorbed into the fluid-absorbent article is recordedit is an acquisition time, reported in seconds. After 5 minutes have elapsed, the load is removed and the stack of 10 filter papers (Whatman) having 9 cm diameter and known dry weight (W1) is placed over the insult point on the fluid-absorbent article or the absorbent pad with ADL respectively. On top of the filter paper, the 2.5 kg weight with 8 cm diameter is added. After 2 minutes have elapsed the weight is removed and filter paper reweighed giving the wet weight value (W2).

    [0700] The rewet under load is calculated as follows:


    RUL [g]=W2W1

    For the rewet under load of the secondary and following insults the procedure for the primary insult is repeated. For each following insults 2, 3 and 4 75 g of aqueous saline solution (0.9% by weight) and 20, 30, 40 filter papers respectively are used.

    [0701] Residual Monomers

    [0702] The level of residual monomers in the water-absorbent polymer particles is determined by the EDANA recommended test method No. WSP 210.3-(11) Residual Monomers.

    [0703] Saline Flow Conductivity (SFC)

    [0704] The saline flow conductivity (SFC) of a swollen gel layer under a pressure of 0.3 psi (2070 Pa) is, as described in EP 0 640 330 A1, determined as the gel layer permeability of a swollen gel layer of water-absorbing polymer particles, the apparatus described on page 19 and in FIG. 8 in the cited patent application having been modified such that the glass frit (40) is not used, and the plunger (39) consists of the same polymer material as the cylinder (37) and now comprises 21 bores of equal size distributed homogeneously over the entire contact area. The procedure and evaluation of the measurement remain unchanged from EP 0 640 330 A1. The flow is detected automatically.

    [0705] The saline flow conductivity (SFC) is calculated as follows:


    SFC [cm.sup.3.Math.s/g]=(Fg(t=0)L0)/(dAWP)

    [0706] where Fg(t=0) is the flow of NaCl solution in g/s, which is obtained using linear regression analysis of the Fg(t) data of the flow determinations by extrapolation to t=0, L0 is the thickness of the gel layer in cm, d is the density of the NaCl solution in g/cm.sup.3, A is the area of the gel layer in cm.sup.2, and WP is the hydrostatic pressure over the gel layer in dyn/cm.sup.2.

    [0707] Vortex

    [0708] 50.01.0 ml of 0.9% NaCl solution are added into a 100 ml beaker. A cylindrical stirrer bar (306 mm) is added and the saline solution is stirred on a stir plate at 60 rpm. 2.0000.010 g of water-absorbent polymer particles are added to the beaker as quickly as possible, starting a stop watch as addition begins. The stopwatch is stopped when the surface of the mixture becomes still that means the surface has no turbulence, and while the mixture may still turn, the entire surface of particles turns as a unit. The displayed time of the stopwatch is recorded as Vortex time.

    [0709] The EDANA test methods are obtainable, for example, from the EDANA, Avenue Eugene Plasky 157, B-1030 Brussels, Belgium.

    EXAMPLES

    [0710] Preparation of the Fluid-Absorbent Polymer Particles

    [0711] The following polymer particles are used: [0712] Water-absorbent polymer particles prepared as described in Example 4 [0713] Water-absorbent polymer particles prepared as described in Example 5 [0714] Water-absorbent polymer particles prepared as described in Example 6 [0715] Water-absorbent polymer particles as described in Example 7 [0716] HySorb B7085 available from BASF Antwerpen N.V., Belgium [0717] Hysorb B7160S available from BASF Antwerpen N.V., Belgium

    [0718] Features and absorption profiles of all polymer particles are summarized in Table 9.

    Example 1Basepolymer

    [0719] The process was performed in a concurrent spray drying plant with an integrated fluidized bed (27) as shown in FIG. 1. The reaction zone (5) had a height of 22 m and a diameter of 3.4 m. The internal fluidized bed (IFB) had a diameter of 3 m and a weir height of 0.25 m.

    [0720] The drying gas was fed via a gas distributor (3) at the top of the spray dryer. The drying gas was partly recycled (drying gas loop) via a cyclone as dust separation unit (9) and a condenser column (12). The drying gas was nitrogen that comprises from 1% to 4% by volume of residual oxygen. Prior to the start of polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume. The gas velocity of the drying gas in the reaction zone (5) was 0.79 m/s. The pressure inside the spray dryer was 4 mbar below ambient pressure.

    [0721] The temperature of the gas leaving the reaction zone (5) was measured at three points around the circumference at the end of the cylindrical part of the spray dryer as shown in FIG. 3. Three single measurements (43) were used to calculate the average temperature (spray dryer outlet temperature). The drying gas loop was heated up and the dosage of monomer solution is started up. From this time the spray dryer outlet temperature was controlled to 122 C. by adjusting the gas inlet temperature via the heat exchanger (20). The gas inlet temperature was 167 C. and the steam content of the drying gas is shown in Tab. 1.

    [0722] The product accumulated in the internal fluidized bed (27) until the weir height was reached. Conditioned internal fluidized bed gas having a temperature of 112 was fed to the internal fluidized bed (27) via line (25). The gas velocity of the internal fluidized bed gas in the internal fluidized bed (27) was 0.65 m/s. The residence time of the product was 150 min. The temperature of the water-absorbent polymer particles in the internal fluidized bed (27) was 80 C.

    [0723] The spray dryer offgas was filtered in cyclone as dust separation unit (9) and sent to a condenser column (12) for quenching/cooling. Excess water was pumped out of the condenser column (12) by controlling the (constant) filling level inside the condenser column (12). The water inside the condenser column (12) was cooled by a heat exchanger (13) and pumped counter-current to the gas. The temperature and the steam content of the gas leaving the condenser column (12) are shown in Tab. 1. The water inside the condenser column (12) was set to an alkaline pH by dosing sodium hydroxide solution to wash out acrylic acid vapors.

    [0724] The gas leaving the condenser column (12) was split to the drying gas inlet pipe (37) and the conditioned internal fluidized bed gas (25). The gas temperatures were controlled via heat exchangers (20) and (22). The hot drying gas was fed to the concurrent spray dryer via gas distributor (3). The gas distributor (3) consists of a set of plates providing a pressure drop of 2 to 4 mbar depending on the drying gas amount.

    [0725] The product was discharged from the internal fluidized bed (27) via rotary valve (28) into sieve (29). The sieve (29) was used for sieving off overs/lumps having a particle diameter of more than 800 m. The weight amounts of overs/lumps are summarized in Tab. 3.

    [0726] The monomer solution was prepared by mixing first acrylic acid with 3-tuply ethoxylated glycerol triacrylate (internal crosslinker) and secondly with 37.3% by weight sodium acrylate solution. The temperature of the resulting monomer solution was controlled to 10 C. by using a heat exchanger and pumping in a loop. A filter unit having a mesh size of 250 m was used in the loop after the pump. The initiators were metered into the monomer solution upstream of the dropletizer by means of static mixers (31) and (32) via lines (33) and (34) as shown in FIG. 1. Sodium peroxodisulfate solution having a temperature of 20 C. was added via line (33) and [2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride solution together with Brggolite FF7 and Blancolen HP having a temperature of 10 C. was added via line (34). Each initiator was pumped in a loop and dosed via control valves to each dropletizer unit. A second filter unit having a mesh size of 140 m was used after the static mixer (32). For dosing the monomer solution into the top of the spray dryer three dropletizer units were used as shown in FIG. 4.

    [0727] A dropletizer unit consisted of an outer pipe (47) having an opening for the dropletizer cassette (49) as shown in FIG. 7. The dropletizer cassette (49) was connected with an inner pipe (48). The inner pipe (48) having a PTFE block (50) at the end as sealing can be pushed in and out of the outer pipe (47) during operation of the process for maintenance purposes.

    [0728] The temperature of the dropletizer cassette (49) was controlled to 8 C. by water in flow channels (55) as shown in FIG. 8. The dropletizer cassette (49) had 256 bores having a diameter of 170 m and a bore spacing of 15 mm. The dropletizer cassette (49) consisted of a flow channel (56) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and one droplet plate (53). The droplet plate (53) had an angled configuration with an angle of 3. The droplet plate (53) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.

    [0729] The feed to the spray dryer consisted of 9.56% by weight of acrylic acid, 33.73% by weight of sodium acrylate, 0.011% by weight of 3-tuply ethoxylated glycerol Triacrylate (purity approx. 85% by weight), 0.071% by weight of [2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.0028% by weight of Brggolite FF7 (Broggemann Chemicals; Heilbronn; Germany), 0.071% by weight of Blancolene HP (Broggemann Chemicals; Heilbronn; Germany) 0.054% by weight of sodiumperoxodisulfate and water. The degree of neutralization was 73%. The feed per bore was 1.4 kg/h.

    [0730] The resulting water-absorbent polymer particles were analyzed. The conditions and results are summarized in Tab. 1 to 3.

    Example 2 Basepolymer

    [0731] The process was performed in a concurrent spray drying plant with an integrated fluidized bed (27) as shown in FIG. 1. The reaction zone (5) had a height of 22 m and a diameter of 3.4 m. The internal fluidized bed (IFB) had a diameter of 3 m and a weir height of 0.25 m.

    [0732] The drying gas was feed via a gas distributor (3) at the top of the spray dryer. The drying gas was partly recycled (drying gas loop) via a cyclone as dust separation unit (9) and a condenser column (12). The drying gas was nitrogen that comprises from 1% to 4% by volume of residual oxygen. Prior to the start of polymerization the drying gas loop was filled with nitrogen until the residual oxygen was below 4% by volume. The gas velocity of the drying gas in the reaction zone (5) was 0.79 m/s. The pressure inside the spray dryer was 4 mbar below ambient pressure.

    [0733] The temperature of the gas leaving the reaction zone (5) was measured at three points around the circumference at the end of the cylindrical part of the spray dryer as shown in FIG. 3. Three single measurements (43) were used to calculate the average temperature (spray dryer outlet temperature). The drying gas loop was heated up and the dosage of monomer solution is started up. From this time the spray dryer outlet temperature was controlled to 112 C. by adjusting the gas inlet temperature via the heat exchanger (20). The gas inlet temperature was 167 C. and the steam content of the drying gas is shown in Tab. 1.

    [0734] The product accumulated in the internal fluidized bed (27) until the weir height was reached. Conditioned internal fluidized bed gas having a temperature of 107 was fed to the internal fluidized bed (27) via line (25). The gas velocity of the internal fluidized bed gas in the internal fluidized bed (27) was 0.65 m/s. The residence time of the product was 150 min. The temperature of the water-absorbent polymer particles in the internal fluidized bed (27) was 77 C.

    [0735] The spray dryer offgas was filtered in cyclone as dust separation unit (9) and sent to a condenser column (12) for quenching/cooling. Excess water was pumped out of the condenser column (12) by controlling the (constant) filling level inside the condenser column (12). The water inside the condenser column (12) was cooled by a heat exchanger (13) and pumped counter-current to the gas. The temperature and the steam content of the gas leaving the condenser column (12) are shown in Tab. 1. The water inside the condenser column (12) was set to an alkaline pH by dosing sodium hydroxide solution to wash out acrylic acid vapors.

    [0736] The gas leaving the condenser column (12) was split to the gas drying unit (37) and the conditioned internal fluidized bed gas (25). The gas drying unit (37) comprises a gas cooler and a demister. In the gas drying unit (37) the gas was cooled down to 40 C. and heated up prior to the drying gas inlet pipe (1). The gas temperatures were controlled via heat exchangers (20) and (22). The hot drying gas was fed to the concurrent spray dryer via gas distributor (3). The gas distributor (3) consists of a set of plates providing a pressure drop of 2 to 4 mbar depending on the drying gas amount.

    [0737] The product was discharged from the internal fluidized bed (27) via rotary valve (28) into sieve (29). The sieve (29) was used for sieving off overs/lumps having a particle diameter of more than 800 m. The weight amounts of overs/lumps are summarized in Tab. 3.

    [0738] The monomer solution was prepared by mixing first acrylic acid with 3-tuply ethoxylated glycerol triacrylate (internal crosslinker) and secondly with 37.3% by weight sodium acrylate solution. The temperature of the resulting monomer solution was controlled to 10 C. by using a heat exchanger and pumping in a loop. A filter unit having a mesh size of 250 m was used in the loop after the pump. The initiators were metered into the monomer solution upstream of the dropletizer by means of static mixers (31) and (32) via lines (33) and (34) as shown in FIG. 1. Sodium peroxodisulfate solution having a temperature of 20 C. was added via line (33) and [2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride solution together with Brggolite FF7 having a temperature of 5 C. was added via line (34). Each initiator was pumped in a loop and dosed via control valves to each dropletizer unit. A second filter unit having a mesh size of 140 m was used after the static mixer (32). For dosing the monomer solution into the top of the spray dryer three dropletizer units were used as shown in FIG. 4.

    [0739] A dropletizer unit consisted of an outer pipe (47) having an opening for the dropletizer cassette (49) as shown in FIG. 7. The dropletizer cassette (49) was connected with an inner pipe (48). The inner pipe (48) having a PTFE block (50) at the end as sealing can be pushed in and out of the outer pipe (47) during operation of the process for maintenance purposes.

    [0740] The temperature of the dropletizer cassette (49) not cooled by water flow channels (55) as shown in FIG. 8. The dropletizer cassette (49) had 256 bores having a diameter of 170 m and a bore spacing of 15 mm. The dropletizer cassette (49) consisted of a flow channel (56) having essential no stagnant volume for homogeneous distribution of the premixed monomer and initiator solutions and one droplet plate (53). The droplet plate (53) had an angled configuration with an angle of 3. The droplet plate (53) was made of stainless steel and had a length of 630 mm, a width of 128 mm and a thickness of 1 mm.

    [0741] The feed to the spray dryer consisted of 9.3% by weight of acrylic acid, 33.4% by weight of sodium acrylate, 0.013% by weight of 3-tuply ethoxylated glycerol triacrylate, 0.054% by weight of [2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 0.0018% by weight of Brggolite FF7, 0.072% by weight of sodiumperoxodisulfate, 0.072% by weight 1-hydroxyethanediphosphonic acid sodium salt and water. The degree of neutralization was 73%. The feed per bore was 1.4 kg/h.

    [0742] The resulting water-absorbent polymer particles were analyzed. The trial conditions and results are summarized in Tab. 1 to 3.

    Examples 3 Basepolymer

    [0743] The example was performed analogous to example 2, except that 0.108% by weight of 1-hydroxyethanediphosphonic acid sodium salt was used instead of 0.072% by weight of 1-hydroxyethanediphosphonic acid sodium salt. The resulting water-absorbent polymer particles were analyzed. The trial conditions and results are summarized in Tab. 1 to 3.

    TABLE-US-00001 TABLE 1 Process conditions of the polymerization for examples 1-3 Steam Steam Content Content T gas T gas T gas T T T CC GD inlet outlet IFB IFB CC GDU Example kg/kg kg/kg C. C. C. C. C. C. 1 0.1100 0.0651 167 122 112 80 54 45 2 0.1100 0.0651 167 112 107 77 54 45 3 0.1100 0.0651 167 112 107 77 54 45 Steam Content CC: steam content of the gas leaving the condenser column (12) Steam Content GD: steam content of the gas prior to the gas distributor (3) T gas inlet: temperature of the gas prior to the gas distributor (3) T gas outlet: temperature of the gas leaving the reaction zone (5) T gas IFB: temperature of the gas entering the internal fluidized bed (27) via line (25) T IFB: temperature of the water-absorbent polymer particles in the fluidized bed (27) T CC: temperature of the gas leaving the condenser column (12) T GDU: temperature of the gas leaving the gas drying unit (37)

    TABLE-US-00002 TABLE 2 Properties of the water-absorbent polymer particles (base polymers) prepared in examples 1-3. Bulk Residual Example Density CRC AUL Monomers Extractables Moisture Unit g/cm.sup.3 g/g g/g Ppm wt. % wt. % 1 62.5 69.8 7.5 6300 11.8 8.2 2 70.0 49.7 9.4 6400 5.6 9.2 3 70.1 49.6 9.3 8100 5.3 9.0

    TABLE-US-00003 TABLE 3 Particles Size Distribution (PSD) of the water-absorbent polymer particles (base polymers) prepared in examples 1-3, measured by sieve fraction analysis 0- 100- 200- 250- 300- 400- 500- 600- 850- >1000 Example 100 m 200 m 250 m 300 m 400 m 500 m 600 m 850 m 1000 m m unit wt % wt % wt % wt % wt % wt % wt % wt % wt % wt % 1 0.0 0.5 3.3 6.7 26.3 31.9 17.1 13.3 0.8 0.1 2 0.0 0.6 3.1 6.1 34.2 38.8 11.6 5.1 0.4 0.1 3 0.1 0.7 2.6 6.0 33.4 37.7 12.5 6.5 0.4 0.1

    Example 4

    [0744] General Description of Surface Crosslinking

    [0745] In a Schugi Flexomix (model Flexomix 160, manufactured by Hosokawa Micron B.V., Doetinchem, the Netherlands) with a speed of 2000 rpm, the water absorbent base polymer was coated with a surface-postcrosslinker solution by using 3 round spray nozzle systems (model Gravity-Fed Spray Set-ups, External Mix Typ SU4, Fluid Cap 60100 and Air Cap SS-120, manufactured by Spraying Systems Co, Wheaton, Ill., USA) and then filled via base polymer feed (70) and dried in a thermal dryer (65) (model NPD 5W-18, manufactured by GMF Gouda, Waddinxveen, the Netherlands) with a speed of the shaft (76) of 6 rpm. The thermal dryer (65) has two paddles with a shaft offset of 90 (80) and a fixed discharge zone (71) with two flexible weir plates (73). Each weir has a weir opening with a minimal weir height at 50% (75) and a maximal weir opening at 100% (74) as shown in FIG. 15.

    [0746] The inclination angle (78) between the floor plate and the thermal dryer was approx. 3. The weir height of the thermal dryer was between 50 to 100%, corresponding to a residence time of approx. 40 to 150 min, by a product density of approx. 700 to 750 kg/m.sup.3. The product temperature in the thermal dryer was in a range of 120 to 165 C. After drying, the surface-postcrosslinked polymer was transported over discharge cone (77) in a cooler (model NPD 5W-18, manufactured by GMF Gouda, Waddinxveen, the Netherlands), to cool down the surface postcrosslinked polymer to approx. 60 C. with a speed of 11 rpm and a weir height of 145 mm.

    [0747] Surface Crosslinking of Base Polymer Prepared in Example 1

    [0748] Ethylene carbonate, water, Span 20 (Croda, Nettetal, Germany)), aqueous aluminum lactate (22% by weight) were premixed and used as surface-postcrosslinker solution as summarized in Tab. 5. As aluminum lactate, Lothragon AI 220 (manufactured by Dr. Paul Lohmann GmbH, Emmerthal, Germany) was used.

    [0749] 4.3 wt % of a 0.05% aqueous solution of Plantacare 818 UP solution (dry, manufactured by BASF SE) and 4.3 wt % of a 0.025% aqueous solution of Plantacare 818 UP were additionally added into the cooler using two nozzles in the first third of the cooler. Both solution having a temperature of approx. 25 C. The nozzles were placed below the product bed.

    [0750] After cooling, the material was sieved with a minimum cut size of 150 m and a maximum cut size of 850 m.

    [0751] The resulting water-absorbent polymer particles were analyzed. The trial conditions and results are summarized in Tab. 4 to 8.

    Example 5 and 6

    [0752] Surface Crosslinking of Base Polymer Prepared in Example 2 and 3

    [0753] Ethylene carbonate, water and an aqueous aluminum sulfate solution (26.8% by weight) were premixed and spray coated as summarized in Tab. 5b. 2.324 wt % of a 0.0538% aqueous solution of Span20 solution and 2.325 wt % of water was additionally added into the cooler using two nozzles in the first third of the cooler. Both solution having a temperature of approx. 25 C. The nozzles were placed below the product bed.

    [0754] The metered amounts and conditions of the coating into the Schugi Flexomix, the conditions, the formulation and values of the drying and cooling step are summarized in Table 4.

    [0755] After cooling, the material was sieved with a minimum cut size of 150 m and a maximum cut size of 710 m.

    [0756] All physical properties of the resulting polymers are summarized in Table 6 to 8:

    TABLE-US-00004 TABLE 4 Process conditions of the thermal dryer for the surface postcrosslinking (SXL) Product Steam Steam Temp. Pressure Pressure Heater Heater Heater Heater Heater Heater Heater Example Set Value Wave Jacket T1 T2 T3 T4 T5 T6 Throughput Weir No. of Pos. of Unit C. Bar Bar C. C. C. C. C. C. kg/h % Nozzles Nozzles 4 140 3.7 3.6 76 104 119 129 130 140 470 80 3 90/180/270 5 170 9.0 9.0 95 100 121 144 160 170 470 80 3 90/180/270 6 158 6.7 6.7 90 94 119 136 149 158 470 80 3 90/180/270

    TABLE-US-00005 TABLE 5 a) Surface-postcrosslinker formulation of the thermal treatment in the heater and remoistening in the cooler Cooler SXL 0.05 wt % 0.025 wt % Al-lactate Plantacare aq. solution of aq. solution of Base EC Water (dry) UP 818 (dry) Plantacare UP 818 (dry) Plantacare UP 818 (dry) Example polymer bop % bop % bop % bop ppm bop % bop % 4 Example 1 2.0 5.0 0.2 25 4.3 4.3 EC: Ethylene carbonate; bop: based on polymer

    TABLE-US-00006 TABLE 5 b) Surface-postcrosslinker formulation of the thermal treatment in the heater aq. Span20 solution EC Water Al-Sulfate (dry) (0.05377% wt %) Water Base (SXL) (SXL) (SXL) (Cooler) (Cooler) Example polymer wt. % bop wt. % bop ppm bop wt. % bop wt. % bop 5 2 2.0 5.0 0.2 2.325 2.325 6 3 2.0 5.0 0.2 2.325 2.325

    TABLE-US-00007 TABLE 6 Physical properties of the polymer particles after surface-postcrosslinking CRC AUL AUHL SFC Residual Monomers Extractables Bulk Density Example g/g g/g g/g 10.sup.7 cm.sup.3 .Math. s/g ppm % g/100 ml 4 54.1 32.7 11.7 0 739 6.5 76 5 32.7 30.6 25.2 32 388 3.1 78.6 6 40.7 33.8 24.5 5 375 2.2 78.1

    TABLE-US-00008 TABLE 7 Particle size distribution of the polymer particles after surface-postcrosslinking - Sieve fractions <150 m >150 m >200 m >250 m >300 m >400 m >500 m >600 m >710 m Example % % % % % % % % % 4 0.1 0.4 2.3 5.9 32.5 35.3 16.9 5.7 0.9 5 0.1 1.0 2.9 7.8 36.7 38.1 10.2 3.0 0.2 6 0.2 1.0 2.7 7.8 36.7 37.5 9.6 3.7 0.9

    TABLE-US-00009 TABLE 8 Color stability of the polymer particles after surface- postcrosslinking (Accelerated Aging Test) 0 d 7 d 14 d 21 d Example L A B L a b L a b L a b 4 94.1 1.7 7.8 86.7 1.3 7.7 85.2 1.3 8.5 83.0 1.2 9.0 5 91.7 0.4 8.9 72.7 4.4 12.6 64.5 6.6 15.0 6 92.3 0.4 8.5 79.9 1.8 11.2 76.5 2.9 12.6

    Example 7

    [0757] Water-absorbent polymer particles that are prepared in accordance to Example 25 of WO 2013/007819 A1.

    TABLE-US-00010 TABLE 9 Physical properties of the polymer particles used for absorbent core preparation. AUNL AUL AUHL FSC CRC 0.0 psi 0.3 psi 0.7 psi SFC SAP (g/g) (g/g) (g/g) (g/g) (g/g) (10.sup.7 cm.sup.3s/g) HySorb 46.3 29.0 42.2 28.9 22.5 26 B7085 HySorb 50.6 30.6 43.4 29.1 22.9 31 B7160S example 4 67.6 54.0 64.6 32.7 11.7 0 example 5 51.1 32.7 48.3 30.6 25.2 32 example 6 62.9 40.7 56.0 33.8 24.5 5 example 7 47.2 26.2 40.4 28.3 24.4 120

    [0758] The fluid-absorbent particles of examples 4, 5, and 6 have a roundness or sphericity of at least 0.8.

    [0759] Preparation of the Fluid-Absorbent Pad

    Example 8 Fluid-Absorbent PadDual Core

    [0760] The fluid-absorbent pad comprises single core system with two SAP layers. The core has a rectangular size of 41 cm10 cm. The fluid-absorbent pad comprises a multi-layered system of spunbond layer coverstock as top sheet (A), layered, high loft acquisition distribution layer (D) and fluid absorbent core (C) made of fluff/SAP mixtures.

    [0761] The fluid absorbent core has layered structure comprising 2 different SAP types uniformly distributed within fluff fibers. Bottom layer of absorbent core holds 6.5 g uniformly distributed fluid-absorbent polymer particles from example 6, whereas top layer holds commercially available Hysorb7085.

    [0762] The total weight of fluff pulp (cellulose fibers) in the core is 7 g. The density of the fluid-absorbent core is in average 0.25-0.30 g/cm.sup.3. The basis weight of the core is 488 g/m.sup.2. The fluid-absorbent core holds 65% by weight fluid-absorbent polymer particles distributed within 2 layers, total quantity of the fluid-absorbent polymer particles within the fluid-absorbent core is 13 g.

    [0763] As an acquisition-distribution layer, Multifunctional Acquitex (Texsus, Italy) having basis weight of 60 g/m.sup.2 was used. The acquisition-distribution layer (D) is rectangular shaped of a size of 16 cm9 cm and placed on the absorbent core that way, that the middle point of the ADL covers the pee point. The pee point is marked 2.5 cm towards the front from the center of the absorbent core.

    Example 9

    [0764] A fluid-absorbent pad of Example 8 was repeated, except that a fluid absorbent polymer particles in the bottom layer of the fluid absorbent core were replaced by the fluid absorbent polymer particles described in example 4.

    Example 10Fluid-Absorbent PadCore with Mixed SAP

    [0765] Prior preparation of the fluid absorbent core, two types of fluid absorbent polymer were mixed in given proportions in Turbula Mixer, type T2F (Willy A. Bachofen AG Maschinenfabrik Switzerland) for 5 min at speed 49 rotations per minute. Physical properties of such prepared fluid absorbent polymer mixtures were measured and are summarized in Table 10. The fluid absorbent polymer mixtures were used directly after mixing for fluid-absorbent pad preparation.

    TABLE-US-00011 TABLE 10 Physical properties of the fluid absorbent polymer mixtures used for absorbent core preparation. AUNL AUL AUHL FSC CRC 0.0 psi 0.3 psi 0.7 psi SFC SAP mixtures ratio (g/g) (g/g) (g/g) (g/g) (g/g) (10.sup.7 cm.sup.3s/g) Hysorb B7085 & 1:1 55.8 35.1 49 31.1 22.2 20 example 6 example 7 & 1:1 55.1 31.7 47.7 30.6 24.7 20 example 6 Hysorb B7160S & 1:2 60.1 36.4 51.2 32.2 22.5 10 example 6 Hysorb B7160S & 1:1 56.1 34.9 49.2 31.2 23.4 12 example 6 Hysorb B7160S & 2:1 54.2 34.1 47.5 30.7 22.8 16 example 6 example 4 & 1:2 56.5 37.9 53.3 32.8 24.1 example 5 example 4 & 1:1 60 40.6 56.4 33.7 23.5 0 example 5 example 4 & 2:1 61.8 45.8 58 34.9 21.9 example 5

    [0766] The fluid-absorbent pad comprises single core system having a rectangular size of 41 cm10 cm. The fluid-absorbent pad comprises a multi-layered system of spunbond layer coverstock as top sheet (A), layered, high loft acquisition distribution layer (D) and fluid absorbent core (C) made of fluff/SAP mixtures.

    [0767] The total weight of fluff pulp (cellulose fibers) is 7 g. The density of the fluid-absorbent core is in average 0.25-0.30 g/cm.sup.3. The basis weight of the core is 488 g/m.sup.2. The fluid-absorbent core holds 65% by weight uniformly distributed fluid-absorbent polymer mixture comprising particles from example 6 and particles of HySorb B7085 (mixed in proportion 1:1). The total quantity of the fluid-absorbent polymer particles within the fluid-absorbent core is 13 g.

    [0768] As an acquisition-distribution layer, Multifunctional Acquitex (Texsus, Italy) having basis weight of 60 g/m.sup.2 was used. The acquisition-distribution layer is rectangular shaped of a size of 16 cm9 cm and placed on the absorbent core that way, that the middle point of the ADL covers the pee point. The pee point is marked 2.5 cm towards the front from the center of the absorbent core.

    Example 11

    [0769] A fluid-absorbent pad of Example 10 was repeated, except that a fluid absorbent polymer mixture used for fluid-absorbent core preparation, contains particles prepared as described in example 7 and in example 6 (mixed in proportion 1:1).

    Example 12

    [0770] A fluid-absorbent pad of Example 10 was repeated, except that a fluid absorbent polymer mixture used for fluid-absorbent core preparation, contains particles prepared as described in example 6 and particles of Hysorb B7160S.

    [0771] The fluid absorbent polymers from example 6 and Hysorb B7160S were mixed in following proportions: [0772] Example 12 a) Hysorb B7160S: example 6, mixed 1:2 [0773] Example 12 b) Hysorb B7160S: example 6, mixed 1:1 [0774] Example 12 c) Hysorb B7160S: example 6, mixed 2:1

    Example 13

    [0775] A fluid-absorbent pad of Example 10 was repeated, except that a fluid absorbent polymer mixture used for fluid-absorbent core preparation, contains particles prepared as described in example 4 and in example 5

    [0776] The fluid absorbent polymers from example 4 and example 5 were mixed in following proportions: [0777] Example 13 a) example 4: example 5, mixed 1:2 [0778] Example 13 b) example 4: example 5, mixed 1:1 [0779] Example 13 c) example 4: example 5, mixed 2:1

    Example 14

    [0780] A fluid-absorbent pad of Example 10 was repeated, except that a fluid absorbent polymer mixture used for fluid-absorbent core preparation, contains particles of HySorb B7085 and particles prepared as described in example 4 (mixed in proportion 1:1).

    Example 15ComparativeFluid-Absorbent PadCore with Single SAP

    [0781] The fluid-absorbent pad comprises single core system having a rectangular size of 41 cm10 cm. The fluid-absorbent pad comprises a multi-layered system of spunbond layer coverstock as top sheet (A), layered, high loft acquisition distribution layer (D) and fluid absorbent core (C) made of fluff/SAP mixtures.

    [0782] The total weight of fluff pulp (cellulose fibers) is 7 g. The density of the fluid-absorbent core is in average 0.25-0.30 g/cm.sup.3. The basis weight of the core is 488 g/m.sup.2. The fluid-absorbent core holds 65% by weight uniformly distributed fluid-absorbent polymer particles of HySorb B7085; the quantity of the fluid-absorbent polymer particles within the fluid-absorbent core is 13 g.

    [0783] As an acquisition-distribution layer, Multifunctional Acquitex (Texsus, Italy) having basis weight of 60 g/m.sup.2 was used. The acquisition-distribution layer is rectangular shaped of a size of 16 cm9 cm and placed on the absorbent core that way, that the middle point of the ADL covers the pee point. The pee point is marked 2.5 cm towards the front from the center of the absorbent core.

    Example 16Comparative, Core with Single SAP

    [0784] A fluid-absorbent pad of Example 15 was repeated, except that a fluid absorbent polymer particles of HySorb B7085 were replaced by the fluid absorbent polymer particles described in example 6.

    Example 17Comparative, Core with Single SAP

    [0785] A fluid-absorbent pad of Example 15 was repeated, except that a fluid absorbent polymer particles of HySorb B7085 were replaced by the fluid absorbent polymer particles described in example 4.

    Example 18Comparative, Core with Single SAP

    [0786] A fluid-absorbent pad of Example 15 was repeated, except that a fluid absorbent polymer particles of HySorb B7085 were replaced by the fluid absorbent polymer particles described in example 7.

    Example 19Comparative, Core with Single SAP

    [0787] A fluid-absorbent pad of Example 15 was repeated, except that a fluid absorbent polymer particles of HySorb B7085 were replaced by the fluid absorbent polymer particles of HySorb B7160S.

    Example 20Comparative, Core with Single SAP

    [0788] A fluid-absorbent pad of Example 15 was repeated, except that a fluid absorbent polymer particles of HySorb B7085 were replaced by the fluid absorbent polymer particles of example 5.

    [0789] Acquisition time under load and rewet value of the fluid absorbent pads from examples 8-20 were determined and results are summarized in Table 11, 12 and 13.

    TABLE-US-00012 TABLE 11 Rewet under load, acquisition times for each liquid insult into the pads with dual core REWET UNDER LOAD [g] Liquid Acquisition Time RUL RUL RUL RUL RUL 1-4 [s] A1-A4 Example SAP type 1 2 3 4 [g] A1 A2 A3 A4 [s] ex. 8 Hysorb7085/ 0.06 0.10 0.58 6.77 7.51 62 92 105 110 369 example 6 ex. 9 Hysorb7085/ 0.05 0.08 0.42 5.07 5.62 68 103 115 124 410 example 4

    TABLE-US-00013 TABLE 12 Rewet under load, acquisition times for each liquid insult into the pads with core consisting mix SAPs REWET UNDER LOAD [g] Liquid Acquisition Time RUL RUL RUL RUL RUL 1-4 [s] Example SAP mix ratio 1 2 3 4 [g] A1 A2 A3 A4 A1-A4 [s] ex. 10 Hysorb7085/ 1:1 0.05 0.19 1.85 8.77 10.86 62 90 102 107 361 example 6 ex. 11 example 6/ 1:1 0.1 0.7 5.1 19.1 25 57 86 100 105 348 example 7 ex. 12a Hysorb 1:2 0.06 2.02 6.61 14.98 23.67 63 98 112 112 385 B7160S/ example 6 ex. 12b Hysorb 1:1 0.07 1.38 7.10 14.33 22.88 63 94 104 109 370 B7160S/ example 6 ex. 12c Hysorb 2:1 0.05 2.19 7.38 19.28 28.9 64 99 108 114 385 B7160S/ example 6 ex. 13a example 4/ 1:2 0.06 0.18 0.55 9.20 9.99 63 101 108 118 390 example 5 ex. 13b example 4/ 1:1 0.07 0.22 0.47 5.85 6.61 64 111 118 128 421 example 5 ex. 13c example 4/ 2:1 0.12 0.12 0.39 3.38 4.01 68 112 123 133 436 example 5 ex. 14 Hysorb7085/ 1:1 0.22 2.02 6.14 13.98 22.36 66 103 113 121 403 example 4

    TABLE-US-00014 TABLE 13 Rewet under load, acquisition times for each liquid insult into the pads with cores consisting single SAP type REWET UNDER LOAD [g] Liquid Acquisition Time RUL RUL RUL RUL RUL1-4 [s] A1-A4 Example SAP type 1 2 3 4 [g] A1 A2 A3 A4 [s] ex. 15 HySorb 0.08 1.56 9.7 23.7 34.04 63 89 104 110 366 B7085 ex. 16 example 6 0.07 0.32 5.6 15.3 21.29 66 102 111 113 392 ex. 17 example 4 0.07 0.14 0.5 3.5 4.21 80 138 138 154 510 ex. 18 example 7 0.05 2.02 9.2 23.9 35.17 63 106 119 129 417 ex. 19 HySorb 0.07 5.41 13.1 19.1 37.68 66 97 114 118 395 B7160S ex. 20 example 5 0.05 0.33 3.7 17.2 21.28 67 117 117 123 424

    [0790] The above examples clearly show that dual cores with permeable fluid-absorbent particles on top layer and high capacity SAP in bottom layer, as well as cores with mixed fluid-absorbent polymer particles exhibit positive synergies in pads' performance and so in performance of the fluid-absorbent article. They show a fast acquisition time under load and better dryness comparing to the single SAP loaded pads with corresponding fluid-absorbent polymer particles. In addition, the examples show that despite the choice of the SAP their mixing ratio contributes to better performance of the pads comparing to the single SAP loaded pads with corresponding fluid-absorbent polymer particles.