Fibrous sheet that disintegrates in water, process for manufacturing said fibrous sheet, core consisting of strips of said fibrous sheet

Abstract

A fibrous sheet having a basis weight of between 20 and 1000 g/m.sup.2 that disintegrates in water, has 10% to 70% starch on the basis of the total weight of the dry fibrous sheet. The disintegration time in water, measured in accordance with standard NF Q34-020 applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds. A loss of strength of the sheet measured in accordance with a defined table test corresponds to a loss of strength of a specimen of said sheet forming an angle of at least 85 after having being wetted with water for a duration of 6 seconds, and/or a residual wet strength of the sheet relative to its dry strength, as measured according to a defined ring crush test, is less than 1%. The fibrous sheet may be used for the manufacture of a water disintegrable core in a roll of tissue paper.

Claims

1. A fibrous sheet having a basis weight of between 100 to 600 g/m.sup.2 that disintegrates in water, comprising: (1) at least 30% of paper making fibres and (2) 15 to 40% starch on a basis of the total weight of the fibrous sheet when dry; wherein the disintegration time in water, measured in accordance with standard NF Q34-020 applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds; wherein a loss of strength measured in accordance with a defined table test corresponds to a loss of strength of a specimen of said sheet forming an angle of at least 85, after having been wetted with water for a duration of 6 seconds; wherein the fibrous sheet is being manufactured according to a wet papermaking process; wherein said starch is substantially uniformly distributed through the thickness of the fibrous sheet; and wherein the paper making fibres are coated with said starch by: (a) incorporating starch in a pulp at a temperature at which starch is not soluble in water, or (b) applying starch in a dry state on a wet web and subsequently drying the web, during the wet papermaking process.

2. A fibrous sheet having a basis weight of between 100 to 600 g/m.sup.2 that disintegrates in water, comprising: (1) at least 30% of paper making fibres and (2) 15 to 40% starch on a basis of the total weight of the fibrous sheet when dry; wherein the disintegration time in water, measured in accordance with standard NF Q34-020 applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds; wherein a residual wet strength of the sheet relative to its dry strength, as measured according to a defined ring crush test, is less than 1%; wherein the fibrous sheet is being manufactured according to a wet papermaking process; wherein said starch is substantially uniformly distributed through the thickness of the fibrous sheet; and wherein the paper making fibres are coated with said starch by: (a) incorporating starch in a pulp at a temperature at which starch is not soluble in water, or (b) applying starch in a dry state on a wet web and subsequently drying the web, during the wet papermaking process.

3. A fibrous sheet having a basis weight of between 100 to 600 g/m.sup.2 that disintegrates in water in less than 120 seconds, comprising: (1) at least 30% of paper making fibres and (2) 15 to 40% starch on a basis of the total weight of the fibrous sheet when dry; wherein a loss of strength measured according to a defined table test corresponds to a loss of strength of a specimen of said sheet forming an angle of at least 85, after having been wetted with water for a duration of 6 seconds; wherein a residual wet strength of the sheet relative to its dry strength, as measured according to a defined ring crush test, is less than 1%; wherein the fibrous sheet is being manufactured according to a wet papermaking process; wherein said starch is substantially uniformly distributed through the thickness of the fibrous sheet; and wherein the paper making fibres are coated with said starch by: (a) incorporating starch in a pulp at a temperature at which starch is not soluble in water, or (b) applying starch in a dry state on a wet web and subsequently drying the web, during the wet papermaking process.

4. A fibrous sheet having a basis weight of between 100 to 600 g/m.sup.2 that disintegrates in water, comprising: (1) at least 30% of paper making fibres and (2) 15 to 40% starch on a basis of the total weight of the fibrous sheet when dry; wherein the disintegration time in water, measured in accordance with the standard NF Q34-020 applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds; wherein a loss of strength measured according to a defined table test corresponds to a loss of strength of a specimen of said sheet forming an angle of at least 85 after having being been wetted with water for a duration of 6 seconds; wherein a residual wet strength of the sheet relative to its dry strength, as measured according to a defined ring crush test is less than 1%; wherein the fibrous sheet is being manufactured according to a wet papermaking process; wherein said starch is substantially uniformly distributed through the thickness of the fibrous sheet; and wherein the paper making fibres are coated with said starch by: (a) incorporating starch in a pulp at a temperature at which starch is not soluble in water, or (b) applying starch in a dry state on a wet web and subsequently drying the web, during the wet papermaking process.

5. A core comprising a helical winding of one or more strips comprising a fibrous sheet according to claim 1.

6. A toilet paper roll comprising a core according to claim 5.

7. A tampon applicator comprising a fibrous sheet according to claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Non-limiting exemplary embodiments of the invention will now be described in greater detail with reference to the appended drawings in which:

(2) FIG. 1 shows a diagram of a paper machine seen in a side view used for the manufacture of a sheet of heavy paper according to process I suitable for the production of a core according to the invention.

(3) FIG. 2 shows a diagram of a paper machine seen in a side view used for the manufacture of a sheet of heavy paper according to process II.

Manufacture According to Process I

(4) Process I is implemented on a paper machine 1, which is itself conventional, as presented in FIG. 1. It is shown from the upstream end to the downstream end in the direction of manufacture. The pulp is contained in the chest 2 in which the fibres are kept in suspension and the additives are incorporated; the paper pulp is pumped into the head box 3, which in particular comprises a pulp distributor in the form of a blade, designated jet extending over the entire width of the machine. The pulp is deposited on the endless wire 4 of the forming table 5. This wire 4 forms a loop and runs endlessly around the parallel rollers of the table supporting it. It is jerked laterally so as to undergo a reciprocating motion that promotes uniform formation of the paper sheet and dewatering thereof. The fibres are aligned along the run direction of the wire. The paper sheet contains 75 to 85% water on leaving the table. The sheet is introduced into the press section 6 where the water content is reduced to 60 or 70%. The presses comprise several pairs of rubber-coated cylinders. This operation also increases the density of the sheet and improves its surface finish by mechanical action.

(5) The paper sheet then enters the dry end, designated the drying section, of the paper machine, which comprises a plurality of dryers 7. The dryers 7 are cast iron drums heated internally with steam at a temperature high enough for the water contained in the sheet to be progressively evaporated until at least 90% dryness is achieved. Conventionally, the surface temperature of the drums is around 95 C. The sheet is held against the dryers by a heavy cotton felt or a drying fabric composed of cotton and artificial fibres.

(6) The conventional machines for manufacturing printing or writing paper also include size presses, for surface treatment and for deposition of an appropriate composition, and optionally a breaker stack or calendering station before the paper is wound up into a reel. This reel is then used as master reel in the subsequent conversion steps.

(7) In the present invention, the paper is essentially dried in the drying section before being reeled up.

(8) To manufacture the sheet C of the invention, starch is added in the wet end of the paper machine before the press. Preferably, the starch is incorporated in the form of a suspension in water.

(9) The starch may be deposited on the sheet by spraying, while said sheet is resting on the wire 4 as it travels along the forming table 5.

(10) The starch may be introduced further upstream, prior to sheet formation. An advantageous zone for introducing it is located at the inlet of the transfer pump between the chest and the head box. Thus, the starch remains in suspension in the manufacturing composition introduced into the head box.

(11) According to an important feature of process I of the invention, the starch introduced at this stage is not soluble in water, i.e. it is water-insoluble. It becomes soluble as the sheet passes through the drying section. The temperature of the successive dryers is advantageously regulated in such a way that the temperature of the sheet is gradually raised until reaching the gelatinization temperature of the starch that it contains. The temperature of the successive drums may be controlled between 60 C. and 100 C. The purpose is to maintain a sufficient amount of water in the sheet for gelatinization to effectively take place and to allow the starch to become soluble. If the amount of water were to be insufficient, some of the starch would not be gelatinized. Once the starch in the sheet has gelatinized and become soluble, said sheet can continue to be dried to the desired dryness.

(12) The pressing, drying and reeling are adapted so as to obtain the desired final moisture content of the product.

(13) The sheet thus continuously produced is reeled up for subsequent use.

(14) The manufacturing parameters of the sheet C are determined so as to obtain a core having the desired properties.

(15) The fibres used are long, short or recycled papermaking fibres and also mixtures thereof.

(16) The water-insoluble starch is preferably chosen so that the size of the insoluble particles is large enough not to easily filter through the wet sheet.

(17) It is also possible to incorporate other additives providing an additional function, such as disinfectants, cleaning agents or perfumes.

(18) Retention agents may also be added so as to improve the retention of starch in the sheet, in particular for sheets of low weight.

(19) Preferably, the starch is coloured so as to check that the binder is correctly distributed through the thickness. In addition, it represents an improvement in aesthetic terms.

(20) Experimental Manufacturing Trial According to Process I on a Pilot Fourdrinier Paper Machine.

(21) The machine comprised three dryer units each composed of two cylinders.

(22) A 270 g/m.sup.2 paper sheet containing about 33% starch was manufactured.

(23) A pulp having a 2.5% concentration was prepared in a 10 m.sup.3 chest.

(24) The pulp, having a mass of 250 kg, was made up of: 35% starch, i.e. 97.2 kg of starch; and 162.5 kg of fibres, one quarter being long fibres and three quarters being short fibres.

(25) After mixing, the content of the mixing chest was transferred to the chest of the machine.

(26) 480 m of paper were manufactured.

(27) The dryness was: On leaving the Fourdrinier, between 16 and 17%; On leaving the presses, 57%; and At reel-up, 91%,
for a dry weight of 243 g/m.sup.2.

(28) The temperatures of the six drying cylinders were controlled so as to have a progressive rise in temperature.

(29) The starch content, which was measured in the sheet, was on average 33% relative to the total weight of the sheet.

A Manufacturing Example According to Process II is Now Described

(30) According to the manufacturing example illustrated in FIG. 2, the paper machine 100 comprises a first unit 102 for forming a ply of papermaking fibres by wet processing on a Fourdrinier table, shown here, or else on a cylinder mould. The ply C1 is formed by depositing, via the head box 121, a pulp formed from papermaking fibres suspended in water on the permeable moving wire 122 of the first forming table 120. The wire forms a loop and runs endlessly around the parallel rollers supporting it. The ply C1 undergoes a first dewatering step as it travels along with the wire 122.

(31) The first fibrous ply C1 is taken up by a pick-up felt 130 which moves translationally in a loop around parallel support rollers, one 131 of which presses on the first ply C1, which is partly dewatered, at the end of travel on the flat portion of the forming table 120 around the roller 123. The first ply C1 is transported by the felt to a second Fourdrinier table 140 of the second unit 104 for forming a second ply C2 of papermaking fibres. This ply C2 is formed here, like the first, by depositing, via a head box 141, a pulp with a fibrous suspension on the moving wire 142 of the table 140. The fibrous ply C2 thus formed is dewatered like the first one through the permeable wire. The pick-up felt presses via a roller 132 on the second fibrous ply C2 so as to take off the second ply at the cylinder 143 at the end of the table 140. The two fibrous plies are joined together as a single sheet C which is directed towards the gap left between two rollers of a press 105 for extracting a further portion of the water from the two plies while pressing the sheet. The sheet is then guided towards the drying unit (not shown), which may be conventional. In such an installation for manufacturing multiply sheets, the number of plies is not limited to two.

(32) To manufacture the sheet C of the invention, a system 106 for depositing starch L, in powder form, is placed upstream of the two cylinders 132 and 143. The system used enables the powder to be distributed uniformly in the desired amount over the width of the second fibrous ply C2 and in a regular fashion in the run direction of the machine. Equipment comprising a product storage hopper, a product metering device and an oscillating brush is used to fulfil all these conditions. In industrial manufacture, the ply of papermaking fibres, here C2, which is formed by wet processing and on which the starch is deposited, has a dryness ranging from about 10% to about 15%.

(33) A powdered water-soluble starch is deposited on the second ply of papermaking fibres C2before the two plies are placed against each other and pressed togetherwhen the ply is sufficiently dewatered and has a dryness sufficient to retain the product in the structure of the ply and to limit the removal of some of the starch with the dewatering water.

(34) The deposited starch is sandwiched between the two plies thus formed, still in the wet state, and reacts with the residual water of each ply.

(35) The fibre ply/starch/fibre ply complex is transported by the felt 130 to the pressing zone 105, the operating conditions of which are adapted, and then into the zone of the machine for drying the sheet.

(36) It is possible to have other means for forming additional plies, whether or not associated with powder deposition means, so as to form a sheet that may comprise, for example, up to ten plies.

(37) The sheet thus continuously produced is reeled up for subsequent use.

(38) The manufacturing parameters of the sheet C are determined so as to obtain a core having the desired properties.

(39) The fibres used are long, short or recycled papermaking fibres and also mixtures thereof.

(40) It is possible to incorporate other additives providing an additional function, such as disinfectants, cleaning agents or perfumes.

(41) Preferably, the starch is coloured so as to check that the starch is correctly distributed on both sides. In addition, it represents an improvement in aesthetic terms.

(42) The amount deposited is between 35 and 150 g/m.sup.2.

(43) The amount of starch in the sheet is therefore between about 10% and about 70% of the total mass of the sheet after drying.

(44) The pressed fibrous sheet has a density between 450 kg/m.sup.3 and 650 kg/m.sup.3.

(45) When dry water-soluble starch is incorporated, it has the advantage of using the water in the two plies to activate the starch. The pressing also ensures that the starch is correctly distributed through the mass of fibres.

(46) Manufacture of the Core

(47) The paper sheet was cut into narrow strips or strands that were then wound in a helix around a cylindrical former. An adhesive was applied to the overlapping parts of the turns so as to bond them together and form a rigid tube. Generally for the core of a roll of toilet paper, one or two strands are wound.

(48) The technique for manufacturing the cores is known per se. It is adapted according to the nature of the binder in so far as it is necessary to take into account the rapid disintegrability of the strips by the adhesive used to join the strands together.

(49) Tests

(50) Core Compression, Disintegration and Down-Toilet Discharge Tests Carried Out with a Sheet Obtained According to Process I

(51) The characteristics of a single-strand core A manufactured according to manufacturing process I were the following: weight of the sheet: 270 g/m.sup.2; quality of the fibres: long fibre/short fibre mixture in the virgin pulp; starch reference: PERFECTACOTE A35 (modified water-insoluble starch) sold by the company Avebe; amount of starch retained by the finished sheet: 90 g/m.sup.2, i.e. 33% of starch on the basis of the dry fibrous sheet; number of wall thicknesses of the cylinder: 1; weight of the wall of the cylinder: 270 g/m.sup.2; and diameter and length of the cylinder forming the core: 40 mm and 97 mm respectively.
Core Compression Test:

(52) The lateral compressive strength of the core was measured using the following method.

(53) The core to be tested was firstly cut into a cylindrical portion bounded by two opposed faces, perpendicular to the axis of the cylinder, said portion having a length of 50 mm in a direction parallel to the axis.

(54) This cylindrical portion was then positioned between the two metal plates of a testing machine, said plates being mutually parallel and initially separated by a distance slightly greater than the length of the cylindrical portion.

(55) The cylindrical portion was placed so as to orient the axis of the cylinder along a direction perpendicular to the plane formed by one or other of the plates.

(56) Said cylindrical portion was then compressed between the two plates, with measurements for a compression distance of 15 mm, at which the force in Newton was recorded.

(57) Concomitantly, the resistance presented by the core was measured up to its maximum, i.e. Just before the core was irreversibly destroyed.

(58) Five measurements were taken each time and the average of the measurements was calculated.

(59) The results are given in the table below together with those of a control core made of a one-strand cardboard also with a wall weight of 280 g/m.sup.2.

(60) TABLE-US-00001 Lateral compressive Weight Mass strength Cardboard 280 g/m.sup.2 3.9 g 272.8 9.6 N control core Tested core A 270 g/m.sup.2 3.6 g 294 12.5 N

(61) This therefore shows that a core according to the invention containing 33% starch has a lateral strength at least equal to that of a conventional cardboard core.

(62) Given that the principal stresses undergone by the core during its production/roll delivery cycle are essentially exerted on the edge, it may be considered that the core according to the invention completely meets the requirements therefore.

(63) Core Disintegration Test:

(64) The disintegration of the core A as manufactured above was measured in accordance with the NF 034-020 standard.

(65) The principle consisted in subjecting a specimen of the product to stirring in a certain volume of water. The time required for the specimen to disintegrate was measured.

(66) This test was applied with the specimen of toilet-paper replaced with a specimen of the sheet according to the invention and a specimen of the cylinder forming the core according to the invention. More precisely, the specimen of the sheet was a specimen measuring 9 centimetres by 8 centimetres, i.e. an area of 72 cm.sup.2, and the specimen of the core was a cylindrical specimen 5 centimetres in length.

(67) The material, equipment and operating method are described in detail in the standard. It should be noted that complete disintegration corresponds to the moment when the pieces of the specimen move from the bottom of the beaker to the top of the stirrer, in other words when there are no longer large pieces beneath the impeller and when the dispersion of the pieces is uniform. At this time T, it is no longer possible to observe an appreciable change in state of the paper between the time T and the time T+5 seconds. The water used for this test was mains water.

(68) It was observed that the specimen of the sheet according to the invention disintegrated very easily. Less than 15 seconds were required for the structure of the sheet to disintegrate and a fibrous suspension was obtained in less than 60 seconds.

(69) The specimen of the cardboard control sheet having a weight of 280 g/m.sup.2 only started to fall apart after 30 seconds, and the sheet was converted into pieces after 3 minutes. Pieces with a size greater than 1 cm.sup.2 still remained after 10 minutes.

(70) It was also observed that the specimen of the core according to the invention formed from a single strip of 270 g/m.sup.2 weight started to disintegrate in water more rapidly than a similar cardboard core obtained by winding a single cardboard strip having a weight of 280 g/m.sup.2.

(71) The term similar core should be understood to mean a core having approximately the same diameter and the same length as the core of the invention.

(72) The specimen of the core according to the invention therefore disintegrated more rapidly than a similar cardboard core. This is because the specimen of the core according to the invention disintegrated in 10 to 15 seconds and a fibrous suspension was obtained in a time of less than 60 seconds.

(73) The turns of the control core specimen opened up after about 60 seconds and the control specimen was in the state of large pieces after 7 minutes. After 10 minutes, pieces greater in size than 1 cm.sup.2 still remained.

(74) Moreover, again for comparison, it was observed in the Afnor NF Q34-020 test that the turns of a 400 g/m.sup.2 two-strand cardboard core came unstuck after 60 seconds, the core only starting to disintegrate after 3 minutes. It disintegrated completely after 10 minutes, but cardboard pieces remained.

(75) Core Discharge Test:

(76) The discharge of the core in a domestic sanitary facility was checked based on the test method described in the guide published by EDANA (European Disposables & Nonwovens Association) for discharging wipes down toilets (FG 510.1 TIER 1 Toilet bowl & drainline clearance test).

(77) The characteristics of the equipment, the test conditions and the test protocol are defined in this test method.

(78) More precisely, two steps were studied in the application of this test to the cores: 1) discharge of the core down the toilet bowl: the core must disappear from the bowl after the flush has be actuated; and 2) elimination of the core from the drain line.

(79) The equipment used for this test was a conventional toilet comprising a floor-standing bowl, a flushing mechanism, a water flush tank and a drain line. The drain line was a transparent plastic tube enabling the change in the products discharged down the bowl to be displayed. This line had a diameter of 100 millimetres and a length of 20 meters, and was installed with a slope of 2%.

(80) The method consisted in introducing a series of ten cores into the bowl using the following procedure: a core was thrown into the bowl and then the flush actuated. The volume of this water flush was 5.5 litres. It was then checked whether the core had been discharged from the bowl and its position in the line was recorded. The operation was repeated with the ten cores, each time recording the position of the cores that were still in the line. Finally, complete removal of the core on leaving the line was noted.

(81) The core according to the invention, namely a single-strand 270 g/m.sup.2 core, was tested and passed the down-bowl discharge test and the removal-from-the-line test.

(82) The similar 280 g/m.sup.2 cardboard single-strand core did not even pass the down-bowl discharge test.

(83) Compression and Disintegration Tests on the Core Made of a Sheet Obtained by Process II

(84) Cores were produced using process II.

(85) The characteristics of the core manufactured were the following: weight of each fibrous ply: 45 g/m2; quality of the fibres: long-fibre/short-fibre mixture in the virgin pulp; starch reference: AVEDEX from AVEBE; amount of starch retained by the finished sheet: 90 g/m.sup.2; 50% starch; number of fibrous plies: 2; weight of the sheet: 180 g/m.sup.2; number of thicknesses of the wall of the cylinder: 2; and weight of the wall of the cylinder: 360 g/m.sup.2.

(86) A water-soluble starch was chosen so that it dissolved rapidly at high concentration.

(87) Manufacture in the laboratory was carried out as follows:

(88) Formation of a fibrous ply of 10% dryness, deposition of the ply on a wire, deposition of powdered starch, joining to another fibrous ply of 10% dryness, pressing by a roller for dewatering purposes and joining of the plies, take-off of the sheet thus formed and drying between two metal wires at 110 C.

(89) A cylindrical core was then manufactured from two sheets formed as above.

(90) The diameter and length of the cylinder forming the core were 40 mm and 97 mm.

(91) Core Compression Test:

(92) The compressive strength of the core in flat compression and in lateral compression was measured.

(93) Five measurements were taken each time, and the average of the measurements was calculated.

(94) The results are given in the table below, together with those of a control core made of a one-strand cardboard with a wall weight of 365 g/m.sup.2.

(95) TABLE-US-00002 Data expressed in N 15 mm flat Lateral compression compression Cardboard control 5.64 0.50 272.8 9.6 core Core D with 30% 6.15 0.92 118 25 starch Core E with 50% 12.11 1.55 265 41 starch

(96) This table therefore shows that a core according to the invention containing 50% starch has a lateral strength similar to that of a cardboard core and that, in this case, the flat compressive strength is greater than that of a similar core made of cardboard. Above 65% starch, the sheet starts to become brittle and may no longer be suitable for manufacturing a core.

(97) Given that the principal stresses undergone by the core during its production/roll delivery cycle are essentially exerted flat, it may be considered that the core according to the invention completely meets the requirements therefore.

(98) Core Disintegration Test:

(99) The disintegratability of the core as manufactured above was measured in accordance with the NF Q34-020 standard.

(100) It was found that the core breaks up very easily, in less than 10 s. to destroy the structure, and that a fibrous suspension is obtained after about 30 s.

(101) It was also observed that the core according to the invention starts to disintegrate in water more rapidly than a similar cardboard core obtained by winding a single strip of cardboard having a weight of 280 g/m.sup.2.

(102) The core according to the invention therefore disintegrates more rapidly than a similar cardboard core, formed from a single strip with a weight of 280 g/m.sup.2, whether or not there is any stirring.

(103) It can be observed that the papermaking fibres are coated with starch. The starch forms a network throughout the sheet that connects the fibres together in substitution for a part of hydrogen bonds. When the sheet is placed in contact with water, starch absorbs it and dissolves rapidly since the fibres are not bound by the starch they dissociate themselves very quickly. This would explain the rapidity with which the sheet loses its cohesion and disintegrate.

(104) Comparative Tests Carried Out on Fibrous Sheets According to the Invention and Cardboard Sheets of the Same Weight.

(105) Three tests were carried out: disintegration test; table test and ring crush test.

(106) Disintegration Test

(107) The disintegration test was made as described above. Compared with the NF Q34-020 standard, the test is carried out on a fibrous sheet or cardboard specimen measuring 89 cm.sup.2, while applying a stirring speed of 400 revolutions per minute. The temperature of water is 20 C.

(108) Table Test

(109) This involves an internal test method for determining the loss of stiffness when the specimen is wetted.

(110) A rectangular specimen measuring 2.54 cm in width by 13 cm in length is cut in the machine direction.

(111) A table with a horizontal plane surface, a vertical plane and a straight edge at the intersection between the horizontal plane surface and the vertical plane is used. The specimen is laid flat on the table perpendicular to the edge. A portion of the specimen (10 cm) extends beyond the edge.

(112) In the dry state, the specimen makes an angle of 0 with the plane.

(113) The specimen is wetted using a motorized burette, the end-piece of which is placed 1 cm above the test piece: 3 ml of water supplied in 6 s. The water is deposited at the centre of the test piece above the edge, at the point where the specimen is going to make an angle with the horizontal plane.

(114) On being wetted, the specimen is folded around the edge: the bend angle relative to the horizontal plane is recorded 6 seconds after the water has been delivered.

(115) Ring Crush Test

(116) The loss of wet strength of a specimen is determined by establishing the ratio of the lateral compressive strength in the wet state to that in the dry state.

(117) A specimen measuring 15 mm in width by 152.4 mm in length is cut in the machine direction.

(118) The specimen is fixed to a ring-shaped support (as described in the standard ISO 12192:2002), placed between two plates, and then subjected to a compressive force at a rate of 10 mm/min. The maximum resistance force is recorded.

(119) For the measurement in the wet state, the specimen fixed in the support is dipped in water during a time less than 2 seconds. The measurement is carried out immediately after the dipping.

(120) Specimens (E2 to E6) of sheets produced according to processes I and II were tested, as were also cardboard control specimens (E7 and E8) of substantially the same weight. The fibres used were virgin fibres.

(121) The type and amount of starch in the specimens can be seen from the following table, where LF stands for long fibres and SF stands for short fibres:

(122) TABLE-US-00003 Disintegration NE Q34-020 Table test specimen of (8 ml Ring crush Starch/ Basis 8 9 cm.sup.2 in 6 s) test (N/15 mm) Reference Process Product Fibres content % Weight Time(s) Angle () Dry Wet w/d (%) Invention II Lab E2 75% LF/ Avedex 50% 280 10 90 >525 0.4 <1 25% SF I Lab E3 75% LF/ Perfect 50% 285 10 90 400 37 1.3 0.2 <1 25% SF I E4 75% LF/ Perfect 32% 280 <10 90 419 40 0.9 0.4 <1 25% SF I Lab E5 100% SF Perfect 28% 290 12-15 90 480 to >525 0.8 0.1 <1 I Pilot E6 100% SF Stackote 14% 288 <10-15 90 448 63 1.4 0.3 <1 Standard E7 Recycle 280 >120 15 304 29 21 3 7 board fibres E8 Rec. fibres 280 >120 15 273 32 34 3 12

(123) With the processes described above, the following products can be obtained: a fibrous sheet having a basis weight of between 20 and 1000 g/m.sup.2 that disintegrates in water, comprising 10% to 70% starch on the basis of the total weight of the dry fibrous sheet, a. the disintegration time in water, measured in accordance with the NF Q34-020 standard applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds, preferably less than 35 seconds, and more particularly less than 15 seconds, b. of which the loss of strength measured in accordance with the table test as reported in the specification corresponds to the loss of strength of a specimen of said sheet forming an angle of at least 85, preferably between 88 and 90, after having being wetted with water for a duration of 6 seconds. a fibrous sheet having a basis weight of between 20 and 1000 g/m2 that disintegrates in water, comprising 10% to 70% starch on the basis of the total weight of the dry fibrous sheet, a. the disintegration time in water, measured in accordance with the NF Q34-020 standard applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds, preferably less than 35 seconds and more particularly less than 15 seconds, b. the residual wet strength of which relative to its dry strength, as measured according to the ring crush test described in the specification, is less than 1%. a fibrous sheet having a basis weight of between 20 and 1000 g/m.sup.2 that disintegrates in water, comprising 10% to 70% starch on the basis of the total weight of the dry fibrous sheet, a. the disintegration time in water, measured in accordance with the NF Q34-020 standard applied to a specimen of the sheet of 98 cm.sub.2, is less than 50 seconds, preferably less than 35 seconds and more particularly less than 15 seconds, b. the residual wet strength of which relative to its dry strength, as measured according to the ring crush test described in the specification, is less than 1%. a fibrous sheet having a basis weight of between 20 and 1000 g/m.sup.2 that disintegrates in water in less than 120 seconds comprising 10% to 70% starch on the basis of the total weight of the dry fibrous sheet, a. of which the loss of strength measured according to the table test as reported in the specification corresponds to the loss of strength of a specimen of said sheet forming an angle of at least 85, preferably between 88 and 90, after having being wetted with water for a duration of 6 seconds, b. the residual wet strength of which relative to its dry strength, as measured according to the ring crush test described in the specification, is less than 1%. a fibrous sheet having a basis weight of between 20 and 1000 g/m.sup.2 that disintegrates in water comprising, 10% to 70% starch on the basis of the total weight of the dry fibrous sheet, a. the disintegration time in water, measured in accordance with the NF Q34-020 standard applied to a specimen of the sheet of 98 cm.sup.2, is less than 50 seconds, preferably less than 35 seconds and more particularly less than 15 seconds, b. of which the loss of strength measured according to the table test as reported in the specification corresponds to the loss of strength of a specimen of said sheet forming an angle of at least 85, preferably between 88 and 90, after having being wetted with water for a duration of 6 seconds, c. the residual wet strength of which relative to its dry strength, as measured according to the ring crush test described in the specification, is less than 1%.

(124) According to the invention, the following products can be made out of any of the above mentioned sheets: A core, consisting of a helical winding of one or more strips, having a fibrous sheet as described before. A toilet paper roll comprising a core as described before. A tampon applicator comprising a fibrous sheet as described before.