COMPOSITE NONWOVEN AND PROCESS FOR PRODUCING A COMPOSITE NONWOVEN

Abstract

A composite nonwoven fabric (1, 51, 61) and a process (100, 101, 102) for the production of the composite nonwoven fabric (1, 51, 61) are shown, wherein the composite nonwoven fabric (1, 51, 61) comprises at least one spunbonded nonwoven (8, 54, 64), which exhibits essentially continuous regenerated cellulosic filaments (4, 55, 65) deposited in a random orientation, and at least one layer (52, 62) of biobased biodegradable short fibers (14, 53, 63). So as to provide a fully biodegradable composite nonwoven fabric of the initially mentioned type, which exhibits a high stability and tensile strength as well as good absorption properties and haptic properties and, in addition, can be produced in a cost-efficient way, it is suggested that the composite nonwoven fabric (1, 51, 61) has at least one mixing area (56, 66) in which the filaments (4, 55, 65) of the spunbonded nonwoven (8, 54, 64) and the short fibers (14, 53, 63) are present in a state of physical interconnection.

Claims

1. A composite nonwoven fabric comprising; at least one spunbonded nonwoven which exhibits essentially continuous regenerated cellulosic filaments deposited in a random orientation; and at least one layer of biobased biodegradable short fibers, wherein the composite nonwoven fabric has at least one mixing area in which the continuous regenerated cellulosic filaments of the at least one spunbonded nonwoven and the biobased biodegradable short fibers are present in a state of physical interconnection.

2. The A composite nonwoven fabric according to claim 1, wherein the biobased biodegradable short fibers are cellulosic short fibers and the composite nonwoven fabric in an absolutely dry state has a cellulose content of at least 93 wt.-%, optionally at least 95 wt.-%, or optionally at least 97 wt.-%.

3. The composite nonwoven fabric according to claim 1, wherein the composite nonwoven fabric comprises between 10 wt.-% and 99 wt.-%, optionally between 15 wt.-% and 95 wt.-%, or optionally between 20 wt.-% and 90 wt.-%, of the continuous regenerated cellulosic filaments of the at least one spunbonded nonwoven and between 1 wt.-% and 90 wt.-%, optionally between 5 wt.-% and 85 wt.-%, or optionally between 10 wt.-% and 80 wt.-%, of the biobased biodegradable short fibers.

4. The composite nonwoven fabric according to claim 1, wherein the composite non woven fabric is essentially free from binders that do not occur naturally in wood.

5. The composite nonwoven fabric according to claim 1, wherein the biobased biodegradable short fibers are selected from the group comprising: natural cellulose fibers, pulp fibers, Viscose, Modal, Cupro and Lyocell fibers, chemically modified cellulose fibers, recycled cellulosic fibers, starch fibers, and combinations thereof.

6. The composite nonwoven fabric according to claim 1, wherein the biobased biodegradable short fibers have a length of between 0.5 mm and 15 mm, optionally between 1 and 12 mm.

7. The composite nonwoven fabric according to claim 1, wherein the composite nonwoven fabric is obtainable by a process according to claim 8.

8. A process for producing a composite nonwoven fabric according to claim 1, comprising extruding a spinning mass containing cellulose through a plurality of nozzle holes of at least one spinneret to form filaments, and drawing the filaments, in each case, in an extrusion direction, wherein the filaments are deposited in a random orientation on a perforated conveying device to form a spunbonded nonwoven and wherein short fibers are added to the spunbonded non woven to form the composite non woven fabric, wherein the filaments of the spunbonded nonwoven are charged with the short fibers in a never-dried state.

9. The process according to claim 8, wherein the filaments of the spunbonded nonwoven are charged with a suspension of the short fibers in the never-dried state.

10. The process according to claim 9, wherein the suspension comprises between 0.01 wt.-% and 2.00 wt.-% of the short fibers.

11. The process according to claim 9, wherein the filaments of the spunbonded nonwoven are charged with the suspension during washing.

12. The process according to claim 9, wherein the filaments of the spunbonded nonwoven are charged with the suspension during formation of the spunbonded nonwoven.

13. The process according to claim 8, wherein the filaments of the spunbonded nonwoven are charged with an air stream comprising the short fibers in the never-dried state.

14. The process according to claim 13, wherein the filaments are charged with a drawing air stream for drawing and the short fibers are added to the drawing air stream in order to charge the filaments of the spunbonded nonwoven with the short fibers in the never-dried state.

15. The process according to claim 8, wherein after the filaments have been charged with the short fibers, the composite nonwoven fabric is subjected to at least one treatment step, the at least one treatment step being selected from the group comprising: hydroentanglement, water jet embossing, water jet perforation, washing, drying and combinations thereof.

16. The process according to claim 8, wherein the spinning mass is a solution of cellulose in a direct solvent, optionally a tertiary amine oxide.

17. The process according to claim 8, wherein, after extrusion from the at least one spinneret, the filaments are coagulated at least partly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In the following, preferred embodiments of the invention are illustrated in further detail with reference to the drawings.

[0057] FIG. 1 shows a schematic illustration of the process according to the invention for the production of a composite nonwoven fabric according to a first embodiment variant,

[0058] FIG. 2 shows a schematic illustration of the process according to the invention for the production of a composite nonwoven fabric according to a second embodiment variant,

[0059] FIG. 3 shows a schematic illustration of the process according to the invention for the production of a composite nonwoven fabric according to a third embodiment variant,

[0060] FIG. 4 shows an electron microscope image of a first composite nonwoven fabric according to the invention, and

[0061] FIG. 5 shows an electron microscope image of a second composite nonwoven fabric according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0062] FIG. 1 shows a process 100 according to the invention for the production of a composite nonwoven fabric 1 and a device 200 for performing the process 100 according to a first embodiment variant of the invention. In a first process step, a spinning mass 2 is produced from a cellulosic raw material and supplied to a spinneret 3 of the device 200. In this case, the cellulosic raw material for producing the spinning mass 2, which is not shown in further detail in the figures, can be a pulp made of wood or other plant-based starting materials, which is suitable for the production of lyocell fibers. However, it is also conceivable that the cellulosic raw material consists at least partly of production waste from the production of spunbonded nonwoven or recycled textiles. In this case, the spinning mass 2 is a solution of cellulose in NMMO and water, with the cellulose content in the spinning mass 2 ranging between 3 wt.-% and 17 wt.-%.

[0063] In a following step, the spinning mass 2 is then extruded through a plurality of nozzle holes in the spinneret 3 to form filaments 4. The extruded filaments 4 are then accelerated and drawn in the extrusion direction in a drawing air stream, which, however, has not been illustrated in further detail in the figures.

[0064] In one embodiment variant, the drawing air stream can emerge between the nozzle holes of the spinneret 3. In a further embodiment variant, the drawing air stream may alternatively emerge around the nozzle holes. However, this is not illustrated in further detail in the figures. Such spinnerets 3 comprising drawing devices for generating a drawing air stream are known from the prior art (U.S. Pat. Nos. 3,825,380 A, 4,380,570 A, and WO 2019/068764 A1).

[0065] In the preferred embodiment that has been shown, the extruded and drawn filaments 4 are furthermore charged with a coagulant from a coagulation device 5. Said coagulant is usually water or an aqueous solution in the form of a liquid, mist or vapour. Due to the contact of the filaments 4 with the coagulant, the filaments 4 are coagulated or, respectively, regenerated at least partly, which, in particular, reduces adhesions between the individual extruded filaments 4.

[0066] The drawn and at least partially coagulated filaments 4 are then deposited in a random orientation on the tray 6 of a conveying device 7 in order to form a cellulosic spunbonded nonwoven 8.

[0067] After the formation, the spunbonded nonwoven 8 is passed across the conveyor belt 9 through a washing 10 in which the spunbonded nonwoven 8 is washed in order to free it from residues of the solvent, namely the NMMO contained in the spinning mass 2. In a preferred embodiment variant, the washing 10 is a multi-stage countercurrent washing with several washing stages 11, wherein fresh washing solution 12 is supplied to the final stage and the increasingly spent washing solution of a washing stage 11 is passed on to the respective preceding washing stage 11.

[0068] Upon washing 10, the spunbonded nonwoven 8 is guided through a wet-laying device 13 in which the never-dried spunbonded nonwoven 8 is charged with cellulosic short fibers 14, the short fibers 14 being present in a suspension 15 and the suspension 15 being applied to or, respectively, sprayed onto the spunbonded nonwoven 8. In this case, the suspension 15 has a content of short fibers 14 of between 0.01 and 2.00 wt.-%. By providing a separate wet-laying device 13 in the process 100 or, respectively, the device 200, an operation of the supply of short fibers that is independent from the surrounding production of spunbonded nonwoven can be ensured.

[0069] During the application of the suspension 15 containing the short fibers 14 to the never-dried spunbonded nonwoven 8, a layer of short fibers 14 is formed over the spunbonded nonwoven 8, and the composite nonwoven fabric 1 is thereby formed. In addition, a mixing area forms in the composite nonwoven fabric, in which the filaments of the spunbonded nonwoven 8 and the short fibers 14 are present in a state of mere physical mixing and therefore stick together without a chemical bond.

[0070] After the wet-laying device 13, the composite nonwoven fabric 1 is then subjected to hydroentanglement 16 in a following step. In the course of this hydroentanglement 16, a further bonding of the spunbonded nonwoven 8 with the layer of short fibers 14 takes place, wherein the physical connections between the filaments of the spunbonded nonwoven 8 and the short fibers 14 are enhanced further by mixing, in particular by interlocking, looping, static friction, etc.

[0071] In order to finally remove the remaining moisture from the composite nonwoven fabric 1 and to obtain a composite nonwoven fabric 1 ready for packaging, the composite nonwoven fabric 1 is subjected to drying 17 following the hydroentanglement 16.

[0072] Finally, the process 200 is concluded by optionally winding 18 and/or packaging the finished composite nonwoven fabric 1.

[0073] In FIG. 2, a second alternative embodiment variant of the process 101 according to the invention and, respectively, of the device 201 is illustrated. In this case, the suspension 15 with the short fibers 14 is not supplied to an independent wet-laying device 13, in contrast to the embodiment variant shown in FIG. 1. Rather, the short fibers 14 are supplied to the washing solution 12 of at least one washing stage 11, preferably the final washing stage 11, of the washing 10 in such a way that the spunbonded nonwoven 8 is simultaneously washed and charged with the short fibers 14 during the washing 10. With regard to further features, reference is made to the explanations concerning FIG. 1.

[0074] This represents the technically most simple and, in addition, also most economical embodiment variant of the invention, since only the washing 10 of an existing spunbond plant has to be converted in such a way that one or several of the existing washing stages 11, in addition to their original function of homogeneously distributing and applying the washing solution 12, also fulfill the function of charging the spunbonded nonwoven 8 with suspensions 15 of short fibers 14.

[0075] In this case, the suspension 15 contains short fibers 14 in a concentration range of between 0.01 wt.-% and 2.00 wt.-% and fibre lengths ranging from 0.5 mm to 20 mm. In a further embodiment variant, which is not illustrated in the figures, the short fibers 14 may also be mechanically fibrillated fibers or, respectively, pulp fibers, with a refiner being additionally required for the fibrillation of the short fibers.

[0076] The suspension 15 is preferably formed by suspending the short fibers 14 in fresh water. The suspension 15 is preferably applied to the spunbonded nonwoven 8 only in the area of the last two washing stages 11 in order to impair a shift in the concentration distribution of solvent in the washing solution across the entire washing 10 only to a minimum extent, thus avoiding additional technical requirements and rising operating costs in connection with the treatment or, respectively, concentration of the solvent-containing wash water in the best possible manner. In addition, by supplying the suspension 15 to the washing 10, the need for washing solution 12 in the washing 10 can be reduced to a corresponding degree.

[0077] In a further embodiment variant, which is illustrated with dashed lines in FIG. 2, downstream of the first spinneret 3, a second spinneret 23 can be provided, through which the spinning mass 2 is also extruded into filaments 24. In doing so, the filaments 24 are deposited on the conveying device 7 over the first spunbonded nonwoven 8 to form a second spunbonded nonwoven.

[0078] In this case, the suspension 15 containing short fibers 14 is applied to the first spunbonded nonwoven 8 between the first spinneret 3 and the second spinneret 23 in order to produce the layer of short fibers 14. The second spunbonded nonwoven is then deposited directly on the layer of short fibers 14 so that a multi-layered composite nonwoven fabric 1 with several cellulosic spunbonded nonwovens 8 and short fibers 14 is formed. Optionally—as described above—the composite nonwoven fabric 1 can, in this case, be charged additionally with short fibers 14 during the washing 10.

[0079] In a further embodiment variant, the multi-layered composite nonwoven fabric 1 is treated in the subsequent hydroentanglement 16 in such a way that the layer structure of alternating spunbonded nonwovens 8 and short fibers 14 can be made largely unrecognizable and thus an even more extensive mixing area is formed in the composite nonwoven fabric 1.

[0080] Accordingly, for all the aforementioned embodiments of the process 100, 101 according to the invention, significant savings in terms of the demand for energy and fresh water will arise, as compared to the prior art, since [0081] a) a spunbonded nonwoven 8 that is already moist and has never been dried is used, rather than a substrate that has already been dried and is wetted again by adding the short fibers 14 in the form of a suspension 15, [0082] b) the wet short fibers 14 that have been added introduce less water per unit mass of cellulose into the still moist nonwoven product than an equivalent amount of non-dried cellulosic spunbonded nonwoven, [0083] c) the need for washing solution 12 in the washing 10 can be reduced by the amounts of water supplied as the suspension 15, and [0084] d) the waste water from a hydroentanglement 16 can be used as fresh water for the washing 10 and, respectively, the production of the suspension 15.

[0085] In addition, in a further embodiment variant, the expenditure on equipment for the process 101 can be further simplified in that the hydroentanglement 16 already takes place on the conveyor belt 9 together with the washing 10. In doing so, the latter may additionally exhibit a three-dimensional embossed structure, which can be transferred to the spunbonded nonwoven by the water jet treatment.

[0086] In FIG. 3, a third embodiment variant of the process 102 according to the invention and of the device 202 is illustrated. In contrast to the embodiment variants illustrated in FIGS. 1 and 2, the short fibers 14 are not applied to the spunbonded nonwoven 8 in the form of a suspension 15 in this case, but rather, they are applied to the spunbonded nonwoven 8 in the form of an air stream 26, using the airlaying technology. With regard to further features of the process 102, reference is made to the explanations concerning FIGS. 1 and 2.

[0087] The supply of the air stream 26 containing short fibers 14 to the spunbonded nonwoven 8 may take place between two spinnerets 3, 23 as well as before, within and/or after the washing 10.

[0088] In order to enable a homogeneous distribution of the short fibers 14 within the air stream 26 and to be able to convey the short fibers 14 to the place of application, special units for opening the fibers as well as for transporting the short fibers 14 are provided, which, however, have not been illustrated in further detail in the figures.

[0089] In a further embodiment variant, which is not illustrated in further detail in the figures, the short fibers 14 can also be supplied directly to the drawing devices in the spinnerets 3, 23 and thus can be pitched with the drawing air stream directly onto the filaments 4 of the spunbonded nonwoven 8. In doing so, the short fibers 14 are mixed directly with the filaments 4 in the spunbonded nonwoven, whereby a mixing area extending across the entire thickness of the composite nonwoven fabric 1 is created. For this purpose, in one embodiment variant, a secondary air stream, which comprises the short fibers 14, can, for example, be introduced below the spinnerets 3, 23, whereby it is merged with the drawing air stream in order to charge the filaments 4 with the short fibers 14.

[0090] In a further embodiment, which is not illustrated in the figures, a multi-layered spunbonded nonwoven 8 is produced by two spinnerets 3, 23 arranged one behind the other, however, it is unravelled into the two spunbonded nonwoven layers prior to the application of the short fibers 14, with the short fibers 14 subsequently being introduced between the two spunbonded nonwoven layers either as a suspension 15 or in a dry state within an air stream 26. Thereupon, the two spunbonded nonwoven layers are reconnected, and the obtained composite nonwoven fabric 1 is solidified in a hydroentanglement 16.

[0091] In order to be able to ensure full biodegradability of the composite nonwoven fabrics 1 according to the invention, the cellulosic short fibers introduced by means of the above-described embodiment variants exclusively consist of the types of substance of industrially produced pulps, pulps recovered from recycling processes, cellulosic short-cut fibers, cellulosic natural fibers or all possible combinations of those groups of substances.

[0092] Electron microscope images of composite nonwoven fabrics 51, 61 produced according to the invention are shown in FIGS. 4 and 5.

[0093] FIG. 4 shows a composite nonwoven fabric 51 in which a limited mixing area 56 is formed between a layer 52 of short fibers 53 (pulp fibers in this case) and a cellulosic spunbonded nonwoven 54 (lyocell spunbonded nonwoven). In the mixing area 56, the filaments 55 of the spunbonded nonwoven 54 are physically mixed with the short fibers 53.

[0094] FIG. 5 shows a composite nonwoven fabric 61 which no longer has an identifiable layer structure. Here, the cellulosic spunbonded nonwoven 64 (lyocell spunbonded nonwoven) penetrates the layer 62 of short fibers 63 (pulp fibers) essentially completely. The mixing area 66 thus extends across the entire thickness of the composite nonwoven fabric 61. Thus, the short fibers 63 are distributed homogeneously across the composite nonwoven fabric 61.

EXAMPLES

[0095] In the following, the advantages of the invention are exemplified using several examples.

[0096] The following measuring methods were used to determine various parameters of the produced composite nonwoven fabrics:

Basis Weight

[0097] The basis weight indicates which mass the composite nonwoven fabric exhibits per unit area. The determination of the basis weight is done according to the NWSP 130.1.R0 standard (15).

Tensile Strength/Elongation

[0098] The tensile strength values provide information about the robustness of the wipe in wiping operations or, respectively, during removal from the package. An increased tensile strength therefore results in a higher resistance to damage under tensile stress. A minor elongation is helpful when the wipes are removed from the package and helps to keep the wipe firmly in place in the wiping hand. The tensile strength and, respectively, the elongation are determined in accordance with DIN EN 29073 Part 3/ISO 9073-3 (version from 1992).

Wicking

[0099] The rise height test (wicking) provides information about the distribution rate of a liquid or, respectively, lotion across the nonwoven surface in the machine and cross directions. The values indicated below refer to the rise heights of water in the nonwoven over a period of 300 s. The rise height is determined according to NWSP 010.1.R0 (15).

Nonwoven Conditioning

[0100] Prior to each measurement, the samples were conditioned at 23° C. (±2° C.) and 50% (±5%) relative humidity over a period of 24 h.

Electron Microscopy

[0101] The electron microscope images were obtained using a measuring device of the type ThermoFisher Quanta 450 (5 kV, Spot 3, WD10, EDT) or Thermo Fisher Scientific, Phenom ProX. The selection of sites was made at random.

[0102] The composite nonwoven fabrics described below were manufactured by the process according to the invention in such a way that single-ply lyocell spunbonded nonwovens with basis weights of 20-45 g/m.sup.2 were produced and loaded with a 0.8-1.5% pulp suspension within the washing by means of an additionally installed wet-laying device. The composite nonwoven fabric was finally treated by hydroentanglement using three pressure stages (with pressures of between 40 bar and 100 bar), was dried to a final moisture content of less than 10% and was obtained in the form of rolled goods with basis weights of 30-80 g/m.sup.2. The nozzle strips used in the hydroentanglement exhibited a single-row pattern of holes with hole diameters of 0.12 mm and a hole spacing of 13 holes/cm.

[0103] The detailed parameters of the tests carried out as well as the measured properties of the associated composite nonwoven fabrics are illustrated below in Table 1.

TABLE-US-00001 TABLE 1 Test parameters and product properties Example product 1 2 3 4 5 Basis weight of the substrate [g/m.sup.2] 45 20 20 20 20 Solids content of the suspension [%] 0.5 0.7 0.8 1.0 1.2 Hydroentanglement pressure p1 [bar] 40 70 40 40 40 Hydroentanglement pressure p2 [bar] 40 80 40 40 40 Hydroentanglement pressure p3 [bar] 60 100 70 40 40 Basis weight of the end product 70 45 45 45 60 [g/m.sup.2] Tensile strength (dry, MD) [N/5 cm] 45 16 30 33 40 Tensile strength (dry, CD) [N/5 cm] 18 7 10 12 15 Tensile strength (wet, MD) [N/5 cm] 14 6 10 11 8 Tensile strength (wet, CD) [N/5 cm] 6 3 5 5 5 Elongation (dry, MD) [%/5 cm] 4 4 4 4 4 Elongation (dry, CD) [%/5 cm] 7 7 7 7 7 Elongation (wet, MD) [%/5 cm] 14 8 8 8 8 Elongation (wet, CD) [%/5 cm] 27 28 18 20 25 Wicking MD [mm] 146 161 149 150 152 Wicking CD [mm] 122 139 132 131 133

[0104] Concurrently with the indicated composite nonwoven fabrics produced according to the invention, a commercially available composite nonwoven fabric based on a polypropylene nonwoven substrate comprising an incorporated pulp with a total basis weight of 45 g/m.sup.2 was examined in terms of its mechanical properties. With dry tensile strengths of 33 N/5 cm in the machine direction (MD) and of 13 N/5 cm in the cross direction (CD), the commercial product has dry strengths comparable to that of the exemplary product 4 listed in Table 1. The strength values provide information about the robustness of the wipe in wiping operations or, respectively, during removal from the package, with the indicated composite nonwoven fabrics according to the invention doing without the use of a synthetic carrier web. By contrast, exclusively wet-laid paper products of comparable basis weights exhibit lower wet tensile strengths of 4-8 N/5 cm, which, however, are hardly sufficient anymore for the normal usage as a wet wipe.

[0105] The aforementioned commercially available composite nonwoven fabric based on a polypropylene nonwoven substrate with an incorporated pulp with a total basis weight of 45 g/m.sup.2 was examined also in terms of its liquid absorption capacity: According to the wicking test, significantly lower rise heights of 94 mm in MD and 73 mm in CD were measured, whereby the product according to the invention is given clear advantages in terms of its loading rate with lotions in conversion processes to produce commercial wet wipes, i.e., the dry rolled goods absorb the lotion significantly faster during the loading process, and the homogeneously distributed liquid inside the closed wipe packages displays the formation of a loading gradient much more slowly due to the weight-related lowering of the liquid.