Multi-ply dispersible nonwoven material

Abstract

The invention relates to a nonwoven material having sufficient strength to be used in a pre-moistened state but also having dispersibility properties which allow the product to be flushed. The material comprises at least two nonwoven webs, at least one of which is hydroentangled. Each of the individual webs has a basis weight of 20-100 gsm. The nonwoven webs are joined together by thermal or mechanical embossing, or a combination of these.

Claims

1. A method of making a nonwoven fabric material, the method comprising: separately hydroentangling at least two nonwoven web layers, each individual nonwoven web layer having a basis weight of 20-100 gsm, and each individual nonwoven web layer comprising wood pulp and non-thermoplastic man-made fibers, the non-thermoplastic man-made fibers having a length of from 5 to 15 mm, joining the at least two separately hydroentangled nonwoven web layers together by thermal embossing, mechanical embossing, or a combination thereof, to obtain the nonwoven fabric material.

2. The method of claim 1, wherein the non-thermoplastic man-made fibers are selected from the group consisting of regenerated cellulose, lyocell, viscose rayon, polylactic acid and polyvinyl alcohol.

3. The method of claim 1, further comprising drying the at least two nonwoven web layers prior to the joining.

4. The method of claim 1, wherein the at least two separately hydroentangled nonwoven web layers are joined together by thermal embossing.

5. The method of claim 4, wherein the temperature during the thermal embossing is 140 C. to 180 C.

6. The method of claim 4, wherein the thermal embossing is carried out at a pressure in the range of 40 to 90 N/mm.sup.2.

7. The method of claim 1, wherein the at least two separately hydroentangled nonwoven web layers are joined together by mechanical embossing.

8. The method of claim 1, further comprising treating the nonwoven fabric material with a wetting liquid.

9. The method of claim 8, wherein the wetting liquid further comprises one or more additional agents selected from the group consisting of emollients, viscosity modifiers, natural or synthetic oil and fats, surfactants, antimicrobial agents, particulates, alcohol, salts, organic solvents, pharmaceutical agents, odor control agents, detergents, silicones, fragrance, pH control agents, whitening agents and surface feel modifiers.

10. The method of claim 8, wherein the wetting liquid is added in an amount not exceeding 2.5 times a weight of the nonwoven fabric material in a dried state per unit area.

11. The method of claim 1, wherein a wet strength of the nonwoven fabric material is greater than 250 g/50 mm.

12. The method of claim 1, wherein the joined web layers comprise a wet strength which is greater than that of the at least two individual web layers.

13. The method of claim 1, wherein each individual web layer has a wet strength of 100 g/50 mm to 600 g/50 mm.

14. The method of claim 1, wherein the nonwoven fabric material has a final basis weight of 40 to 120 gsm.

15. The method of claim 1, wherein the at least two separately hydroentangled nonwoven web layers are wet-laid web layers.

16. The method of claim 1, wherein the nonwoven fabric material comprises an embossing bonding area which is 5% to 33% of the nonwoven fabric material.

17. The method of claim 16, wherein the embossing bonding area is from 20% to 33% of the nonwoven fabric material.

18. The method of claim 16, wherein the embossing bonding area is from 5% to less than 20% of the nonwoven fabric material.

19. The method of claim 16, wherein the embossing bonding area has a discontinuous pattern.

20. The method of claim 1, wherein each individual nonwoven web layer comprises 50%-95% of the wood pulp and 5%-50% of the non-thermoplastic man-made fibers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 shows an alternative method for preparing a nonwoven material according to an embodiment of the invention;

[0017] FIG. 2 shows a further alternative method for preparing a nonwoven material according to an embodiment of the invention;

[0018] FIG. 3 is a diagram showing the wet MD and CD strength profiles of various multi-ply webs joined together by thermal/mechanical embossing, with reference to Table 1, supra.

DETAILED DISCLOSURE

[0019] The material of the invention comprises at least two individual nonwoven web layers formed separately. At least one, preferably several of the webs is/are hydroentangled. The hydroentanglement is carried out using wet laid technology with a composition of 50%-95% wood pulp and 5%-50% short cut fibers and/or natural fibers. The short cut fibers of flushable wipes are man-made fibers which are non-thermoplastic. Non-limiting examples of short-cut man-made fibers useful in the dispersible nonwoven material of the invention are regenerated cellulose, lyocell, viscose rayon, polylactic acid and polyvinyl alcohol. The present invention avoids the use of any glass fiber and oil-based synthetic fibers such as polyester, nylon, polypropylene, polycarbonates, polyethylene, polyvinyl chloride, aramid, polyacrylate, and combinations thereof. The natural fibers might be cotton, hemp, flax, linen, bamboo, sisal, jute, kapok, etc. The fiber length of the short cut man-made fibers and/or natural fibers useful in the dispersible nonwoven material of the invention is in the range of 5 mm to 15 mm. Each individual nonwoven web preferably has a basis weight of 20 gsm to 100 gsm. Each individual nonwoven web preferably has a wet strength of 100 g/50 mm to 600 g/50 mm.

[0020] After hydroentanglement, the two nonwoven webs are dried (using e.g. drying cans) and then joined together by thermal or mechanical embossing. The thermal/mechanical embossing holds the two nonwoven webs together in the presence of the wetting solution. The composite web has a significantly higher strength than the individual webs. The joined embossed fabric material provides sufficient in-use and dispensing strength to the product, but splits into its component webs and disperses fast after flushing down with mild agitation in water. The dispersibility of the subject material is according to GD 3 guidelines; 50 to 100% pass through after 5 min.

[0021] The final basis weight for the nonwoven material according to the present invention is in the range 40 to 120 gsm. Preferably, the wet strength in the conditions of use of the nonwoven according to the present invention is greater than 250 g/50 mm.

[0022] Thermal embossing for the purpose of the present invention may advantageously be carried out at a pressure in the range of 40 to 90 N/mm.sup.2, using an embossing bonding area of 5% to 33% with continuous or discontinuous pattern, and a temperature range of 140 C. to 180 C. Preferably, the embossing pressure may be about 60 N/mm.sup.2, and the temperature about 160 C. Preferably, the bonding area is greater than 5%. Embossing without elevated temperature can advantageously be carried out for the present invention with a pressure of 60 to 160 N/mm.sup.2 and embossing bonding area of 5% to 33% with a continuous/discontinuous pattern.

[0023] To prepare wet wipes, the nonwoven fabric material according to the present invention is treated with a wetting liquid. Advantageously, the wetting liquid may comprise about 98% water and about 2% preservative, for example Lonza Geogard 221. Preferably, wetting liquid is used in an amount not exceeding 2.5 times the weight of the dry nonwoven material per unit area.

[0024] In general, the wetting liquid may further comprise additional agents such as emollients, viscosity modifier, natural or synthetic oil and fats, surfactants, antimicrobial agents, particulates, alcohol, salts, organic solvents, pharmaceutical agents such as dimethyl sulfoxide; odor control agents, detergents, silicones, fragrance, pH control agents, whitening agents and surface feel modifiers.

DESCRIPTION OF PREFERABLE EMBODIMENTS

[0025] FIG. 1 is a schematic representation of an embodiment of a process for preparing a nonwoven according to the present invention. Stock is prepared in a headbox 1 and a first web 2 is laid wet according to procedures known to the person skilled in the art. For example, the web is laid on a plastic wire running at a speed of 2 to 4 m/s (400-800 feet/min) and transferred to the hydroentangling station where the fibrous structure is entangled using high pressure water jets 3. The web is hydroentangled by 3 to 5 different consecutive nozzles with a water jet pressure of 2.75-5.5 MPa (400-800 psi) and laid on top of a second wet laid web 4 prepared in an analogous manner using second headbox 5 and high pressure water jets 6 but not necessarily using identical parameters. The combined web passes through drying station 7 and thermal or mechanical embossing station 8. The wet laid webs 2, 4 have a composition of 50-95% wood pulp fibers and 5-50% shortcut fibers. The proportion of shortcut fiber to wood pulp fiber depends on the type of shortcut fiber used. If the shortcut fibers are of flat cross-section and of short length, then a higher proportion of shortcut fiber is required, and if the fiber is of round cross-section and of long length, then the proportion of shortcut fiber will be low. Preferably, at least 20% of shortcut fiber is used.

[0026] An example of wood pulp fiber which may be used in a nonwoven according to the invention is Grande Prairie ECF Northern Bleached Softwood. An example of shortcut fiber which may be used in a nonwoven according to the invention is Danufil 1.7 dtex 8 mm from Kelheim Fibres GmbH, Germany. Cotton fiber is a further alternative to be used as shortcut fiber.

[0027] FIG. 2 shows another embodiment of a process for preparing a nonwoven web according to the present invention. The equipment shown includes headbox 9 and high pressure water jets 10, as well as drying station 11 and thermal or mechanical embossing station 12. A wet laid and hydroentangled web 13 is laid on another web 14 which is unwound from reel 15, being previously formed and entangled and pre-wound. The combined web is dried and embossed to form a nonwoven according to the present invention. Also two preformed and pre-entangled webs may be unwound and embossed to form a nonwoven material according to the present invention.

Examples

[0028] Prototype samples were prepared using two hydroentangled sheets produced separately at 30 and 40 gsm each with entanglement pressure of 400, 400, and 500 psi which are then thermally joined together at a temperature of 160 C. and a pressure of 60 N/mm.sup.2, with a continuous pattern having embossing bonding area of 24.4%.

[0029] Table 1 shows the composition and ID (corresponding to FIG. 3) of the samples prepared.

TABLE-US-00001 TABLE 1 Various nonwoven webs with different fiber composition and basis weights Composition Sample ID 20% Short Cut Fiber, 80% Wood-30 gsm A1 20% Short Cut Fiber, 80% Wood-40 gsm A2 30% Short Cut Fiber, 70% Wood-30 gsm B1 30% Short Cut Fiber, 70% Wood-40 gsm B2 20% Short Cut Fiber, 80% Wood-60 gsm C 30% Short Cut Fiber, 70% Wood-60 gsm D 20% Short Cut Fiber, 80% Wood-40 gsm- E No Entanglement 100% Wood Pulp-No Entanglement 35 gsm

[0030] In FIG. 3 are shown the wet MD and CD strength profiles of various combinations of the webs of Table 1 joined together by thermal embossing.

[0031] All the samples showed in FIG. 3 split into two separate webs after mild agitation in water and disperse fully (100% slosh box dispersion) after 5 min according to INDA/EDANA flushability GD3 guidelines. Table 2 shows the results.

TABLE-US-00002 TABLE 2 Slosh box dispersion results for samples in FIG. 3 Sample Id Slosh Box (% pass Through)-5 min A1 + A1 99.93 A1 + A2 100.00 A2 + A2 99.52 A2 + E 100.00 A2 + 35 gsm tissue 99.94 B1 + B1 100.00 B2 + B1 99.79 B2 + B2 99.33 B2 + E 99.86 B2 + 35 gsm tissue 100.00