DISPERSIBLE NON-WOVEN FABRICS

Abstract

The present invention relates to a dispersible nonwoven fabric comprising pulp and solvent spun cellulosic fibers, characterized in that the solvent spun cellulosic fibers are fibrillated. Furthermore the invention concerns the use of the fabric in dry wipes and wet wipes.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention is directed towards rapidly dispersible absorbent nonwoven fabrics and methods for making and using such products. This invention is especially directed towards rapidly dispersible wet wipes that are flushable through a standard toilet system arid disintegrate into easily dispersible fragments that biodegrade alter disposal.

Not-woven textiles are defined with the terminology “nonwoven”. The definition of nonwoven is described in the norm ISO 9092:1988. Absorbent nonwoven fabrics include materials such as dry wipes, wet wipes and cosmetic wipes and masks. They are also materials used in hygiene products like panty liners, sanitary napkins and incontinence products. The nonwoven fabrics used in these applications should fulfill the requirements of European Pharmacopoeia.

Disposable absorbent wipes such as toilet wet wipes oiler high levels of convenience, comfort and efficacy that are greatly appreciated by consumers. However, the popularity of these products has created a need regarding their disposal. General disposal methods used tor waste materials such bin disposal for subsequent incineration or landfill are not convenient for the consumers, especially for using of toilet wet wipes. One of the alternative disposal methods is flushing the wet wipes directly into a conventional toilet. Flushing the product in the toilet, dispersing it by mechanical forces and finally biodegrading the material in the sewage system is more convenient and discrete for the consumers. For this disposal method, the suitable material should maintain its structural integrity and strength for use, but also disintegrate readily when flushing into the toilet without causing any blockage in the pumping and drain systems.

Such products like toilet wipes are pre-moistened wipes. Therefore the nonwoven fabrics used tor these applications should maintain their mechanical strength and integrity in the wet state during storage and also be biodegradable in the sewage system.

Flushable wet wipes are known for example from U.S. Pat. No. 5,629,081 and EP 1 285 985 A1.

SUMMARY Of THE INVENTION

The object of die invention is to provide a dispersible nonwoven fabric with good tensile strength but which disintegrate readily when flushed.

By the present invention there is provided a dispersible nonwoven fabric comprising pulp and solvent spun cellulosic fibers characterized in that the solvent spun cellulosic fibers are fibrillated.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an unfibrillated Tencel by light microscope,

FIG. 2: shows an exemplary fibrillated Tencel by light microscope, and

FIG. 3: shows art exemplary fibrillated Tencel by scanning electron microscope.

DETAILED DESCRIPTION OF THE INVENTION

Especially suited as starting material for the filbrillated fibers are solvent spun short cut cellulosic fibers with a length of 2 to 20 mm, preferably 3 to 12 mm, most preferably 4 to 10 mm. The titer of the solvent spun short cut fibers is 0.9 to 6.7 dtex, preferably 1.3 to 1.7 dtex.

Preferably the solvent spun short cut fibers are present in the dispersible nonwoven fabric in an amount of 1 to 90 wt.-%, preferably 5 to 40 wt.-%, most preferably 10 to 30 wt.-% based on the fabric.

A preferred solvent spun short cut fiber is a lyocell fiber, produced according to the Aminoxide-process, which is known e.g. from U.S. Pat. No. 4,246,221 (McCorsley). A suited solvent spun fiber is sold under the trade name “Tencel”.

The dispersible nonwoven fabric has a weight of 30 to 100 g/m2, preferred of 40 to 60 g/m2 and a thickness of 0.1 to 0.7 mm.

The dispersible nonwoven fabric may comprise a dispersing, aid in an amount of 0.1 to 1% wt-%. preferably 0.5 to 1 wt.-% based on the fabric.

To increase the strength, optionally a binder is present in an amount of 0.01 to 5 wt-%, preferably 0.1 to 0.5 wt-% based on the fabric, preferably in form of an acrylic resin or epichlorohydrin based resin, such as polyamide-polyamine-epichlorohydrin resins or polyamide-epichlorohydrin resins. Other examples for suited binders are polyethylenimine resins and aminoplast resins.

Any type of pulps are suited, especially softwood pulps, hardwood pulps or a pulp made from plants like abaca or bamboo.

The dispersible nonwoven fabric according to die invention has a wet tensile strength in machine direction of 2 to 20 N/5 cm, preferably 3 to 13 N/5 cm and most preferably 3 to 7 N/5 cm based on a basis weight of 60 g/m2 and in cross direction 1 to 10 N/5 cm, preferably 1 to 7 N/5 cm and most preferably I to 3 N/5 cm. The wet tensile strength has been measured according to the EDANA Method WSP 110.4 (09) “Standard Test Method for Breaking Force and Elongation of Nonwoven Materials (Strip Method)”.

One standardized test method for testing the properties of disposable wipes is known from “EDANA Guidance Document for Assessing the Flushability of Nonwoven Consumer Products”. This test is used to assess the dispersibility or physical breakup of a flushable product during its transport through household and municipal conveyance systems (e.g., sewer pipe, pumps and lift stations). This test assesses the rate and extent of disintegration of a test material by turbulent water in a rotating tube. Results from this test are used to evaluate the compatibility of test materials with household and municipal wastewater conveyance systems. The principle of the test method is that the rotation of the tube is used to simulate die physical forces acting to disintegrate a product during passage through household sewage pumps and municipal conveyance systems. In this test the product is placed in a clear plastic tube containing 700 ml of tap water or raw wastewater, which is rotated end-over-end. After a specified number of cycles or rotations, the contents in the tube are passed through a series of screens. The various size fractions retained on the screens are weighed, and the rate and extent of disintegration determined.

The lest material is disintegrating when at least 95% of the size fractions pass a 12 mm screen and the residue is less than 5%.

The invention also concerns a process tor the production of a dispersible nonwoven fabric.

According to this wet lay process, pulp is dispersed in water and a solvent spun fiber is dispersed in water, either separately or together as a mixture. A dispersing aid such as CMC (Carboxymeytyl cellulose) may be added to improve dispersion quality. The dispersions are passed through a refiner either separately or are co-refined. The refining energy is from 20 to 400 kWh/t, prefer 40 to 150 kWh/t. A binder solution may be added to the slurry. In the case of separate refining, the slurries are mixed to form an intimate blend to form one slurry, The slurry is then wet-laid, e.g. on a papermaking machine, to form a sheet. The sheet then passes through a hydroentanglement process either on-line or as a separate offline process to form a fabric.

FIG. 1 shows an unfibrillated Tencel (light microscope). Fibrillation or refining is a wet abrasion process that exposes and releases fibrils emerging from the surface region of the filaments. As refining progresses, more fibrils are released from the filaments and the diameter of the residual filaments decreases (FIG. 2: light microscope. FIG. 3: scanning electron microscope).

In further steps the fabric is sliced into the appropriate format, folded and packed.

A treatment, preferably an impregnation, with a liquid or lotion can be carried out before packaging.

The invention is shown by the following examples:

EXAMPLE 1 and EXAMPLE 2 (BOTH COMPARATIVE)

Wetlaid fabrics made of blends of woodpulp (Camfor pulp, a long fiber woodpulp derived from spruce and pine, grown in British Columbia, Canada) with 15% Tencel short cut 1.7 dtex at 6 mm cut length (example 1) or 25% Tencel short cut 1.7 dtex at 6 mm cut length (example 2) without any refining process and without additional of any additives showed a very good dispersibility according to the Tier 1 Test—FG 511.2-Dispersability Tipping Tube Test of the “EDANA Guidance Document for Assessing the Flushability of Nonwoven Consumer Products”. According to example 1, 100% of the disintegrated size fractions pass the 12 mm, the 6 mm and even the 3 mm screen, 21% retain and 79% passes the 1.5 mm screen. But the fabrics did not show a high mechanical strength, both in machine direction (MD) and cross direction (CD) as shown in Table 1.

	TABLE 1
			Tensile	Elongation	Dispersibility of samples
	Fabric	Thickness	Strength wet	wet	Mass of each fraction in % in relation
	weight	dry	[N/5 cm]	[%]	to dry mass
Ex	Fiber blends	[g/m2]	[mm]	MD	CD	MD	CD	>12 mm	>6 mm	>3 mm	>1.5 mm	<1.5 mm
1	15% Tencel	60	0.65	2.0	0.9	2.2	8	0	0	0	21	79
	85% camfor
	pulp
2	25% Tencel	57	0.60	1.9	1.2	2.4	5	0	0	0	28	72
	75% camfor
	pulp

EXAMPLE 3, 4, and 5

Blends of woodpulp (Camfor pulp) with 25% Tencel short cut 1.7 dtex at 6 mm cot length including an addition of 0.5% CMC dispersing aid to the slurry. In these trials the pulp/Tencel blend was refined through Ix disc refiner and 4× conical refiners in series to levels of 40 kWh/t and 60 kWh/t. Acrylic dry strength resin was added to the slurry at 1% (based on dry fiber weight). The fabrics were dispersible and the tensile strength of fabrics was improved (Table 2).

EXAMPLE 6

A blend of 80% woodpulp (Camfor pulp) with 20% Tencel short cut 1.7 dtex at 6 mm cut length was used to make wetlaid fabrics. Fibers were refined to 100 kWh/t, 1% CMC (based on dry fiber weight) as dispersing aid was added and also 0.5% epichlorhydrin based wet strength resin (based on dry fiber weight) was added to increase the wet strength (Table 2). The fabric was dispersible.

	TABLE 2
				Tensile	Elongation	Dispersibility of samples
	Refining	Fabric	Thickness	Strength wet	wet	Mass of each fraction in % in relation
	Energy	weight	dry	[N/5 cm]	[%]	to dry mass
Ex	Fiber blends	(kWh/t)	[g/m2]	[mm]	MD	CD	MD	CD	>12 mm	>6 mm	>3 mm	>1.5 mm	<1.5 mm
3	25% Tencel	40	59	0.28	3.6	1.3	4.2	39	0	0	0	55	45
	75% camfor
	pulp,
4	25% Tencel	60	56	0.25	3.3	1.5	5.0	33	0	0	0	53	47
	75% camfor
	pulp
5	25% Tencel	60	60	0.32	3.4	1.5	1.3	6.6	0	0	0	78	22
	75% camfor
	pulp + acrylic
	resin at 1%
6	20% Tencel	100	57	0.23	5.4	2.1	2.8	17	0	11	34	29	26
	80% camfor
	pulp + 0.5%
	epichlorohydrin

EXAMPLE 7, 8, 9 AND 10

A blend of 75% woodpulp (Camfor) with 25% Tencel short cut 1.7 dtex at 6 mm cut length was used to make wetlaid fabrics. Fibers were refined to 80 kWh/t, 1% CMC as dispersing aid was added and also an epichlorhydrin based wet strength resin was added to increase the wet strength at concentrations of 0.05%, 0.10%, 0.15% and 0.20%. The results, demonstrated in Table 3, show that all samples were dispersible.

The fabric according to the invention can be used in dry wipes and wet wipes like toilette wipes, facial wipes, cosmetic wipes, baby wipes and sanitary wipes for cleaning and densification as well as in absorbent hygiene products such as parity liners, sanitary napkins and incontinence pads.

	TABLE 3
				Tensile	Elongation	Dispersibility of samples
	Refining	Fabric	Thickness	Strength wet	wet	Mass of each fraction in % in relation
	Energy	weight	dry	[N/5 cm]	[%]	to dry mass
Ex	Fiber blends	(kWh/t)	[g/m2]	[mm]	MD	CD	MD	CD	>12 mm	>6 mm	>3 mm	>1.5 mm	<1.5 mm
7	25% Tencel	80	58	0.59	3.7	1.6	11	50	0	0	1	64	35
	75% camfor
	pulp + 0.05%
	epichlorohydrin
	resin
8	As Ex. 7	80	60	0.53	4.1	1.9	11	50	0	0	4	63	33
	except with
	0.10%
	epichlorohydrin
	resin
9	As Ex. 7	80	59	0.29	6.5	2.6	2.9	10	0	27	31	16	26
	except with
	0.15%
	epichlorohydrin
	resin
10	As Ex. 7	80	59	0.42	5.5	2.2	8.8	28	0	2	30	36	32
	except with
	0.20%
	epichlorohydrin
	resin

Claims

1. A dispersible nonwoven fabric comprising pulp and solvent spun cellulosic fibers, wherein the solvent spun cellulosic fibers are fibrillated.

2. The dispersible nonwoven fabric according to claim 1, wherein the fibrillated solvent spun cellulosic fibers are present in an amount of 1 to 90 wt.-% based on the fabric.

3. The dispersible nonwoven fabric according to claim 1, wherein the fibrillated solvent spun fibers are lyocell fibers.

4. The dispersible nonwoven fabric according to claim 1, wherein the fabric has a weight of 30 to 100 g/m2, and a thickness of 0.1 to 0.7 mm.

5. The dispersible nonwoven fabric according to claim 1, wherein the fabric comprises a dispersing aid in an amount of 0.1 to 1% wt.-% based on the fabric.

6. The dispersible nonwoven fabric according to claim 1, wherein the fabric comprises a binder in an amount of 0.01 to 5 wt.-% based on the fabric.

7. The dispersible nonwoven fabric according to claim 6, wherein an acrylic resin or epichlorhydrin based wet strength resin is used as the binder.

8. The dispersible nonwoven fabric according to claim 1, wherein the pulp is a pulp selected from the group consisting of a softwood pulp, a hardwood pulp or a pulp made from plants like abaca or bamboo.

9. The dispersible nonwoven fabric according to claim 1, wherein the fabric is impregnated with a liquid or a lotion.

10. The dispersible nonwoven fabric according to claim 1, wherein the impregnated fabric has a wet tensile strength in machine direction of 2 to 20 N/5 cm, based on a basis weight of 60 g/m and in cross direction 1 to 10 N/5 cm.

11. The dispersible nonwoven fabric according to claim 1, wherein the fabric is disintegrating under agitation in water according to Tier 1 Test FG 511.2-Dispersability Tipping Tube Test of the “ED ANA Guidance Document for Assessing the Flushability of Nonwoven Consumer Products” where at least 95% of the disintegrated size fractions pass a 12 mm screen.

12. A process for production of a dispersible nonwoven fabric according to claim 1 comprising the steps of

a) Providing a dispersion of pulp and a dispersion of solvent spun fiber in water either separately or together as a mixture,

b1) Refining these dispersions separately and mixing the resulting slurries to an intimate blend to form a slurry, or,

b2) Co-refining the mixture of pulp and solvent spun fiber to form a slurry

c) Wet laying the slurry to form a sheet, and

d) Hydroentanglement of the sheet to form a fabric.

13. The process according to claim 12, wherein a dispersing agent is added to the dispersion in step a).

14. The process according to claim 12, wherein a binder is added in step b1) or b2).

15. The process according to claim 12, wherein the refining energy is from 20 to 400 kWh/t.

16. The process according to claim 12, wherein the solvent spun fibers are short cut fibers with a cut length of 2 to 20 mm and a titer of 0.9 to 6.7 dtex.

17. The process according to claim 12, wherein the fabric is sliced, folded and packed.

18. The process according to claim 12, wherein the fabric is treated with a liquid or lotion before packaging.

19. A product comprising a fabric according to claim 1.