# US 8,785,714 B2 · Alkali neutralizing acquisition and distribution structures for use in personal care articles

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- Number: US 8,785,714 B2
- Document ID: US8785714B2
- Status: Granted
- Kind: B2
- Application number: 13/036,606
- Filed: 2011-02-28
- Published: 2012-08-30
- Granted: 2014-07-22
- Earliest claimed: 2011-02-28
- Assignees: Celanese International Corporation
- Applicants: Philip Confalone; Rajeev Farwaha
- Inventors: Philip Confalone; Rajeev Farwaha
- Web page: https://patentgrep.com/patent/US8785714B2

## CPC

- A61F 13/537: characterised by a layer facilitating or inhibiting flow in one direction or plane, e.g. a wicking layer {(A61F13/538 takes precedence)}
- A61F 13/8405: {Additives, e.g. for odour, disinfectant or pH control}
- A61L 15/24: Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof {(A61L15/225 takes precedence)}
- Y10T 442/2484: Coating or impregnation is water absorbency-increasing or hydrophilicity-increasing or hydrophilicity-imparting
- Y10T 442/2738: Coating or impregnation intended to function as an adhesive to solid surfaces subsequently associated therewith
- A61F: FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS (dental prosthetics A61C)
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Disclosed herein are nonwoven fibrous structures for use as body fluid acquisition/distribution elements in personal care products. Such structures comprise natural and/or synthetic fibers wherein the fibers have been consolidated by application thereto, and by cross-linking of, a certain type of cross-linkable, vinyl acetate-ethylene (VAE) emulsion copolymer latex binder. The VAE latex binder is one which also comprises an added organic acidulant such as citric acid. Consolidation of the structures with VAE-based binders to which the organic acidulant has been added imparts to the resulting structures the ability to lower the pH of body fluids such as urine passing through the structures. This effect, in turn, provides odor control and skin care benefits to the absorbent articles, e.g., diapers and adult incontinence products, using such structures as acquisition/distribution elements.

## Claims

### Claim 1

A nonwoven fibrous structure for use as a body fluid acquisition/distribution element in a personal care product, said structure comprising natural or synthetic fibers, or combinations of said fibers, which fibers have been consolidated by application thereto, and by cross-linking of, a cross-linkable, vinyl acetate-ethylene (VAE) emulsion copolymer latex binder, said latex binder comprising from about 1.0 wt % to about 5.0 wt % based on total monomer content of said copolymer of an organic acidulant.

### Claim 2 (depends on 1)

The nonwoven fibrous structure according to claim 1, wherein the synthetic fibers comprise polyester fibers.

### Claim 3 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the natural fibers comprise fluff pulp fibers.

### Claim 4 (depends on 3)

The nonwoven fibrous structure according to claim 3 wherein the fluff pulp fibers comprise cellulosic fluff pulp fibers.

### Claim 5 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the fibers in the structure comprise a blend of from about 40 to about 60 weight % of synthetic fibers and from about 40 to about 60 weight % of natural fibers.

### Claim 6 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the synthetic fibers are crimped.

### Claim 7 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the fibrous structure comprises an airlaid, carded, or airlaid and carded web.

### Claim 8 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the cross-linkable VAE emulsion copolymer in the latex binder comprises from about 75 to about 90 pphm of vinyl acetate; from about 10 to about 25 pphm of ethylene and from about 1 to about 10 pphm of at least one additional cross-linkable co-monomer.

### Claim 9 (depends on 8)

The nonwoven fibrous structure according to claim 8 wherein said at least one additional cross-linkable co-monomer comprises cross-linkable N-methylol groups or their derivatives which are etherified with C1-C6 alkanols.

### Claim 10 (depends on 9)

The nonwoven fibrous structure according to claim 9 wherein the additional cross-linkable co-monomers are derived from N-methylol amides of acrylic acid and methacrylic acid.

### Claim 11 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the crosslinked copolymer of the latex binder has a glass transition temperature, Tg, in the range from about −10° C. to about +30° C.

### Claim 12 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the cross-linkable emulsion copolymer latex binder comprises as a stabilizer at least one emulsifier which is an anionic emulsifier and/or a nonionic emulsifier.

### Claim 13 (depends on 1)

The nonwoven fibrous structure according to claim 1 wherein the organic acidulant in the latex binder is a mono- or poly-carboxylic acid having from about 2 to about 12 carbon atoms and a pKa in water of from about 2 to about 7.

### Claim 14 (depends on 13)

The nonwoven fibrous structure according to claim 13 wherein the organic acidulant in the latex binder is selected from oxalic acid, succinic acid, adipic acid, glutaric acid, tartaric acid, citric acid, and combinations thereof.

### Claim 15 (depends on 13)

The nonwoven fibrous structure according to claim 13 wherein the organic acidulant is citric acid.

### Claim 16 (depends on 1)

A personal care product in the form of an infant diaper or an adult incontinence product, wherein said personal care product comprises a topsheet, an absorbent fluid storage core and at least one nonwoven fibrous structure according to claim 1 interposed as an acquisition/distribution layer between said topsheet and said absorbent fluid storage core.

### Claim 17 (depends on 1)

The nonwoven fibrous structure according to claim 1, which comprises 5 to 40 wt % of said cross-linkable VAE emulsion copolymer latex binder.

### Claim 18

A nonwoven fibrous structure for use as a body fluid acquisition/distribution element in a personal care product, said structure comprising natural or synthetic fibers, or combinations of said fibers, which fibers have been consolidated by application thereto, and cross-linking of, a cross-linkable vinyl acetate-ethylene (VAE) emulsion copolymer latex binder, said latex binder comprising an organic acidulant in an amount which is effective to lower the pH of body fluid which passes through said structure to the extent of at least about 1.2 pH units.

### Claim 19

A process for preparing a nonwoven fibrous structure suitable for use as a body fluid acquisition/distribution element in a personal care product, which process comprises:
(a) providing an aqueous emulsion copolymer latex binder comprising an cross-linkable ethylene-vinyl acetate copolymer which is the emulsion polymerization product of from about 10 to about 25 pphm of ethylene; from about 75 to about 90 pphm of vinyl acetate; and from about 1 to about 10 pphm of at least one additional cross-linkable co-monomer;
(b) adding to said aqueous emulsion copolymer latex binder from about 1.0 to about 5.0 weight percent based on total weight of monomers in said emulsion copolymer of an organic acidulant;
(c) contacting said acidulant-containing aqueous emulsion copolymer latex binder with a nonwoven fibrous structure comprising wet-laid or dry-laid natural and/or synthetic fibers to form a latex binder-containing nonwoven fibrous structure; and thereafter
(d) subjecting said latex binder-containing nonwoven fibrous structure to curing conditions sufficient to cross-link said copolymer and to thereby form an acidulant-containing, consolidated nonwoven fibrous structure.

### Claim 20 (depends on 19)

The process according to claim 19 wherein the synthetic fibers of the nonwoven fibrous structure comprise polyester fibers.

### Claim 21 (depends on 19)

The process according to claim 19 wherein the natural fibers of the nonwoven fibrous structure comprise fluff pulp fibers.

### Claim 22 (depends on 21)

The process according to claim 21 wherein the nonwoven fibrous structure fibers comprise cellulosic fluff pulp fibers.

### Claim 23 (depends on 19)

The process of claim 19 wherein the fibers in the nonwoven fibrous structure comprise a blend of from about 40 to about 60 weight % of synthetic fibers and from to about 40 to about 60 weight % of natural fibers.

### Claim 24 (depends on 19)

The process according to claim 19 wherein the synthetic fibers of the nonwoven fibrous structure are crimped.

### Claim 25 (depends on 19)

The process according to claim 19 wherein the nonwoven fibrous structure comprises an airlaid, carded, or airlaid and carded web.

### Claim 26 (depends on 19)

The process according to claim 19 wherein the additional cross-linkable co-monomers of the ethylene-vinyl acetate copolymer comprise cross-linkable N-methylol groups or their derivatives which are etherified with C1-C6 alkanols.

### Claim 27 (depends on 26)

The process according to claim 26 wherein the additional cross-linkable co-monomers are derived from N-methylol amides of acrylic acid and methacrylic acid.

### Claim 28 (depends on 19)

The process according to claim 19 wherein the crosslinked copolymer of the latex binder has a glass transition temperature, T.sub.g, in the range from about −10° C. to about +30° C.

### Claim 29 (depends on 19)

The process according to claim 19 wherein the cross-linkable emulsion copolymer latex binder comprises as a stabilizer at least one emulsifier which is an anionic emulsifier and/or a nonionic emulsifier.

### Claim 30 (depends on 19)

The process according to claim 19 wherein the organic acidulant which is added to the latex binder is a mono- or poly-carboxylic acid having from about 2 to about 12 carbon atoms and a pKa in water of from about 2 to about 7.

### Claim 31 (depends on 30)

The process according to claim 30 wherein the organic acidulant which is added to the latex binder is carboxylic acid selected from oxalic acid, succinic acid, adipic acid, glutaric acid, tartaric acid, citric acid, and combinations thereof.

### Claim 32 (depends on 30)

The process according to claim 30 wherein the organic acidulant is citric acid.

### Claim 33

A nonwoven fibrous structure for use as a body fluid acquisition/distribution element in a personal care product, said structure comprising natural or synthetic fibers, or combinations of said fibers, which fibers have been consolidated by application thereto, and by cross-linking of, a cross-linkable, vinyl acetate-ethylene (VAE) emulsion copolymer latex binder, said latex binder comprising from about 1.0 wt % to about 5.0 wt % based on total monomer content of said copolymer of an organic acidulant in admixture therewith.