Bonded nonwoven fabrics suitable for diaper coverstock

• US 4,356,229 A
• Filed: 10/20/1980
• Issued: 10/26/1982
• Est. Priority Date: 12/04/1978
• Status: Expired due to Term

• Current Assignee: Rohm and Haas Company (Dow, Inc.)
• Original Assignee: Rohm and Haas Company (Dow, Inc.)
• Inventors: Gill, Robert A., Brodnyan, John G., Stelling, Gary D., De Witt, Walter G. III
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): Buffalow, E. Rollins
• Application Number:
  US06/198,426
• Time in Patent Office: 736 Days
• Field of Search: 428/288, 428/297, 428/913, 128/284, 128/287, 128/155, 128/156, 260/29.6 TA
• US Class Current: 442/86
• CPC Class Codes: A61L 15/225 Mixtures of macromolecular compounds
• CPC Class Codes: C08F 220/1802 C2-(meth)acrylate, e.g. ethyl (meth)acrylate
• CPC Class Codes: C08F 220/1804 C4-(meth)acrylate, e.g. butyl (meth)acrylate, isobutyl (meth)acrylate or tert-butyl (meth)acrylate
• CPC Class Codes: C08L 33/00 Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
• CPC Class Codes: D04H 1/587 characterised by the bonding agents used
• CPC Class Codes: D04H 1/64 the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
• CPC Class Codes: Y10T 442/2221 Coating or impregnation is specified as water proof

Abstract

This invention concerns a nonwoven fabric particularly adapted for use as a diaper coverstock. The fabric consists essentially of fibers and a binder wherein at least 50%, by weight, of the fibers are hydrophobic fibers. The binder comprises a water insoluble, hydrophobic, emulsion copolymer of ethylenically unsaturated monomers comprising (A) 1 to 8% by weight of a monoethylenically unsaturated carboxylic acid, or a mixture thereof, (B) 50 to 75% by weight of a C₄ to C₈ alkyl acrylate or a mixture thereof, and (C) 20 to 49% by weight of methyl methacrylate, styrene, α-methyl styrene or a mixture thereof. The fabric has sufficient wet tensile strength for use as a diaper coverstock.

Claims

1. A nonwoven fabric consisting essentially of fibers and a binder,

(A) at least 50%, by weight, of the fibers being hydrophobic fibers having a moisture regain less than 2.5% of the fiber weight at 70°

F. and 65% RH,

(B) the binder being free of formaldehyde condensates and comprising a water-insoluble, hydrophobic, emulsion copolymer of ethylenically unsaturated monomers comprising

(a) 1 to 8%, by weight, of a monoethylenically unsaturated carboxylic acid or a mixture thereof.

(b) 50 to 75%, by weight, of a C₄ to C₈ alkyl acrylate or a mixture thereof, and

(c) 20 to 49%, by weight, of one or more hard monomers, and

(C) the fabric having a water-wet tensile strength, determined on a 2.5 cm wide specimen having a dry weight between 23 and 26 g/m², of at least 1.5 kg.

2. The fabric of claim 1, the hard monomers being one or more of methyl methacrylate, sytrene and α

-methyl styrene.

3. The fabric of claim 2, the molecular weight of the copolymer being greater than 100,000, the binder being from about 10% to 100% of the dry fiber by weight, and the acid being acrylic, methacrylic or a mixture thereof.

4. The fabric of claim 3, the copolymer being thermoplastic, having a glass transition temperature below 30°

C. and being a copolymer of monomers other than acrylonitrile.

5. The fabric of claim 4, the hydrophobic fibers being polyester fibers, the copolymer having a weight average molecular weight greater than 300,000, the monomers comprising 1 to 5% acid monomers and the wet tensile strength being at least 2.0 kg.

6. The fabric of claim 5, the copolymer being from 20 to 50% of the dry fiber by weight, the fibers being in a carded array and consisting essentially of polyester fibers.

7. The fabric of claim 6 wherein the monomers comprise (a) 2 to 4% by weight of acid monomers and (b) 55 to 70% by weight of butyl acrylate.

8. The fabric of claim 4, the hydrophobic fibers being polyolefin fibers and the monomers comprising (a) 1 to 6% by weight of acid, (b) 55 to 70% by weight of a C₄ to C₈ alkyl acrylate or a mixture thereof and (c) 25 to 40% by weight of styrene, α

-methyl styrene or a mixture thereof.

9. The fabric of claim 8, a major proportion of the fibers being polypropylene fibers, the copolymer having a weight strength being at least 2.0 kg.

10. The fabric of claim 9, the fibers being in a carded array and consisting essentially of polypropylene fibers and the copolymer being from 30% to 60% of the dry fiber by weight.

11. The fabric of claim 10, the monomers comprising (a) 2 to 4% acid monomers, (b) 55 to 70% butyl acrylate and (c) 28 to 40% styrene.

12. The fabric of claim 8 comprising fluorocarbon surfactant up to 2% by weight of the binder.

13. The fabric of claim 7, the surfactant having surface tensions of about 24 and 23 dynes/cm at 0.01% and 0.1, by weight in water, respectively.

14. The fabric of claim 11 comprising a nonionic fluorocarbon surfactant up to 2% by weight of the binder.

15. The fabric of claim 14, the surfactant having surface tensions of about 24 and 23 dynes/cm at 0.01% and 0.1%, by weight in water, respectively.

16. A process of making a nonwoven, wet-strength fabric which comprises associating the hydrophobic fibers and the emulsion copolymer of claim 1 and drying the fibrous product to render it water resistant.

17. A process of making a nonwoven, wet-strength fabric which comprises associating the hydrophobic fibers and the emulsion copolymer of claim 5 and drying the fibrous product to render it water-resistant.

18. A process of making a nonwoven, wet-strength fabric which comprises associating the hydrophobic fibers and the the emulsion copolymer of claim 8 and drying the fibrous product to render it water-resistant.

19. A disposable sanitary product comprising the fabric of claim 1 as a facing layer adapted to be positioned in contact with a wearer or user.

20. A disposable sanitary product comprising the fabric of claim 5 as a facing layer adapted to be positioned in contact with a wearer or user.

21. A disposable sanitary product comprising the fabric of claim 8 as a facing layer adapted to be positioned in contact with a wearer or user.

22. The fabric of claim 1 in the form of diaper coverstock.

23. The fabric of claim 7 in the form of diaper coverstock.

24. The fabric of claim 11 in the form of diaper coverstock.