Latex binder for nonwoven fibers and article made therewith

• US 20030105190A1
• Filed: 07/29/2002
• Published: 06/05/2003
• Est. Priority Date: 08/05/1999
• Status: Abandoned Application

• Current Assignee: OMNOVA Solutions Incorporated
• Original Assignee: OMNOVA Solutions Incorporated
• Inventors: McBain, Carla Dittman, Diehl, David F.
• Application Number:
  US10/207,517
• Publication Number:
  US 20030105190A1
• Time in Patent Office: Days
• US Class Current: 523/201
• CPC Class Codes: C08F 257/02 on to polymers of styrene or alkyl-substituted styrenes
• CPC Class Codes: C08F 265/02 on to polymers of acids, salts or anhydrides
• CPC Class Codes: C08F 8/00 Chemical modification by after-treatment graft polymers, block polymers, crosslinking with unsaturated monomers or with polymers C08F251/00 - C08F299/00; of conjugated diene rubbers C08C
• CPC Class Codes: C08F 8/44 Preparation of metal salts or ammonium salts
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 51/003 grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds C08L51/04, C08L51/06 take precedence
• CPC Class Codes: C08L 55/02 ABS [Acrylonitrile-Butadiene-Styrene] 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: D06M 15/227 of hydrocarbons, or reaction products thereof, e.g. afterhalogenated or sulfochlorinated
• CPC Class Codes: D06M 15/233 aromatic, e.g. styrene
• CPC Class Codes: D06M 15/263 of unsaturated carboxylic acids; Salts or esters thereof
• CPC Class Codes: D06M 15/693 with natural or synthetic rubber, or derivatives thereof
• CPC Class Codes: D21H 17/37 Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates

Abstract

The invention relates to a latex that may be utilized as a binder for nonwoven applications to form a permeable sublayer of personal hygiene articles. The latex is prepared by a process including the steps of (1) polymerizing a monomer mixture comprising styrene, itaconic acid, surfactant and water soluble free radical initiator to form a seed; (2) sequentially adding equal increments of a monomer mixture of styrene, butadiene and acrylic acid to the seed under emulsion polymerization conditions to form a styrene-butadiene-acrylic acid copolymer; and then (3) neutralizing the styrene-butadiene-acrylic acid copolymer to a pH of about 4.5 to 7 to form the latex.

Claims

1. A latex which is particularly beneficial for utilization as a binder for nonwoven applications made by the process which comprises the steps of:

(1) polymerizing a monomer mixture comprising styrene, itaconic acid, surfactant and water soluble free radical initiator to form a seed;

(2) adding a monomer mixture of styrene, butadiene and chain transfer agent and reacting the mixture to between 40-95% conversion;

(3) sequentially adding equal increments of a monomer mixture of styrene, butadiene, acrylic acid and optional functional monomers, in the presence of a chain transfer agent to (2) under emulsion polymerization conditions and reacting to more than 99% conversion; and

then

(4) neutralizing the copolymer from (3) to a pH of about 4.5 to 7 to form the latex.

2. The latex of claim 1 wherein the monomer mixture includes about 20-80 wt % styrene.

3. The latex of claim 1 wherein the monomer mixture also includes about 0.5-2.5 wt % itaconic acid, about 20-80 wt % butadiene and about 6-10 wt % acrylic acid.

4. The latex of claim 3 wherein the monomer mixture includes 8 wt %. acrylic acid.

5. The latex of claim 3 wherein the monomer mixture includes 2 wt % itaconic acid.

6. The latex of claim 1 wherein the monomer mixture includes about 0.05-2.0 wt % surfactant.

7. The latex of claim 1 wherein the copolymer is neutralized by addition of a base selected from potassium hydroxide, sodium bicarbonate, and ammonium hydroxide, sodium hydroxide.

8. A method for making a composite useful as a personal hygiene article which comprises:

(1) treating a nonwoven fabric with a latex binder to form a permeable sublayer, the latex prepared by a process which comprises the steps of;

(a) polymerizing a monomer mixture comprising styrene, itaconic acid, surfactant and water soluble free radical initiator to form a seed;

(b) adding a monomer mixture of styrene, butadiene and chain transfer agent and reacting the mixture to between 40-95% conversion;

(c) sequentially adding equal increments of a monomer mixture of styrene, butadiene, acrylic acid and optional functional monomers, in the presence of a chain transfer agent to (b) under emulsion polymerization conditions and reacting to more than 99% conversion; and

then

(d) neutralizing the copolymer from (c) to a pH of about 4.5 to 7 to form the latex;

(2) providing at least one fluid permeable top sheet layer and at least one substantially fluid impermeable backsheet layer; and

(3) interposing the sublayer material between the topsheet layer and backsheet layer.

9. The method of claim 8 wherein the permeable sublayer of the personal hygiene article is a web comprised of randomly arranged nonwoven fibers having an open structure and high loft.

10. The method of claim 9 wherein the web is formed by carding.

11. The method of claim 9 wherein the fibers are selected from natural textile fibers, artificial organic textile fibers, vinyl resin fibers and mixtures thereof.

12. The method of claim 9 wherein the fibers are selected from polyolefins, polyesters, acrylics, and polyamides.

13. The method of claim 12 wherein the polyolefin fibers include polypropylene, polyethylene, polybutene and their copolymers.

14. The method of claim 12 wherein the polyester fibers include any long synthetic polymer composed of at least 85% by weight of an ester of a dihydric alcohol and terephthalic acid.

15. The method of claim 12 wherein the acrylic fibers include any fiber forming substance containing a long chain synthetic polymer composed of at least 85% by weight acrylonitrile units —

CH₂ CH(CN)—

.

16. The method of claim 9 wherein the fibers are graphite fibers.

17. The method of claim 9 wherein the fibers are of a length of about 0.25 to 2 inches and about 1.2-15 denier.

18. The method of claim 8 wherein the latex binder is applied on the fiber mat is about 15-40 wt %.