Superabsorbent polymer foam

• US 5,338,766 A
• Filed: 03/26/1993
• Issued: 08/16/1994
• Est. Priority Date: 03/26/1993
• Status: Expired due to Term

• Current Assignee: The Procter & Gamble Company
• Original Assignee: The Procter & Gamble Company
• Inventors: Trokhan, Paul D., Phan, Dean V.
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US08/038,580
• Time in Patent Office: 508 Days
• Field of Search: 521/65, 521/64, 521/149, 521/69, 521/72, 521/63
• US Class Current: 521/63
• CPC Class Codes: A61L 15/24 Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof A61L15/225 takes precedence
• CPC Class Codes: A61L 15/425 Porous materials, e.g. foams or sponges
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08L 33/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof
• CPC Class Codes: C08L 35/00 Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical, and containing at least one other carboxyl radical in the molecule, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
• CPC Class Codes: Y10T 428/2481 including layer of mechanically interengaged strands, strand-portions or strand-like strips
• CPC Class Codes: Y10T 428/24851 Intermediate layer is discontinuous or differential
• CPC Class Codes: Y10T 428/249975 Void shape specified [e.g., crushed, flat, round, etc.]
• CPC Class Codes: Y10T 428/249979 Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
• CPC Class Codes: Y10T 428/24998 Composite has more than two layers
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 442/652 Nonwoven fabric is coated, impregnated, or autogenously bonded

Abstract

An improved superabsorbent polymer foam having a morphology to provide improved absorptive properties is disclosed. The foam preferably comprises a superabsorbent polymer formed from a substantially water-soluble, unsaturated monomer having neutralized carboxyl groups and a substantially water-soluble internal crosslinking agent. The monomer and crosslinking agent are expanded in the presence of a substantially water-insoluble blowing agent and a suitable solvent and reacted to form a superabsorbent polymer foam having substantially continuous, intercommunicating channels substantially throughout the foam and a relatively high surface area to mass ratio.

Methods for making the foam and absorbent products, members and articles containing the foam are also disclosed.

Claims

1. A superabsorbent polymer foam comprising a plurality of mutually connected struts of superabsorbent polymer material to form open cells, said foam having:

(a) a surface area to mass ratio of at least about 0.2 m² /g;

(b) an average cell size of less than about 100 microns; and

(c) a density of less than about 0.5 g/cm³.

2. The superabsorbent polymer foam of claim 1 having an average cell size of less than about 50 microns.

3. The superabsorbent polymer foam of claim 1 having an average cell size of less than about 20 microns.

4. The superabsorbent polymer foam of claim 1, 2, or 3 further characterized by a cell size distribution value of less than about 5.

5. A superabsorbent polymer foam comprising a plurality of mutually connected struts of superabsorbent polymer material to form open cells, said superabsorbent polymer material comprising reactants capable of forming said superabsorbent polymer material, said reactants being capable of being made substantially soluble in a solvent;

said reactants being expanded in the presence of (i) said solvent and (ii) a blowing agent which is substantially insoluble in said solvent to form an expanded structure;

said reactants being reacted to form a superabsorbent polymer material which is substantially insoluble in said solvent;

the superabsorbent polymer foam having;

(a) a surface area to mass ratio of at least about 0.2 m² /g;

(b) an average cell size of less than about 100 microns; and

(c) a density of less than about 0.5 g/cm³.

6. The superabsorbent polymer foam of claim 5 wherein said reactants comprise:

(a) a substantially water-soluble, unsaturated monomer comprising neutralized carboxyl groups; and

(b) a substantially water-soluble internal crosslinking agent which is capable of reacting with said monomer to form a substantially water-insoluble polymer material.

7. The superabsorbent polymer foam of claim 6 wherein said monomer is selected from the group consisting of acrylic acid, maleic acid, methacrylic acid, fumaric acid, itaconic acid, maleic arthydride, ethylacrylate, butylacrylate, and mixtures thereof.

8. The superabsorbent polymer foam of claim 7 wherein said internal crosslinking agent is selected from the group consisting of N,N'"'"'-methylenebisacrylamide, triallylamine, triallylphosphate, and di- or polyglycidyl ethers of aliphatic polyvalent alcohols.

9. The superabsorbent polymer foam of claim 8 wherein said solvent is selected from the group consisting of water, lower alcohols, or mixtures thereof.

10. The superabsorbent polymer foam of claim 9 wherein said blowing agent comprises a substantially water-insoluble compound having a vaporization temperature of less than about 50°

C.

11. The superabsorbent polymer foam of claim 10 wherein said internal crosslinking agent is expanded and reacted with said monomer in the presence of a surfactant, an initiator, a viscosity control agent, or mixtures thereof.

12. The superabsorbent polymer foam of claim 6 or 11 having an average cell size of less than about 50 microns and a cell distribution value of from about 1 to about 3.

13. The superabsorbent polymer foam of claim 6 wherein said superabsorbent polymer material additionally comprises an external crosslinking agent.

14. The superabsorbent polymer foam of claim 6 wherein the superabsorbent polymer foam is flexibilized by a plasticizer.