Porous, absorbent, polymeric macrostructures and methods of making the same

• US 5,102,597 A
• Filed: 05/24/1991
• Issued: 04/07/1992
• Est. Priority Date: 04/02/1990
• Status: Expired due to Term

• Current Assignee: The Procter & Gamble Company
• Original Assignee: The Procter & Gamble Company
• Inventors: Roe, Donald C., Berg, Charles J., Lahrman, Frank H.
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US07/705,451
• Time in Patent Office: 319 Days
• Field of Search: 264/126, 521/84.1, 521/88, 521/94, 521/95, 521/142, 521/149, 521/919
• US Class Current: 264/126
• CPC Class Codes: A61F 13/15626 Making fibrous pads without outer layers
• CPC Class Codes: A61F 13/51 characterised by the outer layers wicking or transfer layers A61F13/537
• CPC Class Codes: A61F 13/534 having an inhomogeneous composition through the thickness of the pad A61F13/538, A61F13/539 take precedence; homogeneous cores with tissue wrapping A61F13/53
• CPC Class Codes: 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
• CPC Class Codes: A61F 2013/49031 being elastic in longitudinal direction
• CPC Class Codes: A61F 2013/49076 as "I"-shaped
• CPC Class Codes: A61F 2013/51409 being a film
• CPC Class Codes: A61F 2013/530007 being made from pulp
• CPC Class Codes: A61F 2013/530569 characterized by the particle size
• CPC Class Codes: A61F 2013/530598 in aggregates
• CPC Class Codes: A61F 2013/530642 being cross-linked or polymerised in situ
• CPC Class Codes: A61F 2013/5307 characterized by the quantity or ratio of superabsorbent material
• CPC Class Codes: A61F 2013/530708 characterized by the absorbency properties
• CPC Class Codes: A61F 2013/530766 by the cross-link factor
• CPC Class Codes: A61F 2013/8491 including test methods
• 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: B32B 2305/026 Porous
• CPC Class Codes: B32B 2307/726 Permeability to liquids, absorption
• CPC Class Codes: B32B 2307/7265 Non-permeable
• CPC Class Codes: C08J 2201/05 : Elimination by evaporation or heat degradation of a liquid phase
• CPC Class Codes: C08J 2207/12 : Sanitary use, e.g. diapers, napkins or bandages
• CPC Class Codes: C08J 9/28 : by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• CPC Class Codes: Y10S 521/919 : Sintered product
• CPC Class Codes: Y10T 428/234 : including elements cooperating to form cells
• CPC Class Codes: Y10T 428/239 : Complete cover or casing
• CPC Class Codes: Y10T 428/249964 : Fibers of defined composition
• CPC Class Codes: Y10T 428/249986 : Void-containing component contains also a solid fiber or solid particle

Abstract

Absorbent polymeric macrostructures that are porous and comprise an interparticle crosslinked aggregate having a circumscribed dry volume greater than about 10.0 mm³. The interparticle crosslinked aggregate comprises a multiplicity of precursor particles of substantially water-insoluble, absorbent, hydrogel-forming, polymer material; and an interparticle crosslinking agent reacted with the polymer material of the precursor particles to form crosslink bonds between the precursor particles. Because of the particulate nature of the precursor particles, the macrostructure has pores between adjacent precursor particles. The pores are interconnected by intercommunicating channels such that the macrostructure is liquid permeable.

Claims

1. A method for producing a porous, absorbent, polymeric macrostructure comprising an interparticle crosslinked aggregate having pores interconnected by intercommunicating channels so that the macrostructure is liquid permeable, the method comprising the steps of:

(a) providing a multiplicity of precursor particles of substantially water-insoluble, absorbent, hydrogel-forming, polymer material;

(b) applying an interparticle crosslinking agent onto said precursor particles, said interparticle crosslinking agent being capable of reacting with said polymer material of said precursor particles;

(c) physically associating said precursor particles to form an aggregate having pores interconnected by intercommunicating channels; and

(d) reacting said interparticle crosslinking agent with said polymer material of said precursor particles of said aggregate, while maintaining the physical association of said precursor particles, to form crosslink bonds between said precursor particles to form an interparticle crosslinked aggregate macrostructure.

2. The method of claim 1 additionally comprising the step of surface crosslinking the macrostructure.

3. The method of claim 1 additionally comprising the step of shaping the aggregate to a desired shape, size, and/or density prior to step (d).

4. The method of claim 1 wherein step (d) comprises heating.

5. The method of claim 1 additionally comprising the step of adding reinforcing fibers to said precursor particles.

6. The method of claim 1 wherein said interparticle crosslinking agent comprises a monomer that is polymerized to form polymeric crosslink bonds between said precursor particles.

7. The method of claim 6 wherein step (d) comprises the step of initiating the polymerization reaction by irradiating said monomer.

8. The method of claim 1 wherein said precursor particles have a mass average particle size less than about 500 microns.

9. The method of claim 1 wherein said precursor particles have a mass average particle size less than about 300 microns.

10. The method of claim 1 wherein said precursor particles comprise fibers.

11. A method for producing a porous, absorbent, polymeric macrostructure comprising an interparticle crosslinked aggregate having pores interconnected by intercommunicating channels so that the macrostructure is liquid permeable, the method comprising the steps of:

(a) providing a multiplicity of substantially dry precursor particles of substantially water-insoluble, absorbent, hydrogel-forming, polymer material, said polymer material of said precursor particles being selected from the group consisting of hydrolyzed starch-acrylonitrile graft copolymer;

partially neutralized starch-acrylonitrile graft copolymer;

starch-acrylic acid graft copolymer;

partially neutralized starch-acrylic acid graft copolymer;

saponified vinyl acetate-acrylic ester copolymers;

hydrolyzed acrylonitrile or acrylamide copolymers;

slightly network crosslinked products of any of the foregoing copolymers;

partially neutralized polyacrylic acid;

or slightly network crosslinked products of partially neutralized polyacrylic acid;

(b) applying an interparticle crosslinking agent onto said precursor particles, said interparticle crosslinking agent being selected from the group consisting of polyhydric alcohol compounds, polyglycidyl ether compounds, polyfunctional aziridine compounds, polyfunctional amine compounds, and polyfunctional isocyanate compounds;

(c) physically associating said precursor particles to form an aggregate having pores interconnected by intercommunicating channels;

(d) shaping the aggregate to a desired shape, size, and/or density; and

(e) subsequently heating said interparticle crosslinking agent and said aggregate to react said interparticle crosslinking agent with said polymer material of said precursor particles of said aggregate, while maintaining the physical association of said precursor particles, to form crosslink bonds between said precursor particles to form an interparticle crosslinked aggregate macrostructure.

12. The method of claim 11 additionally comprising the step of adding fibers to said precursor particles prior to reacting said interparticle crosslinking agent with said polymer material of said precursor particles.

13. The method of claim 11 additionally comprising the step of surface crosslinking the macrostructure.

14. The method of claim 11 wherein said precursor particles comprise fibers.

15. The method of claim 11 wherein said interparticle crosslinking agent is mixed with water, an organic solvent, or mixtures thereof.

16. The method of claim 15 wherein step (d) comprises molding the aggregate.

17. The method of claim 15 wherein step (d) comprises forming the aggregate.

18. The method of claim 17 wherein step (d) comprises extruding said aggregate and subsequently rolling said aggregate to form a sheet.

19. The method of claim 11 wherein said interparticle crosslinking agent is selected from the group consisting of trimethylol propane, ethylene glycol, 1,2-propanediol, 1,3-propanediol, or glycerol;

and said polymer material consists essentially of slightly network crosslinked products of partially neutralized polyacrylic acid.

20. The method of claim 19 wherein step (e) is carried out at a temperature in the range of from about 170°

C. to about 220°

C. for between about 3 hours and about 30 minutes.

21. The method of claim 20 wherein said interparticle crosslinking agent is mixed with water, an organic solvent, or mixtures thereof.

22. The method of claim 21 wherein step (d) comprises the steps of extruding the aggregate and then rolling said aggregate to form a sheet.

23. The method of claim 22 wherein step (b) comprises atomizing said interparticle crosslinking agent onto said precursor particles.

24. The method of claim 22 wherein the mass average particle size of said precursor particles is less than about 300 microns.

25. The method of claim 24 wherein at least about 95% by weight of said precursor particles have a particle size between about 150 microns and about 300 microns.

26. The method of claim 22 wherein the mass average particle size of said precursor particles is less than about 180 microns;

and at least about 95% by weight of said precursor particles have a particle size between about 90 microns and about 180 microns.

27. The method of claim 19, 24, 25, or 26 additionally comprising the step of surface crosslinking said precursor particles of said macrostructure simultaneously with step (e).

28. The method of claim 14, 19, 21, or 24 additionally comprising the step of adding reinforcing fibers to said precursor particles prior to reacting said polymer material of said precursor particles with said interparticle crosslinking agent.