Water-swellable material comprising coated water-swellable polymers

• US 20050031868A1
• Filed: 08/05/2004
• Published: 02/10/2005
• Est. Priority Date: 08/06/2003
• Status: Active Grant

• Current Assignee: The Procter & Gamble Company
• Original Assignee: The Procter & Gamble Company
• Inventors: Fossum, Renae Dianna, Schmidt, Mattias, Meyer, Axel
• Granted Patent: US 7,049,000 B2
• Time in Patent Office: Days
• US Class Current: 428/375
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 2333/00 Characterised by the use 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; Derivatives of such polymers
• CPC Class Codes: C08J 3/12 Powdering or granulating
• CPC Class Codes: C08J 3/126 Polymer particles coated by polymer, e.g. core shell structures
• CPC Class Codes: Y10T 428/239 Complete cover or casing
• CPC Class Codes: Y10T 428/23929 Edge feature or configured or discontinuous surface
• CPC Class Codes: Y10T 428/2933 Coated or with bond, impregnation or core
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

This invention relates to a water-swellable material comprising water-swellable polymers that are coated with a coating agent that comprises a phase-separating elastomeric material, which allows swelling of the water-swellable polymers, without breakage of the coating. The invention also relates to a process of making specific coated water-swellable polymers using a phase-separating elastomeric material, and materials obtainable by such a process.

Claims

1. A water-swellable material, comprising water-swellable polymers that are coated with a coating agent, which comprises an elastomeric material that is phase-separating, having at least a first phase with a first glass transition temperature Tg₁ and a second phase with a second glass transition temperature Tg₂,

2. A water swellable material according to claim 1 wherein the difference between Tg₁ and Tg₂ is at least 30°

C.

3. A process for making a water-swellable material that comprises coated water-swellable polymer particles, said process comprising the steps of:

a) obtaining water-swellable polymer particles;

b) applying a coating agent, wherein said coating agent of step b) comprises an elastomeric phase-separating material that has at least a first phase with a first glass transition temperature Tg₁ and a second phase with a second glass transition temperature Tg₂, to at least a part of said water-swellable polymer particles; and

optionally the step of

c) annealing the resulting coated water-swellable polymer particles of step b), so as to obtain said water-swellable material.

4. A process according to claim 3 wherein the coating agent is applied subsequent to step (a).

5. A process according to claim 3 wherein said coating agent is wet-extensible and has a wet-elongation at break of at least 400% and a tensile stress at break in the wet state of at least 1 MPa.

6. A process according to claim 3, wherein the coating agent has, in the wet state, a wet secant elastic modulus at 400% (SM_wet400%) elongation of at least 0.5 MPa.

7. A process according to claim 4, wherein the coating agent has, in the dry state, a dry secant modulus at 400% elongation (SM_dry400%) and a wet secant modulus at 400% elongation (SM_wet400%), wherein the ratio of SM_wet400% to SM_dry400% is between 1.4:

1.0 to 0.6;

1.0.

8. A process according to claim 3, wherein said coating agent has a Moisture Vapour Transmission Rate (MVTR) of at least 800 g/m²/day.

9. A water-swellable material comprising coated water-swellable polymer particles produced according to the process of claim 3.

10. A process according to claim 3 wherein said elastomeric phase-separating material has a Tg₁ of less than 20°

C. and a Tg₂ of more than 50°

C.

11. A water- process according to process according to claim 3, wherein the elastomeric material is a block copolymeric material, having a molecular weight of at least 50 kDa.

12. A process according to claim 11 wherein said coating agent comprises at least one block copolymer selected from the group consisting of polyurethane-co-polyethers, polyurethane-co-polyesters, polyurethane/urea-co-polyethers, polyurethane/urea-co-polyesters, polystyrene block copolymers and blends thereof.

13. A process according to claim 3 wherein at least a portion of said water-swellable polymer particle are individually coated by the coating agent in the form of a continuous shell around, said shell having an average caliper of 1 μ

m to 50 μ

m.

14. A water-swellable material of claim 11 wherein said shell is substantially uniform with a ratio of smallest to largest caliper from 1:

1 to 1;

3.