Process for producing a low water content PVA hydrogel

• US 4,988,761 A
• Filed: 04/26/1989
• Issued: 01/29/1991
• Est. Priority Date: 09/22/1988
• Status: Expired due to Fees

• Current Assignee: Bio-Materials Univers Company, Dow Corning Kabushiki Kaisha, Kyocera Corporation
• Original Assignee: Bio-Materials Univers Company, Dow Corning Kabushiki Kaisha, Kyocera Corporation
• Inventors: Ikada, Yoshito, Gen, Shokyu
• Primary Examiner(s): Schofer, Joseph L.
• Assistant Examiner(s): REDDICK, MARIE L
• Application Number:
  US07/343,468
• Time in Patent Office: 643 Days
• Field of Search: 524/557, 525/61
• US Class Current: 524/557
• CPC Class Codes: A61L 27/16 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: A61L 27/52 Hydrogels or hydrocolloids
• CPC Class Codes: C08J 2329/04 Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
• CPC Class Codes: C08J 3/03 in aqueous media
• CPC Class Codes: C08J 3/09 in organic liquids
• CPC Class Codes: C08L 29/04 Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Abstract

The present invention relates to a method of producing polyvinyl alcohol hydrogel characterized by the following features: the production process consists of a low-temperature processing stage in which the solution of polyvinyl alcohol with a polymerization degree over 1200 is processed at a low temperature so that polyvinyl alcohol is gelated, and a high-temperature processing stage in which the polyvinyl alcohol gelated int he low-temperature processing stage is dried, then processed at higher than 100° C.; in this way, polyvinyl alcohol hydrogel with a saturated water content lower than 40 wt % is obtained. The hydrogels of this invention are useful for providing improved artificial articular cartilage for replacement of cartilage in the human body.

Claims

1. A process of producing polyvinyl alcohol hydrogel comprising (A) subjecting a solution in a mixture of water and water-miscible organic solvent of polyvinyl alcohol with a polymerization degree over 1200, to a temperature below -5°

C. so that the polyvinyl alcohol is gelated, (B) drying said hydrogel at an elevated temperature so that it contains less than about 3% by weight of water, (C) subjecting said hydrogel to a temperature higher than 100°

C. for a time sufficient to reduce the size of the PVA crystals in said hydrogel, (D) saturating the resulting hydrogel with water, whereby polyvinyl alcohol hydrogel with a saturated water content lower than 40 wt % is obtained.

2. A process according to claim 1 wherein said PVA has a degree of saponification higher than 95 mol %.

3. A process according to claim 1 wherein said polyvinyl alcohol has an average degree of polymerization over 1500.

4. A process according to claim 1 wherein the ratio of water to organic solvent is between 5:

95 and 30;

70.

5. A process according to claim 1 wherein said hydrogel is dried to a water content of less than 3% by weight.

6. A process according to claim 1 wherein said heating step is carried out in a vacuum, an inert gas, or an inert liquid.

7. A process according to claim 6 wherein said heating step is carried out between 120°

C. and 160°

C.