Method of manufacturing monolithic structures from polyvinyl alcohol

• US 5,661,217 A
• Filed: 08/05/1994
• Issued: 08/26/1997
• Est. Priority Date: 08/05/1994
• Status: Expired due to Fees

• Current Assignee: Isolyser Co., Inc. (Ecolab, Inc.)
• Original Assignee: Isolyser Co., Inc. (Ecolab, Inc.)
• Inventors: Honeycutt, Travis W., Lee, Baosheng, Khamvongsa, Bryan
• Primary Examiner(s): Clark, W. Robinson H.
• Application Number:
  US08/286,650
• Time in Patent Office: 1,117 Days
• Field of Search: 524/803, 525/56, 525/62
• US Class Current: 525/62
• 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 3/18 Plasticising macromolecular compounds plasticisers C08K
• CPC Class Codes: C08J 5/00 Manufacture of articles or shaped materials containing macromolecular substances manufacture of semi-permeable membranes B01D67/00 - B01D71/00
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets

Abstract

A method of forming a useful molded part or film of polyvinyl alcohol. The polyvinyl alcohol, together with a plasticizer is injection or blow molded to form the useful molded part or melt processed (blown or cast extrusion) to form the film wherein upon forming the useful molded part or film, the plasticizer is substantially removed to create the useful molded part or film which is selectively hot water soluble and which is resistant to the affects of moisture below the solubility temperature.

Claims

1. A method of forming a molded part comprising a member selected from the group consisting of utensils and packaging of polyvinyl alcohol which is characterized as being water soluble only at temperatures above 70°

C., said polyvinyl alcohol being further characterized as having a degree of polymerization between approximately 1000 to 2000, being produced from at least 99% saponified polyvinyl acetate and having less than approximately 1/10% residual sodium acetate by weight, said method comprising injection or blow molding said polyvinyl alcohol with a plasticizer to create said molded part whereupon forming said molded part said plasticizer is substantially removed to the extent that said molded part contains no more than approximately 3% by weight of said plasticizer, based upon the weight of said polyvinyl alcohol contained therein.

2. The method of claim 1 wherein said polyvinyl alcohol, after removal of said plasticizer, is crystallized by heat annealing resulting in a degree of crystallinity of approximately 0.5.

3. The method of claim 1 wherein said plasticizer is added to said polyvinyl alcohol in an amount of approximately 10-40% based upon the weight of said polyvinyl alcohol.

4. The method of claim 1 wherein said plasticizer comprises a member selected from the group consisting of glycerin and polyethylene glycol.

5. The method of claim 1 wherein said plasticizer is substantially removed from said polyvinyl alcohol by adding to said polyvinyl alcohol and plasticizer, a solvent for said plasticizer and subsequently removing said solvent and plasticizer from said polyvinyl alcohol.

6. The method of claim 5 wherein said solvent comprises methanol.

11. The method of claim 1 wherein said plasticizer is substantially removed from said polyvinyl alcohol by adding to said polyvinyl alcohol and plasticizer, a solvent for said plasticizer and subsequently removing said solvent and plasticizer from said polyvinyl alcohol.

12. The method of claim 11 wherein said solvent comprises methanol.

7. A method for forming a film configured into an article selected from the group consisting of packaging, drapes, covers, overwraps, gowns, head covers, face masks, shoe covers, CSR wraps, tapes, underpads and diapers comprised of polyvinyl alcohol which is characterized as being water soluble only at temperatures above 70°

C., said polyvinyl being further characterized as having a degree of polymerization between approximately 1000-2000, being produced from at least approximately 99% saponified polyvinyl acetate and having less than approximately 1/10% residual sodium acetate by weight, said method comprising melt processing said polyvinyl alcohol with a plasticizer to form said film wherein upon forming said film, said plasticizer is substantially removed to the extent that said film contains no more than approximately 3% by weight of said plasticizer based upon the weight of said polyvinyl alcohol contained therein.

8. The method of claim 7 wherein said polyvinyl alcohol after removal of said plasticizer is crystallized by postdrawing or by heat annealing resulting in a degree of crystalllinity of approximately 0.7.

9. The method of claim 7 wherein said plasticizer is added to said polyvinyl alcohol in an amount approximately 10-40% based upon the weight of said polyvinyl alcohol.

10. The method of claim 7 wherein said plasticizer comprises a member selected from the group consisting of glycerin and polyethylene glycol.

13. The method of claim 7 wherein said film of polyvinyl alcohol is made from a process selected from the group consisting of blow extrusion and cast extrusion.