Preparation of biaxially oriented polyvinyl alcohol film
US3985849A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 8, 1974 |
| Grant date | Oct 12, 1976 |
| Priority date | — |
| Expiry date | Nov 8, 1994 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2035/0855
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
Method for preparing a biaxially oriented polyvinyl alcohol film by extruding a mixture of polyvinyl alcohol and water, and if desired, incorporated with a polyhydric alcohol, in a tubular form, drying the tubular film to give a tubular non-stretched film having a degree of crystallization of not more than 44 % and a water content of not more than 20 % by weight, and biaxially stretching the non-stretched film at a stretching ratio of not less than 2 in each of the machine and transverse directions by means of inflation under conditions such that the film surface at the starting point of stretching is maintained at a temperature in the range from about 60.degree. to about 150.degree.C., the surface of the film reaching a maximum temperature at the middle portion of a stretching zone extending from said starting point to a point where the tube reaches a maximum diameter and the difference between maximum and minimum surface temperatures in the stretching zone does not vary more than about 15.degree.C. The prepared biaxially oriented film is excellent in tensile strength, dimensional stability and impact resistance at low temperature, and has a tensile strength of not less than 1,200…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.