| 摘要 |
941,743. Polyvinyl alcohol films. SHIN NIPPON CHISSO HIRYO KABUSHIKI KAISHA. July 12, 1961, No. 25284/61. Heading B5B. [Also in Division C3] Polyvinyl alcohol films are-produced by suspending or immersing polyvinyl formate films in a C 1 to C 4 aliphatic monohydric alcohol, in which neither polyvinyl alcohol nor polyvinyl formate is soluble, and saponifying the polyvinyl formate to polyvinyl alcohol in the presence of a saponifying catalyst and at an elevated temperature below that at which the polyvinyl formate would fuse. The alcohol may be methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol or tertiary butanol. The catalyst may be sodium hydroxide, potassium hydroxide, ammonia, sodium methylate, hydrochloric acid, sulphuric acid or phosphoric acid. In Example 3 a film of polyvinyl formate cast from an acetone solution is saponified in ethanol in the presence of sulphuric acid. |
