| 摘要 |
<p>PURPOSE:To enable to stretch the titled molded product in the ordinary stretching method by a method wherein a molded product consisting of polymer, the main ingradient of which is beta-hydroxybutyric acid, is heated up to the specified temperature and, after that, cooled down and kept on cooling for the specified period of time. CONSTITUTION:beta-hydroxybutyric acid polymer is extracted from aqueous cellulose suspension with 1,2-dichloroethane and added to methanol/water solution in order to precipitate. The resultant precipitate is washed with methanol and dried and finally pressed at 190 deg.C into the shape of a preform. The preform is heated at a temperature, which is below but not lower by 40 deg.C than its melting point, or preferably at a temperature ranging from that lower by 5 deg.C than the melting point to that lower by 30 deg.C than the melting point, and cooled down to below 100 deg.C or preferably to a temperature ranging from 70 deg.C or below to 0 deg.C or higher and kept at the temperature for 1-120sec, preferably for 5-60sec. Finally, the preform is stretched by the percent of stretch of 120% or more, preferably 150% or more, more preferably 200% or more. The preform cooled after heat treatment can be stretched in the ordinary stretching method. The ordinary stretching operation is done normally under the temperature ranging from room temperature to 10 deg.C.</p> |
