PURPOSE: To provide a container decomposable in the natural environment and improved in transparency and impact resistance by a method wherein a copolymer composition is previously formed and then given a shape in a predetermined range of the glass transition temperature of this composition to a certain temperature and at a predetermined draw ratio.
CONSTITUTION: A decomposable container is made in any desired form by using the thermoplastic polymer composition formed from L-lactic acid, d-lactic acid, the mixture thereof or lactide, i.e., the cyclic dimer of lactic acid, and hydroxycarboxylic acids such as glycolic acid and 3-hydroxybutyric acid. In the formation of the container, after being previously made into a desired form, the aforesaid composition is uniaxially or biaxially stretched in the range of the glass transition temperature Tg of the composition Tg+60°C and at a draw ratio if less than 6, preferably 2-3 times. If the draw ratio exceeds 6, the accuracy of the container thickness becomes worse and undesirable for practical usage.
WATANABE TAKAYUKI
KITAHARA YASUHIRO
AJIOKA MASANOBU
