| 摘要 |
PURPOSE:To provide the subject granule capable of being decomposed into non-toxic water and CO2 under natural environment in a short period when buried under the ground or thrown away in sea, etc., as wastes by foaming a thermoplastic polymer containing polylactic acid as a main component. CONSTITUTION:A thermoplastic polymer composition containing polylactic acid or the copolymer of lactic acid with a hydroxycarboxylic acid as a main component is foamed in an expansion ratio of >=2 times to provide the objective granules. The produced granules are preferably obtained by dissolving a foaming agent producing a gas at the melting temperature of the polymer in the pellet- like lactic acid polymer under heating and a raised pressure and subsequently reducing the pressure to generate foams in the polymer. Examples of the foaming agent includes ethane, butane or carbon dioxide. When a high mol.wt. polymer is produced as the lactic acid polymer, the polymer is preferably produced by subjecting a lactide as a raw material to a ring-opening polymerization. |
