| 摘要 |
<p>PURPOSE:To provide a film for packaging a coin which has a proper strength, transparency, and a hydrolytic property by a method wherein a non-stretched film of polylactic acid or a lactic acid - hydroxycarboxylic acid copolymer is stretched in a temperature range of the glass transition point of a polymer. CONSTITUTION:A necessary substance is selected from L-lactic acid, D-lactic acid, and hydroxycarboxylic acid is used as a raw material polymer. By dehydrating and polymerizing the substance, polylactic acid and a lactic acid - hydroxycarboxylic acid copolymer are prepared. By melting and extruding the polylactic acid and lactic acid - hydroxycarboxylic acid copolymer, a non- stretched film is manufactured. The non-stretched film is stretched in a temperature range of a glass transition point(Tg) - Tg+50 deg.C of a polymer. This constitution provides the manufacture of a film for packing a coin being excellent impact strength transparency and having a hydrolytic property.</p> |
