| 摘要 |
<p>PROBLEM TO BE SOLVED: To develop a method for producing a matte stretched film of stereo complex polylactic acid which, during production of the stretched film of stereo complex polylactic acid, suppresses lowering of a molecular weight of polylactic acid as a raw material as much as possible and has heat resistance.SOLUTION: The method for producing a stretched film of stereo complex polylactic acid comprises the steps of: melting and extruding a mixture of 10 to 90 mass% of crystallized poly(L-lactic acid) and 90 to 10 mass% of crystallized poly(D-lactic acid) with the total of the poly(L-lactic acid) and the poly(D-lactic acid) being 100 mass%, at 160 to 250°C so that a retention ratio of a weight average molecular weight (Mw-DL) obtained by weight-averaging a weight average molecular weight (Mw-L) of the crystallized poly(L-lactic acid) and a weight average molecular weight (Mw-D) of the crystallized poly(D-lactic acid), becomes 75% or more, followed by cooling to obtain an at least partially crystallized sheet; stretching the sheet 2 times or more at a temperature of 60 to 90°C in at least one direction to obtain a stretched film; and heat-treating the stretched film under constraint at a temperature of 170 to 210°C for 1 second or more so that diffraction peaks by wide-angle X-ray diffraction appear at around 12°, around 21°, and around 24°.</p> |
