ORIENTED POLYLACTIC ACID FILM AND SHEET AND THEIR PRODUCTION

摘要

PURPOSE: To provide an oriented polylactic acid film or sheet having strength and dimensional stability sufficient for ordinary use and provide a process for the production of the film or sheet. CONSTITUTION: This oriented polylactic acid film or sheet has a planar orientation degreeΔP of >=3.0×10<-3> and satisfies the formulas (ΔHm-ΔHc)>=20J/g and (ΔHm-ΔHc)/ΔHm>=0.75 whereinΔHm is heat of crystal fusion generated by raising the temperature of the film or sheet andΔHc is heat of crystallization generated by the crystallization during temperature increase. The film or sheet is produced by heat-treating a film or sheet of a polylactic acid polymer having a planar orientation degreeΔP of >=3.0×10<-3> under conditions to satisfy (1) the heat-treatment temperature T( deg.C) is between 70 deg.C and the melting point Tm of the polymer and (2) the heat-treatment period t(sec) satisfies the formula Log(t)>=-4.6Log(T)+11. The shrinkage of the film or sheet at 80 deg.C is <=3%.