Packaging and labelling films

摘要

A transparent, dimensionally stable, biaxially oriented PLA film has a haze value of less than 3% and exhibits strain induced crystallinity having been oriented by stretching the film from a substantially non­crystalline state by at least three times its original areal dimensions. A processes for making such films comprises: extruding a blend a PLA rich in L-lactate repeat units (PLLA) and a PLA rich in D-lactate repeat units (PDLA) at a temperature of at least about 220°C to provide an extrudate; quenching the extrude directly after extrusion to a temperature below about 65°C to hinder or prevent crystal formation in the extrudate; reheating the quenched extrudate to a temperature of at least about 65T, and stretching the film by at least three times its starting dimensions simultaneously or sequentially in each of the transverse and longitudinal directions to introduce orientation and crystallinity into the film, crystallinity being in the form of a stereocomplax of P1..LA and PDLA and optionally as well in the o-crystaillne form of PLLA end/or PDLA; and heat setting the stretched and oriented crystalline film at a temperature of at east about .170C to melt out at least a proportion of any a-crystallinity in the film and optionally introduce further stereocomplex crystallinity into the film.