BLOCK COPOLYMER AND PROCESS FOR PRODUCTION OF THERMALLY SHRINKABLE FILM

摘要

Disclosed is a process for production of a thermally shrinkable film which is transparent and excellent in the balance among physical properties (e.g., stiffness, elongation, shrinkage in the length-wise and width-wise directions), particularly has an even film thickness and an excellent film stability, and can be formed by inflation method. Also disclosed is a block copolymer or a hydrogenated product thereof which is excellent in tensile properties, optical properties, hardness, stretching properties, processability, shrinking properties, solvent resistance and the like and suitable for extrusion molding, injection molding and production of a foaming article, or a composition comprising the block copolymer or hydrogenated product. A process for production of a thermally shrinkable film comprising: a first inflation step in which a block copolymer having a vinyl aromatic hydrocarbon content of 65 to 95% by weight and a conjugated diene content of 5 to 35% by weight or a hydrogenated product thereof (I) is used as the raw material to form a tube having a thickness of 0.05 to 0.5 mm; and a second inflation step in which, in continuation with the first inflation step, the tube is stretched in the TD direction by 1.5- to 5-fold in a fluid at a temperature of 65 to 100°C to form a film.