Patent attributes
The present invention provides a block copolymer or a hydrogenated product thereof excellent in low-temperature shrinkability, natural shrinkability, rigidity and the like, excellent in a balance of physical properties such as blocking resistance, resistance to fusion bonding in hot water, impact resistance and the like, and having a few fish eyes (FE's) caused by gels. Further, the invention provides a heat shrinkable film and a heat shrinkable multilayer film suitable for drink container packaging, cap seals and the like, using such a block copolymer or the hydrogenated product thereof. The invention provides a block copolymer having a weight ratio of a vinyl aromatic hydrocarbon and a conjugated diene of 60/40 to 90/10 and a number average molecular weight measured by gel permeation chromatography (GPC) of 30,000 to 500,000, wherein the vinyl aromatic hydrocarbon constituting the block copolymer has a block rate of from 10 to 90% by weight, the vinyl aromatic hydrocarbon polymer blocks constituting the block copolymer have a peak molecular weight within the molecular weight range of 5,000 to 30,000, and 40 to 80% by weight of the vinyl aromatic hydrocarbon polymer blocks have a molecular weight of 35,000 or less.
