| 摘要 |
PURPOSE:To obtain said film of a large stretch ratio and excellent physical properties, by biaxially stretching the styrene-butadiene copolymer of a specified tapered block structure. CONSTITUTION:The tapered block copolymer having a copolymer part which varies gradually its monomer ratio of styrene/butadiene between a styrene block and a butadiene block is formed by polymerizing styrene solely, after that feeding the mixed monomer of styrene and butadiene and continuing polymerization [(provided, a molecular weight distribution (a weight average molecular weight/ a number average molecular weight) >=2)]. Then, the film of a dart impact strength more than 600g.cm is formed by biaxially stretching this. |
