Denki Kagaku Kogyo Kk

Shinichiro Asai

Shigeki Horiie

Susumu Kurematsu

Chiaki Saito

A process for producing a film or sheet of a tapered styrenebutadiene copolymer or mixture thereof, which comprises: Melt extruding and then biaxially stretching a tapered styrenebutadiene copolymer with a molecular weight of 40,000 - 250,000, a total styrene content of 50 - 90 wt. %, and a total butadiene content of 40 - 10 wt. %, wherein said tapered styrene-butadiene copolymer contains: (a) more than 5% of the chain portion having a tapering rate of 0.3 - 4 and a styrene content of 30 - 70 wt. %, (b) more than 35% of the chain portion with a styrene content of more than 80 wt. %, and (c) more than 10% of the chain portion with a styrene content from at least 5 wt. % to less than 50 wt. % between high styrene content chain portions which have a styrene content greater than 80 wt. %.

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Machida, Japan

Shinichiro Asai