Idemitsu Kosan Company, Limited

Ryuichi Takasawa

Shigeru Matsuo

Tomoyoshi Murakami

There are disclosed a novel copolymer comprising having recurring unit represented by the formula: ##STR1## wherein Y represents a phenylene group or a naphthylene group, with a recurring number of k and a recurring unit represented by the formula: ##STR2## wherein Ar represents a divalent aryl group, with a recurring number of l, a value of k/(k+l) is 0.5 to 0.97 and having a reduced viscosity [.eta..sub.sp/c ] of 0.3 dl/g or higher as measured in p-chlorophenol solution at a concentration of 0.2 g/dl at 60.degree. C., and a process for producing the novel copolymer comprising the steps of:

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Sodegaura, Japan

Ryuichi Takasawa