| 摘要 |
PROBLEM TO BE SOLVED: To improve heat resistance, mechanical characteristics and chemical resistance by using a polyvinyl cyclohexane block copolymer which is obtd. by hydrogenation of aromatic rings in a specified styrene-based block copolymer. SOLUTION: This styrene-based block copolymer can be easily obtd. by a well-known polymn. of A segment and B segment such as so-called living anion copolym., for example, by using an org. lithium compd. as an initiator in a hydrocarbon solvent such as hexane and heptane. In this block copolymer, the ratio of A segment to B segment is 60/40 to 99/1, preferably 90/10 to 99/1. Then the aromatic rings in the obtd. copolymer are hydrogenated in the presence of a hydrogenation catalyst having hydrogenating ability for aromatic rings to obtain a polyvinyl cyclohexane block copolymer. When the copolymer is formed into an optical disk, its double refractivity index is <=30nm. |
