JPS5661413A - Preparation of copolymer - Google Patents

Abstract

PURPOSE: To obtain a copolymer, excellent in transparency, etc. and suitable as a rubber reinforcer, by the polymerization of a conjugated diene with a vinyl aromatic compound, in the presence of a polymerization initiator composed of an organic Li compound and a tertiary alkoxide of an alkali metal.

CONSTITUTION: In the preparation of an A-B type random block copolymer (A) of Mooney viscosity (ML₅₊₄100°C) of 30W120, composed of (a) a conjugated diene and (b) a vinyl aromatic compound, containing 35W90% of (b) and having a difference in (b) content between random block A and B≥45%, 10W50pts. based on 100pts. of (A), of random block A, contained in a smaller amount, is polymerized and then 90W50pts. based on 100pts. of (A), of random block B, contained in a larger amount, is polymerized, or they are polymerized in the reverse order, by using a mixture (B) of an organo Li (c) and a tertiary alkoxide of an alkali metal (d) as a polymerization agent, in such an adjusted ratio of (c) to (d) that 15pts. or less of a block vinyl aromatic compound (b') per (A), is contained in (B) when (b') is formed at the terminal of (A), or 30pts. or less of (b') is contained when (b') is formed at a position other than the terminal.

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