| 摘要 |
PROBLEM TO BE SOLVED: To obtain a normally tack-free solid copolymer which softens or melts at a temperature not causing its heat decomposition by selecting a copolymer comprising succinimide units and hydroxycarboxylic acid units and having a weight-average molecular weight in a specified range. SOLUTION: This copolymer is one represented by formula III or the like, comprising 1-33 mol% succinimide units represented by formula I and 67-99 mol% hydroxycarboxylic acid units represented by formula II, and having a weight-average molecular weight of 1,000-100,000. This is produced by melting and reacting highly pure aspartic acid and a cyclic ester compound such as L-lactide in a molar ratio of 1/1 to 1/50 by heating to 120-230 deg.C for 2-100 h in the presence of, optionally, tin octoate. In the formulae, p, r, and s are each o or a positive integer, provided that they can not be 0 simultaneously; q is an integer of 1 or greater; (p+r+s)/(q+1)=2-100; and R is hydrogen or methyl.
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