| 摘要 |
A cyclic ester (e.g., a lactone such as epsilon-caprolactone) is ring-opening addition polymerized with a dihydroxycarboxylic acid in the presence of a basic compound (e.g., an amine). In a polyester polyol obtained by such a process, at least part of a carboxyl group of the polyester polyol forms a carboxylate with the basic compound, and the content of the dihydroxycarboxylic acid in a free form can be remarkably reduced (for example, reduced to not more than 5% by weight relative to the total polyester polyol). According to the present invention, a polyester polyol having a reduced content of a free or unreacted dihydroxycarboxylic acid is provided even in the case of using a dihydroxycarboxylic acid (e.g., a dimethylolalkanoic acid such as dimethylolpropionic acid) as an initiator.
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