Abstract: The invention provides a novel preparation process of a polycondensation type polymer, an excellent polymer which is represented by lactic acid and the preparation process of the polymer, a polycondensation agent used for the preparation process, and an intermediate. Specifically, the invention provides a preparation process of the polycondensation type polymer, for example, polyamide, polyimide, polythioester and polyester, comprising bonding a carboxyl group comprising compound with an active hydrogen group comprising compound in the presence of haloiminium salt. The invention provides excellent polylactic acid having a controlled D/L-isomer ratio in the repeating structural units and preparation process of polylactic acid, and further provides a haloiminium salt compound used for the preparation process and an intermediate compound of acid chloride.

Abstract: An alkali metal compound such as metallic cesium, cesium hydroxide, cesium hydroxide monohydrate, metallic rubidium, rubidium hydroxide or rubidium hydroxide monohydrate is used as a catalyst, crude polyoxyalkylene polyol containing the catalyst is neutralized with a mineral acid or an organic acid, an aqueous solution layer containing an alkali metal salt is brought into contact with an anion exchange resin to adsorb mineral acid anion or organic acid anion, the alkali metal compound catalyst is recovered, alkylene oxide undergoes ring-opening addition polymerization on an active hydrogen compound in the presence of the recovered alkali metal compound catalyst to prepare polyoxyalkylene polyol, the catalyst is thereafter separated, recovered and reused, and such recycle of the alkali metal compound catalyst provides an economical process.