Abstract: A process for producing a polycarbonate having terminal hydroxyl groups obtained by reacting an aliphatic polyol with a carbonate monomer, characterized by comprising the first step of producing a low molecular weight polycarbonate while removing the alcohols produced as by-products from the reaction mixture containing the aliphatic polyol and the carbonate monomer and the second step of adding to the reaction mixture the carbonate monomer in portions or continuously under the conditions that the concentration of the aliphatic polyol in the reaction mixture in the first step is 5% by weight or less and effecting the reaction while removing the alcohols produced as by-products, whereby connecting the low molecular weight polycarbonates to one another through the carbonate monomer to heighten the molecular weight.

Abstract: Disclosed is a thermoplastic polyurethane which is a prepolymer/chain extender reaction product having a number average molecular weight of from 30,000 to 200,000, and a gel content of 5% by weight or less, based on the weight of the thermoplastic polyurethane;wherein the prepolymer is a prepolymer (A) comprising a polytetramethylene carbonate diol component (1) having a number average molecular weight of from 500 to 10,000 and an aliphatic diisocyanate component (2), the prepolymer (A) being represented by the following formula: ##STR1## wherein: X represents ##STR2## in which m is a number having an average value of from 3 to 85; Y represents an aliphatic diisocyanate residue; andn represents a number having an average value of from 1 to 50, andwherein the chain extender component is a chain extender (B) having an active hydrogen atom which is selected from the group consisting of a diol having a molecular weight of 300 or less, a diamine having a molecular weight of 300 or less, hydrazine and water.