Abstract: A thermoplastic polyurethane composition comprises a thermoplastic polyurethane and a tin compound. The tin compound is contained in an amount of 0.3 to 15 ppm as converted into tin atom based on the thermoplastic polyurethane. The thermoplastic polyurethane composition has a retention ratio of long-chain hard segments when melt treated at 220.degree. C. for 60 minutes of at least 85%. The thermoplastic polyurethane composition also has a retention ratio of inherent viscosity when melt treated at 220.degree. C. for 6 minutes and then melt extruded and, thereafter, allowed to stand at 20.degree. C., 60% RH (relative humidity) for 24 hours of at least 85%. The thermoplastic polyurethane composition has excellent mold-ability and gives molded products being excellent in tensile strength and elongation, heat resistance, compression set, resistance to hydrolysis and like properties, and are hence useful as a raw material for various items.

Abstract: A polyurethane made of polyester diol units, organic diisocyanate units and units from a chain extender, wherein the polyester diol units contain dicarboxylic acid units and diol units, wherein at least 30 mole % of the dicarboxylic acid units are units derived from 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid or a mixture thereof, and wherein the polyester diol units have a number-average molecular weight in a range from 500 to 6000 is provided along with the polyester diol for preparing the polyurethane, polyurethane fibers prepared from the polyurethane, a molded article prepared from the polyurethane and processes for producing the polyurethane, polyester diol, dimethyldecanedioic acids and dimethyldecanedials used to prepare the dimethyldecanedioic acids; where the polyurethane and fibers produced therefrom are superior in various properties such as hydrolytic resistance, heat resistance, resistance to hot water, cold resistance, fungal resistance and mechanical performances e.g.

Abstract: Provided is an elastic polyurethane fiber comprising a polyurethane obtained by copolymerizing a polymer diol (A), an organic diisocyanate (B) and a chain extender (C);said polymer diol (A) that constitutes the polyurethane being a polyester diol and/or polyesterpolycarbonate diol having an average molecular weight of 1,000 to 6,000, and satisfying the following condition (I); ##EQU1## wherein the total number of carbon atoms means the number of the carbon atoms contained in the polymer diol and excluding those contained in the ester bonds and carbonate bonds thereof;the diol units that constitute said polymer diol containing branched diols in an amount of at least 10 mol %;said polyurethane constituting said elastic fiber satisfying the following conditions (II) and (III)45%.ltoreq.long chain hard segment content.ltoreq.