Abstract: Polyurethane elastomer fibers with superior mechanical and heat distortion properties are obtained by a method in which (a) a segmented polyurethane polymer is produced on the basis of a macro-diol, an aliphatic diisocyanate, and a chain extender with at least two hydroxy and/or amino groups, where the polymer has a molar excess of isocyanate groups over the hydroxy and/or amino groups from the macro-diol and chain extender; (b) the polyurethane polymer is melt-extruded to form a fiber; and (c) The extruded fiber is subjected to a post-treatment. Steps (a) and (b) are carried out under temperature conditions and within a time interval where essentially no allophanate will be formed, while step (c) is performed under temperature conditions and within a time interval in which the polyurethane polymer is cross-linked through the formation of allophanate.

Abstract: The invention concerns a polyurethane elastomer containing structural units of type (a), in which: the group —O—R1—O—is a macrodiol group with a molecular weight of approximately 500 to 10000, R2 is a bivalent aliphatic, cycloaliphatic and/or aliphatic-cycloaliphatic group; and X is a short-chain olefinically unsaturated group, Y is NH or O, n is an integer from 1 to 10 and m is an integer of at least 4. The invention also concerns a method of preparing this polyurethane elastomer which can be melt-spun to form fibres or melt-extruded to form foils. The fibres or foils can be exposed to energy-rich radiation such that crosslinking of the polyurethane occurs. Fibres according to the invention display superior properties in terms of textile-mechanical properties, in particular good tensile strength, elongation at tear, residual elongation and heat distortion temperature.