Method for producing polyurethane elastomer fibers and fibers produced according to this method

A method for producing polyurethane elastomer fibers, comprising the steps of

• (a) producing a segmented polyurethane polymer based on
• i) a macro-diol with a molecular weight of approximately 500 to 10,000,
• ii) at least one diisocyanate belonging to the class consisting of aliphatic, cyclo-aliphatic and aliphatic-cycloaliphatic diisocyanates, and
• iii) a chain extender with at least two molecular groups belonging to the class consisting of hydroxy and amino groups,
• the polymer having a molar excess of isocyanate groups in the order of 0.2% over the combined total of hydroxy and amino groups from the macro-diol and chain extender, said percentage of 0.2% being in relation to the combined total of hydroxy and amino groups, wherein a preliminary form of polyurethane polymer containing iso-cyanate groups in a proportion to hydroxy- and amino groups not exceeding the stoichiometric ratio is brought to a melted condition and, after an optional cooling-down time interval, is brought together into reaction with at least one of the reagents from the class consisting of diisocyanate and isocyanate-terminated pre-polymers, essentially in the absence of a solvent;
• (b) melt-extruding the polyurethane polymer to form a fiber, wherein steps (a) and (b) are carried out under temperature conditions and within a time interval where essentially no allophanate will be formed;
• (c) subjecting the fiber to a post-treatment under temperature conditions and within a time interval in which cross-linking of the polyurethane polymer will occur through the formation of allophanate;
• and
• (d) exposing the extruded fiber to high-energy radiation to effect an at least partial cross-linking of the polyurethane elastomer.