Thermoplastic polyurethane for producing hydrophilic fibers

A thermoplastic polyurethane obtained by reacting at least the following components:

• A) an isocyanate having two isocyanate groups,
• B1) a first poly(ethylene glycol)polyether diol of the structure (HO—(CH2—CH2—O)x—H) with two isocyanate-reactive groups and a number-average molecular weight Mn of ≧6000 and ≦16 000 g/mol,
• B2) a second poly(ethylene glycol)polyether diol of the structure (HO—(CH2—CH2—O)x—H) with two isocyanate-reactive groups and a number-average molecular weight Mn which is equal to from 10 to 80% of the number-average molecular weight Mn of the first poly(ethylene glycol)polyether diol B1),
• C) a chain extender having two isocyanate-reactive groups and a number-average molecular weight Mn of ≧60 and <600 g/mol,
• D) optionally a catalyst, and
• E) optionally an auxiliary and an added substance,
• wherein said chain extender C) is at least one compound selected from the group consisting of ethanediol, 1,6-hexanediol, 1,4-butanediol, 1,12-dodecanediol, isophoronediamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, N-methylpropylene-1,3-diamine, N,N′-dimethylethylenediamine, terephthalic acid bis(ethylene glycol), terephthalic acid bis-1,4-butanediol, and 1,4-di(-hydroxyethyl)hydroquinone, and
• wherein the equivalence ratio of said isocyanate A) to said poly(ethylene glycol)polyether diols B1) and B2) is between 1.5:1.0 and 10.0:1.0 and the NCO index, formed by multiplying the quotient of the equivalence ratios of the isocyanate groups and the sum total of the isocyanate-reactive groups by 100, is from 90 to 105.