| 摘要 |
Thermoplastic polyurethanes and molding compositions containing the same having improved surface resistance (writing and scratch resistance) and good industrial processability, and the use thereof, such polyurethanes prepared by reacting: (a) one or more organic diisocyanates; (b) a chain extender comprising at least one low molecular weight polyol having on average at least 1.8 and not more than 3.0 Zerewitinoff-active hydrogen atoms and a number-average molecular weight Mn of 60 to 400 g/mol; and (c) at least one polyol component having a number-average molecular weight Mn of 450 to 10,000 g/mol and on average from at least 1.8 to not more than 3.0 Zerewitinoff-active hydrogen atoms; wherein the ratio of the number of isocyanate groups in component (a) to the number of isocyanate-reactive groups in components (b) and (c) is 0.9:1 to 1.1:1; in the presence of (d) a mixture of polyorganosiloxanes of the general formula (R2SiO)n, in an amount of 0.4 to 10 wt. % based on the thermoplastic polyurethane, wherein each R independently represents an organic hydrocarbon radical having 1 to 27 carbon atoms which can be linear and/or branched, and n represents an integer of 3 to 6000, wherein the mixture consists of (d1) 0.2 to 2 wt. %, based on the thermoplastic polyurethane, of one or more polyorganosiloxanes (R2SiO)n wherein n=3 to 300 and (d2) 0.2 to 8 wt. %, based on the thermoplastic polyurethane, of one or more polyorganosiloxanes (R2SiO)n wherein n=1000 to 6000.
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