Patent ID: 8507633

Claim:
A process for the preparation of thermoplastic polyurethane by reacting (a) the isocyanate diphenylmethane 4,4′-diisocyanate with (b) compounds reactive toward isocyanates and having a molecular weight (M w ) of from 500 to 10 000 g/mol and (c) chain extenders having a molecular weight of from 50 to 499 g/mol, optionally in the presence of (d) catalysts and/or (e) conventional additives, wherein the chain extender is a mixture consisting of a main chain extender 1,4-butanediol (c1) and a co-chain extender 1,3-propanediol (c2) and the thermoplastic polyurethane prepared has a rigid phase fraction of greater than 0.40, said rigid phase fraction being defined by the following formula: Rigid ⁢ ⁢ phase ⁢ ⁢ fraction = { ∑ x = 1 k ⁢ [ ( m KVx / M KVx ) * M Iso + m KVx ] } / m ges wherein: M KVx : molar mass of the chain extender x in g/mol m KVx : mass of the chain extender x in g M Iso : molar mass of the isocyanate used in g/mol m ges : total mass of all starting materials in g k: number of chain extenders wherein the proportion of n1 of the main chain extender (c1), based on the total amount of n of the chain extender (c) used, is from 0.80 to 0.999.