Patent ID: 6930162

Claim:
A multi-stage process for the continuous preparation of thermoplastically processable polyurethane elastomers (TPU) with tensile strengths of >30 MPa (measured in accordance with EN ISO 527-3), comprising a) preparing a prepolymer I by reacting A) at least one organic diisocyanate, with B) a polyol 1 having on average at least 1.8 and not more than 3.0 Zerewitinoff-active hydrogen atoms and a number-average molecular weight {overscore (M)} n of 450 to 10,000; b) reacting said prepolymer I prepared in a) with C) a polyol 2 comprising an organic phosphorus-containing compound, which is different than polyol 1, wherein said polyol 2 has on average at least 1.5 and not more than 2.5 Zerewitinoff-active hydrogen atoms and a number-average molecular weight {overscore (M)} n of 100 to 5.000, and polyol 2 being present in an amount of 0.01 to 50 wt. %, based on the total amount of TPU, to yield a prepolymer II, wherein an equivalent ratio of NCO groups to the sum of NCO-reactive groups of from 1.2:1 to 10:1 is established, based on reaction components (A), (B) and (C); c) reacting, in a high-viscosity reactor operating with a high shear energy, said prepolymer II prepared in b) completely with: D) at least one low molecular weight polyol or polyamine having on average at least 1.8 and not more than 3.0 Zerewitinoff-active hydrogen atoms and a number-average molecular weight {overscore (M)} n of 60 to 400 as a chain lengthener; wherein steps a) to c) are optionally carried out in the presence of F) catalysts, and optionally, with the addition of E) 0 to 20 wt. %, based on the total amount of TPU, of further auxiliary substances and additives, with the overall equivalent ratio of NCO groups to the sum of NCO-reactive groups being from 0.9:1 to 1.2:1, based on the sum of all the reaction components of steps a) to c).