| abstract |
The invention is directed to a process for the production of polyurethanes suitable for thermoplastic processing comprising mixing I. at least 75% by weight of preformed thermoplastic polyurethane elastomers, or of a blend of (A) substantially bifunctional, compounds (B) substantially bifunctional chain-extending agents (C) organic diisocyanates and optionally (D) lubricants or other known additives said blend characterized in that it contains no peroxides and polymerization initiators which decompose into radicals under the effect of actinic light and further in that the molar ratio of the sum of said (A) and said (B) to said (C) is between 0.9 to 1.1, with II. (E) from 4 to 24% by weight of a crosslinking agent and III. (F) from 0.01 to 3% by weight of a polymerization inhibitor and/or an antioxidant, by adding said II and said III to said I at a temperature below 230 DEG C., and the cooling the mixture to below 130 DEG C. in less than 5 minutes in a continuous extruder and optionally granulating the resulting polyurethane. |