Patent ID: 8287788
Filing Date: 2012-10-16
Classification: B29C,B29K,C08G

Abstract:
1. A process for the continuous production of thermoplastically processable polyurethane elastomers comprising metering a polyisocyanate (A), a proportion of from 1 to 80 equivalent %, based on the isocyanate group content of the polyisocyanate (A), of a compound (B) having an average of at least 1.8 and at most 3.0 hydrogen atoms having Zerewitinoff activity, with an average molar mass of from 450 g/mol to 5000 g/mol, a proportion of from 12 to 99 equivalent %, based on the isocyanate group content of the polyisocyanate (A), of a chain extender (C) having an average of at least 1.8 and at most 3.0 hydrogen atoms having Zerewitinoff activity per molecule, with an average molar mass of from 60 g/mol to 400 g/mol, and from 0 to 30% by weight, based on the total amount of the polyurethane elastomer, of catalysts and further auxiliaries and additives (D), the molar NCO:OH ratio of polyisocyanate (A) to the entirety composed of said compound (B), of the chain extender (C), and of the further auxiliaries and additives (D) being from 0.9:1 to 1.2:1 into a self-cleaning twin-screw extruder whose external screw diameter is in the range of from 32 to 62 mm, which is operated at shear rates above 6000s wherein said second apparatus is different and separate from the self-cleaning twin-screw extruder.