C - Chemistry – Metallurgy – 08 – G
Patent
C - Chemistry, Metallurgy
08
G
C08G 18/08 (2006.01) B29C 47/40 (2006.01) B29C 69/00 (2006.01) C08L 75/04 (2006.01)
Patent
CA 2160953
Thermoplastic polyurethanes are prepared by reacting a) organic and/or modified organic polyisocyanates with b) at least one oligomeric polyhydroxy and/or polyamino compound having an average molecular weight of from 400 to 10 000 g/mol, in the presence or absence of c) chain extenders having at least two Zerewitinoff-active hydrogen atoms and an average molecular weight of less than 400 g/mol, d) catalysts, e) compounds which are less than difunctional with respect to isocyanates and/or isocyanates which are less than difunc- tional and f) assistants and/or additives in a twin-screw extruder in which both screws rotate in the same direction and which has a length/diameter ratio of from 20 to 60, and discharging the resulting thermoplastic polyurethane from the extruder with shaping, by a process in which at least some of the components a) and b) and of the components c) to f) which may also be used are introduced into a first zone (Z1) of the twin- screw extruder, which zone is equipped with single-flight screw conveying elements which are arranged in a length region begin- ning from 0 to 3/100 and ending at least at 8/100 and at most at 30/100 of the total screw length L, the low-viscosity mixture is then passed through a mixing zone ( Z2 ) having a small shearing ef- fect and comprising double-flight screw conveying elements and/or mixing elements, this mixing zone ( Z2 ) being arranged within a length region from 8/100 to 45/100 with a total length within this region of from 5/100 to 25/100 of the total screw length L, the product is then passed into a retarding zone (Z3) having little shearing effect, this retarding zone (Z3) being arranged within a length region from 20/100 to 50/100 with a total length of the retarding stage within this region of from 0.2/100 to 10/100 of the total screw length L, the polymerization is then carried out at high viscosity in a polymerization zone (Z4) equipped with double-flight conveying screws, the zone (Z4) being present in a length region from 30/100 to 100/100 of the total screw length L, and the polyurethane is discharged, with the pro- viso that the process is carried out in such a way that the val- ue E, defined as Image , where M - is the total torque, in [Nm], acting on the two extruder shafts, n - is the speed of the extruder screws in [min-1], DG- is the smallest internal diameter of the extruder barrel in [cm] and V - is the free reactor volume available between the extruder barrel and the screw elements and any other elements as equipment on the extruder shafts in [cm3], is greater than 750.
Eberhardt Peter
Krech Ruediger
Rotermund Udo
Techritz Klaus
Basf Schwarzheide Gmbh
Robic
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