Process for the production of oxymethylene copolymer molding compositions with a low content of residual formaldehyde
AssigneeDeutsche Gold- und Silber-Scheideanstalt vormals Roessler
InventorsHerbert Amann, Gerhard Morlock, Hellmut Trautwein
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Abstract
Oxymethylene copolymers molding compositions with low portions of residual formaldehyde are produced by heating the polymerizate melts treated with chemical stabilizers in an apparatus in which there are continuously presented new polymerizate surfaces under reduced pressure. The heating of the polymerizate melt takes place in a thin layer evaporator for highly viscous media during an average residence time of 30 to 120 seconds at an average rate of shear between 500 and 2000 s.sup.-1 and at a pressure P.sub.abs of at most 150 mbar. The escaping gases and vapors are drawn off countercurrent to the polymerizate melt.
Claims5
A process for the production of oxymethylene copolymerizate molding compositions having a small portion of residual formaldehyde comprising heating the polymerizate melt treated with chemical stabilizers in an apparatus in which there are continuously presented new polymerizate surfaces under reduced pressure, said heating being carried out in a thin layer evaporator for highly viscous media at an average residence time of 30 to 120 seconds, at a rate of shear between 500 and 2000s.sup.-1 and at a pressure P.sub.abs of not over 150 mbar and drawing off the escaping gases countercurrent to the polymerizate melt.
Dependencies are inferred from the claim text.