Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Degussa Aktiengesellschaft

Herbert Amann

Gerhard Morlock

Hellmut Trautwein

Egbert Schola

The formaldehyde emission in the thermoplastic processing of antioxidant containing oxymethylene copolymer molding compositions is reduced considerably if these molding compositions additionally contain on the surface or homogeneously mixed in a specifically defined formaldehyde binding material which contains in the molecule at least two 4,6-diamino-1,3,5-triazin-2-yl groups. In this way there are avoided deposits on the die and odor annoyance.

Oxymethylene copolymerizate molding compositions with reduced

Trioxane homo-or copolymerizate is produced by continuously feeding the liquid starting material to be polymerized into a mixer in which there is present a powdered to granular oxymethylene homopolymer or copolymer which is fluidized to form a fluidized bed, the speed of feeding, catalyst concentration and polymerization temperature are coordinated to each other in suitable manner and after a polymerization reaction of at least 70 percent polymerizate is continuously or cyclically discharged from the mixer serving as reactor.

Process for the continuous polymerization or copolymerization of trioxane

In a molding composition comprising a polyoxymethylene, a melamine formaldehyde polycondensate and an antioxidation agent, the improvement wherein said melamine formaldehyde polycondensate is a finely divided, cross-linked, substantially water insoluble polycondensate comprising the precipitation product obtained by reacting formaldehyde and melamine in a molar ratio between 1.2:1 and 10.0:1, and wherein said polycondensate is in an amount of about 0.001 to about 30 percent by weight, related to the total weight of said composition.

Polyoxymethylene molding composition containing melamine formaldehyde

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.

Process for the production of oxymethylene copolymer molding

In a molding composition comprising a polyoxymethylene, a melamine formaldehyde polycondensate and an antioxidation agent, the improvement wherein said melamine formaldehyde polycondensate is a finely divided, cross-linked, substantially water insoluble polycondensate comprising the precipitation product obtained by reacting formaldehyde and melamine in a molar ratio between 1.2 : 1 and 10.0 : 1; and wherein said polycondensate is in an amount of about 0.001 to about 30 percent by weight, related to the total weight of said composition.

Solid thermoplastic terpolymer of trioxane is prepared by reacting trioxane in the presence of a prepolymer having recurring units consisting essentially of about 87-99 percent by weight of units derived from at least one cyclic formal and about 13-1 percent by weight of units derived from diglycerin diformal.

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Hanau, Germany

Herbert Amann