Abstract: Colorant concentrates made from free-flowing polyoxymethylene copolymer as carrier, 15-80% by weight of colorant, 2-15% by weight of nitrogen-containing stabilizer and 0-15% by weight of dispersion aid for coloring pellets or molding compositions made from polyoxymethylene (POM) and for producing colored injection moldings or colored POM extrudates. The products produced with this colorant preparation are particularly stable during processing and have very low formaldehyde emissions.

Abstract: The process serves for the preparation of trioxane from formaldehyde in the gas phase in the presence of a tungstomolybdophosphoric acid of the composition H.sub.3 PW.sub.n Mo.sub.m O.sub.40 .multidot.xH.sub.2 O (n=4-8, m=12-n; x=0-32) as catalyst.

Abstract: A continuous process for the preparation of polyacetal copolymers from 1,3,5-trioxane and the comonomers known for this purpose using strong protic acids as an initiator, in which the initiator is added in an amount of 0.01 to 0.6 ppm, based on the total amount of monomers, in finely divided form to the monomer mixture, after the polymerization step the crude polymer is transferred from the polymerization reactor to a mixing unit without further intermediate steps, excess monomer is removed from the crude polymer in the mixing unit or between polymerization reactor and mixing unit by applying reduced pressure and, if desired, generally customary stabilizers, assistants, fillers, reinforcing materials and/or colorants are incorporated into the polymer in the mixing unit.

Abstract: A process for separating a gaseous reaction mixture in the preparation of trioxane is described, in which a) the gaseous mixture leaving the reactor is scrubbed in countercurrent with an organic solvent whose boiling point is above 135.degree. C. in which the trioxane predominantly dissolves and which leaves the formaldehyde predominantly in the gas phase which is returned to the reactor, b) the trioxane together with residual formaldehyde is stripped from the solvent by distillation via a column, the overhead product being partially condensed in the temperature range from 62.degree. to 100.degree. C. c) some of the resulting condensate is applied to the column as reflux and some is taken off as product and d) the non-condensed portion is returned to the scrubbing step a).

Abstract: Process for continuous preparation of homo- and copolyoxymethylenes with stable end groups in a homogeneous phase, in which in a tubular reactor with static mixing elements cyclic formaldehyde oligomers are polymerized in the presence of protonic acids as initiators in amounts of 0.005 to 500 ppm in a polymerization zone, in which the residence time of the reaction components in this zone is 0.1 to 10 min and in which the initiator is deactivated immediately after polymerization, there being a fluid transition between the polymerization and deactivator zones which is determined solely by the addition of deactivator, and in which, besides deactivation, stabilization of the chain ends is carried out in the presence of residual monomers, with the volatile constituents being removed from the reaction mixture in a subsequent vent unit. Stabilization is carried out in the presence of alkaline substances, either at temperatures of 150.degree. C. to 250.degree. C.

Abstract: In the process for the preparation, with simultaneous end group stabilization, of polyacetal copolymers in a homogeneous phase and working up thereof, cyclic formaldehyde oligomers are copolymerized with cyclic acetals in the presence of an initiator in a polymerization reactor and immediately thereafter the initiator is deactivated by addition of basic substances, the unstable chain ends being degraded down to 0.01% to 1% in the presence of residual monomer, the product losing the majority of the residual monomer at the reactor outlet by letting down into a pelletizing device and the residual monomer which remains and the impurities dissolved in the product being removed by extraction with solvents and the product being pelletized, after drying and stabilization.

Abstract: A process for the catalytic preparation of trioxane from formaldehyde in the gas phase employs a catalyst comprising vanadyl hydrogenphosphate hemihydrate which may be unactivated or activated by steam.No byproducts were obtained in the process and the space-time yield is high. Deposits in the reactor do not occur.

Abstract: In a process for the preparation of trioxane from formaldehyde in the gas phase in the presence of a catalyst, the catalyst employed is 11-molybdo-1-vanadophosphoric acid, H.sub.4 PVMo.sub.11 O.sub.40 .multidot.n H.sub.2 O (n=0-32).Advantages of this process are, inter alia, high space-time yields and the suppression of byproducts.