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: The invention relates to a mixture composed essentially of polyoxymethylene (component A), a rubber-elastic graft copolymer in which the particles have been formed from a rubber-elastic, single-phase core based on polydiene and a hard graft shell (component B) and, if appropriate, a polymeric third component (component C). The invention also relates to a three-component mixture of the components A, B' and C, the core, in the case of B', being preponderantly or entirely composed of poly(meth)acrylic acid ester or silicone rubber instead of polydiene.The shaped articles produced from these mixtures are particularly distinguished by good low-temperature impact strength.

Abstract: Continuous process for removing unstable components from crude oxymethylene copolymer, which still contains catalysts, monomeric starting materials and unstable components, by treating the copolymer with deactivators, optionally in the presence of auxiliaries, in a pressure zone, and subsequently removing volatile components in a pressure-release zone in the presence or absence of stabilizers, in which process the crude polymer is fully melted in the absence of the deactivators and auxiliaries immediately after completion of the polymerization step, and the deactivators are subsequently incorporated, alone or together with auxiliaries, under pressure into the resultant polymer melt in at least one pressure zone.By this process, degradation is avoided and significantly better properties are obtained.

Abstract: Silicate catalysts which can be employed for selective oxidation reactions of organic substances, a process for the preparation of these catalysts and their use are described.The catalyst is distinguished by high long-term activity, by the reaction temperature required for the reaction being lower in comparison with catalysts composed of pure silver and by higher conversions and selectivities in the oxidative dehydrogenation of alkanols in comparison with pure silver or silver on supports.

Abstract: The invention relates to a mixture composed of polyoxymethylene (component A), a rubber-elastic graft copolymer in which the particles have been formed from a rubber-elastic, single-phase core based on polydiene and a hard graft shell (component B) and a polymeric third component (component C).The invention also relates to a three-component mixture of the components A, B' and C, the core, in the case of B' being preponderantly or entirely composed of poly(meth)acrylic acid ester or silicone rubber instead of polydiene.The shaped articles produced from these mixtures are particularly distinguished by good low-temperature impact strength.

Abstract: A process for the preparation of carbonyl compounds by the oxydehydrogenation of (C.sub.1 -C.sub.4)-alcohols is carried out at a temperature from 400.degree. to 700.degree. C. in the presence of a silicate catalyst which has been doped with silver and silver ions. By means of the process carried out at relatively low temperatures, for example, are that high yields are achieved, the content of carbon monoxide is low and the product gas contains, apart from carbon dioxide, no further determinable by-products and has a low water/formaldehyde ratio.

Abstract: The invention relates to a mixture composed essentially of polyoxymethylene (component A), a rubber-elastic graft copolymer in which the particles have been formed from a rubber-elastic, single-phase core based on polydiene and a hard graft shell (component B) and, if appropriate, a polymeric third component (component C). The invention also relates to a three-component mixture of the components A, B' and C, the core, in the case of B', being preponderantly or entirely composed of poly(meth)acrylic acid ester or silicone rubber instead of polydiene.The shaped articles produced from these mixtures are particularly distinguished by good low-temperature impact strength.

Abstract: The process dehydrogenates methanol in the presence of a catalyst based on aluminum oxide, alkali metal aluminate and/or alkaline earth metal aluminate with the exclusion of oxygen at a temperature of 650.degree. to 1050.degree. C. in a reactor whose inner wall is composed entirely or partly of aluminum oxide. The process gives anhydrous formaldehyde which contains only very minor impurities.

Abstract: The invention relates to a process for obtaining trioxane from aqueous solutions by high-pressure extraction using an extracting agent which is in the form either of a gas in the supercritical state or of a liquid gas. An intermediate separation is advantageous, especially in the former case.The trioxane can be obtained in high concentration and with a saving of energy by the process according to the invention.

Abstract: The invention relates to a process for the continuous preparation of trioxane, optionally together with cyclic formals, from an aqueous formaldehyde solution in the presence of acidic solid-bed catalysts, the reaction taking place without simultaneous evaporation.The process according to the invention can be carried out even at high formaldehyde concentrations without appreciable paraformaldehyde deposits.

Abstract: The invention provides a process for the continuous manufacture of trioxan, optionally together with cyclic formals, from aqueous formaldehyde solutions in a circulation reactor with evaporator, the vapor/liquid mixture leaving the evaporator is fed in below the liquid level of the reaction mixture. The process of the invention allows to attain especially high space/time yields.

Abstract: In filler-containing plastic molding compositions based on polyoxymethylene, very good compatibility between the filler and the polymer matrix is obtained when alkali metal or alkaline earth metal salts of certain sulfonic acids or alkylsulfuric acids are used as adhesion promoters. The result is that in particular the flow properties of the molding compositions and mechanical properties of the plastic articles prepared therefrom as well as the color properties are improved.

Abstract: A process for the simultaneous synthesis of trioxan and cyclic formals is provided, which comprises reacting a mixture of concentrated formaldehyde and diol and/or epoxide with acid catalysts at a temperature of from 30.degree. to 150.degree. C.

Abstract: In filler-containing molding compositions a very good compatibility between the hydrophilic filler and the hydrophobic polymer matrix is obtained by using as adhesion promotor alkali metal salts of alkyl or alkylene-sulfonic acids or alkyl sulfates, the derivatives thereof and the acids on which the salts are based. The flow properties of the molding compositions and the mechanical properties of the shaped articles made therefrom are improved.

Abstract: The invention provides a molding composition of a mixture of an oxymethylene polymer, an elastomer having a softening temperature of below the crystallite melting point of the oxymethylene polymer and a second order transition temperature of from -120.degree. to +30.degree. C., and a segmented thermoplastic copolyester.The molding composition of the invention is distinguished by improved mechanical properties, especially with respect to the impact strength.

Abstract: Oxymethylene polymers (POM) are obtained in a granular form, by cooling a POM solution or dispersion, whose temperature is above the sintering temperature of the POM, to a temperature slightly below the sintering temperature of the POM, and extracting from the suspension obtained only those POM particles which show a grain diameter of more than 70 .mu.m. As solvent or dispersing agent as well as precipitating and cooling agent there is used a mixture of methanol and water with a methanol content of at least 75% by weight. The POM obtained is suitable as engineering plastic material for the manufacture of shaped articles having improved mechanical properties.

Abstract: Thermoplastic molding compositions having improved properties are composed of a mixture of from 99.999 to 90% by weight of a linear polyoxymethylene and from 0.001 to 10% by weight of a branched or cross-linked polyoxymethylene. The linear polyoxymethylenes are homopolymers of formaldehyde or of trioxane or copolymers of trioxane and at least one compound of monofunctional reaction which can be copolymerized with trioxane. The branched or cross-linked polyoxymethylenes are copolymers of trioxane and a multifunctionally reacting compound, or copolymers of trioxane, a monofunctionally reacting compound and a branched or cross-linked polyether. The molding compositions yield shaped articles having improved mechanical properties.

Abstract: What is disclosed is a plastics material adaptable to biomedical uses, the surface of which material at least partially consists of a graft copolymer having a hydrocarbon main chain and side chains grafted thereon, said side chains being polymers comprising at least one vinyl monomer selected from the group consisting of acrylic acid esters of the formulaCF.sub.3 --(CF.sub.2).sub.x --(CH.sub.2).sub.y --O--CO--CH.dbd.CH.sub.2,where x is an integer from 3 to 16 and y is an integer from 1 to 12, vinylene carbonate, N-vinyl alkylamides of the formula ##STR1## wherein R.sup.1 and R.sup.2 are the same or different and each is hydrogen or alkyl having 1 to 6 carbon atoms.

Abstract: In the case of polyolefins filled with alkaline earth metal carbonates, a very good compatibility of the hydrophilic filler and the hydrophobic polymer matrix is reached when using as adhesion promoters certain organo-phosphorus compounds. As a result, improved mechanical properties are obtained with the articles made of plastic material that has been prepared from such polyolefin molding compositions.

Abstract: A thermoplastic molding composition being a suitable material for technical purposes comprises a mixture of an oxymethylene polymer and of an elastomeric copolyester having short-chain and long-chain diol elements as well. The molding composition is prepared by mixing and homogenizing the components and may contain usual additives, especially stabilizers.