Abstract: The invention relates to a process for preparation of polymer blends comprising at least one polyoxymethylene and at least one thermoplastic elastomer, where the thermoplastic elastomer is micropelletized by a pelletizing process and the pellets obtained in a) are dispersed in the polyoxymethylene matrix via melting of the components and mixing of these at low shear forces, and also to the use of micropelletized thermoplastic elastomers for preparation of polyoxymethylenes with low formaldehyde emission.

Abstract: Multiblock copolymers are described and contain the structural unit of formula I -A-O—R1—O—CO—(R2—CO—)m—X-D-X—(CO—R2)m—CO—X—??(I), where A is a radical derived from a homo- or copolyoxymethylene, R1 is an alkylene radical-having at least two carbon atoms or a cycloalkylene radical, R2 is a direct carbon-carbon bond, or an alkylene, cycloalkylene, arylene, or aralkylene radical, X is selected from —O—, —S—, or —NH—, D is a divalent radical B which is a radical of a hydroxy-terminated, mercaptan-terminated, or amino-terminated polymer which derives from polyalkylene glycols, polyvinyl ethers, polyvinyl ether-alkene copolymers, polyvinyl esters, polyvinyl ester-alkene copolymers, polyvinyl alcohols, polyvinyl alcohol-alkene copolymers, polyvinylaromatics, polyacrylates, polymethacrylates, polyacetals, polycarbonates, polyesters, polyamides, polyimines, polyetherester elastomers, polyetheramide elastomers, polyalkadienes, polyurethanes, polyureas, polysiloxanes, or a triblock copolymer radical -PAO-B-PAO-, wh

Abstract: A process for preparing acetals from aldehydes and alcohols is carried out by generating a reaction/distillation zone charged with an acidic fixed bed catalyst in a distillation column, feeding the aldehyde and the alcohol to the reaction/distillatlon zone and at least partly converting them to the acetal, heating the column bottom disposed below the reaction/distillation zone in order to at least partly evaporate the bottom's mixture and to establish a defined temperature in the reaction/distillation zone, feeding an extractant into a rectifying section of the column, disposed above the reaction/distillation zone and condensing a product having more than 90% by weight of acetal at the top of the column.

Abstract: Copolymers are described containing blocks of the structural repeat units of the formula I and blocks containing structural units of the formula II [—O—CH2—]x, ??(I) [—O—R1—], ??(II) where R1 is a divalent radical derived from a hydroxy-terminated aliphatic or cycloaliphatic oligomer or polymer which, where appropriate, has ether groups and/or carbonyloxy groups in the chain, and x is a whole number, at least 10. The copolymers may be used for producing moldings.

Abstract: Process for removing methanol from formaldehyde-containing solutions. The present invention relates to a process for removing methanol from formaldehyde-containing solutions, with methanol being converted into formaldehyde dimethyl acetal by reactive distillation in the presence of an acidic fixed-bed catalyst, and the resultant mixture comprising methanol, formaldehyde dimethyl acetal and possibly other impurities being distilled off.

Abstract: The invention relates to a process for preparation of polymer blends comprising at least one polyoxymethylene and at least one thermoplastic elastomer, where the thermoplastic elastomer is micropelletized by a pelletizing process and the pellets obtained in a) are dispersed in the polyoxymethylene matrix via melting of the components and mixing of these at low shear forces, and also to the use of micropelletized thermoplastic elastomers for preparation of polyoxymethylenes with low formaldehyde emission.

Abstract: Process for preparing polyoxymethylene homo- and copolymers and apparatus suitable for this purpose An apparatus is described for preparing polyoxymethylene homo- and copolymers. This has the following elements: A) reactor (1) encompassing a polymerization zone (2) and a deactivation zone (3) directly downstream thereof for polymerizing and deactivating polyoxymethylene homo- and copolymers in a homogeneous phase in a manner known per se, B) depressurizing assembly (4), which, if appropriate, has a metering apparatus (5) for additives for the polymer, C) pelletizer (6), D) extraction apparatus (7), and E) if appropriate, a drying apparatus (8). Use of the apparatus and of the polymerization process carried out therein can achieve particularly low residual monomer contents in a simple manner which saves energy.

Abstract: Multiblock copolymers are described and contain the structural unit of formula I -A-O—R1—O—CO—(R2—CO—)m—X-D-X—(CO—R2)m—CO—X—??(I), where A is a radical derived from a homo- or copolyoxymethylene, R1 is an alkylene radical having at least two carbon atoms, or a cycloalkylene radical, R2 is a direct carbon-carbon bond, or an alkylene, cycloalkylene, arylene, or aralkylene radical, X is selected from —O—, —S—, or —NH—, D is a divalent radical B which is a radical of a hydroxy-terminated, mercaptan-terminated, or amino-terminated polymer which derives from polyalkylene glycols, from polyvinyl ethers, from polyvinyl ether copolymers with alkenes, from polyvinyl esters, from polyvinyl ester copolymers with alkenes, from polyvinyl alcohols, or from polyvinyl alcohol-alkene copolymers, from polyvinylaromatics, from polyacrylates, from polymethacrylates, from polyacetals which have no, or up to 50 mol % of, oxymethylene units, from polycarbonates, from polyesters, from polyamides, from polyimines, from polyether

Abstract: A process for preparing acetals from aldehydes and alcohols is carried out by generating a reaction/distillation zone charged with an acidic fixed bed catalyst in a distillation column, feeding the aldehyde and the alcohol to the reaction/distillatlon zone and at least partly converting them to the acetal, heating the column bottom disposed below the reaction/distillation zone in order to at least partly evaporate the bottom's mixture and to establish a defined temperature in the reaction/distillation zone, feeding an extractant into a rectifying section of the column, disposed above the reaction/distillation zone and condensing a product having more than 90% by weight of acetal at the top of the column.

Abstract: The invention relates to a process for preparing trioxane from aqueous formaldehyde solutions in the presence of acidic catalysts. The reaction of the formaldehyde to give trioxane takes place in a reaction column equipped with a circulation evaporator, and the formaldehyde solution used as the starting solution is mixed with a sidestream from the bottom of the reaction column and fed to the upper section of the reaction column via a tubular reactor. The process is notable for a low energy requirement and little by-product formation.

Abstract: Copolymers are described containing blocks of the structural repeat units of the formula I and blocks containing structural units of the formula II [—O—CH2—]x,??(I) [—O—R1—],??(II) where R1 is a divalent radical derived from a hydroxy-terminated aliphatic or cycloaliphatic oligomer or polymer which, where appropriate, has ether groups and/or carbonyloxy groups in the chain, and x is a whole number, at least 10. The copolymers may be used for producing moldings.

Abstract: Copolymers are described containing blocks of the structural repeat units of the formula I and blocks containing structural units of the formula II [—O—CH2—]x??(I), [—O—R1—]??(II), where R1 is a divalent radical derived from a hydroxy-terminated aliphatic or cycloaliphatic oligomer or polymer which, where appropriate, has ether groups and/or carbonyloxy groups in the chain, and x is a whole number, at least 10. The copolymers may be used for producing moldings.

Abstract: Process for removing methanol from formaldehyde-containing solutions. The present invention relates to a process for removing methanol from formaldehyde-containing solutions, with methanol being converted into formaldehyde dimethyl acetal by reactive distillation in the presence of an acidic fixed-bed catalyst, and the resultant mixture comprising methanol, formaldehyde dimethyl acetal and possibly other impurities being distilled off.

Abstract: Copolymers are described containing blocks of the structural repeat units of the formula I and blocks containing structural units of the formula II

Abstract: Molding compositions made from linear polyoxymethylene copolymers which essentially have oxymethylene units and oxyethylene units as structural units in the polymer chain, where the proportion of oxyethylene units in the structural units of the polymer chain is from 1.5 to 2.5 mol %. These molding compositions, and also uncolored or colored moldings produced from these have high stability and extremely low emission of formaldehyde and of residual monomers. At the same time they have a high level of mechanical properties, and they can therefore be utilized without restriction for the customary application sectors and processing methods.

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: A process for the preparation of polyoxymethylene copolymers, wherein 1,3,5-trioxane is polymerized with generally known comonomers in the presence of a strong protonic acid initiator and in the presence of a formaldehyde dialkyl acetal, and wherein the initiator is dissolved in the formaldehyde dialkyl acetal before admixing to the trioxane and the comonomers.

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: This invention relates to a reactor 1 for the continuous production of linear or cyclic acetals, in particular trioxane, dioxolane, tetroxane, dimethoxymethane, diethoxymethane, diethoxyethane and dibutoxyethane. This reactor has internal adjacently arranged evaporator elements 2, which allow for flow-through of a heat transport medium, and which are at least two meters high so as to generate a thermosiphon flow. The clear cross section between the evaporator elements is 20 to 80% of the overall cross section. Using the reactor, circulation ratios of up to 250 can be achieved. Thus, the reliability and availability of a production plant is increased while the susceptibility to breakdown decreases.

Abstract: A process for the preparation of polyoxymethylene copolymers, wherein 1,3,5-trioxane is polymerized with generally known comonomers in the presence of a strong protonic acid initiator and in the presence of a formaldehyde dialkyl acetal, and wherein the initiator is dissolved in the formaldehyde dialkyl acetal before admixing to the trioxane and the comonomers.