Abstract: An initiator for cationic polymerization comprises a salt of a protic acid as well as a protic acid. The molar ratio of protic acid to salt is in the range from 1:0.01 to 1:2000. The initiator is used for example for cationic homo- or copolymerization of trioxane, and permits stable and flexible operation of the polymerization.

Abstract: A process is described for preparation of oxymethylene homo- and copolymers. This encompasses heterogeneous polymerization of a monomer which forms oxymethylene groups in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, followed by the deactivation of the polymer in a homogeneous phase via treatment with a basic aprotic solvent or with an aprotic solvent which comprises a base. Oxymethylene homopolymers with very high stability are also described.

Abstract: Oxymethylene copolymers having a high proportion of terminal alkyl ether groups and having terminal hydroxyalkylene groups are described. These polymers are distinguished by high thermal stability and high hot water resistance.

Abstract: Oxymethylene polymers having a bimodal distribution or having a distribution of higher modality and having a targeted content of a low molecular weight fraction of from 1 to 5 percent by mass are described. Moldings of these polymers are distinguished by high low-temperature notched impact strength associated with a high modulus of elasticity.

Abstract: Processes are described which comprise: (a) providing a mixture comprising a cyclic formal and water, wherein the mixture has a cyclic formal concentration and a water concentration; (b) bringing the mixture into contact with an aqueously selective membrane; (c) creating a pressure differential across the membrane; and (d) obtaining a permeate having a higher water concentration and a lower cyclic formal concentration than the mixture, and a retentate having a lower water concentration and a higher cyclic formal concentration than the mixture.

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: Processes are described which comprise: (a) providing a mixture comprising a cyclic formal and water, wherein the mixture has a cyclic formal concentration and a water concentration; (b) bringing the mixture into contact with an organically selective membrane; (c) creating a pressure differential across the membrane; and (d) obtaining a permeate having a lower water concentration and a higher cyclic formal concentration than the mixture, and a retentate having a higher water concentration and a lower cyclic formal concentration than the mixture.

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: An initiator for cationic polymerization comprises a salt of a protic acid as well as a protic acid. The molar ratio of protic acid to salt is in the range from 1:0.01 to 1:2000. The initiator is used for example for cationic homo- or copolymerization of trioxane, and permits stable and flexible operation of the polymerization.

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: A process and an apparatus are described for preparation of oxymethylene polymers. This process encompasses polymerization, in a homogeneous phase, of a monomer which forms oxymethylene groups, as far as 90% of maximum conversion in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, followed by deactivation of the reaction mixture. The resultant oxymethylene polymers have alkyl ether end groups and are extremely stable.

Abstract: An apparatus is described for preparation of oxymethylene homo- and copolymers. This encompasses heterogeneous polymerization of a monomer which forms oxymethylene groups in the presence of an acetal of formaldehyde and of an initiator for cationic polymerization, followed by the deactivation of the polymer in a homogeneous phase via treatment with a basic aprotic solvent or with an aprotic solvent which comprises a base. Oxymethylene homopolymers with very high stability are also described.

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

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.