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: The present invention relates to a process for the preparation of oxymethylene polymers as well as oxymethylene polymers obtainable therefrom. The process includes polymerization of a monomer, which forms —CH2—O— units in the presence of an acetal of formaldehyde or a polyhydric alcohol and an initiator for cationic polymerization. The initiator may be a heteropoly acid or an acid salt thereof which is dissolved in an alkyl ester of a polybasic carboxylic acid.

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 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: 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: A process and an apparatus for the preparation of oxymethylene polymers is described. The process encompasses the polymerization of a monomer that forms oxymethylene groups, if appropriate in the presence of a cyclic acetal, together with an acetal of formaldehyde and with an initiator for cationic polymerization, preferably in a gas-tight kneader or extruder. The temperature profile of the polymerization here is designed in such a way that the polymerization mixture, which is initially heterogeneous by virtue of precipitating polymer, is converted to a homogeneous phase at the end of the polymerization. The homogeneous phase in which the polymer is present in liquid form is stabilized via addition of deactivators. After removal of volatile constituents, oxymethylene polymers are obtained with high thermal stability and with good mechanical properties.

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: 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: 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: A coating-removing solution for photo-cross-linked and thermally cross-linked photoresist masks and solder resist masks cross-linked by exposure to light and heat and which solution contains a diglycol monoalkyl ether, a glycol monoalkyl ether, an alkali hydroxide, water, and a water-soluble fluoride.

Abstract: Described is a process for the patterned metallisation of structured printed circuit boards in which the fully structured printed circuit board is covered with a solder stop mask, with the solder contact locations being left open, the solder stop mask is heated under such conditions that complete hardening does not yet occur and the copper surface of the printed circuit board is practically not oxidized, metal is deposited out of an aqueous bath at the exposed solder contact locations and after the metal deposit operation the mask is heated sufficiently long to a sufficiently high temperature that the mask is completely hardened throughout. The incomplete pre-hardening step prevents the solution infiltrating under the mask in the metallisation operation and thereby loosening the adhesion thereof.

Abstract: Disclosed is an electrophotographic recording material comprising a photoconductive double layer disposed on an electrically conductive support, which double layer comprises a charge carrier-generating layer and a charge transport layer. The interface region of the charge carrier-generating and charge transport layers defines a mixing zone into which one or more of the constituents of the separate layers have diffused. A process for producing the electrophotographic recording material is also disclosed.