Abstract: Described is the use of metal oxides as heterogeneous catalysts in a process for producing polyamides by polymerization of lactams and optionally further polyamide-forming monomers wherein the metal oxides are used in a form which permits mechanical removal from the reaction mixture and are removed from the reaction mixture during or after the polymerization, to reduce the extractables content of the polyamide obtained.

Abstract: In a process for producing polyamides, a mixture comprising hexamethylenediamine and aminocapronitrile and obtained from the hydrogenation of adiponitrile is reacted with water and a dicarboxylic acid.

Abstract: A process for producing polyamides by reacting at least one lactam and optionally further polyamide-forming monomers with aqueous monomer and oligomer extracts obtained during the extraction with water of the polymer product obtained in the production of polyamides, the water content of the reaction mixture being in the range from 0.5 to 13% by weight comprises conducting the reaction in the presence of metal oxides, beta-zeolites, sheet-silicates or silica gels, which may be doped, as heterogeneous catalysts, the heterogeneous catalysts being used in the form which permits mechanical removal from the reaction mixture and are removed from the reaction mixture in the course of the polymerization or after it has ended.

Abstract: Disclosed are the use of lactams, aminocarboxylic acids or mixtures thereof as acceleratant or cocatalyst in the production of polyamides from aminonitriles and water, and a suitable process therefor.

Abstract: The continuous process for producing polyamides by reacting at least one aminonitrile with water comprises the following steps: (10) reacting at least one aminonitrile with water at a temperature of from 200 to 290° C. at a pressure of from 40 to 70 bar in a flow tube containing a Brönsted acid catalyst selected from a beta-zeolite, sheet-silicate or metal oxide catalyst in the form of a fixed bed, (11) diabatically or adiabatically expanding the reaction mixture from step (1) into a first separation zone to a pressure of from 20 to 40 bar, the pressure being at least 10 bar lower than the pressure in step (1), and to a temperature within the range from 220 to 290° C. by flash evaporation and removal of ammonia, water and any aminonitrile monomer and oligomer, (12) further reacting the reaction mixture from step (2) in the presence of water at a temperature of from 200 to 290° C.

Abstract: A process for the preparation of pulverulent, cationic, crosslinked polymers based on monoethylenically unsaturated monomers containing a quaternized or quaternizable nitrogen atom comprises carrying out the polymerization in supercritical carbon dioxide as inert diluent with mixing at from 31° C. to 150° C. and above 73 bar.

Abstract: Polyamides are produced by reacting aminocarboxylic acid compounds of the general formula I H2N—(CH2)m—COR1  (I) where R1 is OH, O—C1-12-alkyl or NR2R3, where R2 and R3 are independently hydrogen, C1-12-alkyl or C5-8-cycloalkyl, and m is an integer from 3 to 12, optionally in a mixture with aminonitriles and their hydrolysis products and optionally in the presence of water, in a liquid phase at elevated pressure and elevated temperature in the presence of metal oxides as heterogeneous catalysts, the metal oxides being used in a form which permits mechanical removal from the reaction mixture and being removed from the reaction mixture during or after the polymerization.

Abstract: The preparation of polyamides, their oligomers or mixtures thereof, where appropriate with other reaction products, takes place by reacting amino nitrites (A) and, where appropriate, other polyamide-forming monomers and/or oligomers with water (D) in a reactive distillation, wherein the reaction product (P) is discharged from the bottom of the reactive distillation apparatus, and ammonia (N) which is produced and, where appropriate, other low molecular weight compounds which are produced, and water, are taken off overhead.

Abstract: The process for producing polymer blends by reacting at least one aminonitrile with water in the presence of thermoplastic polymers and optionally further polyamide-forming monomers comprises the following steps: (1) reacting at least one aminonitrile with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 35×106 Pa to obtain a reaction mixture, (2) further reacting the reaction mixture at a temperature from 150 to 400° C.

Abstract: In a process for producing polyamides by polymerization of lactams in the presence of metal oxides as heterogeneous catalysts, the metal oxides are used in a form which permits mechanical removal from the reaction mixture and are removed from the reaction mixture in the course of or on completion of the polymerization.

Abstract: Polyamide particles, or polymer particles comprising polyamides, are extracted with aqueous solutions of aminonitiles and optionally further polyamide-forming monomers, polyamide-forming oligomers or mixtures thereof.

Abstract: A continuous process for preparing a polyamide by reacting at least one aminonitrile with water comprises: (1) reacting at least one aminonitrile with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 35×106 Pa in a flow tube containing a Brönsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide to obtain a reaction mixture, (2) further reacting the reaction mixture at a temperature from 150 to 400° C.

Abstract: The batch process for producing a polyamide by reaction of a mixture comprising at least one aminonitrile, and optionally monomers useful for polyamide production, with water, comprises the following steps: (1) reacting the mixture with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 35×106 Pa to obtain a reaction mixture, (2) further reacting the reaction mixture at a temperature from 150 to 400° C. and a pressure which is lower than the pressure in step 1, the temperature and pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phase, and the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phase, and (3) admixing the first liquid or the first solid phase or the mixture of first liquid and first solid phase with a gaseous or liquid phase comprising water at a temperature from 150 to 370° C.

Abstract: The continuous process for producing a polyamide by reacting at least one aminonitrile with water comprises the following steps: (1) reacting at least one aminonitrile with water at a temperature from 90 to 400° C. and a pressure from 0.1 to 15×106 Pa in a flow tube containing packing elements of a Brönsted acid catalyst selected from beta-zeolite, sheet-silicate or titanium dioxide packing elements and metallic packing elements to obtain a reaction mixture, (2) further reacting the reaction mixture at from 150 to 400° C.

Abstract: Process for the preparation of pulverulent polymers by polymerization in supercritical carbon dioxide in the presence of polyoxyalkylene-polysiloxane copolyers The invention relates to a process for the preparation of pulverulent polymers by polymerization of ethylenically unsaturated monomers (a) in supercritical carbon dioxide as inert diluent, where the polymerization is carried out in the presence of polyoxyalkylene-polysiloxane copolymers.

Abstract: The present invention concerns a process for producing dispersions of watsoluble vinyl polymers and a stabilizer for carrying out this process. Such water-soluble, particularly cationic vinyl polymers, are employed on a large scale as process expediters for carrying out, for instance, separating processes in water treatment or waste-water purification, respectively, in the paper, coal and ore industries, in oil production or also in the food stuff industry, among others, for floculation, coagulation, retention or dewatering. According to the present invention, water-soluble vinyl polymers are homo- or copolymerized in the presence of a dispersion stabilizer of the invention. The stabilizer consists of a graft copolymer whose backbone is formed by polyethylene oxide and its grafted branches of cationic vinyl monomers. Among others, cationic, hydrophobically modified vinyl monomers can be advantageously employed.