Abstract: A horizontal solid-bed polymerization reactor which is divided into a plurality of zones, for example a reaction zone, an after-reaction zone, a heating zone and a product discharge zone and possesses inlet and outlet openings for feeding substances into the zones and/or removing substances from the zones, the zones being separated from one another over a part of the reactor cross-section by means of weirs, wherein two drive shafts which are independent of one another and possess mixing elements are introduced into the solid-bed polymerization reactor in the middle.

Abstract: Water-soluble polymer powders are prepared by polymerizing water-soluble ethylenically unsaturated monomers in a powder bed in the presence of polymerization initiators and water while maintaining the powder state, removing the heat of polymerization by distilling off water and circulating the reaction mixture, by a process in which water-insoluble organic peroxides which are liquid at 20.degree. C. are used alone or as a mixture with up to 50% by weight, based on the initiator mixture, of water-soluble, organic azo initiators and/or water-insoluble solid peroxy-containing compounds, as polymerization initiators.

Abstract: Insoluble polymer powders which are only slightly swellable are prepared by polymerization of N-vinylpyrrolidone or a mixture of (a) an N-vinylcarboxamide, acrylamide, methacrylamide, acrylic acid, methacrylic acid, acrylates, methacrylates and/or a vinyl ester and (b) from 0.1 to 10% by weight, based on the total amount of monomers, of, as a crosslinking agent, a compound possessing two or more ethylenically unsaturated double bonds, in a powder bed in the presence of a heat-transfer medium and in the absence of oxygen and polymerization initiators, at from 90.degree. to 220.degree. C., the powder state being maintained, the reaction mass being circulated and the heat-transfer medium evaporated from the polymerization zone.The resulting polymers are used as adsorbents, as formulation assistants for crop protection agents or as ion exchangers.

Abstract: Insoluble polymer powders which are only slightly swellable and are based on N-vinylpyrrolidone are prepared by polymerization of N-vinylpyrrolidone or a mixture of this with copolymerizable monomers and from 0.1 to 10% by weight, based on the total amount of monomers, of a crosslinking agent in a powder bed in the presence of a heat-transfer medium, which is inert to the reactants, and in the absence of oxygen and polymerization initiators, at from 90.degree. to 220.degree. C., while maintaining the powder state, circulating the reaction mass and evaporating the heat-transfer medium from the polymerization zone. The resulting insoluble polymers which are only slightly swellable are used as adsorbents or formulation assistants for fertilizers and crop protection agents.

Abstract: Maleic anhydride copolymer powders are prepared by a process wherein a solution or dispersion of maleic anhydride in an alkyl vinyl ether and/or an alkene, containing from 3 to 25 moles of the alkyl vinyl ether and/or alkene per mole of maleic anhydride, is brought into contact with a powder bed under polymerization conditions, and is polymerized in the bed while the reaction mass is circulated and the powder state is maintained, and the heat generated during polymerization is removed by evaporating excess monomer which boils lower than maleic anhydride.