Abstract: The invention relates to an apparatus for transporting polymer dispersions, said apparatus being capable of being driven by a drive and being designed as an impeller (28). It is possible for said impeller both to be surrounded by a housing and to protrude freely into the polymer dispersion contained in the reactor tank. A number of vanes (2) are mounted in the region of the hub (1) of the impeller (28) in such a way that pumping spaces (5, 25) on the front side (7) and rear side (8) of the impeller (28) are flowed through uniformly.

Abstract: A process for preparing polymer dispersions of at least one of the polymerizable monomers from the groups consisting of alkyl (meth)acrylates, vinyl esters of carboxylic acids having 1-20 carbon atoms, vinylaromatic compounds, nitrites, vinyl halides, vinyl ethers, hydrocarbons having 2-8 carbon atoms, and hydroxyl-containing monomers in emulsion polymerization technology at a polymerization temperature of at least 40° C., in the presence of a free-radical polymerization initiator, which comprises preparing the polymer, which forms to at least 85% by weight from one or more of these monomers. In a first stage, water, as reaction-inert solvent, dispersing assistants where appropriate, seed where appropriate, and a first portion of monomer(s), where appropriate, are introduced.

Abstract: In the process and a correspondingly appropriate device for preparing homo- or copolymers of at least one of the, polymerizable monomers of the group consisting of styrene, butadiene, vinyl chloride, vinyl acetate, vinylidene chloride, alkyl (meth)acrylatc (meth)acrylic acid, (meth)acrylonitrile and (meth)acrylamide reaction is carried out at at least 40° C. in the presence of a dispersing auxiliary and of a free-radical polymerization initiator such that at least 85% by weight of the polymer is formed from these monomers.

Abstract: A particulate polymer P having an average particle diameter d50 of from 0.1 to 50 &mgr;m is prepared by a process in which an emulsion E is prepared from one or more monomers M, which are polymerizable by free radical polymerization to give the polymer P, water, and at least one protective colloid PC by the action of high shear forces, and the emulsion E is subjected to polymerization in a reactor with the use of a free radical polymerization initiator RI wherein, based on the emulsion E, not more than 75% by weight of the emulsion E (initially taken portion of E) are initially taken in the reactor at the beginning of the polymerization and at least 25% by weight of the emulsion E (feed portion of E) are not fed to the reactor until after the beginning of the polymerization.

Abstract: A process for preparing an aqueous polymer dispersion by free-radical polymerization of compounds I and II whose individual solubility in water is very different by the miniemulsion polymerization technique, in which process the reaction mixture is agitated by an external circuit which leads from and back again to the reaction vessel and comprises at least one low-shear pump and at least one heat exchanger having an essentially laminar flow profile. The copolymers prepared in accordance with the invention can be produced in a good yield within short times and exhibit good performance properties.

Abstract: Copolymers of crotonic acid are purified, to remove monomeric crotonic acid, by extracting the copolymers with water at from 50.degree. to 120.degree. C and stirring the system, the flow energy of the water and the energy of stirring being chosen so that the polymer particles just remain suspended.