Wacker-chemie Gmbh

Wilhelm Lechner

Herbert Eck

Hubert Wiest

Klaus Adler

Manfred Hannebaum

Erwin Lieb

Paul-Gerhard Kirst

Josef Hanzalik

A process for the production of an aqueous dispersion stabilized by a water-soluble polyvinyl alcohol and based on copolymers that comprise at least 60% by weight of monomer units selected from the group consisting of esters of acrylic acid, esters of methacrylic acid, styrene, and substituted styrene and mixtures thereof, consisting essentially of subjecting a stabilized dispersion of a monomer mixture containing at least 60% by weight of monomers selected from the group consisting of esters of acrylic acid, esters of methacrylic acid, styrene, substituted styrene and mixtures thereof, said dispersion being an aqueous dispersion stabilized by a water-soluble polyvinyl alcohol, to polymerization at a temperature in excess of 60.degree. C. in the presence of a free-radical-forming catalyst selected from the group consisting of (a) organic catalysts soluble in the monomers and also being at least partially water-soluble, optionally in combination with water-soluble reducing agents and (b) peroxosulfur catalysts, in such a manner that, during the entire duration of the reaction, said monomer mixture is supplied at such a rate by metering in the monomer mixture in the form of a previously obtained emulsion, that the monomer concentration is maintained at less than 20% by weight, based on the total weight of the reaction mixture, and recovering said stabilized dispersion; as well as the aqueous dispersion produced by the process, the use of the aqueous dispersions as a binder in dispersion dyes and adhesives, the said binder having increased resistance against hydrolysis on drying due to the special manufacturing process.

Process for the manufacture of copolymers having increased resistance

An additive composition used in the preparation of low air pore, plastic-containing, hydraulically-setting binders consisting essentially of a mixture of (1) an aqueous copolymer dispersion having a solids content of between 30% and 65% by weight, a glass transition temperature of the solid copolymer of between -10.degree. C. and +40.degree. C., and a K-value of the solid copolymer of from 35 to 80, which aqueous copolymer dispersion being produced from monomer units of vinyl chloride, vinyl acetate and one or more additional copolymerizable monomers selected from the group consisting of ethylene, vinyl alkanoates having from 8 to 18 carbon atoms in the alkanoyl, and (meth)acrylic acid esters with alkanols having 3 to 8 carbon atoms, by free-radical polymerization in the presence of from 1.5% to 5% by weight of protective colloids and from 0 to 3% by weight of nonionic surface-active agents, both based on the dispersion, with (2) from 0.3% to 3% by weight, based on the mixture of a defoamer mixture consisting of

Additive composition used in the preparation of low air pore, plastic

A process for the continuous manufacture of an aqueous ethylene/vinyl acetate copolymer dispersion which comprises continuously copolymerizing ethylene and vinyl acetate and optionally other .alpha.-olefinically unsaturated monomers, in an aqueous emulsion in the presence of an emulsifier and/or a protective colloid, and in the presence of a free-radical-forming redox catalyst system of a reducing agent and an oxidizing agent as well, optionally, as a heavy metal salt, and recovering said ethylene/vinyl acetate copolymer dispersion, characterized by (a) the presence of a molar excess of at least 3 times, preferably from 3 to 10 times, said reducing agent over said oxidizing agent dosed into the reaction medium and (b) adding the monomers continuously to the reaction mixture at such a rate that the concentration of unreacted monomers at no place in the reaction zone exceeds 15% by weight of the total weight of the reaction mixture.

Process for the continuous production of an ethylene/vinyl acetate

An improvement in the production of polyvinyl ester dispersions by polymerization of vinyl esters or copolymerization of vinyl esters with up to 40% by weight of oil-soluble, mono-olefinically-unsaturated monomers in an aqueous emulsion in the presence of water-soluble radical-forming polymerization catalysts, protective colloids and optionally emulsifiers and polymerization aids, the improvement comprising using carboxymethyl celluloses having a substitution degree of at least 10 as said protective colloids; as well as stable mixtures of the said polyvinyl ester dispersions and dextrin.

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Burghausen, Germany

Wilhelm Lechner