Basf Aktiengesellschaft

Guenter Hirsch

Thomas Schwerzel

Kurt Wendel

Heinrich Hartmann

Walter Denzinger

Claus Cordes

Gregor Ley

Hans-Uwe Schenck

Hans J Wolf

Werner Auhorn

Michael Ernst Rohmann

Hans-Werner Becker

Emil Lohrer

Aqueous polymer dispersions containing polymers obtainable by free-radical polymerization of unsaturated monomers, and sugared starch, and the use thereof.

Aqueous polymer dispersions

A polymer powder obtained by drying an aqueous polymer dispersion, wherein the aqueous polymer dispersion is obtained by free-radical polymerization of unsaturated monomers and contains at least one added starch-degradation product which is obtained by hydrolysis in the aqueous phase, is water soluble at room temperature and has a weight average molecular weight M.sub.w of from 2500 to 25000.

Aqueous pigment suspensions which are added to the stock suspension during papermaking and contain, as a dispersant, from 0.1 to 2% by weight, based on the pigment, of a copolymer which contains, as copolymerized units,

Aqueous pigment suspensions based on alkyl (meth) acrylates as

Polymers of acrylic acid or methacrylic acid are prepared by polymerizing acrylic acid and/or methacrylic acid at 50.degree.-180.degree. C. in a C.sub.2 -C.sub.6 -alcohol or mixtures thereof with water having a C.sub.2 -C.dwnarw.6.uparw.-alcohol content of not less than 40% by weight in the presence of free radical polymerization initiators and from 0.01 to 5% by weight, based on the monomers used, of inorganic acids of phosphorus in which the phosphorus has an oxidation number of from 1 to 4, or of water-soluble salts thereof, water-soluble --PO(OH).sub.2 -containing compounds and/or water-soluble salts thereof. The polymers thus prepared are effective milling aids and dispersants for pigments for producing aqueous pigment slurries for use in paper-coating compositions.

Preparation of polymers of acrylic acid or metharcylic acid

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The subject invention relates to compositions which are used as auxiliaries for pigment grinding and as dispersing agents for pigments. The compositions are essentially copolymers based upon acrylic acid, methacrylic acid, and sulfonic acid group containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid.

Grinding or dispersing agents for pigments

An improved paper-coating composition containing, per 100 parts by weight of finely divided pigment, from 5 to 25 parts by weight of one or more copolymers, having a glass transition temperature of from -40.degree. to 50.degree. C., in the form of an aqueous dispersion, and from 0.1 to 10 parts by weight of one or more water-soluble or water-swellable co-binders selected from the group comprising polyvinyl alcohol, cellulose ethers, starch, casein, alginates and high molecular weight carboxyl-containing emulsion polymers. The co-binder is added to the paper-coating composition in the form of a water-in-oil emulsion. Paper-coating compositions having high water retention are obtained, and papers coated with such compositions have improved water resistance.

Paper-coating compositions

An improved paper coating composition containing, per 100 parts by weight of finely divided pigment, from 5 to 25 parts by weight of a copolymer A having a glass transition temperature of from -40.degree. to +50.degree. C. in the form of an aqueous dispersion and from 0.1 to 10 parts by weight of a high molecular weight polymer B which is obtained by polymerizing water-soluble ethylenically unsaturated monomers in a water-in-oil emulsion. Papers having improved water resistance are obtained.

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Mutterstadt, Germany

Guenter Hirsch