Process for preparing water-redispersible polymer powders for dry formulations of construction materials

1 . A process for producing building material dry formulations, comprising:

mixing and homogenizing one or more hydraulically-setting binders, one or more fillers, one or more protective-colloid-stabilized vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders and optionally one or more additives to form a dry mixture;

wherein storage stability of the protective-colloid-stabilized vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible dry powders is improved by drying aqueous dispersions comprising protective-colloid-stabilized vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers, one or more water-soluble inorganic salts, and one or more desiccants;

wherein the one or more water-soluble inorganic salts are selected from the group consisting of alkali metal sulfates;

wherein the one or more desiccants are selected from the group consisting of polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides, polysaccharides and proteins; and

wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders do not contain polyalkylene polyamine.

2 . The process of claim 1 , wherein the one or more water-soluble inorganic salts are selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate.

3 . The process of claim 1 , wherein the one or more water-soluble inorganic salts are sodium sulfate.

4 . The process of claim 1 , wherein the aqueous dispersions or the water-redispersible powders contain 0.1% to 20% by weight of the one or more water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

5 . The process of claim 1 , wherein the aqueous dispersions or the water-redispersible powders contain 0.1% to 4% by weight of the one or more water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

6 . The process of claim 1 , wherein the one or more desiccants are selected from the group consisting of polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides and proteins.

7 . The process of claim 1 , wherein protective colloids and the one or more desiccants are polyvinyl alcohols.

8 . The process of claim 1 , wherein the one or more vinyl acetate-ethylene copolymers are selected from the group consisting of copolymers of vinyl acetate with 1% to 40% by weight of ethylene; copolymers of vinyl acetate with 1% to 40% by weight of ethylene and 1% to 50% by weight of one or more further comonomers from the group of vinyl esters having 3 to 12 carbon atoms in the carboxyl radical; copolymers of vinyl acetate, 1% to 40% by weight of ethylene, and 1% to 60% by weight of acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms; copolymers with 30% to 75% by weight of vinyl acetate, 1% to 40% by weight of ethylene, 1% to 30% by weight of vinyl laurate or vinyl esters of an alpha-branched carboxylic acid having 5 to 13 carbon atoms, and also 1% to 30% by weight of acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms; and copolymers with vinyl acetate, 1% to 40% by weight of ethylene, and 1% to 60% by weight of vinyl chloride; and

where the percentages by weight add up to 100% by weight in each case.

9 . The process of claim 1 , wherein the styrene-(meth)acrylic ester copolymers are based on styrene and one or more monomers from the group consisting of methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate.

10 . The process of claim 1 , wherein the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers have a glass transition temperature Tg of −50° C. to +25° C.

11 . The process of claim 1 , wherein the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers are produced by free-radical-initiated emulsion polymerization and that one or more water-soluble inorganic salts are added before or during the emulsion polymerization.

12 . The process of claim 1 , wherein the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers are produced by free-radical-initiated emulsion polymerization and that one or more water-soluble inorganic salts are added after the emulsion polymerization and before the drying of the aqueous dispersions.

13 . The process of claim 1 , wherein the hydraulically-setting building material dry formulations contain 5% to 50% by weight of hydraulically-setting binders based on the total weight of the hydraulically-setting building material dry formulations.

14 . The process of claim 1 , wherein the hydraulically-setting building material dry formulations are used as reinforcing compounds for thermal insulation composite systems, as adhesives for thermal insulation panels or soundproofing panels, as tile adhesives, or as mortars, self-leveling compounds, screeds or plasters.

15 . The process of claim 1 , wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders contain 1% to 30% of the one or more desiccants based on the total weight of the copolymers.

16 . The process of claim 1 , wherein the building material dry formulations contain 0.1% to 5.0% by weight of polymer powders and 5% to 50% by weight of hydraulically-setting binders, in each case based on the total weight of the building material dry formulations.