PROCESS FOR PREPARING WATER-REDISPERSIBLE POLYMER POWDERS FOR DRY FORMULATIONS OF CONSTRUCTION MATERIALS

Abstract

Vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers along with processes for preparing the same and uses for the same. Wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers are in the form of water-redispersible powders for producing hydraulically-setting building material dry formulations. Where the storage stability of the protective-colloid-stabilized vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers in the form of water-redispersible 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. Where the water-soluble inorganic salts are selected from the group consisting of alkali metal sulfates and where the desiccants are selected from the group comprising polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides, polysaccharides and proteins.

Claims

1-10. (canceled)

11. A use for vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers, comprising: wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers are in the form of water-redispersible powders for producing hydraulically-setting building material dry formulations; wherein the storage stability of the protective-colloid-stabilized vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers in the form of water-redispersible 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 water-soluble inorganic salts are selected from the group consisting of alkali metal sulfates; and wherein the desiccants are selected from the group comprising polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides, polysaccharides and proteins.

12. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the water-soluble inorganic salts are selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate.

13. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein sodium sulfate is used in the form of the water-soluble inorganic salt.

14. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the aqueous dispersions or the water-redispersible powders contain 0.1% to 20% by weight of water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

15. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the aqueous dispersions or the water-redispersible powders contain 0.1% to 4% by weight of water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

16. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the desiccants are selected from the group comprising polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides and proteins.

17. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the protective colloids and the desiccants are polyvinyl alcohols.

18. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the one or more vinyl acetate-ethylene copolymers are selected from the group comprising 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.

19. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the styrene-(meth)acrylic ester copolymers are based on styrene and one or more monomers from the group comprising methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate.

20. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers have a glass transition temperature Tg of −50° C. to +25° C.

21. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, 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.

22. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, 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.

23. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders contain no polyalkylene polyamine.

24. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, 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.

25. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, 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.

26. The use of vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers of claim 11, wherein the vinyl acetate-ethylene and/or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders contain 1% to 30% of desiccants based on the total weight of the copolymers.

Description

EXAMPLE 1

[0078] Production of the polymer powders:

[0079] An aqueous dispersion of a vinyl acetate-ethylene copolymer (glass transition temperature Tg: 17° C.) stabilized with 10% by weight of polyvinyl alcohol (degree of hydrolysis: 88 mol %, Höppler viscosity: 4 mPas in a 4% aqueous solution) was treated with 2.0% by weight, based on the polymer content of the dispersion (solid/solid), of a partially hydrolyzed polyvinyl alcohol (degree of hydrolysis: 88 mol %; Höppler viscosity: 4 mPas in a 4% aqueous solution) and 6.0% by weight, based on the polymer content of the dispersion (solid/solid), of a partially hydrolyzed polyvinyl alcohol (degree of hydrolysis: 88 mol %; Höppler viscosity: 13 mPas in a 4% aqueous solution)

[0080] and also with sodium sulfate (Na.sub.2SO.sub.4) in the amount specified in Table 1 and dried by spray drying in a manner conventional per se, at an entry temperature of 130° C. and an exit temperature of 80° C., to obtain a redispersible powder. To the polymer powder was added 4% by weight of kaolin and 16% by weight of calcium carbonate as anticaking agents.

[0081] Determination of the sedimentation behavior (TS=tube sedimentation) of the polymer powder:

[0082] The sedimentation behavior of the aqueous redispersion of the polymer powder serves as a measure of the redispersibility and thus of the storage stability of the polymer powder.

[0083] The respective polymer powder obtained in example 1 was converted into an aqueous redispersion having a solids content of 50% by adding water under the action of strong shear forces.

[0084] The sedimentation behavior was determined by diluting the aqueous redispersion with water to a solids content of 0.5% and filling a graduated tube with 100 ml of this dispersion and measuring the height of the sedimented solid. The values are reported in cm of sedimentation after 24 hours. The lower the sedimentation value in the tube, the lower the coarse fraction of the redispersion and the higher the fine fraction and the better the redispersibility and storage stability of the polymer powder.

[0085] The resulting values for the sedimentation behavior (TS) are listed in Table 1.

TABLE-US-00001 TABLE 1 Na.sub.2SO.sub.4 content of the polymer powders and sedimentation (TS) test result: Na.sub.2SO.sub.4 content of the polymer powder [% by weight].sup.a) Sedimentation[cm] Comparative 0 1.4 polymer powder 1 Polymer powder 2 1 0.9 Polymer powder 3 2 0.6 .sup.a)% by weight of Na.sub.2SO.sub.4 based on the polymer content of the dispersion (solid/solid)

[0086] For a comparison, the sedimentation behavior (TS) of (comparative) polymer powders 1 to 3 was determined as described above, with the difference that the respective polymer powder was redispersed not in water but in Na.sub.2SO.sub.4-containing water. The Na.sub.2SO.sub.4 content of the Na.sub.2SO.sub.4-containing water was adjusted for the respective polymer powder so that for each redispersion a total Na.sub.2SO.sub.4 concentration of 0.015% by weight was obtained. The resulting values for the sedimentation behavior (TS) are shown in Table 2.

TABLE-US-00002 TABLE 2 Sedimentation (TS) test result: Sedimentation [cm] Comparative polymer powder 1 1.7 Polymer powder 2 1.1 Polymer powder 3 0.7

[0087] The test results in Tables 1 and 2 show that the addition of sodium sulfate to the redispersion adversely affects the sedimentation behavior.

[0088] Surprisingly, the introduction of sodium sulfate into the polymer powders was found to improve the sedimentation behavior and thus the redispersibility and storage stability of the polymer powders, as can be seen from Table 1.

COMPARATIVE EXAMPLE 2

[0089] Comparative example 2 was carried out identically to example 1, the sole difference being that, instead of sodium sulfate, the respective amount of sodium carbonate (Na.sub.2CO.sub.3) specified in Table 3 was added to the aqueous dispersion. The test results for the sedimentation behavior (TS) are also given in Table 3.

TABLE-US-00003 TABLE 3 Na.sub.2CO.sub.3 content of the polymer powders and sedimentation (TS) test result: Na.sub.2CO.sub.3 content of the polymer powder [% by weight].sup.a) Sedimentation[cm] Comparative 0 1.4 polymer powder 4 Comparative 1 1.1 polymer powder 5 Comparative 2 1.3 polymer powder 6 .sup.a)% by weight of Na.sub.2CO.sub.3 based on the polymer content of the dispersion (solid/solid)

EXAMPLE 3

[0090] Example 3 was carried out identically to example 1, the sole difference being that the vinyl acetate-ethylene copolymer had a glass transition temperature Tg of −15° C. The test results for the sedimentation behavior (TS) are also given in Table 4.

TABLE-US-00004 TABLE 4 Na.sub.2SO.sub.4 content of the polymer powders and sedimentation (TS) test result: Na.sub.2SO.sub.4 content of the polymer powder [% by weight].sup.a) Sedimentation[cm] Comparative 0 2.0 polymer powder 7 Polymer powder 8 1 1.1 Polymer powder 9 2 1.0 .sup.a)% by weight of Na.sub.2SO.sub.4 based on the polymer content of the dispersion (solid/solid)

[0091] The polymer powders from example 3 were additionally stored for two weeks in an open container at 35° C. and 75% atmospheric humidity. The sedimentation behavior (TS) was then determined as described for example 1. The test results are given in Table 5.

TABLE-US-00005 TABLE 5 Na.sub.2SO.sub.4 content of the polymer powders and sedimentation (TS) test result: Na.sub.2SO.sub.4 content of the polymer powder [% by weight].sup.a) Sedimentation[cm] Comparative 0 3.8 polymer powder 7 Polymer powder 8 1 2.4 Polymer powder 9 2 1.8 .sup.a)% by weight of Na.sub.2SO.sub.4 based on the polymer content of the dispersion (solid/solid)

EXAMPLE 4

[0092] Example 4 was carried out identically to example 1, the sole difference being that a styrene-n-butyl acrylate copolymer having a glass transition temperature Tg of 20° C. was used instead of the vinyl acetate-ethylene copolymer.

[0093] The test results for the sedimentation behavior (TS) are also given in Table 5.

TABLE-US-00006 TABLE 5 Na.sub.2SO.sub.4 content of the polymer powders and sedimentation (TS) test result: Na.sub.2SO.sub.4 content of the polymer powder [% by weight].sup.a) Sedimentation[cm] Comparative 0 2.7 polymer powder 10 Polymer powder 11 1 1.8 Polymer powder 12 2 1.4 .sup.a)% by weight of Na.sub.2SO.sub.4 based on the polymer content of the dispersion (solid/solid)

[0094] Examples 1, 3 and 4 show that the use according to the invention of the water-soluble salt sodium sulfate brings about a marked reduction in sedimentation in the tube and thus an improvement in the redispersibility and storage stability of the polymer powder.

[0095] This applies both directly after spray drying and after storage in a warm and humid environment, as shown by Example 3.

[0096] By contrast, the redispersibility was not significantly improved by corresponding addition of sodium carbonate (comparative example 2). The differences in sedimentation behavior found for comparative example 2 are within the range of the measurement error (±0.2). Increasing the sodium carbonate content from 1% by weight in comparative polymer powder 5 to 2% by weight in comparative polymer powder 6 in fact resulted in a deterioration in sedimentation behavior.

[0097] Preparation of building material dry formulations:

[0098] The dry mortar formulations shown below were prepared with the polymer powders obtained. The dry mortar formulations were prepared and applied in a conventional manner.

[0099] Tile adhesive with low polymer powder content: [0100] quartz sand 577 parts, [0101] portland cement 400 parts, [0102] cellulose 3 parts, [0103] polymer powder 20 parts.

[0104] Tile adhesive with moderate polymer powder content: [0105] quartz sand 444 parts, [0106] calcium carbonate 80 parts, [0107] portland cement 350 parts, [0108] aluminate cement 70 parts, [0109] retarder 2 parts, [0110] cellulose 4 parts, [0111] polymer powder 60 parts.

[0112] Flexible sealing slurry with high polymer powder content: [0113] quartz sand 300 parts, [0114] calcium carbonate 134 parts, [0115] portland cement 130 parts, [0116] aluminate cement 70 parts, [0117] lightweight filler 50 parts, [0118] finely divided silica 5 parts, [0119] fibers 5 parts, [0120] retarder 1 part, [0121] associative thickener 5 parts, [0122] polymer powder 300 parts.

[0123] The improved redispersibility of the polymer powders according to the invention makes corresponding building products having higher flexural strengths and increased flexibility accessible.