AQUEOUS DISPERSIONS AND EMULSION PAINTS COMPRISING ETHYLHEXYL ACRYLATE-BUTYL ACRYLATE-STYRENE COPOLYMERS

Abstract

The present invention relates to an aqueous emulsion paint comprising a) 5% to 50% by weight of an aqueous polymer dispersion having a solids content in the range from 40% to 60% by weight, obtainable by the free-radical aqueous emulsion polymerization of a monomer mixture comprising ethylhexyl acrylate, butyl acrylate and one or more vinylaromatics, preferably styrene, b) 0.1% to 5% by weight of alkali metal alkylsiliconate and/or water-soluble silicate, c) 20% to 70% by weight of inorganic fillers, d) 0% to 30% by weight of at least one pigment, e) 0.1% to 10% by weight of customary auxiliaries, and f) water,
based in each case on the total amount of the emulsion paint, the pH of the emulsion paint having a value in the range from 10 to 12, and also relates to the aqueous polymer dispersions, to a process for the preparation thereof and to the use thereof as organic binders in emulsion paints having a high pH.

Claims

1.-13. (canceled)

14. An aqueous emulsion paint comprising a) 5% to 50% by weight of an aqueous polymer dispersion having a solids content in the range from 40% to 60% by weight, obtainable by the free-radical aqueous emulsion polymerization of a monomer mixture comprising ethylhexyl acrylate, butyl acrylate and one or more vinylaromatics, b) 0.1% to 5% by weight of alkali metal alkylsiliconate and/or water-soluble silicate, c) 20% to 70% by weight of inorganic fillers, d) 0% to 30% by weight of at least one inorganic pigment, e) 0.1% to 10% by weight of customary auxiliaries, and f) water, based in each case on the total amount of the emulsion paint, the pH of the emulsion paint having a value in the range from 10 to 12.

15. The aqueous emulsion paint according to claim 14, wherein the monomer mixture comprises 10 to 30 parts by weight, based on the total monomers, of ethylhexyl acrylate, 25 to 50 parts by weight, based on the total monomers, of butyl acrylate and 30 to 50 parts by weight, based on the total monomers, of one or more vinylaromatics.

16. The aqueous emulsion paint according to claim 14, wherein the monomer mixture comprises 0.1 to 5 parts by weight, based on the total monomers, of one or more monomers selected from among sulfonic acids, carboxylic acids, the alkali metal or ammonium salts thereof, carboxylic anhydrides, amides and hydroxyalkyl esters.

17. The aqueous emulsion paint according to claim 14, wherein the monomer mixture comprises 0.01 to 5 parts by weight, based on the total monomers, of monomers comprising siloxane groups.

18. The aqueous emulsion paint according to claim 14, wherein the binder polymer which is obtained by free-radical aqueous emulsion polymerization has a minimum film-forming temperature in the range from −5 to 30° C.

19. The aqueous emulsion paint according to claim 14, wherein the binder polymer particles present in the polymer dispersion have an average particle size in the range from 50 to 300 nm.

20. The aqueous emulsion paint according to claim 14, wherein the proportion of water-soluble silicate is 0.06% to 3.3% by weight, calculated as silicon dioxide.

21. The aqueous emulsion paint according to claim 14, which has a pigment volume concentration in the range from 60 to 90.

22. A coating composition comprising a aqueous polymer dispersion having a solids content in the range from 40% to 60% by weight, obtainable by the free-radical aqueous emulsion polymerization of a monomer mixture comprising ethylhexyl acrylate, butyl acrylate and one or more vinylaromatics, as an organic binder, in combination with an alkali metal alkylsiliconate and/or water-soluble silicate.

23. The coating composition as claimed in claim 22, wherein the composition has a pH in the range from 10 to 12

24. An aqueous polymer dispersion obtainable by the free-radical aqueous emulsion polymerization of a monomer mixture comprising ethylhexyl acrylate, butyl acrylate and one or more vinylaromatics, and subsequent adjustment of the pH to a value in the range from 10 to 12 with at least 0.5% by weight of alkali metal alkylsiliconate and/or water-soluble silicates, based on the aqueous polymer dispersion, and optionally with an inorganic base.

25. The aqueous polymer dispersion according to claim 24, wherein said one or more vinylaromatics are styrene.

26. The aqueous polymer dispersion according to claim 24, wherein a monomer mixture comprising: 10 to 30 parts by weight of ethylhexyl acrylate, 25 to 50 parts by weight of butyl acrylate, 30 to 50 parts by weight of one or more vinylaromatics, 0 to 10 parts by weight of one or more monomers selected from among sulfonic acids, carboxylic acids, the alkali metal or ammonium salts thereof, carboxylic anhydrides, amides and hydroxyalkyl esters, 0 to 5 parts by weight of monomers comprising siloxane groups and 0 to 10 parts by weight of other monomers, based in each case on the total monomers, is polymerized.

27. The aqueous polymer dispersion according to claim 24, wherein a monomer mixture comprising 10 to 30 parts by weight of ethylhexyl acrylate, 25 to 50 parts by weight of butyl acrylate, 30 to 50 parts by weight of one or more vinylaromatics, 0.01 to 5 parts by weight of monomers comprising siloxane groups and optionally up to 10% by weight of other monomers, based in each case on the total monomers, is polymerized.

28. The aqueous polymer dispersion according to claim 24, wherein a monomer mixture comprising 10 to 30 parts by weight of ethylhexyl acrylate, 25 to 50 parts by weight of butyl acrylate, 30 to 50 parts by weight of styrene, 0.01 to 5 parts by weight of monomers comprising siloxane groups and optionally up to 10% by weight of other monomers, based in each case on the total monomers, is polymerized.

29. A process for preparing an aqueous polymer dispersion according to claim 24, which comprises free-radically polymerizing the monomer mixture comprising ethylhexyl acrylate, butyl acrylate and one or more vinylaromatics and then adjusting the pH of the dispersion obtained to a value in the range from 10 to 12 with alkali metal alkylsiliconate and/or a water-soluble silicate and optionally an inorganic base.

Description

EXAMPLES E1 AND E2 AND COMPARATIVE EXAMPLES C1, C2 AND C3

[0097] The dispersions E1 and E2 according to the invention and the comparative dispersions C1, C2 and C3 not in accordance with the invention were prepared using the monomers indicated in table 1 and in the indicated amounts in accordance with the general procedure for preparing the polymer dispersion.

TABLE-US-00001 TABLE 1 Monomer composition of the dispersions Dispersion C1 E1 E2 C2 C3 acrylic acid [pphm] 2.7 1.7 1.5 1.2 1.5 acrylamide [pphm] 1.5 — — — — n-butyl acrylate 49.8 39.8 39.8 — — [pphm] ethylhexyl acrylate — 15.7 15.7 49.6 49.8 [pphm] styrene [pphm] 46 42.6 42.8 49 48.7 3-methacryloxy- — 0.2 0.2 0.2 — propyltrimethoxy- silane [pphm] theoretical solids 50 50 50 50 50 content [%] pphm: parts per hundred monomer

[0098] The reaction product is then admixed with the aid of a base at reaction or room temperature, the pH being adjusted to >11 in the process. The precise conditions for adjusting the pH can be found in the individual examples.

[0099] Preparation of the Dispersion D1C1, D2E1, D3E2, D4C2 and D5C3 by Aftertreatment

[0100] The aftertreatment was effected in accordance with the data found in table 2. First, C1, E1 and E2 were neutralized (pH 7) using sodium hydroxide solution. Then, 10 g of SILRES® BS 16 were added to 400 g of the dispersion thus adjusted. If necessary, 20% by weight potassium hydroxide solution was then used to adjust the dispersion to a pH >11 (see pH immediately, table 2).

TABLE-US-00002 TABLE 2 Preparation of the aftertreated dispersions: Exam- Disper- pH pH after ple sion Adjustment of the pH using immediately 24 h D1C1 C1 potassium methylsiliconate 11.3 11.1 potassium hydroxide solution D2E1 E1 potassium methylsiliconate 11.1 11.4 D3E2 E2 potassium methylsiliconate 11.1 11.3

[0101] The potassium methylsiliconate used was SILRES® BS 16.

[0102] Silres BS16 (from Wacker, solids content 55% by weight)

[0103] The dispersions were stored under various conditions. After varying storage times, the properties of the dispersion were examined. The results are collated in table 3.

TABLE-US-00003 TABLE 3 pH after storage Time of measurement D1C1 D2E1 D3E2 7 days, 25° C. 10.8 11.3 11.5 7 days, 50° C. 10.6 11.1 11.4 14 days, 50° C. 10.5 11.2

[0104] The measurement results show that in the case of the dispersion D2E1 prepared in accordance with the invention, the pH is maintained even over a relatively long storage and does not weaken. For dispersions where the pH drops below a value of 11, a more intense attack from microorganisms can generally be expected. The drop in the pH can already be seen as a trend in the storage of the sample D1C1. The dispersions D2E1 according to the invention thus exhibit a better storage stability.

[0105] Preparation of the Dispersions D6E1 and D7E2 by Aftertreatment (According to the Invention)

[0106] The aftertreatment was effected in accordance with the data found in table 2. To this end, the reaction products E1 and E2 were first neutralized (pH 7) using sodium hydroxide solution and then admixed with Trasol® KH-K (potassium waterglass, from BASF) in a mass ratio of 80 to 20 (polymer dispersion/Trasol KW-K) with stirring, and homogenized. The values reported in table 4 resulted for the pH

TABLE-US-00004 TABLE 4 pH of the aftertreated dispersions: Example Dispersion Adjustment of the pH using pH D6E1 E1 potassium waterglass 11.3 D7E2 E2 potassium waterglass 11.3

[0107] Trasol® KH-K (potassium waterglass, solids content 30-40%, K.sub.2O content (ISO 1692): 10.5-11.2%; SiO.sub.2 content (in accordance with ISO 2124): 23.4-24.4)

[0108] The dispersions were stored under various conditions. After varying storage times, the properties of the dispersion were examined. The results are collated in table 5.

TABLE-US-00005 TABLE 5 pH after storage Time of measurement D6E1 D7E2 pH immediately after 11.3 11.3 preparation pH after 14 days 11.3 11.3 pH after 28 days 11.2 11.2 pH after 5 months 11.3 11.3 Viscosity after storage Liquid, no visible Liquid, no visible for 7 days at 50° C. change in viscosity change in viscosity

[0109] A sample of each stored dispersion was thinly applied to a glass plate using a glass rod and assessed for visual defects.

TABLE-US-00006 TABLE 6 Coagulate formation after storage of dispersions D6E1 and D7E2 Duration of storage D6E1 D7E2 Without storage no coagulate no coagulate Assessment Ok Ok 14 days no coagulate minimal grit Assessment Ok Ok 5 months no coagulate minimal grit Assessment Ok Ok

[0110] It becomes clear from the examples described that dispersions prepared by the claimed process are very stable towards a high pH. This can be seen from the fact that the physical properties such as pH, viscosity or stability (coagulate formation) are very constant.

[0111] Further investigations were performed. E1 and C3 were neutralized (pH 7) using sodium hydroxide solution and then admixed with Trasol® KW-N (potassium waterglass having a solids content of 28%) in the mass ratio 80 to 20 (polymer dispersion/Trasol KW-N) with stirring, and homogenized. This affords dispersions D8E1 and D9C3 having an initial pH of 10.9. Both dispersions have a low viscosity and are free-flowing. Stability investigations were once again carried out. After one day of storage at 50° C., dispersion D9C3 became much thicker, meaning that no further investigations were possible, whereas D8E1 still has the same pH of 10.9 and a low viscosity (no visible change from the initial state) even after storage for 14 days at 50° C.

[0112] Emulsion Paint P1 (According to the Invention)

[0113] An emulsion paint having the following compositions was prepared:

TABLE-US-00007 P1 Water 384.0 Tylose ® H 6000 YP 2 (cellulose ether) 6.0 Dispex AA 4140 (dispersant) 5.0 Calgon N 5.0 10% by weight potassium hydroxide solution 1.0 Agitan 260 (defoamer) 4.0 TiO.sub.2 100.0 Aluminum silicate, precipitated 229.4 Talc 51.3 Non-neutralized E1 (pH = 2) 115.5 SILRES BS16 7.2 Water 59.6 Agitan 260 5.0 1000.0

[0114] The above formulation has a solids content of 48.9% by weight and a PVC of 71.7. The paint has a pH of 10 after preparation and was adjusted to a pH of 11.3 with 20% by weight potassium hydroxide solution.

[0115] Alternatively, the dispersion D2E1, which has been adjusted to pH >11 with potassium methylsiliconate and potassium hydroxide solution, can be used as binder in the formulation as a paint, and exhibits a stable pH after storage.

TABLE-US-00008 TABLE 7 Stability investigations on paint formulation P1: Viscosity Viscosity Duration of storage pH KU ICl (cone C) None (directly 11.3 102 1.5 after formulation) 24 h at RT 11.4 7 days at RT 11.1 14 days at RT 11.1 108 1.6 14 days at 50° C. — 106 1.5 RT: room temperature, 25° C.

[0116] The dispersion paint displays very good stability in terms of viscosity and pH.