Process for producing an aqueous dispersion and redispersible dispersion powder produced therefrom

Abstract

The present invention relates to a process for producing a redispersible dispersion powder, to the redispersible dispersion powder obtainable by this process, to an aqueous dispersion obtainable by step (1) of this process, and to a building material composition comprising the redispersible dispersion powder and/or the aqueous dispersion, to the use of the redispersible dispersion powder in a building material composition and to the use of the aqueous dispersion for production of a redispersible dispersion powder.

Claims

1. A process comprising: (1) mixing, to obtain a first aqueous dispersion, at least (i) a second aqueous dispersion, where the second aqueous dispersion comprises particles, where the particles comprise at least one polymer I, where the at least one polymer I comprises monomer units formed from at least one ethylenically unsaturated monomer; and (ii) a polyacid II comprising monomer units formed from methyl-2-propene-1-sulfonic acid, and at least one further ethylenically unsaturated monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, itaconic acid, salts thereof, and mixtures thereof; and wherein, in (1), an additive comprising a polyoxyalkylene group is present, wherein the additive is (a) mixed as a further component in the mixing, or (b) applied by emulsion polymerization to a surface of the particles prior to the mixing, or (c) incorporated as a monomer unit into the at least one polymer I of the particles prior to the mixing; and wherein the first aqueous dispersion has a pH of <4; and (2) drying the first aqueous dispersion in order to obtain the redispersible dispersion powder.

2. The process of claim 1, further comprising (3) mixing the redispersible dispersion powder with an antiblocking agent.

3. The process of claim 1, wherein the first aqueous dispersion has a pH of <3.

4. The process of claim 1, wherein the at least one polymer I comprises monomer units formed from at least one ethylenically unsaturated monomer selected from the group consisting of ethylene, propylene, butadiene, styrene, vinyl acetate, vinyl chloride, vinyl ethers, vinyl esters, acrylic esters, methacrylic esters, and mixtures thereof.

5. The process of claim 1, wherein the at least one polymer I is selected from the group consisting of (ia) styrene-(meth)acrylate copolymers, (ib) styrene-butadiene copolymers, (ic) (meth)acrylate copolymers, and (ic) ethylene-vinyl acetate copolymers.

6. The process of claim 1, wherein the polyacid II comprises monomer units formed from the ethylenically unsaturated monomers acrylic acid or methacrylic acid.

7. The process of claim 1, wherein, in (a) and (b), the additive comprising the polyoxyalkylene group is selected from the group consisting of polyoxyalkenylated (C6-C22) alcohols, (C6-C30) carboxylic acids, (C6-C30)alkylamines, sorbitan esters, triglycerides or alkylphenols, and in (c), the additive comprising the polyoxyalkylene group is incorporated into the at least one polymer I as a polyoxyethylenated ethylenically unsaturated monomer.

8. A redispersible dispersion powder obtainable by the process of claim 1.

9. An aqueous dispersion obtainable by step (1) of the process of claim 1.

10. A building material composition comprising a redispersible dispersion powder obtainable by the process of claim 1 and/or an aqueous dispersion obtainable by step (1) of the process of claim 1.

Description

EXAMPLES

(1) Determination of the Molecular Weight of the Polyacid II:

(2) The sample was prepared for the determination of molar mass by dissolving copolymer solution in the GPC eluent, such that the polymer concentration in the GPC eluent is 0.5% by weight.

(3) Thereafter, this solution was filtered through a syringe filter having a polyethersulfone membrane and pore size 0.45 μm. The injection volume of this filtrate was 50-100 μl.

(4) The average molecular weights were determined on a Waters GPC instrument with the model name Alliance 2690 with a UV detector (Waters 2487) and RI detector (Waters 2410). The following settings and conditions were used: Columns: Shodex SB-G Guard Column for SB-800 HQ series and Shodex OHpak SB 804HQ and 802.5HQ (PHM gel, 8×300 mm, pH 4.0 to 7.5) Eluent 0.05 M aqueous ammonium formate/methanol mixture=80:20 (parts by volume) Flow rate: 0.5 ml/min Temp.: 50° C. Injection: 50 to 100 μl Detection: RI and UV

(5) The molecular weights of the copolymers were determined relative to polyacrylic acid standards from PSS Polymer Standards Service GmbH. The molecular weight distribution curves of the polyacrylic acid standards were determined by means of light scattering.

(6) Provision of Polymer Dispersions and Spraying Aids:

(7) Dispersion 1:

(8) The dispersion comprises a styrene-2-ethylhexyl acrylate copolymer still comprising monomer units that result from the stabilizing auxiliary monomers hydroxyethyl methacrylate (HEMA) and 2,3-epoxypropyl methacrylate (GMA). The dispersion has a solids content of 55% by weight. The polymer has a glass transition temperature of −15° C. and a particle size of about 600 nm. The dispersion additionally comprises 0.5% by weight of (C.sub.18-C.sub.18)alkyl ethoxylate having a degree of ethoxylation of 18, 0.3% by weight of a mixture of sodium diethylhexylsulfosuccinate/isotridecanol ethoxylate having a degree of ethoxylation of 4 and 0.1% by weight of C.sub.12-14-alkyl(EO).sub.30SO.sub.4Na.

(9) Dispersion 2:

(10) The dispersion comprises a styrene-2-ethylhexyl acrylate copolymer still comprising monomer units that result from the stabilizing auxiliary monomers monomer methoxypoly(oxyethylene) methacrylate having a degree of ethoxylation of 17 and of 2,3-epoxypropyl methacrylate (GMA).

(11) The dispersion has a solids content of 56.5% by weight. The polymer has a glass transition temperature of −13° C. and a particle size of about 510 nm. The dispersion additionally comprises 0.5% by weight of polyoxyethylenated C.sub.12-C.sub.14 alcohol ethoxylates having a degree of ethoxylation of 4, sulfated, and 0.3% by weight of sodium laurylsulfate.

(12) Dispersion 3:

(13) The dispersion comprises a styrene-butadiene copolymer still comprising monomer units that result from the stabilizing auxiliary monomers hydroxyethyl methacrylate (HEMA) and acrylic acid. The dispersion has a solids content of 51% by weight. The polymer has a glass transition temperature of 0° C. and a particle size of about 160 nm. The dispersion additionally comprises 1% by weight of C.sub.12-14-alkyl(EO).sub.4SO.sub.4Na, 0.7% by weight of isotridecanol ethoxylates having a degree of ethoxylation of 4 and 0.5% by weight of isotridecanol ethoxylates having a degree of ethoxylation of 8.

(14) Dispersion 4:

(15) The dispersion comprises, as well as the styrene-butadiene copolymer from dispersion 3, also 3% by weight (based on the solids content of the dispersion) of isotridecanol ethoxylate having a degree of ethoxylation of 25.

(16) Spraying Aids (SA)

(17) Spraying Aid 1:

(18) In a reaction vessel equipped with reflux condenser, stirrer, thermometer, dropping funnel and nitrogen sparging, an initial charge of 180 g of water, 94.8 g of Na-methylpropenesulfonic acid and 3 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V50) was heated to 80° C. On attainment of the temperature, while stirring at 80-90° C., a solution of 3 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride, 108 g of acrylic acid, 129 g of methacrylic acid and 150 g of water was metered in over a period of 36 min. The reaction solution was stirred at 80° C. for 1 h and then cooled down to room temperature. The resulting product was a clear polymer solution having a solids content of 52.0% by weight, a pH of 1.4 and a molecular weight M.sub.w of about 2400 g/mol.

(19) Spraying Aid 1A:

(20) Spraying aid 1A was adjusted to a pH of 2.4 with NaOH.

(21) Spraying Aid 1B:

(22) Spraying aid 1A was adjusted to a pH of 3.4 with NaOH.

(23) Comparative Spraying Aid 1C:

(24) Spraying aid 1A was adjusted to a pH of 4.2 with NaOH.

(25) Comparative Spraying Aid 1D:

(26) Spraying aid 1A was adjusted to a pH of 6.1 with NaOH.

(27) Spraying Aid 1E:

(28) Spraying aid 1A was adjusted to a pH of 1.9 with H.sub.2SO.sub.4.

(29) Comparative Spraying Aid 2:

(30) In a reaction vessel equipped with reflux condenser, stirrer, thermometer, dropping funnel and nitrogen sparging, an initial charge of 140 g of water and 2 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V50) was heated to 70° C. On attainment of the temperature, while stirring at 70-90° C., a solution of 2 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride, 3 g of 3-mercaptopropionic acid, 100 g of acrylic acid and 100 g of water was metered in over a period of 36 min. The reaction solution was stirred at 80° C. for 1 h and then cooled down to room temperature. The resulting product was a clear polymer solution having a solids content of 46.3% by weight, a pH of 1.4 and a molecular weight M.sub.w of about 11 600 g/mol.

(31) Comparative Spraying Aid 2A:

(32) An aliquot of spraying aid 2 was adjusted to a pH of 6.0 with NaOH.

(33) Comparative Spraying Aid 2B:

(34) An aliquot of spraying aid 2A was adjusted to a pH of 1.4 with H.sub.2SO.sub.4.

(35) Comparative Spraying Aid 3:

(36) A polyacrylic acid having a pH of ˜2 and a molecular weight M.sub.w of about 5000 g/mol, which is manufactured by BASF and is available under the Sokalan PA 25 XS trade name.

(37) Comparative Spraying Aid 4:

(38) A polyacrylic acid having a pH of ˜8 and a molecular weight M.sub.w of about 8000 g/mol, which is manufactured by BASF and is available under the Sokalan PA 30 trade name.

(39) Spraying Aid 5:

(40) In a reaction vessel equipped with reflux condenser, stirrer, thermometer, dropping funnel and nitrogen sparging, an initial charge of 200 g of water, 81 g of Na-methylpropenesulfonic acid and 1.5 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V50) was heated to 73° C. On attainment of the temperature, while stirring at 73-81° C., a solution of 1.5 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride, 250 g of methacrylic acid and 130 g of water was metered in over a period of 1 h. The reaction solution was stirred at 80° C. for 1 h and then cooled down to room temperature. The resulting product was a clear polymer solution having a solids content of 50.3% by weight, a pH of 1.4 and a molecular weight M.sub.w of about 1400 g/mol.

(41) Spraying Aid 6:

(42) In a reaction vessel equipped with reflux condenser, stirrer, thermometer, dropping funnel and nitrogen sparging, an initial charge of 280 g of water and 195 g of Na-2-acrylamido-2-methylpropanesulfonic acid (AMPS) was heated to 18° C. While stirring, 70 g of a 50% sodium hydroxide solution were added dropwise at 18° C. Subsequently, 68 g of acrylic acid, 2.8 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V50) and 4 g of mercaptoethanol were metered in while stirring over a period of 10 min. The reaction solution was stirred at 70 to 80° C. for 1.5 h and then cooled down to room temperature. The resulting product was a clear polymer solution having a solids content of 48.1% by weight, a pH of 0.8 and a molecular weight M, of about 8400 g/mol.

(43) Spraying Aid 7:

(44) In a reaction vessel equipped with reflux condenser, stirrer, thermometer, dropping funnel and nitrogen sparging, an initial charge of 350 g of water and 313 g of Na-2-acrylamido-2-methylpropanesulfonic acid (AMPS) was heated to 18° C. While stirring, 112 g of a 50% sodium hydroxide solution were added dropwise at 18° C. Subsequently, 27 g of acrylic acid, 2.8 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (Wako V50) and 6 g of mercaptoethanol were metered in while stirring over a period of 14 min. The reaction solution was stirred at 70 to 80° C. for 1.5 h and then cooled down to room temperature. The resulting product was a clear polymer solution having a solids content of 48.5% by weight, a pH of 0.8 and a molecular weight M, of about 7400 g/mol.

(45) Production of a Polymer Powder by Spray Drying:

(46) The spray drying was conducted with a laboratory drier (Niro Atomizer) from Niro with nitrogen as drying gas. The aqueous dispersion comprising the water-soluble spraying aid that was to be dried in each case was sprayed through a two-phase nozzle with a solids content of 40-60%. The inlet temperature of the drier gas was 130 to 140° C.; its outlet temperature was 60 to 70° C. The antiblocking agent used was 0.5% to 1% by weight (based on the solids content of the feed solution) of silica and 9% by weight (based on the solids content of the feed solution) of Luzenac talc (from Imerys).

(47) Determination of the Redispersibility of the Dispersion Powder:

(48) The composition composed of a dispersion with spraying aid (SA) specified in table 1 was used to produce films and their redispersion was tested. For this purpose, the liquid dispersion (5 g of solids) in 10-15 mL of water was admixed with the described amount of the respective spraying aid and dried at 60° C. overnight. Of the resulting film, about 0.5 g was taken up in 10 mL of distilled water while stirring (200 rpm) at room temperature. On rapid redispersion within a few minutes, it was found that these dispersion systems also have excellent spray-driability and a redispersible powder (RDP) is obtained.

(49) Redispersion was assessed as follows: Complete redispersion within a few minutes: very good Virtually complete redispersion within a few minutes: good Incomplete redispersion (parts of the film still apparent): moderate Large parts of the film insoluble or no redispersion: poor

(50) TABLE-US-00001 TABLE 1 Redispersibility of the redispersible dispersion powders Amount of SA to solids content of pH of Redispersibility Redispersibility No. Dispersion SA dispersion SA of the film of the powder i) 1 1 10% by weight 1.4 very good very good ii) 1 1  7% by weight 1.4 very good very good iii) 1 1A 10% by weight 2.4 very good n.d. iv) 1 1B 10% by weight 3.4 moderate n.d. v) (ref. ex.) 1 Ref.-1C 10% by weight 4.2 poor n.d. vi) (ref. ex.) 1 Ref.-1D 10% by weight 6.1 poor poor vii) 1 1E.sup.  10% by weight 1.9 very good n.d. viii) (ref. ex.) 1 Ref.-2 .sup.  10% by weight 1.4 very good very good ix) (ref. ex.) 1 Ref.-2A 10% by weight 6.0 poor n.d. x) (ref. ex.) 1 Ref.-2B 10% by weight 1.4 good n.d. xi) (ref. ex.) 1 Ref.-3 .sup.  10% by weight ~2 very good very good xii) (ref. ex.) 1 Ref.-4 .sup.  10% by weight ~8 poor n.d. xiii) 1 5  7% by weight 1.4 very good very good xiv) 1 5 10% by weight 1.4 very good very good xv) 2 1 10% by weight 1.4 very good very good xvi) 3 1 10% by weight 1.4 poor n.d. xvii) 4 1 10% by weight 1.4 very good very good xviii) 1 6 10% by weight 0.8 poor n.d. xix) 1 7 10% by weight 0.8 poor n.d. (n.d. = not determined)

(51) It is found that it is advantageous for redispersibility when the pH of the dispersion is <4 and when the spraying aid is a polyacid formed from at least one ethylenically unsaturated monomer comprising a sulfonic acid group. Particular preference is given to the use of a spraying aid based on at least one allylic monomer comprising at least one sulfonic acid group.

(52) Production of a Building Material Composition with a Redispersible Dispersion Powder

(53) The redispersible dispersion powder of the present invention was used to produce building material compositions according to table 2. Example 1 here is a comparative example in which, rather than the redispersible dispersion powder, a styrene-acrylate copolymer (Acronal) was used.

(54) TABLE-US-00002 TABLE 2 Constituents Ref. Ref. Ref. Ref. (by weight) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 CEM II/B-S 32, 5R 150 150 150 150 150 150 150 150 150 Calcium aluminate 80 80 80 80 80 80 80 80 80 cement (HAC) Quartz sand 465 465 465 465 465 465 465 465 465 Ground limestone 20 20 20 20 20 20 20 20 20 (CaCO.sub.3) Microsilica 5 5 5 5 5 5 5 5 5 Sand 20 20 20 20 20 20 20 20 20 Dispersion powder 250 (styrene-acrylate copolymer) Dispersion powder 250 ii) Dispersion powder 250 xiii) Dispersion powder 250 i) Dispersion powder 250 xi) (ref. ex.) Dispersion powder 250 xv) Dispersion powder 250 xvii) Dispersion powder 250 viii) (ref. ex.) Dispersion powder 250 xii) (ref. ex.) Powder defoamer 5 1 1 1 1 1 1 1 1 Acrylate powder 1.25 1.25 1.25 1 0 1 1 0 0 thickener Na gluconate 2 1.25 0 1.5 1.5 1.5 2.25 1.5 1.5 Citric acid 0.75 0.75 0 0.75 0.75 0.75 1.125 0.75 0.75 Total 1000 1000 1000 1000 1000 1000 1000 1000 1000 Water 250 250 250 250 250 250 250 250 250

(55) The pot life of the above-described dispersion-modified mineral building material mixture was assessed. The pot life is the use period within which the polymer-modified building material in the made-up state has a viscosity and creaminess appropriate for processing, such that it can be applied to the application substrate with a suitable aid (brick trowel, squeegee, etc.). If this period is exceeded, the building material can no longer be spread smoothly on the application substrate. A pot life of 0.5-2 h is desirable, whereas faster systems are difficult to process and extremely slow systems (pot life >3 h) delay the next working steps.

(56) The dispersion-modified mineral building material mixture was used to produce a thin film (height: 2.0 mm, width 12.0 cm and length 20 to 25 cm). The appearance of the dried building material was examined. If it was homogeneous (no separation), apparently smooth and had no unevenness and cracks, it was found to be good (rated OK in table 3).

(57) If the pH of the dispersion is greater than 4, processing is impossible (see dispersion powder xii) in table 3). If the spraying aid does not comprise any polymer having sulfonic acid groups, processing is impossible (see dispersion powders xi) and viii) in table 3). Furthermore, good processing is possible only when the spraying aid is based on at least one allylic monomer comprising at least one sulfonic acid group.

(58) TABLE-US-00003 TABLE 3 Properties of the building material composition Composition RDP used Appearance Pot life Ex. 4 i) OK 50 min Ex. 2 ii) OK 50 min Ref. ex. 8 viii) (ref. ex.) Processing not possible Ref. ex. 5 xi) (ref. ex.) Processing not possible Ref. ex. 9 xii) (ref. ex.) Processing not possible Ex. 3 xiii) OK 2 h  Ex. 6 xv) OK 2 h  Ex. 7 xvii) A few cracks 2 h