DE19730953A1 - Sulphonated bis:phenol compounds use as drying aid for aqueous polymer dispersion, minimising discoloration - Google Patents

Abstract

The use of bisphenol compound(s) of formula (I) or their salts as drying aids for aqueous polymer dispersions is claimed; in which >= 1 of R<1-8> = a sulphonic acid group (SO3H) and the rest = hydrogen (H); X = alkylene, carbonyl (CO), oxygen (O), sulphur (S) or imino (NR<9>); R<9> = H or alkyl. Also claimed are (a) a method for producing a polymer powder by drying an aqueous polymer dispersion with addition of (I); and (b) the polymer powder per se.

Description

The present invention relates to the use of bisphenol sulfonates as drying aids, especially when spraying drying of aqueous polymer dispersions.

The present invention further relates to a method for producing position of polymer redispersible in aqueous medium vern as well as the redispersible polymer powder and their ver turn.

Aqueous polymer dispersions are widely used in for example as a binder, especially for synthetic resin plasters or highly pigmented interior paints, adhesives or coatings with tel. However, it is often desirable, not the aqueous polymer sat dispersion, but to use the polymer in powder form.

In order to obtain the polymer in powder form, the dispersion be subjected to a drying process, for example one Spray drying or freeze drying. When spraying The polymer dispersion is dried in a warm air stream sprayed and dewatered, the dry air and ver sprayed dispersion preferably in cocurrent through the dryer be performed.

However, the polymer powder obtained has the disadvantage that generally not its redispersibility in aqueous medium can fully satisfy because of the redispersion resulting polymer particle diameter distribution in the Usually differs from that in the aqueous initial dispersion that is. The reason for this is that aqueous polymer dis persions, unlike polymer solutions, no thermodyna form stable systems. Rather, the system tries to Interface polymer / dispersion medium by combining small primary particles to larger secondary particles (specks, Coagulate). This can in the state of the disperse Ver division in an aqueous medium by adding dispersants, such as emulsifiers and protective colloids also for a long time be changed. When drying aqueous polymer dispersions However, the effect of the dispersants is often not sufficient more and there are some irreversible effects Secondary particle formation. That means the secondary particles remain preserve and reduce the application technology during redispersion  African properties of the redispersion Chen aqueous polymer dispersion.

To prevent secondary particles from forming when drying or to reduce at least, it has long been known, so-called Use drying aids. These are often called Spray aids, because spray drying is the formation especially encourages irreversible agglomerated secondary particles. At the same time, they usually reduce the training of others The polymer wall adheres to the dryer wall and thus creates a Increase the powder yield.

The use of drying aids is numerous Publications known. For example, DE-A-24 45 813 describes an in aqueous system redispersible powdered polymer, which as Drying aids 1 to 20 wt .-% of a water-soluble, sul from condensation product containing fonic acid or sulfonate groups contains aromatic hydrocarbons and formaldehyde. At these condensation products are in particular Phenolsulfonic acid or naphthalenesulfonic acid-formaldehyde condensate sate. The polymer dispersions are dried at temperature temperatures below the softening temperature (glass temperature) of the dispersed polymer powder.

EP-A-78 449 describes a process for the production of non-blocking polymer powders redispersible in water Spray drying of aqueous dispersions of polymers with Glass temperatures of less than 50 ° C. The dispersions contain as a spray aid, a water-soluble vinyl copolymer pyrrolidone and vinyl acetate and / or a water-soluble alkali and / or alkaline earth metal salt of a naphthalenesulfonic acid formaldehyde Condensation product. Similarly, EP-A- 407 889 the use of a water soluble alkali or earth alkali salt of a phenolsulfonic acid-formaldehyde condensation product as a spraying aid for the production of in water redispersible polymer powders from aqueous polymer dis persions.

EP-A-629 650 describes the use of polymers which by radical polymerization of monomer mixtures from 15 up to 80% by weight of a monomer of the general formula

wherein R¹, R² and R³ independently of one another are H or C₁-C₃-alkyl stand, R⁴ stands for C₁-C₅ alkylene and X stands for O or NH, and 20 to 85% by weight of a radically copolymerizable monomer are available in aqueous medium, as a spray aid in the Spray drying of aqueous polymer dispersions.

The phenolsulfonic acid-formaldehyde condensates mentioned are effective same spray aids, but they have the disadvantage that they especially in an alkaline medium, for example in an alkaline medium Mortar tends to discolour due to oxygen. The discoloration problem is with naphthalenesulfonic acid formaldehyde Condensates lower, but these are used as spray aids less effective than the phenolsulfonic acid-formaldehyde condensates.

The present invention is therefore based on the object Drying aids to find that allow from aqueous Polymer dispersions to produce polymer powders in water are well redispersible and, when used in verrin tends to discolor.

Surprisingly, it has now been found that this problem has been solved if, as a drying aid, the following compounds of formula I characterized.

The object of the present invention is therefore the use of compounds of the formula I:

wherein R¹-R⁸ independently represent H or SO₃H, but at least one of the radicals R¹-R⁸ represents SO₃H,
X represents alkylene, CO, O, S, SO₂ or NR⁹, where R⁹ represents H or alkyl, or their salts as auxiliaries in the drying of aqueous polymer dispersions.

When X is alkylene, the radical -CR¹⁰R¹¹- is preferred, wherein R¹⁰ and R¹¹ are independently H or alkyl. Before X is preferably alkylene, in particular -C (CH₃) ₂- or -Co-.  

The invention also relates to compounds of the formula I, in which at least one of R¹-R⁴ and one of R⁵- R⁸ is SO₃H and preferably those in which R¹, R⁴, R⁶ and R⁷ are SO₃H (R², R³, R⁵ and R⁸ can be independently stand for H or SO₃H).

The salts of the compounds of the formula I are ins especially the alkali or alkaline earth metal salts or ammonium salts, d. H. Salts with ammonia or organic amines, such as tri ethanolamine, diethanolamine or triethylamine. Preferred salts are the alkaline earth metal salts and especially the calcium salts.

In connection with the above meanings is alkyl or alky len for straight-chain or branched groups, in particular 1 to 12 carbon atoms, preferably 1 to 6 and especially be preferably have 1 to 4 carbon atoms, e.g. B. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, 2-butyl, 1,1-ethylene, 1,2-ethylene, 1,1-propylene, 1,2-propylene, 2,2-propylene, 1,3-propy len, 1,1-butylene, 1,2-butylene, 2,2-butylene.

The compounds of the formula I can be prepared by methods which are known to the person skilled in the art. Spraying aids according to the invention are preferably prepared by sulfonation of the ent speaking bisphenol compounds I (R-R⁸ are here is H) were obtained (see also J. March, Advanced Organic Chemistry ^3rd ed: S. 473 ff, and references cited therein). The degree of sulfonation of the spray aids according to the invention can be controlled by the sulfonation conditions (for example temperature, reaction time, sulfonating agent, stoichiometry) in a manner known to the person skilled in the art. Sulfuric acid is particularly preferably used as the sulfonating agent. The reaction temperature is then generally in the range from 50 to 120 ° C., in particular 65 to 100 ° C.

The compounds of formula I have been found to be effective drying auxiliary in the production of polymer powders from aq proven polymer dispersions. Their effect is comparable that of phenolsulfonic acid-formaldehyde condensates, without that when using the polymer powder obtained in alkali discoloration under the influence of oxygen are.

In addition, it has surprisingly been found that the häu fig undesirable, retarding effect of phenolsulfonic acid rederivatives with the compounds according to the invention with increasing Degree of sulfonation decreases sharply. It is therefore possible to bind the  to set the decelerating effect as desired by Verbin be used with a suitable degree of sulfonation.

The present invention also relates to a method for Preparation of a polymer powder by drying an aqueous gene polymer dispersion, using as a drying aid ver at least one compound of formula I or a salt thereof turns. With alkaline polymer dispersions com the compounds of formula I as salts, preferably as Alkali metal, alkaline earth metal or ammonium salts, in particular as alkaline earth metal salts and very particularly preferably as Cal cium salts for use.

The amount of drying aids to be used preferably carries 1 to 30 wt .-%, based on the weight of the Polymers of the dispersion, preferably 3 to 20 wt .-% and particularly preferably 5 to 15% by weight.

The compounds according to the invention are particularly advantageous for drying polymer dispersions in which the polymer has a glass transition temperature (DSC, midpoint temperature, ASTM D 3418-82) 65 ° C., preferably 50 ° C., particularly preferably 25 ° C. and very particularly preferably 0 ° C. having. In general, the glass transition temperature of the polymers is -60 ° C, preferably -40 ° C and in particular -20 ° C. It proves to be helpful to estimate the glass transition temperature T _{G of} the dispersed polymer. According to Fox (TG Fox, Bull. Am. Phys. Soc. (Ser. II) 1, 123 [1956) and Ullmann's Encyclopedia of Industrial Chemistry, Weinheim (1980), pp. 17, 18), the glass transition temperature applies of copolymers with large molecular weights in good nutrition

where X¹, X². . . , X ⁿ the mass fractions 1, 2,. . . , n and T _g ¹, T _g ². . . , T _g ⁿ the glass transition temperatures of each of only one of the monomers 1, 2,. . . , n mean polymers in degrees Kelvin. The latter are e.g. For example, from Ullmann's Encyclopedia of Indu strial Chemistry, VCH, Weinheim, Vol. A 21 (1992) p 169 or known from J. Brandrup, EH Immergut, Polymer Handbook 3 ^rd ed, J. Wiley, New York 1989th

These are preferably polymers which are built up out:

• (a) 80 to 100% by weight of at least one monomer selected is made from vinyl aromatic compounds, esters α, β-monoethylenically unsaturated C₃-C₆ carboxylic acids and C₁-C₁₂ alkanols, preferably C₁-C₈ alkanols, vinyl and Allyl esters of C₁-C₁₂ carboxylic acids and butadiene, and
• (b) 0 to 20% by weight of at least one other monomer which has at least one ethylenically unsaturated group.

Examples of vinyl aromatic compounds are styrene, α-methyl styrene or vinyl toluenes, such as o-vinyl toluene.

For the esters of α, β-monoethylenically unsaturated carboxylic acids it is in particular to esters of acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid. examples for such esters are methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylic lat, ethylhexyl (meth) acrylate, decyl (meth) acrylate or dodecyl (meth) acrylate.

Usable vinyl and allyl esters are vinyl acetate, vinyl propio nat, vinyl n-butyrate, vinyl laurate and vinyl stearate and the ent speaking allyl ester.

Particularly preferred monomers (a) are n-butyl acrylate, 2-ethyl hexyl acrylate, methyl methacrylate and styrene.

The monomers (b) are preferably the above mentioned α, β-monoethylenically unsaturated C₃-C₆ carboxylic acids and their nitriles, amides, mono- or dialkylamides and hydroxyalkyl ester of it. The N-vinyl derivatives of cycli can also be used Lactams and the mono- or dialkylaminoalkylamides of the mentioned C₃-C₆ carboxylic acids and their quaternization products.

Particularly preferred monomers (b) are acrylamide, methacrylamide, Acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, 2-acrylamido-2-methylpropanesulfonic acid, vinyl pyrrolidone, hydroxy ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, Hydroxypropyl methacrylate, quaternized vinyl imidazole, N, N-dialkylaminoalkyl (meth) acrylates, N, N-dialkylaminoalkyl (meth) acrylamides, trialkylainmonium alkyl (meth) acrylates and tri alkylammoniumalkyl (meth) acrylamides.

Preferred polymer dispersions are furthermore those in which the weight-average diameter d _{w of} the dispersed polymer particles is 100 nm and particularly preferably 300 nm. Usually, d _{w is} 2000 nm. It is also advantageous if the diameters of the dispersed polymer particles are distributed over a wide diameter range.

The d _w value of the particle size is, as usual, defined as the weight average of the particle size, as determined using an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z. and Z.-Polymer 250 (1972) pages 782 to 796. The ultracentrifuge measurement provides the integral mass distribution of the particle diameter of a sample. From this it can be seen what percentage by weight of the part Chen have a diameter equal to or below a certain size.

A suitable measure for characterizing the width of the diameter distribution is the quotient Q = (d₉₀-d₁₀) / d₅₀, where d _{m is} the diameter which is not exceeded by m% by weight of the dispersed polymer particles. Q is preferably 0.5 to 1.5.

The preparation of polymer dispersions with such Particle distribution width is known to the person skilled in the art, e.g. B. from the DE-A-43 07 683.

The ratio of weight average molecular weight M _w to number average molecular weight M _{w of} the polymers can be 1 to 30 or 1 to 20 or 1 to 8. The molecular weight can thus be essentially uniform or distributed over a certain width.

The preparation of the polymer dispersions to be dried is known. In general, it is carried out by radical polymers sation, preferably in polar solvents, in particular is carried out in water. To set the desired Molecular weight can regulate the molecular weight zen can also be used. Suitable molecular weight regulators are e.g. B. Compounds that have a thiol group (e.g. t-Do decyl- or n-dodecyl mercaptan) or aldehydes, such as formaldehyde, Acetaldehyde etc.

Suitable starters are e.g. B. inorganic peroxides such as sodium peroxodisulfate or azo compounds. The polymerization can ever according to monomer composition as solution or emulsion polymers rization take place.

If the polymer dispersion is by emulsion polymerization is produced, this is done in the usual way. In general use a protective colloid, such as polyvinyl alcohol, polyvinyl  pyrrolidone or cellulose derivatives or anionic and / or not ionic emulsifiers, such as ethoxylated mono-, di- or trialkyl phenols, ethoxylated fatty alcohols and alkali or ammonium salts of C₈-C₁₂ alkyl sulfates, sulfuric acid half-esters ethoxylated C₁₂-C₁₈ alkanols, C₁₂-C₁₈ alkylsulfonic acids, C₉-C₁₈ alkylarylsulfone acids and sulfonated alkyl diphenyl ethers. The polymerization temperature is generally in the range of 50 to 120 ° C, ins particularly 70 to 100 ° C.

The dispersion can be a primary dispersion, d. H. a polymer dispersion which is prepared using the ra diical, aqueous emulsion polymerization immediately was. It can also be a secondary dispersion, d. H. a polymer obtained by solution polymerization subsequently converted into an aqueous polymer dispersion.

The polymer dispersion can be dried in a conventional manner take place, for example by freeze-drying or preferably by spray drying. This is the procedure for spray drying conditions that the inlet temperature of the hot air flow in the range of 100 to 200 ° C, preferably 120 to 160 ° C and the initial temperature structure of the warm air flow in the range from 30 to 90 ° C., preferably 60 up to 80 ° C. The spraying of the aqueous polymer dispersion in the warm air flow can be, for example, by means of single or multiple substances nozzles or a rotating disc. The deposition the polymer powder is normally made using Cyclones or filter separators. The sprayed aqueous polymer sat dispersion and the warm air flow are preferably parallel guided.

The compounds of the invention can be the dis persion as an aqueous solution or substance added before drying be set. If it is a primary dispersion, it can Drying aids before, during and / or after the emulsion polymerization are added.

In addition to the drying aids according to the invention, additional Lich also known drying aids, such as polyvinyl alcohol, Polyvinyl pyrrolidone, naphthalenesulfonic acid-formaldehyde condensates sate, phenolsulfonic acid-formaldehyde condensates, homopolymers the 2-acrylamido-2-methylpropanesulfonic acid etc., also used will. Also anti-caking agents, such as highly disperse silica, which usually for drying aqueous polymer dispersers sions can be used to get together to prevent caking of the polymer powder during storage.  

With spray drying, the anti-caking agents are usually sprayed separately.

The present invention also relates to the invention according to available polymer powder. They are suitable as binders in hydraulically setting masses, paints, varnishes, Adhesives, coating materials (especially for paper) and Synthetic resin plasters, as described in EP-A-629 650.

Those obtainable according to the invention are particularly suitable Polymer powder for modifying mineral binders substances (mortar-like preparations) that form a mineral bin contain the agent, which consists of 70 to 100 wt .-% cement and 0 to There is 30% by weight of gypsum. The effect according to the invention is thereby essentially independent of the type of cement. Depending on the project So blast furnace cement, oil shale cement, Portland cement, hydrophobic Portland cement, quick cement, swelling cement or Alumina cement can be used, the use of Portland cement proves to be particularly cheap. Regarding others For details, see DE-A 196 23 413.3.

Typically, the dry compositions contain minera binders based on the amount of mineral Binder, 0.1 to 20 wt .-% modifying polymer powder.

To improve their processing properties, the mineral binding materials are often cellulose derivatives and Microsilica too. The former usually have a thickening effect and the latter Tere usually form thixotropic agents which are the flow ability of the aqueous mortar before it solidified in the brought retirement to humiliate additionally. Calcium carbonate and Quartz sand usually forms the other supplements. By addition defoamers (preferred from the point of view of "dry mortar" in powder form) can be a practical one when solidified Air pore content (5 to 20 vol .-%) of the solidified cementitious Mortar can be reached.

The polymer powders obtainable according to the invention are suitable e.g. B. to modify cementitious repair or reinforcement mortar. Common reinforcement mortars have an increase their crack bridging ability still natural or synthetic Fibers from materials such. B. Dralon (length e.g. 1 to 10 mm, length-related mass z. B. 3 to 10 dtex).

With the highest crack bridging requirements, the cement reinforcing mortar, based on the cement contained, 9 to 20, with lower crack bridging requirements 4 to 9 wt .-% modes  Add the finishing polymer powder. Only with special low crack bridging requirements will be added Amount of modifying polymer powder, in a corresponding Based on the way, limit to 0.1 to 4 wt .-%.

Typical reinforcing mortars consist of mineral dry building compound preparation
20 to 60, preferably 20 to 50% by weight of mineral binder (preferably exclusively cement)
0.1 to 20 frequently 0.1 to 10% by weight of modifying polymer powder obtained according to the invention,
up to 25% by weight of conventional auxiliaries (e.g. defoamers or thickeners) and as a residual amount of additives such as B. sand, fillers (z. B. CaCO₃), pigments (z. B. TiO₂), natural and / or synthetic fibers.

The following examples illustrate the invention without restricting it limit.

Examples 1. Preparation of the dispersions 1.1 Dispersion D1

A mixture of
150 g water
5.6 g of a 20% by weight aqueous solution of an ethoxylated p-isooctylphenol (EO grade 25),
0.48 g of a 35% by weight aqueous solution of a sodium salt of a sulfated and ethoxylated p-isooctylphenol (EO grade 25),
3.9 g of a 10% strength by weight aqueous formic acid solution,
1.7 g sodium hydrogen carbonate and
3.4 g of a 20% by weight aqueous polyacrylamide solution
was heated to 90 ° C. Subsequently, 742.8 g of an aqueous monomer emulsion consisting of consisted of this mixture, starting simultaneously and while maintaining the internal temperature of 90 ° C. in 2 h
403.2 g of n-butyl acrylate,
140.0 g styrene,
11.2 g acrylamide,
5.6 g methacrylamide,
8.4 g of a 20% by weight aqueous solution of an ethoxylated p-isooctylphenol (EO grade 25),
11.5 g of a 35% strength by weight aqueous solution of a sodium salt of a sulfated and ethoxylated p-isooctylphenol (EO grade 25) and
162.9 water
and in 2.5 h a solution of 3.3 g of sodium peroxodisulfate in 90 g of water was continuously added dropwise. The reaction mixture was then stirred for a further 120 min at 90 ° C. and cooled to 60 ° C. After adding a solution of 1.1 g of t-butyl hydroperoxide in 5.5 g of water, a solution of 0.6 g of sodium formaldehyde sulfoxylate in 15 g of water was added at this temperature over the course of 1 h and the mixture was stirred for 0.5 h. After 15 minutes, the mixture was cooled to room temperature and neutralized with 4 ml of a 20% by weight aqueous calcium hydroxide slurry. After filtration, a dispersion with a solids content of 55.3%, a light transmittance of a 0.01% by weight dispersion at 20 ° C. and a layer thickness of 2.5 cm (“LD value”) of 8% and a pH -Value of 8.7 received. The glass transition temperature of the polymer was -15 ° C (DSC mid point, see above).

1.2 Dispersion D2

The procedure was as for dispersion D1, but the monomer emulsion feed consisted of
291.2 g of n-butyl acrylate,
252.0 g styrene,
11.2 g acrylamide,
5.6 g methacrylamide,
8.4 g of a 20% by weight aqueous solution of an ethoxylated p-isooctylphenol (EO grade 25),
11.5 g of a 35% strength by weight aqueous solution of a sodium salt of a sulfated and ethoxylated p-isooctylphenol (EO grade 25) and
162.9 g water,
and was neutralized with 3.5 g of a 10% by weight aqueous ammonia solution instead of 4 ml of a 20% by weight aqueous calcium hydroxide slurry. After filtration, a dispersion with a solids content of 55.4%, a light transmittance of a 0.01% by weight dispersion at 20 ° C. and a layer thickness of 2.5 cm (“LD value”) of 9% and a pH - received value of 7.3. The polymer had a glass transition temperature of + 15 ° C (DSC midpoint, see above).

1.3 Dispersion D3

A mixture of was in a polymerization vessel
500 g water
2.5 g sodium acetate
2.5 g butanol and
10 g of an ethoxylated cellulose (Natrosol® 250 GR)
heated to the polymerization temperature of 80 ° C. Then at first 150 g of feed I and then 10 g of feed II were introduced into the polymerization vessel and polymerized at 80 ° C. for 20 minutes. Subsequently, the remaining amount of feed I (within 3 h) and the remaining amount of feed II (within 3.5 h) were continuously metered in simultaneously while maintaining the 80 ° C. The mixture was then stirred at 80 ° C for 1 h and finally cooled to room temperature.

The solids content of the resulting aqueous polymer dis persion was 50.2% by weight. Their pH was 4 and the LD Value (25 ° C) was 20% (0.01% by weight dilution). The dis Powdered polymer had a glass transition temperature of -2 ° C (DSC midpoint see above).

Inlet I

600 g vinyl propionate
200 g of tert-butyl acrylate
200 g n-butyl acrylate
160 g of a mixture of 150 g of emulsifier solution (20% by weight aqueous solution of ethoxylated p-isooctylphenol with an EO degree of 25) and 10 g of a block copolymer of ethylene oxide and propylene oxide (molar ratio EO: PO = 0.7 and relative number average molecular weight = 3200) and
343 g water

Inlet II

5 g sodium peroxide sulfate in 100 g water.

1.4 Dispersion D4

A solution of 6000 g of water and
17 g of a 45% by weight aqueous solution of the Dowfax 2A1 corresponding surfactant
heated to the polymerization temperature of 80 ° C. Subsequently, 1087 g of feed I and 108 g of feed II were added in succession to the polymerization vessel and polymerized at 80 ° C. for 30 minutes. Subsequently, while maintaining the polymerization temperature, the remaining amounts of feeds I and II were continuously fed simultaneously for 3.5 h. The reaction mixture was then left to stand at 80 ° C. for 4 h. Finally, the mixture was cooled to room temperature and neutralized with 420 g of a 25% by weight aqueous sodium hydroxide solution.

The solids content of the resulting aqueous polymer dispersion was 50.9%. Their pH was 8 and the LD Value (25 ° C) was 46% (0.01% by weight dilution). The dis Powdered polymer had a glass transition temperature of 60 ° C (DSC midpoint).

Inlet I

12 150 g styrene
2250 g butadiene
450 g of a 50% aqueous solution of acrylamide
375 g acrylic acid
120 g of tert-dodecyl mercaptan
117 g of a 45% by weight aqueous solution of the Dowfax 2A1 corresponding surfactant
250 g of a 15% by weight aqueous solution of the sodium salt of the sulfuric acid half-ester of lauryl alcohol and
6033 g water.

Inlet II

150 g sodium peroxide sulfate and
200 g water.

2. Production of the spraying aids 2.1 Spray aids S1

228 g of 2,2-di (4-hydroxyphenyl) propane were added at room temperature submitted and concentrated in portions with stirring with 307 g trated sulfuric acid. After the addition was complete heated to 90 ° C within 15 min and at this for 1 h Stirred inside temperature. The sulfonia obtained afterwards degree of efficiency was 180%. The reaction mixture was on room cooled down temperature and with stirring with 950 ml of demineralized tem water and then with 400 ml of a 50 wt .-% calcium hydroxide slurries in deionized water. You fil the CaSO₄ formed on a 200 µm sieve and he held 602 g of an aqueous solution of spray aid S1 with a solids content of 28%.  

2.2 Spray aids S2

600 g of 2,2-di (4-hydroxyphenyl) propane and 395 g of concentrated As described in S1, sulfuric acid was mixed with at 90 ° C. for 2 h implemented each other. The degree of sulfonation was then 149%. After dilution with 1200 ml of deionized water, Neutralisa tion with 500 ml of a 50 wt .-% calcium hydroxide slurry in deionized water and filtering off the CaSO₄ 1584 g of a solution of spray aid S2 with a solid maintain fabric content of 27%.

2.3 Spray aids S3

300 g of 2,2-di (4-hydroxyphenyl) propane and 197 g of concentrated Sulfuric acid as described in S1 for 2 h at 90 ° C. set. The degree of sulfonation was then 132%. According to Ver thin with 700 ml of deionized water, neutralization with 300 ml of a 35 wt .-% calcium hydroxide slurry in full deionized water and filtering off the CaSO₄ were 982 g egg ner solution of spray aid S3 with a solids content received by 26%.

2.4 Spray aids S4

400 g of 2,2-di (4-hydroxyphenyl) propane and 263 g of concentrated Sulfuric acid as described in S1 for 3 h at 70 ° C. implemented each other. The degree of sulfonation was then 108%. After dilution with 500 ml of deionized water, Neutralisa tion with 365 ml of a 35% by weight calcium hydroxide slurry in deionized water and filtering off the CaSO₄ 939 g of a solution of spray aid S4 with a solid Received 22% fabric content.

2.5 Spraying aids S5

100 g of 4,4'-dihydroxybenzophenone and 138 g of concentrated As described in S1, sulfuric acid was mixed at 90 ° C. for 1 h implemented each other. The degree of sulfonation was then 108%. After dilution with 450 ml of completely deionized water, Neutralisa tion with 200 ml of a 50 wt .-% calcium hydroxide slurry in deionized water and filtering off the CaSO₄ 491 g of solution with a solids content of 26% was obtained.

2.6 Spray aids SV6

1.147 kg of phenol were placed at 60 ° C and in portions with stirring and cooling with 1.38 kg of concentrated sulfur acid such that the internal temperature is always below 110 ° C. After the addition had ended, the mixture was stirred at 105 to 110 ° C. for 3 h Stirred inside temperature. The reaction mixture was on Cooled 50 ° C and with stirring while maintaining an interior temperature from 50 to 55 ° C in portions with 0.84 kg one  30 wt .-% aqueous formaldehyde solution added. After be At the end of the addition, 0.75 kg of completely demineralized water were immediately added added, heated to 95 to 100 ° C and stirred for 4 h Temperature further. It was cooled to 60 ° C and others 50.83 kg of fully demineralized water were added. In case of a lung temperature of 65 ° C gave 2.25 kg of a 35 wt .-% Add calcium hydroxide slurries in deionized water, cooled to room temperature and filtered through a 200 µm Strainer. The pH of the 35% by weight aqueous solution thus obtained Solution was 8.2.

3. Preparation of the inventive and the comparative polymers sat powder

For the production of the dry polymer powder, the Dispersion to a solids content of 40% and spraying auxiliary diluted to a solids content of 20%. Then the dispersion was added quickly and with vigorous stirring Spray aids and if necessary with demineralized tem water a solids content of the mixture of 35%.

Spray drying was carried out in a minor laboratory dryer GEA Wiegand GmbH (stainless steel division) with disc or two-fluid nozzle atomization at a tower entrance temperature temperature of 130 ° C and a tower outlet temperature of 60 ° C (Output: approx. 2 kg spray / h). As an anti-blocking agent approx. 2.0-3.0% by weight at the same time as the spray (based on solid polymer mixture) a finely divided Silicic acid metered into the drying chamber. Quantity ratio nisse, the drying conditions and their results summarized in Table 2.

The redispersibility of the polymer powders was investigated as described in the following:
90 g of demineralized water are weighed into a glass bottle and 10 g of powder are added. The mixture is stirred with an Ultra-Turrax at 9500 rpm for 1 min and filled into a measuring cylinder. The measuring cylinder closed with a plastic stopper is stored for 72 hours without moving. The sediment is determined volumetrically after 72 h. The redispersion is then shaken well and filtered through a 72 µm sieve. The sieve is stored in a drying cabinet at 80 ° C. for 12 hours and the percentage of dry coagulum in the amount of powder weighed in (10 g) is determined.

Table 2

Spray drying results

a) with solids content 10%, assessed after 72 h;
b) based on 100 ml redispersion;
c) coagulate which can be filtered off through a 72 µm sieve and dried overnight at 80 ° C relative to the redispersible amount of powder;
d) i O - OK;
e) Number indicates the diameter of the two-component nozzle in [mm]
f) solid spraying aid, based on 100 parts of polymer (solid).

The tendency to discolouration in colorless cementitious materials became like determined below.

60 parts by weight Standard sand, 40 parts by weight White cement and 4 parts by weight Dispersion powder are with 26 parts. Water turned on and on spread out on a mineral substrate (layer thickness 2 mm). After 7 d of storage at room temperature, the color became a Sample that was stored in the dark and one Sample that was stored in daylight, the color of a compare unmodified reference samples with the same storage chen. The color intensity was based on a school grade system (1-6) rated, d. H. Grade 1 indicates the lowest color intensity, Grade 6 the highest.  

Table 3

Discolouration test on powder-modified, colorless cementitious materials

The setting behavior ( FIG. 1) of the cementitious compositions containing an inventive polymer powder was determined as follows:
A centered hole was cut into a plastic block made of polyurethane foam (cube with an edge length of 22 cm, which was cut open at a height of 2/3 along the base), which can hold exactly one polyethylene cup with a capacity of 300 ml. A narrow channel for a suitable temperature sensor led to this cavity (measuring principle: temperature dependence of the electrical resistance). 300 g of Portland cement PZ 45F were poured into a 300 ml polyethylene cup. Finally, 12 g of the respective 25% strength by weight aqueous solution of the spraying aid and 105 g of fully demineralized water were added and the mixture was stirred with a spatula for about 30 s. The cup was then inserted into the foam block, the lid placed on and the thermometer inserted (= time t₀). The internal temperature of the cement paste produced in this way was permanently recorded for about 72 hours.

Claims (19)

1. Use of at least one compound of the formula I: wherein
R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ independently of one another are H or SO₃H, but at least one of the radicals R¹- R⁸ is SO₃H;
X represents alkylene, CO, O, S or NR⁹, where R⁹ represents H or alkyl, or their salts as auxiliaries in the drying of aqueous polymer dispersions. 2. Use according to claim 1 of compounds of formula I, wherein X is -C (CH₃) ₂- or CO. 3. Use of compounds according to claim 1 in the form of Salts, which are the alkali metal or alkaline earth metal or ammonium salts. 4. Compounds of general formula I, wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ independently of one another are H or SO₃H, however, at least one of the radicals R¹-R⁴ and at least one of the radicals R⁵-R⁸ represents SO₃H, and X which in claim 1 or 2 has defined meaning, or their salts. 5. Compounds according to claim 4 of the general formula I, wherein R¹, R⁴, R⁶ and R⁷ are SO₃H. 6. Compounds according to claim 4 or 5 in the form of the salts, wherein it is the alkali metal, alkaline earth metal or ammonium salts acts. 7. Process for the preparation of a polymer powder Drying an aqueous polymer dispersion with addition a drying aid, characterized in that as a drying aid at least one of the An Proverbs 1 to 3 defined compounds used.   8. The method according to claim 7, characterized in that 1 up to 30 wt .-%, in particular 3 to 20 wt .-%, drying aid medium, based on the polymer of the dispersion, use det. 9. The method according to claim 7 or 8, characterized in that one uses a polymer whose glass transition temperature is 65 ° C is. 10. The method according to any one of claims 7 to 9, characterized in that the polymer is composed of

• a) 80 to 100 wt .-% of at least one monomer which is selected from vinyl aromatic compounds, esters of α, β-monoethylenically unsaturated C₃-C₆-carboxylic acids and C₁-C₁₂ alkanols, vinyl or allyl esters of C₁-C₁₂- Carboxylic acids and butadiene and
• b) 0 to 20% by weight of at least one other monomer which has at least one ethylenically unsaturated group.

11. The method according to claim 10, characterized in that it monomer (a) is n-butyl acrylate, 2-ethylhexyl acrylate lat, methyl methacrylate and / or styrene. 12. The method according to claim 10 or 11, characterized in that the monomer (b) is (meth) acrylamide, (Meth) acrylic acid, (meth) acrylonitrile, acrylamido-2-methyl propanesulfonic acid, vinyl pyrrolidone, hydroxyethyl (meth) acrylate and / or hydroxypropyl (meth) acrylate. 13. The method according to any one of claims 7 to 12, characterized is characterized in that the drying of the polymer dispersion by Spray drying takes place. 14. The method according to claim 13, characterized in that the Input temperature of the hot air flow 100 to 200 ° C and the The initial temperature of the hot air flow is 60 to 80 ° C. 15. Polymer powder, obtainable by a process according to one of claims 7 to 14. 16. Polymer powder comprising at least one compound which is defined by one of claims 1 to 3. 17. Use of the polymer powder according to claim 15 or 16 as a binder in hydraulically setting compositions, paint fabrics, varnishes, adhesives, coating materials and art  resin cleaning as well as for the modification of mineral building material fen. 18. Mineral binding materials containing a polymer powder according to one of claims 15 or 16. 19. Mineral binder building materials according to claim 18 in the form of a dry mortar preparation consisting of
20 to 60% by weight of mineral binder,
0.1 to 20% by weight of polymer powder according to one of claims 15 or 16,
up to 25% by weight of conventional auxiliaries and
as a residual quantity, additives such as sand, fillers, pigments, natural fibers and / or synthetic fibers.