DE19539460A1 - Drying aqueous polymer dispersions - Google Patents

Abstract

The process for drying aqueous dispersions of a polymer (B), in which the dispersion contains, as auxiliary drying agent, at least one polymer (A) containing (in polymerised form) 80-100 wt.% monomer(s) (a) of formula CH2CR1C(O)XCR2R3-R4-SOH (I) or salts thereof and 0-20 wt.% other radically polymerisable monomer(s) (b), in which R1-3 = H or 1-3 C alkyl; R4 = 1-5 C alkylene; and X = O or NH. Also claimed are: (i) the polymer powder containing (A) and (B); (ii) the mineral binder containing such polymer powder(s); (iii) the synthetic resin-plaster drying preparation containing such powder(s); (iv) the aqueous polymer dispersions of (B) with an emulsifier content of not more than 2 wt.%, containing (A) with a Mw of 5000-35,000 as added dispersant; (v) the process for the radical aqueous emulsion polymerisation of ethylenic monomers, in which (A) with a Mw of 5000-35000 is added before, during or after polymerisation; and (vi) the polymer powder obtained by drying as above.

Description

The present invention relates to the use of polymers I, which in polymerized form
<80 to 100% by weight of at least one monomer of general formula I and / or its salts (monomers a)

with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight of at least one radically copolymerizable monomer (monomers b)
are built up as aids in the drying of aqueous dispersions of polymers II different from the polymers I.

In addition, the present invention relates to the Drying resulting, redispersible in water, polymer powder and the use of this powder (e.g. as an additive in mi mineral binders or as binders for synthetic resin Cleaning) and for the production of the powder Dispersions of polymers II.

Aqueous polymer dispersions are generally known. It han is about systems that are essentially spherical in shape intertwined polymer chains (so-called Polymer particles) contained in disperse distribution. As well such as polymer solutions on evaporation of the solvent, white sen aqueous polymer dispersions on evaporation of the aqueous Dispersing medium the potential for the formation of polymer film on why they are used especially as binders, adhesives and coating agents are used. For the properties  aqueous polymer dispersions is of central importance Size of the disperse distribution contained in them Polymer particles. In particular properties such as the viscose act of the aqueous polymer dispersion or the gloss of their Ver Films are based on the diameter of the dispersed polymer particles or, more precisely, the diameter distribution function dependent on the dispersed polymer particles (filming Small polymer particles have the same polymer in usually a higher gloss; a wide diameter distribution tion usually requires a lower viscosity of the aqueous Polymer dispersion; Dispersions of small polymer particles usually have a greater pigment binding capacity Etc.).

A disadvantage of the "aqueous polymer" application form dispersion "is, however, that their place of manufacture is usually from Ge location is different. Your transport from the place of manufacture to the Ge In addition to the transport, however, the place of use ultimately implies the polymer film constituting the bottom essentially alone lymerisats also always the transport of the easy ver available dispersion medium "water". Can also be aqueous Polymer dispersions of mineral binders for the purpose their modification are only added at the place of use, because otherwise harden them before use.

A desirable manifestation of any aqueous Polymer dispersion is therefore that of yours when adding Water redispersing polymer powder.

In principle, when water is added, they are redispersible Polymer powder by drying its aqueous polymer dispersions accessible. Examples of such drying processes are freeze drying and spray drying. Latter Method in which the polymer dispersion in a warm air stream is sprayed and dewatered, is particularly useful for Generation of large quantities of powder. Preferably the dry air and the sprayed dispersion in cocurrent through the Dryer out (see e.g. EP-A 262326 or EP-A 407889).

Disadvantage of the drying of aqueous polymer dispersions polymer powders produced, however, is that their redispersion As a rule, the availability of water is not fully increased able to satisfy than the resultant in the redispersion Polymer particle diameter distribution usually from those in the aqueous starting dispersion (primary particles by knife distribution) is different.  

This fact arises from the fact that aqueous polymer dispersions do not form thermodynamically stable systems. A lot the system tries more, the polymer / dispersant interface medium by combining small primary particles into larger ones To reduce secondary particles (e.g. specks, coagulate), which in State of the disperse distribution in the aqueous medium by addition of dispersant can be prevented for a long time. in the As part of the drying process, the separating effect of the Dispersant often no longer works and it comes in certain Extent of irreversible secondary particle formation. That is, the seconds particles are retained as such during redispersion and reduce the application properties of the in the frame the redispersible aqueous polymer dispersion.

It has now been known for a long time that there are substances, the Zu The appearance of aqueous polymer dispersions irreversible secondary particle formation when drying reduced. These substances are called drying aids summarized. They are often particularly useful as spray aids medium known, since the spray drying to a particular extent Graduation of irreversible secondary particles. Simultaneously They usually reduce the formation of on the dryer sticking polymer coating during spray drying and thus increase the powder yield.

From EP-A 629650 it is known that polymers (polymer sate III) by radical polymerization of monomers mixtures of 15 to 80 wt .-% of at least one monomer general formula I and 20 to 85 wt .-% radical copoly merizable monomers are available in aqueous medium as Spray aids in the spray drying of aqueous polymer dispersions are suitable. US 3965032 relates to use Formation of polymers III as dispersants in aqueous Polymer dispersions. A disadvantage of the polymers III However, EP-A 629650 is that it can be used as Aid in the drying of aqueous polymer dispersions cannot fully satisfy.

The object of the present invention was therefore to use of ge better for drying aqueous polymer dispersions to make available own aids. Accordingly found the use of polymers I defined at the outset.

Polymers I and processes for their preparation in the A wide variety of molecular weights are generally known.  

JP-A 2/173108 describes e.g. B. the production of homo- and Copolymers of 2-acrylamido-2-methylpropanesulfonic acid and their salts. As a possible use for these polymers JP-A 2/173108 sees only the use as a dispersant for inorganic materials in aqueous medium.

US Pat. No. 5,294,686 describes a method for the production molecular 2-acrylamido-2-methylpropanesulfonic acid polymers and their use as dispersants and corrosion inhibitors known.

JP-A 6/122842 relates to the production of polymers I. and their use as an additive in underwater anti-fouling average.

US 3,936,400 recommends low molecular weight 2-acrylamido-2-me thylpropanesulfonic acid polymers as viscosity regulators in the Oil production.

AU-A 35611/84 relates to water-soluble polymers which contain carboxyl, sulfate or sulfonic acid groups and are terminated by -OH, -COOH or C _1- ₃-alkyl groups. These poly merisate are recommended as dispersants for particulate materials.

EP-A 123329 recommends u. a. Copolymers of acrylic acid and 2-Acrylamido-2-methylpropanesulfonic acid as a dispersant in aqueous pigment dispersions.

US 469816 discloses the use of a mixture of two Polymers for dispersing one consist of particles the material. One of the copolymers is polyacrylic acid, the other is poly-2-acrylamido-2-methylpropanesulfonic acid.

DE-A 32 32 811 relates to the production of microcapsules Polyurea capsule walls in the presence of special sulfone polymers containing acid groups. As such, a. Homo polymers of 2-acrylamido-2-methylpropanesulfonic acid with a relative molecular weight of 5000 to 10⁷ used.

EP-A 511520 recommends u. a. the use of polymers I as a dispersant for the preparation of emulsifier-free aqueous Polymer dispersions.

Preferably contain polymers I to be used according to the invention polymerized such monomers a, in which R¹, R², R³, independently gig from each other, is H or CH₃. Furthermore, monomers a of  Advantage where X is NH. As R⁴ C₁ to C₃ alkylene is advantageous arrested. A 2-acrylic is very particularly preferred as monomer amido-2-methylpropanesulfonic acid (or its salts) are used, d. that is, the monomer of the general formula I in which R¹ = H, R² and R³ = CH₃, R⁴ = -CH₂- and X = NH.

Suitable monomers a in salt form are especially alkali metal (e.g. Li, Na, K) and alkaline earth metal (Ca, Mg) salts, however also salts, which by neutralization of the free acid by means of or ganic amines or ammonia are available. In the invention Suitable polymers 1 according to the meaning are, for. B. such at least the proportion by weight of polymerized monomers a 85, or at least 90, or at least 95 or 100% by weight wearing.

Suitable monomers b are all radically polymerizable monomers different from monomers a. These are e.g. B. monoethylenically unsaturated monomers such as olefins, e.g. B. ethylene or propylene, vinyl aromatic monomers such as styrene, α-methylstyrene, o-chlorostyrene or vinyl toluenes, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 carbon atoms such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters from preferably 3 to 6 carbon atoms containing α, β-monoethylenically unsaturated mono- and dicarboxylic acids, such as acrylic acid, methacrylic acid, fumaric acid and itaconic acid, with alkanols generally having 1 to 12, often 1 to 8 and mostly 1 to 4 carbon atoms such as in particular acrylic acid and meth acrylic acid methyl, ethyl, n-butyl, isobutyl, tert-butyl and -2-ethylhexyl esters, dimethyl maleate or n-butyl maleate, the nitriles of aforementioned α, β-mono-ethylenically unsaturated carboxylic acids such as acrylonitrile and C _4-8 conjugated dienes such as 1,3-butadiene and isoprene. Other suitable monomers b are 3 to 6 carbon atoms containing α, β-mono ethylenically unsaturated mono- and dicarboxylic acids and their amides such as, for. As acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide, the monoesters of these carboxylic acids with polyhydric alcohols such as hydroxyethyl acrylate, hydroxypropyl acrylate, and also vinyl sulfonic acid and N-vinylpyrrolidone.

If the polymer I to be used according to the invention contains no monomers b polymerized in, it is generally a homopolymer of a monomer I, for. B. the 2-acrylamido-2-methylpropane sulfonic acid or one of its salts. The weight-average relative molecular weight M _w of polymers I to be used according to the invention (based on the fully neutralized sodium salt form) can be, for. B. 1000 to 10⁶, but also 2000 to 5 · 10⁵ or 5000 to 10⁵ or 1000 to 45000 or 7500 to 35000 or 10,000 to 25,000.

The reference basis for the above information is in the case of the Usually water-soluble Na salts of the polymers I have a molecular weight determination according to the method of gel permeation chromatography phie using four columns in a row

• 1. Inner diameter: 7.8 mm, length: 30 cm, separator material: Toso Hass TSK PW-XL 5000,
• 2.Inside diameter: 7.8 mm, length: 30 cm, separator material: Waters Ultrahydrogel 1000,
• 3.Inside diameter: 7.8 mm, length: 30 cm, separator material: Waters Ultrahydrogel 500,
• 4.Inside diameter: 7.8 mm, length: 30 cm, separator material: Waters Ultrahydrogel 500.

200 µl of a 0.1% by weight aqueous solution of the Polymer neutralized with sodium hydroxide I. The columns are tempered to 35 ° C. An aqueous solution is used as the eluent 0.08 molar solution of a TRIS buffer (pH 7), the 0.15 mol / l NaCl or 0.01 mol / l NaN₃ are added. The through flow rate of the eluent is chosen to be 0.5 ml / min. Before the sample application, the sample is passed through a brand filter Sartorius Minisart RC 25 (pore size 0.20 µm) filtered. As The detector becomes an ERC 7510 differential refractometer from the company ERMA used. The calibration is carried out according to R. Brüssau u. a. in Surfactants, Surf.Det. 28: 596-406 (1991). Relative molecular weights <700 are not taken into account in the aforementioned determination method inspects.

As already mentioned, the manufacture is to be ver according to the invention using polymers known per se. It is done with advantage through radical polymerization. This is preferred in pola ren solvents, especially in water. As Monomers a can be used both in the free acids and in the appropriate amount of water-soluble salts are used. Of course, their mixtures can also be used will. To set the desired molecular weight you can substances regulating the molecular weight are also used. Ge Suitable molecular weight regulators are compounds that have a thiol have group (e.g. tert-dodecyl or n-dodecyl mercaptan).  

Suitable starters are inorganic peroxides such as sodium peroxodisulfate. Depending on the monomer composition, the polymerization can be carried out as solution or emulsion polymerization. The ratio of weight-average molecular weight M _w to average molecular weight M _{n of} the aqueous polymers I to be used according to the invention can be 1 to 30 or 1 to 20 or 1 to 8. That is, the molecular weight can be essentially uniform or distributed over a certain width.

It is expedient if those to be used according to the invention are used Polymer I at least in 100 g of water at 25 ° C and 1 bar Loosen 1 g. As a rule, this will be the case. Often amounts to the solubility of the polymers to be used according to the invention sate I in 100 g of water at least under the aforementioned conditions 10 g.

The redispersible polymer powder is prepared According to the spray drying process, this is the fiction According to the polymer to be used, generally choose so that its glass transition temperature (midpoint temperature, ASTM D 3418-82) above the glass transition temperature of the polyme risats II of the spray-dried aqueous polymer dispersion lies.

It is particularly useful to spray-dry an aqueous polymer dispersion at an inlet temperature T _{E of} the hot air stream of 100 to 200 ° C, preferably 120 to 160 ° C, and an outlet temperature T _{A of} the hot air stream of 30 to 90 ° C, preferably 50 to 70 ° C. The spraying of the aqueous polymer dispersion in a hot air stream can, for. B. by means of single or multi-component nozzles or via a rotating disk. The deposition of the polymer powder is normally carried out using cyclones or filter separators. The sprayed aqueous polymer dispersion and the hot air stream are preferably carried out in parallel.

Against this background, polymerizates I are preferred as spray aids, the glass transition temperature of which fulfills the condition <T _A. According to our own investigations, the glass transition temperatures of homopolymers of the monomers a are above 100 ° C. for not too low molecular weights.

The polymer I to be used according to the invention can be added to drying aqueous dispersion of polymer II as an aqueous Solution or be added directly as an aqueous dispersion. In the case of an aqueous solution of polymer I to be used  preferably stirring the aqueous dispersion of polymer II in the aqueous solution of the polymer I.

It is surprising that addition of polymers I in amounts of 1 or 2 to 5 wt .-%, based on the amount of dry polymer II containing dispersion, already good Redispersibility of the resultant by drying Polymer powder conditional.

Of course, you can, related in the same way, the Polymers I to be used according to the invention also in amounts of 1 to 10 wt .-% or 5 to 40 wt .-% and more, or in amounts of Apply 10 to 20% by weight.

The invention has proven to be particularly favorable Use of polymers I in the case of polymers II, whose glass transition temperature be 50 ° C or 25 ° C or 0 ° C wearing. As a rule, the glass transition temperature of the polyme risate II - 60 ° C, or - 40 ° C or - 20 ° C. Further the use of polymers I according to the invention proves in the case of such polymers II as particularly favorable, the in polymerized form

• A) 80 to 100 wt .-% of at least one monomer from the Group comprising styrene, α-methylstyrene, vinyltoluenes, Ester of 3 to 6 carbon atoms containing α, β-mono ethylenically unsaturated carboxylic acids and Alkanols containing 1 to 12 carbon atoms, butadiene and Vinyl and allyl esters of 1 to 12 carbon atoms Carboxylic acids and
• B) 0 to 20 wt .-% other, at least one ethylenically monomers containing unsaturated groups

are built up (such polymers II are hereinafter referred to as Polymers II *)). That is, possible monomers are A. n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate and Styrene.

Possible monomers B are acrylamide, methacrylamide, acrylic acid, Methacrylic acid, acrylonitrile, methacrylonitrile, 2-acrylic amido-2-methylpropanesulfonic acid, vinyl pyrrolidone, hydroxyethyl acrylate, hydroxymethyl acrylate, hydroxypropyl acrylate, hydroxy propyl methacrylate, quaternized vinyl imidazole, N, N-dialkylami noalkyl (meth) acrylates, N, N-dialkylaminoalkyl (meth) acrylamides,  Trialkylammonium alkyl (meth) acrylates and trialkylammonium alkyl (meth) acrylamides.

Of course, it can be with the polymer to be dried dispersion around a secondary dispersion of a polymer II act. In this case, the polymer II z. B. in itself known manner according to the method of radical poly solution Merisation produced and subsequently in an aqueous Polymer dispersion transferred. In this case the polyme Risat I preferably the finished, the polymer I dispersed containing aqueous polymer dispersion added.

Is it the aqueous polymer II comprising Polymer dispersion around a primary dispersion, i. H. by one such polymer dispersion, which by the method of radicals Mix aqueous emulsion polymerization directly in disperse Distribution is manufactured, this can according to the invention Polymer I to be used as drying aid both before, during and / or after the emulsion polymerization of the Polymer II constituent monomers are added.

In other words, polymer I is generally an aqueous dis add persion of a polymer II, which is already dispersing medium (usually in amounts of up to 3% by weight based on contains the amount of polymer II). As such, both come the commonly used protective colloids as well as emulga gates into consideration as they e.g. B. in DE-A 42 13 965 are. The stabilizing effect of protective colloids is in it steric and / or electrostatic shield tion of the dispersed polymer particles. It are usually such substances, their molecular weight is above 1500. You can stick to the dispersed Polymer particles both chemically and only physically be bound. The stabilizing effect of emulsifiers, their relative molecular weight is regularly <1000, is on it attributed to the fact that, due to their amphiphilic structure (pola rer part and non-polar part) the interfacial tension of the boundary surface polymer / aqueous dispersion medium to reduce In contrast to protective colloids, emulsifiers in Water micelles. They are also such that when added to water at 25 ° C and 1 atm when reaching the critical micelle concentration its surface tension reduce by at least 25%.

According to the invention it is very important that ins particular polymers I to be used according to the invention (ins especially if they contain no monomers b copolymerized),  their weight average relative molecular weight 5000 to 35,000, preferably 7500 to 20,000 or 15,000, not only drying aids that can be used according to the invention form, but at the same time in an excellent way the disperse Stabilize distribution of aqueous polymer dispersions ver to like. That is, to be used according to the invention Polymers I already in the course of the free radical aqueous emuls polymerisation, there is the possibility on the one hand to produce aqueous polymer dispersions of polymers II, their emulsifier content, based on the amount of dispersed Polymer II, 2, or 1 or 0.5 or 0.1 or 0% by weight (the use of emulsifiers is often unimportant wishes, since they are the filming of the aqueous polymer dispersion generally sensitive to the effects of water usually because of their low molecular weight sweat out of the film), and on the other hand at the same time in an excellent way to redispersible polymer powders are dryable. It is not necessary that the aqueous Dispersion of polymer II in addition to polymer I still protection other types of colloids added in the course of their manufacture holds. Rather, the content of polymers I ver different protective colloids, based on the amount of the contained Polymer II, 5% by weight or 3% by weight or 0% by weight gene.

It is particularly noteworthy that the as described above use of such low molecular weight polymers I also the generation of stable fine-particle (weight-average Polymer particle diameter 500 nm, often 200 nm and  50 nm) aqueous polymer dispersions of polymers II enables. It is noteworthy that in this regard use from 1% by weight to 10% by weight of low molecular weight polymers I, based on polymer II to be dispersed, is sufficient especially if it is low molecular weight poly-2-acrylic amido-2-methylpropanesulfonic acid acts as polymer I. (Of course, can also be in a corresponding manner drawn application amounts of up to 25 or up to 50 wt .-% be set). This fact is surprising even in the face of it the recommendation found in the prior art molecular polymers I as dispersants for fine particles use inorganic materials. As in the execution examples pielen is usually shown by a disperser effect on finely divided inorganic materials not on one such effect in the context of the production of aqueous polymer dispersions using the radical aqueous emuls method Sion polymerization are closed.  

The monomer composition of polymer II is relative to the aforementioned relationships are essentially irrelevant. Des The same applies to the type of emulga used gates and protective colloids and for the type of used Polymerization initiator. That is, the aforementioned relationships meet z. B. also in the case of such polymers II to contain less than 70 wt .-% styrene copolymerized.

MaW come as monomers having at least one ethylenically unsaturated group to build up the polymer II in the aforementioned context, including other monoethylenically unsaturated monomers such as olefins, for. B. ethylene, vinyl aromatic monomers such as styrene, α-methylstyrene, o-chlorostyrene or vinylto luole, vinyl and vinylidene halides such as vinyl and vinylidene chloride, esters of vinyl alcohol and monocarboxylic acids having 1 to 18 carbon atoms such as vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl laurate and vinyl stearate, esters of α, β-monoethylenically unsaturated mono- and dicarboxylic acids, preferably having 3 to 6 carbon atoms, such as in particular acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with generally 1 to 12, alkanols preferably having 1 to 8 and in particular 1 to 4 carbon atoms, such as, in particular, methyl, ethyl, n-butyl, isobutyl and 2-ethylhexyl acrylate, methyl isocyanate, dimethyl maleate or n-maleate butyl esters, nitriles of α, β-monoethylenically unsaturated carboxylic acids such as acrylonitrile and C _4-8 -conjugated dienes such as 1,3-butadiene and isoprene. The monomers mentioned generally form the main monomers which, based on the total amount of the monomers to be polymerized by the process of free-radical aqueous emulsion polymerization, normally comprise a proportion of more than 50% by weight. Monomers which, when polymerized, usually give homopolymers which have increased solubility in water are normally only used as modifying monomers in amounts, based on the total amount of the monomers to be polymerized, of less than 50% by weight, generally 0, 5 to 20, preferably 1 to 10 wt .-%, co-polymerized.

Examples of such monomers are 3 to 6 carbon atoms α, β-monoethylenically unsaturated mono- and dicarboxylic acids and whose amides such as As acrylic acid, methacrylic acid, maleic acid, Fu Martic acid, itaconic acid, acrylamide and methacrylamide, also vinyl sulfonic acid and its water-soluble salts and N-vinylpyrroli Don. Monomers, which usually have the internal strength of ver increase filming of the aqueous polymer dispersion are in usually also only in minor quantities, usually 0.5 to 10 wt .-% based on the total amount to be polymerized  Monomers, co-polymerized. Usually such Monomers an epoxy, hydroxy, N-methylol, carbonyl or at least two non-conjugated ethylenically unsaturated Double bonds. Examples of these are N-alkylolamides of 3 up to 10 carbon atoms containing α, β-monoethylenically unsaturated car bonic acids and their esters with Al having 1 to 4 carbon atoms alcohols, among which the N-methylol acrylamide and the N-methylol methacrylamide are very particularly preferred, two vinyl residues pointing monomers, two monomers containing vinylidene residues and two monomers containing alkenyl radicals. Are particularly suitable the di-esters of dihydric alcohols with α, β-monoethylenic unsaturated monocarboxylic acids among which in turn the Acrylic and methacrylic acid are preferably used. At games for such two non-conjugated ethylenically unsaturated Monomers having saturated double bonds are alkylene glycol diacrylate and dimethacrylates such as ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate and Pro pylene glycol diacrylate, divinylbenzene, vinyl methacrylate, Vinyla crylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallylfu marate, methylenebisacrylamide, cyclopentadienyl acrylate or trial lylcyanurate. In this context are of particular importance also the methacrylic acid and acrylic acid-C₁-C₈-hydroxyalkyl esters such as n-hydroxyethyl, n-hydroxypropyl or n-hydroxybutyl acrylate and methacrylate and compounds such as diacetone acrylamide and Acetylacetoxyethyl acrylate or methacrylate. In addition to unsaturated Monomers having double bonds can be found in subordinate Amounts, usually 0.01 to 2 wt .-% based on the poly merizing monomers, molecular weight regulating substances such as tert-dodecyl mercaptan and 3-mercaptopropyltrimethoxysilane be polymerized with. Such sub punch in a mixture with the monomers to be polymerized Polymerization zone added.

Above all, the special suitability of the low-molecular weight Polymers I as the essentially sole dispersant in Framework of radical aqueous emulsion polymerization provision of polymer II in the case of polymer II *.

In other words, the use of polymers I according to the invention enables light in particular both the production of emulsifier-free water ger polymer dispersions, as well as the production of in what this redispersible emulsifier-free polymer powder. Be It is noteworthy that such emulsifiers are essentially free aqueous polymer dispersions through a reduced viscosity Marked are.  

When carrying out the radical aqueous emulsion polymer rization for the production of aqueous dispersions of polymer Saten II, whose disperse distribution essentially using poly merisaten I is stabilized, the method of Monomer feed used. The total of the as Protective colloid to be used polymer I both in the polymer presented risk vessel, as well as together with the polymeri based monomers continuously fed to the polymerization vessel leads.

It should be noted that in the context of the invention Use in addition to the polymers to be used according to the invention I also added drying aids known per se (e.g. Polyvinyl alcohol, polyvinyl pyrrolidone, naphthalenesulfonic acid (or phenolsulfonic acid) formaldehyde condensates etc.) mitver can be applied. The same applies to anti-caking agents such as finely divided silica, often used in spray drying can also be used to caking the polymer powder to prevent during storage.

The polymer resulting from use according to the invention powders are suitable as binders in hydraulically setting Compositions, paints, varnishes, adhesives, coating compositions (especially for paper) and synthetic resin plasters, such as those in the EP-A 629650 are described. The same applies to those at the Pul preparation used starting dispersions. Their feast fabric volume content can be 10 to 75, often 20 to 65, mostly 30 up to 50 vol .-%, based on the volume of the polymer dispersion be.

Finally, it should be noted that when putting together a aqueous solution or dispersion of a polymer I and a aqueous dispersion of a polymer II on their compatibility must be respected. That is, in the case of a cationic stabili based aqueous dispersion of a polymer II should not ionic polymer I system can be added.

Examples a) Preparation of a polymer to be used according to the invention sats I (EPI)

The polymerization was carried out under an inert gas atmosphere leads. 820 g were initially placed in a polymerization vessel Submitted water and heated to 85 ° C. While maintaining At this temperature 10 wt .-% of a solution of 17.6 g of sodium peroxodisulfate in 150 g of water are added and 5 min. touched. After that, maintaining the 85 ° C the remaining amount of sodium peroxodisulfate solution and there spatially separated from a mixture of 800 g of water, 400 g 2-acrylamido-2-methylpropanesulfonic acid, 400 g one 25% by weight aqueous sodium hydroxide solution and 0.04 g 4-methoxyphenol (polymerization retarder) with stirring (both inlets starting simultaneously) within one hour continuously fed to the polymerization vessel. After that the reaction mixture was stirred at 85 ° C. for another hour. The mixture was then cooled to 60 ° C. and a solution with stirring from 7.5 g of sodium hydroxymethyl sulfinate and 30 g of water added for half an hour (to remove any remaining Peroxide).

The resulting clear solution had a solids content of 19.7% by weight and a pH of 12.8. The weight average relative molecular weight of the dissolved polymer EPI was determined to be 10,000.

b) Preparation of a in EP-A 629650 (Example 1, DPIa) Spray auxiliaries recommended comparative polymer I (VPI)

The polymerization was carried out under an inert gas atmosphere leads. A solution of 1.76 g of sodium peroxodisulfate in 1050 g of water and heated to the polymerization temperature of 85 ° C. On were closing while maintaining the polymerisa tion temperature, the polymerization vessel, be at the same time starting, inlets I to III fed synchronously within 2 h leads. The reaction mixture was then at 85 ° C for 1 h left to yourself. Then 3 g of a 20 wt .-% was aqueous solution of the sodium metal salt of hydroxymethane added sulfinic acid and cooled to room temperature.

Inlet I:
280 g of methyl methacrylate and
1 g ester of thioglycolic acid and 2-ethyl hexanol;

Inlet II:
120 g of 2-acrylamido-2-methylpropanesulfonic acid
400 g water and
150 g 20% by weight aqueous sodium hydroxide solution;

Inlet III:
15.84 g sodium peroxodisulfate and
150 g water.

The solids content of the resulting aqueous polymer dispersion was 20% by weight.

c) Production of standard aqueous disperse to be spray-dried sions of polymers II (SDII1 to SDII4)

SDII1: Corresponds to Example 2, DPIIa of EP-A 629650
A solution was made in a polymerization vessel

294 g water
7.7 g of a 10% by weight aqueous formic acid solution
6.6 g of a 20% by weight aqueous solution of polyacrylamide
3.3 g sodium hydrogen carbonate
11 g of a 20% by weight aqueous solution of ethoxylated p-isooctylphenol (EO grade: 25) = emulsifier solution 1 and
0.9 g of a 35% strength by weight aqueous solution of the sodium salt of the sulfuric acid half-ester of ethoxylated p-isooctyl phenol (EO grade: 25) = emulsifier solution 2

submitted and to the polymerization temperature of 90 ° C. warmed up. Subsequently, the Zu runs I (within 2 h) and II (within 2.5 h) while maintaining the polymerization temperature Polymerization vessel fed continuously. After that was the polymerization vessel itself for a further 2 h at 90 ° C left. The mixture was then cooled to room temperature and with 5.5 g of a 20% by weight aqueous calcium hydroxide Slurry neutralized. The solids content of the resul The aqueous polymer dispersion SDII1 was 54.7% by weight. The dispersed polymer had a glass transition temperature of -1 ° C.

Inlet I:
682 g of n-butyl acrylate
385 g styrene
44 g of a 50% by weight aqueous solution of acrylamide
73.3 g of a 15% by weight aqueous solution of methacrylamide
16.5 g of emulsifier solution 1
22.6 g of emulsifier solution 2 and
235 g water.

Inlet II:
6.4 g sodium peroxodisulfate in
180 g water.

SDII2: Corresponds to Example 2, DPIIb of EP-A 629650
A mixture of was in a polymerization vessel

500 g water
2.5 g sodium acetate
2.5 g butenol and
10 g of an ethoxylated cellulose (Natrosol® 250 GR)

heated to the polymerization temperature of 80 ° C. Then were at first 150 g of feed I and then 10 g Feed II entered into the polymerization vessel and 20 min polymerized at 80 ° C. Then begin at the same time nend the remaining amount of feed I (within 3 h) and the Remaining amount of feed II (within 3.5 h) with upright maintenance of 80 ° C continuously metered. After that was stirred at 80 ° C for 1 h and finally to room temperature cooled down.

The solids content of the resulting aqueous polymer dispersion SDII2 was 50.2% by weight. The dispersed polyme risat had a glass transition temperature of -2 ° C.

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 1 and 10 g of a block copolymer of ethylene oxide and propylene oxide (molar ratio EO: PO = 0.7 and the relative number-average molecular weight = 3200) and
343 g water;

Inlet II:
5 g sodium peroxodisulfate in
100 g water.

SDII3: Corresponds to Example 3, DPIIc of EP-A 629650
A solution was made in a polymerization vessel

6000 g of water and
17 g of a 45% by weight aqueous solution of the surfactant corresponding to Dowfax® 2A1

heated to the polymerization temperature of 80 ° C. Then 1087 g of feed I and 108 g were fed in succession Feed II into the polymerization vessel and at 30 min Polymerized at 80 ° C. Subsequently, while maintaining tion of the polymerization temperature, the residual amounts of feed Runs I and II started simultaneously for 3.5 hours Lich fed. The reaction mixture was then 4 h left at 80 ° C. In conclusion was on space cooled temperature and with 420 g of a 25 wt .-% neutralized aqueous sodium hydroxide solution. The fixed salary the resulting aqueous polymer dispersion SDII3 be contributed 50.9% by weight. The dispersed polymer had one Glass transition temperature of 60 ° C.

Inlet I:
12150 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 surfactant corresponding to Dowfax 2A1
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 peroxodisulfate and
200 g water.

SDII4:
Like SDII1, but the 385 g styrene was replaced by 385 g methyl methacrylate. After filtration, a dispersion SDII4 with a solids content of 55.6% by weight was obtained. The dispersed polymer had a glass transition temperature of 0 ° C.

d) spray drying the aqueous polymer dispersions from c) and assessment of the redispersibility of the resulting powder

First, the respective aqueous polymer dispersion SDII1 to SDII4 to a solids content of 36.2% by weight diluted. Then the aqueous solution of the EPI from a) or in the aqueous dispersion of the VPI from a) with vigorous Stir as much of the respective diluted to 36.2 wt .-% Polymer dispersion SDII1 to SDII4 quickly stirred in that an aqueous mixture resulted which had a solids content of 35% by weight (based on the particular dispersed poly Merisat II was therefore always 4.5% by weight of EPI or VPI hold) showed.

The spray drying of the aqueous mixtures was carried out in one Minor laboratory dryer from GEA Wiegand GmbH (business area Reich Niro), DE, with two-substance atomization at one Tower inlet temperature of 130 ° C and one outlet temperature of 60 ° C (output: approx. 2 kg spray / h). As Anti-blocking agents were used at the same time as the spray  2.5% by weight (based on solid polymer mixture) of one finely divided silica (average grain size diameter: 10 µm) are metered into the drying chamber. Assessing the Table 1 shows the respective spray drying.

To check the redispersibility of the obtained Polymer powder was used as follows:

90 g of water were weighed into a glass bottle and at 25 ° C with 10 g of polymer powder. The mixture became with an Ultra-Turrax 1 from Janke & Kunkel, IKA Laboratory technology, Staufen DE, 1 min at 9500 rpm. stirred and in filled a measuring cylinder. Then the one with Plastic stoppers closed measuring cylinders at 25 ° C for 72 hours stored in motion. The redispersion was then poured well and filtered through a 72 µm sieve. That the filter cake containing sieve was gela at 80 ° C for 12 h in the drying cabinet then weighing the percentage weight proportion of the dried coagulum, based on the amount used Amount of powder (10 g) determined. The results also shows Table 1.

Table 1

e) Preparation of aqueous dispersions of polymers II which as a substantially sole dispersant Molecular polymer I according to the invention contain the Spray drying of such aqueous polymer dispersions and Comparative tests D1

200 g of n-butyl acrylate, 200 g of methyl methacrylate and 91.4 g of 19.7% by weight aqueous solution of the polymer EPI from a) were emulsified into feed 1 in 114 g of water. 12 g Sodium peroxodisulfate and 159 g water formed feed 2.

In an inert gas atmosphere in a polymerization vessel 200 g of water and 5 wt .-% of feed 1 submitted. The before layer was heated to 90 ° C. with stirring and 10% by weight of the inlet 2 offset. Then the reaction was kept mixed at 90 ° C for 15 min. After that the Polyme the residual amount while maintaining the 90 ° C at feed 1 (within 2 h) and the remaining amount of feed run 2 (within 2.5 h) fed continuously. After The feed mixture was terminated for a further 2 h stirred at 90 ° C and then cooled to room temperature. The after filtration through a sieve with a mesh size of Aqueous polymer dispersion obtained 250 μm had one Solids content of 43.6 wt .-%, a pH of their aqueous Dispersing medium of 1.9 and an LD value of 6% (the LD value is a measure of the polymer particle size an aqueous polymer dispersion; he gives the light permeability at 25 ° C to a solids content of 0.01% by weight diluted state, relative to pure water and at a layer thickness of 2.5 cm, with exposure to white light). 0.2 g of coagulate remained in the filter. On wet, in a layer thickness of 60 µm on a glass plate doctored film showed essentially no specks (Microcoagulate).

D2

Like D1, with the difference that the inlet 1 from an Emul sion of 208 g n-butyl acrylate, 180 g methyl methacrylate, 8 g Acrylamide, 4 g of acrylic acid and 91.4 g of the 19.7% by weight aqueous solution of the polymer EPI from a) in 114 g of water duration. After filtration through a sieve with a mesh a dispersion of 250 μm obtained had a solid content of 43.9 wt .-%, a pH of their aqueous Dispersing medium of 4.3 and an LD value of 52%. 0.2 g of coagulate remains in the filter. A wet, at a layer thickness of 60 microns on a glass plate squeegee film showed essentially no specks.

D3

Like D1, with the difference that the inlet 1 from an Emul sion of 248 g n-butyl acrylate, 140 g styrene, 8 g acrylamide, 4 g of methacrylamide and 91.4 g of the 19.7% by weight aqueous Solution of the polymer EPI consisted of a) in 114 g of water. The filtrate through a sieve with a mesh size of Dispersion obtained 250 µm had a solids content of 43.3 wt .-%, a pH of their aqueous dispersing medium of 2.1 and an LD value of 49%. Remain in the filter 0.3 g of coagulum back. A wet one, in a layer thickness of 60 microns of film scraped onto a glass plate showed in essentially no specks.

D4

From a mixture of 100 g n-butyl acrylate and 100 g methyl Inlet 1 was formed in methacrylate. A solution from 1.0 g of hydrogen peroxide and 100 g of water formed a zu run 2. Under an inert gas atmosphere were in a polymer onsgefäß 247 g of water, 1.3 g of a 15 wt .-% aqueous Sodium lauryl sulfate solution, 50.8 g of a 19.7% by weight aqueous solution of the polymer EPI from a), 0.04 g of CuSO₄ · 5H₂O and 5 wt .-% of feed 1 submitted. With stirring, the template was heated to 85 ° C and with 10% by weight of feed 2 are added. After that, the mixture Maintained for 15 min at 85 ° C with stirring and then under Maintaining 85 ° C the remaining quantities of feed 1 (within 2h) and inflow 2 (within 2.5h) time right from the start continuously into the polymerization vessel fed. When the feed was complete, the polymerization gel mix for a further 2 h at 85 ° C and then open Cooled to room temperature. After filtration through a sieve dispersion obtained with a mesh size of 250 microns a solids content of 34.2 wt .-%, a pH of their aqueous dispersion medium of 6.8 and an LD value of 88% on. 0.69 g of coagulate looks back in the filter. On wet, in a layer thickness of 60 µm on a glass plate doctored film showed essentially no specks.

D5

From 155 g n-butyl acrylate, 87.5 g styrene, 5 g acrylamide, 2.5 g of methacrylamide, 190.4 g of the 19.7% by weight solution of the Polymer EPI from a) and 20 g of water became an emulsion formed as inlet 1. A solution of 7.5 g sodium peroxodi sulfate in 100 g of water formed a feed 2. Under inert Gas atmosphere were 104 g in a polymerization vessel Water, and 5 wt .-% of feed 1 submitted. The template  was heated to 90 ° C with stirring and with 10 wt .-% of Zu run 2 offset. The mixture was then 15 min kept at 90 ° C with stirring. Then were under Maintaining 90 ° C, starting at the same time, the rest quantities of feed 1 (within 2.0 h) and of feed run 2 (within 2.5 h) of the polymerization vessel fed slowly. After that, the reaction mixture was still Stirred at 90 ° C for 2 h and finally abge to room temperature cools.

After filtration through a sieve with a mesh size of Dispersion obtained 250 µm had a solids content of 43.2% by weight, a pH value of their aqueous dispersing medium of 2.7 and an LD value of 68%. Remained in the filter 0.3 g of coagulum back. A wet one, in a layer thickness of 60 microns film scraped onto a glass plate showed essentially no specks.

VD1

Like D1, feed 1, however, consisted of an emulsion of 200 g of n-butyl acrylate, 200 g of methyl methacrylate and 90 g of 20% by weight aqueous dispersion of the polymer VPI from b) in 114 g of water. After filtration through a sieve with a Mesh size of 250 μm dispersion had a solid substance content of 43.4 wt .-%, a pH of their aqueous Dispersing medium of 1.7 and an LD value of 30%. 5.8 g of coagulate remained in the filter. A wet one Film thickness of 60 µm on a glass plate had numerous specks.

VD2

Like D5, instead of the 190.4 g of the 19.7% by weight aqueous solution Solution of the polymer EPI from a) were, however, 187.5 g 20% by weight aqueous dispersion of the polymer VPI from b) used. After filtration through a sieve with a Mesh size of 250 μm dispersion had a solid content of 42.7 wt .-%, a pH of their aqueous Dispersing medium of 2.1 and an LD value of 43%. 14 g of coagulum remained in the filter. A wet one Film thickness of 60 µm on a glass plate had numerous specks.  

VD3

Like D4, but the original contained a mixture of 247 g Water, 1.3 g of a 15% by weight aqueous sodium lauryl sulfate solution, 50 g of a prepared in analogy to a) 20 wt .-% aqueous solution of a poly-2-acrylic amido-2-methylpropanesulfonic acid, the weight-average re latent molecular weight, however, was 38,000, 0.04 g CuSO₄ · 5H₂O and 5 wt .-% of the feed 1. The reaction mixture already thickened during the monomer feed, so that the Reaction approach had to be stopped.

VD4

Like D1, feed 1, however, consisted of 200 g of n-butyl acrylate, 200 g of methyl methacrylate, 90 g of the 20 wt .-% aqueous Poly-2-acrylamido-2-methyl-propanesulfonic acid solution from VD3 and 116 g water. The approach coagulated after the Auspoly merize.

VD5

Like D1, feed 1, however, consisted of 200 g of n-butyl acrylate, 200 g of methyl methacrylate, 71.2 g of a 25.3% by weight aqueous solution of Sokalan® CP9 (maleic acid copolymer), the as a dispersant for finely divided organic and anorga niche solids is commercially available and 135 g of water. The batch coagulated after the polymerization. This indicates from that dispersant for finely divided organic and organic solids not necessarily as protection colloid to carry out radical aqueous emulsion po Lymerizations are suitable.

The aqueous polymer dispersions D1 to D5 were in be peacefully after the spray described under d) drying process to redispersible polymer powders dryable.

Claims (34)

1. Drying an aqueous dispersion of a polymer II, characterized in that the aqueous dispersion of the polymer II contains at least one polymer I added as drying aid, which in polymerized form to <80 to 100 wt .-% of at least one monomer of the general Formula I and / or their salts (monomers a) with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight of at least one radically copolymerizable monomer (monomers b)
is constructed. 2. Drying according to claim 1, characterized in that the Polymer 1 in polymerized form at 90 to 100% by weight from monomers a and from 0 to 10% by weight of monomers b is building. 3. Drying according to claim 1, characterized in that the Polymer 1 in polymerized form solely from monomers a is constructed. 4. Drying according to one of claims 1 to 3, characterized records that the polymer I 2-acrylamido-2-methylpropane contains copolymerized sulfonic acid and / or its salts.   5. Drying according to claim 3, characterized in that the Polymer I in polymerized form solely from 2-acrylic amido-2-methylpropanesulfonic acid and / or salts thereof is building. 6. Drying according to one of claims 1 to 5, characterized records that the relative weight average molecular weight of the polymer I is 1000 to 10⁶. 7. Drying according to one of claims 1 to 5, characterized records that the relative weight average molecular weight of polymer I is 2000 to 45000. 8. Drying according to one of claims 1 to 7, characterized records that the solubility of polymer I in 100 g Water at 25 ° C and 1 bar is at least 10 g. 9. Drying according to one of claims 1 to 8, characterized records that the aqueous dispersion of polymer II, based on the mass of polymer II, 1 to 40% by weight Polymer I added contains. 10. Drying according to one of claims 1 to 8, characterized records that the aqueous dispersion of polymer II, based on the mass of polymer II, 1 to 20% by weight Polymer I added contains. 11. Drying according to one of claims 1 to 8, characterized records that the aqueous dispersion of polymer II, based on the mass of polymer II, 1 to 5% by weight Polymer I added contains. 12. Drying according to one of claims 1 to 11, characterized records that the glass transition temperature of the polymer II  Is 50 ° C. 13. Drying according to one of claims 1 to 12, characterized in that the polymer II in polymerized form

• A) 80 to 100 wt .-% of at least one monomer from the group comprising styrene, α-methylstyrene, vinyltoluenes, esters of 3 to 6 carbon atoms containing α, β-mono ethylenically unsaturated carboxylic acids and 1 to 12 carbon atoms alkanols , Butadiene and vinyl and allyl esters of 1 to 12 carbon atoms and carboxylic acids
• B) 0 to 20% by weight of other monomers having at least one ethylenically unsaturated group

is constructed. 14. Drying according to one of claims 1 to 13, characterized records that drying by the method of spraying drying takes place. 15. Drying according to claim 14, 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 30 to 90 ° C. 16. Use of polymers I which, in polymerized form, contain <80 to 100% by weight of at least one monomer of the general formula I and / or their salts (monomers a) with R¹, R²₁ R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight of at least one radically copolymerizable monomer (monomer b) are built up as an aid in the drying of aqueous dispersions of polymers II different from the polymers I. 17. Polymer powder containing at least one polymer I in polymerized form
<80 to 100% by weight of at least one monomer of the general formula I and / or salts thereof (monomers a) with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and is composed of 0 to <20% by weight of at least one free-radically copolymerizable monomer (monomer b), and at least one polymer II different from polymer I. 18. Polymer powder according to claim 17, which, based on the Amount of polymer II contained, 1 wt .-% of emulga contains gates. 19. Mineral binder containing at least one Polymer powder according to claim 17 or 18. 20. Use of polymer powders according to claim 17 or 18 in Preparations for coating or gluing. 21. Synthetic resin plaster dry preparation containing at least one Polymer powder according to claim 17 or 18. 22. Aqueous polymer dispersion of a polymer II, the emulsifier content of which is 2% by weight and which, as a dispersant, contains at least one polymer I added in polymerized form
<80 to 100% by weight of at least one monomer of the general formula I and / or salts thereof (monomers a) with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight is composed of at least one radically copolymerizable monomer (monomer b) and has a relative weight-average molecular weight of 5,000 to 35,000. 23. An aqueous polymer dispersion according to claim 22, wherein the relative weight-average molecular weight of polymer I. Is 7500 to 20000. 24. An aqueous polymer dispersion according to claim 22 or 23, wherein the polymer I poly-2-acrylamido-2-methylpropanesulfonic acid is. 25. Aqueous polymer dispersion according to one of claims 22 to 24, the polymer I containing the only one Dispersant forms. 26. Aqueous polymer dispersion according to one of claims 22 to 25, the weight-average polymer particles of which knife is 50 to 200 nm. 27. Use of an aqueous polymer dispersion according to a of claims 22 to 26 as a binder or as an additive in mineral binders. 28. Use of an aqueous polymer dispersion according to a of claims 22 to 26 for the preparation of polymer powder. 29. Use of an aqueous dispersion of a polymer II which contains a polymer I which is different from this polymer II and which, in polymerized form, comprises <80 to 100% by weight of at least one monomer of the general formula I and / or salts thereof (monomers a) with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight is composed of at least one radically copolymerizable monomer (monomer b),
for the production of polymer powders. 30. A process of free radical aqueous emulsion polymerization of at least one ethylenically unsaturated group having monomers, characterized in that a polymer I is added before, during or after the end of the polymerization, the polymer I being in polymerized form
<80 to 100% by weight of at least one monomer of the general formula I and / or salts thereof (monomers a) with R¹, R², R³: independently of one another H or C₁- to C₃-alkyl,
R⁴: C₁ to C₅ alkylene and
X: O or NH,
and
0 to <20% by weight is made up of at least one radically copolymerizable monomer (monomer b) and its relative weight-average molecular weight is 5000 to 35000. 31. The method according to claim 30, characterized in that the Polymer I contains no monomers b copolymerized. 32. The method according to claim 30 or 31, characterized in that that the polymer I during the radical aqueous Emulsion polymerisation only dispersants added forms. 33. Polymer powder, obtainable by drying according to one of the Claims 1 to 15.