USE OF WATER-REDISPERSIBLE POLYMER POWDERS FOR DRY, HYDRAULIC-SETTING BUILDING MATERIAL FORMULATIONS.

Description

[0001] The invention relates to the use of vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers in the form of water-redispersible powders for the production of hydraulically setting dry building material formulations, such as tile adhesives, sealing slurries, self-leveling compounds or reinforcing compounds.

[0002] Dry construction material formulations typically contain hydraulically setting binders, such as cement, as well as fillers, polymers in the form of water-redispersible powders (polymer powders), and possibly other additives, as described, for example, in GB1771962. They are used, for example, as tile adhesives, joint fillers, leveling compounds, waterproofing slurries, plasters, or screeds. Before application, these dry construction material formulations are mixed with water, thereby transforming them into fresh mortar, i.e., their ready-to-use form.

[0003] Polymers in the form of water-redispersible powders are known to be powder compositions that are obtained by drying the corresponding aqueous polymer dispersions in the presence of drying aids. Due to this manufacturing process, the finely divided polymer resin of the dispersion is coated with drying aids, which are usually water-soluble. During drying, the drying aid acts like a coating that prevents the particles from irreversibly sticking together. When the polymer powders are redispersed in water, the drying aid dissolves, and an aqueous redispersion is formed in which, as far as possible, the original polymer particles (primary polymer particles) are present again (Schulze J. in TIZ, No. 9, 1985).

[0004] Polymer powders can be used, for example, to improve the cohesive or adhesive properties of cured building products, particularly mechanical strengths such as (flexural) tensile strength, or the adhesion of the building materials to substrates, such as mineral substrates or insulating materials like polystyrene boards. For this to occur, the polymers must form a film with each other and with the fillers and inorganic binders during application. To achieve a homogeneous film formation of the polymers in the building materials, the polymer powders must be redispersed as completely and finely as possible upon the addition of water. Otherwise, the polymer powders will simply be present in the building materials as a coarse organic filler.

[0005] However, the complete redispersion of polymer powders in water presents a challenge and causes problems, especially after prolonged storage or after storage at higher temperatures or humidity levels, i.e., after storage under humid, warm, or even humid-warm conditions, such as tropical conditions. But even after storage in temperate climates, redispersion problems can occur, for example, if humid and / or humid-warm conditions prevail seasonally or if the polymer powders are stored for extended periods. During storage, the polymer powders should clump together as little as possible, their flowability should be preserved, and primary polymer particles should be released from the polymer powders upon the addition of water.All these problems are particularly pronounced in the case of soft polymers, such as vinyl acetate-ethylene copolymers or corresponding styrene-(meth)acrylic acid ester copolymers. Such copolymers generally have low glass transition temperatures and film particularly efficiently at the application temperature. However, due to the low glass transition temperatures, which are usually below typical storage temperatures, these copolymers also tend to film or block more readily even in the polymer powder. In these cases, providing polymer powders that are completely redispersible in water presents a particular challenge.

[0006] Various approaches have been undertaken over the past few decades to improve the redispersibility of polymer powders. For example, EP 0770640 teaches the addition of polyelectrolytes as drying aids. EP1065226 deals with emulsifier-stabilized, protective colloid-free redispersible powders based on vinyl aromatic copolymers. DE2312408 addresses emulsifier-stabilized polymer powders of base polymers containing carboxylic acid units, which are modified before drying with six-membered, carbocyclic compounds with two vicinal carboxyl substituents and adjusted to an alkaline pH. However, such additives affect the setting behavior of hydraulically setting binders and are therefore frowned upon for modifying generally applicable polymer powders for construction material formulations. The polymers of DE 2312408 are redispersible in water even after film formation.To improve the redispersibility of styrene-butadiene or acrylonitrile-butadiene copolymers, EP0989154 teaches the polymerization of carboxylic acid monomers into the base polymers and the addition of alkali salts of N-alkylsulfosuccinamate-maleic acid copolymers as drying aids. The polymer powders were modified with the antiblocking agents chalk, talc, diatomaceous earth, kaolin, silicates, silicic acid, or calcium carbonate, which are known to be water-insoluble. EP0078449 recommends the use of vinylpyrrolidone-vinyl acetate polymers or (earth)alkali salts of naphthalenesulfonic acid-formaldehyde condensates as drying aids for polymers with low softening points. EP3230394 addresses aqueous polymer dispersions and aqueous adhesive formulations that should not undergo any significant change in viscosity during storage.For EP3230394, it is essential to add polyfunctional alcohols, as well as organic or inorganic salts of (earth)alkali metals, particularly lithium chloride, to the polymer dispersions. These adhesives are used especially as wood glue or paper adhesives, or for bonding other packaging materials. However, polyfunctional alcohols are known to delay the setting of hydraulically setting binders. EP1615861 aims to produce setting-accelerated mortars and teaches the addition of polymer powder compositions modified with (earth)alkali salts of inorganic or organic acids.EP 1897926 deals with aqueous or water-redispersible adhesives containing water-insoluble and / or water-soluble polymers and polyalkylene polyamines, and optionally water-soluble salts, for non-cementary applications, such as bonding paper or cardboard, manufacturing nonwovens, or bonding cigarette paper, particularly for machine nozzle application. GB929704 describes polymer powders based on acrylates or polyvinyl acetates with the aim of increasing throughput in spray dryers by raising the spray temperature and improving the storage stability of polymer powders. Polyvinyl acetates are known to be hard polymers and have a glass transition temperature above 30°C.For this purpose, GB1771962 recommends adding either inert solids, hydrophilic colloids, or soluble salts, or combinations of inert solids and hydrophilic colloids or inert solids and soluble salts, to the spray feeds. WO2017 / 178422 teaches processes in which water-soluble salts of multivalent metals, such as alkaline earth metals, aluminum, zirconium, iron, or zinc, and additionally water-soluble salts of aluminates, silicates, borates, sulfates, or carbonates are introduced into aqueous polymer dispersions and subsequently dried, the various inorganic salts forming a dense shell on the polymer particles that dissolves only in an alkaline medium or as a result of mechanical stress.

[0007] The polymerization of ethylene-unsaturated monomers is typically initiated using initiators, such as alkali persulfates. These initiators decompose into radicals that add to the ethylene-unsaturated monomers, thereby initiating polymer chain growth. Consequently, the initiators are bound to the polymers formed during polymerization via covalent bonds and are therefore not present in the polymer dispersion as low-molecular-weight compounds like alkali sulfates.

[0008] Against this background, the task was to provide vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers for dry building material formulations in the form of water-redispersible powders with improved storage stability, preferably even after storage of the polymer powders under humid, warm, or warm-humid conditions. The polymer powders should preferably be free of additives that strongly interfere with the setting of fresh mortars.

[0009] Surprisingly, the problem was solved by producing the polymer powders by drying aqueous dispersions of ethylene-vinyl acetate and / or styrene-(meth)-acrylic acid ester copolymers containing water-soluble, inorganic salts selected from the group consisting of alkali sulfates.

[0010] The invention relates to the use of vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers in the form of water-redispersible powders for the production of hydraulically setting dry building material formulations, characterized in that the storage stability of the protective colloid-stabilized vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers in the form of water-redispersible powders is improved by drying aqueous dispersions containing protective colloid-stabilized vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers, one or more water-soluble inorganic salts, and one or more drying aids, wherein the water-soluble inorganic salts are selected from the group consisting of alkali sulfates and the drying aids are selected from the group comprising polyvinyl alcohols, polyvinyl acetals, and non-ionic polyvinylpyrrolidones.Non-ionic poly(meth)acrylamides, polysaccharides and proteins.

[0011] The protective colloid-stabilized vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers used according to the invention, in the form of water-redispersible powders, are hereinafter also referred to as polymer powders. The vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers are hereinafter also referred to as copolymers. The water-soluble, inorganic salts exhibit a water solubility of preferably ≥ 1 g per liter of water, particularly preferably ≥ 3 g per liter of water, and most preferably ≥ 10 g per liter of water, each under standard conditions (23 / 50) according to DIN 50014. These values ​​preferably refer to neutral pH values.

[0012] Examples of alkali sulfates are lithium sulfate (Li₂SO₄), sodium sulfate (Na₂SO₄), and potassium sulfate (K₂SO₄). Sodium sulfate and potassium sulfate are preferred. Sodium sulfate is most preferred.

[0013] Preferably, the aqueous dispersions and / or the polymer powders contain 0.1 to 20 wt.%, more preferably 0.3 to 10 wt.%, even more preferably 0.5 to 5 wt.%, particularly preferably 0.8 to 4 wt.% and most preferably 1 to 3 wt.% of water-soluble, inorganic salts, based on the total weight of the copolymers.

[0014] The drying aids are generally polyvinyl alcohols, polyvinyl acetals, non-ionic polyvinylpyrrolidones, non-ionic poly(meth)acrylamides, polysaccharides, and proteins. These drying aids are accessible by methods known to those skilled in the art. Non-ionic drying aids are preferred. The non-ionic drying aids, the non-ionic polyvinylpyrrolidones, and the non-ionic poly(meth)acrylamides generally contain no ionic monomer units and generally do not carry any ionic groups, in particular no ammonium, carboxylic acid, or sulfonic acid groups. The non-ionic polyvinylpyrrolidones preferably consist of vinylpyrrolidone units. The non-ionic poly(meth)acrylamides preferably consist of (meth)acrylamide units.

[0015] Preferred drying aids include polyvinyl alcohols; polyvinyl acetals; polysaccharides, especially in water-soluble form such as starches (amylose and amylopectin), celluloses or their derivatives, such as carboxymethyl, methyl, hydroxyethyl, and hydroxypropyl derivatives; and proteins such as casein or caseinate, soy protein, and gelatin. Polyvinyl alcohols are particularly preferred. Most preferred is the use of no other drying aid in addition to polyvinyl alcohols.

[0016] Polyvinyl alcohols can be partially or fully saponified, for example with a degree of hydrolysis of 80 to 100 mol%, and in particular partially saponified with a degree of hydrolysis of 80 to 95 mol%, preferably 85 to 92 mol%. The polyvinyl alcohols have a Höppler viscosity of preferably 1 to 30 mPa·s in a 4% aqueous solution (Höppler method at 20°C, DIN 53015). Partially saponified, hydrophobically modified polyvinyl alcohols are also preferred, especially with a degree of hydrolysis of 80 to 95 mol% and a Höppler viscosity of preferably 1 to 30 mPa·s in a 4% aqueous solution.Examples include partially saponified copolymers of vinyl acetate with hydrophobic comonomers such as isopropenyl acetate, vinyl pivalate, vinyl ethyl hexanoate, vinyl esters of saturated alpha-branched monocarboxylic acids with 5 or 9 to 11 carbon atoms, dialkyl maleates and dialkyl fumarates such as diisopropyl maleate and diisopropyl fumarate, vinyl chloride, vinyl alkyl ethers such as vinyl butyl ether, and olefins such as ethene and decene. The proportion of hydrophobic units is preferably 0.1 to 10 wt.%, based on the total weight of the partially saponified polyvinyl alcohol. Mixtures of the aforementioned polyvinyl alcohols can also be used.

[0017] Polyvinyl alcohols with a degree of hydrolysis of 85 to 94 mol% and a Höppler viscosity of 3 to 15 mPa·s in 4% aqueous solution (Höppler method at 20°C, DIN 53015) are most preferred.

[0018] Preferably, the aqueous dispersions and / or the polymer powders contain 1 to 30 wt.%, particularly preferably 2 to 20 wt.% and most preferably 3 to 15 wt.% of drying aids, based on the total weight of the copolymers.

[0019] Vinyl acetate-ethylene copolymers can be based on one or more additional monomers besides vinyl acetate and ethylene, for example selected from the group comprising vinyl esters of carboxylic acids with 3 to 15 C atoms, methacrylic acid esters or acrylic acid esters of carboxylic acids with unbranched or branched alcohols with 1 to 15 C atoms, propylene, dienes, vinyl aromatics and vinyl halides.

[0020] Preferred vinyl esters of carboxylic acids with 3 to 15 C atoms are vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methyl vinyl acetate, vinyl pivalate and vinyl esters of alpha-branched monocarboxylic acids with 5 to 13 C atoms, for example VeoVa9R or VeoVa10R (trade names of the company Shell).

[0021] Preferred methacrylic acid esters or acrylic acid esters are esters of unbranched or branched alcohols with 1 to 15 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, and norbornyl acrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate, and 2-ethylhexyl acrylate are particularly preferred.

[0022] The preferred diene is 1,3-butadiene. Preferred vinyl aromatics are styrene and vinyltoluene. A preferred vinyl halide is vinyl chloride.

[0023] The (meth)acrylic acid ester monomer units of the styrene-(meth)acrylic acid ester copolymers are, for example, methacrylic acid esters or acrylic acid esters of carboxylic acids with unbranched or branched alcohols having 1 to 15 carbon atoms. The methacrylic acid esters or acrylic acid esters mentioned above are preferred and particularly preferred.

[0024] The styrene-(meth)acrylic acid ester copolymers can be based on styrene and (meth)acrylic acid esters, as well as on one or more other monomers, for example, selected from the group comprising vinyl esters of carboxylic acids with 2 to 15 carbon atoms, olefins and dienes, vinyltoluene, and vinyl halides. The vinyl esters of carboxylic acids with 3 to 15 carbon atoms, dienes, vinyl halides, vinyl acetate, ethene, and propylene mentioned above are preferred.

[0025] Optionally, one or more auxiliary monomers may be polymerized into the vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers. Preferably, up to 20 wt.%, and particularly preferably 0.1 to 10 wt.%, based on the total weight of the copolymers, are incorporated into the copolymers as auxiliary monomers. Examples of auxiliary monomers are ethylene-unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid, and maleic acid; ethylene-unsaturated carboxylic acid amides and nitriles, preferably acrylamide and acrylonitrile; mono- and diesters of fumaric acid and maleic acid, such as the diethyl and diisopropyl esters, as well as maleic anhydride; ethylene-unsaturated sulfonic acids or their salts, preferably vinylsulfonic acid; and 2-acrylamido-2-methylpropanesulfonic acid.Other examples include pre-crosslinking comonomers such as polyethylene unsaturated comonomers, for example divinyl adipate, diallyl maleate, allyl methacrylate, or triallyl cyanurate, or post-crosslinking comonomers, for example acrylamidoglycolic acid (AGA), methyl methylacrylamidoglycolic acid ester (MAGME), N-methylolacrylamide (NMA), N-methylolmethacrylamide (NMMA), N-methylolallylcarbamate, alkyl ethers such as the isobutoxy ether or esters of N-methylolacrylamide, N-methylolmethacrylamide, and N-methylolallylcarbamate. Epoxy-functional comonomers such as glycidyl methacrylate and glycidyl acrylate are also suitable. Other examples are silicon-functional comonomers, such as acryloxypropyltri(alkoxy) and methacryloxypropyltri(alkoxy) silanes, vinyltrialkoxysilanes and vinylmethyldialkoxysilanes, where the alkoxy groups may include, for example, methoxy, ethoxy and ethoxypropylene glycol ether residues.Monomers with hydroxy or CO groups should also be mentioned, for example, methacrylic acid and acrylic acid hydroxyalkyl esters such as hydroxyethyl, hydroxypropyl, or hydroxybutyl acrylate or methacrylate, as well as compounds such as diacetone acrylamide and acetylacetoxyethyl acrylate or methacrylate. Further examples include vinyl ethers, such as methyl, ethyl, or isobutyl vinyl ethers.

[0026] In an alternative, preferred embodiment, no ethylene-unsaturated mono- and dicarboxylic acids, no mono- and diesters of fumaric acid and maleic acid, no maleic anhydride, and / or no ethylene-unsaturated sulfonic acids are polymerized into the copolymers. Particularly preferred is the polymerization of no auxiliary monomers into the copolymers.

[0027] Vinyl acetate-ethylene copolymers are preferred.

[0028] Examples of suitable copolymers are copolymers of vinyl acetate with ethylene, copolymers of vinyl acetate with ethylene and one or more other vinyl esters different from vinyl acetate, copolymers of vinyl acetate with ethylene and acrylic esters, copolymers of vinyl acetate with ethylene and vinyl chloride, and styrene-(meth)acrylic ester copolymers.

[0029] Preferably, copolymers of vinyl acetate with 1 to 40 wt% ethylene are used; copolymers of vinyl acetate with 1 to 40 wt% ethylene and 1 to 50 wt% of one or more further comonomers from the group of vinyl esters with 3 to 12 carbon atoms in the carboxylic acid residue such as vinyl propionate, vinyl laurate, vinyl esters of alpha-branched carboxylic acids with 5 to 13 carbon atoms such as VeoVa9R, VeoVa10R, VeoVa11R; copolymers of vinyl acetate, 1 to 40 wt% ethylene and preferably 1 to 60 wt% acrylic acid esters of unbranched or branched alcohols with 1 to 15 carbon atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate; and copolymers with 30 to 75 wt% vinyl acetate, 1 to 40 wt% ethylene, 1 to 30 wt% vinyl laurate or vinyl ester of an alpha-branched carboxylic acid with 5 to 13 carbon atoms, as well as 1 to 30 wt%-% Acrylic acid esters of unbranched or branched alcohols with 1 to 15 carbon atoms, in particular n-butyl acrylate or 2-ethylhexyl acrylate; copolymers with vinyl acetate, 1 to 40 wt.% ethylene and 1 to 60 wt.% vinyl chloride; wherein the copolymers may each also contain the aforementioned auxiliary monomers, preferably in the aforementioned amounts, and the values ​​in wt.% add up to 100 wt.%.

[0030] Styrene (meth)acrylic acid ester copolymers of styrene with one or more monomers from the group comprising methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate are also preferred; wherein the copolymers may each contain the aforementioned auxiliary monomers preferably in the aforementioned amounts, and the amounts in wt.% add up to 100 wt.%.

[0031] The monomer selection, or the selection of the weight fractions of the comonomers, is carried out such that a glass transition temperature Tg of -50°C to +25°C, preferably -30°C to +20°C, is generally achieved. The glass transition temperature Tg of the polymers can be determined in a known manner using differential scanning calorimetry (DSC). Tg can also be approximated using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1, 3, page 123 (1956): 1 / Tg = x1 / Tg1 + x2 / Tg2 + ... + xn / Tgn, where xn represents the mass fraction (wt% / 100) of monomer n, and Tgn is the glass transition temperature in Kelvin of the homopolymer of monomer n. Tg values ​​for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

[0032] The polymer powders preferably contain 50 to 90 wt.% of vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers, based on the total weight of the polymer powders.

[0033] Examples of protective colloids include polyvinyl alcohols; polyvinyl acetals; polyvinylpyrrolidones; water-soluble polysaccharides such as starches (amylose and amylopectin), celluloses and their carboxymethyl, methyl, hydroxyethyl, and hydroxypropyl derivatives, dextrins, and cyclodextrins; proteins such as casein or caseinate, soy protein, and gelatin; lignosulfonates; synthetic polymers such as poly(meth)acrylic acid, copolymers of (meth)acrylates with carboxyl-functional comonomer units, poly(meth)acrylamide, polyvinylsulfonic acids, and their water-soluble copolymers; melamine formaldehyde sulfonates, naphthalene formaldehyde sulfonates, and styrene maleic and vinylethermaleic acid copolymers.

[0034] The same embodiments are preferred, particularly preferred, and most preferred as those listed for the drying aids. Polyvinyl alcohols are most preferably used exclusively as protective colloids. It is also most preferred that the protective colloids and the drying aids are identical.

[0035] The polymer powders preferably contain 1 to 20 wt.%, particularly preferably 2 to 15 wt.% of protective colloids, based on the total weight of the polymer powders.

[0036] The copolymers are preferably produced by emulsion polymerization. Emulsion polymerization is typically carried out in an aqueous medium. The polymerization temperature is generally 40°C to 100°C, preferably 60°C to 95°C. When copolymerizing gaseous comonomers such as ethylene, 1,3-butadiene, or vinyl chloride, the process can also be carried out under pressure, generally between 5 bar and 100 bar.

[0037] Polymerization can be initiated using redox-initiator combinations commonly used in emulsion polymerization. Monomer conversion can be controlled by adjusting the initiator dosage as usual. The initiators are generally added in such a way as to ensure continuous polymerization. Examples of suitable oxidation initiators include the sodium, potassium, and ammonium salts of peroxodisulfuric acid, hydrogen peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, potassium peroxodiphosphate, tert-butyl peroxopivalate, cumene hydroperoxide, and azobisisobutyronitrile. The sodium, potassium, and ammonium salts of peroxodisulfuric acid and hydrogen peroxide are preferred. These initiators are generally used in amounts of 0.01 to 2.0 wt%, based on the total weight of the monomers.

[0038] Suitable reducing agents include, for example, the sulfites and bisulfites of alkali metals and ammonium, such as sodium sulfite, the derivatives of sulfoxylic acid such as zinc or alkali formaldehyde sulfoxylates, for example sodium hydroxymethane sulfinate (Brüggolite), and (iso)ascorbic acid. Sodium hydroxymethane sulfinate and (iso)ascorbic acid are preferred. The amount of reducing agent is preferably 0.015 to 3% by weight, based on the total weight of the monomers.

[0039] The aforementioned oxidizing agents, in particular the salts of peroxodisulfuric acid and hydrogen peroxide, can also be used alone as thermal initiators.

[0040] To control the molecular weight, regulating substances can be used during emulsion polymerization processes. If regulators are used, they are typically added in amounts between 0.001 and 5.0 wt%, based on the monomers to be polymerized, and dosed separately or premixed with reaction components. Examples of such substances are n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptopropionic acids or their alkali salts, methyl mercaptopropionic acid ester, isopropanol, phosphonic acid or its derivatives, phosphinic acid or its derivatives, and acetaldehyde. Preferably, 2-mercaptopropionic acid or tert-dodecyl mercaptan is used.

[0041] Protective colloids, optionally in combination with emulsifiers, can be used for stabilization. Polymerization can also be carried out in the presence of emulsifiers using the emulsion polymerization process. Preferred amounts of emulsifiers are 1 to 7 wt%, based on the total weight of the monomers. Examples of emulsifiers include anionic, cationic, or non-ionic emulsifiers, such as anionic surfactants, in particular alkyl sulfates with a chain length of 8 to 18 carbon atoms, alkyl or alkylaryl ether sulfates with 8 to 18 carbon atoms in the hydrophobic residue and up to 40 ethylene or propylene oxide units, alkyl or alkylaryl sulfonates with 8 to 18 carbon atoms, esters and semi-esters of sulfosuccinic acid with monohydric alcohols or alkylphenols, or non-ionic surfactants such as alkyl polyglycol ethers or alkylaryl polyglycol ethers with 8 to 40 ethylene oxide units.

[0042] Polymerization is particularly preferred in the absence of emulsifiers. The aqueous dispersions and / or the polymer powders preferably contain no emulsifiers.

[0043] After completion of the polymerization, residual monomers can be removed by post-polymerization using known methods, for example, by post-polymerization initiated with a redox catalyst. Volatile residual monomers can also be removed by distillation, preferably under reduced pressure, and optionally by passing or over inert carrier gases such as air, nitrogen, or steam.

[0044] The copolymers obtained in this way are preferably in the form of aqueous dispersions stabilized with protective colloids.

[0045] The aqueous dispersions have a solids content of preferably 30 to 75 wt.%, particularly preferably 45 to 60 wt.%.

[0046] The addition of water-soluble, inorganic salts can take place before, during, or preferably after the production of the copolymers by polymerization. Alternatively, chemical substances that convert into water-soluble, inorganic salts through chemical reaction can be used.

[0047] For example, the water-soluble, inorganic salts can be mixed with the ethylene unsaturated monomers before the initiation of polymerization. Alternatively, the water-soluble, inorganic salts can be added during the polymerization of the ethylene unsaturated monomers. Likewise, a portion of the water-soluble, inorganic salts can be added to the ethylene unsaturated monomers before the initiation of polymerization, and the remainder can be added during the polymerization of the ethylene unsaturated monomers.

[0048] Preferably, the water-soluble, inorganic salts are added to the corresponding polymer dispersion after polymerization is complete. Particularly preferably, the water-soluble, inorganic salts are added before drying the aqueous polymer dispersion. For this purpose, one or more water-soluble, inorganic salts are preferably added to the aqueous polymer dispersions, and the resulting mixtures are then dried. Preferably, no water-soluble, inorganic salts are added during the drying of the aqueous polymer dispersions.

[0049] A drying aid is generally added to the aqueous dispersions thus obtained. Typically, the drying aid is used in a total amount of 0.5 to 30 wt.%, particularly 5 to 20 wt.%, based on the solids content of the aqueous dispersion. The total amount of drying aid and protective colloid added before the drying process is preferably 1 to 30 wt.%, based on the solids content of the aqueous dispersion. The addition of the drying aids to the aqueous dispersions is not subject to any particular procedure and can be carried out in the conventional manner.

[0050] The drying of the aqueous dispersions can be carried out, for example, by fluidized bed drying, freeze-drying, or spray drying. Preferably, the dispersions are spray-dried. Spray drying is performed in conventional spray drying systems, with atomization being achieved using single-, dual-, or multi-component nozzles or a rotating disc. The outlet temperature is generally selected in the range of 45°C to 120°C, preferably 60°C to 90°C, depending on the system, the temperature of the resin, and the desired degree of dryness. The viscosity of the atomizing solution is adjusted via the solids content to achieve a value of < 500 mPa·s (Brookfield viscosity at 20 revolutions and 23°C), preferably < 250 mPa·s. The solids content of the dispersion to be atomized is preferably 30 to 75 wt.% and particularly preferably 50 to 60 wt.%.

[0051] In many cases, an antifoam concentration of up to 1.5% by weight, based on the polymer, has proven advantageous. The antifoam is preferably added during atomization.

[0052] To increase shelf life by improving blocking stability, particularly in polymer powders with low glass transition temperatures, the resulting polymer powder can be equipped with one or more antiblocking agents. The antiblocking agents are preferably not added to the aqueous polymer dispersions, i.e., preferably not before drying, but rather during or after drying, especially during drying in the spray drying system. Preferred polymer powders contain antiblocking agents, in particular 1 to 30 wt.%, based on the total weight of the polymeric components. Examples of antiblocking agents are calcium or magnesium carbonate, talc, gypsum, silica, kaolins such as metakaolin, and silicates, preferably with particle sizes in the range of 10 nm to 10 µm. Antiblocking agents are typically water-insoluble.

[0053] The polymer powders preferably do not contain a polyelectrolyte. Polyelectrolytes generally refer to polymers with ionically dissociable groups in aqueous media, which can be components or substituents of the polymer chain. The number of ionically dissociable groups is generally large enough that the polymers are completely soluble in water in their dissociated form. Polyelectrolytes can be, for example, polyacids or polybases.

[0054] The polymer powders preferably do not contain water-soluble halide salts, in particular no water-soluble chloride salts. Water-soluble halide salts have a water solubility of preferably ≥ 1 g per liter of water under standard conditions (23 / 50) according to DIN 50014.

[0055] The polymer powders preferably do not contain polyfunctional alcohols, in particular no alcohols bearing at least one alcohol group and optionally one or more further functional groups selected from the group comprising amine, carbamic, mercaptan, sulfonic, sulfuric, halide, carboxyl, alkoxy, phosphinic, phosphonic, and phosphoric acid groups, wherein the sum of the number of alcohol groups and the number of further functional groups of the alcohols is ≥ 2. The polymer powders preferably do not contain alcohols with ≤ 20, particularly preferably ≤ 15 carbon atoms or > 2 carbon atoms.

[0056] The polymer powders preferably do not contain any polyalkylene polyamines, in particular no polyethyleneimine, especially not with a molecular weight of 300 to 10,000,000. Polyalkylene polyamines are generally based on ethylene-unsaturated monomers bearing amine, ammonium or amide groups and optionally further ethylene-unsaturated monomers.

[0057] The hydraulically setting dry building material formulations preferably contain 0.1 to 30 wt.%, particularly preferably 0.3 to 12.0 wt.% and most preferably 0.5 to 5.0 wt.% polymer powder, in each case based on the total weight of the hydraulically setting dry building material formulations.

[0058] Suitable hydraulically setting binders include, for example, cements, in particular Portland cement, aluminate cement, trass cement, blast furnace cement, magnesia cement, phosphate cement, or blast furnace cement, as well as blended cements, filler cements, fly ash, microsilica, hydraulic lime, and gypsum. Portland cement, aluminate cement, and blast furnace cement, as well as blended cements, filler cements, hydraulic lime, and gypsum, are preferred. Mixtures of two or more hydraulically setting binders, especially those containing cement and hydraulic lime, are also preferred.

[0059] In general, hydraulically setting dry building material formulations contain 5 to 50 wt.%, preferably 10 to 30 wt.%, hydraulically setting binders, based on the total weight of the hydraulically setting dry building material formulations.

[0060] Examples of suitable fillers include quartz sand, quartz flour, calcium carbonate, dolomite, aluminum silicates, clay, chalk, hydrated lime, talc, or mica, as well as lightweight fillers such as pumice, foam glass, aerated concrete, perlite, vermiculite, and carbon nanotubes (CNTs). Any mixture of the aforementioned fillers can also be used. Quartz sand, quartz flour, calcium carbonate, chalk, or hydrated lime are preferred. Fillers are generally, or implicitly, water-insoluble.

[0061] In general, hydraulically setting dry building material formulations contain 30 to 90 wt.%, preferably 40 to 85 wt.% fillers, in each case based on the total weight of the hydraulically setting dry building material formulations.

[0062] Other common additives for hydraulically setting dry building material formulations include thickeners, such as polysaccharides like cellulose ethers and modified cellulose ethers, starch ethers, guar gum, xanthan gum, layered silicates, polycarboxylic acids like polyacrylic acid and their partial esters, as well as polyvinyl alcohols, which may be acetalized or hydrophobically modified, casein, and associative thickeners. Common additives also include retarders, such as hydroxycarboxylic acids or dicarboxylic acids or their salts, saccharides, oxalic acid, succinic acid, tartaric acid, gluconic acid, citric acid, sucrose, glucose, fructose, sorbitol, and pentaerythritol. Setting accelerators, such as alkali or alkaline earth salts of inorganic or organic acids, are also commonly used. Furthermore, the following should also be mentioned: water repellents, preservatives, film-forming agents, dispersants, foam stabilizers, defoamers and flame retardants (e.g.Aluminum hydroxide).

[0063] The additives are used in the usual quantities, which depend on the type of additive. Generally, the quantities range from 0.01 to 10% by weight, based on the total weight of the hydraulically setting dry construction material formulations.

[0064] Hydraulically setting dry construction material formulations are generally produced by mixing and homogenizing one or more hydraulically setting binders, one or more fillers, one or more polymer powders, and optionally one or more additives into a dry mixture. The production of these hydraulically setting dry construction material formulations can be carried out in a conventional manner using standard equipment. The amount of water required for processing the hydraulically setting dry construction material formulations is typically added immediately before application.

[0065] Hydraulically setting dry building material formulations are suitable, for example, for the production of reinforcing compounds for external thermal insulation composite systems (ETICS), or for the production of adhesives or coatings. Examples of adhesives include adhesives for thermal insulation boards and soundproofing boards, tile adhesives, and adhesives for bonding wood and wood-based materials. Examples of coatings include mortars, self-leveling compounds, screeds, and plasters.

[0066] The polymer powders of vinyl acetate-ethylene and / or styrene-(meth)acrylic acid ester copolymers used according to the invention are surprisingly more readily redispersible in water than conventional polymer powders. The improved redispersibility of the polymer powders manifests itself, for example, in the reduced tendency of aqueous redispersions of the polymer powders to settle, as shown in the examples below. This improved redispersibility becomes apparent immediately after drying, particularly after prolonged storage, when stored at higher temperatures or higher humidity, and thus generally also when stored under humid, warm, or even warm-humid, such as tropical, conditions. This effect is primarily due to the water-soluble salts used. The drying aids used also contribute to this effect.

[0067] Advantageously, the polymer powders used according to the invention can be redispersed more easily and therefore also more quickly.

[0068] The polymer powders used according to the invention, when applied in hydraulically setting dry building material formulations, ultimately yield cured building products with advantageous mechanical properties, such as tensile bond strength, flexural strength, or flexibility, and also exhibit high adhesion to substrates. The following examples serve to further illustrate the invention. Example 1:

[0069] Production of the polymer powders: An aqueous dispersion of a vinyl acetate-ethylene copolymer (glass transition temperature Tg: 17°C) stabilized with 10 wt% polyvinyl alcohol (degree of hydrolysis: 88 mol%, Höppler viscosity: 4 mPas in 4% aqueous solution) was treated with 2.0 wt%, based on the polymer content of the dispersion (solid / solid), of a partially saponified polyvinyl alcohol (degree of hydrolysis: 88 mol%; Höppler viscosity: 4 mPas in 4% aqueous solution) and 6.0 wt%, based on the polymer content of the dispersion (solid / solid), of a partially saponified polyvinyl alcohol (degree of hydrolysis: 88 mol%; Höppler viscosity: 13 mPas in 4% aqueous solution), as well as with sodium sulfate (Na₂SO₄) according to the respective values ​​in Table 1, and spray-dried in a conventional manner at a The polymer powder was dried at an inlet temperature of 130°C and an outlet temperature of 80°C, resulting in a redispersible polymer powder. 4 wt% kaolin and 16 wt% ... were added to the polymer powder.-% calcium carbonate added as an anti-caking agent.

[0070] Determination of the settling behavior (RA) of the polymer powder: The settling behavior of the aqueous redispersion of the polymer powder serves as a measure of its redispersibility and thus its storage stability. The polymer powder obtained in Example 1 was converted into an aqueous redispersion with a solids content of 50% by adding water under strong shear forces. The settling behavior was determined by diluting the aqueous redispersion with water to a solids content of 0.5%, filling 100 ml of this dispersion into a graduated tube, and measuring the solids level. The value is given in cm of settling after 24 hours. The lower the tube settling value, the lower the coarse fraction of the redispersion and the higher the fine fraction, and therefore the better the redispersibility and storage stability of the polymer powder. The obtained values ​​for the settling behavior (RA) are listed in Table 1. Table 1: Na2SO4 content of the polymer powders and test results of the settling behavior (RA): Na2SO4 content of the polymer powder [wt%] a)< Seating behavior [cm] Comparison polymer powder 1 0 1,4 Polymer powder 2 1 0, 9 Polymer powder 3 2 0, 6 a) wt% Na₂SO₄, based on the polymer content of the dispersion (solid / solid)

[0071] For comparison, the settling behavior (RA) of the (reference) polymer powders 1 to 3 was determined as described above, with the difference that the respective polymer powder was redispersed not in water, but in water containing Na₂SO₄. The Na₂SO₄ content of the Na₂SO₄-containing water was adjusted for each polymer powder so that a total Na₂SO₄ concentration of 0.015 wt% was obtained for each redispersion. The resulting values ​​for the settling behavior (RA) are listed in Table 2. Table 2: Test results of the sitting behavior (RA): Seating behavior [cm] Comparison polymer powder 1 1,7 Polymer powder 2 1,1 Polymer powder 3 0,7

[0072] The test results in Tables 1 and 2 show that the addition of sodium sulfate to the redispersion worsens the settling behavior.

[0073] Surprisingly, the introduction of sodium sulfate into the polymer powders improved the settling behavior and thus the redispersibility and storage stability of the polymer powders, as shown in Table 1. Comparative example 2:

[0074] Comparative example 2 was carried out identically to example 1, with the only difference being that the amount of sodium carbonate (Na 2 CO 3 ) specified in Table 3 was added to the aqueous dispersion instead of sodium sulfate.

[0075] The test results for the sitting behavior (RA) are also shown in Table 3. Table 3: Na2CO3 content of the polymer powders and test results of the settling behavior (RA): Na₂CO₃ content of the polymer powder [wt%] a)< Seating behavior [cm] Comparison polymer powder 4 0 1,4 Comparative polymer powder 5 1 1,1 Comparison polymer powder 6 2 1,3 a) wt% Na₂CO₃, based on the polymer content of the dispersion (solid / solid) Example 3:

[0076] Example 3 was carried out identically to Example 1, with the only difference being that the vinyl acetate-ethylene copolymer had a glass transition temperature Tg of -15 °C.

[0077] The test results for the sitting behavior (RA) are also shown in Table 4. Table 4: Na2SO4 content of the polymer powders and test results of the settling behavior (RA): Na2SO4 content of the polymer powder [wt%] a)< Seating behavior [cm] Comparison polymer powder 7 0 2, 0 Polymer powder 8 1 1,1 Polymer powder 9 2 1, 0 a) wt% Na₂SO₄, based on the polymer content of the dispersion (solid / solid)

[0078] The polymer powders from Example 3 were also stored uncovered for two weeks at 35°C and 75% relative humidity. Subsequently, the settling behavior (RA) was determined as described for Example 1. The test results are given in Table 5. Table 5: Na2SO4 content of the polymer powders and test results of the settling behavior (RA): Na2SO4 content of the polymer powder [wt%] a)< Seating behavior [cm] Comparison polymer powder 7 0 3,8 Polymer powder 8 1 2,4 Polymer powder 9 2 1,8 a) wt% Na₂SO₄, based on the polymer content of the dispersion (solid / solid) Example 4:

[0079] Example 4 was carried out identically to Example 1, with the only difference being that a styrene-n-butyl acrylate copolymer with a glass transition temperature Tg of 20 °C was used instead of the vinyl acetate-ethylene copolymer.

[0080] The test results for the sitting behavior (RA) are also shown in Table 5. Table 5: Na2SO4 content of the polymer powders and test results of the settling behavior (RA): Na2SO4 content of the polymer powder [wt%] a)< Seating behavior [cm] Comparison polymer powder 10 0 2,7 Polymer powder 11 1 1, 8 Polymer powder 12 2 1,4 a) wt% Na₂SO₄, based on the polymer content of the dispersion (solid / solid)

[0081] Examples 1, 3 and 4 show that the use of the water-soluble salt sodium sulfate results in a significant reduction of tube settling and thus an improvement in the redispersibility and storage stability of the polymer powder.

[0082] This applies both directly after spray drying and after storage in warm and humid conditions, as shown in example 3.

[0083] In contrast, the redispersibility was not significantly improved by the addition of sodium carbonate (Comparison Example 2). The differences in settling behavior observed in Comparison Example 2 are within the range of measurement error (+ / - 0.2). Increasing the sodium carbonate content from 1 wt% in Comparison Polymer Powder 5 to 2 wt% in Comparison Polymer Powder 6 even led to a deterioration in settling behavior.

[0084] Production of dry mortar formulations: The following dry mortar formulations were produced using the polymer powders obtained. The dry mortar formulations were produced and applied using conventional methods.

[0085] Tile adhesive with low polymer powder content: Quartz sand 577 parts, Portland cement 400 parts, cellulose 3 parts, polymer powder 20 parts.

[0086] Tile adhesive with medium polymer powder content: Quartz sand 444 parts, calcium carbonate 80 parts, Portland cement 350 parts, aluminate cement 70 parts, retarder 2 parts, cellulose 4 parts, polymer powder 60 parts. Flexible sealing slurry with high polymer powder content: Quartz sand 300 parts, calcium carbonate 134 parts, Portland cement 130 parts, aluminate cement 70 parts, lightweight filler 50 parts, highly dispersed silica 5 parts, fibers 5 parts, retarder 1 part, associative thickener 5 parts, polymer powder 300 parts.

[0087] The improved redispersibility of the polymer powders used makes corresponding building products with higher flexural strengths and increased flexibility accessible.

Claims

1. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations, characterized in that the storage stability of the protective-colloidstabilized vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders is improved by drying aqueous dispersions comprising protective-colloid-stabilized vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers, one or more water-soluble inorganic salts, and one or more desiccants, the water-soluble inorganic salts being selected from the group consisting of alkali metal sulfates, and the desiccants being selected from the group comprising polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides, polysaccharides, and proteins.

2. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claim 1, characterized in that the water-soluble inorganic salts are selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate.

3. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claim 1, characterized in that sodium sulfate is used in the form of the water-soluble inorganic salt.

4. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 3, characterized in that the aqueous dispersions or the water-redispersible powders contain 0.1% to 20% by weight of water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

5. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 4, characterized in that the aqueous dispersions or the water-redispersible powders contain 0.1% to 4% by weight of water-soluble inorganic salts based on the total weight of the vinyl acetate-ethylene and styrene-(meth)acrylic ester copolymers.

6. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 5, characterized in that the desiccants are selected from the group consisting of polyvinyl alcohols, polyvinyl acetals, nonionic polyvinylpyrrolidones, nonionic poly(meth)acrylamides and proteins.

7. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 6, characterized in that the protective colloids and the desiccants are polyvinyl alcohols.

8. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 7, characterized in that one or more vinyl acetate-ethylene copolymers are selected from the group comprising copolymers of vinyl acetate with 1% to 40% by weight of ethylene; copolymers of vinyl acetate with 1% to 40% by weight of ethylene and 1% to 50% by weight of one or more further comonomers from the group of vinyl esters having 3 to 12 carbon atoms in the carboxyl radical; copolymers of vinyl acetate, 1% to 40% by weight of ethylene, and 1% to 60% by weight of acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms; copolymers with 30% to 75% by weight of vinyl acetate, 1% to 40% by weight of ethylene, 1% to 30% by weight of vinyl laurate or vinyl esters of an alphabranched carboxylic acid having 5 to 13 carbon atoms, and also 1% to 30% by weight of acrylic esters of unbranched or branched alcohols having 1 to 15 carbon atoms; and copolymers with vinyl acetate, 1% to 40% by weight of ethylene, and 1% to 60% by weight of vinyl chloride; where the percentages by weight add up to 100% by weight in each case.

9. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 8, characterized in that the styrene-(meth)acrylic ester copolymers are based on styrene and one or more monomers from the group comprising methyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate.

10. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 9, characterized in that the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers are produced by free-radically initiated emulsion polymerization and one or more water-soluble inorganic salts are added before or during the emulsion polymerization.

11. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 10, characterized in that the vinyl acetate-ethylene or styrene-(meth)acrylic ester copolymers are produced by free-radically initiated emulsion polymerization and one or more water-soluble inorganic salts are added after the emulsion polymerization and before the drying of the aqueous dispersions.

12. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 11, characterized in that vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders contain no polyalkylene polyamine.

13. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 12, characterized in that the hydraulically setting dry building material formulations contain 5% to 50% by weight of hydraulically setting binders based on the total weight of the hydraulically setting dry building material formulations.

14. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 13, characterized in that the hydraulically setting dry building material formulations are used as reinforcing compounds for thermal insulation composite systems, as adhesives for thermal insulation panels or soundproofing panels, as tile adhesives, or as mortars, self-levelling compounds, screeds or plasters.

15. Use of vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders for producing hydraulically setting dry building material formulations according to Claims 1 to 14, characterized in that the vinyl acetate-ethylene and / or styrene-(meth)acrylic ester copolymers in the form of water-redispersible powders contain 1% to 30% by weight of desiccants based on the total weight of the copolymers.