WO2016150780A1

WO2016150780A1 - Two-component coating composition containing a polymer produced in the presence of lignosulphonate

Info

Publication number: WO2016150780A1
Application number: PCT/EP2016/055624
Authority: WO
Inventors: Carmen-Elena Cimpeanu; Rabie Al-Hellani; Juergen Schmidt-Thuemmes; Dirk Lawrenz; Sebastian Roller; Frederic Lucas; Ulrich TROMSDORF
Original assignee: Basf Se
Priority date: 2015-03-26
Filing date: 2016-03-16
Publication date: 2016-09-29

Abstract

The invention relates to a two-component coating composition containing, in a first component, an aqueous polymer dispersion which contains a hydroxy-functional polymer and can be produced by means of radically-initiated emulsion polymerisation from one or more ethylenically-unsaturated, radically-polymerisable monomers in the presence of lignosulphonate and, in a second component, at least one cross-linking agent that is based on at least one polyisocyanate. The invention also relates to a method for producing said aqueous polymer dispersion. The composition can be used for coating wood, and particularly as a clearcoat for coating wood.

Description

Two-component coating composition comprising a polymer prepared in the presence of lignin sulfonate

description

The invention relates to a two-component coating composition comprising in a first component an aqueous polymer dispersion containing a hydroxy-functional polymer preparable by free-radically initiated emulsion polymerization of one or more ethylenically unsaturated, radically polymerizable monomers in the presence of lignosulfonate, and in a second component at least a crosslinker based on at least one polyisocyanate. Also described is a process for preparing the aqueous polymer dispersion. The invention also relates to the use of the composition for wood coating, in particular as a clearcoat for wood coating. Wood surfaces, e.g. For reasons of protection and aesthetics, surfaces of wooden panels, furniture and doors are often coated with transparent varnishes. Use find e.g. Nitro lacquers, acid-hardening alkyd-amino lacquers, lacquers based on unsaturated polyesters, polyurethane lacquers and aqueous lacquers based on polymer dispersions. Here are aqueous paints that are free of organic solvents for reasons of work hygiene and environmental protection advantageous. Aqueous polymer dispersions for wood coating are e.g. known from EP 0279067. Clearcoats for wood coating should u.a. Requirements for scratch resistance, hardness, elasticity, sandability, stacking strength and resistance to chemical attack, eg. B. drinks and detergents meet. In addition to these protective effects, however, the visual impression of the wood surface, i. the typical wood grain not only not affected by the paint as possible but possibly even enhanced. This effect is also known as grain enhancement. In conventional paints, this is not always the case to the extent desired. WO 2013/120790 describes aqueous polymer dispersions preparable by emulsion polymerization in the presence of lignosulfonate. The polymer dispersions are used in paper wipes.

It was an object of the present invention to provide aqueous coating compositions, in particular aqueous, transparent wood coatings, with good protective properties for wood coated therewith and, at the same time, as good a start as possible.

The object is achieved by a two-component coating composition containing

(A) in a first component, an aqueous polymer dispersion comprising a hydroxy-functional polymer, preparable by free-radically initiated emulsion polymerization of one or more ethylenically unsaturated, radically polymerizable monomers in the presence of lignosulfonate, and

(B) in a second component at least one crosslinker based on at least one polyisocyanate. In the following, the term "(meth) acrylic ..." and similar names are sometimes used as a shorthand notation for "acrylic ... or ethacryl ...". In the term Cx-alkyl (meth) acrylate and analogous designations, x denotes the number of C atoms of the alkyl group.

The glass transition temperature can be determined by differential scanning calorimetry (ASTM D 3418-08, so-called "midpoint temperature", heating rate 20 C / min). Viscosity data refer to measurements at 20 C unless otherwise indicated.

The hydroxy groups of the hydroxyl-containing polymer can be obtained, for example, by copolymerization with a hydroxy-containing monomer (eg hydroxyalkyl (meth) acrylate) or by copolymerization with a monomer which contains groups convertible into hydroxyl groups (eg epoxy groups as in glycidyl (meth) acrylate) or by grafting reaction obtained with the lignosulfonate.

The lignin sulfonate is preferably used in an amount of 1 to 100 parts by weight, preferably 10 to 70 parts by weight, per 100 parts by weight of monomers (lignin sulfonate is not counted as a monomer) based on the sum of all the monomers. Lignosulfonates are the salts of lignin sulfonic acid (also called lignosulfonic acid), soluble products of the conversion of lignin by means of sulphurous acid or sulphites. The lignosulfonic acid used in the present invention can thus be obtained in the production of cellulose from wood as a natural raw material. In one stage of the production of cellulose, the lignin of the wood is mixed with sulphurous acid. In this treatment, the lignin is sulfonated and converted to lignosulfonic acid, which then, neutralized with a suitable base, results in the formation of the corresponding salt. Depending on the base used, water-soluble salts of sodium, ammonium, calcium, magnesium, etc. of the mentioned lignosulfonic acid are obtained. The lignosulfonates are generally in the form of a light yellow to dark brown, virtually odorless, non-hygroscopic and sufficiently stable powder (decomposition at about 200 C). Their molecular weight is preferably from 1,000 to 70,000, in particular from 7,000 to 52,000 g / mol. The lignosulfonates are known and have been used for various industrial purposes, such as in the manufacture of vanillin, as industrial cleaning agents, as flotation agents for ores, as dispersants for dyes, insecticides, pesticides, etc. In addition, they are biodegradable products and non-toxic to the people and the environment. Although all salts of lignosulfonic acid can be used in the invention, preferred lignosulfonate used is calcium-lignosulfonate (CAS No. 8061-52-7), sodium lignosulfonate (CAS No. 8061-51 -6), magnesium Lig- ninsulfonat and / or ammonium lignosulfonate. Particularly preferred are sodium magnesium and calcium lignosulfonate. These compounds can each be obtained commercially under the names Bretax® CL (Burgo Group) or Collex® 55 S (Chemische Werke Zell-Wildshausen GmbH). The products are predominantly made from fir wood (Epicea) received. Of course, the lignosulfonate used may be present alone or in admixture with several other lignosulfonates.

Preferably, the polymer is at least 60% by weight, or at least 80% by weight, of main monomers M1 selected from the group consisting of vinyl aromatic compounds, e.g. those having up to 20 C atoms, conjugated aliphatic dienes, vinyl esters of saturated Cr to C 2 O carboxylic acids, esters of acrylic acid or methacrylic acid with monohydric C 1 to C 20 alcohols, aliphatic hydrocarbons having 2 to 8 C atoms and one or two double bonds or Mixtures of these monomers.

To name a few are z. B. (meth) acrylic acid alkyl ester having a C 1 -C 10 -alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate , Isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate. sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, pentyl acrylates, pentyl methacrylates, 2-ethylhexyl methacrylate and 2-ethylhexyl acrylate. In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable. Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for. As vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate. Suitable vinylaromatic compounds are vinyltoluene, alpha- and p-methylstyrene, alpha-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and, preferably, styrene. Suitable hydrocarbons having 2 to 8 carbon atoms and one or two olefinic double bonds are ethylene, propylene, 1,3-butadiene, isoprene and chloroprene.

Preferred major monomers are styrene, butadiene, C1 to C20 alkyl (meth) acrylates, vinyl acetate and ethylene. Particular preference is given to C 1 -C 20 -alkyl (meth) acrylates, in particular C 1 -C 10 -alkyl (meth) acrylates, and mixtures of alkyl (meth) acrylates with vinyl aromatics, in particular with styrene (also referred to as polyacrylate binder in summary); or hydrocarbons having 2 double bonds, in particular 1, 3-butadiene, or mixtures of such hydrocarbons with vinyl aromatics, in particular with styrene (collectively also referred to as polybutadiene binder). For polybutadiene binders, the weight ratio of butadiene to Vinyiaromaten (especially styrene) z. B. 10:90 to 90:10, preferably 20:80 to 80:20. In the case of polyacrylate binders, the weight ratio of C1-C20-alkyl (meth) acrylates to vinyl aromatics (in particular styrene) can be, for example, 10-20% by weight. B. 10:90 to 90:10, preferably 20:80 to 80:20.

Preferably, the main monomers M1 are selected from the group consisting of styrene and alkyl (meth) acrylates having 1 to 20 carbon atoms in the alkyl group and mixtures thereof. The polymer is preferably composed of at least 60% by weight of mixtures of alkyl (meth) acrylates having 1 to 20 C atoms in the alkyl group and styrene.

The polymer is preferably branched or crosslinked, in particular by copolymerization of at least one branching or branching compound other than the main monomers. wetting monomers M2, selected from monomers having at least two radically polymerizable, ethylenically unsaturated groups. The crosslinking monomeric M2 are preferably used in an amount of 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, based on 100 parts by weight of monomers.

The branching or crosslinking monomers are monomers having at least two free-radically polymerizable, ethylenically unsaturated groups, with the exception of the conjugated aliphatic dienes which can be used as main monomers. Suitable branching or crosslinking monomers are e.g. polyfunctional acrylates or polyfunctional methacrylates, in particular alkanediol diacrylates or alkanediol dimethacrylates having preferably 2 to 8 C atoms in the alkane group. Suitable are e.g. Ethylene glycol diacrylate, propylene glycol diacrylate, polyethylene glycol diacrylate, hexanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate. Tri (meth) acrylates are e.g. Trimethylolpropane tri- methacrylates, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate or trimethylolpropane trimethacrylate. Further suitable crosslinking or branching monomers are divinyl compounds, in particular divinyl esters, e.g. Divinylbenzene, divinylsuccinate, divinyl adipate, divinyl maleate, divinyl oxalate, divinyl malonate or divinyl glutarate. Particularly preferred are the above-mentioned alkanediol di (meth) acrylates. Preferably, the branching or crosslinking of the polymer is carried out by

0.01 to 5 parts by weight, based on 100 parts by weight of monomers, of copolymerized alkanediol di (meth) acrylates having preferably 2 to 8 carbon atoms in the alkane group.

Preferably, the polymer is also composed of at least one acid monomer M3. Acid monomers are ethylenically unsaturated, radically polymerizable monomers which have at least one acid group. Ethylenically unsaturated acid monomers are e.g. Monomers having carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. The ethylenically unsaturated carboxylic acids used are preferably alpha, beta-monoethylenically unsaturated mono- and dicarboxylic acids having from 3 to 6 carbon atoms in the molecule. Called e.g. Acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid, crotonic acid, vinylacetic acid, vinyllactic acid and aconitic acid. An acid monomer with phosphonic acid group is e.g. Vinylphosphonic. Suitable ethylenically unsaturated sulfonic acids are, for example, vinylsulfonic acid, styrenesulfonic acid, acrylamidomethipropanesulfonic acid, sulfopropyl acrylate and sulfopropyl methacrylate. Particularly preferred are acrylic acid and methacrylic acid and their mixture. The content of ethylenically unsaturated acids in the emulsion polymer is preferably less than 10 parts by weight, e.g. at least 0.1 part by weight or 0.1 to 9 parts by weight or 0.1 to 5 parts by weight, based on 100 parts by weight of monomers. The monomers containing acid groups can be used in the polymerization in the form of the free acids and in partially or completely neutralized with suitable bases form. Preference is given to using sodium hydroxide solution, potassium hydroxide solution or ammonia as neutralizing agent.

Preferably, the polymer is also composed of at least one auxiliary monomer M4. The amount of auxiliary monomers is preferably at least 0.1 parts by weight, for example of 0.1 to 20 parts by weight, or from 0.2 to 20 parts by weight, or from 1 to 15 parts by weight based on 100 parts by weight of monomers. Auxiliary monomers are, for example, monomers having at least one hydroxyl group, and monomers having at least one glycidyl group. ethylenically unsaturated carboxylic acid nitriles, Ν, Ν-dialkylaminoalkylacrylamides, N, N-dialkylaminoalkylmethacrylamides, N, N-dialkylaminoalkylacrylates, Ν, Ν-dialkylaminoalkylmethacrylates. Preference is given to glycidyl (meth) acrylate and hydroxyalkyl (meth) acrylates. The alkyl groups preferably each have from 1 to 20 or from 1 to 10 carbon atoms. Examples of nitriles are acrylonitrile and methacrylonitrile; particularly preferred is acrylonitrile. Example of N, N-dialkylaminoalkyl (meth) acrylates is dimethylaminoethyl (meth) acrylate. Further optional auxiliary monomers are, for example, ethylenically unsaturated carboxylic acid amides, allyl esters of saturated carboxylic acids, vinyl halides, dialkyl esters of ethylenically unsaturated dicarboxylic acids having preferably 1 to 20 C atoms in the alkyl groups, vinyl ketones, N-vinylpyrrolidone, N-vinylpyrrolidine, N-vinylformamide, vinyl ethers of 1 to 10 C-containing alcohols. The vinyl halides are ethylenically unsaturated compounds substituted with chlorine, fluorine or bromine, preferably vinyl chloride and vinylidene chloride. Vinyl ethers include, for example, vinyl methyl ether or vinyl isobutyl ether. Preferred are vinyl ethers of alcohols containing 1 to 4 carbon atoms. Ethylenically unsaturated carboxylic acid amides are, for example, acrylamide and methacrylamide.

In one embodiment of the invention are used as monomers:

60 to 95 parts by weight of at least one main monomer M1 selected from vinylaromatic compounds, C1 to C18 alkyl esters of acrylic acid and C1 to C18 alkyl esters of methacrylic acid,

0.1 to 5 parts by weight of at least one ethylenically unsaturated acid M3 and

0 to 20 parts by weight of at least one further monoethylenically unsaturated auxiliary monomer M4, different from the monomers M1 and M3, together with

0.01 to 5 parts by weight, based on 100 parts by weight of monomers, copolymerizing, branching or crosslinking monomers M2, selected from monomers having at least two free-radically polymerizable, ethylenically unsaturated groups and

from 1 to 100 parts by weight, preferably from 10 to 70 parts by weight, of lignosulfonate

100 parts by weight of monomers, wherein the sum of the parts by weight of the monomers is 100.

In the emulsion polymerization are usually used initiators which form radicals under the reaction conditions. In general, the concentration of the initiators is from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, particularly preferably from 0.1 to 10% by weight, based on the monomers to be polymerized. It is also possible to use a plurality of different initiators in the emulsion polymerization. Polymerization initiators are, for example, organic peroxides, organic hydroperoxides, hydrogen peroxide, sodium or potassium persulfate, redox catalysts and azo compounds such as 2,2-azobis (4-methoxy-2,4-dimethyl valeronitrile), 2,2-azobis (2,4-dimethylvaleronitrile ) and 2,2-azobis (2-amidinopropane) dihydrochloride. Examples of further initiators are dibenzoyl peroxide, tert-butyl perpivalate, tert-butyl per-2-ethylhexanoate, di-tert-butyl peroxide, diamyl peroxide, dioctanoyl peroxide, didecanoyl peroxide, dilauroyl peroxide, bis (o-toluyl) peroxide, succinyl peroxide, tert. Butyl peracetate, tert-butyl perla- lactate, tert-butyl perisobutyrate, tert-butyl perpivalate, tert-butyl peroctoate, tert-butyl perbenzoate, tert-butyl hydroperoxide, azo-bis-isobutyronitrile, 2,2 ^'azo-bis- (2-methylbutyronitrile), 2,2 azobis (2,4-dimethylvaleronitrile) and ^2,2' (azobis N, N ^' -dimethyleneisobutyroamidine) dihydrochloride. It is also possible to initiate the polymerization by means of high-energy rays such as electron beams or by irradiation with UV light. Preference is given to initiators selected from the group of organic peroxides, organic hydroperoxides and hydrogen peroxide.

Preferred initiators according to the invention are so-called reduction-oxidation initiator systems (redox initiator systems). The redox initiator systems consist of at least one reducing agent and at least one oxidizing agent. The oxidation component is, for example, the initiators for emulsion polymerization already mentioned above. Particularly suitable oxidation components are H2O2 or a peroxide which forms hydrophobic free radicals, for example tert-butyl hydroperoxide. The reduction components are preferably sodium hydroxymethanesulfinate, acetone bisulfite or soluble metal compounds whose metallic component can occur in two or more valence states, eg Fe ² *.

Examples of particularly preferred redox initiator systems are:

Fe ²⁺ / H ₂ 0 ₂

Sodium hydroxymethanesulfinate / tert-butyl hydroperoxide

Acetone bisulfite / tert-butyl hydroperoxide.

An embodiment of the invention relates to an aqueous polymer dispersion, characterized in that as monomers

60 to 95 parts by weight of at least one main monomer M1 selected from styrene, C1 to C18 alkyl esters of acrylic acid and C1 to C18 alkyl esters of methacrylic acid and their mixture,

0.1 to 5 parts by weight of at least one ethylenically unsaturated acid M3 selected from acrylic acid and methacrylic acid and their mixture,

1 to 20 parts by weight of at least one auxiliary monomer M4 selected from the group consisting of glycidyl (meth) acrylate and hydroxyalkyl (meth) acrylates having 2 to 4 C atoms in the alkyl group, together with

0.1 to 5 parts by weight of copolymerizing, branching or crosslinking monomers M2, selected from monomers having at least two radically polymerizable, ethylenically unsaturated groups and

from 1 to 100 parts by weight, preferably from 10 to 70 parts by weight of lignosulfonate

100 parts by weight of monomers are used,

wherein the sum of parts by weight of the monomers is 100

and wherein as initiator for the polymerization, a redox initiator system, preferably Fe ²⁺ / H 2 O 2 or sodium hydroxymethanesulfinate / tert-butyl hydroperoxide is used.

The preparation of the polymer dispersion can be carried out by emulsion polymerization, it is then an emulsion polymer. In the emulsion polymerization in the Usually ionic and / or non-ionic emulsifiers and / or protective colloids or stabilizers used as surface-active compounds to assist in the dispersion of the monomers in the aqueous medium. Protective colloids are polymeric compounds which upon solvation bind large amounts of water and are capable of stabilizing dispersions of water-insoluble polymers. In contrast to emulsifiers, they usually do not lower the interfacial tension between polymer particles and water. A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular substances, Georg-Thieme-Verlag, Stuttgart, 1961, pages 41 1 to 420. Suitable as protective colloids z. B. amphiphilic polymers, ie polymers with hydrophobic and hydrophilic groups. They may be natural polymers such as starch or synthetic polymers. Suitable emulsifiers are both anionic and nonionic surface-active substances whose number average molecular weight is usually below 2000 g / mol or preferably below 1500 g / mol, while the number average molecular weight of the protective colloid is above 2000 g / mol, for example from 2,000 to 100,000 g / mol, in particular from 5,000 to 50,000 g / mol. Anionic and nonionic emulsifiers are preferably used as surface-active substances. Suitable emulsifiers are, for example, ethoxylated Ce- to Cae-fatty alcohols having a degree of ethoxylation of 3 to 50, ethoxylated mono-, di- and tri-C ₄ - to C 12 -alkyl phenols having a degree of ethoxylation of 3 to 50, alkali metal salts of dialkyl esters of Sul - Fibernsteinsäure, alkali metal and ammonium salts of Cs to Ci2 alkyl sulfates, alkali metal and ammonium salts of C12- to Ci8 alkyl sulfonic acids and alkali metal and ammonium salts of C9- to Ci8-alkylarylsulfonic. If emulsifiers and / or protective colloids are used as auxiliaries for dispersing the monomers, the amounts used are, for example, from 0.1 to 5% by weight, based on the monomers. Trade names of emulsifiers are z. Dowfax® A1, Emulan® NP 50, Dextrol® OC 50, Emulsifier 825, Emulsifier 825 S, Emulan® OG, Texapon® NSO, Nekanil® 904 S, Lumiten® I-RA, Lumiten E 3065, Lumiten ® ISC, Disponil® SDS, Disponil LDBS 20, Disponil FES 77, Lutensol AT 18, Steinapol VSL, Emulphor NPS 25. The surfactant is usually in amounts of 0.1 to 10 wt .-%, based on the monomers to be polymerized used. Lignosulfonate may also have the effect of a protective colloid, but is not understood according to the invention as a protective colloid in the sense of the above description.

The emulsion polymerization can be carried out in the presence of seed particles. The master then contains polymer seed, in particular a polystyrene seed, i. an aqueous dispersion of finely divided polymer, preferably polystyrene, having a particle diameter of from 20 to 40 nm.

The emulsion polymerization takes place in an aqueous medium. This may be, for example, completely desalinated water or mixtures of water and a miscible solvent such as methanol, ethanol or tetrahydrofuran. As soon as the particular desired polymerization temperature is reached or within a time period of 1 to 15 minutes, preferably 5 to 15 minutes after the polymerization temperature has been reached, metering of the monomers begins. For example, they may be continuously pumped into the reactor within, for example, 60 minutes to 10 hours, most often within 2 to 4 hours. Preferably, the reaction mixture in the template heated the required temperature at which the polymerization takes place. These temperatures are for example 70 to 95 C, preferably 70 to 85 C. The polymerization can also be carried out under pressure, for example at pressures up to 15 bar, for example at 2 to 10 bar. The monomer feed can be carried out as a batch process, continuously or stepwise.

The polymerization can be carried out in the presence of polymerization regulators (molecular weight regulators). Examples of polymerization regulators which can optionally be used are organic compounds which contain sulfur in bound form, such as mercaptoethylpropionate, thiodiglycol, ethylthioethanol, di-n-butylsulfide, di-n-octylsulfide, diphenylsulfide, diisopropyl-idisulfide, 1, 3-mercaptopropanol, 3-mercaptopropan-1, 2-diol, 1, 4-mercaptobutanol, thioglycolic acid, 3-mercaptopropionic acid, mercaptosuccinic acid, thioacetic acid and thiourea. Further polymerization regulators are aldehydes, such as formaldehyde, acetaldehyde and propionaldehyde, organic acids, such as formic acid, sodium formate or ammonium formate, alcohols, in particular isopropanol, and phosphorus compounds, such as sodium hypophosphite. The amount of all molecular weight regulators is for example 0.01 to 5, preferably 0.1 to 1 wt .-%, based on the monomers used in the polymerization. The regulators are preferably added together with the monomers. However, they may also be present partially or completely in the template. You can also be gradually added to the monomers added. Lignosulfonate also exhibits a regulator effect, but according to the invention is not understood to be a polymerization regulator in the sense of the above description.

After completion of the polymerization, it is optionally possible to add further initiator to the reaction mixture and to carry out postpolymerization at the same, lower or even higher temperature as in the main polymerization. In most cases, in order to complete the polymerization reaction, it is sufficient to stir the reaction mixture at the polymerization temperature for 1 to 3 hours after the addition of all the monomers. The pH during the polymerization may be, for example, from 2 to 7, preferably the pH is from 4 to 6. After the polymerization, the pH is adjusted to a value of 8 to 9, for example.

An aqueous polymer dispersion is obtained whose dispersed particles have an average particle diameter of preferably 80 to 350 nm, in particular from 150 to 280 nm or from 90 to 150 nm. The average particle diameter of the polymer particles can be determined by dynamic light scattering on a 0.005 to 0.01% strength by weight aqueous polymer dispersion at 23 ° C. using an Autosizers HC from Malvern Instruments, England. The data refer in each case to the mean diameter of the cumulant evaluation (cumulant z-average) of the measured autocorrelation function according to the standard

DIN ISO 13321: 1996. The polymers have a glass transition temperature Tg of preferably 0 to 50 C, in particular from 20 to 40 C. The glass transition temperature can be determined by differential scanning calorimetry (ASTM D 3418-08, so-called "midpoint temperature", heating rate 20 ° C / min).

The solids content of the aqueous polymer dispersion of the invention may be e.g. from 40 to 60 wt.%. The solids content may e.g. be adjusted by appropriate adjustment of the amount of water used in the emulsion polymerization and / or the amounts of monomers.

The two-component coating composition contains as second component at least one crosslinker based on at least one polyisocyanate.

The two-component coating compositions according to the invention preferably have a stoichiometry (molar ratio) of isocyanate groups of the crosslinker to isocyanate-reactive groups (in particular those of the hydroxy-functional polymer) of 0.5: 1 to 2: 1, preferably 0.7: 1 to 1.5 : 1, more preferably 1: 1 to 1, 5: 1 on.

As component (B) is preferably at least one, for example one to three, preferably one to two and more preferably exactly one polyisocyanate used, which is obtainable by reacting at least one monomeric isocyanate. The monomeric isocyanates used may be aromatic, aliphatic or cycloaliphatic, preferably aliphatic or cycloaliphatic, which is referred to in this document briefly as (cyclo) aliphatic, particularly preferred are aliphatic isocyanates. Aromatic isocyanates are those which contain at least one aromatic ring system, ie both purely aromatic and also araliphatic compounds. Cycloaliphatic isocyanates are those which contain at least one cycloaliphatic ring system. Aliphatic isocyanates are those which contain exclusively straight or branched chains, ie acyclic compounds. The monomeric isocyanates are preferably diisocyanates which carry exactly two isocyanate groups. In principle, however, it may also be monoisocyanates having an isocyanate group.

In principle, higher isocyanates having an average of more than 2 isocyanate groups into consideration. Triisocyanates such as triisocyanatononane, 2'-isocyanato-ethyl- (2,6-diisocyanatohexanoate), 2,4,6-triisocyanatotoluene, triphenylmethane triisocyanate or 2,4,4'-triisocyanatodiphenyl ether or the mixtures of di-, are suitable for this purpose, for example. Tri- and higher Polyisocyana- th obtained, for example, by phosgenation of corresponding aniline / formaldehyde condensates and represent methylene bridges containing polyphenyl polyisocyanates. These monomeric isocyanates have no significant reaction products of the isocyanate groups with itself. The monomeric isocyanates are preferably isocyanates having 4 to 20 C atoms. Examples of customary diisocyanates are aliphatic diisocyanates such as tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, hexamethylene diisocyanate (1,6-diisocyanatohexane), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethyl endiisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate, (for example methyl or ethyl 2,6-diisocyanatoatohexanoate), trimethylhexane diisocyanate or tetramethylhexane diisocyanate, cycloaliphatic diisocyanates, such as 1,1,4-, 1,3- or 1,2-diisocyanatocyclohexane , 4,4'- or 2,4'-di (isocyanatocyclohexyl) methane, 1-isocyanato-3,3,5-trimethyl-5- (isocyanatomethyl) cyclohexane (isophorone diisocyanate), 1, 3 or 1,4-bis (isocyanatomethyl) cyclohexane or 2,4- or 2,6-diisocyanato-1-methylcyclohexane and also 3 (or 4), 8 (or 9) -bis (isocyanatomethyl) - tricyclic [5.2.1.0 ^{2 6} ] decane isomer mixtures, and aromatic diisocyanates such as 2,4-o- and 2,6-to-luylendiisocyanat and their isomer mixtures, m- or p-xy-lylene diisocyanate, 2,4 '- or 4,4'-diisocyanatodiphenylmethane and their isomer mixtures, 1, 3 or 1, 4-phenylene diisocyanate, 1-chloro-2,4-phenylene diisocyanate, 1, 5-naphthylene diisocyanate, diphenylene-4,4' di-isocyanate, 4,4'-diisocyanato-3,3'-dimethyldiphenyl, 3-methyldi-p henylmethane-4,4'-diisocyanate, tetramethylxylylene diisocyanate, 1, 4-diisocyanatobenzene or diphenyl ether-4,4'-diisocyanate. Particular preference is given to 1,6-hexamethylene diisocyanate,

1, 3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate and 4,4'- or 2,4'-di (isocyanatocyclohexyl) methane, very particular preference is given to isophorone diisocyanate and 1,6-hexamethylene diisocyanate, particular preference is 1, 6-hexamethylene diisocyanate. There may also be mixtures of said isocyanates.

Isophorone diisocyanate is usually present as a mixture, namely of the cis and trans isomers, generally in the ratio of about 60:40 to 80:20 (w / w), preferably in the ratio of about 70:30 to 75 : 25 and most preferably in the ratio of about 75:25. Dicyclohexylmethane-4,4'-di-iso-eyanate may also be present as a mixture of the different cis and trans isomers.

For the present invention, it is possible to use both those diisocyanates which are obtained by phosgenation of the corresponding amines and those which can be obtained without the use of phosgene, ie. H. after phosgene-free process, are produced. According to EP-A-0 126 299 (US Pat. No. 4,596,678), EP-A-126 300 (US Pat. No. 4,596,679) and EP-A-355 443 (US Pat. No. 5,087,739), for example, (cyclo) aliphatic diisocyanates, eg 1, 6-hexamethylenediisocyanate (HDI), isomeric aliphatic diisocyanates having 6 carbon atoms in the alkylene radical, 4,4'- or 2,4'-di (isocyanatocyclohexyl) methane and 1-isocyanato-3-isocyanato-methyl-3 , 5,5-trimethyl-cyclohexane (isophorone diisocyanate or IPDI) are prepared by reacting the (cyclo) aliphatic diamines with, for example, urea and alcohols to (cyclo) -aliphatic Biscarbaminsäureestern and their thermal cleavage into the corresponding diisocyanates and alcohols. The synthesis is usually carried out continuously in a cyclic process and, if appropriate, in the presence of N-unsubstituted carbamic acid esters, dialkyl carbonates and other by-products recycled from the reaction process. Diisocyanates obtained in this way generally have a very low or even immeasurable amount of chlorinated compounds, which is advantageous, for example, in applications in the electronics industry.

The isocyanates used preferably have a total hydrolyzable chlorine content of less than 80 ppm, preferably less than 30 ppm, and in particular less than 25 ppm. This can be measured, for example, by ASTM D4663-98. Of course, mixtures of such monomeric isocyanates, which have been obtained by reacting the (cyclo) aliphatic diamines with, for example, urea and alcohols and cleavage of the obtained (cyclo) aliphatic Biscarbaminsaureester, with such diisocyanates, which have been obtained by phosgenation of the corresponding amines, be used.

The polyisocyanates (B) to which the monomeric isocyanates can be oligomerized are preferably characterized as follows. The average NGO functionality of such compounds is preferably at least 1, 8 and may be up to 8, preferably 2 to 5 and particularly preferably 2.4 to 4. The content of isocyanate groups after the oligomerization, calculated as NGO = 42 g / mol , unless otherwise specified, is preferably from 5 to 25% by weight. The polyisocyanates (B) are preferably the following compounds: 1) polyisocyanates containing isocyanurate groups of aromatic, aliphatic and / or cycloaliphatic diisocyanates. Particular preference is given here to the corresponding aliphatic and / or cycloaliphatic isocyanato-isocyanurates and in particular those based on hexamethylene diisocyanate and isophorone diisocyanate. The isocyanurates present are, in particular, tris-isocyanatoalkyl or trisisocyanatocycloalkyl isocyanurates, which are cyclic trimers of the diisocyanates, or mixtures with their higher homologs having more than one isocyanurate ring. The isocyanato-isocyanurates generally have an NCO content of 10 to 30 wt .-%, in particular 15 to 25 wt .-% and an average NCO functionality of 2.6 to 8.

2) polyisocyanates containing uretdione groups with aromatic, aliphatic and / or cycloaliphatic bound isocyanate groups, preferably aliphatically and / or cyclo-aliphatically bonded and in particular those derived from hexamethylene diisocyanate or isophorone diisocyanate. Uretdione diisocyanates are cyclic dimerization products of diisocyanates.

The polyisocyanates containing uretdione groups are obtained in the context of this invention in a mixture with other polyisocyanates, in particular those mentioned under 1). For this purpose, the diisocyanates can be reacted under reaction conditions under which both uretdione groups and the other polyisocyanates are formed, o- initially formed the uretdione and then these are reacted to the other polyisocyanates or the diisocyanates first to the other polyisocyanates and these then to uretdione groups containing products.

Biuret group-containing polyisocyanates with aromatic, cycloaliphatic or aliphatic bound, preferably cycloaliphatic or aliphatic bound isocyanate groups, in particular tris (6-isocyanatohexyl) biuret or mixtures thereof with its higher homologs. These biuret polyisocyanates preferably have an NCO content of 18 to 23.5 wt .-% and an average NCO functionality of 2.8 to 6 (especially in the case of HDI). 4) polyisocyanates containing urethane and / or allophanate groups with aromatic,

aliphatic or cycloaliphatic bonded, preferably aliphatically or cycloaliphatically bound isocyanate groups, as for example by reacting excess amounts of diisocyanate, for example hexamethylene diisocyanate or isophorone diisocyanate, with monohydric or polyhydric alcohols (A). These urethane and / or allophanate-containing polyisocyanates generally have an NCO content of

12 to 24 wt .-% and an average NCO functionality of 2.3 to 4.5. Such urethane and / or allophanate group-containing polyisocyanates can be used uncatalyzed or, preferably, in the presence of catalysts such as ammonium carboxylates or hydroxides, or allophanatization catalysts, e.g. Zn (II) compounds, in each case in the presence of mono-, di- or polyhydric, preferably monohydric alcohols.

5) oxadiazinetrione-containing polyisocyanates, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such oxadiazinetrione-containing polyisocyanates are accessible from diisocyanate and carbon dioxide.

6) Iminooxadiazindiongruppen containing polyisocyanates, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates containing iminooxadiazinedione groups can be prepared from diisocyanates by means of special catalysts. These are usually present in a mixture with polyisocyanates 1), possibly also with 2) and / or 4).

7) Uretonimine-modified polyisocyanates. 8) carbodiimide-modified polyisocyanates.

9) hyperbranched polyisocyanates, as they are known for example from

DE-A1 10013186 or DE-A1 10013187.

10) polyurethane-polyisocyanate prepolymers of di- and / or polyisocyanates with alcohols.

1 1) polyurea-polyisocyanate prepolymers.

12) The polyisocyanates 1) -1 1), preferably 1), 3), 4) and 6) may, after their preparation in biuret or urethane / allophanate groups having polyisocyanates having aromatic, cycloaliphatic or aliphatic bound preferred (cyclo) aliphatically bonded isocyanate groups, transferred. The formation of biuret groups takes place, for example, by addition of water or reaction with amines. The formation of urethane and / or allophanate groups takes place by reaction with one, two or more valent, preferably monohydric alcohols, optionally in the presence of suitable catalysts. These biuret or urethane / allophanate-containing polyisocyanates generally have an NCO content of 18 to 22% by weight and an average NCO functionality of 2.8 to 6.

13) Hydrophilic modified polyisocyanates, i. Polyisocyanates which contain, in addition to the groups described under 1-12, those which formally arise by addition of molecules with NCO-reactive groups and hydrophilicizing groups to the isocyanate groups of the above molecules. The latter are nonionic groups such as alkylpolyethylene oxide and / or ionic, which are derived from phosphoric acid, phosphonic acid, sulfuric acid or sulfonic acid, or their salts organically modified. These can be used untypically but according to the invention in solvent-based systems, in particular as a partial component of the isocyanate component.

14) Modified Polyisocyanates for Dual Cure Applications, i. Polyisocyanates which contain, in addition to the groups described under 1-13, those which formally arise by addition of molecules with NCO-reactive groups and groups crosslinkable by UV or actinic radiation to the isocyanate groups of the above molecules. These molecules are, for example, hydroxyalkyl (meth) acrylates and other hydroxy-vinyl compounds.

The diisocyanates or polyisocyanates listed above may also be present at least partially in blocked form. Linking classes of compounds are described in D.A. Wieks, Z.W. Wieks, Progress in Organic Coatings, 36, 148-172 (1999), 41, 1-83 (2001) and 43, 131-140 (2001). Examples of classes of compounds used for blocking are phenols, imidazoie, triazoin, pyrazoles, oximes, N-hydroxyimides, hydroxybenzoic acid esters, secondary amines, lactams, CH-acidic cyclic ketones, malonic esters or alkyl acetoacetates.

The polyisocyanate (B) is preferably selected from the group consisting of isocyanurates, iminooxadiazinediones, biurets, uretdiones, urethanes and allophanates, in particular from the group consisting of isocyanurates, urethanes and allophanates, particularly preferably from the group consisting of isocyanurates and allophanates, in particular it is an isocyanurate group-containing polyisocyanate. In a particularly preferred embodiment, the polyisocyanate (B) is isocyanurate-containing polyisocyanates of 1,6-hexamethylene diisocyanate. In a further particularly preferred embodiment, the polyisocyanate (B) is a mixture of isocyanurate-containing polyisocyanates of 1,6-hexamethylene diisocyanate and of isophorone diisocyanate.

The polyisocyanate (B) is preferably a mixture comprising low-viscosity polyisocyanates, preferably polyisocyanates containing isocyanurate groups, having a viscosity of 600-1500 mPa * s, in particular less than 1200 mPa * s, low-viscosity urethanes and / or allophanates having one Viscosity of 200-1600 mPa * s, and / or iminooxadiazinedione groups containing polyisocyanates. The viscosities are based on measurement at 20 ° C. The process for preparing the polyisocyanates can be carried out as described in WO 2005/087828 or as described in WO 2008/068198, there in particular from page 20, line 21 to page 27, line 15, which is hereby incorporated by reference in the present application. The reaction can be stopped, for example, as described there from page 31, line 19 to page 31, line 31 and the workup carried out as described there from page 31, line 33 to page 32, line 40, which hereby incorporated by reference the present application. Alternatively, the reaction can also be stopped, as described in WO 2005/087828 from page 11, line 12 to page 12, line 5, which is hereby incorporated by reference in the present application. In thermally labile catalysts, it is also possible to stop the reaction by heating the reaction mixture to a temperature above at least 80 C, preferably at least 100 C, more preferably at least 120 ° C. This usually already warming of the reaction mixture, as required for the separation of the unreacted isocyanate by distillation in the workup. Both in the case of thermally unstable and thermally unstable catalysts, it is possible to terminate the reaction at lower temperatures by adding deactivators. Suitable deactivators are, for example, hydrogen chloride, phosphoric acid, organic phosphates, such as dibutyl phosphate or diethylhexyl phosphate, carbamates, such as hydroxyalkyl carbamate or organic carboxylic acids. These compounds are added neat or diluted in the appropriate concentration necessary for reaction termination. Preference is given to dibutyl phosphate or diethylhexyl phosphate.

Low-viscosity polyisocyanates or allophanates of diisocyanates can also be prepared, for example, in accordance with WO 2005/087828. In the case of the low-viscosity polyisocyanates, the reaction is carried out at a lower conversion than in the concrete examples of

WO 2005/087828 terminated thermally or by chemical deactivators, but otherwise analogous procedure. In this way, products based on hexamethylene diisocyanate having viscosities of, for example, 900-1500 mPa ^* s can be prepared, but also with lower viscosities, preferably up to 500 mPa ^* s. In an analogous manner allophanates can also be prepared with the same catalysts in which mono- and / or dialcohols, preferably C1-C18 mono- and / or C2-C18 dialcohols, are additionally added to the monomer hexamethylene diisocyanate. These are preferably butanol, pentanol, 2-ethyl-hexanol, 1, 3-hexanediol, and 3,3,5-trimethylpentanediol. Monoalcohols are preferably added in amounts of up to 25% to the end product. The viscosities of the products of hexamethylene diisocyanate and monoalcohol are preferably in a range of 200-1500 mPa ^* s. They contain according to the usual composition of the polyisocyanates 4) significant amounts of isocyanurates, possibly also urethanes. Similarly, it is also possible to prepare highly viscous polyisocyanates or allophanates of diisocyanates in accordance with WO 2005/087828. In the case of the highly viscous polyisocyanates, the reaction is terminated at higher conversion than in the specific examples of WO 2005/087828 thermally or by chemical deactivators. Preferably, the viscosities of polyisocyanates based on hexamethylene diisocyanate are not more than 30 Pa ^* s. A dilution of the high-viscosity compounds in solvents is useful. The invention also relates to the use of the described two-component coating composition for wood coating (wood finish), in particular as clearcoat for wood coating.

The invention also relates to wood coated with the described two-component coating composition. The wood may e.g. selected from oak, spruce, pine, beech, maple, chestnut, sycamore, robinia, ash, birch, pine, elm, walnut, makore or cork.

Wood coatings produced on the basis of the composition according to the invention may contain conventional additives such as waxes, film-forming agents, solvents, matting agents, defoamers, light stabilizers, UV absorbers, dyes, pigments, fillers and / or thickeners. Waxes are e.g. those based on paraffin or polyethylene. The waxes are usually used as 20 to 60 wt. % dispersions added during or after the emulsion polymerization. Waxes with softening points of preferably 50 to 250 C, more preferably from 70 to 130 C, are used. The particle size of the wax particles may be 0.01 to 0.5 pm. For better film formation, film-forming aids, such as e.g. Butylglycol, Diisobutylestergemische of adipic, glutaric and / or succinic acid and other organic solvents in amounts of 3 to 8 wt.% To be added. Furthermore, matting agents such as e.g. Silica compounds in amounts of 0.5 to 2 wt .-% and thickener, for example. be used on basis of polyurethane and / or polyacrylates. Fillers are e.g. Silicates, e.g. Silicates obtainable by hydrolysis of silicon tetrachloride, e.g. Aerosil®; Silica, talc, aluminum silicate, magnesium silicate, calcium carbonate, etc. Suitable light stabilizers include, for example, UV absorbers, e.g. Oxanilides, triazines, benzotriazoles (e.g., Tinuvin®) or benzophenones. They can be used alone or in combination with radical scavengers. Radical scavengers are e.g. sterically hindered amines such as e.g. 2,2,6,6-tetramethylpiperidines, 2,6-di-tert-butylpiperidine or derivatives thereof, e.g. Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate. The light stabilizers may e.g. in amounts of 0.1 to

5.0% by weight, based on the solids content of the composition.

The coating of substrates can be carried out in such a way that the two components of the two-component coating composition are mixed together (preferably immediately before use), applied to the surface to be coated with a coating method known per se to the person skilled in the art, and water and others Volatile components are removed by drying or evaporation at room temperature or at elevated temperatures. This procedure can be repeated one or more times. The application to the surface to be coated can e.g. By brushing, spraying, spraying, blade coating, roller coating, rolling, knife coating or pouring.

The layer thickness of the coating (after drying) is preferably from 3 to 1000 g / m ² and preferably from 10 to 200 g / m ² . The drying takes place at room temperature, but can even at elevated temperatures, for example up to 80 C or up to 60 C in conventional drying channels.

The coatings thus obtained are characterized by a particularly good tempering.

Examples

The solids contents are determined by drying a defined amount of the respective aqueous polymer dispersion (about 5 g) at 140 C in a drying oven to constant weight. In each case, two separate measurements are carried out and the mean value is formed.

A measure of the particle size of the dispersed polymer particles is the LD value. To determine the LD value (light transmittance), the particular polymer dispersion to be investigated is measured in 0.1% strength by weight aqueous dilution in a cuvette with an edge length of 2.5 cm with light of wavelength 600 nm and with the appropriate Permeability of water compared under the same measurement conditions. The permeability of water is given as 100%. The finer the dispersion, the higher the LD value measured by the method described above. The average particle size can be calculated from the measured values, cf. See, for example, Verner, M. Bärta, B. Sedläcek, Tables of Scattering Functions for Spherical Particles, Prague, 1976, Edice Marco, Rada D-DATA, SVAZEK D-1.

In the application tests, the following polymer dispersions were used. Emulsion polymerization for the preparation of lignin-containing dispersions:

Example 1: Dispersion D1

In a polymerization vessel equipped with a stirrer, a reflux condenser and metering devices, 396.23 g of a 55% by weight magnesium lignosulfonate solution (Collex® 55 S, Chemische Werke Zell-Wildshausen GmbH), 136, 61 g of water and

1 1, 67 g of a 15 wt .-% emulsifier solution (Disponil® SDS 15) before. The mixture is heated with stirring to 70 C, then 17.50 g of a 10 wt .-% iron (II) sulfate solution are added. Thereafter, the feed of 35.00 g of a 30 wt .-% hydrogen peroxide solution and 88.00 g of water. At the same time, 154.00 g of styrene, 161.0 g of n-butyl acrylate, 3.50 g of butanediol diacrylate, 3.50 g of acrylic acid, 17.50 g of 2-hydroxyethyl acrylate and 10.50 g of glycidyl methacrylate are added. The monomer feed is added over 180 min and the hydrogen peroxide feed is metered in over 210 min. After the Initiatorzulauf 67.00 g of water are added and then postpolymerized at 70 C for 55 min. Subsequently, the feed of 35.00 g of a 10% tert-butyl hydroperoxide solution is added in 30 minutes and polymerized for 90 minutes. Thereafter, the cooling to room temperature. In the cooling phase, 18.00 g of water are added. The dispersion thus prepared has a solids content of 49.0%, an L D value of 55% (transmission of white light).

Example 2: Dispersion D2

In a polymerization vessel equipped with a stirrer, a reflux condenser and metering devices, 396.23 g of a 55% by weight magnesium lignosulfonate solution (Collex® 55 S, Chemische Werke Zell-Wildshausen GmbH), 136, 61 g of water and 1 1, 67 g of a 15 wt .-% emulsifier solution (Disponil® SDS 15) before. The mixture is heated with stirring to 70 C, then 17.50 g of a 10 wt .-% iron (II) sulfate solution are added. Thereafter, the feed of 35 g of a 30 wt .-% hydrogen peroxide solution and 88.00 g of water begins. At the same time, the feed of 164.50 g of styrene, 161, 0 g of n-butyl acrylate, 3.50 g of butanediol diacrylate, 10.50 g of acrylic acid, and 10.50 g of glycidyl methacrylate. The monomer feed is added over 180 min and the hydrogen peroxide feed is added in 210 min. After the Initiatorzulauf 67.00 g of water are added and then postpolymerized at 70 C for 55 min. Subsequently, the feed of 35.00 g of a 10% tert-butyl hydroperoxide solution is added in 30 minutes and polymerized for 90 minutes. Thereafter, the cooling to room temperature. In the cooling phase, 18.00 g of water are added.

The dispersion thus prepared has a solids content of 49.0%, an LD value of 52% (transmission of white light).

Example 3: Dispersion D3

In a polymerization vessel equipped with a stirrer, a reflux condenser and metering devices, 440.25 g of a 50% by weight calcium lignosulfonate solution (Bretax® CL, Burgo Group), 60.75 g of water and 1 1.67 g of a 15% strength by weight emulsifier solution (Disponil® SDS 15). The mixture is heated with stirring to 70 C, then simultaneously the monomer feed and the initiator feeds are started and dosed over 120 min. The monomer feed consists of 164.00 g of styrene, 161.00 g of n-butyl acrylate, 3.50 g of butanediol diacrylate, 10.50 g of acrylic acid and 10.50 g of glycidyl methacrylate. The initiator system consists of 105.00 g of a 10% tert-butyl hydroperoxide solution and 79.80 g of a 10% strength Rongalit® C solution, which are added separately. At the end of monomer and initiator feeds 67.00 g of water are added and then polymerized for a further 55 min at 70 C. Subsequently, the feed of 35.00 g of a 10% tert-butyl hydroperoxide solution is metered in over 30 minutes and then 9.00 g of water are added and further polymerization is continued for 90 minutes. Thereafter, the cooling to room temperature. In the cooling phase, 9.00 g of water are added.

The dispersion thus prepared has a solids content of 48.9%, an LD value of 71% (transmission of white light). Comparative Example 1: Dispersion D4

In a polymerization vessel equipped with a stirrer, a reflux condenser and metering devices, 1. 15.70 g of water and 16.67 g of a 15% strength by weight emulsifier are added. gator solution (Disponil® SDS 15). The mixture is heated with stirring to 70 C, then simultaneously the monomer feed and the initiator feeds are started and dosed over 120 min. The monomer feed consists of 235.00 g of styrene, 230.00 g of n-butyl acrylate, 5.00 g of butanediol diacrylate, 15.00 g of acrylic acid and 15.00 g of glycidyl methacrylate. The initiator system consists of 150.00 g of a 10% tert-butyl hydroperoxide solution and 1 14.00 g of a 10% Rongalit® C solution, which are added separately. At the end of monomer and initiator feeds 95.71 g of water are added and then after-polymerized at 70 C for 55 min. Subsequently, the feed of 50.00 g of a 10% tert-butyl hydroperoxide solution is metered in over 30 minutes and then 12.85 g of water are added and polymerization is continued for a further 90 minutes. Thereafter, the cooling to room temperature. In the cooling phase, 12.85 g of water are added.

The dispersion thus prepared has a solids content of 48.0%, an LD value of 52% (transmission of white light). Comparative Example 2: Dispersion D5

In a polymerization vessel which is equipped with a stirrer, a reflux condenser and metering devices, 1. 15.73 g of water and 16.67 g of a 15% strength by weight emulsifier solution (Disponil® SDS 15) are initially introduced. The mixture is heated with stirring to 70 C, then simultaneously the monomer feed and the initiator feeds are started and dosed over 120 min. The monomer feed consists of 220.00 g styrene, 230.00 g n-butyl acrylate, 5.00 g butanediol diacrylate, 5.00 g acrylic acid, 25.00 g 2-hydroxyethyl acrylate and 15.00 g glycidyl methacrylate. The initiator system consists of 150.00 g of a 10% tert-butyl hydroperoxide solution and 1 14.00 g of a 10% Rongalit® C solution, which are added separately. At the end of monomer and initiator feeds 95.71 g of water are added and then polymerized for a further 55 min at 70 C. Subsequently, the feed of 50.00 g of a 10% tert-butyl hydroperoxide solution is metered in over 30 minutes and then 12.85 g of water are added and polymerization is continued for a further 90 minutes. Thereafter, the cooling to room temperature. In the cooling phase, 12.85 g of water are added.

The dispersion thus prepared has a solids content of 47.5%, an LD value of 62% (transmission of white light).

Table 1: Compositions of polymer dispersions D1 to D5

S: styrene; n-BA: n-butyl acrylate, GMA: glycidyl methacrylate; HEA: hydroxyethyl acrylate; AS: acrylic acid; BDDA: butanediol diacrylate; FG: solids content Formulation production:

60.0 g of the respective aqueous polymer dispersion were adjusted to a pH of 8.5 at room temperature by adding dimethylethanolamine with stirring (600 rpm) and diluted to 46% solids content by adding deionized water. Subsequently, the respective polymer dispersion was allowed to stir for a further 5 minutes at 600 rpm. Subsequently, the aqueous polymer dispersion obtained a total of 16.5 g Bayhydur ^® 305 (hydrophilic, aliphatic polyisocyanate based on hexamethylene nat (NCO content 16.2%) manufactured by Bayer Material Science) was used as a 80 wt .-% strength solu- solution in methoxypropyl acetate, wherein initially about 5 g of the polyisocyanate mixture was added with slight increase of the stirring speed to 500 rpm and then after 1 minute, the remaining remainder of the polyisocyanate mixture was added at a speed of 500 rpm. The paint formulation obtained in each case was then left to stir for 1 minute at 500 rpm and then 10.0 g of deionized water were added to the paint formulation with stirring at 600 rpm and stirring was continued for 1 minute at 600 rpm. In the following, the coating formulations obtained using the dispersions from Examples 1 to 3 are referred to as Formulations 1 to 3, and the coating formulations obtained using the dispersions from Comparative Examples 1 and 2 are called Comparative Formulations 1 and 2.

Immediately after their preparation, the resulting formulations or comparative formulations were applied to a ground walnut and pinewood (30 × 10 cm) using a 200 μm doctor blade and stored for 15 minutes under standard conditions (23 ° C., 50% relative humidity). Subsequently, the obtained coated wood panels were dried in a drying cabinet for 30 minutes at 60.degree. After cooling, the firing of the resulting coatings was determined.

Table 2: initiation value of the coating formulations obtained (1: poor, 5: very good)

It can be clearly seen from the results that the coating formulations according to the invention have markedly improved tempering in comparison to the corresponding comparative formulations.

Claims

claims

Two-component coating composition containing

(A) in a first component, an aqueous polymer dispersion containing a hydroxy-functional polymer, preparable by free-radically initiated emulsion polymerization of one or more ethylenically unsaturated, radically polymerizable monomers in the presence of lignosulfonate, and

(B) in a second component at least one crosslinker based on at least one polyisocyanate.

Two-component coating composition according to the preceding claim, characterized in that the polymer is at least 60% by weight of main monomers M1 which are selected from the group consisting of vinylaromatic compounds, conjugated aliphatic dienes, vinyl esters of saturated d- to C2- C ronsä acids, esters of acrylic acid or methacrylic acid with monohydric Cr to C 2o alcohols, aliphatic hydrocarbons having 2 to 8 C atoms and one or two double bonds or mixtures of these monomers.

Two-component coating composition according to one of the preceding claims, characterized in that the polymer is branched or crosslinked by copolymerization of at least one branching or crosslinking monomer M2 selected from monomers having at least two radically polymerizable, ethylenically unsaturated groups, preferably in an amount of 0.01 to 10 parts by weight, based on 100 parts by weight of monomers.

Two-component coating composition according to one of the preceding claims, characterized in that lignosulfonate in an amount of 1 to 100 parts by weight, preferably from 10 to 70 parts by weight per 100 parts by weight of monomers, based on the sum of all monomers is used ,

Two-component coating composition according to one of the preceding claims, characterized in that the polymer is composed of at least 60% by weight of alkyl (meth) acrylates having 1 to 20 carbon atoms in the alkyl group or mixtures thereof with styrene.

Two-component coating composition according to one of the preceding claims, characterized in that the polymer is composed of at least 0.1% by weight of one or more acid monomers M3 having at least one acid group and / or at least one auxiliary monomer M4 selected from the group consisting of monomers having at least a hydroxy group, monomers having at least one glycidyl group. ethylenically unsaturated carbonitriles, N, N-dialkylaminoalkylacrylic amides, N, N-dialkyl-aminoalkylmethacrylamiden, Ν, Ν-Dialkylaminoalkylacrylaten, N, N-dial kylaminoalkylmeth-acrylates.

7. Two-component coating composition according to the preceding claim, characterized in that the acid monomers are used to 0.1 to 5 parts by weight and are selected from acrylic acid and methacrylic acid or a mixture thereof and / or that the auxiliary monomers to 1 to 15 wt.% Are used and are selected from the group consisting of glycidyl (meth) acrylate and hydroxyalkyl (meth) acrylates. 8. Two-component coating composition according to one of the preceding claims, characterized in that the branching or crosslinking of the polymer is carried out by 0.01 to 5 parts by weight, based on 100 parts by weight of monomers, copolymerized alkanediol di (meth) acrylates. 9. Two-component coating composition according to one of the preceding claims, characterized in that the polymer has a glass transition temperature of 20 to 40 C.

Two-component coating composition according to one of the preceding claims, characterized in that the initiator used for the polymerization is a Red Ox initiator system and the polymerization takes place at a pH of preferably 4 to 6.

Two-component coating composition according to one of the preceding claims, characterized in that as monomers

0.1 to 5 parts by weight of at least one ethylenically unsaturated acid M3 and

0 to 20 parts by weight of at least one further, different from the monomers M1 and M3 monoethylenically unsaturated auxiliary monomers M4, together with

0.01 to 5 parts by weight, based on 100 parts by weight of monomers, copolymerizing, branching or crosslinking monomers M2, selected from monomers having at least two radically polymerizable, ethylenically unsaturated groups and from 1 to 100 parts by weight of lignosulfonate 100 parts by weight of monomers are used,

wherein the sum of the parts by weight of the monomers is 100.

12. Two-component coating composition according to one of the preceding claims, characterized in that as monomers

60 to 95 parts by weight of at least one main monomer M1 selected from styrene, C1 to C18 alkyl esters of acrylic acid and C1 to C18 alkyl esters of methacrylic acid and their mixture, 0.1 to 5 parts by weight of at least one ethylenically unsaturated acid M3 selected from acrylic acid and methacrylic acid and their mixture,

1 to 20 parts by weight of at least one auxiliary monomer M4 selected from the group consisting of glycidyl (meth) acrylate and hydroxyalkyl (meth) acrylates having 2 to 4 carbon atoms in the alkyl group, together with

from 1 to 100 parts by weight of lignosulfonate per 100 parts by weight of monomers are used,

wherein the sum of parts by weight of the monomers is 100

and wherein an ed-Ox initiator system is used as the initiator for the polymerization.

13. Two-component coating composition according to one of the preceding claims, characterized in that the crosslinker is a polyisocyanate obtainable by

Reaction of at least one monomeric isocyanate selected from the group consisting of isocyanurates, iminooxadiazinediones, biurets, uretdiones, urethanes and allophanates.

Two-component coating composition according to the preceding claim, characterized in that the monomeric isocyanate is selected from the group consisting of 1, 6-hexamethylene diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate, 4,4'- Di (isocyanatocyclohexyl) methane, 2,4'-di (isocyanatocyclohexyl) methane or mixtures thereof.

Two-component coating composition according to one of the preceding claims, characterized in that the molar ratio of isocyanate groups of the crosslinker to isocyanate-reactive groups of 1: 1 to 1, 5: 1. 16. Use of the two-component coating composition according to one of the preceding claims for wood coating, in particular as a clearcoat for wood coating.

17. With a two-component coating composition according to any one of claims 1 to 15 coated wood.