DE19912661A1 - Non-ionically stabilized powder coating dispersion - Google Patents

Abstract

The present invention relates to an aqueous powder clearcoat dispersion consisting of a solid, powdery component A and an aqueous component B, wherein DOLLAR A component A is a powder clearcoat containing DOLLAR A a) at least one epoxy-containing binder with a content of 25 to 45 wt .-%, preferably 25 to 35 wt .-%, of glycidyl-containing monomers, optionally containing vinyl aromatic compounds, preferably styrene, DOLLAR A b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids and / or carboxy-functional polyesters DOLLAR A and DOLLAR A c) optionally, catalysts, auxiliaries, additives typical of powder clearcoat such as degassing agents, leveling agents, UV absorbers, radical scavengers, antioxidants DOLLAR A and DOLLAR A component B is an aqueous dispersion comprising DOLLAR A a) at least one nonionic thickener and DOLLAR A b) if necessary Catalysts, auxiliaries, defoamers, wetting agents, antioxidants ntien, UV absorbers, radical scavengers, biocides, small amounts of solvents, leveling agents, neutralizing agents, preferably amines and / or water retention agents and DOLLAR A c) a dispersant in the form of a nonionic polyurethane dispersion.

Description

The present invention relates to a non-ionically stabilized Powder clearcoat dispersion, which can be used in particular as a coating for Water-based paint coated automobile bodies is suitable.

For the coating of automobile bodies today preferably liquid lacquers used. These cause numerous Environmental problems due to their solvent content. This also applies to the Cases of the use of water-based paints.

For this reason, efforts have increased in recent years undertaken to use powder coatings for the coating. However, the results have so far been unsatisfactory, particularly are increased layer thicknesses to achieve a uniform appearance required. On the other hand, the use of powdered Paint another application technology. The one for liquid paints designed systems can therefore not be used for this. Therefore one strives to powder coatings in the form of aqueous dispersions develop that can be processed with liquid coating technologies.

For example, a method is known from US Pat. No. 4,268,542 known, in which a powder coating slurry is used, which is suitable for Coating of automobiles is suitable. Here, first one conventional powder layer applied to the body and as second layer the clear lacquer slurry. With this clear lacquer slurry based on Acrylate resins use ionic thickeners. Furthermore, these point in one of the examples a content of 0.5 to 30% glycidyl-containing Monomers. In addition, with high baking temperatures (over 160 ° C) be worked.  

DE-OS 196 13 547 is an aqueous powder coating dispersion known that meets the above requirements. The one described there However, clear powder coating dispersion shows after application and Crosslinking as well as the previously known solid powder clearcoats low values regarding the resistance to etching against water, Resin and sulfuric acid. The system also shows one Tendency to yellowing.

From the unpublished German patent application 195 18 392.4 a powder clearcoat dispersion is known, which consists of two components is composed. The first component includes epoxy Binders, crosslinking agents as well as catalysts, auxiliaries and Additives. The second component is a non-ionic thickener that if necessary in a mixture with catalysts, auxiliary substances, defoaming agents, Wetting agents, antioxidants, UV adsorbers, radical scavengers, biocides, Solvents, leveling agents, neutralizing agents are present. As Dispersion aids are preferably carboxy-functional Dispersant used.

The previous powder clearcoats usually contain dispersing agents the basis of ionically stabilized polymers. These lead to in-wet application for cracks in the clear coat. Additional Difficulties are the sedimentation tendency and the pumpability of the Paint dispersion.

In the following, the term powder clear coat dispersion is used as a synonym for Powder clearcoat slurry used.

The present invention has now set itself the task of to provide aqueous powder clearcoat dispersion available with apply the previous liquid paint technology to automobile bodies can, especially at temperatures of 130 ° C is baked  and especially after the wet-on-wet application not to cracking in the Clear varnish leads.

This object is achieved by an aqueous powder clearcoat dispersion consisting of a solid, powdery component A and an aqueous component B, wherein
Component A. contains a powder clearcoat

• a) at least one epoxy binder containing 25 to 45%, preferably 30 to 35% of glycidyl-containing monomers, optionally with containing vinyl aromatic compounds, preferably styrene,
• b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids, carboxy-functional polyesters and / or Tris (alkoxycarbonylamino) triazine and
• c) if necessary. Catalysts, auxiliaries, additives typical for powder clearcoat, such as Degassing agents, leveling agents, UV absorbers, radical scavengers, Antioxidants and

Component B. contains an aqueous dispersion

• a) at least one non-ionic thickener and
• b) optionally catalysts, auxiliary substances, defoaming agents, Dispersion aids, wetting agents, antioxidants, UV absorbers, Free radical scavengers, small amounts of solvents, leveling agents, biocides and / or water retention agents,
• c) a dispersant in the form of a non-ionic Polyurethane dispersion.

The following quantitative ratios are preferred according to the invention:

Component A

• a) 60-80 parts
• b) 15-30 parts
• c) 3-10 parts

Component B

20-50 parts of component a
80-50 parts component b
20-50 parts of component c
1000-5000 parts of distilled water.

The dispersion preferably contains
25-100 parts of component A.
100 parts of component B.

As an epoxy functional binder for the solid powder clearcoat used for Production of the dispersion used are, for example Suitable polyacrylate resins containing epoxy groups, which by Copolymerization of at least one ethylenically unsaturated Monomer containing at least one epoxy group in the molecule with at least one other ethylenically unsaturated monomer, the contains no epoxy group in the molecule, can be produced, wherein at least one of the monomers is an ester of acrylic acid or Is methacrylic acid. Such epoxy group-containing polyacrylate resins are e.g. B. known from EP-A-299 420, DE-B-22 14 650, DE-B-27 49 576, US-A-4,091,048 and US-A-3,781,379).

As examples of ethylenically unsaturated monomers that do not Epoxy group contained in the molecule, alkyl esters of acrylic and Methacrylic acid, which contain 1 to 20 carbon atoms in the alkyl radical, especially methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate and Called 2-ethylhexyl methacrylate. More examples of ethylenic unsaturated monomers that do not contain epoxy groups in the molecule are, acid amides, such as. B. acrylic acid and methacrylic acid amide, vinyl aromatic compounds, such as styrene, methyl styrene and vinyl toluene, Nitriles, such as acrylonitrile and methacrylonitrile, vinyl and vinylidene halides, such as vinyl chloride and vinylidene fluoride, vinyl esters, such as. B. vinyl acetate and  monomers containing hydroxyl groups, such as. B. hydroxyethyl acrylate and Hydroxyethyl methacrylate.

The epoxy group-containing polyacrylate resin usually has an epoxy equivalent weight of 400 to 2500, preferably 420 to 700, a number average molecular weight (determined by gel permeation chromatography using a polystyrene standard) from 2000 to 20,000, preferably from 3000 to 10,000, and a glass transition temperature (T _G ) of 30 to 80, preferably from 40 to 70, particularly preferably from 40 to 60 ° C. (measured with the aid of differential scanning calometry (DSC). Very particularly preferred are approximately 50 ° C. Mixtures of two or more acrylate resins can also be used come.

The epoxy group-containing polyacrylate resin is generally good known methods can be prepared by polymerization.

Crosslinkers are carboxylic acids, especially saturated, straight-chain, Aliphatic dicarboxylic acids with 3 to 20 carbon atoms in the molecule are suitable. Dodecane-1,12-diacid is very particularly preferably used. For Modification of the properties of the finished powder clearcoats can possibly other crosslinkers containing carboxyl groups can also be used. Examples include saturated branched or unsaturated ones straight-chain di- and polycarboxylic acids as well as polymers with carboxyl called groups.

Tris (alkoxycarbonylamino) triazines according to U.S. Patent 4,939,213, U.S. Patent 5,084,541 and EP 0 624577 be used.

These are tris (alkoxycarbonylamino) triazines of the formula

where R = methyl, butyl, ethylhexyl groups. You can also Derivatives of the compounds mentioned are used.

The methyl, butyl mixed esters are preferred according to the invention. This have the advantage of the better than the pure methyl esters Solubility, in polymer melts and mixed butyl-ethylhexyl esters. The pure butyl esters are also preferred according to the invention.

The tris (alkoxycarbonylamino) triazines and their derivatives can according to the invention also in a mixture with conventional Crosslinking agents are used (component C). Come here especially different from the tris (alkoxycarbonylamino) triazines blocked polyisocyanates into consideration.

Likewise, aminoplast resins are e.g. B. melamine, can be used. In principle can any aminoplast resin suitable for transparent top coats or one Mixture of such aminoplast resins can be used.

All of the crosslinkers mentioned can be used individually or in any Find combinations with each other.  

Powder clearcoats which have an epoxy-functional coating are also suitable Crosslinker and an acid functional binder included.

Examples of acidic binders are acidic ones Suitable polyacrylate resins by copolymerization of at least an ethylenically unsaturated monomer containing at least one Contains acid group in the molecule, with at least one other ethylenically unsaturated monomer that has no acid group in the molecule contains, can be produced.

The epoxy group-containing binder or the epoxy group-containing binder Crosslinkers and the carboxyl or binder are usually used used in an amount such that 0.5 per epoxide group equivalent to 1.5, preferably 0.75 to 1.25 equivalents of carboxyl groups available. The amount of carboxyl groups present can be determined by Titra tion with an alcoholic KOH solution.

According to the invention, the binder contains vinyl aromatic compounds, especially styrene. To limit the risk of cracking, lies however, the content does not exceed 35% by weight. 10 to 10 are preferred 25% by weight.

The solid powder coatings may contain one or more suitable ones Catalysts for epoxy curing. Suitable catalysts are phosphonium salts of organic or inorganic acids, quaternary ammonium compounds amines, imidazole and Imidazole derivatives. The catalysts are generally in proportions from 0.001% to about 2% by weight based on the total weight the epoxy resin and the crosslinking agent.

Examples of suitable phosphonium catalysts are Ethyltriphenylphosphonium iodide, ethyltriphenylphosphonium chloride, Ethyltriphenylphosphonium thiocyanate, ethyltriphenylphosphonium acetate-Es acetic acid complex, tetrabutylphosphonium iodide, tetrabutylphos  phonium bromide and tetrabutylphosphonium acetate-acetic acid complex. These and other suitable phosphonium catalysts are e.g. B. described in U.S. Patent 3,477,990 and U.S. Patent 3,341,580.

Suitable imidazole catalysts are, for example, 2-styrylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole and 2-butylimidazole. This and other imidazole catalysts are e.g. B. described in the Belgian Patent No. 756,693.

In addition, the solid powder coating materials can, if necessary, also assistants and Contain additives. Examples of these are leveling agents, antioxidants, UV absorbers, radical scavengers, trickle aids and degassing agents, such as for example benzoin.

Leveling agents based on polyacrylates are suitable, Polysiloxanes or fluorine compounds.

Antioxidants that can be used are reducing agents such as hydrazienes and Phosphorus compounds and radical scavengers such. B. 2.6 di-tert-butylphenol-De derivatives.

UV adsorbers that can be used are preferably triazines and benzotriphenol.

2,2,6,6-Tetramethylpiperdine derivatives are preferred as radical scavengers applicable.

In addition, the solid powder coating materials can, if necessary, also assistants and Contain additives. Examples of these are leveling agents, antioxidants, UV absorbers, radical scavengers, trickle aids and degassing agents, such as for example benzoin.

Component B contains a non-ionic thickener a). Examples modified celluloses, polyurethane thickeners.  

Structural features of such associative thickeners a) are:

• aa) a hydrophilic framework that has sufficient water solubility ensures and
• ab) hydrophobic groups leading to an associative interaction are capable in the aqueous medium.

Long-chain alkyl radicals, for example, such as B. dodecyl, hexadecyl or octadecyl radicals, or alkaryl radicals, such as B. octylphenyl or nonylphenyl radicals are used.

Polyacrylates and cellulose ethers are preferably used as hydrophilic frameworks or particularly preferably used polyurethanes which are hydrophobic Contain groups as polymer building blocks.

Particularly preferred as hydrophilic frameworks are polyurethanes which Contain polyether chains as building blocks, preferably from Polyethylene oxide.

In the synthesis of such polyether polyurethanes, the di- and or serve Polyisocyanates, especially aliphatic diisocyanates, especially preferably optionally alkyl-substituted 1,6-hexamethylene diisocyanate, for Linking of the hydroxyl-terminated polyether units with each other and to link the polyether building blocks with the hydrophobic end group building blocks, for example monofunctional Alcohols and / or amines with the long-chain already mentioned Alkyl radicals or aralkyl radicals can be.

As is known, the non-ionic associative thickeners are due to the Design their hydrophobic groups so that they both Hydrophobic / hydrophobic interactions to those in the powder coating dis persion contained solid particles as well as with each other can. This creates a three-dimensional network and controls. Furthermore, the associative thickeners have to be so high Have content of hydrophilic groups that they are homogeneous in Distribute water and no phase separation to the water occurs. Examples of suitable non-ionic associative thickeners and their  Mechanism of action are described in detail in the textbook "Lackadditive" by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998 described.

Component B can also contain catalysts, leveling agents, Contain antioxidants, UV absorbers, radical scavengers and wetting agents. in the the most important here are those already listed for component A. Substances into consideration.

Component B can also contain auxiliaries, defoamers, Biocides, solvents and neutralizing agents can be added.

Modified polysiloxanes are preferred as defoaming agents Consideration.

Neutralizers that can be used are amines, ammonia and Metal hydroxides.

Finally, the addition of the dispersants c) is essential to the invention. These are compounds based on polyurethanes.

The nonionic dispersants c) essential to the invention in the form of a polyurethane dispersion differ from the nonionic associative thickeners in two ways:

• 1. The hydrophobic groups of the dispersants c) are designed that preferred hydrophobic / hydrophobic contacts to those in the Particles containing powder coating dispersion are formed, so that no three-dimensional network is created, as it is for the Associative thickener is typical.
• 2. The hydrophilicity is reduced. There are only so many hydrophilic groups contained in the dispersant c) that the particles of the hydrophilic structural elements are encased and shielded. The The effect of hydrophilic structural elements is not so strong that they detach the hydrophobic structural elements from the particles and  can introduce into the aqueous phase. It expresses itself clearly comparatively low hydrophilicity through the formation of a second phase in water by the dispersant as such.

The polyurethane resins c) used according to the invention preferably consist of

• 1. at least one organic component with at least two reactive Hydrogen atoms,
• 2. a monofunctional ether and
• 3. a polyisocyanate.

The organic component of the polyurethane composition c) comprises a polyester polyol, a low molecular weight diol and / or triol or Mixtures of these. If necessary. can be a trifunctional hydroxyl group containing monomer can be used.

In a second preferred embodiment, the polyurethane comprises c)

• 1. at least one organic component with at least two reactive Hydrogen atoms,
• 2. a non-ionic stabilizer, ie a non-ionic dispersant c) which is produced by reaction
  • i. a monofunctional polyether with a component containing polyisocyanate to produce an isocyanate intermediate and
  • ii. a component with at least one active amine and at least two active hydroxyl groups and
• 3. at least one component containing polyisocyanate.

The organic component preferably comprises Polyether polyester polyol, a low molecular weight diol and / or triol or Mixtures of these.  

The polyester component can be produced by reaction at least one dicarboxylic acid and at least one Alcohol component, the alcohol having at least two hydroxyl groups contains. The carboxylic acid component contains two or more Carboxyl groups. Examples of suitable dicarboxylic acids are Dimer fatty acids and cycloaliphatic dicarboxylic acids such as Isophthalic acid.

In addition to the carboxylic acids, the polyester resin can also be a or contain more low molecular weight diols or triols. Can be used basically any polyol.

The polyester resins used or mixtures of the polyester resins preferably contain terminal hydroxyl groups. This is accomplished by adding an excess of polyols.

Both monocarboxylic acids and Mono alcohols can be used. Preferably, the Monocarboxylic acids and / or mono alcohols, however, in a very low Weight amount contained in the polyester resin.

The polyester diol components preferably used include between 20 and 80% by weight of the polyurethane resin. Preferably lie the amounts between 50 and 70 wt .-%. Very particularly preferred become 55 to 65 wt .-%.

To produce the polyurethane c), polyester polyols are used with a Molecular weight between 500 and 5000 used. To be favoured Molecular weights between 1000 and 3500.

In addition to the polyester diols, the polyurethane resins can also be used organic components with at least two reactive Contain hydrogen atoms. This is preferably Diols and triols, thiols and / or amines or mixtures of these substances. The  Components used to synthesize the polyester component can also be used as separate components here come. That is, as an additional organic component in the Polyurethane also come di- or trial alcohols, such as. B. Neopentyl glycol or 1,6-hexanediol or trimethylolpropane.

The molecular weight of the diols and / or triols used in the Polyurethane resin is between 0 and 20% by weight. 1 to are preferred 6% by weight.

The polyurethane resin also contains polyisocyanates, in particular Diisocyanates. The isocyanates are between 5 and 40% by weight on the polyurethane mass. 10 to 30% by weight are particularly preferred and especially 10 to 20% by weight. To make the Finally, a monofunctional polyether is used in polyurethane.

In a second variant, a non-ionic stabilizer c) prepared in which preferably a monofunctional polyether a diisocyanate is reacted. The resulting The reaction product is then reacted with a component that at least one active amine group and at least two active Contains hydroxyl groups.

In a particular embodiment, the polyurethane c) comprises a reaction product of:

• 1. A polyester polyol, which in turn is a reaction product of a carboxylic acid with at least two carboxyl groups and a component
  at least two hydroxyl groups,
• 2. at least one low molecular weight component with at least two Hydroxyl groups,
• 3. at least one polyisocyanate-containing component,
• 4. a non-ionic stabilizer, prepared by reacting a monofunctional ether with a polyisocyanate and then reacting the reaction product obtained with a component which
  contains at least one active amine and at least two active hydroxyl groups.

In a fourth variant, the polyurethane c) comprises a reaction product

• 1. a polyester polyol,
• 2. at least one low molecular weight diol or triol,
• 3. a polyisocyanate,
• 4. a monomer containing trihydroxy groups,
• 5. a monofunctional hydroxy group-containing polyether.

The polyesters are synthesized with those described above Carboxylic acid components and an excess of polyols. Of the Excess polyols are chosen so that preferably terminal Hydroxyl groups are formed. The polyols preferably have one Hydroxyl functionality of at least two.

The polyester resin preferably consists of one or more Polyols, preferably from a diol. Diols preferably used are alkylene glycols, such as ethylene glycol, propylene glycol, butylene glycol and Neopentyl glycol, 1,6-hexanediol or other glycols, such as bisphenol-A, Cyclohexanedimethanol, caprolactone diol, hydroxyalkylated bisphenol and similar connections.

The low molecular weight diols preferably used according to the invention are known from the prior art. These include aliphatic Diols, preferably alkylene polyols with 2 to 18 carbon atoms. Examples include 1,4-butanediol, cycloaliphatic diols, such as 1,2-cyclohexanediol and cyclohexanedimethanol.  

According to the invention, organic polyisocyanates are preferred those that include at least two isocyanate groups. In particular, the isocyanates are preferred, e.g. B. p-phenylene diisocyanates, biphenyl 4,4'-diisocyanates, toluene diisocyanates, 3,3'-dimethyl-4,4-biphenylene diisocyanates, 1,4-tetra methylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-tri methylhexane-1,6-diisocyanate, methylene bis (phenyl isocyanate), 1,5-naphth thalenediisocyanates, bis (isocyanatoethyl fumarate), Isophorone diisocyanates and methylene bis (4-cyclohexyl isocyanates).

In addition to the diisocyanates mentioned, others multifunctional isocyanates used. Examples are 1,2,4 Benzene triisocyanates and polymethylene polyphenyl isocyanates.

The use of aliphatic diisocyanates, e.g. B. 1,6-hexamethylene diisocyanate, 1,4-butylene diisocyanate, methylene-bis- (4-cy clohexyl isocyanate), isophorone diisocyanate and 2,4-toluenediisocyanate.

Longer-chain polyurethane resins c) can be obtained by Chain extension with diol and / or triol groups Components. Chain extenders are particularly preferred with at least two active hydrogen groups, e.g. B. diols, thiols, Diamines or mixtures of these substances, e.g. B. alkanolamines, Aminoalkyl mercaptans, hydroxyalkyl mercaptans and the like Links.

Examples of diols used as chain extenders are 1,6-hexanediol, cyclohexanedimethylol and 1,4-butanediol. A special one preferred diol is neopentyl glycol.

The polyethers used according to the invention are preferably mo no- or difunctional polyethers. The monofunctional include for example those produced by the polymerization of Ethylene oxides; Propylene oxides or mixtures thereof. An example for  a suitable polyether is methoxypolyethylene glycol which is under the Brand name Carbowax® MPEG 2000 from Union Carbide Chemicals.

The described polyurethane product c) can with conventional Crosslinkers are mixed. These preferably include Aminoplast resins, e.g. B. Melamine. Likewise, condensation products other amines and amides are used, for. B. aldehyde condensates of triazines, diazines, triazoles, guanidines, guanamines or alkyl and aryl-substituted derivatives of such components. An example such components are N, N'-dimethylurea, dicyandiamides, 2-chloro-4,6-diamino-1,3,5-triazines, 6-methyl-2,4-diamino-, 1,3,5-triazines, 3,5-diamino-triazoles, triaminopyrimidines, 2-mercapto-4,6-di aminopyrimidines, 2,4,6-triethyltriamino-1,3,5-triazines and the like Fabrics.

Formaldehydes are preferred as aldehyde. As well can acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, furfural are used.

The amine-aldehyde condensation products can be methylol or the like Contain alcohol groups. Examples of alcohols that can be used are Methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, Benzyl alcohol and aromatic alcohols, cyclic alcohols, such as Cyclohexanol, monoethers or glycols and substituted alcohols, e.g. B. 3-chloropropanol.

In addition to the isocyanates mentioned, the invention may also blocked polyisocyanates are used as crosslinking agents. These include, for example, organic polyisocyanates such as trimethylene, Tetramethylene, hexamethylene, 1,2-propylene, 1,2-butylene and 2,3-butylene diisocyanates. Cycloalkene components can also be used such as 1,3-cyclopentane, 1,4-cyclohexane and 1,2-cyclohexane diisocyanates. Aromatic components such as phenylene, p-phenylene,  4,4'-diphenyl, 1,5-naphthalene and 1,4-naphthalene diisocyanates can be used. In addition, there are aliphatic-aromatic components such as 4,4'-diphenylene methane, 2,4- or 2,6-tolylene or mixtures thereof, 4,4'-toluidine and 1,4 xylylene diisocyanates. Other examples are core-substituted aromatic components such as 4,4'- Diphenyl ether diisocyanates and chlorodiphenylene diisocyanates. Applicable Triisocyanates are triphenylmethane 4,4 ', 4' 'triisocyanates, 1,3,5-triisocyanate benzene and 2,4,6-triisocyanate toluene. Usable Finally, tetraisocyanates are 4,4'-diphenyl-dimethylmethane, 2,2'-, 5,5'-tetraisocyanates.

Aliphatic, cycloaliphatic aromatic Alkyl mono alcohols are used. These include, for example Methyl, ethyl, chloroethyl, propyl, butyl, cyclohexyl, heptyl, octyl, Nonyl 3,3,5-trimethylhexanol, decyl and lauryl alcohols. As phenolic components are e.g. B. phenols or substituted phenols usable. Examples include cresol, xylenol, nitrophesol, Chlorophenol, ethylphenol, 1-butylphenol and 2,5-di-t-butyl-4-Hy droxytoluene.

Other suitable blocking agents are tertiary hydroxylamines, e.g. B. Diethylethanolamine and oximes such as methyl ethyl ketone oxime, acetone oxime and cyclohexanone oxime.

The crosslinking agents described are in the polyurethane dispersion c) in amounts of 2 to 15% by weight, preferably 4 to 8% by weight available.

The polyurethane dispersion c) obtained is in the powder slurry with a A proportion of 0.5 to 20% by weight, preferably 2 to 15% by weight, is present.

The solid powder coatings are produced by known methods (see e.g. product information from BASF Lacke + Farben AG, "Powder coatings", 1990) by homogenization and dispersion,  for example by means of an extruder, screw kneader and. After The powder coatings are produced by grinding and, if necessary, prepared for dispersion by sieving and screening.

The powder can then be ground by wet grinding or by Stir in dry ground powder coating the aqueous Powder clearcoat dispersion can be produced. Is particularly preferred wet grinding.

The present invention accordingly also relates to a method for Production of an aqueous powder coating dispersion based on the Component A described according to the invention in the component B is dispersed.

After component A has been dispersed in component B, ground, the pH to 4.0 to 7.0, preferably 5.5 to 6.5 adjusted and filtered.

The average grain size is between 1 and 25 µm, preferably below 20 µm. Particularly preferred at 3 to 10 microns. The solids content of the aqueous powder clearcoat dispersion is between 15 and 50%.

The dispersion can before or after wet grinding or Entering the dry powder coating in the water 0 to 5 wt .-% of a Defoamer mixture, an ammonium and / or alkali salt, one carboxyl-functional or nonionic dispersing aid, Wetting agent and / or thickener mixture and the other additives be added. According to the invention, defoamers, Dispersing aids, wetting agents and / or thickeners first in water dispersed. Then small portions of the powder clear coat stirred in. Then defoamers, dispersers auxiliaries, thickeners and wetting agents dispersed. In conclusion again mixed in small portions of powder clearcoat.  

According to the invention, the pH is preferably set using Ammonia or amines. The pH value can initially rise, that a strongly basic dispersion is formed. However, the pH drops within several hours or days back to the above Values.

Another variant for the production of the invention Powder clearcoat dispersion is that a liquid melt Binder and injured person and possibly the additives c) of the component A mixed, in an emulsifying device, preferably with the addition of Given water and stabilizers, the emulsion obtained cooled and filtered.

In order to achieve a high mixing quality, it is essential that Perform the solvent-free mixture in the melt. Accordingly the polymeric components are melted into the viscous resin Dispersing units fed.

For this purpose, binders and crosslinkers have to be melted. The Ratio of crosslinkers to binders is 0.6 to 1: 1.4, preferred 0.8: 1 to 1: 1.2. Crosslinkers and binders are preferably used in separate containers heated. The temperature is selected so that both components are melted and their viscosity is one further processing, especially funding allowed. The higher the Temperature of the melt, the lower the viscosity, and the more better mixing qualities can be achieved. However, largely one Crosslinking reaction can be excluded. The crosslinking reaction runs much faster at higher temperatures. Therefore there is only a narrow temperature-time window in which the available Residence time until cooling is sufficiently long, and at the same time one good emulsification is possible. To use this as efficiently as possible, the binder and crosslinker melt are only immediately before Mixing zone merged.  

Before the components are conveyed through the system, this can be done preferably heated to the desired process temperature with steam become. The molten binder additive Mi and the crosslinker melt in preferably separate, heated feed lines with pumps conveyed through the entire system and dosed into a mixer. About the volume flow of the feed pumps a stoichiometric ratio of Adjust binder / additive mixture and crosslinker melt.

The liquid mixture is then immediately emulsified in water. The organic phase and / or the water becomes an emulsifier added. If used, an aqueous emulsifier / stabilizer tor solution is pressurized to a temperature near the Mixing temperature warmed and in it the liquid binder Ver emulsified.

Mixing and emulsification can be done in two separate or in one multi-stage, machine can be realized. The second solution is over Networking reasons clear advantages, since here the dwell time with the high temperatures is minimized. Possibly. available organic Solvent can subsequently be added directly by vacuum distillation low temperatures are separated from the aqueous phase.

After the emulsification, cooling is carried out immediately. This must be implemented in such a way that, on the one hand, the disperse resin particles occurs, on the other hand the residence time up to Time at which no crosslinking reaction can take place is as short as possible. This goal can e.g. B. by using a Heat exchanger, cooling by injecting cold water or can be achieved by spraying the emulsion into cold water.

To crosslinking reactions during the mixing, emulsifying and To rule out the cooling phase, the dwell time from the beginning of the mixture  be kept as short as possible until the end of the cooling phase. This is less than 5 s, preferably less than 1 s. Therefore continuous process preferred. Machines like Ro Tor stator dispersers (tooth colloid or wet rotor mills, Sprocket dispersing machines, intensive mixers) and static Mixer used.

For subsequent emulsification in water, the binder Crosslinker mixture are sprayed into water or component B. If sufficient fineness is not achieved, Ro tor stator units or static mixers can be used. Another Increase in local performance is through the above described use of a high pressure homogenizer possible. Here the emulsion at pressures in the range of 100-1500 bar, preferably 100 to 1000 bar, particularly 100 to 200 bar, by fine Openings pressed, resulting in a significant reduction in Droplet size and thus greater stability of the emulsion leads during storage.

The presented micronization variants lead to solvent-free Dispersions with average particle sizes in the range of 100 10,000, preferably 150 to 6000, particularly preferably 400 to 4000, most preferably 600-3500 nm and are therefore even finer than that by wet grinding of powder coatings according to the prior art producible aqueous dispersions (particle size 3-20 microns).

With the written procedure can be finely divided Produce polymer dispersions that have molecular weights in the range from 1000 to 20,000, preferably 1000 to 10,000, particularly preferred 1500 to 6000, most preferably 1500 to 4000 g / mol.

The powder clearcoat dispersion according to the invention can be used as a coating basecoats, preferably used in the automotive industry.  

The clearcoat dispersion is particularly suitable for waterborne basecoats Basis of a polyester, polyurethane resin and an aminoplast resin.

The powder clearcoat dispersions of the invention can be with the Apply methods known from liquid coating technology. In particular, they can be applied by spraying.

The powder clearcoat dispersions applied to the basecoat layer are flashed off regularly before baking. this happens expediently first at room temperature and then at slightly elevated temperature. As a rule, the elevated temperature is 40 to 70 ° C, preferably 50 to 65 ° C. Flash off for 2 to 10 Minutes, preferably 4 to 8 minutes at room temperature. At an elevated temperature, the temperature will rise again during the same period vented.

The baking can be carried out at temperatures of 130 ° C become. Baking is possible at 130 to 180 ° C, preferably 135 to 155 ° C.

With the method according to the invention, layer thicknesses of 30 to 50, preferably 35 to 45 microns can be achieved. Clear coats with comparable quality has so far been possible according to the state of the art Use of powder clearcoats only by applying layer thicknesses of 65 up to 80 µm can be achieved.

The invention will now be described with reference to the examples described in more detail:

A. Preparation of the powdered resin

21.1 T xylene are introduced and heated to 130 ° C. At the template are at
130 ° C within 4 h via two separate feed tanks Initiator: 4.5 T TBPEH (tert-butyl perethyl hexanoate) mixed with 4.86 T xylene and monomers:
10.78 T methyl methacrylate, 26.5 T n-butyl methacrylate, 17.39 T styrene and 22.95 T.
Glycidyl methacrylate added. The mixture is then heated to 180 ° C and in
Vacuum <100 mbar the solvent removed.

B. Preparation of the powder clearcoat

77.5 T acrylic resin, 18.8 T dodecanedioic acid (see hardener), 2 T Tinuvin 1130
(UV absorber), 0.9 T Tinuvin 144 (HALS), 0.4 T Additol XL 490 (leveling agent) and
0.4 T benzoin (degassing agent) are mixed intimately on a Henschel fluid
mixed, extruded on a BUSS PLK 46 extruder, on a Hosohawa
Grind the ACM 2 mill and sieve it through a 125 µm sieve.

C. Non-ionically stabilized powder slurry 1. Manufacturer example 1.1 Production of a polyester output stage

40.71 parts by weight of Pripol 1013 (commercially available dimer fatty acid from the company Unichema), 22.413 parts by weight of hexanediol, 12.051 parts by weight Isophthalic acid is slowly reduced to max. 220 ° C heated until the acid number is less than 4. Then the product is brought to 80 ° C cooled and diluted with 24.025 parts by weight of methyl ethyl ketone.  

1.2 Preparation of the non-ionic polyurethane dispersion c)

29.155 parts by weight of the polyester output stage are in one Submitted reactor and with 4,667 parts by weight of Carbowax MPEG 2000, 0.422 parts by weight of trimethylolpropane and 5.195 parts by weight Isophorone diisocyanate and 0.031 parts by weight of dibutyltin laurate. The reaction mixture is heated to 90 ° C until the NCO content in Range is 0.50-0.70%. Then 0.367 wt. Parts of neopentyl glycol and 0.281 parts by weight of trimethylolpropane added. If the NCO value is less than 0.25%, 13.912 Parts by weight of butyl glycol are added at a reactor temperature of 90 ° C. 45.97 parts by weight of delonized water are then added one hour at 70-90 ° C with vigorous stirring the reactor added, whereby the non-ionic polyurethane dispersion c) results.

2nd embodiment

670 g water, 30 g non-ionic polyurethane dispersion according to Manufacturer example 1.2, 300 g powdered resin, 1.9 g anti-foaming agent Troykyd D777 from Troy Chemical Co., 26.3 g urethane thickener Acrysol RM8 from Rohm and Haas were in this order weighed in with stirring and then 10 min. dissolves (20 m / sec). This approach was then carried out in a laboratory sand mill SMC dispersed with grinding media for approx. 3 1/2 hours. The middle Particle size after grinding was 4 µm.

The ground material was mixed with 0.5% Byk 345 (leveling agent containing silicone), 10% aqueous DMEA solution to set a pH of 6.0 and adjusted to spray viscosity with water (300 mPa.s at 1000 s ^-1 ).

3. Comparative example

670 g of water, 1.9 g of Orothan 731 K dispersant from Rohm and Haas, 0.19 g Triton 100 from Rohm and Haas, 300 g powdered Resin, 1.9 g of Troykyd D777 antifoam from Troy Chemical Co., 26.3 g of Acrysol RM8 urethane thickener from Rohm and Haas weighed in this order with stirring and then 10 min. dissolves (20 m / sec.). This approach was then carried out in a Laboratory sand mill SMC dispersed with grinding media for approx. 3 1/2 hours. The average particle size after grinding was 5 µm.

The ground material was mixed with 0.5 Byk 345 (silicone-containing leveling agent), 10% aqueous DMEA solution to adjust a pH of 6.0 and adjusted to spray viscosity with water (300 mPa.s at 1000 s ^-1 ) .

D. Application of Examples C2 and C3 (Comparative Example)

The silver metallic WBL was placed on a filled bonder sheet (Würzburg system, PAT EP 0 228 003 B2 or DE 38 25 278 and Subsequent patents) applied in a layer thickness of 12 µm dry film, 10 min. at RT, 10 min. dried at 80 ° C. After that it got wet in wet the powder slurry in a layer thickness of 40 to 50 µm dry film applied and 10 min. flashed off at RT, 6 min. predried at 50 ° C and then 30 min. Baked at 145 ° C.  

The clear lacquer film from the exemplary embodiment C2. Is characterized by a significantly lower tendency to crack formation. The semi-finished product (Regrind) and the wet paint have a lower Sedimentation tendency as the wet paints of comparative example C3. Furthermore, the regrind is better temperature resistant and more shear stable.

Claims (10)

1. Aqueous powder clearcoat dispersion consisting of a solid, powdery component A and an aqueous component B, wherein
Component A. contains a powder clearcoat

• a) at least one epoxy-containing binder with a content of 25 to 45% by weight, preferably 30 to 35% by weight, of glycidyl-containing monomers, optionally with a content of vinyl aromatic compounds,
  preferably styrene,
• b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids and / or carboxy-functional polyesters and
• c) if necessary. Catalysts, auxiliaries, additives typical of powder clearcoat such as
  Degassing agents, leveling agents, UV absorbers, radical scavengers, antioxidants and

Component B. contains an aqueous dispersion

• a) at least one non-ionic thickener and
• b) If necessary, catalysts, auxiliary substances, defoaming agents, wetting agents, antioxidants, UV absorbers, radical scavengers, biocides, small amounts
  Solvents, leveling agents, neutralizing agents, preferably amines
  and / or water retention agent and
• c) a dispersant in the form of a non-ionic polyurethane dispersion.

2. Aqueous powder clearcoat dispersion according to claim 1, characterized in that their pH is between 4.0-7.0, preferably 5.5 and 6.5. 3. Aqueous powder clearcoat dispersion according to claim 1 or 2, characterized in that their content of vinyl aromatic compounds at most 35, preferably 10-25 % By weight is based on component Aa). 4. Aqueous powder clearcoat dispersion according to one of claims 1-3, characterized in that the epoxy functional Binders are epoxy group-containing polyacrylate resins, the epoxy-functional monomers used, preferably Glycidyl acrylate, glycidyl methacrylate and allyl glycidyl esters. 5. Aqueous powder clearcoat dispersion according to one of claims 1-4, characterized in that the grain size is at most 20 µm, preferably 3 to 10 µm. 6. Aqueous powder clearcoat dispersion according to one of claims 1-5, characterized in that the non-ionic polyurethane dispersion c) contains:

• 1. at least one organic component with at least two reactive hydrogen atoms,
• 2. a monofunctional polyether and
• 3. a polyisocyanate.

7. Aqueous powder clearcoat dispersion according to one of claims 1-5, characterized in that the non-ionic polyurethane dispersion c)

• 1. at least one organic component with at least two reactive hydrogen atoms,
• 2. a non-ionic stabilizer made by reaction
  • i. a monofunctional polyether with a polyisocyanate-containing component for the production of an isocyanate intermediate and
  • ii. a component with at least two active amino groups and at least two active hydroxyl groups and
• 3. at least one polyisocyanate-containing component.

8. A process for the preparation of the aqueous powder clearcoat dispersion according to any one of claims 1-7, characterized in that

• I. a dispersion is prepared from a solid, powdery component A and an aqueous component B, component A containing a clear powder coating
  • a) at least one epoxy-containing binder with a content of 25 to 45% by weight, preferably 30 to 35% by weight, of glycidyl-containing monomers, optionally with a content of vinyl aromatic compounds, preferably styrene,
  • b) at least one crosslinking agent, preferably straight-chain, aliphatic dicarboxylic acids and / or carboxy-functional polyesters and
  • c) if necessary. Catalysts, auxiliaries, additives typical of powder clearcoat such as degassing agents, leveling agents, UV absorbers, radical scavengers, antioxidants and
  Component B. contains an aqueous dispersion
  • a) at least one non-ionic thickener and
  • b) if necessary. Catalysts, auxiliaries, defoamers, dispersion auxiliaries, wetting agents, preferably carboxy-functional dispersants, antioxidants, UV absorbers, leveling agents, neutralizing agents, preferably amines, radical scavengers, small amounts of solvents, biocides and / or water retention agents and
  • c) a dispersant in the form of a non-ionic polyurethane dispersion,
    • II. The dispersion produced from components A and B is possibly ground,
    • III. the pH of the dispersion is adjusted to 4.0 to 7.0, preferably 5.5 to 6.5 and filtered.

9. The method according to claim 8, characterized in that the aqueous Powder clear lacquer dispersion from components A and B. Wet grinding is produced. 10. Use of the aqueous powder clearcoat dispersion according to one of the Claims 1 to 7 for coating painted and not painted automobile bodies made of sheet metal and / or plastic  by means of electrostatically assisted high rotation or pneumatic Application.