DE102008061329A1 - Use of 1,3-substituted imidazolium to catalyze the unblocking of blocked isocyanates in coating composition, preferably electrodeposition coating, coil coating, wire coatings and automobile coating - Google Patents

Abstract

Use of 1,3-substituted imidazolium salts (I) to catalyze the unblocking of blocked isocyanates, is claimed. Use of 1,3-substituted imidazolium salts of formula (I) to catalyze the unblocking of blocked isocyanates, is claimed. R 1>, R 3>1-20C organic residue; either R 2>, R 4>, R 5>H or 1-20C organic residue; or R 4>+ R 5>aliphatic or aromatic ring; X : n-valent organic or inorganic anion; and n : 1-3. Independent claims are included for: (1) a coating composition comprising at least a blocked polyisocyanate, at least one oligomer or polymer having at least two isocyanate-reactive groups and (I); and (2) producing a coating comprising applying the coating composition on an uncoated or coated substrate and curing the coating at 100-300[deg] C. [Image].

Description

The This invention relates to the use of 1,3-substituted imidazolium salts for the catalytic deblocking of blocked isocyanates and coating compositions containing blocked isocyanates and the inventive 1,3-substituted imidazolium salts. The invention also relates a coating method using the invention Imidazolium.

The Coating compositions of blocked polyisocyanates containing hydroxyl groups Polycondensates or polymers (polyesters or polyacrylates) in the form of one-component stoving lacquers (1K lacquers) is stationary of the technique.

It is also known that alcohols with isocyanates to the thermally Abreact very stable urethane group. On the other hand, this means alcohol-blocked isocyanates have very high baking temperatures need to regenerate the isocyanate. Very high stoving temperatures are used, for example, in the coil coating and the cathodic electrodeposition coating (KTL). In these applications are often aromatic polyisocyanates, used with alcohols are blocked.

Exemplary of KTL paints with an alcohol blockage of the isocyanate crosslinkers can, for. For example, the following patent applications are mentioned: EP-A 0 677 539 and WO 96/12771 ,

For the coil coating process are alcohol-blocked isocyanates, for example, from WO 01/060886 A1 known. As deblocking catalysts are used in the WO 01/060886 A1 tetravalent organic tin compounds used. Examples of these are preferably dibutyltin dilaurate (DBTL), dibutyltin diacetate, dibutyltin maleate or tetrabutylstannoxane diacetate. These tin catalysts are mixed with a coil coating varnish with the blocked isocyanate in an amount of 1.2 to 4.0% by weight based on the solid content of the binder, ie, the blocked isocyanate and the hydroxyl group-containing resin.

Also when baking electrocoating, such tin catalysts used.

Of the Use of tin-containing catalysts in coating compositions is due to the many tin compounds inherent toxicity also to avoid in coating compositions. From the "Working Group to Classification and Labeling "of the European Commission were dibutyltin oxide (DBTO) and dibutyltin dilaurate (DBTL) corresponding categorized.

The US 2007/0023288 A1 describes the use of free imidazoles of different substitution pattern, in particular imidazoles without 1,3-disubstitution, as curing catalysts in electrodeposition paints.

The WO 2006/022899 A2 relates to a process for deblocking blocked isocyanates such as ketoxime, pyrazole or phenol blocked isocyanates to produce crosslinked coating agents. In this case, zinc (II) complexes with substituted amidines, inter alia substituted imidazoles used, wherein the imidazoles have no 1,3-substitution pattern and as such are not salted. Coating compositions containing blocked isocyanates include powder coatings, electrodeposition paints, coil coating paints, wire enamels, automotive clearcoats and antistonechip primers.

Across from In the prior art, the task turned tin-containing or at all metal-containing, in particular heavy metal-containing catalysts such For example, zinc-containing catalysts for the catalysis of Deblocking blocked polyisocyanates to avoid or at best to be able to give it up altogether.

worin
R¹ und R³ unabhängig voneinander für einen organischen Rest mit 1 bis 20 Kohlenstoffatomen stehen,
R², R⁴, und R⁵ unabhängig voneinander für ein Wasserstoffatom oder für einen organischen Rest mit 1 bis 20 Kohlenstoffatomen, insbesondere 1 bis 10 Kohlenstoffatomen, stehen, wobei R⁴ und R⁵ auch zusammen einen aliphatischen oder aromatischen Ring ausbilden können,
X für ein organisches oder anorganisches Anion steht, und n für 1, 2 oder 3 steht, zur Katalyse der Deblockierung blockierter Isocyanate, insbesondere in Beschichtungsmittelzusammensetzungen, eignen.Surprisingly, it has been found that 1,3-substituted imidazolium salts of the formula I

wherein
R ¹ and R ³ independently of one another represent an organic radical having 1 to 20 carbon atoms,
R ² , R ⁴ and R ⁵ independently of one another represent a hydrogen atom or an organic radical having 1 to 20 carbon atoms, in particular 1 to 10 carbon atoms, where R ⁴ and R ⁵ may together form an aliphatic or aromatic ring,
X is an organic or inorganic anion, and n is 1, 2 or 3, for catalysing the deblocking of blocked isocyanates, in particular in coating compositions, are suitable.

There the exact mechanism by which the 1,3-substituted imidazolium salts Improve the deblocking of isocyanates is not known herein by "catalysis" the reaction promoting Intervention of the 1,3-substituted imidazolium salts in the deblocking reaction the blocked isocyanates understood.

The The present invention relates to such use as well as to coating compositions containing (a) at least one blocked polyisocyanate, (b) at least an oligomer or polymer which is higher than isocyanate groups having reactive groups and (c) at least one as in the invention Use defined 1,3-imidazolium salt.

The The present invention also relates to a process for preparation a coating, with one or more of the invention Coating agent, wherein the or the inventive Coating agent on an uncoated or coated substrate be applied and the coating at a temperature of 100 ° C to 300 ° C is cured.

(a) Blocked polyisocyanates

When blocked polyisocyanates may be any polyisocyanates be used in which the isocyanate groups with a compound have been reacted so that the formed blocked polyisocyanate resistant to hydroxyl groups at room temperature is, at elevated temperatures, usually in the range from about 100 to about 300 ° C, preferably 130 to 280 ° C and more preferably 140 to 250 ° C but reacts.

In the preparation of the blocked polyisocyanates, any organic polyisocyanates suitable for crosslinking can be used. Preferred are the isocyanates containing from about 3 to about 36, especially from about 8 to about 15, carbon atoms. Examples of suitable diisocyanates are trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyltrimethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1,4-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylene diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, 1-isocyanatomethyl-5-isocyanato-1,3,3 trimethylcyclohexane, bis (4-isocyanatocyclohexyl) methane, bis (4-isocyanatophenyl) methane, 4,4'-diisocyanatodiphenyl ether and 2,3-bis (8-isocyanato-octyl) -4-octyl-5-hexylcyclohexene. It is also possible to use polyisocyanates of higher isocyanate functionality. Examples thereof are tris (4-isocyanatophenylmethane, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 1,3,5-tris (6-isocyanatohexylbiuret), bis- (2,5-diisocyanato-4-methylphenyl ) methane, and polymeric polyisocyanates, such as dimers and trimers of the aforementioned diisocyanates, such as dimers or trimers of diisocyanatotoluene. Also included are, in particular, 4,4'-diisocyanatophenylmethane and 2,4'-diisocyanatophenylmethane, mixtures thereof and their higher molecular homologs, Generally known as MDI, it is also possible to use mixtures of all the above-mentioned polyisocya nate. The organic polyisocyanates contemplated as crosslinking agents in the invention may also be prepolymers derived, for example, from a polyol including a polyether polyol or a polyester polyol.

For the blocking of the polyisocyanates may be any suitable aliphatic, cycloaliphatic or aromatic alkyl monoalcohols, also in mixture. Examples are aliphatic alcohols, such as methyl, ethyl, propyl, butyl, amyl, Hexyl, heptyl, octyl, nonyl, 3,3,5-trimethylhexyl, decyl and Lauryl alcohol or monohydroxy glycols such as butyl glycol, hexyl glycol and especially butyl diglycol or n-propyl glycol; cycloaliphatic Alcohols such as cyclopentanol and cyclohexanol; aromatic alkyl alcohols, such as phenylcarbinol and methylphenylcarbinol.

Other suitable blocking agents are hydroxylamines such as ethanolamine, Oximes such as methyl ethyl ketone oxime, acetone oxime and cyclohexanone oxime or amines such as dibutylamine and diisopropylamine. The said polyisocyanates and blocking agents may be used at appropriate proportions also for the preparation of the partially blocked polyisocyanates described above be used.

Especially the use of alcohol-blocked polyisocyanates is preferred.

(b) oligomers or polymers which are opposite Have isocyanate groups reactive groups

in principle All are suitable against isocyanate groups reactive oligomers or polymers having at least two have isocyanate-reactive groups (hereinafter also usable according to the invention Binder or short binder). Across from Isocyanate-reactive groups are in particular hydroxyl and amino groups. Other isocyanate-reactive groups are those skilled in the art known in the art.

The the oligomeric or polymeric backbone of the oligomers or Polymer-forming structure can be made of a variety of different Polymer classes are chosen. Examples are for example Polyethers, in particular also epoxy resins, polyesters, polyurethanes, Polyureas, polyacrylates and polymethacrylates (in summary called poly (meth) acrylates) called. Also mixed forms of Polymers such as polyether-polyester, polyurethane-polyureas or polyether polyurethanes are suitable as a backbone.

Typical oligomers or polymers used as binders in electrodeposition paints are epoxy resins or epoxy resins with polyester segments wherein the resins are modified with amino groups and neutralized with short chain organic acids such as formic, acetic or lactic acid. Examples are mentioned DE 2701002 . US 4,830,722 and EP 961797 B1 ,

typical Oligomers or polymers used in coil coating coatings as binders can be used based on polyester resins, especially polyester resins with hydroxyl numbers of 1 to 250, preferably 2 to 150 and especially preferably 3 to 30 mg KOH / g.

The under (b) falling oligomers and polymers are of the blocked To distinguish polyisocyanates, they contain no blocked or unblocked isocyanate groups.

(c) 1,3-substituted imidazolium salts of the formula (I)

In the 1,3-substituted imidazolium salts of the formula (I), R ¹ and R ³ independently of one another preferably represent an organic radical having 1 to 10 carbon atoms. The organic radical may also contain further heteroatoms, in particular oxygen atoms, preferably hydroxyl groups, ether groups, ester groups or carbonyl groups.

In particular, R ¹ and R ³ independently of one another represent a hydrocarbon radical which, in addition to carbon and hydrogen, may at most also contain hydroxyl groups, ether groups, ester groups or carbonyl groups.

R ¹ and R ³ are preferably independently of one another a hydrocarbon radical having 1 to 20 carbon atoms, in particular having 1 to 10 carbon atoms, no other heteroatoms, z. As oxygen or nitrogen. The hydrocarbon radical may be aliphatic (including unsaturated aliphatic groups) or aromatic, or both aromatic and aliphatic Contain groups.

As hydrocarbon radicals may be mentioned z. As the phenyl group, the benzyl group, a substituted by one or more C ₁ - to C ₄ alkyl groups phenyl group or benzyl group, alkyl groups and alkenyl groups, especially the allyl group.

More preferably, R ¹ and R ³ independently of one another represent a C ₁ to C ₁₀ alkyl group, an allyl group or a benzyl group. As the alkyl group, a C ₁ to C ₆ alkyl group is particularly preferred, in a particular embodiment, the alkyl group is a C ₁ to C ₄ alkyl group.

Most preferably, R ¹ and R ³ independently of one another represent a methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl group, an allyl group or a benzyl group, of which in turn the methyl, ethyl, n-propyl and n-butyl group is preferred.

In a particular embodiment stand
R ¹ and R ^{3 represent} a methyl group,
R ¹ and R ^{3 represent} an ethyl group,
R ^{1 is} a methyl group and R ^{3 is} an ethyl group,
R ^{1 is} a methyl group and R ^{3 is} a n propyl group,
R ^{1 is} a methyl group and R ^{3 is} a n-butyl group,
R ^{1 is} a methyl group and R ^{3 is} an allyl group,
R ^{1 is} an ethyl group and R ^{3 is} an allyl group,
R ^{1 is} a methyl group and R ^{3 is} a benzyl group,
R ^{1 is} an ethyl group and R ^{3 is} a benzyl group,
R ² , R ⁴ and R ⁵ independently of one another represent a hydrogen atom or an organic radical having 1 to 20 carbon atoms, where R ⁴ and R ⁵ may together form an aliphatic or aromatic ring. The organic radical may contain not only carbon and hydrogen but also heteroatoms such as nitrogen or oxygen; If oxygen is present, it is present in particular in the form of hydroxyl groups, ester groups, ether groups or carbonyl groups.

In particular, R ² , R ⁴ and R ⁵ independently of one another represent a hydrogen atom or a hydrocarbon radical which, in addition to carbon and hydrogen, may at most also contain hydroxyl groups, ether groups, ester groups or carbonyl groups.

R ² , R ⁴ and R ⁵ are each independently a hydrogen atom or a hydrocarbon radical having 1 to 20 carbon atoms, in particular having 1 to 10 carbon atoms, no other heteroatoms, z. As oxygen or nitrogen. The hydrocarbon radical may be aliphatic (which also includes unsaturated aliphatic groups) or may be aromatic or consist of both aromatic and aliphatic groups, wherein R ⁴ and R ^{5 may} also form an aromatic or aliphatic hydrocarbon ring whose hydrogen atoms are optionally substituted by further aromatic or aliphatic Hydrocarbon groups may be substituted (the number of carbon atoms of the optionally substituted hydrocarbon ring including the substituents may preferably be a maximum of 40, in particular a maximum of 20, more preferably a maximum of 15 or a maximum of 10). As hydrocarbon radicals may be mentioned z. The phenyl group, a benzyl group, a phenyl group or benzyl group substituted with one or more C ₁ to C ₄ alkyl groups, alkyl groups, alkenyl groups and, in the case that R ⁴ and R ^{5 form} a ring, a through R ⁴ and R ⁵ formed aromatic 5- or 6-membered ring, a cyclohexene or cyclopentene, wherein hydrogen atoms in these ring systems in particular by one or more C ₁ - to C ₁₀ -, in particular C ₁ - to C ₄ alkyl groups may be substituted. Particularly preferably, R ² , R ⁴ and R ⁵ independently of one another represent a hydrogen atom, a C ₁ - to C ₈ -alkyl group, a C ₁ -C ₈ -alkenyl group, eg. An allyl group, a phenyl group or a benzyl group.

R ² , R ⁴ and R ⁵ very particularly preferably represent, independently of one another, a hydrogen atom, a methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl group, of which the methyl , Ethyl, n-propyl and n-butyl groups are particularly preferred.

In a particular embodiment, R ^{2 is} independently of the other radicals R ⁴ and R ⁵ and the remaining radicals R ¹ and R ^{3 is} a hydrogen atom.

Imidazolium salts of the formula I in which R ^{2 is} a hydrogen atom are particularly advantageous in the context of the present invention, they have good solubility in the abovementioned bandage and high efficiency as a latent catalyst.

In a particular embodiment, R ² , R ⁴ and R ^{5 are} a hydrogen atom, R ^{2 is} a hydrogen atom or a C ₁ - to C ₄ -alkyl group and R ⁴ , R ^{5 is} a hydrogen atom or a C ₁ - to C ₄ - alkyl group.

As individual cases for the cations of the compounds of the formula I may be mentioned:
1-butyl-3-methyl-imidazolium (R ¹ = butyl, R ³ = methyl)
1-butyl-3-ethyl-imidazolium (R ¹ = butyl, R ³ = ethyl)
1,3-dimethylimidazolium (R ¹ = methyl, R ³ = methyl)
1-ethyl-3-methyl-imidazolium (R ¹ = ethyl, R ³ = methyl)
1-ethyl-2,3-dimethyl-imidazolium (R ¹ = ethyl, R ² = methyl, R ³ = methyl).

In Formula I is n is 1, 2 or 3; the anion has accordingly one, two or three negative charges and accordingly lie in the Salt one, two or three imidazolium cations. Preferably stands n is 1 or 2, more preferably n is 1; The anion is therefore particularly preferably monovalent.

X is preferably the anion of an oxygen acid of phosphorus, a thiocyanate anion, a dicyanamide anion (N≡CNC≡N ^- ), a carboxylate or thiocarboxylate, or an anion having a pK _B value less than 13 ( measured at 25 ° C, 1 bar, in water or dimethyl sulfoxide, it being sufficient if an anion in either water or dimethyl sulfoxide has the corresponding pK _B value).

If X is the anion of an oxygen acid of phosphorus, then X may be a purely inorganic anion, eg. B. for a hypophosphite (PH ₂ O ₂ ) ^- , a phosphite (PHO ₃ ) ^2- or a phosphate (PO ₄ ) ^3- or for dimeric or oligomeric compounds which are formed by dehydration of the corresponding acids of the above anions, z. Metaphosphites or metaphosphates.

If X is the anion of an oxygen acid of the phosphor, then X may also contain at least one organic group, eg. Example, an organic group having 1 to 20 carbon atoms, in particular having 1 to 10 carbon atoms, particularly preferably having 1 to 4 carbon atoms. The organic group is preferably bonded to the phosphorus atom via an oxygen atom; Apart from this oxygen atom, the organic group may also contain other heteroatoms, eg. B. further oxygen atoms, preferably as hydroxyl groups, ether groups, ester groups or carbonyl groups. In a particular embodiment, the organic group is a hydrocarbon group without further heteroatoms. Suitable hydrocarbon groups are aliphatic or aromatic groups; particularly preferred are aliphatic groups, in particular are alkyl groups. Particularly preferred organic groups are C ₁ - to C ₂₀ -alkyl groups, very particularly preferred are C ₁ - to C ₁₀ -alkyl groups and in particular C ₁ - to C ₄ -alkyl groups.

If X stands for a thiocyanate anion (also called rhodanide), this means both mesomeric forms (SC≡N ^- ) and (S = C = N ^- ) and mixtures thereof.

In general, X can also be an anion having a pK _B value of less than 13, preferably less than 12, more preferably less than 11, and very preferably less than 10.5.

The pK _B value is measured at 25 ° C, 1 bar optionally in water or dimethyl sulfoxide as solvent; According to the invention, it is therefore sufficient if an anion has the corresponding pK _B value either in water or in dimethyl sulfoxide. Dimethyl sulfoxide is particularly useful when the anion is not well soluble in water. Both solvents can be found in standard works.

For bases that react in several stages with water to the corresponding polyprotic acid, it is sufficient if one stage has the above pK _B value.

The pK _B value is the negative decadic logarithm of the base constant, K _B , which in turn is the dissociation constant of the following reaction: X ^- + H ₂ O → HX + OH ^-

The dissociation constant of the back reaction is the acid constant K _S and the corresponding negative decadic logarithm of the pK _s value.

Insofar as the pK _S value is given in the literature, it can be explained by the simple relationship pK S + pK B = 14 the pK _B value can be calculated.

Suitable anions X having a suitable pK _B value of less than 13 are in particular compounds having one or more carboxylate groups (abbreviated to carboxylates) which have the above pK _B value. Particular examples of such carboxylates are organic compounds having 1 to 20 carbon atoms which contain one or two, preferably one carboxylate group. It may be both aliphatic and aromatic compounds, wherein the aromatic compounds are understood as meaning those containing aromatic groups. Particular preference is given to aliphatic or aromatic compounds which, apart from the oxygen atoms of the carboxylate group, contain no further heteroatoms or at best also contain one or two hydroxyl groups, carbonyl groups or ether groups. Very particular preference is given to aliphatic or aromatic compounds which, apart from the oxygen atoms of the carboxylate group, contain no further heteroatoms. As compounds with two carboxylate groups z. As the anions of the phthalic acid, isophthalic acid, the C ₂ - to C ₆ dicarboxylic acids, eg. Oxalic acid (pK _B 12,77 for the 1st stage, 9,81 for the second stage), malonic acid (pK _B 11,17 for the 1st stage, 8,31 for the second stage), succinic acid (pK _B 9.81 for the 1st stage, 8.52 for the second stage), glutaric acid (pK _B 9.66 for the 1st stage, 8.59 for the second stage), adipic acid (pK _B 9.58 for the 1st stage) Level, 8.59 for the second stage). As compounds having a carboxylate group, mention may be made of the anions of aromatic, aliphatic, saturated or unsaturated C ₁ -C ₂₀ -carboxylic acids, in particular alkanecarboxylic acids, alkenecarboxylic acids, alkincarboxylic acids, alkadienecarboxylic acids, alkadienecarboxylic acids, hydroxycarboxylic acids or ketocarboxylic acids. Suitable alkanecarboxylic acids, alkene carboxylic acids and alkadiene carboxylic acids are also known as fatty acids. Mention may be made in particular of the anions of benzoic acid (pK6 9.8), phenylacetic acid (pK _B 9.69), formic acid (formate, pK _B 10.23), acetic acid (acetates, pKB 9.24), as far as they are not under the exclusion in claim 1, acetylacetic acid (pK _B 10.42), or lactic acid (pK _B = 10.22). As hydroxy or ketocarboxylic acids z. For example, the glycolic acid (pK _B 10.18), or glyoxylic acid (pK _B 10.68) called. Other carboxylic acids are, for. B. Thioethercarbonsäuren, such as methyl mecaptoacetic acid (pK _B 10.28).

Other anions with a corresponding pK _B value less than 13 are, for example, cyanide (CN-, pK _B 4,6) or cyanate (OCN-, pK _B 10,08).

References to the pK _B values and the corresponding pK _S values are to be found in commercially available reference works, a very detailed compilation by R. Williams can also be found on the Internet at the following address: http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf. The values compiled in the list were taken from the following original quotations: Brown, HC et al., Braude, EA and FC Nachod, Determination of Organic Structures by Physical Methods, Academic Press, New York, 1955 (dicarboxylic acids) ; Dawson, RMC et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959 (Carboxylic Acids) ; Dippy, JFJ; Hughes, SR Rozanski, A J. Chem Soc. 1959, 2492 (substituted acetic acids) ; Hildebrand, JH Principles of Chemistry, New York, The Macmillan Company, 1940 (cyanide, cyanate) ,

As anion X - independently of the previously described anions X with a PK _B value less than 13 - also generally carboxylates and thiocarboxylates, ie compounds containing one, two or three carboxylate or thiocarboxylate groups, are suitable.

1,3-Substituted Imidazolium salts with other anions X than the previously mentioned are also, albeit less preferred. Fewer However, preferred anions X can be easily, for example by Replaced ion exchange against the above preferred anions X. become. Particular preference is given to containing organic groups Anions.

Lots The above 1,3-substituted imidazolium salts are also commercially available, for example from BASF SE, Sigma Aldrich or Merck available.

at the aforementioned 1,3-substituted imidazolium salts of the formula (I) are so-called "ionic liquids". They therefore have a melting point <100 ° C.

(d) Other coating agent ingredients

The coating compositions of the invention in addition to the above-mentioned components one or contain several coating agent-typical components.

among them include: rheology additives, wetting agents, Dispersing additives, defoamers, adhesion promoters, light stabilizers, Biocides, leveling and film-forming aids, matting agents, from (c) various catalysts, soluble dyes, color and / or effect pigments and fillers. As another Ingredients may also be different from (b) different self or externally crosslinking binders and of (a) different hardeners may be present, which may be different from those of (b) Binders react.

The Paints according to the invention are preferably substantially free of organometallic crosslinking catalysts, in particular Tin or zinc compounds. The term "essentially free "does not exclude the use of binders and hardeners or other such used in the paint Products from, in particular, tin-containing catalysts are used, but not from the corresponding products be separated. Such, for example, still in the binder or hardener contained traces of non-separated (organo) metal catalysts are in the classification of the coating materials as "im essentially free "of organometallic crosslinking catalysts, especially tin or zinc compounds, harmless. In particular, from "substantially free" of Zinc and / or tin compounds then spoken, if such Compounds in particular such tin compounds in an amount of less than 0.05 wt .-% based on the solids of the coating agent, more preferably less than 0.03% by weight based on the solids of the coating composition are. The solid of the coating composition, d. H. of the coating agent is achieved by drying the coating agent determined for 1 hour at 130 ° C.

The coating compositions (coating compositions) according to the invention preferably contain 0.02 to 5 wt .-% of the 1,3-substituted Imidazolium salt of the formula (I), more preferably 0.02 to 3 Wt .-% and most preferably 0.1 to 2 wt .-% or 0.2 to 1 wt .-%, each based on the solids of the coating composition.

at the coating compositions of the invention they are preferably those which are at temperatures of 100 to 300 ° C, more preferably at temperatures of 130 to 280 ° C and especially at temperatures of 140 to 250 ° C cure. The temperatures mentioned are around oven temperatures.

The Coating agents according to the invention are therefore preferably as electrodeposition paints, coil coating paints, wire enamels, Automotive topcoats, in particular automotive clearcoats or rockfall protection primers used in the vehicle paint. Particularly preferred is the Use of the coating compositions as an aqueous electrodeposition paint, in particular aqueous cathodic electrodeposition paint and as coil coating paint.

Especially Preferably, the inventive Coating compositions for aqueous coating compositions for the electrocoating, especially low-solvent Coating agent for electrodeposition coating. "Low solvent" means herein, that the content of solvents is preferably less than 5 wt .-%, more preferably less than 4 wt .-% based on the total weight the coating composition is. The 1,3-substituted ones Imidazolium salts are not considered as solvents.

preferred Substrates are heat stable substrates, especially those that are stable at the stoving conditions. Which includes in particular metallic substrates which are untreated or pretreated could be. The substrates can be preformed, such as in automobile bodies or after coating be deformed as usual coil coating (coil coating).

at The use according to the invention is carried out catalysis the deblocking of the blocked polyisocyanates preferably at Temperatures above 80 ° C, preferably at temperatures from 100 to 300 ° C, more preferably at temperatures from 130 to 280 ° C and especially at temperatures of 140 up to 250 ° C.

Another object of the invention is a process for producing a coating, wherein the coating composition of the invention is applied to an uncoated or coated substrate and the coating at a temperature between 100 and 300 ° C, more preferably at temperatures of 130 to 280 ° C and completely especially at temperatures of 140 to 250 ° C, is cured. preferred Substrates are in particular metallic substrates.

The The present invention will be illustrated by the following examples become.

EXAMPLES

example 1

Preparation of a crosslinker for an electrocoating composition

A crosslinker is used according to the EP 0 961 797 B1 made as follows:
In a reactor equipped with a stirrer, reflux condenser, internal thermometer and inert gas inlet, 934.4 g of isomers and higher functional oligomers based on 4,4'-diphenylmethane diisocyanate having an NCO equivalent weight of 135 (Basonat ^® A270, Fa. BASF NCO functionality about 2.7, content of 2,2'- and 2,4'-diphenylmethane diisocyanate below 5%) under a nitrogen atmosphere. 0.7 g of dibutyltin dilaurate are added and 373.8 g of butyldiglycol are added dropwise at such a rate that the product temperature remains below 70.degree. In the same way then 491.9 g of n-propyl glycol is added dropwise. In this case, the temperature is allowed to rise to 100 ° C in the course of the addition. After the end of the addition, the temperature is maintained at 100 ° C for a further 90 min. In the subsequent control no NCO groups are detectable. The reaction mixture is diluted by addition of 99.7 g of n-butoxypropanol and 99.7 g of phenoxypropanol, and cooled to 65 ° C. The solids content is 90% (solids content determination: 1 h at 130 ° C).

Example 2

Production of low-solvent aqueous binder dispersion, which is a cathodic depositable Resin and a crosslinker, and a crosslinking catalyst contains

A binder dispersion is used according to EP 0 961 797 B1 made as follows:
In a heat transfer fluid heated laboratory reactor equipped with stirrer, reflux condenser, thermometer and inert gas inlet tube, 1390.2 parts of a commercially available epoxy resin based on bisphenol A with an epoxy equivalent weight (EEW) of 188, 108.6 parts of phenol, 47.1 parts of n-butoxypropanol and Submitted 316.1 parts of bisphenol A and heated to 127 ° C under nitrogen. With stirring, 1.8 g of triphenylphosphine are added, whereupon an exothermic reaction occurs and the temperature rises to 170 ° C. It is allowed to cool again to 130 ° C and then controls the epoxide content. The EEW of 524 indicates that> 98% of the phenolic OH groups have reacted. Then, 181.7 g of Pluriol P 900 (polypropylene glycol MW 900, BASF) are added with simultaneous cooling. 5 minutes later are added at 120 ° C with further cooling 133.6 g of diethanolamine. As soon as the temperature has dropped to 100 ° C. after a brief exotherm (T _max 127 ° C.) (about 30 minutes), 64.9 g of N, N-dimethylaminopropylamine are added. After a brief exotherm (T _max 145 ° C), the batch is allowed to react for 2 hours at 130 ° C until the viscosity remains constant (1350 mPas, Brookfield viscometer CAP 2000+, at 23 ° C, cone CAP 03, 5000 1 / s, 51% in Solvenon PM (BASF)). Then, with simultaneous cooling 7.2 g parts of n-butoxypropanol and 1048.6 g of the crosslinker (Example 1) and carries out at 105 ° C from.

1277.3 parts of the still hot mixture are immediately dispersed in a presented mixture of 899.4 parts of demineralized water (deionized water) and 18.6 parts of 85% formic acid with vigorous stirring. After brief homogenization, 2.4 g of 1-butyl-3-methylimidazolinium acetate are added and homogenized over a period of 30 min. It is then diluted with a further 727.8 parts of demineralized water and filtered through plate filter K900 (Seitz). The dispersion has the following characteristics: Solid (1 hr at 130 ° C): 40.3% MEQ base 0.773 meq / g of solid resin MEQ acid 0.307 meq / g of solid resin

Examples 3-8

Production of other solvent-poor aqueous binder dispersions which are cathodically depositable Resin and a crosslinker, and a crosslinking catalyst contain

Analogously to Example 2, instead of the 1-butyl-3-methylimidazolium acetate added thereto, ande Re added 1,3-substituted imidazolium salts in the amounts listed in Table 1. Table 1 example Amount of imidazolium salt or aqueous solution Type imidazolium salt 3 4.9 g 1-butyl-3-methylimidazolium acetate 4 2.4 g 1.3 Dimethylimidazoliumacetat 5 4.9 g 1.3 Dimethylimidazoliumacetat 6 2.4 g 1-ethyl-3-methylimidazolium acetate 7 48.6 g 1,3-diethylimidazolium acetate (as a 10% aqueous solution) 8th 0 Without addition as a comparison

Example 9

Cationic, water-soluble grinding resin

According to EP 505 445 B1 Example 1.3, a friction resin is produced which, for better handling, is additionally neutralized and diluted with 2.82 parts of glacial acetic acid and 13.84 parts of demineralized water (deionised water). The original solids content is thereby lowered to 60%.

Example 10

Aqueous pigment paste 10 (a)

According to the in EP 505 445 B1 Aqueous pigment paste is prepared from the following starting materials (parts by weight): 40 parts of friction resin (Example 9), 7 parts of deionized water, 0.5 part of carbon black, 11 parts of aluminum silicate and 39 parts of titanium dioxide.

Aqueous Pigment Paste 10 (b) - Comparative Paste

According to the in EP 505 445 B1 an aqueous pigment paste is prepared from the following starting materials (parts by weight): 40 parts of friction resin (Example 9), 7 parts of demineralized water, 0.5 parts of carbon black, 11 parts of aluminum silicate and 39 parts of titanium dioxide and 2.5 parts Dibutyltin oxide (DBTO).

Examples 11-17

Preparation of the electro-dipping baths and deposition of the paint films

• *Pigmentpaste aus Beispiel 10 (a)
• **Pigmentpaste aus Beispiel 10 (b) (DBTO-haltig)

For testing as cathodically depositable electrodeposition paints (KT paints), the aqueous binder dispersions described under Examples 2-8 and the pigment paste described in Example 10 are combined to give the dip coating baths indicated in Table 2. The procedure is such that the binder dispersion is initially charged and diluted with deionized water. Subsequently, the pigment paste is added with stirring. The values given correspond to parts by weight (g). Table 2: Conventional and inventive electrocoating baths 1 2 3 4 5 6 comparison VE water 2420 2337 2314 2368 2522 572 2346 pigment paste 264 * 289 * 264 * 289 * 264 * 289 * 264 ** Binder Example 2 2279 Binder Example 3 2326 Binder Example 4 2385 Binder Example 5 2295 Binder Example 6 2176 Binder Example 7 4091 Binder Example 8 2353 4963 4952 4963 4952 4962 4952 4963

• Pigment paste of Example 10 (a)
• ** Pigment paste from Example 10 (b) (DBTO-containing)

The electrocoating baths are allowed to age for three days at room temperature with stirring. The deposition of the paint films is carried out for two minutes at 220-270 volts separation and 350 volt breakaway voltage (bath temperature 32 ° C) on cathodically switched zinc phosphated steel panels without Cr (VI) rinsing in the pretreatment. Table 3: pH values, conductance values, layer thicknesses and solids of the KT paints according to the invention 1 2 3 4 5 6 comparison PH value 5.82 5.99 5.87 5.98 5.96 6.06 5.93 Conductance (μS / cm) 1933 2030 2150 2220 2110 2513 1875 Layer thickness (μm) 20.2 18.5 19.2 22.5 21.7 21.0 20.2 Solid state (30 min 180 ° C) 21.3 22.3 20.9 23.2 22.0 21.9 21.4

• * DIN 53765 (03.1994): Prüfung von Kunststoffen und Elastomeren – Thermische Analyse – Dynamische Differenzkalorimetrie (DDK)

The deposited films are rinsed with deionized water and baked for 15 minutes at 175 ° C (object temperature) (also at 160 ° C for the determination of the glass transition temperature T _g as a measure of the crosslinking) TABLE 4 Glass transition temperatures T _{g of} the KT paints according to the invention (determined by means of the DSC *) 1 2 3 4 5 6 comparison _Tg (160 ° C) 65 66 64 66 65 68 72 _Tg (175 ° C) 83 87 82 88 84 89 90

• * DIN 53765 (03.1994): Testing of Plastics and Elastomers - Thermal Analysis - Differential Scanning Calorimetry (DDK)

Either under under-firing conditions (as often occurs on body mounts large mass occur) - here as "160 ° C" experiment - as well as normal stoving conditions - here as "175 ° C" attempt - reach the coatings according to the invention in about the same Glass transition temperatures such as those of heavy metals Control coating. The invention thus equals Coating compositions ready. Although the inventive Coating compositions preferably substantially heavy metal-free are, of course, also heavy metal Coating compositions fall under the present invention, by at least part of the heavy metal-containing catalysts by the ionic liquids of the present invention be replaced.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0677539 A [0004]
• WO 96/12771 [0004]
• WO 01/060886 A1 [0005, 0005]
• US 2007/0023288 A1 [0008]
• - WO 2006/022899 A2 [0009]
• - DE 2701002 [0022]
• US 4830722 [0022]
• - EP 961797 B1 [0022]
• - EP 0961797 B1 [0068, 0069]
• - EP 505445 B1 [0072, 0073, 0074]

Cited non-patent literature

• - http://research.chem.psu.edu/brpgroup/pKa_compilation.pdf. [0052]
• Brown, HC et al., Braude, EA and FC Nachod, determination of Organic Structures by Physical Methods, Academic Press, New York, 1955 (dicarboxylic acids) [0052]
• Dawson, RMC et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959 (Carboxylic Acids) [0052]
• - Dippy, JFJ; Hughes, SR Rozanski, A J. Chem Soc. 1959, 2492 (substituted acetic acids) [0052]
• - Hildebrand, JH Principles of Chemistry, New York, The Macmillan Company, 1940 (cyanide, cyanate) [0052]
• - DIN 53765 [0077]

Claims (5)

Use of 1,3-substituted imidazolium salts of the formula (I)

wherein R ¹ and R ³ independently represent an organic radical having 1 to 20 carbon atoms, R ² , R ⁴ , and R ⁵ independently represent a hydrogen atom or an organic radical having 1 to 20 carbon atoms, wherein R ⁴ and R ^{5 may} also together form an aliphatic or aromatic ring, X is an n-valent organic or inorganic anion, and n is 1, 2 or 3, for catalysing the deblocking of blocked isocyanates. Coating composition comprising, (a) at least one blocked polyisocyanate (b) at least one oligomer or polymer having at least two isocyanate-reactive groups and (c) at least one 1,3-substituted imidazolium salt of the formula (I)

wherein R ¹ and R ³ independently represent an organic radical having 1 to 20 carbon atoms, R ² , R ⁴ , and R ⁵ independently represent a hydrogen atom or an organic radical having 1 to 20 carbon atoms, wherein R ⁴ and R ^{5 may} also together form an aliphatic or aromatic ring, X is an n-valent organic or inorganic anion, and n is 1, 2 or 3. Coating composition according to claim 2, characterized in that that it is an electrocoat or a coil coating paint is. Coating composition according to one of the claims 2 or 3, characterized in that it is an aqueous Lacquer acts. Process for producing a coating, characterized in that the coating agent according to one of claims 2 to 4 is applied to an uncoated or coated substrate and the coating is cured at a temperature between 100 and 300 ° C.