Low-viscosity allophanates having actinically hardenable groups

The present invention relates to low-viscosity reaction products of alcohols which contain activated under reaction of actinic radiation with ethylenically unsaturated compounds under polymerization groups, with polyisocyanates a process for their preparation and their use in coating compositions.

The curing of activated double bonds bearing coating systems by actinic radiation, such. As UV light, IR radiation or electron radiation is known and technically established. It is one of the fastest curing methods in coating technology. Coating agents based on this principle are therefore referred to as radiation- or actinic-curing or curable systems.

Due to the ecological and economic requirements of modern paint systems to use as little or no organic solvent for viscosity adjustment, there is a desire to use low-viscosity coating raw materials. Polyisocyanates with allophanate structure, as described, inter alia, in EP-A 0 682 012, have long been known for this purpose.

In the art, these are prepared by reacting a monohydric or polyhydric alcohol with excess aliphatic and / or cycloaliphatic diisocyanate (cf. GB-A 994 890, EP-A 0 000 194 or EP-A 0 712 840). Subsequently, the removal of unreacted diisocyanate by distillation under vacuum. According to DE-A 198 60 041, this procedure can also with OH-functional compounds having activated double bonds, such as Hydroxyalkylacrylaten be carried out, but difficulties arise for the production of particularly low-monomer products. Since the distillation step has to run at temperatures up to 135 ° C in order to reduce the residual isocyanate content sufficiently (<0.5 wt .-% residual monomer), double bonds can react thermally initiated under polymerization during the purification, so that no flawless Products will receive more.

The preparation of low-monomer, allophanate-containing, radiation-curing polyurethane-based binders is described in EP-A 0 867 457 and US Pat. No. 5,739,251. However, these binders do not carry activated double bonds but rather reactive allyl ether groups (structure RO-CH₂-CH = CH₂). Therefore, it requires the addition of reactive diluents (low molecular weight esters of acrylic acid), which bring the necessary UV reactivity.

EP-A 0 825 211 describes a process for the construction of allophanate structures from oxadiazine trions, although no radiation-curing derivatives with activated double bonds are known. Only the use of maleate and / or fumarate-containing polyesters is mentioned, the possibility of radiation curing is not described.

US Pat. No. 5,777,024 describes the preparation of the low-viscosity radiation-curing allophanates by a reaction of hydroxy-functional monomers which carry activated double bonds with isocyanate groups of allophanate-modified isocyanurate polyisocyanates. The radicals bound via the allophanate groups are saturated.

The formation of allophanate compounds by ring opening of uretdiones with alcohols is basically known as a crosslinking mechanism in powder coatings (see Proceedings of the International Waterbome, High-Solids, and Powder Coatings Symposium 2001, 28^th, 405-419 and US-A 2003 0153713). However, the reaction temperatures required for a specific preparation of radiation-curing allophanate-based monomers with activated double bonds are too high (> 130 ° C.).

Historically, the direct reaction of uretdione rings with alcohols to form allophanates was first investigated for solvent-borne isocyanate-free 2K polyurethane coatings. Uncatalysed, this reaction due to the low reaction rate without technical importance (F. Schmitt, Angew. Makromol. Chem. (1989), 171, p. 21-38). With suitable catalysts, however, the crosslinking reaction between HDI-based uretdione hardeners and polyols should already start at 60 to 80 ° C. (K. B. Chandalia; R. A Englebach; S. L.Goldstein; R. W. Good; S. H. Harris; M. J. Morgan; P. J. Whitman; R. T. Wojcik, Proceedings of the International Waterbome, High-Solids, and Powder Coatings Symposium, (2001), p. 77 - 89). The structure of these catalysts has not been published. Commercial products that use this reaction are not known yet.

In summary, it can be stated that the preparation of low-viscosity radiation-curing allophanates by a ring-opening reaction of alcohols bearing activated double bonds with uretdiones at temperatures ≤ 130 ° C. is not explicitly described in the prior art.

Surprisingly, it has now been found that from the reaction of uretdiones with olefinically unsaturated alcohols, which contain preferably activated double bonds, by using ammonium or phosphonium salts of aliphatic or cycloaliphatic carboxylic acids as catalysts, low-viscosity radiation-curing allophanates having low residual monomer contents can be obtained even at temperatures of ≦ 130 ° C. which preferably have viscosities measured at 23 ° C of less than 100,000 mPas.

The invention therefore provides a process for producing radiation-curing binders containing allophanate groups, in which at temperatures ≤ 130 ° C.<ul id="ul0001" list-style="none"><li>A) one or more uretdione group-containing compounds with</li><li>B) one or more OH-functional compounds which, on exposure to actinic radiation with ethylenically unsaturated compounds, exhibit polymerization-reactive groups (radiation-curing groups), and</li><li>C) optionally further NCO-reactive compounds in the presence</li><li>D) one or more compounds containing at least one tetrasubstituted ammonium or phosphonium salt of an aliphatic or cycloaliphatic carboxylic acid as catalyst and</li><li>E) optional auxiliaries and additives</li></ul>be implemented under opening of the uretdione ring to allophanate groups.

In addition, the binders obtainable by the process according to the invention are an object of the invention.

In component A), it is possible to use all organic compounds which have at least one uretdione group.

Preference is given to compounds obtainable by catalytic dimerization of aliphatic, cycloaliphatic and / or araliphatic diisocyanates or polyisocyanates by processes known per se (compare J. Prakt. Chem., 1994, 336, pages 196-198).

Suitable diisocyanates are, for example, 1,4-diisocyanatobutane, 1,6-diisocyanatohexane (HDI), trimethylhexane diisocyanate, 1,3- and 1,4-bis-isocyanatomethylcyclohexane, isophorone diisocyanate (IPDI), 4,4'-diisocyanatodicyclohexylmethane, 1,3- and 1,4-xylylene diisocyanates (XDI commercial product of Takeda, Japan), diphenylmethane-4,4'-diisocyanate and diphenylmethane-2,4'-diisocyanate (MDI), 2,4- and 2,6-toluene diisocyanate (TDI ), or their mixtures. Preference is given to 1,6-diisocyanatohexane.

Examples of catalysts used here are: trialkylphosphines, dimethylaminopyridines, tris (dimethylamino) phosphine.

The result of the dimerization reaction depends on the catalyst used, the process conditions and the diisocyanates used in a manner known to those skilled in the art. In particular, products may arise which have on average more than one uretdione group per molecule, the number of uredione groups being subject to a distribution. Depending on the catalyst used, the process conditions and the diisocyanates used, product mixtures are also formed which, in addition to uretdiones, also have other structural units, for example Isocyanurate and / or iminooxadiazinedione.

Particularly preferred products are obtainable by catalytic dimerization of HDI and have a content of free HDI of less than 0.5 wt .-%, an NCO content of 17 to 25 wt .-%, preferably from 21 to 24 wt .-% and a viscosity at 23 ° C of 20 to 500 mPas, preferably from 50 to 200 mPas.

The obtainable by catalytic dimerization usually NCO-functional compounds are preferably used directly as part of component A), but they can in principle initially be further reacted and then used only in A). This can for example be a blockage of the free NCO groups or the further reaction of NCO groups with NCO-reactive di- or polyfunctional compounds to iminooxadiazinedione, isocyanurate, urethane, allophanate, biuret, urea, oxadiazinetrione, oxazolidinone , Acyl urea or carbodiimide structures. In this case, higher molecular weight compounds containing uretdione groups are obtained, which may be NCO group-containing or NCO-group-free, depending on the selected ratios.

Examples of suitable blocking agents are alcohols, lactams, oximes, malonic esters, alkylacetoacetates, triazoles, phenols, imidazoles, pyrazoles and amines, such as Butanone oxime, diisopropylamine, 1,2,4-triazole, dimethyl-1,2,4-triazole, imidazole, diethyl malonate, acetoacetic ester, acetone oxime, 3,5-dimethylpyrazole, ε-caprolactam, N-tert-butylbenzylamine, cyclopentanonecarboxyethyl ester or any mixtures of these blocking agents. The procedure for blocking NCO groups is familiar to the skilled worker and described by way of example in Progress in Organic Coatings 1999, 36, 148-172.

NCO-reactive di- or polyfunctional compounds for derivatizing the uretdiones used in A) may be the abovementioned di- and / or polyisocyanates, furthermore simple difunctional or polyfunctional alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, Diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentyl glycol, 1,6-hexanediol, 2-ethyl-hexanediol and tripropylene glycol or alkoxylated derivatives of these alcohols. Preferred dihydric alcohols are 1,6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable trihydric alcohols are glycerol or trimethylolpropane or their alkoxylated derivatives. Quaternary alcohols are pentaerythritol or its alkoxylated derivatives.

Actinic radiation is understood as meaning electromagnetic, ionizing radiation, in particular electron beams, UV rays and visible light (Roche Lexikon Medizin, 4th edition, Urban &amp; Fischer Verlag, Munich 1999).

Groups which undergo polymerization under the influence of actinic radiation with ethylenically unsaturated compounds (radiation-curing groups) are, for example, vinyl, vinyl ether, propenyl, allyl, maleyl, fumaryl, maleimide, dicyclopentadienyl, acrylamide, Acrylic and methacrylic groups, preferably activated groups of this type such as vinyl ether, Acrylate and / or methacrylate groups, acrylate groups are particularly preferably used in the compounds of component B).

Examples of suitable hydroxyl-containing compounds of component B) are 2-hydroxyethyl (meth) acrylate, polyethylene oxide mono (meth) acrylate (eg PEA6 / PEM6; Laporte Performance Chemicals Ltd., UK), polypropylene oxide mono (meth) acrylate (eg PPA6, PPM5S; Laporte Performance Chemicals Ltd., UK), polyalkyleneoxide mono (meth) acrylate (eg PEM63P, Laporte Performance Chemicals Ltd. , UK), poly (ε-caprolactone) mono (meth) acrylates such as Tone M100® (Dow, Schwalbach, DE), 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxybutyl vinyl ether, 3-hydroxy-2,2-dimethylpropyl (meth) acrylate, the hydroxy-functional mono-, di-, or as far as possible higher acrylates such as Glycerol di (meth) acrylate, trimethylolpropanedi (meth) acrylate, pentaerythritol tri (meth) acrylate or dipentaerythritol penta (meth) acrylate, which are accessible by reacting polyhydric optionally alkoxylated alcohols such as trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol.

Likewise suitable as constituent of B) are also alcohols which are obtained from the reaction of double-bond-containing acids with optionally double-bond-containing epoxide compounds, for example the reaction products of (meth) acrylic acid with glycidyl (meth) acrylate or bisphenol A diglycidyl ether.

In addition, it is likewise possible to use unsaturated alcohols which are obtained from the reaction of optionally unsaturated acid anhydrides with hydroxyl and epoxide compounds which may have acrylate groups. For example, these are the reaction products of maleic anhydride with 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate.

Particularly preferably, the compounds of component B) of the aforementioned type and have an OH functionality of 0.9 to 1.1.

Very particular preference is given in B) to using compounds of the abovementioned type with primary hydroxyl groups. Such are preferably 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

In addition to the OH-functional unsaturated compounds of component B), it is also possible to use in the process according to the invention further compounds C) which are different from those of B) and have NCO-reactive groups, for example OH, SH or NH.

These may be, for example, NH- or SH-functional compounds with groups which undergo polymerization under the action of actinic radiation with ethylenically unsaturated compounds under polymerization.

Furthermore, hydrophilicizing groups can be incorporated, especially if a use of an aqueous medium, eg in an aqueous paint, is provided. Hydrophilizing groups are ionic groups which may be either cationic or anionic in nature and / or nonionic hydrophilic groups. Cationic, anionic or nonionic dispersing compounds are those which, for example, sulfonium, ammonium, phosphonium, carboxylate, sulfonate, phosphonate groups or the groups which can be converted into the abovementioned groups by salt formation (potentially ionic groups) or contain polyether groups and can be incorporated by existing isocyanate-reactive groups. Preferably suitable isocyanate-reactive groups are hydroxyl and amine groups.

Suitable ionic or potentially ionic group-containing compounds are, for example Mono- and dihydroxycarboxylic acids, Mono and diaminocarboxylic acids, Mono- and dihydroxysulfonic acids, Mono- and diaminosulfonic acids and mono- and dihydroxyphosphonic acids or mono- and diaminophosphonic acids and their salts, such as dimethylolpropionic acid, dimethylol, hydroxypivalic acid, N- (2-aminoethyl) -beta-alanine, 2- (2-amino-ethylamino) -ethanesulfonic acid, Ethylenediamine-propyl- or butylsulfonic acid, 1,2- or 1,3-propylenediamine-β-ethylsulfonic acid, Malic acid, Citric acid, Glycolic acid, Lactic acid, glycine, alanine, taurine, lysine, 3,5-diaminobenzoic acid, an addition product of IPDI and acrylic acid (EP-A 0 916 647, Example 1) and its alkali metal and / or ammonium salts; the adduct of sodium bisulfite with butene-2-diol-1,4, polyethersulphonate, the propoxylated adduct of 2-butenediol and NaHSO₃, eg described in DE-A 2 446 440 (page 5-9, formula I-III) and convertible into cationic groups blocks such as N-methyl-diethanolamine as hydrophilic structural components. Preferred ionic or nonionic ionic compounds are those which have carboxy or carboxylate and / or sulfonate groups and / or ammonium groups. Particularly preferred ionic compounds are those containing carboxyl and / or sulfonate groups as ionic or potentially ionic groups, such as the salts of N- (2-aminoethyl) -β-alanine, of 2- (2-amino-ethylamino) ethanesulfonic acid or the addition product of IPDI and acrylic acid (EP-A 0 916 647, Example 1) and the dimethylolpropionic acid.

Suitable nonionic hydrophilicizing compounds are, for example, polyoxyalkylene ethers containing at least one hydroxy or amino group. These polyethers contain from 30% to 100% by weight of building blocks derived from ethylene oxide. In question are linear polyethers having a functionality of 1 to 3, but also compounds of general formula (I),<chemistry id="chem0001" num="0001"><img file="EP1634902A1_D0001.tif" /></chemistry>in which<dl id="dl0001"><dt>R¹ and R²</dt><dd>each independently of one another denote a divalent aliphatic, cycloaliphatic or aromatic radical having 1 to 18 C atoms, which may be interrupted by oxygen and / or nitrogen atoms, and</dd><dt>R³</dt><dd>represents an alkoxy-terminated polyethylene oxide radical.</dd></dl>

Nonionic hydrophilizing compounds are, for example, also monohydric polyalkylene oxide polyether alcohols containing on average from 5 to 70, preferably 7 to 55, ethylene oxide units per molecule, as are obtainable in a conventional manner by alkoxylation of suitable starter molecules (eg in Ullmanns Encyclopadie der technischen Chemie, 4. Edition, Volume 19, Verlag Chemie, Weinheim pp. 31-38).

Suitable starter molecules are, for example, saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol; the isomers pentanols, hexanols, Octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol, Diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether, unsaturated alcohols such as allyl alcohol, 1,1-dimethylallyl alcohol or oleic alcohol, aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols such as benzyl alcohol, Aniseed alcohol or cinnamyl alcohol, secondary monoamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, Bis (2-ethylhexyl) -amine, N-methyl- and N-ethylcyclohexylamine or dicyclohexylamine and heterocyclic secondary amines such as morpholine, pyrrolidine, Piperidine or 1H-pyrazole. Preferred starter molecules are saturated monoalcohols. Diethylene glycol monobutyl ether is particularly preferably used as starter molecule.

Alkylene oxides which are suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in any desired order or even as a mixture in the alkoxylation reaction.

The polyalkylene oxide polyether alcohols are either pure polyethylene oxide polyethers or mixed polyalkylene oxide polyethers whose alkylene oxide units consist of at least 30 mol%, preferably at least 40 mol%, of ethylene oxide units. Preferred nonionic compounds are monofunctional mixed polyalkylene oxide polyethers having at least 40 mole percent ethylene oxide and at most 60 mole percent propylene oxide units.

In particular, when using a hydrophilicizing agent containing ionic groups its influence on the effect of the catalyst D) must be checked. For this reason, nonionic compounds are preferred as the hydrophilizing agent.

In addition to the ammonium or phosphonium salts of aliphatic carboxylic acids to be used according to the invention, the compounds known per se for catalyzing the reaction of isocyanate groups with isocyanate-reactive groups individually or in any desired mixtures with one another can also be used as compounds of the catalyst component D).

By way of example, tert. Amines such as triethylamine, pyridine, methylpyridine, benzyl-dimethylamine, N, N-Endoethylenpiperazin, N-methyl-piperidine, Pentamethyldiethy-len-triamine, N, N-dimethylaminocyclohexane, N, N'-dimethyl-piperazine, 1,4-diazabicyclo [2.2.2] octane (DABCO) or metal salts such as ferric chloride, tin (II) octoate, tin (II) ethyl caproate, tin (II) palmitate, dibutyltin (IV) dilaurate, dibutyltin (IV) diacetate and molybdenum glycolate or any mixtures of such catalysts.

The tetrasubstituted ammonium or phosphonium salts of aliphatic or cycloaliphatic carboxylic acids of component D) preferably correspond to the general formula (II)<chemistry id="chem0002" num="0002"><img file="EP1634902A1_D0002.tif" /></chemistry>in which<dl id="dl0002" compact="compact"><dt>Z</dt><dd>is nitrogen or phosphorus,</dd><dt>R¹, R², R³, R⁴</dt><dd>independently of one another are hydrogen or identical or different aliphatic, cycloaliphatic or araliphatic radicals having up to 24 carbon atoms and</dd><dt>Y</dt><dd>a carboxylate radical of the general formula (III) is</dd></dl><chemistry id="chem0003" num="0003"><img file="EP1634902A1_D0003.tif" /></chemistry>in which¹X, ²X, ³X are independently of one another substituents selected from the group consisting of hydrogen, halogen, cyano, hydroxyl, amide, ether, ester, thioether, ketone, aldehyde and carboxylate and aliphatic or cycloaliphatic radicals having up to 24 carbon atoms , which are optionally parts of cyclic or polycyclic systems.

As tetrasubstituted ammonium or phosphonium salts of aliphatic or cycloaliphatic carboxylic acids of the formula (II) it is particularly preferable to use tetraalkylammonium carboxylates which are preferably based on aliphatic carboxylic acids with branched alkyl radicals without further functional groups.

Particularly preferred tetraalkylammonium carboxylates are tetrabutylammonium 2-ethylhexanoate, tetrabutylammonium pivalate, choline 2-ethylhexanoate, choline pivalate, methylcholine 2-ethylhexanoate and / or methylcholine pivalate, whose preparation is described in US 5,691,440.

In a preferred embodiment of the invention, exclusively carboxylates of the abovementioned type are used in D) as sole compound of component D).

It is also possible to bring the catalysts D) on carrier materials by methods known in the art and to use as heterogeneous catalysts.

The compounds of the catalyst component D) can advantageously be dissolved in one of the components involved in the process or a part thereof. In particular, the carboxylates to be used according to the invention dissolve very well in the polar hydroxyalkyl acrylates, so that D) dissolved in small amounts of B) can be metered in liquid form as a concentrated solution.

In the process according to the invention, the catalyst component D) is typically used in amounts of from 0.001 to 5.0% by weight, preferably from 0.01 to 2.0% by weight and more preferably from 0.05 to 1.0% by weight Solid content of the process product used.

As constituents of component E), for example, solvents or reactive diluents can be used in the process according to the invention.

Suitable solvents are inert to the functional groups present in the process product from the time of addition to the end of the process. Suitable solvents are, for example, used in lacquer technology, such as hydrocarbons, ketones and esters, for example. Toluene, xylene, isooctane, acetone, butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran, N-methylpyrrolidone, dimethylacetamide, dimethylformamide, but preferably no solvent is added.

As reactive diluents, it is also possible to use compounds which likewise (co) polymerize in the case of UV curing and thus incorporate into the polymer network and are inert toward NCO groups. Such reactive diluents are in P. K. T. Oldring (Ed.), Chemistry &amp; Technology of UV &amp; EB Formulations For Coatings, Inks &amp; Paints, Vol. 2, 1991, SITA Technology, London, S. 237 - 285 described by way of example. These may be esters of acrylic acid or methacrylic acid, preferably of acrylic acid with mono- or polyfunctional alcohols. Suitable alcohols are, for example, the isomeric butanols, pentanols, hexanols, heptanols, octanols, nonanols and decanols, furthermore cycloaliphatic alcohols such as isobornol, cyclohexanol and alkylated cyclohexanols, dicyclopentanol, arylaliphatiseher alcohols such as phenoxyethanol and nonylphenylethanol, and Tetrahydrofurfurylalkohole. Furthermore, alkoxylated derivatives of these alcohols can be used. Suitable dihydric alcohols are, for example, alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentyl glycol, 1,6-hexanediol, 2-ethylhexanediol and tripropylene glycol or even alkoxylated derivatives of these alcohols. Preferred dihydric alcohols are 1,6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable trihydric alcohols are glycerol or trimethylolpropane or their alkoxylated derivatives. Quaternary alcohols are pentaerythritol or its alkoxylated derivatives.

The binders of the invention must be stabilized against premature polymerization. Therefore, as component of component E) before and / or during the reaction are preferably added to phenolic stabilizers which inhibit the polymerization. Phenols such as para-methoxyphenol, 2,5-di-tert-butylhydroquinone or 2,6-di-tert-butyl-4-methylphenol are used. Also suitable are N-oxyl compounds for stabilization such as 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO) or its derivatives. Likewise, the stabilizers can also be chemically incorporated into the binder, while compounds of the abovementioned classes are particularly suitable if they carry even more free aliphatic alcohol groups or primary or secondary amine groups and thus chemically over urethane or urea groups on compounds of component A. ) can be bound. Particularly suitable for this purpose are 2,2,6,6-tetramethyl-4-hydroxy-piperidine-N-oxide. Preference is given to phenolic stabilizers, in particular para-methoxyphenol and / or 2,6-di-tert-butyl-4-methylphenol

Other stabilizers such. B. compounds of the class of HALS (HALS = hindered amine light stabilizers), however, are less preferably used in E), since they are known to allow such effective stabilization and rather can lead to a "creeping" radical polymerization of unsaturated groups.

To stabilize the reaction mixture, in particular the unsaturated groups against premature polymerization, an oxygen-containing gas, preferably air, in and / or be passed over the reaction mixture. It is preferable that the gas has the smallest possible amount of moisture to prevent undesired reaction in the presence of isocyanate.

As a rule, during the preparation of the binders according to the invention, a stabilizer is added and, finally, in order to achieve long-term stability, it is again stabilized with a phenolic stabilizer and, if appropriate, the reaction product is saturated with air.

In the process according to the invention, the stabilizer component is typically used in amounts of from 0.001 to 5.0% by weight, preferably from 0.01 to 2.0% by weight and more preferably from 0.05 to 1.0% by weight, based on the solids content of the process product used.

The ratio of OH groups from component B) to the sum of NCO and uretdione groups from A) is typically from 1.5: 1.0 to 1.0: 1.9, preferably 1.0: 1.0 to 1.0: 1.9, more preferably from 1.0: 1.0 to 1.0: 1.2.

The inventive method is preferably carried out at temperatures of 20 to 130 ° C, more preferably from 40 to 100 ° C, most preferably at 80 to 90 ° C.

Usually, the optionally present NCO groups react faster with the hydroxyl groups of component B) than the uretdione groups of component A). It is therefore possible, if there are several different constituents in B), to control the urethanization and allophanatization according to the order of addition of the constituents such that a constituent of B) is preferably incorporated under urethanization while the last added is preferably incorporated under allophanatization.

The reaction of component A) with B) and other NCO-reactive compounds C) is then complete as soon as all NCO groups have reacted according to the selected stoichiometric ratios with NCO-reactive groups from B) and C) and all uretdione groups according to of the selected stoichiometric ratios have reacted with the hydroxyl groups from B.

However, it is also possible to terminate the allophanatization by adding catalyst-deactivating compounds (eg strong acids such as acidic phosphoric acid esters) or adding further isocyanate-containing compounds which scavenge the remaining compounds of component B).

It is irrelevant whether the process according to the invention is carried out continuously, for example in a static mixer, extruder or kneader or batchwise, for example in a stirred reactor.

Preferably, the inventive method is carried out in a stirred reactor, wherein the order of addition of the components A) - E) is arbitrary.

The course of the reaction can be monitored by suitable meters installed in the reaction vessel and / or by analyzes on samples taken. Suitable methods are known to the person skilled in the art. These are, for example, viscosity measurements, measurements of the refractive index, the OH content, gas chromatography (GC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and near near infrared spectroscopy (NIR). Preferably, the IR control is on possibly existing free NCO groups (for aliphatic NCO groups, band at ca. v = 2272 cm^-1) and in particular on uretdione groups (eg band for uretdiones based on hexamethylene diisocyanate at v = 1761 cm^-1) and GC studies on unreacted compounds from B) and C).

In a preferred embodiment of the invention, a parallel allophanatization and urethanization of the compounds of component A) takes place. For this purpose, A) is introduced, with stabilizers and optionally other auxiliaries and additives from E), then the components B) - E) are added and the reaction mixture brought to reaction temperature.

In a further preferred embodiment, first A) is reacted with B) until complete reaction of the NCO groups. Where E) or parts thereof may already be present. Subsequently, by addition of D) and additionally, if appropriate, by temperature adjustment, the reaction of the uretdione groups of A) with B) is started.

In a particularly preferred embodiment, the reaction of the isocyanate groups and the uretdione groups with an excess of hydroxyl groups of component B. The after reaction A) with B) with catalysis of D) remaining hydroxyl groups are then preferably with other isocyanate-containing compounds, in particular with such possible components of component B) described under urethanization implemented.

The unsaturated allophanates obtainable by the process according to the invention preferably have viscosities measured with a cone-and-plate viscometer at 23 ° C. of ≦ 100 000 mPas, more preferably ≦ 75 000 mPas.

The unsaturated allophanates obtainable by the process according to the invention preferably have number-average molecular weights M_n from 600 to 3000 g / mol, more preferably 750 to 1500 g / mol.

The unsaturated allophanates obtainable by the process according to the invention preferably have contents of free di- or triisocyanate monomers of less than 0.5% by weight, more preferably less than 0.1% by weight.

The binders of this invention can be used to make coatings and lacquers, as well as adhesives, inks, casting resins, dental compositions, sizes, photoresists, stereolithography systems, resins for composites, and sealants. In the case of bonding or sealing, however, it is a prerequisite that at least one of the two substrates to be bonded or sealed to one another is transparent to UV radiation during UV steel hardening, ie i. d. R. must be transparent. In the case of electron radiation, attention must be paid to a sufficient permeability for electrons. Preferred is the use in paints and coatings.

Another object of the invention are coating compositions containing<ul id="ul0002" list-style="none" compact="compact"><li>a) one or more inventively available binder</li><li>b) optionally one or more polyisocyanates having free or blocked isocyanate groups, which are free of groups which undergo polymerization under the action of actinic radiation with ethylenically unsaturated compounds,</li><li>c) optionally further of those from a) various compounds which have polymerization-reactive groups under the action of actinic radiation with ethylenically unsaturated compounds and optionally free or blocked NCO groups,</li><li>d) optionally one or more isocyanate-reactive, active hydrogen-containing compounds</li><li>e) initiators,</li><li>f) optionally solvents and</li><li>g) optionally auxiliaries and additives.</li></ul>

The polyisocyanates of component b) are known per se to the person skilled in the art. Preference is given to using isocyanurate, allophanate, biuret, uretdione and / or iminooxadiazinetrione group-modified compounds based on hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-diisocyanatodicyclohexylmethane and / or trimethylhexamethylene diisocyanate base.

The NCO groups may also be blocked, the blocking agents used being those already mentioned in the description of component A).

The compounds of component c) include, in particular, urethane acrylates based on hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-diisocyanatodicyclohexylmethane and / or trimethylhexamethylene diisocyanate, which may optionally contain isocyanurate, allophanate, biuret, uretdione and / or or Iminooxadiazintriongruppen may be modified, which have no reactive isocyanate-reactive, active hydrogen-containing functions.

NCO-containing urethane acrylates are commercially available from Bayer MaterialScience AG, Leverkusen, DE as Roskydal® UA VP LS 2337, Roskydal® UA VP LS 2396 or Roskydal® UA XP 2510.

Furthermore, the reactive diluents already described and known in the art of radiation-curing coatings can be used as a component of c), provided that they contain no groups reactive with NCO groups.

Compounds of component d) may be saturated or unsaturated. NCO-functional chemical functionalities are activated hydrogen-containing functionalities such as hydroxyl, amine or thiol.

Preference is given to saturated polyhydroxy compounds, for example the polyether polyols known per se from the technology of coating, gluing, printing inks or sealants, polyester polyols, polycarbonate polyols, poly (meth) acrylate polyols, polyurethane polyols which do not undergo polymerization under the influence of actinic radiation with ethylenically unsaturated compounds have reactive groups.

Unsaturated hydroxy-functional compounds are, for example, the epoxy acrylates, polyester acrylates, polyether acrylates, urethane acrylates and acrylated polyacrylates known in the art of radiation-curing coatings, which have an OH number of 30 to 300 mg KOH / g.

Furthermore, the reactive diluents already described and known in the art of radiation-curing coatings can be used as constituent of d), provided they contain reactive groups with NCO groups.

As initiators of component e) for a free-radical polymerization can be used by radiation and / or thermally activatable initiators. Photoinitiators which are activated by UV or visible light are preferred. Photoinitiators are compounds which are known per se and are commercially available, whereby a distinction is made between unimolecular (type I) and bimolecular (type II) initiators. Suitable (type I) systems are aromatic ketone compounds, eg Benzophenones in combination with tertiary amines, alkylbenzophenones, 4,4'-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the types mentioned. Also suitable are (type II) initiators such as benzoin and its derivatives, benzil ketals, acylphosphine oxides, for example 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxides, phenylglyoxylic acid esters, camphorquinone, α-aminoalkylphenones, α, α-dialkoxyacetophenones and α-hydroxyalkylphenones.

The initiators, which are used in amounts between 0.1 and 10 wt .-%, preferably 0.1 to 5 wt .-%, based on the weight of the paint binder, can be used as a single substance or, because of frequent advantageous synergistic effects, also be used in combination with each other.

If electron beams are used instead of UV radiation, you do not need a photoinitiator. Electron radiation is known to those skilled in the art, generated by thermal emission and accelerated via a potential difference. The high-energy electrons then strike through a titanium foil and are directed onto the binders to be cured. The general principles of electron beam curing are described in "Chemistry &amp; Technology of UV &amp; EB Formulations for Coatings, Inks &amp; Paints", Vol. 1, PKT Oldring (Ed.), SITA Technology, London, England, S. 101-157, 1991 described in detail.

In the case of thermal curing of the activated double bonds, this can also be done with the addition of thermally decomposing radical formers. Suitable, as known in the art, eg Peroxy compounds such as dialkoxydicarbonates such as Bis (4-tert-butylcyclohexyl) peroxydicarbonate, dialkyl peroxides such as Dilauryl peroxide, peresters of aromatic or aliphatic acids such as tert-butyl perbenzoate or tert-amyl peroxy 2-ethylhexanoate, inorganic peroxides such as. B. Ammonium peroxodisulfate, potassium peroxodisulfate, organic peroxides such as 2,2-bis (tert-butylperoxy) butane, dicumyl peroxide, tert-butyl hydroperoxide or azo compounds such as 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 1 - [(cyano-1 -methylethyl) azo] formamides, 2,2'-azobis (N-butyl-2-methylpropionamides), 2,2'-azobis (N-cyclohexyl-2-methylpropionamides), 2,2'-azobis {2-methyl- N- [2- (1-hydroxybutyl)] propionamide}, 2,2'-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide, 2,2'-azobis {2-methyl- N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide. Also possible are highly substituted 1,2-diphenylethanes (Benzpinakole), such as. B. 3,4-dimethyl-3,4-diphenylhexane, 1,1,2,2-tetraphenyl-ethanediol-1,2 or their silylated derivatives.

It is also possible to use a combination of UV light and thermally activatable initiators.

The auxiliaries and additives of component e) include solvents of the type mentioned above under E).

Furthermore, e) may also contain UV absorbers and / or HALS stabilizers in order to increase the weather stability of the cured lacquer layer. The combination is preferred. The former should have an absorption range of at most 390 nm, such as triphenyltriazine types (eg Tinuvin® 400 (Ciba Specialty Chemicals GmbH, Lampertheim, DE)), benzotriazoles such as Tinuvin® 622 (Ciba Specialty Chemicals GmbH, Lampertheim, DE) or oxalic acid dianilides (z. B. Sanduvor® 3206 (Clariant, Muttenz, CH))) and are added in 0.5-3.5% by weight, based on solid resin. Suitable HALS stabilizers are commercially available (Tinuvin® 292 or Tinuvin® 123 (Ciba Specialty Chemicals GmbH, Lampertheim, DE) or Sanduvor® 3258 (Clariant, Muttenz, CH). Preferred amounts are 0.5-2.5 wt .-% based on solid resin.

Likewise, in e) pigments, dyes, fillers, flow control and venting additives may be included.

In addition, if necessary, the catalysts known from polyurethane chemistry for accelerating the NCO / OH reaction in e) may be included. These are, for example tin or zinc salts or Zinnorganoverbindungen, tin and / or zinc soaps such as Zinnoctoat, dibutyltin dilaurate, dibutyltin oxide or tertiary amines such. B. diazabicyclo [2,2,2] octane (DABCO).

The application of the coating compositions according to the invention to the material to be coated is carried out by the methods commonly known and used in coating technology such as spraying, knife coating, rolling, casting, dipping, spinning, brushing or spraying or by printing techniques such as screen, gravure, flexographic or offset printing as well as by transfer methods.

Suitable substrates are, for example, wood, Metal, in particular also metal as used in the applications of the so-called wire, coil, Can or container painting is used plastic also in the form of films, especially ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA PE, HDPE, LDPE, LLDPE, UHMWPE PET, PMMA, PP, PS, SB, PURE, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM, and UP (short designations according to DIN 7728T1), Paper, Leather, Textiles, Felt, Glass, Wood, Wood products, Cork, inorganically bound substrates such as wood and fiber cement boards, electronic assemblies or mineral substrates. It can also substrates that consist of various of the aforementioned materials, or already coated substrates such as vehicles, aircraft or ships and their parts, especially bodies or attachments are painted. It is also possible to apply the coating agent only temporarily to a substrate, then to harden partially and completely and, if necessary, to remove it again, for example to remove it Produce films.

For curing, by evaporation, for example, solvents contained can be completely or partially removed.

Subsequently or at the same time, the thermal and / or photochemical curing processes which may be necessary can be carried out successively or simultaneously.

If necessary, the thermal curing may be carried out at room temperature but also at elevated temperature, preferably at 40 to 160 ° C, preferably at 60 to 130 ° C, more preferably at 80 to 110 ° C.

When photoinitiators are used in d), the radiation curing is preferably carried out by the action of high-energy radiation, ie UV radiation or daylight, for example Light of wavelength 200 to 700 nm or by irradiation with high-energy electrons (electron radiation, 150 to 300 keV). For example, high or medium pressure mercury vapor lamps are used as radiation sources for light or UV light, it being possible for the mercury vapor to be modified by doping with other elements such as gallium or iron. Lasers, pulsed lamps (known as UV flash emitters), halogen lamps or excimer emitters are also possible. The radiators can be equipped by design or by using special filters and / or reflectors so that the escape of a portion of the UV spectrum is prevented. For example, for example for occupational hygiene reasons, the UV-C or UV-C and UV-B associated radiation are filtered out. The emitters can be installed immovably so that the material to be irradiated is moved past the radiation source by means of a mechanical device or the emitters can be movable and the material to be irradiated does not change its location during the hardening. The radiation dose for UV curing, which is usually sufficient for crosslinking, is in the range from 80 to 5000 mJ / cm²,

The irradiation may optionally also in the absence of oxygen, for. B. under inert gas atmosphere or oxygen-reduced atmosphere. As inert gases are preferably nitrogen, carbon dioxide, noble gases or combustion gases. Furthermore, the irradiation can be carried out by covering the coating with media transparent to the radiation. Examples include plastic films, glass or liquids such as water.

Depending on the radiation dose and curing conditions, the type and concentration of the optionally used initiator are to be varied in a manner known to the person skilled in the art.

For curing, high-pressure mercury lamps in stationary installations are particularly preferably used. Photoinitiators are then used in concentrations of 0.1 to 10 wt .-%, particularly preferably 0.2 to 3.0 wt .-% based on the solids of the coating. To harden these coatings, a dose of 200 to 3000 mJ / cm is preferred² measured in the wavelength range of 200 to 600 nm used.

When using thermally activatable initiators in d) by increasing the temperature. In this case, the thermal energy can be introduced into the coating by radiation, heat conduction and / or convection, the infrared emitters, near-infrared emitters and / or ovens customary in coating technology usually being used.

The applied layer thicknesses (before curing) are typically between 0.5 and 5000 μm, preferably between 5 and 1000 μm, particularly preferably between 15 and 200 μm. When using solvents, this is removed after application and before curing by the common methods.

<u style="single">Examples</u>

All percentages are by weight unless stated otherwise.

The determination of the NCO contents in% was carried out via back-titration with 0.1 mol / l hydrochloric acid after reaction with butylamine, based on DIN EN ISO 11909.

The viscosity measurements were carried out with a cone plate viscometer (SM-KP), Viskolab LC3 / ISO from Paar Physica, Ostfildern, DE according to ISO / DIS 3219: 1990.

Infrared spectroscopy was performed on liquid films applied between sodium chloride plates on a Model 157 instrument from Perkin Elmer, Überlingen, DE.

Content of residual monomers or volatile constituent components was determined by GC (method with tetradecane as internal standard, oven temperature 110 ° C, injector temperature 150 ° C, carrier gas helium, device: 6890 N, Agilent, Waldbronn, DE, column: Restek RT 50, 30 m , 0.32 mm inside diameter, 0.25 μm film thickness).

The determination of the solid was carried out according to DIN 53216/1 draft 4/89, ISO 3251

The ambient temperature of 23 ° C prevailing at the time of the experiment is referred to as RT.

<u style="single">Desmodur</u>^{<u style="single">®</u>}<u style="single">N 3400:</u> HDI polyisocyanate predominantly containing uretdione structure, viscosity 185 mPas / 23 ° C, NCO content 21.4%, commercial product of Bayer AG, Leverkusen, DE <u style="single">Desmorapid.RTM</u>^{<u style="single">®</u>}<u style="single">Z:</u> Dibutyltin dilaurate (DBTL), commercial product of Bayer AG, Leverkusen, DE <u style="single">Darocur</u>^{<u style="single">®</u>}<u style="single">1173:</u> Photoinitiator, commercial product of Ciba Specialty Chemicals GmbH, Lampertheim, DE <u style="single">Tone</u>^{<u style="single">®</u>}<u style="single">M100:</u> Reaction product of 2 equivalents of ε-caprolactone with 1 equivalent of 2-hydroxyethyl acrylate, OH content = 4.97%, viscosity = 82 mPas / 23 ° C, commercial product of Dow, Schwalbach, DE.

Example 1 describes the preparation of a suitable catalytically active carboxylate which is used in Example 2 for the reaction of compounds containing uretdione groups with ethylenically unsaturated hydroxyl compounds to give corresponding allophanate-containing compounds.

<u style="single">example 1</u>

Choline-ethylhexanoate

In a glass flask with reflux condenser, heatable oil bath, mechanical stirrer and internal thermometer 272.13 g of a 40% solution of choline hydroxide and 145.73 g of 2-ethylhexanoic acid were stirred vigorously at RT for 30 min. On a rotary evaporator, water and methanol were distilled off under reduced pressure gradually increased to 20 mbar at 30-45 ° C. The product was then taken up with n-hexane and again concentrated on a rotary evaporator and dried at 0.1 mbar and 40 ° C for 2 h. This gives a slightly colored, viscous liquid whose 1H-NMR spectrum has equimolar ratios of choline and ethylhexanoate, but only a weak signal in the range of aliphatic carboxylic acids

<u style="single">Example 2</u>

Inventive allophanate-containing binder

In a three-necked flask with reflux condenser, stirrer, dropping funnel and air passage (0.5 1 / h) were 263.47 g Desmodur® N3400, 0.50 g of 2,6-di-tert-butyl-4-methylphenol and 0.07 g Desmorapid® Z at RT and then heated to 60 ° C. 219.54 g of 2-hydroxyethyl acrylate were slowly added dropwise, with a maximum temperature of 70 ° C was reached. Thereafter, the reaction mixture was kept at 65 ° C until the NCO content &lt;0.1%. Subsequently, a mixture of 14.43 g of 2-hydroxyethyl acrylate and 1.49 g of the catalyst from Example 1 was added dropwise. The reaction mixture was further heated and kept at 80 ° C until in the IR spectrum at v = 1768 cm^-1 after 2.5 h only a very weak signal for uretdione groups was detectable. 0.50 g of isophthalic acid dichloride were added and cooled rapidly to RT. A content of hydroxyethyl acrylate of 4.68% was determined by gas chromatography on a sample taken. It was followed by the addition of 39.0 g Desmodur N3400 and 0.07 g Desmorapid® Z. It was stirred at 60 ° C until in the IR spectrum at v = 2272 cm^-1no signal for the isocyanate group was present anymore. The content of hydroxyethyl acrylate was determined by gas chromatography to be 0.18% on a sample taken. A product having a viscosity of 64,500 mPas / 23 ° C., a color number of 104 APHA and an NCO content of less than 0.1% was obtained

<u style="single">Comparative Example 3</u>

Attempt to produce an allophanate-containing binder

The catalysts described in US-A 2003 301 537 13 for the crosslinking of powder coatings from uretdione group-containing curing agents and polymeric hydroxyl compounds without activated double bonds were tested for suitability:

Example 2 was repeated with the difference that instead of the catalyst from Example 3 now 0.51 g of tetrabutylammonium hydroxide were used as the catalyst. The reaction mixture was heated and kept at 80 ° C until in the IR spectrum at ν = 1768 cm^-1 after 2 h only a very weak signal for uretdione groups was detectable. 0.10 g of benzoyl chloride was added and cooled rapidly to RT. The reaction mixture became cloudy. The content of hydroxyethyl acrylate at 2.4% was determined by gas chromatography on a sample taken. To the reaction mixture was added 5.20 g Desmodur® N3400 and stirred at 70 ° C until in the IR spectrum at ν = 2272 cm^-1 no signal for the isocyanate group was present anymore. The content of hydroxyethyl acrylate at 0.17% was determined by gas chromatography on a sample taken. A turbid product having a viscosity of 84,000 mPas / 23 ° C. and an NCO content of 0% was obtained.

<u style="single">Comparative Example 4</u>

Attempt to produce an allophanate-containing binder

The catalysts described in US-A 2003 301 537 13 for the crosslinking of powder coatings from uretdione group-containing curing agents and polymeric hydroxyl compounds without activated double bonds were tested for suitability:

Example 2 was repeated with the difference that instead of the catalyst from Example 3 now 0.67 g of tetrabutylammonium fluoride were used as the catalyst. The reaction mixture was heated and kept at 80 ° C until in the IR spectrum at v = 1768 cm^-1 after 3 h only a very weak signal for uretdione groups was detectable. 0.10 g of benzoyl chloride was added and cooled rapidly to RT. The reaction mixture became cloudy, forming a colorless precipitate. The content of hydroxyethyl acrylate at 1.7% was determined by gas chromatography on a sample taken. 4.30 g of Desmodur® N3400 were added to the reaction mixture and the mixture was stirred at 70 ° C., until in the IR spectrum at ν = 2272 cm^-1 no signal for the isocyanate group was present anymore. The content of hydroxyethyl acrylate at 0.15% was determined by gas chromatography on a sample taken. A turbid product having a viscosity of 92,000 mPas / 23 ° C. and an NCO content of 0% was obtained.

Comparative Examples 3 and 4 show that the substances suitable for the crosslinking of powder coatings consisting of uretdione group-containing hardeners and polymeric hydroxyl compounds are not suitable for a specific synthesis of allophanates from uretdiones and alcohols. The products thus obtained are cloudy and relatively high viscosity, so that they are not suitable for the production of coatings.

<u style="single">Example 5</u>

Paint formulation and paint

A portion of the product of Example 2 was intimately mixed with 3.0% of the photoinitiator Darocur® 1173. By means of a bone doctor with a gap of 90 microns, the mixture was applied as a thin film on a glass plate. After UV irradiation (mercury medium pressure lamps, IST Metz GmbH, Nürtingen, DE, 750 mJ / cm²) was a transparent, hard and solvent-resistant coating with a pendulum hardness 152 s, which was hardly scratched by steel wool (type 0/0/0) with a film-directed force of 500 g in ten double strokes and by 100 double strokes with a cotton wool soaked in butyl acetate did not visibly change.