HK1099034B - Low-viscosity allophanates having actinically hardenable groups - Google Patents

Description

Low viscosity allophanates containing photocurable groups

The invention relates to low-viscosity reaction products of polyisocyanates containing reactive groups and ethylenically unsaturated compounds which are polymerized by exposure to actinic radiation, to a process for preparing them and to their use in coating compositions.

Coating systems with activated double bonds are known for curing by actinic radiation, such as UV light, IR radiation or electron beams, and this process has already been established in industry. This method is one of the fastest curing methods in coating technology.

Because of the environmental and economic requirements of modern coating systems, which necessitate their use of as little organic solvent as possible, or even no organic solvent at all, for viscosity control, it is desirable to use coating materials which are themselves of low viscosity. For this purpose, polyisocyanates having an allophanate structure have long been used, as described in EP-A0682012 and the like.

In industry, these materials are prepared by reacting monohydric or polyhydric alcohols with an excess of aliphatic and/or cycloaliphatic diisocyanates (cf. GB-A994890, EP-A0000194 or EP-A0712840). The unreacted diisocyanate is then removed by distillation under reduced pressure. According to DE-A19860041, this step can also be carried out with OH-functional compounds having an activated double bond, for example hydroxyalkyl acrylates, although difficulties arise in the preparation of products having a particularly low monomer content. In order to be able to reduce the residual isocyanate content sufficiently (residual monomers < 0.5% by weight), the distillation step has to be carried out at temperatures of up to 135 ℃, so that there is a possibility of polymerization of the double bonds under thermal initiation, even during purification, which means that the desired product is no longer obtained.

The preparation of low-monomer-content, allophanate-containing, polyurethane-based, radiation-curable adhesives is described in EP-A0867457 and U.S. Pat. No. 3, 5739251. However, these binders do not have an activated double bond but rather an inactive allyl ether group (formula R-O-CH)₂-CH＝CH₂). It is therefore necessary to add a reactive diluent (low molecular weight ester of acrylic acid) which introduces the desired uv activity.

EP-A0825211 describes the synthesis of allophanate structures from oxadiazinetriones, but does not mention radiation-curable derivatives having an activated double bond. All that is mentioned is the use of polyesters containing maleic and/or fumaric acid esters; no description is given about the possibility of radiation curing.

U.S. Pat. No. 3, 5777024 describes the preparation of low-viscosity radiation-curable allophanates by reacting hydroxyl-functional monomers having an activated double bond with the isocyanate groups of allophanate-modified isocyanurate polyisocyanates. The result is that the allophanate-bonded radicals are saturated.

The formation of allophanate compounds by ring-opening reaction of uretdiones with alcohols is known in principle as a crosslinking mechanism in powder coatings (cf. International society for aqueous, High Solids and powder coatings, Proceedings of the International Waterborn, High-Solids, and powder coatings Symposium), 2001, 28 th, 405-419, and U.S. Pat. No. A20030153713). However, the reaction temperatures required for this purpose are too high for the goal of preparing radiation-curable monomers based on allophanates with activated double bonds (. gtoreq.120 ℃).

Historically, the direct reaction of uretdione rings with alcohols to form allophanates was initially investigated for solvent-borne, isocyanate-free 2K [ 2-component ] polyurethane coatings. Because of the low reaction rate, the reaction is of no technical significance in the absence of a catalyst (f.schmitt, angelw. markromo. chem. (1989), 171, pages 21-38). However, the crosslinking reaction between HDI-based uretdione curing agents (curvatures) and polyols in the presence of suitable catalysts is said to start at temperatures of from 60 to 80 ℃ (K.B. Chandalia; R.AEnglebach; S.L. Goldstein; R.W.good; S.H.Harris; M.J.Morgan; P.J.Whitman; R.T.Wojcik, proceedings of the International Water-base, high solids content and powder coatings society (2001), pp.77-89). The structure of these catalysts has not been disclosed so far. There is no commercial product prepared by this reaction so far.

In summary, there is no detailed description in the prior art of the preparation of low-viscosity radiation-curable allophanates by ring-opening reaction of alcohols having an activated double bond with uretdiones at temperatures below 100 ℃.

It is therefore an object of the present invention to provide a process for preparing allophanate-containing binders having one or more activated double bonds, which is carried out at temperatures below 100 ℃ and the product thus obtained has a viscosity, as undiluted form, at 23 ℃ of preferably ≦ 100,000mPa · s.

Surprisingly, it has been found that the desired binders can be obtained by reacting uretdiones with alcohols containing activated double bonds using phenoxides as catalysts.

The present invention accordingly provides a process for preparing an allophanate group-containing adhesive which contains, at the oxygen atom of the allophanate group which is linked by two single bonds, an organic radical having a reactive group which undergoes polymerization with an ethylenically unsaturated compound on exposure to actinic radiation, in which:

A) one or more compounds containing uretdione groups with

B) One or more OH-functional compounds containing groups capable of undergoing a polymerization reaction with ethylenically unsaturated compounds upon exposure to actinic radiation, and

C) optionally further NCO-reactive compounds

D) In one or more compounds containing a phenoxide group as catalyst and

E) in the presence of optional auxiliaries and additives

The reaction takes place.

The invention also provides other adhesives that may be made by the process of the invention.

In component A), all organic compounds containing at least one uretdione group can be used.

Preferably, these organic compounds are those obtained by catalytic dimerization of aliphatic, cycloaliphatic and/or araliphatic diisocyanates or polyisocyanates by methods known to the person skilled in the art (cf. J.Prakt. chem.1994, 336, pp. 196-198).

Examples of suitable diisocyanates include 1, 4-diisocyanatobutane, 1, 6-diisocyanatohexane (HDI), trimethylhexane diisocyanate, 1, 3-and 1, 4-diisocyanatomethylcyclohexane, isophorone diisocyanate (IPDI), 4 ' -diisocyanatodicyclohexylmethane, 1, 3-and 1, 4-xylylene diisocyanate (commercially available as XDI from Takeda, Japan), diphenylmethane 4, 4 ' -diisocyanate and diphenylmethane 2, 4 ' -diisocyanate (MDI), 2, 4-and 2, 6-diisocyanatotoluene (TDI) or mixtures thereof. 1, 6-hexamethylene diisocyanate is preferred.

Examples of the catalyst used herein include the following: trialkylphosphine, dimethylaminopyridine, tris (dimethylamino) phosphine.

The result of the dimerization reaction depends, in a manner known to the person skilled in the art, on the catalyst used, the reaction conditions and the diisocyanate used. In particular, it is possible to form products which contain on average more than one uretdione group per molecule, the number of uretdione groups being divided. Depending on the catalyst used, the reaction conditions and the diisocyanates used, product mixtures are also formed which, in addition to the uretdiones, contain further structural units, such as isocyanurates and/or iminooxadiazinediones.

Particularly preferred compounds of component A) include the products of the catalytic dimerization of HDI, which have a free HDI content of less than 0.5% by weight, an NCO content of 17 to 25% by weight, preferably 21 to 24% by weight, and a viscosity at 23 ℃ of 20 to 500 mPas, preferably 50 to 200 mPas.

Conventional NCO-functional compounds prepared by catalytic dimerization are preferably used directly as part of component A), but in principle they can also be used first for further reactions and then for A). This further reaction is, for example, a blocking reaction of free NCO groups or a further reaction of NCO groups with NCO-active compounds having a functionality of greater than or equal to 2 to form iminooxadiazinedione, isocyanurate, urethane, allophanate, biuret, oxadiazinetrione, oxazolidinone, acylurea or carbodiimide structures. This gives compounds containing uretdione groups and high molecular weights, which, depending on the chosen proportions, may or may not also contain NCO groups.

Suitable blocking agents are, for example, alcohols, lactams, oximes, malonates, alkyl acetoacetates, triazoles, phenols, imidazoles, pyrazoles and amines, such as butanone oxime, diisopropylamine, 1, 2, 4-triazole, dimethyl-1, 2, 4-triazole, imidazole, diethyl malonate, ethyl acetoacetate, acetoxime, 3, 5-dimethylpyrazole, epsilon-caprolactam, N-tert-butylbenzylamine, cyclopentanone carboxyethyl ester or any desired mixtures of these blocking agents. The procedure for blocking the NCO groups is well known to the person skilled in the art and is described by way of example in the Organic coating developments (Progress in Organic Coatings)1999, 36, 148-172.

NCO-reactive compounds having a functionality of 2 or more may be the diisocyanates and/or polyisocyanates mentioned above, as well as simple alcohols having a functionality of 2 or more, such as ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, dipropylene glycol, butanediol and isomers thereof, neopentyl glycol, 1, 6-hexanediol, 2-ethylhexanediol and tripropylene glycol or alkoxylated derivatives of these alcohols. Preferred diols are 1, 6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable triols are glycerol or trimethylolpropane or their alkoxylated derivatives. The tetrahydric alcohol is pentaerythritol or alkoxylated derivatives thereof.

The compounds of component A) can be used directly in the process according to the invention or else can be prepared starting from any precursor which is prepared by a preceding reaction before the process according to the invention is carried out.

Actinic radiation refers to electromagnetic, ionizing radiation, in particular electron beams, ultraviolet radiation and visible light (Roche Lexikon Medizin, 4 th edition; Urban & Fischer Verlag, Munich 1999).

Among the compounds of component B), the groups which can undergo polymerization with ethylenically unsaturated compounds on exposure to actinic radiation are, for example, vinyl ether, propenyl, allyl, maleoyl, fumaryl, maleimide, dicyclopentadienyl, acrylamide, acrylic and methacrylic groups, preference being given to using reactive groups of the following types: vinyl ether, acrylate and/or methacrylate groups, more preferably acrylate groups.

Examples of suitable hydroxyl-containing compounds of component B) are 2-hydroxyethyl (meth) acrylate, polyethylene oxide mono (meth) acrylates (e.g. PEA6/PEM 6; laporte Performance Chemicals, ltd., uk),Polypropylene oxide mono (meth) acrylates (e.g., PPA6, PPM 5S; Laporte performance Chemicals, ltd., uk), polyalkylene oxide mono (meth) acrylates (e.g., PEM63P, laportepperformance Chemicals, ltd., uk), poly (epsilon-caprolactone) mono (meth) acrylates (e.g., Tone)Dow, Schwalbach, Germany, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, hydroxybutyl vinyl ether, 3-hydroxy-2, 2-dimethylpropyl (meth) acrylate, hydroxy-functional mono-, di-or possibly higher acrylates such as glycerol di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate or dipentaerythritol penta (meth) acrylate, which may be obtained by reacting optionally alkoxylated polyols such as trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol.

Also suitable as component B) are alcohols obtained by reaction of acids containing double bonds with epoxy compounds optionally containing double bonds, for example the reaction products of (meth) acrylic acid with glycidyl (meth) acrylate or bisphenol A diglycidyl ether.

In addition, unsaturated alcohols obtained by reacting an optionally unsaturated acid anhydride with a hydroxyl compound optionally containing an acrylate group and an epoxy compound, for example, a reaction product of maleic anhydride with 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate, can also be used.

Particularly preferred compounds of component B) correspond to the abovementioned classes, having an OH functionality of from 0.9 to 1.1.

Particularly preferred are compounds containing primary hydroxyl groups, since in the process of the invention the primary hydroxyl groups are more reactive than secondary or tertiary hydroxyl groups. Particularly preferred are 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

In addition to the OH-functional unsaturated compounds of component B), it is also possible in the process of the invention to use other compounds C) which, unlike the compounds of B), contain NCO-reactive groups such as OH, SH or NH.

For example, the compounds C) are NH-or SH-functional compounds which contain groups which can undergo a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation.

In addition, groups having a hydrophilic action may be incorporated, in particular if intended for use in aqueous media, for example in aqueous coatings. The groups having a hydrophilic action are ionic groups, which may themselves be cationic or anionic, and/or nonionic hydrophilic groups. Cationic, anionic or nonionic dispersing compounds are those which contain, for example, sulfonium, ammonium, phosphonium, carboxylate, sulfonate or phosphonate groups or can be converted into the abovementioned groups (potentially ionic groups) by salt formation or contain polyether groups and can be bonded via isocyanate-reactive groups already present. Preferred suitable isocyanate-reactive groups are hydroxyl and amino groups.

Examples of ionic compounds or compounds containing potentially ionic groups which are suitable as hydrophilic synthesis components are 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, dimethylolbutyric acid, hydroxypivalic acid, N- (2-aminoethyl) - β -alanine, 2- (2-aminoethylamino) ethanesulfonic acid, ethylenediamine-propyl or butylsulfonic acid, 1, 2-or 1, 3-propylenediamine- β -ethanesulfonic acid, maleic acid, citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, lysine, 3, 5-diaminobenzoic acid, succinic acid, maleic acid, succinic acid, adducts of IPDI and acrylic acid (EP-A0916647, example 1) and alkali metal and/or ammonium salts thereof; adducts of sodium bisulfite and but-2-ene-1, 4-diol, polyether sulfonates, 2-butenediol and NaHSO₃Propoxylated adducts of (A) as described, for example, in DE-A2446440 (pages 5 to 9, formulae I to III), and structural units which can be converted into cationic groups, such as N-methyldiethanolamine. Preferred is separationThe ionic or potentially ionic compounds are compounds having carboxyl or carboxylate and/or sulfonate and/or ammonium groups. Particularly preferred ionic compounds are compounds containing carboxyl and/or sulfonate groups as ionic or potentially ionic groups, for example salts of N- (2-aminoethyl) - β -alanine, 2- (2-aminoethylamino) ethanesulfonic acid or of IPDI adduct with acrylic acid (EP-A-0916647, example 1), and salts of dimethylolpropionic acid.

Suitable nonionically hydrophilicizing compounds are, for example, polyalkylene oxide ethers which contain at least one hydroxyl or amino group. These polyethers comprise from 30 to 100% by weight of units derived from ethylene oxide. Suitable compounds include polyethers of linear structure having a functionality of between 1 and 3, and compounds of the general formula (I),

in the formula (I), the compound is shown in the specification,

R¹and R²Independently of one another, represent a divalent aliphatic, cycloaliphatic or aromatic radical having from 1 to 18 carbon atoms, which may be interrupted by oxygen atoms and/or nitrogen atoms,

R³is an alkoxy-terminated polyethylene oxide group.

Non-ionic hydrophilic compounds are, for example, monohydroxypolyalkylene oxide polyether alcohols containing on average from 5 to 70, preferably from 7 to 55, ethylene oxide units per molecule, such as are obtained in a conventional manner by alkoxylation of suitable starter molecules (e.g.Ullmanns)dertechnischen Chemie, 4 th edition, volume 19, Verlag Chemie, Weinheim, pages 31-38).

Examples of suitable starter molecules are saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, pentanol and isomers thereof, hexanol and isomers thereof, octanol and isomers thereof and nonanol and isomers thereof, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexanes, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol; diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether; unsaturated alcohols, such as allyl alcohol, 1-dimethylallyl alcohol or oleyl alcohol; aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols; araliphatic alcohols, such as benzyl alcohol, anisyl 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. Particular preference is given to using diethylene glycol monobutyl ether as starter molecule.

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

The polyalkylene oxide polyether alcohols are linear polyethylene oxide polyethers or mixed polyalkylene oxide polyethers, at least 30 mol%, preferably at least 40 mol%, of the alkylene oxide units being composed of ethylene oxide units. Preferred nonionic compounds are monofunctional mixed polyalkylene oxide polyethers containing at least 40 mol% ethylene oxide units and not more than 60 mol% propylene oxide units.

In particular when using hydrophilicizing agents containing ionic groups, the effect thereof on the action of the catalysts D) has to be investigated. For this reason, nonionic hydrophilizing agents are preferred.

As compounds of the catalyst component D), it is possible in principle to use, in addition to the phenoxides used according to the invention, any compounds known to the person skilled in the art for catalyzing the reaction of isocyanate groups with isocyanate-reactive groups, alone or as any mixture.

Examples which may be mentioned here include tertiary amines such as triethylamine, pyridine, picoline, benzyldimethylamine, N-ethanopiprazine, N-methylpiperidine, pentamethyldiethylenetriamine, N-dimethylaminocyclohexane, N' -dimethylpiperazine, 1, 4-diazabicyclo [2.2.2] octane (DABCO) or metal salts such as iron (III) chloride, tin (II) octoate, tin (II) ethylhexanoate, tin (II) palmitate, dibutyltin (IV) dilaurate, dibutyltin (IV) diacetate and molybdenum glycolate or any desired mixtures of these catalysts.

However, preference is given to using only phenoxides and/or compounds containing phenoxides as catalysts in D).

The compounds of component D) containing phenoxide groups preferably correspond to the general formula (II),

in the formula:

z is nitrogen or phosphorus, and Z is nitrogen or phosphorus,

R¹、R²、R³、R⁴independently of one another, hydrogen or identical or different, optionally unsaturated, substituent-containing or heteroatom-containing aliphatic, cycloaliphatic or aromatic radicals having up to 24 carbon atoms, Y is a phenoxide of the general formula (III),

in the formula:

q is oxygen, and Q is oxygen,

X¹、X²、X³、X⁴、X⁵independently of one another, are substituents selected from: hydrogenHalogen, cyano, hydroxyl, amide, amine, ether, ester, thioether, ketone, aldehyde and carboxylate groups, and optionally unsaturated, substituent-containing or heteroatom-containing aliphatic, cycloaliphatic or aromatic groups having up to 24 carbon atoms, and optionally forming part of a ring or polycyclic system.

As the compound of the formula (II) containing a phenoxide group, ammonium phenoxide and phosphonium phenoxide are particularly preferably used, and tetraalkylammonium phenoxide and tetraalkylphosphonium phenoxide are particularly preferably used.

Particularly preferred phenolates are tetrabutylammonium 4- (methoxycarbonyl) phenolate, tetrabutylammonium 2- (methoxycarbonyl) phenolate, tetrabutylammonium 4-formylphenolate, tetrabutylammonium 4-carbonitrile phenolate, tetrabutylphosphonium 4- (methoxycarbonyl) phenolate, tetrabutylphosphonium 2- (methoxycarbonyl) phenolate, tetrabutylphosphonium 4-formylphenolate, tetrabutylammonium salicylate and/or tetrabutylphosphonium salicylate.

The phenolates of component D) mentioned above can also be formed simultaneously during the process. Catalytically active phenoxides can be formed during the process by using the corresponding phenols and strong bases, such as tetrabutylammonium hydroxide or tetrabutylphosphonium hydroxide.

In this connection it can be stated that the phenolic stabilizers of component E) can also form phenoxides by reaction with bases, which phenoxides serve as catalysts for component D) where desired. In this case, it should be ensured that these phenoxides, in contrast to the corresponding phenols, no longer have any stabilizing effect. It should also be borne in mind that strong bases such as tetrabutylammonium hydroxide or tetrabutylphosphonium hydroxide will catalyze the formation of other isocyanate derivatives, particularly trimerization reactions.

The catalysts D) can also be applied to support materials by methods known to the person skilled in the art and used as heterogeneous catalysts.

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

In the process of the present invention, the catalyst component D) is generally used in an amount of from 0.001 to 5.0% by weight, preferably from 0.01 to 2.0% by weight, more preferably from 0.05 to 1.0% by weight, based on the solids content of the process product.

In the process of the invention, it is possible to use, for example, solvents or reactive diluents or the like as constituents of component E).

Suitable solvents are inert to the functional groups present in the process product from their addition until the end of the reaction. Suitable solvents are, for example, solvents used in the paint industry, such as hydrocarbons, ketones and esters, for example toluene, xylene, isooctane, acetone, butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, tetrahydrofuran, N-methylpyrrolidone, dimethylacetamide and dimethylformamide, although it is preferred not to add any solvent.

Compounds which also undergo (co) polymerization during UV curing and are incorporated into the polymer network and are inert towards NCO groups can be used as reactive diluents. Such reactive diluents are described by way of example in P.K.T.Oldring (Ed.), Chemistry & Technology of UV & EB Formulations, Inks & paintings, Vol.2, 1991, SITA Technology, London, pp.237-. They may be esters of acrylic or methacrylic acid, preferably acrylic acid, with monofunctional or polyfunctional alcohols. Examples of suitable alcohols include butanol, pentanol, hexanol, heptanol, octanol, nonanol and decanol and isomers of these alcohols, as well as cycloaliphatic alcohols such as isobornyl, cyclohexanol and alkylated cyclohexanols, dicyclopentanol; araliphatic alcohols such as phenoxyethanol and nonylphenylethanol and tetrahydrofurfuryl alcohol. In addition, alkoxylated derivatives of these alcohols may be used. Suitable diols are, for example, the alcohols listed below: ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol and isomers thereof, neopentyl glycol, 1, 6-hexanediol, 2-ethylhexanediol, and tripropylene glycol, and alkoxylated derivatives of these alcohols. Preferred diols are 1, 6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable triols are glycerol or trimethylolpropane or their alkoxylated derivatives. The tetrahydric alcohol is pentaerythritol or alkoxylated derivatives thereof.

The adhesives of the present invention must be stable against premature polymerization. Thus, before and/or during the reaction of components A) to D), phenolic stabilizers which inhibit the polymerization are preferably added as constituents of component E). Phenols used herein are, for example, p-methoxyphenol, 2, 5-di-tert-butylhydroquinone or 2, 6-di-tert-butyl-4-methylphenol. Also suitable are N-oxyl compounds for stabilization, such as 2, 2, 6, 6-tetramethylpiperidine N-oxide (TEMPO) or its derivatives. Stabilizers may also be chemically incorporated into the adhesive; compounds of the above-mentioned kind are suitable for this purpose, in particular if they also contain free aliphatic alcohol groups or primary or secondary amine groups and can therefore be chemically linked to the compounds of component A) via urethane groups or urea groups. Particularly suitable for this purpose is 2, 2, 6, 6-tetramethyl-4-hydroxypiperidine N-oxide. Preference is given to phenolic stabilizers, in particular p-methoxyphenol and/or 2, 6-di-tert-butyl-4-methylphenol.

Other stabilizers, for example compounds from the class of HALS (HALS ═ hindered amine light stabilizers), are conversely unsuitable for use in E), since they are known to be unable to perform such an effective stabilizing action, which may lead to "creeping" free-radical polymerization of the unsaturated groups.

In order to stabilize the reaction mixture, in particular the unsaturated groups, against premature polymerization, an oxygen-containing gas, preferably air, may be introduced into and/or over the reaction mixture. The gas preferably has a very low water content to prevent unwanted reactions in the presence of free isocyanate groups.

In general, the stabilizer is added during the preparation of the binders according to the invention, and after this has been completed, the stabilization is carried out again with a phenolic stabilizer and optionally with an air-saturated reaction product in order to obtain a long-term stabilizer.

In the process of the present invention, the stabilizer component is generally used in an amount of from 0.001 to 5.0% by weight, preferably from 0.01 to 2.0% by weight, more preferably from 0.05 to 1.0% by weight, based on the solids content of the process product.

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

The process of the invention is preferably carried out at a temperature of from 20 ℃ to 100 ℃, more preferably from 40 ℃ to 100 ℃ and particularly preferably from 80 ℃ to 89 ℃.

In general, NCO groups which may be present react more rapidly with the hydroxyl groups of component B) than with the uretdione groups of component A). Thus, if two or more different components are present in B), the urethanation reaction and the allophanation reaction can be controlled by adding these components in such a sequence that one component of B) is preferably combined in the urethanation reaction and the last component added is preferably combined in the allophanation reaction.

However, the allophanatization reaction can also be terminated by addition of an isocyanate-containing compound which deactivates the remaining compounds of the catalyst-deactivating compounds (in the case of phenoxides, for example, strong acids such as acidic phosphates) or else which can scavenge components B) and C).

It is immaterial whether the reaction process is carried out continuously, for example in a static mixer, extruder or compounder, or batchwise, for example in a stirred reactor.

The process of the invention is preferably carried out in a stirred reactor, the order of addition of components A) to E) being arranged arbitrarily.

Can be measured by means of a suitable measuring device installed in the reaction vessel and/or on the basis of the results of the analysis of the samples takenThe progress of the reaction was monitored. Suitable techniques are known to those skilled in the art. These techniques include, for example, viscosity measurements, refractive index measurements, OH content, Gas Chromatography (GC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), and near infrared spectroscopy (NIR). It is preferred to detect any free NCO groups present (for aliphatic NCO groups, the band is about v-2272 cm)^-1Here), in particular, the uretdione group (for example, uretdione based on 1, 6-hexamethylene diisocyanate has a band at v 1761cm^-1Infra red spectrum of (B), and gas chromatography for analysis of unreacted compounds from B) and C).

In a preferred embodiment of the present invention, the compounds of component A) are subjected to an allophanatization reaction and a carbamation reaction in parallel. For this purpose, A), the stabilizers and, if appropriate, further auxiliaries and additives from E) are initially added, and then the components B) to E) are added, and the reaction mixture is brought to the reaction temperature.

In another preferred embodiment, A) is first reacted with B) until the NCO groups have reacted to completion. E) Or a portion of E) may already be present. The reaction of the uretdione groups of A) with B) is then started by adding D) and, if appropriate, adjusting the temperature.

In a particularly preferred embodiment, the isocyanate groups and uretdione groups are reacted with an excess of the hydroxyl groups of component B. The hydroxyl groups remaining after the reaction of A) with B) are subsequently preferably carbamated with other isocyanate-containing compounds, in particular the compounds mentioned as possible constituents of component B), under the catalytic action of D).

The viscosity of the unsaturated allophanates obtained by the process of the invention, in particular those based on the products of the HDI-catalyzed dimerization (preferably employed), at 23 ℃ is preferably 100000 mPas or less, more preferably 60000 mPas or less, and very preferably 40000 mPas or less.

The unsaturated allophanates obtained by the process of the invention, in particular those based on the product of a HDI-catalyzed dimerization reaction (preferably used)Number average molecular weight M_nPreferably 600 to 3000 g/mol, more preferably 750 to 1500 g/mol.

The unsaturated allophanates prepared by the process of the invention preferably contain less than 0.5% by weight of free diisocyanate and/or triisocyanate monomers, more preferably less than 0.1% by weight.

The binders of the invention are useful for the production of coatings and paints, and also adhesives, printing inks, casting resins, dental compounds, sizes, photoresists, stereolithography systems, sealants and resins for composites. However, in adhesive bonding or sealing applications, there is a requirement that, in the case of uv radiation curing, at least one of the two substrates to be bonded or sealed to one another is transparent to uv radiation; in other words, in general, the substrate must be transparent. In the case of electron beams, sufficient penetration of electrons must be ensured. Preferably in paints and coatings.

The present invention also provides a coating composition comprising:

a) one or more binders obtainable according to the invention,

b) optionally one or more polyisocyanates containing free or blocked isocyanate groups which are free of groups which are capable of polymerization with ethylenically unsaturated compounds upon exposure to actinic radiation,

c) optionally further compounds, which are different from the compounds described under a), contain groups which can undergo a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation and optionally contain free or blocked NCO groups.

d) Optionally one or more active hydrogen-containing isocyanate-reactive compounds,

e) an initiator, wherein the initiator is selected from the group consisting of,

f) optionally a solvent and

g) optionally auxiliaries and additives.

The polyisocyanates of component b) are known to the person skilled in the art. Preference is given here to using compounds based on 1, 6-hexamethylene diisocyanate, isophorone diisocyanate, 4' -diisocyanatodicyclohexylmethane and/or trimethylhexamethylene diisocyanate, optionally modified with isocyanurate, allophanate, biuret, uretdione and/or iminooxadiazinetrione groups.

In this case, the NCO groups may also be blocked, the blocking agents used being the compounds already mentioned in the description of component A).

The compounds of component c) include, for example, compounds based preferably on urethane acrylates of 1, 6-hexamethylene diisocyanate, isophorone diisocyanate, 4' -diisocyanatodicyclohexylmethane and/or trimethylhexamethylene diisocyanate, which have optionally been modified with isocyanurate, allophanate, biuret, uretdione and/or iminooxadiazinetrione groups, and which have no active hydrogen-containing isocyanate-group-reactive functional groups.

The NCO-containing urethane acrylate may beUA VP LS 2337、UA VP LS 2396 orUA XP 2510 is commercially available from Bayer AG, Leverkusen, germany.

Other reactive diluents which have been described and known in the art for radiation-curable coatings may also be used as constituents of c), provided that they do not contain any NCO-reactive groups.

The compounds of component d) may be saturated or unsaturated. The chemical functional group that reacts with the NCO group is a functional group containing an active hydrogen atom, such as a hydroxyl, amine, or thiol group.

Preferred are saturated polyols, examples being polyether polyols, polyester polyols, polycarbonate polyols, poly (meth) acrylate polyols and/or polyurethane polyols known in the art of coatings, adhesive binders, printing inks or sealants, which do not contain groups capable of polymerization with ethylenically unsaturated compounds upon exposure to actinic radiation.

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

It is also possible to use as component d) reactive diluents which are already described and known in the art of radiation-curing coatings, provided that they contain NCO-reactive groups.

Initiators which can be activated thermally and/or by radiation can be employed as initiators for component e) of the free-radical polymerization. Photoinitiators activated by ultraviolet or visible light are preferably used herein. Photoinitiators are compounds known to the person skilled in the art and are commercially available, being divided into monomolecular initiators (type I) and bimolecular initiators (type II). Suitable (type I) systems are aromatic ketone compounds, for example, benzophenone in combination with tertiary amines, alkylbenzophenones, 4 '-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the abovementioned types. Other suitable initiators (type II) are, for example, benzoin and derivatives thereof, benzil ketals, acylphosphine oxides (e.g.2, 4, 6-trimethylbenzoyldiphenylphosphine oxide), bisacylphosphine oxides, phenylglyoxylates, camphorquinones, α -aminoalkanoylbenzenes, α -dialkoxyacetophenones and α -hydroxyalkanophenones.

Initiators used in amounts of from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, based on the weight of the film-forming binder, may be used as individual substances or, in view of the frequently advantageous synergistic effects, may be used in combination with one another.

When an electron beam is used instead of ultraviolet radiation, no photoinitiator is required. As known to those skilled in the art, electron beams are generated by thermal emission and acceleration under the action of a potential difference. The energetic electrons are then directed through the titanium foil onto the adhesive to be cured. The general principles of electron beam curing are described in detail in "Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints", volume 1, P.K.T. Oldring (Ed.), SITA Technology, London, England, pp.101-.

If the activated double bonds are thermally cured, the reaction can also be carried out by adding thermally decomposing free-radical initiators. As known to the person skilled in the art, suitable are, for example, peroxides, such as dialkoxy dicarbonates, e.g.bis (4-tert-butylcyclohexyl) peroxydicarbonate, dialkyl peroxides, e.g.dilauryl peroxide, peresters of aromatic or aliphatic acids, e.g.tert-butyl perbenzoate or tert-amyl peroxy-2-ethylhexanoate, inorganic peroxides, e.g.ammonium peroxodisulfate, potassium peroxodisulfate, organic peroxides, e.g.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 ] -formamide, 2' -azobis (N-butyl-2-methylpropionamide), 2, 2 '-azobis (N-cyclohexyl-2-methylpropionamide), 2' -azobis { 2-methyl-N- [2- (1-hydroxybutyl) ] propionamide }, 2 '-azobis { 2-methyl-N- [2- (1-hydroxybutyl) ] propionamide, 2' -azobis { 2-methyl-N- [1, 1-bis (hydroxymethyl) -2-hydroxyethyl ] propionamide. It is also possible to use highly substituted 1, 2-diphenylethanes (benzopinacols), such as 3, 4-dimethyl-3, 4-diphenylhexane, 1, 2, 2-tetraphenylethane-1, 2-diol or silylated derivatives thereof.

A combination of initiators activatable by uv light and thermally may also be used.

The auxiliaries and additives of component E) include solvents of the type described in E).

In addition, e) may also contain UV absorbers and/or HALS stabilizers in order to improve the weathering resistance of the cured coatings. Preferably a combination thereof. The former should have an absorption range of no more than 390 nm, such as triphenyltriazines (e.g.,400(Ciba GmbH, Lampertheim, Germany)), benzotriazoles such as622(CibaGmbH, Lampertheim, germany) or oxalanilide (for example,3206(Clariant, Muttenz, switzerland))) and is added in an amount of 0.5 to 3.5% by weight, based on resin solids. Suitable HALS stabilizers are commercially available (292 or123(CibaGmbH, Lampertheim, Germany) or3258(Clariant, Muttenz, Switzerland). The preferred amounts are based on resin solidsIn an amount of 0.5 to 2.5 wt%.

e) Pigments, dyes, fillers, leveling additives and devolatilizing additives may also be included.

In addition, if desired, known catalysts in polyurethane chemistry for accelerating the NCO/OH reaction can also be included in e). These catalysts are, for example, tin salts or zinc salts or organotin compounds, tin soaps and/or zinc soaps, such as tin octoate, dibutyltin dilaurate, dibutyltin oxide, or tertiary amines, such as diazabicyclo [2.2.2] octane (DABCO).

The coating compositions according to the invention are applied to the materials to be coated by customary methods known in coating technology, for example by spraying (spraying), knife coating, roller coating, curtain coating, dip coating, spin coating, brush or spray coating (squinting) or by printing techniques, for example screen printing, gravure printing, flexography or offset printing, and also by means of transfer.

Suitable substrates are, for example, wood, metal (including in particular metal used in wire enamel, coil coating, can coating or container coating applications), and plastics (including plastics in film form, in particular ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP, PS, SB, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM and UP (abbreviation according to DIN 7728T 1)), paper, leather, fabric, felt, glass, wood materials, cork, inorganically bonded substrates (e.g. wood and fiber cement boards), electronic assemblies or mineral substrates. It is also possible to coat substrates consisting of various of the abovementioned materials or to coat already coated substrates, such as vehicles, aircraft or watercraft and parts thereof, in particular vehicle bodies or parts for external fixing. It is also possible to apply the coating compositions temporarily to the substrate and then to cure them partially or completely, optionally peeling them off again, to produce a film.

For curing, the solvent present can be removed, for example, by flashing off, in whole or in part.

Subsequently or simultaneously, thermal (and optionally also) and photochemical curing operations may be carried out successively or simultaneously.

If desired, the thermal curing can be carried out at room temperature or above, preferably at 40-106 deg.C, more preferably at 60-130 deg.C, and still more preferably at 80-110 deg.C.

If photoinitiators are used in e), radiation curing is preferably carried out by exposure to high-energy radiation, i.e.UV radiation or solar radiation (for example light having a wavelength of 200-700 nm) or by bombardment with high-energy electrons (electron beam, 150 to 300 keV). The light or ultraviolet radiation source used is, for example, a high-pressure or medium-pressure mercury vapor lamp, the mercury vapor being modified by doping with other elements, such as gallium or iron. Lasers, pulsed lamps (known as UV flash lamps), halogen lamps or excimer emitters are also possible. The emitters may be equipped to be blocked from emitting in part of the ultraviolet spectrum as an inherent part of their design or through the use of specific filters and/or reflectors. For example, for occupational hygiene purposes, radiation belonging to UV-C or UV-C and UV-B may be filtered out. The emitter may be mounted in a stationary manner such that the material to be irradiated is moved by mechanical means past the radiation source, or the emitter is moved during curing while the material to be irradiated remains stationary. In general, the radiation dose sufficient for crosslinking in the case of UV curing is set in the range from 80 to 5000 mJ/cm.

If desired, the irradiation can also be carried out in the absence of oxygen, for example in an inert atmosphere or in an oxygen-reduced atmosphere. Suitable inert gases are preferably nitrogen, carbon dioxide, noble gases or combustion gases. Irradiation may also be performed by covering the coating with a medium transparent to the radiation. Examples of such media are, for example, polymer films, glass or liquids such as water.

The type and concentration of any initiator used may be varied in ways known to those skilled in the art depending on the radiation dose and curing conditions.

It is particularly preferred to carry out the curing using a fixedly mounted high-pressure mercury lamp. The photoinitiator is then used in a concentration of 0.1 to 10 wt%, more preferably 0.2 to 3.0 wt%, based on the solids of the coating. For curing, the dosage for curing these coatings is preferably 200 to 3000 mj/cm, measured in the wavelength range from 200 to 600 nm.

In the case of the application of the heat-activated initiator in d) by increasing the temperature, thermal energy can be introduced into the coating by means of radiation, thermal conduction and/or convection, generally using ovens, near-infrared lamps and/or infrared lamps which are customary in coating technology.

The applied film thickness (before curing) is typically from 0.5 to 5000 microns, preferably from 5 to 1000 microns, more preferably from 15 to 200 microns. If a solvent is used, the solvent is removed by conventional methods after application and before curing.

Examples

All percentages are by weight unless otherwise indicated.

Determination of the percentage NCO content was carried out according to DIN EN ISO 11909 by back-titration with 0.1 mol/l hydrochloric acid after reaction with butylamine.

According to ISO/DIS 3219: viscosity measurements were made with a cone and plate viscometer (SM-KP) (Viskolab LC3/ISO from Paar Physica, Ostfiltern, Germany).

An instrument of type 157 (from Perkin Elmer,germany) was measured on an infrared spectrum, the measurement being carried out on a liquid film applied between two sodium chloride sheets.

Measurement of trimer, uretdione, allophanate and/or allophanate in the end product by NMR spectroscopyAmount of carbamate structure. For this purpose, the CDCl of the samples is recorded₃In (1)¹³C-NMR spectra (DPX 400 and AVC 400 from Bruker, Karlsruhe, Germany, resonance frequency 100MHz, relaxation time 4 seconds, 2000 scans, acquisition time 1.03 seconds, excitation angle 30 ℃ C.) the molar ratio of the substructures was determined from the signal integrals at δ (13C) ═ 121.4ppm (1C NCO), 148.4ppm (3C, trimer), 153.8ppm (1C; allophanate), 156.3ppm (1C, carbamate) and 157.1ppm (2C; uretdione).

The amount of residual monomers and the amount of volatile synthesis components were analyzed by GC (using tetradecane as internal standard, oven temperature 110 ℃, chamber temperature 150 ℃, helium as carrier gas, instrument: 6890N, Agilent, Waldbronn, Germany, column: Restek RT 50, 30 m, internal diameter 32 mm, film thickness 0.25 μm).

The solids content was measured according to DIN 53216/1 protocol 4/89, ISO 3251.

The ambient temperature of 23 ℃ which is mainly used when the experiment is carried out is called RT.

N 3400: HDI polyisocyanates having a predominant uretdione structure, viscosity of 185 mPa.s/23 ℃ and an NCO content of 21.4%, commercial products from Bayer AG, Leverkusen, Germany

Z: dibutyl tin dilaurate (OBTL), a commercial product of Bayer AG from Leverkusen, Germany

1173: photoinitiator, Ciba from Lampertheim, GermanyCommercial product of GmbH

M 100: reaction product of 2 equivalents of epsilon-caprolactone with 1 equivalent of 2-hydroxyethyl acrylate, OH content 4.97%, viscosity 82 mPa.s/23 ℃, commercial product of Dow, Schwalbach, Germany

Examples 1-3 describe the preparation of suitable catalytically active phenoxides which were used in examples 4-5 for the reaction of uretdione group-containing compounds with ethylenically unsaturated hydroxyl compounds to form the corresponding allophanate-containing compounds.

Example 1Tetrabutylammonium 4- (methoxycarbonyl) phenoxide

To a glass flask with reflux condenser, heated oil bath, mechanical stirrer and internal thermometer at room temperature was added 38.00 grams of methyl 4-hydroxybenzoate and 277.92 grams of water, and the components were thoroughly stirred together. 162.00 g of tetrabutylammonium hydroxide (40% strength, solvent water) were then added and the reaction mixture was heated to 60 ℃. Stir at 60 ℃ for 1 hour (the contents of the flask became clear). The reaction mixture was then cooled and water was distilled off under reduced pressure of 20 mbar and at a temperature of 30-45 ℃. The product was then washed with butyl acetate and dried in a vacuum oven at 80 ℃ and 10 mbar. A white solid was obtained.

Example 2Tetrabutylammonium 4-formylphenolate

To a glass flask with reflux condenser, heated oil bath, mechanical stirrer and internal thermometer at room temperature was added 7.64 grams of 4-hydroxybenzaldehyde and 93.86 grams of water and the components were thoroughly stirred together. Then 40.54 g tetrabutylammonium hydroxide (40% strength, solvent MeOH) were added and the reaction mixture was heated to 60 ℃. Stir at 60 ℃ for 1 hour (the contents of the flask became clear). The reaction mixture was then cooled and the solvent (methanol and water) was distilled off under reduced pressure of 20 mbar and at a temperature of 30-45 ℃. The product was then washed with butyl acetate and dried in a vacuum oven at 80 ℃ and 10 mbar. An off-white solid was obtained.

Example 3Tetrabutylammonium salicylate

To a glass flask with reflux condenser, heated oil bath, mechanical stirrer and internal thermometer at room temperature was added 35.90 grams of ethyl salicylate and 282.13 grams of water, and the components were stirred together thoroughly. 139.98 g of tetrabutylammonium hydroxide (40% strength, solvent water) are then added and the reaction mixture is heated to 60 ℃. Stir at 60 ℃ for 1 hour (the contents of the flask became clear). The reaction mixture was then cooled and water was distilled off under reduced pressure of 20 mbar and at a temperature of 30-45 ℃. The residue was extracted with 200 ml of toluene at 60 ℃. The mixture was then redistilled. The residue was recrystallized from 50 ml of butyl acetate. The product was filtered off, washed with butyl acetate and dried in a vacuum oven at 80 ℃ and 10 mbar. A white solid was obtained.

Example 4Allophanate-containing adhesives of the invention

42.70 g of a three-necked flask with reflux condenser, stirrer and dropping funnel and aeration (6 l/h) were placed at room temperatureN3400, 0.15 g of 2, 6-di-tert-butyl-4-methylphenol and 0.001 gZ, then the initial charge was heated to 60 ℃. Slowly drop into 75.72 gM100, during which the temperature reaches a maximum of 70 ℃. The reaction mixture was then maintained at 70 ℃ untilUntil the NCO content is < 0.2%. The reaction mixture was then heated to 80 ℃ and 31.05 g of the mixture was added dropwiseM100 and 0.37 g of a reaction mixture consisting of the catalyst prepared according to example 1. The reaction mixture was kept at 80 ℃ until v ═ 1768cm in the IR spectrum^-1Until uretdione groups are no longer detected. The product obtained was clear and had a viscosity of 9300 mPas/23 ℃ and an NCO content of 0%, a trimer content of 6.5 mol%, an allophanate content of 32.0 mol%, a carbamate content of 61.5 mol% and an uretdione content of 0 mol%.

Example 5Allophanate-containing adhesives of the invention

53.48 g were placed in a three-necked flask with reflux condenser, stirrer and dropping funnel and aeration (6 l/h) at room temperatureN3400, 0.08 g of 2, 6-di-tert-butyl-4-methylphenol and 0.001 gZ, then the initial charge was heated to 60 ℃. 31.83 g of 2-hydroxyethyl acrylate are slowly added dropwise, during which the temperature reaches a maximum of 70 ℃. The reaction mixture was then kept at 70 ℃ until the NCO content was < 0.1%. Then a mixture consisting of 15.66 g of 2-hydroxyethyl acrylate and 0.51 g of the catalyst prepared according to example 3 was added dropwise. The reaction mixture was heated to 80 ℃ and held at this temperature until after 3.5 hours, at 1768cm in IR spectrum^-1Until only a very weak uretdione group signal was detected. 0.10 g of benzoyl chloride was added and the mixture was rapidly cooled to room temperature. The hydroxyethyl acrylate content of the extracted sample was found to be 4.15% by gas chromatography analysis. 6.8 g of hydroxyethyl acrylate are added and the mixture is stirred at 80 ℃ until v 2272cm in the IR spectrum^-1No longer examinedAny isocyanate group signal is detected. The hydroxyethyl acrylate content of the extracted sample was found to be 0.07% by gas chromatography analysis. The product obtained was transparent, had a viscosity of 56500 mPas/23 ℃ and an NCO content of 0%.

Comparative example C1Attempts to prepare allophanate-containing binders

The suitability of the catalysts described in U.S. Pat. No. 4, 200330153713 for crosslinking powder coatings (comprising uretdione group-containing curing agents and polymeric hydroxy compounds having no activated double bonds) was examined:

example 5 was repeated, except that the catalyst of example 3 was not used, and 0.51 g of tetrabutylammonium hydroxide was used as the catalyst. The reaction mixture was heated to 80 ℃ and held at this temperature until after 2 hours, v-1768 cm in IR spectrum^-1Until only a very weak uretdione group signal was detected. 0.10 g of benzoyl chloride was added and the mixture was rapidly cooled to room temperature. During this cooling, the reaction mixture became cloudy. The hydroxyethyl acrylate content of the extracted sample was found to be 2.4% by gas chromatography analysis. To the reaction mixture was added 5.20 gN3400, the mixture was stirred at 70 ℃ until v 2272cm in IR spectrum^-1Until no more isocyanate group signals were detected. The hydroxyethyl acrylate content of the extracted sample was found to be 0.17% by gas chromatography analysis. A cloudy product is obtained having a viscosity of 84000 mPas/23 ℃ and an NCO content of 0%.

Comparative example C2Attempts to prepare allophanate-containing binders

The suitability of the catalysts described in U.S. Pat. No. 4, 200330153713 for crosslinking powder coatings (comprising uretdione group-containing curing agents and polymeric hydroxy compounds having no activated double bonds) was examined:

example of the invention5 except that the catalyst of example 3 was not used, and 0.67 g of tetrabutylammonium fluoride was used as the catalyst. The reaction mixture was heated to 80 ℃ and held at this temperature until after 3 hours, v-1768 cm in IR spectrum^-1Until only a very weak uretdione group signal was detected. 0.10 g of benzoyl chloride was added and the mixture was rapidly cooled to room temperature. During this cooling, the reaction mixture became cloudy and a colorless precipitate formed. The hydroxyethyl acrylate content of the extracted sample was found to be 1.7% by gas chromatography analysis. To the reaction mixture was added 4.30 gN3400, the mixture was stirred at 70 ℃ until v 2272cm in IR spectrum^-1Until no more isocyanate group signals were detected. The hydroxyethyl acrylate content of the extracted sample was found to be 0.15% by gas chromatography analysis. A cloudy product is obtained having a viscosity of 92000 mPas/23 ℃ and an NCO content of 0%.

Comparative examples 6 and 7 show that substances suitable for crosslinking powder coatings composed of uretdione group-containing curing agents and polymeric hydroxyl compounds are not suitable for the targeted synthesis of allophanates from uretdiones and alcohols. The products thus obtained are cloudy and have a high viscosity, making them unsuitable for the production of coatings.

Example 6Coating formulation and coating

A portion of the product of example 5 was mixed with 3.0% of a photoinitiator1173 thoroughly mixed. The mixture was applied as a thin film to a glass plate using a doctor blade (bone sector blade) with a gap of 90 μm. Ultraviolet radiation (mercury medium pressure lamp, IST Metz GmbH, N ü rtingen, germany, 750 mj/cm) gave a hard, transparent coating which was not damaged by wiping back and forth 10 times with steel wool (grade 0/0/0) at 500 g force against the film.

Claims (13)

1. A process for preparing an allophanate group-containing adhesive which contains, at the oxygen atom of an allophanate group connected by two single bonds, an organic group having a reactive group which undergoes polymerization with an ethylenically unsaturated compound on exposure to actinic radiation, wherein:

reacting A) one or more compounds containing uretdione groups with

B) One or more OH-functional compounds containing groups which undergo a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation, and

C) optionally further NCO-reactive compounds

D) In one or more compounds containing phenolic groups as catalysts and

E) optionally in the presence of auxiliaries and additives.

2. The process for preparing allophanate group-containing adhesives according to claim 1, wherein the compound of component A) containing uretdione groups is based on 1, 6-hexamethylene diisocyanate.

3. The process for preparing adhesives containing allophanate groups according to claim 1, wherein 2-hydroxyethyl acrylate and/or 4-hydroxybutyl acrylate are used in component B).

4. The process according to claim 1 for preparing an allophanate group-containing binder, wherein tetrabutylammonium 4- (methoxycarbonyl) phenolate, tetrabutylammonium 2- (methoxycarbonyl) phenolate, tetrabutylammonium 4-formylphenolate, tetrabutylammonium 4-nitrilphenolate, tetrabutylphosphonium 4- (methoxycarbonyl) phenolate, tetrabutylphosphonium 2- (methoxycarbonyl) phenolate, tetrabutylphosphonium 4-formylphenolate, tetrabutylammonium salicylate and/or tetrabutylphosphonium salicylate are used as catalysts in component D).

5. The process for preparing an allophanate group-containing adhesive according to claim 1, wherein the process is carried out at a temperature of from 40 ℃ to 100 ℃.

6. The process for preparing adhesives containing allophanate groups according to claim 2, wherein 2-hydroxyethyl acrylate and/or 4-hydroxybutyl acrylate are used in component B).

7. The process according to claim 2 for preparing an allophanate group-containing binder, wherein tetrabutylammonium 4- (methoxycarbonyl) phenolate, tetrabutylammonium 2- (methoxycarbonyl) phenolate, tetrabutylammonium 4-formylphenolate, tetrabutylammonium 4-nitrilphenolate, tetrabutylphosphonium 4- (methoxycarbonyl) phenolate, tetrabutylphosphonium 2- (methoxycarbonyl) phenolate, tetrabutylphosphonium 4-formylphenolate, tetrabutylammonium salicylate and/or tetrabutylphosphonium salicylate are used as catalysts in component D).

8. The process for preparing an allophanate group-containing adhesive according to claim 2, wherein the process is carried out at a temperature of from 40 ℃ to 100 ℃.

9. An adhesive containing allophanate groups and containing groups which undergo polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation, which adhesive is obtainable by a process as claimed in any one of claims 1 to 8.

10. The allophanate group-containing adhesive according to claim 9, wherein the viscosity of the adhesive at 23 ℃ is not more than 100000 mPas.

11. Use of the allophanate group-containing binder according to claim 9 or 10 for the preparation of coatings, paints, adhesives, printing inks, casting resins, dental compounds, sizes, photoresists, stereolithography systems, sealants and resins for composites.

12. A coating composition comprising:

a) one or more allophanate group-containing binders as claimed in claim 9 or 10,

b) optionally one or more polyisocyanates containing free or blocked isocyanate groups which are free of groups which undergo a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation,

c) optionally further compounds, which are different from the compounds described under a), which contain groups which react with ethylenically unsaturated compounds by polymerization on exposure to actinic radiation and optionally contain free or blocked NCO groups,

d) optionally one or more active hydrogen-containing isocyanate-reactive compounds,

e) an initiator, wherein the initiator is selected from the group consisting of,

f) optionally a solvent and

g) optionally auxiliaries and additives.

13. A substrate coated with a coating obtained from the allophanate group containing binder of claim 9 or 10.