HK1180704A - Process for the preparation of low-viscosity, water-emulsifiable allophanates with radiation-curable groups - Google Patents

Description

Process for preparing low viscosity, water-emulsifiable allophanates having radiation-curable groups

Background

The present invention relates to a process for preparing low-viscosity polyisocyanate reaction products which contain allophanate groups, can be readily emulsified in water and contain activated groups which react by polymerization with ethylenically unsaturated compounds under the action of actinic radiation. The invention also relates to products which can be prepared by the process of the invention and to their use.

The curing of coating systems with activated double bonds by actinic radiation is known and is based on industry. Actinic radiation is understood to mean electromagnetic, ionizing radiation, in particular electron beams, UV rays and visible light (Roche Lexikon Medizin, 4 th edition; Urban & Fischer Verlag, Munich 1999). Which is one of the fastest curing methods in coating technology. Coating compositions based on this principle are therefore referred to as radiation-or actinically-curing or-curable systems.

Due to the ecological and economic requirements of paints for viscosity control with current paint (lacquer) systems with as little or no organic solvents as possible, it is desirable, on the one hand, to use paint raw materials which are already of low viscosity and, on the other hand, to be able to carry out the necessary viscosity control using water as solvent.

As is known, particularly low-viscosity, radiation-curable adhesives are urethane acrylates containing allophanate groups. These can be prepared by various processes, for example by direct reaction with excess diisocyanate and subsequent distillation of the excess diisocyanate (EP-A0867457 or WO-A00/39183), by oxadiazinetrione opening (WO-A2004/033522), by uretdione opening (WO-A2005/092942) or also by direct allophanatization of the isocyanate groups to the urethane groups in an equivalent molecular ratio (EP-A1645582). The only last-mentioned application discloses the possibility of obtaining water-emulsifiable binders by hydrophilization. Nevertheless, the products obtained in this way are not particularly stable in emulsion, phase separation having occurred after a short time.

Urethane acrylates which contain allophanate groups and are water-emulsifiable owing to hydrophilic agents incorporated have also been disclosed. EP-A0694531 thus describes a process for preparing such adhesives. Nevertheless, minimization of the viscosity is abandoned by the selective ionic hydrophilization. Furthermore, it is a complex, multi-step process, which has to be carried out at very high temperatures of over 100 ℃, which is disadvantageous for the stability of systems with activated double bonds. Finally, the process is not directed to low viscosity 100% systems and the final emulsion has been obtained.

WO-A2007/063025 likewise describes a water-emulsifiable urethane acrylate containing allophanates. However, these allophanate structures are not produced in the disclosed process, but are introduced via modified isocyanates. Such modified isocyanates can only be prepared with difficulty and at high cost, since the process described in WO-A00/39183 involves distillation processes which can only be converted with difficulty to industry. Finally, the intermediate product must therefore be isolated.

It was therefore an object of the present invention to provide a simple process for preparing radiation-curable polyurethane (meth) acrylates which are based on allophanate structures, have a particularly low viscosity as undiluted systems with a solids content of 100% by weight, and can be emulsified easily by stirring in water. Furthermore, the water-diluted radiation-curable polyurethane dispersions should be storage-stable.

Detailed description of the invention

An embodiment of the present invention is a process for preparing a water emulsifiable radiation curable allophanate having a residual monomer content of less than 0.5% by weight and an NCO content of less than 1% by weight, which process comprises forming polyurethanes (urethanes) containing NCO groups and having radiation curable groups from:

A) at least one compound comprising an isocyanate group,

B) at least one hydroxy-functional compound having groups which react with the ethylenically unsaturated compound by polymerization under the action of actinic radiation (radiation-curing groups),

C) at least one polyoxyalkylene monool which is a polyoxyalkylene monool,

E) optionally in the presence of a catalyst, and

subsequently reacting said polyurethane comprising NCO groups and having radiation-curing groups in the presence of the following substances without further addition of compounds comprising isocyanate groups:

F) an allophanatization catalyst, and

G) optionally a tertiary amine, optionally in the form of,

wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B) and C) is from 1.80:1.0 to 1.46: 1.0.

Another embodiment of the present invention is the above process, wherein at least one compound which is different from B) and/or C) and has NCO-reactive groups is used as component D), wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B), C) and D) is from 1.80:1.0 to 1.46: 1.0.

Another embodiment of the present invention is the above process, wherein in component A) hexamethylene-diisocyanate (HDI), isophorone-diisocyanate (IPDI) and/or 4,4' -diisocyanatodicyclohexylmethane are used.

Another embodiment of the present invention is the above process wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B), C) and D) is from 1.7:1.0 to 1.47: 1.0.

Another embodiment of the present invention is the above process wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B), C) and D) is from 1.65:1.0 to 1.48: 1.0.

Another embodiment of the present invention is the above process, wherein a polyoxyalkylene monool comprising ethylene oxide-derived units in a content of from 30 to 100% by weight is used in C).

Another embodiment of the present invention is the above process, wherein hydroxyethyl (meth) acrylate and/or hydroxypropyl (meth) acrylate is used in component B).

Another embodiment of the present invention is the above process, wherein the allophanatization is carried out until the final product has an NCO content of less than 0.1% by weight.

Another embodiment of the present invention is the above process, wherein component A) is used in an amount of 20 to 60 wt.%, component B) in an amount of 25 to 50 wt.%, component C) in an amount of 10 to 35 wt.%, component D) in an amount of 0 to 40 wt.%, component E) in an amount of 0 to 5 wt.%, component F) in an amount of 0.001 to 5 wt.%, and component G) in an amount of 0 to 5 wt.%, with the proviso that the sum of the wt.% of components A) to G) is 100.

Another embodiment of the present invention is the process described above, wherein the urethanization of components A) to D) is optionally carried out in the presence of E), an NCO value deviating at most from the theoretical% NCO content by 1.5% by weight NCO (absolute) as determined by the NCO content is reached, and subsequently the allophanatization is carried out without further addition of compounds containing isocyanate groups by adding components E) and optionally F).

Another embodiment of the present invention is a radiation-curable, water-emulsifiable allophanate obtainable by the process described above.

Another embodiment of the present invention is a coating composition comprising

a) One or more of the above-described radiation-curable, water-emulsifiable allophanates;

b) optionally a further compound which is different from a) and which contains groups which react with the ethylenically unsaturated compound by polymerization under the action of actinic radiation;

c) optionally other aqueous binders that are non-radiation curable;

d) an initiator;

e) optionally a solvent; and

f) optional auxiliary materials and additives.

Another embodiment of the present invention is a substrate coated with the above-described coating composition.

Detailed Description

Surprisingly, a process has been found for preparing water-emulsifiable, radiation-curable allophanates having a residual monomer content of less than 0.5% by weight and an NCO content of less than 1% by weight, wherein the allophanates are prepared from:

A) at least one compound comprising an isocyanate group,

B) at least one hydroxy-functional compound having groups which react with the ethylenically unsaturated compound by polymerization under the action of actinic radiation (radiation-curing groups),

C) at least one polyoxyalkylene monool which is a polyoxyalkylene monool,

D) optionally at least one compound which is different from B) and/or C and has NCO-reactive groups,

E) optionally in the presence of a catalyst, and,

forming a polyurethane comprising NCO groups and having radiation-curing groups, which is subsequently reacted without further addition of compounds comprising isocyanate groups in the presence of:

F) an allophanatization catalyst, and

G) optionally a tertiary amine, optionally in the form of,

wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B) and C) and optionally D) is from 1.80:1.0 to 1.46:1.0, preferably from 1.70:1.0 to 1.47:1.0, particularly preferably from 1.65:1.0 to 1.48:1.0 and very particularly preferably from 1.60:1.0 to 1.50: 1.0.

In the context of the present invention, the term "water-emulsifiable" means that the polyurethanes of the invention can be mixed with water and thus form emulsions over a wide range of mixing ratios. A solids content of 100% by weight means that the polyurethane system is not diluted with water.

The invention also provides water-emulsifiable polyurethane (meth) acrylates obtainable by the process of the invention.

The invention also provides for the use of the water-emulsifiable polyurethane (meth) acrylates according to the invention obtainable by the process according to the invention for the preparation of coatings and paints and also adhesives, printing inks, casting resins, dental compositions, sizes, photoresists, stereolithography systems, resins for composites and sealing compositions.

In the context of the present invention, "(meth) acrylate" refers to the corresponding acrylate or methacrylate functionality or a mixture of both.

Possible isocyanate-containing compounds (A) are aromatic, aliphatic and cycloaliphatic polyisocyanates. Suitable polyisocyanates are those of the formula Q (NCO)_nHas an average molecular weight of less than 800, wherein n represents a number from 2 to 4 and Q represents an aromatic C₆-C₁₅-hydrocarbon radical, aliphatic C₄-C₁₂-hydrocarbon or alicyclic C₆-C₁₅Hydrocarbon radicals, such as diisocyanates from the following series: 2,4-/2, 6-toluene-diisocyanate (TDI), methyleneMethyldiphenyl-diisocyanate (MDI), Triisocyanatononane (TIN), naphthyl-diisocyanate (NDI), 4,4 '-diisocyanatodicyclohexylmethane, 3-isocyanatomethyl-3, 3, 5-trimethylcyclohexyl-isocyanate (isophorone-diisocyanate = IPDI), tetramethylene-diisocyanate, hexamethylene-diisocyanate (HDI), 2-methylpentamethylene-diisocyanate, 2,2, 4-trimethylhexamethylene-diisocyanate (THDI), dodecamethylene-diisocyanate, 1, 4-diisocyanatocyclohexane, 4,4' -diisocyanato-3, 3 '-dimethyldicyclohexylmethane, 4,4' -diisocyanatodicyclohexyl-2, 2-propane, 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI), 1, 3-diisooctylcyanato-4-methylcyclohexane, 1, 3-diisocyanato-2-methylcyclohexane and alpha, alpha' -tetramethyl-m-or p-xylylene-diisocyanate (TMXDI) and mixtures comprising these compounds.

The abovementioned isocyanates as such or as reaction products with one another give polyisocyanates having a structure of, for example, uretdione, isocyanurate, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione, as described by way of example, in J.Prakt.chem.336 (1994) 185-200 and EP-A0798299, which are likewise suitable as isocyanate-containing compounds (A).

The reaction products of the above-mentioned isocyanates with other isocyanate-reactive compounds give prepolymers which are also suitable as isocyanate-containing compounds A). Such isocyanate-reactive compounds are, in particular, polyols, such as polyether polyols, polyester polyols, polycarbonate polyols and polyfunctional alcohols. Higher molecular weight, and in lesser amounts, also low molecular weight hydroxyl compounds can be used as polyols.

The compounds of component a) can thus be used directly in the process of the invention or prepared by preliminary reactions starting from any desired precursor before the process of the invention is carried out.

Monomeric diisocyanates are preferably used as component A). Particular preference is given to using Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI) and/or 4,4' -diisocyanatodicyclohexylmethane. Very particular preference is given to using hexamethylene diisocyanate.

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

In the context of the present invention, the radicals which react with the ethylenically unsaturated compounds by polymerization under the action of actinic radiation are vinyl ether, maleoyl, fumaryl, maleimide, dicyclopentadiene, acrylamide, acrylic and methacrylic groups, these being preferably vinyl ether, acrylate and/or methacrylate groups, and particularly preferably acrylate groups.

Examples of suitable compounds of component B) containing hydroxyl groups are 2-hydroxyethyl (meth) acrylate, polyoxyethylene mono (meth) acrylate (e.g. PEA 6/PEM 6; laporte Performance Chemicals ltd, UK), polyoxypropylene mono (meth) acrylates (e.g., PPA6, PPM 5S; laporte Performance Chemicals ltd., UK), polyoxyalkylene mono (meth) acrylates (e.g. PEM63P, Laporte Performance Chemicals ltd., UK), poly (epsilon-caprolactone) mono (meth) acrylates, such as Tone M100 Glycerol, pentaerythritol and dipentaerythritol.

Alcohols obtained by reacting acids containing double bonds with epoxides, optionally containing double bonds, are likewise suitable as constituents of B), thus for example reaction products of (meth) acrylic acid with glycidyl (meth) acrylate or bisphenol A diglycidyl ether.

Unsaturated alcohols obtained by reaction of optionally unsaturated anhydrides with hydroxyl groups optionally containing acrylate groups and epoxides can likewise be used. These are, for example, the reaction products of maleic anhydride with 2-hydroxyethyl (meth) acrylate and glycidyl (meth) acrylate.

The compounds of component B particularly preferably correspond to the abovementioned classes and have an OH functionality of from 0.9 to 1.1.

Preferably, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and/or hydroxybutyl (meth) acrylate are used. Very particular preference is given to hydroxyethyl acrylate and/or hydroxypropyl acrylate.

According to the present invention, the polyoxyalkylene monool (C) is used as the compound having a nonionic hydrophilic effect. These polyoxyalkylene monools contain from 30 to 100% by weight of units derived from ethylene oxide. Preference is given to using, for example, polyoxyalkylene monools which are obtainable in a manner known per se by alkoxylation of suitable starter molecules and contain, as a statistical average, from 5 to 70, preferably from 7 to 55, ethylene oxide units per molecule (for example Ullmanns encyclopedia der technischen Chemie, 4 th edition, volume 19, Verlag Chemie, Weinheim pages 31-38).

Suitable starter molecules for preparing these polyoxyalkylene ether monools are, for example, saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol, diethylene glycol monoalkylethers, such as diethylene glycol monobutyl ether, unsaturated alcohols, such as allyl alcohol, 1, 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, and particularly preferred starter molecules are methanol or ethanol.

Alkylene oxides suitable for the alkoxylation reaction are, for example, ethylene oxide, 1-butene oxide and/or propylene oxide, preferably ethylene oxide and/or propylene oxide, which can be used in any desired sequence or in the form of compositions in the alkoxylation reaction.

The polyoxyalkylene monool is a pure polyoxyethylene polyether monool or a mixed polyoxyalkylene polyether monool whose oxyalkylene units comprise at least 30 mol%, preferably at least 50 mol%, of oxyethylene units. Particular preference is given to using pure polyoxyethylene polyether monols.

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

These may be, for example, compounds having NH-or SH-functions which react with the ethylenically unsaturated compounds by polymerization under the action of actinic radiation.

Compounds which are unreactive under the action of actinic radiation, such as polyether polyols, polyester polyols, polycarbonate polyols and mono-or polyfunctional alcohols, may also be used together as component D) to influence the product properties. Low molecular weight, and in lesser amounts, also higher molecular weight hydroxyl compounds can be used as polyols.

Polyols customary in polyurethane chemistry having a molecular weight of 62 to 399, such as ethylene glycol, triethylene glycol, tetraethylene glycol, propane-1, 2-diol and propane-1, 3-diol, butane-1, 4-diol and butane-1, 3-diol, hexane-1, 6-diol, octane-1, 8-diol, neopentyl glycol, 1, 4-bis (hydroxymethyl) may be used as low molecular weight polyols which can be used together as component D)Cyclohexane, bis (hydroxymethyl) tricyclo [5.2.1.0^2.6]Decane or 1, 4-bis (2-hydroxyethoxy) benzene, 2-methyl-1, 3-propanediol, 2,2, 4-trimethylpentanediol, 2-ethyl-1, 3-hexanediol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, bisphenol A, tetrabromobisphenol A, glycerol, trimethylolpropane, hexane-1, 2, 6-triol, butane-1, 2, 4-triol, pentaerythritol, p-cyclohexanediol (quinitol), mannitol, sorbitol, methylglycoside (methyl glycoside) and 4,3,6-dianhydrohexitols (4, 3, 6-dianhydrohexitols).

Low molecular weight monohydroxy compounds may also be used as component D), mention may be made, for example, of saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric 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 oleyl alcohol, aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols, such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol.

Higher molecular weight hydroxyl compounds as component D) include the hydroxyl-polyesters, hydroxyl-polyethers, hydroxyl-polythioethers, hydroxyl-polyacetals, hydroxyl-polycarbonates, dimer fatty alcohols (dimer fatty alcohols) and/or ester-amides customary in polyurethane chemistry, in each case having an average molecular weight of from 400 to 8,000 g/mol, preferably those having an average molecular weight of from 500 to 2,000 g/mol. However, the co-use of such higher molecular weight hydroxyl compounds is not preferred.

Possible compounds of the optional catalyst component E) are urethanization catalysts known per se to the person skilled in the art, for example organotin compounds or amine-type catalysts. Organotin compounds which may be mentioned are, for example: dibutyltin diacetate, dibutyltin dilaurate, dibutyltin bis-acetylacetonate and tin carboxylates, for example tin octoate. The tin catalysts mentioned may optionally be used in combination with amine-type catalysts, for example aminosilanes or 1, 4-diazabicyclo [2.2.2] octane. Lewis acid metal compounds containing molybdenum, vanadium, zirconium, cesium, bismuth or tungsten may also be used.

Dibutyltin dilaurate is preferably used as the urethanization catalyst in E).

In the process of the present invention, catalyst component E) is optionally used together in an amount of from 0.001 to 5.0% by weight, preferably from 0.001 to 0.1% by weight and particularly preferably from 0.005 to 0.05% by weight, based on the solids content of the process product.

Allophanatization catalysts known per se to the person skilled in the art can be used as catalysts F), for example zinc salts, zinc octoate, zinc acetylacetonate and zinc 2-ethylhexanoate, zirconium octoate, bismuth octoate, tin octoate or tetraalkylammonium compounds, for exampleN,N,N-trimethyl-N-2-hydroxypropylammonium hydroxide, and (C) to obtain a mixture,N,N,N-trimethyl-N-ammonium 2-hydroxypropyl 2-ethylhexanoate or choline 2-ethylhexanoate. Preference is given to using metal octoates, particular preference to using zinc octoate.

In the context of the present invention, the term "zinc octoate" is also understood to mean technical grade isomeric product mixtures which may also comprise C in addition to the various isomeric octoates₆To C₁₉-zinc salt content of fatty acids. The corresponding meanings apply equally to the other metal octoates.

Allophanatization catalyst F) is used in an amount of from 0.001 to 5.0% by weight, preferably from 0.001 to 0.1% by weight and particularly preferably from 0.005 to 0.05% by weight, based on the solids content of the product of the process.

In principle, allophanatization catalysts F) can already be used for the urethanization in E), and the two-stage procedure can be simplified to a single-stage reaction. However, this is not preferred, so that only the allophanation catalyst is added when all or a proportion of the urethane groups will react to produce allophanate groups.

The catalyst F) can be added in one portion, together in a plurality of portions, or else continuously. Addition together is preferred.

When the preferred zinc octoate is used as allophanation catalyst F), then the allophanation reaction according to the teaching of EP-A2031005 can proceed very slowly and often incompletely, so that in this case it is preferred to use a tertiary amine as component G). Suitable tertiary amines G) preferably have at least nine carbon atoms, which may comprise both aromatic and aliphatic radicals, which may also be bridged to one another. The amine preferably contains no other functional groups. Examples of suitable compounds areN,N,N-a source of N-xylylenediamine,N,N,N-a benzhydryl-methylamine,N,N,N-a cyclohexyl dimethylamine,N-a methylmorpholine,N,N,N-a tri-phenylmethylamine having a tertiary amino group,N,N,N-a tri-propylamine having a tertiary amino group,N,N,N-a salt of tributylamine,N,N,N-tripentylamine orN,N,N-trihexylamine. In this connection, use is preferably made ofN,N,N-benzyldimethylamine.

When used together, the tertiary amines are used in amounts of from 0.01 to 5.0% by weight, preferably from 0.01 to 0.1% by weight and particularly preferably from 0.05 to 0.5% by weight, based on the solids content of the process product.

The allophanatization reaction is preferably carried out until the NCO content of the end product is less than 0.5% by weight, particularly preferably less than 0.1% by weight.

In principle, when the allophanatization reaction has ended, it is possible to react the residual content of NCO groups with NCO-reactive compounds, for example alcohols. Products having particularly very low NCO contents are obtained.

Catalysts E) and/or F) can also be applied to the support material by methods known to the person skilled in the art and used as heterogeneous catalysts.

Solvents or reactive diluents may be used at any desired point in the process of the invention.

Component A) is used in amounts of from 20 to 60% by weight, preferably from 30 to 50% by weight, particularly preferably from 35 to 45% by weight, component B) is used in amounts of from 25 to 50% by weight, preferably from 30 to 45% by weight, particularly preferably from 35 to 40% by weight, component C) is used in amounts of from 10 to 35% by weight, preferably from 15 to 25% by weight, particularly preferably from 19 to 25% by weight, component D) is used in amounts of from 0 to 40% by weight, preferably from 0 to 15% by weight, very particularly preferably from 0 to 5% by weight, component E) is used in amounts of from 0 to 5% by weight, preferably from 0.001 to 0.1% by weight, particularly preferably from 0.005 to 0.05% by weight, component F) is used in an amount of from 0.001 to 5% by weight, preferably from 0.001 to 0.1% by weight, very particularly preferably from 0.005 to 0.05% by weight, and component G) is used in amounts of 0 to 5 wt.%, preferably 0.01 to 1 wt.%, very particularly preferably 0.05 to 0.5 wt.%, with the proviso that the sum of the wt.% of components A) to G) is 100.

Suitable solvents are inert to the functional groups present in the product of the process from the point of addition to the end of the process. Solvents used in lacquer technology, for example, are suitable, 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.

Compounds which are likewise (co) polymerized during UV curing and are therefore co-incorporated into polymer networks (networks) and are inert towards NCO groups can be used jointly as reactive diluents. Such reactive diluents are described by way of example in P.K.T.Oldring (eds.), Chemistry & Technology of UV & EB Formulations For Coatings, Inks & paintts, Vol.2, 1991, SITA Technology, London, pp.237-285. These may be esters of acrylic or methacrylic acid, preferably acrylic acid, with mono-or polyfunctional alcohols. Suitable alcohols are, for example, the isomeric butanols, pentanols, hexanols, heptanols, octanols, nonanols and decanols, and furthermore, for example, cycloaliphatic alcohols, such as isobornyl alcohol, cyclohexanol and alkylated cyclohexanols, dicyclopentanol, arylaliphatic alcohols, such as phenoxyethanol and nonylphenylethanol, and tetrahydrofurfuryl alcohol. Alkoxylated derivatives of these alcohols may also be used. Suitable difunctional alcohols are, for example, the alcohols mentioned below, such as ethylene glycol, propane-1, 2-diol, propane-1, 3-diol, diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentyl glycol, hexane-1, 6-diol, 2-ethylhexanediol and tripropylene glycol, or alkoxylated derivatives of these alcohols. Preferred difunctional alcohols are hexane-1, 6-diol, dipropylene glycol and tripropylene glycol. Suitable trifunctional alcohols are glycerol or trimethylolpropane or alkoxylated derivatives thereof. The tetrafunctional alcohol is pentaerythritol or an alkoxylated derivative thereof. However, the use of a reactive diluent in combination is not preferred.

[0065] The process of the invention is carried out at temperatures of up to 100 ℃, preferably from 20 to 100 ℃, particularly preferably from 40 to 100 ℃, in particular from 60 to 90 ℃.

The adhesives according to the invention may be stabilized against premature polymerization. Thus, stabilizers which prevent polymerization are added before and/or during the reaction are preferably added as constituents of one or more of the components (A), B), C), D), E) or F)). Examples of suitable stabilizers are, for example, phenothiazine and phenols, such as p-methoxyphenol, 2, 5-di-tert-butylhydroquinone or 2, 6-di-tert-butyl-4-methylphenol. N-oxyl compounds are also suitable for stabilization, for example 2,2,6, 6-tetramethylpiperidine N-oxide (TEMPO) or its derivatives. The stabilizers can also be likewise chemically co-introduced into the binder, in which case compounds of the abovementioned classes are suitable, in particular if they also carry further free aliphatic alcohol groups or primary or secondary amine groups and can therefore be chemically bonded to component a) via urethane or urea groups. 2,2,6, 6-tetramethyl-4-hydroxypiperidine N-oxide is particularly suitable for this purpose.

Other stabilizers, such as compounds of the HALS (HALS = hindered amine light stabilizer) class, may be used as well, but are not preferred.

An oxygen-containing gas, preferably air, may be passed into or through the reaction mixture to stabilize the reaction mixture, particularly unsaturated groups that inhibit premature polymerization. The gas preferably has the lowest possible moisture content to prevent unwanted reactions in the presence of isocyanate.

The stabilizer can be added during the preparation of the binder according to the invention and, in order to achieve long-term stability, can finally be post-stabilized again with a phenolic stabilizer and the reaction product can optionally be saturated with air.

In the process according to the invention, the preferred stabilizer components are used in amounts of from 0.001 to 5.0% by weight, preferably from 0.01 to 2.0% by weight and particularly preferably from 0.05 to 1.0% by weight, based on the solids content of the product of the process.

The process according to the invention is preferably carried out in a stirred reactor.

The course of the reaction can be monitored by suitable measuring instruments installed in the reactor and/or by means of analysis of the samples taken. Suitable methods are known to those skilled in the art. They are, for example, viscosity measurements, NCO content measurements, refractive index measurements, OH content measurements, Gas Chromatography (GC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and near infrared spectroscopy (NIR). The infrared spectrum of the free NCO groups present was monitored (for aliphatic NCO groups the band in the infrared spectrum was approximately v =2272 cm^-1) And GC analysis of the unreacted compounds from A), B), C) and optionally D) is preferred.

In a preferred embodiment, the urethanization of components a) to D) is optionally carried out in the presence of E). An NCO value which can deviate from the theoretical% NCO content by at most 1.5% by weight NCO (absolute), preferably at most 1.0% by weight (absolute), particularly preferably at most 0.7% by weight (absolute), is achieved, as determined by the NCO content, and subsequently allophanatization is carried out without further addition of compounds containing isocyanate groups by adding component E) and optionally F).

In principle, it is possible to carry out the process of the invention in a single step, using a catalyst or a catalyst mixture which catalyzes both the urethanization and allophanatization reactions. In this case, the urethanization and the allophanatization proceed simultaneously. However, this procedure is not preferred.

The unsaturated allophanates obtainable by the process according to the invention, in particular those based on the hexamethylene-diisocyanate preferably used,at a solids content of 100% by weight, preferably has a shear viscosity of less than or equal to 150,000 mPas, particularly preferably less than or equal to 80,000 mPas and very particularly preferably less than or equal to 50,000 mPas at 23 ℃. Viscosity was measured with a cone-plate rotational viscometer, MCR 51 (from Anton Paar, DE) according to ISO/DIS 3219:1990, at 50 s^-1The shear rate of (2).

The radiation-curable, water-emulsifiable allophanates of the invention can be used to prepare coatings and lacquers and also adhesives, printing inks, casting resins, dental compositions, sizing agents, photoresists, stereolithography systems, resins for composites and sealing compositions. However, in the case of gluing or sealing, it is a prerequisite that during curing by radiation, at least one of the two substrates to be glued or sealed to one another must be permeable, i.e. generally transparent, to the radiation used for curing. If an electron beam is used for curing, sufficient permeability to electrons must be ensured. The use of the allophanates of the invention as binders in paints and coatings is preferred.

The invention also provides a coating composition comprising

a) One or more radiation-curable, water-emulsifiable allophanates according to the invention,

b) optionally, a further compound which is different from a) and comprises a group which reacts with the ethylenically unsaturated compound by polymerization under the action of actinic radiation,

c) optionally, other aqueous binders that are non-radiation curable,

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

e) optionally, a solvent, and

f) optionally, auxiliary materials and additives.

The compounds of component b) include non-aqueous compounds, such as in particular polyurethane (meth) acrylates, which are preferably based on hexamethylene-diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane, 4,4' -diisocyanatodicyclohexylmethane and/or trimethylhexamethylene-diisocyanate, which may optionally be modified with isocyanurate, allophanate, biuret, uretdione and/or iminooxadiazinetrione groups and are free from groups reactive toward isocyanate groups.

In addition, it is also possible to use the already described reactive diluents known in the art as radiation-curable coatings as constituents of b), if the reactive diluents do not contain groups reactive with NCO groups.

The compounds of component b) also include compounds dissolved or dispersed in water, such as in particular dispersions comprising unsaturated radiation-curable groups, for example dispersions comprising unsaturated radiation-curable groups and based on polyesters, polyurethanes, polyepoxy (meth) acrylates, polyethers, polyamides, polysiloxanes, polycarbonates, polyepoxyacrylates, polyester acrylates, polyurethane polyacrylates and/or polyacrylates. In this case, unsaturated radiation-curable groups may be present bonded to one of the polymers and/or in the form of radiation-curable monomers (so-called reactive diluents) in the dispersion together with the polymers mentioned.

The compounds of component c) also comprise compounds dissolved or dispersed in water, such as in particular dispersions which do not comprise unsaturated radiation-curable groups, for example dispersions based on polyesters, polyurethanes, polyethers, polyamides, polysiloxanes, polycarbonates, polyurethane polyacrylates and/or polyacrylates.

In particular, if the components b) and c) are compounds which are dissolved or dispersed in water, such as, in particular, dispersions, it is advantageous to add the water-emulsifiable radiation-curable allophanate a) according to the invention, since the solids content of the components b) and c) can be increased in this way without a large increase in the resulting viscosity.

Initiators which can be activated by radiation and/or heat can be used as initiators for component d) for the free-radical polymerization. Photoinitiators activated by UV or visible light are preferred herein. There is a difference in principle between the two photoinitiators, monomolecular (type I) and bimolecular (type II). Suitable (type I) systems are aromatic ketone compounds, for example benzophenones in combination with tertiary amines, alkylbenzophenones, 4,4 '-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the mentioned types. Type II initiators, such as benzoin and its derivatives, benzil ketals (benzil ketals), acylphosphine oxides, such as 2,4, 6-trimethyl-benzoyl-diphenylphosphine oxide, bisacylphosphine oxides, phenylglyoxylic acid esters (phenylglyxylic acid esters), camphorquinones, α -aminoalkylphenones, α, α -dialkoxyacetophenones and α -hydroxyalkylphenylketones (α -hydroxyalkylphenylphenones) are also suitable.

Initiators in amounts of from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, based on the weight of the lacquer binder, can be used as individual substances or else in combination with one another owing to the frequently advantageous synergistic effects.

If an electron beam is used instead of UV radiation, no photoinitiator is required. As is known to the person skilled in the art, electron radiation is generated by means of thermal emission and accelerated by means of a potential difference. The energetic electrons then penetrate the titanium film and are deflected toward the coating composition to be cured. The main principles of electron beam curing are described in detail in Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints, Vol.1, P.K.T.Oldring (eds.), SITA Technology, London, UK, pp.101-.

In the case of thermal curing of the activated double bonds, this can also be effected by adding thermal dissociators which form free radicals. Suitable reagents are, as known to the person skilled in the art, for example peroxy compounds, such as dialkoxydicarbonates, for example bis (4-tert-butylcyclohexyl) peroxydicarbonate, dialkyl peroxides, for example dilauryl peroxide, peresters of aromatic or aliphatic acids, for example tert-butyl perbenzoate or tert-amyl peroxy-2-ethylhexanoate, inorganic peroxides, for example ammonium peroxosulfate, potassium peroxosulfate, organic peroxides, for example 2, 2-di (tert-butylperoxy) butane, dicumyl peroxide, tert-butyl hydroperoxide, or azo compounds, for example 2,2' -azobis [ N- (2-propenyl) -2-methylpropionamide ], 1- [ (cyano-1-methylethyl) azo ] formamide, 2,2' -azobis (N-butyl-2-methylpropionamide), 2,2' -azobis (N-cyclohexyl-2-methylpropionamide), 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. Highly substituted 1, 2-diphenylethanes (benzopinacols), such as 3, 4-dimethyl-3, 4-diphenylhexane, 1,1,2, 2-tetraphenylethane-1, 2-diol or silylated derivatives thereof are also possible.

Combinations of photoinitiators and initiators that can be activated thermally may also be used.

Organic solvents known per se to the person skilled in the art can optionally also be used jointly as component e). However, it is preferred to use water as the sole diluent.

The compositions may also comprise UV absorbers and/or HALS stabilizers as auxiliary materials and additives (component f)) in order to increase the stability of the cured lacquer layer to weathering. Combinations of UV absorbers and HALS stabilizers are preferred. The former advantageously has an absorption range of not more than 390 nm, for example of the triphenyltriazine type (e.g. Tinuvin)^?400 (Ciba Spezialittenchemie GmbH, Lampertheim, DE)), benzotriazoles (e.g., Tinuvin @^?622 (Ciba Spezialittenchemie GmbH, Lampertheim, DE)) or oxanilides (e.g. Sanduvor)^?3206 (Clariant, Muttenz, CH)) and is added in an amount of 0.5 to 3.5% by weight based on the solid resin. Suitable HALS stabilizers are commercially available (Tinuvin)^?292 or Tinuvin^?123 (Ciba Spezialittenchemie GmbH, Lampertheim, DE) or Sanduvor^?3258 (Clariant, Muttenz, CH)). Preferred amounts are based on the solid resin0.5-2.5 wt%.

Likewise, f) may also comprise other auxiliary materials and additives known in the lacquer art, such as pigments, including metal effect pigments, dyes, matting agents, fillers, flow agents (flow), wetting and degassing additives, slip additives, nanoparticles, anti-yellowing additives, thickeners and additives for reducing surface tension.

The coating compositions according to the invention are applied to the materials to be coated using methods which are customary and known in coating technology, for example spraying, knife coating, roller coating, pouring, dipping, spin coating, brushing or fine-mist coating, or by printing techniques, for example screen printing, gravure printing, flexographic or offset printing, and also transfer methods.

Suitable substrates are, for example, wood, metal, in particular, metal used in applications such as so-called wire (wire), coil (coil), can or container painting, and plastics, and also plastics in the form of films, 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, PU, PVC, RF, SAN, PBT, PPE, POM, PU-RIM, SMC, BMC, PP-EPDM and UP (abbreviation according to DIN 7728 part 1), paper, leather, fabric, felt, glass, wood materials, cork, artificial binding substrates, such as wood and fiber cement boards, electronic components or mineral substrates. Substrates comprising various of the above-mentioned materials, or already coated substrates, such as vehicles, aircraft or ships and parts thereof, in particular vehicle bodies or fittings, can also be painted. It is also possible to apply the coating compositions to the substrate only temporarily, then to cure them partially or completely, and optionally to separate them again, for example to produce films.

For curing, the water or solvent present, for example, can be removed completely or partially by evaporation in air, where appropriate.

Thermal and/or photochemical curing may be carried out during or after evaporation in air.

If desired, the thermal curing can be carried out at room temperature, but it is also possible to carry out the curing at elevated temperatures, preferably from 40 to 160 ℃, preferably from 60 to 130 ℃ and particularly preferably from 80 to 110 ℃.

If photoinitiators are used in d), the radiation curing is preferably carried out under the action of actinic radiation, for example by means of UV radiation or daylight, for example light having a wavelength of from 200 to 700 nm, or by means of radiation of high-energy electrons (electron radiation, from 150 to 300 keV). For example, high or medium pressure mercury vapor lamps are used as a source of light or UV radiation, the mercury vapor may be modified by doping with other elements such as gallium or iron. Lasers, pulsed lamps (known as UV flash lamps), halogen lamps or excimer lamps are also possible. The lamp may be equipped by its design or with special filters and/or reflectors to block emission of a portion of the UV spectrum. For example, for industrial hygiene reasons, it is possible, for example, to filter out the radiation assigned to UV-C or UV-C and UV-B. The lamps may be mounted in a fixed position so that the object to be irradiated passes the radiation source by means of mechanical means, or the lamps may be moved, the object to be irradiated not changing its position during curing. The radiation dose which is generally sufficient for crosslinking in UV curing is from 80 to 5,000 mJ/cm²。

The irradiation can also optionally be carried out in the presence 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 these are films of, for example, plastic, glass, or liquids such as water.

The type and concentration of the initiator optionally used varies in a manner known to the person skilled in the art, depending on the radiation dose and the curing conditions.

It is particularly preferred to use a high-pressure mercury vapor lamp mounted in a fixed position for curing. The photoinitiator is then used in a concentration of 0.1 to 10 wt.%, particularly preferably 0.2 to 3.0 wt.%, based on the solids of the coating. For curing these coatings, preference is given to using from 200 to 3,000 mJ/cm, measured in the wavelength range from 200 to 600 nm²The dosage of (a).

If a heat-activatable initiator is used in d), curing is carried out by increasing the temperature. In this case, the thermal energy can be introduced into the coating by radiation, thermal conduction and/or convection, infrared lamps, near infrared lamps and/or ovens which are commonly used in coating technology.

Curing is preferably carried out by actinic radiation.

The layer thickness applied (before curing) is generally from 0.5 to 5,000. mu.m, preferably from 5 to 1,000. mu.m, particularly preferably from 15 to 200. mu.m. If a solvent is used, it is removed by conventional methods after application and before curing.

The invention also provides a process for the preparation of a coating on a substrate, characterized in that a coating composition according to the invention is applied to a substrate as described above and then cured as described above.

The present invention also provides a substrate coated with a coating composition according to the present invention comprising the water-emulsifiable allophanate prepared by the process according to the present invention.

All of the above references are incorporated by reference in their entirety for all useful purposes.

While certain specific structures that embody the invention have been shown and described, it will be apparent to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the basic inventive concept, and as such, are not limited to the specific forms shown and described herein.

Examples

All percentage data relate to weight percentages unless otherwise indicated.

In each case, the NCO content was determined by titration in accordance with DIN EN ISO 11909.

Cone-plate rotational viscometer for viscosity measurements, MCR 51 (from Anton Paar, DE) according to ISO/DIS 3219:1990, in 50 s^-1At a shear rate of (3).

The ambient temperature of 23 ℃ at which the experiment was carried out is called RT.

The OH number was determined in accordance with DIN 53240-2.

The solids content is determined gravimetrically according to DIN EN ISO 3251 after all volatile constituents have been evaporated off.

Example 1:(NCO/OH ratio = 1.51:1.00)

340 g of hexamethylene-diisocyanate and 100 mg of phenothiazine were initially introduced into a 2,000 ml four-necked glass flask having a reflux condenser, a heatable oil bath, a mechanical stirrer, a line for aeration (1 l/h), an internal thermometer and a dropping funnel, and heated to 60 ℃.50 mg of dibutyltin dilaurate and firstly 372 g of hydroxypropyl acrylate and then 220 g of methoxypolyethylene glycol (Pluriol. The mixture was subsequently stirred until the theoretical NCO value of 6.8% was reached. Then 3.38 g ofN,N-dimethylbenzylamine, the mixture being stirred for about 5 minutes until it is homogenized. 4.48 g of zinc octoate (Borchi. A colourless resin was obtained with a viscosity of 18,500 mPas (23 ℃). The product is readily water emulsifiable at approximately 40% solids. The emulsion was stable for several days.

Example 2:(NCO/OH ratio = 1.51:1.00)

336 g of hexamethylene-diisocyanate and 80 mg of phenothiazine were initially introducedIn a 2,000 ml four-necked glass flask having a reflux condenser, a heatable oil bath, a mechanical stirrer, a line for introducing air (1 l/h), an internal thermometer and a dropping funnel, was heated to 60 ℃. 40 mg of dibutyltin dilaurate were added, 297 g of hydroxypropyl acrylate, 121 g of polyethylene glycol methyl ether (Pluriol. The mixture was subsequently stirred until the theoretical NCO value of 7.3% was reached. Then 2.84 g ofN,N-dimethylbenzylamine, the mixture being stirred for about 5 minutes until it is homogenized. 3.76 g of zinc octoate (Borchi. A colourless resin was obtained with a viscosity of 30,000 mPas (23 ℃). The product is readily water emulsifiable at approximately 40% solids. The emulsion was stable for several days.

Example 3:(NCO/OH ratio = 1.51:1.00)

336 g of hexamethylene-diisocyanate and 80 mg of phenothiazine were initially introduced into a 2,000 ml four-necked glass flask having a reflux condenser, a heatable oil bath, a mechanical stirrer, a line for aeration (1 l/h), an internal thermometer and a dropping funnel and heated to 60 ℃. 40 mg of dibutyltin dilaurate were added, 177 g of hydroxyethyl acrylate, 99 g of hydroxypropyl acrylate, 125 g of polyethylene glycol methyl ether having a molecular weight of 750 g/mol (Pluriol. The mixture was subsequently stirred until the theoretical NCO value of 7.5% was reached. Then 2.84 g ofN,N-dimethylbenzylamine, the mixture being stirred for about 5 minutes until it is homogenized. 3.76 g of zinc octoate (Borchi. A colourless resin was obtained with a viscosity of 17,600 mPas (23 ℃). The product is easily available at a solids content of about 40%The ground water can be emulsified. The emulsion was stable for several days.

Example 4 (comparative):(NCO/OH ratio = 1.42:1.00)

355 g of hexamethylene-diisocyanate and 100 mg of phenothiazine were initially introduced into a 2,000 ml four-necked glass flask having a reflux condenser, a heatable oil bath, a mechanical stirrer, a line for aeration (1 l/h), an internal thermometer and a dropping funnel, and heated to 60 ℃.50 mg of dibutyltin dilaurate are added, initially 262 g of hydroxypropyl acrylate, then 61 g of hydroxyethyl acrylate and finally 313 g of polyethylene glycol methyl ether having a molecular weight of 750 g/mol (Pluriol 750, BASF SE Ludwigshafen, DE) are added dropwise, so that the temperature does not exceed 80 ℃. The mixture was then stirred until the theoretical NCO value of 5.38% was reached. Then 3.01 g ofN,N-dimethylbenzylamine, the mixture being stirred for about 5 minutes until it is homogenized. 4.48 g of zinc octoate (Borchi. A colourless resin was obtained with a viscosity of 6,640 mPas (23 ℃). The product can only be emulsified in water with difficulty at a solids content of approximately 40% and separated again into two phases after a short time.

It was found that a higher NCO/OH ratio (leading to a higher molecular weight) is necessary in order to obtain a stable emulsion.

Claims (13)

1. A process for preparing a water-emulsifiable, radiation-curable allophanate having a residual monomer content of less than 0.5% by weight and an NCO content of less than 1% by weight, which process comprises forming a polyurethane which contains NCO groups and has radiation-curable groups from:

A) at least one compound comprising an isocyanate group,

B) at least one hydroxy-functional compound having groups which react with the ethylenically unsaturated compound by polymerization under the action of actinic radiation (radiation-curing groups),

C) at least one polyoxyalkylene monool which is a polyoxyalkylene monool,

E) optionally in the presence of a catalyst, and

a) subsequently reacting the polyurethane comprising NCO groups and having radiation-curing groups in the presence of the following substances without further addition of compounds comprising isocyanate groups:

F) an allophanatization catalyst, and

G) optionally a tertiary amine, optionally in the presence of a tertiary amine,

wherein the ratio of NCO groups of the compound from A) to OH groups of the compounds from B) and C) is from 1.80:1.0 to 1.46: 1.0.

2. The process of claim 1, wherein at least one compound which is different from B) and/or C) and has NCO-reactive groups is used as component D), wherein the ratio of NCO groups of the compounds from A) to OH groups of the compounds from B), C) and D) is from 1.80:1.0 to 1.46: 1.0.

3. The process of claim 1, wherein hexamethylene-diisocyanate (HDI), isophorone-diisocyanate (IPDI) and/or 4,4' -diisocyanatodicyclohexylmethane are used in component A).

4. The process of claim 1 wherein the ratio of NCO groups of said compound from a) to OH groups of said compound from B), C) and D) is from 1.7:1.0 to 1.47: 1.0.

5. The process of claim 1 wherein the ratio of NCO groups of said compound from a) to OH groups of said compound from B), C) and D) is from 1.65:1.0 to 1.48: 1.0.

6. The process of claim 1, wherein a polyoxyalkylene monool comprising ethylene oxide-derived units in an amount of from 30 to 100% by weight is used in C).

7. The process of claim 1 wherein hydroxyethyl (meth) acrylate and/or hydroxypropyl (meth) acrylate is used in component B).

8. The process of claim 1, wherein said allophanatization is carried out until the final product has an NCO content of less than 0.1% by weight.

9. The process of claim 1, wherein component a) is used in an amount of 20 to 60 wt.%, component B) in an amount of 25 to 50 wt.%, component C) in an amount of 10 to 35 wt.%, component D) in an amount of 0 to 40 wt.%, component E) in an amount of 0 to 5 wt.%, component F) in an amount of 0.001 to 5 wt.%, and component G) in an amount of 0 to 5 wt.%, with the proviso that the sum of the wt.% of components a) to G) is 100.

10. The process of claim 1, wherein the urethanization of components A) to D) is optionally carried out in the presence of E), an NCO value deviating at most from the theoretical% NCO content by 1.5% by weight NCO (absolute) as determined by NCO content is reached, and the allophanatization is subsequently carried out by adding components E) and optionally F), without further addition of compounds containing isocyanate groups.

11. A radiation-cured, water-emulsifiable allophanate obtainable by the process of claim 1.

12. A coating composition comprising

a) One or more radiation-cured, water-emulsifiable allophanates of claim 11;

b) optionally, a further compound which is different from a) and comprises a group which reacts with the ethylenically unsaturated compound by polymerization under the action of actinic radiation;

c) optionally, other aqueous binders that are non-radiation curable;

d) an initiator;

e) optionally, a solvent; and

f) optionally, auxiliary materials and additives.

13. A substrate coated with the coating composition of claim 12.