HK1085237B - Radiation-curing binders and a process for their preparation - Google Patents

Description

Radiation-curable adhesive and method for the production thereof

Technical Field

The invention relates to a method for producing binders containing allophanate groups, groups which can react with ethylenically unsaturated compounds in a polymerisation reaction by irradiation, and optionally isocyanate-reactive groups, to the resulting binders and to their use in coating compositions.

Background

It is known that coating systems having activated double bonds can be cured by actinic radiation, such as UV light radiation, IR radiation or electron beams, and have been carried out industrially. This is one of the fastest curing methods in the coating technology field. Coating compositions based on this principle are therefore preferred as radiation-or actinically curing systems.

Particularly good properties are obtained if radiation curing is combined with a second crosslinking step. This type of coating system is known as a dual cure system (e.g., Macromol. Symp.187, 531-542, 2002, p. 534).

The environmental and economic requirements imposed on current coating systems, i.e. the use of organic solvents as far as possible for adjusting the viscosity, or the absence of organic solvents, require the use of coating materials which are already of low viscosity. Polyisocyanates containing allophanate groups, which are described in EP-A0682012, are known to meet this object.

Industrially, these substances can be prepared by reacting a mono-or polyol with an excess of aliphatic and/or cycloaliphatic diisocyanate (e.g.GB-A994890, EP-A0000194 or EP-A0712840). After the reaction, unreacted diisocyanate was removed by distillation under reduced pressure. According to DE-A19860041, this process can also be carried out on OH-functional compounds having activated double bonds, such as hydroxyalkyl acrylates, although difficulties arise with respect to the preparation of specific low-monomer products. Since distillation at up to 135 ℃ is necessary to reduce the residual isocyanate content sufficiently (< 0.5% by weight of residual monomers), it is possible for the double bonds to polymerize under thermally induced conditions, even during purification, meaning that the desired product is not obtained.

EP-A0825211 describes a process for the synthesis of allophanate-based structures from oxadiazinetriones, although derivatives without radiation-curing activated double bonds are known. The polyester containing maleate and/or fumarate is used; the possibility of radiation curing is not described.

US 5777024 describes the preparation of low viscosity radiation-curable allophanates by reacting hydroxy-functional monomers having activated double bonds with allophanate-modified isocyanates containing NCO groups.

Formation of allophanate compounds by ring opening of uretdiones with alcohols is in principle known in the Powder coating art as a crosslinking mechanism (e.g.proceedings of the International Waterborn, High-Solids, and Powder Coatings Symposium 2001, 28)^th405-. For this purpose, however, the reaction temperatures required for the preparation of radiation-curable monomers based on allophanates having activated double bonds areToo high (more than or equal to 130 ℃).

In the past, the direct reaction of uretdione rings with alcohols to allophanates has been investigated for solvent-based, isocyanate-free 2K 2-component polyurethane coatings. Without a catalyst, this reaction is technically unproblematic owing to the low reaction rate (f.schmitt, angelw.makromol.chem. (1989), 171, pages 21-38). However, the reaction between HDI-based uretdione curing agents and polyols is said to be initiated at 60-80 ℃ with a suitable catalyst (K.B. Chandalia; R.A Englebach; S.L. Goldstein; R.W.good; S.H.Harris; M.J.Morgan; P.J.Whitman; R.T.Wojcik, Proceedings of International Waterborn, High-Solids, and Powder Coatings Symposium, (2001), pp.77-89). At present, the structure of these catalysts is not disclosed. Nor do commercial products prepared by such reactions disclosed.

In general, it has not been described in detail in the prior art to prepare low-viscosity radiation-curable allophanates having isocyanate-reactive groups by ring-opening reaction of alcohols having activated double bonds with uretdiones at 130 ℃ or less.

Surprisingly, it has now been found that uretdiones can be reacted with olefinically unsaturated alcohols which preferably contain activated double bonds and saturated compounds having at least two isocyanate-reactive groups, using zinc compounds as catalysts, even at temperatures of < 130 ℃ to give radiation-curable allophanates of low viscosity and low residual monomers. When such a crosslinking agent not only has a radiation curing function but also exhibits reactivity to NCO groups, the crosslinking agent is referred to as a dual-cure crosslinking agent.

Disclosure of Invention

The present invention relates to a method of making an adhesive comprising: 1) allophanate groups, 2) groups which react with ethylenically unsaturated compounds when polymerized by actinic radiation (radiation-curable groups), and 3) optionally NCO-reactive groups, said process comprising: reacting A) with B) at a temperature of 130 ℃ or less and then with C) in the presence of D),

A) one or more uretdione group-containing NCO-functional compounds,

B) one or more compounds containing isocyanate-reactive groups and groups which are capable of reacting with ethylenically unsaturated compounds upon polymerization by actinic radiation (radiation-curing groups),

C) one or more saturated compounds containing hydroxyl groups, other than B), at least one of these compounds having an OH functionality of 2 or more,

D) a catalyst comprising one or more zinc compounds,

the reaction with the compounds C) is carried out at least in proportion to the allophanate groups formed.

The invention also relates to the adhesive obtained by the method of the invention.

The present invention also relates to a coating composition comprising:

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

b) optionally one or more polyisocyanates containing free or protected isocyanate groups and optionally containing groups which are capable of polymerization with ethylenically unsaturated compounds under the action of actinic radiation,

c) optionally a compound other than a) containing groups capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation and optionally containing NCO-reactive groups,

d) optionally one or more active hydrogen-containing isocyanate-reactive compounds free of groups capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation, and

e) one or more initiators.

Detailed Description

For the purposes of the present invention, the terms "radiation-curable group", "actinically curable group" and "group which is capable of reacting with an ethylenically unsaturated compound via polymerization by actinic radiation" are used synonymously.

The compounds of component B) contain groups which are capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation, for example vinyl, vinyl ether, propenyl, allyl, maleoyl, fumaroyl, maleimide, dicyclopentadienyl, acrylamide, acryloyl and methacryloyl groups. Preferred reactive groups are vinyl ether, acrylate and/or methacrylate groups, and more preferred reactive groups are acrylate groups.

NCO-reactive groups include OH-, SH-and NH-functional compounds, preferably hydroxyl, primary or secondary amino and aspartic acid groups, more preferably hydroxyl groups.

Component A) includes any organic compound having at least one uretdione and one NCO group. A) The uretdione group content of the compounds used (according to C)₂N₂O₂Calculated as 84 g/mol) is preferably from 3 to 60% by weight, more preferably from 10 to 50% by weight, most preferably from 25 to 40% by weight.

A) The compounds used in (1) preferably contain, in addition to the uretdione groups, from 3 to 60% by weight, more preferably from 10 to 50% by weight, most preferably from 15 to 25% by weight, of NCO groups (calculated as NCO ═ 42 g/mol).

These compounds are preferably prepared by catalytic dimerization of aliphatic, cycloaliphatic, aromatic and/or araliphatic di-or polyisocyanates by known methods (e.g.J.Prakt. chem.1994, 336, 196-198).

Suitable diisocyanates include 1, 4-diisocyanatobutane, 1, 6-diisocyanatohexane, trimethylhexane diisocyanate, 1, 3-and 1, 4-diisocyanatomethylcyclohexane, isophorone diisocyanate (IPDI), 4 ' -diisocyanatohexylmethane, 1, 3-and 1, 4-xylylene diisocyanate (commercially available from Takeda, Japan as XDI), diphenylmethane 4, 4 ' -diisocyanate and diphenylmethane 2, 4 ' -diisocyanate (MDI), 2, 4-and 2, 6-Toluene Diisocyanate (TDI), or mixtures thereof. For the purposes of the present invention, preference is given to using 1, 6-diisocyanatomethane, isophorone diisocyanate or mixtures thereof.

Examples of catalysts for the dimerization reaction include trialkylphosphines, dimethylaminopyridines and tris (dimethylamino) phosphine. The result of the dimerization depends in a known manner on the catalyst used, the process conditions and the diisocyanate used. Specifically, a product containing an average of 1 or more uretdione groups per molecule can be formed, and the number of uretdione groups has a certain distribution. Depending on the catalyst used, the process conditions and the diisocyanates used, mixed products are also formed which, in addition to the uretdione groups, contain further structural elements, such as isocyanurates and/or iminooxadiazinediones.

Particularly preferred products are obtainable by HDI-catalyzed dimerization, the free HDI content of the products being less than 0.5% by weight; the NCO content is from 17 to 25% by weight, preferably from 21 to 24% by weight, and the viscosity at 23 ℃ is from 20 to 500mPa, preferably from 50 to 200 mPa.

It is preferred to use the customary NCO-functional compounds obtained by catalytic dimerization as part of component A) directly, but these compounds may also be reacted first in one step and then used as component A). Further reactions include reacting free NCO, day 09/2005 or 08 protected NCO groups with NCO-active compounds having two or more functionalities to form iminooxadiazinedione, isocyanate, carbamate, allophanate, biuret, oxadiazinetrione, oxazolinone, acylurea or carbodiimide groups. This reaction produces higher molecular weight uretdione group-containing compounds which, depending on the ratio chosen, have different NCO contents.

Suitable protective agents include: alcohols, lactams, oximes, malonates, ethyl acetoacetate, 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, ethyl cyclopentanone carboxylate, or mixtures of these protective agents. Methods for the protection of NCO groups are known and described in Progress in Organic Coatings 1999, 36, 148-172.

The NCO-reactive compounds having two or more functionalities used for the derivation of the uretdiones used in A) can be the abovementioned di-and/or polyisocyanates, but also simple alcohols having two or more functionalities, such as ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentyl glycol, 1, 6-hexanediol, diethylhexanediol, tripropylene glycol and alkoxylated derivatives of these alcohols. Preferred diols are 1, 6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable triols include glycerol or trimethylolpropane or alkoxylated derivatives thereof. Tetrahydric alcohols include pentaerythritol or alkoxylated derivatives thereof.

Furthermore, it is also possible to carry out the derivatization using compounds which have a hydrophilic action and contain at least one isocyanate-reactive group, either individually or in mixtures. Compounds having a hydrophilic action are preferably used when dissolving or dispersing the products of the invention in water or aqueous mixtures.

Suitable compounds having a hydrophilic action include all ionic, possibly ionic and nonionic hydrophilic compounds having at least one isocyanate-reactive group. As isocyanate-reactive groups, these compounds preferably contain hydroxyl and/or amino functional groups.

Ionic or possibly ionic hydrophilic compounds having at least one isocyanate-reactive group and at least one functional group, e.g. -COOY, -SO₃Y，-PO(OY)₂(Y＝H，NH₄ ⁺Metal cations), -NR₂，-NR₃ ⁺，-PR₃ ⁺(R ═ H, alkyl, aryl) compounds. By means of possibly ionic hydrophilic groups, those compounds are added to the pH effect in the interaction with the aqueous mediumThe dissociation of the fruits is balanced and therefore has negative, positive or neutral charges.

Examples of suitable ionic compounds or compounds containing possible ionic groups are mono-and dihydroxycarboxylic acids, mono-and diaminocarboxylic acids, mono-and dihydroxyphosphoric acids or mono-and diaminophosphoric acids and their salts. Examples include dimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid, N- (2-aminoethyl) -beta-alanine, 2- (2-aminoethylamino) -ethanesulfonic acid, ethylenediamine-propanesulfonic acid or ethylenediamine-butanesulfonic acid, 1, 2-or 1, 3-propanediamine-beta-ethanesulfonic acid, malic acid, citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, lysine, 3, 5-diaminobenzoic acid, the adduct of IPDI and acrylic acid (EP-A0916647, example 1) and alkali metal and/or ammonium salts thereof, the adduct of sodium bisulfite with but-2-ene-1, 4-diol, polyether sulfonates, 2-butanediol and NaHSO₃And also structural units which can be converted into cationic groups, such as N-methyldiethanolamine, are described in DE-A2446440, pages 5 to 9, formulae I to III.

Preferred ionic or possibly ionic compounds are those having carboxyl or carboxylate groups, sulfonate groups and/or ammonium ions. Particularly preferred ionic compounds are salts containing carboxyl and/or sulfonate groups as ionic or possible ionic groups, such as N- (2-aminoethyl) -beta-alanine, 2- (2-aminoethylamino) ethanesulfonic acid, the adduct of IPDI and acrylic acid (EP-A0916647, example 1) and dimethylolpropionic acid.

As hydrophilic nonionic compounds, compounds having a polyether structure, preferably alkylene oxide polyethers, containing at least one hydroxyl or amino group as isocyanate-reactive group can be used.

These compounds having a polyether structure include monofunctional polyalkylene oxide polyether alcohols having an average of from 5 to 7, preferably from 7 to 55, ethylene oxide units per molecule and at least 30 mol% of ethylene oxide, such as are obtained in a known manner by alkoxylation of suitable starter molecules (e.g.in Ullmanns encyclopedie der technischen Chemie, 4 th edition, volume 19, Verlag Chemie, Weinheim, pages 31 to 38).

Examples of suitable starter molecules include: 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, hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane, tetrahydrofuryl alcohol, diethylene glycol monoalkyl ether, azelaic monobutyl ether, unsaturated alcohols (allyl alcohol, 1-dimethylallyl alcohol or oleoyl 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, di (2-ethylhexyl) amine, N-methylcyclohexylamine and N-ethylcyclohexylamine, Or dicyclohexylamine) and also heterocyclic secondary amines (such as morpholine, pyrrolidine, piperidine or 1H-pyrazole). Preferred starter molecules are saturated molecules. 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 any order, separately from one another or in a mixture for the alkoxylation reaction to give protected polyethers or copolyethers.

The compounds having a polyether structure are preferably pure polyethylene oxide polyethers or mixed polyalkylene oxide polyethers, in which at least 30 mol%, preferably at least 40 mol%, of the alkylene oxide units are 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.

Especially when a hydrophilic agent containing an ionic group is used, the influence of the hydrophilic agent on the activity of the catalyst D must be examined. For this reason, if hydrophilic polyisocyanates are used, nonionic hydrophilicizing agents are preferred.

Examples of suitable compounds B) which may be used individually or in mixtures include: 2-hydroxyethyl (meth) acrylate, polyethylene oxide mono (meth) acrylate (e.g., PEA6/PEM 6; Laporte Performance Chemicals Ltd., UK), polypropylene oxide mono (meth) acrylate (e.g., PPA6, PPM 5S; LaportePerformance Chemicals Ltd., UK), polyalkylene oxide mono (meth) acrylate (e.g., PEM63P, Laporte Performance Chemicals Ltd., UK), poly (. epsilon. -caprolactone) mono (meth) acrylate (e.g., Tone M100Dow, Schwalbach, DE), (meth) acrylic acid, 4-hydroxybutyl (meth) acrylate, hydroxybutyl vinyl ether, 2-hydroxypropyl (meth) acrylate, 3-hydroxy-2, 2-dimethylpropyl (meth) acrylate, hydroxy-functional mono-, di-or higher functional acrylates, such as glycerol di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate or dipentaerythritol penta (meth) acrylate, obtainable by reacting polyols, optionally alkoxylated polyols, such as trimethylolpropane, pentaerythritol or dipentaerythritol, with (meth) acrylic acid.

Suitable as component B) are also alcohols obtained by reaction of double bond-containing acids with epoxides which optionally contain double bonds, such as the reaction products of (meth) acrylic acid with glycerol (meth) acrylate or bisphenol A diglycerol ether. Furthermore, it is also possible to use unsaturated alcohols, obtainable by reacting optionally unsaturated anhydrides with hydroxyl compounds and optionally epoxide compounds containing acrylate groups. Examples include the reaction products of maleic anhydride with 2-hydroxyethyl (meth) acrylate and glycerol (meth) acrylate.

Particularly preferred compounds of component B) are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, Tone M100(DOW, Schwalbach, DE), polyethylene oxide mono (meth) acrylate (e.g., PEA6 ™)A PEM 6; laporte Performance Chemicals ltd, UK), polypropylene oxide mono (meth) acrylates (e.g., PPA6, PPM 5S; laporte Performance Chemicals ltd., UK) and the reaction product of acrylic acid and glycerol methacrylate.

Component C) is selected from one or more saturated compounds containing hydroxyl groups, other than B), at least one of these compounds having an OH functionality of 2 or more. The compound may be a monomer and/or a polymer.

Suitable compounds are low molecular weight monoalcohols, diols or polyols, such as short-chain, i.e.aliphatic, araliphatic or cycloaliphatic monoalcohols, diols or polyols containing 2 to 20 carbon atoms. Examples of mono-alcohols include methanol, ethanol, iso-propanol, butanol, pentanol, diacetone alcohol, aliphatic alcohols or fluorinated alcohols (e.g. from DuPont under the trade name ZonylThose obtained).

Examples of the diols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, positionally isomeric diethyloctanediols, 1, 3-butanediol, cyclohexanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol, 1, 2-and 1, 4-cyclohexanediol, hydrogenated bisphenol A (2, -bis (4-hydroxy-cyclohexyl) propane), and 2, 2-dimethyl-3-hydroxypropionic acid, 2-dimethyl-3-hydroxypropionate. Examples of suitable triols include trimethylolethane, trimethylolpropane or glycerol, and examples of suitable polyols include ditrimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol. Effective alcohols are 1, 4-butanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol and trimethylolpropane.

Suitable high molecular weight polyols include polyester polyols, polyether polyols, hydroxy-functional (meth) acrylate (co) polymers, hydroxy-functional polyurethanes or corresponding hybrids (e.g.Rompp Lexikon Chemie, p.465-466, 10-^th ed.1998，Georg-Thieme-Verlag，Stuttgart)。

To prepare the hydroxy-functional polyester, six sets of monomer components may be used.

(cyclo) alkanediols, such as diols having (cyclo) aliphatically bound hydroxyl groups. Examples are the aforementioned low molecular weight diols and polyethylene glycol, polypropylene glycol or polybutylene glycol, which have a number average molecular weight of 200-. Reaction products of these diols with epsilon-caprolactone or other lactones are also suitable diols.

2. Alcohols having a functionality of 3 or more and a molecular weight of 92 to 254, such as glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol; polyethers prepared from these alcohols, such as the reaction product of 1 mole trimethylolpropane with 4 moles ethylene oxide; or the reaction products of these alcohols with epsilon caprolactone or other lactones.

3. Monoalcohols, such as ethanol, 1-and 2-propanol, 1-and 2-butanol, 1-hexanol, 2-ethylhexanol, cyclohexanol and benzyl alcohol.

4. Dicarboxylic acids and/or anhydrides thereof having a number average molecular weight of 104-600, such as phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid, maleic anhydride, fumaric anhydride, malonic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid and hydrogenated dimer fatty acids.

5. Higher polyfunctional carboxylic acids and/or their anhydrides, such as trimellitic acid, trimellitic anhydride.

6. Monocarboxylic acids, such as benzoic acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, caproic acid, caprylic acid, capric acid, lauric acid, and natural and synthetic fatty acids.

Suitable hydroxyl-containing polyesters include the reaction product of at least one component from group 1 or 2 with at least one component from group 4 or 5. The reaction products of the aforementioned alcohols with lactones may also be used. The hydroxyl-containing polyesters have a number average molecular weight of from 500-10,000g/mol, preferably from 800-3000g/mol, and a hydroxyl content of from 1 to 20% by weight, preferably from 3 to 15% by weight. The polyester may be used at 100% solids or as a solution in a solvent or reactive diluent described below and suitable for the process of the present invention.

In addition to the aforementioned polyester polyols, dendritic or hyperbranched compounds are also suitable, such as those obtained from ethoxylated pentaerythritol and dimethylolpropionic acid.

Suitable polycarbonates are obtained by reacting the alcohols mentioned above for the preparation of the polyester polyols with organic carbonates, such as diphenyl carbonate, dimethyl carbonate or diethyl carbonate, by known methods. The number average molecular weight of the polycarbonate is preferably 500-5000g/mol, more preferably 750-2500g/mol, and the hydroxyl functionality is 1.5-3.

Examples of suitable polyethers include alkylene oxide polyethers prepared from the aforementioned low molecular weight mono-, di-, or polyols. Also suitable are polyethers obtained by polymerizing tetrahydrofuran. The molecular weight of the double bond of the polyether is 400-containing 13,000g/mol, preferably 400-containing 2500g/mol, more preferably 500-containing 1200g/mol, and the hydroxyl content is 1-25 wt%, preferably 3-15 wt%.

WO 03/000812, pages 8 to 16, describes in detail (meth) acrylic (co) polymers and suitable processes for their preparation, the (meth) acrylic (co) polymers suitable for the present invention being those having at least one hydroxyl group. The number average molecular weight of the (meth) acrylic (co) polymer is preferably 500-10,000g/mol, more preferably 1000-5000g/mol, and the hydroxyl group content is 1 to 20% by weight, preferably 3 to 15% by weight.

Monomeric diols or triols, and also polyethers and/or polylactones from these alcohols, having a number average molecular weight of less than 1000g/mol are particularly preferred.

Suitable catalyst compounds D) include, in addition to the zinc compounds used in the present invention, the compounds known for catalyzing the reaction of isocyanate groups with isocyanate-reactive groups, alone or in mixtures.

Examples include: tertiary amines (such as triethylamine), pyridine, picoline, benzyldimethylamine, N-endo-ethylene-piperazine, N-methylpiperidine, pentamethyldiethylenetriamine, N-dimethylaminocyclohexane, N' -dimethylpiperazine or 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 mixtures of these catalysts.

Suitable zinc compounds include any organic or inorganic zinc compound, such as zinc oxide, zinc sulfide, zinc carbonate, zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc phosphate, zinc borate, zinc titanate, zinc hexafluorosilicate, zinc sulfite, zinc sulfate, zinc nitrate, zinc tetrafluoroborate, zinc acetate, zinc octanoate, zinc cyclohexanebutyrate, zinc laurate, zinc palmitate, zinc stearate, zinc benzoate, zinc citrate, zinc glycolate, zinc acetylacetonate, zinc 2, 2, 6, 6-tetramethyl-3, 5-heptanedionate, zinc trifluoroacetate, zinc trifluoromethanesulfonate, zinc dimethyldithiocarbamate, and mixtures of these compounds.

Preferably, catalyst D) is zinc octoate and/or zinc acetylacetonate. Preferably, only a zinc compound is used as catalyst D).

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

The compound of catalyst component D) can be conveniently dissolved in one of the components used in the process or in a portion of the components. In particular, the carboxylic acid salts used in the present invention are well soluble in polar hydroxyalkyl acrylates, and therefore, the solution of D) in a small amount of B) can be metered in the liquid form of a concentrated solution.

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

As component E) solvents or active dispersants can be used. Suitable solvents are inert to the functional groups in the product from the time of addition until the end of the process. Suitable solvents include those used in the coatings 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. Preferably, no solvent is added.

Compounds which are (co) polymerized during UV curing and thus added to the polymer network can be used as reactive diluents. When these reactive diluents are brought into contact with the NCO-containing compounds A), they must be inert towards NCO groups. This restriction is not present until these diluents are added after the reaction of A) with B). Such reactive diluents are described, for 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 acrylic or methacrylic acids, preferably esters of acrylic acid with monofunctional or polyfunctional alcohols. Examples of suitable alcohols include: the isomeric butanols, pentanols, hexanols, heptanols, octanols, nonanols and decanols; alicyclic alcohols such as isobornyl alcohol, cyclohexyl alcohol and alkylated cyclohexanol; dicyclopentanol; araliphatic alcohols such as phenoxyethanol and nonylphenylethanol; tetrahydrofuryl alcohol. In addition, alkoxylation products of these alcohols can be used.

Suitable glycols include ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentyl glycol, 1, 6-hexanediol, 2-ethylhexanediol, tripropylene glycol or alkoxylated derivatives of these alcohols. Preferred diols are 1, 6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable triols include glycerol or trimethylolpropane or alkoxylated derivatives thereof. Tetrahydric alcohols include pentaerythritol or alkoxylated derivatives thereof.

The adhesives of the invention must be stable in early polymerization. Therefore, before and/or during the reaction, a phenolic stabilizer is preferably added as a constituent of component E) in order to inhibit the polymerization reaction. Phenols having such a use are, for example, p-methoxyphenyl, 2, 5-di-tert-butylhydroquinone or 2, 6-di-tert-butyl-4-methylphenol. Also suitable for stabilization are N-oxyl compounds, such as 2, 2, 6, 6-tetramethylpiperidine N-oxide (TEMPO) or its derivatives. Stabilizers may also be added to the binder chemically; the abovementioned classes of compounds have suitability in this respect, in particular if the compounds also bear free aliphatic alcohol groups or primary or secondary amine groups, and can therefore be chemically linked to the compounds of component A) via urethane or urea groups. 2, 2, 6, 6-tetramethyl-4-hydroxypiperidine N-oxide is particularly suitable for this purpose. Phenol stabilizers are preferred, in particular p-methoxyphenol and/or 2, 6-di-tert-butyl-4-methylphenol.

In contrast, the use of other stabilizers, such as Hindered Amine Light Stabilizers (HALS), in E) is less preferred, since it is known that they do not achieve such a stabilizing effect and may lead to "creeping" free-radical polymerization of the unsaturated groups.

To stabilize the reaction mixture, in particular the unsaturated groups, in the early polymerization, an oxygen-containing gas, preferably air, can be passed through the reaction mixture. Gases with very low moisture content are preferred to prevent unwanted reactions in the presence of isocyanates.

The binders of the invention are generally stabilized during and at the end of their preparation by adding stabilizers to achieve long-term stability, repeated stabilization with phenolic stabilizers and optionally saturation of the reaction product with air.

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

The method of the invention can be carried out as follows: a) is first reacted with B) until all NCO groups have reacted. The resulting intermediate may be stored and/or transported. The uretdione groups are then reacted with component C).

A) The ratio of NCO groups in (A) to NCO-reactive groups in (B) is from 1: 1 to 1: 1.5, preferably from 1: 1 to 1: 1.2, more preferably 1: 1. A) The ratio of mesouretdione groups to hydroxyl groups in C) is from 1: 0.4 to 1: 6, preferably from 1: 0.9 to 1: 4, more preferably from 1: 0.9 to 1: 2. Furthermore, the sum of NCO groups and uretdione groups in A) substantially exceeds the sum of NCO-reactive groups and uretdione-reactive groups in B).

Depending on the properties selected, the resulting product may be free of hydroxyl groups or still contain hydroxyl groups. These products preferably contain not only radiation-curing groups but also NCO-reactive groups. The process of the invention is preferably carried out at from 20 to 130 ℃ and more preferably at from 40 to 90 ℃.

The viscosity of the adhesives obtained according to the invention is in particular a function of the functionality, molecular weight and chemical properties of component C), and the stoichiometric proportions employed. The use of the preferred monomeric diols or triols, and also polyethers and/or polypropiones having a number average molecular weight of less than 1000g/mol, results in adhesives having a viscosity of less than 100,000 mPas at 23 ℃. The number average molecular weight is preferably 500-5000g/mol, more preferably 800-2000 g/mol.

The process of the invention can be carried out continuously, for example in a static mixer, or batchwise, for example in a stirred reactor.

The process of the invention is preferably carried out in a stirred mixer, in which case the order of addition of components A) and B) in the first step and of intermediates AB) and component C) in the second step is arbitrary. The stabilizers present in E) are preferably added before component B) is subjected to a thermal load. The other part of component E) can be added at any desired time. Preferably, the ammonium or phosphonium salt of the aliphatic or cycloaliphatic carboxylic acid of D) is not added until after the intermediate AB) has been prepared.

The course of the reaction can be monitored with a suitable measuring device arranged in the reactor and/or on the basis of the analysis of the samples taken. Suitable methods are known and include, for example, viscosity determination, refractive index determination, OH content determination, Gas Chromatography (GC), nuclear magnetic resonanceVibration (NMR) spectroscopy, Infrared (IR) spectroscopy, and Near Infrared (NIR) spectroscopy. Preferably, IR is used to detect the presence of any free NCO groups (in the case of aliphatic NCO groups, the band is approximately v-2272 cm^-1) In particular, the uretdione group (e.g.uretdione based on hexamethylene diisocyanate has a band v of 1761cm^-1) The unreacted compounds from B) and C) were analyzed by GC.

The uretdione and hydroxyl groups cannot react completely, but the reaction is stopped after a certain conversion has been reached. Then, a known acidic agent is added to stabilize the isocyanate groups and inhibit further (peristaltic) reactions. Preferred acids or acid derivatives include benzoyl chloride, phthaloyl chloride, phosphorus and/or phosphoric acid, the acid esters of the first 6 acids, sulfuric acid and its acid esters and/or sulfonic acids.

The adhesives of the invention are useful in the manufacture of coatings and paints, as well as adhesives, printing inks, casting resins, dental materials, sizing agents, photoresists, stereolithography systems, dendrimers for composites, and sealants. In the case of bonding or sealing of adhesives, it is required that at least one of the two substrates bonded or sealed to each other is transparent to UV radiation, i.e. must be transparent, if cured with UV radiation. In the case of electron beams, sufficient electron transmission should be ensured. Preferably, the binder is used in paints and coatings.

The coating composition of the present invention comprises:

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

b) optionally one or more polyisocyanates containing free or protected isocyanate groups, optionally containing groups capable of reacting with ethylenically unsaturated compounds upon polymerization by actinic radiation,

c) optionally a compound other than a) containing groups capable of reacting with ethylenically unsaturated compounds in the polymerization reaction by actinic radiation and optionally containing NCO-reactive groups,

d) optionally one or more active hydrogen-containing isocyanate-reactive compounds free of groups capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation,

e) one or more kinds of initiator(s),

f) optionally an additive.

Suitable polyisocyanates b) are aromatic, araliphatic, aliphatic or cycloaliphatic di-or polyisocyanates. Mixtures of these di-or polyisocyanates may also be used. Examples of suitable diisocyanates or polyisocyanates include tetramethylene diisocyanate, Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), 2, 4-and/or 2, 4, 4-trimethylhexamethylene diisocyanate, isomeric bis (4, 4 ' -isocyanatocyclohexyl) methanes or mixtures of any desired isomer contents, isocyanatomethyl-1, 8-octane diisocyanate, 1, 4-cyclohexane diisocyanate, isomeric cyclohexanedimethylene diisocyanates, 1, 4-xylylene diisocyanate and/or 2, 6-tolylene diisocyanate, 1, 5-naphthalenedimethylene diisocyanate, 2, 4 ' -or 4, 4 ' -diphenylmethane diisocyanate, triphenylmethane 4, 4', 4 "-triisocyanates, or adducts prepared from these di-and polyisocyanates and containing urethane, urea, carbodiimide, acylurea, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione, iminooxadiazinedione groups, and mixtures thereof.

Preference is given to polyisocyanate adducts based on oligomeric and/or derivatized diisocyanates, in particular those prepared from hexamethylene diisocyanate, isophorone diisocyanate and the isomeric bis (4, 4' -isocyanatocyclohexyl) methanes and mixtures thereof, where excess diisocyanate has been removed by suitable methods. Particular preference is given to isocyanurate-and/or iminooxadiazinedione-group-containing adducts prepared from HDI and also isocyanurate-group-containing polyisocyanate adducts prepared from IPDI.

It is also possible to use the aforementioned isocyanates blocked with one or more blocking agents. Examples include alcohols, lactams, oximes, malonates, alkyl acetoacetates, triazoles, phenols, imidazoles, pyrroles and amines, such as butanone oxime, diisopropylamine, 1, 2, 4-triazole, dimethyl-1, 2, 4-triazole, imidazole, diethyl malonate, ethyl acetoacetate, acetoxime, 3, 5-dimethylpyrrole, epsilon-caprolactam, N-tert-butylbenzylamine, cyclopentanone carboxyethyl ester and mixtures thereof.

The polyisocyanates b) may optionally contain one or more functional groups capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation. These radicals can be prepared by known methods by reacting the unsaturated isocyanate-reactive compounds listed under B), including the preferred ranges, with saturated polyisocyanates. NCO-containing urethane acrylates of this type are available from Bayer AG, Leverkusen, DE under the name RoskydalUA VP LS2337，RoskydalUA VP LS 2396 or RoskydalUA XP 2510 is commercially available.

Suitable compounds for use as component c) are polymers (such as polyacrylates, polyurethanes, polysiloxanes, polyesters, polycarbonates and polyethers) containing functional groups capable of reacting with ethylenically unsaturated compounds by polymerization with actinic radiation. Such groups include α, β -unsaturated carboxylic acid derivatives such as acrylates, methacrylates, maleates, fumarates, maleimides and acrylamides; a vinyl ether; propenyl ether, allyl ether; compounds containing dicyclopentadienyl units. Acrylates and methacrylates are preferred. Examples include reactive diluents (e.g., Rompp Lexikon Chemie, page 491, 10) known in the art of radiation curing and described as suitable for use in E)^thed.1998, Georg-Thieme \ e-Verlag, Stuttgart) or adhesives known in the art of radiation curing, e.g. polyether acrylatesPolyester acrylates, urethane acrylates, epoxy acrylates, melamine acrylates, silicone acrylates and acrylated polyacrylates, which may also contain isocyanate-reactive groups, preferably hydroxyl groups.

Suitable compounds d) include the hydroxy-functional monomeric or polymeric compounds described under C), and also water, only after coating, in contact with the remaining components, optionally under ambient moisture. In addition, NH-functional compounds such as amine-terminated polyethers, polyamines and aspartates may also be used.

Suitable initiators for the free-radical polymerization, which can be used as component e), are those which can be activated by heat and/or radiation. Photoinitiators which are capable of being activated by UV or visible light are preferred in the present invention. Photoinitiators are known compounds. There is a distinction between unimolecular (type I) initiators and bimolecular (type II) initiators. Suitable (type I) systems comprise aromatic ketone compounds, such as benzophenone, alkylbenzophenones, 4 '-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones in combination with tertiary amines, or mixtures thereof. Suitable (type II) initiators include benzoin and derivatives thereof, benzil ketones, acyl phosphine oxides, 2, 4, 6-trimethylbenzoyldiphenylphosphine oxides, diacylphosphine oxides, phenylglyoxylates, camphorquinones, alpha-aminoalkylphenones, alpha-dialkoxyacetophenones and alpha-hydroxyalkylphenones.

The initiator is used in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, based on the weight of the film-forming binder. The initiators can be used alone or in combination with one another to obtain a good synergistic effect.

When using electron beams instead of UV radiation, no photoinitiator is required. The electron beam is generated by thermal emission and accelerated by a potential difference. The high energy electrons are then directed through the titanium foil to cure the adhesive. The basic principles of electron beam curing are described in detail in Chemistry & Technology of UV & EB from Coatings, Inks & Paints, Vol.1, P.K.T.Oldring (Ed.), SITA Technology, London, England, pp.101-.

Thermal curing can occur by activating the double bonds with the addition of a thermally decomposing free radical initiator. Suitable initiators include peroxy compounds, such as dialkoxy dicarbonates, for example di (4-tert-butylcyclohexyl) peroxydicarbonate; dialkyl peroxides such as dilauryl peroxide; peresters of aromatic or aliphatic acids, such as tert-butyl perbenzoate or tert-amyl peroxy-2-ethylhexanoate; inorganic peroxides such as ammonium hydrogen persulfate or potassium hydrogen persulfate; organic peroxides such as 2, 2-di (t-butylperoxy) butane, dicumyl peroxide or t-butyl hydroperoxide; and azo compounds, such as 2, 2 '-azobis [ N- (2-propyl) -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 or 2, 2' -azobis { 2-methyl-N- [1, 1-bis (hydroxymethyl) -2-hydroxyethyl ] propionamide }. Also suitable are 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.

A combination of initiators activated by UV light and heat may also be used.

Additives f) include the solvents listed under E). In addition, to improve the weathering stability of the cured coating film, f) may contain UV absorbers and/or HALS stabilizers. Combinations of these stabilizers are preferred. The UV absorber should have an absorption range of no more than 390nm, such as triphenyltriazine type (e.g., Tinuvin)400(Ciba Spezialitatenchemie Gmbh, Lampertheim, DE)), benzotriazines (e.g. Tinuvin @, et al622(Ciba Spezialitatenchemie Gmbh, Lampertheim, DE)) or diphenyloxalamides (e.g., Sanduvor)3206(Clariant, Muttenz, CH)). The amount added is 0.5-3.5% by weight based on resin solids. Suitable HALS stabilizers are also commercially available and include (Tinuvin)292 or Tinuvin123(Ciba Spezialitatenchemie Gmbh, Lampertheim, DE) or Sanduvor3258(Clariant, Muttenz, CH). The amount added is 0.5-2.5 wt% based on resin solids.

Component f) may also contain pigments, dyes, fillers, levelling additives and degassing agents.

Furthermore, if desired, catalysts known in the art of polyurethane chemistry for accelerating the NCO/OH reaction may be present in f). Such catalysts include tin or zinc salts, or organotin compounds, tin soaps and/or zinc soaps, such as tin octoate, dibutyltin dilaurate, dibutyltin oxide, tertiary amines, such as diazabicyclo [2.2.2] octane (DABCO), bismuth compounds, zirconium compounds or molybdenum compounds.

The coating compositions of the invention can be applied to the material to be coated by methods known in the art of coating technology, such as spray coating, knife coating, roller coating, pouring, dipping, spin coating, brush coating or spray coating (squinting), or by printing techniques such as screen, gravure, letterpress or offset printing, but also by transfer methods.

Suitable substrates include wood, metal, in particular metal for applications in wire enamels, coil coatings, can coatings or container coatings, and plastics (including 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, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC, BMC, PP-EPDM and UP (abbreviation according to DIN7728T 1)), paper, leather, fabrics, felt, glass, wood, cork, inorganic bonded substrates (such as wood panels and fibre cement slabs), electronic components or mineral substrates. It is also possible to coat substrates comprising the various aforementioned materials or to coat already coated substrates, such as vehicles, aircraft or watercraft and also parts thereof, in particular parts for car bodies or for external mounting. The coating composition may also be applied temporarily to a substrate and then partially or fully cured and optionally removed again to produce a film.

All or part of the solvent may be removed by flash evaporation for curing. Followed by optional thermal or photochemical curing, either sequentially or simultaneously. If desired, the thermal curing can be carried out at room temperature or elevated temperature, preferably at 40 to 160 deg.C, more preferably at 60 to 130 deg.C, most preferably at 80 to 110 deg.C.

e) When a photoinitiator is used, the radiation curing is preferably carried out by high-energy radiation, i.e.UV radiation or sunlight, for example light having a wavelength of 200-700 nm. Sources of light or UV light include high or medium pressure mercury vapor lamps. The mercury vapor may be treated by doping with other elements such as gallium or iron. Lasers, pulsed lamps (known as UV flash lamps), halogen lamps or excimer emitters may also be used. As an inherent part of its design, and throughout the use of a particular filter and/or reflector, a reflector may be provided to prevent emission of part of the UV spectrum. For example, for occupational hygiene reasons, for example, the radiation labeled UV-C or UV-C and UV-B is filtered out. The emitter is mounted in a stationary manner so that the material for irradiation can be fed by mechanical means past the radiation source or the emitter can also be movable, the material for irradiation remaining stationary during curing. When UV curing is carried out, the normal radiation dose sufficient to complete crosslinking is from 80 to 5000mJ/cm²。

The irradiation may also be carried out in the absence of oxygen, such as 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 applying a coating with a medium transparent to the radiation. Examples include polymer films, glass or liquids such as water.

The type and concentration of any initiator used in a known manner may vary depending on the radiation dose and curing conditions.

It is particularly preferred to carry out the curing in a stationary facility using a 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 content of the coating composition. For curing these coatings, it is preferred to use 200-3000mJ/cm, measured at 200-600nm²The dosage of (a).

Curing is carried out by increasing the temperature when d) a thermally activated initiator is used. The thermal energy is introduced to the coating by radiation, heat conduction and/or convection using ovens, near infrared lamps and/or infrared lamps known in the art of coatings technology.

The thickness of the applied film (before curing) is generally from 0.5 to 5000. mu.m, preferably from 5 to 1000. mu.m, more preferably from 15 to 200. mu.m. When a solvent is used, the solvent may be removed after application and before curing by known methods.

Examples

All percentages are by weight unless otherwise indicated.

The% NCO content was determined according to DIN EN ISO 11909 by back titration with 0.1mol/l hydrochloric acid and subsequent reaction with butylamine.

According to ISO/DIS 3219: the viscosity was measured by means of a cone-plate viscometer (SM-KP) from Paar Physica, Ostifildern, DE, Viskolab LC 3/ISO.

Infrared spectroscopy was performed on a liquid film between sodium chloride plates using a model 157 Perkin Elmer, Uberlingen, DE.

The contents of residual monomers and synthesized volatiles were analyzed by GC (method using tetradecane as internal standard, oven temperature 110 ℃, injector temperature 150 ℃, carrier gas helium, instrument: 6890N, Agilent, Waldbronn, DE, column: Restek RT 50, 30m, 0.32mm internal diameter, film thickness 0.25 μm).

The solids content was determined in accordance with DIN 53216/1 draft 4/89, ISO 3251.

The experiment was generally run with an ambient temperature of 23 ℃ called RT.

DesmodurN3400-HDI polyisocyanate predominantly contained uretdione groups and had a viscosity of 185mPas/23 ℃ and an NCO content of 21.4%, and is a product of Bayer Materials Science AG, Leverkusen, DE.

DesmorapidDibutyltin Z-Dilaurate (DBTL), Bayer Materials scienceAG, Leverkusen, DE.

Darocur1173-photoinitiator, Ciba Speczialatechemie GmbH, Lampertheim, DE.

Example 1 describes the preparation of uretdione group-containing urethane acrylates by carbamation. This acrylate was used in examples 2 and 3.

Example 1

Uretdione group-containing urethane acrylates

In a three-necked flask with reflux condenser, stirrer, dropping funnel and air flow (0.5l/h) 194.90 g of Desmodur were initially charged at RTN3400, 0.31 g 2, 6-di-tert-butyl-4-methylphenol and 0.005 g DesmorapidZ, then heated to 60 ℃. 116.00 g of 2-hydroxyethyl acrylate were slowly added dropwise, during which the maximum temperature reached 70 ℃. The reaction mixture was then held at 70 ℃ until the NCO content was < 0.1%. On cooling, the product solidified to a waxy solid.

Example 2

The allophanate-containing adhesive of the invention

In an apparatus similar to example 1, 175.35 g of the urethane acrylate from example 1 were melted at 80 ℃ and 50.0 g of butyl acetate, 24.1 g of an average tetraethoxylated trimethylolpropane-initiated polyether (hydroxyl number 550, dynamic viscosity 505 mPas at 23 ℃) and 0.64 g of zinc (II) acetylacetonate were added. The reaction mixture was stirred at 80 ℃ until 14 hours, after which v-1768 cm in IR spectrum^-1Only very weak signals of uretdione groups were detected. The resulting clear product had a viscosity of 3100 mPas/23 ℃, a solids content of 81.1% and an NCO content of 0%.

Example 3

The allophanate-containing adhesive of the invention

Example 2 was repeated with the difference that 167.13 g of urethane acrylate and 32.04 g of polyether were used. The reaction mixture was stirred at 80 ℃ until 2 hours later, v-1768 cm in IR spectrum^-1Only very weak signals of uretdione groups were detected. 0.20 g of isophthaloyl dichloride was then added with stirring and the reaction mixture was cooled to RT. The clear product obtained had a viscosity of 1870 mPas/23 ℃, a solids content of 80.2%, a hydroxyl number of 32 (theoretical value of 35) and an NCO content of 0%.

Example 4

The allophanate-containing adhesive of the invention

Example 2 was repeated with the difference that only 66.8 g of urethane acrylate and 12.8 g of polyether, 20.0 g of butyl acetate and 0.34 g of polyether were usedZinc (II) ethylhexanoate. The reaction mixture was stirred at 80 ℃ until 8.5 hours, after which v-1768 cm in IR spectrum^-1Only very weak signals of uretdione groups were detected. 0.08 g of isophthaloyl dichloride was then added with stirring and the reaction mixture was cooled to RT. The viscosity of the clear product obtained was 1730 mPas/23 ℃, the solids content 80.8%, the hydroxyl number 37 (theoretical value 35) and the NCO content 0%.

Comparative examples 5 and 6

Preparation of allophanate-containing binders

The catalysts described in US-a 2003/0153712 were tested for their suitability for use in cross-linking powder coating compositions containing a uretdione based curing agent and a polymerizable hydroxy compound without an activated double bond.

Comparative example 5

Example 23 was repeated, except that the catalyst from example 1 was replaced by an equimolar amount of tetrabutylammonium hydroxide.

Comparative example 6

Example 23 was repeated, except that the catalyst from example 1 was replaced by an equimolar amount of tetrabutylammonium fluoride.

(comparative) examples	2	5	6
				Reaction time after addition of catalyst (hours)	14	2.5	2.0
Visual evaluation	Clear and clear	Is very turbid	Is very turbid
				Solids content [% ]]	81.1	81.7	82.2
Viscosity [ mPa. multidot.s/23 DEG C]	3100	12000	16000

Comparison shows that the products of comparative examples 5 and 6 have a higher viscosity and are visually unsuitable for use as coating compositions due to significant haze.

Example 7

Paint formulation and paint

A portion of the product from example 3 was admixed with 3.0% of a photoinitiator1173 and mixed thoroughly. The mixture was applied to a glass plate using a bone hand coater with a gap of 90 μm to form a thin film. After UV irradiation (medium-pressure mercury lamp, IST Metz GmbH, Nurtingen, DE, 750 mJ/cm)²) Obtaining a transparent hard coating resistant to solvents, the Pendel hardness of the coating being 97, by dippingAfter 100 double rubs of the pad with butyl acetate, no change was visible.

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (10)

1. A method of making an adhesive comprising: 1) allophanate groups, 2) groups which are capable of undergoing a polymerization reaction with an ethylenically unsaturated compound under actinic radiation (radiation-curable groups), and 3) optionally NCO-reactive groups, said process comprising: reacting A) with B) at a temperature of 130 ℃ or less and then with C) in the presence of D),

A) one or more uretdione group-containing NCO-functional compounds,

B) one or more compounds containing isocyanate-reactive groups and groups which are capable of polymerization with ethylenically unsaturated compounds under the action of actinic radiation, i.e.radiation-curable groups,

C) one or more saturated compounds containing hydroxyl groups, other than B), at least one of these compounds having an OH functionality of 2 or more, at least one of these compounds being chosen from the following substances: monomeric diols, monomeric triols, polyethers and polylactones derived therefrom having a number average molecular weight of less than 1000g/mol,

D) a catalyst comprising one or more zinc compounds,

the reaction with the compounds C) is carried out at least in proportion to the allophanate groups formed.

2. The method of claim 1, wherein the uretdione group-containing compound is prepared from hexamethylene diisocyanate.

3. The method of claim 1, wherein component B) comprises a compound selected from the group consisting of: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene oxide mono (meth) acrylate, polypropylene oxide mono (meth) acrylate, and the reaction product of acrylic acid and glycidyl methacrylate.

4. The method of claim 2, wherein component B) comprises a material selected from the group consisting of: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene oxide mono (meth) acrylate, polypropylene oxide mono (meth) acrylate, and the reaction product of acrylic acid and glycidyl methacrylate.

5. The process of claim 1 wherein component D) consists of a zinc compound.

6. The process of claim 1 wherein component D) comprises zinc acetylacetonate and/or zinc ethylhexanoate.

7. The process of claim 2 wherein component D) comprises zinc acetylacetonate and/or zinc ethylhexanoate.

8. A process according to claim 3, wherein component D) comprises zinc acetylacetonate and/or zinc ethylhexanoate.

9. The process of claim 4 wherein component D) comprises zinc acetylacetonate and/or zinc ethylhexanoate.

10. The method of claim 1, wherein the reaction is carried out at 20-100 ℃.