HK1100221B - Production of novel radiation-hardening binding agents - Google Patents

Description

Preparation of novel radiation-curable adhesives

The invention relates to a process for the preparation of novel binders which contain groups which are capable of polymerization with ethylenically unsaturated compounds on exposure to actinic radiation and optionally also contain groups which are reactive toward isocyanates, and to the use of the binders in coating compositions.

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

Particularly advantageous properties can be obtained if the radiation curing is combined with a separately controllable second crosslinking step. Such coating systems are known as dual cure systems (e.g., Macromol. Symp.187, 531-541, 2002).

Because of the environmental and economic requirements imposed on modern coating systems, which necessitate the use of as little as possible, or even no, organic solvents for viscosity control, it is desirable to use coating materials which are themselves of low viscosity. Polyisocyanates with allophanate structures have been mentioned for a long time, as described in EP-A0682012.

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

EP-A0825211 describes the synthesis of allophanate structures from oxadiazinetriones, although no radiation-curable derivatives with activated double bonds are mentioned. All that is mentioned is the use of polyesters containing maleic and/or fumaric acid esters; no description is given about the possibility of radiation curing.

U.S. Pat. No. 5,5777024 describes the preparation of low viscosity radiation-curable allophanates by reacting hydroxy-functional monomers having an activated double bond with NCO-containing allophanate-modified isocyanurates.

The formation of allophanate compounds by ring-opening reaction of uretdiones with alcohols is known as a crosslinking mechanism in Powder Coatings (cf. International Water, High Solids and Powder coating treatises, and Powder Coatings Symposium), 2001, 28 th, 405 th, 419 and US-A20030153713). However, the reaction temperatures required for this purpose are too high for the targeted preparation of radiation-curing monomers based on allophanates with activated double bonds (. gtoreq.120 ℃).

Historically, the direct reaction of uretdione rings with alcohols to form allophanates was initially investigated for solvent-borne, isocyanate-free 2K [ 2-component ] polyurethane coatings. There is no technical value in not catalyzing the reaction because of the low reaction rate (f. schmitt, angelw. markromo. chem. (1989), 171, pages 21-38). However, the crosslinking reaction between 1, 6-Hexamethylene Diisocyanate (HDI) uretdione curing agents (cures) and polyols is said to start at 60-80 ℃ with a suitable catalyst (K.B. Chandalia; R.AEnglebach; S.L. Goldstein; R.W.good; S.H.Harris; M.J.Morgan; P.J.Whitman; R.T.Wojcik, International Water, high solids and powder coatings proceedings (2001), pp.77-89). The structure of these catalysts has not been disclosed so far. Commercial products prepared by this reaction have not been disclosed so far.

In summary, it is believed that the ring opening reaction of alcohols with uretdiones at temperatures below 100 ℃ to prepare low viscosity radiation curable allophanates is not known in the prior art.

It is therefore an object of the present invention to provide a process for preparing low-viscosity allophanates which contain photocurable groups and advantageously isocyanate-reactive groups and are therefore suitable as crosslinkers in dual-cure applications; based on their allophanate structure, these compounds should have a lower viscosity than corresponding compounds which contain only urethane structures. Furthermore, temperatures below 100 ℃ should be sufficient for their preparation and/or work-up.

It has now been found that adhesives containing photocurable groups and optionally NCO-reactive groups and meeting the above requirements can be obtained by reacting uretdione-functional and NCO-functional compounds with alcohols containing photocurable double bonds and with polyhydroxyl compounds using phenoxides as catalysts.

For the purposes of the present invention, the terms "radiation-curable group", "photocurable group" and "group which is capable of undergoing a polymerization reaction with ethylenically unsaturated compounds upon exposure to actinic radiation" are intended to be identical.

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

NCO-reactive groups mean OH-, SH-and NH-functional compounds, in particular hydroxyl, primary and/or secondary amino groups, and/or aspartate groups. Preferred is a hydroxyl group.

The present invention accordingly provides a process for preparing allophanate group-containing adhesives which contain groups which are capable of undergoing a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation and optionally also contain NCO-reactive groups, in which A) is reacted first with B) and then with C) in the presence of D) and optionally E):

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

B) one or more compounds containing groups which are capable of undergoing a polymerisation reaction with ethylenically unsaturated compounds on exposure to actinic radiation and containing isocyanate-reactive groups,

C) one or more hydroxyl-containing compounds different from B), at least one of these compounds having an OH functionality of 2 or more,

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

E) an auxiliary agent and an additive agent,

with the compounds of component C) at least in proportion to form allophanate groups (thermal with a compound of component C) proceeding at least with a reaction of reacting with allophanate groups).

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

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

Preferably, the uretdione group content of the compounds used in A) (as C)₂N₂O₂84 g/mol) of 3 to 60 wt.%, more preferably 10 to 50 wt.%, and particularly preferably 25 to 40 wt.%.

Preferably, the compounds used in a) have an NCO group content (calculated as NCO ═ 42 g/mol) of 3 to 60% by weight, more preferably 10 to 50% by weight, and particularly preferably 15 to 25% by weight, while having the above-mentioned uretdione group content.

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

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

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

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

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

NCO-functional compounds prepared by catalytic dimerization are preferably used directly in component A); alternatively, some of the isocyanate groups may be reacted first and the product obtained then used in A). This further reaction is, for example, a blocking reaction of some free NCO groups, or a further reaction of NCO groups with NCO-active compounds known from isocyanate chemistry (for example, as described, inter alia, in j.prakt. chem.1994, 336, page 185), to form iminooxadiazinedione, isocyanurate, uretdione, urethane, allophanate, biuret, urea, oxadiazinetrione, oxazolidinone, acylurea or carbodiimide structures. This procedure gives high molecular weight compounds containing uretdione groups, which, depending on the chosen proportions, may also contain different amounts of NCO groups.

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

For example, NCO groups can also be used partly together with compounds having a hydrophilic action and containing at least one isocyanate-reactive group, which compounds can be used individually or as mixtures. It is particularly desirable to use compounds having a hydrophilic action when the product of the process of the invention is to be dispersed or dissolved in water or is an aqueous mixture.

Compounds having a hydrophilic action are understood to mean all ionic, potentially ionic and nonionic hydrophilic compounds which contain at least one isocyanate-reactive group. These compounds preferably contain hydroxyl and/or amino functional groups as isocyanate-reactive groups.

Preference is given to using compounds which contain at least one isocyanate-reactive group and at least one further functional groupAs component C) of hydrophilic compounds of ionic or potentially ionic type, these other functional groups being, for example, -COOY, -SO₃Y、-PO(OY)₂(Y＝H，NH₄ ⁺Metal cation), -NR₂、-NR₃ ⁺、-PR₃ ⁺(R ═ H, alkyl, aryl). Potentially ionically hydrophilicizing compounds are those which, after interaction with aqueous media, reach an optionally pH-dependent dissociation equilibrium and are therefore negatively, positively or neutrally charged.

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

As hydrophilic nonionic compounds, compounds having a polyether structure may be used, with alkylene oxide-based polyethers containing at least one hydroxyl or amino group as isocyanate-reactive group being preferred.

These compounds having a polyether structure may be, for example, monofunctional polyalkylene oxide polyether alcohols having at least 30 mol% of ethylene oxide and an average content of from 5 to 70, preferably from 7 to 55, ethylene oxides per molecule, such as are obtained in a conventional manner by alkoxylation of suitable starter molecules (for example Ullmanns)dertechnischem Chemie, 4 th edition, volume 19, Verlag Chemie, Weinheim, pages 31-38).

Examples of suitable starter molecules are saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, pentanol and isomers thereof, hexanol and isomers thereof, octanol and isomers thereof and nonanol and isomers thereof, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexanes, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol; diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether; unsaturated alcohols, such as allyl alcohol, 1-dimethylallyl alcohol or oleyl alcohol; aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols; araliphatic alcohols, such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol; secondary monoamines, such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis (2-ethylhexyl) amine, N-methyl-and N-ethylcyclohexylamine or dicyclohexylamine, and heterocyclic secondary amines, such as morpholine, pyrrolidine, piperidine or 1H-pyrazole. Preferred starter molecules are saturated monoalcohols. Particular preference is given to using diethylene glycol monobutyl ether as starter molecule.

Alkylene oxides suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in the alkoxylation reaction independently of one another in any order or as a mixture in this reaction to give the blocked polyethers or copolyethers.

Preferably, the compound having a polyether structure is a simple polyethylene oxide polyether or a mixed polyalkylene oxide polyether in which at least 30 mol%, preferably at least 40 mol%, of the alkylene oxide units consist of ethylene oxide units.

Particularly preferred are monofunctional mixed polyalkylene oxide polyethers which contain at least 40 mol% ethylene oxide units and not more than 60 mol% propylene oxide units.

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

Suitable compounds of component B) which may be used individually or as mixtures are 2-hydroxyethyl (meth) acrylate, polyethylene oxide mono (meth) acrylates (e.g. PEA6/PEM 6; laportepform Chemicals, ltd., uk), polypropylene oxide mono (meth) acrylates (e.g., PPA6, PPM 5S; laporte Performance Chemicals, ltd., uk), polyalkylene oxide mono (meth) acrylates (e.g., PEM63P, Laporte Performance Chemicals, ltd., uk), poly (epsilon-caprolactone) mono (meth) acrylates (e.g., Tone)Schwalbach, germany, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxy-2, 2-dimethylpropyl (meth) acrylate, hydroxy-functional mono-, di-or possibly higher acrylates, such as glycerol di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate or dipentaerythritol penta (meth) acrylate, which may be prepared by reacting optionally alkoxylated polyols, such as trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol, optionally as industrially obtained mixtures.

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

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

Particularly preferred compounds of B) are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate,schwalbach, germany), polyethylene oxide mono (meth) acrylates (e.g., PEA6/PEM 6; laporte Performance Chemicals, ltd., uk), polypropylene oxide mono (meth) acrylates (e.g., PPA6, PPM 5S; laporte Performance Chemicals, ltd., uk) and the reaction product of acrylic acid and glycidyl methacrylate.

Component C) comprises one or more hydroxyl-containing compounds different from B), at least one of these compounds having a functionality of > 2. These compounds may be monomeric and/or polymeric.

Examples of suitable low molecular weight monohydric, dihydric or polyhydric alcohols are short chain (i.e. containing from 2 to 20 carbon atoms) aliphatic, araliphatic or cycloaliphatic monohydric, dihydric or polyhydric alcohols. Examples of monohydric alcohols are methanol, ethanol, the isomeric propanols, butanols, pentanols, and diacetone alcohols, fatty alcohols or fluorinated alcohols, such as by nameAlcohol from DuPont. Examples of diols are 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, 2-bis (4-hydroxycyclohexyl) propane), 2-bis (2-hydroxy-cyclohexyl) propane)-dimethyl-3-hydroxypropionic acid 2, 2-dimethyl-3-hydroxypropyl ester. Examples of suitable triols are trimethylolethane, trimethylolpropane or glycerol. Examples of suitable polyols are di (trimethylolpropane), pentaerythritol, dipentaerythritol and sorbitol. Preferred are 1, 4-butanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol and trimethylolpropane.

Also suitable are high molecular weight polyols, such as polyester polyols, polyether polyols, hydroxyl-functional (meth) acrylate (co) polymers, hydroxyl-functional polyurethanes or corresponding hybrids (reference,lexikon Chemie, pp.465-466, 10 th edition, 1998, Georg-Thieme-Verlag, Stuttgart).

In the preparation of the hydroxy-functional polyesters, the following 6 monomer components can be used in particular:

(Cyclo) alkanediols, e.g. diols having a hydroxyl group attached to an aliphatic (cyclo) group, such as the compounds mentioned above for low molecular weight diols, and molecular weight M_nFrom 200 to 4000 g/mol, preferably from 300 to 2000 g/mol, more preferably from 450 to 1200 g/mol, of polyethylene glycol, polypropylene glycol or polytetramethylene glycol. The diols mentioned above can also be used as reaction products of these diols with epsilon-caprolactone or other lactones.

2. A hydroxyl number of 3 or more and a molecular weight M_nAlcohols 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 alcohols obtained by reaction with epsilon-caprolactone or other lactones, in the range of 92 to 254 grams per mole.

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

4. Molecular weight M_n104 to 600 g/mol dicarboxylic acid and-Or anhydrides thereof, such as phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid, maleic anhydride, fumaric acid, malonic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, hydrogenated dimer fatty acids.

5. Higher functional carboxylic acids and/or their anhydrides, for example, trimellitic acid and trimellitic anhydride.

6. Monocarboxylic acids, such as benzoic acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, caproic acid, caprylic acid, capric acid, lauric acid, 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. Alternatively, the above reaction products of alcohols with lactones may also be used. Number average molecular weight M of hydroxyl group-containing polyester_nFrom 500 to 10000 g/mol, preferably from 800 to 3000 g/mol, and a hydroxyl group content of from 1 to 20% by weight, preferably from 3 to 15% by weight. The polyesters may be used as such or as a solution in a reactive diluent or solvent suitable for use in the process of the invention.

Suitable are not only the polyester polyols described but also dendritic or hyperbranched compounds, for example those obtained from ethoxylated pentaerythritol and dimethylolpropionic acid.

For example, suitable polycarbonate polyols are prepared by reacting the alcohols mentioned above for polyether polyols with organic carbonates, such as diphenyl carbonate, dimethyl carbonate or diethyl carbonate, by known methods. They generally have a number average molecular weight of from 500 to 5000 g/mol, preferably from 750 to 2500 g/mol, and a hydroxyl functionality of from 1.5 to 3.

Suitable polyethers are, for example, alkylene oxide polyethers prepared from the abovementioned low molecular weight monools, diols or polyols. Or byPolyether obtained by polymerizing tetrahydrofuran. Number average molecular weight M of polyether_nFrom 400 to 13000 g/mol, preferably from 400 to 2500 g/mol, particularly preferably from 500 to 1200 g/mol, and a hydroxyl group content of from 1 to 25% by weight, preferably from 3 to 15% by weight.

(meth) acrylate (co) polymers are described in detail in WO03/000812 on pages 8 to 16 and are directed to suitable preparation processes, only those (meth) acrylate (co) polymers containing at least one hydroxyl group being suitable for use in the present invention. Number average molecular weight M of (meth) acrylate (co) polymer_nPreferably 500 to 10000 g/mol, more preferably 1000 to 5000 g/mol, and a hydroxyl group content of 1 to 20% by weight, more preferably 3 to 15% by weight.

Particular preference is given to using one or more compounds selected from the following group in component C): monomeric diols and triols, polyethers derived therefrom and average molecular weights M_n<1000 g/mol of polylactone.

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

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

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

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

general formula (I)

In the formula:

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

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

general formula (II)

In the formula:

q is oxygen, and Q is oxygen,

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

As compounds of the general formula (I) containing phenolate radicals, particular preference is given to using ammonium phenolate and phosphonium phenolate, particular preference to using tetraalkylammonium phenolate and tetraalkylphosphonium phenolate.

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

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

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

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

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

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

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

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

Compounds which also undergo (co) polymerization during uv curing and are thus incorporated into the polymer network can be used as reactive diluents. If these compounds have been brought into contact with NCO-containing compounds A), they must be inert towards NCO groups. This restriction is not necessary if they are added only after the reaction of A) with B). Such reactive diluents are described by way of example in P.K.T.Oldring (Ed.), Chemistry & Technology of UV & EB Formulations For Coatings, Inks & paintts, Vol.2, 1991, SITA Technology, London, pp.237 and 285. They may be esters of acrylic or methacrylic acid, preferably acrylic acid, with monofunctional or polyfunctional alcohols. Examples of suitable alcohols include butanol, pentanol, hexanol, heptanol, octanol, nonanol and decanol and isomers of these alcohols, as well as cycloaliphatic alcohols such as isobornyl, cyclohexanol and alkylated cyclohexanols, dicyclopentanol; araliphatic alcohols such as phenoxyethanol and nonylphenylethanol and tetrahydrofurfuryl alcohol. In addition, alkoxylated derivatives of these alcohols may be used. Suitable diols are, for example, the alcohols listed below: ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, diethylene glycol, dipropylene glycol, butylene glycol and isomers thereof, neopentyl glycol, 1, 6-hexanediol, 2-ethylhexanediol, and tripropylene glycol, and alkoxylated derivatives of these alcohols. Preferred diols are 1, 6-hexanediol, dipropylene glycol and tripropylene glycol. Suitable triols are glycerol or trimethylolpropane or their alkoxylated derivatives. The tetrahydric alcohol is pentaerythritol or alkoxylated derivatives thereof.

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

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

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

In general, the stabilizer is added during the preparation of the binders according to the invention, and at the end, in order to achieve long-term stability, the stabilization is carried out again with a phenolic stabilizer, and the reaction product is optionally saturated with air.

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

The process of the invention is carried out in this order: A) first with B) until complete conversion of the NCO groups. The formed intermediate is optionally stored and/or transported. Followed by reaction of the uretdione groups with component C).

The ratio of NCO groups in component A) to NCO-reactive groups in component B) is from 1:1 to 1:1.5, preferably from 1:1 to 1:1.2, particularly preferably 1:1. A) The ratio of uretdione groups in (A) to hydroxyl groups in (C) is from 1:0.4 to 1:6, preferably from 1:0.9 to 1:4, particularly preferably from 1:0.9 to 1: 2. In addition, it is necessary that the total amount of NCO groups and uretdione groups in A) is greater than the total amount of NCO-reactive groups and uretdione-reactive groups in B).

Depending on the choice of the proportions of components A) to C), process products are obtained which are free of isocyanate-reactive groups, such as OH groups, or still contain such groups.

The process of the invention is preferably carried out at a temperature of from 20 ℃ to 100 ℃, more preferably from 40 ℃ to 90 ℃. In particular the reaction of the uretdione groups with the hydroxyl groups is carried out at from 60 ℃ to 90 ℃.

The viscosity of the adhesives obtained according to the invention depends, inter alia, on the functionality, molecular weight and chemical nature of the component C) used and on the stoichiometry used. For example, when using the preferred monomeric diols or triols and the polylactones and/or polyethers obtained therefrom having an average molecular weight of less than 1000 g/mol, the resulting adhesives preferably have a viscosity at 23 ℃ of less than 100000mPas, more preferably less than 75000mPas, very preferably less than 40000 mPas. The number average molecular weight is preferably from 500 to 5000, particularly preferably from 800 to 2000 g/mol.

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

Preferably, the process of the invention is carried out in a stirred reactor, the order of addition of components A) and B) in the first step and of the intermediate resulting from A) and B) and C) in the second step being arbitrary. E) The stabilizer of (1) is preferably added before component B) is heated. The other part of component E) can be added at any time and on time. The phenoxide compound of D) is preferably not added until after intermediates of A) and B) have been prepared.

The course of the reaction can be monitored by means of measuring devices installed in the reaction vessel and/or on the basis of the results of the analysis of the samples. Suitable techniques are known to those skilled in the art. These techniques include, for example, viscosity measurements, refractive index measurements, OH content measurements, Gas Chromatography (GC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), and near infrared spectroscopy (NIR). It is preferred to detect any free NCO groups present (for aliphatic NCO groups, the band is about v-2272 cm)^-1Here), in particular, the uretdione group (for example, uretdione based on 1, 6-hexamethylene diisocyanate has a band at v 1761cm^-1Infra red spectrum of (B), and gas chromatography for analysis of unreacted compounds from B) and C). The reaction of the uretdione groups with the hydroxyl groups may not proceed to completion but may be terminated after a certain conversion has been reached. Further (creep) reactions are suppressed by the addition of acidic agents, for example, those known to the person skilled in the art for stabilizing isocyanate groups. Particularly suitable are acids or acid derivatives, such as benzoyl chloride, phthaloyl chloride, phosphinic acid, phosphonous acid and/or phosphorous acid, phosphinic acid, phosphonic acid and/or phosphoric acid and also the acid esters of the 6 acids mentioned above, sulfuric acid and its acid esters and/or sulfonic acids.

The binders according to the invention can be used for the production of coatings and paints, as well as adhesives, printing inks, casting resins, dental compounds, sizes, photoresists, stereolithography systems (sterolithography), resins for composite materials and sealants. However, in adhesive bonding or sealing applications, there is a requirement that, in the case of uv radiation curing, at least one of the two base sheets to be bonded or sealed to one another be transparent to uv radiation; in other words, in general, the substrate must be transparent. In the case of electron beams, sufficient penetration of electrons should be ensured. Preferably in paints and coatings.

The present invention also provides a coating composition comprising:

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

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

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

d) optionally one or more active hydrogen-containing isocyanate-reactive compounds which are free of groups capable of polymerization with ethylenically unsaturated compounds upon exposure to actinic radiation,

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

f) optionally auxiliaries and additives.

The polyisocyanates b) are aromatic, araliphatic, aliphatic or cycloaliphatic diisocyanates or polyisocyanates. Mixtures of such diisocyanates or polyisocyanates may also be used. Examples of suitable diisocyanates or polyisocyanates are 1, 4-diisocyanatobutane, 1, 6-diisocyanatohexane (HDI), isophorone diisocyanate (IPDI), 2, 4-and/or 2, 4, 4-trimethylhexamethylene diisocyanate, bis (4, 4 '-isocyanatocyclohexyl) methane and its isomers or mixtures thereof in any desired isomer content, isocyanatomethyl-1, 8-octa-diisocyanate, 1, 4-diisocyanatocyclohexane, diisocyanatocyclohexane and its isomers, 1, 4-diisocyanatobenzene, 2, 4-and/or 2, 6-diisocyanatotoluene, 1, 5-diisocyanatonaphthalene, 2, 4' -or 4, 4 '-diphenylmethane diisocyanate, triphenylmethane-4, 4' -triisocyanate or derivatives thereof having a urethane, urea, carbodiimide, acylurea, isocyanurate, allophanate, biuret, oxadiazinetrione, uretdione, iminooxadiazinedione structure, and mixtures thereof. Preferred are polyisocyanates based on oligomerized and/or derivatized diisocyanates and which are free of excess diisocyanate by suitable methods, especially those based on 1, 6-hexamethylene diisocyanate, isophorone diisocyanate and bis (4, 4' -isocyanatocyclohexyl) methane and its isomers, and mixtures thereof. Particularly preferred are the oligomeric isocyanurates and iminooxadiazinediones of HDI and mixtures thereof, and also the oligomeric isocyanurates of IPDI.

It is also possible to optionally use the abovementioned isocyanates blocked with compounds known to the person skilled in the art of coatings technology. Examples of blocking agents which may be mentioned are the following: alcohols, lactams, oximes, malonates, alkyl acetoacetates, triazoles, phenols, imidazoles, pyrazoles and amines, such as butanone oxime, diisopropylamine, 1, 2, 4-triazole, dimethyl-1, 2, 4-triazole, imidazole, diethyl malonate, ethyl acetoacetate, acetoxime, 3, 5-dimethylpyrazole, epsilon-caprolactam, N-tert-butylbenzylamine, cyclopentanone, carboxyethyl ester or any desired mixtures of these blocking agents.

The polyisocyanates b) may optionally contain one or more functional groups which are capable of polymerization with ethylenically unsaturated compounds upon exposure to actinic radiation. These radicals can be prepared by the unsaturated isocyanate-reactive compounds specified under B), including the preferred ranges, and the saturated polyisocyanates by methods known per se. The NCO-containing urethane acrylate may beVP LS2337、VP LS2396 orXP 2510 is available from Bayer AG, Leverkusen, Germany.

Polymers such as polyacrylates, polyurethanes, polysiloxanes, polyesters, polycarbonates, polyethers which contain groups which can be polymerized with ethylenically unsaturated compounds by exposure to actinic radiation can be used as compounds of component c). Such groups areα, β -unsaturated carboxylic acid derivatives such as acrylates, methacrylates, maleates, fumarates, maleimides, acrylamides and vinyl ethers, propenyl ethers, allyl ethers and compounds containing dicyclopentadienyl units. Preferred are acrylates and methacrylates. Examples include reactive diluents known in the art of radiation curing and exemplified in E) (reference,lexikon Chemie, page 491, 10 th edition, 1998, Georg-Thieme-Verlag, Stuttgart) or adhesives known from radiation curing technology, such as polyether acrylates, polyester acrylates, urethane acrylates, epoxy acrylates, melamine acrylates, silicone acrylates, polycarbonate acrylates and acrylated polyacrylates, which optionally contain isocyanate-reactive groups, in particular hydroxyl groups.

Suitable compounds d) are, for example, the hydroxy-functional monomer compounds or polymers described under C) and water, which is brought into contact with the remaining components only after coating, optionally in the form of ambient moisture. In addition, NH-functional compounds such as amine-terminated polyethers, polyamines and aspartates may be used.

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

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

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

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

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

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

In addition, to improve the weathering resistance of the cured coating, f) may also comprise UV absorbers and/or HALS stabilizers. Preferably a combination thereof. The former should have an absorption range of no more than 390 nm, such as triphenyltriazines (e.g.,GmbH, Lampertheim, Germany)), benzotriazoles such as622(Ciba GmbH, Lampertheim, germany) or oxalanilide (for example,3206(Clariant, Muttenz, switzerland))) and is added in an amount of 0.5 to 3.5% by weight, based on resin solids. Suitable HALS stabilizers are commercially availableOr(Ciba GmbH, Lampertheim, Germany) or(Clariant, Muttenz, Switzerland). Preferably, the amount used is from 0.5 to 2.5 weight percent based on resin solids.

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

In addition, if necessary, the f) may also contain known catalysts in polyurethane chemistry for accelerating the NCO/OH reaction. These catalysts are, for example, tin salts or zinc salts or organotin compounds, tin soaps and/or zinc soaps, such as tin octoate, dibutyltin dilaurate, dibutyltin oxide, or tertiary amines, such as diazabicyclo [2.2.2] octane (DABCO), for example bismuth compounds, zirconium compounds or molybdenum compounds.

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

Suitable substrates are, for example, wood, metals, including in particular metals used in wire enamel, coil coating, can coating or container coating applications, 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 (abbreviations according to DIN7728T 1), paper, leather, fabrics, felt, glass, wood materials, cork, inorganically bonded substrates, such as wood boards and fiber cement boards, electronic assemblies or mineral substrates. It is also possible to coat substrates composed of various of the abovementioned materials or to coat already coated substrates, such as vehicles, aircraft or watercraft, and also parts thereof, in particular vehicle bodies or parts for external mounting. For example, it is also possible to apply the coating compositions temporarily to the substrate, then to cure them partially or completely, and optionally to peel them off again, in order to produce a film.

For curing, the solvent present can be removed completely or partly, for example by flash drying.

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

If necessary, the thermal curing can be carried out at room temperature or at elevated temperature, preferably at from 40 to 106 deg.C, more preferably from 60 to 130 deg.C, and even more preferably from 80 to 110 deg.C.

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

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

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

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

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

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

Examples

All percentages are by weight unless otherwise indicated.

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

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

An instrument of type 157 (from Perkin Elmer,germany) on a liquid film applied between two sodium chloride sheets.

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

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

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

3400: HDI polyisocyanates, which contain predominantly uretdione structures and have a viscosity of 185mPas/23 ℃ and an NCO content of 21.4%, are commercially available from Bayer AG, Leverkusen, Germany;

dibutyltin dilaurate (OBTL), a commercial product of Bayer AG, Leverkusen, Germany;

photoinitiator, Ciba from Lampertheim, GermanyCommercial products of GmbH;

linear polyester containing hydroxyl groups, solvent-free, having a hydroxyl content of 8.5%, an equivalent weight of 200 g/eq and a viscosity of 850mPas at 23 ℃ (diluted to 75% solids with methoxypropyl acetate).

Example 1 describes the preparation of a suitable catalytically active phenate for use in examples 2 to 6 of the present invention.

Example 1Tetrabutylammonium salicylate

To a glass flask with reflux condenser, heated oil bath, mechanical stirrer and internal thermometer at room temperature was added 35.90 grams of ethyl salicylate and 282.13 grams of water, and the components were stirred together thoroughly. 139.98 g of tetrabutylammonium hydroxide (40% strength in water) are then added and the reaction mixture is heated to 60 ℃. Stirring was carried out at 60 ℃ for 1 hour (the contents of the flask became transparent). The reaction mixture was then cooled and water was distilled off under reduced pressure of 20 mbar and at a temperature of 30-45 ℃. The residue was dissolved in 200 ml of toluene at 60 ℃. The mixture was then redistilled. The residue was recrystallized from 50 ml of butyl acetate. The product was filtered off, washed with butyl acetate and dried in a vacuum oven at 80 ℃ and 10 mbar. A white solid having a melting point of 93 ℃ was obtained.

Example 2Allophanate-containing adhesives of the invention

47.02 g of air (6 l/h) were introduced into a three-necked flask with reflux condenser, stirrer and dropping funnel at room temperature0.10 g of 2, 6-di-tert-butyl-4-methylphenol and 0.001 gThe initial charge was then heated to 60 ℃. 28.00 g of 2-hydroxyethyl acrylate are slowly added dropwise, during which the temperature reaches a maximum of 70 ℃. The reaction mixture was then kept at 70 ℃ until the NCO content<Up to 0.1%. Then 20.00 g of butyl acetate and 4.42 g of trimethylolpropane were added and dissolved in the reaction mixture. 0.41 g of the catalyst from example 1 was added. The reaction mixture was heated to 80 ℃ and held at this temperature until after 5.5 hours, at 1768cm in IR spectrum^-1Until only a very weak uretdione group signal peak was detected. The product obtained is clear, has a viscosity of 8700mPas/23 ℃, a solids content of 81.8% and an NCO content of 0%.

Examples 3-6 were carried out according to a procedure similar to example 2. The amounts used are given in [ g ], the materials added, the reaction times and the results are given in the table below.

^*) Polyethers prepared from trimethylolpropane, ethoxylated on average 4-fold (4-fold) (hydroxyl number 550, dynamic viscosity 505 mPas at 23 ℃ C.)

Comparative examples 1 and 2: attempts to prepare allophanate-containing binders

The suitability of the catalysts described in U.S. Pat. No. 4, 200330153713 for the crosslinking of powder coatings (comprising uretdione-group-containing curing agents and polymeric hydroxy compounds which do not have an active double bond) was investigated:

comparative example C1: example 2 was repeated, but in this comparative example the catalyst of example 1 was replaced by an equimolar amount of tetrabutylammonium hydroxide.

Comparative example C2: example 2 was repeated, but in this comparative example the catalyst of example 1 was replaced by an equimolar amount of tetrabutylammonium fluoride.

Examples	2	C1	C2
				Reaction time after catalyst addition	5.5 hours	2.5 hours	2.0 hour
Visual evaluation	Is transparent	Very turbid	Very turbid
				Solids content [% ]]	81.8	81.7	82.2
Viscosity [ mPas ] at 23 ℃]	8700	12000	16000

The comparison shows that the products according to comparative examples C1 and C2 have a higher viscosity and cannot be used as coating compositions because of the pronounced cloudiness.

Claims (9)

1. A process for preparing an allophanate group-containing adhesive which contains groups which are capable, on exposure to actinic radiation, of undergoing a polymerization reaction with an ethylenically unsaturated compound and optionally also contains NCO-reactive groups, wherein, in the presence of D) and optionally E), a) is reacted first with B) and then with C):

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

B) one or more compounds containing groups which are capable of undergoing a polymerisation reaction with ethylenically unsaturated compounds on exposure to actinic radiation and containing isocyanate-reactive groups,

C) one or more hydroxyl-containing compounds different from B), at least one of these compounds having an OH functionality of 2 or more,

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

E) an auxiliary agent and an additive agent,

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

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

3. The process for preparing adhesives containing allophanate groups according to claim 1 or 2, characterized in that 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene oxide mono (meth) acrylate, polypropylene oxide mono (meth) acrylate and/or the reaction product of acrylic acid and glycidyl methacrylate are used in component B).

4. The process for preparing allophanate group-containing adhesives according to claim 1 or 2, wherein one or more compounds selected from the group consisting of: monomeric diols and triols, polyethers obtained from the monomeric diols and triols, and polylactones having an average molecular weight Mn <1000 g/mol.

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

6. The process for preparing an allophanate group-containing adhesive according to claim 1 or 2, wherein the temperature in the process is from 20 ℃ to 100 ℃.

7. Adhesive containing allophanate groups and containing groups which are capable of undergoing a polymerization reaction with ethylenically unsaturated compounds on exposure to actinic radiation, which is obtainable by a process as claimed in any one of claims 1 to 6.

8. A coating composition comprising:

a) one or more allophanate group-containing binders as claimed in claim 7,

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

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

d) optionally one or more active hydrogen-containing isocyanate-reactive compounds which are free of groups capable of polymerization reaction with ethylenically unsaturated compounds upon exposure to actinic radiation,

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

f) optionally auxiliaries and additives.

9. Substrates coated with coatings obtained from the allophanate group-containing binders as claimed in claim 7.