HK1152541B - Tin-free aqueous polyurethane dispersions - Google Patents

Description

Tin-free aqueous polyurethane dispersions

RELATED APPLICATIONS

The present application claims the benefit of german patent application No.102009051557.7, filed on 31/10/2009, which is incorporated herein by reference in its entirety for all useful purposes.

Technical Field

The present invention relates to radiation-curable coating compositions based on tin-free aqueous polyurethane dispersions, to a process for their preparation, to the use of the coating compositions as lacquers and/or adhesives, and to objects and substrates provided with these lacquers and/or adhesives.

Background

Aqueous radiation curable polyurethane dispersions have hitherto been synthesized via tin catalyzed urethanization. The main reason for the catalysis is that temperatures of 70 ℃ should not be substantially exceeded during the synthesis of the polyurethane in order to avoid thermally initiated polymerization of unsaturated groups capable of free radical polymerization. At such low temperatures, the aliphatic isocyanates, which are preferably used in aqueous radiation-curable polyurethane dispersions, for example, react only very slowly. Dibutyltin Dilaurate (DBTL) is the preferred catalyst for the synthesis of aqueous radiation curable polyurethane dispersions to date, due to the high selectivity and high catalytic activity of the OH-NCO addition.

For the catalysis of urethanization, various other metallic and non-metallic catalysts, such as tertiary amines, compounds of tin, zinc, zirconium, copper, bismuth, titanium and molybdenum, are known from lacquer applications of one-component (1C) and two-component (2C) polyurethane dispersions, i.e. the reaction of hydroxyl-functional polyurethane dispersions with blocked and unblocked polyisocyanates by baking on substrates. These catalysts are optimized for the preparation of 1C or 2C paints, i.e. they are said to have, for example, similar pot life and temperature activity behavior as DBTL or to favor the isocyanate-alcohol reaction over the isocyanate-water reaction. For the synthesis of polyurethanes of aqueous radiation curable polyurethane dispersions they are unsuitable and significantly inferior to DBTL due to side reactions (e.g. allophanatization), low catalytic activity under the typical reaction conditions of aqueous radiation curable polyurethane dispersion synthesis, or due to the performance of obtaining too low molecular weights.

Aqueous radiation curable polyurethane dispersions prepared with unsuitable catalysts show a coarse particle pattern, either settling immediately or are significantly more highly viscous than aqueous radiation curable polyurethane dispersions of the same composition catalyzed with DBTL.

Bell in Solvent-Borne urea Resins, vol.1: surface Coatings, Chapman and Hall, New York, 1993, p.153 and following Raw Materials and the use of same, describe various amine and metal based catalysts for catalyzing OH-NCO addition in 2C applications. The suitability of these catalysts for synthesizing polyurethanes from aqueous radiation curable polyurethane dispersions is not described.

WO 2008148739a1 describes various catalysts which are suitable in principle for the preparation of polyurethanes of aqueous radiation-curable polyurethane dispersions. DBTL is clearly preferred and is also used in the examples.

DE 102007006492a1 and EP 753531a1 describe various catalysts which are suitable in principle for the preparation of polyurethanes of aqueous radiation-curable polyurethane dispersions. DBTL is clearly preferred and is also used in the examples.

It is generally desirable to change the radiation curable aqueous polyurethane dispersions used in the preparation of wood paints to new paints that do not contain organotin compounds. A representative example of such a requirement is the specification required for IKEA for coatings in IOS-MAT-066, 2006, page 4.

It is also an object to provide alternative tin-free polyurethanes for aqueous radiation curable polyurethane dispersions to replace existing DBTL catalyzed polyurethanes for aqueous radiation curable polyurethane dispersions. In this respect, the properties of the aqueous radiation curable polyurethane dispersions should not deviate from those of aqueous radiation curable polyurethane dispersions synthesized via DBTL catalysis.

Disclosure of Invention

It has surprisingly been found that bismuth salts in the presence of acids having a pKa value of < 2.5 are particularly suitablePolyurethane acrylates for aqueous radiation curable polyurethane dispersions were synthesized. The urethane acrylates for aqueous radiation-curable polyurethane dispersions catalyzed in this way correspond physically and in the use properties to the DBTL-catalyzed urethane acrylates for aqueous radiation-curable polyurethane dispersions. It is a further object of a preferred embodiment of the present invention to achieve 10³-10⁶The weight-average molecular weight Mw of the urethane acrylate in the g/mol range. In this connection, it is possible to achieve the weight average molecular weight Mw of the urethane acrylates as achieved by DBTL-catalyzed systems.

An embodiment of the present invention is a tin-free, radiation-curable aqueous dispersion based on one or more urethane acrylates (i), wherein the one or more urethane acrylates (i) are obtained by

A) One or more compounds comprising at least one group reactive with isocyanate and at least one unsaturated group capable of free radical polymerization;

B) one or more compounds different from A) and comprising at least one group reactive with isocyanates;

C) one or more compounds comprising at least one group reactive with isocyanates and at least one group having a hydrophilizing action; and

D) one or more organic polyisocyanates;

in that

F) One or more bismuth (III) salts; and

G) acids having a pKa value of less than 2.5,

in the presence of a catalyst.

Another embodiment of the present invention is the above tin-free, radiation-curable aqueous dispersion, wherein the one or more urethane acrylates (i) are prepared from the additional component E) by reacting A), B), C), D) and E) in the presence of F) and G), wherein E) is different from A), B), C) and D) and comprises at least one group which is reactive with isocyanates.

Another embodiment of the present invention is the above tin-free, radiation curable aqueous dispersion, wherein the tin-free, radiation curable aqueous dispersion further comprises as component (ii) a reactive diluent having at least one group capable of undergoing free radical polymerization.

Another embodiment of the invention is the above tin-free, radiation-curable aqueous dispersion wherein component F) comprises one or more bismuth (III) carboxylates.

Another embodiment of the present invention is the above tin-free, radiation curable aqueous dispersion wherein component F) is selected from the group consisting of bismuth (III) neodecanoate, bismuth (III) 2-ethylhexanoate, bismuth (III) citrate, and mixtures thereof.

Another embodiment of the invention is the above tin-free, radiation curable aqueous dispersion wherein component G) is selected from the group consisting of di (n-butyl) phosphate, methanesulfonic acid, p-toluenesulfonic acid and mixtures thereof.

Another embodiment of the present invention is the above tin-free, radiation-curable aqueous dispersion, wherein component F) is present in the tin-free, radiation-curable aqueous dispersion in an amount in the range from 1 to 30,000ppm, based on the solids content of the aqueous radiation-curable polyurethane dispersion, and component G) is present in the tin-free, radiation-curable aqueous dispersion in an amount in the range from 10 to 300 mol%, based on the amount of component F) used.

Another embodiment of the present invention is the above tin-free, radiation-curable aqueous dispersion, wherein component G) is present in the tin-free, radiation-curable aqueous dispersion in an amount of 100 mol%, based on the amount of component F) used.

Another embodiment of the invention is the above tin-free, radiation-curable, aqueous dispersion, wherein the one isOr a plurality of urethane acrylates (i) having a molecular weight of 10³-10⁶Weight average molecular weights Mw in the g/mol range.

Another embodiment of the present invention is the above tin-free, radiation curable aqueous dispersion wherein component a) is selected from the group consisting of hydroxy-functionalized polyester (meth) acrylates, polyether (meth) acrylates, polyetherester (meth) acrylates, epoxy (meth) acrylates, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, and mixtures thereof.

Another embodiment of the present invention is the above tin-free, radiation-curable aqueous dispersion, wherein the molar ratio of the isocyanate groups of component D) to the isocyanate-reactive groups of components A), B) and C) is in the range from 0.8: 1 to 2.5: 1.

A further embodiment of the present invention is a process for preparing the above tin-free, radiation-curable aqueous dispersion, which comprises

(1) Reacting components A), B), C) and D) in the presence of components F) and G) in one or more reaction steps to obtain a urethane acrylate (i), wherein a neutralizing agent is added before, during or after the reaction of components A), B), C) and D) to generate the ionic groups required for dispersing the obtained urethane acrylate; and

(2) the dispersion is formed by adding water to the urethane acrylate or transferring the urethane acrylate to an aqueous reservoir.

Yet another embodiment of the present invention is a coating composition prepared from the above tin-free, radiation curable aqueous dispersion.

Another embodiment of the present invention is a topcoat composition wherein the coating is a paint or adhesive.

Another embodiment of the present invention is a topcoat composition, wherein the coating composition further comprises a crosslinker based on an amino resin, a blocked polyisocyanate, a non-blocked polyisocyanate, a hydrophilized polyisocyanate, a polyazepine, a polycarbodiimide, one or more other dispersions, or a combination thereof.

Yet another embodiment of the present invention is a substrate coated with the above coating composition.

Description of the invention

The invention relates to aqueous radiation-curable dispersions based on urethane acrylates (i), characterized in that the urethane acrylates (i) comprise as building components:

A) one or more compounds having at least one group reactive with isocyanate and at least one unsaturated group capable of free radical polymerization,

B) one or more compounds different from A) and having at least one group which is reactive toward isocyanates,

C) one or more compounds having at least one group which is reactive with isocyanates and additionally at least one group which has a hydrophilicizing action;

D) one or more organic polyisocyanates selected from the group consisting of,

E) optionally compounds which are different from A) to D) and have at least one group which is reactive toward isocyanates,

their use as catalysts

F) Bismuth (III) salt and

G) the reaction is carried out in the presence of an acid having a pKa value of < 2.5, preferably < 2.0.

The dispersion optionally contains component (ii) which includes a reactive diluent containing at least one group capable of undergoing free radical polymerization.

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

The amounts of the building components A) and optionally (ii) are such that the content of copolymerizable double bonds is from 0.5 to 6.0, preferably from 1.0 to 5.5, particularly preferably from 1.5 to 5.0mol/kg of the non-aqueous constituents of the dispersion.

Component (ii) is used in amounts of from 0 to 65% by weight, preferably from 0 to 40% by weight, particularly preferably from 0 to 35% by weight, the wt.% of components (i) and (ii) adding up to 100% by weight.

Component a comprises one or more compounds having at least one group reactive with isocyanate and at least one unsaturated group capable of free radical polymerization. Such compounds are, for example, oligomers and polymers containing unsaturated groups, such as polyester (meth) acrylates, polyether-ester (meth) acrylates, unsaturated polyesters having allyl ether structural units, polyepoxide (meth) acrylates and monomers containing unsaturated groups having a molecular weight of < 700g/mol and also combinations of the compounds mentioned.

Among the polyester (meth) acrylates, polyester (meth) acrylates containing hydroxyl groups and having an OH number of from 15 to 300mg KOH/g of substance, preferably from 60 to 200mg KOH/g of substance, are used as component A). A total of 7 groups of monomer components can be used as component A) in the preparation of the hydroxy-functional polyester (meth) acrylates.

The first group (a) contains alkanediols or diols or mixtures of these. The alkanediol has a molecular weight of between 62 and 286 g/mol. The alkanediol is preferably selected from the group consisting of ethylene glycol, 1, 2-and 1, 3-propanediol, 1, 2-, 1, 3-and 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, neopentyl glycol, cyclohexane-1, 4-dimethanol, 1, 2-and 1, 4-cyclohexanediol, 2-ethyl-2-butylpropanediol, glycols containing ether oxygen, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycols, polypropylene glycols or polybutylene glycols having a number average molecular weight Mn in the range from 200-to 4,000, preferably 300-. The reaction products of the above diols with epsilon-caprolactone or other lactones can be used as such diols.

The second group (b) contains trifunctional and higher than trifunctional alcohols having a molecular weight in the range from 92 to 254g/mol and/or polyethers obtained starting from these alcohols. Particularly preferred trifunctional and higher than trifunctional alcohols are glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol. A particularly preferred polyether is the reaction product of 1mol of trimethylolpropane and 4mol of ethylene oxide.

The third group (c) contains monohydric alcohols. Particularly preferred monoalcohols are selected from the group consisting of ethanol, 1-and 2-propanol, 1-and 2-butanol, 1-hexanol, 2-ethylhexanol, cyclohexanol and benzyl alcohol.

The fourth group (d) contains dicarboxylic acids and/or their anhydrides having molecular weights in the range of 104-600 g/mol. Preferred dicarboxylic acids and anhydrides thereof are selected from 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 dimers of fatty acids such as those listed under group six (f).

The fifth group (e) contains trimellitic acid or trimellitic anhydride.

The sixth group (f) contains 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 such as myristic acid, palmitic acid, margaric acid, stearic acid, behenic acid, cerotic acid, palmitoleic acid, oleic acid, eicosenoic acid, linoleic acid, linolenic acid, and arachidonic acid.

The seventh group (g) contains acrylic acid, methacrylic acid and/or dimeric acrylic acid.

Polyester (meth) acrylates containing hydroxyl groups which are suitable as component A) contain the reaction product of at least one component of group (a) or (b) with at least one component of group (d) or (e) and at least one component of group (g).

(a) Particularly preferred components of the group are selected from the group consisting of ethylene glycol, 1, 2-and 1, 3-propanediol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, cyclohexane-1, 4-dimethanol, 1, 2-and 1, 4-cyclohexanediol, 2-ethyl-2-butylpropanediol, the ether oxygen-containing diols selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and tripropylene glycol. (b) Preferred components of the group are selected from glycerol, trimethylolpropane, pentaerythritol or the reaction product of 1mol of trimethylolpropane and 4mol of ethylene oxide. (d) Particularly preferred components of groups (a) and (e) are selected from phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, maleic anhydride, fumaric acid, succinic anhydride, glutaric acid, adipic acid, dodecanedioic acid, hydrogenated dimers of fatty acids such as those listed under group (f), and trimellitic anhydride. (g) The preferred component of the group is acrylic acid.

Groups having dispersing action, which are generally known from the prior art, can optionally be incorporated into these polyester (meth) acrylates. Thus, polyethylene glycol and/or polyethylene glycol methyl ether can be used as a proportion of the alcohol component. Polyethylene glycols and polypropylene glycols starting from alcohols and their block copolymers and the monomethyl ethers of these polyglycols can be used as compounds. Polyethylene glycol monomethyl ethers having a number average molecular weight Mn in the range of 500-1,500g/mol are particularly suitable.

After esterification, it is also possible to react some of the still free, unesterified carboxyl groups, in particular those of (meth) acrylic acid, with mono-, di-or polyepoxides. Preferred epoxides are glycidyl ethers of monomeric, oligomeric or polymeric bisphenol a, bisphenol F, hexanediol and/or butanediol or their ethoxylated and/or propoxylated derivatives. In particular, this reaction can be used to increase the OH number of polyester (meth) acrylates, since in each case OH groups are formed in the epoxide-acid reaction. The acid value of the product obtained is between 0 and 20mg KOH/gBetween substances, preferably between 0 and 10mg KOH/g of substance and particularly preferably between 0 and 5mg KOH/g of substance. The reaction is preferably carried out by means of catalysts such as triphenylphosphine, thiodiglycol, ammonium halides and/or phosphorus halidesAnd/or zirconium or tin compounds such as tin (II) ethylhexanoate.

The preparation of polyester (meth) acrylates has been described in: page 3, line 25 to page 6, line 24 of DE-a 4040290, page 5, line 14 to page 11, line 30 of DE-a 3316592, and Chemistry & Technology of UV & EB Formulations For Coatings, Inks & paintings (Chemistry and Technology For UV and EB Formulations For Coatings, Inks and Paints), p.k.t.oldring editions, volume 2, 1991, SITA Technology, london, page 123-135.

Polyether (meth) acrylates containing hydroxyl groups and originating from the reaction of acrylic acid and/or methacrylic acid with polyethers are likewise suitable as component A), so that, for example, homopolymers, copolymers or block copolymers of ethylene oxide, propylene oxide and/or tetrahydrofuran on any desired hydroxyl-and/or amine-functional starter molecule, such as trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerol, pentaerythritol, neopentyl glycol, butanediol and hexanediol, are formed.

Epoxy (meth) acrylates known per se which contain hydroxyl groups and have OH numbers in the range from 20 to 300mg KOH/g, preferably 100-280mg KOH/g, particularly preferably 150-250mg KOH/g, or urethane (meth) acrylates which contain hydroxyl groups and have OH numbers in the range from 20 to 300mg KOH/g, preferably 40 to 150mg KOH/g, particularly preferably 50 to 140mg KOH/g, are likewise suitable as component A). Such compounds have likewise been described in Chemistry&Technology of UV&EB Formulations For Coatings，Inks&Paints (chemistry and Technology for UV and EB formulations for coatings, inks and Paints), p.k.t.oldring, eds, volume 2, 1991, SITA Technology, london, pages 37-56. Epoxy (meth) acrylates containing hydroxyl groups, in particular acrylic acid and/or methacrylic acidThe reaction products of acids with epoxides (glycidyl compounds) of monomeric, oligomeric or polymeric bisphenol A, bisphenol F, hexanediol and/or butanediol or their ethoxylated and/or propoxylated derivatives are based. Epoxy (meth) acrylates containing hydroxyl groups likewise include addition products of acrylic and/or methacrylic acid with epoxides of unsaturated fats (fatty acid triglycerides), e.g.3005F(Cognis，Düsseldorf，DE)。

Oligomers and polymers which contain unsaturated groups and are preferred as component A) are compounds selected from the following group: polyester (meth) acrylates, polyether-ester (meth) acrylates and polyepoxide (meth) acrylates, which contain hydroxyl groups in addition to unsaturated groups.

Monomers containing unsaturated groups and having a molecular weight of < 700g/mol are, for example, caprolactone-extended modifications of 2-hydroxyethyl (meth) acrylate, such as12A (Cognis, DE), 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxy-2, 2-dimethylpropyl (meth) acrylate, di-, tri-or penta (meth) acrylates (based on average monohydroxy functions) of polyfunctional alcohols such as trimethylolpropane, glycerol, pentaerythritol, bis (trimethylolpropane), dipentaerythritol, ethoxylated, propoxylated or alkoxylated trimethylolpropane, glycerol, pentaerythritol, bis (trimethylolpropane), dipentaerythritol or technical-grade mixtures thereof.

Alcohols which can be obtained from the reaction of double bond-containing acids with monomeric epoxide compounds which optionally contain double bonds can additionally also be used as monohydroxy-functional alcohols which contain (meth) acrylate groups. Preferred reaction products are selected from glycidyl (meth) acrylates with glycidyl (meth) acrylates or with tertiary saturated monocarboxylic acids. Examples of tertiary saturated monocarboxylic acids are 2, 2-dimethylbutyric acid, ethylmethylbutanoic acid, ethylmethylpentanoic acid, ethylmethylhexanoic acid, ethylmethylheptanoic acid and/or ethylmethyloctanoic acid.

Preferred monomers among those containing unsaturated groups and having a molecular weight of < 700g/mol are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate and the addition products of glycidyl ethylmethylheptanoate with (meth) acrylic acid, and technical-grade mixtures thereof.

The compounds listed under component A) can be used individually or as mixtures.

Component B) comprises monomeric mono-, di-and/or trihydric alcohols having in each case a molecular weight of from 32 to 240g/mol, such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, 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, 1, 3-butanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol, 1, 2-and 1, 4-cyclohexanediol, hydrogenated bisphenol A (2, 2-bis (4-hydroxycyclohexyl) propane), a diol derived from dimer fatty acids, 2, 2-dimethyl-3-hydroxypropionic acid (2, 2-dimethyl-3-hydroxypropyl ester), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane and/or castor oil. Neopentyl glycol, 1, 4-butanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol and/or trimethylolpropane are preferred.

Component B) furthermore comprises oligomeric and/or polymeric hydroxy-functional compounds. These oligomeric and/or polymeric hydroxy-functional compounds are, for example, polyesters, polycarbonates, polyethercarbonate polyols, C2-, C3-and/or C4-polyethers, polyether esters and polycarbonate polyesters having a functionality of from 1.0 to 3.0, in each case having a weight-average molecular weight Mw in the range from 300-4,000, preferably from 500-2,500 g/mol.

Hydroxy-functional polyesterols are those based on mono-, di-and tricarboxylic acids and monomeric di-and triols, as have been listed as component B), and polyesterols based on lactones. Such carboxylic acids are, for example, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, adipic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, hexahydrophthalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, hydrogenated dimers of fatty acids, and also saturated and unsaturated fatty acids such as palmitic acid, stearic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid and technical-grade mixtures thereof. In dicarboxylic acids and tricarboxylic acids, similar anhydrides can also be used.

Hydroxy-functional polyether alcohols are obtainable, for example, by polymerization of cyclic ethers or by reaction of alkylene oxides with starter molecules.

Hydroxy-functional polycarbonates are hydroxy-terminated polycarbonates which are obtainable by reaction of diols, lactone-modified diols or bisphenols, for example bisphenol A, with phosgene or carbonic diesters, for example diphenyl carbonate or dimethyl carbonate. Hydroxy-functional polyether carbonate polyols are, for example, those described in DE-A102008000478 for the formation of polyurethane dispersions.

Component C) comprises compounds having at least one group which is reactive toward isocyanates and additionally at least one group which has a hydrophilicizing action.

Groups having a hydrophilizing action include: ionic groups C1) and/or ionic groups C1) derived from potentially ionic groups C2) (for example by salt formation), which can have anionic properties C1.1), such as sulfonium, phosphoniumCarboxylate, sulfonate, phosphonate groups, or C1.2) having cationic properties, such as ammonium groups; potentially ionic groups C2), i.e.can be formed, for example, byGroups which are converted into ionic groups C1) by salt action; and/or nonionic groups C3), for example polyether groups, which can be introduced into the macromolecule via groups reactive with isocyanates. Preferred suitable isocyanate-reactive groups are hydroxyl and amino groups.

Compounds containing potentially ionic groups C2) include compounds having potentially anionic groups C2.1), for example monohydroxy-and dihydroxy-carboxylic acids, monoamino-and diamino-carboxylic acids, monohydroxy-and dihydroxy-sulfonic acids, monoamino-and diamino-sulfonic acids, monohydroxy-and dihydroxy-phosphonic acids, monoamino-and diamino-phosphonic acids and/or compounds having potentially cationic groups C2.2), for example ethanolamine, diethanolamine, triethanolamine, 2-propanolamine, dipropanolamine, tripropanolamine, N-methylethanolamine, N-methyl-diethanolamine and N, N-dimethylethanolamine.

Preferred compounds containing a potentially anionic group C2.1) are those selected from the group consisting of dimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid, N- (2-aminoethyl) -alanine, 2- (2-amino-ethylamino) -ethanesulfonic acid, ethylenediamine-propyl-or-butylsulfonic acid, 1, 2-or 1, 3-propylenediamine-ethanesulfonic acid, 3- (cyclohexylamino) propane-1-sulfonic acid, malic acid, citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, lysine, 3, 5-diaminobenzoic acid, isophoronediamine (1-amino-3, 3, 5-trimethyl-5-aminomethylcyclohexane or IPDA) and the addition products of acrylic acid (EP-A916647, example 1) adduct of sodium bisulfite on but-2-ene-1, 4-diol polyether sulfonate and 2-butenediol and NaHSO₃Such as described in DE-A2446440, pages 5 to 9, formulae I to III.

Particularly preferred compounds containing potentially ionic groups C2) are compounds containing carboxyl, sulfonic and/or tertiary amino groups, such as 2- (2-amino-ethylamino) -ethanesulfonic acid, 3- (cyclohexylamino) propane-1-sulfonic acid, addition products of isophoronediamine and acrylic acid (EP 916647A1, example 1), hydroxypivalic acid, dimethylolpropionic acid, triethanolamine, tripropanolamine, N-methyldiethanolamine and/or N, N-dimethylethanolamine.

Very particularly preferably, component C) comprises hydroxypivalic acid and/or dimethylolpropionic acid as compounds having potentially ionic groups.

Suitable groups C3) having a non-ionic hydrophilicizing action are, for example, polyoxyalkylene ethers which contain at least one hydroxyl or amino group and one or more oxyalkylene units, at least one of which is an oxyethylene unit. These polyoxyalkylene ethers can be obtained in a manner known per se by alkoxylation of suitable starter molecules.

Suitable starter molecules are, for example, saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol, diethylene glycol monoalkylethers, such as diethylene glycol monobutyl ether, unsaturated alcohols, such as allyl alcohol, 1, 1-dimethylallyl alcohol or oleyl alcohol, aromatic alcohols, such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols, such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol, monoamines, such as dimethylamine, diethylamine, sec-dipropylamine, diisopropylamine, dibutylamine, bis (2-ethylhexyl) amine, n-methyl-and N-ethylcyclohexylamine or dicyclohexylamine, and also heterocyclic secondary amines such as morpholine, pyrrolidine, piperidine or 1H-pyrazole. Trimethylolpropane is likewise suitable, which is alkoxylated only at one OH group. Preferred starter molecules are saturated monoalcohols and trimethylolpropane alkoxylated on only one OH group. Diethylene glycol monobutyl ether is particularly preferred for use as the starter molecule.

Alkylene oxides suitable for the alkoxylation reaction are, for example, ethylene oxide, 1-butene oxide and propylene oxide, which can be used in any desired sequence or else in mixtures in the alkoxylation reaction.

The polyoxyalkylene polyether alcohol is a pure polyoxyethylene polyAn ether or mixed polyoxyalkylene polyether comprising at least 30 mol%, preferably at least 40 mol%, of oxyethylene units in its oxyalkylene units. Preferred nonionic compounds are monofunctional mixed polyoxyalkylene polyethers containing at least 40 mol% of ethylene oxide units and not more than 60 mol% of propylene oxide units. Polyoxyalkylenes which start on trimethylolpropane and have an OH functionality of 2, for exampleD3403(Evonik Industries AG, Essen, DE) andn120 (Perstorp AG, Sweden) is likewise preferred.

The acids mentioned under component C2.1) are converted into the corresponding salts by reaction with neutralizing agents such as triethylamine, ethyldiisopropylamine, dimethylcyclohexylamine, dimethylethanolamine, ammonia, N-ethylmorpholine, LiOH, NaOH and/or KOH. Here, the degree of neutralization is preferably between 50 and 125%. The degree of neutralization is defined as follows: as a quotient of base and acid for acid functionalized polymers; for base-functionalized polymers, as the quotient of acid and base. If the degree of neutralization is above 100%, then in the case of acid-functionalized polymers, more base is added than is the acid group in the polymer; in the case of base-functionalized polymers, more acid is added than is the base group in the polymer.

The bases mentioned under component C2.2) are converted into the corresponding salts by reaction with neutralizing agents, for example inorganic acids (for example hydrochloric acid, phosphoric acid and/or sulfuric acid) and organic acids (for example formic acid, acetic acid, lactic acid, methanesulfonic acid, ethanesulfonic acid and/or p-toluenesulfonic acid). Here, the degree of neutralization is preferably between 50 and 125%.

The compounds listed under component C) can also be used in the form of mixtures.

Ionic hydrophilization and a combination of ionic and nonionic hydrophilization are preferred over purely nonionic hydrophilization.

Component D) comprises a polyisocyanate selected from aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates or mixtures of such polyisocyanates. Suitable polyisocyanates are, for example, 1, 3-cyclohexane-diisocyanate, 1-methyl-2, 4-diisocyanato-cyclohexane, 1-methyl-2, 6-diisocyanato-cyclohexane, tetramethylene-diisocyanate, 4, 4 '-diisocyanatodiphenylmethane, 2, 4-diisocyanatotoluene, 2, 6-diisocyanatotoluene, alpha' -tetramethyl-m-or-p-xylylene-diisocyanate, 1, 6-hexamethylene-diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate or IPDI), 4, 4' -diisocyanato-dicyclohexylmethane, 4-isocyanatomethyl-1, 8-octane-diisocyanate (triisocyanatononane, TIN) (EP-A928799), homologues or oligomers of these polyisocyanates listed above having biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and/or uretdione groups, and mixtures thereof. 1, 6-hexamethylene-diisocyanate, 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate or IPDI) and 4, 4 '-diisocyanato-dicyclohexylmethane, homologues or oligomers of 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone-diisocyanate or IPDI) and 4, 4' -diisocyanato-dicyclohexylmethane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and/or uretdione groups and mixtures thereof are preferred.

Monoamines and diamines and/or monofunctional or difunctional amino alcohols are used as component E) in order to increase the weight-average molecular weight Mw of the polyurethane acrylates. Preferred diamines are those which are more reactive with respect to water than with respect to isocyanate groups, since extension of the polyester-urethane (meth) acrylate optionally occurs in an aqueous medium. The diamine is particularly preferably selected from ethylenediamine, 1, 6-hexamethylenediamineMethyl diamine, isophorone diamine, 1, 3-and 1, 4-phenylene diamine, piperazine, 4, 4' -diphenylmethane diamine, amino-functional polyethylene oxides, amino-functional polypropylene oxides (by name)D series is well known [ Huntsman corp. Europe, Zavantem, Belgium]) And hydrazine. Ethylene diamine is very particularly preferred.

Preferred monoamines are selected from the group consisting of butylamine, ethylamine andamines of the M series (huntsman corp. europe, Zavantem, Belgium), amino-functional polyethylene oxides, amino-functional polypropylene oxides and/or amino alcohols.

The catalysts F) used for the urethanization in the preparation of the radiation-curable polyurethane dispersions according to the invention are bismuth (III) salts, such as bismuth (III) bromide, bismuth (III) chloride, bismuth (III) fluoride, bismuth (III) iodide, bismuth (III) nitrate, bismuth (III) oxide, bismuth (III) phosphate, bismuth (III) sulfide, bismuth (III) trifluoromethanesulfonate, bismuth (III) acetate, bismuth (III) neodecanoate, bismuth (III) salicylate, bismuth (III) 2,2, 6, 6-tetramethyl-3, 5-heptanedionate, bismuth (III) 2-ethylhexanoate, bismuth (III) naphthenate (salts of naphthenic acids: average C6 to C7 cyclic carboxylic acids obtained from naphtha fraction) and bismuth (III) citrate.

Bismuth (III) carboxylates are preferably used, such as bismuth (III) acetate, bismuth (III) neodecanoate, bismuth (III) salicylate, bismuth (III) 2,2, 6, 6-tetramethyl-3, 5-heptanedioate, bismuth (III) 2-ethylhexanoate, bismuth (III) naphthenate and bismuth (III) citrate. Bismuth (III) neodecanoate, bismuth (III) 2-ethylhexanoate and bismuth (III) citrate are particularly preferred.

Possible acids G) for use in combination with the bismuth (III) salt are organic and/or inorganic acids having pKa values of < 2.5, preferably < 2.0.

Suitable acids are, for example, hydrochloric, hydrobromic and hydroiodic acid, chlorous acid, chloric acid, perchloric acid, iodic acid, periodic acid, perchloric acid, nitric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, selenic acid, selenious acid, sulfurous acid, sulfuric acid, hydrogen sulfate, thiocyanic acid, methyl phosphate, ethyl ester, n-propyl ester, n-butyl ester, dimethyl ester, di- (n-propyl) ester, di- (n-butyl) ester and di- (2-ethylhexyl) ester, methanesulfonic acid, p-toluenesulfonic acid, 2, 6-dihydroxybenzoic acid, sulfamic acid, nitroacetic acid, trimethylammonium acetic acid, dichloroacetic acid, difluoroacetic acid, tribromoacetic acid, trichloroacetic acid and trifluoroacetic acid, malonic acid, maleic acid, bromomaleic acid, chloromaleic acid, chlorofumaric acid, bromofumaric acid, oxalic acid, oxaluric acid, aniline carboxylic acid, 4-nitrobenzoic acid, protonated amino acids and saccharin with pKa values < 2.5.

Di (n-butyl) phosphate, methanesulfonic acid and p-toluenesulfonic acid are preferred.

It has surprisingly been found that the weight-average molecular weight Mw of the urethane acrylate (i) can be controlled via the ratio of the acid G) to the bismuth salt F).

The bismuth (III) salt is used in an amount of from 1 to 30,000ppm, preferably from 10 to 10,000ppm, particularly preferably from 50 to 1,000ppm, relative to the solids content of the aqueous radiation-curable polyurethane dispersion (amount of residue after evaporation of all volatile constituents). The amount of acid used in combination with the bismuth (III) salt is based on the amount of bismuth (III) salt used and is between 10 and 300 mol%, preferably 15 and 150 mol%, particularly preferably 20 and 110 mol%.

If 100 mol% of acid G) is used relative to the bismuth (III) salt F), the highest weight-average molecular weight Mw of the urethane acrylate (i) is achieved.

The radiation-curable aqueous urethane acrylate (i) prepared by the process according to the invention has a value of 10³-10⁶g/mol, preferably 3 x 10³-9*10⁵g/mol, particularly preferably 10⁴-7*10⁵Weight average molecular weight Mw in g/mol. The determination of the weight-average molecular weight Mw of the urethane acrylates is carried out by means of gel permeation chromatography, with polystyrene as standard and N, N-dimethylacetamide as mobile phase.

Component (ii) comprises reactive diluents, which are understood to be those compounds which contain at least one group capable of undergoing free-radical polymerization, preferably acrylate and methacrylate groups, and preferably contain no groups which are reactive with isocyanates or hydroxyl groups.

Preferred compounds (ii) contain 2 to 6, particularly preferably 4 to 6 (meth) acrylate groups.

Particularly preferred compounds (II) have a boiling point of more than 200 ℃ at normal pressure.

Reactive diluents are generally described in Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints (Chemistry and Technology for UV and EB Formulations for Coatings, Inks and Paints) edited by p.k.t.olding, volume II, chapter III: reactive diluents for UV & EB Curable Formulations, Wiley and SITA Technology, London, 1997.

Reactive diluents are, for example, alcohols, such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, dihydrodicyclopentadienol, tetrahydrofurfuryl alcohol, 3, 3, 5-trimethylhexanol, octanol, decanol, dodecanol, 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, 1, 3-butanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol, 1, 2-and 1, 4-cyclohexanediol, hydrogenated bisphenol a (2, 2-bis (4-hydroxycyclohexyl) propane), glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol fully esterified with (meth) acrylic acid, as well as ethoxylated and/or propoxylated derivatives of these alcohols listed above, and technical-grade mixtures obtained during the (meth) acrylation of the above-mentioned compounds.

Component (ii) is preferably a (meth) acrylate selected from the group consisting of tetra-and hexa-ols, such as pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, ethoxylated, propoxylated or alkoxylated pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol and also the (meth) acrylates of ethoxylated and/or propoxylated derivatives of the alcohols listed above, and the technical-grade mixtures obtained during the (meth) acrylation of the above-mentioned compounds.

All processes known in the prior art can be used for the preparation of the dispersions according to the invention, such as emulsifier-shear, acetone, prepolymer mixing, melt emulsification, ketimine and solid spontaneous dispersion processes or their derivatization processes. A summary of these processes is found in Methoden der Organischen Chemie (methods of organic chemistry), Houben-Weyl, 4 th edition, part/2 of E20, page 1682, Georg Thieme Verlag, Stuttgart, 1987. Melt emulsification and acetone processes are preferred. The acetone process is particularly preferred.

The invention also provides a process for the preparation of radiation-curable aqueous dispersions based on urethane acrylates (i), characterized in that the urethane acrylate (i) is obtained by reacting components A) to C) with component D) in the presence of components F) and G) in one or more reaction steps, the neutralizing agent can be added before, during or after the preparation of the addition products of A) to D) to generate the ionic groups required for the dispersing operation, the dispersing step is subsequently carried out by adding water to the addition products of A) to D) or transferring the addition products of A) to D) to a reservoir containing water, chain extension can be carried out with component E) before, during or after dispersion.

The present invention also provides a process according to the above recitations, wherein one or more reactive diluents (component (ii)) containing at least one group capable of undergoing free radical polymerization are admixed.

For the preparation of radiation-curable aqueous dispersions based on urethane acrylates (i), components A), B) and C) are initially introduced into the reactor and optionally diluted with acetone. Component (ii) can optionally also be added to components A) to C). Bismuth (III) salt F) and acid G) are added to catalyze the addition to polyisocyanate D), and the mixture is heated to start the reaction. Temperatures of 30-60 ℃ are generally required for the reaction. One polyisocyanate or more polyisocyanates D) are then metered in. The reverse process is also possible, the polyisocyanate D) being initially introduced and then the isocyanate-reactive components A), B) and C) being added. Components A), B) and C) can also be added successively and in any desired order. A stepwise reaction of the components is likewise possible, i.e.component D) is reacted separately with one or more isocyanate-reactive components A), B) and/or C) before the adduct obtained is reacted further with components which have not yet been used.

Instead of the combination of bismuth (III) salt and acid, the bismuth (III) salt and the acid can also be premixed and added as a mixture. It is also possible to purify or separate the active metal species from the mixture and use them as catalysts.

For monitoring the reaction, the isocyanate content is determined at regular intervals by titration or by infrared or near infrared spectroscopy.

The molar ratio of isocyanate groups in D) to isocyanate-reactive groups in A), B) and C) is from 0.8: 1 to 2.5: 1, preferably from 1.2: 1 to 1.5: 1.

After the preparation of the urethane acrylates (i) from components A), B), C) and D) by the process according to the invention in the presence of F) and G), the salification of the groups having a dispersing action of component C) is carried out if a salification has not already been carried out in the starting molecules. In the case where component C) contains acid groups, bases selected from triethylamine, ethyldiisopropylamine, dimethylcyclohexylamine, dimethylethanolamine, ammonia, N-ethylmorpholine, LiOH, NaOH and/or KOH are preferably used. In the case where component C) contains basic groups, acids selected from the group consisting of lactic acid, acetic acid, phosphoric acid, hydrochloric acid and/or sulfuric acid are preferably used. If compounds containing only ether groups are used as component C), the neutralization step is omitted.

Thereafter, a reactive diluent (ii) or a mixture of reactive diluents (ii) can optionally be added. Component (ii) is preferably mixed therein at 30 to 45 ℃. Once it has dissolved, a final reaction step is optionally carried out thereafter, in which the molecular weight is increased and the desired dispersion of the coating system of the invention is formed. The urethane acrylates (i) synthesized from components A), B), C) and D) in the presence of F) and G) and optionally a reactive diluent (ii) optionally dissolved in acetone are introduced with vigorous stirring into the dispersing water containing the amine E) or, conversely, the dispersing water/amine mixture is stirred into the urethane acrylate solution. In addition, a dispersion is formed which is comprised in the coating system of the present invention. The amount of amine E) used depends on the unreacted isocyanate groups still present. The reaction of the isocyanate groups still free with the amines E) can take place to an extent of 35% to 150%. In the case of the use of a deficiency of amine E), the isocyanate groups still free react slowly with water. If an excess of amine E) is used, unreacted isocyanate groups are no longer present and an amine-functional polyurethane is obtained. Preferably, from 80% to 110%, particularly preferably from 90% to 100%, of the remaining free isocyanate groups are reacted with the amine E).

In a further variant, the molecular weight increase with amine E) can be carried out in acetone solution, i.e. before dispersion, and optionally before or after addition of the reactive diluent (ii).

In a further variant, the molecular weight increase can be carried out after the dispersing step with the amine E).

If desired, the organic solvent, if present, can be distilled off. The dispersion then has a solids content of from 20 to 60% by weight, in particular from 30 to 58% by weight.

It is likewise possible to carry out the dispersing and distilling steps in parallel, i.e. simultaneously or at least partly simultaneously.

The invention also provides for the use of the radiation-curable aqueous dispersions according to the invention for producing coatings, in particular paints and adhesives.

The dispersions of the invention form clear films after removal of water by conventional methods such as heat, thermal radiation, flowing optionally dry air and/or microwaves. The film is cured by subsequent crosslinking induced by radiation chemistry and/or free radicals to give a lacquer layer which has particularly high quality and chemical resistance.

Electromagnetic radiation having an energy (optionally with the addition of a suitable photoinitiator) sufficient to carry out free-radical polymerization of the (meth) acrylate double bonds is suitable for the polymerization reaction induced by radiation chemistry.

The polymerization reaction induced by radiation chemistry is preferably carried out by radiation having a wavelength below 400nm, such as UV, electron beam, X-ray or gamma ray. Ultraviolet radiation is particularly preferred, and curing with ultraviolet radiation is initiated in the presence of a photoinitiator. There are two main types of photoinitiators, monomolecular (type I) and bimolecular (type II). Suitable (type I) systems are aromatic ketone compounds, for example benzophenones, which are combined with tertiary amines, alkylbenzophenones, 4, 4 '-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the stated types. (type II) initiators, such as benzoin and its derivatives, benzil ketals, acylphosphine oxides, 2, 4, 6-trimethylbenzoyl-diphenylphosphine oxide, bisacylphosphine oxide, phenylglycolate, camphorquinone, α -aminoalkylphenyl methanones, α, α -dialkoxyacetophenones and α -hydroxyalkylphenyl ketones, are also suitable. Photoinitiators which can be easily incorporated into aqueous coating compositions are preferred. Such products are, for example500 (mixture of benzophenone and (1-hydroxycyclohexyl) phenylketone, Ciba, Lampertheim, DE),819DW (phenyl-bis- (2, 4, 6-trimethylbenzoyl)Alkyl) -phosphine oxides, Ciba, Lampertheim, DE),KIP EM (oligo [ 2-hydroxy-2-methyl-1- [4- (1-methylethenyl) -phenyl)]-acetone]Lamberti, Aldizzate, Italy). Mixtures of these compounds can also be used.

Polar solvents such as acetone and isopropanol can also be used for the introduction of the photoinitiator.

UV curing is advantageously carried out at from 30 to 70 ℃ since the degree of conversion of the (meth) acrylate groups increases at higher temperatures. This can lead to better resistance performance. Nevertheless, the possible thermal sensitivity of the substrate during UV curing has to be taken into account, so that the optimum curing conditions for a particular coating composition/substrate combination can be determined by the person skilled in the art in simple preliminary experiments.

Here, the position of the radiation emitter or emitters which initiate the free-radical polymerization can be fixed and the coated substrate moved past the emitter using suitable conventional equipment, or the radiation emitter can be moved by conventional equipment, so that the position of the coated substrate is fixed during the curing process. It is also possible, for example, to carry out the irradiation in a chamber, wherein the coated substrate is introduced into the chamber and the irradiation is then switched on for a period of time, after which the substrate is removed again from the chamber.

If appropriate, curing is carried out in an inert gas atmosphere (i.e.excluding oxygen) in order to prevent free-radical crosslinking from being inhibited by oxygen.

If the curing is carried out thermally by means of free radicals, aqueous emulsions of water-soluble peroxides or initiators which are not water-soluble are suitable. These agents which form free radicals can be used in combination with promoters in a known manner.

The aqueous radiation-curable polyurethane dispersions according to the invention can be applied to a wide variety of substrates by the customary techniques, preferably spraying, rolling, flooding, printing, knife coating, pouring, brushing and dipping.

In principle, all substrates can be lacquered or coated with the aqueous radiation-curable polyurethane dispersions according to the invention. Preferred substrates are selected from mineral bases, wood material, furniture, parquet, doors, window frames, metal objects, plastics, paper, cardboard, cork, mineral substrates, textiles or leather. They are suitable here as primers and/or as topcoats. In addition, the aqueous radiation-curable polyurethane dispersions according to the invention can also be used or employed as adhesives, for example in contact adhesives, in heat-activated adhesives or in laminating adhesives.

The aqueous radiation curable polyurethane dispersions according to the invention can be used as such and together with other dispersions in binder mixtures. These can be dispersions which likewise contain unsaturated groups, for example dispersions which contain unsaturated polymerizable groups and are based on polyesters, polyurethanes, polyepoxy (meth) acrylates, polyethers, polyamides, polysiloxanes, polycarbonates, epoxy acrylates, polyester acrylates, polyurethane polyacrylates and/or polyacrylates.

The coating systems according to the invention can also comprise those based on polyesters, polyurethanes, polyethers, polyamides, polyvinyl esters, polyvinyl ethers, polysiloxanes, polycarbonates and/or polyacrylates which contain functional groups such as alkoxysilane groups, hydroxyl groups and/or isocyanate groups, optionally in blocked form. Thus a dual cure system is prepared which is capable of curing via two different mechanisms.

So-called crosslinkers can furthermore likewise be added to the coating systems of the invention for dual-cure systems. Non-blocked and/or blocked polyisocyanates, polyaziridines, polycarbodiimides and melamine resins are preferred possibilities. Non-blocked and/or blocked hydrophilicized polyisocyanates are particularly preferred for aqueous coating compositions. Preferably 20% by weight or less, particularly preferably 10% by weight, based on the solids content of the coating composition, of a solid crosslinking agent is added.

The coating systems according to the invention can also comprise dispersions based on polyester, polyurethane, polyether, polyamide, polysiloxane, polyvinyl ether, polybutadiene, polyisoprene, chlorinated rubber, polycarbonate, polyvinyl ester, polyvinyl chloride, polyacrylate or polyurethane polyacrylate, polyester acrylate, polyether acrylate, alkyd, polycarbonate, polyepoxy or epoxy (meth) acrylate bases which do not contain functional groups. The crosslinking density can thus be reduced, the physical drying can be influenced, for example facilitated, or an adjustment of the elastification or the adhesion can be carried out.

Amino-crosslinking resins (based on melamine or urea) and/or selected from the group consisting of resins having carbamate, uretdione, imino groupsPolyisocyanates with free or blocked polyisocyanate groups (based on polyisocyanates) optionally containing hydrophilicizing groups among hexamethylene diisocyanate, isophorone diisocyanate and/or toluene diisocyanate of diazinedione, isocyanurate, biuret and/or allophanate structure can also be added to the coating compositions comprising the aqueous radiation-curable urethane acrylates of the invention. Carbodiimides or polyazetidines may also be used as additional crosslinking agents.

Binders, auxiliary substances and additives known in the lacquer art, such as pigments, dyes or matting agents, can be added to or mixed with the coating compositions of the invention. These are flow and wetting additives, slip additives, pigments (including metal effect pigments), fillers, nanoparticles, light stabilizer particles, anti-yellowing additives, thickeners and additives for reducing the surface tension.

The coating composition according to the invention is suitable for coating on films, deformation of the coating film taking place between physical drying and UV curing.

The coating compositions according to the invention are particularly suitable for clear lacquers on substrates of wood and plastics, where blocking resistance after physical drying and good chemical resistance after radiation curing are important.

The coating compositions according to the invention having a pigment content of > 10% by weight (based on the total formulation) are likewise particularly suitable for use on wood and plastics. If incomplete reaction of the radiation-curable groups in the coating system occurs during the radiation curing because the pigment content is too high, a non-blocking coating is obtained.

The present invention also provides a coating composition comprising: the aqueous radiation-curable dispersions of the invention based on urethane acrylates and crosslinking agents based on amino resins, blocked polyisocyanates, unblocked polyisocyanates, polyaziridines and/or polycarbodiimides, and/or one or more further dispersions.

The invention also provides a substrate coated with the coating composition of the invention.

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

While certain specific configurations that embody the present invention have been shown and described, it will be obvious to those skilled in the art that various modifications and rearrangements of the parts can be made without departing from the spirit and scope of the inventive concept, and the invention is not limited to the specific forms shown and described herein.

Detailed Description

Examples

The method comprises the following steps:

the determination of the weight-average molecular weight Mw of the urethane acrylates by means of gel permeation chromatography is based on the following system:

pump Hewlett Packard 1100 series II

Injector Hewlett Packard 1100 series II

Chromatographic column heating oven VDS-Optilab Jetstream 2 Plus

Detector refractive index Detector, Hewlett Packard 1100 series II

Chromatography column 1.PSS HEMA 40; 50X 7.8mm

2.PSS HEMA 1000；300×7.8mm

3.PSS HEMA 300；300×7.8mm

4.PSS HEMA 40；300×7.8mm

5.PSS HEMA 40；300×7.8mm

Mobile phase of N, N-dimethylacetamide

Flow rate 0.6ml/min

Pressure 100 bar

The temperature is 30 DEG C

Injection volume 100. mu.l

The sample concentration was 13.4g/l

Molecular weight standards PSS Polymer-Standard-Service GmbH, Mainz, DE

Molecular sample [ g/mol ] 162; 374; 1620; 9130; 18100; 32500; 67500;

128000；246000；659000；1000000

the NCO content in each case was monitored titratively in accordance with DIN 53185.

The solids content of the polyurethane dispersions is determined after all nonvolatile constituents have evaporated off, in accordance with DIN 53216.

The average particle size was determined by laser correlation spectroscopy.

The flow time is determined in accordance with DIN 53211 by means of a 4mm DIN cup.

To determine the storage stability of the aqueous radiation-curable polyurethane dispersions, the samples were stored at 40 ℃ for 7 days and then evaluated for sedimentation, coagulation or serum formation. The samples were storage stable (OK) if no change was visually detected after storage.

Catalysts for the synthesis of aqueous radiation curable polyurethane dispersions:

desmorapid Z: dibutyl tin dilaurate from Bayer Material Science AG, Leverkusen, DE

Desmorapid SO: tin (II) 2-ethylhexanoate from Bayer Material Science AG, Leverkusen, DE

Borchikat 24: bismuth (III) 2-ethylhexanoate from Borchers GmbH, Langenfeld, DE

Borchikat 22: zinc 2-ethylhexanoate (II) from Borchers GmbH, Langenfeld, DE

VEXP 0519: titanium (IV) catalyst for the 2C system of Johnson Matthey, London, England

VEXP 0588: zirconium (IV) catalyst for the 2C system of Johnson Matthey, London, England

VEXP 0584: zirconium (IV) catalyst for the 2C system of Johnson Matthey, London, England

Abbreviations used:

SC: solid content, APS: average particle size, FT: flow time, Mw: weight average molecular weight, OK: is stable, n.d.: not determined

1) DBTL catalyzed preparation of radiation curable aqueous polyurethane dispersions (comparative example) 400.6 parts of polyester acrylatePE 44F (BASF AG, Ludwigshafen, DE), component A), 5.4 parts of hexanediol, component B), 34.0 parts of dimethylolpropionic acid, component C), 77.2 parts of hexamethylene diisocyanate, component D), 66.6 parts of 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane, component D), and 0.63 parts (1.00mmol) of Desmorapid Z (dibutyltin dilaurate, Bayer MaterialScience AG, Leverkusen, DE) are dissolved in 190 parts of acetone and reacted with stirring at 60 ℃ to an NCO content of 1.7% by weight (theoretical 1.7% by weight). Neutralization was performed by adding 20.2 parts of triethylamine and stirring therein. The clear solution is introduced into 950 parts of water with stirring. Thereafter, a mixture of 8.4 parts of ethylenediamine, component E, and 24.0 parts of water is added to the dispersion with stirring. Acetone was distilled from the dispersion under a slight vacuum. A UV curable aqueous polyurethane dispersion 1) was obtained having a Solids Content (SC) of 39.8 wt.%, a Flow Time (FT) of 24 seconds, an Average Particle Size (APS) of 80nm and a pH of 8.4. Gel permeation chromatogram showed 2.00 x 10⁵The weight-average molecular weight Mw of the dispersed urethane acrylate in g/mol.

The following examples 2) to 18) are carried out analogously to example 1), but using further catalysts and optionally adding acid.

Examples 2) to 8) show that alternative carbamation catalysts (as known from 2C system applications) are not suitable for replacing DBTL in example 1). This also includes bismuth (III) 2-ethylhexanoate, example 2). Examples 2), 3), 5) and 8) all have lower weight-average molecular weights Mw, and therefore higher APS, than example 1) and, if appropriate, inadequate storage stability at elevated temperatures. Examples 4), 6) and 7) are relatively highly viscous and not particularly finely divided, and do not reach the quality of example 1).

Examples 9) to 12) according to the invention show that the combination of bismuth (III) 2-ethylhexanoate and the strong acid di (n-butyl) phosphate gives comparable results for APS, FT and Mw to those of example 1). Examples 9) to 12) according to the invention show that for a constant amount of bismuth salt and an increased amount of acid, the weight average molecular weight Mw of the urethane acrylate and the fineness of the aqueous radiation-curable polyurethane dispersion increase and their maximum values are reached at equimolar amounts of bismuth salt and acid. When the acid is in excess of the bismuth salt, the weight average molecular weight Mw decreases again.

Examples 13) to 15) according to the invention show that other bismuth (III) salts and other strong acids also exhibit the same action as in example 9).

Examples 16) to 18) show that the addition of strong acids to tin (II) 2-ethylhexanoate does not have the same effect as in examples 9) to 11). The results even show that the weight average molecular weight Mw decreases as the amount of acid increases.

19) Preparation of the polyesters (component B)

6,574 parts of isophthalic acid, 1,327 parts of trimethylolpropane, 7,207 parts of neopentyl glycol and 4 parts of trimethylolpropane are mixed under stirring4100 (butyl stannate, Arcema inc., philiadelphia, PA, USA) were heated together to 190 ℃. This temperature was maintained until an acid value of less than 1.5mg KOH/g of material was reached. A polyester having an average functionality of 2.3 and a hydroxyl number of 365mgKOH/g of material was obtained.

20) Preparation of radiation curable aqueous polyurethane dispersions

1,595 parts of 2-hydroxyethyl acrylate, component A, are metered into 2,236 parts of 4, 4' -diisocyanatodicyclohexylmethane, component D, 2,244 partsN3300(HDI trimer, Bayer AG, Leverkusen, DE), component D, and 0.75 part of dibutyltin dilaurate in 1,519 parts of acetone at 60 ℃ were added, and the mixture was stirred further at 60 ℃ until an NCO content of 8.2% by weight was reached. 1,373 parts of the polyester according to example 19), component B, 305 parts of dimethylolpropionic acid, component C, and 0.75 parts of DBTL (1.18mmol) dissolved in 421 parts of acetone are then added at 40 ℃ and the mixture is heated to 60 ℃ with stirring. When an NCO content of 0.6% by weight has been reached, the mixture is cooled to 40 ℃ and then taken up in 147 parts of triethylamineAnd (c). The clear solution was introduced into 11,350 parts of water with stirring. Thereafter, a mixture of 43.6 parts of ethylenediamine, component E, and 100 parts of water is added to the dispersion with stirring. Acetone was distilled from the dispersion under a slight vacuum. A UV curable aqueous polyurethane dispersion 20) having a solids content of 43 wt.%, an average particle size of 132nm and a pH of 8.0 was obtained. Gel permeation chromatogram of the dispersion showed 1.68 x 10⁴Weight average molecular weight Mw in g/mol.

21) Preparation of the radiation-curable aqueous polyurethane dispersions according to the invention

The preparation is carried out as in example 20), but instead of DBTL 0.76 part of Borchikat 24(1.18mmol) and 0.25 part of di (n-butyl) phosphate (1.18mmol) are used. A UV curable aqueous polyurethane dispersion 21) having a solids content of 42 wt.%, an average particle size of 114nm and a pH of 8.7 was obtained. Gel permeation chromatogram showed 1.93 x 10⁴Weight average molecular weight Mw in g/mol.

22) Preparation of radiation curable aqueous polyurethane dispersions

468g ofN3300 (trimer with isocyanurate structural units based on hexamethylene diisocyanate, Bayer Material Science, Germany), component D, 2.6g of neopentyl glycol, component B, 34.8g of dimethylolpropionic acid, component C, 0.40g of DBTL (0.60mmol) and 0.4g of 2, 6-di-tert-butyl-4-methylphenol (inhibitor)) Dissolved in 300g of acetone and the resulting solution is then homogenized. 204.2g of hydroxyethyl acrylate, component A, were metered in at 55 ℃ so that the temperature did not rise above 65 ℃. When the theoretical NCO value of 0.3% by weight has been reached, 3.0g of ethylenediamine, component E, in a solution of 32g of acetone are added and the mixture is stirred for 30 minutes. After 19g of triethylamine was added, 980g of distilled water was addedDispersion is carried out and the acetone is then distilled off under a slight vacuum. A UV curable aqueous polyurethane dispersion 22) having a solids content of 37%, a pH of 7.9 and an average particle size of 97nm was obtained. Gel permeation chromatogram showed 3.43 x 10³Weight average molecular weight Mw in g/mol.

23) Preparation of the radiation-curable aqueous polyurethane dispersions according to the invention

The preparation is carried out as in example 22), but instead of DBTL 0.40 parts of Borchikat 24(0.60mmol) and 0.13 parts of di (n-butyl) phosphate (0.60mmol) are used. A UV curable aqueous polyurethane dispersion 23) having a solids content of 39 wt.%, an average particle size of 103nm and a pH of 8.2 was obtained. Gel permeation chromatogram showed 3.31 x 10³Weight average molecular weight Mw in g/mol.

Examples 21) and 23) show that, in comparison with examples 20) and 22), virtually the same aqueous radiation-curable polyurethane dispersions can be synthesized with the combination of bismuth (III) 2-ethylhexanoate and di (n-butyl) phosphate as when catalyzed with DBTL.

Formulation of clear lacquer systems

Application and curing conditions of clear lacquer systems

After UV curing, the coated substrates were stored (glass, 1h at room temperature in a desiccator) and then tested.

¹Mixtures of benzophenones and (1-hydroxycyclohexyl) phenylketones, Ciba, Lampertheim, DE

²Solutions of polyether-modified polydimethylsiloxanes, BYK, Wesel, DE

³Solutions of urea-modified polyurethanes, BYK, Wesel, DE

⁴To test the reactivity, the hardness achieved after curing was measured in rockburst seconds (to DIN53157) as a function of the various belt speeds. The coating has excellent reactivity if the pendulum impact hardness is maintained at values above 100 pendulum seconds even at the highest belt speeds.

⁵UV unit, Barber-n, type HOK-6/2 (approximately 80W/cm)

Data of the use tests of clear lacquer systems

⁶Film clarity was evaluated visually after knife coating the film onto a glass plate and subsequent physical drying:

score 5: clear, no detectable haze or fogging

And 4, grading: slight fogging was detectable at an observation angle of about 10-20 deg.

And 3, scoring: slight blurring was detectable at observation angles of about 45-80 deg.

And (3) scoring 2: significant blur

Score 1: matt or grained surfaces

⁷The resistance was evaluated by visual inspection after 16 hours of exposure:

score 5: no visible changes (not damaged)

And 4, grading: slight variations in the brightness or hue are only visible if the light source is reflected on the test surface on or near the print and directly into the eye of the observer, or some bounded print is just detectable (detectable swelling ring, or no detectable softening with the fingernail).

And 3, scoring: slight marks are visible from several viewing angles, e.g. just detectable almost complete circles or circular areas (detectable swelling ring, detectable scratch trace of fingernail)

And (3) scoring 2: severe imprint, but essentially no change in surface structure (closed swelling ring, detectable scratch track).

Score 1: severe imprint, but essentially no change in surface structure, can scratch through the imprint to the substrate.

Score 0: severe marking, surface structure changes or surface materials are completely or partially destroyed or filter paper adheres to the surface.

⁸Whitening after scoring was tested using coin scoring. The result was evaluated as excellent if there was no detectable whitening at all at the scratch point (score 5).

Tests of the service properties of the binders of examples 9, 10 and 11 in the clearcoat show that the same good results are obtained with respect to the clearcoats prepared from the DBTL-catalyzed binder of example 1.

Claims (16)

1. Tin-free, radiation-curable aqueous dispersions based on one or more urethane acrylates (i), wherein the one or more urethane acrylates (i) are prepared by:

A) one or more compounds comprising at least one group reactive with isocyanate and at least one unsaturated group capable of free radical polymerization;

B) one or more compounds different from A) and comprising at least one group reactive with isocyanates;

C) one or more compounds comprising at least one group reactive with isocyanates and at least one group having a hydrophilizing action; and

D) one or more organic polyisocyanates;

in that

F) One or more bismuth (III) salts; and

G) acids having a pKa value of less than 2.5,

in the presence of a catalyst.

2. The tin-free, radiation-curable aqueous dispersion according to claim 1, wherein the one or more urethane acrylates (i) are prepared from the additional component E) by reacting A), B), C), D) and E) in the presence of F) and G), wherein E) is different from A), B), C) and D) and comprises at least one group which is reactive with isocyanates.

3. The tin-free, radiation curable aqueous dispersion of claim 1, wherein the tin-free, radiation curable aqueous dispersion further comprises as component (ii) a reactive diluent having at least one group capable of undergoing free radical polymerization.

4. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein component F) comprises one or more bismuth (III) carboxylates.

5. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein component F) is selected from the group consisting of bismuth (III) neodecanoate, bismuth (III) 2-ethylhexanoate, bismuth (III) citrate, and mixtures thereof.

6. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein component G) is selected from the group consisting of di (n-butyl) phosphate, methanesulfonic acid, p-toluenesulfonic acid, and mixtures thereof.

7. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein component F) is present in the tin-free, radiation-curable aqueous dispersion in an amount in the range from 1 to 30,000ppm, based on the solids content of the aqueous radiation-curable polyurethane dispersion, and component G) is present in the tin-free, radiation-curable aqueous dispersion in an amount in the range from 10 to 300 mol%, based on the amount of component F) used.

8. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein component G) is present in the tin-free, radiation-curable aqueous dispersion in an amount of 100 mol%, based on the amount of component F) used.

9. The tin-free, radiation curable aqueous dispersion of claim 1, wherein the one or more urethane acrylates (i) have a molecular weight in the range of 10³-10⁶Weight average molecular weights Mw in the g/mol range.

10. The tin-free, radiation curable aqueous dispersion of claim 1 wherein component a) is selected from the group consisting of hydroxy-functionalized polyester (meth) acrylates, polyether ester (meth) acrylates, epoxy (meth) acrylates, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, and mixtures thereof.

11. The tin-free, radiation-curable aqueous dispersion of claim 1, wherein the molar ratio of isocyanate groups of component D) to isocyanate-reactive groups of components a), B) and C) is in the range from 0.8: 1 to 2.5: 1.

12. A process for preparing the tin-free, radiation-curable aqueous dispersion of claim 1, which comprises

(1) Reacting components A), B), C) and D) in the presence of components F) and G) in one or more reaction steps to obtain a urethane acrylate (i), wherein a neutralizing agent is added before, during or after the reaction of components A), B), C) and D) to generate the ionic groups required for dispersing the obtained urethane acrylate; and

(2) the dispersion is formed by adding water to the urethane acrylate or transferring the urethane acrylate to an aqueous reservoir.

13. A coating composition prepared from the tin-free, radiation-curable aqueous dispersion of claim 1.

14. The coating composition of claim 13, wherein the coating is a paint or an adhesive.

15. The coating composition of claim 13, wherein the coating composition further comprises a crosslinker based on an amino resin, a blocked polyisocyanate, a non-blocked polyisocyanate, a hydrophilized polyisocyanate, a polyazepine, a polycarbodiimide, or a combination thereof.

16. A substrate coated with the coating composition of claim 15.