WO2010057824A1

WO2010057824A1 - Metal oxo complex as catalyst for polyurethane curing

Info

Publication number: WO2010057824A1
Application number: PCT/EP2009/065037
Authority: WO
Inventors: Zhihua Zhang; Bir Darbar Mehta; Hui Keat Chua; Andreas FECHTENKÖTTER
Original assignee: Basf Se
Priority date: 2008-11-21
Filing date: 2009-11-12
Publication date: 2010-05-27

Abstract

The invention relates to a curable composition comprising the following components: A) at least one isocyanate, B) at least one binder, and C) at least one metal oxo complex containing at least one metal M bound to at least 4 oxygen atoms. Furthermore, the invention refers to a kit of parts comprising as separate parts said components A), B), and/or C) for joint application. The invention also refers to the use of metal oxo complexes as cure promoters in curable compositions and to their use as catalysts for polyurethane curing. Furthermore the present invention refers to coatings obtainable by curing of said compositions.

Description

Metal oxo complex as catalyst for polyurethane curing

Description

The invention relates to a curable compositions comprising the following components:

A) at least one isocyanate,

B) at least one binder, and

C) at least one metal oxo complex containing at least one metal M bound to at least 4 oxygen atoms.

Furthermore, the invention refers to a kit of parts comprising as separate parts said components A), B), and/or C) for joint application. The invention also refers to the use of metal oxo complexes as cure promoters in curable compositions and to their use as catalysts for polyurethane curing. Furthermore the present invention refers to coatings obtainable by curing of said compositions.

Coating applications are becoming increasingly more demanding in terms of performance, safety and environmental compliance. Coatings based on isocyanates and binders, i.e., a component containing hydrogen atoms reactive to isocyanates, in the follow- ing referred to as polyurethane coatings, are known to provide high chemical resistance, flexibility, abrasion resistance, weathering and impact resistance. The protection afforded by such coatings is of particular significance in the automotive, construction, marine and chemical sectors.

Polyurethane coatings or films can for instance be made by reacting multifunctional hydroxyl or amino group containing compounds (polyols or polyamines) and multifunctional isocyanates (polyisocyanates) by means of an isocyanate addition polymerization process. The reaction between the isocyanate groups and the active hydrogen atoms of the binder is usually accelerated by the means of catalysts.

Generally a distinction can be made between one-component (1 K) and two-component (2K) coating materials. Two-component coating materials are not mixed until shortly before application and thus have only a limited processability time. Systems of this kind are distinguished by rapid curing after the components have been mixed. One- component systems, in contrast, have a long pot life. This has been achieved to date, for example, by blocking the NCO groups. But when such coatings are cured the blocking agents escape.

Two-component curable mixtures comprising polyisocyanates and binders, in particular binders based on polyols or polyamines, are well-known in the art to provide excellent performance and cure at low temperatures. However, due to the reactivity of the isocyanates and the binder, it is often difficult to obtain long pot-lifes of the mixture of the polyisocyanate and the binder and yet still enjoy the benefits of rapid cure. This is especially true for low VOC materials, which will incorporate relatively low levels of solvent.

The catalysis of isocyanate addition reactions plays an important part in technical poly- urethane chemistry such as the production of polyurethane foams, elastomers, lacquers, coatings and adhesives.

Tertiary amines and metal compounds have been used as catalysts, examples being triethylene diamine, tin(ll) octoate and di-n-butyl tin dilaurate. These compounds catalyze urethane formation (reaction of isocyanate groups with alcoholic hydroxyl groups) and urea formation (reaction of isocyanate groups with water) as well as the trimeriza- tion of isocyanate groups, addition of isocyanate groups to urethane groups (allophan- ate formation) and addition of isocyanate groups to urea groups (biuret formation).

Organic tin compounds are frequently used as catalysts in both, one component and two component polyurethane systems. A survey of the catalysts commonly used and the mechanism of their action may be found in A. Farkas and G. A. Mills, Advan. Catalysis, 13, 393 (1962), J. H. Saunders and K. C. Frisch, Polyurethanes, Part I, Wiley Interscience, New York, 1962, Chapter Vl, and K. C. Frisch and L. P. Rumao, J. Mac- romol, Sci. Revs. Macromol Chem., C5(1), 103-150 (1970).

Amines often exhibit insufficient catalytic activity, odor, and toxicity. Catalytically active tin compounds known from the prior art, in particular tin carboxylates and tin alkoxides also have several disadvantages.

First, these active tin compounds are sensitive to hydrolysis. Therefore, they cannot readily be incorporated in the usual polyol formulations, which generally contain traces of moisture because they would gradually lose at least some of their catalytic activity when stored in the polyol formulations.

A second disadvantage of these active tin compounds is that when they are used for organic polyisocyanates (i.e. the polyisocyanate component of 2-component systems or isocyanate prepolymers of the kind used as binders in one component systems such as moisture drying coating compounds), they should be incorporated only shortly before the systems are applied because their presence would seriously impair the storage stability of the polyisocyanates due to the above-mentioned side reactions which are catalyzed by tin compounds.

In addition, organo-tin catalysts have recently come under increasing pressure from users on account of toxicological concerns. Accordingly there is an increasing demand for more toxicologically favorable alternatives to the organo-tin catalysts. It is known that various sizes and shapes of fillers (e.g. calcium carbonate, silica, carbon black, etc.) can be incorporated into a polymer to control both polymer morphology and the resulting physical properties. Furthermore it is known that the catalysts used to promote the curing reaction influence and therefore control the resulting physical properties of the resulting polymers.

As an alternative to tin-catalysts organometallic complexes have been developed as polyurethane curing agents. It is for instance known from He et al., J. Coat. Technol. 2002, 74, 31-36 that zirconium diacetoacetate and its derivatives show activity as polyurethane curing agents.

Metal oxo complexes are known as building blocks for the fabrication of inorganic- organic hybrid films (Gross et al., Monatsh. Chem.2006, 137, 583-593) as well as rein- forcing filler in polymer matrix (Trsbelsi et al., Macromolecules 2005, 38, 6068-6078; Sangermano et al., Macromol. Chem. Phys. 2007, 208, 1730-1736). Metal oxo complexes are typically produced by the reaction between metal sources and carboxylic acid to form multinuclear clusters. For instance, the zirconium oxo complex Zr4U2(OMc)i2, bearing methacrylic functionalities can be prepared by reacting zirco- nium butoxide with methacrylic acid.

None of the prior art documents disclose metal oxo complexes containing at least one metal bound to at least four oxygen atoms as polyurethane curing agents.

It was an objective of the present invention to provide curable compositions based on polyisocyanates which have an extended pot life and high storing stability. It was another object of the present invention to provide polyurethane cure promoters which do not contain tin or organic amines. At the same time it was an object to provide polyurethane cure promoters which act as functional fillers for polyurethane. The polyurethane formulation prior to curing ought to be homogeneous and easy to disperse. The drying process ought to proceed without problems leading to coatings and/or films with high optical quality.

It was yet another objective of the present invention to provide coatings based on poly- isocyanates with high scratch resistance. The coatings furthermore ought to be resistant to chemicals and weathering. The corresponding surface ought to be of high optical quality. The coatings ought to exhibit sufficient flame retardancy and excellent mechanical performance characteristics.

It was yet another objective of the present invention to provide coatings exhibiting low VOC (volatile organic component). In particular, the VOC due to any catalyst ought to be zero. The composition ought to contain no volatile heavy metal compound, in par- ticular no volatile organometallic compound. The catalyst used to promote the curing reaction ought to exhibit low toxicity and ought to be less sensitive to hydrolysis

It was yet another objective to provide catalysts for isocyanate curing with lower toxicity and to provide an environmentally friendly urethane reaction catalyst having effectiveness as a reaction catalyst without using a toxic compound and to provide a two-part type urethane coating composition using the catalyst.

In addition, for coating compositions, especially clearcoat or topcoat compositions, it is desired that the coating have a high degree of scratch resistance to protect the appearance of the coating system as a whole.

The present invention provides a two-component curable mixture which, in some applications as a coating composition, has improved scratch resistance over other two- component curable mixtures comprising polyisocyanates and active hydrogen containing resins. The curable composition as provided herein also provides excellent performance characteristics at low temperatures and has an extended pot life.

The curable compositions according to this invention comprise a component (A) con- taining at least one isocyanate (subsequently referred to as isocyanate component

(A)), a component (B) containing at least one binder (subsequently referred to as binder component (B)), and at least one metal oxo cluster containing at least one metal bound to at least four oxygen atoms (referred to as component (C)).

Isocyanate component (A)

An isocyanate for the purpose of the present invention is an organic molecule containing at least one -NCO group per molecule. If the isocyanate molecule contains two - NCO groups, it is a diisocyanate. An isocyanate containing two or more isocyanate groups or an isocyanate representing a mixture of different isocyanates, where the number average of isocyanate groups per molecule is at least 2, is referred to as poly- isocyanate throughout this invention.

It is preferred if isocyanate component (A) is a polyisocyanate. Preferably isocyanate component (A) has an average number of at least 2 NCO groups per molecule (number-weighted average).

Preferably, component (A) contains at least one oligomer of at least one diisocyanate. As parent diisocyanates preferably diisocyanates having from 4 to 20 carbon atoms are used. In principle, the parent diisocyanates can be used as such or as mixture with oligomers. Preferably, however, diisocyanates are used in oligomeric form. Examples of conventional diisocyanates are aliphatic diisocyanates, such as tetrame- thylene diisocyanate, 1 ,5-pentamethylene diisocyanate, hexamethylene diisocyanate (1 ,6-diisocyanatohexane), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, derivatives of lysine diisocyanate, trimethylhexane diisocyanate or tetramethylhexane diisocyanate, cycloa- liphatic diisocyanates, such as 1 ,4-, 1 ,3- or 1 ,2-diisocyanatocyclohexane, 4,4'- or 2,4'- di(isocyanatocyclohexyl)methane, 1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)- cyclohexane (isophoronediisocyanate), 1 ,3- or 1 ,4-bis(isocyanatomethyl)cyclohexane or 2,4- or 2,6-diisocyanato-1-methylcyclohexane, and 3(or 4),8(or 9)-bis(isocyanato- methyl)tricyclo[5.2.1.02,6]decane isomer mixtures, and aromatic diisocyanates, such as toluene 2,4- or 2,6-diisocyanate and the isomer mixtures thereof, m- or p-xylylene diisocyanate, 2,4'- or 4,4'-diisocyanatodiphenylmethane and the isomer mixtures thereof, phenylene 1 ,3- or 1 ,4-diisocyanate, 1-chlorophenylene 2,4-diisocyanate, naphthylene 1 ,5-diisocyanate, biphenylene 4,4'-diisocyanate, 4,4' diisocyanato-3,3'- dimethylbiphenyl, 3-methyldiphenylmethane 4,4'-diisocyanate, tetramethylxylylene diisocyanate, 1 ,4-diisocyanatobenzene or 4,4'-diisocyanatodiphenyl ether.

Also suitable in principle are higher isocyanates, having on average more than 2 isocy- anate groups. Examples that are suitable include triisocyanates such as triisocyana- tononane, 2,4,6-triisocyanatotoluene, triphenylmethane triisocyanate or 2,4,4'- triisocyanato-diphenyl ether, or the mixtures of diisocyanates, triisocyanates and higher polyisocyanates that are obtained by phosgenating corresponding aniline/formaldehyde condensates and represent polyphenyl polyisocyanates containing methylene bridges.

Cycloaliphatic and aliphatic diisocyanates are preferred. Particularly preferred are 1- isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)-cyclohexane (isophorone diisocyanate), 1 ,6 diisocyanatohexane, 4,4'-di(isocyanatocyclohexyl)methane, and 3(or 4),8(or 9)-bis(isocyanatomethyl)tricyclo[5.2.1.02,6]decane isomer mixtures.

Component (A) may comprise polyisocyanates and polyisocyanate-containing mixtures which contain biuret, urethane, allophanate and/or isocyanurate groups, preferably polyisocyanates containing isocyanurate groups and/or polyisocyanates containing allophanate groups. Particular preference is given to polyisocyanates comprising predominantly isocyanurate groups. With very particular preference the fraction of the iso- cyanurate groups corresponds to an NCO value of at least 5%, preferably at least 10%, more preferably at least 15% by weight (calculated as C3N3O3 with a molar mass of 126 g/mol).

Examples of preferred polyisocyanates as component (A) include:

1 ) Polyisocyanates having isocyanurate groups and obtained from aromatic, aliphatic and/or cycloaliphatic diisocyanates. Particularly preferred here are the corre- sponding aliphatic and/or cycloaliphatic isocyanatoisocyanurates and in particular those based on hexamethylene diisocyanate and isophorone diisocyanate. The iso- cyanurates present are in particular trisisocyanatoalkyl or trisisocyanatocycloalkyl iso- cyanurates, which are cyclic trimers of the diisocyanates, or are mixtures with their higher homologs having more than one isocyanurate ring. The isocyanatoisocyanurates generally have an NCO content of from 10 to 30% by weight, in particular from 15 to 25% by weight, and an average NCO functionality of from 2.6 to 8.

2) Uretdione diisocyanates having aromatically, aliphatically and/or cycloaliphati- cally bonded isocyanate groups, preferably having aliphatically and/or cycloaliphatically bonded groups and in particular those derived from hexamethylene diisocyanate or isophorone diisocyanate. Uretdione diisocyanates are cyclic dimerization products of diisocyanates. The uretdione diisocyanates can be used as a sole component or as a mixture with other polyisocyanates, in particular those mentioned under 1 ).

3) Polyisocyanates having biuret groups and having aromatically, cycloaliphatically or aliphatically bonded, preferably cycloaliphatically or aliphatically bonded, isocyanate groups, in particular tris(6-isocyanatohexyl)biuret or mixtures thereof with its higher homologs. These polyisocyanates having biuret groups generally have an NCO content of from 18 to 22% by weight and an average NCO functionality of from 2.8 to 6.

4) Polyisocyanates having urethane and/or allophanate groups and having aromatically, aliphatically or cycloaliphatically bonded, preferably aliphatically or cycloaliphatically bonded, isocyanate groups, as can be obtained, for example, by reaction of ex- cess amounts of hexamethylene diisocyanate or of isophorone diisocyanate with mono- or polyhydric alcohols, such as, for example, methanol, ethanol, isopropanol, n- propanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-hexanol, n-heptanol, n- octanol, n-decanol, n-dodecanol (lauryl alcohol), 2 ethylhexanol, n-pentanol, stearyl alcohol, cetyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 1 ,3-propanediol monomethyl ether, cyclopentanol, cyclohexanol, cyc- looctanol, cyclododecanol, trimethylolpropane, neopentyl glycol, pentaerythritol, 1 ,4- butanediol, 1 ,6 hexanediol, 1 ,3 propanediol, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3- propanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, glycerol, 1 ,2-dihydroxypropane, 2,2-dimethyl-1 ,2-ethanediol, 1 ,2- butane-diol, 1 ,4-butanediol, 3-methylpentane-1 ,5-diol, 2-ethylhexane-1 ,3-diol, 2,4- diethyl-octane-1 ,3-diol, neopentyl glycol hydroxypivalate, ditrimethylolpropane, dipen- taerythritol, 2,2-bis(4-hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3-, and 1 ,4 cyclohex- anedimethanol, 1 ,2-, 1 ,3-, or 1 ,4-cyclohexanediol or mixtures thereof. These polyisocyanates having urethane and/or allophanate groups generally have an NCO content of from 12 to 24% by weight, in particular 18-24% by weight for those based on HDI, and an average NCO functionality of from 2.5 to 4.5. 5) Polyisocyanates comprising oxadiazinetrione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates comprising oxadiazinetrione groups can be prepared from diisocyanate and carbon dioxide.

6) Polyisocyanates comprising iminooxadiazinedione groups, preferably derived from hexamethylene diisocyanate or isophorone diisocyanate. Such polyisocyanates comprising iminooxadiazinedione groups can be prepared from diisocyanates by means of specific catalysts.

7) Uretonimine-modified polyisocyanates.

8) Carbodiimide-modified polyisocyanates.

9) Hyperbranched polyisocyanates, of the kind known for example from DE-A1 10013186 or DE-A1 10013187.

10) Polyurethane polyisocyanate prepolymers, from di- and/or polyisocyanates with alcohols.

1 1 ) Polyurea-polyisocyanate prepolymers.

The polyisocyanates 1 ) to 1 1) can be used as a mixture, if appropriate also as a mixture with diisocyanates.

Preference is given to polyisocyanates containing isocyanurate and/or biuret groups. In addition, these mixtures may also contain minor amounts of uretdione, biuret, ure- thane, allophanate, oxadiazinetrione, iminooxadiazinedione and/or uretonimine groups, preferably at less than 25% by weight in each case, more preferably less than 20% by weight in each case, very preferably less than 15% by weight in each case, in particular below 10% by weight in each case and especially below 5% by weight in each case, and very specially below 2% by weight in each case, based on the respective functional group.

Particularly preferred as isocyanates in component (A) are isocyanurates of isophorone diisocyanate having an NCO content to DIN EN ISO 11909 of 16.7% - 17.6%, and/or an average NCO functionality of 3.0 to 4.0, preferably 3.0 to 3.7, more preferably 3.1 to 3.5. Compounds of this kind containing isocyanurate groups preferably have a HA- ZEN/APHA color number to DIN EN 1557 of not more than 150.

Also particularly preferred as isocyanate in component (A) is the isocyanurate of 1 ,6- hexamethylene diisocyanate, having an NCO content to DIN EN ISO 11909 of 21.5 - 23.5%, and/or an average NCO functionality of 3.0 to 8, preferably 3.0 to 3.7, more preferably 3.1 to 3.5. Compounds of this kind containing isocyanurate groups preferably have a color number to DIN ISO 6271 of not more than 60. Compounds of this kind containing isocyanurate groups preferably have a viscosity at 23°C to DIN EN ISO 3219 of 1000 to 20 000 mPas, preferably 1000 to 4000 mPas, at a shear rate of 1000 s-¹.

In one preferred embodiment the isocyanate component (A) has a total chlorine content of less than 400 mg/kg, more preferably a total chlorine content of less than 80 mg/kg, very preferably less than 60, in particular less than 40, especially less than 20, and less than 10 mg/kg even.

Binder component (B)

A binder for the purpose of the present invention is a compound containing at least two hydrogen atoms reactive to isocyanates. Preferably, the binder contains hydroxyl groups (OH groups) and/or primary and/or secondary amino groups.

For the purpose of the present invention, a polyol is an organic molecule comprising an average number of at least 2 OH groups per molecule (number-weighted). Further- more, a polyamine is an organic molecule comprising an average number of at least 2 primary or secondary amino groups per molecule (number-weighted).

Preferably, the binder component (B) contains at least one polyol or at least one polyamine or both, at least one polyol and at least one polyamine. Particularly preferably, the binder component (B) contains at least one polyol.

Component (B) preferably exhibits an OH number to DIN 53240-2 of at least 15, preferably at least 40, more preferably at least 60, and very preferably at least 80 mg KOH/g resin solids. The OH number can be up to 350, preferably up to 240, more pref- erably up to 180, and very preferably up to 140 mg KOH/g resin solids. Preferred OH numbers, measured in accordance with DIN 53240-2, are 40-350 mg KOH/g resin solids for polyesters, preferably 80-180 mg KOH/g resin solids, and 15-250 mg KOH/g resin solids for polyacrylate-ols, preferably 80-160 mg KOH/g.

The preferred OH numbers are also dependent on the application. According to Manfred Bock, "Polyurethane fur Lacke und Beschichtungen", p. 80, Vincentz-Verlag, 1999, lower OH numbers are advantageous for effective adhesion and corrosion control. For topcoat materials, for example, use is made of polyacrylates having OH numbers of about 40 to 100; for weather-resistant coating materials, OH numbers of around 135; and for high chemical resistance, those with OH numbers of around 170 mg KOH/g resin solids are used. Polyesters for aircraft coatings have in some cases much higher OH numbers. Examples of such binders are polyacrylate polyols, polyester polyols, polyether polyols, polyurethane polyols; polyurea polyols; polyester polyacrylate polyols; polyester poly- urethane polyols; polyurethane polyacrylate polyols, polyurethane-modified alkyd res- ins; fatty acid modified polyester polyurethane polyols, copolymers with allyl ethers, graft polymers of the stated groups of compound with, for example, different glass transition temperatures, and also mixtures of the binders stated. Preference is given to polyacrylate polyols, polyester polyols and polyether polyols.

By way of example this may be at least one polyacrylate polyol that contains per molecule on average at least two, preferably two to ten, more preferably three to ten, and very preferably three to eight hydroxyl groups.

The binders may additionally have an acid number to DIN EN ISO 3682 of up to 200 mg KOH/g, preferably up to 150 and more preferably up to 100 mg KOH/g. The acid number ought preferably to be at least 10, more preferably at least 80 mg KOH/g. Alternatively it may be less than 10, so that the binder is virtually acid-free.

Polyacrylate polyols of this kind preferably have a molecular weight Mn of at least 1000, more preferably at least 2000 and very preferably at least 5000 g/mol. The molecular weight Mn may for example be up to 200 000, preferably up to 100 000, more preferably up to 80 000 and very preferably up to 50 000 g/mol.

The polyacrylate polyols are copolymers of at least one (meth)acrylic ester with at least one compound having at least one, preferably precisely one hydroxy group and at least one, preferably precisely one (meth)acrylate group.

The latter may be, for example monoesters of α,β-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid (referred to in this specification for short as "(meth)acrylic acid"), with diols or polyols, which have preferably 2 to 20 C atoms and at least two hydroxy groups, such as ethylene glycol, diethylene glycol, triethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, 1 ,1-dimethyl-1 ,2-ethanediol, dipropyl- ene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, tripropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, neopentyl glycol, neopentyl glycol hy- droxypivalate, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, 2-butyl-2-ethyl-1 ,3- propanediol, 1 ,6-hexanediol, 2-methyl-1 ,5-pentanediol, 2-ethyl-1 ,4-butanediol, 2-ethyl- 1 ,3-hexanediol, 2,4-diethyl-octane-1 ,3-diol, 2,2-bis(4-hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3- and 1 ,4-bis(hydroxymethyl)cyclohexane, 1 ,2-, 1 ,3- or 1 ,4-cyclohexanediol, glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol), maltitol, isomalt, poly-THF with a molar weight between 162 and 4500, preferably 250 to 2000, poly-1 ,3- propanediol or polypropylene glycol with a molar weight between 134 and 2000 or polyethylene glycol with a molar weight between 238 and 2000.

Preference is given to 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2- or 3- hydroxypropyl acrylate, 1 ,4-butanediol monoacrylate or 3-(acryloyloxy)-2-hydroxypropyl acrylate and particular preference to 2-hydroxyethyl acrylate and/or 2-hydroxyethyl methacrylate.

The hydroxyl-bearing monomers are used in the copolymerization in a mixture with other polymerizable monomers, preferably free-radically polymerizable monomers, preferably those composed of more than 50% by weight of C1-C20, preferably C1-C4, alkyl (meth)acrylate, (meth)acrylic acid, vinylaromatics having up to 20 C atoms, vinyl esters of carboxylic acids comprising up to 20 C atoms, vinyl halides, nonaromatic hydrocarbons having 4 to 8 C atoms and 1 or 2 double bonds, unsaturated nitriles and mixtures thereof. Particular preference is given to those polymers composed of more than 60% by weight of C1-C10 alkyl (meth)acrylates, styrene, vinylimidazole or mixtures thereof.

Above these the polymers may comprise hydroxy-functional monomers in accordance with the above hydroxy group content and, if appropriate, further monomers, examples being (meth)acrylic acid glycidyl epoxy esters, ethylenically unsaturated acids, especially carboxylic acids, acid anhydrides or acid amides.

Further polymers are, for example, polyesterols, as are obtainable by condensing poly- carboxylic acids, especially dicarboxylic acids, with polyols, especially diols. In order to ensure a polyester polyol functionality that is appropriate for the polymerization, use is also made in part of triols, tetrols, etc, and also triacids etc.

Polyester polyols are known for example from Ullmanns Enzyklopadie der technischen Chemie, 4th edition, volume 19, pp. 62 to 65. It is preferred to use polyester polyols which are obtained by reacting dihydric alcohols with dibasic carboxylic acids. In lieu of the free polycarboxylic acids it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or mixtures thereof to prepare the polyester polyols. The polycarboxylic acids may be aliphatic, cycloali- phatic, araliphatic, aromatic or heterocyclic and may if appropriate be substituted, by halogen atoms for example, and/or unsaturated. Examples thereof that may be mentioned include the following:

Oxalic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, azelaic acid, 1 ,4-cyclohexanedicarboxylic acid or tetrahydrophthalic acid, suberic acid, azelaic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic anhydride, dimeric fatty acids, their isomers and hydrogena- tion products, and also esterifiable derivatives, such as anhydrides or dialkyl esters, Ci C₄ alkyl esters for example, preferably methyl, ethyl or n-butyl esters, of the stated ac- ids are employed. Preference is given to dicarboxylic acids of the general formula HOOC-(CH2)y-COOH, where y is a number from 1 to 20, preferably en even number from 2 to 20, and preferably succinic acid, adipic acid, sebacic acid, and dodecanedi- carboxylic acid.

Suitable polyhydric alcohols for preparing the polyesterols include 1 ,2-propanediol, ethylene glycol, 2, 2-dimethyl-1 ,2-ethanediol, 1 ,3-propanediol, 1 ,2-butanediol, 1 ,3- butanediol, 1 ,4-butanediol, 3-methylpentane-1 ,5-diol, 2-ethylhexane-1 ,3-diol, 2,4- diethyloctane-1 ,3-diol, 1 ,6-hexanediol, PoIy-THF having a molar mass of between 162 and 4500, preferably 250 to 2000, poly-1 ,3-propanediol having a molar mass between 134 and 1178, poly-1 ,2-propanediol having a molar mass between 134 and 898, polyethylene glycol having a molar mass between 106 and 458, neopentyl glycol, neopentyl glycol hydroxypivalate, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, 2,2-bis(4- hydroxycyclohexyl)propane, 1 ,1-, 1 ,2-, 1 ,3- and 1 ,4-cyclohexanedimethanol, 1 ,2-, 1 ,3- or 1 ,4-cyclohexanediol, trimethylolbutane, trimethylolpropane, trimethylolethane, neo- pentyl glycol, pentaerythritol, glycerol, ditrimethylolpropane, dipentaerythritol, sorbitol, mannitol, diglycerol, threitol, erythritol, adonitol (ribitol), arabitol (lyxitol), xylitol, dulcitol (galactitol), maltitol or isomalt, which if appropriate may have been alkoxylated as described above.

Preferred alcohols are those of the general formula HO-(CH2)_X-OH, where x is a number from 1 to 20, preferably an even number from 2 to 20. Preferred are ethylene glycol, butane-1 ,4-diol, hexane-1 ,6-diol, octane-1 ,8-diol and dodecane-1 ,12-diol. Additionally preferred is neopentyl glycol.

Also suitable, furthermore, are polycarbonate diols of the kind obtainable, for example, by reacting phosgene with an excess of the low molecular mass alcohols specified as synthesis components for the polyester polyols.

Also suitable are lactone-based polyester diols, which are homopolymers or copoly- mers of lactones, preferably hydroxy-terminated adducts of lactones with suitable di- functional starter molecules. Suitable lactones are preferably those which derive from compounds of the general formula HO-(CHb)Z-COOH, where z is a number from 1 to 20 and where one H atom of a methylene unit may also have been substituted by a Ci to a C₄ alkyl radical. Examples are ε-caprolactone, β-propiolactone, gamma- butyrolactone and/or methyl-ε-caprolactone, 4-hydroxybenzoic acid, 6-hydroxy-2- naphthoic acid or pivalolactone, and mixtures thereof. Examples of suitable starter components include the low molecular mass dihydric alcohols specified above as a synthesis component for the polyester polyols. The corresponding polymers of ε- caprolactone are particularly preferred. Lower polyester diols or polyether diols as well can be used as starters for preparing the lactone polymers. In lieu of the polymers of lactones it is also possible to use the corresponding, chemically equivalent polycon- densates of the hydroxycarboxylic acids corresponding to the lactones.

Also suitable as polymers, furthermore, are polyetherols, which are prepared by addition reaction of ethylene oxide, propylene oxide or butylene oxide with H-active components. Polycondensates of butanediol are also suitable.

In addition it is possible to use hydroxy-functional carboxylic acids, such as dimethylol- propionic acid or dimethylolbutanoic acid, for example.

The polymers can of course also be compounds containing primary or secondary ami- no groups.

Component (C)

According to the invention, the curable composition comprises as component (C) at least one metal oxo complex containing at least one metal M, preferably Zr, Ti and/or Bi, bound to at least 4 oxygen atoms.

Preferably component (C) comprises at least one metal oxo complex according to formula (I) M¹aM² _bOχ(OR¹)y(OOCR²)z L_p (I) wherein

R¹ and R² may be the same or different and each independently represents a Cβ - C30 aryl, Ci to C40 alkyl, C5 to C40 cycloalkyl, or siloxy group, M¹ and M² each is a metal selected from the group consisting of elements of group IVB of the periodic table and Bi, with the proviso that M¹ is different from

M², a is an integer of from 1 to 18, b is an integer of from 0 to 16, with the proviso that the sum of a and b is at least 4, - z is an integer of from 0 to 16, preferably from 12 to 16,

- x is an integer of from 1 to 16, preferably from 2 to 6,

- y is an integer of from 0 to 6, preferably from 0 to 4, p is an integer of from 0 to 16, preferably from 0 to 6,

- with the proviso that z, x, y, and p are selected such that each metal atom is bound to at least 4 oxygen atoms, L is selected from the group consisting of OH, amine, alkoxide, acetylacetonate, isocyanate, alkyl, aryl, monoatomic oxygen, and OR¹, wherein R¹ has the meaning as defined above.

Preferably, at least one of M¹ and M² is selected from Zr, Ti and Bi. It is particularly preferred if M¹ and M² both are selected from Ti, Zr, and Bi if b > 0.

L is preferably acetylacetonate.

According to a preferred embodiment, a is an integer of from 2 to 6 and b is an integer of from 0 to 4 with the proviso that the sum of a and b is at least 4.

In a particularly preferred embodiment b is zero, i.e., the metal oxo complex is based on only one metal M¹. According to another particularly preferred embodiment a and b each is at least 1 and the sum of a and b is at least 4.

According to a particularly preferred embodiment which may be part of the preferred embodiment mentioned before z is an integer of from 12 to 16, x is an integer of from 2 to 6, y is an integer of from 0 to 4, and p is an integer of from 0 to 6 with the proviso that z, x, y, and p are selected such that each metal atom is bound to at least 4 oxygen atoms.

In a very particularly preferred embodiment M¹ is Zr, a is 4, b is 0, x is 2, y is 0, z is 12, and p is 0, in particular Zr₄O₂(OMc)I₂ with OMc being 0OC-C(CHs)=CH₂.

In another very particularly preferred embodiment the metal oxo complex has the following structure: Ti(OPr)₄-X (0OCR)_x and in particular structure (II)

(H)

with R = -(CH₂)T-CH =CH-CH₂-(CH₂)6-CH₃. Structure (II) in the following is referred to as "Ti-a".

The curable compositions according to the present invention preferably contain from 0.5 to 30 %, preferably from 0.5 to 10% by weight of component C) relative to the total weight of components (A), (B), and (C).

Further components

Preferably, a curable composition according to the invention further comprises at least one solvent (D).

Examples of solvents (D) are alcohols, esters, ester alcohols, ethers, ether alcohols, aromatic and/or (cyclo)aliphatic hydrocarbons and their mixtures and halogenated hydrocarbons. Via the amino resins it is also possible to introduce alcohol as well into the mixtures.

Preference is given to alkanoic acid alkyl esters, alkanoic acid alkyl ester alcohols, al- koxylated alkanoic acid alkyl esters and mixtures thereof. Examples of esters include n-butyl acetate, ethyl acetate, 1 -methoxyprop-2-yl acetate and 2-methoxyethyl acetate, and also the monoacetyl and diacetyl esters of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol or tri- propylene glycol, such as butyl glycol acetate, for example. Further examples are car- bonates, as well, such as preferably 1 ,2-ethylene carbonate, 1 ,2-propylene carbonate or 1 ,3-propylene carbonate.

Ethers are, for example, tetrahydrofuran (THF), dioxane, and the dimethyl, diethyl or din-butyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol or tripropylene glycol.

Alcohols are for example methanol, ethanol, isopropanol, n-propanol, n-butanol, isobu- tanol, sec-butanol, n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol (lauryl alcohol), 2-ethylhexanol, cyclopentanol or cyclohexanol.

Alkanoic ester alcohols are for example poly(C2 to C3) alkylene glycol (Ci to C₄) mo- noalkyl ether acetates.

Ether alcohols are for example poly(C2 to C3) alkylene glycol di(Ci to C₄) alkyl ethers, dipropylene glycol dimethyl ether, preferably butyl glycol.

Aromatic hydrocarbon mixtures are those comprising predominantly aromatic C7 to Ci₄ hydrocarbons and being able to comprise a boiling range from 110 to 300⁰C, particular preference being given to toluene, o-, m- or p-xylene, trimethylbenzene isomers, tetramethylbenzene isomers, ethylbenzene, cumene, tetrahydronaphthalene and mixtures comprising them.

Examples thereof are the Solvesso® grades from ExxonMobil Chemical, especially Solvesso® 100 (CAS no. 64742-95-6, predominantly Cg and C10 aromatics, boiling range about 154-178°C), 150 (boiling range about 182 - 207⁰C) and 200 (CAS no.

64742-94-5), and also the Shellsol® grades from Shell, Caromax® grades from Petro- chem Carless, Caromax® 18, for example, or products from DHC, Hydrosol® A/170, for example. Hydrocarbon mixtures comprising paraffins, cycloparaffins and aromatics are also available commercially under the names Kristalloel (for example, Kristalloel 30, boiling range about 158-198°C or Kristalloel 60: CAS no. 64742-82-1), white spirit (likewise, for example CAS no. 64742-82-1 ) or solvent naphtha (light: boiling range about 155-180⁰C, heavy: boiling range about 225 - 300°C). The aromatics content of such hydrocarbon mixtures is generally more than 90%, preferably more than 95%, more preferably more than 98% and very preferably more than 99% by weight. It may be advisable to use hydrocarbon mixtures having a particularly reduced naphthalene content. The density at 20⁰C to DIN 51757 of the hydrocarbons may be less than 1 g/cm³, preferably less than 0.95 and more preferably less than 0.9 g/cm³.

The aliphatic hydrocarbon content is generally less than 5%, preferably less than 2.5% and more preferably less than 1 % by weight.

Halogenated hydrocarbons are, for example chlorobenzene and dichlorobenzene or its isomer mixtures. (Cyclo)aliphatic hydrocarbons are for example decalin, alkylated de- calin, and isomer mixtures of linear or branched alkanes and/or cycloalkanes.

Preference is given to n-butyl acetate, ethyl acetate, 1 -methoxyprop-2-yl acetate, 2- methoxyethyl acetate, and mixtures thereof.

Mixtures of this kind can be produced in a volume ratio 10:1 to 1 :10, preferably in a volume ratio of 5:1 to 1 :5 and more preferably in a volume ratio of 1 :1 , not counting any solvent still comprised in the reaction mixture from the transetherification, and particularly not the alcohols R¹OH and R²OH.

Preferred examples are butyl acetate/xylene, 1 :1 methoxypropyl acetate/xylene, 1 :1 butyl acetate/solvent naphtha 100, 1 :2 butyl acetate/Solvesso® 100, and 3:1 Kristalloel 30/Shellsol® A.

Alcohols are for example methanol, ethanol, n-propanol, isopropanol, n-butanol, sec- butanol, isobutanol, pentanol isomer mixtures, hexanol isomer mixtures, 2-ethylhexanol or octanol.

Examples of further, typical coating additives (E) that can be used include antioxidants, stabilizers, activators (accelerants), fillers, pigments, dyes, antistats, flame retardants, thickeners, thixotropic agents, surface-active agents, viscosity modifiers, plasticizers or chelating agents.

Suitable thickeners, besides free-radically (co)polymerized (co)polymers, include typical organic and inorganic thickeners such as hydroxymethylcellulose or bentonite.

Examples of chelating agents that can be used include ethylenediamineacetic acid and its salts, and β-diketones.

Suitable fillers comprise silicates, examples being silicates obtainable by silicon tetrachloride hydrolysis, such as Aerosil® from Degussa, siliceous earth, talc, aluminum silicates, magnesium silicates, calcium carbonates, etc. Suitable stabilizers comprise typical UV absorbers such as oxanilides, triazines and benzotriazole (the latter available as Tinuvin® grades from Ciba-Spezialitatenchemie) and benzophenones. They can be used alone or together with suitable free-radical scavengers, examples being sterically hindered amines such as 2,2,6,6- tetramethylpiperidine, 2,6-di-tert-butylpiperidine or derivates thereof, e.g., bis(2, 2,6,6- tetramethyl-4-piperidyl) sebacate. Stabilizers are used typically in amounts of 0.1 % to 5.0% by weight, based on the solid components comprised in the preparation.

Pigments may likewise be comprised. Pigments, according to CD Rompp Chemie Lex- ikon - Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995, with reference to DIN 55943, are particulate, organic or inorganic chromatic or achromatic colorants which are virtually insoluble in the application medium.

Virtually insoluble here means a solubility at 25°C of below 1 g/1000 g of application medium, preferably below 0.5, more preferably below 0.25, very preferably below 0.1 and in particular below 0.05 g/1000 g of application medium.

Examples of pigments comprise any desired systems of absorption pigments and/or effect pigments, preferably absorption pigments. There are no restrictions whatsoever concerning the number and selection of the pigment components. They can be adapted as desired to the particular requirements, such as the desired color impression, for example.

By effect pigments are meant all pigments which exhibit a platelet-shaped construction and impart specific decorative color effects to a surface coating. The effect pigments comprise, for example, all of the effect-imparting pigments which can be employed commonly in vehicle finishing and industrial coating. Examples of effect pigments of this kind are pure metal pigments, such as aluminum, iron or copper pigments; interference pigments, such as titanium dioxide-coated mica, iron oxide-coated mica, mixed oxide-coated mica (e.g., with titanium dioxide and Fe2U3 or titanium dioxide and O2O3), metal oxide-coated aluminum, or liquid-crystal pigments.

The color-imparting absorption pigments are, for example, typical organic or inorganic absorption pigments which can be used in the coatings industry. Examples of organic absorption pigments are azo pigments, phthalocyanine pigments, quinacridone pigments and pyrrolopyrrole pigments. Examples of inorganic absorption pigments are iron oxide pigments, titanium dioxide and carbon black.

The solids content of the coating compositions of the invention is laid down for the pur- poses of this specification as the ratio of the sum of the components (A), (B) and (C) to the sum of components (A), (B), (C) and (D). In accordance with the invention, said solids content is for example between 25% and 90% by weight, preferably between 40% and 80% by weight.

The components (A) and (B) are typically employed in a ratio of from 0.2 : 1 to 5 : 1 (based on the ratio of the NCO groups in (A) to OH groups in (B)), preferably in the ratio of from 0.4 : 1 to 3 : 1 , more preferably in the ratio of from 0.5 : 1 to 2 : 1 , and very preferably in the ratio of from 0.8 : 1 to 1.2 : 1.

Applications

It is preferred to use the metal oxo complexes as defined in the invention as cure promoters in curable compositions.

It is preferred to use the metal oxo complexes as defined in the invention as catalyst for polyurethane curing.

Curing of the compositions according to the invention leads to coatings which are also a subject of the present invention.

They are particularly suitable for use as primers, surfacers, pigmented topcoat materials and clearcoat materials in the sectors of industrial, wood, automotive, especially OEM, finishing or decorative coating. The combination of these materials provides fast reacting, durable coatings having extended pot-life and excellent cure. The coating compositions are especially suitable for applications where there is a need for particu- larly high application reliability, external weathering resistance, optical qualities, scratch resistance, solvent resistance and/or chemical resistance. The compositions of this invention could also be utilized as adhesives, elastomers and plastics.

The coating materials of the invention are suitable for coating substrates such as wood, paper, textile, leather, nonwoven, plastics surfaces, glass, ceramic, mineral building materials such as cement moldings and fiber-cement slabs, or coated or uncoated metals, preferably plastics or metals, particularly in the form of sheets, more preferably metals.

The coating materials of the invention are suitable as or in interior coatings, preferably also as or in exterior coatings, i.e., applications where they are exposed to daylight, on parts of buildings, coatings on vehicles and aircraft, and for industrial applications. In particular the coating materials of the invention are used as or in automotive clearcoat, basecoat and topcoat materials or primers. Further preferred applications are in can coating and coil coating. The substrates are coated with the coating materials of the invention in accordance with conventional techniques which are known to the skilled worker, and which involve applying at least one coating material or coating formulation of the invention to the target substrate in the desired thickness, and removing the volatile constituents of the coating material with heating if appropriate (drying). This operation may, if desired, be repeated one or more times. Application to the substrate may be made in a known way, for example by spraying, troweling, knife coating, brushing, rolling, roller-coating or pouring. The coating thickness is generally in a range from about 3 to 1000 g/m² and preferably 10 to 200 g/m². Curing may then be carried out.

Curing is generally accomplished by drying the coatings - following application of the coating material to the substrates - at a temperature if appropriate below 80⁰C, preferably room temperature to 60⁰C and more preferably room temperature to 40⁰C, over a period of up to 72 hours, preferably up to 48 hours, more preferably up to 24 hours, very preferably up to 12 hours and in particular up to 6 hours, and subjecting the applied coatings to thermal treatment (curing) under an oxygen-containing atmosphere, preferably air or under inert gas, at temperatures between 80 and 270, preferably between 100 and 240 and, more preferably between 120 and 180°C. Curing of the coating material takes place as a function of the amount of coating material applied and of the crosslinking energy introduced via high-energy radiation, heat transfer from heated surfaces, or via convection of gaseous media, over a period of seconds, for example, in the case of coil coating in combination with NIR drying, up to 5 hours, for example, high-build systems on temperature sensitive materials, usually not less than 10 minutes, preferably not less than 15, more preferably not less than 30, and very preferably not less than 45 minutes. Drying essentially comprises removal of existing solvent, and in addition there may also, even at this stage, be reaction with the binder, whereas curing essentially comprises reaction with the binder.

In addition to or instead of thermal curing, the curing may also take place by means of IR and NIR radiation, with NIR radiation here denoting electromagnetic radiation in the wavelength range from 760 nm to 2.5 μm, preferably from 900 to 1500 nm.

Curing takes place in a time of 1 second to 180 minutes, preferably of 1 minute to 45 minutes.

Examples of suitable substrates for the coating materials of the invention include thermoplastic polymers, especially polymethyl methacrylates, polybutyl methacrylates, polyethylene terephthalates, polybutylene terephthalates, polyvinylidene fluorides, polyvinyl chlorides, polyesters, polyolefins, acrylonitrile-ethylenepropylene-diene-styrene copolymers (A-EPDM), polyetherimides, polyether ketones, polyphenylene sulfides, polyphenylene ethers or mixtures thereof. Mention may further be made of polyethylene, polypropylene, polystyrene, polybutadi- ene, polyesters, polyamides, polyethers, polycarbonate, polyvinylacetal, polyacryloni- trile, polyacetal, polyvinyl alcohol, polyvinyl acetate, phenolic resins, urea resins, me- lamine resins, alkyd resins, epoxy resins or polyurethanes, block or graft copolymers thereof, and blends of these.

Mention may preferably be made of ABS, AES, AMMA, ASA, EP, EPS, EVA, EVAL, HDPE, LDPE, MABS, MBS, MF, PA, PA6, PA66, PAN, PB, PBT, PBTP, PC, PE, PEC, PEEK, PEI, PEK, PEP, PES, PET, PETP, PF, Pl, PIB, PMMA, POM, PP, PPS, PS, PSU, PUR, PVAC, PVAL, PVC, PVDC, PVP, SAN, SB, SMS, UF, UP plastics (abbreviated names in accordance with DIN 7728) and aliphatic polyketones.

Particularly preferred substrates are polyolefins, such as PP (polypropylene), which optionally may be isotactic, syndiotactic or atactic and optionally may be unoriented or may have been oriented by uniaxial or biaxial stretching, SAN (styrene-acrylonitrile- copolymers), PC (polycarbonates), PVC (polyvinyl chlorides), PMMA (polymethyl me- thacrylates), PBT (poly(butylene terephthalate)s), PA (polyamides), ASA (acrylonitrile- styrene-acrylate copolymers) and ABS (acrylonitrile-butadiene-styrene-copolymers), and also their physical mixtures (blends). Particular preferably is given to PP, SAN, ABS, ASA and blends of ABS or ASA with PA or PBT or PC. Especially preferred are polyolefins, PMMA and PVC.

Especially preferred is ASA, particularly in accordance with DE 196 51 350 and the ASA/PC blend. Preference is likewise given to polymethyl methacrylate (PMMA) or impact-modified PMMA.

A further-preferred substrate for coating with the coating materials of the invention are metals. The metals in question are especially those which have already been coated with another coating film, such as with an electrocoat, surfacer, primer or basecoat. These coating films may be solvent-based, water-based or powder coating-based, may be crosslinked, part-crosslinked or thermoplastic, may have been cured through their volume or may have been applied wet-on-wet.

As far as the type of metal is concerned, suitable metals may in principle be any de- sired metals. In particular, however, they are metals or alloys which are typically employed as metallic materials of construction and require protection against corrosion.

The surfaces in question are in particular those of iron, steel, Zn, Zn alloys, Al or Al alloys. These may be the surfaces of structures composed entirely of the metals or alloys in question. Alternatively the structures may have been only coated with these metals and may themselves be composed of materials of other kinds, such as of other metals, alloys, polymers or composite materials, for example. They may be surfaces of castings made from galvanized iron or steel. In one preferred embodiment of the present invention the surfaces are steel surfaces.

Zn alloys or Al alloys are known to the skilled worker. The skilled worker selects the nature and amount of alloying constituents in accordance with the desired end-use application. Typical constituents of zinc alloys comprise, in particular, Al, Pb, Si, Mg, Sn, Cu or Cd. Typical constituents of aluminum alloys comprise, in particular, Mg, Mn, Si, Zn, Cr, Zr, Cu or Ti. The alloys may also be Al/Zn alloys in which Al and Zn are present in an approximately equal amount. Steel coated with alloys of these kinds is avail- able commercially. The steel may comprise the typical alloying components known to the skilled worker.

Also conceivable is the use of the coating compositions of the invention for treating tin- plated iron/steel (tinplate).

The invention further concerns a kit of parts comprising as separate parts components A), B), and C) or a kit of parts comprising component B) as one separate part and a mixture of A) and C) as a second separate part or a kit of parts comprising component A) as a first separate part and a mixture of B) and C) as a second separate part for joint application, the application preferably comprising the curing in the form of a coating.

The examples which follow are intended to illustrate the properties of the invention, but without restriction thereof.

Examples

Example 1 : Preparation of Zr4U2(OMc)i2

132 g of methacrylic acid (H-OMc) was added drop-wise to 108 ml of an 80 wt.-% solu- tion of Zr(OBu)₄ in n-butanol under stirring and inert nitrogen gas atmosphere. The solution was then kept at room temperature for 1 day. Colorless crystals of Zr4U2(OMc)i2 were obtained.

Example 2: Preparation of titanium oleate oxo complex "Ti-a" according to structure (II)

48 ml of Ti(i-OPr)₄ was added to 208 ml of oleic acid under vigorous stirring and inert nitrogen gas atmosphere to form a homogenous, slightly yellow solution. After heating at 8O⁰C for 0.5 hr, acetone was added to cause precipitation of the titanium oleate oxo complex "Ti-a" which was a lightly yellowish oily compound.

Examples 3 to 6: Preparation of polyurethane coatings Example 3

0.1 g zirconium oxo complex according to example 1 was added to 2ml of butyl acetate, followed by addition of 1.0 g of hexamethylene diisocynate, and 1.0 g of 1 ,5- pentanediol in a 20ml glass vial. The system cured to a complete solid in 30 minutes.

Example 4

0.1 g titanium oxo complex according to example 2 was added to 2ml of butyl acetate, followed by addition of 1.0 g of hexamethylene diisocyanate, and 1.0 g of 1 ,5- pentanediol in a 20 ml glass vial. The system cured to a complete solid in 15 minutes.

Examples 5 and 6

Polyurethane coatings according to examples 5 and 6 were prepared using Lupranol® 1301 (trifunctional polyether polyol by BASF SE with solely secondary OH groups and an OH number according to DIN 53240 of 398 mg KOH/g and a viscosity at 25°C of 640 mPa.s according to DIN 51550) as binder component B) and Basonat® HI 100

(polyisocyanate based on isocyanurated hexamethylene diisocyanate by BASF SE with an NCO content of 21.5 to 22.5 wt.-% according to DIN EN ISO 11909 and a viscosity at 23°C of 2500 to 4000 mPa.s at shear rate D = 1000 S^"1 according to DIN EN ISO 3219) as isocyanate component A). To that end, 0.1 g of zirconium oxo complex (ex- ample 5 = oxo complex according to example 1 and example 6 = oxo complex according to example 2) was completely dissolved in 2 ml n-butyl acetate. Subsequently 1.75 g of Lupranol® 1301 and 2.374 g of Basonat® HI 100 were added to the catalyst dispersion and stirred strongly for 20 minutes. Then the curable coating compositions were applied to a commercially available Polyethylene terephthalate (PET) sheet using a coil bar coater. At room temperature, the coatings cured in 60 minutes in case of example 5 and in 45 minutes in the case of example 6.

Claims

1. A curable composition comprising the following components:

A) at least one isocyanate, B) at least one binder, and

2. A curable composition according to claim 1 , wherein component C) comprises at least one metal oxo complex according to formula (I)

M¹aM²bOχ(OR¹)_y(OOCR²)z Lp (I) wherein R¹ and R² may be the same or different and each represents a C6- C30 aryl, C1 -C40 alkyl, C5-C40 cycloalkyl, or siloxy group; M¹ and M² each is a metal selected from the groups consisting of elements of group IVB of the periodic table and Bi with the proviso that M¹ is different from M², preferably Ti, Zr, and Bi, a is an integer of from 1 to 18, b is an integer of from 0 to 16, with the proviso that the sum of a and b is at least 4, z is an integer of from 0 to 16, x is an integer of from 1 to 16, y is an integer of from 0 to 6, p is an integer of from 0 to 16, with the proviso that z, x, y, and p are selected such that each metal atom is bound to at least 4 oxygen atoms,

L is selected from OH, amine, alkoxide, acetylacetonate, isocyanate, alkyl, aryl, monoatomic oxygen, and OR¹, wherein R¹ has the meaning as defined above.

3. A curable composition according to claims 1 or 2, wherein the at least one metal M is selected from Zr, Ti and Bi.

4. A curable composition according to claims 1 to 3, wherein b is zero.

5. A curable composition according to claims 1 to 3, wherein a and b each is at least 1 and the sum of a and b is at least 4.

6. A curable composition according to claim 2, wherein M is Zr, a is 4, b is 0, x is 2, y is 0, z is 12, and p is 0.

7. A curable composition according to claims 1 to 6, wherein the binder B) is a polyol.

8. A curable composition according to claims 1 to 7, wherein the isocyanate A) is a polyisocyanate.

9. A curable composition according to claims 1 to 8 containing from 0.5 to 30 % by weight of component C) relative to the total weight of components (A), (B), and (C).

10. A kit of parts comprising as separate parts components A), B), and C) or a kit of parts comprising component B) as one separate part and a mixture of A) and C) as a second separate part or a kit of parts comprising component A) as a first separate part and a mixture of B) and C) as a second separate part according to any of claims 1 to 9 for joint application.

1 1. Use of metal oxo complexes as defined in claims 1 to 6 as cure promoter in curable compositions.

12. Use of metal oxo complexes as defined in claims 1 to 6 as catalyst for polyure- thane curing.

13. Coating obtainable by curing of a composition according to any of claims 1 to 9.