Radiation curable powder coating compositions

1. A radiation curable powder composition which comprises, per 100 parts by weight of (a), (b) and (c),

(a) 70 to 99.4 parts by weight of at least one ethylenically unsaturated resin,

(b) 0.5 to 20 parts by weight of at least one phosphorous containing compound, and

(c) 0.1 to 10 parts by weight of at least one amine,

wherein the phosphorous containing compound (b) is an organic derivative of phosphinic acid, phosphonic acid or phosphoric acid, and

wherein said organic derivative has at least one organic moiety having at least one functional group.

2. The radiation curable powder composition according to claim 1 ,

wherein the amine (c) is an organic compound comprising at least one group of formula

wherein each R′ independently represents hydrogen, alkyl, alkenyl, aryl, heterocycle or a combination thereof, each optionally substituted by one or more hydroxyl and/or amino derivatives, and optionally containing 1 to 3 ether bridges, 1 to 3 amino bridges, 1 to 3 —CO—bridges, and/or 1 to 3 —COO—bridges; wherein two R′ moieties may be linked together in order to form a ring.

3. The radiation curable powder composition according to claim 2 ,

wherein the amine (c) is selected from the group consisting of a compound of formula (I), a compound of formula (II), a compound of formula (III) a compound of formula (IV), a polymer containing one or more groups of formula (V), and a mixture thereof,

wherein

each R 1 is independently chosen from hydrogen, alkyl, alkenyl, aryl, heterocycle or combinations thereof, each optionally substituted by one or more hydroxyl, and optionally containing 1 to 3 ether bridges, 1 to 3 —CO—bridges, and/or 1 to 3 —COO— bridges; wherein two R 1 moieties may be linked together in order to form a ring;

each R independently represents an alkylene, alkenylene, arylene or aralkylene chain which may contain from 1 to 3 ether bridges, 1 to 3 —CO— bridges and/or 1 to 3 —COO— bridges and which is optionally substituted by one or more hydroxyl.

4. The radiation curable powder composition according to claim 3 ,

wherein the amine (c) is selected from the group consisting of propylamine, butylamine, sec-butylamine, tert-butylamine, pentylamine, hexylamine, 2-ethylhexylamine, cyclohexylamine, octylamine, aniline, ethylenediam me, 1,2-diaminopropane, 1,3-diaminopropane, 2,2-dimethyl-1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-exanediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 3-(methylamino)propylamine, 3 -(dimethylamino)propylamine, 3 -(dimethylamino)propylamine, isophoronediamine, 4, 4′-diaminodicyclohexylmethane 3,3 ′-dimethyl-4,4′-diamino-dicyclohexylmethane, 4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 3-(diethylamino)propylamine, 3-methoxypropylamine, N-ethyl-1,2-dimethylpro-pylamine, iminobispropylamine, 3,3 ′-iminobis(N,N′-dimethyipropylamine), diethylamine, dipropylamine, dibutylamine, dihexylamine, di-(2-ethylhexyl)amine, triethylamine, tn-n-butylamine, tributylamine, trihexylamine, tni-(2-ethylhexyl)amine, tridecylamine, 3-amino-1-propanol, aminoethoxyethanol, aminoethanol, N,N-bis(3-aminopropyl)methylamine, 2-(diethylamino)ethylamine, diethylenetriamine, 2-methoxyethylamine, methylenedianiline, 4,7,10-trioxatridecane- 1,1 3-diamine, N—(2-aminoethyl)- 1,2-ethanediamine, di(2-methoxyethyl)amine, N,N′-bis (3-aminopropyl)ethylenediamine, N-(2-aminoethyl)- 1,3-propylenediamine, N,N-diethylethanolamine, N,N-dimethylaminodiglycol, N,N-dimethylbutylamine, N,N-dimethylcyclohexylamine, N,N-dimethylethanolamine, dimethylethylamine, ditridecylamine, N-ethylcyclohexylamine, N-methylcyclohexylamine, methyldiethanolamine, N-mono-methylethanolamine, N,N,N′,N″,N″-pentamethyldiethylenetriam me, N,N,N′,N′-tetramethyl- 1,6-hexanediamine, N,N,N′,N′-tetraethyl- 1,6-hexanediamine, 1,8-diazabicyclo-5,4,0-undec-7-ene, 1,4-diazabicyclo-2,2,2-octane, 1,3,5 -tnis(dimethylaminopropyl)-hexahydrotriazine, 1,4-dimethylpiperazine, N,N ′-dimethylpiperazine, 2,2,2 -dimorpholinodiethylether, morpholine, N-methylmorpholine, N-ethylmorpholine, cis-2,6-dimethylmorpholine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-methylpiperidine, N-ethylpiperidine, hydroxyethylpiperidine, imidazole, 2,4,6-triamino-1,3,5-triazine optionally substituted by one or more of hydroxymethyl, methoxymethyl and/or butoxymethyl, andamine containing acrylic copolymer incorporating at least one of 2-(tert-butylamino)ethyl methacrylate and 2-(diethyl-amino)ethyl methacrylate.

5. The radiation curable powder composition according to claim 4 ,

wherein the amine is N,N,N′,N′-tetramethyl- 1,6-hexanediamine.

6. The radiation curable powder composition according to claim 1 ,

wherein the phosphorous containing compound (b) corresponds to formula (VI):

wherein

each R 2 independently represents alkyl, aryl or alkenyl, each optionally containing 1 to 3 ether bridges, 1 to 3 —CO— bridges, and/or 1 to 3 —COO— bridges, and each optionally substituted by 1 to 10 halogen, hydroxyl and/or amino derivatives,

each R 3 is independently hydrogen or R 4 , wherein R 4 is as defined for R 2 ; and

n is0to3.

7. The radiation curable powder composition according to claim 6 ,

wherein the phosphorous containing compound (b) corresponds to formula VII:

wherein

each R 5 is independently hydrogen or an alkyl group having from 1 to 8 carbon atoms;

each R 6 is independently selected from the group consisting of hydrogen, an alkyl group having from 1 to 8 carbon atoms, and a haloalkyl group having from 1 to 8 carbon atoms;

each A is independently an alkylene group containing from 1 to 9 carbon atoms, optionally containing 1 to 3 ether bridges; and

m is 1 to 3.

8. The radiation curable powder composition according to claim 7 ,

wherein R 5 is hydrogen or methyl, R 6 is hydrogen, A is an ethylene group, and m is 1, 2 or 3.

9. The radiation curable powder composition according to claim 1 ,

wherein the ethylenically unsaturated resin (a) is selected from the group consisting of

(a1) ethylenically unsaturated group containing polyesters,

(a2) ethylenically unsaturated group containing acrylic copolymers,

(a3) ethylenically unsaturated group containing polyphenoxy resins,

(a4) ethylenically unsaturated group containing non-aromatic epoxy resins,

(a5) ethylenically unsaturated group containing polyurethanes,

(a6) ethylenically unsaturated group containing polyesteramides,

and mixtures thereof.

10. The radiation curable powder composition according to claim 9 ,

wherein the ethylenically unsaturated group containing polyester (a1) is obtained from:

the reaction of a diisocyanate with an hydroxyalkyl(meth)acrylate and a hydroxyl group containing polyester, or

the reaction of a compound having an ethylenically unsaturated group and an epoxy functional group with a polyester containing carboxyl groups.

11. The radiation curable powder composition according to claim 9 , wherein the ethylenically unsaturated polyester (a1) has

a number average molecular weight ranging from 1,100 - 16,000, and

a degree of unsaturation from 0.17 to 4.00 milliequivalents of double bonds per gram of polyester.

12. The radiation curable powder composition according to claim 9 , comprising at least one ethylenically unsaturated group containing polyester (a1) which is amorphous, or a mixture of at least one ethylenically unsaturated group containing polyester (a1) which is amorphous with at least one ethylenically unsaturated group containing polyester (a1) which is semi-crystalline.

13. The radiation curable powder composition according to claim 9 ,

wherein the ethylenically unsaturated group containing acrylic copolymers (a2) are obtained from the reaction of:

an acrylic copolymer obtained from 40 to 95 mole percentage of at least one monomer having acrylic or methacrylic groups, 0 to 60 mole percentage of another ethylenically unsaturated monomer, and 5 to 60 mole percentage of an ethylenically unsaturated monomer having functional groups selected from the group consisting of epoxy, carboxyl, hydroxyl and isocyanate, with

a compound having an ethylenically unsaturated group and a functional group capable of reacting with carboxyl, epoxy, isocyanate or hydroxyl, and

wherein said acrylic copolymers (a2) have:

a number average molecular weight ranging from 1,000 to 20,000,

a degree of unsaturation from 0.35 to 3.50 milliequivalents of double bonds per gram of acrylic copolymer,

a melt viscosity (cone/plate at 200° C.) of less than 50,000 mPa.s, and

a glass transition temperature ranging from 45 to 100° C.

14. The radiation curable powder composition according to claim 9 ,

wherein the ethylenically unsaturated group containing polyphenoxy resin (a3) is the reaction product of (meth)acrylic acid with a glycidyl group containing polyphenoxy resin, and wherein said polyphenoxy resin (a3) has:

a number average molecular weight ranging from 500 to 5,000,

a glass transition temperature ranging from 30 to 80° C.,

a degree of unsaturation ranging from 0.2 to 6.0 milliequivalents of double bonds per gram of polyphenoxy resin, and

a melt viscosity (cone/plate at 200° C.) of less than 25,000 mPa.s.

15. The radiation curable powder composition according to claim 9 , comprising at least one ethylenically unsaturated group containing polyester (a1), or a mixture of least one ethylenically unsaturated group containing polyester (a1) with at least one ethylenically unsaturated group containing polyphenoxy resin (a3) and/or at least one ethylenically unsaturated group containing acrylic copolymer (a2).

16. The radiation curable powder composition according to claim 1 , which comprises, per 100 parts of the total weight of(a), (b), (c) and (d),

from 0 to 20 parts by weight of an ethylenically unsaturated monomer or oligomer (d),

from 0 to 15 parts by weight of photo-initiators,

from 0 to 10 parts by weight of additives selected from the group consisting of UV light absorbers, light stabilizers, fluidity-regulating agents, degassing agents and coating properties modifying substances, and/or

from 0 to 40 parts by weight of pigments and/or fillers.

17. A powder varnish or powder paint comprising the radiation curable powder composition according to claim 1 .

18. A process for coating an article, wherein the radiation curable powder composition according to claim 1 is deposited on the article, followed by melting the thus obtained coating and radiation curing the coating in the molten state.

19. An article that is partially or entirely coated by the process of claim 18 .

20. The curable powder composition according to claim 1 , wherein said organic derivative of phosphinic acid, phosphonic acid or phosphoric acid (b) is unsaturated.

21. The curable powder composition according to claim 20 , wherein said unsaturated derivative (b) has at least one unit of olefinic unsaturation.

22. The curable powder composition according to claim 21 , wherein said at least one unit of olefinic unsaturation in the phosphorous containing compound (b) is terminally located.

23. The curable powder composition according to claim 9 , wherein the ethylenically unsaturated resin (a) is an ethylenically unsaturated group containing polyester (a1).

24. The curable powder composition according to claim 23 , wherein the ethylenically unsaturated resin (a) comprises at least one further ethylenically unsaturated resin selected from the group consisting of ethylenically unsaturated group containing acrylic copolymers (a2), ethylenically unsaturated group containing polyphenoxy resins (a3) and ethylenically unsaturated group containing non-aromatic epoxy resins (a4).