7 173 071

7,173,071 Title:

Photo-cured and stabilized coatings

Abstract:

Photo-curable coating formulations which comprise a durable and/or red-shifted reactable hydroxyphenylbenzotriazole ultraviolet light absorber (UVA) are effectively photocured employing a combination of .alpha.-hydroxy ketone and bisacylphosphine oxide photoinitiators. The reactable UVA's are reacted into the coating upon curing. The combination of the photoinitiators bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenylketone is especially effective for this purpose.

Claims:

What is claimed is:

1. A process for forming a protective film coating which process comprises curing a coating composition by irradiating said composition with ultraviolet radiation or daylightor with light sources equivalent to daylight, wherein said coating composition comprises a) at least one ethylenically unsaturated polymerizable compound, b) at least one durable and/or red-shifted reactable hydroxyphenylbenzotriazole UV absorbercomprising an ethylenically unsaturated polymerizable group and c) a combination of photoinitiators comprising i) at least one .alpha.-hydroxy ketone photoinitiator and ii) at least one bisacylphosphine oxide photoinitiator, wherein thehydroxyphenylbenzotriazoles of component b) are of the formula ##STR00010## where E.sub.1 is t-butyl or .alpha.-cumyl and G.sub.2 is phenylsulfone or --CF.sub.3; wherein the alpha-hydroxy ketone photoinitiator of component c) i) is of formula##STR00011## where R.sub.11 and R.sub.12 independently of one another are hydrogen, C.sub.1 C.sub.6 alkyl, phenyl, C.sub.1 C.sub.6 alkoxy, phenyl, C.sub.1 C.sub.6 alkoxy, OSiR.sub.16(R.sub.17).sub.2 or --O(CH.sub.2CH.sub.2O).sub.q--C.sub.1 C.sub.6 alkyl,or R.sub.11 and R.sub.12, together with the carbon atom to which they are attached, form a cyclohexyl ring; q is a number from 1 to 20; R.sub.13 is OH, C.sub.1 C.sub.16 alkoxy or --O(CH.sub.2CH.sub.2O).sub.q--C.sub.1 C.sub.6 alkyl; R.sub.14 ishydrogen, C.sub.1 C.sub.18 alkyl, C.sub.1 C.sub.18 alkoxy, --OCH.sub.2CH.sub.2--OR.sub.15, a group CH.sub.2.dbd.C(CH.sub.3)-- or is ##STR00012## I is a number from 2to 10; R.sub.15 is hydrogen, --COCH.dbd.CH.sub.2 or --COC(CH.sub.3).dbd.CH.sub.2; andR.sub.16 and R.sub.17 independently of one another are C.sub.1 C.sub.8 alkyl or phenyl; and wherein the bisacylphosphine oxide photoinitiator of component c) ii) is of formula ##STR00013## wherein R.sub.50, is C.sub.1 C.sub.12 alkyl, cyclohexyl orphenyl which is unsubstituted or is substituted by 1 to 4 halogen or C.sub.1 C.sub.8 alkyl, R.sub.51 and R.sub.52 are each independently of the other C.sub.1 C.sub.8 alkyl or C.sub.1 C.sub.8alkoxy, R.sub.53 is hydrogen or C.sub.1 C.sub.8 alkyl, andR.sub.54 is hydrogen or methyl.

2. A process according to claim 1 where the hydroxyphenylbenzotriazoles are ##STR00014##

3. A process according to claim 1 where in the .alpha.-hydroxy ketone photoinitiators, R.sub.11 and R.sub.12 independently of one another are hydrogen, C.sub.1 C.sub.6 alkyl or phenyl or R.sub.11 and R.sub.12, together with the carbon atom towhich they are attached, form a cyclohexyl ring; R.sub.13 is OH; and R.sub.14 is hydrogen, C.sub.1 C.sub.12 alkyl, C.sub.1 C.sub.12 alkoxy, --OCH.sub.2CH.sub.2OR.sub.15, --C(CH.sub.3).dbd.CH.sub.2 or is ##STR00015##

4. A process according to claim 1 where in the .alpha.-hydroxy ketone photoinitiators, R.sub.11 and R.sub.12 independently of one another are methyl or ethyl or R.sub.11 and R.sub.12, together with the carbon atom to which they are attached,form a cyclohexyl ring; R.sub.13 is hydrogen and R.sub.14 is hydrogen, C.sub.1 C.sub.4 alkyl, C.sub.1 C.sub.4 alkoxy, or --OCH.sub.2CH.sub.2OH.

5. A process according to claim 1 where the .alpha.-hydroxy ketone photoinitiators are selected from a group consisting of .alpha.-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone,2-hydroxy-2-methyl-1-(4-isopropylphenyl)propanone, 2-hydroxy-2-methyl-1-(4-dodecylphenyl)propanone and 2-hydroxy-2-methyl-1-[(2-hydroxyethoxy)phenyl]propanone.

6. A process according to claim 1 where in the bisacylphosphine oxide photoinitiators, R.sub.50 is C.sub.2 C.sub.10 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted by 1 to 4 C.sub.1 C.sub.4 alkyl, Cl or Br.

7. A process according to claim 1 where in the bisacylphosphine oxide photoinitiators, R.sub.50 is C.sub.4 C.sub.12 alkyl or cyclohexyl, R.sub.5, and R.sub.52 are each independently of the other C.sub.1 C.sub.8 alkyl or C.sub.1 C.sub.8alkoxyand R.sub.53 is hydrogen or C.sub.1 C.sub.8 alkyl.

8. A process according to claim 1 where in the bisacylphosphine oxide photoinitiators, R.sub.51 and R.sub.52 are methyl or methoxy and R.sub.53 is hydrogen or methyl and R.sub.50 is isobutyl, phenyl or isooctyl.

9. A process according to claim 1 where the bisacylphosphine oxide photoinitiator is bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide or bis(2,6-dimethoxybenzoyl)-isooctylphosphine oxide.

10. A process according to claim 1 where the hydroxyphenylbenzotriazoles are present from about 0.5% to about 5% by weight, based on the weight of the coating composition.

11. A process according to claim 1 where the hydroxyphenylbenzotriazole are present from about 2% to about 4% by weight, based on the weight of the coating composition.

12. A process according to claim 1 where the .alpha.-hydroxy ketone photoinitiators are present from about 1% to about 7% by weight, based on the weight of the coating composition.

13. A process according to claim 1 where the .alpha.-hydroxy ketone photoinitiators are present from about 2% to about 6% by weight, based on the weight of the coating composition.

14. A process according to claim 1 where the .alpha.-hydroxy ketone photoinitiators are present from about 3% to about 5% by weight, based on the weight of the coating composition.

15. A process according to claim 1 where the bisacylphosphine oxide photoinitiators are present from about 0.1% to about 2% by weight, based on the weight of the coating composition.

16. A process according to claim 1 where the bisacylphosphine oxide photoinitators are present from about 0.2% to about 1.5%, based on the weight of the coating composition.

17. A process according to claim 1 where the bisacylphosphine oxide photoinitators are present from about 0.5 to about 1% by weight, based on the weight of the coating composition.

18. A process according to claim 1 where the weight ratio of .alpha.-hydroxy ketone component i) to bisacylphosphine oxide component ii) is from about 5:1 to about 15:1.

19. A process according to claim 1 where the weight ratio of .alpha.-hydroxy ketone component i) to bisacylphosphine oxide component ii) is from about 7:1 to about 12:1.

20. A process according to claim 1 where the weight ratio of .alpha.-hydroxy ketone component i) to bisacylphosphine oxide component ii) is from about 8:1 to about 11:1.

21. A process according to claim 1 where the thickness of the protective film coating is from about 0.2 mil to about 5 mil.

22. A process according to claim 1 where the thickness of the protective film coating is from about 0.5 mil to about 3.5 mil.