Copolymerizable photoinitiators

1. A copolymerizable benzophenone having a general formula I:

wherein:

X is 0, S or NR 3 , and R 3 is H or a linear or branched C 1 -C 10 alkyl;

R 1 is H or methyl; and

R 2 is H, a halogen, a linear or branched C 1 -C 10 alkoxy, a linear or branched C 1 -C 10 alkyl, a linear or branched C 1 -C 10 alkylthio or a group NR 4 R 5 ,

wherein R 4 and R 5 are independently linear or branched C 1 -C 10 alkyl.

2. The copolymerizable benzophenone of claim 1 wherein in formula I X is 0 or S and R 2 is H, a linear or branched C 1 -C 5 alkyl or a linear or branched C 1 -C 5 alkoxy.

3. The copolymerizable benzophenone of claim 2 wherein in formula I X is 0 or S, R 1 is methyl, and R 2 is H.

4. A process for preparing a copolymerizable benzophenone having a general formula I:

wherein:

X is 0, S or NR 3 , and R 3 is H or a linear or branched C 1 -C 10 alkyl;

R 1 is H or methyl; and

R 2 is H, a halogen, a linear or branched C 1 -C 10 alkoxy, a linear or branched C 1 -C 10 alkyl, a linear or branched C 1 -C 10 alkylthio or a group NR 4 R 5 ,

wherein R 4 and R 5 are independently linear or branched C 1 -C 10 alkyl;

comprising the steps of:

A) Friedei-Crafts acylation of a diphenyl compound of formula (i):

where X is S, 0 or NR 3 and R 3 is H or linear or branched C 1 -C 10 alkyl, with a benzoyl halide of formula (ii),

where R 2 is H, halogen, linear or branched C 1 -C 10 alkoxy, linear or branched C 1 -C 10 alkyl, linear or branched C 1 -C 10 alkylthio or a group NR 4 R 5 , in which R 4 and R 5 are independently linear or branched C 1 -C 10 alkyl, and Y is Cl or Br,

the acylation being catalyzed by a Lewis acid and the molar ratio between the diphenyl compound of formula (i) and the benzoyl halide of formula (ii) being from about 1 to about 1.10, to obtain an intermediate benzophenone derivative;

B) Friedei-Crafts acylation of the intermediate benzophenone derivative with an alpha-halo acyl halide of formula (iii),

where Z and W are independently Br or Cl and R 1 is H or methyl, the molar ratio of the intermediate benzophenone derivative and the alphahalo acyl halide of formula (iii) being from about 1 to about 1.1; and

C) de-hydrohalogenation of the acylation product obtained from step B) by heating or maintaining the reaction mass at a temperature comprised between 10 and 40° C. for from about 30 to about 90 minutes and/or by adding further amounts of Lewis acid.

5. The process for preparing a copolymerizable benzophenone of claim 4 wherein the Lewis acid is aluminum trichloride.

6. The process for preparing a copolymerizable benzophenone of claim 4 wherein in the alpha-halo acyl halide of formula (iii), Z and W are Cl.

7. A polymerizable composition comprising from about 80 to about 99.9 parts by weight of at least one ethylenically unsaturated compound and from 0.1 to 20 parts by weight of at least one copolymerizable benzophenone of formula I

wherein:

X is 0, S or NR 3 , and R 3 is H or a linear or branched C 1 -C 10 alkyl;

R 1 is H or methyl; and

R 2 is H, a halogen, a linear or branched C 1 -C 10 alkoxy, a linear or branched C 1 -C 10 alkyl, a linear or branched C 1 -C 10 alkylthio or a group NR 4 R 5 ,

wherein R 4 and R 5 are independently linear or branched C 1 -C 10 alkyl.

8. The polymerizable composition of claim 7 comprising from about 85 to about 99 parts by weight of at least one ethylenically unsaturated compound and from about 1 to about 15 parts by weight of the copolymerizable benzophenone of formula I.

9. The polymerizable composition of claim 7 further comprising from about 0.2 to about 15% by weight of at least one coinitiator.

10. The polymerizable composition of claim 9 wherein the coinitiator is selected from the group consisting of aliphatic, cycloaliphatic, aromatic, arylaliphatic, heterocyclic, oligomeric and polymeric amines, and combinations thereof.

11. A method for coating a substrate comprising: a) applying on the substrate a polymerizable composition of claim 7 in an amount sufficient to result in a coating, after photopolymerization, having a thickness of from about 0.2 to about 100 micron; and

b) photopolymerizing the coating with a light source with emission bands in the UV-visible region.

12. The method of claim 11 wherein the polymerizable composition of claim 7 , comprises from about 85 to about 99 parts by weight of at least one ethylenically unsaturated compound and from about 1 to about 15 parts by weight of the copolymerizable benzophenone of formula I.

13. The method of claim 12 further comprising from about 0.2 to about 15% by weight of at least one coinitiator.

14. The method of claim 13 wherein the coinitiator is selected from the group consisting of aliphatic, cycloaliphatic, aromatic, arylaliphatic, heterocyclic, oligomeric and polymeric amines, and combinations thereof.