Copolymerizable photoinitiators

A Copolymerizable benzophenone having a general formula I:

• wherein:
• X is O, S or NR3, and R3 is H or a linear or branched C1-C10 alkyl;
• R1 is H or methyl;
• and
• R2 is H, a halogen, a linear or branched C1-C10 alkoxy, a linear or branched C1-C10 alkyl, a linear or branched C1-C10 alkylthio or a group NR4R5,
• wherein R4 and R5 are independently linear or branched C1-C10 alkyl.

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

• wherein:
• X is O, S or NR3, and R3 is H or a linear or branched C1-C10 alkyl;
• R1 is H or methyl;
• and
• R2 is H, a halogen, a linear or branched C1-C10 alkoxy, a linear or branched C1-C10 alkyl, a linear or branched C1-C10 alkylthio or a group NR4R5,
• wherein R4 and R5 are independently linear or branched C1-C10 alkyl;
• comprising the steps of:
• A) Friedei-Crafts acylation of a diphenyl compound of formula (i):
• where X is S, O or NR3 and R3 is H or linear or branched C1-C10 alkyl,
• with a benzoyl halide of formula (ii),
• where R2 is H, halogen, linear or branched C1-C10 alkoxy, linear or branched C1-C10 alkyl, linear or branched C1-C10 alkylthio or a group NR4R5, in which R4 and R5 are independently linear or branched C1-C10 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 R1 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.

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 O, S or NR3, and R3 is H or a linear or branched C1-C10 alkyl;
• R1 is H or methyl;
• and
• R2 is H, a halogen, a linear or branched C1-C10 alkoxy, a linear or branched C1-C10 alkyl, a linear or branched C1-C10 alkylthio or a group NR4R5,
• wherein R4 and R5 are independently linear or branched C1-C10 alkyl.

A method for preparing a photocrosslinked polymer comprising:

• a′) preparing a photocrosslinkable polymer by chemically or thermally initiated radical polymerization of a polymerizable composition of claim 7;
• b′) applying the photocrosslinkable polymer on a substrate;
• and
• c′) photocrosslinking the photocrosslinkable polymer with a light source with emission bands in the UV-visible region.