Thermally stable cationic photocurable compositions

1. A cationic photocurable composition comprising

at least one cationically polymerizable compound,

at least one onium salt photoinitiator,

at least one moisture scavenger, and

at least one stabilizer selected from the group consisting of sterically hindered nitroxyl stabilizers, sterically hindered phenolic antioxidants, organic phosphorous stabilizers and mixtures thereof;

wherein the moisture scavenger is an activated substantially water free zeolite or triethylorthoformate,

wherein the weight ratio of the moisture scavenger to the stabilizer is from 100-0.1 to 100-10.

2. A composition according to claim, 1 wherein the stabilizer is a sterically hindered nitroxyl compound.

3. A composition according to claim 1 wherein the phenolic antioxidant is an ester of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with a monohydric alcohol, a polyhydric alcohol or a thiol.

4. A composition according to claim 3 wherein the nitroxyl stabilizer is bis(1-oxyl-2,2,6,6tetramethylpiperidin-4-yl) sebacate or 4-hydroxy-1-oxyl-2,2,6,6-tetramethylpiperidine.

5. A composition according to claim 3 , wherein the organic phosphorous stabilizer is selected from the group consisting of

6. A composition according to claim 1 , wherein the onium salt photoinitiator is of the formula (I), or (IV)

R 1 and R 2 independently of one another are phenyl substituted by C 1 -C 24 alkyl or C 1 -C 24 alkoxy;

A − is an anion;

R 103 is a direct bond, S, O, CH 2 , (CH 2 ) 2 , CO or NR 109 ;

R 104 , R 105 , R 106 and R 107 independently of one another are H, C 1 -C 20 alkyl, C 3 -C 8 cycloalkyl, C 1 -C 20 alkoxy, C 2 -C 20 alkenyl, CN, OH, halogen, C 1 -C 6 alkylthio, phenyl, naphthyl, phenyl-C 1 -C 7 alkyl, naphtyl-C 1 -C 3 alkyl, phenoxy, naphthyloxy, phenyl-C 1 -C 7 alkyloxy, naphtyl-C 1 -C 3 alkyloxy, phenyl-C 2 -C 6 alkenyl, naphthyl-C 2 -C 4 alkenyl, S-phenyl, (CO)R 109 , O(CO)R 109 , (CO)OR 109 , SO 2 R 109 or OSO 2 R 109 ;

R 108 is C 1 -C 20 alkyl, C 1 -C 20 hydroxyalkyl,

R 109 is H, C 1 C 12 alkyl, C 1 -C 12 hydroxyalkyl, phenyl, naphthyl or biphenylyl;

R 110 is a direct bond, S, O or CH 2 ;

R 111 , R 112 , R 113 and R 114 independently of one another have one of the meanings as given for R 104 ;

or R 111 and R 113 are joined to form a fused ring system with the benzene rings to which they are attached;

R 115 is

 and

Z A is an anion.

7. A composition according to claim 6 , wherein the onium salt photoinitiator is of the formula (I).

8. A composition according to claim 1 , wherein the content of moisture scavenger is from 0.01 to 20 wt. %.

9. A composition according to claim 1 , wherein the content of the stabilizer is from 10 −4 to 1 wt %, based on the total composition.

10. A cationic photoinitiator composition comprising

at least one onium salt photoinitiator;

at least one moisture scavenger; and

at least one stabilizer selected from the group consisting of sterically hindered nitroxyl stabilizers, sterically hindered phenolic antioxidants, organic phosphorous stabilizers and mixtures thereof;

wherein the moisture scavenger is an activated substantially water free zeolite or triethylorthoformate,

wherein the weight ratio of the moisture scavenger to the stabilizer is from 100-0.1 to 100-10.

11. A method for the photopolymerisation or crosslinking of a composition comprising

at least one cationically polymerizable compound,

at least one onium salt photoinitiator,

at least one moisture scavenger, and

at least one stabilizer selected from the group consisting of sterically hindered nitroxyl stabilizers, sterically hindered phenolic antioxidants, organic phosphorous stabilizers and mixtures thereof,

characterized in that the composition is subjected to radiation having a wavelength in the range of 200 nm to 600 nm;

wherein the moisture scavenger is an activated substantially water free zeolite or triethylorthoformate,

wherein the weight ratio of the moisture scavenger to the stabilizer is from 100-0.1 to 100-10.

12. A surface coating, a liquid industrial coating, a coil coating, a can coating, a powder coating, a printing ink, a printing plate, a dental composition, a stereolithography resin, an adhesive, an anti-adhesive coating, a color filter, a resist material or an image-recording material comprising a composition according to claim 1 .

13. A method according to claim 11 for the preparation of a surface coating, a liquid industrial coating, a coil coating, a can coating, a powder coating, a printing ink, a printing plate, a dental composition, a stereolithography resin, an adhesive, an anti-adhesive coating, a color filter, a resist material or an image-recording material.

14. A coated substrate that is coated on at least one surface with a composition according to claim 1 .

15. A composition according to claim 6 , wherein Z A is selected from the group consisting of PF 6 , SbF 6 , AsF 6 , BF 4 , (C 6 F 5 ) 4 B, CI, Br, HSO 4 , CF 3 —SO 3 , F—SO 3 ,

CH 3 —SO 3 , CIO 4 , PO 4 , NO 3 , SO 4 , CH 3 —SO 4 and