Water-based photopolymerizable compositions and their use

Claim 2

A composition in the form of an aqueous dispersion comprising water, at least one dispersed cationically curable epoxy resin, a water-soluble colloid, and a photosensitive sulphonium or iodonium salt capable on exposure to actinic radiation of effecting cationic polymerisation and thus insolubilization of the said epoxy resin.

Claim 3

A composition according to claim 1 in which the curable compound is a mixture of (1) one or more low viscosity epoxy diluents selected from the group consisting of glycidyl ether, glycidyl acrylates, 4-vinylcyclohexene dioxide, limonene dioxide, 1,2-cyclohexene dioxide and 3,4-epoxycyclohexylmethyl-3,4-cyclohexanecarboxylate, and (2) one or more high molecular weight epoxy resins.

Claim 4

A composition according to claim 1 comprising, by weight of the said composition, 40-80% of water, 10-60% of epoxy resin (including reactive diluent), 4-14% of water soluble colloid, 1 to 10% of onium salt, and 0 to 50% of sensitiser effective in increasing the spectral sensitivity of the onium salt.

Claim 5

A composition according to claim 1 in which the photoinitiator is an iodonium salt of the formula: ##STR2## where X - is tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, trifluoromethanesulphonate, or perchlorate, and R 1 and R 2 are each selected from hydrogen, halogen, straight or branched alkyl, alkoxy, aryl, acyl, nitro or cyano.

Claim 6

A composition according to claim 4 in which the photoinitiator is 4,4-dimethyldiphenyliodonium hexafluorophosphate or diphenyliodonium hexafluorophosphate.

Claim 7

A composition according to claim 1 in which the photoinitiator is a sulphonium salt of the formula: (R.sup.3).sub.a (R.sup.4).sub.b (R.sup.5).sub.c S.sup.⊕.X.sup.⊖ where X - is tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, trifluoromethanesulphonate, perchlorate or hexafluoroantimonate, R 3 is a monovalent aromatic radical, which may be substituted by one or more alkyl, aryl, alkoxy, hydroxy, phenoxy, thiophenoxy, mercaptan or acyl groups or halogen atoms, R 4 is a monovalent organic aliphatic radical selected from alkyl, cycloalkyl and substituted alkyl, R 5 is a polyvalent organic radical forming a heterocyclic or fused ring structure with S + , a is a whole number from 0 to 3 inclusive, b is a whole number from 0 to 2 inclusive, and c is 0 or 1, and a+b+c=3.

Claim 8

A composition according to claim 6 in which the photoinitiator is a sulphonium salt of the formula: ##STR3##

Claim 9

A composition according to claim 1 which also comprises a sensitizer to increase the spectral sensitivity of the photosensitive onium salt.

Claim 10

A composition according to claim 8, in which the said sensitiser is 9,10-diethoxyanthracene or an alkylated 9,10-diethoxyanthracene.

Claim 11

A composition according to claim 1 which also comprises a surfactant as dispersion stabilizers.

Claim 12

A composition according to claim 1 in which the said colloid is polyvinylalcohol, polyvinylpyrrolidone, gelatin, hydroxyethylcellulose or hydroxypropylcellulose.

Claim 13

A composition according to claim 1 which also comprises one or more of an inert polymeric filler, an inert organic filler, a plasticiser, an organic solvent, a biocide, a defoamer, a pigment, or a dye.

Claim 14

A composition according to claim 12 in which the said plasticizer is dibutylphthalate.

Claim 15

A composition according to claim 12 in which the said inert filler is a polyvinylacetate homopolymer, a polyvinylacetate-polyvinylchloride copolymer, starch, silica, kaolin or titanium dioxide.

Claim 16

A composition according to claim 12 comprising, by weight of the said composition, 50 to 70% of water, 25 to 50% of epoxy resin (including reactive diluent), 2 to 5% of iodonium or sulphonium salt, 0 to 3% of sensitiser effective in increasing the spectral sensitivity of the onium salt, 0 to 2% of an inert polymer, 0 to 2% of a surfactant, 0 to 3% of a plasticiser, 4 to 14% of a water-soluble colloid, and 0 to 15% of organic solvent.

Claim 17

A composition according to claim 10 in which the surfactant is a non-ionic surfactant.

Claim 18

A composition according to claim 12 in which the dye is one which gives a colored contrast on exposure to actinic light.