GB912022A - Improvements in or relating to photo-sensitive epoxy resin compositions - Google Patents

Abstract

A variety of surfaces may be coated with a composition comprising an epoxy resin and a curing agent therefor which contains the group <FORM:0912022/III/1> and is photoactivatable. The coating is then exposed and cured. If part of the surface is masked, e.g. with a negative, the masked, uncured portions may be washed away with a solvent to give printing plates or decorative effects (see Groups XV and XX). In Example (1) glass plates are coated with a solution of methyl vinyl nitros amine in a conventional epoxy resin, the mixing and coating being conducted in subdued yellow light. The coated plates are then exposed to U.V. light, and may subsequently be cured by heating. In the other examples other materials, e.g. silicated aluminium, polyethylene terephthalate, and chromic acid treated aluminium are similarly coated. It is also stated that aluminium, zinc, copper, magnesium, iron, noble metals, wood, plastics, ceramics, and glass may be coated. A variety of solvents may be used and the coatings may be applied by knife-coating melted materials, or by painting, brushing or dipping.ALSO:A composition comprises an epoxy resin and a curing agent therefor which contains the group <FORM:0912022/IV(a)/1> and is photoactivatable. Long lists of suitable and unsuitable nitrosamines are given, of which the following are used in the specific examples:-methyl vinyl nitrosamine, allyl prop-1-enyl nitrosamine, 1,2-bis(vinyl nitrosamino)ethane, and 1,4-bis(vinyl nitrosamino) cyclohexane. The specified epoxy resins are polyglycidyl ethers of diethylene glycol or of bisphenol A, polyglycidyl(meth)-acrylate, and vinyl cyclohexene dioxides. Long lists of suitable solvents are also given which include ketones, ethers, esters, halohydrocarbons and xylene. In Example (4) there is also added an acid-terminated polyester derived from isosebacic acid, ethylene glycol, and glycerol. The compositions are illuminated and then cured. Uses: The compositions may be used to coat a variety of materials, e.g. for ornamental purposes, and if a mask is used when the surface is illuminated, the masked, uncured portions may be washed away to provide printing plates (see Group XX). Spacers and insulators for electrical equipment may be prepared by coating a sheet of PTFE, curing and then removing the cured coating. Paper and cloth may also be coated (see Group VIII).ALSO:Ethylenically a ,b - unsaturated secondary nitrosamines are prepared by nitrosation of the appropriate secondary b -haloamines and by subsequent dehydrohalogenation. In examples (a) N-benzylethanolamine is chlorinated with thionyl chloride, to form N-benzyl-b -chloroethylamine hydrochloride, which is nitrosated with NaNO2 in aqueous HCl to form N-nitroso-N-benzyl-b -chloroethylamine, which is dehydrohalogenated with Na methoxide in ethereal solution to form benzyl vinyl nitrosamine. (b) N,N1-di-(b -hydroxyethyl)ethylene diamine dihydrochloride is similarly treated, except that PCl5 is the chlorinating agent, to give N,N1-dinitroso-N,N1-divinyl ethylene diamine. Alternatively an allyl nitrosamine may undergo rearrangement in the presence of a base to form the corresponding a ,b -propenyl nitrosamine. In an example allyl decyl nitrosamine is converted into prop-1-enyl decyl nitrosamine in the presence of Na and ethenol. The preferred nitrosamines are of the formulae:- <FORM:0912022/IV (b)/1> <FORM:0912022/IV (b)/2> <FORM:0912022/IV (b)/3> where n is 1 or 2; R1 is H, alkyl of up to 7C, or cycloalkyl of 5-6C; R2 and R3 are H, alkyl or cycloalkyl such that the sum of C atoms in R1, R2 and R3 is not greater than 16; R4 is alkyl, alkenyl, aralkyl, cycloalkyl, alkylene, aralkylene, or cycloalkylene, in which any ethylenic unsaturation is at least 1C from the C by which R4 is attached to the N atom of the nitrosamine group; and Z is an alkylene radical the skeleton of which comprises the carbon atoms necessary to complete a ring having from 5-6 members.