GB567776A - Improvements in or relating to light activated adhesives - Google Patents

Abstract

Surfaces, of which not more than one is opaque, are bonded together by interposing a cementing layer comprising a liquid photopolymerizable organic compound containing a CH2 = C< group, and a photopolymerization catalyst and exposing it to light through a transparent member of the assembly. Specified photopolymerizable compounds are acrylic and methacrylic acids, esters, amides and nitriles; methyl vinyl and phenyl vinyl ketones; acrolein; vinyl thioacetate, propionate, isobutyrate, acetate and chloracetate; indene and styrene; divinyl and phenyl vinyl ethers; N - vinyl succinimide; vinyl naphthalene; vinylidene chloride; ethylidene dimethacrylate; methylene dimethacrylate; chloroprene and isoprene. The photopolymerization catalyst is an organic compound having a chain of two or three adjacent carbon atoms, each attached to one oxygen atom, at least one of the oxygen atoms being linked by a double bond to a carbon, no oxygen atom being attached to more than one of the carbon atoms, any valencies of the oxygen atoms not satisfied by an adjacent carbon atom being satisfied by hydrogen or a monovalent hydrocarbon radical, and the valencies of the carbon chain not satisfied by oxygen being satisfied by hydrogen or monovalent aliphatic or aromatic radicals. Preferred classes are alpha-carbonyl alcohols (R.CO.CHOH.R1), acyloins and polyketaldonyl compounds (R.(CO) .R1, where x = 2 or 3). Specified are glycollic aldehyde, benzoin, acetoin, butyroin, 3-hydroxy-4-methyl-pentanone-2, toluin, tert.-butylbenzoin, 12-hydroxy-13-ketotetracosane, o- and p-tert.-butyltoluin, diacetyl, pentandione - 2.3, octanedione - 2.3, 1-phenyl butanedione-1.2, benzil, 2.2-dimethyl-4 - phenyl butanedione - 3.4, glyoxal, phenyl glyoxal, diphenyl triketone and 1.2-cyclohexanedione. The photopolymerizable compound may be mixed with a polymer of a compound containing a CH2 = C< group to form a syrup before cementing, and may contain also benzoyl, lauroyl, acetyl, butyroyl, succinyl peroxides or ascaridole. Opaque surfaces listed include metals, cloth, paper, wood, leather, natural or synthetic rubber; and transparent surfaces listed include glass and polymeric materials derived from polymers of compounds containing a CH2 = C< group. The irradiation by light may be stopped before polymerization is complete. The invention is of particular use in the uniting of sheets of polymethyl methacrylate, e.g. for aircraft, and includes the filling of crevices in sheets of polymethyl methacrylate. Specifications 567,777 and 567,778 are referred to.