Polymerizable solutions of methyl methacrylate polymers in methyl methacrylate

摘要

A polymerizable composition comprises a methyl methacrylate homopolymer, or copolymer, dissolved in methyl methacrylate monomer, a polymerizable methacrylate compound having at least 3 methacrylate ester groups being incorporated in the composition as cross-linking agent. Polymers specified include copolymers of methyl methacrylate with one or more alkyl (meth)acrylates, e.g. ethylacrylate, n-butyl methacrylate or 2-ethylhexylacrylate, unsaturated acids, e.g. methacrylic acid, a -halo-substituted alkylacrylates, acrylonitrile, vinyl acetate, vinyl chloride or fluoride, or vinylidene chloride or fluoride. One or more of the aforesaid monomers may be included in the monomer solvent for the polymer. Specified polymethacrylate compounds include glycerol trimethacrylate, pentaerythritol trimethacrylate or tetramethacrylate, glucose pentamethacrylate and trimethylol-propane trimethacrylate. In Example 1, a solution of polymethyl methacrylate in methyl methacrylate is mixed with trimethylolpropane trimethacrylate, a paste of benzoyl peroxide catalyst and butyl benzyl phthalate plasticizer, hydroquinone, TiO2 and paraffin wax and finally N,N-dimethyl-p-toluidine is added as activator. The constituents of the compositions of the invention in Examples 2 and 3 are the same as those in Example 1, with the following exceptions: in Example 2, the polymer is a methyl methacrylate/methacrylic acid copolymer and the catalyst is bis-(p-chlorobenzoyl) peroxide; in Example 3, the polymethacrylate compound is pentaerythritol tetramethacrylate and the stabilizer is 2,4-dimethyl-6-tertiarybutyl/phenol.ALSO:A substrate is coated with a composition comprising a methyl methacrylate homo-or copolymer dissolved in methyl methacrylate monomer and, as cross-linking agent, a polymerizable compound containing at least 3 methacrylate ester groups. The coating is hardened by polymerizing the composition, preferably by inclusion of a peroxide compound and an amine activator. Two identical coating compositions may be prepared, except that one contains a peroxide and the other an amine, and mixed immediately before application, during application or after application e.g. by spraying or curtain coating one of said composition on to the substrate and then applying the other. Alternatively, either peroxide or the amine is incorporated in a prime coating, e.g. in a solution or dispersion of polymethyl methacrylate, polyvinyl acetate, nitro-cellulose, cellulose acetate butyrate, a vinyl chloride polymer or an alkyd resin, the primer solvent is evaporated and the composition of the invention, containing the second catalyst component, applied. During hardening the coated substrate may be covered with glass or immersed in water, or paraffin wax may be included in the coating to form a vapour-impermeable layer over the surface. Stabilizers, plasticizers, pigments, fillers and extenders, pigment dispersing agents, colour stabilizers, antifoam agents and mildew inhibitors may be included in the coating applied. In Example 1 glass plates are coated with a solution in methyl methacrylate of (1) polymethyl methacrylate, (2) trimethylolpropane trimethacrylate, (3) titanium dioxide, (4) paraffin wax, (5) benzoyl peroxide, (6) N, N-dimethyl p-toluidine, (7) hydroquinone and (8) butyl benzyl phthalate. In Example 2 (1) is replaced by a methyl methacrylate methylatemethacrylic acid copolymer and (5) by bis(p-chlorobenzoyl) peroxide. In Example 3 (2) is pentaerythritol tetramethacrylate and stabilizer (7) is 2, 4-dimethyl-6-tert butyl phenol.