| 摘要 |
<p>Coating compositions suitable as primers for methyl methacrylate top-coats comprise pigment, solvent and a resin binder having as essential constituents 55-95% of an oil modified alkyd resin, 3-20% of an aminoplast and 1-50% of a vinyl acetate polymer, copolymer or mixture of polymers and/or copolymers. Conventional baking-type alkyd resins are used. Numerous polycarboxylic acids and polyols are listed. The alkyds are modified during preparation by addition of drying oils, semi-drying oils, nondrying oils, fatty acids derived from these oils, or tall oil. Any conventional aminoplast resin compatible with the other resins and soluble in the solvents therefor, can be used. When a vinyl acetate copolymer is used, it contains less than 40% of another ethylenically unsaturated compound such as vinyl stearate or oleate, vinyl chloride, crotonic acid, maleate esters, itaconate or citraconate esters or mixtures. In addition to the essential constituents of the binder, up to 10% of esterified epoxyhydroxy polyether may be added. The pigments specified include metallic flakes, oxides, hydroxides and salts, carbon black and organic dyes ; they should be present in an amount above the critical pigment volume concentration. In the examples the composition consists of dehydrated castor oil-modified glycerol phthalate, a butylated urea-formaldehyde resin, the reaction product of epichlorohydrin and bis-(4-hydroxyphenyl)-2, -2-propane with dehydrated castor oil, a pigment made up from Fe2O3, Al2O3 and Si O2, a complex mixture of aromatic solvents, and (1) a copolymer from 92% vinyl acetate and 8% di (2-ethylhexyl) maleate (2) a vinyl acetate homopolymer (5) vinyl acetate copolymerised with (a) vinyl stearate (b) lauryl maleate. Specifications 483,399, 763,158 and 807,895 are referred to.ALSO:A resinous coating composition suitable as a primer for methyl methacrylate top-coats comprises pigment, solvent and a resin binder having as essential constituents oil modified alkyd resin, aminoplast resin and a vinyl acetate polymer or copolymer (see Group IV(a)). Preferably an esterified epoxy-hydroxy polyether resin is also included. The coating composition can be applied to the substrate by any of the standard fluid coating techniques such as flow, dip, spray, brush or roller coating, and then baked. The substrates can be composed of metal, glass, ceramics, asbestos or wood.</p> |
