GB903333A - Improved methacrylate coating composition - Google Patents

Abstract

A coating composition comprises nitrocellulose and a copolymer of 10-30% methyl methacrylate and 90-70% butyl methacrylate having a reduced viscosity of 0,35-0,46, the proportion of copolymer to nitrocellulose being from 3:1 to 1:1 by weight. Reduced viscosity is defined as <FORM:0903333/IV(a)/1> where C=gms. copolymer per 100 mls. solution in ethylene dichloride and is measured at 25 DEG C. The copolymer may also contain minor proportions of other methacrylate or acrylate esters, e.g. ethyl, propyl, butyl and octyl acrylates and similar or higher alkyl methacrylates, or esters of other unsaturated acids, e.g. maleic and itaconic acids, and acrylic and methacrylic acids, e.g. 1-3% by weight methacrylic acid. Small proportions of other film-forming materials, e.g. polyethylene or alkyd resins may also be incorporated. Desirably the proportion of copolymer to nitrocellulose is within the range of from 2:1 to 1,5:1 by weight, and the nitrocellulose of a type containing approximately 12% nitrogen and, in solution in a mixture of 95 parts by volume of acetone and 5 parts by volume of water, having a viscosity in the range from 8 poises at 20 DEG C., when 40 gms. of the nitrocellulose are dissolved in 100 mls. of the solvent mixture to 40 poises at 20 DEG C. when 20 gms. of the nitrocellulose are dissolved in 100 mls. of the solvent-mixture. Plasticizers may be incorporated in a proportion of up to 30% of the combined weight of the copolymer and nitrocellulose, e.g. methyl cyclohexanol phthalate, butyl benzyl phthalate, dioctyl phthalate, di-n-butyl isophthalate, butyl citrate, polypropylene adipate and other alkyl and aryl phthalates and phosphates. Conventional nitrocellulose lacquer solvents may be used, e.g. aromatic hydrocarbons, ketones, esters, glycol ethers and alcohols. Those specified include toluene, xylol, acetone, methyl isobutyl ketone, ethylene glycol monoethyl ether acetate, isopropyl alcohol and n-butyl alcohol. Pigments specified include titanium dioxide.