GB567523A - Coating compositions - Google Patents

Abstract

A surfacing composition comprises a solid granular ethyl cellulose of ethoxy content between 46.8 per cent and 48.5 per cent, dispersed in a vehicle in which the ethyl cellulose is substantially insoluble at normal temperature and which comprises a drying or semi-drying oil or oil-modified alkyd resin, but is free from volatile solvent. The composition may be subjected to a baking treatment directly after it has been applied to an article, or a top-coating composition may be applied and the two compositions may be baked together. The baking may be carried out at 275-350 DEG F. and for a sufficient length of time to cause fusion of the ethyl cellulose particles and partial solution in the remainder of the composition. The viscosity of the ethyl cellulose as determined at 25 DEG C. on a 5 per cent solution in a solvent composed of 80 parts toluene and 20 parts denatured ethyl alcohol, by weight, may be from 7 to 100 centipoises. The ethyl cellulose should be present in an amount of 6 to 10 per cent of the total composition. The liquid vehicle may be a drying or semi-drying oil or an alkyd resin modified with such an oil. It should be substantially free from volatile matter so as to avoid swelling and blistering on baking. The vehicle may have an acid number of 4-10 and a viscosity of 9-17 poises. The oil-modified alkyd resin may be one which has been modified with a synthetic drying oil or synthetic drying oil acid, with or without monobasic acids or natural resins. In examples, ethyl cellulose grains are mixed with soya bean or linseed oil-modified glyceryl phthalate, dehydrated castor oil or heat-bodied linseed oil, and barytes, whiting, lithopone, talc, or titanium dioxide, to form a white putty-like composition. In other examples, ethyl cellulose grains are mixed with heat-bodied linseed oil or soya bean oil and lithopone and barytes. Other pigments which may be used are zinc oxide, antimony oxide, white lead, blanc fixe, silica, china clay, powdered slate, asbestine, red iron oxide, metal chromates, cyanides, sulphides, phosphates, selenides, molybdates, phthalocyanines, and organic dyes. The top-coat may be of the lacquer or enamel type. In an example, the top-coat composition comprises titanium dioxide, zinc oxide, soya bean oil-modified glyceryl phthalate, dehydrated castor oil-modified glyceryl phthalate, urea-formaldehyde-monohydric alcohol resin, petroleum naphtha, butyl alcohol and xylol. In another example, the top-coat composition comprises a mixture of glyceryl phthalate condensation products modified respectively with 52 per cent linseed oil, 40 per cent linseed oil, 46 per cent linseed and chinawood oil, together with chinawood oil-modified phenol-formaldehyde resin, iron oxide, ferrite yellow, bone black, titanium dioxide, antimony oxide, diatomaceous earth, silica, cresylic acid, manganese naphthenate and petroleum naphtha.