GB543913A - Improvements in or relating to coating compositions - Google Patents

Abstract

543,913. Cellulose derivative compositions ; resinous condensation products. DU PONT DE NEMOURS & CO., E. 1. Sept. 13, 1940, No. 14163. Convention date, Sept. 27, 1939. [Classes 2 (ii) and 2 (iii)] A coating composition comprises a polyvinyl butyraldehyde resin and a cellulose derivative compatible therewith, the proportions falling between 75 parts of resin to 25 parts of cellulose derivative and 25 parts of resin to 75 parts of cellulose derivative. Preferably, it comprises also a synthetic or natural resin which is compatible with the other two ingredients. The composition is particularly suitable for priming purposes. It may be applied by spraying, brushing, dipping, or other methods to wood or other surfaces. It gives .coatings which are themselves resistant to scratching and which impart a high degree of scratch-resistance to superposed top coatings. The polyvinyl resin may be obtained by treating a polyvinyl acetate with a hydrolysing agent (e.g. sulphuric acid) and condensing the product with butyraldehyde to give a solid but soluble resinous body. It may be condensed to the extent of 80 per cent. of butyral groups with not more than 2 per cent. of residual acetate groups and 18 per cent. of residual hydroxyl groups. The cellulose derivative may be cellulose nitrate or ethyl cellulose. The additional resin may be shellac, or a sulphonamide resin such as formaldehyde-p-toluene sulphonamide resin. In an example, polyvinyl butyral resin is mixed with cellulose nitrate of low viscosity type, shellac, ethyl alcohol, n-butyl alcohol, toluol, n-butyl acetate, amyl acetate, and ethyl acetate. The polyvinyl resin used gives a viscosity of 3,000 centipoises when in the form of a 20 per cent solution in a mixture of denatured ethyl alcohol 52 per cent., and toluol 28 per cent. When the primer coating is dry, it is roughened by sanding and then a top coat of cellulose lacquer is applied. This may consist of low viscosity cellulose nitrate, blown castor oil,. damar resin, ethyl alcohol, n-butyl alcohol, ethyl acetate, n-butyl acetate, toluol, and petroleum naphtha. The polyvinyl butyraldehyde composition may be used for coating steel surfaces. It may be used for enamelling finger nails, a top coat of a cellulose nitrate composition being subsequently applied. The primer coating may be provided with a top coat of varnish, paint, or other finish having a basis of cellulose derivative, oleo-resin, alkyd-resin, urea-formaldehyde, phenol-formaldehyde, polyvinyl resin such as a polyvinyl chloracetate, or a vinyl acetate.