摘要:
A hard, abrasion resistant varnish, for coating the surfaces of solid substrates, comprises a solution in a mixture of solvents:a--4 to 90% by weight, in relation to the total of constituents (a), (b) and (c), of a colloidal silica,b--9 to 95% by weight, in relation to the total of constituents (a), (b) and (c), of the product of hydrolysis and partial condensation of at least one trialkoxysilane;c--1 to 87% by weight, in relation to the total of constituents (a), (b) and (c), of the product of hydrolysis and partial condensation of at least one epoxidized trialkoxysilane;d--0.5 to 9% by weight, in relation to the total of constituents (a), (b) and (c), and (d), of a soluble melamine-formaldehyde and urea-formaldehyde resin.The varnish can optionally contain an acid hardener and secondary adjuvants such as dyes, film tension agents and agents for protection from light.The varnish in contact with the solid substrate to be coated is hardened by heating at about 120.degree. for a time not exceeding 2 hours.