Method for the formation of abrasion-resistant coating film

Claim 1

In a method for forming an abrasion-resistant coating film by heat-curing a coating composition on the surface of a substrate, said composition composed mainly of a partially hydrolyzed product of alkoxysilane represented by the formula: R.sub.n.sup.4 Si(OR.sup.5).sub.4-n wherein n is an integer of 0 to 2; R 4 is alkyl having 1 to 6 carbon atoms, phenyl, allyl, vinyl, methacryloxy, methacryloxyalkyl, mercaptoalkyl, aminoalkyl, epoxyalkyl, epoxyalkyloxy, epoxyalkyloxyalkyl, tetrahydrofuryl or fluoroalkyl; and R 5 is alkyl having 1 to 4 carbon atoms, the improvement which comprises using as a curing catalyst at least one alkali metal salt selected from the group consisting of (A) alkali metal salts of thio-acids, dithio-acids and their derivatives represented by the formula: ##STR7## wherein X is --NR 1 R 2 or R 3 ; R 1 and R 2 are each hydrogen, alkyl having 1 to 4 carbon atoms, phenyl, benzyl or allyl; R 3 is hydrogen, alkyl having 1 to 4 carbon atoms, phenyl, benzyl or alkoxy having 1 to 6 carbon atoms; Y is oxygen or sulfur; and M is lithium, sodium or potassium; (B) alkali metal salts of barbituric acid and its derivatives represented by the formula, ##STR8## wherein R 6 and R 7 are each hydrogen, alkyl having 1 to 5 carbon atoms, phenyl, benzyl, allyl or cyclohexyl; R 8 is hydrogen or methyl; Y is oxygen or sulfur; and M is lithium, sodium or potassium and (C) alkali metal salt of a β-dicarbonyl compound represented by the formula: ##STR9## wherein R 9 is hydrogen, alkyl having 1 to 4 carbon atoms or alkylene having 3 to 4 carbon atoms; R 10 and R 11 are each alkyl, alkoxy having 1 to 4 carbon atoms, alkoxycarbonyl having 2 to 5 carbon atoms, phenyl, benzyl or alkylene having 3 to 4 carbon atoms; and M is lithium, sodium or potassium.