Method for the formation of abrasion-resistant coating film

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.sup.4 is alkyl having 1 to 6 carbon atoms, phenyl, allyl, vinyl, methacryloxy, methacryloxyalkyl, mercaptoalkyl, aminoalkyl, epoxyalkyl, epoxyalkyloxy, epoxyalkyloxyalkyl, tetrahydrofuryl or fluoroalkyl;
• and R.sup.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.sup.1 R.sup.2 or R.sup.3 ;
• R.sup.1 and R.sup.2 are each hydrogen, alkyl having 1 to 4 carbon atoms, phenyl, benzyl or allyl;
• R.sup.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.sup.6 and R.sup.7 are each hydrogen, alkyl having 1 to 5 carbon atoms, phenyl, benzyl, allyl or cyclohexyl;
• R.sup.8 is hydrogen or methyl;
• Y is oxygen or sulfur;
• and M is lithium, sodium or potassium and
• (C) alkali metal salt of a .beta.-dicarbonyl compound represented by the formula:
• ##STR9## wherein R.sup.9 is hydrogen, alkyl having 1 to 4 carbon atoms or alkylene having 3 to 4 carbon atoms;
• R.sup.10 and R.sup.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.