Catalysts for curing silane coating compositions

Abstract

Improved curing catalysts are disclosed for use in a coating composition containing a film-forming organosilane polymer. The catalysts can cure hydrolytically stable compositions, which do not prematurely gell by moisture. The coating composition can be used as a one package clearcoat over a conventional pigmented basecoat, or as a basecoat, monocoat or primer when a suitable amount of pigment is incorporated therein. The coating composition provides improved properties, including increased chemical etch resistance.

What is claimed is: 
     
       1. A composition useful for coating a substrate, which composition comprises: (a) from about 20 to 90% by weight, based on the weight of the binder, of a film-forming organosilane polymer, having a weight average molecular weight of about 1000-30,000; and   (b) from about 0.1 to 10% by weight, based on the weight of the composition, of an effective amount of a curing catalyst which is a titanium chelate comprising a trialkanolamine, wherein said alkanol has 1 to 4 carbon atoms; and   (c) from about 25 to 50% by weight, based on the weight of the composition, of a liquid organic carrier.   
     
     
       2. The composition of claim 1, wherein said catalyst, employed to catalyze the crosslinking of the silane moieties in said organsilane polymer, is a chelate of titanium. 
     
     
       3. The composition of claim 1, wherein the organosilane polymer comprises one or more ethylinically unsaturated non-silane-containing monomers selected from the group consisting of styrene, alkyl acrylate, alkyl methacrylate, cycloaliphatic acrylate, cycloaliphatic methacrylate, aryl acrylates, aryl methacrylate and any mixtures thereof; and one or more ethylenically unsaturated silane-containing monomers selected from the group consisting of alkoxy silane, acyloxy silane, and any mixtures thereof, wherein said alkyl has 1-12 carbon atoms, said cycloaliphatic has 5 to 8 carbon atoms, and said aryl has 6 to 12 carbon atoms. 
     
     
       4. The coating composition of claim 1, wherein the composition comprises about 0.1 to 5.0% by weight, based on the weight of the composition, of said catalyst. 
     
     
       5. The coating composition of claim 1, wherein the organosilane polymer is hydrolytically stable. 
     
     
       6. The coating composition of claim 5, wherein silane functionalities in said organosilane polymer comprise alkoxy groups attached to a silicon atom, wherein the alkoxy groups have at least 2 carbon atoms. 
     
     
       7. A composition useful for coating a substrate, which composition comprises an organosilane polymer and a curing catalyst which catalyst is a trialkanolamine metal catalyst having the following structure: ##STR5## wherein m, n or p are independently 1 to 4; R is an unsubstituted or substituted alkyl or alkanol having 1 to 6 carbon atoms; and M is titanium.