Method for improving adhesion of silicone resin coating composition

Claim 1

A method for maintaining or rejuvenating initial adhesion to a thermoplastic acrylic-primed solid plastic substrate of an aqueous coating composition comprising a dispersion of colloidal silica in an aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH) 3 , wherein R is selected from the group consisting of alkyl having from 1 to 3 carbon atoms and aryl, at least 70 weight percent of the silanol being CH 3 Si(OH) 3 , said composition containing 10 to 50 weight percent solids, said solids consisting essentially of 10 to 70 weight percent colloidal silica and 30 to 90 weight percent of the partial condensate, said composition also including a small, effective amount of a polysiloxane polyether copolymer and a small, effective amount of an ultraviolet screening agent, said method comprising adding a small effective amount of an aliphatic alcohol-water compatible liquid organic solvent for said partial condensate, said solvent also being capable of softening, but not dissolving said thermoplastic acrylic, said solvent being a β-hydroxy ketone having the structural formula: ##STR5## wherein R 1 is a monovalent hydrocarbon radical of from 1 to 18 carbon atoms and R 2 and R 3 are, independently, a monovalent hydrocarbon radical of from 1 to 18 carbon atoms or hydrogen.

Claim 2

A method for maintaining or rejuvenating initial adhesion to a thermoplastic acrylic-primed solid plastic substrate of an aqueous coating composition comprising a dispersion of colloidal silica in an aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH) 3 , wherein R is selected from the group consisting of alkyl having from 1 to 3 carbon atoms and aryl, at least 70 weight percent of the silanol being CH 3 Si(OH) 3 , said composition containing 10 to 50 weight percent solids, said solids consisting essentially of 10 to 70 weight percent colloidal silica and 30 to 90 weight percent of the partial condensate, said composition also including a small, effective amount of a polysiloxane polyether copolymer and a small, effective amount of an ultraviolet screening agent, said method comprising adding a small effective amount of an aliphatic alcohol-water compatible liquid organic solvent for said partial condensate, said solvent also being capable of softening, but not dissolving said thermoplastic acrylic, said solvent being a β-hydroxy ketone having the structural formula: ##STR5## wherein R 1 is a monovalent hydrocarbon radical of from 1 to 18 carbon atoms and R 2 and R 3 are, independently, a monovalent hydrocarbon radical of from 1 to 18 carbon atoms or hydrogen.