Discoloration prevention in pyrithione-containing coating compositions

A process for inhibiting dry film-discoloration of a pyrithione-containing coating composition being a paint comprising a resin selected from the group consisting of vinyl, alkyd, epoxy, acrylic, polyester resins, and combinations thereof, said discoloration being attributable to ultraviolet light degradation of said pyrithione, which comprises incorporating into said coating composition an effective amount of a zinc compound selected from the group consisting of zinc salts of organic acids, zinc salts of inorganic acids, zinc hydroxide, zinc oxide, and combinations thereof, said zinc compound being employed in said coating composition in an amount of from 0.001% to 10% based upon the weight of the coating composition.

A process for removing an undesirable discoloration in an aqueous antimicrobial composition being a paint comprising a resin selected from the group consisting of vinyl, alkyd, epoxy, acrylic, polyester resins, and combinations thereof, said composition containing a dissolved metal ion selected from the group consisting of ferric ion, cupric ion, and combinations thereof, and containing pyrithione, which comprises contacting said composition with a zinc ion in a molar amount at least equal to the amount of said dissolved metal ion in said composition, wherein said amount of said zinc ion is between 100 ppm and 10,000 ppm in said composition.

An aqueous antimicrobial coating composition, characterized by antimildew efficacy and protected against discoloration attributable to the presence of pyrithione therein, said composition being selected from the group consisting of water-based paints, adhesives, caulks and sealants, and combinations thereof, said composition comprising water, a pyrithione salt or acid, an organic base medium and a zinc compound, said zinc compound being present in said composition in an amount of from 0.001% to 10% based upon the weight of the coating composition.

A coated substrate comprising a substrate selected from the group consisting of wood, metal, plastic substrates, and combinations thereof, and a coating on said substrate, said coating comprising pyrithione and a zinc compound selected from the group consisting of zinc salts of organic acids, zinc salts of inorganic acids, zinc hydroxide, zinc oxide, and combinations thereof, wherein said zinc compound is present in said coating in an amount of from 0.001% to 10%, based upon the weight of the coating composition.