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Abstract

An improved pigment-free abrasion resistant coating composition for plastic substrates which is particularly suited for the protective coating of optical lenses formed from synthetic polymers such as acrylics, polyesters, polycarbonates, and the like. The coating composition is characterized by significantly improved adhesive qualities over prior art materials. The composition includes a major amount of a pigment-free aqueous composition comprising a dispersion of colloidal silica in a lower aliphatic alcohol-water solution of the partial condensate of a silanol of the formula RSi(OH).sub.3 in which R is selected from the group consisting of alkyl radicals of 1 to 3 inclusive carbons, the vinyl radical, cyanoethyl radical, the 3,3,3-trifluoropropyl radical, the gamma-glycidoxypropyl radical, at least 70 weight percent of the silanol being CH.sub.3 Si(OH).sub.3, said composition containing 10 to 50 weight percent solids consisting essentially of 10 to 70 weight percent colloidal silica and 30 to 90 weight percent of the partial condensate, said composition containing sufficient acid to provide a pH in the range of about 3 to about 6; and, based on the above solids from about 3.5% to about 20% by weight of a pigment-free resin selected from the group consisting of amino resins and amino resins which have been at least partially alkylated with at least one aliphatic alcohol having from 1 to 8 carbons and mixtures thereof. Examples of resins to be added to the partial silanol condensate and colloidal silica composition are urea-formaldehyde resins, melamine-formaldehyde resins and the corresponding methylated resins. The invention also includes plastic materials having the above cured coating compositions thereon.

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