Coating liquid composition to form hard coat film on plastics
AssigneeCentral Glass Company, Limited
InventorToshikazu Nagashima
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Abstract
The invention relates to a coating liquid composition useful to form a hard and transparent coating film on plastics. The novel liquid composition comprises a partial polycondensation product of a trialkoxysilane R.sup.1 Si(OR.sup.2).sub.3, wherein R.sup.1 is a C.sub.1 or C.sub.2 alkyl group and R.sup.2 is a C.sub.1 -C.sub.3 alkyl group, a colloidal silica, water, an aliphatic lower alcohol and anhydride of a polybasic carboxylic acid having a cyclic structure. The content of the acid anhydride must be at least 0.005 wt % when pH of the coating liquid composition is adjusted to 6.0-7.0. The primary merit of using such an acid anhydride is improved storage stability of the coating liquid composition.
Claims6
A coating liquid composition particularly useful to form a hard coating film on plastics articles, comprising:
- an aqueous colloidal silica solution;
- a partial polycondensate of an organotrialkoxysilane represented by the formula R.sup.1 Si(OR.sup.2).sub.3, wherein R.sup.1 is an alkyl group having not more than 2 carbon atoms and R.sup.2 is an alkyl group having more than 3 carbon atoms, said partial polycondensate having a number average molecular weight of from about 1000 to about 2000 and said partial polycondensate of the organotrialkoxysilane being formed by mixing said organotrialkoxysilane with an anhydride of a polybasic cyclic carboxylic acid and then mixing the resultant mixture with said aqueous colloidal silica solution having a pH of from about 8 to 9 to cause hydrolytic condensation of said organotrialkoxysilane;
- and
- a lower alkyl alcohol selected from the group consisting of isopropyl alcohol and n-propyl alcohol;
- wherein, the weight ratio of the colloidal silica in said aqueous colloidal silica solution, as SiO.sub.2, to the organotrialkoxysilane is from 1:10 to 5:10;
- wherein the content of the acid anhydride remaining in the liquid composition is at least 0.005% by weight when the pH of the liquid composition is adjusted to 6.0 to 7.0;
- and
- wherein the organotrialkoxysilane of the formula R.sup.1 Si(OR.sup.2).sub.3 is the sole alkoxysilane used in the liquid coating composition.
Dependencies are inferred from the claim text.