| 摘要 |
A coating composition comprises a solution in one or more polar solvents of from 2-25% by weight of a mixture of (a) a polysilicic acid (calculated as SiO2) and (b) an organic polymer containing polar groups, the weight ratio of (a):(b) being 10:90 to 90:10 and from 0.05-5% by weight based on (a) and (b) of (c) a block copolymer of a C2-C4 alkylene oxide and a dialkyl siloxane having 1-4 carbons in each alkyl group. The polysilicic acid (a) is the soluble product obtained by an hydrolysis of ethyl silicate which is terminated before silica gel is formed. The polymer (b) may be a polyamide, e.g. a mixture of polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaproamide, or a hydroxyl-containing polymer such as polyvinyl butyral containing free hydroxyl groups, polyvinyl alcohol partially converted into an acetal with propionaldehyde, partially hydrolysed polyvinyl acetate, hydrolysed vinyl acetate-tetrafluoroethylene copolymer, tetrafluoroethylene-2-hydroxyethyl vinyl ether, -4-hydroxybutyl vinyl ether, or -3-hydroxypropyl vinyl ether copolymer, or tetrafluoroethylene-4-hydroxybutyl vinyl ether-2-hydroxyethyl vinyl ether copolymer. Block copolymer (c) is preferably derived from dimethyl siloxane and polyethylene oxide or polypropylene oxide. Suitable solvents are alcohols and halogenated hydrocarbons; for coating on polymethylmethacrylate an acid, e.g. acetic and hydrochloric acids, is added and glycol ethers, such as ethylene glycol monobutyl ether, are preferably added.ALSO:A coating composition comprises a solution in one or more polar solvents of from 2-25% by weight of a mixture of (a) a polysilicic acid (calculated as SiO2) and (b) an organic polymer containing polar groups, the weight ratio of (a): (b) being 10:90 to 90:10 and from 0.05-5% by weight based on (a) and (b) of (c) a block copolymer of a C2-C4 alkylene oxide and a dialkyl siloxane having 1-4 carbons in each alkyl group. The polysilicic acid (a) is the soluble product obtained by a hydrolysis of ethyl silicate which is terminated before silica gel is formed. The polymer (b) may be a polyamide, e.g. a mixture of polyhexamethylene adipamide, polyhexamethylene sebacamide and polycaproamide, or a hydroxyl-containing polymer such as polyvinyl butyral containing free hydroxyl groups, polyvinyl alcohol partially converted into an acetal with propionaldehyde, partially hydrolysed polyvinyl acetate, hydrolysed vinyl acetate-tetrafluoroethylene copolymer, tetrafluoroethylene-2-hydroxyethyl vinyl ether, -4-hydroxybutyl vinyl ether, or -3-hydroxypropyl vinyl ether copolymer, or tetrafluoroethylene-4-hydroxybutyl vinyl ether-2-hydroxyethyl vinyl ether copolymer. Block copolymer (c) is preferably derived from dimethyl siloxane and polyethylene oxide or polypropylene oxide. Suitable solvents are alcohols and halogenated hydrocarbons; for coating on polymethylmethacrylate an acid, e.g. acetic and hydrochloric acids, is added and glycol ethers, such as ethylene glycol monobutyl ether, are preferably added. The coating compositions are applied to thermoplastic sheets, particularly polymethmethacrylate, polyethyleneterephthalate, polyvinylfluoride or polycaproamide, metals, glass, wood or painted surfaces to give clear coatings. The solutions are applied by spraying, spreading, dipping or curtain coating in layers up to 17 microns in thickness and air cured at 170 DEG C. |
