| 摘要 |
A binder composition comprises a condensate of Si(OR)4, in which R is an alkyl radical of 1 to 4 C atoms, the condensate having a SiO2 content upwards of 35%, on a molecular basis, water in amount sufficient to provide 0.15 to 0.5 mole of H2O for each alkoxy group of the condensate, and as solvent, a monoalkylene glycol monoalkyl ether, dialkylene glycol monoalkyl ether, dialkylene glycol dialkyl ether or monoalkylene glycol dialkyl ether having a B.P. within the range 250 DEG to 300 DEG F., and a flash point within the range 115 DEG to 165 DEG F., the solvent-condensate ratio on a weight basis lying within the limits 0.5:1 to 10:1. The preferred condensate has the average formula <FORM:1105393/C3/1> wherein n is substantially 1. The binder is made by mixing the condensate with additional water and the solvent and, desirably, an acid, e.g. HCl and/or H2SO4, to give the mixture a pH of 1.4 to 3.5, after which it is allowed to age prior to use. The compositions are used for binding Zn dust alone or together with fillers, e.g. Ca and Mg metasilicates, asbestos, fibrous talc and gypsum, and/or pigments, e.g. Fe2O3, CdS, TiO2 and lithopones. Examples are given of the above preparation of the filled and unfilled compositions.ALSO:A binder composition comprising a condensed alkyl slicate having a SiO2 content of at least 35%, on a molecular basis, water in amount sufficient to provide 0.15 to 0.5 mole of H2O for each alkoxy group of the condensate, and as solvent an alkyleneglycol alkylether having a B.P. and flash point within the range 250 DEG to 300 DEG F and 115 DEG to 165 DEG F respectively, the solvent-condensate ratio (by wt.) being from 0.5:1 to 10:1 (see Division C3), is used for binding Zn dust alone or together with fillers, e.g. Ca and Mg metasilicates, asbestos, fibrous talc and gypsum, and/or pigments, e.g. Fe2O3, CdS, TiO2 and lithopones, and the resulting compositions are then used for coating clean, sand-blasted or wet steel or galvanised surfaces (Ex. II, sand-blasted steel surface; Ex. VI sand-blasted iron surface; Ex. VII clean steel surface). If desired, the coating can be heat cured at 700 DEG to 800 DEG F. |
