GB1292938A - Improvements in or relating to compositions containing hydrocarbonether polysilicates - Google Patents

Abstract

1292938 Alkoxyalkyl polysilicate compositions; foundry mould compositions ANDERSON DEVELOPMENT CO 19 April 1971 [25 Sept 1970] 22521/71 Headings C3N and C3T [Also in Division B2] A liquid composition comprises (1) at least 30 wt. per cent of a liquid organic polysilicate in which at least 50% of the number of organic groups are ROCH 2 CH 2 O- or ROCH 2 CH 2 OCH 2 CH 2 O- groups, R being a C 1-12 hydrocarbon group free of aliphatic unsaturation, any other organic groups being C 1-4 alkyl groups, and the SiO 2 content of the polysilicate being at least 19 wt. per cent, and optionally (2)-water and/or (3) an organic solvent, in which any alcohol or glycol ether present is such that the total number of alkoxy and glycol ether residues in (1) plus (3) contains at least 50% glycol ether groups as specified above, the SiO 2 content of the total composition (1) plus (2) plus (3) being 6-22 wt. per cent. Preferably, the composition has pH not above 6. There may be mixed with the liquid composition fillers, e.g. 0À4-9 p.b.w. per 100 of composition of a metal powder, for paints, or 3-12 p.b.w. per 100 of a refractory powder, for foundry shell moulds, and with the latter 4 p.b.w. of ZnCl 2 and/or 0À05-3 p.b.w. of hydroxypropyl-cellulose. The polysilicate (1) may be prepared by heating an alkyl orthosilicate or polysilicate, e.g. (EtO) 4 Si, with the ethylene glycol monoether at pH 1À4-3À5 or by reaction of SiCl 4 with the glycol ether, and hydrolysis of the product to the required extent. C 1-4 alkyl silicates and organic solvents are then added, if necessary, to give the desired compositions. In Example 1 ethyl silicate 40 is heated with 2- ethoxyethanol and water equivalent to 55% hydrolysis, water equivalent to hydrolysis up to 75% and a little HCl is then added to give a stable liquid. A paint is obtained by adding water and ethoxyethanol to a theoretical hydrolysis of 85-110% and SiO 2 content 7-17À3 wt. per cent, then Zn dust (25 p.b.w. per 9 of binder) and 2 wt. per cent of bentonite and 5 wt. per cent of talc. The paint is applicable to steel, cast iron, galvanized steel, glass, Al, Cu and tinned steel. A similar binder is obtained starting from SiCl 4 . In Examples 2-3 a similar binder solution is mixed with silica flour in 1 : 4 weight ratio, or with zircon flour and silica flour (1 : 3 : 1), or with two grades of silica flour after thinning with isopropanol, to give slurries for preparing shell moulds by the stucco process. In Examples 4-5 moulds are cast from a 1 : 5 : 1 mixture of binder, zircon flour and silica flour in which the binder contains 10% aqueous NH 3 and 90% 53% hydrolysed ethoxyethyl silicate.