Sodium silicate soln. mfr. - by reacting sand and sodium hydroxide soln. at elevated temp. and press. in a tubular reactor

摘要

Na silicate solns. are made by reacting sand with caustic soda soln. at =200 degrees C and elevated press. in a tubular reactor of the type known for decomposing bauxite. Pref. the ratio SiO2:Na2O is 2:1 to 2:1:1 and the temp. is 240-280 degrees C, or the ratio SiO2:Na2O is 1.0:1 to 1.1:1 and the temp. is 200-240 degrees C. The strength of the NaOH soln. is pref. chosen such that the resulting soln. has a solids content of 35-57%. Using reactors of the type used for decomposing bauxite with NaOH (see e.g. NL7201115, 7201203 and 7601199) allows temps. of 200 degrees C to be used and avoids the problems and inconvenience encountered when using autoclaves for the reaction. The desired end prod. is produced directly with only a few minutes' residence time in the reactor, and due to the high temps. used, no viscosity problems are encountered in handling water glass solns. with a concn of 35-57% solids. The process can be carried out continuously and automatically with low energy consumption and low investment costs.