Abstract: A binding agent system based on water glass is disclosed, comprising an aqueous alkali silicate solution having the general composition: xSiO2·yM2O ·zH2O, with M standing for the alkali ions Li+, K+, or Na+, and a hygroscopic base, which is added in the ratio 1:4 to 1:6, with the modulus Na2O/SiO2 being equal to 2.5 to 3.5 at a proportion of solids of 20 to 40% and with 30% sodium hydroxide in an aqueous solution being used as the hygroscopic base. According to the present invention, the aqueous alkali silicate solution contains an emulsion solution having 8 to 10% silicone oil in relation to the quantity of binder, with the silicone oil having a boiling point?250°. The quantity of binder for a core sand mixture is 1.0 to 2.5%, in relation to the total quantity of granular solid, with the production method being performed in a core shooter comprising a vertically positioned housing having a horizontal air intake. The core sand mixture is introduced via a funnel into a slotted sand cylinder.

Abstract: The invention relates to a method for the production of core preforms for foundry in which a) a mixture of inorganic, refractory foundry sand and a water glass-based inorganic binder is produced, b) the mixture is poured into a heated core box c) the water contained in the mixture is withdrawn by a physical method and d) the core preform is taken out of the core box. The process is characterized by the fact that e) the heated core box is subjected to a depression during filling f) the temperature/dwell time is adjusted after the closing of the core box so that a dimensionally stable and good bearing shell is formed on the edge of the preform g) the preform is immediately removed after opening of the core box and, under the effect of microwaves, is subjected to a complete drying.