Binding agent, core sand mixture and a method for producing the same

摘要

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. The connection between the funnel and the sand cylinder is closed during the shooting. The core sand mixture located in the slotted sand cylinder is compacted using an air pressure of p₁ and then shot into the core box at a pressure p₂>p₁.