CLAY MATERIAL ACTIVATION METHOD Russian patent published in 1995 - IPC

FIELD: foundry, in particular, usage of calcic-magnesium clay materials, primarily bentonites. SUBSTANCE: method involves artificially substituting calcium, magnesium and iron cations by sodium cations by various activators; introducing sodium-bearing compound as activator into moistened clay material in two stages: at the first stage simple salts and/or sodium-bearing compound bases (calcined soda and/or caustic soda, and/or trisodiumphosphate) are introduced to provide substitution of calcium cations, adsorbed on clay surface by sodium cations; at the second activation stage, providing mixing while introducing complex-forming sodium compounds condensed phosphates (tripolyphosphate or sodium pyrophosphate) to effectuate substitution of magnesium and iron cations remaining in clay material by sodium cations. An amount of activators at each stage is determined by predetermined dependence between activator and calcium cation concentration or total concentration of magnesium and ferriferrous iron in 100 g of clay material. EFFECT: improved physical-mechanical properties of clay materials (breaking strength limit within moisture condensation zone and thermal stability), and, as a result, improved processing characteristics of sand mixtures reduced usage of materials and increased quality of casts. 3 cl, 2 tbl