Blocking the pores in granules - esp. for foundry moulding sands, using reactive binders or fillers

摘要

Treatment of porous granular prim. materials for prepn. of foundry sands comprises soaking and filling the pores in the grains with mineral or quick drying organic impregnants which form chemical bonds or solidify in the pores. Specific. impregnants include Al(H2PO4)3, together with additives which react chemically with it, e.g. Al(OH3), Al2O3, powdered Al pigment, Hg(OH)2 or MgO. Other impregnants are an aq. soln. of dextrin, sulphite lye, pitch, asphalt, wax, plastics and resins. Method may be used for impregnating porous natural sands, ceramic materials, artificial sands and natural rocks for use as foundry sands after grinding and classification. The amt. of binder required to mould the grains into foundry moulds is reduced by up to two thirds.