GB1230094A - - Google Patents

Abstract

1,230,094. Dicalcium silicate. AIRBRIGHT & WILSON Ltd. 3 May, 1968 [4 May, 1967; 6 June, 1967], Nos. 20858/67 and 26110/67. Heading C1A. [Also in Division C3] Siliceous material and a calcareous material are reacted in the solid phase in the presence of a mineralizer and a phase stabilizer to boron dicalcium silicate having 1À6-2À4 moles CaO per mole SiO 2 . The mineralizer is a compound which promotes the solid state reaction and may be an alkali or alkaline earth metal fluoride or fluosilicate, preferably CaF 2 or cuspidene. The phase stabilizer inhibits the conversion of the #-dicalcium silicate to the # form and preferred phase stabilizers are oxides or salts containing P or B, e.g. P 2 0 5 , B 2 O 3 , Ca 3 (PO 4 ) 2 , NaBO 3 , Na 4 P 2 O 7 . The mineralizer and stabilizer may be the same, e.g. sodium silicofluroide or used in combination, e.g. as in fluoropatite. The mineralizer preferably provides at least 2% wt. F based on the weight of SiO2 in the product and the quantity of stabilizer may be adjusted togive a product containing 60-80% of the # dicalcium silicate. The preferred calcareous material is limestone. The siliceous material may be sand, silica or a monocalcium slag containing less than 1.6 moles CaO per SiO 2 and is preferably a phosphorus furnace slag. The reaction may be carried out at 980-1350‹ C., preferably 1050-1150‹ C. Moist moulding sand may be hardened by mixing sodium silicate and the product of the invention, such treated sands being used in the moulding of metals (see Division C3).