PURPOSE: To manufacture high purity silica by ultrafiltering an aqueous soln. of an alkali silicate, treating it with an ion exchange resin to prepare purified silica sol. adding a specified coagulating agent to deposit and precipitate silica, separating the silica from the mother liquor, and heat treating it.
CONSTITUTION: A commercially available aqueous soln. of sodium silicate or potassium silicate contg. 20W35% SiO2 is diluted to prepare an aqueous soln. contg. <10% SiO2. This aqueous soln. is ultrafiltered to remove collidal particles, and it is diluted to ≤5% concn. of SiO2 and brought into contact with an ion exchange resin to prepare acidic silica sol. This silica sol is reacted with a coagulating agent which is gasified by heating such as NH4NO3, NH4Cl or (NH4)2CO3. Silica is deposited and precipitated by the reaction. The precipitated silica is separated from the mother liquor, and the coagulating agent sticking to the silica is gasified by heating to manufacture extremely high purity silica.
MITA MUNEO
MORISHITA TOSHIHIKO
KOSHIMIZU HITOSHI
TORII KAZUYOSHI
