METHOD OF MANUFACTURING POROUS SILICA PARTICLE AND POROUS SILICA PARTICLE FOR VACUUM HEAT INSULATION MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a porous silica particle capable of efficiently manufacturing the porous silica particle having low particle density.SOLUTION: A porous silica particle is obtained by adding a secondary precipitant to W/O type emulsion containing an alkali silicate aqueous solution such as a partially solated water glass and the like by adding a small amount of a primary precipitant in advance and an organic solvent to form precipitate, washing and drying the precipitate. An addition amount of the primary precipitant is 0.2 to 0.4 mol/l and the addition amount of the secondary precipitant is 1.0 to 2.0 mol/l. The obtained porous silica particle has a true density of 0.4 g/cmor less and a particle diameter of a rage of 0.5 to 30 μm, and if it is vacuum packed by a packaging film, a density of the pack is 0.1 to 0.25 g/cmand a heat conductivity is 4.5 to 6 mW/mK. Therefore the porous silica particle is suitable as a core material for a vacuum heat insulation material.