PURPOSE: To obtain the subject sol exhibiting excellent film-forming property when dried on a solid surface by adding an aqueous solution containing a water-soluble Ca salt or Mg salt to an colloidal aqueous solution of active silicic acid, adding a specific alkali metal compound to the solution and heating the mixture.
CONSTITUTION: An aqueous solution containing a water-soluble Ca salt and/or Mg salt is added to a colloidal aqueous solution of active silicic acid of pH2-4 having an SiO2 content of 1-6wt.%. The weight ratio of the Ca or Mg compound to SiO2 is 1,500-3,500ppm in terms of CaO or MgO. The obtained aqueous solution is mixed with an alkali metal hydroxide, a water-soluble organic base or their water-soluble silicate at a molar ratio (SiO2/M2O) of 20-200 and heated at 60-150°C for 0.5-40hr to obtain a stable alkaline aqueous silica sol having an SiO2 concentration of 1-6wt.% and composed of amorphous colloidal silica particles having thin and long shape with particle diameter ratio (D1/D2) of ≥5 (D1 mμ is particle diameter measured by dynamic light-scattering and D2 mμ is particle diameter measured by N2 gas adsorption), D1 of 40-300mμ and uniform thickness falling within 5-20mμ by electron microscopy and extending along only one plane.
ANDO MIKIO
TANIMOTO KENJI
KAGAMIYA TSUTOMU
KAWASHIMA MAKOTO
Next Patent: PURIFICATION TREATMENT FOR ANHYDROUS BERYLLIUM CHLORIDE