| abstract |
An amorphous, pulverulent, dry silica is prepared which is particularly useful for reinforcing rubber. It is produced by: A. PREPARING SEED PARTICLES BY ADDING A MINERAL ACID TO A DILUTE ALKALI METAL SILICATE SOLUTION CONTAINING 1 TO 3% BY WEIGHT OF SiO2 to form a sol having a pH of about 4.5 - 6.5 and allowing the sol to set into a firm aquagel, B. DILUTING AND DISPERSING THE AQUAGEL IN WATER TO FORM AN AQUEOUS DISPERSION OF AQUAGEL SEED PARTICLES, C. MIXING WITH SAID DISPERSION AN ALKALI METAL SILICATE SOLUTION, D. ADDING ACID TO SAID SEED DISPERSION-ALKALI METAL SILICATE MIXTURE AT A TEMPERATURE OF ABOUT 75* - 100* C to quickly lower the pH to about 1 to 4 and precipitate silica, E. SEPARATING THE WET PRECIPITATED SILICA FROM THE ASSOCIATED LIQUID AND DRYING THE FRESHLY PRECIPITATED SILICA. |