Method of preparing silica pigments

Claim 1

A METHOD OF PREPARING A FINELY DIVIDED, PARTICULATE, SILICEOUS PIGMENT CAPABLE OF REINFORCING GR-S RUBBER TO PRODUCE RUBBER HAVING A TENSILE STRENGTH OF AT LEAST 2400 POUNDS PER SQUARE INCH WHICH COMPRISES FORMING A CONFINED BODY OF AN AQUEOUS SOLUTION OF ALKALI METAL SILICATE CONTAINING 10 TO 150 GRAMS OF SIO2 PER LITER OF SOLUTION, GRADUALLY ADDISNG OVER A PERIOD OF AT LEAST 5 MINUTES AN AMOUNT OF ACIDIFICATION AGENT HAVING AN ANION WHICH FORMS A WATER SOLUBLE COMPOUND WITH ALKALI METAL TO SAID SOLUTION IN AMOUNT SUFFICIENT TO PRECIPITATE SILICA IN THE FORMS OF FLOCS FROM THE SOLUTION AND TOS INCREASE THE MOL RATIO OF THE TOTAL SIO2 IN SAID BODY TO UNNETURALIZED ALKALI METAL OXIDE OF SAID SILICATE TO ABOUT 10, AND AT A RATE FAST ENOUGH TO PRODUCE SILICA HAVING A SURFACE AREA NOT OVER 200 SQUARE METERS PER GRAM BUT SLOW ENOUGH TO PRODUCE SILICA HAVING A SURFACE AREA OF AT LEAST 75 SQUARE METERS PER GRAM, THE AVERAGE ULTIMATE PARTICLE SIZE OF SAID SILICA BEING 0.015 TO 0.04 MICRON, HOLDING THE TEMPERATURE OF THE SOLUTION SUBSTANTIALLY CONSTANT DURING SAID ADDITION, THEREAFTER ADDING FURTHER ACIDIFICATION AGENT TO REDUCE THE ALKALI METAL OXIDE CONTENT OF THE RESULTING PIGMENT BELOW 2 PERCENT, AND SEPARATING THE RESULTING PIGMENT FROM ITS MOTHER LIQUOR.

Claim 2

A METHOD OF PREPARING A FINELY DIVIDED, PARTICULATE, SILICEOUS PIGMENT CAPABLE OF REINFORCING GR-S RUBBER TO PRODUCE RUBBER HAVING A TENSILE STRENGTH OF AT LEAST 2400 POUNDS PER SQUARE INCH WHICH COMPRISES FORMING A CONFINED BODY OF AN AQUEOUS SOLUTION OF ALKALI METAL SILICATE CONTAINING 10 TO 150 GRAMS OF SIO2 PER LITER OF SOLUTION, GRADUALLY ADDISNG OVER A PERIOD OF AT LEAST 5 MINUTES AN AMOUNT OF ACIDIFICATION AGENT HAVING AN ANION WHICH FORMS A WATER SOLUBLE COMPOUND WITH ALKALI METAL TO SAID SOLUTION IN AMOUNT SUFFICIENT TO PRECIPITATE SILICA IN THE FORMS OF FLOCS FROM THE SOLUTION AND TOS INCREASE THE MOL RATIO OF THE TOTAL SIO2 IN SAID BODY TO UNNETURALIZED ALKALI METAL OXIDE OF SAID SILICATE TO ABOUT 10, AND AT A RATE FAST ENOUGH TO PRODUCE SILICA HAVING A SURFACE AREA NOT OVER 200 SQUARE METERS PER GRAM BUT SLOW ENOUGH TO PRODUCE SILICA HAVING A SURFACE AREA OF AT LEAST 75 SQUARE METERS PER GRAM, THE AVERAGE ULTIMATE PARTICLE SIZE OF SAID SILICA BEING 0.015 TO 0.04 MICRON, HOLDING THE TEMPERATURE OF THE SOLUTION SUBSTANTIALLY CONSTANT DURING SAID ADDITION, THEREAFTER ADDING FURTHER ACIDIFICATION AGENT TO REDUCE THE ALKALI METAL OXIDE CONTENT OF THE RESULTING PIGMENT BELOW 2 PERCENT, AND SEPARATING THE RESULTING PIGMENT FROM ITS MOTHER LIQUOR.