Paper coating clay and method for treating the same

Claim 1

A PROCESS FOR TREATING KAOLIN CLAY TO RENDER SAID CLAY AMENABLE TO THE FORMATION OF HIGH CLAY SOLIDS SLIPS HAVING MATERIALLY REDUCED VISCOSITY AT HIGH SHEAR RATES WHICH COMPRISES FORMING A PUGGABLE MIXTURE OF ABOUT 69 TO 80 PARTS BY WEIGHT OF UNCALCINED KAOLINITE AND ABOUT 31 TO 20 PARTS BY WEIGHT OF WATER, SAID KAOLINITE HAVING AN AVERAGE EQUIVALENT SPHERICAL DIAMETER WITHIN THE RANGE OF 0.5 TO 0.8 MICRON, PUGGING SAID MIXTURE WITH A WORK INPUT OF AT LEAST 10 HP. HRS./TON OF SAID KAOLINITE IN SAID MIXTURE, SAID WORK INPUT BEING SUFFICIENT TO PRODUCE A ZIGZAG PATTERN ON A HAGAN RHEOGRAM OF A 70% SOLIDS DEFLOCCULATED AQUEOUS SLIP OF THE WORKED CLAY, DILUTING THE KAOLINITE THUS PUGGED WITH WATER TO FORM A SLIP CONTAINING ABOUT 35 TO 50 PARTS BY WEIGHT OF KAOLINITE TO 65 TO 50 PARTS BY WEIGHT OF WATER, AND HEATING SAID SLIP AT TEMPERATURE WITHIN THE RANGE OF ABOUT 300*F. TO ABOUT 550*F. FOR A TIME WITHIN THE RANGE OF 1 SECOND TO 12 HOURS UNDER AT LEASTA AUTOGENOUS PRESSURE.