Method for reducing the viscosity and for refining kaolin clays

A method for increasing the brightness of crude kaolin clay ores comprising contacting a crude clay/water slurry of said kaolin clay ore with an inorganic polymeric complex having the general formula:

• [Al(OH).sub.2.25 A.sub..75 ].sub.x
• wherein x = 6 to 24 and A is selected from the group consisting of Cl.sup.-,(SO.sub.4.sup.--).sub.0.5 and NO.sub.3.sup.- ;
• subjecting the crude clay/water slurry to a high shear mixing action or kneading;
• fractionating the crude clay/water slurry to form coarse and fine fractions of said clay;
• and leaching the fine fraction of the classified clay/water slurry with from 2 to 3 lbs. of zinc hydrosulfite per ton of clay.

A method for increasing the brightness of crude kaolin clays, said method comprising the steps of contacting a crude kaolin clay/water slurry with a polymeric complex having the general formula:

• [Al(OH).sub.y Cl.sub.3-y ].sub.x
• wherein x = 6 to 24 and y = 1 to 2.75;
• subjecting the crude clay/water slurry to a high shear mixing action or kneading;
• fractionating the crude clay/water slurry to form coarse and fine fractions of said clay;
• and leaching the fine fraction of the classified clay/water slurry with from 2 to 3 lbs. of zinc hydrosulfite per ton of clay.

A method for refining crude kaolin clay ores having a wide initial crude clay/water viscosity range, said method comprising the steps of:

• forming a slurry of crude kaolin clay in water having a solids content of from about 10 to about 40% by weight;
• degritting the crude clay/water slurry;
• contacting the crude clay/water slurry with an inorganic polymeric complex having the formula
• [Al(OH).sub.y A.sub.3-y ].sub.x
• wherein x = 6 to 24, y = 1.0 to 2.75, and A is selected from the group consisting of Cl.sup.-, (SO.sub.4.sup.--).sub.0.5 and NO.sub.3.sup.- ;
• subjecting the crude clay/water slurry to a high shear mixing action or kneading;
• fractionating the crude clay/water slurry to form coarse and fine fractions of said clay;
• leaching the fine fraction of the classified clay/water slurry at room temperature;
• filtering the leached clay/water slurry;
• concentrating the resulting filter cake to a desired clay solids;
• and
• recovering the clay as a finished clay pigment product.