Method of manufacturing polymer-grade clay for use in nanocomposites

A method of removing impurities from a layered clay comprising:

• grinding the clay such that at least about 90% by weight of the clay has a particle size less than about 5,000 .mu.m;
• slurrying the ground clay in water;
• passing the ground clay slurry through a hydrocyclone to remove a portion of the impurities in the form of relatively large particles, thereby removing all particles having a size larger than about 100 .mu.m to form a hydrocyclone-treated product;
• ion-exchanging said hydrocyclone-treated product to replace at least about 90% of clay multivalent interlayer cations with monovalent cations;
• and
• subjecting the ion-exchanged clay to sufficient centrifugal force for separation of particles having a size larger than about 10 .mu.m.

A method of purifying clay containing impurities comprising:

• grinding of the clay to a particle size less than about 500 .mu.m;
• slurrying the clay and impurities in water;
• sequentially treating the slurry containing clay and impurities by:
• removing a portion of the particles in the slurry to provide a first partially purified clay;
• wherein at least about 95% by volume of particles are smaller than about 100 .mu.m;
• removing additional particles from the first partially purified clay to provide a second partially purified clay having at least about 95% by volume of the particles smaller than about 70 .mu.m;
• removing additional particles from the second partially purified clay to provide a third partially purified clay having at least about 95% by volume of the particles smaller than about 50 .mu.m;
• removing additional particles from the third partially purified clay to provide a fourth partially purified clay having at least about 95% by volume of the particles smaller than about 40 .mu.m;
• treating the fourth partially purified clay to remove at least about 95% of the clay interlayer multivalent cations and replacing said multivalent cations with monovalent cations to provide a monovalent, partially purified clay;
• and
• subjecting the monovalent partially purified clay to sufficient centrifugal force to separate particles therefrom having a size larger than 10 .mu.m and such that at least about 95% by volume of the remaining particles have a size smaller than 6 .mu.m, to form said purified clay.