| 摘要 |
A process for beneficiating a crude kaolinitic clay mineral to produce a clay filler for use in papermaking to improve the brightness, the color characteristics and the light scattering efficiency of the paper product. The crude kaolin clay is blunged with water containing a dispersing agent consisting of a blend of from about 20% to about 50% by weight of a water-soluble carbonate, about 20% to about 50% by weight of a water-soluble polyacrylate, and from 0% to about 60% by weight of a water-soluble anionic phosphate, to form a high solids fluid aqueous clay suspension having an acidic pH. This clay suspension is then fractionated to reduce the percentage of particles therein larger than 45 microns to not more than 0.2% by weight. The fractionated clay suspension is treated with an alkaline leaching solution containing a reducing agent effective in converting ferric ions to ferrous ions. The treated clay suspension has a solids content of at least 65% by weight, a low grit content, an acid pH, and a brightness of at least 84, and is suitable without further dewatering for use as a clay filler in making paper.
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