Stabilized calcium carbonate composition using sodium silicate and one or more weak acids or alum and uses therefor

Abstract

An improved form of calcium carbonate which is acid resistant to enable its use as a filler material in the making of neutral to weakly acidic paper, and a process for producing this acid-resistant calcium carbonate is provided. This acid-resistant calcium carbonate composition comprises calcium carbonate and at least about 0.1% to about 25% based on the dry weight of the calcium carbonate, of sodium silicate, together with at least 0.1% to about 25 percent, based on the dry weight of the calcium carbonate, of a weak acid, such as phosphoric acid, formic acid, fluoroboric acid, polyacrylic acid, or alum, or a mixture of weak acids, such as phosphoric acid and polyacrylic acid.

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