Inorganic filler and process for production thereof

摘要

An inorganic filler composed of a modified montmorillonite group clay mineral and having an X-ray diffraction pattern inherent to montmorillonite, an oil absorption of at least 100 ml/100 g and a Hunter whiteness of at least 80%. The modified clay mineral is produced by reacting a clay mineral of the montmorillonite group which 10 to 200% by weight based on the dry weight of the mineral, of an alkaline earth metal hydroxide in the presence of water, and reacting the reaction product with a salt of a metal of Group IIb, III or IV of the periodic table containing an acid radical which gives a soluble alkaline earth metal salt upon reaction. The inorganic filler is especially suitable for use in lightweight paper.