The industrially applied alkaline magnesium carbonate is represented by the chemical formula mMgCO3-Mg(OH)2-nH2O. The values represented by m and n in this chemical formula vary according to the production conditions, and thus are not constant. Usually, m is 3 ~ 5, n is 3 ~ 8.
Alkaline magnesium carbonate is usually obtained in the form of amorphous aggregated particles of flaky microcrystals, characterized by a low bulk density (bulk density) of 0.2 to 0.3 g/mL and a fairly high specific surface area of 10 to 40 m2/g.
By utilizing the above properties, alkaline magnesium carbonate has been applied in such fields as rubber, paint, paper, pharmaceutical products, cosmetics, construction materials and ceramic materials. Specifically, as a rubber filler, it has properties such as imparting transparency to blended natural rubber and improving the strength of rubber.
As a method for preparing basic magnesium carbonate, there are many methods, such as the soda ash method using a soluble magnesium salt (such as magnesium chloride) reacting with sodium carbonate, the ammonium carbonate method using a soluble magnesium salt reacting with ammonium carbonate, and the gas method using magnesium hydroxide reacting with carbon dioxide gas. In any of these methods, the preparation of alkaline magnesium carbonate must be by long maturation of normal magnesium carbonate (expressed by the chemical formula MgCO3-nH2O, n in the formula is generally 3) or magnesium bicarbonate (Mg(HCO3)2), which as an intermediate product is obtained by the reaction of magnesium source with carbonate source.
The development of alkaline magnesium carbonate has been started long ago. For example, a method to prepare alkaline magnesium carbonate by maturing a suspension containing normal magnesium carbonate in a short time under appropriate temperature conditions, which has excellent properties and can be applied as a filler in rubber; and a method to prepare alkaline magnesium carbonate by reacting a water-soluble magnesium source with a water-soluble carbonate in the presence of a water-soluble sulfate is proposed, which has excellent properties and can be applied as a filler in can be applied to synthetic resins as fillers.
In addition, an alkaline magnesium carbonate with a specific oil adsorption capacity and specific surface area, which was prepared by cyclically heating an aqueous solution of magnesium bicarbonate; an alkaline magnesium carbonate with a specific X-ray diffraction pattern, which was obtained by heating a suspension of normal magnesium carbonate in the coexistence of hydroxycarboxylic acid, is proposed. Moreover, attention is focused on publications on the shape of alkaline magnesium carbonate particles, wherein alkaline magnesium carbonate in the form of spherical porous particles is proposed, which is formed by aggregation of primary particles and has specific characteristics such as stacking density and specific surface area.