Calcium-magnesium carbonate composite and method for the preparation
thereof
    10.
    发明授权
    Calcium-magnesium carbonate composite and method for the preparation thereof 失效
    碳酸钙 - 碳酸钙复合材料及其制备方法

    公开(公告)号:US5230734A

    公开(公告)日:1993-07-27

    申请号:US917163

    申请日:1992-07-20

    IPC分类号: C01F11/18 C09C1/00 D21H19/38

    摘要: A calcium-magnesium carbonate composite consisting of particles of calcium carbonate and magnesium carbonate hydroxide and having excellent properties, for example, as a pigment for paper coating is proposed, which is a uniform blend of:(A) particles of calcium carbonate having a crystalline structure of aragonite with a columnar particle configuration having a length in the range from 0.5 to 3 .mu.m and a diameter in the range from 0.1 to 0.3 pm with an aspect ratio in the range from 5 to 15; and(B) particles of magnesium carbonate hydroxide having a plate-like particle configuration with a particle diameter in the range from 2 to 7 .mu.m and a thickness in the range from 0.05 to 0.5 .mu.m,the blend having an overall specific surface area in the range from 15 to 30 m.sup.2 /g and the weight proportion of the particles of calcium carbonate to the particles of magnesium carbonate hydroxide being in the range from 95:5 to 50:50 calculated as the respective hydroxides. The carbonate composite can be prepared by the step-wise carbonation reaction of a mixed aqueous slurry of calcium and magnesium hydroxides with carbon dioxide gas under very strictly controlled conditions.