| 摘要 |
1285891 Bleaching alkaline earth metal carbonates ENGLISH CLAYS LOVERING POCHIN & CO Ltd 9 Oct 1969 [15 Oct 1968] 48798/68 Heading C1A An alkaline earth metal carbonate is bleached by contacting with a gas comprising ozone at below 20‹ C. The carbonate may be ground, either before or during contact with the ozone, so that at least 60% of the particles by weight are smaller than 2 microns equivalent spherical diameter. The carbonate may be in the form of an aqueous suspension, preferably containing a dispersing agent, which may be a salt of a polyacrylic or a polymethacrylic acid. The gas comprising ozone may be ozonized air or oxygen containing from 0À1 to 15% ozone by weight. The required bleaching can usually be achieved by contact for from 1 minute to 5 hours. Starting materials referred to are limestone, chalk whiting, dolomite, strontianite and witherite. |
