Лако-красочные материалы — производство

The activated clay is blended with the other raw materials and dry-ground, usually in batch or continuous ball mills, to a mean size approaching 15 pm. Typical recipes (in wt.%) are:

The ground mixture is heated to about 750 °C under reducing conditions, nor­mally in a batch process. The traditional way to do this is to use directly fired kilns with the blend in lidded crucibles of controlled porosity, or muffle kilns. To improve throughput, the practice in the Holliday Pigments’ production facilities is to den — sify the ground material to form bricks, which are then stacked in a pre-determined pattern and fired in chambers, which are indirectly heated using gas-fired burners. The sodium carbonate reacts with the sulfur and reducing agent at 300 °C to form sodium polysulfide [3.165]. At higher temperatures the clay lattice reforms into a three-dimensional framework, which at 700 °C is transformed to the sodalite struc­ture, with entrapped sodium and polysulfide ions.