Abstract A process for producing calcined mineral products having improved brightness and significantly reduced abrasion is disclosed. In accordance with the invention, mineral such as kaolin clay, are delaminated by agitating a slurry of the minerals in the presence of a hard, abrasive grinding media, such as glass beads, which have a specific gravity higher than the mineral-water suspension or mixture. The delaminated particulates are then filtered, dried and calcined at a temperature in excess of 750* C to remove the water of hydration and bring about a sharp exothermic reaction. In one method embodiment, the minerals or clays are subjected to a high intensity magnetic field, prior to the delamination, to remove foreign matter or contaminants which are deleterious to the production of a calcined pigment having a high brightness and a low abrasive index. The calcined products of the invention may be used in the coating and filling of paper, in paints, as reinforcing fillers or pigments in elastomers and the like.
The method in accordance with claim 1, said method further comprising continuing said agitation to produce a clay fraction having an average particle size of less than 2 microns.
Claim 2
Dependent Claim
64 words
The method in accordance with claim 1 wherein said granular grinding medium is glass beads which occupy at least 30 percent of the volume of the media-slurry mixture in the delamination of said coarse clay fractions, said glass beads being substantially uniform and spherical and having diameters in the range of from about 10 mesh to 60 mesh on the Tyler standard screen scale.
Claim 3
Dependent Claim
127 words
The method in accordance with claim 1, said method further comprising preparing a kaolin clay-water slurry of predetermined solids content, passing said slurry through a magnetic separator substantially continuously, retaining said slurry within the high intensity magnetic field of said separator to effect separation of magnetically susceptible contaminants, passing said magnetically separated slurry to a feed tank, establishing a predetermined kaolin solids content and particle size within said feed tank, continuously pumping said slurry from the feed tank to a delamination vessel at a controlled flow rate to maintain predetermined conditions within said delamination vessel and to maintain a predetermined retention time within said delamination vessel, continuously withdrawing delaminated kaolin clay pigments from said vessel and calcining said pigments at a temperature of at least 800* C.