| 摘要 |
A coarse particle kaolin clay is provided having an average Stokes equivalent particle diameter of about 4.5-6.0 microns, a BET surface area of about 8-11 m2/g, and preferably having a median Malvern particle size of about 9.0-10.5 microns as determined by laser light-scattering measurement and a high aspect ratio preferably of about 12-14 as determined by Sphericity Model calculations. The coarse particle kaolin clay provides low viscosity build, good reinforcement properties and excellent surface finish qualities as a filler in thermoset composite materials, such as polyester molding compounds, and also provides excellent pigmenting properties in paints and industrial coatings. Preparation of the coarse particle clay involves blunging and degritting a crude kaolin clay, conducting three separate centrifugation steps with the desired product stream being, in sequence, the coarse underflow clay from the primary centrifuge, the coarse underflow from the secondary centrifuge, and then the fine overflow from the tertiary centrifuge, followed by magnetic separation, screening, chemical leaching, drying and milling to produce a kaolin clay product having the above-described physical properties and performance characteristics. |
