초록

Provided is a kaolin having a finer particle size and a narrower particle size distribution, in combination with suitable morphology. Also provided are a method of preparing the kaolin product and methods of use.

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1. A fully or partially calcined kaolin having a GE brightness of at least about 92 and a particle size distribution of: equal to or greater than 99% by weight of particles with an equivalent spherical diameter (e.s.d.) of less than 10 microns;equal to or greater than 93% by weight of particles with

1. A fully or partially calcined kaolin having a GE brightness of at least about 92 and a particle size distribution of: equal to or greater than 99% by weight of particles with an equivalent spherical diameter (e.s.d.) of less than 10 microns;equal to or greater than 93% by weight of particles with an e.s.d. of less than 5 microns;equal to or greater than 85% by weight of particles with an e.s.d. of less than 2 microns;equal to or greater than 77% by weight of particles with an e.s.d. of less than 1 micron; andequal to or greater than 25% by weight of particles with an e.s.d. of less than 0.5 microns,wherein the fully or partially calcined kaolin has a +325 mesh residue content of 300 ppm or less and a median particle size of from 0.50 to 0.59 microns. 2. The fully or partially calcined kaolin according to claim 1 having a particle size distribution of: 99% to 100% by weight of particles with an e.s.d. of less than 10 microns;93% to 100% by weight of particles with an e.s.d. of less than 5 microns;85% to 98% by weight of particles with an e.s.d. of less than 2 microns;77% to 92% by weight of particles with an e.s.d. of less than 1 micron; and25% to 46% by weight of particles with an e.s.d. of less than 0.5 microns. 3. The fully or partially calcined kaolin according to claim 1, having a +325 mesh residue content of 90 ppm or less. 4. The fully or partially calcined kaolin according to claim 1, having a sodium oxide content less than or equal to 0.1% by weight of the fully or partially calcined kaolin. 5. The fully or partially calcined kaolin according to claim 1, having a GE brightness of at least about 92 to about 96. 6. The fully or partially calcined kaolin according to claim 1, having an oil absorption of greater than 100 to 140 lbs oil/100 lbs fully or partially calcined kaolin. 7. The fully or partially calcined kaolin according to claim 1, having a scattering coefficient at 457 nanometers of about 0.305 to about 0.335 m2/g. 8. The fully or partially calcined kaolin according to claim 1, having a scattering coefficient at 577 nanometers of about 0.223 to about 0.230 m2/g. 9. The fully or partially calcined kaolin according to claim 1, having a surface area of about 17.0 to about 25.0 m2/g. 10. The fully or partially calcined kaolin according to claim 1 having an Einlehner abrasion loss of 9 to 18 mg/105 rev. 11. The fully or partially calcined kaolin according to claim 1 having a gloss of about 30% to about 45%. 12. A paper coating formulation or paper binding formulation comprising a fully or partially calcined kaolin according to claim 1. 13. A paint comprising a fully or partially calcined kaolin according to claim 1. 14. A fully or partially calcined kaolin having a GE brightness of at least about 92 and a particle size distribution of: equal to or greater than 99% by weight of particles with an equivalent spherical diameter (e.s.d.) of less than 10 microns;equal to or greater than 93% by weight of particles with an e.s.d. of less than 5 microns;equal to or greater than 85% by weight of particles with an e.s.d. of less than 2 microns;equal to or greater than 77% by weight of particles with an e.s.d. of less than 1 micron; andequal to or greater than 25% by weight of particles with an e.s.d. of less than 0.5 microns,wherein the fully or partially calcined kaolin has a sodium oxide content of less than or equal to 0.25% by weight of the fully or partially calcined kaolin. 15. The fully or partially calcined kaolin according to claim 14, having a +325 mesh residue content of 300 ppm or less. 16. The fully or partially calcined kaolin according to claim 14, having a GE brightness of at least about 92 to about 96. 17. The fully or partially calcined kaolin according to claim 14, having a median particle size (d50) of 0.50 to 0.59 microns. 18. The fully or partially calcined kaolin according to claim 14, having a surface area of about 17.0 to about 25.0 m2/g. 19. The fully or partially calcined kaolin according to claim 14 having an Einlehner abrasion loss of 9 to 18 mg/105 rev. 20. The fully or partially calcined kaolin according to claim 14 having a gloss of about 30% to about 45%. 21. A fully or partially calcined kaolin having a GE brightness of at least about 92 and a particle size distribution of: equal to or greater than 99% by weight of particles with an equivalent spherical diameter (e.s.d.) of less than 10 microns;equal to or greater than 93% by weight of particles with an e.s.d. of less than 5 microns;equal to or greater than 85% by weight of particles with an e.s.d. of less than 2 microns;equal to or greater than 77% by weight of particles with an e.s.d. of less than 1 micron; andequal to or greater than 25% by weight of particles with an e.s.d. of less than 0.5 microns,wherein the fully or partially calcined kaolin has a +325 mesh residue content of 300 ppm or less and an oil absorption of from 120 to 140 lbs oil/100 lbs fully or partially calcined kaolin. 22. A method for preparing the fully or partially calcined kaolin of claim 1, comprising the steps of: providing a first kaolin feedstream having at least about 88-89% by weight of the particles having size of 1 μm or less;classifying the first kaolin feedstream by centrifugation to provide a fine particle size distribution of at least about 97-98% by weight of the particles having size of 1 μm or less;filtering the first kaolin feedstream to produce a filter cake;dispersing the filtrate in a sodium-free dispersion agent to provide a second kaolin feedstream; anddrying and heat treating the second kaolin feedstream,wherein the method for preparing the fully or partially calcined kaolin does not include a reductive bleaching step. 23. The method according to claim 22, further comprising flocculating the first feedstream prior to the filtering step. 24. The method according to claim 22, wherein the sodium-free dispersion agent is an ammonia-based dispersion agent. 25. The method according to claim 22, wherein the second kaolin feedstream has a pH of about 10. 26. The method according to claim 22, wherein heat treating comprises calcining at a temperature of from about 900° C. to about 1200° C. to produce a fully calcined kaolin. 27. The method according to claim 22, wherein the providing step comprises processing a blunged/degritted hydrous kaolin crude feedstock by one or more of magnetic separation, flotation, ozonation, or selective flocculation to produce the first kaolin feedstream having at least about 88-89% by weight of the particles having size of 1 μm or less. 28. The method according to claim 22, wherein the method excludes delamination processes. 29. The method according to claim 22, wherein the classifying step, filtering step, dispersing step, and drying and calcining step exclude a sodium-based dispersion agent.