초록 ▼

The present invention relates to a kaolin composition having improved physical properties, for example, for use in the production of paper products. The composition can comprise kaolin having a shape factor of at least about 20. The kaolin can have a particle size distribution such that at least abo

The present invention relates to a kaolin composition having improved physical properties, for example, for use in the production of paper products. The composition can comprise kaolin having a shape factor of at least about 20. The kaolin can have a particle size distribution such that at least about 94% by weight of the kaolin can have an esd of less than about 2 μm and/or at least about 80% by weight of the kaolin can have an esd of less than 1 μm. The amount of the kaolin having an esd of less than about 0.25 μm can range from about 25% to about 60% by weight. The Hercules viscosity of the kaolin product is less than 4000 rpm at 18 dynes at 63% solids and less than 1500 rpm at 18 dynes at 69% solids when measured using the “A” bob. The present invention also relates to an improved method for making the kaolin product from sedimentary kaolin.

대표청구항 ▼

What is claimed is: 1. A composition comprising kaolin having a shape factor ranging from 32 to 49, wherein at least about 85% by weight of the kaolin has an esd of less than about 1 μm, the amount of the kaolin having an esd of less than about 0.25 μm ranges from 35% to about 60% by we

What is claimed is: 1. A composition comprising kaolin having a shape factor ranging from 32 to 49, wherein at least about 85% by weight of the kaolin has an esd of less than about 1 μm, the amount of the kaolin having an esd of less than about 0.25 μm ranges from 35% to about 60% by weight. 2. The composition according to claim 1, wherein the kaolin has a Hercules viscosity of less than about 4000 rpm at 18 dynes at 63% solids when measured using the “A” bob. 3. The composition according to claim 1, wherein at least about 94% by weight of the kaolin has an esd of less than about 2 μm. 4. The composition according to claim 1, wherein at least about 95% by weight of the kaolin has an esd of less than about 2 μm. 5. The composition according to claim 1, wherein at least about 96% by weight of the kaolin has an esd of less than about 2 μm. 6. The composition according to claim 1, wherein at least about 98% by weight of the kaolin has an esd of less than about 2 μm. 7. The composition according to claim 1, wherein the amount of the kaolin having an esd of less than about 2 μm ranges from about 94% to about 99% by weight. 8. The composition according to claim 1, wherein at least about 88% by weight of the kaolin has an esd of less than about 1 μm. 9. The composition according to claim 1, wherein at least about 92% by weight of the kaolin has an esd of less than about 1 μm. 10. The composition according to claim 1, wherein the kaolin has a shape factor ranging from 35 to 49. 11. The composition according to claim 1, wherein the kaolin has a shape factor ranging from 40 to 49. 12. The composition according to claim 1, wherein the kaolin has a shape factor ranging from about 35 to about 40. 13. The composition according to claim 1, wherein the amount of the kaolin having an esd of less than about 0.25 μm ranges from 35% to about 50% by weight. 14. The composition according to claim 1, wherein the kaolin has a shape factor ranging from 45 to 49, at least about 96% by weight of the kaolin has an esd of less than about 2 μm, at least about 85% by weight of the kaolin has an esd of less than about 1 μm, and the amount of the kaolin having an esd of less than about 0.25 μm ranges from 35% to about 45% by weight. 15. A method of refining kaolin, comprising: (a) providing a degritted kaolin slurry having a shape factor of at least about 10 and including at least about 80% by weight particles having an esd of less than about 2 μm; (b) wet media grinding the degritted kaolin slurry consuming in the range of from about 10 to about 200 Kw-hr/ton of energy; and (c) classifying the slurry to a fine fraction wherein from about 96% to about 98% by weight of the classified kaolin has an esd of about 2 μm and the classified kaolin has a shape factor of less than or equal to 49. 16. The method according to claim 15, wherein the degritted kaolin slurry provided in (a) has a shape factor of at least about 20. 17. The method according to claim 15, wherein the degritted kaolin slurry provided in (a) has a shape factor of at least about 30. 18. The method according to claim 15, wherein the degritted kaolin slurry provided in (a) has a shape factor of at least about 40. 19. The method according to claim 15 , wherein the amount of the kaolin in part (c) having an esd of less than about 0.25 μm ranges from about 25% to about 60% by weight. 20. The method according to claim 15, further comprising spray-drying the fine fraction. 21. The method according to claim 15, wherein the kaolin slurry is subjected to a beneficiation step selected from: selective flocculation, ozone treatment, flotation, magnetic separation, leaching, or any combination thereof. 22. The method according to claim 15, further comprising leaching the kaolin fine fraction and filtering and drying the leached kaolin fine fraction. 23. A coated paper comprising: a fibrous substrate; and a coating on the substrate comprising kaolin having a shape factor of at least 32, wherein at least about 85% by weight of the kaolin has an esd of less than about 1 μm, the amount of the kaolin having an esd of less than about 0.25 μm ranges from about 25% to about 60% by weight. 24. The paper according to claim 23, wherein at least about 94% by weight of the kaolin has an esd of less than about 2 μm. 25. The paper according to claim 23, wherein the kaolin has a Hercules viscosity of less than 4000 rpm at 18 dynes at 63% solids when measured using the “A” bob. 26. The paper according to claim 23, wherein the coating further comprises calcium carbonate. 27. A method of making a coated paper comprising: coating a fibrous substrate with a paper coating composition comprising kaolin having a shape factor of at least 32, at least 85% by weight of the kaolin has an esd of less than 1 μm, the amount of the kaolin having an esd of less than about 0.25 μm ranges from about 25% to about 60% by weight. 28. The method of claim 27, wherein at least about 94% by weight of the kaolin has an esd of less than about 2 μm. 29. The method of claim 27, wherein the kaolin has a Hercules viscosity of less than 4000 rpm at 18 dynes at 63% solids when measured using the “A” bob. 30. A coated paper comprising: a fibrous substrate; and a coating on the substrate comprising kaolin having a shape factor of at least 32, at least about 85% by weight of the kaolin having an esd of less than about 1 μm and the amount of the kaolin having an esd of less than about 0.25 μm ranges from about 25% to about 60% by weight, wherein gloss of the coated paper is greater than about 45 TAPPI units.