Stabilized kaolin slurry and methods for improving kaolin slurry stability
Disclosed herein are stabilized kaolin slurries comprising a kaolin comprising no more than about 80% by weight of particles having an equivalent spherical diameter of less than 2 microns and at least one stabilizer, wherein the stabilized kaolin slurry has a 28-day pour test result of at least about 80% poured. Also disclosed are methods of making such stabilized kaolin slurries.
1. A method of making a stabilized kaolin slurry, comprising: filtering and rinsing a kaolin slurry to remove salt residue therefrom until said resulting kaolin has a conductivity of no more than about 100 μS; resolubilizing said resulting kaolin to form a resolubilized slurry; and adding at least one stabilizer to the resolubilized slurry, wherein said stabilized kaolin slurry comprises kaolin having a shape factor of at least 25.
2. The method according to claim 1 , wherein said stabilized kaolin slurry has a 28-day pour test result of at least 80% poured.
3. The method according to claim 2 , wherein said stabilized kaolin slurry has a 28-day pour test result of at least 85% poured.
4. The method according to claim 3 , wherein said stabilized kaolin slurry has a 28-day pour test result of at least 89% poured.
5. The method according to claim 1 , wherein said resulting kaolin has a conductivity of no more than about 80 μS.
6. The method according to claim 1 , wherein said stabilized kaolin slurry comprises kaolin having no more than about 80% by weight of particles having an equivalent spherical diameter (ESD) of less than 2 microns.
7. The method according to claim 6 , wherein said stabilized kaolin slurry comprises kaolin having about 25% to about 70% by weight particles having an ESD of less than 2 microns.
8. The method according to claim 6 , wherein said stabilized kaolin slurry comprises kaolin having about 20% to about 65% by weight particles having an ESD of less than 2 microns.
9. The method according to claim 8 , wherein said stabilized kaolin slurry comprises kaolin having about 25% to about 45% by weight particles having an ESD of less than 2 microns.
10. The method according to claim 9 , wherein said stabilized kaolin slurry comprises kaolin having about 35% by weight particles having an ESD of less than 2 microns.
11. The method according to claim 1 , wherein said at least one stabilizer comprises carboxymethylcellulose.
12. The method according to claim 1 , wherein said at least one stabilizer comprises at least one cellulosic thickener chosen from alkyl celluloses, ethyl hydroxyethyl celluloses, hydroxymethyl celluloses, hydroxyethyl celluloses, and hydroxypropyl celluloses.
13. The method according to claim 1 , wherein said at least one stabilizer is chosen from montmorillonite, smectite clays, hydrophobically modified ethoxylated urethanes, polyacrylates, polyvinyl pyrrolidone, sodium alginate, xanthan gum, silica thickeners, sodium magnesium silicate, acrylic acid copolymers, and nonionic hydrophobically modified polyethers.
14. The method according to claim 1 , wherein said at least one stabilizer is present in an amount ranging from about 0.01% to about 4% by weight, relative to the total weight of the slurry.
15. The method according to claim 1 , wherein substantially no dispersant is added to said kaolin slurry.
16. The method according to claim 1 , further comprising adding at least one dispersant.
17. The method according to claim 16 , wherein the at least one dispersant is chosen from polyacrylates, polyphosphates, and silicates.
18. The method according to claim 16 , wherein the at least one dispersant is present in an amount ranging from about 100 ppm to about 500 ppm on a dry basis relative to the total weight of the stabilized kaolin slurry.
19. The method according to claim 1 , further comprising flocculating said kaolin slurry prior to said filtering and rinsing.
20. The method according to claim 19 , wherein said flocculation comprises lowering the pH of said kaolin slurry to a value of about 5 or less.
21. The method according to claim 1 , further comprising spray drying said kaolin slurry prior to said filtering and rinsing.
22. A method for improving the stability of a kaolin slurry comprising: filtering and rinsing a kaolin slurry with water to remove salt residue therefrom, wherein said kaolin slurry comprises kaolin having no more than about 80% by weight particles having an ESD of less than 2 microns; and adding an effective amount of at least one stabilizer, such that the stabilized kaolin slurry has a 28 -day pour test result of at least 80% poured, wherein said kaolin slurry has a solids content of greater than 40%, wherein the method further comprises adjusting the pH of said kaolin slurry to have a range of about 4.5 to about 6.5 and adding at least one dispersant to said kaolin slurry, and wherein the at least one dispersant is present in an amount ranging from about 100 ppm to about 500 ppm on a dry basis relative to the total weight of the kaolin slurry.
23. The method according to claim 22 , wherein said at least one dispersant is chosen from polyacrylates, polyphosphates, and silicates.
24. The method according to claim 22 , wherein said stabilized kaolin slurry has a Brookfield viscosity at 50% adjusted solids ranging from about 300 cps to about 700 cps using a #2 spindle at 20 rpm.
25. The method according to claim 22 , wherein said stabilized kaolin slurry has a Hercules viscosity at 50% adjusted solids of less than about 10 dynes at 4400 rpm using an “A” bob.
26. The method according to claim 22 , wherein said slurry comprises kaolin having about 25% to about 70% by weight particles having an ESD of less than 2 microns.
27. The method according to claim 26 , wherein said slurry comprises kaolin having about 25% to about 45% by weight particles having an ESD of less than 2 microns.
28. The method according to claim 27 , wherein said slurry comprises kaolin having about 35% by weight particles having an ESD of less than 2 microns
29. The method according to claim 22 , wherein said stabilized kaolin slurry has a 28-day pour test result of at least about 85% poured.
30. The method according to claim 29 , wherein said stabilized kaolin slurry has a 28-day pour test result of at least about 89% poured.
31. A method of making a stabilized kaolin slurry, comprising: filtering and rinsing a kaolin slurry to remove salt residue therefrom until said resulting kaolin has a conductivity of no more than about 100 μS; resolubilizing said resulting kaolin to form a resolubilized slurry; adding at least one stabilizer to the resolubilized slurry; and adding at least one dispersant, wherein the at least one dispersant is present in an amount ranging from about 100 ppm to about 500 ppm on a dry basis relative to the total weight of the stabilized kaolin slurry.
32. A method of making a stabilized kaolin slurry, comprising: filtering and rinsing a kaolin slurry to remove salt residue therefrom until said resulting kaolin has a conductivity of no more than about 100 μS; resolubilizing said resulting kaolin to form a resolubilized slurry; adding at least one stabilizer to the resolubilized slurry; and flocculating said kaolin slurry prior to said filtering and rinsing, wherein said flocculation comprises lowering the pH of said kaolin slurry to a value of about 5 or less.