Process for producing nano-scale crystalline boehmite
A crystalline Boehmite product and a method of forming said product is provided in which the crystalline Boehmite exhibits an average particle size (d50) that is less than 7,000 nanometers. This method comprises preparing an aqueous slurry by mixing together water, large aluminum oxide precursors, a highly dispersible Boehmite grade, and optionally, an organic dispersing agent; adjusting the pH of the slurry; heating the slurry for a predetermined duration of time; collecting the slurry to form a wet cake; and drying the wet cake to obtain the crystalline Boehmite product. The crystalline Boehmite product may be mixed with a plastic resin to form a flame retardant plastic mixture, which can be subjected to a conventional plastic processing method to form a flame retardant composite.
1. A method of forming a crystalline Boehmite product, the method comprising:
preparing an aqueous slurry by mixing together water, large aluminum oxide precursors, a highly dispersible Boehmite grade, and optionally, a dispersing agent;
adjusting the pH of the slurry to be between about 8.0 to about 12.0;
heating the slurry to a temperature between 120° C. and 250° C. for a duration of time that is from about 1.0 hour up to about 24 hours;
collecting the slurry to form a wet cake; and
drying the wet cake to obtain the crystalline Boehmite product;
wherein the crystalline Boehmite product exhibits an average particle size (d 50 ) that is greater than about 100 nanometers and less than about 3,000 nanometers;
wherein the large aluminum oxide precursors exhibit an average particle size (d 50 ) of 50 micrometers or more; and
wherein the crystalline Boehmite product comprises a crystallite size that is between about 30 nanometers to about 120 nanometers.
2. The method according to claim 1 , wherein the method includes the use of an organic dispersing agent.
3. The method according to claim 2 , wherein the organic dispersing agent is polyacrylic acid, a salt of polyacrylic acid, an acrylates copolymer, or a mixture thereof.
4. The method according to claim 1 , wherein the pH of the slurry is adjusted to be between about 10.0 and about 12.0.
5. The method according to claim 1 , wherein the slurry is heated to a temperature between about 170° C. to about 220° C.
6. The method according to claim 5 , wherein the slurry is heated to a temperature of about 180° C.
7. The method according to claim 1 , wherein the slurry is heated for a time duration between about 1 hour and about 10 hours.
8. The method according to claim 7 , wherein the slurry is heated for a time duration between about 2 hours and about 5 hours.
9. The method according to claim 1 , wherein the average particle size (d 50 ) of the crystalline Boehmite product is between about 500 nanometers and 2,000 nanometers.
10. The method according to claim 1 , wherein the highly dispersible Boehmite acts as a seed material.
11. The method according to claim 1 , wherein the large aluminum oxide precursors are a coarse grade Gibbsite.
12. The method according to claim 1 , wherein the highly dispersible Boehmite exhibits a particle size that is less than 100 nm and is formed using heat and/or shear with concentrations of 0.5% to 7.5% mineral or organic acid relative to the alumina content.
13. The method according to claim 1 , further comprising
mixing the crystalline Boehmite product with a plastic resin to form a flame retardant plastic mixture; and
subjecting the flame retardant plastic mixture to a conventional plastic processing method to form a flame retardant composite.
14. The method according to claim 13 , wherein the plastic resin is selected as either a thermoplastic or a thermoset resin.
15. The method according to claim 14 , wherein the plastic resin is a thermoplastic resin selected as one from the group of olefin resins, aromatic polyesters, polyesters, and polyam ides.
16. The method according claim 14 , wherein the plastic resin is a thermoset resin selected as one from the group of an epoxy resin, vinyl ester resin, phenol resin, unsaturated polyester resin, polyimide, polyurethane, and melamine resin.
17. The method according to claim 13 , wherein the plastic processing method is compounding, extrusion, or molding.