Claims
- 1. A method of manufacture, comprising the steps of:
- (1) bringing
- (a) aluminum hydroxide selected from the group consisting of gibbsite, bayerite, and norstrandite, and
- (b) seed effective for boehmite growth,
- in a liquid aqueous medium to form a mixture comprising aluminum hydroxide, seed and liquid aqueous medium and
- (2) hydrothermally digesting the mixture in a pressure vessel for producing colloidal boehmite at the expense of the aluminum hydroxide.
- 2. A method as claimed in claim 1, including a dispersing agent in the digesting step.
- 3. A method as claimed in claim 1, wherein at least 50% of the quantity seed plus aluminum hydroxide is aluminum hydroxide.
- 4. A method as claimed in claim 1, the seed having a surface area of at least about 100 m.sup.2 /g
- 5. A method as claimed in claim 1, the aluminum hydroxide having an average particle size equal to or less than 5 microns.
- 6. A method as claimed in claim 1, the step of digesting being at about 180 to 220.degree. C. for about one hour.
- 7. A method as claimed in claim 1, percent solids in the digest being in the range 2 to 40%.
- 8. A method as claimed in claim 7, percent solids in the digest being in the range 41/2 to 20%.
- 9. A method as claimed in claim 1, pH during digest being in the range of 2 to 11.
- 10. A method as claimed in claim 9, pH during digest being in the range of 4 to 10.
- 11. A method as claimed in claim 1, wherein the digest is an acidic digest.
- 12. A method as claimed in claim 1, wherein the digest is a basic digest.
- 13. A method as claimed in claim 1, the boehmite having a surface area in the range 35-250 m.sup.2 /g.
- 14. A method as claimed in claim 1, the seed being, except for minor contamination, a material other than said aluminum hydroxide.
- 15. A method of making colloidal boehmite which forms a glassy film upon drying, the colloidal boehmite having properties including boehmite particle surface area of about 35 to 250 m.sup.2 /g and aqueous dispersibility, comprising the steps of:
- (1) forming a mixture of
- (a) aluminum hydroxide selected from the group consisting of gibbsite, bayerite and nordstrandite, the aluminum hydroxide having a fine particle size of about 5 microns or less,
- (b) seed effective for boehmite growth, the seed being amorphous alumina or boehmite, the seed having a surface area of at least about 100 m.sup.2 /g and a median particle size less than about 500 Angstroms, and
- (c) a liquid aqueous medium,
- (2) hydrothermally digesting the mixture in a pressure vessel for a time sufficient to substantially convert the aluminum hydroxide to said colloidal boehmite, wherein the temperature of the digest is about 180 to 220.degree. C., the percent solids of the aluminum hydroxide and the seed in the digest is in the range of 2 to 40% Al.sub.2 O.sub.3, and the pH during digest is in the range of 2 to 11, and
- (3) peptizing the mixture before or after said digesting step.
- 16. A method as claimed in claim 13, the boehmite being dispersible to a median particle size less than about 500 Angstroms.
- 17. A method of producing microcrystalline boehmite comprising reacting in an autoclave a hydrated alumina boehmite precursor in the presence of water and boehmite seed material having a crystal size less than about 0.05 microns, the temperature, pressure, and pH being maintained at conditions under which boehmite is a stable phase for a time sufficient to convert the major portion of said precursor to microcrystalline beohmite.
- 18. A method of producing microcrystalline boehmite as recited in claim 17, wherein the crystal size of said boehmite seed material is less than about 0.005 microns.
- 19. A method of making a microcrystalline boehmite product comprising heating under autogenous pressure a boehmite alumina precursor in an aqueous medium having an acidic or basic pH in the presence of boehmite seed particles finer than about 0.05 microns, said seed particles being present in an amount of at least 5% by weight of the precursor alumina, calculated as Al.sub.2 O.sub.3, said heating being carried out above 180.degree. C. for about one hour.
- 20. A method as in claim 19 in which said pH is about 4 and said boehmite seed particles are present in an amount of at least 15% by weight of the precursor alumina, calculated as Al.sub.2 O.sub.3.
- 21. A method as in claim 20, wherein the boehmite seed particles are finer than about 0.005 microns and are present in an amount of about 50% by weight of the precursor alumina, calculated as Al.sub.2 O.sub.3.
- 22. In a process of producing a product from a boehmite material, the improvement wherein the boehmite material is prepared by:
- a. bringing a hydrated boehmite precursor and seed effective for boehmite growth together in a liquid aqueous medium to form a mixture comprising hydrated boehmite precursor, seed and liquid aqueous medium; and
- b. hydrothermally digesting the mixture in a pressure vessel to produce colloidal boehmite at the expense of the hydrated boehmite precursor.
Parent Case Info
This is a continuation of co-pending application Ser. No. 534,665 filed on Sept. 22, 1983, now abandoned.
US Referenced Citations (5)
Continuations (1)
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Number |
Date |
Country |
Parent |
534665 |
Sep 1983 |
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