Claims
- 1. A method of making a stable anionic sol containing anionic colloidal alumina hydrate which consists essentially of the steps of:
- (a) calcining alumina hydrate to form coarse particles of crystalline alumina monohydrate, and
- (b) reducing the average diameter of the coarse particles so formed to less than 1 micron in all dimensions by an operation consisting essentially of attrition milling said coarse particles with a dispersion liquid to produce a colloidal dispersion of the particles in the liquid.
- 2. A method according to claim 1, in which the dispersion liquid is an aqueous solution of an alkali.
- 3. A method according to claim 1, in which the alumina hydrate has been obtained from bauxite by the Bayer process.
- 4. A method according to claim 1, in which the alumina hydrate is calcined at from 300.degree. C. to 750.degree. C.
- 5. A method according to claim 1, in which the alumina monohydrate is quenched in water after calcining.
- 6. A method according to claim 1, in which the pH value of the colloidal dispersion produced is above 10.
- 7. A method according to claim 1, in which the relative proportions of dispersion liquid and the coarse particles are such as to produce a concentration of alumina monohydrate, measured as Al.sub.2 O.sub.3, of 25 through 45 g per 100 ml of dispersion.
- 8. A method according to claim 1, in which the average diameter of the alumina hydrate calcined in step (a) is about 50 microns.
- 9. A method according to claim 1, in which a mineralizer or a compound which yields a mineralizer on firing is added to the calcined particles before milling.
- 10. A method according to claim 9, in which the mineralizer is magnesium oxide.
- 11. A method of making a mixed anionic sol containing anionic colloidal alumina hydrate and anionic colloidal silica in the dispersed state, which comprises mixing a stable anionic sol containing anionic colloidal alumina hydrate made by a method according to claim 1 with an anionic colloidal silica dispersion.
- 12. A method according to claim 11, in which a volatile base is incorporated in the mixed sol.
- 13. A method of making a stable mixed anionic sol containing anionic colloidal alumina hydrate and anionic colloidal silica in the dispersed state, which consists essentially of the steps of:
- (a) calcining alumina hydrate to form coarse particles of crystalline alumina monohydrate, and
- (b) reducing the average diameter of the coarse particles so formed to less than 1 micron in all dimensions by an operation consisting essentially of attrition milling said coarse particles with a dispersion liquid containing dispersed colloidal silica to produce a colloidal dispersion of alumina monohydrate and silica particles in the liquid.
- 14. A method of making a stable mixed anionic sol containing anionic colloidal alumina hydrate and anionic colloidal silica in the dispersed state, which consists essentially of the steps of:
- (a) calcining alumina hydrate to form coarse particles of crystalline alumina monohydrate,
- (b) mixing said particles with silica, and
- (c) reducing the average diameter of the coarse particles of crystalline alumina monohydrate to less than 1 micron in all dimensions by an operation consisting essentially of attrition milling the mixture so formed with a dispersion liquid to produce a colloidal dispersion of alumina monohydrate and the silica particles in the liquid.
Priority Claims (1)
Number |
Date |
Country |
Kind |
8302952 |
Feb 1983 |
GBX |
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Parent Case Info
This application is a continuation-in-part of application Serial No. 768,249, filed 8/22/85, now abandoned in favor of the present case, itself a continuation-in-part of Application Ser. No. 576,575 filed 2/3/84, abandoned in favor of Ser. No. 768,249.
US Referenced Citations (10)
Non-Patent Literature Citations (3)
Entry |
"Plant and Equipment Survey Mixers--Part 2", Processing, Sep. 1981, pp. 29, 31, 33 & 35. |
Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, vol. 2, John Wiley & Sons, Inc., 1978, pp. 223 & 224. |
Conoco Catapal.RTM., SB Alumina Data Sheet, 10-1977. |
Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
768249 |
Aug 1985 |
|
Parent |
576575 |
Feb 1984 |
|