METHOD FOR THE PRODUCTION OF A FINELY CRYSTALLINE BOEHMITE AND APPLICATION OF SAID BOEHMITE AS FLAME RETARDANT IN PLASTICS

Abstract

Method for the production of a finely crystalline boehmite and application of said boehmite as flame retardant in plastics. The abstract of the disclosure is submitted herewith as required by 37 C.F.R. §1.72(b). As stated in 37 C.F.R. §1.72(b): A brief abstract of the technical disclosure in the specification must commence on a separate sheet, preferably following the claims, under the heading “Abstract of the Disclosure.” The purpose of the abstract is to enable the Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure. The abstract shall not be used for interpreting the scope of the claims. Therefore, any statements made relating to the abstract are not intended to limit the claims in any manner and should not be interpreted as limiting the claims in any manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the evolution of the BET-surface in relation to the duration of grinding for 3 crystalline precursor boehmites;

FIG. 2 shows a comparison of the evolution of BET-surface in relation to the duration of grinding for a time span of 180 minutes, wherein a dispersion having a pH-value of 9 and second dispersion having a pH-value of 4 are compared; and

FIG. 3 shows the results of the determination of the evolution of pore volumes during the experiments of FIG. 2.

Claims

1. A method for the industrial production of boehmite comprising the steps of: A) mixing aluminummonohydrate with a boehmite crystal structure in water sufficient to form an aqueous dispersion of said aluminummonohydrate in said water;B) grinding the dispersion, formed in step A, while maintaining said dispersion in a pH range of 2 to 4 and forming boehmite seed crystals;C) mixing, a production quantity of a hydrate and a sufficient quantity of said boehmite seed crystals in a sufficient quantity of a basic aqueous solution, sufficiently to form a sufficient dispersion of said hydrate and said boehmite seed crystals in said basic aqueous solution;D) heating said dispersion, formed in step C), sufficiently in a temperature range of 110 degrees Celsius to 180 degrees Celsius for a sufficient time to autocatalytically convert at least a substantial portion or essentially all of said aluminummonohydrate to boehmite with a median grain size diameter in the range of 50 to 400 nanometers and a surface in the range of 10 to 40 meters squared per gram, measured by the Braunauer-Emmet-Teller method.

2. The method according to claim 1 including further steps of: E) repeating steps C and D;F) taking a portion of the boehmite produced in the original step D or a repeated step D;G) using said boehmite from step F as seed crystals;H) mixing a further production quantity of a hydrate and a sufficient quantity of said boehmite seed crystals from step G, in a sufficient quantity of a basic aqueous solution, sufficiently to form a sufficient dispersion of said hydrate and said boehmite seed crystals in said basic aqueous solution;I) heating said dispersion, formed in step F, sufficiently in a temperature range of 110 degrees Celsius to 180 degrees Celsius for a sufficient time to autocatalytically convert at least a substantial portion or essentially all of said aluminummonohydrate to boehmite with a median grain size diameter in the range of 50 to 400 nanometers and a surface in the range of 10 to 40 meters squared per gram, measured by the Braunauer-Emmet-Teller method.

3. The method according to claim 2 characterized in that the solid concentration of crystalline seed is one of: 0.5 to 50 percent, and1 to 20 percentin relation to the hydrate source.

4. The method according to claim 3 characterized in that the concentration of sodium hydroxide solution in the dispersion is one of: 4 to 50 grams per liter, and30 to 40 grams per literin relation to free Na2O.

5. The method according to claim 4 characterized in that the hydrate source has a median grain size distribution one of: 0.5 to 100 μm, and0.5 to 10 μmand a concentration within the dispersion of one of:10 to 500 grams per liter, and50 to 150 grams per liter.

6. The method of combining the boehmite with a plastic, according to claim 1, including mixing said boehmite with a plastic to produce a flame retardant plastic.

7. The method of combining the boehmite with a plastic, according to claim 6, including forming said flame retardant plastics into one of: insulation of electrical cables, and sheathings of electrical cables.

8. The method according to claim 5 including further steps of; J) taking a portion of the boehmite produced;K) using said boehmite from step I as seed crystals;L) mixing a further production quantity of a hydrate and a sufficient quantity of said boehmite seed crystals from step J, in a sufficient quantity of a basic aqueous solution, sufficiently to form a sufficient dispersion of said hydrate and said boehmite seed crystals in said basic aquesous solution;M) heating said dispersion, formed in step K), sufficiently in a temperature range of 110 degrees Celsius to 180 degrees Celsius for a sufficient time to autocatalytically convert at least a substantial portion or essentially all of said aluminummonohydrate to boehmite with a median grain size diameter in the range of 50 to 400 nanometers and a surface in the range of 10 to 40 meters squared per gram, measured by the Braunauer-Emmet-Teller method.

9. Method for making boehmite seed crystals comprising the steps of: A) mixing aluminummonohydrate with a boehmite crystal structure in water sufficient to form an aqueous dispersion of said boehmite crystal structured aluminummonhydrate in said water;B) grinding the dispersion, formed in step A, while maintaining said dispersion in a pH range of 2 to 4 and forming boehmite seed crystals.

10. The method according to claim 9 characterized in that the pH-value is adjusted with one of: an organic acid, andacetic acid.

11. The method according to claim 10 characterized in that the dispersion in step A) comprises a fraction of solid content of: 5 to 50 weight percent, and10 to 25 weight percentof aluminummonohydrate-source.

12. The method according to claim 11 characterized in that in step B) the temperature of the dispersion is kept in a range of 50 to 70° C. during grinding.

13. The method according to claim 12 characterized in that the aluminummonohydrate source has an median grain size diameter of at least 500 nanometers and a Braunauer-Emmet-Teller surface of at least 20 meters squared per gram.

14. The method according to claim 9 characterized in that the dispersion in step A) comprises a fraction of solid content of: 5 to 50 weight percent, and10 to 25 weight percentof aluminummonohydrate-source.

15. The method according to claim 9 characterized in that in step B) the temperature of the dispersion is kept in a range of 50 to 70° C. during grinding.

16. The method according to claim 10 characterized in that in step B) the temperature of the dispersion is kept in a range of 50 to 70° C. during grinding.

17. The method according to claim 9 characterized in that the aluminummonohydrate source has an median grain size diameter of at least 500 nanometers and a Braunauer-Emmet-Teller surface of at least 20 meters squared per gram.

18. The method according to claim 10 characterized in that the aluminummonohydrate source has a median grain size diameter of at least 500 nanometers and a Braunauer-Emmet-Teller surface of at least 20 meters squared per gram.

19. The method according to claim 11 characterized in that the aluminummonohydrate source has an median grain size diameter of at least 500 nanometers and a Braunauer-Emmet-Teller surface of at least 20 meters squared per gram.

20. A boehmite comprising a median grain size diameter in the range of 50 to 400 nanometers, a Braunauer-Emmet-Teller surface in the range of 10 to 40 meters squared per gram and a pore volume in the range of 0.05 to 0.5 centimeters cubed per gram measured according to Gurwitsch method.