Beta-aluminum oxide ceramics obtainable by extrusion of a mixture that contains a sodium compound

Abstract

Use of a composition comprising A) from 55 to 90% by weight of aluminum oxide, B) from 5 to 35% by weight of a sodium compound which at a pH of 7 at 20 C. has a solubility in water of 300 g/l and can be converted by thermal means virtually exclusively into sodium oxide as only solid, C) from 0 to 15% by weight of a magnesium compound and/or a lithium compound selected from the group consisting of: magnesium oxide, magnesium carbonate, magnesium nitrate, lithium oxide, lithium carbonate, lithium nitrate and D) from 0 to 30% by weight of zirconium dioxide
for producing a shaped ceramic body by extrusion.

Claims

1. A process for producing a shaped ceramic body, comprising: A. mixing a composition comprising i) from 55 to 90% by weight of aluminum oxide as component A), ii) from 5 to 35% by weight of a sodium compound which at a pH of 7 and 20 C. has a solubility in water of 300 g/l and can be converted by thermal means virtually exclusively into sodium oxide as only solid as component B), iii) from 0 to 15% by weight of a magnesium compound and/or a lithium compound selected from the group consisting of: magnesium oxide, magnesium carbonate, magnesium nitrate, lithium oxide, lithium carbonate, lithium nitrate as component C), and iv) from 0 to 30% by weight of zirconium dioxide as component D) with water and/or alcohols to give a suspension, B. milling the suspension in a ball mill, C. drying the suspension, D. converting the dried suspension into a moldable composition by combining with water, a binder and optionally other additives, E. extruding the moldable composition, and F. thermally treating the extruded moldable composition in the temperature range from 1200 C. to 1700 C.; wherein the composition after milling has a particle size distribution D.sub.50 in the range from 0.5 to 1.5 microns; wherein the amount of the composition of i) to iv) is from 20 to 50% by weight, based on the moldable composition.

2. The process according to claim 1, wherein the shaped ceramic body is a ceramic capable of conducting sodium ions.

3. The process according to claim 1, wherein the sodium compound of the component B) is selected from the group consisting of: sodium oxalate, sodium carbonate, sodium hydrogencarbonate, sodium acetate, and sodium cyanate.

4. The process according to claim 1, wherein at least some magnesium compound or a lithium compound is used in iii).

5. The process according to claim 1, wherein sodium oxalate is used in ii).

6. A moldable composition which is suitable for producing shaped ceramic bodies and is obtained by a process comprising: A. mixing a composition comprising i) from 55 to 90% by weight of aluminum oxide as component A), ii) from 5 to 35% by weight of a sodium compound which at a pH of 7 and 20 C. has a solubility in water of 300 g/l and can be converted by thermal means virtually exclusively into sodium oxide as only solid as component B), iii) from 0 to 15% by weight of a magnesium compound and/or a lithium compound selected from the group consisting of: magnesium oxide, magnesium carbonate, magnesium nitrate, lithium oxide, lithium carbonate, lithium nitrate as component C), and iv) from 0 to 30% by weight of zirconium dioxide as component D) with water and/or alcohols to give a suspension, B. milling the suspension in a ball mill, C. drying the suspension, D. converting by combining with water, a binder and optionally other additives into the moldable composition, and wherein the amount of the composition of i) to iv) is from 20 to 50% by weight, based on the moldable composition; wherein the composition after milling has a particle size distribution D.sub.50 in the range from 0.5 to 1.5 microns.

7. The moldable composition according to claim 6, wherein the sodium compound of the component B) is selected from the group consisting of: sodium oxalate, sodium carbonate, sodium hydrogencarbonate, sodium acetate, and sodium cyanate.

8. The moldable composition according to claim 6, wherein at least some magnesium compound or a lithium compound is used in iii).

9. The moldable composition according to claim 6, wherein sodium oxalate is used in ii).

10. A process for producing a shaped ceramic body comprising mixing a composition comprising A) from 55 to 90% by weight of aluminum oxide, B) from 5 to 35% by weight of a sodium compound which at a pH of 7 at 20 C. has a solubility in water of 300 g/l and can be converted by thermal means virtually exclusively into sodium oxide as only solid, C) from 0 to 15% by weight of a magnesium compound and/or a lithium compound selected from the group consisting of: magnesium oxide, magnesium carbonate, magnesium nitrate, lithium oxide, lithium carbonate, lithium nitrate and D) from 0 to 30% by weight of zirconium dioxide, with a suspension medium to give a suspension; milling the suspension in a ball mill; drying the suspension; converting the dried suspension into a moldable composition by combining with water, a binder and optionally other additives; and extruding the moldable composition; wherein the moldable composition is not calcined before extrusion; wherein the amount of A) to D) in the moldable composition, based on the moldable composition, is in the range from 20 to 50% by weight; and wherein the composition after milling has a particle size distribution D.sub.50 in the range from 0.5 to 1.5 microns.

11. The process according to claim 10, wherein the sodium compound of the component B) is selected from the group consisting of: sodium oxalate, sodium carbonate, sodium hydrogencarbonate, sodium acetate, and sodium cyanate.

12. The process according to claim 10, wherein the shaped ceramic body is a ceramic capable of conducting sodium ions.

13. The process according to claim 10, wherein at least some magnesium compound or a lithium compound is used in C).

14. The process according to claim 10, wherein sodium oxalate is used in B).

Description

EXAMPLES

(1) LuvitecK90 is a registered trademark of BASF SE. The product is a vinylpyrrolidone homopolymer having a molar mass Mw of about 1400 kDa and a molar mass Mn of about 325 kDa. Further information on the product may be found in the brochure PVP and more . . . LUVITEC, LUVICROSS und COLLACRALVALSpezialpolymere fr technische Anwendungen (version of January 2010) of BASF SE.

(2) Methocel K4M Premium is a trademark of DowWolff Cellulosics. The product is a methyl ester of cellulose, also known as additive E 461.

(3) Comparison of sodium formate and sodium oxalate with polyvinylpyrrolidone (Luvitec K90) in water.

Example C1 (for Comparison)

(4) 18 g of sodium formate were slowly added while stirring to 50 g of a 1% strength by weight solution of Luvitec K90 in water until saturated was reached. Luvitec K90 precipitated as a greasy precipitant.

Example 1 (According to the Invention)

(5) 6.8 g of sodium oxalate were slowly added while stirring to 50 g of a 1% strength by weight solution of Luvitec K90 in water. No greasy precipitate was formed and insoluble sodium oxalate settled at the bottom of the vessel.

(6) Comparison of sodium formate and sodium oxalate with methyl cellulose (Methocel K4M Premium from DowWolff Cellulosics) in water.

Example C2 (for Comparison)

(7) 6.8 g of sodium formate were slowly added while stirring to 50 g of a 1% strength by weight solution of Methocel K4M Premium in water until saturation was reached. Foaming occurred.

Example 2 (According to the Invention)

(8) 6.8 g of sodium oxalate were slowly added while stirring to 50 g of a 1% strength by weight solution of Methocel K4M Premium in water. No foaming occurred and insoluble sodium oxalate settled at the bottom of the vessel.

(9) The examples and comparison examples show that sodium salts which are readily soluble in water (sodium formate) lead to precipitation or salting-out of the binder systems, in contrast to sodium salts which are sparingly soluble in water (sodium oxalate).