WO1997015530B1

WO1997015530B1 - Micronized alkaline earth metal carbonate

Info

Publication number: WO1997015530B1
Application number: PCT/DE1996/002006
Authority: WO
Filing date: 1996-10-22
Publication date: 1997-07-03
Anticipated expiration: 1998-04-26

Abstract

The invention concerns a micronized alkaline earth metal carbonate prepared with or without the use of an agent preventing crystal growth, and a process for its preparation and use. The prepared micronized calcium carbonate, barium carbonate with a BET surface area ranging from 3 to 30 m2/g or strontium carbonate with a BET surface area ranging from 3 to 50 m2/g is suitable in particular for preparing capacitors, thermistors and other oxide ceramic electrical components containing calcium oxide, barium oxide or strontium oxide, and high-temperature superconductors. Ammonium salts or alkylammonium salts of carboxylic acids having a total of between 3 and 12 carbon atoms and at least two COOH groups or at least two OH groups, e.g. salts of maleic acid or nitric acid, are used as agents preventing crystal growth.

Claims

AMENDED CLAIMS [received at the International Bureau on 14 May 1997 (14.05.97); original claims 1-4, 8 and 14-16 changed; all other claims unchanged (4 pages)]

1. A process for the preparation of particle-form alkaline earth metal carbonate EaCOß, wherein at least 95% of the particles have a diameter of <1.0 microns and Ea is Ba or Sr, wherein an Ea (OH) 2 solution with a concentration from 0.1 to 0.75 mol / 1 of Ea (OH) 2 with CO2 to form a reaction mixture, wherein per liter of solution about 2 to 30 1 CÜ2 gas used, the reaction mixture passes through a continuous mixing reactor, in the shear, shear and frictional forces of interengaging tools act on the reaction mixture at high relative speed, and after passing through the reactor, EaCC> 3 formed from the reaction mixture is separated off and dried.

2. The method according to claim 1, characterized in that BaCOß is produced.

3. The method according to claim 1, characterized in that the separated SrCθ3 or BaCC> 3 is washed one or more times with water before drying.

4. The method according to claim 1, characterized in that one carries out the precipitation of SrC03 or BaCC> 3 in the solution with CO2 ver¬ at a temperature in the range of 0 ° C to 130 ° C, preferably 40 to 130 ° C. ,

5. The method according to claim 1, characterized in that the number of revolutions of the rotor 2,000 to 8,000 rev / min carries be¬.

6. The method according to claim 1, characterized in that the residence time of the reaction mixture in the mixing reactor to 5 see. 1 9

7. The method according to claim 1, characterized in that before, during and / or added after the precipitation of a Kri¬ stall growth preventing agent.

8. A process for the preparation of particulate BaCC> 3 or SrC03 according to claim 1 or 7, characterized in that using a crystal growth verhin¬ reducing agent selected from the group comprising ammonium salts and Aikylammoniumsalze of carboxylic acids, the total of 3 to 12 C atoms and at least 2 COOH groups or minde¬ least 2 OH groups, an Ea (OH) 2 solution having a concentration of 0.1 to 0.75 mol / 1 of Ea (OH) 2 with CO2 under Forming a reaction mixture is added, whereby per liter of solution about 2 to 30 liters of CO 2 gas are used, the reaction mixture is passed through a mixing reactor in which shear, shear and frictional forces act upon the reaction mixture, after passing the device from the Reak¬ tion mixture formed EaC03, namely BaCθ3 or SrCθ3 separates off and dried.

9. The method according to claim 8, characterized in that one uses an ammonium salt or alkyl ammonium salt of citric acid, malic acid, adipic acid, gluconic acid, glucaric acid, glucuronic acid, tartaric acid or maleic acid, preferably an ammonium salt of citric or maleic acid.

10. The method according to claim 9, characterized in that one uses ammonium citrate or maleate, which has been prepared by introducing NH3 or by adding aqueous NH3 solution in aqueous citric acid solution or maleic acid solution to reach a pH of 6 to 8.

11. The method according to claim 8, 9 or 10, characterized ge indicates that the carboxylic acid salt is used in the form of a wäß¬ rigen solution. 20

12. The method according to claim 8, characterized in that one uses the carboxylic acid salt in an amount of at least 0.01 wt .-%, preferably 0.01 to 5 wt .-%, based on the produced EaCθ3 or the EaCθ3 to be produced.

13. The method according to claim 8, characterized in that admixing the carboxylic acid salt immediately after passing through the reaction mixture through the reactor.

14. Particulate BaCO 3 having a BET surface area in the range from 3 to 30 m ² / g, SrCO 3 having a BET surface area in the range from 3 to 50 m ² / g, where at least 95%, preferably at least 99%, in particular 100% of the particles have a diameter <1.0 .mu.m, obtained by a process of claims 1 to 13 using crystal growth-preventing agents selected from the group um¬ comprising ammonium salts and Aikylammoniumsalze of Carbonsäu¬ ren, the total of 3 have up to 12 carbon atoms and at least 2 COOH groups or at least 2 OH groups.

15. BaCθ3 or SrCθ3 according to claim 1, characterized gekenn¬ characterized in that ammonium salts or Aikylammoniumsalze the Ap¬ felsäure, adipic acid, citric acid, gluconic acid, Glucarsäu¬ re, glucuronic acid, tartaric acid or maleic acid wur¬ used.

16. Particulate BaCO 3 having a BET surface area in the range of 3 to 30 m ² / g, particulate SrCO 3 having a BET surface area in the range of 3 to 50 m ² / g, wherein at least 90% of the particles have a diameter in the range of 0 , 1 to 1.0 μm, obtained by the process of claims 1 to 6, and which is free from the crystal growth prevent¬ the means. 2 1

17. Use of barium carbonate according to claim 14, 15 or 16 for thermal solid reactions, in particular for the production of oxide-containing ceramic materials for elektri¬ cal and magnetic applications, in particular for the manufacture of oxide superconductors, of thermistors, capacitors.

18. Use of strontium carbonate according to claim 14, 15 or 16 for thermal solid-state reactions, in particular for the production of oxide-containing ceramic materials for elek¬ trical and magnetic applications, in particular for the production of oxide superconductors, of thermistors, capacitors Kon¬.