Anhydrous sodium carbonate having a low pore content

Patent metadata

Field	Value
Publication number	US-9388053-B2
Application number	US-201214362926-A
Country	US
Kind code	B2
Filing date	Nov 10, 2012
Priority date	Dec 9, 2011
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

The present invention relates to a highly pure, anhydrous sodium carbonate having a low pore content for use in pharmaceutical formulations and in the foods industry. Furthermore, a novel process for the preparation of this sodium carbonate is provided.

First claim

The invention claimed is:

1. Crystalline sodium carbonate, which crystalline sodium carbonate:
is an anhydrous product,
is a highly pure product shown by a sodium carbonate content of not less than 99.5% determined acidimetrically,
consists of particles having a smooth surface structure and a low pore content shown by a BET pore volume of about 0.0013 cm 3 /g or less,
has a drying loss after preparation of not more than 0.2% by weight, and
has a BET surface area of less than 1 m 2 /g.

2. Crystalline sodium carbonate according to claim 1 , which
has a BET surface area of less than 0.5 m 2 /g,
and
has a drying loss after preparation of less than 0.15% by weight.

3. Crystalline sodium carbonate according to claim 1 , which has a water vapour absorption capacity (WVAC) of <5% by weight at 60% relative humidity; <10% by weight at 70% relative humidity; <15% by weight at 80% relative humidity and <50% at 90% relative humidity.

4. Crystalline sodium carbonate according to claim 1 , which has a bulk density in the range from 1.050 to 1.140 g/ml, a tapped density in the range from 1.18 to 1.30 g/ml and an angle of repose in the range from 30.0° to 31.5°.

5. Process for the preparation of crystalline sodium carbonate according to claim 1 , which comprises:
preparing an aqueous solution in which sodium hydrogencarbonate and sodium hydroxide solution are dissolved in an amount such that the solution has a density in the range from 1.2 to 1.4 g/ml at 65° C. and sodium hydrogencarbonate (NaHCO 3 ) and sodium hydroxide solution (NaOH) are present therein in a molar ratio of 1:1 to 1:1.3,
subsequently, successively adding a catalytic amount of hydrogen peroxide and activated carbon to the solution, which is then filtered after mixing,
feeding the clear solution obtained from the previous step to a crystallisation apparatus, in which liquid is removed by vacuum evaporation and a suspension density in the range from 1.54-1.86 g/ml is set at which the crystallisation is carried out,
separating off the crystals formed in the previous step by filtration, centrifugation or spinning-off, and
introducing the crystals into a dryer and drying them with continuous mixing until the product obtained has a drying loss of not more than 0.2% by weight.

6. Process according to claim 5 , wherein the process is carried out in a loop crystalliser.

7. Process according to claim 5 , wherein the process is carried out batchwise.

8. Process according to claim 5 , wherein the temperature during the crystallisation is set in the range from 50 to 95° C., while the density of the suspension is in the range from 1.54-1.86 g/ml.

9. Process according to claim 5 , wherein the aqueous solution is mixed with 30% hydrogen peroxide in a ratio of 700:1 to 900:1, based on the weight of the entire solution, and with activated carbon in a ratio of 20000:1 to 10000:1, based on the weight of the entire solution.

10. Process according to claim 5 , wherein the crystallisation is carried out at a temperature in the range from 70 to 90° C. and a suspension density in the range from 1.62-1.78 g/ml.

11. Process according to claim 5 , wherein the crystallisation is carried out at a temperature in the range from 50 to 60° C., and a suspension density in the range from 1.72 to 1.75 g/ml.

12. Process according to claim 5 , wherein,
for the separating off and drying of the crystals, the crystals are fed to a screen centrifuge by means of a mixer screw, washed with water and introduced into a mixer dryer via a flow dryer and dried at a temperature of 115 to 125° C. with continued mixing until the product obtained has a drying loss of less than 0.2% by weight,
or
after spinning-off, the crystals are fed to a fluidised-bed dryer via a screw conveyor and dried at a temperature in the range from 175 to 200° C., with a residence time, so that the product obtained has a drying loss of not more than 0.2% by weight.

13. A composition comprising crystalline carbonate according to claim 1 , optionally after prior grain classification by sieving or grinding, in the form of a solid pharmaceutical formulation.

14. An effervescent formulation comprising vitamins and/or mineral substances and/or trace elements and/or hydrolysis-sensitive active compounds and crystalline sodium carbonate of claim 1 .

15. A tablet, granule or effervescent formulation comprising acidic active compounds and/or hydrolysis-sensitive active compounds and crystalline sodium carbonate of claim 1 .

16. A composition of claim 13 , wherein the composition is in the form of a tablet, capsule, powder or granule.

17. Crystalline sodium carbonate, according to claim 1 , which has a drying loss after preparation of not more than 0.15% by weight.

18. Crystalline sodium carbonate according to claim 1 , which has a BET surface area of less than 0.2 m 2 /g.

19. The process according to claim 5 , wherein: the aqueous solution has a density in the range from 1.25 to 1.34 g/ml.

20. The process according to claim 5 , wherein: the aqueous solution has a density in the range from 1.28 to 1.31 g/ml.

21. The process according to claim 5 , wherein: a suspension density in the range from 1.58-1.82 g/ml is set at which the crystallisation is carried out.

22. The process according to claim 5 , wherein: a suspension density in the range from 1.62-1.78 g/ml is set at which the crystallisation is carried out.

23. Process according to claim 5 , wherein the process is carried out continuously.

24. Process according to claim 5 , wherein the temperature during the crystallisation is set in the range from 55 to 90° C.

25. Process according to claim 5 , wherein the aqueous solution is mixed with 30% hydrogen peroxide in a ratio of 800:1 to 760:1, based on the weight of the entire solution, and with activated carbon in a ratio of 16500:1 to 14000:1, based on the weight of the entire solution.

26. Process according to claim 5 , wherein the crystallisation is carried out at a temperature of 55° C.

27. Process according to claim 5 , wherein, after spinning-off, the crystals are fed to a fluidised-bed dryer via a screw conveyor and dried at a temperature in the range from 180 to 195° C., with a residence time, so that the product obtained has a drying loss of not more than 0.2% by weight.

28. A composition of claim 13 , wherein the composition is in the form of a capsule suitable for oral administration.

Assignees

• Merck Patent Gmbh

Inventors

• Klatyk Jens
• Peth Hans-Kurt
• Wedel Thorsten
• Moddelmog Guenter

Classifications

• C01P2006/12

  Surface area · CPC title

• C01P2006/10

  Solid density · CPC title

• C01D7/26

  by precipitation or adsorption · CPC title

• C01D7/07 Primary

  Preparation from the hydroxides · CPC title

• C01P2006/82

  water content · CPC title