Process for the purification of a liquid-crystal mixture

Patent metadata

Field	Value
Publication number	US-9737854-B2
Application number	US-201414760273-A
Country	US
Kind code	B2
Filing date	Dec 16, 2014
Priority date	Dec 18, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

In a process for the purification of a liquid-crystal mixture ( 7 ), the liquid-crystal mixture ( 7 ) is passed through a first electrodialysis cell ( 2 ) and a concentrate solution ( 14 ) is passed through a second electrodialysis cell ( 8 ) which is adjacent to the first electrodialysis cell ( 2 ) and is separated by an ion-exchanger membrane ( 9 ), and an electric field transverse to a direction of passage of the liquid-crystal mixture ( 7 ) through the first electrodialysis cell ( 2 ) is generated with the aid of an anode/cathode arrangement ( 15, 16 ) arranged outside the electrodialysis cells ( 2, 8 ) so that ionized constituents of the liquid-crystal mixture ( 7 ) are discharged at the ion-exchanger membrane ( 9 ) and removed from the liquid-crystal mixture ( 7 ).

First claim

The invention claimed is:

1. Process for the purification of a liquid-crystal mixture ( 7 ), which comprises passing the liquid-crystal mixture ( 7 ) through a first electrodialysis cell ( 2 ), passing a concentrate solution ( 14 ) through a second electrodialysis cell ( 8 ) which is adjacent to the first electrodialysis cell ( 2 ) with the first and second electrodialysis cells separated by an ion-exchanger membrane ( 9 ), and, with the aid of an anode/cathode arrangement ( 15 , 16 ) arranged outside the electrodialysis cells ( 2 , 8 ), generating an electric field transverse to a direction of passage of the liquid-crystal mixture ( 7 ) through the first electrodialysis cell ( 2 ) so that ionised constituents of the liquid-crystal mixture ( 7 ) are discharged at the ion-exchanger membrane ( 9 ) and removed from the liquid-crystal mixture ( 7 ).

2. Process according to claim 1 , which comprises passing the liquid-crystal mixture ( 7 ) through the first electrodialysis cell ( 2 ) multiple times.

3. Process according to claim 1 , which comprises passing the liquid-crystal mixture ( 7 ) successively through a plurality of electrodialysis cells having an arrangement, comparable to the first electrodialysis cell ( 2 ), of an ion-exchanger membrane ( 9 ) and an adjacent second electrodialysis cell ( 8 ) and an electric field.

4. Process according to claim 1 , which comprises passing the liquid-crystal mixture ( 7 ) through the first electrodialysis cell ( 2 ) over a period of more than one hour.

5. Process according to claim 1 , wherein the concentrate solution ( 14 ) used is deionised water.

6. Process according to claim 1 , wherein the ion-exchanger membrane ( 9 ) used is a membrane having a breakdown voltage of greater than 10 volts and an electric potential difference which effects the greatest possible drop in voltage at the ion-exchanger membrane ( 9 ), but which is below the breakdown voltage, is pre-specified with the aid of the anode/cathode arrangement ( 15 , 16 ).

7. Process according to claim 6 , wherein the ion-exchanger membrane ( 9 ) used is a membrane having a breakdown voltage of greater than 80 volts.

8. Process according to claim 6 , wherein the ion-exchanger membrane ( 9 ) used is a membrane having a breakdown voltage of greater than 400 volts.

9. Process according to claim 1 , wherein the anode ( 15 ) and the cathode ( 16 ) are flushed with transformer oil ( 19 ) while the process is being carried out.

10. Process according to claim 1 , wherein low-pulsation pumps are used to convey the liquid-crystal mixture ( 7 ) and the concentrate solution ( 14 ).

11. Process according to claim 1 , further comprising thoroughly mixing and homogenizing the liquid-crystal mixture ( 7 ) before introducing it into the first electrodialysis cell ( 2 ).

12. Process according to claim 1 , which comprises passing the liquid-crystal mixture ( 7 ) through the first electrodialysis cell ( 2 ) over a period of more than four hours.

13. Process according to claim 1 , wherein the ion-exchange membrane ( 9 ) is a cation-exchanger membrane and the anode and the cathode are separated from the first and second electrodialysis cells by anion-exchanger membranes.

Assignees

• Merck Patent Gmbh

Inventors

• Kaetzel Uwe

Classifications

• C09K2019/3009

  Cy-Ph · CPC title

• C09K2019/0466

  the linking chain being a -CF2O- chain · CPC title

• C09K19/02

  characterised by optical, electrical or physical properties of the components, in general · CPC title

• C09K2019/3006

  Cy-Cy-Cy · CPC title

• C09K2219/00

  Aspects relating to the form of the liquid crystal [LC] material, or by the technical area in which LC material are used · CPC title