Precise modifying method for fine particle dispersion liquid

Patent metadata

Field	Value
Publication number	US-11111145-B2
Application number	US-201716074665-A
Country	US
Kind code	B2
Filing date	Feb 1, 2017
Priority date	Feb 2, 2016
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

Abstract

A method for modifying a fine particle dispersion liquid with which dispersibility and dispersion stability can be improved includes performing filtration to remove impurities in a dispersion liquid using a dispersion liquid modifying device provided with a removal unit that uses a filtration membrane. The quantity of impurities is reduced from a first region until said quantity reaches a second pH-dependent region. In the second pH-dependent region, the dispersibility of the fine particles in the dispersion liquid is in a range in which the dispersibility depends more on a change in dispersion liquid pH than on a change in the quantity of impurities in the dispersion liquid. With the quantity of impurities reduced to the second pH-dependent region, the dispersibility of the fine particles is controlled by adjusting the pH of the fine particle dispersion liquid.

First claim

The invention claimed is:

1. A method for reforming a fine particle dispersion solution that includes impurities, comprising:
removing impurities in the fine particle dispersion solution by carrying out filtration with a filtration membrane, thereby controlling a dispersion property of the fine particle dispersion solution,
wherein the filtration comprises steps A and B below,
A) decreasing the amount of impurities by filtration and transferring from a first stage to a second stage, wherein the amount of the impurities are defined in the first and second stages,
wherein the first stage has a concentration of impurities of 0.02% or more by weight and the second stage has a concentration of impurities of 0.00005% to 0.02% by weight,
B) controlling the dispersion property by controlling a pH of the fine particle dispersion solution using a pH controlling agent in the second stage.

2. The method for reforming the fine particle dispersion solution according to claim 1 , wherein the impurities are removed from the fine particle dispersion solution by filtration with a cross flow method while supplying the fine particle dispersion solution to the filtration membrane.

3. The method for reforming the fine particle dispersion solution according to claim 2 , wherein the filtration membrane is an ultrafiltration membrane.

4. The method for reforming the fine particle dispersion solution according to claim 1 , wherein
amount of the impurities is reduced by repeating a discharge process and a removal process,
the discharge process is a process in which a physical energy is applied to aggregates of the fine particles included in the fine particle dispersion solution so that a dispersing process is carried out to disperse the aggregates of the fine particles to smaller particles compared with the aggregates of the fine particles thereby discharging the impurities included in the aggregates into the fine particle dispersion solution, and
the removal process is a process in which the impurities in the fine particle dispersion solution after the discharge process are removed by the filtration membrane before re-aggregation takes place entirely by the impurities in the solution.

5. The method for reforming the fine particle dispersion solution according to claim 1 , wherein
after a process to remove the impurities by the filtration membrane, a concentration process to concentrate the fine particles in the fine particle dispersion solution to a concentration range of 0.1 to 15.0% by weight by the filtration membrane is carried out.

6. The method for reforming the fine particle dispersion solution according to claim 1 , wherein
the filtration is repeated plural times.

7. A method for producing a fine particle dispersion solution, comprising:
the method for reforming the fine particle dispersion solution according to claim 1 and a process to obtain the fine particle dispersion solution before carrying out the method for reforming the fine particle dispersion solution, and
the process to obtain the fine particle dispersion solution comprises:
mixing a fine particle raw material solution including at least a fine particle raw material which is a raw material of the fine particles with a fine particle separating solvent including at least a fine particle separating substance to separate the fine particles in between processing surfaces which are disposed so as to be able to approach to and separate from each other, at least any one of which rotates relative to the other, and
simultaneously separating the fine particles in the mixed fluid thus formed.

8. A method for reforming a fine particle dispersion solution that includes fine particles, aggregates of fine particles, and impurities, comprising:
while a physical energy is applied to the aggregates to discharge the impurities included in the aggregates into the fine particle dispersion solution, removing impurities in the fine particle dispersion solution by carrying out filtration with a filtration membrane, thereby controlling a dispersion property of the fine particle dispersion solution,
wherein the filtration comprises steps A and C below,
A) decreasing the amount of impurities by filtration and transferring from a first stage to a second stage, wherein the amount of the impurities are defined in the first and second stages,
wherein the first stage has a concentration of impurities of 0.02% or more by weight and the second stage has a concentration of impurities of 0.00005% to 0.02% by weight,
C) controlling the dispersion property by controlling a pH of the fine particle dispersion solution in the second stage.

9. The method for reforming the fine particle dispersion solution according to claim 8 , wherein the amount of the impurities is correlated to a conductivity of the fine particle dispersion solution, the first stage is a conductivity changing stage in which a conductivity of the fine particle dispersion solution decreases from an initial value at a starting time of processing till 100 μS/cm.

10. The method for reforming the fine particle dispersion solution according to claim 8 , wherein the impurities are removed from the fine particle dispersion solution by filtration with a cross flow method while supplying the fine particle dispersion solution to the filtration membrane.

11. The method for reforming the fine particle dispersion solution according to claim 10 , wherein the filtration membrane is an ultrafiltration membrane.

12. The method for reforming the fine particle dispersion solution according to claim 8 , wherein
amount of the impurities is reduced by repeating a discharge process and a removal process,
the discharge process is a process in which a physical energy is applied to aggregates of the fine particles included in the fine particle dispersion solution so that a dispersing process is carried out to disperse the aggregates of the fine particles to smaller particles compared with the aggregates of the fine particles thereby discharging the impurities included in the aggregates into the fine particle dispersion solution, and
the removal process is a process in which the impurities in the fine particle dispersion solution after the discharge process are removed by the filtration membrane before re-aggregation takes place entirely by the impurities in the solution.

13. The method for reforming the fine particle dispersion solution according to claim 8 , wherein
after a process to remove the impurities by the filtration membrane, a concentration process to concentrate the fine particles in the fine particle dispersion solution to a concentration range of 0.1 to 15.0% by weight by the filtration membrane is carried out.

14. The method for reforming the fine particle dispersion solution according to claim 8 , wherein
the filtration is repeated plural times.

15. A method for producing a fine particle dispersion solution, comprising:
the method for reforming the fine particle dispersion solution according to claim 8 and a process to obtain the fine particle dispersion solution before carrying out the method for reforming the fine particle dispersion solution, and
the process to obtain the fine particle dispersion solution comprises:
mixing a fine particle raw material solution including at least a fine particle raw material which is a raw material of the fine particles with a fine particle separating solvent including at least a fine particle separating substance to separate the fine particles in between processing surfaces which are disposed so as to be able to approach to and separate from each other, at least any one of which rotates re

Assignees

• M Technique Co Ltd

Inventors

• Enomura Masakazu
• Honda Daisuke

Classifications

• B01F23/51 Primary

  Methods thereof · CPC title

• B01F23/56

  by introducing solids in liquids, e.g. dispersing or dissolving · CPC title

• B01F23/808

  Filtering the mixture · CPC title

• B01F23/511

  characterised by the composition of the liquids or solids · CPC title

• C01B13/14

  Methods for preparing oxides or hydroxides in general (particular individual oxides or hydroxides, see the relevant groups of subclasses C01B - C01G or C25B, according to the element combined with the oxygen or hydroxy group) · CPC title