Method for producing purified active silicic acid solution and silica sol

Patent metadata

Field	Value
Publication number	US-10400147-B2
Application number	US-201213617453-A
Country	US
Kind code	B2
Filing date	Sep 14, 2012
Priority date	Sep 16, 2011
Publication date	Sep 3, 2019
Grant date	Sep 3, 2019

Abstract

A method for producing an active silicic acid solution in which the existing amount of foreign matters as plate-like fine particles is reduced and a method for producing a silica sol in which such foreign matters are reduced. The method fulfills the following condition: the existing amount of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm is measured to be 0% to 30% in accordance with measuring method A, the method including the steps of: preparing an active silicic acid solution by subjecting an alkali silicate aqueous solution having a silica concentration of 0.5% by mass to 10.0% by mass to cation-exchange to remove alkaline components; and filtering the active silicic acid solution through a filter whose removal rate of particles having a primary particle size of 1.0 μm is 50% or more.

First claim

The invention claimed is:

1. A method comprising:
preparing an active silicic acid solution by subjecting an alkali silicate aqueous solution having a silica concentration of 0.5% by mass to 10.0% by mass to cation-exchange to remove alkaline components, wherein the active silicic acid solution that is prepared contains an amount of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm; and
filtering the active silicic acid solution through a filter having a removal rate of particles having a primary particle size of 1.0 μm of 50% or more to produce a purified active silicic acid solution in which an amount (%) as measured by a measuring method A of the plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm is reduced relative to an amount (%) as measured by the measuring method A of the plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm contained in the active silicic acid solution,
wherein:
the filter is at least one selected from the group consisting of a pleated filter, a depth filter, and a diatomaceous-earth-containing filter;
the amount (%) of the plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm in the purified active silicic acid solution is in a range of from 0% to 30% as measured by the measuring method A;
the measuring method A comprises:
observing under a scanning electron microscope at a magnification of 5,000 times a membrane filter through which 30 mL of a solution to be observed has been passed, the solution to be observed having a silica concentration of 4% by mass and a temperature of 25° C., and the membrane filter having a filtration area of 4.90 cm 2 and an absolute pore size of 0.4 μm;
measuring as one count a state in which one or more of the plate-like fine particles exist within one visual field area having a length of 15 μm and a width of 20 μm; and
determining the presence or absence of the count with respect to each visual field area of 100 non-overlapping visual field areas to measure a total number of counts as the amount (%) of the plate-like fine particles;

the solution to be observed in the measuring method A is the purified active silicic acid solution; and
the amount (%) as measured by the measuring method A of the plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm in the active silicic acid solution is 73% or more.

2. The method according to claim 1 , wherein the removal rate is 60% or more.

3. The method according to claim 1 , wherein the removal rate is 70% or more.

4. The method according to claim 1 , wherein the removal rate is 80% or more.

5. The method according to claim 1 , wherein the removal rate is 90% or more.

6. The method according to claim 1 , wherein the alkaline components of the alkali silicate aqueous solution are at least one selected from the group consisting of a sodium ion, a potassium ion, a lithium ion, a rubidium ion, and a cesium ion.

7. The method according to claim 1 , further comprising:
adding the purified active silicic acid solution into an alkaline aqueous solution to obtain a mixture; and
heating the mixture to polymerize active silicic acid to produce a silica sol;
wherein an amount of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm in the silica sol is in a range of from 0% to 30% as measured by the measuring method A in which the solution to be observed is the silica sol.

8. The method according to claim 7 , wherein the alkaline components of the alkaline aqueous solution are at least one selected from the group consisting of an alkali metal ion, an ammonium ion, amine, and a quaternary ammonium ion.

9. The method according to claim 1 , wherein the amount (%) as measured by the measuring method A of the plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm in the active silicic acid solution is in a range of from 73% to 75%.

10. The method according to claim 1 , wherein the amount (%) as measured by the measuring method A of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm in the purified active silicic acid solution is in a range of from 0% to 17%.

11. The method according to claim 1 , wherein a filtering rate in a range of from 13 L/min to 400 L/min per 1 m 2 of a filtration area of the filter is employed to filter the active silicic acid solution through the filter.

Assignees

• Ema Kiyomi
• Takakuma Noriyuki
• Nishimura Tohru
• Kawashita Naoki
• Yamaguchi Kouji
• Nissan Chemical Ind Ltd

Inventors

• Ema Kiyomi
• Takakuma Noriyuki
• Nishimura Tohru
• Kawashita Naoki
• Yamaguchi Kouji

Classifications

• C01B33/1485

  Stabilisation, e.g. prevention of gelling; Purification · CPC title

• C09K13/04

  containing an inorganic acid · CPC title

• C09K3/1463 Primary

  Aqueous liquid suspensions · CPC title

• C01B33/1435

  using ion exchangers · CPC title

• C01B33/1412

  by oxidation of silicon in basic medium · CPC title