# US 2020/0392004 A1 · Method for producing silica sol having elongated particle shape

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- Number: US 2020/0392004 A1
- Document ID: US20200392004A1
- Status: Published application
- Kind: A1
- Application number: 16/975,448
- Filed: 2019-02-25
- Published: 2020-12-17
- Earliest claimed: 2018-02-26
- Assignees: Nissan Chemical Corporation
- Applicants: Nissan Chemical Corporation
- Inventors: Satoru MURAKAMI; Takuya FUKUOKA; Kazuya KUROIWA
- Web page: https://patentgrep.com/patent/US20200392004A1

## CPC

- C01B 33/1435: {using ion exchangers}
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01B 33/142: by acidic treatment of silicates
- C01P 2002/02: Amorphous compounds
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer
- C01P 2006/80: Compositional purity
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

A method for producing a silica sol containing a small amount of metal impurities and wherein colloidal silica having an elongated particle shape is dispersed in a solvent, by addition of a compound as an anion source and ammonia as an alkali source and heating of the resultant mixture at a predetermined temperature, includes the following steps: (a) preparing a raw material liquid by adding at least one compound as an anion source selected from the group of inorganic acids, organic acids, and ammonium salts of these acids, and ammonia to a silica sol as a raw material having SiO2 of 1% by mass to 30% by mass and a pH of 2 to 5 so the mass ratio of the compound to SiO2 is 0.5% to 1.9%; and (b) heating the raw material liquid prepared in step (a) at 80° C. to 200° C. for 0.5 hours to 20 hours.

## Claims

### Claim 1

A method for producing a silica sol containing elongated amorphous colloidal silica particles dispersed in a liquid medium and having an SiO2 concentration of 6% by mass to 30% by mass, wherein the silica particles contained in the silica sol exhibit a DL/DB ratio of 2.5 or more and a DL of 30 nm to 300 nm wherein DL is an average particle diameter (nm) as measured by the dynamic light scattering method, and DB is a primary particle diameter (nm) as measured by the nitrogen gas adsorption method, and the silica particles have a particle length of 50 nm to 1,000 nm as determined by observation with an electron microscope, the production method comprising the following steps (a) and (b):
(a) a step of preparing a raw material liquid by adding at least one compound as an anion source selected from the group consisting of inorganic acids, organic acids, and ammonium salts of these acids, and ammonia to a silica sol as a raw material having an SiO2 concentration of 1% by mass to 30% by mass and a pH of 2 to 5 so that the mass ratio of the compound to SiO2 is 0.5% to 1.9%; and
(b) a step of heating the raw material liquid prepared in the step (a) at 80° C. to 200° C. for 0.5 hours to 20 hours, to thereby produce a silica sol.

### Claim 2 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the silica sol as a raw material used in the step (a) is produced from a colloidal aqueous solution of activated silica prepared by bringing an aqueous alkali silicate solution exhibiting a ratio by mole of SiO2/M2O (wherein M is sodium or potassium) of 1 to 4.5 into contact with a strong acid-type cation exchange resin or with both a strong acid-type cation exchange resin and a strong base-type anion exchange resin.

### Claim 3 (depends on 2)

The method for producing a silica sol according to claim 2, wherein the silica sol as a raw material used in the step (a) is produced from a colloidal aqueous solution of activated silica prepared by treating the aqueous alkali silicate solution with a strong acid at a temperature of 1° C. to 98° C., and then bringing the treated aqueous solution into contact with a strong acid-type cation exchange resin or with both a strong acid-type cation exchange resin and a strong base-type anion exchange resin.

### Claim 4 (depends on 2)

The method for producing a silica sol according to claim 2, wherein the silica sol as a raw material used in the step (a) is produced from a colloidal aqueous solution of activated silica prepared by bringing the aqueous alkali solution or the treated aqueous solution into contact with a carboxylic acid-type chelating resin, a hydroxyl group-type chelating resin, and/or an amine-type chelating resin before or after contact with a strong acid-type cation exchange resin or with both a strong acid-type cation exchange resin and a strong base-type anion exchange resin.

### Claim 5 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the compound as an anion source used in the step (a) is at least one compound as an anion source selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, acetic acid, formic acid, oxalic acid, citric acid, lactic acid, malic acid, gluconic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and an ammonium salt of any of these.

### Claim 6 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the silica sol as a raw material used in the step (a) contains colloidal particles having a primary particle diameter (DB or Ds) of 5 nm to 50 nm.

### Claim 7 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the ammonia added in the step (a) is in the form of ammonia gas or an aqueous ammonia solution.

### Claim 8 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the step (a) comprises a step of adding the compound as an anion source to the silica sol as a raw material, followed by addition of the ammonia.

### Claim 9 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the step (a) comprises a step of adding the ammonia to the silica sol as a raw material, followed by addition of the compound as an anion source and subsequent addition of the ammonia.

### Claim 10 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the raw material liquid prepared in the step (a) has a pH of 8 to 12.

### Claim 11 (depends on 1)

The method for producing a silica sol according to claim 1, wherein, in the step (b), the raw material liquid is heated in an autoclave apparatus at 100° C. to 180° C.

### Claim 12 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the method further comprises a step of bringing the silica sol produced in the step (b) into contact with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

### Claim 13 (depends on 12)

The method for producing a silica sol according to claim 12, wherein the method further comprises a step of bringing the silica sol produced in the step (b) into contact with a carboxylic acid-type chelating resin, a hydroxyl group-type chelating resin, and/or an amine-type chelating resin before or after contact with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

### Claim 14 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the method further comprises a step of replacing the aqueous medium of the produced silica sol with an organic medium.

### Claim 15 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the mass ratio of each of Ca and Mg to SiO2 is 0.01 ppm to 50 ppm in the silica sol.

### Claim 16 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the mass ratio of Na to SiO2 is 0.1 ppm to 50 ppm, and the mass ratio of K to SiO2 is 0.1 to 50 ppm in the silica sol.

### Claim 17 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the amorphous colloidal silica particles exhibit a DL/DB ratio of 3 to 30 wherein DL is an average particle diameter (nm) as measured by the dynamic light scattering method, and DB is a primary particle diameter (nm) as measured by the nitrogen gas adsorption method.

### Claim 18 (depends on 1)

The method for producing a silica sol according to claim 1, wherein the silica sol is an acidic silica sol or an ammonia-containing alkaline silica sol.