# US 10,865,115 B2 · Highly dispersible precipitated silica and method of preparation thereof

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- Number: US 10,865,115 B2
- Document ID: US10865115B2
- Status: Granted
- Kind: B2
- Application number: 15/315,825
- Filed: 2015-05-30
- Published: 2017-08-24
- Granted: 2020-12-15
- Earliest claimed: 2014-06-03
- Assignees: Brisil Technologies Private Limited
- Applicants: Brisil Technologies Private Limited
- Inventors: Abhisek Poddar; Nikhaar Jain; Tanmay Pandya
- Web page: https://patentgrep.com/patent/US10865115B2

## CPC

- C01B 33/193: of aqueous solutions of silicates
- C08K 3/36: Silica
- C09C 1/3027: {Drying, calcination}
- C01P 2004/50: Agglomerated particles
- C01P 2006/12: Surface area
- C01P 2006/14: Pore volume
- C01P 2006/16: Pore diameter
- C01P 2006/17: Pore diameter distribution
- C08K 2201/006: Additives being defined by their surface area
- C08K 2201/011: Nanostructured additives
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

The present invention provides highly dispersible precipitated silica having improved structure and properties for use as reinforcing filler in elastomeric compositions and method of preparation thereof. The present invention further provides an alkaline silicate solution having reduced dielectric constant by digesting biogenic silica source with alkaline solution such that soluble organic compounds present in the biogenic silica source leach into the alkaline silicate solution. The alkaline silicate solution obtained as above is then acidified with a mineral acid under particular conditions of pH, temperature, time etc. to obtain the highly dispersible precipitated silica of the present invention.

## Claims

### Claim 1

A process for preparation of highly dispersible precipitated silica comprising the steps of:
a) preparing an alkaline silicate solution having reduced dielectric constant in a first reactor vessel by digesting biogenic silica source with an alkaline solution at a temperature ranging from 80-120° C. such that soluble organic compounds in the biogenic silica source leach into the alkaline silicate solution;
b) adding water into a second reactor vessel and maintaining a suitable temperature;
c) adding the alkaline silicate solution as obtained in step (a) and an acidifying agent simultaneously to the second reactor vessel while maintaining suitable pH in the range of 8-8.5 and a suitable temperature for a suitable time so as to reach a final silica concentration range of 20-80 g/L;
d) stopping the addition of the alkaline silicate solution and continuing adding the acidifying agent so as to reach a pH of 3-4 to obtain an aqueous silica dispersion;
e) filtering the aqueous silica dispersion to obtain a filtered cake; and
f) washing and drying the filtered cake to obtain the highly dispersible precipitated silica;
wherein the biogenic silica source and the alkaline solution are in a ratio of 1:4 to 4:1;
modulus of the alkaline silicate solution is in the range of 2 to 3.3 and
the highly dispersible precipitated silica has the following pore size distribution of mesopores measured by Mercury Intrusion Porosimetry (MIP):
Pore Volume by
Pore Volume by
Mercury
Pore Volume by
Mesopore
Mercury Intrusion
Intrusion (ml/g)
Mercury Intrusion
size
(ml/g)
MIP surface
(ml/g)
Interval
MIP surface area
area 240-280
MIP surface area
(nm)
200-240 (m2/g)
(m2/g)
140-200 (m2/g)
10 to 20
0.05-0.15
0.15-0.25
0.05-0.2
20 to 30
0.15-0.4
0.4-0.5
0.1-0.3
30 to 40
0.2-0.5
0.1-0.2
0.25-0.35
40 to 50
0.1-0.25
0.1-0.2
0.1-0.3.

### Claim 2 (depends on 1)

The process of claim 1, wherein the alkaline solution as used in step (a) is selected from the group consisting of sodium hydroxide, potassium hydroxide, and a combination thereof.

### Claim 3 (depends on 1)

process of claim 1, wherein the biogenic silica source is selected from the group consisting of rice husk char, paddy straw char, wheat straw char, sugarcane, and baggase char.

### Claim 4 (depends on 1)

The process of claim 1, wherein the acidifying agent is selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

### Claim 5 (depends on 1)

The process of claim 1, wherein the biogenic silica source is digested with the alkaline solution for a time period ranging from 3 hours to 8 hours.

### Claim 6 (depends on 1)

The process of claim 1, wherein the suitable temperature in step (c) ranges from 70-90° C.

### Claim 7 (depends on 1)

The process of claim 1, wherein the suitable time in step (c) ranges from 40 to 90 minutes.