# US 7,608,234 B2 · Precipitated silicas with particular pore size distribution

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- Number: US 7,608,234 B2
- Document ID: US7608234B2
- Status: Granted
- Kind: B2
- Application number: 11/517,395
- Filed: 2006-09-08
- Published: 2007-05-03
- Granted: 2009-10-27
- Earliest claimed: 2005-09-09
- Assignees: Degussa AG
- Inventors: Oleg Stenzel; Hans-Detlef Luginsland; Stefan Uhrlandt; Andre Wehmeier
- Web page: https://patentgrep.com/patent/US7608234B2

## CPC

- C01B 33/193: of aqueous solutions of silicates
- B60C 1/00: Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
- B60C 1/0016: {Compositions of the tread}
- C08K 3/36: Silica
- C01P 2006/12: Surface area
- C01P 2006/17: Pore diameter distribution
- C01P 2006/19: Oil-absorption capacity, e.g. DBP values
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- B60C: VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
- C08K: Use of inorganic or non-macromolecular organic substances as compounding ingredients (paints, inks, varnishes, dyes, polishes, adhesives C09)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

Precipitated silicas useful, for example, as fillers in elastomer mixtures or vulcanizates have a particularly broad pore size distribution of the pores with a pore diameter smaller than that of the maximum of the derivative of the pore volume distribution function, and have simultaneously very low microporosity and high rubber activity.

## Claims

### Claim 1

A precipitated silica, having the following physicochemical parameters:
a relative breadth γ of pore size distribution of
4.0-10.0 (g nm)/ml,
a BET surface area of
90-320 m2/g,
a CTAB surface area of
100-200 m2/g,
a Sears number V2 of
26-40 ml/(5 g), and
Sears number V2/CTAB ratio of
0.16-0.28 ml/(5 m2).

### Claim 2 (depends on 1)

The precipitated silica according to claim 1, wherein the BET/CTAB ratio is ≧0.9 and ≦1.6.

### Claim 3 (depends on 1)

The precipitated silica according to claim 1, wherein a zeta potential at pH 5 is from −12 to −30 mV.

### Claim 4 (depends on 1)

The precipitated silica according to claim 1, wherein an oil adsorbency measured as DBP number is from 200 to 330 g/(100 g).

### Claim 5 (depends on 1)

The precipitated silica according to claim 1, wherein an Al2O3 content is from 0.001 to 5% by weight.

### Claim 6 (depends on 1)

The precipitated silica according to claim 1, which is in the form of a granulated material, and wherein a (Ro-Tap) sieve residue on a 300 μm sieve is at least 80% by weight.

### Claim 7 (depends on 1)

The precipitated silica according to claim 1, which is in the form of a granulated material, and wherein a <75 μm (Ro-Tap) sieve fraction is at most 10% by weight.

### Claim 8 (depends on 1)

The precipitated silica according to claim 1, having a carbon content of from 0.1 to 20.0% by weight.

### Claim 9 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 28-40 ml/(5 g).

### Claim 10 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 30-40 ml/(5 g).

### Claim 11 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 32-40 ml/(5 g).

### Claim 12 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 34-40 ml/(5 g).

### Claim 13 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 36-40 ml/(5 g).

### Claim 14 (depends on 1)

The precipitated silica according to claim 1, which has a Sears number V2 of 38-40 ml/(5 g).

### Claim 15 (depends on 1)

An elastomer mixture, a vulcanizable rubber mixture or a vulcanizate, comprising the precipitated silica according to claim 1.

### Claim 16 (depends on 1)

A vulcanizable rubber mixture or vulcanizate, comprising:
at least one precipitated silica according to claim 1, as filler.

### Claim 17 (depends on 1)

A tire, comprising:
at least one precipitated silica according to claim 1.

### Claim 18 (depends on 1)

A process for producing the precipitated silica according to claim 1, comprising in succession:
a) using an aqueous solution of at least one member selected from the group consisting of an alkali metal silicate, an alkaline earth metal silicate, an organic base, an inorganic base and mixtures thereof as initial charge, the alkali number of the initial charge being from 20 to 40,
b) simultaneously metering into said initial charge alkali metal silicate, alkaline earth metal silicate or mixtures thereof and an acidifier with stirring at from 55 to 85° C. until a viscosity rises,
c) stopping the feed for from 35 to 85 minutes,
d) simultaneously feeding alkali metal silicate, alkaline earth metal silicate or mixtures thereof and acidifier at a temperature of from 55 to 85° C., until a solids content of from 90 to 140 g/l has been reached,
g) continuing stirring of a resultant suspension for from 1 to 120 minutes at from 80 to 98° C.,
h) acidifying said suspension with an acidifier to a pH of from 2.5 to 5.0, and
i) filtering of said suspension to obtain said precipitated silica and drying of said precipitated silica.