Silica with reduced tribo-charge for toner applications

Patent metadata

Field	Value
Publication number	US-12528704-B2
Application number	US-202217667727-A
Country	US
Kind code	B2
Filing date	Feb 9, 2022
Priority date	Feb 11, 2021
Publication date	Jan 20, 2026
Grant date	Jan 20, 2026

Abstract

Surface-treated fumed silica, with a tribo-electro static charge of −500 μC/g to +500 μC/g, a ratio of the tribo-electro static charge to BET surface area of −3.5 μC/m 2 to +3.5 μC/m 2 , a methanol wettability of at least 20% by volume methanol in methanol/water mixture, a ratio of carbon content to BET surface area of at most 0.020 wt. %*g/m 2 , a process for its preparation and the use thereof.

First claim

The invention claimed is:

1 . Surface treated fumed (pyrogenic) silica, comprising:
an average primary particle size, d50, of 5 nm to 30 nm; a numerical median particle size, d50, of less than 10 μm; a tribo-electrostatic charge of −500 μC/g to +500 μC/g; a ratio of the tribo-electrostatic charge to BET surface area of −3.5 μC/m 2 to +3.5 μC/m 2 ; a methanol wettability of at least 20% by volume methanol in a methanol/water mixture; and a ratio of carbon content to BET surface area of at most 0.020 wt. % x g/m 2 .

2 . The surface treated fumed silica of claim 1 wherein the surface treated fumed silica is a silica-based doped oxide, comprising at least 50% by weight of silicon dioxide.

3 . The surface treated fumed silica of claim 1 , wherein the BET surface area of the silica is 30 m2/g to 500 m2/g and the tribo-electrostatic charge is-200 to +50 uC/g.

4 . The surface treated fumed silica of claim 1 , obtained using a surface treatment agent selected from the group consisting of: organosilanes; silazanes; acyclic polysiloxanes; cyclic polysiloxanes; and mixtures thereof.

5 . The surface treated fumed silica of claim 2 , wherein numerical median particle size d 50 of the silica is less than 10 μm, as determined by static light scattering after 120 s of ultrasonic treatment at 25° C. of a 5% by weight dispersion of the silica in methanol.

6 . The surface treated fumed silica of claim 1 , wherein the carbon content of the silica is from 0.1% to 5% by weight and the tribo-electrostatic charge is −100 to 0 μC/g.

7 . The surface treated fumed silica of claim 1 , having a loss on drying of less than 0.4% by weight, as determined according to method A of ASTM D280-01.

8 . The surface treated fumed silica of claim 1 , having a tamped density of silica powder of not more than 250 g/L.

9 . The surface treated fumed silica of claim 1 , wherein the span (d 90 -d 10 )/d 50 of particle size distribution of the silica is less than 3.0.

10 . The surface treated fumed silica of claim 1 , wherein the methanol wettability of the silica is 30%-70% by volume methanol in methanol/water mixture.

11 . The surface treated fumed silica of claim 4 , wherein numerical median particle size d 50 of the silica is less than 10 μm, as determined by static light scattering after 120 s of ultrasonic treatment at 25° C. of a 5% by weight dispersion of the silica in methanol.

12 . The surface treated fumed silica of claim 11 , wherein the carbon content of the silica is from 0.1% to 5% by weight.

13 . The surface treated fumed silica of claim 12 , having a loss on drying of less than 0.4% by weight, as determined according to method A of ASTM D280-01.

14 . The surface treated fumed silica of claim 4 , wherein the silica is a silica-based mixed oxide.

15 . The surface treated fumed silica of claim 4 , wherein the methanol wettability of the silica is 30%-70% by volume methanol in methanol/water mixture.

16 . A composition comprising the silica of claim 1 .

17 . The composition of claim 16 , wherein the composition is selected from the group consisting of: a toner; a paint; a coating; a silicone; a pharmaceutical or cosmetic preparation; an adhesive; or a sealant.

Assignees

• Evonik Operations Gmbh

Inventors

• Giesseler Mareike
• Menzel Frank
• Lygin Alexander
• Golchert Rainer

Classifications

• G03G9/1136

  containing silicon atoms · CPC title

• C09D183/04

  Polysiloxanes · CPC title

• C01P2006/40

  Electric properties · CPC title

• C01P2006/12

  Surface area · CPC title

• C01P2006/11

  Powder tap density · CPC title