Silica and also epoxy resins

• US 8,480,846 B2
• Filed: 02/10/2009
• Issued: 07/09/2013
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Evonik Operations GmbH (Rag-Stiftung)
• Original Assignee: Evonik Degussa GmbH
• Inventors: Meyer, Juergen, Scholz, Mario, Buckel, Pia, Hille, Andreas
• Primary Examiner(s): Feely, Michael J
• Application Number:
  US12/812,554
• Publication Number:
  US 20100286311A1
• Time in Patent Office: 1,610 Days
• Field of Search: 423/335, 423/337, 427/212, 427/213.31, 427/213.32, 427/215, 427/218, 427/219, 427/387, 427/421.1, 427/427.4, 428/402, 428/403, 428/404, 428/405, 428/407, 523/440, 523/443, 523/466, 156/330
• US Class Current: 156/330
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 33/183 by oxidation or hydrolysis in the vapour phase of silicon compounds such as halides, trichlorosilane, monosilane
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/11 Powder tap density
• CPC Class Codes: C01P 2006/12 Surface area
• CPC Class Codes: C01P 2006/22 Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
• CPC Class Codes: C08K 3/36 Silica
• CPC Class Codes: C08L 63/00 Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• CPC Class Codes: C09C 1/30 Silicic acid
• CPC Class Codes: C09C 1/3081 Treatment with organo-silicon compounds
• CPC Class Codes: C09J 163/00 Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
• CPC Class Codes: Y02P 20/129 Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• CPC Class Codes: Y10T 428/2995 Silane, siloxane or silicone coating

Abstract

Fumed silicon dioxide powder in the form of aggregated primary particles having a BET surface area of 175±15 m²/g and a thickening effect, based on the BET surface area, of greater than 18 mPas g/m² is hydrophobicized with polydimethylsiloxane. This hydrophobic fumed silica has a BET surface area of 110±25 m²/g. It can be used in epoxy resins. These epoxy resins in turn can be used as adhesives.

Claims

1. A process for preparing a fumed hydrophilic silicon dioxide powder comprising aggregated primary particles having a BET surface area of 175±

15 m²/g, wherein a thickening effect of the powder, based on the BET surface area, is greater than 18 mPas·

g/m², the process comprising;

vaporizing a silicon compound;

transferring the vaporized silicon compound, optionally with a carrier gas, into a mixing chamber,

separately, transferring a fuel gas and primary air into the mixing chamber, and mixing with the silicon compound vapour;

igniting the mixture in a burner wherein a flame is burnt into a reaction chamber;

introducing secondary air surrounding the flame into the reaction chamber;

separating solid silicon dioxide from gaseous substances; and

treating the separated solid with a steam at 250°

C. to 750°

C.,

wherein

the primary air is optionally preheated or enriched with oxygen,

a ratio of secondary air/primary air is from 0.05 to 3,

a total amount of oxygen is at least sufficient for the complete combustion of the fuel gas and the silicon compound, and

an adiabatic flame temperature T_ad is from 1840 to 1900°

C., wherein T_ad=temperature of feedstocks+sum of the reaction enthalpies of the sub-reactions/heat capacity of the substances which depart from the reaction chamber, comprising silicon dioxide, water, hydrogen chloride, carbon dioxide, oxygen, nitrogen and, a carrier gas, if the latter is not air or nitrogen, on the basis of the specific heat capacity of these substances at 1000°

C.

2. The process as claimed in claim 1, wherein the silicon compound is SiCl₄, and the fuel gas is H₂.

3. The process as claimed in claim 2, wherein for 100 kg/h of SiCl₄ transferred to the mixing chamber, 53 Nm³/h of H₂, 155 Nm³ of primary air and 55 Nm³ of secondary air are employed.

4. The process as claimed in claim 2, wherein the secondary air/primary air ratio is 0.35.

5. The process as claimed in claim 1, wherein the thickening effect relative to the surface area of the powder is 20.08 mPas·

g/m².

6. A hydrophobic fumed silica, wherein

a BET surface area is 110±

25 m²/g,

an average aggregate surface area is 53 257±

500 nm²,

an average aggregate circumference is 3605±

500 nm,

an average maximum aggregate diameter is 394±

5 nm,

an average minimum aggregate diameter is 242±

5 nm, and

an average primary particle diameter is 18±

5 nm,

wherein

the hydrophobic fumed silica is obtained by a process comprising;

spraying the hydrophilic fumed silica obtained by the process according to claim 1 with polydimethylsiloxane, followed by mixing and then heat treatment for 1 to 6 hours.

7. The hydrophobic fumed silica according to claim 6, wherein the heat treatment is conducted at 360°

C. for 3 hours under a nitrogen atmosphere.

8. An adhesive composition which comprises the hydrophobic fumed silica according to claim 6 and an epoxy resin.

9. An epoxy resin composition comprising the hydrophobic fumed silica according to claim 6.

10. A method to adhere two surfaces comprising applying the epoxy resin composition according to claim 9 to at least one of the two surfaces.