Highly dispersible fine hydrophobic silica powder and process for producing the same
A high dispersible hydrophobic fine silica powder can be made, wherein the silica powder has hydrophobicity of more than 50%, triboelectrostatic charge of more than −500 μC/g, decomposition rate of an organic group on the powder surface of less than 15%, transmittance of a 5% alcoholic dispersion liquid of more than 40% preferably, and a specific surface area of more than 200 m 2 /g. This high dispersible hydrophobic fine silica powder can be made by mixing a hydrophobic agent comprising a volatile organic silicon compound in the gas state with a fine silica powder in a fluidized bed type reaction vessel at the time of a hydrophobic treatment, and controlling a gas flow rate to more than 5.0 cm/sec at the time of this mixing.
1. A high dispersible hydrophobic fine silica powder, wherein
hydrophobicity is more than 50%, and
triboelectrostatic charge to an iron powder is more than −500 μC/g.
2. The high dispersible hydrophobic fine silica powder according to claim 1 , wherein transmittance of a 5% alcoholic dispersion liquid is more than 40%.
3. The high dispersible hydrophobic fine silica powder of claim 2 , wherein said high dispersible hydrophobic fine silica powder is synthesized by a vapor phase method, and has a specific surface area of more than 200 m 2 /g by the BET method and an amount of residual hydrochloride of less than 100 ppm.
4. A production method of the high dispersible hydrophobic fine silica powder according to claim 3 , wherein a hydrophobic agent comprising a volatile organic silicon compound is mixed in the gas state with a fine silica powder in a fluidized bed type reaction vessel at the time of a hydrophobic treatment, and a gas flow rate at the time of this mixing is more than 5.0 cm/sec.
5. The production method of the high dispersible hydrophobic fine silica powder according to claim 4 , wherein a gas flow rate in the fluidized bed type reaction vessel is more than 3.0 cm/sec at the time of the hydrophobic treatment.
6. A production method of the high dispersible hydrophobic fine silica powder according to claim 2 , wherein a hydrophobic agent comprising a volatile organic silicon compound is mixed in the gas state with a fine silica powder in a fluidized bed type reaction vessel at the time of a hydrophobic treatment, and a gas flow rate at the time of this mixing is more than 5.0 cm/sec.
7. The production method of the high dispersible hydrophobic fine silica powder according to claim 6 , wherein a gas flow rate in the fluidized bed type reaction vessel is more than 3.0 cm/sec at the time of the hydrophobic treatment.
8. The high dispersible hydrophobic fine silica powder claim 1 , wherein said high dispersible hydrophobic fine silica powder is synthesized by a vapor phase method, and has a specific surface area of more than 200 m 2 /g by the BET method and an amount of residual hydrochloride of less than 100 ppm.
9. A production method of the high dispersible hydrophobic fine silica powder according to claim 8 , wherein a hydrophobic agent comprising a volatile organic silicon compound is mixed in the gas state with a fine silica powder in a fluidized bed type reaction vessel at the time of a hydrophobic treatment, and a gas flow rate at the time of this mixing is more than 5.0 cm/sec.
10. The production method of the high dispersible hydrophobic fine silica powder according to claim 9 , wherein a gas flow rate in the fluidized bed type reaction vessel is more than 3.0 cm/sec at the time of the hydrophobic treatment.
11. A production method of the high dispersible hydrophobic fine silica powder according to claim 1 , wherein a hydrophobic agent comprising a volatile organic silicon compound is mixed in the gas state with a fine silica powder in a fluidized bed type reaction vessel at the time of a hydrophobic treatment, and a gas flow rate at the time of this mixing is more than 5.0 cm/sec.
12. The production method of the high dispersible hydrophobic fine silica powder according to claim 11 , wherein a gas flow rate in the fluidized bed type reaction vessel is more than 3.0 cm/sec at the time of the hydrophobic treatment.