US 5,372,905 AGrant
Surface-Modified Pyrogenically Produced Titanium Dioxide
Issue Date:1994-12-13
•1 Claims
•1 Drawing Sheets
Abstract
Surface-modified, pyrogenically produced titanium dioxide which is has the following physico-chemical properties:
Metadata
Assignee
- Degussa Aktiengesellschaft
Inventors
- Hans Deusser
- Dieter Kerner
- Jurgen Meyer
- Gunther Michael
- Andreas Stubbe
Application Information
Application Number:US 1410849
Filing Date:1993-10-26
Priority Date:1992-01-31
Art Unit:157
Classifications
IPC:
G03F 900
Field of Search:
430428110;109404;405
Patent Drawings (1 sheets)
Description
The present invention relates to a surface-modified, pyrogenically produced titanium dioxide.
Background of the Invention
It is known to use powdery toners containing surface-modified pyrogenically produced silicon dioxide in electrostatic developing processes. Various silanes, especially dimethyldichlorosilane, are used for surface modification (See U.S. Pat. No. 3,720,617).
It is also known that pyrogenically produced silicon dioxide waterproofed with compounds of the general formula ##STR1## can be added to positively chargeable resin powders in order to increase their flowability (See published European Patent Application EP-A 0,293,009).
It also is known that a titanium dioxide which has been surface-modified with halogen silanes can be added to electrographic developing powders (See published German patent application DE-A 12 09 427).
Furthermore, Published German Patent Application DE-A 34 26 685 (Canon) teaches the addition of a titanium dioxide to positively chargeable toners in which the titanium dioxide had been treated with simultaneously with the adhesion promoters .gamma.-aminopropyltriethoxysilane and trimethylethoxysilane.
A similarly treated titanium dioxide is described in Published Japanese Patent Application JP-OS 31442 (Nippon Aerosil Corporation).
The known method has the disadvantage that it must use an organic solvent system. Alcohols, hydrocarbons and halogenated hydrocarbons are used as solvents which cannot be completely removed from the reaction product.
Summary of the Invention
The object of the present invention is to avoid these problems and produce a solvent-free, waterproofed titanium dioxide.
The present invention provides a surface-modified, pyrogenically produced titanium dioxide which is surface modified with a silane mixture consisting of silane A (trimethoxyoctylsilane) and silane B (3-aminopropyltriethoxysilane) having the chemical following formulas: ##STR2##
The surface-modified, pyrogenically produced titanium dioxide has the following physico-chemical characteristics:
The present invention also provides a method of producing the surface-modified, pyrogenically produced titanium dioxide in which the pyrogenically produced titanium dioxide is placed in a mixer and sprayed, with the mixer running, with a mixture of silanes A and B. The silanes and the pyrogenically produced titanium dioxide are mixed after the addition of the silane mixture, and the resulting mixture is tempered at 100.degree. to 150.degree. C., preferably at 115.degree. to 125.degree. C.
The ratio of titanium dioxide to silane mixture can be 0.5 to 40 parts by weight silane mixture per 100 parts by weight titanium dioxide.
The silane mixture can consist of 1 to 99 parts by weight silane A and 99 to 1 parts by weight silane
A mixture can be used with preference consisting of 50.+-.20 parts by weight silane A and 50.+-.20 parts by weight silane B.
A particularly suitable titanium dioxide is P 25 which has been produced pyrogenically from TiCl.sub.4 by flame hydrolysis, in an oxyhydrogen flame, and which has the following physico-chemical characteristics:
The waterproofed titanium dioxide of the invention has the advantage that it has no solvent components.
It can be used in toners for copiers.
Detailed Description of Preferred Embodiments
The following examples illustrate the invention:
Example 1
2 kg P 25 TiO.sub.2 produced pyrogenically from TiCl.sub.4 in an oxyhydrogen flame and exhibiting the data indicated above are placed in a 135 liter Lodige mixer and sprayed with 100 g of a silane mixture consisting of 50 g trimethoxyoctylsilane and 50 g 3-aminopropyltriethoxysilane with the mixer running. The mixture is mixed for an additional 15 minutes. The silanized oxide is tempered for 2 hours at 120.degree. C.
The physico-chemical properties of the surface-modified titanium dioxide are as follows:
Example 2
The titanium dioxide waterproofed according to Example 1 is tested in a positive toner system. The toner system consists of the following components:
The repeated activation was tested with this toner system and a high charge stability in comparison to the raw toner was found (see FIG. 1).
Copy-Blau PR is a charge regulating agent for positive toners. It is characterized as follows:
Area of application
1. Charge regulating agents for positive toners (1- or 2-component toners for copiers or laser printers)
2. Clearing agents for black toners
Chemical
characterization: triphenylmethane derivative
Thermal resistance: >200 C
Solubility: insoluble in water slightly soluble in organic solvents
The toner resin used is characterized as follows:
The q/m measurement takes place under the following conditions:
98% carrier (spherical ferrite (80-100 m))
2% titanium dioxide according to example 1
Activation: Rolling fixture, 360 rpms in 40 ml glass bottle, weighed portion 40 g, developer
Claims
What is claimed is:
1. An electrophotographic toner comprising a pigment and a surface modified pyrogenically produced titanium dioxide which has been surface modified with a mixture of silane A and silane B corresponding to the chemical formulas: ##STR3## said surface-modified, pyrogenically produced titanium dioxide having the following physico-chemical properties: Surface (m.sup.2 /g) 5 to 120 Stamping Density (g/l) 50 to 250 Drying loss (%) <5 Annealing loss (%) 3.5 to 15 C content (%) 0.5 to 12 pH 4 to 10. ______________________________________
Patent Citations (1)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| US5212037 | 1993-05-01 | Julien et al. |
Non-Patent Literature (4)
- German Office Action with English translation enclosed.
- Chemical Abstract vol. 102 (8) No. 70140U re: JP 59052255 A2 with English translation of abstract.
- Chemical Abstract vol. 113 (20) No. 181399g re JP 02108069 A2 with English translation of abstract.
- Chemical Abstract vol. 100 (22) No. 183164g re JP 5818405 with English translation of abstract.