JP3983234B2 - Manufacturing method of toner external additive - Google Patents

Description

The present invention relates to a method for producing a toner external additive .

In electrostatic charge image developing toners used in copying machines, laser printers, etc., silica powder surface-treated with a silane coupling agent is used as an external additive as a fluidity improver. In the toner external additive material, the silica powder needs to be hydrophobized in order to reduce the change in charge amount due to humidity. If this is insufficient, the silica powder is uniformly applied to the toner surface. Therefore, excellent printability cannot be maintained over a long period of time. Thus, although there have been many proposals as a uniform processing method of silica powder with a silane coupling agent (for example, Patent Document 1), it is not yet sufficient. The solution to this problem is how to reduce the generation of aggregated particles by reducing the factors caused by the self-condensability of the silane coupling agent droplets or silica powder during the surface treatment.
JP 2001-261327 A

An object of the present invention is to provide a method for producing a toner external additive comprising a silica powder with little aggregation.

That is, the present invention is a silica powder moisture content is 0.02~1μm volume average diameter of 0.5 wt% or less, a temperature of above 100 ° C., in a suspended state, hexamethyldisilazane concentration A method for producing a toner external additive comprising contacting with 0.05 to 2% by volume of a gas.

In the present invention, and this is preferable fluidity index of measured toner out添材the following method is 80% or more.
(Liquidity index)
10 g of styrene resin having an average diameter of 5 μm and 0.1 g of a sample (toner external additive) are placed in a mixer and mixed at room temperature at 480 rpm for 10 seconds, and 2 g of the obtained mixed powder is 150 μm, 75 μm, and 45 μm three-stage sieve. After adding and classifying the vibration of 0.25 mm amplitude for 3 minutes, the value calculated by the following formula 1 from the amount of residual powder on each sieve.
100-50A-30B-10C (1)
A: Amount of residual powder on 150 μm sieve B: Amount of residual powder on 75 μm sieve C: Amount of residual powder on 45 μm sieve

Moreover, in this invention, it is preferable to have the relationship of the following 2 type | formulas and 3 type | formulas .
0.5 ≦ DAt / DAs ≦ 2.5 (2)
1.0 ≦ DMt / DMs ≦ 1.5 (3)
DAt: Volume average diameter of silica powder after hexamethyldisilazane treatment by dynamic light scattering method DAs: Volume average diameter of silica powder before hexamethyldisilazane treatment by dynamic light scattering method DMt: After hexamethyldisilazane treatment Mode diameter of silica powder by dynamic light scattering method DMs: Mode diameter of silica powder by dynamic light scattering method before hexamethyldisilazane treatment

According to the present invention, there is provided a method for producing a toner external additive made of silica powder with small aggregation.

What is important in the present invention is that hexamethyldisilazane is used as the silane coupling agent, and the water content of the surface-treated silica powder (hereinafter also referred to as silica powder raw material) is controlled to 0.5% by mass or less. That is. When the water content of the silica powder raw material exceeds 0.5 mass%, the condensation reaction of hexamethyldisilazane tends to occur on the silica surface, and the silica powders are aggregated. The lower limit of the moisture content is preferably 0.01% by mass. The water content can be adjusted, for example, by subjecting the silica powder raw material to a heat treatment in a floating state with a heating gas of 100 ° C. or higher. The moisture content can be measured by the Karl Fischer method.

The particle diameter of the silica powder raw material is 0.02 to 1 μm in volume average diameter. In particular, the maximum particle size is preferably 4 μm or less and the average sphericity is 0.9 or more. The average sphericity can be measured as follows.

A particle image taken with a stereomicroscope such as “Model SMZ-10” (Nikon Corporation), a scanning electron microscope, a transmission electron microscope or the like is taken into an image analysis apparatus such as Nihon Avionics Co., Ltd. To measure the projected area (A) and perimeter (PM) of the particles. When the area of a perfect circle corresponding to the perimeter (PM) is (B), the roundness of the particle can be displayed as A / B. Therefore, assuming a perfect circle having the same circumference as the sample particle (PM), PM = 2πr and B = πr ² , so that B = π × (PM / 2π) ² , and each particle Is calculated as sphericity = A / B = A × 4π / (PM) ² . The sphericity of 200 arbitrary particles thus obtained is obtained, and the average value is defined as the average sphericity.

In the present invention, the surface treatment of the silica powder raw material is performed by bringing the silica powder raw material into contact with a gas containing hexamethyldisilazane in a suspended state. When hexamethyldisilazane is treated with droplets, the effect of suppressing the formation of aggregated particles is small. Hexamethyldisilazane concentration of the gas containing hexamethyldisilazane 0.05-2% by volume, preferably 0.2 to 1.5% by volume. If the hexamethyldisilazane concentration in the gas is less than 0.05% by volume, the amount of treatment with hexamethyldisilazane is small, so that sufficient surface treatment becomes difficult, and if it exceeds 2% by volume, hexamethyldisilazane is locally produced. May react and cause aggregation due to self-condensation. The gas containing hexamethyldisilazane can be adjusted by mixing a gasified silane coupling agent with a carrier gas such as nitrogen or air.

The silane coupling agent used in the present invention is hexamethyldisilazane . Silane coupling agents such as dimethyl diene Toshiki Sila emissions, is a f hexyl trimethoxysilane the fluidity index is smaller than hexamethyldisilazane (Comparative Examples 4 and 5).

As in the present invention, in order to surface-treat a silica powder raw material with a gas containing hexamethyldisilazane , it is necessary to float the silica powder raw material. For example, a heater such as a ribbon heater is arranged on the outer periphery of a stainless steel cylindrical container, for example, a stainless steel net of 20 μm for uniformly supplying gas to the lower inlet, and the upper outlet to the upper outlet. In order to prevent the powder from splashing out of the system, for example, a processing container to which a filter cloth is attached is put in a silica powder raw material in a state in which the internal temperature is maintained at 100 ° C. A method of supplying a carrier gas to float the silica powder raw material while supplying a gas containing hexamethyldisilazane from below the processing vessel and bringing it into contact with the silica powder raw material can be mentioned. Alternatively, a method may be used in which a gas containing hexamethyldisilazane is fed into a place where the silica powder raw material is stirred and floated with a stirring device such as a mixer. In any case, the gas containing hexamethyldisilazane is gasified by, for example, dropping hexamethyldisilazane into an electric kettle heated to an internal temperature of 200 to 300 ° C., and gasifying it. It can be mixed with gas and supplied to the processing vessel. The concentration of hexamethyldisilazane gas can be adjusted by adjusting the supply rate of hexamethyldisilazane when the carrier gas flow rate is kept constant and dropping into an electric kettle or the like.

The contact between the floating silica raw material powder and the gas containing hexamethyldisilazane is performed at a temperature of 100 ° C. or higher. The reason is to prevent condensation of hexamethyldisilazane gas and to prevent moisture generated as a by-product of the reaction between hexamethyldisilazane and silica powder from being adsorbed on the silica powder surface. The upper limit of the contact temperature is not particularly limited, but is preferably 350 ° C. for the purpose of preventing the decomposition of hexamethyldisilazane . A particularly preferred contact temperature is 180 to 250 ° C. The contact time is preferably 1.0 to 10 seconds.

In the present invention, for example, the water content of the silica powder source, the concentration of hexamethyldisilazane gas, by controlling the conditions of the contact temperature of the hexamethyldisilazane gas, the two equations, treated to have three equations relationship It is particularly preferable to do this. The ratio of the mode diameter (DMt / DMs) and the ratio of volume average diameter (DAt / DAs) are indices indicating the degree of change in the particle size of the silica powder due to aggregation before and after the surface treatment. This indicates that the silica powder is not agglomerated.

For the particle size distribution measurement by the dynamic light scattering method, for example, “MICROTRACK UPA150” manufactured by Nikkiso Co., Ltd. is used as a measuring device, and the sample is dispersed in an organic solvent selected from, for example, methyl ethyl ketone, toluene, ethanol, etc., and slurried. Done. In the present invention, since the change in the particle size distribution before and after the surface treatment is observed, the type of the organic solvent is not affected, but the same organic solvent must be used in the measurement before and after the surface treatment. The measuring device automatically calculates the mode diameter, the volume average diameter, and the like from the obtained particle size distribution result.

The toner external additive produced by the present invention can be used in the same manner as a conventional toner external additive. For example, per 100 parts by mass of a styrene resin, 70 to 110 parts by mass of magnetic powder such as iron oxide (Fe ₃ O ₄ ), 1 to 5 parts by mass of a charge control agent such as a monoazo iron complex, and 2 to 5 parts by mass of waxes. The mixture containing the mixture is melt-kneaded at 100 to 150 ° C., and then cooled, pulverized, and classified to produce toner particles having an average particle diameter of 3 to 10 μm. 2 parts by weight are mixed.

Example 1
15 kg of silica powder raw material (Note: Volume average diameter DAs by dynamic light scattering method is 0.29 μm and mode diameter DMs is 0.05 μm) is charged into the above processing container (dimension: diameter 600 mm cylinder). While 800 NL / min nitrogen was fed from below and floated, the internal temperature of the processing vessel was heated to 220 ° C. and held for 20 minutes. Thereby, the moisture content of the silica powder raw material became 0.2 mass%. Processing was performed by supplying a gas containing a silane coupling agent to the heated / floating state. The silane coupling agent used was hexamethyldisilazane (“HMDS-3” manufactured by Shin-Etsu Chemical Co., Ltd.). By supplying 400 g at 40 g / min, hexamethyldisilazane with respect to the total amount of gas supplied. The gas concentration was 0.60% by volume. About the silica powder after surface treatment, the particle size distribution by the dynamic light scattering method was measured. The results are shown in Table 1.

Example 2
Surface treatment was performed in the same manner as in Example 1 except that 800 g of hexamethyldisilazane was supplied at 80 g / min, so that the concentration of hexamethyldisilazane gas relative to the total amount of gas supplied was 1.2% by volume. Silica powder was produced.

Comparative Example 1
Surface treatment was performed in the same manner as in Example 1 except that 2000 g of hexamethyldisilazane was supplied at a rate of 200 g / min and the concentration of hexamethyldisilazane gas was 3.0% by volume with respect to the total amount of gas supplied. Silica powder was produced.

Comparative Example 2
Surface treatment was performed according to Example 1 except that the internal temperature of the processing vessel was 80 ° C. and the moisture content of the silica powder raw material was 1.0 wt% without heat treatment.

Comparative Example 3
Surface treatment was performed according to Example 1 except that hexamethyldisilanezane was sprayed in a liquid rather than gaseous form.

Comparative Example 4
A surface-treated silica powder was produced in the same manner as in Example 1 except that hexyltriethoxysilane (“KBM-3063” manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silane coupling agent.

Comparative Example 5
A surface-treated silica powder was produced in the same manner as in Example 1 except that dimethyldiethoxysilane (“KBE-22” manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the silane coupling agent.

An application test of the silica powder obtained above as a toner external additive was performed. In the test, 10 g of a styrene resin having an average diameter of 5 μm and 0.1 g of a sample were put in a mixer, mixed at room temperature at 480 rpm for 10 seconds, and 2 g of the obtained mixed powder was put on a three-stage sieve of 150 μm, 75 μm, and 45 μm, Classification was performed by applying a vibration of 0.25 mm amplitude for 3 minutes. From the amount of residual powder on each sieve, the fluidity index was calculated by the above formula 1. The results are shown in Table 1.

From Table 1, it was shown that according to the toner external additive produced by the method of the present invention, the fluidity index of the resin particles can be greatly improved and is suitable as the toner external additive.

The toner external additive produced by the present invention can be used, for example, as an external additive for an electrostatic charge image developing toner.

Claims (3)

The silica powder having a volume average diameter in water content of 0.5 wt% or less 0.02 to 1 .mu.m, a temperature above 100 ° C., in a suspended state, hexamethyldisilazane concentration from 0.05 to 2 vol A method for producing a toner external additive, wherein the toner is brought into contact with a gas in an amount of 5 %. 2. The production method according to claim 1, wherein the fluidity index of the toner external additive measured by the following method is 80% or more .
(Liquidity index)
10 g of styrene resin having an average diameter of 5 μm and 0.1 g of a sample (toner external additive) are placed in a mixer and mixed at room temperature at 480 rpm for 10 seconds. 2 g of the obtained mixed powder is 150 μm, 75 μm, and 45 μm three-stage sieve. After adding and classifying the vibration of 0.25 mm amplitude for 3 minutes, the value calculated by the following formula 1 from the amount of residual powder on each sieve.
100-50A-30B-10C (1)
A: Residual amount of powder on 150 μm sieve
B: Residual amount of powder on 75 μm sieve
C: Amount of residual powder on a 45 μm sieve The process according to claim 1, wherein the to have the following two equations, three equations of the relationship.
0.5 ≦ DAt / DAs ≦ 2.5 (2)
1.0 ≦ DMt / DMs ≦ 1.5 (3)
DAt: Volume average diameter of silica powder after hexamethyldisilazane treatment by dynamic light scattering method DAs: Volume average diameter of silica powder before hexamethyldisilazane treatment by dynamic light scattering method DMt: After hexamethyldisilazane treatment Mode diameter of silica powder by dynamic light scattering method DMs: Mode diameter of silica powder by dynamic light scattering method before hexamethyldisilazane treatment