JP3737207B2 - How to mix powder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a powder mixing method capable of uniformly and rapidly treating base particles and small particles, and is applied to the production of electrophotographic developer toners and the like.
[0002]
[Prior art]
As a powder technology that mixes base particles and small particles, adheres the small particles to the surface of the base particles, and modifies the surface, for example, in order to make the developing toner for electrophotography have fluidity, toner It is generally employed to add and adhere inorganic particles such as silica powder or organic powder to the particles.
[0003]
Conventional methods for mixing powder particles in which the base particles and small particles are mixed to modify the surface of the base particles include a method in which the base particles and small particles are placed in an airtight container and shaken, or A method of stirring particles at high speed with a propeller, a method of mixing and stirring using a pulverizer, and the like have been used. In these methods, uniform adhesion and mixing may be difficult, and if the blended base particles or small particles are heat-meltable, they may adhere to the blade due to heat generated during propeller rotation, There was a problem that aggregation occurred.
[0004]
[Problems to be solved by the invention]
However, when silica powder or the like is mixed with toner base particles mainly composed of a thermoplastic resin, if the high-speed stirring by the propeller is continued for a long time, the toner as the base particles melts and adheres to the propeller. In order to prevent this, a method in which high-speed stirring is repeated for a short time while taking an interval has been adopted, which has the disadvantage that the production efficiency is very poor. In addition, a method has been proposed in which mother particles and small particles are placed in a closed container, and the container is circularly moved and rotated and mixed and adhered, but if the specific gravity of the mother particles and small particles is different, mixing is performed. There is a drawback that particles with insufficient or high specific gravity accumulate on the bottom of the container and are compressed.
[0005]
The object of the present invention is to solve the above-mentioned drawbacks, and the base particles and the small particles can be mixed rapidly and uniformly, and the base particles and the small particle adhesion layer by a blade or the like at the time of mixing. Therefore, it is intended to provide a mixing method of powder and granule which is excellent in workability without causing damage and contamination of the container, and no accumulation and compression of base particles and the like at the bottom of the container.
[0006]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors achieved the above object by adding a spherical medium to the base particles and small particles to be mixed and mixing them in a specific rotation container. The present invention has been completed by finding out what can be done.
[0007]
That is, the present invention
In a method of mixing powder particles in which mother particles and small particles are mixed and the small particles adhere to the surface of the mother particles, the mother particles, small particles, and spherical medium are placed in a mixing container and the mixing container is moved circularly. And mixing with shaking while rotating, and then separating the granular material with small particles attached to the surface of the base particle from the spherical medium by sieving or the like. . Further, it is a method for mixing powders in which the diameter of the base particles is 10 times or more the diameter of the small particles, and the base particles are electrophotographic developer toner.
[0008]
Hereinafter, the present invention will be described in detail.
[0009]
The base particles used in the present invention may have an average particle size of 1 μm to several hundreds of μm, and are not limited to particle size distribution, particle shape, particle material, and the like, and can be widely used.
[0010]
The small particles used in the present invention are particles having a smaller particle size than the base particles, and the average particle size may be 0.001 μm to several tens of μm. The particle size distribution, particle shape, particle material, etc. It is not limited and can be used widely. The small particles to be mixed may be one kind of small particles, or two or more kinds of small particles can be mixed at the same time.
[0011]
The spherical medium used in the present invention preferably has a diameter of 0.1 mm to several centimeters, which is very large compared to the base particles. These are for improving the mixing ability and improving workability of sieving the mixed product and the spherical medium. The material of the spherical medium is not particularly limited, and one or more materials can be used. Specific examples of the spherical medium include glass beads, plastic beads, ceramic beads, metal beads and the like, and these can be used alone or in combination of two or more.
[0012]
Next, the mixing method and the mixing container of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a mixing container, which is preferably cylindrical and can be sealed. A predetermined amount of base particles and small particles are weighed into a container, and then a spherical medium is added and sealed. As shown in FIG. 1, the mixing container 1 rotates around the rotation axis indicated by the one-dot chain line B inside the container object while causing a circular motion a around the rotation axis indicated by the one-dot chain line A outside the container object. Furthermore, the rotating shaft B is swung with respect to the rotating shaft A like B ′ and B ″, and the mixing container 1 is shaken c to mix the particles.
[0013]
That is, if the mixing container 1 is circularly moved in the direction of arrow a and the mixing container 1 is rotated in the direction of b while continuing its rotation, the direction of the centrifugal force in the rotation and the direction of the centrifugal force in the circular movement are different. In some cases, the direction is reversed, so mixing can be done well. Further, the base particles and the small particles are uniformly dispersed by addition of the spherical medium, and the powder whose surface has been modified to be shaken in the c direction is not compressed in the container or the container bottom. The spherical medium is removed by sieving the obtained granular material to obtain a granular material having a modified surface. In this method, even if mixing is performed at a high speed, the temperature does not easily rise as compared with stirring by a propeller or the like, and the stirring ability can be equal or higher.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.
[0015]
Example 1
A pigment dispersion was prepared by dispersing a pigment in a thermoplastic resin. The obtained pigment dispersion was pulverized and spheroidized to prepare a toner having an average particle size of 10 μm. This is the base particle in mixing. As small particles to be added, R-972 (trade name: 1 nm, manufactured by Nippon Aerosil Co., Ltd.), which is negatively charged silica, was used.
[0016]
20 g of base particles were weighed into a plastic container, and 0.2 g of small particles were added and sealed. Further, 2 g of glass beads (diameter 2 mm) were added as a spherical medium, and then the mixture was stirred and mixed for 30 seconds using the apparatus shown in FIG. The toner in the container after mixing was not compressed on the bottom of the container. Glass beads were removed from the obtained toner through a 100-mesh sieve. When the toner was observed with a scanning electron microscope, it was confirmed that the negatively-charged silica was uniformly adhered and there was no aggregation of the toner.
[0017]
Example 2
The same amount of toner and negatively charged silica as in Example 1 were put into a sealed container, and 5 g of spherical medium plastic having a diameter of 1 cm was added as a spherical medium. After the addition, the mixture was mixed in the same manner as in Example 1. The toner obtained after mixing was not compressed in the container, and the negatively charged silica was uniformly dispersed on the toner surface.
[0018]
Example 3
20 g of spherical polyethylene having an average particle diameter of 20 μm was measured as a base particle in a plastic container, and 1 g of titanium oxide having an average particle diameter of 0.3 μm was added as a small particle and sealed. Thereafter, mixing was performed in the same manner as in Example 1. After mixing, compression of polyethylene as a base particle was not observed in the container. When the obtained surface modified particles were observed with a scanning electron microscope, it was observed that the base particles were uniformly coated with titanium oxide.
[0019]
Example 4
50 g of ferrite spheres having an average particle diameter of 100 μm as base particles were weighed in a plastic container, and 1 g of nylon spheres having an average particle diameter of 5 μm were added and sealed as small particles. Thereafter, mixing was performed in the same manner as in Example 1. After mixing, compression of the ferrite spheres as the base particles was not observed in the container. When the obtained surface modified particles were observed with a scanning electron microscope, it was observed that the base particles were uniformly coated with nylon spheres.
[0020]
Comparative Example 1
The base particles and small particles used in Example 1 were weighed in the same amount and mixed with a propeller mixer at 9000 rpm for 30 seconds. When the mixture was observed with a scanning electron microscope after mixing, aggregation of the mother particles due to the heat of the mother particles was observed, and adhesion of the resin was also observed on the propeller.
[0021]
Comparative Example 2
The same amount of base particles and small particles used in Example 1 were weighed and mixed without adding a spherical medium and without shaking the container. Although the obtained surface was uniformly coated with silica, the toner was compressed at the bottom of the container.
[0022]
Comparative Example 3
The same amount of base particles and small particles used in Example 3 were weighed and mixed with a propeller mixer at 9000 rpm for 30 seconds. After mixing, the mixture was observed with a scanning electron microscope. As a result, aggregation of the base particles due to heat was observed, and adhesion of the resin was also observed on the propeller.
[0023]
Comparative Example 4
The same amount of base particles and small particles used in Example 4 were weighed and mixed with a propeller mixer at 9000 rpm for 30 seconds. When the mixture was observed with a scanning electron microscope after mixing, no aggregation of the base particles was observed, but the blades of the propeller mixer were worn by the ferrite spheres.
[0024]
【The invention's effect】
As is clear from the above explanation, according to the method for mixing granular materials of the present invention, the base particles and the small particles can be quickly and uniformly dispersed, and the base particles and the small particle adhesion layer are damaged or contaminated by the stirring medium. In addition, there was no compression of the base particles in the container, and workability could be improved.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic diagram for explaining a method of mixing powder particles of the present invention.
[Explanation of symbols]
1 Mixing container

Claims (3)

In a method of mixing powder particles in which mother particles and small particles are mixed and the small particles adhere to the surface of the mother particles, the mother particles, small particles, and spherical medium are placed in a mixing container and the mixing container is moved circularly. While rotating together , the mixing vessel is mixed by shaking the rotation axis of the mixing vessel with respect to the axis of the circular motion , and thereafter, the granular material having small particles attached to the surface of the base particle is separated from the spherical medium. A method for mixing granular materials. The method for mixing powder particles according to claim 1, wherein the diameter of the base particles is at least 10 times the diameter of the small particles. 3. The method for mixing powder particles according to claim 1, wherein the base particle is an electrophotographic developing toner.

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