JP2011136781A - Powder transfer classification method and transfer classification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method and a manufacturing device of toner, which further efficiently and stably provides the toner having sharp grain size distribution to a target particle size, by further cutting fine powder, by increasing production capacity (crushing processing capacity), while reducing a load of a crushing device. <P>SOLUTION: This transfer classification device includes a power fluidizing tank 10 having an air discharge mechanism on a bottom part for fluidizing powder, an air current type classification device 40 for separating the powder into a coarse particle and a particulate, and a transfer device 20 for supplying the powder to the air current type classification device from the powder fluidizing tank. The powder fluidizing tank 10 includes a bulk density control means for controlling so that the bulk density of the fluidized powder becomes constant. The transfer device 20 levels the pulsation of a transfer quantity when transferring the powder by a plurality of pumps of respectively shifting a phase. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method of supplying raw material powder to an airflow classifier and an apparatus therefor.
In particular, the present invention relates to a toner classification method and a classification apparatus for classifying a powder material used in an image forming method such as an electrophotographic method, an electrostatic recording method, an electrostatic printing method, or a toner jet recording method by an air current.

  In the classification of electrophotographic toner, a container or hopper for primary storage of powder, or a filter-type filtration device or collection device for separating the toner into solid and gas during powder transfer, pulverization or classification, powder Feeders for quantitative supply are used, but various easily cohesive or sticky materials that meet various quality requirements such as increase in specific surface area and low-temperature and high-speed fixing of powder toner as powder is atomized Due to the use, the fluidity is lowered, and the material is agglomerated and adhered to the inner wall surface of the feeder and repeatedly collapses. Therefore, it is difficult to quantitatively discharge from the feeder.

  On the other hand, in order to classify fine particle powder such as toner for electrophotography, generally, a classification device using a swirling airflow is used, for example, a dispersion separator (DS type: manufactured by Nippon Pneumatic Co., Ltd.) is used. (Patent Documents 1 to 6).

  FIG. 1 shows a configuration example of a conventional classification system, and FIG. 1 (A) uses a typical airflow classifier (DS type: manufactured by Nippon Pneumatic Co., Ltd.) used for classifying fine particle powder. An example of a conventional classification system configuration is shown. The airflow type DS classifier (1) in this system configuration example is schematically composed of a dispersion chamber (2), a main casing (4), a classification chamber (6), and a lower casing (8) from top to bottom. And a hopper (10). An inlet (12) is connected to the upper part of the dispersion chamber (2), and an exhaust port (14) is connected to the central portion of the upper end wall. The inlet (12) is disposed substantially tangentially to the outer peripheral surface of the dispersion chamber (2), and the primary air flow and the powder material are supplied into the dispersion chamber (2) through the inlet (12). Under the dispersion chamber (2), a conical center core (16) having a mountain height at the center is disposed, and an annular coarse powder outlet is provided near the lower outer periphery of the center core (16). (18) is formed. On the other hand, a secondary air inlet, that is, a louver (20) is provided on the outer peripheral portion of the lower peripheral wall of the classification chamber (6).

  The powder material supplied from the feeder (22) is supplied into the dispersion chamber (2) through the inlet (12) together with the primary air flow, and descends while forming a swirling vortex in the dispersion chamber (2). While gathering at the outer peripheral portion of the dispersion chamber (2), it enters the classification chamber (6). On the other hand, the primary air flow is discharged to the outside through the exhaust port (14). A secondary air flow is supplied to the classification chamber (6) through the louver (20), and the secondary air flow disperses the powder material that has entered the dispersion chamber, and the swirling speed is accelerated to increase coarse particles and fine particles. The coarse particles are discharged through the coarse powder outlet (18), and the fine particles are discharged through the fine powder outlet (24).

The classification principle in the airflow DS classifier (1) is that coarse particles in the powder material are produced when the secondary air flow flowing into the classification chamber (6) causes the powder material to flow semi-freely in a swirling manner. And the centrifugal force and centripetal force acting on the fine particles are different. Therefore, in the classification chamber (6), it is desirable to improve the classification accuracy by classifying into coarse particles and fine particles in a dispersed state as much as possible. From this, in order to realize reliable dispersion in the dispersion chamber (2). In addition, the particle state of the powder material supplied to the classifier (1) is important.
Therefore, as shown in FIG. 1 (B), it has been proposed to supply the fluidized powder flow to the airflow classifier via a fluid tank.

However, the powder material supplied to the airflow-type DS classifier is practically limited in being introduced into the dispersion chamber in a state close to primary particles only by mixing it with primary air as in the prior art. In order to obtain primary particles, an increase in the amount of primary air or the use of a dispersing device such as an acceleration type with a large amount of high-pressure air as the primary air causes turbulence in the dispersion chamber or inflow of excess air into the dispersion chamber. Therefore, the balance between centrifugal force and centripetal force acting on coarse particles and fine particles is disturbed. For this reason, even if the powder material introduced into the dispersion chamber is in a state close to primary particles, it is difficult to maintain the original characteristics of the classification device, and the classification accuracy is lowered accordingly. That is, even the ultrafine particles are mixed into the coarse particles in the powder particles coming out of the classifier, and as a result, the product cannot obtain a highly accurate particle size distribution.
Polymerized toners that are produced by chemical reaction without pulverization in recent years also have similar problems in the classification stage.

An airflow classification system that solves the above problem is proposed in Patent Document 7.
This airflow classifying system includes a fluidizing device as shown in FIG. 3 for fluidizing a powder material by an airflow and sufficiently fluidizing it in advance while applying vibration to the powder material supplied to the dispersion chamber. Thus, the powder material can be supplied to the dispersion chamber in a state close to the primary particles.

  However, in recent years, as the closed circuit classification in which the airflow classifier is combined in two or more stages in series and connected between them by a conveyance path becomes more mainstream, more precise classification is required, and the classification chamber is in the state of primary particles. However, it is no longer possible to meet the above-mentioned demands only by supplying the product.

The present invention further improves and develops the technique described in Patent Document 7 (Japanese Patent Laid-Open No. 11-197606).
The present inventor has intensively studied in order to enable more precise classification. As a result, the amount of powder supplied from the feeder that supplies the powder to the fluidizing device looks constant in a long time, but looks in a short time. There is a pulsation in which the amount of powder supplied changes, the amount of powder fluidized in the fluidizer changes, the amount of powder supplied to the classifier changes, and centrifugal action works on coarse particles and fine particles. We found that the force and centripetal force changed and hindered precise classification.

  Therefore, the present invention controls the solid-gas mixed phase flow to the fluid supply type powder classifier, thereby preventing a change in the amount of powder supplied into the classification chamber and the centrifugal force acting on coarse particles and fine particles. And by controlling the balance of centripetal force, it eliminates the aggregation of fine particles, enhances the dispersion effect of the raw material in the dispersion chamber even for highly adherent raw materials, improves the dispersion efficiency and classification accuracy, and reduces the target particle size and coarse powder. It is possible to divide sharply, the powder returning to the pulverization process is only coarse powder that does not contain the product particle size, preventing the product particle size powder from being classified again, Reduces the load on the pulverizer, increases the production capacity (crushing capacity), cuts fine powders, and produces a toner with a sharp particle size distribution with respect to the target particle size. Of toner that can be obtained And to provide a manufacturing apparatus.

The object of the present invention is to prevent a change in the bulk density of fluidized powder that has been fluidized by gas introduction and supplied into a classification chamber, and to prevent a change in the supply amount of the powder. Solved.
That is, the said subject is solved by following (1)-(9) of this invention.
(1) “Powder fluidizing tank having an air release mechanism for fluidizing powder at the bottom, an airflow classifier for separating powder into coarse particles and fine particles, and from the powder fluidizing tank A transfer device for supplying the powder to the airflow classifier, and the powder fluidizing tank has a means for controlling the bulk density of the fluidized powder to be constant. In addition, the powder transfer / classifying device is characterized in that the transfer device equalizes the pulsation of the transfer amount at the time of powder transfer by a plurality of pumps whose phases are shifted from each other.
(2) “The bulk density control means includes a powder weight measuring device and a powder surface level measuring device in the powder fluidization tank, and the powder transfer / classification according to the above (1)” apparatus."
(3) “Powder transfer / classification apparatus according to (1) or (2), wherein the powder is toner”
(4) The powder transfer / classifying apparatus according to any one of (1) to (3), further including a powder storage unit for discharging the powder to the powder fluidization tank . "
(5) “It further has compressed gas injection means for accelerating the dispersion of the powder by jetting and joining the compressed gas flow to the powder flow supplied from the powder fluidization tank to the airflow classifier. The powder transfer / classification apparatus according to any one of (1) to (4), which is characterized.
(6) “The powder transfer / classifying apparatus according to (5), wherein the gas of the compressed gas flow is helium or a mixed gas of helium and air”.
(7) “The airflow classifier includes a dispersion chamber and a classification chamber, and the powder supplied together with the primary airflow into the dispersion chamber is coarse particles by a secondary air flow that flows from the periphery of the classification chamber. The powder transfer / classification apparatus according to any one of (1) to (6) above, wherein the powder transfer / classification apparatus is characterized in that it is separated into fine particles and fine particles.
(8) “Powder fluidizing step of releasing gas from the gas releasing mechanism at the bottom to fluidize the powder in the powder fluidizing tank, and the fluidized powder from the fluidizing tank by an air flow type A powder transfer / classification method comprising: a fluidized powder transfer step for supplying to a classification device; and a powder classification step for separating the powder into coarse particles and fine particles by the airflow type classification device, The powder fluidization step in the powder fluidization tank includes a bulk density control operation for controlling the fluidized powder to have a constant bulk density, and the powder transfer step includes A powder transfer / classification method characterized in that the pulsation of the powder transfer amount is leveled by a plurality of pumps, each of which is out of phase. "
(9) “A step of accelerating the dispersion of the powder by jetting a compressed gas flow from the compressed gas jetting means into the powder flow supplied from the powder fluidization tank to the airflow classifier. The method for transferring and classifying powder according to item (8), characterized by comprising: "

As will be apparent from the following detailed and specific description, by using the fluid supply type powder classification method and apparatus according to the present invention, by controlling the balance between centrifugal force and centripetal force acting on coarse particles and fine particles, It has been found that even if the raw material has a high adhesion property by eliminating the aggregation of the fine particles, the dispersion effect of the raw material in the dispersion chamber can be enhanced and the dispersion efficiency and classification accuracy can be improved.
The present invention makes it possible to sharply divide the target particle size and coarse powder over a long period of time, so that the return to the pulverization process is only coarse powder that does not include the product particle size. A toner that has a sharp particle size distribution with respect to the target particle size and can be stably obtained in a higher yield by reducing the load, increasing the production capacity (crushing capacity), and cutting fine powder. We were able to provide manufacturing equipment.

It is a whole flowchart which shows the example of the conventional airflow type classifier and the classification method. It is a figure of the whole flow which shows one example of the airflow type | formula classification apparatus and classification method of this invention. It is the schematic which shows an example of the powder flow tank used with the conventional airflow classifier and the classification method. It is an assembly drawing which shows an example of the powder fluidization tank in this invention. It is the schematic which shows the pump structural example used by this invention. It is a schematic block diagram of the example of the airflow type classifier in this invention. It is a figure which shows the particle size distribution of the toner obtained by the Example and the comparative example.

[Airflow type powder transfer classification system (apparatus and method)]
Hereinafter, the airflow type transfer classification device and the transfer classification method of the present invention will be described in detail and specifically.
As can be understood from one example of the powder transfer classification apparatus shown in FIG. 2, the airflow type powder (for example, typically toner) transfer classification apparatus (1) of the present invention is for fluidizing the powder. A powder fluidizing tank (10) having an air release mechanism at the bottom, an airflow classifier (40) for separating powder into coarse particles and fine particles, and the airflow type from the powder fluidizing tank (10). A transfer device (20) (a portion having a plurality of pump transfer devices (21) in the figure) for supplying the powder to the classification device (40). The powder fluidization tank (10) has a bulk density control means for controlling the fluidized powder powder so that the bulk density is constant, and the transfer device (20) is shifted in phase. Further, the pulsation of the transfer amount during powder transfer is leveled by a plurality of pumps (21).
The airflow classifier (40) typically includes a dispersion chamber and a classification chamber, and secondary air into which the powder material supplied together with primary air flows into the dispersion chamber from the periphery of the classification chamber. Separation into coarse particles and fine particles by flow. And this powder transfer classifier comprises a powder fluidization tank for storing the powder material to be supplied to the dispersion chamber of the classifier (intermediate storage section when there is a powder storage section upstream), the powder And a transfer device for supplying powder from the body fluidization tank to the dispersion chamber. In this case, the powder fluidization tank has an air release mechanism (fluidization) for fluidizing the powder from the bottom. In which air is continuously injected into the powder and fluidized to a level where the bulk density is constant and transportable, and the transfer device is a powder having the controlled bulk density. It includes a plurality of pumping means for supplying a constant amount of the flow without blurring. With this configuration, both the “quality” and “amount” of the powder flow that is fluidized by gas introduction and supplied to the classifier are provided. Charged at the same time.
It is preferable to measure the discharge amount from the transfer device with a flow meter and control the powder transfer rate by the pump in order to keep the powder supply amount constant.

  In addition, the airflow type powder (for example, typically toner) transfer classification method of the present invention includes a powder fluidization step of fluidizing powder using a gas in a powder fluidization tank as an intermediate storage unit. A powder transfer step of supplying the fluidized powder to an airflow classifier, and a powder classification step of separating the powder into coarse particles and fine particles by the airflow classifier.

For example, in the case of a pulverized toner, the weight average particle diameter is measured by an air jet pulverizer using a pulverizing plate or a mechanical pulverizer that finely pulverizes a toner composition powder containing at least a binder resin and a colorant. After primary pulverization to 7 to 30 μm and primary pulverization, the obtained primary pulverized particles are stored in a powder storage unit and powder is supplied by a feeder, or directly powder flow tank To supply.
In the electrophotographic toner classification method using the apparatus of this specific example, the discharged powder is placed on a compressed gas stream in the middle of transfer and supplied to the classifier as a primary air stream. By causing the powder to join the tip of the nozzle from which the compressed gas is ejected, the re-agglomerated slow aggregate can be more sufficiently primary particles and the powder supply amount is stabilized.
That is, according to the apparatus of this example, the bulk density suitable for the air flow transfer is obtained in the powder flow tank (10), and the powder flows out of the powder flow tank (21) and passes through a plurality of pumps (22). As needed, compressed air is jetted from the compressed air jet nozzle (22) into the powder flow transferred while leveling the pulsation of the transfer amount at the time of transfer, and further dispersed, and the classifier (40) It is configured to be transferred to.
In the system of this example, since the primary particles in the powder flow tank (10) are further dispersed, gas enters between the particles, and it is not necessary to use an excessive gas flow. The generated agglomerates can be crushed to make primary particles more sufficiently, and the airflow in the dispersion chamber is not disturbed.
Hereinafter, specific examples of the transfer classification method using each unit device and the combination of these unit devices will be described in more detail.

[Powder fluidization tank]
One specific example of the powder flow tank (10) according to the present invention shown in FIG. 4 (also referred to as an intermediate storage section when there is a powder storage section further upstream) is a fluid drum (51), It is arranged on a platform scale (50) for powder weight measurement, and a top cover member (51a) of the fluid drum (51) has a toner inlet (52), a fluid drum suction pipe (53), and an air vent pipe. (54) and a level meter (55) are provided.
The fluid drum suction pipe (53) and the level meter (55) have their tips inserted into the inner space of the fluid drum (51). The air vent pipe (54) has a valve (56) and a filter cloth filter. (57) is provided. The bottom member (51b) of the fluid drum (51) is provided with a bottom member (51b) of the fluid drum (51) at an upper part with a slight space for pipe space from the bottom of the cylindrical wall member of the drum. From the lower side of the bottom member (51b), the tips of the plurality of air flow introduction pipes (58) are inserted into the blow holes provided in a balanced manner so that the air can be uniformly blown into each region of the bottom member (51b). -Sealed. In this example of the figure, the bottom member (51b) has a flat bottom. However, in the present invention, the bottom member (51b) does not necessarily have a flat bottom, such as a powder flow tank shown in FIG. Further, in consideration of the ease of taking out the discharged residual powder, it may be inclined toward the remaining powder take-out hole.

The instrumentation section (59) includes a flow meter (59a) and a precision regulator (59b) for controlling the bulk density of the powder flow to be constant. The flow meter (59a) is interposed in the pipelines of the plurality of air flow introduction pipes (58), monitors the air flow state of each pipe (58), and based on the result, each pipe (58b) is It is possible to control the air flow introduction state to 59a).
The material before toner fine pulverization and classification is first charged into the fluid drum (51) through the toner inlet (52), and this powder material is fed into the air flow introduction pipe (58) in the drum (51). The suspension is suspended and fluidized by compressed air introduced through the air, and is sucked into the transfer device through the suction pipe (53) while suppressing the adhesion of particles and the occurrence of secondary aggregation.

As a method for measuring the powder weight, for example, the powder flow drum (tank) which is an intermediate storage unit is measured with a platform scale (50), the powder weight is measured, and the volume is measured from a level meter (55) attached to the flow drum. Can be calculated. Of course, the unit of bulk density is g / cc.
The preferred range of the bulk density in the present invention varies depending on the type of powder, the transport conditions, and the like, so it cannot be said unconditionally, but the bulk amplitude during transport / classification may fall within the range of less than 0.2 g / cc. Preferably, it is less than 0.1 g / cc, more preferably less than 0.05 g / cc. The powder level can be detected by an optical sensor or the like.

[Transfer device (multiple pumps)]
The transfer device (20) in the present invention is for transferring the powder from the powder flow tank as an intermediate storage part that has been converted into primary particles to a classifier, and an example of the main part is shown in FIG. Thus, there are a plurality of pumps (see FIG. 5a) for sucking and transferring powder. The plurality of pump means level the pulsation of the transfer amount at the time of powder transfer by a plurality of pumps (21) whose phases are shifted from each other. By providing this pump (suction pump) between the intermediate storage unit and the dispersion chamber, the amount of powder supplied to the dispersion chamber can be adjusted without being affected by the change in the amount of powder in the intermediate storage unit.

  More preferably, the pump is a mobile pump that does not easily apply mechanical stress to delicate powder such as toner, which has been improved by reciprocating pumps and has been devised in various ways to ensure chargeability and easy melting. Such mobile reciprocating pumps are well described in Japanese Patent Application Laid-Open Nos. 2007-114745, 2007-25625, and 3549053, but both the powder inlet and the outlet are below the bellows. Located in. The reciprocating pump sucks and discharges air containing powder by a reciprocating motion of a piston or a plunger, and generates a pulsating flow. In any case, in order to smooth the pulsating flow of the transfer amount, it is preferable to connect a plurality of powder pumps in parallel and shift the phase of each pump to equalize the pulsation. Preferably, see FIG.

[Compressed air ejection nozzle]
As described above, the transfer device (20), for example, like a spray gun, jets compressed air into a powder stream transferred from a compressed air jet nozzle, and further unites the compressed air to a classifier. It is preferable to have a compressed air jet nozzle (22) for transfer.

At this time, the distal end portion that discharges the material into the material supply pipe to the classifier on the discharge side of the plurality of pumps can be joined with compressed air like a spray gun to further promote dispersion. Dispersion can be further promoted by joining the tip portion that discharges the material into the material supply pipe to the classifier on the discharge side of the plurality of pumps with the compressed helium.
Furthermore, good results can be obtained when combined with a mixture of compressed helium and compressed air for limited resource utilization and improved production efficiency (reduced use of pure helium).

[Airflow classifier]
As shown in FIG. 6, an example of the airflow classifier (40) according to the present invention is schematically shown in this example from the top to the bottom, from the dispersion chamber (2) to the main casing (4). ), A classification chamber (6), a lower casing (8), and a hopper (10). An inlet (12) is connected to the upper part of the dispersion chamber (2), and an exhaust port (14) is connected to the central portion of the upper end wall. The inlet (12) is disposed substantially tangentially to the outer peripheral surface of the dispersion chamber (2), and the primary air flow and the powder material are supplied into the dispersion chamber (2) through the inlet (12). Under the dispersion chamber (2), a conical center core (16) having a mountain height at the center is disposed, and an annular coarse powder outlet is provided near the lower outer periphery of the center core (16). (18) is formed. On the other hand, a secondary air inlet, that is, a louver (20) is provided on the outer peripheral portion of the lower peripheral wall of the classification chamber (6).

The powder material supplied from the direction of the arrow is supplied into the dispersion chamber (2) through the inlet (12) together with the primary air flow, and descends while forming a swirl vortex in the dispersion chamber (2). They gather at the outer periphery of the dispersion chamber (2) and enter the classification chamber (6). On the other hand, the primary air flow is discharged to the outside through the exhaust port (14). A secondary air flow is supplied to the classification chamber (6) through the louver (20), and the secondary air flow disperses the powder material that has entered the dispersion chamber, and the swirling speed is accelerated to increase coarse particles and fine particles. The coarse particles are discharged through the coarse powder outlet (18), and the fine particles are discharged through the fine powder outlet (24).
The classification principle in the airflow classifier (1) in this example is that the secondary air flow flowing into the classification chamber (6) causes the coarse powder in the powder material to flow semi-freely in a swirling manner. Classification is performed by utilizing the difference in centrifugal force and centripetal force acting on particles and fine particles. Therefore, in the classification chamber (6), it is desirable to improve the classification accuracy by classifying into coarse particles and fine particles in a dispersed state as much as possible. From this, in order to realize reliable dispersion in the dispersion chamber (2). In addition, the particle state of the powder material supplied to the classifier (1) is important.

  In this specification, the airflow type powder classifier using the centrifugal force effect is described as a specific example of obtaining the effect by means for solving the problem, but the Coanda effect is obtained using compressed air. It can be applied to elbow jets that classify powders into multiple sizes, and also to impeller-type mechanical centrifugal force classifiers such as TSP: toner separator and TTSP: tandem toner separator air classifier. Is possible.

[Powder storage]
Returning to the apparatus configuration diagram of FIG. 2 again, in the transfer classification system (method and apparatus) of the present invention, the powder storage section (9) is arranged (although not essential) upstream of the powder flow tank (10). From here, for example, the feeder attached to the storage unit (9) can discharge the powder to be fluidized into the powder flow tank (10). Then, air can join the fluidized powder. The powder storage unit (9) has means for controlling the discharge amount from the powder storage unit (9) so that the powder weight or the powder surface of the powder flow tank (10) is constant. Have.

Hereinafter, the present invention will be described more specifically with reference to comparative examples and examples based on the drawings and tables. However, the present invention is not limited to the following examples.
An example using the apparatus of FIG. 3 showing an example of the configuration and method (system) of an electrophotographic toner manufacturing apparatus suitable for carrying out the present invention will be described.
This apparatus has a powder flow tank (intermediate storage unit), a plurality of pumps, and a compressed air jet nozzle for supplying to an airflow classifier, and a fluidized toner whose volume density is adjusted by the powder flow tank The pulsation of the transfer amount is leveled by a plurality of pumps, further dispersed by a compressed air jet nozzle, and injected from the nozzle to the tip of the airflow classifier. The classified material is classified into three types of product particle size, coarse powder, and fine powder in a highly dispersed state.

A mixture having the following composition was melt-kneaded and cooled, and then coarsely pulverized to obtain a coarsely pulverized product having an average particle size of about 400 μm. The coarsely pulverized product was pulverized to 2 to 6 μm by a pulverizer and classified under the same conditions by the following classification system. The pulsation of the transfer amount of the powder sucked from the powder flow tank and in a constant bulk density state was leveled by a reciprocating pump described in Japanese Patent No. 4335216, and quantification was classified by a classifier.
[Comminuted mixture composition]
Styrene-acrylic copolymer 100 parts by weight Carbon black 10 parts by weight Polypropylene 5 parts by weight Zinc salicylate 2 parts by weight

The classified toner was evaluated by the following method.
[Measurement of particle size distribution]
The particle size distribution of the toner particles can be measured by a Coulter counter method, and examples of the measuring device include Coulter counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.
First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using first grade sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the number distribution of channels of each particle diameter is measured by using the measurement apparatus with a 100 μm aperture as the aperture. From the obtained distribution, the weight average particle diameter (D4) and the number average particle diameter of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

[Measurement of powder bulk density in powder fluidization tank]
As described above, when calculating the powder bulk density of the powder fluidization tank, as a means for measuring the powder weight, for example, the powder fluidization tank is measured with a platform scale, and the powder weight is measured. The volume can be calculated from a level meter attached to the chemical bath. The unit of bulk density is g / cc. When cutting out from a conventional screw feeder, when there is a screw pitch at the discharge port, a large amount of powder is supplied, and conversely, when a screw pitch frame overlaps the discharge port, a small amount of powder is supplied. When thrown into a classifier, the air ratio increases, supply variation increases, and classification becomes unstable.

  As described above, the bulk density in the present invention of the fluidized powder in the present invention cannot be generally specified because the preferred range varies depending on the powder type, transfer conditions, etc. The runout width is preferably within a range of less than 0.2 g / cc, more preferably less than 0.1 g / cc, and particularly preferably less than 0.05 g / cc. Thus, the bulk density of 0.20 to 0.25 g / cc in Table 1 indicates that it is within a certain range, and 0.15 to 0.35 g / cc indicates that it is outside the certain range.

[Measurement of powder height and uniformity]
The powder height is easily measured by an optical sensor. In the bulk density adjustment, a constant value is controlled by flowing air from the bottom of the fluid tank based on the weight and volume of the supplied powder.
The measuring method of uniformity (powder height uniformity of the intermediate layer storage part) described in Table 1 is also the same as the above, and the evaluation standard is that the bulk density and a certain amount of powder can be supplied to the classifier. It is a judgment standard.
For uniformity adjustment, for example, powder is transferred by a mobile pump that has already been developed.
Further, when the compressed air and helium are ejected from the compressed gas ejection nozzle described above, the discharge amount is controlled in order to supply a constant amount to the classifier.

[Measurement of water content of toner]
The water content of the toner can be easily measured by a known measurement method. The best moisture content is less than 10% relative humidity, and the range of good moisture content is 10-30%. If it exceeds 30%, it becomes an undesirable range.

[Measurement of embrittlement of toner after classification]
Here, the helium content is most preferably 99% or more, and a good range of 70 to 99%. If it is less than 70%, it is not preferable, and the content decreases in proportion to the decrease.

[Comparative Example 1]
Using a conventional airflow classification system shown in FIG. 2, toner pulverized from a feeder at a supply rate of 20 kg / hr was supplied to a fluidizing device and classified.
The bulk density and the powder surface height in the fluidizer were not adjusted.
The bulk density of the powder is 0.15-0.35g / cc, and it is not uniform in the charged powder, and it is easy to receive the moisture of the outside air when it is thrown in a large amount by rotating the screw or in a small amount. Yes, relative humidity is over 30%.
The particle size distribution of the obtained toner is shown in FIG.
This classification system had a broad distribution and was bad in the overall evaluation.

[Comparative Example 2]
Using the conventional airflow classification system shown in FIG. 2, the feeder pitch is narrowed to stabilize the supply amount of the pulverized toner as compared with Comparative Example 1, and the pulverized toner at the supply amount of 20 kg / hr is supplied to the fluidizing device. Supply and classify.
The bulk density and the powder surface height in the fluidizer were not adjusted.
The bulk density of the powder is 0.15-0.35g / cc, and it is not uniform in the charged powder, and it is easy to receive the moisture of the outside air when it is thrown in a large amount by rotating the screw or in a small amount. Yes, the water content of the toner is 30% or more in terms of relative humidity.
The particle size distribution of the obtained toner is shown in FIG.
This classification system had a broad distribution and was bad in the overall evaluation.
It can be seen that the toner supply amount fluctuation cannot be prevented by adjusting the feeder pitch.

Using the airflow classification system of the present invention provided with a transfer device and a compressed airflow ejection nozzle for supplying powder constantly between the flow device and the classifier of the conventional airflow classification system shown in FIG. The toner pulverized at an amount of 20 kg / hr was supplied to a fluidizer and classified.
The number of pumps is two, and the supply amount of pulverized toner is stabilized by flowing compressed air in the material supply pipe.
The bulk density of the powder is 0.20 to 0.25 g / cc, the charged powder is uniform, the flow pump is in a stable charged state, and the compressed air is dried air. The water content is less than 10% in relative humidity.
The particle size distribution of the obtained toner is shown in FIG.
Although the distribution is sharper than those of Comparative Examples 1 and 2, the toner supply amount is not yet sufficiently stabilized, and the cut of fine powder (3 μm or less) is slightly better than that of Comparative Example.

Classification was performed in the same manner as in Example 1 except that the number of pumps in Example 1 was changed to 4.
The particle size distribution of the obtained toner is shown in FIG.
It can be seen that the distribution is sharper than that of Example 1 and the supply amount of the toner is sufficiently stabilized. The fine powder (3 μm or less) cut was still insufficient, and the dispersion of the toner charged into the airflow classifier was slightly better than the comparative example.

Classification is performed in the same manner as in Example 2 except that the bulk density in the fluidizing device and the height of the powder surface are adjusted to be constant, and a mixed gas of compressed air and helium (70%) is allowed to flow through the material supply pipe. went.
The bulk density of the powder is 0.20 to 0.25 g / cc, the charged powder is uniform, and it is in a stable charged state by the flow pump. Since the humidity of helium is low, the moisture content of the toner is The relative humidity is less than 10%.
The particle size distribution of the obtained toner is shown in FIG.
The distribution was considerably sharper than that of Example 2, and the overall evaluation was good.
This is because the amount of toner supplied is sufficiently stabilized, and fine powder (less than 3 μm) is cut sufficiently. As a result, the dispersion state of the toner introduced into the airflow classifier is very sufficient.

Classification was performed in the same manner as in Example 3 except that high-purity helium gas (99%) was allowed to flow through the material supply pipe.
The bulk density of the powder is 0.20 to 0.25 g / cc, the charged powder is uniform, and it is in a stable charged state by the flow pump. Since the humidity of helium is low, the moisture content of the toner is The relative humidity is less than 10%.
The particle size distribution of the obtained toner is shown in FIG.
From Example 3, the distribution was very sharp, and the overall evaluation was the best.
This indicates that the toner supply amount is sufficiently stabilized, fine powder (3 μm or less) is sufficiently cut, and the dispersion state of the toner charged into the airflow classifier is very good.
Such a result is thought to be due to the high purity of helium, helium has smaller molecules than air (1.0), density is 0.1785, 1 / 5.6 of air, specific gravity is 0.138, 1 / 7.2 of air. It is.
Therefore, since helium gas can penetrate into extremely small holes, it enters the portion where the toner is agglomerated and improves dispersibility.
In general, hydrogen embrittlement is known, but helium can also be embrittled, adhesion and aggregation between toners can be decomposed, and dispersibility is improved.
Furthermore, helium has a dehumidifying effect, and adhesion and aggregation between toners can be decomposed by the influence of moisture, and dispersibility is improved.
In addition, it is a gas that is easy to handle because it is chemically stable and harmless to humans.

About FIG. Airflow type DS classifier 2. Dispersion chamber 4. Body casing 6. Classification room8. Lower casing 10. Hopper 12. Inlet 14. Exhaust port 16. Center core 18 coarse powder outlet 20. Louver 22. Feeder 24. Fine powder outlet

2 and 5 1 Airflow type powder transfer classification device 9 Powder storage unit 10 Powder fluidization tank 20 Transfer device 21 Pump 22 Compressed air ejection nozzle 40 Airflow type classification device

About FIG. Intermediate storage unit 102. Spring 104. Mount 106. Vibration motor 108. Container 110. Air introduction pipe 112. Mesh 114. Filter 116. Exhaust pipe 118. Powder material input tube 120. Powder material extraction tube

About FIG. 4 10 Powder flow tank 50 Platform scale 51 Fluid drum 52 Toner inlet 53 Fluid drum suction tube 54 Air vent tube 55 Level meter 56 Valve 57 Filter cloth filter 51a Cover member 51b Bottom member 58 Airflow inlet tube 59 Instrumentation section 59a Flow meter 59b Precision regulator

About FIG. 6 40 Airflow classifier 2 Dispersion chamber 4 Main body casing 6 Classification chamber 8 Lower casing 10 Hopper 12 Inlet 14 Outlet 16 Center core 18 Coarse powder outlet 20 Secondary air inlet (louver)
24 Fine powder outlet

JP-A-8-57424 JP-A-5-303230 JP-A-6-296935 Japanese Utility Model Publication No. 3-102282 Japanese Utility Model Publication No. 62-79582 Japanese Utility Model Publication No. 6-52970 JP-A-11-197606

Claims (9)

  A powder fluidization tank having an air release mechanism at the bottom for fluidizing powder, an airflow classifier for separating powder into coarse particles and fine particles, and an airflow classifier from the powder fluidization tank A transfer device for supplying the powder to the powder fluidizing tank, the powder fluidizing tank has a bulk density control means for controlling the fluidized powder powder so that the bulk density of the fluidized powder is constant, And the said transfer apparatus equalizes the pulsation of the transfer amount at the time of powder transfer by several pumps which respectively shifted the phase, The powder transfer and classification apparatus characterized by the above-mentioned.   2. The powder transfer / classification apparatus according to claim 1, wherein the bulk density control unit includes a powder weight measurement device and a powder level measurement device in the powder fluidization tank.   The powder transfer / classification apparatus according to claim 1, wherein the powder is toner.   4. The powder transfer / classification apparatus according to claim 1, further comprising a powder storage unit for discharging the powder to the powder fluidization tank. A compressed gas injection means for accelerating dispersion of powder by jetting and joining a compressed gas flow to a powder flow supplied from the powder fluidization tank to the airflow classifier. Item 5. The powder transfer / classification apparatus according to any one of Items 1 to 4.   6. The powder transfer / classifying apparatus according to claim 5, wherein the gas of the compressed gas flow is helium or a mixed gas of helium and air.   The airflow classifier includes a dispersion chamber and a classification chamber, and the powder supplied together with the primary airflow into the dispersion chamber is converted into coarse particles and fine particles by a secondary air flow flowing from the periphery of the classification chamber. The apparatus for transferring and classifying powder according to any one of claims 1 to 6, wherein the apparatus is used for separation.   A powder fluidizing step for fluidizing the powder in the powder fluidizing tank by releasing gas from the gas releasing mechanism at the bottom, and supplying the fluidized powder from the fluidizing tank to the airflow classifier A powder transfer / classification method comprising: a fluidized powder transfer step, and a powder classification step of separating the powder into coarse particles and fine particles by the airflow classifier, wherein the powder fluidization The powder fluidizing step in the tank includes a bulk density control operation for controlling the fluidized powder to have a constant bulk density, and the powder transferring step has a phase in each case. A method for transferring and classifying powder, characterized in that the pulsation of the amount of powder transferred is leveled by a plurality of displaced pumps.   The method further comprises a step of accelerating the dispersion of the powder by jetting and joining the compressed gas flow from the compressed gas injection means to the powder flow supplied from the powder fluidization tank to the airflow classifier. The method for transferring and classifying powder according to claim 8.

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