JP2001215752A - Method of producing toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a toner by using an air-flow classification device by which melt-sticking of the toner in the classification device hardly occurs and stable classification can be performed. SOLUTION: In the method of producing a toner by using high pressure air injected through a high pressure air supply nozzle to classify the toner fine powder by the Coanda effect, the temperature T1 of the high pressure air and the glass transition temperature Tg of the toner fine powder are controlled to satisfy Tg-40>T1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a toner, which classifies a group of fine toner particles by utilizing the Coanda effect.

[0002]

2. Description of the Related Art Various types of airflow classifiers and airflow classifiers are used for classifying toner fine powder groups. Among them, there are a classifier using a rotary wing and a classifier without a movable part. Among them, the classifiers having no moving parts include a fixed wall centrifugal classifier and an inertial force classifier. The former production method requires at least two times of classification, such as fine powder classification and coarse powder classification, and requires a large capital investment. Further, as the particle size of the toner particles becomes smaller, high-speed rotation and high air volume classification are required in order to achieve classification, which imposes limitations on equipment. for that reason,
In recent years, classifiers utilizing the Coanda effect have begun to be widely used. As shown in FIG. 1, the air flow classifier transfers a group of toner fine powder supplied from a material supply nozzle 1 by high-pressure air ejected from a high-pressure air supply nozzle 2 and passes through a material acceleration nozzle 3. It is transported to the classification room 4. The toner fine powder group ejected with the airflow at a high speed from the ejector 47 having an opening in the classification area of the classification chamber 4 has a classifier whose tip is narrowed by the centrifugal force of the curved airflow flowing along the Coanda block 41 in the classification chamber. Classified by the edge blocks, ie, the F edge block 42 and the M edge block 43, the fine powder outlet 40a, the medium powder (product toner) outlet 40b, and the coarse powder outlet 40
c. In such a classifier, the toner fine powder group finely pulverized by the collision type air current pulverizer or the like generates heat due to collision or friction with the side wall due to turbulence of the air flow in the raw material acceleration nozzle 3, and the raw material acceleration nozzle 3 There is a problem that the classifying performance is lowered by being fused on the middle or in the vicinity of the ejector 47, on the Coanda block 41, the classifying edge blocks 42, 43, and the like, so that stable continuous operation is hindered.

On the other hand, the toner is required to be capable of melting at a lower temperature from the viewpoints of higher copying speed and lower power consumption, so that the glass transition temperature Tg of the toner fine powder is lowered. It is becoming a design.

[0004] Therefore, in the case of the above-mentioned toner manufacturing apparatus, more and more fine toner particles adhere to the inside of the apparatus.
It tends to be easily fused.

As a method for solving such fusion of the toner fine powder group, Japanese Patent No. 2769858 proposes to apply a fluororesin processing to the classification edge. Further, Japanese Patent Application Laid-Open No. 8-182929 proposes to reduce the turbulence in the nozzle by changing the shape of the inner wall surface of the material acceleration nozzle.

When the classification edge is subjected to a fluororesin processing, as described later, the temperature is about 40 to 50 ° C. near the tip of the edge.
Temperature rises, and the powder particles collide and rub at 200 m / sec, so that the coated fluororesin softens and peels off relatively easily under the influence of collisions and the like.
He did not actually use it for his intended purpose. Also,
Even if the turbulence in the material acceleration nozzle is reduced, the turbulence does not disappear at all, and collision with the inner wall of the nozzle actually occurs. Further, when the temperature in the nozzle is higher than the fusion temperature of the toner, the collision causes adhesion.

Further, in recent years, toner particles have been gradually miniaturized in order to improve image quality in copiers and printers. Is getting bigger. When an external force such as an impact force or a frictional force acts on such agglomerates, for example, the toner particles tend to generate a fused material in the above-described classifier.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a toner by an airflow classifier which is less likely to cause toner fusion or the like in a classifier and which can perform stable classification for a long time. It is in.

[0009]

The present inventors have focused on the glass transition temperature Tg of the toner fine powder and the temperature T1 of the high-pressure air for transporting the same, and as a result of intensive studies, as a result, have solved the above-mentioned problems. Reached. That is, the present invention relates to a toner manufacturing method for classifying a group of toner fine powders by the Coanda effect using high-pressure air injected from a high-pressure air supply nozzle, wherein the temperature of the high-pressure air is T1, and the glass transition temperature of the toner fine powder is Tg. , Tg-40> T1 is provided.

The present inventors conducted computer simulations on the flow of gas by high-pressure air in a high-pressure air supply nozzle, a raw material accelerating nozzle, a classifying chamber, and the like, and the state of temperature distribution on the inner wall surface at each location due to this gas flow. It was analyzed by airflow analysis. As a result, it has been found that the high temperature portion of the inner wall surface of the raw material accelerating nozzle and the inner wall surface of the classification chamber based on the calculation result correspond to the toner adhering portion.

Hereinafter, the temperature distribution of the raw material supply nozzle 1, the high pressure air supply nozzle 2, the raw material acceleration nozzle 3, and the classifying chamber 4 of the apparatus shown in FIG. The invention will be described in detail.

FIG. 2 shows a calculation space based on an enlarged sectional view of the material supply nozzle 1, the high-pressure air supply nozzle 2 and the material acceleration nozzle 3, and FIG. 3 shows a calculation space based on an enlarged sectional view of the classification chamber 4 part. Space shown.

Next, based on FIG. 2 showing the calculation space of the raw material supply nozzle 1, the high-pressure air supply nozzle 2, and the raw material acceleration nozzle 3, grid creation software “Gambit” (manufactured by Fluent Asia Pacific) is used. A calculation grid as shown in FIG. Here, the number of calculation grids is 323571. With respect to this calculation grid, an airflow analysis was performed using analysis software “FLUENT5” (manufactured by Fluent Asia Pacific). The calculation conditions used RSM as a turbulence model, and considered the influence of air friction. The setting condition is that the atmospheric pressure is 0.1013.
25 MPa, the pressure difference from the atmospheric pressure of the powder supply port of the raw material supply nozzle 1 is 0 MPa, the pressure difference from the atmospheric pressure of the inlet of the high pressure air supply nozzle 2 is -0.02 MPa, and the ejector 47 of the raw material acceleration nozzle 3 0.3M pressure difference from atmospheric pressure
Pa. Further, the air temperature at the inlets of the raw material supply nozzle 1 and the high pressure air supply nozzle 2 was set to 27 ° C. (300 K). In addition, the temperature of the wall was not specified to obtain the temperature distribution of only the gas. At this time, the flow rate of the gas in the ejector 47 of the raw material acceleration nozzle 3 is calculated as 23
0 m / sec.

FIG. 5 shows the temperature distribution in the raw material acceleration nozzle 3 obtained from the above calculation. In FIG. 5, the temperature distribution state is indicated by the shading of the color, but the display temperature range is set to 25 ° C. to 49 ° C. for easy understanding. The left side of the figure shows the temperature (K) corresponding to the shading.
According to this figure, in the temperature distribution in the raw material accelerating nozzle 3, the portion where the concentration is high is approximately 25 ° C., and the temperature increases as the concentration decreases, and the portion that appears almost white is 49 ° C. or higher. I understand. That is, 45 ° C. in the injection portion of the high-pressure air supply nozzle (around 3a in FIG. 2).
From the above, it can be seen that the temperature rises to around 25 ° C. near the center of the raw material acceleration nozzle where the air flow becomes laminar, and to approximately 40 ° C. at the tip of the raw material acceleration nozzle (around 3b in FIG. 2).

FIG. 6 is an enlarged view of the injection portion of the high-pressure air supply nozzle (around 3a in FIG. 2), and FIG. 7 is an enlarged view of the tip portion of the raw material acceleration nozzle (around 3b in FIG. 2). showed that.

Based on the above results, the glass transition temperature T
When toner fine powder having a g of about 60 ° C. is supplied from the material supply nozzle, a portion where the toner is fused or adhered in the material accelerating nozzle and a portion where the temperature is about 40 ° C. or more from the above calculation result. Was found to be almost the same.

Next, based on FIG. 3 which is a calculation space of the classifying room 4, a calculation grid as shown in FIG. 8 was created using grid creation software “Gambit”. Here, the number of calculation grids is 93174. An airflow analysis was performed on the calculated grid using analysis software “FLUENT5”. The calculation conditions used RSM as a turbulence model, and considered the influence of air friction. The setting conditions are as follows: the pressures of the intake ports 44 and 45 (see FIGS. 1 and 3) opened to the classifying chamber 4 are set to the atmospheric pressure of 0.101325 MPa, the ejector 47 of the raw material accelerating nozzle 3 and the discharge port 4 in the classifying chamber.
The flow rates of Oa, 40b, and 40c (see FIGS. 1 and 3) were 230 m / sec, 47 m / sec, and 25 m / s, respectively.
ec and 33 m / sec. In addition, since the state of the air flow near the center of the raw material acceleration nozzle 3 obtained from the above calculation results is laminar and the temperature is about 25 ° C., these conditions are classified. The condition of the calculation space of the room 4 was set.

FIG. 9 shows the temperature distribution in the classification chamber 4 obtained from the above settings. In FIG. 9, the temperature distribution state is shown by shading of the color.
The display temperature range was from 26 ° C to 50 ° C. The left side of the figure shows the temperature (K) corresponding to the shading. According to this figure, in the temperature distribution in the classifying chamber 4, a portion with a high concentration is about 2%.
6 ° C, the temperature increases as the concentration decreases,
It can be seen that the gray part is 50 ° C. or higher. That is, the temperature rises to 37 ° C. at the surfaces of the ejector 47 and the Coanda block 41, which are the tips of the raw material accelerating nozzles, and the tip of the F edge block 42 (see FIG. 1).
It can be seen that the temperature has risen to 0 ° C.

For reference, FIG. 10 shows the result of simulation of the flow of the toner fine powder group in the classification chamber.

Based on the above results, the glass transition temperature T
When the toner fine powder whose g is about 60 ° C. is supplied from the raw material supply nozzle, the ejector 47 in the classification chamber, the side wall portion of the Coanda block 41, and the F edge block 42
It has been found from the above calculation result that the portion where the toner is fused or adhered to the tip of the above and the portion where the temperature is about 40 ° C. or more almost match.

In the present invention, the temperature of the high-pressure air itself injected from the high-pressure air supply nozzle rises as shown in the calculation results of FIGS. Softening of the body can be prevented. This cooling temperature setting depends on the type of toner fine powder to be used.However, if the temperature is excessively low, the cost is increased, and if the cooling is insufficient, the effect of preventing fusion and adhesion of the toner is sufficient. I can't get it. Therefore, assuming that the glass transition temperature of the toner fine powder to be used is Tg, at least the high-pressure air temperature T1
By satisfying Tg-40> T1, preferably Tg-50> T1, it is possible to satisfy the requirements from the viewpoint of cost and the prevention of fusion or adhesion.

To further enhance the effect of preventing fusion or adhesion, the temperature of the toner fine powder group itself in the raw material supply nozzle is T2, the temperature of the raw material acceleration nozzle itself is T3, and the temperature of the classification chamber itself is T4. And Tg-40>
T2, T3, T4, especially Tg-50> T2, T3, T4
It is preferable to control so that

[0023]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Example 1) Bisphenol A / isophthalic acid condensed polyester (weight average molecular weight = Mw 13,000): 91 parts by mass Carbon black: Mogal L (Cabot): 6
Parts by mass ・ Low molecular weight ethylene / propylene copolymer: 3 parts by mass

The above materials, which are the raw materials of the toner for electrophotography, are mixed well with a Henschel mixer (Model FM75, manufactured by Mitsui Miike Kakoki Co., Ltd.), and then a twin-screw kneader (PCM45 type) set at a temperature of 150 ° C. And Ikegai Iron Works Co., Ltd.). Next, the obtained kneaded material was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely crushed material for toner production. A pulverized raw material having a diameter of 7.0 μm was obtained. The obtained pulverized raw material is introduced into a multi-segment classification device as shown in FIG. 1 at a rate of 28 kg / h through a vibrating feeder and a raw material accelerating nozzle 3 via a quantitative feeder, and utilizing the Coanda effect. The powder was classified into three types: fine powder, medium powder and coarse powder. At this time, in Example 1, as the high-pressure air injected from the high-pressure air supply nozzle, cooling air adjusted to a temperature T1 = 2 ° C. was used. Here, the glass transition temperature of the raw material powder is 61
゜ C. The temperature distribution inside the classifier according to the conditions at this time is 30 deg. In the injection part 3a of the high-pressure air supply nozzle.
~ 36 ° C, 2 near the center of the nozzle where the air flow becomes laminar
-10 ° C, about 1 at the tip 3b of the material acceleration nozzle
The temperature was calculated to be 0 ° C. In addition, the temperature of the ejector 47, the tip of the raw material acceleration nozzle, the surface of the Coanda block 41, and the tip of the F-edge block 42 are increased by 17 ° C. In particular, the temperature of the curved surface of the Coanda block is calculated to be about 42 ° C. Was done. Under these conditions, 20
After continuous operation for a long time, the toner was hardly fused to any of the material supply nozzle, the ejector, the surface of the Coanda block, and the F edge block, and the classification distribution was very stable from the beginning. After operating for 20 hours, the classifier was disassembled and the total amount of toner fused on the raw material accelerating nozzle, the ejector, the Coanda block, and the classification edge (toner fusion amount) was measured to be 1.5 g or less. Met.

(Comparative Example 1) The same pulverized raw material as used in Example 1 was passed through a vibrating feeder and a raw material accelerating nozzle 3 through a quantitative feeder at a rate of 28.0 kg / h.
It was introduced into a multi-segmentation classifier as shown in FIG. 1 and classified into fine powder, medium powder and coarse powder using the Coanda effect. At this time, in Comparative Example 1, the temperature of the high-pressure air injected from the high-pressure air supply nozzle was T1 = 27 ° C. The temperature distribution inside the classifier according to the conditions at this time is:
At the injection part 3a of the high pressure air supply nozzle, about 55 ° C,
The calculation was performed at 27-36 ° C. near the center of the nozzle where the air flow becomes laminar, and around 40 ° C. at the tip 3b of the raw material acceleration nozzle. A temperature rise of 37 ° C. was observed at the tip of the ejector 47, the surface of the Coanda block 41, and the tip of the F-edge block 42, which are the tip of the raw material accelerating nozzle, and the calculated value was about 65 ° C. particularly for the curved surface of the Coanda block. . Continuous operation was performed in the same manner as in Example 1. As a result, after about 2 hours, the occurrence of toner fusion began to increase, and abnormalities in classification accuracy began to appear. As it is
When the operation was continued, an abnormal air flow of the raw material acceleration nozzle occurred, and classification under normal classification conditions became impossible. After 3 hours, the classification operation was stopped, the classifier was disassembled, and the total amount of toner fused on the raw material acceleration nozzle, the ejector, the Coanda block, and the classification edge (toner fusion amount) was measured. As a result, it was about 18 g.

[0027]

As described above in detail, according to the toner manufacturing method of the present invention, in order to prevent the physical properties of the toner fine powder group, particularly the fusing or adhesion, the high pressure is applied according to the glass transition temperature of the toner fine powder. By controlling the temperature of the air, fusion and adhesion of the toner in the apparatus are less likely to occur, and the classifier operates in a stable state at all times, and it is possible to provide a high quality product.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an airflow classifier.

FIG. 2 is a diagram showing a calculation space of a material supply nozzle, a high-pressure air supply nozzle, and a material acceleration nozzle.

FIG. 3 is a diagram showing a calculation space of a classification room.

FIG. 4 is a grid diagram of a calculation space of a material supply nozzle, a high-pressure air supply nozzle, and a material acceleration nozzle.

FIG. 5 is a diagram showing a temperature distribution in a raw material acceleration nozzle.

FIG. 6 is an enlarged view showing a temperature distribution of an injection portion of a high-pressure air supply nozzle.

FIG. 7 is an enlarged view showing a temperature distribution at the tip of a raw material acceleration nozzle.

FIG. 8 is a grid diagram of a calculation space of a classification room.

FIG. 9 is a diagram showing a temperature distribution in a classification chamber.

FIG. 10 is a diagram illustrating a flow of a group of toner fine powders in a classification chamber obtained from a simulation result.

[Explanation of symbols]

 1: Raw material supply nozzle 2: High pressure air supply nozzle 3: Raw material acceleration nozzle 3a: Near injection of high pressure air supply nozzle 3b: Near tip of raw material acceleration nozzle 4: Classification room 40a: Fine powder discharge port 40b: Medium powder (product toner) Discharge port 40c: coarse powder discharge port 41: Coanda block 42: F edge block 43: M edge block 44: intake port 45: intake port 46: intake edge block 47: ejector 48: side wall 49: side wall

Claims (1)

[Claims] 1. A toner manufacturing method for classifying a group of fine toner particles by the Coanda effect using high-pressure air injected from a high-pressure air supply nozzle, wherein the temperature of the high-pressure air is T1, and the glass transition temperature of the fine toner powder is Tg. Wherein Tg-40> T1.