JPH0359676A - Manufacture of toner for electrostatic charge image development - Google Patents

Abstract

PURPOSE:To obtain a fine pulverized product with a fine grading distribution by providing an annular guide chamber which communicates with a powder supply cylinder above a classification chamber and providing plural louvers which have tips in the tangential direction of the inner circumferential direction of a guide chamber between a guide chamber and the classification chamber. CONSTITUTION:The upper part of the classification chamber 4 is closed with the annular guide chamber 5 fitted above a main body casing 1 and a conic (umbrella-shaped) upper cover 6 which is high at the center part. Then a partition wall between the classification chamber 4 and guide chamber 5 is provided with louvers 7 arrayed on the partition wall between the classification chamber 4 and guide chamber 5 in the circumferential direction and a powder material and air which are sent in the guide chamber 5 are rotated and supplied into the classification chamber 4 through between the respective louvers 7. Consequently, the powder material flows in the classification chamber 4 with nearly uniform concentration, so the powder having the fine distribution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a manufacturing method for obtaining a toner for developing an electrostatic image by pulverizing solid particles having a binder resin.

[Background technology]

In image forming methods such as electrophotography, electrostatography, and electrostatic printing, toners are used to develop electrostatic images.

The general manufacturing method for electrostatic image developing toner, which requires the final product to be fine particles, includes a binder resin to fix it on the transfer material, and various colorants to give the toner its color. , a charge control agent for imparting charge to particles, and JP-A-54-42141, JP-A-55
In the so-called one-component development method as shown in Japanese Patent No. 18656, various magnetic materials are used to impart transportability to the toner itself, and a release agent and a fluidity imparting agent are added as needed in a dry process. After mixing, the mixture is melted and kneaded using general-purpose kneading equipment such as a roll mill or extruder, cooled and solidified, and then pulverized using various types of pulverizing equipment such as jet air flow type pulverizers and mechanical impact type pulverizers, and then pulverized using various types of wind classifiers. By performing classification, the particle size can be adjusted to the size required for toner. If necessary, a fluidizing agent, a lubricant, etc. are dry-mixed into the toner. When used in a so-called two-component development method, the toner is mixed with various magnetic carriers and then used for image formation.

Furthermore, with the recent widespread use and mass consumption of copies, printed matter, etc., there is a demand for low-cost, high-performance developers.

As mentioned above, various types of pulverizers are used to obtain toner particles, which are fine particles, but a jet airflow type pulverizer that uses a jet airflow is generally used to grind toner containing mainly binder resin. used for.

Furthermore, these pulverizers are connected to a classifier, as shown in the flow shown in Figure 3, and the pulverized particles are classified into fine particles and coarse particles by the classifier, and the coarse particles are sent back to the pulverizer. It is used as a pulverization means to perform back-pulverization to obtain fine particles as a pulverized product.

Conventionally, the classifier used as this crushing means is:
There are rotor type classifiers that classify by forcibly creating a swirling airflow by rotating classification blades, and spiral airflow classifiers that classify by creating a swirling airflow using airflow introduced from the outside. For classification, a spiral air classifier with no moving parts in the powder contacting part is preferably used. As a typical example of this, a dispersion separator (DS-UR type: manufactured by Nippon Pneumatic Kogyo Co., Ltd.) as shown in FIG. 4 is generally used.

However, the powder material supply section to the classification chamber of this type of air classifier as shown in FIG. A supply cylinder 80 is connected to the upper outer peripheral surface of the guide cylinder 50. The supply cylinder 80 is connected to the outer periphery of the guide cylinder 50 so that the crushed material supplied via the supply cylinder 80 is introduced in a tangential direction to the circumference of the guide cylinder. When the powder material is supplied into the guide tube 50 from the supply tube 80, the powder material descends while rotating along the inner peripheral surface of the guide tube 50.

In this case, the powder material descends in a band shape from the supply tube 80 along the inner peripheral surface of the guide tube 50, so the distribution and concentration of the powder material flowing into the classification chamber 40 becomes uneven (the powder material flows into the classification chamber along the inner circumference of the guide tube 50). Powder material flows only from part of the surface), resulting in poor dispersion. Further, if the throughput is large, the powder material is more likely to aggregate, and furthermore, the dispersion is not sufficiently performed, resulting in a problem that highly accurate classification cannot be performed.

Therefore, the finely pulverized product becomes a powder with a wide particle size distribution, and as a result, there is a problem in that it causes a phenomenon such as a decrease in yield in the classification step to remove the fine powder in the next step. In addition, some of the powder that has been crushed to a size smaller than the desired particle size is
Since it is recirculated to the pulverizer as a coarse powder, ultrafine powder (powder too small to be suitable as a toner) is likely to be generated. This ultra-fine powder has a strong attraction to the particles, so it is difficult to remove even with a classification process that removes the fine powder. When such powder is used as a toner, it may cause a decrease in image density, capri phenomenon, and even This causes deterioration of image quality such as unevenness on the developing sleeve.

In addition, in order to obtain a larger amount of finely pulverized products or to obtain finer pulverized products, increasing the amount of high-pressure gas supplied is an effective means for jet stream pulverizers. With airflow classifiers, the problem is that as the amount of air flowing into the classification chamber increases, the velocity of particles swirling in the classification chamber toward the center increases, resulting in an increase in the separated particle size (particle size of the finely pulverized product). Therefore, the original purpose cannot be achieved.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a toner for developing electrostatic images, which solves the above-mentioned drawbacks.

Specifically, an object of the present invention is to provide a method for producing a toner for developing electrostatic images that has good performance by obtaining a finely pulverized product with a fine particle size distribution.

A further object of the present invention is to provide a manufacturing method for efficiently manufacturing toner for developing electrostatic images having a smaller particle size.

[Summary of the invention]

The pulverizing means used in the method for producing toner for developing electrostatic images of the present invention has a slanted classification plate with a high central part at the bottom of a classification chamber, and the powder material is supplied together with conveying air in the classification chamber. is swirled by the airflow flowing through the classification looper and centrifuged into fine powder and coarse powder, and the fine powder is discharged to the fine powder discharge chute connected to the discharge port provided in the center of the classification plate, and the coarse powder is This is an air classifier that discharges the powder from an outlet formed on the outer periphery of the classification plate, and an annular guide chamber that communicates with the powder supply tube is provided in the upper part of the classification chamber, and between the guide chamber and the classification chamber. For example, an air classifier equipped with a plurality of loopers whose tips are oriented tangentially to the inner circumferential direction of the guide chamber and a jet air crusher are connected as shown in the flowchart shown in FIG. 3.

[Detailed description of the invention]

FIG. 3 is a flowchart showing the configuration of the crushing means used in the method for producing toner for developing electrostatic images of the present invention, and FIGS. 1 and 2 show the configuration of the air classifier used in the production method of the present invention. 1 is a diagram schematically illustrating an embodiment; FIG.

In FIG. 1, l indicates a cylindrical main casing, and 2
indicates a lower casing, to which a hopper 3 for discharging coarse powder is connected. The inside of the main body casing 1 is
A classification chamber 4 is formed, and the upper part of the classification chamber 4 is closed by an annular guide chamber 5 attached to the upper part of the main body casing l and a conical (umbrella-shaped) upper cover 6 whose central part is raised. .

A plurality of loopers 7 arranged in the circumferential direction are provided on the partition wall between the classification chamber 4 and the guide chamber 5, and the powder material and air sent into the guide chamber 5 are swirled into the classification chamber 4 from between each looper 7. Let it flow.

Classifying loopers 9 arranged in the circumferential direction are provided in the lower part of the main body casing 1, and classified air that causes a swirling flow is introduced into the classification chamber 4 from the outside through the classifying loopers 9.

A conical (umbrella-shaped) classification plate 10 with a high central portion is provided at the bottom of the classification chamber 4, and a coarse powder discharge port 11 is formed around the outer periphery of the classification plate 10. In addition, a fine powder discharge chute 12 is connected to the center of the classification plate 10, and the lower end of the chute 12 is connected to the L
The bent end portion is located outside the side wall of the lower casing 2. Further, the chute is connected to a suction fan via a fine powder collection means such as a cyclone or a dust collector, and the suction fan applies suction force to the classification chamber 4, and the suction flows into the classification chamber 4 from between the loopers 9. The air creates the swirling flow required for classification.

The air classifier has the above-mentioned structure, and the powder material (consisting of the powder material pulverized from the jet mill, the air used for pulverization, and the newly supplied pulverized raw material) is supplied from the supply cylinder 8 into the guide cylinder 5. When the air containing the powder material is supplied, the air containing the powder material passes from the guide chamber 5 between the loopers 7 and flows into the classification chamber 4 while being swirled and dispersed at a uniform concentration.

The powder material flowing into the classification chamber 4 while swirling is rotated by the suction fan connected to the fine powder discharge chute 12, and the swirl is increased by the suction air flow flowing from between the classification loopers 9 at the bottom of the classification chamber. The coarse powder swirling around the outer periphery of the classification chamber 4 is centrifugally separated into coarse powder and fine powder by the centrifugal force acting on the classification chamber 4, and the coarse powder is discharged from the coarse powder discharge port 11 and transferred to the hopper 3 at the bottom.
It is then discharged from the jet mill and fed again to the jet mill. Further, the fine powder moving toward the center along the upper inclined surface of the classification plate 10 is discharged as a finely pulverized product to the fine powder collecting means by the fine powder discharge chute 12.

All of the air that flows into the classification chamber 4 together with the powder material flows in the form of a swirling flow, so the velocity toward the center of the particles swirling within the classification chamber 4 is relatively small compared to the centrifugal force.
In the classification chamber 4, classification into small separated particles is performed, and fine powder with a very small particle size can be discharged to the fine powder discharge chute 12.

Moreover, since the powder material flows into the classification chamber at a substantially uniform concentration, it is possible to obtain powder with a fine distribution.

Therefore, it is possible to obtain a finely pulverized product as a powder with a fine distribution, so that ultrafine powder is not generated as described above, and as a result, a toner with good performance can be obtained when it is made into a final product. .

At the same time, it is suitable for improving pulverization processing capacity.

In addition, when increasing the throughput of a jet mill or obtaining pulverized products with small particle sizes, it is necessary to increase the pressure of the high-pressure gas used for pulverization or use a large jet mill. It is effective to increase the amount of high-pressure gas used for pulverization, but in this case, the amount of air supplied from the jet mill to the classifier (the amount of air flowing in from the supply tube 8) increases, so the above-mentioned The effect becomes more noticeable.

Hereinafter, the present invention will be explained in detail based on examples.

Example 1 A toner raw material consisting of a mixture of the above formulation was melt mixed using a two-screw type extruder PCM-30 (manufactured by Ikegai Tekko Co., Ltd.). After cooling, a coarsely pulverized product of O81 to 1 mm was obtained using a hammer mill.

The obtained coarsely pulverized material was supplied to a pulverizing means (configuration shown in the flow chart shown in Fig. 3) consisting of a jet mill PJM-1 type (manufactured by Nippon Pneumatic Kogyo Co., Ltd.) and an air classifier shown in Fig. 1. , 4Ni/min (5
kgf/c rrr) of pressurized air was supplied to perform fine pulverization so that the volume average particle size of the finely pulverized product was 11 μm (measured using a Coulter counter; the same applies hereinafter).

The particle size distribution of the finely pulverized product at this time is a volume average particle size of 11
．． 0 μm, 6.35 μm or less volume frequency 12.8%
, the volume frequency of 20.2 μm or more was 0.8%.

Fine powder was removed from this finely pulverized product using an elbow jet classifier (manufactured by 8 Iron Mining Co., Ltd.), and the volume average particle size was 11.6 μm.
m, 6.35 μm or less volume frequency 2.4%, 20.2
A classified product with a volume frequency of 1.0% of μm or more was obtained with a yield of 81%. To this classified product, 0.4% by weight of silica was externally added and mixed to prepare a toner sample.

Comparative Example 1 The coarsely ground material used in Example 1 was fed in the same amount as in Example 1,
Conventional air classifier DS-UR as shown in Figure 4
Mold (manufactured by Nippon Pneumatic Kogyo Co., Ltd.) and jet mill PJ
Similar to Example 1, 4N r was
Fine pulverization was performed using pressurized air at rr/min (5 kgf/crtr) to give a volume average of 11 μm.

The particle size distribution of the finely pulverized product at this time is a volume average particle size of 11
．． 1 μm, 6.35 μm or less volume frequency 15.3%
, the volume frequency of 20.2 μm or more was 1.3%.

Fine powder was removed from this finely pulverized product using an elbow jet classifier, and the volume average diameter was 11.6 μm, the volume frequency of 5.35 μm or less was 2.7%, and the volume frequency of 20.2 μm or more was 1.6%.
A classified product with a yield of 74% was obtained. To this classified product, 0.4% by weight of silica was externally added and mixed to prepare a toner sample.

Both toner samples of Example 1 and Comparative Example 1 were transferred to a copying machine NP.
A copying test was conducted using -5040 (manufactured by Canon).

As a result of a durability test of 10,000 sheets of each in a normal environment of 23° C. and 65% RH, the toner of Example 1 had an initial image density of 1.32. The image density during durability was 1.37±0.03, showing a substantially uniform image density, and the decrease in density due to toner replenishment was within 0.05, which had almost no effect on the image. Furthermore, no cleaning defects or filming occurred during the durability test.

On the other hand, the toner of Comparative Example 1 had an initial image density of only 1°10, which rose to a level of 1.35±0.07 as the durability progressed, but when the toner was replenished, the image density returned to 1°10. The image density decreased to .05, and a considerable number of sheets were required to return to a sufficient image density again. Approximately 30 more
A cleaning failure occurred around 000 sheets. When a similar durability test was conducted in a low humidity environment of 15° C. and 10% RH, the toner of Comparative Example 1 caused wavy unevenness on the developing sleeve, and white spots occurred in the all-black image.

Example 2 The coarsely pulverized material used in Example 1 was pulverized using the same pulverizing means as in Example 1. 6rrf/min (
Pressurized air of 8 kgf/crrr) was supplied to perform pulverization so that the volume average particle size of the pulverized product was 11 μm. The amount of finely pulverized material (=the amount of coarsely pulverized material supplied) at this time was about 1.5 times that of Example 1, and the particle size distribution of the obtained pulverized product was 11.0 μm in volume average particle size.6. 35
The volume frequency of 20.2 μm or more was 13.0% and 0.9%, respectively.

Fine powder was removed from this finely pulverized product using an elbow jet classifier, and the volume average particle diameter was 11.6 μm, the volume frequency of 6.35 μm or less was 2.5%, and the volume frequency of 20.2 μm or more was 1.1%.
A classified product of 80% was obtained. To this classified product, 0.4% by weight of silica was externally added and mixed to prepare a toner sample.

When this toner was subjected to a copying test in the same manner as in Example 1, good images were obtained as in Example 1.

Comparative Example 2 The coarsely pulverized material used in Example 1 was pulverized using the same pulverizing means as in Comparative Example 1. 6 rrr/m to jet mill
i n (8 kgf/crrr) of pressurized air was supplied, and the supply amount was the same as in Example 2 (1. of Example 1 and Comparative Example 1).
When the coarsely pulverized product was supplied at a rate of 5 times), the volume average particle size of the finely pulverized product was 13.5 μm. Therefore, by reducing the supply amount to 1.1 times that of Example 1 and Comparative Example 1 (22% reduction of Example 2), the volume average particle diameter was 11.2 μm, and the volume frequency was 18.
A finely pulverized product with a volume frequency of 7% and 20.2 μm or more and a volume frequency of 2.4% was obtained.

Fine powder is removed from this finely pulverized product using an elbow jet classifier to obtain a classified product with a volume average particle diameter of 11.9 μm, a volume frequency of 2.3% of 6.35 μm or less, and a volume frequency of 2.7% of 20.2 μm or more at 65%. It was obtained in a yield of . To this classified product, 0.4% by weight of silica was externally added and mixed to prepare a toner sample.

When this toner was subjected to a copying test in the same manner as in Example 1, the initial image density was 1.07 t under normal environment.
As durability progressed, the image density rose to a level of 1.33±0.07, but when toner was replenished, the image density decreased to 1.
．． 05, and it took a considerable number of sheets to get the image density back to a sufficient level again. Furthermore, a cleaning failure occurred around approximately 20,000 sheets.

Further, as in Comparative Example 1, wavy unevenness occurred on the developing sleeve in a low humidity environment.

Example 3 A toner raw material consisting of a mixture of the above formulation was coarsely pulverized in the same manner as in Example 1.

Furthermore, fine pulverization was performed using the same pulverization means as in Example 1. 4rd/min (5kgf
/crrr) of pressurized air was supplied, and the product was pulverized to a volume average diameter of 7 μm as a pulverized product. The particle size distribution of this finely pulverized product is as follows: volume average particle size 7.0 μm15.
041t m or less volume frequency 20.2%, 12.7 μm
The volume frequency was 0.4%. This finely pulverized product was classified using an elbow jet classifier to obtain a volume average particle size of 7.6 μm with a yield of 78%.5. Q4μm or less volume frequency 7.5%
, a classified product with a volume frequency of 1.0% of 12.7 μm or more was obtained. To this classified product, 0.6% by weight of silica was externally added and mixed to prepare a toner sample.

Example 4 The coarsely pulverized material used in Example 3 was finely pulverized using the same pulverizing means as in Example 1. 6rrf/min (
Pressurized air of 8 kgf/crtr) was supplied to perform pulverization so that the volume average particle size of the pulverized product was 11 μm. At this time, the amount of finely pulverized material (=the amount of coarsely pulverized material supplied) was about 1.5 times that of Example 3, and the particle size distribution of the obtained finely pulverized product was 7.0 μm or less in volume average particle size and 15.04 μm or less. Volume frequency 20.5%, 12.7 μm or more Volume frequency 1.
It was 1%.

This finely pulverized product was classified by an elbow jet classifier to have a volume average particle size of 7.6 μm and a volume frequency of 7.048 m or less.
．． A classified product with a volume frequency of 7% and a volume frequency of 12.7 μm or more of 1.1% was obtained with a yield of 80%. To this classified product, 0.6% by weight of silica was externally added and mixed to prepare a toner sample.

Comparative Example 3 The coarsely pulverized material used in Example 3 was pulverized using the same conventional pulverizing means as in Comparative Example 1. 4 rrf/ to jet mill
Min (5 kgf/c rrf) of pressurized air was supplied to perform pulverization so that the volume average particle size of the pulverized product was 7 μm. The amount of finely pulverized products (=the amount of coarsely pulverized material supplied) at this time was about 0.75 times that of Example 3, and the particle size distribution of the obtained finely pulverized products was as follows: volume average particle diameter of 6.9 μm;
5.04 μm or less volume frequency 30.2%, 12.7 μm
The volume frequency of m or more was 4.6%.

This finely pulverized product was classified using an elbow jet classifier to obtain a classified product with a volume average particle size of 7.6 μm, a volume frequency of 7.7% below 5.04 μm, and a volume frequency of 1.1% above 12.7 μm. Obtained in yield. This classified product contains 0.6 silica.
A toner sample was prepared by externally adding % by weight.

Comparative Example 4 The coarsely pulverized material used in Example 3 was pulverized using the same conventional pulverizing means as in Comparative Example 1. 6 rrf/ to jet mill
Fine pulverization was carried out by supplying pressurized air of ,
The volume average particle diameter was reduced to only 8.6 μm, and the desired toner could not be obtained.

Example 3. A copying test was conducted on each toner sample of Example 4 and Comparative Example 3 using a copying machine NP-4835 (manufactured by Canon). When the toners of Example 3 and Example 4 were subjected to durable printing up to 50,000 sheets in a normal environment, there was no decrease in density during replenishment, and the initial density of 1.38 was maintained within a range of ±0.05. However, the toner of Comparative Example 3 had an initial density of 1.20, and the image density increased with durability to 1.35±0.07. However, when toner was replenished, the value dropped to 1.15 again. In addition, a cleaning failure occurred after 30,000 sheets were printed.

Further, in a low humidity environment, the toner of Comparative Example 3 had worse fogging than Examples 3 and 4.

As explained above, by using the toner manufacturing method of the present invention, image density is stably high compared to conventional methods.
An excellent toner for developing electrostatic images that has good durability and is free from image defects such as fog and poor cleaning can be obtained at a low cost. Further, there is an advantage that an electrostatic image developing toner having a smaller particle size can be effectively obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an embodiment of a classifier used in the manufacturing method of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1. FIG. 3 is a flowchart showing the configuration of the crushing means used in the manufacturing method of the present invention. FIG. 4 is a schematic cross-sectional view of a conventional classifier.

Claims (1)

[Claims] In a manufacturing method in which a composition containing at least an adhesive resin and a colorant is melt-kneaded, the kneaded product is cooled and solidified, and the solidified product is pulverized by a pulverizing means to obtain a toner, the bottom of the classification chamber is sloped so that the center part is higher. In the classification chamber, the powder material supplied together with the conveying air is swirled by the airflow flowing in through the classification louver, centrifugally separated into fine powder and coarse powder, and the fine powder is transferred to the classification plate. This is an air classifier that discharges fine powder to a fine powder discharge chute connected to a discharge port provided in the center, and discharges coarse powder from a discharge port formed on the outer periphery of the classification plate. Powder is supplied to the upper part of the classification chamber. An air classifier and a jet air pulverizer are provided with an annular guide chamber that communicates with the cylinder, and a plurality of louvers whose tips are oriented in a tangential direction to the inner circumferential direction of the guide chamber between the guide chamber and the classification chamber. 1. A method for producing a toner for developing an electrostatic image, comprising a pulverizing means communicated with a machine.