JPH0679167B2 - Method for producing toner for developing electrostatic image - Google Patents

Description

TECHNICAL FIELD The present invention relates to a production method for pulverizing solid particles having a binder resin to obtain a toner for developing an electrostatic image.

[Prior Art] In an image forming method such as an electrophotography method, an electrostatic photography method, and an electrostatic printing method, a toner is used to develop an electrostatic charge image.

As a general method for producing a toner for developing an electrostatic image which requires that the final product be fine particles, a binding resin for fixing the toner on a transfer material, and various colorants for producing a tint of the toner are used. , A charge control agent for imparting an electric charge to particles, and a so-called one-component developing method as disclosed in JP-A-54-42141 and JP-A-55-18656. Using various magnetic materials for imparting, a dry release agent and a fluidity-imparting agent are optionally dry-mixed, and then melt-kneaded by a general-purpose kneading device such as a roll mill and an extruder, and then cooled and solidified. After that, the particles are pulverized by various pulverizers such as a jet stream type pulverizer and a mechanical impact type pulverizer, and classified by various air classifiers, so that the toner has a required particle size. If necessary, a fluidizing agent, a lubricant and the like are dry mixed to obtain a toner. When it is used in a so-called two-component developing method, it is used as an image forming toner after being mixed with various magnetic carriers.

Further, with the recent generalization and mass consumption of copied materials, printed materials, etc., low-cost, high-performance developers have been demanded.

As described above, various crushing devices are used to obtain the toner particles that are fine particles, but the crushing of the toner mainly composed of the binder resin is performed by a jet airflow crusher using a jet airflow, particularly a collision. Type airflow mills are preferably used.

Further, these crushers are connected to a classifier to classify the crushed particles into fine particles and coarse particles by the classifier as shown in the flow chart of FIG. 6, and the coarse particles are returned to the crusher again. It is used as a pulverizing means for carrying out re-pulverization to obtain fine particles as a finely pulverized product.

Conventionally, as a classifier used as this crushing means,
There are rotor type classifiers that forcibly create a swirling airflow by rotating the classifying blades and a spiral airflow classifier that creates a swirling airflow by an airflow introduced from the outside, but toner mainly composed of binder resin For classification, a spiral airflow classifier having no moving part in the powder contact part is preferably used. As a typical example thereof, a dispersion separator (DS-UR type: manufactured by Nippon Pneumatic Mfg. Co., Ltd.) as shown in FIG. 7 is generally used.

However, the powder material supply part to the classification chamber of this type of airflow classifier as shown in FIG. 7 has a cyclone shape, and the guide cylinder 50 is provided at the center of the upper surface of the upper cover 60.
Is provided upright, and the supply cylinder 80 is connected to the upper outer peripheral surface of the guide cylinder 50. The supply cylinder 80 is provided on the outer circumference of the guide cylinder 50.
The powder material supplied via 80 is connected so as to be introduced in the circumferential tangential direction in the guide cylinder. When the powder material is supplied from the supply cylinder 80 into the guide cylinder 50, the powder material is supplied to the guide cylinder 50.
It descends while turning along the inner surface of 50. In this case, the powder material descends in a strip shape from the supply cylinder 80 along the inner peripheral surface of the guide cylinder 50, so that the distribution and concentration of the powder material flowing into the classification chamber 40 become non-uniform (to the classification chamber inner circumference of the guide cylinder 50). Powder material flows in only from a part of the surface), and the dispersion is poor. Further, when the treatment amount is large, there is a problem that the powder material is more likely to agglomerate, the dispersion is not sufficiently performed, and highly accurate classification cannot be performed.

Therefore, the finely pulverized product becomes a powder having a wide particle size distribution, and as a result, there is a problem that a phenomenon such as a decrease in yield occurs in a classification process for removing the fine powder in the next process. In addition, since a part of the powder pulverized to a desired particle size or less is recirculated to the pulverizer as coarse powder, ultrafine powder (fine powder that is unsuitable as a toner) is likely to be generated.

Since this ultrafine powder has a strong attractive force to particles, it is difficult to remove it even by using a classifying process for removing fine powder.When such powder is used as a toner, a decrease in image density, fog phenomenon, and further development This causes deterioration of image quality such as unevenness on the sleeve.

On the other hand, a collision type air flow crusher using a jet airflow conveys an object to be crushed by a jet airflow, collides the object to be crushed with a collision member, and crushes by the collision force. The machine has a structure as shown in FIG.

A collision member 46 is provided opposite to the outlet 44 of the acceleration tube 42 connected to the high-pressure gas supply nozzle 33, and the flow of the high-pressure gas supplied to the acceleration tube 42 causes the object to be crushed to communicate with the middle of the acceleration tube 42. The object to be crushed is sucked from the mouth 31 into the accelerating pipe 42, is jetted together with the high-pressure gas, collides against the collision surface 47 of the collision member, and is crushed by the impact.

However, in the above conventional example, it is difficult to sufficiently disperse the object to be pulverized sucked and introduced into the acceleration tube in the high-pressure airflow, and the particle mixture airflow in which the object to be pulverized is placed in the high-pressure air stream ejected from the acceleration tube outlet. Is separated into a high concentration content stream and a low concentration content stream.
As a result, the particles collide with each other on the opposing collision member partially, and re-aggregation easily occurs on the collision member, degrading the classification accuracy in the classifier, and lowering the pulverization efficiency and the processing capacity. Is causing.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a toner for developing an electrostatic charge image, which solves the above-mentioned drawbacks.

More specifically, an object of the present invention is to provide a method for producing a toner for developing an electrostatic charge image having good performance by obtaining a finely pulverized product having a fine particle size distribution.

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

[Means and Actions for Solving Problems] The present invention relates to a powder material prepared by melt-kneading a composition containing at least a binder resin and a colorant, cooling and solidifying the kneaded product, and pulverizing a solidified product. In a method for producing an electrostatic charge image developing toner by pulverizing the powder material with a pulverizing means equipped with an air stream classifier and a collision type air stream pulverizer in communication with the air stream classifier. In the air flow classifier, the carrier air is supplied to a supply cylinder arranged in the upper part of the classification chamber, and an annular guide chamber communicating with the supply cylinder is provided between the guide chamber and the classification chamber. The powder material is swirlingly descended together with the conveying air into the central portion of the classifying chamber while passing through a plurality of louvers whose tips are directed in the tangential direction of the inner circumferential circle of the guide chamber, and the louvers are introduced between the louvers. The powder introduced into the classification chamber from The swirling speed of the material is further accelerated by the classifying air sucked and introduced from between the plurality of classifying louvers provided around the classifying chamber so that the central portion located at the bottom of the classifying chamber becomes higher. On the formed inclined classifying plate, the powder material is centrifugally separated by the classifying air to classify into coarse powder and fine powder, and the classified fine powder is fine powder provided in the central portion of the classifying plate. Used to generate toner particles by discharging from the discharge port to a fine powder discharge chute, the classified coarse powder is discharged from the coarse powder discharge port provided on the outer periphery of the classifying plate, and the discharged coarse powder is discharged. It is introduced into the collision type crusher, and the coarse powder introduced is accelerated in the collision type crusher by the high pressure gas in the accelerating pipe, and is provided between the crushed object supply port and the accelerating pipe outlet of the accelerating pipe. Accelerating tube by the air introduced from the secondary air inlet The coarse powder inside is dispersed, the coarse powder ejected from the accelerating pipe is crushed by colliding with a collision member provided in the crushing chamber, and the crushed coarse powder is introduced into the airflow classifier. The present invention relates to a method for producing a toner for developing an electrostatic charge image.

FIG. 6 is an example of a flow chart showing the constitution of the pulverizing means used in the method for producing an electrostatic image developing toner of the present invention, and FIGS. 1 and 2 are the air flow classification used in the production method of the present invention. FIG. 3 is a view schematically showing an embodiment of a machine, and FIGS. 3 to 5 are views schematically showing an embodiment of a collision type airflow crusher.

In FIG. 1, reference numeral 1 denotes a cylindrical main body casing, 2
Indicates a lower casing, and a homper 3 for discharging coarse powder is connected to the lower portion thereof. Inside the main body casing 1,
A classifying chamber 4 is formed, and the upper part of the classifying chamber 4 is closed by an annular guide chamber 5 attached to the upper part of the main body casing 1 and a conical (umbrella) upper cover 6 whose central portion is higher. .

A plurality of louvers 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 the louvers 7. Let it flow in.

A classification louver 9 arranged in the circumferential direction is provided in the lower portion of the main body casing 1, and classification air that causes a swirling flow to the classification chamber 4 from outside is taken in through the classification louver 9.

A conical (umbrella) classifying plate 10 having a high central portion is provided at the bottom of the classifying chamber 4, and a coarse powder discharge port 11 is formed on the outer periphery of the classifying plate 10. A fine powder discharge chute 12 is connected to the center of the classifying plate 10, the lower end of the chute 12 is bent into an L shape, and the bent end is located outside the side wall of the lower casing 2. Further, the chute is connected to a suction fan through a fine powder collecting means such as a cyclone or a dust collector, and a suction force is applied to the classification chamber 4 by the suction fan.
The swirling flow required for classification is caused by the suction air flowing into the classification chamber 4 from between the louvers 9.

The airflow classifier has the above-mentioned structure, and is supplied from the supply cylinder 8 into the guide cylinder 5 (from the powder material crushed by the collision-type airflow crusher, the air used for crushing, and the newly supplied crushing raw material. When the air containing the powder material is supplied, the air containing the powder material passes from the guide chamber 5 between the louvers 7 and swirls into the classification chamber 4 while being dispersed at a uniform concentration.

The powder material flowing into the classifying chamber 4 while swirling is swirled by a suction fan connected to the fine powder discharging chute 12 along with a suction air flow flowing between the classification louvers 9 in the lower part of the classifying chamber, so that each particle The coarse powder, which is centrifugally separated into coarse powder and fine powder by the centrifugal force that acts on, swirls around the outer periphery of the classification chamber 4, is discharged from the coarse powder discharge port 11 and is discharged from the lower hopper 3 again to collide airflow grinding. Supplied to the machine.

Further, the fine powder that moves to the central portion 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.

Since all the air flowing into the classification chamber 4 together with the powder material flows as a swirl flow, the velocity of the particles swirling in the classification chamber 4 toward the center becomes relatively smaller than the centrifugal force,
In the classification chamber 4, classification with a small particle size 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 a powder having a fine distribution.

Therefore, a finely pulverized product can be obtained as a finely-divided powder, so that, as described above, no ultrafine powder is generated, and as a final product, a toner having good performance can be obtained.

Further, in FIG. 3, the powder material 45 to be crushed is
From the crushed object supply port 31 provided in the acceleration tube 32, the acceleration tube 32
Is supplied to. Compressed gas such as compressed air is introduced into the accelerating pipe 32 from the compressed gas supply nozzle 33.
The pulverized material 45 supplied to 32 is instantly accelerated and has a high speed. Further, a secondary air introduction port 41 provided between the crushed object supply port 31 of the acceleration tube 32 and the acceleration tube outlet 34.
Further, by introducing the secondary air, the crushed object in the acceleration tube is dispersed, the crushed object is ejected from the acceleration tube outlet 34 more uniformly, and the collision surface 37 of the opposing collision member 36 is efficiently collided. As a result, the pulverizability can be improved as compared with the conventional one. The secondary air introduced here contributes to deaggregate and disperse the agglomerates of the object to be pulverized that move at high speed in the acceleration tube. In addition, there is an effect of accelerating the flow along the inner wall of the accelerating pipe, which is a portion where the accelerating gas flow velocity distribution is slow in the accelerating pipe.

It should be noted that, as shown in FIG. 3, the collision member 36 has a cone-shaped tip portion on the collision surface, which is caused by extreme heat generation on the collision member like a material containing a thermoplastic resin. A material that is easily fused is preferable in terms of preventing fusion. further,
In order to promote the secondary collision from the collision member to the wall of the crushing chamber and improve the crushing efficiency, it is more preferable to use a collision member having a conical shape whose tip portion has an apex angle of 110 ° or more and less than 180 °.

As explained above, since the material to be crushed in the accelerating tube is well dispersed, it is possible to obtain a finely crushed product with a fine particle size distribution without causing the powder to agglomerate and cause excessive crushing. To be

Therefore, synergistically with the effect of the airflow classifier described above, a toner having good performance can be efficiently obtained as a final product. Furthermore, the effect of the method of the present invention becomes more remarkable as the particle size becomes smaller.

[Examples] Hereinafter, the present invention will be described in detail based on Examples.

Example 1 The toner raw material composed of the mixture of the above formulation was melt-kneaded using a twin-screw extruder PCM-30 (manufactured by Ikegai Tekko KK). After cooling, a hammer mill was used to obtain 0.1 to 1 mm of coarsely pulverized material.

The obtained coarsely pulverized material was subjected to an air flow classifier shown in FIG. 1 and a collision type air flow pulverizer shown in FIG.
It is supplied to a crushing means (a flow chart shown in FIG. 6) having a 0 ° conical shape), and is fed to a collision type air flow crusher through a compressed gas supply nozzle at 4.0 Nm ³ / min (5 kgf / cm ² ). The next air is 0.0 from each of the six locations of F, G, H, J, L, and M in FIG.
By introducing compressed air of 5 Nm ^{3 /} min (5.5 kgf / cm ² ), finely pulverized product was pulverized so as to have a volume average particle diameter of 11 μm (measured by Coulter counter, the same applies below).

The particle size distribution of the finely pulverized product at this time is 11.0 volume average particle size.
The volume frequency was 12.1% for μm and 6.35 μm or less, and 0.6% for 20.2 μm or more.

This finely pulverized product was removed of fine powder with an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd.) to obtain a volume average particle size of 11.6 μm, 6.35.
A classified product having a volume frequency of 2.3 μm or less and a volume frequency of 0.9% or more 20.3 μm was obtained with a yield of 83%. Silica 0.
4% by weight was externally added and mixed to obtain a toner sample.

Comparative Example 1 The coarsely pulverized product used in Example 1 was replaced with a conventional airflow classifier DS-UR type (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) as shown in FIG. 7 and a conventional type as shown in FIG. Type collision type air flow crusher Jet mill PJM-I type (collision tube of the collision member is a plane perpendicular to the axial direction of the acceleration surface)
Volume average 11μ using pressurized air of m ³ / min (5kgf / cm ² )
Fine pulverization was performed so as to obtain m.

The fine pulverization processing amount (= coarse pulverized material supply amount) at this time is about 0.6 times that of Example 1, and the particle size distribution of the finely pulverized product has a volume average particle diameter of 11.1 μm, 6.35 μm or less and a volume frequency of 15.3%, 20.2μ
The volume frequency was 1.3% or more.

The fine powder is removed from this finely pulverized product by an elbow jet classifier, and the volume average diameter is 11.6 μm, 6.35 μm or less. Volume frequency 2.
A classified product with a volume frequency of 7%, 20.2 μm or more and a volume frequency of 1.6% was obtained with a yield of 74%. 0.4% by weight of silica is externally added and mixed to this classified product,
It was used as a toner sample.

Both toner samples of Example 1 and Comparative Example 1 were copied by a copying machine NP-
A copying test was conducted using 5040 (manufactured by Canon). 23 ° C, 6
As a result of carrying out a durability test on 100,000 sheets in a normal environment of 5% RH, the toner of Example 1 had an initial image density of 1.32, and an image density during running of 1.37 ± 0.03, showing substantially uniform image density. The decrease in density due to replenishment was within 0.05, which had almost no effect on the image. In addition, no cleaning failure 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 and rose to a level of 1.35 ± 0.07 as the durability progressed, but at the time of toner replenishment, the image density again decreased to 1.05, and was again sufficient. It took a considerable number of sheets to return to a proper image density. In addition, cleaning failure occurred around 30,000 sheets. A similar durability test was performed at 15 ℃, 10
When it was carried out in a low humidity environment of% RH, the toner of Comparative Example 1 had wavy unevenness on the developing sleeve, and white spots occurred on the entire black image.

Example 2 A toner raw material composed of the mixture having the above formulation was subjected to the same method as in Example 1 to obtain a coarsely pulverized product.

Further, fine pulverization was performed using the same pulverizing means as in Example 1. 4.6N from compressed gas supply nozzle to collision type airflow crusher
m ³ / min (6 kgf / cm ² ), secondary air is F, G,
Compressed air of 0.05 Nm ^{3 /} min (5.5 kgf / cm ² ) was introduced from each of H, J, L, and M, and the volume average particle size was 7μ as a finely pulverized product.
Fine pulverization was performed so as to obtain m. The particle size distribution of this finely pulverized product has a volume average particle size of 7.0 μm, 5.04 μm or less and a volume frequency of 20.
The volume frequency was 0%, 12.7 μm or more and 0.4%. This finely pulverized product was classified using an elbow jet classifier, and the yield was 79
% Average volume particle size 7.6 μm, 5.04 μm or less Volume frequency 7.5%, 1
A classified product having a volume frequency of 1.0% of 2.7 μm or more was obtained. To this classified product, 0.6% by weight of silica was externally added and mixed to obtain a toner sample.

Comparative Example 2 The coarsely pulverized product used in Example 2 was finely pulverized by the same conventional pulverizing means as in Comparative Example 1. Collision type air flow crusher 4.6 Nm ³ / m
A pressurized air of in (6 kgf / cm ² ) was supplied, and finely pulverized as a finely pulverized product so as to have a volume average particle size of 7 μm.

The fine pulverization processing amount (= coarse pulverized material supply amount) at this time is about 0.55 times that of Example 2, and the particle size distribution of the obtained fine pulverized product is volume average particle size 6.9 μm, 5.04 μm or less and volume frequency. 30.3%,
The volume frequency was 12.7 μm or more and 4.7%.

This finely pulverized product is classified by an elbow jet classifier, and the volume average particle size is 7.6 μm, 5.04 μm or less Volume frequency 7.7%, 1
A classified product having a volume frequency of 2.7 μm or more and 1.2% was obtained with a yield of 61%. To this classified product, 0.6% by weight of silica was externally added and mixed to obtain a toner sample.

The toner samples of Example 2 and Comparative Example 2 were prepared by using a copying machine NP-48.
A copying test was conducted using 35 (manufactured by Canon). When the number of durable sheets was increased to 50,000 in a normal environment, the toner of Example 2 had an initial density of 1.38 ±
While the image density was maintained in the range of 0.05 and the cleaning failure and the development of the image stain did not occur, the toner of Comparative Example 2 had an initial density of 1.20 and the image density increased with the endurance of 1.35. It became ± 0.07, but when it was replenished with toner, it fell to 1.15 again. In addition, cleaning failure occurred at 30,000 sheets.

Example 3 The coarsely pulverized product used in Example 2 was finely pulverized by the same pulverizing means as in Example 1.

4.6Nm ³ / min from compressed gas supply nozzle to collision type airflow crusher
(6 kgf / cm ² ), the secondary air is F, G, H, J, L,
Compressed air of 0.05 Nm ^{3 /} min (5.5 kgf / cm ² ) was introduced from each of 6 locations of M, and finely pulverized as a finely pulverized product so that the volume average particle diameter was 6 μm. The particle size distribution of this finely pulverized product is as follows: volume average particle size 5.9 μm, 4.00 μm or less Volume frequency 15.2%,
The volume frequency was 10.08 μm or more and 1.5%. This finely pulverized product is classified using an elbow jet classifier, yield 75%, volume average particle size 6.5 μm, 4.00 μm or less, volume frequency 5.3%, 10.08
A classified product having a volume frequency of 1.6 μm or more was obtained. 1.2% by weight of silica was externally added to and mixed with this classified product to obtain a toner sample.

Comparative Example 3 The coarsely pulverized product used in Example 2 was finely pulverized by the same conventional pulverizing means as in Comparative Example 1. Collision type airflow crusher 4.6Nm ³ / min
(6 kgf / cm ² ) of pressurized air was supplied and finely pulverized as a finely pulverized product so that the volume average particle diameter was 6 μm.

The amount of finely pulverized product (= amount of coarsely pulverized material supplied) at this time is about 0.5 times as large as that in Example 3, and the particle size distribution of the obtained finely pulverized product has a volume average particle size of 6.2 μm, 4.00 μm or less and volume frequency. 15.8%,
The volume frequency was 10.08 μm or more and 3.3%.

This finely pulverized product is classified by an elbow jet classifier, and the volume average particle size is 6.7 μm, 4.00 μm or less. Volume frequency 5.6%, 1
A classified product having a volume frequency of 2.4% of 0.08 μm or more was obtained in a yield of 65%. 1.2 weight% silica is externally added to this classified product and mixed,
It was used as a toner sample.

The toner samples of Example 3 and Comparative Example 3 were copied to the copying machine NP.
A copy test was performed using -4835 (manufactured by Canon). When the number of durable sheets was increased to 50,000 in a normal environment, the toner of Example 3 showed an initial density of 1.25 without any decrease in density during replenishment.
Was maintained at an image density in the range of ± 0.05, and cleaning failure and development of image stain did not occur, whereas the toner of Comparative Example 3 had an initial density of 1.05, and the image density increased with durability. , 1.20 ± 0.07, but it dropped to 1.05 again when toner was replenished. Also, cleaning failure occurred after 20,000 sheets.

Further, in a low humidity environment, the toner of Comparative Example 3 was
Fog was worse than

[Effect of the Invention] As described above, by using the toner manufacturing method of the present invention, the image density is stable and high as compared with the conventional method.
An excellent electrostatic charge image developing toner having good durability and free from image defects such as fog and cleaning failure can be obtained at low cost. Further, there is an advantage that an electrostatic charge image developing toner having a smaller particle diameter can be effectively obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of an air classifier used in the manufacturing method of the present invention, and FIG. 2 is AA ′ of FIG.
FIG. FIG. 3 is a schematic sectional view of an embodiment of a collision type air flow crusher used in the manufacturing method of the present invention, and FIGS. 4 and 5 are BB ′ and CC of FIG. 3, respectively. ′ It is a cross-sectional view. FIG. 6 is a flowchart showing the structure of the crushing means used in the manufacturing method of the present invention. FIG. 7 and FIG. 8 are schematic views of a conventional airflow classifier and a collision type airflow crusher, respectively. 4 …… Classification room, 5 …… Guide room 8 …… Supply cylinder, 7 …… Louver 9 …… Classification louver, 10 …… Classification plate 31 …… Grinding object supply port, 32 …… Acceleration tube 33 …… Compression Gas supply nozzle, 34 ...... Accelerator pipe outlet 35 …… Grinding chamber, 36 …… Collision member 37 …… Collision member collision surface, 39 …… Discharge port 41 …… Secondary air supply port

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Mitsumura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasuhide Goseki 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Co. Ltd. (56) Reference Japanese Unexamined Patent Publication No. 1-207152 (JP, A) Actually opened 60-189377 (JP, U) Actually opened 58-13956 (JP, U) JP-B 5-78392 (JP , B2) Sukeko 57-20298 (JP, Y2)

Claims (2)

[Claims] 1. A powder material prepared by melt-kneading a composition containing at least a binder resin and a colorant, cooling and solidifying the kneaded material, and pulverizing a solidified product, using an air stream classifier and the air stream classifier. In a manufacturing method for obtaining a toner for developing an electrostatic charge image by pulverizing with a pulverizing means equipped with a collision type air flow pulverizer communicating with the powder material, the powder material is classified in the air flow classifier together with a conveying air into a classification chamber. Tangential line in the inner circumferential direction of the guide chamber, which is provided between the guide chamber and the classification chamber from an annular guide chamber which is supplied to the supply cylinder disposed in the upper part of the guide chamber and communicates with the supply cylinder. The powder material is dispersed and introduced into the central portion of the classification chamber while swirling and descending with the conveying air through a plurality of louvers whose ends are oriented in the direction, and the powder introduced into the classification chamber from between the louvers. The rotation speed of the body material is set around the classification chamber. Is further accelerated by the classification air sucked and introduced from between the plurality of classification louvers, and the classification is performed on the inclined classifying plate formed so that the central part located at the bottom of the classifying chamber becomes higher. The powder material is classified into coarse powder and fine powder by centrifuging with air, and the classified fine powder is discharged from a fine powder discharge port provided in the center of the classifying plate to a fine powder discharge chute to remove toner particles. Used to generate, the classified coarse powder is discharged from a coarse powder discharge port provided on the outer periphery of the classifying plate, and the discharged coarse powder is introduced into the collision type crusher to perform the collision type crushing. In the machine, the introduced coarse powder is accelerated by the high pressure gas in the accelerating tube, and is accelerated by the air introduced from the secondary air introducing port provided between the crushed material supply port of the accelerating tube and the accelerating tube outlet. Coarse powder in the tube is dispersed and ejected from the acceleration tube. The coarse powder was pulverized by colliding the collision member provided in the grinding chamber, milled method for producing a toner for developing electrostatic images, characterized in that the crude powder is introduced into the gas stream classifier. 2. The crushing means is a collision type airflow crusher in which a tip portion of a collision surface of a collision member has a cone shape with an apex angle of 110 ° or more and less than 180 °. (1) A method for producing a toner for developing an electrostatic image as described in (1).