JPH0531392A - Impact-type air current pulverizer and pulverization of raw material for powder - Google Patents

Abstract

PURPOSE:To improve the efficiency of pulverizing toner or color resin for toner. CONSTITUTION:The subject impact-type air current pulverizer consists of a speed acceleration tube 3 for accelerating the speed of transport of raw material for powder using a high pressure air, a pulverization chamber 8 and an impact member 6 provided in the pulverization chamber at an opposite position to the speed acceleration tube outlet. In addition supply apertures 1 for raw material for powder are provided in the speed acceleration tube and a secondary air introduction aperture 10 is formed between the supply aperture for raw material for powder ad the speed acceleration tube outlet. Further, the technique to pulverize the raw material for powder is introduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision type air flow pulverizer using a jet air flow (high pressure gas) and a method for pulverizing powder raw materials.

The present invention also relates to a collision type air flow pulverizer and a pulverization method of powder raw materials for efficiently producing toner or colored resin powder for toner used in an image forming method by electrophotography.

[0003]

2. Description of the Related Art A collision type air flow crusher using a jet air flow conveys a powder raw material by a jet air flow, collides the powder raw material with a collision member, and pulverizes the powder by the impact force.

The details will be described below with reference to FIG.

Acceleration tube 3 connected to compressed gas supply nozzle 2
The collision member 4 is provided facing the outlet 13 of the
The powder raw material 7 is sucked into the accelerating pipe 3 from the powder raw material supply port 1 which is connected to the middle of the accelerating pipe 3 by the flow of the high pressure gas supplied to the colliding member 4. It collides with a collision surface and is crushed by the impact. When the powder raw material 7 is used for pulverizing to a desired particle size, a classifier is placed between the powder raw material supply port 1 and the discharge port 5 to form a closed circuit, and the powder raw material is fed to the classifier. 7 is supplied, the coarse powder is supplied from the powder raw material supply port 1, the powder is pulverized, and the pulverized product is returned to the classifier from the discharge port 5 to be classified again, and the fine powder is desired. It becomes a finely pulverized product with a particle size of.

However, in the above-mentioned conventional example, it is difficult to sufficiently disperse the powder raw material 7 sucked and introduced into the accelerating pipe 3 in the high-pressure air flow. Therefore, the powder flow ejected from the accelerating pipe outlet 13 is dust. It separates into a dense stream and a thin stream.

Therefore, the powder flow that hits the facing collision surface 14 becomes partial (local), and the efficiency decreases,
Causes a decrease in processing capacity. Further, if the treatment capacity is increased in such a state, the dust concentration is further increased locally, so that the efficiency is further lowered, and in particular, in the case of the resin-containing material, a fused substance is generated on the collision surface 14, which is preferable. Absent.

Moreover, when the powder raw material 7 containing a large amount of rough flow is introduced into the accelerating tube 3 by suction, the suction capacity of the powder raw material supply port 1 is lowered, and as a result, the processing capacity is lowered.

In order to improve the efficiency of crushing particles inside the accelerating tube 3, a crushing tube provided with a high-pressure gas feed tube for ejecting secondary high-pressure gas in front of the accelerating tube outlet 13 is disclosed in JP-B-46.
No. 22778. This is the accelerator tube 3
Although a crusher intended to promote internal collision and crushing only in the accelerating tube 3 is a useful means, it is a collision-type airflow crusher for crushing by colliding with the collision member 4. Is not a useful method. This is because if the secondary high-pressure gas is introduced to promote the collision in the acceleration tube 3, the carrier flow due to the high-pressure gas introduced from the compressed gas supply nozzle 2 is obstructed, and the powder flow ejected from the acceleration tube outlet 13 Will slow down. Therefore, the impact force that collides with the collision member 4 decreases, and the pulverization efficiency decreases, which is not preferable.

Therefore, a crusher and a crushing method having good crushing efficiency have been desired.

On the other hand, the toner or the colored resin powder for toner used in the image forming method by electrophotography usually contains at least a binder resin and a colorant or magnetic powder. The toner develops the electrostatic charge image formed on the latent image carrier, and the formed toner image is transferred to a transfer material such as plain paper or a plastic film and fixed by heat fixing means, pressure roller fixing means or heat pressure roller fixing. The toner image on the transfer material is fixed to the transfer material by a fixing device such as a means. Therefore, the binder resin used for the toner has a characteristic of being plastically deformed when heat and / or pressure is applied.

At present, a toner or a colored resin powder for a toner is melt-kneaded with a mixture containing at least a binder resin and a colorant or a magnetic powder (and optionally a third component), and the melt-kneaded product is cooled. Then, the cooled product is crushed and the crushed product is classified. Generally, the crushed product is roughly crushed (or medium crushed) by a mechanical impact crusher, and then the crushed coarse powder is finely crushed by a collision type air flow crusher using a jet stream. is there.

In such a case, in the conventional collision type air flow crusher and crushing method as shown in FIG. 7, if it is attempted to further improve the processing capacity, the powder raw material supply port 1 provided in the acceleration tube 3 is insufficiently sucked. Occurs, or a fusion product is generated on the collision surface 14, and stable production cannot be performed. Therefore, in order to more efficiently generate the toner or the colored resin powder for the toner used in the image forming method by electrophotography, an efficient collision type airflow crusher and a crushing method that solve the above problems are desired. .

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an efficient collision type air flow crusher and a powder raw material crushing method in which the above problems are solved.

An object of the present invention is to provide a collision type air flow pulverizer for efficiently pulverizing powder mainly composed of a thermoplastic resin and a pulverizing method for powder raw material.

An object of the present invention is to provide a collision type airflow pulverizer and a powder raw material pulverizing method capable of efficiently producing toner or colored resin particles for toner used in a copying machine and a printer having a heating and pressure roller fixing means. To provide.

The object of the present invention is to obtain an average particle size of 20 to 2000.
An object of the present invention is to provide a collision type air flow pulverizer and a powder raw material pulverizing method capable of efficiently finely pulverizing resin particles having an average particle diameter of 3 to 15 μm.

[0018]

According to the present invention, an accelerating pipe 3, a crushing chamber 8 for accelerating the conveyance of a powder raw material 7 by a high pressure gas, and a powder raw material 7 ejected from the accelerating pipe 3 by a collision force. In a collision type air flow pulverizer provided with a collision member 4 for crushing, and the collision member 4 is provided in the crushing chamber so as to face the acceleration pipe outlet 13, a plurality of powder raw material supply ports 1 are provided in the acceleration pipe 3. The present invention relates to a collision type airflow crusher, characterized in that an accelerating tube secondary air inlet 10 is provided between a powder raw material supply port and an accelerating tube outlet 13.

In the present invention, the powder raw material 7 is accelerated and conveyed by the high pressure gas in the accelerating tube 3, the powder raw material 7 is discharged from the accelerating tube outlet 13 into the crushing chamber, and the powder raw material 7 is applied to the opposing collision member 4.
In the pulverizing method of the powder raw material in which the powder raw materials are crushed by colliding with each other, the powder raw material 7 is introduced from a plurality of powder raw material supply ports 1 provided in the accelerating pipe 3 and accelerated with the powder raw material supply port 1 of the accelerating pipe. A pulverizing method of powder raw material, characterized in that secondary air is introduced into the accelerating pipe 3 from an accelerating pipe secondary air introducing port 10 provided between the pulverizing raw material 7 and the pulverizing raw material 7. .

The collision type air flow pulverizer of the present invention can efficiently pulverize the powder, which is the raw material to be pulverized, to the order of several μm by utilizing the high speed air flow.

In particular, the collision type air flow pulverizer of the present invention can efficiently pulverize a powder of a thermoplastic resin or a powder containing a thermoplastic resin as a main component to the order of several μm efficiently by using a high speed air flow. .

The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an air flow type crusher of the present invention and a flow chart of a crushing method in which a crushing process using the crusher and a classifying process by a classifier are combined. The powder raw material 7 to be crushed is supplied to the accelerating pipe 3 through the powder raw material supply port 1 (see FIG. 4) provided in the accelerating pipe 3. Compressed gas such as compressed air is introduced into the accelerating tube 3 from the compressed gas supply nozzle 2, and the powder raw material 7 supplied to the accelerating tube 3 is instantaneously accelerated to have a high speed. The powder raw material 7 discharged into the crushing chamber 8 from the accelerating pipe outlet 13 at high speed collides with the collision surface 14 of the collision member 4 and is pulverized.

In the present invention, in FIG. 1 and FIG. 2, the accelerating pipe 3 is provided with seven powder raw material supply ports 1, and the accelerating pipe secondary air is provided between the powder raw material supply port 1 and the accelerating pipe outlet 13. An inlet 10 is provided and secondary air is introduced into the accelerating tube 3 to improve the suction capability of the powder material supply port 1, and the powder is efficiently and further dispersed and sent into the accelerating tube 3. The powder raw material 7 in 3 is dispersed, the powder raw material 7 is ejected from the acceleration pipe outlet 13 more uniformly, and the powder raw material 7 is efficiently collided with the opposing collision surface 14, so that the pulverization efficiency can be improved as compared with the conventional case. The introduced secondary air loosens the agglomeration of the powder moving at a high speed in the acceleration tube 3 and contributes to the dispersion of the powder.

FIG. 6 shows an enlarged sectional view of the accelerating tube 3, which will be described in more detail. As a result of extensive studies on the method of introducing the secondary air to be introduced, the following conclusions were reached.

That is, regarding the introduction position of the secondary air, the distance between the powder raw material supply port 1 and the acceleration pipe outlet 13 is x, the powder raw material supply port 1 and the acceleration pipe secondary air introduction port 10 are shown in FIG. If the distance is y, then x and y are

[0026]

[Outside 3] Good results were obtained when

Regarding the introduction angle of the secondary air introduction port, in the case of the acceleration tube secondary air introduction port 10, when the angle with respect to the axial direction of the acceleration tube 3 is Ψ (FIG. 5), Ψ is 10 ° ≦. Good pulverization results were obtained when the condition of Ψ ≦ 80 °, more preferably 20 ° ≦ Ψ ≦ 80 °, was satisfied.

Regarding the air volume of the secondary air introduced, the air volume of the carrier air flow by the high pressure gas introduced from the compressed gas supply nozzle 2 is αNm ³ / min, and the total amount of the secondary air introduced from the secondary air inlet is When the air volume is βNm ³ / min,

[0029]

[Outside 4] Good results were obtained when pulverization was carried out under the conditions satisfying

The technical idea of the present invention is that the powder raw material 7 is introduced into the carrier flow of the high-pressure gas introduced from the compressed gas supply nozzle 2 and ejected from the accelerating tube outlet 13 to collide with the collision surface 14 of the collision member 4. In a collision type air flow crusher that collides the powder raw material 7 with the powder and pulverizes the powder raw material 7, the dispersion state of the powder raw material 7 in the acceleration tube 3 and suction of the powder raw material supply port 1 under the powder raw material supply hopper pipe 15 It is based on the idea that force may affect grinding efficiency. That is,
The powder raw material 7 supplied from the accelerating tube 3 flows into the accelerating tube 3 in an agglomerated state, so that the dispersion in the accelerating tube 3 becomes insufficient, and therefore, when it is ejected from the accelerating tube outlet 13, the dust concentration varies. Occurs, the collision surface 14 cannot be effectively used,
Further, it was considered that the suction force of the powder raw material supply port 1 was reduced for coarse particles, the supply of the powder raw material 7 was insufficient, and the pulverization efficiency was reduced. This phenomenon becomes more remarkable as the crushing amount increases.

Therefore, the present inventors have devised a plurality of powder supply ports and the introduction of secondary air in order to solve this problem. The idea of introducing the secondary air into the accelerating pipe 3 so as to disperse the powder raw material 7 from the plurality of powder raw material supply ports 1 without obstructing the carrier flow of the high-pressure gas and to improve the suction ability of the powder raw material 7. The present invention has been completed based on the above.

As another example, in FIG. 3 and FIG.
Cross-sectional view with two and four powder raw material supply ports (B in FIG. 5)
-B 'part cross section) is shown. Further, the cross section of the acceleration tube 3 is not limited to the circular shape.

On the other hand, the inner diameter of the accelerating tube outlet 13 is usually 10 to 10.
It is preferably 100 mm and has an inner diameter smaller than the diameter of the collision member 4.

The distance between the acceleration tube outlet 13 and the tip of the collision member 4 is preferably 0.3 to 3 times the diameter of the collision member 4. If it is less than 0.3 times, over-pulverization tends to occur, and if it exceeds 3 times, the pulverization efficiency tends to decrease.

The crushing chamber 8 of the collision type air flow crusher according to the present invention is not limited to the box type shown in FIG.

As the secondary air, either a highly compressed gas or a normal pressure gas may be used. It is very preferable to install an opening / closing device such as a valve at each secondary air inlet to control the amount of introduced air. The number of the accelerating tube secondary air introduction ports 10 to be attached to which position in the upper direction of the accelerating tube 3 may be appropriately set depending on the powder raw material 7, the target particle diameter, and the like. FIG. 6 shows, as an example, a cross-sectional view taken along the line BB ′ in the case where the accelerating tube secondary air introduction ports 10 are attached at eight locations in the circumferential direction of the accelerating tube 3. In this case, 8
The distribution of the secondary air from the location may be appropriately set.

As described above, according to the apparatus and method of the present invention, the powder raw material 7 can be dispersed and supplied from the plurality of powder raw material supply ports 1 into the accelerating pipe 3, and the secondary air can be supplied. Of the powder raw material 7 from the powder raw material supply port 1 is improved and the dispersion of the powder raw material 7 in the accelerating pipe 3 is good, so that the collision surface 14 can be efficiently treated. Clash,
The grinding efficiency is improved. That is, the processing capacity is improved as compared with the conventional crusher, and the particle size of the obtained product can be made smaller with the same processing capacity.

Further, in the conventional example, since the powder raw material 7 collides with the collision surface 14 in an agglomerated state, a fused material is likely to be generated especially when powder mainly containing a thermoplastic resin is used as the raw material. On the other hand, according to the present invention, the colliding surface 14 collides with the colliding surface 14 in a dispersed state, so that a fused substance is not easily generated.

Further, in the conventional example, since the powder raw material 7 is agglomerated, there is a problem that over-pulverization is likely to occur, and thus the obtained pulverized product has a wide particle size distribution. On the other hand, according to the present invention, over-pulverization can be prevented, and a pulverized product having a sharp particle size distribution can be obtained.

Further, according to the present invention, the powder raw material 7 can be dispersed and supplied from the plurality of powder raw material supply ports 1 into the accelerating pipe 3, and the secondary air can be introduced efficiently, The air suction capability at the powder raw material supply port 1 is improved, so that the transport capability of the crushing raw material 7 in the accelerating pipe 3 is improved, and the crushing throughput can be increased more than before.

The effect of the apparatus and method of the present invention becomes more remarkable as the particle size becomes smaller. Hereinafter, the present invention will be described in detail based on examples.

[0042]

【Example】

Example 1 Polyester resin (weight average molecular weight (Mw) = 50,
000, Tg = 6 ° C.) 100 parts by weight Phthalocyanine pigment 6 parts by weight Low molecular weight polyethylene 2 parts by weight Negatively charged control agent (azo metal complex) 2 parts by weight

The above pigments were mixed in a Henschel mixer to obtain a mixture. Next, this mixture is melt-kneaded at about 180 ° C. in an extruder, then cooled and solidified, and a cooled product of the melt-kneaded product is heated to 100 to 1000 μm with a hammer mill.
The powder raw material 7 was coarsely pulverized into m particles. This coarsely pulverized product was used as a powder raw material and pulverized by the pulverizer and flow shown in FIG. A fixed wall type air classifier was used as a classifying means for classifying the crushed powder into fine powder and coarse powder.

The acceleration tube of the collision type airflow crusher is shown in FIG.

[0045]

[Outside 5] ψ = 45 °

8 secondary air inlets in the circumferential direction (Fig. 6)
The accelerating tube which satisfies the condition of was used.

From the compressed gas supply nozzle, a = 6.4 Nm ³
/ Min (6.0 kg / cm ² ) compressed air is introduced,
Secondary air is 0.1 Nm ^{3 /} min (6.0 kg) from each of 8 locations A, B, C, D, E, F, H and G in FIG.
/ Cm ² ) of compressed air was introduced.

[0048]

[Outside 6]

19 kg from the powder raw material charging port 1 shown in FIG.
The raw material to be ground was supplied at a rate of / hour. The pulverized powder raw material was conveyed to a classifier, fine powder was removed as a classified powder, and coarse powder was again charged into the accelerating tube together with the powder raw material through the charging port 1.

19 kg / g of pulverized powder having a weight average particle diameter of 6.0 μm (measured by a Coulter counter) as fine powder.
Collected at the rate of time.

No fusion deposit was generated even after continuous operation for 6 hours.

The particle size distribution of the toner can be measured by various methods, but in the present invention, it was measured using a Coulter counter.

That is, a Coulter counter TA-II type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) for outputting number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) are connected. , Electrolyte is 1st class sodium chloride
% NaCl aqueous solution is prepared. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, as a dispersant is added in an amount of 0.1 to 100 ml in the electrolytic aqueous solution of 100 to 150 ml.
Add ~ 5 ml, and then add 2 to 20 mg of the measurement sample. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter counter TA-II type is used to use a 100 μ aperture as an aperture,
The particle size distribution of the particles of 2 to 40 μm was measured based on the number, and then the value according to the present invention was determined.

Example 2 The same raw material to be ground as in Example 1 was crushed by the crusher and the flow shown in FIG.

A fixed wall type air classifier was used as a classifying means for classifying the pulverized powder into fine powder and coarse powder.

The acceleration tube of the collision type airflow crusher is shown in FIG.

[0057]

[Outside 7] ψ = 45 °

8 secondary air inlets in the circumferential direction (Fig. 6)
The accelerating tube which satisfies the condition of was used.

From the compressed gas supply nozzle a = 6.4 Nm ³
/ Min (6.0 kg / cm ² ) compressed air is introduced,
Secondary air is 0.1 Nm ^{3 /} min (6.0 kg) from each of 8 locations A, B, C, D, E, F, H and G in FIG.
/ Cm ² ) of compressed air was introduced.

[0060]

[Outside 8]

19 kg from the powder raw material charging port 1 shown in FIG.
The raw material to be ground was supplied at a rate of / hour. The pulverized powder raw material was conveyed to a classifier, fine powder was removed as a classified powder, and coarse powder was again charged into the accelerating tube together with the powder raw material through the charging port 1.

19 kg / g of pulverized powder having a weight average particle diameter of 6.0 μm (measured by a Coulter counter) as fine powder.
Collected at the rate of time.

Example 3 The same material as the material to be ground as in Example 1 was ground with the grinder and flow shown in FIG.

A fixed wall type air classifier was used as a classifying means for classifying the pulverized powder into fine powder and coarse powder.

The acceleration tube of the collision type airflow crusher is shown in FIG.

[0066]

[Outside 9] ψ = 45 °

8 secondary air inlets in the circumferential direction (Fig. 6)
The accelerating tube which satisfies the condition of was used.

From the compressed gas supply nozzle, a = 6.4 Nm ³
/ Min (6.0 kg / cm ² ) compressed air is introduced,
Secondary air is 0.1 Nm ^{3 /} min (6.0 kg) from each of 8 locations A, B, C, D, E, F, H and G in FIG.
/ Cm ² ) of compressed air was introduced.

[0069]

[Outside 10]

19 kg from powder raw material charging port 1 shown in FIG.
The raw material to be ground was supplied at a rate of / hour. The pulverized powder raw material was conveyed to a classifier, fine powder was removed as a classified powder, and coarse powder was again charged into the accelerating tube together with the powder raw material through the charging port 1.

19 kg / g of pulverized powder having a weight average particle diameter of 6.0 μm (measured by a Coulter counter) as fine powder.
Collected at the rate of time.

Comparative Example 1 The same powder raw material 7 as in Example 1 was pulverized by the pulverizer and the flow shown in FIG.

A fixed wall type air classifier was used as a classifying means for classifying the crushed powder into fine powder and coarse powder.

Compressed air with a flow rate of 6.4 Nm ³ / min (pressure 6.0 kg / cm ² ) was introduced into the acceleration tube 3 of the collision type airflow pulverizer from the compressed gas supply nozzle 2, and the powder raw material supply port 1 The powder raw material 7 was supplied at a rate of 26 kg / hour. The pulverized powder raw material 7 was conveyed to a classifier, fine powder was removed as a classified powder, and coarse powder was again fed into the accelerating tube 3 together with the powder raw material 7 from the powder raw material supply port 1.

As a result, the fine powder has a volume average particle diameter of 7.5.
A pulverized powder of μm (measured by Coulter counter) was collected at a rate of 26 kg / hour.

Table 1 shows the results of Examples 1 to 3 and Comparative Example 1 obtained as described above.

[0077]

[Table 1]

[0078]

As described above, according to the collision type air flow crusher and the crushing method of the present invention, the accelerating pipe for accelerating the powder raw material by the high pressure gas, the crushing chamber, and the blasting from the accelerating pipe. In a crusher equipped with a collision member for crushing the powder raw material by a collision force, the powder raw material is dispersed and supplied into the acceleration tube by providing a plurality of powder raw material supply ports in the acceleration tube, and By introducing secondary air into the accelerating tube, the suction capacity of the powder material supply port is improved, the powder in the accelerating tube is ejected with good dispersion, the powder material collides with the collision surface efficiently, and the grinding efficiency is improved. To do.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a collision-type airflow crusher of the present invention and a flow chart of a crushing method in which a crushing process using the crusher and a classifying process by a classifier are combined.

FIG. 2 is a diagram showing a specific example of a cross section taken along the plane BB ′ of FIG.

FIG. 3 is a diagram showing a specific example of a cross section taken along the plane BB ′ of FIG. 1.

FIG. 4 is a diagram showing a specific example of a cross section taken along the line BB ′ of FIG. 1.

FIG. 5 is a cross-sectional view of the acceleration tube of the collision type airflow crusher of the present invention.

6 is a diagram showing a specific example of a cross section taken along the line AA ′ in FIG. 1. FIG.

FIG. 7 is a schematic cross-sectional view of a collision-type airflow crusher of a conventional example, and a diagram showing a flowchart of a crushing method combining a crushing process using the crusher and a classifying process by a classifier.

[Explanation of symbols]

1 Powder raw material supply port 2 Compressed gas supply nozzle 3 Accelerator 4 collision member 5 outlets 7 Powder raw material 8 crushing room 10 Secondary air inlet 13 Accelerator outlet 14 collision surface

Continued front page    (72) Inventor Yasuhide Goseki             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation

Claims (5)

[Claims] 1. A collision member for crushing the powder raw material ejected from the accelerating pipe by a collision force, the accelerating tube for accelerating the powder raw material by high-pressure gas, and the crushing member. In a collision type air flow crusher provided in the crushing chamber facing the acceleration pipe outlet, the acceleration pipe is provided with a plurality of powder raw material supply ports, and the acceleration pipe secondary is provided between the powder raw material supply port and the acceleration pipe outlet. A collision type airflow crusher characterized by having an air inlet. 2. The distance between the powder raw material supply port provided in the acceleration pipe and the acceleration pipe outlet is x, and the distance between the powder raw material supply port and the acceleration pipe secondary air introduction port provided in the acceleration pipe is y. If
x and y are The collision type airflow crusher according to claim 1, wherein 3. The collision-type airflow according to claim 1, wherein the introduction angle Ψ of the secondary air introduction port of the acceleration tube satisfies 10 ° ≦ Ψ ≦ 80 ° with respect to the axial direction of the acceleration tube. Crusher. 4. The powder is conveyed by high pressure gas in the acceleration tube.
In a pulverizing method of a powder raw material, which accelerates and discharges powder from an accelerating tube outlet into a crushing chamber and collides the powder with an opposing collision member to pulverize, a plurality of powder raw material supply ports provided in the accelerating tube The powder raw material is introduced into the accelerating tube from the accelerating tube secondary air inlet provided between the powder raw material supply port and the accelerating tube outlet of the accelerating tube to obtain the powder raw material. A method for pulverizing a powder raw material, which comprises pulverizing. 5. air amount ArufaNm ³ / min of high pressure gas for transporting accelerate the powder raw material is introduced into the acceleration tube, BetaNm the air volume of the secondary air introduced into the acceleration tube and the powder material feed hopper tube ³ / As min, α and β are [External 2] 5. Grinding under conditions satisfying
A method for pulverizing the powder raw material as described.