JP2805332B2 - Grinding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for pulverizing a powder material by a collision type air flow pulverizer using a jet air flow (high-pressure gas). Especially,
The present invention relates to a pulverizing method for efficiently producing a toner or a colored resin powder for a toner used in an image forming method by an electrophotographic method.

[Related Art] A collision-type airflow pulverizer using a jet airflow conveys a powdery raw material by a jet airflow, collides the powdery raw material with a collision member, and pulverizes the powdery raw material by the impact force.

Conventionally, the collision surface 14 of the collision member in such a crusher,
As shown in FIG. 3 and FIG. 4, a flat plate which is perpendicular or inclined (for example, 45 °) to the jet stream direction (axial direction of the accelerating tube) on which the powder material is loaded has been used. (See JP-A-57-50554 and JP-A-58-148453).

In the pulverizer shown in FIG. 3, a powder raw material having a coarse particle size is supplied from an inlet 1 to an acceleration tube 3 and is jetted from a jet nozzle 2 so that the powder raw material is converted into a collision surface 14 of a collision member 4. And is pulverized by the impact force, and is discharged out of the pulverization chamber through the discharge port 5.

However, when the collision surface 14 is perpendicular to the axial direction of the acceleration tube 3, the ratio of the raw material powder blown out from the jet nozzle 2 and the powder reflected by the collision surface 14 coexist near the collision surface 14 is high. Therefore, the powder concentration in the vicinity of the collision surface 14 becomes high, so that the pulverization efficiency is not good. Further, the primary collision at the collision surface 14 is mainly performed, and it cannot be said that the secondary collision with the crushing chamber wall 6 is effectively used. Further, in a pulverizer in which the angle of the collision surface is perpendicular to the accelerating tube 3, when the powder raw material is a material that is a thermoplastic resin, fusion and agglomerates are easily generated due to local heat generation at the time of collision. In order to make stable operation of the equipment difficult and to improve the crushing impact force
It becomes impossible to use a highly compressed gas of 6.5 kg / cm ² or more.

A toner or a colored resin powder for a toner used in an image forming method by an electrophotographic method usually contains at least a binder resin and a colorant or a 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 is heated and fixed, a pressure roller is fixed, or a heat and pressure roller is used. The toner image of the transfer material is fixed on the transfer material by a fixing device such as a fixing unit. Therefore, the binder resin used for the toner has a property of being plastically deformed when heat and / or pressure is applied. At present, a toner or a colored resin powder for a toner is prepared by melt-kneading a mixture containing at least a binder resin and a colorant or a magnetic powder (and further containing a third component as necessary), cooling the melt-kneaded product, and cooling. It is prepared by crushing the product and classifying the crushed product. The crushing of the cooled product is usually carried out through a process of coarse crushing (or medium crushing) by a mechanical impact crusher, and then the crushed coarse powder is finely crushed by a collision type airflow crusher using a jet stream.
It was difficult to increase the concentration of the material to be pulverized, and preferably to pulverize using a highly compressed gas of 7.0 kg / cm ² or more.

On the other hand, as shown in FIGS. 4 and 5, when the angle of the collision surface 14 is 45 ° with respect to the accelerating tube, the powder concentration near the collision surface 14 is lower than that of the pulverizer of FIG. However, the above-mentioned problems when pulverizing a thermoplastic resin are small. However, at the time of collision, the crushing force used for crushing is small, and crushing due to secondary collision with the crushing chamber wall 6 is small. 1.5
The crushing ability drops.

Therefore, when the material to be pulverized and sometimes, when pulverizing a material containing a thermoplastic resin, the pulverization efficiency is good, and 6.5 kg / cm
^A pulverization method that can improve the pulverization ability even when ^two or more highly compressed gases are used has been desired.

[Problem to be solved by the invention] A problem to be solved by the present invention is to provide a pulverization method in which the above-mentioned problem is solved.

Means and Action for Solving the Problems According to the present invention, a powder material containing a thermoplastic resin is accelerated by a high-pressure gas in an acceleration tube, and the powder material is discharged from the acceleration tube outlet. In a pulverization method for pulverizing the raw material by colliding the raw material with a collision surface of a collision member provided in a pulverization chamber opposed to the pulverization chamber, the accelerating tube has a cross-sectional area perpendicular to an axial direction of the accelerating tube in an accelerating tube outlet direction. The high-pressure gas supplied into the acceleration tube is a compressed gas of 6.5 kg / cm ² or more, accelerated in the tube passage, and discharged from the acceleration tube outlet. The powdered raw material collides with a collision member having a cone-shaped collision surface having a vertex angle of 120 ° to 170 ° at the tip portion to be pulverized, and the powder after the collision is substantially dispersed in the entire circumferential direction. Pulverization characterized by secondary collision of the ground powder with a pulverization chamber wall to further pulverize Law on.

According to the present invention, in order to solve the reduction of the crushing ability due to fusion, agglomerates and coarse particles generated when crushing a resin or a sticky thing, as shown in FIG. 1 and FIG. The tip portion of the impact plate surface was formed in a conical shape having an apex angle of 120 ° to 170 °.

In this way, when crushing thermoplastic resin or sticky material, there is no fusion, agglomeration, or coarse particles that occur when the collision plate has an angle of 90 ° to the accelerating tube. The concentration can be increased.

Furthermore, by using such a collision plate, it is possible to make the powder that has been crushed by the collision plate and rebounded with good dispersion collide with the crushing chamber a second time, thereby further increasing the crushing efficiency. .

In addition, since the powder was rebounded from the collision plate with good dispersion and collided secondly with the wall of the grinding chamber, highly compressed gas of 6.5 kg / cm ² or more was used to finely pulverize thermoplastic resin as raw material. And the crushing ability is improved compared to the case where the angle of the collision plate is perpendicular to the acceleration tube.

Hereinafter, the present invention will be described based on examples and comparative examples.

Example 1 Example 1 A powder was pulverized by using an impinging airflow pulverizer shown in FIGS. 1 and 2 of the accompanying drawings. As a classification means for classifying the pulverized powder into fine powder and coarse powder, a fixed wall type air classifier was used.

The impingement type air current pulverizer has a columnar impacting member 4 made of an aluminum oxide ceramic having a diameter (b) of 60 mm, and the tip of the impacting member 4 has a cone having an apex angle (θ) of 120 °. It has a shape. The inner wall of the crushing chamber 8 is ceramic-coated. The inner diameter of the acceleration tube outlet 13 is 25 mm,
The center axis of the acceleration tube 3 and the tip of the collision member 4 coincide with each other. Closest distance from accelerator tube exit 13 to collision surface 14 (a)
Is 60 mm, and the closest distance (c) between the collision member 4 and the crushing chamber wall 6 is 20 mm. The cross section along the AB plane of the impinging airflow pulverizer has a U-shape as shown in FIG. The distance between the collision member 4 and the left and right and below the crushing chamber wall 6 is 20 to 40 mm.
It is.

 The following was used as raw material 7.

The toner raw material consisting of the mixture of the above formulation is
After melt-kneading for 1.0 hour, the mixture was cooled and solidified, and the cooled melt-kneaded product was roughly pulverized into particles of 100 to 1000 μm with a hammer mill to obtain a powder raw material.

When the powder material is supplied at a rate of 33 kg / hour from the inlet 1, the powder material is accelerated in the acceleration tube 3 by the compressed air 8.0 kgf / cm ² wiped out from the nozzle 2, and the outlet of the acceleration tube is accelerated.
The powder raw material 7 was discharged into the pulverizing chamber 8 from 13 and was hit against the collision surface 14 and pulverized by the impact force. With it
Due to the conical collision surface 14 inclined at 120 °, the colliding powder material is dispersed in all circumferential directions,
Secondary collision, where it was further crushed.

The crushed powder raw material is smoothly classified from the outlet 5
24, the fine powder was removed as a classified powder, and the coarse fraction was again charged together with the powder raw material from the charging port 1. A ground powder having a weight average particle size of 12 μm was collected as a fine powder at a rate of 33 kg / hour.

As described above, the collision surface of the collision member 4 has a conical shape with an apex angle (θ) of 120 °, so that the colliding powder material is dispersed in the entire circumferential direction, and the crushed powder material is in contact with the opposing crushing wall. Next collision. Therefore, it was confirmed that the powder concentration did not increase because no fusion, agglomerates, and coarse particles were generated near the collision member, and further, the secondary collision caused the pulverization ability to be much higher than before. Was.

Example 2 A powder raw material similar to that of Example 1 was used and the apex angle (θ) shown in FIG.
Using a collision member having a conical collision surface with a 160-degree inclination, pulverization was performed in the same manner as in Example 1, but the dust concentration near the collision surface during the pulverization did not increase and secondary collision occurred. In the same manner as in Example 1, it was confirmed that the pulverizing ability was much higher than before. The input amount of the powder raw material was adjusted according to the processing amount.

Example 3 A powder material similar to that of Example 1 was subjected to the apex angle (θ) shown in FIG.
When crushing was performed in the same manner as in Example 1 using a collision member having a conical collision surface inclined at 170 degrees, the dust concentration near the collision surface during the crushing did not increase, and secondary collision occurred. Therefore, it has been confirmed that the pulverizing ability is much higher than before.

Comparative Example 1 The same powdery raw material as in Example 1 was pulverized by a conventional impingement airflow pulverizer shown in FIG. In the crusher, the acceleration tube 3
Pulverized in the same manner as in Example 1 using a collision member 4 having a planar collision surface 14 perpendicular to However, nozzle 2
Compressed air blown from the container was pulverized at 6.0 kg / cm ² .

The powder raw material that collided with the collision surface 14 was reflected in a direction opposite to the discharge direction, so that the powder concentration near the collision surface became extremely high. Therefore, the supply ratio of the powder raw material is 10 kg /
If the time is exceeded, fusion, agglomerates, and coarse particles begin to occur on the collision member, and the fusion may clog the outlet 13 of the acceleration tube or the classifier. Therefore, the pulverization throughput is 10
It had to be reduced to Kg, which was the limit of the grinding capacity.

Comparative Example 2 The same powdery raw material as in Example 1 was pulverized by a conventional impingement airflow pulverizer shown in FIG. In the crusher, the acceleration tube 3
The compressed air blown out from the nozzle ² was crushed at 8.0 kg / cm ² in the same manner as in Example 1 by using the collision member 4 having the planar collision surface 14 perpendicular to the compressed air. Since the powder raw material colliding with the collision surface 14 is reflected in a direction opposite to the discharge direction, the powder concentration near the collision surface becomes extremely high, and further,
Since the impact force increased, fusion, agglomerates, and coarse particles began to form on the collision member, and the fusion clogged the accelerating tube outlet 13 and the classifier, making it impossible to achieve the pulverizing function. Was.

Comparative Example 3 A powdery raw material similar to that of Example 1 was pulverized by the impingement airflow pulverizer shown in FIGS. When the pulverizer was pulverized in the same manner as in Example 1 using a collision member having a 45-degree collision surface, the powder material that collided with the collision surface was more distant from the accelerating tube outlet 13 than in Comparative Example 1. No fusing or agglomeration occurred due to reflection to the surface. However, the impact force was weakened at the time of collision, so that the pulverization efficiency was poor, and only about 10 kg of fine powder having a weight average particle diameter of 12 μm was obtained per hour.

The results of Examples 1 to 3 and Comparative Examples 1 to 3
It is shown in the table.

Example 4 The following were used as powder raw materials.

The toner raw material consisting of the mixture of the above formulation is
After melt-kneading for 1.0 hour, the mixture was cooled and solidified, and the solid was roughly pulverized into particles of 100 to 1000 μm with a hammer mill to obtain a powder raw material.

The compressed air was supplied from the inlet 1 at a rate of 10.5 kg / hour, the compressed air of 8.0 kgf / cm2 was introduced from the nozzle 2, and the collision member having a cone-shaped collision surface with a vertical angle (θ) of 120 ° was inclined. The pulverized powder was crushed by a collision type air current crusher shown in FIGS. 1 and 2 and the crushed powder was classified into fine powder and coarse powder by a classifier 24. As fine powder, a powder having a weight average particle size of about 12 μm was collected at a rate of 10.5 kg per hour.

Example 5 The same powdery raw material as in Example 4 was obtained by using an impingement type air-flow pulverizer shown in FIG. 1 equipped with an impingement member having a conical impingement surface having an apex angle (θ) of 160 °. Then, when the powder was pulverized in the same manner as in Example 4, fine powder having a weight average particle size of about 12 μm was collected at a rate of 9.8 kg per hour.

Comparative Example 4 The same powdery raw material as in Example 4 was pulverized by a collision airflow pulverizer shown in FIG. 3 into which compressed air of 6.0 kgf / cm ² was introduced. Fine powder having a weight average particle size of about 12 μm was obtained. Only 7 kg was collected per hour.

Comparative Example 5 The same powdery raw material as in Example 4 was pulverized by a collision type air flow pulverizer shown in FIG. 3 into which compressed air of 8.0 kgf / cm ² was introduced. Coarse particles began to form, and the fused material clogged the classifier at the outlet 13 of the accelerating tube, making it impossible to achieve the pulverizing function.

Comparative Example 6 The same powdery raw material as in Example 4 was pulverized by a collision type air-flow pulverizer shown in FIGS. 4 and 5 into which 8.0 kgf / cm ² of compressed air was introduced. Only 5.6 kg of fines per hour were collected.

The results of Examples 4 to 6 and Comparative Examples 4 to 6
It is shown in the table.

[Effect of the Invention] As described above, the shape of the tip of the collision member is a specific conical shape, and in order to strike the powder material on the collision surface, even if a highly compressed gas of 6.5 kg / cm ² or more is injected, It prevents fusion, agglomerates, coarse particles, and the like during pulverization, and enables stable operation of the apparatus. In addition, a strong impact force can be maintained until the secondary collision of the powder material. Therefore, the conventional pulverizing ability can be remarkably improved by using a thermoplastic resin material as a raw material and using a highly compressed gas of 6.5 kg / cm ² or more.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross section and a pulverizing / classifying process of an impingement type air current pulverizer used in the present invention in which an impinging member has a conical shape, and FIG. 2 is a pulverizer shown in FIG. A-
It is the figure which showed roughly the cross section in the B side. FIG. 3 is a diagram schematically showing a cross section and a pulverizing / classifying step of a collision type air flow pulverizer as a comparative example in which a collision surface of a collision member is perpendicular to an axial direction of an acceleration tube. FIG. 4 schematically shows a cross section and a pulverizing / classifying process of a collision type air flow pulverizer as a comparative example in which the collision surface of the collision member is inclined upward by 45 ° with respect to the axial direction of the acceleration tube. FIG. 5 is a perspective view of the collision type airflow pulverizer A shown in FIG.
It is the figure which showed roughly the cross section in -B figure. DESCRIPTION OF SYMBOLS 1 ... Powder raw material input port 2 ... Compressed gas supply nozzle 3 ... Acceleration tube 4 ... Collision member 5 ... Discharge port 6 ... Pulverizing chamber wall 7 ... Powder raw material 8 ... Pulverizing chamber 11: Powder machine wall, 13: Accelerator tube outlet 14: Collision surface, 24: Classifier a ... Distance between accelerator tube outlet and collision member b: Collision member diameter c: Collision member to grinding chamber Shortest distance of the wall

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B02C 19/06 G03G 9/08

Claims (2)

(57) [Claims] 1. A powder material containing a thermoplastic resin is accelerated by a high-pressure gas in an acceleration tube, and the powder material is discharged from an outlet of the acceleration tube. In a pulverization method for pulverizing the raw material by colliding the powder material with a collision surface of a collision member, the accelerating tube has a pipe passage in which a cross-sectional area perpendicular to an axial direction of the accelerating tube increases gradually toward an accelerating tube outlet direction. The high-pressure gas supplied into the accelerating tube is a compressed gas of 6.5 kg / cm ² or more, and the powder raw material accelerated in the tube passage and discharged from the accelerating tube outlet is apex angle at the tip portion. Crushed by colliding with a collision member having a cone-shaped collision surface of 120 ° to 170 °, dispersing the powder after the collision substantially in all circumferential directions, and dispersing the dispersed powder on the wall of the grinding chamber. A crushing method characterized by further crushing by collision. 2. The pulverizing method according to claim 1, wherein said pulverizing raw material has a particle size of 100 to 1000 μm.