JPH0251664B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder heat treatment apparatus. More specifically, thermoplastic particles are melted and
The present invention relates to a heat treatment device for spheroidizing.

Conventionally, thermoplastic particle spheronizing equipment atomizes a suspension dissolved or dispersed in water or an organic solvent using a two-fluid nozzle or rotating disk method, and then dries it in hot air to form particles with a spherical diameter. A wet method such as the so-called spray dryer method, or a dry method in which thermoplastic particles are dispersed in a hot air stream to achieve spheroidization, is employed.

However, in the conventional wet method,
The solvent had to be removed before spherical particles were obtained, making it inevitable to add additional equipment such as a large drying room, solvent recovery equipment, and explosion prevention safety measures. In addition, when using the dry method to process fine powder with a particle size of 100 μm or less, thermal fusion of thermoplastic particles tends to generate coarse particles and adhesion of thermoplastic particles to the jet nozzle and container wall. These factors often led to a decrease in yield and productivity or non-uniform heat treatment conditions.

Conventionally, in order to prevent the thermoplastic particles from being thermally fused to the wall surface of the jet nozzle in the thermoplastic particle dispersion airflow, a flow path was provided around the outer periphery of the jet nozzle, and a cooling medium such as water or cold air was flowed through the flow path. A method for cooling the jet nozzle part is described in Japanese Patent Application Laid-Open No. 53-60379, but in this method, the inner wall of the jet nozzle drops below the dew point and water droplets are generated on the surface of the inner wall of the nozzle, resulting in heat generation. This caused the adhesion of plastic particles, which hindered the stable processing of large amounts of powder.

Furthermore, Japanese Patent Publication No. 55-2165 describes the introduction of cooling air between the dispersion airflow and the hot airflow for the purpose of preventing particles from adhering to the dispersion airflow jet nozzle opening. In this method, the temperature around the thermal meeting area where the dispersed air flow and the hot air flow mix decreases due to the introduction of cooling air, resulting in a significant decrease in thermal efficiency. The flying up of particles due to airflow turbulence is unavoidable, and it has been impossible to completely prevent thermoplastic particles from adhering or thermally adhering to the nozzle opening and its wall surface.

The present invention has been made to eliminate all of the above-mentioned drawbacks. That is, the first object of the present invention is to provide a highly productive heat treatment apparatus for thermoplastic particles in which the thermoplastic particles do not adhere to or are thermally fused to the inner wall surface of a dispersion air jet jetting nozzle. The second object of the present invention is to provide a long-lasting, high-yield, high-productivity method in which thermoplastic particles do not adhere or heat-fuse to the inner wall surface and around the tip of a dispersion air jet nozzle. The present invention aims to provide a heat treatment apparatus for thermoplastic particles that can be operated continuously for hours.

Among the above-mentioned objects of the present invention, the first object is to provide a heat treatment apparatus for melting and spheroidizing thermoplastic particles in an air stream, by providing a cooling jacket on the outer periphery of a jetting nozzle for dispersing the thermoplastic particles; This is achieved by an apparatus for heat treatment of thermoplastic particles characterized in that an air gap is provided between the nozzle and the cooling jacket.

Among the above objects of the present invention, the second object is to provide a heat treatment apparatus for melting and spheroidizing thermoplastic particles in an air flow, by providing a cooling jacket on the outer periphery of a jetting nozzle for dispersing the thermoplastic particles. providing a gap between the jet nozzle and the cooling jacket;
Furthermore, the present invention is achieved by a thermoplastic particle heat treatment apparatus characterized in that a slit for forming an air curtain is provided at the outer periphery of the tip of the ejection nozzle.

The apparatus according to the present invention will be described in detail below with reference to the drawings, but the embodiments of the present invention are not limited thereby.

FIG. 1 shows an example of an apparatus for ejecting a dispersed air stream containing thermoplastic particles according to the present invention.

In FIG. 1, 15 is an ejector mixing chamber to which a popper 18 is connected to the upper part and a pressurized air flow introduction pipe 17 is connected from the horizontal direction through the side wall.
An ejector throat portion 16 is connected to the opposite side wall of the connected wall portion. 16 is further connected to a dispersion airflow supply pipe 2, which is connected to the side wall of the swirling chamber 3 from a horizontal tangential direction of 3, and a dispersion airflow jetting nozzle 4 directed downward is provided at the center of the bottom of the swirling chamber 3.
are connected. A cooling jacket 5 having a hollow interior surrounds the outer periphery of the nozzle 4 at a position where a gap 19 is formed between the nozzle 4 and the jacket 5 and a slit 9 is formed at the outer periphery of the tip of the nozzle 4. It is installed in Further, a coolant inlet pipe 6 and a coolant discharge pipe 7 are connected to the upper wall of the cooling jacket 5 by penetrating the upper wall, and a compressed air inlet pipe 8 is connected to the upper wall of the cavity 19. has been done.

In the device shown in FIG. 1, when compressed air 13 is ejected into the ejector mixing chamber 15 through the compressed air introduction pipe 17, thermoplastic particles 14 are sucked together with the air from the hopper and are subjected to strong shearing within the throat section 16. Under the action, the agglomerated particles are crushed and uniformly dispersed. Further, the dispersion airflow 1 of thermoplastic particles is swirled in the swirling chamber 3, guided into the lower jet nozzle part 4, swirled near the inner wall surface of the nozzle by centrifugal force, descended, and then started from around the tip of the nozzle 4 at a constant rate. The particles are ejected as a Hollow Cone Flow 12 at a constant ejection angle, constant linear velocity, and uniform particle concentration. 1 in the empty cone flow 12 of this dispersed air flow
If hot air flow 11 is introduced from the outer periphery of 2 and mixed to cause thermal association, the individual thermoplastic particles have good dispersibility and spread in a conical shape at a constant concentration, so heat treatment can be performed under uniform conditions. This makes it possible to form thermoplastic particles into uniform and high-quality spheres. At this time, by introducing compressed air from 8, air is blown out from slit 9, forming an air curtain. Furthermore, by circulating a coolant such as cold water or cold air through a cooling jacket provided on the outer circumference of the slit 9, the jet nozzle portion 4 and the nozzle portion 4 are cooled.
Inside, there is a hot air flow 1 around the outer periphery of the cooling jacket 5.
It is possible to maintain a state close to room temperature at all times without being affected by the temperature of the jet nozzle part 4, prevent thermal fusion on the inner wall of the jet nozzle, and at the same time, by providing the gap 19, the jet nozzle part 4 and the cooling jacket 5 can be connected to each other. Since there is no direct contact with the spray nozzle, it is possible to prevent the temperature of the inner wall of the ejection nozzle from dropping below the dew point, and it is also possible to prevent the adhesion of thermoplastic particles due to the generation of water droplets.

In addition, by blowing out the air curtain 10 from the slit part, it is possible to prevent thermoplastic particles from adhering to the tip of the jet nozzle part 4, and also to prevent the formation of icicle-like deposits of particle deposits at the tip of the nozzle part. can do.

As in the apparatus shown in FIG. Even if it is not an empty conical flow, it can be ejected from a jet nozzle with a cooling jacket provided on the outer periphery through a gap, or from a jet nozzle with a cooling jacket provided on the outer periphery with a gap and a slit at the tip. It is effective if the device heat-treats the dispersed airflow of thermoplastic particles. More preferably, the dispersed airflow of thermoplastic particles is spun around near the inner wall of the nozzle, while
It is more preferable to use a heat treatment apparatus having means for ejecting a uniform empty conical flow from the tip of the ejection nozzle. This is considered to be because the particle concentration distribution of the ejected empty conical flow is uniform, so that the heat treatment state at the thermal meeting part can be made uniform.

In the device shown in Fig. 1, the ejection angle of the empty conical flow 12 almost matches the angle θ between the tangent to the tip of the inner wall of the nozzle and the horizontal line, but the preferred range of θ is 30°≦
An example is θ70°. Further, the coolant flowing through the cooling jacket may be water or other coolant having a temperature of 50° C. or lower. In addition, the temperature of the compressed air jetting out from the slit 9 is below 50℃, and the jetting flow has a linear velocity of 10~
40m/S, preferably with a slit gap of 0.3 to 2.0mm, so that the air volume of the air curtain is extremely small compared to the dispersed airflow 1, without disturbing the temperature distribution around the thermal meeting area or reducing thermal efficiency. Adhesion and fusion of thermoplastic particles at the tip of the nozzle 4 can be prevented.

FIG. 2 is a top plan view of the apparatus shown in FIG. 1, showing how the dispersed airflow of thermoplastic particles dispersed by the ejector is tangentially blown into the swirling chamber 3 and swirled. It is.

Further, FIG. 3 shows a longitudinal sectional view showing another form of the heat treatment apparatus of the present invention. In the apparatus shown in FIG. 3, the tip of the cooling jacket 5 has an acute angle, and this angle is parallel to the blowing angle of the hot air stream. This will prevent turbulence in the hot air flow,
The heat treatment effect is also improved, and there is no particle adhesion to the tip of the jacket 5.

FIG. 4 is a typical flow diagram when using the thermoplastic particle heat treatment apparatus of the present invention. The dispersion airflow of thermoplastic particles created by the ejectors 15 and 16 is swirled in the swirling chamber 3, and the lower swirling nozzle 4
It is ejected from the air to form an empty conical flow 12. A hot air stream 1 heated by a heater 20 is added to this dispersed air stream 12.
1 is blown from the direction of the arrow, and thermal association takes place. At this time, pour cooling water into the cooling jacket 5,
An air curtain 10 is formed from the slit 9. Cooling air 22 is introduced into the vicinity of the side wall of the heat treatment chamber 21 from the upper part of the side wall, and the spherical thermoplastic particles are cooled by this cooling air 22 and are discharged from the exhaust port 2.
3 and is collected by a cyclone 24 and a dust collector 25.

As detailed above, according to the heat treatment apparatus of the present invention, it is possible to completely prevent thermoplastic particles from adhering or thermally adhering to the inner wall surface of the dispersion nozzle part and the dispersion nozzle tip, and to achieve long-term continuous operation and high yield. , high productivity can be achieved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of a device for ejecting a dispersion air stream containing thermoplastic particles of the present invention, and FIG. 2 is a plan view of the device shown in FIG. 1 viewed from above.
FIG. 3 is a longitudinal sectional view showing another form of the heat treatment apparatus of the present invention, and FIG. 4 is an example of a flow diagram when the heat treatment apparatus of the present invention is used. 3...Swirling chamber, 4...Ejection nozzle, 5...Cooling jacket, 9...Slit, 15...Ejector mixing chamber, 16...Ejector throat section, 2
0... Heater, 21... Heat treatment chamber, 23... Discharge port, 24... Cyclone, 25... Dust collector, 2
6...Water supply device, 27...Compressed air generator, 2
8, 29, 30...Blower.

Claims (1)

[Claims] 1. In a heat treatment apparatus for heat-treating powder in an air stream, a cooling jacket is provided on the outer periphery of a jetting nozzle for dispersing the powder, and a gap is provided between the jetting nozzle and the cooling jacket. A powder heat treatment device characterized by: 2. The powder heat treatment apparatus according to claim 1, wherein the void is used as a slit for forming an air curtain around the outer periphery of the dispersion nozzle tip of the powder dispersion air stream. 3. Claims characterized in that the heat treatment includes means for making the dispersed air flow of the powder into a uniform empty conical flow, and means for introducing a heated air flow from the outer periphery of the flow to heat treat the thermoplastic particles. The powder heat treatment apparatus according to item 1 or 2.