JPH0737027B2 - Drying and crystallization equipment for powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for drying and crystallizing powder and granules, and more particularly to an apparatus for drying and crystallizing powder and granules mainly made of synthetic resin.

(Prior Art) Generally, when molding is performed using a wettable resin material such as polycarbonate or polyester terephthalate, which becomes sticky due to temperature rise and melts and adheres, if the water content of the resin material is a certain value or more, the molding conditions are Not only will it be difficult, but the physical properties of the molded product will deteriorate.
It is dried at a temperature of 70 ℃ ~ 180 ℃ and keeps the water content below a certain value. For example, in the case of polycarbonate, 0.01%
In the following, or in the case of polyester terephthalate (hereinafter referred to as PET resin), it was necessary to set the water content to 0.005% or less.

In particular, when drying the granular material of the PET resin which is a crystalline synthetic resin, the general synthetic resin becomes sticky at a temperature about 20 to 30 ° C lower than its melting point, whereas the PET resin is more sticky than its melting point. A PET resin having a significantly low temperature, for example, a melting point of 255 ° C., becomes tacky at a temperature about 150 ° C. lower than the melting point, that is, about 100 ° C. However, in the case of PET resin, 1
Even if heated above 00 ℃, the surface of the granular material becomes sticky, but at the same time, the crystallization of the PET resin proceeds, and the crystallization rate is about 20%, and the adhesion on the surface of the granular material is reduced. Then
After that, it does not show tackiness.

Also, the time required for crystallization is far less than the time required for drying. Therefore, the time required for crystallization of the granular material is much shorter than the time required for drying the granular material made of PET resin to the above-mentioned water content of 0.0005% or less required at the time of molding. First, a so-called two-step process is performed in which a crystallization process is first performed and then a drying process is performed. In other words, by first crystallizing the powder or granules, the temperature at which the surface of the powder or granules becomes sticky is increased, and the drying process, which is the post-treatment, can be performed at the highest possible temperature. And thus PET as a whole
The time required for drying the resin is shortened.

Thus, conventionally, as a device for drying or crystallizing the granular material made of the synthetic resin material, a punching metal is provided at the bottom of a hopper having a discharge port at the bottom, and a punching metal is provided below the punching metal. Provided is a drying / crystallizing device for supplying hot air and agitating the resin material in the hopper by an agitator attached to a rotating shaft facing the vertical direction at the center of the hopper to dry or crystallize the resin material. Has been done.

Further, without using the punching metal, a hot air supply pipe extending in the vertical direction is attached to the central portion of the hopper,
There is also provided a drying / crystallization apparatus in which the lower end of the supply pipe is opened downward in the hopper so that hot air is supplied into the hopper.

(Problems to be solved by the invention) By the way, when a food or the like which is generally porous or has a laminated structure and contains a large amount of water is dried, water moves from the inside of the food or the like to the surface by a capillary phenomenon and evaporates on the surface. Since it is a constant rate drying, it is possible to suppress the rise in surface temperature,
The drying of a substance having a uniform structure such as a synthetic resin material is a rate-decreasing drying which is carried out by diffusive movement of water from the inside of the substance to the surface. Therefore, it is impossible to expect evaporation of a large amount of water to suppress the rise of the surface temperature. . Therefore, in the rate-decreasing drying, the higher the drying temperature is, the more the water diffusion is promoted and the faster the drying speed is. For example, according to the hot air drying in the nylon-6 batch type drying tank, the water content is 10,000 ppm. When 1000ppm of Nylon-6 is dried, it takes about 1 at 90 ℃ hot air temperature.
It takes 3 hours, but at 100 ° C, it takes 7 hours, and at 110 ° C, it takes 4 hours, so that it is possible to dry quickly by raising the air temperature. The same applies to the case of crystallization of PET resin. For example, it takes about 2 hours at a hot air temperature of 120 ° C.
It only takes about 10 minutes at ℃.

However, there are limits to raising the drying temperature. That is, when the temperature of the hot air for drying the granular material made of the synthetic resin material is set higher than a certain temperature with respect to the melting point temperature, the surfaces of the granular material are softened and fused to each other, and uniform hot air drying is possible. If not, or because the surface is oxidized and colored and cannot be used as a molding material, the drying time could not be significantly shortened by raising the hot air temperature.

The same applies to the case of crystallizing a granular material made of PET resin in a short time, and heating at a certain temperature higher than the melting point causes a problem of fusion, and heating with hot air causes Since it is heated from the outside, crystallization proceeds on the surface side of the powder and granules, which prevents the diffusion of water from the inside of the powder and granules to the surface and seals the water inside. In the above, it becomes a factor that the drying speed is suppressed. It should be noted that if the crystallization of the powdery or granular material is to be made uniform, the crystallization temperature may be lowered, but there is a problem that it takes a long time for the crystallization.

To solve the problem of fusion, there is a method of using a stirring blade and increasing the rotation speed to separate the powder or granules to be fused. There is a problem that occurs and the fusion problem cannot be solved.

The present invention is invented in view of the above problems, paying attention to the fact that heating by microwaves is heating from the inside of the object to be heated, and a powder or granular material mainly made of a synthetic resin material,
Heated by the microwave in a batch or continuous processing tank, the microwave accelerates the diffusion of moisture to the surface of the granular material by the internal heating of the granular material, and the crystallization from inside the granular material in the PET resin. And, by lowering the surface temperature of the powder or granules by supplying cooling air into the treatment tank, without causing agglomeration due to softening of the powder or granule surface or discoloration due to oxidation on the powder or granule surface, An object of the present invention is to provide a drying / crystallization apparatus capable of drying or crystallizing a powder or granular material mainly made of a synthetic resin material and performing dry crystallization in a short time as compared with drying or crystallization by hot air.

(Means for Solving the Problems) As shown in the embodiments of the drawings, the present invention is a device for drying and crystallizing powder particles made of a synthetic resin material, which comprises a material inlet (1
1) and a material outlet (12), and a treatment tank (1) disposed between the material inlet (11) and the material outlet (12). A microwave device (3) for irradiating and heating a powder or granular material inserted into (1) with a microwave, and a microwave device (3) disposed on the material outlet (12) side with respect to the microwave device (3), A cooling air supply device for supplying cooling air having a temperature lower than the surface temperature of the granular material to the granular material heated by the microwave irradiated from the microwave device (3) to lower the surface temperature of the granular material. (5) is provided.

(Function) In the above-described powdery-particle drying / crystallizing device, the microwave device (3) is applied to the powdery particles mainly composed of the synthetic resin charged into the processing tank (1) through the material inlet (11). The microwave is radiated to heat the powder and granules from the inside thereof to promote diffusion of moisture from the inside of the powder and granules to the surface of the powder and crystallization inside the powder and granules, and after irradiation with the microwave. The cooling air supply device (5) supplies cooling air having a temperature lower than the surface temperature of the powder particles heated by the microwave to the heated particles of the powder particles. The surface temperature of the powder and granules is removed, and the moisture on the surface of the powder and granules is removed. Therefore, the softening and melting of the surface of the powder and granules are avoided, the adhesion of the powder and granules to each other is prevented, and the surface of the powder and granules is prevented. By heating from the inside of the granular material without causing discoloration due to oxidation of It can be dried, crystallized rapidly granular material compared to the drying and crystallization by heat from the surface of the granular material by a conventional hot air.

(Example) Hereinafter, an example of a device for drying and crystallizing powder and granules according to the present invention will be shown, but the present invention is not limited thereto.

First, in the embodiment shown in FIG. 1, (1) in the figure is provided with a material inlet (11) and a material outlet (12) in the vertical middle part of opposite side walls and is made of a metal which reflects microwaves. In the treatment tank, a plurality of air blow holes (13) are provided on the bottom surface of the treatment tank (1) to be connected to a blower pipe (52) described later, and an air discharge hole (14) is provided in the upper ceiling. It is open to the atmosphere. In addition, near the center of the ceiling of the processing tank (1),
The waveguide (32) having a downward opening is provided, and the base thereof is provided with the controller (31) for controlling the microwave radiation output, and the microwave device (3) for radiating the microwave is provided.

Further, (4) is a flat conveyor, which is made of a material through which microwaves are transmitted and has an endless belt-like body (41) having a large number of holes through which air passes, and the belt-like body (41) is a material. From the inlet (11) to the material outlet (12) through the inside of the processing tank (1), and from the outlet (12) to the outside of the lower portion of the processing tank (1), the material inlet (11) ), One drive wheel (42) and a plurality of rotating wheels (43) are arranged.

The blower pipe (52) constitutes a cooling air supply device (5) together with a blower (51) whose suction port is open to the atmosphere,
By the air blow of the blower (51), cooling air is blown into the treatment tank (1) through a large number of air blow holes (13) connected to the air blow pipes (52), and the air discharge holes (14). ) To the outside of the processing tank (1).

Reference numeral (53) is an electric heater used for adjusting the temperature of air blown from the air blower (51), and controls the temperature of the cooling air according to the material to be dried.

(6) is a storage hopper for storing the dried or crystallized powder and granules, and is provided with a rotary feeder (61) at the lower part thereof. Further, (62) is a sensor of an automatic continuous moisture measuring device (63) for automatically measuring the moisture content of the powder or granular material in the storage hopper (6).

Further, although the flat conveyor (4) is arranged inside the treatment tank (1) and outside the tank (1) to move the granular material, the means for moving the granular material is not limited to this. Not a thing.

The above-mentioned embodiment is configured as described above, and can be used for drying or crystallization and drying / crystallization,
In use, when powder particles made of a synthetic resin material stored in the raw material hopper (21) are supplied to the conveyor (4) by a screw feeder (22), the processing tank (1) is sequentially driven by driving the conveyor (4). ) Inside,
The microwave radiated from the microwave device (3) is introduced into the processing tank (1) through the waveguide (32) to heat the powder and granular material of the conveyor (4) from the inside. Become.

On the other hand, a large number of ventilation holes (1
3) through the cooling air supply device (5) consisting of the air blower (51), the air blow pipe (52) and the like into the treatment tank (1) and heated from inside by the microwave. The temperature of the surface of the granular material is made lower than the internal temperature.
However, it promotes the diffusion of moisture to the surface of the inside of the granular material or the crystallization from the inside of the granular material, and lowers the surface temperature of the granular material, so avoiding softening and melting on the surface of the granular material. As a result, it is possible to prevent the particles from sticking to each other and prevent discoloration due to the oxidation of the surfaces of the particles.

Moreover, since water on the surface of the granular material can be removed, it is possible to quickly dry or crystallize the granular material.

The powder or granules dried or crystallized in this way are successively conveyed by the conveyor (4) to the material outlet (12) of the processing tank (1).
And is stored in a storage hopper (6) provided below the material outlet (12) and, if necessary, molded by pneumatic transportation from a rotary feeder (61) provided below the hopper (6). It is transported to a machine or a dryer provided separately. It is preferable to use dehumidified air as the cooling air because the cooling air removes the water content of the granular material.

Further, a temperature sensor (15) for continuously detecting the surface temperature of the granular material which is heated from the inside by the microwave and whose surface is cooled by the cooling air is provided, and the cooling air is based on the detection result. By controlling the flow rate of cooling air from the supply device (5), the temperature, the microwave radiation output of the microwave device (3), and the like, the powder or granular material can be dried or crystallized with higher efficiency. It is possible to do.

Next, FIG. 2 shows another embodiment, in which (1) is a vertical cylindrical processing tank formed of a material through which microwaves pass, and the upper part of the processing tank (1). A material inlet (11) and an air discharge hole (14) are provided at the bottom, and a material outlet (12) provided with a rotary feeder (61) is provided at the bottom. (16) is a cylindrical body formed of a metal that reflects microwaves, and the lower part of the cylindrical body (16) is the treatment tank (1).
And the outer peripheral surface of the processing tank (1) which vertically extends through the cylindrical body (16) and extends downward along the vertical direction of the processing tank (1). A waveguide (32) having a microwave device (3) having a controller (31) at the base end is provided in the cylindrical body (16) by providing an annular space (17) having a predetermined length around the It is connected to the side and opened to the annular space (17).

Further, (52) is a blower pipe for sending cooling air to the treatment tank (1), which is made to project into the treatment tank (1) at the lower extension of the cylindrical body (16), and the treatment is performed at the tip thereof. Tank (1)
An opening (54) that opens in a conical shape is provided downward at the center of the. Further, the other end of the blower pipe (52) is connected to a heater (5) in an air discharge hole (14) provided in the upper part of the processing tank (1).
3), dehumidifier (56), blower (51) and filter (5)
5) and the cooling air supply device (5) is constituted. A temperature sensor (34) is connected to the controller (31) of the microwave device (3).

Reference numeral (57) is a ventilation hole provided near the rotary feeder (61), which is connected to the ventilation pipe (52) through a valve (58) and is a powder particle retained in the lower portion of the treatment tank (1). It sends the air that carries the water of the body.

Further, (62) is a sensor of the automatic continuous moisture measuring device (63) for detecting the moisture of the powder or granular material accumulated in the lower portion of the processing tank (1).

With the above-described structure, the microwave radiated from the microwave device (3) is charged from the material inlet (11) into the processing tank (1) with a powder or granular material mainly made of a synthetic resin material. Is guided to the annular space (17) provided around the treatment tank (1) by the waveguide (32), while cooling air is blown from the opening (54) of the cooling air supply device (5), While heating the powder and granules from the inside by microwaves, the powder and granules are fluidized to form a fluidized bed, and by doing so, the powder and granules from the inside of the powder and granules are uniformly stirred by the microwave. Allows heating and lowering of the surface temperature of the granules, promotes diffusion of moisture from inside the granules to the surface and crystallization inside the granules, and avoids softening and melting on the surface of the granules. , Preventing the particles from sticking to each other and oxidizing the surface of the particles. Discoloration is prevented, and the cooling air is discharged from the air discharge hole (14), passes through the filter (55), the blower (51), the dehumidifying device (56) and the electric heater (53), and then the blower pipe (52). It returns to the inside of the processing tank (1) through the opening (54). The powder or granules staying in the lower part of the treatment tank (1) are discharged by a rotary feeder (61) which is appropriately operated without being fixed due to an increase in surface temperature due to the air blown from the air blow hole (57) and continuously dried or crystallized. It becomes possible. Also, the temperature sensor (3
The microwave device (3) based on the detection result of 4).
The microwave radiation output from the control unit is controlled to the optimum heating temperature according to the charged granular material, and the sensor (62) of the automatic continuous moisture measuring device (63) is installed in the lower part of the processing tank (1). By measuring the water content of the powder or granules staying, so that the value of this water content is constant, by controlling the controller (31) and the air volume of the cooling air, the temperature, the humidity and the staying amount of the powder or granules, This allows efficient drying or crystallization.

Although the cooling air supply device (5) constitutes a wind circulation path, it is not necessary to constitute a circulation path by opening the air discharge hole (14) to the atmosphere. The air may be taken into the blower (51).

Therefore, as an example of synthetic resin material, pellet size 2.5m
Nylon-6 having a water content of 21600 ppm before treatment and a target water content of drying (1000 ± 200) ppm of mφ × 2.5 mml was supplied to the drying / crystallization apparatus of the embodiment shown in FIG. 1 at 10 kg / hr. Then
Cooling air at room temperature is blown at a rate of 30 m ³ / hr and Table-1
The results shown in are obtained.

The above Table 1 shows that the heating from the inside of the granular material by microwaves and the reduction of the surface temperature of the granular material by the cooling air make it possible to dry in a significantly shorter time than the drying by the conventional hot air. This is an example showing that

FIG. 3 shows a batch-type embodiment for the purpose of crystallization. The treatment tank (1) has a circular cross section, its lower end is conical, and the cooling air supply device ( Ventilation hole (13) for blowing cooling air from 5) into the treatment tank (1)
Is equipped with. In addition, a material inlet (11) and an air discharge hole (14) are provided in the upper part of the processing tank (1), and a rotary shaft (upwardly and downwardly extending) having a plurality of blades (17) at one end ( 16) rotatably provided, the other end of which is connected to a drive device (not shown), and the drive device drives the drive device to load the PET particles into the treatment tank (1) from the material inlet (11). The body is allowed to stir as needed.
Further, (19) is an isolation wall made of a synthetic resin capable of transmitting microwaves, and (32) is a waveguide connected to one side of the processing tank (1). The processing tank (1)
Although the partition wall (19) provided at the connection portion with is permeable to microwaves, it prevents the powder or granules charged into the processing tank (1) from entering the waveguide (32). Further, the controller (31) and the microwave device (3) are provided at the base of the waveguide (32). Further, (10) is a partition plate made of punching metal provided at the upper end of the conical portion in the treatment tank (1), and the blower hole (1
It allows the cooling air from 3) to pass and prevents the powder particles from falling down.

Further, the embodiment shown in FIG. 4 is one in which a powdery material made of PET resin which is a crystallization resin can be continuously crystallized and dried in one treatment tank. The processing tank (1) shown is extended downward and the rotary shaft (1
6) is also extended downward, and a stirring blade (17) similar to that shown in FIG. 3 is provided at the upper portion, and a plurality of stirring rods (18) are provided at the downwardly extended portion. It should be noted that the stirring operation of the powder and granules by the stirring rods (18) is made weaker than the stirring operation of the blades (17) which is performed only for crystallization to avoid unnecessary stirring of the powder and granules. The generation of dust due to long-term stirring operation of the powder and granules is suppressed.

Next, when an uncrystallized PET resin composed of pellets having a size of 2 to 3 mmφ and a water content of 2160 ppm was crystallized by the batch type drying / crystallization apparatus shown in FIG. 3 and the conventional example,
The results are shown in Table-2. In addition, after each crystallization treatment, using a conventional drying device with hot air, the drying temperature
After drying at 150 ° C. for 3 hours, the results shown in Table 3 below were obtained.

As is clear from Table 2, when the PET resin is crystallized by the drying / crystallizing apparatus according to the present invention, the time required for crystallization is shorter than that of the conventional low temperature method (10
Moreover, in the case of crystallization by the high temperature method of the conventional example, the water content at the end of the drying time is 73 PPm and does not reach the target water content of 50 PPm or less, but according to the present invention, the low temperature method is used. Similarly, the target water content was 33PPm, which is lower than 50PPm.

Incidentally, when the uncrystallized PET resin having the same size and water content was dried together with crystallization by the drying / crystallization apparatus shown in FIG. 4, the water content could be 52 PPm in 70 minutes. Therefore, the drying time can be remarkably shortened as compared with the case of using a conventional drying device using hot air after crystallization.

(Effects of the Invention) As described above, according to the powdery-particle drying / crystallization apparatus of the present invention, the powdery-particles are heated from the inside by the microwave radiated from the microwave device (3). Diffusion of moisture from the inside of the powder to the surface, or in crystallization of PET resin promotes crystallization from inside the powder, and to the heated powder after irradiation with the microwave. Since the cooling air supply device (5) supplies cooling air having a temperature lower than the surface temperature of the powder or granules whose temperature has risen as a result of being heated, the surface temperature of the powder or granules is equal to or smaller than that of the microparticles. With heating by the irradiation of waves, the temperature can be suppressed to a temperature lower than the temperature at which it becomes sticky, and the water content on the surface of the granular material can be removed. Therefore, avoiding softening and melting on the surface of the granular material. , Preventing the particles from sticking to each other, and Since it is possible to prevent the discoloration of the surface of the powder or granules due to oxidation, therefore, the clogging of the punching metal found in the conventional drying and crystallization apparatus with hot air while being capable of rapid drying and crystallization, and the powder and granules It is possible to effectively dry and crystallize without concern about uneven drying or crystallization due to sticking.

In the case of the PET resin of the present invention, it can be used only for crystallization, but it can be dried at the same time as crystallization.

Therefore, it is not necessary to separately use the crystallization device and the drying device as in the conventional example, and thus it is possible to reduce the equipment cost and the equipment space.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, and FIG.
FIG. 3, FIG. 3 and FIG. 4 are schematic sectional explanatory views showing other embodiments. (1) …… Treatment tank (3) …… Microwave device (5) …… Cooling air supply device

Claims (1)

[Claims] 1. A device for drying and crystallizing a granular material made of a synthetic resin material, comprising a processing tank (1) having a material inlet (11) and a material outlet (12), and the material inlet (11). ) And the material outlet (12), and a microwave device for irradiating and heating microwaves to the granular material inserted from the material inlet (11) into the treatment tank (1) ( 3) and the powder granules disposed on the material outlet (12) side with respect to the microwave device (3) and heated by the microwaves emitted from the microwave device (3), A drying / crystallizing device for powdery or granular material, comprising: a cooling air supply device (5) for supplying a cooling air having a temperature lower than the surface temperature of the body to lower the surface temperature of the powdery or granular material.