JPH01163006A - Drying and crystallizing device for powdery and granular material - Google Patents

Abstract

PURPOSE:To eliminate discoloration caused by solidifying or oxidization generated by softened surface of a powdery or granular material and dry or crystallize the same in a short time by radiating microwaves to powdery or granular material composed mainly of synthetic resin put in from a material inlet into a treating tank and feeding the surface of the powdery or granular material with cooling air of low temperature while the powdery or granular material is heated from its inside. CONSTITUTION:When a powdery or granular material composed of a synthetic resin material stored in a raw material hopper 21 is fed into a conveyor 4 by a screw feeder 22, said material is fed into a treating tank 1 successively by driving the conveyor 4, And microwaves radiated from a microwave device 3 are introduced into the treating tank 1 through a waveguide 32 to heat up the powdery or granular material in the conveyor 4. On the other hand, cooling air is introduced from a cooling air feeding device 5 constituting of a blower 51, a blowing tube 52 and the like, through a number of blast holes 13... provided at the bottom of the treating tank 1, into the treating tank 1, and the surface temperature of the powdery or granular material heated up from inside by microwaves is adjusted to be lower than the temperature of the inside.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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 and melts when the temperature rises, if the water content of the resin material exceeds a certain value, the molding conditions may change. Not only is this difficult, but the physical properties of the molded product deteriorate, so resin materials are usually dried at a temperature of 70°C to 180°C to keep the water content below a certain value. For example, in the case of polycarbonate, o
, oi% or less, or in the case of polyester terephthalate (hereinafter referred to as PET resin), it was necessary to have a water content of 0.005% or less.

In particular, when drying the powder of PET resin, which is a crystalline synthetic resin, the general synthetic resin has a temperature of 20 to 30% lower than its melting point.
Whereas PET resin becomes sticky at temperatures much lower than its melting point, e.g.
C. PET resin becomes sticky at a temperature about 150.degree. C. lower than its melting point, that is, about 100.degree. However, in the case of PET resin, even when heated to 100°C or higher, the surface of the powder becomes sticky, but at the same time the crystallization of the PET resin progresses, and the crystallization rate is about 20%. The adhesion of the powder surface is reduced and no longer shows adhesion.

Also, the time required for crystallization is much less than the time required for drying. Therefore, the time required for crystallization of the powder or granule is longer than the time required to dry the powder or granule made of PET resin until the water content reaches 0005% or less, which is required during molding. Since the length is relatively short, a so-called two-stage process is performed in which the crystallization process is first performed and then the drying process is performed. In other words, by first crystallizing the powder, the temperature at which the surface of the powder becomes sticky is raised, and the drying process, which is the post-processing, can be performed at as high a temperature as possible, and the time required for the drying process is increased. This shortens the time required for drying the PET resin as a whole. 'However, conventional equipment for drying or crystallizing the powdered material made of the synthetic resin material has been equipped with a punching metal at the bottom of a hopper with a discharge port at the bottom. Hot air is supplied from below, and the resin material inside the hopper is agitated by an agitator attached to a rotating shaft facing vertically in the center of the hopper to dry or crystallize the resin material. equipment is provided.

Moreover, without using the punching metal, a hot air supply pipe directed in the vertical direction is installed in the center of the hob par,
There has also been provided a drying/crystallization apparatus in which the lower end of the supply pipe is opened downward into the hopper to supply hot air into the hopper.

(Problems to be Solved by the Invention) Generally speaking, when drying foods that have a porous or layered structure and contain a large amount of water, water moves from the inside of the food to the surface by capillary action and evaporates on the surface. Since it is a constant rate drying method, it is possible to suppress the rise in surface temperature.
Drying of materials with a uniform structure, such as synthetic resin materials, is a lapse rate drying process in which water diffuses and moves from the inside of the material to the surface, so we cannot expect a large amount of water to evaporate to suppress the rise in surface temperature. . Therefore, in lapse rate drying, a higher drying temperature promotes water diffusion and increases the drying speed.
When drying 11,000 pp of Opp ■ nylon-8, it takes about 13 hours at a hot air temperature of 90°C, but it takes 7 hours at 100°C and 4 hours at 110°C (but it can be dried faster by increasing the air blowing temperature. Also, PE
The same is true when crystallizing T resin; for example, it takes about 2 hours at a hot air temperature of 120°C, but only 1 hour at 170°C.
It takes about 0 minutes.

However, there is a limit to how high the drying temperature can be raised.

In other words, when the temperature of the hot air used to dry powder and granules made of synthetic resin material is set higher than a certain temperature relative to the melting point, the surfaces of the powder and granules soften and fuse with each other, making it possible to uniformly dry the particles with hot air. Otherwise, the surface would become oxidized and colored, making it unusable as a molding material, so it was not possible to significantly shorten the drying time by increasing the temperature of the hot air.

The same is true when crystallizing powder or granules made of PET resin in a short period of time; heating at a temperature higher than a certain level above the melting point will cause problems with melting, and heating with hot air will Since heating is applied from the outside, crystallization proceeds first on the surface side of the powder, preventing moisture from diffusing from the inside of the powder to the surface, trapping moisture inside, and reducing the drying process that takes place later. This is a factor that suppresses the drying rate. Incidentally, in order to uniformly crystallize the powder, the crystallization temperature may be lowered, but there is a problem in that crystallization takes a long time.

In addition, to solve the problem of melting, there is a method of using stirring blades and increasing the rotation speed to separate the powder and granules that are trying to fuse, but this method causes the powder and granules to become fine and dust Due to the problems that occur, the problem of fusion cannot be solved.

The present invention was invented in view of the above-mentioned problems, and it focuses on the fact that heating by microwaves heats the object to be heated from the inside.
Promotion of diffusion of moisture to the surface of the powder or granule by internal heating of the powder or granule by the microwave in a batch or continuous processing tank, and crystallization of the PET resin from the inside of the powder or granule into the processing tank. By supplying a cooling air of It is an object of the present invention to provide a drying crystallization apparatus capable of drying or crystallizing a powder mainly made of a synthetic resin material and dry crystallizing it in a short time compared to the conventional method.

(Means for Solving the Problems) As shown in the embodiments of the drawings, the present invention is an apparatus for drying and crystallizing powder and granules made of a synthetic resin material, which includes a material inlet (1
1) and a treatment tank (1) with a material outlet (12), and the treatment 4! (1) A microwave device (3) that radiates microwaves to the powder and granules in the microwave device (3) and a cooling air whose temperature is lower than the surface temperature of the powder and granules heated by the microwaves emitted from the microwave device (3). It is characterized by being equipped with a cooling air supply device (5) that supplies cooling air and lowers the surface temperature of the powder or granular material.

(Function) However, in the drying/crystallization apparatus for powder and granular materials described above, the microwave device (3) is used to charge the powder and granular materials mainly made of synthetic resin into the processing tank (1) from the material inlet (11). By radiating microwaves to heat the powder or granular material from inside, while supplying cooling air from the cooling air supply device (5) at a temperature lower than the surface temperature of the powder or granular material heated by the microwave, Since the surface temperature of the granular material is lowered and moisture on the surface of the granular material is removed, softening and melting on the surface of the granular material is avoided, and adhesion of the granular materials to each other is prevented, and By heating from inside the powder without causing discoloration due to oxidation on the powder or granule surface, the powder or granule can be dried more quickly than conventional drying and crystallization by heating from the surface of the powder or granule using hot air.・It can be crystallized.

(Example) Examples of the apparatus for drying and crystallizing powder and granular materials according to the present invention will be shown below, but the present invention is not limited thereto.

First, in the embodiment shown in FIG. 1, (1) in the figure is a metal material that has a material inlet (11) and a material outlet (12) in the vertical middle part of opposing side walls, and that reflects microwaves. The processing tank (1) is provided with a plurality of ventilation holes (13) on the bottom surface and connected to a ventilation pipe (52) to be described later, and an air discharge hole (14) is provided on the upper ceiling. hand,
It is open to the atmosphere. Further, near the center of the ceiling of the treatment tank (1), a waveguide (32) opening downward is provided, and a controller (31) for controlling the microwave radiation output is provided at the base of the waveguide (32). A microwave device (3) that emits waves is provided.

Further, (4) is a flat conveyor, which is made of a material through which microwaves can pass and has an endless cane strip (41) with a large number of holes through which air passes; From the inlet (11) through the inside of the processing tank (1) to the material outlet (12), and from the outlet (12) to the processing tank (1).
one driving wheel (42) and a plurality of rotating wheels (43) passing through the lower part of 1) and returning to the material inlet (11);
. . .

Further, the blow pipe (52) constitutes a cooling air supply device (5) together with a blower (51) whose suction port is open to the atmosphere, and the cooling air is processed by the air blowing from the blower (51). Air is blown into the tank (1) through a large number of air holes (13) connected to the air pipe (52), and is discharged to the outside of the processing tank (1) through the air exhaust hole (14). be.

Note that (53)' is an electric heater used to adjust the temperature of the air blown from the blower (51), and controls the temperature of the cooling air depending on the material to be dried.

(6) is a storage hopper for storing dried or crystallized powder and granules, and a rotary feeder (61) is installed at the bottom of the storage hopper.
It is equipped with Furthermore, (82) said storage hopper (6
) This is a sensor of the automatic continuous moisture measuring device fi (83) that automatically measures the moisture content of powder and granular materials in ).

Further, the flat conveyor (4) is arranged inside and outside the processing tank (1) to move the powder and granules, but the means for moving the powder and granules is limited to this. It's not a thing.

The above embodiment is configured as described above and can be used for drying or crystallization and drying/crystallization.
In use, the powder made of synthetic resin material stored in the raw material hopper (21) is transferred to the screw feeder (22).
When supplied to the conveyor (4), the conveyor (4) is driven to sequentially enter the processing tank (1),
Microwaves emitted from the microwave device ff (3) are introduced into the processing tank (1) via a waveguide (32) to heat the powder and granular material on the conveyor (4) from inside. become.

On the other hand, a large number of ventilation holes (1) are provided at the bottom of the processing tank (1).
3) Cooling air is blown into the processing tank (1) from a cooling air supply device (5) consisting of an air blower (51), an air pipe (52), etc. via... and heated from the inside by microwaves. The temperature at the surface of the powdered material is lower than the internal temperature. Therefore, while promoting the diffusion of moisture inside the powder to the surface or crystallization from inside the powder,
In addition, the temperature of the surface of the powder is suppressed to prevent the powder from sticking due to surface softening, and discoloration due to surface oxidation is prevented.Moreover, since the cooling air removes moisture on the surface of the powder, This enables rapid drying or crystallization of the powder.

The powder and granules dried or crystallized in this way are sequentially transported by the conveyor (4) to the material outlet (1) of the processing tank (1)'.
2) and stored in a storage hopper (8) provided below the material outlet (12), and if necessary, pneumatically transported from a rotary feeder (61) provided at the bottom of the hopper (6). It is transported to a molding machine or a separate dryer. Note that since the cooling air removes moisture from the powder, it is preferable to use dehumidified air as the cooling air.

Furthermore, a temperature sensor (15) is provided that continuously detects the surface temperature of the powder, which is heated from the inside by the microwave and whose surface is cooled by the cooling air. Volume of cooling air from supply device ra' (5),
By controlling the temperature and the microwave radiation output of the micro-arytenoids r11(3), it becomes possible to dry or crystallize the powder with even higher drying or crystallization efficiency.

Next, FIG. 2 shows another embodiment, in which (1) is a vertical cylindrical processing tank made of a material that transmits microwaves, and the upper part of the processing tank (1) is Material entrance (11)
and an air exhaust hole (14), and a material outlet (12) with a rotary feeder (61) at the bottom. (16) is a cylindrical body formed of a metal that reflects microwaves, and the lower part of the cylindrical body (16) extends downward along the processing tank (1).
B) and the processing tank (
1), a ring core space (17) having a predetermined length is provided around the vertical center of the processing tank (1), and a microwave equipped with a controller (31) at the base end is provided. A waveguide (32) with a device (3) is connected to the cylinder (16).
It is connected to the - side of the annular space (17) and opens into the annular space (17).

Further, (52) is a blower pipe for sending cooling air to the processing tank (1), which is inserted into the processing tank (1) at the lower extension part of the cylindrical body (16), and the tip of the pipe is configured to send cooling air to the processing tank (1). Tank (
1) an opening (54) that opens downward into the conical cane in the center;
We will set up the following. Furthermore, a heater (53), a dehumidifier (56), a blower (51), and a filter (55) are connected to the air exhaust hole (14) provided at the top of the processing tank (1) at the other end of the blast pipe (52). Connect through the cooling air supply device (
5). (34) is a temperature sensor,
Said microwave 1i? ff1 (3) controller (31
).

Further, (57) is a ventilation hole provided near the rotary feeder (61), which is connected to the ventilation pipe (52) via a valve (58), and is used to remove powder particles staying at the bottom of the processing tank (1). It sends air that carries water in the body.

Further, (82) is a sensor of an automatic continuous moisture measuring device (θ3), which detects the moisture of the powder and granular material staying at the bottom of the processing tank (1).

With the above structure, powder and granules mainly made of synthetic resin material are charged into the processing tank (1) through the material inlet (11), and microwaves are emitted from the microwave device (3). into the processing tank (1) by the waveguide (32).
into an annular space (17) provided around the cooling air supply device (5), while blowing cooling air from the opening (54) of the cooling air supply device (5).
The powder and granules are heated from the inside using microwaves, and the powder and granules are fluidized to form a fluidized mass. By doing so, while forcibly stirring, the powder and granules are uniformly heated from the inside by microwaves. By heating the powder and lowering the surface temperature of the powder, it prevents agglomeration due to softening of the surface of the powder and discoloration due to oxidation, while removing moisture from the powder or crystallizing from inside the powder. The cooling air is passed through the air exhaust hole (
14), filter (55) and blower (5).
1), the processing tank (
1) Go back within. The powder and granules staying in the lower part of the processing tank (1) are discharged by the rotary feeder (61) which is operated as appropriate, and are continuously dried. Or crystallization becomes possible.Also, the temperature sensor (
Based on the detection result of the microwave device (34),
) to set the optimum heating temperature according to the powder and granular material to be charged, and the lower part of the processing tank (1) is controlled by the sensor (62) of the automatic continuous moisture measuring device (63). The controller (3) measures the moisture content of the powder and granules remaining in the
1) Efficient drying or crystallization can be performed by controlling the volume of cooling air, temperature, humidity, and amount of granular material retained.

Although the cooling air supply device (5) constitutes a wind circulation path, by opening the air exhaust hole (14) to the atmosphere, it is not necessary to constitute a circulation path, and the air Air may be introduced into the blower (51) from above.

Therefore, as an example of synthetic resin material, pellet size 2.
5■■φ×2.5■■ history and moisture content before treatment 216
00 pI) IN dry target moisture content (1000±200
) ppm of nylon-6 was supplied at a rate of 10 kg/hr to the drying/crystallization apparatus of the example shown in Figure 1, and cooling air at room temperature was blown at a rate of 30 m'/hr. The following results were obtained.

Below, the margin continues on the next page.

Table-1 *The time the powder and granules stay in the processing tank Table 1 shows the amount of time that the powder and granules stay in the processing tank by heating the powder and granules from inside using microwaves and lowering the surface temperature of the powder and granules using cooling air. This is an example showing that drying can be done in a significantly shorter time than conventional drying using hot air.

Figure 3 shows a batch type embodiment for the purpose of crystallization, in which the processing tank (1) has a circular cross section, its lower end is conical, and a cooling air supply device ( 5) into the processing tank (1).
). Furthermore, a material inlet (11) and an air exhaust hole (14) are provided in the upper part of the processing tank (1), and a rotating shaft ( 16) is provided to be freely rotatable, and the other end is connected to a drive device (not shown), and by driving the drive device,
The granular material made of PET resin charged into the processing tank (1) from the material inlet (11) can be stirred as necessary. Further, (19) is a separation wall made of synthetic resin through which microwaves can pass, and (32) is a separation wall made of synthetic resin that allows microwaves to pass through.
1) is a waveguide connected to the negative side of the waveguide (32
) is provided at the connection part with the processing tank (1).
9) allows microwaves to pass through, but prevents the granular material to be 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). This is a partition plate made of punched metal provided at the upper end, and allows the cooling air from the ventilation hole (13) to pass therethrough, and prevents the powder from falling downward.

The embodiment shown in FIG. 4 is one in which a powder made of PET resin, which is a crystallized resin, can be continuously crystallized and dried in one treatment tank. The shown treatment tank (1) is extended downward and 1. The rotating shaft (16) also extends downward, and the upper portion thereof is provided with a stirring blade (17) similar to that shown in FIG. 3, and the downward extension is provided with a plurality of stirring rods (18)... There is. The stirring operation of the powder and granular material by the stirring rod (18) is made weaker than the stirring action of the blade (17), which is performed only for the purpose of crystallization, so that the stirring operation of the powder and granular material is less than necessary. This prevents dust from being generated when the powder or granules are subjected to long-term stirring operations.

Next, size 2 = 3s φ, water content n2180PP
When the uncrystallized PET resin consisting of the pellets of (1) was crystallized using the batch type drying/crystallization apparatus shown in FIG. 3 and the conventional example, the results shown in Table 2 were obtained. Further, after each crystallization treatment, drying was performed for 3 hours at a drying temperature of 150° C. using a conventional hot air drying device, and the results shown in Table 3 below were obtained.

Table 2 Table 3 As is clear from Table 2, when PET resin is crystallized using the drying/crystallization apparatus according to the present invention, the time required for crystallization is longer than that of the high temperature method compared to the conventional low temperature method. Similarly, for a short time (
10 minutes), and in the case of crystallization by the conventional high temperature method, the water content at the end of the drying time was 73 PPm.
However, the water content does not reach the target water content Q50PPm or less.
According to the present invention, the target water content is 1150 PPm as in the low temperature method.
This resulted in a lower level of 33 PPm.

Furthermore, when uncrystallized PET resins of the same size and water content were dried together with crystallization using the drying/crystallization apparatus shown in Figure 4, the water content could be reduced to 52 PPm in 70 minutes. Therefore, the drying time can be significantly shortened compared to the case of using a conventional drying device using hot air after crystallization.

(Effects of the Invention) As explained above, according to the drying/crystallization apparatus of the present invention, instead of the conventional drying or crystallization using hot air, the microwave radiated from the microwave device (3) A cooling air supply device heats the powder or granule from inside by waves, promoting the diffusion of moisture from inside the powder to the surface or, in the case of crystallization of PET resin, crystallization from the inside of the powder. By supplying cooling air at a temperature lower than the surface temperature of the granular material heated by microwaves from (5), the surface temperature of the granular material is suppressed and moisture on the surface of the granular material is removed.
Since it does not cause softening of the powder surface, viscosity of the powder due to melting, and discoloration due to surface oxidation, clogging of the punching metal that occurs in conventional hot air drying/crystallization equipment and There is no concern about uneven drying or crystallization due to sticking (it can be dried or crystallized in a significantly shorter time than heating with hot air, and therefore drying or crystallization can be performed in a continuous operation). Moreover, by operating continuously, the number of conventional drying and crystallization equipment can be reduced and the remaining space can be used for other purposes.

Furthermore, in the case of PET resin, the present invention can be used only for its crystallization, but it can also be used for drying at the same time as crystallization.

Therefore, it is no longer necessary to use a crystallization device and a drying device separately as in the conventional example, thereby reducing equipment costs and equipment space.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional explanatory diagram showing one embodiment of the present invention, and FIG.
3, and 4 are schematic cross-sectional explanatory views showing other embodiments. (1)...Processing tank (3)...Microwave device (5)...Cooling air supply v2 position

Claims (1)

[Claims] A drying/crystallization device for powder and granules made of synthetic resin material, including a processing tank (1) equipped with a material inlet (11) and a material outlet (12), and a powder in the processing tank (1). A microwave device (3) that emits microwaves to the body, and the microwave device (
3) A cooling air supply device (5) that supplies cooling air at a temperature lower than the surface temperature of the powder or granule heated by the microwave emitted from the granule to lower the surface temperature of the powder or granule. Characteristic drying and crystallization equipment for powder and granular materials.