JPH0813462B2 - Method and apparatus for pressure swing hot air drying of resin material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel hot-air drying method using a pressure swing and an apparatus used for carrying out this drying method.

[Conventional technology]

The resin material used for resin molding needs to be appropriately dried before being processed by a molding machine.If the drying is insufficient or the dried state is uneven, the quality of the resin molded product will deteriorate. Will end up.

Therefore, conventionally, a so-called hot air type drying method has been adopted in which a dryer is provided in a hopper containing a resin material, and hot air is blown from a lower portion of the hopper with a blower or the like to dry the resin material.

However, in such a conventional hot-air drying method, when the hot-air temperature is raised or the air volume is increased, the resin material suffers from physical property changes such as oxidation and yellowing. Further, when the temperature is low, changes such as oxidation and yellowing can be prevented to some extent, but it takes a long time to dry, so that there is a problem that efficiency decreases.

Therefore, in order to shorten the drying time, a method of reducing the partial pressure of water vapor existing inside the hopper by reducing the pressure inside the hopper to dry with hot air is also considered, but reducing the inside of the hopper to dry with hot air. In this case, the dry gas introduced from the gas inlet creates a constant short-circuit path and moves to the exhaust port, which causes a problem that the temperature of the resin material is uneven and the quality of the molded product is deteriorated.

Further, generally, during resin molding in which a resin material is melted and molded by a molding machine, unnecessary gas is likely to be generated during melting, and if this gas is left as it is, gloss may be deteriorated depending on the resin material. , The surface is rough,
It deteriorates the quality.

By the way, as such a countermeasure, there is a vent pipe provided near the connection part with the molding machine at the lower part of the hopper to suck and discharge gas. However, the vent pipe is used to degas the resin material. In this case, the suction action of the vent pipe causes the pellet to enter the vent pipe and be blocked.

[Problems to be Solved by the Invention] The present invention has been achieved as a result of intensive studies by the present inventors in order to solve the above problems. An object of the present invention is to provide a good hot-air drying method and a drying device that can effectively carry out the drying method.

A second object of the present invention is to provide a hot-air drying method capable of preventing uneven drying, good drying efficiency, and also capable of efficiently removing harmful gas generated during resin molding, and an apparatus capable of carrying out the drying method. It is in.

[Means for Solving the Problems] The present invention proposed to achieve the above object includes a plurality of related inventions, and the first invention is such that a hopper containing a resin material is heated. In the hot air drying method in which the exhaust gas generated by the introduction of the dry gas is discharged from the hopper while the dry gas is introduced, and the resin material contained in the hopper is dried by hot air, particularly, the dry gas. While introducing into the hopper, the steps of depressurizing and pressurizing the inside of the hopper are alternately repeated.

The second invention alternately performs a step of depressurizing and pressurizing the inside of the hopper while introducing a dry gas into the hopper. In the depressurizing step, a negative pressure is applied to the inside of the hopper so that the inside of the molding machine is pushed from below the hopper. The generated gas is sucked and discharged, while the pressurizing step is characterized in that the inside of the hopper is set to a positive pressure and the dry gas is introduced into the hopper.

A third aspect of the present invention relates to a hot-air type drying device that implements the first aspect of the present invention, in which a gas introduction port and an exhaust port provided in a hopper are connected to a gas supply source to form a dry gas distribution line, and The dry gas distribution line is provided with pressure adjusting means for adjusting the air amount or the air pressure of the dry gas and / or the exhaust gas flowing through the dry gas distribution line to control the internal pressure of the hopper to be positive or negative. The pressure adjusting means provided in the gas distribution line is switched and controlled at a predetermined timing to alternately pressurize and depressurize the inside of the hopper to perform hot air drying.

A fourth aspect of the present invention relates to a hot-air type drying apparatus that implements the second aspect of the present invention, in which the hopper is provided with an exhaust port and a drying gas inlet port and sucks gas generated inside the molding machine. A gas suction port for forced discharge is provided in the lower part, and it is configured to be placed above the molding machine.The gas introduction port and the exhaust port are connected to a gas supply source to form a dry gas distribution line. The dry gas flow line is provided with pressure adjusting means for switching and adjusting the air amount or air pressure of the dry gas and / or the exhaust gas flowing through the dry gas flow line to control the internal pressure of the hopper to be positive or negative. The suction port is connected to a gas suction source via a gas withdrawal control means for withdrawing gas, and by controlling the pressure adjusting means and the gas withdrawal control means at predetermined timing, molding is performed when the molding machine operates. On board While in the resulting gas was sucked and discharged, pressurized alternately inside the hopper, by reduced pressure is configured to perform the hot-air drying.

In the method of the present invention having the above characteristics, the pressurization and depressurization of the hopper are such that the supply amount of the dry gas into the hopper and / or the supply pressure or the discharge amount of the exhaust gas outside the hopper and / or
Alternatively, the configuration can be controlled by changing the discharge pressure (fifth invention), and when the hopper is mounted on an injection molding machine or the like and used, pressurization and depressurization in the hopper are performed. The switching control can be performed in conjunction with the operation process of the molding machine on which the hopper is placed (sixth invention).

[Operation] According to the present invention, there is the following unique operation. That is, in the first invention, while supplying the heated dry gas into the hopper, the inside of the hopper is alternately pressurized and depressurized at a specific timing. Therefore, when the hopper is in a depressurized state, When the partial pressure of water vapor is reduced and drying is carried out quickly, and when the hopper is in a pressurized state, the heated drying gas introduced into the hopper diffuses into the resin layer and heats it to a uniform temperature, so uneven drying occurs. It never happens.

That is, in the first aspect of the present invention, the inside of the hopper containing the resin material is pressure-swinged at a specific timing, and the drying unevenness, which is a defect at the time of depressurization, is eliminated at the time of pressurization, and the defect at the time of pressurization is eliminated. The deterioration of the quality is eliminated when the pressure is reduced, and as a result, the drying efficiency is good and ideal hot air drying without unevenness in drying is realized.

Further, in the present invention, the pressure inside the hopper is swung, and a shock due to the external environmental pressure is forcibly applied to the resin material housed inside the hopper. Therefore, the film coefficient of the resin material becomes large, and highly efficient drying is achieved. Is performed.

According to the results of experiments conducted by the present inventors in order to confirm the effect of the present invention, it was confirmed that the time was shortened by 4 times or more as compared with the conventional hot air drying method, and it was proved that the hot air drying method is extremely efficient. .

In the second invention method, during hot air drying, the gas generated inside the molding machine is removed from the lower part of the hopper at the same time, so the harmful gas generated during the operation of the molding machine is removed, and the quality of the molded product deteriorates. To be prevented.

Further, the action of alternately pressurizing and depressurizing the inside of the hopper by the pressure swing is the same as that of the first invention.

In the third invention, the first invention method is effectively implemented, and in the fourth invention, the second invention method is effectively implemented.

In particular, in the third invention, the pressure swing inside the hopper is controlled by switching the pressure adjusting means provided in the dry gas flow line formed by connecting the gas inlet and exhaust port of the hopper to the gas supply source. This pressure adjusting means is performed by changing the air flow rates or air pressures of the dry gas and the exhaust gas. Further, in the fourth invention, in addition to the switching control of the pressure swing in the third invention, by controlling the pressure withdrawal control means to suck and discharge from the lower part of the hopper, the gas is dried during hot air drying. Can also be removed.

In the fifth invention, the inside of the hopper can be pressurized and depressurized by controlling the supply amount and supply pressure of the dry gas and the discharge amount and discharge pressure of the exhaust gas. In the sixth invention, the pressure swing of the hopper is formed. It is controlled in conjunction with the operation process of the machine.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a basic configuration of a hot-air type drying device which is a third invention of the present invention.

In the figure, A is a hopper that contains a resin material (not shown), and an inlet 1 and an outlet 2 for the dry gas are provided in the upper part of the hopper. The inlet 1 is an air supply conduit 31 and the outlet 2 is It is connected via an exhaust line 32 to a ring blower 4 provided in the gas supply source B, which forms a dry gas flow line (D). Further, a control valve 5 is connected to the discharge port of the ring blower 4, and an opening valve 10 connected in parallel with the control valve 5 is closed, and when the control valve 5 is opened to drive the ring blower 4, drying is performed. The gas is pumped into the hopper A and the inside of the hopper A has a positive pressure. Conversely, when the opening valve 10 is opened and the control valve 5 is closed, the supply of the dry gas into the hopper A is stopped and the exhaust gas is sucked. As the amount increases, the inside of the hopper A becomes negative pressure.

In this embodiment, the valve 5 provided at the discharge port of the ring blower 4 constitutes the pressure adjusting means. However, a vacuum pump is provided at the gas supply source B to make the air volume of the dry gas constant and to supply the supply pressure. The configuration may be changed, and an ejector or the like may be added to the dry gas distribution line (D) to change the pressure inside the hopper A to positive or negative.

In this example, the dry gas supplied from the gas supply source B was heated by the heater 6 and then supplied into the hopper A through the inlet 1 to dry the resin material through the resin layer in the hopper A. The dry gas is configured to return from the exhaust port 2 to the gas supply source B through the exhaust pipe line 32.

As the dry gas used in the present invention, dry air is used for ordinary resin materials, but an inert gas such as nitrogen gas is used for resin materials that do not like to be oxidized during dry heating. Gas is used.

Next, the method of the present invention when the apparatus of the present invention having the above-mentioned configuration is used will be described.

A feature of the first invention of the present invention is that when a drying gas is introduced into the hopper to dry the resin material contained in the hopper A with hot air, the step of pressurizing and depressurizing the inside of the hopper A is repeated. In the apparatus shown in the embodiment, the control valve 5 constituting the pressure adjusting means is opened during the pressurizing step, and the control valve 5 is closed during the pressure reducing step.

Further, the pressurization and depressurization steps in the present invention should be understood as mutually opposing concepts, and the depressurization step has the meaning of reducing the partial pressure of water vapor inside the hopper A to shorten the drying time. Therefore, it is desirable to obtain a pressure sufficiently lower than the normal pressure. However, the pressurizing process does not cause a short circuit in the dry gas introduced into the hopper A as compared with the depressurizing process. Any material can be used as long as it can diffuse sufficiently, and the concept may include normal pressure.

FIG. 2 shows a device according to the fourth aspect of the present invention. In addition to the configuration of the second aspect of the invention shown in FIG. Gas suction port 7
Is connected to a gas supply source B by an intake line 8, and a control valve 9 constituting a gas extraction control means D is provided in this line 8. Further, the hopper A is configured to be directly placed on the molding machine C.

In the apparatus of the fourth invention having such a configuration, in the pressurizing step of the hopper A, uniform heating can be performed in order to effectively diffuse the heated dry gas in the hopper A, and in the depressurizing step, the molding machine can be used. The harmful gas generated inside C is extracted. By the way, what is important in such an apparatus is that when the gas inside the hopper A is decompressed and the gas is extracted, the heated dry gas accumulated in the hopper A is unnecessarily sucked and released to prevent heat radiation. In consideration of this point, the apparatus of (1) sets the pressure value when the hopper A is depressurized.

FIG. 3 is a block diagram more specifically showing the drying apparatus of the fourth invention shown in FIG.

 In this embodiment, air is used as the dry gas.

In the figure, A is a hopper main body, which has a double wall structure in which an inner wall 17 is provided inside an outer wall 16, and a cone-shaped bottom portion (lower portion) of the hopper A and a main body portion are separated by a partition wall 18. .

On the upper side wall of the hopper A, a dry gas inlet 11
a and the exhaust port 11b are provided, and the resin material 30
.. is provided with a material input port 12 for inputting, and a discharge port 19 for discharging the stored resin material 30 ... Is provided in the lower part.

The inlet 11a for the dry gas is an inlet tube 1 having a heater 15 built-in.
4, the other end opening of the introduction pipe 14 reaches almost the bottom of the hopper A. The heater 15 has a dry gas inlet 11
The dry air introduced from a is heated to a high temperature.

The exhaust port 11b is used to discharge the exhaust gas generated by the dry gas heated by the heater 15 from the dry gas introduction port 11a through the resin material of the hopper A.
Connected to 28.

Reference numeral 13 is a gas suction port provided in the lower part of the hopper A for sucking and discharging the gas generated inside the molding machine when the hopper A is placed on the molding machine (see FIG. 2). In this embodiment, the partition wall 18 prevents the exhaust gas from mixing with the gas generated inside the molding machine.

The exhaust port 11b is connected to the suction port of the blower 22 via the exhaust pipe 21, and the pressure gauge 2
9, a filter 23 for removing dust contained in the exhaust gas, a heat exchanger 24 for cooling the exhaust gas are provided, and the other dry gas inlet 11a is an outlet of the blower 22 via the air supply conduit 27. Is connected to the discharge port of the blower 22 in parallel with another valve 23 whose one end is open to the atmosphere. I am trying to do it.

And, the gas suction port 13 provided at the bottom of the hopper A is
It is connected to the suction port of the blower 22 through another intake line 28.

Reference numeral 21 'is a bypass valve 21 provided between the suction port and the discharge port of the blower 22 to adjust the speed of the air to be pressure fed into the hopper A.

The bypass valve 21, the atmosphere release valve 23, and the decompression adjustment valve 25 are controlled by a controller (not shown). During the pressurization process of the hopper A, the atmosphere release valve 23 is closed and the decompression adjustment valve 25 is opened. The pressure-fed air from the blower 22 is fed into the hopper A through the introduction port 11a through the air feed line 27, but the pressure-fed air is fed to the heater 15 on the way.
The resin material 30 ... Heated in the hopper A is heated by the opening of the heating gas introducing pipe 14 and is accommodated in the hopper A along the path shown by the broken line in the figure, and becomes exhaust gas.
Emitted from 11b. In this case, in the present invention, since the inside of the hopper A is pressurized, the heating gas introduced into the hopper A diffuses in a wide range, and the resin layer can be heated uniformly.

On the other hand, during the depressurization process, the air release valve 23 is opened and the depressurization adjustment valve 25 is squeezed.

As a result, the partial pressure of water vapor in the hopper A is reduced, the drying efficiency is increased, and the gas suction port 13 starts the suction operation, so that the gas generated inside the molding machine (not shown) is transferred to the hopper A. It is discharged through the compartment 20 surrounded by the outer wall 16, the inner wall 17, and the partition wall 18.

As described above, according to the present invention, by alternately repeating pressurization and depressurization in the hopper and swinging the pressure, sufficient degassing can be performed, and at the same time, highly efficient drying can be easily performed, and uniform drying can be performed. The resin material can be provided.

In the above embodiment, the blower is used to perform the pressure swing of the hopper, but the present invention is not limited to this, and for example, a vacuum pump using a diaphragm, a compressor, an air ejector, or the like may be used. It goes without saying that the inside may be pressurized or depressurized.

〔The invention's effect〕

According to the present invention, by introducing a drying gas into the hopper and alternately swinging the inside of the hopper to pressurize and depressurize, hot-air drying without drying unevenness and remarkably improved drying efficiency is realized. it can.

Further, in the invention in which the gas is sucked from the gas suction port provided in the lower part of the hopper when the inside of the hopper is decompressed, there is no unevenness in drying, and the drying efficiency is remarkably improved, and the harmful gas is effectively removed. Since it can be removed, the quality of the resin molded product can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic constitution of a hot air drying device of the present invention, FIG. 2 is a block diagram showing the basic constitution of another hot air drying device of the present invention, and FIG. 3 is FIG. FIG. 3 is a more specific configuration diagram of the hot air drying device shown in FIG. (Explanation of symbols) A ... Hopper B ... Gas supply source C ... Molding machine D ... Dry gas flow path 5,25 ... Pressure adjusting means 9 ... Gas extracting means 6, 13 ... Gas suction port 1 , 11a …… Dry gas inlet 2, 11b …… Exhaust port 30 …… Resin material

Claims (6)

[Claims] Claim: What is claimed is: 1. While introducing a heated dry gas into a hopper containing a resin material, exhaust gas generated through the resin layer in the hopper is discharged from the hopper, and the inside of the hopper is discharged. In the hot-air drying method of a resin material, which is adapted to dry the resin material housed in, the steps of depressurizing and pressurizing the inside of the hopper are alternately repeated while introducing the dry gas into the hopper. A method of pressure swing hot-air drying of a resin material, characterized by: 2. An exhaust gas generated by passing a heated dry gas through a resin layer in a hopper, which is placed above a molding machine, and containing a resin material, and discharged from the hopper. Then, in the hot air drying method of the resin material, which is adapted to dry the resin material housed in the hopper with hot air, the steps of depressurizing and pressurizing the inside of the hopper are alternately performed while introducing the drying gas, and the depressurization is performed. In the step, the inside of the hopper is set to a negative pressure to suck and discharge the gas generated inside the molding machine from the lower part of the hopper, while in the pressurizing step, the inside of the hopper is set to a positive pressure and the dry gas is stored in the hopper. A method for hot-air drying of a pressure swing type of a resin material, which is characterized in that 3. A hot-air drying apparatus for resin material, which comprises a hopper for accommodating a resin material to be dried and provided with an exhaust port and an inlet for drying gas, wherein the gas inlet and the exhaust port are gas. The inside of the hopper is formed by connecting to a supply source to form a dry gas distribution line, and adjusting the air volume or pressure of the dry gas and / or exhaust gas flowing through the dry gas distribution line in the dry gas distribution line. Is provided with a pressure adjusting means for controlling the positive and negative pressures, and the pressure adjusting means provided in the dry gas distribution line is switch-controlled at a predetermined timing to alternately pressurize the inside of the hopper.
A pressure swing hot air drying device designed to reduce the pressure. 4. A gas suction port for accommodating a resin material to be dried, having an exhaust port and an inlet port for a dry gas in an upper part thereof, and for sucking and forcibly discharging the gas generated inside the molding machine. In a hot air dryer of resin material provided with a hopper that is provided in the lower part and placed above the molding machine, a dry gas flow line is formed by connecting the gas inlet and exhaust port to a gas supply source. Along with the formation, the dry gas distribution line is provided with a pressure adjusting means for adjusting the air flow rate or the air pressure of the dry gas and / or the exhaust gas flowing through the dry gas distribution line to control the inside of the hopper to a positive or negative pressure. The gas suction port is connected to a gas suction source through a gas withdrawal control means for withdrawing gas, and controls the pressure adjusting means and the gas withdrawal control means at a predetermined timing. By controlling the hot air drying apparatus, the gas generated inside the molding machine during the operation of the molding machine is extracted and the inside of the hopper is alternately pressurized and depressurized to perform hot air drying. 5. Switching control by changing the supply amount and / or the supply pressure of the dry gas into the hopper or the discharge amount and / or the discharge pressure of the exhaust gas to the outside of the hopper by the pressurization and the depressurization of the hopper. The hot-air drying method of the pressure swing type according to claim 1 or 2, wherein the method is configured as follows. 6. The hot-air drying apparatus according to claim 2, wherein the switching control between pressurization and depressurization is performed in conjunction with an operation process of a molding machine on which the hopper is placed.