JPH09314093A - Waste plastic bulk reducing device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to repeatingly reduce bulk of plastic by providing a pressurizing part provided on the bottom side part of a treating vessel and for pressurizing a waste plastic material starting to be softened to reduce the bulk, a hot air circulating passage for circulating at a high temp. and a cooling part of cooling the treating vessel after finishing the bulk reducing operation. SOLUTION: When the waste plastic material 28 is charged in the treating vessel 2 to start the bulk reducing treatment, a blower 7 and a heater 8 are operated by a control part 24 to heat the gas for circulating to make a high temp. gas. The high temp. gas becomes the hot air, is charged into the treating vessel 2 from a hot air discharging port 10 and heats the waste plastic material 28 in the treating vessel 2 to soften and bulk-reduce the waste plastic material 28 and the waste plastic material 28 is compressed in the pressurizing part 3 to accelerate the bulk reducing speed while heating with the high temp. gas. And after the bulk reducing operation is finished, the supply of current to the heating part 8 is stopped, a cooling water is passed through a cooling part wound around the outer periphery of the treating vessel 2 with a raw water valve 36 opened to cool the treating vessel 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste plastic volume reduction device and a waste plastic volume reduction treatment method for heat-softening and reducing the volume of waste plastic materials such as expanded polystyrene produced in homes, businesses, stores and the like. It is about.

[0002]

2. Description of the Related Art Conventionally, a large amount of waste has been discharged from homes, business establishments, stores, and the like. Due to a shortage of processing facility capacity such as incineration and landfill, and an increase in processing costs including collection, transportation, and the like. Measures are urgent. As a countermeasure, reducing the amount of waste is the fundamental solution, but the use of resources through recycling is also very effective. Above all, waste plastic materials are attracting attention as targets for recycling because the raw materials are valuable energy resources such as petroleum, and they do not rot even if they are landfilled, and are bulky. Among them, expanded polystyrene and PET bottles are frequently used as distribution containers because of their light weight, cushioning properties, low cost, etc., and since alternative materials for them have not been found so far, they have been recycled as recycled containers. It is strongly desired to use it. Therefore,
There is a method in which the expanded polystyrene, PET bottles, etc. are collected and collected in one place, melted by heating to reduce the volume, and then collected.

However, in the case of recycling in this way, there is a problem that since it is bulky, the transportation cost is high, which increases the overall recycling cost. There was also a problem that the facility would become a large-scale facility and the energy consumption during operation would increase.

Therefore, in order to solve these problems, the following technique (Japanese Patent Laid-Open No. 06-47365) has been proposed. This technology circulates heated air in a processing container, catalytically oxidizes the circulated air, heats and melts the waste plastic material, and recovers the waste plastic material to reduce the volume and deodorize the waste plastic material. .

[0005]

However, the volume reducing apparatus for waste styrofoam material described in Japanese Patent Laid-Open No. 06-47365 can remove styrene generated during volume reduction without lowering thermal efficiency. However, there is a problem that the temperature of the once heated processing container does not drop within a short time even after the volume reduction operation is completed, and it takes a considerable amount of time to recover the volume-reduced waste plastic material in the processing container. It was Further, when the amount of waste plastic material is large and it is necessary to perform volume reduction processing in several times, there is a problem that the volume reduction operation cannot be performed continuously.

In view of the above, the present invention solves the above-mentioned conventional problems. The temperature of the processing container can be lowered in a short time after the end of the volume reduction operation, and the volume reduction processing can be repeatedly performed. It is intended to provide a safe waste plastic volume reduction device.

Another object of the present invention is to provide a method for reducing the volume of waste plastic, which heats and pressurizes the waste plastic material to cool the treatment container after the volume reduction treatment and cools the treatment container faster.

[0008]

In order to solve the above-mentioned problems, the waste plastic volume reducing apparatus of the present invention is characterized in that a cooling section for cooling the processing vessel after the volume reducing operation is provided on the outer peripheral portion of the processing vessel. And

With this, the temperature of the processing container can be lowered in a short time after the volume reducing operation, and the volume reducing process can be repeatedly performed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is
A processing container equipped with an opening / closing lid that can soften the waste plastic material inside, a pressurizing part that is provided on the bottom side of the processing container and pressurizes the waste plastic material that has started softening to reduce its volume, and a waste plastic that is in communication with the processing container It is provided with a hot air circulation path for circulating high-temperature gas for softening the material, and a cooling unit for cooling the processing container after the volume reducing operation is provided on the outer peripheral portion of the processing container. By passing water through the section, there is an effect that the temperature in the processing container can be cooled to a temperature that is safe for work in a short time.

Further, according to the second aspect of the invention, since the cooling section is provided with the cooling water circulation path and the radiator, it has an effect of efficiently cooling the inside of the processing container with a simple structure.

Further, in the invention described in claim 3, when the volume reducing operation is completed, the passage of the cooling water to the cooling portion is started, and when the gas temperature in the processing container is lowered to a predetermined temperature or lower, the cooling water is supplied. Since the control section for stopping the water flow is provided, it has an effect of allowing the cooling water to flow until the gas temperature becomes equal to or lower than a predetermined temperature.

Further, in the invention as set forth in claim 4, the waste plastic material is heated above the softening point to below the melting point, and then the softened waste plastic material is pressurized to reduce the volume, and is treated after the volume reducing operation is completed. Since the container is cooled, the cooling of the processing container can be accelerated.

(Embodiment 1) Hereinafter, a waste plastic volume reducing apparatus and a waste plastic volume reducing processing method according to an embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG. 1 is a side sectional view of a waste plastic volume reducing device according to an embodiment of the present invention. FIG. 2 is a relationship diagram of temperature and time in the processing container of the waste plastic volume reducing apparatus according to the embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a main body of a waste plastic volume reducing device, which will be described in detail below.
A processing container 2 that is softened by hot air of about 0 ° C., a pressurizing unit 3 that pressurizes and reduces the volume of waste plastic material, and a hot air circulation path 11 that circulates high temperature gas are provided. The heat-resistant container 22 has a structure in which hot air does not leak out of the main body 1, and the material thereof is preferably a plastic such as polyamide system having excellent heat resistance. In order to install and use this waste plastic volume reducing device in a store such as a supermarket, it is appropriate that the processing container 2 has a volume of about 100 to 200 liters. The reason for this is that the installation area is not so large with such a size, and the movement is easy. On the other hand, the collection rate of the waste plastic material 28 will be further increased in the future, and the size of the store will be increased, so
In that case, it is more economical to shorten the time required for one volume reduction operation and increase the processing amount instead of increasing the number of waste plastic volume reduction devices installed. And, in this case, the installation area is not so large. In such a case, a collection container may be provided on the waste plastic volume reducing device side so that the waste plastic material may be temporarily stocked.

An appropriate number of hot air side discharge ports 18 are provided on the side surface side of the processing container 2, and an opening / closing lid 6 having an O-ring elastic body 5 is provided on the upper surface side thereof. This opening / closing lid 6
Is opened when the waste plastic material 28 is put into the processing container 2, and is closed and closed when the volume reduction processing is performed in the processing container 2. The opening / closing lid 6 is provided with a safety lock (not shown) for safety of work, and the safety lock is released only when the temperature of the high temperature gas circulating in the processing container 2 becomes about 50 ° C. or lower. As described above, it is controlled by the control unit 24 described later. Further, the pressurizing unit 3 is movable up and down and is provided on the bottom side of the processing container 2,
The waste plastic material 28, which has started to soften due to the high temperature gas of about ℃, is sandwiched between the open / close lid 6 and the volume to reduce the volume. The pressurizing unit 3 includes a pressurizing actuator 4 and a piston 25 that is reciprocated by the pressurizing actuator 4 and directly pressurizes the waste plastic material 28. The pressurizing actuator 4 is an expandable rubber balloon-like air bag or the like, which is inflated by the air pumped from the air pump 21 to push up the piston 25 and reduce the volume of the waste plastic material 28, after which the pressure control valve 13 is opened. The pressured portion 3 is returned to its original position by discharging the air accumulated therein. When reducing the volume, the waste plastic material 28
Does not leak out. As described above, the structure of the pressurizing unit 3 is relatively simple, the air pump 21 may have a small exhaust capacity, the weight is light, the noise can be suppressed small, and the pressurizing unit 3 can be installed in a store such as a supermarket. . A blower 7 is provided in the hot air circulation path 11 that communicates with the processing container 2 and circulates high temperature gas in the processing container 2. Further, the hot air circulation passage 11 has a heating portion 8 which is an electric heater for heating the circulating gas, and a hot air discharge port 10 of the hot air circulation passage 11.
A temperature sensor 9 is provided near the. The temperature of the hot gas detected by the temperature sensor 9 is transmitted to the control unit 24, and the electric power supplied to the heating unit 8 is controlled by switching a switch circuit or the like to adjust the temperature of the hot gas to a temperature of about 160 ° C. To do. An optimum range of this temperature is selected depending on the type of waste plastic material, but it is desirable that the temperature is above the softening point and below the melting point. At temperatures below the softening point, the waste plastic material does not soften and cannot be volume-reduced by pressurization, and above the melting point, the melted waste plastic material adheres to the inside of the processing container 2 and becomes difficult to collect. This is because there is a possibility that a large amount of combustible gas will be released. Reference numeral 19 denotes a gas flow path, which is formed between the processing container 2 and the heat-resistant container 22 and communicates with the blower 7 to circulate high-temperature gas.

Reference numeral 12 denotes a discharge passage, one end of which is a hot air circulation passage 1
A part of the circulating high-temperature gas is branched from 1 to be discharged as an exhaust gas to the outside of the system. When the waste plastic material 28 is Styrofoam, this exhaust gas contains a foaming gas such as butane, toluene, and xylene, and a combustible gas such as styrene monomer gas vaporized during the volume reduction process of several thousand p.
Includes about pm. The flammable concentration of these combustible gases is 15000 ppm or more and 80000 ppm or less,
Although the exhaust gas is not burned in the processing container 2 in the normal dissolution treatment, the exhaust passage 12 is provided with an oxidizing section 14 for oxidizing the exhaust gas to burn it in a flameless manner. Oxidation part 1
4 is provided with an oxidation catalyst 15 that promotes the oxidation of the exhaust gas heated by the catalyst heating unit 16, and a processing gas temperature sensor 17 that detects the discharge temperature of the gas discharged by the oxidation process. The oxidation catalyst 15 is, for example, a platinum-containing compound supported on a mullite ceramic containing aluminum oxide or silicon oxide as a main component. The processed gas smokelessly burned by the oxidation catalyst 15 is discharged into the exhaust passage 12.
Through the process gas exhaust port 20 to the outside of the system.

An air inlet 23 is provided in the heat resistant container 22 and always sucks air from the outside during circulation of hot air. The amount of the sucked air and the amount of the processing gas exhausted from the exhaust passage 12 are balanced, so that the combustible gas in the main body 1 can be prevented from becoming too high in concentration. Reference numeral 24 is a control unit for controlling the operation for reducing the volume of the waste plastic volume reducing device, which is the temperature of the circulating high temperature gas, the circulating air volume, the pressure of the air supplied into the pressurizing unit 3, and the cooling described in detail later. It controls the start time of water flow to the part 30, the end time of water flow, and locking / unlocking of a safety lock provided on the opening / closing lid 6. Reference numeral 27 is a gallery part for radiating the heat generated in the main body 1 to the outside of the system.

Here, the cooling unit 30 will be described. The cooling unit 30 is formed by spirally winding a metal pipe, such as brass or copper, having excellent thermal conductivity around the outer circumference of the processing container 2, and passing cooling water through the pipe to process the processing container 2 The heat in the processing container 2 is removed to lower the temperature in the processing container 2. The metal pipe may have any shape as long as it can pass cooling water inside and can have a large contact area with the processing container 2.
Although not shown in the figure, in order to increase the contact area with the processing container 2, it is also appropriate to interpose a metal foil or the like having excellent thermal conductivity in the space formed in the contact portion between the pipe and the processing container 2. Is. The lower end of this pipe is connected to the water supply passage 30a, and the upper end is connected to the water discharge passage 30b. Further, a drainage channel 30c is branched from the water supply channel 30a. A switching valve 35 switches the direction of the valve in response to a signal from the control unit 24 to drain the cooling water in the cooling unit 30 to the drainage channel 30c. Reference numeral 36 denotes a raw water valve which is connected to a water supply or the like and can be opened / closed by a signal from the control section 24 to start or stop the supply of tap water. During the volume reduction operation of the waste plastic material 28, the processing container 2 is heated by the high temperature gas to about 160 ° C., but cooling water does not pass through the cooling unit 30 during this operation. The heat of the processing container 2 is not absorbed by the cooling unit 30 and the temperature does not drop.

The operation of the waste plastic volume reducing apparatus 1 constructed as described above will be described below with reference to FIG. The open / close lid 6 is opened and the waste plastic material 28 is put into the processing container 2 (at this time, the safety lock is released by a signal from the control unit 24). Next, the opening / closing lid 6 is hermetically closed, the blower 7 is energized by a signal from the control unit 24 to start blowing air, and then the heating unit 8 is energized to heat the circulating gas to a high temperature gas. The heating temperature at this time is about 160 ° C., and the temperature sensor 9 detects this, and the detection signal is transmitted to the control unit 24 so that the temperature is controlled to be maintained at a predetermined temperature. The hot gas becomes hot air and is discharged from the hot air discharge port 10 into the processing container 2 as indicated by an arrow b, and heats and softens the waste plastic material 28 put into the processing container 2. Next, the hot gas is discharged from the side discharge port 1 as shown by arrow c.
8 and flows through a gas flow path 19 formed between the inner surface side of the heat-resistant container 22 and the outer surface side of the processing container 2 to reach the intake port of the blower 7, and the hot air circulation path 11 as shown by arrow d.
Is circulated. When the waste plastic material 28 in the processing container 2 is heated by the high temperature gas, the apparent volume occupied by the waste plastic material 28 becomes small, and the volume thereof decreases. That is, when the waste plastic material 28 is heated, the waste plastic material 28 shrinks while maintaining its original shape, and its bulk is significantly reduced. Then, in order to further reduce the volume and to increase the volume reduction rate, the material is compressed by the pressurizing part 3 while heating is started while being heated with a high-temperature gas. However, in the case of a PET bottle or the like, if heating is excessively advanced, it will crystallize and become hard on the contrary, so it is necessary to finish the pressurization by that time. When the pressure control valve 13 is closed and the air pump 21 is operated, air is pressure-fed to the pressurizing actuator 4 formed of an air bag or the like, and the piston 25 moves to the arrow g.
Then, the waste plastic material 28 in the processing container 2 is compressed with the opening / closing lid 6 to reduce the volume.

When the volume reducing operation is completed and the electric power supply to the heating unit 8 is stopped, the control unit 24 transmits an open signal to the raw water valve 36, opens the raw water valve 36, and starts the passage of cooling water. To be done. At this time, the switching valve 35 is switched so that the cooling water flow direction is a → b. The cooling water that has passed through the cooling part 30 wound around the outer periphery of the processing container 2 gradually rises from the lower part to the upper part, and the heat of the processing container 2 is taken up to become a high temperature and discharged from the discharge passage 30b. . The discharged cooling water may be poured directly into sewage, etc.,
It is also good to store the water in a water tank etc. once and then let it flow into the sewer after the water temperature has dropped.

When water is continuously supplied, the heat of the processing container 2 is absorbed by the cooling water and its temperature begins to drop rapidly, causing a temperature difference from the high temperature gas circulating in the processing container 2 to cause the high temperature gas to flow. The temperature of the heat is gradually reduced as it is transferred to the processing container 2. In the first embodiment, the temperature of the high temperature gas is 50
When the temperature falls below about ° C, it is determined that the temperature has dropped to a safe level for work, and the safety lock provided on the opening / closing lid 6 is released. Then, at this point, the water flow to the cooling unit 30 is stopped. When the high temperature gas in the processing container 2 reaches about 50 ° C., the temperature sensor 9 detects the temperature and transmits it to the control unit 24. At this time, a timer is separately provided, and a time slightly longer than the time at which the high temperature gas reaches about 50 ° C. is set to this timer, and the time-out signal of this timer is also input to the control unit 24 in addition to the signal of the temperature sensor 9. However, if the control unit 24 stops the water flow when both signals are input, the work can be performed more safely. After the water flow is stopped, the switching valve 35 is switched by the control unit 24 so that the cooling water flow direction becomes b → c.
By doing so, most of the cooling water accumulated in the cooling unit 30 flows down through the cooling unit 30 and is drained from the drainage channel 30c. The drained cooling water may be directly supplied to the sewer or the like, or may be stored in a water tank or the like once and then supplied to the sewer or the like after the water temperature is lowered. At the time of stopping the water flow, the control unit 24 sends a release signal to the safety lock to release the lock, and at the same time, transmits a signal to a display means such as a safety display lamp to display that the safety lock has been released. Next, the user opens the open / close lid 6 and collects the volume-reduced waste plastic material 28 at the bottom of the processing container 2, and the volume-reduction operation is completed. In this state, since the cooling water is not accumulated in the cooling unit 30,
Next, when the volume reduction operation is started and the high temperature gas is circulated, heat is rarely transferred from the processing container 2 to the cooling unit 30, and more energy than necessary for raising the temperature in the processing container 2 is not required. .

Here, when the cooling water is passed, the processing container 2
How the internal temperature drops will be described with reference to FIG. In FIG. 2, the horizontal axis represents the elapsed time (t minutes) after the end of the volume reducing operation, and the vertical axis represents the temperature inside the processing container 2 (θ ° C.). A curve a in the figure is a conventional example in which the cooling unit 30 is not provided when the waste plastic material 28 made of a PET bottle of about 200 liters is put into the waste plastic volume reducing device and the volume is reduced, and a curve b is shown. Is according to the first embodiment. The cooling unit 30 is a copper pipe having an inner diameter of 10φ of 2 m.
It was wound around the outer periphery of the processing container 2 at m intervals, and tap water having a water temperature of about 20 ° C. was used as cooling water, and water was passed at a flow rate of about 10 liters / minute. When the piston 25 provided in the pressurizing unit 3 finishes pressurizing and returns to its original position, an operation end signal is sent to the control unit 24, and the control unit 24 sends power from the power supply unit (not shown) to the heating unit 8. Stop the power supply. At this time, the temperature in the processing container 2 is about 160 ° C., but if it is left as it is, the temperature gradually decreases as shown by the curve a according to the conventional example, but until it reaches about 50 ° C. which is a temperature at which there is no problem in work. It takes 40 minutes. On the other hand, in the case where the treatment vessel 2 is cooled by passing water through the cooling unit 30 at the same time as the end of the volume reduction operation, the temperature drops sharply as shown by the curve b, and it takes 5 minutes in only 15 minutes.
It reaches about 0 ℃. In this way, the time required for the temperature to drop to about 50 ° C. can be shortened to 1/3 or less of that of the conventional example.

(Embodiment 2) Next, an example in which a cooling water circulation path and a radiator are provided in the cooling section will be described with reference to FIG. FIG. 3 is a side sectional view of a waste plastic volume reducing device according to another embodiment of the present invention. Descriptions of the symbols given to FIG. 3 that are the same as those in FIG. 1 are omitted here.
In FIG. 3, reference numeral 31 is a circulation pump for circulating the cooling water stored in the water storage section 34 to the cooling section 30. A radiator 32 is provided in the cooling water circulation path 37 to radiate the heat of the processing container 2 absorbed by the cooling water to the atmosphere. An air cooling fan 33 is provided to enhance the heat radiation effect.

When the volume reducing operation is completed and the supply of electric power to the heating unit 8 is stopped, the control unit 24 energizes the circulation pump 31 to start rotation, and the cooling water previously stored in the water storage unit 34 is supplied. Let water pass. At this time, the switching valve 35 is switched so that the cooling water flow direction is a → b. The cooling water passed through the cooling unit 3 is wound around the outer circumference of the processing container 2.
0 gradually rises from the lower part to the upper part, the heat of the processing container 2 is removed, the temperature becomes high, and the water is discharged to the cooling water circulation path 37.
The discharged cooling water radiates heat when passing through the radiator 32 to lower the water temperature and is stored in the water storage portion 34, and is circulated again to cool the processing container 2. When the high temperature gas in the processing container 2 reaches about 50 ° C. by passing cooling water for a predetermined time, the temperature sensor 9 detects the temperature and a detection signal is transmitted to the control unit 24. The control unit 24 stops the supply of electric power from the power supply unit to the circulation pump 31, and stops the flow of cooling water. Next, the switching valve 35 is switched by the control unit 24 so that the cooling water flow direction becomes b → c. By doing so, most of the cooling water accumulated in the cooling unit 30 flows down through the cooling unit 30 and is stored in the water storage unit 34. At this time, the control unit 24
Sends a release signal to the safety lock to release the lock, and also transmits a signal to display means such as an indicator lamp to indicate that the safety lock has been released. Next, the opening / closing lid 6 is opened and the volume of the waste plastic material 28 is reduced to the bottom of the processing container 2.
Is collected and the volume reduction operation ends. In this state, the cooling unit 3
Since the cooling water is not accumulated in 0, the heat transfer from the processing container 2 to the cooling unit 30 is small when the volume reduction operation is started next and the high temperature gas is circulated.
It does not require more energy than necessary to raise the internal temperature.

[0025]

As is apparent from the above, the waste plastic volume reducing apparatus of the present invention is provided with a pressurizing section which is provided on the bottom side of the processing vessel and pressurizes and reduces the volume of the waste plastic material that has started to soften, and the processing vessel. It is equipped with a hot-air circulation path that circulates high-temperature gas for softening the waste plastic material that is communicated with, and a cooling unit that cools the processing container after the volume reduction operation is provided at the outer peripheral part of the processing container. After the operation is completed, the temperature of the processing container can be lowered in a short time, the volume can be reduced repeatedly, and a large amount of waste plastic material can be processed even though it is small.

Further, since the cooling section is provided with the cooling water circulation passage and the radiator, the temperature of the processing container can be lowered in a shorter time.

Further, a control unit is provided which, when the volume reducing operation is completed, starts the passage of cooling water to the cooling unit and stops the passage of cooling water when the gas temperature in the processing container falls below a predetermined temperature. Therefore, the water flow time of the cooling water can be controlled by the control unit, and the waste plastic material can be treated conveniently and safely.

Further, in the waste plastic volume reduction treatment method of the present invention, the waste plastic material is heated above the softening point to below the melting point, and then the softened waste plastic material is pressurized to reduce its volume. By cooling the processing container later, the operation time of the waste plastic volume reduction processing can be shortened.

[Brief description of drawings]

FIG. 1 is a side sectional view of a waste plastic volume reducing device according to an embodiment of the present invention.

FIG. 2 is a relationship diagram of temperature and time in a processing container of the waste plastic volume reducing device according to the embodiment of the present invention.

FIG. 3 is a side sectional view of a waste plastic volume reducing device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Processing container 3 Pressurizing part 4 Pressurizing actuator 5 O-ring elastic body 6 Opening / closing lid 7 Blower 8 Heating part 9 Temperature sensor 10 Hot air discharge port 11 Hot air circulation path 12 Exhaust path 13 Pressure control valve 14 Oxidizing part 15 Oxidation Catalyst 16 Catalyst heating part 17 Processed gas temperature sensor 18 Side discharge port 19 Gas flow path 20 Processed gas exhaust port 21 Air pump 22 Heat resistant container 23 Air inlet port 24 Control part 25 Piston 27 Gallery part 28 Waste plastic material 30 Cooling part 30a Water supply Channel 30b Discharge channel 30c Drain channel 31 Circulation pump 32 Radiator 33 Fan 34 Water reservoir 35 Switching valve 36 Raw water valve 37 Cold water circulation channel

Claims (4)

[Claims] 1. A processing container provided with an opening / closing lid and capable of softening a waste plastic material inside thereof, a pressurizing portion provided on the bottom side of the processing container for pressurizing and reducing the volume of the waste plastic material which has started softening, And a hot air circulation path that circulates a high-temperature gas that is in communication with the processing container and that softens the waste plastic material,
A waste plastic volume-reducing device, wherein a cooling unit is provided on an outer peripheral portion of the processing container to cool the processing container after the volume reducing operation is completed. 2. The waste plastic volume reducing device according to claim 1, wherein the cooling section includes a cooling water circulation path and a radiator. 3. A control unit that starts the passage of cooling water to the cooling unit when the volume reducing operation is completed, and stops the passage of cooling water when the gas temperature in the processing container falls below a predetermined temperature. The waste plastic volume reduction device according to claim 1 or 2, further comprising: 4. The waste plastic material is heated above the softening point to below the melting point, and then the softened waste plastic material is pressurized to reduce the volume, and after the volume reducing operation is completed, the processing container is cooled. Waste plastic volume reduction method.