JP2000229331A - Method and apparatus for pretreating plastic molding raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove moisture and gas contained in a raw material at the time of molding of a plastic and to prevent the mixing of foreign matter contained in the open air into the raw material. SOLUTION: A plastic molding raw material is charged in a drying hopper 1 to be dried at first by hot air to sufficiently dry the raw material and the dried raw material is subsequently degassed by a vacuum pump 4. Air is removed while inert gas is further injected into the hopper to send the raw material to a transport hopper 27 and the influence of the open air is eliminated to supply the raw material of superior quality to a molding machine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for pre-treating a plastic molding material when supplying a raw material to a molding machine during a plastic molding operation.

[0002]

2. Description of the Related Art As is well known, when pellets, which are plastic raw materials, are supplied to a molding machine such as an injection molding machine or an extrusion molding machine, if they contain moisture or air, they are burned when the raw materials are molded. Defects such as bubbles, bubbles and silver may occur. To this end, it is known to dry under vacuum.

[0003] However, according to the prior art, since heating and drying are performed under vacuum, heat transfer by convection is not performed, and drying is performed by radiation and conduction. For this reason, it is difficult to uniformly heat the entire raw material, and drying requires the arrangement of a heating medium inside and outside the hopper, which complicates the structure.

Further, according to the prior art, since the raw material is exposed to the outside air during transportation and supply, there is a possibility that foreign materials and moisture contained in the outside air may be absorbed by the raw material.

[0005]

SUMMARY OF THE INVENTION Accordingly, a main object of the present invention is to provide a method for pre-treating a plastic raw material, in which the heating operation is performed uniformly, whereby the drying can be sufficiently performed and the gas contained in the plastic raw material can be sufficiently removed. In providing the device.

Another object of the present invention is to provide a method and an apparatus for pretreating a plastic raw material which can efficiently dehumidify and degas the plastic raw material.

Another object of the present invention is to provide a method and an apparatus for pretreating a plastic raw material which do not absorb foreign substances and moisture from the outside.

[0008]

According to the present invention, in a plastic molding material pretreatment method for supplying a raw material to a molding machine during a plastic molding operation, the plastic molding material is pneumatically transferred to a drying hopper. Then, after the raw material charged into the drying hopper is dried with hot air, the drying hopper is heated and kept warm by a heater, and the inside of the drying hopper is held in vacuum by a vacuum pump for a certain period of time. After degassing a gas such as gas, and then injecting an inert gas into the drying hopper, which does not hinder the molding, and keeping the raw material in the drying hopper under the inert gas for a certain time, Only the required amount is transported to the transport hopper.

Further, according to the present invention, in a plastic molding raw material pretreatment apparatus for supplying a raw material to a molding machine during plastic molding operation, a drying hopper into which the plastic raw material is charged is provided, and the drying hopper is provided with a blower. And a heater are connected in series to a circulating air line, and an exhaust line to a vacuum pump is connected to the upstream side of the blower in the circulating line, and a lower part of the drying hopper is connected to a discharge hopper through a discharge line. Is connected.

Further, according to the present invention, the drying hopper, the circulation line, the discharge line, and the discharge hopper have a sealed structure.

Therefore, in the drying hopper, since the plastic raw material is first heated by the heated air, a uniform drying operation can be performed. Next, the drying hopper is evacuated to discharge gases such as air and gas. Therefore, efficient pre-processing work is performed.

In addition, since it has a sealed structure and is kept under an inert gas in the drying hopper, foreign materials and moisture are not absorbed by the raw material. Thus, according to the present invention, drying and degassing can be performed while maintaining the cleanness of the plastic raw material, and the plastic raw material can be supplied to a molding machine such as an injection molding machine, so that molding defects can be reduced and molding stability can be obtained. be able to.

[0013]

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

FIG. 1 shows an embodiment of the present invention. In the figure, a portion surrounded by reference numeral 25 indicates a preform processing apparatus for forming raw material. The plastic raw material to be pretreated, for example, pellets, is stored in a raw material hopper 26 having a closed structure. The raw material hopper 26 may be, for example, a raw material container. The supply line L1 connected to the lower part of the raw material hopper 26 is connected to the vicinity of the upper part of the drying hopper 1 via the automatic valve 9. The drying hopper 1 has a second heater 6
And a drying hopper temperature sensor 22. The lower portion of the drying hopper 1 is connected to the discharge hopper 2 via a discharge line L2 having an automatic valve 10. The discharge hopper 2 is connected to a transport hopper 27 via a supply line L3. The transport hopper 27 includes a raw material detection sensor in a known manner, and supplies the raw material to the molding machine 29.

The blower 3 is connected to a line L5 on the downstream side of the branch point B1 of the blowing line L4, and the line L5 is dried in series via the first heater 5, the heater outlet temperature sensor 23 and the automatic valve 13. It is connected to a heating pipe P installed downward in the hopper 1. Heated air is discharged from the heating pipe P into the drying hopper 1. On the other hand,
An exhaust line L6 is connected to the top of the drying hopper 1, and an outlet temperature sensor 20 and a vacuum sensor 21 are provided on the exhaust line L6. An automatic valve 11 and a cooling unit provided in series are provided. The point B2 is connected to the intake side of the blower 3 via a line L7. These lines L4, L5, L6, L7 constitute a circulating air line. An automatic valve 15 is provided on a line L8 branched from the branch point B1, and this line L8 is connected to the supply line L1.

An automatic valve 16 is provided on another line L9 branched from the branch point B1, and this line L9 is connected to a supply line L3.

A branch point B on the downstream side of the automatic valve 13 in the line 5
The line L10 branched from 3 is connected to the inert gas supply source 30 via the automatic valve 14, and the line L11 connected to the inert gas supply source 30 is connected to the discharge hopper 2 via the throttle valve 8. Are linked.

Further, a return line L1 is provided in the transport hopper 27.
2 and is connected to a branch point B2 via an automatic valve 17. Reference numeral 24 in the figure is a control unit.

A line L13 branched from a branch point B4 of the line L6 has an automatic valve 12 and is connected to the vacuum pump 4.

FIG. 1 does not show the inlet / outlet of the outside air for partially breathing the outside air when the material is transported or dried, and filters provided at various places so as to prevent foreign matter from entering the material.

Next, the operation will be described. FIG. 2 is a flowchart showing the entire process.

First, when the operation is started and an operation switch (not shown) is turned on (step S1), the primary transport of the raw material is performed (step S2), and the raw material is sent to the drying hopper 1. When the raw material detection sensor 18 of the drying hopper 1 detects that a predetermined amount of raw material has been charged (step S3), the raw material is dried (step S4). When the drying operation is completed (Step S5), a vacuum deaeration operation is performed (Step S6). When the vacuum degassing operation is completed (step S7), a purging operation using an inert gas is performed (step S8). When the gas purging operation is completed (Step S9), the raw material is sent to the transport hopper 27 (Step S10), and when the transport operation is completed (Step S1).
1) The work is over.

Next, each of the above steps will be described in more detail.

(A) Raw Material Primary Transport Step The raw material in the raw material hopper 26 storing the raw material is transported to the drying hopper 1. At that time, first, the automatic valves 9, 11 and 1
After opening 5, the blower 3 is operated. Then, the raw material enters the drying hopper 1 from the line L1, and when the raw material detection sensor 18 attached to the drying hopper 1 detects the raw material, it is determined that a predetermined amount of the raw material has been introduced into the drying hopper 1, and the blower 3 is stopped. , Close the automatic valves 9, 11 and 15.

The above steps are shown in FIG. When the operation switch is turned on (step S11), if the raw material is sent and the raw material detection sensor 18 of the drying hopper 1 has not detected the raw material (step S12), the automatic valve 9 opens (step S13). 11 opens (step S14),
Then, the automatic valve 15 opens (step S15). Then
The blower 3 starts operating (step S16). The sensor 18 detects that a predetermined amount of raw material has been charged into the drying hopper 1.
Is detected (step S17), the blower 3 is stopped (step S18), and the automatic valve 9 is closed (step S1).
9), the automatic valve 11 is closed (step S20), and the automatic valve 15 is closed (step S21), and the operation is completed.

(B) Raw Material Drying Step In the step of drying the raw material in the drying hopper 1, first, the automatic valves 11 and 13 are opened, and then the blower 3 is operated. First, the temperature of the heater outlet temperature sensor 23 is set to the set temperature.
And the second heater 6 is also controlled by the temperature of the drying hopper temperature sensor 22.

Then, the air heated by the first heater 5 in the line L5 enters the drying hopper 1 from the heating pipe P to dry the raw material. At the same time, the cooling unit 7 is operated for the purpose of lowering the intake air temperature of the blower.

Therefore, the heated air from the drying hopper 1 passes through the line L6, is cooled by the cooling unit 7, and is sucked into the blower 3 from the line L7.

When the temperature of the drying hopper outlet temperature sensor 20 rises to near the set temperature and is operated for a predetermined time set by the control unit 24, the control unit 24 terminates the raw material drying step and sets the first heater 5 and the 2 heater 6
FF, and after a certain period of time, the blower is stopped.
And 13 are closed, and the cooling unit 7 is stopped.

FIG. 4 is a flowchart showing the above steps.

In this step, when the sensor 18 detects a raw material (step S22), the automatic valve 11 is opened (step S22).
23), the automatic valve 13 is opened (Step S24), and the blower 3 is operated (Step S25). Next, the first and second heaters 5 and 6 are controlled and operated (step S2).
6, S27), and operates the cooling unit 7 (Step S)
28). This operation is continued until the drying hopper outlet temperature becomes equal to or higher than the set temperature (step S29), and after a lapse of a predetermined time (step S30), the first and second heaters 5 and 6 are stopped (steps S31 and S32). ). After a lapse of a predetermined time (step S33), the blower 3 is stopped (step S34), the automatic valve 11 is closed (step S35), and the automatic valve 13 is closed (step S36).
Then, the cooling unit 7 is stopped (step S37),
Work is over.

(C) Raw Material Vacuum Deaeration Step After the vacuum pump 4 is operated, the automatic valve 12 is opened, and the air in the drying hopper 1 is discharged through the lines L6 and L13. The inside of the hopper 1 is evacuated and held.

At this time, the second heater 6 is controlled so that the temperature of the drying hopper temperature sensor 22 is maintained at the set temperature to keep the temperature of the raw material.

When the degree of vacuum detected by the vacuum sensor 21 reaches the degree of vacuum set by the control unit 24 or less and the operation is continued for a predetermined time similarly set by the control unit 24, the automatic valve 12 , The vacuum pump 4 is stopped.

FIG. 5 is a flowchart showing the above process. Subsequent to step S37, when the drying operation of the raw material is completed (step S38), the vacuum pump 4 is operated (step S39), and the automatic valve 12 is opened (step S4).
0). Then, the second heater 6 is controlled and operated (step S41). The degree of vacuum in the drying hopper 1 is maintained at or below a predetermined degree of vacuum (Step S42). After a predetermined time has elapsed (Step S43), the second heater 6 is stopped (Step S44), and the automatic valve 12 is closed (Step S45). ), The vacuum pump 4 is stopped (step S46).

(D) Raw material inert gas purging step Next, the automatic valve 14 is opened, and the line L10
When the inert gas is guided through the inert gas and the raw material is kept under the inert gas for a predetermined time or more set by the control unit 24, the pre-processing before the forming of the raw material is completed.

This step is shown in FIG.

Following the step S46, when the vacuum degassing operation is completed (step S47), the automatic valve 14 is opened (step S48), and an inert gas is supplied. The pressure in the drying hopper 1 becomes equal to or higher than the set value (step S4).
9) and after a lapse of a predetermined time (step S50),
The automatic valve 14 is closed (step S51), and the supply of the inert gas is stopped.

(E) Raw Material Secondary Transport Step Next, the raw material having undergone the preliminary treatment is transported to the transport hopper 27 installed on the molding machine 29. The material presence / absence detection of the transport hopper 27 is detected by a material detection sensor 28.

When the amount of the raw material is small in the transport hopper 27, the automatic valve 10 is first opened for a predetermined time (set by the control unit 24), and the raw material is discharged from the drying hopper 1 to the discharge hopper 2 in a certain amount.
The automatic valves 16 and 17 are opened, the blower 3 is operated, air is sent from the line L9 to the line L3, and the raw material in the discharge hopper 2 is transported to the transport hopper 27.

The transport time set in the control unit 24 is
When the blower 3 is operated, the blower 3 is stopped, and then the automatic valves 16 and 17 are closed. Normally, the raw material in the transport hopper 27 gradually decreases due to the molding by the molding machine 29, and when the raw material detection sensor 28 stops detecting the raw material (when the raw material in the transport hopper decreases), the drying hopper 1 After discharging a certain amount of the raw material therein to the discharge hopper 2, the raw material is transported to the transport hopper 27.

It should be noted that even if the transport hopper 27 has been transported N times or more (the number of transports N is set by the control unit 24) and is continuously transported to the same transport hopper 27 three times, the raw material of the transport hopper 27 is detected. If the sensor 28 does not detect the raw material, the control unit 24 determines that the preprocessed raw material in the drying hopper 1 is empty, and returns to the primary transport process.

The above steps are shown in FIG. Subsequent to step S51, after the inert gas purge is completed (step S52), if it is detected that the amount of the raw material in the transport hopper 27 has decreased (step S53), the automatic valve 10 opens (step S54), and a certain period of time elapses. Later (step S55), the automatic valve 10 is closed (step S5).
6). During this time, the raw material is discharged to the discharge hopper 2. Next, when the automatic valve 16 is opened (Step S57), the automatic valve 17 is opened (Step S58), and the blower 3 is operated (Step S59), the air lines L4, L9, L3, L1 are opened.
2. Flow through L7. In this way, the raw material is transported from the discharge hopper 2 to the transport hopper 27, and after a lapse of a predetermined time (step S60), the blower 3 is stopped (step S60).
61), after a lapse of a predetermined time (step S62), the automatic valve 16 is closed (step S63), the automatic valve 17 is closed (step S64), and the operation switch is turned off (step S65), thus ending the operation.

If the operation switch is not off in step S65, the process returns to step S53. Next, a system for continuously supplying raw materials to three molding machines 29A, 29B and 29C using two molding raw material pretreatment devices 25A and 25B of the present invention will be described with reference to FIG.

In FIG. 8, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

The transport hopper and the raw material detection sensor are respectively 27A, 27B, 27C, 28A, 28B,
Automatic valves 31A, 31B and 31C are provided on the lines indicated by 8C and leading to the transport hopper, respectively.

(Primary Material Transporting Process) First, the raw material is transported from the closed-structure raw material hopper 26 to the drying hopper 1 of the forming raw material pretreatment device 25A until the raw material detection sensor 18 detects the raw material.

Next, the forming raw material pretreatment device 25A
The raw material drying step, the raw material vacuum deaeration step, and the raw material inert gas purging step described in the previous section are sequentially completed to complete the preliminary processing of the raw materials, and the processed raw materials are formed into molding machines 29A to 2A as described later.
The raw material is transported to transport hoppers 27A to 27C on 9C.

(Material Secondary Transport Step) For example, when the raw material is transported to the transport hopper 27A, the automatic valve 10 of the forming raw material pretreatment device 25A is opened for a predetermined time, and the raw material is transferred from the drying hopper 1 to the discharge hopper 2 by a predetermined amount. After discharging, the automatic valve 31A is opened, and the automatic valves 16 and 1 of the forming raw material pretreatment device 25A are opened.
7, the blower 3 is operated, and the raw material in the discharge hopper 2 is transported to the transport hopper 27A.

When the raw material is transported to the transport hopper 27B or 27C, the same operation is performed by opening the automatic valve 31B or 31C.

On the other hand, the forming raw material pre-processing apparatus 25B completes the raw material pre-processing through the drying → vacuum → purge step after executing the raw material primary transferring step after the raw material primary transferring step of the same apparatus 25A is completed. I do.

The preform processing apparatus 25A continues to transport the raw materials to the transport hoppers 27A to 27C. As described in the previous section, when the control unit 24 determines that the raw materials in the drying hopper 1 are exhausted, the raw material in the initial process is used. Return to the primary transportation process.

At this time, the molding raw material pretreatment device 25B
However, if the preliminary processing of the raw material has been completed, the raw material is transported to the transport hoppers 27A to 27C in the forming raw material preliminary processing device 25B. As described above, if the raw material pre-processing capacity of the forming raw material pre-processing apparatus is larger than the raw material consumption of the forming machines 29A to 29C, the forming raw material pre-processing apparatus is installed in parallel, so that a plurality of forming machines can be continuously connected. Raw materials can be supplied.

It should be noted that the raw material pre-processing capacity (1 batch processing amount / pre-processing time) of the forming raw material pre-processing apparatus is A kg / H
Then, by installing two molding raw material pretreatment devices in parallel, a raw material of Akg / H can be continuously supplied to the molding machine.

If three or four molding raw material pretreatment devices are installed in parallel, the ability to continuously supply them to the molding machine is 2 × Akg / H and 3 × Akg / H.

FIG. 9 shows an example in which drying, vacuum degassing, and inert gas purging are performed by separate hoppers. In the figure, components corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

In this example, the lower part of the drying hopper 1a is connected to the vacuum hopper 1b via an automatic valve 10a. Another vacuum pump 48 is connected to the vacuum hopper 1b via a line L20, a vacuum sensor 71 and an automatic valve 62 are provided on the line L20, and the degree of vacuum in the vacuum hopper 1b is increased. Vacuum sensor 72 and heater 51
Are provided.

The lower part of the vacuum hopper 1b is connected to a purge hopper 1c via an automatic valve 10b, and the purge hopper 1c is provided with a raw material detection sensor 81. The purge hopper 1c has an inert gas supply source 30.
And a line L21 having an automatic valve 63
And is connected to the vacuum pump 4 via.

The lower part of the purge hopper 1c is an automatic valve 10
c, and is connected to the discharge hopper 2. The discharge hopper 2 is connected to the molding machine 29 by a line L3 having a blower 45.
Automatic valves 31d and 31e are provided on the lines connected to the transport hoppers 27d and 27e of d and 29e, respectively. The transport hoppers 28d and 28e are provided with raw material detection sensors 28d and 28e, respectively, and return line L2
2 is connected to each hopper 27d, 27e.

In FIG. 9, the entrance and exit of the outside air for breathing a part of the outside air during transportation and drying of the raw material, and filters provided at various places so that foreign matter does not enter the raw material are omitted.

FIG. 10 is a flowchart showing the whole process of the apparatus shown in FIG. First, when the operation is started and an operation switch (not shown) is turned on (step S70), the above-described primary transport of the raw material is performed (step S71). When a predetermined amount of the raw material is sent into the drying hopper 1a (step S72), the raw material is dried (step S7).
3). When the drying operation of the raw material is completed (Step S)
74), the control unit 24 detects the presence or absence of the raw material in the vacuum hopper 1b (step S75), and if there is no raw material (NO),
The vacuum pump 4 is operated to open the automatic valve 12 to evacuate the inside of the drying hopper 1a, and then the automatic valve 1a is opened to send the raw material in the drying hopper 1a to the vacuum hopper 1b (step S).
76). When a predetermined amount of the raw material is detected in the vacuum hopper 1b (step S77), the vacuum pump 48 is heated by the third heater 51 while keeping the vacuum hopper 1b warm.
Vacuum degassing operation of the raw material (step S78),
If the vacuum deaeration work is completed (step S7)
9) It is detected whether or not there is a raw material in the purge hopper 1c (step S80). Vacuum pump 4 if there is no raw material
Is operated to open the automatic valve 63 to evacuate the purge hopper 1c, and then open the automatic valve 10b to open the vacuum hopper 1c.
The reduced amount in b is sent to the purge hopper 1c (step S8).
1). When a predetermined amount of the raw material has been fed into the purge hopper 1c (step S82), the automatic valve 14 is opened to purge the inert gas (step S83). When the gas purge is completed (step S84), the molding machine 28d
(E) It is detected whether or not there is a raw material in the upper transport hopper 27d (e) (step S85). When the amount of the raw material decreases, first, the automatic valve 10c is opened for a predetermined time to discharge a predetermined amount of the raw material in the purge hopper 1c to the discharge hopper 2, and then the automatic valve 31d
(E) is opened, the blower 45 is operated for a predetermined time, and the raw material in the discharge hopper 2 is transported to the transport hopper 27d (e) (step S86). When the secondary transport is completed (Step S87), the process returns to the step of detecting whether there is any weight loss in the transport hopper 27d (e) (Step S85). The raw material secondary transport (step S87) is restarted.

The primary transportation of the raw material (step S71),
Raw material drying (step S73), raw material discharge in the drying hopper (step S76), raw material vacuum degassing (step S7)
8), the raw material discharge in the vacuum hopper (step S81), the inert gas barge (step S83), and the secondary transportation of the raw material (step S86) can be performed at the same time.
The raw material pre-processing capacity (processing amount / processing time)
If the amount is larger than d (e), the raw material can be continuously supplied to a plurality of molding machines by one apparatus.

In this example, as in the above-described embodiment, a suitable process can be performed by turning on and off the automatic valve and the blower.

[0064]

According to the present invention, as described above, the primary and secondary transportation, drying, and vacuum deaeration of the raw material are performed while maintaining the cleanness of the raw material, and the molding machine is used. Can be continuously supplied, so that molding defects such as yellowing, bubbles, and foreign matter that occur during molding can be reduced.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing one embodiment of a forming raw material pretreatment apparatus.

FIG. 2 is a flowchart illustrating the operation of the apparatus shown in FIG. 1;

FIG. 3 is a flowchart showing a primary transportation step of raw materials of the apparatus shown in FIG. 1;

FIG. 4 is a flowchart showing a drying process of the apparatus shown in FIG. 1;

FIG. 5 is a flowchart showing a vacuum deaeration step of the apparatus shown in FIG. 1;

6 is a flowchart showing an inert gas purging step of the apparatus shown in FIG.

FIG. 7 is a flowchart showing a raw material secondary transporting step of the apparatus shown in FIG. 1;

FIG. 8 is a flow sheet diagram showing another embodiment of the present invention.

FIG. 9 is a flow sheet diagram showing another embodiment of the present invention.

FIG. 10 is a flowchart for explaining the operation of the apparatus shown in FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Drying hopper 1b ... Vacuum hopper 1c ... Purge hopper 2 ... Discharge hopper 3 ... Blower 4 ... Vacuum pump 5 ... 1st heater 6 ... 2nd Heater 7 Cooling unit 8 Throttle valve 9-17 Automatic valve 18 Raw material detection sensor 19 Raw material temperature sensor 20 Drying hopper outlet temperature sensor 21 Vacuum sensor 22 Drying hopper temperature sensor 23 Heater outlet temperature sensor 24 Control unit 25 Forming material pretreatment device 26 Material hopper (closed structure) 27 Transport hopper 28 ... Material detection sensor 29 ... Molding machine 30 ... Inert gas supply source 45 ... Second blower 48 ... Second vacuum pump 51 ... Third heater 62,63 ... Automatic valve 71 ... True Empty sensor 72: Raw material detection sensor 73: Vacuum hopper temperature sensor 81: Raw material detection sensor

Continued on the front page (72) Inventor Kenzo Ogi 1-9-2 Shinkawa, Chuo-ku, Tokyo F-term in Kubota Colortronic Co., Ltd. 4F201 AL04 AL06 AL07 AL20 BA04 BC01 BC02 BC03 BC07 BC12 BC15 BN24 BN35 BN39 BQ01 BQ04 BQ05 BQ08 4F206 AL04 AL06 AL07 AL20 JA07 JE06 JE11 JF01 JF11 JF41 4F207 AL04 AL06 AL07 AL20 KA01 KE06 KF01

Claims (3)

[Claims] 1. A plastic molding raw material pretreatment method for supplying a raw material to a molding machine during a plastic molding operation, wherein the plastic molding raw material is pneumatically transported and charged into a drying hopper. After drying with hot air, the inside of the drying hopper is kept in a vacuum for a certain period of time by a vacuum pump while heating and keeping the temperature of the drying hopper by a heater, and degass air, gas, etc. contained in the raw material in the drying hopper, After that, an inert gas that does not hinder the molding is injected into the drying hopper, and the raw material in the drying hopper is kept under the inert gas for a certain period of time, and then the necessary amount of the raw material is transported to the transport hopper. Characteristic plastic raw material pretreatment method. 2. A plastic molding raw material pretreatment apparatus for supplying a raw material to a molding machine during plastic molding operation, comprising a drying hopper into which the plastic raw material is charged, wherein the drying hopper includes a blower and a heater. A circulating air line connected in series is connected, and an exhaust line leading to a vacuum pump is connected to the upstream side of the blower of the circulating line, and a lower part of the drying hopper is connected to a discharge hopper via a discharge line. A plastic molding raw material pretreatment device characterized by the above-mentioned. 3. The plastic material pretreatment apparatus according to claim 2, wherein the drying hopper, the circulation line, the discharge line, and the discharge hopper have a sealed structure.