JPH0768552A - Feeding device and feeding method for forming raw material - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an apparatus and a method for supplying a raw material for molding, which can reduce the concentration of impurities mixed in the raw material, reduce the quality defects of the molded article, and improve the product yield. [Constitution] Container 15 containing raw materials for molding and dryer
20 is connected by a raw material supply pipe 2 and a return pipe 3 to form a circulation path 4. The blower 5 circulates the carrier gas in the circulation path 4 to carry the molding raw material from the container 15 to the dryer 20. Since the raw material is transported by the gas that circulates in the closed circulation path 4, impurities such as dust mixed in the transport gas are reduced as compared with the case where an open transportation mechanism is used, and as a result, the impurities mixed in the raw material. As a result, the quality defects of the molded product due to the inclusion of impurities are reduced and the product yield is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supply device and a supply method for supplying raw materials for molding various plastic products such as substrates for magneto-optical recording media.

[0002]

BACKGROUND ART Conventionally, in injection molding, if moisture is contained in a raw material for molding, silver streaks (silver stripes) and the like are generated on the surface of the molded article, and the product becomes defective. A drying machine was provided between the molding machine and the injection molding machine to sufficiently dry the raw material and then supply the raw material to the molding machine. And the supply of molding raw material from this container to the dryer is
Usually, it is performed by pressurizing or depressurizing the conveying air in the raw material supply pipe to generate a pressure difference, and conveying the raw material using the pressure difference. At this time, the transport air is introduced from the atmosphere through the filter in the container part,
After the raw material was transported, it was released from the dryer into the atmosphere, and a so-called open transport mechanism was used.

[0003]

However, when the raw material is supplied by using the conventional open type transport mechanism, impurities such as dust are mixed in the raw material, which causes the quality defect of the molded product. there were. That is, since the air for transportation is introduced from the atmosphere, it is difficult to completely remove the impurities such as dust contained in the air through the filter, and the impurities are mixed in the raw material to be transported.
When injection molding is performed using a raw material containing such impurities, particularly when a very low level of impurity concentration is required, such as a substrate of a magneto-optical recording medium, it is possible to comply with the request. However, there is a problem in that the quality of the molded product becomes poor and the product yield decreases.

An object of the present invention is to provide an apparatus and a method for supplying a raw material for molding, in which the concentration of impurities mixed in the raw material can be made extremely low, quality defects of the molded article due to the incorporation of impurities can be reduced, and the product yield can be improved. To do.

[0005]

A supply device of the present invention is a supply device for forming raw material, which conveys the raw material by a conveying gas from a container in which the raw material for molding is placed to a dryer,
The present invention is characterized in that a circulation mechanism for circulating the raw material carrying gas between the container and the dryer is provided, and the molding raw material is carried from the container to the dryer by the circulated carrying gas. At this time, 0.1 μm particles were trapped in the path for returning the carrier gas from the dryer to the container.
It is preferable to provide a filter capable of capturing 99.99% or more. Further, air is used as the carrier gas, and an air introduction part for introducing this air from the atmosphere into the circulation path between the container and the drier is provided, and a capture rate of particles of 0.1 μm is 99.99. %
It is preferable to provide a filter that can be captured as described above. In addition, as the circulation mechanism, for example, a blower or the like is provided in the middle of the circulation path, a pressure difference is generated by pressurizing or decompressing a part of the path, and a mechanism for circulating the transport air by the pressure difference is used. .

[0006] The supply method of the present invention is a method for supplying a molding raw material from a container containing a molding raw material to a dryer by a carrier gas, and conveys the raw material from the container to the dryer. The returning gas is returned from the dryer to the container, and the carrier gas is circulated between the container and the dryer. At this time, the carrier gas returned from the dryer to the container is 0.1 μm.
It is preferable to remove the impurities mixed in the carrier gas by passing through a filter capable of trapping the particles of 9) at a trapping rate of 99.99% or more. Furthermore, using air as the carrier gas,
0.1 μ when the pressure of the carrier gas, air, in the circulation path between the container and the dryer becomes lower than atmospheric pressure.
It is preferable to introduce air from which impurities have been removed through a filter capable of capturing m particles having a capture rate of 99.99% or more from the atmosphere into the circulation path.

[0007]

In the present invention as described above, since the carrier gas for transporting the raw material from the container to the dryer is circulated between the container and the dryer to form a closed system, impurities contained in the carrier gas are extremely small. In addition, the amount of impurities mixed in the raw material is reduced, the quality defects of the molded product are reduced, and the product yield is improved. In addition, since dust that causes poor quality of molded products has a size of about 0.1 μm or more, the capture rate of particles of 0.1 μm is 99.99 in the circulation path of the carrier gas.
If a filter capable of capturing at a rate of not less than 100% is provided, the impurities contained in the carrier gas are extremely reduced, and thereby the quality defects of the molded product due to the inclusion of impurities are significantly reduced, and the product yield is further improved. Further, air is used as the carrier gas, and when the pressure of the carrier air in the circulation path becomes lower than the atmospheric pressure, 0.1 μm of the air introduction part is used.
If air is introduced from the atmosphere through a filter that can trap the particles of 99.99% or more, the air introduced from the atmosphere at the time of start-up etc. will also have less impurities, and the quality defects of molded products will be reduced. The yield is improved and the life of the filter in the circulation path is extended because the impurities to be removed by the filter in the circulation path are small. In addition, if air is used as the carrier gas, the system becomes an inexpensive system, and when the pressure in the circulation path becomes lower than the atmospheric pressure, the pressure difference is used to introduce the air, forcing it. There is no need to install a mechanism for introducing air, and equipment costs are reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In addition, in FIG. 1, for easy understanding of the invention, the piping of the portion where the raw material is conveyed is shown by a solid line, and the pipe through which only the air that conveys the raw material is sent is shown by a dotted line.
As shown in FIG. 1, a molding raw material supply device 1 according to the present embodiment.
Is a device for supplying the raw material pellets from the material container 15 in which the pelletized raw material for molding such as polycarbonate is put into the dryer 20 for drying the raw material for molding.

Between the lower end of the hopper 16 of the material container 15 and the input hopper 21 of the dryer 20, the raw material supply pipe 2 is provided.
Connected by. In addition, the input hopper 21 of the dryer 20
An air return pipe 3 for conveying the raw material is connected between the hopper 16 and the lower end of the hopper 16 of the material container 15. These pipes 2 and 3 are connected to each other at the lower end of the hopper 16 of the container 15, and the input hopper 21 of the dryer 20 is partially interposed to form the circulation path 4.

In the return pipe 3 of the circulation path 4, a blower 5,
The filter 6 and the valve 7 are sequentially provided. When the blower 5 is operated with the valve 7 open, the upstream side of the blower 5 in the circulation path 4, that is, the dryer 20.
A negative pressure is generated on the side by suction, and a pressure difference occurs in the circulation path 4. Due to this pressure difference, the transport air circulates in the circulation path 4, and the raw material pellets are supplied from the material container 15 to the dryer 20. Therefore, each of the pipes 2, 3, the blower 5, and the valve 7 constitute a circulation mechanism of the supply device 1. In addition, the filter 6 captures 0.1 μm particles.
It is a high-performance filter that can capture at 99.99% or more,
The impurities mixed in the air for transportation circulating in the circulation path 4 are removed.

On the upstream side of the filter 6 of the return pipe 3 of the circulation path 4, that is, on the side of the blower 5, an air introduction section 8 for introducing air from the atmosphere into the circulation path 4 is connected. The air introduction passage 8 is provided with a high-performance filter 9 capable of trapping particles of 0.1 μm with a trapping rate of 99.99% or more similar to the filter 6, and is mixed with the air introduced into the circulation passage 4. It is designed to remove impurities.

Between the return pipe 3 and the supply pipe 2, a bypass pipe 10 for bypassing a portion of the material container 15 connected to the lower end of the hopper 16 is connected. A valve 11 for use is provided. The pipes 2, 3 and 10, the blower 5, the filters 6 and 9, the valves 7 and 11, and the air introduction unit 8 constitute the supply device 1 in this embodiment. The raw material supply pipe 2 is composed of a pipe having no valve and is arranged so that the number of bent portions is as small as possible.
Further, the bent portion of the pipe 2 is configured so that the curvature thereof is as small as possible and the change is gentle. Further, in the equipment that comes into contact with the raw material pellets such as the pipe 2 and the material container 15, the contact surface is set to have a surface roughness Rmax of 10 μm or less by electrolytic polishing or the like.

The material container 15 is placed on a platform scale 17 so that the molding raw material stored in the container 15 can be measured by the platform scale 17.

The dryer 20 has a feeding hopper 21 into which the raw material pellets fed from the material container 15 through the pipe 2 are fed, and a drying hopper which blows hot air onto the raw material pellets fed into the feeding hopper 21 to dry them. 22 and 22. As described above, the raw material supply pipe 2 and the return pipe 3 for conveying air are connected to the input hopper 21, and a not-shown plate is arranged at the opening portion of the return pipe 3 in the hopper 21 to return the pipe. Only the air for conveyance flows into 3, and the raw material pellets are configured to drop into the drying hopper 22.

A hot air supply device 25 for supplying hot air into the drying hopper 22 of the dryer 20 is disposed adjacent to the dryer 20. The hot air supply device 25 includes a suction pipe 26 for sucking air in the drying hopper 22, a dehumidifying device 27 for dehumidifying the air sucked in the pipe 26, a heater 28 for heating the dehumidified air, and a heated air. And a filter 29 for removing impurities.

At the lower end of the drying hopper 22 of the dryer 20,
A raw material supply pipe 31 for supplying the dried raw material pellets to various molding machines 40A to 40C such as an injection molding machine is connected. The pipe 31 is branched according to the number of molding machines 40A to 40C installed in a clean room of a factory, and the branch pipes 31A to 31C are divided into the molding machines 40A.
-40C of raw material input hoppers 41A-41C.

Further, the hopper 4 of each molding machine 40A-40C
Branch pipes 32A to 32C of an air return pipe 32 that conveys the raw material pellets are connected to 1A to 41C, respectively. These branch pipes 32A to 32C are combined into one return pipe 32, and this pipe 32 is connected between the dehumidifying device 27 and the heater 28 of the hot air supply device 25. These pipes 31, 31A to 31C, 32A
32C, 32 are heaters 28, filters 29,
It is connected through the drying hopper 22 and has a circulation path 33.
Is configured.

A blower 34 is provided in the return pipe 32 of the circulation path 33, and each branch pipe 32A to 32C is provided with
Valves 35A to 35C are provided respectively. Then, when the blower 34 is operated with the valves 35A to 35C open, a pressure difference is generated as in the supply device 1, and the carrier air circulates only in the circulation path 33 in which the valves 35A to 35C are opened. , The molding machine 40 from the drying hopper 22
The raw material pellets are conveyed to A to 40C. Therefore, each pipe 31, 31A to 31C, 32,
A circulation mechanism is constituted by 32A to 32C, a blower 34, and valves 35A to 35C.

These pipes 31, 31A to 31C, 32,
32A to 32C, a blower 34, and valves 35A to 35C, from the dryer 20 to the molding machine 40A in this embodiment.
A supply device 30 that conveys the raw material pellets to 40C is configured. The pipes 31 and 31A to 31C are pipes having no valve and are arranged so that the number of bent portions is as small as possible. In addition, the pipes 31, 31
The bent portions of A to 31C are configured so that the curvature is as small as possible and the change is gentle. further,
Pipes 31, 31A to 31C, dryer 20, molding machine 40
In the equipment that comes into contact with the raw material pellets such as the hoppers 41A to 41C of A to 40C, the contact surface has a surface roughness Rmax of 10 μm or less by electrolytic polishing or the like.

In this embodiment, raw material pellets made of PC (polycarbonate), which is a raw material for molding, carried from a raw material manufacturing plant or the like is first stored in the material container 15. Then, the valve 7 of the return pipe 3 is opened and the blower 5 is operated to circulate the carrier air in the circulation path 4. By the circulation of the transport air, the raw material pellets are supplied to the dryer 20 from the lower end of the hopper 16 of the container 15. Since the transport air circulates in the closed circulation path 4 at a state of substantially atmospheric pressure, the air introduction section 8 is normally used.
Air is not introduced into the circulation path 4 from the air introduction section 8, but when the pressure in the circulation path 4 is reduced due to air leakage to the side of the dryer 20 or the like at the time of starting the plant, the air introduction unit 8
From outside, the outside air is automatically introduced into the circulation path 4 through the filter 9.

The raw material pellets, which have been transferred into the feeding hopper 21 of the dryer 20 together with the conveying air, fall into the drying hopper 22 of the dryer 20 and are applied to the dry hot air generated by the hot air supply mechanism 25. It is thoroughly dried.
The air carrying the raw material pellets flows into the return pipe 3 through the perforated plate provided in the input hopper 21, and the blower 5
Is circulated and the valve 7 is opened, circulating in the circulation path 4.

On the other hand, when the blower 34 of the supply device 30 is operated, the valves 35A to 35C are opened, and the carrier air is circulated in the circulation path 33, the raw material pellets dried in the dryer 20 are dried in the drying hopper 22. From each molding machine 40A-4
It is conveyed to each hopper 41A to 41C of 0C. The opening and closing of the valves 35A to 35C are performed by the molding machines 40A to 40C.
Is controlled by a level sensor (not shown) provided in each of the hoppers 41A to 41C. That is, the hopper 4
When the raw material pellets in 1A to 41C are below a certain level, the valves of the return pipes 32A to 32C connected to the hoppers 41A to 41C are opened, and the blower 34 is operated to move the inside of the circulation path 33. Air for conveyance circulates and raw material pellets are supplied into predetermined hoppers 41A to 41C. On the other hand, while the raw material pellets in all the hoppers 41A to 41C are held at a certain level or higher,
The valves 35A to 35C are closed and the blower 34 is also stopped.

The raw material pellets charged into the hoppers 41A to 41C are sent into the respective molding machines 40A to 40C, and predetermined products are molded.

In this embodiment, when the raw material pellets are supplied from the raw material container 15 to the dryer 20, the raw material is conveyed by using the conveying air circulated in the closed circulation path 4. Since the supply device 1 is used, the concentration of impurities such as dust contained in the conveying air can be extremely reduced as compared with the conventional case using the open type conveying mechanism, and as a result, the impurity concentration of the raw material can be lowered, and the molding can be performed. Machine 40A-40C
It is possible to almost completely eliminate the inclusion of impurities in the product molded by. Therefore, like the substrate of a magneto-optical recording medium,
It is possible to produce a product that requires an extremely low level of impurity concentration, reduce the quality defects of the molded product, and improve the product yield. Similarly, dryer 2
Even when supplying the raw material pellets from 0 to each of the molding machines 40A to 40C, since the supply device 30 that conveys the raw material is used by using the conveying air circulated in the closed circulation path 33, the conveyance is performed. The concentration of impurities such as dust contained in the working air can be extremely reduced, products with extremely low levels of impurity concentrations can be produced, and the quality defects of molded products can be reduced, further improving the product yield. You can

In addition, the circulation path 4 of the supply device 1 has 0.1
Since a high-performance filter 6 capable of trapping particles of μm with a trapping rate of 99.99% or more is arranged, it is possible to circulate in the closed circulation path 4 so that impurities are not mixed in the carrier air originally. Can be further removed, which allows the molding of products with very low levels of impurity concentrations. Similarly, also in the supply device 30, the carrier air passes through the filter 29, so that impurities in the carrier air can be removed, and a product having a lower level of the impurity concentration can be molded.

Further, since the filter 9 having the same high performance as the filter 6 is arranged also in the air introduction section 8 for introducing air from the atmosphere into the circulation path 4, air containing less impurities is circulated in the circulation path 4. Can be introduced. Therefore, the impurities removed by the filter 6 in the circulation path 4 are reduced, and the life of the filter 6 can be extended. Further, the introduction of the outside air from the air introduction unit 8 does not need to be forcedly performed by using a valve, an inhaler, or the like, and is automatically performed by the change in the pressure balance between the atmosphere and the circulation path 4, so that it can be reliably performed. Atmosphere can be introduced and facility costs can be reduced.

Since the pipe 10 bypassing the outlet of the container 15 of the circulation path 4 is provided, the raw material pellets remaining in the pipe 2 may be supplied to the dryer 20 side by the air circulating through the bypass pipe 10. it can. Therefore, when the type of raw material pellets supplied from the container 15 is changed, the inside of the pipe 2 can be easily cleaned, and mixing of different types of raw materials can be prevented.

The supply of the raw material pellets from the container 15 to the dryer 20 is stopped by the blower 5 or the valve 7 is used.
Can be interrupted by closing the valve and can be restarted by opening the valve 7 and operating the blower 5, so that the supply control of the raw material pellets can be easily performed. Similarly, the supply of the raw material pellets from the dryer 20 to the molding machines 40A to 40C can be easily controlled by the blower 34 and the valves 35A to 35C. In addition, valves 35A-3
Since the air for transportation does not circulate in the path closed by 5C, the raw material pellets are not transported, and the valves 35A to 35C are not transported.
Since the raw material pellets are transported only to the route where the
The raw material pellets can be transferred only to the predetermined molding machines 40A to 40C simply by controlling the opening and closing of the valves 35A to 35C. Therefore, it is not necessary to provide a distribution valve in each of the pipes 31A to 31C, the number of parts can be reduced, and the facility cost can be reduced.

Further, since pipes having no valve are used as the pipes 2, 31, 31A to 31C through which the raw materials of the respective supply devices 1 and 30 are conveyed, Teflon (trade name) or the like which constitutes the seal of the valve is not used. It is possible to prevent Teflon powder from being generated by rubbing against the pellets and mixing of the powder as impurities into the raw material to cause defective quality of the molded product. Further, when the valve is present, the raw material fine powder generated by rubbing the conveyed raw material pellets against the pipe or the like is retained in the valve portion. However, since the valve is not present in the present embodiment, the retention of the raw material fine powder can be prevented. . For this reason, it is possible to prevent the occurrence of defective phenomena such as silver streak in the product due to the influence of the fixed amount of the fine powders, which is the raw material fine powders retained in the fixed amount together with the pellets, into the molding machines 40A to 40C.
Product quality defects can be reduced and yield can be improved.

Further, the pipes 2, 31, 31A to 31C, the material container 15, the dryer 20, and the hoppers 41A to 41C.
Since the surface roughness of the pipes and equipment that come into contact with the raw material pellets such as is set to Rmax = 10 μm or less by electrolytic polishing, it is possible to reduce the amount of fine powder generated when the raw material pellets rub against the pipes and equipment. It is possible to further reduce quality defects and improve yield.

Further, since each of the supply devices 1 and 30 uses air as a gas for carrying the raw material, it is easy to manage and can be operated at a low cost.

It should be noted that the present invention is not limited to the above-described embodiments, but includes modifications and improvements as long as the object of the present invention can be achieved. For example, in the above-described embodiment, both the circulation path 4 and the air introduction unit 8 are
Although the high-performance filters 6 and 9 are arranged, the filters may be provided on only one of them. However, if the filters 6 and 9 are provided on both sides, there are advantages that impurities can be removed more reliably and that the life of the filter 6 on the circulation path 4 side can be lengthened.

Further, in the above-mentioned embodiment, the pipes 2, 31, 31A to 31C for transferring the raw material pellets are pipes having no valve, but valves may be provided if necessary. However, not providing the valve is advantageous in that it is possible to prevent accumulation of fine powder of the raw material and generation of impurities from the sealing material, and to reduce quality defects of the molded product.

Further, the gas for carrying the raw material is not limited to air, and a gas suitable for the raw material may be used. However, the use of air has the advantages of being easy to manage and inexpensive. If the carrier gas is other than air,
Instead of the air introduction part 8, a mechanism for introducing the gas into the circulation path 4 may be provided.

In the supply device 30, the return pipe 32 was connected to the heater 28 of the hot air supply device 25.
Supply pipe 31 from the blower 34 to the lower end of the drying hopper 22
You may connect to. Specific configurations of the other supply devices 1 and 30, the material container 15, the dryer 20, the hot air supply device 25, and the like are not limited to those in the above-described embodiment, and may be set as appropriate for implementation.

[0036]

According to the supply apparatus and the supply method of the present invention as described above, since the gas carrying the raw material is circulated, the impurities mixed in the carrying gas can be reduced, and thus the impurities mixed in the raw material. It is possible to reduce the concentration of the product, to form a product with a low level of impurity concentration, to reduce the quality defects of the formed product, and to improve the product yield.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Supply Device 2 Raw Material Supply Pipe 3 Return Pipe 4 Circulation Path 5 Blower 6,9 Filter 7 Valve 8 Air Inlet 15 Material Container 20 Dryer 25 Hot Air Supply Device 30 Supply Device 31 Raw Material Supply Pipe 32 Return Pipe 33 Circulation Path 34 Blower 35A-35C Valve 40A-40C Molding machine 41A-41C Hopper

Claims (6)

[Claims] 1. A molding raw material supply device for conveying the raw material from a container containing the molding raw material to a dryer by a conveying gas, which is used for conveying the raw material from the container to the dryer. An apparatus for supplying a raw material for molding, comprising: a circulation mechanism for returning the working gas from the dryer to the container and circulating it between the container and the dryer. 2. The apparatus for supplying a raw material for molding according to claim 1, wherein a filter capable of trapping 0.1 μm particles at a trapping rate of 99.99% or more is provided in the path for returning the carrier gas from the dryer to the container. An apparatus for supplying a raw material for molding, which is characterized in that: 3. The forming raw material supply device according to claim 1, wherein air is used as the carrier gas, and air is introduced from the atmosphere into the circulation path of the carrier gas between the container and the dryer. An apparatus for supplying a raw material for molding, characterized in that a filter capable of capturing 0.1 μm particles at a capture rate of 99.99% or more is provided in the air introduction section. 4. A method of supplying a molding raw material, wherein the raw material is conveyed from a container containing the molding raw material to a dryer by a conveying gas, and the gas for conveying the raw material from the container to the dryer is dried. A method for supplying a forming raw material, characterized in that the carrier gas is returned to the container and the carrier gas is circulated between the container and the dryer. 5. The method of supplying a molding raw material according to claim 4, wherein the carrier gas returned from the dryer to the container is filtered through a filter capable of capturing 0.1 μm particles at a capture rate of 99.99% or more to remove impurities. A method for supplying a forming raw material, comprising: 6. The method of supplying a molding raw material according to claim 4, wherein air is used as the carrier gas, and the pressure of the carrier gas in the circulation path between the container and the dryer is atmospheric pressure. A method for supplying a molding raw material, characterized in that the air from which impurities have been removed through a filter capable of trapping 0.1 μm particles at a trapping rate of 99.99% or more is introduced from the atmosphere into the circulation path when the temperature becomes lower than .