JPH03274132A - Method and apparatus for starting operation of thermoplastic resin molding apparatus - Google Patents

Abstract

PURPOSE:To rapidly discharge air from a filter apparatus at the start time of operation, in allowing a resin to flow in the empty filter apparatus in which the resin does not yet flow, by filling the filter apparatus with the resin while the interior of the filter apparatus is held to a vacuum state from the part on the downstream side thereof. CONSTITUTION:Prior to starting operation, at first, a two-position three-way valve 15 is preliminarily set to a first position state. Thereafter, the extrusion of a resin is started from an extruder 2 and, at the point of time when the molten resin passes through a gear pump 4, the operation of a vacuum pump 14 is started to bring the region from the pump 14 to the leading end of the molten resin containing the interior of the disc filter apparatus 6 on the upstream side of the pump 14 to a vacuum state. By this method, extrusion is continued in the vacuum state and the disc filter apparatus 6 is perfectly filled with the molten resin and, at the point time when the leading end of the flow of the molten resin passes through the disc filter apparatus 6, the operation of the vacuum pump 14 is stopped to gradually return the pressure in the runner to atmospheric pressure and the two-position three-way valve 15 is changed over to the other position and the extrusion of the molten resin is continued in this state.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method and apparatus for starting operation of a thermoplastic resin molding apparatus, and particularly to the field of sheet and film molding, particularly the field of stretched sheet and film molding. Used in

<Prior Art> First, with reference to FIG. 7, a system of a molding apparatus for molding (film forming) a sheet or film from a thermoplastic resin will be described.

Resin raw materials such as pellets are supplied from hopper 1,
While being heated in the extruder 2, the mixture is kneaded, made into a molten state, and extruded.

The molten resin passes through the straight pipe 3 and reaches the gear pump 4, which is installed to improve the discharge accuracy, and is quantitatively extruded.

Thereafter, the molten resin passes through the bent pipe 5 and reaches a filtering device 6, which will be described in detail later, where it is filtered.

This is to remove foreign matter and gel (solid fine particles formed by three-dimensional cross-linking of resin) in the molten resin and prevent them from contaminating molded products (sheets and films), resulting in defective products. It is.

After filtration, the molten resin is passed through a bent pipe 7. After passing through 81 straight pipes and 9 curved pipes,
It reaches the base 10.

Then, it is extruded into a sheet or film shape by a die 10, brought into close contact with the surface of a cooling drum 11, cooled, and then peeled off by a peeling roll 12 as a cooled sheet or film 13 for the next process. sent to.

Next, with reference to FIG. 8, a filtration device having a disk-shaped filter element (hereinafter simply referred to as a "disc filter device") will be described as an example of the filtration device 6.

The bottom 21a of the bottomed cylindrical filter case 21 with a lid includes:
The upstream inlet 22 communicating with the curved pipe 5 is opened, and the lid 21 is opened.
A downstream outlet 23 communicating with the curved pipe ma is opened at b.

In communication with the downstream outlet 23, the lid 21b is integrally provided with a plurality of collecting holes 24 that extend into the filter case 21, are closed on the upstream side (lower side in the figure), and are relatively large on the outer circumferential surface and communicate between the inside and outside.
A center post 24 having a shape is formed.

Around the center post 24, a large number of hollow disk-shaped disk filter elements 25 having a large number of minute filter holes (not shown) communicating between the inside and the outside are stacked around the center post 24.

The inner space of the filtration case 21 communicating with the upstream inlet 22 is connected to the disc filter element 25 through the filtration hole.
It communicates with the internal space and also includes a disc filter element 2.
5 internal space communicates with the center post 24 internal space via the collecting hole 24a, and the center post 24 internal space communicates with the downstream outlet 23.

The disk filter element 25 is made of a stainless steel fiber fabric in the shape of a hollow disk, and is sintered to prevent the texture from shifting and causing uneven density even when resin pressure is applied during filtration. For example, sintering treatment is used to integrate and fix the fibers that are in contact with each other.
During this sintering, it is necessary to adjust the sintering temperature for 2 hours, etc. so that the gaps between the textures that will become the filter holes are not blocked.

In use, the molten resin discharged by the gear pump 4 flows into the filtration case 21 from the upstream inlet 22, is pushed out by the following molten resin, passes through the filtration hole, and enters the disk filter element 25. Finally,
filtered.

The molten resin filtered by each disc filter element 25 passes through the collecting hole 24a and passes through the center post 24.
and flows out from the disc filter device 6 via the downstream outlet 23.

Although this type of filtration device can have a very large filtration area, it has a drawback that it has a very complicated structure.

<Problems to be Solved by the Invention> By the way, in such a thermoplastic resin molding apparatus, when the molding apparatus is newly assembled and started operation, or when the filtration apparatus becomes clogged during operation, a new filtration apparatus is required. When replacing the device, the inside of the filtration device is filled with air, so if you start or restart operation in this state, some of the air will remain in the filtration device, and this air will form bubbles in the resin. There is an inconvenience that air bubbles are contained in the sheet or film that is ejected from the nozzle because it is ejected in small amounts over a long period of time.

This is because the internal volume of the filtration device is large and the internal structure is complex, so even if the filtration device is filled with resin when starting (resuming) operation, the air inside the filtration device cannot be completely filled with molten resin. It cannot be replaced and pushed out from the cap,
This is thought to be because air remains somewhere in the filtration device during molding, and this air gradually becomes bubbles and mixes into the molten resin.

Therefore, as a countermeasure against this, conventionally, a bleed valve 22 is installed at a location where air is likely to accumulate (for example, location A in Fig. 8).
When the operation starts (restarts), the valve is opened and from here,
For a while, the air in the disc filter device 6 is discharged along with the resin, and when no air bubbles are found mixed in the resin that flows out, the bleed valve 26 is closed, and from this point on, the regular film forming process is started. I'm trying to start.

Alternatively, you can vary the resin temperature and extrusion speed (
By moving the filter up and down) to change the flow of resin within the filtration device, the stagnant air is pushed out of the system.

However, although such a conventional method has some effects, it still has the problem that air is mixed into the resin flowing out from the base IO for a long period of time.

Sheets and films containing air bubbles not only reduce their commercial value, but especially when they are used to produce stretched sheets or films, the stress of stretching concentrates on the air bubbles, causing them to break. There was a problem in that the raw material production yield and productivity deteriorated significantly.

In view of the above-mentioned problems, the present invention aims to start operation of a thermoplastic resin molding device that can quickly exhaust air from the filtration device when starting (resuming) operation so as to avoid air bubbles from being mixed into the resin. An object of the present invention is to provide a method and apparatus.

Means for Solving the Problems> In order to achieve the above object, the present invention provides the method (1) and the device (2) below.

(1) At the start of operation of a thermoplastic resin molding device, in which the molten thermoplastic resin that is continuously extruded from an extruder is filtered by a filtration device and molded by flowing out from a nozzle, resin still flows in. When resin is allowed to flow into an empty filtration device, the filtration device is filled with resin while maintaining the inside of the filtration device in a vacuum state from the downstream side.

(2) A thermoplastic resin molding device that molds a molten thermoplastic resin that is continuously extruded from an extruder by filtering it with a filtration device and flowing it out from a mouthpiece through piping, wherein the piping is The branch is connected to the vacuum negative pressure device, while at the start of operation, the filtration device side and the vacuum negative pressure device side are communicated and the mouthpiece side is shut off, and at other times, the filtration device side and the vacuum negative pressure device side are connected. A switching device is provided that communicates with the mouthpiece side and shuts off the vacuum negative pressure device side.

<Effect> The above configurations each produce the following effects.

(1) When the thermoplastic resin molding apparatus starts operating, the filtration apparatus is filled with resin from the downstream side of the filtration apparatus while maintaining the inside of the filtration apparatus in a vacuum state.

Thereby, the air in the filter device can be quickly and completely replaced with the molten resin.

(2) In thermoplastic resin molding equipment, the piping provided on the downstream side of the filtration equipment is branched and a vacuum negative pressure device is connected, and when the molding equipment starts operating, the opening/closing device connects the filtration equipment side to the vacuum The filtration device is communicated with the negative pressure device side to fill the filtration device with resin while maintaining the filtration device in a vacuum state.

Thereby, the air in the filter device can be quickly and completely replaced with the molten resin.

After the start of operation, that is, after the leading edge of the flow of molten resin has passed through the filtration device, immediately shut off the vacuum negative pressure device side using the opening/closing device to return to normal pressure, and then close the filtration device side and the nozzle side. The resin is made to flow through the cap, and molding is performed.

<Example> An example of the present invention will be described below based on the drawings, but the present invention is not limited to the following example unless it exceeds the gist thereof.

The system of the molding apparatus of this embodiment will be explained with reference to FIG.

Incidentally, the same parts as in the conventional example are given the same reference numerals, and the description thereof will be omitted.

A vacuum pump 14 as a vacuum negative pressure device is connected to the downstream side of the disc filter device 6 via a second position f3-way valve 15 as an opening/closing device through a piping 16.

That is, between the curved pipe 7 and the straight pipe 8 as piping, at the - position, the disc filter device 6 side and the vacuum pump 14 side are communicated, and the mouthpiece 10 side is cut off, and at another position,
A 2-position 3-way valve 15 (2-position 3-way valve 15 (
(described in detail later).

Incidentally, gaskets for vacuum sealing are provided at the connection points between the disk filter device 6 and the curved pipe 5.7 and the connection points between the two-position three-way valve 15 and the curved pipe 7.

When using the above equipment, start (or restart) operation
Prior to this, first, the 2-position 3-way valve 15 is placed in the 1-position state.

After that, the extruder 2 starts extruding the resin, and when the molten resin passes through the gear pump 4, the vacuum pump 14
operation is started, and the area on the upstream side up to the tip of the molten resin, including the inside of the disk filter device 6, is brought into a vacuum state.

The degree of vacuum is preferably 730 s+nHg or more (residual pressure in the target area is 30 sn1g or less), but is not particularly limited.

In this way, extrusion continues in the vacuum state, and the inside of the disc filter device 6 is completely filled with the molten resin. When the leading edge of the flow of the molten resin passes through the disc filter device 6, the operation of the vacuum pump 14 is stopped. Then, the inside of the flow path is gradually returned to normal pressure, the two-position three-way valve 15 is switched to another position, and extrusion of the molten resin is continued.

By the above operations, a sheet or film without air bubbles can be flowed out from the mouthpiece 10 from the beginning of operation.

In addition, in order to detect the position of the tip of the molten resin in the flow path,
For example, a resin temperature sensor, a resin pressure sensor, etc. may be provided at necessary locations in the flow path (a location where the gear pump 4 has passed and a location where the disc filter device 6 has passed), and the 2-position 3-way valve 15 may be set at one position or the other position. It is a good idea to automatically switch to .

Furthermore, if a trap is provided in the middle of the pipe 16, it is possible to prevent the molten resin and volatile components therein from directly flowing into the vacuum pump 14.

As explained above, in this embodiment, when starting (or restarting) operation with the disk filter device 6 filled with air, the two-position three-way valve 15 is set to one position, and the disk filter device 6 vacuum pump I4
After the filtration device 6 was filled with molten resin, the 2-position 3-way valve 15 was moved to the other position to start film formation, so that no air bubbles were formed in the resin. Therefore, it is possible to avoid air bubbles from being mixed into the sheet or film that is the molded product from the initial stage of extrusion, and it is possible to obtain high-quality molded products with good productivity.

Furthermore, since no air bubbles are mixed in, such sheets and films do not break even when subjected to stretching, and the production yield is improved.

Furthermore, the filtration device is not limited to a disc filter type, but may also be a candle filter, a cylindrical filter, etc., and the effects of the present invention are exhibited in the case of a filtration device with a relatively complex structure and a large internal volume. .

Thermoplastic resins applicable to the method and apparatus of the present invention include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyethylene, polypropylene, polybutene, poly4-methylpentene-1-ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol. Polyolefins such as copolymers, nylon 6, nylon 66, nylon 610. Nylon 11. Nylon 12. Nylon such as polymethaxylylene adipate, polymethyl methacrylate, polyt
Examples include acrylic polymers such as -butyl acrylate and polyisopropyl acrylate, polystyrene, polyphenylene sulfide, polyether ether ketone, and modified products and mixtures thereof.

Next, a specific example of the two-position three-way valve 15 will be described in detail with reference to FIGS. 2 to 6.

In addition, FIG. 2 is a front view of the two-position three-way valve 15, FIG. 3 is a left side view thereof, FIG. 4 is a view taken along the IV-IV arrow, and FIG. -■ sectional view, and FIG. 6 is a v-■ sectional view showing the state of other positions.

A spool valve 32 is slidably fitted into a sliding hole 31a having a circular cross section formed in the valve case 31 in the axial direction.

The valve case 31 is also formed with an upstream port 33 and a downstream port 34 in a direction perpendicular to the sliding hole 31a.

The spool valve 32 has an upstream port 33 in communication with the upstream port 33 in the retracted position (-position, the state shown in FIG. 5), is bent and extends in the axial direction, and has a negative overflow port 35 at the distal end surface of the spool valve 32. A flow path B is formed.

The spool valve 32 is also formed with a flow path C that communicates with the upstream port 33, extends perpendicularly to the axial direction, and communicates with the downstream port 34 in the advanced position (other position shown in FIG. 6). ing.

Furthermore, four guide rods 36 are provided on one end surface of the valve case 31 so as to protrude through four guide holes 38a of a positioning guide plate 38, which will be described later.

A plate-shaped stopper 37 is fixed to the tips of these guide rods 36, and has a screw hole (not shown) at the center thereof, into which a screw rod 40 (described later) is screwed.

At the base end of the spool valve 32, there is a positioning guide plate 3 that comes into contact with the base end of the valve case 31 at the advanced position of the spool valve 32.
8 is fixed by port 39.

Furthermore, a positioning guide plate 3 is provided at the base end of the spool valve 32.
Penetrate through the center position of 8. One end of the threaded rod 40 is locked so as to be rotatable and to restrict movement in the axial direction.

In other words, at one end of the threaded rod 40 there is a flange 41 with a larger diameter than that of the threaded rod 40.
is fixed by a bolt 42, and is rotatably housed in a hole 43 formed in the spool valve 32 via a bearing 44.

A handle 45 for rotating the threaded rod 44 is attached to the other end of the threaded rod 40.

The sliding surfaces of the valve case 31 and the spool valve 32 are provided with gland seals 46 and 47 at the distal end and base end, respectively.
The ground seals 46 and 47 are fixed by pressing plates 46a and 47a.

In use, the threaded rod 40 is rotated by manually rotating the handle 45, but since the threaded rod 40 is screwed into the fixed stopper 37,
The threaded rod 40 moves in the axial direction by rotation, and the positioning guide plate 38 and the spool valve 32 slide in the axial direction while being guided by the guide rod 36.

By such a rotational operation of the handle 45, when the spool valve 32 is in the retracted position, the upstream side port 33 and the negative pressure side port 35 are communicated through the flow path B, and the downstream side port 34 is blocked.

Further, at the advanced position of the spool valve 32, the upstream side port 33 and the downstream side port 34 are communicated with each other by the flow path C, and the negative overflow port 3
5 is blocked.

Note that the opening/closing device is not limited to the above-described one, but it is necessary to design it so that resin does not accumulate in the flow path.

Experimental examples and comparative examples are shown below.

(Tsukasa Experimental Example At the start of operation of the molding apparatus, the 2-position 3-way valve 15 was set to 1 position, and extrusion was started at an extremely slow discharge rate of 70 kg/h in the initial stage of extrusion.

When the molten resin passes through the gear pump 4, the vacuum pump 14 is started to operate, and while the inside of the disc filter device 6 is kept at a vacuum level of 759 former Hg (residual pressure 1 mmHg),
The extrusion continued.

After the inside of the disc filter device 6 was completely filled with the molten resin, the inside of the flow path was returned to normal pressure, the 2-position 3-way valve was switched to another position, and extrusion was continued.

After confirming that the molten resin flowed out from the nozzle 10, the extrusion speed was gradually increased to form a film at a discharge rate of 600 kg/h to obtain a continuous sheet with a thickness of about 150 μ2 and a width of 1400 m+.

This sheet was in good condition with no bubbles.

Furthermore, while continuing film formation, in the next step, biaxial stretching was performed using a longitudinal stretching machine and a horizontal stretching machine under the conditions of 3 times the length x 3.2 times the width, and the number of breaks in the horizontal stretching machine was calculated. I checked.

As a result, as shown in Table 1, almost no breakage occurred.

The conditions of the apparatus are as follows.

The resin used for the bottom shape was polyamide (manufactured by Noha Mitsubishi Kakai Co., Ltd.).

Diameter: 200mmφ, L/D=28 Discharge rate: 500cc/rev Disc filter device (70 12-inch leaf disks are used) 2-position, 3-way valve Resin flow path diameter: 50mmφ Trap
Vacuum pump with a vacuum-resistant tank with an internal volume of 601 mm installed in the piping between the 2-position 3-way valve and the vacuum pump.
b) Comparative example A filtration device with bleed pulp (see 26 in Figure 8) was used, and at the beginning of extrusion, extrusion was started at an extremely slow discharge rate of 70 kg/h, and the flow was discharged from the bleed pulp. When it was judged that air (bubbles) was no longer mixed in the resin, the bleed valve was closed and the extrusion speed was gradually increased to form a film at a discharge rate of 600 kg/h, with a thickness of approximately 150 μm and a width of 140 μm. (1+u+ continuous sheet was obtained.

Tick 1020° extruder gear pump filtration device This sheet sometimes contained air bubbles.

Furthermore, while continuing film formation, in the next step, biaxial stretching was performed using a longitudinal stretching machine and a horizontal stretching machine under the conditions of 3 times the length x 3.2 times the width, and the number of breaks in the horizontal stretching machine was calculated. I checked.

As shown in Table 1, although the number of breaks decreased over time, the number of breaks was extremely large compared to the experimental example.

The conditions of the apparatus are the same as in the experimental example and are as follows.

Further, the resin used was polyamide (Tubatic 1020, manufactured by Mitsubishi Kaya Co., Ltd.), as in the experimental example.

Extruder diameter 200++ugφ, L/D=28
Gear pump discharge amount 500cc/rev filtration device
Disc filter device (using 70 12-inch leaf disks, with bleed valve) Sheet die (face length 1500 mm) Mouth table 1 <Effects of the invention> As explained above, according to the present invention, the following effects are obtained. be able to.

Start operation with the filtration device filled with air (
When restarting), the air inside the filtration device is discharged to form a vacuum layer, and the filtration device is filled with resin in this state, and then the resin is allowed to flow out from the mouthpiece. This prevents air bubbles from entering the molded product from the initial stage of extrusion, making it possible to obtain high-quality molded products, improving the quality of molded products, and increasing production yield. can be increased.

Therefore, the industrial utility value of the present invention is extremely large.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an apparatus showing an embodiment of the present invention, Fig. 2 is a front view of a two-position three-way valve, and Fig. 3 is a left side view thereof.
Fig. 4 is a view taken along the IV-IV arrow, Fig. 5 is a sectional view along V-■ showing the state at one position, Fig. 6 is a sectional view along V-■ showing the state at other positions, and Fig. 7 is a conventional FIG. 8, a system diagram of an exemplary device, is a vertical cross-sectional view of a conventional filtration device.

Claims (2)

[Claims] (1) At the start of operation of a thermoplastic resin molding device, in which the molten thermoplastic resin that is continuously extruded from an extruder is filtered by a filtration device and molded by flowing out from a nozzle, resin still flows in. A thermoplastic resin molding apparatus characterized in that when the resin is introduced into an empty filtration device, the filtration device is kept in a vacuum state from the downstream side, and the filtration device is filled with resin. How to start driving. (2) A thermoplastic resin molding device that molds a molten thermoplastic resin that is continuously extruded from an extruder by filtering it with a filtration device and flowing it out from a mouthpiece through piping, wherein the piping is The branch is connected to the vacuum negative pressure device, while at the start of operation, the filtration device side and the vacuum negative pressure device side are communicated and the mouthpiece side is shut off, and at other times, the filtration device side and the vacuum negative pressure device side are connected. 1. An operation start device for a thermoplastic resin molding apparatus, characterized in that an opening/closing device is provided that communicates with the mouthpiece side and shuts off the vacuum negative pressure device side.