JP6853460B2 - How to stop the operation of the molding machine - Google Patents

Description

The present invention relates to a method for stopping the operation of a molding machine that can prevent molding defects from occurring when the operation of various molding machines such as an extrusion molding machine and an injection molding machine is stopped and then restarted.

Molding machines such as extrusion molding machines and injection molding machines are known as devices for molding resin products. Taking an extrusion molding machine as an example, the structure thereof will be briefly described. As shown in FIG. 3, the extrusion molding machine 1 has a tubular cylinder 2, a transfer screw 3 and a cylinder 2 arranged inside the cylinder 2. It is roughly configured by a motor 4 provided at the rear end and rotatably supporting the transport screw 3 (see Non-Patent Document 1).

A raw material input port 2a is formed on the upper surface of the rear end portion of the cylinder 2, and a hopper 5 is attached to the raw material input port 2a. A die 6 is attached to the front end of the cylinder 2, and a heater 7 is arranged around the cylinder 2.

When the raw material resin X is charged into the hopper 5, the raw material resin X drawn into the cylinder 2 from the raw material input port 2a is sequentially sent to the front of the cylinder 2 by the rotation of the transport screw 3. In this process, the raw material resin X receives heat from the heater 7, melts, is uniformly kneaded by the rotation of the transport screw 3, is sent to the mold (die) 6, and is extruded to produce a resin molded product. Obtainable.

In addition, "The raw material resin sent into the cylinder is melted by heating it with a heater, and this is uniformly kneaded by the rotation of the transport screw, and this is sent out to the mold to produce a resin molded product of a predetermined shape. The point of "obtaining" is common to other molding machines such as injection molding.

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When the scheduled operation is completed, the transfer screw 3 is stopped and the heating heater 7 is turned off to stop the operation of the extrusion molding machine 1. Then, the temperature of the molten raw material resin X in the cylinder 2 gradually decreases, and the surface side in contact with the inner wall of the cylinder 2, which is the most chillable part, is first cured, and then gradually centered. It hardens toward.

Here, in the case of a synthetic resin such as the raw material resin X, its volume is contracted when it changes (solidifies) from a molten state to a solid. Therefore, when the molten raw material resin X in the cylinder 2 is solidified by cooling, a very slight gap A is generated between the solidified raw material resin X and the inner wall of the cylinder 2 due to the volume shrinkage of the raw material resin X. (See the circle in FIG. 3). Outside air flows into the gap A from the hopper 5 side to form an air layer.

Normally, the raw material resin X does not adhere to the inner wall of the cylinder 2 after the raw material resin X has shrunk in volume, but in rare cases, a small amount of the raw material resin X may be left behind (hereinafter, "residual"). Resin X'”), the presence of this residual resin X'causes molding defects during the restart of the extrusion molding machine 1 as described below.

That is, when the heating heater 7 is turned on when the operation of the extrusion molding machine 1 is restarted, the volume of the solidified raw material resin X in the cylinder 2 is large, so that the temperature of the raw material resin X in the solidified state slowly rises as a whole. Eventually, when the solidified raw material resin X reaches the softening temperature, it melts, and the space between the cylinder 2 and the transport screw 3 is filled again with the melted raw material resin X without any gaps.

On the other hand, the residual resin X'adhering to the inner wall of the cylinder 2 has a very small volume, and the temperature rises sharply in combination with the fact that the heat from the heater 7 is directly applied from the cylinder 2. Therefore, the residual resin X'reaches the softening temperature (further rises to a temperature far exceeding this softening temperature) before the raw material resin X in the cylinder 2 reaches the softening point, and enters the gap A. It reacts with oxygen in the air that has entered and is burnt and carbonized (or, if not burnt, it is thermally decomposed and its composition is denatured).

Eventually, as described above, the raw material resin X melted again to fill the space between the cylinder 2 and the transport screw 3, and when the transport screw 3 started to be fed forward by the rotation of the transport screw 3, it was burnt on the cylinder 2 ( Alternatively, a frictional force due to the molten raw material resin X being sent forward in the cylinder 2 is constantly applied to the residual resin X'(which has been thermally decomposed).

In this way, the residual resin X'adhering to the inner wall of the cylinder 2 is constantly subjected to a frictional force due to the heat-melted raw material resin X being sent forward in the cylinder 2, but this scorching is performed at some timing. Residual resin X'(or pyrolyzed) may peel off from the inner wall of the cylinder 2 during product molding, and the peeled-off residual resin X'is combined with the molten raw material resin X in a mold (die). There is a problem that it is sent to No. 6 and appears as black spots on the surface of the product, resulting in a defective product. And, this problem is not a problem that occurs only in an extrusion molding machine, but is also a problem that occurs in other molding machines including an injection molding machine.

The present invention has been made in view of such conventional problems, and provides a method for stopping the operation of a molding machine, which does not cause a defective product when the operation is restarted after the operation of the molding machine is stopped. That is.

The invention according to claim 1 is "a tubular cylinder 12, a transport screw 14 disposed inside the cylinder 12, and a motor 16 provided at the rear end of the cylinder 12 and rotatably supporting the transport screw 14. It includes a hopper 18 attached to a raw material input port 12a formed on the upper surface of the rear end portion of the cylinder 12, a mold 20 provided at the front end portion of the cylinder, and a heating heater 22 arranged around the cylinder 12. It is a method of stopping the operation of the molding machine 10.
After the planned operation is completed, the injection agent 24 containing the base resin 26 and the foaming agent 28 which is liquid at room temperature and whose vaporization temperature is lower than the softening temperature of the base resin 26 is injected from the hopper 18 into the cylinder 12. At the same time as injecting, the injection agent 24 is heated and kneaded by the transport screw 14 and sent out to the front of the cylinder 12, and the base resin 26 is heated and melted by the heating heater 22 and the foaming agent 28 is vaporized to vaporize the inside of the cylinder 12. The foam 30 is formed in the entire region Z where the base resin 26 is melted , and then the heating heater 22 is turned off. "

The invention according to claim 2 is "a tubular cylinder 12, a transport screw 14 disposed inside the cylinder 12, and a motor 16 provided at the rear end of the cylinder 12 and rotatably supporting the transport screw 14. A hopper 18 attached to a raw material input port 12a formed on the upper surface of the rear end portion of the cylinder 12, a mold 20 provided at the front end portion of the cylinder 12, and a heating heater 22 arranged around the cylinder 12 are provided. It is a method of stopping the operation of the forming machine 10 provided.
The base resin 26 is injected into the cylinder 12 from the hopper 18 and
A foaming agent spraying tool 40 having a small-diameter spray hole 42 formed at its tip is arranged near the raw material input port 12a or above the hopper 18 .
After completing the operation was scheduled, emitting a foaming agent spraying device 40, the ambient temperature was pumped low blowing agent 28 than the softening temperature of the liquid in it vaporization temperature of the base resin 26, more raw material inlet 12a near the pumping The foaming agent 28 is sprayed or sprayed on the base resin 26 existing in the base resin 26 or the base resin 26 stored in the hopper 18.
The base resin 26 sprayed or sprayed with the foaming agent 28 is sent to the front of the cylinder 12 while being heated and kneaded by the transport screw 14.
The base resin 26 is heated and melted by the heater 22, and the foaming agent 28 is vaporized to form the foam 30 in the entire region Z where the base resin 26 is melted inside the cylinder 12, and then the foam 30 is formed. The heating heater 22 is turned off. "

In the method of stopping the operation of the molding machine 10 according to claims 1 and 2, the heater 22 is turned off after the foam 30 is formed inside the cylinder 12 as described above. Here, since the foam 30 was formed by heating and melting the base resin 26 with the heating heater 22 and vaporizing the foaming agent 28, the inside of the melted base resin 26 was vaporized. The foaming agent 28 is uniformly dispersed throughout. That is, an outward expansion force is generated in the foam 30 by the vaporized foaming agent 28, and the foam 30 constantly presses the inner wall of the cylinder 12 by this expansion force.

When the heating heater 22 is turned off while the foam 30 is formed in the cylinder 12, the molten base resin 26 constituting the foam 30 first begins to solidify, but the foaming agent 28 Since the vaporization temperature is lower than the softening temperature of the base resin 26, the vaporized foaming agent 28 remains as a gas at the temperature at which the base resin 26 begins to solidify. That is, the expansion force of the foam 30 is still maintained, and the expansion force suppresses the volume shrinkage when the base resin 26 is solidified.

Therefore, a gap A due to the volume shrinkage of the base resin 26 is not formed between the cylinder 12 and the foam 30 after cooling and solidification, and the residual resin as in the conventional case is formed on the inner wall of the cylinder 12. No X'is attached, and no defective product is produced when the operation of the molding machine 10 is restarted after the operation is stopped.

It is a figure which shows the operation stop method of 1st Example which concerns on this invention. It is a figure which shows the operation stop method of the 2nd Example which concerns on this invention. It is a figure which shows the prior art.

The "method of stopping the operation of the molding machine 10" of the present invention is applied when stopping the operation of various molding machines such as an extrusion molding machine and an injection molding machine, and the injection agent 24 is injected into the molding machine 10. It is roughly composed of an "injection step of the injection agent 24", a "formation step of the foam 30" performed after the injection agent 24 is injected into the molding machine 10, and a "cooling step of the foam 30".

In the following, a case where the extrusion molding machine 10 is used as the molding machine 10 will be described as a typical example. However, in the present invention, the raw material resin is heated and melted in a mold like an extrusion molding machine or an injection molding machine. It can be applied to any molding machine 10 as long as it forms a resin molded product having a predetermined shape.

First, the structure of the extrusion molding machine 10 as the molding machine 10 will be briefly described. As shown in FIG. 1, the extrusion molding machine 10 has a tubular cylinder 12 and a transfer screw 14 arranged inside the cylinder 12. It is roughly composed of a motor 16 provided at the rear end of the cylinder 12 and rotatably supporting the transport screw 14.

A raw material input port 12a is formed on the upper surface of the rear end portion of the cylinder 12, and a hopper 18 is attached to the raw material input port 12a. A mold (die) 20 is provided at the front end of the cylinder 12, and a heater 22 is arranged around the cylinder 12.

When stopping the operation of the extrusion molding machine 10 configured as described above, the injection agent 24 is adjusted and charged into the hopper 18. Here, the injection agent 24 is a mixture of the base resin 26 and the foaming agent 28, and the foam 30 is formed by heating the injection agent 24 in the cylinder 12 (this). The points will be described later).

The base resin 26 is a granular (pellet-like) thermoplastic resin, and the raw material resin being molded by the molding machine 10 may be used, or a general-purpose thermoplastic resin of a different type may be used. Good. In the latter case, for example, if a thermoplastic resin having a color different from that of the raw material resin being molded is used, the tip of the cylinder 12 can be confirmed by checking the color change of the resin molded product coming out of the mold (die) 20. There is an advantage that it can be easily visually determined whether or not the foam 30 (described later) is formed.

The foaming agent 28 is for expanding the volume of the base resin 26 that has been heated and melted in the cylinder 12, and is liquid at room temperature, but in the cylinder 12, it is vaporized by receiving heat from the heating heater 22. A material having a vaporization temperature lower than the melting point (softening temperature) of the base resin 26 is selected.

For example, when "high-density polyethylene" is selected as the base resin 26, one having a vaporization temperature lower than the melting point (120 to 140 degrees) of the high-density polyethylene is selected as the foaming agent 28, and the base resin 26 is selected. When "polypropylene" is selected as the foaming agent 28, a foaming agent 28 whose vaporization temperature is lower than the melting point of polypropylene (168 ° C.) is selected.

As a specific example of such a foaming agent 28, for example, water or a general-purpose plastic cleaning liquid can be used. In this embodiment, a plastic cleaning liquid manufactured by Maruyasu Co., Ltd. (trade name: Gel Clean + (plus)) ) Is used. This plastic cleaning liquid is adjusted by adding a surfactant that enhances the permeability to the base resin 26 and an alkaline agent that decomposes carbides and stains to water.

(Injector adjustment process)
When preparing the injection agent 24, the foaming agent is added at a ratio of 5 to 30 cc to 1 kg of the base resin 26, and the two are sufficiently mixed. In the state where the injection agent 24 is adjusted, the entire surface of the base resin 26 is slightly wet with the foaming agent 28. If the amount of the foaming agent 28 added is too large, there is a problem that when the injection agent 24 fed into the cylinder 12 is sent out by the transport screw 14, the injection agents 24 slip together and cannot be effectively sent forward. There is.

(Injection step of injection agent 24)
In order to inject the injection agent 24 adjusted as described above into the cylinder 12 of the extrusion molding machine 10 after the scheduled operation is completed, the injection agent 24 may be injected into the hopper 18. The injection agent 24 charged into the hopper 18 is drawn into the cylinder 12 from the raw material charging port 12a by the rotation of the transport screw 14, and is sent to the front of the cylinder 12. When the injection agent 24 is sent to the front of the cylinder 12, the injection agent 24 receives heat from the heater 22 and gradually rises in temperature, and a foam 30 is formed in the cylinder 12 as described later. ..

(Forming process of foam 30)
The base resin 26 constituting the injection agent 24 is sent forward by the transport screw 14 in the cylinder 12 while receiving the heat from the heater 22, and has advanced to some extent from the raw material input port 12a (this embodiment). In the case of (1/3), the softening temperature is reached and the resin melts. The molten base resin 26 is a fluid having a high viscosity, and the space between the cylinder 12 and the transport screw 14 is filled with the melted base resin 26 without any gaps.

On the other hand, like the base resin 26, the foaming agent 28 receives heat from the heater 22 and gradually rises in temperature, and reaches the vaporization temperature at a position before the base resin 26 reaches the softening temperature. Vaporizes in the cylinder 12. The vaporized foaming agent 28 expands its volume to nearly 1000 times when the volume in the liquid state is set to 1. Then, the foaming agent 28 after vaporization is mixed and kneaded in the base resin 26 melted by the rotation of the transport screw 14, and is uniformly diffused throughout. As a result, the foam 30 is formed in the cylinder 12.

In the foam 30 formed in the cylinder 12, as shown in the circle of FIG. 1, closed cells made of the vaporized foaming agent 28 are uniformly dispersed throughout the molten base resin 26. There is. Then, due to the expansion force of the foaming agent 28 after vaporization, a force in the outward expansion direction is generated in the foam 30, and the expansion force constantly presses the inner wall of the cylinder 12. There is.

(Cooling step of foam 30)
When the foam 30 is formed up to the tip portion in the cylinder 12 as described above, it is extruded into the mold (die) 20. Then, the rotation of the transport screw 14 is stopped, and then the heater 22 is turned off.

When the heater 22 is turned off, the temperature of the fluid foam 30 in the fluid state in the cylinder 12 gradually decreases because the heat supply is cut off, and the foam 30 comes into contact with the inner wall of the cylinder 12, which is the most chillable part. The base resin 26 on the front surface side first begins to solidify.

As described in the prior art, the base resin 26 in the molten state generates a force (shrinkage force) in the direction of shrinking its volume by solidifying. However, as described above, the foam 30 generates an expansion force due to the foaming agent 28 after vaporization, and this expansion force overcomes the contraction force to hinder the volume shrinkage of the base resin 26, and this expansion force is also present. The base resin 26 solidifies in a state where the expanding force continues to press the inner wall of the cylinder 12.

Therefore, a gap A due to the volume shrinkage of the base resin 26 is not formed between the cylinder 12 and the foam 30 after cooling and solidification, and as a result, the inner wall of the cylinder 12 is as described in the conventional case. There is no such thing as residual resin X'adhering, and no defective product is produced when the operation is restarted after the operation of the molding machine 10 is stopped.

As described above, according to the method of stopping the operation of the molding machine 10 of the present embodiment, a gap A as described in the prior art may be formed between the inner wall of the cylinder 12 and the foam 30 after cooling and solidification. (That is, a small amount of residual resin X'does not adhere to the inner wall of the cylinder 12), and as a result, causes molding defects when the operation of the molding machine 10 as described in the prior art is restarted. There is no such thing.

Further, when the foaming agent 28 constituting the foam 30 is a plastic cleaning liquid, there is an advantage that the surfaces of the cylinder 12 and the transport screw 14 are simultaneously cleaned by the action of the contained surfactant and alkaline agent. There is also.

In the above-described embodiment, the foam material is continuously injected into the cylinder 12 to cover the entire region where the base resin 26 is melted (hereinafter, referred to as “melted region Z”). 30 is formed, but if the foam 30 is formed at least at the end on the mold (die) 20 side and the end on the raw material input port 12a side in the molten region Z, it will be described below. As such, it does not cause molding defects. As a method of forming the foam 30 at the end on the mold (die) 20 side and the end on the raw material input port 12a side, the injection agent 24 and the base material resin 26 are used, and the injection agent 24-base material resin 26 is used. -A method of injecting a fixed amount in the order of the injectable agent 24 can be considered.

In this embodiment, the base resin 26 exists in the central portion of the molten region Z, and when this portion is cooled and solidified, a gap A is formed by volume shrinkage and remains on the inner wall of the cylinder 12 as in the prior art. Resin X'may adhere. However, as described above, the foam 30 is formed at the end of the melting region Z on the mold (die) 20 side and the end on the raw material input port 12a side, and the outside air flows into the gap A. Since this is not the case, as in the past, when reheated by the heater 22, it reacts with oxygen in the air that has entered the gap A and is charred and carbonized (or, if not burnt, it is thermally decomposed to form a composition. It does not cause deformation) and does not cause molding defects.

Further, in the above-described embodiment, in the step of adjusting the injection agent 24, the injection agent 24 is adjusted by mixing the base resin 26 and the foaming agent 28 in advance, and this is injected into the cylinder 12. , The injection agent 24 may be adjusted in the molding machine 10.

As a method of adjusting the injection agent 24 in the cylinder 12, for example, a method of spraying the foaming agent 28 on the base resin 26 in the cylinder 12 by using the foaming agent spraying tool 40 as shown in FIG. 2 can be considered. ..

The foaming agent spraying tool 40 is a pipe-shaped (or tube-shaped) member having a closed tip, and a plurality of small-diameter spray holes 42 are bored on the outer surface of the tip portion. A tank (not shown) is connected to the other end side of the foaming agent sprayer 40 so that the foaming agent 28 stored in the tank can be pumped toward the tip end side of the foaming agent sprayer 40. ..

The tip portion of the foaming agent spraying tool 40 is inserted from the hopper 18 side toward the cylinder 12 side, and the tip portion thereof is arranged in the vicinity of the raw material input port 12a.

When the operation of the molding machine 10 is stopped by using the foaming agent sprayer 40, the base resin 26 is charged into the hopper 18. Then, the base resin 26 is drawn into the cylinder 12 by the rotation of the transport screw 14.

After that, when the foaming agent 28 is pumped, the droplet-shaped foaming agent 28 is sprayed from the tip of the foaming agent spraying tool 40. The base resin 26 near the raw material input port 12a and the sprayed foaming agent 28 are stirred and mixed by the rotation of the transport screw 14, and the injection agent 24 is adjusted in the cylinder 12 and sent to the front of the cylinder 12. , The foam 30 is formed in the cylinder 12 as described above. After confirming that the foam 30 has been formed, the rotation of the transport screw 14 may be stopped, and then the heater 22 may be turned off. The atomized foaming agent 28 may be sprayed by further reducing the spraying hole 42 formed at the tip of the foaming agent spraying tool 40. Further, the foaming agent spraying tool 40 may be arranged above the hopper 18 so that the foaming agent 28 is sprayed or sprayed on the base resin 26 stored in the hopper 18 and sent into the cylinder 12. Good.

Also in these examples, as in the above-described embodiment, the gap A as described in the prior art does not occur between the inner wall of the cylinder 12 and the foam 30 after solidification (that is, in the inner wall of the cylinder 12). A small amount of residual resin X'does not adhere), and as a result, molding defects do not occur when the operation of the molding machine 10 as described in the prior art is restarted.

1: (Extrusion) molding machine, 2: Cylinder, 2a: Raw material input port, 3: Conveyance screw, 4: Motor, 5: Hopper, 6: Mold (die), 7: Heater, 10: (Extrusion) molding Machine, 12: Cylinder, 12a: Raw material input port, 14: Conveyance screw, 16: Motor, 18: Hopper, 20: Mold (die), 22: Heater, 24: Injection agent, 26: Base resin, 28 : Foaming agent, 30: Foam, 40: Foaming agent spraying tool, 42: Spraying hole, A: Gap, X: Raw material resin, X': Residual resin, Z: Melted region

Claims (2)

A tubular cylinder, a transport screw disposed inside the cylinder, a motor provided at the rear end of the cylinder to rotatably support the transport screw, and a raw material formed on the upper surface of the rear end of the cylinder. A method for stopping the operation of a molding machine including a hopper attached to a slot, a mold provided at the front end of the cylinder, and a heating heater arranged around the cylinder.
After the planned operation is completed, an injection agent containing a base resin and a foaming agent which is liquid at room temperature and whose vaporization temperature is lower than the softening temperature of the base resin is injected from the hopper into the cylinder. , The injection agent is heated and kneaded by the transport screw and sent out to the front of the cylinder.
By heating and melting the base resin with the heater and vaporizing the foaming agent, a foam is formed in the entire region where the base resin is melted inside the cylinder, and then, after that,
A method for stopping the operation of a molding machine, which comprises turning off the heater. A tubular cylinder, a transport screw disposed inside the cylinder, a motor provided at the rear end of the cylinder to rotatably support the transport screw, and a raw material formed on the upper surface of the rear end of the cylinder. A method for stopping the operation of a molding machine including a hopper attached to a slot, a mold provided at the front end of the cylinder, and a heating heater arranged around the cylinder .
The base resin is injected into the cylinder from the hopper and
A foaming agent sprayer having a small-diameter spray hole formed in the tip portion thereof is placed near the raw material input port or above the hopper.
After the scheduled operation is completed, a foaming agent that is liquid at room temperature and has a vaporization temperature lower than the softening temperature of the base resin is pumped to the foaming agent sprayer, and is present in the vicinity of the raw material input port by the pumping. The foaming agent is sprayed or sprayed on the base resin or the base resin stored in the hopper.
The base resin on which the foaming agent is sprayed or sprayed is sent to the front of the cylinder while being heat-kneaded by the transport screw.
By heating and melting the base resin with the heater and vaporizing the foaming agent, a foam is formed in the entire region where the base resin is melted inside the cylinder, and then, after that,
A method for stopping the operation of a molding machine, which comprises turning off the heater.

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