JP2000071293A - Method for injection holding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent method for injection molding effective as a remedy of various problems caused by a content of gas by suppressing generation of the gas of molten resin to be injected by a simple process. SOLUTION: In the method for injection molding comprising the steps of feeding molten resin 3 to a front part of an injecting driver 2 such as an injecting screw, an injecting plunger or the like in an injecting cylinder 1, urging the driver 2 retracted rearward by the resin 3 fed to the front part forward and injecting the resin 3 into a mold 4 from a front end of the cylinder 1; the resin 3 fed to the front part of the driver 2 before injecting is pressurized to a predetermined pressure or higher by a pressing force of the injecting direction of the driver 2, and generation of gas in the resin 3 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an injection molding method.

[0002]

2. Description of the Related Art Conventionally, when a resin is molded by a molding machine having a molding mechanism, a resin material is liable to contain water, and a reinforcing agent or the like is blended for the purpose of improving performance.
A unique gas containing water vapor is generated in the melting stage.

[0003] In order to reduce this gas (volatile gas), it is general to dry the resin material to be charged into a molding machine before charging it. However, no matter how much pre-drying is performed, there is no gas generated. I can't.

When the molten resin is injected and molded while containing the gas, there is a problem that the quality of the molded product is deteriorated.

Further, the molten resin has an elasticity. If the elasticity is large, there is a problem that the same molded product cannot be obtained due to the cushioning property of the molten resin when the pressure is maintained and molded in the cavity. . It is considered that the most important cause of the elasticity (cushioning property) of the molten resin, which is the cause of the problem that the same molded article cannot always be obtained, is the gas content. Therefore, the cushioning property of the molten resin can be suppressed by reducing the amount of the gas, and the same molded product can be always formed.

[0006] In this regard, conventionally, while performing the preliminary drying,
Although the gas generated at the stage where the resin material is heated and melted in the injection cylinder is devised so as to be extracted from the introduction hopper side of the injection cylinder, the front portion from the screw compression zone portion,
That is, at present, the gas generated in the molten resin that is sent to the front of the injection screw and stopped is injected into the cavity of the mold together with the molten resin during molding.

Although the mold has a mechanism such as an air vent in the mold, its position is limited by the production of the mold and the shape of the product, and it cannot be said to be a complete solution.

[0008] Further, there is a type equipped with a special gas removing device such as a vacuum generating device inside or outside the mold or a vent-type molding machine. However, there are problems in the performance, maintenance method, high cost and the like. Yes, it is not yet a well-established technology.

On the other hand, the idea of simply forming a gas vent hole in the injection cylinder cannot be adopted because the nozzle at the front end of the injection cylinder is extremely high in pressure.

[0010]

Therefore, while working on the technical problem of how to reduce the generation of such gas for many years, the present inventor has found that the main factor of the generation of this gas is water content. It was considered that preventing this moisture from evaporating in the molten resin and generating it as steam gas would suppress the gas that causes these problems.

Further, the inventors have found an epoch-making idea that the boiling point of water is higher as the pressure is higher, and that the generation of steam gas can be suppressed accordingly in a high pressure state.

That is, the present inventor seeks to change the way of thinking and finds the above-mentioned point of interest, so that the molten resin fed to the front of the injection driving body before the injection driving control of the injection driving body is slightly stopped. However, it has been found that the generation of gas can be suppressed by waiting until the start of injection in a pressurized state for as long as possible, and the present invention as an epoch-making injection molding method that solves the above problem is completed. It was.

[0013]

The gist of the present invention will be described with reference to the accompanying drawings.

The molten resin 3 is fed into a front portion of an injection driving body 2 such as an injection screw or an injection plunger in the injection cylinder 1, and the injection driving body 2 retreated backward by the molten resin 3 fed into the front portion is moved forward. In the injection molding method in which the molten resin 3 is extruded into the mold 4 from the front end of the injection cylinder 1, the molten resin 3 which has been fed into the front portion of the injection driving body 2 before being injected is pressurized and melted. 3
The present invention relates to an injection molding method characterized by suppressing generation of gas in the inside.

Further, the molten resin 3 before being injected, which has been fed into the front portion of the injection driving body 2, is pressed at a predetermined pressure or more by the pressing force of the injection driving body 2 in the injection direction. The method according to claim 1, wherein the generation of the gas is suppressed.

When the mold 4 is released from the mold 4 at the front end of the injection cylinder 1 at the front of the injection driving body 2 or at the injection nozzle or runner in front of the injection cylinder 1, A break prevention mechanism 6 for preventing peeling
Wherein a predetermined pressure is applied to the molten resin 3 by suppressing the peeling of the molten resin 3 even if the molten resin 3 is pressurized before injection. The present invention relates to the injection molding method according to any one of the above.

Further, after a measuring step in which at least a predetermined amount of the molten resin 3 is fed into the front portion of the injection driving body 2 and stopped,
The pressurization of the molten resin 3 is continued or continued for a predetermined time until the injection filling step of extruding the injection driving body 2 forward to inject the molten resin 3 into the mold 4 is started. The present invention relates to the injection molding method described in any one of 1 to 3.

When the injection driving body 2 is pushed forward to perform injection filling, the position of the injection driving body 2 when the molten resin 3 is pressurized or when the molten resin 3 is pressurized is determined as a reference of a movement start position. The injection molding method according to any one of claims 1 to 4, wherein the injection driving body 2 is controlled to move forward by a predetermined stroke.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention (how to implement the invention) will be briefly described with reference to the drawings, showing the operational effects thereof.

The pressure of the molten resin 3 before being injected, which has been sent to the front part of the injection driving body 2, is suppressed, and generation of gas in the molten resin 3 is suppressed.

That is, by keeping the molten resin 3 which has been fed into the front portion of the injection driving body 2 before injection in a pressurized state, the molten resin 3 is melted compared to the conventional method in which no pressure is applied as in the present invention. Since the boiling point of the water in the resin 3 becomes higher, the formation of steam is suppressed, and the generation of gas can be suppressed.

In the conventional method described above, after the injection filling step is completed, the resin in the cavity 7 in the mold 4 is cooled and solidified while keeping the pressure therein.
In preparation for the next injection, for example, the injection screw (injection driving body 2) rotates for the first time to feed a predetermined amount of the molten resin 3 to the front part of the injection driving body 2 and stop it.

Then, the mold 4 is released, and the cavity 7 is released.
After discharging the solidified resin molded product in the mold, the mold 4 is closed, and the injection driving body 2 which has already completed the feeding stop (measurement step) and has completed the injection preparation is driven for injection, and the molten resin 3 is injected again. Then, resin is injected (filled) into the cavity 7.

Therefore, in the conventional method, the molten resin 3 is in a state of being fed into the front part of the injection driving body 2 and stands by for a predetermined time even if it is slight. Vapor gas is generated.

According to the present invention, ideally, the molten resin 3 which is stopped and held is kept in a pressurized state continuously during the standby time until the molten resin 3 is fed and stopped and injected. Thus, generation of gas as described above can be suppressed.

Ideally, the longer the pressurizing time, the better. However, even if the pressurizing time is short, if the pressurization can be continued for a predetermined time, the generation of gas can be suppressed accordingly.

Further, such pressurization can be easily performed by pressing the injection drive body 2 forward (in the injection direction) in the same manner as the injection drive control of the injection drive body 2. By applying a predetermined pressure at a predetermined timing, the present invention can be easily realized and is a revolutionary injection molding method excellent in practicality.

With respect to this pressing force, the higher the pressing force, the more the effect can be expected. As a result of a trial production experiment based on this embodiment, it is possible to obtain a good gas pressure by setting the pressing state to at least 5 kg / cm ² or more. It has been confirmed that the effect of suppressing the occurrence of the above is produced.

It has also been confirmed that it is desirable to keep the pressure at 500 kg / cm ² or less in view of the mold strength and the pressure resistance of the seal structure.

On the other hand, in order to apply a desired pressure (sufficient enough to exert a gas suppressing effect) to the molten resin 3 by this pressing force, particularly during discharging the molded product by releasing the mold. In other words, if a break prevention mechanism 6 is provided to prevent the molten resin 3 from separating from the nozzle portion or the runner portion due to this pressure, the separation can be prevented and reliably prevented. The desired pressure can be applied, and furthermore, the anti-separation mechanism 6 can reliably prevent the departure to the extent that a problem occurs even if pressure is applied, regardless of whether the mold is released or closed. It is possible to keep applying pressure to the molten resin 3 for a long time during the standby state before injection,
The gas suppressing effect is further improved.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described with reference to the drawings.

The molten resin 3 is fed to the front of an injection driving body 2 such as an injection screw or an injection plunger in the injection cylinder 1 and the injection driving body 2 retreated backward by the molten resin 3 fed to the front is moved forward. The injection molding method of extruding the molten resin 3 from the front end of the injection cylinder 1 into the mold 4 and further pressing the injection driving body 2 forward to keep the resin fed into the mold 4 by an injection molding method. Therefore, the molten resin 3 before injection, which has been sent to the front part of the injection driving body 2 before being injected, is pressed to suppress generation of gas in the molten resin 3.

More specifically, the molten resin 3 before injection, which has been fed into the front portion of the injection driving body 2, is
At least 5 kg / cm ² by the pressing force in the injection direction of
Pressurization at a pressure of 500 kg / cm ² or less suppresses generation of gas in the molten resin 3.

That is, a predetermined amount of the molten resin 3 is injected into the injection drive 2
After the weighing step in which the molten resin 3 is fed into the front part of the mold, the injection driving body 2 is pushed forward to inject the molten resin 3 into the mold 4 until the start of the injection filling step. The resin 3 is kept under pressure.

Therefore, since the molten resin 3 which is continuously stopped during the standby time is kept in the pressurized state, the generation of gas as described above can be suppressed.

The longer the pressurizing time, the better, but if the pressurizing time is short, the gas generation can be suppressed correspondingly to the pressurizing time if the pressurizing is continued for a predetermined time.

Further, such pressurization can be easily performed by pressing the injection drive 2 forward, similarly to the injection drive control of the injection drive 2. Therefore, this injection driving body 2
Because it can be pressurized for a predetermined time at a predetermined timing using
The present invention is a revolutionary injection molding method that can be easily realized and has excellent practicality.

In this embodiment, the pressure is 5 kg
/ cm ² or more and 500 kg / cm ² or less.

That is, it was confirmed that a good gas suppressing effect was produced by applying a pressure of at least 5 kg / cm ² or more, and a pressure resistance of 500 kg / cm ² was obtained from the mold strength and the sealing structure. It was also confirmed that it was desirable to keep the size to cm ² or less.

In this embodiment, when the mold 4 is released from the front end of the injection cylinder 1 at the front of the injection driving body 2 or the injection nozzle or runner in front of the injection cylinder 1. A release prevention mechanism 6 for preventing the molten resin 3 from peeling off is provided, and even if the molten resin 3 is pressurized before injection, the molten resin 3 can be released even when the mold is released. That is, a predetermined pressure can be reliably applied to the molten resin 3.

In other words, in order to apply a desired pressure (sufficient enough to exert the gas suppressing effect) to the molten resin 3 by this pressing force, the mold is released from the mold 4 and the molded product is discharged particularly during the discharge. Can be granted. In other words, the pressure can prevent the molten resin 3 from coming off from the nozzle portion and the runner portion, and can reliably apply the desired pressure. In this embodiment, a desired pressure is applied to the molten resin 3 for a long time during the standby state before injection, regardless of whether the mold is released or closed. The gas suppression effect can be further improved.

Specifically, the spillover prevention mechanism 6 of the present embodiment insulates the heat for heating the injection cylinder 1 and removes the molten resin 3 remaining in the injection port of the injection nozzle. A heat insulating portion 6A for preventing the molten state from being maintained even when the mold or the injection nozzle part is separated from the mold is provided in the injection nozzle part. When the melted resin 3 in the injection nozzle
Is solidified or semi-solidified, whereby the injection port of the injection nozzle portion is clogged and closed, and the remaining molten resin 3 is prevented from peeling off from the injection port at the tip of the injection port of the injection nozzle portion. Make up.

The solidified or semi-solidified resin 10 for clogging the injection port of the injection nozzle portion is injected into the mold 4 at the next injection, and is transferred to the cold slug receiver 9 at the end of the sprue portion 8A of the runner portion 8. The heat insulating portion 6A is configured so as to have a solidified capacity that can be accommodated.

In this embodiment, a heater is provided on the outer periphery of the injection cylinder 1 and on the outer periphery of the base of the injection nozzle portion 4 for melting the resin material introduced from the inlet and maintaining the molten state. Is provided with a heat insulating portion 6A so that the heat is not transmitted well to the injection port of the injection nozzle portion.

The heat insulating portion 6A does not need to completely shut off the heat, and the injection port side at the front end of the injection nozzle portion is cooled when the mold 4 is released or when the injection nozzle portion is separated from the mold 4. In this case, it is sufficient that the molten resin 3 in the injection port behind the injection port is solidified so as to block and close the injection port (injection port).

Conversely, if the heat is cut off too much, the molten resin 3 in the cavity 7 cools down when the molten resin 3 in the cavity 7 is kept under pressure after the molten resin 3 is injected or after the pressure retention is completed. If it is solidified together with the unnecessary molten resin in the runner section 8 and molded and discharged when molding, the purpose cannot be achieved. The resin 3 always tries to solidify and has a great influence on the injection conditions. Once solidified, the solidified resin cannot be discharged at the next injection pressure, resulting in molding failure.

In this embodiment, in consideration of the above,
As described above, when the injection port side at the front end of the injection nozzle section is cooled, such as when the mold 4 is released or the injection nozzle section is separated from the mold 4, the molten resin 3 in the injection port path is solidified. Then, a setting is made such that an appropriate heat-insulating action is exerted to close the portion having the smallest diameter at the base end of the injection port.

More specifically, in this embodiment, an improved prototype experiment is repeated, and a groove is simply formed to form an air heat insulating layer, or a heat insulating material having poor heat conductivity is arranged on the outer periphery of the injection port.

For example, as a heat insulating material, asbestos having a thermal conductivity of about 80% lower than that of steel as a base material for forming the injection nozzle portion and having a heat insulating degree of about 20% of the base material may be employed.

Further, as in the present embodiment, a heat insulating material for preventing heat from being transmitted to the injection port may be buried in the injection nozzle as the heat insulating section 6A. From the middle, the front end side is formed of a material with low thermal conductivity,
As described above, the heat insulating portion 6A may be configured so that the molten resin 3 in the injection port is solidified when the mold is released.

In this embodiment, the solidified resin 10 is discharged from the injection port by a normal injection pressure at the time of the next injection, and is stored in the cold slug receiver 9 which is a recess at the front end of the sprue portion 8A of the mold 4. The subsequent molten resin 3 is configured to be injected and injected into each cavity 7 via a runner 8B branched from a slightly upper portion of the cold slag receiver 9.

The storage capacity of the cold slag receiver 9, the diameter of the injection port, and the heat insulating portion 6A so that the solidified resin 10 clogging the injection port is stored in the cold slag receiver 9.
The solidification capacity of the resin 10 is set according to the degree of heat insulation.

In the present embodiment, the solidified resin 10 smoothly spreads in the mold 4 during the next injection.
The injection port is formed in an open tapered hole whose diameter increases toward the front end (outward) so as to be ejected and discharged toward the front end.

In this embodiment, when the injection driving body 2 is pushed forward to perform injection filling, the position of the injection driving body 2 when the molten resin 3 is being pressurized or when the molten resin 3 is being pressurized is set. By controlling the forward movement of the injection driving body 2 by a predetermined stroke as a reference of the movement start position, the gas and air components in the molten resin 3 can be compressed and exhausted, or the capacity under constant pressure compression can be measured. it can.

That is, the compressed state may be maintained by the pressurization, or the pressurization may be stopped once, the injection driving body 2 is sucked back, and the mold 4 is opened to discharge the molded product. When the mold 4 is closed and ready for injection, the filling control unit is operated to inject the molten resin 3.
Correction is performed so that the position where the injection driving body 2 has already advanced by compression is set as the initial position of a certain stroke. That is, this correction position is set as a stroke start reference (movement start position P), and the drive is always driven forward by a certain stroke from this movement start position P.

As a result, the molten resin 3 which is always measured once
Is performed, and injection control is performed to advance a predetermined stroke based on the position (movement start position P) obtained by this compression. Therefore, even if the molten resin 3 contains gas or air, it is always The capacity at a constant compression can be injected by extrusion of a constant stroke, and the amount of resin actually injected into the mold 4 becomes constant for each molding shot.
Compared to the past, highly precise metering can be realized.

That is, in the related art, even if the feeding and metering to the front of the injection cylinder is accurate, there is a variation in the actual amount of the injection resin that is extruded and injected by applying the injection pressure, and the highly accurate metering and injection is performed. However, according to this embodiment, the weighing accuracy is dramatically improved.

More specifically, in the present embodiment, the actual injection stroke of the filling driving device is obtained by adding the correction stroke amount to the reference stroke. In other words, although the stroke is always constant from the movement start position P, the fixed stroke drive control is performed after the correction stroke is performed up to the movement start position P from the sucked back position.
Therefore, in the present embodiment, the actual stroke length of the filling driving device is successively adjusted and varied by the compression inspection for each molding shot.

Further, the filling driving device is always set to a constant stroke, and the correction stroke amount is simultaneously adjusted by the pressure-holding drive device by the same compression stroke (correction stroke) again by detecting the liquid amount during compression of the pressure-holding drive device. It may be driven.

Thus, the molten resin that has been measured once is always compressed, and the injection control for moving the molten resin forward by a predetermined stroke based on the position obtained by this compression (movement start position P) is performed. Even with the molten resin 3 contained, the volume at a constant compression can always be injected by extrusion with a constant stroke, and the amount of resin actually injected into the mold 4 becomes constant for each molding shot, and is And highly accurate metering can be achieved.

That is, in the related art, even if the feeding and metering to the front of the injection cylinder is accurate, there is a variation in the actual amount of resin extruded and injected by applying the injection pressure, and the highly accurate metering and injection is not performed. However, according to the present embodiment, the measurement accuracy is dramatically improved.

In the present embodiment, the molten resin 3 is compressed under a pressurized state for a predetermined time in order to suppress the gas. However, by detecting the compression movement position, it is possible to perform high-precision metering injection.

[0063]

According to the present invention, as described above, the generation of molten resin gas to be injected by a simple method can be suppressed.
This is a revolutionary injection molding method that is effective as a solution to various problems caused by gas content.

According to the second aspect of the present invention, the existing structure can be used, and only by controlling the pressure by the injection driving body driven by injection, the molten resin in the standby state is pressurized to generate gas. This is an epoch-making injection molding method that can suppress and can realize the present invention very easily.

Further, according to the third aspect of the present invention, it is possible to prevent peeling and to surely apply the desired pressure, and furthermore, the mechanism for preventing the peeling even if pressure is applied by the peeling preventing mechanism. Peeling can be reliably prevented, and regardless of whether the mold is released or closed, it is possible to continue applying pressure to the molten resin for a long time during the standby state before injection, and the gas suppression effect is further improved. It is an extremely innovative injection molding method that will be improved.

According to the fourth aspect of the present invention, there is provided a more excellent injection molding method in which the molten resin in the standby state can be reliably pressurized and the gas suppressing effect can be surely exhibited.

In the fifth aspect of the present invention, the molten resin is compressed in a pressurized state for a predetermined time in order to suppress the gas. It is a better injection molding method that can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view of the present embodiment.

FIG. 2 is an operation explanatory sectional view of a main part after injection is completed in this embodiment.

FIG. 3 is an operation explanatory cross-sectional view of a main part in a standby state after completion of a pressure maintaining operation and in a standby state after completion of a measuring step of feeding a predetermined amount of molten resin to a front part of an injection driving body after completion of pressure holding.

FIG. 4 is an operation explanatory cross-sectional view of a main part in a state where the mold is released after the completion of the measuring step of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 Injection driving body 3 Molten resin 4 Die 6 Drip prevention mechanism

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Onozuka 2-11-14 Kugahara, Ota-ku, Tokyo Inside Sankyo Chemical Co., Ltd. (72) Inventor Osamu Nakazawa 2-11-14 Kuugahara, Ota-ku, Tokyo Sankyo Kasei F term (reference) 4F206 AR072 JA07 JD01 JD04 JL02 JM12 JN03 JQ03 JT02 JT11

Claims (5)

[Claims] 1. A molten resin is fed into a front portion of an injection driving body such as an injection screw or an injection plunger in an injection cylinder, and the injection driving body retreated backward is pushed forward by the molten resin fed into the front portion. In the injection molding method of injecting the molten resin into the mold from the front end of the injection cylinder, the pressure of the molten resin before injection, which has been sent to the front of the injection driving body, is suppressed to suppress generation of gas in the molten resin. Injection molding. 2. A gas before being injected, which has been fed into a front portion of the injection driving body, is pressed at a predetermined pressure or more by a pressing force of the injection driving body in an injection direction to generate gas in the molten resin. 2. The injection molding method according to claim 1, wherein the injection molding is performed. 3. The molten resin is poured onto the front end of the injection cylinder at the front of the injection driving body or the injection nozzle or runner in front of the injection cylinder when the mold is released. It is characterized in that a separation prevention mechanism is provided to prevent the molten resin from being peeled even if the molten resin is pressurized before injection, and a predetermined pressure is applied to the molten resin. The injection molding method according to claim 1. 4. After a weighing step in which at least a predetermined amount of molten resin is sent to a front portion of the injection driving body and stopped, the injection driving body is pushed forward to start an injection filling step of injecting the molten resin into a mold. The pressurization of the molten resin is continuously or continuously performed for a predetermined period of time.
4. The injection molding method according to any one of claims 1 to 3. 5. When the injection driving body is pushed forward to perform injection filling, the injection driving is performed while the molten resin is being pressurized or the position of the injection driving body when being pressurized is used as a reference of a movement start position. The injection molding method according to any one of claims 1 to 4, wherein the body is controlled to move forward by a predetermined stroke.