JP2002178367A - Method and apparatus for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a molding in a high quality by suppressing mixture of solid particles with the molding in the case of injection molding a resin. SOLUTION: A method for injection molding comprises the steps of heating to melt the resin in a heating cylinder 6 and injecting the resin from a nozzle 7 of a distal end in a mold. The method further comprises the steps of supplying a gas containing a smaller content of the solid particles than that of an atmosphere in which the cylinder 6 is installed, to an interior 8 of the cylinder 6 from an opening 26 of the cylinder 6 at least at a periphery of the opening 26 of the cylinder 6, at the end of the opposite side to the nozzle 7 or/and an end at an opposite side to the nozzle 7 to a resin supply port 19 of the cylinder 6; and molding the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection molding apparatus for molding high-quality plastic parts by injection molding.

[0002]

2. Description of the Related Art In plastic molded articles used for optical applications and molded articles requiring high appearance quality, foreign matter mixed in the molded articles is a major factor of quality deterioration.
Foreign matter in the molded product may be caused by the group particles floating in the atmosphere where the molding machine or the resin transport path is placed, entering the heated cylinder and entering the molded product, or oxidizing the resin generated in the heated cylinder. In many cases, this is caused by the incorporation of a deteriorated product into a molded product.

[0003] As a method of preventing solid particles in the environment from being mixed into the heating cylinder, the entire molding system may be installed in a highly clean atmosphere, or the resin may be transferred from a resin-encapsulated bag or a resin tank into the heating cylinder. Only the inside of the transport route has a clean atmosphere.

In Japanese Patent Application Laid-Open No. 9-254190, foreign matter adhering to resin pellets is removed in a resin hopper and in a step of transporting the resin to the resin hopper.

[0005]

However, in the method of installing the entire molding system in a clean environment,
Since extremely expensive environmental equipment is required, there is a problem that the cost of the molded article increases.

In the method of increasing the cleanliness in the resin transport path and removing foreign matter from the resin pellets during the process of transporting the resin to the resin hopper or the resin hopper, the heating cylinder is rotated with the rotation or forward and backward movement of the screw. There is a problem that solid particles floating in the environment enter the gap between the inner diameter of the heating cylinder and the screw from the opening on the side opposite to the nozzle in the above, and the solid particles are mixed into the molded product. In particular, when the resin pellets are transported from a resin tank such as a resin dryer to a molding machine by suction using a pump or the like, a negative pressure is generated in the heating cylinder, and the negative pressure causes the solid particles to enter through the opening described above. Is easily promoted.

On the other hand, in order to prevent the oxidation deterioration of the resin from being mixed into the molded product, nitrogen gas is supplied into the heating cylinder from the vicinity of the resin supply port of the heating cylinder to reduce the oxygen concentration in the heating cylinder. Therefore, a method for preventing the oxidative deterioration of the resin has been performed.

However, even when the nitrogen gas is supplied into the heating cylinder, the molding machine is installed from the opening of the heating cylinder at the end opposite to the nozzle with the rotation or forward and backward movement of the screw. Oxygen in the ambient atmosphere enters the gap between the inner diameter of the heating cylinder and the screw, making it impossible to reduce the oxygen concentration.

In particular, when the resin pellets are transported to the molding machine by suction from a resin tank such as a resin dryer by a pump or the like, the inside of the heating cylinder becomes a negative pressure, and the pressure of oxygen from the opening of the heating cylinder is reduced. Invasion is likely to be encouraged.

The present invention has been made in consideration of such conventional problems, and generates solid particles in an atmosphere mixed into a molded article or generated in a heating cylinder without using expensive environmental facilities. It is an object of the present invention to provide an injection molding method and an injection molding apparatus that can reduce oxidatively degraded products of a resin, thereby enabling injection molding of a low-cost, high-quality molded product.

[0011]

An injection molding method according to the present invention is an injection molding method for heating and melting a resin in a heating cylinder and injecting the resin into a mold from a nozzle at a tip end. At least the heating inside the heating cylinder from the opening of the heating cylinder at the end opposite to the nozzle and / or from the opening of the heating cylinder at the end opposite to the nozzle to the resin supply port of the heating cylinder. It is characterized by supplying a gas having a lower solid particle content than the atmosphere in which the cylinder is installed.

In the heating cylinder, an end opposite to the nozzle for injecting resin is opened, and gas in the atmosphere easily enters the inside of the heating cylinder from this opening. Also,
The resin supply port is also open, and gas from the atmosphere easily enters the inside of the heating cylinder from this resin supply port. According to the present invention, at least the periphery of the heating cylinder opening at the end opposite to the nozzle or / and the inside of the heating cylinder from the opening of the heating cylinder at the end opposite to the nozzle to the resin supply port of the heating cylinder. By supplying a gas having a lower content of solid particles than the atmosphere, the number of solid particles in the heating cylinder is reduced. This allows
Since the number of solid particles mixed in the molded article is reduced, a high-quality molded article can be injection-molded.

Further, according to the present invention, only a gas having a small solid particle content is supplied to a necessary portion, and a simple, inexpensive and high-quality molded product can be formed.

According to a second aspect of the present invention, in the first aspect of the present invention, the gas is supplied to the resin hopper while the resin is being supplied to the resin hopper connected to the resin supply port. While the supply of the resin is stopped, the supply of the gas is stopped or the supply amount is reduced.

In the present invention, the gas supply amount is adjusted in accordance with the resin supply state to the resin hopper, so that the gas consumption amount can be reduced.

A third aspect of the present invention is the invention according to the first or second aspect, wherein the gas is an inert gas.

By using the inert gas as described above, the oxygen concentration in the heating cylinder can be reduced.
Oxidation degradation of the resin can be suppressed. For this reason, the oxidation deterioration of the resin mixed into the molded product is reduced, and a high-quality molded product can be molded.

According to a fourth aspect of the present invention, there is provided an injection molding apparatus comprising: a heating cylinder for heating and melting a resin and injecting the resin into a mold from a tip nozzle; and a fixed particle content higher than an atmosphere in which the heating cylinder is installed. Gas supply means for supplying a gas having a small volume, wherein the gas supply means is provided around at least an opening of the heating cylinder at an end opposite to the nozzle or / and an opening of the heating cylinder at an end opposite to the nozzle. The gas is supplied to the inside of the heating cylinder from the section to the resin supply port of the heating cylinder.

According to the present invention, the gas supply means supplies a gas having a smaller content of solid particles than the atmosphere, and at least around the opening of the heating cylinder at the end opposite to the nozzle or / and the nozzle. Since the heat is supplied to the inside of the heating cylinder from the opening of the heating cylinder at the opposite end to the resin supply port of the heating cylinder, the number of solid particles in the heating cylinder can be reduced. Thereby, the number of solid particles mixed in the molded article is reduced, and a high-quality molded article can be injection-molded. Further, the gas supply means only supplies gas to a necessary portion, has a simple structure, and can form an inexpensive and high-quality molded product.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments shown in the drawings. In each of the embodiments, the same members are assigned the same reference numerals to correspond to each other.

(Embodiment 1) FIG. 1 shows Embodiment 1 of the present invention. The injection molding apparatus according to this embodiment includes a heating cylinder 6 having a nozzle 7 attached to a longitudinal end.
And a screw 11 inserted inside the inner diameter portion 8 of the heating cylinder 6 with a clearance 9 of about 0.02 mm.
And The nozzle 7 is for injecting resin into a mold (not shown).

The base end of the heating cylinder 6, that is, the end opposite to the nozzle 7, is inserted into the injection flange 1 fixed to a molding machine main body (not shown). Also,
This base end is fixed by a nut 4 to a water-cooled cylinder 2 fixed to the injection flange 1. Further, the heater 5 is arranged around the outer diameter portion of the heating cylinder 6.

The base end of the heating cylinder 6, that is, the end opposite to the nozzle 7, is an open opening 26. The heating cylinder 6 has a resin supply port 19 for supplying the resin pellets 14 therein. Resin pellets are supplied from the resin hopper 3 to the resin supply port 19.

The resin hopper 3 is fixed on the water cooling cylinder 2, and a resin dropping port at the lower end communicates with a resin outlet 18 formed in the water cooling cylinder 2. In this case, the heating cylinder 6 is assembled to the water cooling cylinder 2 so that the resin outlet 18 of the water cooling cylinder 2 and the resin supply port 19 of the heating cylinder 6 communicate with each other.

The screw 11 is connected to a motor (not shown) via a flange 10, whereby the screw 11 rotates in the heating cylinder 6. The screw 11 has
A flight 20 is provided from the vicinity of the resin supply port 19 of the heating cylinder 6 to the nozzle 6 side.

A resin inlet 1 is provided on the side of the resin hopper 3.
2 is open. Resin inlet 12 is resin pellet 1
4 is connected via a resin transport pipe 13 to a resin tank 15 in which the resin 4 is stored and a compressor 16. A filter 17 for filtering air is provided between the resin tank 15 and the compressor 16 of the resin transport pipe 13. ing.

The injection flange 1 has an internal space 22 in which a base end is provided with a compressor 21.
The tip of the injection pipe 23 connected to is inserted.
The tip of the injection pipe 23 is connected to the opening 26 of the heating cylinder 6.
Is inserted into the injection flange 1 so as to face the inner side. A filter 24 for removing solid particles from the atmosphere is provided at an intermediate portion of the injection pipe 23. Therefore, the gas that passes through the filter 24 and is discharged from the injection pipe 23 has a smaller fixed particle content than the gas in the atmosphere in which the heating cylinder 6 is installed.

In the above configuration, the compressor 2
2. The injection pipe 23 and the filter 24 constitute gas supply means. In this embodiment, the gas supply means supplies gas having a small content of fixed particles toward the opening 26 of the heating cylinder 6. It has become.

Next, the operation of this embodiment will be described.
When the compressor 16 is driven for a predetermined time, the filter 1
The clean air 25 is supplied to the resin tank 15 via the resin tank 7, and the resin pellets 14 in the resin tank 15 are pressure-fed into the resin hopper 3 via the resin transport pipe 13 and the resin inlet 12. The resin pellets supplied into the resin hopper 3 drop into the resin supply port 19 of the heating cylinder 6 via the resin outlet 18 of the water cooling cylinder 2.

In this state, when the screw 11 rotates while retreating to the side opposite to the nozzle 6, the resin pellet 14 from the resin supply port 19 of the heating cylinder 6
Nozzle 6 along flight 20 while being melted by
Move to the side. The molten resin is injected from the nozzle 6 into a mold (not shown) by the screw 11 advancing in the direction of the nozzle 6, and is molded by the mold. .

By repeating the rotation and the back-and-forth movement of the screw 11 as described above, continuous molding of the molded product is performed.
When the amount of 4 reaches the lower limit, the resin pellets 14 are again supplied by the compressor 16.

On the other hand, during molding, the compressor 21 of the gas supply means is constantly driven. This compressor 2
By the drive of 1, the atmosphere in which the molding machine (heating cylinder 6) is installed is injected into the internal space 22 of the injection flange 1 via the injection pipe 23 and the filter 24. At the time of this injection, since the solid particles in the gas are removed by the filter 24, clean air containing less solid particles than the atmosphere is provided near the opening 26 of the heating cylinder 6 in the internal space 22 of the injection flange 1. 27. Therefore, the number of solid particles that enter the heating cylinder inner diameter portion 8 from the vicinity of the opening 26 of the heating cylinder 6 is reduced with the rotation and the back and forth movement of the screw.

According to such an embodiment, the number of solid particles entering the inner diameter portion 8 of the heating cylinder 6 from the opening portion 26 of the heating cylinder 6 is reduced. The number of solid particles mixed in the mixture decreases. For this reason, the number of solid particles mixed in the molded article is reduced, and a high-quality molded article can be injection-molded. Further, in this embodiment, a gas having a small content of solid particles is merely supplied to the opening 26 of the heating cylinder 6, so that a simple, inexpensive and high-quality molded product can be formed.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention, in which a compressor 21, a filter 24 and an injection pipe 28 constitute a gas supply means.
In this embodiment, the tip of the injection pipe 28 is inserted into the inner diameter portion 8 of the heating cylinder 6. In this case, the injection pipe 28 is inserted into the heating cylinder 6 so as to be located between the resin supply port 19 and the opening 26.
The rest is the same as the first embodiment.

In such an embodiment, the gas is injected into the clearance 9 between the resin supply port 19 of the heating cylinder 6 and the opening 26 of the heating cylinder 6 by the drive 21 of the compressor. At this time, in the middle of the injection pipe 28,
Since the filter 24 is disposed, the clearance 9 is filled with the clean air 29.

According to this embodiment, the heating cylinder 6
Since the clean air 29 is directly injected into the clearance 9 in the inside, the solid particles that enter the inside of the heating cylinder 6 from the opening 26 are further reduced as compared with the first embodiment.
For this reason, the number of solid particles mixed into the inside of the molded article is further reduced, and the molded article can be molded with high quality.

(Embodiment 3) FIG. 3 shows Embodiment 3 of the present invention. In this embodiment, the nitrogen gas generator 30
And an injection pipe 31 connected to the nitrogen gas generator 30 and having a tip inserted into the heating cylinder 6, and a filter 32 provided at an intermediate portion of the injection pipe 31 to form a gas supply unit. In this case, the injection pipe 3
1 is inserted into the heating cylinder 6 so as to be located between the resin supply port 19 and the opening 26, and the nitrogen gas from the nitrogen gas generator 30 is supplied to the resin supply port 19 and the opening 26. Is injected into the clearance 9.

In this embodiment, the nitrogen gas from the nitrogen gas generator 30 is injected into the clearance 9 between the resin supply port 19 and the opening 26 of the heating cylinder 6 via the injection pipe 31. At this time, since the filter 32 is attached in the middle of the injection pipe 31, the clearance 9 is filled with clean nitrogen gas 33.

According to such an embodiment, since the clean nitrogen gas 33 is directly injected into the clearance 9, as in the second embodiment, the clean nitrogen gas 33 enters the inner diameter portion 8 of the heating cylinder 6 through the opening 26. Since the number of solid particles to be formed decreases and the number of solid particles mixed into the inside of the molded article decreases, molding can be performed with high quality. Further, by supplying the clean nitrogen gas 33 to the inner diameter portion 8 of the heating cylinder 6, the intrusion of oxygen from the opening 26 into the heating cylinder 6 is suppressed. Thereby, the inner diameter portion 8 of the heating cylinder 6
Since the oxygen concentration of the molten resin decreases, the oxidative deterioration of the molten resin is suppressed. Accordingly, the number of oxidized and degraded products that enter the inside of the molded article is reduced, and a molded article of higher quality can be molded.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment. In this embodiment, a seal ring 35 is arranged between an injection flange 34 for fixing the water cooling cylinder 2 and the flange 10 on the motor side. Further, a one-way valve 37 through which gas flows only from the internal space 36 to the outside of the injection flange 34 is connected to the internal space 36 of the injection flange 34.

In this embodiment, air is injected from the injection pipe 23 into the internal space 38 of the injection flange 36 by driving the compressor 21. The injection pipe 23 injects air toward the opening 26 of the heating cylinder 6 in the internal space 38, but since the filter 24 is attached in the middle of the injection pipe 23, the injection flange 3
Opening 26 of heating cylinder 6 in internal space 36 of
The vicinity is filled with clean air 27 from which solid particles have been removed. Therefore, the number of solid particles entering the inner diameter portion 8 of the heating cylinder 6 from the clearance 9 near the opening 26 is reduced.

Further, since the space between the injection flange 34 and the flange 10 is sealed by the seal ring 35, solid particles entering the internal space 36 of the injection flange 34 from the external atmosphere are reduced. In addition, the resin gas generated when the resin pellets 14 are heated inside the heating cylinder 6 is supplied to the clean air 2 by the one-way valve 37.
7 and is released into the atmosphere outside the injection flange 34.

According to such an embodiment, the number of solid particles entering the inner diameter portion 8 of the heating cylinder 6 from the opening 26 of the heating cylinder 6 is further reduced as compared with the first embodiment. This further reduces the number of solid particles mixed into the inside of the molded article. At this time, the release of the resin gas generated in the inner diameter portion 8 of the heating cylinder 6 to the outside atmosphere is not hindered, and the clean air 2
7 can be satisfied reliably.

(Fifth Embodiment) FIG. 5 shows a fifth embodiment. In this embodiment, the resin hopper 38 includes:
A resin inlet 41 connected to a resin tank 40 by a resin transport pipe 39 and a hopper inlet 44 connected to an intake pump 43 by an intake pipe 42 are provided. Further, the hopper intake port 44 is covered with a filter net 45 having holes smaller than the size of the resin pellet 14. Further, a tank inlet 47 provided with a filter 46 is connected to an upper portion of the resin tank 40.

An injection pipe 48 having one end connected to the nitrogen gas generator 30 and the other end connected to the internal space 36 of the injection flange 34 is arranged on the injection flange 34.
In the middle of the injection pipe 48, a filter 32 and a flow control valve 49 interlocked with the suction pump 43 are provided. These nitrogen gas generator 30, injection pipe 48, filter 3
2 and the flow control valve 49 constitute gas supply means.

In this embodiment, when the air inside the intake pipe 42, the resin hopper 38 and the resin transport pipe 39 is sucked by the drive of the intake pump 43, the resin tank is opened from the tank intake 47 through the filter 46. When the clean air 50 is supplied into the inside of the resin tank 40,
The resin pellets 14 therein are transported together with the clean air 50 into the resin hopper 38 via the resin transport pipe 39 and the resin inlet 41. At this time, since the hopper intake port 44 is blocked by the filter net 45, the resin pellets 14 are not sucked from the hopper intake port 44 to the intake pipe 42 side.

Further, nitrogen gas is injected into the internal space 36 of the injection flange 34 through the injection pipe 46 by the nitrogen gas generator 30. Since the filter 32 is installed in the middle of the injection pipe 46, the vicinity of the opening 26 of the heating cylinder 6 in the internal space 36 is filled with clean nitrogen gas 51 from which solid particles have been removed. When the suction pump 43 is driven, the flow control valve 49 is operated, and the internal space 3 of the injection flange 34 is moved from the injection pipe 46.
When the injection amount of nitrogen gas 51 injected into 6 is increased and the intake pump 43 stops, the flow control valve 49 is operated, and the injection amount of nitrogen gas 51 is reduced.

Further, the injection flange 34 and the flange 10
Is sealed by the seal ring 35, so that the number of solid particles and the amount of oxygen that enter the internal space 36 of the injection flange 34 from the external atmosphere are reduced. Also,
The resin gas generated when the resin pellets 14 are heated inside the heating cylinder 6 is released to the outside atmosphere of the injection flange 34 together with the clean nitrogen gas 51 by the one-way valve 37.

According to such an embodiment, since the air in the resin hopper 38 is sucked by the suction pump 43, the resin outlet 18 of the water-cooled cylinder 2 is The amount of oxygen that enters the inner diameter portion 8 of the heating cylinder 6 through the port 19 is smaller than in the fourth embodiment.

When the suction pump 43 is driven, air and nitrogen in the resin hopper 38, the resin outlet 18, the resin supply port 19, and the clearance 9 of the heating cylinder 6 are sucked, and at the same time, the injection flange 34 is sucked. The amount of clean nitrogen gas 51 injected into the internal space 36 is increased. Therefore, the amount of oxygen that enters the inner diameter portion 8 of the heating cylinder 6 from the opening portion 26 of the heating cylinder 6 during transportation of the resin pellet 14 can be further reduced.

Further, the injection flange 34 and the flange 10
Is sealed by the seal ring 35, the amount of oxygen that enters the internal space 36 of the injection flange 34 from the external atmosphere is reduced, and the resin pellet 1
4 is not transported, the internal space 36 of the injection flange 34
The amount of the nitrogen gas 51 to be injected into is reduced. For this reason, the consumption of nitrogen gas can be saved.

Thus, in this embodiment, the oxidation degradation of the resin pellets 14 in the heating cylinder 6 can be more reliably suppressed with a smaller amount of nitrogen than in the third embodiment. Opening 2 of cylinder 6
Since the amount of solid particles entering the inside of the heating cylinder 6 from the inside 6 decreases, the amount of foreign substances mixed into the inside of the molded article decreases. Thereby, a higher quality molded product can be molded.

The present invention is not limited to the above embodiment, but can be variously modified. For example, an inert gas other than a carbon dioxide gas, a rare gas, a hydrogen gas, and another nitrogen gas may be supplied into the heating cylinder to suppress the generation amount of the oxidation degradation product. When supplying a gas having a low content of solid particles, the gas may be supplied to both the opening 26 of the heating cylinder 6 and the inner diameter portion 8 of the heating cylinder 6 extending from the opening 26 to the resin supply port 19.

[0054]

According to the first aspect of the present invention, at least the periphery of the opening of the heating cylinder at the end opposite to the nozzle and / or the resin of the heating cylinder from the opening of the heating cylinder at the end opposite to the nozzle. Since a gas containing less solid particles than the atmosphere is supplied to the inside of the heating cylinder over the supply port, the number of solid particles in the heating cylinder can be reduced, and solid particles mixed into the molded product Is reduced, and a high-quality molded product can be molded.

According to the second aspect of the present invention, in addition to having the same effect as the first aspect of the present invention, the gas supply amount is adjusted according to the supply state of the resin to the resin hopper.
Gas consumption can be saved.

According to the invention of claim 3, claims 1 and 2
In addition to having the same effect as the invention of the above, the oxygen concentration in the heating cylinder can be reduced and the oxidative deterioration of the resin can be suppressed, so that the oxidized deterioration of the resin mixed into the molded product is reduced. As a result, a high quality molded product can be formed.

According to the fourth aspect of the present invention, since the gas supply means supplies a gas having a smaller content of solid particles than the atmosphere, the number of solid particles in the heating cylinder can be reduced, and high quality The molded article can be injection-molded, and the gas supply means has a simple structure, so that an inexpensive and high-quality molded article can be molded.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a second embodiment of the present invention.

FIG. 3 is a sectional view of a third embodiment of the present invention.

FIG. 4 is a sectional view of a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fifth embodiment of the present invention.

[Explanation of symbols]

 6 Heating cylinder 7 Nozzle 19 Resin supply port 21 Compressor 23 Injection pipe 24 Filter 26 Opening

Claims (4)

[Claims] 1. An injection molding method for heating and melting a resin in a heating cylinder and injecting the resin into a mold from a nozzle at a tip end, wherein at least a periphery of an opening of the heating cylinder at an end opposite to the nozzle. And / or a gas containing less solid particles than the atmosphere in which the heating cylinder is installed, inside the heating cylinder from the opening of the heating cylinder at the end opposite to the nozzle to the resin supply port of the heating cylinder. And an injection molding method. 2. The method according to claim 1, wherein the supply of the gas is performed while supplying the resin to the resin hopper connected to the resin supply port, and the supply of the gas is stopped while the supply of the resin to the resin hopper is stopped. 2. The injection molding method according to claim 1, wherein the stop or the supply amount is reduced. 3. The injection molding method according to claim 1, wherein the gas is an inert gas. 4. A heating cylinder for heating and melting the resin and injecting the resin into a mold from a tip nozzle, and a gas supply means for supplying a gas having a fixed particle content smaller than the atmosphere in which the heating cylinder is installed. Wherein the gas supply means extends from at least the periphery of the opening of the heating cylinder at the end opposite to the nozzle or / and the opening of the heating cylinder at the end opposite to the nozzle to the resin supply port of the heating cylinder. An injection molding apparatus for supplying the gas to the inside of the heating cylinder.