JP2009166463A - Gas foam injection molding machine - Google Patents

Abstract

An object of the present invention is to shorten the overall length of a screw used in a gas foam injection molding machine.
A heating cylinder has a screw arranged so as to be able to rotate and move forward and backward, and the screw is kneaded and plasticized with a raw material resin to form a molten resin, and fed from the first stage. A gas injection device for injecting gas into the second stage, and injecting the molten resin mixed with the gas into the mold. In the gas foam injection molding machine adapted to obtain a foam molded product by filling, P / D, which is the ratio of the screw pitch P and screw diameter D in the first stage, is set to 0.7 to 0.8. The configuration is such that P / D, which is the ratio of the pitch P of the screw and the diameter D of the screw in the second stage, is set to 1.0 to 1.2.
[Selection] Figure 1

Description

  The present invention relates to a gas foam injection molding in which a screw includes a first stage in which a raw material resin is kneaded and plasticized to form a molten resin, and a second stage in which a gas is mixed into the molten resin fed from the first stage. Related to the machine.

  A screw disposed in the heating cylinder so as to be able to rotate and move back and forth is a first stage for kneading and plasticizing the raw material resin to form a molten resin, and a gas for mixing the molten resin fed from the first stage with a gas. A gas injection device for injecting gas into the second stage, and injecting and filling molten resin mixed with gas into the mold to obtain a foam molded product Such a gas foam injection molding machine is known, and a screw for such a gas foam injection molding machine is disclosed in, for example, Japanese Patent Laid-Open No. 2005-1388 (Patent Document 1).

  FIG. 3 is a front view of an essential part showing a configuration example of an essential part of an injection system mechanism in a conventional gas foam injection molding machine. In FIG. 3, 101 is a head stock (heating cylinder holding block), 102 is a heating cylinder whose rear side is fixed and held by the head stock 101, and 103 is able to rotate and move forward and backward in the heating cylinder 102. The screw 103 is rotationally driven by a driving force of a metering servo motor (not shown) and is linearly driven by a driving force of an injection servo motor (not shown). .

  The screw 103 includes a first stage 104, a second stage 105, and a screw head 106. Between the first stage 104 and the second stage 105, a molten resin is contained in the second stage. A pressure-operated check valve (backflow prevention valve) 107 is provided to prevent backflow from 105 to the first stage 104.

  The first stage 104 of the screw 103 is supplied to the rear part of the first stage 104 by rotation of the screw 103 from a hopper (not shown) through the resin supply hole 101a of the headstock 101 and the resin supply hole 102a of the heating cylinder 102. The raw material resin (resin pellet) is transferred forward while being kneaded and plasticized by heat transfer from the heating cylinder 102 heated by the band heater and frictional heat such as the shearing action of the resin by the rotation of the screw 103. It has the function of melting and weighing one shot of molten resin and feeding it to the second stage 105 side. That is, the first stage 104 has a feed zone (supply area) and a compression zone (compression) from the rear to the front in the same manner as a screw of a general inline screw type injection molding machine without the second stage 105. Area), a metering zone (measuring area) is formed, and a length obtained by adding the length of the first stage 104 and the length of the screw head is a general in-line screw type having no second stage 105. The overall length of the screw of the injection molding machine is approximately the same. Note that P / D, which is a ratio of the pitch P of the screw in the first stage 104 and the diameter D of the screw 103, is approximately 1.0 (this is a general case without the second stage 105). It is roughly equivalent to the P / D of the screw of the inline screw type injection molding machine).

  On the other hand, the second stage 105 of the screw 103 has a function of mixing the gas into the molten resin fed from the first stage 104, and the gas injection device 108 makes a predetermined second to the rear side of the second stage 105. The SCF (supercritical flow) gas injected at a predetermined pressure during the time period is uniformly mixed with the molten resin by the rotation of the screw 103, and the molten resin mixed (mixed) with the SCF gas is transferred forward. It has become. The length of the second stage 105 is about 1/4 to 1/3 of the total length of a screw of a general inline screw type injection molding machine that does not have the second stage 105.

  Therefore, the total length of the screw 103 shown in FIG. 3 is longer by the length of the second stage 105 than the total length of the screw of a general in-line screw type injection molding machine without the second stage 105. ing.

  In the example shown in FIG. 3, the second stage 105 is configured with a double-pitch screw having a dense pitch, and the screw thread is partially divided. The cross flow is promoted in the molten resin so that a relatively high pressure gas is uniformly dispersed in the molten resin.

  In addition, after the metering process is completed, the pressure in the heating cylinder 102 on the second stage 105 side is used to operate the check valve 107 so as to prevent the backflow of the molten resin from the second stage 105 to the first stage 104. P2 is set to satisfy P2> P1 with respect to the pressure P1 in the heating cylinder 102 on the first stage 104 side. For this reason, the gas injection device 108 injects P2 into the heating cylinder 102 on the second stage 105 side. The pressure of the gas to be set is set to a predetermined pressure or higher so that the pressure P2 in the heating cylinder 102 on the second stage 105 side overcomes the pressure P1 in the heating cylinder 102 of the first stage 104.

A nozzle (check nozzle) 109 having a built-in opening / closing valve (not shown) is provided at the distal end side of the heating cylinder 102. During the injection process, an opening / closing valve member (such as a closing needle) in the nozzle 109 is connected to a valve drive source. When the screw 103 is driven forward in this state in the open state by the valve 110 and the valve drive mechanism 111, the molten resin mixed with the gas is injected and filled in a mold (not shown). The gas rapidly expands in the mold in the mold, and a foam molded product having a large number of bubbles in the resin is molded.
JP 2005-1388 A

  Although the gas foam injection molding machine shown in FIG. 3 and described above requires a special screw design screw 103 and a gas injection device 108, the mold opening / closing system mechanism has the same structure as a general injection molding machine. Therefore, it is possible to efficiently produce a foam-molded product with a relatively simple configuration and a simple molding process.

  However, as described above, the total length of the screw 103 is longer by the length of the second stage 105 than the total length of the screw of a general in-line screw type injection molding machine that does not have the second stage 105. , Increasing the overall length of the machine. In addition, a pressure-actuated check valve 107 is provided between the first stage 104 and the second stage 105, and the number of parts is increased by that amount, and the check valve 107 is slid many times due to use over time. Wear occurs in the check valve 107, and when this wear proceeds, the check valve 107 must be replaced.

  This invention is made | formed in view of said point, The place made into the objective is to shorten the full length of the screw used for a gas foam injection molding machine.

In order to achieve the above-mentioned object, the present invention has a screw disposed in a heating cylinder so as to be able to rotate and move forward and backward, and the screw kneads and plasticizes a raw material resin to form a molten resin; And a second stage for mixing gas into the molten resin fed from the first stage, and a gas injection device for injecting gas into the second stage is provided, and the molten resin mixed with gas In a gas foam injection molding machine in which a foam molded product is obtained by injecting and filling a mold into a mold, P / D, which is the ratio of the screw pitch P and screw diameter D in the first stage, is set to 0. .7 to 0.8, and P / D, which is the ratio between the screw pitch P and the screw diameter D in the second stage, is set to 1.0 to 1.2.
Further, the pressure in the heating cylinder on the second stage side is made lower than the pressure in the heating cylinder on the first stage side.
The gas injected into the molten resin of the second stage is carbon dioxide having a pressure lower than the pressure in the heating cylinder on the first stage side.
Moreover, the raw material resin supply apparatus which supplies raw material resin to the rear part of a 1st stage has a function which can adjust the quantity of raw material resin to supply.
In addition, there is no check valve at the boundary between the first stage and the second stage.

  In the present invention, P / D, which is a ratio of the pitch P of the screw in the first stage and the diameter D of the screw, is set to 0.7 to 0.8, which is compared with P / D≈1.0 in the conventional first stage. Since the screw pitch P in the first stage is set to be narrow, it is possible to apply a greater compressive force to the resin than in the conventional first stage, and a shorter length than in the conventional first stage. The raw material resin can be kneaded, plasticized and melted. Therefore, the total length of the screw can be made substantially the same as the total length of the screw of a general in-line screw type injection molding machine having no second stage, that is, the total length L of the screw and the diameter of the screw. L / D, which is the ratio to D, can be approximately 20 (in other words, the L / D of the screw is about the same as that of a screw of a general in-line screw type injection molding machine having no second stage. The total length of the gas foam injection molding machine can be made shorter than before. Furthermore, since the total length of the screw is approximately the same as the general-purpose screw, there is no specificity for the length of the screw, and a general-purpose member can be used as a member such as a heating cylinder or a heating cylinder cover. , Can contribute to cost reduction. Further, the P / D of the second stage is set to 1.0 to 1.2, and the P / D of the second stage is larger than the P / D of the first stage (the pitch P of the screw of the second stage) Therefore, in the second stage, the compressive force applied to the resin is significantly smaller than that in the first stage, and even if the gas is applied to the molten resin in the second stage. The pressure in the heating cylinder on the second stage side can be made lower than the pressure in the heating cylinder on the first stage side. Therefore, even if there is no check valve at the boundary between the first stage and the second stage, there is no possibility that the molten resin flows backward from the second stage side to the first stage side. The cost can be reduced by that amount, and there is no need to replace the check valve due to wear. Further, the gas (foaming agent) injected into the molten resin in the second stage is carbon dioxide, and carbon dioxide has a much higher solubility in the molten resin compared to nitrogen (the solubility is about 4 to 9 times in mol units). It can greatly contribute to lowering the pressure of carbon dioxide injected into the molten resin, and the high solubility of carbon dioxide in the molten resin enables uniform dispersion and mixing of carbon dioxide in the molten resin ( Mixing) can be reliably achieved in a short time, and thus can greatly contribute to the molding of a foam molded product of good quality. Furthermore, since the raw material resin supply device for supplying the raw material resin to the rear part of the first stage has a function capable of adjusting the amount of the raw material resin to be supplied, the supply amount of the raw material resin (resin pellet) can be freely adjusted. Since the pressure in the heating cylinder on the first stage side can be adjusted by adjusting the supply amount of the raw material resin, the pressure in the heating cylinder on the first stage side can be adjusted in the heating cylinder on the second stage side. Making it higher than the pressure can be achieved more easily.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 2 relate to a gas foam injection molding machine according to an embodiment of the present invention (hereinafter referred to as the present embodiment), and FIG. 1 illustrates the essential features of an injection system mechanism in the gas foam injection molding machine of the present embodiment. It is a principal part front view which shows the structure of a part.

  In FIG. 1, 1 is a head stock (heating cylinder holding block), 2 is a heating cylinder whose rear side is fixed and held on the head stock 1, 3 is a band heater wound around the outer periphery of the heating cylinder 2, 4 is a nozzle with an on-off valve (shutoff nozzle) provided on the front end side of the heating cylinder 2, and 5 is a screw disposed in the heating cylinder 2 so as to be able to rotate and move forward and backward. The screw 5 is rotationally driven by a driving force of a metering servo motor (not shown), and is linearly driven by a driving force of an injection servo motor (not shown).

  Reference numeral 6 denotes a raw material resin supply device (pellet feeder) arranged on the head stock 1 and capable of adjusting the supply amount of the raw material resin (resin pellets). Through the resin supply hole 1a and the resin supply hole 2a of the heating cylinder 2, the raw material resin is supplied to the inside of the rear end side of the heating cylinder 2 (the rear part of the first stage 5a described later of the screw 5). . The details of the raw material resin supply device 6 will be described later with reference to FIG.

  The screw 5 includes a first stage 5a, a second stage 5b, and a screw head 5c. A portion of the heating cylinder 2 corresponding to the second stage 5b is disposed within the heating cylinder 2. A gas injection device 7 for injecting carbon (injecting carbon dioxide into the molten resin of the second stage 5b) is provided.

  The first stage 5a of the screw 5 causes the band heater 3 to feed the raw material resin supplied to the rear part of the first stage 5a from the raw material resin supply device 6 through the resin supply hole 1a and the resin supply hole 2a by the rotation of the screw 5. It melts by transferring it forward while kneading and plasticizing by heat transfer from the heated heating cylinder 2 and frictional heat such as the shearing action of the resin due to the rotation of the screw 5, and measures the molten resin for one shot. Thus, it has a function of feeding to the second stage 5b side. That is, the first stage 5a has a feed zone (supply area) and a compression zone (compression area) from the rear to the front in the same manner as a screw of a general inline screw injection molding machine that does not have the second stage 5b. ), A metering zone (measuring basin) is formed.

  In this embodiment, P / D, which is the ratio of the screw pitch P in the first stage 5a and the diameter D of the screw 5, is set to 0.7 to 0.8, and this P / D = 0. 7 to 0.8 are smaller than P / D≈1.0 of the first stage of the screw in the conventional gas foam injection molding machine. As described above, in this embodiment, the P / D of the first stage 5a is set to 0.7 to 0.8, and the screw pitch P in the first stage 5a is set narrower than the conventional one. It is configured such that a compressive force larger than that of the first stage can be applied to the resin, and the raw material resin can be kneaded, plasticized and melted in a shorter length than the conventional first stage. Thus, the overall length of the first stage 5a can be made considerably shorter than the overall length of the conventional first stage, and the overall length of the second stage 5b is equivalent to the overall length of the conventional second stage. The total length of the screw 5 of this embodiment is significantly shorter than the total length of the screw of the conventional gas foam injection molding machine. That is, the total length of the screw 5 of the gas foam injection molding machine of this embodiment is substantially the same length as the total length of the screw of a general inline screw type injection molding machine that does not have the second stage, L / D, which is the ratio of the total length L of the screw 5 to the diameter D of the screw 5, is approximately 20 (this L / D≈20 is a general in-line screw type injection molding having no second stage). It is the same value as the L / D of the machine screw).

  Further, the second stage 5b of the screw 5 uniformly disperses and mixes (mixes) a gas as a foaming agent (here, carbon dioxide) into the molten resin fed from the first stage 5a. It has the function of transporting the molten resin mixed with water forward. That is, the second stage 5b is supplied with low pressure (higher than atmospheric pressure) carbon dioxide injected from the gas injector 7 to the rear side of the second stage 5b for a predetermined time period. By rotating, the molten resin mixed with carbon dioxide is transferred forward while being dispersed and uniformly mixed in the molten resin. However, in the present embodiment, carbon dioxide is used as the gas as the foaming agent, and the solubility of the carbon dioxide in the molten resin is much higher than that of nitrogen, so the second stage 5b (screw 5) is rotated so much. Even if not, carbon dioxide is easily and easily uniformly dispersed and mixed in the molten resin.In this embodiment, the first step is to transfer the molten resin mixed with carbon dioxide forward. This is the main function of the two stage 5b.

  In this embodiment, P / D, which is a ratio of the pitch P of the screw in the second stage 5b and the diameter D of the screw 5, is set to 1.0 to 1.2, and P of the second stage 5b is set. /D=1.0 to 1.2 is a larger value than P / D = 0.7 to 0.8 of the first stage 5a. In the present embodiment, since the P / D of the second stage 5b is made larger than the P / D of the first stage 5a in this way (the pitch P of the screw of the second stage 5b is set to the value of the first stage 5a). Since the pitch is larger than the pitch P of the screw), the second stage 5b can greatly reduce the compressive force applied to the resin as compared with the first stage 5a. In this embodiment, even if low pressure carbon dioxide is injected into the molten resin in the second stage 5b, the pressure in the heating cylinder 2 on the second stage 5b side (pressure due to the resin pressure and gas pressure) The pressure is lower than the pressure (resin pressure) in the heating cylinder 2 on the first stage 5a side, and in this embodiment, there is no check valve at the boundary between the first stage 5a and the second stage 5b. It has a structure.

  Here, in this embodiment, for example, when the raw material resin to be used is polypropylene (PP), the resin pressure in the heating cylinder 2 on the first stage 5a side is 3.0 to 8.0 MPa, and the second stage 5b. The resin pressure in the heating cylinder 2 on the side is set to 1.0 to 5.0 MPa, and the pressure of carbon dioxide injected into the heating cylinder 2 on the second stage 5b side is set to 0.8 to 1.5 MPa, respectively. It has become so.

  The nozzle (shutoff nozzle) 4 with an on-off valve shown in FIG. 1 is capable of moving back and forth within the nozzle outer casing 8 in which a plurality of nozzle components are integrated, and the nozzle outer casing 8. In addition, a closing needle 9 capable of closing / opening the most advanced nozzle opening of the nozzle outer casing 8 and a valve driving source 10 capable of driving the closing needle 9 forward and backward through a driving arm 11 are provided. The closing needle 9 is maintained in a closed state except during the injection process, and is in an open state only during the injection process.

  In the configuration shown in FIG. 1, during the weighing process, the raw material resin supplied from the raw material resin supply device 6 to the rear portion of the first stage 5 a of the screw 5 through the resin supply hole 1 a and the resin supply hole 2 a is rotated by the rotation of the screw 5. The first stage 5a is kneaded and plasticized, and the molten resin is fed from the first stage 5a side to the second stage 5b side. On the second stage 5b side, carbon dioxide injected by an appropriate amount from the gas injection device 7 at an appropriate timing is uniformly dispersed and mixed in the molten resin, and the molten resin mixed with carbon dioxide is transferred forward. To do. Then, one shot of molten resin mixed with carbon dioxide is stored on the front side of the screw head 5c of the screw 5, and the measuring step is completed when the screw 5 is retracted by a predetermined stroke. When the metering process is completed and immediately before the start timing of the injection process after a predetermined time, the closing needle 9 of the nozzle 4 with the on-off valve is moved from the closed position to the open position, and then the screw 5 Is driven forward, the molten resin mixed (mixed) with carbon dioxide from the nozzle 4 is injected and filled into the mold, whereby the carbon dioxide rapidly expands in the mold at atmospheric pressure. Thus, a foam molded product having a large number of bubbles in the resin is molded.

  FIG. 2 is a sectional side view showing the configuration of the raw material resin supply device (pellet feeder) 6. In FIG. 2, 21 is a holding block composed of a lower base 22 fixed on the headstock 1 and an upper base 23 fixed on the lower base 22, and 24 is fixed on the upper part of the upper base 23. The hopper 23a is a screw storage space formed along the longitudinal direction inside the upper base 23, and 23b is formed in the upper base 23 so as to communicate the lower opening of the hopper 24 and the screw storage space 23a. The resin supply hole 23c is formed in the upper base 23 so as to communicate the screw storage space 23a with the resin supply hole 22a of the lower base 22, and 22a is connected to the resin supply hole 1a of the headstock 1. The resin supply hole 25 formed in the lower base 22 so as to communicate with the resin supply hole 23c of the upper base 23 is rotatable in the screw storage space 23a. Setting has been screw, 26 is attached to the upper substrate 23, a feed control motor with a reduction gear mechanism for rotating the screw 25.

  In the configuration shown in FIG. 2, the raw material resin (resin pellets) dropped and supplied from the lower opening of the hopper 24 into the screw storage space 23 a through the resin supply hole 23 b is rotated by the screw 25 driven to rotate by the supply control motor 26. By the screw feeding action by the screw, the raw material resin that has been transferred in the direction of the resin supply hole 23c in the screw storage space 23a and reached above the resin supply hole 23c is the resin supply hole 23c, the resin supply hole 22a, the resin supply hole 1a, and the resin. It is supplied into the rear part of the heating cylinder 2 (the rear part of the first stage 5a of the screw 5) through the supply hole 2a.

  In the present embodiment, a controller (not shown) that controls the entire gas foam injection molding machine controls the rotation speed, rotation timing, and the like of the supply control motor 26. The supply amount of the raw material resin supplied to the rear part of the first stage 5a of the screw 5 can be freely adjusted.

  As described above, in this embodiment, in the gas foam injection molding machine in which the screw 5 includes the first stage 5a and the second stage 5b, the ratio of the screw pitch P to the diameter D of the screw 5 in the first stage 5a. When a certain P / D is set to 0.7 to 0.8 and compared with P / D≈1.0 in the conventional first stage, the screw pitch P in the first stage 5a is set narrower. Thus, a compressive force greater than that of the conventional first stage can be applied to the resin, and the raw material resin can be kneaded, plasticized and melted in a shorter length than the conventional first stage. Therefore, the total length of the screw 5 can be made substantially the same as the total length of the screw of a general in-line screw type injection molding machine having no second stage. L / D, which is a ratio to the diameter D of the screw, can be set to approximately 20 (in other words, L / D of the screw 5 is a general in-line screw type injection molding machine having no second stage. It is possible to make the gas foam injection molding machine shorter than before. Furthermore, since the total length of the screw 5 is substantially the same as the total length of the general-purpose screw, the specificity of the length of the screw 5 is lost, and a general-purpose member is used as a member such as the heating cylinder 2 or the heating cylinder cover. Can contribute to cost reduction. Further, the P / D of the second stage 5b is set to 1.0 to 1.2, and the P / D of the second stage 5b is made larger than the P / D of the first stage 5a (of the second stage 5b). Since the screw pitch P is wider than that of the first stage 5a), the compression force applied to the resin is significantly smaller in the second stage 5b than in the first stage 5a. Even if carbon dioxide is injected into the molten resin in the second stage 5b, the pressure in the heating cylinder 2 on the second stage 5b side can be made lower than the pressure in the heating cylinder 2 on the first stage 5a side. Therefore, even if there is no check valve at the boundary between the first stage 5a and the second stage 5b, there is no possibility that the molten resin flows backward from the second stage 5b side to the first stage 5a side, and the check valve is eliminated. Thus, the cost can be reduced by that amount, and the check valve is not replaced due to wear. Further, the gas (foaming agent) injected into the molten resin in the second stage 5b is carbon dioxide, and the solubility of the carbon dioxide in the molten resin is much higher than that of nitrogen (about 4 to 9 times the solubility in mole units). Can greatly contribute to lowering the pressure of the carbon dioxide injected into the molten resin, and the high solubility of the carbon dioxide in the molten resin enables uniform dispersion and mixing of carbon dioxide in the molten resin. Can be reliably achieved in a short time, and thus can greatly contribute to the molding of a foam molded product of good quality. Furthermore, since the raw material resin supply device 6 for supplying the raw material resin to the rear portion of the first stage 5a has a function capable of adjusting the amount of the raw material resin to be supplied, the supply amount of the raw material resin (resin pellet) can be freely adjusted. Since the pressure in the heating cylinder 2 on the first stage 5a side can be adjusted by adjusting the supply amount of the raw material resin, the pressure in the heating cylinder 2 on the first stage 5a side is adjusted to the second stage. Increasing the pressure in the heating cylinder 2 on the 5b side can be achieved more easily.

It is a principal part cutting front view which shows the structure of the principal part of the injection system mechanism in the gas foam injection molding machine which concerns on one Embodiment of this invention. It is a cutaway side view which shows the structure of the raw material resin supply apparatus in the gas foam injection molding machine which concerns on one Embodiment of this invention. It is a principal part cutting front view which shows the structural example of the principal part of the injection type | system | group mechanism in the conventional gas foam injection molding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Headstock 1a Resin supply hole 2 Heating cylinder 2a Resin supply hole 3 Band heater 4 Nozzle with an on-off valve 5 Screw 5a 1st stage 5b 2nd stage 5c Screw head 6 Raw material resin supply apparatus 7 Gas injection apparatus 8 Nozzle outer casing structure Body 9 Closing needle 10 Valve drive source 11 Drive arm 21 Holding block 22 Lower base 22a Resin supply hole 23 Upper base 23a Screw storage space 23b Resin supply hole 23c Resin supply hole 24 Hopper 25 Screw 26 Supply control motor

Claims (5)

The screw has a screw disposed in a heating cylinder so as to be able to rotate and move forward and backward. The screw kneads and plasticizes the raw material resin to form a molten resin, and the molten resin fed from the first stage. A gas injection device for injecting gas into the molten resin of the second stage, and injecting and filling the molten resin mixed with gas into the mold In the gas foam injection molding machine adapted to obtain a foam molded product,
P / D which is a ratio of the pitch P of the screw in the first stage and the diameter D of the screw is set to 0.7 to 0.8, and the pitch P of the screw in the second stage and the diameter D of the screw are set. A gas foam injection molding machine, wherein the ratio P / D is set to 1.0 to 1.2. In the gas foam injection molding machine according to claim 1,
A gas foam injection molding machine, wherein the pressure in the heating cylinder on the second stage side is lower than the pressure in the heating cylinder on the first stage side. In the gas foam injection molding machine according to claim 2,
The gas foam injection molding machine characterized in that the gas injected into the molten resin of the second stage is carbon dioxide having a pressure lower than the pressure in the heating cylinder on the first stage side. In the gas foam injection molding machine according to claim 2 or 3,
The raw material resin supply device for supplying the raw material resin to the rear part of the first stage has a function capable of adjusting the amount of the supplied raw material resin. In the gas foam injection molding machine according to claim 2 or 3,
A gas foam injection molding machine characterized in that a check valve is not provided at a boundary between the first stage and the second stage.

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