WO2025027676A1 - Filter attachment, and device and method for manufacturing foam-molded body - Google Patents

Abstract

The present invention provides a filter attachment as well as a device and method for manufacturing a foam-molded body, whereby the amount of molten resin supplied can be optimized while viewing the plasticization state of molten resin in a starvation zone, and molten resin can be kept from flowing back and sticking to the introduction vessel due to vent clogging or the like.　Provided is a filter attachment 400 that is removably provided in a tubular introduction vessel 300 for introducing a physical foaming agent into molten resin in a starved state, the filter attachment being characterized by comprising a tubular filter-holding member 410 and a physical foaming agent introduction filter 101 held at the tip of the filter-holding member 410, the filter-holding member 410 comprising, on the outer circumferential portion thereof, a sliding member 415 that allows the inner circumferential surface of the introduction vessel 300 to slide in the axial direction of the introduction vessel 300.

Description

Filter-equipped body, foam-molded body manufacturing device and manufacturing method

The present invention relates to a filter-equipped body, a manufacturing device for a foamed molded body, and a manufacturing method.

In foam injection molding methods using nitrogen or carbon dioxide as a physical foaming agent, there is a method in which a high-pressure fluid that becomes a supercritical fluid is sheared and kneaded with the molten resin to dissolve it. In contrast, Patent Document 1 discloses a method for molding a foam molded body using nitrogen or carbon dioxide, which are relatively low pressure, without the need for a supercritical fluid. With this method, fine foam cells can be formed in the molded body through a simple process using a low-pressure physical foaming agent without using special high-pressure equipment.

The manufacturing method of the foamed molded body described in Patent Document 1 uses a manufacturing device having a plasticization zone where a thermoplastic resin is plasticized and melted to become a molten resin, a starvation zone where the molten resin is in a starvation state, a plasticization cylinder formed with an inlet for introducing a physical foaming agent into the starvation zone, and an introduction rate adjustment vessel connected to the inlet, and the manufacturing method includes: plasticizing and melting the thermoplastic resin to become the molten resin in the plasticization zone; supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction rate adjustment vessel, introducing the pressurized fluid at the constant pressure from the introduction rate adjustment vessel to the starvation zone to maintain the starvation zone at the constant pressure; bringing the molten resin into a starvation state in the starvation zone; contacting the molten resin in the starvation state with the pressurized fluid in the starvation zone while maintaining the starvation zone at the constant pressure; and molding the molten resin in contact with the pressurized fluid containing the physical foaming agent into a foamed molded body.

In the conventional foam molding manufacturing method described above, the molten resin in the starvation zone may flow back into the inlet for introducing the physical foaming agent, which is provided in the cylinder and opens into the starvation zone, resulting in a vent-up. In this case, the molten resin may solidify and remain in the inlet. If the resin remains in the inlet, the physical foaming agent cannot be supplied stably, so it is necessary to remove the remaining resin, which is time-consuming.
In addition, when degassing the gas in the plasticizing cylinder during cleaning after the molding of the foam is completed, the gas (physical foaming agent) accumulated in the introduction rate adjusting container is introduced into the plasticizing cylinder all at once, which may result in a loud foaming sound.

To solve such problems, the invention described in Patent Document 2 is known.
The present invention relates to a filter for introducing a physical foaming agent, which is used when introducing a physical foaming agent into a starved molten resin, and which comprises a filter body and a plurality of fine holes provided in the filter body so as to penetrate the filter body in the thickness direction of the filter body, the fine holes comprising: resin contact side holes which open on one surface side of the filter body and are in contact with the molten resin; and physical foaming agent introduction holes which open on the other surface side of the filter body and communicate with the resin contact side holes, through which the physical foaming agent is introduced, the resin contact side holes having a diameter which is equal to or smaller than that of the physical foaming agent introduction holes and which is 10 to 80 μm.

Patent No. 6777553 JP 2023-30774 A

In the methods for producing foamed molded articles as described in Patent Documents 1 and 2, the amount of molten resin in the starvation zone needs to be brought into a starvation state (a state in which the starvation zone is not filled with molten resin but is left unfilled).
For this reason, in the manufacturing method of foamed molded bodies described in Patent Document 1, a hole is formed in the bottom of the speed control vessel into which the physical foaming agent is introduced, and through this hole it is possible to adjust the amount of molten resin supplied while visually checking the screw in the starvation zone.
In contrast, in the manufacturing method of foamed molded bodies described in Patent Document 2, a filter for introducing physical foaming agent is provided at the inlet to introduce the physical foaming agent into the starvation zone. However, the presence of this filter for introducing physical foaming agent makes it difficult to visually confirm the screw, which can make it difficult to optimize the supply amount of molten resin.

The present invention was made in consideration of the above circumstances, and aims to provide a filter-equipped body, a foam molding manufacturing device, and a manufacturing method that can optimize the amount of molten resin supplied while visually checking the plasticization state of the molten resin in the starvation zone, and can prevent the molten resin from flowing back into the introduction container and solidifying due to venting up, etc.

In order to solve the above problems, the present invention provides a filter-equipped body that is detachably provided in a cylindrical introduction vessel that introduces a physical foaming agent into a molten resin in a starved state, comprising:
The present invention comprises a cylindrical filter holding member and a filter for introducing a physical foaming agent held at a tip of the filter holding member,
The filter holding member is characterized in that it is provided, on its outer periphery, with a sliding member that enables the filter holding member to slide along the inner periphery of the introduction container in the axial direction of the introduction container.

Here, the filter for introducing a physical foaming agent has, for example, a filter body and a plurality of fine holes provided in the filter body so as to penetrate the filter body in the thickness direction.
The fine holes may be formed in a straight shape in the thickness direction of the filter body, or may be formed as follows.
That is, the micropores include resin contact side holes that open on one surface side of the filter body and are in contact with the molten resin, and physical foaming agent introduction holes that open on the other surface side of the filter body and communicate with the resin contact side holes, through which the physical foaming agent is introduced, and the resin contact side holes may have a diameter that is equal to or smaller than the diameter of the physical foaming agent introduction holes and is 10 to 80 μm.

In the present invention, the filter holding member that holds the filter for introducing a physical foaming agent is provided with a sliding member on its outer periphery that allows it to slide on the inner peripheral surface of the introduction container in the axial direction of the introduction container, so that when optimizing the supply amount of resin while visually checking the plasticization state of the molten resin in the starvation zone, the operator grasps the filter holding member and pulls it out in the axial direction of the introduction container, whereby the filter holding member slides on the inner peripheral surface of the introduction container in the axial direction by the sliding member, and the filter holding member can be removed from the introduction container. This allows the starvation zone to be visually checked through the introduction port. Therefore, the supply amount of molten resin can be optimized while visually checking the plasticization state of the molten resin in the starvation zone.
In addition, after optimizing the supply amount of molten resin, the filter for introducing a physical foaming agent can be provided at the inlet by grasping the filter holding member holding the filter for introducing a physical foaming agent and inserting it into the introduction container, thereby preventing the molten resin from flowing back into the introduction container and becoming stuck there due to venting up, for example.

In addition, in the above-mentioned configuration of the present invention, the sliding member may be a ball retainer provided on the outer periphery of the filter holding member.

With this configuration, a ball retainer is provided on the outer periphery of the filter holding member as a sliding member, so the filter holding member can be easily and reliably inserted and removed from the introduction container in the axial direction.

In addition, in the above-mentioned configuration of the present invention, the outer diameter of the tip of the filter holding member may be set so that the gap between the outer peripheral surface of the tip and the inner peripheral surface of the tip of the introduction container is 50 μm or less.

With this configuration, the gap between the outer peripheral surface of the tip of the filter holding member and the inner peripheral surface of the tip of the introduction container is narrow, at 50 μm or less, so that the starved molten resin can be prevented from entering the introduction container through the gap.

The manufacturing apparatus for foamed molded articles of the present invention includes a plasticization zone in which a thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone in which the molten resin is in a starvation state, and includes a plasticization cylinder provided with an inlet for introducing a physical foaming agent into the starvation zone;
An introduction container connected to the introduction port;
a physical foaming agent supply mechanism connected to the introduction container and supplying a physical foaming agent to the plasticizing cylinder via the introduction container;
The introduction container is provided with the filter-equipped body,
Supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction vessel, and introducing the pressurized fluid at the constant pressure from the introduction vessel to the starvation zone to maintain the starvation zone at the constant pressure;
While maintaining the starvation zone at the constant pressure, the molten resin in the starved state is brought into contact with a pressurized fluid containing a physical foaming agent at the constant pressure in the starvation zone;
The molten resin that has been brought into contact with a pressurized fluid containing the physical foaming agent is molded into a foamed molded product;
When optimizing the amount of molten resin supplied to the starvation zone, the filter-equipped body is removed from the introduction vessel and the starvation zone is visually observed through the introduction port.

The method for producing a foamed molded article of the present invention includes a plasticization cylinder having a plasticization zone in which a thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone in which the molten resin is in a starvation state, the plasticization cylinder being provided with an inlet for introducing a physical foaming agent into the starvation zone;
an introduction container connected to the introduction port;
a production apparatus having the filter-equipped body provided in the introduction vessel,
The manufacturing method includes:
In the plasticization zone, the thermoplastic resin is plasticized and melted to form the molten resin;
supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction vessel, and introducing the pressurized fluid at the constant pressure from the introduction vessel to the starvation zone to maintain the starvation zone at the constant pressure;
starving the molten resin in the starvation zone;
contacting the starved molten resin with the pressurized fluid in the starvation zone while maintaining the starvation zone at the constant pressure;
The molten resin that has been contacted with a pressurized fluid containing the physical foaming agent is molded into a foamed molded product,
When optimizing the amount of molten resin supplied to the starvation zone, the filter-equipped body is removed from the introduction vessel and the starvation zone is visually observed through the introduction port.

According to the foam molded body manufacturing apparatus and manufacturing method of the present invention, the filter holding member of the filter-equipped body is provided on its outer periphery with a sliding member that allows the filter holding member to slide on the inner periphery of the introduction container in the axial direction of the introduction container, so that when optimizing the supply amount of resin while visually checking the plasticization state of the molten resin in the starvation zone, the operator can grasp the filter holding member and pull it out in the axial direction of the introduction container, whereby the filter holding member slides on the inner periphery of the introduction container in the axial direction by the sliding member, and the filter holding member can be removed from the introduction container. Therefore, the supply amount of resin can be optimized while visually checking the plasticization state of the molten resin in the starvation zone.
In addition, after optimizing the amount of resin supplied, a filter holding member holding a filter for introducing a physical foaming agent can be inserted into the introduction container to prevent the molten resin from flowing back into the introduction container and solidifying due to venting up, for example.

The present invention makes it possible to optimize the amount of resin supplied while visually checking the plasticization state of the molten resin in the starvation zone, and also prevents the molten resin from flowing back into the introduction container and solidifying by venting up, etc.

FIG. 1 is a schematic cross-sectional view of an extrusion manufacturing apparatus for foamed molded articles, showing an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing the introduction container according to the first embodiment with the filter-equipped body removed. FIG. 4 is a schematic cross-sectional view showing a state in which a filter-equipped body is inserted into the introduction container according to the first embodiment. FIG. 2 is a schematic cross-sectional view showing a state in which a filter-equipped body is inserted into an introduction container and a lid is closed. 3 is a flowchart showing the extrusion manufacturing method for the foam molded article according to the first embodiment. 1A shows a filter for introducing a physical foaming agent, in which (a) is a plan view, (b) is a bottom view, and (c) is a cross-sectional view taken along line AA in (a). FIG. 2 is a cross-sectional view of a main part of the filter for introducing a physical foaming agent according to the first embodiment. FIG. 2 is a bottom view of a main part of the filter for introducing a physical foaming agent according to the first embodiment. 10A is a cross-sectional view of a first modified example, and FIG. 10B is a cross-sectional view of a second modified example, showing deformations of the microholes according to the first embodiment. FIG. 13 is a bottom view of a main part of a modified example of the filter for introducing a physical foaming agent according to the first embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. This embodiment contributes to "9. Build resilient infrastructure, promote inclusive and sustainable industry and technological innovation" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

In this embodiment, a foamed molded article is manufactured using a manufacturing apparatus 1000 shown in Fig. 1. The manufacturing apparatus 1000 mainly includes a plasticizing cylinder 210 having a screw 20 installed therein, a cylinder 100 which is a physical foaming agent supply mechanism that supplies a physical foaming agent to the plasticizing cylinder 210, a mold clamping unit (not shown) having a mold, and a control device (not shown) for controlling the operation of the plasticizing cylinder 210 and the mold clamping unit.
The molten resin that has been plasticized and melted in the plasticizing cylinder 210 flows from the right to the left in Fig. 1. Therefore, within the plasticizing cylinder 210 of this embodiment, the right side in Fig. 1 is defined as the "upstream" or "rear" and the left side is defined as the "downstream" or "front".

The plasticizing cylinder 210 has a plasticizing zone 21 where the thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone 23 downstream of the plasticizing zone 21 where the molten resin becomes in a starved state.
The "starvation state" refers to a state in which the molten resin does not fill the starvation zone 23, but is not filled therewith. Therefore, there is space in the starvation zone 23 other than the portion occupied by the molten resin. The plasticizing cylinder 210 is also formed with an inlet 202 for introducing a physical foaming agent into the starvation zone 23, and an introduction rate adjusting container (introduction container, pressure adjusting container) 300 is connected to the inlet 202. The cylinder 100 supplies the physical foaming agent to the plasticizing cylinder 210 via the introduction rate adjusting container 300.

Note that although the manufacturing apparatus 1000 has only one starvation zone 23, the manufacturing apparatus used in this embodiment is not limited to this. For example, in order to promote the penetration of the physical foaming agent into the molten resin, the manufacturing apparatus may have a plurality of starvation zones 23 and inlets 202 formed therein, and the physical foaming agent may be introduced into the plasticizing cylinder 210 from the plurality of inlets 202. Also, although the manufacturing apparatus 1000 is an injection molding apparatus, the manufacturing apparatus used in this embodiment is not limited to this and may be, for example, an extrusion molding apparatus.

In the manufacturing apparatus 1000, the resin pellets are plasticized and melted by the rotation of the screw 20 in the plasticizing cylinder 210, and the molten resin is sent to the front side in the plasticizing cylinder 210. In addition, the molten resin is sent to the front side in the plasticizing cylinder 210 by the rotation of the screw 20.
On the upper side of the plasticizing cylinder 210, there are provided, from the upstream side, a resin supply port 201 for supplying thermoplastic resin to the cylinder 210, and an inlet 202 for introducing a physical foaming agent into the plasticizing cylinder 210.
At the resin supply port 201, a hopper 211 for supplying resin and a feed screw 212 are disposed, and at the introduction port 202, an introduction speed adjusting container 300 is connected.

The plasticizing cylinder 210 has a plasticizing zone 21 provided on the upstream side and a starvation zone 23 provided on the downstream side. The plasticizing zone 21 is a zone where the thermoplastic resin is plasticized and melted to become molten resin. The starvation zone 23 is a zone where the molten resin is in a starved state. The "starvation state" refers to a state in which the molten resin does not fill the starvation zone 23 but is not filled therewith, or a state in which the density of the molten resin has decreased. Therefore, there may be space in the starvation zone 23 other than the portion occupied by the molten resin.

The plasticizing cylinder 210 has, from the upstream side to the downstream side, a plasticizing zone 21, a compression zone 22, a flow speed adjustment zone 25, a starvation zone 23, and a recompression zone 24. As described above, the plasticizing zone 21 is a zone where the thermoplastic resin is plasticized and melted to become a molten resin. The compression zone 22 is a zone where the thermoplastic resin is shear kneaded, plasticized and melted, and the molten resin is compressed. As described above, the starvation zone 23 is a zone where the molten resin becomes starved. The recompression zone 24 is a zone where the molten resin is recompressed. The flow speed adjustment zone 25 will be described later.

As described above, the plasticizing cylinder 210 is provided with the inlet 202 as an opening for introducing the physical foaming agent into the starvation zone 23. The inlet 202 is connected to an introduction rate adjusting container 300 (hereinafter, sometimes referred to as the introduction container 300). The cylinder 100 is connected to the introduction container 300 by a pipe 154 via a pressure reducing valve 151, a pressure gauge 152, and a release valve 153. The cylinder 100 supplies the physical foaming agent into the cylinder 210 via the introduction container 300.
In addition, a shutoff valve 28 that opens and closes by driving an air cylinder is provided at a nozzle tip 29 of the plasticizing cylinder 210, and high pressure can be maintained inside the plasticizing cylinder 210. A mold (not shown) is in close contact with the nozzle tip 29, and molten resin is injected from the nozzle tip 29 to fill a cavity formed by the mold.

The method for producing a foamed molded article according to this embodiment will be described with reference to the flow chart shown in FIG.
(1) The thermoplastic resin is plasticized and melted.
First, in the plasticizing zone 21 of the plasticizing cylinder 210, the thermoplastic resin is plasticized and melted to form a molten resin (step S1 in FIG. 5). As the thermoplastic resin, various resins can be used depending on the desired heat resistance and the application of the molded body.
Specifically, for example, thermoplastic resins such as polypropylene, polymethyl methacrylate, polyamide, polyethylene, polycarbonate, polybutylene terephthalate, amorphous polyolefin, polyetherimide, polyethylene terephthalate, polyether ether ketone, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), polyphenylene sulfide, syndiotactic polystyrene, polyamide imide, polylactic acid, polycaprolactone, and composite materials thereof can be used. Crystalline resins are particularly preferable because they are easy to form fine cells. These thermoplastic resins may be used alone or in combination of two or more types.
In addition, these thermoplastic resins may be mixed with various inorganic fillers such as glass fiber, talc, carbon fiber, and ceramic, and organic fillers such as cellulose nanofiber, cellulose, and wood flour. The thermoplastic resin is preferably mixed with an inorganic filler or organic filler that functions as a foaming nucleating agent, or an additive that increases melt tension. By mixing these, the foam cells can be made fine. The thermoplastic resin may also contain various other general-purpose additives as necessary.

The thermoplastic resin is plasticized and melted in the plasticizing cylinder 210 in which the screw 20 is installed. A band heater (not shown) is arranged on the outer wall surface of the plasticizing cylinder 210, which heats the plasticizing cylinder 210. Furthermore, shear heat is generated by the rotation of the screw 20, which causes the thermoplastic resin to plasticize and melt.

(2) Maintain pressure in the starvation zone.
Next, a physical foaming agent at a constant pressure is supplied to the introduction rate adjusting vessel 300, and a pressurized fluid at a constant pressure is introduced from the introduction rate adjusting vessel 300 into the starvation zone 23, thereby maintaining the starvation zone 23 at the constant pressure (step S2 in FIG. 5).

A pressurized fluid is used as the physical foaming agent. In this embodiment, "fluid" means any of liquid, gas, and supercritical fluid. In addition, from the viewpoint of cost and environmental load, carbon dioxide, nitrogen, and the like are preferable as the physical foaming agent. Since the pressure of the physical foaming agent in this embodiment is relatively low, for example, a fluid that is decompressed to a constant pressure by a pressure reducing valve 151 and taken out from a cylinder 100 in which a fluid such as a nitrogen cylinder, carbon dioxide cylinder, or air cylinder is stored can be used. In this case, a pressure boosting device is not required, so the cost of the entire manufacturing device can be reduced. In addition, if necessary, a fluid that has been pressurized to a predetermined pressure may be used as the physical foaming agent. For example, when nitrogen is used as the physical foaming agent, the physical foaming agent can be generated by the following method. First, atmospheric air is compressed by a compressor and passed through a nitrogen separation membrane to purify the nitrogen. Next, the purified nitrogen is pressurized to a predetermined pressure using a booster pump, a syringe pump, or the like to generate the physical foaming agent. Compressed air may also be used as the physical foaming agent. In this embodiment, forced shear mixing of the physical foaming agent and the molten resin is not performed. Therefore, even if compressed air is used as a physical foaming agent, oxygen, which has low solubility in molten resin, is less likely to dissolve in the molten resin, and oxidation deterioration of the molten resin can be suppressed.

The pressure of the physical foaming agent introduced into the starvation zone 23 is constant, and the pressure of the starvation zone 23 is maintained at the same constant pressure as the physical foaming agent introduced. The pressure of this physical foaming agent is preferably 0.5 MPa to 30 MPa, more preferably 1 MPa to 25 MPa, and even more preferably 1 MPa to 15 MPa. Although the optimal pressure varies depending on the type of molten resin, by setting the pressure of the physical foaming agent to 1 MPa or more, the amount of physical foaming agent required for foaming can be permeated into the molten resin, and by setting the pressure to 30 MPa or less, the heat resistance of the foamed molded article can be improved. If the foaming agent is produced at a pressure of more than 12 MPa (high pressure), the foaming agent is likely to remain undissolved.
The pressure of the physical foaming agent pressurizing the molten resin is "constant" means that the fluctuation range of the pressure relative to a predetermined pressure is preferably within ±20%, more preferably within ±10%. The pressure in the starvation zone 23 is measured, for example, by a pressure sensor 27 provided at a position opposite the inlet 202 of the plasticizing cylinder 210.

In addition, as the screw 20 advances and retreats, the starvation zone 23 moves forward and backward within the plasticizing cylinder 210, but the pressure sensor 27 shown in FIG. 1 is provided at a position that is always within the starvation zone 23 at the most advanced position and the most retreated position of the starvation zone 23. In addition, the position facing the inlet 202 is always within the starvation zone 23. Therefore, although the pressure sensor 27 is not provided at a position facing the inlet 202, the pressure indicated by the pressure sensor 27 and the pressure at the position facing the inlet 202 are almost the same. In addition, in this embodiment, only the physical foaming agent is introduced into the starvation zone 23, but other pressurized fluids other than the physical foaming agent may be introduced into the starvation zone 23 at the same time to an extent that does not affect the effects of the present invention. In this case, the pressurized fluid containing the physical foaming agent introduced into the starvation zone 23 has the above-mentioned constant pressure.

In addition, in this embodiment, the physical foaming agent is supplied from the cylinder 100 through the introduction container 300 and from the introduction port 202 to the starvation zone 23. The physical foaming agent is reduced to a predetermined pressure using the pressure reducing valve 151, and then introduced from the introduction port 202 to the starvation zone 23 without passing through a booster device or the like. In this embodiment, the amount and introduction time of the physical foaming agent introduced into the plasticizing cylinder 210 are not controlled. Therefore, a mechanism for controlling them, such as a drive valve using a check valve or solenoid valve, is not required, and the introduction port 202 does not have a drive valve and is always open. In this embodiment, the physical foaming agent supplied from the cylinder 100 maintains a constant pressure of the physical foaming agent from the pressure reducing valve 151 through the introduction speed adjustment container 300 to the starvation zone 23 in the plasticizing cylinder 210.

As shown in FIG. 2, the inlet 202 for the physical foaming agent has a larger inner diameter D1 than the inlet for the physical foaming agent of the conventional manufacturing apparatus. Therefore, even if the physical foaming agent is at a relatively low pressure, it can be efficiently introduced into the plasticizing cylinder 210. Even if a part of the molten resin comes into contact with the inlet 202 and solidifies, the large inner diameter D1 allows it to function as an inlet without being completely blocked. For example, when the inner diameter of the plasticizing cylinder 210 is large, that is, when the outer diameter of the plasticizing cylinder 210 is large, it is easy to increase the inner diameter D1 of the inlet 202. On the other hand, if the inner diameter D1 of the inlet 202 is too large, the molten resin will stagnate, causing molding defects, and the introduction container 300 connected to the inlet 202 will be large, increasing the cost of the entire apparatus. Specifically, the inner diameter D1 of the inlet 202 is 20% of the inner diameter of the plasticizing cylinder 210.
Preferably, the inner diameter D1 of the inlet 202 is 3 mm to 150 mm, more preferably 5 mm to 100 mm, regardless of the inner diameter of the plasticizing cylinder 210.
Here, the inner diameter D1 of the inlet 202 means the inner diameter of the opening on the inner wall 210a of the plasticizing cylinder 210, as shown in Fig. 2. The shape of the inlet 202, i.e., the shape of the opening on the inner wall 210a of the plasticizing cylinder 210, is not limited to a perfect circle, but may be an ellipse or a polygon. When the shape of the inlet 202 is an ellipse or a polygon, the diameter of a perfect circle having the same area as the area of the inlet 202 is defined as the "inner diameter D1 of the inlet 202".

Next, the introduction container 300 connected to the introduction port 202 will be described.
The introduction vessel 300 has the function of making the pressure of the physical foaming agent and the pressure of the starvation zone 23 in the plasticizing cylinder 210 the same constant pressure, and maintaining the starvation zone 23 at said constant pressure. For example, when a large amount of physical foaming agent is consumed in the starvation zone 23, the supply of physical foaming agent may not be able to keep up, and the pressure in the starvation zone 23 may suddenly drop. However, the introduction vessel 300 makes it possible to stably supply the physical foaming agent, and thus suppresses pressure fluctuations in the starvation zone 23.

In addition, the introduction container 300 is formed to have a certain volume or more, slowing down the flow rate of the physical foaming agent introduced into the plasticizing cylinder 210 and ensuring the time for the physical foaming agent to remain in the introduction container 300. The introduction container 300 is directly connected to the plasticizing cylinder 210 heated by a band heater (not shown) arranged around it, and the heat of the plasticizing cylinder 210 is also conducted to the introduction container 300. As a result, the physical foaming agent inside the introduction container 300 is heated, the temperature difference between the physical foaming agent and the molten resin is reduced, the temperature of the molten resin in contact with the physical foaming agent is prevented from being extremely lowered, and the amount of the physical foaming agent dissolved (permeated) into the molten resin is stabilized. In other words, the introduction container 300 functions as a buffer container with a function of heating the physical foaming agent. On the other hand, if the volume of the introduction container 300 is too large, the cost of the entire device increases. The volume of the introduction vessel 300 depends on the amount of molten resin present in the starvation zone 23, but is preferably 5 mL to 20 L, more preferably 10 mL to 2 L, and even more preferably 10 mL to 1 L. By setting the volume of the introduction vessel 300 within this range, the residence time of the physical foaming agent can be secured while taking costs into consideration.

Also, as described below, the physical foaming agent is consumed in the plasticizing cylinder 210 by contacting and penetrating the molten resin. In order to keep the pressure in the starvation zone 23 constant, the consumed amount of physical foaming agent is introduced from the introduction container 300 to the starvation zone 23. If the volume of the introduction container 300 is too small, the frequency of replacement of the physical foaming agent increases, making the temperature of the physical foaming agent unstable, and as a result, there is a risk of the supply of the physical foaming agent becoming unstable. Therefore, it is preferable that the introduction container 300 has a volume that can retain the amount of physical foaming agent consumed in the plasticizing cylinder 210 for 1 to 10 minutes. Also, for example, the volume of the introduction container 300 is preferably 0.1 to 5 times the volume of the starvation zone 23 to which the introduction container 300 is connected, and more preferably 0.5 to 2 times. In this embodiment, the volume of the starvation zone 23 refers to the volume of the region (starvation zone 23) in the empty plasticizing cylinder 210 that does not contain molten resin, where the diameter of the screw 20 shaft and the depth of the screw flight are constant.

As shown in FIG. 2, the introduction container 300 is mainly composed of a cylindrical container body 310, a connecting portion 320 that connects the container body 310 to the plasticizing cylinder 210, a flange portion 330 provided on the upper portion of the connecting portion 320, and a lid 340 for the container body 310 (see FIG. 4).
One end of the cylindrical container body 310 is connected to the inlet 202 via a connecting part 320, and the starvation zone 23 of the plasticizing cylinder 210 communicates with the internal space 312 via the inlet 202. A lid 340 (see FIG. 4) is provided at the other end (the end opposite the inlet 202) of the cylindrical container body 310 in an openable and closable manner. A pipe 154 for supplying a physical foaming agent to the internal space 312 is connected to the container body 310.

Furthermore, when the shape of the internal space 312 of the introduction container 300 is considered, the introduction container 300 has a cylindrical first straight section 31 connected to the introduction port 202 and whose inner diameter does not change, and a cylindrical second straight section 32 that is provided adjacent to the first straight section 31 and has a larger diameter than the first straight section 31 and whose inner diameter does not change. That is, as shown in FIG. 2, the introduction container 300 has a structure in which the first straight section 31, which is a cylinder having a small inner diameter D1, and the second straight section 32, which is a cylinder having a large inner diameter D2, are arranged so that their central axes are aligned on the same straight line m, and a step surface 33 perpendicular to the straight line m is provided at the boundary between the second straight section 32 and the first straight section 31. In this embodiment, the extension direction of the straight line m that coincides with the central axis of the first straight section 31 and the second straight section 32 coincides with the extension direction of the cylindrical introduction container 300. In this embodiment, the first straight section 31 and the step surface 33 are formed by the connecting section 320, and the second straight section 32 is formed by the container body 310.

The flange portion 330 is formed integrally with the container body 310 on the outer periphery of the tip portion (outer periphery of the lower end portion) of the container body 310 , and the lower surface of the flange portion 330 is in close contact with the outer periphery of the plasticizing cylinder 210 .
In addition, a flange portion 331 having a smaller diameter than the flange portion 330 is provided integrally with the flange portion 330 at the center of the lower surface of the flange portion 330, and this flange portion 331 is fitted into a recess 210a formed at the upper end of the inlet 202 of the plasticizing cylinder 210 so as to be recessed from the outer circumferential surface of the plasticizing cylinder 210 and coaxial with the inlet 202. In this manner, the introduction container 300 is connected to the inlet 202 of the plasticizing cylinder 210.

As shown in Fig. 4, the lid 340 is provided on the second straight portion 32 of the container body 310 in an openable and closable manner. It is preferable that the lid 340 can be opened and closed by an operator's hand without using a special tool. For example, a male thread portion 340a may be formed on the body of the lid 340, while a female thread portion 310a may be formed on the upper end opening of the container body 310, and the male thread portion 340a may be screwed into the female thread portion 310a, thereby allowing the lid 340 to be provided on the container body 310 in an openable and closable manner.
In the molding of a foamed molded body, the molding conditions may be set in advance (condition setting). In setting the molding conditions, the rotation speeds of the feed screw 212 and the screw 20, etc. are optimized, and it is confirmed whether a stable starvation state is created in the starvation zone 23. At the same time, it is confirmed whether the molten resin bulges out from the inlet 202 into the introduction container 300.
For this reason, it is preferable that the lid 340 can be opened and closed in a simple manner without using bolts, and that the filter-equipped body 400 described later can be removed from the introduction container 300 to remove the resin that has entered the introduction container 300. By making the lid 340 openable and closable by the operator's hand, the work efficiency of setting the molding conditions is improved. The sealing mechanism of the lid 340 is arbitrary, but a sealing mechanism with a built-in spring or a clutch-type high-pressure sealing mechanism can be used. In this embodiment, a polyimide sealing member 332 with a built-in spring is used. This sealing member 332 expands due to the gas pressure of the physical foaming agent remaining in the internal space 312, and the sealing property is improved. In addition, a disc-shaped deviation prevention member 340b that prevents the seal member 332 from escaping is provided at the tip (lower end) of the body of the lid 340 with a predetermined gap between it and the inner circumferential surface of the container body 310.

The material constituting the introduction container 300 is preferably pressure resistant from the viewpoint of containing pressurized fluid, and from the viewpoint of promoting solidification of the molten resin on the wall surface and suppressing the intrusion of the molten resin into the container, it is preferable that the material has a large heat capacity, is less likely to increase in temperature, and is easy to remove heat from the attached resin. Furthermore, from the viewpoint of heating the physical foaming agent, it is preferable that the material has a high thermal conductivity and is easy to transfer heat from the container body 310. From these viewpoints, the introduction container 300 is preferably made of a metal such as stainless steel (SUS).

(3) Starving the molten resin.
Next, the molten resin is caused to flow into the starvation zone 23, where the molten resin is put into a starvation state (step S3 in FIG. 5). The starvation state is determined by the balance between the amount of molten resin sent from the upstream of the starvation zone 23 to the starvation zone 23 and the amount of molten resin sent from the starvation zone 23 to its downstream. If the former is smaller, the starvation state occurs.

In this embodiment, the compression zone 22, where the molten resin is compressed and the pressure increases, is provided upstream of the starvation zone 23, so that the molten resin is starved in the starvation zone 23. In the compression zone 22, the diameter of the screw 20 is made larger (thicker) than that of the plasticization zone 21 located upstream, and a large diameter portion 20A is provided in which the screw flight is gradually shallower, and a seal portion 26 is further provided adjacent to the downstream side of the large diameter portion 20A. The seal portion 26 has a large (thicker) diameter of the screw 20 shaft like the large diameter portion 20A, and furthermore, no screw flight is provided, and instead of the screw flight, a plurality of shallow grooves are formed on the shaft of the screw 20. The large diameter portion 20A and the seal portion 26 reduce the clearance between the inner wall of the plasticization cylinder 210 and the screw 20 by increasing the diameter of the shaft of the screw 20, and the amount of resin supplied downstream can be reduced, so that the flow resistance of the molten resin can be increased. Therefore, in this embodiment, the large diameter portion 20A and the seal portion 26 are a mechanism for increasing the flow resistance of the molten resin.
The seal portion 26 also has the effect of suppressing the backflow of the physical foaming agent, that is, the movement of the physical foaming agent from the downstream side to the upstream side of the seal portion 26 .

Due to the presence of the large diameter portion 20A and the seal portion 26, the resin flow rate supplied from the compression zone 22 to the starvation zone 23 decreases, the molten resin is compressed in the upstream compression zone 22 and the pressure increases, and the molten resin is not filled (starved) in the downstream starvation zone 23. In order to promote the starvation state of the molten resin, the screw 20 has a structure in which the shaft diameter of the portion located in the starvation zone 23 is smaller (thinner) and the screw flight is deeper than the portion located in the compression zone 22. Furthermore, it is preferable that the screw 20 has a structure in which the shaft diameter of the portion located in the starvation zone 23 is smaller (thinner) and the screw flight is deeper than the portion located in the compression zone 22. Furthermore, it is preferable that the shaft diameter and the depth of the screw flight of the screw 20 are approximately constant throughout the starvation zone 23. This allows the pressure in the starvation zone 23 to be kept approximately constant, stabilizing the starvation state of the molten resin. In this embodiment, the starvation zone 23 is formed in a portion of the screw 20 where the diameter of the axis of the screw 20 and the depth of the screw flights are constant, as shown in FIG.

The mechanism for increasing the flow resistance of the molten resin provided in the compression zone 22 is not particularly limited as long as it is a mechanism for temporarily reducing the flow path area through which the molten resin passes in order to limit the resin flow rate supplied from the compression zone 22 to the starvation zone 23. In this embodiment, both the large diameter portion 20A of the screw and the seal portion 26 are used, but only one of them may be used. Mechanisms for increasing the flow resistance other than the large diameter portion 20A of the screw and the seal portion 26 include a structure in which the screw flights are provided in the opposite direction to other portions, a labyrinth structure provided on the screw, etc.

The mechanism for increasing the flow resistance of the molten resin may be provided on the screw as a separate member such as a ring, or may be provided integrally with the screw as part of the screw structure. If the mechanism for increasing the flow resistance of the molten resin is provided as a separate member such as a ring, the size of the clearance portion, which is the flow path for the molten resin, can be changed by changing the ring, which has the advantage that the magnitude of the flow resistance of the molten resin can be easily changed.

In addition to the mechanism for increasing the flow resistance of the molten resin, the molten resin can also be starved in the starvation zone 23 by providing a backflow prevention mechanism (sealing mechanism) between the compression zone 22 and the starvation zone 23 to prevent the molten resin from flowing back from the starvation zone 23 to the upstream compression zone 22. For example, a sealing mechanism such as a ring or steel ball that can move upstream due to the pressure of the physical foaming agent can be used. However, since the backflow prevention mechanism requires a drive unit, there is a risk of resin stagnation. For this reason, a mechanism for increasing flow resistance that does not have a drive unit is preferable.

In this embodiment, the amount of thermoplastic resin supplied to the plasticizing cylinder 210 may be controlled to stabilize the starvation state of the molten resin in the starvation zone 23. If the amount of thermoplastic resin supplied is too large, it becomes difficult to maintain the starvation state. In this embodiment, a general-purpose feed screw 212 is used to control the amount of thermoplastic resin supplied. By limiting the amount of thermoplastic resin supplied, the metering speed of the molten resin in the starvation zone 23 becomes greater than the plasticization speed in the compression zone 22. As a result, the density of the molten resin in the starvation zone 23 is stably reduced, and the penetration of the physical foaming agent into the molten resin is promoted.

In this embodiment, the length of the starvation zone 23 in the flow direction of the molten resin is preferably long to ensure the contact area and contact time between the molten resin and the physical foaming agent, but if it is too long, it will have the disadvantage of increasing the molding cycle and screw length. For this reason, the length of the starvation zone 23 is preferably 2 to 12 times the inner diameter of the plasticizing cylinder 210, and more preferably 4 to 10 times. In addition, it is preferable that the length of the starvation zone 23 covers the entire range of the metering stroke in injection molding. In other words, it is preferable that the length of the starvation zone 23 in the flow direction of the molten resin is equal to or longer than the length of the metering stroke in injection molding. The screw 20 moves forward and backward as the molten resin is plasticized, metered, and injected, but by making the length of the starvation zone 23 equal to or longer than the length of the metering stroke, the inlet 202 can always be positioned (formed) within the starvation zone 23 during the production of the foamed molded body. In other words, even if the screw 20 moves forward and backward during the production of the foamed molded body, no zone other than the starvation zone 23 comes to the position of the inlet 202. As a result, the physical foaming agent introduced from the inlet 202 is always introduced into the starvation zone 23 during the production of the foamed molded body. By providing a starvation zone having a sufficient and appropriate size (length) in this way and introducing a constant pressure of physical foaming agent therein, it becomes easier to maintain the starvation zone 23 at a constant pressure. In this embodiment, the length of the starvation zone 23 is approximately the same as the length of the portion of the screw 20 where the diameter of the screw 20 shaft and the depth of the screw flight are constant, as shown in FIG. 1.

Furthermore, a flow rate adjustment zone 25 is provided between the compression zone 22 and the starvation zone 23. Comparing the flow rate of the molten resin in the compression zone 22 upstream of the flow rate adjustment zone 25 with the flow rate of the molten resin in the starvation zone 23 downstream, the flow rate of the molten resin in the starvation zone 23 is faster. The inventors have found that by providing the flow rate adjustment zone 25 as a buffer zone between the compression zone 22 and the starvation zone 23 and suppressing this sudden change (increase) in the flow rate of the molten resin, the foamability of the produced foamed molded product is improved. Although the details of the reason why the foamability of the foamed molded product is improved by providing the flow rate adjustment zone 25 as a buffer zone between the compression zone 22 and the starvation zone 23 is unclear, it is speculated that one of the reasons is that the physical foaming agent flowing in from the starvation zone 23 is kneaded with the molten resin due to the molten resin being retained in the flow rate adjustment zone 25, and the contact time is extended. In this embodiment, the flow rate of the molten resin is adjusted by providing a pressure reduction section and a compression section in the portion of the plasticizing screw 20 located in the flow rate adjustment zone 25 shown in FIG. 1, that is, by changing the depth of the screw flight, or in other words, by changing the size (thickness) of the screw diameter.

(4) Contact of Molten Resin with Physical Foaming Agent Next, while the starvation zone 23 is maintained at a constant pressure, the starved molten resin is brought into contact with the physical foaming agent at a constant pressure in the starvation zone 23 (step S4 in FIG. 5). That is, in the starvation zone 23, the molten resin is pressurized at a constant pressure by the physical foaming agent. Since the starvation zone 23 is not filled with molten resin (starved state) and has a space in which the physical foaming agent can exist, the physical foaming agent and the molten resin can be efficiently brought into contact with each other. The physical foaming agent that has come into contact with the molten resin penetrates into the molten resin and is consumed. When the physical foaming agent is consumed, the physical foaming agent that has stayed in the introduction container 300 is supplied to the starvation zone 23. As a result, the pressure in the starvation zone 23 is maintained at a constant pressure, and the molten resin continues to come into contact with the physical foaming agent at a constant pressure.

In conventional foam molding using a physical foaming agent, a predetermined amount of high-pressure physical foaming agent was forcibly introduced into the plasticizing cylinder within a predetermined time. Therefore, it is necessary to pressurize the physical foaming agent to a high pressure and accurately control the amount and time of introduction into the molten resin, and the physical foaming agent is in contact with the molten resin only for a short introduction time. In contrast, in this embodiment, the physical foaming agent is not forcibly introduced into the plasticizing cylinder 210, but a constant pressure physical foaming agent is continuously supplied into the plasticizing cylinder so that the pressure in the starvation zone 23 is constant, and the physical foaming agent is continuously brought into contact with the molten resin. This stabilizes the amount of dissolution (penetration amount) of the physical foaming agent into the molten resin, which is determined by the temperature and pressure. In addition, since the physical foaming agent of this embodiment is always in contact with the molten resin, a necessary and sufficient amount of the physical foaming agent can permeate into the molten resin. As a result, the foam molded product produced in this embodiment has fine foam cells, despite the use of a low-pressure physical foaming agent compared to conventional molding methods using physical foaming agents.

In addition, the manufacturing method of this embodiment does not require control of the amount and time of introduction of the physical foaming agent, and therefore does not require check valves, solenoid valves, or other actuating valves, or control mechanisms for controlling these, reducing equipment costs. In addition, the physical foaming agent used in this embodiment has a lower pressure than conventional physical foaming agents, so the load on the equipment is also smaller.

In this embodiment, the starvation zone 23 is always kept at a constant pressure during the production of the foam molded article. That is, in order to replenish the physical foaming agent consumed in the plasticizing cylinder, all steps of the method for producing a foam molded article are carried out while continuously supplying the physical foaming agent at the constant pressure. Also, in this embodiment, for example, when performing multiple shots of injection molding continuously, the next shot of molten resin is prepared in the plasticizing cylinder even during the injection step, the molding cooling step, and the molding removal step, and the next shot of molten resin is pressurized at a constant pressure by the physical foaming agent. That is, in multiple shots of injection molding continuously performed,
One cycle of injection molding is performed in a state where the molten resin and the physical foaming agent at a constant pressure are always present and in contact with each other, i.e., in a state where the molten resin is always pressurized by the physical foaming agent at a constant pressure in the plasticizing cylinder, one cycle of injection molding is performed, which includes a plasticization metering step, an injection step, a molding cooling step, an ejection step, etc. Similarly, when performing continuous molding such as extrusion molding, molding is performed in a state where the molten resin and the physical foaming agent at a constant pressure are always present and in contact with each other in the plasticizing cylinder, i.e., in a state where the molten resin is always pressurized by the physical foaming agent at a constant pressure in the plasticizing cylinder.

(5) Foam molding Next, the molten resin in contact with the physical foaming agent is molded into a foam molded body (step S5 in FIG. 5). The plasticizing cylinder 210 used in this embodiment is disposed downstream of the starvation zone 23 and adjacent to the starvation zone 23, and has a recompression zone 24 in which the molten resin is compressed and the pressure increases. First, the molten resin in the starvation zone 23 is caused to flow into the recompression zone 24 by the rotation of the plasticizing screw 20. The molten resin containing the physical foaming agent is pressure-adjusted in the recompression zone 24, and is extruded forward of the plasticizing screw 20 and metered. At this time, the internal pressure of the molten resin extruded forward of the plasticizing screw 20 is controlled as a screw back pressure by a hydraulic motor or an electric motor (not shown) connected to the rear of the plasticizing screw 20. In this embodiment, in order to homogeneously dissolve the physical foaming agent in the molten resin without separating it and to stabilize the resin density, it is preferable to control the internal pressure of the molten resin extruded forward of the plasticizing screw 20, i.e., the screw back pressure, to be about 1 to 6 MPa higher than the pressure in the starvation zone 23, which is kept constant. In this embodiment, a check ring 50 is provided at the tip of the screw 20 so that the compressed resin in front of the screw 20 does not flow back upstream. As a result, the pressure in the starvation zone 23 is not affected by the resin pressure in front of the screw 20 during metering.

The method of molding the foamed molded body is not particularly limited, and the molded body can be molded by, for example, injection foam molding, extrusion foam molding, foam blow molding, etc. In this embodiment, injection foam molding is performed by injecting and filling a measured amount of molten resin from the plasticizing cylinder 210 shown in FIG. 1 into a cavity (not shown) in a mold. For injection foam molding, a short shot method may be used in which the mold cavity is filled with molten resin at a filling volume of 75% to 95% of the mold cavity volume, and the mold cavity is filled while the bubbles expand, or a core back method may be used in which the cavity volume is expanded and foamed after filling with molten resin at a filling volume of 100% of the mold cavity volume. Since the obtained foamed molded body has foam cells inside, the shrinkage of the thermoplastic resin during cooling is suppressed, sink marks and warpage are reduced, and a molded body with a low specific gravity is obtained.

In the manufacturing method of this embodiment described above, since it is necessary to control the amount of physical foaming agent introduced into the molten resin, the introduction time, etc., it is possible to omit or simplify complex control devices, thereby reducing equipment costs. Furthermore, in the manufacturing method of the foamed molded body of this embodiment, the molten resin in a starved state is brought into contact with the physical foaming agent at a constant pressure in the starvation zone 23 while the starvation zone 23 is maintained at a constant pressure. This makes it possible to stabilize the amount of physical foaming agent dissolved (penetrated) into the molten resin by a simple mechanism.

1 to 4, the manufacturing apparatus 1000 of this embodiment includes a filter-equipped body 400. The filter-equipped body 400 is detachably provided in the introduction container 300.
As shown in FIG. 2, the filter-equipped body 400 includes a cylindrical filter holding member 410 and a filter 101 for introducing a physical foaming agent (hereinafter, sometimes abbreviated to filter 101) held at the tip of the filter holding member 410.

The filter holding member 410 includes a cylindrical main body 411 and a donut-shaped disk-shaped flange 412 fixed to the upper end of the main body 411. An operator can grasp the filter-equipped body 400 by grasping the flange 412.
The main body 411 has a straight hole 411a formed therein, and the filter 101 is provided at the lower end of the hole 411a. The filter 101 is fitted into the folder 110.
The filter 101 is formed in a disk shape with a thickness of about 2 to 3 mm and a diameter of about 30 mm.
The folder 110 is formed in a cylindrical shape, and the filter 101 is fitted and fixed to the inner peripheral surface of approximately the lower half of the folder 110. Furthermore, the lower end surface of the filter 101 and the lower end surface of the folder 110 are approximately flush with each other.
Further, a male thread portion 110c is formed on the outer peripheral surface of the folder 110, and this male thread portion 110c is screwed into a female thread portion formed on the inner peripheral surface of the lower end portion of the main body portion 411 of the filter holding member 410. In this way, the folder 110 is attached to the lower end portion of the main body portion 411 of the filter holding member 410. Therefore, the filter 101 is attached to the lower end portion of the main body portion 411 via the folder 110.

Further, a sliding member 415 that allows the inner peripheral surface of the introduction container 300 to slide in the axial direction of the introduction container 300 is provided on the outer periphery of the upper part of the main body 411 of the filter-equipped body 400. This sliding member 415 is a ball retainer 415 provided on the outer periphery of the main body 411. As shown in Fig. 3, when the filter-equipped body 400 is inserted into the introduction container 300, this ball retainer 415 abuts or presses against the inner peripheral surface of the introduction container 300 with almost no gap, and in this state, the multiple balls of the ball retainer 415 are able to roll on the inner peripheral surface of the introduction container 300 in the axial and circumferential directions of the introduction container 300.
Furthermore, a flange portion 411 b is provided on the outer periphery of the main body portion 411 lower end side than the sliding member (ball retainer) 415 so as to protrude radially outward from the outer periphery of the main body portion 411 .

Then, as shown in FIG. 3, the filter-equipped body 400 equipped with the filter 101 is inserted into the introduction container 300 from the upper end opening, and the flange portion 411b of the filter-equipped body 400 abuts against the step surface 33 of the introduction container 300, whereby the filter-equipped body 400 is axially positioned in the introduction container 300. In this state, the lower end surface of the filter 101 and the lower end surface of the introduction port 202 of the plasticizing cylinder 210 are flush with each other, so that the filter 101 faces the starvation zone 23 of the plasticizing cylinder 210.

The outer diameter of the tip 410a of the filter holding member 410 of the filter-equipped body 400 is set so that the gap S between the outer circumferential surface of the tip 410a and the inner circumferential surface of the tip of the introduction container 300 is 50 μm or less. In other words, the tip 410a of the filter holding member 410 is inserted inside the connecting portion 320 of the tip of the introduction container 300, but the filter-equipped body 400 needs to be removed from the introduction container 300 as necessary. For this reason, a predetermined gap S is provided between the outer circumferential surface of the tip 410a of the filter holding member 410 and the inner circumferential surface of the connecting portion 320 of the introduction container 300, and this gap S is set to 50 μm or less.

As shown in Figures 6 and 7, the filter 101 has a disk-shaped filter body 102 and a large number (plurality of) fine holes 103 that penetrate the filter body 102 in the thickness direction.
The micropores 103 are provided with a resin contact side hole 103a which opens onto one surface side of the filter body 102 and comes into contact with the molten resin, and a physical foaming agent introduction hole 103b which opens onto the other surface side of the filter body 102 and is connected to the resin contact side hole 103a, through which a physical foaming agent is introduced.

Moreover, the filter 101 is formed from a finely perforated porous metal material manufactured using a metal 3D printer.
That is, one method for manufacturing three-dimensional objects in a three-dimensional modeling device that produces three-dimensional objects made of metal, a so-called metal 3D printer, is a metal powder additive manufacturing method in which metal material powder is evenly scattered to form a powder layer, and a laser beam or an electron beam is irradiated onto a specified irradiation area on the powder layer to melt and solidify the material powder in the specified irradiation area, and the process is repeated to stack sintered layers to generate the three-dimensional object.
In this embodiment, the filter body 102 is manufactured by a metal powder additive manufacturing method, and a large number of fine holes 103 each having an oil contact side hole 103a and a physical foaming agent introduction hole 103b are formed at the same time.
The filter 101 is not limited to being made of metal, but may be made of resin.

The resin contact side hole 103a and the physical foaming agent introduction hole 103b are arranged coaxially, and the diameter of the resin contact side hole 103a is equal to or smaller than that of the physical foaming agent introduction hole 103b, but in this embodiment, the diameter of the resin contact side hole 103a is smaller than that of the physical foaming agent introduction hole 103b (for example, about 1/2 the diameter of the physical foaming agent introduction hole 103b) as shown in Figures 7 and 8. Also, the axial length of the resin contact side hole 103a is shorter than that of the physical foaming agent introduction hole 103b.
The diameter d1 of the resin contact side hole 103a is 10 to 80 μm, and the diameter d2 of the physical foaming agent introduction hole 103b is 20 to 400 μm.

Here, the diameter d1 of the resin contact side hole 103a is specified to be 10 to 80 μm because it is technically difficult to form the resin contact side hole with a diameter of less than 10 μm, and also because if the diameter d1 exceeds 80 μm, the molten resin will enter the resin contact side hole 103a and solidify, making it easy for the resin contact side hole 103a to become blocked.
The diameter d2 of the physical foaming agent introduction holes 103b is specified to be 20 to 400 μm because, if the diameter d2 of the physical foaming agent introduction holes is less than 20 μm, the passage of the physical foaming agent is deteriorated, making it difficult to reliably introduce the physical foaming agent into the molten resin in a starved state, and, if the diameter d2 exceeds 400 μm, the diameter of the physical foaming agent introduction holes 103b becomes too large, resulting in a decrease in the number of the physical foaming agent introduction holes 103b.

In addition, the resin contact side hole 103a and the physical foaming agent introduction hole 103b have a circular cross-sectional shape in this embodiment, but are not limited to this and may be a triangular shape, a polygonal shape with four or more sides, an oval shape, an elliptical shape, a cloud shape, a star shape, or the like, or these may be mixed appropriately.
When the cross-sectional shape of the resin contact side hole 103a and the physical foaming agent introduction hole 103b is other than circular, the diameter of the resin contact side hole 103a and the physical foaming agent introduction hole 103b is defined as the diameter of a perfect circle having the same area as the cross-sectional area of the resin contact side hole 103a and the physical foaming agent introduction hole 103b.

In addition, in this embodiment, the inner peripheral surfaces of the resin contact side hole 103a and the physical foaming agent introduction hole 103b are formed straight in the axial direction, but this is not limited to this. For example, as shown in FIG. 9(a), the inner peripheral surface of the physical foaming agent introduction hole 103b may be formed so as to be inclined with respect to the axial direction. In this case, the physical foaming agent introduction hole 103b is formed so that its diameter becomes smaller toward the resin contact side hole 103a side. Also, as shown in FIG. 9(b), the inner peripheral surfaces of the physical foaming agent introduction hole 103b and the resin contact side hole 103a may be formed so as to be inclined with respect to the axial direction. In this case, the physical foaming agent introduction hole 103b is formed so that its diameter becomes smaller toward the resin contact side hole 103a side, and the resin contact side hole 103a is formed so that its diameter becomes smaller as it moves away from the physical foaming agent introduction hole 103b.

In the case shown in FIG. 9(a), the diameter of the physical foaming agent introduction hole 103b is the maximum diameter on the inlet side where the physical foaming agent is introduced, and in the case shown in FIG. 9(b), the diameter of the physical foaming agent introduction hole 103b is the maximum diameter on the inlet side where the physical foaming agent is introduced, and the diameter of the resin contact side hole 103a is the maximum diameter on the inlet side adjacent to the physical foaming agent introduction hole 103b in the axial direction.

As shown in FIG. 8, the micropores 103 are provided in multiple (multiple) positions at predetermined intervals vertically and horizontally on the surface of the disk-shaped filter body 102, and the pitch P1 between adjacent micropores 103, 103 in the vertical direction is equal to the pitch P2 between adjacent micropores 103, 103 in the horizontal direction, but the pitch P1 and the pitch P2 may be different.
The thickness t1 of the partition between adjacent physical foaming agent introduction holes 103b, 103b in the vertical direction and the thickness t2 of the partition between adjacent physical foaming agent introduction holes 103b, 103b in the horizontal direction are 0.01 to 1.0 mm.

The reason why the thicknesses t1, t2 of the partitions between adjacent physical foaming agent introduction holes 103b, 103b in the vertical and horizontal directions are set to 0.01 to 1.0 mm is that if the thicknesses t1, t2 of the partitions are less than 0.01 mm, the thicknesses t1, t2 of the partitions will be too thin, reducing the strength of the physical foaming agent introduction filter 101, and if they exceed 1.0 mm, the thicknesses t1, t2 of the partitions will be too thick, reducing the number of physical foaming agent introduction holes 103b.

In this embodiment, the plurality (large number) of micropores 103 are arranged vertically and horizontally, but the present invention is not limited to this. For example, as shown in Fig. 10, they may be arranged in a staggered manner, and further, the physical foaming agent introduction holes 103b, 103b adjacent to each other in the vertical direction may be arranged so as to overlap each other partially in the vertical direction. In this way, the number of micropores 103 per unit area can be increased.
In this case, it is preferable that the thickness t3 of the partition wall between the diagonally adjacent physical foaming agent introduction holes 103b, 103b is thinner than the thickness t2 of the partition wall between the horizontally adjacent physical foaming agent introduction holes 103b, 103b. The thickness t3 of the partition wall between the diagonally adjacent physical foaming agent introduction holes 103b, 103b is 0.01 to 1.0 mm.

In addition, in this embodiment, the micropores 103 are configured to have a resin contact side hole 103a that opens on one surface side of the filter body 102 and contacts the molten resin, and a physical foaming agent introduction hole 103b that opens on the other surface side of the filter body 102 and communicates with the resin contact side hole 103a, through which a physical foaming agent is introduced. The resin contact side hole 103a and the physical foaming agent introduction hole 103b of the micropores 103 have different diameters, but the micropores 103 may be formed in a straight shape with the same diameter all along their axial direction.

When manufacturing a foamed molded body using the manufacturing apparatus 1000 equipped with the filter-equipped body 400 as described above, to optimize the amount of molten resin supplied to the starvation zone 23, as shown in FIG. 2, remove the lid 340 (see FIG. 4) and the filter-equipped body 400 from the inlet container 300, and visually check the amount of molten resin in the starvation zone 23 through the inlet 202 of the plasticizing cylinder 210, and adjust the amount of molten resin supplied to optimize the amount.

According to this embodiment, the filter-equipped body 400 is provided, and the filter holding member 410 of this filter-equipped body 400, which holds the filter 101, is provided on its outer periphery with a sliding member (ball retainer) 415 that allows the inner peripheral surface of the introduction container 300 to slide in the axial direction of the introduction container 300. Therefore, when optimizing the supply amount of resin while visually checking the plasticization state of the molten resin in the starvation zone 23, the operator grasps the flange portion 412 of the filter holding member 410 and pulls it out in the axial direction of the introduction container 300. The filter holding member 410, i.e., the filter-equipped body 400, slides in the axial direction on the inner peripheral surface of the introduction container 300 by the sliding member 415, so that the filter-equipped body 400 can be removed from the introduction container 300. This allows the starvation zone 23 to be visually checked through the introduction port 202. Therefore, the supply amount of molten resin can be optimized while visually checking the plasticization state of the molten resin in the starvation zone 23.

In addition, after optimizing the supply amount of molten resin, the filter holding member 410 holding the filter 101 for introducing a physical foaming agent, i.e., the filter-equipped body 400, can be grasped and inserted into the introduction container 300 to provide the filter 101 at the introduction port 202, thereby preventing the molten resin from flowing back into the introduction container 300 and becoming stuck there due to venting up, for example.
Furthermore, since the gap between the outer surface of the tip of the filter holding member 410 and the inner surface of the tip of the introduction container 300 is narrow at 50 μm or less, it is possible to prevent starved molten resin from entering the introduction container 300 through the gap.

Furthermore, since the diameter of the resin contact side hole 103a of the physical foaming agent introduction filter 101 is equal to or smaller than the diameter of the physical foaming agent introduction hole 103b and is 10 to 80 μm, by providing such a physical foaming agent introduction filter 101 at the introduction port 202 for introducing a physical foaming agent into the starvation zone 23 of the plasticizing cylinder 210, it is possible to suppress the intrusion of the molten resin in the starvation zone 23 into the resin contact side hole 103a. Therefore, the molten resin does not solidify and remain in the introduction port 202 where the physical foaming agent introduction filter 101 is provided.
Furthermore, the physical foaming agent can be reliably introduced from the inlet 202 through the resin contact side holes 103a into the molten resin in a starved state (starvation zone 23).
Therefore, vent-up can be suppressed and the physical foaming agent can be stably supplied to the molten resin in a starved state (starvation zone 23).

Furthermore, since the diameter of the physical foaming agent introduction holes 103b is 20 to 400 μm, the physical foaming agent can be reliably and stably introduced into the molten resin in a starved state (starvation zone 23).
Furthermore, since the thickness t1 of the partitions between the vertically adjacent physical foaming agent introduction holes 103b, 103b and the thickness t2 of the partitions between the horizontally adjacent physical foaming agent introduction holes 103b, 103b are 0.01 to 1.0 mm, a sufficient number of the physical foaming agent introduction holes 103b can be secured while suppressing a decrease in strength of the physical foaming agent introduction filter 101.

21 Plasticization zone 23 Starvation zone 101 Filter 202 Inlet 210 Plasticization cylinder 300 Inlet container 400 Filter-equipped body 410 Filter holding member 415 Sliding member (ball retainer)
1000 Manufacturing Equipment

Claims (5)

A filter-equipped body that is removably provided in a cylindrical introduction vessel that introduces a physical foaming agent into a starved molten resin, comprising:
The present invention comprises a cylindrical filter holding member and a filter for introducing a physical foaming agent held at a tip of the filter holding member,
The filter-equipped body is characterized in that the filter holding member is provided, on its outer periphery, with a sliding member that enables the filter holding member to slide along the inner periphery of the introduction container in the axial direction of the introduction container. The filter-equipped body according to claim 1, characterized in that the sliding member is a ball retainer provided on the outer periphery of the filter holding member. The filter-equipped body according to claim 1, characterized in that the outer diameter of the tip of the filter holding member is set so that the gap between the outer peripheral surface of the tip and the inner peripheral surface of the tip of the introduction container is 50 μm or less. An apparatus for producing a foamed molded article, comprising:
a plasticizing cylinder having a plasticizing zone in which a thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone in which the molten resin is in a starvation state, the plasticizing cylinder being provided with an inlet for introducing a physical foaming agent into the starvation zone;
An introduction container connected to the introduction port;
a physical foaming agent supply mechanism connected to the introduction container and supplying a physical foaming agent to the plasticizing cylinder via the introduction container;
The introduction container is provided with a filter-equipped body according to any one of claims 1 to 3,
Supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction vessel, and introducing the pressurized fluid at the constant pressure from the introduction vessel to the starvation zone to maintain the starvation zone at the constant pressure;
While maintaining the starvation zone at the constant pressure, the molten resin in the starved state is brought into contact with a pressurized fluid containing a physical foaming agent at the constant pressure in the starvation zone;
The molten resin that has been brought into contact with a pressurized fluid containing the physical foaming agent is molded into a foamed molded product;
A foam molding manufacturing apparatus characterized in that, when optimizing the amount of molten resin supplied to the starvation zone, the filter-equipped body is removed from the inlet container and the starvation zone is visually observed through the inlet of the inlet container. A method for producing a foamed molded article, comprising the steps of:
a plasticizing cylinder having a plasticizing zone in which a thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone in which the molten resin is in a starvation state, the plasticizing cylinder being provided with an inlet for introducing a physical foaming agent into the starvation zone;
an introduction container connected to the introduction port;
A manufacturing apparatus having a filter-equipped body according to any one of claims 1 to 3 provided in the introduction vessel,
The manufacturing method includes:
In the plasticization zone, the thermoplastic resin is plasticized and melted to form the molten resin;
supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction vessel, and introducing the pressurized fluid at the constant pressure from the introduction vessel to the starvation zone to maintain the starvation zone at the constant pressure;
starving the molten resin in the starvation zone;
contacting the starved molten resin with the pressurized fluid in the starvation zone while maintaining the starvation zone at the constant pressure;
The molten resin that has been contacted with a pressurized fluid containing the physical foaming agent is molded into a foamed molded product,
A method for producing a foamed molded body, characterized in that when optimizing the amount of molten resin supplied to the starvation zone, the filter-equipped body is removed from the inlet container and the starvation zone is visually observed through the inlet of the inlet container.

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