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

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

[0001] The present invention relates to a filter-equipped body, and an apparatus and method for manufacturing a foamed molded body.

[0002] One method of foam injection molding using nitrogen or carbon dioxide as a physical foaming agent involves shear-kneading a high-pressure fluid that becomes a supercritical fluid with a molten resin to dissolve it. In contrast, Patent Document 1 discloses a method of molding a foamed molded body using relatively low-pressure nitrogen, carbon dioxide, or the like, without requiring a supercritical fluid. This method allows fine foam cells to be formed in a molded body through a simple process using a low-pressure physical foaming agent without using a special high-pressure device.

[0003] The method for producing a foamed molded article described in Patent Document 1 uses a production apparatus having a plasticization zone where a thermoplastic resin is plasticized and melted to form a molten resin, and a starvation zone where the molten resin is in a starvation state, the production apparatus having a plasticization cylinder formed with an inlet for introducing a physical foaming agent into the starvation zone, and an introduction rate adjusting vessel connected to the inlet, and the production method includes: plasticizing and melting the thermoplastic resin to form the molten resin in the plasticization zone; supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction rate adjusting vessel and introducing the pressurized fluid at the constant pressure from the introduction rate adjusting vessel into the starvation zone to maintain the starvation zone at the constant pressure; starving the molten resin in the starvation zone; bringing the starved molten resin into contact with the pressurized fluid in the starvation zone while maintaining the starvation zone at the constant pressure; and molding the molten resin that has been contacted with the pressurized fluid containing the physical foaming agent into a foamed molded article.

[0004] In the conventional foam molding method described above, vent-up, where molten resin in the starvation zone flows back into the inlet for introducing the physical foaming agent, can occur during foam molding. This can cause the molten resin to solidify and remain at the inlet. If solidified resin remains at the inlet, a stable supply of physical foaming agent cannot be achieved, and the remaining resin must be removed, which is time-consuming. Furthermore, when degassing the gas in the plasticizing cylinder during cleaning after foam molding is completed, the gas (physical foaming agent) accumulated in the introduction rate adjustment container is introduced into the plasticizing cylinder all at once, which can cause a loud foaming sound.

[0005] To solve these problems, an invention described in Patent Document 2 is known. This invention relates to a filter for introducing a physical foaming agent into a starved molten resin, the filter comprising a filter body and a plurality of micropores formed through the filter body in the thickness direction, the micropores including resin contact side holes that open on one surface side of the filter body and come into 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 to introduce the physical foaming agent, the resin contact side holes having a diameter equal to or smaller than the diameter of the physical foaming agent introduction holes and ranging from 10 to 80 μm.

[0006] Japanese Patent No. 6777553 Japanese Patent Laid-Open No. 2023-30774

[0007] In the methods for producing molded foams described in Patent Documents 1 and 2, the amount of molten resin in the starvation zone must be kept starved (i.e., the starvation zone is not filled with molten resin and is not filled). For this reason, in the method for producing molded foams described in Patent Document 1, a hole is formed in the bottom of the speed-regulating vessel into which the physical foaming agent is introduced, and the amount of molten resin supplied can be adjusted through this hole while visually observing the screw in the starvation zone. In contrast, in the method for producing molded foams described in Patent Document 2, a physical foam introduction filter is provided at the inlet for introducing the physical foaming agent into the starvation zone. However, the presence of this physical foam introduction filter makes it difficult to visually observe the screw, which can make it difficult to optimize the amount of molten resin supplied.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a filter-equipped body, a foam molding manufacturing apparatus, and a manufacturing method thereof that can optimize the supply amount of molten resin while visually checking the plasticization state of the molten resin in the starvation zone, and that can prevent the molten resin from flowing back into the introduction container and solidifying due to venting or the like.

[0009] In order to solve the above-mentioned problems, the filter-equipped body of the present invention is a filter-equipped body that is removably mounted on a cylindrical introduction vessel that introduces a physical foaming agent into starved molten resin, and is characterized in that it comprises a cylindrical filter holding member and a filter for introducing a physical foaming agent held at the tip of the filter holding member, and the filter holding member is provided at its outer periphery with a sliding member that allows the inner circumferential surface of the introduction vessel to slide in the axial direction of the introduction vessel.

[0010] Here, the filter for introducing a physical foaming agent has, for example, a filter body and a plurality of micropores provided through the filter body in the thickness direction of the filter body. The micropores may be formed straight 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 come into 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 to introduce the physical foaming agent, 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.

[0011] In the present invention, the filter holding member holding the physical foaming agent introduction filter is provided with a sliding member on its outer periphery that allows it to slide along the inner periphery of the introduction container in the axial direction of the introduction container. Therefore, when optimizing the resin supply rate while visually checking the plasticization state of the molten resin in the starvation zone, an operator grasps the filter holding member and pulls it out in the axial direction of the introduction container. The filter holding member then slides along the inner periphery of the introduction container in the axial direction by the sliding member, allowing the filter holding member to be removed from the introduction container. This allows the starvation zone to be visually checked through the introduction port. Therefore, the molten resin supply rate can be optimized while visually checking the plasticization state of the molten resin in the starvation zone. Furthermore, after optimizing the molten resin supply rate, the filter holding member holding the physical foaming agent introduction filter can be attached to the introduction port by grasping and inserting it into the introduction container. This prevents the molten resin from backflowing and solidifying in the introduction container due to venting, etc.

[0012] In the above-described configuration of the present invention, the sliding member may be a ball retainer provided on the outer periphery of the filter holding member.

[0013] According to this configuration, the ball retainer is provided as a sliding member on the outer periphery of the filter holding member, so that the filter holding member can be easily and reliably inserted into and removed from the introduction container in the axial direction.

[0014] In addition, in the above-described configuration of the present invention, the outer diameter of the tip portion of the filter holding member may be set so that the gap between the outer peripheral surface of the tip portion and the inner peripheral surface of the tip portion of the introduction container is 50 μm or less.

[0015] With this configuration, the gap between the outer surface of the tip of the filter holding member and the inner surface of the tip of the introduction container is narrow, at 50 μm or less, so that starved molten resin can be prevented from entering the introduction container through the gap.

[0016] The apparatus for producing a foamed molded article of the present invention has 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 further comprises: a plasticizing cylinder provided with an inlet for a physical foaming agent to the starvation zone; an introduction container connected to the inlet; and a physical foaming agent supply mechanism connected to the introduction container and supplying the physical foaming agent to the plasticizing cylinder via the introduction container, wherein the introduction container is provided with the filter-equipped body; a pressurized fluid containing the physical foaming agent at a constant pressure is supplied to the introduction container and the pressurized fluid at the constant pressure is introduced from the introduction container to the starvation zone to maintain the starvation zone at the constant pressure; while the starvation zone is maintained at the constant pressure, the molten resin in the starvation state is brought into contact with the pressurized fluid containing the physical foaming agent at the constant pressure in the starvation zone; and the molten resin that has been contacted with the pressurized fluid containing the physical foaming agent is molded into a foamed molded article, 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.

[0017] The method for producing a foamed molded article of the present invention uses a production apparatus having a plasticization zone in which a thermoplastic resin is plasticized and melted to form a molten resin, and a starvation zone in which the molten resin is put into a starvation state, the production apparatus comprising: a plasticizing cylinder provided with an inlet for introducing a physical foaming agent into the starvation zone; an introduction container connected to the inlet; and the filter-equipped body provided in the introduction container, and the production method includes: plasticizing and melting the thermoplastic resin to form the molten resin in the plasticization zone; supplying a pressurized fluid containing the physical foaming agent at a constant pressure to the introduction container and introducing the pressurized fluid at the constant pressure from the introduction container into the starvation zone to maintain the starvation zone at the constant pressure; bringing the molten resin into a starvation state in the starvation zone; bringing the molten resin in the starvation zone into contact with the pressurized fluid while the starvation zone is maintained at the constant pressure; and molding the molten resin that has been contacted with the pressurized fluid containing the physical foaming agent into a foamed molded article. 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.

[0018] According to the foam molding manufacturing apparatus and manufacturing method of the present invention, the filter holder of the filter-equipped body has a sliding member on its outer periphery that allows it to slide axially along the inner periphery of the introduction vessel. Therefore, when optimizing the resin supply rate while visually checking the plasticization state of the molten resin in the starvation zone, an operator grasps the filter holder and pulls it out in the axial direction of the introduction vessel. The sliding member causes the filter holder to slide axially along the inner periphery of the introduction vessel, allowing the filter holder to be removed from the introduction vessel. Therefore, the resin supply rate can be optimized while visually checking the plasticization state of the molten resin in the starvation zone. Furthermore, after optimizing the resin supply rate, inserting the filter holder holding the physical foaming agent introduction filter into the introduction vessel can prevent the molten resin from backflowing and solidifying in the introduction vessel due to venting or other reasons.

[0019] According to the present invention, the amount of resin supplied can be optimized while visually checking the plasticization state of the molten resin in the starvation zone, and the molten resin can be prevented from flowing back into the introduction container and solidifying due to venting or the like.

[0020] 1 is a schematic cross-sectional view of an extrusion manufacturing apparatus for a foam molded article, showing an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of the apparatus, showing a state in which a filter-equipped body has been removed from an introduction container; FIG. 1 is a schematic cross-sectional view of the apparatus, showing a state in which a filter-equipped body has been inserted into ... and a lid has been placed; FIG. 2 is a flowchart showing an extrusion manufacturing method for a foam molded article; FIG. 2 shows a filter for introducing a physical foaming agent, where (a) is a plan view, (b) is a bottom view, and (c) is a cross-sectional view taken along line A-A in (a); FIG. 3 is a cross-sectional view of a main part of the filter for introducing a physical foaming agent; FIG. 4 is a bottom view of a main part of the filter for introducing a physical foaming agent; FIG. 5 shows deformations of micropores, where (a) is a cross-sectional view of a first modified example, and (b) is a cross-sectional view of a second modified example; FIG. 6 is a bottom view of a main part of a modified filter for introducing a physical foaming agent, showing a modification of the filter for introducing a physical foaming agent.

[0021] Hereinafter, 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 industrialization, foster innovation and build resilient infrastructure" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0022] In this embodiment, a foam molded article is produced using a production apparatus 1000 shown in Figure 1. The production 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 hand to the left hand in Figure 1. Therefore, within the plasticizing cylinder 210 of this embodiment, the right hand in Figure 1 is defined as "upstream" or "rear," and the left hand is defined as "downstream" or "front."

[0023] The plasticizing cylinder 210 has a plasticizing zone 21 where the thermoplastic resin is plasticized and melted to form a molten resin, and a starvation zone 23 downstream of the plasticizing zone 21 where the molten resin is starved. The "starvation state" refers to a state in which the molten resin does not fill the starvation zone 23, leaving it underfilled. Therefore, there is space in the starvation zone 23 other than the area occupied by the molten resin. The plasticizing cylinder 210 also has 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.

[0024] 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, 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 inlet ports 202 formed therein, and the physical foaming agent may be introduced into the plasticizing cylinder 210 through the plurality of inlet ports 202. Furthermore, 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.

[0025] In the manufacturing apparatus 1000, the rotation of the screw 20 in the plasticizing cylinder 210 plasticizes and melts the resin pellets, and the molten resin is sent to the front side of the plasticizing cylinder 210. The rotation of the screw 20 also sends the molten resin to the front side of the plasticizing cylinder 210. On the upper side of the plasticizing cylinder 210, there are provided, in order from the upstream side, a resin supply port 201 for supplying the thermoplastic resin to the cylinder 210, and an inlet 202 for introducing the physical foaming agent into the plasticizing cylinder 210. A resin supply hopper 211 and a feed screw 212 are disposed in the resin supply port 201, and an introduction speed adjustment container 300 is connected to the inlet 202.

[0026] The plasticizing cylinder 210 has a plasticizing zone 21 located upstream and a starvation zone 23 located downstream. 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, or a state in which the density of the molten resin has decreased. Therefore, there may be space within the starvation zone 23 other than the area occupied by the molten resin.

[0027] The plasticizing cylinder 210 has, from upstream to downstream, a plasticizing zone 21, a compression zone 22, a flow rate 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 to plasticize and melt, 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 rate adjustment zone 25 will be described later.

[0028] As described above, the plasticizing cylinder 210 is provided with an inlet 202 as an opening for introducing the physical foaming agent into the starvation zone 23. An introduction rate adjusting container 300 (hereinafter also referred to as the introduction container 300) is connected to the inlet 202. The cylinder 100 is connected to the introduction container 300 via a pressure reducing valve 151, a pressure gauge 152, and an open valve 153 via piping 154. The cylinder 100 supplies the physical foaming agent into the cylinder 210 via the introduction container 300. 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, enabling the interior of the plasticizing cylinder 210 to be maintained at high pressure. 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 the cavity formed by the mold.

[0029] The manufacturing method of the foam molded article of this embodiment will be described with reference to the flowchart shown in FIG. 5 . (1) Plasticizing and Melting the Thermoplastic Resin. 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 ). Various thermoplastic resins can be used depending on the desired heat resistance and the intended use of the molded article. Specifically, 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, and polycaprolactone, as well as composite materials thereof, can be used. Crystalline resins are particularly desirable because they readily form fine cells. These thermoplastic resins can be used alone or in combination. These thermoplastic resins may also be mixed with various inorganic fillers such as glass fiber, talc, carbon fiber, and ceramic, or 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 foam nucleating agent, or an additive that increases melt tension. By mixing these, the foam cells can be made finer. The thermoplastic resin may also contain various other general-purpose additives as needed.

[0030] The thermoplastic resin is plasticized and melted in the plasticizing cylinder 210, which houses the screw 20. A band heater (not shown) is provided on the outer wall surface of the plasticizing cylinder 210, which heats the plasticizing cylinder 210. Furthermore, shear heat generated by the rotation of the screw 20 is added, causing the thermoplastic resin to plasticize and melt.

[0031] (2) Maintaining the pressure in the starvation zone: Next, a physical foaming agent at a constant pressure is supplied to the introduction rate adjusting vessel 300, and 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).

[0032] A pressurized fluid is used as the physical foaming agent. In this embodiment, the term "fluid" refers to a liquid, gas, or supercritical fluid. Furthermore, from the viewpoints of cost and environmental impact, carbon dioxide, nitrogen, or the like is preferred as the physical foaming agent. Because the pressure of the physical foaming agent in this embodiment is relatively low, for example, a fluid can be used that is depressurized to a constant pressure using a pressure reducing valve 151 and extracted from a cylinder 100 containing a fluid, such as a nitrogen cylinder, carbon dioxide cylinder, or air cylinder. In this case, a pressure boosting device is not required, thereby reducing the overall cost of the manufacturing apparatus. If necessary, a fluid 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 produced 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, syringe pump, or the like to produce 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.

[0033] The pressure of the physical blowing agent introduced into the starvation zone 23 is constant, and the pressure in the starvation zone 23 is maintained at the same constant pressure as the introduced physical blowing agent. The physical blowing agent pressure is preferably 0.5 MPa to 30 MPa, more preferably 1 MPa to 25 MPa, and even more preferably 1 MPa to 15 MPa. While the optimal pressure varies depending on the type of molten resin, maintaining the physical blowing agent pressure at 1 MPa or higher allows the amount of physical blowing agent required for foaming to penetrate into the molten resin, while maintaining the pressure at 30 MPa or lower improves the heat resistance of the foamed molded article. Manufacturing at a pressure greater than 12 MPa (high pressure) tends to result in residual foaming agent. Note that "constant" pressure of the physical blowing agent pressurizing the molten resin means that the pressure fluctuation range relative to the 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 located opposite the inlet 202 of the plasticizing cylinder 210.

[0034] Furthermore, as the screw 20 advances and retreats, the starvation zone 23 moves back and forth within the plasticizing cylinder 210. However, the pressure sensor 27 shown in FIG. 1 is located at a position that is always within the starvation zone 23 at both the most advanced and most retreated positions of the starvation zone 23. The position facing the inlet 202 is also always within the starvation zone 23. Therefore, although the pressure sensor 27 is not located 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 substantially the same. Furthermore, although only the physical foaming agent is introduced into the starvation zone 23 in this embodiment, a pressurized fluid other than the physical foaming agent may be introduced into the starvation zone 23 simultaneously, provided that the effects of the present invention are not affected. In this case, the pressurized fluid containing the physical foaming agent introduced into the starvation zone 23 has the above-mentioned constant pressure.

[0035] In this embodiment, the physical foaming agent is supplied from the cylinder 100 through the introduction container 300 and then through 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 into the starvation zone 23 through the introduction port 202 without passing through a pressure booster or other device. 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 these, such as a drive valve using a check valve or solenoid valve, is not required. 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 rate adjusting container 300 to the starvation zone 23 in the plasticizing cylinder 210.

[0036] As shown in FIG. 2 , the physical foaming agent inlet 202 has a larger inner diameter D1 than the physical foaming agent inlet of a conventional manufacturing apparatus. Therefore, even a relatively low-pressure physical foaming agent can be efficiently introduced into the plasticizing cylinder 210. Furthermore, even if a portion of the molten resin contacts the inlet 202 and solidifies, the large inner diameter D1 allows the inlet to function as an inlet without being completely blocked. For example, when the inner diameter of the plasticizing cylinder 210 is large, i.e., 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 may stagnate, resulting in molding defects. Furthermore, the introduction container 300 connected to the inlet 202 may become larger, increasing the overall cost of the apparatus. Specifically, the inner diameter D1 of the inlet 202 is preferably 20% to 100% of the inner diameter of the plasticizing cylinder 210, more preferably 30% to 80%. Alternatively, regardless of the inner diameter of the plasticizing cylinder 210, the inner diameter D1 of the inlet 202 is preferably 3 mm to 150 mm, and more preferably 5 mm to 100 mm. Here, the inner diameter D1 of the inlet 202 refers to the inner diameter of the opening on the inner wall 210a of the plasticizing cylinder 210, as shown in FIG. 2. Furthermore, 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 also 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."

[0037] Next, we will explain the introduction vessel 300 connected to the introduction port 202. The introduction vessel 300 functions to maintain the pressure of the physical foaming agent and the pressure of the starvation zone 23 in the plasticizing cylinder 210 at the same constant pressure, thereby maintaining the starvation zone 23 at this constant pressure. For example, if 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, which could cause a sudden drop in pressure in the starvation zone 23. However, the introduction vessel 300 makes it possible to stably supply the physical foaming agent, thereby suppressing pressure fluctuations in the starvation zone 23.

[0038] Furthermore, the introduction container 300 is formed to have a certain volume or more, slowing the flow rate of the physical foaming agent introduced into the plasticizing cylinder 210 and ensuring time for the physical foaming agent to reside within the introduction container 300. The introduction container 300 is directly connected to the plasticizing cylinder 210, which is heated by a band heater (not shown) located around it, so that heat from the plasticizing cylinder 210 is also conducted to the introduction container 300. This warms the physical foaming agent inside the introduction container 300, reducing the temperature difference between the physical foaming agent and the molten resin. This prevents the temperature of the molten resin in contact with the physical foaming agent from dropping too low, stabilizing the amount of physical foaming agent dissolved (permeated) into the molten resin. In other words, the introduction container 300 functions as a buffer container with the function of heating the physical foaming agent. On the other hand, if the introduction container 300's volume is too large, the cost of the entire apparatus 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.

[0039] As described below, the physical foaming agent is consumed within the plasticizing cylinder 210 by contacting and penetrating the molten resin. To maintain a constant pressure in the starvation zone 23, the consumed amount of physical foaming agent is introduced from the introduction container 300 into the starvation zone 23. If the volume of the introduction container 300 is too small, the physical foaming agent is replaced more frequently, which may cause the temperature of the physical foaming agent to become unstable and, as a result, the supply of the physical foaming agent to the plasticizing cylinder 210 to become unstable. Therefore, it is preferable that the introduction container 300 have a volume large enough to retain the amount of physical foaming agent consumed in the plasticizing cylinder 210 over a period of 1 to 10 minutes. For example, the volume of the introduction container 300 is preferably 0.1 to 5 times, and more preferably 0.5 to 2 times, the volume of the starvation zone 23 to which the introduction container 300 is connected. In this embodiment, the volume of the starvation zone 23 means 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.

[0040] As shown in FIG. 2 , the introduction container 300 is primarily composed of a cylindrical container body 310, a connecting portion 320 connecting 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 (see FIG. 4 ) for the container body 310. One end of the cylindrical container body 310 is connected to the introduction port 202 via the connecting portion 320, and the starvation zone 23 of the plasticizing cylinder 210 communicates with the internal space 312 via the introduction port 202. A lid 340 (see FIG. 4 ) is provided at the other end of the cylindrical container body 310 (the end opposite the introduction port 202) 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.

[0041] Furthermore, when attention is paid to the shape of the internal space 312 of the introduction container 300, the introduction container 300 has a cylindrical first straight section 31 that is connected to the introduction port 202 and has a constant inner diameter, 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 has a constant inner diameter. 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 with a small inner diameter D1, and the second straight section 32, which is a cylinder with 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 that is 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 axes 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 portion 31 and the step surface 33 are formed by the connecting portion 320 , and the second straight portion 32 is formed by the container body 310 .

[0042] The flange portion 330 is integrally formed with the container body 310 on the outer periphery of the tip end (outer periphery of the lower end) of the container body 310, and the underside of the flange portion 330 is in close contact with the outer periphery of the plasticizing cylinder 210. A flange portion 331 having a smaller diameter than the flange portion 330 is integrally formed with the flange portion 330 at the center of the underside of the flange portion 330. This flange portion 331 is fitted into a recess 210a formed at the upper end of the inlet 202 of the plasticizing cylinder 210, recessed from the outer periphery of the plasticizing cylinder 210 and coaxial with the inlet 202. The connecting portion 320 is fitted into the inlet 202. In this manner, the inlet container 300 is connected to the inlet 202 of the plasticizing cylinder 210.

[0043] As shown in FIG. 4 , the lid 340 is openably and closably mounted on the second straight portion 32 of the container body 310. The lid 340 is preferably manually openable and closable without the use of special tools. For example, a male thread 340a may be formed on the barrel of the lid 340, while a female thread 310a may be formed on the upper opening of the container body 310, and the male thread 340a may be threaded onto the female thread 310a, thereby allowing the lid 340 to be openably and closably mounted on the container body 310. When molding a foamed molded article, molding conditions may be set in advance (condition setting). The molding conditions include optimizing the rotation speeds of the feed screw 212 and the screw 20, and confirming that a stable starvation state is maintained in the starvation zone 23. At the same time, it is also confirmed that the molten resin does not bulge from the inlet 202 into the introduction container 300. For this reason, it is preferable that the lid 340 can be opened and closed simply without using bolts, and that the filter-equipped body 400 (described later) can be removed from the introduction container 300 to remove any resin that has entered the introduction container 300. Making the lid 340 manually openable and closable improves the efficiency of setting molding conditions. The lid 340 may have any sealing mechanism, including a spring-equipped sealing mechanism or a clutch-type high-pressure sealing mechanism. In this embodiment, a polyimide sealing member 332 with a spring is used. This sealing member 332 expands due to the gas pressure of the physical foaming agent remaining in the internal space 312, improving sealing performance. A disc-shaped anti-detachment member 340b 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, to prevent the sealing member 332 from escaping.

[0044] 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 preventing the molten resin from penetrating into the container, it is preferable that the material has a large heat capacity, is resistant to temperature rise, and easily absorbs 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 easily transfers heat from the container body 310. From these viewpoints, the introduction container 300 is preferably made of a metal such as stainless steel (SUS).

[0045] (3) Starving the molten resin. Next, the molten resin is caused to flow into the starvation zone 23, where the molten resin is caused to starve (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.

[0046] In this embodiment, a compression zone 22, where the molten resin is compressed and pressure increases, is provided upstream of the starvation zone 23, thereby starving the molten resin in the starvation zone 23. The compression zone 22 includes a large-diameter portion 20A in which the diameter of the screw 20 shaft is larger (thicker) than that of the plasticization zone 21 located upstream, and the screw flights are gradually shallower. Furthermore, a seal portion 26 is 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, similar to the large-diameter portion 20A. Furthermore, the screw 20 shaft is not provided with screw flights; instead, multiple shallow grooves are formed in the screw 20 shaft instead of screw flights. By increasing the diameter of the screw 20 shaft, 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, thereby reducing the amount of resin supplied downstream, thereby increasing the flow resistance of the molten resin. Therefore, in this embodiment, the large diameter portion 20A and the seal portion 26 function as a mechanism for increasing the flow resistance of the molten resin. The seal portion 26 also has the effect of suppressing backflow of the physical foaming agent, i.e., the movement of the physical foaming agent from the downstream side to the upstream side of the seal portion 26.

[0047] The presence of the large-diameter portion 20A and the seal portion 26 reduces the resin flow rate supplied from the compression zone 22 to the starvation zone 23, compressing the molten resin in the upstream compression zone 22 and increasing the pressure, while the downstream starvation zone 23 is underfilled with molten resin (starvation state). To promote the starvation state of 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 flights are deeper than those 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 flights are deeper than those in the compression zone 22 throughout the entire starvation zone 23. Furthermore, it is preferable that the shaft diameter and screw flight depth of the screw 20 are approximately constant throughout the entire starvation zone 23. This maintains the pressure in the starvation zone 23 approximately constant, stabilizing the starvation state of molten resin. In this embodiment, the starvation zone 23 is formed in a portion of the screw 20 where the diameter of the shaft of the screw 20 and the depth of the screw flight are constant, as shown in FIG.

[0048] 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 that temporarily reduces the flow path area through which the molten resin passes in order to limit the flow rate of resin 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 screw flights are provided in the opposite direction to other portions, a labyrinth structure provided on the screw, etc.

[0049] 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 of making it easy to change the magnitude of the flow resistance of the molten resin.

[0050] In addition to the mechanism for increasing the flow resistance of the molten resin, a backflow prevention mechanism (sealing mechanism) that prevents the molten resin from flowing back from the starvation zone 23 to the upstream compression zone 22 can also be provided between the compression zone 22 and the starvation zone 23 to starve the molten resin in the starvation zone 23. 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 a 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.

[0051] 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. This is because 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 higher 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.

[0052] 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. However, if the length is too long, it can adversely affect the molding cycle and screw length. Therefore, the length of the starvation zone 23 is preferably 2 to 12 times, and more preferably 4 to 10 times, the inner diameter of the plasticizing cylinder 210. Furthermore, the length of the starvation zone 23 preferably covers the entire range of the metering stroke in injection molding. That is, the length of the starvation zone 23 in the flow direction of the molten resin is preferably equal to or longer than the length of the metering stroke in injection molding. Although the screw 20 moves forward and backward as the molten resin is plasticized, metered, and injected, 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 a foamed molded article. In other words, even if the screw 20 moves forward and backward during the production of a foamed molded article, no zone other than the starvation zone 23 will come to the position of the inlet 202. As a result, the physical foaming agent introduced through the inlet 202 is always introduced into the starvation zone 23 during the production of a foamed molded article. By providing a starvation zone of sufficient and appropriate size (length) in this way and introducing a constant pressure of physical foaming agent therein, it becomes easier to maintain a constant pressure in the starvation zone 23. 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 shaft diameter of the screw 20 and the depth of the screw flight are constant, as shown in FIG. 1.

[0053] 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 discovered that 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 improves the foamability of the produced foamed molded article. While the details of why providing the flow rate adjustment zone 25 as a buffer zone between the compression zone 22 and the starvation zone 23 improves the foamability of the foamed molded article are unclear, it is speculated that one factor may be that the molten resin remains in the flow rate adjustment zone 25, causing the physical blowing agent flowing in from the starvation zone 23 to be mixed with the molten resin, thereby lengthening the contact time. 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 Figure 1, i.e., by changing the depth of the screw flight, or in other words, by changing the size (thickness) of the screw diameter.

[0054] (4) Contact of Molten Resin with Physical Foaming Agent Next, while maintaining a constant pressure in the starvation zone 23, 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. Because the starvation zone 23 is not filled with molten resin (starved state) and has space in which the physical foaming agent can exist, efficient contact between the physical foaming agent and the molten resin is achieved. The physical foaming agent that comes 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 remaining in the introduction container 300 is supplied to the starvation zone 23. This maintains a constant pressure in the starvation zone 23, and the molten resin continues to be in contact with the physical foaming agent at a constant pressure.

[0055] In conventional foam molding using a physical blowing agent, a predetermined amount of high-pressure physical blowing agent is forcibly introduced into the plasticizing cylinder within a predetermined time. Therefore, it is necessary to pressurize the physical blowing agent to a high pressure and precisely control the amount and time of introduction into the molten resin, and the physical blowing agent only comes into contact with the molten resin for a short period of time. In contrast, in the present embodiment, instead of forcibly introducing the physical blowing agent into the plasticizing cylinder 210, a constant pressure of the physical blowing agent is continuously supplied into the plasticizing cylinder to maintain a constant pressure in the starvation zone 23, thereby continuously bringing the physical blowing agent into contact with the molten resin. This stabilizes the amount of dissolution (penetration) of the physical blowing agent into the molten resin, which is determined by the temperature and pressure. Furthermore, because the physical blowing agent in this embodiment is constantly in contact with the molten resin, a necessary and sufficient amount of physical blowing agent can penetrate into the molten resin. As a result, the foam molded article produced in this embodiment has finer foam cells than conventional molding methods using a physical blowing agent, despite using a lower-pressure physical blowing agent.

[0056] Furthermore, since the manufacturing method of this embodiment does not require control of the amount and time of introduction of the physical foaming agent, it does not require drive valves such as check valves and solenoid valves, nor any control mechanisms for controlling these, thereby reducing equipment costs. Furthermore, 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.

[0057] In this embodiment, the starvation zone 23 is maintained at a constant pressure throughout the production of a foam molded article. That is, all steps of the foam molded article production method are carried out while continuously supplying the physical foaming agent at the constant pressure to replenish the physical foaming agent consumed in the plasticizing cylinder. Furthermore, in this embodiment, for example, when performing continuous multiple-shot injection molding, the next shot of molten resin is prepared in the plasticizing cylinder and pressurized at a constant pressure by the physical foaming agent even during the injection, cooling, and ejection steps. That is, in continuous multiple-shot injection molding, the molten resin and the physical foaming agent at a constant pressure are always present and in contact within the plasticizing cylinder. That is, the molten resin is constantly pressurized at a constant pressure by the physical foaming agent within the plasticizing cylinder during one injection molding cycle, including the plasticizing metering step, injection step, cooling, and ejection steps. Similarly, when continuous molding such as extrusion molding is performed, 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, that is, the molten resin is always pressurized at a constant pressure by the physical foaming agent in the plasticizing cylinder.

[0058] (5) Foam Molding Next, the molten resin contacted with the physical foaming agent is molded into a foam molded article (step S5 in FIG. 5). The plasticizing cylinder 210 used in this embodiment is located downstream of and adjacent to the starvation zone 23 and has a recompression zone 24 where the molten resin is compressed and the pressure increases. First, the rotation of the plasticizing screw 20 causes the molten resin in the starvation zone 23 to flow into the recompression zone 24. The molten resin containing the physical foaming agent is pressure-adjusted in the recompression zone 24 and extruded forward of the plasticizing screw 20 to be metered. At this time, the internal pressure of the molten resin extruded forward of the plasticizing screw 20 is controlled as screw back pressure by a hydraulic motor or electric motor (not shown) connected rearward of the plasticizing screw 20. In this embodiment, in order to uniformly 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 approximately 1 to 6 MPa higher than the pressure in the starvation zone 23, which is maintained constant. In this embodiment, a check ring 50 is provided at the tip of the screw 20 to prevent the compressed resin in front of the screw 20 from flowing back upstream. This ensures that the pressure in the starvation zone 23 is not affected by the resin pressure in front of the screw 20 during metering.

[0059] The molding method for the foam molded article is not particularly limited, and the molded article can be formed by, for example, injection foam molding, extrusion foam molding, foam blow molding, etc. In this embodiment, injection foam molding is performed by injecting 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 to a volume that fills 75% to 95% of the mold cavity volume, and the bubbles expand as the mold cavity fills. Alternatively, a core-back method may be used, in which the mold cavity is filled with molten resin to 100% of its volume, and then the cavity volume is expanded and foamed. The resulting foam molded article has internal foam cells, which suppresses shrinkage of the thermoplastic resin during cooling, reducing sink marks and warpage, and resulting in a molded article with a low specific gravity.

[0060] In the manufacturing method of this embodiment described above, since it is not necessary to control the amount and time of introduction of the physical foaming agent into the molten resin, a complex control device can be omitted or simplified, thereby reducing equipment costs. Furthermore, in the manufacturing method of a foamed molded article of this embodiment, the starved molten resin 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 allows the amount of physical foaming agent dissolved (permeated) into the molten resin to be stabilized using a simple mechanism.

[0061] 1 to 4, the manufacturing apparatus 1000 of this embodiment includes a filter-equipped body 400. The filter-equipped body 400 is removably 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 physical foaming agent introduction filter 101 (hereinafter, sometimes abbreviated as filter 101) held at the tip of the filter holding member 410.

[0062] 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. The operator can grasp the flange 412 to hold the filter-equipped body 400. The main body 411 has a straight hole 411a inside, and the filter 101 is provided at the lower end of this hole 411a. The filter 101 is fitted into a folder 110. The filter 101 is formed in a disk shape with a thickness of approximately 2 to 3 mm and a diameter of approximately 30 mm. The folder 110 is formed in a cylindrical shape, and the filter 101 is fitted and fixed to the inner circumferential surface of approximately the lower half of the folder 110. The lower end surfaces of the filter 101 and the folder 110 are substantially flush with each other. Furthermore, 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.

[0063] A sliding member 415 that allows the filter-equipped body 400 to slide on the inner peripheral surface of the introduction container 300 in the axial direction of the introduction container 300 is provided on the outer peripheral portion 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 peripheral portion 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 between them. In this state, the multiple balls of the ball retainer 415 can roll on the inner peripheral surface of the introduction container 300 in the axial and circumferential directions of the introduction container 300. A flange 411b is provided on the outer peripheral portion of the main body 411, lower end side than the sliding member (ball retainer) 415, so as to protrude radially outward from the outer peripheral surface of the main body 411.

[0064] 3, the filter-equipped body 400 having 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, thereby positioning the filter-equipped body 400 in the axial direction 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.

[0065] Furthermore, the outer diameter of the tip portion 410a of the filter holding member 410 of the filter-equipped body 400 is set so that the gap S between the outer peripheral surface of the tip portion 410a and the inner peripheral surface of the tip portion of the introduction container 300 is 50 μm or less. In other words, the tip portion 410a of the filter holding member 410 is inserted inside the connecting portion 320 of the tip portion of the introduction container 300, but the filter-equipped body 400 needs to be removed from the introduction container 300 as needed. For this reason, a predetermined gap S is provided between the outer peripheral surface of the tip portion 410a of the filter holding member 410 and the inner peripheral surface of the connecting portion 320 of the introduction container 300, and this gap S is set to 50 μm or less.

[0066] 6 and 7, the filter 101 has a disk-shaped filter body 102 and a large number (plurality) of micropores 103 provided through the filter body 102 in the thickness direction of the filter body 102. The micropores 103 include resin contact side holes 103a that open on one surface side of the filter body 102 and come into contact with the molten resin, and physical foaming agent introduction holes 103b that open on the other surface side of the filter body 102, communicate with the resin contact side holes 103a, and through which a physical foaming agent is introduced.

[0067] The filter 101 is formed from a metallic microporous material manufactured using a metal 3D printer. Specifically, one method for manufacturing a three-dimensional object using a three-dimensional printing device (a so-called metal 3D printer) for manufacturing a three-dimensional object made of metal is known as a metal powder additive manufacturing (MPA) method, in which a metallic material powder is uniformly dispersed to form a powder layer, and a laser beam or electron beam is irradiated onto a predetermined irradiation area on the powder layer to melt and solidify the material powder in the predetermined irradiation area, repeatedly stacking sintered layers to produce a three-dimensional object. In this embodiment, while manufacturing the filter body 102 using the MPA method, multiple micropores 103 each having an oil-contacting side hole 103a and a physical foaming agent introduction hole 103b are formed. The filter 101 is not limited to being made of metal, but may also be made of resin.

[0068] The resin contact side hole 103a and the physical foaming agent introduction hole 103b are arranged coaxially. The diameter of the resin contact side hole 103a is equal to or smaller than the diameter of the physical foaming agent introduction hole 103b. In this embodiment, however, as shown in FIGS. 7 and 8, the diameter of the resin contact side hole 103a is smaller than the diameter of the physical foaming agent introduction hole 103b (for example, approximately half the diameter of the physical foaming agent introduction hole 103b). The axial length of the resin contact side hole 103a is shorter than the axial length 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.

[0069] The diameter d1 of the resin contact side holes 103a is specified to be 10 to 80 μm because it is technically difficult to form the resin contact side holes with a diameter of less than 10 μm, and because if the diameter d1 exceeds 80 μm, the molten resin will enter the resin contact side holes 103a and solidify, making the resin contact side holes 103a more likely to be 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 will be impaired, making it difficult to reliably introduce the physical foaming agent into the starved molten resin, and if the diameter d2 exceeds 400 μm, the diameter of the physical foaming agent introduction holes 103b will be too large, resulting in a decrease in the number of physical foaming agent introduction holes 103b.

[0070] In addition, although the resin contact side holes 103a and the physical foaming agent introduction holes 103b have a circular cross section in this embodiment, they are not limited to this and may be triangular, polygonal with more sides than a square, oval, elliptical, cloud-like, star-like, or a combination thereof. When the resin contact side holes 103a and the physical foaming agent introduction holes 103b have a cross section other than circular, the diameters of the resin contact side holes 103a and the physical foaming agent introduction holes 103b are defined as the diameters of perfect circles having the same area as the cross sections of the resin contact side holes 103a and the physical foaming agent introduction holes 103b.

[0071] In this embodiment, the inner circumferential 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 limiting. For example, as shown in FIG. 9( a), the inner circumferential surface of the physical foaming agent introduction hole 103b may be formed to be inclined with respect to the axial direction. In this case, the diameter of the physical foaming agent introduction hole 103b is formed to become smaller toward the resin contact side hole 103a. Also, as shown in FIG. 9( b), the inner circumferential surfaces of the physical foaming agent introduction hole 103b and the resin contact side hole 103a may be formed to be inclined with respect to the axial direction. In this case, the diameter of the physical foaming agent introduction hole 103b is formed to become smaller toward the resin contact side hole 103a, and the diameter of the resin contact side hole 103a is formed to become smaller with increasing distance from the physical foaming agent introduction hole 103b.

[0072] In the case shown in FIG. 9( a), the diameter of the physical foaming agent introduction hole 103 b 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 103 b is the maximum diameter on the inlet side where the physical foaming agent is introduced, and the diameter of the resin contact side hole 103 a is the maximum diameter on the inlet side adjacent to the physical foaming agent introduction hole 103 b in the axial direction.

[0073] 8, a plurality (a large number) of micropores 103 are provided at predetermined intervals in the vertical and horizontal directions on the surface of the disk-shaped filter body 102, and the pitch P1 between vertically adjacent micropores 103 is equal to the pitch P2 between horizontally adjacent micropores 103, but the pitch P1 and the pitch P2 may be different. The thickness t1 of the partition wall between vertically adjacent physical foaming agent introduction holes 103b and the thickness t2 of the partition wall between horizontally adjacent physical foaming agent introduction holes 103b are 0.01 to 1.0 mm.

[0074] The reason why the thicknesses t1 and t2 of the partition walls between the vertically and horizontally adjacent physical foaming agent introduction holes 103b, 103b are specified to be 0.01 to 1.0 mm is that if the thicknesses t1 and t2 of the partition walls are less than 0.01 mm, the thicknesses t1 and t2 of the partition walls become too thin, reducing the strength of the physical foaming agent introduction filter 101, and if the thicknesses t1 and t2 exceed 1.0 mm, the thicknesses t1 and t2 of the partition walls become too thick, reducing the number of the physical foaming agent introduction holes 103b.

[0075] In this embodiment, the plurality (numerous) of micropores 103 are arranged vertically and horizontally, but this is not limiting. For example, as shown in FIG. 10 , the micropores 103 may be arranged in a staggered pattern, and vertically adjacent physical foaming agent introduction holes 103b, 103b may be arranged so that they partially overlap in the vertical direction. This increases the number of micropores 103 per unit area. In this case, it is preferable that the thickness t3 of the partition wall between diagonally adjacent physical foaming agent introduction holes 103b, 103b is thinner than the thickness t2 of the partition wall between horizontally adjacent physical foaming agent introduction holes 103b, 103b. Furthermore, the thickness t3 of the partition wall between diagonally adjacent physical foaming agent introduction holes 103b, 103b is 0.01 to 1.0 mm.

[0076] In addition, in this embodiment, the micropores 103 are configured to include resin contact side holes 103a that open on one surface side of the filter body 102 and come into contact with the molten resin, and physical foaming agent introduction holes 103b that open on the other surface side of the filter body 102 and communicate with the resin contact side holes 103a, through which a physical foaming agent is introduced.The resin contact side holes 103a and the physical foaming agent introduction holes 103b of the micropores 103 have different diameters, but the micropores 103 may also be formed straight and have the same diameter along their axial direction.

[0077] 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 Figure 2, the lid 340 (see Figure 4) and the filter-equipped body 400 are removed from the inlet container 300, and the amount of molten resin in the starvation zone 23 is visually confirmed through the inlet 202 of the plasticizing cylinder 210, and the amount of molten resin supplied is adjusted to optimize the amount.

[0078] According to this embodiment, the filter-equipped body 400 includes a filter holding member 410 that holds the filter 101. The filter holding member 410 has a sliding member (ball retainer) 415 on its outer periphery that allows it to slide axially along the inner periphery of the introduction container 300. Therefore, when optimizing the amount of resin supplied while visually checking the plasticization state of the molten resin in the starvation zone 23, an operator grasps the flange 412 of the filter holding member 410 and pulls it axially out of the introduction container 300. The filter holding member 410, i.e., the filter-equipped body 400, slides axially along the inner periphery of the introduction container 300 by the sliding member 415, allowing the filter-equipped body 400 to be removed from the introduction container 300. This allows the starvation zone 23 to be visually checked through the introduction port 202. Therefore, the amount of molten resin supplied can be optimized while visually checking the plasticization state of the molten resin in the starvation zone 23.

[0079] Furthermore, after optimizing the supply rate of molten resin, the filter holding member 410 holding the physical foaming agent introduction filter 101, 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, etc. Furthermore, since the gap between the outer peripheral surface of the tip of the filter holding member 410 and the inner peripheral 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.

[0080] Furthermore, 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. Therefore, by providing such a physical foaming agent introduction filter 101 at the inlet 202 for introducing a physical foaming agent into the starvation zone 23 of the plasticizing cylinder 210, it is possible to prevent molten resin in the starvation zone 23 from entering the resin contact side hole 103a. This prevents molten resin from solidifying and remaining in the inlet 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 hole 103a into the molten resin in the starvation state (starvation zone 23). This prevents vent-up and ensures a stable supply of physical foaming agent to the molten resin in the starvation zone 23.

[0081] 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 starvation 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 ensured while suppressing a decrease in the strength of the physical foaming agent introduction filter 101.

[0082]

[0083] 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 apparatus

Claims

1. A filter-equipped body that is removably mounted on a cylindrical introduction vessel for introducing a physical foaming agent into starved molten resin, the filter-equipped body comprising a cylindrical filter holding member and a filter for introducing a physical foaming agent held at the tip of the filter holding member, the filter holding member having a sliding member on its outer periphery that allows the inner periphery of the introduction vessel to slide in the axial direction of the introduction vessel.

2. A filter-equipped body according to claim 1, wherein said sliding member is a ball retainer provided on the outer periphery of said filter holding member.

3. A filter-equipped body as described in 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.

4. An apparatus for manufacturing a foamed molded product, comprising: 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 apparatus comprising: a plasticization cylinder provided with an inlet for a physical foaming agent to the starvation zone; an introduction container connected to the inlet; and a physical foaming agent supply mechanism connected to the introduction container and supplying a physical foaming agent to the plasticization cylinder via the introduction container, the introduction container being provided with a filter-equipped body as described in any one of claims 1 to 3; a pressurized fluid containing the physical foaming agent at a constant pressure is supplied to the introduction container, the pressurized fluid at the constant pressure is introduced from the introduction container to the starvation zone, and the starvation zone is maintained at the constant pressure; while the starvation zone is maintained at the constant pressure, the molten resin in the starvation state is brought into contact with the pressurized fluid containing the physical foaming agent at the constant pressure in the starvation zone; and the molten resin that has been contacted with the 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.

5. A method for producing a foamed molded product, using a production device having a plasticization zone where a thermoplastic resin is plasticized and melted to become a molten resin, and a starvation zone where the molten resin is in a starvation state, the production device having a plasticization cylinder provided with an inlet for introducing a physical foaming agent into the starvation zone, an introduction container connected to the inlet, and a filter-equipped body according to any one of claims 1 to 3 provided in the introduction container, the production method comprising: 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 container and introducing the pressurized fluid at the constant pressure from the introduction container 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; bringing the molten resin in the starvation state into contact with the pressurized fluid in the starvation zone while the starvation zone is maintained at the constant pressure; and molding the molten resin that has been contacted with the pressurized fluid containing the physical foaming agent 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.

Images