Method for producing foamed particle molded body

Abstract

Provided is a method for producing a foamed particle molded body that can reduce the amount of steam supplied into a mold and improve energy loss during in-mold forming. The method for producing a foamed particle molded body is a method for filling a thermoplastic resin foamed particle (50) into a cavity (10) of a split mold (100) composed of a first mold (30A) and a second mold (30B), heating by steam, and performing in-mold forming, the first mold (30A) and / or the second mold (30B) having an exhaust chamber (20) provided in a manner that allows communication with the cavity (10), the method comprising: a pre-pressing step of supplying a pressurized gas other than steam into the cavity (10) and adjusting the pressure in the cavity (10) filled with the foamed particle (50) to a pressure (P1) that is greater than atmospheric pressure; and a heating step of supplying steam at a pressure (P2) that is higher than the pressure (P1) into the cavity (10) adjusted to the pressure (P1) in the pre-pressing step, discharging the steam supplied into the cavity (10) to the exhaust chamber (20), and thereby heating the foamed particle (50), in the heating step, the pressure in the exhaust chamber (20) is adjusted to a pressure (P3) that is greater than atmospheric pressure and lower than the pressure (P2) while supplying the steam at the pressure (P2) into the cavity (10).

Description

Technical Field

[0001] This invention relates to a method for manufacturing foamed granule molded articles using thermoplastic resin foamed granules. Background Technology

[0002] Foamed granule molded parts, which are made by in-mold molding of thermoplastic resin foamed granules, are widely used in various technical fields such as vehicle components, cushioning materials, building materials, and thermal insulation materials. This foamed granule molded body is typically manufactured by supplying thermoplastic resin foamed granules into a space formed by a pair of molds, supplying steam into the space, heating and fusing the thermoplastic resin foamed granules. Hereinafter, the space is sometimes referred to as a cavity.

[0003] More specifically, for example, Patent Document 1 discloses the following method. First, pre-foamed propylene resin particles are compressed under gas pressure and filled into a pair of molds along with the compressed gas. Next, after the compressed gas is discharged from the molds to reduce the internal pressure, steam is supplied to the molds to heat and fuse the foamed particles inside, thereby manufacturing a foamed particle molded body. Hereinafter, this manufacturing method is sometimes referred to as Prior Art 1. Furthermore, Patent Document 2 discloses a method for manufacturing an in-mold foamed polypropylene resin molded body based on a compression filling method using multi-stage foamed polypropylene resin particles. According to Patent Document 2... Figure 1 As can be seen, the mold diagram shows a cavity filled with foamed particles and a steam chamber, and the steam supplied to the steam chamber is introduced into the cavity.

[0004] Furthermore, the following method is also known: using a mold with cavities and chambers identical to the mold disclosed in Patent Document 1, thermoplastic resin foamed granules are filled into the cavity without the introduction of pressurized gas, and then steam heating is performed to manufacture a foamed granule molded body. Hereinafter, this manufacturing method is sometimes referred to as Prior Art 2. In the steam heating, the air in the chamber and the cavity is first replaced with steam at atmospheric pressure. Then, after the mold is sealed, steam is further supplied into the chamber, and the steam is introduced into the first space and the second space of the chamber, causing the pressure and temperature of the first space, the second space and the cavity to rise, thereby heating and fusing the foamed granules to manufacture a foamed granule molded body.

[0005] As described above, existing in-mold molding involves supplying foamed particles to the cavity, and then supplying high-pressure steam to the mold, which has an internal pressure of atmospheric pressure, thereby smoothly supplying steam to the cavity within the mold and heating and fusing the foamed particles. Existing technical documents Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 8-300387 Patent Document 2: Japanese Patent Application Publication No. 2010-138226 Summary of the Invention (a) Technical problems to be solved

[0007] The purpose of this invention is to provide a method for manufacturing foamed granule molded articles that can reduce the amount of steam supplied to the mold and improve energy loss during in-mold molding. (II) Technical Solution

[0008] The method for manufacturing a foamed granule molded body according to the present invention is characterized in that thermoplastic resin foamed granules are filled into the cavity of a split molding mold composed of a first mold and a second mold, the foamed granules are heated by steam and in-mold molding is performed, the first mold and / or the second mold has an exhaust chamber provided in a manner that allows ventilation to the cavity, and the manufacturing method includes the following steps: a pre-compression step of supplying pressurized gas other than steam into the cavity and adjusting the pressure in the cavity filled with the foamed granules to a pressure (P1) exceeding atmospheric pressure; and a heating step of supplying steam (P2) higher than the pressure (P1) into the cavity adjusted to the pressure (P1) by the pre-compression step, discharging the steam supplied to the cavity to the exhaust chamber, thereby heating the foamed granules, wherein in the heating step, while supplying steam at the pressure (P2) into the cavity, the pressure in the exhaust chamber is adjusted to a pressure (P3) greater than atmospheric pressure and lower than the pressure (P2). (III) Beneficial Effects

[0009] The method for manufacturing foamed granules of the present invention uses a pressurized gas other than steam to pre-adjust the pressure inside the cavity to a pressure greater than atmospheric pressure (P1), and then supplies steam to the cavity at a pressure (P2) higher than the pressure inside the cavity (P1), which can significantly reduce the amount of steam supplied compared to conventional in-mold molding. Attached Figure Description

[0010] Figure 1 This is a longitudinal cross-sectional view of the molding die used in the first embodiment of the present invention. Figure 2 for Figure 1 The enlarged cross-sectional view of the forming mold shown. Figure 3 This is a longitudinal cross-sectional view of the molding die used in the second embodiment of the present invention. Figure 4 This is a longitudinal cross-sectional view of the molding die used in the third embodiment of the present invention. Figure 5A pressure versus temperature graph is shown for a model of the manufacturing method of the present invention. Figure 6 A pressure versus temperature graph is shown for a model of an existing manufacturing method. Detailed Implementation

[0011] The following describes the manufacturing method of the foamed granule molded body of the present invention (hereinafter, sometimes simply referred to as the manufacturing method of the present invention). Furthermore, preferred numerical ranges of the invention will sometimes be appropriately shown in the following description. Additionally, in this invention, gauge pressure refers to pressure calculated based on atmospheric pressure, which is expressed as absolute pressure minus atmospheric pressure. In this specification, the unit for gauge pressure is denoted as MPa (G). Furthermore, in this invention, pressure (P1) refers to the pressure within the cavity adjusted through the pre-pressing process. Pressure (P2) refers to the pressure of the steam used in the heating process. Pressure (P3) refers to the pressure in the exhaust chamber during the heating process. These pressures satisfy the relationship that atmospheric pressure < pressure (P1) < pressure (P2), and also satisfy the relationship that atmospheric pressure < pressure (P3) < pressure (P2). Additionally, pressure (P3) is the molding pressure used when manufacturing the molded body.

[0012] The manufacturing method of the present invention manufactures a foamed particle molded body by filling a cavity of a split molding die composed of a first mold and a second mold with thermoplastic resin foamed particles, heating the foamed particles with steam, and performing in-mold molding. The first mold and / or the second mold has a cavity and an exhaust chamber configured to allow ventilation of the cavity. The manufacturing method of the present invention includes a pre-pressing step and a heating step. The pre-pressing process involves supplying pressurized gas (excluding steam) into the cavity filled with foamed particles, adjusting the pressure within the cavity to a level greater than atmospheric pressure (P1). Alternatively, the filling process can be performed before or simultaneously with the pre-pressing process. The filling process involves filling the cavity with thermoplastic resin foamed particles. The heating process is performed after or simultaneously with the pre-pressing process. The heating process involves supplying steam at a pressure (P2) higher than the pre-pressing pressure (P1) into the cavity, which has been adjusted to the pre-pressing pressure (P1), and then discharging the steam supplied to the cavity into the exhaust chamber, thereby heating the foamed particles. Furthermore, in this invention, during the heating process, while supplying steam at the pre-pressing pressure (P2) into the cavity, the pressure in the exhaust chamber is adjusted to a pressure (P3) greater than atmospheric pressure but lower than the pre-pressing pressure (P2). The manufacturing method of the present invention, by performing the aforementioned process, shapes thermoplastic resin foamed particles to produce foamed particle molded bodies.

[0013] According to the inventors' research, in existing in-mold molding processes, most of the steam supplied to the mold is used to increase the overall internal pressure of the mold before the foamed particles are heated and fused, resulting in significant energy loss. This is because the steam supplied to the mold, which displays atmospheric pressure, is consumed in heating the mold, and therefore the steam pressure and temperature drop immediately after supplying it. In other words, it is speculated that in existing in-mold molding processes, the amount of steam supplied is several to ten times the actual amount required to heat and fuse the foamed particles filled in the cavity. In view of the aforementioned problems, the key to the manufacturing method of the present invention is that, in the pre-pressing process, the pressure inside the cavity of the mold is pre-adjusted to a pressure greater than atmospheric pressure (P1) using a pressurized gas other than steam, and simultaneously, in the subsequent heating process, steam at a pressure higher than the pressure inside the cavity (P2) is supplied to the cavity. Furthermore, in the manufacturing method of the present invention, in the heating process, while supplying steam at the pressure of P2 to the cavity, the pressure in the exhaust chamber is adjusted to a pressure greater than atmospheric pressure but lower than the pressure of P2 (P3). Thus, during the heating process, steam can easily flow from the cavity to the exhaust chamber. Furthermore, in this invention, steam refers to water vapor. The pressure inside the mold cavity during the pre-pressing process can be appropriately adjusted to a predetermined pressure. Moreover, during the heating process, the steam supply can be adjusted while maintaining the predetermined pressure inside the mold cavity. This adjustment can be appropriately determined in conjunction with the resin constituting the foaming particles used. Further details will be provided later.

[0014] According to the present invention described above, compared with existing in-mold molding, the amount of steam used can be significantly reduced, and the energy loss of in-mold molding can be improved. In other words, the manufacturing method of the present invention, by performing a heating process after the pre-pressing process, can effectively use the supplied steam for heating and welding the foamed particles, and can appropriately shorten the heating time compared with the prior art. The present invention will be further described in detail below. Furthermore, the pre-pressing process and the heating process of the manufacturing method of the present invention can be completely synchronized or partially synchronized, thereby obtaining the same effect as described above.

[0015] [First Implementation Plan] (Split-type molding die) First, use Figure 1 , 2 The split molding die 100 used in the manufacturing method of this embodiment will be described. Figure 1This is a longitudinal sectional view of the split molding die 100 used in this embodiment. Figure 2 for Figure 1 The enlarged cross-sectional view of the split molding mold 100 shown is omitted from the illustration of the thermoplastic resin foam particles 50 inside the cavity 10. like Figure 1 As shown, the split molding mold 100 used in this embodiment includes a first mold 34 and a second mold 36. A cavity 10 and an venting chamber 20 are provided in the split molding mold 100. The first mold 34 includes a first inner mold 30A and a first frame 40A, and the second mold 36 includes a second inner mold 30B and a second frame 40B. The first inner mold 30A and the second inner mold 30B are paired to form a pair of complementary molds 30. The internal space of the pair of complementary molds 30 is a cavity 10. An exhaust chamber 20 is provided on the back side of the first inner mold 30A and / or the back side of the second inner mold 30B. In this embodiment, the exhaust chamber 20 is the space between the first inner mold 30A and the first frame 40A covering the first inner mold 30A, and the space between the second inner mold 30B and the second frame 40B covering the second inner mold 30B. However, the exhaust chamber 20 of the present invention is not limited to this. For example, the exhaust chamber 20 may be provided only on one of the first mold 34 or the second mold 36, or it may be provided on both the first mold 34 and the second mold 36. The first frame 40A and the second frame 40B form a frame 40, which constitutes the outer casing of the split molding mold 100. A pair of complementary molds 30 are provided on the inner side of the frame 40. The frame 40 is provided with an exhaust port 66 for discharging gas from the exhaust chamber 20 to the outside of the split molding mold 100. By providing the exhaust port 66, ventilation between the exhaust chamber 20 and the outside of the split molding mold 100 is possible. In this embodiment, the exhaust ports 66 are respectively provided on the wall surface of the first frame 40A and the wall surface of the second frame 40B, and each exhaust port 66 is provided with an opening / closing mechanism 67 that allows the opening to be opened and closed. Regarding this invention, the opening / closing mechanism refers to a mechanism that switches between the open and closed states of the through hole; examples include a drain valve, but it is not limited to this. In this embodiment, the first inner mold 30A is a concave mold, and the second inner mold 30B is a convex mold. However, the pair of complementary molds 30 used in this invention are not limited to this; for example, both the first inner mold 30A and the second inner mold 30B can be concave molds. In addition, for the aforementioned terms, the first inner mold 30A will also be referred to as the mold cavity side inner mold, and the second inner mold 30B will be referred to as the mold core side inner mold.

[0016] Cavity 10 is a space for filling thermoplastic resin foam particles 50, which are used to manufacture foam particle molded bodies. One end region of a filling feeder 52, which extends through frame 40, is inserted into cavity 10. However, the phrase "one end region of filling feeder 52 is inserted into cavity 10" simply means that thermoplastic resin foam particles 10 can be supplied into cavity 10 from this end region. Therefore, it includes both the form where the end region extends into cavity 10 and the form where the end region is opposite the inner surface of cavity 10. The other end region of filling feeder 52 is located outside the split molding die 100, and thermoplastic resin foam particles 50 are filled from this end. Thermoplastic resin foam particles 50 are sometimes appropriately abbreviated as foam particles 50. Vent holes 64 are provided in a pair of complementary molds 30 to ensure ventilation of at least one of the cavities 10 and the venting chambers 20. Pressurized gas or steam other than steam can be vented between the cavities 10 and the venting chambers 20 via the vent holes 64. In this embodiment, the vent holes 64 are provided in the molding wall 32, which serves as the wall surface of the first inner mold 30A, thereby allowing ventilation between the venting chambers 20 and the cavity 10 located on the back side of the first inner mold 30A. The molding wall 32 is a wall surface that separates the cavity 10 of the split molding mold 100 from the venting chambers 20. However, the vent holes 64 of the present invention include those provided in the second inner mold 30B, and those provided in both the first inner mold 30A and the second inner mold 30B. The vent holes 64 can be normally open, but in this embodiment, an opening / closing mechanism 65 is provided to open and close the opening in order to effectively regulate the internal pressure of the cavity 10.

[0017] The split molding mold 100 is provided with a steam supply section 60 for supplying steam to the interior. In this embodiment, the steam supply section 60 is a tubular body for supplying steam from the outside of the split molding mold 100 to the interior. When the steam inlet side is considered the upstream side and the steam outlet side is considered the downstream side, it has one or more supply holes 68 for ejecting steam to the downstream end region. More specifically, in this embodiment, the steam supply section 60 has a main channel 60A for introducing steam from the outside of the split molding mold 100 to the interior and multiple branch channels 60B branching from the main channel 60A. Supply holes 68 are formed in the downstream end region of the branch channels 60B. In this embodiment, the supply holes 68 are located on the same surface as the cavity surface, allowing steam to be directly introduced into the cavity 10. The cavity surface refers to the same surface as the molding wall 32 of a pair of complementary molds 30 that serve as the cavity 10. However, the supply holes 68 of the present invention are not limited to this. Although the illustrations are omitted, the present invention includes, for example, the following configuration: the downstream region of the branch channel 60B penetrates the molding wall 32 and is inserted into the cavity 10, thereby providing a supply hole 68 inside the cavity 10. The supply hole 68 opens into the interior of the cavity 10, allowing steam to be supplied into the cavity 10 through the opening. In this embodiment, steam supply sections 60 are provided on the molding walls 32 of both the first inner mold 30A and the second inner mold 30B, configured to supply steam to the cavity 10 from opposite sides. Furthermore, the plurality of supply holes 68 are arranged in a staggered manner across the cavity 10, thereby facilitating the distribution of steam throughout the cavity 10.

[0018] From the perspective of ensuring that the pressurized gas supplied to the cavity 10 in the pre-pressing process can be smoothly discharged from the cavity 10 to at least one of the exhaust chambers 20 in the heating process, and that the steam supplied in the heating process can easily spread throughout the cavity 10, the following configuration is preferred. Specifically, in this embodiment, a split molding die 100 is used, wherein the steam supply hole 68 for supplying steam to the cavity 10 is disposed on the same surface as the cavity surface, and the first die 34 and / or the second die 36 are provided with vent holes 64 on the cavity surface that allow ventilation between the cavity 10 and the exhaust chambers 20. In the split molding die 100 described above, the ratio of the total open area of ​​the vent holes 64 to the total open area of ​​the steam supply holes 68 is preferably greater than 1 and less than 10, more preferably more than 1.1 and less than 7, and even more preferably more than 1.2 and less than 5. Furthermore, the numerical range of the ratio of the total opening area of ​​the vent 64 to the total opening area of ​​the supply hole 68 can be listed as follows: taking any one of greater than 1, 1.1, or 1.2 as the lower limit, and taking any one of 10, 7, or 5 as the upper limit. Furthermore, from the perspective of reducing the total opening area of ​​the vent holes 64 relative to the total area of ​​the inner peripheral surface of the molding wall 32 separating the cavity 10 and the exhaust chamber 20, thereby making it easier for the steam supplied in this heating process to spread throughout the entire cavity 10, the following configuration is preferred. Additionally, the inner peripheral surface of the molding wall 32 will also be referred to as the cavity surface below. That is, in the split molding mold 100, the ratio of the total opening area of ​​the vent holes 64 to the total area of ​​the cavity surface is preferably greater than 0% and less than 2%, more preferably more than 0.05% and less than 1.5%, further preferably more than 0.07% and less than 1.2%, and even more preferably more than 0.1% and less than 1%. Furthermore, the numerical range of the ratio of the total opening area of ​​the vent holes 64 to the total area of ​​the cavity surface can be, for example, listed as the following range: a lower limit of any one of greater than 0%, 0.05%, 0.07%, and 0.1%, and an upper limit of any one of 2%, 1.5%, 1.2%, and 1%. Furthermore, whether the exhaust chamber 20 is provided in either the first mold 34 or the second mold 36, or in both, the ratio of the total opening area of ​​the vent holes 64 to the total area of ​​the cavity surface preferably meets the stated numerical range. As described above, the pair of complementary molds 30 in the split molding die 100 are provided with vent holes 64, and the steam supply section 60 is provided with supply holes 68. The ratio of the total open area of ​​the vent holes 64 to the total open area of ​​the supply holes 68 can be 1.2 times or more and 5 times or less, and the ratio of the total open area of ​​the vent holes 64 to the total area of ​​the inner circumferential surface of the molding wall 32 separating the cavity 10 and the exhaust chamber 20 can be greater than 0% and less than 2%. By ensuring that both the ratio of the total open area of ​​the vent holes 64 to the total open area of ​​the supply holes 68 and the ratio of the total open area of ​​the vent holes 64 to the total area of ​​the inner circumferential surface of the molding wall 32 satisfy the aforementioned ranges, steam can be easily distributed throughout the cavity 10, which is therefore particularly preferable. In particular, in the split molding die 100 which implements any one of the first to third forms or combinations of the configuration position of the supply hole 68 described below, the above-mentioned ratio and proportion of the opening area of ​​the vent hole 64 can be implemented. In this embodiment, the following processes are performed using the split molding die 100 described above.

[0019] The aforementioned split molding mold 100 is typically made of metal, but in the heating process described later, there is a possibility that the heat from the steam supplied to the molding mold is absorbed by the metal. From this perspective, the split molding mold 100 can be made of a component with a thermal conductivity lower than that of the metal. Furthermore, a component with a thermal conductivity lower than that of the metal can be used to cover the surface of the split molding mold 100 made of metal components. In particular, a component with low thermal conductivity can be used to form the molding wall 32 that forms the cavity 10; additionally, a component with low thermal conductivity can be used to cover the inner and / or outer surfaces of the molding wall 32. The method of covering is not limited; examples include: applying a coating containing a component with a thermal conductivity lower than that of the metal to the entire split molding mold 100 made of metal components or a portion of the molding wall 32 to form a coating layer; or attaching an adhesive tape made using a component with a thermal conductivity lower than that of the metal. Among them, resin components can be exemplified as “components with thermal conductivity less than that of metals”, and more specifically, examples include polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and polyether imide (PEI).

[0020] (Filling process) The filling process in this embodiment will be described. The filling process is the process of filling the cavity 10 with foamed particles 50. In this embodiment, the foamed particles 50 are filled into the cavity 10 by a filling feeder 52 provided in the split molding die 100. The filling method of the foamed particles 50 can be appropriately implemented with reference to existing in-mold filling methods. In this embodiment, the foamed particles 10 are filled into the cavity 10 provided inside a pair of complementary molds 30 that have been closed under atmospheric pressure.

[0021] For example, the foamed particles 50 can be filled into the cavity 10 under a condition where the internal pressure is increased and the secondary foaming property is improved by pre-pressurizing with pressurized gas. Because the manufacturing method of the present invention implements the pre-pressurization process described later, the foamed particles 50 that have undergone the pressurization process as described above are less likely to be compressed due to pre-pressurization, which is therefore preferable. The internal pressure of the foamed particles 50 is not particularly limited. When the base resin of the foamed particles 50 is a polypropylene-based resin, the internal pressure of the foamed particles 50 is preferably 0.1 MPa(G) or more and 0.2 MPa(G) or less. Furthermore, when the base resin of the foamed particles 50 is a polyethylene-based resin, the internal pressure of the foamed particles 50 is preferably 0.03 MPa(G) or more and 0.13 MPa(G) or less. Furthermore, when the base resin of the foamed particles 50 is a polystyrene-based resin, the internal pressure of the foamed particles 50 is preferably 0.01 MPa(G) or more and 0.1 MPa(G) or less. The internal pressure (pressure inside the air bubble) of the foamed particles can be measured by the method described in Japanese Patent Application Publication No. 2003-201361.

[0022] In addition, in this specification, the base resin refers to the resin that accounts for 50% or more by mass in 100% by mass of the resin component constituting the thermoplastic resin foam particles.

[0023] The foamed granules 50 are made using thermoplastic resin. The foamed granules 50 can be manufactured with appropriate reference to existing known methods for manufacturing thermoplastic resin foamed granules. For example, firstly, the desired material is placed in an extruder for melt kneading to prepare a resin melt. The resin melt is then extruded from the extruder in a strip shape and cut into appropriate lengths to produce granular resin particles. Next, the resin particles are placed in a pressure vessel along with a dispersion medium such as water. While impregnating the granules with a foaming agent, the mixture is heated to a foaming temperature. The foamed granules are then released under a pressure lower than the pressure inside the pressure vessel, thereby enabling foaming and manufacturing the foamed granules.

[0024] Examples of thermoplastic resins constituting the foamed particles 50 include polyolefin resins (represented by polypropylene resins and polyethylene resins), polystyrene resins, polyamide resins, polyester resins, polycarbonate resins, modified polyphenylene ether resins, polyvinyl chloride resins, polymethacrylic acid resins, and acrylonitrile resins. Preferably, the base resin for the foamed particles 50 is one or more selected from the group consisting of polypropylene resins, polyethylene resins, and polystyrene resins, and more preferably one or more selected from polyolefin resins. That is, the foamed particles 50 are more preferably polyolefin resin foamed particles. Furthermore, since polypropylene resin foamed particles typically require high molding pressure during in-mold molding, conventional methods consume a large amount of steam. Therefore, from the perspective of further fully obtaining the effects of the present invention, it is preferable to use polypropylene resin foamed particles as thermoplastic resin foamed particles. In other words, the manufacturing method of the present invention is preferably applicable to the manufacture of polypropylene resin foamed molded articles.

[0025] Polypropylene resins: The polypropylene resin refers to propylene homopolymer and / or propylene copolymer containing more than 50% by mass of structural units derived from propylene. Examples of propylene homopolymers include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene. These resins, as propylene homopolymers, can be used alone or in combination of two or more. The content of propylene structural units derived from polypropylene resin in the propylene-based copolymer is preferably 80% by mass or more, more preferably 90% by mass or more. The content of propylene structural units derived from the propylene-based copolymer is preferably 99% by mass or less, more preferably 98% by mass or less. Examples of such propylene-based copolymers include copolymers of propylene with ethylene and / or α-olefins having 4 to 20 carbon atoms. Examples of such α-olefins include 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-butene. Other examples of propylene-based copolymers include ethylene-propylene random copolymers, propylene-butene random copolymers, and ethylene-propylene-butene random copolymers. These propylene-based copolymers can be, for example, random copolymers or block copolymers, but are preferably random copolymers. Examples of such propylene-based copolymers include impact-resistant polypropylene (block polypropylene), which is composed of two or more phases, including a continuous phase of a propylene polymer and a rubber phase such as an ethylene-α-olefin copolymer existing as a dispersed phase in the continuous phase. These resins, exemplified as propylene copolymers, can be used alone or in combination of two or more. Furthermore, the polypropylene resin can be a linear polypropylene resin, a branched polypropylene resin, or a combination thereof.

[0026] Polyethylene resins: The polyethylene-based resin refers to ethylene homopolymers and ethylene-based copolymers containing 50% by mass or more structural units derived from ethylene. Specific examples of polyethylene-based resins include high-density polyethylene (PE-HD), medium-density polyethylene (PE-MD), low-density polyethylene (PE-LD), linear low-density polyethylene (PE-LLD), and linear ultra-low-density polyethylene. Other specific examples of polyethylene-based resins include ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate copolymers, and ethylene-α-olefin copolymers. The content of ethylene structural units derived from polyethylene resin in the ethylene-based copolymer is preferably 80% by mass or more, more preferably 90% by mass or more. The content of ethylene structural units in the polyethylene-based copolymer is preferably 99% by mass or less, more preferably 98% by mass or less.

[0027] Polystyrene resins: The styrene component in the polystyrene-based resin is 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more.

[0028] Examples of styrene monomers constituting the styrene-based resins include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-methoxystyrene, p-n-butylstyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, styrene sulfonic acid, and sodium styrene sulfonate. Furthermore, monomers capable of copolymerizing with styrene may also be used to achieve the desired objectives of the present invention. Examples of acrylic monomers capable of copolymerizing with styrene include methyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.

[0029] Other polymers: To the extent that it does not impede the purpose and effects of the present invention, the foamed particles 50 may also contain other polymers besides the aforementioned thermoplastic resin. Examples of such other polymers include olefin-based thermoplastic elastomers (TPO), urethane-based thermoplastic elastomers (TPU), and other thermoplastic elastomers. The other polymers may be one type or a combination of two or more.

[0030] The content of the other polymers in the foamed granules 50 is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 0% by mass. That is, the foamed granules particularly preferably contain substantially only thermoplastic resin as a polymer.

[0031] Furthermore, those skilled in the art can distinguish between thermoplastic resins and thermoplastic elastomers. Thermoplastic resins typically exhibit a flexural modulus of 100 MPa or more. From the perspective of the formability of foamed granules, the flexural modulus of thermoplastic resins is preferably 3000 MPa or less, more preferably 2000 MPa or less, further preferably 1500 MPa or less, and particularly preferably 1200 MPa or less. On the other hand, thermoplastic elastomers exhibit rubber elasticity at room temperature and typically exhibit a flexural modulus of less than 100 MPa. The flexural modulus of thermoplastic polymers is determined according to JIS K7171:2008.

[0032] Any additives: To the extent that it does not impede the purpose and effect of the present invention, the foamed particles 50 may appropriately contain any additives. For example, as any additives, various known additives can be listed, such as conductive materials, antioxidants, flame retardants, flame retardant additives, radiation inhibitors, bubble regulators, lubricants, crystal nucleating agents, light stabilizers such as UV inhibitors, antistatic agents, and colorants.

[0033] Bulk density of foamed granules The bulk density of the foamed particles 50 used in this invention is not particularly limited, but is preferably 10 kg / m³. 3 The above, preferably 15 kg / m 3 The above is further optimized to 20 kg / m 3 The above, and preferably 200 kg / m 3 The following is more preferably 100 kg / m 3 The following is a further preferred value: 50 kg / m 3 the following. In other words, the bulk density of the foamed particles of the present invention is preferably 10 kg / m³. 3 Above and 200kg / m 3 The following is more preferably 15 kg / m 3 Above and 100kg / m 3 The following is a further preferred value: 20 kg / m 3 Above and 50kg / m 3 The following is a preferred method. By setting the bulk density of the foamed particles 50 to the range described, a lightweight foamed particle molded body with excellent weldability can be obtained. The bulk density of the foamed particles 50 was determined by the method described in the examples below.

[0034] The foamed particles 50 can be single-layer foamed particles having only a granular foam layer, or multi-layer foamed particles having a granular foam layer as a core layer and a covering layer covering the foam layer. The covering layer can cover the entire surface of the foam layer or a portion of the surface of the foam layer. Furthermore, the single-layer foamed particles or the granular foam layer can have through-holes.

[0035] (Pre-compression process) In this embodiment, the pre-pressing process is performed after the filling process is completed. In the pre-pressing process of this embodiment, pressurized gas other than steam is supplied to each exhaust chamber 20 and the mold cavity 10 to adjust the pressure inside the mold cavity 10 to a pressure greater than atmospheric pressure. The pressurized gas is a gas used to pressurize the pressure inside the mold cavity 10 to a pressure greater than atmospheric pressure (P1). The pressurizing gas, other than steam, can be, for example, an inorganic gas, an organic gas, or a mixture of both. From the perspective of safety and economy, the pressurizing gas is preferably selected from one or more inorganic gases, such as air, nitrogen, and carbon dioxide, with air being particularly preferred.

[0036] In the pre-compression process, there are no particular restrictions on the method of supplying pressurized gas. For example, such as Figure 1As shown, an air inlet 69 can be provided to allow air to enter the interior of the split molding die 100, and pressurized gas can be supplied from this air inlet 69. Alternatively, the air inlet 69 can be omitted, and any one or more of the exhaust holes 66 can be used as air inlets for pressurized gas. Furthermore, a flow channel switching mechanism (omitted in the figure) can be provided in the steam supply unit 60. Using this flow channel switching mechanism, pressurized gas other than steam can be supplied from the steam supply unit 60 to the split molding die 100 during the pre-pressing process, and then the flow channel can be switched to supply steam to the split molding die 100 during the heating process described later. During the pre-pressing process, the exhaust holes 66 not used for supplying pressurized gas can be closed, and the vent holes 64 provided in the pair of complementary molds 30 can be opened. This allows the internal pressure of the exhaust chamber 20 and the cavity 10 to be adjusted to a pressure greater than atmospheric pressure (P1).

[0037] The pressure (P1) within the cavity 10 after the pre-compression process only needs to be greater than atmospheric pressure, and is not limited to a specified value. From the perspective of suppressing the compression of the filled foamed particles 50 due to the pressure of pressurized gas other than steam, the pressure (P1) within the cavity 10 during the pre-compression process is preferably adjusted to 0.5 MPa (G) or less, more preferably to 0.4 MPa (G) or less. If the pressure (P1) within the cavity 10 adjusted by the pre-compression process is within the aforementioned pressure range, it is possible to suppress the expansion of voids within the cavity 10 due to the shrinkage of the foamed particles 50, and to prevent shrinkage or decreased internal welding in the resulting foamed particle molded body. Furthermore, from the perspective of being able to sufficiently reduce the amount of steam used in the heating process described later by pre-pressurizing, the pressure (P1) inside the cavity 10 is preferably adjusted to 0.02 MPa (G) or more, and more preferably to 0.05 MPa (G) or more. From the above perspective, the pressure (P1) inside the cavity 10 adjusted by the pre-pressing process is preferably 0.02 MPa (G) or more and 0.5 MPa (G) or less, more preferably 0.05 MPa (G) or more and 0.4 MPa (G) or less.

[0038] In addition, the heating temperature of the resin constituting the foaming particles 50 used can be considered to adjust the pressure (P1) in the cavity 10 during the pre-pressing process. For example, when the base resin of the foamed granules 50 is a polypropylene resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.15 MPa(G) or more, more preferably 0.18 MPa(G) or more, even more preferably 0.2 MPa(G) or more, and preferably 0.5 MPa(G) or less, more preferably 0.45 MPa(G) or less, and even more preferably 0.4 MPa(G) or less. In other words, when the base resin of the foamed granules 50 is a polypropylene resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.15 MPa(G) or more and 0.5 MPa(G) or less, more preferably 0.18 MPa(G) or more and 0.45 MPa(G) or less, and even more preferably 0.2 MPa(G) or more and 0.4 MPa(G) or less. Furthermore, when the base resin of the foamed granules 50 is a polyethylene-based resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.03 MPa(G) or more, more preferably 0.05 MPa(G) or more, even more preferably 0.07 MPa(G) or more, and preferably 0.5 MPa(G) or less, more preferably 0.4 MPa(G) or less, and even more preferably 0.3 MPa(G) or less. In other words, when the base resin of the foamed granules 50 is a polyethylene-based resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.03 MPa(G) or more and 0.5 MPa(G) or less, more preferably 0.05 MPa(G) or more and 0.4 MPa(G) or less, and even more preferably 0.07 MPa(G) or more and 0.3 MPa(G) or less. Furthermore, when the base resin of the foamed granules 50 is a polystyrene-based resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.02 MPa(G) or more, more preferably 0.03 MPa(G) or more, even more preferably 0.04 MPa(G) or more, and preferably 0.4 MPa(G) or less, more preferably 0.3 MPa(G) or less, and even more preferably 0.2 MPa(G) or less. In other words, when the base resin of the foamed granules 50 is a polystyrene-based resin, the pressure (P1) within the cavity 10 adjusted by the pre-compression process is preferably 0.02 MPa(G) or more and 0.4 MPa(G) or less, more preferably 0.03 MPa(G) or more and 0.3 MPa(G) or less, and even more preferably 0.04 MPa(G) or more and 0.2 MPa(G) or less.

[0039] Furthermore, from the perspective of easily adjusting the pressure (P1) inside the cavity 10 to the desired pressure during the pre-pressing process, it is preferable to adjust the pressure while supplying pressurized gas as described above, and discharge the remaining pressurized gas from the exhaust port 66 to the outside of the split molding mold 100.

[0040] (Heating process) By performing the pre-pressing process, the pressure (P1) inside the cavity 10 is adjusted to a pressure greater than atmospheric pressure at the start of the heating process. In this state, the heating process is performed, in which steam at a pressure (P2) higher than the pressure (P1) inside the cavity 10 is supplied from the steam supply unit 60 provided in the split molding mold 100, thereby heating the foamed particles 50. Furthermore, during the heating process, steam at pressure (P2) is supplied into the cavity while adjusting the pressure in the exhaust chamber to a pressure (P3) greater than atmospheric pressure and lower than the pressure (P2). During the heating process, the exhaust port 66 can be closed to adjust the relationship between the pressure (P1) and the pressure (P2), thereby adjusting the pressure (P3); or the exhaust port 66 can be opened to exhaust air from the exhaust port 66 to the outside of the split molding mold 100, thereby adjusting the pressure (P3). From the perspective of venting pressurized gas other than steam from the cavity 10 in the early pre-pressing process, it is preferable to open the vent hole 66 and adjust the venting from the vent hole 66 to the outside of the split molding mold 100. In conventional in-mold molding, since steam is supplied to the mold at atmospheric pressure, a large amount of steam is required to raise the pressure and temperature inside the mold to preferred values. However, in the heating step of the manufacturing method of the present invention, the pressure inside the cavity 10 is already adjusted to a high pressure greater than atmospheric pressure, and furthermore, since steam with a pressure even higher is supplied, the temperature inside the cavity 10 can rise rapidly. To explain the effects of the present invention more specifically, [details omitted]. Figure 5 , Figure 6 The diagram shows a graph of the manufacturing method of the present invention and a graph of a conventional in-mold molding model. Specifically, in Figure 5 , Figure 6The diagram shows the surface pressure (MPa(G)), cavity pressure (MPa(G)), temperature of the first inner mold (°C), and internal temperature (°C) of the foamed particle molded body formed in the venting chamber over time. The surface pressure and internal temperature of the foamed particle molded body described here refer to the surface pressure and internal temperature of the foamed particle group within the cavity during the stage before the foamed particles fuse together. The surface pressure is measured by a pressure gauge installed on the molding walls of a pair of complementary molds; it is the pressure exerted by the foamed particle molded body on the inner surface of the molding wall during in-mold molding.

[0041] First, use Figure 5 A model illustrating the manufacturing method of the present invention will be described. Figure 5 In the model shown, after filling the cavity 10 with foamed particles 50, the following pre-compression process is performed: compressed air is supplied through the air inlet 69 until the pressure inside the cavity 10 exceeds atmospheric pressure and reaches 0.25 MPa (G). Next, as a heating process, steam at 0.45 MPa (G) is supplied to the cavity 10 for 7 seconds through the supply holes 68 of the steam supply unit 60, which is located within each exhaust chamber 20. The amount of steam used in this heating process is 0.29 kg. During this short steam supply, the pressure inside the cavity 10 is maintained at the same level as at the end of the pre-compression process, and the internal temperature of the molded article rapidly rises to approximately 130°C. Then, the pressure in the split molding die 100 is released, and a cooling process is performed to obtain the foamed particle molded article. In addition, such as Figure 5 As shown, in the model of the present invention, it was confirmed that the temperature of the first mold 30A remained basically constant during the heating process, and the heat of the steam was not absorbed by the mold.

[0042] Next, regarding Figure 6 The existing in-mold forming model is illustrated below. Figure 6 The model shown, except that it lacks a steam supply section 60 and the air inlet 69 functions as a steam supply section, uses a design similar to... Figure 1The conventional molding die 100 shown is constructed in the same manner as the existing molding die. Furthermore, the foaming particles used are the same amount of the same substance as those used in the model of the present invention described above. First, foaming particles are filled into the cavity of the conventional molding die, and then steam is used to replace the air inside the molding die for 5 seconds. Next, 0.60 MPa (G) steam is supplied through the air inlet provided in the first frame for primary heating, followed by 0.60 MPa (G) steam being supplied through the air inlet provided in the second frame for secondary heating, and then 0.60 MPa (G) steam is supplied through the air inlets provided in both frames for double-sided heating. In the primary heating, the cavity is heated by supplying steam through the air inlet 69 provided in the first frame, and then the steam supplied to the exhaust chamber is discharged from the second frame side. In the secondary heating, the supply and discharge of steam are performed in the reverse manner of the primary heating. As a result, it takes approximately 10 seconds for the pressure inside the cavity and the internal temperature of the molded article to rise sufficiently through the primary and secondary heating. In addition, the amount of steam used in the heating process is 4.08 kg. Next, the pressure of the molding die is released, and a cooling process is carried out to obtain the foamed granule molded body. In addition, such as Figure 6 As shown, in existing in-mold forming models, it was confirmed that the temperature of the first mold rises significantly during the heating process, and the heat of the steam is absorbed by the mold.

[0043] As mentioned above, Figure 5 The steam consumption of the model of the present invention shown is approximately Figure 6 The existing in-mold molding method used only 7% of the required steam, and the steam output time was also short. Based on these results, it is clear that the manufacturing method of the present invention reduces steam consumption and eliminates energy loss.

[0044] Pressure difference (P2-P1): From the perspective of more fully obtaining the effects of the present invention, the pressure difference (P2-P1) expressed as the pressure of the steam supplied to the cavity 10 by the steam supply unit 60 in the heating process (P2) minus the pressure (P1) in the cavity 10 supplied with pressurized gas through the pre-pressurization process is preferably 0.05 MPa or more and 0.45 MPa or less, more preferably 0.10 MPa or more and 0.40 MPa or less, and even more preferably 0.15 MPa or more and 0.35 MPa or less. When the pressure difference (P2-P1) is above the lower limit of the aforementioned preferred pressure range, the heating time of the heating process can be shortened. That is, the steam output time is shortened. As a result, the foamed particles 50 begin to expand midway through the heating process, making it difficult for steam to pass between the foamed particles 50, and suppressing the occurrence of a temperature difference between the periphery of the supply hole 68 and the end of the cavity 10. Therefore, by making the pressure difference (P2-P1) above the lower limit of the aforementioned preferred pressure range, it is easy to obtain a good foamed particle molded body that does not have any one or more of the following: shrinkage at the periphery of the supply hole 68, overall shrinkage of the molded body, or uneven heating. On the other hand, when the pressure difference (P2-P1) is below the upper limit of the aforementioned preferred pressure range, it is possible to suppress the excessive compression of the foamed particles according to the pressure difference (P2-P1). Therefore, the filling rate of the foamed particles 50 to the cavity 10 is maintained at a high level, the weldability is good, there is no uneven heating, and it is easy to obtain a uniformly foamed foamed particle molded body. In addition, in the heating process, the pressure (P2) of the steam supplied to the cavity 10 by the steam supply unit 60 refers to the average pressure of the steam supplied to the cavity 10 by the steam supply unit 60. Furthermore, the pressure (P1) in the cavity 10 after the pre-compression process in which pressurized gas is supplied refers to the pressure in the cavity after the pre-compression process.

[0045] Pressure difference (P1-P3): From the perspective of more fully obtaining the effects of the present invention, the pressure difference (P1-P3) expressed as the difference between the pressure (P1) of the pre-pressing process and the pressure (P3) of the heating process is preferably -0.1 MPa or more and +0.1 MPa or less, more preferably -0.05 MPa or more and +0.05 MPa or less, and even more preferably the pressure (P1) and the pressure (P3) are the same pressure. If the pressure difference (P1-P3) meets the above range, then in the heating process, the compressed air in the cavity other than steam can be effectively replaced with steam, and molding can be performed with a short steam output time.

[0046] Steam exhaust regulation: As described above, in the heating process, steam at a pressure (P2) higher than the pressure (P1) inside the mold cavity 10 is supplied by the steam supply unit 60 into the mold cavity 10. This adjusts the pressure inside the mold cavity 10 to a pressure suitable for the heating and welding of the foamed particles 10. To more fully implement this adjustment, during the heating process, steam exhaust regulation can be performed simultaneously with the supply of steam into the mold cavity 10, as described below. Furthermore, by performing steam exhaust regulation, the aforementioned pressure difference (P2-P1) can also be easily adjusted. In the steam exhaust regulation, a portion of the steam within the cavity 10 is discharged from the cavity 10 to each exhaust chamber 20 through vent holes 64 provided in the molding walls 32 constituting the pair of complementary molds 30. The vent holes 64 are provided in the molding walls 32 that separate the cavity 10 from the exhaust chambers 20, ensuring ventilation between the exhaust chambers 20 and the cavity 10. This can be achieved by simultaneously opening and closing the opening / closing mechanism 65 provided in the vent holes 64 to regulate the pressure within the cavity 10. Furthermore, in the steam exhaust regulation, steam within the cavity 10 can be discharged from the cavity 10 to the exhaust chamber 20 via the vent 64 provided on the molding wall 32, and the steam within the exhaust chamber 20 can be discharged from the exhaust chamber 20 to the outside of the split molding mold 100 via the exhaust port 66 connecting the exhaust chamber 20 to the outside of the split molding mold 100. This can also be implemented by simultaneously opening and closing the opening / closing mechanism 65 provided on the vent 64 and / or the opening / closing mechanism 67 provided on the exhaust port 66 to regulate the pressure within the cavity 10. In the steam exhaust regulation, since the pressure difference (P2-P1) is easily adjusted, it is preferable to regulate the exhaust via the opening / closing mechanism 65 provided on the vent 64. By performing the above-described steam exhaust regulation, the heating temperature of the foamed particles 50 filled within the cavity 10 can be adjusted. This allows for better bonding of the thermoplastic resin foamed particles 50 to each other.

[0047] Furthermore, the temperature change within the cavity 10 can be confirmed by monitoring a thermometer installed within the cavity 10 while implementing the aforementioned steam exhaust regulation. The temperature within the cavity 10 refers to any one or more of the following: the ambient temperature within the cavity 10, the temperature of the foamed particles 50 filled within the cavity 10, and the temperature of the foamed particle molded body formed within the cavity 10.

[0048] By performing the filling, pre-pressing, and heating processes described above, a foamed granule molded body is manufactured. The manufacturing method of this invention consists of a cycle from the closing of the split molding mold 100 to its opening. Mold opening is typically performed after confirming that the surface pressure of the foamed granule molded body formed within the cavity 10 is suitable for removal. Before mold opening, this invention may perform one or a combination of the cooling processes described below.

[0049] (Cooling process) The cooling process is a process of cooling the foamed granule molded body manufactured within the cavity 10. The cooling method is not particularly limited; examples include, for instance, the pressure relief method, vacuum method, air cooling method, natural cooling method, and water cooling method described below. One or more of the above methods can be used to implement the cooling process. The pressure relief method is to reduce the internal pressure by relieving the pressure of the split molding mold 100, thereby lowering the temperature. The vacuum method involves liquefying steam by creating a vacuum inside the split molding mold 100, and then cooling it by utilizing the heat of vaporization of the water adhering to the split molding mold 100. Air cooling is achieved by blowing air or other gases into the split molding mold 100 to lower its temperature. Furthermore, air cooling can also remove water droplets generated within the split molding mold 100. The natural cooling method involves placing the molded part 100 at ambient temperature with the exhaust and ventilation holes open to cool it down. The water cooling method involves supplying cooling water into the split molding mold 100 to cool it down.

[0050] Location of the supply port: In order to implement the heating process more effectively, the arrangement position of the supply hole 68 provided in the steam supply section 60 in the split molding mold 100 is preferably any one or more of the following first to third forms.

[0051] The first configuration of the supply hole 68 is such that it is positioned on the same surface as the molding wall 32 of the pair of complementary molds 30. That is, in this first configuration, since the steam supply hole 68 is positioned on the same surface as the cavity surface, during the heating process, steam at a pressure higher than that inside the cavity 10 can be directly supplied to the cavity 10 from the supply hole 68 without passing through the exhaust chamber. Figure 2The branch channel 60B shown terminates at the molding wall 32 of the second inner mold 30B, and the supply hole 68 is configured such that it is an opening in the molding wall 32 of the second inner mold 30B. Similarly, in this embodiment, a supply hole 68 is also provided in the molding wall 32 of the first inner mold 30A. Furthermore, it is not strictly required that the cavity surface and the supply hole 68 be positioned on the same surface; it is sufficient that the difference between the cavity surface and the opening surface of the supply hole 68 is approximately less than half the thickness of the molding wall 32. For example, when the thickness of the molding wall 32 is 10 mm, the difference between the cavity surface and the opening surface of the supply hole 68 should be less than 5 mm. Furthermore, the difference between the outer surface of the molding wall 32 and the opening surface of the supply hole 68 should also be less than 5 mm. Here, the difference between the cavity surface and the opening surface refers to the distance between the cavity surface and the opening surface facing the cavity surface. Since the supply hole 68, which serves as a steam outlet, in the first configuration is adjacent to a pair of complementary molds 30, a portion or all of the pair of complementary molds 30 can be sufficiently heated, thereby ensuring a moderately uniform surface on the foamed granule molded body and improving its aesthetics. Furthermore, the first configuration is preferred when it is necessary to transfer textures or other appearance designs onto the surface of the foamed granule molded body. In other words, the first configuration provides a foamed granule molded body that achieves the excellent effects of the present invention and has excellent appearance design.

[0052] In the first configuration, an exhaust chamber 20 is preferably provided on the back side of the first inner mold 30A and / or the back side of the second inner mold 30B, and a supply hole 68 for supplying steam to the cavity 10 is disposed on the same surface as the cavity 10. Furthermore, the first mold 34 and / or the second mold 36 may have a vent hole 64 on the surface of the cavity 10, allowing ventilation between the cavity 10 and the exhaust chamber 20. The average distance between the supply hole 68 and the vent hole 64 is preferably 30 mm or more, more preferably 40 mm or more, further preferably 45 mm or more, and even more preferably 50 mm or more. If the average distance is satisfied, it is easy to form a directional flow of steam supplied from the supply hole 68 to the cavity 10 towards the vent hole 64. As a result, pressurized gas and steam other than steam present in the cavity can be quickly replaced, further reducing steam consumption, while facilitating uniform steam supply to each foaming particle, making it easier to obtain a molded body with excellent weldability. On the other hand, from the perspective of uniformly supplying steam, the average distance between the supply hole 68 and the vent hole 64 is preferably 100 mm or less, more preferably 90 mm or less, and even more preferably 80 mm or less. In other words, from the perspective of easily forming a directional and uniform steam flow from the supply hole 68 to the vent hole 64 in the cavity 10, the average distance between the supply hole 68 and the vent hole 64 is preferably 40 mm or more and 100 mm or less, more preferably 45 mm or more and 90 mm or less, and even more preferably 50 mm or more and 80 mm or less. Additionally, the average distance is obtained by measuring the distance d1 from the center of the opening of each supply hole 68 to the center of the opening of the vent hole 64 closest to that opening (refer to...). Figure 2 The measured values ​​are then averaged arithmetically.

[0053] The second configuration involves the downstream region of the steam supply section 60 being inserted into the inner side of the molding wall 32 forming a pair of complementary molds 30, with the supply hole 68 disposed within the cavity 10 (illustration omitted). In this configuration, during the heating process, steam at a pressure higher than the pressure inside the cavity 10 can be supplied from the interior of the foamed particle molded body through the supply hole 68 to the cavity 10, which has been adjusted to a pressure greater than atmospheric pressure. Therefore, in this second configuration, the supplied steam can be primarily used for heating and welding the foamed particles 50, resulting in less energy loss. In this second configuration, since the steam supply volume and steam flow rate are easily adjustable, the inner diameter (aperture) of the supply hole 68 disposed within the cavity 10 is preferably 2 mm or more and 8 mm or less, more preferably 2 mm or more and 6 mm or less. Furthermore, if the outer diameter of the supply hole 68 is too large, the mark left by the steam supply section 60 inserted into the cavity 10 on the surface of the molded body will increase, which is detrimental in terms of appearance design and impact resistance. Therefore, the outer diameter of the supply hole 68 is preferably 15 mm or less, more preferably 10 mm or less. From the perspective of more efficient steam supply, the insertion length of the steam supply section 60 into the inner side of the molding wall 32 is preferably less than half the thickness of the cavity 10. Furthermore, for the present invention, the thickness of the cavity 10 refers to the thickness in the direction C between the first mold 34 and the second mold 36 (refer to...). Figure 3 The thickness of the cavity 10 refers to the internal dimensions of the cavity 10. In other words, the thickness of the cavity 10 is the distance from one inner side of the molding wall 32 to the other inner side of the molding wall 32 opposite to it.

[0054] The third configuration is one in which the supply hole 68 is located on the outside of the cavity 10, i.e., within the exhaust chamber 20 (illustration omitted). This third configuration is the same as the first configuration described above, but excludes configurations where the difference between the surface of the molding wall 32 and the opening surface of the supply hole 68 is approximately less than half the thickness of the molding wall 32. In the third configuration, since not all the steam ejected from the supply hole 68 is introduced into the cavity 10, energy loss increases compared to the first and second configurations where steam is supplied directly to the cavity 10 without passing through the exhaust chamber 20. However, because the manufacturing method of this invention involves pre-pressing, the amount of steam used can be reduced even in the third configuration compared to conventional in-mold molding. In the third configuration, from the perspective of reducing steam energy loss, a smaller volume of the exhaust chamber 20 is preferable. Specifically, it is preferable that the volume of each exhaust chamber 20 in the first mold 34 and the second mold 36 is smaller than the volume of the cavity 10, and more preferably, the sum of the volumes of all exhaust chambers 20 is smaller than the volume of the cavity 10.

[0055] (Foamed granule molded body) A preferred form of the foamed granule molded body manufactured by the manufacturing method of the present invention will be described.

[0056] density: The density of the foamed granule molded body manufactured by the present invention is preferably 10 kg / m³. 3 The above, preferably 15 kg / m 3 The above is further optimized to 20 kg / m 3 That's all. Furthermore, the density is preferably 200 kg / m³. 3 The following is more preferably 100 kg / m 3 The following is a further preferred value: 50 kg / m 3 the following. In other words, the density is preferably 10 kg / m³. 3 Above and 200kg / m 3 The following is more preferably 15 kg / m 3 Above and 100kg / m 3 The following is a further preferred value: 20 kg / m 3 Above and 50kg / m 3 the following. In addition, the density of the foamed granule molded body is calculated by dividing the mass of the foamed granule molded body by the volume calculated based on its size.

[0057] Shrinkage rate: Compared to existing technologies, the foamed granule molded body manufactured by the manufacturing method of the present invention tends to have a reduced shrinkage rate, and is therefore preferred. This improvement in shrinkage rate is presumably due to the present invention appropriately shortening the heating time by performing a heating process after the pre-pressing process. That is, compared to existing technologies, because the manufacturing method of the present invention shortens the heating time of the heating process, it is less likely to impart excessive heat capacity to the foamed granules 50, thereby improving the shrinkage rate of the foamed granule molded body. Furthermore, the method for confirming the shrinkage rate is described in the Examples section below.

[0058] Contraction (depression): When the foamed granule molded body is manufactured in the same manner as the manufacturing method of the present invention, except that the pre-compression process is not performed, the heating time of the heating process becomes significantly longer. In this case, the foamed granules 50 may become tightly packed together midway through the heating process, making it difficult for the supplied steam to pass between the foamed granules. In this situation, the vapor pressure around the supply hole 68 increases and the heating temperature increases significantly, resulting in the foamed granule molded body around the overheated supply hole 68 shrinking and becoming concave. In contrast, the manufacturing method of the present invention, which performs the heating process after the pre-compression process, is less likely to produce the aforementioned concavity caused by shrinkage due to overheating in the foamed granule molded body.

[0059] [Second Implementation Plan] use Figure 3 The second embodiment of the present invention will be described. Except for the filling process performed as shown below, the second embodiment is implemented in the same manner as the first embodiment described above. Figure 3 This is a longitudinal cross-sectional view of the molding die used in the second embodiment of the present invention, showing the state in which the gap distance X is set.

[0060] That is, the filling process in this embodiment is the same as that in the first embodiment described above in that it uses a split molding mold 100, which forms the cavity 10 by closing a pair of complementary molds 30 having a first inner mold 30A and a second inner mold 30B that is paired with the first inner mold 30A. In the second implementation scheme, such as Figure 3 As shown, by setting a gap distance X between the first inner mold 30A and the second inner mold 30B in the mold-closing direction C, the volume of the cavity 10 is expanded. Thus, the volume of the cavity 10 is larger than if the first inner mold 30A and the second inner mold 30B were fully closed. As a result, foam particles 50 are filled into the expanded cavity 10. Next, by fully closing the pair of complementary molds 30, the volume of the cavity 10 is reduced, thereby compressing the foam particles 50 within the cavity 10, thus performing the filling process. The filling process of the second embodiment is sometimes referred to as a gap-filling process. In addition, the first inner mold 30A and the second inner mold 30B are fixedly set on the first frame 40A and the second frame 40B respectively. Therefore, for ease of explanation in the attached drawings, the gap distance X between the two refers to the distance between the first frame 40A and the second frame 40B.

[0061] By performing the gap-filling process, the foamed particles 50 can be filled into the cavity 10 in a moderately dense state, and the gaps between the foamed particles can be appropriately reduced. As a result, a foamed particle molded body with better weldability between the foamed particles 50 can be manufactured. Furthermore, since the gaps between the foamed particles are appropriately reduced by performing the gap-filling process, the flow of steam between the foamed particles 50 is moderately suppressed. As a result, overheating is well avoided, and a foamed particle molded body with low shrinkage can be manufactured.

[0062] By setting the gap ratio to a specific value or below, it is possible to suppress the excessive compaction of the foamed particles 50 and the resulting poor steam flow between them. As a result, it is possible to suppress shrinkage around the steam supply hole 68 in the manufactured foamed particle molded body, or uneven heating in the corner area between the supply hole 68 and the cavity 10. From the above perspective, the gap ratio is preferably 35% or less, more preferably 25% or less. Furthermore, by setting the gap ratio to a specific value or higher, it is possible to suppress the formation of voids between the foamed particles 50 filling the cavity 10 and to prevent a decrease in the weldability of the resulting foamed particle molded body. From the above perspective, the gap ratio is preferably 5% or higher, and more preferably 8% or higher. In addition, the gap ratio can be determined by the ratio of the gap distance (mm) to the thickness (mm) of the cavity 10.

[0063] Furthermore, from the perspective of preventing the foamed particles 50 from being over-compressed, when performing the gap filling process, it is more preferable to use foamed particles 50 that have been pre-pressurized with pressurized gas and are in a state of increased internal pressure and secondary foaming properties, as described in the first embodiment.

[0064] [Third Implementation Plan] use Figure 4 The third embodiment of the present invention will be described. Figure 4 This is a longitudinal sectional view of the molding die used in the third embodiment of the present invention. Except for the filling and pre-pressing processes shown below, the third embodiment is implemented in the same manner as the first embodiment described above.

[0065] That is, the filling process in this embodiment is a process of filling the cavity 10 with thermoplastic resin foam particles 50, which have been pre-compressed using pressurized gas other than steam, together with the pressurized gas. Sometimes the filling process in the third embodiment is referred to as a compression filling process. In this embodiment, when performing the compression filling process, the thermoplastic resin foam particles 50 are supplied to the cavity 10 together with the pressurized gas. That is, the compression filling process includes part or all of the filling process of filling the cavity 10 with foam particles and the pre-compression process of pressurizing the cavity. More specifically, such as Figure 4As shown, in the third embodiment, the filling feeder 52 of the split molding die 100 used for filling the foamed particles 50 is connected to a pressurized filling tank 200 capable of pressurizing the filled foamed particles. The pressurized filling tank 200 is connected to a pressurization pressure regulating unit 202 and an exhaust pressure regulating unit 204. By adjusting these pressure regulating units, the foamed particles filled in the pressurized filling tank 200 can be pressurized at the desired pressure. The pressurized foamed particles, in a compressed state, are supplied to the cavity 10 from the filling feeder 52 along with the pressurized gas.

[0066] As described above, the pre-compression process and the filling process are carried out simultaneously in this embodiment. However, if the internal pressure of the cavity 10 does not reach the desired pressure, the pre-compression process can be carried out separately. On the other hand, when the internal pressure of the cavity 10 is made greater than the desired pressure by performing the compression filling process, pressurized gas exhaust regulation can be performed. The pressurized gas exhaust regulation described above can be implemented in the same way as the steam exhaust regulation described in the first embodiment. The pressurized gas exhaust regulation is implemented by discharging a portion of the pressurized gas in the cavity 10 to at least one of the exhaust chambers 20 via a vent 64 provided in the molding wall 32 constituting a pair of complementary molds 30, while simultaneously regulating the pressure in the cavity 10 by opening and closing the opening and closing mechanism 65 provided in the vent 64. In another embodiment of the pressurized gas exhaust regulation, a portion of the pressurized gas within the cavity 10 is discharged from the cavity 10 to at least one of the exhaust chambers 20 via a vent 64 provided on the molding wall 32, and a portion of the pressurized gas within the exhaust chamber 20 is discharged from the exhaust chamber 20 to the outside of the split molding mold 100 via an exhaust port 66 that communicates the exhaust chamber 20 with the outside of the split molding mold 100. Furthermore, while venting gas to the outside of the split molding mold 100, the pressure within the cavity 10 can be adjusted by opening and closing the opening and closing mechanism 65 provided on the vent 64 and / or the opening and closing mechanism 67 provided on the exhaust port 66, thereby implementing the pressurized gas exhaust regulation.

[0067] The preferred range of the compression pressure for compressing the foamed particles 50 during compression filling varies depending on the resin constituting the foamed particles 50. For example, when the base resin of the foamed particles 50 is a polypropylene-based resin, the compression filling pressure is preferably 0.10 MPa(G) or higher, more preferably 0.15 MPa(G) or higher, and even more preferably 0.18 MPa(G) or higher. On the other hand, when the base resin of the foamed particles 50 is a polypropylene-based resin, the compression filling pressure is preferably 0.30 MPa(G) or lower, more preferably 0.25 MPa(G) or lower, and even more preferably 0.23 MPa(G) or lower. In other words, when the base resin of the foamed particles 50 is a polypropylene-based resin, the compression filling pressure is preferably 0.10 MPa(G) or higher and 0.30 MPa(G) or lower, more preferably 0.15 MPa(G) or higher and 0.25 MPa(G) or lower, and even more preferably 0.18 MPa(G) or higher and 0.23 MPa(G) or lower. Furthermore, when the base resin of the foamed granules 50 is a polyethylene-based resin, the pressure during compression filling is preferably 0.05 MPa(G) or more, more preferably 0.08 MPa(G) or more, and even more preferably 0.10 MPa(G) or more. On the other hand, when the base resin of the foamed granules 50 is a polyethylene-based resin, the pressure during compression filling is preferably 0.20 MPa(G) or less, more preferably 0.17 MPa(G) or less, and even more preferably 0.15 MPa(G) or less. In other words, when the base resin of the foamed granules 50 is a polyethylene resin, the pressure during compression filling is preferably 0.05 MPa(G) or more and 0.20 MPa(G) or less, more preferably 0.08 MPa(G) or more and 0.17 MPa(G) or less, and even more preferably 0.10 MPa(G) or more and 0.15 MPa(G) or less. Furthermore, when the base resin of the foamed particles 50 is a polystyrene-based resin, the pressure during compression filling is preferably 0.03 MPa(G) or more, more preferably 0.04 MPa(G) or more, and even more preferably 0.05 MPa(G) or more. On the other hand, when the base resin of the foamed granules 50 is a polystyrene-based resin, the pressure during compression filling is preferably 0.15 MPa(G) or less, more preferably 0.10 MPa(G) or less, and even more preferably 0.08 MPa(G) or less. In other words, when the base resin of the foamed granules 50 is a polystyrene-based resin, the pressure during compression filling is preferably 0.03 MPa(G) or more and 0.15 MPa(G) or less, more preferably 0.04 MPa(G) or more and 0.10 MPa(G) or less, and even more preferably 0.05 MPa(G) or more and 0.08 MPa(G) or less.

[0068] Furthermore, from the perspective of preventing the foamed particles 50 from being over-compressed, when performing compression filling, it is more preferable to use foamed particles 50 that have been pre-pressurized with pressurized gas and are in a state of increased internal pressure and secondary foaming properties, as described in the first embodiment. Example

[0069] The present invention will now be described in detail through embodiments, but the present invention is not limited to these embodiments. Furthermore, in this embodiment, appropriate use of... Figures 1-4 The molding dies shown are molding dies with the same structure. The thermoplastic resin foamed granules used in the examples and comparative examples are described below. Furthermore, the bulk density and internal pressure of the polypropylene and polyethylene resin foamed granules used in each example and comparative example, as well as the bulk density of the polystyrene resin foamed granules, are shown in the table of the examples. Additionally, MFR is an abbreviation for melt flow rate. <Polypropylene resin foamed granules 1 (referred to as EPP1 in the table)> Foamed granules were made from an ethylene-propylene random copolymer with a melting point of 141.5°C, an ethylene content of 3.1% by mass, and an MFR (load 2.16 kg, 230°C, JIS K7210-1:2014) of 7 g / 10 min. <Polypropylene resin foamed granules 2 (referred to as EPP2 in the table)> Foamed granules were made from an ethylene-propylene random copolymer with a melting point of 153°C, an ethylene content of 1.4% by mass, and an MFR (load 2.16 kg, 230°C, JIS K7210-1:2014) of 7 g / 10 min. <Polyethylene resin foamed granules (referred to as EPE in the table)> Foamed granules were made from an ethylene-α-olefin copolymer with a melting point of 121°C and a density of 0.928 g / cm³. 3 The MFR (load 2.16kg, 190℃, JIS K7210-1:2014) is 1.0g / 10min. <Polystyrene-based resin foamed granules (referred to as EPS in the table)> Styrodia FA200, manufactured by JSP CORPORATION, was used as the foamed styrene-based resin granules.

[0070] <Example 1> First, pre-pressurized polypropylene resin foam granules are filled into a pressurized filling tank. Then, pressurized air is supplied into the tank, and the mixture is allowed to stand for 24 hours to achieve an internal pressure of 0.14 MPa (G) for the polypropylene resin foam granules. In the manufacture of the foam granule molded body, a device equipped with… Figure 1 A split molding die with the same configuration. Specifically, a split molding die is used that has a cavity capable of forming a flat molded body with a length of 306 mm × width of 255 mm × height of 61.2 mm when the die is closed. In the pair of complementary molds of the split molding die, the ratio of the total open area of ​​the vent holes provided on the molding wall to the total open area of ​​the supply holes for supplying steam is 3.4 times, and the ratio of the total open area of ​​the vent holes provided on the molding wall to the total area of ​​the inner circumferential surface of the molding wall forming the cavity is 0.6%. Furthermore, the average distance between the supply holes and the vent holes provided on the molding wall in the pair of complementary molds is 52 mm. The split molding die is adjusted to leave a gap distance of 6 mm. In this state, polypropylene resin foam particles pre-pressurized are filled, and a filling process is performed (see reference). Figure 3 The seam allowance is 10%. Next, pressurized air is supplied from the air inlet of the frame of the split molding mold to pressurize each exhaust chamber. At the same time, pressurized air is also supplied to the cavity through the vent to carry out the pre-pressurization process so that the pressure inside the cavity is 0.25MPa(G). Next, a heating process is performed by directly supplying steam with an output pressure of 0.45 MPa (G) into the mold cavity for 6 seconds through a steam supply unit equipped with a supply hole in the cavity. The pressure difference (P2-P1) obtained by subtracting the pressure in the cavity (P1) adjusted by the pre-pressurization process from the output pressure (P2) of the steam used in the above heating process is 0.20 MPa. The pressure in the split molding mold is 0.25 MPa (G). The amount of steam consumed in the above heating process is 0.24 kg. In addition, the pressure in the split molding mold refers to the pressure (P3) in the exhaust chamber. The maximum temperature of the first inner mold refers to the highest temperature in the heating process when the temperature inside the molded body is measured by a thermocouple pre-positioned in the cavity. In addition, the inside of the molded body here refers to the position at half the longitudinal and transverse directions of the molded body and 20 mm from the cavity of the first inner mold towards the inside of the molded body. After the heating process, a cooling process is performed. In the cooling process, first, the internal pressure of the split molding die is released for 5 seconds, followed by 261 seconds of vacuum cooling, then 5 seconds of air cooling, and finally 5 seconds of natural cooling. Once the surface pressure of the foamed granules in the cavity drops to 0.05 MPa(G), the cooling process ends, the split molding die is opened, and the foamed granules are removed. The surface pressure at removal is recorded as the removal surface pressure in Table 1. Furthermore, the surface pressure of the foamed granules in the cavity after the heating process is recorded as the maximum surface pressure after heating in Table 1. In addition, the time from ensuring the specified gap distance and about to fill with foam particles to the end of cooling and mold opening was measured and taken as the time required for one molding, i.e., the cycle time, as shown in Table 1.

[0071] The foamed granule molded articles obtained by the above method were measured and evaluated in the following manner. Furthermore, the bulk density of the foamed granules used in the examples before filling the mold cavity was measured. The method for measuring the bulk density is shown below, and the measurement results are presented in Table 1. Additionally, for the evaluation criteria described below, ◎ indicates very good, 〇 indicates good, △ indicates poor, and × indicates poor.

[0072] (Bulk density of foamed particles) Prepare foamed granules under internal pressure. Then, fill a graduated cylinder with a mass of W (g) of foamed granules and allow it to accumulate naturally. Gently tap the bottom of the graduated cylinder several times on a horizontal surface to stabilize the filling height of the foamed granules. Read the volume V (L) of the foamed granules indicated by the graduations on the graduated cylinder. Divide the mass W of the foamed granules by the volume V (W / V) to convert the unit to [kg / m³]. 3 From this, the bulk density of the foaming particles can be calculated.

[0073] (Density of foamed granule molded body) The density of the foamed granule molded body is calculated by dividing the mass of the foamed granule molded body by the volume calculated based on its dimensions.

[0074] (Shrinkage rate) The shrinkage rate (shrinkage rate) of the dimensions of the foamed granule molded body relative to the dimensions of the split molding die used in in-mold molding was determined using the following method. First, after in-mold molding, the foamed granule molded body removed from the split molding die was left to stand for 24 hours at a temperature of 23°C and a relative humidity of 50% for curing. Then, the long side dimension (LB) of the foamed granule molded body was measured. The shrinkage rate of the foamed granule molded body relative to the dimensions of the split molding die was obtained by calculating the ratio of the difference between the long side dimension (LA) of the cavity and the long side dimension (LB) of the foamed granule molded body to the long side dimension (LA) of the cavity ([LA-LB] / LA)×100).

[0075] (Internal welding) The foamed granule molded body is bent to break it, and the number of foamed granules present on the fracture surface (C1) and the number of broken foamed granules (C2) are counted. The ratio of the number of broken foamed granules to the number of foamed granules present on the fracture surface [(C2 / C1)×100] is calculated as the material failure rate. Five measurements were performed using different test pieces to determine the material failure rate of each test piece. The arithmetic mean was calculated and used to evaluate the results according to the following evaluation criteria. ◎: Material failure rate is over 91% 〇: The material failure rate is 71% or higher but less than 91%. △: Material failure rate is greater than 0% and less than 71%. ×: Material failure rate is 0%

[0076] (Contraction (depression)) First, the outer surface of the foamed granule molded body removed from the mold is visually inspected. Next, the foamed granule molded body is left to stand for 24 hours at 23°C and 50% relative humidity for curing. After curing, the foamed granule molded body is again visually inspected and evaluated as follows. ◎: Minimal shrinkage before ripening, and no shrinkage observed after ripening. 〇: Significant shrinkage was confirmed before maturation, but the shrinkage recovered after maturation. △: Significant shrinkage was observed both before and after ripening. ×: Significant shrinkage was observed both before and after aging, and areas of localized melting were also observed.

[0077] (Uneven heating) The uneven heating was evaluated by visually inspecting the outer surface of the foamed granule molded body removed from the split molding die, and in the following manner. ◎: The foaming is uniform throughout, and it has been confirmed that there is no uneven heating. 〇: Although there are gaps (pores) between foamed particles in some areas on the surface, the foaming is generally uniform, and it has been confirmed that there is almost no uneven heating. △: The foamed particles have partially detached from the surface, confirming that the foaming was insufficient due to uneven heating. ×: A large number of foamed particles fell off the surface, confirming that the overall foaming was insufficient due to uneven heating.

[0078] (Leakage test) A test piece with a thickness of 50 mm and dimensions of 150 mm on each side was cut from the center of the foamed granule molded body used for the test. Additionally, a cylindrical acrylic tube with an inner diameter of 80 mm, a thickness of 6 mm, and a height of 120 mm was prepared. A silicone sealant was applied to the open end face of one side of the tube, and the test piece and tube were positioned and bonded together so that the center of the tube opening roughly aligned with the center of the length and width of the test piece. After the silicone sealant dried, the test piece was placed underneath, and water was poured into the tube through the opening on the other side. The water depth was set to 5 cm. The tube was left to stand for 24 hours, and the presence of leakage through the test piece was confirmed according to the following evaluation criteria. Furthermore, there were no examples in this embodiment or comparative example that received a △ (poor) evaluation. 〇: The lower surface of the test piece was dry, the water depth was 5cm, and no leakage was confirmed. △: The lower surface of the test piece is confirmed to be wetted, with a water depth of more than 2.5cm and less than 5cm, indicating a leak. ×: The lower surface of the test piece is wetted, and the water depth is less than 2.5cm, confirming a leak.

[0079] (Leakage test) Referencing Appendix A of JIS Z2332:2012, the pressure variation method and pressurization method are used to conduct a leak test and determine the gas leakage rate of the foamed granule molded body. First, a metal test piece holder is prepared for the leak test. This holder is a disc-shaped piece with a thickness of 30 mm and a diameter of 180 mm, and has an opening that extends along its thickness. Within the opening of the test piece holder, there is a first opening with a diameter of 80 mm and a depth of 25 mm, opening from one side to the other, and a second opening continuous with the first opening with a diameter of 70 mm and a depth of 5 mm. Furthermore, four bolt insertion holes are evenly spaced around the opening of the test piece holder. In addition, a pressurized gas supply device is prepared as a pressurized gas introduction device, which has a pressurized gas flow channel and a first flange welded to the downstream end of the pressurized gas flow channel. A flow control valve, a regulator, and a discharge valve are provided on the upstream side of the pressurized gas supply device. The first flange is a disc-shaped flange with a thickness of 14 mm and a diameter of 180 mm, and has a flange opening with a diameter of 80 mm extending along the thickness direction. Four bolt insertion holes are evenly spaced around this flange opening. Furthermore, a separate second flange with the same shape as the first flange is prepared. Additionally, a sealing gasket is provided on one side of both the first and second flanges.

[0080] A cylindrical test piece with a diameter of 80 mm and a height of 25 mm is cut from the center of the foamed granule molded body used for testing. The test piece is then placed at the first opening of the test piece mounting platform. During placement, a silicone sealant is used to bond the test piece and the platform together in a manner that prevents airflow and creates a gap, thus obtaining a test specimen for leakage testing. The first flange is disposed on the first opening side of the test specimen used for leakage testing, and the second flange is disposed on the second opening side. Bolts are inserted through bolt holes provided in each flange to fix the test specimen used for leakage testing to the pressurized gas supply device. Furthermore, a pressure sensor, a pressure gauge, and a recorder are connected to the pressurized gas supply device. Additionally, gaskets disposed on the first and second flanges ensure a tight seal between the first and second flanges and the test specimen mounting platform clamped by the first and second flanges, thereby creating a sealed interior for the test specimen used for leakage testing. Next, turn on the power to the pressurized gas supply device. With the discharge valve open, reset the pressure gauge to zero and then close the discharge valve. Then, with the flow control valve closed, start introducing air, gradually opening the flow control valve and adjusting it using the regulator until it reaches the gauge pressure at the start of the test, i.e., 3 kPa. After confirming that the gauge pressure has reached 3 kPa, quickly close the flow control valve, stop the pressurized gas supply, and start the test. The test ends after confirming that the pressurized gas has decayed to atmospheric pressure through the test piece and inside the test body used for the leak test. Measure the time from the start to the end of the test. Then, calculate the gas leakage rate using the following formula (1). [Formula 1] Q=V(P2-P1) / Δt ……(1) Q: Leakage rate (Pa·L / s) P1: Gauge pressure (Pa) of the leakage test apparatus at the start of the test. P2: Gauge pressure (Pa) of the leakage test apparatus at the end of the test. Δt: Time from the start to the end of the detection process (s) V: Volume of the test piece (L)

[0081] <Examples 2-7, 9, 10, and Comparative Example 1> Except for the changes shown in Tables 1 and 2, the foamed granule molded articles were manufactured in the same manner as in Example 1. The foamed granules used and the manufactured foamed granule molded articles were measured and evaluated in the same manner as in Example 1. These results are shown in Tables 1 and 2.

[0082] <Example 8> Except for the changes shown in Table 2 and the following filling and pre-compression processes, the foamed granule molded articles were manufactured in the same manner as in Example 1. Furthermore, the foamed granules used and the manufactured foamed granule molded articles were measured and evaluated in the same manner as in Example 1. These results are shown in Table 2. In Example 8, the device with Figure 4 A molding die with the same structure was used. First, polypropylene resin foam granules, before pressurization, were filled into a pressurized filling tank. Then, pressurized air was supplied into the tank, and the mixture was allowed to stand for 24 hours to increase the internal pressure of the polypropylene resin foam granules to 0.10 MPa (G). Then, the foam granules with increased internal pressure and pressurized air were compressed and filled into the mold cavity. Through the above compression filling, the pressure of the mold cavity was adjusted to 0.25 MPa (G). That is, in Example 8, the filling process and the pre-compression process were performed simultaneously.

[0083] <Examples 11-13, Comparative Example 2> Examples 11-13 and Comparative Example 2 were implemented using polyethylene-based resin foamed granules. Specifically, foamed granule molded articles were manufactured in the same manner as in Example 1, except that the contents were changed as shown in Table 3. Furthermore, the foamed granules used and the manufactured foamed granule molded articles were measured and evaluated in the same manner as in Example 1. These results are shown in Table 3.

[0084] <Examples 14-17, Comparative Example 3> Examples 14-17 and Comparative Example 3 were carried out using polystyrene-based resin foamed granules. Specifically, foamed granule molded articles were manufactured in the same manner as in Example 1, except that the contents were changed as shown in Table 4. Furthermore, the foamed granules used and the manufactured foamed granule molded articles were measured and evaluated in the same manner as in Example 1. These results are shown in Table 4.

[0085] <Comparative Example 4> Prepare an existing split molding mold, which, except for lacking a steam supply section, is similar to... Figure 1The molded part is the same as the one shown. Then, foamed particles identical to those used in Example 1 are prepared. The foamed particles, with an internal pressure adjusted to 0.14 MPa, are filled into an exhaust chamber ensuring a gap distance of 6 mm, and then the mold is closed. The gap ratio is 10%. Then, without performing a pre-pressurization process, with the opening and closing mechanism of the molded part open, steam with an output pressure of 0.60 MPa (G) is supplied to the molded part for 5 seconds to replace the air inside the molded part with steam. Next, as unilateral heating, steam with an output pressure of 0.60 MPa (G) is supplied from the first frame side into the exhaust chamber for 5 seconds, pressurizing to 0.26 MPa (G) to heat the foamed particles. Further, as reverse unilateral heating, steam with an output pressure of 0.60 MPa (G) is supplied from the second frame side into the exhaust chamber for 3 seconds, pressurizing to 0.36 MPa (G) to heat the foamed particles. Next, as bilateral heating, steam with an output pressure of 0.60 MPa (G) is supplied for 7 seconds, and heating is performed by opening and closing the supply holes on both sides (first frame side and second frame side) of the split molding die to maintain the pressure inside the split molding die at 0.38 MPa (G), and then the heating process ends. Additionally, during heating, the exhaust holes of the frames provided in the split molding die are closed except for those used for supplying steam, while the vent holes provided in the pair of complementary molds are open. This allows the steam supplied to the split molding die to be introduced into the chamber. Furthermore, the pressure inside the split molding mold refers to the indoor pressure. The total steam consumption used in the heating process is 4.08 kg. After performing the heating process described above, the cooling time shown in Table 5 was used, except that the cooling method was the same as in Example 1. Then, after confirming that the surface pressure reached the value shown in Table 5, the foamed granule molded body was removed from the molding die. Using the foamed granules used in Comparative Example 4 and the foamed granule molded body obtained through Comparative Example 4, the same measurements and evaluations as in Example 1 were performed. The results are shown in Table 5.

[0086] <Comparative Examples 5 and 6> Except for the changes shown in Table 5 and the omission of double-sided heating, the foamed granule molded body was manufactured in the same manner as in Comparative Example 4. Furthermore, the same measurements and evaluations as in Example 1 were performed using the foamed granules and the manufactured foamed granule molded body. These results are shown in Table 5.

[0087] <Example 18> A split molding die with a cavity capable of forming a flat molded body with a length of 1004 mm × width of 308 mm × height of 153 mm when the mold is closed was used, and the contents shown in Table 6 were modified, except that the foamed granule molded body was manufactured in the same manner as in Example 1. The foamed granules used and the manufactured foamed granule molded body were measured and evaluated in the same manner as in Example 1. In addition, for Example 18, a water leakage test and a leak test were performed. These results are shown in Table 6. <Comparative Example 7> A split molding die with a cavity capable of forming a flat molded body with a length of 1004 mm × width of 308 mm × height of 153 mm when the mold is closed was used, and the contents shown in Table 7 were modified, but double-sided heating was not performed. The foamed granule molded body was manufactured in the same manner as in Comparative Example 4. Furthermore, the foamed granules used and the manufactured foamed granule molded body were subjected to the same measurements and evaluations as in Example 1. In addition, for Comparative Example 7, a water leakage test and a leak test were performed. These results are shown in Table 7.

[0088] As shown in Tables 1 to 7, it was confirmed that compared with Comparative Examples 4 to 7, which implemented the existing in-mold molding, the steam output time and consumption in the heating process of each embodiment were significantly reduced. Furthermore, in Examples 1-10 and 18, the steam output time was short and the consumption was low, and good foamed granule molded articles were produced in all cases. In contrast, in Comparative Example 1, which did not undergo a pre-pressing process, the steam output time was long and the consumption was high. In addition, the foamed granule molded articles obtained in Comparative Example 1 had poor bonding between the foamed granules, and a portion of the foamed granule molded article remained in the state of foamed granules, making it impossible to maintain the shape of the foamed granule molded article, and therefore, the molded article could not be evaluated. In Examples 11-13, the steam output time was short and the consumption was low, and good foamed granule moldings were produced in all cases. In contrast, in Comparative Example 2, which did not undergo a pre-compression process, the steam output time was long and the steam consumption was high. Furthermore, in Comparative Example 2, the foamed granules had poor bonding, making it impossible to measure density and shrinkage rate. In Examples 14-17, the steam output time and consumption were short, and good foamed granule moldings were produced. In contrast, in Comparative Example 3, which did not undergo a pre-compression process, the steam output time was long, and the steam consumption was high. When comparing Example 18 and Comparative Example 7, which underwent water leakage test and leak test, it was confirmed that the foamed granule molded body manufactured by the manufacturing method of the present invention is a foamed granule molded body that is not easily permeable by liquids and gases and has high airtightness.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] [Table 5]

[0094] [Table 6]

[0095] [Table 7]

[0096] The present invention described above includes the following technical concept. (1) A method for manufacturing a foamed granule molded body, characterized in that thermoplastic resin foamed granules are filled into the cavity of a split molding mold composed of a first mold and a second mold, and the foamed granules are heated by steam and in-mold molded. The first mold and / or the second mold have an exhaust chamber configured to allow ventilation to the cavity. The manufacturing method includes the following steps: A pre-compression process involves supplying pressurized gas (excluding steam) into the cavity to adjust the pressure within the cavity filled with the foamed particles to a pressure greater than atmospheric pressure (P1); and A heating process involves supplying steam at a pressure (P2) higher than the pressure (P1) to the cavity, which has been adjusted to the pressure (P1) through the pre-compression process, and then discharging the steam supplied to the cavity into the exhaust chamber, thereby heating the foamed particles. During the heating process, steam at the pressure (P2) is supplied into the cavity while the pressure in the exhaust chamber is adjusted to a pressure (P3) that is greater than atmospheric pressure but lower than the pressure (P2). (2) The method for manufacturing foamed granules according to (1), characterized in that, In the heating process, steam at a pressure (P2) higher than the pressure (P1) inside the mold cavity is supplied from the steam supply unit into the mold cavity. Simultaneously, the steam inside the mold cavity is discharged to the outside of the mold cavity through a vent. The vent is located in the molding wall that separates the inside of the mold cavity from the exhaust chamber and ensures ventilation between the exhaust chamber and the mold cavity. The pressure inside the exhaust chamber is adjusted via an exhaust port with an opening and closing mechanism, causing the thermoplastic resin foam particles to fuse together. The exhaust port with the opening and closing mechanism is provided in at least one of the first mold and the second mold, ensuring ventilation between the exhaust chamber and the outside of the molding mold. (3) The method for manufacturing foamed granules according to (1) or (2) is characterized in that, in the pre-pressing process, the pressure inside the cavity is adjusted to above 0.05 MPa (G) and below 0.4 MPa (G). (4) The method for manufacturing a foamed granule molded body according to any one of (1) to (3) is characterized in that, in the heating process, the pressure difference (P2-P1) expressed by subtracting the pressure (P1) from the pressure (P2) is 0.15 MPa or more and 0.35 MPa or less. (5) The method for manufacturing a foamed granule molded body according to any one of (1) to (4) is characterized in that the pressure difference (P1-P3) represented by the difference between the pressure (P1) in the pre-pressing process and the pressure (P3) in the heating process is -0.1 MPa or more and +0.1 MPa or less. (6) The method for manufacturing a foamed granule molded body according to any one of (1) to (5), characterized in that the thermoplastic resin foamed granules are polypropylene resin foamed granules. (7) The method for manufacturing a foamed granule molded body according to any one of (1) to (6) is characterized in that the supply hole for supplying the steam is disposed on the same surface as the cavity surface, and in the heating process, steam with a pressure higher than that in the cavity is directly supplied from the supply hole into the cavity. (8) The method for manufacturing a foamed granule molded body according to any one of (1) to (7), characterized in that the supply hole for supplying steam to the cavity is disposed on the same surface as the cavity surface, and the first mold and / or the second mold have vent holes on the cavity surface that allow ventilation between the cavity and the exhaust chamber. The average distance between the supply hole and the vent hole is 40mm or more. (9) The method for manufacturing a foamed granular molded body according to any one of (1) to (8), characterized in that the supply hole for supplying steam to the cavity is disposed on the same surface as the cavity surface, and the first mold and / or the second mold have vent holes on the cavity surface that allow ventilation between the cavity and the exhaust chamber. The total opening area of ​​the vent holes is more than 1.2 times and less than 5 times the total opening area of ​​the supply holes. The ratio of the total opening area of ​​the vent holes to the total area of ​​the cavity surface is greater than 0% and less than 2%. (10) The method for manufacturing foamed granular molded articles according to any one of (1) to (9), characterized in that, The cavity is formed by a first inner mold disposed in the first mold and a second inner mold disposed in the second mold. The exhaust chamber is located on the back side of the first inner mold and / or the back side of the second inner mold. (11) The method for manufacturing a foamed granular molded body according to any one of (1) to (10) is characterized in that it includes a filling step, wherein the filling step is performed before or simultaneously with the pre-compression step. The filling process comprises the following steps: Using the pair of complementary molds, a gap is provided between the first inner mold and the second inner mold in the mold closing direction, causing the volume of the cavity to expand. Thermoplastic resin foam particles are filled into the expanded cavity. Next, the pair of complementary molds are fully closed to reduce the volume of the cavity, thereby compressing the thermoplastic resin foam particles within the cavity. (12) The method for manufacturing a foamed granular molded body according to any one of (1) to (11) is characterized in that it includes a filling step, wherein the filling step is performed before or simultaneously with the pre-compression step. The filling process involves filling the cavity with thermoplastic resin foam particles that have been compressed using pressurized gas other than steam. During the filling process, the thermoplastic resin foam particles are supplied to the cavity along with the pressurized gas, thereby performing part or all of the pre-compression process at the same time as the filling process. Explanation of reference numerals in the attached figures

[0097] 10: Cavity; 20: Venting chamber; 30: Pair of complementary molds; 30A: First inner mold; 30B: Second inner mold; 32: Molding wall; 34: First mold; 36: Second mold; 40: Frame; 40A: First frame; 40B: Second frame; 50: Thermoplastic resin foam granules; 52: Filler feeder; 60: Steam supply unit; 60A: Main runner; 60B: Branch runner; 64: Vent hole; 65: Opening and closing mechanism; 66: Vent hole; 67: Opening and closing mechanism; 68: Supply hole; 69: Air inlet hole; 100: Split molding mold; 200: Pressurized filling tank; 202: Pressurized pressure regulating unit; 204: Vent pressure regulating unit; C: Mold closing direction; d1: Distance; X: Gap distance.

Claims

1. A method for manufacturing a foamed granular molded body, characterized in that, Thermoplastic resin foam particles are filled into the cavity of a split molding die consisting of a first mold and a second mold. The foam particles are then heated with steam and in-mold molded. The first mold and / or the second mold have an exhaust chamber configured to allow ventilation to the cavity. The manufacturing method includes the following steps: A pre-compression process involves supplying pressurized gas (excluding steam) into the cavity to adjust the pressure within the cavity filled with the foamed particles to a pressure greater than atmospheric pressure (P1); and A heating process involves supplying steam at a pressure (P2) higher than the pressure (P1) to the cavity, which has been adjusted to the pressure (P1) through the pre-compression process, and then discharging the steam supplied to the cavity into the exhaust chamber, thereby heating the foamed particles. During the heating process, steam at the pressure (P2) is supplied into the cavity while the pressure in the exhaust chamber is adjusted to a pressure (P3) that is greater than atmospheric pressure but lower than the pressure (P2).

2. The method for manufacturing foamed granular molded articles according to claim 1, characterized in that, In the pre-compression process, the pressure (P1) is adjusted to be above 0.05 MPa (G) and below 0.4 MPa (G).

3. The method for manufacturing foamed granular molded articles according to claim 1 or 2, characterized in that, In the heating process, the pressure difference (P2-P1) expressed by subtracting the pressure (P1) from the pressure (P2) is 0.15 MPa or more and 0.35 MPa or less.

4. The method for manufacturing foamed granular molded articles according to any one of claims 1 to 3, characterized in that, The pressure difference (P1-P3) represented by subtracting the pressure (P3) in the heating process from the pressure (P1) in the pre-compression process is greater than -0.1 MPa and less than +0.1 MPa.

5. The method for manufacturing foamed granular molded articles according to any one of claims 1 to 4, characterized in that, The thermoplastic resin foam particles are polypropylene resin foam particles.

6. The method for manufacturing foamed granular molded articles according to any one of claims 1 to 5, characterized in that, A steam supply hole for supplying steam into the cavity is disposed on the same surface as the cavity surface. Meanwhile, the first mold and / or the second mold have vent holes on the cavity surface that allow ventilation between the cavity and the exhaust chamber. The average distance between the supply hole and the vent hole is 40 mm or more.

7. The method for manufacturing foamed granular molded articles according to any one of claims 1 to 6, characterized in that, A steam supply hole for supplying steam into the cavity is disposed on the same surface as the cavity surface. Meanwhile, the first mold and / or the second mold have vent holes on the cavity surface that allow ventilation between the cavity and the exhaust chamber. The total open area of ​​the vent holes is more than 1.2 times and less than 5 times the total open area of ​​the supply holes. The ratio of the total open area of ​​the vent holes to the total area of ​​the cavity surface is greater than 0% and less than 2%.

8. The method for manufacturing foamed granular molded articles according to any one of claims 1 to 7, characterized in that, The cavity is formed by a first inner mold of the first mold and a second inner mold of the second mold, and the venting chamber is provided on the back side of the first inner mold and / or the back side of the second inner mold.

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