Method for manufacturing extruded articles

Abstract

To successfully manufacture extrusion molded bodies with a surface layer extruded in a hollow shape and a foam core material consisting of fused foam particles filled in the hollow portion formed by such a surface layer.SOLUTION: The thermoplastic resin is extruded from a die 22 to extrude a skin layer 2 into a hollow shape, and steam is supplied from a steam supply section 350 of a steam supply pipe 35 located along the extrusion direction of the skin layer 2 in a hollow section 4 formed by the skin layer 2, while filling the hollow section of the skin layer 2 with thermoplastic resin foam particles from a foam particle introduction channel 31 located in the hollow section 4 formed by the skin layer 2 toward the extrusion direction of the skin layer 2, steam is discharged from a steam discharge section 360 of a steam discharge pipe 36 located along the extrusion direction of the skin layer 2 in the hollow section 4 formed by the skin layer 2, to fuse the foam particles together.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an extruded article comprising a hollow extruded surface layer and a foamed core material formed by fusing foamed particles filled into the hollow portion formed by the surface layer. [Background technology]

[0002] Conventionally, hollow molded products are known, which are made by extruding thermoplastic resin into a hollow shape. Such hollow molded products are used in various applications where lightness is required, but the disadvantage in terms of strength due to their hollow nature is unavoidable. For this reason, Patent Document 1 proposes a foam-filled extruded product (1) in which a core body (2) is made by fusing foam particles (21) made of thermoplastic resin together into a hollow part formed by an extruded surface layer (11) made of hollow extruded thermoplastic resin, from the viewpoint of eliminating the disadvantage in terms of strength while maintaining lightness. The symbols in parentheses in the explanation relating to Patent Document 1 are those used in Patent Document 1. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-291244 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in the first embodiment of Patent Document 1, the foam particles (21) are fused together by heat transfer from the high-temperature extruded skin layer (11) in a molten state. In practice, it is difficult to sufficiently transfer heat to the center of the core body (2), which may result in poor fusion of the foam particles (21) in the center of the core body (2) or insufficient secondary foaming of the foam particles (21). On the other hand, in order to sufficiently fuse the foam particles (21), it is described that the inside of the molded body is heated with steam by a steam introduction pipe (887). However, the steam introduction pipe (887) obstructs the flow of the molten resin, leaving problems such as a deterioration in the appearance of the extruded skin layer (11).

[0005] Therefore, in view of the above-mentioned problems, the present inventors diligently studied how to successfully manufacture an extruded molded body comprising a hollow extruded surface layer and a foamed core material formed by fusing foamed particles filled in the hollow portion formed by the surface layer, and as a result, completed the present invention. [Means for solving the problem]

[0006] A method for manufacturing an extruded article according to the present invention comprises a hollow extruded surface layer and a foamed core material formed by fusing foamed particles filled in the hollow portion formed by the surface layer, comprising the steps of: extruding a thermoplastic resin from a die to extrude the surface layer into a hollow shape; filling the hollow portion formed by the surface layer with thermoplastic resin foamed particles from a foamed particle introduction channel located in the hollow portion formed by the surface layer toward the extrusion direction of the surface layer; and supplying steam from a steam supply section provided on the side of a steam supply pipe arranged in the hollow portion formed by the surface layer toward the extrusion direction of the surface layer, while discharging the steam from a steam discharge section provided on the side of a steam discharge pipe arranged in the hollow portion formed by the surface layer toward the extrusion direction of the surface layer, thereby fusing the foamed particles together. Then, through holes are formed along the longitudinal direction of the foam core material. This method includes the process of [doing something]. [Effects of the Invention]

[0007] According to the present invention, an extruded molded article comprising a hollow extruded surface layer and a foamed core material formed by fusing foamed particles filled into the hollow portion formed by the surface layer can be successfully manufactured. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram showing an example of an extruded molded article manufactured by the method for manufacturing an extruded molded article according to an embodiment of the present invention. [Figure 2] Figure 1 is an explanatory diagram showing the state in which only the surface layer has been formed in the manufacturing method of the extruded article shown. [Figure 3] This is a schematic diagram illustrating an example of a manufacturing apparatus suitable for carrying out a method for manufacturing an extruded article according to an embodiment of the present invention. [Figure 4] This is an explanatory diagram showing the preferred positional relationship between the steam supply section of the steam supply pipe and the steam discharge section of the steam discharge pipe. [Modes for carrying out the invention]

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings.

[0010] Figure 1 shows an example of an extruded body 1 manufactured by the manufacturing method of the extruded body according to this embodiment. The extruded body 1 comprises a hollow extruded surface layer 2 and a foamed core material 3 filled in the hollow portion 4 formed by the surface layer 2.

[0011] In this embodiment, the skin layer 2 can be molded using any thermoplastic resin that can be extruded into a hollow shape. More specifically, examples include, but are not limited to, polyolefin resins such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polypropylene (propylene homopolymer: h-PP), propylene-ethylene random copolymer (r-PP), and propylene-ethylene block copolymer (b-PP); polystyrene resins such as polystyrene (styrene homopolymer: GPPS), high-impact polystyrene (HIPS), styrene-methyl methacrylate copolymer (MS), acrylonitrile-styrene copolymer (AS), polystyrene-modified polyphenylene ether (modified PPE), and acrylonitrile-styrene-butadiene copolymer (ABS); polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polylactic acid (PLA); polycarbonate resins such as bisphenol-type polycarbonate (PC); or mixtures thereof. The surface layer 2 can be appropriately selected from thermoplastic resins that can be extruded, taking into consideration the mechanical properties such as strength and heat resistance required for the extruded body 1.

[0012] Furthermore, various additives can be added to the thermoplastic resin that forms the surface layer 2. Examples of additives include conductivity imparters, antioxidants, heat stabilizers, weathering agents, UV inhibitors, flame retardants, inorganic fillers, antibacterial agents, electromagnetic shielding agents, gas barrier agents, antistatic agents, and reinforcing fibers such as glass fibers and carbon fibers. These additives are added to an extent that allows them to exert their intended purpose and effect, and the amount added is generally 30 parts by weight or less, preferably 20 parts by weight or less, and more preferably 10 parts by weight or less, per 100 parts by weight of the thermoplastic resin.

[0013] The foamed core material 3 is a fused body of thermoplastic resin foamed particles, formed by fusing the foamed particles together. Preferably, the foamed core material 3 is fused and integrated with the inner circumferential surface of the surface layer 2 within the hollow portion 4 formed by the surface layer 2.

[0014] As the thermoplastic resin used for the foamed particles, it is preferable to use a resin that has high compatibility with the thermoplastic resin forming the surface layer 2, in order to fuse well with the surface layer 2 and increase the strength of the extruded molded product 1. In particular, it is preferable to use the same type or the same thermoplastic resin as the thermoplastic resin forming the surface layer 2. From this viewpoint, when a polyolefin resin is selected as the thermoplastic resin forming the surface layer 2, it is preferable to use a polyolefin resin for the foamed particles forming the foamed core material 3. Also, when a polystyrene resin is selected as the thermoplastic resin forming the surface layer 2, it is preferable to use a polystyrene resin or a composite resin of polystyrene resin and polyethylene resin for the foamed particles forming the foamed core material 3.

[0015] The foamed particles forming the foamed core material 3 are, for example, commercially available foamed particles, specifically the polypropylene resin foam manufactured by JSP Co., Ltd., under the product name "P-Block (registered trademark)," with a bulk density of 15-90 kg / m³. 3 Among the polyethylene resin foams manufactured by JSP Co., Ltd., under the product name "L-Block (registered trademark)," the bulk density is 15-80 kg / m³. 3 This is a polylactic acid-based resin foam particle manufactured by JSP Co., Ltd., with the product name "LACTIF (registered trademark)" and a bulk density of 15-80 kg / m³. 3 Examples include foamed polystyrene resin particles obtained by foaming JSP Co., Ltd.'s product name "Styrodia®" to a predetermined bulk density in a pre-foaming machine, and foamed composite resin (polyethylene / polystyrene) particles obtained by foaming JSP Co., Ltd.'s product name "Ellenpol NEO®" to a predetermined bulk density in a pre-foaming machine. Furthermore, foamed particles can also be obtained by referring to conventionally known publications such as Japanese Patent Publication No. 53-1313, WO2012 / 086305, and Japanese Patent Application Publication No. 2012-025869.

[0016] The shape of the foam particles can be any shape, such as cylindrical, spherical, prismatic, or ellipsoidal, and their size can also be set arbitrarily. From the viewpoint of filling performance, the shape of the foam particles is preferably spherical or cylindrical.

[0017] The bulk density of the expanded particles used in this embodiment is not particularly limited, but generally, expanded particles with a bulk density of 10 to 100 kg / m 3 are preferably used. In particular, in the case of polyolefin-based resin expanded particles or polystyrene-based resin expanded particles, from the viewpoint of facilitating the control of the secondary foaming ability by steam, expanded particles with a bulk density of 15 to 50 kg / m 3 are more preferably used.

[0018] Next, an example of a manufacturing apparatus suitable for implementing the manufacturing method of the extrusion molded body according to this embodiment will be described. Note that FIG. 3 schematically shows an example of the manufacturing apparatus.

[0019] The manufacturing apparatus 10 shown in FIG. 3 includes an outer skin layer forming unit 20 that extrudes a thermoplastic resin in a hollow shape to form the outer skin layer 2, an expanded particle introducing unit 30 that introduces expanded particles into the hollow portion 4 formed by the hollowly extruded outer skin layer 2, a cooling unit 40 including a sizing die 41, and a take-up unit 50 including a conveyor 51. Also, the arrow X in the figure indicates the extrusion direction.

[0020] The outer skin layer forming unit 20 is supplied with a thermoplastic resin melted and kneaded in an extruder 21, and includes a die 22 that extrudes the softened thermoplastic resin in a hollow shape to form the outer skin layer 2. In the example shown, the die 22 for extruding the outer skin layer 2 includes a die body 23 and a resin flow path portion 24 disposed inside the die body 23. And the thermoplastic resin supplied from the extruder 21 is configured to be extruded in a hollow shape from a discharge port 24a that opens from the resin flow path portion 24 through the resin flow path portion 24.

[0021] In the illustrated example, the resin channel section 24 is formed so that the surface layer 2 is extruded into a cylindrical shape, but the invention is not limited to this. By appropriately changing the shape of the discharge port 24a opening from the resin channel section 24, it is also possible to extrude it into an elliptical or rectangular cylindrical shape. In addition, it is also possible to extrude it into a hollow shape with a semicircular cross-section, a fan-shaped cross-section, a trapezoidal cross-section, or other irregular cross-sectional shapes.

[0022] The foam particle introduction unit 30 includes a foam particle introduction passage 31 located within a hollow section 4 formed by a hollow extruded surface layer 2. In the illustrated example, the foam particle introduction passage 31 is formed in a cylindrical body section 32 that penetrates axially through the inner circumference of the resin flow channel section 24 of the die 22 that extrudes the surface layer 2, and protrudes in the extrusion direction of the surface layer 2. Foam particles supplied from a hopper 34 located upstream of the cylindrical body section 32 are transported by a screw feeder 33 located within the foam particle introduction passage 31, and are then discharged from a discharge port 31a opening at the tip of the foam particle introduction passage 31 toward the extrusion direction of the surface layer 2. The foam particle discharge port 31a opening at the tip of the cylindrical body section 32 is located on the side of the surface layer 2 toward the extrusion direction of the surface layer 2, rather than the surface discharge port 24a of the resin flow channel 24 that forms the surface layer 2. In this process, it is preferable that the foamed particles are packed and compressed into the hollow portion 4 formed by the surface layer 2, and that the direction in which the foamed particles are packed coincides with the extrusion direction of the surface layer 3. Here, a compressed state means that the foamed particles are packed at least more densely than when the bulk density of the foamed particles was measured. Specifically, it is preferable that the foamed particles are packed about 1.01 to 1.5 times more densely than their bulk density, and more preferably about 1.02 to 1.2 times more densely. Note that, for illustrative purposes, Figure 3 omits illustrations of the foam particles being transported within the screw feeder 33 and the foam particles being discharged from the foam particle discharge port 31a of the foam particle introduction passage 31.

[0023] In configuring the foam particle introduction passage 31 in this way, the screw shape of the screw feeder 33 provided in the foam particle introduction passage 31 can be appropriately selected so that the foam particles are filled into the hollow section 4 formed by the surface layer 2. However, a screw shape with screw blades formed around a central axis (screw with shaft) or a screw shape consisting only of spiral blades (screw without shaft) is preferred. For example, when using a screw without shaft, even if the foam particles become clogged at the tip of the foam particle introduction passage 31 during transport, the screw can still be transported at a constant pressure while spinning freely. Therefore, it is suitable for cases where polystyrene-based resin foam particles containing an organic foaming agent and exhibiting excellent secondary foaming properties are molded with low-pressure steam. On the other hand, in the case of olefin-based resin foam particles molded with relatively high-pressure steam, the drain water generated by the condensation of steam may hinder the transport of the foam particles, so it is preferable to use a screw with shaft. In any case, by appropriately selecting the screw shape, the foam particles can be filled into the hollow section 4 formed by the surface layer 2 in a more compressed state.

[0024] Furthermore, the cylindrical body portion 32 is provided with a steam supply pipe 35 and a steam discharge pipe 36, which protrude from around the discharge port 31a that opens at the tip of the foam particle introduction passage 31 and are arranged along the extrusion direction of the surface layer 2. Because the steam supply pipe 35 and the steam discharge pipe 36 are arranged along the extrusion direction of the surface layer 2, they do not affect the formation state of the surface layer 2, so that an extruded foam with a smooth surface layer 2 and excellent appearance can be formed. When providing the steam supply pipe 35 and the steam discharge pipe 36 in the cylindrical body 32, for example, one steam supply pipe 35 and one steam discharge pipe 36 may be provided facing each other in the radial direction of the cylindrical body 32, or one or both of the steam supply pipe 35 and the steam discharge pipe 36 may be provided in multiples at arbitrary intervals along the circumferential direction of the cylindrical body 32. Furthermore, it is preferable that holes are formed in the cylindrical body 32 around the foam particle introduction passage 31 into which the steam supply pipe 35 and steam discharge pipe 36 are inserted. In addition, it is preferable that the bottom surface, which is the tip of the cylinder of the cylindrical body 32, is flat except for the holes forming the foam particle introduction passage 31 and the holes into which the steam supply pipe 35 and steam discharge pipe 36 are inserted, in order to prevent backflow of the filled foam particles.

[0025] The steam supply pipe 35 and the steam discharge pipe 36 are preferably metal pipes capable of supplying and discharging steam, and their outer diameter is preferably 5 to 30 mm. Furthermore, both the steam supply pipe 35 and the steam discharge pipe 36 have their ends closed, and it is preferable that a steam supply section 350 is provided on the side of the steam supply pipe 35, and a steam discharge section 360 is provided on the side of the steam discharge pipe 36. The steam supply section 350 of the steam supply pipe 35 and the steam discharge section 360 of the steam discharge pipe 36 are shaped and sized in a way that prevents foam particles from entering the pipes. For example, slit-shaped or elongated pores can be created by drilling them on the sides of the steam supply pipe 35 and the steam discharge pipe 36, respectively.

[0026] In this manner, when providing the steam supply section 350 and steam discharge section 360 in the steam supply pipe 35 and steam discharge pipe 36, respectively, the number of holes to be drilled is not particularly limited. The arrangement of multiple holes is also not particularly limited; they may be arranged in one or more rows along the longitudinal direction, or in a staggered or random pattern. For example, the steam supply section 350 and steam discharge section 360 can be provided by drilling a total of nine holes, for example, in the form of slits with a width of 0.1 to 0.5 mm and a length of 5 to 20 mm, at three locations on the tip side of each pipe 35 and 36, and three locations along the circumferential direction. The width and length of the holes to be drilled are such that the total opening area of ​​the holes is 10 to 100 mm. 2It is preferable to make appropriate adjustments so that this is the case. The pores to be drilled in the steam supply pipe 35 and the steam discharge pipe 36 are preferably drilled in the peripheral wall portions of the respective pipes 35 and 36. From the viewpoint of ensuring uniform steam supply and discharge, it is preferable that these pores are drilled evenly in the peripheral wall portions of the pipes 35 and 36.

[0027] The arrangement of the steam supply pipe 35 and the steam discharge pipe 36 (for example, the length protruding from the tip of the cylindrical body 32), and the number and arrangement of the pores drilled in the steam supply pipe 35 and the steam discharge pipe 36 can be set as appropriate. However, it is preferable that steam is supplied from the steam supply section 350 of the steam supply pipe 35 to the foamed particles filled in the hollow section 4 formed by the surface layer 2, and that this steam moves toward the die 22 side and is discharged from the steam discharge section 360 of the steam discharge pipe 36.

[0028] For example, as shown in Figure 4, if pores are drilled in a similar arrangement on the tip side of the steam supply pipe 35 and the steam discharge pipe 36, and a steam supply section 350 and a steam discharge section 360 are provided in each, it is preferable to arrange the steam supply pipe 35 and the steam discharge pipe 36 along the extrusion direction of the surface layer 2 such that the length of the steam discharge pipe 36 protruding from the tip of the cylindrical body 32 is shorter than that of the steam supply pipe 35. The arrow X in the figure indicates the extrusion direction.

[0029] In particular, in this embodiment, it is preferable to arrange the steam supply pipe 35 and the steam discharge pipe 36 such that the steam discharge section 360a, located at the tip of the steam discharge pipe 36, is positioned further away from the die 22 than the steam supply section 350c, which is located at the tip of the steam supply pipe 35. This will be explained later.

[0030] In the method for manufacturing an extruded article according to this embodiment, the manufacturing apparatus 10 described above is suitably used to first extrude a thermoplastic resin from the die 22 to extrude the surface layer 2 into a hollow shape. Simultaneously, foamed thermoplastic resin particles are filled into the hollow portion 4 formed by the surface layer 2 from a foamed particle introduction channel 31 located within the hollow portion 4 formed by the surface layer 2, in the direction of extrusion of the surface layer 2. Furthermore, the extrusion temperature of the surface layer 2 is preferably 5 to 40°C higher, and more preferably 10 to 30°C higher, than the melting point or softening point of the thermoplastic resin forming the surface layer 2.

[0031] Then, while continuing these processes, steam is supplied from the steam supply section 350 of the steam supply pipe 35, which is positioned along the extrusion direction of the surface layer 2 within the hollow section 4 formed by the surface layer 2, and steam is discharged from the steam discharge section 360 of the steam discharge pipe 36, which is positioned along the extrusion direction of the surface layer 2 within the hollow section 4 formed by the surface layer 2. At this time, it is preferable that the steam is supplied in a state in which the foam particles are packed and compressed within the hollow section 4 formed by the surface layer 2. When steam is supplied, the foam particles are heated and softened, and secondary foaming occurs, causing the foam particles to fuse together to form a fused body, and the foam core material 3 is formed.

[0032] In such a process, the pressure of the steam supplied from the steam supply section 350 of the steam supply pipe 35 (the pressure inside the steam supply pipe 35) is preferably 0.1 to 0.5 MPa (G) in gauge pressure. On the other hand, when discharging steam from the steam discharge section 360, it is preferable to reduce the pressure inside the steam discharge pipe 36 (preferably to 0.01 to 0.1 MPa (G)) by connecting the steam discharge pipe 36 to a suction pump or the like, so that steam is drawn in and the steam is efficiently discharged from the steam discharge section 360.

[0033] Furthermore, the steam supply pipe 35 and the steam discharge pipe 36 can be arranged parallel to the screw feeder 33 located in the foam particle introduction passage 31 and penetrate the cylindrical body 32 in the extrusion direction, as shown in the figure, taking their routing into consideration. In this case, the cylindrical body 32 may be equipped with a temperature control mechanism as needed to facilitate secondary foaming of the foam particles. In particular, it is preferable that the cylindrical body 32 be temperature-controlled to 50 to 100°C, so that the foam particles are preheated, which facilitates secondary foaming by steam heating and makes molding in a limited molding space easier.

[0034] By performing the above steps in succession, the continuously formed extruded body 1 is cooled by the sizing die 41, picked up by the conveyor 51, and then cut to a predetermined length as needed.

[0035] According to this embodiment, among the foamed particles filled in the hollow portion 4 formed by the surface layer 2, the foamed particles located near the surface layer 2 fuse with adjacent foamed particles due to the heat from the softened surface layer 2 after extrusion molding, and also fuse with the inner surface of the surface layer 2, becoming one with it.

[0036] Furthermore, by arranging the steam supply pipe 35 and the steam discharge pipe 36 in a specific configuration and heating the foamed particles with steam, secondary foaming of the foamed particles is possible, thereby filling the gaps between the filled foamed particles and fusing them together. In addition, it is possible to increase the volume of the foamed core material 3 formed by fusing the foamed particles together, and to ensure uniformity in the foaming ratio and degree of fusion of the foamed core material 3.

[0037] Therefore, according to this embodiment, an extruded body 1 comprising a hollow extruded surface layer 2 and a foamed core material 3 formed by fusing foamed particles filled in the hollow portion 4 formed by the surface layer 2 can be successfully manufactured. In particular, in this embodiment, the foamed particles in the center of the foamed core material 3 can also be successfully fused together by steam supplied from the steam supply section 350 of the steam supply pipe 35, which is arranged along the extrusion direction of the surface layer 2 within the hollow portion 4 formed by the surface layer 2. For this reason, it is suitable for manufacturing thick extruded bodies 1, and even in extruded bodies 1 with a maximum thickness of 100 mm or more, the foamed core material 3 portion can be manufactured well, and in particular, the fusion rate of the foamed core material 3 can be improved. If the extruded body 1 is cylindrical, its maximum thickness is equal to its diameter.

[0038] Furthermore, if the foamed particles undergo secondary foaming and the gaps between them are filled, the steam may have difficulty reaching the foamed particles filling the hollow portion 4 formed by the surface layer 2, or it may not reach the steam discharge section 360 of the steam discharge pipe 36, potentially resulting in localized insufficient heating. To effectively avoid such problems, it is preferable to supply steam from the steam supply section 350 of the steam supply pipe 35 so that the steam moves toward the die 22 side and is discharged from the steam discharge section 360 of the steam discharge pipe 36.

[0039] In this embodiment, the foamed particles filled in the hollow portion 4 formed by the surface layer 2 move together with the surface layer 2 in the direction of extrusion of the surface layer 2, and the foamed particles fuse together. As a result, subsequent foamed particles that have not yet fused move sequentially toward the steam supply section 350 of the steam supply pipe 35. Therefore, by causing the steam supplied from the steam supply section 350 of the steam supply pipe 35 to move toward the die 22 side in the opposite direction of extrusion of the surface layer 2, the steam can pass through the gaps between subsequent foamed particles, causing secondary foaming and fusion of the subsequent foamed particles, and reach and be discharged to the steam discharge section 360 of the steam discharge pipe 36. As a result, secondary foaming of the foamed particles occurs stably, and the foamed particles in the hollow portion 4 fuse together uniformly. Furthermore, since the steam remaining inside the foamed core material 3 is efficiently discharged by the steam discharge section 360, it is also possible to suppress the retention of drain water generated by the condensation of steam inside the foamed core material 3.

[0040] From this perspective, as mentioned above, it is preferable to arrange the steam supply pipe 35 and the steam discharge pipe 36 such that the steam discharge section 360a, located at the furthest end of the steam discharge pipe 36, is located furthest from the tip of the steam supply pipe 35 towards the die 22, relative to the steam supply section 350c, which is located at the furthest end of the steam supply pipe 35 towards the die 22. In this configuration, considering the take-up speed of the extruded body 1 by the conveyor 51, it is preferable to set the separation distance D along the extrusion direction of the surface layer 2 between the steam supply section 350c, which is located at the furthest end of the steam supply pipe 35 towards the die 22, and the steam discharge section 360a, which is located at the furthest end of the steam discharge pipe 36, to 20 to 500 mm, and more preferably to 20 to 200 mm. In this way, by arranging the steam supply pipe 35 and the steam discharge pipe 36 such that a certain distance is provided between the steam supply section 350 and the steam discharge section 360, a good flow of steam is generated that is reversed in the extrusion direction of the surface layer 2 and directed toward the die 22, thereby making it easier to fuse the foamed particles. Furthermore, if there is only one steam supply unit 350 in the steam supply pipe 35, the steam supply unit 350 located furthest from the tip of the steam supply pipe 35 towards the die 22 will be that single existing steam supply unit 350, and the same applies to the steam discharge pipe 36.

[0041] In the configuration described above, if multiple steam supply pipes 35 and steam discharge pipes 36, or both, are provided, it is not necessary for all steam supply pipes 35 and steam discharge pipes 36 to be arranged to satisfy the above relationship, as long as a steam flow is generated that is reversed in the extrusion direction of the surface layer 2 and directed toward the die 22. It is sufficient that the above relationship is satisfied between at least one steam supply pipe 35 and at least one steam discharge pipe 36, and it is preferable that the above relationship is satisfied between the steam supply pipe 35 located furthest toward the extrusion direction and at least one steam discharge pipe 36.

[0042] Furthermore, when forming the foamed core material 3 using olefin-based resin foamed particles, the secondary foaming temperature of the olefin-based resin foamed particles is high, and the molding temperature is high, which necessitates setting a high steam pressure for supplying from the steam supply pipe 35. In such cases, in order to actively suck up the drain water generated by the condensation of steam, it is preferable to provide a steam discharge pipe 36 separately, in addition to the steam discharge pipe 36 arranged to satisfy the above relationship for one steam supply pipe 35, such that the steam discharge section 360 is located near the steam supply section 350 of the steam supply section 350.

[0043] Furthermore, it is preferable to form drain holes in the foam core material 3 for discharging drain water generated by the condensation of steam remaining inside the foam core material 3. In this embodiment, since the steam supply pipe 35 and the steam discharge pipe 36 are arranged in the hollow portion 4 formed by the surface layer 2 along the extrusion direction of the surface layer 2, these pipes 35 and 36 prevent the fusion of foam particles filled in the hollow portion of the surface layer 2, and through holes along the extrusion direction (longitudinal direction) can be easily formed in the molded foam core material 3 as traces of these pipes 35 and 36, and such through holes can be used as drain holes. [Examples]

[0044] The present invention will be described in more detail below with reference to specific examples.

[0045] [Example 1] The polystyrene resin, melted and kneaded in the extruder 21, was extruded from the die 22 at a resin temperature of 190°C to extrude the outer layer 2 into a hollow shape. The die 22 was circular in shape with a diameter of 100 mm. The bulk density was 36 kg / m³. 3 Polystyrene / polyethylene composite resin foam particles were filled into the hollow section 4 formed by the surface layer 2 from a foam particle introduction passage 31 located within the hollow section 4 formed by the surface layer 2, in the direction of extrusion of the surface layer 2. When filling the foam particles, the rotation speed of the shaftless screw-type screw feeder 33, which is located within the cylindrical section 32 of the foam particle introduction passage 31, was set to 47 rpm, and the cylindrical section 32 was temperature-controlled to 80°C. Furthermore, the foamed particles in the areas where the steam supply section 350 and the steam discharge section 360 are located were compressed and filled into the hollow section 4.

[0046] Then, while continuing these processes, steam was supplied into the hollow portion 4 formed by the surface layer 2 from the steam supply section 350 of the steam supply pipe 35, which was arranged along the extrusion direction of the surface layer 2, and steam was discharged into the hollow portion 4 formed by the surface layer 2 from the steam discharge section 360 of the steam discharge pipe 36, which was also arranged along the extrusion direction of the surface layer 2. The supplied steam heated and softened the foam particles, and caused secondary foaming, which fused the foam particles together. At this time, there were two steam supply pipes 35, the pressure inside the steam supply pipes 35 was 0.35 MPa (G), and there were two steam discharge pipes 36, the pressure inside the steam discharge pipes 36 was -0.05 MPa (G). The steam supply pipe 35 and the steam discharge pipe 36 are positioned such that the separation distance D along the extrusion direction of the surface layer 2 is 100 mm between the steam supply section 350c, which is located furthest from the tip of the steam supply pipe 35 that is furthest from the die 22, and the steam discharge section 360a, which is located closest to the tip of the steam discharge pipe 36 that is furthest from the die 22.

[0047] By performing the above processes in sequence, the continuously formed extruded body 1 was cooled by the sizing die 41 and then taken up by the conveyor 51 at a take-up speed of 0.35 m / min. The sizing die 41 is circular in shape, with a diameter of 120 mm. A gap of approximately 15 mm was provided between the die 22 and the sizing die 41.

[0048] The extruded body 1 produced in this manner has a surface layer 2 thickness of 2.5 mm, a weight per unit length of 1.3 kg / m, and a foam core material 3 density of 38 kg / m³. 3 The thickness (diameter of the cylinder) of the extruded body 1 was 120 mm. Furthermore, when the manufactured extruded body 1 was cut in a direction perpendicular to its longitudinal direction and the cut surface was observed, no leakage of drain water was found.

[0049] [bulk density] The bulk density of the expanded particles used in the present invention is a value calculated by the following method. First, place 500 or more expanded particles in an environment of 23°C in temperature, 50% in relative humidity, and 1 atm for 24 hours or more. The group of expanded particles thus obtained is filled into a graduated cylinder so as to naturally deposit, and the bulk volume (unit: L) of the group of expanded particles is read from the scale of the graduated cylinder. Then, the value obtained by dividing the mass (unit: g) of the group of expanded particles in the graduated cylinder by the above-mentioned bulk volume and performing unit conversion is the bulk density of the expanded particles (unit: kg / m 3 3

[0050] [Formed body weight] The extrusion-formed body was cut out so that the length in the extrusion direction was 1 m, and the weight of the formed body was measured. This measurement was performed at 5 or more locations in total. The measured thickness values were averaged arithmetically to obtain the formed body weight.

[0051] [Skin thickness] A circular cross-section perpendicular to the extrusion direction of the extrusion-formed body was cut out, and the thickness of the skin layer portion of the cross-section was measured at 6 locations at equal intervals along the circumferential direction of the skin layer. This measurement was performed at 5 or more locations (5 cross-sections) with different extrusion directions. The measured thickness values were averaged arithmetically to obtain the skin thickness of the skin material.

[0052] [Evaluation of the surface state of the skin layer] The surface state of the skin layer was evaluated visually. ○: No excessive unevenness is seen on the surface of the skin layer 2. ×: Concavities and convexities with a depth of 1 mm or more due to molding defects are formed on the surface of the skin layer 2.

[0053] [Evaluation of the fusion property of the foamed core material] The fusion rate of the foamed core material was measured as follows. First, the foamed core material portion was cut out from the extrusion-formed body to collect a test piece. This test piece was divided so as to be approximately equal, and the fracture surface was exposed. The total number of expanded particles present on this fracture surface and the total number of expanded particles broken inside the expanded particles were counted. Then, the value obtained by expressing the ratio of the latter value to the former value as a percentage (%) was defined as the fusion rate of the test piece.

[0054] [Examples 2-5, Comparative Example 1] Extruded body 1 was manufactured in the same manner as in Example 1, except that the conditions were changed as shown in Table 1.

[0055] [Table 1]

[0056] [Example 6, Comparative Example 2] Extruded body 1 was produced in the same manner as in Example 1, except that the conditions were changed as shown in Table 2 and polystyrene-based resin foam particles with excellent secondary foaming properties were used as the foam particles for the core material.

[0057] [Table 2]

[0058] Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention. [Explanation of Symbols]

[0059] 1. Extruded body 2 Epidermal layer 3. Foam core material 4 Hollow part 22 Dies 31 Foaming particle introduction channel 35 Steam supply pipe 350 (350a, 350b, 350c) Steam supply unit 36 Steam exhaust pipe 360 (360a, 360b, 360c) Steam discharge section 33 Screw Feeder

Claims

1. A method for manufacturing an extruded molded body comprising a hollow extruded surface layer and a foamed core material formed by fusing foamed particles filled in the hollow portion formed by the surface layer, A process of extruding a thermoplastic resin from a die to extrude the surface layer into a hollow shape, A step of filling the hollow portion formed by the surface layer with thermoplastic resin foam particles from a foam particle introduction channel located within the hollow portion formed by the surface layer, toward the direction of extrusion of the surface layer, Steam is supplied from a steam supply section located on the side of a steam supply pipe positioned along the extrusion direction of the surface layer within the hollow portion formed by the surface layer, while the steam is discharged from a steam discharge section located on the side of a steam discharge pipe positioned along the extrusion direction of the surface layer within the hollow portion formed by the surface layer, thereby fusing the foam particles together and forming through holes along the longitudinal direction of the foam core material. Process and A method for manufacturing an extruded article, characterized by comprising the following:

2. A method for manufacturing an extruded article according to claim 1, wherein the steam supply pipe and the steam discharge pipe are arranged such that the steam discharge section located furthest from the tip of at least one steam supply pipe towards the die is located furthest from the tip of at least one steam supply pipe towards the die.

3. A method for manufacturing an extruded article according to claim 1, wherein the distance between the steam supply unit located furthest from the tip of at least one steam supply pipe towards the die and the steam discharge unit located furthest from the tip of at least one steam discharge pipe, along the extrusion direction of the surface layer, is 20 to 500 mm.

4. A method for manufacturing an extruded article according to any one of claims 1 to 3, wherein the foam particle introduction passage is equipped with a screw feeder, and the foam particles are filled into the hollow portion formed by the surface layer while being compressed by the screw feeder.

5. The method for manufacturing an extruded article according to any one of claims 1 to 4, wherein the maximum thickness of the extruded article is 100 mm or more.

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