Method for producing hollow molded article

Abstract

To manufacture a hollow molded product having stable capacity while recycling a resin raw material without wasting the same.SOLUTION: A method for manufacturing a resin pipe body includes a resin introducing step of introducing a molten resin raw material (Rm) into a main cavity (14) of a mold (10) for molding a pipe body (1), and a hollow portion forming step of forming a hollow portion (3) by passing a core (24) through the resin raw material introduced into the main cavity to extrude the resin raw material located on a center side of the main cavity from the main cavity into a sub cavity (16). In the resin-introducing step, a recycled material (R2 portion) obtained by recycling the resin-raw material extruded into the sub cavity is used, the recycled material is supplied to the outer peripheral side of the main cavity, and a material (R1 portion) of the resin-raw material is supplied to the center side of the main cavity.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a hollow molded article. [Background technology]

[0002] Floating core molding is a known technique for producing hollow resin molded products. In floating core molding, a mold is used that contains a main cavity with a pressure port at one end and a sub-cavity connected to the other end of the main cavity via a communication port. A core is placed against the pressure port in the main cavity, and molten resin material is injected into the main cavity. The core is then forced toward the communication port by pressure from the pressure port, forming a hollow resin material, which is then pressed against the molding surface that defines the main cavity to solidify.

[0003] An example of a method for manufacturing a tube using such floating core molding is disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-123212 Summary of the Invention [Problem to be solved by the invention]

[0005] In the floating core molding described above, it is preferable to recycle the resin material extruded into the sub-cavity by crushing or other methods to avoid waste. However, repeated recycling of the resin material leads to thermal degradation. Therefore, when recycled resin material is used to mold a hollow molded product, if too much recycled resin material is extruded into the sub-cavity, the quality of the hollow molded product deteriorates, making it difficult to produce hollow molded products with stable performance.

[0006] An object of the present disclosure is to produce a hollow molded product with stable performance while recycling resin raw materials without waste.

Means for Solving the Problems

[0007] In order to achieve the above object, in the technology of the present disclosure, when introducing a resin raw material into the main cavity, a recycled material is supplied to the outer peripheral side of the main cavity forming the hollow molded product, and a virgin material is supplied to the central side of the main cavity forming the hollow portion of the hollow molded product.

[0008] Specifically, the first disclosure is directed to a method for manufacturing a resin hollow molded product. The method for manufacturing a hollow molded product according to the first disclosure includes a resin introduction step of introducing a molten resin raw material into a main cavity of a mold for molding the hollow molded product, and a hollow portion forming step of forming a hollow portion by passing a pressurizing body through the inside of the resin raw material introduced into the main cavity and extruding the resin raw material located on the central side of the main cavity from the main cavity into a sub-cavity. In the resin introduction step, a recycled material obtained by recycling the resin raw material extruded into the sub-cavity in the hollow portion forming step is used, the recycled material is supplied to the outer peripheral side of the main cavity, and the virgin material of the resin raw material is supplied to the central side of the main cavity.

[0009] The second disclosure is the method for manufacturing a hollow molded product according to the method for manufacturing a hollow molded product of the first disclosure, wherein the volume Vm [mm 3 of the hollow molded product and the volume Vh [mm 3 of the hollow portion satisfy the relational expression represented by Vh < Vm.

[0010] The third disclosure is the method for manufacturing a hollow molded product according to the method for manufacturing a hollow molded product of the first disclosure, wherein the volume Vm [mm 3 of the hollow molded product and the volume Vh [mm 3 of the hollow portion satisfy the relational expression represented by Vh > Vm. The amount Ar [mm 3 of the recycled material introduced into the main cavity in the resin introduction step and the amount Av [mm 31. The difference Vd between the volume Vh of the hollow portion and the volume Vm of the hollow molded product satisfies the relational expression represented by Ar - Av < Vd.

[0011] The fourth disclosure is a method for manufacturing a hollow molded product according to any one of the first to third disclosures, wherein the hollow molded product is a tubular body and has an attached shaped portion protruding to the outer peripheral side.

[0012] The fifth disclosure is a method for manufacturing a hollow molded product according to any one of the first to fourth disclosures. In the step of forming the hollow portion, as the pressurizing body, fluid is injected from a pressurizing port that opens at one end in the longitudinal direction of the cavity in the mold, or, as the pressurizing body, a core disposed at a position corresponding to the opening of the pressurizing port in the cavity is moved to the other end side in the longitudinal direction of the cavity by the pressure of the fluid injected from the pressurizing port.

[0013] The sixth disclosure is a method for manufacturing a hollow molded product according to any one of the first to fifth disclosures. In the step of forming the hollow portion, the resin raw material extruded from the main cavity is fed in a molten state to a resin injection machine that injects the resin raw material into the main cavity, and is used as the recycled material in the step of introducing the resin.

Effects of the Invention

[0014] According to the above first disclosure, recycled material is used in the resin introduction step. The recycled material is obtained by recycling the resin raw material extruded from the main cavity of the mold in the hollow part forming step. Therefore, the resin raw material can be recycled without waste. And in the resin introduction step, the recycled material is supplied to the outer peripheral side of the main cavity, and the virgin material of the resin is supplied to the central side of the main cavity. By doing so, when the pressurizing body passes through the inside of the resin raw material in the hollow part forming step, most or all of the surplus resin extruded from the main cavity can be made into the virgin material. Thereby, it is possible to avoid using a recycled material made of a resin raw material that has significantly deteriorated due to repeated recycling, or to reduce the proportion of the recycled material in the resin raw material for forming the hollow molded product. Therefore, a hollow molded product with stable performance can be manufactured.

[0015] According to the above second disclosure, the volume Vm of the hollow molded product is larger than the volume Vh of the hollow part. When molding such a hollow molded product, the amount of the resin raw material extruded from the main cavity in the hollow part forming step is less than the amount of the resin raw material forming the hollow molded product. Therefore, all of the surplus resin generated in the molding of one hollow molded product can be consumed in one molding process of the hollow molded product. Thereby, the recycled material can be composed only of the surplus resin recycled once, and no extra recycled material needs to be generated. And the recycled material becomes a product by one recycling process. This is advantageous for manufacturing a hollow molded product with stable performance.

[0016] According to the above third disclosure, the volume Vm of the hollow molded product is smaller than the volume Vh of the hollow part. When molding such a hollow molded product, the amount of the resin raw material extruded from the main cavity in the hollow part forming step is more than the amount of the resin raw material forming the hollow molded product. For this reason, the amount Ar of the recycled material introduced into the main cavity in the resin introduction step is made less than the amount Av of the virgin material by at least the difference Vd between the volume Vh of the hollow part and the volume Vm of the hollow molded product (Ar - Av < Vd). By doing so, even if the thickness of the hollow molded product is relatively thin, the recycled material can be composed only of the surplus resin recycled once. And the recycled material becomes a product by one recycling process. This is advantageous for manufacturing a hollow molded product with stable performance.

[0017] According to the fourth disclosure, a tube having an attached portion protruding outward is manufactured. The attached portion of the tube is formed from recycled material. This allows for the manufacture of a tube with stable performance while recycling the resin raw material without wasting it. Furthermore, since the volume of the tube increases by the amount of the attached portion, the volume of the tube can be made larger relative to the volume of the hollow portion. In other words, the ratio of the inner diameter forming the hollow portion to the outer diameter of the tube can be made larger without changing the quality of the tube.

[0018] According to the fifth disclosure, a fluid or a core is used as the pressurizing body. When a fluid is introduced as the pressurizing body into the resin material introduced into the main cavity, the pressure of the fluid presses the resin material against the molding surface of the mold, and a portion of the resin material is extruded from the main cavity, forming a hollow portion. Also, when the core moves due to the pressure of the fluid introduced from the pressurizing port as the pressurizing body, the movement of the core extrudes a portion of the resin material from the main cavity, forming a hollow portion. In this way, the resin material located toward the center of the main cavity can be extruded into the sub-cavity to form a hollow portion.

[0019] According to the sixth disclosure, the excess resin extruded from the main cavity in the hollow portion forming step is used as recycled material in its molten state, thereby eliminating the need for a recycling process such as pelletizing the excess resin. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a tube molding apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a resin introducing step in the manufacturing method of the tubular body according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating a resin introducing step in the manufacturing method of the tubular body according to the embodiment. [Figure 4]FIG. 4 is a cross-sectional view illustrating the state inside the main cavity of the mold taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a diagram illustrating a hollow portion forming step in the manufacturing method of the tube according to the embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating the state inside the main cavity of the mold taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a diagram illustrating a post-treatment step in the manufacturing method of the tubular body according to the embodiment. [Figure 8] FIG. 8 is a diagram illustrating a schematic configuration of a tube forming apparatus according to a third modified example. [Figure 9] FIG. 9 is a diagram illustrating a state immediately after the start of the resin introducing step in the manufacturing method of the tubular body according to the third modified example. [Figure 10] FIG. 10 is a diagram illustrating a state at the completion of the resin introducing step in the manufacturing method of the tube body according to the third modified example. [Figure 11] FIG. 11 is a diagram illustrating a post-treatment step in the manufacturing method of the tube according to the third modification. [Figure 12] FIG. 12 is a diagram for explaining a manufacturing method of a tube according to the fourth modified example. [Figure 13] FIG. 13 is a diagram illustrating a hollow portion forming step in a manufacturing method of a tube according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Exemplary embodiments will be described in detail below with reference to the drawings. In the following embodiments, a manufacturing method for a hollow molded product according to the present disclosure will be described using an example of floating core molding. Note that the drawings are intended to conceptually explain the technology of the present disclosure. Therefore, in the drawings, dimensions, ratios, or numbers may be exaggerated or simplified to facilitate understanding of the technology of the present disclosure.

[0022] <<Embodiment>> The product manufactured by the manufacturing method of a hollow molded product of this embodiment is a resin pipe 1. The pipe 1 is an example of a hollow molded product, and is used, for example, as a water pipe for carrying engine cooling water, or as a pipe for carrying blow-by gas or EGR (Exhaust Gas Recirculation) gas. The pipe 1 has a hollow portion 3 for passing a fluid such as a gas or a liquid.

[0023] The tubular body 1 may be a straight pipe that extends straight, or may be a curved or bent pipe. The synthetic resin that forms the tubular body 1 is selected arbitrarily depending on the application of the tubular body 1. Examples of synthetic resins include polyamide resins (PA) such as nylon 6 and nylon 66, polyphenylene sulfide (PPS), and polypropylene (PP).

[0024] -Tube molding equipment- 1, the molding device 7 for the tubular body 1 includes a mold 10, a resin injector 30, a metering device 50, a gas injector 60, and a control unit 70. The gas injector 60 is an example of a fluid injector.

[0025] <Mold> The mold 10 is a mold for molding the tubular body 1. The mold 10 comprises a fixed mold 10a and a movable mold 10b. The fixed mold 10a is fixed in a fixed position. The movable mold 10b is provided so that it can move toward and away from the fixed mold 10a. The mold 10 has a cavity 12. The cavity 12 is formed between the fixed mold 10a and the movable mold 10b by closing the two molds 10a and 10b. A molded body 100 having a hollow portion 3 molded in the cavity 12 includes a product portion 102 that forms the tubular body 1 and an unnecessary portion 104 other than the product portion 102.

[0026] The cavity 12 is a cylindrical space having a predetermined inner diameter, and includes a main cavity 14 and a sub-cavity 16. The main cavity 14 is a hollow portion for molding the product portion 102. The main cavity 14 is formed in a space having an extent corresponding to the outer shape of the tube body 1. The sub-cavity 16 is a hollow portion into which excess resin raw material Rm extruded from the main cavity 14 together with the core 24 is discharged. The sub-cavity 16 has a volume capable of accommodating excess resin Rs extruded from the main cavity 14.

[0027] The main cavity 14 and the sub-cavity 16 are connected via a communication passage 18. Excess resin Rs extruded from the main cavity 14 to the sub-cavity 16 flows through the communication passage 18. The communication passage 18 narrows from the main cavity 14 side toward the sub-cavity 16 side, and is formed to a size that does not allow the core 24 to pass through along the way. In the example shown in FIG. 1, the main cavity 14 is shown as having a simplified straight shape, but the main cavity 14 may have a curved or bent shape. Furthermore, the sub-cavity 16 may have any shape.

[0028] The mold 10 is provided with a resin supply path 20. The resin supply path 20 is a flow path for introducing the resin raw material Rm sent from the resin injector 30 into the cavity 12. The resin supply path 20 is provided using a direct gate system and is configured to include a sprue and a gate. The sprue opens on the outer surface of the mold 10. The gate communicates with the sprue and opens on the outer peripheral surface of the main cavity 14. The resin supply path 20 may also use other gate methods, such as a side gate system.

[0029] The mold 10 is provided with a pressure port 22. The pressure port 22 is a flow path for introducing the gas Gs sent from the gas injector 60 into the cavity 12. One end of the pressure port 22 opens to one end of the cavity 12 in the longitudinal direction. Specifically, one end of the pressure port 22 opens to an end of the main cavity 14 located opposite the sub-cavity 16. A setting section 23 for setting a core 24 is provided at the opening of the pressure port 22 on the cavity 12 side. The other end of the pressure port 22 opens to the outer surface of the mold 10.

[0030] A core 24 is provided in the mold 10. The core 24 is an example of a pressurizing body. The core 24 is set in the setting section 23 and placed in the cavity 12 with its back to the pressurizing port 22. In this example, the core 24 is spherical and has an outer diameter smaller than the inner diameter of the main cavity 14. The core 24 is sized so that it clogs the communicating passage 18 midway. The shape of the core 24 may be bullet-shaped, hemispherical, or another shape. The core 24 may be made of metal or resin. The core 24 may be made of ceramic or an elastic material such as silicone.

[0031] The mold 10 is provided with a shutter 25 and an actuator 28. The shutter 25 is a metal plate-like member that opens and closes the communication passage 18. A shutter accommodating portion 26 that accommodates the shutter 25 is formed at the end of the communication passage 18 on the main cavity 14 side in the mold 10. The shutter accommodating portion 26 opens to the outer peripheral surface of the communication passage 18. The shutter 25 is accommodated in the shutter accommodating portion 26 so as to be able to freely move in and out of the communication passage 18. The shutter 25 is switchable between a closed state that blocks the main cavity 14 and the sub-cavity 16, and an open state that allows communication between them. The shutter 25 is connected to the actuator 28.

[0032] The actuator 28 is configured to be able to advance and retract the shutter 25 relative to the communication passage 18. The actuator 28 may be an electric device or a hydraulic device. The actuator 28 blocks the communication between the main cavity 14 and the sub-cavity 16 by advancing the shutter 25 into the communication passage 18. The actuator 28 retracts the shutter 25 from the communication passage 18 into the shutter accommodating portion 26, thereby connecting the main cavity 14 and the sub-cavity 16. The actuator 28 operates in response to a control signal input from the control unit 70.

[0033] <Resin injection machine> The resin injector 30 is configured to inject a predetermined amount of molten resin raw material Rm into the cavity 12 of the mold 10 via the resin supply path 20. The resin injector 30 is connected to the outer surface opening of the resin supply path 20 in the mold 10. Virgin material R1 and recycled material R2 are used as the resin raw material Rm. The virgin material R1 is a material consisting only of new materials. The recycled material R2 is a material recycled from used resin raw material Rm, and is made by regenerating surplus resin Rs, which will be described later.

[0034] The resin injection machine 30 includes a virgin material injection device 32 and a recycled material injection device 34. The virgin material injection device 32 has a first hopper 33 into which virgin material R1 of the resin raw material Rm is fed. The virgin material injection device 32 heats and melts the virgin material R1 fed into the first hopper 33, and injects the molten virgin material R1. The recycled material injection device 34 has a second hopper 35 into which recycled material R2 of the resin raw material Rm is fed. The recycled material injection device 34 heats and melts the recycled material R2 fed into the second hopper 35, and injects the molten recycled material R2.

[0035] The resin injection machine 30 has a resin injection path 36. The resin injection path 36 is a flow path connected to the resin supply path 20 of the mold 10, and the raw resin material Rm is injected from the virgin material injection device 32 and the recycled material injection device 34. The recycled material injection device 34 injects the recycled material R2 upstream of the virgin material injection device 32 into the resin injection path 36. The virgin material injection device 32 injects the virgin material R1 into the recycled material R2 flowing through the resin injection path 36. The virgin material injection device 32 and the recycled material injection device 34 each operate in response to a control signal input from the control unit 70.

[0036] <Measuring device> The metering device 50 is configured to measure the recycled material R2. When the tube 1 is molded using the molding device 7, excess resin Rs is extruded into the secondary cavity 16 of the mold 10. This excess resin Rs is recycled to form recycled material R2. The recycled material R2 is carried into the metering device. The metering device 50 measures the amount of recycled material R2 required for one tube molding and deposits it into the second hopper 35 of the recycled material injection device 34. The metering device 50 operates in response to a control signal input from the control unit 70.

[0037] <Gas injector> The gas injector 60 is configured to inject gas Gs at a predetermined pressure into the main cavity 14 of the mold 10 through the pressure port 22. The gas injector 60 is connected to the outer surface opening of the pressure port 22 in the mold 10. The gas injector 60 includes a compressor. The gas handled by the gas injector 60 in this example is nitrogen gas. Nitrogen gas is an example of an inert gas. The gas injector 60 may also have a function to generate gas.

[0038] A gas flow path 62 is provided between the gas injector 60 and the mold 10. The gas flow path 62 is a path through which the gas Gs flows from the gas injector 60 to the pressure port 22. A first valve 64 is provided in the gas flow path 62. The gas flow path 62 is opened and closed by the first valve 64. The first valve 64 is electrically operated and controls the start and stop of the injection of the gas Gs into the main cavity 14. The gas injector 60 and the first valve 64 each operate in response to a control signal input from the control unit 70.

[0039] <Control unit> The control unit 70 is a controller based on a well-known microcomputer. The control unit 70 has a processor and a memory. The memory stores various programs and data. The processor reads and executes the programs from the memory, and controls the molding operation of the tube body 1 by the molding device 7.

[0040] The control unit 70 is electrically connected to the opening / closing mechanism (not shown) of the mold 10, the actuator 28, the virgin material injection device 32, the recycled material injection device 34, the gas injector 60, the first valve 64, and the metering device 50. The control unit 70 controls the mold opening, mold closing, and mold clamping operations by the opening / closing mechanism of the mold 10, the opening and closing operation of the shutter 25 by the actuator 28, the injection operation of the resin raw material Rm by the resin injector 30, the injection operation of the gas Gs by the gas injector 60, and the metering operation of the recycled material R2 by the metering device 50.

[0041] -Tube body manufacturing method- The tube 1 is manufactured using the molding device 7. The manufacturing method of the tube 1 includes a preparation step, a resin introduction step, a hollow portion formation step, a cooling step, a demolding step, and a post-treatment step.

[0042] In the preparation step, after the core 24 is set in the setting section 23 of the opened mold 10, the opening / closing mechanism of the mold 10 is operated to close the mold 10. This forms the cavity 12 in the mold 10, and the core 24 is positioned in a position corresponding to the pressure port 22 of the main cavity 14, with its back to the pressure port 22 (see FIG. 1). Furthermore, pressure is applied to the closed mold 10 to close the mold 10. Then, as shown in FIG. 2, the actuator 28 is operated to advance the shutter 25 into the communication path 18 to close it, thereby isolating the main cavity 14 and the sub-cavity 16 from each other by the shutter 25.

[0043] Next, a resin introduction step is performed. As shown in Fig. 3, in the resin introduction step, virgin material R1 and recycled material R2 of the resin raw material Rm are used, and molten resin raw material Rm is introduced into the main cavity 14 of the mold 10. Specifically, the virgin material injection device 32 and the recycled material injection device 34 are each operated to inject the resin raw material Rm consisting of the virgin material R1 and the recycled material R2 into the resin injection path 36. In the resin injection path 36, the recycled material R2 is present on the outer periphery, and the virgin material R1 is present on the center.

[0044] This resin raw material Rm is injected into the main cavity 14 through the resin supply path 20, so that recycled material R2 is supplied to the outer periphery of the main cavity 14 and virgin material R1 is supplied to the center of the main cavity 14, as shown in Fig. 4. The resin raw material Rm is then spread throughout the entire area of ​​the main cavity 14, filling the main cavity 14 with the resin raw material Rm. At this time, the resin raw material Rm introduced from the resin supply path 20 flows through the main cavity 14, but is blocked by the shutter 25 and does not flow into the sub-cavity 16.

[0045] Next, a hollow portion forming step is performed. In this hollow portion forming step, the actuator 28 is operated to retract the shutter 25 into the shutter housing portion 26 to open the gap between the main cavity 14 and the sub-cavity 16, thereby connecting the two cavities 12. Next, as shown in FIG. 5, the first valve 64 is opened and the gas injector 60 is operated to inject gas Gs from the gas injector 60 through the pressure port 22 into the main cavity 14 filled with the resin raw material Rm. The pressure of this gas Gs moves the core 24 from one end of the main cavity 14 in the longitudinal direction, where the pressure port 22 is open, to the other end, i.e., toward the sub-cavity 16.

[0046] The core 24 that has moved toward the sub-cavity 16 stops at the communicating passage 18. In this way, as also shown in Figure 6, by passing the core 24 inside the resin raw material Rm introduced into the main cavity 14, the trace of the core 24's passage becomes a hollow portion 3, and a hollow portion 3 is formed in the resin raw material Rm. At this time, as the core 24 moves, the excess resin raw material Rm on the center side of the main cavity 14 is pushed out into the sub-cavity 16 through the communicating passage 18. Most or all of the excess resin Rs pushed out into the sub-cavity 16 is virgin material R1.

[0047] Next, a cooling step is performed. In the cooling step, the resin raw material Rm is cooled in the mold 10. When the resin raw material Rm is cooled, it solidifies, and a molded body 100 having a hollow portion 3 is molded in the cavity 12. Next, a demolding step is performed. In the demolding step, the opening and closing mechanism of the mold 10 is operated to open the mold 10. Then, the molded body 100 is removed from the open mold 10.

[0048] Thereafter, a post-processing step is performed. As shown in Fig. 7, in the post-processing step, unnecessary portions 104 other than the product portion 102 constituting the tubular body 1 of the molded body 100 removed from the mold 10 are cut and removed at predetermined positions (the positions of cut lines CL shown by dashed lines in the upper drawing of Fig. 7). The unnecessary portions 104 removed at this time include accompanying molded portions 104a, 104b molded at one end on the pressure port 22 side and the other end on the sub-cavity 16 side, as well as gate residue 104c.

[0049] In this manner, the tube body 1 can be manufactured. In manufacturing this tube body 1, the excess resin Rs extruded into the secondary cavity 16 of the mold 10 is removed from the mold 10 and reused. The excess resin Rs removed from the mold 10 is subjected to a recycling process. In the recycling process, the excess resin Rs is crushed and pelletized to produce a recycled material R2. This recycled material R2 is sent to a weighing device 50 and used in the subsequent tube molding.

[0050] -Features of the embodiment- According to the manufacturing method of the tubular body 1 of this embodiment, recycled material R2 is used in the resin introduction step. The recycled material R2 is recycled resin raw material Rm extruded from the main cavity 14 of the mold 10 in the hollow portion forming step. Therefore, the resin raw material Rm can be recycled without being wasted. In the resin introduction step, recycled material R2 is supplied to the outer periphery of the main cavity 14, and virgin material R1 of the resin raw material Rm is supplied to the center of the main cavity 14. This allows most or all of the excess resin Rs extruded from the main cavity 14 when the core 24 passes through the resin raw material Rm in the hollow portion forming step to be converted into virgin material R1. This avoids the use of recycled material R2 made from resin raw material Rm that has been significantly deteriorated due to repeated recycling, or reduces the proportion of recycled material R2 in the resin raw material Rm used to mold the tubular body 1. Therefore, a tubular body 1 with stable performance can be manufactured.

[0051] According to the manufacturing method of the tubular body 1 of this embodiment, the core 24 is used as a pressurized body. When the core 24 moves due to the pressure of the gas Gs introduced from the pressure port 22 as a pressurized body, a part of the resin raw material Rm is extruded from the main cavity 14 by the movement of the core 24, thereby forming the hollow portion 3. In this way, the resin raw material Rm located on the central side of the main cavity 14 can be extruded into the sub-cavity 16 to form the hollow portion 3. When the tubular body 1 is manufactured using such core floating molding, a tubular body 1 with a uniform wall thickness and a smooth inner surface can be realized.

[0052] 《First Modified Example》 The tubular body 1 manufactured in this first modified example is a relatively thick-walled tubular body 1. The volume Vm [mm 3 of the tubular body 1 and the volume Vh [mm 3 of the hollow portion 3 satisfy the relational expression represented by Vh < Vm. Specifically, the outer radius r [mm] of the tubular body 1 and the radius x [mm] of the hollow portion 3 satisfy r 2 > 2 × x 2 (see FIG. 6). For example, when the outer diameter of the tubular body 1 is 20 mm, the inner diameter of the hollow portion 3 is designed to be 14 mm or less.

[0053] When manufacturing such a tubular body 1, in the resin introduction step, the amount of the recycled material R2 in the resin raw material Rm introduced into the main cavity 14 is set to the same amount as the volume amount of the hollow portion 3, and the remaining amount is the virgin material R1. The resin raw material Rm is introduced from the resin injection machine 30 into the main cavity 14 of the mold 10 and filled so as to be the amounts of the virgin material R1 and the recycled material R2. The subsequent hollow portion forming step, cooling step, demolding step, and post-treatment step are performed in the same manner as in the above embodiment.

[0054] According to the manufacturing method of the tubular body 1 of this first modified example, the volume Vm of the tubular body 1 is larger than the volume Vh of the hollow portion 3 (Vh < Vm). When molding such a tubular body 1, the amount of the resin raw material Rm extruded from the main cavity 14 in the hollow portion forming step is less than the amount of the resin raw material Rm forming the tubular body 1. Therefore, the surplus resin Rs generated in the molding of one tubular body 1 can be completely consumed in one molding process of the tubular body 1. As a result, the recycled material R2 can be composed only of the surplus resin Rs recycled once, and no extra recycled material R2 needs to be generated. And the recycled material R2 becomes a product in one recycling process. This is advantageous for manufacturing the tubular body 1 with stable performance.

[0055] <<Second Modified Example>> In this second modified example, the wall thickness of the tubular body 1 to be manufactured with respect to the hollow portion 3 is different from that of the above embodiment. The tubular body 1 of this example is a relatively thin-walled tubular body 1. The volume Vm [mm 3 of the tubular body 1 and the volume Vh [mm 3 of the hollow portion 3 satisfy the relational expression represented by Vh > Vm. Specifically, the outer radius r [mm] of the tubular body 1 and the radius x [mm] of the hollow portion 3 satisfy r 2 < 2 × x 2 >. For example, when the outer diameter of the tubular body 1 is 20 mm, the inner diameter of the hollow portion 3 is designed to be 15 mm or more.

[0056] When manufacturing such a tubular body 1, in the resin introduction step, the amount of the recycled material R2 among the resin raw materials Rm introduced into the main cavity 14 is made at least less than the amount obtained by subtracting the volume Vm of the tubular body 1 from the volume Vh of the hollow portion 3, by more than the amount of the virgin material R1. That is, the amount Ar [mm 3 of the recycled material R2, the amount Av [mm 3 of the virgin material R1, and the difference Vd between the volume Vh of the hollow portion 3 and the volume Vm of the tubular body 1 satisfy the relational expression represented by Ar - Av < Vd. 3 of the recycled material R2 introduced into the main cavity 14 in the resin introduction step, the amount Av [mm 3 of the virgin material R1, and the difference Vd between the volume Vh of the hollow portion 3 and the volume Vm of the tubular body 1 satisfy the relational expression represented by Ar - Av < Vd. 3

[0057] The resin raw material Rm is introduced from the resin injection machine 30 and filled into the main cavity 14 of the mold 10 so that the amounts of the virgin material R1 and the recycled material R2 are as described above. The subsequent hollow portion forming step, cooling step, demolding step, and post-treatment step are performed in the same manner as in the above embodiment.

[0058] -Features of the Second Modified Example- According to the manufacturing method of the tubular body 1 of this second modified example, the volume Vm of the tubular body 1 is smaller than the volume Vh of the hollow portion 3. When molding such a tubular body 1, the amount of the resin raw material Rm extruded from the main cavity 14 in the hollow portion forming step is larger than the amount of the resin raw material Rm forming the tubular body 1. Therefore, the amount Ar of the recycled material R2 introduced into the main cavity 14 in the resin introduction step is made less than the amount Av of the virgin material R1 by at least the difference Vd between the volume Vh of the hollow portion 3 and the volume Vm of the tubular body 1 (Ar - Av < Vd). By doing so, even if the wall thickness of the tubular body 1 is relatively thin, the recycled material R2 can be constituted only by the surplus resin Rs recycled once. And the recycled material R2 becomes a product by one recycling process. This is advantageous for manufacturing the tubular body 1 with stable performance.

[0059] <<Third Modified Example>> In this third modified example, the configuration of the tubular body 1 to be manufactured is different from that of the above embodiment. The tubular body 1 of this example has a flange 5 protruding on the outer peripheral side (see FIG. 11). The flange 5 is an example of an attached shape portion. The flange 5 is used, for example, for connection with the attachment target of the tubular body 1. The molding device 7 for molding the tubular body 1 of this example has a different configuration of the cavity 12 of the mold 10 and the resin injection machine 30 (strictly speaking, the resin injection path 36) from that of the above embodiment.

[0060] As shown in Figure 8, the main cavity 14 of the mold cavity 12 includes a flange molding portion 14a that is a portion for molding the flange 5. The mold 10 is formed with an auxiliary supply path 21 that opens into the flange molding portion 14a. The resin injection path 36 of the resin injector 40 includes a main flow path 37 and a bypass flow path 38. The main flow path 37 corresponds to the resin injection path 36 of the above embodiment, and is a flow path that injects the resin raw material Rm made of virgin material R1 and recycled material R2 from the resin supply path 20 into the main cavity 14.

[0061] The bypass flow path 38 is a flow path that branches off from the main flow path 37 upstream of the injection position of the virgin material injection device 32 in the resin injection path 36, and is connected to the auxiliary supply path 21 of the mold 10. A second valve 40 is provided between the injection position of the virgin material injection device 32 in the resin injection path 36 and the branching portion of the bypass flow path 38. This second valve 40 is configured to be electrically operated and opens and closes the main flow path 37. In addition, a third valve 42 is provided midway through the bypass flow path 38. This third valve 42 is configured to be electrically operated and opens and closes the bypass flow path 38. The second valve 40 and the third valve 42 each operate in response to a control signal input from the control unit 70.

[0062] When manufacturing the tubular body 1 using such a molding apparatus 7, in the resin introducing step, recycled material R2 is first introduced as molten resin raw material Rm into the flange molding portion 14a of the main cavity 14. Specifically, the second valve 40 is closed to block the main flow path 37 of the resin supply path 20 downstream of the branching position of the bypass flow path 38, while the third valve 42 is opened to open the bypass flow path 38. Then, as shown in Fig. 9, the recycled material injection device 34 is operated to inject recycled material R2 into the resin injection path 36 and introduce it from the bypass flow path 38 via the auxiliary supply path 21 into the flange molding portion 14a.

[0063] Next, the second valve 40 is opened to open the main flow path 37. Furthermore, the virgin material injection device 32 is operated to inject the virgin material R1 into the recycled material R2 flowing through the main flow path 37, and the resin raw material Rm consisting of the virgin material R1 and recycled material R2 is introduced from the main flow path 37 through the resin supply path 20 into the main cavity 14. In this way, as shown in FIG. 10 , the recycled material R2 is supplied to the outer periphery of the main cavity 14, including the flange molding portion 14a, and the virgin material R1 is supplied to the center of the main cavity 14, thereby filling the main cavity 14 with the resin raw material Rm.

[0064] Thereafter, the hollow portion forming step, cooling step, and demolding step are performed in the same manner as in the above embodiment. Then, as shown in Fig. 11, the post-processing step is performed in the same manner as in the above embodiment, and unnecessary portions 104 other than the product portion 102 constituting the tubular body 1 of the molded body 100 removed from the mold 10 are cut and removed at a predetermined position (the position of the cut line CL shown by the dashed line in the upper diagram of Fig. 11).

[0065] -Features of the third modified example- According to the manufacturing method of the tube 1 of the third modification, a tube 1 having a flange 5 protruding outward is manufactured. The flange 5 of the tube 1 is formed from recycled material R2. This makes it possible to manufacture a tube 1 with stable performance while recycling the resin raw material Rm without wasting it. Furthermore, since the volume of the tube 1 increases by the amount of the flange 5 (attached shaped portion), the volume of the tube 1 can be made larger relative to the volume of the hollow portion 3. In other words, the ratio of the inner diameter of the hollow portion 3 to the outer diameter of the tube 1 can be made larger without changing the quality of the tube 1.

[0066] Fourth Variation In this fourth modified example, the configuration of the molding apparatus 7 for the tubular body 1 differs from that of the first embodiment. As shown in Fig. 12, the molding apparatus 7 of this example further includes a storage container 80. The sub-cavity 16 of the mold 10 forms a discharge flow path 82 that communicates with the outside of the mold 10. The discharge flow path 82 discharges, from the mold 10, an excess of the resin raw material Rm extruded from the main cavity 14. A circulation flow path 84 is connected to the discharge flow path 82 at an opening to the outside of the mold 10.

[0067] The circulation flow path 84 sends the surplus resin Rs discharged from the discharge flow path 82 in a molten state to the resin injector 30, where it is circulated to the recycled material injection device 34. The storage container 80 is provided midway along the circulation flow path 84 and temporarily stores the resin raw material Rm while heating it. The resin raw material Rm (surplus resin Rs) circulated to the recycled material injection device 34 is reused as recycled material R2. A heating device may be provided in the circulation flow path 84 to maintain the resin raw material Rm in a molten state.

[0068] When manufacturing the tube 1 using such a molding device 7, the resin raw material Rm extruded from the main cavity 14 in the hollow portion forming step is sent in a molten state to the resin injector 30 via the discharge flow path 82 formed by the sub-cavity 16 and the circulation flow path 84. The resin raw material Rm is then placed in the recycled material injection device 34 and used as recycled material R2 in the resin introduction step.

[0069] When the amount of recycled material R2 is insufficient in the production of the tubular body 1, recycled material R2 may be fed from the second hopper 35 to the recycled material injection device 34. Furthermore, when an excess of resin raw material Rm enters the recycled material injection device 34 from the circulation flow path 84, the amount of resin raw material Rm sent to the recycled material injection device 34 may be reduced by, for example, discharging the resin raw material Rm from the storage container 80 or midway through the circulation flow path 84.

[0070] -Features of the fourth variant- According to the manufacturing method of the tube body 1 of the fourth modification, the excess resin Rs extruded from the main cavity 14 in the hollow portion forming step is used in a molten state as the recycled material R2. This makes it possible to omit the regeneration process step of recycling the excess resin Rs, such as pelletizing it.

[0071] Other Embodiments In the above embodiment, the tube body 1 is manufactured using core floating molding, but this is not limiting. The tube body 1 may also be molded using gas injection molding (gas-assisted molding). In this case, in the hollow portion forming step of manufacturing the tube body 1, as shown in FIG. 13 , the first valve 64 is opened and the gas injector 60 is operated to inject gas Gs at a predetermined pressure from the pressure port 22 into the main cavity 14 filled with the resin raw material Rm as a pressurized body. The injected gas Gs then reaches the communicating passage 18 or the sub-cavity 16.

[0072] In this way, when the gas Gs is introduced as a pressurized body into the resin raw material Rm introduced into the main cavity 14, the pressure of the gas Gs presses the resin raw material Rm against the molding surface of the mold 10, and pushes a portion of the resin raw material Rm out of the main cavity 14, thereby forming the hollow portion 3. After a predetermined time has passed since the amount of gas Gs injected by the gas injector 60 has reached a predetermined amount corresponding to the volume of the main cavity 14, the first valve 64 is closed, and the injection of the gas Gs into the main cavity 14 is completed.

[0073] Thereafter, the cooling step, demolding step, and post-treatment step are carried out in the same manner as in the above embodiment, whereby the tube body 1 can be manufactured.

[0074] In the above embodiment, in the hollow portion forming step of manufacturing the tube 1, nitrogen gas is used as the gas Gs that pressurizes the core 24, but this is not limiting. Nitrogen gas is merely one example of a fluid that pressurizes the core 24, and any inert gas other than nitrogen gas, such as argon gas, or any other type of gas may be used as long as it does not react with the resin raw material Rm at the temperature and pressure when passing through the core 24.

[0075] Furthermore, instead of gas Gs, a liquid such as water or glycerin may be used as the fluid that pressurizes core 24 during floating core molding. The technology of the present disclosure is also applicable to other methods of manufacturing tubular body 1 that use fluid-assisted molding, such as water-assisted molding, which uses a liquid such as water, in which a fluid other than gas is used as the pressurizing agent.

[0076] In the third modified example, the flange 5 is provided on the tubular body 1 as the attached portion, but this is not limiting. The flange 5 is merely one example of the attached portion, and the attached portion may be a reinforcing piece such as a rib or other functional portion as long as it is a portion that protrudes toward the outer periphery of the tubular body 1.

[0077] In the above embodiment, the molding device 7 for one pipe body 1 and the method for manufacturing the pipe body 1 using the same are illustrated and described, but the present invention is not limited to this. The molding device for the pipe body 1 may be configured to mold multiple pipe bodies 1 simultaneously, or multiple pipe bodies 1 may be manufactured collectively. Furthermore, the manufactured pipe body 1 may be one in which the pipe main body and branch pipes branching from the pipe main body are integrally molded.

[0078] In the above embodiment, a method for manufacturing the tube 1 has been described as an example of a hollow molded product, but the present disclosure is not limited to this. The technology of the present disclosure can also be applied to a manufacturing method for hollow molded products other than the tube 1, such as vehicle interior parts such as trims and assist grips, and vehicle exterior parts such as protectors and garnishes, whose hollowness is intended to reduce weight or increase rigidity.

[0079] As described above, preferred embodiments have been described as examples of the technology of the present disclosure. However, the technology of the present disclosure is not limited to these, and can be applied to embodiments in which appropriate modifications, substitutions, additions, omissions, etc. are made. It will be understood by those skilled in the art that various modifications are possible to the above-described embodiments without departing from the spirit of the technology of the present disclosure, and that such modifications also fall within the scope of the technology of the present disclosure.

[0080] It should be noted that the terms "first," "second," etc. mentioned above are used merely to distinguish the terms to which these terms are attached, and do not limit the number or order of the terms. [Industrial Applicability]

[0081] As described above, the present disclosure is useful for a method for producing a hollow molded article. [Explanation of symbols]

[0082] Gs Gas (pressurized body, fluid) Rm Resin raw material R1 virgin material R2 recycled material 1. Tube body (plastic molded product) 3 Hollow part 5 Flange (attached part) 10. Mold 14 Main cavity 16 Secondary cavity 22 Pressure port 24 Core (pressure body) 30 resin injection machine

Claims

1. A method for manufacturing a hollow molded resin product (1), comprising the steps of: a resin introduction step of introducing a molten resin raw material (Rm) into a main cavity (14) of a mold (10) for molding the hollow molded product (1); a hollow portion forming step of passing a pressurizing body through the resin raw material (Rm) introduced into the main cavity (14) to extrude the resin raw material (Rm) located on the center side of the main cavity (14) from the main cavity (14) into a sub-cavity (16) to form a hollow portion (3), In the resin introducing step, a recycled material (R2) obtained by recycling the resin raw material (Rm) extruded into the sub-cavity (16) in the hollow portion forming step is used, and the recycled material (R2) is supplied to the outer periphery of the main cavity (14), and a virgin material (R1) of the resin raw material (Rm) is supplied to the center of the main cavity (14). A method for producing a hollow molded article, comprising:

2. The method for producing a hollow molded product according to claim 1, The volume Vm [mm ３ ], the volume Vh [mm ３ ] satisfies the relational expression Vh<Vm. A method for producing a hollow molded article, comprising:

3. The method for producing a hollow molded product according to claim 1, The volume Vm [mm ３ ], the volume Vh [mm ３ ] satisfies the relational expression Vh>Vm, The amount Ar [mm of the recycled material (R2) introduced into the main cavity (14) in the resin introduction step ３ ], the amount Av of the virgin material (R1) [mm ３ ], and the difference Vd between the volume Vh of the hollow portion 3 and the volume Vm of the hollow molded product 1 satisfies the relational expression Ar-Av<Vd. A method for producing a hollow molded article, comprising:

4. In the method for producing a blow molded article according to any one of claims 1 to 3, The hollow molded product (1) is a tubular body (1) and has an attached shaped portion (5) protruding on the outer periphery. A method for producing a hollow molded article, comprising:

5. The method for producing a hollow molded product according to claim 1, In the hollow portion forming step, As the pressurizing body, a fluid (Gs) is injected from a pressure port (22) that opens at one end in the longitudinal direction of the main cavity (14) of the mold (10), or a core (24) as the pressurizing body, which is disposed at a position corresponding to the opening of the pressurizing port (22) in the main cavity (14), is moved toward the other end in the longitudinal direction of the main cavity (14) by the pressure of the fluid (Gs) injected from the pressurizing port (22); A method for producing a hollow molded article, comprising:

6. The method for producing a hollow molded product according to claim 1, The resin raw material (Rm) extruded from the main cavity (14) in the hollow portion forming step is sent in a molten state to a resin injector (30) that injects the resin raw material (Rm) into the main cavity (14), and is used as the recycled material (R2) in the resin introducing step. A method for producing a hollow molded article, comprising:

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