Pressure container manufacturing method

Abstract

To suppress an occurrence of a void in a boundary surface of a base member and a barrier layer.SOLUTION: A pressure container A manufacturing method is a method for manufacturing a pressure container A including base members 11 and 14, and barrier layers 12 and 15 formed by heat-treating a barrier material 21 applied to internal surfaces 11S and 14S of the base members 11 and 14. A decompression heating process for vaporizing a vaporization component of the barrier material 21 is performed by heating the barrier material 21 applied to the base members 11 and 14 under a decompressed environment where a pressure is lower than an atmospheric pressure. By heating the barrier material 21 under the decompressed environment, the vaporization component in the barrier material 21 is vaporized, and discharged to the outside of the barrier layers 12 and 15 so that the remaining vaporization component inside the barrier layers 12 and 15 is reduced.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a pressure vessel. [Background technology]

[0002] Patent Document 1 discloses a pressure vessel in which a synthetic resin barrier layer is formed on the inner peripheral surface of a synthetic resin liner. One possible method for manufacturing this type of pressure vessel is to form the liner after molding it and then form a barrier layer on the inner surface of the liner. One possible method for forming the liner is to heat and harden a fiber-reinforced resin material containing a thermosetting resin while it is wound around a mandrel. One possible method for forming a barrier layer on the inner peripheral surface of an already-molded liner is to apply a thermosetting resin with gas barrier properties to the liner and then heat it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-105441 Summary of the Invention [Problem to be solved by the invention]

[0004] In a pressure vessel in which a liner has been formed and a barrier layer has been formed by the above-mentioned method, if the material for the barrier layer contains a vaporizable component, bubbles may be generated in the barrier layer due to pressure changes, temperature changes, etc. of the pressure vessel, and these bubbles may remain as voids at the interface between the liner and the barrier layer. If voids exist at the interface between the liner and the barrier layer, the blister resistance at the interface between the liner and the barrier layer will decrease, causing peeling of the barrier layer.

[0005] The present invention was completed in light of the above circumstances, and an object of the present invention is to suppress the occurrence of voids. [Means for solving the problem]

[0006] The present disclosure provides: A method for manufacturing a pressure vessel having a base member and a barrier layer formed by heat-treating a barrier material applied to the inner surface of the base member, the method comprising: The method includes a reduced pressure heating step of heating the barrier material applied to the base member in a reduced pressure environment lower than atmospheric pressure to vaporize vaporized components of the barrier material. [Effects of the Invention]

[0007] This configuration can suppress the occurrence of voids at the interface between the base member and the barrier layer. [Brief explanation of the drawings]

[0008] [Figure 1] Front view of the pressure vessel of Example 1 [Figure 2] Cross section of a pressure vessel [Figure 3] FIG. 10 is a partially enlarged cross-sectional view showing the connection structure between the cylindrical member and the dome-shaped member. [Figure 4] FIG. 1 is a perspective view showing a state in which a base material made of a fiber-reinforced resin is wound around a mandrel in a molding process for manufacturing a cylindrical base member. [Figure 5] 1 is a perspective view showing a state in which a cylindrical base member is heated and cooled in a molding process of the cylindrical base member; FIG. [Figure 6] FIG. 10 is a perspective view showing a state in which the formed cylindrical base member is removed from the mandrel in the forming process of the cylindrical base member; [Figure 7] 10 is a cross-sectional view showing a state in which the cylindrical base member is heated in a reduced pressure environment in the pre-vaporization step. [Figure 8] Partially enlarged cross-sectional view of Figure 7 [Figure 9] FIG. 10 is a perspective view showing a state in which a barrier material is applied to the inner peripheral surface of a cylindrical base member in a coating step. [Figure 10] 10A and 10B are cross-sectional views showing the state in which the cylindrical base member and the barrier material are heated in the heating step and the decompression heating step. [Figure 11] Partially enlarged cross-sectional view of Figure 10 DETAILED DESCRIPTION OF THE INVENTION

[0009] First, embodiments of the present disclosure will be listed and described. Any combination of the following multiple embodiments within a range that does not cause contradictions is also included in the description of the present invention. The method for manufacturing a pressure vessel of the present disclosure includes: (1) A method for manufacturing a pressure vessel having a base member and a barrier layer formed by heat-treating a barrier material applied to the inner surface of the base member, the method comprising a reduced-pressure heating step of heating the barrier material applied to the base member in a reduced-pressure environment lower than atmospheric pressure to vaporize vaporized components of the barrier material. According to this manufacturing method, since the boiling points of the vaporized components are lowered in a reduced-pressure environment, by heating the barrier material in a reduced-pressure environment, the vaporized components in the barrier material are vaporized and released outside the barrier layer, thereby reducing the amount of vaporized components remaining in the barrier layer. This prevents bubbles from forming in the barrier layer after formation and prevents voids from forming at the interface between the base member and the barrier layer.

[0010] (2) In (1), a coating step of coating the barrier material made of powder paint on the inner surface of the base member; a heating step of heating and melting the barrier material applied to the inner surface in the application step under atmospheric pressure, In the reduced pressure heating step, the barrier material melted in the heating step is preferably heated in a reduced pressure environment lower than atmospheric pressure.

[0011] According to this manufacturing method, the process from applying the barrier material made of powder paint to the inner surface of the base member to molten state is carried out in an atmospheric pressure environment, so there is no risk of the barrier material applied to the inner surface of the base member becoming detached from the base member due to vacuuming.

[0012] (3) In paragraph (1) or (2), a molding step of molding the base member using a base material containing a vaporizable component that vaporizes when heated; Preferably, the method further includes a pre-vaporization step of vaporizing the vaporized components of the base material by heating the base member formed in the molding step before applying the barrier material to the inner surface of the base member. In this configuration, the vaporized components within the base member are released to the outside of the base member in advance in the pre-vaporization step, reducing the amount of bubbles generated from the base material in the reduced-pressure heating step for forming the barrier layer. This effectively prevents voids from forming at the interface between the base member and the barrier layer.

[0013] (4) In (3), the pre-vaporization step is preferably performed under a reduced pressure environment lower than atmospheric pressure. This configuration allows the vaporized components in the base member to be effectively released in the pre-vaporization step, thereby more effectively suppressing the generation of voids at the interface between the base member and the barrier layer.

[0014] (5) In (4), it is preferable that the pressure in the pre-vaporization step is lower than the pressure in the reduced pressure heating step. This configuration allows most of the vaporized components in the base member that can be vaporized by the pressure in the reduced pressure heating step to be released to the outside of the base member in the pre-vaporization step. This effectively prevents voids from occurring in the reduced pressure heating step.

[0015] Example 1 A first embodiment of the present invention will be described below with reference to FIGS. 1 to 11. A pressure vessel A in this first embodiment is a capsule-shaped vessel for storing a high-pressure fluid (liquefied gas or vaporized gas) such as hydrogen or ammonia. As shown in FIG. 2, the pressure vessel A is structurally composed of one cylindrical member 10, a pair of roughly hemispherical dome-shaped members 13, and a reinforcing layer 16. The dome-shaped members 13 are assembled to the cylindrical member 10 so as to close the openings at both ends. The cylindrical member 10 is composed of a cylindrical base member 11 and a cylindrical barrier layer 12 formed on an inner surface 11S of the cylindrical base member 11. The dome-shaped member 13 is composed of a roughly hemispherical dome-shaped base member 14 and a dome-shaped barrier layer 15 formed on an inner surface 14S of the dome-shaped base member 14.

[0016] When the cylindrical member 10 and the dome-shaped member 13 are assembled, the cylindrical base member 11 and the dome-shaped base member 14 form a capsule-shaped container body 17. The container body 17 is a member that forms a storage space 18 for storing a high-pressure fluid. A gas barrier layer 19 is formed on the inner surface of the container body 17 by the cylindrical barrier layer 12 and the dome-shaped barrier layer 15. The gas barrier layer 19 exhibits a gas barrier function that prevents the vaporized gas stored in the pressure vessel A from permeating the container body 17 (the cylindrical base member 11 and the dome-shaped base member 14) and leaking to the outside of the pressure vessel A.

[0017] The reinforcing layer 16 surrounds and reinforces the assembled cylindrical member 10 and dome-shaped member 13. The reinforcing layer 16 is formed to cover the outer surface of the container body 17 (cylindrical base member 11 and dome-shaped base member 14). The reinforcing layer 16 is made of a fiber-reinforced resin material such as carbon fiber reinforced plastic (CFRP) or glass fiber reinforced plastic (GFRP). The reinforcing layer 16 has both a holding function that holds the cylindrical member 10 and dome-shaped member 13 in an assembled state and a reinforcing function that increases the strength and rigidity of the container body 17.

[0018] The pressure vessel A is manufactured by the following procedure: the cylindrical member 10 and the dome-shaped member 13 are manufactured separately, the cylindrical member 10 and the pair of dome-shaped members 13 are combined together, and the reinforcing layer 16 is formed. The cylindrical member 10 is manufactured by the following procedure: the cylindrical base member 11 is manufactured, and the cylindrical barrier layer 12 is formed on the manufactured cylindrical base member 11. The manufacturing method of the cylindrical member 10 will be described below.

[0019] The cylindrical base member 11 and the dome-shaped base member 14 are formed using a base material 20. The base material 20 may be a fiber-reinforced resin material such as carbon fiber reinforced plastic (CFRP) or glass fiber reinforced plastic (GFRP). The base material 20 contains a vaporizable component. Examples of the vaporizable component of the base material 20 include butanediol, 2-ethylhexyl acrylate, polyol compounds, imidazole compounds, butanediol diglycidyl ether, butyl acrylate, and other acrylic compounds. The vaporizable component vaporizes significantly when heated, and may also vaporize gradually over time even in a room temperature environment.

[0020] The cylindrical barrier layer 12 and the dome-shaped barrier layer 15 are formed using a barrier material 21 made of a synthetic resin with gas barrier properties. Examples of synthetic resins with gas barrier properties include ethylene vinyl alcohol copolymer resin (EVOH) and polyamide (PA). These barrier materials 21 contain vaporizable components that vaporize when heated. The vaporizable components contained in the barrier material 21 are low-molecular-weight synthetic resin components that are the substance of the barrier material 21, and air that has become mixed in the barrier material 21. The air that has become mixed in the barrier material 21 is trapped within the barrier material 21 and remains among the powder when the barrier material 21 in a powder state before melting is applied to the cylindrical base member 11.

[0021] The manufacturing procedure for the cylindrical member 10 will be described below. The manufacturing process for the cylindrical member 10 includes a molding process for molding the cylindrical base member 11, a reduced pressure vaporization process for vaporizing the vaporized components of the base material 20 and the barrier material 21, and a barrier layer formation process for forming the cylindrical barrier layer 12. The reduced pressure vaporization process includes a pre-vaporization process and a reduced pressure heating process. The barrier layer formation process includes a coating process, a heating process, and a reduced pressure heating process. The reduced pressure heating process comprises the reduced pressure vaporization process and the barrier layer formation process.

[0022] The processing contents and execution procedures of the above steps are described below. In the molding step, as shown in FIG. 4, a base material 20 made of an elongated fiber-reinforced resin material is hoop-wound around the outer circumferential surface of a cylindrical mandrel 23 by a filament winding method. The fiber-reinforced resin material is a fiber bundle (not shown) made of filament-like fibers such as carbon fiber, glass fiber, or Kepler fiber, impregnated with a liquid thermosetting resin (e.g., epoxy resin), or a fiber bundle impregnated with a thermosetting resin in a semi-cured state (prepreg fiber). Next, the base material 20 is heated to, for example, 150°C to 160°C while still wound around the mandrel 23 to melt it, and then cooled and solidified (see FIG. 5). After the base material 20 solidifies and the cylindrical base member 11 is molded, the cylindrical base member 11 is removed from the mandrel 23 as shown in FIG. 6. In this manner, the cylindrical base member 11 is manufactured.

[0023] After the molding step, a pre-vaporization step is carried out before the cylindrical barrier layer 12 is formed. In the pre-vaporization step, a vacuum heat treatment furnace 24 is used. The internal space of the vacuum heat treatment furnace 24 functions as a reduced-pressure heat treatment chamber 25. The reduced-pressure heat treatment chamber 25 can be kept airtight. A decompression device 26 is connected to the reduced-pressure heat treatment chamber 25 to evacuate the reduced-pressure heat treatment chamber 25. Within the reduced-pressure heat treatment chamber 25, a pair of rollers 27 with their axes oriented horizontally are arranged side by side in a horizontal direction intersecting the axes. The rollers 27 are driven to rotate by a motor (not shown). A heater 28 is provided on the inner wall of the reduced-pressure heat treatment chamber 25.

[0024] In the pre-vaporization step, as shown in FIG. 7, the molded cylindrical base member 11 is placed in a reduced-pressure heat treatment chamber 25 and placed on rollers 27. Next, a vacuum is drawn inside the airtight reduced-pressure heat treatment chamber 25 using a pressure reducing device 26, creating a reduced-pressure environment with a pressure lower than atmospheric pressure. In this state, electricity is applied to a heater 28, which heats the cylindrical base member 11. The outer peripheral surface of the cylindrical base member 11 is heated by radiant heat from the heater 28, and the entire cylindrical base member 11, from the outer peripheral surface to the inner peripheral surface, is heated by thermal conduction. The heating temperature in the pre-vaporization step is set, for example, to a temperature between 230°C and 255°C, i.e., a temperature at which the cylindrical base member 11 does not soften.

[0025] When the cylindrical base member 11 is heated, the vaporized components in the base material 20 vaporize to form tiny bubbles B, as shown in Fig. 8, and are released to the outside of the cylindrical base member 11 from the outer and inner surfaces of the cylindrical base member 11. Furthermore, because the cylindrical base member 11 is placed in a reduced pressure environment that is lower than atmospheric pressure, the boiling point of the vaporized components is lower than when placed in an atmospheric pressure environment. Therefore, in this pre-vaporization step, the vaporization process of the vaporized components in the cylindrical base member 11 progresses effectively by heating in a reduced pressure environment.

[0026] After the preliminary vaporization step is completed, a barrier layer formation step is performed to form a cylindrical barrier layer 12 on the cylindrical base member 11. In the barrier layer formation step, first, a coating step is performed to coat the cylindrical base member 11 with a barrier material 21. The coating step is performed by electrostatic powder coating in an atmospheric pressure environment after the cylindrical base member 11 is removed from the reduced pressure heat treatment chamber 25 and removed from the vacuum heat treatment furnace 24. Specifically, as shown in FIG. 9, a coating gun 31 connected to a high voltage generator 30 is used, and the nozzle 32 of the coating gun 31 is set so that it faces the interior of the cylindrical base member 11. The cylindrical base member 11 is connected to a ground member. A powder coating material, which is the barrier material 21, is discharged from the nozzle 32 of the coating gun 31, and the discharged powder coating is applied by electrostatic attraction to the entire inner surface of the cylindrical base member 11 and the outer peripheries of the openings at both ends of the cylindrical base member 11.

[0027] After the application step, a heating step is carried out to heat the powder coating (barrier material 21) applied to the cylindrical base member 11 to a molten state. In the heating step, as shown in FIG. 10, the cylindrical base member 11 to which the barrier material 21 has been applied is housed in a reduced-pressure heat treatment chamber 25 and placed on a roller 27. The roller 27 is driven to rotate by a motor (not shown), thereby rotating the cylindrical base member 11. In the initial stage of the heating step, the reduced-pressure heat treatment chamber 25 is not evacuated, but is instead carried out at atmospheric pressure. Since the reduced-pressure heat treatment chamber 25 is not evacuated, there is no risk that the barrier material 21 (powder coating) applied to the inner surface 11S of the cylindrical base member 11 will be sucked into the decompression device 26. Therefore, the barrier material 21 remains applied to the inner surface 11S of the cylindrical base member 11.

[0028] In the heating step, the outer peripheral surface of the cylindrical base member 11 is heated by radiant heat from the heater 28, and the entire cylindrical base member 11, from the outer peripheral surface through the inner peripheral surface to the inner peripheral surface of the coating film of the barrier material 21, is heated by thermal conduction. The temperature to which the cylindrical base member 11 and the barrier material 21 are heated in the heating step is set to a temperature lower than the heating temperature in the pre-vaporization step. The heating temperature in the heating step is set to, for example, 200°C or higher and 240°C or lower.

[0029] When heated, the barrier material 21 changes from a powder state to a molten state, and its viscosity causes it to adhere to the inner surface 11S of the cylindrical base member 11. The molten barrier material 21 drips due to gravity, but because the cylindrical base member 11 is rotating, it does not collect in one place. Therefore, the thickness of the molten barrier material 21 is uniform around the entire circumference of the cylindrical base member 11. By heating the cylindrical base member 11 and the barrier material 21, vaporized components remaining in the cylindrical base member 11 vaporize and become bubbles B, which are released to the outside of the cylindrical base member 11. At the same time, vaporized components in the barrier material 21 also vaporize and become bubbles B, which are released to the outside of the barrier material 21. Because the molten barrier material 21 is in a flowable state, the vaporized vaporized components (bubbles B) are easily released from the inner surface of the barrier material 21 to the outside of the barrier material 21.

[0030] After the barrier material 21 has reached a molten state, a reduced pressure heating step is carried out. In this reduced pressure heating step, the reduced pressure heating chamber 25 is evacuated to a pressure lower than atmospheric pressure while the cylindrical base member 11 and the barrier material 21 remain in a heated state within the reduced pressure heating chamber 25. The pressure in the reduced pressure heating step is set higher than the pressure in the pre-vaporization step. Because the molten barrier material 21 adheres to the inner surface 11S of the cylindrical base member 11 due to its viscosity, there is no risk of it detaching from the inner surface 11S of the cylindrical base member 11 during the evacuation process.

[0031] As described above, by heating the cylindrical base member 11 and the barrier material 21 in a reduced pressure environment, a uniform coating film is formed on the inner surface 11S of the cylindrical base member 11. After a predetermined heating time has elapsed, the reduced pressure heating process is terminated, and the coating film on the cylindrical base member 11 and the barrier material 21 is cooled. The cylindrical base member 11 continues to rotate during the cooling process. When the barrier material 21 (coating film) solidifies, a cylindrical barrier layer 12 integrated with the cylindrical base member 11 is formed. This completes the manufacturing process for the cylindrical member 10.

[0032] In the reduced pressure heating step, the vaporized components remaining in the cylindrical base member 11 are vaporized and released to the outside of the cylindrical base member 11 by heating, and the vaporized components remaining in the barrier material 21 are also vaporized and released to the outside of the barrier material 21. Furthermore, since the boiling points of the vaporized components are lower in a reduced pressure environment than when placed in an atmospheric pressure environment, in the reduced pressure heating step, the vaporization process of the vaporized components in the cylindrical base member 11 and the vaporized components in the barrier material 21 progresses effectively by heating in a reduced pressure environment.

[0033] Furthermore, the vaporized components in the cylindrical base member 11 are sufficiently vaporized in the pre-vaporization step and the heating step. In particular, since the heating temperature in the pre-vaporization step is set higher than the heating temperatures in the heating step and the reduced-pressure heating step, most of the vaporized components in the cylindrical base member 11 that can be vaporized by the heating temperature in the reduced-pressure heating step are released to the outside of the cylindrical base member 11 in the pre-vaporization step before the heating step and the reduced-pressure heating step are started. Furthermore, since the pressure in the pre-vaporization step is set lower than the pressure in the reduced-pressure heating step, most of the vaporized components in the cylindrical base member 11 that can be vaporized by the pressure in the reduced-pressure heating step are released to the outside of the cylindrical base member 11 in the pre-vaporization step before the reduced-pressure heating step is started. Therefore, voids caused by the vaporized components in the cylindrical base member 11 at the interface 29 between the cylindrical base member 11 and the barrier material 21 (cylindrical barrier layer 12) are effectively suppressed.

[0034] The dome-shaped member 13 is also manufactured by the above-described nucleation process including the heating treatment and the decompression treatment, similar to the cylindrical member 10. Therefore, it is possible to suppress the generation of voids at the interface 29 between the inner surface 14S of the dome-shaped base member 14 and the dome-shaped barrier layer 15.

[0035] The pressure vessel A is constructed by combining the manufactured cylindrical member 10 with a pair of dome-shaped members 13. When combining the cylindrical member 10 and the dome-shaped member 13, as shown in Figure 3, the opening edges of the dome-shaped member 13 are fitted onto the openings at both ends of the cylindrical member 10, and the cylindrical barrier layer 12 and the dome-shaped barrier layer 15 are tightly attached to each other. As a result, the cylindrical base member 11 and the dome-shaped base member 14 form a storage space 18, and the cylindrical barrier layer 12 and the dome-shaped barrier layer 15 form a gas barrier layer 19 on the inner surface of the container body 17.

[0036] After the cylindrical member 10 and the dome-shaped member 13 are joined together, a reinforcing layer 16 is formed on the outer surface of the container body 17. The reinforcing layer 16 is formed by the filament winding method, as with the cylindrical base member 11. That is, a long, thin fiber-reinforced resin material is hoop-wound around the outer surface of the container body 17. The fiber-reinforced resin material is the same material as the base material 20 used to form the cylindrical base member 11 and the dome-shaped base member 14. The fiber-reinforced resin material wound around the container body 17 is heated to adhere to the outer surface of the container body 17. This completes the formation of the reinforcing layer 16 and the manufacture of the pressure vessel A.

[0037] The pressure vessel A manufactured by the manufacturing method of this Example 1 has a cylindrical base member 11, a dome-shaped base member 14, a cylindrical barrier layer 12, and a dome-shaped barrier layer 15. The cylindrical barrier layer 12 is formed by heat-treating a barrier material 21 applied to the inner surface 11S of the cylindrical base member 11. The dome-shaped barrier layer 15 is formed by heat-treating a barrier material 21 applied to the inner surface 14S of the dome-shaped base member 14.

[0038] The manufacturing method of Example 1 includes a reduced-pressure heating step in which the barrier material 21 applied to the cylindrical base member 11 and the dome-shaped base member 14 is heated in a reduced-pressure environment lower than atmospheric pressure to vaporize the vaporized components of the barrier material 21. The boiling point of the vaporized components decreases in a reduced-pressure environment. Heating the barrier material 21 in a reduced-pressure environment vaporizes the vaporized components in the barrier material 21 and releases them outside the cylindrical barrier layer 12 and the dome-shaped barrier layer 15, thereby reducing the amount of vaporized components remaining in the cylindrical barrier layer 12 and the dome-shaped barrier layer 15. This prevents bubbles from forming in the cylindrical barrier layer 12 after the formation of the cylindrical barrier layer 12 and prevents voids from forming at the interface 29 between the cylindrical base member 11 and the cylindrical barrier layer 12. Furthermore, it prevents bubbles from forming in the dome-shaped barrier layer 15 after the formation of the dome-shaped barrier layer 15 and prevents voids from forming at the interface 29 between the dome-shaped base member 14 and the dome-shaped barrier layer 15.

[0039] The manufacturing method of Example 1 includes a coating step and a heating step. In the coating step, a barrier material 21 made of powder paint is coated on the cylindrical base member 11 and the inner surface 14S of the dome-shaped base member 14. In the heating step, the barrier material 21 coated on the inner surface 11S of the cylindrical base member 11 and the inner surface 14S of the dome-shaped base member 14 in the coating step is heated and melted in an atmospheric pressure environment. In the reduced pressure heating step, the melted barrier material 21 in the heating step is heated in a reduced pressure environment lower than atmospheric pressure. According to this manufacturing method, the processes from coating the barrier material 21 made of powder paint on the cylindrical base member 11 and the inner surface 14S of the dome-shaped base member 14 to melting it are performed in an atmospheric pressure environment. Therefore, there is no risk that the barrier material 21 coated on the inner surface 14S of the cylindrical base member 11 and the dome-shaped base member 14 will come off the base members due to evacuation.

[0040] The manufacturing method of this Example 1 includes a molding step and a pre-vaporization step. In the molding step, a cylindrical base member 11 and a dome-shaped base member 14 are molded using a base material 20 containing vaporizable components that vaporize when heated. In the pre-vaporization step, the cylindrical base member 11 molded in the molding step is heated to vaporize the vaporizable components of the base material 20 before applying a barrier material 21 to the inner surface 11S of the cylindrical base member 11. Similarly, in the pre-vaporization step, the dome-shaped base member 14 molded in the molding step is heated to vaporize the vaporizable components of the base material 20 before applying a barrier material 21 to the inner surface 14S of the dome-shaped base member 14. In the pre-vaporization step, the vaporizable components in the cylindrical base member 11 are released outside the cylindrical base member 11, and the vaporizable components in the dome-shaped base member 14 are released outside the dome-shaped base member 14. Therefore, the amount of bubbles generated from the base material 20 is reduced during the decompression and heating process for forming the cylindrical barrier layer 12 and the dome-shaped barrier layer 15. This effectively prevents voids from being generated at the interface 29 between the cylindrical base member 11 and the barrier layer 12, and between the dome-shaped base member 14 and the dome-shaped barrier layer 15.

[0041] In this Example 1, the pre-vaporization step is performed in a reduced pressure environment lower than atmospheric pressure. With this configuration, the vaporized components in the cylindrical base member 11 and the dome-shaped base member 14 can be effectively released in the pre-vaporization step, so that the generation of voids at the interface 29 between the cylindrical base member 11 and the cylindrical barrier layer 12 and at the interface 29 between the dome-shaped base member 14 and the dome-shaped barrier layer 15 can be more effectively suppressed.

[0042] In this embodiment 1, the pressure in the preliminary vaporization step is set lower than the pressure in the reduced pressure heating step. With this configuration, most of the vaporized components in the cylindrical base member 11 that can be vaporized by the pressure in the reduced pressure heating step can be released to the outside of the cylindrical base member 11 in the preliminary vaporization step. Also, most of the vaporized components in the dome-shaped base member 14 that can be vaporized by the pressure in the reduced pressure heating step can be released to the outside of the dome-shaped base member 14 in the preliminary vaporization step. This effectively suppresses voids that occur in the reduced pressure heating step.

[0043] <Other Examples> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments are also included within the technical scope of the present invention. The pressure vessel may be manufactured in a manner that does not involve a pre-vaporization step. The pre-vaporization step may be carried out in an atmospheric pressure environment without reducing the pressure. The heating temperature in the pre-vaporization step may be the same as the heating temperature in the reduced pressure heating step, or may be lower than the heating temperature in the reduced pressure heating step. The pressure in the pre-vaporization step may be the same as the pressure in the reduced pressure heating step, or may be lower than the pressure in the reduced pressure heating step. The barrier material is not limited to powder paint, but may also be liquid paint. [Explanation of symbols]

[0044] A...Pressure vessel 11... Cylindrical base member (base member) 12...Cylindrical barrier layer (barrier layer) 14... Dome-shaped base member (base member) 15...Dome-shaped barrier layer (barrier layer) 20...Base material 21...Barrier materials

Claims

1. A method for manufacturing a pressure vessel having a base member and a barrier layer formed by heat-treating a barrier material applied to the inner surface of the base member, the method comprising: A method for manufacturing a pressure vessel, comprising a reduced pressure heating step of heating the barrier material applied to the base member in a reduced pressure environment lower than atmospheric pressure to vaporize vaporizable components of the barrier material.

2. a coating step of coating the barrier material made of powder paint on the inner surface of the base member; a heating step of heating and melting the barrier material applied to the inner surface in the application step under atmospheric pressure, The method for manufacturing a pressure vessel according to claim 1, wherein in the reduced pressure heating step, the barrier material melted in the heating step is heated in a reduced pressure environment lower than atmospheric pressure.

3. a molding step of molding the base member using a base material containing a vaporizable component that vaporizes when heated; 3. The method for manufacturing a pressure vessel according to claim 1, further comprising a pre-vaporization step of vaporizing vaporized components of the base material by heating the base member formed in the molding step before applying the barrier material to the inner surface of the base member.

4. The method for manufacturing a pressure vessel according to claim 3, wherein the pre-vaporization step is carried out under a reduced pressure environment lower than atmospheric pressure.

5. The method for manufacturing a pressure vessel according to claim 4, wherein the pressure in the pre-vaporization step is lower than the pressure in the reduced pressure heating step.

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