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 having a base material 20 containing a vaporization component, and barrier layers 12 and 15 formed on internal surfaces 11S and 14S of the base members 11 and 14, which includes a decompression vaporization process for vaporizing a vaporization component in the base materials 11 and 14 by heating the base members 11 and 14 under a decompressed environment where a pressure is lower than an atmospheric pressure. By heating the base materials 11 and 14 under the decompressed environment, the vaporization component in the base materials 11 and 14 is vaporized, and discharged to the outside of the base members 11 and 14 so that the vaporization component remaining in the base members 11 and 14 is reduced.SELECTED DRAWING: Figure 8

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 formed by the above-mentioned method, if the liner material contains a vaporizable component, bubbles may be generated in the liner 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 having a base material including a vaporizable component and a barrier layer formed on an inner surface of the base member, the method comprising: The method includes a reduced pressure vaporization step of heating the base member in a reduced pressure environment lower than atmospheric pressure to vaporize the vaporizable components in the base material. [Effects of the Invention]

[0007] This configuration can suppress the occurrence of voids at the boundary 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] FIG. 10 is a cross-sectional view showing the cylindrical base member being heated in a reduced pressure environment in the primary 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] 10 is a cross-sectional view showing the state in which the cylindrical base member and the barrier material are heated in the heating step and the secondary vaporization 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.

[0010] The method for manufacturing a pressure vessel of the present disclosure includes: (1) A method for manufacturing a pressure vessel having a base member having a base material containing vaporizable components and a barrier layer formed on the inner surface of the base member, the method including a reduced-pressure vaporization step of heating the base member in a reduced-pressure environment lower than atmospheric pressure to vaporize the vaporizable components in the base material. According to the method for manufacturing a pressure vessel disclosed herein, since the boiling points of the vaporizable components are lowered in a reduced-pressure environment, by heating the base material in a reduced-pressure environment, the vaporizable components in the base material are vaporized and released to the outside of the base member, thereby reducing the amount of vaporizable components remaining in the base member. This suppresses the generation of bubbles from the base member after the barrier layer is formed, and suppresses the generation of voids at the interface between the base member and the barrier layer.

[0011] (2) The reduced pressure vaporization step preferably includes a primary vaporization step of heating the base member under reduced pressure before applying the barrier material of the barrier layer to the inner surface of the base member. According to this configuration, during the primary vaporization step, vaporized components are released not only from the outer surface of the base member but also from the inner surface, thereby effectively reducing the residual vaporized components in the base member.

[0012] (3) In (2), the reduced pressure vaporization step preferably includes a secondary vaporization step in which, after the primary vaporization step, the barrier material applied to the inner surface of the base member is heat-treated under a reduced pressure environment to form the barrier layer. With this configuration, the vaporized components in the base member can be released even in the step of forming the barrier layer, so that the generation of voids at the interface between the base member and the barrier layer can be more effectively suppressed.

[0013] (4) In (3), it is preferable that the pressure in the primary vaporization step is lower than the pressure in the secondary vaporization step. This configuration allows most of the vaporized components in the base member that can be vaporized by the pressure in the secondary vaporization step to be released to the outside of the base member in the primary vaporization step. This effectively prevents voids from occurring in the secondary vaporization step.

[0014] (5) In (3) or (4), it is preferable that the heating temperature in the primary vaporization step is higher than the heating temperature in the secondary vaporization step. This configuration allows most of the vaporized components in the base member that can be vaporized by the heating temperature in the secondary vaporization step to be released to the outside of the base member in the primary vaporization step. This effectively prevents voids from being generated during heating in the secondary vaporization 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 forming process for forming the cylindrical barrier layer 12. The reduced pressure vaporization process includes a primary vaporization process and a secondary vaporization process. The barrier layer forming process includes a coating process, a heating process, and a secondary vaporization process. The secondary vaporization process comprises the reduced pressure vaporization process and the barrier layer forming 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 primary vaporization step is carried out before the cylindrical barrier layer 12 is formed. In the primary 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 primary 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 primary 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 points of the vaporized components are lower than when placed in an atmospheric pressure environment. Therefore, in this primary 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 primary 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 primary 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 secondary vaporization step is carried out. In the secondary vaporization step, while the cylindrical base member 11 and the barrier material 21 are still heated in the reduced pressure heat treatment chamber 25, the reduced pressure heat treatment chamber 25 is evacuated to a pressure lower than atmospheric pressure. The pressure in the secondary vaporization step is set higher than the pressure in the primary 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 vacuuming 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 secondary vaporization 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 secondary vaporization 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 primary vaporization step and the heating step. In particular, since the heating temperature in the primary vaporization step is set higher than the heating temperatures in the heating step and the secondary vaporization step, most of the vaporized components in the cylindrical base member 11 that can be vaporized by the heating temperature in the secondary vaporization step are released to the outside of the cylindrical base member 11 in the primary vaporization step before the heating step and the secondary vaporization step are started. Furthermore, since the pressure in the primary vaporization step is set lower than the pressure in the secondary vaporization step, most of the vaporized components in the cylindrical base member 11 that can be vaporized by the pressure in the secondary vaporization step are released to the outside of the cylindrical base member 11 in the primary vaporization step before the secondary vaporization 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 having a base material 20 containing a vaporizable component, a cylindrical barrier layer 12 formed on the inner surface 11S of the cylindrical base member 11, a dome-shaped base member 14 having the base material 20 containing a vaporizable component, and a dome-shaped barrier layer 15 formed on the inner surface 14S of the dome-shaped base member 14.

[0038] The manufacturing method of this Example 1 includes a reduced pressure vaporization step in which the cylindrical base member 11 and the dome-shaped base member 14 are heated in a reduced pressure environment lower than atmospheric pressure to vaporize the vaporized components in the cylindrical base member 11 and the dome-shaped base member 14. According to this manufacturing method, the boiling points of the vaporized components are lowered in a reduced pressure environment, so by heating the base material 20 in a reduced pressure environment, the vaporized components in the base material 20 can be vaporized and effectively released to the outside of the cylindrical base member 11 and the dome-shaped base member 14.

[0039] This makes it possible to significantly reduce the amount of vaporized components remaining in the cylindrical base member 11 and the dome-shaped base member 14. According to the manufacturing method of this Example 1, it is possible to suppress the generation of bubbles from the cylindrical base member 11 after the formation of the cylindrical barrier layer 12, and to suppress the generation of voids at the interface 29 between the cylindrical base member 11 and the cylindrical barrier layer 12. Furthermore, it is possible to suppress the generation of bubbles from the dome-shaped base member 14 after the formation of the dome-shaped barrier layer 15, and to suppress the generation of voids at the interface 29 between the dome-shaped base member 14 and the dome-shaped barrier layer 15.

[0040] The reduced pressure vaporization process includes a primary vaporization process. In the primary vaporization process, the cylindrical base member 11 is heated in a reduced pressure environment before the barrier material 21 of the cylindrical barrier layer 12 is applied to the inner surface 11S of the cylindrical base member 11. Similarly, in the primary vaporization process, the dome-shaped base member 14 is heated in a reduced pressure environment before the barrier material 21 of the dome-shaped barrier layer 15 is applied to the inner surface 14S of the dome-shaped base member 14. During the primary vaporization process, vaporized components are released not only from the outer surface but also from the inner surface of the cylindrical base member 11, thereby effectively reducing the residual vaporized components in the cylindrical base member 11. Furthermore, since vaporized components are released not only from the outer surface but also from the inner surface of the dome-shaped base member 14, thereby effectively reducing the residual vaporized components in the dome-shaped base member 14.

[0041] The reduced-pressure vaporization process includes a secondary vaporization process. In the secondary vaporization process, after the primary vaporization process, the barrier material 21 applied to the inner surface 11S of the cylindrical base member 11 is heat-treated in a reduced-pressure environment to form the cylindrical barrier layer 12. Similarly, in the secondary vaporization process, after the primary vaporization process, the barrier material 21 applied to the inner surface 14S of the dome-shaped base member 14 is heat-treated in a reduced-pressure environment to form the dome-shaped barrier layer 15. In the process of forming the cylindrical barrier layer 12, the vaporized components in the cylindrical base member 11 can be released, which more effectively prevents voids from forming at the interface 29 between the cylindrical base member 11 and the cylindrical barrier layer 12. In the process of forming the dome-shaped barrier layer 15, the vaporized components in the dome-shaped base member 14 can be released, which more effectively prevents voids from forming at the interface 29 between the dome-shaped base member 14 and the dome-shaped barrier layer 15.

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

[0043] The heating temperature in the primary vaporization step is set higher than the heating temperature in the secondary vaporization step. This method allows most of the vaporized components in the cylindrical base member 11 that can be vaporized by the heating temperature in the secondary vaporization step to be released to the outside of the cylindrical base member 11 in the primary vaporization step. Also, most of the vaporized components in the dome-shaped base member 14 that can be vaporized by the heating temperature in the secondary vaporization step can be released to the outside of the dome-shaped base member 14 in the primary vaporization step. This effectively suppresses voids that occur during heating in the secondary vaporization step.

[0044] <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 reduced pressure vaporization step may not be performed in the step of forming the barrier layer, but may be performed only in the primary vaporization step before the barrier layer is formed. The reduced pressure vaporization step may not be performed before the barrier layer is formed, but may be performed only in the secondary vaporization step for forming the barrier layer. In the step of forming the barrier layer, heating may be performed without reducing the pressure. The heating temperature in the primary vaporization step may be the same as the heating temperature in the secondary vaporization step, or may be lower than the heating temperature in the secondary vaporization step. The pressure in the primary vaporization step may be the same as the pressure in the secondary vaporization step, or may be higher than the pressure in the secondary vaporization step. The barrier material is not limited to powder paint, but may also be liquid paint. [Explanation of symbols]

[0045] 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. 1. A method for manufacturing a pressure vessel comprising: a base member having a base material containing a vaporizable component; and a barrier layer formed on an inner surface of the base member, the method comprising: A method for manufacturing a pressure vessel, comprising a reduced pressure vaporization step of heating the base member in a reduced pressure environment lower than atmospheric pressure to vaporize vaporizable components in the base material.

2. The method for manufacturing a pressure vessel according to claim 1 , wherein the reduced pressure vaporization step includes a primary vaporization step of heating the base member in a reduced pressure environment before applying the barrier material of the barrier layer to the inner surface of the base member.

3. 3. The method for manufacturing a pressure vessel according to claim 2, wherein the reduced pressure vaporization process includes a secondary vaporization process in which, after the primary vaporization process, the barrier material applied to the inner surface of the base member is heat-treated in a reduced pressure environment to form the barrier layer.

4. The method for manufacturing a pressure vessel according to claim 3, wherein the pressure in the primary vaporization step is lower than the pressure in the secondary vaporization step.

5. 5. The method for manufacturing a pressure vessel according to claim 3, wherein the heating temperature in the primary vaporization step is higher than the heating temperature in the secondary vaporization step.

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