Fiber structure, heat insulating material, housing device, battery, flying object, and method for producing fiber structure

Abstract

To provide a fiber structure having excellent heat insulating properties.SOLUTION: A fiber structure contains a plurality of fibers substantially composed of polyimide resin. A ratio of the mass of the plurality of fibers to the mass of the fiber structure is 70 mass% or more. A thickness of the fiber structure is 1 mm or more. A basis weight of the fiber structure is 40 g / m2 or more and 150 g / m2 or less. A length of each of the plurality of fibers may be 1.0 mm or more and 10.0 mm or less. A width of each of the plurality of fibers may be 1 μm or more and 100 μm or less. A thermal conductivity of the fiber structure measured according to JIS L1927 may be 0.020 W / m K or more and 0.040 W / m K or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to textile structures, insulation, containment devices, batteries, flying vehicles, and methods of producing textile structures. [Background technology]

[0002] Patent Documents 1 and 2 disclose polyimide fiber paper obtained by piling and pressing fibers made of a non-thermoplastic polyimide resin. [Prior art document] [Patent documents] [Patent Document 1] JP 2019-035157 A [Patent Document 2] JP 2023-051247 A Summary of the Invention [Means for solving the problem]

[0003] In a first aspect of the present invention, a fiber structure is provided. The fiber structure includes, for example, a plurality of fibers substantially made of a polyimide resin. In the fiber structure, the ratio of the mass of the plurality of fibers to the mass of the fiber structure is, for example, 70 mass% or more. In the fiber structure, the thickness of the fiber structure is, for example, 1 mm or more. In the fiber structure, the basis weight of the fiber structure is, for example, 40 g / m 2 More than 150g / m 2 The following is the result.

[0004] In any of the above fiber structures, the length of each of the plurality of fibers may be 1.0 mm or more and 10.0 mm or less.In any of the above fiber structures, the width of each of the plurality of fibers may be 1 μm or more and 100 μm or less.

[0005] Any of the above fiber structures may have a film-like, sheet-like or plate-like shape. In any of the above fiber structures, the plurality of fibers may include first fibers whose length direction is arranged in a direction substantially parallel to the in-plane direction of the fiber structure. The plurality of fibers may include second fibers whose length direction is arranged in a direction substantially parallel to the thickness direction of the fiber structure. In any of the above fiber structures, the ratio of the number of second fibers to the number of first fibers in a cross section of the fiber structure observed using a scanning electron microscope may be less than 30%.

[0006] In any of the above fiber structures, the thermal conductivity of the fiber structure measured in accordance with JIS L 1927 in a first environment where the pressure is 100 kPa and the temperature is room temperature may be 0.020 W / m·K or more and 0.040 W / m·K or less. The fiber structure according to claim 1.

[0007] In any of the above fiber structures, the thermal conductivity of the fiber structure estimated from the heater power effective value required to maintain the temperature of the thermocouple placed in the center of the interior of the MB-type aluminum case placed in the second environment where the pressure is 5 kPa and the temperature is -60°C at 20°C or more and 30°C or less may be 0.005 W / m·K or more and 0.030 W / m·K or less. The heater power effective value is measured, for example, in a state where the MB-type aluminum case is entirely covered with the fiber structure having an aluminum vapor deposition layer on its surface. The thickness of the fiber structure used to measure the heater power effective value is, for example, 9.0 mm. The thickness of the aluminum vapor deposition layer used to measure the heater power effective value is, for example, 150 nm. The dimensions of the MB-type aluminum case used to measure the heater power effective value are, for example, 140 mm in length, 60 mm in width, and 140 mm in height.

[0008] In a second aspect of the present invention, a fiber structure is provided. The fiber structure is obtained by, for example, stacking a plurality of nonwoven fabrics produced by a wet method, dispersing a polyimide precursor inside the stacked nonwoven fabrics, and then imidizing the polyimide precursor. In the fiber structure, each of the nonwoven fabrics includes, for example, a plurality of fibers substantially made of a polyimide resin. The thickness of the fiber structure is, for example, 1 mm or more.

[0009] In a third aspect of the present invention, there is provided a thermal insulation material, which comprises, for example, any one of the fiber structures according to the first or second aspect.

[0010] The heat insulating material may include a reflective portion that reflects radiant heat. In the heat insulating material, the reflective portion is disposed on at least a part of a surface of the fiber structure, for example.

[0011] In a fourth aspect of the present invention, a storage device is provided. The storage device includes, for example, a storage section for storing an article. In the storage device, the storage section includes, for example, a first member having a placement surface on which the article is placed. In the storage device, the storage section includes, for example, a second member disposed on the placement surface side of the first member and forming a space for storing the article together with the first member. In the storage device, the second member includes, for example, any of the fiber structures according to the first or second aspect.

[0012] In the above-mentioned storage device, the storage section may include an exhaust member for exhausting gas inside the space to the outside of the space when the pressure of the gas inside the space becomes greater than a predetermined value.

[0013] In a fifth aspect of the present invention, there is provided a battery. The battery includes, for example, the storage device according to the fourth aspect. The battery includes, for example, a power storage device disposed inside the space of the storage device.

[0014] In a sixth aspect of the present invention, an aircraft is provided. The aircraft includes, for example, the battery according to the fifth aspect. The aircraft includes, for example, a thrust generating device that generates thrust by utilizing the electric energy stored in the battery.

[0015] In a seventh aspect of the present invention, a method for producing a fiber structure is provided. The method includes, for example, a lamination step of laminating a plurality of nonwoven fabrics produced by a wet method to produce a laminate having a thickness of 1 mm or more. The method includes, for example, a dispersion step of dispersing a polyimide precursor inside the plurality of nonwoven fabrics constituting the laminate. The method includes, for example, an imidization step of imidizing the polyimide precursor. In the method, each of the plurality of nonwoven fabrics includes, for example, a plurality of fibers substantially composed of a polyimide resin.

[0016] In any of the above methods, the laminating step may include laminating a plurality of nonwoven fabrics such that a pressure applied to each of the plurality of nonwoven fabrics is less than 50 Pa. In any of the above methods, the dispersing step may include dispersing a polyimide precursor inside the plurality of nonwoven fabrics such that a pressure applied to each of the plurality of nonwoven fabrics is less than 50 Pa. In any of the above methods, the imidizing step may include imidizing the polyimide precursor such that a pressure applied to each of the plurality of nonwoven fabrics is less than 50 Pa.

[0017] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0018] [Figure 1] 1 shows a schematic diagram of an example of the system configuration of an aircraft 100. [Diagram 2] An example of a cross-sectional view of a storage battery 110 is shown diagrammatically. [Diagram 3] An example of a cross-sectional plan view of a storage battery 110 is shown diagrammatically. [Figure 4] An example of a cross section of a heat insulating member 410 in the thickness direction is shown generally. [Diagram 5] An example of a method for manufacturing the storage battery 110 is shown in schematic form. [Figure 6] An example of a method for manufacturing the heat insulating member 220 is shown in schematic form. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] According to one embodiment exemplified in the present specification (sometimes referred to as the present embodiment), a fiber structure is provided that includes a plurality of fibers. Each of the plurality of fibers is, for example, a short fiber substantially made of a polyimide resin. In this embodiment, the fiber structure includes the short fiber as a main component, and the ratio of the mass of the plurality of fibers to the mass of the fiber structure is, for example, 70 mass% or more.

[0020] The above-mentioned fiber structure has, for example, a thickness of 1 mm or more and a basis weight of 40 g / m 2 More than 150g / m 2 The above-mentioned fiber structure has a composition, structure and / or physical properties that are particularly suitable for use as a thermal insulation material for a thermal insulation device mounted on an aircraft capable of flying in the stratosphere.

[0021] Vacuum insulation panels (sometimes called VIPs) are used as the insulation material for insulation devices. However, when a VIP is used as the insulation material for an insulation device mounted on an aircraft capable of flying in the stratosphere, the residual air inside the VIP expands due to pressure fluctuations accompanying the ascent and descent of the aircraft, which may damage the VIP. In particular, when the insulation device is used to insulate a battery mounted on the aircraft, damage to the VIP of the insulation device exposes the battery to an extremely low temperature environment, resulting in a significant decrease in the charge and discharge characteristics of the battery.

[0022] On the other hand, polyimide films have the excellent properties described above and are used in a wide range of fields, including the aerospace, automotive, and communications fields. However, due to the properties of the film, it is difficult to improve the thermal insulation of polyimide films.

[0023] In response to this, the present inventors have laminated a plurality of nonwoven fabrics produced by a wet method, dispersed a polyimide precursor inside the laminated plurality of nonwoven fabrics, and then imidized the polyimide precursor to produce a nonwoven fabric having a thickness of 1 mm or more and a basis weight of 40 g / m2, the main component of which is fibers substantially made of polyimide resin. 2 More than 150g / m 2 Furthermore, the present inventors have found that a fiber structure having a thickness of 1 mm or more and a basis weight of 40 g / m or less can be obtained. 2 More than 150kg / m 2 The inventors have found that the following fiber structures have excellent thermal insulation properties: Furthermore, the inventors have found that these fiber structures have excellent thermal insulation properties in a stratospheric environment.

[0024] The fiber structure has a basis weight of 40 g / m 2 More than 150g / m 2 ≦100%, and is very lighter than the VIP described above. In addition, since the fiber structure is mainly composed of polyimide resin, it can function not only as a heat insulating material but also as a fireproof material. That is, when a VIP is used as a heat insulating material for a battery, a separate fireproof material is required, but when the fiber structure is used as a heat insulating material for a battery, an additional fireproof material is not required or the mass of the additional fireproof material can be reduced. As a result, when the fiber structure is used as a heat insulating material for a battery, the energy density per unit mass of the battery [Wh / kg-storage cell] and / or the capacity per unit mass of the active material [mAh / g-active material] can be improved.

[0025] As described above, according to the present embodiment, for example, the amount of energy per mass in a rechargeable battery can be improved, and a rechargeable battery that is lighter and can store more power can be realized. The rechargeable battery can be brought to a disaster site, for example, and used to supply energy to disaster victims. Therefore, the fiber structure, the heat insulating material, the storage device, the battery, and the aircraft according to the present embodiment, as well as the manufacturing method thereof, can contribute to the achievement of Goal 7 "Affordable and clean energy" or Goal 13 "Take urgent action to combat climate change" of the Sustainable Development Goals (SDGs).

[0026] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0027] In this specification, when a numerical range is expressed as "A to B", the expression means A or more and B or less. In addition, "substituted or unsubstituted" means "substituted with any substituent or not substituted with any substituent". The type of the above-mentioned substituent is not particularly limited unless otherwise stated in the specification. In addition, the number of the above-mentioned substituents is not particularly limited unless otherwise stated in the specification.

[0028] (Overview of the Aircraft 100) 1 illustrates an example of a system configuration of an aircraft 100. In this embodiment, the aircraft 100 includes a storage battery 110, a power control circuit 120, one or more electric motors 130, one or more propellers 140, one or more sensors 150, and a control device 160. In this embodiment, the storage battery 110 has one or more (sometimes referred to as one or more) power storage packs 112.

[0029] In this embodiment, the flying object 100 flies using electrical energy stored in the storage battery 110. Examples of the flying object 100 include an airplane, an airship or a balloon, a helicopter, a drone, and the like.

[0030] In this embodiment, the storage battery 110 receives electrical energy from an external charging device (not shown) via the power control circuit 120 and stores the electrical energy in one or more power storage packs 112. The external charging device may be a power generation device mounted on the aircraft 100. Examples of the power generation device include a solar power generation device and a fuel cell. The storage battery 110 also supplies the electrical energy stored in the one or more power storage packs 112 to the electric motor 130 via the power control circuit 120.

[0031] In this embodiment, the power storage pack 112 stores electric energy (sometimes referred to as charging the power storage pack 112). Also, the power storage pack 112 releases the stored electric energy (sometimes referred to as discharging the power storage pack 112). The power storage pack 112 may be a secondary battery.

[0032] The mass energy density of the power storage pack 112 is preferably 350 [Wh / kg-power storage pack] or more, more preferably 400 Wh / kg-power storage pack] or more, more preferably 500 Wh / kg-power storage pack] or more, even more preferably 600 Wh / kg-power storage pack] or more, and even more preferably 700 Wh / g-power storage pack] or more. This provides a power storage pack 112 that is particularly suitable for use as a power source for an aircraft.

[0033] The volumetric energy density of the storage pack 112 is 300 [Wh / m 3 - Storage pack] 1200 [Wh / m 3 - Storage pack] or less, 400 [Wh / m 3 - Storage pack] 1000 [Wh / m 3 When the power storage pack 112 is mounted on the aircraft 100 as part of the power source of the aircraft 100, the volumetric energy density of the power storage pack 112 may be 600 [Wh / m 3 - Storage pack] or less, 800 [Wh / m 3 - Energy storage pack] or less.

[0034] In this embodiment, the power control circuit 120 controls the input and output of power of the storage battery 110. The power control circuit 120 may control the input and output of power of the storage battery 110 based on an instruction from the control device 160. The power control circuit 120 includes, for example, a plurality of switching elements that operate based on a control signal from the control device 160.

[0035] In this embodiment, the electric motor 130 receives electric energy from the storage battery 110 via the power control circuit 120. The electric motor 130 rotates the propeller 140 using the electric energy received from the storage battery 110. In this way, the electric motor 130 can generate propulsion force for the flying object 100 using the electric energy stored in the power storage pack 112.

[0036] In this embodiment, the sensor 150 measures various physical quantities related to the position and attitude of the flying object 100. Examples of sensors for measuring various physical quantities related to the position and attitude of the flying object 100 include a GPS signal receiver, an acceleration sensor, an angular acceleration sensor, and a gyro sensor. The sensor 150 may measure various physical quantities related to the state of the storage battery 110. Examples of sensors for measuring various physical quantities related to the state of the storage battery 110 include a temperature sensor, a current sensor, and a voltage sensor.

[0037] In this embodiment, the control device 160 controls the flying object 100. The control device 160 may control the input and output of power to the storage battery 110 by controlling the power control circuit 120. For example, the control device 160 controls the output current, output voltage, input current, input voltage, etc. of the storage battery 110. This allows the control device 160 to control the position and attitude of the flying object 100. The control device 160 may control the position and attitude of the flying object 100 by controlling the power control circuit 120 based on the output from the sensor 150.

[0038] The storage battery 110 may be an example of a battery. The power storage pack 112 may be an example of an item or a power storage device. The electric motor 130 may be an example of a propulsion generating device.

[0039] (An example of another embodiment) In this embodiment, the details of the aircraft 100 are described using an example in which the aircraft 100 is equipped with a storage battery 110. However, the aircraft 100 is not limited to this embodiment. In other embodiments, the battery installed in the aircraft 100 may be a primary battery.

[0040] (Overview of storage battery 110) An example of the storage battery 110 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 shows an example of a cross-sectional view of the storage battery 110. Fig. 3 shows an example of a plan cross-sectional view of the storage battery 110. In this embodiment, Fig. 2 shows an example of a B-B' cross section in Fig. 3, and Fig. 3 shows an example of an A-A' cross section in Fig. 2.

[0041] In this embodiment, the storage battery 110 includes, for example, a power storage pack 112 and a heat insulating device 200. In this embodiment, the heat insulating device 200 includes, for example, a base plate 210, a heat insulating member 220, a reflecting member 230, and a welding member 240. According to this embodiment, an accommodation space 260 for accommodating the power storage pack 112 is formed inside the heat insulating device 200 by the base plate 210 and the heat insulating member 220.

[0042] In this embodiment, the base plate 210 includes, for example, a mounting surface 212 and a vent valve 214. In this embodiment, the heat insulating member 220 includes, for example, short fibers 222 arranged in a direction substantially parallel to the in-plane direction of the heat insulating member 220. The heat insulating member 220 may include short fibers 224 arranged in a direction substantially parallel to the thickness direction of the heat insulating member 220.

[0043] According to one embodiment, the plurality of short fibers 222 are chemically or physically bonded together. For example, the plurality of short fibers 222 are bonded together by an adhesive (not shown). According to another embodiment, the plurality of short fibers 222 and the plurality of short fibers 224 are chemically or physically bonded together. For example, the plurality of short fibers 222 and the plurality of short fibers 224 are bonded together by an adhesive (not shown).

[0044] 2 and / or 3, the normal direction of the placement surface 212 is indicated as the z direction in the drawings. Similarly, the in-plane direction of the placement surface 212 is indicated as the x direction or the y direction in the drawings.

[0045] (Details of the insulation device 200) In this embodiment, the heat insulation device 200 houses the electricity storage pack 112. The heat insulation device 200 protects the electricity storage pack 112, for example, by insulating the electricity storage pack 112.

[0046] In this embodiment, the base plate 210 supports or holds the power storage pack 112. The base plate 210 forms the accommodation space 260 together with the thermal insulation member 220. As described above, the power storage pack 112 is disposed inside the accommodation space 260 of the thermal insulation device 200. The power storage pack 112 is placed, for example, on the mounting surface 212 of the base plate 210. In one embodiment, the power storage pack 112 is placed in contact with the mounting surface 212. In another embodiment, the power storage pack 112 is placed on the mounting surface 212 via another member.

[0047] In this embodiment, the vent valve 214 controls the movement of materials between the inside of the accommodation space 260 and the outside of the accommodation space 260. The vent valve 214 is configured to close when the pressure of the gas inside the accommodation space 260 becomes greater than a predetermined value, and to open when the pressure of the gas inside the accommodation space 260 becomes greater than a predetermined value. In this way, the vent valve 214 can exhaust the gas inside the accommodation space 260 to the outside of the accommodation space 260 when the pressure of the gas inside the accommodation space 260 becomes greater than the predetermined value.

[0048] In this embodiment, the heat insulating member 220 suppresses the transfer of heat between the inside of the storage space 260 and the outside of the storage space 260. The heat insulating member 220 has, for example, a film-like, sheet-like or plate-like shape. The heat insulating member 220 is disposed on the side of the mounting surface 212 of the base plate 210. The heat insulating member 220 forms the storage space 260 together with the base plate 210. The details of the heat insulating member 220 will be described later.

[0049] In this embodiment, the reflecting member 230 reflects radiant heat. The reflecting member 230 is disposed, for example, on at least a part of the surface of the heat insulating member 220. When the heat insulating member 220 has a film-like, sheet-like, or plate-like shape, the reflecting member 230 is disposed, for example, on at least a part of the surface opposite to the surface on the side of the storage space 260, out of the two surfaces of the heat insulating member 220. The reflecting member 230 has, for example, a film-like, sheet-like, or plate-like shape.

[0050] Examples of the reflective member 230 include a metal foil, a metal deposition layer, a metal deposition film, and a laminate film. An example of the metal used in the above member is aluminum. The laminate film includes, for example, (i) a plurality of resin layers, and (ii) a reflective layer that is disposed between two resin layers included in the plurality of resin layers and reflects radiant heat. An example of the reflective layer is a metal layer. An example of the metal layer is an aluminum layer. In this way, when the laminate film is used as the reflective member 230, the reflective member 230 can have a strength sufficient to withstand gas or flames generated by thermal runaway of the electricity storage pack 112.

[0051] In this embodiment, the welding member 240 joins the base plate 210 and the reflective member 230. The welding member 240 joins the base plate 210 and the reflective member 230 by, for example, welding. The welding member 240 may join the base plate 210 and the heat insulating member 220. The welding member 240 joins the base plate 210 and the heat insulating member 220 by, for example, welding. Examples of the welding member 240 include thermoplastic resins such as polyethylene resin and polypropylene resin.

[0052] In this embodiment, the storage space 260 accommodates therein the electricity storage pack 112. As described above, the heat insulating member 220 is disposed on the mounting surface 212 of the base plate 210, so that the storage space 260 is formed on the mounting surface 212 side of the base plate 210.

[0053] (Details of the heat insulating member 220) In this embodiment, the heat insulating member 220 has a fiber structure. The heat insulating member 220 may be a member substantially made of the fiber structure. The ratio of the mass of the fiber structure to the mass of the heat insulating member 220 may be 70 mass% or more.

[0054] The heat insulating member 220 has, for example, a film-like, sheet-like or plate-like shape. The heat insulating member 220 may be a fiber structure having a film-like, sheet-like or plate-like shape.

[0055] (Details of the fiber structure) (Composition of fiber structure) The fiber structure includes a plurality of fibers. The ratio of the mass of the plurality of fibers to the mass of the fiber structure may be 70% by mass or more. The ratio of the mass of the fibers having specific characteristics to the mass of the fiber structure may be 70% by mass or more. The specific characteristics will be described in detail later. The ratio is preferably 80% by mass or more, more preferably 90% by mass or more.

[0056] The fiber structure may include a plurality of fibers and an adhesive for bonding the fibers together. The type of resin used as the adhesive is not particularly limited, but examples of the adhesive include polyimide resin, bismaleimide resin, epoxy resin, acrylic resin, and polyvinyl alcohol resin. The mass ratio of the adhesive to the mass of the fiber structure may be 30% by mass or less. The above ratio is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0057] The above-mentioned fiber structure may be substantially free of a pulp component. The pulp component is defined as, for example, a fiber (sometimes called a long fiber) having a length to diameter (sometimes called a width) ratio of more than 300. The mass ratio of the pulp component to the mass of the above-mentioned fiber structure may be less than 30% by mass. The above-mentioned ratio is preferably 15% by mass or less, more preferably 5% by mass or less.

[0058] (fiber) Each of the plurality of fibers contained in the fiber structure may be a fiber substantially made of a polyimide resin. The ratio of the mass of the polyimide resin to the mass of the plurality of fibers may be 70 mass% or more. Each of the plurality of fibers may contain impurities (sometimes referred to as inevitable impurities) that are present in the raw materials of the polyimide resin or that are inevitably mixed in during the manufacturing process of the polyimide resin. The polyimide resin may be a non-thermoplastic polyimide resin.

[0059] The length of each of the multiple fibers contained in the fiber structure may be 1.0 mm or more and 10.0 mm or less. The length of the fiber indicates the size of the fiber in the longitudinal direction. The mass ratio of the fibers having a length of 1.0 mm or more and 10.0 mm or less (sometimes referred to as short fibers) to the mass of the above-mentioned fiber structure may be 70 mass% or more.

[0060] The length of each of the plurality of fibers is preferably 1.0 mm or more and 10.0 mm or less, more preferably 2.0 mm or more and 5.0 mm or less. When the fiber length is within the above numerical range, the fiber structure exhibits excellent heat insulating properties. The fiber structure exhibits excellent heat insulating properties, particularly in a stratospheric environment.

[0061] The width of each of the multiple fibers contained in the fiber structure may be 1 μm or more and 100 μm or less. The width of the fiber indicates the size of the fiber in the short direction or the diameter of the fiber. The ratio of the mass of the fibers having a width of 1 μm or more and 100 μm or less to the mass of the fiber structure may be 70 mass% or more.

[0062] The width of each of the plurality of fibers is preferably 3 μm to 75 μm, more preferably 5 μm to 50 μm. When the fiber width falls within the above numerical range, the fiber structure exhibits excellent heat insulating properties. The fiber structure exhibits excellent heat insulating properties, particularly in a stratospheric environment.

[0063] Each of the fibers contained in the fiber structure may be a short fiber having a length of 1.0 mm or more and 10.0 mm or less and a width of 1 μm or more and 100 μm or less. The proportion of the mass of the short fiber having the above length and width to the mass of the fiber structure may be 70 mass% or more.

[0064] Each of the multiple fibers may be a short fiber obtained by a shaving process of a polyimide resin. The shaving process of a polyimide resin is performed, for example, by the following procedure. First, a roll of polyimide film is prepared. For example, a strip-shaped polyimide film is wound into a cylindrical shape to produce a roll of polyimide film. Next, the roll of polyimide film is rotated. Next, a blade for shaving the polyimide film is pressed against the side of the rotating roll of polyimide film. This results in a bundle of polyimide fibers according to the thickness of the polyimide film and the shaving width. Then, the bundle of polyimide fibers is cut. This results in a short fiber of polyimide resin.

[0065] In the step of preparing a polyimide fiber bundle, the width of the short fibers can be adjusted by adjusting the thickness and / or the shaving width of the polyimide film, and the length of the short fibers can be adjusted in the step of cutting the polyimide fiber bundle.

[0066] (Polyimide resin) In this embodiment, the polyimide resin is obtained, for example, by polymerizing an aromatic diamine component and an aromatic acid anhydride component in an organic solvent. Examples of the aromatic diamine component include one or more components selected from the group consisting of paraphenylenediamine, 1,3-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether. Aromatic diamine components other than the above aromatic diamine components may be used as raw materials for the polyimide resin. Examples of the aromatic acid anhydride component include one or more components selected from the group consisting of 4,4'-oxydiphthalic anhydride, pyromellitic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Aromatic acid anhydride components other than the above aromatic acid anhydride components may be used as raw materials for the polyimide resin.

[0067] (Structure of fiber structure) The above-mentioned fiber structure has, for example, a film-like, sheet-like or plate-like shape. The thickness of the above-mentioned fiber structure may be 1 mm or more. The thickness of the fiber structure is defined, for example, as the minimum value among the measured values ​​of the width, length and height of the fiber structure. The thickness of the fiber structure is preferably 1 mm or more and 20 mm or less, more preferably 3 mm or more and 15 mm or less.

[0068] When the thickness of the fiber structure falls within the above numerical range, the fiber structure exhibits excellent heat insulating properties. The above-mentioned fiber structure exhibits excellent heat insulating properties, particularly in a stratospheric environment. The heat insulating properties of the fiber structure will be described in detail later.

[0069] The above-mentioned fiber structure may be an assembly of the above-mentioned fibers. The above-mentioned fiber structure is obtained, for example, by stacking a plurality of nonwoven fabrics produced by a wet method, dispersing a polyimide precursor inside the stacked nonwoven fabrics, and then imidizing the polyimide precursor. Each of the above-mentioned nonwoven fabrics may contain a plurality of fibers.

[0070] Each of the fibers contained in the nonwoven fabric may have the same configuration as the fibers contained in the fiber structure described above. Each of the fibers contained in the nonwoven fabric may be a fiber substantially made of a polyimide resin. The ratio of the mass of the polyimide resin to the mass of the fibers contained in the nonwoven fabric may be 70 mass% or more. Each of the fibers may contain the inevitable impurities described above.

[0071] According to the wet method, nonwoven fabrics are produced by the same manufacturing method as paper. According to the wet method, nonwoven fabrics can be produced using shorter fibers than those produced by the dry method. Furthermore, the short fibers contained in nonwoven fabrics produced by the wet method are often arranged so that the length direction of the short fibers is approximately parallel to the in-plane direction of the nonwoven fabric. The in-plane direction of the nonwoven fabric is defined, for example, as the direction perpendicular to the thickness direction of the nonwoven fabric.

[0072] According to this embodiment, in the manufacturing process of the fiber structure, a plurality of nonwoven fabrics produced by a wet method are laminated, so that the fiber structure contains the short fibers 222 described above. The fiber structure may contain the pulp component (long fibers) described above. The fiber structure may not substantially contain the pulp component described above. In a cross section of the fiber structure observed using a scanning electron microscope, the ratio of the number of short fibers 224 to the number of short fibers 222 may be less than 30%. The fiber structure may contain the pulp component or long fibers described above, or may not substantially contain the pulp component or long fibers.

[0073] When the thickness of the fiber structure is t, the width of the observation area observed by the scanning electron microscope may be Nt (N is 0.05 or more and 10 or less). The height of the observation area may be Mt (M is 0.5 or more and 1 or less). The width of the observation area may be approximately parallel to the in-plane direction of the fiber structure, and the height of the observation area may be approximately parallel to the thickness direction of the fiber structure.

[0074] According to the present embodiment, the manufacturing process of the fiber structure includes a process of dispersing a polyimide precursor inside the laminated nonwoven fabrics and then imidizing the polyimide precursor. As a result, the main failure mode of the fiber structure is a cohesive failure mode. In other words, even though multiple nonwoven fabrics are laminated in the manufacturing process of the fiber structure, interfacial failure between the layers of the multiple nonwoven fabrics is suppressed.

[0075] (Physical properties of fiber structures) The basis weight of the above fiber structure is 40 g / m 2 More than 150g / m 2 The basis weight of the fibrous structure can be calculated, for example, by measuring the weight and area of ​​a sample piece and dividing the weight of the sample piece by the area of ​​the sample piece.

[0076] The basis weight of the fiber structure is preferably 40 g / m 2 More than 120g / m 2 More preferably, it is 40 g / m or less. 2 More than 100g / m 2 When the basis weight of the fiber structure falls within the above numerical range, the fiber structure exhibits excellent heat insulating properties. The above fiber structure exhibits excellent heat insulating properties, particularly in a stratospheric environment. A fiber structure having a basis weight within the above numerical range is particularly suitable as a heat insulating material for a heat insulating device mounted on an aircraft capable of flying in the stratosphere.

[0077] (Thermal insulation properties of fiber structures) The fiber structure constituting the heat insulating member 220 has excellent heat insulating properties due to the above-mentioned novel configuration. Specifically, the above-mentioned fiber structure has an extremely low thermal conductivity.

[0078] In one embodiment, the thermal conductivity of the fiber structure measured by a steady state method in an environment (sometimes referred to as a first environment) at a pressure of 100 kPa and room temperature (e.g., 15°C or higher and 25°C or lower) is 0.020 W / m·K or higher and 0.040 W / m·K or lower. The thermal conductivity is measured, for example, in accordance with JIS L 1927. The thermal conductivity in the first environment is preferably 0.025 W / m·K or higher and 0.035 W / m·K or lower, and more preferably 0.027 W / m·K or higher and 0.033 W / m·K or lower.

[0079] In another embodiment, the thermal conductivity of the fiber structure estimated from the effective electric power value of a heater required to maintain the temperature of a thermocouple installed in the center of an MB-type aluminum case placed in an environment (sometimes referred to as a second environment) where the pressure is 5 kPa and the temperature is -60°C between 20°C and 30°C is 0.005 W / m·K or more and 0.030 W / m·K or less. The estimated value of the thermal conductivity in the second environment is preferably 0.010 W / m·K or more and 0.020 W / m·K or less, and more preferably 0.012 W / m·K or more and 0.018 W / m·K or less.

[0080] (Procedure for estimating thermal conductivity in the stratospheric environment) The estimated value of the thermal conductivity of the fiber structure in the second environment above indicates an estimated value of the thermal conductivity of the fiber structure in a stratospheric environment. Generally, the thermal conductivity of an object is measured in accordance with JIS L 1927 under conditions of a pressure of 100 kPa and room temperature. However, since the pressure in a stratospheric environment is very small, the thermal conductivity of the fiber structure cannot be measured in accordance with JIS L 1927. Therefore, in this embodiment, the thermal conductivity of the fiber structure in a stratospheric environment is estimated by the following procedure.

[0081] First, an MB-type aluminum case (manufactured by Takachi Electrical Industry Co., Ltd., MB14-6-14) is prepared. The dimensions of the MB-type aluminum case are 140 mm in length, 60 mm in width, and 140 mm in height. The MB-type aluminum case may be an example of an article that imitates the electricity storage pack 112.

[0082] Next, a 5.4Ω film heater (MINCO HK5417R5.3L12B) is installed inside the MB aluminum case. The heater is installed near the center of the bottom surface of the MB aluminum case. Also, 12 thermistors (RS PRO 827-5937) are installed inside the MB aluminum case. The above thermistors are arranged at each of the eight corners of the MB aluminum case, two locations near the center of the top surface of the MB aluminum case, on the heater, and at an approximate center position inside the MB aluminum case. The thermistor arranged at an approximate center position inside the MB aluminum case is, for example, suspended from the top surface of the MB aluminum case. One of the two thermistors arranged near the center of the top surface is used, for example, to control the film heater. The output of the thermistor arranged at an approximate center position inside the case is used, for example, to calculate the effective power value of the film heater.

[0083] Next, a fiber structure to be estimated for thermal conductivity is prepared. The thickness of the fiber structure is, for example, 9.0 mm. Next, an aluminum vapor deposition layer having a thickness of 150 nm is formed on one side of the fiber structure to be estimated for thermal conductivity. Any known procedure may be adopted as a procedure for producing the aluminum vapor deposition layer. Then, the entire outer surface of the MB-type aluminum case is covered with the fiber structure having the aluminum vapor deposition layer on its surface. This prepares a sample for estimating thermal conductivity in a stratospheric environment.

[0084] Next, the above sample is placed inside a thermostatic chamber (MZH-32H, manufactured by ESPEC Co., Ltd.) A cubic container with a side length of 1500 mm is used as the thermostatic chamber.

[0085] Next, the pressure inside the thermostatic chamber is adjusted to normal pressure (specifically, 100 kPa). The temperature inside the thermostatic chamber is adjusted to -60°C. Next, a voltage of 10.5 V is applied to the heater, and measurement of the current value of the heater is started. A digital temperature controller (MITCTR manufactured by Misumi) is used to control the operation of the heater so that the heater turns ON when the temperature measured by the thermistor installed at the approximate center inside the MB-type aluminum case becomes 20°C or lower, and the heater turns OFF when the temperature becomes 30°C or lower. After that, the output time of the heater is measured using the digital temperature controller until the ON / OFF cycle of the heater becomes approximately constant. Based on the above measurement results, the effective power value of the heater under the condition of a pressure of 100 kPa and a temperature of -60°C is derived.

[0086] Next, while maintaining the temperature inside the thermostatic chamber at -60°C, adjust the pressure inside the thermostatic chamber to a pressure equivalent to an altitude of 60,000 feeds (specifically, 5 kPa). While adjusting the pressure inside the thermostatic chamber, keep applying a voltage of 10.5 V to the heater, and start measuring the current value of the heater. Also, use a digital temperature controller (MITSUMI MTCTR) to control the operation of the heater so that the heater turns ON when the temperature measured by the thermistor installed at the approximate center inside the MB-type aluminum case becomes 20°C or lower, and turns OFF when the temperature becomes 30°C or lower. After that, use the digital temperature controller to measure the output time of the heater until the ON / OFF cycle of the heater becomes approximately constant. Also, based on the above measurement results, derive the effective power value of the heater under the condition of a pressure of 5 kPa and a temperature of -60°C.

[0087] Next, the heater's effective power value (sometimes referred to as the first effective power value) in an environment where the pressure is 100 kPa and the temperature is -60°C (the first environment described above) is compared with the heater's effective power value (sometimes referred to as the second effective power value) in an environment where the pressure is 5 kPa and the temperature is -60°C (the second environment described above). Based on the above comparison result and the thermal conductivity of the fiber structure in the first environment, the thermal conductivity of the fiber structure in the second environment is estimated.

[0088] For example, when the second effective power value is half the first effective power value, the insulating effect of the fiber structure in the second environment can be estimated to be twice as high as the insulating effect of the fiber structure in the first environment. Therefore, for example, when the second effective power value is half the first effective power value, the thermal conductivity of the fiber structure in the second environment can be estimated to be twice as high as the thermal conductivity of the fiber structure in the first environment.

[0089] The heat insulating device 200 may be an example of a storage device or a storage section. The base plate 210 may be an example of a first member. The placement surface 212 may be an example of a placement surface on which an article is placed. The vent valve 214 may be an example of an exhaust member. The heat insulating member 220 may be an example of a heat insulating material or a second member. The short fibers 222 may be an example of a first fiber. The short fibers 224 may be an example of a second fiber. The reflective member 230 may be an example of a reflective section. A combination of the heat insulating member 220 and the reflective member 230 may be an example of a heat insulating material.

[0090] (An example of another embodiment) In this embodiment, the details of the heat insulating device 200 are described by taking as an example a case in which the base plate 210 and the reflective member 230 are welded by the welding member 240. However, the heat insulating device 200 is not limited to this embodiment. In other embodiments, the heat insulating device 200 may not include the welding member 240.

[0091] 4 is a schematic diagram showing an example of a cross section in the thickness direction of a heat insulating member 410. The heat insulating member 410 may be another example of the heat insulating member 220. In this embodiment, the heat insulating member 410 includes one or more polyimide layers 420 and one or more aerogel layers 430.

[0092] The polyimide layer 420 includes a plurality of fibers substantially made of polyimide resin. In one embodiment, at least one of the one or more polyimide layers 420 may be a nonwoven fabric having a thickness of less than 1 mm. The polyimide layer 420 may be a nonwoven fabric made by a dry method or a nonwoven fabric made by a wet method. In another embodiment, at least one of the one or more polyimide layers 420 may be a fiber structure as described above or may be a layer including a fiber structure as described above. In yet another embodiment, at least one of the one or more polyimide layers 420 may be a foam of polyimide resin.

[0093] The aerogel layer 430 may be a layer substantially made of silica aerogel, or may be a nonwoven fabric containing silica aerogel. Examples of the material of the nonwoven fabric include glass fiber, ceramic fiber, polyimide fiber, and aramid fiber.

[0094] (Manufacturing method of storage battery 110) FIG. 5 shows an example of a manufacturing method of the storage battery 110. According to this embodiment, first, in step 512 (step may be abbreviated as S), the electricity storage pack 112 is prepared. Next, in S514, the heat insulating member 220 is prepared. The process of preparing the heat insulating member 220 will be described in detail later. Next, in S516, the base plate 210, the reflecting member 230, and the welding member 240 are prepared. For example, the reflecting member 230 is formed on one surface of the heat insulating member 220. After that, in S518, the storage battery 110 is assembled. Specifically, for example, the electricity storage pack 112 is placed on the mounting surface 212 of the base plate 210. In addition, the heat insulating member 220 is arranged on the side of the mounting surface 212 of the base plate 210. The heat insulating member 220 is arranged so as to cover the electricity storage pack 112. The heat insulating member 220 is disposed, for example, such that the surface of the heat insulating member 220 opposite the surface on which the reflecting member 230 is formed is in contact with the surface of the electricity storage pack 112. In this manner, the storage battery 110 is fabricated.

[0095] (Method of manufacturing the heat insulating member 220) 6A and 6B are schematic diagrams illustrating an example of a method for manufacturing the heat insulating member 220. FIG. 6A and 6B may be an example of S514 in FIG.

[0096] According to this embodiment, first, in S612, short fibers of polyimide resin are prepared. The short fibers of polyimide resin are obtained by the above-mentioned polyimide resin cutting process. As described above, the short fibers of polyimide resin are substantially made of polyimide resin. The polyimide resin may be a non-thermoplastic polyimide resin.

[0097] The polyimide fibers shaved off in the shaving step are cut into short fibers having a length of 1.0 mm to 10 mm in the longitudinal direction, thereby obtaining short fibers of polyimide resin.

[0098] Next, in S614, the polyimide resin staple fibers are processed into a sheet. This produces a fiber web (sometimes called fleece) containing polyimide resin staple fibers as a main component. The fleece may be a nonwoven fabric produced by a wet method (sometimes called wet nonwoven fabric).

[0099] The procedure for producing the wetlaid nonwoven fabric is not particularly limited, but includes, for example, a slurry forming step and a papermaking step. The details of the procedure for producing the wetlaid nonwoven fabric are, for example, as follows.

[0100] First, in a slurry formation process, water, a water-soluble polymer compound, and short fibers of polyimide resin are mixed to prepare a slurry in which short fibers of polyimide resin are dispersed in water. The above-mentioned slurry may contain various additives used in the production of paper or wet nonwoven fabric. Examples of the above-mentioned additives include dispersants, defoamers, and viscosity modifiers. Next, the above-mentioned slurry is used in a papermaking process, where the above-mentioned slurry is treated using a known papermaking technique to prepare a wet nonwoven fabric in which short fibers of polyimide resin are temporarily fixed using a water-soluble polymer as a binder (sometimes called temporary fixing paper, fiber web, fleece, etc.). The thickness of the temporary fixing paper obtained in the papermaking process is, for example, 1.0 mm or less.

[0101] The water-soluble polymer compound may be any polymer compound that is water-soluble and has a decomposition temperature lower than the glass transition point of polyimide, and the type of the polymer compound is not particularly limited. Examples of the water-soluble polymer compound include starch, alginic acid, carboxymethyl cellulose, casein, vinylon, polyvinyl alcohol, vinyl acetate, polyvinyl acetate, and / or derivatives thereof.

[0102] Next, in S622 and S624, the inside of the laminate in which the multiple temporary adhesive papers are laminated is impregnated with a polyimide precursor solution, thereby obtaining a laminate of temporary adhesive papers in which the polyimide precursor is dispersed.

[0103] In this embodiment, the details of the procedure for producing a laminate containing a polyimide precursor are described by taking as an example a case where a laminate is produced by stacking a plurality of temporary fixing papers in S622, and then the inside of the laminate is impregnated with a polyimide precursor solution in S624. However, the procedure for producing a laminate containing a polyimide precursor is not limited to this embodiment. According to another embodiment, a laminate containing a polyimide precursor is produced by impregnating the inside of each of a plurality of temporary fixing papers with a polyimide precursor solution, and then stacking the plurality of temporary fixing papers.

[0104] The polyimide precursor may be, for example, a polyamic acid that becomes a non-thermoplastic polyimide by an imidization reaction. The polyimide precursor may be (i) a precursor of a non-thermoplastic polyimide obtained by polymerizing an aromatic diamine component and an aromatic acid anhydride component in an organic solvent, or (ii) a non-thermoplastic polyimide precursor in which the solvent is replaced with a solvent different from that used in the polymerization after condensation polymerization.

[0105] Next, in S626, the polyimide precursor dispersed inside the laminate is imidized. Specifically, the laminate containing the polyimide precursor is heated. In S626, the laminate containing the polyimide precursor is heated to a temperature equal to or higher than the decomposition temperature of the water-soluble polymer used to temporarily fix the short fibers of the polyimide resin and equal to or higher than the temperature at which imidization of the polyimide precursor is promoted. The laminate containing the polyimide precursor is heated to, for example, 300°C or higher.

[0106] As a result, the polyimide precursor becomes a polyimide resin that bonds the short fibers contained in the temporary fixing paper. Furthermore, the multiple temporary fixing papers that make up the laminate are bonded by the polyimide resin. As a result, a fiber structure having a thickness of 1.0 mm or more and mainly composed of polyimide resin is obtained. Furthermore, according to the above procedure, a fiber structure whose main failure mode is a cohesive failure mode is obtained.

[0107] (Pressure applied to temporary paper) In S622, various settings may be adjusted so that the pressure applied to the temporary tacking paper is less than 50 Pa. This results in a paper with a basis weight of 40 g / m 2 More than 150g / m 2 In at least one of S622, S624, and S626, various settings may be adjusted so that the pressure applied to the temporary fixing paper or laminate is less than 50 Pa. This allows the insulation member 220 to be manufactured with a fiber structure having a basis weight of 40 g / m 2 More than 150g / m 2 A thermal insulation member 220 having the following fiber structure can be produced. When the pressure applied to the temporary fixing paper or laminate in S622, S624, and S626 is less than 50 Pa, a fiber structure with a low basis weight is produced. A fiber structure with a low basis weight has properties that are particularly suitable as a material for the thermal insulation member 220 for an aircraft.

[0108] S622 may be an example of a lamination step, S624 may be an example of a dispersion step, and S626 may be an example of an imidization step. EXAMPLES

[0109] In order to more specifically describe the storage battery 110 or the heat insulating member 220, the details of the storage battery 110 or the heat insulating member 220 will be described in the following examples. However, various modifications or improvements may be made to the following examples, and the storage battery 110 and the heat insulating member 220 are not limited to the following examples.

[0110] Example 1 In Example 1, a fiber structure was produced according to the following procedure. First, a polyimide film (Kapton 100H, manufactured by Toray DuPont Co., Ltd.) was wound into a roll to prepare a roll of polyimide film. The thickness of the polyimide film was 25 μm. Short fibers of polyimide resin were scraped out from the roll of polyimide film according to the above-mentioned procedure. The average length (number basis) of the short fibers measured by the Canadian Standard Freeness Tester (JIS P 8226-2:2011) was 3 mm. Similarly, the average width (number basis) of the short fibers measured by observation with an optical microscope was 50 μm.

[0111] Next, a slurry consisting of the water-soluble polymer, whose decomposition temperature is lower than the glass transition temperature of polyimide, and the short fibers of the polyimide resin was used to make paper, and a roll-shaped fiber paper in which the short fibers of the polyimide resin were temporarily fixed with the water-soluble polymer was obtained. The thickness of the fiber paper was 0.4 mm.

[0112] Next, 24 sheets each having a size of 200 mm×300 mm were cut out from the roll of fiber paper. The 24 sheets were stacked together and a pressure of 20 Pa was applied to obtain a laminate.

[0113] Next, a polyimide precursor solution was prepared and the above laminate was entirely immersed in it, thereby obtaining a laminate having the polyimide precursor dispersed therein.

[0114] Next, the laminate containing the polyimide precursor was heated for 15 minutes at a temperature of 380° C. As a result, a fiber structure containing polyimide resin as a main component was obtained.

[0115] (Thickness) A dial thickness gauge (H type) was used to measure the thickness of the fiber structure obtained in Example 1. As shown in Table 1, the thickness of the fiber structure obtained in Example 1 was 9 mm.

[0116] (Weighing) The mass of the fiber structure obtained in Example 1 was measured. The measured mass of the fiber structure was divided by the area of ​​the fiber structure to calculate the basis weight of the fiber structure. The area of ​​the fiber structure obtained in Example 1 was 200 mm × 300 mm, which is the same as the area of ​​the sheet described above. As shown in Table 1, the basis weight of the fiber structure obtained in Example 1 was 90 g / m 2 It was.

[0117] (Thermal conductivity in the first environment) The thermal conductivity of the fiber structure obtained in Example 1 in the first environment was measured by a steady-state method. Specifically, the thermal conductivity was measured by a steady-state method using a KES-F7 II Thermo Lab (compliant with JIS L 1927) manufactured by Katotex Co., Ltd. As shown in Table 1, the thermal conductivity of the fiber structure obtained in Example 1 in the first environment was 0.03 W / m K.

[0118] (Thermal conductivity in the second environment) According to the above-mentioned procedure, the thermal conductivity of the fiber structure obtained in Example 1 in the second environment was estimated. Specifically, first, an aluminum vapor deposition layer was formed on one surface of the fiber structure obtained in Example 1. The thickness of the aluminum vapor deposition layer was 150 nm. Next, an MB-type aluminum case (manufactured by Takachi Electric Industry Co., Ltd., MB14-6-14) was prepared. In addition, according to the above-mentioned procedure, 12 thermistors and a 5.4Ω film heater (manufactured by MINCO, HK5417R5.3L12B) were installed inside the MB-type aluminum case.

[0119] After placing the MB-type aluminum case inside a thermostatic chamber (MZH-32H, manufactured by ESPEC Co., Ltd.), the 5.4Ω film heater was connected to a power source via a digital temperature controller (MTCTR, manufactured by Misumi Co., Ltd.) The dimensions of the thermostatic chamber were 1500 mm wide, 1500 mm long, and 1500 mm high.

[0120] Next, the heater power effective value in the first environment was measured. Specifically, first, the pressure inside the thermostatic chamber was adjusted to 100 kPa. Also, the temperature inside the thermostatic chamber was adjusted to -60°C. Next, a voltage of 10.5 V was applied to the heater, and measurement of the current value of the heater was started. Also, using the digital temperature regulator, the heater was controlled so that the heater was turned ON when the temperature measured by the thermistor installed at the approximate center position inside the MB-type aluminum case was 20°C or less, and the heater was turned OFF when the temperature was 30°C or less. Then, using the digital temperature regulator, the heater output time was measured until the heater ON / OFF cycle became approximately constant.

[0121] Based on the heater output time, the effective heater power value in the first environment was derived. As shown in Table 1, the effective heater power value in the first environment was 19.5W.

[0122] Next, the effective heater power value was measured in the second environment. Specifically, the effective heater power value in the second environment was measured in the same manner as in the first environment, except that the pressure inside the thermostatic chamber was adjusted to 5 kPa. As shown in Table 1, the effective heater power value in the second environment was 9.7 W.

[0123] The thermal conductivity of the fiber structure obtained in Example 1 in the second environment was estimated based on the ratio between the effective heater power in the first environment and the effective heater power in the second environment. As shown in Table 1, the estimated thermal conductivity of the fiber structure obtained in Example 1 in the second environment was 0.006 W / m K. The estimated value of the thermal conductivity in the second environment may be an example of the thermal conduction characteristics in the second environment.

[0124] Comparative Example 1 The thermal conductivity in the first environment was measured and the thermal conductivity in the second environment was estimated in the same manner as in Example 1, except that a 7 mm thick foamed polyimide resin (SOLIMIDE TA-301, manufactured by BOYD Corp.) was prepared instead of producing a fiber structure. The measurement results and the estimation results are shown in Table 1. The catalog values ​​of the thickness and weight of the foamed polyimide resin are also shown in Table 1.

[0125] (Reference example 1) The thermal conductivity in the first environment was measured and the thermal conductivity in the second environment was estimated in the same manner as in Example 1, except that a vacuum insulation panel (U-Vacua series TZB9830E, manufactured by Panasonic Corporation) with a thickness of 10 mm was prepared instead of producing a fiber structure. The measurement results and estimation results are shown in Table 1. The catalog values ​​of the thickness and weight of the vacuum insulation panel are also shown in Table 1. The above vacuum insulation panel had substantially no air remaining and was not damaged even in the second environment.

[0126] [Table 1]

[0127] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0128] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before" or "prior to," and that the process may be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, it does not mean that the process must be performed in this order. [Explanation of symbols]

[0129] 100 flying object, 110 storage battery, 112 storage pack, 120 power control circuit, 130 electric motor, 140 propeller, 150 sensor, 160 control device, 200 heat insulating device, 210 base plate, 212 mounting surface, 214 vent valve, 220 heat insulating member, 222 short fiber, 224 short fiber, 230 reflecting member, 240 welding member, 260 storage space, 410 heat insulating member, 420 polyimide layer, 430 aerogel layer

Claims

1. A fiber structure comprising a plurality of fibers substantially made of a polyimide resin, A ratio of the mass of the plurality of fibers to the mass of the fiber structure is 70 mass% or more, The thickness of the fiber structure is 1 mm or more, The basis weight of the fiber structure is 40 g / m ２ 150g / m or more ２ Below is the Textile structure.

2. The length of each of the plurality of fibers is 1.0 mm or more and 10.0 mm or less. The fiber structure according to claim 1 .

3. The width of each of the plurality of fibers is 1 μm or more and 100 μm or less. The fiber structure according to claim 2 .

4. The fiber structure has a film-like, sheet-like or plate-like shape, The plurality of fibers are A first fiber whose length direction is substantially parallel to an in-plane direction of the fiber structure; A second fiber having a length direction substantially parallel to a thickness direction of the fiber structure; Including, In a cross section of the fiber structure observed using a scanning electron microscope, the ratio of the number of the second fibers to the number of the first fibers is less than 30%. The fiber structure according to claim 1 .

5. The thermal conductivity of the fiber structure measured in accordance with JIS L 1927 in a first environment having a pressure of 100 kPa and room temperature is 0.020 W / m·K or more and 0.040 W / m·K or less. The fiber structure according to claim 1 .

6. the thermal conductivity of the fiber structure estimated from the effective value of heater power required to maintain the temperature of a thermocouple placed in the center of an MB-type aluminum case in a second environment having a pressure of 5 kPa and a temperature of -60°C at 20°C or more and 30°C or less is 0.005 W / m K or more and 0.030 W / m K or less; The effective electric power value of the heater is measured in a state where the MB-type aluminum case is entirely covered with the fiber structure having an aluminum vapor deposition layer on its surface, The thickness of the fiber structure used in measuring the effective power value of the heater is 9.0 mm; The thickness of the aluminum deposition layer used to measure the effective power value of the heater is 150 nm. The dimensions of the MB-type aluminum case used to measure the effective power value of the heater are 140 mm in length, 60 mm in width, and 140 mm in height. The fiber structure according to claim 1 .

7. A fiber structure obtained by stacking a plurality of nonwoven fabrics produced by a wet method, dispersing a polyimide precursor inside the stacked nonwoven fabrics, and then imidizing the polyimide precursor, Each of the plurality of nonwoven fabrics includes a plurality of fibers substantially made of a polyimide resin; The thickness of the fiber structure is 1 mm or more. Textile structure.

8. The fiber structure according to any one of claims 1 to 7 is provided. Thermal insulation material.

9. The fiber structure further includes a reflecting portion disposed on at least a portion of a surface thereof and configured to reflect radiant heat. The insulation material according to claim 8.

10. A storage section for storing an item is provided, The storage section includes: A first member having a placement surface on which the article is placed; A second member is disposed on the side of the placement surface of the first member and forms a space for accommodating the article together with the first member; Equipped with The second member has the fiber structure according to any one of claims 1 to 7. Containment device.

11. The storage section includes: an exhaust member for exhausting the gas inside the space to the outside of the space when the pressure of the gas inside the space becomes greater than a predetermined value; Further comprising:

11. The containment device of claim 10.

12. A container device according to claim 10; An electric storage device disposed inside the space of the accommodation device; Equipped with a battery.

13. A battery according to claim 12; a thrust generating device that generates thrust by utilizing the electric energy stored in the battery; An aircraft equipped with

14. A lamination step of laminating a plurality of nonwoven fabrics produced by a wet method to produce a laminate having a thickness of 1 mm or more; a dispersing step of dispersing a polyimide precursor inside the plurality of nonwoven fabrics constituting the laminate; an imidization step of imidizing the polyimide precursor; having Each of the plurality of nonwoven fabrics includes a plurality of fibers substantially made of a polyimide resin. A method for producing a fibrous structure.

15. The laminating step includes laminating the nonwoven fabrics such that a pressure applied to each of the nonwoven fabrics is less than 50 Pa; The dispersing step includes dispersing a polyimide precursor inside the nonwoven fabrics such that a pressure applied to each of the nonwoven fabrics is less than 50 Pa; The imidization step includes imidizing the polyimide precursor such that a pressure applied to each of the nonwoven fabrics is less than 50 Pa. A method for producing the fibrous structure of claim 14.

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