Fibrous structure, heat insulation material, housing device, battery, flying body, and method for producing fibrous structure

Abstract

This fibrous structure includes a plurality of fibers made substantially of a polyimide resin. The proportion of the mass of the plurality of fibers with respect to the mass of the fibrous structure is at least 70 mass%. The thickness of the fibrous structure is at least 1 mm. The balance weight of the fibrous structure is 40-150 g / m2. The length of each of the plurality of fibers may be 1.0-10.0 mm. The width of each of the plurality of fibers may be 1-100 μm. The thermal conductivity of the fibrous structure as measured in accordance with JIS L 1927 may be 0.020-0.040 W / m·K.

Description

Fiber structure, thermal insulation material, storage device, battery, aircraft, and method for producing a fiber structure

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

[0002] Patent Documents 1 and 2 disclose polyimide fiber paper obtained by collecting and pressing fibers made of a non-thermoplastic polyimide resin. [Prior art documents] [Patent documents] [Patent document 1] JP 2019-035157 A [Patent document 2] JP 2023-051247 A General disclosure

[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 150g / m or more ２ The polyimide resin may be a non-thermoplastic polyimide resin, and the ratio of the mass of the non-thermoplastic polyimide resin to the mass of the plurality of fibers may be 70% or more.

[0004] In any of the above-described 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-described 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-mentioned fiber structures may have a film-like, sheet-like, or plate-like shape. In any of the above-mentioned 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-mentioned fiber structures, in a cross section of the fiber structure observed using a scanning electron microscope, the ratio of the number of second fibers to the number of first fibers may be less than 30%.

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

[0007] In any of the above-described fiber structures, the thermal conductivity of the fiber structure estimated from the heater's RMS power required to maintain the temperature of a thermocouple located at the center of an MB-type aluminum case placed in a second environment where the pressure is 5 kPa and the temperature is −60°C between 20°C and 30°C may be 0.005 W / m·K or more and 0.030 W / m·K or less. The heater's RMS power is measured, for example, when the MB-type aluminum case is entirely covered with a fiber structure having an aluminum vapor-deposited layer on its surface. The thickness of the fiber structure used to measure the heater's RMS power is, for example, 9.0 mm. The thickness of the aluminum vapor-deposited layer used to measure the heater's RMS power is, for example, 150 nm. The dimensions of the MB-type aluminum case used to measure the heater's RMS power 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 can be obtained, for example, by stacking multiple nonwoven fabrics produced by a wet process, dispersing a polyimide precursor inside the stacked multiple nonwoven fabrics, and then imidizing the polyimide precursor. In the fiber structure, each of the multiple nonwoven fabrics contains, for example, multiple fibers substantially made of polyimide resin. The thickness of the fiber structure can be, for example, 1 mm or more. The ratio of the mass of the polyimide resin to the mass of the multiple fibers can be 70% or more.

[0009] In a third aspect of the present invention, there is provided a thermal insulating 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 the surface of the fiber structure, for example.

[0011] In a fourth aspect of the present invention, there is provided a storage device. 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 mounting surface on which the article is placed. In the storage device, the storage section includes, for example, a second member arranged on the side of the mounting surface 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-described 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 exceeds 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 storage device.

[0014] In a sixth aspect of the present invention, there is provided an aircraft, which includes, for example, the battery according to the fifth aspect, and which includes, for example, a thrust generating device that generates thrust using electrical energy stored in the battery.

[0015] In a seventh aspect of the present invention, there is provided a method for producing a fiber structure. The method includes, for example, a lamination step of laminating multiple nonwoven fabrics produced by a wet process 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 multiple nonwoven fabrics that constitute the laminate. The method includes, for example, an imidization step of imidizing the polyimide precursor. In the method, each of the multiple nonwoven fabrics includes, for example, multiple fibers substantially composed of a polyimide resin. The ratio of the mass of the polyimide resin to the mass of the multiple fibers may be 70% or more.

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

[0017] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions.

[0018] 1A and 1B schematically show an example of the system configuration of the aircraft 100. FIG. 1C schematically shows an example of a cross-sectional view of the storage battery 110. FIG. 1D schematically shows an example of a horizontal cross-sectional view of the storage battery 110. FIG. 1E schematically shows an example of a cross-section in the thickness direction of the heat insulating member 410. FIG. 1F schematically shows an example of a method for manufacturing the storage battery 110. FIG. 1G schematically shows an example of a method for manufacturing the heat insulating member 220.

[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 staple fiber substantially made of a polyimide resin. In this embodiment, the fiber structure includes the staple 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 150g / m or more ２ As a result, a lightweight material with excellent thermal insulation properties can be obtained. Furthermore, polyimide resins have excellent electrical insulation properties, heat resistance, cold resistance, heat resistance, chemical resistance, and mechanical properties. Therefore, the above-mentioned fiber structure has a composition, structure, and / or physical properties that are particularly suitable 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 referred to as VIPs) are sometimes used as insulation materials for thermal insulation devices. However, when a VIP is used as insulation material for a thermal insulation device mounted on a flying vehicle capable of flying in the stratosphere, residual air inside the VIP expands due to pressure fluctuations accompanying the ascent and descent of the flying vehicle, which may result in damage to the VIP. In particular, when a thermal insulation device is used to insulate a battery mounted on the flying vehicle, damage to the VIP of the thermal insulation device exposes the battery to an extremely low temperature environment, significantly reducing the charge / discharge characteristics of the battery.

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

[0023] In response to this, the present inventors have stacked a plurality of nonwoven fabrics produced by a wet method, dispersed a polyimide precursor inside the stacked 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, which is essentially composed of fibers made of polyimide resin as the main component. ２ 150g / m or more ２Furthermore, 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 above fiber structure has a basis weight of 40 g / m ２ 150g / m or more ２ or less, and is very lighter than the above-described VIP. In addition, since the above-described fiber structure is composed mainly of a polyimide resin, it can function not only as a thermal insulator but also as a fire-resistant material. That is, when a VIP is used as a thermal insulator for a battery, a separate fire-resistant material is required. However, when the above-described fiber structure is used as a thermal insulator for a battery, an additional fire-resistant material is not required or the mass of the additional fire-resistant material can be reduced. As a result, when the above-described fiber structure is used as a thermal insulator 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, it is possible to improve the amount of energy per mass in a rechargeable battery, thereby realizing a lighter rechargeable battery that can store more power. The rechargeable battery can be brought to a disaster site, for example, and used to supply energy to disaster victims. Therefore, the fiber structure, thermal insulation material, storage device, battery, and aircraft according to the present embodiment, as well as the manufacturing methods thereof, can contribute to the achievement of Goal 7 "Affordable and clean energy" or Goal 13 "Climate action" 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 as claimed. 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. Furthermore, "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 specified in the specification. Furthermore, the number of the above-mentioned substituents is not particularly limited unless otherwise specified in the specification.

[0028] (Overview of Air Vehicle 100) Fig. 1 shows a schematic diagram of an example of the system configuration of the air vehicle 100. In this embodiment, the air vehicle 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, 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 (this may be referred to as charging the power storage pack 112). The power storage pack 112 also releases the stored electric energy (this may be 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, even more preferably 500 Wh / kg-power storage pack] or more, still 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 electricity 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 - Storage pack] or less.

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

[0035] In this embodiment, the electric motor 130 receives electrical energy from the storage battery 110 via the power control circuit 120. The electric motor 130 uses the electrical energy received from the storage battery 110 to rotate the propeller 140. In this way, the electric motor 130 can generate propulsion force for the aircraft 100 using the electrical 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 air vehicle 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 air vehicle 100. The control device 160 may control the position and attitude of the air vehicle 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 article or a power storage device. The electric motor 130 may be an example of a propulsion force generating device.

[0039] (Another embodiment) In the present embodiment, the details of the aircraft 100 have been 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] (Outline of storage battery 110) An example of the storage battery 110 will be described using Figures 2 and 3. Figure 2 schematically shows an example of a cross-sectional view of the storage battery 110. Figure 3 schematically shows an example of a plan cross-sectional view of the storage battery 110. In this embodiment, Figure 2 shows an example of a B-B' cross section in Figure 3, and Figure 3 shows an example of an A-A' cross section in Figure 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, the base plate 210 and the heat insulating member 220 form an accommodation space 260 inside the heat insulating device 200 for accommodating the power storage pack 112.

[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 with 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 with an adhesive (not shown).

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

[0045] (Details of Heat 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 by, for example, 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, together with the heat insulating member 220, forms the accommodation space 260. As described above, the power storage pack 112 is disposed inside the accommodation space 260 of the heat insulating 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 disposed in contact with the mounting surface 212. In another embodiment, the power storage pack 112 is disposed on the mounting surface 212 via another member.

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

[0048] In this embodiment, the heat insulating member 220 suppresses heat transfer 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, sheet, or plate shape. The heat insulating member 220 is disposed on the mounting surface 212 side of the base plate 210. The heat insulating member 220 forms the storage space 260 together with the base plate 210. 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 portion 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 portion of one of the two surfaces of the heat insulating member 220 that is opposite to the surface on the side of the storage space 260. 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 vapor deposition layer, a metal vapor deposition film, and a laminate film. An example of the metal used in the above-mentioned 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 of 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. As a result, when a laminate film is used as the reflective member 230, the reflective member 230 can have enough strength 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, for example, by welding. The welding member 240 may also 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, for example, by 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 the power storage pack 112 therein. As described above, the heat insulating member 220 is disposed on the mounting surface 212 of the base plate 210, thereby forming the storage space 260 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 also be a fiber structure having a film-like, sheet-like or plate-like shape.

[0055] (Details of the fiber structure) (Composition of the fiber structure) The fiber structure includes a plurality of fibers. The mass ratio of the plurality of fibers to the mass of the fiber structure may be 70 mass% or more. The mass ratio of fibers having specific characteristics to the mass of the fiber structure may be 70 mass% or more. Details of the specific characteristics will be described later. The above ratio is preferably 80 mass% or more, more preferably 90 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. This ratio is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0057] The fibrous 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 fibrous structure may be less than 30% by mass. The mass ratio is preferably 15% by mass or less, more preferably 5% by mass or less.

[0058] (Fibers) 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 production process of the polyimide resin. The polyimide resin may be a non-thermoplastic polyimide resin.

[0059] The length of each of the plurality of fibers contained in the fiber structure may be 1.0 mm or more and 10.0 mm or less. The length of a fiber indicates the size of the fiber in the longitudinal direction. The mass ratio of 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 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.

[0061] The width of each of the plurality of fibers contained in the fiber structure may be 1 μm or more and 100 μm or less. The width of a fiber refers to 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 or more and 75 μm or less, more preferably 5 μm or more and 50 μm or less. When the fiber width falls within the above numerical range, the above-mentioned fiber structure exhibits excellent heat insulating properties. The above-mentioned 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 corresponding to the thickness of the polyimide film and the shaving width. Then, the bundle of polyimide fibers is cut. This results in short fibers 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 also 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 also be used as raw materials for the polyimide resin.

[0067] (Structure of Fiber Structure) The fiber structure has, for example, a film-like, sheet-like, or plate-like shape. The thickness of the 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 range, the fiber structure exhibits excellent thermal insulation properties. The above-mentioned fiber structure exhibits excellent thermal insulation properties, particularly in a stratospheric environment. The thermal insulation properties of the fiber structure will be described in detail below.

[0069] The fiber structure may be an assembly of the fibers. The fiber structure may be 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 nonwoven fabrics may contain a plurality of fibers.

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

[0071] According to the wet method, nonwoven fabrics are produced by a manufacturing method similar to that of paper. The wet method allows nonwoven fabrics to 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 above-mentioned fiber structure, multiple nonwoven fabrics produced by a wet method are laminated, and therefore the above-mentioned fiber structure contains the above-mentioned short fibers 222. The above-mentioned fiber structure may contain the above-mentioned pulp component (long fibers). The above-mentioned fiber structure may be substantially free of the above-mentioned pulp component. 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%. Note that the above-mentioned fiber structure may contain the above-mentioned pulp component or long fibers, or may be substantially free of the pulp component or long fibers.

[0073] When the thickness of the fiber structure is t, the width of the observation area under 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 this embodiment, the process for producing the fiber structure includes a step of dispersing a polyimide precursor inside a plurality of stacked nonwoven fabrics and then imidizing the polyimide precursor. As a result, the main failure mode of the fiber structure becomes a cohesive failure mode. In other words, even though a plurality of nonwoven fabrics are stacked in the process for producing the fiber structure, interfacial failure between the layers of the plurality of nonwoven fabrics is suppressed.

[0075] (Physical properties of fiber structure) The basis weight of the above fiber structure was 40 g / m ２ 150g / m or more 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 above fiber structure is preferably 40 g / m ２ 120g / m or more ２ More preferably, it is 40 g / m or less. ２ More than 100g / m ２The following are the results. When the basis weight of a fiber structure falls within the above numerical range, the fiber structure exhibits excellent thermal insulation properties. The above fiber structure exhibits excellent thermal insulation properties, particularly in a stratospheric environment. A fiber structure having a basis weight falling within the above numerical range is particularly suitable as a thermal insulation material for a thermal insulation device mounted on an aircraft capable of flying in the stratosphere.

[0077] (Thermal insulation properties of the fibrous structure) The fibrous structure constituting the heat insulating member 220 has excellent thermal insulation properties due to the novel configuration described above. Specifically, the above-mentioned fibrous 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 heater power value 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 at 20°C or higher and 30°C or lower is 0.005 W / m K or higher and 0.030 W / m K or lower. The estimated value of the thermal conductivity in the second environment is preferably 0.010 W / m K or higher and 0.020 W / m K or lower, and more preferably 0.012 W / m K or higher and 0.018 W / m K or lower.

[0080] (Procedure for estimating thermal conductivity in a stratospheric environment) The estimated value of the thermal conductivity of a fiber structure in the second environment above indicates the estimated value of the thermal conductivity of a 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 low, the thermal conductivity of a fiber structure cannot be measured in accordance with JIS L 1927. Therefore, in this embodiment, the thermal conductivity of a fiber structure in a stratospheric environment is estimated by the following procedure.

[0081] First, an MB-type aluminum case (MB14-6-14, manufactured by Takachi Electric Industrial Co., Ltd.) 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 5.4 Ω film heater (MINCO HK5417R5.3L12B) is installed inside the MB-type aluminum case. The heater is installed near the center of the bottom surface of the MB-type aluminum case. Also, 12 thermistors (RS PRO 827-5937) are installed inside the MB-type aluminum case. The thermistors are located at each of the eight corners of the MB-type aluminum case, two locations near the center of the top surface of the MB-type aluminum case, on the heater, and approximately at the center inside the MB-type aluminum case. The thermistor located approximately at the center inside the MB-type aluminum case is, for example, suspended from the top surface of the MB-type aluminum case. One of the two thermistors located near the center of the top surface is used, for example, to control the film heater. The output of the thermistor located approximately at the center inside the case is used, for example, to calculate the effective power value of the film heater.

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

[0084] Next, the 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. A voltage of 10.5 V is applied to the heater, and measurement of the heater's current value begins. A digital temperature controller (MITSUMI MTCTR) is used to control the heater's operation so that the heater turns on when the temperature measured by a thermistor installed at approximately the center inside the MB-type aluminum case falls below 20°C and turns off when the temperature falls below 30°C. The digital temperature controller is then used to measure the heater's output time until the heater's ON / OFF cycle becomes approximately constant. Based on the above measurement results, the effective heater power value is calculated under conditions of a pressure of 100 kPa and a temperature of -60°C.

[0086] Next, while maintaining the temperature inside the thermostatic chamber at -60°C, the pressure inside the thermostatic chamber is adjusted to a pressure equivalent to an altitude of 60,000 feet (specifically, 5 kPa). While adjusting the pressure inside the thermostatic chamber, a voltage of 10.5 V is left applied to the heater, and measurement of the heater's current value begins. Furthermore, using a digital temperature controller (Misumi MTCTR), the heater's operation is controlled so that it turns on when the temperature measured by a thermistor installed at approximately the center inside the MB-type aluminum case falls below 20°C and turns off when the temperature falls below 30°C. The digital temperature controller is then used to measure the heater's output time until the heater's ON / OFF cycle becomes approximately constant. Furthermore, based on the above measurement results, the effective heater power value under conditions of a pressure of 5 kPa and a temperature of -60°C is derived.

[0087] Next, the heater's RMS power value (sometimes referred to as the first RMS 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 RMS power value (sometimes referred to as the second RMS power value) in an environment where the pressure is 5 kPa and the temperature is −60° C. (the second environment described above). Furthermore, based on the 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 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 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 item 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 reflecting member 230 may be an example of a reflecting section. The combination of the heat insulating member 220 and the reflecting member 230 may be an example of a heat insulating material.

[0090] (Another embodiment) In the present embodiment, the details of the heat insulating device 200 have been described using as an example a case in which the base plate 210 and the reflective member 230 are welded together 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 schematically shows 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 process or a nonwoven fabric made by a wet process. In another embodiment, at least one of the one or more polyimide layers 420 may be the fibrous structure described above or may be a layer including the fibrous structure described above. In yet another embodiment, at least one of the one or more polyimide layers 420 may be a polyimide resin foam.

[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 for the nonwoven fabric include glass fiber, ceramic fiber, polyimide fiber, and aramid fiber.

[0094] (Method of Manufacturing Storage Battery 110) FIG. 5 schematically illustrates an example of a method of manufacturing 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. Thereafter, 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. Furthermore, the heat insulating member 220 is arranged on the mounting surface 212 side 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 to 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 for manufacturing the heat insulating member 220) Fig. 6 shows an example of a method for manufacturing the heat insulating member 220. Fig. 6 may be an example of S514 in Fig. 5 .

[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-described polyimide resin shaving 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 in the shaving step are then cut into lengths 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 a fleece) containing polyimide resin staple fibers as a main component. The fleece may be a nonwoven fabric produced by a wet method (sometimes called a wet-laid nonwoven fabric).

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

[0100] First, in the slurry formation process, water, a water-soluble polymer compound, and polyimide resin staple fibers are mixed to produce a slurry in which the polyimide resin staple fibers are dispersed in water. The slurry may contain various additives used in the production of paper or wetlaid nonwoven fabrics. Examples of such additives include dispersants, antifoaming agents, and viscosity modifiers. Next, in the papermaking process, the slurry is processed using known papermaking techniques to produce a wetlaid nonwoven fabric (sometimes referred to as temporary binding paper, fiber web, fleece, etc.) in which the polyimide resin staple fibers are temporarily bound using the water-soluble polymer as a binder. The thickness of the temporary binding paper obtained in the papermaking process is, for example, 1.0 mm or less.

[0101] The water-soluble polymer compound is not particularly limited as long as it is water-soluble and has a decomposition temperature lower than the glass transition point of polyimide. 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 interior of the laminate in which the plurality of temporary tape sheets are stacked is impregnated with a polyimide precursor solution, thereby obtaining a laminate of temporary tape sheets 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 using as an example a case where a laminate is produced by stacking a plurality of temporary tacking papers in S622, and then the interior 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 interior of each of a plurality of temporary tacking papers with a polyimide precursor solution, and then stacking the plurality of temporary tacking 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 obtained by replacing the solvent with a solvent different from that used in the polymerization after condensation polymerization.

[0105] Next, in S626, the polyimide precursor dispersed within 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 polyimide resin short fibers 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 tacking paper. Furthermore, the multiple temporary tacking 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 composed primarily of polyimide resin is obtained. Furthermore, according to the above procedure, a fiber structure whose main failure mode is cohesive failure is obtained.

[0107] (Pressure Applied to Temporarily Tacked Sheet) In S622, various settings may be adjusted so that the pressure applied to the temporarily tacked sheet is less than 50 Pa. This allows the sheet to be taut when the basis weight is 40 g / m ２ 150g / m or more２ In at least one of S622, S624, and S626, various settings may be adjusted so that the pressure applied to the temporary tacking 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 or less. ２ 150g / m or more ２ The thermal insulation member 220 can be produced having the following fibrous structure: When the pressure applied to the temporary tacking paper or laminate in steps S622, S624, and S626 is less than 50 Pa, a low-basis-weight fibrous structure is produced. A low-basis-weight fibrous structure has properties that make it 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.

[0109] To more specifically describe the storage battery 110 or the heat insulating member 220, the storage battery 110 or the heat insulating member 220 will be described in detail using 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 DuPont-Toray Co., Ltd.) was wound into a roll to prepare a polyimide film roll. The thickness of the polyimide film was 25 μm. Following the procedure described above, short fibers of polyimide resin were scraped from the polyimide film roll. The average length (by number) of the short fibers measured using a Canadian Standard Freeness Tester (JIS P 8226-2:2011) was 3 mm. Similarly, the average width (by number) of the short fibers measured by observation with an optical microscope was 50 μm.

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

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

[0113] Next, a polyimide precursor solution was prepared and the entire laminate was immersed in it, thereby obtaining a laminate in which the polyimide precursor was dispersed.

[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 a polyimide resin as a main component was obtained.

[0115] (Thickness) Using a dial thickness gauge (H type), the thickness of the fiber structure obtained in Example 1 was measured. As shown in Table 1, the thickness of the fiber structure obtained in Example 1 was 9 mm.

[0116] (Weight) 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 the same as the area of ​​the sheet described above, 200 mm × 300 mm. 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 under first environment) The thermal conductivity of the fiber structure obtained in Example 1 under 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 under the first environment was 0.03 W / m K.

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

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

[0120] Next, the effective heater power value under the first environment was measured. Specifically, first, the pressure inside the thermostatic chamber was adjusted to 100 kPa. 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 heater current value was initiated. Using the digital temperature controller, the heater was controlled so that the heater turned ON when the temperature measured by a thermistor installed at approximately the center inside the MB-type aluminum case fell below 20°C, and the heater turned OFF when the temperature fell below 30°C. The heater output time was then measured using the digital temperature controller until the heater's ON / OFF cycle became approximately constant.

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

[0122] Next, the effective heater power value under the second environment was measured. Specifically, the effective heater power value under the second environment was measured using the same procedure as for the effective heater power value under 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 under the second environment was 9.7 W.

[0123] The thermal conductivity of the fibrous 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 fibrous 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 Corporation) was prepared instead of producing a fiber structure. The measurement results and estimation results are shown in Table 1. The catalog values ​​for 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 10 mm thick vacuum insulation panel (U-Vacua series TZB9830E, manufactured by Panasonic Corporation) was prepared instead of producing a fiber structure. The measurement results and estimation results are shown in Table 1. The catalog values ​​for the thickness and weight of the vacuum insulation panel are also shown in Table 1. The above vacuum insulation panel had substantially no remaining air and was not damaged even in the second environment.

[0126]

[0127] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within 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," "prior to," etc., and that the processes can 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, this does not mean that the processes must be performed in this order.

[0129] 100 Aircraft, 110 Storage battery, 112 Power storage pack, 120 Power control circuit, 130 Motor, 140 Propeller, 150 Sensor, 160 Control device, 200 Heat insulation device, 210 Base plate, 212 Mounting surface, 214 Vent valve, 220 Heat insulation member, 222 Short fiber, 224 Short fiber, 230 Reflective member, 240 Welding member, 260 Storage space, 410 Heat insulation member, 420 Polyimide layer, 430 Aerogel layer

Claims

1. A fiber structure comprising a plurality of fibers substantially made of a polyimide resin, wherein the 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, and the basis weight of the fiber structure is 40 g / m ２ 150g / m or more ２ The following is a fiber structure.

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

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

4. The fiber structure of claim 1, wherein the fiber structure has a film-like, sheet-like or plate-like shape, the plurality of fibers include first fibers whose length direction is arranged in a direction approximately parallel to the in-plane direction of the fiber structure, and second fibers whose length direction is arranged in a direction approximately parallel to the thickness direction of the fiber structure, and in a cross-section of the fiber structure observed using a scanning electron microscope, the ratio of the number of second fibers to the number of first fibers is less than 30%.

5. The fiber structure according to claim 1, wherein 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.

6. The fiber structure according to claim 1, wherein the thermal conductivity of the fiber structure estimated from the heater effective power value required to maintain the temperature of a thermocouple placed in the center of the interior of an MB-type aluminum case placed 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 heater effective power value is measured in a state where the entire MB-type aluminum case is covered with the fiber structure having an aluminum vapor deposition layer on its surface, the fiber structure used in measuring the heater effective power value has a thickness of 9.0 mm, the aluminum vapor deposition layer used in measuring the heater effective power value has a thickness of 150 nm, and the MB-type aluminum case used in measuring the heater effective power value has dimensions of length 140 mm, width 60 mm and height 140 mm.

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, wherein each of the plurality of nonwoven fabrics contains a plurality of fibers substantially made of a polyimide resin, and the thickness of the fiber structure is 1 mm or more.

8. A thermal insulation material comprising the fiber structure according to any one of claims 1 to 7.

9. The heat insulating material according to claim 8, further comprising a reflective portion arranged on at least a portion of the surface of the fiber structure and reflecting radiant heat.

10. A storage device comprising a storage section for storing an item, the storage section comprising: a first member having a placement surface on which the item is placed; and a second member arranged on the side of the placement surface of the first member and forming, together with the first member, a space for storing the item, the second member having a fiber structure described in any one of claims 1 to 7.

11. The storage device according to claim 10, further comprising: 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.

12. A battery comprising: a storage device according to claim 10; and a power storage device disposed inside the space of the storage device.

13. An aircraft comprising: the battery according to claim 12; and a thrust generating device that generates thrust by utilizing the electrical energy stored in the battery.

14. A method for producing a fiber structure, comprising: 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 dispersion step of dispersing a polyimide precursor inside the plurality of nonwoven fabrics constituting the laminate; and an imidization step of imidizing the polyimide precursor, wherein each of the plurality of nonwoven fabrics contains a plurality of fibers substantially made of a polyimide resin.

15. The method for producing a fiber structure according to claim 14, wherein the laminating step includes a step of laminating the plurality of nonwoven fabrics such that a pressure applied to each of the plurality of nonwoven fabrics is less than 50 Pa; the dispersing step includes a step of 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; and the imidizing step includes a step of imidizing the polyimide precursor such that a pressure applied to each of the plurality of nonwoven fabrics is less than 50 Pa.

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