Abstract:
This flexible thermal-control material ( 10 A) is obtained by stacking: a reflective layer ( 12 ) which reflects sunlight; and an infrared-ray emission layer ( 13 ) which emits infrared rays. The infrared-ray emission layer ( 13 ) is configured from a radiation-crosslinked fluororesin material. Accordingly, a flexible thermal-control material is achieved which satisfies all of a plurality of conditions related to solar absorption (α), total hemispheric infrared ray emissivity (ε), radiation resistance, and atomic oxygen resistance.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a flexible thermal-control material and a production method therefor. 
       BACKGROUND ART 
       [0002]    In order to prevent an increase in temperature of an airframe due to incidence of solar light, a surface of an artificial satellite or a rocket used in space is coated with a thermal-control material having a function of reflecting the solar light and radiating thermal energy of the solar light to space. 
         [0003]    A flexible thermal-control material, a so-called flexible optical solar reflector (OSR), having flexibility which is easily processed according to a surface shape of the airframe or a structure to be coated, is paid attention as the thermal-control material. 
         [0004]    PTL 1 discloses a flexible thermal-control material including a metal layer on a polyimide film. In PTL 1, the surface of the polyimide film is subjected to roughening treatment, and accordingly secondary reflection of solar light is prevented and reflectivity and diffuseness are improved. 
       CITATION LIST 
     Patent Literature 
       [0005]    [PTL 1] Japanese Unexamined Patent Application Publication No. 2007-253399 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    According to the findings of the inventors, in a flexible thermal-control material, it is required that all conditions of a low solar absorptance coefficient (a), a high total semi-sphere infrared emissivity (s), high tolerance to radiation, and high tolerance to atomic oxygen in space are satisfied, in order to realize long-term use in space. However, the flexible thermal-control material disclosed in PTL 1 does not satisfy all conditions described above. 
         [0007]    Accordingly, it is desired to realize a flexible thermal-control material which satisfies all conditions described above. 
         [0008]    The present invention has been made to address the aforementioned problems and provides a flexible thermal-control material which satisfies all of a solar absorptance coefficient (α), a total semi-sphere infrared emissivity (ε), radiation resistance, and high tolerance to atomic oxygen in space, and a production method therefor. 
       Solution to Problem 
       [0009]    The invention provides a flexible thermal-control material which is formed by laminating: a reflection layer which reflects solar light; and an infrared radiation layer which radiates infrared light, in which the infrared radiation layer is configured with a radiation crosslinked fluorine resin material. 
         [0010]    In the flexible thermal-control material, it is preferable that a support layer is further laminated on a surface of the reflection layer on the side opposite to the surface where the infrared radiation layer is laminated. 
         [0011]    In the flexible thermal-control material, it is preferable that a protection layer is further laminated on a surface of the infrared radiation layer on the side opposite to the surface where the reflection layer is laminated. 
         [0012]    In the flexible thermal-control material, it is preferable that a conductive layer is further laminated on the protection layer. 
         [0013]    In the flexible thermal-control material, it is preferable that an antioxidant layer is further laminated on a surface of the reflection layer on the side opposite to the surface where the infrared radiation layer is laminated. 
         [0014]    In the flexible thermal-control material, it is preferable that the antioxidant layer is provided between the reflection layer and the support layer. 
         [0015]    In the flexible thermal-control material, it is preferable that the flexible thermal-control material is fixed to a surface of an adherend by a bonding layer. 
         [0016]    In the flexible thermal-control material, it is preferable that the flexible thermal-control material is fixed to a surface of an adherend by a fastening member. 
         [0017]    In the flexible thermal-control material, it is preferable that the adherend is a propellant tank of a rocket or an artificial satellite used in space. 
         [0018]    In the flexible thermal-control material, it is preferable that the propellant tank is a liquid hydrogen tank. 
         [0019]    In the flexible thermal-control material, it is preferable that a surface of the adherend is any one of a polyisocyanurate foam (PIF) heat insulating layer and a polyimide foam heat insulating layer or a heat insulating layer of a laminated body thereof. 
         [0020]    In the flexible thermal-control material, it is preferable that the surface of the adherend includes a degassing groove in any one of a polyisocyanurate foam (PIF) heat insulating layer and a polyimide foam heat insulating layer or a heat insulating layer of a laminated body thereof. 
         [0021]    The invention provides a production method for a flexible thermal-control material which is formed by laminating at least a reflection layer and an infrared radiation layer and in which the infrared radiation layer is configured with a radiation crosslinked fluorine resin, the method including: a radiation crosslinking step of performing crosslinking of a fluorine resin by emitting radioactive rays and forming the infrared radiation layer; and a step of forming the reflection layer by laminating a metal film on the surface of the infrared radiation layer obtained in the radiation crosslinking step. 
         [0022]    In the production method, it is preferable that the production method further includes an antioxidant layer formation step of further laminating an antioxidant layer on the surface of the reflection layer. 
         [0023]    The invention provides a production method for a flexible thermal-control material which is formed by laminating a support layer, a reflection layer, and an infrared radiation layer and in which the infrared radiation layer is configured with a radiation crosslinked fluorine resin, the method including: a radiation crosslinking step of performing crosslinking of a fluorine resin by emitting radioactive rays and forming the infrared radiation layer; and a laminated body formation step of forming the reflection layer by laminating a metal film on the support layer and forming a laminated body by laminating a fluorine resin which is not yet subjected to radiation crosslinking on the reflection layer, before the radiation crosslinking step. 
         [0024]    In the production method, it is preferable that the support layer is formed with a polyimide material or a polyester material. 
         [0025]    In the production method, it is preferable that the metal film is formed by vapor deposition. 
       Advantageous Effects of Invention 
       [0026]    The invention exhibits an effect of providing a flexible thermal-control material which satisfies all of a solar absorptance coefficient (α), a total semi-sphere infrared emissivity (ε), radiation resistance, and high tolerance to atomic oxygen in space, and a production method therefor. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]      FIG. 1  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 1. 
           [0028]      FIG. 2  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 2. 
           [0029]      FIG. 3  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 3. 
           [0030]      FIG. 4  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 4. 
           [0031]      FIG. 5  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 5. 
           [0032]      FIG. 6  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 6. 
           [0033]      FIG. 7  is a schematic view showing an example of applying the flexible thermal-control material on an adherend. 
           [0034]      FIG. 8  is an enlarged schematic sectional view showing an enlarged A part of  FIG. 7 . 
           [0035]      FIG. 9  is an enlarged schematic sectional view showing an enlarged A part of  FIG. 7 . 
           [0036]      FIG. 10  is an enlarged schematic sectional view showing an enlarged A part of  FIG. 7 . 
           [0037]      FIG. 11  is a diagram showing an example of a schematic view of a rocket. 
           [0038]      FIG. 12A  is a sectional view in a longitudinal direction of a flexible thermal-control material which is applied on a liquid hydrogen tank. 
           [0039]      FIG. 12B  is a B-B line sectional view of  FIG. 12A . 
           [0040]      FIG. 13  is a sectional view of another flexible thermal-control material of the example which is applied on a liquid hydrogen tank. 
           [0041]      FIG. 14  is a schematic view showing an example of a first production method for a flexible thermal-control material. 
           [0042]      FIG. 15  is a schematic view showing an example of a second production method for a flexible thermal-control material. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0043]    Hereinafter, the invention will be described with reference to the accompanied drawings. The invention is not limited to the following embodiments or examples. In addition, constituent elements of the following embodiments or examples include constituent elements which can be and are easily replaced by a person skilled in the art, or the same constituent elements. 
       Example 1 
       [0044]      FIG. 1  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 1. As shown in  FIG. 1 , a flexible thermal-control material  10 A according to the example includes a reflection layer  12  and an infrared radiation layer  13 . In the example of  FIG. 1 , the reflection layer  12  is provided on an adherend side (lower side of the drawing) and the infrared radiation layer  13  is provided on the outer side (upper side of the drawing) of the reflection layer  12 . That is, in the example of the drawing, the reflection layer  12  is provided on an airframe side  20  which is the adherend and the infrared radiation layer  13  is provided as a surface of a space side  21 . That is, in this example, the infrared radiation layer  13  is set as a layer exposed to space. 
       &lt;Reflection Layer&gt; 
       [0045]    The reflection layer  12  is preferably a high-reflectivity material layer. Accordingly, it is possible to reduce heat input to the airframe, by reflecting solar light. Herein, the high-reflectivity material layer is a layer configured with a material which is generally called high-reflectivity metal. As specific examples of such high-reflectivity metal, silver (Ag), aluminum (Al), and gold (Au) can be used, for example, but the specific examples are not limited thereto. In addition, as the high-reflectivity metal, an alloy or various composite materials can be used, in addition to the simple substance of metal elements. 
       &lt;Infrared Radiation Layer&gt; 
       [0046]    The infrared radiation layer  13  is a layer having a function of radiating heat to space without absorbing solar light which is reflected by the reflection layer  12 . Since space is in a vacuum state without oxygen, heat transfer due to radiation which does not require a heat transfer medium, is dominantly performed. It is important to efficiently radiate heat of the airframe to space. 
         [0047]    The infrared radiation layer  13  is a layer configured with a radiation crosslinked fluorine resin. As the fluorine resin, a simple substance or a mixture of fluorine resins such as a tetrafluoroethylene propylenehexafluoride copolymer (FEP), a tetrafluoroethylene.perfluoroalkylvinyl ether copolymer (PFA), and polytetrafluoroethylene (PTEE) can be used as an original material. In addition, ionizing radioactive rays such as a γ ray, an X ray, or an electron ray is preferably used as a radial ray. The original materials such as FEP or PFA are irradiated with ionizing radioactive rays having dose of several tens KGy to 200 KGy in a temperature range which is equal to or higher than a crystalline melting point thereof, that is, 20° C. higher than the crystalline melting point, and in an inert gas atmosphere of nitrogen or argon, and accordingly, it is possible to obtain a radiation crosslinked fluorine resin having improved transparency and improved radiation resistance or heat resistance and mechanical properties. 
         [0048]    By using the radiation crosslinked fluorine resin as the infrared radiation layer  13 , it is possible to ensure sufficient transparency for solar light to be incident to the reflection layer  12  and to ensure radioactive properties for radiating heat energy of solar light to space. In addition, the radiation crosslinked fluorine resin has excellent radiation resistance and resistance to atomic oxygen, and accordingly, it is possible to realize a flexible thermal-control material which hardly causes performance degradation due to the space environment, by using the radiation crosslinked fluorine resin as the infrared radiation layer  13 . 
         [0049]    A thickness of the infrared radiation layer  13  is preferably from 50 μm to 300 μm. In this range, excellent balance between a solar absorptance coefficient (α) and a total semi-sphere infrared emissivity (ε) is obtained. 
         [0050]    According to the configuration described above, it is possible to realize a flexible thermal-control material having excellent balance in which the solar absorptance coefficient (α) is equal to or less than 0.2 and the total semi-sphere infrared emissivity (ε) is equal to or greater than 0.8. By using a radiation crosslinked fluorine resin having excellent radiation resistance and resistance to atomic oxygen as the infrared radiation layer, it is possible to improve radiation resistance and resistance to atomic oxygen of the entire thermal-control material (thermal-control film) and to provide a flexible thermal-control material which hardly causes performance degradation in space. Although the control effect of an increase in temperature of the airframe decreases, it is also possible to set the thickness of the infrared radiation layer  13  to be smaller than 50 μm, if it is in an acceptable range in thermal design. 
         [0051]    According to the configuration described above, it is possible to provide a flexible thermal-control material which is excellently adhered to various structures which is an adherend. In addition, by setting a roll molded body by winding the sheet-like flexible thermal-control material around a core, it is possible to perform the application to an adherend having a cylindrical outer shape. 
       Example 2 
       [0052]      FIG. 2  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 2. As shown in  FIG. 2 , a flexible thermal-control material  10 B is formed by further laminating an antioxidant layer  14  on a surface of the reflection layer  12  on the side opposite to the surface where the infrared radiation layer  13  is laminated, in the flexible thermal-control material  10 A according to Example 1. That is, the antioxidant layer  14  is further provided on the lower side of the reflection layer  12  (lower side of the drawing), that is, the structure (airframe side  20  which is an adherend) side coated with the flexible thermal-control material  10 B. In the example, the same reference numerals are used for the same constituent elements as those in Example 1 and the description thereof will be omitted. 
         [0053]    The antioxidant layer  14 , for example, can be configured with a nickel-base superalloy (inconel or the like), chromium, nickel, and gold (vapor deposition on an aluminum surface). Among these, a nickel-base superalloy is particularly preferable, from viewpoints of anti-oxidation properties and corrosion resistance. 
         [0054]    According to the configuration described above, it is possible to further improve an anti-oxidation effect by atomic oxygen in space. In addition to the configuration of the embodiment, in a case of providing a support layer, the antioxidant layer is preferably provided between the reflection layer and the support layer. 
       Example 3 
       [0055]      FIG. 3  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 3. As shown in  FIG. 3 , a flexible thermal-control material  10 C is formed by further laminating a support layer  15  on a surface on the side opposite to the surface where the infrared radiation layer  13  is laminated, in the flexible thermal-control material  10 A according to Example 1. That is, the support layer  15  is further provided on the lower side of the reflection layer  12  (lower side of the drawing), that is, the structure (airframe side  20  which is an adherend) side coated with the flexible thermal-control material  100 . 
         [0056]    As will be described later, there are two methods of producing the flexible thermal-control material containing the radiation crosslinked fluorine resin as the infrared radiation layer  13 . That is, a first method of forming a radiation crosslinked fluorine resin and laminating the reflection layer  12  and the antioxidant layer  14  thereon and a second method of forming a necessary layer structure and performing radiation crosslinking of the fluorine resin are used. In a case of the previous first method, mechanical properties of the fluorine resin are improved by the radiation crosslinking, and accordingly it is easy to provide a metal layer on the fluorine resin. However, in a case of the latter second method, it is difficult to provide a metal layer on the uncrosslinked fluorine resin, and accordingly, a metal layer is formed on the support layer  15  and the fluorine resin is laminated thereon by heat sealing and then the fluorine resin is subjected to radiation crosslinking in the conditions described above, and therefore, it is suitable for producing the flexible thermal-control material. 
         [0057]    As the support layer  15 , it is preferable to use a polyimide material such as a polyimide resin from viewpoints of strength and heat resistance. Alternatively, a polyester material such as polyethylene-telephthalate (PET), which is a material having a function and an effect of preventing generation of cracks or tears on the reflection layer and the infrared radiation layer may be used. 
         [0058]    According to the configuration described above, it is possible to apply suitable hardness or strength to the flexible thermal-control material so as to be applied. Accordingly, it is possible to prevent generation of cracks on the reflection layer  12 , when attaching or bonding the flexible thermal-control material to a structure (airframe) such as a rocket or an artificial satellite. 
       Example 4 
       [0059]      FIG. 4  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 4. As shown in  FIG. 4 , a flexible thermal-control material  10 D is formed by further laminating a protection layer  16  on a surface of the infrared radiation layer  13  on the side opposite to the surface where the reflection layer  12  is laminated, in the flexible thermal-control material  10 C according to Example 3. That is, the protection layer  16  is further provided on the upper side of the infrared radiation layer  13  (upper side of the drawing), that is, on the space side  21 . 
         [0060]    The protection layer  16  preferably has a solar absorptance coefficient (a) in an acceptable range and a transparent protection layer is further preferable. 
         [0061]    The protection layer  16  provides a function and an effect of preventing surface contamination of the flexible thermal-control material. For example, when applying the flexible thermal-control material to a rocket, a propellant tank of the rocket becomes an adherend, and the outer surface of the propellant tank of the rocket is coated with the flexible thermal-control material. In this case, the protection layer  16  is provided on the surface of the infrared radiation layer  13  on the space side  21  so as to provide a function and an effect of preventing surface contamination or damage to the flexible thermal-control material  10 D from the application of the material to the rocket fire. 
         [0062]    As the protection layer  16 , it is preferable to configure silsesquioxane having higher resistance to atomic oxygen among the silicone materials. It is possible to obtain higher resistance to atomic oxygen, by coating the surface of the flexible thermal-control material with silsesquioxane. 
         [0063]    In addition, as the protection layer  16 , a hard coat material of a fluorine material can be used, for example, in order to prevent damage to the surface. 
         [0064]    Further, as the protection layer  16 , a resin material in which nanoparticles such as hollow silica are dispersed may be used, for example. As a result, a gas barrier layer or a heat-resistant barrier layer for preventing oxidative degradation due to aerodynamic heating at the time of the rocket fire is formed, and accordingly, it is possible to improve gas barrier properties or insulating performance. 
       Example 5 
       [0065]      FIG. 5  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 5. As shown in  FIG. 5 , a flexible thermal-control material  10 E is formed by further laminating a conductive layer  17  on the infrared radiation layer  13  in the flexible thermal-control material  10 C according to Example 3. That is, the conductive layer  17  is further provided on the surface of the infrared radiation layer  13 , that is, the outermost surface on the space side  21 . 
         [0066]    The conductive layer  17  has a function and an effect of preventing damage to the flexible thermal-control material  10 E due to an electric discharge. In addition, the conductive layer  17  is preferably a transparent conductive layer having transparency so as to allow solar light to be incident to the reflection layer. 
         [0067]    As the conductive layer  17 , a metal compound material having conductivity such as indium tin oxide (ITO), antimony tin oxide (ATO), or TiO 2  (titanium dioxide) doped with Nb, or carbon-based material such as carbon nanotube can be used. 
         [0068]    According to the configuration described above, it is possible to provide a flexible thermal-control material having reduced risk of damage due to an electric discharge. 
       Example 6 
       [0069]      FIG. 6  is a schematic sectional view showing a configuration example of a flexible thermal-control material according to Example 6. As shown in  FIG. 6 , a flexible thermal-control material  10 F is formed by further laminating the conductive layer  17  on the protection layer  16  in the flexible thermal-control material  10 D according to Example 5. That is, the conductive layer  17  is further provided on the surface of the protection layer  16 , that is, the outermost surface on the space side  21 . 
         [0070]    According to the configuration described above, it is possible to provide a flexible thermal-control material exhibiting a protection effect and having reduced risk of damage due to an electric discharge, by further providing the conductive layer  17  on the surface of the protection layer  16 . 
       Example 7 
     Application Example (1) of Flexible Thermal-Control Material 
       [0071]      FIG. 7  is a schematic view showing an example of applying the flexible thermal-control material on an adherend. In the example of the drawing, an adherend is a propellant tank (for example, liquid hydrogen tank) of a rocket.  FIGS. 8 to 10  are enlarged schematic sectional views showing an enlarged A part of  FIG. 7 . 
         [0072]    In the example of the laminated body shown in  FIG. 7 , a surface of a tank main body  30   a  of a propellant tank  30  such as a liquid hydrogen tank is coated with the flexible thermal-control material  100  according to Example 3. Herein, a polyisocyanurate foam (PIF) heat insulating layer (hereinafter, referred to as a “PIF heat insulating layer”)  31  is formed on the surface of the propellant tank and the flexible thermal-control material  100  is applied to the surface thereof. 
         [0073]      FIG. 8  is a diagram specifically illustrating a relationship between the surface of the propellant tank of  FIG. 7 , that is, the PIF heat insulating layer  31 , and the flexible thermal-control material  100 . As shown in  FIG. 8 , the flexible thermal-control material  100  in which the reflection layer  12  is laminated on the support layer  15  and the infrared radiation layer  13  is further laminated on the surface thereof, is adhered onto the PIF heat insulating layer  31  through a bonding layer  18  and covers the tank main body  30   a.    
         [0074]    The bonding layer  18  is a layer configured with a pressure sensitive adhesive or an adhesive, for example. As a pressure sensitive adhesive or an adhesive, a material which hardly causes generation of gas in a vacuum environment as in space is preferable. 
         [0075]    In the embodiment, the flexible thermal-control material  10 C is adhered to the PIF heat insulating layer on the surface of the liquid hydrogen tank by the bonding layer  18 , but the flexible thermal-control material  10 C can also be adhered to the surface of the liquid hydrogen tank by a fastening member. As the fastening member, a fastener for fastening and fixing a component to another component can be used, for example. A rivet can be used, for example, as the fastener. 
         [0076]      FIG. 9  is a diagram in which the flexible thermal-control material  10  ( 10 A to  10 F) is provided by the bonding layer  18  using a polyimide foam heat insulating layer  61 , instead of the PIF heat insulating layer  31  of  FIG. 8 . The polyimide foam heat insulating layer  61  is a foam in which air bubbles have an open-cell structure and exhibits an effect of vacuum insulation. A thickness of the polyimide foam heat insulating layer  61  is, for example, preferably approximately from 10 mm to 50 mm. 
         [0077]      FIG. 10  is a diagram in which the flexible thermal-control material  10  ( 10 A to  10 F) is provided on a heat insulating layer  62  having a laminated body structure of two layers which are the PIF heat insulating layer  31  of  FIG. 8  and the polyimide foam heat insulating layer  61 . 
         [0078]    The polyimide foam heat insulating layer  61  is a foam in which air bubbles have an open-cell structure and exhibits an effect of vacuum insulation. A thickness of the heat insulating layer  62  of two layers which are the PIF heat insulating layer  31  and the polyimide foam heat insulating layer  61  is, for example, preferably approximately from 10 mm to 50 mm. 
         [0079]    In the example, the PIF heat insulating layer  31  is provided on the tank main body  30   a  side, but the polyimide foam heat insulating layer  61  side may be set as the tank main body  30   a  side and the PIF heat insulating layer  31  may be provided on the upper layer thereof. 
       Example 8 
     Application Example (2) of Flexible Thermal-Control Material 
       [0080]      FIG. 11  is a diagram showing an example of a schematic view of a rocket. As shown in  FIG. 11 , a satellite  73  is provided on a head portion side of a liquid hydrogen tank  71  which is a propellant tank through a pedestal  72 . A liquid oxygen tank  75  is provided on a rear side of the liquid hydrogen tank  71  through a rod  74  and performs a supply operation to an engine  76  side. 
         [0081]      FIG. 12A  is a sectional view in a longitudinal direction of a flexible thermal-control material which is applied on a liquid hydrogen tank and  FIG. 12B  is a B-B line sectional view of  FIG. 12A . 
         [0082]    In the example, the PIF heat insulating layer  31  is formed on the surface of the liquid hydrogen tank  71  and the flexible thermal-control material  10  ( 10 A to  10 F) according to Examples described above is coated on the surface of the PIF heat insulating layer  31 . The flexible thermal-control material  10  ( 10 A to  10 F) is the same material as in examples 1 to 6 and the description thereof will be omitted. 
         [0083]    In the example, a degassing groove  32  is formed along an axial direction of the PIF heat insulating layer  31  and perform degassing of exhaust gas (for example, low molecular component)  33  generated in the PIF heat insulating layer  31 . 
         [0084]    Accordingly, negative effects such as vapor deposition due to exhaust gas  33  on the flexible thermal-control material  10  ( 10 A to  10 F) formed on the surface of the PIF heat insulating layer  31  or the satellite  73  are prevented and the satellite  73  is protected. 
         [0085]      FIG. 13  is a sectional view of another flexible thermal-control material of the example which is applied on a liquid hydrogen tank. 
         [0086]    In the example, the heat insulating layer  62  having a two-layered structure of the PIF heat insulating layer and the polyimide foam heat insulating layer  61  is provided on the surface of the tank main body  30   a  of the liquid hydrogen tank  71  and the flexible thermal-control material  10  ( 10 A to  10 F) according to Examples described above is coated on the surface of the heat insulating layer  62  having a two-layered structure. 
         [0087]    In the example, the degassing groove  32  is continuously formed along an axial direction of in a boundary between the PIF heat insulating layer  31  and the polyimide foam heat insulating layer  61  and performs degassing of exhaust gas (for example, low molecular component)  33  generated in the heat insulating layer  62 . The degassing groove  32  is formed by setting a boundary surface between the PIF heat insulating layer  31  and the polyimide foam heat insulating layer  61  as an approximate gear wheel structure, but the invention is not limited thereto. 
         [0088]    As described above, it is possible to suitably realize heat insulation in space which was insufficiently realized with only the PIF heat insulating layer, by coating the outer surface of the propellant tank of the rocket with the flexible thermal-control material according to the invention. In the related art, in a structure used in space such as a rocket or an artificial satellite, heat input from the outside is prevented by the PIF heat insulating layer and evaporation of liquid hydrogen which is propellant is prevented, but in space in a vacuum state without oxygen, heat input due to radiation is dominantly performed and sufficient heat insulating performance cannot be obtained with only the PIF heat insulating layer. It is possible to prevent problems regarding heat input due to radiation in space to improve heat insulating performance, by further coating the PIF surface with the flexible thermal-control material according to the invention. 
       Example 9 
     Production Example 1 of Flexible Thermal-Control Material 
       [0089]      FIG. 14  is a schematic view showing an example of a first production method for a flexible thermal-control material. Hereinafter, the production method for the flexible thermal-control material will be described with reference to  FIG. 14 . 
         [0090]    In Step S 102 , a light-adhesion laminated body in which a FEP resin  42  is laminated on a polyimide resin sheet which is a support structure  41  is prepared. The light-adhesion means laminating at a degree of adhesion so as to peel the FEP resin  42  off from the support structure after radiation crosslinking. Such a light-adhesion laminated body can be obtained by heat sealing or plasma treatment. 
         [0091]    In Step S 104 , the light-adhesion laminated body laminated in Step S 102  is subjected to crosslinking under the following conditions using ionizing radioactive rays  45 . The FEP resin  42  is peeled off from the support structure  41  after the crosslinking. 
       (Crosslinking Conditions) 
       [0092]    Crosslinking temperature: from 260° C. to 280° C. 
         [0093]    Ionizing radioactive ray: electron ray 
         [0094]    Dose: several tens KGy to 200 KGy 
         [0095]    Crosslinking atmosphere: inert gas atmosphere (argon or nitrogen) 
         [0096]    In Step S 106 , a metal film which is a reflection layer  43  is formed on the surface of the FEP resin  42  which is peeled off from the support structure  41  after the crosslinking in Step S 104 . The metal film can be formed by accumulating high-reflectivity metal such as aluminum or silver by a vapor deposition method. 
         [0097]    In Step S 108 , an antioxidant layer  44  is formed on the reflection layer  43  which is formed in Step S 106 . The antioxidant layer  44 , for example, can be formed by a method of chemically or physically accumulating a nickel-base superalloy (inconel the like) thin film, or a method of adhering a nickel-base superalloy thin film on the reflection layer  43 . 
         [0098]    In the flexible thermal-control material formed by the example, the FEP resin  42  which is a radiation crosslinked fluorine resin becomes an infrared radiation layer and a layer on the space side  21 , and the antioxidant layer  44  becomes the airframe side  20 . 
       Example 10 
     Production Example 2 of Flexible Thermal-Control Material 
       [0099]      FIG. 15  is a schematic view showing an example of a second production method for a flexible thermal-control material. Hereinafter, the production method for the flexible thermal-control material will be described with reference to  FIG. 15 . The description overlapping with that in Example 9 will be suitably omitted. 
         [0100]    In Step S 202 , a metal film which is a reflection layer  52  is formed on an upper surface of a support layer  51  formed of a polyimide resin film. The metal film can be formed by accumulating high-reflectivity metal such as aluminum or silver by a vapor deposition method. In addition, a FEP resin  53  which is a fluorine resin which is not yet subjected to radiation crosslinking is laminated on the upper surface of the reflection layer  52  to form a laminated body. The FEP resin  53  can be laminated on the surface of the reflection layer  52  by heat sealing. 
         [0101]    In Step S 204 , the laminated body formed in Step S 202  is subjected to crosslinking under the following conditions using ionizing radioactive rays  55 . 
       (Crosslinking Conditions) 
       [0102]    Crosslinking temperature: from 260° C. to 280° C. 
         [0103]    Ionizing radioactive ray: electron ray 
         [0104]    Dose: several tens KGy to 200 KGy 
         [0105]    Crosslinking atmosphere: inert gas atmosphere (argon or nitrogen) 
         [0106]    In Step S 206 , a flexible thermal-control material containing the radiation crosslinked FEP resin  53  as an infrared radiation layer is obtained. In the flexible thermal-control material formed by the example, the support layer  51  formed of a polyimide resin film becomes a layer on the airframe side  20 , and the FEP resin  53  which is the radiation crosslinked fluorine resin becomes an infrared radiation layer and a layer on the space side  21 . 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               10  ( 10 A to  10 F) Flexible thermal-control material 
               12  Reflection layer 
               13  Infrared radiation layer 
               14  Antioxidant layer 
               15  Support layer 
               17  Conductive layer 
               18  Bonding layer 
               20  Airframe side (adherend side) 
               21  Space side 
               30  Propellant tank (adherend) 
               31  PIF heat insulating layer (surface of propellant tank) 
               41  Support structure 
               42  FEP resin 
               43  Reflection layer 
               44  Antioxidant layer 
               51  Support layer 
               52  Reflection layer 
               53  FP resin 
               61  Polyimide foam heat insulating layer