Patent Publication Number: US-2023150750-A1

Title: Vacuum insulation material, and thermally insulating container and thermally insulating wall using same

Description:
TECHNICAL FIELD 
     The present disclosure relates to a vacuum heat insulator, and a heat insulating container and a heat insulating wall using the vacuum heat insulator. 
     BACKGROUND ART 
     PTL 1 discloses a heat insulating box in which an inside of the heat insulating box is exhausted and evacuated to be a vacuum heat insulating material. PTL 2 discloses a vacuum heat insulating material in which a moisture adsorbent or a gas adsorbent that adsorbs invading moisture or air is further installed in advance in an outer packaging material made of a resin material having low gas permeability in order to secure heat insulation performance over a long period of time. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Unexamined Japanese Patent Publication No. H09-119771 
     PTL 2: Unexamined Japanese Patent Publication No. 2012-102758 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a vacuum heat insulator capable of maintaining high heat insulation performance for a long period of time by avoiding deactivation of a gas adsorbent and maximizing adsorption capability of the gas adsorbent, and a heat insulating container and a heat insulating wall using the vacuum heat insulator. 
     A vacuum heat insulator according to the present disclosure includes an outer packaging material including a resin sheet, and a core material and a gas adsorption device each contained in the outer packaging material. The gas adsorption device includes a vacuum sealed container containing a gas adsorbing substance that adsorbs a gas, an opening pin that opens the vacuum sealed container by a physical load from an outside, and a load-bearing spacer that suppresses displacement of the opening pin to less than or equal to a predetermined amount 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a sectional view of a refrigerator including a vacuum heat insulator according to a first exemplary embodiment. 
         FIG.  2    is a perspective view of a refrigerator door to which the vacuum heat insulator according to the first exemplary embodiment is applied. 
         FIG.  3 A  is a sectional view taken along line IIIA-IIIA in  FIG.  2   . 
         FIG.  3 B  is a sectional view taken along line IIIB-IIIB of  FIG.  3 A . 
         FIG.  4 A  is a sectional view of the vacuum heat insulator according to the first exemplary embodiment. 
         FIG.  4 B  is a sectional view taken along line IVB-IVB in  FIG.  4 A . 
         FIG.  4 C  is a sectional view and a top view of a vacuum sealed container included in a gas adsorption device contained in the vacuum heat insulator according to the first exemplary embodiment. 
         FIG.  4 D  is a sectional view and a top view of the gas adsorption device contained in the vacuum heat insulator according to the first exemplary embodiment. 
         FIG.  4 E  is a diagram illustrating a configuration of an opening pin of the gas adsorption device contained in the vacuum heat insulator according to the first exemplary embodiment. 
         FIG.  5    is a flowchart illustrating a method of manufacturing the refrigerator door including the vacuum heat insulator according to the first exemplary embodiment. 
         FIG.  6    is a perspective view and a component development perspective view of a heat insulating container according to a second exemplary embodiment. 
         FIG.  7 A  is a sectional view of the heat insulating container according to the second exemplary embodiment. 
         FIG.  7 B  is a sectional view taken along line VIIB-VIIB of  FIG.  7 A . 
         FIG.  8    is a flowchart illustrating a method of manufacturing the heat insulating container according to the second exemplary embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     (Knowledge and the Like Underlying the Present Disclosure) 
     In recent years, from the viewpoint of prevention of global warming, improvement of energy saving is strongly desired, and improvement of energy saving is an urgent problem also in household electrical appliances. In particular, in heat-retaining and cold-keeping devices such as refrigerators, freezers, and vending machines, a heat insulating material having excellent heat insulation performance is required from the viewpoint of efficiently using heat. 
     As a general heat insulating material, a material selected from a fiber material such as glass wool and a foam such as urethane foam is used. In order to improve the heat insulation performance of these heat insulating materials, it is necessary to increase a thickness of each of the heat insulating materials. However, in a case where a space to be filled with the heat insulating material is limited, for example, in a case where space saving is required or in a case where effective use of the space is required, it is difficult to apply the general heat insulating material described above. 
     Therefore, a vacuum heat insulating material has been proposed as a high-performance heat insulating material. The vacuum heat insulating material is a heat insulator in which a core material having a role of a spacer is inserted into an outer packaging material having a gas barrier property, and the inside is sealed by being depressurized. 
     This vacuum heat insulating material has heat insulation performance about 20 times that of urethane foam, and has excellent characteristics that sufficient heat insulation performance can be obtained even when the thickness is reduced. 
     Accordingly, the vacuum heat insulating material attracts attention as an effective means for improving energy saving property by improving heat insulation performance while satisfying customer&#39;s demand for increasing an internal volume of a heat insulating box. 
     For example, in a refrigerator, in a heat insulating box constituting a refrigerator body, a heat insulating space between an inner box and an outer box is filled with urethane foam by foaming. Then, a vacuum heat insulating material is additionally installed in the heat insulating space to enhance the heat insulating property. This increases the internal volume of the heat insulating box. 
     Generally, a heat insulating space of a heat insulating box such as a refrigerator has a complicated shape. On the other hand, since it is generally difficult to perform processing that follows a complicated shape, particularly processing in a thickness direction, the vacuum heat insulating material is provided in a flat plate shape. For this reason, there is a limit to improvement of an area that can be covered by the vacuum heat insulating material, in other words, a ratio of the area of the vacuum heat insulating material to a total heat transfer area of the heat insulating box. 
     Therefore, for example, a technique has been proposed in which a heat insulating space of a heat insulating box is filled with open-cell urethane from an air feeding inlet port for blow molding of the heat insulating box and the open-cell urethane is foamed, and then the inside of the heat insulating box is exhausted and evacuated by a vacuum evacuation device connected to the air feeding inlet port, thereby forming the heat insulating box itself as a vacuum heat insulating material (See, for example, PTL 1). 
     Similarly to PTL 1, the present applicant has also proposed a technique in which a heat insulating space of a heat insulating box to be a refrigerator body is filled with open-cell urethane and the open-cell urethane is foamed, and then vacuuming is performed to make the heat insulating box itself a vacuum heat insulating material. 
     For the heat insulating space having a complicated shape, a vacuum heat insulator suitable for the complicated shape can be obtained as follows. That is, for each of the inner box and the outer box, an outer packaging material molded in accordance with a desired heat insulating space is produced by blow molding or vacuum molding a resin. Then, a core material obtained by foaming a resin such as open-cell urethane forming the heat insulating space itself is covered with an outer packaging material, and the inside is vacuum-sealed. 
     The heat insulator thus obtained in the heat insulating space having a complicated shape has higher overall heat insulation performance than a conventional heat insulator including a planar vacuum heat insulating material and urethane foam for filling gaps between the vacuum heat insulating material, and the inner box and the outer box. Therefore, it is possible to produce an effect of reducing the thickness of the heat insulating material to increase the internal volume or an effect of reducing the appearance, and an effect of reducing the weight. 
     As described above, the vacuum heat insulator formed by vacuum-sealing open-cell urethane as the core material and the resin molding material as the outer packaging material can vacuum-insulate the entire area of the heat insulating space even when the vacuum heat insulator has a complicated external appearance like a heat insulating box. Accordingly, by using such a vacuum heat insulator in, for example, a refrigerator, the thickness of the heat insulating box itself can be reduced, and the internal capacity (storage space) can be further increased. 
     Further, such a vacuum heat insulator is not complicated in shape, but can be applied to applications in which heat insulating properties are strongly expected, for example, an LNG storage tank for storing an ultra-low temperature substance such as liquefied natural gas (LNG), or a panel for a heat insulating container such as a tank of an LNG transport tanker. This makes it possible to effectively suppress intrusion of heat into the heat insulating container while reducing a wall thickness of the heat insulating container. Therefore, in the case of the LNG tank, the generation of a boil-off gas (BOG) can be effectively reduced, and a natural vaporization rate (boil-off rate, BOR) of LNG can be reduced. 
     In such a vacuum heat insulator, in order to secure heat insulation performance over a long period of time, a resin material having low gas permeability is used as an outer packaging material, and a moisture adsorbent or a gas adsorbent that adsorbs invading moisture or air is installed in the vacuum heat insulator in advance (See, for example, PTL 2). 
     When the gas adsorbent is exposed to an atmospheric pressure before evacuation, the gas adsorbent is immediately deactivated because of its very high adsorption rate, and after evacuation, the gas adsorbent is brought into a state of hardly adsorbing any more gas. For this reason, conventionally, the gas adsorbent is sealed in a vacuum sealed container in advance, and the container of the gas adsorbent is opened by some method from the outside after a state in which there is almost no residual gas around the gas adsorbent after evacuation. As a result, the gas adsorbent exhibits its original adsorption capability. 
     That is, the container of the gas adsorbent should not be already opened when the container is to be opened, or should not be unopened when the container is to be opened. In the former case, it is considered that the gas adsorbent is already deactivated when it is desired to open the container of the gas adsorbent, and in the latter case, the performance of the gas adsorbent cannot be exhibited at all. In either case, regardless of the initial performance, a degree of vacuum cannot be maintained for a long period of time, and there is a problem that the heat insulation performance of the vacuum heat insulating material cannot be maintained. 
     The inventors have found that there is a problem as described above, and have come to constitute the subject matter of the present disclosure in order to solve the problem. 
     The present disclosure provides a vacuum heat insulator capable of maximizing adsorption capability of a gas adsorbent and maintaining high heat insulation performance over a long period of time, and a heat insulating container and a heat insulating wall using the vacuum heat insulator. 
     Exemplary embodiments will be described in detail below with reference to the drawings. However, an unnecessarily detailed description will be omitted in some cases. For example, detailed description of already well-known matters or redundant description of substantially the same configuration may be omitted. 
     Note that the accompanying drawings and the following description are provided to help those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter recited in the claims. 
     First Exemplary Embodiment 
     A first exemplary embodiment will be described below with reference to  FIGS.  1  to  5   .  FIG.  1    is a sectional view of refrigerator  1  including vacuum heat insulator  60  according to the first exemplary embodiment.  FIG.  2    is a perspective view of refrigerator door  25  to which vacuum heat insulator  60  is applied.  FIG.  3 A  is a sectional view taken along line IIIA-IIIA in  FIG.  2   .  FIG.  3 B  is a sectional view taken along line IIIB-IIIB of  FIG.  3 A .  FIG.  4 A  is a sectional view of vacuum heat insulator  60 .  FIG.  4 B  is a sectional view taken along line IVB-IVB in  FIG.  4 A .  FIG.  4 C  illustrates a sectional view and a top view of vacuum sealed container  34  included in gas adsorption device  56  included in vacuum heat insulator  60 .  FIG.  4 D  illustrates a sectional view and a top view of gas adsorption device  56 .  FIG.  4 E  is a diagram illustrating a configuration of an opening pin of gas adsorption device  56 .  FIG.  5    is a flowchart illustrating a method of manufacturing refrigerator door  1  including vacuum heat insulator  60 . 
     [1-1. Configuration] 
     [1-1-1. Application Example to Refrigerator Door] 
     Hereinafter, vacuum heat insulator  60  according to the present exemplary embodiment will be described with reference to an example applied to refrigerator door  25 . 
     In  FIG.  1   , refrigerator  1  includes refrigerator door  25 . A foamed heat insulating material (not illustrated) is filled between outer box  2  and inner box  3  of refrigerator  1  to form heat insulating box  7 . Inside heat insulating box  7 , freezing chamber  9  and refrigerating chamber  10  partitioned by partitioning body  8  are disposed. 
     Compressor  11  is disposed in machine chamber  22  in an upper part of heat insulating box  7 , and evaporation pan  13  is disposed in lower machine chamber  23 . Evaporator  12  is disposed in cooling chamber  24  formed on a back surface of freezing chamber  9 . 
     Freezing chamber  9  and cooling chamber  24  are partitioned by cooling chamber wall body  21 . Refrigerator door  25  is disposed in each of front opening parts  7   a  of heat insulating box  7  corresponding to freezing chamber  9  and refrigerating chamber  10 . 
     As illustrated in  FIGS.  3 A and  3 B , refrigerator door  25  includes outer plate  27 , outside exterior appearance component  14 , inner plate  26 , and inside exterior appearance component  15 . Gas barrier layer  31  against oxygen and the like is formed inside outer plate  27 . Outside exterior appearance component  14  is disposed on a surface of outer plate  27  and is made of a glass plate, a metal plate, or the like. Gas barrier layer  31  against oxygen and the like is formed inside inner plate  26 . Inside exterior appearance component  15  is disposed on a surface of inner plate  26 , and is made of ABS resin or the like. Refrigerator door  25  includes open-cell urethane foam  5  (a core material of the vacuum heat insulator) filled in a heat insulating space between outer plate  27  and inner plate  26 . Here, outer plate  27  and inner plate  26  correspond to outer packaging material  55 . 
     Note that outer packaging material  55  wraps an outer surface of open-cell urethane foam  5  (the core material of the vacuum heat insulator). 
     Specifically, vacuum heat insulator  60  according to the present exemplary embodiment includes core material (open-cell urethane foam  5 ) that serves as a spacer, and outer packaging material  55  having a gas barrier property. Vacuum heat insulator  60  is configured such that the core material is inserted into outer packaging material  55 , an inside of the vacuum heat insulator is depressurized through exhaust port  16  provided in a part of inner plate  26 , and the vacuum heat insulator is sealed using sealing material  17 . An outer periphery of each of outer plate  27  and inner plate  26  is bonded and sealed by thermal welding layer  32 . 
     Further, as illustrated in  FIGS.  3 A and  3 B , outside exterior appearance component  14  and inside exterior appearance component  15  are bonded to vacuum heat insulator  60  according to the present exemplary embodiment with an adhesive or the like to complete refrigerator door  25 . 
     Note that  FIGS.  4 A and  4 B  illustrate a state before outside exterior appearance component  14  and inside exterior appearance component  15  of refrigerator door  25  are bonded to each other, that is, vacuum heat insulator  60  according to the present exemplary embodiment. 
     [1-1-2. Manufacturing Method] 
     Next, a method of manufacturing refrigerator door  25  including vacuum heat insulator  60  according to the first exemplary embodiment will be described. 
     In  FIG.  5   , outer plate  27  and inner plate  26  are made of a resin sheet having a high oxygen gas barrier property and a high water vapor gas barrier property. Outer plate  27  and inner plate  26  mainly need to be configured to suppress permeation of air and water vapor. 
     For example, a multilayer sheet in which an ethylene-vinyl alcohol copolymer resin (EVOH), which is a material having low oxygen permeability, is sandwiched between polypropylene, polyethylene, or the like, which is a material having low water vapor permeability, is prepared by an extrusion molding machine or the like in order to improve moldability (step  1 ). Then, the multilayer sheet prepared in step  1  is molded into a shape conforming to the shape of a part where heat insulation is required by vacuum molding, pressure molding, blow molding, or the like (step  2 ). 
     Note that a similar effect can be obtained by using polyvinyl alcohol (PVA) instead of EVOH. Inner plate  26  is provided with exhaust port  16  to which a welding mechanism (not illustrated) is connected, and inner plate  26  is sealed with sealing material  17  having at least a metal foil having a high oxygen gas barrier property. 
     When outer plate  27  is a complete plane, a resin laminate film containing a metal layer of aluminum, stainless steel, or the like is often used. This is because, by using a film, the thickness can be set to less than or equal to 0.1 mm, uniform heating is facilitated at the time of heat welding described later, and highly reliable vacuum heat insulator  60  can be obtained. However, when outer plate  27  is not a flat surface from the viewpoint of designability and the like, a resin sheet having a thickness of 0.2 mm or more is used similarly to inner plate  26 . 
     Open-cell urethane foam  5  is molded by injecting a urethane liquid into a metal mold (not illustrated) having a shape of a heat insulating space between outer plate  27  and inner plate  26 , and foaming and releasing the urethane liquid (step  3 , step  4 ). 
     A method of manufacturing refrigerator door  25  will be described below with reference to  FIG.  5   . 
     Next, a gas adsorbent that adsorbs various gases and gas adsorption device  56  (described later) are installed in box-shaped inner plate  26  together with open-cell urethane foam  5 . 
     Then, a molded article of open-cell urethane foam  5  is housed in inner plate  26  and covered with outer plate  27  (step  5 ). Heat and pressure are applied to an outer peripheral part where inner plate  26  and outer plate  27  are in contact with each other, and inner plate  26  and outer plate  27  are thermally welded (step  6 ). 
     At this time, as illustrated in  FIG.  3 A  or  FIG.  4 A , when the adhesive layer (thermal welding layer  32 ) between outer plate  27  and inner plate  26  is a polypropylene layer, the polypropylene resins are thermally welded. 
     As the gas adsorbent, gas adsorbent  19  that selectively adsorbs air or moisture adsorbent  18  that adsorbs moisture is known. This gas adsorbent adsorbs a remaining gas that cannot be exhausted by evacuation or a trace amount of gas that has permeated through inner plate  26  or outer plate  27  having a high gas barrier property in a long period of time, so that a degree of vacuum can be maintained for a long period of time. 
     As illustrated in  FIGS.  4 C,  4 D, and  4 E , gas adsorption device  56  includes vacuum sealed container  34 , opening pin  35 , and load-bearing spacer  39 . Vacuum sealed container  34  contains gas adsorbing substance  33  including zeolite or the like that adsorbs various gases. Opening pin  35  opens vacuum sealed container  34  by a physical load from the outside. Load-bearing spacer  39  suppresses displacement of opening pin  35  to less than or equal to a predetermined amount. 
     For example, as illustrated in  FIG.  4 E , opening pin  35  includes pin part  38  that opens vacuum sealed container  34 , spring part  36  that biases pin part  38  outward, and pin support part  37 . Pin support part  37  supports pin part  38  and has a function as a coupling part that couples pin part  38  and spring part  36 . 
     Returning to  FIG.  5   , next, outer shapes of inner plate  26  and outer plate  27  that have been thermally welded are cut into predetermined shapes (step  7 ). 
     Vacuum heat insulator  60  including inner plate  26  and outer plate  27  that are thermally welded is evacuated for a predetermined time through exhaust port  16  by a vacuum evacuation device (not illustrated) (step  8 ). Then, exhaust port  16  is welded and sealed by ultrasonic welding or the like using sealing material  17  (step  9 ). Accordingly, vacuum heat insulator  60  can be obtained. 
     In order to shorten the exhaust time and improve the productivity, it is desirable that a vent hole (not illustrated) of open-cell urethane foam  5  (core material) is connected to exhaust port  16 . Note that sealing material  17  includes an adhesive layer, a metal foil, and a heat-resistant protective layer (not illustrated) in order from the closest to exhaust port  16 . 
     The adhesive layer is disposed inside the metal foil. A melting point of the adhesive layer is less than or equal to 180° C. The heat-resistant protective layer is disposed outside the metal foil. The heat-resistant protective layer is a heat-resistant layer having a melting point of higher than or equal to 200° C. 
     Note that in the present exemplary embodiment, exhaust port  16  is substantially circular, and a hole diameter of exhaust port  16  is more than or equal to 1 mm. 
     Vacuum heat insulator  60  is aged at about 20° C. to 40° C. for several hours to several days after sealing of exhaust port  16  (step  10 ). As a result, residual moisture in vacuum heat insulator  60  is adsorbed by moisture adsorbent  18 . Thereafter, as illustrated in 
       FIGS.  4 C,  4 D, and  4 E , gas adsorption device  56  including vacuum sealed container  34  in which gas adsorbing substance  33  is enclosed and opening pin  35  is pushed by physically applying a load through outer plate  27 , so that vacuum sealed container  34  is opened by opening pin  35  (step  11 ). As a result, gas adsorbing substance  33  is exposed to a sealed space of vacuum heat insulator  60 , and it is possible to adsorb the residual gas excluding moisture and the gas entering from the outside through outer plate  27  or inner plate  26  over a subsequent long period. After step  11 , inside exterior appearance component  15  and outside exterior appearance component  14  are bonded to obtained vacuum heat insulator  60 , respectively (step  12 , step  13 ), to complete refrigerator door  25 . 
     [1-2. Operation] 
     In gas adsorption device  56  of vacuum heat insulator  60  configured as described above in the present exemplary embodiment, load-bearing spacer  39  is provided between pin support part  37  that supports pin part  38  of opening pin  35  and vacuum sealed container  34  that contains gas adsorbing substance  33 . As a result, it is possible to prevent outer plate  27  from pushing opening pin  35  of gas adsorption device  56  and opening vacuum sealed container  34  due to a compressive stress applied to outer plate  27  by the atmospheric pressure after the step of evacuating vacuum heat insulator  60  shown in step  8 . 
     Load-bearing spacer  39  is provided for the purpose of preventing pin part  38  from approaching a distance less than or equal to a distance to vacuum sealed container  34  in which gas adsorbing substance  33  is sealed. Thus, load-bearing spacer  39  does not need to be located between vacuum sealed container  34  and pin part  38 , and may be located between vacuum sealed container  34  and pin support part  37 . A material used for load-bearing spacer  39  may be the same material as open-cell urethane foam  5  selected for the purpose of withstanding a compressive stress caused by atmospheric pressure. 
     In the opening step of vacuum sealed container  34  shown in step  11 , a load stronger than atmospheric compression, for example, a load of about 500 KPa is slowly applied to an immediate upper part of opening pin  35 . As a result, load-bearing spacer  39  is also compressed, and vacuum sealed container  34  in which gas adsorbing substance  33  is sealed is eventually opened by pin part  38 . 
     [1-3. Effects and the Like] 
     As described above, in the present exemplary embodiment, vacuum heat insulator  60  includes outer packaging material  55 , open-cell urethane foam  5  (core material), and gas adsorption device  56 . Outer packaging material  55  is made of a resin sheet (not illustrated). Open-cell urethane foam  5  is enclosed in outer packaging material  55 . 
     Gas adsorption device  56  includes vacuum sealed container  34 , opening pin  35 , and load-bearing spacer  39 . Vacuum sealed container  34  contains gas adsorbing substance  33  that adsorbs various gases. Opening pin  35  opens vacuum sealed container  34  by a physical load from the outside. Load-bearing spacer  39  suppresses displacement of opening pin  35  to less than or equal to a predetermined amount. 
     By providing load-bearing spacer  39  so that opening pin  35  does not approach vacuum sealed container  34  constituting gas adsorption device  56  by a distance or less due to a compressive stress by atmospheric pressure, it is possible to avoid opening of vacuum sealed container  34  during evacuation and before vacuum sealing. Therefore, it is possible to avoid that gas adsorbing substance  33  adsorbs a large amount of residual gas during evacuation and before vacuum sealing and the subsequent adsorption capability is impaired, so that the performance of vacuum heat insulator  60  can be maintained. 
     Further, after all the residual moisture is adsorbed by moisture adsorbent  18  after the vacuum sealing, vacuum sealed container  34  of gas adsorption device  56  is reliably opened by opening pin  35 , so that the degree of vacuum and the heat insulation performance of refrigerator door  25  can be maintained for a long period of time. Accordingly, refrigerator door  25  having high reliability can be provided. 
     Note that opening pin  35  includes pin part  38  that opens vacuum sealed container  34 , spring part  36 , and pin support part  37  (coupling part) that couples pin part  38  and spring part  36 . Since pin support part  37  of opening pin  35  is supported by load-bearing spacer  39 , it is possible to prevent outer plate  27  from pushing opening pin  35  of gas adsorption device  56  and opening vacuum sealed container  34  by the compressive stress applied to outer plate  27  due to the atmospheric pressure after the step of evacuating vacuum heat insulator  60 . Further, by pressing outer packaging material  55  from the surface of outer packaging material  55 , a force pressed from the surface of outer packaging material  55  is received by pin support part  37  when vacuum sealed container  34  of gas adsorption device  56  is opened by opening pin  35 . Therefore, pin part  38  can reliably open vacuum sealed container  34 . 
     Load-bearing spacer  39  is provided for the purpose of preventing pin part  38  from approaching vacuum sealed container  34  of gas adsorption device  56  by a certain distance or less. Therefore, load-bearing spacer  39  does not need to be between vacuum sealed container  34  and pin part  38 , and may be between vacuum sealed container  34  and pin support part  37 . Thus, when it is desired to open vacuum sealed container  34 , pin part  38  can be opened without being disturbed by load-bearing spacer  39 . Accordingly, vacuum degree and heat insulation performance of refrigerator door  25  can be maintained for a long period of time, whereby vacuum heat insulator  60  having high reliability can be provided. 
     Note that load-bearing spacer  39  needs to withstand atmospheric compression. Therefore, it is desirable that load-bearing spacer  39  has a compressive strength of 200 kPa or more at 10% strain. 
     Note that load-bearing spacer  39  itself is also exposed to the vacuum space for a long period of time. Therefore, load-bearing spacer  39  is desirably made of a material that emits less gas. When open-cell urethane foam  5  used as the core material of vacuum heat insulator  60 , for example, is used as the material of load-bearing spacer  39 , evacuation is performed by vacuum evacuation similarly to the core material, and the residual gas is adsorbed by gas adsorbing substance  33 . 
     Note that vacuum heat insulator  60  according to the present exemplary embodiment is used as a heat insulating wall (not illustrated) used for an inner wall or an outer wall of a refrigeration device (not illustrated) or a refrigerator (not illustrated). Accordingly, it is possible to provide a heat insulating wall which is inexpensive and can maintain heat insulation performance for a long period of time. In addition, energy saving of the device can be enhanced. 
     Second Exemplary Embodiment 
     A second exemplary embodiment will be described below with reference to FIGS.  6  to  8 .  FIG.  6    illustrates a perspective view and a component development perspective view of heat insulating container  40  according to the second exemplary embodiment.  FIG.  7 A  is a sectional view of heat insulating container  40 .  FIG.  7 B  is a sectional view taken along line VIIB-VIIB of  FIG.  7 A .  FIG.  8    is a flowchart illustrating a method of manufacturing heat insulating container  40 . 
     [2-1. Configuration] 
     In  FIGS.  6 ,  7 A, and  7 B , heat insulating container  40  according to the present exemplary embodiment includes outer box  27   b , inner box  26   b , and open-cell urethane foam  5   b  (core material) filling a heat insulating space between outer box  27   b  and inner box  26   b . Gas barrier layer  31   b  against oxygen or the like is formed inside outer box  27   b  and inner box  26   b . Here, outer box  27   b  and inner box  26   b  correspond to outer packaging material  55 . 
     Similarly to the configuration described in the first exemplary embodiment, in heat insulating container  40  serving as the vacuum heat insulator also in the present exemplary embodiment, the inside of outer packaging material  55  is decompressed through exhaust port  16   b , and exhaust port  16   b  is sealed using sealing material  17   b . Outer box  27   b  and inner box  26   b  are bonded and sealed by thermal welding layer  32   b  on the outer peripheries of outer box  27   b  and inner box  26   b.    
     When the heat insulating space between outer box  27   b  and inner box  26   b  is filled with open-cell urethane foam  5   b , air adsorbent  42   b  that selectively adsorbs air, moisture adsorbent  41   b  that adsorbs moisture, and gas adsorption device  56  described in the first exemplary embodiment are placed in the heat insulating space. The basic configuration of the vacuum heat insulator of heat insulating container  40  according to the present exemplary embodiment is similar to the configuration of the vacuum heat insulator according to the first exemplary embodiment so as to achieve effects similar to the effects described in the first exemplary embodiment. 
     [2-2. Manufacturing Method] 
       FIG.  8    is a flowchart illustrating a method of manufacturing heat insulating container  40  in the present second exemplary embodiment. The basic manufacturing flow is the same as in steps  1  to  11  of the first exemplary embodiment. 
     In the case of heat insulating container  40 , neither outer box  27   b  nor inner box  26   b  has a planar shape. For this reason, a resin sheet having a thickness of 0.2 mm or more is used for both outer box  27   b  and inner box  26   b.    
     In  FIGS.  7 A and  7 B , in the opening step of the gas adsorption device  56 , it is necessary to push opening pin  35  (see  FIG.  4 D ) through a sheet thicker than that in first exemplary embodiment. Therefore, a load larger than that in the first exemplary embodiment, for example, a load of 1 MPa or more is slowly applied. As a result, load-bearing spacer  39  is also compressed, and vacuum sealed container  34  (see  FIG.  4 D ) of gas adsorption device  56  is eventually opened by pin part  38  (see  FIG.  4 E ). 
     [2-3. Operation, Effect, and the Like] 
     In the present exemplary embodiment, inner plate  26  in the first exemplary embodiment corresponds to inner box  26   b , and outer plate  27  corresponds to outer box  27   b . By forming inner box  26   b  and outer box  27   b  into a box shape, it is possible to provide heat insulating container  40  that is inexpensive and can maintain high heat insulation performance over a long period of time. 
     Note that, in the vacuum heat insulators according to the first and second exemplary embodiments, gas adsorption device  56  is used for the purpose of maintaining the heat insulation performance of the vacuum heat insulating material with high reliability over a long period of time. 
     Gas adsorption device  56  is installed for the purpose of adsorbing a residual gas represented by nitrogen and oxygen and a gas represented by nitrogen and oxygen entering from the outside at a predetermined entry amount after sealing at a predetermined adsorption rate with respect to the vacuum heat insulating material vacuum-sealed after evacuation is performed for a predetermined time, and maintaining the vacuum heat insulating material at a predetermined equilibrium pressure. 
     A main factor of lowering the adsorption capability of gas adsorbent  19  is that gas adsorbent  19  already adsorbs the gas around gas adsorbent  19  before evacuation or during evacuation. In this case, an adsorption amount by gas adsorbent  19  does not reach an amount to be adsorbed originally. 
     Note that, as for moisture contained in the residual gas and the entering gas from the outside, originally, inexpensive moisture adsorbent  18  should be installed in the same space, and all of the moisture should be adsorbed by moisture adsorbent  18 , and the remaining nitrogen, oxygen gas, and the like should be adsorbed by gas adsorbent  19 . However, since gas adsorbent  19  adsorbs moisture, there is a case where gas adsorbent  19  cannot adsorb the gas to be originally adsorbed accordingly. 
     The present disclosure solves both of the above two problems. Specifically, the zeolite as gas adsorbing substance  33  is sealed in vacuum sealed container  34  until the vacuum heat insulating material is vacuum sealed after evacuation. Thereafter, the residual moisture is completely adsorbed by moisture adsorbent  18  for a predetermined time or under a temperature condition. Thereafter, vacuum sealed container  34  is opened by opening pin  35  or the like integrated with vacuum sealed container  34  of gas adsorbing substance  33  by a force physically applied from the outside. This makes it possible to adsorb gases other than surrounding moisture. 
     In this manner, the pressure is kept constant over a long period of time, so that the heat insulation performance of the vacuum heat insulating material can be reliably maintained over a long period of time. 
     INDUSTRIAL APPLICABILITY 
     The vacuum heat insulator in the present disclosure can maintain high heat insulation performance for a long period of time by avoiding deactivation of the gas adsorbing substance and maximizing the adsorption capability of the gas adsorbing substance. Accordingly, it is possible to provide a high-quality vacuum heat insulator which is inexpensive and has high heat insulation performance, and the vacuum heat insulator can be widely applied as a heat insulator for consumer devices such as a refrigerator and an electric water heater, a heat insulator for a vending machine, an automobile, and a house, a heat insulating container and a heat insulating wall using the heat insulator. Further, the present invention can also be applied as a heat insulating container such as a case for accommodating food in a storage chamber. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               1 : refrigerator 
               2 ,  27   b : outer box 
               3 ,  26   b : inner box 
               5 ,  5   b : open-cell urethane foam (core material) 
               7 : heat insulating box 
               7   a : front opening part 
               8 : partitioning body 
               9 : freezing chamber 
               10 : refrigerating chamber 
               11 : compressor 
               12 : evaporator 
               13 : evaporating pan 
               14 : outside exterior appearance component 
               15 : inside exterior appearance component 
               16 ,  16   b : exhaust port 
               17 ,  17   b : sealing material 
               18 ,  41   b : moisture adsorbent 
               19 : gas adsorbent 
               21 : cooling chamber wall body 
               22 : machine chamber 
               23 : lower machine chamber 
               24 : cooling chamber 
               25 : refrigerator door 
               26 : inner plate 
               27 : outer plate 
               31 ,  31   b : gas barrier layer 
               32 ,  32   b : thermal welding layer 
               33 : gas adsorbing substance 
               34 : vacuum sealed container 
               35 : opening pin 
               36 : spring part 
               37 : pin support part (coupling part) 
               38 : pin part 
               39 : load-bearing spacer 
               40 : heat insulating container 
               42   b : air adsorbent 
               55 : outer packaging material 
               56 : gas adsorption device 
               60 : vacuum heat insulator