JP2006161834A - Heat insulation block, and cold storage cabinet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight heat insulation block having a high heat insulation performance formed into a shaped body by filling an airtight bag with a granular material and reducing inside pressure. <P>SOLUTION: The bag 2 formed by an airtight synthetic resin film is filled with the poeder and granular material 3 consisting of porous spherical particles made by a reversed micelle method and having an almost uniform grain size, and the pressure inside the bag is reduced to make the shaped body. Preferably, the shaped body is a plate-like matter having a predetermined thickness, and a joint part to be fitted or overlapped with the end of another shaped body is formed to part of or the whole of the end of the plate-like matter. Preferably, the porous spherical particle is a glass particle such as quartz glass particle, and the diameter of the porous spherical particle is 3 to 30 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat insulating block that can be used as a heat insulating material for walls and floors such as a low temperature storage, and a low temperature storage in which a wall portion is constituted by a block for heat insulation.

  Insulation materials used to insulate walls and floors of low-temperature warehouses, etc. have different thermal insulation performance required according to the temperature of the low-temperature storage to be stored, and the lower the temperature, that is, the greater the temperature difference from the outside temperature. It is necessary to use a material having a low thermal conductivity. As a use of the heat insulating material, there are a low temperature storage in a wide temperature range from a cryogenic low temperature storage to a household freezer, a refrigerator and the like.

  Here, the heat conductivity of the heat insulating material depends on the heat conductivity, bulk density, porosity (porosity), pore shape, etc. of the material constituting the heat insulating material, the porosity is large, the bulk density is low, A porous material containing many fine pores is excellent in heat insulation. The thermal conductivity of gas is lower than that of solid, and the thermal insulation performance is improved by sealing the gas in fine pores and other voids of the thermal insulation material and hindering thermal conduction by convection of the gas.

  As a porous material that can be used as a heat insulating material, rigid urethane foam is widely used in household freezers, refrigerators, etc., but the temperature in the low-temperature storage is reduced, the wall of the low-temperature storage is lightened or the wall thickness is reduced. In the case of reducing the thickness, it is necessary to further increase the heat insulation of the heat insulating material. Further, as a heat insulating material with higher heat insulation, a vacuum heat insulating material with reduced heat conduction by gas is disclosed in, for example, Patent Document 1 below. The vacuum heat insulating material disclosed in the following Patent Document 1 is packed with a fine powder of inorganic material such as pearlite or silica having a low thermal conductivity in a breathable inner bag, and further packed in an airtight outer bag. It has a structure that is vacuum-tightly integrated and hermetically sealed, and is used to insulate the refrigerator wall. When compared with conventional rigid urethane foam, this vacuum insulation material has a low thermal conductivity, so the thickness of the insulation material can be made thinner and lighter. Can be thin.

  On the other hand, as a low-temperature storage for storing low-temperature storage such as liquid nitrogen and liquefied natural gas, a double shell structure is used to fill the heat insulation layer between the outer wall of the inner tank and the inner wall of the outer tank as pearlite as a granular heat insulating material. There is a heavy shell cryogenic storage tank. Examples of the double-shell low-temperature storage tank in which the heat insulating layer is filled with pearlite include the structures disclosed in Patent Documents 2 to 4 below.

Japanese Patent Laid-Open No. 04-160298 JP 09-137626 A Japanese Patent Laid-Open No. 08-121695 Japanese Patent Laid-Open No. 08-004981

  However, conventional pearlite, silica, and other inorganic fine powders are filled into a bag and vacuum-tight and hermetically sealed, and the pearlite is used as a filler. Since it is a material obtained by firing natural glass mineral at a high temperature, there are the following problems.

First, since pearlite has a bulk density of about 1000 kg / m ³ (= 1 g / cm ³ ) when densely packed, the thermal conductivity as a heat insulating material increases, and the storage temperature is liquid nitrogen or liquefied natural. In the case of a cryogenic level such as gas, it is necessary to thicken the heat insulating material used for the wall portion of the low temperature storage, and as a result, the structure of the wall portion becomes heavy.

  Secondly, since pearlite remains cracked during firing, it will be pulverized when used in an environment with mechanical vibration for a long period of time, resulting in an increase in bulk density, resulting in a cavity where pearlite is not filled in the sealed space. If the bag body filled with pearlite is made of a deformable material, the molding of the heat insulating material may be broken. As a result, it may be necessary to devise a method in which the pearlite particles are connected by a binder and the molding does not collapse. In addition, when a plurality of heat insulating materials are molded into a block shape and used in combination with a plurality of blocks, if the block shape is broken, a gap is generated between the blocks, and the heat insulating performance is remarkably deteriorated.

  Thirdly, pearlite has an irregular particle shape rather than a spherical shape, and the powder particles have a large adsorption surface area, so that moisture is easily adsorbed and it is difficult to evacuate the heat insulating layer.

  Further, even in the case of a heat insulating material using an inorganic fine powder such as silica as a filler, the same problem as in the case of the above pearlite occurs if the properties of the fine powder are not uniform.

  Furthermore, in the double-shell low-temperature storage tank using pearlite as a filler for the conventional heat insulation layer, since it has a double-shell structure, the material obtained by calcination of natural glass minerals such as pearlite at high temperature Therefore, there are the following problems.

First, because of the double shell structure, the weight of the structure itself is heavy, and pearlite has a bulk density of about 1000 kg / m ³ (= 1 g / cm ³ ) when densely packed, and liquid nitrogen. Or liquefied gas tank lorry (an example of a double-shell cryogenic storage tank) that transports liquefied natural gas, etc., the weight of the entire double-shell cryogenic storage tank becomes heavy, and the vehicle weight during transportation The weight increases and the transportation cost increases. Moreover, since the bulk density is large, the amount of heat conduction inevitably increases.

  Secondly, since pearlite remains cracked during firing, it is pulverized when used in an environment with mechanical vibration for a long time (for example, a liquefied gas tank lorry, etc.), the bulk density increases, and the heat insulation layer There may be cavities that are not filled with granular insulation. As a result, the heat insulation performance deteriorates due to heat conduction by convection of the filling gas (or residual gas after decompression) in the heat insulation layer in the cavity.

  Thirdly, because pearlite has poor fluidity of the granular material, there is a possibility that pearlite may not be uniformly filled in the heat insulation layer due to the occurrence of bridges, etc. Therefore, advanced work know-how is required at the time of filling to prevent this It becomes.

  Fourthly, pearlite has an irregular particle shape rather than a spherical shape, and the powder particles have a large adsorption surface area, so that moisture is easily adsorbed and it is difficult to evacuate the heat insulating layer. Moreover, if it is going to eliminate the fault of this moisture adsorptivity, it will be necessary to perform baking in the vicinity of a construction site, and to shorten the time from the time of pearlite manufacture to the time of filling in a heat insulation layer, and it will become high-cost.

  The present invention has been made in view of the above-mentioned problems, and a first object of the present invention is to eliminate the above-mentioned problems and to fill the inside of a bag body having airtightness with a reduced pressure inside. It is a block for heat insulation made into a molded body, and is to provide a heat insulation block having light weight and high heat insulation performance, and a second object is to provide a low temperature storage with light weight and high heat insulation performance. There is.

  In order to achieve this first object, the heat insulating block according to the present invention has a particle size synthesized by the reverse micelle method inside a bag formed using a synthetic resin film having airtightness. It is characterized in that a powder body made of uniform porous spherical particles is filled, and the inside of the bag body is decompressed to form a molded body.

According to the heat insulating block having the above characteristics, the porous spherical particles having a substantially uniform particle diameter synthesized using the reverse micelle method have a spherical particle shape (spherical or substantially spherical) and a substantially uniform particle size. Since it is formed as a uniform granular material, the gap distance between the particles is substantially constant and can be shortened below the mean free path of the filling gas. As a result, even at a low vacuum of about 10 ⁻¹ Pa (about 10 ⁻³ Torr) Convection in the voids between particles can be effectively suppressed, and extremely high heat insulation with little conduction loss can be realized. As a result, when the wall portion of the low-temperature storage is configured by combining the heat insulation blocks having the above characteristics, a high degree of heat insulation performance of 0.02 W / mK or less obtained by vacuum heat insulation can be easily realized.

In addition, since the particle shape is spherical and the particle size is substantially uniform, the void ratio between the particles in the state where the heat insulating layer is densely packed is low, but the single particle is in the particle Due to the high porosity, the bulk density is reduced to about 150 to 300 kg / m ³ (= 0.15 to 0.3 g / cm ³ ), which is significantly reduced compared to pearlite. It can be made lightweight and the wall of the cold storage can be lightened.

  In addition, since it is synthesized using the reverse micelle method, there is no cracking during firing, such as pearlite, so there is very little possibility of pulverization due to mechanical vibration, and a large cavity that impairs heat insulation in the bag Is very unlikely to occur. In addition, when the synthetic resin film forming the bag body is flexible, the particle shape of the powder body filled in the bag body is spherical and the particle size is substantially uniform, so that the fluidity Even when a large number of heat insulating blocks are combined, even if the joint surface between the blocks is bent due to gravity or the like, the surface of the bag body of each block can be deformed following the bending. No gap is generated in the wall, so that high heat insulation can be maintained throughout the wall.

  Further, in the heat insulation block having the above characteristics, the molded body is a plate-like body having a predetermined thickness, and an edge of another plate-like body is formed on a part or all of the edge of the plate-like body. It is preferable that a joint portion that is fitted or superposed on the portion to be joined is formed. By forming joints at the edge, when multiple heat insulation blocks are combined, positioning between adjacent blocks is defined by the joints, enabling efficient combination without gaps between the blocks. Become.

  Furthermore, in the heat insulating block having the above characteristics, it is preferable that the porous spherical particles are vitreous such as quartz glass particles. In general, since the contribution of the lattice vibration of the heat medium to the heat conduction becomes large at low temperatures, the heat conduction at low temperatures can be more effectively suppressed because the granular heat insulating material is vitreous.

Furthermore, in the heat insulating block having the above characteristics, the porous spherical particles preferably have a diameter of 3 to 30 μm. If the particle size is too large, the gap distance between the particles increases, and convection occurs there, resulting in poor heat insulation. Conversely, if the particle size is too small, the particles are easily scattered during handling and difficult to handle. It is preferable that it is -30 micrometers. Further, from the viewpoint of fluidity, the smaller the particle size, the smaller the particle size, and the higher the fluidity because the intermolecular attractive force is negligible. However, when the particle size is several μm, the thermal fluctuation at the normal temperature becomes about the same as the kinetic energy of the particles, and the intermolecular force cannot be ignored. Therefore, at a bulk density of about 300 kg / m ³ , less than 10 μm is the most fluid. Well desirable.

  In order to achieve the second object, the low temperature storage according to the present invention includes a heat insulating block having the above characteristics stacked on the inner side of an outer wall, and an inner tank made of an airtight film-like material inside the stacked heat insulating block. It is characterized by forming.

  According to the low-temperature storage having the above characteristics, a low-temperature storage having light weight and high heat insulation performance can be easily realized by using the heat insulation block according to the present invention that is light and has high heat insulation performance. Moreover, since there is no operation | work which fills a heat insulation layer with a granular heat insulating material compared with the conventional double shell low temperature storage tank, workability | operativity improves. In addition, the heat insulation block absorbs the stress applied to the outer wall from the inside of the inner tank, so the inner tank can be significantly lighter than conventional double-shell low-temperature storage tanks. Can be achieved.

  An embodiment of a heat insulating block according to the present invention (hereinafter referred to as “the present invention block” as appropriate) will be described with reference to the drawings.

As shown in FIG. 1, the present invention block 1 is formed in a bag 2 molded into a predetermined three-dimensional shape such as a rectangular parallelepiped by a synthetic resin film such as a low-density polyethylene film having airtightness and flexibility. After the granular heat insulating material 3 made of porous spherical particles is densely packed, the inside of the bag body 2 is evacuated, and the pressure is reduced to about 10 ⁻¹ Pa (about 10 ⁻³ Torr). The opening for vacuuming is hermetically sealed and formed as a three-dimensional shaped molded body of the bag body 2. However, although the heat insulation can be improved by reducing the pressure to about 10 ⁻¹ Pa, it may be further reduced to a low vacuum.

The granular heat insulating material 3 used in the present invention block 1 is a granular material composed of porous spherical particles having a substantially uniform particle size synthesized by the reverse micelle method, and specifically, produced in the following manner. It is a granular material of quartz glass particles. That is, by a reverse micelle method, a water glass solution (sodium silicate aqueous solution), which is an aqueous solution containing particle raw materials in an oily organic solvent, is emulsified and dispersed, and a precipitating agent such as sodium carbonate is added to the emulsified and dispersed water glass colloid. When added, water glass particles (emulsion particles) that have been spheroidized due to the surface tension in the colloid are precipitated as glass particles while maintaining their shape, so the precipitated glass particles are separated by filtration, washed, and dried to form a particle shape. However, quartz glass particles having a substantially spherical shape and a substantially constant particle size are produced as the granular heat insulating material 3. As a method for making the particle diameters substantially uniform, a porous film such as a polymer film having a large number of through-holes with uniform pore diameters is used, and a water glass solution is passed through the porous film in an organic solvent. A known membrane emulsification reverse micelle method can be used in which emulsion particles are injected and emulsified and dispersed to obtain emulsion particles of the particle material. Details of the membrane emulsification reverse micelle method are disclosed in, for example, Japanese Patent Application Laid-Open No. 04-54605, Japanese Patent Application Laid-Open No. 05-240, Japanese Patent Application Laid-Open No. 05-23565, Japanese Patent Application Laid-Open No. 05-192907, and the like. The quartz glass particles produced in the above manner have a bulk density of about 150 to 300 kg / m ³ (= 0.15 to 0.3 g / cm ³ ).

  In the present embodiment, the generated quartz glass particles preferably have a particle size in the range of 3 to 30 μm, particularly about 10 μm from the viewpoint of fluidity of the granular material. Further, as a variation in the particle diameter of the quartz glass particles, the standard deviation based on volume is preferably suppressed to less than 50%, more preferably less than 20% of the average particle diameter. Therefore, the particle size within the variation range is defined as substantially uniform.

In addition, as the granular heat insulating material 3 having a bulk density of about 150 to 300 kg / m ³ (= 0.15 to 0.3 g / cm ³ ) and a particle size of approximately ^{3 to 30} μm, Suzuki Oil & Fat Co., Ltd. A granular material of porous inorganic fine particles (quartz glass particles) commercially available under the trade name “Godball” (registered trademark) manufactured by the same company can be used.

  Next, an embodiment of a low-temperature storage according to the present invention using the present invention block 1 will be described based on the drawings.

  FIG. 4 schematically shows a schematic cross-sectional structure when the low-temperature storage 6 according to the present invention is applied to a tank lorry (not shown) for transporting a low-temperature liquefied gas (low-temperature storage) 7 such as liquefied natural gas. Show. As shown in FIG. 4, the low temperature storage 6 has an inner tank 9 that accommodates the liquefied gas 7 on the inner side of the outer wall 8 and the above-described inventive block 1 is densely stacked to form a heat insulating layer. Configured. The outer wall 8 is formed by welding a steel material such as stainless steel, and the inner tank 9 is a synthetic resin film such as an airtight and flexible low density polyethylene film or a metal such as aluminum on the synthetic resin film. It is formed of a film (film material) laminated with a film. The inner tank 9 is supported by the block 1 of the present invention from the inner wall of the outer wall 8. When the low temperature storage 6 is applied to a tank lorry, the outer wall 8 and the inner tank 9 have a circular or oval cross-sectional shape in the direction perpendicular to the paper surface of FIG. In addition, the site | part shown with the code | symbol 10 in the figure is an inlet / outlet for inject | pouring the liquefied gas 7 into the inner tank 9, and taking out from the inner tank 9. FIG.

  Hereinafter, another embodiment will be described.

  <1> In the above embodiment, the shape of the block 1 of the present invention is a rectangular parallelepiped in FIG. 1, but the shape of the block 1 of the present invention is not limited to the shape of a rectangular parallelepiped.

  For example, as shown in FIG. 2, the three-dimensional shape of the bag body 2 is a plate-like body having a predetermined thickness, and another plate-like body is formed on part or all of the edge portion 4 of the plate-like body. Are formed into a three-dimensional shape provided with a joining portion 5 that is fitted or overlapped with the end edge portion 4 and is joined to the inside of the bag body 2 with the granular heat insulating material 3 and then the inside of the bag body 2 is filled. It is also preferable to form the block 1 of the present invention as a molded body in which the joint portion 5 is provided at the end edge portion 4 by evacuation and decompression. By providing the joint 5 at the edge 4, for example, as shown in FIG. 3, when combining a plurality of the blocks 1 of the present invention to form a thermal insulator for a large wall surface of a low temperature storage, an efficient combination is possible. It becomes. Moreover, since a gap or the like is not easily generated between the blocks at the time of combination, a heat insulating wall that maintains the high heat insulating performance of the block 1 of the present invention can be configured.

  In addition, the installation location and the shape in the edge part 4 of the junction part 5 are not limited to what is shown in FIG.

  <2> In the above-described embodiment, the quartz glass particle powder is used as the granular heat insulating material 3, but the granular heat insulating material 3 is not limited to the quartz glass particle powder. Therefore, the porous spherical particles may be glass containing an inorganic material other than quartz.

  <3> In the above embodiment, the flexible synthetic resin film is used for the bag body 2, but the synthetic resin film used for the bag body 2 may be a hard film that does not have flexibility. . Therefore, the synthetic resin film used for the bag 2 is not limited to the low density polyethylene film exemplified in the above embodiment. Furthermore, you may form the bag body 2 using the film which laminated metal films, such as aluminum, to the synthetic resin film.

  <4> In the above embodiment, the method for synthesizing the granular heat insulating material 3 made of quartz glass particles using the reverse micelle method has been briefly described. However, the porous film and organic solvent used in the reverse micelle method As the precipitating agent, those used in the known membrane emulsification reverse micelle method can be used.

  <5> In the above embodiment, the vapor phase component remaining in the bag body 2 of the present invention block 1 after depressurization was not specified, but as the gas phase component inside the bag body 2 other than air, It is more preferable to use a rare gas. Air is usually contained in the gas phase inside the bag body 2, and when the pressure is reduced as it is, air and moisture are often contained as residual gases. However, since nitrogen, oxygen, and water, which are the main components of air, are polyatomic molecules, they have vibration and rotation energy in addition to the kinetic energy of the whole molecule, and have high thermal conductivity. Therefore, by using a rare gas as the gas phase component inside the bag body 2, the heat conduction due to the gas phase component inside the bag body 2 can be reduced, and the heat insulation performance can be improved. Further, a rare gas having a molecular weight as large as possible is desirable as a gas phase component inside the bag body 2. Specifically, when the temperature in the low-temperature storage constructed using the block 1 of the present invention is an extremely low temperature of liquid nitrogen level, Ar (argon), a low temperature around normal temperature (-20 to -30 ° C). In some cases, Kr (krypton), Xe (xenon) or the like is desirable.

  <6> In the above embodiment, the case where the low temperature storage 6 according to the present invention is applied to a tank truck or the like that transports a low temperature liquefied gas (low temperature storage) 7 such as liquefied natural gas is exemplified. Is not limited to liquefied gas, and is not limited to a vehicle such as a tank truck as an application target of the low temperature storage 6. For example, you may apply to the low temperature store which fixes the low temperature store 6 on the ground. Further, the shape and material of the outer wall 8 and the inner tank 9 of the low-temperature storage 6 are not limited to the above embodiment, and various shapes such as a vertical cylindrical shape, a spherical shape, a box shape, and the like are possible. It is.

The perspective view which fractures | ruptures part in one Embodiment of the block for heat insulation which concerns on this invention, and shows schematic structure inside and outside The perspective view which shows the general | schematic structure in another embodiment of the block for heat insulation which concerns on this invention. The top view which shows the state which combined the block for heat insulation which concerns on this invention shown in FIG. Sectional drawing which shows the general | schematic cross-section in one Embodiment of the low-temperature storage which concerns on this invention

Explanation of symbols

1: Block for heat insulation according to the present invention 2: Bag body 3: Granular heat insulating material 4: Edge edge portion 5: Joint portion 6: Low temperature storage according to the present invention 7: Low temperature storage 8: Outer wall 9: Inner tank 10: Low temperature Store entry / exit

Claims (6)

  The inside of a bag formed using a synthetic resin film having airtightness is filled with a granular material composed of porous spherical particles having a substantially uniform particle size synthesized using a reverse micelle method, A heat insulating block characterized in that the inside is reduced in pressure to form a molded body.   The molded body is a plate-like body having a predetermined thickness, and a part or all of the edge portion of the plate-like body is fitted to or joined to the edge portion of the other plate-like body. The heat insulating block according to claim 1, wherein a joint portion is formed.   The heat insulating block according to claim 1, wherein the porous spherical particles are glassy.   The heat insulating block according to claim 2, wherein the porous spherical particles are quartz glass particles.   The diameter of the said porous spherical particle is 3-30 micrometers, The block for heat insulation of any one of Claims 1-4 characterized by the above-mentioned. The heat insulation blocks according to any one of claims 1 to 5 are stacked inside the outer wall,
A low-temperature storage, wherein an inner tank is formed of an airtight film-like material inside the stacked heat insulation blocks.

Images