JP2009074604A - Vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum heat insulating material of high insulation efficiency, using easily available textile materials. <P>SOLUTION: The vacuum heat insulating material 1 is provided with an external capsule material 200 and a core material 100 accommodated inside the external capsule material 200 and the external capsule material 200 is composed capable of maintaining the inside thereof to a reduced pressure state. The core material 100 is composed by stacking a plurality of sheets of non-woven fabric 110. The non-woven fabric 110 is formed by using a glass fiber 111 and a bit of binders through the paper making process, by which the glass fiber 111 is included, thereby disposing in the parallel direction with the surface of the non-woven fabric 110. In the glass fiber 111, the aspect ratio (L/D) between an average textile length L and an average textile diameter D is 3,000 or less and the maximum deflection volume δ is represented as the maximum deflection volume δ of the two points beams δ=(5WL<SP>4</SP>)/(6ED<SP>4</SP>) using the Young's modulus E of the core material 100 and the self weight W per unit length of the glass fiber 111 and using the average textile length L and the average textile diameter D and satisfies the relation δ<2D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vacuum heat insulating material.

  Conventionally, a heat insulating material having various structures and performances is used for a refrigerator, a cold box, a warm box, and the like that are used for heating, cooling, and warming various foods. Among them, the vacuum heat insulating material can realize a very excellent heat insulating property and is used for many applications. The vacuum heat insulating material generally exhibits heat insulating performance by filling the outer packaging material with the core material, sealing the outer packaging material, and maintaining the inside of the outer packaging material in a reduced pressure state. The heat insulating performance of the vacuum heat insulating material depends on the material and structure of the core material.

  As for the conventional vacuum heat insulating material, an inorganic fiber aggregate is mainly used as a core material. The heat insulating performance of the vacuum heat insulating material is improved by performing various treatments and processing when forming the inorganic fiber aggregate used for the core material.

  For example, in the heat insulation panel described in Japanese Utility Model Laid-Open No. 61-69795 (Patent Document 1) and the vacuum heat insulation panel described in Japanese Utility Model Publication No. 62-141184 (Patent Document 2), lamination of sheets used as a core material is performed. The body is composed of waste paper or plastic sheets.

Moreover, for example, the vacuum heat insulating material described in Japanese Patent Application Laid-Open No. 2002-81596 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2005-265038 (Patent Document 4) uses fibers in a single layer sheet constituting a core material. The sheets are arranged in the heat transfer direction, that is, in the direction perpendicular to the thickness direction of the vacuum heat insulating material, and this sheet is laminated to improve the heat insulating effect. In addition, by making the average fiber diameter of the fibers in the sheet 6 μm or less, the thermal resistance of the fibers themselves is increased, and by reducing the void diameter in the fiber assembly, heat conduction by the gas inside the core material is performed. Suppressed.
Japanese Utility Model Publication No. 61-69795 Japanese Utility Model Publication No. 62-141184 JP 2002-81596 A JP 2005-265038 A

  However, in the heat insulation panel described in Japanese Utility Model Laid-Open No. 61-69795 (Patent Document 1) and the vacuum heat insulation panel described in Japanese Utility Model Laid-Open No. 62-141184 (Patent Document 2), the thermal resistance of the sheet is small. The thermal conductivity of the performance index is about 6 (mW / m · K), which is disadvantageous in that it is high as a current heat insulating material.

  Moreover, in the vacuum heat insulating material described in Japanese Patent Application Laid-Open No. 2002-81596 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2005-265038 (Patent Document 4), by using thin fibers having a fiber diameter of 6 μm or less, the lamination resistance Increases the heat insulation effect, but increases the entanglement of the fibers constituting the core material. When the entanglement between the fibers increases inside the core material, the contact area between the fibers increases, and the solid heat conduction in the sheet increases. In addition, when the fibers are entangled, heat conduction due to a heat shortcut in the heat transfer direction is likely to occur, which is an impediment to the heat insulation effect. Furthermore, in the vacuum heat insulating material described in JP-A-2002-81596 (Patent Document 3) and JP-A-2005-265038 (Patent Document 4), a thin fiber having a fiber diameter of 6 μm or less is used as a core material. Is assumed. Such fibers that are usually much thinner than the fibers that are usually used are not readily available and are disadvantageous in terms of material costs.

  Accordingly, an object of the present invention is to provide a vacuum heat insulating material having high heat insulating performance using a fiber material that can be easily obtained.

The vacuum heat insulating material according to the present invention includes an outer packaging material and a core material housed in the outer packaging material, and the outer packaging material is configured to be able to keep the inside in a reduced pressure state. Is formed by laminating a plurality of non-woven fabrics. In the non-woven fabric, the non-woven fabric is produced by a paper making method using inorganic fibers and a small amount of binder, so that the inorganic fibers are arranged in a direction parallel to the surface of the non-woven fabric. In the inorganic fiber, the aspect ratio (L / D) of the average fiber length L and the average fiber diameter D is 3000 or less, and the maximum deflection δ is the Young's modulus E of the inorganic fiber and the unit of the inorganic fiber. The maximum deflection amount is expressed as δ = (5WL ⁴ ) / (6ED ⁴ ) as the maximum deflection amount δ of the two-point support beam using the own weight W per length, the average fiber length L, and the average fiber diameter D. δ satisfies the relational expression δ <2D.

  By producing the nonwoven fabric constituting the core material by the papermaking method, the inorganic fibers constituting the nonwoven fabric are arranged in parallel in the direction along the surface of the nonwoven fabric within the nonwoven fabric. By doing in this way, the inorganic fiber which penetrates from one side of a nonwoven fabric to the other side is hard to generate. Therefore, even when a core material is configured by laminating a plurality of non-woven fabrics, inorganic fibers that penetrate from one surface of the core material to the other surface are unlikely to be generated, and therefore, from one surface of the core material to the other surface This makes it difficult to create a heat shortcut.

  On the other hand, the inorganic fiber is a fiber having an aspect ratio (L / D) of 3000 or less between the average fiber length L and the average fiber diameter D. The average fiber length L is an average length between the contact points of the fibers along the fiber length direction of one fiber. A fiber having a large aspect ratio has a large fiber length with respect to the fiber diameter, and the fibers are considered to be easily entangled. As a result of various studies by the inventor, it was found that inorganic fibers having an aspect ratio of 3000 or less are less likely to be entangled with each other. Thus, by producing a nonwoven fabric using inorganic fibers having an aspect ratio of 3000 or less, the nonwoven fabric has few entanglements between inorganic fibers, and heat transfer through the fibers can be suppressed.

In the non-woven fabric, a plurality of inorganic fibers overlap each other. When one inorganic fiber is supported on two inorganic fibers, it bends downward between two contact points with the inorganic fiber supporting the inorganic fiber. If the maximum deflection amount δ at this time is smaller than twice the average fiber diameter D, the inorganic fiber supported on the other inorganic fiber is further below the inorganic fiber supporting the inorganic fiber. It becomes difficult to entangle with fibers. The maximum deflection amount δ is expressed by an equation of the maximum deflection amount of the two-point support uniform load beam supported at two contact points with the inorganic fiber supporting the inorganic fiber. Therefore, by using the inorganic fiber satisfying the condition of the maximum deflection amount δ = (5WL ⁴ ) / (6ED ⁴ ) <2D for the nonwoven fabric of the core material, the inorganic fibers stacked vertically in the nonwoven fabric are less likely to contact each other. Since the entanglement of the inorganic fibers is less likely to occur, a heat shortcut due to the fibers is less likely to occur.

  By doing in this way, even if it uses the fiber material normally obtained without using a thin fiber, the contact and the entanglement between the fibers are reduced, and from one surface of the core material to the other surface. Since the fiber which penetrates becomes difficult to generate | occur | produce, the vacuum heat insulating material with high heat insulation performance can be provided using the fiber material which can be obtained easily. Moreover, since the easily available fiber material can be used, the manufacturing cost of a vacuum heat insulating material can be held down.

  In the vacuum heat insulating material according to the present invention, the inorganic fibers are preferably glass fibers.

  Through various studies by the inventors, it has been found that a vacuum heat insulating material using glass fibers has a lower thermal conductivity than a vacuum heat insulating material using other inorganic fibers, for example, ceramic fibers. Thus, by doing so, the heat insulation performance can be improved.

  In the vacuum heat insulating material according to the present invention, the binder is preferably an organic binder.

  By doing in this way, the softness | flexibility of the folding of a nonwoven fabric can be improved. Moreover, the manufacturing cost of a vacuum heat insulating material can be suppressed.

In the vacuum heat insulating material according to the present invention, the density of the core material is preferably included in the range of 100 to 400 kg / m ³ .

When the density of the core material is less than 100 kg / m ³ , the void diameter inside the core material becomes large, so that heat conduction occurs due to the gas contained in the void inside the core material. Therefore, the heat insulation property of a vacuum heat insulating material deteriorates. Moreover, the intensity | strength of a vacuum heat insulating material falls and the handleability of a vacuum heat insulating material worsens.

On the other hand, when the density of the core material is larger than 400 kg / m ³ , the contact between the nonwoven fabrics constituting the core material and the contact between the inorganic fibers are increased. Therefore, the influence of heat conduction by solids such as inorganic fibers and non-woven fabrics is increased, and the heat insulating properties as a vacuum heat insulating material are deteriorated.

Therefore, by making the density of the core material within the range of 100 to 400 kg / m ³ in this way, the void diameter formed by the core material is set to an optimum value, and the heat conduction of the gas and the fiber diameter contact are made. Insulation performance can be exhibited while suppressing the heat conduction of the solid due to.

  As described above, according to the present invention, it is possible to provide a vacuum heat insulating material with high heat insulating performance using a fiber material that can be easily obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a vacuum heat insulating material as one embodiment of the present invention. FIG. 1A shows a state before the inside of the outer packaging material is decompressed, and FIG. 1B shows a state when the inside of the outer packaging material is decompressed.

  As shown in FIG. 1, in the vacuum heat insulating material 1, a core material 100 is accommodated inside a gas barrier outer packaging material 200 formed in a bag shape.

  As the outer packaging material 200 for storing the core material 100 in a reduced pressure state, a material having a high gas barrier property, a heat-sealing layer, a flawed protective layer, etc. and capable of keeping the inner packaging material 200 in a reduced pressure state for a long period of time is used. To do. Further, a plurality of films having such characteristics may be laminated to form the outer packaging material 200.

  As a specific example of the structure of the outer packaging material 200, the outermost layer is made of polyethylene terephthalate (PET) resin, the intermediate layer is made of an ethylene-vinyl alcohol copolymer resin having an aluminum vapor deposition layer, and the innermost layer is made of high-density polyethylene. Examples include a gas barrier film using a resin, a gas barrier film using nylon as the outermost layer, two layers of an aluminum-deposited PET resin and an aluminum foil as the intermediate layer, and a high-density polyethylene resin as the innermost layer.

  In order to maintain the initial heat insulation performance and the temporal heat insulation performance of the vacuum heat insulating material 1, it is preferable to use a getter agent such as a gas adsorbent or a water adsorbent in the vacuum heat insulating material 1.

  As shown to (A) of FIG. 1, the core material 100 is comprised by laminating | stacking the some nonwoven fabric 110. FIG. Each nonwoven fabric 110 is produced by a papermaking method using glass fibers as inorganic fibers and a small amount of an organic binder. Although it is possible to use an inorganic binder for the binder, if an inorganic binder is used, the flexibility of bending of the fiber assembly, that is, the nonwoven fabric 110 is inferior, and the cost when used as a product is less than the organic binder. Since it becomes expensive compared with the case where it uses, it is preferable to use an organic binder. Also, the amount of binder should be kept as small as possible.

As shown in FIG. 1B, when the inside of the outer packaging material 200 is depressurized, the core material 100 is compressed by the atmospheric pressure outside the outer packaging material 200, and the nonwoven fabrics 110 constituting the core material 100 are pressed against each other. Touch as you can. The density of the core material 100 in a state where the inside of the outer packaging material 200 is decompressed is included in the range of 100 to 400 kg / m ³ .

  A nonwoven fabric is comprised as mentioned above, a nonwoven fabric is laminated | stacked, a core material is comprised, a core material is arrange | positioned inside an outer packaging material, and it pressure-reduces, and comprises a vacuum heat insulating material.

  FIG. 2 schematically shows an arrangement (A) of the core material and the outer packaging material and an internal state (B) of the vacuum heat insulating material when the pressure inside the outer packaging material is reduced as one embodiment of the present invention. It is a perspective view. Only a part of each nonwoven fabric, core material, and outer packaging material is shown.

  As shown in FIG. 2A, the core material 100 is formed by laminating a plurality of nonwoven fabrics 110. The core material 100 is covered with an outer packaging material 200. The outer packaging material 200 is gas barrier, is formed in a bag shape, and covers the entire core material 100.

  As shown in FIG. 2B, when the inside of the bag-shaped outer packaging material 200 is decompressed, the core material 100 is compressed. When the core material 100 is compressed, the nonwoven fabrics 110 come into contact with each other so as to be pressed against each other.

  FIG. 3 is a perspective view schematically showing fibers in contact with each other in one nonwoven fabric.

  As shown in FIG. 3, in the nonwoven fabric produced by the papermaking method, the uppermost glass fiber 111, the second glass fiber 112 from the top, and the third glass from the top are laminated in the vertical direction. The glass fiber 113 of the first layer and the fourth layer from the top, that is, the glass fiber 114 of the lowermost layer, are arranged along a direction parallel to the surface of the nonwoven fabric. The uppermost glass fiber 111 is supported by the two second-layer glass fibers 112 at the fulcrum 111a and the fulcrum 111b.

  FIG. 4 is a perspective view schematically showing the uppermost glass fiber supported by the glass fiber of the second layer in FIG. 3.

  As shown in FIG. 4, the uppermost glass fiber 111 shown in FIG. 3 is supported at the fulcrum 111a and the fulcrum 111b by the glass fiber 112 of the second layer. Let the average fiber diameter of each glass fiber 111,112 be the average fiber diameter D. Further, an average length of the glass fibers 111 between the fulcrum 111a and the fulcrum 111b is defined as an average fiber length L. The glass fibers 111, 112, 113, and 114 are glass fibers having an aspect ratio (L / D) <3000.

The glass fiber 111 supported at the fulcrum 111a and the fulcrum 111b bends downward. Since the equation representing the deflection of the two-point supported uniform load beam in general material mechanics is applied to the deflection amount of the glass fiber 111, the maximum deflection amount δ of the glass fiber 111 at this time is the core material 100 (FIG. Using the Young's modulus E of the glass fiber 1), the own weight W per unit length of the glass fiber 111, the average fiber length L and the average fiber diameter D of the glass fiber 111, δ = (5WL ⁴ ) / (6ED ⁴ ). The glass fiber 111 is a glass fiber in which the maximum deflection amount δ = (5WL ⁴ ) / (6ED ⁴ ) satisfies the relational expression δ <2D. Since the maximum deflection amount δ of the glass fiber 111 is smaller than 2D, the portion of the uppermost glass fiber 111 that bends downward does not come into contact with the lowermost glass fiber 114.

  As described above, as the glass fiber used for the core material, a glass fiber having material characteristics that reduces the entanglement structure between the fibers is selected. However, when a non-woven fabric is produced using fibers having few entanglements between fibers, it is difficult to maintain the strength as a thin-layer non-woven fabric sheet with only the fibers. Therefore, a thin-layer nonwoven fabric is produced using a small amount of an organic binder so that it can be handled easily as a thin-layer nonwoven fabric sheet and the influence of heat conduction can be suppressed as much as possible. By using the organic binder, although the heat insulation performance is deteriorated due to the heat conduction of the binder, the entanglement between the fibers can be suppressed to a minimum, so that the contact area between the fibers can be minimized. Thus, the solid heat conduction reduction effect by minimizing the contact area between the fibers and the solid heat conduction reduction effect by reducing the proportion of fibers contributing to the heat shortcut in the heat transfer direction by fiber entanglement 2 One effect is obtained.

As described above, the vacuum heat insulating material 1 includes the outer packaging material 200 and the core material 100 accommodated in the outer packaging material 200, and the outer packaging material 200 is configured to be able to keep the inside in a reduced pressure state. The core material 100 is configured by laminating a plurality of non-woven fabrics 110. In the non-woven fabric 110, the non-woven fabric 110 is produced by a paper making method using glass fibers (111, 112, 113, 114) and a small amount of binder. Thus, the glass fibers (111, 112, 113, 114) are arranged and included in a direction parallel to the surface of the nonwoven fabric 110. In the glass fibers (111, 112, 113, 114), the average fiber length L and The aspect ratio (L / D) with the average fiber diameter D is 3000 or less, and the maximum deflection amount δ is determined by the Young's modulus E and the glass of the glass fiber (111, 112, 113, 114). Fibers and its weight W per unit length of the (111, 112, 113, 114), using the average fiber length L and the average fiber diameter D, δ = ^(5WL 4) as [delta] maximum deflection amount of two-point support beam / (6ED ⁴ ), and the maximum deflection amount δ satisfies the relational expression δ <2D.

  The direction in which the glass fiber (111, 112, 113, 114) which comprises the nonwoven fabric 110 along the surface of the nonwoven fabric 110 is formed in the inside of the nonwoven fabric 110 by producing the nonwoven fabric 110 which comprises the core material 100 with a papermaking method. Are arranged in parallel with each other. By doing in this way, the glass fiber (111,112,113,114) which penetrates from the one surface of the nonwoven fabric 110 to the other surface is hard to generate | occur | produce. Therefore, even when the core material 100 is configured by laminating a plurality of nonwoven fabrics 110, glass fibers (111, 112, 113, 114) penetrating from one surface of the core material 100 to the other surface are unlikely to be generated. Therefore, a heat shortcut from one surface of the core member 100 to the other surface is less likely to occur.

  On the other hand, the glass fibers (111, 112, 113, 114) are fibers having an aspect ratio (L / D) of 3000 or less between the average fiber length L and the average fiber diameter D. The average fiber length L is an average length between the contact points of the fibers along the fiber length direction of one fiber. A fiber having a large aspect ratio has a large fiber length with respect to the fiber diameter, and the fibers are considered to be easily entangled. As a result of various studies by the inventors, if glass fibers (111, 112, 113, 114) having an aspect ratio of 3000 or less are found, the glass fibers (111, 112, 113, 114) are hardly entangled. was gotten. Thus, the nonwoven fabric 110 with few entanglement between glass fibers (111,112,113,114) is produced by producing the nonwoven fabric 110 using the glass fiber (111,112,113,114) whose aspect ratio is 3000 or less. Thus, heat transfer through the fiber can be suppressed.

In the nonwoven fabric 110, several glass fiber (111,112,113,114) has overlapped up and down. When one glass fiber (111, 112, 113, 114) is supported on two glass fibers (111, 112, 113, 114), the glass fiber (111, 112, 113, 114) Between the two contacts with the glass fibers (111, 112, 113, 114) supporting If the maximum deflection amount δ at this time is smaller than twice the average fiber diameter D, the fibers supported on the other glass fibers (111, 112, 113, 114) will become the glass fibers (111, 112, 113, 114) is less likely to be entangled with the glass fibers (111, 112, 113, 114) below the glass fibers (111, 112, 113, 114) that support the glass fibers (111, 112, 113, 114). The maximum deflection amount δ is the maximum deflection of the two-point supported uniform load beam supported at two contact points with the glass fibers (111, 112, 113, 114) that support the glass fibers (111, 112, 113, 114). Expressed by the quantity formula. Accordingly, the glass fiber (111, 112, 113, 114) satisfying the condition that the maximum deflection amount δ = (5WL ⁴ ) / (6ED ⁴ ) satisfies δ <2D is used for the nonwoven fabric 110 of the core material 100, so The glass fibers (111, 112, 113, 114) stacked in the upper and lower directions are less likely to come into contact with each other, and the glass fibers (111, 112, 113, 114) are less likely to be entangled with each other. Less likely to occur.

  By doing in this way, even if it uses the fiber material normally obtained without using a thin fiber, the contact and entanglement of fibers become less, and from one side of core material 100 to the other side Since the fiber which penetrates becomes difficult to generate | occur | produce, the vacuum heat insulating material 1 with high heat insulation performance can be provided using the fiber material which can be obtained easily. Moreover, since the easily available fiber material can be used, the manufacturing cost of the vacuum heat insulating material 1 can be suppressed.

  Moreover, in this way, in the vacuum heat insulating material 1, the glass fibers (111, 112, 113, 114) are glass fibers.

  Through various studies by the inventors, it has been found that the vacuum heat insulating material 1 using glass fibers has a lower thermal conductivity than the vacuum heat insulating material 1 using other inorganic fibers, for example, ceramic fibers. Thus, by doing so, the heat insulation performance can be improved.

  As described above, in the vacuum heat insulating material 1, the binder is an organic binder.

  By doing in this way, the softness | flexibility of the bending of the nonwoven fabric 110 can be improved. Moreover, the manufacturing cost of the vacuum heat insulating material 1 can be suppressed.

Further, in this way, in the vacuum heat insulating material 1, the density of the core material 100 is included in the range of 100 to 400 kg / m ³ .

When the density of the core material 100 is less than 100 kg / m ³ , the gap diameter inside the core material 100 is increased, so that heat conduction is caused by the gas contained in the gap inside the core material 100. Therefore, the heat insulation property of the vacuum heat insulating material 1 is deteriorated. Moreover, the intensity | strength of the vacuum heat insulating material 1 falls and the handleability of the vacuum heat insulating material 1 worsens.

On the other hand, when the density of the core material 100 is larger than 400 kg / m ³ , the contact between the nonwoven fabrics 110 constituting the core material 100 and the contact between the glass fibers (111, 112, 113, 114) are increased. Therefore, the influence of heat conduction due to the glass fiber (111, 112, 113, 114) or the nonwoven fabric 110 is increased, and the heat insulating properties as the vacuum heat insulating material 1 are deteriorated.

Therefore, by making the density of the core material 100 included in the range of 100 to 400 kg / m ³ in this way, the gap diameter formed by the core material 100 is set to an optimum value, and the heat conduction of the gas and the fiber Insulating performance can be exhibited while suppressing heat conduction of solids due to radial contact.

  The heat insulation effect obtained using the vacuum heat insulating material of one embodiment of this invention is demonstrated. Thermal conductivity was measured about the vacuum heat insulating material of this invention, and the conventional vacuum heat insulating material as a comparative example.

As an inorganic fiber of the core material used for the vacuum heat insulating material of one embodiment of the present invention, the average fiber diameter D is 10 μm, the average fiber length L is 1.2 cm, the aspect ratio L / D is 1200, and the maximum deflection amount δ is. A glass fiber having 17 μm, Young's modulus E of 7.7 × 10 ⁵ kg / cm ² and density of 2.52 g / cm ³ was used. Using this glass fiber and a small amount of organic binder, a thin layer nonwoven fabric was prepared by a papermaking method, and a large number of the nonwoven fabrics were laminated to prepare a core material. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the heat conductivity was as excellent as 1.5 mW / mK. Thermal conductivity measured the thermal conductivity in the average temperature of 25 degreeC with the thermal conductivity measuring apparatus.

  Moreover, focusing on the following three conditions as the core material used in the conventional vacuum heat insulating material, the thermal conductivity was also measured for seven comparative examples that were distinguished depending on whether or not they met each condition. Condition I was that the aspect ratio (L / D) of the average fiber length L and the average fiber diameter D of the inorganic fibers constituting the core material was 3000 or less. Condition II was that the maximum deflection amount δ of the inorganic fibers in the core material was not more than twice the average fiber diameter D. Condition III was that a thin layer nonwoven fabric was prepared by a paper making method using inorganic fibers, and a large number of the nonwoven fabrics were laminated to form a core material. Regarding the vacuum heat insulating materials of these comparative examples, the thermal conductivity was measured at an average temperature of 25 ° C. using a thermal conductivity measuring device.

(Comparative Example 1)
As a conventional vacuum heat insulating material, a core material that does not satisfy the conditions I and II but conforms to the condition III was used. As an inorganic fiber of the core material, the average fiber diameter D is 1 μm, the average fiber length L is 0.7 cm, the aspect ratio L / D is 7000, the maximum deflection δ is 115 μm, and the Young's modulus E is 7.7 × 10 ⁵ kg. Glass fiber with a density of 2.52 g / cm ³ / cm ² was used. Using this glass fiber and a small amount of organic binder, a thin layer nonwoven fabric was prepared by a papermaking method, and a large number of the nonwoven fabrics were laminated to prepare a core material. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the thermal conductivity was 2.2 mW / mK.

(Comparative Example 2)
As a conventional vacuum heat insulating material, a core material not conforming to any of the conditions I, II and III was used. The core material was produced by forming a fiber wool fiber aggregate into a sheet and drying it at 110 ° C. for 1 hour in order to remove moisture contained in the obtained core material. The bulk density of the sheet-like fiber assembly was 219 kg / m ³ and the average fiber diameter D was 4 μm. The average fiber length L was 3 cm, the aspect ratio L / D was 7500, and the maximum deflection δ was 11390 μm. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the thermal conductivity was 2.2 mW / mK.

(Comparative Example 3)
As a conventional vacuum heat insulating material, a core material that meets the conditions I and II but does not meet the condition III was used. The core material was produced by forming a fiber wool fiber aggregate into a sheet and drying it at 110 ° C. for 1 hour in order to remove moisture contained in the obtained core material. The average fiber diameter D of the glass wool fiber was 0.8 μm, the average fiber length L was 0.2 cm, the aspect ratio L / D was 2500, and the maximum deflection δ was 0.34 μm. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the thermal conductivity was 1.8 mW / mK.

(Comparative Example 4)
As a conventional vacuum heat insulating material, a core material that conforms to conditions I and III but does not conform to condition II was used. As the inorganic fibers of the core material, glass fibers having an average fiber diameter D of 3.5 μm, an average fiber length L of 1 cm, an aspect ratio L / D of 2857, and a maximum deflection amount δ of 61 μm were used. Using this glass fiber and a small amount of organic binder, a thin layer nonwoven fabric was prepared by a papermaking method, and a large number of the nonwoven fabrics were laminated to prepare a core material. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the thermal conductivity was 2.2 mW / mK.

(Comparative Example 5)
As a conventional vacuum heat insulating material, a core material that conforms to Condition I and does not conform to Conditions II and III was used. The core material was produced by forming a fiber wool fiber aggregate into a sheet and drying it at 110 ° C. for 1 hour in order to remove moisture contained in the obtained core material. The average fiber diameter D of the glass wool fiber was 7 μm, the average fiber length L was 2 cm, the aspect ratio L / D was 2857, and the maximum deflection δ was 445 μm. When the thermal conductivity of the vacuum heat insulating material produced using this core material was measured, the thermal conductivity was 5 mW / mK.

(Comparative Examples 6 and 7)
The core material used as Comparative Example 6 that does not conform to Condition I and conforms to Condition II and Condition III, and the core material used as Comparative Example 7 that does not conform to Condition I and Condition III and conforms to Condition II, not exist.

  Table 1 shows the thermal conductivity λ (mW / mK), the aspect ratio L / D, and the average fiber diameter D for the vacuum heat insulating material of one embodiment of the present invention and Comparative Examples 1 to 5. (Μm), maximum deflection amount δ (μm), and average fiber length L (cm) are shown.

  As shown in Table 1, by using the vacuum heat insulating material of one embodiment of the present invention that meets all three conditions of Condition I, Condition II and Condition III, a vacuum heat insulating material having excellent heat insulating performance is obtained. I was able to get it.

(Comparative Example 8)
As a conventional vacuum heat insulating material, a vacuum heat insulating material using ceramic fibers as the inorganic fiber of the core material was produced, and the thermal conductivity at an average temperature of 24 degrees was measured. The bulk density of the core material was 310 kg / m ³ . The thermal conductivity was 3.9 mW / mK.

  Thus, by using ceramic fibers as the core material, the thermal conductivity value was increased as compared with the vacuum heat insulating material of the present invention using glass fibers. Since the thermal conductivity of the ceramic itself is larger than that of glass, it is preferable to use glass fiber as the core material in view of heat insulation performance.

  As described above, by using the vacuum heat insulating material according to the present invention, it is possible to provide a device such as a refrigerator excellent in heat insulating performance and energy saving.

  It should be considered that the embodiments and examples disclosed above are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of the claims, and includes all modifications and variations within the meaning and scope equivalent to the scope of the claims.

It is sectional drawing which shows typically the structure of a vacuum heat insulating material as one embodiment of this invention. FIG. 1A shows a state before the inside of the outer packaging material is decompressed, and FIG. 1B shows a state when the inside of the outer packaging material is decompressed. As one embodiment of this invention, it is a perspective view showing typically an arrangement (A) of a core material and an outer packaging material, and a state (B) inside a vacuum heat insulating material when the inside of the outer packaging material is decompressed. . It is a perspective view which shows typically the fiber which mutually contacts in the nonwoven fabric of 1 sheet. It is a perspective view which shows typically the inorganic fiber of the uppermost layer currently supported by the inorganic fiber of the 2nd layer of FIG.

Explanation of symbols

  1: vacuum heat insulating material, 100: core material, 200: outer packaging material, 110: non-woven fabric, 111, 112, 113, 114: glass fiber.

Claims (4)

Outer packaging materials,
A core material housed inside the outer packaging material,
The outer packaging material is configured to be able to keep the inside in a reduced pressure state,
The core material is configured by laminating a plurality of nonwoven fabrics,
In the non-woven fabric, the non-woven fabric is produced by a paper making method using inorganic fibers and a small amount of a binder, so that the inorganic fibers are included in a direction parallel to the surface of the non-woven fabric,
In the inorganic fiber, the aspect ratio (L / D) between the average fiber length L and the average fiber diameter D is 3000 or less, and the maximum deflection δ is the Young's modulus E of the inorganic fiber and the unit length of the inorganic fiber. The maximum deflection amount is expressed as δ = (5WL ⁴ ) / (6ED ⁴ ) as the maximum deflection amount δ of the two-point support beam using the dead weight W per length, the average fiber length L, and the average fiber diameter D. δ is a vacuum heat insulating material that satisfies the relational expression of δ <2D.   The vacuum heat insulating material according to claim 1, wherein the inorganic fibers are glass fibers.   The vacuum heat insulating material according to claim 1, wherein the binder is an organic binder. The vacuum heat insulating material according to any one of claims 1 to ³ , wherein the density of the core material is included in a range of 100 to 400 kg / m ³ .

Images