JP2006161972A - Vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum heat insulating material with a solid component having less heat conduction by suppressing the compression of a core material due to atmospheric pressure applied thereto during vacuum packaging. <P>SOLUTION: The vacuum heat insulating material comprises the core material 3 formed of glass fibers 1 and a facing material. The glass fibers 1 of the core material 3 have greater one of tensile break strength, tensile modulus and bending modulus. With the tensile break strength or the tensile modulus being greater, peripheral spaces are held without breaking fibers when compressed by the atmospheric pressure and the peripheral fibers hardly contact each other, suppressing an increase in the heat conduction of the solid component. With the bending modulus being greater, the fibers are hardly bent and the fibers hardly contact each other, suppressing an increase in the heat conduction of the solid component. Thus, the vacuum heat insulating material is obtained with the solid component having less heat conduction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vacuum heat insulating material, and more particularly to a core material.

  Conventionally, a core material for a vacuum heat insulating material has been used an inorganic material having low thermal conductivity and low gas generation. Particularly, a vacuum heat insulating material using a core material obtained by laminating glass fibers is excellent. It has heat insulation performance (see, for example, Patent Document 1).

  FIG. 7 shows an enlarged side view of the core material of the conventional vacuum heat insulating material described in Patent Document 1. As shown in FIG. As shown in FIG. 7, the inorganic fibers 1 are arranged in a direction perpendicular to the heat transfer direction and in a direction parallel to the heat transfer direction.

About the conventional vacuum heat insulating material comprised as mentioned above, the operation | movement is demonstrated below. Since the fibers arranged in the direction perpendicular to the heat transfer direction are in contact with each other at a point, the heat conduction of the solid component by these fibers is small. Since only the fibers in the direction perpendicular to the heat transfer direction are weak against pressure, they are compressed by the atmospheric pressure that acts during vacuum packaging. However, durability against atmospheric pressure during vacuum packaging is ensured by the fibers parallel to the heat transfer direction.
JP-A-60-208696

  However, in the above conventional configuration, since the fibers parallel to the heat transfer direction easily transfer heat, there is a problem that the heat conduction of the solid component increases.

  On the other hand, in the core material composed only of fibers perpendicular to the heat transfer direction, the heat conduction of the solid component increases due to the following factors.

  A fiber having a low tensile breaking strength, tensile elastic modulus, and bending elastic modulus is easily broken by a tensile force and is easily bent by a force acting from the lateral direction. Accordingly, the force generated in the core material by the compressive force due to the atmospheric pressure causes breakage or large bending.

  A compressive force is applied to the glass fiber through the jacket material. Since the fibers inside the core material are intertwined, a plurality of points are fixed by the compressive force of the surrounding fibers, and when a force is applied in a direction in which these points are separated, a tensile force is generated. When this tensile force exceeds the tensile breaking strength of the fiber, the fiber breaks.

  When the fiber breaks, the space held by the presence of the fiber disappears, and the fibers that are not in contact with each other come into contact with each other, so that heat is easily transmitted. Furthermore, heat is easily transferred also when the broken portion of the fiber comes into contact with the nearby fiber.

  Further, when a force acts in a direction perpendicular to the longitudinal direction of the fiber due to the compressive force, it bends, and since the bending elastic modulus is small, the bending is large. When the fibers are separated from each other, they become closer to each other by bending, and when the bending is large, the fibers come into contact with each other so that heat is easily transmitted.

  The present invention solves the above-mentioned conventional problems, and provides a vacuum heat insulating material that suppresses heat conduction of a solid component caused by fibers in the direction parallel to the heat transfer direction and is not easily compressed by atmospheric pressure. With the goal.

  In order to solve the above-mentioned conventional problems, the vacuum heat insulating material of the present invention is produced by laminating glass fibers having a large tensile breaking strength, tensile elastic modulus, or bending elastic modulus in a direction perpendicular to the heat transfer direction. The core material thus produced is produced by vacuum packaging.

  Due to the increased tensile breaking strength or tensile elastic modulus, the fibers do not break even when compressed by atmospheric pressure, the surrounding space is maintained, the surrounding fibers are difficult to contact each other, and the heat conduction of the solid component is increased. Is suppressed. Since the flexural modulus is increased, the fibers are less likely to bend, the fibers are less likely to contact each other, and an increase in the heat conduction of the solid component is suppressed. Accordingly, it is possible to obtain a vacuum heat insulating material in which the heat conduction of the solid component is kept low.

  The vacuum heat insulating material of the present invention has a more excellent heat insulating performance than a vacuum heat insulating material manufactured using a core material manufactured using glass having the same thermal conductivity.

  The invention according to claim 1 is provided with a core material made of glass fiber and a jacket material made of a laminate film, the core material is covered with the laminate film, and the inside is sealed after decompression, Since any one of tensile rupture strength, tensile elastic modulus, and flexural modulus is reinforced, the core material is a vacuum heat insulating material that is difficult to be compressed by atmospheric pressure.

  When the tensile breaking strength or tensile modulus of the glass fiber is large, even if a tensile force is applied to the fiber entangled in the core material due to atmospheric pressure, it is difficult to break, and the presence of this fiber maintains the space. When the flexural modulus is large, it is difficult for the glass fiber to be bent by a force in a direction perpendicular to the length direction applied to the glass fiber by atmospheric pressure. Since the bending is small, even if the distance of the glass fiber when it is not bent is small, it becomes difficult to contact.

  Therefore, it can suppress that heat comes to be transmitted when a glass fiber bends. As the core material, the core material is difficult to be compressed by the atmospheric pressure applied when vacuum packaging is performed, and heat is hardly transmitted by maintaining the space in the core material, thereby obtaining a vacuum heat insulating material that keeps the heat conduction of the solid component low. be able to.

  The mechanical strength of glass is dominated by the tensile force acting on the surface and breaks when the tensile force exceeds a limit. Glass is inherently very strong in mechanical strength, but normal glass becomes brittle because it breaks easily due to stress concentration on the Griffith cracks existing on the surface. Has become dominant.

  For this reason, the glass is strengthened by improving the durability against the tensile force by preliminarily applying a compressive stress to the surface of the glass. In order to impart compressive stress to the glass surface, there are mainly a quenching method and a method by ion exchange. The method of quenching is performed by blowing air on the heated glass. Ion exchange is performed by exchanging Na ions in the glass with K ions.

  Glass fibers can be reinforced in a similar manner. It is effective to quench the glass fiber from the fiberizing apparatus in a molten state and quench the glass fiber by cooling air before blowing.

  When the Griffith crack is removed from the surface, the mechanical strength increases, so that the strength can also be increased by treating the glass fiber with hydrofluoric acid.

  The method for increasing the mechanical strength of the glass fiber is not limited to those described above.

  Invention of Claim 2 is a vacuum heat insulating material in which the glass fiber is hard to be fractured | ruptured by pressurization in the invention of Claim 1.

  The fact that glass fibers are not easily broken by pressurization means that many glass fibers remain long even when pressed, and if the fiber length is long, the space near the fiber is retained. As a result, the thermal conductivity of the entire core material is reduced. Accordingly, it is possible to obtain a vacuum heat insulating material in which the heat conduction of the solid component is kept low.

  Invention of Claim 3 is a vacuum heat insulating material in which the glass fiber is strengthened by rapid cooling in the invention of Claim 1 or 2.

  Since the rapid cooling of the glass fiber is facilitated by blowing a cooling gas to the glass immediately after fiberization in the molten state, a core material having a large tensile rupture strength, tensile elastic modulus, or bending elastic modulus of the fiber is obtained. It is possible to obtain a vacuum heat insulating material that suppresses the heat conduction of the solid component at a low cost.

  The invention according to claim 4 is a vacuum heat insulating material in which the glass fiber is reinforced by ion exchange in the invention according to claim 1 or 2.

  When the glass is strengthened by ion exchange, a glass fiber having a larger tensile break strength, tensile elastic modulus, or flexural modulus than that of the glass strengthened by rapid cooling can be obtained. Therefore, by using this fiber for the core material, it is possible to obtain a vacuum heat insulating material in which the heat conduction of the solid component is kept low.

  Invention of Claim 5 is a vacuum heat insulating material with which the glass fiber is strengthened by processing with hydrofluoric acid in the invention of Claim 1 or 2.

  When the glass fiber is reinforced with hydrofluoric acid, the Griffith crack on the surface is removed, so that a glass fiber having a strength close to the theoretical strength can be obtained. Therefore, by using this fiber for the core material, it is possible to obtain a vacuum heat insulating material in which the heat conduction of the solid component is kept low.

The invention according to claim 6 is the invention according to claims 1 to 5, wherein the vacuum heat insulating material is compressed so that the density of the core part of the vacuum heat insulating material is 300 kg / m ³ or more, and the vacuum heat insulating material is compressed. The tensile rupture strength in the direction perpendicular to the heat transfer direction of the core material disassembled and taken out is 700 kPa or more calculated from the core material cross-sectional area when the vacuum heat insulating material is compressed.

  The tensile breaking strength of the core material is caused by the tensile breaking strength of the glass fiber. When the core material has a tensile strength at break of 700 kPa or more, a space in the core material is maintained, and a vacuum heat insulating material in which the heat conduction of the solid component is suppressed can be obtained.

The invention according to claim 7 compresses the vacuum heat insulating material so that the density of the core material part of the vacuum heat insulating material is 300 kg / m ³ or more and 350 kg / m ³ or less in the invention of claim 1 to 5. Then, after the vacuum heat insulating material is left in an atmosphere of 133 Pa or less, the thickness of the core material portion where the vacuum heat insulating material is left under atmospheric pressure is 10% compared to the thickness of the core material portion after compression. It is thicker than that.

  When the pressure applied to the compressed core material is removed, the density decreases. Therefore, once the vacuum insulation material was disassembled and reused, there was little effect on the heat conduction of the solid component, and the heat conduction of the solid component was kept low even if the core material was reused. A vacuum heat insulating material can be obtained.

  The invention according to claim 8 is a vacuum heat insulating material in which the core material is covered with a gas barrier outer covering material and the inside of the outer covering material is sealed under reduced pressure, and the core member has a tensile breaking strength and a tensile strength. Glass fibers reinforced in either elastic modulus or flexural modulus are laminated in a direction perpendicular to the heat transfer direction and laminated so that the fibers adjacent to the heat transfer direction do not face the same direction. It is a vacuum heat insulating material formed by pressure forming.

  When the tensile breaking strength or tensile modulus of the glass fiber is large, even if a tensile force is applied to the fiber entangled in the core material due to atmospheric pressure, it is difficult to break, and the presence of this fiber maintains the space. When the flexural modulus is large, it is difficult for the glass fiber to be bent by a force in a direction perpendicular to the length direction applied to the glass fiber by atmospheric pressure. Since the bending is small, even if the distance of the glass fiber when it is not bent is small, it becomes difficult to contact.

  Therefore, it can suppress that heat comes to be transmitted when a glass fiber bends. As the core material, the core material is difficult to be compressed by the atmospheric pressure applied when vacuum packaging is performed, and heat is hardly transmitted by maintaining the space in the core material, thereby obtaining a vacuum heat insulating material that keeps the heat conduction of the solid component low. be able to.

  The mechanical strength of glass is dominated by the tensile force acting on the surface and breaks when the tensile force exceeds a limit. Glass is inherently very strong in mechanical strength, but normal glass becomes brittle because it breaks easily due to stress concentration on the Griffith cracks existing on the surface. Has become dominant.

  For this reason, the glass is strengthened by improving the durability against the tensile force by preliminarily applying a compressive stress to the surface of the glass. In order to impart compressive stress to the glass surface, there are mainly a quenching method (called a heating rapid cooling method or an air cooling strengthening method) and an ion exchange method (called an ion exchange method or a chemical strengthening method). The method of quenching is performed by blowing air on the heated glass. Ion exchange is performed by exchanging Na ions in the glass with K ions.

  Glass fibers can be reinforced in a similar manner. It is effective to quench the glass fiber from the fiberizing apparatus in a molten state and quench the glass fiber by cooling air before blowing.

  When the Griffith crack is removed from the surface, the mechanical strength increases, so that the strength can also be increased by treating the glass fiber with hydrofluoric acid.

  The method for increasing the mechanical strength of the glass fiber is not limited to those described above.

  The invention according to claim 9 is a vacuum heat insulating material in which the core material is covered with a gas barrier outer covering material, and the inside of the outer covering material is sealed under reduced pressure, and the core member has a compressive stress layer on the surface. A vacuum heat insulating material obtained by laminating glass fibers formed in a direction perpendicular to the heat transfer direction and heating and press-molding them so that fibers adjacent to the heat transfer direction do not face the same direction. is there.

  Glass fiber with a compressive stress layer formed on its surface has higher mechanical strength and has higher tensile rupture strength, tensile elastic modulus and flexural modulus than glass fiber without a compressive stress layer formed on the surface. In addition, even when a force is applied from a direction perpendicular to the length direction of the fiber, it has a characteristic that it is difficult to bend and break.

  Therefore, glass fibers with a compressive stress layer formed on the surface are laminated in a direction perpendicular to the heat transfer direction, and the fibers adjacent to each other in the heat transfer direction are not oriented in the same direction. The core material is less compressed by pressure than the core material formed by similarly forming a conventional glass fiber having no compression stress layer formed on the surface, and even if the pressure is applied, the fiber length However, since many glass fibers remain long, the porosity of the core material is high, the path through which heat travels through the glass fibers is small, and the heat conduction of the solid component of the core material is small. Therefore, a vacuum heat insulating material excellent in heat insulating performance can be provided.

  In the invention according to claim 10, the compressive stress layer in the invention according to claim 9 is formed by an air cooling strengthening method, and is a quenching method (heating quenching method or air cooling strengthening method), that is, Glass fiber in which mechanical strength is increased by forming a compressive stress layer on the surface by blowing a cooling gas onto the glass fiber immediately after fiberization in a molten state and quenching it to create a density difference between the surface layer and the inside. Can be obtained.

  According to an eleventh aspect of the present invention, the compressive stress layer in the ninth aspect of the invention is formed by an ion exchange method, and a method by ion exchange (ion exchange method or chemical strengthening method), that is, Na A glass fiber containing ions is immersed in an aqueous solution containing K ions, and Na ions in the glass fibers are exchanged with K ions larger than Na ions, whereby a compressive stress layer is formed on the surface and mechanical strength is increased. It is possible to obtain a glass fiber having a large thickness.

  The invention according to claim 12 is a vacuum heat insulating material in which the core material is covered with a gas barrier outer covering material and the inside of the outer covering material is sealed under reduced pressure, and the core member has a surface Griffith crack. It is a vacuum heat insulating material formed by laminating the removed glass fibers in a direction perpendicular to the heat transfer direction and heating and press-molding them so that the fibers adjacent in the heat transfer direction do not face the same direction. .

  A normal glass fiber has a Griffith crack on its surface. Therefore, when a force is applied to the glass fiber, stress concentrates on the Griffith crack existing on the surface, and the glass fiber is likely to break from the Griffith crack.

  Griffith cracks on the surface of the glass fiber can be removed by treating the glass fiber with hydrofluoric acid. Removing the Griffith crack from the surface of the glass fiber increases the mechanical strength, which is close to the theoretical strength. A glass fiber having strength can be obtained.

  The glass fiber from which the surface Griffith crack has been removed has a higher mechanical strength than the glass fiber from which the surface Griffith crack has not been removed, and even if a force is applied from a direction perpendicular to the length direction of the fiber, It has the characteristic that it is difficult to bend and break easily.

  Therefore, the glass fibers from which the Griffith cracks on the surface have been removed are laminated in a direction perpendicular to the heat transfer direction and laminated so that the fibers adjacent to the heat transfer direction do not face the same direction. The core material is more difficult to compress by pressure than the core material formed by similarly forming the conventional glass fiber from which the surface Griffith crack has not been removed, and the fiber length is long even when pressed. Since many glass fibers remain, the porosity of the core material is high, there are few ways for heat to travel through the glass fibers, and the heat conduction of the solid component of the core material is small. Therefore, a vacuum heat insulating material excellent in heat insulating performance can be provided.

  The invention according to claim 13 is such that the Griffith crack on the surface of the glass fiber in the invention according to claim 12 is removed by hydrofluoric acid treatment, and the glass fiber is treated with hydrofluoric acid. By this, the glass fiber from which the Griffith crack of the surface was removed and mechanical strength became large can be obtained.

  In the invention described in claim 14, the core material in the invention described in any one of claims 8 to 13 does not include a binder.

  Glass fiber can be molded without using a binder under the specified heating and pressing conditions, and heat transmitted between adjacent fibers can be increased compared to molding with a binder. It is possible to reduce the conduction.

  Therefore, in the invention according to any one of claims 8 to 13, a vacuum heat insulating material having further excellent heat insulating performance can be provided by using a core material formed by heating and pressing to use a binder. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The heat conduction mechanism described in the present embodiment schematically shows a process in which heat is transmitted through the fibers constituting the core material. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a vacuum heat insulating material according to Embodiment 1 of the present invention. FIG. 2 is a schematic view showing a cross section of the core material of the vacuum heat insulating material in the same embodiment. FIG. 3 is a schematic view showing a cross section of the core material after vacuum packaging of the vacuum heat insulating material in the same embodiment. FIG. 4 is a schematic view showing a cross section of a tensile strength measurement test piece in the same embodiment.

  In FIG. 1, the vacuum heat insulating material 2 includes a core material 3, a jacket material 4, and an adsorbent 5. 2 to 3, the core material 3 is composed of glass fibers 1a arranged substantially parallel to the cross section of the core material and glass fibers 1b arranged substantially perpendicular to the cross section of the core material. FIG. 4 shows glass fibers 1a arranged substantially parallel to the cross section of the test piece and glass fibers 1b arranged substantially perpendicular to the cross section of the test piece.

  In the following description, the glass fiber that does not specify the arrangement direction will be described with reference numeral 1 attached to the glass fiber.

  The core material 3 is formed by forming the glass fiber 1 into a plate shape, and the jacket material 4 is configured using linear low density polyethylene as a sealant layer, aluminum as a metal foil, and nylon as an outermost layer. It is a laminated film. The adsorbent 5 is calcium oxide.

  The glass fiber 1 constituting the core material 3 is baked by rapidly cooling the fiber in a state of 700 ° C., which is a temperature near the softening point, with air in the step of fiberizing the glass. It has been put in.

  Accordingly, the flexural modulus and tensile breaking strength are increased. Glass wool obtained by laminating the fibers thus produced was used as raw cotton for producing the core material 3. The core material 3 was formed and formed by compressing glass fiber while heating.

  The core material 3 produced in this way was inserted into the outer cover material 4 which was made in advance with a three-side seal together with the adsorbent 5 and then sealed down after reducing the pressure to 13 Pa to produce a vacuum heat insulating material 2. As shown in FIG. 3, the glass fiber 1a facing substantially parallel to the cross section is in contact only through the glass fiber 1b facing substantially perpendicular to the cross section.

  Since the atmospheric pressure is applied to the jacket material 4, the core material 3 receives a compressive force from the jacket material 4, so that the glass fiber 1 a oriented substantially parallel to the cross section is separated by the glass fiber 1 b oriented substantially perpendicular to the cross section. Bends in the direction that shrinks. Here, since the bending elastic modulus of the glass fiber 1 is large, the bending is small, and the contact with the other glass fiber 1 of the bent glass fiber 1 is suppressed.

  Further, a tensile force is generated in the fibers entangled inside the core member 3 due to the atmospheric pressure. Due to the increased tensile breaking strength or tensile elastic modulus, the fibers do not break even when compressed by atmospheric pressure, the surrounding space is maintained, the surrounding fibers are difficult to contact each other, and the heat conduction of the solid component is increased. Is suppressed.

  Evaluation of the vacuum heat insulating material produced by setting the temperature of the air which cools to -10 degreeC was performed.

  The thermal conductivity was 0.0015 W / mK. This is because the heat conduction of the solid component is reduced because the contact between the fibers inside the core material 3 is suppressed.

  The tensile strength at break of the core material 3 was 800 kPa. This is because the tensile breaking strength of the core material 3, which is an aggregate of the glass fibers 1, is increased by increasing the tensile breaking strength of the glass fiber 1.

  The test piece was attached to a tensile test apparatus so that a tensile force was applied to the long side direction of the test piece, and the distance between the test piece and the fixed part of the test apparatus was increased.

  As shown in FIG. 4, the test piece has fibers substantially parallel to the cross-sectional direction, and the total breaking force when these fibers are pulled becomes the tensile breaking strength of the core material 3. When the core material 3 which is an aggregate of fibers is pulled, the core material 3 may break due to the fiber breaking, or may break due to the fiber coming off.

  The force for pulling out the fiber is smaller than the force for breaking the fiber. For this reason, the force required to break the core material 3 due to the fibers coming out is smaller than the force necessary to break the core material 3 due to the fibers breaking.

  Accordingly, when the fiber breaks due to the fiber being pulled out, the tensile breaking strength of the core material 3 is estimated even if it is small. In order to accurately measure the tensile strength of the core material 3, the maximum value obtained by optimizing the fixing conditions of the tensile test apparatus and the core material 3 is taken as the tensile rupture strength of the core material 3.

  The average fiber length of the fibers constituting the glass wool before preparation of the core material 3 was 53 mm. This is because the tensile breaking strength of the fiber is increased due to the rapid cooling.

  The restoration rate after compression of the core material 3 was 29.5%. This is because the glass fiber 1 constituting the core material 3 has a high flexural modulus, and the core material 3 that is an aggregate of fibers is easily restored even when compressed. The compression ratio was measured as follows.

  The core material 3 was compressed and then placed in a vacuum chamber, the chamber pressure was reduced to 13 Pa, and the core material 3 was left for 1 minute. Since the chamber internal pressure is low, the core 3 part of the vacuum heat insulating material 2 is in a state where no pressure is applied, as in the case where the vacuum heat insulating material 2 is disassembled. Accordingly, the thickness is restored by the bending elastic modulus of the fibers of the core material 3. The chamber was removed after returning to atmospheric pressure. The core material 3 of the vacuum heat insulating material 2 taken out is thicker than before being installed in the chamber.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. The glass fiber 1 in which any one of the tensile breaking strength, the tensile elastic modulus, and the bending elastic modulus is reinforced is oriented in a direction perpendicular to the heat transfer direction, and fibers adjacent to the heat transfer direction do not face the same direction. It is the vacuum heat insulating material 2 laminated | stacked on and heat-press-molding.

  If the tensile strength or tensile modulus of the glass fiber 1 is large, even if a tensile force is applied to the fiber entangled in the core material 3 due to atmospheric pressure, the glass fiber 1 is not easily broken, and the presence of this fiber maintains the space. When the bending elastic modulus is large, it is difficult for the glass fiber 1 to be bent by a force in a direction perpendicular to the length direction applied to the glass fiber 1 by atmospheric pressure. Since bending is small, even if the distance of the glass fiber 1 when not bent is small, it becomes difficult to contact.

  Therefore, it can suppress that heat comes to be transmitted when the glass fiber 1 bends. As the core material 3, the core material 3 is hardly compressed by the atmospheric pressure applied when vacuum packaging is performed, and heat is not easily transmitted by maintaining the space in the core material 3, and the heat insulation of the solid component is kept low. The material 2 can be obtained.

  The mechanical strength of glass is dominated by the tensile force acting on the surface and breaks when the tensile force exceeds a limit. Glass is inherently very strong in mechanical strength, but normal glass becomes brittle because it breaks easily due to stress concentration on the Griffith cracks existing on the surface. Has become dominant.

  For this reason, the glass is strengthened by improving the durability against the tensile force by preliminarily applying a compressive stress to the surface of the glass.

  It is effective that the glass fiber 1 is quenched from the fiberizing apparatus in a molten state and rapidly cooled by blowing cooling air onto the fiber before cooling.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. However, the glass fiber 1 having a compressive stress layer formed on the surface thereof is oriented in the direction perpendicular to the heat transfer direction and laminated so that the fibers adjacent to the heat transfer direction do not face the same direction. This is a vacuum heat insulating material 2 formed by molding.

  The glass fiber 1 having a compressive stress layer formed on the surface has a higher mechanical strength and a higher tensile rupture strength, tensile elastic modulus, and bending elastic modulus than a glass fiber having no compressive stress layer formed on the surface. Therefore, even if a force is applied from a direction perpendicular to the length direction of the fiber, it has a characteristic that it is difficult to bend and break.

  Therefore, the glass fiber 1 having a compressive stress layer formed on the surface is laminated in a direction perpendicular to the heat transfer direction and the fibers adjacent in the heat transfer direction are stacked so as not to face the same direction. The core material 3 formed is harder to be compressed by pressure than a core material formed by similarly forming a conventional glass fiber having no compression stress layer formed on the surface, and even if pressed, Since many glass fibers with a long fiber length remain, the porosity of the core material 3 is high, the path through which heat travels through the glass fiber 1 is small, and the heat conduction of the solid component of the core material 3 is small. Therefore, the vacuum heat insulating material 2 excellent in heat insulating performance can be provided.

  In the present embodiment, the compressive stress layer is formed by an air cooling strengthening method. A method of quenching (heating quenching method or air cooling strengthening method), that is, by cooling the glass fiber immediately after fiberization in a molten state by quenching it, and making a difference in density between the surface layer and the interior, The glass fiber 1 in which the compressive stress layer is formed and the mechanical strength is increased can be obtained.

  Moreover, the core material 3 of this Embodiment does not contain a binder. The glass fiber 1 can be molded without using a binder under predetermined heating and pressing conditions, and is transmitted between adjacent fibers as compared with the case of molding with a binder. It is possible to reduce heat conduction.

  Therefore, by using the core material 3 that is formed by heating and pressing to use the binder, it is possible to provide a vacuum heat insulating material that is further excellent in heat insulating performance.

(Embodiment 2)
FIG. 5 is a schematic diagram showing a cross section of the core material 3 of the vacuum heat insulating material 2 according to Embodiment 2 of the present invention.

  The glass fiber 1 has enhanced tensile strength and tensile modulus by ion exchange. When ion exchange is performed, the tensile breaking strength becomes very large because compressive stress is applied to the surface of the glass fiber 1. Due to the increased tensile breaking strength, the fibers do not break even when compressed by atmospheric pressure, the surrounding space is maintained, the surrounding fibers are less likely to contact each other, and the increase in heat conduction of the solid component is suppressed. .

  Therefore, heat is not easily transmitted and low thermal conductivity can be realized.

  The thermal conductivity was 0.0016 W / mK, the tensile strength at break was 900 kPa, the average fiber length was 20 mm, and the core 3 had a restoration rate after compression of 23.3%.

  The method for producing the vacuum heat insulating material 2 and the method for measuring each physical property, such as a method for producing the core material 3 from raw cotton, a bag making method for the jacket material 4, and the like, are the same as those in the first embodiment.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. The glass fiber 1 in which any one of the tensile breaking strength, the tensile elastic modulus, and the bending elastic modulus is reinforced is oriented in a direction perpendicular to the heat transfer direction, and fibers adjacent to the heat transfer direction do not face the same direction. It is the vacuum heat insulating material 2 laminated | stacked on and heat-press-molding.

  If the tensile strength or tensile modulus of the glass fiber 1 is large, even if a tensile force is applied to the fiber entangled in the core material 3 due to atmospheric pressure, the glass fiber 1 is not easily broken, and the presence of this fiber maintains the space. When the bending elastic modulus is large, it is difficult for the glass fiber 1 to be bent by a force in a direction perpendicular to the length direction applied to the glass fiber 1 by atmospheric pressure. Since bending is small, even if the distance of the glass fiber 1 when not bent is small, it becomes difficult to contact.

  Therefore, it can suppress that heat comes to be transmitted when the glass fiber 1 bends. As the core material 3, the core material 3 is hardly compressed by the atmospheric pressure applied when vacuum packaging is performed, and heat is not easily transmitted by maintaining the space in the core material 3, and the heat insulation of the solid component is kept low. The material 2 can be obtained.

  The mechanical strength of glass is dominated by the tensile force acting on the surface and breaks when the tensile force exceeds a limit. Glass is inherently very strong in mechanical strength, but normal glass becomes brittle because it breaks easily due to stress concentration on the Griffith cracks existing on the surface. Has become dominant.

  For this reason, the glass is strengthened by improving the durability against the tensile force by preliminarily applying a compressive stress to the surface of the glass.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. However, the glass fiber 1 having a compressive stress layer formed on the surface thereof is oriented in the direction perpendicular to the heat transfer direction and laminated so that the fibers adjacent to the heat transfer direction do not face the same direction. This is a vacuum heat insulating material 2 formed by molding.

  The glass fiber 1 having a compressive stress layer formed on the surface has a higher mechanical strength and a higher tensile rupture strength, tensile elastic modulus, and bending elastic modulus than a glass fiber having no compressive stress layer formed on the surface. Therefore, even if a force is applied from a direction perpendicular to the length direction of the fiber, it has a characteristic that it is difficult to bend and break.

  Therefore, the glass fiber 1 having a compressive stress layer formed on the surface is laminated in a direction perpendicular to the heat transfer direction and the fibers adjacent in the heat transfer direction are stacked so as not to face the same direction. The core material 3 formed is harder to be compressed by pressure than a core material formed by similarly forming a conventional glass fiber having no compression stress layer formed on the surface, and even if pressed, Since many glass fibers with a long fiber length remain, the porosity of the core material 3 is high, the path through which heat travels through the glass fiber 1 is small, and the heat conduction of the solid component of the core material 3 is small. Therefore, the vacuum heat insulating material 2 excellent in heat insulating performance can be provided.

  In the present embodiment, the compressive stress layer is formed by an ion exchange method, and a method by ion exchange (ion exchange method or chemical strengthening method), that is, a glass fiber containing Na ions is used as K. By immersing in an aqueous solution containing ions and exchanging Na ions in the glass fibers with K ions larger than Na ions, a glass fiber 1 having a compressive stress layer formed on the surface and having increased mechanical strength is obtained. be able to.

  Moreover, the core material 3 of this Embodiment does not contain a binder. The glass fiber 1 can be molded without using a binder under predetermined heating and pressing conditions, and is transmitted between adjacent fibers as compared with the case of molding with a binder. It is possible to reduce heat conduction.

  Therefore, by using the core material 3 that is formed by heating and pressing to use the binder, it is possible to provide a vacuum heat insulating material that is further excellent in heat insulating performance.

(Embodiment 3)
FIG. 6 is a schematic diagram showing a cross section of the core material 3 of the vacuum heat insulating material 2 according to Embodiment 3 of the present invention.

  The glass fiber 1 is treated with hydrofluoric acid to remove the Griffith crack on the surface, thereby strengthening the tensile strength at break. Since the surface Griffith crack is removed, the tensile breaking strength of the glass fiber 1 becomes very large. Due to the increased tensile breaking strength, the fibers do not break even when compressed by atmospheric pressure, the surrounding space is maintained, the surrounding fibers are less likely to contact each other, and the increase in heat conduction of the solid component is suppressed. . Therefore, heat is not easily transmitted and low thermal conductivity can be realized.

  The thermal conductivity was 0.0015 / mK, the tensile strength at break was 1000 kPa, the average fiber length was 20 mm, and the recovery rate after compression of the core material was 22.6%. Since the Griffith crack is removed from the surface of the fiber, the tensile strength at break is increased.

  A method for producing the vacuum heat insulating material 2 and a method for measuring each physical property, such as a method for producing the core material 3 from raw cotton, a bag making method for the jacket material 4, and the like, are the same as those in the first embodiment.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. The glass fiber 1 in which any one of the tensile breaking strength, the tensile elastic modulus, and the bending elastic modulus is reinforced is oriented in a direction perpendicular to the heat transfer direction, and fibers adjacent to the heat transfer direction do not face the same direction. It is the vacuum heat insulating material 2 laminated | stacked on and heat-press-molding.

  If the tensile strength or tensile modulus of the glass fiber 1 is large, even if a tensile force is applied to the fiber entangled in the core material 3 due to atmospheric pressure, the glass fiber 1 is not easily broken, and the presence of this fiber maintains the space. When the bending elastic modulus is large, it is difficult for the glass fiber 1 to be bent by a force in a direction perpendicular to the length direction applied to the glass fiber 1 by atmospheric pressure. Since bending is small, even if the distance of the glass fiber 1 when not bent is small, it becomes difficult to contact.

  Therefore, it can suppress that heat comes to be transmitted when the glass fiber 1 bends. As the core material 3, the core material 3 is hardly compressed by the atmospheric pressure applied when vacuum packaging is performed, and heat is not easily transmitted by maintaining the space in the core material 3, and the heat insulation of the solid component is kept low. The material 2 can be obtained.

  The mechanical strength of glass is dominated by the tensile force acting on the surface and breaks when the tensile force exceeds a limit. Glass is inherently very strong in mechanical strength, but normal glass becomes brittle because it breaks easily due to stress concentration on the Griffith cracks existing on the surface. Has become dominant.

  The vacuum heat insulating material 2 of the present embodiment is a vacuum heat insulating material 2 in which the core material 3 is covered with a gas barrier outer covering material 4 and the inside of the outer covering material 4 is sealed under reduced pressure. However, the glass fiber 1 from which the Griffith crack on the surface has been removed is laminated so that the fibers adjacent to the heat transfer direction are not oriented in the same direction while being oriented in the direction perpendicular to the heat transfer direction. It is the vacuum heat insulating material 2 formed.

  A normal glass fiber has a Griffith crack on its surface. Therefore, when a force is applied to the glass fiber, stress concentrates on the Griffith crack existing on the surface, and the glass fiber is likely to break from the Griffith crack.

  Griffith cracks on the surface of the glass fiber can be removed by treating the glass fiber with hydrofluoric acid. Removing the Griffith crack from the surface of the glass fiber increases the mechanical strength, which is close to the theoretical strength. A glass fiber having strength can be obtained.

  The glass fiber 1 from which the surface Griffith crack has been removed has higher mechanical strength than the glass fiber from which the surface Griffith crack has not been removed, and even if a force is applied from a direction perpendicular to the length direction of the fiber. It has the characteristics that it is difficult to bend and break.

  Therefore, the glass fiber 1 from which the Griffith crack on the surface has been removed is laminated in such a manner that the fibers are oriented in a direction perpendicular to the heat transfer direction and adjacent fibers in the heat transfer direction do not face the same direction. The core material 3 thus formed is less likely to be compressed under pressure than the core material obtained by similarly molding a conventional glass fiber from which the surface Griffith crack has not been removed. Since many glass fibers remain long, the porosity of the core material 3 is high, the path through which heat travels through the glass fiber 1 is small, and the heat conduction of the solid component of the core material 3 is small. Therefore, the vacuum heat insulating material 2 excellent in heat insulating performance can be provided.

  In the present embodiment, the Griffith crack on the surface of the glass fiber is removed by hydrofluoric acid treatment. By treating the glass fiber with hydrofluoric acid, it is possible to obtain glass fiber 1 in which the Griffith crack on the surface is removed and the mechanical strength is increased.

  Moreover, the core material 3 of this Embodiment does not contain a binder. The glass fiber 1 can be molded without using a binder under predetermined heating and pressing conditions, and is transmitted between adjacent fibers as compared with the case of molding with a binder. It is possible to reduce heat conduction.

  Therefore, by using the core material 3 that is formed by heating and pressing to use the binder, it is possible to provide a vacuum heat insulating material that is further excellent in heat insulating performance.

  In the first to third embodiments, the core material 3 is molded without using a binder during molding, but the molding method of the core material 3 is not limited to this, and various organic and inorganic materials can be used. What was shape | molded using the binder may be used. However, the core material molded using the binder material has larger contact points between adjacent fibers than the core material molded without the binder material, and in some cases, the thermal conductivity is increased. It becomes worse than the core material molded without using the material.

  The fiber is strengthened in tensile strength at break, tensile elastic modulus and bending elastic modulus by quenching by air cooling, ion exchange, and surface treatment with hydrofluoric acid, but the method of reinforcing the fiber is limited to these. is not.

  In the embodiment, the glass fiber 1 was reinforced by changing the conditions for reinforcing the glass fiber 1. The relationship between the heat conductivity of the vacuum heat insulating material 2 using the glass fiber 1 reinforced under each condition as a constituent element of the core material 3 and the physical properties of the fiber and the core material 3 as Examples 1 to 6, and 200 ° C. Comparative Examples 1 and 2 show the relationship between the thermal conductivity of the vacuum heat insulating material using the glass fiber cooled in step 1 and the glass fiber not reinforced as a constituent element of the core material, and the physical properties of the fiber and core material (Table 1). Shown in 1).

（表１）に示されているように、冷却を行う空気の温度が低くなるに従って熱伝導率が小さくなっている。

As shown in Table 1, the thermal conductivity decreases as the temperature of the cooling air decreases.

  This is because, as the fiber cooling temperature decreases, the bending elastic modulus of the fiber increases, so that even when atmospheric pressure is applied to the core material, the fiber is less likely to be bent, and the fibers are less likely to contact each other. .

  The restoration rate after compressing the core material 3 increases as the fiber cooling temperature decreases, and it can be seen from this result that the fiber bending elastic modulus increases as the cooling temperature is lowered.

  Furthermore, the heat conductivity of the vacuum heat insulating material 2 produced using the fiber which applied the compressive stress to the surface by ion exchange, and the fiber which removed the Griffith crack with hydrofluoric acid as a core material is small.

  This is because the tensile break strength of the fiber is increased by ion exchange and hydrofluoric acid treatment, the fiber is less likely to break, and heat is less likely to be transmitted by holding the space.

  The thermal conductivity of the vacuum heat insulating material using the fiber cooled at 200 ° C. as a constituent element of the core is larger than that when cooled at a lower cooling temperature.

  Moreover, the heat conductivity of the vacuum heat insulating material using the glass fiber which has not been reinforced as a constituent element of the core material is higher than that when the fiber is reinforced.

  These are because the bending elastic modulus and tensile breaking strength of the fiber are small, so that when the atmospheric pressure is applied, the fiber is greatly bent or broken and the space inside the core cannot be maintained.

  From the above results, it can be seen that when the strength of the fiber is increased, the core material is less likely to be compressed at atmospheric pressure, and the internal space is maintained, thereby reducing the thermal conductivity.

  As mentioned above, since the vacuum heat insulating material concerning this invention has the outstanding heat insulation performance, high heat insulation performance is obtained by thinner thickness. Therefore, in addition to uses such as a refrigerator and a cooler box, the present invention can be applied to uses such as a liquid crystal projector, a copy machine, and a notebook computer that require high heat insulation performance in a narrow space.

Sectional drawing of the vacuum heat insulating material in Embodiment 1 of this invention The schematic diagram of the core material in Embodiment 1 of this invention Schematic of the cross-section of the core material after vacuum packaging in Embodiment 1 of the present invention Schematic diagram of cross section of tensile strength measurement test piece in Embodiment 1 of the present invention Schematic diagram of a cross-section of the core material in the second embodiment of the present invention Schematic diagram of the cross-section of the core material in Embodiment 3 of the present invention Sectional view of the core material cross section of a conventional vacuum insulation material

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass fiber 2 Vacuum heat insulating material 3 Core material 4 Cover material

Claims (14)

  It comprises a core material made of glass fiber and a jacket material made of a laminate film, the core material is covered with the laminate film, and the inside is sealed after decompression, and the glass fiber has a tensile breaking strength and a tensile elastic modulus. The vacuum heat insulating material is hard to be compressed in the thickness direction by atmospheric pressure because one of the flexural modulus is reinforced.   The vacuum heat insulating material according to claim 1, wherein the glass fiber is not easily broken by pressure.   The vacuum heat insulating material according to claim 1 or 2, wherein the glass fiber is reinforced by rapid cooling.   The vacuum heat insulating material according to claim 1 or 2, wherein the glass fiber is reinforced by ion exchange.   The vacuum heat insulating material according to claim 1 or 2, wherein the glass fiber is reinforced by hydrofluoric acid treatment. The vacuum heat insulating material is compressed so that the density of the core portion of the vacuum heat insulating material is 300 kg / m ³ or more, and the vacuum heat insulating material is disassembled and taken out in a direction perpendicular to the heat transfer direction of the core material taken out. The vacuum heat insulating material according to any one of claims 1 to 5, wherein a tensile breaking strength is 700 kPa or more calculated from a cross-sectional area of the core material when the vacuum heat insulating material is compressed. The vacuum heat insulating material is compressed so that the density of the core portion of the vacuum heat insulating material is 300 kg / m ³ or more and 350 kg / m ³ or less, and the vacuum heat insulating material is left in an atmosphere of 133 Pa or less, and then the vacuum heat insulating material The vacuum heat insulating material according to any one of claims 1 to 6, wherein a thickness of the core material portion in which the material is left under atmospheric pressure is 10% or more thicker than a thickness of the core material portion after compression. Covering the core material with a gas barrier outer covering material, and vacuum insulating material formed by sealing the inside of the outer covering material under reduced pressure,
The core material is oriented in the direction perpendicular to the heat transfer direction, and the fibers adjacent in the heat transfer direction are in the same direction, with the glass fiber reinforced in any one of tensile breaking strength, tensile elastic modulus, and bending elastic modulus. Vacuum heat insulating material that is laminated and heat-pressed so that it does not face. Covering the core material with a gas barrier outer covering material, and vacuum insulating material formed by sealing the inside of the outer covering material under reduced pressure,
The core material is laminated and heated so that glass fibers having a compressive stress layer formed on the surface thereof are oriented in a direction perpendicular to the heat transfer direction and fibers adjacent to the heat transfer direction do not face the same direction. Vacuum insulation material formed by pressure molding.   The vacuum heat insulating material according to claim 9, wherein the compressive stress layer is formed by an air cooling strengthening method.   The vacuum heat insulating material according to claim 9, wherein the compressive stress layer is formed by an ion exchange method. Covering the core material with a gas barrier outer covering material, and vacuum insulating material formed by sealing the inside of the outer covering material under reduced pressure,
The core material is laminated and heated so that the glass fibers from which the Griffith cracks on the surface have been removed are oriented in a direction perpendicular to the heat transfer direction and fibers adjacent in the heat transfer direction do not face the same direction. Vacuum insulation material formed by pressure forming.   The vacuum heat insulating material according to claim 12, wherein the Griffith crack on the surface of the glass fiber is removed by hydrofluoric acid treatment.   The vacuum heat insulating material according to any one of claims 8 to 13, wherein the core material does not include a binder.

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