JP2006064091A - Vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum heat insulating material having excellent pin-hole resistance by using a cover material having excellent durability against the generation of pin-hole due to sticking. <P>SOLUTION: Only a non-drawn film is used as a plastic film used for the cover material 6. The non-drawn film 6 has a large elongation percentage against tensile breaking, and the film is hard to be broken even if foreign matter is stuck. Since a drawn film, of which elongation percentage against tensile breaking is small, is not used, simultaneous breakdown of the non-drawn film when the drawn film is broken can be prevented. Consequently, the cover material 6 having excellent pin-hole resistance can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vacuum heat insulating material, and more particularly to a jacket material having high durability against pinholes caused by piercing or the like.

  Conventionally, a stretched film having a high tensile breaking strength has been used as a laminate film structure in order to ensure puncture resistance and moisture resistance (see, for example, Patent Document 1).

  FIG. 5 shows a cross-sectional view of a laminate film for packaging electronic parts disclosed in Patent Document 1.

As shown in FIG. 5, the conventional packaging laminate film is composed of a stretched nylon film 1, a vapor deposition film 2, a gas barrier layer 3, and a heat seal layer 4. Since the stretched nylon film 1 has a high strength, it is difficult to break due to an edge of the package.
JP-A-9-193305

  However, in the conventional laminate film, when a sharp foreign object piercing force is applied, the elongation in the vicinity of the contact point with the foreign object increases and the stretched film breaks. Since the unstretched film has a higher tensile breaking elongation than the stretched film, it does not break even if it is stretched to such an extent that the stretched film breaks.

  However, even if there is an unstretched film with a high tensile breaking elongation in the laminate film structure, it is laminated with the stretched film, so the unstretched film breaks simultaneously with the break of the stretched film, and vacuum insulation When used as a jacket material for the material, a through-pinhole could occur due to the piercing force of a foreign substance existing inside the jacket material.

  For these reasons, the conventional laminate film has a problem that it is not suitable as a jacket material for a vacuum heat insulating material having high pinhole resistance.

  An object of this invention is to provide the vacuum heat insulating material excellent in pinhole resistance.

  In order to achieve the above object, the present invention comprises a plastic film that constitutes a plastic laminate film as an outer covering material of a vacuum heat insulating material, only with an unstretched plastic film.

  Except when the foreign material is very sharp, when the piercing force by the foreign material acts on the film, the film is stretched to break.

  In general, when a film having a different tensile elongation at break exists in the structure of the laminated film, if the film having the smallest tensile elongation at break breaks, the laminated film is simultaneously broken. Moreover, in the same film, a crack arises from the part which reached the tensile elongation at break, and the film breaks. Therefore, by forming the entire laminate film with a film having a high tensile breaking elongation, it is possible to prevent breakage due to the piercing force of foreign matter.

  The present invention can obtain a vacuum heat insulating material excellent in pinhole resistance by applying a laminate film for packaging excellent in pinhole resistance.

  The invention of a vacuum heat insulating material according to claim 1 is a vacuum heat insulating material in which a core material is covered with a jacket material made of a metal foil or a plastic laminate film having a vapor deposition layer, and the inside is decompressed. The plastic film constituting the laminate film is composed only of an unstretched plastic film.

  Since the unstretched film has a higher tensile breaking elongation than the stretched film, it is difficult to break when pulled by a foreign object piercing force. In addition, a laminate film including a stretched film having a small tensile break elongation is stretched by dragging the laminated unstretched film when the entire laminate film is stretched and the stretched film having a small tensile break elongation is broken. It will be broken, and as a result, the entire laminate film will be broken.

  Such a phenomenon does not occur in a laminated film composed only of an unstretched film, and the tensile breaking elongation of the laminated film is equal to the tensile breaking elongation of the unstretched film.

  Therefore, by using such a laminate film as a jacket material, a vacuum heat insulating material having excellent pinhole resistance due to piercing can be obtained.

  The invention of the vacuum heat insulating material according to claim 2 is such that the tensile elongation at break of the unstretched film in the invention according to claim 1 is 500% or more.

  Generally, the tensile elongation at break of a biaxially stretched film such as nylon is about 100%. For this reason, if there is a foreign substance in the outer bag made of a laminated film containing stretched nylon in the structure, it easily breaks beyond the tensile break elongation due to the piercing force caused by the atmospheric pressure when vacuum packaging.

  On the other hand, when the tensile elongation at break is 500% or more, the puncture force of the foreign matter is dispersed by the elongation, and breakage hardly occurs.

  Therefore, by using such a laminate film as a jacket material, a vacuum heat insulating material having excellent pinhole resistance due to piercing can be obtained.

  The invention of the vacuum heat insulating material according to claim 3 is such that the tensile elastic modulus of the unstretched film in the invention according to claim 1 or 2 is 950 MPa or less.

  When foreign matter is present in the outer jacket material, the piercing force works due to the atmospheric pressure when vacuum packaging is performed. The foreign material and the jacket material come into contact with each other at the tip of the foreign material. In addition to the piercing force caused by atmospheric pressure, a force that stretches the outer covering material by the length of the foreign substance acts on this contact point. The force to stretch the jacket material increases as the tensile elastic modulus increases and the elongation increases, so if the size of the foreign material is the same, the smaller the tensile elastic modulus, the smaller the force, The film is less likely to break and pinholes are less likely to occur.

  Therefore, by using such a laminate film as a jacket material, a vacuum heat insulating material having excellent pinhole resistance due to piercing can be obtained.

  The invention of a vacuum heat insulating material according to claim 4 has a metal foil or a vapor deposition layer outside the unstretched film according to any one of claims 1 to 3.

  The distortion due to the piercing force applied to the laminate film is greatest near the contact point between the laminate film and the foreign matter, and the distortion decreases as the distance from the contact point increases. Therefore, in the case of a piercing by a foreign substance existing inside the jacket material, the distortion becomes smaller toward the outside.

  Generally, since a metal has a small tensile elongation at break, a crack is easily generated in a metal foil or a metal vapor-deposited layer. Therefore, it is desirable to install the metal foil and the metal vapor deposition layer in a portion having the smallest distortion in the laminate film configuration.

  Therefore, by using such a laminate film as a covering material, it is possible to obtain a vacuum heat insulating material that is less prone to crack in the metal foil or the metal vapor deposition layer and has excellent gas barrier properties.

  In addition to the invention described in any one of claims 1 to 4, the invention of the vacuum heat insulating material described in claim 5 is covered with a bag made of a stretched film.

  Generally, an unstretched film has a smaller tensile elastic modulus than that of a stretched film. Therefore, a laminate film composed only of an unstretched film is easily stretched by an external force. When the laminate film is stretched, the metal foil and the metal vapor deposition layer constituting the laminate film are stretched and cracks are generated.

  By covering with a bag made of stretched film after vacuum packaging, it becomes difficult to be stretched by an external force.

  Therefore, with the above-described configuration, pinholes due to piercing are unlikely to occur and are not easily stretched, so that a vacuum heat insulating material with excellent handleability can be obtained.

  In the present invention, the tensile elongation at break of the film is a value when a tensile test is performed in the direction in which the value of each film is the largest.

  In addition, the tensile elongation at break is a value obtained by dividing the change in length up to breaking when the strip-shaped film is stretched by the length before stretching, and the test method is not specified.

  In general, an unstretched film is a film in which a melted film is formed into a flat shape by extrusion or the like and is not processed by tension. The unstretched film is in a rounded state when the constituent molecules are bent. Therefore, since the molecules can be stretched from the folded and rounded state until they are stretched and aligned, the unstretched film has a high tensile elongation at break.

  On the other hand, the stretched film is stretched and stretched because the molecules that have been bent are stretched and aligned in the same direction.

  The stretching method includes uniaxial stretching that stretches in one direction and biaxial stretching that stretches in two directions. A uniaxially stretched film is tough in the stretched direction and has a low tensile elongation at break. The unstretched direction is brittle and easily breaks.

  Moreover, since the stretched film differs in the direction of alignment of molecules depending on the degree of stretching, the limit that can be stretched differs, and as a result, the tensile elongation at break differs.

  In the present invention, the unstretched film is a film having a tensile elongation at break of 400% or more in the direction where the tensile elongation at break is the largest, and the unstretched film has a tensile elongation at break of less than 400%. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

  In each embodiment, in order to evaluate the puncture by the foreign material contained in the core material, the core material containing a large proportion of the foreign material is vacuum packaged.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of the vacuum heat insulating material of the first embodiment.

  As shown in FIG. 1, the vacuum heat insulating material 5 is formed by covering the core material 7 and the moisture adsorbent 8 with a covering material 6 and sealing the inside under reduced pressure.

  FIG. 2 shows a cross section of the jacket 6 of the vacuum heat insulating material according to the first embodiment.

  As shown in FIG. 2, the jacket material 6 is obtained by laminating a sealant layer 9, a metal foil 10, and a protective layer 11 from the core material 7 side.

  The sealant layer 9 is an unstretched linear low-density polyethylene film and has a thickness of 50 μm. The metal foil 10 is an aluminum foil and has a thickness of 6 μm. The protective layer 11 is an unstretched polypropylene film and has a thickness of 30 μm.

  The sealant layer 9, the metal foil 10, and the protective layer 11 are laminated by dry lamination using a known adhesive.

  The core material 7 has a mean fiber diameter of 10 μm, which is thicker than usual, and a firing temperature of 500 ° C., which is higher than usual, in order to increase the ratio of contained foreign matter. The moisture adsorbent 8 is made of a known calcium oxide.

  The core material 7 thus produced was inserted into a jacket material 6 that had been sealed on three sides in advance by thermal welding, the interior was reduced to 13 Pa, sealed by thermal welding, and introduced into the atmosphere.

  1000 vacuum heat insulating materials were produced by the above method.

  About the vacuum heat insulating material produced as mentioned above, the operation | movement is demonstrated below.

  The sealant layer 9 is an unstretched linear low-density polyethylene film, and the tensile break elongation in the direction with the largest tensile break elongation in each direction is 600%.

  The metal foil 10 is an aluminum foil, and the tensile breaking elongation in the direction having the largest tensile breaking elongation in each direction is 15%.

  The protective layer 11 is an unstretched polypropylene film, and the tensile breaking elongation in the direction having the largest tensile breaking elongation in each direction is 700%.

Since the inside of the jacket material 6 has a low pressure of 13 Pa, a compressive stress of about 1 kg / cm ² acts on the inside due to atmospheric pressure. Foreign matter existing inside the jacket material 6 is pressed against the jacket material 6 from the inside by this compressive stress.

  The outer cover material 6 pressed against the foreign matter is stretched by the force so as to follow the shape of the foreign matter, but the innermost film has a very high tensile breaking elongation of 600%, and the contact point of the foreign matter having the largest elongation. It does not exceed this value even in the vicinity and does not break.

  Since the metal foil 10 has a small tensile elongation at break, the metal foil 10 is broken and a crack is generated. However, since the metal foil 10 is very thin as 6 μm and has low strength, the laminated film cannot be broken by dragging.

  The protective layer 11 has a lower elongation than the sealant layer 9 because it is away from the contact point between the foreign matter and the jacket material 6. Furthermore, it does not break because the tensile elongation at break is large.

  Therefore, no pinhole is generated in the jacket material 6.

  The initial value of the thermal conductivity of the vacuum heat insulating material 5 produced in the present embodiment is 0.0025 W / mK, and no pinhole is generated.

  In order to evaluate the influence of the gas penetration | invasion from the crack of the metal foil 10, it was 0.0060 W / mK as a result of measuring the heat conductivity after performing the test equivalent to 10-year progress.

(Embodiment 2)
FIG. 3 shows a cross section of the jacket 6 of the vacuum heat insulating material of the present embodiment.

  As shown in FIG. 3, the jacket material 6 is obtained by laminating a sealant layer 9, a metal foil 10, and a protective layer 11 from the core material 7 side.

  The sealant layer 9 is an unstretched polypropylene film and has a thickness of 50 μm. The metal foil 10 is an aluminum foil and has a thickness of 6 μm. The protective layer 11 is an unstretched linear low-density polyethylene film and has a thickness of 30 μm.

  The method for producing the vacuum heat insulating material such as the laminating method, the bag making method, the core material producing method, the vacuum sealing method, etc., of the jacket material 6 is the same as that of the first embodiment.

  The operation of the vacuum heat insulating material 5 manufactured as described above will be described.

  The sealant layer 9 is an unstretched polypropylene film having a tensile elongation at break of 700% in the direction with the largest tensile elongation at break in each direction, and a tensile modulus of elasticity of 600 MPa in the same direction.

  The metal foil 10 is an aluminum foil, and the tensile breaking elongation in the direction having the largest tensile breaking elongation in each direction is 15%.

  The protective layer 11 is an unstretched linear low-density polyethylene film, and the tensile breaking elongation in the direction with the largest tensile breaking elongation in each direction is 600%, and the tensile elastic modulus in the same direction is 300 MPa.

Since the inside of the jacket material 6 has a low pressure of 13 Pa, a compressive stress of about 1 kg / cm ² acts on the inside due to atmospheric pressure. Foreign matter existing inside the jacket material 6 is pressed against the jacket material 6 from the inside by this compressive stress.

  The outer cover material 6 pressed against the foreign matter is stretched by the force so as to follow the shape of the foreign matter. The innermost film has a very high tensile breaking elongation of 700%, and the contact point of the foreign matter having the largest elongation. It does not exceed this value even in the vicinity and does not break.

  Since the metal foil 10 has a small tensile elongation at break, the metal foil 10 is broken and a crack is generated. However, since the metal foil 10 is as thin as 6 μm and has a low strength, the laminated film cannot be pulled and broken.

  Since the protective layer 11 is separated from the contact point between the foreign matter and the jacket material 6, the protective layer 11 has a lower elongation than the sealant layer 9. Therefore, the tensile breaking elongation of the protective layer 11 is smaller than the tensile breaking elongation of the sealant layer 9, but the laminate film does not break.

  Therefore, no pinhole is generated in the laminate film.

  The initial value of the thermal conductivity of the vacuum heat insulating material 5 produced in the present embodiment is 0.0025 W / mK, and no pinhole is generated.

  In order to evaluate the influence of the gas penetration | invasion from the crack of the metal foil 10, it was 0.0055 W / mK as a result of measuring the heat conductivity after performing the test equivalent to 10-year progress.

  Under the conditions of Embodiment 2, no pinholes were generated, but when a film having a low tensile elongation at break or a film having a high tensile modulus was used, the generation of pinholes was observed.

  (Table 1) shows the relationship between the tensile elongation at break, tensile modulus, and pinhole generation rate.

（表１）から、引張破断伸度が大きくなるに従って、ピンホールの発生率が減少していることが判る。また、引張弾性率が小さくなるに従って、ピンホールの発生率が減少していることが判る。また、引張破断伸度が５００％以上、引張弾性率が９５０ＭＰａ以下の条件を満たした場合に、ピンホールが発生しなくなることが判る。

From Table 1, it can be seen that as the tensile elongation at break increases, the incidence of pinholes decreases. Moreover, it turns out that the incidence rate of pinholes decreases as the tensile elastic modulus decreases. It can also be seen that pinholes do not occur when the tensile elongation at break is 500% or more and the tensile modulus is 950 MPa or less.

(Embodiment 3)
FIG. 4 shows a cross section of the vacuum heat insulating material of the present embodiment.

  As shown in FIG. 4, the vacuum heat insulating material of the present embodiment covers the core material 7 from the core material 7 side with an outer cover material in which a sealant layer 9, a protective layer 11, and a metal foil 10 are laminated. Is sealed under reduced pressure, and further covered with a protective bag 12.

  The sealant layer 9 is an unstretched polypropylene film and has a thickness of 50 μm. The metal foil 10 is an aluminum foil and has a thickness of 6 μm. The protective layer 11 is an unstretched linear low-density polyethylene film and has a thickness of 30 μm.

  The method for producing the vacuum heat insulating material such as the method for laminating the jacket material, the bag making method, the method for producing the core material, and the vacuum sealing method is the same as in the first embodiment.

  The operation of the vacuum heat insulating material produced as described above will be described.

  The sealant layer 9 is an unstretched polypropylene film having a tensile elongation at break of 700% in the direction with the largest tensile elongation at break in each direction, and a tensile modulus of elasticity of 600 MPa in the same direction.

  The metal foil 10 is an aluminum foil, and the tensile breaking elongation in the direction having the largest tensile breaking elongation in each direction is 15%.

  The protective layer 11 is an unstretched linear low-density polyethylene film, and the tensile breaking elongation in the direction with the largest tensile breaking elongation in each direction is 600%, and the tensile elastic modulus in the same direction is 300 MPa.

  The protective bag 12 is a biaxially stretched polyethylene terephthalate film, has a tensile elongation at break of 60% in the direction of the largest tensile elongation at break and a tensile modulus of 4000 MPa.

  In this embodiment, the stacking order of the metal foil 10 and the protective layer 11 is opposite to the stacking order of the metal foil 10 and the protective layer 11 in Embodiment 2, but the metal foil 10 affects the pinhole resistance. Therefore, the appearance mechanism of pinhole resistance is the same as that of the second embodiment.

  On the other hand, since the metal foil 10 is on the outer side having the smallest elongation, cracks due to tension do not occur.

  Moreover, since it is covered with the protective bag 12 having a large tensile elastic modulus, it has a handling property equivalent to that of a vacuum heat insulating material in which a laminated film including a stretched film is used as the outer covering material 6 in the structure.

  The initial value of the thermal conductivity of the vacuum heat insulating material manufactured in this embodiment is 0.0025 W / mK, and no pinhole is generated.

  In order to evaluate the influence of the gas intrusion from the crack of the metal foil, the result of measuring the thermal conductivity after a test corresponding to the passage of 10 years was 0.0050 W / mK.

  Compared to the second embodiment, the thermal conductivity after a test corresponding to the passage of 10 years is small, but this is because the metal foil 10 is on the outside, so that there are few cracks caused by stretching by foreign object sticking. It is because it has become.

  The vacuum heat insulating material according to the present invention is extremely excellent in pinhole resistance of the jacket material. For this reason, it can also be applied to cooking appliances such as refrigerators, electric water heaters, IH cooking heaters, information devices such as printing machines, copiers, liquid crystal projectors, notebook computers, and industrial equipment such as semiconductor manufacturing equipment.

Sectional drawing of the vacuum heat insulating material in Embodiment 1 of this invention Sectional drawing of the jacket material of the vacuum heat insulating material in Embodiment 1 of this invention Sectional drawing of the jacket material of the vacuum heat insulating material in Embodiment 2 of this invention Sectional drawing of the vacuum heat insulating material in Embodiment 3 of this invention Cross section of conventional vacuum insulation jacket

Explanation of symbols

5 Vacuum insulation material 6 Outer coating material 7 Core material 10 Metal foil 12 Protective bag

Claims (5)

  In a vacuum heat insulating material in which a core material is covered with a jacket material composed of a metal foil or a plastic laminate film having a vapor deposition layer, and the inside is decompressed, the plastic film constituting the plastic laminate film is an unstretched plastic film Only vacuum insulation.   The vacuum heat insulating material according to claim 1, wherein the unstretched film has a tensile elongation at break of 500% or more.   The vacuum heat insulating material according to claim 1 or 2, wherein a tensile elastic modulus of the unstretched film is 950 MPa or less.   The vacuum heat insulating material as described in any one of Claim 1 to 3 which has a metal foil or a vapor deposition layer in the outer side of an unstretched film.   The vacuum heat insulating material as described in any one of Claim 1 to 4 covered with the bag produced with the stretched film.

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