JP2012047211A - Vacuum heat insulating material and refrigerator using the same - Google Patents

Abstract

An object of the present invention is to provide a vacuum heat insulating material that improves surface smoothness without deteriorating heat insulating performance and has good appearance quality, and a refrigerator using the same.
A vacuum heat insulating material comprising: a core material composed of a plurality of laminated bodies; and a jacket material having a gas barrier property that houses the core material and maintains the inside in a reduced pressure state. The vacuum heat insulating material is provided with a resin fiber laminate having a Vickers hardness of 65 or more and 80 or less, which is obtained by melt spinning and laminating a resin on one surface or both surfaces in contact with the jacket material.
[Selection] Figure 1

Description

  The present invention relates to a vacuum heat insulating material and a refrigerator using the same.

  As background art of this technical field, there are JP-A-11-281245 (Patent Document 1) and Japanese Patent No. 3914908 (Patent Document 2).

  Patent Document 1 describes that a core material of a water-foamed rigid continuous urethane foam is used.

  Patent Document 2 describes a core material in which a binder material such as sodium silicate or phenol resin powder is blended with “artificial mineral fiber heat insulating material” (JIS A9504), finely pulverized urethane, or the like.

JP-A-11-281245 Japanese Patent No. 3914908

  In Patent Document 1, gas is generated from inside the urethane foam as a core material, and the degree of vacuum decreases with time.

  In Patent Document 2, the heat transfer of the binder material portion of the core material is increased, and the heat insulation performance may be reduced.

  In addition, for example, when the core material is formed as a glass wool laminate, irregularities are generated on the surface of the vacuum heat insulating material due to variation in the basis weight (density), and the appearance quality may be deteriorated.

  Therefore, an object of the present invention is to provide a vacuum heat insulating material that improves surface smoothness without deteriorating heat insulating performance and has good appearance quality, and a refrigerator using the same.

  In order to solve the above problems, for example, the configuration described in the claims is adopted. For example, in the vacuum heat insulating material provided with a core material composed of a plurality of laminates and a jacket material having a gas barrier property that stores the core material and maintains the inside in a reduced pressure state, the core The material is provided with a resin fiber laminate having a Vickers hardness of 65 or more and 80 or less obtained by melt spinning and laminating a resin on one surface or both surfaces in contact with the jacket material.

  According to the present invention, it is possible to provide a vacuum heat insulating material that improves surface smoothness without deteriorating heat insulating performance and has good appearance quality, and a refrigerator using the same.

It is sectional drawing of the vacuum heat insulating material which concerns on embodiment of this invention. It is sectional drawing of the vacuum heat insulating material regarding a prior art. It is sectional drawing of the refrigerator provided with the vacuum heat insulating material which concerns on this embodiment. It is the table | surface which put together the relationship between a prior art example, an Example, and a comparative example. It is a figure showing the surface shape of the resin fiber laminated body of Example 5. It is a figure showing the surface shape of the resin fiber laminated body of Example 6. FIG.

  First, the basic structure, function, and effect of the vacuum heat insulating material according to the embodiment of the present invention will be described with reference to the drawings. The vacuum heat insulating material which concerns on embodiment of this invention arrange | positions the core material and adsorbent of a long-fiber web laminated body in the space covered with the jacket material, and seals after reducing the inside of the jacket material. is there. On the outside of the long fiber web laminate, a core material made of a laminate of plastic resin fibers and having reduced environmental load is disposed.

  The core material of the vacuum heat insulating material has a function of a spacer for maintaining the shape, and is preferably formed of fibers having high voids even when subjected to compressive stress during decompression.

  The plastic resin fiber of the present embodiment desirably has a molecular chain that is rigid, difficult to entangle, is brittle, and has a flexural modulus of about 3000 MPa or more. Polystyrene, which is a general-purpose product, is particularly preferable. Polystyrene has a hydrophobic nonpolar group, has low hygroscopicity, and the molecular weight is not limited as long as it is made into a fiber, and is preferably about 200,000 to 400,000.

  When general-purpose polyethylene or polypropylene fibers are used in place of polystyrene fibers, the hygroscopicity is low, but the flexural modulus is low and the creep phenomenon increases. Therefore, it is difficult to obtain high voids due to compressive stress during decompression, and the heat insulation performance is inferior compared with polystyrene. However, since it has a heat insulation performance about 5 times that of a hard polyurethane resin that is a conventional heat insulating material, it can be applied.

  The long fiber web of the core material is preferably glass wool having an average fiber diameter of about 4 μm. The plastic resin fiber used as the cured core material preferably has an average fiber diameter of about 30 μm or less, particularly 5 to 20 μm, from the viewpoint of thermal conductivity. Since the stiffness of the fiber is proportional to the product of the fourth power of the fiber diameter and the Young's modulus, the fiber becomes soft when the fiber diameter is small. Therefore, about 5 μm or more is preferable. On the other hand, when the fiber diameter is too thick, the fiber is close to line contact, and the thermal conductivity is increased by reducing the contact thermal resistance. In addition, the average fiber diameter measured the fiber diameter of the visual field containing about 10 fibers using the scanning electron microscope.

Further, when the density of the core material is 150 kg / m ³ or less, the strength tends to decrease and the thermal conductivity tends to increase. On the other hand, it becomes heavier at 300 kg / m ³ or more, and the thermal conductivity is increased from the viewpoint of porosity and the like. That is, the density of the core material is preferably 150 to 300 kg / m ³ . The density of the core material is a density after evacuation accommodated in the jacket material, and was calculated from the weight of the core material obtained by subtracting the weight of the jacket material and the adsorbent and the volume of the vacuum heat insulating material.

  The plastic resin fiber assembly is a long fiber web formed by melt spinning a resin and directly forming it by extrusion from a nozzle. For example, polystyrene fibers are spun at an extrusion temperature of about 200 to 320 ° C., and when the temperature is low, the extrusion torque increases.

  The long fiber aggregate is preferably a core material that is not adhesively bonded by thermal bonding, needle punching, or the like, and is formed and collected so as to produce an oriented web. For example, a polystyrene resin is extruded from the tip of a nozzle by a melt blown method, and fibers are drawn by air injection and collected on a collector to form a web. In the spunbond method, a web is formed in the same manner by continuously extruding from a plurality of spinning nozzle tips and collecting fibers from an ejector on a collector by jetting air.

  The fiber shape is not limited to a circle, and may be a substantially circular shape, a substantially Y shape, a substantially elliptical shape, a substantially star shape, a substantially polygonal shape, or the like. Since polystyrene has a small mold shrinkage rate, it is possible to provide a fiber assembly with relatively little variation in fiber diameter. Recycled polystyrene resin may be used.

  In the process of spinning and fiberizing the molten resin, the state of the fiber surface can be changed by the following operation. That is, by changing the amount of resin discharged, the amount of hot air blown during spinning, and the distance between the spinning nozzle and the fiber recovery conveyor, the stretchability of the resin can be changed, and the hardness of the fiber laminate can be increased. I can control it.

  When the discharge amount of the resin is large, the temperature of the resin becomes higher when drawing and spinning. Therefore, it tends to be fused with adjacent fibers, and the fiber diameter becomes thick, so that the surface of the completed fiber laminate becomes hard.

  Further, if the amount of hot air blown during spinning is reduced, the stretchability of the resin is reduced and the fiber is easily cut and the surface of the completed fiber laminate is hardened.

  Also, if the distance between the spinning nozzle and the fiber collection conveyor is shortened, the time from spinning to collection is shortened. Then, heat generation of the fiber itself cannot be eliminated, and fusion with the adjacent fiber occurs. And a fiber diameter becomes thick and the surface of the completed fiber laminated body becomes hard.

  In addition, the resin fiber laminate is a laminate obtained by spinning one or more of polypropylene, polystyrene, polyethylene terephthalate, polycarbonate, and polyphenylene sulfide by a melt blown method or a spunbond method.

  The jacket material is preferably made of a material that forms a space for storing the core material and seals this space under reduced pressure along the outer shape of the core material. For example, if a material with high rigidity is used as the jacket material, it becomes difficult to bend, and this may cause a pinhole after bending. Therefore, as the jacket material, a laminate film having a bag shape is used.

  The jacket material includes an outermost layer having impact resistance, an intermediate layer having gas barrier properties, and an innermost layer to be heat-sealed. For the outermost layer, the puncture resistance is improved by using a polyamide film or a biaxially stretched polypropylene film. The intermediate layer is provided with an ethylene-vinyl alcohol copolymer film having an aluminum vapor deposition layer. Examples of the innermost layer include high-density polyethylene, linear low-density polyethylene, and high-density polypropylene. High-density polyethylene is preferable from the viewpoint of sealing properties and chemical attack properties. In addition, another layer of polyethylene terephthalate film having an aluminum vapor deposition layer as an intermediate layer may be disposed to form a four-layer structure.

  More specifically, a biaxially stretched polypropylene film as the outermost layer and an ethylene-vinyl alcohol copolymer film having an aluminum vapor deposition layer as an intermediate layer or a polyethylene terephthalate having an aluminum vapor deposition layer and an ethylene-vinyl alcohol copolymer having an aluminum vapor deposition layer. A polymer, a plastic laminate film made of linear low density polyethylene in the innermost layer, and a biaxially oriented polypropylene film or plastic laminate film made of high density polyethylene in the outermost layer. In this embodiment, the core material is covered with an outer cover material and the pressure is reduced. However, after the core material is covered with an inner packaging material (polyethylene as an example), the core material is further covered with an outer covering material (outer packaging material) to reduce the pressure. May be.

  Next, the adsorbent will be described. The adsorbent only needs to absorb gas such as carbon dioxide, oxygen, nitrogen, and water vapor. As an example, adsorbents of dosonite, hydrotalcite, metal hydroxide, or absorbents of molecular sieves, silica gel, calcium oxide, zeolite, hydrophobic zeolite, activated carbon, potassium hydroxide, lithium hydroxide are used.

  The vacuum heat insulating material mentioned above can be used for the refrigerator which has a heat insulation box. In the refrigerator, the space between the outer box and the inner box is filled with foamed resin foam to form a heat insulating box. A vacuum heat insulating material is also disposed in the space filled with the foamed resin foam. A vacuum heat insulating material is installed on the inner box surface or the outer box surface in advance, and then a foamed resin foam is injected and integrally molded, or a vacuum heat insulating material in which the vacuum heat insulating material and the foamed resin foam are integrally molded is prepared. In addition, there is a method of sticking or sandwiching the vacuum heat insulating material on the inner box or the outer box. These methods are appropriately used depending on an article that requires heat insulation performance. That is, it can be applied to each product that needs to be kept warm. Examples include vehicles, building materials, medical equipment, and the like. In addition to refrigerators and freezers for home use and business use, vending machines, product display shelves, cold storage, cooler boxes and the like are included. In particular, it is effective for all products that include a heat exchange section and require heat insulation.

  According to the vacuum heat insulating material of this embodiment, it is possible to improve the heat insulation / cooling function, reduce the amount of heat leakage, and save energy. Moreover, since the external appearance shape by the side of a resin fiber laminated body becomes favorable, the external appearance property at the time of installing in a refrigerator box can be improved.

  Next, the structure of the vacuum heat insulating material and refrigerator which concerns on embodiment of this invention is demonstrated with reference to drawings.

  First, a conventional vacuum heat insulating material will be described. As shown in FIG. 2, conventionally, the adsorbent 14 is held in a glass wool core 13, inserted into the jacket 15, and sealed under reduced pressure. Since the conventional vacuum heat insulating material 16 is glass wool, its heat insulation is good, but it is inferior in terms of environmental load, and it has been difficult to achieve both heat insulation performance and environmental load reduction. Further, in terms of bendability (three-dimensional molding), the fiber is cut when the glass wool is bent forcibly. In addition, the thickness of the bent portion is reduced, or pinholes that occur due to the thinning of the outer portion of the jacket material 2 are likely to occur, which may deteriorate the heat insulating performance of the vacuum heat insulating material.

  Next, in FIG. 1, the vacuum heat insulating material 1 is sealed under reduced pressure by inserting a resin fiber laminate 3 of polystyrene long fibers 3, an inorganic fiber laminate 5 of glass wool, and an adsorbent 4 into the jacket material 2. According to this vacuum heat insulating material 1, by using the resin fiber laminate 3 and the inorganic fiber laminate 5, it is possible to achieve both improvement of heat insulation performance and reduction of environmental load.

  The inorganic fiber laminate 5 is composed of a plurality of laminates, and two or more layers of glass wool are laminated. Furthermore, by laminating the resin fiber laminate 3 having a high hardness thereon, a vacuum heat insulating material excellent in surface smoothness can be produced, and a vacuum heat insulating material and a refrigerator excellent in appearance can be provided. The adsorbent is sandwiched between the flexible inorganic fiber laminates 5 so that it can be prevented that the adsorbent reaches the jacket material and is damaged during decompression. Moreover, what is necessary is just to provide the resin fiber laminated body 3 in the side which contact | connects the outer case 12 at least, and can improve an external appearance shape by this. In other words, the resin fiber laminate 3 may be provided on one surface or both surfaces in contact with the jacket material.

  Next, the structure which applied the vacuum heat insulating material to the refrigerator is demonstrated. As shown in FIG. 3, the refrigerator main body 10 has a vacuum heat insulating material 1 attached to a part of the inner surface side of an outer box 12 formed by press-molding an iron plate, and further includes an inner box 11 and an outer box 12 made of resin. A box body 9 is formed by foam-filling a foam heat insulating material 8 such as rigid polyurethane foam in the space between the two. A part of the vacuum heat insulating material 1 has a shape bent along the uneven shape of the heat insulating portion.

  Next, the performance of the vacuum heat insulating material according to the present embodiment will be described with reference to test results. In the performance test, the thermal conductivity of the vacuum heat insulating material alone and the amount of shrinkage of the steel sheet when the refrigerator using the vacuum heat insulating material was left in an environment of −10 ° C. were measured. The results are shown in FIG. In addition, the heat conductivity of a vacuum heat insulating material is described by the relative value when the heat conductivity in a prior art example is set to 100. Further, the steel sheet shrinkage ratio before and after being left in the -10 ° C environment is similarly expressed as a relative value when the shrinkage ratio in the conventional example is 100. Hereafter, a prior art example, each Example, and a comparative example are demonstrated.

(Conventional example)
First, a conventional example will be described. In the conventional example, a gas adsorbent (Molecular Sieves 13X) is sandwiched between core materials made only of glass wool that does not contain a binder, inserted into the outer cover material of a gas barrier film, and vacuum sealed by a vacuum packaging machine. Stopped.

  The thermal conductivity of the vacuum heat insulating material was measured at 10 ° C. using AUTO-λ manufactured by Eihiro Seiki Co., Ltd. The measured value at this time is set to 100.

  Moreover, about the refrigerator using the vacuum heat insulating material of a prior art example, after filling foaming heat insulation material, after 24 hours, the swelling of a steel plate is measured (previous history), and after that, in the thermostatic chamber set to -10 degreeC. The swelling of the steel sheet after being left for 24 hours is measured (post history), and the value obtained by calculating the shrinkage amount of the steel sheet from this previous history and subsequent history is set to 100.

Example 1
Next, the vacuum heat insulating material of Example 1 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. At this time, the fiber surface state can be changed hard by lowering the spinning temperature, and the resin continuous fiber web that has collected them forms a hard layer. The Vickers hardness of the polystyrene resin fiber laminate at this time was 65. The surface state of the resin fiber laminate was a flat plate.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Moreover, the relative value with the conventional example was 95 about the calculated value of the shrinkage | contraction amount of the steel plate similar to the above.

(Example 2)
Next, the vacuum heat insulating material of Example 2 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. The hardness was adjusted by lowering the spinning temperature, and the Vickers hardness of the polystyrene resin fiber laminate was 70. The surface state of the resin fiber laminate was a flat plate.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Moreover, the relative value with the conventional example was 93 about the calculated value of the shrinkage | contraction amount of the steel plate similar to the above.

(Example 3)
Next, the vacuum heat insulating material of Example 3 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. The hardness was adjusted by lowering the spinning temperature, and the Vickers hardness of the polystyrene resin fiber laminate was 75. The surface state of the resin fiber laminate was a flat plate.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Moreover, the relative value with the conventional example was 91 about the calculated value of the shrinkage | contraction amount of the steel plate similar to the above.

Example 4
Next, the vacuum heat insulating material of Example 4 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. The hardness was adjusted by lowering the spinning temperature, and the Vickers hardness of the polystyrene resin fiber laminate was 80.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Moreover, the relative value with the conventional example was 91 about the calculated value of the shrinkage | contraction amount of the steel plate similar to the above.

(Example 5)
Next, the vacuum heat insulating material of Example 5 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. At this time, as shown in FIG. 5, an embossed pattern was disposed on the surface of the laminated body by a heat roller in the post-spinning resin fiber laminated body 3a. The Vickers hardness of the polystyrene resin fiber laminate at this time was 70.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Moreover, the relative value with the conventional example was 91 about the calculated value of the shrinkage | contraction amount of the steel plate similar to the above.

(Example 6)
Next, the vacuum heat insulating material of Example 6 is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool which is an inorganic fiber. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. At this time, as shown in FIG. 6, a checkered pattern was arranged on the surface of the laminate by a heat roller in the resin fiber laminate 3b after the spin lamination. The Vickers hardness of the polystyrene resin fiber laminate at this time was 70.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 99 relative to the conventional example.

  Further, the calculated value of the shrinkage amount of the steel plate similar to the above was 92 relative to the conventional example.

(Comparative example)
Next, the vacuum heat insulating material of a comparative example is as follows. As the core material, a laminated body of polystyrene resin fibers spun and fiberized is laminated on a laminated body of glass wool of inorganic fibers. For polystyrene resin fibers, general-purpose polystyrene resins are used, and after melt blown spinning, polystyrene is passed through a hole provided at the tip of the nozzle, then high-temperature air is jetted to collect the fiber that has been drawn and collected on the collector. A long fiber web was formed. The Vickers hardness of the polystyrene resin fiber laminate was 85.

  The adsorbent (Molecular Sieves 13X) was sandwiched between the composite core material produced in this way, and was inserted into the outer cover material of the gas barrier film and vacuum sealed with a vacuum packaging machine. The thermal conductivity was 100 relative to the conventional example.

  This is because by reducing the fiberizing temperature as a condition for increasing the fiber hardness, the resin fiber diameter is increased and the porosity of the core material is decreased.

  Further, the calculated value of the shrinkage amount of the steel plate similar to the above was 92 relative to the conventional example.

  From this, according to each Example, the basis weight of the glass wool which is an inorganic fiber laminated body by installing a resin fiber laminated body with large hardness (Vickers hardness 65 or more and 80 or less) on an inorganic fiber laminated body. It is possible to suppress surface irregularities due to variations in the surface. Moreover, the distortion which generate | occur | produces in the outer case outer surface of the refrigerator which installed the vacuum heat insulating material by suppressing the surface unevenness | corrugation of a vacuum heat insulating material can be suppressed, and the refrigerator excellent in the external appearance can be provided.

  As described above, the surface property of the vacuum heat insulating material can be improved by using a melt-spun resin fiber laminate on a flexible inorganic fiber laminate that has not been cured with a binder, thereby improving the surface properties of the vacuum heat insulating material. Appearance can be improved.

  Moreover, the unevenness | corrugation by the distortion which arises in the refrigerator outer plate | board which is a vacuum heat insulating material sticking position can be improved by providing uniformly the embossing or checkered pattern in the surface of the said resin fiber laminated body.

  Further, since a spunbond method, a melt blow method, or the like is used as a manufacturing method at the time of fiberization, the resin to be used may be a recycled resin, and an environmental load can be reduced.

DESCRIPTION OF SYMBOLS 1 Vacuum heat insulating material 2 Cover material 3, 3a, 3b Resin fiber laminated body 5 Inorganic fiber laminated body 7 Heat insulation box 8 Foam heat insulating material 9 Box 10 Refrigerator main body 11 Inner box 12 Outer box

Claims (5)

In a vacuum heat insulating material comprising: a core material composed of a plurality of laminates; and a jacket material having a gas barrier property that stores the core material and maintains the inside in a reduced pressure state,
The vacuum insulating material according to claim 1, wherein the core material is provided with a resin fiber laminate having a Vickers hardness of 65 or more and 80 or less, which is obtained by melt spinning and laminating a resin on one surface or both surfaces in contact with the jacket material.   The vacuum heat insulating material according to claim 1, wherein the resin fiber laminate has a surface embossed or checkered.   The vacuum heat insulating material according to claim 1 or 2, wherein the core material is formed by stacking the resin fiber laminate on an inorganic laminate having flexibility.   The vacuum according to claim 1 or 2, wherein the resin fiber laminate is spun by a melt blown method or a spunbond method as one or more of polypropylene, polystyrene, polyethylene terephthalate, polycarbonate, and polyphenylene sulfide. Insulation. In the refrigerator provided with a foam heat insulating material and a vacuum heat insulating material between the outer box and the inner box,
The vacuum heat insulating material comprises a core material composed of a plurality of laminates, and a jacket material having gas barrier properties,
The refrigerator is characterized in that the core material is provided with a resin fiber laminate having a Vickers hardness of 65 to 80, which is obtained by melt spinning and laminating a resin on one surface or both surfaces in contact with the jacket material.

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