JP5251830B2 - Fiber sheet and vacuum insulation - Google Patents

Description

  The present invention relates to a vacuum heat insulating material in which a core material formed by laminating fiber sheets is covered with a jacket material having a gas barrier property and the inside is decompressed and sealed.

  In a conventional vacuum heat insulating material, a core material is formed by laminating fiber sheets made of fibers such as polyester resin so as to have a predetermined thickness. The fiber sheet is made of a material with low thermal conductivity to increase the porosity of the core material, and the heat transfer resistance is increased by placing the fibers in parallel in the direction perpendicular to the stacking direction and making the fibers contact each other. Realizes high thermal insulation performance.

  In the vacuum heat insulating material in which such fiber sheets are laminated, the contact surface between the fiber sheets is perpendicular to the thickness direction (heat transfer direction) of the vacuum heat insulating material, and this contact surface is in the thickness direction. Since there are few heat transfer paths, it becomes a favorable heat insulation surface. Therefore, if the thickness of the vacuum heat insulating material is constant, the heat insulating properties are improved as the number of fiber sheets to be laminated increases.

  The fiber sheet is produced by the same manufacturing method as the nonwoven fabric. The fiber sheet needs a certain degree of tensile strength, and when the fiber sheet has a low tensile strength, when the fiber sheet is wound into a roll, the fiber sheet is cut or stretched, or cannot be wound. The problem that the taking speed cannot be increased and the problem that the fiber sheet is stretched and the dimensional accuracy is lowered during the cutting process of the fiber sheet are caused, and this causes a decrease in productivity.

  Therefore, in order to give the fiber sheet tensile strength, the needle punching method repeatedly stabs and pulls up many needles with hooks perpendicularly to the plane of the sheet, and the fibers in the fiber sheet are They are entangled with each other. Thereby, the tensile strength is given to the fiber sheet to improve the handleability during production (for example, see Patent Document 1).

JP 2008-57793 A (page 4)

  However, in the conventional method in which tensile strength is given to the fiber sheet by the needle punch method, the fibers are entangled perpendicularly to the fiber orientation of the fiber sheet constituting the core material. In the case of producing a thin fiber sheet, there is a problem that it is difficult to entangle the fibers. Therefore, in order to ensure the tensile strength of the fiber sheet required for productivity, in the case of a thin fiber sheet, or in the case of a thin fiber sheet, there are many places where the fibers are entangled with each other by a needle punch. There was a need to do.

  When the fiber sheet is thick, the number of laminated fiber sheets in the core material of the vacuum heat insulating material having a predetermined thickness is reduced, so that the heat insulating performance is limited. In addition, when thin fiber sheets are used, the number of fiber sheets stacked in the vacuum insulation core material of a predetermined thickness increases, but there are more places where the fibers are entangled with each other by the needle punch of the fiber sheet. Since the longitudinal direction of the fibers is the same direction as the heat transfer direction, the entangled fibers become a heat transfer path in the heat transfer direction, and there is a problem that heat insulation performance cannot be improved. Therefore, in vacuum insulation materials composed of fiber sheets using the conventional needle punch method, there is a trade-off relationship between high tensile strength and high heat insulation performance of the fiber sheets, and both productivity and good heat insulation properties are compatible. There was a problem that was difficult.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a fiber sheet and a vacuum heat insulating material having high productivity and high heat insulating performance.

  The fiber sheet according to the present invention is a fiber sheet formed into a sheet shape with thermoplastic fibers, and is disposed discretely, and has through-heat fusion portions in which thermoplastic fibers are thermally fused in the penetration direction, and discrete And a surface heat-sealed portion in which the surface thermoplastic fibers are heat-sealed in a direction parallel to the surface.

  Further, a vacuum heat insulating material according to the present invention includes a core material obtained by laminating a fiber sheet including the above-described through heat fusion part and a surface heat fusion part, and an outer covering material that seals the core material under reduced pressure. Is.

  This invention is discretely arranged on a fiber sheet formed into a sheet shape with thermoplastic fibers, and through-heat fusion parts in which thermoplastic fibers are thermally fused in the penetration direction, and discretely arranged on the surface. An object of the present invention is to obtain a fiber sheet and a vacuum heat insulating material having high productivity and high heat insulation performance by including a surface heat fusion portion in which thermoplastic fibers on the surface are heat fused in parallel directions.

It is a schematic diagram of the fiber sheet by Embodiment 1 of this invention. It is a schematic diagram of the vacuum heat insulating material by Embodiment 1 of this invention. It is a characteristic view of the fiber sheet by Embodiment 2 of this invention. It is a characteristic view of the vacuum heat insulating material by Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a perspective view of a fiber sheet in Embodiment 1 for carrying out the present invention. In FIG. 1, a fiber sheet 1 is a sheet formed by superposing polyester fibers, which are thermoplastic resins having a fiber diameter of about 10 μm, for example. As a method for producing this fiber sheet, for example, a spunbond method can be used. In this spunbond method, polyethylene terephthalate, which is a polyester resin, is heated and melted, discharged from a spinneret equipped with a number of nozzles to form a thread, stretched with air while being cooled by an ejector, and horizontally below it. A continuous nonwoven web is formed by superimposing fibers while being dispersed on the moving belt conveyor surface. Thereafter, the nonwoven web on the belt conveyor is passed between an embossing roll having a heated protruding shape and a flat roll disposed through a gap with respect to the embossing roll, so that the fibers of the nonwoven web are partially The fiber sheet 1 is produced by bonding to each other by heat fusion.

  The embossing roll for producing the fiber sheet 1 includes protrusions having different heights alternately. The high protrusions heat-bond the fibers on the upper and lower surfaces of the nonwoven web to form a through heat-bonding portion 2 in which the upper and lower fibers are bonded, and the lower protrusions are fibers only on one surface layer of the nonwoven web. The surface heat fusion part 3 which bonded only the fiber of the surface layer was formed by heat-seal | fusing together. As shown in FIG. 1, the fiber sheet 1 manufactured in this way has a surface in which only the surface heat layer 2 on one side and the surface heat-bonded part 2 on the upper and lower surfaces of the fiber sheet 1 are bonded in the penetrating direction The heat fusion part 3 is formed. This penetration heat fusion part 2 is a hollow shape thinner than the other part of the fiber sheet 1, and the surface heat fusion part 3 has substantially the same thickness as the fiber sheet 5.

  FIG. 2 is a schematic cross-sectional view of the vacuum heat insulating material 4 in the present embodiment. The core material 5 is configured by laminating a large number of fiber sheets 1. For example, the core material 5 is configured by laminating about one hundred fiber sheets 1 having a thickness of about 0.1 mm to form a laminate having a thickness of about 10 mm. . The core material 5 is sealed with a jacket material 6 having gas barrier properties. The inside of the jacket material 6 is sealed under reduced pressure, and a gas adsorbent 7 is arranged inside.

  As the jacket material 6, for example, a laminated film having a multilayer structure with an aluminum foil sandwiched therebetween can be used. As such a laminate film, for example, from the outermost layer, a polyamide resin film (thickness of about 6 μm), a polyethylene terephthalate film (thickness of about 10 μm), an aluminum foil (thickness of about 6 μm), and high-density polyethylene (thickness of about 50 μm) There is a four-layer structure. Two laminated films are overlapped, and a sealed structure is formed by heat-sealing four sides.

  The gas adsorbent 7 adsorbs outgas generated from the core material 5 and moisture desorbed from the core material 5 in addition to air and moisture entering from the outside with the passage of time after the vacuum sealing, and the vacuum heat insulating material 4 It has the role of keeping the vacuum inside.

  In the vacuum heat insulating material configured as described above, the penetration heat fusion part for bonding the fibers on the upper and lower surfaces of the sheet suppresses the separation of the fibers by bonding the fibers in the stacking direction and gives the fiber sheet a tensile strength. give. Also, the through-heat fusion part acts to reduce heat insulation performance by forming a heat transfer path to crush and bond the fibers in the lamination direction, but the fiber sheets can be made thin, so they are laminated The point contact between the fibers increases more than the surface contact or the line contact between the fibers at the contact surface between the fiber sheets, and the heat insulation performance can be improved.

  Furthermore, since the penetration heat fusion part is a hollow shape thinner than the other part of the fiber sheet, it does not contact the upper and lower fiber sheets when laminated. For this reason, by reducing the area of the through heat fusion part and widening the interval, the heat conducted through the through heat fusion part becomes longer and the heat transfer resistance increases. As a result, the thermal conductivity in the thickness direction of the fiber sheet can be lowered.

  On the other hand, the surface heat-sealed part where the fibers of the surface layer are bonded to each other does not serve as a heat transfer path between the laminated fiber sheets because the heat-sealed layer is not connected in the thickness direction in the fiber sheet. It only acts to increase the tensile strength of the fiber sheet. That is, by providing a part of the heat-sealed portion only on the surface layer on one side of the fiber sheet, the tensile strength can be increased even if the fiber sheet is thin, so that productivity can be increased and heat insulation performance can be increased. Can be high.

  The load acting on the fiber sheet is mainly a load in the planar direction acting at the time of winding and cutting, and the tearing load that separates the fiber sheet in the thickness direction is not large. Therefore, the tensile load can be increased by reducing the area of the through heat fusion part for bonding the fibers on the upper and lower surfaces of the fiber sheet and increasing the area of the surface heat fusion part for bonding the fibers of the surface layer.

  Furthermore, the surface heat-sealed part that bonds the fibers of the surface layer restrains the movement of the fibers when subjected to a compressive load in the vacuum heat insulating material. Higher heat insulation performance can be realized.

  In the present embodiment, a through heat fusion portion and a surface heat fusion portion are formed in the nonwoven fabric web by passing between an embossing roll and a flat roll having protrusions with different heights alternately. However, embossing is performed in two stages, with two pairs of embossing rolls and flat rolls, one embossing roll having only high protrusions and the other embossing roll having only low protrusions. Also good. The clearance of the gap between the embossing roll and the flat roll, the shape, arrangement, and arrangement of the protrusions of the embossing roll can be set as appropriate.

  In this embodiment, polyethylene terephthalate, which is a polyester resin, is used as the thermoplastic resin. However, other thermoplastic resins such as polypropylene, polyethylene, and polyamide resins can also be used.

Embodiment 2. FIG.
In the second embodiment, the tensile strength of the fiber sheet and the fiber when the basis weight of the fiber sheet using the polyethylene terephthalate fiber and the interval between the discrete heat-bonding portions arranged discretely are changed. The heat insulation characteristic of the vacuum heat insulating material produced using the sheet | seat is evaluated. The basis weight is defined as the mass per square meter of fiber sheet.

A non-woven web having a basis weight of 18 g / m ² and a thickness of about 0.1 mm was subjected to embossing roll processing similar to that of Embodiment 1 to form a penetration heat fusion part and a surface heat fusion part. At this time, five types of fiber sheets were produced in which the distance between the closest through heat-sealed portions was 0.8 mm, 1.0 mm, 1.2 mm, 1.8 mm, 2.4 mm, and 3.4 mm. At this time, the high protrusion has a cylindrical shape with a height of 0.5 mm and φ0.5 mm, and the lower protrusion has a cylindrical shape with a height of 0.45 mm and φ0.5 mm. . The gap between the embossing roll and the flat roll was set so that the projection having a height of 0.5 mm was in contact with the flat roll. The embossing roll was set to about 200 ° C. The ratio of the total area of the through heat fusion part and the total area of the surface heat fusion part was set to 50:50.

  When embossing roll processing is performed in this way, in a non-woven web having a thickness of about 0.1 mm, the part where the high protrusions are in contact is almost completely compressed, and the penetration heat is bonded to the upper and lower fibers. Although it becomes a fusion | melting part, the part which the processus | protrusion with low height contacted becomes the surface heat fusion part compressed, leaving a thickness of about 0.05 mm. The surface heat-sealed portion recovers its thickness after embossing roll processing, and has almost the same thickness as the uncompressed portion of the fiber sheet.

Furthermore, using the nonwoven fabric web having a basis weight of 35 g / m ² and a thickness of about 0.2 mm, and using the nonwoven fabric web having a basis weight of 70 g / m ² and a thickness of about 0.3 mm, the above-mentioned basis weight is 18 g / m ^2. As in the case of the non-woven web having a thickness of about 0.1 mm, the distance between the closest through heat fusion portions is 0.8 mm, 1.0 mm, 1.2 mm, 1.8 mm, 2.4 mm, and 3.4 mm. 5 types of fiber sheets were produced. Here, the distance between the nearest through heat fusion parts is the distance (length L) between the outer peripheral parts of the nearest through heat fusion parts as shown by the double-ended arrows in FIG. 1 of the first embodiment. ).

  A total of 15 types of fiber sheets having different distances between the closest through heat-sealed portions with respect to the respective fabric weights thus produced were subjected to a tensile strength test based on the strip method defined in JIS L1096. At this time, a test piece obtained by cutting each fiber sheet into a width of 25 mm and a length of 200 mm was used.

  FIG. 3 is a characteristic diagram of the fiber sheet in the present embodiment. The horizontal axis in FIG. 3 is the distance between the nearest through-heat fusion parts (mm), and the vertical axis is the stress at 5% elongation (N / 25 mm). Here, the stress at 5% elongation (N / 25 mm) is a load necessary when the fiber sheet of the above-mentioned test piece is elongated by 5% in the length direction. From FIG. 3, it can be seen that, in the fiber sheets having different fiber sheet weights, the tensile strength decreases as the interval between the through-heat fusion portions that join the fibers on the upper and lower surfaces becomes longer. When the distance between the closest heat-sealed portions is larger than 3.5 mm, the tensile strength of the fiber sheet is insufficient, and winding with a roll becomes difficult, resulting in a significant reduction in productivity.

  Next, each of these 15 types of fiber sheets was cut into A4 size. As shown in FIG. 2 of the first embodiment, about 100 kinds of fiber sheets are laminated so as to have a thickness of about 10 mm, and the jacket material is processed into a bag shape with a laminate film together with a gas adsorbent. And vacuum-evacuation was performed in a vacuum packaging machine, and the opening of the jacket material was heat-sealed at about 2 Pa to produce a vacuum heat insulating material.

  The heat conductivity in the thickness direction of the vacuum heat insulating material, which was manufactured in this manner and varied in the basis weight of the fiber sheet and the interval between the nearest through heat-sealed portions arranged discretely, was measured. The thermal conductivity was measured using a thermal conductivity measuring device (Auto HC-073: manufactured by Eihiro Seiki Co., Ltd.).

  FIG. 4 is a characteristic diagram of the vacuum heat insulating material in the present embodiment. The horizontal axis in FIG. 4 is the distance (mm) between the nearest through heat-sealed portions, and the vertical axis is the thermal conductivity (W / m · K). From FIG. 3, it can be seen that, in the vacuum heat insulating materials having different fiber sheet weights, the thermal conductivity decreases as the interval between the through heat fusion portions that join the fibers on the upper and lower surfaces becomes longer. It can also be seen that the thermal conductivity increases as the basis weight increases.

For example, when the distance between the nearest through heat-sealed portions is 1.5 mm, a fiber sheet having a weight per unit area of 35 g / m ² is used for a vacuum heat insulating material using a fiber sheet having a basis weight of 18 g / m ² . The heat conductivity of the vacuum heat insulating material is 1.1 times, and the heat conductivity of the vacuum heat insulating material using the fiber sheet having a basis weight of 70 g / m ² is 1.4 times. On the other hand, in order to achieve the same thermal conductivity as that of the vacuum heat insulating material using the fiber sheet having a spacing of 1.5 mm and a weight of 18 g / m ² , the weight per unit area is 35 g / m. ^In the vacuum heat insulating material using the fiber sheet of No. ² , in the vacuum heat insulating material using the fiber sheet having a distance of 2.5 mm and the basis weight of 70 g / m ^{2 in} the nearest through heat fusion part, It is necessary to set the gap between the landing portions to 3.5 mm.

  From this embodiment, based on the tensile strength of the fiber sheet and the thermal conductivity of the vacuum heat insulating material produced using this fiber sheet, the distance between the closest through-heat fusion parts of the fiber sheet is 3.5 mm or less. Preferably there is.

DESCRIPTION OF SYMBOLS 1 Fiber sheet 2 Through-heat-fusion part 3 Surface heat-fusion part 4 Vacuum heat insulating material 5 Core material 6 Cover material 7 Gas adsorbent

Claims (3)

In the fiber sheet formed into a sheet shape with thermoplastic fibers,
Discretely arranged, through heat-sealed portions in which the thermoplastic fibers are heat-sealed in the penetration direction;
A fiber sheet comprising: a surface heat-sealed portion that is discretely arranged and heat-sealed with the thermoplastic fibers on the surface in a direction parallel to the surface. The fiber sheet according to claim 1, wherein the distance between the nearest through heat-sealed portions arranged discretely is 3.5 mm or less. A core material on which the fiber sheets of claim 1 are laminated;
A vacuum heat insulating material comprising an outer jacket material that seals the core material under reduced pressure.

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