JP2010121652A - Vacuum thermal insulating material and thermal insulation box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum thermal insulating material having excellent thermal insulating performance. <P>SOLUTION: In the vacuum thermal insulating material constituted of a core material 2, and an outer covering material 1 having gas barrier properties to cover the core material 2, its inside is sealed hermetically under a reduced pressure. The core material 2 is formed of a long fiber assembly made of a thermoplastic resin. In the core material 2, one layer is formed by sandwiching the top and bottom of the layer made of the long fiber assembly without the deposition between the fibers with the layer made of the long fiber assembly having the deposition between the fibers. The core material is formed by laminating one layer or a plurality of layers. The layer having the deposition between the fibers has fiber basis weight per unit area of not more than 5 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vacuum heat insulating material and a heat insulating box, and more particularly to a vacuum heat insulating material suitable for use in a cold heat apparatus.

  Conventionally, urethane foam has been used as a heat insulating material for refrigerators, but in recent years, vacuum heat insulating material with better heat insulation performance than urethane foam has been embedded in urethane foam due to market demands for energy saving and space-saving capacity expansion. The form to be used has come to be used. Such a vacuum heat insulating material is used not only for a refrigerator but also for a cooling device such as a heat storage, a vehicle air conditioner, and a water heater.

The vacuum heat insulating material is a powder, foam, fiber or the like inserted as a core material in an outer packaging material made of a gas barrier aluminum foil laminate film or the like, and the inside is kept at a vacuum level of several Pa or less.
Further, an adsorbent for adsorbing gas and moisture is disposed in the outer packaging material in order to suppress the deterioration of the degree of vacuum, which is a factor of lowering the heat insulating performance of the vacuum heat insulating material.
As the core material of the vacuum heat insulating material, there are powders such as silica, foams such as urethane, fiber bodies, etc., but at present, glass fibers having excellent heat insulating performance are mainly used.

  Examples of the shape of the fibrous body include cotton-like ones, laminated sheets (for example, see Patent Documents 1 and 2), and laminated sheets so that fiber orientations alternate (see Patent Document 3). ing.

  The fiber material includes organic fibers such as polypropylene fiber, polylactic acid fiber, aramid fiber, LCP (liquid crystal polymer) fiber, polyethylene terephthalate fiber, polyester fiber, polyethylene fiber, and cellulose fiber (for example, patents). Reference 4).

Japanese Patent Laying-Open No. 2005-344832 (page 3-4, FIG. 1) Japanese Patent Laying-Open No. 2006-307921 (page 5-6, FIG. 2) Japanese Examined Patent Publication No. 7-103955 (second page, FIG. 2) JP-A-2006-283817 (page 5-8)

As mentioned earlier, glass fibers are mainly used as the core material in current vacuum insulation materials, but since glass fibers are hard and brittle, dust is scattered during the manufacture of vacuum insulation materials. Contact with mucous membranes may cause irritation, and handling and workability are problematic.
Also, when considering the scene of recycling, for example, in the refrigerator, the product is pulverized together at the recycling factory, and the glass fiber is mixed with urethane waste and is used for thermal recycling. There is a disadvantage that it is not good.

  On the other hand, as shown in Patent Document 4, the polyester fiber is used as a core material, although it has excellent handleability and recyclability, but its thermal conductivity, which is an index representing heat insulation performance, is 0.0030 [W / mK]. The heat conductivity is inferior to the heat conductivity of 0.0020 [W / mK] of a general vacuum heat insulating material using glass fiber as a core material.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a vacuum heat insulating material excellent in heat insulating performance.

  The vacuum heat insulating material according to the present invention comprises a core material and an outer packaging material having a gas barrier property that covers the core material, and the core material is a set of long fibers of a thermoplastic resin in a vacuum heat insulating material sealed inside under reduced pressure. It is formed by the body.

  In the vacuum heat insulating material according to the present invention, the core material covered with the outer packaging material having gas barrier properties is formed from the long fiber aggregate of the thermoplastic resin, so that the fiber orientation in the heat insulating direction can be suppressed and the heat insulating performance is improved. Can be made.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view of a vacuum heat insulating material according to Embodiment 1 of the present invention, FIG. 2 is a schematic view of a long fiber assembly of a core material of the vacuum heat insulating material viewed from above, and FIG. It is sectional drawing of the long-fiber assembly of a core material.
As shown in FIG. 1, the vacuum heat insulating material according to Embodiment 1 of the present invention includes a core material 2 and an outer packaging material 1 having a gas barrier property that covers the core material 2, and is configured by sealing the inside under reduced pressure. ing. A moisture adsorbent 3 for suppressing the deterioration of the degree of vacuum with time is disposed inside the outer packaging material 1.

The outer packaging material 1 is a plastic laminate film, polyethylene is used for the innermost sealing layer, an aluminum foil of about 6 μm is used for the gas barrier layer outside the sealing layer, and polyethylene terephthalate is used for the outer side of the aluminum foil, The outermost layer is made of polyamide.
Moreover, the moisture adsorbent 2 arrange | positioned inside the outer packaging material 1 is CaO which entered the nonwoven fabric bag.
Further, the core material 2 plays a role of supporting the atmospheric pressure to secure a space in the vacuum heat insulating material and a function of finely dividing the space in the vacuum heat insulating material to reduce the heat conduction of the gas. It is formed of a long fiber assembly.

The long fiber assembly forming the core material 2 is composed of resin long fibers, and has a layered structure as shown in the cross-sectional view of FIG. The layered long fiber assembly as the core material 3 is manufactured as follows.
First, the raw material resin pellets are heated and melted by an extruder.
The material of the resin pellet may be a thermoplastic resin such as polyester, polypropylene, nylon, PPS (polyphenylene fluoride resin), PS (polystyrene), LCP (liquid crystal polymer), PLA (polylactic acid resin), but here Uses polyester.

The melted polyester, which is a thermoplastic resin, is passed through a filter for removing foreign substances and then sent to a spinning nozzle by a gear pump. Polyester extruded from a number of nozzle holes of the spinning nozzle is compressed air, hot air, or mechanically stretched to obtain the desired fiber diameter. At this time, the resin temperature, cooling, and stretching conditions are adjusted. Thus, it is important that each single fiber is not cut and becomes a continuous fiber.
Spinning is performed vertically (in the direction of gravity), and continuous fibers having a desired fiber diameter are collected on a conveyor installed under the spinning nozzle. At this time, each fiber falls on the conveyor so as to draw an ellipse, and the conveyor is sent at an arbitrary speed to be laminated so that the polyester having the structure shown in the schematic diagram of FIG. 2 or the cross-sectional view of FIG. Can be obtained.

Therefore, the long fiber aggregate referred to here is an aggregate of long continuous fibers dropped and stacked on a conveyor.
In addition, the thickness of a long-fiber assembly can be adjusted by sending a conveyor at arbitrary speeds.
Table 1 shows the results of manufacturing a vacuum heat insulating material using the core material 2 of the obtained long fiber assembly and measuring the thermal conductivity of the vacuum heat insulating material. As a comparison, the results of a vacuum heat insulating material using a cotton-like core material of polyester short fibers are also shown.

  As can be seen from Table 1, by making the vacuum heat insulating material a structure using the core material 2 of such a long fiber aggregate, the orientation of the fibers in the heat insulating direction can be suppressed, and the thickness that is the heat insulating direction. Since the solid heat transfer path for each fiber in the direction can be long, the heat insulation performance can be improved.

Embodiment 2. FIG.
FIG. 4 is a cross-sectional view of the core material of the vacuum heat insulating material according to the second embodiment of the present invention.
Since the layered long fiber aggregate constituting the core material 2 obtained in the first embodiment has no bonding between fibers such as welding, the heat insulation performance can be improved by contact thermal resistance, but on the other hand, the strength as a sheet It is difficult to handle.

  Therefore, as a method for obtaining the strength as a sheet and improving the handleability, a method using a binder (see Japanese Patent Application Laid-Open No. 2004-52744) and a method of performing hot press processing such as a dot shape can be considered. In addition, it is difficult to adjust the degree of binder impregnation in the thickness direction, and the latter has a demerit that heat transfer in the thickness direction is increased by partially providing melted portions.

Therefore, in the second embodiment, as shown in FIG. 4, the sheet strength that can withstand handling with the same material as the long fiber aggregate 2b above and below the long fiber aggregate 2b, which is a layer without inter-fiber welding described above. Thin fiber assemblies 2a and 2c, which are layers having inter-fiber welds, were formed.
As a manufacturing method, the spinning units on the conveyor are arranged in three rows, and the 2a layer is formed in the second row, the 2b layer in the second row, and the 2c layer in the third row.
The layers 2a and 2c were welded between fibers by adjusting the temperature and air pressure using a method of stretching with hot air. These 2a and 2c layers have no problem even if the fibers are cut during spinning to become short fibers.
The 2b layer is formed by the method described in the first embodiment.

Since the thin fiber aggregates 2a and 2c have obtained sheet strength by imparting welds between the fibers, if the basis weight is large, the sheet becomes thick and increases heat transfer in the thickness direction, which is the heat insulation direction, and decreases the heat insulation performance. Therefore, the basis weight of 2a and 2c is preferably lower, and is set to 5 g / m ² .
Table 2 shows the results of the evaluation of the heat insulation performance produced in the vacuum heat insulating material using long fiber assemblies produced by changing the basis weight of the 2b layer with respect to the 2a and 2c layers.
The basis weight is the weight per unit area, and the unit is g / m ² . If the fiber diameter is the same, the thickness of the fiber assembly also changes in proportion to the basis weight. Therefore, the long fiber assembly was laminated and used so as to have a thickness of about 10 mm when used as a vacuum heat insulating material.

According to the results shown in Table 2, when the core material 2 in the vacuum heat insulating material is used, the basis weight of the 2b layer adversely affects the heat insulating performance when the proportion of the 2a and 2c layers in the thickness direction increases. On the other hand, the 2b layer is preferably thicker, and if the basis weight of the 2a layer and the 2c layer is 5 times or more, the influence of the 2a layer and the 2c layer hardly appears. Can be improved.
Furthermore, in order to improve the handleability, it is desirable to weld both ends of the sheets of the 2a layer and the 2c layer by hot pressing, but the welding area should be smaller at the end of the region used as the core material 2. % Or less is preferable.

FIG. 5 is a cross-sectional view of a refrigerator-freezer using a heat insulating box having the vacuum heat insulating material of the first or second embodiment.
As shown in FIG. 5, the refrigerator 31 includes a heat insulating box 32 that forms a housing of the refrigerator and a refrigeration cycle.
The heat insulating box 32 includes an outer box 33 formed by press-molding an iron plate and an inner box 34 formed by molding ABS resin or the like via a flange (not shown). Inside the heat insulation box 32, the vacuum heat insulating material 10 is disposed in advance, and the space other than the vacuum heat insulating material 10 is foam-filled with a hard urethane foam 35.

The heat insulation box 32 is partitioned by a partition plate 36, and the upper part is a refrigerator compartment 37 and the lower part is a freezer compartment 38.
A door body 39 is attached to the refrigerator 31, and the vacuum heat insulating material 10 is disposed inside the door body 39, and the space other than the vacuum heat insulating material 10 is foam-filled with a hard urethane foam 35. Yes.
The said vacuum heat insulating material 10 uses the thing of the structure similar to what was shown in Embodiment 1 or 2. FIG.
Therefore, the heat insulation box 32 having the vacuum heat insulating material 10 with improved heat insulation performance is improved in heat insulation performance, and the refrigerator refrigerator using the heat insulation box 32 is also improved in heat insulation performance.

Sectional drawing of the vacuum heat insulating material of Embodiment 1 of this invention. The schematic diagram which looked at the long-fiber assembly of the core material of the vacuum heat insulating material from the upper surface. Sectional drawing of the long-fiber assembly of the core material of the vacuum heat insulating material. Sectional drawing of the core material of the vacuum heat insulating material of Embodiment 2 of this invention. Sectional drawing of the refrigerator-freezer using the heat insulation box which has the vacuum heat insulating material of the Embodiment 1 or 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Outer packaging material, 2 Core material, 2a, 2c Layer with interfiber welding, 2b Layer without interfiber welding, 3 Adsorbent.

Claims (5)

In a vacuum heat insulating material consisting of a core material and an outer packaging material having a gas barrier property covering the core material, the inside of which is sealed under reduced pressure,
A vacuum heat insulating material, wherein the core material is formed of a long-fiber aggregate of a thermoplastic resin.   The core material is formed by laminating the upper and lower layers of the long fiber aggregates with no interfiber welding between the long fiber aggregates and the layers with interfiber welds as one layer or by stacking one or more layers. The vacuum heat insulating material according to claim 1. The vacuum heat insulating material according to claim 2, wherein the basis weight of the layer having the inter-fiber weld is 5 g / m ² or less.   The vacuum heat insulating material according to claim 2 or 3, wherein the basis weight of the layer having no inter-fiber welding is five times or more the total basis weight of the layer having the inter-fiber welding.   A heat insulating box comprising the vacuum heat insulating material according to claim 1.

Images