JP2006029505A - Vacuum heat insulating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum heat insulating material having extremely low environmental load, when manufactured and recycled, and improved handling property and workability while maintaining good heat insulating performance for a long period. <P>SOLUTION: The vacuum heat insulating material comprises at least a core material and an enclosing material storing the core material and keeping itself in a depressurized condition. The core material is a sheet fiber assembly which contains 50 wt% or more polyester fibers having fiber sizes of 1-6 deniers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a vacuum heat insulating material used as a heat insulating material for a refrigerator, a vending machine, a cold box, a cold car, and the like.

  Conventionally, heat insulating materials having various structures and performances are used in refrigerators, vending machines, cold storage boxes, cold cars, and the like. In recent years, a vacuum heat insulating material having a very excellent heat insulating property has been used in many applications. The vacuum heat insulating material generally has a structure in which a core material is filled in an outer packaging material made of a gas barrier metal deposition film or the like, and the inside thereof is decompressed and sealed. The heat insulating properties, productivity, and handling performance of such a vacuum heat insulating material greatly depend on the core material, but as a core material that is currently widely used, open cell polyurethane foam (Patent Document 1), the average fiber diameter is Examples thereof include a glass fiber aggregate (Patent Document 2) of about 0.5 to 8 μm and a composite of a glass fiber aggregate and other thermoplastic resin fibers (Patent Document 3).

However, the general-purpose core for vacuum heat insulating material has the following problems.
Although the core material using the open-cell polyurethane foam is very excellent in workability, handleability, lightness and the like, it has a poor heat insulating property as compared with a fibrous material such as glass fiber.

  Although the core material using the glass fiber aggregate having an average fiber diameter of about 0.5 to 8 μm has no outgas (gas component volatilized from the core material) and has excellent heat insulation properties, the glass fiber The material itself has great difficulty in handling and workability. In order to improve handling, some improvements have been made to the work of inserting the core material into the outer packaging material by applying needle punch to the laminated glass fiber, but the handling and workability difficulties derived from the material itself are difficult. Is not something that can be solved. In particular, the problems of working environment and handling at the time of recycling the core material remain. For example, if the outer packaging material is opened at the time of recycling, the glass fiber aggregate core material scatters, which causes problems not only in handling and workability but also in terms of environmental burden.

  A core material using a composite of glass fiber aggregates and other thermoplastic resin fibers is not satisfactory, although a slight improvement in handleability is observed. Similar to thermoplastic resin fibers, some composites of rock wool, pulp, and other fibers are also seen, but because glass fibers are used, the difficulties in handling and workability derived from the glass fibers themselves and the environmental burden are Still remains.

A vacuum heat insulating material using only organic fibers such as thermoplastic resin fibers as a core material is also conceivable, but no example is realized due to the problem of outgas generated from organic fibers. In particular, an example in which a 0.75d polyester fiber collection is used as a core material can be seen (Patent Document 4), but if used in a wrinkled form, handling properties are extremely poor and cannot be considered as a practical product. Therefore, it is conceivable to make the cotton collection into a sheet for the purpose of improving the handleability, but when using ultrafine fibers as described above, the needle punch method is difficult to use, so a binder is used by the chemical bond method. And there is a problem that outgas is generated, the change with time is large, and the heat insulation is greatly deteriorated with time.
JP-A-6-213561 JP-A-8-28776 JP 2003-155651 A JP 2002-188791 A

  The present invention has been made in order to solve the above-described problems, and is a vacuum heat insulating material having an extremely low environmental load at the time of production and recycling, and is excellent in handleability and workability and good for a long period of time. It aims at providing the vacuum heat insulating material which maintains heat insulation.

  The present invention comprises at least a core material and an outer packaging material that can store the core material and maintain the inside in a reduced pressure state, and the core material contains 50% by weight or more of polyester fiber having a fiber thickness of 1 to 6 denier. It is related with the vacuum heat insulating material characterized by being a sheet-like fiber assembly to do.

  The organic fiber core material was not actually considered as a core material for vacuum heat insulating material due to problems such as a decrease in heat insulation due to outgassing, but the inventors of the present invention have a specific thickness. Focusing on the polyester fiber, it has been found that the fiber in the form of a sheet exhibits a heat insulating property that exceeds that of the conventional open-cell urethane foam over a long period of time, and has led to the present invention.

  In the vacuum heat insulating material of the present invention, since the core material is made of polyester fiber, the environmental load is small, and the recyclability after use is very excellent. Moreover, the vacuum heat insulating material of the present invention exhibits a heat insulating property that exceeds the vacuum heat insulating material using the open-cell urethane foam employed in refrigerators and the like over a long period of time, and is easier to handle and work than glass fiber. Excellent.

  The vacuum heat insulating material of the present invention comprises at least a core material and an outer packaging material that can accommodate the core material and maintain the inside in a reduced pressure state.

  In the present invention, the core material is a sheet-like fiber assembly containing polyester fibers having a fiber thickness of 1 to 6 denier, preferably 1 to 3 denier. Specifically, the core material is formed by processing the fiber assembly containing the polyester fiber into a sheet shape, and by using such a core material, the handling property and workability can be improved. In addition, the environmental load during manufacturing and recycling can be reduced. Furthermore, good heat insulation can be exhibited over a long period of time. The average fiber diameter of the polyester fiber having the above fiber thickness is usually 9 to 25 μm, preferably 9 to 17 μm. The average fiber diameter was measured by processing two diameters per 10 fibers with a CCD camera image for 10 fibers, and calculating the average value of the diameters at a total of 20 positions as the average fiber diameter value.

  “Sheet” means having a flat plate shape. When the fiber assembly is used as it is, if the core material is not in the form of a sheet, the handling of the core material will be reduced, so the process of storing the core material in the outer packaging will become too complicated and workability will deteriorate. To do. Furthermore, the initial heat insulation is not expressed.

  In the present invention, the thickness of such a sheet-like fiber assembly (core material) is not particularly limited as long as the object of the present invention is achieved, and is usually about 1 mm to 50 mm when used as a vacuum heat insulating material. What is necessary is just about 5 mm-20 mm. In addition, the sheet-like fiber assembly may be a single-layer sheet, but a single-layer polyester fiber sheet having a thickness of about 5 mm or more as a vacuum heat insulating material is difficult to manufacture. And it is preferable to set it as a sheet-like fiber assembly (core material). The fiber assembly is preferably processed without using any other material such as a binder. For example, the fiber assembly is processed into a sheet by a so-called needle punch method or the like. The chemical bond method using a binder causes a problem in that the heat insulating property is lowered over time due to outgas generation. The needle punching method is a method of repeatedly piercing or pulling up many needles with hooks against a polyester fiber lump in which the directions of fibers are aligned to some extent, that is, a polyester fiber web. It is the method of making it into a sheet form by mutually entanglement.

If the average fiber diameter of the polyester fiber is too small, the needle punch machine cannot be used, so that it is used in a wrinkled form or is formed into a sheet form by a chemical bond method, and the above-mentioned problems arise. On the other hand, if the average fiber diameter is too large, the heat insulating property tends to decrease, and in order to ensure good heat insulating property, it is necessary to have a high density exceeding 300 kg / m ³ , and the weight becomes a problem.
When other organic fibers such as polyethylene fibers are used in place of the polyester fibers, the heat insulating property is deteriorated with time due to outgas generation.

  In the present invention, the term “polyester fiber” means a fiber made of a polymer in which chemical structural units are bonded mainly by ester bonds, and the production method is not particularly limited. For example, it may be a polyester fiber obtained by a reaction between a dicarboxylic acid component and a diol component, or a polyester fiber obtained by a reaction between hydroxycarboxylic acid components having a hydroxyl group and a carboxyl group in one molecule. May be.

  Specific examples of the polyester fiber include polyethylene terephthalate (PET) fiber, polybutylene terephthalate (PBT) fiber, polypropylene terephthalate fiber, and polyarylate fiber. For example, PET fiber is obtained by a reaction of dimethyl terephthalate (DMT) and ethylene glycol (EG) or terephthalic acid (TPA) and EG, and PBT fiber is DMT and tetramethylene glycol (TMG) or TPA and TMG. It can be obtained by the reaction of In view of sheet formability, mass productivity and cost, polyethylene terephthalate fiber is preferable. Of course, there is no problem even if recycled PET fibers are used.

  The polyester fibers are not particularly limited, but those having a softening point of about 200 to 260 ° C. and a strength of about 0.3 to 1.2 GPa are preferable from the viewpoint of ease of fiber production.

  Examples of the method for fiberizing polyester include a melt spinning method, a wet spinning method, and a dry spinning method. In the present invention, the melt spinning method is preferable. The melt spinning method is a system in which a polymer melt is discharged into the air from a pore nozzle, cooled and solidified with air while thinning the discharged molten yarn, and then taken up at a constant speed. In this method, a polyester fiber having a fiber thickness of about 1 to 6 denier can be easily produced.

  The content of the polyester fiber in the fiber assembly is not particularly limited as long as the object of the present invention is achieved, and is usually 50% by weight or more based on the total amount of the core material from the viewpoint of preventing temporal deterioration of heat insulation due to outgas generation, Preferably it is 90-100 weight%. From the viewpoint of further improving the heat insulating properties, the core material is most preferably made of only polyester fibers.

  Other fibers that may be contained in the fiber assembly together with the polyester fiber include, for example, polyethylene fiber, polypropylene fiber, acrylic fiber, aramid fiber, nylon fiber, polyvinyl alcohol fiber, fluorine fiber, polyurethane fiber, polynosic fiber, rayon fiber, etc. Synthetic fibers, inorganic fibers such as alumina and potassium titanate, natural fibers such as hemp, silk, cotton and wool.

In the present invention, the density of the core material is preferably 100 to 300 kg / m ³ , more preferably 150 to 300 kg / m ³ . When the density is too small, the strength as the core material is lowered and the heat insulating property tends to be lowered. On the other hand, when too large, there exists a tendency for it to become heavy and for heat insulation to fall. That is, if the density is too light or too heavy, the heat insulating property tends to decrease. In the average fiber diameter, the most preferable density is 170 to 270 kg / m ³ .

  In this specification, the density of the core material is obtained by measuring the density after the core material is accommodated in the outer packaging material and vacuumed. That is, after creating the vacuum heat insulating material, the weight of the outer packaging material and the getter material measured in advance is subtracted from the weight of the vacuum heat insulating material to obtain the weight of the core material. Further, the volume of the getter material or the like measured in advance is subtracted from the volume of the vacuum heat insulating material to obtain the volume of the core material. In addition, since the thickness of the outer packaging material is very small, it is not considered in the volume calculation. The density is calculated from the weight and volume of the obtained core material.

  As the outer packaging material for storing the core material, any material can be used as long as it has gas barrier properties and can maintain the inside at a reduced pressure, and is preferably heat-sealable. Preferable specific examples include, for example, a gas barrier film having a four-layer structure of nylon, aluminum vapor-deposited PET (polyethylene terephthalate), aluminum foil, and high-density polyethylene as the innermost layer, from the outermost layer, polyethylene terephthalate resin, intermediate Gas barrier film consisting of aluminum foil as the layer, high density polyethylene resin as the innermost layer, PET resin as the outermost layer, ethylene-vinyl alcohol copolymer resin having an aluminum vapor deposition layer as the intermediate layer, and gas barrier consisting of high density polyethylene resin as the innermost layer A film etc. are mentioned.

  In the vacuum heat insulating material of the present invention, it is possible to obtain a vacuum heat insulating material excellent in heat insulating properties by only including a core material in the outer packaging material. Alternatively, it is preferable to enclose a gas adsorbent (getter material) that adsorbs at least one of the constituent gases of air.

A preferred embodiment of the method for producing a vacuum heat insulating material of the present invention will be described below.
The fiber assembly is formed into a sheet shape by a needle punch method or the like to obtain a core material. The obtained core material is cut into an appropriate size and shape (for example, a square shape), and dried to remove moisture and the like contained therein. The drying is performed at 120 ° C. for about 1 hour, but it is preferable to vacuum dry at 120 ° C. in order to further remove moisture and the like of the polyester fiber. Furthermore, you may use together the drying by far infrared rays. About a vacuum degree, it is preferable to dry at about 0.5-0.01 Torr.

  Next, the core material is inserted into an outer packaging material sealed in a bag shape. At this time, a getter material may be inserted together. In this state, it is put in a vacuuming device and evacuated under reduced pressure so that the internal pressure becomes a degree of vacuum of about 0.1 to 0.01 Torr. Thereafter, the bag-shaped opening of the outer packaging material is sealed by heat sealing, and a vacuum heat insulating material is obtained. It should be noted that the core material density can be controlled by pressing at room temperature in order to adjust the core material thickness.

<Fiber used for core material>
The polyester fibers listed in the table were used. The polyester fibers were all polyethylene terephthalate fibers having a fiber length of 51 mm.

<Example 1>
The polyester fibers listed in the table were processed into a sheet by the needle punch method. The sheet basis weight immediately after processing was 550 g / m ² . The sheet was cut into a size of 200 mm × 200 mm and dried at a temperature of 120 ° C. for 1 hour. Four sheets after drying are laminated, and the laminated sheet is inserted into a gas barrier film outer packaging material having a four-layer structure of nylon, aluminum vapor-deposited PET, aluminum foil, and high-density polyethylene as a core material. A piece of Getters: COMBO) was inserted into the outer packaging. Thereafter, evacuation was performed with an evacuation apparatus so that the internal pressure was 0.01 Torr, and sealing was performed by heat sealing. The obtained vacuum heat insulating material had a size of 200 mm × 200 mm and a thickness of 10 mm. The density of the core material of the obtained vacuum heat insulating material was 220 kg / m ³ .

<The manufacturing method of Examples 2-8 and Comparative Examples 1-2>
A vacuum heat insulating material was obtained in the same manner as in Example 1 except that the type and amount of fibers used for the core material were changed as shown in the table. In Comparative Example 2, cotton fibers were used as they were without being processed into sheets.

<Comparative Example 3>
First, it was cut into 200 mm × 200 mm × 10 mm using an open cell polyurethane foam. The core material was dried at a temperature of 120 ° C. for 1 hour. After drying, it was inserted into the same outer packaging material as in the example, and at the same time, one getter material was inserted into the outer packaging material. After that, vacuuming was performed with a vacuuming device so that the internal pressure was 0.01 Torr, and sealing was performed by heat fusion to obtain a vacuum heat insulating material.

<Initial insulation>
The initial heat insulation was evaluated by measuring the thermal conductivity at an average temperature of 20 ° C. using “Autoλ HC-074” (manufactured by Eihiro Seiki Co., Ltd.). The measurement was made after 1 day from the vacuuming step.

<Long-term insulation>
Evaluation of long-term heat insulation is carried out by putting the vacuum heat insulating material evaluated for initial heat insulation into a constant temperature bath of 70 ° C. and taking it out after 4 weeks, and using “Autoλ HC-074” (manufactured by Eihiro Seiki Co., Ltd.) This was done by measuring the thermal conductivity at a temperature of 20 ° C.

<Workability>
The workability when inserting the fiber assembly into the outer packaging material was evaluated according to the following criteria.
○: The fiber assembly can be easily inserted into the outer packaging material;
X: The core material is brittle, and the fiber assembly cannot be uniformly inserted into the outer packaging material.

Claims (6)

  A sheet-like fiber comprising at least a core material and an outer packaging material capable of accommodating the core material and maintaining the inside in a reduced pressure state, wherein the core material contains 50% by weight or more of a polyester fiber having a fiber thickness of 1 to 6 denier A vacuum heat insulating material characterized by being an aggregate.   The vacuum heat insulating material according to claim 1, wherein the polyester fiber has an average fiber diameter of 9 to 25 µm.   The vacuum heat insulating material according to claim 1 or 2, wherein the polyester fiber is a polyethylene terephthalate fiber.   The vacuum heat insulating material according to any one of claims 1 to 3, wherein the fiber assembly is processed into a sheet shape by a needle punch method. The vacuum heat insulating material according to any one of claims 1 to 4, wherein the density of the core material is 150 to 300 Kg / m ³ . The vacuum heat insulating material according to any one of claims 1 to 5, wherein the core material is a fiber assembly made only of polyester fibers.