JP2011185374A - Heat retainer and electric water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat retainer effectively utilizing heat, and high in degree of freedom of design. <P>SOLUTION: The heat retainer includes a heat source and a sheet, and a distance between the heat source and the sheet is 1.0-50 mm. The sheet includes at least a resin film having independent cavities. The cavities in the resin film are oriented orthogonally to a thickness direction of the resin film. The cavities have an L/r ratio equal to or greater than 10, where r (μm) denotes an average length of the cavities in the thickness direction, and L (μm) denotes an average length of the cavities in the orientation direction of the cavities, and the thickness of the resin film is 1.0 mm or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat insulator that can be used in an electric water heater or the like.

  Electrical appliances such as electric water heaters and refrigerators have a heat retention function for maintaining the internal temperature. Electric water heaters use electric power to boil water, but electric power is also used for heat retention after the water is boiled. And the heat insulating material is used in order to suppress the electric power used for heat retention. Similarly to electric water heaters, electric power is used in refrigerators to retain heat in cold storage rooms and cold rooms, and heat insulating materials are used to suppress the use of electric power. In recent years, a reduction in energy consumption is desired. If the electrical appliance can be kept warm with low power consumption, energy consumption can be reduced. Furthermore, heat can be effectively utilized.

Up to now, as a heat-retaining member that can be used in an electric water heater or the like, a core material such as glass wool, and a jacket material of a laminated structure having a heat-welded layer, a gas barrier layer, and a protective layer, the heat A member has been proposed in which the welding layer is made of a resin film having a melting point of 200 ° C. or higher, and the melting point of the resin film of the gas barrier layer and the protective layer is higher than the melting point of the resin film of the thermal welding layer (for example, Patent Documents). 1). This member can be used even in a high temperature environment and can retain heat for a long time.
However, since this member uses glass wool or the like as the core material, the member is not sufficiently flexible, and it is difficult to arbitrarily deform the member according to the shape of the heat source. Therefore, when the said member is used for the apparatus which consists of a heat source and the said member, there exists a problem that the freedom degree of design of an apparatus becomes low.

In addition, a metal-deposited plastic film has been proposed as a film having heat retention (see, for example, Patent Document 2). This proposed metal-deposited plastic film is formed of a metal-deposited film and a porous plastic film having a cavity. This metal-deposited plastic film has the advantage that the adhesion strength of the metal-deposited film is high.
However, although this porous plastic film has a cavity and is a structure that enhances heat retention, the cavity has a structure in which many of the cavities are connected to each other at specific points, and is not an independent cavity. Since the orientation and shape of the cavity are not controlled, there is a problem that the heat retention is not sufficient. In addition, depending on how the porous plastic film is arranged with respect to the heat source, there is a problem with respect to downsizing of articles.

  Accordingly, there is a demand for provision of equipment that enables effective use of heat by heat retention and that has a high degree of design freedom.

JP 2004-332929 A Japanese Patent Laid-Open No. 55-48990

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to provide a heat insulator capable of effectively utilizing heat and having a high degree of design freedom.

Means for solving the problems are as follows. That is,
<1> It has a heat source and a sheet,
The distance between the heat source and the sheet is 1.0 mm or more and 50 mm or less,
The sheet has at least a resin film having an independent cavity,
The cavity in the resin film is oriented perpendicular to the thickness direction of the resin film,
The L / r ratio when the average length of the cavity in the thickness direction is r (μm) and the average length of the cavity in the orientation direction of the cavity is L (μm) is 10 or more, and
The heat retainer is characterized in that the resin film has a thickness of 1.0 mm or less.
In the heat retaining device of <1>, by setting the space between the heat source and the sheet to be 1.0 mm or more and 50 mm or less, heat from the heat source is reduced by the air in the space while enabling downsizing. It becomes difficult to be transmitted to the outside of the heat insulator. The resin film has independent cavities, is oriented perpendicular to the thickness direction of the resin film, and has a specific range of aspect ratios. Therefore, the heat from the heat source is more difficult to be transmitted to the outside of the heat retainer, and the heat source is insulated to efficiently retain heat. The resin film can be freely deformed due to the flexibility of the resin film. As a result, the heat retainer enables effective use of heat and further increases the degree of freedom in design.
<2> The heat retainer according to <1>, wherein the sheet has a heat conductive layer on a surface on a heat source side of the resin film, and the thickness of the heat conductive layer is 1.0 mm or less.
In the heat retaining device of <2>, the heat conductive layer is disposed on a surface on the heat source side of the resin film, so that the heat from the heat source is transferred to the resin film before being transferred to the resin film. Since the heat is transmitted in the surface direction of the conductive layer, the heat from the heat source spreads uniformly on the sheet. As a result, there is no uneven heat retention of the heat source, and uniform heat retention is possible.
<3> The heat retainer according to any one of <1> to <2>, wherein the resin film includes a deformation preventing material on a surface opposite to a surface on the heat source side.
In the heat retainer of <3>, the deformation preventing material is disposed on a surface opposite to the heat source side surface of the resin film, so that the heat retention is not affected. Deformation such as warpage is suppressed, and the heat insulator can withstand long-term use.
<4> The heat retainer according to <3>, wherein the plurality of deformation preventing materials are arranged in a direction orthogonal to a direction parallel to a direction in which the sheet having a planar shape is deformed.
<5> The heat retainer according to any one of <1> to <4>, wherein the resin film is made of only a crystalline polymer.
<6> The heat retainer according to any one of <1> to <5>, wherein the resin film has a thermal conductivity of 0.08 W / mK or less.
<7> The heat retainer according to any one of <1> to <6>, wherein the ratio of independent cavities is 80% by volume or more with respect to all the cavities.
<8> The heat retainer according to any one of <2> to <7>, wherein the heat conductivity of the heat conductive layer is 1.0 W / mK or more.
<9> The heat retainer according to any one of <1> to <8>, wherein the heat source is a hot water storage container.
<10> An electric water heater having the heat retainer according to <9>.

  ADVANTAGE OF THE INVENTION According to this invention, the said various problems in the past can be solved, the effective use of a heat | fever is possible, and the heat retention device with a high design freedom can be provided.

Drawing 1 is a figure showing an example of the manufacturing method of the resin film which has an independent cavity, and is a flow figure of a biaxially stretched film manufacturing device. FIG. 2A is a perspective view of a resin film for explaining an aspect ratio and having an independent cavity. FIG. 2B is a view for explaining the aspect ratio, and is a cross-sectional view taken along the line A-A ′ of the resin film having independent cavities in FIG. 2A. FIG. 2C is a diagram for explaining the aspect ratio, and is a B-B ′ sectional view of the resin film having independent cavities in FIG. 2A. FIG. 3 is a perspective view in which deformation preventing materials are arranged in a resin film having a cylindrical independent cavity. 4 is a cross-sectional photograph of the resin film 7 produced in Example 14 (a cross-sectional photograph corresponding to the A-A ′ section of FIG. 2A). FIG. 5 is a cross-sectional photograph of the resin film 10 produced in Comparative Example 4.

(Insulator)
The heat retainer of the present invention has at least a heat source and a sheet, and further has other configurations as necessary.

<Heat source>
The heat source is not particularly limited as long as it is a member that is at least one of higher and lower temperatures than normal temperature, and can be appropriately selected according to the purpose. For example, a hot water storage container for an electric water heater, a refrigerator warmer room And refrigerator rooms and water bottles.

<Sheet>
The sheet has at least a resin film having an independent cavity, and further has other configurations as necessary.

-Resin film having independent cavities-
The said cavity which the resin film which has the said independent cavity has means the domain of a vacuum state, or a gaseous phase which exists in the said resin film inside. The independent cavities refer to a state in which two or more cavities are not connected in a state where resin exists around the cavities. The independent cavity can be confirmed by image analysis of a photograph taken with an optical microscope or a scanning electron microscope.

  The ratio of the independent cavities is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 80% by volume or more, more preferably 90% by volume or more, and 95% by volume with respect to all the cavities. The above is particularly preferable. When the ratio of the independent cavities is within the particularly preferable range, it is advantageous in terms of heat retention. Here, the ratio of the independent cavities can be obtained by image analysis of a photograph taken with an optical microscope or a scanning electron microscope.

  The cavity is oriented perpendicular to the thickness direction of the resin film having the independent cavity. The cavity has an aspect ratio in a specific range. The resin film having independent cavities has independent cavities, and the cavities have a specific orientation and an aspect ratio in a specific range, whereby high heat retention can be obtained. Therefore, the heat retainer of the present invention can effectively use heat.

The aspect ratio is an L / r ratio when the average length of the cavities in the thickness direction is r (μm) and the average length of the cavities in the orientation direction of the cavities is L (μm). , And may be abbreviated as “aspect ratio”).
The aspect ratio is not particularly limited as long as it is 10 or more, and can be appropriately selected according to the purpose, but is preferably 15 or more, and more preferably 20 or more. When the aspect ratio is 20 or more, it is advantageous in that heat retention and cushioning properties of the seat can be improved.

  2A to 2C are diagrams for specifically explaining the aspect ratio, in which FIG. 2A is a perspective view of a resin film having an independent cavity, and FIG. 2B has an independent cavity in FIG. 2A. It is AA 'sectional drawing of a resin film, FIG. 2C is BB' sectional drawing of the resin film which has the independent cavity in FIG. 2A.

  In the manufacturing process of the resin film having the independent cavities, the cavities are usually oriented along the first stretching direction. Therefore, the “average length of the cavities in the thickness direction (r (μm))” is a cross section perpendicular to the surface 1a of the resin film 1 having independent cavities and perpendicular to the first stretching direction (FIG. 2A). This corresponds to the average thickness r (see FIG. 2B) of the cavity 100 in the AA ′ cross section in FIG. The “average length (L (μm)) of the cavities in the orientation direction of the cavities” is a cross section perpendicular to the surface 1a of the resin film 1 having independent cavities and parallel to the first stretching direction. This corresponds to the average length L (see FIG. 2C) of the cavity 100 in the (BB ′ cross section in FIG. 2A).

In addition, said 1st extending | stretching direction shows the extending direction of 1 axis | shaft, when extending | stretching is only 1 axis | shaft. Usually, since longitudinal stretching is performed along the direction in which the molded body flows during production, this longitudinal stretching direction corresponds to the first stretching direction.
Moreover, when extending | stretching is biaxial or more, at least 1 direction is shown among the extending directions aiming at cavity formation. Usually, even in stretching with two or more axes, longitudinal stretching is performed along the flow direction of the molded body during production, and a cavity can be formed by this longitudinal stretching. It corresponds to the first stretching direction.

  Here, the average length (r (μm)) of the cavity in the thickness direction can be measured by an image of an optical microscope or an electron microscope. Similarly, the average length (L (μm)) of the cavities in the alignment direction of the cavities can be measured by an image of an optical microscope or an electron microscope.

  The average number P of the cavities in the thickness direction is not particularly limited and may be appropriately selected according to the purpose, but is preferably 5 or more, more preferably 10 or more, and even more preferably 15 or more. .

In the manufacturing process of the resin film having the independent cavities, the cavities are usually oriented along the first stretching direction. Therefore, the “number of the cavities in the thickness direction orthogonal to the orientation direction of the cavities” is a cross section perpendicular to the surface 1a of the resin film 1 having independent cavities and perpendicular to the first stretching direction (FIG. 2A). Corresponds to the number of cavities 100 included in the film thickness direction.
Here, the average number P of the cavities in the thickness direction can be measured by an image of an optical microscope or an electron microscope.

  There is no restriction | limiting in particular as the heat conductivity of the resin film which has the said independent cavity, Although it can select suitably according to the objective, It is preferable that it is 0.08 (W / mK) or less, and 0.06. More preferably (W / mK) or less. When the thermal conductivity is within the preferable range, it is advantageous in that heat retention can be improved.

  Here, the thermal conductivity can be calculated by a product of measured values of thermal diffusivity, specific heat, and density. The thermal diffusivity can be generally measured by a laser flash method (for example, TC-7000 (manufactured by Vacuum Riko Co., Ltd.)). The specific heat can be measured by DSC according to the method described in JIS K7123. The density can be calculated by measuring the mass of a certain area and its thickness.

  The thickness of the resin film having an independent cavity is not particularly limited as long as it is 1.0 mm or less, and can be appropriately selected according to the purpose, but is preferably 0.01 mm or more and 0.5 mm or less. 0.02 mm or more and 0.2 mm or less is more preferable, and 0.04 mm or more and 0.18 mm or less is particularly preferable. When the thickness of the resinous film exceeds 1.0 mm, the workability may be lowered, and particularly, it may be difficult to bend the independent cavity. On the other hand, when the thickness is within the particularly preferable range, it is advantageous in that it can be easily handled and can be bent sufficiently following a heat source having a small curvature radius. In the present invention, the thickness refers to one thickness when the resin film having the independent cavity is used as a single sheet, and when a plurality of stacked films are used, a plurality of stacked layers are used. The total thickness of the sheets.

The material of the resin film having an independent cavity is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the resin film may be composed of only a crystalline polymer or other components other than the crystalline polymer. May be included.
Among these, what consists only of the said crystalline polymer is advantageous at the point which can improve heat retention.

--Crystalline polymer--
In general, polymers are classified into crystalline polymers and amorphous (amorphous) polymers, but even crystalline polymers are not 100% crystalline, and long chain molecules are regularly formed in the molecular structure. It includes aligned crystalline regions and non-regularly arranged amorphous (amorphous) regions.
Therefore, the crystalline polymer only needs to include at least the crystalline region in the molecular structure, and the crystalline region and the amorphous region may be mixed.

  There is no restriction | limiting in particular as said crystalline polymer, According to the objective, it can select suitably, For example, polyolefin (for example, low density polyethylene, high density polyethylene, polypropylene, etc.), polyamides (PA) (for example, Nylon-6), polyacetals (POM), polyesters (eg, PET, PEN, PTT, PBT, PPT, PHT, PBN, PES, PBS, etc.), syndiotactic polystyrene (SPS), polyphenylene sulfide ( PPS), polyether ether ketones (PEEK), liquid crystal polymers (LCP), fluororesin, isotactic polypropylene (isoPP) and the like. Among these, polyolefins, polyesters, syndiotactic polystyrene (SPS), and liquid crystal polymers (LCP) are preferable, and polyolefins and polyesters are more preferable from the viewpoints of durability, mechanical strength, production, and cost. Two or more kinds of these polymers may be blended or copolymerized.

The melt viscosity of the crystalline polymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 Pa · s to 700 Pa · s, more preferably 70 Pa · s to 500 Pa · s, and more preferably 80 Pa · s. s to 300 Pa · s is more preferable. When the melt viscosity is 50 Pa · s to 700 Pa · s, the shape of the melt film discharged from the die head at the time of melt film formation is stable, and it is easy to form a uniform film. It is preferable in that it becomes appropriate and is easy to extrude, and the melted film at the time of film formation is leveled to reduce unevenness.
Here, the melt viscosity can be measured by a plate type rheometer or a capillary rheometer.

There is no restriction | limiting in particular as intrinsic viscosity (IV) of the said crystalline polymer, Although it can select suitably according to the objective, 0.4-1.2 are preferable and 0.6-1.0 are more preferable. 0.7 to 0.9 is particularly preferable. When the IV is 0.4 to 1.2, the strength of the formed film is increased, and this is preferable in that the film can be efficiently stretched.
Here, the IV can be measured by an Ubbelohde viscometer.

There is no restriction | limiting in particular as melting | fusing point (Tm) of the said crystalline polymer, Although it can select suitably according to the objective, 40 to 350 degreeC is preferable, 100 to 300 degreeC is more preferable, 100 to 260 degreeC is preferable. ° C is particularly preferred. The melting point is preferably 40 ° C. to 350 ° C. in that it is easy to keep the shape in the temperature range expected for normal use, and even without using special techniques required for processing at high temperatures, It is preferable at the point which can form a uniform film.
Here, the melting point can be measured by a differential thermal analyzer (DSC).

--- Polyester resin ---
The polyesters (hereinafter referred to as “polyester resins”) mean a general term for polymer compounds having an ester bond as a main bond chain. Therefore, as the polyester resin suitable as the crystalline polymer, the exemplified PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PTT (polytrimethylene terephthalate), PBT (polybutylene terephthalate), PPT (polypenta). Methylene terephthalate), PHT (polyhexamethylene terephthalate), PBN (polybutylene naphthalate), PES (polyethylene succinate), PBS (polybutylene succinate), as well as by polycondensation reaction of dicarboxylic acid component and diol component All the polymer compounds obtained are included.

  The dicarboxylic acid component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, oxycarboxylic acids, and polyfunctional acids. Can be mentioned.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfoisophthalic acid. Among these, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are preferable, and terephthalic acid, diphenyldicarboxylic acid, and naphthalenedicarboxylic acid are more preferable.

  Examples of the aliphatic dicarboxylic acid include oxalic acid, succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, and fumaric acid. Examples of the alicyclic dicarboxylic acid include cyclohexane dicarboxylic acid. Examples of the oxycarboxylic acid include p-oxybenzoic acid. Examples of the polyfunctional acid include trimellitic acid and pyromellitic acid. Among the aliphatic dicarboxylic acids and alicyclic dicarboxylic acids, succinic acid, adipic acid, and cyclohexanedicarboxylic acid are preferable, and succinic acid and adipic acid are more preferable.

  There is no restriction | limiting in particular as said diol component, According to the objective, it can select suitably, For example, aliphatic diol, alicyclic diol, aromatic diol, diethylene glycol, polyalkylene glycol etc. are mentioned. Of these, aliphatic diols are preferred.

Examples of the aliphatic diol include ethylene glycol, propane diol, butane diol, pentane diol, hexane diol, neopentyl glycol, and triethylene glycol. Among these, propanediol, butanediol, pentanediol, and hexanediol are particularly preferable.
Examples of the alicyclic diol include cyclohexanedimethanol.
Examples of the aromatic diol include bisphenol A and bisphenol S.

  There is no restriction | limiting in particular as melt viscosity of the said polyester resin, Although it can select suitably according to the objective, 50 Pa.s-700 Pa.s are preferable, 70 Pa.s-500 Pa.s are more preferable, 80 Pa.s ˜300 Pa · s is particularly preferred. The higher the melt viscosity, the easier it is to develop cavities during stretching. However, when the melt viscosity is 50 Pa · s to 700 Pa · s, it is easier to extrude during film formation, and the resin flow stabilizes and stays. It becomes difficult to stabilize, quality is stabilized, stretching tension is properly maintained at the time of stretching, it is easy to stretch uniformly, it is difficult to break, and a molten film discharged from the die head at the time of film formation This is preferable from the viewpoint of improving physical properties, such as being easy to maintain, being able to be stably molded, and being difficult to damage the product.

  There is no restriction | limiting in particular as intrinsic viscosity (IV) of the said polyester resin, Although it can select suitably according to the objective, 0.4-1.2 are preferable, 0.6-1.0 are more preferable, 0.7 to 0.9 is particularly preferable. When the IV is larger, cavities are more likely to be generated during stretching. However, when the IV is 0.4 to 1.2, extrusion becomes easier during film formation, and the resin flow is stable and it is difficult to generate stagnation. It is preferable in that the quality is stabilized. Furthermore, when the IV is 0.4 to 1.2, the stretching tension is appropriately maintained at the time of stretching, and therefore, it is easy to stretch uniformly and it is preferable in that a load is not easily applied to the apparatus. In addition, when the IV is 0.4 to 1.2, it is preferable in that the product is hardly damaged and the physical properties are increased.

  There is no restriction | limiting in particular as melting | fusing point of the said polyester resin, Although it can select suitably according to the objective, From viewpoints, such as heat resistance and film forming property, 70 to 300 degreeC is preferable, and 90 to 270 degreeC is preferable. More preferred.

  In addition, as said polyester resin, the said dicarboxylic acid component and the said diol component may respectively superpose | polymerize with 1 type, and may form the polymer, and the said dicarboxylic acid component and / or the said diol component are 2 or more types. A polymer may be formed by copolymerization. Further, as the polyester resin, two or more kinds of polymers may be blended and used.

  In the blend of two or more polymers, the polymer added to the main polymer has a melt viscosity and an intrinsic viscosity that are close to those of the main polymer, and the addition amount is smaller when the film is formed or melted. It is preferable in that the physical properties are enhanced during extrusion and the extrusion becomes easy.

  In addition, for the purpose of improving the flow characteristics of the polyester resin, controlling light transmittance, and improving the adhesion with the coating solution, a resin other than polyester may be added to the polyester resin.

  The resin film having independent cavities made of only a crystalline polymer can form cavities in a simple process even without adding a cavity forming agent such as inorganic fine particles or incompatible resins. Thereby, the recyclability of the resin film having the independent cavity can be enhanced. Furthermore, no special equipment for dissolving the inert gas in the resin in advance is required. In addition, it mentions later about the manufacturing method of the resin film which has the said independent cavity which consists only of crystalline polymers.

  Here, the resin film having independent cavities made of only the crystalline polymer may contain other components other than the crystalline polymer as necessary as long as it does not contribute to the expression of the cavities. Examples of the other components include a heat resistance stabilizer, an antioxidant, an organic lubricant, a nucleating agent, a dye, a pigment, a dispersant, and a coupling agent. Whether or not the other component contributes to the development of the cavity can be determined by whether or not a component other than the crystalline polymer (for example, each component described later) is detected in the cavity or at the interface portion of the cavity.

-Other ingredients-
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, resin etc. which are not compatible with inorganic type microparticles | fine-particles and the said crystalline polymer are mentioned.

-Manufacturing method of resin film having independent cavity-
--Method for producing resin film having independent cavities made only of crystalline polymer--
There is no restriction | limiting in particular as a manufacturing method of the resin film which has the independent cavity which consists only of the said crystalline polymer, Although it can select suitably according to the objective, The extending | stretching which stretches | stretches a polymer molded object 2 to 8 times at least. It is preferable to include a process. The method for producing a resin film having independent cavities may further include other steps such as a film forming step, if necessary.
In addition, the said polymer molded object shows only what consists only of the said crystalline polymer, and does not have a cavity in particular, For example, a polymer film, a polymer sheet, etc. are mentioned.

--- Drawing process ---
In the stretching step, the polymer molded body is stretched at least uniaxially. And by the said extending process, while a polymer molded object is extended | stretched, the cavity oriented along the 1st extending | stretching direction is formed in the inside, and the resin film which has an independent cavity is obtained.

The reason why the cavities are formed by stretching is that the at least one crystalline polymer constituting the polymer molded body is composed of a plurality of types of crystal states and includes a crystal containing crystals that are difficult to stretch during stretching. It is considered that when the resin is peeled and stretched in such a manner that the resin is torn, this serves as a cavity forming source to form a cavity.
Note that such void formation by stretching is possible not only when there is only one kind of crystalline polymer but also when two or more kinds of crystalline polymers are blended or copolymerized.

  The stretching method is not particularly limited as long as the effects of the present invention are not impaired, and examples thereof include uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching. It is preferable that longitudinal stretching is performed along the direction in which the molded body flows.

In general, in the longitudinal stretching, the number of longitudinal stretching stages and the stretching speed can be adjusted by the combination of rolls and the speed difference between the rolls.
The number of stages of the longitudinal stretching is not particularly limited as long as it is one or more, but it can be stretched more than two stages in terms of more stable and high-speed stretching and production yield and machine restrictions. It is preferable to do. Further, longitudinal stretching in two or more stages is advantageous in that a cavity can be formed by stretching in the second stage after confirming the occurrence of necking in the first stage.

--- Stretching speed ---
The stretching speed of the longitudinal stretching is not particularly limited as long as the effects of the present invention are not impaired, and can be appropriately selected according to the purpose, but is preferably 10 mm / min to 36,000 mm / min, and is preferably 800 mm / min. ˜24,000 mm / min is more preferable, and 1,200 mm / min to 12,000 mm / min is still more preferable. When the stretching speed is 10 mm / min or more, it is preferable in that sufficient necking can be easily expressed. Further, when the stretching speed is 36,000 mm / min or less, uniform stretching is facilitated, the resin is not easily broken, and the cost is reduced without requiring a large stretching apparatus for high-speed stretching. It is preferable in that it can be performed. Therefore, when the stretching speed is 10 mm / min to 36,000 mm / min, sufficient necking is easily developed, uniform stretching is facilitated, the resin is not easily broken, and high speed stretching is intended. This is preferable in that the cost can be reduced without requiring a large stretching apparatus.

  More specifically, the stretching speed in the case of one-stage stretching is preferably 1,000 mm / min to 36,000 mm / min, more preferably 1,100 mm / min to 24,000 mm / min, and 1,200 mm / min. Min to 12,000 mm / min is more preferable.

  In the case of two-stage stretching, it is preferable that the first-stage stretching is a preliminary stretching whose main purpose is to develop necking. The stretching speed of the preliminary stretching is preferably 10 mm / min to 300 mm / min, more preferably 40 mm / min to 220 mm / min, and still more preferably 70 mm / min to 150 mm / min.

  In the two-stage stretching, it is preferable that the second-stage stretching speed after the necking is expressed by the preliminary stretching (first-stage stretching) is changed from the preliminary stretching speed. The stretching speed of the second stage after causing necking by the preliminary stretching is preferably 600 mm / min to 36,000 mm / min, more preferably 800 mm / min to 24,000 mm / min, and 1,200 mm. / Min to 15,000 mm / min is more preferable.

--- Stretching temperature ---
The temperature during stretching is not particularly limited and can be appropriately selected according to the purpose.
When the stretching temperature is T (° C) and the glass transition temperature is Tg (° C),
(Tg-30) (° C.) ≦ T (° C.) ≦ (Tg + 70) (° C.)
It is preferable to stretch at a stretching temperature T (° C.) in the range indicated by
(Tg-25) (° C.) ≦ T (° C.) ≦ (Tg + 70) (° C.)
It is more preferable to stretch at a stretching temperature T (° C.) in the range indicated by
(Tg-20) (° C.) ≦ T (° C.) ≦ (Tg + 70) (° C.)
More preferably, the film is stretched at a stretching temperature T (° C.) in the range indicated by.

In general, the higher the stretching temperature (° C.), the lower the stretching tension and the easier the stretching, but the stretching temperature (° C.) is {glass transition temperature (Tg) −30} ° C. or more, {glass transition temperature ( Tg) +70} ° C. or lower is preferable in that the void content increases, the aspect ratio tends to be 10 or more, and the voids are sufficiently developed.
Here, the stretching temperature T (° C.) can be measured with a non-contact thermometer. The glass transition temperature Tg (° C.) can be measured by a differential thermal analyzer (DSC).

In the stretching step, lateral stretching may or may not be performed as long as it does not hinder the appearance of cavities. In the case of lateral stretching, the film may be relaxed or heat-treated using a lateral stretching process.
In addition, the molded body after stretching may be further subjected to treatment such as heat shrinkage by applying heat or application of tension for the purpose of shape stabilization.

The method for producing the polymer molded body is not particularly limited and may be appropriately selected depending on the purpose. For example, when the crystalline polymer is a polyolefin, a polyester resin, a polyamide, or the like, a melt film is formed. It can manufacture suitably with a method.
Moreover, the polymer molded body may be produced independently of the stretching step or continuously.

Drawing 1 is a figure showing an example of the manufacturing method of the resin film which has an independent cavity, and is a flow figure of a biaxially stretched film manufacturing device.
As shown in FIG. 1, after the raw material resin 11 is hot-melted and kneaded inside an extruder 12 (a twin screw extruder or a single screw extruder is used depending on the raw material shape and production scale). , And discharged from the T-die 13 in a soft plate shape (film or sheet shape).
Next, the discharged film or sheet F is cooled and solidified by the casting roll 14 to form a film. The formed film or sheet F (corresponding to “polymer molded body”) is sent to the longitudinal stretching machine 15.
And the film or sheet | seat F formed into a film is again heated within the longitudinal stretch machine 15, and is stretched | stretched longitudinally between the rolls 15a from which speed differs. By this longitudinal stretching, a cavity is formed in the film or sheet F along the stretching direction. The film or sheet F in which the cavities are formed is gripped at both ends by the left and right clips 16a of the transverse stretching machine 16, and is stretched laterally while being sent to the winder side (not shown). It becomes the resin film 1 which has a cavity. In addition, you may use the film or sheet | seat F which performed only the longitudinal stretch in the said process as the resin film 1 which does not use for the horizontal stretcher 16, and has an independent cavity.

-Other manufacturing methods-
The method for producing the resin film having an independent cavity other than the method for producing the resin film having an independent cavity made of only the crystalline polymer is not particularly limited and can be appropriately selected depending on the purpose. For example, a method of making inorganic fine particles or the like contained in a resin film such as a polyester resin film, and the inorganic fine particles and the resin interface are peeled off at the time of stretching the resin, the main component resin A two-phase structure (for example, a sea-island structure) is formed by adding and kneading another resin (for example, a polyester-based resin) that is incompatible with the resin (incompatible) and kneading the resin. Examples thereof include a method in which an interface between a resin as a main component and another resin added and kneaded therein is peeled off.

-Other configurations-
There is no restriction | limiting in particular as said other structure, According to the objective, it can select suitably, For example, what has a heat conductive layer in the single side | surface of the resin film which has an independent cavity, etc. are mentioned. The sheet may have a resin film other than the resin film having the independent cavity (for example, a resin film having no cavity). In addition, in the said sheet | seat, the resin film which has the said independent cavity may be used by 1 sheet, and may laminate | stack and use several sheets. In addition, when laminating | stacking the resin film which has the said several independent cavity, you may use an adhesive agent, unless the effect of this invention is impaired.

  The thickness of the sheet is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.01 mm or more and 1.0 mm or less, more preferably 0.02 mm or more and 0.5 mm or less, and 0.04 mm. The thickness is particularly preferably 0.2 mm or less. If the thickness of the sheet exceeds 1.0 mm, workability may be deteriorated, particularly bending may be difficult. On the other hand, when the thickness of the sheet is within the particularly preferable range, it is advantageous in that it can be easily handled and can be bent sufficiently following a heat source having a small curvature radius.

There is no restriction | limiting in particular as a shape of the said sheet | seat, According to the objective, it can select suitably, For example, planar shape, cylindrical shape, etc. are mentioned.
The sheet may be used, for example, by rounding the sheet cut into a quadrangle and joining two opposite sides to form a cylinder. The cylindrical sheet can be arranged so as to have a predetermined distance along the curved side surface of the cylindrical heat source when the heat source is cylindrical. Thus, since the sheet | seat can be arrange | positioned freely according to the shape of the said heat source, the heat retention device of this invention has a high freedom degree of design.

-Thermal conduction layer-
The thermal conductive layer is a layer formed from a material having thermal conductivity.
There is no restriction | limiting in particular as heat conductivity of the said heat conductive layer, Although it can select suitably according to the objective, 1.0 W / mK or more is preferable, 20 W / mK or more is more preferable, 100 W / mK or more is preferable. Particularly preferred. If the thermal conductivity is less than 1.0 W / mK, the time for heat to be uniformly conducted in the surface may be long and the heat retention may be deteriorated. If the thermal conductivity is within the particularly preferable range, it is advantageous in terms of heat retention.
There is no restriction | limiting in particular as the material which has the said heat conductivity, According to the objective, it can select suitably, For example, an amorphous silica (1.5W / mK), a crystal | crystallization (9W / mK), a diamond (2,000W) / MK), stainless steel (30 W / mK), iron (80 W / mK), graphite (150 W / mK), aluminum (236 W / mK), copper (400 W / mK or more), silver (420 W / mK or more), gold ( 320 W / mK). These may be used individually by 1 type and may use 2 or more types together.
Among these, graphite, aluminum, and copper are preferable in terms of cost and workability.

There is no restriction | limiting in particular as thickness of the said heat conductive layer, According to the objective, it can select suitably, 1.0 mm or less is preferable, 1 * 10 < ^-6 > mm or more and 0.3 mm or less are more preferable, 1 * 10 ^{A range of −5} mm to 0.1 mm is particularly preferable. If the thickness of the heat conductive layer exceeds 1.0 mm, processing may be difficult. On the other hand, when the thickness of the heat conductive layer is within the particularly preferable range, it is advantageous in terms of workability when a heat retainer is formed.

There is no restriction | limiting in particular as a formation position of the said heat conductive layer, According to the objective, it can select suitably, Any of the single side | surface of the resin film which has the said independent cavity, and both surfaces may be sufficient.
Moreover, there is no restriction | limiting in particular as a formation position of the said heat conductive layer in arrangement | positioning relationship with the said heat source, According to the objective, it can select suitably, The surface by the side of the said heat source in the resin film which has the said independent cavity , And the surface on the opposite side of the surface on the heat source side in the resin film having the independent cavity may be used.
Among these, the formation position of the heat conductive layer is the surface on the heat source side in the resin film having the independent cavity, that is, the sheet is on the heat source side in the resin film having the independent cavity. Having the heat conductive layer on the surface is advantageous in terms of heat uniformity.

  The method for forming the heat conductive layer on the surface of the resin film having the independent cavity is not particularly limited and may be appropriately selected depending on the purpose. For example, the surface of the resin film having the independent cavity The method of forming by vapor deposition using a vapor deposition apparatus, the method of sticking the film which has thermal conductivity on the surface of the resin film which has the said independent cavity, etc. are mentioned. When the heat conductive layer is attached to the resin film having an independent cavity, an adhesive may be used as necessary as long as the effects of the present invention are not impaired.

<Distance between heat source and seat>
The distance between the heat source and the sheet is not particularly limited as long as it is 1.0 mm or more and 50 mm or less, and can be appropriately selected according to the purpose, preferably 1.0 mm or more and 20 mm or less, and 1.0 mm or more. 10 mm or less is more preferable, and 1.0 mm or more and 2.5 mm or less is particularly preferable. If the distance between the heat source and the sheet is less than 1.0 mm, the sheet may come into contact with the heat source due to the undulation of the sheet and the heat retention may be impaired. If the distance exceeds 50 mm, the heat source and the sheet The flow of air existing in the space between the two increases and heat escapes, which may impair heat retention. On the other hand, if it is within the particularly preferable range, the flow of air existing in the space between the heat source and the sheet is small, which is advantageous in that the heat retention is not impaired.
The method for adjusting the distance between the heat source and the sheet is not particularly limited and may be appropriately selected depending on the purpose. For example, a metal wire (wire) or a resin between the heat source and the sheet And a method of sandwiching the spacer.
The number of the metal wires in the case where the metal wires are sandwiched between the heat source and the sheet is not particularly limited and may be appropriately selected according to the purpose, and may be one or two or more. Good.
For example, when the heat source is cylindrical, the distance between the heat source and the sheet can be adjusted by arranging a plurality of metal wires serving as spacers at equal intervals on the outer periphery of the heat source.

<Other configurations>
-Deformation prevention material-
The deformation preventing material is a member that prevents deformation of the sheet due to heat.
If deformation of the sheet can be prevented, a decrease in heat retention of the sheet due to deformation of the sheet is suppressed, and as a result, effective use of heat by the heat retainer of the present invention becomes possible. Specific examples of the deformation of the sheet include warpage and swell of the sheet due to heat.

There is no restriction | limiting in particular as a material which comprises the said deformation | transformation prevention material, According to the objective, it can select suitably, For example, plastics, such as a metal, a thermoplastic resin, a thermosetting resin, etc. are mentioned.
There is no restriction | limiting in particular as a shape of the said deformation | transformation prevention material, According to the objective, it can select suitably, For example, a sheet form, columnar shape, etc. are mentioned.

There is no restriction | limiting in particular as a formation position of the said deformation | transformation prevention material, According to the objective, it can select suitably, The said heat source side surface in the resin film which has the said independent cavity, and the resin film which has the said independent cavity Any of the surfaces on the opposite side of the surface on the heat source side may be used.
Among these, the formation position of the deformation preventing material is a surface opposite to the surface on the heat source side in the resin film having the independent cavity, from the heat source without affecting the heat retention. It is advantageous in that the undulation of the sheet due to the heat of can be suppressed.

Further, as the formation position of the deformation preventing material, the plurality of deformation preventing materials are arranged in a direction orthogonal to a direction parallel to a direction in which the sheet having a planar shape is deformed. This is advantageous in that deformation (for example, warpage) of the sheet due to heat from the heat source can be prevented without impairing flexibility.
An example of a configuration in which a plurality of the deformation preventing materials are arranged in a direction perpendicular to a direction parallel to a direction in which the resin film having an independent cavity that has a planar shape is deformed is described with reference to FIG. explain. FIG. 3 is a perspective view of a resin film 31 having cylindrical independent cavities in which columnar deformation preventing materials 32 are arranged. In FIG. 3, the plurality of deformation preventing materials 32 are parallel to the bending direction of the resin film 31 having a cylindrical independent cavity (the direction in which the resin film having an independent cavity having a planar shape is deformed). Are arranged at an appropriate interval in a direction perpendicular to.

  There is no restriction | limiting in particular as a method of forming the said deformation | transformation prevention material in the surface of the resin film which has the said independent cavity, According to the objective, it can select suitably, For example, the method of sticking etc. are mentioned. When pasting, an adhesive may be used as necessary as long as the effects of the present invention are not impaired.

(Electric water heater)
The electric water heater of this invention has the said heat retention machine, and also has another member as needed.

<Other members>
There is no restriction | limiting in particular as said other member, According to the objective, it can select suitably, For example, a housing | casing, a heater, an electrical wiring, a switch etc. are mentioned.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and modifications may be made without departing from the spirit described above and below. Included in the technical scope.

Example 1
PBT (100% polybutylene terephthalate resin, polyester) having an intrinsic viscosity (IV) = 0.71 is extruded from a T-die at 245 ° C. using a melt extruder and solidified by a casting drum to give a polymer having a thickness of 390 μm. A molded body (polymer film) was produced. This polymer molded body (polymer film) was uniaxially stretched (longitudinal stretching).
Specifically, in a heated atmosphere at 40 ° C., uniaxial stretching was performed at a speed of 100 mm / min, and after confirming that necking had occurred, uniaxial stretching was further performed in the same direction at a speed of 510 mm / min. A resin film 1 having a thickness of 110 μm (resin film 1 having an independent cavity) was produced. This resin film 1 was a sheet 1.
About the said resin film, the below-mentioned measurement and evaluation were performed. The measurement results and evaluation results are shown in Table 1.
Next, the outer casing of the electric water heater (trade name: VIP thermos NC-SU221, manufactured by Matsushita Electric Industrial Co., Ltd.) was removed, and only a hot water storage container and a heater part were used. A spacer 1 (a metal wire having a diameter of 1.0 mm) was wound around the hot water storage container. The sheet 1 was wound around the hot water storage container around which the spacer 1 was wound so that the distance between the hot water storage container and the sheet 1 was uniformly 1.0 mm, and a heat insulator was manufactured.
The following evaluation was performed on the heat insulator. The evaluation results are shown in Table 1.

<Measurement>
<< 1 >> Measurement of thermal conductivity Thermal diffusivity was measured using TC-7000 (manufactured by Vacuum Riko Co., Ltd.). Both sides of the resin film were blackened by spraying and measured at room temperature. The density and specific heat were measured by the method described later, and the thermal conductivity was determined from the product of the three measured values.
The density was determined by cutting out a certain area, measuring the mass with a balance, measuring the thickness with a film thickness meter, and dividing the mass by the volume.
The specific heat was determined by the method described in JIS K7123. As the DSC, Q1000 (manufactured by TA Instruments) was used.

<<< 2 >> Measurement of Thickness—Resin Film Thickness— Measured using a long range contact displacement meter AF030 (measurement unit) and AF350 (instruction unit) manufactured by Keyence Corporation.
-Thickness of the deposited layer-
A small piece of the sheet whose cross section was exposed was embedded with an embedding resin to prepare an ultrathin section, and then the thickness was measured with a transmission electron microscope (JEM2010 type, manufactured by JEOL Ltd.). Or the cross section of the sheet | seat was exposed and thickness was measured with the scanning electron microscope (S-4700 type | mold, Hitachi High-Technologies make).

<< 3 >> Presence / absence of voids Photographs taken with an optical microscope or a scanning electron microscope were observed to confirm the presence / absence of voids.

<< 4 >> Presence or absence of independent cavities The photographs taken with an optical microscope or a scanning electron microscope were subjected to image analysis to confirm the presence or absence of independent cavities.

<< 5 >> Percentage of independent cavities The photographs taken with an optical microscope or a scanning electron microscope were subjected to image analysis to determine the percentage of independent cavities.

<< 6 >> Direction of Orientation The direction of orientation is confirmed by a photograph taken with an optical microscope or a scanning electron microscope, exposing each cross section in a direction parallel to and perpendicular to the longitudinal stretching direction of the resin film. did.
In addition, the description in Table 1 and Table 2 has the following meaning.
MD: All the cavities are oriented in the longitudinal stretching direction (direction perpendicular to the thickness direction).
Many MD directions: 60% or more and less than 100% of the cavities are oriented in the longitudinal stretching direction (direction perpendicular to the thickness direction).
MD / TD equivalent: 50% of the cavities are oriented in the longitudinal stretching direction (direction perpendicular to the thickness direction), and 50% of the cavities are oriented in the transverse stretching direction (direction perpendicular to the thickness direction).

<< 7 >> Measurement of Aspect Ratio A section perpendicular to the surface of the resin film and perpendicular to the longitudinal stretching direction (see FIG. 2B), perpendicular to the surface of the resin film and parallel to the longitudinal stretching direction A simple cross section (see FIG. 2C) was examined using a scanning electron microscope at an appropriate magnification of 300 to 3,000, and a measurement frame was set in each of the cross-sectional photographs. This measurement frame was set so that 50 to 100 cavities were included in the measurement frame.
Next, the number of cavities included in the measurement frame is measured, and the number of cavities included in the measurement frame having a cross section perpendicular to the longitudinal stretching direction (see FIG. 2B) is m and the cross section parallel to the longitudinal stretching direction. The number of cavities included in the measurement frame (see FIG. 2C) was n.
Then, the longitudinal stretching direction perpendicular cross section of the measurement frame measured one by one in the thickness of the cavity (r _i) included in (see FIG. 2B), and the thickness of the average and r. Further, the length (L _i ) of each cavity included in the measurement frame (see FIG. 2C) having a cross section parallel to the longitudinal stretching direction was measured, and the average length was defined as L.
That is, r and L can be represented by the following formulas (2) and (3), respectively.
r = (Σr _i ) / m (2)
L = (ΣL _i ) / n (3)
Then, L / r was calculated as an aspect ratio.

<Evaluation>
<< 1 >> Flexibility The flexibility of the produced sheet was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.
○: The hot water storage container can be surrounded without making a crease, and the sheet can be returned to its original flat shape by removing it from the heat source.
Δ: Partially creased, but the hot water storage container can be surrounded, and when the sheet is removed from the heat source, it can be restored to its original flat shape with the partially creased.
X: It breaks and cannot surround the hot water storage container, and when the sheet is removed from the heat source, it cannot be returned to its original flat shape while being deformed.

<<< 2 >> Power consumption reduction effect The produced heat insulator was kept at 90 ° C. for 48 hours, and the power consumption (W _X ) at that time was measured. The power consumption (W _X ) was compared with the power consumption (W ₀ ) of the heat retainer of Comparative Example 1, and the reduction effect was quantified by the following equation.
Reduction effect (%) = [(W ₀ −W _X ) / W ₀ ] × 100
Table 1 shows the results of evaluating the reduction effect according to the following evaluation criteria.
◎: Reduction effect of 2% or more ○: Reduction effect of 1% or more and less than 2% △: Reduction effect of more than 0% and less than 1% ×: No reduction effect (0% or less)

<< 3 >> Uniformity of heat The uniformity of heat was measured with a small thermal image camera (manufactured by CPA-0150 Chino) represented by color display when the temperature changed.
Table 1 shows the results of evaluation according to the following evaluation criteria based on the measurement results.
○: Select any 30 points on the image and measure the temperature, and the temperature difference range is within 2 ° C from the average value △: Select any 30 points on the image and measure the temperature, and the temperature difference range is the average value To 2 ° C to less than 5 ° C ×: Select 30 points on the image and measure the temperature, and the temperature difference range is 5 ° C or more from the average value

<< 4 >> Deformation Prevention Effect After the produced heat retainer was kept at 90 ° C. for 48 hours, the swell of the sheet was visually confirmed.
The results of evaluation based on the following evaluation criteria are shown in Table 1.
○: No swell is visually observed.
Δ: One or two places were in contact with the heat source due to the undulation.
X: Three or more places were in contact with the heat source due to the swell.

(Example 2)
The resin film 1 obtained in Example 1 was stretched in the transverse direction with a tenter. Specifically, in a warming atmosphere of 50 ° C., the film is stretched twice at 300 mm / min, heat-set at 150 ° C., cooled and wound, and a resin film 2 having a thickness of 53 μm (with an independent cavity) Resin film 2) was produced. This resin film 2 was designated as a sheet 2.
Next, in Example 1, a sheet 2 was used instead of the sheet 1, and a heat insulator was produced in the same manner as in Example 1.
About the said resin film and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 3)
Using a vapor deposition apparatus (trade name: VPC-410, ULVAC Kiko Co., Ltd.), copper having a thickness of 100 nm was vapor-deposited on one side of the resin film 1 obtained in Example 1 to produce a sheet 3.
Next, a heat retainer was produced in the same manner as in Example 1, except that the sheet 3 was used instead of the sheet 1 and the heat conductive layer was on the surface of the hot water storage container.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

Example 4
Using a vapor deposition apparatus (trade name: VPC-410, ULVAC Kiko Co., Ltd.), copper having a thickness of 100 nm was vapor-deposited on one side of the resin film 2 obtained in Example 2 to produce a sheet 4.
Next, in Example 1, a heat retainer was produced in the same manner as in Example 1 except that the sheet 4 was used in place of the sheet 1 and the heat conductive layer was on the surface of the hot water storage container.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 5)
The resin film 1 obtained in Example 1 was stacked on eight sheets using an adhesive (aerosol adhesive, spray glue 99, manufactured by 3M) to a thickness of 0.88 mm. Subsequently, using a vapor deposition device (trade name: VPC-410, manufactured by ULVAC Kiko Co., Ltd.), aluminum having a thickness of 50 nm was vapor-deposited on one surface of the overlapped resin film to produce a sheet 5.
Next, in Example 1, except that the sheet 5 is used instead of the sheet 1 and the heat conductive layer of the sheet 5 is on the surface of the hot water storage container, the heat retainer is the same as in Example 1. Was made.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 6)
In Example 4, aluminum having a thickness of 100 nm was evaporated instead of copper, and a sheet 6 was obtained.
Next, in Example 1, a heat retainer was produced in the same manner as in Example 1 except that the sheet 6 was used instead of the sheet 1 and the heat conductive layer was on the surface of the hot water storage container.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 7)
PET (polyethylene terephthalate 100% resin, polyester) having intrinsic viscosity (IV) = 0.69 is extruded from a T-die at 295 ° C. using a melt extruder and solidified by a casting drum to form a polymer having a thickness of 380 μm. A body (polymer film) was prepared. Subsequently, the polymer molded body (polymer film) was uniaxially stretched (longitudinal stretching).
Specifically, uniaxial stretching was performed at a speed of 100 mm / min in a heated atmosphere at 70 ° C., and after confirming that necking had occurred, further uniaxial stretching was performed in the same direction at a speed of 510 mm / min. A resin film 3 having a thickness of 100 μm (resin film 3 having an independent cavity) was produced. This resin film 3 was used as a sheet 7.
Next, a heat retainer was produced in the same manner as in Example 1 except that the sheet 7 was used instead of the sheet 1 in Example 1.
About the said resin film and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 8)
The resin film 3 obtained in Example 7 was stretched in the transverse direction with a tenter. Specifically, the film is stretched 3.5 times at a rate of 300 mm / min in a heated atmosphere at 120 ° C., heat-set at 200 ° C., cooled and wound, and a resin film 4 having a thickness of 50 μm (with an independent cavity) Resin film 4) was produced.
Next, two sheets of graphite film (trade name: HT1220AP, manufactured by Graphtec Co., Ltd.) having a thickness of 0.5 mm are bonded to one side of the resin film 4 with an adhesive (aerosol adhesive, spray glue 99, manufactured by 3M), and the sheet 8 Was made.
Next, in Example 1, a heat retainer is performed in the same manner as in Example 1 except that the sheet 8 is used instead of the sheet 1 and that the heat conductive layer of the sheet 8 is on the surface of the hot water storage container. Was made.
About the said resin film, the said sheet | seat, and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

Example 9
The aluminum foil (trade name: Mitsubishi foil, manufactured by Mitsubishi Aluminum Co., Ltd.) having a thickness of 0.012 mm was bonded to one surface of the resin film 4 obtained in Example 8 with an adhesive (aerosol adhesive, spray paste 99, manufactured by 3M). Sheet 9 was produced.
Next, in Example 1, the sheet retainer is used in place of the sheet 1, and the heat retainer is the same as in Example 1 except that the heat conductive layer of the sheet 9 comes to the surface on the hot water storage container side. Was made.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 10)
Five sheets of the resin film 3 obtained in Example 7 were stacked with an adhesive (aerosol adhesive, spray glue 99, manufactured by 3M) to a thickness of 0.5 mm. Two sheets of graphite film (trade name: HT1220AP, manufactured by Graphtec Co., Ltd.) having a thickness of 0.5 mm were bonded to one side of the laminated resin film with an adhesive (aerosol adhesive, spray paste 99, manufactured by 3M) to prepare a sheet 10. .
Next, in Example 1, except that the sheet 10 is used in place of the sheet 1 and the heat conductive layer of the sheet 10 is on the surface of the hot water storage container, the heat retainer is the same as in Example 1. Was made.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 11)
Polypropylene (100% polypropylene resin, manufactured by Aldrich, weight average molecular weight 190,000, number average molecular weight 50,000, MFI: 35 g / 10 min (ASTM D1238, 230 ° C., 2.16 kg), Tm: 170 ° C. to 175 ° C.) It was extruded from a T-die using a melt extruder and solidified with a casting drum to produce a polymer molded body (polymer film) having a thickness of 410 μm. Subsequently, the polymer molded body (polymer film) was uniaxially stretched (longitudinal stretching).
Specifically, using a roll stretching machine, it was confirmed that necking occurred at 25 ° C., and then the stretching roll was uniaxially stretched at a speed of 510 mm / min, and a resin film 5 having a thickness of 70 μm. (Resin film 5 having an independent cavity) was produced. This resin film 5 was used as a sheet 11.
Next, a heat retainer was produced in the same manner as in Example 1 except that the sheet 11 was used instead of the sheet 1 in Example 1.
About the said resin film and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 12)
The resin film 5 obtained in Example 11 was stretched in the transverse direction with a tenter. Specifically, the film was stretched 5 times at 50 mm / min in a heated atmosphere of 40 ° C., heat-set at 100 ° C., cooled and wound up, and a resin film 6 having a thickness of 10 μm (resin film having an independent cavity) 6) was produced. Next, using a vapor deposition apparatus (trade name: VPC-410, manufactured by ULVAC Kiko Co., Ltd.), copper having a thickness of 100 nm was vapor-deposited on one surface of the resin film 6 to produce a sheet 12.
Next, in Example 1, the sheet retainer was used instead of the sheet 1, and the heat retainer was the same as in Example 1 except that the heat conductive layer of the sheet 12 was on the surface of the hot water storage container. Was made.
About the said resin film, the said sheet | seat, and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 13)
The five resin films 5 obtained in Example 11 and the five resin films 6 obtained in Example 12 were overlapped with an adhesive (aerosol adhesive, spray glue 99, manufactured by 3M) to have a thickness of 0.4 mm. A resin film was prepared. Next, using a vapor deposition apparatus (trade name: VPC-410, manufactured by ULVAC Kiko Co., Ltd.), copper having a thickness of 100 nm was vapor-deposited on one surface of the stacked resin films, thereby producing a sheet 13.
Next, in Example 1, the sheet retainer was used in the same manner as in Example 1 except that the sheet 13 was used instead of the sheet 1 and the heat conductive layer of the sheet 13 was on the surface of the hot water storage container. Was made.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.

(Example 14)
To a low polymer obtained by a normal esterification reaction using 166 parts by mass of terephthalic acid and 75 parts by mass of ethylene glycol, 0.03 part by mass of an 85% aqueous solution of phosphoric acid as an anti-coloring agent and antimony trioxide as a polycondensation catalyst Was added to carry out a polycondensation reaction to obtain polyethylene terephthalate having an intrinsic viscosity (IV) = 0.66. The hopper was filled with 15 parts by mass of polymethylpentene (TPX, type RT18, hereinafter abbreviated as PMP) manufactured by Mitsui Chemicals, Inc. with 100 parts by mass of polyethylene terephthalate, in a chip state. Subsequently, it was extruded from a T-die at 245 ° C. using a melt extruder and solidified by a casting drum to produce a polymer molded body (polymer film) having a thickness of 2,100 μm. Then, this polymer molded object (polymer film) was formed into a film with the normal sequential biaxial stretching apparatus. Specifically, longitudinal stretching is performed at a peripheral speed ratio of 3.3 times in a 90 ° C. heating atmosphere with an infrared heater, and then transverse stretching is performed 3.5 times in a transverse direction in a heating atmosphere at 130 ° C. with a tenter. After heat fixing at 220 ° C., the film was relaxed by 4% in the width direction. Then, it cooled and wound up and produced the resin film 7 (resin film 7 which has an independent cavity) with a thickness of 180 micrometers.
Next, using a vapor deposition apparatus (trade name: VPC-410, manufactured by ULVAC Kiko Co., Ltd.), copper having a thickness of 100 nm was vapor-deposited on one surface of the resin film 7 to produce a sheet 14.
Next, in Example 1, except that the sheet 14 was used instead of the sheet 1 and the heat conductive layer of the sheet 14 was on the surface of the hot water storage container, the heat retainer was the same as in Example 1. Was made.
About the said resin film, the said sheet | seat, and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 1.
Moreover, the cross-sectional photograph (cross-sectional photograph equivalent to the AA 'cross section of FIG. 2A) of the produced resin film 7 is shown in FIG.

(Example 15)
4 sheets of graphite film (trade name: HT1220AP, manufactured by Graphtec Co., Ltd.) having a thickness of 0.5 mm are bonded to one side of the resin film 2 obtained in Example 2 with an adhesive (aerosol adhesive, spray glue 99, manufactured by 3M). A sheet 15 was produced.
Next, in Example 1, the sheet retainer is used in place of the sheet 1, and the heat retainer is the same as in Example 1 except that the heat conductive layer of the sheet 15 is on the surface of the hot water storage container. Was made.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 16)
In Example 1, a spacer 2 (MDX6 with a diameter of 3.0 mm: a strand manufactured by Mitsubishi Gas Chemical Co., Ltd .: a thread extruded from a mold diameter of 3.0 mm) is used instead of the spacer 1, and the hot water storage container and the sheet 1 are A heat insulator was produced in the same manner as in Example 1 except that the distance was uniformly set to 3.0 mm.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 17)
In Example 4, a heat retainer was manufactured in the same manner as in Example 4 except that the heat conductive layer of the sheet 4 was on the surface opposite to the surface on the hot water storage container side.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 18)
30 sheets of deformation preventing material 1 (20 cm long × 1 cm wide × 0.3 cm thick aluminum plate) were attached to the sheet 1 obtained in Example 1 at intervals of 0.5 cm.
Next, the spacer 1 was wound around the hot water storage container of the electric water heater from which the housing of Example 1 was removed. Around the hot water storage container around which the spacer 1 was wound, the sheet 1 on which the deformation preventing material 1 was adhered and the hot water storage container were wound so that the distance was uniformly 1.0 mm. The deformation preventing material 1 is arranged in a direction orthogonal to the direction parallel to the bending direction of the sheet 1, and the deformation preventing material 1 is attached to the surface of the sheet 1 opposite to the surface on the heat source side. It was wrapped so that it was attached.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 19)
30 sheets of the deformation preventing material 1 were attached to the resin film surface of the sheet 4 obtained in Example 4 at intervals of 0.5 cm.
Next, in Example 18, a heat retainer was performed in the same manner as in Example 18 except that the sheet 4 with the deformation preventing material 1 attached was used instead of the sheet 1 with the deformation preventing material 1 attached. Was made.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 20)
30 sheets of the deformation preventing material 1 were attached to the resin film surface of the sheet 5 obtained in Example 5 at intervals of 0.5 cm.
Next, in Example 18, a heat retainer was performed in the same manner as in Example 18 except that the sheet 5 with the deformation preventing material 1 attached was used instead of the sheet 1 with the deformation preventing material 1 attached. Was made.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 21)
30 sheets of the deformation preventing material 1 were attached to the resin film surface of the sheet 9 obtained in Example 9 at intervals of 0.5 cm.
Next, in Example 18, a heat retainer was performed in the same manner as in Example 18 except that the sheet 5 with the deformation preventing material 1 attached was used instead of the sheet 1 with the deformation preventing material 1 attached. Was made.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Example 22)
30 sheets of the deformation preventing material 1 were attached to the resin film surface of the sheet 13 obtained in Example 13 at intervals of 0.5 cm.
Next, in Example 18, a heat retainer was performed in the same manner as in Example 18 except that the sheet 13 with the deformation preventing material 1 attached was used instead of the sheet 1 with the deformation preventing material 1 attached. Was made.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 1)
The spacer 1 was wound around the hot water storage container of the electric water heater from which the housing of Example 1 was removed. Subsequently, around the hot water storage container around which the spacer 1 is wound, an aluminum foil having a thickness of 0.012 mm (trade name: Mitsubishi foil, so that the distance between the hot water storage container and the sheet 1 is uniformly 1.0 mm) A heat insulator for comparison was manufactured.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 2)
PBT (100% polybutylene terephthalate resin, polyester) having an intrinsic viscosity (IV) = 0.71 is extruded from a T-die at 245 ° C. using a melt extruder and solidified by a casting drum to give a polymer having a thickness of 120 μm. A molded body (polymer film) was produced. The polymer molded body (polymer film) was not stretched to produce a resin film 8 without a cavity. Using a vapor deposition apparatus (trade name: VPC-410, manufactured by ULVAC Kiko Co., Ltd.), aluminum having a thickness of 50 nm was vapor-deposited on one surface of the resin film 8 to produce a sheet 16.
Next, in Example 1, a sheet 16 was used instead of the sheet 1, and the comparative example was the same as in Example 1 except that the heat conductive layer of the sheet 16 was on the surface of the hot water storage container. A heat insulator was produced.
About the said resin film, the said sheet | seat, and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 3)
PET (polyethylene terephthalate 100% resin, polyesters) having an intrinsic viscosity (IV) = 0.66 is extruded from a T-die at 295 ° C. using a melt extruder and solidified with a casting drum to obtain a thickness of 1.50 mm. A polymer molded body (polymer film) was obtained. The polymer molded body (polymer film) was not stretched to produce a resin film 9 having no voids. Next, a graphite film having a thickness of 0.5 mm (trade name: HT1220AP, manufactured by Graphtec Corporation) was bonded to one side of the resin film 9 with an adhesive to prepare a sheet 17.
Next, in Example 1, a sheet 17 was used in place of the sheet 1, and the comparative example was the same as in Example 1 except that the heat conductive layer of the sheet 17 was on the surface of the hot water storage container. A heat insulator was produced.
About the said resin film, the said sheet | seat, and the said heat insulator, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 4)
Carbon dioxide was infiltrated into an unstretched PET (polyethylene terephthalate) film having a thickness of 400 μm at an osmotic pressure of 60 kg / cm ² . This film was sandwiched between two SPS (syndiotactic polystyrene) films having a thickness of 50 μm and laminated at a lamination temperature of 200 ° C. In this laminating process, the impregnated carbon dioxide foamed by heating during laminating to form a porous plastic part. After foaming, the two SPS films were peeled off to obtain a plastic foamed resin film 10 having a porosity of about 36 vol% and a thickness of 1.5 mm as a whole.
Next, copper having a thickness of 100 nm was vapor-deposited on one surface of the resin film 10 using a vapor deposition apparatus (trade name: VPC-410, manufactured by ULVAC KIKOH Co., Ltd.) to produce a sheet 18.
Next, in Example 1, a sheet 18 was used in place of the sheet 1, and the comparative example was the same as in Example 1 except that the heat conductive layer of the sheet 18 was on the surface of the hot water storage container. A heat insulator was produced.
About the said sheet | seat and the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.
Moreover, the cross-sectional photograph of the produced resin film 10 is shown in FIG.

(Comparative Example 5)
In Example 1, a spacer 3 (0.5 mm diameter metal wire) was used, and the distance between the hot water storage container and the sheet 1 was uniformly 0.5 mm. A heat insulator for comparison was produced.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

(Comparative Example 6)
In Example 1, eight spacers 4 (20 cm long × 6.0 cm wide × 0.3 cm thick aluminum plate) are used, and the eight spacers 4 are arranged radially around the hot water storage container. A comparative heat-retaining device was manufactured in the same manner as in Example 1 except that the distance between the hot water storage container and the sheet 1 was uniformly 60 mm using the width.
About the said heat retention device, the same measurement and evaluation as Example 1 were performed. The results are shown in Table 2.

  From the above results, the heat insulators of Examples 1 to 22, which are the heat retainers of the present invention, have excellent flexibility in the sheets constituting the members, and when used in an electric water heater, the power consumption of the electric water heater It has been found that there is an effect of reducing. Since the reduction in power consumption indicates the prevention of heat dissipation from the heat source, it has been found that heat can be effectively utilized by the heat retainer of the present invention.

  Since the heat retainer of the present invention enables effective use of heat and has a high degree of design freedom, it can be suitably used for, for example, an electric water heater.

DESCRIPTION OF SYMBOLS 1 Resin film which has an independent cavity 1a Surface 11 Raw material 12 Extruder 13 T die 14 Casting roll 15 Casting roll 15 Longitudinal stretching machine 15a Roll 16 Lateral stretching machine 16a Clip 100 Cavity F Film or sheet L Length of cavity in the orientation direction of the cavity r Length of cavity in thickness direction orthogonal to orientation direction of cavity 31 Resin film having independent cavity 32 Deformation preventing material

Claims (10)

A heat source and a sheet,
The distance between the heat source and the sheet is 1.0 mm or more and 50 mm or less,
The sheet has at least a resin film having an independent cavity,
The cavity in the resin film is oriented perpendicular to the thickness direction of the resin film,
The L / r ratio when the average length of the cavity in the thickness direction is r (μm) and the average length of the cavity in the orientation direction of the cavity is L (μm) is 10 or more, and
The heat retainer, wherein the resin film has a thickness of 1.0 mm or less.   The heat retainer according to claim 1, wherein the sheet has a heat conductive layer on a surface on the heat source side of the resin film, and the thickness of the heat conductive layer is 1.0 mm or less.   The heat retainer according to any one of claims 1 to 2, wherein the resin film has a deformation preventing material on a surface opposite to a surface on the heat source side.   The heat retainer according to claim 3, wherein the plurality of deformation preventing materials are arranged in a direction orthogonal to a direction parallel to a direction in which the sheet having a planar shape is deformed.   The heat retainer according to any one of claims 1 to 4, wherein the resin film is made of only a crystalline polymer.   The heat retainer according to any one of claims 1 to 5, wherein the thermal conductivity of the resin film is 0.08 W / mK or less.   The heat retainer according to any one of claims 1 to 6, wherein a ratio of independent cavities is 80% by volume or more with respect to all cavities.   The heat retainer according to any one of claims 2 to 7, wherein the heat conductivity of the heat conductive layer is 1.0 W / mK or more.   The heat retainer according to any one of claims 1 to 8, wherein the heat source is a hot water storage container. An electric water heater having the heat retainer according to claim 9.