JP2021050825A - Heat insulating material and apparatus using the same - Google Patents

Abstract

To provide a heat insulating material which can suppress deterioration in heat conductivity by maintaining a structure of the heat insulating material with respect to compression stress, and an apparatus using the heat insulating material.SOLUTION: A heat insulating material of this invention includes a composite layer containing fiber and silica aerogel, and a resin column provided in a thickness direction of the composite layer. A part of the resin column appears on one surface of the composite layer. A length of the resin column is smaller than a thickness of the composite layer. In an apparatus of this invention, the heat insulating material is disposed between a plurality of heating elements.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat insulating material using hydrophobic airgel and a device using the heat insulating material.

In recent years, the number of vehicles equipped with secondary batteries, such as electric vehicles and hybrid vehicles, is increasing due to heightened environmental awareness. The vehicle-mounted battery is composed of a plurality of lithium-ion batteries (battery cells). It is assumed that the battery cell will cause thermal runaway due to a malfunction in the manufacture of the battery cell, a collision of a car, or an incorrect handling of the battery cell. One battery cell runs away from heat, and a large amount of heat is transferred to another adjacent battery cell, causing a kind of fire, leading to a major accident.

Therefore, at present, a modified PPE resin or an aramid resin is used as a thermal insulator between the battery cells to prevent burning between the battery cells.

However, due to the small size of the in-vehicle battery, the gap between the battery cells is narrowed, and the risk of burning between the battery cells is increased. Currently, the modified PPE resin and aramid resin used as thermal insulators between cells have high thermal conductivitys of 0.17 W / mk and 0.04 W / mk. Therefore, the shrinkage between the battery cells causes burning. Therefore, heat insulation between battery cells has been considered by using silica airgel having a lower thermal conductivity than modified PPE resin or aramid resin as a thermal insulator between battery cells (Patent Document 1).

Japanese Patent No. 5624254

Silica airgel is characterized by low thermal conductivity (0.02 W / mk), but since the bonding force between silica secondary particles of silica airgel is small and extremely fragile, when external stress is applied, silica airgel becomes It has the drawback of being destroyed and degrading its properties.

As the battery cell expands due to deterioration of the battery cell, the gap between the cells is reduced, compressive stress is generated in the fragile silica airgel between the cells, and the silica airgel is destroyed. When the silica airgel is destroyed, the thermal conductivity increases and the heat insulating property of the battery cell deteriorates. This makes it impossible to prevent the battery cells from burning.

Therefore, in view of the above problems, it is an object of the present invention to provide a heat insulating material that retains the structure of the heat insulating material and suppresses deterioration of thermal conductivity against compressive stress, and an apparatus using the heat insulating material. ..

In order to solve the above problems, a heat insulating material containing a composite layer containing fibers and silica airgel and a resin strut provided in the thickness direction of the composite layer is used. An electronic device in which the heat insulating material is arranged between a plurality of heating elements is used.

According to the heat insulating material of the present invention, the compressive stress applied to the heat insulating material can be dispersed by the resin column, and the heat insulating property of the heat insulating material can be maintained. If the heat insulating material of the present application is used between the battery cells, the compressive stress applied to the silica airgel in the heat insulating material can be dispersed by the resin columns, and the heat insulating property between the battery cells can be maintained for a long period of time. As a result, it is possible to suppress burning due to thermal runaway between battery cells, and it is possible to provide a safe in-vehicle battery. Further, if the heat insulating resin column is made of a porous resin, heat conduction from the battery cell can be suppressed.

Sectional drawing of the heat insulating material of embodiment Sectional drawing which shows application example of the heat insulating material of embodiment Schematic diagram of the silica airgel of the embodiment (A)-(b) Cross-sectional view for explaining the insertion of the resin column in the heat insulating material of the embodiment. (A) Surface view of uncompressed normal silica airgel, (b) Surface view of compressed silica airgel Sectional drawing of application example of heat insulating material of embodiment (A)-(b) Cross-sectional view of an application example of the heat insulating material of the embodiment Sectional drawing of application example of heat insulating material of embodiment (A)-(b) Cross-sectional view for explaining the heat insulating material of Example 2. (A)-(b) Cross-sectional view for explaining the heat insulating material of Example 3. Insulation material manufacturing flowchart

Hereinafter, embodiments will be described with reference to the drawings.

(Embodiment)
FIG. 1 shows a cross-sectional view of a heat insulating material 100 containing silica airgel according to an embodiment of the present invention.

FIG. 2 shows a structure in which the heat insulating material 100 is mounted between the battery cells 106 of the vehicle-mounted battery as an embodiment. As the battery cell 106 expands due to deterioration of the battery cell 106, the gap between the battery cells 106 is reduced, and the heat insulating material 100 is deformed. In this embodiment, compressive stress is generated in the fragile silica airgel in the heat insulating material 100 due to the above deformation, the silica airgel is prevented from being destroyed, and the prevention of burning between battery cells is suppressed.

<Structure of heat insulating material 100>
In FIG. 1, the heat insulating material 100 has a composite layer 101 of silica airgel 103 having a nano-sized porous structure on fibers 102. The resin columns 104 are arranged parallel to each other in the thickness direction, and have the size of the resin columns 104 and the number of resin columns 104 corresponding to the compressive stress. Further, the upper and lower parts are sandwiched between the laminated films 105 as needed.

The resin column 104 disperses the compressive stress and keeps the shape of the heat insulating material 100. As a result, the silica airgel does not come off, the thermal conductivity is maintained, and the burning of the battery cell can be suppressed.

<Structure of composite layer 101>
The composite layer 101, which is the main component of the heat insulating material 100, impregnates the fibers 102 with the gelled silica airgel in the process of manufacturing the silica airgel 103. The gel is then reacted to form a wet gel. Finally, it is obtained by hydrophobicizing the surface of the wet gel and drying it with hot air. The fiber 102 is preferably a fiber such as PET (polyethylene terephthalate), acrylic oxide obtained by subjecting the fiber to a flame-retardant treatment from the viewpoint of safety, or glass wool.

The diameter of the fiber 102 is preferably 0.1 to 30 um. When the diameter of the fiber 102 is larger than 30 um, heat is easily transferred through the fiber 102, so that the thermal conductivity increases and the heat insulating property deteriorates. As a result, the heat generated from the battery cell 106 is transferred to the adjacent battery cell 106, so that the temperature rise of the battery cell 106 causes burning.

<Silica Airgel 103>
FIG. 3 describes the structure of the silica airgel 103. The silica airgel 103 is a network in which silica secondary particles 202 having a diameter of about 10 nm formed by gathering silica primary particles 201 having a diameter of about 1 nm have voids 203 having an interparticle distance of about 10 to 60 nm. It is a collection of structures.

Silica airgel 103 uses a metal alkoxide such as water glass or tetramethoxysilane as a gel raw material, and mixes a solvent such as water or alcohol with a catalyst as needed to react with the gel raw material in the solvent to form a wet gel. It is formed and the solvent inside is dried.

However, when the wet gel is normally dried with hot air, it shrinks due to the surface tension when the solvent dries and crushes the voids, so that it does not function as a heat insulating material. Therefore, supercritical drying or hydrophobizing the silanol groups on the surface of the wet gel with a silylating agent is performed so that surface tension hardly acts when the solvent dries, and then hot air drying is performed. Is required.

<Structure of resin support 104>
In order to manufacture the resin strut 104, it is conceivable to melt the resin and pour it into the holes provided in the silica airgel 103. However, when a hole is made in the silica airgel 103, the fibers are melted by heating and the hole is made, the silica airgel 103 becomes hydrophilic and absorbs moisture, and the heat insulating property is deteriorated.

Therefore, as shown in FIGS. 4A and 4B, the resin support column 104 is prepared in advance, and the resin support column 104 is inserted into the composite layer 101. Further, it is preferable that the resin column 104 is made of a porous resin and an air layer is provided inside the resin column to enhance the heat insulating property. The porous resin has pores in the resin, the pore diameter is about 5μ to 200μ, and the porosity is preferably 10 to 60%. The pore diameter and porosity are selected from the strength and thermal conductivity of the resin column 104. Further, the diameter of the resin column 104 is in the range of 1/2 to 10 times the thickness of the composite layer 101 because the thermal conductivity characteristic decreases as the diameter increases and the reinforcing strength decreases as the diameter decreases. Is desirable.

Further, as the material of the resin support column 104, fluororesin, polystyrene, polypropylene, polyethylene or the like can be used. This porous resin has the effect of suppressing heat transfer through the resin column 104.

In particular, as the heat insulating material 100 between the battery cells 106, which is sensitive to heat generation, when compressive stress is applied to the heat insulating material 100 between the battery cells 106 due to the expansion of the battery cells 106, the silica airgel on the surface is as shown in FIG. 5 (b). Cracks (air gaps) occur when the battery is destroyed. FIG. 5A is a surface observation photograph of the composite layer 101 in the initial normal state. FIG. 5B is a surface observation photograph of the composite layer 101 from which compression is applied to the composite layer 101 to remove silica airgel.

As a result of removing the silica airgel, the thermal conductivity of the heat insulating material 100 increases, and the battery cell 106 burns. Therefore, the size and quantity of the resin columns 104 in the heat insulating material 100 are determined according to the compressive stress.

The resin column 104 may appear on the surface of the heat insulating material 100. The positions of the plurality of resin columns 104 are aligned, and the compression direction of the heat insulating material 100 is constant and stable.

<Thermal conductivity required for the heat insulating material 100>
In this embodiment, as an insulator between the battery cells 106, a heat insulating material 100 used in a space where the space is limited is intended. An example is shown below. In order to explain an example of application of the heat insulating material 100 to the battery cell 106, the battery cell arrangement of the lithium ion battery for a vehicle is shown in FIG. The heat insulating material 100 is arranged between the battery cell 106 and the battery cell 106.

Due to the miniaturization of the in-vehicle battery, the gap between the battery cells 106 is about 0.3 mm to 1.0 mm. The thermal conductivity of the modified PPE resin, which is a conventional heat insulating material, is 0.17 W / mk. When this modified PPE resin is used in a gap of 1.0 mm, burning has been confirmed from the experimental results. In order to prevent burning, the heat insulating material 100 needs to have a thermal conductivity of 0.20 W / mk or less.

<Example 1>
An example is shown in FIG. The heat insulating material 100 is arranged between the battery cells 106. In this case, the length of the resin column 104 should be shorter than the thickness of the composite layer 101 of the heat insulating material 100. If the length of the resin column 104 is the same as or longer than the thickness of the composite layer 101 of the heat insulating material 100, heat conduction may occur on the surface of the heat insulating material 100 and the heat conduction characteristics may be deteriorated.

It is desirable that a part of the resin column 104 comes into contact with the laminate film 105, and the other comes into contact with the laminate film 105 when the distance between the battery cells 106 decreases due to expansion of the battery cells 106 or the like.

Therefore, the length of the resin column 104 is preferably shorter than the thickness of the composite layer 101. However, 70% or more of the thickness of the composite layer 101 is desirable.

That is, the surface of the heat insulating material 100 is brought into close contact with the side surface of the battery cell 106 so that the heat insulating characteristics can be efficiently exhibited.

When the laminated film 105 is not used, it directly contacts or does not contact the resin column 104.

As shown in FIGS. 7 (a) and 7 (b), the resin column 104 may be inserted from one side or both sides of the composite layer 101. As shown in FIG. 7A, it is desirable that the shape of the resin column 104 is narrower toward the tip and is easier to insert into the composite layer 101. Its shape is columnar, and is determined by the thickness of the composite layer 101 such as columnar, elliptical, and square columnar and the compressive stress from the outside. Further, as shown in FIG. 7B, the shape of the resin columns 104 from both sides can be changed on both sides. A recessed type combined structure such as a concave portion and a convex portion is preferable.

The resin column 104 shown in FIG. 7A may be inserted from both sides of the composite layer 101. The resin strut 104 on one surface is the first resin strut, and the resin strut on the other surface is the second resin strut.

When forming a plurality of resin columns 104 due to the relationship of compressive stress, several resin columns 104 can be formed at a time by connecting the upper portions with the connecting portion 107 as shown in FIG. In addition, it is easy to fix the position of the resin support column 104. As the material of the connecting portion 107, a resin such as fluororesin, polystyrene, polypropylene, or polyethylene is used. By using a porous resin from the viewpoint of thermal conductivity, the characteristics can be further improved. The thickness of the connecting portion 107 should be thin as long as the shape of the resin column 104 can be maintained so as not to cause heat conduction.

<Example 2>
The porous resin column 104 of FIG. 9A is impregnated with the adhesive 108 containing a solvent and inserted into the heat insulating material 100 which is the composite layer 101 of the fiber 102 and the silica airgel 103. After that, by heating, the adhesive 108 flowing out from the porous resin column 104 and the fibers 102 in the composite layer 101 are adhered to each other. Finally, the adhesive 108 is located across both the resin column 104 and the composite layer 101.

As shown in FIG. 9B, the adhesive 108 may be dropped onto the surface of the composite layer 101 in advance, and then the porous resin column 104 may be inserted. Further, the adhesive 108 is preferably a thermosetting type.

The composite layer 101 is flexible and can be bent. If the composite layer 101 is bent only by inserting the porous resin support column 104, the porous resin support column 104 may fall off due to the stress at the time of bending. In this embodiment, since the adhesive 108 is used, it can be prevented from falling off.

<Example 3>
FIG. 10 shows an embodiment. The structure is such that a resin 109 having a melting point lower than that of other resins (main body) is used at the tip of the porous resin column 104.

For example, a fluororesin having a heat resistant temperature of 260 ° C. is used for the resin column 104, and a PP (polypropylene) resin having a melting point of 110 ° C. is used as a resin 109 having a low melting point at the tip. After inserting the resin column 104 into the composite layer 101, the resin 109 having a low melting point is heated by the heater 110 to melt the tip of the resin column 104 (FIG. 10 (a)), thereby forming a rivet structure (FIG. 10 (b)). Can be made.

That is, there is a flat plate-like portion on the surface of the composite layer 101, and the main body of the resin column 104 is located inside the composite layer 101. Due to this structure, it is possible to suppress the falling of the resin column when a strong bending stress is applied. In this case, the resin strut 104 needs to be longer than the thickness of the composite material of the fiber layer and the silica airgel layer.

Further, the insertion angle may be set in addition to the vertical direction with respect to the composite material. By setting the angle, the heat transfer path becomes longer and the thermal conductivity can be reduced.

<Manufacturing method of heat insulating material 100>
An example of a method for manufacturing the heat insulating material 100 is shown in FIG. 11.

(1) Impregnation Step First, fibers (mesh weight 34 g / m ² , thickness 0.6 mm, dimensions 9 cm × 14 cm) are impregnated with a sol solution. The sol solution is prepared by adding 1.4 wt% of concentrated hydrochloric acid (12N) as a catalyst to high molar sodium silicate (silicic acid aqueous solution, Si concentration 14%) and stirring.

Next, the sol is left at room temperature of 23 ° C. for about 20 minutes to gel the sol. At this time, in order to promote gelation and shorten the time, it may be heated with a heater (about 50 ° C. to 130 ° C.). Next, it is formed to a desired thickness using a biaxial roll or the like.

(2) Curing step Next, pure water is poured into the container to prevent drying, and the container is placed in a constant temperature bath at 80 ° C. for 12 hours to promote the dehydration condensation reaction of silanol to grow silica particles and make them porous. Form a quality structure.

(3) Hydrophobicization Step Next, after immersing the gel sheet in hydrochloric acid (specified in 6 to 12), the gel sheet is left at room temperature of 23 ° C. for 1 hour to incorporate hydrochloric acid into the gel sheet.

Next, the gel sheet is immersed in a mixed solution of, for example, octamethyltrisiloxane, which is a silylating agent, and 2-propanol (IPA), and placed in a constant temperature bath at 55 ° C. for reaction for 2 hours. When the trimethylsiloxane bond begins to be formed, hydrochloric acid is discharged from the gel sheet, and the upper layer is separated into trisiloxane and the lower layer is separated into hydrochloric acid water.

(4) Drying Step Next, the gel sheet is transferred to a constant temperature bath at 150 ° C. and dried for 2 hours to obtain a heat insulating material 100 in which the fibers carry silica airgel having a nano-sized porous structure.

(5) Resin Strut Insertion Step Next, the resin strut 104 made of porous resin is inserted into the heat insulating material 100.

For the porous resin, a resin strut is manufactured by dispersing gas in the resin. The composition of the resin column can be produced by using a resin such as fluorine, polyethylene, polypropylene, polytetrafluoroethylene, and polyetheretherketone.

(6) Laminating Step The laminating film 105 is attached to the upper and lower surfaces of the heat insulating material 100.

<Throughout>
The embodiments and examples can be combined. This resin strut is not limited to silica airgel, and can be widely applied to heat insulating materials.

Although an example between the battery cells 106 of the in-vehicle battery is shown, it can be applied to other devices. The heat insulating material of the embodiment can be arranged between the heat generating members to block the heat between the heat generating members.

The heat insulating material of the present invention can maintain heat insulating properties by dispersing compressive stress, and is widely used in in-vehicle devices and electronic devices. It is applied to heat-related products such as information devices, mobile phones, and displays.

100 Insulation 101 Composite layer 102 Fiber 103 Silica airgel 104 Resin prop 105 Laminate film 106 Battery cell 107 Connecting part 108 Adhesive 109 Low melting point resin 110 Heater 201 Silica primary particles 202 Silica secondary particles 203 Voids

Claims (10)

A composite layer that is a single layer containing fibers and silica airgel,
In the composite layer which is the one layer, the resin columns arranged in the thickness direction are included.
A heat insulating material containing a first resin column having a plurality of resin columns, one of which appears on one surface of the composite layer, which is the one layer, and does not appear on the other surface. The heat insulating material according to claim 1, further comprising a second resin strut in which a part thereof appears on the other surface of the composite layer which is the one layer and does not appear on the one surface. A composite layer containing fibers and silica airgel,
In the composite layer, the resin columns arranged in the thickness direction are included.
A connecting portion for connecting the plurality of resin columns at the upper portion thereof is provided.
The resin strut is a heat insulating material that becomes thinner toward the tip and thinner than the rear. The heat insulating material according to claim 3, wherein the connecting portion appears on one surface of the heat insulating material and does not appear on the other side. The heat insulating material according to any one of claims 1 to 4, wherein the length of the resin column is shorter than the thickness of the composite layer. The heat insulating material according to any one of claims 1 to 5, wherein the plurality of resin columns are porous resins. The heat insulating material according to any one of claims 1 to 6, wherein the resin support is impregnated with an adhesive. The heat insulating material according to claim 7, wherein the adhesive is present in the resin column and in the composite layer. The resin column includes a main body portion and a tip portion, the main body portion is in the composite layer and has a columnar shape, and the tip portion is located on the surface of the composite layer and has a flat plate shape. The heat insulating material according to any one of the above. A device in which the heat insulating material according to any one of claims 1 to 9 is arranged between a plurality of heating elements.

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