JP2017215014A - Heat insulating material and apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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 a 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, has increased due to increasing environmental awareness. The on-vehicle battery is composed of a plurality of lithium ion batteries (battery cells). It is assumed that the battery cell is subject to thermal runaway due to malfunctions during manufacturing of the battery cell, car collision, or incorrect handling of the battery cell. One battery cell runs out of heat, and a large amount of heat is transferred to other adjacent battery cells, causing similar burning, leading to a major accident.

  Therefore, currently, 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 danger of burning between the battery cells is increasing. At present, the thermal conductivity of modified PPE resins and aramid resins used between cells as thermal insulators is as high as 0.17 W / mk and 0.04 W / mk. For this reason, similar burning occurs due to shrinkage between battery cells. Then, the heat insulation between battery cells is considered using the silica airgel whose heat conductivity is lower than modified PPE resin and 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). However, since the silica aerogel has a small bonding force between silica secondary particles and is extremely fragile, when an external stress is applied, the silica aerogel There is a drawback that it is destroyed and its characteristics deteriorate.

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

  Then, in view of the said subject, in this invention, it aims at providing the apparatus using the heat insulating material which maintained the structure of the heat insulating material with respect to the compressive stress, and suppressed the deterioration of thermal conductivity, and the heat insulating material. .

  In order to solve the above-described problem, a heat insulating material including a composite layer including fibers and silica aerogel and a resin support 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 struts, and the heat insulating properties of the heat insulating material can be maintained. If the present heat insulating material 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 struts, and the heat insulating property between the battery cells can be maintained for a long time. As a result, similar burning due to thermal runaway between battery cells can be suppressed, and a safe vehicle-mounted battery can be provided.
Furthermore, if the heat insulating resin support is made of a porous resin, heat conduction from the battery cell can be suppressed.

Cross-sectional view of heat insulating material of embodiment Sectional drawing which shows the example of application of the heat insulating material of embodiment Schematic diagram of silica airgel of embodiment Sectional drawing explaining insertion of the resin support | pillar in the heat insulating material of (a)-(b) embodiment (A) Surface view of a normal silica airgel that is not compressed, (b) Surface view of a compressed silica airgel Sectional drawing of the application example of the heat insulating material of embodiment Sectional drawing of the application example of the heat insulating material of (a)-(b) embodiment Sectional drawing of the application example of the heat insulating material of embodiment (A)-(b) Sectional drawing explaining the heat insulating material of Example 2 (A)-(b) Sectional drawing explaining the heat insulating material of Example 3 Heat insulation manufacturing flowchart

Embodiments will be described below with reference to the drawings.
(Embodiment)
FIG. 1 shows a cross-sectional view of a heat insulating material 100 containing silica aerogel in an embodiment of the present invention.

FIG. 2 shows a structure in which a heat insulating material 100 is mounted between battery cells 106 of a vehicle-mounted battery as an embodiment.
When the battery cell 106 expands due to the 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, the deformation causes a compressive stress in the fragile silica aerogel in the heat insulating material 100 to prevent the silica aerogel from being destroyed, and to prevent similar firing between battery cells.

<Configuration of heat insulating material 100>
In FIG. 1, a heat insulating material 100 has a composite layer 101 of silica airgel 103 having a nano-sized porous structure on a fiber 102. The resin struts 104 are arranged in parallel to the thickness direction, and have the size of the resin struts 104 and the number of resin struts 104 corresponding to the compressive stress. Further, the laminate film 105 is sandwiched between the upper and lower sides as necessary.

  By the resin support 104, the heat insulating material 100 disperses the compressive stress and keeps its shape. As a result, the silica airgel is not detached, the thermal conductivity is maintained, and the battery cells can be prevented from burning.

<Configuration 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 silica airgel in a gel state in the process of manufacturing the silica airgel 103. The gel is then reacted to form a wet gel. Finally, the wet gel surface is hydrophobized and dried with hot air. The fiber 102 is preferably a fiber such as PET (polyethylene terephthalate) or an acrylic oxide or glass wool obtained by subjecting the fiber to a flame retardant treatment from the viewpoint of safety.

  The diameter of the fiber 102 is desirably 0.1 to 30 um. When the diameter of the fiber 102 is larger than 30 μm, heat is easily transferred through the fiber 102, so that the thermal conductivity is increased and the heat insulating property is deteriorated. As a result, the heat generated from the battery cell 106 is transmitted to the adjacent battery cell 106, thereby causing a similar firing due to the temperature rise of the battery cell 106.

<Silica airgel 103>
FIG. 3 illustrates 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 aggregating silica primary particles 201 having a diameter of about 1 nm have voids 203 having an interparticle distance of about 10 to 60 nm. A collection of structures.

  Silica aerogel 103 uses water 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 necessary 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, crushes the voids, and does not function as a heat insulating material. Therefore, so that the surface tension hardly works when the solvent dries, it is supercritical drying, or the silanol group on the surface of the wet gel is hydrophobized by silylation using a silylating agent and then dried with hot air. Is required.

<Structure of resin support column 104>
In order to produce the resin strut 104, it is conceivable that the resin is melted and poured into a hole provided in the silica airgel 103. However, when a hole is made in the silica airgel 103, if the fiber is melted by heating and the hole is made, the silica airgel 103 becomes hydrophilic and absorbs moisture, so that the heat insulation characteristics deteriorate.

  Therefore, as shown in FIGS. 4A and 4B, the resin strut 104 is prepared in advance, and the resin strut 104 is inserted into the composite layer 101. Furthermore, it is preferable that the resin strut 104 is made of a porous resin, and an air layer is provided inside the resin strut to enhance heat insulation. The porous resin has pores in the resin, preferably has a pore diameter of about 5 μ to 200 μ and a porosity of 10 to 60%. The pore diameter and the porosity are selected from the strength and thermal conductivity of the resin strut 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 when the diameter is small. It is desirable.

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

  In particular, as the heat insulating material 100 between the battery cells 106 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. When cracked, cracks (air gaps) are generated. 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 in which the composite layer 101 is compressed and the silica airgel is removed.

  As a result of the removal of the silica airgel, the thermal conductivity of the heat insulating material 100 increases, and the battery cells 106 are burned off. For this reason, the size and quantity of the resin strut 104 in the heat insulating material 100 are determined according to the compressive stress.

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

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

  The gap between the battery cells 106 is about 0.3 mm to 1.0 mm due to the miniaturization of the vehicle-mounted battery. 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, it is confirmed from the experimental results. In order not to perform the firing, the heat insulating material 100 needs to have a thermal conductivity of 0.20 W / mk or less.

<Example 1>
FIG. 6 shows an embodiment. A heat insulating material 100 is disposed between the battery cells 106. In this case, the length of the resin column 104 is preferably shorter than the thickness of the composite layer 101 of the heat insulating material 100. If the length of the resin strut 104 is the same as or longer than the thickness of the composite layer 101 of the heat insulating material 100, the resin strut 104 is exposed to the surface of the heat insulating material 100, and heat conduction characteristics may deteriorate.

  It is desirable that a part of the resin column 104 is in contact with the laminate film 105 and the other is in contact with the laminate film 105 when the distance between the battery cells 106 is reduced due to expansion of the battery cell 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, this is because the surface of the heat insulating material 100 is in close contact with the side surface of the battery cell 106 so that the heat insulating properties are efficiently exhibited.

  When the laminate film 105 is not used, the resin support 104 is directly contacted or not contacted.

  The resin strut 104 may be inserted from one side or both sides of the composite layer 101 as shown in FIGS. 7 (a) and 7 (b). As shown in FIG. 7A, the shape of the resin support column 104 is thinner than the rear portion as it goes to the tip portion, and it is desirable that the shape is easy to insert into the composite layer 101. The shape is a columnar shape, and is determined by the thickness of the composite layer 101 such as a columnar shape, an elliptical columnar shape, a quadrangular prism shape, and a compressive stress from the outside. Further, as shown in FIG. 7B, the shape of the resin strut 104 from both sides can be changed on both sides. A structure in which the insertion type is combined, such as a concave portion and a convex portion, is preferable.

  In addition, the structure which inserted the resin support | pillar 104 shown to Fig.7 (a) from both surfaces of the composite layer 101 may be sufficient. The resin support 104 on one surface is a first resin support, and the resin support on the other surface is a second resin support.

  In the case where a plurality of resin struts 104 are formed from the relationship of compressive stress, a plurality of resin struts 104 can be formed at a time by connecting the upper portions with connecting portions 107 as shown in FIG. Moreover, it is easy to fix the position of the resin column 104. As a material for the connecting portion 107, a resin such as a fluororesin, polystyrene, polypropylene, or polyethylene is used. The characteristics can be further improved by using a porous resin from the viewpoint of thermal conductivity. The thickness of the connecting portion 107 is preferably thin as long as the shape of the resin support column 104 can be maintained so as not to conduct heat.

<Example 2>
The porous resin strut 104 in FIG. 9A is impregnated with an adhesive 108 containing a solvent, and inserted into the heat insulating material 100 that is the composite layer 101 of the fibers 102 and the silica airgel 103. Thereafter, by heating, the adhesive 108 flowing out from the porous resin column 104 and the fibers 102 in the composite layer 101 are bonded. 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 on the surface of the composite layer 101 in advance, and then the porous resin strut 104 may be inserted. 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 struts 104, the porous resin struts 104 may fall off due to stress during bending. In this embodiment, since the adhesive 108 is used, it can be prevented from falling off.

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

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

That is, there is a flat plate 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.
With this structure, the resin support can be prevented from dropping when it receives a strong bending stress. 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.

  The insertion angle may be added to the composite material in the vertical direction. By providing an angle, the heat transfer path becomes longer and the thermal conductivity can be lowered.

<The manufacturing method of the heat insulating material 100>
An example of the manufacturing method of the heat insulating material 100 is shown in the flowchart of FIG.

-Impregnation process First, a fiber (weight per unit area 34 g / m ² , thickness 0.6 mm, dimensions 9 cm × 14 cm) is impregnated using 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 allowed to gel at room temperature 23 ° C. for about 20 minutes. At this time, in order to promote gelation and shorten the time, heating may be performed with a heater (about 50 ° C. to 130 ° C.). Next, it forms in desired thickness using a biaxial roll.
(2) Curing process Next, pure water is poured into the container to prevent drying, and the mixture is placed in a thermostatic bath at 80 ° C. for 12 hours to promote silanol dehydration condensation reaction. Form a quality structure.
(3) Hydrophobization step Next, the gel sheet is immersed in hydrochloric acid (6 to 12 N) and then left at room temperature for 23 hours to take hydrochloric acid into the gel sheet.

Next, the gel sheet is immersed in, for example, a mixed solution of octamethyltrisiloxane, which is a silylating agent, and 2-propanol (IPA), placed in a constant temperature bath at 55 ° C., and allowed to react for 2 hours. When the trimethylsiloxane bond starts to form, 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 process Next, the heat insulating material 100 which made the fiber carry the silica airgel which has a nano-sized porous structure by making a gel sheet to a 150 degreeC thermostat and drying for 2 hours is made.
(5) Resin Strut Inserting Step Next, the resin strut 104 made of porous resin is inserted into the heat insulating material 100.

For porous resin, a resin column is manufactured by dispersing gas in the resin. The resin strut can be manufactured using a resin such as fluorine, polyethylene, polypropylene, polytetrafluoroethylene, or polyetheretherketone.
(6) Lamination process The laminate film 105 is affixed on the upper and lower surfaces of the heat insulating material 100.

<Overall>
Embodiments and examples can be combined. This resin support | pillar is not restricted to a silica airgel, It can apply widely to a heat insulating material.

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

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

DESCRIPTION OF SYMBOLS 100 Heat insulating material 101 Composite layer 102 Fiber 103 Silica airgel 104 Resin support | pillar 105 Laminate film 106 Battery cell 107 Connection part 108 Adhesive 109 Low melting point resin 110 Heater 201 Silica primary particle 202 Silica secondary particle 203 Void

Claims (11)

A composite layer comprising fibers and silica airgel;
The heat insulating material containing the resin support | pillar arrange | positioned in the thickness direction in the said composite layer. The heat insulating material according to claim 1, wherein a part of the resin support column appears on one surface of the composite layer. There are a plurality of the resin struts, a first resin strut whose part appears on one surface of the composite layer, and a second resin strut whose part appears on the other surface of the composite layer; The heat insulating material of Claim 1 or 2 containing. The length of the said resin support | pillar is a heat insulating material of any one of Claim 1 to 3 shorter than the thickness of the said composite layer. The heat insulating material according to any one of claims 1 to 4, wherein the plurality of resin struts are porous resins. The heat insulating material according to any one of claims 1 to 5, further comprising a connecting portion that connects the plurality of resin struts. The heat insulating material according to any one of claims 1 to 6, wherein the resin strut is impregnated with an adhesive. The heat insulating material according to claim 7, wherein the adhesive is present across the resin strut and the composite layer. The heat insulating material according to any one of claims 1 to 8, wherein the resin strut includes a main body portion and a tip portion, and the tip portion has a melting point lower than that of the main body portion. 10. The resin post according to claim 1, comprising: a main body portion and a tip portion, wherein the main body portion is in a columnar shape in the composite layer, and the tip portion is located on a surface of the composite layer and has a flat plate shape. The heat insulating material of any one. The apparatus which has arrange | positioned the said heat insulating material of any one of Claims 1-10 between several heat generating bodies.

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