Heat-storable heat-conductive material

Abstract

To provide a heat-storable heat-conductive material which has such followability as to be capable of being filled into a narrow part without a gap, and has less deterioration of a heat storage amount by a change with the elapse of time.SOLUTION: A heat-storable heat-conductive material contains a heat storage material, a heat-conductive filler, and an oil gelling agent or a two-pack curable base resin, wherein the melting point of the heat storage material is 48°C or higher.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a heat storage type heat conduction material.

Background Art

[0002] Heat conduction materials provided between a heating element and a heat dissipation member for heat transfer are known in various forms, such as grease type, gap filler type, sheet type, etc. By using these heat conduction materials, for example, the heat generated by the heating element can be efficiently dissipated from heat dissipation members such as metal casings and heat sinks. By installing such a heat conduction material between the heating element and the heat dissipation member, the thermal resistance between the heating element and the heat dissipation member can be reduced.

[0003] In the field of automotive parts and the like, in recent years, markets such as lithium-ion batteries (LIBs) as automotive power sources for electric vehicles (EVs) have been expanding. However, in the battery cases of secondary batteries such as these lithium-ion batteries (LIBs), due to downsizing and increased output, etc., heat generated in the secondary battery during charging and discharging is likely to stay inside the casing, and there is a problem that the limit temperature for using the secondary battery is reached in a short time. In particular, in automotive parts and the like, the interior temperature of the vehicle may be exposed to a thermally severe environment where it reaches 40°C or higher. Under such high-temperature conditions, there are problems such as the secondary battery immediately reaching the limit temperature for use and the continuous operating time of the battery becoming short.

[0004] For this reason, the development of heat dissipation design for such secondary batteries and the like is urgently required. Especially in lithium-ion secondary batteries, if a high-temperature state exceeding the limit temperature for use continues for a long time, there is a risk of battery damage. Therefore, heat countermeasures to suppress and mitigate the temperature rise of the battery are an urgent task.

[0005] In order to be used even in such thermally harsh ambient environmental conditions where it is difficult to obtain a temperature difference from the ambient environment, it is effective to utilize a heat storage material for heat dissipation measures for components where it is difficult to obtain a temperature difference from the ambient environment. In Patent Document 1, by combining a thermoplastic base polymer, a thermally conductive filler, and a heat storage material, a molded body with a predetermined hardness is ensured to enhance the adhesion to the heat dissipation object, and even for a heat dissipation object under conditions where it is difficult to obtain a temperature difference from the ambient environment due to the influence of a thermally harsh ambient environmental temperature (atmospheric temperature), the effect of suppressing and alleviating its temperature rise is enhanced.

[0006] In particular, if a battery, for example, a lithium-ion battery or the like, is used as the heat dissipation object, by using a heat storage material that utilizes the latent heat having a phase change temperature within the operating temperature range of the battery, the temperature rise of the battery within the operating temperature region of the battery can be alleviated. At this time, if only the heat storage material is used, the heat dissipation effect is limited because the temperature will rise again when the limit of the heat storage capacity is exceeded. However, since the thermally conductive filler is included, a heat conduction path is ensured, so the heat dissipation performance is enhanced and the extension of the operable time is made possible (for example, refer to Patent Document 1).

[0007] For such heat storage, techniques that use the latent heat of phase transition during the solidification and melting of substances are known. Among them, paraffin compounds in particular have excellent characteristics such as a high heat storage density and no corrosiveness to metals. Also, when the heat generating part exists inside the housing that houses it, a heat transfer material with low viscosity and fluidity may be poured into the housing for use. In the heat transfer material used in such a case, as the integration of various electronic devices progresses, a material that can be injected and filled into a narrower space without entrapping air bubbles or the like and without gaps is required.

[0008] For example, Patent Document 2 discloses a latent heat storage material with excellent durability, which does not exude or phase-separate the latent heat storage material from the carrier material even under a heat cycle that repeats phase transitions by solidification and melting.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, the latent heat storage material disclosed in Patent Document 2 has a structure in which a latent heat storage material composed of n-paraffin is supported on a hydrogenated styrene-ethylene / propylene block copolymer. For this reason, there has been a problem that it has almost no fluidity and cannot be injected into a narrow gap for use. Also, regarding durability, there has been a concern that the heat storage amount decreases due to changes over time.

[0011] The present invention has been made in view of such a background, and an object thereof is to provide a heat storage thermal conductive material that has fluidity enabling it to be filled into a narrow part without gaps and has little deterioration in the heat storage amount due to changes over time.

Means for Solving the Problems

[0012] In order to solve the above problems, the heat storage thermal conductive material according to an embodiment of the present invention proposes the following means. (1) The heat storage thermal conductive material according to Aspect 1 of the present invention includes a heat storage material, a thermally conductive filler, and an oil gelling agent or a two-component curable base resin, and is characterized in that the melting point of the heat storage material is 48°C or higher.

[0013] (2) Aspect 2 of the present invention is the heat storage thermal conductive material according to Aspect 1, wherein the heat storage material is characterized in that the average molecular weight is 400 or higher.

[0014] (3) Aspect 3 of the present invention is the heat storage thermal conductive material according to Aspect 1, wherein the heat storage material is microcrystalline wax.

[0015] (4)Aspect 4 of the present invention is characterized in that in the heat storage thermal conductive material according to any one of Aspects 1 to 3, the oil gelling agent contains a fatty acid metal salt or a mixture of a fatty acid metal salt and a fatty acid.

[0016] (5)Aspect 5 of the present invention is characterized in that in the heat storage thermal conductive material according to Aspect 4, the oil gelling agent is aluminum 2-ethylhexanoate.

Advantages of the Invention

[0017] According to the present invention, it is possible to provide a heat storage thermal conductive material that has fluidity enabling filling without gaps in narrow parts and has little deterioration in the heat storage amount due to changes over time.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, with reference to the drawings, a heat storage thermal conductive material according to an embodiment of the present invention will be described. Each of the embodiments shown below is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show the main parts enlarged for the sake of clarity of the features of the present invention, and the dimensional ratios of the respective components are not necessarily the same as the actual ones.

[0019] The heat storage thermal conductive material of the present embodiment includes a heat storage material, a thermally conductive filler, an oil gelling agent or a two-component curable base resin, and the melting point of the heat storage material is 48°C or higher. The heat storage material is for enhancing the effect of suppressing and alleviating the temperature rise of a heat dissipation object under conditions where it is difficult to obtain a temperature difference with the surrounding environment due to the influence of a harsh ambient temperature (atmospheric temperature). Examples of such heat storage materials may be mixtures of alkanes having 16 or more carbon atoms, that is, paraffins. As an example of paraffin, normal paraffin (especially a mixture of linear alkanes having about 16 to 40 carbon atoms) can be mentioned. As an example of a heat storage material, normal paraffin having a melting point of 48°C and a latent heat of fusion of 206 J / g can be mentioned. The melting point of normal paraffin depends on the temperature range in which heat is to be stored, but about 48°C to 81°C is suitable for the use of the present invention.

[0020] Also, microcrystalline wax can be used as a heat storage material. Microcrystalline wax is a wax that is solid at normal temperature, has more carbon atoms and a higher molecular weight than general paraffin wax, and also has a higher melting point. For example, the carbon number distribution of microcrystalline wax is generally about 30 to 60, the molecular weight is about 500 to 800, and the melting point is about 70°C to 110°C.

[0021] Such microcrystalline wax is defined in JIS as a wax that is solid at normal temperature and separated and purified from the residue of vacuum distillation of crude oil or heavy distillate oil, and is classified into a plurality of categories according to the melting point and the like. Microcrystalline wax has a composition mainly composed of hydrocarbons (isoparaffins) having side chains on the main chain, and contains a small amount of linear hydrocarbons (normal paraffins) and cyclic hydrocarbons (napthenes). Because it contains many isoparaffins and cycloparaffins with small crystal particle sizes in terms of composition, it becomes microcrystalline. Such microcrystalline wax has high viscosity, is rich in stretchability, and is excellent in brittleness resistance at low temperatures below room temperature.

[0022] Such normal paraffin and microcrystalline wax are solid-liquid phase transition type latent heat storage materials. This solid-liquid phase transition type latent heat storage material is a phase change type heat storage material (phase change material) that, when absorbing heat from a heat dissipation object, undergoes a phase change from a solid phase to a liquid phase and stores heat by the latent heat of that phase change (melting).

[0023] Among solid-liquid phase transition type latent heat storage materials, normal paraffin and microcrystalline wax in particular have a relatively large latent heat, a large heat storage amount per unit volume, and can obtain stable heat release and heat storage effects even when melting and solidification are repeated. In addition, it is difficult to corrode the heat dissipation object, is inexpensive, and has favorable properties as a heat storage material in that the phase change temperature (melting point) can be easily adjusted according to the molecular weight and the like.

[0024] Thus, when using a phase change material such as a solid-liquid phase transition type as a heat storage material, a material corresponding to the required phase change temperature (in the case of a solid-liquid phase transition type phase change material, corresponding to the melting point), that is, a material having a phase change temperature (melting point) in the target temperature range may be selected.

[0025] Specifically, from the viewpoints of performance, durability, etc., those having a latent heat temperature range within the range of 48°C or higher and 81°C or lower are preferable. If the latent heat temperature range is less than 48°C, the durability characteristics may deteriorate due to volatilization and oxidative degradation of the heat storage material at high temperatures, and there is a concern that the thermal conductivity and heat storage amount of the heat storage and heat transfer material may decrease when held at a high temperature for a long time. If the latent heat temperature range is greater than 81°C, the battery may become hot even at a temperature below the melting point of the heat storage material, and the characteristics may deteriorate. From these points as well, normal paraffin and microcrystalline wax are suitable as latent heat storage materials.

[0026] These latent heat storage materials may contain any fatty acid. Examples of fatty acids include myristic acid with a melting point of 54°C, palmitic acid with a melting point of 63°C, docosanoic acid with a melting point of 82°C, and the like.

[0027] The heat-conductive filler is for propagating the heat of the object to be cooled or the heat stored in the heat storage material toward the low-temperature side. The heat-conductive filler may be in the form of powder or particles that can be uniformly kneaded with the base resin. Further, when applying the heat storage and heat conduction material of the present embodiment to a heat dissipation medium such as an electrical component or a semiconductor element, it is preferable to use a material having insulation properties as the heat-conductive filler. By using an insulating heat-conductive filler, the heat storage and heat conduction material can also have insulation properties.

[0028] The heat-conductive filler may be, for example, ceramic particles having insulation properties. Specifically, metal oxides such as aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, beryllium oxide, copper oxide, zirconium oxide, calcium oxide, etc., and metal nitrides such as boron nitride, aluminum nitride, silicon nitride, etc. can be mentioned. Among these, aluminum oxide and boron nitride are preferable as the heat-conductive filler. In particular, aluminum oxide is particularly preferable as a constituent component of the heat-conductive filler in terms of being inexpensive and easily available. In the present embodiment, aluminum oxide (alumina) is used as the heat-conductive filler. Note that the heat-conductive filler in the present embodiment refers to a filler having a higher thermal conductivity than the base resin.

[0029] Also, as the heat-conductive filler, it is preferable to use particulate ones having a specific surface area of 0.5 m 2 / g or more and an average particle diameter (d50) of 40 μm or less. When the specific surface area of the heat-conductive filler is less than 0.5 m 2 / g, there is a concern that the heat storage and heat conduction material may fluidize and flow out from the placement location in the temperature range where the heat storage material is at or above the melting point. Also, there is a concern that the heat-conductive filler may precipitate and the heat storage and heat conduction material may become non-uniform. Although there is no particular limitation on the upper limit of the specific surface area of the heat-conductive filler, the specific surface area of the heat-conductive filler is desirably 400 m 2 / g or less.

[0030] On the one hand, when the average particle diameter (d50) of the thermally conductive filler measured by a laser diffraction scattering type particle size distribution measuring device (MT3300EXII: manufactured by Microtrac Bel Corporation) exceeds 40 μm, there is a concern that the heat storage material may separate from the heat storage thermally conductive material in the temperature range where the heat storage material is above its melting point. In addition, there is a concern that the thermally conductive filler may precipitate and the heat storage thermally conductive material may become non-uniform. Although there is no particular limitation on the lower limit of the average particle diameter of the thermally conductive filler, it is desirable that the average particle diameter of the thermally conductive filler be 0.005 μm or more.

[0031] The compounding ratio of the thermally conductive filler is adjusted so that when the heat storage material is 90 parts by mass, the thermally conductive filler accounts for 20 parts by mass or more. When the heat storage material is 90 parts by mass and the thermally conductive filler is less than 20 parts by mass, there is a concern that the heat storage material may separate from the heat storage thermally conductive material in the temperature range where the heat storage material is above its melting point. It is desirable that the thermally conductive filler be 3000 parts by mass or less when the heat storage material is 90 parts by mass.

[0032] The oil gelling agent and the two-component curable base resin are shape-retaining components for preventing the heat storage material from melting and flowing and maintaining the shape when the heat storage thermally conductive material reaches a temperature above its melting point. Specific examples of the oil gelling agent include fatty acid metal salts or mixtures of fatty acid metal salts and fatty acids. Examples of the fatty acid metal salts include 2-ethylhexanoate. Examples of 2-ethylhexanoate include aluminum 2-ethylhexanoate, zinc 2-ethylhexanoate, iron 2-ethylhexanoate, cobalt 2-ethylhexanoate, and manganese 2-ethylhexanoate. Among these, in this embodiment, aluminum 2-ethylhexanoate (Al(-OH)[-OCOCH(C2H5)C4H9]2) with excellent shape-retaining properties is used. The fatty acid to be mixed with the fatty acid metal salt may be any monocarboxylic acid having a carboxy group in the hydrocarbon chain, and for example, 2-ethylhexanoic acid can be mentioned.

[0033] In this embodiment, the oil gelling agent may be added in a range of, for example, 1% by mass or more and 20% by mass or less when the heat storage material is 100 parts by mass. By adding such an oil gelling agent, when the temperature becomes equal to or higher than the melting point, the heat storage material is prevented from melting and flowing, the deterioration of the heat storage and heat conductive material is suppressed, and for example, a decrease in the heat storage amount due to changes over time can be suppressed.

[0034] The two-component curable base resin is a resin that solidifies by mixing two liquid resin components and mainly solidifies by polymerization. As one material of the two-component curable base resin, a hydroxyl group-containing compound such as a polybutadiene polyol composition or a polyester polyol composition can be mentioned. As the other material of the two-component curable base resin, an isocyanate compound or the like can be mentioned. By mixing these two components of resin, a resin which is a shape-retaining component is produced by a polymerization reaction.

[0035] It is also preferable that the heat storage and heat conductive material of this embodiment further contains a dispersant. The dispersant prevents aggregation of the heat conductive filler constituting the heat storage and heat conductive material, for example, ceramic particles, and appropriately disperses the ceramic particles in the heat storage and heat conductive material. Such a dispersant stabilizes the ceramic particles in the heat storage and heat conductive material by means of the repulsion between particles due to charge and the physical separation between particles caused by the attachment of the dispersant component to the outer peripheral surface of the ceramic particles, so that the dispersed ceramic particles do not re-aggregate.

[0036] Examples of such dispersants include sodium polycarboxylate, ammonium polycarboxylate, alkylamine salt of polycarboxylic acid, amino alcohol polyphosphate, nonionic surfactants, and the like. In this embodiment, a nonionic surfactant was used as the dispersant.

[0037] Nonionic surfactants are surfactants with hydrophilic groups that do not ionize when dispersed in water. Examples of nonionic surfactants include, as ester types, glycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, etc., in which polyhydric alcohols such as glycerin, sorbitol, and sucrose (saccharose) are ester-bonded to fatty acids. Also, as ether types, polyoxyethylene alkyl phenyl ethers of the alkylphenol type, etc., can be mentioned. Further, as ester-ether types, polyoxyethylene sorbitan fatty acid esters of the fatty acid type, etc., can be mentioned.

[0038] It is also preferable that the heat storage type thermal conductive material of the present embodiment further contains an anti-settling agent. The anti-settling agent prevents the settlement of the thermally conductive filler constituting the heat storage type thermal conductive material and disperses it uniformly. As the anti-settling agent, for example, fumed silica can be used.

[0039] It is preferable that the heat storage type thermal conductive material having the above configuration has a viscosity of 500 Pa·s or less before curing. If the viscosity before curing exceeds 500 Pa·s, there is a concern that the fluidity of the heat storage type thermal conductive material becomes too low and the heat storage type thermal conductive material cannot be filled into fine gaps.

[0040] According to the heat storage type thermal conductive material having the above configuration, by combining a heat storage material having a melting point of 48°C or higher, such as microcrystalline wax, with an oil gelling agent or a two-component curable base resin, a heat storage type thermal conductive material with a fillable viscosity without generating cavities and capable of suppressing a decrease in the heat storage amount due to changes over time can be obtained.

[0041] As described above, one embodiment of the present invention has been explained. However, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Example

[0042] The effect of the heat storage thermal conductive material of the present invention was verified. The constituent components are as follows. (Example 1 and 3 of the present invention) · Heat storage substance: n-paraffin (Wax145: manufactured by Nippon Seiro Co., Ltd.) molecular weight 350 - 550, melting point 63°C · Thermal conductive filler: alumina (AL43A: manufactured by Sumitomo Chemical Co., Ltd.) · Shape-retaining component: two-component curable urethane resin (R15HT: manufactured by Idemitsu Kosan Co., Ltd. and MR200: manufactured by Tosoh Corporation) · Anti-settling agent: fumed silica (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd.) · Dispersant: nonionic surfactant (SN Dispersant 9228: manufactured by San Nopco Ltd.)

[0043] (Example 2 of the present invention) · Heat storage substance: n-paraffin (Wax115: manufactured by Nippon Seiro Co., Ltd.) molecular weight 350 - 550, melting point 48°C · Thermal conductive filler: alumina (AL43A: manufactured by Sumitomo Chemical Co., Ltd.) · Shape-retaining component: two-component curable urethane resin (R15HT: manufactured by Idemitsu Kosan Co., Ltd. and MR200: manufactured by Tosoh Corporation) · Anti-settling agent: fumed silica (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd.) · Dispersant: nonionic surfactant (SN Dispersant 9228: manufactured by San Nopco Ltd.)

[0044] (Example 4 of the present invention) · Heat storage material: Microcrystalline wax (Hi-mic-2045: manufactured by Nippon Seiro Co., Ltd.), molecular weight 500 - 800, melting point 70°C · Thermal conductivity filler: Hexagonal boron nitride (HFL: manufactured by Air Products Japan Co., Ltd.) · Shape-retaining component: Aluminum 2-ethylhexanoate (Octop Al T: manufactured by Hop Pharm Co., Ltd.) · Anti-settling agent: Fumed silica (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd.) · Dispersant: Nonionic surfactant (SN Dispersant 9228: manufactured by Sannopco Co., Ltd.)

[0045] (Comparative Example 1) · Heat storage material: Docosane (manufactured by Sasol Chemicals Japan Co., Ltd.), molecular weight 311, melting point 44°C · Thermal conductivity filler: Alumina (AL43A: manufactured by Sumitomo Chemical Co., Ltd.) · Shape-retaining component: Two-component curable urethane resin (RT15HT: manufactured by Idemitsu Kosan Co., Ltd. and MR200: manufactured by Tosoh Corporation) · Anti-settling agent: Fumed silica (Aerosil R972: manufactured by Nippon Aerosil Co., Ltd.) · Dispersant: Nonionic surfactant (SN Dispersant 9228: manufactured by Sannopco Co., Ltd.)

[0046] The above-described components were blended at the ratios (parts by mass) shown in Table 1 below to prepare the heat storage thermal conductive materials (samples) of the inventive examples and comparative examples. Then, for each heat storage thermal conductive material, the initial thermal conductivity, initial heat storage amount, thermal conductivity and heat storage amount after maintaining at 120°C for 24 hours, and thermal conductivity and heat storage amount after maintaining at 120°C for 240 hours were confirmed. These results are shown in Table 1.

[0047]

Table 1

[0048] According to the results shown in Table 1, in Invention Examples 1 to 4 of the present invention using a heat storage material with a melting point of 48°C or higher, the decrease after 24 hours at 120°C all remained at 20% or less. On the other hand, in the comparative example using docosane with a melting point of 44°C as the heat storage material, the decrease in the heat storage amount reached 75% after 24 hours at 120°C, and the deterioration due to the change over time in a high-temperature environment was large. Therefore, the deterioration-resistant characteristics of Invention Examples 1 to 4 of the present invention using a heat storage material with a melting point of 48°C or higher were confirmed.

Claims

Claim 1 A heat storage thermal conductive material comprising a heat storage material, a thermal conductive filler, and an oil gelling agent or a two-component curable base resin, wherein the heat storage material has a melting point of 48°C or higher. Claim 2 The heat storage thermal conductive material according to claim 1, wherein the heat storage material has an average molecular weight of 400 or higher. Claim 3 The heat storage thermal conductive material according to claim 1, wherein the heat storage material is microcrystalline wax. Claim 4 The heat storage thermal conductive material according to any one of claims 1 to 3, wherein the oil gelling agent contains a fatty acid metal salt or a mixture of a fatty acid metal salt and a fatty acid. Claim 5 The heat storage thermal conductive material according to claim 4, wherein the oil gelling agent is aluminum 2-ethylhexanoate.

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