heat storage material composition

Abstract

To provide a heat storage material composition which enables rapid heat storage and heat dissipation and can be stably used repeatedly.SOLUTION: There is provided a heat storage material composition which comprises a solid-liquid phase change material for performing a phase change between a solid and a liquid in a predetermined temperature range, water, a nucleating material, a graphite powder, a fine powder which has a specific gravity close to that of water, is hardly wettable with water and has high thermal conductivity. Further, a hydrophilic thickener is preferably added in a heat storage material composition. Furthermore, a melting point adjuster may be appropriately added in a heat storage material composition. Thus, heat storage and heat dissipation are enabled and stable repeated use is possible. The heat storage material composition is useful for a heat storage material in various fields.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heat storage material composition. [Background technology]

[0002] Conventionally, heat storage materials (latent heat storage materials, sensible heat storage materials, heat storage materials, etc.) that store heat (heat absorption) and release heat (heat release) by utilizing a phase change (solid-liquid phase change) between solid and liquid within a predetermined temperature range have been known. Heat storage materials are widely used in various fields, for example, in air conditioning systems for buildings (houses, office buildings, etc.) that require a large amount of cold or hot heat, and in waste heat recovery systems for factories.

[0003] As a technology relating to heat storage materials, for example, Japanese Patent Laid-Open Publication No. 11-323319 (Patent Document 1) discloses a latent heat storage material composition in which sodium acetate trihydrate is blended with hydrophilic fumed silica, hydrophilic fumed alumina, and calcium salt as phase separation inhibitors, which is said to prevent phase separation even when subjected to repeated heat cycles of melting and solidification over a long period of time.

[0004] Japanese Patent Laid-Open Publication No. 2000-63810 (Patent Document 2) discloses a latent heat storage material composition comprising 100 parts by weight of calcium chloride hydrate having the general formula CaCl·nH₂O (where n is 4.5 to 6.5), 10 to 35 parts by weight of a polyhydric alcohol, 1 to 30 parts by weight of one or more alkali metal or alkaline earth metal halides (excluding strontium chloride and barium chloride), and 0.1 to 20 parts by weight of strontium chloride and / or barium chloride, and optionally 0.1 to 20 parts by weight of one or more fibrous minerals such as attapulgite, wollastonite, or sepiolite. The composition has a relatively low freezing point (5 to 25°C) and is therefore suitable for use as a heat storage material in air-conditioning heating and cooling systems.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 2015-218212 (Patent Document 3) discloses a latent heat storage material composition containing a latent heat storage material (A) as the main component, and a melting point adjuster (B), a phase separation inhibitor (C) having microcrystal formation, supercooling prevention, and thickening effects, and / or a melting point adjuster (B') having microcrystal formation, and a supercooling inhibitor (D) as essential components in predetermined amounts, the latent heat storage material composition being obtained by blending the latent heat storage material with the melting point adjuster, phase separation inhibitor, and supercooling inhibitor in predetermined amounts, melting, mixing, and cooling. This composition is composed primarily of aggregates of fine particles that are flexible or fluid at room temperature and pressure, and does not undergo phase separation or supercooling, allowing for excellent, stable repeated heat storage and heat release, and can also be used as a flowable heat transfer medium.

[0006] Furthermore, Japanese Patent Laid-Open Publication No. 2016-108535 (Patent Document 4) discloses a heat storage material composition containing a sugar alcohol and a supercooling stabilizer, wherein the supercooling stabilizer is (i) a salt that has a solubility of 9 g or more in 100 mL of water at 20° C. and is a monovalent anion, (ii) a polymer whose monomer is the salt, or (iii) a polymer with a molecular weight of 7,000 to 4,000,000 and whose monomer is an alcohol that has a solubility of 9 g or more in 100 mL of water at 20° C. This is said to enable the supercooled state to be stably maintained at room temperature or a temperature close to room temperature.

[0007] For example, in International Publication No. 2007 / 099798 (Patent Document 5), the applicant has disclosed a heat storage material composition containing calcium chloride as a main component, strontium chloride and barium chloride as nucleating agents, and a cellulose-based material as a thickener, which is said to be resistant to deterioration and has high durability and heat resistance even when repeatedly exposed to high temperatures exceeding room temperature.

[0008] Furthermore, in JP 2019-137854 A (Patent Document 6), the present applicant has disclosed a heat storage material composition containing a solid-liquid phase change material that undergoes a phase change between solid and liquid within a predetermined temperature range, water, a nucleating material whose main component is strontium chloride, and graphite powder, which is said to achieve a rapid solid-liquid phase change and enable repeated use. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-323319 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-63810 [Patent Document 3] Japanese Patent Application Publication No. 2015-218212 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-108535 [Patent Document 5] International Publication No. 2007 / 099798 [Patent Document 6] Japanese Patent Application Publication No. 2019-137854 Summary of the Invention [Problem to be solved by the invention]

[0010] The heat storage material compositions that utilize the above-mentioned solid-liquid phase change usually have a low overall thermal conductivity, making it difficult to quickly store heat from the surrounding environment or release heat to the surrounding environment, and there is a problem that it takes a long time to store and release heat.

[0011] The present applicant has attempted to shorten the heat storage and heat release time by adding graphite powder with high thermal conductivity to the heat storage material composition, as in the technique described in Patent Document 6.

[0012] However, although graphite powder has good thermal conductivity, the specific gravity of graphite powder is higher than that of water, so even if graphite powder is added to a heat storage material composition, the graphite powder settles to the bottom of the heat storage material composition, leaving no graphite powder in the upper part of the heat storage material composition, which makes it difficult to improve the overall thermal conductivity of the heat storage material composition. These problems cannot be solved by the techniques described in Patent Documents 1 to 6 above.

[0013] Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a heat storage material composition that enables rapid heat storage and release and can be used repeatedly and stably. [Means for solving the problem]

[0014] The heat storage material composition of the present invention contains a solid-liquid phase change material that undergoes a phase change between solid and liquid within a predetermined temperature range, water, a nucleating material, graphite powder, and a fine powder that has a specific gravity close to that of water, is not easily wetted by water, and has high thermal conductivity. [Effects of the Invention]

[0015] According to the present invention, rapid heat storage and release is possible, and stable repeated use is also possible. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a table showing ingredients of the heat storage material compositions of Example 1 and Comparative Examples 1-2. [Figure 2] 1 is a graph showing the temperature changes of the heat storage material compositions of Example 1 and Comparative Example 1-2 during the fifth heat cycle. [Figure 3] 1 is a table showing ingredients of the heat storage material compositions of Examples 2-3 and Comparative Example 1. [Figure 4] 1 is a graph showing the temperature changes of the heat storage material compositions of Example 2-3 and Comparative Example 1 during the sixth heat cycle. [Figure 5] 1 is a table showing ingredients of the heat storage material compositions of Examples 3-4 and Comparative Example 1. [Figure 6]1 is a graph showing the temperature changes of the heat storage material compositions of Examples 3-4 and Comparative Example 1 during the sixth heat cycle. [Figure 7] 1 is a table showing ingredients of the heat storage material compositions of Examples 4 to 7 and Comparative Example 1. [Figure 8] 1 is a graph showing the temperature changes of the heat storage material compositions of Examples 4-7 and Comparative Example 1 during the third heat cycle. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings to help understand the present invention. Note that the following embodiment is an example of the present invention and is not intended to limit the technical scope of the present invention.

[0018] The inventors have confirmed that in a heat storage material composition containing a solid-liquid phase change material that undergoes a phase change between solid and liquid within a predetermined temperature range, water, a nucleating material, and graphite powder, the rate of heat storage and heat release is improved to a certain extent due to the high thermal conductivity of the graphite powder (the thermal conductivity of graphite is approximately 2000 W / (m·K), and the thermal conductivity of copper is approximately 400 W / (m / K)). Here, graphite means graphite.

[0019] However, the specific gravity of the heat storage material composition (aqueous solution) is approximately 1.5, and the specific gravity of the graphite powder is approximately 2.0, which is higher than the specific gravity of water. Therefore, the graphite powder settles to the bottom of the heat storage material composition, and no graphite powder is present in the upper part of the heat storage material composition, which is found to be unlikely to lead to an improvement in the overall thermal conductivity of the heat storage material composition.

[0020] The inventor has been researching the above-mentioned heat storage material composition for many years, and has focused on fine powder that has a specific gravity close to that of water, is not easily wetted by water, and has high thermal conductivity, and has completed the present invention based on the examples described below.

[0021] That is, the heat storage material composition according to the present invention contains a solid-liquid phase change material that undergoes a phase change between solid and liquid within a predetermined temperature range, water, a nucleating material, graphite powder, and a fine powder that has a specific gravity close to that of water, is resistant to water wettability, and has high thermal conductivity, thereby enabling rapid heat storage and release, and stable repeated use.

[0022] In other words, by adding fine powder, the fine powder does not settle to the bottom of the heat storage material composition but remains at the top of the heat storage material composition and is uniformly dispersed, thereby increasing the thermal conductivity of the upper part of the heat storage material composition. On the other hand, by adding graphite powder to the heat storage material composition, the graphite powder remains at the bottom of the heat storage material composition and is uniformly dispersed, thereby increasing the thermal conductivity of the lower part of the heat storage material composition. In this way, the combination of graphite powder and fine powder can increase the overall thermal conductivity of the heat storage material composition, making it possible to increase the heat storage and heat release rate of the heat storage material composition.

[0023] Furthermore, even if the heat storage material composition repeatedly melts and solidifies in a heat cycle in which the temperature is lowered from a high temperature to a low temperature and then raised back to a high temperature, the graphite powder and fine powder act as a medium for heat conduction to the solid-liquid phase change material, ensuring stable heat storage and release by the heat storage material composition and suppressing supercooling, making it possible to use the composition repeatedly over a long period of time.

[0024] The solid-liquid phase change material is not particularly limited, but examples include calcium chloride, sodium acetate, and sodium hydrogen phosphate. Calcium chloride is a component that undergoes a phase change between calcium chloride hexahydrate crystals (solid) and calcium chloride water liquid (liquid) in the thermal storage material composition as the temperature of the surrounding environment changes. The calcium chloride in the thermal storage material composition can be anhydrous (CaCl2) or its hydrate {CaCl2·nH2O (n = 1 to 6)}. Calcium chloride dihydrate is particularly preferred because it is relatively easy to obtain. The amount of water added to the thermal storage material composition is the amount required to generate calcium chloride hexahydrate. This amount varies slightly depending on the amount of water added due to the addition of other components, but is generally approximately 6 moles per mole of CaCl2. When a hydrate is used as calcium chloride, the amount of water is approximately 6 moles, including the water of crystallization in the hydrate.

[0025] Other solid-liquid phase change materials also undergo a phase change similar to that of calcium chloride within a predetermined temperature range, although the temperature range for the phase change is different. These types of solid-liquid phase change materials may be appropriately combined.

[0026] The type of nucleating material is not particularly limited, but examples include barium chloride (BaCl2), strontium chloride (SrCl2), sodium dihydrogen phosphate (NaH2PO4), barium sulfide (BaS), etc. Here, barium chloride, strontium chloride, sodium dihydrogen phosphate, and barium sulfide form hydrates, so for example, their anhydrides or hydrates of these compounds may be used. Furthermore, other nucleating materials such as disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O) and fly ash may also be included.

[0027] The type of graphite in the graphite powder is not particularly limited, but examples include scaly graphite, amorphous graphite, artificial graphite, coke, expanded graphite, spherical graphite, specially treated graphite, spherical graphite, carbon fiber, and carbon nanotubes. It is also preferable that the graphite powder be subjected to a hydrophilic surface treatment to improve dispersibility in an aqueous solution containing a solid-liquid phase change material. These types of graphite powder may be combined as appropriate.

[0028] Furthermore, there is no particular limitation on the average particle size of the graphite powder, but for example, the average particle size is preferably 5 μm to 20 μm, and more preferably 5 μm to 15 μm.

[0029] Here, the type of fine powder is not particularly limited, but an example is carbon black. Carbon black has the same components as graphite powder, is resistant to water wetting, and has excellent thermal conductivity. Furthermore, although the specific gravity of carbon black is approximately 1.8 to 1.9, the apparent specific gravity of carbon black in fine powder form is extremely low, at approximately 0.04 to 0.08. Therefore, when carbon black is added as a fine powder to a heat storage material composition, the carbon black remains in the upper part of the heat storage material composition and is uniformly dispersed, thereby increasing the thermal conductivity of the upper part of the heat storage material composition.

[0030] Here, carbon black refers to a spherical or chain-like conductive substance in the form of fine powder produced by gas-phase thermal decomposition or incomplete combustion of natural gas or hydrocarbon gas. There are no particular limitations on the type of carbon black, but examples include acetylene black, furnace black, thermal black, and channel black. These types of carbon black may also be used in combination.

[0031] Although there is no particular limitation on the average particle size of the carbon black, the average particle size is preferably 10 to 100 nm, and more preferably 20 to 90 nm. Here, the average particle size of the carbon black can be measured, for example, by employing a photon correlation method (dynamic light scattering method) or a laser diffraction / scattering method (static light scattering method).

[0032] Although there are no particular limitations on the dibutyl phthalate (DBP) oil absorption of carbon black, the DBP oil absorption is preferably 30 ml / 100 g to 200 ml / 100 g, and more preferably 50 ml / 100 g to 150 ml / 100 g. The DBP oil absorption of carbon black can be measured, for example, in accordance with JIS K 6217-4.

[0033] In addition to carbon black, the fine powder may be, for example, carbon fiber that has been crushed and the crushed material has been subjected to a surface treatment to impart water repellency, or plastic or metal that has been crushed and the crushed material has been subjected to a surface treatment to impart water repellency.

[0034] Furthermore, a higher total concentration of the graphite powder and the fine powder is preferable because the graphite powder and the fine powder in the heat storage material composition come into contact with each other to form a graphite powder-fine powder network, thereby increasing the thermal conductivity of the entire heat storage material composition, but if the total concentration of the graphite powder and the fine powder is too high, it will hinder the melting and solidification of the solid-liquid phase change material. Therefore, for example, the total concentration of the graphite powder and the fine powder is preferably 1 wt% to 10 wt% of the total heat storage material composition, and more preferably 2 wt% to 8 wt% of the total heat storage material composition.

[0035] Furthermore, there is no particular limitation on the concentration of the graphite powder, but for example, it is preferably in the range of 0.5% by weight to 5.0% by weight relative to the total heat storage material composition. Furthermore, there is no particular limitation on the concentration of the fine powder, but for example, it is preferably in the range of 0.5% by weight to 5.0% by weight relative to the total heat storage material composition. Furthermore, there is no particular limitation on the mixing ratio of the graphite powder to the fine powder, but for example, it is preferably 1.0:0.2 to 1.0:5.0 by weight, and more preferably 1.0:0.5 to 1.0:2.5 by weight. Furthermore, it is preferable that the concentration of the fine powder is equal to or higher than the concentration of the graphite powder.

[0036] Furthermore, it is preferable to further add a hydrophilic thickener to the heat storage material composition. By adding a hydrophilic thickener, the heat storage material composition becomes compatible with water, increasing the viscosity of the entire heat storage material composition. Even if there is a slight difference in the specific gravity of the heat storage material composition, the specific gravity of the graphite powder, and the specific gravity of the fine powder, segregation of the graphite powder and the fine powder in the heat storage material composition is suppressed, and the graphite powder is uniformly dispersed below the heat storage material composition, and the fine powder can be fixed in a uniformly dispersed state above the heat storage material composition. Therefore, it is possible to maintain a high thermal conductivity of the entire heat storage material composition, accelerate the solid-liquid phase change of the solid-liquid phase change material, and increase the rate of melting and solidification of the solid-liquid phase change material.

[0037] The type of hydrophilic thickener is not particularly limited, and examples thereof include water-soluble copolymers such as PEG / PPG, hydroxyethylcelluloses such as carboxymethylcellulose and hypromellose (methylhydroxyethylcellulose), hydroxypropylmethylcellulose, cellulose ethers, cellulose derivatives, cellulose nanofibers, polyethylene glycol, carboxyvinyl polymers, acrylic acid / alkyl methacrylate copolymers, crosslinked acrylic acid-based water-soluble polymers such as polyacrylates, xanthan gum, diutan gum, polysaccharides, sodium polyacrylate, finely powdered silica, silica flour, diatomaceous earth fine powder, glycerin, agar, etc. These types of thickeners may also be used in combination as appropriate.

[0038] Furthermore, the thickener has an affinity with water in the heat storage material composition to form a network and increase viscosity, so it is effective even at a low concentration, but if the thickener concentration is too high, it will interfere with the melting and solidification of the solid-liquid phase change material. Therefore, for example, the concentration of the thickener is preferably 0.1 wt% to 3.0 wt%, and more preferably 0.1 wt% to 2.0 wt%, of the total heat storage material composition. Here, when the fine powder is carbon black, the carbon black itself has a thickening effect, so it is not necessary to add a hydrophilic thickener.

[0039] Furthermore, a melting point adjuster may be added to the heat storage material composition as appropriate. Here, the melting point adjuster refers to a lowering agent that lowers the freezing point (melting point) of the solid-liquid phase change material and changes the latent heat generation temperature. Examples include ammonium bromide (NH4Br) and ammonium chloride (NH4Cl). Specifically, the latent heat generation temperature of calcium chloride hexahydrate is approximately 30°C, which is its freezing point. However, depending on the intended use of the heat storage material, it may be desirable to lower the freezing point to a temperature lower than approximately 30°C, such as around 20°C. In such cases, adding a melting point adjuster to the heat storage material composition can intentionally lower the freezing point of the solid-liquid phase change material in the heat storage material composition, thereby making it suitable for the intended use of the heat storage material. The concentration of the melting point adjuster is not particularly limited, and is set, for example, to 1.0% to 20.0% by weight based on the total heat storage material composition.

[0040] Furthermore, there are no particular limitations on how the heat storage material composition can be used, but one example is a method in which the heat storage material composition is filled into a container and sealed, and used as a heat storage material. Because the heat storage material composition has high thermal conductivity, there are no particular limitations on the shape of the container, and the design can be changed appropriately to suit the application, for example, to a plate shape, a cylinder shape, etc.

[0041] Furthermore, there are no particular limitations on the uses of the heat storage material composition, and it can be used, for example, as a heat storage material in air conditioning and heating equipment, factory exhaust heat recovery equipment, agricultural equipment such as vinyl greenhouses, electronic devices such as terminal devices and mobile terminal devices, location identification devices used in automobiles, buses, etc. The heat storage material can be used by storing heat from the surrounding environment during the day and releasing it into the surrounding environment at night, thereby making effective use of thermal energy. [Example]

[0042] Examples and comparative examples of the present invention will be specifically described below, but the application of the present invention is not limited to these examples.

[0043] Example 1 The heat storage material composition was manufactured by adjusting the solid-liquid phase change material (calcium chloride dihydrate) (CaCl2·2H2O) to 54.0 wt%, the melting point adjuster (ammonium bromide) (NH4Br) to 10 wt%, the water to 25.5 wt%, the nucleating material to 4.5 wt%, the graphite powder to 2.5 wt%, the carbon black to 2.5 wt%, and the hydrophilic thickener to 1.0 wt%. By adding the melting point adjuster, the freezing point (melting point) of the heat storage material composition was set to 18°C.

[0044] Here, the nucleating material used was a mixture of barium chloride dihydrate (BaCl2·2H2O), strontium chloride dihydrate (SrCl2·2H2O), and sodium dihydrogen phosphate (NaH2PO4) in appropriate proportions. The graphite powder used was flaky graphite with an average particle size of 10.3 μm. Furnace black was used as the carbon black. The hydrophilic thickener used was a mixture of cellulose ether and polyethylene glycol in appropriate proportions. This manufactured heat storage material composition was designated Example 1.

[0045] <Comparative Example 1> A heat storage material composition was produced in the same manner as in Example 1, except that the graphite powder, carbon black, and hydrophilic thickener were not added and the amount of water added was adjusted in the heat storage material composition of Example 1. This produced heat storage material composition was designated Comparative Example 1.

[0046] <Comparative Example 2> A heat storage material composition was produced in the same manner as in Example 1, except that no carbon black was added and the amount of water added was adjusted in the heat storage material composition of Example 1. This produced heat storage material composition was designated Comparative Example 2. Note that Fig. 1 shows ingredient tables for the heat storage material compositions of Example 1 and Comparative Examples 1-2.

[0047] <Evaluation method> For the heat storage material compositions of Example 1 and Comparative Example 1-2, the temperature change of each heat storage material composition was measured by repeating a heat cycle a predetermined number of times in which the ambient temperature of each heat storage material composition was lowered from approximately 35°C to approximately 5°C over a predetermined time (cooling) and then raised again from approximately 5°C to 35°C (heating).

[0048] <Evaluation results> A graph of the temperature changes of the heat storage material compositions of Example 1 and Comparative Example 1-2 during the fifth heat cycle is shown in Figure 2. As shown in Figure 2, it can be seen that during cooling in the heat cycle, the heat storage material composition of Example 1 had a higher cooling temperature per unit time and a faster cooling rate than the heat storage material composition of Comparative Example 1-2.

[0049] On the other hand, it can be seen that during heating in the heat cycle, the heat storage material composition of Example 1 has a higher heating temperature per unit time, a faster heating rate, and a faster rise in the graph compared to the heat storage material composition of Comparative Example 1-2.

[0050] <Example 2> A heat storage material composition was produced in the same manner as in Example 1, except that the concentration of graphite powder was 1.0 wt %, the concentration of carbon black was 1.0 wt %, and the amount of water added was adjusted in the heat storage material composition of Example 1. This produced heat storage material composition was designated Example 2.

[0051] Example 3 A heat storage material composition was produced in the same manner as in Example 1, except that in the heat storage material composition of Example 1, the concentration of graphite powder was set to 5.0 wt%, the concentration of carbon black was set to 1.0 wt%, and the amount of water added was adjusted. This produced heat storage material composition was designated Example 3. Note that Figure 3 shows ingredient tables for the heat storage material compositions of Examples 2-3 and Comparative Example 1. Examples 2-3 and Comparative Example 1 were also evaluated using the same evaluation methods as described above.

[0052] <Evaluation results> Figure 4 shows a graph of the temperature changes of the heat storage material compositions of Example 2-3 and Comparative Example 1 during the sixth heat cycle. Figure 4 also shows the ambient temperature and a photograph of the appearance of the heat storage material composition of Example 2-3. As shown in Figure 4, it can be seen that during cooling in the heat cycle, the heat storage material composition of Example 2-3 had a higher cooling temperature per unit time and a faster cooling rate than the heat storage material composition of Comparative Example 1.

[0053] On the other hand, it can be seen that during heating in the heat cycle, the heat storage material composition of Example 2-3 had a higher heating temperature per unit time, a faster heating rate, and a faster rise in the graph compared to the heat storage material composition of Comparative Example 1. It can also be seen that no separation of water was observed in any of the heat storage material compositions of Example 2-3, and that the water was dispersed uniformly.

[0054] Furthermore, the heat storage material composition of Example 3 had a higher cooling temperature per unit time and a faster cooling rate than the heat storage material composition of Example 2. Furthermore, the heat storage material composition of Example 3 had a higher heating temperature per unit time and a faster heating rate than the heat storage material composition of Example 2. In other words, it was found that the cooling rate and heating rate improved as the concentration of graphite powder increased.

[0055] Example 4 A heat storage material composition was produced in the same manner as in Example 1, except that in the heat storage material composition of Example 1, the concentration of graphite powder was set to 1.0 wt%, the concentration of carbon black was set to 5.0 wt%, and the amount of water added was adjusted. This produced heat storage material composition was designated Example 4. Note that Figure 5 shows ingredient tables for the heat storage material compositions of Examples 3-4 and Comparative Example 1. Examples 3-4 and Comparative Example 1 were also evaluated using the same evaluation methods as described above.

[0056] <Evaluation results> Figure 6 shows a graph of the temperature changes of the heat storage material compositions of Examples 3-4 and Comparative Example 1 during the sixth heat cycle. Figure 6 also shows the ambient temperature and a photograph of the appearance of the heat storage material composition of Example 4. As shown in Figure 6, it can be seen that during cooling in the heat cycle, the heat storage material composition of Examples 3-4 had a higher cooling temperature per unit time and a faster cooling rate than the heat storage material composition of Comparative Example 1.

[0057] On the other hand, it can be seen that during heating in the heat cycle, the heat storage material compositions of Examples 3-4 had a higher heating temperature per unit time, a faster heating rate, and a faster rise in the graph compared to the heat storage material composition of Comparative Example 1. It can also be seen that water separation was not observed in the heat storage material composition of Example 4, and that the water was dispersed uniformly. In other words, it was found that, similar to graphite powder, the cooling rate and heating rate improved as the carbon black concentration increased.

[0058] <Example 5> A heat storage material composition was produced in the same manner as in Example 1, except that in the heat storage material composition of Example 1, the concentration of graphite powder was 2.5% by weight, the carbon black was thermal black, the concentration of carbon black was 2.5% by weight, no hydrophilic thickener was added, and the amount of water added was adjusted. This produced heat storage material composition was designated Example 5.

[0059] Example 6 A heat storage material composition was produced in the same manner as in Example 1, except that in the heat storage material composition of Example 1, the concentration of graphite powder was 5.0% by weight, the carbon black was thermal black, the concentration of carbon black was 1.0% by weight, no hydrophilic thickener was added, and the amount of water added was adjusted. This produced heat storage material composition was designated Example 6.

[0060] Example 7 A heat storage material composition was produced in the same manner as in Example 1, except that in the heat storage material composition of Example 1, the concentration of graphite powder was 1.0 wt%, thermal black was used as the carbon black, the concentration of carbon black was 5.0 wt%, no hydrophilic thickener was added, and the amount of water added was adjusted. This produced heat storage material composition was designated Example 7. Note that Figure 7 shows ingredient tables for the heat storage material compositions of Examples 4-7 and Comparative Example 1. Examples 4-7 and Comparative Example 1 were also evaluated using the same evaluation methods as described above.

[0061] <Evaluation results> Figure 8 shows a graph of the temperature changes of the heat storage material compositions of Examples 4-7 and Comparative Example 1 during the third heat cycle. The ambient temperature is also shown in Figure 8. As shown in Figure 8, it can be seen that during cooling in the heat cycle, the heat storage material compositions of Examples 4-7 had a higher cooling temperature per unit time and a faster cooling rate than the heat storage material composition of Comparative Example 1.

[0062] On the other hand, it can be seen that during heating in the heat cycle, the heat storage material compositions of Examples 4-7 had a higher heating temperature per unit time, a faster heating rate, and a faster rise in the graph compared to the heat storage material composition of Comparative Example 1. In other words, it was found that regardless of the type of carbon black, the combination of graphite powder and carbon black resulted in good cooling and heating rates. Furthermore, due to the thickening effect of the carbon black itself, it was possible to achieve uniform dispersion without adding a hydrophilic thickener.

[0063] This shows that adding graphite powder and carbon black to the heat storage material composition enables rapid heat storage and release, and also enables stable repeated use.

[0064] In the examples and comparative examples of the present invention, evaluations were performed by adding ammonium bromide as a melting point adjuster so that the solidification point (melting point) of the heat storage material composition would be 18° C., but the same effects were obtained even without adding a melting point adjuster. Also, the same effects were obtained even when the phosphorus graphite in the graphite powder was replaced with other types of graphite powder. [Industrial Applicability]

[0065] As described above, the heat storage material composition according to the present invention is useful as a heat storage material in various fields, and is effective as a heat storage material composition that enables rapid heat storage and release and can be used repeatedly and stably.

Claims

1. A solid-liquid phase change material that changes phase between solid and liquid in the temperature range of 5°C to 35°C; Water and a nucleating material; Graphite powder; A fine powder with a specific gravity close to that of water, which is resistant to water wetting and has high thermal conductivity. Contains The fine powder includes carbon black. Heat storage material composition.

2. The concentration of the graphite powder is in the range of 0.5% by weight to 5.0% by weight based on the total heat storage material composition; The mixing ratio of the graphite powder to the carbon black is within a range of 1.0:0.2 to 1.0:5.0 by weight. The heat storage material composition according to claim 1 .

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