Latent heat storage material composition

Abstract

To provide a latent heat storage material composition that promotes supercooling of the latent heat storage material to facilitate control of the crystallization temperature, and in particular a latent heat storage material composition that is capable of utilizing low-temperature thermal energy while reducing safety and health problems.SOLUTION: A latent heat storage material composition comprises a fatty acid ester (A) and a polymer (B) having, as a monomer, at least one selected from the group consisting of an unsaturated hydrocarbon, acrylic acid, methacrylic acid, and esters thereof, wherein the freezing point of the fatty acid ester in the latent heat storage material composition is decreased, and the temperature difference between the melting point and the freezing point of the fatty acid ester is 14°C or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a latent heat storage material composition, and in particular to a latent heat storage material composition with accelerated supercooling, which allows the utilization of low-temperature thermal energy and reduces safety and health problems. [Background technology]

[0002] Latent heat storage materials store and release heat by repeatedly melting and solidifying (crystallizing), and the temperature at which the stored thermal energy is extracted is determined by the crystallization temperature of the heat storage material. From the perspective of more effective use of thermal energy, it is desirable to be able to control the temperature and timing at which heat is extracted so that it is needed. Known prior art for controlling the crystallization temperature involves adding a nucleating agent to compounds prone to supercooling, such as hydrated salt compounds such as sodium acetate trihydrate and sugar alcohols such as erythritol, to prevent supercooling. Meanwhile, little is known about substances that promote supercooling, such as those disclosed in Patent Documents 1 and 2. Patent Documents 1 and 2 both relate to promoting supercooling of sugar alcohols, but because sugar alcohols are inherently prone to supercooling, even if it is possible to further promote supercooling, it is difficult to control the crystallization temperature. Regarding the control of the crystallization temperature of latent heat storage materials, Patent Document 3 discloses a heat storage material composition that can easily control the crystallization temperature by promoting supercooling of the latent heat storage material. This patent uses a fatty acid with eight or more carbon atoms as the heat storage material, enabling heat storage at temperatures close to or above room temperature. Recently, there has been an increasing demand for low-temperature transportation of pharmaceuticals and other products, and technologies that can utilize thermal energy at temperatures below room temperature are needed. To utilize thermal energy at lower temperatures based on the technology of Patent Document 3, it becomes necessary to use fatty acids with shorter chain lengths. However, this reduces the expected effect of promoting supercooling, and such fatty acids have an unpleasant odor and pose health risks. Furthermore, short-chain fatty acids have high acidity, which can lead to corrosion of containers and chemical burns when they come into contact with skin, posing safety concerns in handling. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-187230 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-153206 [Patent Document 3] Japanese Patent Publication No. 2020-45411 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to develop a latent heat storage material composition that can promote supercooling of the latent heat storage material and easily control the crystallization temperature, and in particular to develop one that can utilize low-temperature thermal energy and has reduced safety and health problems. [Means for solving the problem]

[0005] As a result of intensive research aimed at solving the above problems, the present inventors have found that supercooling can be promoted by adding a specific component to a fatty acid ester, and have completed the present invention. The present inventors have also found that supercooling can be promoted by adding a specific component to a higher alcohol, and have completed the present invention. That is, the present invention is characterized by the following items [1] and [2]. [1] A latent heat storage material composition comprising a fatty acid ester (A) and a polymer (B) having as a monomer at least one selected from the group consisting of an unsaturated hydrocarbon, and acrylic acid, methacrylic acid, and esters thereof, wherein the freezing point of the fatty acid ester in the latent heat storage material composition is reduced, and the temperature difference between the melting point and the freezing point of the fatty acid ester is 14°C or more. [2] A latent heat storage material composition comprising a higher alcohol (C) and a polymer (B) having as a monomer at least one selected from the group consisting of an unsaturated hydrocarbon, and acrylic acid, methacrylic acid, and esters thereof, wherein the freezing point of the higher alcohol in the latent heat storage material composition is reduced, and the temperature difference between the melting point and the freezing point of the alcohol is 12°C or more. [Effects of the Invention]

[0006] The latent heat storage material composition of the present invention promotes supercooling in compounds that are not prone to supercooling, making it easy to control the crystallization temperature, and therefore heat can be extracted at the required temperature and timing, making it possible to use thermal energy more effectively.Furthermore, low-temperature thermal energy can be used, and safety and health problems can be reduced. DETAILED DESCRIPTION OF THE INVENTION

[0007] The fatty acid ester (A) constituting the latent heat storage material composition of the present invention can be selected according to the target heat storage temperature. Examples include methyl laurate, butyl laurate, methyl myristate, ethyl myristate, isopropyl myristate, methyl pentadecanoate, methyl palmitate, ethyl palmitate, 2-ethylhexyl palmitate, methyl heptadecanoate, methyl stearate, ethyl stearate, propyl stearate, isopropyl stearate, methyl nonadecanoate, methyl arachidate, ethyl arachidate, methyl behenate, and methyl lignocerate. Among these, those with melting points below 15°C are preferred because they allow for the utilization of thermal energy at low temperatures. Furthermore, using fatty acids with 12 or more carbon atoms is preferred because of their enhanced supercooling promotion effect. Furthermore, selecting fatty acid esters with no branched carbon structure is preferred because of their enhanced supercooling promotion effect. Specific examples of preferred fatty acid esters (A) include methyl laurate, butyl laurate, ethyl myristate, and ethyl palmitate. Examples of the higher alcohol (C) constituting the latent heat storage material composition of the present invention include lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, arachidyl alcohol, and behenyl alcohol.

[0008] The polymer (B) constituting the latent heat storage material composition of the present invention will be explained below. The polymer (B) is a polymer containing at least one monomer selected from the group consisting of unsaturated hydrocarbons, acrylic acid, methacrylic acid, and esters thereof. Examples of unsaturated hydrocarbons include ethylene, propylene, butene, pentene, hexene, butadiene, isoprene, cyclopentene, cyclohexene, norbornene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, and styrene. Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Of these, the polymer (B) of the present invention is preferably a polymer containing at least one monomer selected from the group consisting of unsaturated hydrocarbons. The unsaturated hydrocarbon is preferably an unsaturated aliphatic hydrocarbon. Among unsaturated aliphatic hydrocarbons, chain-like unsaturated hydrocarbons, i.e., alkenes (olefins), are more preferred. That is, the polymer (B) of the present invention preferably has a polyolefin structure, and examples of such polymers include polyethylene, polypropylene, and other polymers obtained by polymerizing α-olefins. Among these, the polymer (B) of the present invention is preferably one having a polyethylene structure.

[0009] The degree of polymerization of the polymer (B) is preferably 100 or more, as this has a high effect of promoting supercooling.

[0010] The polymer (B) may be a copolymer of an unsaturated hydrocarbon and a monomer other than acrylic acid, methacrylic acid, and their esters. It may also be graft-polymerized or crosslinked, and an appropriate polymer may be selected from the viewpoints of compatibility with the fatty acid (A), supercooling promotion effect, ease of handling as a latent heat storage material composition, and physical properties. It may also be a mixture of multiple polymers.

[0011] When a monomer other than unsaturated hydrocarbons, acrylic acid, methacrylic acid, and esters thereof is used as a copolymerization component, the monomer is not particularly limited, and examples thereof include acrylamide and its derivatives, methacrylamide and its derivatives, acrylonitrile, methacrylonitrile, vinyl ethers, vinyl esters, vinyl halides, maleic acid and its esters or anhydrides, etc.

[0012] It is preferable to select the polymer (B) such that the polarity, as expressed by the solubility parameter or the like, is close to that of the fatty acid ester (A), because this increases the compatibility between the fatty acid ester (A) and the polymer (B) and makes them easier to mix.

[0013] Specific examples of suitable polymers (B) include polyethylene, polypropylene, ethylene-propylene copolymer, EPDM, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-glycidyl methacrylate copolymer, polyethylene-graft-maleic anhydride, polypropylene-graft-maleic anhydride, etc.

[0014] The proportion of the fatty acid ester (A) relative to the total amount of the fatty acid ester (A) and the polymer (B) constituting the latent heat storage material composition of the present invention is preferably 1% or more and 99% or less by weight. If the proportion of the fatty acid ester (A) is less than 1%, the heat storage capacity of the latent heat storage material composition will be small, and if it exceeds 99%, the effect of adding the polymer (B) will be small. The proportion of the fatty acid ester (A) is more preferably 10% or more and 70% or less, and even more preferably 20% or more and 50% or less. The proportion of the higher alcohol (C) relative to the total amount of the higher alcohol (C) and the polymer (B) constituting the latent heat storage material composition of the present invention is preferably 1% or more and 99% or less by weight. If the proportion of the higher alcohol (C) is less than 1%, the heat storage capacity of the latent heat storage material composition will be small, and if it exceeds 99%, the effect of adding the polymer (B) will be small. The proportion of the higher alcohol (C) is more preferably 10% or more and 70% or less, and even more preferably 20% or more and 50% or less.

[0015] In the present invention, the crystallization temperature (freezing point) can be easily controlled by the type of combination of the fatty acid ester (A) or higher alcohol (C) and the polymer (B). Even if the fatty acid ester (A) or higher alcohol (C) and the polymer (B) are the same components, the crystallization temperature (freezing point) can be easily controlled by adjusting the ratio of the fatty acid ester (A) or higher alcohol (C). The freezing point of the fatty acid ester in the latent heat storage material composition of the present invention is reduced, and the temperature difference between the melting point and the freezing point of the fatty acid ester is 14° C. or more. This temperature difference is more preferably 16° C. or more, and even more preferably 18° C. or more. The freezing point of the higher alcohol in the latent heat storage material composition of the present invention is lowered, and the temperature difference between the melting point and the freezing point of the higher alcohol is 12° C. or more. This temperature difference is more preferably 14° C. or more, and even more preferably 16° C. or more. In order to increase the temperature difference between the melting point and the freezing point in this way, it is necessary to select the fatty acid ester (A) or higher alcohol (C) and the polymer (B) appropriately, and also to keep the ratio of (A) or (C) to the total amount of (A) or (C) and (B) at a certain level or less.

[0016] The latent heat storage material composition of the present invention can be used in combination with other latent heat storage materials as long as the object of the present invention is not impaired.

[0017] Other latent heat storage materials include aliphatic hydrocarbons, aliphatic alcohols, and inorganic materials.

[0018] Examples of the aliphatic hydrocarbon include n-dodecane, n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, n-eicosane, and paraffin wax.

[0019] Examples of the aliphatic alcohol include erythritol and pentaerythritol.

[0020] Inorganic salts include inorganic salts such as lithium nitrate trihydrate, sodium sulfate decahydrate, sodium acetate trihydrate, and aluminum potassium sulfate dodecahydrate.

[0021] The method for preparing the latent heat storage material composition of the present invention is not particularly limited, but examples thereof include a method in which the fatty acid ester (A) or higher alcohol (C) and the polymer (B) are mixed in a solvent by stirring or ultrasonication, a method in which at least one of them is mixed in a molten or liquid state, and a method in which they are mixed mechanically using a ball mill, mixer, homogenizer, etc.

[0022] The latent heat storage material composition of the present invention can be used, for example, by sealing it in a plastic or metal bag or container, or by forming a solution into a film, or by compression molding or melt molding. It is preferable that the polymer (B) has a three-dimensional network structure by crosslinking or the like, since this prevents leakage when the fatty acid ester (A) or higher alcohol (C) becomes liquid at or above its melting point. Furthermore, the latent heat storage material composition of the present invention can be dispersed in a polymer component other than the polymer (B) as a matrix.

[0023] In this case, the polymer component that serves as the matrix may be any of various thermoplastic resins, thermosetting resins, elastomers, gels, and the like.

[0024] Examples of thermoplastic resins include polyethylene, polypropylene, polyvinyl alcohol, EVA resin, EVOH resin, polystyrene, AS resin, ABS resin, ASA resin, AES resin, acrylic resin such as PMMA, MS resin, MBS resin, SBC resin, cycloolefin resin, polyacetal resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin, liquid crystal polymer, PPS, PEEK, PPE, polysulfone resin, polyimide resin, fluorine resin, and thermoplastic elastomer.

[0025] Examples of the thermosetting resin include epoxy resin, phenol resin, silicone resin, and thermosetting acrylic resin.

[0026] Examples of elastomers include conjugated diene rubbers such as butadiene rubber, styrene-butadiene rubber, nitrile rubber, and butyl rubber, ethylene-α-olefin copolymer rubbers such as EPM and EPDM, and hydrogenated conjugated diene polymers such as SEBS.

[0027] Examples of gels include sodium polyacrylate, polyacrylamide derivatives, polysaccharides, and gelatin.

[0028] The latent heat storage material composition of the present invention can be used in combination with components other than those described above, such as a thermally conductive filler, as long as the object of the present invention is not impaired, for example, to promote heat transfer to the heat storage material.

[0029] Specific examples of the thermally conductive filler include carbon-based compounds such as graphite, carbon fiber, carbon nanofiber, carbon nanotube, graphene, and diamond; metal oxides such as aluminum oxide, magnesium oxide, silicon oxide, titanium oxide, zinc oxide, and zirconium oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; metal carbonates such as magnesium carbonate and calcium carbonate; nitrides such as boron nitride, aluminum nitride, and silicon nitride; and carbides such as silicon carbide and boron carbide.

[0030] These fillers may be added during the process of producing the latent heat storage material composition of the present invention, or may be mixed with the latent heat storage material composition of the present invention before use. [Example]

[0031] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0032] In each of the examples and comparative examples, evaluations were carried out as follows. (Melting point and freezing point) Measurements were performed using a TA Instruments Discovery DSC under nitrogen flow under the following heating and cooling conditions. (a) When methyl laurate or butyl laurate was used as the component, the temperature was increased from -40°C to 30°C at 10°C / min, and the melting peak top (melting point) was measured. The temperature was also decreased from 30°C to -400°C at 5°C / min, and the crystallization peak top (freezing point) was measured. (a) When ethyl myristate was used as the component, the temperature was increased from -30°C to 60°C at 10°C / min, and the melting peak top (melting point) was measured. The temperature was also decreased from 60°C to -30°C at 5°C / min, and the crystallization peak top (freezing point) was measured. (c) When stearyl alcohol or myristyl alcohol was used as the component, the temperature was increased from 10°C to 90°C at 10°C / min, and the melting peak top (melting point) was measured. The temperature was also lowered from 90°C to 0°C at a rate of 5°C / min, and the peak top of crystallization (freezing point) was measured.

[0033] [Example 1] 50 parts by weight of (a) methyl laurate and 50 parts by weight of (b) EPDM were mixed in a molten state at 180°C and then cooled to room temperature to obtain a latent heat storage material composition. As a result of DSC measurement, the melting point was 3°C, the freezing point was -18°C, and the temperature difference between the melting point and the freezing point was 21°C.

[0034] [Examples 2 to 10, Comparative Examples 1 to 3] A latent heat storage material composition was obtained in the same manner as in Example 1, except that (a) and (b) shown in Table 1 were used. The results of each DSC measurement are shown in Table 1.

[0035] [Table 1] Low-density polyethylene: Aldrich LDPE, MFR = 25 g / 10 min Polypropylene: Novatec BC06C made by Japan Polypropylene PE-g-MA: Polyethylene-graft-maleic anhydride (Aldrich), viscosity 1700-4500 cp (140°C) PP-g-MA: Polypropylene-graft-maleic anhydride (Aldrich), maleic acid content 8-10 wt% EGMA: Ethylene-glycidyl methacrylate copolymer (Aldrich), contains 8 wt% glycidyl methacrylate EPDM: EPT (ethylene propylene terpolymer) manufactured by Mitsui Chemicals

[0036] [Example 11] 50 parts by weight of (c) stearyl alcohol and 50 parts by weight of (b) PE-g-MA were mixed in a molten state at 180°C and then cooled to room temperature to obtain a latent heat storage material composition. DSC measurement results showed that the melting point was 60°C, the freezing point was 48°C, and the temperature difference between the melting point and the freezing point was 12°C.

[0037] [Examples 12 to 18, Comparative Examples 4 to 5] A latent heat storage material composition was obtained in the same manner as in Example 1, except that (c) and (b) shown in Table 2 were used. The results of each DSC measurement are shown in Table 1.

[0038] [Table 2]

[0039] A comparison of each example and comparative example shows that by combining component (a) or (c) with component (b), the melting point remains almost unchanged while the freezing point is lowered, promoting supercooling. It is also clear that the lower the weight ratio of component (a) or (c), the lower the freezing point, demonstrating that the object of the present invention, which is to control the crystallization temperature, can be achieved by changing the composition of the latent heat storage material composition. [Industrial Applicability]

[0040] By using the latent heat storage material composition of the present invention, it is possible to promote supercooling of the latent heat storage material and control the crystallization temperature, making it possible to extract energy at any temperature, maintain the heat storage state for a long period of time, and reducing safety and health problems. When a fatty acid ester is used, thermal energy at a lower temperature can be used. The latent heat storage material composition of the present invention can be used as a heat-retaining material that generates heat at low temperatures, leading to effective use of thermal energy. Furthermore, by utilizing the heat storage (heat absorption) effect, it can be used to cool electronic components and suppress sudden heat generation.

Claims

1. A latent heat storage material composition comprising a fatty acid ester (A) and a polymer (B) having as a monomer an unsaturated hydrocarbon and at least one selected from the group consisting of acrylic acid, methacrylic acid, and esters thereof, wherein the freezing point of the fatty acid ester in the latent heat storage material composition is reduced, and the temperature difference between the melting point and the freezing point of the fatty acid ester is 14°C or more.

2. A latent heat storage material composition comprising a higher alcohol (C) and a polymer (B) having as a monomer at least one selected from the group consisting of an unsaturated hydrocarbon, and acrylic acid, methacrylic acid, and esters thereof, wherein the freezing point of the higher alcohol in the latent heat storage material composition is reduced, and the temperature difference between the melting point and the freezing point of the higher alcohol is 12°C or more.

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