Composition and heat storage material comprising the composition

Abstract

The present invention provides a composition that exhibits excellent heat retention in a relatively high-temperature range and reduces the effects of supercooling, and a heat storage material comprising the composition for said heat storage material. [Solution] One embodiment of the present invention is a composition comprising water, formate, trimethylolethane, and phosphates. The phosphates are preferably sodium phosphates. The composition is preferably for use as a heat storage agent. Another embodiment of the present invention is a heat storage material comprising a container and the composition stored in the container.

Description

Technical Field

[0001] The present invention relates to a composition and a heat storage material comprising the composition.

Background Art

[0002] One of the heat storage materials for maintaining a predetermined temperature is a phase change material. The phase change material refers to a material having a function of maintaining a constant temperature by utilizing the latent heat during the phase change from a solid phase to a liquid phase.

[0003] One of the characteristics required for a heat storage material is, particularly in food applications and pharmaceutical applications, a function of maintaining heat in a relatively high temperature range (for example, 0 °C or higher). Conventionally, many of the technologies used for heat preservation in such a high temperature range were heat storage materials using paraffin, but paraffin is a combustible material, so there was a problem with safety.

[0004] There have been attempts to improve safety by using a heat storage material using a hydrate having heat retention properties at 0 °C or higher. For example, Patent Document 1 discloses a latent heat storage material having a melting point in the range of 9 to 10 °C, which is a combination of sodium sulfate decahydrate and ammonium chloride or ammonium bromide.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Thus, latent heat storage materials using hydrates with melting points in a relatively high temperature range have existed for some time, but such materials are highly susceptible to supercooling. For example, sodium acetate trihydrate has a melting point of 58°C, but solidification may not occur even when cooled to near room temperature. When supercooling is a major factor, it is necessary to lower the set temperature of the freezer used to freeze the latent heat storage material, but the lower the set temperature of the freezer, the more electricity is consumed, and so on, which limits the use of latent heat storage materials.

[0007] Therefore, the present invention aims to provide a composition that has excellent heat retention properties in a relatively high temperature range and reduces the effects of supercooling, and a heat storage material comprising the composition. [Means for solving the problem]

[0008] The inventors of this invention have conducted diligent research and have found that the above problems can be solved by a composition containing specific components. That is, the present invention is as follows.

[0009] One embodiment of the present invention is a composition. The composition comprises water, formate, trimethylolethane, and phosphates.

[0010] The phosphate salts are preferably sodium phosphate salts. The aforementioned composition is preferably for use as a heat storage material.

[0011] Another embodiment of the present invention is a heat storage material comprising a container and the composition stored within the container. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a composition that has excellent heat retention properties in a relatively high temperature range and has reduced effects of supercooling, and a heat storage material comprising the composition. [Modes for carrying out the invention]

[0013] In the following, if the upper and lower limits are listed separately, it shall be assumed that a numerical range is substantially disclosed by combining any upper and lower limit.

[0014] In the following, if a compound is described, its isomers will also be described.

[0015] In the following, unless otherwise specified, all measurements will be conducted at room temperature (25°C).

[0016] The following describes in detail the components, physical properties, and uses of the composition, but the present invention is not limited thereto.

[0017] <<Ingredients>> The composition according to this disclosure preferably comprises water (component 1), formate (component 2), trimethylolethane (component 3), and phosphates (component 4). The composition according to this disclosure may also contain other components. Each component will be described below.

[0018] <1st component: water> The water used may be pure water or ultrapure water such as distilled water, ion-exchanged water, or RO (reverse osmosis) water.

[0019] The water content in the composition can be adjusted by considering the concentration of other components. From the viewpoint of heat storage, for example, when the total amount of the composition is 100.00% by mass, the water content is preferably 15.00% by mass or more, 20.00% by mass or more, 30.00% by mass or more, 35.00% by mass or more, or 40.00% by mass or more. In addition, in a composition containing the second, third, and fourth components, a relatively high water content (for example, 35.00% by mass or more) makes it easier to obtain a uniform composition. Furthermore, the water content is preferably 80.00% by mass or less, 60.00% by mass or less, 50.00% by mass or less, or 45.00% by mass or less. By setting the water content within these ranges, the latent heat of the composition can be increased.

[0020] <Second component: formate> The formate is preferably an alkali metal salt and / or an alkaline earth metal salt, more preferably an alkali metal salt (for example, a lithium salt, a sodium salt or a potassium salt), still more preferably a sodium salt or a potassium salt, and particularly preferably a sodium salt.

[0021] By including formate in the composition, it is easy to obtain a composition excellent in latent heat amount and the like and preferable as a heat storage material. In particular, by using sodium formate as the formate, it becomes easy to obtain a composition having a melting point around 12 °C while maintaining the latent heat.

[0022] When the total amount of the composition is 100.00% by mass, the content of formate (for example, sodium formate) is preferably 5.00% by mass or more, 8.00% by mass or more, 10.00% by mass or more, 15.00% by mass or more, or 20.00% by mass or more, and is preferably 60.00% by mass or less, 50.00% by mass or less, 40.00% by mass or less, 35.00% by mass or less, less than 32.50% by mass, or 32.00% by mass or less. By setting the content of formate (for example, sodium formate) within such a range, it is easy to obtain a composition excellent in latent heat amount.

[0023] <Third component: trimethylolethane> By using a composition in which formate and trimethylolethane are combined, it is easy to obtain a composition excellent in latent heat amount and the like and suitable for heat retention in a region where the temperature is relatively high (for example, a temperature range of 0.0 °C or more and less than 14.0 °C, or 10.0 °C or more and less than 14.0 °C).

[0024] The trimethylolethane content of the composition, when the total amount is 100.00% by mass, is preferably 5.00% by mass or more, 10.00% by mass or more, 15.00% by mass or more, 20.00% by mass or more, 25.00% by mass or more, or 30.00% by mass or more, and is also preferably 60.00% by mass or less, 50.00% by mass or less, 45.00% by mass or less, or 40.00% by mass or less. By setting the trimethylolethane content within this range, it is easy to obtain a composition with excellent latent heat content.

[0025] In the composition, the ratio of trimethylolethane content to formate content (trimethylolethane / formate) is preferably 3.0 or less, 2.5 or less, or 2.0 or less. The lower limit of this content ratio is, for example, 0.2, 0.5, or 0.8. By setting this content ratio within such a range, it is easier to obtain a uniform composition with excellent latent heat content.

[0026] In the composition, the ratio of trimethylolethane content to water content (trimethylolethane / water) is preferably 3.0 or less, 2.5 or less, 2.0 or less, 1.5 or less, or 1.2 or less. The lower limit of this content ratio is, for example, 0.2, 0.4, 0.5, or 0.6. By setting this content ratio within such a range, it is easier to obtain a uniform composition with excellent latent heat content.

[0027] <Fourth component: Phosphates> The fourth component is phosphates.

[0028] Compositions containing the first, second, and third components have relatively high melting points, excellent latent heat content, and tend to be relatively unaffected by supercooling. However, when such compositions undergo repeated freezing and thawing cycles, their behavior during the initial freezing cycle sometimes differed from that during subsequent freezing cycles. More specifically, while compositions containing the first, second, and third components may have a melting point around 12°C, freezing sometimes did not occur during the initial freezing cycle unless cooled to around -10°C. Furthermore, it was confirmed that when this composition was frozen again after undergoing multiple freeze-thawing cycles, freezing occurred at temperatures above 6°C. This is thought to be because, after preparing the composition, freezing and thawing made the composition more likely to become a heterogeneous solution, making it easier for seed crystals to remain in the solution, and these seed crystals made it easier for freezing to occur at higher freezing temperatures. Thus, the state in which freezing at higher freezing temperatures becomes easier after multiple freeze-thawing cycles is called the freeze-activated state. Thus, while compositions in a freeze-activated state exhibit excellent freeze stability, leaving them in a high-temperature environment (e.g., 40°C) deactivates the freeze-activated state. Once deactivated, the composition becomes difficult to freeze again unless cooled to around -10°C. Therefore, there is room for improvement in the freeze stability of the compositions when intended for use in high-temperature environments such as during the summer. According to this disclosure, by further incorporating a fourth component into a composition containing the first, second, and third components, it is believed that while maintaining properties related to latent heat and melting point, the ease of crystal nucleation is specifically improved, the freeze-activated state is more easily maintained, and the composition is more likely to maintain a state in which the effects of supercooling are reduced even when exposed to a high-temperature environment (for example, a 40°C environment).

[0029] The phosphates are preferably alkali metal salts and / or alkaline earth metal salts, more preferably alkali metal salts (e.g., lithium salts, sodium salts, or potassium salts), even more preferably sodium salts or potassium salts, and particularly preferably sodium salts. The phosphates may also be ammonium salts.

[0030] Examples of phosphates include orthophosphate, hypophosphorous acid, phosphorous acid, and condensed phosphates. Examples of condensed phosphates include polyphosphates (pyrophosphate, tripolyphosphate, tetrapolyphosphate, pentapolyphosphate, etc.), metaphosphates (trimetaphosphate, tetrametaphosphate, hexametaphosphate, etc.), and ultraphosphate.

[0031] Preferred examples of phosphates include monosodium phosphate (sodium dihydrogen phosphate), disodium phosphate (disodium hydrogen phosphate), trisodium phosphate, and sodium pyrophosphate.

[0032] In the composition, when the total content of the first, second, and third components is 100.0 parts by mass, the content of the fourth component is preferably 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 part by mass or more, or 1.2 parts by mass or more, and also preferably 10.0 parts by mass or less, 8.0 parts by mass or less, 5.0 parts by mass or less, or 3.0 parts by mass or less. By setting the content in this manner, the stability of the composition can be further enhanced.

[0033] In the composition, the ratio of the content of component 4 to the content of component 2 (formate) (component 4 / component 2) is preferably 0.01 or more, 0.02 or more, 0.03 or more, or 0.05 or more, and also preferably 0.30 or less, 0.20 or less, 0.10 or less, or 0.08 or less. Furthermore, the ratio of the content of component 4 to the content of component 3 (trimethylolethane) (component 4 / component 3) in the composition is preferably 0.01 or more, 0.02 or more, 0.03 or more, or 0.05 or more, and also preferably 0.30 or less, 0.20 or less, 0.10 or less, or 0.08 or less. By using such content ratios, the stability of the composition can be further enhanced.

[0034] When phosphates are used as raw materials in the preparation of the composition, they may be in hydrate or anhydrous form. If the phosphates are in hydrate form, the phosphate content in the composition is calculated by subtracting the amount equivalent to the water of hydration in the phosphates.

[0035] <Other ingredients> The composition may contain known components such as phase separation inhibitors, dispersants, colorants (dyes, pigments), antibacterial agents, viscosity modifiers, supercooling inhibitors (e.g., ice-nucleating bacteria, calcium carbonate, sodium sulfate, borax, activated carbon, silver iodide, mineral-based nucleating agents, etc.), defoamers, dispersants, surfactants, stabilizers, pH adjusters, emulsifiers, and organic solvents other than water.

[0036] The composition preferably contains a phase separation inhibitor. Examples of phase separation inhibitors include sodium silicate, water glass, polyacrylic acid, sodium polyacrylate, polycarboxylate polyether polymer, polycarboxylic acid polymer, polyglycerin, polyglycerin ester, polyglycerin ether, sodium acrylic acid / maleic acid copolymer, sodium acrylic acid / sulfonic acid monomer copolymer, acrylamide / dimethylaminoethyl methacrylate dimethyl sulfate copolymer, acrylamide / sodium acrylate copolymer, polyethylene glycol, polypropylene glycol superabsorbent polymer (SAP), thickening polysaccharides, and layered silicates. Examples of thickening polysaccharides include cellulose, xanthan gum, guar gum, locust bean gum, tara gum, gum arabic, gelatin, tremel gum, and salts thereof, as well as modified versions thereof (e.g., hydroxypropyl methylcellulose, carboxymethylcellulose). By using such a layer separation inhibitor (especially a thickening polysaccharide), the layer separation inhibitor can dissolve or disperse in water to appropriately improve viscosity, thereby stabilizing the composition without significantly reducing its heat storage performance and preventing a decrease in heat storage performance when the composition is repeatedly used (freezed and thawed).

[0037] The content of the phase separation inhibitor is preferably 0.1% by mass or more, 0.2% by mass or more, or 0.5% by mass or more, and preferably 10.0% by mass or less, 5.0% by mass or less, or 2.0% by mass or less, when the total amount of the composition is 100.0% by mass.

[0038] The content of other components is preferably 10.0% by mass or less, 5.0% by mass or less, or 3.0% by mass or less, when the total amount of the composition is considered to be 100.0% by mass.

[0039] <<Physical properties / properties>> <Thermal properties> The compositions of this disclosure may have a melting point of less than 14.0°C. More specifically, the compositions of this disclosure may have a melting point in a relatively high temperature range, such as 0.0°C to less than 14.0°C, 5.0°C to less than 14.0°C, 8.0°C to less than 14.0°C, or 10.0°C to less than 14.0°C.

[0040] The latent heat content of the composition disclosed herein may be 80.0 J / g or more, 100.0 J / g or more, 115.0 J / g or more, 120.0 J / g or more, or 150.0 J / g or more.

[0041] The melting point and latent heat of the composition are obtained by differential scanning calorimetry (DSC). Specifically, they are as follows: Approximately 10 mg of the composition is placed in an aluminum pan for DSC measurement, heated to 25°C, then cooled to -35°C at a rate of 1°C / min to solidify, and then heated back up to 25°C at a rate of 1°C / min. The melting point and latent heat are obtained from the peaks and areas that appear during the phase change. If the composition has multiple peaks (melting peaks), the temperature corresponding to the peak with the highest latent heat of fusion is taken as the melting point of the composition.

[0042] <Viscosity> The viscosity of the composition can be appropriately changed depending on the application and is not particularly limited. If the composition contains a gel component, the viscosity of the composition can be 1.0 Pa·s or higher, 2.0 Pa·s or higher, 5.0 Pa·s or higher, 10 Pa·s or higher, 100 Pa·s or higher, or 500 Pa·s or higher. The upper limit of the viscosity of the composition is not particularly limited, but for example, it is 2000 Pa·s or lower.

[0043] The viscosity of the composition was measured at 25°C using a Type B rotational viscometer.

[0044] <<Application>> The composition according to this disclosure is preferably used as a heat storage material, a food and beverage warming device, or a medical product warming device. In other words, the preferred form of the composition according to this disclosure is a composition for heat storage, a food and beverage warming device, or a medical product warming device. Furthermore, the composition according to this disclosure can also be preferably used as a material constituting a contact-cooling component, etc. Moreover, the composition according to this disclosure can be preferably used as a heat storage material for various applications such as temperature-controlled transport of precision equipment, air conditioning, and floor heating.

[0045] The following describes, as an example of a specific method of using the composition relating to this disclosure, preferred examples of a heat storage material comprising the composition relating to this disclosure, as well as preferred examples of food and beverage warming devices and medical product warming devices comprising the composition relating to this disclosure.

[0046] <Heat storage material> The heat storage material comprises a container and a composition stored inside the container.

[0047] As the composition is as described above, a detailed explanation will be omitted. As mentioned above, the composition may be gelled (containing a gel component). Using a gelled composition can suppress leakage of liquid material when the container is damaged.

[0048] The material of the container may have flexibility that allows it to deform in response to the phase changes (solidification and melting) of the composition.

[0049] The heat storage material may be a so-called soft type, in which the container is made of easily deformable material such as a resin film or a metal film, or a so-called hard type, in which it is made of a material that is not easily deformable, such as a thick resin material (for example, a hollow molded body).

[0050] The heat storage material only needs to have at least the composition sealed inside the container, and may be configured such that the composition can be removed or injected without damaging the container, for example by having an openable and closable lid, or it may be configured such that it is difficult to remove the composition except by damaging the container.

[0051] The size and shape of the heat storage material can be changed as appropriate depending on its intended use.

[0052] The heat storage material may include components other than the container and composition.

[0053] <Food and beverage warming devices and medical product warming devices> Food and beverage warming devices and medical product warming devices include, for example, a container and a composition according to the present disclosure stored inside the container.

[0054] As the composition is as described above, a detailed explanation will be omitted.

[0055] The container is, for example, a box-shaped article having a space inside the container capable of accommodating an object to be kept warm, such as food. A composition storage section containing the composition according to this disclosure is provided on one or more of the inner sides, inner bottom, or inner top surfaces of the container, or on the entire surface. The composition storage section may be detachable from the container or integrated with the container. The container usually has an opening and closing mechanism, which can be operated to create a sealed or open state. Preferably, the container is made of a material with thermal insulation properties. By accommodating an object to be kept warm, such as food or medical supplies, in the space inside the container while the composition is solidified, the object to be kept warm can be maintained.

[0056] Examples of items that can be kept warm by food and beverage warming devices include fresh produce such as chilled vegetables and fruits, processed foods such as ham, and beverages (water, tea-based beverages, coffee-based beverages, fruit juices, vegetable juices, sports drinks, etc.).

[0057] Examples of items that can be kept warm by medical product warming devices include certain medical products that require low-temperature storage, such as vaccines, blood products, red blood cell preparations, and cells. [Examples]

[0058] The following examples will specifically describe the composition (composition for heat storage material), but the present invention is not limited to the following.

[0059] <<Preparation of Composition>> The compositions for Examples 1-13 and Comparative Examples 1-3 were obtained by mixing each component shown in Tables 1 and 2 in the amounts (parts by mass) shown in Tables 1 and 2 and stirring the mixture.

[0060] In the table, product name: Unet XD-50 (manufactured by Unitech Foods) is a mixture of carrageenan, xanthan gum, and pectin.

[0061] <<Rating>> <Melting point and latent heat> Based on the differential scanning calorimetry described above, the melting point and latent heat of each composition were measured. The measurement results for each item are shown in Tables 1 and 2.

[0062] <Freezing test> Each composition was subjected to a freezing procedure by being left in a -15°C cold bath for 6 hours, followed by a thawing procedure by being left in a 23°C environment for 6 hours. The freezing and thawing procedures were performed consecutively for two cycles. The temperature changes during the first and second cycles were observed, and the temperature at which freezing heat occurred was identified. The temperature at which freezing heat occurred in the first cycle was defined as the initial freezing temperature, and the temperature at which freezing heat occurred in the second cycle was defined as the subsequent freezing temperature. The initial freezing temperatures and subsequent freezing temperatures for each composition are shown in Tables 1 and 2.

[0063] <Freeze-activity retention test> 30g of each composition was frozen once at -15°C, then left to stand at 40°C for 12 hours. After that, it was left to stand at 6°C for 12 hours to check whether freeze-heat occurred. If freeze-heat occurred, it was evaluated as ○; if freeze-heat did not occur, it was evaluated as ×. The evaluation results are shown in Tables 1 and 2.

[0064] [Table 1]

[0065] [Table 2]

[0066] As described above, the composition according to this embodiment has a melting point in a relatively high temperature range of 0.0°C to less than 14.0°C, the effect of supercooling is reduced, and the latent heat content is sufficiently high. Furthermore, the composition according to this embodiment has a sufficiently high initial freezing temperature and excellent freeze activity retention, so it can freeze stably even after being exposed to high-temperature environments such as summer use. Thus, the composition according to this embodiment is useful as a heat storage material. Furthermore, the composition according to this embodiment is advantageous in terms of high safety. In addition, since the composition according to this embodiment can be manufactured without a homogenization process such as heating, it is considered advantageous in terms of reducing energy consumption during manufacturing (lower environmental impact). [Industrial applicability]

[0067] The composition of the present invention exhibits excellent heat retention in relatively high temperature ranges and also reduces the effects of supercooling, making it suitable for use as a heat storage material.

Claims

1. Water and, Formate and, Trimethylolethane and Phosphates and, A composition containing the following:

2. The composition according to claim 1, wherein the phosphates are sodium phosphate salts.

3. The composition according to claim 1, for use as a heat storage material.

4. A heat storage material comprising a container and a composition according to any one of claims 1 to 3 stored inside the container.

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