JP2016188349A - Emulsion-type heat storage material and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in an emulsion-type heat storage material, means that can exhibit a heat storage property over a long period of time even when a thickener or nucleating material is not added (that is, even while retaining a high calorific value).SOLUTION: The emulsion-type heat storage material is produced by a method including a step of phase inverting a water-in-oil type emulsion into an oil-in-water type emulsion by adding an alkali aqueous solution into an oil phase that contains a paraffin compound, a non-ionic surfactant having an alkyl group of 18 or more carbon atoms, and a fatty acid, and is heated to a temperature higher than the melting point of the paraffin compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an emulsion-type heat storage material and a method for producing the same.

  As a heat storage material for utilizing latent heat generated in accordance with a phase change of a substance, organic compounds represented by ice and aliphatic hydrocarbons, inorganic salts, and the like are known. Emulsion type, capsule type, fixed type, etc. are being studied as heat storage materials using aliphatic hydrocarbons, but fluid type emulsion type and capsule type are excellent considering thermal efficiency and ease of control. ing.

  Since the emulsion type is easier to prepare than the capsule type, it is advantageous in terms of cost, and is considered to become the mainstream in the future from the viewpoint of mass supply.

  Here, paraffin compounds such as n-paraffin and paraffin wax are known as phase change materials (PCM) used for emulsion-type heat storage materials. These paraffin compounds can store heat in a medium to low temperature range (0 to 80 ° C.), have a high heat storage density, and do not deteriorate even when phase changes are repeated. However, since these paraffin compounds are solidified during heat dissipation, there is a problem that the thermal conductivity is lowered. As a method for solving such a problem, a technique is known in which a paraffin compound is emulsified (slurried below the freezing point) using water and a surfactant (see, for example, Patent Document 1).

  Here, in general, increasing the content of a phase change material such as a paraffin compound contained in the heat storage material is effective in improving the amount of heat of the heat storage material. However, on the other hand, since it is necessary to add a certain amount of thickener in order to emulsify, there is a limit to increasing the content of the phase change material.

  Furthermore, the paraffin compound in the heat storage material that has been emulsified also has a problem that it exhibits a phenomenon that the freezing point falls below the melting point (so-called supercooling phenomenon). In order to prevent this supercooling phenomenon, a method of adding a nuclear material having a melting point higher than that of a paraffin compound has also been proposed (see, for example, Patent Document 2). However, this method also has a problem that the amount of latent heat of the heat storage material is reduced.

JP 57-40582 A JP 2000-336350 A

  As described above, even with the emulsion-type heat storage material proposed by the conventional technology, there is still room for improvement in terms of heat storage (particularly, heat storage over a long period of time).

  Then, an object of this invention is to provide the means which can exhibit heat storage property over a long time, maintaining a high calorie | heat amount in an emulsion type heat storage material.

  The present inventor has intensively studied to solve the above problems. As a result, a phase inversion emulsification method using a nonionic surfactant having a relatively large carbon number as a surfactant and a fatty acid salt (soap) generated at the oil-water interface by adding an alkali to the fatty acid as a surfactant It has been found that the above-mentioned problems can be solved by simultaneously performing the soap emulsification method to be used to produce an emulsion-type heat storage material, thereby completing the present invention.

  That is, according to one aspect of the present invention, the oil phase contains a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms, and a fatty acid, and is heated to a temperature higher than the melting point of the paraffin compound. There is provided a method for producing an emulsion-type heat storage material, which comprises a step of phase-inversion of a water-in-oil emulsion into an oil-in-water emulsion by adding an alkaline aqueous solution.

  According to another aspect of the present invention, the paraffin compound includes a nonionic surfactant having an alkyl group having 18 or more carbon atoms and a fatty acid salt, and the content of the paraffin compound is 64% by mass or more. An emulsion-type heat storage material is also provided.

  ADVANTAGE OF THE INVENTION According to this invention, in an emulsion type heat storage material, it becomes possible to exhibit heat storage property over a long time, maintaining a high calorie | heat amount.

It is a graph which shows the result of having evaluated the thermal characteristic (thermal storage property) about the emulsion type thermal storage materials 5 and 6 obtained in Examples 5-6, and the comparative emulsion type thermal storage material 4 obtained in Comparative Example 4. FIG.

  One embodiment of the present invention relates to a method for producing an emulsion-type heat storage material. The manufacturing method includes adding an aqueous alkaline solution to an oil phase that includes a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms, and a fatty acid, and is heated to a temperature higher than the melting point of the paraffin compound. Thus, the method includes a step of phase inversion of the water-in-oil emulsion into the oil-in-water emulsion (hereinafter also simply referred to as “phase inversion step”).

[Oil phase]
In the method for producing an emulsion-type heat storage material according to this embodiment, first, an oil phase is prepared. The oil phase contains a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms, and a fatty acid. Hereinafter, the components of the oil phase will be described.

(Paraffin compound)
Paraffin compounds are used as heat storage materials. That is, when the phase change from the solid state (solid phase) to the liquid state (liquid phase), the paraffin compound can exist in a state where latent heat of fusion at the time of the phase change is stored. And by maintaining this state for a long time, the heat storage material exhibits heat storage (latent heat storage system). As a paraffin compound, only 1 type may be used independently and 2 or more types may be used together.

  Here, the paraffin compound is a general term for paraffin (n-paraffin, isoparaffin) and petroleum wax. Among the saturated hydrocarbons, those whose carbon skeleton has a chain structure (alkane) is “paraffin”. Paraffins with 4 or more carbon atoms (ie hydrocarbons with butane or more) have isomers due to the shape of the chain structure, of which all carbon atoms in the molecule have a straight structure without branching. Is “n-paraffin” and is also referred to as “linear paraffin”. Further, paraffin having a branched structure in the carbon skeleton chain structure is “isoparaffin” and is also referred to as “branched paraffin”.

  As the n-paraffin, a compound having an alkylene group having 10 to 30 carbon atoms is preferable. Specific examples thereof are shown together with representative values of melting points: n-decane (melting point: −29.7 ° C.), n-undecane (melting point: −26 ° C.), n-dodecane (melting point: −12 ° C.), n-tridecane. (Melting point: −5 ° C.), n-tetradecane (melting point: 6 ° C.), n-pentadecane (melting point: 9.9 ° C.), n-hexadecane (melting point: 18 ° C.), n-heptadecane (melting point: 21 ° C.), n-octadecane (melting point: 28-30 ° C), n-nonadecane (melting point: 32-34 ° C), n-icosane (melting point: 36.7 ° C), n-henicosane (melting point: 40.5 ° C), n- And triacontane (melting point: 65.8 ° C.).

  As the branched paraffin, a compound having an alkylene group having 10 to 30 carbon atoms is preferable. Specific examples thereof include isododecane, isotridecane, isotetradecane, isopentadecane, isooctadecane, isononadecane, and isoicosane.

  On the other hand, “petroleum wax” is a wax produced from a petroleum refining process, and includes paraffin wax and microcrystalline wax. Paraffin wax is a white wax (wax) having a good crystallinity and extracted at a normal temperature and extracted from a vacuum distillation distillate portion of crude oil, with n-paraffin having about 20 to 30 carbon atoms as a main component. It is a mixture of hydrocarbons with a molecular weight of about 300-500, containing a small amount of isoparaffin. The melting point of paraffin wax is usually about 40 to 70 ° C. Microcrystalline wax is a wax extracted from the residue of crude oil under reduced pressure distillation, and the constituent hydrocarbons are mostly isoparaffin and cycloparaffin. For this reason, a crystal | crystallization becomes small compared with paraffin wax, molecular weight is large, and melting | fusing point is as high as about 60-90 degreeC.

  Paraffin wax having about 20 to 40 carbon atoms and microcrystalline wax having about 30 to 60 carbon atoms are preferable in terms of heat of fusion and availability. Examples of the paraffin wax products include paraffin wax 115, 120, 125, 130, 135, 140, 150, and 155 manufactured by Nippon Seiwa Co., Ltd.

  The melting point of the paraffin compound is preferably in the range of −30 to 130 ° C. as a value measured by the differential scanning calorimetry (DSC method) from the viewpoint of effective use of heat in the living temperature region and the high temperature region. More preferably, it is in the range of -100 ° C. Further, the heat of fusion measured by the differential scanning calorimetry (DSC method) of the paraffin compound is preferably 100 kJ / kg or more from the viewpoint of utilizing latent heat due to the phase change in various fields. In addition, the melting point of the paraffin compound in this specification corresponds to Tim when measured according to JIS K-7121.

(Nonionic surfactant having an alkyl group having 18 or more carbon atoms)
The oil phase used in the production method according to the present invention contains a nonionic surfactant having an alkyl group having 18 or more carbon atoms. When the number of carbon atoms of the alkyl group of the nonionic surfactant is less than 18, an emulsion having a small particle size (that is, a stable) cannot be obtained, and even if the concentration of the paraffin compound is increased, it is sufficient. There is a problem that a sufficient amount of heat cannot be maintained (Comparative Example 1 and Comparative Example 4 described later).

  The nonionic surfactant is not particularly limited as long as it functions as an emulsifier in the phase inversion step to be described later, but is preferably a fat having an alkyl group having 18 or more carbon atoms (more preferably 18 to 22 carbon atoms). Alkylene oxide adducts of group monoalcohols are used. Carbon number of the alkyl group is preferably 18-22. Examples of the aliphatic monoalcohol having an alkyl group having 18 or more carbon atoms include stearyl alcohol and behenyl alcohol, and stearyl alcohol is particularly preferable. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide, and ethylene oxide is particularly preferable. When the alkylene oxide adduct is an adduct of two or more alkylene oxides, it may be in any form of random addition or block addition. Furthermore, the average addition mole number of alkylene oxide in the alkylene oxide adduct is preferably 3 to 40, and more preferably 5 to 20.

The nonionic surfactant may be synthesized by itself or may be a commercially available product. The Examples of commercially available nonionic surfactants, Newcol 1807 (polyoxyethylene stearyl ether _{(C 18 H 37 -O- (CH} 2 CH 2 O) n -H (n = 7)), Nippon Emulsifier stock company Ltd.), Newcol 1820 (polyoxyethylene stearyl ether _{(C 18 H 37 -O- (CH} 2 CH 2 O) n -H (n = 20)), manufactured by Nippon emulsifier Co., Ltd.).

  Examples of the nonionic surfactant having an alkyl group having 18 or more carbon atoms include sorbitan fatty acid ester, fatty acid ester, polycyclic phenyl, and alkylene of hydrogenated castor oil, in addition to an alkylene oxide adduct of an aliphatic monoalcohol. Oxide adducts and the like may be used.

  Moreover, as long as the nonionic surfactant having an alkyl group having 18 or more carbon atoms described above is included in the oil phase, other surfactants (nonionic surfactant having an alkyl group having less than 18 carbon atoms, cation) , Anionic and amphoteric surfactants) may be used in combination. However, the content of the nonionic surfactant having an alkyl group having 18 or more carbon atoms in the surfactant contained in the oil phase is preferably 70% by mass or more, more preferably 90% by mass or more. Yes, and particularly preferably 99% by mass or more.

(fatty acid)
The oil phase used in the production method according to the present invention contains a fatty acid. This fatty acid is neutralized (saponified) by a base contained in an alkaline aqueous solution added in the phase inversion step described later to be changed into soap (fatty acid salt), and is surface active in the same manner as the nonionic surfactant described above. Functions as an agent (emulsifier).

  Fatty acid means an aliphatic monocarboxylic acid, and includes a saturated fatty acid that does not contain an unsaturated bond in the hydrocarbon portion and an unsaturated fatty acid that contains an unsaturated bond (usually one double bond) in the hydrocarbon portion. is there.

  The fatty acid is not particularly limited. Linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and the like can be mentioned. As for these fatty acids, only 1 type may be used independently and 2 or more types may be used together. Among these, saturated fatty acids having 16 to 22 carbon atoms are preferable, and stearic acid and behenic acid are particularly preferable.

(Composition of oil phase)
The blending amount of each component contained in the oil phase is not particularly limited, but the blending amount of the nonionic surfactant is preferably from 100 parts by weight of the paraffin compound from the viewpoint of emulsion stability and thermal characteristics. Is 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass. Moreover, the blending amount of the fatty acid is preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the paraffin compound from the viewpoint of emulsion stability and thermal characteristics. .

[Phase inversion process]
In the method for producing an emulsion-type heat storage material according to the present invention, an alkaline aqueous solution is added to the above-described oil phase heated to a liquid state. When an alkaline aqueous solution is added, at the beginning of the addition, the oil phase constitutes a continuous phase (dispersion medium), and water as a solvent of a small amount of the added aqueous alkali solution constitutes a dispersed phase (w / w o) A type emulsion is formed. Thereafter, as the amount of the aqueous alkali solution added is increased, the continuous phase (dispersion medium) and the dispersion phase are switched at a certain point in time, water constitutes the continuous phase (dispersion medium), and the oil phase constitutes the dispersion phase. Into an oil-in-water (o / w) emulsion (phase inversion). The method of preparing an emulsion (emulsion) in this way is called “phase inversion emulsification method”.

(Heat treatment)
Before adding the aqueous alkali solution, the oil phase is heated. The heating temperature at this time is a temperature higher than the melting point of the paraffin compound contained in the oil phase. Thereby, the said oil phase will be in a liquid state. For this reason, the heating temperature is not uniquely determined and can be appropriately determined in consideration of the melting point of the paraffin compound used in the oil phase. From the viewpoint of ensuring that the oil phase is in a liquid state, the heating temperature is preferably 5 ° C. or more higher than the melting point of the paraffin compound or the surfactant (preferably the paraffin compound and the surfactant). On the other hand, from the viewpoint of the stability of the emulsion, it is preferable that the heating temperature is not too high. Usually, even if the heating temperature is high, “the melting point of the paraffin compound or the surfactant (preferably the paraffin compound and the surfactant) + 15 ° C "or less.

  In order to sufficiently proceed the phase inversion emulsification, it is preferable to stir the heated oil phase, more preferably to continue stirring even after the start of addition of the alkaline aqueous solution described later, and to continue stirring even during the addition of the alkaline aqueous solution. It is more preferable that stirring is continued for a certain period of time after the addition of the alkaline aqueous solution. The means for stirring is not particularly limited, and conventionally known knowledge can be referred to as appropriate.

(Alkaline aqueous solution)
In the phase inversion step in the method for producing an emulsion-type heat storage material according to the present invention, an alkaline aqueous solution is added to the oil phase (in a heated and stirred liquid state). An alkaline aqueous solution is a solution in which a base is dissolved in water.

  The base contained in the aqueous alkali solution is not particularly limited. For example, alkali metal salts such as potassium fluoride, sodium fluoride, lithium fluoride, potassium chloride, sodium chloride and lithium chloride; alkaline earths such as calcium chloride and magnesium chloride Metal salts; alkali metal carbonates such as sodium hydrogen carbonate, lithium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, lithium carbonate and potassium carbonate; carbonates of alkaline earth metals such as calcium carbonate and magnesium carbonate; sodium hydroxide, Alkali metal hydroxides such as potassium hydroxide and lithium hydroxide; Alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; Trimethylamine, Triethylamine, Tripropylamine, Tributylamine, Tricyclohexyla Emissions, tribenzylamine, such as a tertiary amine such as triphenylamine and pyridine. As for these bases, only 1 type may be used independently and 2 or more types may be used together. Here, as described above, the fatty acid contained in the oil phase is saponified by the neutralization reaction with the base by the addition of the alkaline aqueous solution, and changed to soap (fatty acid salt). This soap (fatty acid salt) is produced at the interface between the oil phase containing the fatty acid and the aqueous phase containing the base, and also functions as a surfactant (emulsifier). That is, the method for producing an emulsion-type heat storage material according to the present invention is characterized in that a phase inversion emulsification method and a soap emulsification method are used together in emulsifying a paraffin compound that is a heat storage component. The performance of the fatty acid salt (soap) as a surfactant (emulsifier) is preferably such that the cation constituting the fatty acid salt (soap) is a metal cation. Preferably, a base containing an alkali metal or an alkaline earth metal is used. Further preferred bases are alkali metal or alkaline earth metal hydroxides, and particularly preferred are alkali metal hydroxides (potassium hydroxide, sodium hydroxide, etc.).

  There is no restriction | limiting in particular about the composition of the aqueous alkali solution added in a phase inversion process, its addition amount, etc. However, from the viewpoint of the stability of the emulsion, the composition and addition amount of the alkaline aqueous solution should be adjusted so that the equivalent (chemical equivalent) of the added base is close to the equivalent of the acid (fatty acid) contained in the oil phase. It is preferable to adjust. More specifically, the content of the base contained in the added aqueous alkali solution is preferably 0.5 to 1.5 equivalents relative to the fatty acid contained in the oil phase, and 0.8 to 1. It is more preferably 2 equivalents, more preferably 0.9 to 1.1 equivalents, and particularly preferably 0.95 to 1.05 equivalents.

  There is no particular limitation on the concentration of the base in the aqueous alkali solution to be added, and further considering the final concentration of water contained in the obtained emulsion-type heat storage material while considering the chemical equivalent relationship with the fatty acid described above, Appropriate concentrations can be determined. As an example, the concentration of the base in the alkaline aqueous solution to be added is preferably 5 to 40% by mass, and more preferably 10 to 25% by mass.

[Emulsion type heat storage material]
By the production method according to the present invention, an emulsion-type heat storage material is obtained. This emulsion-type heat storage material has an unprecedented excellent characteristic that it can exhibit heat storage properties for a long time while maintaining a high amount of heat. In order to reflect this characteristic, according to one aspect of the present invention, the content of the paraffin compound includes a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms, a fatty acid salt, and water. An emulsion-type heat storage material in which is 64 mass% or more is also provided.

  Here, although there is no restriction | limiting in particular about content of each component contained in the obtained emulsion-type heat storage material, Content of the nonionic surfactant which has the said C18 or more alkyl group is 100 mass parts of paraffin compounds. On the other hand, it is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass. Further, the content of the fatty acid salt (a salt of a fatty acid contained in the oil phase and a cation derived from a base) is preferably 3 to 20 parts by mass, more preferably 5 to 100 parts by mass of the paraffin compound. -15 parts by mass. Furthermore, the content of water is preferably 15 to 35 parts by mass, and more preferably 20 to 30 parts by mass with respect to 100 parts by mass of the paraffin compound.

  In addition, the emulsion-type heat storage material provided by another embodiment of the present invention has an advantage that it can exhibit heat storage over a long period of time, and one of the causes is high emulsion stability (that is, , Emulsion particle size is small). When this characteristic is expressed quantitatively, the average particle diameter of the emulsion in the emulsion-type heat storage material according to the present invention (referred to as a value measured by the light scattering method) is preferably 2.65 μm or less, more preferably 2 μm. Or less, more preferably 1.5 μm or less. The lower limit of the average particle diameter of the emulsion is not particularly limited, but is usually 0.5 μm or more.

  The emulsion-type heat storage material according to the present invention may contain a thickener and a core material (supercooling preventive agent) as long as the effects of the present invention are not impaired.

  As the thickener, a polymer compound that is easily soluble in water is preferable. Examples thereof include dimethyl distearyl ammonium hectorite, cyclodextrin, polyacrylic acid, sodium polyacrylate, and (meth) acrylic acid copolymer. As the core material (supercooling inhibitor), known amines, alcohols, carboxylic acids and the like can be used.

  The emulsion-type heat storage material according to the present invention may further include other conventionally known components that can be included in the heat storage material, in addition to the thickener and the core material (supercooling preventive agent). As said other component, a cryogen, a rust preventive agent, antiseptic | preservative, an antifoamer, etc. can be included, for example.

  Here, the total amount of the essential components (that is, the paraffin compound, the nonionic surfactant having an alkyl group having 18 or more carbon atoms, the fatty acid salt, and water) in the emulsion type heat storage material according to the present invention is an emulsion type. The total amount of the heat storage material is preferably 70% by mass or more, more preferably 90% by mass or more, particularly preferably 99% by mass or more, and most preferably 100% by mass. . In consideration of this, it is preferable to appropriately determine the amount of the optional component added.

  The emulsion-type heat storage material according to the present invention can be suitably applied to heat storage for heating and cooling of buildings, houses, etc., freezing and refrigeration of food, heat transfer systems, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not restrict | limited at all by the following Example.

Example 1
C16 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS6) 60 g, stearic acid (reagent) 3 g, C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ − O- (CH ₂ CH ₂ O) _n —H (n = 7)), Nippon Emulsifier Co., Ltd., product name: New Coal 1807) 1.2 g are mixed and stirred thoroughly for 5 minutes while heating to 55 ° C. Mixed. While further stirring and mixing, 20.8 g of 3% by weight potassium hydroxide aqueous solution (equivalent to stearic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. An emulsion-type heat storage material 1 having a paraffin compound concentration of 75% by mass was obtained.

(Example 2)
C16 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS6) 60 g, stearic acid (reagent) 3 g, C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ − 1.2 g of O— (CH ₂ CH ₂ O) _n —H (n = 20)), Nippon Emulsifier Co., Ltd., product name: New Coal 1820), and stirred sufficiently for 5 minutes while heating to 55 ° C. Mixed. While further stirring and mixing, 20.8 g of 3% by weight potassium hydroxide aqueous solution (equivalent to stearic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. An emulsion-type heat storage material 2 having a paraffin compound concentration of 75% by mass was obtained.

(Comparative Example 1)
C16 normal paraffin with a melting point of 19 ° C. (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS6) 60 g, stearic acid (reagent) 3 g, C16 nonionic surfactant (synthetic product: ethylene oxide 4 of 1-hexadecanol) Mole adduct) (1.2 g) was mixed and thoroughly stirred and mixed for 5 minutes while heating to 55 ° C. While further stirring and mixing, 20.8 g of 3% by weight potassium hydroxide aqueous solution (equivalent to stearic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. A comparative emulsion heat storage material 1 having a paraffin compound concentration of 70% by mass was obtained.

(Comparative Example 2)
60 g C16 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS6) with a melting point of 19 ° C. and 3 g of stearic acid (reagent) are mixed and stirred thoroughly for 5 minutes while heating to 55 ° C. Mixed. While further stirring and mixing, 20.8 g of 3% by weight potassium hydroxide aqueous solution (equivalent to stearic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. A comparative emulsion heat storage material 2 having a paraffin compound concentration of 75% by mass was obtained.

Example 3
90 g of paraffin wax having a melting point of 47 ° C. (Nippon Seiwa Co., Ltd., product name: paraffin wax 115), 9 g of behenic acid (reagent), C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ —O— ( (CH ₂ CH ₂ O) _n —H (n = 7)), Nippon Emulsifier Co., Ltd., product name: New Coal 1807) 0.9 g were mixed and sufficiently stirred and mixed for 5 minutes while heating to 55 ° C. While further stirring and mixing, 39.6 g of 4% by weight aqueous potassium hydroxide solution (equivalent to behenic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. An emulsion-type heat storage material 3 having a paraffin compound concentration of 65% by mass was obtained.

Example 4
90 g of paraffin wax having a melting point of 47 ° C. (Nippon Seiwa Co., Ltd., product name: paraffin wax 115), 9 g of behenic acid (reagent), C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ —O— ( 1.8 g of CH ₂ CH ₂ O) _n —H (n = 7)), Nippon Emulsifier Co., Ltd., product name: New Coal 1807) were mixed and sufficiently stirred and mixed for 5 minutes while heating to 55 ° C. While further stirring and mixing, 39.6 g of 4% by weight aqueous potassium hydroxide solution (equivalent to behenic acid) was gradually added dropwise over 5 minutes to emulsify, and further 100.0 g of water was added and stirred. An emulsion-type heat storage material 4 having a paraffin compound concentration of 64% by mass was obtained.

(Comparative Example 3)
90 g of paraffin wax having a melting point of 47 ° C. (Nippon Seiwa Co., Ltd., product name: paraffin wax 115) and 9 g of behenic acid (reagent) were mixed and sufficiently stirred and mixed for 5 minutes while heating to 55 ° C. While further stirring and mixing, 39.6 g of a 4 mass% potassium hydroxide aqueous solution (equivalent to behenic acid) was gradually added dropwise over 5 minutes, but an emulsion could not be obtained.

(Example 5)
45 g of C19 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS-90) with a melting point of 33 ° C. and 45 g of paraffin wax (Nippon Seiwa Co., Ltd., product name: paraffin wax 115) with a melting point of 47 ° C., behenine Acid (reagent) 9 g, C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ —O— (CH ₂ CH ₂ O) _n —H (n = 7)), Nippon Emulsifier Co., Ltd., product name : New Coal 1807) 1.8 g was mixed and thoroughly stirred and mixed for 5 minutes while heating to 55 ° C. While stirring and mixing, 39.6 g of 4% by weight aqueous potassium hydroxide solution (equivalent to behenic acid) was gradually added dropwise over 5 minutes to emulsify, and 100.0 g of water was further added and stirred. An emulsion-type heat storage material 5 having a paraffin compound concentration of 63% by mass was obtained.

(Example 6)
45 g C19 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS-90) having a melting point of 33 ° C. and 45 g paraffin wax (Nippon Seiwa Co., Ltd., product name: paraffin wax 115) having a melting point of 47 ° C., stearin Acid (reagent) 9 g, C18 nonionic surfactant (polyoxyethylene stearyl ether (C ₁₈ H ₃₇ —O— (CH ₂ CH ₂ O) _n —H (n = 20)), Nippon Emulsifier Co., Ltd., product name : New Coal 1820) 1.8 g was mixed and thoroughly stirred and mixed for 5 minutes while heating to 55 ° C. While stirring and mixing, 49.9 g of an aqueous 3.8 mass% potassium hydroxide solution (equivalent to stearic acid) is gradually added dropwise over 5 minutes to emulsify, and 100.0 g of water is added and stirred. Thus, an emulsion type heat storage material 6 having a paraffin compound concentration of 60% by mass was obtained.

(Comparative Example 4)
45 g C19 normal paraffin (JX Nippon Oil & Energy Corporation, product name: normal paraffin TS-90) having a melting point of 33 ° C. and 45 g paraffin wax (Nippon Seiwa Co., Ltd., product name: paraffin wax 115) having a melting point of 47 ° C., stearin 9 g of acid (reagent) and 1.8 g of a C16 nonionic surfactant (synthetic product: 1-hexadecanol ethylene oxide 4 mol adduct) were mixed and sufficiently stirred and mixed for 5 minutes while heating to 55 ° C. While stirring and mixing, 49.9 g of an aqueous 3.8 mass% potassium hydroxide solution (equivalent to stearic acid) is gradually added dropwise over 5 minutes to emulsify, and 100.0 g of water is added and stirred. Thus, a comparative emulsion heat storage material 4 having a paraffin compound concentration of 60% by mass was obtained.

≪Evaluation≫
The emulsion type heat storage material and the comparative emulsion type heat storage material obtained in the above Examples and Comparative Examples were evaluated by the following methods.

[Evaluation of stability of emulsion-type heat storage material (measurement of emulsion particle size)]
As an index of the stability of the emulsion-type heat storage material, the average particle diameter of the emulsion in the emulsion-type heat storage material was measured by a light scattering method and evaluated based on the following evaluation criteria. The results are shown in Table 1 and Table 2 below:
A: The average particle size of the emulsion is 2.0 μm or less;
○: The average particle size of the emulsion is more than 2.0 μm and 2.5 μm or less;
(Triangle | delta): The average particle diameter of an emulsion is more than 2.5 micrometers and 3.0 micrometers or less;
X: The average particle diameter of an emulsion is more than 3.0 micrometers.

[Measurement of heat quantity of emulsion type heat storage material]
As an index of the heat storage property of the emulsion-type heat storage material, the heat quantity of the emulsion-type heat storage material was measured by a differential scanning calorimetry (DSC) measurement method, and the percentage value of the actual measurement value with respect to the theoretical value was evaluated based on the following evaluation criteria. The results are shown in Table 1 and Table 2 below:
○: The measured value exceeds 80% of the theoretical value;
Δ: The measured value is more than 50% and not more than 80% of the theoretical value;
X: The measured value is 50% or less with respect to the theoretical value.

  In Tables 1 and 2 below, in light of the evaluation criteria in the stability evaluation and calorimetry of the emulsion-type heat storage material, ◎: 20 points, ○: 10 points, Δ: 5 points, ×: 0 points From the total score in the case, 総 合: 30 points or more, ◯: 15 points or more and less than 30 points, x: less than 15 points is also described.

[Evaluation of thermal characteristics of emulsion-type heat storage materials]
The emulsion-type heat storage materials 5 and 6 obtained in Examples 5-6 and the comparative emulsion-type heat storage material 4 obtained in Comparative Example 4 were each put in a nylon-polyethylene bag and heat-sealed, and 50 ° C. Until heated. Next, the heated bag was placed in a constant temperature water bath at 25 ° C., and the temperature change with time was measured to evaluate the thermal characteristics (heat storage property). The results are shown in FIG.

  As is clear from the results shown in FIG. 1, a rapid decrease in temperature was observed in the comparative emulsion heat storage material obtained in Comparative Example 4. On the other hand, the emulsion-type heat storage material according to the present invention obtained in Examples 5 and 6 maintained a temperature in the vicinity of 40 ° C. that is the target maintenance temperature for a long time. It should be noted that the time taken for the temperature to drop to 35 ° C. after being placed in a constant temperature water bath at 25 ° C. was 18 minutes in Comparative Example 4, but 45 minutes in both Example 5 and Example 6. It was.

  As described above, it can be seen that the emulsion-type heat storage material according to the present invention can exhibit a heat storage property for a long time while maintaining a high amount of heat.

Claims (11)

  By adding an alkaline aqueous solution to an oil phase containing a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms and a fatty acid and heated to a temperature higher than the melting point of the paraffin compound, A method for producing an emulsion-type heat storage material, comprising the step of phase inversion of a water-type emulsion into an oil-in-water emulsion.   The manufacturing method of the emulsion-type heat storage material of Claim 1 with which the said paraffin compound contains n-paraffin.   The method for producing an emulsion-type heat storage material according to claim 1 or 2, wherein the alkyl group has 18 to 22 carbon atoms.   The method for producing an emulsion-type heat storage material according to any one of claims 1 to 3, wherein the nonionic surfactant is an alkylene oxide adduct of an aliphatic monoalcohol having the alkyl group.   The manufacturing method of the emulsion-type heat storage material of Claim 4 whose average addition mole number of the alkylene oxide in the alkylene oxide adduct of the said aliphatic monoalcohol is 3-40.   The method for producing an emulsion-type heat storage material according to any one of claims 1 to 5, wherein the fatty acid is a saturated fatty acid having 16 to 22 carbon atoms.   The method for producing an emulsion-type heat storage material according to any one of claims 1 to 6, wherein the base contained in the alkaline aqueous solution is a hydroxide of an alkali metal or an alkaline earth metal.   The method for producing an emulsion-type heat storage material according to any one of 1 to 7, wherein a content of a base contained in the alkaline aqueous solution is 0.9 to 1.1 equivalents relative to the fatty acid.   An emulsion-type heat storage material comprising a paraffin compound, a nonionic surfactant having an alkyl group having 18 or more carbon atoms, a fatty acid salt, and water, wherein the content of the paraffin compound is 64% by mass or more.   The nonionic surfactant is contained in 0.5 to 10 parts by mass, the fatty acid salt is contained in 3 to 20 parts by mass, and the water is contained in 5 to 40 parts by mass with respect to 100 parts by mass of the paraffin compound. The emulsion-type heat storage material as described.   The emulsion-type heat storage material according to claim 9 or 10, wherein the average particle size of the emulsion is 2.65 µm or less.