JP2015199869A - Heat storage material and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat storage material which is excellent in balance between the strength and the heat storage capacity, withstands repeated use and is safe for the human body and the environment and in a safe capsule form.SOLUTION: A heat storage material includes a core containing a heat storage material and a shell containing a resin, and the shell has a porosity of 5-80%, calculated by numerical expression (1): porosity(%)=[{volume of shell-(weight of shell/true specific gravity of shell)}/volume of shell]×100.

Description

  The present invention relates to a heat storage material. Specifically, the present invention relates to a heat storage material having a large particle size, excellent heat resistance and durability to external force, and a large amount of heat storage, and a method for manufacturing the same.

The heat storage material is a material that can take out the energy stored in the substance as heat as needed. As the energy, for example, the amount of heat required for temperature change in the same phase of the substance (sensible heat), melting, evaporation, energy required for phase change or phase transition of a certain kind of phase transition between crystals (latent heat), substance The energy etc. which generate | occur | produce with the chemical change of this can be mentioned.
The heat storage material is used in the presence or absence of a heat exchange medium such as water, for example, heat pumps; air conditioning applications such as buildings, houses, and underground shopping areas; vehicle air conditioning and canister applications; temperature rise prevention applications for electronic components such as IC chips Temperature control for clothing; Cold storage for fresh food or organ transport containers; Temperature control for structural materials on roads, bridges, etc .; Anti-fog for mirror surfaces such as curved mirrors; Anti-freezing for road surfaces; Cooling of household appliances such as refrigerators・ Constant temperature application: Used in various industrial fields in a wide range of temperatures, such as cold insulation materials for daily necessities and warmer applications. Such a heat storage material is used by processing the heat storage material alone or in combination with other substances into various forms such as granular, gel, and emulsion.

Among the above, the granular heat storage material has an advantage that it can be used by being kneaded as it is in a building material or the like. Here, in order to prevent volatilization or exudation of the heat storage material, the granular heat storage material is used by being coated with a barrier material or encapsulated in a barrier bag and processed into a capsule shape. It is preferable. Various aspects have been proposed as such a capsule-shaped heat storage material.
For example, Patent Document 1 discloses a microcapsule for heat transfer having a particle size of 10 μm or less manufactured using an emulsifier having a specific molecular weight;
Patent Document 2 discloses a microcapsule type heat storage material having a two-layer structure with an average particle diameter of 1 to 15 μm, which is manufactured through a step of applying centrifugal force to a mixture of a hydrophobic liquid and a hydrophilic liquid;
Patent Document 3 discloses microcapsules having an average particle diameter of 0.5 to 50 μm, which are produced by an in situ method and include a latent heat storage material.

Japanese Patent Application Laid-Open No. 07-204491 Japanese Patent Laid-Open No. 10-137777 JP 2001-288458 A

As described in the background section above, the capsule-shaped heat storage material has a structure in which the heat storage material is covered with the shell made of the barrier material as described above. Therefore, the mechanical strength of the capsule and the heat storage amount are usually in a trade-off relationship. That is, in order to increase the mechanical strength of the capsule, it is advantageous to increase the thickness of the shell, while in order to obtain a large amount of heat storage, it is advantageous to increase the proportion of the heat storage material (that is, to reduce the thickness of the shell). That's why. In this regard, a capsule heat storage material that is excellent in balance between mechanical strength and heat storage amount has not been known. In addition, even if the capsule shows toughness that can withstand external forces, it is pointed out that the shell may be destroyed by repeated heat storage and heat dissipation, and the heat storage material of the core may leak and become unusable. Yes. This phenomenon is considered to be caused by the fact that the shell cannot follow the volume change accompanying the phase change of the heat storage material during heat storage-heat radiation. There is no known capsule-shaped heat storage material that can be used repeatedly for a long time.
Furthermore, the capsule-shaped heat storage material of the prior art has a size of about 50 μm at most, and does not have a sufficient size to obtain an industrially useful heat storage amount. Furthermore, since many of the conventionally known heat storage material capsules are manufactured by an in situ method using formaldehyde, there are concerns about adverse effects on the human body and the environment.
The present invention solves the above problems of the prior art.
Accordingly, an object of the present invention is to provide a capsule-shaped heat storage material that has an excellent balance between strength and heat storage, can withstand repeated use, and is safe for the human body and the environment. The capsule heat storage material preferably has a size that is industrially easy to use.

The present inventors diligently studied to solve the above problems. As a result, the inventors have found that the above problem can be solved by the following configuration, and have completed the present invention.
According to the present invention, the above objects and advantages of the present invention are:
A heat storage material having a core containing a heat storage material and a shell containing a resin,
It is achieved by the heat storage material characterized in that the porosity calculated by the following formula (1) for the shell is 5 to 70%.
Porosity (%) = [{shell volume− (shell weight / true shell specific gravity)} / shell volume] × 100 (1)

ADVANTAGE OF THE INVENTION According to this invention, the capsule heat storage material which is excellent in the balance of intensity | strength and the amount of heat storage, can endure repeated use, and is safe with respect to a human body and the environment is provided. According to a preferred aspect of the present invention, the heat storage material can have a size that is industrially easy to use.
Accordingly, the heat storage material of the present invention is, for example, a heat pump; an air conditioning application for buildings, houses, underground shopping areas, etc .; an air conditioning system for automobiles, an application for canisters; an application for preventing the temperature rise of electronic components such as IC chips; Cooling applications for containers; Constant temperature applications for structural materials on roads, bridges, etc .; Antifogging applications for mirror surfaces such as curved mirrors; Antifreezing applications for road surfaces; Cooling and constant temperature applications for household appliances such as refrigerators; It can be suitably used in various industrial fields such as a warmer application.

The heat storage material of the present invention has a core and a shell.
The shell in the heat storage material of the present invention may cover the core completely or may cover only a part of the core, but is a capsule-shaped heat storage material that covers the core completely. It is preferable.

<Core>
The core in the heat storage material of the present invention contains at least a heat storage material. An embodiment that further contains at least one selected from the group consisting of a resin and rubber together with the heat storage material is also preferable.
[Heat storage material]
The heat storage material contained in the core of the heat storage material of the present invention is at least one selected from the group consisting of saturated hydrocarbons, fatty acids, fatty acid metal salts, fatty acid esters, aliphatic ethers, aliphatic ketones and aliphatic alcohols. It is preferable that
The saturated hydrocarbon is preferably a chain.
As this saturated hydrocarbon, those having about 7 to 60 carbon atoms are preferably used since the phase change temperature is useful. Saturated hydrocarbons can be roughly classified into two types according to their carbon number. Relatively low-molecular saturated hydrocarbons having preferably about 7 to 24 carbon atoms and petroleum waxes having preferably 20 or more carbon atoms. Since a preferable aspect changes with these types, it demonstrates in order below.
The saturated hydrocarbon having about 7 to 24 carbon atoms may be either linear or branched. However, from the viewpoint of increasing the latent heat amount of the heat storage material, it is preferably a linear saturated hydrocarbon. The carbon number of this type of saturated hydrocarbon is more preferably 11-20. The carbon number of this type of saturated hydrocarbon can be appropriately selected from the above range as the saturated hydrocarbon according to the desired phase change temperature. From the viewpoint of further expanding the usable temperature range, a material having a melting peak temperature (melting point) in a temperature range of about -20 to 50 ° C when measured by a differential scanning calorimeter (DSC) is used. It is preferable. Here, melting | fusing point refers to the extrapolation melting start temperature (Tim) in the crystal melting peak at the time of measuring based on JISK-7121.

Examples of preferable saturated hydrocarbons having about 7 to 24 carbon atoms together with their melting points are as follows.
n-undecane (-21 ° C), n-dodecane (-12 ° C), n-tridecane (-5 ° C), n-tetradecane (6 ° C), n-pentadecane (9 ° C), n-hexadecane (18 ° C) N-heptadecane (21 ° C.), n-octadecane (28 ° C.), n-nonadecane (32 ° C.), n-icosane (37 ° C.), n-henicosane (41 ° C.) and n-docosan (46 ° C.).
Examples of the petroleum wax include paraffin wax and microcrystalline wax.
Paraffin wax is a saturated hydrocarbon that is solid at room temperature and is produced by separation and purification from a distillation product obtained by distillation under reduced pressure using petroleum or natural gas as a raw material. As the paraffin wax, those having about 20 to 40 carbon atoms are preferable from the viewpoint of latent heat amount and availability. Examples of commercially available paraffin waxes include HNP-9, HNP-51, FNP-0090, and FT115 (all of which are trade names, manufactured by Nippon Seiwa Co., Ltd.).
Microcrystalline wax is a saturated hydrocarbon that is solid at room temperature and is manufactured by separating and refining from vacuum distillation residue oil or heavy distillate oil using petroleum as a raw material. As the microcrystalline wax, those having about 30 to 60 carbon atoms are preferable from the viewpoint of latent heat quantity and availability.

As the fatty acid, a fatty acid having 8 to 30 carbon atoms can be preferably used. The fatty acid may be any of a linear saturated fatty acid, a linear unsaturated fatty acid, a branched saturated fatty acid, and a branched unsaturated fatty acid. However, the linear saturated fatty acid is preferably used because it has a large amount of latent heat. Specific examples of the linear saturated fatty acid include octanoic acid (C8), nonanoic acid (C9), decanoic acid (capric acid) (C10), dodecanoic acid (lauric acid) (C12), tetradecanoic acid (myristic acid) ( C14), hexadecanoic acid (palmitic acid) (C16), octadecanoic acid (stearic acid) (C18), eicosanoic acid (C20), docosanoic acid (C22), tetracosanoic acid (C24), hexacosanoic acid (C26), octacosanoic acid (C26) C28) and triacontanoic acid (C30).
Examples of the fatty acid metal salt include lithium 12-hydroxystearate and aluminum 2-ethylhexanoate.
Examples of the fatty acid ester include butyl lactate, ethyl lactate, methyl oleate, diethyl succinate, ethyl decanoate, methyl decanoate, methyl hexadecanoate, butyl dodecanoate, n-hexadecyl palmitate, stearyl stearate and the like. Can do.

As the aliphatic ether, a fatty acid ether having 14 to 60 carbon atoms can be used. Specific examples of the aliphatic ether include heptyl ether, octyl ether, tetradecyl ether, hexadecyl ether and the like, and the number of oxygen atoms is one from the viewpoint of high latent heat and ease of synthesis. An ether having a symmetric structure can be preferably used.
Examples of the aliphatic ketone include 2-octanone, 3-octanone, 2-nonanone, 3-nonanone, and cycloheptanone.
As the aliphatic alcohol, an aliphatic alcohol having 8 to 60 carbon atoms can be used. Specific examples of the aliphatic alcohol include 2-dodecanol, 1-tetradecanol, 7-tetradecanol, 1-octadecanol, 1-eicosanol, 1,10-decanediol, and the like. Of these, primary alcohols are preferably used because they exhibit a high amount of latent heat.
Of the above, a compound selected from saturated hydrocarbons is used; or at least one selected from the group consisting of fatty acid esters, aliphatic ketones, aliphatic alcohols and aliphatic ethers;
Preference is given to using mixtures with fatty acid metal salts.
In the present invention, the heat storage material may be used alone or in combination of two or more. However, from the viewpoint of increasing the amount of latent heat at a desired temperature, it is preferably used as a single type or a mixture of two types.

[Resin and rubber]
The core of the heat storage material of the present invention can further contain at least one selected from the group consisting of a resin and rubber in addition to the above heat storage material.
The resin is not particularly limited as long as appropriate physical properties such as shear resistance and heat resistance can be imparted to the obtained heat storage material.
Examples of the resin in the core of the heat storage material of the present invention include vinyl alcohol (co) polymer, acrylic resin, acrylamide resin, urethane resin, epoxy resin, polyamic acid, polyimide, polyamide, cellulose, polyester, polyolefin, and the like. In addition, a cured product of the photocurable composition may be used. The polyolefin of the above is a concept excluding those corresponding to the saturated hydrocarbons exemplified above as the heat storage material.

The said photocurable composition is a composition containing the component hardened | cured by reaction caused by light irradiation. As this photocurable composition, what was described as photocurable resin in Unexamined-Japanese-Patent No. 2011-071299, Unexamined-Japanese-Patent No. 2006-348198 etc. can be used, for example.
Examples of the curable component in the photocurable composition include a photopolymerizable monomer and a photopolymerizable oligomer. Among these, it is preferable to use a photopolymerizable oligomer. The polystyrene-reduced number average molecular weight of this photopolymerizable oligomer measured by gel permeation chromatography (GPC) is preferably 300 to 30,000, and more preferably 500 to 20,000.
Photopolymerizable oligomers can be classified into photopolymerizable oligomers that are cured by radical reaction and photopolymerizable oligomers that are cured by cationic reaction.

The photopolymerizable oligomer cured by the radical reaction is an oligomer having a C═C double bond (for example, a C═C double bond contained in a (meth) acryloyl group, a vinyl group, etc.) as a polymerizable group. Examples include (meth) acrylate oligomers, urethane (meth) acrylate oligomers, epoxy (meth) acrylate oligomers, ester (meth) acrylate oligomers, unsaturated polyester oligomers, and high acid value unsaturated polyepoxides. , Polyene / thiol oligomers, cinnamic acid oligomers, unsaturated polyamides, and the like. Specific examples thereof include (meth) acrylate oligomers such as resins having polyethylenic glycol photopolymerizable ethylenically unsaturated groups at both ends (polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth)). Acrylate, polyalkylene glycol di (meth) acrylate having 4 to 10 carbon atoms in the alkyl chain, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc.), anionic unsaturated acrylic resin, cation Unsaturated acrylic resins, etc .;
Examples of unsaturated polyester oligomers include high acid value unsaturated polyesters.
The photopolymerizable oligomer that cures by the cationic reaction is an oligomer having an epoxy group, a vinyl ether group, or the like as a polymerizable group. Examples thereof include epoxy oligomers and vinyl ether oligomers.
Examples of commercially available photocurable oligomers as described above include ENT-1000, ENT-2000, ENT-3400, ENT-4000, ENTG-2000, and ENTG-3800 (all are trade names, Kansai Paint Co., Ltd.). Manufactured) and the like.

The photopolymerizable composition in the present invention preferably contains a polymerization initiator in addition to the curable component as described above. This photopolymerization initiator is classified into a photopolymerization initiator that generates radicals by light irradiation and a photopolymerization initiator that generates cations by light irradiation. Examples of photopolymerization initiators that generate radicals upon light irradiation include, for example, benzoyl peroxide, azoisobutyronitrile, and the like;
Examples of photopolymerization initiators that generate cations by light irradiation include aryldiazonium salts such as phenyldiazonium hexafluorophosphate: diaryliodonium salts such as diphenyliodonium hexafluoroantimonate: and triphenylsulfonium hexafluoroantimonate A triarylsulfonium salt etc. can be mentioned, respectively.
The content of the photopolymerization initiator in the photopolymerizable composition is preferably 0.001 to 10% by mass, more preferably 0.1 to 5% with respect to 100 parts by mass of the curable component as described above. % By mass.

The weight average molecular weight Mw in terms of polystyrene measured by GPC for the resin in the core of the heat storage material of the present invention is 1,000 to 10,000,000 from the viewpoint of imparting appropriate strength to the heat storage material to be obtained. Is more preferable, 5,000 to 5,000,000 is more preferable, and 10,000 to 1,000,000 is particularly preferable.
The melting point of the resin is preferably one having a melting point exceeding the melting point Tim of the heat storage material to be used, and more preferably having a melting point of Tim + 20 ° C. or more, from the viewpoint of heat resistance in the obtained heat storage material. Specific examples of the melting point of the resin include a range of 80 to 250 ° C., preferably 90 to 240 ° C., and more preferably 100 to 230 ° C.

Examples of the rubber include conjugated diene (co) polymer, hydrogenated conjugated diene (co) polymer, ethylene-α-olefin copolymer, acrylic rubber (ACM), chloroprene rubber (CR), fluororubber, Silicone rubber, urethane rubber (UR), ethylene-vinyl acetate copolymer, ionomer and the like can be mentioned, and one or more selected from these can be preferably used. Among these, use of at least one selected from the group consisting of a conjugated diene (co) polymer and a hydrogenated product thereof, and an ethylene-α-olefin copolymer makes it possible to obtain an appropriate strength for the obtained heat storage material. It is preferable at the point which can provide.
As the conjugated diene (co) polymer, any of synthetic rubber and natural rubber can be used. Specific examples of the synthetic rubber include butadiene rubber (BR), styrene / butadiene rubber (SBR), nitrile rubber (NBR), isoprene rubber (IR), butyl rubber (IIR), and the like. One or more selected from can be preferably used.

Examples of the hydrogenated product of the conjugated diene (co) polymer include a hydrogenated product of a block copolymer of an alkenyl aromatic compound and a conjugated diene compound, an olefin elastomer, and the like. Specific examples thereof include hydrogenated and bare hands of block copolymers of alkenyl aromatic compounds and conjugated diene compounds such as styrene-ethylene / butylene-styrene block copolymers (SEBS), styrene-ethylene / propylene-styrene blocks. Copolymer (SEPS), styrene-ethylene / butylene block copolymer (SEB), styrene-ethylene / propylene block copolymer (SEP) and the like;
As the olefin elastomer, for example, an alkenyl aromatic compound such as styrene-ethylene / butylene-olefin crystal block copolymer (SEBC) -olefin crystal block copolymer: olefin crystal-ethylene / butylene-olefin crystal block copolymer ( Examples thereof include olefin crystal block copolymers such as CEBC).

As the hydrogenated product of the conjugated diene (co) polymer in the present invention, it is preferable to use an olefin crystal block copolymer from the viewpoint that fluidity during molding is appropriate.
Examples of the ethylene-α-olefin copolymer include a binary copolymer rubber of ethylene and α-olefin, and a terpolymer rubber of ethylene, α-olefin and non-conjugated diene. The α-olefin is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 3 to 8 carbon atoms, and one or more selected from these can be used. Specific examples of such α-olefins include propylene and 1-octene. Examples of the non-conjugated diene include ethylidene-2-norbornene.

The polystyrene-reduced weight average molecular weight Mw measured by GPC for the rubber in the core in the heat storage material of the present invention is preferably 10,000 to 1,000,000, more preferably 100,000 to 700,000. More preferably, it is 200,000 to 600,000, and particularly preferably 250,000 to 500,000. From the viewpoint of imparting appropriate mechanical strength to the obtained heat storage material and suppressing phase separation in the core together, the Mw of the rubber is preferably 100,000 or more, while the heat storage material is molded. From the viewpoint of ensuring the fluidity of the material, the Mw of the rubber is preferably 1,000,000 or less, and more preferably 700,000 or less.
The melt flow rate MFR of the rubber is not particularly limited, but a value of 0.01 to 100 g / min can be exemplified as a temporary guide. The measurement conditions for this MFR should be set appropriately depending on the type of rubber, and those skilled in the art know the measurement conditions for each resin as their own knowledge, or easily know the appropriate measurement conditions by referring to textbooks. be able to. For example, in the case of a hydrogenated product of a conjugated diene (co) polymer, it can be measured according to JIS K-7210 at 230 ° C. with a load of 10 kg.

The content ratio of at least one selected from the group consisting of resin and rubber in the core of the heat storage material of the present invention is preferably 0.1 to 150 parts by mass, more preferably 100 parts by mass of the heat storage material. It is 1-100 mass parts, More preferably, it is 1-25 mass parts.
As the at least one selected from the group consisting of the resin and rubber, it is preferable to use rubber in that the productivity and impact resistance of the obtained heat storage material can be further improved.

[Other ingredients]
The core of the heat storage material of the present invention may contain other components in addition to the above heat storage material and at least one selected from the group consisting of resin and rubber. Examples of the other components include a filler and a function-imparting agent.
Examples of the filler include iron, silver, copper, graphite, nickel, tin, tungsten, brass, phosphor bronze, titanium oxide, zinc oxide, ferrite, aramid, aluminum nitride, boron nitride, aluminum hydroxide, calcium hydroxide, and oxidation. Aluminum, magnesium oxide, barium sulfate, carbon black, graphite, carbon nanotube, expanded graphite, glass, asbestos, calcium carbonate, magnesium carbonate, potassium titanate, talc, silica, calcium silicate, kaolin, diatomaceous earth, montmorillonite, pumice, Ebonite, cotton flock, cork, fluororesin and the like can be mentioned, and one or more selected from these can be used. The shape of the filler is not particularly limited, and can be any shape such as powder, flake, fiber, whisker, and the like. For the purpose of improving the dispersibility of the granular heat storage material of the present invention in the core or coating layer, it may be used after being subjected to appropriate surface treatment such as hydrophobization treatment or hydrophilic treatment.
Examples of the function-imparting agent include antioxidants, antistatic agents, weathering agents, ultraviolet absorbers, antiblocking agents, crystal nucleating agents, flame retardants, vulcanizing agents, vulcanizing aids, antibacterial and antifungal agents. Agents, dispersants, anti-coloring agents, foaming agents, rust inhibitors, heavy metal deactivators, melting point modifiers (freezing point depressants), etc., and one or more selected from these may be used. be able to.
The use ratio of the other components in the core of the heat storage material of the present invention is preferably 10 parts by mass or less, more preferably 3 parts by mass or less, particularly preferably 100 parts by mass of the heat storage material. It does not contain other components.

<Shell>
The shell in the heat storage material of the present invention contains a resin.
[resin]
As the resin contained in the shell, for example, a water-soluble resin, a polar organic solvent-soluble resin, a water-alcohol mixed solvent-soluble resin, or the like is preferably used because the heat storage material of the present invention can be easily produced. . Examples of the water-soluble resin include polyvinyl alcohol resins (polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, polyvinyl acetal, etc.);
Polysaccharides such as starch, agarose, cellulose, chitins, chitosans;
Resins having an ether bond (polyethylene oxide, polypropylene oxide, polyethylene glycol, polyvinyl ether, etc.);
Examples thereof include resins having a carbamoyl group [polyacrylamide, polyvinylpyrrolidone, polyacrylic hydrazide, etc.].
Examples of the polar organic solvent-soluble resin include polylactic acid, polyalkylene succinate [polybutylene succinate, polybutylene succinate adipate, polybutylene succinate terephthalate, and polyethylene succinate];
Examples of the water-alcohol mixed solvent-soluble resin include ethylene-vinyl alcohol copolymer and polyalkyl (meth) acrylate.

The ethylene content in the ethylene-vinyl alcohol copolymer is preferably 10 to 70 mol%, more preferably 20 to 60 mol%. The number of carbon atoms in the alkyl group of the polyalkyl (meth) acrylate is preferably 1-20, and more preferably 1-10. Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, and an i-propyl group.
These resins may be used alone or in combination of two or more.
The important average molecular weight Mw in terms of polystyrene measured by GPC for these resins is preferably 1,000 to 10,000,000, more preferably 5,000 to 5,000,000, and particularly preferably 10. , 1,000 to 1,000,000.
Among these resins, it is preferable to use polyvinyl alcohol or an ethylene-vinyl alcohol copolymer from the viewpoint of gas barrier properties and availability.

[Other ingredients]
In addition to the resin as described above, the shell of the heat storage material of the present invention may contain the same filler, function-imparting agent, and the like as those described above as other components that the core can contain. Good.
The proportion of the other components used in the shell of the heat storage material of the present invention is preferably 10 parts by mass or less, more preferably 3 parts by mass or less, and particularly preferably other than 100 parts by mass of the resin. It does not contain the component of.

[Porosity]
A gap is provided in the shell of the heat storage material of the present invention.
The heat storage material of the present invention can prevent leakage of the heat storage material contained in the core by having a shell covering the core,
Since the shell has voids, it is possible to prevent the shell from being destroyed due to the volume change of the heat storage material during heat storage and heat dissipation, and thus it is possible to more effectively prevent leakage of the heat storage material for a long period of time.
The porosity of the shell in the heat storage material of the present invention is 5 to 80%, preferably 10 to 75%, and more preferably 15 to 70%.
The porosity of the shell can be obtained by the following formula (1).
Porosity (%) = [{shell volume− (shell weight / true shell specific gravity)} / shell volume] × 100 (1)
The average pore diameter of the voids of the shell in the heat storage material of the present invention is preferably 0.01 to 100 μm, more preferably 0.1 to 10 μm, and further preferably 0.3 to 5 μm. The average pore diameter of the voids is preferably a size that does not exceed the thickness of the shell. The average pore diameter of the void can be determined from an image taken using a scanning electron microscope.

<Heat storage material>
Examples of the shape of the heat storage material of the present invention include a true sphere, a partially distorted sphere, a daruma shape, a columnar shape, a weight shape, a rectangular parallelepiped shape, and a combination thereof.
The average particle diameter of the heat storage material of the present invention is preferably 0.01 to 30 mm, more preferably 0.3 to 10 mm, and further preferably 0.7 to 5 mm. This average particle diameter is a number average particle diameter defined as a value obtained by dividing the sum of the particle diameters of a plurality of measurement target particles randomly collected by the number of measurement targets. The number average particle diameter can be measured with a commercially available optical measuring device such as “Digital Microscope VHX-900” manufactured by Keyence Corporation. A heat storage material having a number average particle diameter in the above range is preferable because it exhibits suitable handling properties in industrial applications.

The ratio of the core to the shell in the heat storage material of the present invention is preferably 0.1 to 80% by weight, more preferably 0.5 to 70% by weight as the weight ratio of the shell to the total weight of the core and shell. It is preferably 1 to 60% by weight. The content ratio of the core in the heat storage material of the present invention is preferably 30 to 99.9 mass%, more preferably 50 to 99 mass%, and more preferably 70 to 99 mass% with respect to the total mass of the heat storage material. More preferably, it is made into%. Furthermore, the average thickness of the shell in the heat storage material of the present invention is preferably 0.1 to 10,000 μm, more preferably 1 to 1000 μm, and further preferably 50 to 1000 μm. The average thickness of the shell is the largest value (d1) and the smallest value (d2) of the shell thickness (d) measured for the cross section of each particle in a plurality of particles to be measured randomly. Is the number average thickness defined as a value obtained by dividing Σ (dx) of each obtained (dx) by the number of objects to be measured. The measurement can be performed with a commercially available optical measurement device such as “Digital Microscope VHX-900” manufactured by Keyence Corporation. The heat storage material having the core-shell ratio, core content, and shell thickness as described above is a sufficiently large heat storage amount that is industrially useful, high toughness that can ensure freedom of handling, and bleeding of the heat storage material. It is extremely preferable in that it has a high barrier property that shields the light.
The heat storage material of the present invention exhibits a high heat storage amount. The heat storage amount of the heat storage material of the present invention is 50 J / g or more, can be 70 to 200 J / g, and particularly 90 to 170 J / g.
The heat storage material of the present invention is excellent in durability. The heat storage material of the present invention can endure 1,000 times or more of heat storage-heat dissipation cycle, and in particular, can endure 3000 times or more of heat storage-heat dissipation cycle.

<Method for producing heat storage material>
The heat storage material of the present invention can be produced by any method, for example, a dropping method using a capsule production apparatus equipped with a concentric double nozzle.
The heat storage material of the present invention can be produced, for example, by a method through a step of extruding the core forming material and the shell forming composition from the inner nozzle and the outer nozzle of the concentric double nozzle and dropping them into the coagulating liquid. it can. According to this method, since the heat storage material seamless to the shell can be manufactured, the leakage of the heat storage material can be more reliably prevented, which is preferable.
The core-forming material essentially contains a heat storage substance, optionally contains the resin, and may further contain other components. It is preferable that the core forming material is made of only a heat storage material or does not contain a component (for example, a solvent) other than the resin and other components selected from the components exemplified above as the other components.

The shell-forming composition is preferably a liquid composition in which the resin and other optional components are preferably dissolved or dispersed in a solvent.
This composition for forming a shell may further contain a foaming agent in order to make it easier to form voids in the shell of the heat storage material to be obtained. Foaming agents can be classified into chemical foaming materials and physical foaming agents. Examples of the chemical foaming agent include a hollow particle type foaming agent and a pyrolytic foaming agent;
As a physical foaming agent, for example, inorganic gas such as carbon dioxide, nitrogen, air, etc.
Each can be illustrated. These foaming agents may be used independently and may use 2 or more types together. As the foaming agent, specifically, for example, those described in JP 2014-19745 A, JP 2013-7045 A, etc. can be preferably used. The ratio of the foaming agent to be used should be set as appropriate depending on the desired porosity, but may be 0.01 to 50% by weight with respect to the total weight of the shell-forming composition.
Even when the shell-forming composition does not contain the foaming agent as described above, a heat storage material having a shell with an appropriate porosity can be produced by the method described later.

A preferable solvent in the composition for forming a shell is preferably composed of a good solvent for the resin constituting the shell of the heat storage material of the present invention, or a mixed solvent of the good solvent and a poor solvent for the resin. More specifically, it differs depending on the type of resin constituting the shell of the heat storage material of the present invention. When the shell is made of a water-soluble resin,
When made of a polar organic solvent soluble resin,
It is convenient to consider separately from the case of a water-alcohol mixed solvent soluble resin.

First, when the shell is made of a water-soluble resin, a preferable solvent in the shell-forming composition is:
It is preferably a mixed solvent consisting of water alone or a water-miscible organic solvent which is a poor solvent for the water-soluble resin. As described above, the case where the resin constituting the shell is a polyvinyl alcohol resin, a polysaccharide, a resin having an ether bond, a resin having a carbamoyl group, or the like belongs to this type.
Examples of the organic solvent include alcohols, aldehydes, ketones, ethers, and the like. As said alcohol, aliphatic alcohol or ether alcohol is preferable, and both monoalcohol and polyhydric alcohol can be used preferably. Examples of the monoalcohol include methanol, ethanol, n-propanol, i-propanol, 2-methoxyethanol, 2-ethoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether and the like;
Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, glycerin, sorbitan, and the like. Can do. Examples of the aldehyde include formaldehyde, acetaldehyde, propionaldehyde, glyoxal and the like;
Examples of the ketone include acetone, 2-butanone, and the like. The ether is preferably a cyclic ether, and specific examples include tetrahydrofuran, dioxolane, tetrahydropyran, dioxane, trioxane, and the like.
These organic solvents can be used individually by 1 type, or may mix and use 2 or more types.
The use ratio of water and the organic solvent in the mixed solvent contained together with the water-soluble resin in the shell-forming composition is preferably 1 to 80% by weight as the ratio of the organic solvent to the total amount of the mixed solvent. More preferably, it is 70 weight%, and it is still more preferable that it is 10-60 weight%.

Next, when the shell is made of a polar organic solvent-soluble resin, a preferred solvent in the composition for forming a shell is
It is preferably composed of only the above polar organic solvent or a mixed solvent composed of the polar organic solvent and water. As described above, the case where the resin constituting the shell is polylactic acid, polyalkylene succinate or the like belongs to this type.
As the polar organic solvent, a water-miscible solvent is preferably used. For example, it is selected from aldehydes, ketones, ethers and the like. As said aldehyde, a ketone, and ether, when the shell consists of water-soluble resin, the same thing as the aldehyde, ketone, and ether which were illustrated above as a poor solvent of this water-soluble resin can be used, respectively. These organic solvents can be used individually by 1 type, or may mix and use 2 or more types. When the resin constituting the shell is polylactic acid, it is preferable to use a mixture of at least one selected from aldehydes and ketones and at least one selected from ether as the organic solvent. In this case, the use ratio of each organic solvent is preferably 10 to 90% by weight, more preferably 20 to 80% by weight as the use ratio of ether with respect to the total amount of the organic solvent.
The use ratio of water and the polar organic solvent in the mixed solvent contained in the shell-forming composition together with the polar organic solvent-soluble resin is 1 to 70% by weight as the ratio of the polar organic solvent to the total amount of the mixed solvent. Preferably, it is 5-60 weight%, More preferably, it is 7-50 weight%.

Finally, when the shell is made of a water-alcohol mixed solvent soluble resin, a preferred solvent in the shell-forming composition is the water-alcohol mixed solvent. As described above, the case where the resin constituting the shell is an ethylene-vinyl alcohol copolymer, polyalkyl (meth) acrylate,.
As the alcohol, when the shell is made of a water-soluble resin, the same alcohol as exemplified above can be used as a poor solvent for the water-soluble resin. Alcohol can be used individually by 1 type, or may mix and use 2 or more types.
The use ratio of water and alcohol in the mixed solvent contained in the shell-forming composition together with the water-alcohol mixed solvent-soluble resin is preferably 10 to 90% by weight as the ratio of alcohol to the total amount of the mixed solvent, It is more preferably 20 to 80% by weight, and further preferably 30 to 70% by weight.

The concentration of the polymer in the shell-forming composition is preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and still more preferably 2 to 30% by weight.
The shell-forming composition can be prepared by dissolving a resin that becomes a shell in a solvent as described above according to its type. The temperature at which the resin is dissolved in the solvent can be, for example, 80 to 100 ° C., and preferably 90 to 100 ° C.

The coagulating liquid is preferably a poor solvent for the resin that becomes the shell, and more preferably a poor solvent for the resin that becomes the shell and miscible with the solvent of the shell-forming composition. It is convenient to consider the coagulation liquid according to the type of resin that becomes the shell. Hereinafter, when the shell resin is made of a water-soluble resin,
When made of a polar organic solvent soluble resin,
This will be explained in order, divided into the case of water-alcohol mixed solvent soluble resin.
First, when the resin used as the shell is a water-soluble resin, alcohol is preferable as the coagulating liquid. The alcohol in this case is preferably an aliphatic alcohol having 1 to 3 carbon atoms, and specific examples include methanol, ethanol, n-propanol, i-propanol and the like.
Next, when the resin used as the shell is a polar organic solvent-soluble resin, water is used as the coagulation liquid, a polar organic solvent that is a poor solvent for the resin, or a combination of water and a polar organic solvent. It is preferred to use a mixture. In this case, the solidification of the resin can be ensured by setting the total content ratio of water and the polar organic solvent which is a poor solvent to 80% by weight or more. When the resin dissolves well in a mixed solvent composed of a plurality of polar organic solvents, one kind of polar organic solvents constituting the mixed solvent can be used as the coagulating liquid. For example, when the resin is polylactic acid, one or more selected from aldehydes and ketones or one or more selected from ether can be suitably used as the coagulating liquid.
Furthermore, when the resin used as the shell is a water-alcohol mixed solvent soluble resin, it is preferable to use water or alcohol as the coagulation liquid. As alcohol in this case, a C1-C3 aliphatic alcohol is preferable.

It is preferable to use the coagulation liquid by adjusting the temperature to a temperature lower than room temperature. The temperature of the coagulation liquid is preferably -5 to 20 ° C, more preferably 0 to 10 ° C.
It is preferable to use an excessive amount of the coagulating liquid with respect to the heat storage material to be manufactured. Specifically, it is preferably 100 parts by weight or more with respect to a total of 100 parts by weight of the core-forming material and the shell-forming composition dropped into the coagulation liquid, and 1,000 to 10,000 parts by weight. More preferably.
When the core-forming material and the shell-forming composition are extruded from the inner nozzle and the outer nozzle of a concentric double nozzle and dropped into the coagulating liquid, a heat storage material having a two-layer structure consisting of a core and a shell can be obtained. it can. Here, by appropriately adjusting the supply rate (extrusion rate) and the ratio between the core-forming material and the shell-forming composition, the particle size of the heat storage material, the mass ratio of the core and the shell, and the thickness of the shell Etc. can be controlled arbitrarily. Appropriate feed rates of the composition are readily known by a few preliminary experiments by those skilled in the art.

<Method for forming void in shell>
As for the heat storage material of this invention, a shell has a space | gap. The formation of the shell having voids will be described below separately for the case where the shell-forming composition contains a foaming agent and the case where it does not contain the foaming agent.
When the shell-forming composition contains a foaming agent, the coagulating liquid is formed when the shell-forming composition is extruded from the outer nozzle of the concentric double nozzle, or the shell-forming composition and the core-forming material are integrated. After being dripped into the capsule shape to form a capsule, voids can be formed in the shell by foaming by an appropriate method according to the foaming agent used. For example, when a pyrolytic foaming agent is used as the foaming agent, foaming is performed by heat-treating the obtained capsule. As the foaming method, specifically, methods described in, for example, JP 2014-19745 A, JP 2013-7045 A, and the like can be preferably applied. The average pore diameter of the voids can be controlled by the type of foaming agent used and the foaming method employed, and the porosity can be controlled by the proportion of foaming agent used. These optimum conditions can be easily known by a few preliminary experiments by those skilled in the art.

  On the other hand, when the shell-forming composition does not contain a foaming agent, the porosity of the shell and the average particle size of the voids in the heat storage material are controlled by the combination of the coagulating liquid used and the solvent of the shell-forming composition. can do. Specifically, the higher the affinity between the coagulation liquid and the solvent for the shell-forming composition, the higher the porosity of the shell and the smaller the average particle size of the voids. Conversely, if the affinity between the two is too low, the porosity of the shell tends to be low, and the particle size of the voids tends to vary. These are general trends and are not an absolute guide, but the optimal coagulant composition for a particular shell-forming composition can be readily determined by a few preliminary experiments by those skilled in the art.

(1) Average particle diameter The average particle diameter of the obtained heat storage material was measured using the dimension measuring function of Digital Microscope VHX-900 (manufactured by Keyence Corporation). The average particle diameter is represented by the biaxial average diameter represented by the following mathematical formula (2), and was evaluated as the number average diameter represented by the following mathematical formula (3) from the measured values of 10 measurement target heat storage materials collected at random. .
Biaxial average diameter = {(major axis diameter) + (minor axis diameter)} / 2 (2)
Number average diameter = {Σ (measured particle diameter)} / (number of measurements) (3)
(2) Shell thickness The average thickness of the shell was measured using the dimension measuring function of a digital microscope VHX-900 (manufactured by Keyence Corporation). The average thickness is represented by the measured particle thickness represented by the following mathematical formula (4), and was evaluated as the number average thickness represented by the following mathematical formula (5) from the measured values of 10 randomly measured heat storage materials. .
Measurement particle thickness = {(maximum value) + (minimum value)} / 2 (4)
Number average thickness = {Σ (measured particle thickness)} / (measured number) (5)

(3) Melting point and latent heat amount The melting point and latent heat amount of the obtained heat storage material were measured using a differential scanning calorimeter (DSC).
When the weight of one heat storage material was 15 mg or less, the heat storage material was halved with a cutter, each cut surface was placed down and placed on a sample pan, and DSC measurement was performed. When the weight of one heat storage material exceeded 15 mg, it was divided into portions of 15 mg or less and measured. The average value was adopted when the measurement was divided.
In the measurement, the sample was held at 170 ° C. for 10 minutes, then cooled from 170 ° C. to −30 ° C. at a rate of 10 ° C./min, held at −30 ° C. for 10 minutes, and then from −30 ° C. to 100 ° C. The temperature was increased at a rate of 1 minute.
From the DSC chart obtained as described above, the extrapolated melting start temperature and the heat of fusion of the melting peak corresponding to the blended heat storage material are obtained according to JIS K-7121, and these values are the melting point and heat storage material of the heat storage material, respectively. The amount of latent heat was evaluated.
(4) Porosity The porosity of the shell is determined based on the volume of the shell and the shell from the supply ratio, average particle diameter and shell thickness of the core forming material and the shell forming composition supplied to the concentric double nozzle of the vibration dropping device. The weight was determined by calculation, and these values were determined by substituting these values into the above formula (1) together with the literature value of the true specific gravity of the resin constituting the shell.

(5) Bleed property About 10 g of the obtained heat storage material was used as one measurement sample.
The test was performed by placing the sample in a thermostat programmed to repeat the cycle consisting of the following i) to iv) 100 times.
i) maintained at 60 ° C. for 30 minutes ii) cooled from 60 ° C. to −20 ° C. at a cooling rate of 2 ° C./min iii) maintained at −20 ° C. for 30 minutes, and iv) −20 at a heating rate of 2 ° C./min After the sample after 100 cycles was taken out and cooled sufficiently, the leakage of the heat storage material was visually confirmed, and when no leakage of the heat storage material was observed, the bleed resistance “A (good)”, The case where slight leakage of the heat storage material was confirmed was evaluated as bleed resistance “B (possible)”, and the case where leakage of the heat storage material was clearly confirmed was evaluated as bleed resistance “C (defect)”.

(6) Capsule strength The capsule strength of the obtained heat storage material was measured using a creep meter (model number “Leoner RE3305”) manufactured by Yamaden Co., Ltd. This creep meter is a compression test apparatus having a mechanism for applying a load at a constant speed from the vertical direction to an object to be measured.
Plunger shape is W13mm × D30mm × H25mm triangular prism, tip angle is 30 ° and tip is 1mm width, and maximum load point (maximum load applied at the time of breakage of measured object) is measured at compression speed of 0.5mm / sec. did.
In the measurement, one randomly selected heat storage material was used as the object to be measured, and the average value of the measurements performed three times was examined. The case where this value was 10 (N) or higher was evaluated as the capsule strength “A (good)” and the case where it was less than 4 (N) as the capsule strength “C (bad)”.
(7) Heat resistance About 10 g of the obtained heat storage material was used as one measurement sample.
A sample was placed in a thermostatic bath set to an internal temperature of 100 ° C., and after 2 hours had passed, the sample was taken out and cooled sufficiently, and then leakage of the heat storage material was visually confirmed. When no leakage of heat storage material is observed, heat resistance “A (good)”, when slight leakage of heat storage material is confirmed, heat resistance “B (possible)”, leakage of heat storage material is clearly confirmed The case was evaluated as heat resistance “C (defect)”.

Each component used in the examples and comparative examples is as follows.
<Core>
[Heat storage material]
n-Octadecane: manufactured by Sasol Germany GmbH, “PARAFOL 18-97”
n-Tetradecane: “TS Paraffin TS-4” manufactured by JX Nippon Oil & Energy Corporation
Methyl hexadecanoate: “Pastel M-16”, manufactured by Lion Corporation
[Rubber]
Conjugated diene rubber: “SEEPS Septon 4077” manufactured by Kuraray Co., Ltd., weight average molecular weight = about 350,000 <shell>
[resin]
Polyvinyl alcohol: “GOHSENOL NL-05” manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
Ethylene-vinyl alcohol copolymer: “Ethylene-vinyl alcohol copolymer EVAL G156B” manufactured by Kuraray Co., Ltd.
Polymethyl methacrylate: manufactured by Nacalai Tesque, "Polymethyl methacrylate (molecular weight: 415,000)"
Polylactic acid: “Ingeo biopolymer” manufactured by Nature Works LLC

Example 1
(1) Core-forming material A commercial product of n-octadecane as a heat storage material was used as it was as a core-forming material.
(2) Composition for forming a shell By dissolving an ethylene-vinyl alcohol copolymer in a mixed solvent composed of water and methanol (water: methanol = 50: 50 (weight ratio)), a solution with a concentration of 15% by mass is obtained. A shell-forming composition was prepared.
(3) Manufacture of heat storage material The manufacture of the heat storage material was performed using a vibration dripping device (manufactured by Büch) having a concentric double nozzle.
The shell-forming composition is passed through the outer nozzle of the vibration dropping device, and the core-forming material is passed through the inner nozzle, forming droplets while vibrating the nozzle at a frequency of 9,000 times / minute, A capsule-type heat storage material having a core-shell two-layer structure was produced by dropping the solution into a coagulating liquid composed of water whose temperature was adjusted to 5 ° C. At this time, the flow rate of each nozzle was adjusted so that the core-shell ratio after drying was core: shell = 70: 30 (mass ratio).
Further, heat storage agent capsules having different particle diameters were produced by setting the nozzle frequency at the time of dropping to 6,000 times / minute.
(4) Evaluation of heat storage material About the heat storage material manufactured above, various evaluation was performed according to the above-mentioned method.
The evaluation results are shown in Table 1.

Example 2
(1) Core forming material In a round bottom flask, 95 parts by mass of n-tetradecane as a heat storage substance and 5 parts by mass of conjugated diene rubber as rubber were used as a core forming material.
(2) Shell-forming composition A polyvinyl alcohol was dissolved in water to prepare a shell-forming composition in the form of a solution having a concentration of 12% by mass.
(3) Manufacture and evaluation of heat storage material Using the materials prepared above as the core forming material and the shell forming composition,
Two types with different particle diameters were used in the same manner as in Example 1 except that methanol whose temperature was adjusted to 3 ° C. was used as the coagulation liquid and the nozzle frequency of the vibration dropping device was as shown in Table 1. A heat storage material was manufactured and evaluated.
The evaluation results are shown in Table 1.

Examples 3-5 and Comparative Examples 1 and 2
The types and usage ratios (parts by mass) of the heat storage material and rubber in the core forming material and the resin and solvent in the shell forming composition, the core-shell ratio, the composition and temperature of the coagulating liquid, and the nozzle frequency of the vibration dropping device A heat storage material was produced and evaluated in the same manner as in Example 1 or Example 2 according to whether or not rubber was used in the core forming material except that it was as described in Table 1. In Examples 4 and 5 and Comparative Examples 1 and 2, only the heat storage material having one particle size was obtained without changing the particle size.
The evaluation results are shown in Table 1.

Claims (5)

A heat storage material having a core containing a heat storage material and a shell containing a resin,
The said heat storage material characterized by the porosity calculated by following Numerical formula (1) about the said shell being 5 to 80%.
Porosity (%) = [{shell volume− (shell weight / true shell specific gravity)} / shell volume] × 100 (1)   The heat storage material according to claim 1, wherein the resin contained in the shell is at least one selected from the group consisting of a polyvinyl alcohol resin, a cellulose resin, a resin having an ether bond, and a resin having a carbamoyl group. .   The heat storage material contained in the core is at least one selected from the group consisting of saturated hydrocarbons, fatty acids, fatty acid metal salts, fatty acid esters, aliphatic ethers, aliphatic ketones and aliphatic alcohols. Or the heat storage material of 2.   The heat storage material of Claim 1 or 2 whose weight ratio of the shell in a heat storage material is 0.1 to 80 weight%.   The heat storage material according to claim 1 or 2, wherein the number average particle diameter of the heat storage material is 0.01 to 30 mm.