JP2001207164A - Heat-storing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-storing sheets of a new type that is more inexpensive than the conventional heat-storing sheet and has increased heat storage capacity by using the polymerization reaction system in which unreacted monomer does not remain substantially, when the capsule wall of a resin layer is formed on the periphery of the core substance mainly comprising a latent heat- storing material of a freely phase-transitional compound. SOLUTION: At least one layer of capsule walls mainly comprising a thermoplastic resin formed by the radical polymerization is formed on the periphery of the core substance mainly including a readily phase-transitional compound, and the outermost layer of the capsule walls is made of a resin mainly comprising a thermoplastic resin mainly from a vinyl monomer that gives a glass transition point of -140 deg.C--20 deg.C, when the monomer is singly polymerized, whereby the objective microcapsulated heat-storing material is obtained. The resultant microcapsulated material is made into sheets, whereby the objective heat-storing sheets are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heat storage sheet.

[0002]

2. Description of the Related Art In recent years, there has been a demand for saving energy by using natural heat energy such as sunlight for heating a house. At this time, as a method of utilizing the sensible heat of a fluid such as water as a heat storage medium or a heat transfer medium required, or as a method of obtaining higher thermal efficiency, a latent heat storage material is microencapsulated and suspended in water. A method has been considered. Conventionally, this type of heat storage system, or
As a microcapsule used in a heat transfer system, a microcapsule having a capsule wall made of a melamine resin film around a core substance mainly composed of a latent heat storage material such as an aliphatic hydrocarbon has been known (Japanese Patent Application Laid-Open No. HEI 9-260572). No. 5-163486). The melamine resin used in the heat storage microcapsules is obtained by condensation polymerization of melamine and formaldehyde, and in this polymerization system, in order to increase the reaction rate of melamine, at the time of polymerization, more than twice the number of moles of formaldehyde of melamine is used. Since it is added, formaldehyde harmful to the human body may remain in the system. Further, as can be seen from the above cited examples, in a system in which the melamine monomer is added to the core substance, the melamine resin does not become the capsule wall of the wax, and there is a possibility that the melamine resin alone forms particles. There is. Furthermore, melamine resin is expensive to use for general purposes, and it is difficult to introduce such a heat storage system in terms of cost.

The heat storage microcapsules may be used in a fluid medium as described above or, as disclosed in Japanese Patent Application Laid-Open No. 63-238188, may be used in the form of fine particles at a temperature not lower than the latent heat storage material transformation temperature. The powder is sprayed, and the heat storage material is sealed into a heat storage mat to prevent agglomeration and coalescence of the heat storage material, or is adhered to the surface of the thin plate-shaped substrate as shown in JP-A-2-287096. It is used as various building materials by applying an agent and processing it into a heat storage sheet to which a pellet-like latent heat storage material is attached. In other words, in the conventional technology, when the heat storage microcapsules are used for a wall or a floor of a house, the heat storage microcapsules must be processed into a certain shape in advance to be formed into a molded body, and then applied, for example, to a hollow panel. It is necessary to fill the microcapsules in a slurry state, impregnate a porous base material, or attach the microcapsules to a sheet base material, and applicable members are limited. Therefore, there is a demand for an easy-to-use and inexpensive heat storage microcapsule that can be obtained by radical addition polymerization using a general-purpose monomer and applied to an arbitrary place to form a film and exhibit heat storage performance.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has a capsule wall made of a thermoplastic resin around a core material mainly composed of a compound capable of phase transition. When forming a non-reacted monomer, use a reaction form in which substantially no unreacted monomer remains, and since the outermost layer of the microcapsules is covered with a thermoplastic resin having an adhesive property, a sheet is formed without using a binder resin or the like. It is an object of the present invention to provide a heat storage sheet that is inexpensive and has a high heat storage amount as compared with conventional products.

[0005]

Means for Solving the Problems As a result of repeated studies on the above-mentioned problems, the present inventors have found that one layer of a capsule wall made of a resin film is provided around a core material mainly composed of a compound capable of phase transition. When manufacturing the microcapsules formed above,
By using a thermoplastic resin that can be synthesized by a radical addition polymerization mechanism as a main component as a capsule wall, a microencapsulated heat storage material can be efficiently produced, and
The outermost layer of the capsule wall is used as the glass transition temperature of the homopolymer.
It has been found that by using a vinyl monomer having a temperature of 140 ° C. to −20 ° C. as a main component, tackiness can be imparted and a sheet can be formed without adding a binder resin or the like.

The phase-changeable compound (hereinafter referred to as a latent heat storage material), which is a main component of the core material of the microcapsule of the present invention, is used for storing heat by utilizing the latent heat accompanying the phase change. Specific examples include an organic compound and an inorganic compound, which are not particularly limited. Examples of the organic compound include aliphatic hydrocarbons, aromatic hydrocarbons, fatty acids, alcohols, and the like. Examples of the inorganic compound include calcium chloride hexahydrate (melting point 29 ° C.), sodium carbonate 10
Hydrate (32 ° C), sodium sulfate decahydrate (3
2 ° C), sodium hydrogen phosphate dodecahydrate (36
° C), zinc nitrate hexahydrate (36 ° C), nickel nitrate 6
Hydrate, sodium thiosulfate pentahydrate and the like.
In particular, when used as a heat storage material for houses, the
A substance having a melting point of not less than 50 ° C and not less than 50 ° C is preferred.

It is preferable to use an aliphatic hydrocarbon since the latent heat storage material can be freely designed in accordance with the purpose by using it alone or as a mixture. For example, pentadecane, hexadecane, heptadecane, octadecane can be used. , Nonadecane, icosan, docosan and the like. Carbon, metal powder, alcohol, and the like may be added to the organic compound for the purpose of adjusting the thermal conductivity and specific gravity of the microcapsules.

In the present invention, at least the outermost layer (surface) of the capsule wall of the microcapsule is a thermoplastic resin mainly composed of a vinyl monomer having a glass transition temperature of a homopolymer of -140 ° C to -20 ° C. There is a feature. When the glass transition temperature of the homopolymer of a vinyl monomer, which is the main component of the thermoplastic resin of the outermost layer, exceeds -20 ° C, sufficient adhesiveness cannot be imparted to the microcapsules, and the temperature is -140 ° C. If it is less than 1, the polymer is not suitable as a polymer generally used industrially, and is limited to the above range.

The glass transition temperature of the homopolymer is -14.
The vinyl monomer having a temperature of 0 ° C to -20 ° C is not particularly limited. Examples thereof include ethyl acrylate (glass transition temperature of a homopolymer = -24 ° C, hereinafter, only the temperature is indicated in parentheses), n-propyl acrylate (-37 ° C), n
-Butyl acrylate (-54 ° C), isobutyl acrylate (-24 ° C), sec-butyl acrylate (-
21 ° C.), n-hexyl acrylate (−57 ° C.), 2
-Ethylhexyl acrylate (-85 ° C), n-octyl methacrylate (-25 ° C), isooctyl acrylate (-45 ° C), n-nonyl methacrylate (-3
5 ° C.), alkyl (meth) acrylates such as n-decyl methacrylate (−45 ° C.), conjugated diene monomers having 4 to 6 carbon atoms, vinyl methyl ether (−31 ° C.), vinyl ethyl ether (-33
C) and vinyl ethers such as vinyl propyl ether (-49 C). Of the above vinyl monomers,
Alkyl (meth) acrylate is preferably used from the viewpoint of adjusting the glass transition temperature, tackiness, economy and the like. These can be used alone or in combination of two or more.

The thermoplastic resin of the outermost layer (surface) includes:
In addition to the vinyl monomer, other monomers copolymerizable with the vinyl monomer can be used. The other monomer copolymerizable with the vinyl monomer is not particularly limited, and for example, it is preferable to use a general-purpose monomer having a high radical polymerization activity such as (meth) acrylate, a styrene derivative, and a vinyl acetate derivative. They may be used alone or in combination of two or more. Further, it may be copolymerized with a polyfunctional monomer or the like for the purpose of improving the mechanical strength of the capsule wall.

The (meth) acrylate monomer is not particularly restricted but includes, for example, methyl acrylate, methyl methacrylate, ethyl methacrylate, n
Alkyl (meth) acrylates such as -propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate And a polar group-containing (meth) acrylate such as 2-hydroxyethyl (meth) acrylate, and these can be used alone or in combination of two or more.

The monomer other than the above-mentioned (meth) acrylate is not particularly limited. For example, styrene derivative monomers such as styrene, α-methylstyrene, p-methylstyrene and p-chlorostyrene, vinyl acetate, propionic acid Examples thereof include vinyl esters such as vinyl, unsaturated nitriles such as acrylonitrile and methacrylonitrile, acrylic acid and methacrylic acid, and these can be used alone or in combination of two or more.

The above-mentioned polyfunctional monomer is not particularly limited. For example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,6-hexanediol di ( Di (meth) acrylates such as meth) acrylate and trimethylolpropane di (meth) acrylate; trimethylolpropane tri (meth) acrylate; ethylene oxide-modified trimethylolpropane tri (meth) acrylate; pentaerythritol tri (meth) acrylate And other tri (meth) acrylates. Other polyfunctional monomers include pentaerythritol tetra (meth) acrylate, dipentaeristol hexa (meth) acrylate, diallyl phthalate, diallyl maleate, diallyl fumarate, diallyl succinate, triallyl isocyanurate and the like. And divinyl compounds such as divinylbenzene and butadiene, etc., and these can be used alone or in combination of two or more.

The above glass transition temperature is from -140 ° C to -20.
The ratio of the vinyl monomer at ℃ is preferably 51 to 100% by weight, more preferably 60 to 100% by weight in the thermoplastic resin of the outermost layer in view of easy development of tackiness.

In the capsule wall, the thermoplastic resin three-dimensionally covers the surface of the heat storage material to prevent the heat storage material from flowing out. The capsule wall may have a single layer or a multilayer structure of two or more layers depending on the purpose. In the case of two or more layers, the inner thermoplastic resin layer that is not the surface is not particularly limited as long as it is a thermoplastic resin that can be synthesized by radical polymerization. For example, poly (meth) acrylate, a polystyrene derivative, or a polyvinyl acetate derivative It is preferable to use general-purpose resins synthesized from monomers having high radical polymerization activity, such as those described above, and these may be used alone or as a copolymer.

The (meth) acrylate monomer used for the polymerization of the inner thermoplastic resin layer is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl ( Alkyl (meth) acrylates such as meth) acrylate, cumyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, and 2-hydroxyethyl (meth) And (meth) acrylates containing a polar group such as acrylate. These can be used alone or in combination of two or more.

The monomer other than the (meth) acrylate used for the polymerization of the inner thermoplastic resin layer is not particularly limited, and includes, for example, styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene. Styrene derivative monomers such as vinyl acetate, vinyl esters such as vinyl propionate, unsaturated nitriles such as acrylonitrile and methacrylonitrile, acrylic acid, and methacrylic acid.These may be used alone or in combination of two or more. it can.

If necessary, a polyfunctional monomer may be added to the inner thermoplastic resin in order to improve the mechanical strength of the capsule wall. Although the type of the polyfunctional monomer is not particularly limited, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) Di (meth) acrylates such as acrylate and trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth)
Tri (meth) acrylates such as acrylate and pentaerythritol tri (meth) acrylate; Other polyfunctional monomers include pentaerythritol tetra (meth) acrylate, dipentaeristol hexa (meth) acrylate, diallyl phthalate, diallyl maleate, diallyl fumarate, diallyl succinate, triallyl isocyanurate and the like. And divinyl compounds such as divinylbenzene and butadiene, etc., and these can be used alone or in combination of two or more.

The microcapsule of the present invention comprises a mixture of a latent heat storage material mainly composed of an organic compound capable of phase transition and a radical polymerizable monomer used for forming the capsule wall.
It is obtained by emulsifying and suspending in water and radically polymerizing the monomers in the oil droplets. In particular, when a highly hydrophobic aliphatic hydrocarbon is used as the core material, the radically polymerizable monomer generates a polymer near the interface of a thermodynamically stable aqueous phase in oil droplets, and a stronger capsule wall can be obtained. The suspension polymerization method uses a dispersant and a polymerization initiator.

The above dispersant is added for the purpose of improving the dispersion stability of the mixed emulsion suspension of the latent heat storage material and the monomer and efficiently conducting the polymerization. Examples of the dispersant include an anionic surfactant and a nonionic surfactant. Activator, partially saponified polyvinyl acetate, cellulose dispersant, gelatin and the like. Particularly preferred are anionic surfactants, such as sodium alkylbenzenesulfonate.
As the polymerization initiator, compounds that generate oil-soluble free radicals, for example, organic peroxides such as benzoyl peroxide, lauroyl peroxide, dibutyl peroxydicarbonate, α-cumylperoxy neodecanoate, Examples include azo-based initiators such as azobisisobutyronitrile, and redox initiators. In the above suspension polymerization method, a pH adjuster, an antioxidant and the like may be added as necessary.

The above suspension polymerization method is roughly classified into two methods, namely, a batch polymerization method and an emulsion addition method, depending on the difference in the monomer addition method, and is not particularly limited. In the batch polymerization method, for example, first, a latent heat storage material, a radical polymerizable monomer, and a polymerization initiator are mixed in advance to prepare a monomer solution. on the other hand,
Pour ion-exchanged water and dispersant into the jacketed polymerization reaction tank, decompress the polymerization tank, remove oxygen, and then return the pressure to atmospheric pressure with nitrogen to bring it under a nitrogen atmosphere. And add it into the polymerization tank. After emulsifying and suspending the polymerization liquid with a stirring blade, the inside of the vessel is heated to a predetermined temperature by a jacket to start polymerization. Further, the monomer solution may be mixed and emulsified in advance with a dispersant and a part of charged water, and then added to the polymerization tank.

The emulsion addition method is, for example, first,
An emulsion monomer liquid is prepared in advance by sufficiently emulsifying a latent heat storage material, a radical polymerizable monomer, a polymerization initiator, a dispersant, and ion-exchanged water by stirring. Next, ion-exchanged water was put into the polymerization reaction vessel with a jacket, the inside of the polymerization vessel was decompressed to remove oxygen, and then the pressure was returned to atmospheric pressure with nitrogen to form a nitrogen atmosphere. After the temperature is raised, the above-mentioned emulsified monomer liquid is added all at once, or a certain amount is added dropwise to carry out polymerization.

The resin solid content of the slurry containing the microcapsules obtained as a result of the polymerization is not particularly limited, but is preferably from 10 to 70 in view of productivity and stability of the polymerization reaction.
% By weight is preferred. The average particle size of the microcapsules in the slurry is not particularly limited, but when used as a slurry, separation of the microcapsules and water tends to occur when the size is large, and the strength of the capsule wall is reduced when the size is too small. 10 μm is appropriate. The slurry containing the microcapsules, if necessary, ethylene glycol, polyethylene glycol, antifreezing agents such as various inorganic salts, preservatives, thickeners, pigments, dispersants, flame retardants, for improving sheet strength Additives for various purposes, such as short fibers, may be added and used.

The present invention is attained by forming a sheet of the microencapsulated heat storage material having adhesiveness. The method of forming the sheet is not particularly limited.For example, a method of developing the dried microencapsulated heat storage material powder on release paper, heating and adjusting the thickness with a rolling roll to form a sheet, After applying the slurry containing the capsules on release paper as it is, heat it to evaporate the water,
A method of forming a sheet may be mentioned, but a method of applying and drying a slurry is preferable because the manufacturing process can be simplified.

The heat storage sheet of the present invention is used by directly attaching it to a site where heat storage performance is required. When more heat storage performance is required, the heat storage sheet can be adjusted by forming a plurality of layers. In addition, in order to store and transport the heat storage sheet, the sheet is sandwiched between release papers or the like, and is formed into a roll to facilitate handling.

[0026]

Hereinafter, embodiments of the present invention will be described.
It is not limited to the following example. Example 1 (Synthesis of microencapsulated heat storage material) Paraffin wax melted at 50 ° C as a latent heat storage agent (melting point 18
C) 100 parts by weight, 100 parts by weight of n-butyl acrylate (Tg of homopolymer = -54 ° C.), 1 part by weight of trimethylolpropane triacrylate, 1 part by weight of 2,2-azobisisobutyronitrile are mixed and stirred. Then, 120 parts by weight of ion-exchanged water and 1 part of sodium dodecylbenzenesulfonate were added and stirred to prepare an emulsion monomer liquid. On the other hand, 80 parts by weight of ion-exchanged water was put into the polymerization vessel,
Stirring was started. After depressurizing the inside of the polymerization vessel and deoxidizing the inside of the vessel, returning the pressure to atmospheric pressure with nitrogen,
The above emulsified monomer liquid was added all at once. 80 ℃ of polymerization tank
And the polymerization was started. The polymerization was completed in 30 minutes, and after an aging period of 1 hour, the polymerization tank was cooled to room temperature. An emulsified suspension containing a microencapsulated heat storage material having a solid content of about 50% by weight and an average particle size of about 3 μm was obtained.

(Preparation of heat storage sheet) Emulsion suspension 1
After adding 10 parts by weight of a 1% aqueous solution of sodium polyacrylate to 00 parts by weight, a 6 mm thick
Coating was performed using a coater adjusted so as to become. Further, this was placed in a hot-air dryer and dried at a temperature of 80 ° C. for 6 hours to obtain a heat storage sheet having a thickness of 3 mm. Using the obtained sheets, various evaluations were performed by the evaluation methods described below.
Table 1 shows the evaluation results.

Example 2 In the synthesis of the microencapsulated heat storage material of Example 1,
A heat storage sheet was obtained and evaluated in the same manner as in Example 1, except that the acrylate monomer used was 2-ethylhexyl acrylate (Tg of homopolymer = -75 ° C). Table 1 shows the evaluation results.

Comparative Example 1 In the synthesis of the microencapsulated heat storage material of Example 1,
A heat storage sheet was obtained and evaluated in the same manner as in Example 1, except that the acrylate monomer used was methyl methacrylate (Tg of homopolymer = 100 ° C.).
Table 1 shows the evaluation results.

[Evaluation] (Workability) Nail driving test: The obtained sheet was 3 mm in diameter.
And the condition of the sheet was judged. ○: No damage ×: Damage Cutting test: The obtained sheet was cut using a cutter to determine the state of the sheet. ○: no damage ×: damage (heat storage) A test piece was cut out from the obtained sheet, and the measurement temperature range was 5 to 50 ° C. using a differential scanning calorimeter (DSC6200, manufactured by Seiko Instruments Inc.). The heat storage rate per unit weight was measured at a rate of 2 ° C./min. The heat storage amount per unit area was also calculated from the measured values.

[0031]

[Table 1]

[0032]

As described above, the heat storage sheet of the present invention is
It is excellent in workability such as cutting and nailing, and it has adhesiveness, so it can be directly attached to the place where heat storage is required, and the amount of heat storage can be adjusted arbitrarily by destacking It can be used for various purposes.

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Claims (5)

[Claims] 1. A microencapsulated heat storage material in which at least one or more capsule walls mainly composed of a thermoplastic resin obtained by radical polymerization are formed around a core substance mainly composed of a compound capable of phase transition. Wherein the outermost layer of the capsule wall is a thermoplastic resin whose main component is a vinyl monomer having a glass transition temperature of a homopolymer of −140 ° C. to −20 ° C. Heat storage sheet. 2. The thermoplastic resin of the outermost layer is an acrylic copolymer mainly composed of an alkyl (meth) acrylate monomer having a glass transition temperature of a homopolymer of −140 ° C. to −20 ° C. The heat storage sheet according to claim 1, wherein: 3. The heat storage sheet according to claim 1, wherein the outermost layer of the thermoplastic resin has tackiness at room temperature. 4. The heat storage sheet according to claim 1, wherein the core material has a melting point of 0 ° C. or more and less than 50 ° C. 5. The heat storage sheet according to claim 1, wherein the core substance is an aliphatic hydrocarbon.