JP7528431B2 - Heat storage material and method for producing the same - Google Patents

Description

The present invention relates to a heat storage material that can maintain an appropriate temperature and save energy depending on various usage modes. In particular, the present invention relates to a heat storage material that is useful for maintaining an appropriate temperature in living spaces such as houses and inside automobiles.

In recent years, there has been an increasing demand for energy conservation in residential spaces such as homes and offices, and there is a demand for building materials used in homes and other buildings that contribute to energy conservation. In general, efficient heating and cooling is achieved by using insulating materials on floors, ceilings, walls, etc., but various materials are being considered for further energy savings. There is also a high demand for energy conservation in closed spaces such as automobiles and airplanes, and inside refrigerators in refrigerated vehicles.

Examples of such heat storage materials that have been disclosed include heat storage foams in which a coating liquid containing heat storage particles is applied to a foamed resin, and building materials in which heat storage particles are applied to foam materials (see Patent Documents 1 and 2).

Japanese Patent Application Publication No. 10-300373 JP 2001-303030 A

Heat storage materials that have air bubbles and heat storage particles have insulating and heat storage properties due to the air bubbles and heat storage particles, but for practical use in building materials, etc., further improvements in heat storage, heat retention, and insulation properties are required.

The problem that the present invention aims to solve is to provide a heat storage material that has suitable moldability while containing heat storage particles, and in which the porosity and heat storage particle content can be suitably adjusted, and further, to provide a heat storage material that can contain voids and heat storage particles at a high density.

The present invention solves the above problems by providing a heat storage material in which heat storage particles are coated with a resin and the coated particles are bonded together by the resin, and when the heat storage particles are mixed with an aqueous dispersion of the resin, the amount of the aqueous dispersion of the resin absorbed per 100 parts by mass of the heat storage particles is 70 parts by mass or less.

The heat storage material of the present invention has a structure in which heat storage particles are coated with a resin, and the coated particles are bonded together with voids between them. This structure allows the heat storage particles, voids, or both to be contained at a high density compared to a structure in which heat storage particles are held in a molded foam material or a structure in which isolated bubbles or heat storage particles are dispersed in a resin matrix. In addition, since the void ratio and the content of heat storage particles can be easily adjusted, the heat storage, heat retention, and insulation properties can be appropriately adjusted according to the desired application.

Furthermore, since it is possible to reduce the weight while still having excellent heat storage, heat retention, and insulation properties, it is also easy to install when made into a large shape and easy to handle during transportation. Also, compared to heat storage materials that do not have voids, it is possible to achieve suitable heat storage, heat retention, and insulation properties even with a low content of heat storage material. Furthermore, it can be easily molded and processed into various shapes, the heat storage particles are unlikely to fall off, and it is easy to impart flexibility, making it suitable for a variety of uses.

The heat storage material of the present invention can be used for a variety of purposes, including as wall materials and wallpaper in residential spaces such as houses, the interiors of automobiles, trains, aircraft, agricultural greenhouses, and other closed spaces such as the inside of refrigerators in refrigerated vehicles and refrigeration equipment and the inside of aircraft cabinets, and as a material for electrical components that generate heat, such as computer CPUs and storage batteries, and can contribute favorably to energy conservation in a variety of applications.

3 is a micrograph of a cross section of the heat storage material of Example 1. 1 is a micrograph of a cross section of the heat storage material of Example 3.

The heat storage material of the present invention is a heat storage material in which heat storage particles are coated with a resin and the coated particles are bonded with the resin, and when the heat storage particles are mixed with an aqueous dispersion of the resin, the amount of the aqueous dispersion of the resin absorbed per 100 parts by mass of the heat storage particles is 70 parts by mass or less.

[Heat storage particles]
The heat storage particles used in the present invention may be various known heat storage particles such as organic heat storage particles, inorganic heat storage particles, etc. Among them, heat storage particles containing a latent heat storage material that undergoes a solid-liquid phase change are preferred because they are easy to handle and form into a molded product.

Taking into consideration problems such as seepage during melting due to phase change and dispersibility when mixed in, it is preferable to use encapsulated organic heat storage particles that encapsulate a latent heat storage material such as paraffin in an outer shell made of an organic material, or inorganic heat storage particles made of an inorganic material.
Among these heat storage particles, heat storage capsule particles in which an organic latent heat storage material such as paraffin or fatty acid ester is covered with an outer shell made of an organic material such as melamine or acrylic are preferably used. In addition, as the heat storage particles, those that absorb a small amount of water are preferably used.

Examples of such heat storage particles include Thermomemory FP-16, FP-25, FP-31, and FP-39 manufactured by Mitsubishi Paper Mills, which use an outer shell made of melamine resin, and Riken Resin PMCD-15SP, 25SP, and 32SP manufactured by Miki Riken Kogyo Co., Ltd. Examples of particles using an outer shell made of silica include Riken Resin LA-15, LA-25, and LA-32 manufactured by Miki Riken Kogyo Co., Ltd. Examples of particles using an outer shell made of polymethyl methacrylate resin include Micronal DS5001X and 5040X manufactured by BASF, and examples of particles using an outer shell made of urethane resin include CALGRIP NJ2021 and NJ2721 manufactured by JSR Corporation.

The particle diameter of the heat storage particles used in the present invention is not particularly limited, but the average particle diameter is preferably 10 to 3000 μm. By using particles in this range, it is easy to form voids in the obtained heat storage material and to realize good moldability. The particle diameter is preferably 30 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. In addition to forming suitable voids and having good moldability, the average particle diameter of the heat storage particles is preferably 3000 μm or less, more preferably 2000 μm or less, and particularly preferably 1000 μm or less, because it is easy to hold the particles in a suitable manner. It is preferable that the average particle diameter of the primary particles is in the above range.

The average particle size of the heat storage particles is measured using a laser diffraction particle size distribution measuring device (LA-950V2 manufactured by Horiba, Ltd.), and the resulting median diameter (particle size equivalent to 50% of the cumulative distribution, 50% particle size) is taken as the average particle size.

A latent heat storage material undergoes a phase change at a specific melting point. That is, when the room temperature exceeds the melting point, the phase changes from solid to liquid, and when the room temperature falls below the melting point, the phase changes from liquid to solid. The melting point of the latent heat storage material can be adjusted according to the mode of use, and materials that exhibit a solid/liquid phase transition in a temperature range of about -20°C to 120°C can be used as appropriate. For example, in order to maintain an appropriate temperature in a living space such as a house, or in the interior of a car, train, airplane, agricultural house, etc., and to conserve energy, a latent heat storage material whose melting point is designed to be a temperature suitable for daily life, specifically 10 to 35°C, preferably 15 to 30°C, can be mixed to achieve the appropriate temperature maintenance performance. In order to adjust the appropriate temperature maintenance performance in winter or summer in more detail, a latent heat storage material with a melting point of about 25 to 28°C is mixed in if the purpose is to maintain the heating effect in winter. Alternatively, if the goal is to maintain cooling efficiency in the summer, latent heat storage material with a melting point of around 20 to 23°C can be mixed in. To achieve both effects, two or more types of latent heat storage material with different melting point designs can be mixed in. Also, if you want to save energy inside refrigeration equipment, etc., you can use a latent heat storage material with a melting point of around -10°C to 5°C.

[resin]
The resin used in the present invention is a resin that coats the heat storage particles and bonds the coated particles together. The resin bonds the coated particles together in a three-dimensional network, thereby forming a heat storage material having voids.

In the present invention, by using a resin that absorbs 70 parts by mass or less of the aqueous dispersion of the resin per 100 parts by mass of the heat storage particles when the aqueous dispersion of the resin is mixed with the heat storage particles used, it is easy to ensure suitable voids in the heat storage material, and the heat storage particles coated with the resin can be bonded by the resin, and a heat storage material with suitable strength can be obtained. In addition, it is easy to ensure good coating properties during the production of the heat storage material, and it is easy to mold the heat storage material. The absorption amount is more preferably 60 parts by mass or less, even more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass or less. The absorption amount of the aqueous dispersion of the resin to the heat storage particles can be measured, for example, in accordance with JIS K5101-13-1. Note that, as the aqueous dispersion of the resin, an aqueous dispersion in which 55 parts by mass of resin is dispersed in 45 parts by mass of water is used.

There are no particular limitations on the type of resin, and any resin that can form a structure with voids can be used without particular limitations. Among them, emulsion resins that can form voids by mechanical foaming are preferably used because they are easy to form the overall structure of the heat storage material and are easy to form good voids and ensure porosity. Examples of such emulsion resins include acrylic emulsions, urethane emulsions, ethylene vinyl acetate emulsions, vinyl chloride emulsions, and epoxy emulsions. Among them, acrylic emulsions are particularly preferred because they have excellent heat resistance and insulation, and urethane emulsions are particularly preferred because they have excellent flexibility.

The particle diameter of the emulsion resin is preferably 30 to 1500 nm, and particularly preferably 50 to 1000 nm, because this facilitates favorable bonding between the heat storage particles and the heat storage particles coated with the resin. The average particle diameter of the emulsion particles can be the 50% median diameter measured by dynamic light scattering, for example, the 50% median diameter on a volume basis measured by a Microtrac UPA type particle size distribution measuring device manufactured by Nikkiso Co., Ltd.

[Heat storage material]
The heat storage material of the present invention is a structure in which the heat storage particles are coated with the resin and the coated particles are bonded by the resin. The heat storage material of the present invention can contain both heat storage particles and voids at a high density compared to a structure in which heat storage particles are held in a molded foam material or a structure in which closed bubbles or heat storage particles are dispersed in a resin matrix. In addition, since the porosity and the content of heat storage particles can be easily adjusted, the heat storage property, heat retention property, and heat insulation property can be suitably adjusted according to the desired application. Furthermore, since it is lightweight and easy to mold and process into various shapes, the heat storage particles are unlikely to fall off, and flexibility can be easily imparted, it can be suitably applied to various applications.

The heat storage material of the present invention has a structure in which heat storage particles are coated with a resin, and the coating resin bonds between the coated particles, with gaps being formed between the coated particles. The specific gravity of the heat storage material is preferably 0.15 to 0.9, and is preferably 0.3 to 0.9, as this makes it easier to obtain suitable temperature retention. In addition, it is easy to reduce the weight, and suitable processability is also easily obtained.

The content of heat storage particles in the heat storage material of the present invention can be adjusted as appropriate depending on the desired application, but it is preferably 15 to 80% by mass, and more preferably 30 to 50% by mass, as this makes it easier to achieve suitable heat storage and insulation properties.

The resin content in the heat storage material is preferably 20 to 85% by mass, and more preferably 50 to 70% by mass, since this makes it easier to adjust the content of voids and heat storage particles and to increase the content of both.

In addition, since it is easier to obtain suitable temperature retention and heat insulation, the content ratio of the heat storage particles and the resin, expressed as the solid mass ratio of heat storage particles/resin, is preferably 80/20 to 15/85, and more preferably 50/50 to 30/70.

The heat storage material of the present invention can be molded into various shapes, and can also be easily molded into sheets that are easy to handle. It is also easy to process, such as by cutting, and is therefore easy to handle.

The shape and size may be adjusted as appropriate depending on the desired application, but for example, when used as a sheet for building materials, the thickness is preferably 1 mm or more, and more preferably 2 mm or more.

The heat storage material of the present invention can ensure suitable flexibility and excellent conformability to various materials by setting the mandrel diameter at which cracks occur in a bending resistance test conforming to JIS K5600-5-1 (1999) to 25 mm or less, preferably 20 mm or less, and more preferably 16 mm or less.

The bending resistance of the heat storage material measured according to the Gurley method specified in JIS L1913 (2010) is preferably 0.1 to 30 mN, more preferably 0.5 to 20 mN, and even more preferably 1 to 10 mN. By keeping the bending resistance within this range, suitable flexibility and excellent conformability to various materials can be ensured.

The heat storage material of the present invention preferably has a tensile strength of 0.1 MPa or more, which allows for a layer that is flexible yet strong, and is less likely to crack during processing or transportation, making it easier to obtain suitable processability, handling, transportability, bending suitability, etc. It is more preferable that the tensile strength is 0.2 MPa or more. There is no particular upper limit to the tensile strength, but it is preferably about 15 MPa or less, more preferably 10 MPa or less, and particularly preferably 5 MPa or less.

In addition, by setting the elongation rate at tensile break of the heat storage material to 10% or more, embrittlement of the sheet can be suppressed, and cracks and chips are less likely to occur even if bending or distortion occurs during processing or transportation, etc., which is preferable. The elongation rate at tensile break is more preferably 30% or more, and even more preferably 50% or more. The upper limit of the elongation rate is preferably 1000% or less, more preferably 500% or less, and even more preferably 300% or less. By setting the elongation rate within this range, it is possible to achieve suitable flexibility while maintaining toughness, and it is easy to obtain good processability, ease of handling, transportability, and ability to follow various materials.

The tensile strength and elongation at break are measured in accordance with JIS K6251. Specifically, a heat storage sheet formed from a single heat storage layer in a sheet form is cut into a dumbbell shape No. 2, and a test specimen is created with two marks with an initial gauge distance of 20 mm. This test specimen is attached to a tensile tester and pulled to break at a speed of 200 mm/min. The maximum force (N) until break and the gauge distance (mm) at break are measured, and the tensile strength and elongation at break are calculated using the following formula.

The tensile strength TS (MPa) is calculated by the following formula.
TS=Fm/Wt
Fm: Maximum force (N)
W: Width of parallel part (mm)
t: thickness of parallel part (mm)

The tensile elongation at break Eb (%) is calculated according to the following formula.
Eb=(Lb-L0)/L0×100
Lb: Gauge distance at break (mm)
L0: Initial gauge length (mm)

The heat storage material of the present invention may contain various additives as necessary. Examples of such additives that can be preferably used include flame retardants, adsorbents for harmful substances such as formaldehyde, coloring pigments, and deodorants.

[Production method]
A preferred method for producing the heat storage material of the present invention is to mechanically foam an emulsion resin composition containing a resin, heat storage particles, and an aqueous medium, and then coat or cast the composition and dry it. In the production, the composition may be cured by applying heat or ultraviolet light, if necessary, after drying.

As the aqueous medium used in the emulsion resin composition, water is preferably used. It may also be a mixture of water and a water-soluble solvent. As the water-soluble solvent, for example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, butyl cellosolve, etc., polar solvents such as N-methylpyrrolidone, etc., can be used, and one or more kinds may be used.

The heat storage material of the present invention may contain, in addition to the emulsion resin composition, a surfactant, a thickener, a flame retardant, a crosslinking agent, and other additives as necessary. For example, any surfactant can be used to refine and stabilize the foamed foam. There are no particular limitations on the surfactant, and any of anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc. may be used. From the viewpoint of the stability of the foamed foam, anionic surfactants are preferred, and fatty acid ammonium surfactants such as ammonium stearate are particularly preferred. The surfactants may be used alone or in combination of two or more.

The emulsion resin composition used in the present invention may contain a necessary amount of a thickener to improve the stability of the foamed foam and the film-forming properties. Examples of the thickener that can be used include acrylic acid-based thickeners, urethane-based thickeners, and polyvinyl alcohol-based thickeners. Of these, acrylic acid-based thickeners and urethane-based thickeners are preferably used.

The emulsion resin composition of the present invention may contain a necessary amount of a flame retardant to improve the flame retardancy of the heat storage material. The flame retardant is not particularly limited, and organic flame retardants and inorganic flame retardants can be used as appropriate. Examples of organic flame retardants include phosphorus compounds, halogen compounds, and guanidine compounds. Specific examples include primary ammonium phosphate, secondary ammonium phosphate, phosphoric acid triester, phosphorous acid ester, phosphonium salt, phosphoric acid triamide, chlorinated paraffin, ammonium bromide, decabromobisphenol, tetrabromobisphenol A, tetrabromoethane, decabromodiphenyl oxide, hexabromophenyl oxide, pentabromo oxide, hexabromobenzene, guanidine hydrochloride, guanidine carbonate, and guanylurea phosphate. Inorganic flame retardants include, for example, antimony or aluminum compounds, boron compounds, and ammonium compounds, and specific examples include antimony pentoxide, antimony trioxide, sodium tetraborate decahydrate (borax), ammonium sulfate, and ammonium sulfamate. These may be used alone or in combination of two or more.

The emulsion resin composition of the present invention may contain a required amount of a curing agent to improve the strength of the heat storage material. The curing agent may be appropriately selected depending on the type of water-dispersible resin used, and examples of the curing agent include epoxy-based curing agents, melamine-based curing agents, isocyanate-based curing agents, carbodiimide-based curing agents, and oxazoline-based curing agents.

When an acrylic emulsion resin is used, the content of the emulsion resin in the emulsion resin composition is preferably 30 to 200 parts by mass, and more preferably 50 to 150 parts by mass, per 100 parts by mass of the aqueous medium. By setting the content within this range, it is easy to adjust the viscosity to a good range and also easy to obtain stable foamability. The content of the heat storage particles in the emulsion resin composition may be such that the ratio of heat storage particles to resin in the heat storage material is the above-mentioned ratio.

When a surfactant is used in the emulsion resin composition, the content is preferably 30 parts by mass or less, more preferably 0.5 to 20 parts by mass, and even more preferably 3 to 15 parts by mass, per 100 parts by mass (solid content) of emulsion resin, since this makes it easier to obtain suitable foaming properties. When a thickener is used, the content is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass, per 100 parts by mass (solid content) of emulsion resin.

[Heat storage laminate]
The heat storage material of the present invention is preferably formed into a heat storage laminate by laminating it with various functional layers. As a preferred example of lamination with a functional layer, a laminate with a heat insulating layer can be exemplified. The heat storage material of the present invention can realize extremely excellent temperature retention and heat insulation by laminating it with the heat insulating layer. When the laminate with the heat insulating layer is used as a building material such as the wall surface, floor surface, or ceiling surface of a building, for example, the heat storage layer effectively absorbs and releases heat from the indoor side, and the effect of maintaining a suitable temperature in the room can be particularly preferably exhibited. It is also effective in preventing the outflow of heat from the room or reducing the influence of heat from the outside air. The heat storage laminate of the present invention can suppress temperature changes in the room and keep the room at a suitable temperature by these combined actions. In addition, when air conditioning equipment such as air conditioners and refrigeration equipment is used, the energy consumption can be reduced. This can contribute to energy saving in the room.

As the insulating layer, a layer with a thermal conductivity of less than 0.1 W/m·K can be preferably used. This insulating layer prevents heat from escaping from the heat storage layer to the outside air and reduces the temperature effect of the outside air. The insulating layer is not particularly limited as long as it can form a layer with a thermal conductivity of less than 0.1 W/m·K. For example, insulating sheets such as foamed resin sheets and resin sheets containing insulating materials, and insulating boards such as extrusion polystyrene, bead polystyrene, polyethylene foam, urethane foam, and phenol foam can be appropriately used. Among them, insulating sheets are preferred because they are easy to install, and resin sheets containing insulating materials are more preferred because they can reduce thermal conductivity. In addition, foamed sheets are preferred because they are easy to obtain and inexpensive.

The insulation layer can be easily constructed by forming it into a sheet, but it is particularly preferable that the mandrel diameter measured using a cylindrical mandrel bending tester (JIS K 5600) be 2 to 32 mm.

The insulating material used in the insulating layer is one that enhances the insulating properties of the heat storage laminate, and examples of such materials include porous silica, porous acrylic, hollow glass beads, vacuum beads, and hollow fibers. Any known material may be used as the insulating material 5. In the present invention, porous acrylic is particularly suitable for use. The particle size of the insulating material is not limited, but is preferably about 1 to 300 μm.

When using a resin sheet containing a heat insulating material as the heat insulating layer, the heat insulating material is mixed into the base resin material and then sheet molding is performed. As mentioned above, examples of the resin material include polyvinyl chloride, polyphenylene sulfide, polypropylene, polyethylene, polyester, and acrylonitrile-butadiene-styrene resin. As polyester, A-PET, PET-G, etc. can be used. Among them, polyvinyl chloride resin, which is self-extinguishing, is preferably used in terms of low flammability in the event of a fire.

For example, the sheet is formed by molding polyvinyl chloride resin, plasticizer, and insulating material using a molding machine such as extrusion molding or calendar molding.

The content of the insulating material in the insulating layer is preferably 20% by mass or more, more preferably 20 to 80% by mass, even more preferably 30 to 80% by mass, and particularly preferably 40 to 80% by mass. By keeping the content of the insulating material within this range, the insulating effect can be optimally exhibited, and the insulating layer can be easily formed.

Additives such as plasticizers and flame retardants may be added to the insulating layer as needed.

There are no particular limitations on the thickness of the insulating layer, but the thicker it is, the better the heat retention inside the room will be. In order to maintain the bendability and workability of the sheet, it is preferable for the thickness to be around 50 to 3,000 μm.

In addition, by laminating it with a non-flammable layer such as non-flammable paper, the flame retardancy can be improved, making it particularly suitable for application to living spaces. In addition, by laminating it with, for example, a thermal diffusion layer or a heat insulating layer, the heat storage properties can be more effectively expressed. In addition, a decorative layer or a decorative layer can be provided for application to the interior walls of living spaces, etc.

An example of a configuration in which a non-combustible layer is laminated is a configuration in which non-combustible paper is laminated on one or both sides of the heat storage material of the present invention. A configuration in which non-combustible paper is laminated on one side may be a configuration in which the heat storage material of the present invention is laminated to the non-combustible paper, but it is preferable because it is easy to form a configuration in which the foaming composition that forms the heat storage material of the present invention is directly applied to the non-combustible paper and dried. In addition, a configuration in which non-combustible paper is laminated on both sides of the heat storage material of the present invention may be a configuration in which non-combustible paper is laminated on both sides of the heat storage material of the present invention, but it can be easily formed by laminating the heat storage material surfaces of non-combustible paper laminated heat storage materials in which the foaming composition is applied to the non-combustible paper and dried.

The fireproof paper is not particularly limited as long as it is fireproof, but for example, paper coated, impregnated, or internally loaded with a fireproof agent can be used. Examples of fireproof agents include metal hydroxides such as magnesium hydroxide and aluminum hydroxide, basic compounds such as phosphates, borates, and stephamates, and glass fibers.

When the thermal diffusion layer is applied in a laminated configuration to a closed space such as a room, the thermal diffusion layer has the effect of equalizing the heat in the room, and disperses heat from inside the room (such as the living space of a house, the interior of a car, train, airplane, etc., the inside of a refrigerator in a refrigerated car, the inside of an airplane's cabinet, etc.), allowing it to be transferred with little thermal resistance to the heat storage layer. In the heat storage layer, the heat storage particles absorb heat from inside the room and release it back into the room, allowing the temperature environment inside the room to be controlled at an appropriate temperature.

As the thermal diffusion layer, a layer with high thermal conductivity of 5 to 400 W/m·K can be preferably used. High thermal conductivity allows locally concentrated heat to be diffused and transferred to the heat storage layer, improving thermal efficiency and making the room temperature uniform.

Materials for the thermal diffusion layer include, for example, aluminum, copper, iron, and graphite. In the present invention, aluminum is particularly suitable for use. The reason why aluminum is suitable is that it also exhibits an insulating effect by reflecting radiant heat. In particular, in heating appliances that use radiant heat, the insulating effect can improve heating efficiency. Examples of heating appliances that mainly use radiant heat include electric floor heating, hot water floor heating, and infrared heaters. In addition, it can improve flame retardant performance from the perspective of disaster prevention.

The thermal diffusion layer may be in any suitable form, such as a layer made of a sheet of the above material or a vapor-deposited layer of the above material. When aluminum is used as the material, it is preferable to use a flexible material such as aluminum foil or an aluminum vapor-deposited layer.

The thickness of the thermal diffusion layer is not particularly limited, but a thickness of about 3 to 500 μm is preferable because it makes it easier to ensure suitable thermal diffusion and ease of handling.

The heat storage material of the present invention is suitable for use mainly as an interior material for the inner walls, ceilings, floors, etc. of buildings, but can also be used as a covering material for window sash frames and as an interior material for vehicles, etc. It can also be used not only in the walls, floors, and ceilings of buildings, but also in the interiors of automobiles, trains, airplanes, etc. It can also be used as a low-temperature maintaining material for refrigeration equipment and for electrical components that generate heat, such as CPUs and storage batteries in personal computers. It can also be used in combination with a heater such as a planar heating element to achieve energy saving effects through heat storage.

In addition, since the heat storage material of the present invention is easy to ensure excellent flexibility, conformability to various materials, and toughness, it can be preferably used in applications where it covers materials with curved or complex surface shapes, or where deformation occurs, such as bedding, sofas, and clothing. It can also be easily wrapped around cylindrical objects, and can be suitably used for insulation applications such as wrapping it around the stems or bases of curved, long-stalked plants.

Example 1
Water-dispersed acrylic emulsion resin (1) (DIC DICNAL MF-342 Kai 15: non-volatile content 55%) 100 parts by weight, anionic surfactant 6 parts by weight, thickener 3 parts by weight, heat storage particles (1) (average primary particle diameter 150 μm, melting point 27 ° C.) in which an organic latent heat storage material is microencapsulated using an outer shell made of a urethane resin were blended, and the mixture was stirred and mixed with a disperser (2000 rpm, 3 minutes) to prepare a mechanical foaming binder. The absorption amount of the water-dispersed acrylic emulsion resin relative to 100 parts by weight of the heat storage particles used was 28 parts by weight. This was applied to a PET film with an applicator, and then heated at a dryer temperature of 100 ° C. for 5 minutes as pre-drying, and then heat-treated at a dryer temperature of 140 ° C. for 10 minutes to harden, forming a heat storage material having a thickness of 3.5 mm. The specific gravity of this heat storage material was 0.39, the mass of the heat storage material was 1390 g/m ² , and the mass of the heat storage particles contained in the heat storage material was 897 g/m ^2. A cross section of the obtained heat storage material was examined with an electron microscope (Keyence Corporation Digital Microscope VHX-900).

Example 2
A heat storage material having a thickness of 3.3 mm was formed in the same manner as in Example 1, except that 20 parts by mass of the heat storage particles (1) were used instead of 100 parts by mass of the heat storage particles (1) used in Example 1. The specific gravity of this heat storage material was 0.27, the mass of the heat storage material was 884 g/ ^m2 , and the mass of the heat storage particles contained in the heat storage material was 236 g/ ^m2 .

Example 3
A heat storage material having a thickness of 3.2 mm was formed in the same manner as in Example 1, except that 100 parts by mass of heat storage particles (2) (average primary particle diameter 1 mm, melting point 26°C) in which an organic latent heat storage material was microencapsulated with an outer shell made of acrylic resin was used instead of 100 parts by mass of the heat storage particles (1) used in Example 1. The specific gravity of this heat storage material was 0.43, the mass of the heat storage material was 1354 g/ ^m2 , and the mass of the heat storage particles contained in the heat storage material was 874 g/ ^m2 . A cross section of the obtained heat storage material was confirmed with an electron microscope (Keyence Corporation Digital Microscope VHX-900).

(Comparative Example 1)
100 parts by mass of water-dispersed acrylic emulsion resin (DICNAL MF-342 Kai 15, manufactured by DIC Corporation: non-volatile content 55%), 6 parts by mass of anionic surfactant, 3 parts by mass of thickener, and 100 parts by mass of heat storage particles (H1) (average primary particle size 5 μm, melting point 27° C.) in which latent heat storage material is microencapsulated with an outer shell made of melamine resin were mixed and stirred and mixed with a disper (2000 rpm, 3 minutes) to prepare a mechanical foaming binder. The prepared binder had no fluidity and could not be applied with an applicator.

(Comparative Example 2)
A mechanical foaming binder was prepared in the same manner as in Comparative Example 1, except that 100 parts by mass of heat storage particles (H2) (average primary particle size 5 μm, melting point 25° C.) in which an organic latent heat storage material was microencapsulated with an outer shell made of acrylic resin was used instead of 100 parts by mass of the heat storage particles (3) used in Example 1. The binder had no fluidity and could not be applied with an applicator.

The following evaluations were carried out on the heat storage materials and heat storage particles used in the above examples and comparative examples. The results are shown in the table below.

<Resin absorption amount>
The amount of resin absorbed into the heat storage particles was measured by the following method in accordance with JIS K5101-13-1. A sample of 1 g of heat storage particles was weighed and placed on a glass plate, and 4 to 5 drops of water-dispersed emulsion resin were gradually added from a burette at a time, and the resin was kneaded into the sample with a steel palette knife. This was repeated, and the dropwise addition was continued until the heat storage particles and resin became lumpy. Thereafter, the dropwise addition was repeated so as to completely mix the mixture, and the end point was the point at which the mixture became smooth and hard, and the absorption amount was taken as the amount of resin absorbed, and the amount of resin absorbed per 100 parts by mass of heat storage particles was calculated.

<Heat storage evaluation test>
The sheets prepared in the examples and comparative examples were placed on a Peltier-type temperature change plate. A thermocouple was set on the opposite side of the surface in contact with the plate, and the sheet placed on the plate was covered with a heat insulating material from above. The temperature change of the thermocouple was recorded by a data logger. The temperature of the plate was set to 35°C and maintained for 30 minutes to maintain a constant temperature. Thereafter, the temperature change of the thermocouple was measured when the temperature of the plate was changed from 35°C to 15°C over 1 minute. The time from the start of the plate temperature change until the temperature of the thermocouple reached 20°C was calculated to evaluate the heat retention.
◎: Time required to reach 20°C is 5 minutes or more. ○: Time required to reach 20°C is 3 minutes or more. ×: Time required to reach 20°C is less than 3 minutes.

As is clear from the above table, the heat storage materials of the present invention in Examples 1 to 3 could be molded well and had suitable heat storage properties. On the other hand, the heat storage materials in Comparative Examples 1 and 2 could not be molded well.

Example 4
A heat storage material was formed in the same manner as in Example 1, except that the thickness of the heat storage material was 3 mm. The specific gravity of this heat storage material was 0.4, the mandrel diameter at which cracks occurred in the bending test was 2 mm, the bending resistance according to the Gurley method was 6 mN, the latent heat from 0°C to 40°C was 109 kJ/ ^m2 , the tensile strength was 0.3 MPa, and the elongation at tensile break was 70%.

Example 5
A heat storage material was formed in the same manner as in Example 1, except that the thickness of the heat storage material was 1.7 mm. The specific gravity of this heat storage material was 0.4, the mandrel diameter at which cracks occurred in the bending test was 2 mm, the bending resistance according to the Gurley method was 1 mN, the latent heat from 0°C to 40°C was 58 kJ/ ^m2 , the tensile strength was 0.2 MPa, and the elongation at tensile break was 110%.

The following evaluations were carried out on the heat storage materials obtained in Examples 4 and 5. The results are shown in the table below.
<Flexibility test>
The sheets prepared in the examples and comparative examples were cut to a size of 100 mm x 300 mm to prepare test specimens. The prepared test specimens were wrapped around a wooden round bar with a diameter of 25 mm, which resembled the base of a long-stem plant, and the fitting property was evaluated when the test specimens were installed using a pinch-type fixing jig. Three testers evaluated each sheet three times, and the work time required to wrap the test specimens around the round bar so that the maximum gap between the test specimens and the round bar was 5 mm or less was measured and evaluated according to the following criteria.
A: Could be fitted in less than 20 seconds.
A: The device was able to be fitted in 20 seconds or more and less than 1 minute.
△: Installation was possible in 1 minute or more and less than 5 minutes.
×: The maximum gap could not be reduced to 5 mm or less even after 5 minutes of work, or the test specimen was cracked.

(Comparative Example 3)
90 parts by mass of polyvinyl chloride resin particles having a degree of polymerization of 900 (ZEST PQ92 manufactured by Shin-Daiichi Vinyl Corporation), 70 parts by mass of polyester plasticizer (Polysizer W-230H manufactured by DIC Corporation: viscosity 220 mPa·s, gelation end temperature 136 ° C.), 1 part by mass of heat stabilizer (MTX-11P manufactured by Daikyo Kasei Kogyo Co., Ltd.), 5 parts by mass of dispersant (Disperplast-1150 manufactured by BYK Corporation), 1.6 parts by mass of colorant (1) kneaded with a plasticizer at a concentration of 10% by mass of carbon black, and 60 parts by mass of heat storage particles (1) (average primary particle diameter 150 μm, melting point 27 ° C.) microencapsulated with an organic latent heat storage material using an outer shell made of urethane resin were mixed to prepare a plastisol coating liquid. This was applied to a PET film using an applicator coater, then heated at a dryer temperature of 150°C for 8 minutes to gel, and the PET film was peeled off to form a non-aqueous dispersion-type heat storage material with a thickness of 3 mm. The specific gravity of the obtained heat storage material was 1.0, the mandrel diameter at which cracks occurred in the bending test was 25 mm, the bending resistance by the Gurley method was 50 mN, the latent heat amount from 0°C to 40°C was 111 kJ/ ^m2 , the tensile strength was 1.4 MPa, and the elongation at tensile break was 60%.

<Temperature retention evaluation test>
The heat storage materials prepared in Example 4 and Comparative Example 3 having the same latent heat were cut into 5 cm squares to prepare test specimens. The prepared test specimens were placed on a Peltier-type temperature change plate, and a thermocouple was set on the opposite side of the surface in contact with the plate, and the test specimens placed on the plate were covered with a heat insulating material from above. The temperature change of the thermocouple was recorded by a data logger. The temperature of the plate was set to 35°C and maintained for 30 minutes to maintain a constant temperature state. Thereafter, the temperature change of the thermocouple was measured when the temperature of the plate was changed from 35°C to 10°C over 1 minute. The time from the start of the plate temperature change until the temperature of the thermocouple reached 15°C was calculated, and the heat retention was evaluated according to the following criteria.
○: Time required to reach 15°C is 5 minutes or more ×: Time required to reach 15°C is less than 5 minutes

As is clear from the above examples and comparative examples, the heat storage material of the present invention has suitable flexibility, conformability, and excellent temperature retention.

Claims (8)

A heat storage material characterized in that the heat storage particles are coated with a resin, the coated particles being bonded in a three-dimensional network shape by the resin, and voids are formed between the coated resin, and when the heat storage particles are mixed with an aqueous dispersion of the resin, the amount of the aqueous dispersion of the resin absorbed per 100 parts by mass of the heat storage particles is 70 parts by mass or less. The heat storage material according to claim 1, which has a specific gravity of 0.15 to 0.9. The heat storage material according to claim 1 or 2, wherein the solid mass ratio of the resin to the heat storage particles is 80/20 to 15/85. The heat storage material according to claims 1 to 3, wherein the heat storage particles are heat storage capsule particles containing a latent heat storage material in an outer shell. The heat storage material according to any one of claims 1 to 4, wherein the resin is an acrylic emulsion resin. A heat storage laminate comprising the heat storage material according to any one of claims 1 to 5 and a heat insulating layer laminated thereon. A method for producing a heat storage material according to any one of claims 1 to 5 , comprising mechanically foaming an emulsion resin composition which contains a resin, a foaming agent, heat storage particles, and an aqueous medium, and in which the amount of the resin that is absorbed in the aqueous dispersion per 100 parts by mass of the heat storage particles when the aqueous dispersion of the resin is mixed with the heat storage particles is 70 parts by mass or less, and then coating or casting is performed, followed by drying. The method for producing a heat storage material according to claim 7 , wherein the expansion ratio of the mechanical foaming is 1.1 to 5 times.