JPH0472377A - Thermal energy storage material - Google Patents

Abstract

PURPOSE:To obtain a thermal energy storage material, consisting essentially of paraffins and a hydrocarbon-based organic polymeric binder component, further containing a specific gravity regulating material component, having a large quantity of thermal energy storage and excellent in thermal energy storing and heat radiating properties without causing phase separation or melting and liquefying the paraffins. CONSTITUTION:The objective thermal energy storage material, consisting essentially of 100 pts.wt. paraffins (e.g. paraffin, wax, stearic acid or polyethylene glycol) and 5-30 pts.wt. hydrocarbon-based organic polymeric binder component (e.g. styrene-based block copolymer elastomer) and further containing a specific gravity regulating material component (e.g. powder of Al, Fe or Pb).

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heat storage material, and more particularly to a heat storage material containing paraffins as a main component and used in a heat storage device for storing and utilizing thermal energy. .

[Conventional technology]

Conventional heat storage materials utilize the sensible heat of substances based on their principle.
There are those that utilize the latent heat of phase change of substances, and those that utilize the heat of chemical reaction of substances. Currently, heat storage materials that utilize the phase change latent heat of substances are attracting attention from a practical standpoint, and are being used in heat recovery and storage devices, heat storage type air conditioners, heat storage type building materials, various heat retention devices, moisturizing devices, etc.

As heat storage materials that utilize this phase change latent heat, there are so-called organic heat storage materials that use organic substances such as pentaerythritol, polyethylene, crosslinked polyethylene, and paraffin. Recently, paraffins have been attracting particular attention because they have few phenomena and are excellent in long-term life, and paraffins are particularly promising for thermal energy storage at temperatures below 100°C.

In a heat storage device using paraffin as a heat storage material, a closed container is required, such as storing the heat storage material in a pipe, because the paraffin is liquefied due to heat storage, and the heat storage device naturally uses an indirect heat exchange method. There are many issues, such as the need to fully utilize heat conduction during the heat storage and heat dissipation processes.

Therefore, instead of storing it in a container, a method of microencapsulation has been proposed, and a method of storing a heat storage material in polyolefin, usually cross-linked polyolefin, and encapsulating it in a capsule has also been proposed, but the manufacturing process However, problems such as complexity and high cost arise in molded products, such as paraffin and other substances phase-separating and oozing out at high temperatures, and surface area decreasing due to mutual fusion of heat storage materials, resulting in a reduction in heat exchange rate. . The heat storage material used in this type of heat storage device is desired to be a heat storage material that has high heat storage and heat dissipation properties, that is, heat exchangeability, and can be used in direct heat exchange type devices in order to improve efficiency.

[Problem to be solved by the invention]

The problem to be solved by the present invention is to solve the above-mentioned difficulties of conventional organic heat storage materials of this type using paraffins. The objective is to develop a heat storage material that can be applied to direct heat exchange type heat storage devices and has excellent heat exchange properties.

[Means for Solving the Problem] This problem consists mainly of 100 parts by weight of paraffins and 5 to 30 parts by weight of a hydrocarbon-based organic polymeric binder component, and further contains a specific gravity adjusting material component. The problem is solved by providing a heat storage material characterized by the following.

The organic polymeric binder component used in the present invention has rubber-like properties, is sufficiently mixed with paraffins, and supports the paraffins in a well-enveloped state, so that the amount of the organic polymeric binder component used in the present invention is overwhelmingly greater than the amount of paraffins. Although it is a small amount, room temperature~
It does not easily cause paraffin liquefaction or phase separation even at high temperatures of 40°C or higher, has shape retention ability, and has excellent moldability. In particular, it is preferable to mix by mechanical means during this mixing, and by mixing by mechanical means, it becomes easier to support the paraffins in a well-enveloped state with an overwhelmingly small amount of the binder component. In addition, the content of the specific gravity adjusting material component can be adjusted to make it almost the same as the specific gravity of the heat medium, so it can be applied to direct heat exchange type heat storage devices, and heat exchange performance, that is, heat storage performance and heat dissipation performance, is greatly improved. .

[Function and structure of the invention]

Paraffins used in the present invention include JI
An organic compound whose T6 soup measured in accordance with S K 7121 (Method for Measuring the Transition Temperature of Plastics) is above the operating temperature, that is, room temperature, and below the deformation temperature of the organic polymeric binder component used is used. Ru. For example, typical examples include those in the temperature range of room temperature to 100°C, preferably room temperature to about 80°C. However, the room temperature in this case means the lowest temperature that the heat storage material of the present invention encounters during its operation.

Preferred specific examples of paraffins include various paraffins, waxes, fatty acids such as stearic acid and palmitic acid, and alcohols such as polyethylene glycol.
Used as a mixture of more than one species.

At the above-mentioned operating temperatures, some paraffins have only one crystal transition temperature, in which case the temperature is T.
, x), and some have multiple crystal transition temperatures of two or more. Mixtures of two or more paraffins often also have multiple crystal transition temperatures of two or more. In those cases, the highest crystal transition temperature is T + w a
Corresponds to x. The paraffins used in the present invention do not necessarily have a clear melting point (temperature at which the entire phase changes from solid to liquid).
For many paraffins, T6□8 generally corresponds to the melting point, although it is not limited to those exhibiting this. In the case of paraffins having multiple crystal transition temperatures of two or more at the operating temperature, all of these crystal transition temperatures can be utilized for heat storage.

The hydrocarbon-based organic polymeric binder component used in the present invention is at least one selected from the group (a) to (e) shown below.

(a) Thermoplastic elastomers: Examples include those known as "thermoplastic elastomers J" in the fields of rubber and plastics. In particular, paraffin T, which is used at least at room temperature or above in the above sense. In the temperature range of +10°C, preferably at least room temperature or higher, and in the temperature range of +20°C, a material having rubber elasticity is used.Of course,
It is also preferable to maintain rubber elasticity even at temperatures higher than T+20°C. Specifically, a thermoplastic elastomer that meets the above conditions is appropriately selected from various conventionally known thermoplastic elastomers such as styrene, olefin, urethane, and ester-based thermoplastic elastomers.

Preferred specific examples are styrenic block copolymer elastomers and olefin elastomers. Examples of the styrenic block copolymer elastomer in this case include ABA (where A is polystyrene and B is polybutadiene, polyisoprene, or ethylene/butylene obtained by adding hydrogen to these).

Examples of olefinic thermoplastic elastomers include ethylene-propylene copolymers, mixtures of ethylene-propylene-diene terpolymers with polyethylene or polypropylene, ethylene-propylene copolymers, and ethylene-propylene-diene ternary copolymers. Examples include those in which ethylene or propylene is graft-polymerized to the original copolymer.

Since such thermoplastic elastomers have rubber elasticity at temperatures below Tmax, they can effectively envelop paraffins. Furthermore, the above elastomer is T
□、In order to maintain rubber elasticity even at higher temperatures,
It is possible to obtain a heat storage material that does not melt or drip even at such high temperatures, does not cause phase separation of paraffins, and does not cause bleeding.

(b) Low-crystalline polyolefin thermoplastic R: α-olefins, such as copolymers of ethylene, propylene, butene, homopolymers, copolymers of α-olefins chemically containing halogens, carboxylic acids, or derivatives thereof; Copolymers of carboxylic acid or its derivatives and α-olefin, with an olefin content of 4
0 to 100%, preferably 60 to 100%, and the degree of crystallinity measured by X-ray analysis is 50% or less, preferably 5 to 100%.
40% low crystallinity polyolefin. For example, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butene copolymer, ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethylene-hexene copolymer, ethylene-octene copolymer. Polymer, chlorinated polyethylene, etc., JIS K 676
Gate FR (190-6) measured at 0.01-20
g/10 minutes, preferably 0.1 to 5 g/10 minutes. These may be used alone or in combination of two or more,
In particular, the maximum crystal transition temperature (usually corresponds to the melting point) measured by JIS K 712N Plastic Transition Temperature Measuring Method) is the T na of the paraffin used.
at least 10°C higher than X, more preferably T
Those at least 20°C higher than □8 are preferably used.

Such polyolefins generally do not have a high heat distortion temperature due to their low crystallinity, and therefore, although the heat storage material of the present invention has a limited use temperature, it has good miscibility with paraffins and has the various advantages described above. have

(c) Mixture of hydrocarbon rubber and crystalline polyolefin: This mixture preferably contains 5 to 2000 parts by weight, especially 50 to 5 parts by weight, of hydrocarbon rubber per 100 parts by weight of crystalline polyolefin.
Compositions comprising 0.00 parts by weight are preferred.

Crystalline polyolefins include homopolymers such as polymethylene, polyethylene, and polystyrene; copolymers of methylene with ethylene, propylene, etc.; copolymers of ethylene with methylene, propylene, butene, etc., and propylene. These include copolymers of olefins, such as copolymers with other olefins as main components, copolymers of olefins such as ethylene, propylene, butene, and other monomers, such as vinyl acetate, acrylic acid, methacrylic acid, etc., among others. JIS
The highest crystal transition temperature measured by K 7121 is T ffi of the paraffins used! A temperature of at least 10°C higher than l x is used, preferably at least 20°C higher than T m a x . In particular, the transition temperature of these crystalline polyolefins is
It is preferable that it is sufficiently higher than max. For example, when TIl,

Hydrocarbon rubbers include natural rubber, SBR, BRlIRl
Examples include IIR, EPM, EPDM, and ethylene-vinyl acetate copolymer rubber. Each of these hydrocarbon rubbers is well known in itself, and any conventionally known rubber can be used. The use of this hydrocarbon rubber imparts rubbery properties to the heat storage material of the present invention and improves its compatibility with paraffins.

On the other hand, the use of crystalline polyolefin keeps the deformation temperature high.

(d) A crosslinked composition comprising a hydrocarbon rubber and a crosslinking agent for the hydrocarbon rubber: This composition has sufficient rubber-like properties, and the deformation temperature is maintained at a high temperature by crosslinking.

The hydrocarbon rubbers used here include those described in (c) above, and a wide variety of crosslinking agents for hydrocarbon rubbers can be used as long as they can crosslink the rubber. Natural rubber, SBR, BRlIR, I IR,
Sulfur-based vulcanizing agents are preferred for EPM and EPDM, and oximes such as p-xylene dioxime can also be used for natural rubber and 5BR1IIR. Also natural rubber, EPM, E
For PDM and ethylene vinyl acetate copolymer rubber, organic peroxide crosslinking agents such as dicumyl peroxide can also be used. The amount of crosslinking agent used is preferably about 0.5 to 20 parts by weight per 100 parts by weight of the hydrocarbon rubber.

Further, when a sulfur-based crosslinking agent is used in this composition, a vulcanization accelerator can also be used in combination, if necessary.

Examples of the vulcanization accelerator include guanidine accelerators such as diphenylguanidine, thiazole accelerators such as 2-mercaptobenzothiazole, thiuram accelerators such as tetramethylthiuram disulfide, and other aldehyde amine compounds. , aldehyde-ammonia compounds, dithiocarbamate compounds, etc. can also be used.

Furthermore, metal oxides such as zinc oxide and amines such as triethanolamine can also be used. When oximes are used as a crosslinking agent, it is preferable to use lead oxide as an auxiliary agent in addition to sulfur and the above-mentioned vulcanization accelerator.

When an organic peroxide is used as a crosslinking agent, vinyl-tris (β-
Silane coupling agents such as methoxyethoxy)silane, acrylic ester compounds, and the like can also be used as crosslinking aids. The crosslinking aid may be used in an appropriate amount to obtain a suitable degree of crosslinking, and is usually about 0 to 30 parts by weight per 100 parts by weight of the hydrocarbon rubber.

(e) A water-crosslinkable composition containing a hydrocarbon polymer, a hydrolyzable silane compound, an organic peroxide, and, if necessary, a condensation catalyst for the silane compound: The composition is free from water and moisture. It has the property of crosslinking in the presence of water (water crosslinkability), and exhibits rubber-like properties in the water crosslinked state.

The hydrocarbon polymers used here include general-purpose rubbers such as natural rubber, SBR, and BRlIR, as well as homopolymers such as polymethylene, polyethylene, and polystyrene, and copolymers mainly composed of methylene and ethylene, propylene, etc. , mainly ethylene, methylene,
Copolymers of olefins such as copolymers of propylene, butene, etc., copolymers of olefins such as propylene-based copolymers with other olefins, copolymers of olefins such as ethylene, propylene, butene, and other polymers such as vinyl acetate, acrylic acid, Examples include copolymers with methacrylic acid and the like.

The silane compound has the general formula RR'5iYz (
However, R is a hydrocarbon group or a hydrocarbonoxy group containing monovalent olefinic unsaturation, Y is a hydrolyzable organic group, and R'' is a group R or a group Y. Further specific examples include those known as this type of silane compound, such as vinyltriethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane, etc.The silane compound is used in an amount of 100 parts by weight of the hydrocarbon polymer. The silane compound is generally used in an amount of 0.05 to 10 parts by weight, particularly 0.5 to 5 parts by weight.The silane compound is grafted onto a hydrocarbon polymer by the action of an organic peroxide, which will be described later. It acts to form crosslinking points between polymers.

For organic peroxides, temperatures above the decomposition temperature, especially 100
Compounds capable of generating free radicals in the hydrocarbon polymer at temperatures above °C are used, such as dicumyl peroxide, 2.5-di(t-
butylperoxy)-hexyne-3 and the like. The organic peroxide is generally used in an amount of 0.005 to 2 parts by weight, particularly 0.05 to 0.5 parts by weight, based on 100 parts by weight of the hydrocarbon polymer.
Used in weight parts. The organic peroxide acts to generate free radicals in the hydrocarbon polymer and graft the silane compound onto the hydrocarbon polymer.

In this composition, a condensation catalyst of a silane compound can also be used if necessary. As the condensation catalyst in this case, those commonly known as silanol condensation catalysts are used, such as dibutyltin dilaurate, stannous acetate,
Examples include carboxylic acid salts such as lead naphthenate and zinc caprylate, organometallic compounds such as titanate esters, and chelate compounds. The amount of this type of condensation catalyst used is about 0.1 part by weight or less per 100 parts by weight of the hydrocarbon polymer, and the condensation catalyst has the effect of promoting the crosslinking reaction by water.

This composition is thoroughly mixed with paraffins for at least 30 seconds in a closed mixer set at a temperature above the decomposition temperature of the organic peroxide, usually above 140"C. In this step, the organic peroxide is converted into a hydrocarbon. Radicals are generated in the hydrocarbon polymer, and the silane compound is grafted onto the hydrocarbon polymer, thereby making the composition water-crosslinkable.

The degree of crosslinking after water crosslinking of the heat storage material formed by mixing the present composition with paraffins is 1% or more, preferably 2% or more.

The heat storage material of the present invention can be appropriately crosslinked if necessary.

The crosslinking method may be a chemical crosslinking method using a crosslinking agent as described in (d) above, a silane crosslinking method as described in (e) above, or an irradiation crosslinking method.

In the irradiation crosslinking method, the hydrocarbon organic polymer is usually prepared by mixing 0.5 to 5 parts by weight of triallyl isocyanate, trimethylolbroban trimecrylate, etc. as a crosslinking aid to 100 parts by weight of the binder component. This is a method of crosslinking by irradiating radiation, electron beam, etc. at a dose of 5 to 30 Mrad. For the above (a) to (C) as necessary,
Any of a chemical crosslinking method, a silane crosslinking method, and an irradiation crosslinking method may be applied.

In the above (d) and (e), the heat storage material of the present invention is J
1% based on the degree of crosslinking determined according to IS C3005
As mentioned above, it is preferable that the crosslinking amount is preferably 2% or more. By setting the degree of crosslinking to 1% or more, preferably 2% or more, the temperature of the heat storage material can be lowered to T 11 of the paraffins used.
It is possible to maintain the shape without melting even if the temperature exceeds 11X. Although (a) to (C) do not necessarily need to be crosslinked, if they are crosslinked, a heat storage material with excellent long-term performance can be obtained.

In the present invention, the amount of the organic polymeric binder component is 5 to 30 parts by weight per 100 parts by weight of paraffins. If it is less than 5 parts by weight, it will be brittle at Tm a, and at high temperatures above T-U, the heat storage material will tend to partially melt and liquefy, making it difficult to hold it in the desired shape, while if it exceeds 30 parts by weight. If the amount is too large, the amount of paraffin compounded will decrease, and the amount of heat storage will decrease proportionally.

In the present invention, the composition comprising the paraffins and the organic polymeric binder component described above contains a specific gravity adjusting material component. The specific gravity adjusting material component in this case is for making the specific gravity of the heat medium used in the direct heat exchange type heat storage device and the specific gravity of the heat storage material of the present invention almost the same, and the specific gravity of the heat medium is the same as that of the heat storage material of the present invention. If the specific gravity is greater than , the high specific gravity component is used, and in the opposite case, the low specific gravity component is used. The high specific gravity component is a component with a specific gravity of 1 or more, preferably about 2 to 15. Preferred specific examples include various metals, metal oxides,
Examples include inorganic fillers, and more specifically, metals include aluminum, iron and lead powder, and metal oxides include:
ZnO, TiO□, pbo, etc., and examples of inorganic fillers include talc, clay, silicate, calcium carbonate, glass, etc. As the low specific gravity component, gas (generally foamed) and various foams are used. Generally, the specific gravity of a composition consisting of the above-mentioned paraffins and an organic polymeric binder component is about 0.8 to 1.0.
It often contains high specific gravity components. These specific gravity adjusting material components are blended in appropriate amounts depending on the type of heat medium used so that the specific gravity of the heat storage material is approximately the same as the specific gravity of the heat medium. It is also possible to cover the surface with foil or the like. As for the specific gravity of the heat medium, if the heat storage process is emphasized in the heat storage device, select the specific gravity at the temperature before heat storage, and if the heat release process is important, select the specific gravity at the temperature before heat release (i.e., the temperature in the state of heat storage). ), and adjust the specific gravity of the heat storage material accordingly. Since the heat storage material thus has almost the same specific gravity as the heat medium, the heat exchange between the heat medium is carried out efficiently and without waste, and as a result, heat storage and heat dissipation properties are greatly improved. Therefore, when the heat storage material of the present invention is used in a direct exchange type heat storage device, the heat storage and heat dissipation properties are extremely good.
It is also extremely effective in recovering low-grade heat below °C.

Various types of heat medium are widely used in the present invention, and preferred examples include ethylene glycol and water, with water being particularly preferred.

In the present invention, in addition to the paraffins, the organic polymeric binder component, and the specific gravity adjusting material component, various additives may be blended as necessary. Examples include anti-aging agents, antioxidants, colorants, pigments, antistatic agents, as well as fungicides, flame retardants, anti-nail agents, etc. depending on the application.

In the present invention, it is necessary to mix the paraffins and the hydrocarbon-based organic polymeric binder component, and in this case, it is preferable to mix by mechanical means.

In particular, when hydrocarbon rubber and polyolefins are used together as the polymeric binder component, when a thermoplastic elastomer is used, or when the above two cases are used together, other means rather than mechanical means may be used. Although the paraffins can be successfully mixed with the organic polymeric binder component by mixing with the organic polymeric binder component, in other cases, mixing by this mechanical means is extremely preferable. Mixing by mechanical means means
Either of the components to be mixed is mixed by at least swelling, preferably dissolving, of the remaining components in the melt of at least one of both the paraffins and the hydrocarbon-based organic polymeric binder component, or by high temperature. It means the act of stirring, mixing, or kneading in a state where it can be fluidized and deformed by external force. For example, a hydrocarbon-based organic polymeric binder is dissolved in a paraffin melt kept at 100 to 200°C, and the resulting high-temperature solution is stirred and mixed. ~250″C
Examples include embodiments in which kneading and mixing are carried out using a conventional kneading machine such as a two-roll mill, a Banbury mixer, an extruder, and a twin-screw kneading extruder. It is preferable that the degree of mixing be as sufficient as possible, but generally, the object of the present invention is achieved by mixing for about 1 to 150 minutes and visually determining that the mixture is well mixed. Ru.

When a hydrocarbon-based organic polymer binder component and paraffins are mixed by mechanical means to form a composition like this, even if the amount of paraffins used is large (
Surprisingly, even though this amount is converted into an amount of paraffins of 333 to 2000 parts by weight per 100 parts by weight of the binder component, the resulting composition is rich in moldability and has high paraffin content. type of migration problem is highly improved.

Although the method of homogeneous mixing by mechanical means seems to be common sense at first glance, it is truly unexpected that both of the above components can be uniformly mixed in the above proportions by this method. It's something you can't get.

When using the heat storage material of the present invention, in principle, it can be used in all conventional ways of using this type of heat storage material, such as spherical, pellet, rod, plate, powder, granular, block, sheet, and film shapes. However, in a direct heat exchange type heat storage tank, from the viewpoint of heat exchange efficiency, the shape of the heat storage material is preferably spherical, pellet, or cylindrical.

〔Example] The present invention will be described in detail below with reference to Examples.

Examples 1 to 6, Comparative Examples 1 to 3 After thoroughly mixing and kneading each component with the composition shown in Table 1 (all proportions are parts by weight) and molding it into a plate shape with a thickness of about 55 mm,
It was shredded to obtain a pellet-shaped heat storage material with approximately 5 squares. Here, Example 1 and Comparative Example were mixed and kneaded in a container at 130 to 180°C, and then poured into a mold and molded.
and Comparative Example 2, after mixing and kneading with a roll mill,
Press molding was carried out at 165°C for 30 minutes, and in Example 5.6 and Comparative Example 3, dibutyl Tin dilaurate was applied to the surface, crosslinked in hot water, and then shredded.

For each Example and Comparative Example, the characteristics shown in Table 1 were measured by the following methods.

Specific gravity: Underwater displacement method Maximum heat storage temperature: JTS K 7121 (DSC device) Heat storage amount: JIS K 7122 (DSC device)
However, the heat of dissolution (KJ/kg) was converted into Kcal/kg and displayed.

Degree of crosslinking: JIS C3005 Measurement results are shown in Table 1. Examples 1 to 6 and Comparative Examples 1.3 had a satisfactory amount of heat storage, whereas Comparative Example 2 had an insufficient amount of heat storage. there were. Next, the heat storage materials of each of the other Examples and Comparative Examples except for Comparative Example 2 were filled into a direct heat exchange type heat storage tank using water as a heat medium to the extent that it occupied about 2 volumes, and heat storage and heat radiation were repeated. I observed the situation. A stirring device is attached to the heat storage tank.

The heat storage materials of Examples 1 to 6 flowed almost uniformly in the medium,
While the heat storage and heat release cycle was repeated, in Comparative Example 1, because the polymer binder component was too small, the heat storage material melted and blocked, floating on the surface of the medium, resulting in insufficient heat storage and heat release. On the other hand, in Comparative Example 3, the particles were still floating on the surface of the medium, and both heat storage and heat radiation were insufficient.

〔Effect of the invention〕

The heat storage material of the present invention has a large heat storage capacity (paraffins do not undergo phase separation, melting, or liquefaction, and has excellent heat storage and heat dissipation properties. Therefore, when applied to a direct heat exchange type heat storage device, for example, heat storage and heat dissipation are possible. An extremely excellent heat storage device is obtained, and heat can be recovered effectively even at temperatures below 100°C, where heat recovery is difficult.

(that's all)

Claims (1)

[Claims] A heat storage material comprising 100 parts by weight of paraffins and 5 to 30 parts by weight of a hydrocarbon-based organic polymeric binder component, and further comprising a specific gravity adjusting material component.