JPH0472379A - Heat storage material - Google Patents

Abstract

PURPOSE:To obtain a heat storage material consisting essentially of paraffins and polyolefin based thermoplastics having low crystallinity, having high-level (>=35kcal/kg) latent heat and free from crack even when molded into sheet. CONSTITUTION:The aimed heat storage material consisting essentially of paraffins (e.g. paraffin, wax, stearic acid, polyethylene glycol, etc.) and polyolefin based thermoplastics (preferably having 5-40wt.% crystallinity, e.g. PE or PP) having low crystallinity and preferably used at an amount of 5-30 pts.wt. based on 100 pts.wt. of the paraffins. Furthermore, maximum crystal transfer temperature Tmax of the above-mentioned plastics is preferably at least 10 deg.C higher than Tmax of paraffins.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat storage material, and more particularly to a heat storage material using paraffins as a main component.

[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. At present, from a practical standpoint, heat storage materials that utilize phase change heat of substances are attracting attention, and are being used in heat storage type air conditioners, track storage building materials, and various heat retaining appliances and devices.

As one of the energy storage materials that utilize this phase change latent heat, there is a so-called organic storage material that uses a percussion material such as paraffin. This organic heat storage material has fewer problems such as supercooling and phase separation during use.
Long! It has been attracting attention due to its excellent iJI life.

Originally, latent heat type heat storage materials, including inorganic and organic types, store arcs when the phase changes from solid to liquid, and radiate heat when the phase changes from liquid to solid. Therefore, in order to utilize these latent heat type heat storage materials, consideration must be given to maintaining a form that does not flow and leak when liquefied. The method of storing the liquid in an airtight container or bag is expensive and impractical if you use a container with sufficient strength, and if you use a simple container, it will easily break and cause the liquid to leak or overflow. This poses a problem when used for a long period of time.

Therefore, instead of storing in a container, methods such as (a) storing in a porous material, and (b) microencapsulation have been proposed, and methods that combine these methods are being used. Furthermore, a method has also been proposed in which (c) the polyolefin is housed in a polyolefin, usually a crosslinked polyolefin, and encapsulated in a capsule.

However, even with the above methods, the oozing of paraffin, etc. cannot be completely prevented and has become a major problem.
Other problems arise, such as the manufacturing process being complicated and increasing costs, and the content of heat storage material per unit volume decreasing. Furthermore, in the above-mentioned (b) micro-encapsulation method, spaces are created between the capsules, and the existence of these spaces reduces the heat storage performance per unit volume.

Another known conventional method is to knead it into crystalline polyolefin such as crystalline polyethylene.
There are some difficulties in handling. For example, they may be hard and difficult to handle, or they may break during normal handling. Furthermore, there is the problem that paraffin and the like phase separate and ooze out at high temperatures, and in order to prevent this, it is necessary to make the container strong, which is not practical.

In general, heat storage materials are often installed in limited spaces, and there is a strong demand for as much heat storage as possible per unit volume.

[Problem to be solved by the invention]

One problem to be solved by the present invention is to solve the above-mentioned drawbacks of the conventional heat storage material for hammering machines.
An organic heat storage material having a high level of latent heat of /kg or more, which has the highest crystal transition temperature (T□
9 As described later, in many cases it corresponds to the melting point. ) There is no melting, dripping, phase separation, or liquid bleeding even at temperatures above T The objective is to develop a heat storage material with high flexibility.

(Means for solving the problem) This problem was solved by using a polyolefin-based thermoplastic plastic with low crystallinity (hereinafter simply referred to as non-grade polyolefin) and a composition containing paraffins. This problem is solved by using a low-crystalline polyolefin instead of the conventionally proposed crystalline polyolefin, and the maximum allowable operating temperature of the heat storage material of the present invention is lower than that of conventional products. problem(
In many cases, the temperature is below 60°C), but because of its low crystallinity, it has good miscibility with paraffins, and as a result, the product of the present invention does not contain paraffins in the operating temperature range of, for example, 30 to 60°C. It does not have the disadvantage of phase separation and oozing out, and has excellent moldability and can be easily molded into a sheet or plate shape. In addition, in order to exhibit sufficient performance with a blending amount of low crystalline polyolefin of about 5 to 30 parts by weight (based on 100 parts by weight of paraffins), the product of the present invention has a large blending amount of paraffins and a large amount of heat storage.

[Operation and structure of the invention]

The heat storage material of the present invention basically consists of paraffins and a low-crystalline polyolefin, and more preferably consists of 100 parts by weight of paraffin m and 5 to 30 parts by weight of the low-crystalline polyolefin. It is a thing,
30kcal/kg or more, preferably 35kcal/k
It has a high level of latent heat of more than 100 g.

Paraffins used in the present invention include JI
T-1181 measured in accordance with S K 712H Plastic Transition Temperature Measuring Method) is at the operating temperature, i.e. room temperature to 8.
An organic compound having a temperature range G of about 0°C, preferably room temperature to 60°C, more preferably room temperature to about 50°C is used. However, 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, wax-filled fatty acids such as stearic acid and valmitic acid, and alcohols such as polyethylene glycol, which may be used alone or in combination with two or more. 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.
Yu, it becomes 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 m x
Corresponds to x.

The paraffins used in the present invention are not necessarily limited to those that exhibit a clear melting point (the temperature at which the entire phase changes from solid to liquid), but for many paraffins, Tmax generally corresponds to the melting point. . At the operating temperature,
In the case of paraffins having multiple crystal transition temperatures of two or more, all of these crystal transition temperatures can be used for heat storage.

The low crystalline polyolefins used in the present invention include α-olefins such as ethylene, propylene,
Copolymers of butene-1, homopolymers and copolymers of α-olefins chemically containing halogens, carboxylic acids or derivatives thereof, copolymers of carboxylic acids or derivatives thereof and α-olefins, etc. - For boat fishing. Olefin content 40-100% by weight, preferably 60%
-100% by weight, and a low crystallinity polyolefin having a crystallinity of 50% by weight or less, preferably 5 to 40% by weight, as measured by X-ray diffraction.

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, chlorinated polyethylene, etc.
Measured with K 6760? IFR (190℃) is 0.
01-20g/10 min, preferably 0.1-5g/10
It's worth it. These are used in one or more types, but among them, JIS K7121 (Method for Measuring Transition Temperature of Plastics) T for paraffins. A temperature at least 10°C higher than X, preferably at least 20°C higher than T, is 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. .

On the other hand, in the present invention, such low crystalline polyolefins can also be used in a crosslinked form. As for the crosslinking method in this case, any conventionally known chemical crosslinking, solan crosslinking, irradiation crosslinking, etc. can be used. For example, chemical crosslinking with organic peroxides, hydrolyzable puran compounds, organic peroxides, and Depending on the conditions, a condensation catalyst of a solan compound is added, and a crosslinking agent such as silane crosslinking, triallylisocyanurate, or trimethylolpropane trimethacrylate is added to crosslink the water crosslinkable composition obtained by silane grafting with water. This is irradiation cross-linking, etc., in which the material is exposed to an electron beam or the like.

Crosslinking is employed when necessary when the heat storage material of the present invention is used at relatively high temperatures for a long period of time, for example when used in floor heating equipment, etc., but it may slightly impair the moldability intended by the present invention. be. From this point of view, irradiation crosslinking and furan crosslinking methods are somewhat advantageous.

In the present invention, 5 to 30 parts by weight of low crystalline polyolefin is blended with 100 parts by weight of paraffins. In this case, if the amount is less than 5 parts by weight, it is insufficient to keep the shape of the paraffin.
If the amount exceeds X, melting, dripping, or liquid bleeding tends to occur, and if it exceeds 30 parts by weight, the amount of storage per unit volume will decrease, which is not preferable.

In the present invention, various known additives may be added to these components as necessary. For example, in addition to anti-aging agents, antioxidants, colorants, pigments, and antistatic agents, we also use anti-mold agents, flame retardants, and anti-staining agents depending on the application.
Furthermore, metal powder, metal fibers, metal oxides, carbon, carbon fibers, etc. can be used to improve heat conductivity.

The heat storage material of the present invention can be in various shapes such as a sheet, granules, and pellets, but as explained above, sheet or plate shapes are particularly preferred.

The heat storage material of the present invention can be prepared by adding the necessary components by an appropriate method, such as by impregnating paraffins into a hydrocarbon-based organic polymer/NN acid component, or by mechanical means combining paraffins and a hydrocarbon-based organic polymer binder component. Although it can be produced by a method of mixing in a vacuum cleaner or the like, the latter method of mechanical mixing is particularly preferred. The reason for this is that in heat storage materials manufactured by a method of permeation and impregnation, the impregnated paraffin may gradually migrate and the surface of the heat storage material may become sticky within a relatively short period of time. On the other hand, when a hydrocarbon-based organic polymer binder component and paraffins are mixed by mechanical means to form a uniform composition, even if the amount of paraffins used is large as described above (this amount is (The amount of paraffins is 333 to 2,000 parts by weight per 100 parts by weight of the binder component.) Surprisingly, the resulting composition has excellent moldability and is free from paraffins. The problem of migration to the surface of the molded product is highly improved. In this case, mixing by mechanical means means that the remaining components at least swell and preferably dissolve in the melt of at least one component of both the paraffins and the hydrocarbon organic polymer, or It means the act of stirring, mixing, or kneading in a state where any of the components to be mixed can be fluidized and deformed by an external force depending on the temperature. For example, a method in which a hydrocarbon-based organic polymer is dissolved in a melt of paraffins kept at 100 to 200°C, and the resulting high-temperature solution is stirred and mixed, the temperature at which each mixed component softens, e.g., 50 to 100°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. The degree of mixing is preferably as sufficient as possible, but for -i, the purpose is achieved by mixing for about 1 to 30 minutes and visualizing it to be uniformly mixed. . When ingredients other than the above two ingredients are mixed, these ingredients may also be mixed together by mechanical means. When the heat storage material is crosslinked, it may be mixed by mechanical means and, if necessary, formed into a desired shape. During mixing, workability will be improved if the low-crystalline polyolefin is added in the form of pellets or granules. The temperature during mixing is, for example, 60 to 200°C.

The above-mentioned composition, which has been mixed and turned into a solution, is molded as it is or after being slightly cooled. Molding may be performed by pouring into a mold to form a desired sheet or plate shape.Also, since the heat storage material of the present invention solidifies when the temperature is below the Tm a Also good. Alternatively, it may be attached, coated, or impregnated onto a film, cloth, fiber, etc. to form a sheet or plate. Furthermore, it can be packed in polyethylene bags and made into sheets or plates during the cooling process.On the other hand, if an extruder is used, it can be extruded into sheets or plates. It can also be formed into a pipe shape. rod,
If the pipe is shredded, it becomes granules or pellets.

In order to obtain an irradiation-crosslinked heat storage material, the above-mentioned crosslinking aid is usually added in an amount of 0.5 to 5 parts by weight when preparing the composition, and after the heat storage material is formed, it is irradiated with an electron beam of about 20 Mrad. Bye.

The silane crosslinked heat storage material is a composition containing paraffins and low-crystalline polyolefin as main components, 100 parts by weight of low-crystalline polyolefin, 0.5 to 5 parts by weight of a nitrogen-based compound, and OIA oxides o, os ~ 0. The Smi part is mixed in advance and heated to 140°C using an extruder, twin-screw kneading extruder, etc.
Extrusion molding is carried out in the same manner as described above at the above set temperature, and then crosslinked with moisture by leaving it in the air or immersing it in hot water.

When using the heat storage material of the present invention, in principle all conventional methods of use of this kind of heat storage material can be adopted, but in particular, the heat storage material of the present invention E in sorted form can be used with a protective film such as polyethylene, polypropylene, polyester, etc. It is preferable to cover with a film and further provide a heat-uniforming layer using a metal foil such as aluminum.

〔Example〕

The present invention will be explained in detail below with reference to Examples and Comparative Examples.

Examples 1 to 5, Comparative Examples 1 to 4 Regarding the Mi composition shown in Table 1 (all proportions are parts by weight), paraffins were first heated to 100 to 140°C in a container and melted, and then The ingredients were added and mixed by stirring for approximately 30-60 minutes. Pour this into a mold and cool it in the air, 130
M thermal materials of Examples 1 to 5 and Comparative Examples 1 to 4 having a thickness of m x 10 m x 2 m were obtained.

The properties shown in Table 1 were measured for these heat storage materials by the following methods.

Maximum heat storage temperature: The heat storage material of the present invention exhibits heat storage characteristics that reflect the crystal transition temperature characteristics of the paraffins used. The maximum heat storage temperature is the temperature at which the greatest heat storage or heat absorption occurs, and in most cases, the temperature of T11)1 for paraffins.
Appears at or near the melting point.

This temperature was measured using an OSC device according to JIS K 7121.

Heat storage amount +, the heat of fusion (kJ/kg) is measured by a DSC device according to lrS K 7122, and kcal/kg
It was converted and displayed.

Flexibility: The heat storage material was cut into a strip with a width of 1Q mm, held at both ends and bent at 90 degrees at room temperature, and examined to see if it would break.

Shape retention: 2 to 3 degrees Celsius above the maximum heat storage temperature in the oven
The state of heat storage at high temperature was visually observed, and those that did not melt and maintained substantially their original shape were judged to be good. What about defects? It is melted and liquefied.

Seepage: A heat storage material with good shape retention is sealed in a polyethylene film bag, and the temperature is 1
The sample was left at a temperature 0° C. higher for 24 hours and visually observed to see if the paraffins had separated. Those with almost no abnormalities were considered good. Defects are those in which separation is clearly recognized.

Workability: The mixing state when mixed at 130° C. for 40 minutes was visually observed, and cases where it was insufficient were judged as defective.

The measurement results are shown in Table 1, and the heat storage materials of Examples 1 to 5 of the present invention all had a heat storage amount of 35 kcal/kg or more, and also satisfied other practically necessary properties. . On the other hand, in the comparative examples, the amount of M27 was insufficient or other properties were insufficient.

Example 6 The composition shown in Table 1 was supplied to a twin-screw kneading extruder with a Norinder temperature of 200°C, extruded at a screw rotation speed of 4 Orpm, poured into a mold in the same manner as in Examples 1 to 5, cooled in air, and Immerse in water at 30°C and cross-link it to 1.30
A plate-shaped heat storage material having a thickness of m x 110 wm x 2 ts was obtained. Table 1 shows the properties of this heat storage material measured in exactly the same manner as in Examples 1 to 5, and the properties were satisfactory as in Examples 1 to 5.

Example 7 The composition of Example 1 was mixed in the same manner as above, and a plate-shaped heat storage material having a size of 300 N x 350 rm x 20 m in thickness was prepared in the same manner. This was sealed in a 0.1n thick polyethylene sheet bag, and then heat-sealed with a three-layer aluminum laminated first sheet of polyethylene/aluminum/polyester (30μm/25μm/25μIl), with foam insulation on both sides about 5fl thick. This was then placed in a cloth bag to create a heat storage cushion. When this was heated in an oven to store heat and used as a cushion at an outdoor party, it remained warm and comfortable for about 4 hours. The temperature is about 10
It was 'c. When working with heat storage materials, heat can be easily stored using Jiden by interposing a heat generating heater wire between the heat storage materials. In this case, the heater wire may have a power of about 100 V and 30W to 50W.

〔Effect of the invention〕

The arc storage material of the present invention has a high level of activity of 30 kcal/kg or more, preferably 35 kcal/kg or more, and also melts, drips, and phase separation even at temperatures above the T, □ or melting point of the paraffins used. , no liquid burritos, etc.
2. Not brittle even below the melting point. /- It does not break even when molded into a sheet shape and has appropriate flexibility. As described above, the energy storage material of the present invention is suitable for various heat storage type heat retention appliances,
In addition, it can be widely used in storage type building materials, air conditioning equipment, equipment, etc.

Claims (3)

[Claims] (1) A heat storage material comprising paraffins and low-crystalline polyolefin thermoplastics as main components. (2) The heat storage material according to claim 1, wherein the low-crystalline polyolefin thermoplastic plastic is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the paraffin. (3) The highest crystal transition temperature Tmax of low-crystalline polyolefin thermoplastics is Tm of paraffins.
The heat storage material according to any one of claims 1 to 2, which is at least 10°C higher than ax.