JPH0366788A - Heat accumulating material - Google Patents

Abstract

PURPOSE:To obtain a heat accumulating material having latent heat of high level, proper flexibility and improved physical stability, comprising a paraffin and a thermoplastic elastomer as main components. CONSTITUTION:The objective heat accumulating material comprising (A) 100 pst.wt. paraffins such as paraffin, wax, stearic acid, palmitic acid or polyethylene glycol and (B) 5-30 pts.wt. thermoplastic elastomer such as a styrene-based, olefin-based, urethane-based or ester-based thermoplastic elastomer to give the objective heat accumulating material.

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. Currently, heat storage materials that utilize the zero-phase change latent heat of substances are attracting attention from a practical standpoint, and are being used in heat storage type air conditioners, heat storage type building materials, and various heat retention appliances and devices.

As one type of heat storage material that utilizes this phase change latent heat, there is a so-called organic heat storage material that uses an organic substance such as paraffin. This organic heat storage material has fewer problems such as supercooling and phase separation during use.
It has long been attracting attention because of its long lifespan.

Originally, latent heat type heat storage materials, including inorganic and organic types, store heat 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 compound 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 microencapsulation method (b) above, 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 especially in the case of thermal storage floor heating systems, which are the preferred use for heat storage materials, the installation space is extremely limited, and the amount of heat storage per unit volume is small. But there is a strong demand for something bigger.

[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.
An organic heat storage material having a high level of latent heat of l/kg or more, which has the highest crystal transition temperature (T) of the paraffins used.
□Yo, as mentioned later, in many cases it corresponds to the melting point. )
Even in the above conditions, there is no melting, dripping, phase separation, or liquid bleeding, and even in T The aim is to develop a heat storage material with properties.

[Means to solve the problem]

this! Ill can be solved by using a composition containing paraffins and a thermoplastic elastomer as a heat storage material. In particular, the thermoplastic elastomer used in the present invention is a paraffin that exhibits rubber elasticity at least at T1.8 or less. Therefore, since it has rubber elasticity at temperatures below T, □, the thermoplastic elastomer can support the paraffin in a well-wrapped state, and it is easy to handle, difficult to break, and easy to form into sheets or plates. It is. In addition, this elastomer has a compounding amount of 5 to 30 parts by weight (1 part paraffin).
100 parts by weight), the heat storage material of the present invention contains a large amount of paraffins and has a large amount of heat storage.Furthermore, the elastomer has rubber elasticity even at temperatures higher than T, □. In order to maintain the heat storage temperature, the heat storage material of the present invention does not melt or drip, and does not cause phase separation of paraffins or bleed, thus solving the problems of conventional heat storage materials.

[Function and structure of the invention]

The heat storage material of the present invention basically consists of paraffins and a thermoplastic elastomer, and more preferably consists of paraffin Igloo and 5 to 30 parts by weight of the elastomer, 30kca
It has a high level latent heat of 1/kg or more, preferably 35 kcal/kg or more.

Paraffins used in the present invention include JI
S K 7121 (Method for measuring transition temperature of plastics)
T measured according to...! is the operating temperature, i.e. room temperature ~ 10
An organic compound having a temperature range of 0°C, preferably room temperature to about 80°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, 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.
It becomes mmx. ), and some have multiple crystal transition temperatures of two or more. Mixtures of two or more paraffins also often have multiple crystal transition temperatures of two or more; in those cases, the highest crystal transition temperature is T1. Applies to.

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, generally T, 18 corresponds to the melting point. 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.

Among the thermoplastic elastomers used in the present invention, which are known or can be known as "thermoplastic elastomers" in the fields of rubber and plastics, paraffins used at least at room temperature or above are used. In the temperature range of T a a
In the temperature range of °C, materials with rubber elasticity are used.

Of course, it is also possible to use materials that maintain rubber elasticity even at temperatures higher than T, 8+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. Preferred specific examples are styrenic block copolymer elastomers and olefin elastomers. Examples of the styrene block copolymer elastomer in this case include A-B-A (where A is polystyrene and B is polybutadiene, polyisoprene, or ethylene/butylene with hydrogen added thereto). . Examples of olefin-based thermoplastic elastomers include mixtures of ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, and polyethylene or polypropylene;
Examples include propylene copolymers and ethylene-propylene-diene terpolymers obtained by graft polymerization of ethylene or propylene.

In the present invention, 5 to 30 parts by weight of thermoplastic elastomer is blended with 100 parts by weight of paraffin. In this case, if the amount does not reach 5 parts by weight, it is insufficient to maintain the shape, and therefore, at T + am□ or higher, melting, dripping, and liquid bleeding tend to occur;
If it is less than a a 1), it will become brittle and break easily. 30 again
If it exceeds 1 part by weight, the amount of heat storage per unit volume will decrease, which is not preferable.

In the present invention, various known additives may be further 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-kite agents depending on the application, as well as metal powders and metal fibers to improve heat conductivity. , metal oxide, carbon, carbon fiber, etc. can be used.

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 method for forming the heat storage material of the present invention is not particularly limited, but preferred examples are as follows. That is, a composition containing paraffins and a thermoplastic elastomer as main components is first prepared using a conventional mixing/stirring machine such as a two-roll machine, an extruder, a twin-screw kneading extruder, or a stirring mixer. When using a stirrer, the thermoplastic elastomer and other components are added to the molten paraffin and stirred. At this time, workability will be improved if the thermoplastic elastomer is added in the form of pellets or granules. The addition temperature is preferably in the thermoplasticization range of the thermoplastic elastomer, and is usually 100 to 200°C.

The above-mentioned composition, which has been mixed and turned into a solution, is shaped as it is or after being slightly cooled. The bottom shape can be made into a desired sheet or plate shape by pouring it into a mold, and since the heat storage material of the present invention solidifies when the temperature is below the paraffin T or □, it can be made into a block shape and then cut into a sheet or plate shape. It can also be made into a sheet or plate by attaching, coating, or impregnating it onto a film, cloth, fiber, etc. It can also be made into a sheet or plate by being punctured in a polyethylene bag or the like during the cooling process. On the other hand, if an extruder is used, it can be extruded into a sheet or plate shape, and it can also be molded into a rod or pipe shape using the extruder. If you shred a rod or vibrator, it will become granules or pellets.

When using the heat storage material of the present invention, in principle, all conventional methods of use of this type of heat storage material can be adopted, but in particular, the heat storage material of the present invention in sheet form can be used as a protective film, such as a film made of polyethylene, polypropylene, polyester, etc. It is preferable to further provide a heat-uniforming layer thereon using a gold N foil such as aluminum, or it may be covered with a laminate film made by laminating the above film and a metal foil such as aluminum.

〔Example〕

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

Examples 1 to 5, Comparative Examples 1 to 4 For the compositions shown in Table 1 (all proportions are parts by weight), paraffins such as paraffin, microcrystalline wax, and stearic acid were heated to 130°C to 180°C in a container. Temperature, melt and add other thermoplastic elastomers, ethylene-propylene-diene terpolymer rubber (EPDM
), polyethylene, etc. were added and mixed with stirring for about 60 to 120 minutes. Pour this into a mold and let it air cool, 130m x 1
) Heat storage materials of Examples 1 to 5 and Comparative Examples 1 to 4 in the form of plates of 0 m x 2 mm thickness 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 It appears at or near the melting point of TII□ of the class. This temperature was measured using a DSC device according to JIS K 7121.

Heat storage amount: The heat of fusion (kJ/kg) was measured using an OSC device according to JIS 7122, and was converted to kcal/kg and displayed.

Flexibility: The heat storage material was cut into a strip with a width of 10 fi, gripped at both ends, bent at 90 degrees, and examined for breakage.

Shape retention: Shape B heated in an oven to the highest temperature range expected in practical use (Shape 7 where heat is stored above the maximum heat storage temperature)
The material was visually observed, and those that maintained approximately the original shape were judged to be good. The defective product is melted.

Seepage: Heat storage materials with good shape retention were sealed in polyethylene film bags, left at a predetermined temperature for 24 hours, and visually observed to see if paraffins had separated. Those with almost no abnormalities were considered good. Defects are those in which separation is clearly recognized.

The measurement results are shown in Table 1, and the heat storage materials of Examples 1 to 5 of the present invention all have a heat storage amount of 35 kcal/kg or more, and also satisfy other practically necessary properties. Ta.

On the other hand, the comparative examples had an insufficient amount of heat storage or other characteristics were insufficient.

71 Example 6 The composition of Example 1 was mixed in the same manner as above, and a plate-shaped heat storage material having a thickness of 80 QwX 25 QmX 20 m was prepared by the same operation. This was sealed in a polyethylene sheet bag with a thickness of 0.1, and then heat-sealed with a ξNate sheet containing three layers of polyethylene/aluminum/polyester (30μ-/25μ■/25μ-). A heat storage board was manufactured.

A sandwich body with a structure in which a 100V, 67W heating wire heater was inserted between two of these heat storage boards was fabricated, and the sandwich body was installed between the flooring material and the insulation layer provided below. A regenerative floor heating unit was constructed. Results of continuous measurement of floor surface temperature by subjecting the heating wire heater in the regenerative floor heating UNIATO to an energization cycle in which one cycle (24 hours) consisted of energizing for 8 hours and then powering off for 16 hours. After the temperature was raised to 28°C, it remained stable for 24 hours at 26-28°C.

〔Effect of the invention〕

The heat storage material of the present invention has a high level of latent heat of 30 kcal/kg or more, preferably 35 kcal/kg or more, and is capable of melting, dripping, phase separation, and liquid even at T a m I+ or the melting point of the paraffins used. The heat storage material of the present invention is suitable for use in regenerative floor heating that uses late-night electricity. It is suitable for use in floor heating and can be used for similar purposes.

(that's all)

Claims (3)

[Claims] (1) A heat storage material comprising paraffins and a thermoplastic elastomer as main components. (2) The heat storage material according to claim 1, wherein the thermoplastic elastomer is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the paraffin. (3) The heat storage material according to claim 1 or 2, which has a sheet-like or plate-like shape.