JPH05117638A - Heat storage material - Google Patents

Abstract

PURPOSE:To prepare a heat storage material which is used for a directly heat- exchanging heat storage tank where no blocking occurs during heat exchange by forcibly and homogeneously mixing a silane-grafted org. hydrocarbon polymer with a paraffin and then cross-linking the polymer with water. CONSTITUTION:A heat storage material is prepd. by forcibly and homogeneously mixing 100 pts.wt. silane-grafted org. hydrocarbon polymer (e.g. one prepd. by grafting 2 pts.wt. vinyltrimethoxysilane onto 100 pts.wt. blend of 50wt.% ethylene-propylene coplymer with 50wt.% polyethylene in the presence of 0.04 pt.wt. dicumyl peroxide at 200 deg.C) with a paraffin pref. in an amt. of 5-30 pts.wt. and then cross-linking the polymer with water. Since the polymer used as a binder, is cross-linked, the heat storage material allows no blocking to occur during the repetition of heat storage and heat release, enables a smooth heat exchange, and is very excellent as a heat storage material of direct heat- exchange type.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat storage material.

[0002]

2. Description of the Related Art When a latent heat storage material is used in a direct heat exchange type heat storage tank, a means such as encapsulation or encapsulation in a sturdy container is required in order to melt and liquefy the heat storage material during heat storage. Therefore, there is a problem that the heat storage material becomes expensive and not practical. Therefore, a direct heat exchange type heat storage tank is not adopted particularly when paraffins are used as the heat storage material.

On the other hand, various heat storage materials have been developed,
As one of them, the heat storage material that the present inventor has newly developed (filed on July 27, 1990, Japanese Patent Application No. 2-200916).
No.), this new heat storage material does not melt and liquefy during heat storage as described above, so it has an extremely excellent performance that it can be directly used in a heat exchange type heat storage tank. At this time, the heat storage material to be put in the heat storage tank is usually particulate, spherical, linear, block-shaped or the like, and has any size. However, in order to increase the heat storage amount as much as possible, a large amount of heat storage material is put into the heat storage tank. For example, when water or ethylene glycol is used as a heat medium and heat storage-heat dissipation is repeated in the heat storage tank, the heat storage material gradually increases. There was a new problem that the particles stick to each other and solidify, so-called blocking occurs, and heat exchange is not performed well.

Blocking also occurs when the heat storage material is transferred in a state where heat is stored.

[0005]

Therefore, the problem to be solved by the present invention is to directly heat the heat storage material based on the new heat storage material already developed by the present inventor (hereinafter referred to as the prior application heat storage material). The object is to eliminate the above-mentioned difficulties that occur when used in an alternating heat storage tank. More specifically, it is to eliminate the blocking of the heat storage material based on the heat storage material of the prior application.

[0006]

The object of the present invention is to forcefully and uniformly mix paraffins, preferably 100 parts by weight thereof, with silane-grafted hydrocarbon organic polymer, preferably 5-30 parts by weight thereof. After that, it is solved by water crosslinking.

[0007]

In the present invention, the hydrocarbon-based organic polymer is silane-grafted and is water-crosslinked. Therefore, even in a heating medium such as water or ethylene glycol, By doing so, even if heat storage-heat dissipation are repeated, the heat storage materials do not block each other. For this reason, heat exchange is smoothly performed, and it becomes extremely suitable as a direct heat exchange type heat storage material.

In the present invention, a silane-grafted hydrocarbon organic polymer is used. In the hydrocarbon-based organic polymer used at this time, the main chain is basically a hydrocarbon, and the content of other components (for example, O, N, Si, halogen, etc.) in the main chain is 10% by weight. Hereinafter, one kind or two kinds or more of the hydrocarbon-based organic polymer, which is preferably 5% by weight or less, is used. Examples of such hydrocarbon organic polymers are shown below.

(1) Polyolefin polymers: homopolymers of α-olefins such as polymethylene, polyethylene and polypropylene, copolymers of olefins,
Other monomers with α-olefins such as vinyl acetate,
Examples thereof include copolymers with ethyl acrylate, ethyl methacrylate and the like, and these lightly halogenated polymers. It may be amorphous to low crystalline,
It may be crystalline.

[0010]

(2) Hydrocarbon rubbers: natural rubber, styrene-butadiene-copolymer rubber, butyl rubber, isoprene rubber, ethylene-propylene copolymer rubber, acetylene-propylene-diene terpolymer rubber, ethylene −
Examples thereof include vinyl acetate copolymer rubber and ethylene-ethyl acrylate copolymer rubber.

In the present invention, the hydrocarbon-based organic polymer is silane-grafted. This silane grafting is usually performed by the following method. That is, at a temperature of 140 ° C. or higher, in the presence of a compound that generates a free radical in a hydrocarbon organic polymer, for example, a compound represented by the general formula RR′SiY
Silane represented by ₂ (provided that R is a hydrocarbon group containing a monovalent olefinic unsaturation or a hydrocarbonoxy group, Y is a hydrolyzable organic group, and R'is a group R or a group Y) Is grafted at a temperature of 140 ° C. or higher in the presence of Here, as a compound that generates a free radical, an organic peroxide such as dicumyl peroxide is 0.00
1 part by weight to 1 part by weight, and as silane, 0.5 parts by weight to 5 parts by weight of a silane compound such as vinyltrimethoxysilane and vinyltriethoxysilane are each added to 100 parts by weight of the hydrocarbon-based organic polymer. Used.

As the paraffins used as the heat storage component in the present invention, T _max measured according to JIS K7121 (Plastic transition temperature measuring method) is a use temperature, that is, room temperature to 100 ° C., preferably room temperature to 80 ° C.
Organic compounds in the front and rear temperature ranges are used. However, the room temperature at this time means the lowest temperature that the heat storage material of the present invention encounters during its operation.

Preferred specific examples of paraffins include:
Examples thereof include various paraffins, waxes, waxes, fatty acids such as stearic acid and palmitic acid, higher alcohols and polyethylene glycols, and one of these may be used alone or as a mixture of two or more.

In the present invention, the amount of the silane-grafted hydrocarbon organic polymer used is preferably 5 to 30 parts by weight based on 100 parts by weight of paraffins.
If the amount is less than 5 parts by weight, the flexibility of the obtained composition tends to be low and the composition tends to be brittle, and paraffins tend to exude or melt easily at T _max or more, while an excessive amount exceeding 30 parts by weight. Therefore, the amount of paraffins used decreases and the amount of heat storage tends to decrease in proportion.

In the present invention, in addition to the above-mentioned silane-grafted hydrocarbon-based organic polymer, a non-silane-grafted hydrocarbon-based organic polymer may be used in combination, and the amount thereof used is The total of both may be 30 parts by weight or less with respect to 100 parts by weight of paraffins.

Examples of the hydrocarbon-based organic polymer which is not silane-grafted include the above-mentioned (1) polyolefin-based polymers (2) hydrocarbon-based rubbers, and one or more of the following thermoplastic elastomers. These are used for improving the mixing property of the paraffins and the silane-grafted hydrocarbon-based organic polymer, for improving the exudation property of the paraffins, or for improving the physical properties such as flexibility.

Thermoplastic elastomers: Among those known or known as "plastic elastomers" in the fields of rubber and plastics, T _{max of} paraffins used at least at the above room temperature and above.
In the temperature range of + 10 ° C., preferably, one having rubber elasticity is used at least at room temperature or higher and in the temperature range of T _max + 20 ° C. Of course, a material that maintains rubber elasticity even at a temperature higher than T _max + 20 ° C can be used.

Specifically, styrene type, olefin type,
Various conventionally known thermoplastic elastomers such as urethane type and ester type can be exemplified.

Further, in the present invention, various additives can be mixed in addition to the above components, if necessary.
For example, in addition to a specific gravity adjusting material, a reinforcing material, a foaming material, a dropping point improving material described in Japanese Patent Application No. 2-200916, an antiaging agent, an antioxidant, a coloring material, a mildewproofing agent, a flame retardant, and a heat transfer improving property. Materials can be used.

The silane-grafted hydrocarbon organic polymer is forcibly and uniformly mixed with paraffins.

In the mixing, both are first melted and mixed. The melting temperature is at least the melting temperature of paraffins and hydrocarbon organic polymers. As long as the mixing is performed by mechanical means, any of various mixing means may be adopted, and typical examples thereof include stirring, mixing, kneading and the like.

The mixing by mechanical means means that the remaining components are at least swollen, preferably dissolved in the melt of at least one component in both the paraffins and the silane-grafted hydrocarbon organic polymer. It means an action of stirring, mixing, or kneading in a state in which any component to be mixed can be flow-deformed by an external force due to, or due to a high temperature. For example, a mode in which a hydrocarbon-based organic polymer is dissolved in a melt of paraffins maintained at 100 to 200 ° C, and the resulting high-temperature solution is stirred and mixed, a temperature at which each mixed component is softened, for example, 50 to 250 ° C. In this case, an embodiment in which the kneading and mixing is performed by using an ordinary kneader such as a two-roll, a Banbury mixer, an extruder and a twin-screw kneading extruder is exemplified.

It is preferable that the degree of mixing is as sufficient as possible, but generally, the degree is such that it is judged by visual observation that the mixing has been carried out for about 1 to 150 minutes, and that the mixture has been uniformly mixed. still,
This mixing is forced.

In principle, mixing materials and additives other than the silane-grafted hydrocarbon-based organic polymer are forcibly and uniformly mixed with paraffins.

Here, a method of silane-grafting at the same time as mixing and a method of silane-grafting after mixing at the stage of mixing the hydrocarbon-based organic polymer which is not silane-grafted with paraffins are also conceivable, but the mixing is uniform. There are drawbacks such as not being able to do and complicated work,
It doesn't work.

In the present invention, this homogeneous mixture is water crosslinked. In this case, various conventionally known water-crosslinking means may be adopted as the means for water-crosslinking, and hot water treatment, natural cross-linking and the like are preferred. In the heat storage material shape described later, the degree of crosslinking is at least 0.1 mm in terms of gel fraction in at least 0.1 mm of the surface layer, and preferably at least 2%. Insufficient crosslinking may result in insufficient prevention of blocking.

In the present invention, the heat storage material (fine mixture) can be finely granulated before or after the water crosslinking. This can be expected to have the effect that the heat storage ← → heat dissipation cycle can be performed smoothly. The degree of atomization is about 0.1 to 200 mmφ, and the shape thereof may be a spherical or granular shape, or an appropriate shape such as a pellet shape or a square shape. The means for making the particles fine may be any means capable of making the particles into the above size.

[0029]

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

[0030]

Examples 1 to 4 The heat storage material raw material composition comprising the paraffin and the silane-grafted hydrocarbon organic polymer (silane-grafted resin) shown in Table 1 and others was melted at 150 ° C., stirred and mixed, and then plate-shaped. And pelletized (about 5 mm square) by a pelletizer. After water-crosslinking the pellets, heat release and blocking in the heat storage state were measured. The results are shown in Table 1.

However, the resins used in Table 1 are as follows, and the silane-grafted resin is obtained by silane-grafting the following.

Resin A: A 50/50 blend of an ethylene propylene copolymer and polyethylene. Resin B: 70/30 blend of ethylene propylene copolymer and polyethylene. Resin C: Polyethylene. Resin D: Thermoplastic elastomer.

Silane grafting means: For resins A and B, 2 parts by weight of vinyltrimethoxysilane and 0.04 parts by weight of dicumyl peroxide were premixed with 100 parts by weight of the resin and extruded at 200 ° C. with a 30 mmφ extruder. , Silane-grafted. The resin C was silane-grafted in the same manner as the resins A and B except that dicumyl peroxide was changed to 0.06 part by weight.

The blocking of Table 1 was measured by the following method.

A heat storage material and water were put in a beaker in a weight ratio of 1: 2, and room temperature and heat storage heat cycles were carried out once per day for 7 days, and it was visually observed whether or not the pellets were blocked.

[0036]

[Comparative Examples 1 and 2] Using the components shown in Table 1, the same processes as in the above Examples were carried out to obtain heat storage materials. The results are also shown in Table 1.

[0037]

[Table 1]

[0038]

EFFECTS OF THE INVENTION In the present invention, since the hydrocarbon-based organic polymer used as the binder component is cross-linked, even if heat storage-heat radiation is repeated, there is no blocking during this period.
Since heat can be smoothly exchanged, it is extremely excellent as a direct heat exchange type heat storage material.

Claims (3)

[Claims] 1. A heat storage material comprising a silane-grafted hydrocarbon organic polymer forcibly and uniformly mixed with paraffins and then water-crosslinked. 2. The heat storage material according to claim 1, which comprises 100 parts by weight of paraffins and 5 to 30 parts by weight of a silane-grafted hydrocarbon organic polymer. 3. The heat storage material according to claim 1, wherein the homogeneous mixture is made into fine particles before and after water crosslinking.