JPH0781135B2 - Latent heat storage material and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent heat type heat storage material. More specifically, it relates to a heat storage material using a crystalline resin capable of storing heat energy as latent heat and reversibly releasing it.

[0002]

2. Description of the Related Art Conventionally, a heat storage material utilizing latent heat of fusion of crystallization in a resin having crystallinity has been known, and polyethylene is particularly known as a crystalline resin exhibiting a high heat storage effect.

A heat storage material made of such a crystalline resin is
Usually, it is used by filling it into a predetermined heat exchange container or pipe in the form of particles.

[0004]

However, when the heat storage material is heated to a temperature higher than its melting point during heat storage, the individual granular materials are fused and coalesced with each other, resulting in the heat storage material as a whole. However, there is a disadvantage that the surface area of the is decreased and the heat exchange efficiency is decreased.

With respect to this point, it has been proposed to crosslink the surface of such crystalline resin particles by irradiation with electron beams or γ rays to improve the surface melting point, but the irradiation treatment on the entire surface of the particles is performed uniformly. It was a difficult and impractical method.

Further, it is proposed to coat a crystalline resin strand with a silane-modified polyethylene by an extrusion method, cut the crystalline resin strand to form coated crystalline resin particles, and cross-link them in the presence of water (Japanese Patent Laid-Open No. 58-27773). (Japanese Patent Laid-Open No. 48195/1990), and a proposal has been made to improve the surface heat resistance by encapsulating the crystalline resin in microcapsules having rubber elasticity.

However, in any of the above methods, there are problems that the manufacturing process is complicated and it is difficult to uniformly form the heat resistant surface layer.

The present invention has been made under such circumstances, and it is an object of the present invention to provide a heat-storing crystalline resin particle having a heat-resistant surface and a method for producing such a resin particle easily and uniformly.

[0009]

Thus, according to the present invention, the surface layer of the heat-storing crystalline resin particles is covered with the non-crystalline vinyl-based crosslinked polymer layer having a melting point higher than that of the crystalline resin.
Covered with a non-crystalline vinyl-based cross-linked polymer layer
Provided is a latent heat type heat storage material which is partially mixed in the surface layer of crystalline resin particles . Further, the surface layer of the crystalline resin particles having heat storage property is subjected to the polymerization conditions of the vinyl type monomer while absorbing the vinyl type monomer and its cross-linking material, so that the surface layer of the crystalline resin particles is more than the crystalline resin. Provided is a method for manufacturing a latent heat storage material, which comprises integrally molding a high melting point amorphous polymer layer.

As the crystalline resin particles in the present invention, those having a high heat storage property are preferably used.
Examples include high-density polyethylene, polypropylene, polyamide, polyester, and the like, and their crystallinity is 30-
It is preferable to use 90%. Further, the molecular weight is suitable to be applied as a usual molding material, so that the melting point is near the intended heat exchange temperature,
For example, it is selected to be 80 to 200 ° C.

The particle size of the crystalline resin particles is usually about 1 to 20 mm.

On the other hand, various vinyl-polymerizable monomers can be used as the vinyl-based monomer in the present invention. For example, vinyl aromatic-based monomers such as styrene, methylstyrene, ethylstyrene, chlorostyrene and vinyltoluene, and the like. Suitable are acrylic monomers such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Examples of the cross-linking agent include polyfunctional compounds that can be three-dimensionally cross-linked between these monomers and between growth polymers at the time of polymerization of the vinyl-based monomer, for example, divinylbenzene,
Trimethyl propanol diacrylate, trimethyl propanol dimethacrylate, trimethylol propane triacrylate, etc. are mentioned.

In the present invention, the heat-resistant non-crystalline polymer layer is formed on the surface layer of the crystalline resin particles by polymerizing the vinyl monomer while allowing the resin particles to absorb the vinyl monomer and the crosslinking agent. It is carried out by subjecting to conditions. Then, more specifically, for example, in a state where the crystalline resin particles are dispersed and stirred in an aqueous medium, a required amount of the mixed liquid of the vinyl-based monomer and the crosslinking agent is gradually dropped into the medium. It can be carried out by subjecting these to the polymerization conditions of the vinyl-based monomer while adding them to the crystalline resin particles to absorb them. Further, the polymerization of the vinyl-based monomer is carried out by adding a radical polymerization initiator (for example, benzoyl peroxide, dicumyl peroxide, azobisisobutyronitrile, t-butyl perbenzoate, etc.) to the dropped vinyl-based monomer or crosslinking agent. ) Is added and the temperature of the medium system is maintained at 70 to 90 ° C. Of course, at this time, various additives such as a dispersant and a solvent may be used.

Here, the vinyl monomer is used in such a small amount that it can be absorbed by the surface layer of the crystalline resin particles but cannot be absorbed inside the particles. If absorbed to the inside, the melting point of the crystalline resin particles as a whole is increased and the characteristics as a heat storage material are greatly impaired, which is not suitable. More specifically, the amount of the vinyl-based monomer used depends on the type and particle size of the crystalline resin, but usually 5 to 50 parts by weight of the vinyl monomer (however, the final amount is 100 parts by weight of the crystalline resin). It is preferable to set such that the absorption amount is converted into a different amount.

The amount of the cross-linking agent used is preferably 1 to 50 parts by weight, and the amount of the polymerization initiator used is 0.1 to 0.5 parts by weight, based on 100 parts by weight of the vinyl monomer. Is preferred. Further, the polymerization time is not particularly limited, but usually about 3 to 15 hours is sufficient.

By such polymerization, a thin polymer layer having a higher melting point than that of the crystalline resin and being non-crystalline (usually 100 in thickness) is three-dimensionally cross-linked by the monomer and the crosslinking agent absorbed in the surface layer of the crystalline resin particles. .About.1000 μm) is formed. The thin polymer layer is partially mixed with the inside of the surface layer of the crystalline resin particles and grown so as to cover the surface thereof, and is integrated with the crystalline resin particles.

The heat storage material of the present invention thus obtained has a core layer of crystalline resin particles having heat storage properties, and its surface is covered with a high melting point amorphous polymer layer. In addition, the surface layer does not soften or melt even at the melting point of the core layer, and coalescence between particles is prevented even at an operating temperature, which is useful as a filler for heat exchange.

[0018]

Example 1 To a 5 L autoclave, 2000 g of water and 6 g of magnesium pyrophosphate and 0.4 g of sodium dodecylbenzene sulfonate as a suspending agent were added to prepare an aqueous medium, and then a density of 0.9.
52 g of high-density polyethylene resin particles having a melting point of 131 ° C. (trade name: Hi-Zex 6300M, manufactured by Mitsui Petrochemical Co., Ltd., particle size: 5 mm) were suspended in 500 g, and the stirring speed was adjusted to 400 rpm.

Separately, 15 g of divinylbenzene as a crosslinking agent
And 1.5 g of benzoyl peroxide as a polymerization catalyst
And 0.15 g of t-butyl perbenzoate, 500 g
Is dissolved in the styrene monomer to prepare a monomer solution, and the solution is dropped into the aqueous medium at a rate of 51 g / hour and absorbed at high density polyethylene resin particles and maintained at a temperature of 90 ° C. for 10 hours. Polymerization was carried out, the temperature was raised to 130 ° C., the mixture was stirred for 2 hours, then cooled and taken out.

The particles obtained (the heat storage material of the present invention) were high density polyethylene particles coated with polystyrene and having a thickness of 0.5 m / m.

The heat storage material was heated at 180 ° C. in a hot air dryer.
Even after heating for 30 minutes, neither deformation of particles nor coalescence of particles was observed.

Example 2 To a 5 L autoclave was added 2000 g of water and 6 g of magnesium pyrophosphate as a suspending agent and 0.4 g of sodium dodecylbenzene sulfonate to prepare an aqueous medium, and then a density of 0.9.
52, high-density polyethylene resin particles having a melting point of 131 ° C. (trade name: Hi-Zex 6300M, manufactured by Mitsui Petrochemical Co., Ltd.) 5
00 g was suspended and adjusted to a stirring speed of 400 rpm.

Separately, 25 g of trimethyl propanol dimethacrylate as a crosslinking agent and 1.5 g of benzoyl peroxide as a polymerization catalyst were dissolved in 500 g of MMA (methyl methacrylate) monomer to prepare a monomer solution.
The solution was dropped into the aqueous medium at a rate of 51 g / hour to allow the high density polyethylene resin particles to absorb the solution at 78 ° C.
Polymerization is carried out by maintaining the temperature at 10 ° C for 10 hours and then 100 ° C.
The temperature was raised to 1, and the mixture was stirred for 2 hours, cooled, and taken out.

The obtained particles (heat storage material of the present invention) were high density polyethylene particles coated with a crosslinked polymethylmethacrylate having a thickness of 0.5 m / m.

The heat storage material is heated at 180 ° C. in a hot air dryer.
Even after heating for 30 minutes, neither deformation of particles nor coalescence of particles was observed.

Example 3 Instead of the high-density polyethylene resin particles used in Example 2, polypropylene resin particles (trade name: Noblene S-1) were used.
PMMA-coated polypropylene resin particles (coated particles A) of the present invention were obtained in the same manner except that No. 31 (Sumitomo Chemical Co., Ltd., particle size 5 nm) was used.

The coated particles A and the polystyrene-coated polyethylene resin particles (coated particles B) obtained in Example 1 were subjected to thermal analysis to examine the effect of the coating layer on the heat storage effect.

The results are shown below in comparison with the uncoated material. Measurement: SEIKO Differential Scanning Calorimeter Temperature increase / decrease measurement from 30 ° C. to 220 ° C. was performed at 10 ° C./min. Results: Shown in [Table 1].

[0029]

[Table 1]

As shown in these results, both the coated particles A and B tend to have a slightly lower calorific value as compared with the raw material particles (polypropylene or polyethylene), but practically almost no adverse effects due to the coating layer occur. It was found that it can be used as a stable granular heat storage material without receiving it.

[0031]

EFFECTS OF THE INVENTION According to the present invention, there is provided a latent heat type granular heat storage material having excellent heat resistance, which does not cause deformation of particles or coalescence between particles even at the melting temperature of crystalline resin particles.

Claims (2)

[Claims] (1) An amorphous vinyl-based crosslinked polymer layer having a melting point higher than that of the crystalline resin is coated on the surface layer of the crystalline resin particles having a heat storage property , and the amorphous vinyl is used.
The crosslinked polymer layer is partially inside the surface layer of the crystalline resin particles.
A latent heat storage material that is mixed . (2) The surface layer of the crystalline resin particles, wherein the surface layer of the crystalline resin particles having a heat storage property is subjected to a polymerization condition of the vinyl monomer while absorbing the vinyl monomer and its crosslinking agent. 1. A method for producing a latent heat storage material, which comprises integrally forming an amorphous polymer layer having a higher melting point than the crystalline resin.