JPS6086191A - Polyolefin thermal energy storage material having heat-resistant resin film - Google Patents

Abstract

PURPOSE:A stable, inexpensive and nontoxic thermal energy storage material, obtained by adding a phenolic compound, etc. to a molded article of an intermolecularly crosslinked polyolefin (copolymer), and coating the surface of the article with a heat-resistant resin film without corroding a metallic material, and utilizing the latent heat of melting. CONSTITUTION:A thermal energy storage material obtained by molding a particularly highly crystalline polyolefin, e.g. crystalline polyethylene (PE) or polypropylene (PP), or a copolymer thereof into a given shape, crosslinking the resultant molded article intermolecularly by the radiation or water crosslinking method, etc., adding a phenolic compound or amine, e.g. cresol or phenylenediamine, thereto, and coating the surface of the article with a heat-resistant resin film, e.g. fluororesin, silicone resin, PVC, PP or polyimide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat storage body using crystalline polyolefin and utilizing the latent heat of bath granite.

"Thermal storage" is a technology that allows you to consume any amount of thermal energy at any time by temporarily storing thermal energy, such as solar heat or factory waste heat, whose generation amount and generation time are unstable. However, given the current energy situation, it is becoming increasingly important. The principles of heat storage known to date can be broadly classified as follows.

(1) A method that utilizes the sensible heat of a substance. (2) A method that utilizes the phase change latent heat of a substance. (3) A method that utilizes the heat of chemical reaction of a substance. Substances that can be used for such heat storage purposes are For example, in (1), a substance with a large heat capacity per unit volume ab, such as water or rock,
In addition, in (3), substances such as calcium hydroxide that easily undergo reversible reactions depending on temperature as described below and have a large heat of reaction have been studied as heat storage compounds.

Ca(OH)2□-CaO+H2O On the other hand, as a type of heat storage body that utilizes the second latent heat of change in (2), such as mirabilite (Na2804 ・10H-zO) and hypo (Na28203 ・5H2O)
A so-called latent heat of fusion type heat storage body that utilizes the latent heat of fusion during solidification has been studied.

However, since most of the inorganic hydrated compounds such as Glauber's Salt and Hypo cause supercooling and phase separation phenomena, it is difficult to maintain stable operation as a heat storage material for a long period of time. It also has the disadvantage of corroding metal materials.

Therefore, the present inventors conducted various studies on heat storage compatibility using the latent heat of molten metal, which has many drawbacks, and found that crystalline polyolefin has no supercooling or phase separation and guarantees stable heat storage operation. We have come to the conclusion that it is basically harmless, does not have corrosive properties comparable to the metal phase t1, and is relatively inexpensive compared to industrial organic phase t1.

However, when polyolefin is used as a heat storage material, (a) a viscous melt melts in the heating/melting zone, which fuses together and forms a lump, which may block the flow path of the heat medium or deteriorates heat exchange with the (b) Also,
Since the body bond expands greatly during melting, it generates large stress in the heat storage device. ; There are other inconveniences.

In order to avoid these inconveniences, a heat storage body that is convenient for heat exchange and handling is constructed by filling and sealing the above heat storage material into a small container with appropriate strength and a predetermined shape. A heat storage device was formed by integrating a large number of heat storage bodies configured in this way, and the purpose of heat storage was achieved by exchanging heat with a heat medium (fluid such as air, water, oil, etc.). . Heat storage materials such as Glauber's Salt and Hypo are soluble in water as a heat medium, and from this point of view as well, the use of small containers was inevitable.

However, in this case, since a very large number of heat storage bodies, sometimes tens of thousands, are used in the heat storage device, the method of filling and sealing the heat storage material into a small container as described above is not suitable. The costs involved in manufacturing the container, filling it with the heat storage charge, and sealing it were enormous, and sometimes the cost of manufacturing and processing the small container was higher than the cost of the heat storage charge itself.

This has increased the cost of the latent heat of fusion type heat storage device and has been a major factor hindering its widespread practical use.

In view of the above circumstances, the present invention provides a crystalline polyolefin having excellent properties as a molten latent heat type heat storage body as described above.
The purpose is to provide a highly economical heat storage material that does not need to be sealed in an expensive small container, does not cause sticking or clumping even when used as a fluidized bed, and is durable and can be used for a long period of time. The gist is to crosslink the molecules of crystalline polyolefin or its copolymer in a predetermined shape, add a phenol compound or amine to it, and cover the surface with a heat-resistant resin film. .

That is, by configuring the present invention as described above, crystalline polyethylene becomes gel-like and does not flow even when melted by heating, has appropriate strength, and does not exhibit stickiness in the molten state. 7, making it even less susceptible to thermal deterioration. Therefore, the purpose of the present invention is to eliminate the need for an expensive small container when used as a heat storage body, to prevent sticking or clumping when used as a fluidized bed, and to have durability for long-term use. We were able to achieve this goal.

Further, according to the present invention, since the volumetric expansion coefficient of the polyolefin when melted is reduced, large stress is not generated in the heat storage device housing the polyolefin during heating.

Here, among the three treatments of (1) intermolecular crosslinking of crystalline polyolefin or its copolymer, (2) addition of a phenol compound or amine, and (3) coating with a heat-resistant resin film, if (1 If the treatment in (2) is missing, the heat storage bodies will stick to each other and become lumps when heated and melted, and if the treatment in (2) is missing, the amount of latent heat of fusion will decrease due to thermal deterioration after long-term use, and finally cannot store heat.

In addition, if the treatment in (3) is not completed, the surface of the heat storage body that is molten at high temperature will exhibit some stickiness when used as a fluidized bed, causing the heat storage bodies to stick to each other and form lumps before being used again. This causes the inconvenience of not being able to do so. Therefore, the above three processes are essential for the purpose of the present invention.

These three processes can be performed in any order.

In the present invention, a crystalline polyolefin such as crystalline polyethylene or crystalline polypropylene or a copolymer thereof, particularly a highly crystalline polyolefin or a copolymer thereof, is used as a heat storage material. Use a product that has been molded into a predetermined shape. In addition, by setting the diameter (or thickness) of these molded bodies to 2 to 8 mm, a heat storage device having satisfactory thermal responsiveness can generally be constructed.

Further, in the present invention, methods for crosslinking the molecules of the crystalline polyolefin or its copolymer include a radiation method, a water crosslinking method, an ionic crosslinking method, a peroxide method, a vulcanization method, and the like.

Among these, cobalt-600 gamma rays are preferred as the ionizing radiation used in the radiation method, but the present invention is not limited to this, and all so-called ionizing radiations such as E-son rays and short wavelength X-rays can be used.

The irradiation dose of ionizing radiation is 105 to 108 rad, and if it is less than that, fusion and agglomeration will occur, and if it is more than that, the heat of fusion of the polyolefin will decrease and the heat storage density will become small, which is not preferable. .

Further, it is preferable that the atmosphere for irradiating the ionizing radiation is a vacuum or an inert gas.

Phenol compounds or amines used in the present invention include phenol, cresol, hydroquinone, catechol, anisole, quinreno-/L/, N-nitrosoaniline, N-nitrosamine, phenylenediamine,
Examples include ethylenediamine and derivatives of these substances. These substances may be used alone or in combination of two or more.

These substances are added to polyolefins or copolymers thereof by, for example, the following treatment. 1. Polyolefin or its copolymer has a melting point of 10 to 2
The substance or its powder is added to the melt by heating to 0° C. and mixed by mechanical stirring. Alternatively, these substances or fine powder thereof are mixed with polyolefin or its copolymer which has been softened by heating, and mechanically stirred to adhere to the surface. Another method is to immerse polyolefin or its copolymer in a solution of these substances, leave it for a while, and then dry it to remove the solvent.

The amount of the pheno-tv compound or amine added to the polyolefin or copolymer thereof is usually several percent by weight.
However, depending on the usage period of the heat storage body, if the period is long, the amount added can be increased or decreased as appropriate.

Furthermore, examples of the heat-resistant resin used in the present invention include fluororesin, silicone resin, polyvinyl chloride, polypropylene, and polyimide.

Methods for coating surfaces with these resin films include melting polymer powder, dipping in polymer emulsion and drying,
Application with paste resin, spraying with polymer solution,
Examples include baking, sizing, thermal spraying of polymer powder, and graft polymerization on the surface.

The heat storage body thus obtained has a high heat storage density, does not undergo hot water cooling or phase separation, and does not cause fusion or agglomeration during melting. Moreover, the coefficient of volumetric expansion during melting is significantly reduced, and the heat storage capacity does not decrease even during long-term use, so stable heat storage operation is possible.

As described above, the heat storage body of the present invention prevents fusion, agglomeration, and thermal deterioration using a cheap and economical method, and is suitable for recovering and utilizing low-temperature thermal energy such as solar energy and factory waste heat. It is.

Next, the present invention will be explained in more detail with reference to Examples.

EXAMPLE A heat storage test apparatus was manufactured as shown in FIG. 1, and the heat storage bodies 1 to be filled therein were treated to prevent agglomeration and thermal deterioration by various methods as described below. In FIG. 1, 2 is an adiabatic phase open layer, 3 is a steel plate container, 4 is a perforated plate, 5 is an electric heater, and 6 is an air pump. Air introduced from 6 is heated at 5, and while its temperature is monitored by a thermocouple 7 and a temperature meter 8, it is blown into the layer of the heat storage body 1 to raise its temperature. At this time, if the temperature of the air at the blowing point is kept constant at 15 to 25 degrees Celsius above the melting point of the polyolefin, the polyolefin will melt, and the heat of fusion will cause the polyolefin to I decided to make prefectural bonds internally.

That's it.

Next, when the output of the electric heater 5 is adjusted so that the temperature of the blown air is 15 to 25 degrees Celsius below the melting point of the polyolefin, the polyolefin solidifies while releasing its heat of fusion. During this time, air at a constant temperature corresponding to its melting point will be available at the outlet 9 of the test apparatus in FIG.

The polyolefin used at this time was under the trade name 5hole.
x F 6050 C1 A polyethylene pellet with a diameter of approximately 3 mm. When such a heat storage body becomes agglomerated due to repeated melting and solidification, the air flow path in the layer of the heat storage body becomes narrower, making efficient heat exchange between the heat storage body and air unnecessary. This causes great inconvenience.

Therefore, for the purpose of preventing agglomeration and thermal deterioration, samples were prepared by performing the following treatment.

(1) After irradiating polyethylene with 107 rad of cobalt 6o gamma rays, soak it in a polytetrafluoroethylene skewer solution containing water, shake well to disperse, and then remove the moisture in an air thermostat at 102°C. After evaporation and removal, the surface of the polyethylene was coated with a polytetrafluoroethylene thin film. This was immersed for 2 nights in a 1% benzene solution of 2,6 C(-butyl fresol), washed lightly with benzene, and dried in the air.

(2) After crosslinking polyethylene with water, soak it in a solvent containing 20% by weight of silicone resin monomer, shake well to disperse it, add an appropriate amount of catalyst, and shake the whole thing in an air constant temperature bath at 115°C. While the solvent is being evaporated and removed, the silicone resin is polymerized and the surface of the polyethylene pellet is coated with a thin film of silicone resin. This e
It was treated in the same manner as in (1) with a 15% by weight benzene solution of N-phenyl-N'-cyclohexyl-ido-phenylenediamine.

(3) 5x107 rad cobalt 6d on polyethylene
While irradiating with gamma rays, vinyl chloride vapor is sent in using argon gas to remove polyethylene and vinyl chloride (vf).
The surface of polyethylene was graft-polymerized and coated with vinyl chloride. 2,2'-methylene-vinu(4-methyl-6-L-butylphenol)
It was treated in the same manner as in (1) with a wt % benzene solution.

(4) Polyethylene was heated to dissolve t,4111, and 5% by weight of N,N'-diphenyl-)-phenylene diamine was added and stirred to dissolve. ;1 This was formed into a spherical shape with a diameter of 3 mm, cooled in a chamber 1jRri, and then irradiated with cobalt-60 gamma rays of 3×10 7 rad. Thereafter, the surface was coated with a polytetrafluoroethylene film in the same manner as in (1).

The heat storage pellet that has been subjected to the various treatments described above is placed in the test equipment shown in Figure 1, and heated and cooled as already explained to melt and solidify the polyethylene. After repeating this process once a day for 6 months, it was taken out to observe and observe the state of nodule formation, and the latent heat of fusion was measured. As a result, these (1) to (4)
The sample showed almost no sticking, the individual pellet particles easily separated and scattered, and the latent heat of fusion hardly changed.

Comparative Example A 6-month test was conducted in the same manner as in the actual example using the test equipment shown in FIG. 1 using samples treated as follows.

(1) Polyethylene was irradiated with 107 rad of cobalt-60 gamma rays.

(2) The polyethylene treated in (1) is soaked in a polytetrafluoroethylene teinubation solution containing water, shaken well to disperse it, and then evaporated in an air constant temperature bath at 102°C. The surface of the polyethylene was then coated with a polytetrafluoroethylene thin film.

(3) 2.6% of the polyethylene treated in (1)
The mixture was soaked overnight in a 10% by weight solution of monobutyl cresol in benzene, then washed lightly with benzene and dried in air/ζ.

(4) Soak polyethylene in polytetrafluoroethylene Daynepersion solution with water added, shake well to disperse, and then evaporate and remove water in an air constant temperature bath at 102°C. It was coated with a thin fluoroethylene film. After immersing this in a 10% by weight benzene solution of monobutyl cresol for 2.6 nights,
Washed briefly with benzene and dried in air.

If we take this result as 1, we get 4 as shown in the following table.

As mentioned above, if any one of the three treatments (1) intermolecular crosslinking, (2) addition of a phenol compound or amine, and (3) coating with a heat-resistant resin U4 film fails, it will stick.
Due to compaction or thermal deterioration, the wharf could not be used for the 4th period.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a heat storage device according to an embodiment of the present invention. In the figure, 1 is a heat storage body, 2 is a heat insulator, 3 is a steel plate container, 4 is a perforated plate, 5 is a "fL air heater, 6 is an air pump, 7 is a heat-4 pair, 8 is a temperature meter, and 9 is a It's the exit.

Claims (1)

[Claims] A heat storage body characterized in that the molecules of a crystalline polyolefin or a copolymer thereof in a predetermined shape are crosslinked, a phenol compound or an amine is added thereto, and the surface thereof is covered with a heat-resistant resin film.