JPS6296582A - Heat storing composition - Google Patents

Abstract

PURPOSE:To reduce the deterioration of the heat storing characteristics accompanying the repeated use, by dissolving a small amt. of a particular maleic acid copolymer in a heat storing material compsn. based on a hydrate or its eutectic mixture and having a transition temp. of 10-100 deg.C in terms of temp. at which the compsn. changes into an anhydride or a hydrate having a low degree of hydration. CONSTITUTION:A heat storing material compsn. comprised of a heat storing material compsn. based on a hydrate or its eutectic mixture and having a transition temp. of 10-100 deg.C in terms of temp. at which the compsn. changes into an anhydride or a hydrate having a low degree of hydration and 0.1-5.0wt% water-soluble copolymer of acrylic acid, methacrylic acid and/or styrene and maleic acid or a water-soluble salt thereof dissolved and contained therein. It is preferred that the maleic acid copolymer have a degree of copolymerization of the acrylic acid, methacrylic acid and/or styrene (component A) with maleic acid (component B) of about 100/50-100/300 in terms of an A to B molar ratio and a molecular weight of about 1,000-50,000. A preferable water-soluble salt of the maleic acid copolymer is an alkali metal salt, an ammonium salt, or an alkanolamine salt.

Description

[Detailed description of the invention] The present invention relates to a heat storage material composition.

The heat storage material can store thermal energy as sensible heat and/or latent heat. For heat storage, it is advantageous to use a heat storage material that can utilize fvI heat. This is because the amount of heat stored per unit volume of the heat storage material is large, so the heat storage device can be downsized, and thermal energy can be taken in and taken out at a constant temperature.

Many hydrates and their eutectic mixtures melt on heating with a characteristic transition salinity, transforming the hydrate into anhydrous or less hydrated hydrates, and solidify on cooling. The anhydride or the hydrate with a low degree of hydration returns to the original hydrate with a high degree of hydration. There are 10 thermal storage systems that store and utilize solar energy and waste heat emitted during refrigeration.
It is desirable to operate in a temperature range of ~100 °C, and in such systems, hydrates or eutectic mixtures thereof with a transition temperature to anhydrous or less hydrated hydrates of 10 to 100 °C are preferred. It is preferable to use it as a heat storage material.

One drawback of this type of heat storage material is the anharmonic nature of the phase transition. In other words, many of these heat storage materials do not become single-phase when melted. For example, when sodium sulfate decahydrate is heated to its melting point (32°C) and melted, water of crystallization is released and it becomes anhydrous sodium sulfate. Most sodium sulfate anhydrous salts.

It dissolves in the released water to form a liquid phase, but the remaining small portion of anhydrous sodium sulfate does not dissolve and remains in the solid phase, and because of its high density, it settles out.

When this two-phase mixture is cooled and solidified without stirring, the sodium sulfate in the liquid phase combines with water to form decahydrate, but the precipitated solid phase sodium sulfate only interacts with water molecules in the vicinity. Combine to form a layer of decahydrate. This one
The solid layer of anhydrous sodium sulfate prevents further binding of the remaining anhydrous sodium sulfate with the remainder of the water of crystallization. This means a decrease in the amount of heat storage that can be recovered and used. In order to avoid this, in the process of anharmonic melting of sodium sulfate decahydrate,
It is necessary to prevent the anhydrous salt from settling and to keep it uniformly dispersed in its solution. This is achieved by increasing the viscosity of the solution system, so-called gelling, according to Stokes' law. For this purpose, it has been known to incorporate various thickening agents and hydrogels into heat storage material compositions exhibiting anharmonic melting. Such thickening agents and hydrogels that have been proposed so far include, for example, wood pulp and sawdust.

Starch, organic alginates, polymers of acrylic acid or methacrylic acid, or partially hydrolyzed polyacrylamide or polymethacrylamide cross-linked with polyvalent metal ions (Japanese Unexamined Patent Publication No. 16387-1987) and olefinic carboxylic acids and a polyalkenyl polyether of a polyhydric alcohol JP-A-57-1530
77) as well as silica gel,
These include inorganic materials such as diatomaceous earth, finely powdered silica gel, and attapulgide-type clay (U.S. Pat. No. 3,986,969).

Another disadvantage of hydrates and their eutectic mixtures as heat storage materials is that they do not solidify when cooled even below the freezing point.
This often causes a so-called supercooling phenomenon. This supercooling phenomenon can be advantageously overcome by adding appropriate nucleating agents. For example, 1o sodium sulfate
For heat storage materials based on hydrate and sodium carbonate decahydrate and their eutectic mixtures, sodium tetraborate decahydrate, or borax, is
For heat storage materials based on dihydrates and their eutectic mixtures, ammonium magnesium sulfate hexahydrate.

and based on calcium chloride hexahydrate and its eutectic mixture (for heat storage materials, barium hydroxide and strontium hydroxide, respectively, are known to be suitable nucleating agents).

According to the present invention, when an effective amount of acrylic acid, methacrylic acid and/or a water-soluble copolymer of styrene and maleic acid or a water-soluble salt thereof is added to a heat storage material composition based on a hydrate or a eutectic mixture thereof, It was found that the deterioration of the heat storage material composition due to repeated cycles of heat storage and heat dissipation (decrease in the amount of heat storage that can be recovered and used) can be significantly reduced compared to the case where the copolymer is not added.

Thus, the present invention provides a heat storage material composition based on a hydrate or a eutectic mixture thereof having a transition temperature to an anhydride or a hydrate with a low degree of hydration of 10 to 100'C. Provided is a heat storage material composition containing an acid and/or a water-soluble copolymer of styrene and maleic acid or a water-soluble salt thereof dissolved in an amount of 0.1% to 5.0% by weight.

The heat storage material composition of the present invention, as a heat storage material, has a transition temperature of 10 to 100°C to an anhydride or a hydrate with a low degree of hydration.
contains a hydrate or a eutectic mixture thereof. A heat storage material with this transition temperature range was chosen because it is intended for use in heat storage systems that desirably operate in this temperature range.

Examples of suitable hydrates include calcium chloride hexahydrate (melting point 29°C), sulfuric acid (IJ) hydrate (melting point 3
2°C) 1 Disodium hydrogen phosphate dodecahydrate (melting point is 3
5.5℃), sodium thiosulfate pentahydrate (melting point is 50℃)
), sodium acetate trihydrate (melting point 58°C).

Barium hydroxide octahydrate (melting point 75℃), zinc nitrate 6
water salt (melting point: 35°C), potassium fluoride tetrahydrate (melting point: 18.5°C), and sodium carbonate monohydrate (melting point: 35°C).
5° C.), the preferred hydrate is sodium sulfate 10
water salt, disodium hydrogen phosphate dodecahydrate.

Sodium thiosulfate pentahydrate and sodium carbonate IO hydrate. Eutectic mixtures of these hydrates can also be used as heat storage materials. Suitable salts to form a eutectic by mixing with hydrates depend on the type of hydrate involved;
For example, for sodium sulfate decahydrate, sodium chloride, ammonium chloride, potassium chloride, and potassium nitrate can be used alone or in combination.

As used herein, "a heat storage material composition based on a hydrate or a eutectic mixture thereof" refers to a heat storage material composition that contains a hydrate or a eutectic mixture thereof as a heat storage material together with a necessary amount of water, an appropriate amount of a nucleating agent, and Refers to compositions useful in the operation of thermal storage systems, which may include/or thickeners (or hydrogels).

In the present invention, such a heat storage material composition contains dissolved acrylic acid, methacrylic acid, and/or a water-soluble copolymer of styrene and maleic acid, or a water-soluble salt thereof.

The maleic acid copolymer used in the present invention needs to have a copolymerization rate and molecular weight such that the copolymer is dissolved in the composition, and preferred acrylic acid, methacrylic acid and/or styrene (component A). and maleic acid (component B)
The copolymerization ratio with A is about 100:50 to about 100:300 at a molar ratio of 9, and the preferred molecular weight range is about 1000 to about 5000.

It is. Water-soluble salts of such maleic acid copolymers can also be used in the practice of this invention. Preferred salts are alkali metal salts, ammonium salts and alkanolamine salts.

The maleic acid copolymer or its salt may be added to the heat storage material as it is, but it may also be added and dissolved in the heat storage material in the form of a dispersant composition containing it as a main component. Dispersant compositions containing a water-soluble maleic acid copolymer or a water-soluble salt thereof as a main component suitable for use in the composition are available from Kao Soap Co., Ltd. under the registered trademark names of "Demol" and "Poise". is commercially available and can be conveniently used in the practice of the present invention.

The compositions of the invention must be supplemented with an effective amount of a water-soluble maleic acid copolymer or salt thereof, as described above, although not strictly critical - based on the weight of the composition. When added in an amount substantially less than 0.1% by weight, no significant improvement is observed over that without addition.
Even if substantially more than 5.0% by weight of the copolymer or salt thereof is added, based on the weight of the composition, the effect of the addition tends to be saturated. The preferred amount added is 0.1 to 1% by weight.

The effects of the present invention will be demonstrated below using specific examples.

Actual gun example 1 Sodium sulfate 37.5 parts by weight water
47.7 parts by weight Sodium chloride 7.7 parts by weight Ammonium chloride
7.0 parts by weight Borax 3
．． 0 parts by weight Diatoms ± 7.0 parts by weight Demol E P J 1.0 parts by weight The heat storage material composition according to the present invention having the above composition and from the above composition
A control composition was prepared with a similar composition except that Demol EPJ was removed. The initial heat storage amount and the heating/cooling cycle (L cycle is 4 hours) when these M heat material compositions are heated at 40°C for 2 hours and then cooled at 30°C for 2 hours are calculated as follows:
The amount of heat accumulated after repeating 0 times was measured.

The results are shown in the table below.

Example 2 Sodium sulfate 90.0 parts by weight water
113.0 parts by weight borax
8.0 parts by weight Acrylic acid-acrylamide copolymer 10.0 parts by weight [Demol L P J 2.0 parts by weight To the mixture of the above composition, about 40% by weight of formaldehyde and 14% by weight were added.
5 ml of an aqueous solution containing % by weight of methanol was added with stirring, and then methanol 201 was added. The viscosity of the mixture gradually increased until it became a stiff dry gel. The mixture contained no excess water beyond that required to fully hydrate the entire amount of sodium sulfate and completely converted to a solid upon cooling.

In addition to the heat storage material composition according to the present invention thus prepared, a control composition was prepared in the same manner except that "Demol LPJ" was removed from the above composition.
The initial heat storage amount when heated at 0° C. for 2.5 hours and then cooled at 20° C. for 2.5 hours and the heat storage amount after repeating the heating/cooling cycle (one cycle is 5 hours) 100 times were measured.

The results are shown in the table below.

Example 3 Disodium hydrogen phosphate 100.0 parts by weight water
170.0 parts by weight Ammonium sulfate magnesium hexahydrate 10.0 parts by weight Hydrogel rN-100J (manufactured by Sumitomo Chemical) 17.0 parts by weight Demol P J 1.0 parts by weight Thermal storage material composition according to the present invention having the above composition A control composition having the same composition except that "Demol P" was removed from the above composition was prepared by the method described in Example 2, and the heat storage properties were determined by subjecting it to the heating and cooling cycle described on the same side 60 times. We investigated changes in

The results are shown in the table below.

Example 4 Sodium carbonate decahydrate 100.0 parts by weight water
10.0 parts by weight borax
3.0 parts by weight Hydrogel Sumikagel R 5-50 J (manufactured by Sumitomo Chemical) 17.0 parts by weight [BOIZE-52041.0 parts by weight 12 material composition according to the present invention having the above composition and "BOIZE" from the above composition A control composition having the same composition except for "-520" was prepared by the method described in Example 2, and was subjected to the heating/cooling cycle described on the same side 60 times to examine changes in heat storage characteristics.

The results are shown in the table below.

According to the results of the above examples, it can be seen that the heat storage material composition of the present invention shows substantially less deterioration of the M thermal properties after 9 repeated uses than a comparable control composition.

Claims (1)

[Claims] The transition temperature to anhydrous or less hydrated hydrate is 1
In a heat storage material composition based on a hydrate or a eutectic mixture thereof having a temperature of 0 to 100°C, acrylic acid, methacrylic acid and/or a water-soluble copolymer of styrene and maleic acid or a water-soluble salt thereof is Weight% to 5.0% by weight
A heat storage material composition characterized in that it contains a dissolved heat storage material.