JPS63218786A - Thermal energy storing agent for latent heat - Google Patents

Abstract

PURPOSE:To obtain the titled composition in the form of gelatinized layers with hardly any phase separation and deterioration of quantity of latent heat by repeating melting and coagulation, by blending sodium sulfate decahydrate (eutectic substance) with an isostearate and hydrous and amorphous silicon dioxide. CONSTITUTION:The aimed thermal energy storing agent composition for latent heat obtained by blending (A) 100pts.wt. principal component consisting of sodium sulfate decahydrate or an eutectic substance thereof with (B) particularly preferably 0.5-2pts.wt. alkali metal salt of isostearic acid and (C) particularly preferably 7-15pts.wt. hydrous and amorphous silicon dioxide produced by a wet process.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a latent heat storage agent composition containing sodium sulfate decahydrate or a eutectic thereof as a main component, and the latent heat storage agent composition of the present invention is extremely useful as a latent heat storage agent because it has a gelatinous layered form with little phase separation and little decrease in the amount of latent heat storage due to repeated melting and solidification.

[Conventional technology]

Conventionally, sodium sulfate decahydrate or its eutectic has a large latent heat of fusion and a melting point of around 30°C, so it has been used as a useful latent heat for air conditioning by utilizing solar heat, exhaust heat, or late-night electricity. Known as a heat storage agent.

However, there are two problems when using sodium sulfate decahydrate or its eutectic as a heat storage agent. One of these is the so-called supercooling phenomenon, in which the material does not solidify even if the temperature drops below the freezing point during cooling. This supercooling phenomenon is a fatal drawback as a heat storage agent for ordinary heating because when heat is radiated, the latent heat of fusion is not released at the set temperature, and the temperature decreases while it remains a liquid.

As a means for preventing supercooling, it is described in US Pat. Substances are known to play a similar role.

Another problem is that sodium sulfate decahydrate or its eutectic may undergo anharmonic melting. That is, when sodium sulfate decahydrate is melted, it separates into two phases: a saturated aqueous solution of sodium sulfate and a solid sodium sulfate, and the solid sodium sulfate precipitates at the bottom of the container because it has a higher density than a saturated aqueous solution. When the separated system is cooled, crystals of sodium sulfate decahydrate are formed on top of the precipitated solid sodium sulfate, forming a barrier, so the solid sodium sulfate combines with water and the sulfuric acid Prevents formation of sodium decahydrate. Therefore, solid sodium sulfate is precipitated by repeating melting and solidification, that is, heat storage and heat radiation, and does not participate in heat storage, so that the amount of heat storage decreases.

To solve this problem, we developed polyvalent metal ion-bonded cross-linked products of wood pulp, methylcellulose, starch, alginate, and polyacrylic acid as phase separation inhibitors (Japanese Patent Laid-Open No. 54-16
387), carboxymethyl cellulose (JP 60-11575), combination of natural gelling agents such as guar gum, locust bean gum, and carrageenan with polyhydric alcohol (JP 58-117273) silica gel, attapal guide. Model clay (U.S. Patent No. 3.986.
Attempts have been made to increase the viscosity by adding various thickening agents such as No. 969 Specification @) to create a so-called gelled state.

Alternatively, an alkali metal salt of lauric acid (
It has been proposed to add an alkali metal salt of oleic acid (Japanese Unexamined Patent Publication No. 57-200482).

[Problem that the invention seeks to solve]

Although the method of adding various organic thickeners described above can prevent the precipitation of sodium sulfate in the initial stage, it does not have the ability to prevent the gradual growth of sodium sulfate crystals due to repeated melting and solidification. In attapul guide type clay and silica gel, the amount of heat storage also decreases due to crystal growth.

In addition, the method of adding an alkali metal salt of uric acid or an alkali metal salt of oleic acid, as described above, is recognized to have the effect of dispersing sodium sulfate particles to some extent and preventing crystal growth; Alkali metal salts have the disadvantage of poor dispersion power and high melting point, making them incompatible with each other. On the other hand, alkali metal salts of oleic acid have the disadvantage that dispersed particles tend to become coarse. Moreover, since oleic acid has an unsaturated bond in its molecule, it also has the disadvantage of thermal deterioration when used for a long period of time, and both are not satisfactory.

In addition, the organic phase separation inhibitor is sodium sulfate 10
It has poor compatibility with water salts, tends to separate in a short period of time during long-term thermal cycles, and is used to being burned in heating applications. Further, similar separation is observed in aqueous apal guide type clay and silica gel, and these are not sufficient as separation preventive agents.

Therefore, an object of the present invention is to provide a latent heat storage device that can finely and uniformly disperse crystals of sodium sulfate decahydrate or its eutectic product even after repeated melting and solidification, has good phase formation properties, and reduces the decrease in heat storage amount. An object of the present invention is to provide a drug composition.

[Means for solving problems]

The present invention achieves the above object by providing a latent heat storage agent composition containing sodium sulfate decahydrate or a eutectic thereof as a main component, which contains one or more alkali metal salts of isostearic acid and wet-produced hydrated amorphous silicon dioxide. This has been achieved using a latent heat storage agent composition that exhibits little phase separation.

The latent heat storage agent composition of the present invention will be explained in detail below.

As the sodium sulfate decahydrate or its eutectic product used in the present invention, sodium sulfate decahydrate or a eutectic product obtained by adding a known melting point regulator such as sodium chloride, ammonium chloride, potassium chloride, etc. Can be mentioned.

Isostearic acid constituting the salt used in the present invention is
It is liquid at room temperature and has a moderate viscosity (1650 cp: q/2
It has thermally stable properties at 0℃).

Suitable alkali metals constituting the salt with the isostearic acid include sodium, potassium, and lithium.

The above alkali metal salt of isostearic acid is a transparent liquid at room temperature, has an appropriate viscosity, and has excellent compatibility and dispersibility with the above sodium sulfate decahydrate or its eutectic. .

In addition, the above-mentioned alkali metal salt of isostearic acid has a smaller amount of foaming than the alkali metal salts of oleic acid and lauric acid in sodium sulfate decahydrate or its eutectic, and is also superior in this respect. .

The above alkali metal salt of isostearic acid is preferably added in an amount of 0.1 part by weight or more per 100 parts by weight of sodium sulfate decahydrate or its eutectic; Since there is no change in the heat storage amount reduction suppressing effect of
It is preferable to add up to 2 parts by weight.

In addition, the hydrated amorphous silicon dioxide produced by wet production of the phase forming agent used in the present invention is a fine white powder (apparently has a specific gravity of 1
= +0.2 g/d), has good water dispersibility and thermally stable properties.

The hydrous amorphous silicon dioxide produced by the above-mentioned wet process is "Carplex"#67.80 manufactured by Geotsugi Pharmaceutical.
Commercially available products such as 1120, FPS series, etc. can be used, and these wet-produced hydrated amorphous silicon dioxides have a higher quality than dry-produced hydrated amorphous silicon dioxide (e.g., Soda-type Rheolosil QS-102). The apparent specific gravity is slightly higher, and because it is a wet process, there is less dust when handling it, and it is also wettable with water, making it easy to work with and able to obtain an appropriate viscosity.

It is preferable to add 5 parts by weight or more of the above-mentioned hydrated amorphous silicon dioxide produced by the wet process to 100 parts by weight of sodium sulfate decahydrate or its eutectic. The limit is approximately 20 parts by weight, and it is particularly preferable to add 7 to 15 parts by weight.

Further, the latent heat storage agent composition of the present invention may contain a conventionally known nucleating substance t (nucleating agent) as described above to prevent overcooling, or may not contain a nucleating agent. , supercooling may be maintained until some kind of shock is applied.

〔Example〕

Examples and comparative examples of the present invention are shown below, but the present invention is not limited thereto.

Example 1 Sodium sulfate decahydrate 87.5 parts by weight Borax (
Nucleating agent) 3.5 parts by weight A latent heat storage agent composition of the present invention (product of the present invention) was obtained using the above formulation. In addition, for comparison, a latent heat storage agent composition (conventional product) having the above-mentioned composition and without adding sodium isostearate was obtained.

These latent heat storage agent compositions were heated to 50°C for 1 hour.
The changes in heat storage amount and separated water of each latent heat storage agent composition after 300 cycles of cooling in a 0°C water bath for 30 minutes are shown in Table 1 below. It can be seen that the latent heat storage agent composition of the present invention to which silicon dioxide is added has an effect of suppressing a decrease in heat storage amount.

Note that the measurement of separated water was carried out using a test tube (φ25 m) containing the composition in 5 (ld).

Table 1 Example 2 Sodium sulfate decahydrate 83.5 parts by weight Sodium chloride 5.0 parts by weight Borax
3.5 parts by weight A product of the present invention and a conventional product were obtained using the above-mentioned composition. These products of the present invention and conventional products were repeatedly heated and cooled under the same conditions as in Example 1, and changes in heat storage amount and separated water were measured. The changes in heat storage amount and separated water before and after the repetition are shown in Table 2 below.

Table 2 As is clear from the results shown in Table 2 above, when the amount of sodium isostearate added is 0.1 part by weight or more, there is an effect of suppressing the decrease in heat storage amount. More preferably, the suppressing effect is high at 0.5 parts by weight or more, and 5 parts by weight only reduces the initial heat increase, and it is considered that addition of more than this is not practically necessary. Regarding phase separated water, addition of 0.1% has a separation suppressing effect, and more preferably 0.5% or more has a high separation suppressing effect.

Example 3 A product of the present invention and a conventional product were obtained using the same formulation as in Example 2, except that potassium isostearate and lithium isostearate were used in the amounts shown in Table 3 below in place of sodium isostearate. These inventive products and conventional products were repeatedly heated and cooled under the same conditions as in Example 1, and changes in heat storage amount and hot water were measured. Changes in heat storage amount and separated water before and after repetition are shown in Table 3 below.
It was as follows.

Table 3 As is clear from the results shown in Table 3 above, it can be seen that potassium isostearate and lithium isostearate also have the effect of suppressing the decrease in heat storage amount and the effect of suppressing separated water due to repeated use, similar to sodium isostearate.

Example 4 Products of the present invention were obtained using the same formulation as in Example 2, except that the amount of hydrated amorphous silicon dioxide (“Carplex” manufactured by Geotsugi Pharmaceutical Co., Ltd.) by wet manufacturing was changed to the amount shown in Table 4 below. Ta. Regarding these products of the present invention, Example 1
Heating and cooling were repeated under the same conditions as in case 2, and changes in heat storage amount and separated water were measured. The changes in heat storage amount and separated water before and after the repetition were as shown in Table 4 below.

Comparative Example 1 Bentonite, montmorillonite, Rheolosil QS-102, and xanthan gum were used as thickening agents in place of wet-processed amorphous silicon dioxide in the amounts shown in Table 4 below, and the amount of sodium isostearate added was 2 parts by weight. Conventional products were obtained using the same formulation as in Example 2.

These conventional products were repeatedly heated and cooled under the same conditions as in Example 1, and changes in heat storage amount and separated water were measured. The changes in heat storage amount and separated water before and after the repetition were as shown in Table 4 below.

Table 4 As is clear from the results shown in Table 4 above, the latent heat storage agent composition of the present invention has a sufficient effect of suppressing a decrease in the amount of heat storage and an effect of suppressing separated water. -102) is more effective than the 'ft1 thermal storage agent composition.

Comparative Example 2 Conventional products were obtained using the same formulation as in Example 2, except that sodium oleate and sodium laurate were used in the amounts shown in Table 5 below in place of sodium isostearate. These conventional products were repeatedly heated and cooled under the same conditions as in Example 1, and changes in heat storage amount and separated water were measured.

The changes in heat storage amount and separated water before and after the repetition were as shown in Table 5 below.

Table 5 As is clear from the results shown in Table 5 above, products to which sodium oleate or sodium laurate is added also exhibit a heat storage reduction suppressing effect, but in terms of stability of heat storage amount, the present invention with sodium isostearate added The latent heat storage agent composition was more effective. Furthermore, no difference was observed in the effect of suppressing separated water.

From the above Examples and Comparative Examples, in the latent heat storage agent composition containing sodium sulfate 1O hydrate or its eutectic as a main component, alkali metal salts of isostearic acid such as sodium isostearate, potassium isostearate, lithium isostearate, etc. It can be seen that by adding one or more types of hydrated amorphous silicon dioxide produced by wet production, a decrease in the amount of heat storage and a decrease in separated water due to repeated heat cycles can be suppressed.

〔Effect of the invention〕

The latent heat storage agent composition of the present invention can finely and uniformly disperse crystals of sodium sulfate decahydrate or its eutectic even after repeated melting and solidification, has good phase formation properties, and has little decrease in heat storage amount. It is extremely useful as a latent heat storage agent.

Claims (1)

[Claims] A latent heat storage agent composition containing sodium sulfate decahydrate or a eutectic thereof as a main component, characterized by containing one or more alkali metal salts of isostearic acid and hydrated amorphous silicon dioxide produced by wet production. A latent heat storage agent composition with little phase separation.