JPH11323319A - Latent heat storage agent composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition that does not undergo a phase separation even if a heat cycle of melting-solidification is repeated over a long period of time by mixing a sodium acetate trihydrate or its eutectic with a hydrophilic fumed silica, a hydrophilic fumed alumina and a calcium salt. SOLUTION: It is preferable that a ratio by weight of a fumed silica and a fumed alumina is 95:5-50:50 and that the total content of the fumed silica and the fumed alumina is 3-25 pts.wt. per 100 pts.wt. sodium acetate trihydrate or its eutectic. It is preferable that the fumed silica and the fumed alumina have an average particle size of not more than 0.1 μm. As a calcium salt, one or more selected from a calcium formate, a calcium acetate, a calcium chloride, a calcium tartrate and a calcium lactate can be used and the content thereof is preferably 0.1-30 pts.wt. per 100 pts.wt. sodium acetate trihydrate or its eutectic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to sodium acetate 3
The present invention relates to a latent heat storage material composition containing a water salt as a main component, and particularly to a latent heat storage material capable of stably generating latent heat for a long period of time without causing phase separation even when a heat cycle of melting and solidification is repeated. Composition.

[0002]

2. Description of the Related Art Generally, as a heat storage material, a material utilizing sensible heat or latent heat of a substance is known. Among them, the heat storage material using latent heat has a larger amount of heat storage per unit weight and unit volume than the heat storage material using sensible heat, so if you use less than the heat storage material using sensible heat to store the same amount of heat There is an advantage that the apparatus can be downsized. Also, the heat storage material using latent heat has a solidification point (transition point) unique to the substance, unlike the heat storage material using sensible heat,
Therefore, it has a feature of releasing heat at a constant temperature. Among them,
Inorganic hydrate salts are known to have a large latent heat storage capacity. Among them, sodium acetate trihydrate has a large latent heat storage capacity and a transition temperature of 58 ° C, which is suitable for applications such as heating. It is a promising heat storage material.

However, since the melting point of sodium acetate trihydrate is not a harmonic melting point but a peritectic point, even when cooled to its original melting point, it does not release latent heat and is cooled. When the thermal cycle is repeated, anhydrous sodium acetate crystals grow, and the crystals settle to the bottom, causing a phase separation phenomenon in which the desired latent heat cannot be generated.

Among them, the mechanism of the phase separation phenomenon is considered as follows. That is, when sodium acetate trihydrate is heated to its melting point of 58 ° C., it is decomposed into anhydrous sodium acetate and water. Next, the decomposed anhydrous salt is dissolved in water. However, at a temperature near the melting point, the anhydrous salt becomes supersaturated and does not completely dissolve. The anhydrous salt that could not be dissolved at this time
If fine crystals are dispersed in the melt in a state close to homogeneity, they react with surrounding water during cooling and solidification, and return to trihydrate easily. However, this is not the case. Then, it precipitates at the bottom and separates into an anhydrous salt crystal precipitate and a melt.

Among the above problems of sodium acetate trihydrate, various proposals have been made for the prevention of the supercooling phenomenon. For example, Japanese Patent Application Laid-Open No. 57-59981 discloses sodium pyrophosphate as a supercooling preventing material. Can be added, and JP-A-60-92383 discloses phosphoric acid 1
The addition of disodium hydrogen has been reported.

On the other hand, in order to prevent the phase separation phenomenon, Japanese Unexamined Patent Publication No. Sho 57-31982 discloses adding sodium polyacrylate as a phase separation preventing material.
JP-A-8-79081 reports that a carboxylic acid is added, and JP-A-60-58480 reports that xanthan gum is added.

[0007]

According to the experiments conducted by the present inventors, the supercooling phenomenon of sodium acetate trihydrate can be almost completely solved by adding sodium pyrophosphate or disodium monohydrogen phosphate. Was. However, the phase separation phenomenon of sodium acetate trihydrate is disclosed in
With sodium polyacrylate described in JP-A-7-31982 and carboxylic acid described in JP-A-58-79081, it was found that phase separation occurs after several tens of cycles of melting and coagulation, and no heat is generated. . Also, Japanese Patent Application Laid-Open
In the xanthan gum described in -58480,
Better results were obtained than these separation preventing materials, but 4
It has been found that phase separation occurs due to thermal degradation of xanthan gum by melting-coagulation exceeding 00 cycles.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a sodium acetate trihydrate latent heat storage material composition in which phase separation does not occur even when a heat cycle of melting and solidification is repeated for a long time. And

[0009]

The latent heat storage material composition of the present invention is a latent heat storage material composition containing sodium acetate trihydrate or a eutectic thereof and a phase separation preventing material. , Hydrophilic fumed silica, hydrophilic fumed alumina and a calcium salt.

That is, the present inventor repeatedly conducted research to obtain a sodium acetate trihydrate latent heat storage material which stably generates heat upon prolonged melting and solidification. As a result, fumed silica and fumed alumina were used as phase separation preventing materials. It has been found that excellent effects can be obtained by using a calcium salt and calcium salts, and the present invention has been completed.

In the present invention, it is not clear how the above-mentioned phase separation preventing material works and a good phase separation preventing effect is obtained. However, each of silica, alumina and calcium salt is used alone or in combination. Since long-term stable dispersibility could not be obtained with the combination of the two, these fine particles were dispersed throughout the composition so as to hold each other in a well-balanced manner, so that anhydrous sodium acetate crystals precipitated. It is considered that the latent heat storage material composition which is uniformly dispersed and maintained in the melt as fine without being formed as a whole and has excellent long-term stability as a whole is formed.

Particularly, in the present invention, it is presumed that calcium ions exert some action on silica and alumina. That is, calcium tartrate provides good dispersibility, whereas sodium tartrate does not provide sufficient dispersibility.

In the present invention, the weight ratio of fumed silica to fumed alumina is preferably 95: 5 to 50:50, and the total content of fumed silica and fumed alumina is sodium acetate trihydrate. Alternatively, the amount is preferably 3 to 25 parts by weight per 100 parts by weight of the eutectic.

The average particle size of fumed silica and fumed alumina is preferably 0.1 μm or less.

As the calcium salt, calcium formate,
One or more selected from the group consisting of calcium acetate, calcium chloride, calcium tartrate and calcium lactate can be used, and the content thereof is 0.1% per 100 parts by weight of sodium acetate trihydrate or a eutectic thereof. ~ 30
It is preferably in parts by weight.

The latent heat storage material composition of the present invention further comprises sodium pyrophosphate and / or phosphoric acid 1 as a supercooling preventing material.
It may contain disodium hydrogen.

[0017]

Embodiments of the present invention will be described below in detail.

The latent heat storage material composition of the present invention has a melting point of 58 ° C.
Acetate trihydrate (CH ₃ COONa · 3H ₂ O)
Alternatively, the eutectic material is used as a main material, and fumed silica, fumed alumina and a calcium salt are contained as a phase separation preventing material.

The fumed silica and fumed alumina used as the phase separation preventing material are hydrophilic anhydrides, and have an average primary particle diameter of 0.1 μm or less, preferably 0.05 μm or less. Are preferred.
When the particle size is large, for example, when the particle size is several μm, sedimentation is likely to occur, and a good phase separation preventing effect cannot be obtained.

The weight ratio of fumed silica to fumed alumina is preferably in the range of 95: 5 to 50:50, and more preferably fumed silica: fumed alumina = 95: 5 to 75:25. Range. If the weight of fumed alumina is larger than that of fumed silica, the dispersibility is reduced, and a good phase separation preventing effect cannot be obtained.

Further, the added amount of fumed silica and fumed alumina is preferably about 3 to 25 parts by weight, more preferably about 7 to 15 parts by weight, based on 100 parts by weight of sodium acetate trihydrate. If the amount is too small, a sufficient effect of preventing phase separation cannot be obtained, but if it is too large, the amount of heat storage is reduced. Therefore, it is preferable to minimize the amount in the above range.

Calcium salts used simultaneously as phase separation preventing materials include calcium formate, calcium acetate,
Examples thereof include calcium chloride, calcium tartrate, and calcium lactate, and these can be used alone or in combination of two or more. Here, calcium formate is anhydrous, calcium acetate is anhydrous, monohydrate, dihydrate, calcium chloride is anhydrous, monohydrate, dihydrate, tetrahydrate, hexahydrate, calcium tartrate is anhydrous. , Tetrahydrate and calcium lactate can be used from anhydrous salts to pentahydrate salts. Among the above, those having different salts of crystallization water are monohydrate for calcium acetate, dihydrate for calcium chloride, and 4 for calcium tartrate.
Among water salts and calcium lactate, pentahydrate is particularly preferred. In addition, even if it is a calcium salt, calcium carbonate,
In the case of calcium fluoride, calcium gluconate, and the like, the dispersing effect may be inferior, so that the above-mentioned calcium salt is preferably used.

The amount of the calcium salt to be added is preferably 0.1 to 30 parts by weight, particularly preferably 5 to 15 parts by weight, per 100 parts by weight of sodium acetate trihydrate. The water of crystallization of the salt is not included.)

In the present invention, a small amount of water may be added for the purpose of stabilizing sodium acetate trihydrate. However, since the addition of water causes a problem of lowering the melting point, the amount of water added is desirably 10 parts by weight or less based on 100 parts by weight of sodium acetate trihydrate.

The latent heat storage material composition of the present invention further comprises sodium pyrophosphate and / or phosphoric acid 1
It may contain disodium hydrogen, and in this case, the content of the supercooling preventing material is preferably 1 to 20 parts by weight per 100 parts by weight of sodium acetate trihydrate. The water of crystallization in the cooling inhibitor is not included.)

The latent heat storage material composition of the present invention may further contain, if necessary, a melting point regulator such as sodium thiosulfate, potassium chloride and ethylene glycol, a surfactant and the like.

[0027]

The present invention will be described more specifically below with reference to examples and comparative examples.

Examples 1 to 7, Comparative Examples 1 and 2, fumed silica (average primary particle size: 0.012 μm) and fumed silica having a compounding ratio shown in Table 1 as a phase separation preventing material were added to 100 g of sodium acetate trihydrate as a main material. 10 g of a mixture of silica alumina (average primary particle size 0.013 μm) and calcium chloride 2
10 g of water salt and 5 g of sodium pyrophosphate dehydrate as a nucleating material (supercooling preventing material) were mixed, and this mixture was dissolved in a water bath at 70 ° C. and stirred sufficiently. Then, about 25 g of a part of this mixture was 18 mm in diameter.
In a polypropylene test tube, and sealed with a silicone stopper.

The sample set in this way was kept at 30 ° C. and 70 ° C.
A temperature cycle test in which the sample was alternately put into a water bath at 25 ° C. for 25 minutes was performed 100 times, and the dispersibility of the sample was observed.

As a result, a combination of fumed silica, fumed alumina and calcium chloride (Examples 1 to 3)
7) In particular, among these, those in which fumed silica: fumed alumina = 95: 5 to 50:50 (weight ratio) (Examples 2 to 6) showed phase separation even in 100 cycles as shown in Table 1. No uniform dispersion was observed.

[0031]

[Table 1]

EXAMPLE 8 8.5 g of fumed silica and 1.5 g of fumed alumina were used as a phase separation preventing material in 100 g of sodium acetate trihydrate.
g, 15 g of calcium acetate monohydrate and 5 g of disodium monohydrogen phosphate 12 hydrate as a nucleating agent are mixed with 70 g of a mixture.
It melt | dissolved in the water bath of ° C, and it stirred thoroughly. Thereafter, about 25 g of the mixture was placed in a polypropylene test tube having a diameter of 18 mm and sealed with a silicone stopper. In addition, a thermocouple was passed through the center of the silicon stopper, and the thermocouple was set so that the tip of the thermocouple was located substantially at the center of the heat storage material composition in the test tube.

The sample set in this way was kept at 30 ° C. and 70 ° C.
A temperature cycle test was conducted in which the samples were alternately placed in a water bath at 25 ° C. for 25 minutes. As a result, in this sample, no phase separation was observed even after 1,500 cycles, the exothermic peak was almost the same as in the first cycle, and the solidification starting temperature was hardly changed at about 56 ° C.

FIG. 1 shows the change in water temperature in the heat cycle and the heat generation peaks at the first and 1500th cycles.

Example 9 In Example 8, 10 g of calcium chloride dihydrate and 1 g of calcium tartrate tetrahydrate were used instead of calcium acetate monohydrate.
A sample was prepared in the same manner except that the sample was used, and a temperature cycle test was performed in the same manner.

As a result, in this sample, no phase separation was observed even after 1500 cycles, the exothermic peak was almost the same as in the first cycle, and the solidification starting temperature was hardly changed at about 53 ° C.

FIG. 2 shows the change in water temperature during the heat cycle and the heat generation peaks at the first and 1500th cycles.

Comparative Example 3 A sample was prepared in the same manner as in Example 8 except that calcium acetate monohydrate was not added, and a temperature cycle test was performed in the same manner.

As a result, in this sample, phase separation occurred in one hundred and several tens of cycles, and at that time, the exothermic peak was significantly reduced.

Comparative Example 4 A sample was prepared in the same manner as in Example 8 except that fumed silica and fumed alumina were not added, and a temperature cycle test was performed in the same manner.

As a result, in this sample, phase separation occurred in more than ten cycles, and at that time, the exothermic peak was significantly reduced.

Comparative Example 5 A sample was prepared in the same manner as in Example 8, except that 2 g of xanthan gum was added instead of fumed silica, fumed alumina and calcium acetate monohydrate.
Similarly, a temperature cycle test was performed.

As a result, in this sample, phase separation occurred around 400 cycles, and the exothermic peak was 500 to 700.
Significantly reduced in cycles.

[0044]

As described in detail above, according to the latent heat storage material composition of the present invention, even if the heat cycle of melting and solidification is repeated many times, phase separation does not occur, and the latent heat storage material can be stably formed over a long period of time. And a latent heat storage material composition having practically excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a graph showing changes in water temperature in a heat cycle and heat generation peaks in a first cycle and a 1500th cycle in Example 8.

FIG. 2 is a graph showing changes in water temperature in a heat cycle and heat generation peaks in a first cycle and a 1500th cycle in Example 9.

Claims (7)

[Claims] 1. A latent heat storage material composition comprising sodium acetate trihydrate or a eutectic thereof and a phase separation preventing material, wherein the phase separation preventing material includes hydrophilic fumed silica, hydrophilic fumed alumina and calcium. A latent heat storage material composition comprising a salt. 2. The latent heat storage material composition according to claim 1, wherein the weight ratio of the fumed silica and the fumed alumina is 95: 5 to 50:50. 3. The method according to claim 1, wherein the total content of said fumed silica and fumed alumina is 3 to 25 parts by weight per 100 parts by weight of sodium acetate trihydrate or its eutectic. The latent heat storage material composition as described in the above. 4. The latent heat storage material composition according to claim 1, wherein the average particle size of the fumed silica and fumed alumina is 0.1 μm or less. 5. The method according to claim 1, wherein the calcium salt is at least one member selected from the group consisting of calcium formate, calcium acetate, calcium chloride, calcium tartrate, and calcium lactate. Item 2. The latent heat storage material composition according to item 1. 6. The content of the calcium salt is from 0.1 to 100 parts by weight of sodium acetate trihydrate or a eutectic thereof.
The latent heat storage material composition according to any one of claims 1 to 5, wherein the content is 30 parts by weight. 7. The latent heat storage material composition according to claim 1, further comprising sodium pyrophosphate and / or disodium monohydrogen phosphate as a supercooling prevention material.