JP2001003039A - Latent heat-storing material composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a latent heat-storing material composition which is not prone to phase separation and little decreases in stored heat even when it is repeatedly thawed and freezed. SOLUTION: A latent heat-storing material composition contains sodium acetate as a main component and water, wherein the weight ratio of sodium acetate (based on anhydrous sodium acetate) to water (including water contained as water of crystallization in the system) is 55:45 to 68:32 and a total of 0.05-5 pts.wt. of one or more of alkali salts of branched saturated fatty acids with 18 or more carbon atoms and/or one or more of branched saturated higher alcohols with 18 or more carbon atoms is contained based on the total of 100 pts.wt. of sodium acetate and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a latent heat storage material composition used for electric heat storage type floor heating and heat pump type air conditioning.

[0002]

2. Description of the Related Art Hitherto, a latent heat storage material containing sodium acetate trihydrate as a main component has a large latent heat of fusion and a melting point of around 58 ° C. It is known as a useful latent heat storage material.

[0003] However, sodium acetate trihydrate separates into two phases during melting, a saturated aqueous solution of sodium acetate and a solid sodium acetate, and the solid sodium acetate precipitates at the bottom of the vessel due to its higher specific gravity than the saturated aqueous solution. ,To separate.

When the system is cooled, sodium acetate trihydrate crystals are formed on the precipitated sodium acetate solid to form a barrier, and the sodium acetate solid is combined with water to form sodium acetate trihydrate. Interfere with

[0005] Therefore, solidification of sodium acetate precipitates due to the repetition of melting and solidification, that is, heat storage and heat radiation, and the solid does not contribute to heat storage.
The problem that the supercooling phenomenon becomes large and solidification does not occur at a predetermined temperature occurs.

In order to solve this problem, natural gels such as wood pulp, methylcellulose, starch, alginate, polyvalent metal salts of crosslinked polyacrylic acid, carboxymethylcellulose, guar gum, locust bean gum and carrageenan are used as phase separation inhibitors. Attempts have been made to increase the viscosity by adding a thickening agent such as silica gel, attapulgite type clay, etc. in combination with an agent and a polyhydric alcohol, and to obtain a so-called gelled state.

[0007]

However, the method of adding the above-mentioned various thickeners can prevent precipitation of sodium acetate at an early stage, but it is necessary to prevent the growth of sodium acetate crystals by repeated melting and solidification. There is no ability to prevent this, and the amount of heat stored is still reduced by crystal growth.

Accordingly, an object of the present invention is to provide a latent heat storage material composition which is stable against phase separation and has a small decrease in heat storage amount even after repeated melting and solidification.

[0009]

That is, the present invention relates to a latent heat storage material composition containing sodium acetate as a main component and water, comprising sodium acetate (anhydrous equivalent): water (contained in the system as water of crystallization). = 55: 45-6
8:32 by weight, and based on 100 parts by weight of sodium acetate and water in total, at least one kind of alkali metal salt of a branched saturated fatty acid having 18 or more carbon atoms and / or branching having 18 or more carbon atoms. A latent heat storage material composition comprising a total of 0.05 to 5 parts by weight of at least one saturated higher alcohol.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The latent heat storage material composition of the present invention will be described below in detail.

The latent heat storage material composition of the present invention contains sodium acetate as a main component and water. When sodium acetate in the system is converted into an anhydride and water is included in the system as water of crystallization and the total water content is included, the weight ratio of sodium acetate and water in the present invention is:
The weight ratio of sodium acetate: water = 55: 45 to 68:32, preferably 58:42 to 63:37.

If the amount of water is less than the above amount, the coagulation temperature and the amount of latent heat storage are reduced. If the amount of water is too large, the degree of supercooling is increased and the amount of latent heat storage is reduced.

In the present invention, in order to prevent phase separation, at least one kind of alkali metal salt of a branched saturated fatty acid having 18 or more carbon atoms and / or at least one kind of a branched saturated higher alcohol is added in a total amount of 0.05 to 4.5. Use 5 parts by weight.

The branched saturated fatty acids constituting the above salts have 18 or more carbon atoms, and specific examples thereof include isostearic acid, isoarachinic acid, and isobehenic acid. More than one species may be mixed, but isostearic acid is preferred from the viewpoint of phase separation preventing effect and economy.

The alkali metal constituting the salt with the branched saturated fatty acid is not particularly restricted but includes lithium, sodium, potassium and the like. These may be used alone or in combination of two or more. Good. Further, sodium and potassium are preferred in view of the phase separation preventing effect and economy.

Further, the carbon number of 18 used in the present invention is
Examples of the above branched saturated higher alcohols include, for example, isostearyl alcohol, isoaraquinyl alcohol, isobehenyl alcohol and the like. These may be used alone or in combination of two or more. In addition, isostearyl alcohol and isobehenyl alcohol are preferable in terms of phase separation preventing effect and economic efficiency.

In the present invention, the alkali metal salt of a branched saturated fatty acid having 18 or more carbon atoms and a branched saturated higher alcohol used for preventing phase separation can be used in combination.

In the present invention, the amounts of the alkali metal salt of the branched saturated fatty acid having 18 or more carbon atoms and the branched saturated higher alcohol used for preventing phase separation are 100 parts by weight of the total amount of sodium acetate and water. , 0 in total.
It is from 0.5 to 5 parts by weight, preferably from 0.1 to 3 parts by weight, more preferably from 0.2 to 1 part by weight.

If the amount is less than the above amount, the effect of preventing phase separation is insufficient. If the amount exceeds the above amount, the effect is not improved any more, and the amount of latent heat storage is reduced.

The latent heat storage material composition of the present invention contains sodium acetate as a main component, but may contain a heat storage component other than sodium acetate, if desired, as long as the object of the present invention is not impaired.

The heat storage components other than sodium acetate include:
For example, sodium thiosulfate (pentahydrate) can be used, but it is preferable that at least 60% by weight of the heat storage component is sodium acetate.

The latent heat storage material composition of the present invention further comprises a known freezing point depressant for controlling the heat storage temperature, and other known phase separation inhibitors for imparting stability to a long-term heat history. Can be optionally contained within a range of a commonly used amount and within a range not to impair the object of the present invention.

Examples of such freezing point depressants include sodium chloride, potassium chloride, ammonium chloride and urea.

Examples of such other known phase separation inhibitors include three-dimensional redox polymer of methylcellulose, starch, anlginate, sodium polyacrylate, acrylamide, carboxymethylcellulose, attapulgite-type clay, silicon dioxide and the like. can do.

[0025]

Hereinafter, the present invention will be described based on examples.
The present invention is not limited to these examples.

The units of the formulation shown in the following tables are all parts by weight. In addition, various samples used in this example are:
Using the samples shown below, latent heat storage material compositions for each test were prepared according to the formulation shown in each table. Sample 1: aqueous solution of 58% by weight of sodium acetate Sample 2: amorphous silicon dioxide powder Sample 3: crystalline sodium pyrophosphate (60 mesh pass) Sample 4: sodium isostearate Sample 5: potassium isostearate Sample 6: isostearyl alcohol sample 7 : Isobehenyl alcohol Sample 8: Isononanoic acid Sample 9: Isooctanol Sample 10: Sodium stearate

(Heat History Test of Latent Heat Storage Material Composition) Height 1
A heat storage material composition was placed in a test tube having a diameter of 50 mm and an inner diameter of 20 mm.
g weighing (liquid depth about 100mm, after sealing, 75 ℃
And a heat history of 40 ° C. The heat history was repeated 300 times, with one state in which the internal latent heat storage material completely solidified and melted. When measuring the amount of latent heat storage, the upper surface of the test tube,
Extract and mix equal parts of the sample near the center and bottom,
It was measured by a differential scanning calorimeter (manufactured by Seiko Denshi Kogyo KK).

Examples 1 to 9 and Comparative Examples 1 to 8 The sample compositions of the present invention (Examples) and the comparative sample compositions (Comparative Examples) having the formulations shown in Tables 1 and 2 below are described above. Tables 1 and 2 below show the measured values of the latent heat storage amount before and after the heat history of each composition based on the test method. In addition, Tables 1 and 2 below also show the amount of water released from the upper surface of the sample at the time after the heat history test.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The effect of the present invention is to provide a latent heat storage material composition which is stable against phase separation and has a small decrease in heat storage even after repeated melting and solidification.

Claims (1)

[Claims] 1. A latent heat storage material composition containing sodium acetate as a main component and water, wherein sodium acetate (anhydrous conversion): water (including water contained in the system as water of crystallization) = 55: 45. -68: 32, and at least one kind of alkali metal salt of a branched saturated fatty acid having 18 or more carbon atoms and / or at least 18 carbon atoms, based on 100 parts by weight of sodium acetate and water in total. A latent heat storage material composition comprising a total of 0.05 to 5 parts by weight of at least one kind of branched saturated higher alcohol.