JPH1180720A - Cold storage material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cold storage material excellent in supercooling-preventing effect by including a sodium chloride aqueous solution and sodium carbonate. SOLUTION: This cold storage material contains (A) preferably 5-30 wt.% sodium chloride aqueous solution as a cold storage medium and (B) sodium carbonate (e.g. sodium carbonate octahydrate) as a supercooling-preventing agent, respectively. The component B is preferably contained in an amount of 1-20 pts.wt. based on 100 pts.wt. component A. The cold storage material preferably shows phase change phenomenon within the temperature range of -40 to -2 deg.C. Furthermore, the cold storage material is obtained by compounding, e.g. pure water or ion exchange water with sodium chloride at a prescribed amount to sufficiently mixing these components and then compounding the mixture with sodium carbonate in a prescribed amount to sufficiently mixing these components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold storage material using an aqueous solution of sodium chloride as a cooling medium.

[0002]

BACKGROUND OF THE INVENTION In recent years,
Development of cold storage materials is being pursued for the purpose of using surplus electricity. As the cold storage material, for example, there is a latent heat storage material utilizing absorption heat accompanying phase transition such as melting and solidification of a substance serving as a cooling medium. Among these latent heat storage materials, those using an inorganic material such as an inorganic salt or an inorganic hydrated salt as a refrigerant medium are larger in heat conductivity and latent heat amount than those using an organic material, and are nonflammable. Among them, those using an aqueous solution of sodium chloride as a storage medium,
It also has the advantage of non-toxicity, low reactivity, moderate solubility and eutectic temperature close to the frozen food storage temperature.

However, the regenerator material using the above-mentioned inorganic material as a regenerator has a problem of causing a supercooling phenomenon. The term “supercooling” means that when a substance is cooled, a phenomenon of a transition does not appear even when a temperature exceeds a phase transition temperature from a liquid to a solid, that is, the substance does not solidify. Therefore, when a regenerator material that causes this supercooling phenomenon is used, the regenerator material must be cooled to a temperature lower than the temperature at which the regenerator material is to be actually used (phase transition temperature of the regenerator material) and solidified. There is a problem that a refrigerator equipment for coagulating the material is expensive and requires extra energy.

[0004] In order to suppress the above-described supercooling phenomenon, a substance (supercooling inhibitor) serving as a core of the refrigerant medium during solidification is added to the refrigerant medium. As such a supercooling inhibitor, for example, JP-A-59-93780 discloses that a silver halide such as silver iodide is added to a refrigerant storage medium of an aqueous sodium chloride solution. However, since silver halide is not water-soluble, it does not disperse evenly in the cold storage material, so that the effect of preventing supercooling is partial and the cold storage material is not uniformly solidified.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a regenerative material having a supercooling prevention effect in a regenerative material using a sodium chloride aqueous solution as a regenerator.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by using a regenerator material containing an aqueous solution of sodium chloride and sodium carbonate. That is,
The present invention is to prevent supercooling of a regenerator material using a sodium chloride aqueous solution as a refrigerant storage medium by using sodium carbonate as a supercooling inhibitor. Since sodium carbonate is water-soluble, it can be uniformly dispersed in the cold storage material to solidify the cold storage material uniformly, and thus has an excellent supercooling prevention effect.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, an aqueous sodium chloride solution is used as a refrigerant. The concentration of sodium chloride in the aqueous solution is not particularly limited, but is preferably 5 to 30% by weight from the viewpoint of stability of cold storage temperature and cooling temperature.
Especially, 15 to 27% by weight is more preferable. If the concentration of sodium chloride is outside the above range, the temperature difference between coagulation and melting tends to increase.

In the present invention, sodium carbonate is used as a supercooling inhibitor. As the sodium carbonate, sodium carbonate decahydrate, anhydrous sodium carbonate,
Examples thereof include sodium carbonate monohydrate and sodium carbonate heptahydrate. Among them, sodium carbonate decahydrate is particularly preferable from the viewpoint of dissolution stability in a cold storage material. In the cold storage material of the present invention, the content of sodium carbonate is preferably from 1 to 20 parts by weight, especially from 3 to 10 parts by weight, based on 100 parts by weight of the aqueous sodium chloride solution, from the viewpoint of the effect of preventing supercooling and dissolution stability. Parts are more preferred. If the content of sodium carbonate is too small, the effect of preventing supercooling tends to be insufficient, and if the content is too large, sodium carbonate tends to precipitate in the cold storage material, and the uniformity of the cold storage material tends to be impaired. is there.

The regenerator material of the present invention contains the above-mentioned aqueous sodium chloride solution and sodium carbonate. In the present invention, in addition to the above-mentioned essential components, various additives may be added within a range not to impair the object of the present invention. Good. Examples of the additive include a water-absorbing resin, attapulgaya clay, gelatin, agar, a thickening agent such as silica gel, or a melting point modifier such as alcohols, and the like, and in the cold storage material of the present invention, the cold storage material of the present invention As long as the purpose is not impaired, impurities may be contained.

[0010] In the cold storage material of the present invention, the phase transition temperature is preferably about -40 to -2 ° C from the viewpoint of practical use, and more preferably -30 to -15 ° C. More preferred. The regenerator material of the present invention is preferably used for frozen storage or refrigerated storage of foods and pharmaceuticals such as frozen foods by using a non-toxic aqueous solution of sodium chloride as a refrigerant storage medium and having the above-mentioned phase transition temperature.

In the present invention, the method for producing the cold storage material is not particularly limited. For example, after a predetermined amount of sodium chloride is mixed with pure water or ion-exchanged water and thoroughly mixed,
There is a method in which a predetermined amount of sodium carbonate, which is a supercooling inhibitor, is blended and sufficiently mixed to produce a cold storage material.
The order of mixing sodium chloride and sodium carbonate is not particularly limited, and may be any order. The order may be reversed. Further, in order to promote dissolution of sodium chloride and sodium carbonate, the mixture may be heated to about 50 ° C. and mixed. When an additive is added, it may be added at the same time as the addition of sodium carbonate or after the addition of sodium carbonate.

In the present invention, the form of the cold storage material is not particularly limited. However, the cold storage material is usually packaged with an organic material such as a corrosion-resistant metal or inorganic material or plastic. Its shape is massive,
The shape may be an appropriate shape, such as a plate shape or a sheet shape, depending on the use of the cold storage material and its arrangement position. The use of the cold storage material of the present invention is not particularly limited. For example, the cold storage material can be suitably used for refrigeration of food and cold storage at the time of delivery, refrigeration of chemicals and pharmaceuticals, and the like.

[0013]

【Example】

(Examples 1 to 7, Comparative Examples 1 to 3) With respect to the regenerator materials having the compositions shown in Tables 1 and 2, the solidification start temperature and the melting start temperature were measured, and the degree of supercooling was evaluated. The results are shown in Tables 1 and 2. The evaluation method is as follows. (Coagulation start temperature and melting start temperature) After cooling to −45 ° C. at a rate of temperature decrease of 1 ° C./min and holding for 20 minutes by DSC (differential scanning calorimeter), −10 ° C. at a rate of temperature rise of 2 ° C./min. Under the program of elevating the temperature, the solidification start temperature and the melting start temperature of the cold storage material were measured. (Degree of supercooling) The degree of supercooling was calculated from the difference between the solidification start temperature and the melting start temperature. (Uniformity) The uniformity of the effect of preventing supercooling when the cold storage material was solidified was visually observed. ○, those that are uniform
Those that were non-uniform were rated as x.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

The regenerator material of the present invention is excellent in the effect of preventing supercooling by containing an aqueous solution of sodium chloride and sodium carbonate. In addition, since the phase transition phenomenon occurs in a temperature range of −40 ° C. to −2 ° C., it is particularly suitably used for frozen storage or refrigerated storage of foods such as frozen foods and pharmaceuticals. Further, when the content of sodium carbonate is 1 to 20 parts by weight with respect to 100 parts by weight of the aqueous sodium chloride solution, the supercooling prevention effect is further excellent. Also,
When the concentration of sodium chloride in the aqueous sodium chloride solution is 5 to 30% by weight, the supercooling prevention effect is further improved.

Claims (4)

[Claims] 1. A cold storage material comprising an aqueous sodium chloride solution and sodium carbonate. 2. The cold storage material according to claim 1, wherein a phase transition phenomenon occurs in a temperature range of -40 ° C. to −2 ° C. 3. The regenerative material according to claim 1, wherein the content of sodium carbonate is 1 to 20 parts by weight based on 100 parts by weight of the aqueous sodium chloride solution. 4. The cold storage material according to claim 1, wherein the concentration of sodium chloride in the aqueous sodium chloride solution is 5 to 30% by weight.