JP2002003827A - Cryogenic refrigerant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cryogenic refrigerant high in durability at -25 deg.C or lower. SOLUTION: This refrigerant is a thick brine containing 17-25% magnesium chloride and 20-35% calcium chloride, and is accommodated in a case made of a polyethylene, polypropylene, or nylon sheet which is 1.5 mm or more in thickness. The upside or underside of the case is transparent and the surface shape is granulated or corrugated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature cryogen at -25.degree.

[0002]

2. Description of the Related Art Although refrigeration agents at -25.degree. C. have been put to practical use, those suitable for refrigerated transportation at -25.degree. C. or lower have not been put to practical use.

[0003]

The present invention is to find a freezing agent at -25 ° C. or lower, and to investigate and solve the problems when putting it to practical use.

[0004]

As a frozen body capable of obtaining and maintaining a low-temperature freezing agent of -25 ° C. or lower, a frozen magnesium chloride solution or a calcium chloride solution is used. These must be used as an aqueous solution having a concentration of at least 16% by weight or more. Magnesium chloride 17-25%, calcium chloride 20-35
Since the concentration in the range of% is maintained for a long time, it is not useful as a refrigerating agent unless it is in this range. (Upper limit%
Is saturated, and more may be adjusted but has no meaning. )

[0005] Since all of these aqueous solutions have high thermal conductivity, the duration of the low temperature becomes short even if they are used until complete freezing is confirmed. In addition, since the liquid temperature rises rapidly as the frozen solid finishes melting, it must be possible to determine whether or not the frozen solid remains. For this purpose, at least one side must be transparent, that is, the inside state must be visually recognizable. In this sense, the term “transparent” as used herein includes a translucent state if it can be distinguished by eyes. The low-temperature cryogen described in the present invention is characterized in that the frozen body is a completely white body (ice is a transparent body), so that a melting state or a frozen state can be easily distinguished through a transparent surface.

Strictly speaking, it is necessary that both the upper surface and the lower surface are transparent, and it is necessary that the entire surface is transparent.
In addition, when the printing unit is always set to the lower surface, since the frozen state is determined on the upper surface, only the upper surface may be mostly transparent.

[0007] Since the low-temperature cryogen has a low temperature of -25 ° C or less, the heat inflow rate is high, and therefore, the duration is short. Therefore, in the present invention, the material of the container has been pursued to have practicality.

As the container for the low-temperature cryogen of the present invention, containers other than those made of polyethylene, polypropylene or nylon (including composite materials and laminate materials thereof) were not suitable. Materials other than these materials have drawbacks such as lack of low-temperature resistance, poor strength, and too low thermal conductivity, and are not used. However, since these material containers have a high thermal conductivity, it is practical to increase the durability by setting the thickness to 1.5 mm or more for polyethylene containers and 1 mm or more for polypropylene and nylon containers.

It has been found that in a container, the strength, the impact resistance and the duration can be increased by making the surface (upper surface and / or lower surface) granular or corrugated.

[0010]

Example 1 A polyethylene bag having a thickness of 0.2 mm and a polyethylene container (hard case) having a thickness of 1.5 mm were prepared.
26.5x19.5x20.5cm and thickness 2c
m, and the temperature was measured. From this table, it can be seen that a thickness of 1.5 mm is good.

[0011]

Example 2 A medium having a thickness of 2.0 mm was filled with 500 g of a 30% aqueous solution of calcium chloride in a medium-density polyethylene container, and frozen with dry ice. This was placed in a room with Styrofoam facing down, and the temperature was measured. As can be seen from the table, the calcium chloride solution was 0.1 m thick.
In the case of a frozen body put in a polyethylene bag of m, the retention time is extremely short, but in the case of 2 mm, a large extension of the duration is recognized, and it can be put to practical use.

[0012]

Example 3 500 ml of a 30% aqueous solution of calcium chloride
Was placed in a polyethylene rectangular bottle having a thickness of 2 mm, and was brought into close contact with dry ice to form a frozen body in 3 hours. At room temperature,
This was compared with 500 g of dry ice. (Room temperature 25-26
℃) Dry ice was observed under the same conditions,
Below 4 and 4 hours, it decreased to 1/5. After 4 hours,
There is no refrigerating capacity, and it turns out that there is no difference with the thing of this invention. That is, the present invention can be used instead of dry ice.

[0013]

Example 4 550 ml of 22% aqueous solution of magnesium chloride
Was placed in a 1.5 mm thick polyethylene container and a 1 mm thick polypropylene container, and the retention times were compared.

[0014]

Example 5 550 m of a 22% aqueous solution of magnesium chloride
l is a polyethylene hard case (135 mm x 195
mm × 26 mm, thickness 1.5 mm). Case 1
In (a), a hot stick was used on each of the front and back surfaces, and 442 granular protrusions each having a diameter of 5 mm were provided on one surface. In 1b, 884 granular projections having a diameter of 3 mm were provided on one side. 1
In (c), 25 corrugated plate-like projections having a width of 4 mm were provided on one side.
Also, 1d is a conventional one without a projection. These were left at room temperature and the temperature changes were compared. (Room temperature 24 ° C) In the case of a projection surface and a wave surface, the connection time is prolonged. That is, the one having the protrusions is excellent in the cool keeping property.

[0015]

As described above, a low-temperature cryogen that replaces dry ice has not been put to practical use. Dry ice is 5 years a year in Japan alone
One million tons are used, which is directly related to global warming. In the present invention, it has been shown that if a polyethylene container having a thickness of 1.5 mm or more is used, durability can be provided until it can be used repeatedly, and moreover, durability equivalent to that of dry ice can be provided. To make it frozen,
It consumes electrical energy and leads to CO ₂ generation, but at a lower rate than dry ice. Moreover, since it can be used repeatedly, it has an epoch-making property of saving resources, and the effect of its practical use is great.

[Brief description of the drawings]

Fig. 1 Surface shape of the cold storage case

[Explanation of symbols]

 1a Large projection 1b Small projection 1c Wavy 1d Conventional case

Claims (9)

[Claims] 1. A low-temperature cryogen obtained by dissolving magnesium chloride in water. 2. The low-temperature cryogen according to claim 1, wherein the concentration is in the range of 17 to 25%. 3. A low-temperature cryogen obtained by dissolving calcium chloride in water. 4. The low-temperature cryogen according to claim 3, wherein the concentration is in the range of 20 to 35%. 5. The low-temperature cryogen according to claim 1, 2, 3 or 4, wherein at least one of the upper surface and the lower surface or at least the central portion is transparent, and the frozen state can be confirmed. Low temperature cryogen. 6. The method according to claim 1, wherein the container is sealed in a container made of polyethylene, polypropylene or nylon.
The low-temperature cryogen according to 2, 3, 4, or 5. 7. The low-temperature cryogen according to claim 6, wherein the polyethylene container has a thickness of 1.5 mm or more. 8. The low-temperature cryogen according to claim 6, wherein the polypropylene or nylon container has a thickness of 1 mm or more. 9. The method according to claim 5, wherein the surface is granular or corrugated.
The low-temperature cryogen according to 6, 7, or 8.