JPH08269440A - Cold-reserving agent - Google Patents

Abstract

PURPOSE: To obtain a cold-reserving agent which can simply and easily keep the coldness of a material which must be kept out of contact with water and can easily be posttreated. CONSTITUTION: A temp.-sensitive water-absorbing polymer which has a temp.- sensing point with respect to water of 10-40 deg.C is packaged with a water- permeable material such as fabric, nonwoven fabric, or porous plastics, thus giving a cold-reserving agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling agent which is easy to handle and post-process.

[0002]

2. Description of the Related Art It is known that low-temperature preservation is effective for keeping freshness of vegetables, flowering trees, fish and meat. Therefore, in recent years, the use of refrigerated vehicles has become widespread for the transportation of freshness of these items. However, the use of refrigerated vehicles adds significantly to the cost and is not suitable for small-lot transportation. On the other hand, the method of attaching ice when transporting fish has long been used. This method can be applied to fish, such as fish, that may be in direct contact with water, but it is difficult to apply to vegetables and flowering trees, and it has the problem that ice-melted water spills. .

As a method for solving such a problem, a method in which water is sealed with a packaging material is used by cooling with ice, or a so-called superabsorbent polymer gel in which water is absorbed is used in cooling with ice. A method has been proposed. (For example, JP-A-60-171042, etc.)

[0003]

However, the former is,
It is difficult to completely prevent water from spilling due to breakage of the packaging material during use, and its use is limited. The latter also has a problem in treating the gel after use. That is, since the water-containing gel contains a large amount of water, it is difficult to burn and difficult to incinerate, and when it is recycled for use, it is necessary to return a waste water-containing heavy product, which increases the cost. In addition to maintaining the freshness of vegetables, flowers, fish, meat, etc., there is a strong demand for simple ice packs, such as keeping cool home coolers and preventing food from spoiling in the summer, but there are still strong requirements. The reality is that they are not.

[0004]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have diligently studied a cold-preserving agent which is less likely to damage the object to be kept cold, has no problem of defrosting water and is easy to post-process. As a result, they have found that the problem can be solved by using a temperature-sensitive water-absorbing polymer, and have reached the present invention. That is, the present invention has a temperature-sensitive point for water of 10 ° C to 40 ° C.
The present invention provides a cold-preserving agent in which the temperature-sensitive water-absorbing polymer between the two is packaged with a material having water permeability such as cloth and nonwoven fabric porous plastic fill.

The temperature-sensitive water-absorbing polymer used in the present invention is N-isopropyl (meth) acrylamide, N,
N-, such as N-diethyl acrylate, N-n-propyl (meth) acrylamide, acryloyl pyrrolidine, acryloyl piperidine, N-ethyl acrylamide
Temperature-sensitive obtained by copolymerizing a monomer selected from alkyl-substituted (meth) acrylamides as a main component with (meth) acrylic acid or its alkali metal salt, and optionally other vinyl monomer It is obtained by crosslinking a hydrophilic polymer.

Examples of the crosslinking method of the temperature-sensitive polymer include a method of copolymerizing a divinyl type monomer during polymerization, a method of copolymerizing a vinyl monomer having a crosslinking reactivity and then crosslinking with a crosslinking agent, a method of crosslinking by radiation, and the like. is there. The temperature-sensitive water-absorbing polymer thus obtained absorbs water at temperatures below the set temperature-sensing point, hardly absorbs water at temperatures above the temperature-sensing point, and absorbs water below the temperature-sensing point. Then, when the temperature rises above the temperature sensing point, the absorbed water is discharged to the outside.

The temperature-sensitive point of the temperature-sensitive water-absorbent polymer can be controlled by the type and composition ratio of the monomers used. For example, a temperature-sensitive water-absorbing polymer obtained by homopolymerizing and cross-linking N-isopropylacrylamide has a temperature-sensitive point around 32 ° C. The temperature sensitive point can be changed by copolymerizing N-isopropylacrylamide with another monomer.

The temperature-sensitive water-absorbent polymer used in the present invention has a temperature-sensitive point of 10 ° C. or higher and 40 ° C. or lower. If the temperature-sensing point is 10 ° C or less, water cannot be absorbed in the environment generally used, and in the environment generally used, the temperature may be higher than the temperature-sensing point, which may cause inconvenient drainage of water. is there. If the temperature-sensing point is 40 ° C. or higher, forced heating is required for dehydration after use, which limits the field of use. Considering the use in the summer under normal environment, it is preferable to set the temperature sensitive point between 25 and 30 ° C.

The cold-preserving agent of the present invention is produced by packaging a temperature-sensitive water-absorbing polymer in a material having water permeability such as cloth, non-woven fabric and porous film. The shape of the temperature-sensitive water-absorbent polymer used in the present invention is not particularly limited, but is generally powder or granules. The amount of the temperature-sensitive water-absorbing polymer used and the size of the material to be packaged are sufficient as long as the polymer after water absorption is sufficiently packaged, for example, 25
In the case of a non-woven fabric of cm × 20 cm, the amount of the temperature-sensitive water-absorbing polymer used depends on the polymer used, but is 5 to 5.
About 10 g is sufficient.

The method of using the cold insulating agent of the present invention is as follows. The cold insulating agent of the present invention is immersed in water having a temperature not higher than the temperature sensitive point to swell the temperature sensitive water-absorbing polymer. Then, it is taken out from water, cooled to 0 ° C. or lower, frozen, and used for cold storage. After use, when the cold-preserving agent of the present invention is exposed to a temperature environment at or above the temperature-sensitive point, the water which the temperature-sensitive water-absorbing polymer has absorbed and retained will be released to the outside. The water-releasing ice pack has a weight, volume and water content close to those of the initial temperature-sensitive water-absorbing polymer itself and the packaging material, and can be disposed of.
Further, in the case of recycling, only the composition of the present cold-preserving agent that is lightweight and less bulky needs to be returned, and the transportation cost is greatly reduced.

The present invention will be described below with reference to specific examples. Reference example N-isopropylacrylamide 21.
6 g, diacetone acrylamide 3.2 g, acrylic acid 1.1 g, and methylenebisacrylamide 0.14 g were dissolved, and the aqueous solution was cooled to 0 ° C. After substituting with nitrogen gas, 0.08 g of tert-butyl hydroperoxide and 0.1 g of Rongalit were added as polymerization initiators, and polymerization was carried out for 5 hours under adiabatic condition. After the polymerization reaction, the obtained gel was roughly crushed and immersed in a large amount of warm water at 60 ° C. or higher to separately obtain a contracted gel polymer. This is dried, pulverized, and classified to have a temperature-sensitive water-absorbent polymer 1 having a particle diameter of 0.15 to 0.71 mm.
5 g was obtained. The temperature-sensitive point of the obtained temperature-sensitive water-absorbent polymer was about 30 ° C. The equilibrium water absorption capacity of this temperature-sensitive water-absorbent polymer is 120 times (W / W) at 20 ° C and 5 at 35 ° C.
It was twice (W / W).

Example 10 g of the temperature-sensitive water-absorbent polymer synthesized in the reference example was added to 30 c
It was placed in a m × 30 cm non-woven fabric bag and sealed so that the temperature-sensitive water-absorbent polymer was not spilled, and used as a cooler. 20 this
After immersing the temperature-sensitive polymer in water at ℃ for 3 hours to absorb and swell it, the temperature-sensitive polymer was taken out from the water and drained. It was then left in the home refrigerator overnight to freeze. The weight at this point was 1030 g. This was placed in a foamed steel container with a lid having an internal capacity of 8 liters, and allowed to stand under the condition of an external temperature of 30 ° C., and the change with time of the internal temperature was examined. The results are shown in Table 1.

[0013]

[Table 1]

After the lapse of 12 hours, the ice pack was in a thawed state, but no water stain was observed from the bag. The cooling agent was taken out and left in an environment of 35 ° C. for 24 hours. During this period, the cooling agent drained water, and after standing for 24 hours, the weight of the cooling agent was 70 g. This used ice pack could be easily incinerated as general waste.

[0015]

As described above, by using the cold insulating agent of the present invention, it is possible to easily keep cold the material which does not want to get wet with water, and to easily post-process the cold insulating agent. be able to.

Claims (1)

[Claims] 1. A cooling agent in which a temperature-sensitive water-absorbing polymer having a temperature-sensitive point to water of 10 ° C. to 40 ° C. is packaged with a material having water permeability such as cloth, nonwoven fabric, and porous plastic fill.