JPH01204989A - Bagged material for cooling - Google Patents

Abstract

PURPOSE:To obtain a low-cost bagged material for cooling, which retains its cooling power over a long period of time and can be reused repeatedly, by combining an inner bag containing an aqueous material with an outer bag containing a cooling agent and a water-absorptive resin comprising a specified mixture. CONSTITUTION:This bagged material for cooling consists of an inner bag containing an aqueous material and an outer bag containing a cooling agent and a water- absorptive resin comprising a mixture of an acrylic acid/vinyl alcohol copolymer with a sodium acrylate polymer. As the aqueous material, an ordinary water, e.g., tap water or well water, or a purified water, e.g., distilled water is mainly used. The ratio of the cooling agent to the aqueous material has a great influence on the time during which the cooling power is retained. If the amount of the aqueous material is excessive in relation to the cooling agent, the cooling agent is dissolved at once to cool so that the temperature of the solution is lowered rapidly; however, the cooling power will not be retained for a long time since no subsequent reaction occurs. If the water content is extremely high, a drop in the temperature due to heat absorption will be small because of the large heat capacity of the aqueous material.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cooling bag filled with a coolant that absorbs heat during melting.

Problems to be Solved by the Prior Art and the Invention Cooling bags that mix coolant and water between the bags and utilize an endothermic reaction due to dissolution are disclosed in Japanese Patent Laid-Open Nos. 57-124668 and 1983- Publication 96970.

JP-A-58-180575, JP-A-59-4947
It is publicly known from Publication No. 6. However, in these cooling bags, when used, a coolant such as ammonium nitrate or urea reacts with water instantaneously, so although it is easy to obtain a low temperature, it is not possible to maintain a low temperature for a long time. As a means to extend the holding time at low temperature, a method of granulating the coolant and coating the surface (Japanese Patent Application Laid-Open No. 58-18748
2) Method using a coolant of 281 or higher (Japanese Unexamined Patent Publication No. 5)
7-124668, JP-A-60-142179) or a method using a water-containing agent outside the water plate (JP-A-60-142179).
-60177 Publication) etc. have been proposed. However, in neither case has the low-temperature retention time been dramatically improved.

Recently, cold storage agents using water-absorbing resin have been commercially available, and
It began to be used for transporting vegetables, etc. A method has been proposed for extending the cooling time by applying this water-absorbing resin to a coolant. Japanese Patent Application Laid-Open No. 60-142179 is
A method using solid particles of sodium thiosulfate as a coolant and a fibrous material as a gelling agent, JP-A-59-1
20675 discloses a method using a water-retaining agent that has been gelled in advance, and JP-A-60-171042 discloses a method using a water-retaining agent 10.
In this method, 30 to 100 parts by weight of a water-absorbing polymer is sealed in an outer bag together with a coolant.

In both of these methods, the water released from the water-absorbent resin and the coolant gradually react with each other, so the cooling duration is longer, and the material feels nice on the skin. It has many advantages such as being reusable. However, the method of using a fibrous material as a gelling agent is not effective because the reaction between the fibrous material that has absorbed released moisture and the coolant is too slow, and unreacted coolant remains after use. Moreover, it has the disadvantage that it is more expensive than granular water-absorbing resin.

The above method using a gelled water retention agent has poor mixing of the gelling agent and the cooling agent, and requires external force to be applied by constantly kneading the cooling bag, making handling inconvenient and slowing down the manufacturing process. It has drawbacks such as complexity.

On the other hand, the method described above in which a water-absorbing polymer is sealed together with a coolant in an outer bag is simple to manufacture and effective.

However, water-absorbing polymers generally have a
It is ~10 times more expensive, and the aforementioned method of using 80 to 100 parts by weight of water-absorbing polymer for 100 parts by weight of dead metal solution requires about 2 to 5 times the raw material cost, which poses a cost problem.

The present invention provides a cooling bag that can be kept cool for a long time, is inexpensive, and can be reused repeatedly.

Means for Solving the Problems The present invention provides a cooling bag comprising an inner bag filled with a water-containing agent and an outer bag filled with a coolant and a water-absorbing resin, wherein the water-absorbing resin is made of acrylic acid. It is characterized by being made of a mixture of vinyl alcohol copolymer and sodium acrylate polymer.

The water-containing agent used in the present invention is mainly ordinary water, such as tap water, well water, purified distilled water, or the like. For long-term storage of the water-containing agent, a small amount of preservative may be added. When using a material that exhibits weak acidity with a pEI of 5 to 6 when dissolved in water, such as ammonium nitrate, as a coolant, add Ca(OH)s+ to the water so that the liquid after the coolant is dissolved becomes neutral. It is effective to add , Na2CO3, etc. to make a weakly alkaline water-containing agent with a pEI of about 7 to 8.

The coolant in the present invention may be any material as long as it absorbs heat when dissolved in water, but materials that are well soluble in water, absorb a large amount of heat, are inexpensive, and are harmless to humans and animals are preferred. All of these materials are known, and representative examples include ammonium nitrate and ammonium nitrite as inorganic materials.

Sodium nitrate, calcium nitrate, ammonium chloride,
Examples of organic materials include ammonium hydrogen carbonate and sodium thiosulfate, and examples of organic materials include urea + dM potassium potassium chloride and tetrahydrate. Of course, one type of these materials or a mixture of two or more types may be used. Since coolants generally exhibit deliquescent properties, attempts have been made to coat their surfaces in some way to absorb moisture in the air and prevent them from becoming sticky.

For example, ammonium nitrate is coated with stearic acid or the like, and it is preferable to use a coolant that has undergone such treatment. Since the coolant rapidly reacts with water and absorbs heat, it is more appropriate to use granular or granular particles rather than powder, and the particle size should be uniform in the range of 0.5 to 2.6 fl. It is desirable to be present. Further, in order to slow down the reaction rate, it is preferable to use a material with few pores and high density.

The blending ratio of the coolant and water-containing agent has a large effect on the cooling time. If the amount of water-containing agent is too large relative to the coolant, the coolant will dissolve and cool at once, causing the temperature of the solution to rise rapidly. However, since no subsequent reaction occurs, the cold storage time becomes shorter. In this case, if the water content is very high, the heat capacity of the water-containing agent will be large and the temperature drop due to heat absorption will be small.

Furthermore, if the amount of water-containing agent is too small relative to the coolant, the coolant will remain undissolved and the coolant will not be used effectively.

The appropriate mixing ratio of the coolant and the water-containing agent is preferably determined by the solubility of the coolant in water. For example, considering the case where ammonium nitrate is used as a coolant, the solubility of ammonium nitrate in water is 118 grams at 0°C and 214 grams at 25°C per 100 grams of water, so the solubility changes depending on the temperature. The mixing ratio of the coolant and the water-containing agent is preferably determined so that the solubility is about 16°C. In the case of ammonium nitrate, 100 grams of water equals 174 grams of coolant.

When applying a ratio of coolant and water-containing agent that matches the solubility of 15°C, the temperature of the solution drops to below 0°C the moment the coolant and water-containing agent are mixed, so some of the coolant remains undissolved. death,
As time passes and the temperature of the liquid gradually increases, the solubility increases and the coolant gradually dissolves. The temperature that feels a little cold to human skin is about 15°C, and up to that point, the coolant gradually melts and absorbs heat, extending the cold storage time.

The water absorbent resin in the present invention is a mixture of an acrylic acid/vinyl alcohol copolymer and a sodium acrylate polymer. Acrylic acid/vinyl alcohol co-polymer resin is stable against heat and ultraviolet light even in a wet state, and swells in water to form a hydrogel, forming a very stable gel. Sodium acrylate polymer resin has a fast water absorption rate and high water absorption capacity, but is known to have low gel stability. When these water-absorbing resins are mixed with a coolant and used as a cooling bag, a portion of the released water-containing agent directly reacts with the coolant and absorbs heat, and a portion is taken into the water-absorbing resin.

Therefore, there is no unnecessarily rapid temperature drop at the initial stage of the reaction, and the water-containing agent released from the water-absorbing resin and the coolant gradually react with each other as the temperature rises, which has the effect of extending the cooling time. However, when these water-absorbing resins are blended alone, the gelling effect of the acrylic acid/vinyl alcohol co-polymer resin is extremely reduced because the solution is an electrolyte, and gel-like formation cannot occur unless a large amount of resin is blended. It became clear. It has also been revealed that gels that have absorbed more water are stable and less likely to release the water-containing agent that reacts with the remaining coolant, resulting in a shorter cooling time. Furthermore, it has been revealed that the sodium acrylate polymer resin is greatly affected by the electrolyte solution and does not become gel-like unless a large amount of resin is used. Therefore, when each is used alone, 10 to 10 parts by weight of coolant are used.
Unless 20 parts by weight or more of resin is blended, it will not become gel-like and the cold storage time will hardly be extended compared to when it is not blended.

As a result of many experiments on blending water-absorbing resins, the above 2.
It has been found that gelation can be achieved with a very small amount of water-absorbing resin. For example, I found that it started to rise and became sherbet-like. The reason for this is not clear, but
This is presumed to be the result of the synergistic effects of the excellent instantaneous absorbency of the sodium acrylate polymer, the crosslinking effect of the composite structure of polyacrylic acid and polyvinyl alcohol, and the stretching effect of the polyvinyl alcohol phase.

Figure 4 shows the results of various combination experiments regarding the appropriate mixing ratio of acrylic acid/vinyl alcohol copolymer resin (hereinafter referred to as A resin) and sodium acrylate polymer resin (hereinafter referred to as B resin). .

The cold storage time in the figure is the temperature of the liquid when conducted using the same experimental method as shown in Example 1 below (70 grams of ammonium nitrate, total amount of water-absorbing resin 7.8 grams, and 46 grams of water-containing agent). This is the time it takes for the temperature to reach 15°C. As is clear from the figure, the total weight of resin A and resin B is 10
When set to 0, even if the blending ratio of A resin is 80% or less, 7
Even if it is 0% or more, the cold storage time will be shortened. Therefore, it has been revealed that the appropriate blending ratio of resin A is 80% to 70%, and within this range, there is almost no difference depending on the blending ratio.

When the above-mentioned water absorbent resin mixture is applied to the cooling bag of the present invention, there is no gelation effect when the content is 8% or less, and 8% to 1%
It is appropriate to mix 0%. The gelation effect increases as the amount is increased, but if it is added in excess of 10%, the water retention agent will be firmly incorporated into the water absorbent resin, interfering with the reaction between the coolant and the water retention agent, so it is difficult to keep it cool. It became clear that time was actually getting shorter. Furthermore, water-absorbing resins are more expensive than coolants, and it is not economical to use them in large quantities.

Next, in the present invention, 1. Water-absorbing resin is mixed and formulated with a coolant to provide a cooling bag with extended cooling time, a soft feel, and a reusable cooling bag.

The water-absorbing resin absorbs the released water-containing agent, releases water depending on the liquid temperature, and the coolant and water react. Therefore, the appropriate amount of the water-containing agent according to the present invention requires a slightly larger amount than the above-mentioned solubility at 15°C. Figure 2 shows the appropriate amount of water-containing agent when changing the blending ratio of the water-absorbing resin. The larger the blending ratio of the water-absorbing resin is, the more the appropriate water content will be.

For example, when using 100 grams of ammonium nitrate as a coolant and mixing it with 4% (4 grams) of water-absorbing resin, from Figure 2, the amount of water equivalent to the solubility of ammonium nitrate (174 grams) at 15°C is 1.15 times as much water-containing agent is required, which can be calculated using the following formula.

The solubility of the coolant used in the present invention in 100 grams of water at 16°C is 50 to 250 grams, and when 8 to 10 parts by weight of water-absorbing resin is mixed therein per 100 parts by weight of the coolant. According to the same calculation as above, the appropriate amount of water-containing agent is 40 to 2 parts by weight per 100 parts by weight of coolant.
The amount is 60 parts by weight.

Example 1 FIG. 1 shows an example of the cooling bag of the present invention, in which a water-resistant outer bag 1 contains an inner bag 2, a coolant 4, and water-absorbing resins 5 and 5'.
is included. Inner bag 2 contains tap water 4 as water retention agent 8
6 grams were enclosed.

This inner bag 2 is easily torn by an external force such as a knock from the outside, and the coolant 4 and water absorbent resin 5 and 6 of the outer bag 1 are removed.
’ can be mixed with

Coolant 4 contains 70% of granular ammonium nitrate of 1-2H.
gram, water-absorbing resin 5 contains 1.4 grams of granular human resin with an average particle size of 0.1 to 0.8 mm, and water-absorbing resin 5'
The powder B resin with an average particle size of 0.021 meters or less is 1
．． Contains 4 grams.

In order to measure the cooling performance of this example, a hole was made in a part of the outer bag 1, a thermometer was inserted through the hole, a seal was made to prevent the liquid inside from leaking outside, and the inner bag 2 was torn. Temperature changes were measured. The cooling capacity of the cooling bag is strongly influenced by the external temperature, so taking this into account, we placed it in a constant temperature bath kept at 80°C and measured the temperature change over time, and the results were reported in the 8th section. Shown in the figure. For comparison, similar tests were conducted on commercially available cooling bags (conventional products C and D). As is clear from the figure, it was found that the cooling bag of the present invention had a smaller initial temperature drop than the conventional product, and could extend the cooling time. In addition, the cooling bag of the present invention becomes sherbet-like when the inner bag 2 is broken and water reacts,
It was also soft to the touch. - After using the product of the present invention and the conventional product 0. Nine conducts an experiment to see if D can be used as a cold storage agent by keeping it in the freezer for six hours.

The results are shown in Table 1, and compared to the conventional product, 1.
It has been revealed that the cold storage effect is 5 to 2.5 times greater.

51 Table Example 2 In FIG. 1, the water retention agent 8 was prepared by adding a small amount of soda carbonate to 66 grams of tap water to adjust the pH to 7.8.

Coolant 4: 56 grams of ammonium nitrate, 1 g of urine 14
The water absorbent resin 6 was made to be 1.8 grams of Mu resin, and the water absorbent resin 6' was made to be 1.8 grams of B resin.

The cooling performance was measured in the same manner as in Example 1, and the results are shown in FIG. 8 and Table 1. In the case of this example as well, it was found that it is softer and has a longer cold storage time than conventional products, and can be reused as a cold storage agent.

As can be seen from the effects of the invention, the cold storage time can be extended significantly compared to conventional products, the product has a good texture, can be reused many times, and can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an embodiment of the present invention.
A graph showing the amount of water-containing agent required when the water-absorbing resin of the present invention is blended. Figure 8 is a graph showing the cold retention performance of the product of the present invention and a conventional product. Figure 4 is a graph showing the amount of water-containing agent required when the water-absorbing resin of the present invention is blended. It is a graph showing the relationship between the blending ratio of A resin and B resin and the cold storage time. 1... Outer bag, 2... Inner bag. 8... Water-containing agent, 4... Cooling agent. 5.5'... Water-absorbing resin. Agent Patent Attorney Ya Watanabe - Figure 19 Figure 2

Claims (1)

[Claims] 1. A cooling bag consisting of an inner bag filled with a water-containing agent and an outer bag filled with a coolant and a water-absorbing resin, wherein the water-absorbing resin is made of acrylic acid/vinyl alcohol copolymer and sodium acrylate. A cooling bag characterized by being made of a mixture of polymers.