JPS5953576A - Improvement of heat insulation agent - Google Patents

Abstract

PURPOSE:To obtain a low temp. heat insulating material usable for a long period, having low variably of quality, by adding a chelating agent to react with an alkaline earth metal ion to form a water-soluble chelate compound to a low temp. heat insulating material of water-containing gel consisting of PVA and sodium borate. CONSTITUTION:A low temp. heat insulation material consisting of water-containing gel comprising water, PVA, and sodium borate as main agents is blended with a chelating agent (e.g., ethylenediamine tetraacetate, etc.) to react with an alkaline earth metal ion (e.g., calcium ion, etc.) to form a water-soluble chelate compound in an amount to give an equivalent with alkaline earth metal ion in water, to improve the low temp. heat insulation material.

Description

[Detailed description of the invention] The present invention relates to a method for improving a hydrogel ice pack.

More specifically, it is characterized in that a chelating agent that forms a water-soluble chelate compound with alkaline earth metal ions is added to an ice pack made of a water-containing gel mainly composed of water, polyvinyl alcohol, and sodium borate. This invention relates to a method for improving a hydrogel ice pack. Water here refers to polyvinyl alcohol.

A hydrogel composed of sodium borate as a main ingredient refers to a known gel-like substance that is produced when sodium borate is added as a gelling agent to an aqueous polyvinyl alcohol solution. However, in addition to the above-mentioned main ingredient, the gel-like substance may contain auxiliary agents such as 11-hydric acid as a gelling aid, alcohols as a freezing point depressant, and a fungicide to prevent mold from forming in the gel. It also includes cases where auxiliary agents are contained. Such a gel-like substance (hereinafter referred to as polyvinyl alcohol) (sodium nitrate-based hydrous gel is simply referred to as Meishui Gel-O or Gel) is used in bags and bottles made of plastic films such as polyvinyl chloride and polyethylene. JJ71i is aware that it is widely used as a refrigerant for cold preservation, that is, as a cold storage agent, to keep food and drinks and fish and fish cold, and for medical purposes, as an ice pillow and a substitute for ice packs.

E: El + 1 shot ψjet this bo υ vinyl alcono + 7. This invention provides a method for adding a chelating agent that forms a water-soluble chelate compound with an alkaline earth metal to a sodium oxalate thread water-containing gel ice pack,
Effects (1) Longevity of conventional products The water-containing gel of the present invention without the addition of a chelating agent has the drawback that it changes over time in a relatively short period of time, resulting in a decrease in cold storage performance. While it is relatively difficult to manufacture a small number of products, the method of the present invention improves the drawbacks of conventional products such as tel j i+, which causes less deterioration over time and can be used for a longer period of time. The point is that the quality of products can be improved with less variation in quality between products.

Conventional polyvinyl alcohol, sodium oxalate rt
zl< Gel ice packs have the disadvantage that they change in temperature over a relatively short period of time, resulting in a decrease in cold storage performance (like soil GIE), and it is difficult to produce products with little variation in quality during manufacturing. It has the disadvantage of being relatively hard IAa.I will explain this further.

Regarding the decline in cold storage performance due to slow change (C)' While repeating the process, the gel, which was colorless and transparent at the time of manufacture, changes color over time.
1. It becomes a local state, and the adhesiveness of the gel decreases in parallel with the coiling. For example, even if you cut the gel and put the two pieces together, it will not restore due to the deterioration of the adhesive force. After being used, a syneresis phenomenon occurs.

The ice pack in this state not only looks good but also looks like
I.

Heat exchange with the outside world increases due to convection of water, which reduces cold storage performance, and also reduces dimensional stability due to deterioration of adhesiveness. This type of change over time also occurs when the ice pack is left at room temperature, but normally it progresses slowly at 1σ, and the above-mentioned freezing
This is a phenomenon that occurs noticeably when freezing occurs repeatedly.

It is relatively difficult to produce chestnut products with little variation in quality. There is a considerable difference in the degree of the above-mentioned change over time between products manufactured using the same raw materials under conditions that are above the apparent level.
There is L. For example, it is made with apparently the same raw materials and manufacturing thread production (7
Example 11: After using a product for one month, it exhibits a konnyaku-like appearance.
H: In disputes over the use of the same material, it sometimes happens that no significant change is observed for more than 6 months. The reason is t!
It's not clear.

The present invention uses conventional polyvinyl alcohol,
Since sodium-based self-hydrating gel ice packs have the above-mentioned drawbacks, research has been conducted to eliminate these drawbacks and improve the ice pack W, which is more stable and can be used for a longer period of time. It was a success. That is, the following was clarified as a result of the research according to the present invention 1. The present invention was invented based on this result.

1 Polyvinyl alcohol, #1 Sodium borate hydrogel ) Alkaline earth gold A present in the water used
11 Adverse effects of calcium ions on I + 'lν I
These 'alkaline earth metal ions, particularly calcium ions, significantly accelerate the aging of the gel even if only a small amount of 'C' is present.

2. When chelating agents that form water-soluble chelate compounds with alkaline earth ions open the chain of these ions, the harmful effects of these ions can be blocked. However, there are considerable differences in the effects depending on the type of chelating agent, and ethylenediaminetetacetate is particularly superior.

3. By using the chelating agent mentioned above, the variation in the interstitium of flql can be reduced.

The actual 17Q if1] will be listed and explained below. Hydrogel ice packs have various compositions depending on the purpose of use, and the composition given in the experimental example is one example.

Test example: Drug polyvinyl alcohol (hereinafter referred to as PVA; 1α): A4
1ζ type 1 meeting Ne1ri La Shikou PVA-117 (average degree of polymerization 175o ± 50° phosphoric rcqa, s ± 0.5mot
%, PVA content 94.0 or more) Chelating agent: Dibutorium dibutylene diamine ditrapercentate (EDTA N11.) Reagent Special grade.

All other drugs are reagent grade. used.

Purity of water used Water: Distilled water Tap water Analytical value pH 6,92*Hardness Oa OOs conversion 72. I PPM, solid content 1100
P.P.

Ground water: well water 9 analysis value PH8.2, hardness Oa 0
0 a conversion: 117 PPM, solid content: 197 PM Sample Preparation: Dissolve 5 parts by weight of PVA in 90 parts by weight of water at a temperature of 80°C or higher, and in the case of adding EDTAN a, add and dissolve a predetermined amount of this. A solution prepared by dissolving 0.5 parts by weight of sodium borate in 10 parts by weight of water at a temperature of 80° C. or higher is added to this solution while stirring, mixed well, and then allowed to cool. The solution forms a colorless and transparent hydrogel.

Approximately 10 of this gel was packed into a colorless and transparent polyethylene film bag to serve as an experimental sample.

Experimental method: Leave the sample in a freezer at -20°C for 15 hours or more to allow it to solidify.
I left it for more than an hour to let it thaw naturally. Repeat this operation 10 times and visually observe the state wA (degree of transparency) of the sample when it is thawed during that time.If no change is observed, that is, if it remains colorless and transparent at the time of preparation, If a decrease in transparency is observed, it is acceptable.If there is obvious cloudiness or cloudiness, depending on the degree, the soup bowl will be illuminated.

Experimental result It is shown in Table 1 to Table 5.

懺１ Effects of Water Quality From the experimental results of Table 1, the changes in hydrogel over time, that is, the decrease in transparency and cloudiness, differ depending on the quality of the water used, and in the order of groundwater, tap water, and pure water. You can see that it progresses faster. In the case of groundwater with a high degree of hardness, this tendency is particularly severe and the colorless and transparent state at the time of preparation cannot be maintained even after the first freezing and thawing. However, even in the case of pure water, there is no change over time, and as the number of times of freezing and thawing increases, a slight decrease in transparency is observed.

This can be said to suggest that the cause of the decrease in melt transparency is not necessarily limited to the hardness of toilet water.

Next, we investigated the effect of adding BDTA Na to tap water and groundwater, and the experimental results shown in Table 2 show that the addition of BDTA Na significantly inhibits gel change over time, and when used in an appropriate amount, the effect is the same as when using pure water. It can be seen that it has Table 3 shows the effects of adding calcium compounds and magnesium compounds to pure water, and investigating the effects of these alkaline earth metal ions on clouding the gel, as well as the effects of using BI)TA and rJst in combination. This is the result of an experiment. The results show that the addition of these alkaline earth metal compounds has the effect of accelerating the clouding of the begel compared to the tal mixture (pure water data in Table 1), and is particularly noticeable in the case of calcium compounds. In fact, it can be seen that this effect is almost completely inhibited by the combined use of F+DTANat. Table 4 is an experiment conducted in connection with the experiment in Table 2 to determine the appropriate amount of BDTA Na2, and the results show that excessive use of EDTA Na2 has the effect of promoting clouding. Table 5 shows the amount of EDTA Na in pure water that is larger than usual.
2 and [EDTA, Oa) Nag wo wazo Jq
, and in a model experiment in which both were added together, EDTA
It can be seen that while Na2 has a clouding promoting effect, a chelate compound of this and calcium does not have this effect.

As shown in the above experimental results, one of the main causes of accelerated aging of polyvinyl alcohol and sodium balate-based hydrogel ice packs is the harmful effect of alkaline earth metal ions, especially calcium ions, contained in the water used. Since it is clear that water that does not contain these ions can be used to achieve the object of the present invention, it is possible to achieve the purpose of the present invention by using water that does not contain these ions. To remove calcium ions, use the appropriate equipment and number of units.

Moreover, if the chelating agent of the claimed invention is used b D T A
t'' of the clouding prevention effect of ν1 gel with addition of Na2,
On the upper side 6- As a primary effect, the ipsilateral side has mold prevention that prevents the growth of mold in the hydrous gel 1 and 1. It also has the advantage that it works effectively even when the method is used, so when this point is taken into consideration, the method of the present invention is also used.

As the chelating agent used in the invention, any agent can be used as long as it can effectively cleave alkaline earth metal ions, especially calcium ions, in an aqueous solution. In addition to the above-mentioned ethylene shea and tetraacetate, examples of such drugs include nitrilotriacetate,
Examples include diethylene triamine (penquacetate), triethylenetetramine (hexaacetate) IN-hydroxyethylethylenediamine triacetate, and ethylenediaminetetraprobionate.

However, there are some differences in effectiveness among these drugs. Among them, ethylenediaminetetraacetate is highly effective and is particularly recommended. Compared to this, for example, nitrilotriacetate is slightly less effective, and for example, diethylenetriapone pentaacetate is even less effective. The cause is not clear.

In the present invention, the amount of the chelating agent added to the hydrous gel cannot be generalized because it varies depending on the amount of alkaline earth metal ions, especially calcium ions, in the water used, but it is appropriate to approximately equivalent amount to these harmful ions. ．． It is. Normal industrial water is generally 0.01 to 0.1% by weight, and at most 0.01% by weight.
2% by weight will make your feet stronger. As mentioned earlier in the explanation of the experimental examples, excessive use of ethylenediaminetetraacetate has the effect of promoting clouding of the gel, and care must be taken when attempting to utilize the above-mentioned antifungal effect.

The method of adding the chelating agent is usually either in a pv ice aqueous solution or in a sodium bamboo borate aqueous solution: it is convenient to add and dissolve it in advance, but any other method can be used as appropriate.

Examples of implementing the present invention are shown below.

Example 1 5 parts of polyvinyl alcohol with a degree of polymerization of 1750 and a degree of saponification of 99 degrees, and 0.032 parts by weight of disodium ethylenediaminetetraacetate were dissolved in 90 parts by weight of water containing calcium ions at an Oa OOs exchange rate of $72 PPM at a temperature of 90°C. To this solution, a solution prepared by dissolving 0.5 parts by weight and 1 part of sodium borate in 1 part by weight of the same water at a temperature of 90° C. is added with stirring, mixed well, and then allowed to cool. The mixture will become a colorless, transparent, jelly-like hydrogel.

In the freeze-thaw test described above (text experiment example), this water-containing gel showed a decrease in transparency at the third freeze-thaw in the case without the addition of disodium ethylenediaminetetraacetate.
The original colorless and transparent state was maintained for more than 100 times.

Example 2 Degree of polymerization: 1710. 2 parts by weight of polyvinyl alcohol with a saponification degree of 98aIb and 0.0 parts of disodium nitrilotriacetate
2 parts by weight were dissolved in 1 part by weight of 80 parts of water containing calcium ions of 72 PPM in terms of Oa OO @ at a temperature of 90°C, and to this solution, 0 parts by weight of sodium borate was dissolved in 1 part by weight of 20 parts of the same water.
．． A solution prepared by dissolving 6 parts by weight at a temperature of 90° C. was added with stirring, mixed well, and then allowed to cool. The mixture will become a colorless, transparent, jelly-like hydrogel.

In the case of the water-containing gel without the addition of nitrilotriacid-resistant disodium, a decrease in transparency was observed in the first freeze-thaw test, but it maintained its original colorless and transparent state for more than 10 times.

Patent applicant: Toshin Co., Ltd. Representative Natsuko Otaki

Claims (1)

[Scope of Claims] l A chelate forming a compound with an alkaline earth metal ion (water-soluble)/1 chelate 1 in a cold pack made of a water-containing gel composed of water, polyvinyl alcohol, and sodium balate as main ingredients. 14. A method of producing the hydrogel ice pack, which is characterized in that the agent is mixed in a 14-way direction. 2. The feature of adding ethylenediaminetetra-7tate as a chelating agent. 3. The method for improving the hydrogel ice pack according to Claim 1, Item 11. 3. Addition h1 of ethylenediamine-tetra-7tate 111i The method for improving a water-containing gel ice pack according to claim 2, wherein the ratio of W to mold 11 is 0.001 to 0.2.