JPS6154073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a gel-like cold storage agent that is pre-cooled in a refrigerator or freezer and used to cool various objects or the human body when necessary.

Conventionally, various types of cold storage agents have been proposed, but most of them are ones that are made by dispersing or dissolving water-soluble polymers and are fluid at room temperature, or are made into gels that are placed in bags or various containers. It is something that
Among these cold storage agents, those that are in sol form at room temperature may flow out and wet or stain the object to be cooled if the bag or container is damaged at room temperature. Gel-like products are becoming more popular among consumers. In addition, the cool storage agent must have the ability to sufficiently cool the object to be cooled, and for this purpose, the material used for the cold storage agent must have a large heat of fusion and specific heat. Water is the cheapest and most suitable such substance. Furthermore, since cold storage agents are used to cool food and the head and affected areas of the human body, in the unlikely event that the bag or container containing them is damaged, the contents may come into contact with food or the human body. It must be highly safe so that there will be no problems even when it is used. For this reason, the present inventors conducted various studies in order to obtain a cold storage agent that contains as much water as possible, is gel-like at room temperature, and is highly safe.

Various gel-like cold storage agents have been proposed in the past, but they have had problems in terms of safety and toxicity, and the gel's freezing resistance is poor, and water may separate when repeatedly frozen and thawed. Furthermore, when the water content is low, there is no separation of water by repeated freezing and thawing, but the cooling capacity is small and the cooling capacity is small, so a fully satisfactory product has not yet been obtained. In particular, there is an antinomic relationship between increasing the water content and improving the freezing resistance of the gel.The higher the water content, the worse the freezing resistance of the gel. Moisture content must be reduced.

The present inventors have completed the present invention as a result of intensive studies to obtain a gel body that can fully satisfy all of these antinomic requirements.

That is, the present invention involves mixing borax or/and boric acid into a colloidal aqueous dispersion containing 2 to 10% by weight of galactomannan, 0.5 to 5% by weight of pregelatinized starch, and 0 to 20% by weight of propylene glycol. This is a method for producing a gel-like cold storage agent, which comprises gelling the colloidal water dispersion.

The present invention requires that galactomannan and pregelatinized starch be used together as gel-forming substances. By using galactomannan and pregelatinized starch together, a stable gel body with excellent freezing resistance and no separation of water even after repeated freezing and thawing can be obtained despite the extremely high water content. It will be done.

The amounts of galactomannan and pregelatinized starch are 2 to 10% by weight, respectively, in the colloidal water dispersion.
It is necessary to set the amount to 0.5 to 5% by weight; if it is outside the above range, the gel's freezing resistance will be poor, and water will separate when freezing and thawing are repeated. In particular, 3-6% by weight of galactomannan, 1% by weight of pregelatinized starch
An amount of ~3% by weight is preferable in terms of the freezing resistance of the gel.

Examples of galactomannans that can be used in the present invention include guar gum and locust bean gum, with guar gum being particularly preferred. Although propylene glycol is not an essential component, in order to disperse galactomannan and pregelatinized starch in water, first wet them with propylene glycol and then mix with water to disperse galactomannan and pregelatinized starch. A homogeneous dispersion can be easily prepared, and when gelled, a gel with high elasticity is obtained, and it also helps to lower the freezing point of the gel, but as the amount increases, the heat capacity of the gel body decreases, making it difficult to use as a refrigerant. The function as such is impaired.

In the present invention, a preferred method of preparing the colloidal water dispersion is to wet the galactomannan with a small amount of propylene glycol, then mix with water, homogenize, and then add starch to the α- A method of mixing a colloidal aqueous dispersion of modified starch also involves wetting galactomannan and already commercially available pregelatinized starch with a small amount of propylene glycol and then mixing with water.
This is a method of homogenization.

Examples of pregelatinized starches include corn starch, sweet potato starch, potato starch, wheat starch, rice starch,
Various starches such as tapioca starch can be used after being pregelatinized, and various commercially available pregelatinized starches obtained by pregelatinizing the above-mentioned starches can also be used. Galactomannan and α thus prepared
The colloidal water dispersion of starch is thoroughly mixed to make it homogeneous, and the galactomannan and α
It is necessary to continue stirring and mixing for a certain period of time so that the -converted starch is sufficiently hydrated.

Next, borax or/and boric acid are mixed into the colloidal water dispersion to gel the colloidal water dispersion. In this case, the degree of gelation is very important; if the degree of gelation is too strong, the gel will freeze,
If thawing is repeated, the water will separate, and if the degree of gelation is too weak, the contents will become a gel that will be pushed out if the bag or container containing it is damaged. It is not preferable as a cold storage agent for the purpose of the invention.

While conducting studies on gelation using borax and/or boric acid, the present inventors found that when borax or boric acid is used alone, it is 0.01 to 2% by weight, preferably 0.05% by weight, based on the colloidal dispersion. It is sufficient to use ~1% by weight, and gelation can be controlled by using boric acid, other inorganic acids, and organic acids in combination, and in this case, the amount of these acids should be appropriately controlled regardless of the amount of borax. It has been found that a gel with favorable performance can be obtained. The acid that can control gelation is most preferably boric acid, but examples include inorganic acids such as carbonic acid, hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as acetic acid, citric acid, tartaric acid, and sorbic acid. When boric acid is used in combination with borax, there is no particular quantitative range and it can be used as appropriate depending on the quantitative balance with borax. It may be used in an amount such as %. When using boric acid alone, adjust the pH so that the gel is slightly basic.
need to be controlled.

Borax and boric acid may be mixed in the form of fine powder with the aqueous dispersion of galactomannan and pregelatinized starch, but it is preferable to mix them after dissolving them in a small amount of water. The borax may then be mixed in, but preferably they are mixed into the colloidal dispersion of galactomannan and pregelatinized starch at the same time.

The cold storage agent obtained by the present invention includes colorants, fragrances,
Various other components such as preservatives, fungicides, freezing point depressants, and crystal formation inhibitors can be contained.

In particular, when producing a cold storage agent used to cool objects that are to be cooled to a temperature lower than 0°C, a freezing point depressant such as sodium chloride or calcium chloride is used to solidify at an appropriate temperature. You can control it like this.

Furthermore, since various reversible thermochromic substances have recently been developed, it is also possible to disperse such substances into the gel-like cold storage agent of the present invention so that the temperature of the cold storage agent can be immediately determined. can.

The gel-like cold storage agent obtained in the present invention has elasticity,
It also has mechanical strength, and even if the container is damaged, it will not be pushed out. Even if it does get out of the container, it can be easily removed because it is a gel, and even if it comes into direct contact with food, the gel will not be pushed out. The body is highly safe and there are no problems.

In addition, since it contains a large amount of water, it has an extremely large heat capacity, so it has a large cooling capacity, and even after repeated freezing and thawing, water does not separate, making it extremely resistant to freezing.

The gel-like cold storage agent obtained by the present invention can be used, for example, in bags or containers made of synthetic resin of various shapes to cool the head or affected areas of the human body, or to preserve various foods or cool them during transportation. It can also be used as a cooling medium for various types of gear.

In particular, it is extremely useful as a medium for storing and transporting cold energy, as the use of nighttime electricity and the use of natural gas cold energy are being discouraged due to recent energy conservation issues.

EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Example 1 5 parts by weight of guar gum plus propylene glycol
After adding 10 parts by weight and moistening, add 80 parts by weight of water,
Mix and continue stirring with a kneader for about 10 minutes.
A colloidal water dispersion of guar gum is prepared.
On the other hand, 2 parts by weight of cornstarch is dispersed in 10 parts by weight of water and then heated to about 80°C to prepare an aqueous dispersion of pregelatinized starch. The thus prepared aqueous dispersion of pregelatinized starch was added to the above aqueous dispersion of guar gum, stirred and mixed in a kneader until a homogeneous state was obtained, and then 0.15 parts by weight of borax was added. An aqueous solution obtained by dissolving this in 10 parts by weight of water was added and mixed with stirring to obtain a highly elastic gel-like cold storage agent. The cold storage agent obtained in this way was filled into a glass sample bottle using an extrusion filling machine, placed in a -18℃ freezer, frozen, and thawed repeatedly. However, almost no water was separated during thawing. Nakatsuta.

Example 2 2.5 parts by weight of potato starch and 90% water heated to 100°C
This colloidal dispersion was mixed and stirred in a kneader for about 15 minutes with 4.5 parts by weight of guar gum moistened with 5 parts by weight of propylene glycol to form a homogeneous colloidal dispersion. Prepare a dispersion. Thereafter, an aqueous solution obtained by dissolving 0.5 parts by weight of boric acid and 0.2 parts by weight of borax in 10 parts by weight of water was added and further mixed and stirred to obtain a highly elastic gel body. This gel body was repeatedly frozen and thawed in the same manner as in Example 1, but water did not separate during thawing.

Example 3 An aqueous solution consisting of 0.4 parts by weight of boric acid, 0.15 parts by weight of borax, and 10 parts by weight of water was used instead of an aqueous solution consisting of 0.04 parts by weight of borax and 10 parts by weight of water, and these aqueous solutions were added and mixed. A gel body was prepared in exactly the same manner as in Example 1 except that 5 parts by weight of common salt was mixed before mixing, and a gel body with excellent performance as in Example 1 was obtained.

Claims (1)

[Claims] 1. A colloidal aqueous dispersion containing 2 to 10% by weight of galactomannan, 0.5 to 5% by weight of pregelatinized starch, and 0 to 20% by weight of propylene glycol,
A method for producing a gelled cold storage agent, which comprises gelling the colloidal dispersion by mixing borax and/or boric acid.