JPS6154074B2 - - 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 and 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 have the disadvantage that if the bag or container is damaged at room temperature, they will flow out and wet or stain the object to be cooled. Gel-like products are becoming more popular among consumers. In addition, the cold storage agent must have the ability to sufficiently cool the object to be cooled.
For this purpose, the material used for the cold storage agent should have a higher heat of fusion and specific heat, and water is the cheapest and most suitable such material. 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 if 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, toxicity, and filling into containers, and the gel's freeze resistance is poor, so it cannot be frozen and thawed repeatedly. Water separates, and if 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 it has not been possible to obtain a fully satisfactory product. be. In particular, there is a trade-off between reducing the fluidity of the gel and making it easier to fill the gel container. It becomes difficult to fill the gel into containers, and gelation must be delayed to maintain fluidity for a long time in order to make it easier to fill the gel into containers.

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, in the present invention, dialdehyde starch is mixed 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 is characterized by gelling a gel-like 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 amount of galactomannan and pregelatinized starch is 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, locust bean,
Among them, guar gum is particularly preferred.
Although propylene glycol is not an essential component, in order to disperse galactomannan and pregelatinized starch in water, first moisten them with propylene glycol and mix with water to disperse galactomannan and pregelatinized starch. Although a homogeneous dispersion can be easily prepared and it is useful for lowering the freezing point of the gel, when the amount is increased, the heat capacity of the gel body becomes small and its function as a cold storage agent 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, an aqueous dialdehyde solution is mixed with the colloidal aqueous dispersion to gel the colloidal aqueous dispersion. In this case, the degree and speed of gelation are very important; if the degree of gelation is too strong, water will separate if the gel is repeatedly frozen and thawed; on the other hand, if the degree of gelation is too weak, water will separate. If the bag or container containing the gel is damaged, the contents will form a gel that will be pushed out. If the gelation rate is too fast, it will be difficult to fill the container, and if the gelation rate is too slow, it will be difficult to fill the container. If the sealed bag or container is damaged, the contents will be pushed out, which is not preferable as a cold storage agent aimed at in the present invention.

By using dialdehyde starch,
When filled into a container, the gel is weakly cross-linked, but after filling, chemical cross-linking results in a gel with high strength and almost no syneresis.

While conducting studies on gelation using dialdehyde starch, the present inventors found that when dialdehyde starch is used alone, it is 0.01 to 5% by weight, preferably 0.1 to 1% by weight, based on the colloidal dispersion.
It has been found that it is sufficient to use % by weight, and that a gel with preferable performance can be obtained by using boric acid and borax in combination and controlling their amounts as appropriate.
When using boric acid and borax together, there is no particular quantitative range; for example, dialdehyde starch 0.1% by weight.
When used, boric acid or borax may be used in an amount of 0.01 to 0.2% by weight.

It is preferable to use dialdehyde starch by dissolving it in hot water, and dissolving it in an aqueous solution to which an acid such as acetic acid is added is stable and convenient for use. When using boric acid or an acid such as acetic acid, adjust the pH to make the gel weakly basic.
need to be controlled.

The cold storage agent obtained by the present invention includes colorants, fragrances,
Various other components such as a preservative and fungicide, a bactericidal agent, a freezing point depressant, and a crystal formation inhibitor 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 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. is highly safe and has 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 in propylene glycol
After adding 10 parts by weight and moistening, 80 parts by weight of water is added and mixed, and mixing and stirring are continued for about 10 minutes using a kneader to prepare a colloidal water dispersion of guar gum. On the other hand, 2 parts by weight of cornstarch is dispersed in 10 parts by weight of water and then heated to about 90 to 95°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 0.2% of dialdehyde starch was added in advance. 4 parts by weight of an aqueous solution obtained by heating and dissolving 3.8 parts by weight of water were added, and the mixture was stirred and mixed to obtain a gel-like cold storage agent. The cold storage agent thus obtained was filled into glass sample bottles using an extrusion filling machine, placed in a refrigerator at -18°C, frozen, and then thawed. Tests were repeated, but almost no water could be separated after 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 2 parts by weight of the same dialdehyde starch aqueous solution used in Example 1, 0.1 part by weight of boric acid, and 0.03 parts by weight of borax in 10 parts by weight of water was added, and the mixture was further mixed and stirred. , a gel body was obtained. This gel body was repeatedly frozen and thawed in the same manner as in Example 1, but no water separated during thawing.

Example 3 Instead of an aqueous solution consisting of 0.1 part by weight of boric acid, 0.03 parts by weight of borax, and 10 parts by weight of water, an aqueous solution consisting of 0.1 part by weight of borax and 10 parts by weight of water was used, and these aqueous solutions were added. A gel body was prepared in exactly the same manner as in Example 2 except that 5 parts by weight of common salt was mixed before mixing, and a gel body with excellent performance as in Example 2 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 gel-like cold storage agent, which comprises mixing dialdehyde starch and gelling the colloidal water dispersion.