JP2665787B2 - ice pack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a freshener such as seafood, ham, vegetables and the like, and a cold-keeping agent used for keeping freshness and keeping cold during the distribution of juice, wine, blood and the like. It is about.

(Prior Art and Problems) Conventionally, fish and shellfish have been distributed in boxes together with ice. However, ice has a short cooling time, and there is a problem that the melted water comes into contact with foods and the like to be soiled or leaked to the outside.

In order to make up for these drawbacks, bags or plastic containers made of polyethylene or the like have recently been filled with a liquid or gel-like material, and the frozen product has been widely used as a cooling agent.

Of these, gel-filled ones are mainly used because those filled with a liquid may cause the contents to flow out due to bag breakage and contaminate foods and the like.

Guar gum, polyvinyl alcohol, sodium polyacrylate, polyacrylamide, sodium carboxymethylcellulose (hereinafter abbreviated as CMC) as a gel composition to be filled in a cool bag or a plastic container,
High-viscosity aqueous solutions of water-soluble polymers such as sodium alginate, starch, and starch grafted with acrylic acid or acrylamide, or cross-linking these water-soluble polymers with inorganic salts such as borates or organic cross-linking agents A hydrogel is used.

However, a high-viscosity aqueous solution of a water-soluble polymer gradually flows out when the cold storage bag is broken or the plastic container is broken, and furthermore, because of its tackiness, there is a disadvantage that it adheres to foods and the like and becomes soiled.

On the other hand, guar gum and polyvinyl alcohol formed by forming a complex with a borate to form a gel have no tackiness but still have fluidity. Because of this, the contents may flow out due to bag breakage, etc., and even if the bag breaks etc. do not occur, it will flow and change the shape, so it may be frozen as a deformed shape,
When packaging in a heat insulating material, it had the drawback that packaging was not possible.

Further, guar gum contains proteins, fats, and the like in its components, and is a nutrient source for microorganisms, and thus has a drawback that it easily rots during preparation or distribution.

In addition, crosslinked products of polyvinyl alcohol, sodium polyacrylate, and polyacrylamide and those obtained by graft-polymerizing acrylonitrile or acrylic acid to starch have no tackiness and low fluidity, but are filled in bags, etc. The gel is easily broken by touching the product with hand or vibrating during transportation.If the gel is sealed in a bag and exposed to sunlight, the cross-links are released and the viscosity is reduced, and the gel becomes liquid. There is a drawback that the substance may separate. In addition, there is a possibility that the liquid that has been separated from the bag when the bag is broken flows out and soils foods and the like.

These water-soluble polymers and cross-linked polymers are usually 4 to water.
It is used at a concentration of 1515%, and when added as a refrigerating agent by adding a large amount thereof, the latent heat of fusion is reduced, and there is also a disadvantage that the refrigerating time, which is the original function, is shortened.

An aqueous gel obtained by gelling CMC with a polyvalent metal salt is an excellent cooling agent that solves the above-mentioned problem, but the gelation rate is too high, so that the aqueous gel is filled into a bag or the like by an automatic filling machine. There was a drawback that the work became difficult.

The present invention has been achieved as a result of intensive studies to solve these disadvantages.

(Means for Solving the Problems) That is, the present invention is a cooling agent comprising an aqueous gel of carboxymethylhydroxyethylcellulose polyvalent metal salt.

Sodium carboxymethyl hydroxyethyl cellulose (hereinafter abbreviated as CMHEC) used in the present invention can be prepared by a known method (for example, US Pat. No. 2,618,632, US Pat. No. 3,467,955).
Or the method described in JP-B-48-18586), the cellulose is converted into an alkali cellulose, then carboxymethylated with monochloroacetic acid, and further reacted with ethylene oxide to be hydroxyethylated, or conversely, the alkali cellulose is firstly converted. And hydroxycarboxymethylation with ethylene oxide, followed by reaction with monochloroacetic acid to carry out carboxymethylation.

Degree of substitution (DS) of carboxymethyl group of CMHEC of the present invention
Is preferably 0.3 to 1.5, more preferably
It is in the range of 0.4 to 1.0. Even with a DS of 0.3 or less, the compound is dissolved in water due to the presence of the hydroxyethyl group, but the presence of the hydroxyethyl group suppresses gelation due to the polyvalent metal salt, and it is difficult to develop the necessary rigidity as a cooling agent.

On the other hand, the degree of molar substitution of the hydroxyethyl group of CMHEC (M
The preferred range of S) is 0.5 to 4.0, more preferably 0.7 to 3.0. With MS of 0.5 or less, the suppression of the gelation rate by the hydroxyethyl group is not sufficient, and the elasticity of the obtained aqueous gel is not sufficient. MS 0.7
By doing so, a desired aqueous gel in which the effect of the hydroxyethyl group is exhibited can be obtained. On the other hand, when the MS is 4.0 or more, the side chain tends to be long, and the gelation rate can be suppressed, but the generated gel has fluidity, and may flow out at the time of bag breaking or may be deformed in the bag. is there. This trend is MS
Although it is slightly recognized even at 4.0 or less, it has a sufficient function as a cooling agent. But if you want to be perfect, MS is 3.0
It is desirable to do the following.

The viscosity of a 1% aqueous solution of CMHEC of the present invention is 10 to 10,000 c.
The range of ps is preferred. At 10 cps or less, since the molecular chain is short, it is difficult to generate a three-dimensional structure. If the concentration is not high, an aqueous gel having a desired hardness cannot be obtained. CMHEC of 10,000cps or more
In this case, it has a high viscosity itself, it is difficult to uniformly mix with the gelling agent, and it is difficult to obtain a uniform aqueous gel.
If the concentration of CMHEC is lowered to 1.5% or less to facilitate mixing with the gelling agent, it becomes difficult to obtain an aqueous gel having a desired hardness.

As polyvalent metal salts used as a gelling agent for CMHEC,
Aluminum compounds, iron compounds, chromium compounds and the like can be used. However, since iron compounds and chromium compounds have problems such as coloring, it is preferable to use aluminum compounds capable of preparing a colorless and transparent gel. As the aluminum compound, potassium alum, aluminum acetate, aluminum sulfate, aluminum nitrate and the like can be used.

The refrigerating agent of the present invention can be obtained by adding an aqueous solution of a polyvalent metal salt to an aqueous solution of 0.5 to 10% by weight, preferably 1.5 to 5% by weight of CMHEC, and mixing and gelling. In this case, a uniform gel can also be obtained by mixing CMHEC wetted or dispersed with glycerin, ethylene glycol, ethanol or another new aqueous organic liquid with an aqueous solution of a polyvalent metal salt.

In preparing the cooling agent of the present invention, preservatives, coloring agents, polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, and sorbitol for adjusting the freezing temperature (cooling temperature), sodium chloride, potassium chloride, and nitric acid. The addition of salts such as sodium and sodium sulfate is also included in the scope of the present invention.

In addition, other water-soluble polymers such as guar gum, polyvinyl alcohol, sodium acrylate and the like can be used in combination with CMHEC.

(Effects of the Invention) The aqueous gel composed of these polyvalent metal salts of CMHEC does not rot because it does not contain substances that cause decay, such as proteins and fats. In addition, it has a three-dimensional strong structure due to an ionic reaction, has little fluidity, and is a stable cooling agent that does not cause remarkable lowering of viscosity or water separation due to detachment of crosslinking due to light or the like.

In addition, since the aqueous gel of CMHEC polyvalent metal salt can be prepared at a concentration of 1.5 to 5%, which is lower than 4 to 15% of other water-soluble polymers, the maximum heat of fusion of water can be maximized. Since it can be used, it has the feature that it is possible to maintain a long cooling time, which is the most important function as a cooling agent. This is because CMHEC is a rod-shaped polymer, so the spread of molecules in solution is large,
This is probably because a large three-dimensional structure is easily formed.

Further, since the gelation rate of the aqueous gel of the CMHEC polyvalent metal salt is suppressed, the filling operation of the bag or the like with an automatic filling machine is easy. In addition, the aqueous gel which has been completely gelled after filling has elasticity, and has the advantage that the gel is less likely to be broken during handling of the cooling agent.

It is considered that these properties are due to the fact that the formation of the three-dimensional structure by the carboxyl group and the polyvalent metal ion of CMHEC is suppressed by steric hindrance and molecular motion of the hydroxyethyl group.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples. In Examples,% indicates% by weight, and part indicates parts by weight.

Example 1 DS0.45 of carboxymethyl group, hydroxyethyl group
MS1.80, CMHEC2.5% aqueous solution 1 with 1100 cps viscosity
Charge 00 parts into a 300 ml beaker. It was then charged in small portions with stirring _{(2 O Al 2 O (CH} 3 COO) 4 · 4H) 5% aqueous solution of 6.3 parts of aluminum acetate, subsequently stirring is continued for 4-5 minutes.
Thereafter, the mixture was filled in a plastic bag and allowed to stand for 6 to 12 hours to prepare a cooling agent.

 Table 1 shows the physical properties of the prepared cold insulator.

Comparative Column 1 A cooling agent was prepared in the same manner as in Example 1 using CMHEC having a viscosity of 1080 cps of a DS0.26, MS1.80, 1% aqueous solution, and the physical properties thereof are shown in Table 1.

Examples 2 to 7 MS and addition amounts of carboxymethyl group DS and hydroxyethyl group of CMHEC, and the amount of aluminum acetate added was changed to prepare a cooling agent in the same manner as in Example 1.

 Table 1 shows the physical properties of the prepared cold insulator.

Comparative Example 2 A cooling agent was prepared in the same manner as in Example 1 by using CMHEC having a viscosity of 1060 cps of an aqueous solution of DS0.45, MS0.45, and 1%, and the physical properties thereof are shown in Table 1.

Comparative Example 3 DS1.57, MS1.82, 1% aqueous solution of CMHEC with viscosity of 1020 cps
Charge 100 parts of a 2.5% aqueous solution into a 300 ml beaker. Next, 7.2 parts of a 5% aqueous solution of aluminum acetate is charged little by little while stirring, and stirring is continued for 4 to 5 minutes. Thereafter, the mixture was filled in a plastic bag and allowed to stand for 6 to 12 hours to prepare a cooling agent.

 Table 1 shows the physical properties of the prepared cold insulator.

Comparative Example 4 A cooling agent was prepared in the same manner as in Example 1 using CMHEC having a viscosity of 8,700 cps of a DS0.61, MS4.08, 1% aqueous solution, and the physical properties thereof are shown in Table 1.

Example 8 In the same manner as in Example 1, a cooling agent was prepared using ferric chloride instead of aluminum acetate as a polyvalent metal salt.
The physical properties are shown in Table 1.

Comparative Examples 5 to 8 The physical properties of a cooling agent prepared with CMC and a commercially available cooling agent using guar gum and sodium polyacrylate were shown as comparative examples.

Method for evaluating physical properties of cold insulator (1) Hardness A gel material was cut into 2 cm cubes, and a cylindrical rod having a contact area of 1 cm ² was placed at the center of the gel material, and a predetermined weight was placed on the rod. A weight of a weight was placed thereon, and the hardness was measured by the total weight [g] of the weight of the cylinder and the weight when the cylinder penetrated or broken into the gel-like material.

It is considered that this weight is required to be 30 g / cm ² or more as a cooling agent.

(2) Fluidity 100 g of gel material is filled in a polypropylene bag of 10 cm length, 9 cm width and 0.07 m / m thickness, heat sealed, and one side of the plastic bag is fixed with clips and suspended for 4 hours. .

 The shape change at this time was evaluated based on the following criteria.

：: No change in shape △: Slightly change in shape ×: Remarkably change in shape (3) Adhesion After holding a 2 cm cubic gel-like material with a forefinger thoroughly wiped with a dry towel, the gel-like material adheres to the finger. The degree was evaluated according to the following criteria.

：: Not adhered to the finger at all △: Slightly adhered to the finger ×: Adhered significantly to the finger (4) Cooling time 20 g of gel was packed in a bag made of polypropylene and -20
After leaving it in a freezer at 20 ° C. for 20 hours to completely freeze it, it was left in a thermostat at a temperature of 25 ° C., and it was sometimes judged whether or not thawing was performed with a Teflon round bar (5 mm diameter), and the cooling time (min) was measured.

(5) Separation 20g of the gel is packed in a polypropylene bag and stored at -20 ° C.
After 20 times of freezing and thawing at 25 ° C. for 4 hours were repeated 5 times, the water separation state was evaluated according to the following criteria.

：: No water separation △: Slight water separation ×: Extremely water separation (6) Putrefaction 20 g of a gel was filled in a polypropylene bag and left at room temperature for 30 days to check for decay. When decayed, mold generation and viscosity reduction water separation were observed.

：: no decay ×: decay was observed (7) Light stability The gel was filled in a polypropylene bag and allowed to stand three times for 8 hours under sunlight. The subsequent state change was evaluated according to the following criteria.

：: No change △: Slightly separated and softened ×: Significantly separated and viscosity decreased (8) Gelation speed It is said that the viscosity that can be filled by an automatic filling machine is 50,000 cps or less. The time required to reach 50,000 cps after mixing the gelling agent and the water-soluble polymer was evaluated according to the following criteria.

○: 1 hour or more △: 3 to 59 minutes ×: 3 minutes or less

Claims (1)

(57) [Claims] (1) a carboxymethyl group having a degree of substitution of 0.4 to 1.5;
A cold preservative comprising an aqueous gel of carboxymethyl hydroxyethyl cellulose polyvalent metal salt having a hydroxyethyl group substitution degree of 0.5 to 3.0.