JPH0617037A - Cold storage agent composition - Google Patents

Abstract

PURPOSE:To obtain a cold storage agent composition which is resistant to bacterial attack and can give an aqueous solution which is still highly viscous and behaves as a non-Newtonian fluid even when the amount of the constituent water-soluble cellulose ether problematic in storage stability is reduced. CONSTITUTION:The composition is prepared by adding 0.3-1wt.% water-soluble cellulose ether to a colloidal silica sol having a silica content of 10-40wt.% and a particle size of 100mum or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to cold storage in the medical field,
The present invention relates to a cold-preserving agent composition used for keeping cold and storing fresh food, and particularly to a highly viscous cold-preserving agent composition having excellent viscosity stability.

[0002]

2. Description of the Related Art A viscous aqueous solution placed in a water-insoluble plastic bag such as polyethylene and frozen in a freezer is used as a cooler. This ice pack has an appropriate viscosity in the ice pack solution in the temperature range of about 5 ° C where substantial performance is expected, and for medical use, the ice pack changes its shape appropriately along the affected area, and then its shape It is devised so that the cooling effect of the affected area is exhibited while maintaining the above-mentioned condition, and in the case of fresh food, the cooling effect is exhibited in the form of the shape of the fresh food or the shape of the fresh food container.

Further, the ice pack is designed so as to have an appropriate viscosity so that even if the ice pack bag is damaged during use or after use, a large amount of the contents will not leak out at once. In order to prepare an aqueous solution of a cooling agent having such a viscosity, generally, a water-soluble polymer having a viscosity such as polyvinyl alcohol or a particle of a water-absorbing polymer which gives a apparent volume-like feel to the solution due to water-absorbing polymer enlarges the particles. Is used.

However, when these polymers are added and cooled to be in a state of about 5 ° C. at which the actual efficacy is expected, a necessary shape change is performed, and the solution fluidity necessary for maintaining the shape is 500 cps or more. In order to prepare an aqueous solution having a viscosity of 7 and having a slight non-Newtonian flow, it was necessary to mix at least 1% or more of various polymers. For example, in the case of a water-soluble polymer having a low viscosity developing property such as polyvinyl alcohol, it is necessary to use it at a concentration of more than tens of percent, and for a water-absorbing polymer, a relatively low addition amount is required to obtain a desired hardness. However, since there is no fluidity such as the original viscosity and non-Newtonian fluidity is apparently large fluidity, there is a problem that the fitting property to the part to be cooled is poor.

On the other hand, water-soluble cellulose ethers such as carboxymethyl cellulose, methyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxyethyl ethyl cellulose have relatively low viscosities and high viscosities, and have a fluidity. However, it is used as an excellent water-soluble polymer. Particularly, carboxymethyl cellulose and the like are inexpensive and are used as those exhibiting high viscosity even at low concentration. However, inexpensive water-soluble cellulose ethers such as carboxymethyl cellulose have a low degree of ether substitution with respect to natural cellulose and are easily attacked by bacteria and the like,
If the cold insulator after use is left to stand, it is decomposed by the action of bacteria and the like to lower the viscosity, and there are problems such as generation of mold.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an aqueous solution which exhibits a high viscosity and a non-Newtonian flow even when the amount of the water-soluble cellulose ether having a problem of storage stability is reduced. The present invention is intended to provide a cold-preserving composition which is obtained and is not attacked by bacteria and the like.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that when a colloidal silica having a particle diameter of 100 μm or less is added to an aqueous solution of a water-soluble cellulose derivative, the viscosity of the cellulose derivative is small. The viscosity of the aqueous solution can be increased more than several times while maintaining the excellent non-Newtonian flow characteristics. Also, when this system is cooled to around 5 ° C, the solution viscosity increases and exhibits a high viscosity, and storage stability is improved. The present invention has been completed based on the finding that a cold-preserving agent having a problematic water-soluble cellulose ether content as low as possible can be obtained and storage stability can be improved.

The colloidal silica used in the present invention is
For example, a silica sol is used in which a sodium silicate component is hydrated in water, the system is made acidic with an ion exchange resin, and the sol is stabilized by adding a trace amount of an alkaline component in a dispersing device. If the silica is a stable sol, it can be used as the colloidal silica sol used in the present invention. Actually, it is industrially necessary to make silica particles finer than 1 to 100 μm and fine particles exist as a stable sol. However, colloidal silica having a particle size of 1 to 100 μm is used in the present invention. The particle concentration of colloidal silica is 40% by weight or less because if it is 40% by weight or more, aggregation is likely to occur, and the minimum concentration required to obtain the required viscosity by mixing with cellulose ether is 10% by weight or more. Is used.

The water-soluble cellulose ether used in the present invention includes all water-soluble cellulose ethers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl ethyl cellulose, and the like. It is preferable to use as high viscosity as possible (that is, high degree of polymerization) in order to reduce the amount used, and the viscosity should be 100c as measured at 20 ° C in a 2% aqueous solution.
Those of ps or more are used. In addition, it is desirable to minimize the amount of cellulose ether added, but in general,
It is preferably used in the range of 0.3 to 1% by weight.

[0010]

When the colloidal silica is mixed with the water-soluble cellulose ether solution, the solution viscosity is increased and the fluidity of the solution is not significantly changed. It is considered that the mechanism is that a part of the water-soluble cellulose ether molecule is adsorbed on the surface of the colloidal silica, and the state becomes a cross-linking point to increase the viscosity. Actually, when dioxane was added to the thus thickened product as a desorbent of cellulose ether, the viscosity of this solution was almost the same as that of cellulose ether at a concentration where colloidal silica was not added. It is considered that the adsorption of cellulose ether on the colloidal silica is acting.

[0011]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these descriptions. Examples 1 to 7 and Comparative Examples 1 to 5 In the types and amounts shown in Table 1, a colloidal silica (Nissan Chemical Co., Ltd. Snowtex) solution was mixed with the following water-soluble cellulose derivative, water-soluble polymer or water-absorbing polymer. To prepare solutions, and measure the viscosity of each solution at 20 ° C, the viscosity when cooled to 5 ° C, and the viscosity decrease rate (%) from the initial viscosity when left at 20 ° C for 2 weeks. It was measured with a viscometer at rotor No. 4 and a rotation speed of 30 rpm. Also,
In the viscosity measurement at each temperature, the rotor rotation speed was changed to measure the viscosity, and the measured viscosity value against the measurement rotation speed was plotted on a log-log graph, and the negative slope of the straight line connecting the points was calculated.
It was calculated as tan θ. It should be noted that the larger the tan θ, the higher the non-Newtonian property of the measurement solution and the worse the fit to the object to be cooled. The above results are shown in Table 1.
It was shown to.

The abbreviations in the table mean the following.・ MC-1: Methylcellulose-1 (Shin-Etsu Chemical Co., Ltd., SM
-100, 2% aqueous solution viscosity: 100 cps ・ HPMC: hydroxypropylmethyl cellulose (same as above,
90SH-100,000, 2% aqueous solution viscosity: 100cps ・ HEMC: Hydroxyethylmethylcellulose (Same as above, S
EB-30T, 2% aqueous solution viscosity: 32000cps) -CMC: carboxymethyl cellulose (manufactured by Daicel Chemical Industries, 2% aqueous solution viscosity: 8000cps) -HEC: hydroxyethyl cellulose (same as above, SP-900,
2% aqueous solution viscosity: 85000cps) -HPC: hydroxypropylcellulose (Shin-Etsu Chemical Co., Ltd., MP, 2% aqueous solution viscosity: 6500cps) -HEEC: hydroxyethylethylcellulose (Berol, E481FQ, 2% aqueous solution viscosity: 76500cps)- PVA: Polyvinyl alcohol (Shin-Etsu Chemical Co., Ltd., P
A20S) ・ MC-2: Methylcellulose-2 (Same as above, SM-15, 2% aqueous solution viscosity: 15cps) ・ Water-absorbing polymer: Sodium acrylate polymer (Sumikagel N-100, manufactured by Sumitomo Chemical Co., Ltd.)

[0013]

[Table 1]

[0014]

EFFECTS OF THE INVENTION According to the cooling agent composition of the present invention, the required viscosity of 500 cps or more is developed without increasing the non-Newtonian property of the solution system, and in addition to exhibiting a high viscosity particularly in a low temperature range, It also reduces the decrease in viscosity when left standing.

Claims (2)

[Claims] 1. A colloidal silica sol having a silica content of 10 to 40% by weight and a particle size of 100 μm or less,
A cooling agent composition comprising 0.3 to 1% by weight of a water-soluble cellulose ether. 2. The ice pack composition according to claim 1, wherein the water-soluble cellulose ether has a viscosity of 100 cps or more as measured at 20 ° C. in a 2% aqueous solution.