JP6587108B2 - Cooler - Google Patents

Description

The present invention relates to a cold insulator provided with a cold insulating composition in which a color change during cooling can be easily visually recognized.
This application claims priority on October 30, 2014 based on Japanese Patent Application No. 2014-221679 for which it applied to Japan, and uses the content for it here.

The cold insulator is widely used for cold storage during storage and transportation of various fresh products, and is usually used repeatedly. Such a cold-retaining tool includes a cold-retaining composition having a cold-retaining action, and is configured by enclosing the cold-retaining composition in a thermally conductive container.
As the composition for cold insulation, those containing a colorant are known so that the presence thereof can be easily visually recognized from the outside of the cold insulation device. For example, the composition for cold insulation colored with a dye is enclosed. A cold insulator whose disclosing amount can be easily confirmed from the outside is disclosed (see Patent Document 1).

  However, the cold insulator described in Patent Document 1 is difficult to visually check the cooling state, such as the presence or absence of freezing, even if the cold-keeping composition contains a dye, and it is at a desired temperature that can be kept cold. There is a problem that the cold insulator is sufficiently cooled until it is difficult to visually check the cooling state.

JP 2006-97984 A

  An object of the present invention is to provide a cold insulator that can be easily visually confirmed whether a cooling state is in a target state.

The present invention is a cold-retaining tool comprising a cold-retaining composition containing water, an inorganic salt, a thickener and a pH indicator, wherein the thickener is a polysaccharide, and the cold-retaining composition is the inorganic Provided is a cold insulator having a pH (A) of 7.0 or more when all components other than salt and water are replaced with water and satisfying the relationship of the following formula (I).
pH indicator pKa−0.5 ≦ pH (A) ≦ pH indicator pKa + 3.5 (I)

In the cold insulator of the present invention, the pH of the cold-retaining composition may satisfy the relationship of the following formula (II).
pKa of pH indicator-0.5 ≦ pH of composition for cold preservation ≦ pKa of pH indicator + 3.5 (II)
In the cold insulation tool of the present invention, the cold insulation composition has a pH (B) of 5.0 or more and 9.0 or less when all the components other than the thickener and water are replaced with water. But you can.
In the cold insulation tool of the present invention, the composition for cold insulation has a content of the inorganic salt of 0.5 to 33% by mass, and a content of the thickener of 0.1 to 10% by mass, The content of the pH indicator may be 1 to 30 ppm.

In the cold insulator of the present invention, the pKa of the pH indicator may be 4.0 or more and 11.8 or less.
In the cold insulator of the present invention, the inorganic salt is hydrochloride, sulfate, nitrate, carbonate, hydrogen phosphate, hydrogen carbonate, phosphate, alkali metal chloride or alkaline earth metal chloride. It may be one or more selected from the group consisting of
In the cold insulator of the present invention, the thickener may be one or more selected from the group consisting of carboxyalkyl cellulose, guar gum, hydroxyalkyl guar gum, pectin, xanthan gum, tamarind gum and carrageenan.

  The cold insulator according to the present invention can be easily visually confirmed whether the cooling state is in a target state.

  A preferred example of the cold insulator of the present invention will be described below. However, the present invention is not limited to these examples. For example, additions, omissions, substitutions, and other changes (amount, number, position, size, etc.) are possible without departing from the spirit of the present invention. It is.

The cold-retaining tool of the present invention is a cold-retaining tool comprising a cold-retaining composition containing water, an inorganic salt, a thickener and a pH indicator, wherein the thickener is a polysaccharide, and the cold-retaining composition is The pH (A) when all the components other than the inorganic salt and water are replaced with water is 7.0 or more and satisfies the relationship of the following formula (I).
pH indicator pKa−0.5 ≦ pH (A) ≦ pH indicator pKa + 3.5 (I)

  Since the color of the composition for cold insulation reflecting the presence or absence of color development of the pH indicator largely changes before and after freezing, the cold insulator is in a state where the cooling state is intended (a state where the object can be sufficiently cooled). It can be easily visually confirmed whether or not there is. And the color of the composition for cold preservation before and after freezing does not mainly reflect the color of components other than pH indicators, such as the said inorganic salt and a thickener.

pH (A) is the pH of the replacement composition when all the components other than the inorganic salt and water are replaced with water in the cold-retaining composition, and the content (mass%) in the cold-retaining composition ) And the same content (mass%) as that of the inorganic salt-containing water (for example, an aqueous solution of inorganic salt) containing only the inorganic salt.
The pH (A) is preferably a pH at a temperature at which the pH indicator is dissolved in the composition for cold preservation, and the temperature of the inorganic salt-containing water is any temperature of 23 to 27 ° C. The pH is more preferably, and the pH when the temperature of the inorganic salt-containing water is 25 ° C. is particularly preferable.

  The pH (A) is 7.0 or more, preferably 7.05 or more, and more preferably 7.1 or more. Moreover, it is preferable that pH (A) is 12.2 or less, and it is more preferable that it is 11.8 or less.

In the cold-retaining composition, when the pH of the replacement composition when all the components other than the thickener and water are replaced with water is “pH (B)”, this pH (B) is, in other words, The pH of the thickener-containing water (for example, a thickener aqueous solution) containing only the thickener at the same content (mass%) as the content (mass%) in the cold-retaining composition.
The pH (B) is preferably a pH at a temperature at which the pH indicator is dissolved in the composition for cold preservation, and the temperature of the thickener-containing water is any temperature of 23 to 27 ° C. In this case, the pH is more preferably, and the pH when the temperature of the thickener-containing water is 25 ° C. is particularly preferable.

  The pH (B) is preferably 5.0 or more, and more preferably 6.0 or more. Moreover, it is preferable that pH (B) is 9.0 or less, and it is more preferable that it is 8.2 or less.

The cold-retaining composition uses a polysaccharide as a thickening agent, and can adjust the acidity of the cold-retaining composition as an inorganic salt, and also affects the color development of the pH indicator. Depending on the change or presence or absence of color development of the pH indicator by using an aqueous solution having a pH within a specific range, and further combining a pH indicator having a suitable color change range with these thickeners and inorganic salts. The color change is remarkably increased.
Hereinafter, each component will be described.

The said inorganic salt (salt of an inorganic compound) functions as one component of a cryoprotectant, and the freezing temperature of the composition for cold preservation is mainly determined by the kind and quantity.
Further, the inorganic salt does not correspond to the pH indicator, and is a component that can be precipitated as crystals or amorphous (amorphous) at the time of freezing the composition for cold insulation, and is involved in the color change of the composition for cold preservation by precipitation. It is possible. As described above, the color of the composition for cold preservation before and after freezing mainly reflects the color at the time of color development of the pH indicator, but the color of the composition for cold preservation after freezing (when frozen) is precipitated. It is somewhat affected by the color of the inorganic salt (usually white).

The amount of the inorganic salt dissolved before the freezing, preferably in the refrigerated composition at 0 ° C. or higher, is preferably as large as possible. The amount dissolved in the total amount of the inorganic salt is 90% by mass or more. Preferably, it is 95% by mass or more, more preferably 98% by mass or more, and may be 100% by mass (total amount).
Further, the amount of the inorganic salt deposited in the composition for cold preservation after freezing is preferably 90% by mass or more, more preferably 95% by mass or more, and 98% by mass or more. More preferably, it may be 100% by mass (total amount).

The inorganic salt is not particularly limited as long as the pH (A) satisfies the above conditions.
As the metal ions in the cation constituting the inorganic salts, for example, lithium ion ^(Li +), sodium ion ^(Na +), potassium ion ^{(K +)} of an alkali metal such as ions; magnesium ions ^{(Mg 2+),} calcium Ions of alkaline earth metals such as ions (Ca ²⁺ ); ions of transition metals such as iron ions (Fe ³⁺ , Fe ²⁺ ), copper ions (Cu ²⁺ , Cu ⁺ ); zinc ions (Zn ²⁺ ), aluminum ions ( And ions of Group 12 or Group 13 metals such as Al ³⁺ ).
Examples of the non-metal ion in the cation constituting the inorganic salt include ammonium ion (NH ₄ ⁺ ) and the like.

Examples of the anion constituting the inorganic salt include halogen ions such as chloride ion (Cl ⁻ ), bromide ion (Br ⁻ ), iodide ion (I ⁻ ); sulfate ion (SO ₄ ²⁻ ); nitrate ion. (NO ₃ ⁻ ); carbonate ion (CO ₃ ²⁻ ); bicarbonate ion (HCO ₃ ⁻ ); hydrogen sulfate ion (HSO ₄ ⁻ ); phosphate ion (PO ₄ ³⁻ ); hydrogen phosphate ion (HPO ₄₎ ^2- ); dihydrogen phosphate ion (H ₂ PO ₄ ⁻ ); sulfite ion (SO ₃ ²⁻ ); thiosulfate ion (S ₂ O ₃ ²⁻ ); chlorate ion (ClO ₃ ⁻ ); perchloric acid Ion (ClO ₄ ⁻ ); a group formed by removing a hydrogen ion (H ⁺ ) from an acid group such as a carboxy group (—C (═O) —OH) or a sulfo group (—S (═O) ₂ —OH). Ion etc. which have are mentioned.

The inorganic salt is not particularly limited. For example, alkali metal chlorides such as sodium chloride (NaCl) and potassium chloride (KCl); hydrochlorides such as ammonium chloride (NH ₄ Cl); sodium sulfate (Na ₂ SO ₄ ) , Potassium sulfate (K ₂ SO ₄ ), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), magnesium sulfate (MgSO ₄ ), aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), nickel sulfate (NiSO ₄ ), alum (AlK) Sulfates such as (SO ₄ ) ₂ ), ammonium alum (Al (NH ₄ ) (SO ₄ ) ₂ ); sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), ammonium nitrate (NH ₄ NO ₃ ), calcium nitrate four Hydrates (Ca (NO ₃ ) ₂ .4H ₂ O), calcium nitrate (Ca (NO ₃ ) ₂ Nitrates such as sodium carbonate (Na ₂ CO ₃ ), carbonates such as potassium carbonate (K ₂ CO ₃ ); bicarbonates such as potassium bicarbonate (KHCO ₃ ) and sodium bicarbonate (NaHCO ₃ ); calcium chloride (CaCl ₂ ), chlorides of alkaline earth metals such as magnesium chloride (MgCl ₂ ); sodium dihydrogen phosphate (NaH ₂ PO ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), ammonium dihydrogen phosphate Dihydrogen phosphates such as (NH ₄ H ₂ PO ₄ ); disodium hydrogen phosphate (Na ₂ HPO ₄ ), dipotassium hydrogen phosphate (K ₂ HPO ₄ ), diammonium hydrogen phosphate ((NH ₄ ) of sodium sulfite _(Na 2 SO ₄₎ and the like; phosphate salts such as trisodium phosphate _{(Na 3 PO 4); 2} HPO 4) and phosphoric acid hydrogen salts Thiosulfates such as sodium thiosulfate _{(Na 2 S 2 O 3)} ;; chlorate and potassium chlorate (KClO _3);; sulfate sodium perchlorate (NaClO ₄₎ perchlorate such as bromide Alkali metal bromides such as potassium (KBr) and sodium bromide (NaBr); Alkali metal iodides such as potassium iodide (KI) and sodium iodide (NaI); Borax (Na ₂ B ₄ O ₇ ) and the like Borate and the like.

  The said inorganic salt may be used individually by 1 type, and may use 2 or more types together.

The inorganic salts are hydrochloride, sulfate, nitrate, carbonate, hydrogen phosphate, bicarbonate, phosphate, alkali metal chloride, alkaline earth metal chloride, sulfite, chlorate, One or more selected from the group consisting of perchlorates, thiosulfates, alkali metal bromides, alkali metal iodides and borates are preferred.
The inorganic salt is selected from the group consisting of hydrochloride, sulfate, nitrate, carbonate, hydrogen phosphate, hydrogen carbonate, phosphate, alkali metal chloride and alkaline earth metal chloride. It is more preferable that it is 1 type or more.
By using such an inorganic salt, the composition for cold preservation has a large color change before and after freezing and is excellent in handleability.

  The inorganic salt is preferably dihydrogen phosphate or hydrogen phosphate in that there are many types of pH indicators that can be used in combination, and the color change of the composition for cold preservation before and after freezing is greater. More preferably, it is a dihydrogen salt.

  Among the above, the inorganic salt is selected from the group consisting of hydrogen phosphate, carbonate, sulfate, and alkali metal chloride because the color change before and after freezing of the composition for cold preservation becomes larger. One or more types are particularly preferred.

  The content of the inorganic salt in the composition for cold insulation is not particularly limited as long as the pH (A) is in a predetermined range, but is preferably 0.5 to 33% by mass, and preferably 1 to 31% by mass. It is more preferable that, for example, 0.5 to 22% by mass, 1 to 19% by mass, and the like can be set.

The said thickener improves the viscosity of the said composition for cold preservation, is a component which does not correspond to the said pH indicator, and is a polysaccharide in this invention.
The thickening agent is usually a component that suppresses precipitation both when the cryopreservation composition is not frozen and when it is frozen. In the present specification, “the thickener does not precipitate when the cryogenic composition is frozen” means that the thickener is solidified while being dissolved in water when the cryogenic composition is frozen, It is presumed that the thickener molecules are not solidified and are solidified while surrounded by water molecules, and the thickener molecules are not solidified by aggregation. Guessed.

  In the composition for cold preservation before freezing and after freezing, the thickener is preferably as less as the amount deposited, and the amount deposited in the total amount of the thickener is 10% by mass or less. It is preferably 5% by mass or less, more preferably 2% by mass or less, and may be 0% by mass (the entire amount may not be precipitated).

  The thickener (polysaccharide) is not particularly limited, and examples thereof include carboxyalkyl cellulose such as carboxymethylcellulose (CMC); guar gum; hydroxyalkyl guar gum such as hydroxypropyl guar gum; pectin; xanthan gum; tamarind gum; .

  The said thickener may be used individually by 1 type, and may use 2 or more types together.

  Although content of the said thickener of the composition for cold preservation is not specifically limited unless the effect of this invention is impaired, It is preferable that it is 0.1-10 mass%, and it is 0.3-4 mass%. Is more preferable.

  The pH indicator (acid-base indicator) determines the color of the composition for cold preservation by reflecting the presence or absence of color development. The composition for cold preservation changes a color before and after freezing by containing a pH indicator.

  The pH indicator may be a known one and is not particularly limited. For example, bromocresol purple, alizarin yellow R, phenol red, bromophenol blue, bromocresol green, bromothymol blue, methyl yellow, congo red, methyl orange, methyl Examples include red, methyl purple, phenolphthalein, litmus, p-nitrophenol, chlorophenol red, neutral red, p-naphtholphthalein, cresol red, thymol blue, and thymolphthalein.

The pH indicator preferably has a pKa (acid dissociation constant) of 4.0 or more, and more preferably 5.0 or more. Further, the pH indicator preferably has a pKa of 11.8 or less, more preferably 11.5 or less.
In addition, unless otherwise indicated, pKa of the pH indicator in this invention means the value when a solvent is water and temperature is 25 degreeC.

  The pH indicator may be used alone or in combination of two or more, but usually it is preferable to use one alone.

  The content of the pH indicator in the cold-retaining composition is not particularly limited as long as the intended color change of the cold-retaining composition is achieved, but is preferably 1 to 30 ppm, and more preferably 5 to 20 ppm. .

The cold-retaining composition satisfies the relationship of the formula (I). That is, the lower limit value of pH (A) is a value smaller by 0.5 than the pKa of the pH indicator, and the upper limit value of pH (A) is a value that is larger by 3.5 than the pKa of the pH indicator. is there.
The lower limit value of pH (A) is preferably a value that is smaller by 0.3 than the pKa of the pH indicator, and more preferably a value that is smaller by 0.1 than the pKa of the pH indicator. Further, the upper limit value of pH (A) is preferably a value that is 3.3 larger than the pKa of the pH indicator, and more preferably a value that is 3.0 larger than the pKa of the pH indicator. By being in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

  The said composition for cold preservation may contain the other component which does not correspond to these in the range which does not impair the effect of this invention other than water, the said inorganic salt, a thickener, and a pH indicator. Examples of the other components include solvents other than water; various known additives such as preservatives; salts other than inorganic salts (that is, organic salts and salts of organic compounds); thickeners other than polysaccharides, and the like. It is done.

The solvent is preferably one that can dissolve the inorganic salt, thickener, and pH indicator, and examples of such a solvent include alcohol.
The said solvent may be used individually by 1 type, and may use 2 or more types together.

Water and the solvent function as one component of a cryogen, and together with the inorganic salt, the freezing temperature of the cryogen composition is determined mainly by the type and amount thereof.
In the composition for cold preservation, the ratio of the content of the solvent to the total content of water and the solvent is preferably 10% by mass or less, more preferably 5% by mass or less, and 2% by mass or less. It is particularly preferred that it may be 0% by mass.

Examples of the preservative include food preservatives and antioxidants, and examples include sodium pyrithione, paraben (paraoxybenzoic acid ester), protamine, and organic nitrogen sulfur compounds.
What is necessary is just to adjust suitably content of the said preservative in the composition for cold preservation according to the kind of preservative.

Examples of the organic salt include organic acid salts and organic base salts.
Examples of the salt of the organic acid include a salt formed by reacting an acid group of an organic acid such as carboxylic acid or sulfonic acid with an inorganic base or an organic base.
Examples of the salt of the organic base include salts formed by reacting a group containing a nitrogen atom of a nitrogen-containing organic compound such as a primary amine, secondary amine, and tertiary amine with an inorganic acid or an organic acid. Can be mentioned.
The said organic salt may be used individually by 1 type, and may use 2 or more types together.

  In the composition for cold preservation, the ratio of the content of the organic salt to the total content of the inorganic salt and the organic salt (total content of the salt) is preferably 5% by mass or less, and preferably 3% by mass or less. More preferably, it is particularly preferably 1% by mass or less, and may be 0% by mass.

Examples of thickeners other than the polysaccharide include acrylic polymers such as polyacrylic acid and sodium polyacrylate (polyacrylic acid in which one or more hydrogen atoms may be substituted with groups other than hydrogen atoms and Salt thereof, carboxyvinyl polymer); and alkylene glycols such as propylene glycol.
Thickeners other than the polysaccharides may be used alone or in combination of two or more.
In the present specification, unless otherwise specified, the simple description “thickener” means “thickener that is a polysaccharide”.

  In the composition for cold preservation, the ratio of the content of the thickener other than the polysaccharide to the total content of the thickener that is the polysaccharide and the other thickener (total content of the thickener) is It is preferably 10% by mass or less, more preferably 5% by mass or less, particularly preferably 2% by mass or less, and may be 0% by mass.

  The composition for cold preservation is composed of the inorganic salt and the polyvalent salt with respect to the total content of components other than water and the solvent (the inorganic salt, the thickener as a polysaccharide, the pH indicator, and other components other than the solvent). The total content ratio of the thickener and the pH indicator, which are saccharides, is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. When the ratio of the total content is equal to or more than the lower limit value, the color change of the composition for cold preservation before and after freezing becomes larger.

From the point that the color change of the composition for cold preservation before and after freezing becomes larger, the composition for cold preservation has a pH (C) of pH (C) before freezing (when it is not frozen). Those satisfying the relationship of the following formula (II) are preferable.
pH indicator pKa−0.5 ≦ pH (C) ≦ pH indicator pKa + 3.5 (II)

  The pH (C) is the pH before freezing (when not frozen) of the cold-retaining composition, preferably the pH at the temperature at which the pH indicator is dissolved in the cold-retaining composition, It is more preferably a pH when the temperature of the cold-retaining composition is any one of 23 to 27 ° C., and particularly preferably a pH when the temperature of the cold-retaining composition is 25 ° C.

  The pH (C) is preferably 5.3 or more, and more preferably 6.4 or more. Moreover, it is preferable that pH (C) is 12.0 or less, and it is more preferable that it is 11.5 or less.

As described above, the composition for cold preservation is preferably such that the lower limit value of pH (C) is 0.5 smaller than the pKa of the pH indicator, and the upper limit value of pH (C) is The value is preferably 3.5 larger than the pKa of the pH indicator.
The lower limit value of pH (C) is more preferably a value that is smaller by 0.4 than the pKa of the pH indicator, and particularly preferably a value that is smaller by 0.3 than the pKa of the pH indicator. . The upper limit of pH (C) is more preferably a value that is 3.3 larger than the pKa of the pH indicator, and particularly preferably a value that is 3.0 larger than the pKa of the pH indicator. . By being in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

The composition for cold preservation is obtained by blending water, the inorganic salt, the thickener, the pH indicator, and, if necessary, the other components.
The blending method of each component is not particularly limited, and can be arbitrarily adjusted so that each component is uniformly dissolved or dispersed at a temperature higher than the freezing temperature of the composition for cold preservation.
For example, when blending each component, all the components may be added and then mixed, or some components may be mixed while being added sequentially, and all components may be mixed while being added sequentially. May be.
The mixing method is not particularly limited, a method of mixing by rotating a stirrer or a stirring blade; a method of mixing using a mixer, a three-roller, a kneader, a bead mill or the like; a method of mixing by adding ultrasonic waves, etc. What is necessary is just to select suitably from a well-known method.

The cold-retaining tool of the present invention includes the cold-retaining composition, and is configured by holding the cold-retaining composition by holding means such as a container that can enclose a liquid material.
The material of the holding means is not particularly limited as long as it is transparent to the extent that the color change (discoloration) of the held cooling composition can be visually recognized. Preferred examples include polyethylene and polypropylene. And synthetic resins such as polyamides, polyesters, and the like. Among these, polyolefin is preferable from the viewpoint of excellent low-temperature brittleness resistance, water resistance, chemical resistance, and the like, and high-density polyethylene that is easy to mold and has high strength is more preferable.

Since the color-retaining composition largely changes in color before and after freezing, the presence or absence of freezing can be easily visually confirmed. And this color change of the composition for cold insulation can be visually recognized from the outside of the cold insulator, and thereby, it can be easily visually confirmed whether or not the cold insulator is sufficiently cooled to a desired temperature. ing.
In addition, since the effect of the cold-retaining composition is not impaired even if cooling and heating are repeated, such as repeated freezing and thawing, the cold-retaining tool provided with the composition is suitable for repeated use. is there.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples. In the following description, the unit “ppm” of the content (blending amount, concentration) of the pH indicator is based on the mass ratio.

Of the raw materials used in the examples and comparative examples, thickeners and pH indicators are shown below.
(Thickener)
・ CMC (Carboxymethylcellulose): “Serogen” manufactured by Daiichi Kogyo Seiyaku
・ GG (Guar gum): “Guapack PF-20” manufactured by Sankisha Co., Ltd.
CVP (carboxy vinyl polymer): “Aronbis AH-305X” manufactured by Toa Gosei Co., Ltd.
(PH indicator)
・ BCP: Bromocresol purple (Wako Pure Chemical Industries, Ltd.)
・ AYR: Alizarin Yellow R (Wako Pure Chemical Industries, Ltd.)
・ PR: Phenol red (manufactured by Wako Pure Chemical Industries)
・ BPB: Bromophenol blue (manufactured by Wako Pure Chemical Industries, Ltd.)
・ BCG: Bromocresol Green (Wako Pure Chemical Industries, Ltd.)

[Example 1]
<Manufacture of composition for cold preservation and cold insulation tool>
Water (97 parts by mass), diammonium hydrogen phosphate (2 parts by mass), CMC (1 part by mass), and BCP were added and mixed at room temperature (20 to 25 ° C.) to obtain a composition for cold preservation. At this time, the blending amount of BCP was adjusted so that the content in the obtained composition for cold insulation was 10 ppm. Table 1 shows each compounding component other than water and its content (concentration), pH (A), pH (B), and the like. And the pH (C) before freezing of the obtained composition for cold preservation was measured. The results are shown in Table 1. The pH (A), pH (B), and pH (C) were all measured with the temperature of the measurement object being 25 ° C.
In Table 1, the numerical value described in the unit of “mass%” in the column of inorganic salt indicates the content of the inorganic salt of the composition for cold preservation and the concentration of the aqueous inorganic salt solution at the time of pH (A) measurement. . Similarly, the numerical value described in the unit of “mass%” in the column of the thickener indicates the content of the thickener in the composition for cold preservation and the concentration of the thickener aqueous solution at the time of pH (B) measurement. . The same applies to the following tables.
Next, the obtained composition for cold insulation was sealed in a high-density polyethylene container to obtain a cold insulation tool.

<Evaluation of composition for cold preservation>
(Color change)
The obtained cold-retaining composition (cold-retaining tool) was cooled to −25 ° C., and the color change of the cold-retaining composition before and after freezing was visually evaluated according to the following criteria. The results are shown in Table 1.
In Table 1, “color change” described in the column of the evaluation result indicates a color change of the composition for cold preservation before and after freezing. For example, “blue purple → yellow” means a composition for cold preservation. Indicates that the color was blue-purple before freezing and yellow after freezing.
○: The color change before and after freezing is large and the cooling state is very easy to visually recognize.
(Triangle | delta): The color change before and behind freezing can be discriminate | determined and the visual recognition of a cooling state is possible.
X: The color change before and after freezing is unclear, and it is difficult or impossible to visually recognize the cooling state.

<Manufacture of composition for cold preservation and cold insulation, evaluation of composition for cold insulation>
[Examples 2 to 19, Comparative Examples 1 to 13]
A composition for cold insulation and a cold insulation tool were produced in the same manner as in Example 1 except that the composition components and concentrations of the cold insulation composition were as shown in Tables 1 to 5, and the cold insulation composition was evaluated. The results are shown in Tables 1-5. For example, in Example 6, four kinds of sodium chloride, potassium chloride, sodium sulfate, and diammonium hydrogen phosphate are used in combination as the inorganic salt, but the content in these cold-retaining compositions and pH (A ) The concentration in the aqueous solution at the time of measurement is 10% by mass for sodium chloride, 5% by mass for potassium chloride, 2% by mass for sodium sulfate, and 0.1% by mass for diammonium hydrogen phosphate. In the table, “-” means that the component is not blended, and accordingly, the corresponding pH (A) or pH (B) is not measured.

  As is clear from the above results, in Examples 1 to 19, the thickener used is a polysaccharide, and the pH (A) is within a predetermined range regardless of the number of types of inorganic salts used. In addition, by satisfying the relationship of the above formula (I), the color of the composition for cold preservation clearly changes before and after freezing, reflecting the change in color development of the pH indicator, and the cooling state is easy. It was visible. In addition, Examples 1-19 all satisfy | filled the relationship of the said Formula (II).

  On the other hand, in Comparative Examples 1-5, the color change of the composition for cold preservation is unclear before and after freezing because the relationship of the formula (I) is not satisfied, and it is difficult to visually recognize the cooling state. Or was impossible. Moreover, in Comparative Examples 6-8, when pH (A) is outside the predetermined range, color change of the composition for cold preservation is unclear before and after freezing, and is it difficult to visually recognize the cooling state? Or it was impossible. Moreover, although Comparative Examples 9-12 are the cases where the whole amount of the thickener was replaced with water (without using the thickener) in the composition for keeping cold of Comparative Examples 1-4, Comparative Example 1 was used. Similarly to -4, the color change of the composition for cold preservation was unclear before and after freezing, and the visual observation of the cooling state was difficult or impossible. Further, Comparative Example 13 is a case where an inorganic salt-free refrigeration composition was used, but as with other comparative examples, the color change of the refrigeration composition was unclear before and after freezing, Visibility of the cooling state was difficult or impossible.

  The present invention can be used as a cold insulator for various fresh products.

Claims (7)

A cold insulator provided with a cold insulating composition containing water, an inorganic salt, a thickener and a pH indicator,
The thickener is a polysaccharide;
The cold insulation composition has a pH (A) of 7.0 or more and satisfies the relationship of the following formula (I) when all the components other than the inorganic salt and water are replaced with water. .
pH indicator pKa−0.5 ≦ pH (A) ≦ pH indicator pKa + 3.5 (I) The cold-retaining tool according to claim 1, wherein a pH of the cold-retaining composition satisfies a relationship represented by the following formula (II).
pKa of pH indicator-0.5 ≦ pH of composition for cold preservation ≦ pKa of pH indicator + 3.5 (II)   The cold-retaining tool according to claim 1, wherein the cold-retaining composition has a pH (B) of 5.0 or more and 9.0 or less when all the components other than the thickener and water are replaced with water. .   In the composition for cold preservation, the content of the inorganic salt is 0.5 to 33% by mass, the content of the thickener is 0.1 to 10% by mass, and the content of the pH indicator is 1. The cold insulator according to claim 1, which is ˜30 ppm.   The cold insulator according to claim 1, wherein the pH indicator has a pKa of 4.0 or more and 11.8 or less.   The inorganic salt is selected from the group consisting of hydrochloride, sulfate, nitrate, carbonate, hydrogen phosphate, bicarbonate, phosphate, alkali metal chloride and alkaline earth metal chloride 1 The cold insulator according to claim 1, wherein the cold insulator is a seed or more.   The cold insulator according to claim 1, wherein the thickener is at least one selected from the group consisting of carboxyalkyl cellulose, guar gum, hydroxyalkyl guar gum, pectin, xanthan gum, tamarind gum and carrageenan.