JP2016132729A - Cold insulation tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold insulation tool capable of easily sighting whether cooling conditions lie in target conditions or not.SOLUTION: Provided is a cold insulation tool having a composition for cold insulation containing water, an inorganic salt, a thickener and a pH indicator, in which the thickener being an organic acid salt, and the pH of the composition for cold insulation and the pKa of the pH indicator satisfy the relation of the following equation (I): the pKa of the pH indicator-0.7<the pH of the composition for cold insulation<the pKa of the pH indicator+1.4 (I).SELECTED DRAWING: None

Description

  The present invention relates to a cold insulator provided with a cold-retaining composition in which a color change during cooling can be easily visually recognized.

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 is configured by providing a cold-retaining composition having a cold-retaining action, and 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).

JP 2006-97984 A

  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.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the cooler which can be visually recognized easily whether a cooling state exists in the target state.

In order to solve the above-mentioned problems, the present invention is a cold insulator provided with a cold-retaining composition containing water, an inorganic salt, a thickener and a pH indicator, wherein the thickener is an organic acid salt, Provided is a cold insulator characterized in that the pH of the composition for cold insulation and the pKa of the pH indicator satisfy the relationship of the following formula (I).
pKa of the pH indicator-0.7 <pH of the composition for cold preservation <pKa of the pH indicator + 1.4 (I)

  ADVANTAGE OF THE INVENTION According to this invention, the cooler which can be visually recognized easily whether a cooling state exists in the target state is provided.

<< Cold insulation >>
The cold insulator according to the present invention is a cold insulator provided with a cold insulating composition containing water, an inorganic salt, a thickener and a pH indicator, wherein the thickener is an organic acid salt, and the cold insulating composition The pH of the product and the pKa of the pH indicator satisfy the relationship of the following formula (I).
pKa of the pH indicator-0.7 <pH of the composition for cold preservation <pKa of the pH indicator + 1.4 (I)

  In such a cooler, since the color of the composition for cooling that reflects the presence or absence of color development of the pH indicator largely changes before and after freezing, the cooling state is a target state (a state in which 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.

<Cold insulation composition>
The cold-retaining composition uses an organic acid salt as a thickener, while a pH indicator having a color change range suitable for the acidity of the cold-retaining composition is used in combination to change the color development of the pH indicator. Alternatively, the color change depending on the presence or absence is remarkably increased.
Hereinafter, each component will be described.

[Inorganic salt]
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).

When the inorganic salt is not frozen (before freezing), preferably in the composition for cold preservation at 0 ° C. or higher, the larger the amount dissolved, the more the amount dissolved in the total amount of the inorganic salt. It is preferably 90% by mass or more, more preferably 95% by mass or more, further preferably 98% by mass or more, and particularly preferably 100% by mass (total amount).
Further, the amount of the inorganic salt deposited in the composition for cold preservation at the time of freezing (after freezing) is preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 95% by mass or more, It may be preferably 98% by mass or more, particularly preferably 100% by mass (total amount).

The inorganic salt is not particularly limited.
As the metal ions in the cations constituting the inorganic salt, ions of alkali metals such as lithium ions (Li ⁺ ), sodium ions (Na ⁺ ), potassium ions (K ⁺ ); magnesium ions (Mg ²⁺ ), calcium ions ( Ions of alkaline earth metals such as 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 (Al ³⁺⁾ And ions of Group 12 or Group 13 metals such as
Examples of the non-metal ion in the cation constituting the inorganic salt include ammonium ion (NH ₄ ⁺ ).

As anions constituting the inorganic salt, halogen ions such as chloride ions (Cl ⁻ ), bromide ions (Br ⁻ ), iodide ions (I ⁻ ), sulfate ions (SO ₄ ²⁻ ), nitrate ions (NO) ₃ ^-); carbonate ion _(CO ^{three 2-);} hydrogen carbonate ion (HCO ₃ ^-); hydrogen sulfate ion (HSO ₄ ^-); phosphoric acid ion _(PO ^{4 3-);} hydrogen phosphate ions _(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 ⁻ ); perchlorate ion ( ClO ₄ ⁻ ); having 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). An ion etc. can be illustrated.

The inorganic salt is not particularly limited, but 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 ) and sulfuric acid Potassium (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 (SO ₄ ) ₂ ), sulfate salts such as ammonium alum (Al (NH ₄ ) (SO ₄ ) ₂ ); sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), ammonium nitrate (NH ₄ NO ₃ ), calcium nitrate tetrahydrate things _{(Ca (NO 3) 2 ·} 4H 2 O), nitric acid and calcium nitrate (Ca _(NO 3)) ; Sodium carbonate _(Na 2 _CO 3), carbonates such as potassium carbonate _(K 2 CO _3); potassium bicarbonate (KHCO _3), sodium hydrogen carbonate (NaHCO ₃₎ hydrogen carbonates such as, calcium chloride (CaCl ₂₎ Alkaline earth metal chlorides such as magnesium chloride (MgCl ₂ ); sodium dihydrogen phosphate (NaH ₂ PO ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), ammonium dihydrogen phosphate (NH ₄ H) ₂ PO ₄ ) dihydrogen phosphates; disodium hydrogen phosphate (Na ₂ HPO ₄ ), dipotassium hydrogen phosphate (K ₂ HPO ₄ ), diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) salts; sulfites such as sodium sulfite _(Na 2 SO _4); phosphates such as trisodium phosphate _(Na 3 PO _4); hydrogen phosphate etc. Chlorates, such as potassium acid (KClO _3); thiosulfates such as sodium thiosulfate _{(Na 2 S 2 O 3)} ;; sodium perchlorate (NaClO ₄₎ perchlorate such as potassium bromide (KBr) Alkali metal bromide such as sodium bromide (NaBr); alkali metal iodide such as potassium iodide (KI) and sodium iodide (NaI); borate such as borax (Na ₂ B ₄ O ₇ ) Etc. can be exemplified.

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

  From the group consisting of dihydrogen phosphate, hydrogen phosphate and phosphate, the inorganic salt has 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 becomes larger. One or more selected are preferable, and dihydrogen phosphate is more preferable.

  The inorganic salt is preferably an alkali metal chloride, hydrochloride, sulfate, carbonate, or hydrogen phosphate in that the color change of the composition for cold preservation before and after freezing becomes larger.

  Although content of the said inorganic salt of the said composition for cold preservation is not specifically limited, It is preferable that it is 0.5-32 mass%, and it is more preferable that it is 1-26 mass%.

In the cold-retaining composition, when the pH of the replacement composition when all the components other than the inorganic salt and water are replaced with water is “pH (B)”, in other words, this pH (B) is: It is the pH of the inorganic salt-containing water (for example, an inorganic salt aqueous solution) containing only the inorganic salt at the same content (mass%) as the content (mass%) in the cold-retaining composition.
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 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 (B) is preferably 4.5 or more, more preferably 5.0 or more, and particularly preferably 5.5 or more.
The pH (B) is preferably 13.0 or less, more preferably 12.5 or less, and particularly preferably 12.0 or less.
When pH (B) is in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

[Thickener (organic acid salt)]
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 an organic acid salt in this invention.
The thickener is usually a component that suppresses precipitation both when the cryopreservation composition is not frozen (before freezing) and when frozen (after freezing). 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 at the time of non-freezing and freezing, the thickening agent is preferably as the amount of the precipitated thicker, and the amount of the thickener 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 particularly preferably 0% by mass (the total amount is not precipitated).

The thickener is not particularly limited as long as it is an organic acid salt.
The organic acid salt has one or more acid groups forming a salt in one molecule, and a part of the acid groups in one molecule may form a salt. All may form a salt. Moreover, the bonding position of the acid group forming the salt is not particularly limited.
When the organic acid salt has two or more acid groups forming a salt in one molecule, these two or more salts may all be the same or different. Only the part may be the same.

The kind of the acid group that forms the salt and the acid group that does not form the salt of the organic acid salt is not particularly limited, and is preferably a carboxy group (—C (═O) —OH), Sulfo group (—S (═O) ₂ —OH), phosphono group (—P (═O) (— OH) ₂ ), thiocarboxy group (—C (═O) —SH), thionocarboxy group (— C (= S) -OH), dithiocarboxy group (-C (= S) -SH) and the like can be exemplified, and more preferable examples include a carboxy group, a sulfo group and a phosphono group.
In addition, the acid group that forms a salt and the acid group that does not form a salt may be other than the above as long as they can donate a hydrogen ion (H ⁺ ), and may be a hydroxyl group (—OH), A mercapto group (—SH), an enol group (—CH═C (—OH) —) and the like can be exemplified.

  The organic acid salt has an acid group that forms a salt and an acid group that does not form a salt, each of which may be only one type, or two or more types, and when these are two or more types, these acids All the groups may be the same, all may be different, or only a part may be the same.

  In the acid group of the organic acid salt, the kind of cation forming the salt is not particularly limited, and is the same as the cation constituting the inorganic salt, primary amine, secondary amine, third A cation formed by bonding a hydrogen ion to a nitrogen atom of a nitrogen-containing organic compound such as a secondary amine can be exemplified.

In one molecule of the organic acid salt, an anion of one acid group may form a salt with one cation, or an anion of one acid group forms a salt with two or more cations. In the case where a salt is formed with two or more cations, these two or more cations may all be the same, or all may be different, and only some may be the same. Also good.
In addition, in one molecule of the organic acid salt, one cation may form a salt with two or more acid group anions, or a salt with two or more acid group anions These two or more anions may all be the same, may all be different, or may be partially the same.
Further, the organic acid salt may be one in which one cation forms a salt with one or more anions of acid groups in two or more molecules of the organic acid salt.

Preferred examples of the organic acid salt include
A salt of polyacrylic acid or a polyacrylic acid derivative obtained by polymerizing one or more monomers selected from the group consisting of acrylic acid and acrylic acid derivatives;
One or more monomers selected from the group consisting of acrylic acid and acrylic acid derivatives, and one or more monomers selected from the group consisting of other monomers not corresponding to any of acrylic acid and acrylic acid derivatives, A salt of an acrylic copolymer obtained by polymerization;
One or more polymers selected from the group consisting of polyacrylic acid, polyacrylic acid derivatives and the acrylic copolymers, and any of the polyacrylic acid, polyacrylic acid derivatives and the acrylic copolymers Examples thereof include a salt of a copolymer obtained by copolymerization with one or more polymers selected from the group consisting of other polymers not applicable.
In the present specification, “derivative” means a compound in which one or more hydrogen atoms of the original compound are substituted with a group (substituent) other than a hydrogen atom. Acrylic acid derivatives include methacrylic acid.

  More preferable examples of the organic acid salt include a carboxyvinyl polymer salt and a polyacrylic acid salt.

The molecular weight of the organic acid salt is not particularly limited as long as it functions as a thickener, but the weight average molecular weight is preferably 5000 to 10000000, and more preferably 8000 to 7000000. When the weight average molecular weight of the organic acid salt is within such a range, the composition for cold preservation can maintain an appropriate viscosity when not frozen, and the color change before and after freezing becomes larger.
In addition, in this specification, a weight average molecular weight is calculated | required on the polystyrene conversion standard by GPC (gel permeation chromatography).

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

  Although content of the said organic acid salt of the said 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 is 0.3-4 mass%. It is more preferable.

When the pH of the replacement composition in the case where the components other than the organic acid salt (thickener) and water are all replaced with water is “pH (C)” in the composition for cold preservation, this pH (C ) In other words, an organic acid salt-containing water containing only the organic acid salt (thickening agent) at the same content (mass%) as the content (mass%) in the cold insulation composition (for example, organic PH of the aqueous acid salt solution).
The pH (C) 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 organic acid salt-containing water is any temperature of 23 to 27 ° C. The pH is more preferable, and the pH when the temperature of the organic acid salt-containing water is 25 ° C. is particularly preferable.

The pH (C) is preferably 4.0 or more, more preferably 4.5 or more, and particularly preferably 5.0 or more.
Moreover, it is preferable that pH (C) is 10.0 or less, It is more preferable that it is 9.5 or less, It is especially preferable that it is 9.0 or less.
When pH (C) is in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

[PH indicator]
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. Examples include 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, more preferably 4.3 or more, and particularly preferably 4.6 or more.
Further, the pH indicator preferably has a pKa of 12.1 or less, more preferably 11.8 or less, and particularly preferably 11.5 or less.
When the pKa of the pH indicator is within such a range, the color change of the composition for cold preservation before and after freezing becomes larger.
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 3 to 15 ppm. .

The cold-retaining composition has a pH (the pH of the cold-retaining composition when not frozen, hereinafter abbreviated as “pH (A)”) and the pKa of the pH indicator represented by the following formula (I )
pH indicator pKa-0.7 <pH (A) <pH indicator pKa + 1.4 (I)

That is, the lower limit value of pH (A) is larger than a value smaller by 0.7 than the pKa of the pH indicator, and the upper limit value of pH (A) is a value larger by 1.4 than the pKa of the pH indicator. Smaller than.
The lower limit value of pH (A) is preferably a value smaller by 0.6 than the pKa of the pH indicator (“pH indicator pKa−0.6 ≦ pH (A)”), More preferably, it is a value smaller than the pKa of the pH indicator by 0.55 (“pH indicator pKa−0.55 ≦ pH (A)”).
The upper limit value of pH (A) is preferably a value 1.3 larger than the pKa of the pH indicator (“pH (A) ≦ pKa + 1.3 of pH indicator”), and the pH indicator It is more preferable that the value is 1.1 larger than the pKa of (pH (A) ≦ pKa of the pH indicator + 1.1).
When pH (A) is in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

  pH (A) is the pH at the time of non-freezing (before freezing) of the composition for cold preservation, preferably the pH at the temperature at which the pH indicator is dissolved in the composition for cold preservation, 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 (A) is preferably 5.0 or more, more preferably 5.3 or more, and particularly preferably 5.6 or more after satisfying the relationship of the formula (I). .
The pH (A) is preferably 12.0 or less, more preferably 11.7 or less, and preferably 11.3 or less after satisfying the relationship of the formula (I). Particularly preferred.
When pH (A) is in such a range, the color change of the composition for cold preservation before and after freezing becomes larger.

[Other ingredients]
In addition to water, the inorganic salt, the organic acid salt (thickening agent), and the pH indicator, the composition for cold preservation contains other components that do not fall within the scope of the effects of the present invention. Also good. Examples of the other components include solvents other than water; various known additives such as preservatives; salts that do not fall under any of the inorganic salts and the organic acid salts that are thickeners (organic salts, organic salts, Compound salts); thickeners other than organic acid salts can be exemplified.
The said other component may be used individually by 1 type, and may use 2 or more types together.

(solvent)
The solvent is preferably one that can dissolve the inorganic salt, organic acid salt (thickening agent), and pH indicator, and examples thereof 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.

(Preservative)
Examples of the preservatives include food preservatives and antioxidants, and examples include sodium pyrithione, paraben (paraoxybenzoate 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.
The said preservative may be used individually by 1 type, and may use 2 or more types together.

(Organic salt)
Examples of the organic salt (organic compound salt) include organic acid salts (excluding those that are thickeners) and organic base salts.
Examples of the salt of the organic acid include a carboxy group (—C (═O) —OH), a sulfo group (—S (═O) ₂ —OH), and a phosphono group (—P (═O) (— OH) ₂ ). Acid groups such as thiocarboxy group (—C (═O) —SH), thionocarboxy group (—C (═S) —OH), dithiocarboxy group (—C (═S) —SH), etc. Examples thereof include salts formed by reacting with a 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. .
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 1.5% by mass or less.

(Thickeners other than organic acid salts)
The thickener other than the organic acid salt is usually the non-freezing (before freezing) and freezing (after freezing) of the composition for cold preservation, similarly to the thickening agent which is the organic acid salt. It is a component that suppresses precipitation. That is, in the composition for cold preservation at the time of non-freezing and freezing, the thickener other than the organic acid salt is preferably as the amount deposited is smaller, the total amount of the thickener other than the organic acid salt Of these, the amount deposited is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less, and 0% by mass (the total amount is precipitated). Is not particularly preferred.

Examples of the thickener other than the organic acid salt include carboxyalkyl cellulose such as carboxymethylcellulose (CMC); guar gum; hydroxyalkyl guar gum such as hydroxypropyl guar gum; pectin; xanthan gum; tamarind gum; carrageenan; Can be illustrated.
Thickeners other than the organic acid salt 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 an organic acid salt”.

  In the composition for cold preservation, the content of the thickener other than the organic acid salt with respect to the total content of the thickener and the thickener other than the organic acid salt (total content of the thickener). The ratio is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

  The said composition for cold preservation is the said inorganic salt with respect to the total content of components other than water and the said solvent (The said inorganic salt, the thickener which is organic acid salt, a pH indicator, and other components other than the said solvent), The ratio of the total content of the thickener and the pH indicator, which are organic acid salts, 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.

The composition for cold preservation is obtained by blending water, the inorganic salt, the organic acid salt (thickening agent), 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.

<Cold insulation>
The cold-reserving tool according to the present invention is provided with the cold-retaining composition, and is configured, for example, by holding the cold-retaining composition by holding means such as a container capable of enclosing 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. Examples thereof include synthetic resins such as polyolefins, polyamides, and polyesters. 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, 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)
CVP-1 (carboxyvinyl polymer): “Aronbis AH-305X” manufactured by Toa Gosei Co., Ltd.
CVP-2 (carboxyvinyl polymer): “Reogic 270” manufactured by Toa Gosei Co., Ltd.
CVP-3 (carboxyvinyl polymer): “Reogic 845H” manufactured by Toa Gosei Co., Ltd.
-PA (acrylic polymer): “AQUALIC FH-S” manufactured by Nippon Shokubai Co., Ltd.
・ CMC (Carboxymethylcellulose): “Serogen” manufactured by Daiichi Kogyo Seiyaku
・ GG (Guar gum): “Guapack PF-20” manufactured by Sankisha 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.)
・ BTB: Bromothymol 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>
At room temperature (20 to 25 ° C.), water (88 parts by mass), ammonium chloride (10 parts by mass), CVP-1 (1 part by mass) and BCG were added and mixed to obtain a composition for cold preservation. At this time, the blending amount of BCG was adjusted so that the content in the obtained composition for cold insulation was 10 ppm. And pH (A) of the obtained composition for cold preservation was measured. Table 1 shows each compounding component other than water and its content (concentration), pH indicator pKa, pH (A), pH (B), pH (C) and the like.
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 (B) 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 (C) 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 10, Comparative Examples 1 to 10]
A composition for cold insulation and a cold insulation tool were produced in the same manner as in Example 1 except that the components and concentrations of the cold insulation composition were as shown in Table 1 or 2, and the cold insulation composition was evaluated. The results are shown in Table 1 or 2. For example, in Example 9, four types 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 the pH (B ) 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 1% by mass for diammonium hydrogen phosphate.

  As is clear from the above results, in Examples 1 to 10, the thickener used is an organic acid salt, and the relationship of the formula (I) regardless of the number of types of inorganic salts used. By satisfying the above, before and after freezing, the color of the composition for cold preservation clearly changed reflecting the change in color development of the pH indicator, and the cooling state could be easily visually confirmed.

  On the other hand, in Comparative Examples 1 to 4 and 6, the thickener used is a non-organic acid salt and does not satisfy the relationship of the formula (I). The color change of the composition was unclear and it was difficult or impossible to see the cooling state. Further, in Comparative Example 5, the relationship of the formula (I) was satisfied, but the thickener used was a non-organic acid salt, so that the color change of the composition for cold preservation was changed before and after freezing. It was unclear and it was difficult or impossible to see the cooling state. Moreover, in Comparative Examples 7 to 10, the thickener used is an organic acid salt, but the color change of the composition for cold preservation before and after freezing by not satisfying the relationship of the formula (I). Was unclear and it was difficult or impossible to visually recognize the cooling state.

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

Claims (1)

A cold insulator provided with a cold insulating composition containing water, an inorganic salt, a thickener and a pH indicator,
The thickener is an organic acid salt;
A cold insulator characterized in that the pH of the cold-retaining composition and the pKa of the pH indicator satisfy the relationship of the following formula (I).
pKa of the pH indicator-0.7 <pH of the composition for cold preservation <pKa of the pH indicator + 1.4 (I)