JP2001089755A - Cold energy-storing material, and cooling medium containing the cold energy-storing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold energy-storing material which has excellent durability to repeated freezing and melting treatments, and to provide a cooling medium containing the cold energy-storing material. SOLUTION: This cold energy-storing material comprises a water-absorbing resin and water. The water-absorbing material has a liquid-absorbing ratio of >=7 g/g measured using a 0.9 wt.% aqueous sodium chloride solution under a pressure of 20 g/cm2, and a saturated liquid-absorbing ratio of <=50 g/g. The cooling medium is the dispersion of the cold energy-storing material in a dispersing medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold storage material containing a water absorbent resin and water, and a cooling medium containing the cold storage material.

[0002]

2. Description of the Related Art Cold storage materials are used, for example, as cooling means for foods, medicines and the like, and as cooling means for cooling devices and the like. These regenerative materials mainly use latent heat at the time of freezing and thawing (phase change) of a substance. Further, in order to more effectively use the latent heat, a device utilizing a eutectic composition is disclosed.

[0003] Specifically, for example, Japanese Patent Laid-Open No. 4-6483
No. 9, JP-A-4-81492 and JP-A-6-271841 disclose a regenerator material containing a water-absorbing resin. Also, Japanese Patent Application Laid-Open Nos. 1-245082 and 11-158462.
Japanese Patent Application Laid-Open Publication No. H11-139686 discloses a regenerator material obtained by adding a water-absorbing resin or the like to a eutectic composition (aqueous liquid) comprising an inorganic electrolyte substance and water.

[0004] As a main component of these regenerative materials, as described above, a liquid containing water (water itself or an aqueous solution of a water-soluble inorganic or organic substance. (Collectively referred to as) is generally used. This is for improving the handleability of the aqueous liquid. That is, although the aqueous liquid alone can be used as a cold storage material, it has a problem that, for example, when the container accommodating the aqueous liquid is damaged, the aqueous liquid flows out and contaminates the surroundings.

[0005]

As described above, the cold storage material is frozen and thawed when used (cool storage / cooling). For example, a cold storage material mainly composed of hydrogel is
Each time the freezing / thawing is performed, the volume of the aqueous liquid contained therein changes, and the volume of the hydrogel changes. That is, the water-absorbent resin forming the hydrogel is expanded and contracted.

When the above-mentioned cold storage material is used repeatedly (freezing and thawing are repeated), the stability of the water-absorbent resin constituting the hydrogel is reduced due to repeated expansion and contraction. Gel softens, dissolves,
And other problems occur. This decrease in stability is presumed to be due to the disconnection of the network structure (crosslinked structure and the like) of the water-absorbent resin.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a cold storage material having excellent durability against repeated freezing and thawing, and a cold storage material including the cold storage material. To provide a cooling medium.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the absorption capacity under pressure measured with a 0.9% by weight aqueous sodium chloride solution and the saturated absorption capacity were measured. It has been found that a regenerator material comprising a water-absorbent resin having a magnification within a predetermined value range and water has excellent durability (freezing / thawing resistance) against repeated freezing and thawing. . Furthermore, the present inventors have found that dispersing the cold storage material in a dispersion medium can provide a cooling medium having excellent freezing / thawing resistance, and have completed the present invention.

That is, in order to solve the above-mentioned problems, the cold storage material of the present invention is a cold storage material containing a water-absorbing resin and water, and is measured using a 0.9% by weight aqueous sodium chloride solution. Further, the water absorbing resin is characterized in that the liquid absorbing capacity under pressure of 20 g / cm ² is 7 g / g or more and the saturated liquid absorbing capacity is 50 g / g or less.

[0010] In the cold storage material of the present invention, in order to solve the above-mentioned problem, the water-absorbent resin is subjected to a hydrophobic treatment and / or a cross-linking treatment in the vicinity of the surface. It is characterized by:

In order to solve the above-mentioned problems, a cooling medium according to the present invention is characterized in that the above-described cold storage material is dispersed in a dispersion medium.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Note that the present invention is not limited by this.

[0013] The cold storage material according to the present invention is a "water-absorbent resin".
And cold water, comprising 0.9% by weight
The water-absorbent resin has a liquid absorption capacity under a pressure of 20 g / cm ² of 7 g / g or more and a saturated liquid absorption capacity of 50 g / g or less, measured using an aqueous sodium chloride solution.

The above "water-absorbing resin" is 0.9% by weight.
"20 g / c measured using an aqueous sodium chloride solution
m ² , the absorption capacity under pressure ”and the“ saturation absorption capacity (hereinafter referred to as “saturation absorption capacity D”) ”(each described below) are within the above range. The type, shape, degree of cross-linking and the like of the bacterium are not particularly limited. Specifically, for example, crosslinked poly (meth) acrylic acid (salt) such as crosslinked acrylic acid-sodium acrylate copolymer; crosslinked poly (meth) acrylate having a polyoxyalkylene group; poly ( (Meth) acrylamide crosslinked product; copolymerized crosslinked product of (meth) acrylic acid (salt) and (meth) acrylamide such as sodium acrylate-acrylamide copolymer crosslinked product; hydroxyalkyl (meth) acrylate and (meth) acrylic Cross-linked copolymer with acid (salt); cross-linked polydioxolane; cross-linked polyethylene oxide; cross-linked polyvinyl pyrrolidone;
Cross-linked poly (meth) acrylate having a sulfonic acid group, cross-linked sulfonated polystyrene, cross-linked polyvinyl alcohol sulfonate, 2-acrylamide-2-
Water-absorbing resin having a sulfonic acid group such as a methylpropanesulfonic acid (salt) crosslinked (co) polymer, a sulfoalkyl (meth) acrylate (salt) crosslinked (co) polymer; a crosslinked polyvinylphosphonic acid, -Acryloyloxyethyl) acid phosphate crosslinked (co) polymer, mono (2-methacryloyloxyethyl) acid phosphate crosslinked (co) polymer, etc., water-absorbing resin having a phosphate group; crosslinked polyvinylpyridine; starch-poly ( Meta)
Saponified acrylonitrile graft copolymer; starch-poly (meth) acrylic acid (salt) graft copolymer crosslinked product; reaction product of polyvinyl alcohol and maleic anhydride (salt); polyvinyl alcohol-acrylic acid graft copolymer A polyisobutylene-maleic acid (salt) crosslinked copolymer; an N-vinylacetamide crosslinked (co) polymer;
Betaine monomer (co) polymer; copolymer of anionic monomer and cationic monomer; and the like. Only one kind of these water-absorbing resins constituting the cold storage material according to the present invention may be used, or two or more kinds thereof may be used.

The above water-absorbent resin has been subjected to “hydrophobizing treatment” and / or “cross-linking treatment (surface cross-linking treatment)” or the like in the vicinity of the surface thereof.
g / cm ² absorption capacity under pressure ”and“ saturated absorption capacity D ”
Is included in the range of the above values. The above “hydrophobizing treatment” refers to a treatment for hydrophobizing the vicinity of the surface of the water-absorbent resin using a hydrophobizing agent. The method of performing the hydrophobic treatment is not particularly limited,
Specifically, for example, the method can be suitably performed by a method of impregnating or vapor-depositing a water-absorbing resin with a hydrophobizing agent (a solution thereof). The hydrophobizing agent is capable of bonding (chemical bonding) and / or adsorbing (chemical adsorption / physical adsorption) with the vicinity of the surface of the water-absorbing resin, and is compared with the vicinity of the surface before the hydrophobizing agent treatment. There is no particular limitation as long as the vicinity of the surface after the treatment can be hydrophobized. Specifically, for example, a surfactant having an HLB of 10 or less; a hydroxyl-containing compound such as a monoalcohol having 4 or less carbon atoms; a silane compound; an epoxy-containing compound; an amino-containing compound; an amide-containing compound;
And the like.

The above-mentioned surface cross-linking treatment refers to a treatment for forming a cross-linked structure near the surface of the water-absorbent resin using a surface cross-linking agent. More specifically, it means that a surface cross-linking agent having a reactivity with a functional group such as a carboxyl group usually included in the water-absorbing polymer is applied to the vicinity of the surface of the above-mentioned water-absorbing polymer to crosslink. The surface cross-linking treatment is performed, for example, by mixing the surface cross-linking agent (the solution) and the water-absorbing polymer, and then heating the mixture at 80 to 220 ° C. to react the carboxyl group near the surface with the surface cross-linking agent. It can be carried out.

The type of the surface cross-linking agent is not particularly limited, but specifically, for example, ethylene glycol, diethylene glycol, propylene glycol,
Triethylene glycol, tetraethylene glycol,
Polyethylene glycol, 1,3-propanediol,
Dipropylene glycol, 2,2,4-trimethyl-
1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4
-Diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, poly Polyhydric alcoholic compounds such as oxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, etc .; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, poly Glycerol polyglycidyl ether, polypropylene glycol diglycidyl ether,
Epoxy compounds such as glycidol; polyamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, polyallylamine and polyethyleneimine; 2,4-tolylenediisocyanate;
Polyvalent isocyanate compound such as hexamethylene diisocyanate; polyvalent oxazoline compound such as 1,2-ethylenebisoxazoline; 1,3-dioxolane-2-
On, 4-methyl-1,3-dioxolan-2-one,
4,5-dimethyl-1,3-dioxolan-2-one,
4,4-dimethyl-1,3-dioxolan-2-one,
4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one,
1,3-dioxan-2-one, 4-methyl-1,3-
Alkylene carbonates such as dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one; epichlorohydrin, epibromohydrin, α-methyl Haloepoxy compounds such as epichlorohydrin; polyvalent metal-containing compounds such as hydroxides or chlorides such as zinc, calcium, magnesium, aluminum, iron and zirconium; adducts of polyamines with epichlorohydrin (Sponges, etc.);
2,2-bishydroxymethylbutanol-tris-
And polyvalent aziridine such as [3- (1-aziridinyl) propionate].

The above-mentioned “hydrophobizing treatment” and / or
By performing the “surface cross-linking treatment”, the strength of the water absorbent resin is improved. Therefore, there is an effect that the stability of the cold storage material containing the water-absorbing resin is improved, and in addition, the liquid absorption capacity under pressure is improved. Therefore, for example, it is possible to provide a cold storage material that can be suitably used even under pressure.

When the regenerator material according to the present invention further comprises a polyvalent metal salt (for example, a freezing point (melting point) regulator, a part of a supercooling inhibitor described below), and / or
Or, when the cold storage material is used in the presence environment of a polyvalent metal salt, and the like, an amide group,
A water-absorbing resin having a nonionic group such as a hydroxyl group, a polyalkylene glycol group, or an alkoxypolyalkylene glycol group; a water-absorbing resin having a sulfonic acid group exemplified in the description of the above “water-absorbing resin”; It is more preferable to use a water-absorbing resin. These water-absorbing resins are salt-resistant water-absorbing resins that hardly deteriorate with respect to polyvalent metal salts. Further, from the viewpoint of water absorption performance, (meth)
A water-absorbing resin containing acrylic acid (salt) is more preferable.

The above "20 g / cm ² absorption capacity under pressure"
"" Means the liquid absorption capacity of the water-absorbent resin under a pressurized condition of 20 g / cm ² , and is measured using a measuring device shown in FIG. The measuring device, as shown in FIG.
A saline solution supply unit 7 having a balance 1, a container 2 loaded on the balance 1 and containing a predetermined amount of physiological saline (0.9 wt% aqueous sodium chloride solution) 12; a glass filter having a diameter of 70 mm 6; and a measuring unit 5 mounted on the glass filter 6. Further, the above-mentioned saline solution supply section 7 and the measurement section 5 are connected to each other by the conduit 4 via the glass filter 6, and the physiological saline solution 12 can be moved from the saline solution supply section 7 to the measurement section 5. It has a configuration.

The container 2 has an opening 2a at the top.
And an opening 2b on the side surface thereof.
a, the outside air suction pipe 3 is fitted into the opening 2b.
Is provided with a conduit 4. Outside air suction pipe 3
Is provided such that its lower end is immersed in the physiological saline solution 12. The upper surface of the glass filter 6 is fixed at a position slightly higher than the lower end of the outside air suction pipe 3. The measuring unit 5 includes a filter paper 8,
It comprises a support cylinder 9, a wire mesh 10 attached to the bottom of the support cylinder 9, and a weight 11. More specifically, the filter paper 8 and the support cylinder 9 are placed in this order on the upper surface of the glass filter 6, and the inside of the support cylinder 9
That is, the weight 11 is placed on the wire net 10. The inner diameter of the support cylinder 9 is 60 mm. The wire net 10 is made of stainless steel, and is formed in 400 mesh (mesh size 38 μm).

The water-absorbent resin 13 as a sample for measuring “20 g / cm ² absorption capacity under pressure” is evenly spread on the wire net 10. That is, at the time of measurement, the water absorbent resin 13
Is sandwiched between the wire mesh 10 and the weight 11. In addition, the weight 11 is
The weight is adjusted so that a load (pressure) of 20 g / cm ² can be applied uniformly.

The measurement of the liquid absorption capacity under pressure of 20 g / cm ² is performed in the following procedure. First, after a predetermined amount of the physiological saline solution 12 is put in the container 2, predetermined preparations such as fitting the outside air suction pipe 3 into the opening 2a of the container 2 are performed. Next, the filter paper 8 is placed on the upper surface of the glass filter 6, and in parallel with this placing operation, 0.9 g of the water-absorbent resin 13 is uniformly placed inside the support cylinder 9 (that is, on the wire mesh 10). Then, the weight 11 is placed on the water absorbent resin 13. Subsequently, the support cylinder 9 on which the water absorbent resin 13 and the weight 11 are placed is placed on the filter paper 8. As a result, the water-absorbent resin 13 starts absorbing the physiological saline solution 12 under the condition that a load of 20 g / cm ² is applied (under pressure). Then, the weight W2 (g) of the physiological saline solution 12 absorbed by the water-absorbent resin 13 is measured using the balance 1 for one hour from the time when the support cylinder 9 is placed on the filter paper 8. The liquid absorption capacity under pressure (g / g) of 20 g / cm ² is determined according to the following equation.

20 g / cm ² absorption capacity under pressure (g / g)
= W2 (g) / weight of water-absorbent resin (0.9 g) The "saturated liquid absorption ratio D" is measured as follows. Non-woven bag (60 mm x 60 m)
m), and heat-sealed the mouth of the bag. Then, the bag is immersed in a beaker containing 120 g of a 0.9% by weight aqueous sodium chloride solution to absorb liquid. After one hour, the bag is pulled up from the beaker, and after draining, the weight W1 (g) of the bag is measured. Drain the bag with the bag pulled up from the beaker.
After leaving it for 5 seconds, three kitchen towels (trade name, Extra Dry; manufactured by Oji Paper Co., Ltd.) were stacked and folded in half.
(The area equivalent to the size of a four-folded surface), and further fold it in half, and sandwich the bag with a kitchen towel. After sandwiching, a 200 g weight is placed on it and allowed to stand for 15 seconds.

Subsequently, the same operation is carried out on the nonwoven bag containing no water-absorbent resin (blank test), and the weight W0 (g) of the bag after draining is measured. The saturated absorption capacity D (g / g) is determined according to the following equation.

Saturated liquid absorption capacity D (g / g) = (W1−W0) / w The value of w (g) is not particularly limited, but may be about 0 regardless of the type of water-absorbing resin. If it is 0.2 g, it is more preferable to immerse it in a 0.9% by weight aqueous solution of sodium chloride for one hour to ensure a saturated liquid absorbing state.

[0027] The regenerative material of the present invention further comprises water. Water has the following features: 1) heat capacity is extremely large; and 2) the water absorption ratio of the water-absorbent resin is particularly large. Note that a water-soluble substance can be dissolved in water, if necessary. Hereinafter, "water" itself and a mixture of water and the "water-soluble substance" are collectively referred to as "aqueous liquid". Examples of the “water-soluble substance” include water-soluble organic solvents such as methyl alcohol, acetone, ethylene glycol, propylene glycol, polyethylene glycol, and glycerin. One or more of these water-soluble organic solvents can be used. When only the water-soluble organic solvent is used instead of water, 1) the heat capacity is smaller than that of water, and 2) water absorption. The amount that can be absorbed by the resin is small (that is, these water-soluble organic solvents are more easily absorbed by the water-absorbent resin when dissolved in water)
Therefore, a suitable cold storage material cannot be obtained.

The regenerator material according to the present invention mainly utilizes latent heat upon freezing and thawing (phase change) of an aqueous liquid, and additionally utilizes sensible heat transfer. Further, these aqueous liquids are usually contained in the above-described water-absorbent resin in a form to be absorbed. Therefore, there is no fear that the problem that the aqueous liquid flows out and contaminates the surroundings occurs.

As described above, the water-absorbing resin contained in the cold storage material of the present invention has a liquid absorption capacity under pressure of 20 g / cm ² measured using a 0.9% by weight aqueous sodium chloride solution of 7 g / cm ^2.
g or more and the saturated liquid absorption capacity (saturated liquid absorption capacity D) is 50 g
/ G or less. 20 g / cm ^{2 of the} water absorbent resin
When the absorption capacity under pressure and the saturation absorption capacity D are within the above ranges, the expansion and contraction of the water-absorbent resin (the water content contained inside) occurs each time the cold storage material (hydrogel) is frozen and thawed. (Due to variations in the volume of the liquid). That is, the regenerator material according to the present invention is excellent in durability even when used repeatedly, and there is no fear that problems such as softening or dissolution of the hydrogel will occur.

The water absorption under pressure of 20 g / cm ² of the water-absorbent resin may be 7 g / g or more as described above, but is more preferably 15 g / g or more, and more preferably 2 g / g or more.
It is particularly preferably 0 g / g or more. According to this, the durability of the cold storage material according to the present invention can be further improved.

The regenerator material according to the present invention further has a saturated liquid absorption capacity (hereinafter referred to as a saturated liquid absorption rate A) of the water-absorbent resin measured by using the aqueous liquid as A, and a weight of the water-absorbent resin. When B is the weight of the aqueous liquid and C is C /
It is more preferable that the value of (A × B) be in the range of 0.1 or more and 0.95 or less.

The above-mentioned saturated liquid absorption capacity A means a saturated liquid absorption capacity measured using an aqueous liquid contained in the cold storage material of the present invention. The measuring method is the same as that of the above-mentioned "saturation absorption capacity D" except that the aqueous liquid is used instead of the 0.9% by weight aqueous sodium chloride solution. Further, the value of (A × B) is specifically,
The amount of the aqueous liquid that can be absorbed by the water-absorbent resin (saturation amount), and the value of C more specifically indicates the amount of the aqueous liquid that is actually absorbed by the water-absorbent resin.

Therefore, the value of C / (A × B) is 1.0, that is, a state in which the water-absorbent resin absorbs (contains) an aqueous liquid until it becomes saturated. Point to. Further, that the value is in the range of 0.1 or more and 0.95 or less means that the aqueous liquid is contained in the range of 10% or more and 95% or less based on the saturated state. . By setting the value to 0.95 or less, 1) since the aqueous liquid contained in the cold storage material is less than the saturation amount (has a margin), the stability of the cold storage material when freezing and thawing is repeated is repeated. Is further improved. Further, by setting the value to 0.1 or more, it is possible to prevent 2) an increase in the amount of the water-absorbing resin used or a decrease in the cold storage capacity of the cold storage material from becoming a level that cannot be overlooked industrially.

The regenerator material according to the present invention may further contain a freezing point (melting point) regulator and / or a supercooling inhibitor. As the freezing point regulator, specifically, for example, sodium chloride, potassium chloride, calcium chloride,
Ammonium chloride, sodium (hydrogen) carbonate, potassium (hydrogen) carbonate, ammonium (hydrogen) carbonate, disodium hydrogen phosphate dodecahydrate, sodium orthophosphate
Water-soluble inorganic substances such as dodecahydrate, ammonium bromide, sodium borate, sodium sulfate and sodium acetate trihydrate; water-soluble organic substances such as ethylene glycol and urea; and the like. By further containing the above freezing point modifier, the freezing point (melting point) can be lowered as compared with the case of the above water alone. That is,
Since the latent heat of fusion relating to the eutectic with water can be used, a greater cold storage capacity can be exhibited.

The supercooling inhibitor is not particularly limited, but specific examples thereof include potassium bromate, tripotassium phosphate, borax (sodium borate), silicate, and ice. Quartzite (Na ₃ AlF ₆ ) and the like. In the above supercooling inhibitor, the regenerator material has a freezing point (melting point)
It is particularly effective when it comprises a regulator. One of these freezing point regulators and supercooling inhibitors may be used alone, or two or more thereof may be used.

The regenerator according to the present invention may further contain a gel stabilizer. The gel stabilizer refers to a substance capable of stabilizing (mainly preventing deterioration) a water-containing gel obtained by absorbing water in a water-absorbing resin, and is not particularly limited. Examples thereof include a sulfur-containing reducing agent and And oxygen-containing reducing inorganic salts. Specific examples of the sulfur-containing reducing agent include thiol (mercaptan); sulfurous acid; and (water) sulfides such as hydrogen sulfide and sodium hydrogen sulfide. Further, as the oxygen-containing reducing inorganic salt, specifically, for example, sulfites, bisulfites, pyrosulfites, dithionites,
Trithionate, tetrathionate, thiosulfate (these are
A sulfur-containing reducing agent), nitrite, and the like. One of these gel stabilizers may be used, or two or more thereof may be used.

The regenerator material according to the present invention has a freezing point (melting point)
When further containing additives such as a regulator, a supercooling inhibitor, a gel stabilizer, etc., these additives are mixed with 1) a water-absorbing resin comprising water, and 2) a mixture of the additives with water. (Or dissolved) and then added by a method such as absorption into a water-absorbing resin. The amounts of these additives used are not particularly limited. Further, the cold storage material according to the present invention more preferably contains the above water-absorbent resin and water as main components, but may further contain a resin other than the water-absorbent resin. Although the use of the cold storage material described above is not particularly limited, it is suitably used, for example, as a cooling means for medicines, foods and the like.

The regenerative material of the present invention can be dispersed in a dispersing medium as a cooling medium, if necessary. The dispersion medium is
The liquid is not particularly limited as long as it can disperse the cold storage material and satisfies the condition that it is immiscible with water (in the temperature range used).

Specific examples of the dispersion medium include oils such as animal oils, vegetable oils, and mineral oils; hydrocarbons such as paraffin; higher alcohols; ethers; nitriles; Organic silicon compounds such as compounds (including silicone oil); and the like. In addition, in terms of safety and handling,
Animal oils with a high boiling point and a low melting point,
Vegetable oils and the like; hydrocarbons having 6 or more carbon atoms; higher alcohols; ethers having 6 to 14 carbon atoms;
Organic silicon compounds such as alkyl silicon compounds; and the like are more preferable, and animal oils; vegetable oils; liquid paraffin; silicone oils; Further, from the viewpoint of the temperature range used, it is more preferable that the dispersion medium does not solidify at a temperature of 0 ° C. or higher.

The regenerative material dispersed in the dispersion medium may be only one type, or two or more types. As the cold storage material, a material containing a water-absorbing resin subjected to the above-described hydrophobic treatment is more preferable because of its good dispersibility in a dispersion medium.

The above cooling medium is, for example, packed in a bag,
It can be suitably used as a cooling means having flexibility even during freezing. Further, when the cooling medium is, for example, a material obtained by dispersing a cold storage material in a large amount of a dispersion medium having excellent fluidity, the cooling medium is circulated between the heat storage tank and the heat exchanger. It can be suitably used as a cooling means in a cooling device or the like.

The above-mentioned cooling medium may further contain a gel dispersibility improver. What is a gel dispersibility improver?
It is intended to improve the dispersibility of the cold storage material in the dispersion medium and prevent aggregation of the cold storage materials, and is not particularly limited, but includes, for example, a surfactant and a hydrophobic powder. be able to. The above surfactant has an HLB value of 10
The following are preferable in terms of dispersion performance, and sorbitan monostearate, sorbitan monooleate, sorbitan monomaleate, sorbitan monopalmitate, sorbitan tristearate, sorbitan trioleate, polyoxyalkylene alkyl ether, polyoxyalkylene 2 Particularly preferred are secondary alcohol ethers and the like. In addition, the above-mentioned hydrophobic powder can be used as both an organic substance and an inorganic substance as long as it is a hydrophobic powder.For example, inorganic substances such as aerosil, silica gel, alumina, diatomaceous earth, montmorillonite, kaolin, and bentonite are more preferably used. used. Only one type of these gel dispersibility improvers may be used, or two or more types may be used.

[0043]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Acrylic obtained by mixing sodium acrylate, acrylamide, and N, N-methylenebisacrylamide (crosslinking agent) in the order of 39.93: 70: 0.07 (molar ratio). 34 of acid monomers
A polymerization reaction was carried out under stirring in a nitrogen atmosphere using 4000 parts by weight of an aqueous solution containing 6.2 parts by weight of sodium persulfate (oxidizing initiator) and 0.62 parts by weight of L-ascorbic acid (reducing agent). Thus, a gel-like hydropolymer (a crosslinked copolymer of (meth) acrylic acid (salt) and (meth) acrylamide) finely divided into a particle size of about 5 mm was obtained.

The above gelled hydropolymer was dried with a hot air drier at 150 ° C., and then pulverized with a hammer type pulverizer.
The resultant was classified with a metal sieve (mesh: 20 mesh) to obtain a 20-mesh pass classified product (average particle size: 350 μm). Subsequently, the classified product of the 20-mesh pass was finely pulverized by a mill type pulverizer to obtain a water-absorbent resin A as a classified product of a 60-mesh pass and a 100-mesh on. Using a 0.9% by weight aqueous sodium chloride solution, 20 g of the water-absorbent resin A
/ Cm ^{2 The} absorption capacity under pressure and the saturated absorption capacity (saturated absorption capacity D) were measured and found to be 16.7, respectively.
(G / g) and 27.4 (g / g). That is,
The water-absorbent resin A satisfied the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. Then, after drying the water-absorbent resin A, 0.2 g of the water-absorbent resin A was again allowed to absorb a 0.9% by weight aqueous solution of sodium chloride (aqueous liquid) to obtain a cold storage material A according to the present invention. Subsequently, the cold storage material A was subjected to a freeze / thaw test described below.

(Freezing / Thawing Test) The regenerator material A was placed in a non-woven bag (60 mm × 60 mm), the mouth of which was heat-sealed, and then placed in a beaker containing 120 g of 0.9% by weight aqueous sodium chloride solution. Dipped. After one hour from the start of the immersion, the bag was pulled up from the beaker, and drained by the same method as in the measurement of the saturated liquid absorption ratio D described above, and the weight W4 (g) of the bag was measured. As described in the description of the method for measuring the saturated liquid absorption magnification D, 0.2 g of the water-absorbent resin A is brought into a saturated liquid absorption state by immersing it in a 0.9% by weight aqueous sodium chloride solution for one hour. Therefore, the cold storage material A is also in a saturated liquid absorbing state.

Further, the same operation was carried out on the nonwoven fabric bag containing no regenerator A (blank test), and the weight W3 (g) of the bag after draining was measured. The saturated liquid absorption capacity E ₀ (g / g) at the time of zero freezing / thawing cycle was determined according to the following equation.

Saturated liquid absorption capacity E ₀ (g / g) = (W4−W3) /0.2 Subsequently, the saturated liquid absorption capacity E put in the nonwoven fabric bag described above.
The cold storage material A after the ₀ measurement was sealed in a polyethylene bag (Unipack; trade name, manufactured by Seinichi Co., Ltd.) with a size of 7 cm × 10 cm. Then, the above unipack was immersed in acetone cooled to −50 ° C. with dry ice for 3 minutes, and then immersed in warm water at 50 ° C. for 3 minutes. Thereby, the freezing material A was frozen and thawed. This freezing / thawing was repeated 10 times.

Then, the above-mentioned unipack was water-bathed at a temperature of 25 ° C. for a predetermined time to adjust the temperature of the cold storage material A to 25 ° C. Then, the nonwoven fabric bag was taken out of the unipack, and the above-mentioned saturated liquid absorption ratio E _{0 was obtained.} The saturation absorption capacity E ₁₀ (g /
g) was determined.

[0050] After saturated liquid absorption magnification E ₁₀ Measurements, cold accumulating material A further 10 cycles of freezing and thawing of 20 times, repeated 30 times,
Each time, freeze / thaw cycle 20 times, 30 times, 4
The saturation absorption ratios E ₂₀ , E ₃₀ and E ₄₀ (g / g) at the time of 0 times were determined. 20 g / cm ² absorption capacity under pressure of water-absorbent resin A,
The measurement results of the saturated liquid absorption ratio D and the saturated liquid absorption ratios E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , and E ₄₀ (g / g) of the cool storage material A are summarized in Table 1 below. Was.

The stability of the cold storage material A before and after the freeze / thaw test was evaluated by touch. Specifically, the difference in the tactile sensation between the cold storage material A before the freeze / thaw test and the cold storage material A after 40 freeze / thaw cycles (after the freeze / thaw test) was evaluated. The evaluation criteria are three levels of "○", "△", "x",
“○” indicates a state in which no difference in tactile sensation occurs, and “△”
Indicates that the cold storage material A is slightly softened, although there is no practical problem, and "x" indicates the cold storage material A softened to a practically problematic level. The evaluation of the stability of the cold storage material A is also shown in Table 1 below.

Example 2 A mixture of sodium acrylate, acrylic acid, and N, N-methylenebisacrylamide (crosslinking agent) in the order of 74.95: 25: 0.5 (molar ratio). 37% by weight of acrylic acid monomer
4000 parts by weight of an aqueous solution were mixed with 2.0 parts by weight of sodium persulfate (oxidizing initiator) and L-ascorbic acid (reducing agent)
The polymerization reaction was carried out with stirring in a nitrogen atmosphere using 0.08 parts by weight to obtain a gel-like hydrated polymer (crosslinked poly (meth) acrylic acid (salt)) having a particle size of about 5 mm. .

After drying the above gelled hydropolymer with a hot air drier at 150 ° C., it was pulverized by a hammer type pulverizer.
The resultant was classified with a metal sieve (mesh: 20 mesh) to obtain a 20-mesh pass classified product (average particle size: 350 μm). Subsequently, the classified product of the 20-mesh pass was finely pulverized by a mill-type pulverizer to obtain a water-absorbent resin B as a classified product of a 60-mesh pass and a 100-mesh on. Using a 0.9% by weight aqueous sodium chloride solution, 20 g of the water absorbent resin B was used.
/ Cm ^{2 The} absorption capacity under pressure and the saturated absorption capacity (saturated absorption capacity D) were measured to be 20.2
(G / g) and 21.0 (g / g). That is,
The water-absorbent resin B satisfied the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. After drying the water-absorbent resin B, 0.2 g of the water-absorbent resin B was again allowed to absorb a 0.9% by weight aqueous solution of sodium chloride (aqueous liquid) to obtain a regenerator material B according to the present invention. Subsequently, the cold storage material B was subjected to the freeze / thaw test described in Example 1 above.

The water absorption capacity of the water-absorbent resin B at 20 g / cm ² under pressure and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , and E _{40 of the} cold storage material B The measurement results of (g / g) are summarized in Table 1 below. Table 1 below also summarizes the evaluation of the stability of the cold storage material B.

Example 3 Acrylic acid obtained by mixing sodium acrylate, acrylic acid, and trimethylolpropane triacrylate (crosslinking agent) in the order of 74.95: 25: 0.05 (molar ratio) 37 of system monomer
A polymerization reaction was carried out under stirring in a nitrogen atmosphere using 4000 parts by weight of an aqueous solution of 4000% by weight with 2.0 parts by weight of sodium persulfate (oxidizing initiator) and 0.08 parts by weight of L-ascorbic acid (reducing agent). Thus, a gel-like hydropolymer (cross-linked poly (meth) acrylic acid (salt)) finely divided to a particle size of about 5 mm was obtained.

After drying the above gelled hydropolymer with a hot air drier at 150 ° C., it was pulverized with a hammer type pulverizer.
The resultant was classified with a metal sieve (mesh: 20 mesh) to obtain a 20-mesh pass classified product (average particle size: 350 μm). Subsequently, the classified product of the 20-mesh pass was finely pulverized by a mill-type pulverizer to obtain a water-absorbent resin C as a classified product of a 60-mesh pass and a 100-mesh on. Using a 0.9% by weight aqueous sodium chloride solution, 20 g of the water absorbent resin C was used.
/ Cm ^{2 The} absorption capacity under pressure and the saturated absorption capacity (saturated absorption capacity D) were measured, and were 8.9, respectively.
(G / g) and 36.8 (g / g). That is,
The water-absorbent resin C satisfied the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. After drying the water-absorbent resin C, 0.2 g of the water-absorbent resin C was again allowed to absorb a 0.9% by weight aqueous solution of sodium chloride (aqueous liquid) to obtain a regenerator C according to the present invention. Subsequently, the cold storage material C was subjected to the freeze / thaw test shown in Example 1 above.

The water absorption capacity of the water-absorbent resin C at 20 g / cm ² under pressure and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , E _{40 of the} cold storage material C The measurement results of (g / g) are summarized in Table 1 below. Table 1 below also shows the evaluation of the stability of the cold storage material C.

[Comparative Example 1] As a water-absorbing resin constituting a cold storage material, a water-absorbing resin D (IM-300; trade name, manufactured by Sanyo Chemical Co., Ltd.) as a classified product of 60 mesh pass and 100 mesh on was used. Using a 0.9% by weight aqueous solution of sodium chloride, the water absorption capacity of the water-absorbent resin D at 20 g / cm ² under pressure and the saturated liquid absorption capacity (saturated liquid absorption capacity D) were measured. .9 (g / g), 50.
3 (g / g). That is, the water-absorbent resin D did not satisfy the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. After drying the water-absorbent resin D, 0.2 g of the water-absorbent resin D was again allowed to absorb a 0.9% by weight aqueous sodium chloride solution to obtain a cool storage material D for comparison. continue,
The cold storage material D was subjected to the freeze / thaw test shown in Example 1 above.

The water absorption capacity of the water-absorbent resin D at 20 g / cm ² under pressure and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , E _{40 of the} cold storage material D The measurement results of (g / g) are summarized in Table 1 below. Table 1 also shows the evaluation of the stability of the cold storage material D.

Example 4 A water-absorbent resin E (KI gel 201K-300; trade name, manufactured by Kuraray Co., Ltd.) as a classified product of 60 mesh pass, 100 mesh-on was used as the water-absorbent resin constituting the cold storage material. Using a 0.9% by weight aqueous sodium chloride solution, 20 g / cm
^{2 When the} absorption capacity under pressure and the saturation absorption capacity (saturated absorption capacity D) were measured, the absorption capacity was 8.1 (g / g).
g) and 25.4 (g / g). That is, the water-absorbent resin E satisfied the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. Then, after drying the water-absorbent resin E, a 0.2% by weight aqueous solution of sodium chloride (aqueous liquid) was again absorbed into 0.2 g of the water-absorbent resin E to obtain a cold storage material E according to the present invention. Subsequently, the regenerator material E was used in the first embodiment.
The samples were subjected to a freeze / thaw test shown in Table 1 below.

The water absorption capacity of the water-absorbent resin E at 20 g / cm ² under pressure and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , E _{40 of the} cold storage material E The measurement results of (g / g) are summarized in Table 1 below. Table 1 below also summarizes the evaluation of the stability of the cold storage material E.

[Comparative Example 2] A water-absorbent resin F (S-50; trade name, manufactured by Sumitomo Chemical Co., Ltd.) as a classified product of 60-mesh pass and 100-mesh was used as a water-absorbent resin constituting a cold storage material. Using a 0.9% by weight aqueous sodium chloride solution, the water absorption capacity of the water-absorbent resin F under a pressure of 20 g / cm ² was measured, and the saturated water absorption capacity (saturated liquid absorption capacity D) was measured. .1 (g / g), 53.
2 (g / g). That is, the water-absorbent resin F did not satisfy the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. Then, after drying the water-absorbent resin F, a 0.9% by weight aqueous sodium chloride solution was again absorbed into 0.2 g of the water-absorbent resin F to obtain a cool storage material F for comparison. continue,
The cold storage material F was subjected to the freeze / thaw test shown in Example 1 above.

The water absorption capacity of the water-absorbent resin F under pressure of 20 g / cm ² and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , E _{40 of the} cold storage material F The measurement results of (g / g) are summarized in Table 1 below. Table 1 below also shows the evaluation of the stability of the cold storage material F.

Example 5 Glycerin (surface crosslinking agent) was added to 100 parts by weight of the water absorbent resin C obtained in Example 3 above.
After 0.5 parts by weight, 2 parts by weight of water and 2 parts by weight of ethyl alcohol are added and mixed, the mixture is subjected to a heat treatment at 210 ° C. so that the vicinity of the surface of the water-absorbent resin C undergoes secondary crosslinking (surface crosslinking treatment). The obtained water absorbent resin G was obtained. Using a 0.9% by weight aqueous solution of sodium chloride, 20 g / cm
⁽² ) When the absorption capacity under pressure and the saturation absorption capacity (saturated absorption capacity D) were measured, they were 29.4 (g /
g) and 30.2 (g / g). That is, the water-absorbent resin G satisfied the conditions required for the water-absorbent resin constituting the cold storage material of the present invention. Then, after drying the water-absorbent resin G, a 0.2% by weight aqueous solution of sodium chloride (aqueous liquid) was again absorbed into 0.2 g of the water-absorbent resin E to obtain a regenerator G according to the present invention. Subsequently, the cold storage material G was used in the first embodiment.
The samples were subjected to a freeze / thaw test shown in Table 1 below.

The water absorption capacity of the water-absorbent resin G at 20 g / cm ² under pressure and the saturated liquid absorption capacity D, and the saturated liquid absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , and E _{40 of the} cold storage material G The measurement results of (g / g) are summarized in Table 1 below. Table 1 below also summarizes the evaluation of the stability of the cold storage material G.

[0066]

[Table 1]

According to Table 1 above, the cold storage materials A, B, C, E and G according to the present invention obtained in Examples 1 to 5 are all the cold storage materials obtained in Comparative Examples 1 and 2. Compared to D and F,
1) Saturation absorption capacity E ₀ , E ₁₀ , E ₂₀ , E ₃₀ , E ₄₀ (g /
The measured value of g) is almost constant and stable. In addition, 2) excellent stability after the freeze / thaw test. In other words, it can be seen that the regenerator material according to the present invention has little (less) stability deterioration and excellent durability (freezing / thawing resistance) even when freezing / thawing is repeated.

Further, according to the comparison between Example 3 and Example 5, it is found that the regenerator material using the water-absorbing resin subjected to the surface cross-linking treatment is more excellent in stability.
It is also found that the surface treatment improves the strength of the water-absorbing resin and further improves the liquid absorption capacity of the cold storage material under pressure.

[0069]

As described above, according to the present invention, freezing
Cold storage material with excellent durability against repeated melting,
In addition, it is possible to provide a cooling medium including the cold storage material.

[Brief description of the drawings]

FIG. 1 shows a water-absorbent resin 20 as a cold storage material according to the present invention.
FIG. 2 is a schematic configuration diagram showing an example of a measuring device for measuring a liquid absorption capacity under g / cm ² under pressure.

[Explanation of symbols]

12 Physiological saline (0.9% by weight aqueous sodium chloride solution) 13 Water-absorbing resin

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) F25D 3/00 C09K 5/00 FF Term (Reference) 3L044 AA04 BA01 DC03 KA04 4F006 AA22 AB34 AB65 AB67 AB69 BA11 EA01 4F070 AB13 AC36 AC45 AC46 AC84 AE08 GA06 GA08 4J002 AB041 BB181 BC121 BE061 BG011 BG071 BG131 BH021 BJ001 BQ001 CH021 CH051 DE026

Claims (3)

[Claims] 1. A regenerator material comprising a water-absorbent resin and water, wherein said water-absorbent resin has an absorption capacity under pressure of 20 g / cm ² measured using a 0.9% by weight aqueous solution of sodium chloride. A regenerative material having a water absorption ratio of 7 g / g or more and a saturated liquid absorption capacity of 50 g / g or less. 2. The cold storage material according to claim 1, wherein said water-absorbent resin has been subjected to hydrophobic treatment and / or cross-linking treatment in the vicinity of its surface. 3. A cooling medium characterized by dispersing the regenerative material according to claim 1 or 2 in a dispersion medium.