JP2000273446A - Gelling agent for cold reserving material, gel and gel- like cold reserving material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a protruding material formed at the time of freezing by providing a gel-like cold retaining material with shape retaining properties. SOLUTION: This aqueous gel is a transparent aqueous gel without fluidity prepared by reacting gelatin with a copolymer of an ethylenically unsaturated compound and an ammonium maleate. Furthermore, the solubility thereof at the time of preparation is good. The resultant aqueous gel can be utilized as a cold reserving material to thereby ensure good shape retaining properties without causing deformation under an external pressure at the time of freezing and thawing. Furthermore, a protruding material (a navel) formed on the surface of the cold reserving material at the time of freezing can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a gel-like cold insulator. More specifically, the present invention relates to a gel-like cold insulator useful for cooling perishables and the like.

[0002]

2. Description of the Related Art Conventionally, as a gel-like cold insulator used for cooling perishables and the like, a material in which a granular water-absorbing gel of a water-absorbing resin is put in a bag of nylon or polyolefin or a hard plastic container is known.

[0003]

However, this cold insulator has the following disadvantages. (1) Deformation due to external pressure before freezing makes it difficult to form into the desired shape, and even after freezing, if the frozen state loosens with the passage of time, it easily shifts or deforms due to external pressure. There was a problem of inferiority. (2) During the freezing process of the cold insulator, a projection-like portion (navel) was formed at the center of the cold insulator due to the freezing temperature, which was inconvenient in appearance and handling.

[0004]

The present inventors have conducted intensive studies to obtain a gelling agent or gelled product for a cold insulator which has improved the above-mentioned problems, and as a result, surprisingly, an ethylenically unsaturated compound and maleic acid A reaction occurs when a copolymer of ammonium salt and gelatin is combined, and as a result of further development of the invention, it has been found that a gelled product having shape-retaining properties and not forming protruding portions in a freezing process was found. That is, the present invention provides a gelling agent for a cold insulator containing a reaction product of a copolymer (A) of an ethylenically unsaturated compound and an ammonium maleate salt with gelatin (B) as an essential component. It is a gelled material, a gel-like cold insulator.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a copolymer (A) of an ethylenically unsaturated compound and an ammonium maleate salt is used.
May be those obtained by forming a copolymer of an ethylenically unsaturated compound and maleic anhydride and then reacting with ammonia, or those obtained by copolymerizing a reaction product of maleic anhydride and ammonia with an ethylenically unsaturated compound. May be. The former is obtained by reacting a copolymer obtained by copolymerizing an ethylenically unsaturated compound and maleic anhydride in a solvent with ammonia, and the latter is obtained in the presence or absence of a solvent. It is obtained by copolymerizing a reaction product of maleic acid and ammonia with an ethylenically unsaturated compound. Preferably the former. The ethylenically unsaturated compound used here is not particularly limited as long as it is an unsaturated compound capable of copolymerizing maleic anhydride, and specifically, for example,

(1) Linear or branched C 2 -C 2
4 olefins ethylene, propylene, butene-1, butene-2, 1-
Pentene, isobutylene, 2-methyl-1-butene, 1
-Hexene, 2-methyl-1-pentene, 3-methyl-
1-pentene, 4-methyl-pentene, 2-ethyl-1
-Butene, 2-methyl-4-dimethyl-1-pentene,
Monoenes such as 2-methyl-4-dimethyl-2-pentene, 1-dodecene, 1-tetradecene, 1-hexadecene, and octadecene; dienes such as isoprene and diisobutylene; (2) aromatics having 8 to 30 carbon atoms (3) halogen-containing olefins having 8 to 30 carbon atoms such as vinyl chloride, vinyl fluoride, ethylene tetrafluoride, vinylidene chloride, and vinylidene fluoride; (4) vinyl ether methyl Vinyl alkyl such as vinyl ether
24) ethers, (meth) allylalkyl (having 1 to 1 carbon atoms)
24) Ether, poly (2-200) oxyalkylene (2-4 carbon atoms) monoallyl monoalkyl (1 carbon atom)
24) ethers and the like;

(5) (meth) acrylate alkyl or hydroxyalkyl groups having 1 to 2 carbon atoms
2, alkyl (meth) acrylate [methyl (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, behenyl (meth) acrylate, etc.]; poly (2-200) oxyalkylene (C2
To 4) mono (meth) acrylate [2-hydroxyethyl (meth) acrylate and the like]; (6) carboxyl group-containing unsaturated compound having 3 to 22 carbon atoms (meth) acrylic acid, monoalkyl maleate (carbon number 1-24) esters, fumaric acid, itaconic acid, itaconic acid glycol monoether and the like]; (7) sulfonic acid group-containing unsaturated compound vinyl sulfonic acid, 3-sulfopropyl (meth) acrylate, α-methylstyrene sulfonic acid, (8) Phosphoric acid group-containing unsaturated compound hydroxyalkyl (meth) acrylate (C2 to C1)
0) Phosphoric acid monoester, 2-hydroxyethyl (meth)
Acryloyl phosphate;

(9) Amide group-containing unsaturated compound acrylamide [(meth) acrylamide, N-methyl (meth) acrylamide, etc.]; cyclic acrylamide (N
(10) amino-containing unsaturated compound tertiary amine having 2 to 24 carbon atoms [(meth) allylamine,
Dimethylaminoethyl (meth) acrylate and the like]; quaternized products thereof (quaternized using a quaternizing agent such as methyl chloride, dimethyl sulfate, benzyl chloride and dimethyl carbonate) and the like]; (11) Epoxy group-containing (12) Others Vinyl alcohol, nitroethylene, acrylonitrile, etc. obtained by saponifying vinyl propionate and vinyl acetate. Of these, linear or branched olefins having 2 to 24 carbon atoms and vinyl ethers, preferably isobutylene, methyl vinyl ether and polyoxyalkylene monoallyl monoalkyl ether, particularly preferably isobutylene and methyl Vinyl ether. These monomers may be used alone or in combination of two or more.

The above-mentioned ethylenically unsaturated compound and maleic anhydride can be polymerized in the presence or absence of a solvent by a known method such as thermal radical polymerization, photoradical polymerization, or anionic polymerization. The temperature is, for example, from 0 to 200 ° C. under normal pressure or under pressure. In the case of thermal radical polymerization, azo compounds (such as azobisisobutyronitrile), peroxides (t
-Butyl peroxybenzoate).
In the case of photo-radical polymerization, a photo-radical initiator (such as benzoin alkyl ether) and a sensitizer (such as anthraquinone)
However, in the case of anionic polymerization, a Ziegler-Natta catalyst, a metallocene catalyst or the like is used in combination. The obtained copolymer may be used after removing the solvent, or may be used even in the presence of the solvent. Preferably, the solvent is removed.
The composition ratio of the ethylenically unsaturated compound and maleic anhydride in the polymer may be any as long as the ammonia reactant of the produced copolymer is soluble in water. The composition ratio of the compound and the ethylenically unsaturated compound is usually from 100: 1 to 1: 100, preferably from 10: 1 to 1:10, and particularly preferably from 5: 1 to 1: 5. The molecular weight of the produced copolymer is usually 2,000 to 5,000,000,
Preferably it is 3,000 to 3,000,000.

Various methods can be adopted for the reaction between the copolymer and ammonia. The solid powder of the copolymer is dispersed in a slurry in a solvent, and the ammonia gas is brought into contact with the solvent while bubbling. A method or a method of dissolving the copolymer powder in aqueous ammonia is preferably employed. The reaction ratio of the copolymer to ammonia is 0.5 to 2 moles, preferably 0.8 to 2 moles of ammonia per mole of maleic anhydride groups contained in the copolymer. The viscosity of the aqueous solution of the reaction product (at a concentration of 5% by weight) at 25 ° C. is usually 5 to 100,000 mPa · s, preferably 10 to 10,000 mPa · s, particularly preferably 15 to 5,000 mPa · s. -It is s.

In the present invention, gelatin (B) includes
Alkali-treated gelatin is preferred, but acid-treated gelatin and gelatin hydrolyzate can also be used, as long as it has at least one free amino group. Alkali-treated gelatin, for example, is obtained by removing bovine bone minerals to form ossein, and then immersing it in a suspension of slaked lime, cutting the cowhide into an appropriate size, washing with water and then adding 2 g of lime to the lime solution. It is obtained by performing a pretreatment with such a lime solution, which is soaked for up to three months. Acid-treated gelatin is obtained by immersing pork skin in diluted hydrochloric acid or diluted sulfuric acid for several tens of hours. Gelatin may be in the form of granules, powders or sheets, and the molecular weight is preferably from 3,000 to 30,000. In particular, in order to obtain gel shape retention, the molecular weight is 5,000.
0 to 20,000 is preferred.

In the reaction between the copolymer (A) of the ethylenically unsaturated compound and ammonium maleate and the gelatin (B), the proportion used cannot be specified unconditionally by the number of free amino groups of the gelatin. (B) 1 to get the nature
The reaction of (A) is usually 3 to 50 parts by mass, preferably 5 to 40 parts by mass with respect to 00 parts by mass. As the reaction method of (A) and (B), for example, (1) (A) and (B)
(2) a method of mixing (B) with an aqueous solution of (A), (3) a method of mixing (A) with an aqueous solution of (B), (4) (A) and (B) There is a method in which both are mixed after the aqueous solution is prepared in advance, but a uniform gel is easily obtained, and the preferred method is (4). Here, the concentration of the aqueous solution of (A) is preferably 1 to 30% by mass, particularly preferably 5 to 20% by mass. The concentration of the aqueous solution of (B) is preferably from 20 to 60% by mass, particularly preferably from 30 to 50% by mass.

As the reaction between (A) and (B) progresses, the viscosity of the system increases. It gels as it proceeds further. The end point of the reaction can be confirmed by the gel strength. The method for measuring the gel strength is described below. The temperature at which (A) and (B) are reacted is not particularly limited. For example, when the reaction is performed at 40 to 60 ° C., the reaction is completed within several hours, and when the reaction is performed at room temperature, one day and night are required. . The reaction between (A) and (B) is such that the amino group in (B) replaces the ammonia in (A) to form a salt or reacts to form an amide bond to increase the viscosity. Presumed. The gel strength of the reaction product of (A) and (B) is usually from 20 to 1,000 g, preferably from 30 to 1,000 g.
600, particularly preferably 50-500. If the gel strength is less than 20, the shape retention of the gel becomes poor,
If it exceeds 1,000, cracks easily occur and it is difficult to handle. (Measurement method of gel strength) The temperature of the gel was adjusted to 25 ° C.
A rod having a 5.7 mm metal ball was connected to a Shimadzu autograph (AGS-500B, manufactured by Shimadzu Corporation). The metal sphere was pushed into the gel at a speed of 5 cm / min, and the stress (g) immediately after the metal sphere completely entered the gel was measured. This is the gel strength (g). After the reaction between (A) and (B), an aqueous gel having high transparency is obtained. The solid concentration of the aqueous gel is usually 5 to 60% by mass, preferably 1 to 60% by mass.
The content is 0 to 50% by mass, particularly preferably 15 to 40% by weight.

The water-absorbing resin (C) can be further added to the gelling agent for a cold insulator of the present invention. By adding (C), the gel strength of the gelled product is improved, and (A)
And the amount of the reactant (B) can be reduced. (C)
Examples thereof include (1) one kind selected from a water-soluble monomer containing starch or cellulose (a) and a hydrophilic group such as a carboxyl group or a sulfonic acid group and / or a monomer which becomes water-soluble by hydrolysis. The above monomer (b) and a crosslinking agent (c)
And a water-absorbent resin obtained by polymerizing as an essential component and performing hydrolysis as necessary. Used in the production of the water absorbent resin exemplified above (A), (B) and
The proportion of (c), the production method and specific examples of the water-absorbing resin are described in
No. 2-25886, JP-B-53-46199, JP-B-53-46200 and JP-B-55-21041.

Examples of the water-absorbing resin other than those exemplified above include those obtained by polymerizing (2) (a) and (b) (hydrolyzate of starch-acrylonitrile graft polymer, cellulose-acrylonitrile graft polymer) (3) a crosslinked product of (a) (such as a crosslinked product of carboxymethylcellulose); (4) a copolymer of (b) and (c) (a partially hydrolyzed product of crosslinked polyacrylamide, Crosslinked acrylic acid-acrylamide copolymer, crosslinked sulfonated polystyrene, JP-A-52-14689 and JP-A-52-14689
No. 27455, saponified vinyl ester-unsaturated carboxylic acid copolymer, cross-linked polyacrylic acid (salt), cross-linked acrylic acid-acrylate copolymer, cross-linked isobutylene-maleic anhydride Copolymers and crosslinked carboxylic acid-modified polyvinyl alcohols); and (5) polymers of (b) having self-crosslinking properties (such as self-crosslinking polyacrylic acid salts). Further, two or more of the above-described water-absorbing resins may be used in combination. Among these water-absorbing resins, more preferable ones are
Among those exemplified as (1) and (4), crosslinked polyacrylamide copolymer, crosslinked polyacrylic acid (salt), crosslinked acrylic acid-acrylate copolymer, crosslinked isobutylene-anhydride A maleic acid copolymer and a crosslinked carboxylic acid-modified polyvinyl alcohol.

The water absorption capacity of the water absorbent resin (C) is as follows:
The mass is preferably 10 to 2,000 times, more preferably 100 to 1,500 times. The shape of the water-absorbent resin (C) may be powder, granular or fibrous. The particle size is not particularly limited, but is preferably 100 to 5,000 microns in average particle size, particularly preferably 200 to 3,000 microns. When the average particle size is 5,000 microns or less, the water absorption rate is high. On the other hand, when the average particle size is 100 microns or more, water is absorbed sufficiently without forming a cage when absorbing water. The amount of the water-absorbing resin added is preferably 0.1 to 100 parts by mass of the total gel.
It is from 0.5 to 5 parts by mass, more preferably from 0.1 to 4 parts by mass. When the amount of the water-absorbing resin is 5 parts by mass or less, a uniform gel is obtained. On the other hand, when the amount of the water-absorbing resin added is 0.0
When the amount is 5 parts by mass or more, the effect of improving the gel strength is large. In the present invention, the absorption capacity of the water-absorbent resin is a value obtained by measuring by the following method. <Absorbency of Water Absorbent Resin> A sample (sample amount: Eg) of a water absorbent resin was placed in a nylon mesh bag (250 mesh), and the bag was immersed in excess water (deionized water). After 60 minutes of immersion, the bag was pulled up into the air, allowed to stand and drained for 15 minutes, and then the mass (Fg) was measured to determine the absorption capacity from the following formula. [The same operation as above was performed using only the net bag, and the mass (Gg) for this was subtracted as a blank. ] Absorbency = (FG) / E

As a method of charging the water-absorbent resin (C) into the cold insulator, the water-absorbent resin (C) is charged at the time of the above-mentioned reaction method of (A) and (B), and for example, (1) (A) and (B) are directly mixed. (C) at the same time as (A), (B) and (C) are added to the aqueous solution of (A), and (3) (B) is added to the aqueous solution of (A).
And (4) a method of mixing (A) and (C) with an aqueous solution of (B), and a method of mixing (A) and (C) with an aqueous solution of (B). A method of mixing (A) with (C) swollen in advance with an aqueous solution, (6) (A)
(B) a method in which each aqueous solution is prepared in advance, and then immediately after mixing the two or after mixing (C), (7)
(A) and (B) a method in which each of the aqueous solutions and (C) swelled with water are prepared in advance, and then the three are mixed. A uniform gel is easily obtained, and the preferable method is (6) or
(7).

In the mixed system of (A), (B) and, if necessary, (C), (C) swells greatly at room temperature for 5 to 30 minutes, after which the reaction between (A) and (B) proceeds I do. At that time, only (C) may be mixed with (A) or (B) or a reaction may occur. It is presumed that the unneutralized carboxylic acid group in (C) is thickened by forming a salt or an amide bond with the amino group of gelatin. The gel strength of the reaction product of (A) and (B) containing (C) is usually 30.
Ｇ1,000 g, preferably 50-600 g, particularly preferably 70-500 g. The gel strength can be measured in the same manner as the method for measuring the gel strength of the reaction product of (A) and (B).

As the aqueous solution used here, besides (A), (B) and (C), if necessary, other additives can be mixed. No particular limitation is imposed on water-soluble or water-dispersible materials, but, for example, deodorants, fragrances, bactericides, fungicides, preservatives, defoamers, foaming agents, antiblocking agents, and ultraviolet absorbers And other additives such as an agent, a surfactant, an oxygen scavenger, an antioxidant, a bulking agent, and a freezing point depressant. Any concentration of these compounds can be used according to the purpose. These aqueous solutions or aqueous dispersions may be prepared in advance and mixed with the aqueous solutions of (A) and (B), or (A),
(B) and (C) may be coexistent and mixed.
When mixing (A), (B) and (C), necessary additives must be mixed.

The gel-like cold insulator of the present invention is usually in the form of a packing member filled with gel. The shape of the packaging member may be any shape such as a bag shape, a box shape, a cylindrical shape, a ball shape, a spherical shape, and is not particularly limited. The size can also be arbitrarily set within a range in which the cooling capacity can be exhibited according to the purpose of use. The material of the packaging member is not particularly limited as long as it is insoluble in water. For example, a water-resistant polyethylene / nylon laminate film, polyethylene / nylon /
Even if a plastic film such as an EVA laminate film is thin, the film strength, water resistance, heat sealability,
It has excellent workability and is convenient if used as a bag. Further, an aluminum foil, a laminated film of an aluminum foil and a plastic film, a thick plastic container, a rubber container, a metal container and the like can be used. When a transparent material is used for the packaging member, a transparent gelling material may be preferred, and the gelling material of the present invention is particularly effective.

As a method for producing a cold insulator in which a gelled product is filled in a packaging member, a preformed gelled product is put into a package to be used as a cold insulator, and a gelling agent and water are put into the package and packed. There is a method in which the material is gelled in a material to form a cold insulator, but the latter is preferred. As the latter method, for example, aqueous solutions (A) and (B) are prepared in advance,
Immediately after the aqueous solutions of (A) and (B) are uniformly mixed, the mixed solution is injected from the opening of a rectangular PE film bag sealed on three sides, and the opening is sealed to prevent an air layer from entering. There is a method in which the gel is left in a place at 25 ° C. for one day to produce an elastic gel. Insulation is used to transport fresh food,
It is used to store reagents that need to be refrigerated. In addition, even if it is used in place of ice like a cooler box, water does not leak, so it is easy to handle. It can be stored and transported at a lower temperature than ice. In addition, a similar object may be used by putting an object such as a fresh food product in the gel itself without putting it in the packaging material.

[0022]

EXAMPLES The present invention will be further described with reference to the following production examples and examples, but the present invention is not limited thereto.
The following parts represent parts by mass.

Example 1 (1) Preparation of solution A-1 Ion-exchanged water (84 parts) and an aqueous ammonia solution having a 29% ammonia content (6 parts) were added to Gantaz AN 119 (10 parts), and the mixture was stirred at room temperature. Dissolved uniformly over time. G uniformly dissolved with an ammonia neutralization rate of 80%
An aqueous solution of anterzAN119 was obtained. Note) Ganterz AN119: methyl vinyl ether / maleic anhydride copolymer, weight average molecular weight 2.13
× 10 ⁶ , manufactured by ASP Japan Co., Ltd. (2) Preparation of solution B-1 Ion-exchanged water (750 parts) was added to gelatin SE-1 (45 parts) and sugar (5 parts), and the mixture was heated to 60 to 70 ° C. And uniformly dissolved. Note) Gelatin SE-1: alkali-treated gelatin, manufactured by Nippi Gelatin Industry Co., Ltd. (3) Preparation of gel To solution B-1 (40 parts), add solution A-1 (2 parts) and ion-exchanged water (58 parts). A homogeneous and clear aqueous solution was prepared. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel.

Example 2 (1) Preparation of Solution A-2 Ion-exchanged water (82.5 parts) and an aqueous ammonia solution (7.5 parts) having an ammonia content of 29% were added to Gantaz AN 119 (10 parts) at room temperature. And uniformly dissolved in 30 minutes. A uniformly dissolved aqueous solution of GanterzAN119 having an ammonia neutralization ratio of 100% was obtained. (2) Preparation of gelled product Solution A-2 was added to solution B-1 (79 parts) prepared in Example 1.
(12 parts) and ion-exchanged water (9 parts) were added to prepare a uniform and transparent aqueous solution. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel.

Example 3 (1) Preparation of Solution A-3 Ion-exchanged water (84 parts) and an aqueous ammonia solution having an ammonia content of 29% (6 parts) were added to Isoban-04 (10 parts) and stirred at room temperature. Then, it was uniformly dissolved in one hour. Isovan-04 uniformly dissolved with an ammonia neutralization ratio of 80%
Was obtained. Note) Isoban-04: isobutylene / maleic anhydride copolymer, molecular weight 6 × 10 ⁴ , manufactured by Kuraray Co., Ltd. (2) Preparation of gel Solution A-3 was added to solution B-1 (79 parts) prepared in Example 1.
(8 parts) and ion-exchanged water (13 parts) were added to prepare a uniform and transparent aqueous solution. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel.

Example 4 (1) Preparation of Solution A-4 Isovan-04 (10 parts) was added to ion-exchanged water (82.5
Parts) and an aqueous ammonia solution (7.5 parts) having an ammonia content of 29% were added and stirred at room temperature to dissolve uniformly in 30 minutes. A homogeneously dissolved aqueous solution of Isovan-04 having an ammonia neutralization ratio of 100% was obtained. (2) Preparation of gel Solution A-4 was added to solution B-1 (40 parts) prepared in Example 1.
(6 parts) and ion-exchanged water (54 parts) were added to prepare a uniform and transparent aqueous solution. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel.

Example 5 (1) Preparation of Gel The solution B-1 (20 parts) prepared in Example 1 was replaced with the solution B (2 parts) prepared in Example 1, and Sunfresh ST-
500D (1.5 parts) and ion exchange water (76.5 parts)
Was added to prepare a uniform and transparent aqueous solution. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel. Note) Sun Fresh ST-500D: acrylic water-absorbent resin, average particle size 400 microns, absorption capacity 400 times,
Sanyo Chemical Industries

Example 6 (1) Preparation of gel Solution B-1 (40 parts) prepared in Example 1 was mixed with solution C (6 parts) prepared in Example 2 and Sun Fresh ST-500
D (0.6 part) and ion-exchanged water (53.4 parts) were added to prepare a uniform and transparent aqueous liquid. The aqueous solution thus obtained was allowed to stand at room temperature for one day to perform a gelling reaction, thereby obtaining a uniform and transparent aqueous gel. Example 7 (1) Preparation of Gel Solution E-1 (1 part) prepared in Example 4 was added to solution B-1 (10 parts) prepared in Example 1, and Sun Fresh ST-500.
D (1.5 parts) and ion-exchanged water (87.5 parts) were added to prepare a uniform and transparent aqueous solution. The aqueous solution thus obtained was allowed to stand at room temperature for one day, and a gelling reaction was performed to obtain a uniform and transparent gel.

Comparative Example 1 (1) Preparation of Gel Sunfresh ST-500D (1.5 parts) and ion-exchanged water (98.5 parts) were added and uniformly mixed. After about 5 minutes, a uniform gel was obtained. Obtained. Comparative Example 2 (1) Preparation of Gel Agar (1.7 parts) was added to ion-exchanged water (98.3 parts) and dissolved by heating at 90 to 100 ° C. to prepare a transparent aqueous solution. The aqueous solution thus obtained was left at room temperature for 1 day to obtain a uniform gel. Note) Agar: agar (powder), manufactured by Wako Pure Chemical Industries

Comparative Example 3 (1) Preparation of gel Soagina MV101 in ion-exchanged water (96.5 parts)
(3.5 parts) was added and dissolved by heating at 60 to 70 ° C. to prepare a transparent aqueous solution. The aqueous solution thus obtained was left at room temperature for 1 day to obtain a uniform gel. Note) Soagina MV101: Carrageenan, manufactured by Mitsubishi Acetate Co., Ltd. Table 1 shows the evaluation results of Examples 1 to 7 and Comparative Examples 1 to 3.

[0031]

[Table 1]

The evaluation method is as follows. (1) Gel stability (a) Initial gel appearance The appearance of the gel prepared by allowing it to stand at room temperature for 1 day is visually determined.
The evaluation was as follows. …: Transparent わ ず か: Slightly cloudy ×: Cloudy (b) Freezing stability (a) is frozen at -20 ° C for 16 hours, and is frozen at room temperature for 8 hours.
The gel was thawed by standing for a period of time, and the appearance of the gel when reconstituted was visually judged and evaluated as follows. ○: No change △: Slight change ×: Change

(C) Low-temperature stability The gel of (a) was left in a thermostat at 0 ° C. for 24 hours to examine the presence or absence of a separated product. ○: No change △: Slightly water-separated ×: Water-separated (d) High-temperature stability The gel of (a) is left in a constant temperature bath at 70 ° C. for 24 hours to examine whether the gel is broken and becomes liquid. Was. …: No change Δ: Slightly destroyed and turned into a liquid X: Become a liquid (2) Gel strength The gel strength was measured in accordance with the above-described measurement method. A measure of shape retention.

(3) Protrusions The aqueous solution and the powder described in the above embodiment are placed in a three-side sealed rectangular PE film bag, mixed uniformly, and one of them is sealed to prevent an air layer from entering. , -2
The mixture was frozen in a refrigerator at 0 ° C., and it was visually determined whether or not a protrusion was formed on the surface of the cold insulator. …: No protrusions were generated. △: Slight protrusions were observed. ×: Projections were generated.

[0035]

EFFECTS OF THE INVENTION The gelling agent for a cold insulator, the gel and the cold insulator of the present invention have the following features. (1) Since the gelled product of the present invention has good shape retention, it can be easily formed into a fixed shape, does not deform during freezing and thawing, and is easy to handle. (2) The gelled product of the present invention has no water separation even after repeated freezing and thawing, and is particularly easy to handle without spilling contents such as water due to breakage of the bag during thawing. (3) The gelled product of the present invention does not generate projections when frozen, and is excellent in aesthetic appearance. From the above, the gelling agent and the gel of the present invention are useful as a gelling agent for a cold insulator.

Claims (7)

[Claims] 1. A gelling agent for a cold insulator comprising, as an essential component, a reaction product of a copolymer (A) of an ethylenically unsaturated compound and an ammonium maleate salt with gelatin (B). 2. The gelling agent according to claim 1, wherein (A) is a reaction product obtained by reacting a copolymer of an ethylenically unsaturated compound and maleic anhydride with ammonia. 3. The gelling agent according to claim 1, wherein the ethylenically unsaturated compound (A) is isobutylene or methyl vinyl ether. 4. The gelling agent according to claim 1, further comprising a water absorbent resin (C). 5. A gel comprising the hydrogel of the gelling agent according to claim 1. Description: 6. The gel according to claim 5, wherein the aqueous solution of (A), the aqueous solution of (B) and, if necessary, (C) are mixed. 7. A gel-like cold insulator obtained by gelling the gelling agent according to claim 1 in a packaging member.