JPH06122871A - Gel-like cold insulator and its production - Google Patents

Abstract

PURPOSE:To obtain a gel-like cold insulator retaining flexibility even in case of being frozen, also maintaining the flexibility at low temperatures even after repeated use, by a specific method using water-absorbing gel particles of a water-insoluble and water-absorbing polymer. CONSTITUTION:Water-absorbing gel particles of water-insoluble and water- absorbing polymer (pref. a partial hydrolyzate of crosslinked polyacrylamide) is coated with water-insoluble and water-nonabsorbing polymer film (e.g. gun arabic) followed by mixing with a water-soluble polymer (pref. anionic acrylamide-based copolymer), water and a hydrophilic alcohol compound (pref. glycerol, or a combination of glycerol with a hydrophilic polyether compound and/or diethylene glycol) to suspend the surface-coated water-absorbing gel particles in a water-based gel containing the water-soluble polymer, water and hydrophilic alcohol compound, thus obtaining the objective cold insulator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gel-like cold insulating material having low temperature flexibility.

[0002]

[Prior art]

Conventionally, as a cold insulating material having low-temperature flexibility, a water-absorbing cross-linked polymer dispersed in a continuous phase composed of a teleblock copolymer elastomer and an oil component (for example, JP-A-60-79061). ); Those containing a vinyl chloride resin gelled by mixing a plasticizer and a hydrous hydrogel or a water-soluble polymer (for example, JP-A-63-178156); by surface-coating the hydrous hydrogel, A device in which the number of times of repeated use is increased (for example, Japanese Patent Laid-Open No. 1-21391) is known.

[0004]

[Problems to be Solved by the Invention]
For those, the cold storage time is insufficient, and
However, there was a problem that the low-temperature flexibility deteriorates as the number of repeated uses increases.

[0005]

Means for Solving the Problems The present inventor has conducted extensive studies to obtain a cold insulating material having a long cold storage time, excellent low temperature flexibility, and low temperature flexibility even after repeated use. The invention was reached.

That is, according to the present invention, the water-absorbent gel particles of the water-insoluble water-absorbent polymer surface-coated with the water-insoluble, non-water-absorbent polymer film are contained in an aqueous gel containing a water-soluble polymer, water and hydrophilic alcohols. Gel-like cold insulating material characterized by being suspended in a water-soluble polymer; and a water-soluble polymer obtained by surface-coating water-absorbing gel particles of a water-insoluble water-absorbing polymer with a water-insoluble, non-water-absorbing polymer film. The method for producing the gel-like cold insulating material is characterized in that water, hydrophilic alcohols are mixed.

Examples of the water-absorbent gel particles of the water-insoluble water-absorbent polymer used in the present invention include natural water-insoluble water-absorbent polymer particles such as gelatin gel particles,
Water-absorbent gel particles of a synthetic water-absorbent resin can be used. Examples of the synthetic water-absorbent resin include starch or cellulose (a), a water-soluble monomer containing a carboxyl group and / or a sulfonic acid group and / or a monomer (b) which becomes water-soluble by hydrolysis. A water-absorbent resin obtained by polymerizing the cross-linking agent (c) as an essential component and performing hydrolysis if necessary is mentioned. Details of (a), (b) and (c) used in the production of the water absorbent resin exemplified above, the proportions of (a), (b) and (c), the production method and the specific examples of the water absorbent resin are JP-A-52-2588
No. 6, JP-B-53-46199, JP-B-53-462
No. 00 and Japanese Patent Publication No. 55-21041.

Water-absorbent resins other than those exemplified above include, for example, those obtained by polymerizing (a) and (b) (hydrolyzate of starch-acrylonitrile graft polymer,
Cellulose-acrylonitrile graft polymer hydrolyzate, etc., (a) crosslinked product (carboxymethylcellulose crosslinked product, etc.), (b) and (c) copolymer (crosslinked polyacrylamide partially hydrolyzed product, Crosslinked acrylic acid-acrylamide copolymer, crosslinked sulfonated polystyrene, vinyl ester-unsaturated carboxylic acid copolymer saponified product, crosslinked polyacrylic acid salt,
Crosslinked acrylic acid-acrylic ester copolymer,
(Crosslinked isobutylene-maleic anhydride copolymer, and crosslinked carboxylic acid-modified polyvinyl alcohol)
In addition, the polymer (b) having self-crosslinking (such as a self-crosslinking polyacrylic acid salt) can be mentioned. Further, two or more kinds of the water absorbent resins exemplified above may be used in combination.

Among the above water-absorbent resins, preferred ones are; and, among them, a partial hydrolyzate of crosslinked polyacrylamide, a crosslinked acrylic acid-acrylic ester copolymer, a crosslinked isobutylene-maleic anhydride copolymer. And a crosslinked carboxylic acid-modified polyvinyl alcohol.

The above water-absorbent resin has a water-absorbing performance for pure water of at least 50 ml / g, particularly 100-1000 ml / g.
g is suitable.

The weight ratio of water in the water-absorbing gel to the water-insoluble water-absorbing polymer is usually 100: 0.1-10, preferably 100: 0.5-8. If the water-insoluble water-absorbing polymer is less than 0.1, the cold storage heat amount decreases, and if it exceeds 10, the flexibility during freezing decreases. The shape of the water-absorbent gel particles is not particularly limited and is usually round. The size of the particles is usually 0.05 to 10 mm, preferably 0.5 to
It is 5 mm.

In the present invention, the water-absorbent gel particles further coated with a water-insoluble, non-water-absorbing polymer film are used. When such a surface coating is applied, not only the number of times of repeated use is increased but also the cold insulation capacity is improved. In this case, the surface coating may be formed of a water-soluble polymer and then the surface may be cured before use.

Examples of the polymer coating include gum arabic and gum tragacanth. Examples of the water-soluble polymer before surface hardening that can be used for the polymer coating include sodium alginate and polyvinyl alcohol. As an auxiliary agent for curing the coating film formed of these water-soluble polymers, higher fatty acid soaps, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, or organic acids such as oleic acid and acetic acid are used. The thickness of the polymer coating is usually such that it covers the surface of the water-absorbing gel thinly. An example of the method of surface coating when a water-insoluble non-water-absorbing polymer is used is mixing with a water-absorbing gel of a water-insoluble water-absorbing polymer. Examples of the method of surface coating and curing treatment using a water-soluble polymer include 10 to 2 of these surface coating agents.
Hydrogel containing 0% by weight aqueous solution of water-insoluble water-absorbent polymer 1
A water-insoluble non-water-absorbing polymer film is formed by adding 0.2 to 1.5 parts by weight with respect to parts by weight, and then adding 10 to 20% by weight of the above curing aid as it is to perform a curing treatment.

Examples of the water-soluble polymer used as a constituent of the aqueous gel in the present invention include carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, sodium alginate, starch, agar, pullulan and acrylamide copolymers. The acrylamide copolymer may be nonionic, anionic or cationic, and examples of the nonionic include polyacrylamide and polymethacrylamide. As the anionic property, a partial hydrolyzate of polyacrylamide or polymethacrylamide, a copolymer of acrylic acid or methacrylic acid and acrylamide or methacrylamide and salts thereof, acrylic acid or methacrylic acid and acrylamide or methacrylamide and 2-acrylamide. -2 methylpropanesulfonic acid,
3 with vinyl sulfonic acid or vinyl methyl sulfonic acid
Examples include the original copolymer and salts thereof. Examples of the cationic property include copolymers of acrylamide and acryloyl or methacryloyloxyethyltrimethylammonium chloride, copolymers of acrylamide and trimethylammonium chloride, and the like.

Of these, preferred are cationic, nonionic and anionic acrylamide copolymers, and particularly preferred are anionic acrylamide copolymers. The water-soluble polymers exemplified above may be used in combination of two or more.

The water-soluble polymer has an intrinsic viscosity of 10 (dl / dl) measured at 30 ° C. in a 1N sodium nitrate aqueous solution.
g) or more, and the spinnability of a 0.1% by weight aqueous solution is 5
It is preferably 0 mm or more. By using a material having a high spinnability, the shape retention of the cold insulating material becomes good.

The weight ratio of water to the water-soluble polymer in the aqueous gel is usually 100: 0.1-10, preferably 100 :.
It is 0.5-8. If the water-soluble polymer content is less than 0.1, the shape-retaining property at room temperature is deteriorated, and if it exceeds 10, the flexibility during freezing is deteriorated.

The weight ratio of the water-insoluble water-absorbing polymer to the water-soluble polymer in the cold insulating material of the present invention is usually 1: 0.1-1.
It is 0, preferably 1: 0.2 to 3. When the water-soluble polymer is less than 0.1, the number of times of repeated use is reduced, and when it exceeds 10, it takes time to take out the highly spinnable gel-like material from the manufacturing facility during the production of the gel-like material.

As the hydrophilic alcohols used in the present invention, hydrophilic means water-soluble or water-dispersible, and examples thereof include glycerin, ethylene glycol, diethylene glycol, ethanol and hydrophilic polyethers [ethylene glycol. , Poly (oxyethylene / oxypropylene) triol, poly (oxyethylene / oxypropylene) glycol, poly (oxyethylene / oxypropylene) glycol / monobutyl ether, etc.]
Can be given. You may use together 2 or more types of hydrophilic alcohols illustrated above. Of these, preferred are hydrophilic polyethers, diethylene glycol, glycerin and combinations thereof, and particularly preferred are glycerin and combined use of glycerin with hydrophilic polyethers and / or diethylene glycol.

The weight ratio of water (sum of water in each gel) and hydrophilic alcohols in the cold insulating material of the present invention is usually 100:
It is 1-80, preferably 100: 10-65. If the hydrophilic alcohols are less than 1, the flexibility at the time of freezing decreases,
If it exceeds 80, the shape retention property at room temperature deteriorates.

The weight ratio of the water-insoluble water-absorbing polymer and the hydrophilic alcohol in the gelling material of the present invention is usually 1:10.
60, preferably 1: 20-40. More preferably, it is 1:25 to 35. 10 hydrophilic alcohols
If it is less than 60, the flexibility during freezing is lowered, and if it exceeds 60, the number of times of repeated use is lowered.

The cold insulating material of the present invention may be mixed with a filler or glass powder within a range that does not impair flexibility according to the purpose of use, and examples of the filler include calcium carbonate, aluminum oxide, aluminum octylate, and powder. Examples thereof include mica, expanded polyethylene, expanded polystyrene, urethane foam, talc and cork. Examples of the glass powder include borate glass, silicate glass, phosphate glass and the like. From the viewpoint of reactivity with the water-soluble polymer, borate glass or a mixture of borate glass and another oxide glass is desirable. The oxide glass is used by melting and cooling a plate glass and then crushing it. The particle size of the glass powder is not particularly limited, but it is desirable that the particle size be small and have the same particle size.

If desired, the cold insulating material of the present invention may be mixed with other additives such as colorants such as pigments, heat-sensitive dyes, preservatives, ultraviolet absorbers and antioxidants.

The gel-like cold insulating material of the present invention is usually in a state where the gel-like material is filled in the packaging member. The shape of the packaging member may be any shape such as a bag shape, a box shape, a cylindrical shape, a ball shape, and a spherical shape, and is not particularly limited. The size can also be arbitrarily set within the range where the cold storage 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 water resistant. For example, polyethylene / nylon laminate film, polyethylene / nylon / EVA laminate film, etc., even if thin, film strength, water resistance, heat sealability, It is convenient to use a bag with excellent workability as a bag.

As an example of the method for producing the cold insulating material of the present invention, the present gelled material is obtained by the following three steps. That is, step 1: water-insoluble non-water-absorbing polymer is added to water-insoluble water-absorbing polymer to form a gel, and a water-insoluble non-water-absorbing polymer is added and mixed with a universal mixer or the like, or surface-coated with a water-soluble polymer. Then, a curing aid is added and mixed with a universal mixer or the like; Step 2: The water-soluble polymer, water and alcohol are mixed with the universal mixer or the like. Process 3: process 1 and process 2
The gelled product obtained above is thoroughly mixed with a high-viscosity mixer or the like.

The gel-like cold insulating material of the present invention is usually -30 to-
5 ° C., preferably −20 to −15 ° C.,
It can be used as a cold insulating material by freezing it for 1 to 24 hours.

[0028]

【Example】

The present invention will be further described below with reference to examples, but the present invention is not limited thereto. Parts in the examples are parts by weight. Example 1 Water-absorbent resin [Sunwet IM- manufactured by Sanyo Kasei Co., Ltd.
5000] 4 parts and 200 parts of water were added and mixed well with a universal mixer, and 15 parts of polyvinyl alcohol was added to 20 parts of hot water.
A solution dissolved in 0 part was added and mixed well to obtain white water-absorbent gel particles (step 1). Acrylamide-based copolymer [SAN FLOOK AH-210P manufactured by Sanyo Chemical Industries, Ltd.] 4
And 200 parts of water were added and mixed well with a universal mixer. 150 parts of glycerin, 6 parts of diethylene glycol,
Polyethylene glycol (molecular weight 300; hereinafter PEG-
6 parts (abbreviated as 300) were added and thoroughly mixed with a universal mixer to obtain a white gel (step 2). The gel obtained in step 2 was added to the gel obtained in step 1 and mixed well with a universal mixer (step 3). Table 1 shows the test results of the cold retention time, the initial flexibility, and the softness retention property of the obtained gel-like cold insulation material after repeated use 30 times and further frozen.

Example 2 A gel-type cold insulating material was obtained by the same method except that 15 parts of oleic acid was further added in the step 1 of Example 1. The performance measurement results of this product are shown in Table 1.

Example 3 A gel-type cold insulating material was obtained by the same method except that 15 parts of polyvinyl alcohol was changed to 10 parts of sodium alginate in the step 1 of Example 1. The performance measurement results of this product are shown in Table 1.
Shown in.

Example 4 In step 2 of Example 1, diethylene glycol was replaced with poly (octyethylene.oxypropylene) glycol.
Monoether (New Pole 50HB manufactured by Sanyo Kasei Co., Ltd.
-660), and a gel-type cold insulating material was obtained by the completely same method. The performance measurement results of this product are shown in Table 1.

Example 5 A gel-type cold insulating material was obtained by the same method except that 20 parts of talc powder was further added in step 2 of Example 1. The performance measurement results of this product are shown in Table 1.

Example 6 In step 2 of Example 4, boric acid glass powder was further added.
A gel-like cold insulating material was obtained in exactly the same manner except that 5 parts were added. The performance measurement results of this product are shown in Table 1.

Comparative Example 1 3 parts of a water absorbent resin and 3 parts of an acrylamide copolymer were thoroughly mixed with a universal mixer. This mixture of powders was added to an aqueous solution prepared by mixing 120 parts of water, 68 parts of glycerin, 3 parts of ethylene glycol, and 3 parts of PEG-300, and the mixture was stirred and stood still to obtain a comparative gel-like cold insulating material. The performance measurement results of this product are shown in Table 1.

Comparative Example 2 A comparative gel-like cold insulating material was obtained in the same manner as in Example 1 except that the operation of adding an aqueous solution prepared by dissolving 15 parts of polyvinyl alcohol in 200 parts of hot water was omitted. The performance measurement results of this product are shown in Table 1.

Comparative Example 3 A comparative gel-like cold insulating material was prepared based on the example of JP-A-60-79061. The performance measurement results of this product are shown in Table 1.

Comparative Example 4 A comparative gel-like cold insulating material was prepared based on Example 1 of JP-A-63-178156. The performance measurement results of this product are shown in Table 1.

Comparative Example 5 A comparative gel-like cold insulating material was prepared based on Example 1 of JP-A-1-121391. The performance measurement results of this product are shown in Table 1.

[0040]

[Table 1]

Note 1: The cold storage time was such that a product that had been frozen at -20 ° C for 12 hours was left in a room at 25 ° C, and the time until it reached 10 ° C was measured. Sample weight is 600g, 250mm ×
A 250 mm × 10 mm polyethylene / nylon-based laminate bag was used.

Note 2 The initial flexibility was confirmed in the state of pressing a product frozen at -20 ° C for 12 hours with a finger. ◯ indicates that it is easily deformed, Δ indicates that it is deformed when it is pressed hard, and × indicates that it is not deformed.

Note 3: The softness-holding property is determined by immersing a sample frozen at -20 ° C for 12 hours in warm water at 25 ° C and returning it to room temperature.
After repeating 0 times, what was further frozen at −20 ° C. for 12 hours was confirmed by pressing with a finger. The criterion is the same as in (2).

[0044]

【The invention's effect】

The present invention has the following effects. (1) The cold storage time is improved from the conventional one. (2) The cold insulating material of the present invention is usually used by freezing at -30 to -5 ° C, but it has flexibility even during freezing, and this flexibility does not change even after repeated use. The conventional cold insulating material loses flexibility during freezing during repeated use and finally solidifies. (3) It can be used by closely adhering to the shape of the object to be kept cold, and it is the same when repeatedly used. Since the gel-like cold insulating material obtained by the present invention has the above-mentioned effects, it is useful for cold insulating pillows and cold insulating of blood, specimens, frozen desserts, foods and the like. Further, it is useful as a cold insulation material used for preventing a breakdown at the time of cooling down after exercising a race horse, for treating a leg and a hoof of a horse, and for cooling down after a human exercise.

Claims (7)

[Claims] 1. A water-insoluble polymer particle, which is surface-coated with a water-insoluble non-water-absorbing polymer film, suspended in an aqueous gel containing a water-soluble polymer, water and a hydrophilic alcohol. A gel-like cold insulating material characterized by being present. 2. The cold insulating material according to claim 1, wherein the water-insoluble water-absorbing polymer has a water absorption performance for pure water of 100 to 1000 ml / g. 3. The water-soluble polymer is acrylamide, (meth) acrylic acid (salt), 2-methyl-2-acrylamidopropanesulfonic acid (salt), (meth) acryloyloxyethyltrimethylammonium quaternary salt, (meth). At least one of acryloyloxyethyl dialkylamine salts
The cold insulating material according to claim 1, which is a (co) polymer having at least one species as a constituent unit. 4. An intrinsic viscosity of the water-soluble polymer measured at 30 ° C. in a 1N sodium nitrate aqueous solution is 10 (dl /
g) or more, and the spinnability of a 0.1% by weight aqueous solution is 5
The cold insulating material according to any one of claims 1 to 3, which has a length of 0 mm or more. 5. The cold insulating material according to claim 1, wherein the hydrophilic alcohol is one or more selected from ethanol, glycerin, diethylene glycol, ethylene glycol or hydrophilic polyethers. 6. The cold insulating material according to claim 1, wherein the packaging material is filled with the gel-like material. 7. A water-soluble polymer, water, and a hydrophilic alcohol are mixed with water-absorbent gel particles of a water-insoluble water-absorbent polymer whose surface is coated with a water-insoluble, non-water-absorbent polymer film. The method for producing the gel-like cold insulating material according to claim 1.