JPH01223190A - Cold-accumulation agent and production thereof - Google Patents

Abstract

PURPOSE:To obtain an easily producible compact cold-accumulation agent durable to repeated use and capable of reducing distribution cost, by compounding a gel composed of a specific highly water-absorbing polymer, an organic substance to depress freezing point and water. CONSTITUTION:The objective cold accumulation agent is produced by using a gel substance composed of (A) a highly water-absorbing polymer which is a polymeric electrolyte containing carboxylate, (B) one or more kinds of organic freezing point depressant preferably selected from (poly)ethylene glycol, (poly) propylene glycol, glycerol and sugars and (C) water.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a gel-like cold storage agent.

[Conventional technology]

BACKGROUND ART It is extremely important to maintain the freshness of perishable foods that require refrigeration, frozen foods, especially seafood, etc. over a long period of time, and freshness has been maintained by keeping them cold.

BACKGROUND ART In recent years, in order to keep cold, bagged cold storage agents have been provided in which a gel-like cold storage agent is sealed in a sealed bag.

Conventionally, a gel refrigerant (Japanese Patent Application Laid-Open No. 1983-1991) was formed by dissolving freezing point depressants such as inorganic salts such as sodium chloride and calcium chloride in an aqueous solution of a water-soluble polymer and adding a gelling agent to the solution.
5-164278, JP-A-56-53175) is placed in containers such as bags of various shapes and sealed, and the containers are cooled and solidified to produce a cold storage agent, a monomer mainly composed of acrylamide and methacrylamide A gel-like cold storage agent obtained by polymerizing the body in an aqueous solution containing an inorganic salt freezing point depressant (JP-A-60-120783, JP-A-6L-13076)
4) is put into containers of various shapes, sealed, and then cooled and solidified to produce a cold storage agent.

Also known are gel-like cold storage agents in which a superabsorbent polymer absorbs an aqueous solution of inorganic salts such as sodium chloride and calcium chloride.

However, although various gel-like cold storage agents have been proposed in the past, the gel's freezing resistance is poor, and water may separate when frozen and thawed repeatedly, and if the water content is further reduced, freezing may occur. Although there is no water separation due to repeated thawing, the freezing capacity becomes significantly smaller and weaker. In particular, there are starch graft polymers (Japanese Patent Publication No. 53-46199), which are super absorbent polymers that absorb and retain a large amount of water with a small amount of weight, and cross-linked polyacrylates (Japanese Patent Publication No. 54-30710). Since the above-mentioned superabsorbent polymer is an anionic polymer electrolyte, even if it shows high water absorption ability for low concentration electrolyte solution of 1% by weight or less or distilled water, it cannot absorb electrolyte of 1% by weight or more. A major disadvantage of using a solution is that the water absorption capacity is significantly reduced.

For this reason, the refrigerating capacity is extremely small, making it impractical.

On the other hand, a method of manufacturing a cold storage agent by enclosing it in a container such as a bag is technically very difficult (Japanese Patent Laid-Open No. 61-1
According to this method, an acrylic monomer and a crosslinkable monomer are polymerized in an aqueous solution containing an inorganic salt freezing point depressant to produce a gel refrigerant; When enclosing this in a container such as a bag, it is essential to enclose the aqueous solution in the packaging material under conditions that do not allow polymerization to complete, and to place this bag-shaped container under conditions that complete polymerization of the aqueous solution. The conditions are as follows. As a result, the manufacturing process becomes complicated, a large amount of equipment is required, productivity is extremely low, and costs are high (there are disadvantages such as sticking).

[Problem that the invention seeks to solve]

The present invention eliminates these drawbacks and provides a cold storage agent that can be easily and easily made even at home.

(Means for Solving the Problems) The present invention is characterized in that it contains a gel-like material consisting of a super absorbent polymer which is a polymer electrolyte containing II carboxylate, an organic freezing point depressing substance, and water. (2) After storing a super absorbent polymer, which is a polymer electrolyte containing a carboxylate, and an organic freezing point depressing substance in a container, water is further injected to form a gel-like substance. (3) After storing a super absorbent polymer, which is a polymer electrolyte containing a carboxylate, in a container, an aqueous solution containing an organic freezing point depressing substance is further injected to form a gel-like material. This is a method for producing a cold storage agent, which is characterized by forming a product.

The super absorbent polymer is not particularly limited as long as it contains a monomer unit having a carboxylate (containing a carboxyl group or a salt of a carboxyl group) in the constituent components of the polymer or copolymer. Examples of crosslinked starch/(meth)acrylate copolymers (meaning acrylate polymers or methacrylate polymers, hereinafter the same), styrene-maleic anhydride copolymers, etc. Salt, crosslinked poly(meth)acrylate, crosslinked polyvinyl alcohol/(meth)acrylate graft copolymer, crosslinked polysaccharide/(meth)acrylate graft copolymer, polysaccharide Cross-linked products of saponified salts of acrylonitrile graft copolymers, salts of cross-linked products of (meth)acrylic acid/acrylamide/sulfonated acrylamide terpolymer copolymers, Crosslinked products, crosslinked products of saponified polysaccharide/(meth)acrylic acid alkyl ester graft copolymers, crosslinked products of saponified polysaccharide/acrylamide copolymers, (meth)acrylic acid alkyl ester/vinyl acetate copolymers A cross-linked product of a saponified product of a combination, a cross-linked product of a saponified product of a starch/acrylonitrile/acrylamido-2-methylpropanesulfonic acid graft copolymer, a cross-linked product of a saponified product of a starch/acrylonitrile/vinyl sulfonic acid graft copolymer,
(meth)acrylic acid (salt)/dimethylamino (meth)
Crosslinked product of alkyl ester acrylate copolymer, (meth)
A salt of a crosslinked product of a saponified product of an acrylic acid alkyl ester/dimethylamino (meth)acrylic acid alkyl ester copolymer, a crosslinked product of a (meth)acrylic acid (salt)/diethylamino (meth)acrylic acid alkyl ester copolymer, Salt of saponified crosslinked product of (meth)acrylic acid alkyl ester/diethylamino (meth)acrylic acid alkyl ester copolymer, crosslinked product of (meth)acrylic acid (salt)/dimethylaminopropylacrylamide copolymer, itaconic acid (Salt)/crosslinked product of dimethylaminoethyl methacrylate copolymer, crosslinked product of salt of inbutylene/maleic anhydride copolymer, salt of reaction product of polyvinyl alcohol/maleic anhydride, vinyl ester/ethylenically unsaturated carboxylic acid or saponified salts of copolymers of derivatives thereof. These may be used alone or in combination of two or more kinds. Super water-absorbing polymers, which are polymer electrolytes containing carboxylates having a crosslinked structure, have a high water absorption capacity, excellent water retention ability, and It is preferable because it has excellent strength after water absorption, but is not limited to the above-mentioned super absorbent polymers, but crosslinked polyvinyl alcohol,
Gelled products such as crosslinked polyethylene glycol, crosslinked polyvinylpyrrolidone, crosslinked polyacrylamide, graphite locust bean gum, carrageenan, and pregelatinized starch can also be used.

The organic coagulant-depressing substance used in the present invention refers to the high water absorption capacity of the superabsorbent polymer having the carboxylate,
Any organic substance may be used without particular limitation as long as it has excellent water retention capacity, does not inhibit water absorption rate, and has excellent gel strength after water absorption.

1111 (sucrose, invert sugar), methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, Ethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monopropyl ether, diethylene glycol motsubutyl ether, diethylene glycol, Diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, etc. can also be used, but they have a low cold storage effect and are economically inferior.

In manufacturing the cold storage agent of the present invention, it can be manufactured into a container by mixing desired amounts of a superabsorbent polymer, an organic freezing point depressing substance, and water, and the amounts of each used are determined as desired. It may be determined by the solidification temperature or melting temperature, but for boat fishing, 20 to 10 parts of water is used for 1 part by weight of superabsorbent polymer.
00 parts by weight, preferably 50 to 500 parts by weight, and the organic freezing point depressing substance is within the range of an aqueous solution concentration (by weight) of 2 to 70% water.

For mixing, a stirrer is not essential, but a stirrer, universal mixer, kneader, etc. may also be used (an aqueous solution of an organic freezing point depressing substance may be added to the superabsorbent polymer, or Water may be added to the mixture of the super absorbent polymer and the organic freezing point depressing substance, and then the gel-like cold storage agent obtained in the present invention is press-fitted into containers such as various bags using an extruder. In addition, after storing the superabsorbent polymer in a container such as a bag, an aqueous solution of an organic freezing point depressing substance can be added to create a gel-like cold storage agent. It is possible to produce a package of a cold storage agent at the same time as producing the agent.

Furthermore, a gel-like cold storage agent is generated in the container by storing a mixture of a super absorbent polymer and an organic freezing point depressing substance in a container such as a bag in advance, and then injecting a predetermined amount of water as needed. It is possible to manufacture a cold storage agent at the same time as packaging.

In this case, simply by injecting an amount of water suitable for the cold storage temperature through the injection port of a container such as a bag, a gel-like cold storage agent is immediately generated, and a cold storage agent having a desired cold storage temperature can be freely produced. Therefore, it becomes possible to store and transport superabsorbent polymers and organic freezing point depressing substances in a water-free state, thereby significantly reducing storage space and logistics costs.

It is also possible to add mineral oil, a plasticizer, a dispersant, an inorganic filler, and an organic filler to the cold storage agent of the present invention, if necessary. Typical mineral oils include paraffinic process oil, naphthenic process oil, aromatic process oil, and spindle oil. Plasticizers include phthalate esters such as dioctyl phthalate and dibutyl phthalate, adipate esters such as dioctyl adipate, and phosphoric acid esters such as tricresyl phosphate and trioctyl phosphate.Dispersants include liquid paraffin and chloride. Vegetable oils such as paraffin oil, castor oil, and linseed oil, animal oils, fatty acids and fatty acid salts such as stearic acid and calcium stearate, organic titanium compounds such as tributyl titanate, tristearyl titanate, di(octylphosphate) ethylene titanate, etc. Examples include mixtures of. Furthermore, oily substances and liquid substances with low hygroscopicity, such as low molecular weight liquid polymers such as urethane prepolymers and liquid polybutene, are also contained in the cylinder, and ethylene-vinyl acetate copolymer is dissolved in chlorinated paraffin. Mineral oil, plasticizer, and dispersant containing resin components are also included in the cylinder. Examples of inorganic fillers include talc, clay, calcium carbonate, and silica, and examples of organic fillers include various carbon blacks and pigments. In addition, antistatic agents are added to plastic bags and containers, and rust preventive agents for metals are added when pipes and containers made of iron, steel, aluminum, copper, etc. are used.

Examples of the present invention will be shown below, but the present invention is not limited thereto.

[Example-1] 0.1 part of lauroyl peroxide as a polymerization initiator was added to 60 parts of vinyl acetate and 40 parts of methyl acrylate, and the mixture was dispersed in 300 parts of water containing 3 parts of partially saponified polyvinyl alcohol. Suspension polymerization was carried out at 65° C. for 6 hours in an atmosphere. This copolymer was suspended in a saponification solution consisting of 200 parts of methanol, 10 parts of water, and 40 parts of 5N NaOH, and the saponification reaction was carried out at 25°C for 1 hour and then at 65°C for 5 hours. After thoroughly washing this with methanol, it was dried under reduced pressure to obtain a dry saponified product with an average particle vk of 230μ.

This was pulverized by a jet mill to obtain a finely powdered superabsorbent polymer having a particle size of 50 μm or less.

5g of the superabsorbent polymer obtained was sized to a width of 16C11 and a length of 22C.
When 500a I of a 7% by weight aqueous solution of propylene glycol was filled from the injection port into a plastic bag having an injection port with a check valve, gelation immediately proceeded.

This cold storage agent was stored in a freezer at -1θ°C and solidified.

When this solidified cold storage agent was left at room temperature, the constant temperature rise stopped at -5°C, indicating that the cold storage agent had a cold storage temperature of -5°C.

[Example-2] Sodium acrylate 74.95 mol%, acrylic acid 2
43 of an acrylate monomer consisting of 5 mol% and 0.05 mol% of trimethylolpropane triacrylate.
% aqueous solution was subjected to suspension polymerization at 70°C in a nitrogen atmosphere using 0.6 part of ammonium persulfate and 0.2 part of sodium bisulfite to obtain a gel-like hydrous copolymer. This gel-like water-containing copolymer was dried in a hot air dryer at 180° C. and then ground in a hammer-type grinder to obtain a dried product with an average particle size of 150 μm.

100 parts of this dried material were mixed with 2 parts of glycerin, 2 parts of water, and 2 parts of ethyl alcohol using a paddle mixer, and the resulting mixture was continuously heat-treated using a paddle dryer. This was pulverized by a jet mill to obtain a finely powdered superabsorbent polymer having a particle size of 60 μm or less.

8g of the obtained superabsorbent polymer and 4g of propylene glycol
0 g was placed in a plastic bag similar to that used in Example 1. Thereafter, when 500+*j of water was added through the injection port, gelation immediately proceeded.

This cold storage agent was stored in a freezer at -10°C to solidify.

When this solidified cold storage agent was left at room temperature, the constant temperature rise stopped at -4°C, indicating that the cold storage agent had a cold storage temperature of -4°C.

[Example 3] Dissolve 1 part of Ethyl Seven Rose N-200 (manufactured by Herkie Swords Co., Ltd.) in 23011 J of cyclohexane.

This solution is heated to 75°C. Add to this 12 parts of acrylic acid, 26 parts of dimethylaminoethyl methacrylate, and 70 parts of water.
1 part, 5 parts of 35% hydrochloric acid, and 0.02 parts of ammonium persulfate as a polymerization initiator were added dropwise over 2 hours.

Stirring was continued for an additional 30 minutes to complete the copolymerization.

Next, the water content of the polymer suspended in cyclohexane was reduced to 20% by azeotropic dehydration. To this was added an aqueous solution of 0.02 part of ethylene glycol diglycidyl ether dissolved in 1 part of water at 75°C, and the reaction was continued for further 2 hours. Next, cyclohexane was removed and dried under reduced pressure at 100°C to obtain a dried product with an average particle size of 250μ.

This was pulverized by a jet mill to obtain a finely powdered superabsorbent polymer having a particle size of 5 μm or less. When 7 g of the obtained superabsorbent polymer was placed in a plastic bag similar to that used in Example 1, and a 30% by weight aqueous solution of propylene glycol was added through the injection port of the bag, gelation immediately proceeded.

This cold storage agent was stored in a freezer at -20°C and solidified.

When this solidified cold storage agent was left at room temperature, -16℃
The temperature rise stopped and was kept constant. i.e. -1
It was found that this is a cold storage agent with a cold storage temperature of 6°C.

[Example 4] 5 g of a super absorbent polymer mainly composed of a copolymer of acrylic acid and vinyl alcohol (Sumikagel 5-SO, a product manufactured by Sumitomo Chemical Co., Ltd.) was used in the same manner as in Example 1. When the bag was placed in a plastic bag (left-hand side with reverse stopper) and 500+1 of a 22% by weight aqueous solution of propylene glycol was sealed through the injection port, gelation immediately proceeded. This cold storage agent is heated to -15℃
It was stored in the freezer to solidify. When this solidified cold storage agent was left at room temperature, the temperature stopped rising to a certain level at -10°C, indicating that the cold storage agent had a cold storage temperature of -10°C.

[Example 5] 45 g of the finely powdered superabsorbent polymer obtained in Example 1 and 150 g of polyethylene glycol were placed in a plastic bag similar to that used in Example 1, and 400all of water was further sealed through the injection port. Thereupon, gelation proceeded immediately.

This cold storage agent was stored in a freezer at -15°C to solidify.

When this solidified cold storage agent was left at room temperature, -15℃
It was found that the temperature rise stopped at a certain level, indicating that the cold storage agent had a cold storage temperature of -15°C.

[Example-6] 5 g of finely powdered super absorbent polymer obtained in Example 2 Example 1
When the bag was placed in a plastic bag similar to that used in 1 (reverse check left-hand side) and a 13% by weight aqueous solution of ethylene glycol was filled in through the injection port of the bag, gelation immediately proceeded.

This cold storage agent was stored in a freezer at -10°C to solidify.

When this solidified cold storage agent was left at room temperature, the constant temperature rise stopped at -5°C, indicating that the cold storage agent had a cold storage temperature of -5°C.

〔Effect of the invention〕

The cold storage agent of the present invention can have a freezing point or a melting point below zero, and does not deteriorate even after repeated use, and can be easily used in ordinary households for chilling cold foods, keeping frozen foods cold, ice cream, etc. It can be used for manufacturing, and can be manufactured by simply adding water during use.
Storage space and logistics costs can be significantly reduced.

Claims (6)

[Claims] (1) A cold storage agent characterized by containing a gel-like substance consisting of a superabsorbent polymer which is a polymer electrolyte containing a carboxylate, an organic freezing point depressing substance, and water. (2) The cold storage agent according to claim 1, wherein the organic freezing point depressing substance is one or more selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, and sugars. (3) A cold storage agent characterized in that a super absorbent polymer, which is a polymer electrolyte containing a carboxylate, and an organic freezing point depressing substance are stored in a container, and then water is further injected to form a gel-like substance. Manufacturing method. (4) A cool storage agent characterized by storing a super absorbent polymer, which is a polymer electrolyte containing a carboxylate, in a container, and then injecting an aqueous solution containing an organic freezing point depressing substance to generate a gel-like substance. Manufacturing method. (5) Claim 3 or 4, wherein the organic freezing point depressing substance is one or more selected from the group consisting of ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, and sugars. Manufacturing method. (6) A cold storage agent material characterized in that a super absorbent polymer, which is a polymer electrolyte containing a carboxylate, and an organic freezing point depressing substance are housed in a container.