JP2602040B2 - Cooling material and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cold insulator and a method for producing the same.

[Related Art] Most of the conventional cold insulating materials have a cooling medium sealed in a container made of a water-impermeable base material.

[Problems to be Solved by the Invention] However, in the conventional cold insulator, as a result of suddenly cooling the outside air with the cold insulator previously cooled, the temperature change causes dew condensation on the surface of the cold insulator. The dew water reduces the freshness of articles to be kept cool, for example, fresh vegetables, fish and shellfish, livestock meat, dairy products, and the like. There was a problem, such as hurting, and a solution was desired.

[Means for Solving the Problems] The present inventors have repeatedly studied to obtain a cold insulator which does not cause condensation and does not reduce the strength of the packaging container, and as a result, have reached the present invention.

That is, the present invention provides a cold insulator obtained by enclosing a cold insulating medium in a container made of a water-impermeable base material, and partially or entirely the outer surface of the base material with an intermediate layer mainly composed of a water-absorbent resin. And a water-absorbent resin between the water-impermeable base material and the water-permeable water-insoluble base material, provided with an outer layer comprising a water-permeable and water-insoluble base material. A method for producing a cold insulating material, characterized in that a cooling medium is enclosed in a container prepared with the water-impermeable base material side of a laminated sheet provided with a water absorbing / water retaining layer mainly composed of a medium (second invention). is there.

In the present invention, starch or cellulose (a) is used as the water-absorbing resin in the layer mainly composed of the water-absorbing resin.
And a water-soluble monomer and / or a water-absorbent resin obtained by polymerizing a monomer (b) which becomes water-soluble by hydrolysis and a cross-linking agent (c) as essential components and performing hydrolysis as required. .

Details of (a), (b) and (c), the proportions of (a), (b) and (c), the production method and specific examples of the water-absorbent resin used in the production of the water-absorbent resin are described in 52−2588
No. 6, JP-B-53-46199, JP-B-53-46200 and JP-B-55-21041.

Examples of the water-absorbing resin other than the above resins include those obtained by polymerizing (a) and (b), such as a hydrolyzate of a starch-acrylonitrile graft polymer and a hydrolyzate of a cellulose-acrylonitrile graft polymer;
Copolymers of (b) and (c), such as cross-linked polyacrylamide and its partial hydrolysates, cross-linked sulfonated polystyrene, cross-linked poval, JP-A-52-14689 and JP-A-52-27455. Cross-linked vinyl ester-unsaturated carboxylic acid copolymer saponified, cross-linked polyacrylate and acrylic acid-acrylate copolymer, cross-linked isobutylene-maleic anhydride copolymer, and cross-linked Polyethylene oxide and the like. Further, a polymer (b) having self-crosslinking properties, for example, a self-crosslinking type polyacrylate, JP-B-54-30
The resin described in Japanese Patent Publication No. 710 or a polymer having at least a hydroxyl group and a carboxylate group in a molecule, for example, the resin described in Japanese Patent Publication No. 54-37994 can also be used.

Two or more of the above water-absorbing resins may be used. Among these, the polymers (a), (b) and (c) mentioned first are preferred in terms of water absorbing ability, water retaining ability and the like.

The water-absorbing resin has a water absorbing performance of at least 50 ml / g, preferably 100 to 1,000 ml / g. The shape of the water-absorbent resin is not particularly limited, and may be any shape such as a powder, a particle, a flake, and a fiber. However, as described later, when the water-absorbing resin is used as a non-aqueous coating liquid together with a non-aqueous resin binder, it is preferably in the form of a fine powder having a particle diameter of 200 μm or less.

In the present invention, vegetable fibers such as pulp and cotton; vegetable powders such as sawdust and peat moss; and mineral porous materials such as perlite, zeolite and hillite can be used in combination with the water-absorbent resin as fillers and fillers. In addition, pigments, ultraviolet absorbers, antioxidants, fungicides, activated carbon, freshness preserving agents, and the like can be added as necessary.

Examples of the water-impermeable substrate include synthetic resin films such as polyester film, nylon, polyethylene film, and polypropylene film; laminated films of these; metal films such as aluminum foil; and multilayers of synthetic resin films and metal films. Laminated films may be used. From the viewpoint of flexibility, a synthetic resin film and a laminated laminated film of the synthetic film are preferable.

Examples of the water-insoluble base material having water permeability include fibrous sheets such as paper (eg, cellulose acetate paper), non-woven fabric, woven fabric, and knitted fabric; cellophane; vinylon; Shaped laminate and the like. Preferred substrates are paper, nonwoven fabrics and sheet-like laminates of these with cellophane, vinylon and perforated synthetic resin sheets.

In the present invention, although the amount of the water-absorbing resin used in the laminated sheet can be suitably selected by water absorption performances the request, usually 1 to 100 g / m ^2, preferably 5~55g / m ^2.

The laminated sheet is, for example, a method of sandwiching a powdery water-absorbent resin with a water-impermeable base material and a water-insoluble base material having water permeability, a non-aqueous coating of the water-absorbent resin in a fine powder state together with a nonaqueous resin binder Liquid, and after fixing this coating liquid on a water-impermeable base material or a water-insoluble base material having water permeability, dried, and further laminated another base material,
Alternatively, a method of drying after laminating the other substrate after fixation may be used.

As a non-aqueous resin binder used when manufacturing a laminated sheet by any of these methods, it has low solubility in water to be absorbed, and is effective in absorbing water of a water-absorbent resin and increasing the volume when swelling. A flexible resin exhibiting excellent adhesiveness is preferable, and examples thereof include an ethylene-vinyl acetate copolymer, a chlorinated polyolefin, a urethane resin, and a linear thermoplastic polyester resin. These non-aqueous resin binders are dissolved in non-aqueous solvents (alcohols, acetates, ketones, hydrocarbon solvents alone or in a mixed solvent),
Further, a water-absorbent resin fine powder is dispersed to prepare a non-aqueous coating liquid. Examples of a method for fixing the coating liquid include a gravure printing method, a roll coating method, and a screen transfer method, but are not limited thereto.

In the present invention, a container or bag is prepared with the water-impermeable substrate side of the laminated sheet inside, and a cooling medium is enclosed in the container or bag to form a cooling material. There are no conventional cooling media for cooling materials, such as the following.

A flexible gel formed by dissolving a water-soluble organic polymer (starch, carboxymethylcellulose, gelatin, casein, guar gum, polyvinyl alcohol, polyvinylpyrrolidone, polystyrene oxide, polyacrylate, etc.) in water.

A gel of a water-absorbing resin that has absorbed water or a mixed solvent mainly composed of water.

A cooling medium in which a freezing point depressing substance (polyhydric alcohols, urea, ammonium nitrate, etc.) is added to the above-mentioned or other gel-like substance.

Substances that absorb heat when dissolved in water (urea, ammonium nitrate,
Sodium nitrate, sodium carbonate decahydrate, diammonium phosphate, sodium tetraborate decahydrate, sodium thiosulfate decahydrate) and water containing a water-soluble organic polymer or water-absorbing resin. Medium.

If necessary, a preservative, a fungicide, an antioxidant, an ultraviolet absorber and the like may be added to the cooling medium.

The method of manufacturing the cold insulator will be described below with reference to the drawings. First, as shown in FIG. 4, a laminated sheet is prepared by sequentially laminating a water-impermeable base material 2, a water-absorbent resin 1, and a water-permeable water-insoluble base material 3. Next, using the laminated sheet, a container or bag for a cold insulator is produced. The shape and manufacturing method of the container for the cold insulator are not limited as long as the impermeable base material 2 side of the laminated sheet is on the inside and there is no leakage of the medium 4 for cooling the content. For example, a method of folding a laminated sheet so that the water-impermeable substrate 2 side is on the inside and heat-sealing the two sides (FIG. 1). A method of heat-sealing both ends and the lower end of the stack (FIG. 2). Two more water-impermeable substrates 2 'and 2 "are further laminated on the water-impermeable substrate 2 of the laminated sheet, and both ends and the lower end are heat-sealed. The container shown in Fig. 3 is provided with an air valve 6 in order to make the space between the two impermeable substrates 2 'and 2 "an air layer. Further, the medium 4 for a cold insulator is sealed in the container for the cold insulator. That is, after the cooling medium 4 is placed in a container for a cooling material having a desired shape, the opening is sealed by a heat sealing method or the like to produce a cooling material. In the case of the cold insulator shown in FIG. 3, air is appropriately introduced from the air valve 6 and the valve is closed when used.

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

Example 1 10 g / m ² fine powdery water-absorbent resin Sunwet IM-1000
A non-aqueous coating liquid comprising [starch-sodium polyacrylate copolymer, manufactured by Sanyo Chemical Industry Co., Ltd.] and a polyurethane binder of 3 g / m ² was prepared, and the coating liquid was used as the water-absorbing resin layer 1. , 30 μm thick polyethylene film. Next, a water-insoluble water-insoluble base material 3 composed of 30 g / m ² cellulose acetate paper and 15 g / m ² non-woven fabric was overlaid so that the non-woven fabric became the outermost layer, and then dried to produce a laminated sheet. . Add the laminated sheet to 15
Cut to 0mm x 150mm size, polyethylene film 2
The container was folded in two with the inside facing inward, and the two sides were heat-sealed to produce a container for a cold insulator.

0.25 g of water-absorbent resin Sunwet IM-1000 (water absorption capacity 960 times) and 0.75 g of carboxymethyl cellulose in this container
And a gel-like cooling medium 4 consisting of 180 cc of water and
The opening was heat-sealed to produce a cold insulator (a) of the present invention.

The cold insulator (a) was placed in a freezer and frozen at -16 ° C.
Then, it was taken out of the room at 25 ° C. and thawed, and the central temperature of the cold insulator was measured at regular intervals. At the same time, the state of formation of dew water was visually observed. Table 1 shows the test results.

Example 2 The present invention was carried out in the same manner as in Example 1 except that the used amount of the water-absorbent resin sun wet IM-1000 in the water-absorbent resin layer 1 was changed from 10 g / m ² to 5 g / m ^2. (B) was prepared.

This cold insulator (b) was tested in the same manner as in Example 1, and the center temperature and the state of formation of dew water were visually observed. Table 1 shows the test results.

Comparative Example 1 A cold insulator (a) was obtained in the same manner as in Examples 1 and 2, except that a container made of polyethylene film was used instead of the cold insulator container of Examples 1 and 2. Table 1 shows the test results obtained by conducting a test on the cold insulator (a) in the same manner as in Examples 1 and 2, and examining the center temperature and the presence or absence of dew water.

It is clear that the cold insulators (a) and (b) of the present invention have no formation of dew condensation water and can extend the cold keeping duration.

[Effects of the Invention] The following effects can be obtained by using the cold insulator of the present invention.

(1) The generation of dew water can be prevented.

The dew condensation generated by the water-absorbent resin layer provided on the surface of the cold insulator is immediately absorbed and held to prevent dew formation. As a result, articles to be kept cool, for example, fresh vegetables, fish and shellfish, livestock meat, dairy products, etc. are not wetted by dew condensation water, so that freshness is maintained. In addition, there is no fear that the strength of the container packing the products to be kept cool is reduced by the dew condensation water. Further, there is no fear of delamination of the label stuck to the insulated product or bleeding of the printed material on the label surface due to the dew condensation water.

(2) Drip (meat juice) generated from meat such as fresh fish meat can be absorbed.

When fresh fish meat or the like cooled to a temperature below the freezing point is thawed, free water from the protein tissue destroyed by freezing contains soluble components and drips, making the appearance extremely unsightly. Since the water-absorbent resin layer provided on the surface of the cold insulator of the present invention absorbs drip, the appearance of fresh fish meat and the like is not impaired.

(3) Cooling duration is extended.

The water-absorbent resin layer on the surface of the cold insulator that has absorbed the dew condensation water and the drip appropriately suppresses the conduction of heat. As a result, it is possible to extend the duration of the cold insulator.

[Brief description of the drawings]

FIGS. 1 to 3 are cross-sectional views showing one example of the cold insulator of the present invention using containers for cold insulators having various shapes. Fig. 1 is 1
FIG. 2 shows an example in which a container is produced by folding two laminated sheets in two, FIG. 2 shows an example in which a container is produced from two laminated sheets, and FIG. 3 shows an example in which an air layer is provided on one surface of the container. 4th
The figure is a cross-sectional view of the laminated sheet used for the cold insulator of the present invention. DESCRIPTION OF SYMBOLS 1 ... Water-absorbing resin layer, 2 ... Water-impermeable base material, 3 ... Water-insoluble base material having water permeability, 4 ... Cooling medium, 5 ... Air layer, 6 ... Air valve.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Akamatsu 1 at Sanyo Kasei Kogyo Co., Ltd., 11-11, Hitotsubashi-Honcho, Higashiyama-ku, Kyoto-shi, Kyoto (72) Eiji Miyashita 2-7-12 Tsukiji, Chuo-ku, Tokyo No. 15 Yamakyo Building 505 Inside Felix Co., Ltd.

Claims (2)

(57) [Claims] 1. A cooling material comprising a cooling medium sealed in a container made of a water-impermeable base material, wherein a part or all of the outer surface of the base material is provided with an intermediate layer mainly composed of a water-absorbing resin. hand,
A cold insulator characterized by having an outer layer made of a water-permeable water-insoluble base material. 2. A laminated sheet having a water-absorbing / water-retaining layer mainly composed of a water-absorbing resin provided between a water-impermeable substrate and a water-insoluble substrate having water permeability, with the water-impermeable substrate side inside. A method for producing a cold insulating material, wherein a cooling medium is enclosed in the produced container.