JPH04363239A - Gas barrier material and base material for vessel using the same material - Google Patents

Abstract

PURPOSE:To obtain the gas barrier material excellent in wetness by coating a thin paper with the polymer having gas-barrier property such as polyvinyl alcohol resin, and ethylene-vinyl alcohol copolymer resin, etc. CONSTITUTION:Polyvinyl alcohol resin, ethylene-vinyl alcohol copolymer resin and the polymer with gas-barrier property selected from polysaccharide group are prepared in soluble form. A thin paper is coated with the solution of the polymer by the coating with a roll-coater, etc., or the impregnation by dipping, and then the materials are dried, thereby producing gas barrier material. When the base material for a liquid vessel is formed by using the gas barrier material, the gas barrier material A composed of the polymer-coated layer 1 with gas barrier property and the thin paper 2 is positioned between the resin layer 4 of the side brought in contact with the liquid surface and the base paper 5 of the liquid vessel. While the gas barrier material is integrally formed with the base paper 5 of the liquid vessel by an adhesive layer 3, the resin layer 6 of out side is laminated thereon.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier material having a high gas barrier property, particularly a high oxygen gas barrier property, and a base material for containers using the material.

0002

[Prior Art] Today, containers for liquid foods such as milk and juices are made using a combination of paper and synthetic resin.
"cartons" are often used, but cartons with high oxygen gas barrier properties are required especially for products that require long-term storage or products that are susceptible to oxidative deterioration, so aluminum foil is used as an oxygen gas barrier material. Aluminum foil is also commonly used in containers for frozen foods, instant foods, etc. to preserve flavor.

However, in recent years, it has become a problem that aluminum foil remains as a residue in the incinerator when it is incinerated after use. Furthermore, since aluminum foil requires a large amount of electric power during production, it also poses a problem from the viewpoint of energy conservation. Therefore, various proposals have been made to achieve high oxygen gas barrier properties without using aluminum foil.

For example, it is possible to use polymeric oxygen gas barrier materials such as ethylene-vinyl alcohol copolymer resins, polyester resins, and polyamide resins; One of the methods is to provide a moisture barrier layer to prevent the barrier effect of these oxygen gas barrier materials from deteriorating, and to further enhance the barrier effect, oxygen scavengers and oxygen absorbers are added.

[0005]

[Problems to be Solved by the Invention] The base materials for liquid containers with high oxygen gas barrier properties that have been put into practical use or proposed so far are in the form of multilayer composite materials, and the barrier layer is formed by hot melt extrusion (
(including coextrusion), or it is generally formed into a film and then undergoes a bonding process.

[0006] When the barrier layer is formed by hot melt extrusion, there is a problem with the thermal history when the thermoplastic resin is mixed with various compounds (oxidant scavenger, oxygen absorber, etc.) and hot melt extruded. Therefore, the compound must have heat resistance, and the types of compound are naturally limited.

[0007] Furthermore, when the barrier material is once formed into a film and then bonded together, care must be taken to prevent the film from being scratched or pinholes being formed, which poses problems in processing and handling of the film.

[0008] Furthermore, when forming a barrier layer by processing a barrier material in the form of a solution, the heat resistance of the compound is not a problem, but the "wettability" to the adherend is a problem. come.

[0009]

[Means for Solving the Problems] In view of the above circumstances, the present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, the first aspect of the present invention is a gas barrier material characterized by coating a thin paper with a polymer substance having gas barrier properties, and the second aspect of the present invention is a gas barrier material using the above gas barrier material. Each content includes a base material for a container, which is characterized by:

[0010] The polymeric substance having gas barrier properties used in the present invention refers to a substance that can be dissolved in water or a solvent and coated, and includes, for example, polyvinyl alcohol resin, ethylene-vinyl alcohol copolymer resin, Saccharides and the like are preferred, and these may be used alone or in combination of two or more.

[0011] As the polyvinyl alcohol resin, one having a degree of saponification of 95% or more and a degree of polymerization in the range of 200 to 3,000 is suitable, and when particularly high water resistance and moisture resistance are required, methylol group-modified resin is preferred. A cross-linked type of polyvinyl alcohol resin is suitable.

[0012] Polysaccharides include starch, glycogen, cellophane, mannan, glucomannan, pectin,
galactan, gum arabic, inulin, dextrin,
Alginic acid, carrageenan, etc. can be used.

[0013] In the present invention, it is preferable to use a reducing agent in combination, especially when oxygen gas barrier properties are desired. Reducing agents used in the present invention include inorganic and organic reducing agents, oxygen scavengers, oxygen absorbers, antioxidants, and antioxidants, and specifically, iron powder, ferrous salts, and tocopherols. ,
Coenzyme Q, gallic acid, phenolic antioxidant (
BHT, BHA), polymeric phenolic antioxidants (
Irganox 1010), ascorbic acid and its salts, glucose, sorbitol, mannitol, methionine, tannic acid, uric acid, citric acid, flavonoids (catechin, etc.), polyhydric phenol polymers, and the like. Furthermore, regarding oxygen absorption, enzymes such as hemoglobin, which have a catalytic effect, and SOD (superoxide di
smutase) substance (metallic enzyme), chelate resin,
Examples include complex ion inclusion polymers, oligomers, and artificial enzymes such as phthalocyanine derivative complexes.

[0014] These may be used alone or in combination of two or more, and further in combination with inorganic or organic acid salts of transition metals such as iron, cobalt, nickel, and copper.

The thin letters used in the present invention include Western paper, Japanese paper, fibers made of polysaccharides such as cellulose such as rayon, and papers made of synthetic or semi-synthetic fibers such as vinylon, olefin, polyester, and cellulose acetate. and paper mixed with these fibers.

[0016] Also, the basis weight is 15g/m2 to 50g/m2
Preferably, the range is . The basis weight is appropriately determined depending on the required strength as a gas barrier material, the amount of coating of a polymeric substance having gas barrier properties, and the like.

[0017] The production of the gas barrier material is accomplished by preparing a polymeric substance having gas barrier properties in the form of a solution, coating it on a thin paper, and then drying the solvent. Coating is done using a roll coater, bar coater, etc.
Further, impregnation coating by dipping can also be used. Further, the coating may include not only a single layer but also a multilayer, and for example, a gas barrier layer containing a reducing agent and a gas barrier layer not containing a reducing agent may be formed into two layers.

The gas barrier material obtained as described above is widely used as a gas barrier for liquid containers, frozen food containers, etc., and in particular for various container base materials that require oxygen gas barrier properties.

FIG. 1 shows an example of a base material for a liquid container using the gas barrier material of the present invention. In FIG. 1, a gas barrier material A consisting of a polymer coating layer 1 having gas barrier properties and a thin paper 2 is located between a liquid contact side resin layer 4 and a liquid container base paper 5, Liquid container base paper 5
are integrated with the adhesive layer 3. 6 is an outer resin layer.

Regarding the bonding of the gas barrier material A and the liquid container base paper 5, the gas barrier material A may be bonded to the liquid container base paper 5 via the adhesive layer 3 as shown in FIG. Alternatively, the liquid container base paper 5 and the thin paper 2 may be bonded and integrated in advance, and then the polymer substance coating layer 1 having gas barrier properties may be provided.

[0021]Also, dry lamination, wet lamination, extrusion lamination, etc. can be applied to the bonding method, but extrusion lamination is particularly preferred since it is not necessary to take residual solvent, residual moisture, etc. into consideration. At this time, in order to improve the adhesive strength with the barrier material, the barrier material may be treated with an anchor coating agent as necessary.

[0022] In the case of the extrusion lamination method, the material for the adhesive layer is not particularly limited as long as it is a resin that can be extrusion laminated, and examples thereof include polyethylene resin, polypropylene resin, polyester resin, polyamide resin, etc. These may be used alone or in combination of two or more.

[0023]

[Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples, but these are not intended to limit the present invention.

Example 1 Glucomannan (commercially available konnyaku flour "seiko" was used) was used as a polymeric substance having oxygen gas barrier properties at a solid content of 2
Adjust to a paste-like aqueous solution of % by weight, and apply this as a thin letter onto Japanese paper (basis weight: 36 g/m2) (solid content: 19
g/m2) and dried at room temperature to produce a barrier material.

[0025] The barrier material thus produced and the milk carton base paper (basis weight: 340
g/m2; manufactured by Weyerhaeuser) and low density polyethylene resin "Mirason-16SP" (density: 0.923 g/cm3, M
I: 4.5g/10min; manufactured by Mitsui Petrochemical Industries, Ltd.)
Polysandran was laminated and bonded together using a resin temperature of 315° C. and a thickness of 20 μm.

Next, extrusion lamination of the above-mentioned "Mirason-16SP" to a thickness of 25 μm was performed on the base paper side of the pasted materials using a cooling mirror roll under the same conditions. -16SP" was extrusion laminated to a thickness of 45 μm using a cooling mat roll to produce a base material for a liquid container.

Comparative Example 1 According to Example 1, glucomannan as a polymer substance having oxygen gas barrier properties was adjusted to a glue-like aqueous solution with a solid content of 2% by weight, and an OPP film (thickness: : 25 μm) and dried at room temperature to produce a glucomannan film (thickness: 20 μm), but it became wrinkled and a uniform and smooth film could not be obtained. It was difficult to use as

Example 2 Milk carton base paper (basis weight: 34
0g/m2, manufactured by Weyerhaeuser Co.) and washi paper (basis weight: 36g/m2) as a thin letter were extrusion laminated using polyester resin "RT-54" as adhesive layer resin.
3CA" (density: 1.4 g/cm3; manufactured by Nippon Unipet Co., Ltd.) and laminated and bonded together under conditions of a resin temperature of 295° C. and a thickness of 30 μm.

Next, polyvinyl alcohol resin "GOHSENOL AH-
17'' (degree of polymerization: 1700, degree of saponification: 97.0-98
．． 5%; manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) and L-ascorbic acid as a reducing agent were dissolved in water at a weight ratio of 7:3 to obtain an aqueous solution with a solid content of 15% by weight.

[0030] This aqueous solution was coated on the Japanese paper surface of the above-mentioned bonded product prepared in advance (solid content 27 g/m2),
It was dried in a gear oven dryer at 40°C to form a layer of barrier material.

[0031] On this barrier material layer side, "Mirason-16SP" was laminated by extrusion lamination using a cooling mat roll at a resin temperature of 315°C and a thickness of 45 μm, and then on the milk carton base paper side, the same procedure as above was applied. Lamination was performed to a thickness of 25 μm using a cooling mirror roll to produce a liquid container base material.

The oxygen gas permeability of the liquid container base materials produced in Examples 1 and 2 above was measured using a gas permeability measuring device manufactured by Toyo Seiki Seisakusho Co., Ltd. according to ASTM-D-1434M-CI.
Measured according to. The results are as follows. Oxygen gas permeability (cc/m2 ・24hrs ・atm)
Example 1
0.47 Example 2
0.21

Next, the heat sealability of the base material for liquid containers was investigated on the outer surface of the container, on the liquid contact side, and on the liquid contact surfaces.
Both had good heat sealability, and it was confirmed that there were no problems in making cans for liquid containers.

[0034]

Effects of the Invention The gas barrier material of the present invention is not formed by hot melt molding but by simply coating a thin paper with a polymer substance having gas barrier properties. etc.), the heat resistance is not a problem at all. Furthermore, since the gas barrier material solution is applied onto the porous thin paper, the wettability is extremely good.

Furthermore, in the present invention, since the thin paper serves as a reinforcing material, it is possible to use gas barrier materials that are normally impossible or difficult to form into a film, or even those that can be formed into a film but are difficult to handle and use. Furthermore, the use of thin paper also contributes to improved adhesion between the barrier material and the adjacent layer due to its surface fibers.

Although the present invention has been explained with a focus on gas barrier properties, particularly oxygen gas barrier properties, the base material for containers using the material is not only a moisture barrier, but also has moisture content, taste components, flavor components, etc. of foods. Of course, it is also effective in preventing escaping out of the container and preserving flavor.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a container base material using the gas barrier material of the present invention.

[Explanation of symbols]

1 Coating layer of polymer material with gas barrier properties 2
Thin letter 3 Adhesive layer 4 Liquid contact side resin layer 5 Liquid container base paper 6 Outer side resin layer

Claims (4)

[Claims] 1. A gas barrier material comprising a thin paper coated with a polymer substance having gas barrier properties. 2. The gas barrier material according to claim 1, wherein the polymer substance having gas barrier properties comprises at least one selected from polyvinyl alcohol resins, ethylene-vinyl alcohol copolymer resins, and polysaccharides. 3. The gas barrier material according to claim 1, wherein the polymer substance having gas barrier properties contains a reducing agent. 4. A container base material comprising the gas barrier material according to claim 1.