JPH04331246A - Gas barrier material and container material produced therefrom - Google Patents

Abstract

PURPOSE:To obtain a gas barrier material which is produced from a polymer having gas barrier properties and in which heat resistance is not at all required of the gas barrier polymer and ingredients incorporated therein by applying the gas barrier polymer to a moisture-impermeable plastic film. CONSTITUTION:A moisture-impermeable plastic (preferably a film of a polyolefin, such as PE or PP, which has excellent moisture impermeability and heat sealability) is coated with a polymer which has gas barrier properties and can be applied as a solution in water or in a solvent (e.g., PVA resins or ethylene-vinyl alcohol copolymer resins) to thereby obtain a gas barrier material. When oxygen gas barrier properties are especially desired, it is preferable to use a reducing agent (e.g., iron powder) in combination with the gas barrier polymer. For example, a gas barrier material A consisting of a coating layer 1 made of the gas barrier polymer and a moisture-impermeable plastic film 2 is united with a container substrate paper 3 through the medium of an adhesive layer 4, and an outer resin layer 5 is further formed therein to obtain a container material.

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]

[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 moisture-proof plastic film with a polymer substance having gas barrier properties, and the second aspect of the present invention is a gas barrier material characterized by coating a moisture-proof plastic film with a polymer substance having gas barrier properties. Each content includes a base material for a container characterized by using the following.

[0009] 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.

[0010] 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 polyvinyl alcohol resin is preferred.

The ethylene-vinyl alcohol resin preferably has an ethylene content of 20 to 40% by weight and a saponification degree of 85% or more.

[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, etc.), polymeric phenolic antioxidants (Irganox 1010, etc.), ascorbic acid and its salts, glucose, sorbitol, mannitol,
Examples include methionine, tannic acid, uric acid, citric acid, flavonoids (catechin, etc.), and polyhydric phenol polymers.

[0014] These are more effectively used singly 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 moisture-proof plastic film used in the present invention includes polyolefins such as polyethylene and polypropylene, which have excellent moisture-proof properties and heat-sealing properties;
Films of modified polyolefin, polyester, etc. are suitable.

[0016] The production of the gas barrier material is achieved by preparing a polymeric substance having gas barrier properties in the form of a solution, coating it on a moisture-proof plastic film, and then drying the solvent. Coating is performed using a roll coater, a bar coater, etc. Impregnation coating by dipping can also be used. Note that, prior to coating, the surface of the moisture-proof plastic film to be coated may be subjected to surface treatment for enhancing adhesion, such as treatment with an anchor coating agent, if necessary. 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 moisture-proof plastic film 2 is integrated with a liquid container base paper 3 by an adhesive layer 4, and a moisture-proof plastic The film 2 forms a resin layer on the liquid contact side. Reference numeral 5 denotes an outer resin layer, and a resin having excellent moisture-proofing properties and heat-sealing properties is used.

Regarding the bonding of the gas barrier material A and the liquid container base paper 3, there is a method of bonding the gas barrier material A to the liquid container base paper 3 via an adhesive layer 4 as shown in FIG. preferable.

[0020]Also, dry lamination, wet lamination, extrusion lamination, etc. can be applied to the bonding method, but extrusion lamination is particularly suitable 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.

[0021] 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. are used alone or in combination of two or more.

[0022]

[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 A paste-like aqueous solution with a solid content of 2% by weight was prepared using commercially available konjac flour "seifu" (main component: glucomannan) as a polymeric substance having oxygen gas barrier properties. On the other hand, as a moisture-proof plastic film, a commercially available polyethylene film (thickness: 40 μm) was prepared, and an ethylene-vinyl acetate anchor coating agent "Seikadyne 570" was prepared in advance.
B) (manufactured by Dainichiseika Kagyo Co., Ltd.) was applied at 0.1 g/m2 (solid content), and then the aqueous solution was applied at 28 g/m2 (solid content) and dried. Next, 0.2 g/m2 (solid content) of a polyethyleneimine anchor coating agent "Toyobain 210K" (manufactured by Tosoh Corporation) was applied onto this layer.

[0024] The surface coated with the polyethyleneimine anchor coating agent of the barrier material prepared in this manner and the milk carton base paper (basis weight: 340
g/m2; manufactured by Weyerhaeuser Paper Company) by an extrusion lamination method, and low-density polyethylene resin "Mirason-16P" (density: 0.923) was used as adhesive layer resin.
g/cm3, MI: 3.7 g/10 min; manufactured by Mitsui Petrochemical Industries, Ltd.), the resin temperature was set to 31
They were laminated and bonded together under the conditions of 5° C. and a thickness of 20 μm.

Next, the above-mentioned "Mirason 16P" was extrusion laminated to a thickness of 20 μm on the base paper side of the bonded materials using a cooling mirror roll under the same conditions to produce a base material for a liquid container.

Example 2 Glucomannan commercially available konjac flour "seifu" (main component: glucomannan) was used as a polymeric substance having oxygen gas barrier properties, and a glue-like aqueous solution with a solid content of 2% by weight (
A) was adjusted. On the other hand, as a polymer substance having oxygen gas barrier properties, polyvinyl alcohol resin "GOHSENOL AH-17 (polymerization degree: 1700, saponification degree: 90.0
~98.5%, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) and commercially available glucose as a reducing agent at a weight ratio of 85:15 to prepare an aqueous solution (B) with a total solid content of 20% by weight. Aqueous solution (A) and aqueous solution (B) were mixed at a weight ratio of 1:3, and an aqueous solution (C
) was adjusted.

On the other hand, a commercially available polyethylene film (thickness: 40 μm) was prepared as a moisture-proof plastic film, and was coated with an ethylene-vinyl acetate anchor coating agent in advance.
After coating 0.1 g/m2 (solid content) of ``Seikadyne 570B'' (manufactured by Dainichiseika Chemical Industry Co., Ltd.), the aqueous solution (C
) was applied (total solid content: 28 g/m2) and dried. Next, on this layer, a polyethyleneimine anchor coating agent "Toyobain 210K" (manufactured by Tosoh Corporation) is applied.
0.2 g/m2 (solid content) was applied.

[0028] The surface coated with the polyethyleneimine anchor coating agent of the barrier material prepared in this way and the milk carton base paper (basis weight: 340
g/m2; manufactured by Weyerhaeuser Paper Company) by an extrusion lamination method, and low-density polyethylene resin "Mirason-16SP" (density: 0.92) was used as adhesive layer resin.
3 g/cm3, MI: 4.5 g/10 minutes; manufactured by Mitsui Petrochemical Industries, Ltd.), the resin temperature was 3.
They were laminated and bonded together under the conditions of 15° C. and a thickness of 20 μm.

Next, on the base paper side of the bonded above materials, extrusion lamination with a thickness of 20 μm was performed using the above-mentioned “Mirason-16SP” as the outer resin using a cooling mirror roll under the same conditions to form a material for liquid containers. A base material was prepared.

Comparative Example 1 A base material for a liquid container was prepared in the same manner as in Example 1, except that the polymer material having oxygen gas barrier properties was not used.

The oxygen gas permeability of the liquid container substrates prepared in Examples 1 and 2 and Comparative Example 1 was measured using a gas permeability measuring device manufactured by Toyo Seiki Seisakusho Co., Ltd., according to ASTM-D-
The results measured in accordance with 1434M-CI are as follows. Oxygen gas permeability (cc/m2 ・24hrs ・atm
) Example 1 1.
5 Example 2 0.
9 Comparative Example 1 43
0

[0032] Next, the heat sealability of the base material for liquid containers was examined on the outer surface of the container, on the liquid-contacting surface, and on the liquid-contacting surfaces, and it was found to be good, and it was confirmed that there would be no problems in manufacturing liquid containers. It was done.

[0033]

Effects of the Invention The gas barrier material of the present invention is made by simply coating a moisture-proof plastic film with a polymer substance having gas barrier properties, rather than by hot melt molding. The heat resistance of reducing agents, etc.) is not a problem at all.

Furthermore, in the present invention, since the moisture-proof plastic film 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 that are difficult to handle and use even if they can be formed into a film. .

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
Moisture-proof plastic film 3 Liquid container base paper 4 Adhesive layer 5 Outer resin layer

Claims (4)

[Claims] 1. A gas barrier material comprising a moisture-proof plastic film 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.