JPH06246868A - Multilayer laminated body - Google Patents

Abstract

PURPOSE:To obtain a multilayer laminated body which is superior in high gas barrier properties, by a method wherein an olefin-vinyl acetate copolymer saponification matter resin layer whose thickness is specified is laminated on a thin film of a metal or a metallic oxide formed on the surface of a plastic base. CONSTITUTION:The laminated body is obtained by laminating an olefin-vinyl acetate copolymer saponification matter resin layer having a thickness of at least 1mum on a thin film of a metal or a metallic saponification matter formed on the surface of a plastic base. Olefin-vinyl acetate copolymer saponification matter resin is manufactured by saponifying a copolymer to be obtained by a radical polymerization between olefin and vinyl acetate. Although olefin contents and a saponification degree are not limited especially, it is preferable that the olefin contents are 20-50mol.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer laminate having a gas barrier property against permeation of oxygen gas and the like, and a fragrance component's aroma retaining property (hereinafter, also referred to as gas barrier property). The present invention relates to a multilayer laminate having a high gas barrier property and suitable as a material for food storage containers and the like.

[0002]

2. Description of the Related Art Currently, frozen foods, retort foods, etc.
It has the features of being able to be stored for a considerably long period of time and being easy to cook, and is expected to become even more popular in the future. In the field of packaging materials (films, sheets, pouches, tubes, bottles, etc.) for these foods, materials having higher gas barrier properties are required in order to enable further long-term storage. Conventionally, as a method for obtaining a material having a plastic material as a base material and having excellent gas barrier properties, a method of forming and laminating a thin film of a metal such as aluminum or a metal oxide such as silicon oxide on the surface of the plastic material by vapor deposition or sputtering. Proposed (JP-A-49-41469 and 49-349)
No. 84, No. 59-62143, No. 60-61252.
Nos. 60-23037 and 60-61253). In addition, since these thin films are apt to crack when bent, they act as a protective film on the outer surface, and when these thin films are on the inner surface of the packaging material, they do not have heat-adhesive properties (heat-sealing properties). In this case, a polyolefin film such as polyethylene or polypropylene is further laminated and used.

[0003]

However, even if a protective film is formed on the surface of the thin film as described above, the thickness of the thin film of metal or metal oxide (hereinafter referred to as metal) is attempted to obtain a higher gas barrier property. However, if the film thickness is increased, the thin film becomes brittle, cracks and pinholes are easily generated, and on the contrary, the gas barrier property is lost. In view of the above circumstances, the present invention has an object to provide a multilayer laminate that overcomes the above-mentioned limit and is excellent in a high gas barrier property.

[0004]

Means for Solving the Problems As a result of intensive studies for solving these problems, the present inventors have found that it is not necessary to increase the thickness of a thin film of metal or the like, and the olefin-vinyl acetate The inventors have found that the problem can be solved by laminating a copolymer saponified resin layer, and completed the present invention.
That is, the gist of the present invention is a multi-layer in which an olefin-vinyl acetate copolymer saponified resin layer having a thickness of at least 1 μm is laminated on a metal or metal oxide thin film formed on the surface of a plastic substrate. It is in a laminate. The details of the present invention will be described below.

The plastic substrate according to the present invention includes:
A thermoplastic resin can be used as a general molding material, particularly as a molding material for containers, films and other packaging materials.
Specifically, polyethylene, polypropylene, polyolefins such as ethylene-α-olefin copolymers, modified polyolefins obtained by modifying these polyolefins with unsaturated ethylenic carboxylic acid, polyvinyl chloride,
Examples include various resins such as polystyrene, ABS resin, polyacetal, polycarbonate, and polyester.

The metal or the like laminated on the surface of the plastic substrate is aluminum, titanium, chromium,
Examples include simple metals such as nickel, and metal oxides such as aluminum oxide, silicon oxide, titanium oxide, ferrite, and indium oxide.

These metals and the like are formed in a thin film on the surface of the plastic base material, and the forming method is not particularly limited, but the vacuum, heating vapor deposition method and sputtering method are the most common. is there. The thickness of the thin layer is not particularly limited, but is usually 100 to 30 for the purpose of the present invention.
It is selected in the range of 00Å. If the thickness of the thin layer is less than 100 Å, a high gas barrier property cannot be obtained, and if it exceeds 3,000 Å, the thin layer loses flexibility, cracks easily occur, and coloring is large.

The olefin-vinyl acetate copolymer saponified resin used in the present invention is produced by saponifying a copolymer obtained by radical polymerization of olefin and vinyl acetate. Examples of the olefin in the olefin-vinyl acetate copolymer saponified resin include α-olefins having 2 to 12 carbon atoms. Among them, ethylene is easily polymerized, and the ethylene-vinyl acetate copolymer saponified resin is used. It is most preferably used because of its excellent gas barrier property.

The olefin content and saponification degree of the olefin-vinyl acetate copolymer saponified resin are not particularly limited, but the olefin content is preferably 15 to 60 mol%, more preferably 20 to 50 mol%. . If the olefin content is less than 15 mol%, melt extrusion molding may be difficult, and conversely, if it exceeds 60 mol%, the gas barrier property may be deteriorated, both of which are not preferable. On the other hand, the saponification degree is 9
0 mol% or more is preferable, and 96 mol% or more is more preferable. If the degree of saponification is less than 90 mol%, gas barrier properties are not exhibited, which is not preferable.

As a method for laminating the olefin-vinyl acetate copolymer saponified resin for obtaining the multilayer laminate according to the present invention, a known method using a thermoplastic resin or a resin solution can be used. For example, a method of coating a solution in which the saponified resin is dissolved in a solvent, a method of laminating a film obtained by an extrusion molding method, or an extrusion laminating method of laminating simultaneously with extrusion can be adopted.

As the solvent in the coating method, a mixed solvent such as n-propanol / water, i-propanol / water or t-butanol / water is usually used. The coating method includes an air knife method, a gravure roll method, a reverse roll method, a bar coating method, a spray coating method, and the like, and there are many known documents (for example, Japanese Patent Publication No.
7-48489, JP-A-57-64517, JP-A-57-64519 and JP-A-57-64521). The concentration of the polymer solution used is usually 1 to 50% by weight, preferably 5 to 30% by weight. The coating is performed once or a plurality of times and then dried. As a drying method, a hot air drying method, a radiant heat drying method, or a high frequency heating method can be employed. This high-frequency heating method is effective as a method of removing a solvent such as water when the solvent is mainly composed of water or when a relatively large amount of water is mixed.

As the film laminating method, a wet laminating method, a dry laminating method, a solventless laminating method, a wax laminating method, a thermal laminating method or the like can be used.

On the other hand, when the extrusion laminating method is adopted, the melting index of the saponified resin of olefin-vinyl acetate copolymer (MFR, load of 2. according to JIS-K 6758).
16 kg, measured at a temperature of 230 ° C.) is not particularly limited, but a range of 1 to 100 g / 10 minutes is suitable in terms of melt molding.

The thickness of the saponified olefin-vinyl acetate copolymer saponified resin layer in the multilayer laminate according to the present invention must be at least 1 μm, and if the thickness is less than 1 μm, the desired gas barrier property cannot be obtained. Although the gas barrier property is improved as the thickness is increased, it is not necessary to set the thickness to 50 μm or more in consideration of the gas barrier property and the economical efficiency. Therefore, 3-40 μm is usually selected in consideration of both factors.

Before laminating the saponified olefin-vinyl acetate copolymer resin by any of the above methods, for example, a titanium-based, urethane-based or other known anchor coating agent or dry laminating adhesive is coated. You can leave it. Further, when a higher adhesive strength or low-temperature adhesiveness than that of the saponified resin layer is required, another thermoplastic resin may be further laminated according to the required physical properties.

[0016]

The present invention will be described in detail with reference to examples. The gas barrier properties (oxygen permeability,
The method for measuring the aroma retention property is described below. (1) Oxygen permeation test The oxygen permeation amount complies with ASTM D3985-81, and using an oxygen permeation tester OXTRN-10 / 50A (manufactured by Modern Control Co.), temperature 23 ° C, humidity 65% RH and temperature 23 ° C, humidity. It was measured at 90% RH. (2) Perfume test A pouch is made using a multilayer laminate, various flavor component-containing solutions are sealed, and after a lapse of a predetermined time, the flavor component sorbed on the pouch inner surface film is extracted, and the amount is gas chromatographed. The method of measurement was taken using a graph.
According to this method, the larger the sorption amount, the lower the fragrance retaining property. A specific measuring method will be described. On the surface corresponding to the outer surface of the pouch, an aluminum foil having a thickness of 9 μm was inserted through a polyethylene terephthalate film having a thickness of 12 μm, respectively, and a dry laminate (adhesive AD950 manufactured by Toyo Morton Co., Ltd. was used for the dry laminate).
Using A / B, aging was carried out for 4 days in a constant temperature room at 40 ° C. after lamination. The amount of adhesive applied is 4 when dried.
It was adjusted to g / m ² . ) Was performed to prepare a multilayer laminate for aroma retention test. The aroma retention test was conducted on a part of Examples and Comparative Examples, but in the Examples, ethylene-
Heat-sealing was performed so that the vinyl acetate copolymer saponified resin layer was on the inner surface, and in the comparative example, the polypropylene layer was on the inner surface, and a 18 cm × 10 cm pouch was prepared, and various flavor components were dissolved in the interface. An activator aqueous solution (0.5% aqueous solution of Ryoto Sugar Ester S-1170, manufactured by Mitsubishi Kasei Foods Co., Ltd.) was sealed in an amount of 300 ml and kept in a thermostatic chamber at 23 ° C. for 70 days. After that, the pouch was opened, the flavor component sorbed by the film on the inner surface of the pouch was extracted with ether, and the flavor component remaining in the aqueous surfactant solution was also extracted with ether. Next, each was quantified using gas chromatography, and the sorption amount and the residual amount converted to the original aqueous solution concentration were calculated. From the obtained results, the distribution ratio of flavor sorption was calculated according to the following formula. Distribution ratio = Sorption amount / Residual amount That is, the larger the distribution ratio is, the stronger the flavor sorption is. When the distribution ratio is 1, half of the flavor contained in the aqueous solution before encapsulation is on the inner surface side of the pouch. It has been sorbed, and the concentration of the remaining flavor in the aqueous solution decreases as the distribution ratio becomes larger than 1.

Examples 1 to 9 [Vapor deposition treatment of metal and metal oxide on plastic substrate] Each of a plurality of commercially available polyester films [manufactured by Toray Industries, Inc., trade name: Lumirror P11, thickness 25 μm] 700 Å silicon monoxide or aluminum on one side
Was vacuum-deposited to a thickness of. Further, 700 Å vacuum vapor deposition of silicon monoxide or aluminum was carried out on each of a plurality of unstretched polypropylene films (Showa Denko KK, trade name: Show Allomer Film A, thickness 50 μm). The vacuum deposition is a vacuum deposition machine using a tungsten board as a heating resistor [EBH6 type manufactured by Nippon Vacuum Technology Co., Ltd.].
Was used as a vapor deposition source with a purity of 99.99% or more, and the degree of vacuum was 2 × 10 ⁻⁴ Torr. Then, the thickness of the deposited film was calculated by the gravimetric method.

[Preparation of Solution of Saponified Ethylene-Vinyl Acetate Copolymer] Saponified ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVOH) has an ethylene content of 2
Soarnol DT [manufactured by Nippon Synthetic Chemical Co., Ltd., trade name] having 9 mol% and a saponification degree of 99 mol%, and Soarnol A having ethylene content of 44 mol% and saponification degree of 90 mol% [manufactured by Nippon Synthetic Chemical Co., Ltd., Brand name], and dissolved in a mixed solvent of distilled water and n-propyl alcohol in a mixed solvent of 45/55 (wt%) at a temperature of 70 ° C. with stirring so that the polymer concentration becomes 15 wt%, and EVOH A solution was prepared. Also,
As a commercially available EVOH solution, Soarnol 30L [trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.] (3 in water / alcohol solvent)
0% by weight) was used.

[Preparation of Multilayer Laminate] The above EVOH solution was applied to the vapor deposition surface of the above vapor deposition film to give a final film thickness of about 20.
It was coated to have a thickness of μm. The coating film obtained by applying the EVOH solution was air-dried for a whole day and night, and then vacuum-dried at a temperature of 50 ° C. for 7 days to prepare a multilayer laminate of the invention. [Measurement] The oxygen permeation amount was measured for each of the multilayer laminates obtained in Examples and Comparative Examples. The aroma retention test was conducted on a part of the examples and comparative examples. The results of each measurement are shown in Table 1.

Comparative Example 1 The vapor-deposited film of Example 1 was used for measurement without applying the EVOH liquid. The measurement results are shown in Table 1. Comparative Example 2 The vapor-deposited film of Example 2 was used for measurement without applying the EVOH liquid. The measurement results are shown in Table 1. Comparative Example 3 The vapor-deposited film of Example 5 was used for measurement without applying the EVOH liquid. The measurement results are shown in Table 1. Comparative Example 4 The vapor-deposited film of Example 6 was used for measurement without applying the EVOH liquid. The measurement results are shown in Table 1.

Examples 10 to 12 The vapor-deposited film of Example 1 and the EVOH solution of Example 9 were used for coating with different final thicknesses of EVOH, and subjected to measurement of oxygen transmission rate. The measurement results are shown in Table 1.

Example 13 Soarnol DT [Nippon Gosei Kagaku Co., Ltd.] was used as EVOH.
On the vapor-deposited layer of the vapor-deposited film used in Example 1 using a 25 mmφ extrusion laminating machine (manufactured by Yoshii Iron Works Co., Ltd.) at a temperature of 220.
Extrusion laminated at 0 ° C. The oxygen transmission amount of the obtained laminate was measured. The results are shown in Table 1.

Comparative Example 5 Adhesive 900 (manufactured by Toyo Morton Co., Ltd., trade name) was applied to the vapor-deposited film of Example 1 as an adhesive at a ratio of 3 / m ² , and the Sialo allomer A film [Showa era] was provided on one side on the vapor-deposition side. Product name of polypropylene film manufactured by Denko KK, thickness 6
0 μm] was laminated. After lamination, aging treatment was carried out at 40 ° C. for 3 days. The oxygen permeation amount and the aroma retaining property of the obtained laminate were measured. The results are shown in Table 1.

The contents of each symbol in Table 1 are as follows. 1) Plastic substrate PET: Polyester film PP: Unstretched polypropylene film 2) Types of metals and metal oxides SiO: Silicon monoxide Al: Aluminum 3) Types of EVOH A: Soarnol DT solution B: Soanol A solution C : Soarnol 30L 4) Flavor component A: Myrcene B: d-limonene C: n-caproic acid ester D: Linalool E: n-octyl alcohol

[0025]

[Table 1]

[Table 2]

[0026]

As described above, since the multilayer laminate according to the present invention has a high gas barrier property, it can be used for food packaging, pharmaceutical packaging,
It is preferably used in fields such as cosmetic packaging.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Harada, Ibichu, Ibocho, Ibocho, Tatsuno, Hyogo Prefecture 1 of 251 Iwaho, Showa Polymer Co., Ltd. No. 1 Showa Polymer Co., Ltd. Osaka Research Center

Claims (2)

[Claims] 1. A metal or metal oxide thin film formed on the surface of a plastic substrate and having a thickness of at least 1 μm.
A multi-layer laminate in which saponified resin layers of the above olefin-vinyl acetate copolymer are laminated. 2. The olefin of the olefin-vinyl acetate copolymer saponification resin is ethylene, and the ethylene content is 1.
The multilayer laminate according to claim 1, wherein the multilayered product has an amount of 5 to 60% by weight and a saponification degree of vinyl acetate of 90 mol% or more.