JP3012756B2 - Multilayer laminate and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer laminate having a gas barrier property against permeation of oxygen gas and the like, and more particularly 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 features such as long-term storage and easy cooking, and is expected to spread more and more in the future. The field of packaging materials for these foods (films, sheets, pouches, tubes, bottles, etc.)
There is a demand for a material having a higher gas barrier property to enable further long-term storage. Conventionally, as a method of obtaining a material having excellent gas barrier properties using a plastic material as a base material, 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. Have been proposed (JP-A-49-41469, JP-A-49-349).
No. 84, No. 59-62143, No. 60-61252
Nos. 60-23037 and 60-61253). In addition, since these thin films are easily cracked by bending, they serve as a protective film on the outer surface, and when these thin films come to the inner surface of the packaging material, they do not have heat bonding property (heat sealing property). In addition, a polyolefin film such as polyethylene and 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, etc.) is intended to obtain higher gas barrier properties. If the thickness is increased, the thin film becomes brittle, cracks and pinholes are easily generated, and conversely, the gas barrier property is lost. Under the circumstances described above, an object of the present invention is to provide a multilayer laminate that overcomes the above-mentioned limitations and has a high degree of gas barrier properties.

[0004]

The present inventors have made intensive studies to solve these problems. As a result, it is not necessary to increase the thickness of a thin film of metal or the like. The inventors have found that the problem is solved by forming a layer by a solution coating method and laminating the same, and have completed the present invention. That is, the gist of the present invention is that a polyvinyl alcohol-based resin layer having a thickness of at least 3 μm formed by a solution coating method is laminated on a metal or metal oxide thin film formed on the surface of a plastic substrate. In a multilayer laminate. The gist of the present invention is a plus
Form a metal or metal oxide thin film on the surface of a tic substrate
And a polyvinyl alcohol having a thickness of at least 3 μm
Coal-based resin layer is formed by solution coating method and laminated
To produce a multilayer laminate. Hereinafter, the contents of the present invention will be described in detail.

The plastic substrate according to the present invention includes:
Thermoplastic resins can be used as general molding materials, especially as molding materials 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 an unsaturated ethylenic carboxylic acid, etc., polyvinyl chloride,
Various resins such as polystyrene, ABS resin, polyacetal, polycarbonate, and polyester are exemplified.

[0006] The metal or the like laminated on the surface of the plastic substrate includes aluminum, titanium, chromium, and the like.
Simple metals such as nickel, aluminum oxide, silicon oxide, titanium oxide, ferrite antimony oxide, zinc oxide, indium oxide, silver oxide, chromium oxide, cobalt oxide, molybdenum oxide, zirconium oxide, tungsten oxide, copper oxide, nickel oxide, oxide Metal oxides such as vanadium, magnesium oxide, manganese oxide, lanthanum oxide, lead oxide, cadmium oxide, bismuth oxide, and the like can be given. These may be used alone, respectively.
Two or more kinds may be used in combination.

[0007] These metals and the like are formed in a thin film on the surface of the plastic substrate, but the forming method is not particularly limited, but a vacuum, a heat evaporation method or a sputtering method is most common. is there. Although the thickness of the thin film is not particularly limited, it is usually 100 to 30 for the purpose of the present invention.
It is chosen in the range of 00Å. If the thickness of the thin film is less than 100 °, a high degree of gas barrier property cannot be obtained, and if it exceeds 3000 °, the thin layer lacks flexibility and is easily cracked.

The polyvinyl alcohol resin used in the present invention is a partially or completely saponified polyvinyl acetate resin (hereinafter abbreviated as PVA resin) or a partially or completely saponified copolymer of vinyl acetate and a modified comonomer. Modified polyvinyl alcohol resin (hereinafter referred to as modified P)
Abbreviated as VA resin. ). First, the PVA resin used in the present invention is obtained by partial or complete saponification of a polyvinyl acetate resin, and the polyvinyl acetate resin is made of vinyl acetate as a monomer, and is formed by bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization. Among these various polymerization methods, a solution polymerization method is generally employed. In this solution polymerization method, a vinyl acetate monomer is diluted with a solvent such as methanol, ethanol, or methyl acetate, a catalyst is added, and polymerization is performed.
It is produced by removing the heat of polymerization with the heat of evaporation of the solvent. The produced polyvinyl acetate resin is partially or completely saponified using an alkali catalyst or an acid catalyst, and provided as a PVA resin to the multilayer laminate of the present invention.

[0009] The modified PVA resin is a modified PVA resin obtained by partially or completely saponifying a copolymer of vinyl acetate and a modified comonomer. Here, as the modified comonomer to be used in the production of the modified PVA resin, an olefin having 4 to 18 carbon atoms (for example, 1-butene, isobutene, pentene, hexene, heptene, octene, nonene, decene, etc.), vinyl carboxylate (for example, , Vinyl versatate, vinyl stearate, etc.), alkyl vinyl ethers (eg, lauryl vinyl ether, methyl vinyl ether, etc.), (meth) acrylates (eg, methyl methacrylate), acrylamides (eg, acrylamide, methacrylamide, N, N-) Dimethylacrylamide, etc.), unsaturated (di) carboxylic acids or their anhydrides or esters (for example, acrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, etc.), sulfonic acid monomers (for example, vinyl sulfone) Phosphate, such as acrylic acid), a cationic monomer (e.g., dimethyl ethyl methacrylate, vinyl imidazole, vinyl pyridine, vinyl succinate imide) Others (vinylene carbonate, allyl alcohol, allyl acetate), and the like.

[0010] Among the polyvinyl alcohol resins in the present invention, the above PVA resin is composed of 30 to 100 mol% of vinyl alcohol units and 70 to 0 mol% of vinyl acetate units, and has a polymerization degree of 100 to 5, 000 is suitable for achieving a high degree of gas barrier properties imparted by the present invention. Further, considering the coating properties and mechanical strength, the degree of polymerization is 200 to 1,800 and the degree of saponification is 50.
Those having mol% or more are preferably used. Saponification degree 30
If the amount is less than mol%, the gas barrier property is not sufficiently developed, which is not preferable. In particular, the partially saponified PVA resin can obtain a strong interlayer adhesive strength without using an adhesive in the lamination with the following metal or metal oxide thin film on the plastic substrate during coating. Has features. The modified PVA resin has a modified comonomer content of 0.1.
Those containing 10 to 10 mol% and a saponification degree of 40 to 100 mol% are preferable from the viewpoint of imparting a high degree of gas barrier properties.
Further, the degree of polymerization is 100 to 5,000, especially 300.
The case where it is 2,000 is more preferably used in terms of coatability and mechanical strength.

In the present invention, PVA resin or modified PV
A resin is a PVA resin or a modified PVA resin in a solution state.
Directly or via an anchor coat agent on a thin film such as metal
Lamination is performed by a so-called solution coating method.
In laminates, layer destruction occurs due to flex fatigue.
Pinholes may be generated and gas barrier properties may decrease.
Solution coating method.
Layer is prevented from breaking, and sufficient bending fatigue resistance is obtained.
You. The reason is not always clear, but the solution
It is presumed that it is because it permeates inside. In the case where the PVA resin or the modified PVA resin has a thin film of a metal or the like on both surfaces, the effect is exhibited by laminating at least one surface.

When applying the PVA resin or the modified PVA resin solution, a solvent such as water, alcohols, or glycols is used. The concentration of the PVA resin or the modified PVA resin is preferably 1 to 50% by weight, and 5% by weight. -30% by weight is more preferred. If the polymer concentration is less than 1% by weight,
With a single coating, a desired polyvinyl alcohol-based resin film cannot be obtained. If it exceeds 50% by weight,
Problems arise in the solution preparation operation and the application operation, which are not preferable. As a method of applying the PVA resin or the modified PVA resin solution, a usual method of coating a paper or a film can be used as it is.

The multilayer laminate thus obtained can be used in various fields as a packaging material. For this purpose, it is necessary to further perform various forms such as vacuum forming and pressure forming, or to provide a sheet or film. Can be.

The thickness of the PVA resin or the modified PVA resin in the multilayer laminate according to the present invention must be at least 3 μm. If the thickness is less than 3 μm, desired gas barrier properties cannot be obtained. The gas barrier property increases as the thickness increases, but it is not necessary to make the thickness 50 μm or more in consideration of gas barrier properties and economy. Therefore, 3 to 40 μm is usually selected in consideration of both. Further, the present invention will be described in detail with reference to examples.

[0015]

EXAMPLES First, a method of measuring gas barrier properties (oxygen permeability) in Examples will be described. (Oxygen permeation test) The amount of oxygen permeation was measured according to ASTM D3985-
In accordance with No. 81, the PVA layer of the multilayer laminated material was disposed on the oxygen-rich side, and the temperature was 23 ° C. and the humidity was 65% using an oxygen permeation tester OXTRN-10 / 50A (manufactured by Modern Control)
The measurement was performed at RH and a temperature of 23 ° C. and a humidity of 90% RH.

(Examples 1 to 10) [Production of vapor-deposited film] Commercially available polyester film [trade name: Lumirror P11, manufactured by Toray Industries, Ltd., thickness 12 μm]
m], silicon monoxide or aluminum was vacuum-deposited on one side of each of the plurality of sheets to a thickness of 700 °. Further, silicon monoxide or aluminum was vacuum-deposited on one side of each of a plurality of unstretched polypropylene films (manufactured by Showa Denko KK, trade name: Show Allomer Film A, thickness 50 μm) to a thickness of 700 °. Vacuum deposition is performed using a vacuum deposition machine [EBH6 type, manufactured by Nippon Vacuum Engineering Co., Ltd.] using a tungsten board as a heating resistor, using a deposition source having a purity of 99.99% or more and a degree of vacuum of 2 × 10 ^{−. 4} Tor
r. Then, the thickness of the deposited film was calculated by a gravimetric method.

[Preparation of PVA aqueous solution] As PVA, Gohsenol GL03 [trade name, manufactured by Nippon Synthetic Chemical Co., Ltd.
Polymerization degree 300, saponification degree 86.5-89 mol%], Poval PVA105 [manufactured by Kuraray Co., Ltd., trade name, polymerization degree 50]
0, saponification degree 98.5 ± 0.5 mol%], Poval PVA11
7 (manufactured by Kuraray Co., Ltd., trade name, degree of polymerization 1,700, degree of saponification 98.5 ± 0.5 mol%) and Poval PVA224
[Kuraray Co., Ltd., trade name, polymerization degree 2,400, saponification degree 8
8.0 ± 1.5 mol%], and the polymer concentration in water was 1
The mixture was heated and dissolved at a temperature of 60 ° C. with stirring so as to be 5% by weight to prepare a PVA aqueous solution.

[Preparation of Multilayer Laminate] The above-mentioned PVA aqueous solution was applied to the vapor-deposited surface of the vapor-deposited film to a final thickness of about 20 μm.
It was coated to a thickness of μm. The coating film obtained by applying the PVA aqueous solution was air-dried all day and night, and then vacuum-dried at a temperature of 30 ° C. for 7 days to produce a multilayer laminate of the present invention.

[Measurement] The oxygen permeation amount was measured for each of the multilayer laminates obtained in Examples and Comparative Examples. Table 1 shows the results of each measurement.

Comparative Example 1 The deposited film of Example 1 was used for measurement without applying a PVA solution. Table 1 shows the measurement results. (Comparative Example 2) Example 8 without applying a PVA solution
Was used for measurement. Table 1 shows the measurement results. (Comparative Example 3) Example 2 without applying a PVA solution
Was used for measurement. Table 1 shows the measurement results. (Comparative Example 4) Example 7 without applying a PVA solution
Was used for measurement. Table 1 shows the measurement results.

(Comparative Example 5)
Adcoat 900 (trade name, manufactured by Toyo Morton Co., Ltd.) was applied as an adhesive at a rate of 3 / m ^2, and a polypropylene film (thickness: 60 μm) and Aroma A film (trade name, manufactured by Showa Denko KK) were laminated. After lamination, aging treatment was performed at 40 ° C. for 3 days. The oxygen permeation amount of the obtained laminate was measured. Table 1 shows the results.

(Examples 11 to 13) Using the vapor-deposited film of Example 1 and the PVA solution of Example 9,
Was coated at different final thicknesses and subjected to measurement of oxygen permeation. Table 1 shows the measurement results. (Example 14) Using the multilayer laminate of Example 3, a bending fatigue test described below was performed. In the bending fatigue resistance test, the bending fatigue causes the deposition layer or the coating layer to break, and the pinholes increase the amount of oxygen permeation. By examining this relationship, the bending resistance on the oxygen permeability of the multilayer laminate is examined. The purpose is to determine the fatigue. Actually, the cylinder diameter is 90 mm, stroke 17
8mm, twist angle 440 degrees, twist stroke 89m
m, a linear stroke of 63.5 mm and a reciprocating speed of 40 times / min. Using a Gelboflex tester manufactured by Tester Sangyo Co., Ltd., bending is performed every 10 times up to 10 times, and 50 times at 100 times or more. Each time a flex fatigue test was performed. The number of flexions of the gelbo flex tester was changed, and the oxygen permeation amount at each stage under the conditions of 23 ° C. and 65% RH was measured. When evaluated in this way, the number of bending times was
~ 250 times, MOCON OXTRAN-10 /
It showed an oxygen permeation amount of 2,000 cc or more, which is the detection limit of 50 A, and it was found that the deposited layer or the coating layer was destroyed. (Comparative Example 6) Using the vapor-deposited film of Comparative Example 1, the same procedure as in Example 14 was carried out, and oxygen permeation of 2,000 cc or more, which is the detection limit of MOCON OXTRAN-10 / 50A, when the number of times of bending is 10 or less, was used. The amount indicated indicates that the deposited layer or the coating layer was destroyed.

The contents of each symbol in Table 1 are as follows. 1) Type of film (plastic substrate) PET: Polyester film PP: Unstretched polypropylene film 2) Type of metal and metal oxide SiO: Silicon monoxide Al: Aluminum 3) Type of PVA A: Gohsenol GL03 B: Poval PVA105 C: Poval PVA117 D: Poval PVA224

[0024]

[Table 1]

[0025]

As described above, the multilayer laminate according to the present invention has a high degree of gas barrier properties and flex fatigue resistance, and is therefore suitably used in the fields of food packaging, pharmaceutical packaging, cosmetic packaging and the like.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Harada 251-1 Ibocho, Ibocho, Tatsuno City, Hyogo Prefecture Inside Showa Polymer Co., Ltd. 251-1 Showa Polymer Co., Ltd. Osaka Research Laboratories (56) References JP-A-1-160554 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00

Claims (3)

(57) [Claims] 1. A solution coating method on a metal or metal oxide thin film formed on the surface of a plastic substrate .
A multilayer laminate in which a formed polyvinyl alcohol-based resin layer having a thickness of at least 3 μm is laminated. 2. A polyvinyl alcohol resin comprising 30 to 100 mol% of a vinyl alcohol unit and a vinyl acetate unit of 7
0 to 0 mol% and a degree of polymerization of 100 to 5,000
The multilayer laminate according to claim 1, wherein 3. A metal or metal acid on a surface of a plastic substrate.
A thin film of the oxide, on which a thickness of at least 3 μm
Solution coating method of polyvinyl alcohol resin layer
The method for producing a multilayer laminate formed and laminated according to the above.