JPH058318A - Manufacture of laminated wrapping material - Google Patents

Abstract

PURPOSE:To provide a manufacture of laminated wrapping material having no risks of generating cracks on a thin film and spoiling a gas barrier property at the time of laminating a sheet onto another sheet, wherein the former is formed of a thin film of an inorganic or metallic compound having a good gas barrier property. CONSTITUTION:On one surface of a polyethyleneterephthalate film, the evaporated layer of silicon dioxide is formed by a method of vacuum evaporation and, on the evaporated layer, a heat buffering layer consisting of a polyethylene terephthalate film is laminated without heating the wrapping material, following this, polyethylene is extruded on the heat buffering layer to coat thereover, to thereby form a sealant layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminated packaging material, and more particularly to a method for producing a packaging material containing a transparent thin film layer of an inorganic or metal compound.

[0002]

2. Description of the Related Art Conventionally, as packaging materials for foods and pharmaceuticals,
Those mainly composed of a plastic film are widely used, and the form thereof is generally a bag (pouch) container.

The packaging material is required to have various functions and performances depending on the contents, but the contents are prevented from oxidative deterioration, and the active ingredients of the contents (for example, aroma components and medicinal components of pharmaceuticals).
A gas barrier property is often required in order to prevent permeation / dissipation, etc., or to prevent drying.

In order to impart this gas barrier property, a layer made of a material excellent in gas barrier property is usually laminated on a plastic film which constitutes a packaging material, and polyvinyl alcohol, polyvinylidene chloride, metal foil, metal,
A thin film layer of an inorganic or metal compound is used. In particular, a thin film layer of silicon oxide is excellent in transparency, exhibits an extremely high gas barrier property, and can be produced at a relatively low cost, and therefore its practical application has been studied extensively (Japanese Patent Publication No. S51-51).
-48511, Japanese Patent Publication No. 53-12953,
JP-B-52-3418, JP-B-52-24608
No.

[0005]

However, the Japanese Patent Publication No. 51-48511 and the Japanese Utility Model Publication No. 52-24608 described above are required.
Since the transparent thin film layer of an inorganic or metal compound as disclosed in Japanese Patent Publication No. JP-A-2003-242242 is an extremely thin glass-like layer, there is a problem that fine cracks are likely to occur. This is remarkable when heat is applied to the transparent thin film layer, and it is considered that the reason is that the base sheet having the transparent thin film layer expands and contracts due to heat and the transparent thin film layer cannot follow this expansion and contraction. When this crack occurs, the gas barrier property is significantly reduced.

By the way, one of the functions required as a packaging material is that it has thermal adhesiveness so that it can be easily processed when it is formed into a bag-shaped package.

In order to impart this thermal adhesiveness, it is common to laminate a thermal adhesive resin (hereinafter referred to as a sealant), and as a laminating method, a film (sealant) made of a thermal adhesive resin is used. There is a method of laminating and a method of so-called extrusion coating in which a thermo-adhesive resin is extruded in a film shape and, at the same time, laminated by the adhesiveness to form a sealant. Generally, the sealant is the thickest layer in the packaging material, and is also the main layer of the packaging material that imparts strength and flexibility to the packaging material.

In order to provide this layer thickly, there is a method in which a base sheet having a transparent thin film layer formed thereon and a thermoadhesive resin film (sealant) prepared in advance are bonded to each other with an extruded thermoadhesive resin interposed therebetween. Easy and
This is the preferred method. The method of sticking the sealant film via the adhesive is not preferable when the obtained sheet is required to have transparency because the transparency is deteriorated by the influence of the adhesive.

Further, the use of an adhesive increases the rigidity of the sheet and reduces the flexibility thereof, which is also not preferable when the obtained sheet is required to have transparency. Most of commercially available packages using metal foil currently have a thermoadhesive resin extrusion-coated on the metal foil, and a thermoadhesive resin film (sealant) is laminated on the metal foil.

However, when the heat-adhesive resin layer is directly extrusion-coated on the above-mentioned transparent thin film layer, the mechanical tension during the coating operation and the heat of the molten heat-adhesive resin elongate the base sheet to form fine particles in the transparent thin film layer. In addition to the occurrence of such cracks, the extrusion-coated heat-adhesive resin layer and the heated substrate sheet shrink with cooling, which promotes the generation of cracks.

Therefore, the present invention provides a packaging material having an excellent gas barrier property without cracking in a transparent thin film layer of an inorganic or metal compound even when a heat-adhesive resin layer is laminated by extrusion coating. , Its manufacturing method is provided.

[0012]

Means for Solving the Problems That is, according to the present invention, when a heat-adhesive resin layer is extrusion-coated and laminated on the transparent thin film layer of a base sheet on which a transparent thin film layer of an inorganic or metal compound is formed, On a thin film layer, a plastic film is laminated without heating to form a heat buffer layer, and then a heat-adhesive resin layer is extrusion-coated on the heat buffer layer. is there.

[0013]

According to the above-mentioned method for producing a packaging material of the present invention, a base sheet having a transparent thin film layer on which a heat buffer layer blocks heat of an extrusion coating layer of a thermoadhesive resin to be laminated thereon is provided. It prevents expansion and contraction, and does not cause cracks in the transparent thin film layer. Therefore, the transparent thin film layer makes the packaging material exhibit excellent gas barrier properties, and prevents oxidative deterioration of the packaging contents and permeation / dissipation of the active ingredient.

[0014]

EXAMPLE A substrate sheet used in the present invention is a plastic film capable of forming a transparent thin film layer of an inorganic or metal compound, and the adhesion, transparency, easiness of processing, price, etc. of the transparent thin film layer are taken into consideration. Then, a polyethylene terephthalate film is most preferable, and as other films, stretched polypropylene, unstretched polypropylene, polyethylene, stretched nylon and the like can be used.

The transparent thin film layer of an inorganic or metal compound is an oxide, a nitride, a sulfide of an inorganic material or a metal such as silicon, magnesium, indium, aluminum or titanium.
Alternatively, compounds such as fluorides, more specifically Si _X O _Y
(x = 1,2; y = 0,1,2,3), Al ₂ O ₃ , Si ₃ N ₄ , ZnS, MgF ₂ , MgO, etc., vacuum deposition method, ion plating method, sputtering method, plasma Vapor deposition method or CVD (Chemical V
apor Deposition) method and the like.

The thickness of the transparent thin film layer varies depending on the type of the inorganic or metal compound, but in the case of silicon oxide, at least 800 Å is necessary, preferably 900 Å or more, in order to obtain the desired gas barrier property. Set up. In addition, in order to ensure flexibility as a packaging material, 2000 Å
It is preferable to provide the following thickness. Also, in the case of aluminum oxide, at least 400Å, preferably 45
Provide a thickness of 0 Å or more and 600 Å or less.

In the present invention, a thermal buffer layer is laminated on the transparent thin film layer of the inorganic or metal compound.

The heat buffer layer is a layer for preventing the expansion and contraction of the base sheet due to the heat of the extrusion coating layer of the heat adhesive resin, which will be described later, and is made of a material having a sufficient heat buffer property and a plastic film having a thickness. It

Specifically, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, a polyamide film or the like is used, and the thickness is required to be at least 10 μm, preferably 12 μm or more.

The thermal buffer layer needs to be laminated at a temperature at which the base sheet does not substantially expand or contract. That is, it is not appropriate to form the thermal buffer layer by a method that requires heating, such as an extrusion coating method or a thermal laminating method, and a dry laminating method using a solvent-based adhesive or a non-solvent method using a solventless adhesive. A solvent laminating method or the like is suitable.

An extrusion coating layer of a heat adhesive resin is formed on the heat buffer layer. This layer is generally an adhesive layer for laminating the above-mentioned base sheet / heat buffer layer laminate and a heat-adhesive resin film (sealant), but in some cases, base sheet / heat buffer layer lamination It can also be a means of forming a sealant directly on the body.

Polyethylene is most commonly used as the heat-adhesive resin, but in some cases, an ionomer resin may be used for the purpose of imparting a hot-sealing property, and an ethylene-vinyl acetate copolymer may be used for the purpose of imparting a low-temperature heat-sealing property. It is also possible to use a polymer resin or the like.

This extrusion coating heats and melts the heat-adhesive resin to form a predetermined thickness from the T-die between the adherend sheets (in the present invention, the base sheet / heat buffer layer laminate and the sealant film). It is a method of extruding in a film shape, pressure bonding, cooling and laminating. When the extrusion coating is used as a means for directly forming the above-mentioned sealant, it means a method of extruding onto a sheet to be laminated (in the present invention, a laminated body of a base sheet / thermal buffer layer), pressure bonding, cooling and laminating. .

The temperature condition of the molten resin in the extrusion coating has a great influence on the adhesion between the layers. If the resin temperature is too low, the laminated extrusion coating layer does not exhibit sufficient adhesive strength. Preferable temperature conditions are 300 ° C. or higher when the resin is polyethylene and 280 ° C. or higher when it is an ionomer resin.

The thickness of the extruded coating layer is preferably set to 50 μm as an upper limit from the viewpoint of processing efficiency. When it is desired to form a layer having a thickness larger than this, as described above, other films ( Sealant film)
It is preferable that the extrusion coating layer is used as an adhesive layer and laminated, or two or more extrusion coating layers are formed.

The packaging material according to the present invention includes at least the above-mentioned base sheet, a transparent thin film layer of an inorganic or metal compound, a heat buffer layer, and a heat-adhesive resin extrusion coating layer,
Other layers can be laminated if necessary. For example,
An ionomer resin may be laminated for the purpose of imparting hot sealability, and an ethylene-vinyl acetate copolymer resin or the like may be laminated for the purpose of imparting low temperature heat sealability. Any of the layers used in the present invention can be transparent to produce a transparent packaging material. It is obvious that the print layer can be formed at an appropriate position.

The packaging material according to the present invention obtained as described above is used by being formed into an appropriate shape, for example, a bag shape. The handling of the packaging material of the present invention is the same as the conventional packaging material, and there is no problem.

Next, the results of the experiment according to the present invention will be shown.

Experiment 1 A silicon oxide thin film layer having a thickness of 1000 Å was formed by a vacuum deposition method on a base sheet made of a biaxially stretched polyethylene terephthalate film (trade name P-11, manufactured by Toray Industries, Inc., thickness 12 μm). did. On the silicon oxide thin film layer, the following thermo-adhesive resin was extruded from a T-die and directly laminated (processing speed 40 m / min, line tension;
6, No. 12 is 10 kg, others are 5 kg).

The oxygen permeability of the obtained laminate was measured.
The results are shown in Table 1. Further, the peel strength between the silicon oxide thin film layer and the thermoadhesive resin layer was measured. The results are shown in Table 2.

Thermal adhesive resin No. used 1-3: Ethylene-methacrylic acid copolymer resin (methacrylic acid content 11 wt%) No. 4: Ionomer resin (metal component: zinc) N
o. 5-7: Ethylene-methacrylic acid copolymer resin (methacrylic acid content 6 wt%) No. 8: Low density polyethylene No. 9 to 13: Low-density polyethylene ★ All have a thickness of 45 µm ★ No. 8 and No. 9 to 13 have different resin grades

[0032]

[Table 1]

[0033]

[Table 2]

From the above results, it has been found that when the processing temperature of the extrusion coating exceeds 250 ° C., the gas barrier property decreases, that is, the inorganic or metal compound thin film layer is cracked. Particularly, those having a high line tension (No. 6 and No. 12) had a remarkable decrease in gas barrier property. Further, at a processing temperature of 250 ° C. or lower where cracks do not occur in the inorganic or metal compound thin film layer, sufficient peeling strength cannot be obtained and a practical packaging material cannot be obtained.

Then, a packaging material was obtained by the method of the present invention, and the same evaluation was performed.

Experiment 2 A silicon oxide thin film layer having a thickness of 1000 Å was formed by a vacuum deposition method on a base sheet made of a biaxially stretched polyethylene terephthalate film (trade name P-11, manufactured by Toray Industries, Inc., thickness: 12 μm). did. A biaxially stretched polyethylene terephthalate film (trade name E-
5200, manufactured by Toyobo Co., Ltd., thickness 12 μm) was laminated by a dry laminating method, and then the following thermo-adhesive resin was extruded from the T die on the thermal buffer layer and laminated (processing speed). 40 m / min, line tension; 5 kg).

The oxygen permeability of the obtained laminate was measured.
The results are shown in Table 3. Further, the peel strength between the heat buffer layer / heat adhesive resin layer of the laminate was measured. The results are shown in Table 4.

Thermal adhesive resin No. used 14: Low density polyethylene No. 15: Ethylene-ethyl acrylate copolymer resin (ethyl acrylate content 6 wt%) * Both thickness 45 μm

[0039]

[Table 3]

[0040]

[Table 4]

From the above results, if a thermal buffer layer is provided on the inorganic or metal compound thin film layer as in the present invention, and a thermoadhesive resin is extrusion-coated thereon, the processing temperature is 2
It can be seen that even when the temperature exceeds 50 ° C., the gas barrier property does not decrease, that is, the inorganic or metal compound thin film layer is not cracked. And sufficient peeling strength was obtained and a practical packaging material was obtained.

The following is an example of manufacturing a practical laminated packaging material according to the present invention. First, a 1500Å-thick silicon oxide thin film is formed on one surface of a first polyethylene terephthalate (PET) film (thickness: 13 μm) by a vacuum deposition method. Next, the second PET film (13 μm)
Urethane adhesive is applied to one side of the above, and the adhesive side is overlaid on the silicon oxide thin film layer of the first PET film, and the first P
The ET film and the second PET film are attached together. Next, between the surface of the second PET film where the urethane adhesive layer is not formed and the printing layer surface of the third PET film (thickness 13 μm) having a printing layer on one surface, polyethylene (S-PE ) Is extruded in the form of a film having a thickness of 12 μm, and both are laminated. Finally, polyethylene is extrusion-coated to a thickness of 50 μm on the surface of the first PET film on which the silicon oxide thin film layer is not formed. Thus, a laminated packaging material having the following constitution is obtained. Third PET film / printing layer / S-PE / second PET
Film / Urethane adhesive / SiO-First PET film / PE

[0043]

As described above, according to the present invention, even if a base sheet having an inorganic or metal compound thin film layer is extrusion-coated with a heat-adhesive resin, cracks are generated in the inorganic or metal compound thin film layer. Since it has no gas and has sufficient gas barrier properties, the contents can be protected. Since the obtained packaging material can be transparent, it is possible to see through the contents, and the packaging material can be widely used as a packaging material.

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Claims (2)

[Claims] 1. A plastic film is heated on the transparent thin film layer for extrusion-coating and laminating a heat-adhesive resin layer on the transparent thin film layer of a base sheet on which a transparent thin film layer of an inorganic or metal compound is formed. Characterized by laminating without forming a thermal buffer layer, and then extrusion coating a thermoadhesive resin layer on the thermal buffer layer,
Manufacturing method of laminated packaging material. 2. The method for producing a laminated packaging material according to claim 1, wherein the transparent thin film layer of an inorganic or metal compound is a vacuum deposited layer of silicon oxide.