JPH06238801A - Transparent packing material excellent in bending properties - Google Patents

Abstract

PURPOSE:To prevent the lowering of oxygen barrier properties even when bending due to rubbing is generated and to facilitate disposal, in a packing material obtained by successively laminating barrier films each constituted of a thermally adhesive resin layer, a polyethylene layer, and the membrane layer composed of an inorg. substance formed on a base material film, by laminating the membrane layer on the side of the polyethylene layer. CONSTITUTION:A packing material A is obtained by successively laminating barrier films 4 each constituted of a thermally adhesive resin layer 1, a polyethylene layer 2 and the membrane layer 3 composed of an inorg. substance formed on a base material film 41. The thermally adhesive resin layer 1 is a layer enabling heat sealing performed, for example, in order to form the packing material A into a bag at the time of the packing with content and the polyethylene layer 2 imparts bending resistance to the packing material A. The barrier film 4 wherein the membrane layer 3 is formed on the base material film 41 is excellent in oxygen barrier properties and steam barrier properties and the membrane layer 3 is provided on the side of the polyethylene layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material having a high oxygen barrier property, and more particularly to a transparent packaging material having excellent bending resistance.

[0002]

2. Description of the Related Art Conventionally, a laminated material including a layer of polyvinylidene chloride is used as a transparent packaging material having a high oxygen barrier property. As a packaging material for cheese or the like, a nylon film (Ny) is used because it is required to have flexibility in addition to the above oxygen barrier property, and polyvinylidene chloride is used as a material having oxygen barrier property, moisture resistance, and printability. The stretched nylon film (K-ONy) coated with was preferred. Also,
As an actual packaging material, a thermo-adhesive resin for imparting heat-sealing property is laminated on the above film. Specifically, the structure of K-ONy / LLDPE (linear low density polyethylene) has been used because of its simple structure and satisfying the required quality.

However, in recent years, since polyvinylidene chloride contains chlorine, chlorine gas is released during incineration and pollutes the atmosphere, so that a packaging material having no polyvinylidene chloride is desired.

To meet this requirement, it is conceivable to use another saponified film of ethylene-vinyl acetate copolymer having excellent transparency and oxygen barrier property, but this film is inferior in printability. It is practically difficult to adopt because other printing substrates must be laminated, the saponified ethylene-vinyl acetate copolymer film itself is expensive, and the temperature / humidity dependency of the barrier property is high. There was a field.

On the other hand, a barrier film in which a thin film of an inorganic substance such as silicon oxide is formed on a base material film such as polyester or nylon has begun to be used as a material which is transparent and has an excellent oxygen barrier property.

[0006]

Therefore, the conventional K-O
It was considered that a packaging material satisfying the requirements could be obtained by using the barrier film instead of Ny. However, as a result of the study by the present inventors, if the barrier film / heat-adhesive resin is simply configured, when the packaging material is bent, such as when it is wrapped in cheese when it is wrapped, It was revealed that the oxygen barrier property of the packaging material was reduced. The cause of this is not clear, but it is considered that pinholes or cracks are generated in the thin film of the inorganic substance due to bending such as fir tree.

Therefore, the present invention uses a barrier film having a thin film of an inorganic substance that is transparent and has an excellent oxygen barrier property, and does not cause pinholes or the like in the thin film of an inorganic substance even if there is bending such as firs. It is intended to provide a transparent packaging material which does not deteriorate in flexibility and is excellent in bending resistance.

[0008]

Means for Solving the Problems That is, the present invention relates to a packaging material in which a thermal adhesive resin, polyethylene, and a barrier film formed by forming a thin film layer of an inorganic substance on a base film are sequentially laminated. It is a transparent packaging material having excellent bending resistance, characterized in that the thin film layer faces the polyethylene side.

In a preferred embodiment of the present invention, the base film of the barrier film is a stretched nylon film. In addition, the thin film of the inorganic material is preferably a thin film of silicon oxide.

[0010]

In the packaging material of the present invention described above, the thin film layer of the inorganic substance exhibits an excellent oxygen barrier property, and imparts the oxygen barrier property to the packaging material. Then, polyethylene is laminated on the outer surface of the heat-adhesive resin that functions as a heat-sealing layer when packaging the contents, and a thin film layer of an inorganic substance is formed adjacent to the polyethylene, so that bending such as fir tree is a packaging material. Even if it is applied, the thin film of the inorganic substance is protected, pin holes are not generated, and the high oxygen barrier property is maintained.

[0011]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of the packaging material of the present invention,
FIG. 2 is a sectional view showing another embodiment of the packaging material of the present invention.

As shown in FIG. 1, the packaging material A of the present invention comprises a heat-adhesive resin 1, polyethylene 2, a base film 4
1. A packaging material in which a barrier film 4 formed by forming a thin film layer 3 of an inorganic substance on 1 is sequentially laminated, wherein the thin film layer 3 of an inorganic substance faces the polyethylene 2 side, and is resistant to bending. It is an excellent transparent packaging material.

The heat-adhesive resin 1 having the above-mentioned structure is a layer that enables heat sealing to be performed in order to make the packaging material A into a bag shape, for example, when packaging the contents. Polyolefin resins such as polypropylene, polypropylene, ethylene-vinyl acetate copolymer, and ionomer are generally used. In particular, it is preferable to use linear low density polyethylene because of its good low-temperature sealing property and little resin odor. The thickness of the thermoadhesive resin 1 is usually 20 to 100 μm.

Polyethylene 2 imparts flex resistance to the packaging material A. The method of forming polyethylene 2 is
The polyethylene melted by heating between the heat-adhesive resin 1 and the barrier film 4 is extruded in the form of a film, and the heat-adhesive resin 1 and the barrier film 4 are pressed together from the outer surface side to bond them to each other and to form a polyethylene layer. Can be formed by a so-called sand laminating method.
Further, the polyethylene 2 may be laminated by a method such as a dry lamination method using an adhesive, which is formed in advance as a film, for example, a uniaxially stretched polyethylene film.

The uniaxially stretched polyethylene film prevents the occurrence of pinholes at the corners of the package when the product is thin like the sliced cheese and has a small thickness with respect to the width, or when the product is packaged while maintaining the low temperature. It is effective because it is excellent in bending resistance (rubbing resistance) and openability after packaging.

The thickness of polyethylene 2 is preferably at least 15 μm in order to impart bending resistance to the packaging material. When the polyethylene 2 is formed by using the above-mentioned sand laminating method, the thickness is 30
It is preferable that the thickness is not more than μm. When the thickness is more than 30 μm, the heat may cause cracks in the thin film 3 of the inorganic substance, and the oxygen barrier property may deteriorate.

The barrier film 4 having the thin film layer 3 of an inorganic substance is known as a packaging material excellent in oxygen barrier property and water vapor barrier property. For example, Japanese Patent Publication Sho 53-
Japanese Patent No. 12953 discloses a barrier film in which a thin film of silicon oxide having a thickness of about 1000Å is formed on a polyester film by vacuum vapor deposition. Also in the present invention, a conventionally known barrier film 4 having a thin film layer 3 of an inorganic substance formed thereon can be used.

Base film 41 of barrier film 4
As the film (that is, a film forming a thin film of an inorganic substance), polyester, polypropylene, saponified ethylene-vinyl acetate copolymer, nylon, a co-extruded film containing these films, or a laminated product thereof, etc. A film can be used. In particular, in the present invention, it is preferable to use a stretched nylon film as the base material film 41 in order to impart flexibility and printability to the packaging material. The base film 41 has a thickness of usually 10 to 40 μm.

The inorganic substance thin film 3 formed on the base film 41 may be any one as long as it is excellent in transparency and oxygen barrier property, and may be known silicon oxide, magnesium oxide, aluminum oxide or the like. An inorganic substance is deposited to a thickness of 100 to 2000 by a method such as vacuum deposition, sputtering, ion plating, or plasma CVD.
The one formed in Å can be adopted. The above-mentioned inorganic substances are suitable because they are generally excellent in transparency and oxygen barrier property. Among them, silicon oxide is particularly preferable from the viewpoint of easy thinning, transparency, cost, and safety.

The thin film 3 of the inorganic material of the barrier film 4 described above and the polyethylene 2 described above are preferably provided adjacent to each other. When laminating the polyethylene 2 described above, an anchor coat layer for the purpose of improving adhesiveness may be formed on the thin film 3 of the inorganic substance, if necessary.

Further, the packaging material of the present invention is usually provided with a printing layer 6 such as characters and pictures. The printing layer 6 can be provided on either the outer surface side or the inner surface side (that is, on the inorganic substance thin film 3) of the barrier film 4. Of course, the print layer 6 may not be provided if unnecessary.

As shown in FIG. 2, the outer surface of the barrier film 4 may be further laminated with another outer layer film 5 (for example, a printing substrate) if necessary. In this case, the printing layer 6 may be formed on the outer layer film 5. The packaging material A of the present invention obtained as described above is a thermoadhesive resin 1
It is used by being formed into a bag shape by a normal method such as a four-sided seal or a three-sided seal with the inside as the inner surface, or a well-known method such as pillow packaging.

<Experiment 1> A packaging material having the following constitution was prepared, and in order to evaluate the bending resistance, the oxygen permeability after the bending operation by the gelbo flex tester described below was measured by the MOCON method. The results are shown in Table 1 (results are average values).

Sample 1: ONy (15μm) / SiO (400Å) / Print / S-PE
(15μm) / LLDPE (60μm) sample 2: ONy (15μm) / SiO (400Å) / printing / HDPE (20μm) / LLDP
E (30μm) Sample 3: ONy (15μm) / SiO (400Å) / Print / LLDPE (60μm) Sample 4: K-ONy (15μm) / Print / HDPE (20μm) / LLDPE (30μm) Sample 5: K-ONy (15 μm) / printing / LLDPE (50 μm) The abbreviations for the above configurations indicate the following, respectively. In addition, printing was performed on each SiO. SiO: Silicon oxide thin film (ONy or KO by vacuum deposition method)
Formed on Ny) S-PE: Polyethylene by sand laminating method HDPE: Uniaxially stretched high density polyethylene film (laminated by dry laminating method)

Bending operation Bending test standard: conforming to MIL-B131C Test operation: A-440 ° (twist) x 3.5 "+2.
5 "(straight line)

[0026]

[Table 1]

As is clear from the above results, those using the barrier film having a thin film of silicon oxide (Samples 1 to 3) are those using the film coated with polyvinylidene chloride (Samples 4 and 5). Compared with the above, the initial value is small in oxygen permeability even after repeated bending.
The oxygen permeability of the present invention (Samples 1 and 2) was not so large even after repeated bending, as compared with the polyethylene (Sample 3) having no polyethylene between the barrier film and the heat-adhesive resin. The decrease in oxygen barrier property is small.

[0028]

As described above, the packaging material of the present invention having the above-mentioned structure has a small decrease in oxygen barrier property even when there is bending such as firs, and is transparent with excellent oxygen barrier property. It is a packaging material. Since the packaging material of the present invention does not use a material that generates harmful chlorine gas, it does not pollute the environment even when incinerated, and is easy to dispose. Moreover, its configuration is simple and economical.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a packaging material of the present invention.

FIG. 2 is a sectional view showing another embodiment of the packaging material of the present invention.

[Explanation of symbols]

 1 ... Thermal adhesive resin 2 ... Polyethylene 3 ... Inorganic substance thin film 4 ... Barrier film 41 ... Base film 5 ... Outer layer film 6 ... Printing layer A ... Packaging material

Claims (3)

[Claims] 1. A packaging material in which a heat-adhesive resin, polyethylene, and a barrier film formed by forming a thin film layer of an inorganic substance on a base film are sequentially laminated, and the thin film layer of the inorganic substance faces the polyethylene side. A transparent packaging material with excellent bending resistance, which is characterized by 2. The transparent packaging material according to claim 1 or 2, wherein the base film is a stretched nylon film. 3. The transparent packaging material according to claim 1, wherein the thin film of the inorganic substance is a thin film of silicon oxide.