JPH06190964A - Production of laminated film - Google Patents

Abstract

PURPOSE:To enhance the adhesiveness of a silicon oxide membrane and a resin layer without providing an adhesive layer by laminating a polyolefin resin on the silicon oxide membrane of a plastic film at specific temp. by extrusion lamination and ageing the obtained laminate. CONSTITUTION:A polyolefin resin is laminated to the silicon oxide membrane provided to at least the single surface of a plastic film at 300 deg.C or higher by extrusion lamination and the obtained laminate is aged. The plastic film having the silicon oxide membrane is obtained by forming the silicon oxide membrane on a plastic film having a polar group on the surface thereof by vacuum vapor deposition, sputtering or ion plating. The ageing temp. is pref. 50-80 deg.C. By this method, the bonding strength of the silicon oxide membrane and the polyolefin resin layer can be enhanced without providing an adhesive layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film having a high gas barrier property, capable of retorting, and having excellent adhesiveness, microwave oven suitability and transparency, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a plastic film such as polyamide, polypropylene, or cellophane coated with polyvinylidene chloride (hereinafter abbreviated as PVDC) has been widely used as a packaging material requiring a gas barrier property. In addition, as a material having a higher gas barrier property, aluminum (hereinafter referred to as Al
Has also been used as a gas barrier material in the form of foil or vapor deposited layer. These are used differently depending on the application, but the plastic film coated with PVDC has a relatively low gas barrier property, and changes color to yellow with the passage of time, impairing the aesthetics of the contents and giving a yellowish back printing. I can see it. Although Al has an excellent gas barrier property, it is opaque and thus lacks visibility of the contents. Further, since it is a metal, the contents cannot be heated in a microwave oven.

A plastic film obtained by vapor-depositing silicon oxide on these materials is disclosed in Japanese Patent Laid-Open No. 49-41469. This material has excellent gas barrier properties, is less likely to deteriorate due to humidity, is transparent, and is suitable for microwave ovens. However, since the silicon oxide thin film formed by vapor deposition has high rigidity, it has a defect that cracks easily occur due to bending, heat shrinkage of the base plastic film, and the like, and the heat sealability is poor.

Therefore, when it is used as a packaging material,
Attempts have been made to laminate a heat seal layer such as a polyolefin resin on a thin film of silicon oxide. However, there is generally a problem that the adhesion between the silicon oxide thin film and the polyolefin is low. As an improvement method, for example, JP-A-62-103139 and JP-A-3-76640 disclose a method of improving adhesiveness by using a urethane adhesive and laminating it by a dry laminating method. However, it is necessary to dissolve the adhesive in a large amount of organic solvent in order to provide the adhesive layer, which is not preferable in terms of environmental hygiene, and in order to obtain a laminated film, manufacture of a film of polyolefin resin and coating of the adhesive are required. There are problems that the process of drying and drying is required, the cost is high, and the low molecular weight compound may be transferred to food.

Further, JP-A-1-253434 discloses a method of laminating a polyolefin resin or a modified polyolefin resin by an extrusion laminating method. This method is more cost effective than the dry laminating method, and can be laminated without providing an adhesive layer. However, when laminating without using an adhesive, there is a problem that the adhesive strength between the polyolefin resin layer and the silicon oxide thin film becomes weak.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a polyolefin resin is extruded on a silicon oxide thin film surface of a plastic film having a silicon oxide thin film by an extrusion laminating method without providing an adhesive layer made of an adhesive, an adhesive resin or the like. An object of the present invention is to provide a manufacturing method capable of obtaining a laminated film having high adhesion between a silicon oxide thin film and a resin layer when laminated.

[0007]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, it was found that by laminating a polyolefin resin by an extrusion laminating method and then performing aging, an adhesive layer made of an adhesive, an adhesive resin or the like was not provided. Also found that the silicon oxide thin film of the plastic film having the silicon oxide thin film and the polyolefin resin layer can be firmly bonded to each other, and thus the present invention has been completed.

The plastic film having a silicon oxide thin film according to the present invention is a plastic film having a polar group on the surface, on which a silicon oxide thin film is formed by vacuum deposition, sputtering, ion plating, etc., and has a gas barrier property. If it is within the range, the manufacturing method,
The thickness of the base film and thin film are not limited,
Considering crack resistance and transparency, the thickness of the thin film is 200-
The range of 2000Å is preferable.

As the polyolefin in the present invention,
High density, medium density, low density polyethylene, polypropylene, poly 4-methylpentene-1, and the like, and mixtures thereof may be mentioned. These are stabilizers if necessary,
Lubricants, antistatic agents, fillers and other additives may be added. These polyolefins can be laminated on the silicon oxide thin film by the extrusion laminating method.

In order to improve the adhesive strength by aging in the present invention, it is necessary to have a certain degree of adhesive strength before aging, and for that purpose, 300 ° C.
It is necessary to extrusion laminate at the above molding temperature. Thirty
At a temperature lower than 0 ° C., no change in the adhesive strength is observed even after aging. It is considered that the reason why the adhesive strength is improved by aging is that polar groups generated on the surface of the polyolefin resin due to thermal oxidation during laminate molding are oriented toward the silicon oxide thin film side due to aging. It is considered that the adhesive strength does not change so much because there are few groups and there are few polar groups oriented to the thin film side even after aging treatment. But,
If it exceeds 320 ° C., smoke generation during molding increases and problems such as deterioration of heat seal strength due to deterioration of the polyolefin resin layer occur, so 300 to 320 ° C. is preferable.

Further, by performing an inter-air gap treatment such as blowing ozone between the air gaps,
The molding temperature may be lower than 300 ° C as long as a polar group sufficient for adhesion is formed on the surface of the polyolefin resin even at a temperature lower than ° C.

In the aging in the present invention, it is sufficient that the laminate is uniformly heated, and an apparatus such as a hot air circulation type oven can be used. Aging condition is 30 ℃
To the melting point of the resin to −10 ° C., and there is no particular limitation as long as good adhesion can be obtained. However, if the temperature is 40 ° C. or less, the adhesive strength is slightly improved, but practically sufficient strength is not obtained, and if the temperature is too high, deterioration of the polyolefin resin layer due to aging for a long time is considered, so the aging temperature is 50. The range of -80 ° C is preferred.
Further, the lower the humidity during aging, the greater the improvement in adhesive strength, and when the humidity is 90% or more, the adhesive strength does not change much before and after aging. It is considered that this is because the invasion of water into the adhesive interface causes some interaction between the polar groups on the surface of the polyolefin and water molecules, and the polar groups of the polyolefin contributing to the adhesion with the silicon oxide thin film are reduced. . Therefore, the humidity at the time of aging is preferably low, preferably 70% or less. Although the aging time varies depending on the temperature, a time of about 1 to 2 days is sufficient to obtain sufficient adhesive strength. By performing aging under the above conditions, the adhesive strength between the silicon oxide thin film and the polyolefin resin layer is greatly improved.

[0013]

The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 (Production of Polyolefin Resin) Polyethylene was produced using a high-pressure polyethylene production facility having an autoclave type reactor. The obtained polyethylene is MFR
(190 ° C) 8.0 g / 10 minutes, density 0.918 g / c
It was m ³ . (Manufacture of laminated body) Silicon oxide vapor deposition film has a width of 850 m
A polyethylene terephthalate (hereinafter abbreviated as PET) film having a thickness of m and a thickness of 12 μm was manufactured by depositing a silicon oxide thin film with a thickness of 600 Å by an ion sputtering method. A polyethylene resin layer was laminated on the silicon oxide vapor deposition surface side of the obtained film by an extrusion laminating method. The extrusion laminate molding machine was equipped with a 90 mmφ extruder and had a roll surface width of 1300 mm. The molding conditions are a molding speed of 100 m / min and a laminate thickness of 10 μ.
m, the slit width of the die was 0.8 mm, and the resin temperature immediately below the die was 320 ° C. The obtained laminate was aged for 48 hours in a hot air circulation type oven at 70 ° C. and a humidity of 55%. (Evaluation) Adhesive strength is a width of 15 m in the flow direction of molding the laminate
Cut into strips of m and cut at 1 at a speed of 300 mm / min.
The peel strength when peeled at 80 ° was measured. The evaluation results are shown in Table 1.

Example 2 MFR (230 ° C.) 21.0 as a polyolefin resin
Adhesion strength was measured by aging in the same manner as in Example 1 except that polypropylene having a g / 10 min and a density of 0.901 g / cm ³ was used and extrusion lamination was performed at a resin temperature of 305 ° C. immediately below the die. The evaluation results are shown in Table 1.

Example 3 The same operation as in Example 1 was carried out except that aging was carried out for 48 hours in a hot air circulation type oven at 40 ° C. and a humidity of 55%.
The evaluation results are shown in Table 1.

Example 4 The same operation as in Example 1 was carried out except that aging was carried out for 48 hours in a hot air circulation type oven at 30 ° C. and a humidity of 55%.
The evaluation results are shown in Table 1.

Comparative Example 1 The laminate obtained in Example 1 was evaluated for the adhesive strength immediately after molding without aging. The evaluation results are shown in Table 1.

Comparative Example 2 Example 1 except that the resin temperature just below the die was 290 ° C.
Extrusion lamination and aging were performed in the same manner as in. The evaluation results are shown in Table 1.

[0020]

[Table 1]

[0021]

When extrusion-laminating a polyolefin on the thin film surface of a plastic film having a silicon oxide thin film, a silicon oxide thin film and a polyolefin resin layer can be formed without providing an adhesive layer made of an adhesive or an adhesive resin. A laminated film having good adhesive strength was obtained.

Claims (1)

[Claims] 1. A silicon oxide thin film of a plastic film having a silicon oxide thin film on at least one surface thereof, comprising:
A method for producing a laminated film, comprising laminating a polyolefin resin by extrusion laminating at a temperature of 0 ° C. or higher, and then performing aging.