JPH05131590A - Gas-barrier laminated film - Google Patents

Abstract

PURPOSE:To increase the adhesion force between a thin film of silicon oxide and a resin layer in a laminated film, reduce the amount of organic solvent used in producing such a film and mold the film at a shaping temperature of at most 250 deg.C at the time of extruding lamination in order to impart a good barrier property to the laminated film. CONSTITUTION:The laminated film consists of a plastic film having a thin film of silicon oxide on at least one side and a resin layer having acid anhydride group formed on the thin silicon oxide film of the plastic film via a thin layer of silane coupling agent having amino group at the terminal portion. Therefore, the laminated film is obtained which has a strong layer-to-layer adhesion force, a satisfactory barrier property and lessened liability to bending or heat shrinkage which may cause cracking.

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 being retorted, 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. Further, as a plastic film having a higher gas barrier property, there are polyvinyl alcohol (hereinafter abbreviated as PVA) and ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH), and also inorganic material aluminum (hereinafter abbreviated as Al). It has been used as a gas barrier material in the form of foils and vapor deposited layers.

These are properly used depending on the application, but a plastic film coated with PVDC has a relatively low gas barrier property, and PVA and EVOH have an excellent gas barrier property in a dry state, but a gas barrier property under high humidity conditions. Sex deteriorates. Although Al has an excellent gas barrier property, it is opaque and thus lacks visibility of the contents. Further, since it is a metal, it cannot be heated in a microwave oven.

A plastic film obtained by vapor-depositing silicon oxide on these materials is disclosed in JP-A-49-41469. This material has excellent gas barrier properties, is less affected by humidity, is transparent, and is suitable for microwave ovens. However, since the silicon oxide thin film formed by vapor deposition has high rigidity, cracks are likely to occur due to bending or thermal shrinkage of the base plastic film, and the heat sealability is poor.

Therefore, when it is used as a packaging material, attempts have been made to laminate a polyolefin on a silicon oxide thin film, but there is generally a problem that the adhesion between the silicon oxide thin film and the polyolefin is low. As a method for improving this, for example, JP-A-60-203431 and JP-A-62-
103139 discloses a method of improving the adhesiveness with a polyolefin by using a urethane adhesive. However, since a urethane adhesive requires a large amount of organic solvent, it is not preferable in terms of environmental hygiene, and in order to obtain sufficient adhesive strength, heat treatment at about 40 ° C. for a long time of about 2 days is required. It has drawbacks.

Further, JP-A-49-34984 discloses a method of forming a coating resin layer after coating a solution of a silane coupling agent on a thin film of silicon oxide and drying it. However, when this method is carried out by the dry laminating method, the silane coupling agent alone cannot obtain a sufficient adhesive strength with the polyolefin, so that it is necessary to use it in combination with another dry laminating adhesive. Therefore, a large amount of organic solvent such as ethyl acetate and toluene is required, and the initial adhesive strength is weak, so that heat treatment at about 40 ° C. for about 2 days is required to obtain sufficient adhesive strength. Have. Further, when this method is carried out by an extrusion laminating method, it is necessary to perform molding at a temperature of 280 ° C. or higher in order to obtain good adhesiveness with a polyolefin. According to the knowledge of the present inventors, such high temperature molding is performed. It was not possible to obtain a film having sufficient gas barrier properties.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a high initial adhesive strength, uses a small amount of an organic solvent during production, and can be formed at a forming temperature of 250 ° C. or lower when it is produced by extrusion lamination molding, and it can be formed with a silicon compound. An object of the present invention is to obtain a laminated film having high adhesiveness between the thin film and the resin layer and a method for producing the laminated film.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that a silicon oxide can be obtained by using a silane coupling agent having an amino group at the terminal and a resin having an acid anhydride group. The inventors have found that the thin film and the resin layer can be firmly adhered to each other, and have completed the present invention.

[0009] That is, the above problem is to provide an acid anhydride group on a silicon oxide thin film of a plastic film having a silicon oxide thin film on at least one surface through a thin layer of a silane coupling agent having an amino group at a terminal. This is solved by a laminated film in which the resin having the same is laminated and a manufacturing method thereof.

The plastic film in the present invention is formed by a known method such as T-die casting method and inflation method, and may be stretched if necessary. Although the thickness is not particularly limited, it is preferably 5 to 100 μm in consideration of easy handling as a film. Known surface treatments such as corona treatment and anchor coat treatment may be applied as necessary.

Typical materials for the plastic film include polyester, polyethylene, polypropylene, polyamide and cellophane. Various additives such as an antistatic agent and a lubricant may be added to these as required.

The silicon oxide thin film in the present invention can be formed on one side or both sides of the above plastic film by a known method such as vacuum deposition or ion sputtering. The thickness is preferably 200 to 2000 Å because of the gas barrier property and the necessity of preventing the occurrence of cracks due to bending.

As the silane coupling agent having an amino group at the terminal in the present invention, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl ) -Γ-aminopropylmethyldimethoxysilane and the like.

A thin layer of the silane coupling agent can be provided by diluting these silane coupling agents with a solvent, applying the same on a silicon oxide thin film surface of a plastic film by a known method such as a gravure coater, and then drying. .. In addition, stabilizers and other additives may be added if necessary. As the solvent of the silane coupling agent, water, methanol, ethanol, 2-propanol and the like are suitable, and these can be mixed and used.
The concentration of the silane coupling agent varies depending on the solvent, but is usually 0.01 to 5%, preferably 0.1 to 2%.

Drying can be carried out by a known method such as blowing hot air or using a heating roll. The drying temperature is preferably 50 ° C. to 90 ° C., though it varies depending on the solvent, the concentration, and the drying time. If the temperature is 50 ° C. or lower, the drying time is too long to be practical, and if the temperature is 90 ° C. or higher, the printing pitch shift becomes large.

The resin having an acid anhydride group in the present invention is an ethylene polymer having a carboxylic acid anhydride group in the molecule.

The ethylene-based polymer referred to herein is a homopolymer of ethylene, a copolymer of ethylene and another monomer,
It also includes mixtures of these. Here, the other monomer is not particularly limited as long as it can be copolymerized with ethylene, for example, propylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, methyl acrylate, ethyl. Acrylate, butyl acrylate, methyl methacrylate, vinyl acetate, acrylic acid,
Methacrylic acid and the like can be mentioned.

As a method for introducing an acid anhydride group into the molecule of an ethylene polymer, a method of copolymerizing a radically polymerizable acid anhydride when polymerizing ethylene by a high pressure method, , There is a method of graft-copolymerizing a radical-polymerizable acid anhydride using a radical initiator such as an organic peroxide, and any resin having an acid anhydride group produced by these methods can be used in the present invention. However, it can be preferably used. Further, it may be a multi-component copolymer composed of three or more components obtained by copolymerizing ethylene and another comonomer other than the acid anhydride.

The radical-polymerizable acid anhydride referred to herein is preferably a cyclic one, and specific examples thereof include maleic anhydride, itaconic anhydride, citraconic anhydride and dodecenyl succinic anhydride. Depending on the case, it is possible to use two or more of them together.

Further, these resins having an acid anhydride group can be used as a mixture with other resins as long as the adhesiveness can be maintained. If desired, stabilizers, lubricants, antistatic agents, pigments, fillers and other additives may be added.

The resin having an acid anhydride group can be laminated on the thin layer of the silane coupling agent having an amino group at the terminal by a known method such as extrusion lamination.

When the resin layer having an acid anhydride is provided by the extrusion laminating method, a silane coupling agent having an amino group at the terminal is coated on the silicon oxide thin film in advance by using equipment such as a gravure coater. After being dried, a resin layer having an acid anhydride can be laminated using a general extrusion laminating machine. If an extrusion laminating machine equipped with an anchor coater is used, the silane coupling agent having an amino group at the terminal and the resin layer having an acid anhydride can be laminated in one step.

The resin temperature in extrusion lamination is 250
C. or lower, preferably 200 to 220.degree. 250 ° C
If it exceeds the range, cracks are likely to occur in the silicon oxide thin film during extrusion lamination, and the gas barrier property deteriorates.

In the present invention, since the silane coupling agent having an amino group at the end can be diluted with water, the amount of the organic solvent used can be greatly reduced as compared with the conventional urethane adhesive.

Further, in the present invention, it is not yet clear what action causes a strong adhesive strength to be exhibited immediately after molding. However, since the silane coupling agent having an amino group at the terminal has a functional group capable of chemically reacting with both the silicon oxide thin film and the resin having an acid anhydride group, this chemical reaction is a major factor for adhesion. It seems that it has become.

[0026]

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

Example 1 (Production of Resin Having Acid Anhydride Group) A copolymer of ethylene and maleic anhydride was produced using a high-pressure polyethylene production facility having an autoclave type reactor. The obtained copolymer had an MFR (190 ° C.) of 8.6 g / 10 minutes and a unit derived from maleic anhydride of 2.2% by weight. The copolymer composition was determined by infrared absorption spectrum.

(Production of Laminate) Commercially available silicon oxide vapor deposition film (Toyo Ink Mfg. Co., Ltd. GT1000S, width 6)
A thin layer of a silane coupling agent having an amino group at the terminal was laminated on an extruding laminating machine with an anchor coat device at 90 mm and a thickness of 12 μm), and further a resin layer having an acid anhydride group was laminated thereon.

A commercially available γ-aminopropyltriethoxysilane was used as the silane coupling agent having an amino group at the terminal, and 24 g of γ-aminopropyltriethoxysilane, 12 kg of water and 12 kg of ethanol were mixed to give a concentration of 0. A 1% by weight solution was prepared.

The extrusion laminate molding machine was equipped with an extruder having a diameter of 90 mm and had a roll surface width of 1300 mm.
Molding conditions are 2g / m ² (we of coating amount of anchor coater)
t), the drying temperature was 80 ° C., the molding speed was 100 m / min, the laminate thickness was 25 μm, the die slit width was 0.8 mm, and the resin temperature immediately below the die was 217 ° C.

(Evaluation) The amount of organic solvent used was calculated from the concentration and the coating amount. Since the coating amount is 2 g / m ² and the ethanol concentration is 50%, the amount of the organic solvent used is 1 g / m ² . The peel strength was evaluated twice immediately after molding the laminate and twice after aging at 40 ° C. for 2 days. The laminated body is cut into a strip shape with a width of 15 mm in the molding flow direction, and this is cut to 300 m.
The peel strength when peeled at 180 ° at a speed of m / min was measured. The oxygen transmission rate is an oxygen transmission rate measuring device (Modern Control (USA), type OX-TRAN 10/5.
0) was used under the conditions of a measurement temperature of 23 ° C. and a relative humidity of 90%. The evaluation results are shown in Table 1.

Example 2 The copolymer of ethylene and maleic anhydride obtained in Example 1 was treated with MFR (190 ° C.) of 21.0 g / 10 minutes and density of 0.917 g / c.
It was mixed with high-pressure polyethylene of m ³ in a weight ratio of 30/70. Upon mixing, both were dry-blended with a tumbler, then melt-kneaded at 170 ° C. using a 40 mmφ single-screw extruder and pelletized. The MFR (190 ° C.) of the mixture was 14.0 g / 10 minutes, and the unit derived from maleic anhydride was 0.6% by weight. Extrusion lamination molding and evaluation were performed in the same manner as in Example 1 except that this resin was used as the resin having an acid anhydride group. The evaluation results are shown in Table 1.

Example 3 A terpolymer of ethylene, ethyl acrylate and maleic anhydride was produced using a high pressure polyethylene production facility having an autoclave type reactor. The obtained copolymer had an MFR (190 ° C.) of 32 g / 10 minutes, a maleic anhydride-derived unit of 2.9% by weight, and an ethyl acrylate-derived unit of 10.6% by weight. Extrusion laminate molding and evaluation were performed in the same manner as in Example 1 except that this terpolymer was used as the resin having an acid anhydride group. The evaluation results are shown in Table 1.

Example 4 MFR (190 ° C.) 21.0 g / 10 minutes, density 0.917 g / cm ³
0.5% by weight of maleic anhydride and 0.01% by weight of dicumyl peroxide were mixed in a high-pressure polyethylene as described above in a tumbler, and the mixture was modified at 250 ° C. in a φ40 mm single screw extruder and pelletized. The obtained modified polyethylene has MFR (1
90 ° C) 13.0 g / 10 minutes, unit derived from maleic anhydride 0.
It was 35% by weight. Extrusion lamination molding and evaluation were performed in the same manner as in Example 1 except that this modified polyethylene was used as the resin having an acid anhydride group. Table 1 shows the evaluation results
It was shown to.

Example 5 Extrusion laminate molding and evaluation were carried out in the same manner as in Example 1 except that commercially available N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane was used as the silane coupling agent. The evaluation results are shown in Table 1.

Comparative Example 1 Extrusion lamination and evaluation were performed in the same manner as in Example 1 except that a resin having an acid anhydride group was extrusion-laminated directly on the vapor deposition surface of a silicon oxide vapor deposition film without using a silane coupling agent. It was The evaluation results are shown in Table 1.

Comparative Example 2 Extrusion lamination molding and evaluation were carried out in the same manner as in Example 1 except that a commercially available γ-methacryloxypropyltrimethoxysilane was used as the silane coupling agent having no amino group at the terminal. The evaluation results are shown in Table 1.

Comparative Example 3 MFR (190 ° C.) was used instead of the resin having an acid anhydride group.
Extrusion lamination molding and evaluation were carried out in the same manner as in Example 1 except that high pressure polyethylene having a density of 21.0 g / 10 minutes and a density of 0.917 g / cm ² was used. The evaluation results are shown in Table 1.

Comparative Example 4 Extrusion lamination molding and evaluation were carried out in the same manner as in Example 1 except that the high-pressure polyethylene of Comparative Example 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.

Comparative Example 5 A vapor-deposited surface of a silicon oxide vapor-deposited film and a commercially available high-pressure polyethylene film on the market were bonded by dry lamination using a urethane adhesive. The results are shown in Table 1.

[0041]

[Table 1]

[0042]

The adhesive strength between the silicon oxide thin film and the resin layer is strong from the beginning, and the amount of the organic solvent used during production is small,
A laminated film was obtained which could be produced at a forming temperature of 250 ° C. or lower when produced by extrusion laminating. Since this laminated film has a resin laminated on a thin film of silicon oxide, cracks are unlikely to occur due to bending or thermal shrinkage of the base plastic.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaya Tahira, 3-2, Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Akira Kawasaki Plastics Research Laboratory

Claims (3)

[Claims] 1. A resin having an acid anhydride group is provided on a silicon oxide thin film of a plastic film having a silicon oxide thin film on at least one surface via a thin layer of a silane coupling agent having an amino group at a terminal. Laminated laminated film. 2. A resin having an acid anhydride group after a solution of a silane coupling agent having an amino group at the terminal is applied and dried on a silicon oxide thin film of a plastic film having a silicon oxide thin film on at least one surface. A method for producing a laminated film, which comprises providing a layer. 3. The method for producing a laminated film according to claim 2, wherein an extrusion laminating method is used as a method for providing the resin layer having an acid anhydride.