JP2856882B2 - Composite film and manufacturing method thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a packaging film, particularly a composite film suitable as a packaging film for retort foods and the like, and a method for producing the same.

[Related Art and Problems to be Solved by the Invention] In addition to the performance required for food packaging materials, retort packaging materials are required to have resistance to retort treatment. This retort treatment is usually performed under a pressurized condition at a temperature of 100 to 120 ° C. for about 30 to 60 minutes.
On the other hand, nylon films are excellent in optical properties such as abrasion resistance, gloss and transparency, and are particularly excellent in oil resistance, heat and cold resistance, and can be used in a wide temperature range. Widely used as packaging materials. However, nylon films do not have sufficient gas barrier properties such as oxygen gas barrier properties and water vapor barrier properties. Therefore, in order to impart gas barrier properties and to form a composite, a nylon film is coated with a coating agent containing a vinylidene chloride-based polymer and a laminating agent containing a polyisocyanate component and a polyol component in that order, and a film is laminated. Is provided.

The composite film having the above-mentioned structure shows high gas barrier properties before retort treatment, but when subjected to retort treatment, the gas barrier properties are significantly reduced. In addition, the retort treatment causes the composite film to become cloudy, and the transparency is significantly reduced.

Therefore, the object of the present invention is to provide a retort treatment,
An object of the present invention is to provide a composite film having high gas barrier properties and transparency.

Another object of the present invention is to provide a method for producing a composite film having the above excellent properties.

[Constitution of the Invention] In the present invention, at least one surface of a substrate film is sequentially coated with a coating layer containing a vinylidene chloride-based polymer, a laminating agent layer composed of a polyisocyanate component and a polyol component, and a polymer film layer. A composite film comprising a protective layer for regulating the penetration of components of the laminating agent layer into the coating layer between the coating layer and the laminating agent layer.

The present invention also provides a coating step of sequentially coating at least one surface of the base film with a coating agent containing a vinylidene chloride-based polymer, a laminating agent containing a polyisocyanate component and a polyol component, and a polymer on the laminating agent. A laminating step of laminating a film, comprising: after applying the coating agent, forming a protective layer for controlling the penetration of the components of the laminating agent into the coating agent layer, on the protective layer The present invention also provides a method for producing a composite film in which the above-mentioned laminating agent is applied.

As the base film, for example, polyethylene,
Ethylene-ethyl acrylate copolymer, ionomer,
Olefin polymers such as polypropylene, ethylene-propylene copolymer and poly-4-methylpentene-1; ethylene-ville alcohol copolymer; polyvinyl chloride: polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride -Vinylidene chloride polymers such as acrylonitrile copolymers; styrene polymers such as polystyrene, styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene copolymers; polyesters such as polyethylene terephthalate and polybutylene terephthalate; nylons or polyamides; Various films made of acrylonitrile; polycarbonate; polyimide; cellophane and the like can be used.

Among the above base films, a film made of an olefin polymer (particularly a polypropylene film), a film made of a polyester (particularly a polyethylene terephthalate film) and a nylon film are preferable. Particularly preferred substrate films are nylon films that can be used over a wide temperature range. Examples of the nylon constituting the nylon film include nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, and copolymerized nylon, for example, nylon 6/66, nylon 66/610, nylon 6/11. And the like, and at least one of these nylons is used.

The base film may be unstretched, or may be uniaxially or biaxially stretched. Examples of the stretching method include a conventional stretching method, for example, roll stretching, rolling stretching, belt stretching, tenter stretching, tube stretching, and a stretching method combining these. The stretching ratio can be appropriately set according to the desired film properties, and is, for example, about 1.5 to 20 times, and preferably about 2 to 15 times.

The stretching treatment is performed at a temperature not higher than the melting point of the polymer constituting the film and not lower than the secondary transition point.
Further, after stretching the film, a heat treatment may be performed under tension to fix the molecular orientation. Stretching, especially biaxial stretching or orientation, can significantly increase the strength of the film.

The surface of the base film may be subjected to a corona discharge treatment, a high-frequency treatment, or the like, if necessary.

The base film may be a single-layer film or a laminated film in which two or more films are laminated. The thickness of the substrate film is not particularly limited, and is, for example, about 1 to 250 μm, and preferably about 5 to 100 μm.

A coating layer containing a vinylidene chloride-based polymer is formed on at least one surface of the base film. This coating layer imparts high gas barrier properties to the base film.

The vinylidene chloride-based polymer is preferably a copolymer of vinylidene chloride and another polymerizable monomer. Examples of the polymerizable monomer include vinyl chloride, vinyl acetate, crotonic acid, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, and heptyl. Various acrylates such as acrylate, octyl acrylate, and 2-ethylhexyl acrylate, acrylonitrile, methacrylonitrile, methacrylic acid, and methacrylate corresponding to the above acrylate are exemplified. One or two or more of these polymerizable monomers are used. Among the above copolymers, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer,
Copolymers such as vinylidene chloride-vinyl acetate copolymer, vinylidene chloride-acrylic acid copolymer, vinylidene chloride-methacrylic acid copolymer, vinylidene chloride-acrylate copolymer, and vinylidene chloride-methacrylate copolymer are preferred.

At least one of these vinylidene chloride polymers is used.

The melting point of the vinylidene chloride-based polymer can be appropriately selected according to the retort processing temperature, but it can be selected by a differential scanning calorimeter (DSC).
Melting point is 125 ° C. or higher, preferably 130 ° C. or higher, more preferably 140 ° C. or higher. When the melting point of the vinylidene chloride-based polymer is less than 125 ° C., for example, at a retort treatment temperature of about 120 ° C., the coating film tends to become cloudy and the gas barrier property tends to decrease. In addition, as the melting point of the vinylidene chloride-based polymer increases, a coating film that can withstand a high retorting temperature can be obtained, and the clouding of the coating film and a decrease in gas barrier properties can be further prevented. Retort processing is usually 10
The reaction is performed at a temperature of about 0 to 120 ° C. for about 30 to 60 minutes.

The thickness of the coating layer is not particularly limited as long as the gas barrier property is not impaired, but is usually 0.01 to 5 μm, preferably 0.1 to 5 μm.
It is about 3 μm. If the film thickness is less than 0.01 μm, it is difficult to impart high gas barrier properties, and if it exceeds 5 μm, it is not economical, and in some cases, the properties of the base film may be reduced.

The coating layer containing a vinylidene chloride-based polymer can be formed by applying a coating agent containing a vinylidene chloride-based polymer to a base film and drying. The coating agent may be an aqueous coating solution containing an emulsion-type vinylidene chloride-based polymer obtained by emulsion polymerization or the like, or may be a solvent-type coating solution containing a solvent-soluble vinylidene chloride-based polymer and an organic solvent. Good.

As the organic solvent of the solvent-type coating solution, a solvent capable of dissolving or dispersing the vinylidene chloride-based polymer, for example, acetone, methyl ethyl ketone, ketones such as cyclohexanone, dioxane, ethers such as tetrahydrofuran, and aromatics such as benzene and toluene. Halogenated hydrocarbons such as hydrocarbons, methylene chloride and ethylene chloride and mixed solvents thereof can be used.

The application means is not particularly limited, and includes a conventionally used means such as a dip coater, a roll coater, a gravure coater, and an air knife coater.

A protective layer is formed on the coating layer. In this protective layer, the penetration of the components of the laminating agent layer into the coating layer may be controlled chemically or chemically by chemical affinity or chemical bonding force. The protective layer has the above function, and can be formed of a material that is transparent at room temperature and has heat resistance and water resistance. The protective layer is, for example, a thermosetting resin such as an epoxy resin; a coating of a photocurable resin such as an ultraviolet curable resin or an electron beam curable resin; a metal thin film formed by thin film forming means such as vapor deposition or sputtering; However, a film containing a thermoplastic resin is preferable from the viewpoint of workability and the like. Examples of the thermoplastic resin include a vinyl chloride-vinyl acetate copolymer, a fluorine-containing polymer, an acrylic polymer, cotton acetate, nitrified cotton, and an ethylene-vinyl alcohol copolymer. A particularly preferred thermoplastic resin is an ethylene-vinyl alcohol copolymer. The protective layer containing the ethylene-vinyl alcohol copolymer may be formed by an extrusion lamination method or the like.However, in order to form a thin film, it is preferable to form the protective layer using a coating solution containing a solvent-soluble ethylene-vinyl alcohol copolymer. preferable. The solvent-soluble ethylene-vinyl alcohol copolymer is a copolymer having an ethylene content of 5 to 50 mol%, preferably 10 to 45 mol%, more preferably 25 to 35 mol%.
Solvent-soluble ethylene-vinyl alcohol copolymer,
Usually, for example, a molecular weight of 1 to 100,000, preferably a molecular weight of 4 to
MFI (melt flow index) under the conditions of about 50,000, temperature 210 ° C, and load 2160g, about 5 to 10 g / 10 minutes, temperature 210
C., a load of 50 kg, an apparent melt viscosity with a nozzle of 1 mm.phi..times.10 mm of 5,000 to 15,000 poise, preferably about 7,500 to 12,500 poise, and a saponification degree of 99.5% or more. Such a copolymer can usually be solubilized in a mixed solvent of water and alcohol,
A protective layer made of a thin film can be formed.

The thickness of the protective layer can be selected within a range that can regulate the penetration of the components of the laminating agent layer into the coating layer, for example,
It is about 0.01 to 5 μm, preferably about 0.1 to 3 μm.

On the protective layer, a laminating agent layer composed of a two-part curable urethane-based adhesive containing a polyisocyanate component and a polyol component is formed.

As the polyisocyanate component, conventional compounds, for example, hexamethylene-1,6-diisocyanate, 1,3,6
Aliphatic polyisocyanates such as hexamethylene triisocyanate and lysine diisocyanate; p-phenylene diisocyanate, ω, ω-diisocyanate-1,3
-Dimethylbenzene, ω, ω-diisocyanate-1,4
-Dimethylbenzene, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, triphenylmethane triisocyanate, Aromatic polyisocyanates such as 1,5-naphthalenediisocyanate; isophorone diisocyanate, dicyclohexylmethane-4,4'-
Diisocyanate, ω, ω-diisocyanate-1,3-
Dimethylcyclohexane, ω, ω-diisocyanate-
1,4-dimethylcyclohexane, cyclohexane-1,4-
Examples thereof include alicyclic polyisocyanates such as diisocyanate; and araliphatic polyisocyanates such as xylylene diisocyanate and tetramethyl xylylene diisocyanate. These polyisocyanate components are:
Polyisocyanate compound is added to polyhydric alcohol,
Adduct having an isocyanate group at the terminal, isocyanate compound generated by the Burette reaction, dimer,
It may be a trimer. The polyisocyanate component can be used alone or as a mixture of two or more.

As the polyol component, a compound commonly used in a two-component curable urethane adhesive, for example, a polyhydric alcohol,
A polyester polyol obtained by a reaction with a polyvalent carboxylic acid or a lower alkyl ester or an acid anhydride thereof, and having a hydroxy group; obtained by reacting the polyester polyol with a polyisocyanate component;
And a polyester polyurethane polyol having a hydroxy group. These polyol components can be used alone or in combination.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol,
Dipropylene glycol, tripropylene glycol,
Polypropylene glycol, 1,3-butanediol, tetramethylene glycol, hexamethylene glycol,
Aliphatic polyhydric alcohols such as neopentyl glycol, trimethylolpropane and pentaerythritol; 1,4-
Alicyclic polyhydric alcohols such as cyclohexanedimethanol; aromatic polyhydric alcohols such as 2,2-bis (2-hydroxyethylphenyl) propane;

Examples of polycarboxylic acids include, for example, aliphatic polycarboxylic acids such as succinic acid, adibic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid, maleic acid, fumaric acid, and itaconic acid; Alicyclic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid;
Examples include aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, and pyromellitic acid.

The polyol component is a modified polyol obtained by reacting a polyol component with an ethylenically unsaturated carboxylic acid or an acid anhydride thereof in the presence of a radical generator, as disclosed in JP-A-61-209282. It may be. Further, a polyhydric alcohol, a polyether polyol, a polyether polyurethane polyol, or the like may be added to the polyol component as long as the retort treatment is not impaired.

The weight average molecular weight of the polyol component is usually 500 to 100.
It is about 000.

When the laminating agent containing such a polyisocyanate component and a polyol component is applied directly on the coating layer instead of on the protective layer, the polyisocyanate component in the laminating agent may have moisture in the air or, in some cases, Reacts with the active hydrogen atoms of the vinylidene chloride-based polymer contained in the coating layer, and a part of the isocyanate component is deactivated.
Therefore, since the polyol component becomes excessive in the laminating agent layer, the unreacted polyol component remains in the laminating agent layer even when the polyol component is cured by the polyisocyanate component as a curing agent. When the composite film is subjected to the retort treatment, transparency and gas barrier properties are reduced. This means that unreacted polyol components remaining in the laminate agent layer penetrate into the coating layer,
It is presumed that the crystallization of the vinylidene chloride polymer is inhibited.

On the other hand, in the present invention, since the laminating agent layer is formed on the protective layer, crystallization of the vinylidene chloride-based polymer contained in the coating layer is not hindered by the components of the laminating agent layer. Therefore, even after the retort treatment, the high gas barrier property of the vinylidene chloride-based polymer is developed, and the composite film is not clouded. In particular, when a coating layer containing the vinylidene chloride-based polymer and a protective layer containing an ethylene-vinyl alcohol copolymer are combined, the ethylene-vinyl alcohol copolymer has excellent oxygen gas barrier properties. High gas barrier properties can be provided.

The thickness of the laminating agent layer can be selected within a range that does not impair the adhesive strength with the polymer film layer, and is usually 0.1 to 10 μ
m, preferably about 0.5 to 5 μm.

The laminating agent layer can be formed by applying a laminating agent containing the polyisocyanate component and the polyol component on the coating layer. The laminating agent is usually used as an organic solvent solution. Examples of the organic solvent include aliphatic hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate. A mixed solvent thereof.

After laminating the polymer film layer on the laminating agent layer, the curing of the laminating agent layer can be performed, for example, at a temperature of about 30 to 50 ° C.

The polymer film layer laminated on the laminating agent layer can be composed of the same base film as described above, depending on the use of the composite film. The lamination of the polymer film layer can be carried out by pressing a polymer film on the laminating agent by a conventional method.

Further, the composite film of the present invention may have at least a layer structure composed of the base film, the coating layer, the laminating agent layer and the polymer film layer, and the polymer film may be formed by a method such as dry lamination or extrusion lamination. At least one polymer film layer may be further laminated on the film layer.

In such a composite film, at least one of the base film and the polymer film layer preferably has thermal bonding properties in order to form a bag by heat sealing, impulse sealing, ultrasonic bonding, or the like. The polymer film layer having thermal bonding properties is not particularly limited, and can be formed of, for example, polyethylene, polyethylene containing ethylene-vinyl acetate, unstretched polypropylene, or the like. Further, the base film and the polymer film layer are formed of a polymer having thermal bonding properties, for example, a vinyl chloride-vinyl acetate copolymer, a solvent-soluble ethylene-
Thermal bondability may be imparted by a coating layer such as a vinyl alcohol copolymer and a styrene-butadiene copolymer. The thickness of the polymer film layer can be selected within the same range as the thickness of the base film, and the thickness of the coating layer is usually about 0.1 to 5 μm.

A preferred composite film is composed of the base film, the coating layer, the protective layer, the laminating agent layer, and the polymer film layer having thermal bonding properties.

Note that a coating layer, a laminating agent layer, and a polymer film layer may be formed on both sides of the base film, respectively. In this case, it is preferable that at least one of the polymer film layers on both surfaces has thermal bonding properties.

The coating layer, the protective layer, and the laminating agent layer are, for example, olefin polymers such as ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer; acrylic polymer; styrene polymer; polyester; polyacetal; Vinyl; polyvinyl chloride; vinyl chloride-vinyl acetate copolymer; polyamide; polyurethane;
Polycarbonates; chlorinated polyolefins; and polymers such as cellulosic polymers may be included. The base film, the covering layer, the protective layer, the laminating agent layer, and the polymer film layer may contain an additive. Examples of the additives include antioxidants, ultraviolet absorbers, heat stabilizers, plasticizers, antistatic agents, tackifiers, plasticizers, fillers, lubricants such as waxes and fine powdery lubricants, dyes and pigments, and the like. You.

[Effect of the Invention] The composite film of the present invention does not become cloudy even when subjected to retort treatment, and retains high transparency and gas barrier properties.

In addition, according to the method for producing a composite film of the present invention, a composite film having excellent characteristics as described above can be obtained.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples.

Examples 1 and 2 100 parts by weight of vinylidene chloride (90% by weight) -acrylate (10% by weight) copolymer (melting point 145 ° C.), melting point 78
One part by weight of wax at 0 ° C. and 0.1 part by weight of fine silica powder having an average particle size of 3 μm as a lubricant were uniformly mixed in tetrahydrofuran / toluene = 70/30 (weight ratio) to prepare a coating solution. This coating solution was applied to one surface of a biaxially stretched nylon 6 film having a thickness of 15 μm using a bar coater so that the coating amount after drying was 2.0 g / m ² to form a coating layer.

Mixed solvent of water and isopropanol (polymerization weight ratio 1:
1) an ethylene-vinyl alcohol copolymer (trade name: Soarnol, manufactured by Nippon Synthetic Chemical Co., Ltd .; ethylene content: 29)
Mol%), and dissolved by heating to prepare a coating solution having an ethylene-vinyl alcohol copolymer content of 10% by weight. This coating solution was applied to the coating layer, and the applied amount after drying was 0.5 g / m.
² (Example 1) and 1.0 g / m ² (Example 2) to form a protective layer.

Then, the polyol component (Toyo Morton Co., Ltd., AD
-806) and a polyisocyanate component (manufactured by Toyo Morton Co., Ltd., RT-8), the isocyanate group of the polyisocyanate compound / the hydroxy group of the polyol component = 1 /
The mixture was mixed at 1 (molar ratio) to prepare a laminating agent. The obtained laminating agent was coated on the protective layer, and the coated amount after drying was 3.
The solution was applied so as to have a concentration of 5 g / m ^2, and a non-stretched polypropylene film (manufactured by Toyobo Co., Ltd., P-1143) was pressure-bonded and laminated on the application surface to obtain a composite film.

Comparative Example 1 In Example 1, a composite film was obtained in the same manner as in Examples 1 and 2 without using the coating liquid containing the ethylene-vinyl alcohol copolymer.

Example 3 and Example 4 Instead of the vinylidene chloride-based polymer of Example 1, a vinylidene chloride (85% by weight) -methacrylic acid (15% by weight) copolymer (melting point: 145 ° C.) obtained by an emulsion polymerization method was used. Except for using the emulsion, a composite film was obtained in the same manner as in Example 1.

Comparative Example 2 A composite film was obtained in the same manner as in Example 3 except that the coating liquid containing the ethylene-vinyl alcohol copolymer was not used.

Then, the composite films obtained in the respective Examples and Comparative Examples were subjected to a retort treatment at a temperature of 105 ° C. for 30 minutes, and the haze (%) before and after the retort treatment, the white turbidity visually, and the oxygen gas permeability were evaluated. The oxygen gas permeability was measured by a gas chromatography method as follows.

A measuring instrument (Lyssy Gas Permeablity Testin) was prepared using oxygen gas with a humidity of 80% and helium gas as a compensation gas.
g Apparatus L-66) at a temperature of 20 ° C. The unit is cc / m ^2/24 hours.

The results are shown in the table together with the coating amount of the protective layer coating liquid containing the ethylene-vinyl alcohol copolymer.

As is clear from the table, the composite film of the comparative example becomes cloudy due to the retort treatment, the haze is significantly increased, and the oxygen gas barrier property is also significantly reduced. On the other hand, the composite films obtained in the examples are transparent even after the retort treatment, and have small haze and oxygen gas permeability.

Claims (5)

(57) [Claims] 1. A layer structure in which at least one surface of a substrate film is sequentially coated with a coating layer containing a vinylidene chloride-based polymer, a laminating agent layer composed of a polyisocyanate component and a polyol component, and a polymer film layer. A composite film having a protective layer interposed between the coating layer and the laminating agent layer, the protective layer restricting penetration of components of the laminating agent layer into the coating layer. 2. The composite film according to claim 1, wherein the base film is a nylon film. 3. The composite film according to claim 1, wherein the protective layer contains an ethylene-vinyl alcohol copolymer. 4. The composite film according to claim 1, wherein the polymer film layer has a thermal bonding property. 5. A coating step of sequentially coating at least one surface of a base film with a coating agent containing a vinylidene chloride-based polymer and a laminating agent containing a polyisocyanate component and a polyol component, and a polymer film on the laminating agent. And a laminating step of laminating, after applying the coating agent, forming a protective layer that regulates the penetration of the components of the laminating agent into the coating agent layer,
A method for producing a composite film, comprising applying the laminating agent on the protective layer.