JPH05271447A - Gas-barrier film - Google Patents

Abstract

PURPOSE:To produce a film laminate excellent in gas barrier porperties and transparency by forming a layer of a compsn. comprising a specific film-forming resin and sericite and/or illite on at least one side of a thermoplastic resin film. CONSTITUTION:A gas-barrier film is produced by forming, on at least one side of a thermoplastic resin film, a layer of a compsn. which comprises 99-10wt.% film-forming resin having a permachor value (pi) defined by the formula (wherein delta is the cohesive strength of a polymer chain; and fv is a free volume) of 750cal/cc or higher and 1-90wt.% sericite and/or illite. Thus, a plastic film having both high gas barrier properties hardly susceptible to the influence of humidity and a high transparency and excellent in handling properties is obtd. economically without the necessity for multilayering such as laminating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated plastic film suitable as a packaging material which is excellent in blocking gas such as oxygen, nitrogen and carbon dioxide gas and has excellent transparency.

[0002]

2. Description of the Related Art Films made of thermoplastic resins such as polyolefins, polystyrenes, polyvinyl chlorides, polyesters and polyamides, especially oriented films of polypropylene, polyesters, polyamides, etc.
It has excellent mechanical properties, heat resistance and transparency, and is widely used as a packaging material. However, when these films are used for food packaging, their oxygen permeability is insufficient because their gas permeability is too large, and it is easy to cause alteration of the contents such as due to oxidative deterioration or due to aerobic microorganisms. Usually, a method such as stacking another film layer having a good oxygen barrier property is often used. The most typical means is to laminate a metal foil such as aluminum or to deposit such a metal on the surface of the thermoplastic resin film, and effectively use excellent gas barrier property, especially oxygen barrier property. Has been done.

However, these aluminum laminates and vapor-deposited films become opaque, and there is a drawback that the contents cannot be seen when foods are packaged using these, and the diversification of packaging forms in recent years. In line with the trend of fashion, there is an increasing demand for transparent and excellent gas barrier properties. On the other hand, various transparent plastic film materials having a small gas permeability have been conventionally known, such as a film made of polyvinyl alcohol, polyethylene vinyl alcohol, or polyvinylidene chloride resin. However, each of these films alone has insufficient physical properties such as strength, elongation, water resistance, and heat resistance as compared with oriented polypropylene, polyester, and polyamide films.
In particular, polyvinyl alcohol, polyethylene vinyl alcohol, etc. have extremely high hygroscopicity, and the end face of the roll-shaped film becomes petal-like due to moisture absorption, and it is difficult to handle. Will fall.

Therefore, these films cannot be used alone as a film for a packaging material, and usually 1
At present, these films having a thickness of about 0 to 40 μm are used by being laminated together with the polypropylene film or the polyester film. Moreover, each of these films is expensive individually and not only becomes more expensive by making multiple layers but also the total layer thickness becomes very thick, and it is difficult to obtain high transparency. There are problems such as. Further, the level of gas barrier property obtained by these films is still not sufficient as compared with the above aluminum laminated film, so that it has high transparency and high gas barrier property,
In reality, there is a strong demand for a low-cost film that can be used alone.

On the other hand, in order to solve these problems, a method of applying a barrier resin such as the above-mentioned polyvinyl alcohol, polyethylene vinyl alcohol, or polyvinylidene chloride to oriented polypropylene, polyester, polyamide or the like has been studied. However, regarding polyvinyl alcohol and polyethylene vinyl alcohol, the gas barrier property is excellent under low environmental humidity, but under high environmental humidity, the gas barrier property is significantly reduced due to its hygroscopic property. .. Further, with respect to polyvinylidene chloride, its gas barrier property does not depend on environmental humidity, but it cannot be said to be sufficient, and it is currently used by increasing the coating thickness. Nevertheless, its gas barrier level is still inadequate, far from that of aluminum vapor deposition.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional problems, and its purpose is to provide a high gas barrier property which is not easily affected by humidity and a high transparency. It is an object of the present invention to provide a plastic film which is satisfactory and does not require multi-layering such as lamination and has excellent handleability and economical efficiency.

[0007]

That is, the gas barrier film of the present invention has a permacol value (π) defined by Chemical Formula 1 of 75 cal / cc or more on at least one side of a base film made of a thermoplastic resin. And a composition comprising a film-forming resin (A) and sericite and / or illite (B), and the weight ratio of (B) / (A) is 1/99 to 90/10. A gas barrier film having a layer formed of the composition as described above.

The substrate film used in the gas barrier film of the present invention is not particularly limited as long as it is a thermoplastic resin having a transparent film forming ability, but a polyolefin resin such as polyethylene or polypropylene,
Polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate and copolymers thereof, polyether resins such as polyoxymethylene, nylon-6. , Nylon-66, polymethaxylylene adipamide, and other polyamide resins, polystyrene, poly (meth) acrylic acid ester, polyacrylonitrile,
Vinyl-based resins such as polyvinyl acetate and copolymers thereof, polycarbonate-based resins and the like, cellulosic resins such as cellophane and acetate, and further polyimide, polyetherimide, polyphenylene sulfide, polyether. Sulfone, polysulfone, polyetherketone, polyetherketoneketone, fluorine-containing polymer, and many other resin simple substances, copolymers, mixtures, and laminates, in unstretched or uniaxial or orthogonal biaxial directions. Examples include a stretched oriented film and the like. Above all, from the gist of the present invention,
The base film is preferably a biaxially stretched film of polypropylene, polyester, polyamide or the like from the viewpoints of heat-resistant dimensional change, mechanical strength, moldability and economy.

The thickness of the film is not particularly limited,
It is usually 1 to 250 μm, and 3 to 5 as a packaging material.
The case of 0 μm is particularly preferable. This base film may be a single film or a composite multilayer film, and the composite method and the number of layers in the multilayer film are arbitrary.

The present invention essentially comprises laminating a specific composition layer on at least one surface of such a thermoplastic resin film. Sericite and illite (B) used in the compounded composition to be laminated on the surface are represented by the basic chemical formula K _1.0 (H ₃ O) _1.0 Al as described in “Chemical Dictionary” published by Kyoritsu Publishing. ₄ (SiAl) ₈ O
₂₀ (HO) ₄ and K _0.5 [(H ₃ O) _0.5 ] (Al ₃
It means that represented by Fe ^II ) ₄ (SiAl) ₈ O ₂₀ (OH) ₄ . The shape is generally a hexagonal plate shape or an irregular hexagonal shape, but other shapes may be used. The compound (B) is
It may be a natural product or a synthetic product. Further, it may be subjected to a treatment such as a firing treatment.

The average particle size of the compound (B) measured by an electron microscope is preferably 2 μm or less. If the average particle size exceeds 2 μm, the effect of improving the gas barrier property decreases and the transparency decreases, which is not preferable. It is extremely important that the compound (B) has good dispersibility in the laminated layers. The means for improving the dispersibility is not particularly limited, but it is effective to use, for example, one purified by a deionization method or one subjected to a surface treatment for improving the dispersibility. .. Further, in order to improve the dispersibility, it is preferable to use it as a sol after being subjected to a dispersion treatment rather than being used as a powder as it is. The means for forming the sol is not limited, and various dispersing means can be arbitrarily used. Further, there is no limitation on the combined use of a dispersion aid such as a surfactant or a polymer dispersant when forming the sol.

The resin (A) having a film-forming property used in the present invention has a permacol value [π, M. Salem; Futur-Pack. '8
5 Proceedings P119 ('85)] must be 75 cal / cc or more. Preferably, it is 80 cal / c · c or more. 75cal /
If it is less than c · c, the effect of imparting the gas barrier property decreases, which is not preferable. Examples of resins satisfying the above characteristics include polyvinylidene chloride-based resins, polyacrylonitrile-based resins and polyvinyl alcohol-based resins. These resins may be used alone or in combination of two or more. In the present invention, in the compounded composition of the resin (A) having film forming properties and the sericite and / or the illite (B), the compounding ratio is 1/99 to 90 by the weight ratio of (B) / (A). Must be / 10 5 /
It is preferably 95 to 80/20. If the ratio is smaller than 1/99, the effect of improving the gas barrier property becomes insufficient, which is not preferable. On the other hand, when it exceeds 90/10, the effect of improving the gas barrier property is saturated, and the strength and flexibility of the film deteriorate, which is not preferable.

As the compounding method for obtaining the composition comprising (A) and (B), any known mixing method can be adopted, but the compounding effects of (A) and (B) are most effective. In order to obtain the desired properties, it is a preferred embodiment to mix the solution of (A) or the dispersion in the solvent with the sol which is the dispersion of the (B) in the solvent. The solvent is not particularly limited, but an aqueous solvent is preferred for safety reasons. In addition, a method of synthesizing (B) in the solution or dispersion of (A) and, conversely, polymerizing (A) in the sol of (B) is also recommended as a method for enhancing the compounding effect of both. To be done. The means for mixing is also not limited, and known methods such as a high-speed stirring method, a high-pressure dispersion method, and an ultrasonic dispersion method can be arbitrarily used. A method combining these methods is also suitable. The compounded composition may further contain additives such as other metal oxide fine particles, a colorant, an antistatic agent, an antiblocking agent, a lubricant composed of inorganic or organic fine particles, and an antioxidant. It doesn't matter.

As a method for laminating the compounded composition layer on the surface of a base film, a method of previously laminating the composition into a film shape or a base film, that is, a laminating method or an extrusion coating for melt-extruding on the base film is used. A known method such as a coating method in which a solution or dispersion of the composition is applied to the surface of the base film is used. The most preferable method is to coat the surface of the base film by a coating method, and then dry and heat-treat. As a coating method, a usual method such as a roll coating method such as gravure or reverse, a doctor knife method, an air knife, or a nozzle coating method can be used. The thickness of the blended composition layer to be laminated by such a method varies depending on the substrate film, the target level, etc., but is usually 10 μm or less, preferably 5 μm or less, most preferably 3 μm or less in dry thickness. Is desirable. There is no particular lower limit, but if 0.1 μm or less, it is difficult to obtain a substantially sufficient effect. Before the main lamination, the base film may be subjected to corona treatment or other surface activation treatment or anchor treatment using a known anchor treatment agent such as urethane resin.

(Examples) The present invention will be described below with reference to examples. Unless otherwise stated, the concentration indication in the examples is based on weight, and the evaluation was based on the following method. [Oxygen permeability] Based on ASTM-D-1003-61, it was measured at 25 ° C dry and 25 ° C at 80% RH. [Haze] It was based on ASTM-D-1003-61.

Example 1 A corona-treated surface of a corona-treated polypropylene film having a thickness of 25 μm and subjected to corona discharge treatment was roll-coated on a corona-treated surface side of a copolymerized polyester and a trifunctional isocyanate in a ratio of 4: 1 of methyl ethyl ketone / toluene. A solution dissolved in an equal amount of mixed solvent was applied and dried so that the coating amount after drying was 0.2 g / m ² . The coated surface of the treated film has a degree of polymerization of 300 and a degree of saponification of 98.5.
% Polyvinyl alcohol aqueous solution and hexagonal plate-shaped natural sericite water sol having an average particle size of 1.0 μm, which is purified by a deionization method, in a kaolinite / polyvinyl alcohol weight ratio of 0.1 / 0. 1.9 and then uniformly dispersed using a high-pressure homogenizing disperser by a roll coating method so that the coating amount after drying is 2.5 μm, and after drying, at 130 ° C. for 2 minutes. Was heat-treated (space) to obtain a laminated film. The characteristics of the obtained laminated film are shown in the table. The laminated film obtained in this example is excellent in transparency and oxygen gas barrier property.

Comparative Example 1 The characteristics of the laminated film obtained by the same method as in Example 1 are shown in the table except that in the method of Example 1, the addition of sericite was stopped and only the polyvinyl alcohol aqueous solution was used as the coating liquid. The laminated film obtained in this comparative example has good transparency, but is inferior in oxygen gas barrier property under high humidity. Comparative Example 2 The characteristics of the laminated film obtained by the same method as in Example 1 are shown in the table, except that in the method of Example 1, the blending of polyvinyl alcohol was stopped and only the water sol of kaolinite was used as the coating liquid. The laminated film obtained in this comparative example has a markedly poor oxygen gas barrier property. Comparative Example 3 The characteristics of the biaxially oriented polypropylene film before lamination used in the method of Example 1 are shown in the table. The film of this comparative example has good transparency, but has a markedly poor oxygen gas barrier property.

Example 2 A laminate obtained by the same method as in Example 1 except that the deionized and purified sericite was replaced by illite having an average particle size of 0.5 μm in the same manner as in Example 1. The characteristics of the film are shown in the table. The laminated film obtained in this example is also excellent in transparency and oxygen gas barrier property. Comparative Example 4 The characteristics of the laminated film obtained in the same manner as in Example 2 are shown in the table, except that in the method of Example 2, the blending of polyvinyl alcohol was stopped and only the water sol of illite was used as the coating liquid. The laminated film obtained in this comparative example has a markedly poor oxygen gas barrier property.

Examples 3 and 4 In the method of Example 1, the substrate film was a 12 μm biaxially stretched polyester film, a polyvinylidene chloride copolymer resin was used as the film forming resin, and the composition ratios shown in the table were used. Also, the coating amount of the blended composition after drying is 3.
The characteristics of the laminated film obtained by the same method as in Example 1 are shown in the table except that the thickness is changed to 5 μm. The laminated film obtained in this example is also excellent in transparency and oxygen gas barrier property.

Comparative Example 5 In the same manner as in Examples 3 and 4, except that the mixing of the water sol of sericite or illite was stopped and only the aqueous dispersion of the polyvinylidene chloride copolymer resin was used as the coating liquid, The characteristics of the laminated film obtained by the same method as in 4 are shown in the table. The laminated film obtained in this comparative example had an oxygen gas barrier property of Example 3
It is inferior to the laminated film of No. 1 and the compounding effect of sericite and illite is remarkable.

Example 5 In the method of Example 1, a copolymer resin of polyvinyl alcohol and polyvinylidene chloride (polyvinyl alcohol unit / polyvinylidene chloride unit ratio 9/1 by weight) is used as the film-forming resin. Other than that, the characteristics of the laminated film obtained by the same method as in Example 1 are shown in the table. The laminated film obtained in this example is also excellent in transparency and oxygen gas barrier property.

Comparative Example 6 The characteristics of the laminated film obtained by the same method as in Example 5 except that the addition of the water sol of sericite was stopped in the method of Example 5 are shown in the table. The laminated film obtained in this comparative example is
It can be seen that the oxygen gas barrier property under high humidity is inferior to that of the laminated film of Example 5, and the compounding effect of sericite is remarkable. Example 6 In the method of Example 2, polyvinyl alcohol was used as the film-forming resin, poly (ethylene vinyl alcohol) copolymer was used, and the blending ratio with illite was changed as shown in Table 1, and the blending composition was further changed. The characteristics of the laminated film obtained by the same method as in Example 2 are shown in the table, except that the coating amount of the product is changed to a thickness of 3.5 μm after drying. The laminated film obtained in this example also has excellent transparency, and
Excellent in blocking oxygen gas.

Comparative Example 7 The characteristics of a laminated film obtained by the same method as in Example 6 except that the addition of the water sol of sericite was stopped in the method of Example 6 are shown in the table. The laminated film obtained in this comparative example is
It can be seen that the oxygen gas barrier property is inferior to that of the laminated film of Example 5, and the effect of compounding sericite is remarkable. Example 6 A 15 μm biaxially stretched nylon film as a base film and a 1: 1 mixture (weight ratio) of polyvinyl alcohol and a polyvinylidene chloride copolymer as a film-forming resin.
The characteristics of the laminated film obtained by the same method as in Example 3 except that is used are shown in the table. The laminated film obtained in this example is also excellent in transparency and oxygen gas barrier property. Comparative Example 8 The characteristics of the laminated film obtained by the same method as in Example 6 except that the addition of sericite was stopped in the method of Example 7 are shown in the table. The laminated film obtained in this Comparative Example is inferior to the laminated film of Example 6 in the oxygen gas barrier property under high humidity, and it can be seen that the compounding effect of sericite is remarkable.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

INDUSTRIAL APPLICABILITY As shown in the above examples, the method of the present invention provides a transparent film having a high gas barrier property, and can be used for food packaging, aseptic packaging of medicines and medical instruments, and electrical packaging. It can be widely used for packaging machine parts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Yamada 1-1-1 Katata, Otsu City, Shiga Prefecture Inside Toyobo Co., Ltd.

Claims (1)

[Claims] 1. A thermoplastic resin film having a permacol value (π) defined in Chemical Formula 1 of 75 ca on at least one side.
A composition comprising a resin (A) having a film-forming property of 1 / cc or more and sericite and / or illite (B), and the weight ratio of (B) / (A) is 1/99 to 9.
A gas barrier film having a layer formed of a composition blended as 0/10. [Chemical 1] (Where δ is the cohesive force of the polymer chain and fv is the free volume)