JP3070692B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated plastic film suitable as a packaging material having excellent barrier properties and transparency for gases such as oxygen, nitrogen and carbon dioxide.

[0002]

2. Description of the Related Art Conventionally, films made of thermoplastic resins such as polyolefin, polystyrene, polyvinyl chloride, polyester, and polyamide, especially films of oriented polypropylene, polyester, and polyamide, have been used.
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 gas permeability is too large, so their oxygen barrier properties are insufficient, and they tend to cause deterioration of the contents such as due to oxidative deterioration or aerobic microorganisms. Usually, a method of stacking another film layer having good oxygen barrier properties is often used.

[0003] As the most typical means, a method of laminating a metal foil such as aluminum or evaporating such a metal on the surface of the thermoplastic resin film is used. It is being used effectively. However, these aluminum laminates and vapor-deposited films are opaque, and when they are used for food packaging, there is a drawback that the contents cannot be seen. Along with this trend, there is an increasing demand for films that are transparent and have excellent gas barrier properties. On the other hand, various transparent plastic film materials having a small gas permeability are conventionally known, and examples thereof include films made of polyvinyl alcohol, polyethylene vinyl alcohol, and polyvinylidene chloride resin. However, these films alone are insufficient in physical properties such as strength, elongation, water resistance, and heat resistance as compared with oriented polypropylene, polyester, and polyamide films, and particularly, polyvinyl alcohol and polyethylene vinyl. Alcohol and the like have extremely high hygroscopicity, making the roll-shaped film difficult to handle, for example, the end face becomes petal-like due to the moisture absorption, and the target gas barrier property is greatly reduced by the moisture absorption.

Therefore, these films cannot be used alone as films for packaging materials.
At present, these films having a thickness of about 0 to 40 [mu] m are used by laminating them with the above-mentioned polypropylene film, polyester film and the like. In addition, these films are expensive alone, and when they are multi-layered, not only becomes more expensive, but also the total layer thickness becomes extremely thick, and it is difficult to obtain a high degree of transparency. There are problems such as. In addition, since the level of gas barrier properties obtained by these films is still not enough compared to the aluminum laminated film, it has high transparency and high gas barrier properties,
The fact is that there is a strong demand for low-cost films that can be used alone.

On the other hand, in order to solve these problems, a method of applying a barrier resin such as polyvinyl alcohol, polyethylene vinyl alcohol and polyvinylidene chloride to oriented polypropylene, polyester, polyamide or the like has been studied. However, polyvinyl alcohol and polyethylene vinyl alcohol have excellent gas barrier properties under low environmental humidity, but have a problem in that under high environmental humidity, the gas barrier properties are significantly lower than their moisture absorption properties. . Further, with respect to polyvinylidene chloride, its gas barrier properties do not depend on environmental humidity, but it cannot be said that it is sufficient, and at present, it is used by increasing the coating thickness. Nevertheless, their gas barrier levels are still inadequate and far from levels such as aluminum deposition.

[0006]

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to simultaneously provide a high gas barrier property and a high transparency which are hardly affected by humidity. An object of the present invention is to provide a plastic film that is satisfactory, does not require multilayering such as lamination, and is excellent in handleability and economy.

[0007]

That is, in the laminated film of the present invention, at least one surface of a film made of a thermoplastic resin has a Permacol value (π) defined by the following general formula.
(A) having an average particle size of not less than 75 cal / cc
A composition comprising aluminum oxide and / or hydroxide (B) having a thickness of not more than 00 nm , wherein (B) /
A laminated film having a layer formed of a composition blended so that (A) is 1/99 to 90/10 by weight.

The base film used in the laminated film of the present invention is not particularly limited as long as it is a thermoplastic resin having a transparent film forming ability. Polyolefin resins such as polyethylene and polypropylene, polyethylene terephthalate, polyethylene Polyester resins such as isophthalate, polyethylene 2,6-naphthalate, polybutylene terephthalate and copolymers thereof, and polyether resins such as polyoxymethylene, nylon-6, nylon-6
6. Polyamide resins such as polymethaxylylene adipamide and the like, vinyl resins such as polystyrene, poly (meth) acrylate, polyacrylonitrile, polyvinyl acetate and copolymers thereof, Cellulosic resins such as polycarbonate resins and cellophane, acetate, and the like, as well as polyimide, polyetherimide, polyphenylene sulfide, polyether sulfone, polysulfone, polyether ketone, polyether ketone ketone, and a fluorine-containing polymer, It consists of simple substance, copolymer, mixture, and laminate of many other resins. An oriented film which has not been stretched or stretched in a uniaxial or orthogonal biaxial direction can be exemplified. Above all, from the gist of the present invention, the base film may be a biaxially stretched polypropylene, polyester, polyamide, or other film in terms of heat-resistant dimensional change and mechanical strength, as well as moldability and economy. It is suitable.

Although the thickness of the film is not particularly limited,
Usually, the thickness is 1 to 250 μm, and the packaging material is 3 to 5 μm.
It is particularly preferred that the thickness is 0 μm. This base film may be a single substance, and the method of combination and the number of layers in the multilayer film are arbitrary. The present invention essentially consists of laminating a specific composition layer on at least one surface of such a thermoplastic resin film. The aluminum oxide and / or hydroxide (B) used in the composition to be laminated on the surface preferably has an average particle size measured by an electron microscope of 100 μm or less. In the case of particles having anisotropy, the shorter particle size may satisfy the above range.

When the thickness exceeds 200 nm, the effect of improving gas barrier properties is reduced, and the transparency is undesirably reduced. The production method and shape of the aluminum oxide and hydroxide are not limited as long as the above particle size is satisfied. As a production method, any of conventionally known methods such as a chlorine method, a sulfuric acid method, an alkoxide method, and a combustion method can be used. The shape is not particularly limited, but a shape having a higher aspect ratio than a spherical shape is preferable. Flat or fiber-shaped ones are particularly preferred. For prevention of agglomeration, composite particles with other metal oxides such as alkali metals, alkaline earth metals, and silica may be used. The aluminum oxide and hydroxide may be used as a powder, but since the particle size is extremely small and the cohesiveness is high, re-dispersion becomes difficult when powdered.
Therefore, it is preferable to use it in a sol state. When used as a sol, the sol may be any of an acidic type, a basic type and a neutral type, but the neutral type is most preferred. Further, the use of a dispersing aid such as a surfactant or a polymer dispersant is not limited at all.

The resin (A) having a film forming property used in the present invention has a Permacol value [π, M, Salame; Futur-Pack '] defined by the following general formula.
85 Proceedings P119 ('85)] must be 75 cal / c · c or more.

(Where δ is the cohesive force of the polymer chain and fv is free volume) It is preferably at least 80 cal / cc. If it is less than 75 cal / c · c, the effect of imparting gas barrier properties is undesirably reduced. Examples of the resin satisfying the characteristics include a polyvinylidene chloride-based resin, a polyacrylonitrile-based resin, and a polyvinyl alcohol-based resin. These resins may be used alone or in combination of two or more. In the present invention, a film-forming resin (A) and an oxide of aluminum and / or
Alternatively, in the compounding composition of hydroxide (B), the compounding ratio is required to be 1/99 to 90/10 by weight ratio of (B) / (A), and 5/95 to 80/20. Preferably, there is.

If the ratio is less than 1/99, the effect of improving gas barrier properties is not sufficient, which is not preferable.
Conversely, when the ratio exceeds 90/10, the effect of improving gas barrier properties is saturated, and the strength and flexibility of the film are undesirably reduced. As a compounding method for obtaining the composition comprising (A) and (B), any known mixing method can be used, but the alignment effect of (A) and (B) is most effectively obtained. For this purpose, it is a preferred embodiment to mix the solution (A) or the dispersion in the solvent with the sol which is the dispersion in the solvent (B). The solvent is not particularly limited, but an aqueous solvent is preferred from the viewpoint of safety. Also, the method of synthesizing (B) in the solution or dispersion of (A), or conversely, performing the polymerization of (A) in the sol of (B) is also recommended as a method for enhancing the mixing effect of both. Is done. The means for mixing is not limited, and a known method such as a high-speed stirring method, a high-pressure dispersion method, or an ultrasonic dispersion method can be arbitrarily used. A method combining these methods is also suitable.

[0013] If necessary, additives such as other metal oxide-based fine particles, a colorant, an antistatic agent, an anti-blocking agent, a lubricant comprising inorganic or organic fine particles, an antioxidant and the like may be added to the composition. May be contained. As a method of laminating the compounded composition layer on the surface of the base film, a method of laminating the composition in advance into a film and bonding the base film to the base film, that is, a lamination method, an extrusion coating method of melt-extruding the base film, or A known method such as a coating method of applying a solution or a dispersion of the composition to the surface of the base film is used. The method of drying and heat-treating after applying to the base film surface by the coating method is most preferable. Roll coating methods such as gravure and reverse,
Conventional methods such as a doctor knife method, an air knife, and a nozzle coating method can be used.

To be laminated by such a method,
The thickness of the composition layer varies depending on the base film, the target level, and the like, but is usually 10 μm or less in dry thickness,
Preferably it is 5 μm or less, most preferably 3 μm or less. There is no particular lower limit, but if it is 0.1 μm or less, it is difficult to obtain a substantially sufficient effect. In addition,
Prior to the main lamination, the base film may be subjected to a corona treatment or other surface activation treatment, or an anchor treatment using a known anchor treatment agent such as a urethane resin.

[0015]

The present invention will be described below with reference to examples. In addition, the density | concentration display in an example is a weight basis unless there is particular notice, and evaluated by the following method. (Oxygen permeability) Measured at 25 ° C. dry and 25 ° C., 80% RH according to ASTM-D-1003-61. (Haze) Based on ASTM-D-1003-61.

Example 1 A corona-treated surface of a biaxially oriented polypropylene film having a thickness of 25 μm that had been subjected to corona discharge treatment was subjected to a roll coating method to provide a copolymerized polyester and a trifunctional isocyanate at a ratio of 4: 1 of methyl ethyl ketone / toluene. A solution dissolved in an equivalent amount of the mixed solvent was applied and dried so that the applied 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 average particle size 5 nm
A water sol of aluminum oxide (measured with a transmission electron microscope) was mixed with aluminum oxide / polyvinyl alcohol in a weight ratio of 0.1 / 0.9, and uniformly dispersed using a high-pressure homogenous disperser. The coating solution was applied by a roll coating method so as to have a coating amount after drying of 2.5 μm, and after drying, heat treatment was performed at 130 ° C. for 2 minutes to obtain a laminated film. Table 1 shows the properties of the obtained laminated film.
Shown in The laminated film obtained in this example is excellent in transparency and excellent in blocking oxygen gas.

Examples 2 to 3 In the method of Example 1, an aluminum oxide water sol having an average particle diameter of 10 nm and an aluminum hydroxide having an average particle diameter of 15 nm were used instead of the aluminum oxide water sol having an average particle diameter of 5 nm. Table 1 shows the characteristics of the laminated film obtained by the same method as in Example 1 except that the mixing ratio with polyvinyl alcohol was changed to 0.2 / 0.8. Each of the laminates obtained in these examples has good transparency and excellent barrier properties against oxygen gas.

Comparative Example 1 The laminated film obtained in the same manner as in Example 1 except that the blending of aluminum oxide and aluminum hydroxide was stopped and only a polyvinyl alcohol aqueous solution was used as a coating liquid. Table 1 shows the characteristics. The laminated film obtained in this comparative example has good transparency, but has poor oxygen gas barrier properties under high humidity. Comparative Examples 2 to 4 In the methods of Examples 1 to 3, the properties of the laminated films obtained by the same method as in Example 1 were changed except that the mixing of polyvinyl alcohol was stopped and only the aqueous sol of inorganic fine particles was used as a coating liquid. Shown in The laminated film obtained in this comparative example is remarkably inferior in oxygen gas barrier properties.

Comparative Example 5 The properties of the biaxially stretched polypropylene film before lamination used in the methods of Examples 1 to 3 are shown in Table 1. The film of this comparative example has good transparency, but is remarkably inferior in oxygen gas barrier properties. Examples 4 and 5 In the method of Examples 1 and 3, the substrate film was
m, a biaxially stretched polyester film, a polyvinylidene chloride copolymer resin as a film-forming resin, the composition ratio shown in Table 1 and the thickness of 3.5 μm after drying the applied amount of the composition. Table 1 shows the characteristics of the laminated film obtained by the same method as in Example 1 except that the characteristics were changed as follows. The laminated films obtained in these examples are also excellent in transparency and excellent in blocking oxygen gas. Comparative Example 6 The procedure of Examples 4 and 5 was repeated except that the mixing of the aqueous sol of aluminum oxide and aluminum hydroxide was stopped, and only the aqueous dispersion of the polyvinylidene chloride copolymer resin was used as the coating liquid. Table 1 shows the properties of the laminated film obtained by the same method. The laminated films obtained in these comparative examples are inferior to the laminated films of Examples 3 and 4 in the oxygen gas barrier property, and it can be seen that the effect of blending aluminum oxide and aluminum hydroxide is remarkable.

Example 6 In the method of Example 3, a copolymer resin of polyvinyl alcohol and polyvinylidene chloride (the ratio of polyvinyl alcohol units / polyvinylidene chloride units is 9/1 by weight) is used as the film-forming resin. Table 1 shows the characteristics of the laminated film obtained by the same method as in Example 3 except for the above. The laminated film obtained in this example is also excellent in transparency and excellent in blocking oxygen gas. Comparative Example 7 Table 1 shows the properties of the laminated film obtained in the same manner as in Example 3, except that the mixing of the aqueous sol of aluminum hydroxide in the method of Example 6 was stopped. The laminated film obtained in this comparative example is inferior to the laminated film of Example 6 in oxygen gas barrier properties, indicating that the effect of adding aluminum hydroxide is remarkable.

Example 7 A 15 μm biaxially stretched nylon film was used as a base film, and a 1: 1 mixture (weight ratio) of polyvinyl alcohol and polyvinylidene chloride copolymer and aluminum oxide of 5 nm in a weight ratio of 0.1% were used. Table 1 shows the properties of the laminated film obtained by laminating the acid mixture composition blended at 8: 0.2 in the same manner as in Example 1. The laminated film obtained in this example is also excellent in transparency and excellent in oxygen gas barrier properties. Comparative Example 8 Table 1 shows the properties of the laminated film obtained by the same method as in Example 7 except that the blending of aluminum oxide was stopped in the method of Example 7. The laminated film obtained in this comparative example is
The barrier property against oxygen gas is inferior to that of the laminated film of Example 7, and it can be seen that the effect of blending aluminum oxide is remarkable.

[0022]

As described in the above examples, the method of the present invention provides a film which is transparent and has a gas barrier property.
It can be widely used for packaging electric and mechanical parts.

[0023]

[Table 1]

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──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-15722 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7 / 04

Claims (1)

(57) [Claims] 1. A resin (A) having a Permacol value (π) of at least 75 cal / cc defined by the following general formula and an average of at least one surface of a film made of a thermoplastic resin.
A composition comprising aluminum oxide and / or hydroxide (B) having a particle size of 200 nm or less ;
A laminated film having a layer formed of a composition blended so that (B) / (A) is 1/99 to 90/10 by weight. [Formula 1] π = 71 [ln (δ ² /fv)−5.7] (where δ is the cohesive force of the polymer and fv is free volume)