JP3024198B2 - Laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a film laminate having excellent gas impermeability and transparency such as oxygen, nitrogen, carbon dioxide gas and water vapor, and enhanced ultraviolet impermeability. It is about the body.

(Prior art) Conventionally, films made of thermoplastic resins such as polyolefins, polyesters, polyamides, polystyrenes, and polyvinyl chlorides, especially oriented polypropylenes, polyesters and polyamides, have excellent mechanical properties and heat resistance. It is widely used as a packaging material because of its properties and transparency. However, these films are oxidatively degraded, spoiled by aerobic microorganisms, degraded by light, for packaging of foods and pharmaceuticals that dislike alteration, etc., because the gas permeability is too large, the oxygen barrier property is insufficient, In addition, the ability to block ultraviolet rays that cause deterioration and deterioration due to light is insufficient.

For this reason, a method such as laminating a film layer having good shielding properties against oxygen and ultraviolet rays is usually adopted in many cases.

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. However, these aluminum laminates and vapor-deposited films are opaque, and when they are used for packaging, there is a drawback that the contents cannot be seen. In addition, there is an increasing demand for a film that is transparent and has excellent gas and ultraviolet ray blocking properties.

On the other hand, a method of laminating a transparent resin layer having a small gas permeability as a method of imparting gas barrier properties while being transparent is conventionally known. However, when vinylidene chloride-based resin or polyacrylonitrile-based resin is used, the gas barrier property is not sufficient, and when vinyl alcohol-based resin is used, the gas barrier property is greatly reduced due to moisture absorption. There is a problem that the gas barrier property under the environment is not sufficient.

In addition, as a method of imparting the ultraviolet shielding property while being transparent, there is known a method of laminating a resin layer containing an organic ultraviolet absorber such as a benzoluriasol-based, benzophenone-based, or salicylate-based.

However, in these methods, in order to avoid volatilization and deterioration of the ultraviolet absorbent due to heating during the production, not only the production method and processing conditions of the film but also the ultraviolet absorbent used are limited. Another problem is that the film is extremely expensive because a large amount of ultraviolet absorber is required.

Under these circumstances, conventionally, a film which is transparent and has excellent gas and ultraviolet light impermeability has not satisfied the market requirements.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances and aims to solve the conventional problems. It is an object of the present invention to provide a laminate having a high degree of transparency and a high gas and ultraviolet shielding property. It is intended to provide a film.

(Means for Solving the Problems) The problem is that at least one surface of a film made of a thermoplastic resin has a film forming property having a permacol value (π) defined by the following general formula of 75 ca / cc or more. A layer composed mainly of a resin (A) and titanium dioxide (B) having an average particle diameter of 200 nm or less and containing (B) / (A) in a weight ratio of 1/99 to 90/10 is used. This can be achieved by a laminated film formed.

(Where δ is the cohesive force of the polymer chain, fv is free volume) The substrate film used in the film laminate of the present invention is not particularly limited as long as it is a thermoplastic resin having a transparent film forming ability. , Polyethylene, polyolefin resins such as polypropylene, polyethylene terephthalate, polyethylene isophthalate, polyethylene 2,
6-naphthalate, polyester resins such as polybutylene terephthalate, polyamide resins such as nylon-6, nylon-6,6, and the like;
Vinyl resins such as polystyrene, poly (meth) acrylate, polyacrylonitrile, polyvinyl acetate, etc., polycarbonate, triacetate, cellophane, polyimide, polyphenylene sulfide, polyetherimide, polyether sulfone,
Unstretched films of polysulfone, polyetheretherketone, polyetherketoneketone, and many other resins alone, copolymers, mixtures, and composites, or oriented films stretched in uniaxial or orthogonal biaxial directions, etc. Can be mentioned.

Among them, films of biaxially stretched polypropylene, polyester, polyamide and the like are preferable in terms of transparency, mechanical strength, economy and the like.

The thickness of the film is not particularly limited.
To 250 μm, and the packaging material is particularly preferably 3 to 50 μm. The 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 consists of laminating a specific composition layer on at least one surface of such a thermoplastic resin film.

The titanium dioxide (A) used in the composition to be laminated on the surface has an average particle size of 20 as measured by an electron microscope.
It must be 0 nm or less. Preferably it is 100 nm or less. If it exceeds 200 nm, the effect of improving the gas barrier properties is reduced, and the transparency is undesirably deteriorated.

As long as the titanium dioxide satisfies the above particle size, its production method and shape are not limited. As the production method, chlorine method,
Any of conventionally known methods such as 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. A flat shape is particularly preferred. Composite particles composited with another metal oxide such as an alkali metal, an alkaline earth metal, and aluminum for preventing aggregation and the like are also included.

The titanium dioxide may be used as a powder, but it is preferable to use the titanium dioxide in a sol state since the titanium dioxide has an extremely fine particle size and a high cohesiveness, so that it is difficult to redisperse when powdered. 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. Also,
Use of a dispersing aid such as a surfactant or a polymer dispersant is not limited at all.

The resin (B) having a film forming property used in the present invention has a Permacol value [π, M. Salame; Future-Pack '85 Proceedings P199 (') defined by the following general formula.
85) See] 75ca / cc or more.

(Where δ is the cohesive force of the polymer chain, fv is free volume) Preferably, it is 80 ca / cc or more. If it is less than 75 ca / cc, 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. Even when these resins are used alone, an embodiment in which two or more kinds are blended is also included in the present invention.

In the present invention, in the compounding composition of the resin (A) having film-forming properties and the titanium dioxide (B), the compounding ratio is 1/99 to 90/10 by weight ratio of (B) / (A). And it is preferably 5/95 to 80/20.

If the ratio is smaller than 1/99, the effect of improving the gas and ultraviolet shielding properties is not sufficient, which is not preferable.

Conversely, if the ratio exceeds 90/10, the effect of improving the gas and ultraviolet shielding 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 compounding 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.

Further, the method of synthesizing (B) in the solution or dispersion of (A), or conversely, the polymerization of (A) in the sol of (B) is also effective in obtaining the blending effect. Recommended.

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.

The compounding composition further contains additives such as other metal oxide-based fine particles, a coloring agent, an antistatic agent, a blocking resistant agent, a lubricant comprising inorganic or organic fine particles, and an antioxidant, if necessary. It does not matter.

As a method of laminating the compound composition layer on the surface of the base film, a method in which the composition is formed into a film in advance and bonded to the base film, that is, a lamination method or an extrusion coating method in which the composition is melt-extruded into the base film. Alternatively, a known method such as a coating method of applying a solution or a dispersion of the composition to the surface of the substrate film can be used, but a method of drying and heat-treating after application to the surface of the substrate film by a coating method is most preferable. . Roll coating methods such as gravure and reverse, doctor knife method and air knife,
An ordinary method such as a nozzle coating method can be used.

The thickness of the composition layer to be laminated by such a method varies depending on the base film, the target level, and the like, but is usually 10 μm or less, preferably 5 μm or less in dry thickness.
It is desirably equal to or less than μ, most preferably equal to or less than 3 μ. There is no particular lower limit, but if it is 0.1 μm or less, it is difficult to obtain a substantially sufficient effect. Before performing the 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.

(Examples) Hereinafter, the present invention will be described 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)

25 ° C dry and 25 ° C in accordance with ASTM-D-1434-66
Measured at 80% RH.

(Haze)

 It was based on ASTM-D-1003-61.

(UV blocking)

The absorption spectrum of light was measured using a Hitachi V-3210 Model Recording Spectrophotometer, and the result was indicated by a transmittance of 350 nm.

Example 1 Copolymer polyester and trifunctional isocyanate were mixed in the same amount of methyl ethyl ketone / toluene at a ratio of 4: 1 by a roll coating method on a corona-treated surface side of a biaxially stretched polypropylene film having a thickness of 25 μm subjected to corona discharge treatment. 0.2 g as a coating amount after drying the solution dissolved in the solvent
/ m ² and dried.

The coated surface of the treated film has a polymerization degree of 300 and a saponification degree of 9
8.5% polyvinyl alcohol aqueous solution, average particle size 1.0
mm (measured with a transmission electron microscope) with a titanium dioxide water sol in a weight ratio of titanium dioxide / polyvinyl alcohol
Mix so that it becomes 1/1, apply the coating liquid uniformly dispersed using a high-pressure homogenous disperser by a roll coating method so that the coating amount after drying becomes 2.5μ, and after drying 130 ° C
For 2 minutes to obtain a laminated film.

The characteristics of the obtained laminated film are shown in Table 1, and the light absorption spectrum is shown in FIG.

The film obtained in this example is excellent in transparency and excellent in blocking oxygen gas and ultraviolet rays. Further, it can be seen from the light absorption spectrum that only the ultraviolet rays can be more efficiently blocked without lowering the transparency.

Comparative Example 1 Table 1 shows the properties of the laminated film obtained by the same method as in Example 1 except that the blending of titanium dioxide was stopped and only the aqueous solution of polyvinyl alcohol was used as the coating liquid. FIG. 1 shows the absorption spectrum.

The film obtained in this comparative example has good transparency, but is inferior in oxygen gas barrier properties and ultraviolet barrier properties under high humidity.

Comparative Example 2 Table 1 shows the properties of the laminated film obtained in the same manner as in Example 1, except that the blending of polyvinyl alcohol was stopped and only the aqueous sol of titanium dioxide was used as the coating liquid.

The film obtained in this example is excellent in the property of blocking ultraviolet rays, but is inferior in the property of blocking oxygen gas.

Comparative Example 3 Table 1 shows the properties of the biaxially stretched polypropylene film before lamination used in the method of Example 1. Although the film of this comparative example has good transparency, both the oxygen gas and the ultraviolet light have remarkably poor blocking properties.

Comparative Example 4 In the method of Example 1, the average particle size of titanium dioxide was set to 34.
A laminated film was obtained in the same manner as in Example 1 except that the thickness was set to 0 nm. The laminated film obtained in this comparative example was white, had extremely poor transparency, and had poor oxygen gas barrier properties under high humidity.

Example 2 In the method of Example 1, the base film was a 12 μm biaxially stretched polyester film, a polyvinylidene chloride copolymer resin was used as a film-forming resin, and the coating amount of the blend composition was 3.5 μm after drying. Other than changing
A laminated film was obtained in the same manner as in Example 1.

The film obtained in this example is also excellent in transparency and excellent in blocking oxygen gas and ultraviolet rays.

Comparative Example 5 The characteristics of the laminated film obtained by the same method as in Example 2 except that the blending of titanium dioxide was stopped and only the aqueous dispersion of the polyvinylidene chloride copolymer resin was used as the coating liquid. Are shown in Table 1.

Although the laminated film obtained in this comparative example has good transparency, it is inferior to the laminated film of Example 2 in the shielding property against oxygen gas and ultraviolet rays, and it can be seen that the compounding effect of titanium dioxide is remarkable. .

Example 3 In the method of Example 1, a copolymer resin of polyvinyl alcohol and polyvinylidene chloride (the ratio of polyvinyl alcohol units / polyvinylidene chloride units was 9/1 by weight) was used as the film-forming resin, and titanium dioxide was used. Table 1 shows the properties of the laminated film obtained by the same method as in Example 1 except that the ratio by weight to the film-forming resin was 1/3.

The laminated film obtained in this example is excellent in transparency and excellent in blocking oxygen gas and ultraviolet rays.

Comparative Example 6 Table 1 shows the properties of the laminated film obtained in the same manner as in Example 3, except that the blending of titanium dioxide was stopped.

Although the laminated film obtained in this comparative example has good transparency, it is inferior to the laminated film of Example 3 in the shielding property against oxygen gas and ultraviolet light, and it can be seen that the compounding effect of titanium dioxide is remarkable. .

Example 4 Using a 15 μm biaxially stretched film as a basic film,
A 1: 1 mixture (weight ratio) of polyvinyl alcohol and polyvinylidene chloride copolymer (weight ratio) and a 50: 1 nm titanium oxide mixed at a weight ratio of 1: 1 are laminated in the same manner as in Example 1. Table 1 shows the characteristics of the thus obtained laminated film.

The laminated film obtained in this example has excellent transparency,
Moreover, it is excellent in blocking properties of oxygen gas and ultraviolet rays.

Comparative Example 7 Table 1 shows the properties of the laminated film obtained in the same manner as in Example 4 except that the compounding of titanium dioxide was stopped.

Although the laminated film obtained in this comparative example has good transparency, it is inferior to the laminated film of Example 4 in the shielding property against oxygen gas and ultraviolet light, and it can be seen that the compounding effect of titanium dioxide is remarkable. .

(Effect of the Invention) As shown in the above examples, the method of the present invention is to provide a film which is transparent and has a gas and ultraviolet ray shielding property.
It can be widely used for packaging electric and mechanical parts.

[Brief description of the drawings]

FIG. 1 is an absorption spectrum diagram showing the light transmittance of the laminated films obtained by Example 1 and Comparative Example 1 of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-103440 (JP, A) JP-A-59-136332 (JP, A) JP-A-2-217245 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04

Claims (1)

(57) [Claims] 1. A film made of a thermoplastic resin, on at least one side of which is provided with a permacol value (π) defined by the following general formula:
(A) with film-forming properties of ≧ 75 ca / cc
And a layer composed mainly of titanium dioxide (B) having an average particle diameter of 200 nm or less, wherein a composition in which (B) / (A) is blended in a weight ratio of 1/99 to 90/10 is formed. Laminated film. (Where δ is the cohesive force of the polymer chain and fv is the free volume)