JPH04270650A - Gas barrier-type film - Google Patents

Abstract

PURPOSE:To provide a film laminate with high transparency and excellent shielding properties against has such as hydrogen gas. CONSTITUTION:A gas barrier-type film is composed of a blended composition of film-forming resin with specific permachor value and kaolinite laminated at least, on one surface of a film of thermal plastic resin.

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 which is suitable as a packaging material and has excellent barrier properties against gases such as oxygen, nitrogen and carbon dioxide, and excellent transparency.

[0002] Conventionally, films made of thermoplastic resins such as polyolefin, polystyrene, polyvinyl chloride, polyester, and polyamide, particularly films made of oriented polypropylene, polyester, and polyamide, have excellent mechanical properties, heat resistance, It has transparency and is widely used as a packaging material. However, when these films are used for food packaging, their gas permeability is too high, so their oxygen barrier properties are insufficient, and the contents are susceptible to deterioration due to oxidative deterioration or aerobic microorganisms. , usually a method such as laminating other film layers with good oxygen barrier properties is often used. The most typical method is to laminate a metal foil such as aluminum or to vapor-deposit such a metal on the surface of the thermoplastic resin film, which makes effective use of its excellent gas barrier properties, especially oxygen barrier properties. has been done.

[0003] However, these aluminum laminates and vapor-deposited films are opaque and have the disadvantage that the contents cannot be seen when food is packaged using them. Coupled with the trend toward fashion, the demand for transparent films with excellent gas barrier properties is increasing. On the other hand, various transparent plastic film materials with low gas permeability have been known, such as films made of polyvinyl alcohol, polyethylene vinyl alcohol, and polyvinylidene chloride resins. However, when used alone, these films have insufficient physical properties such as strength, elongation, water resistance, and heat resistance compared to oriented films such as polypropylene, polyester, and polyamide.
In particular, polyvinyl alcohol, polyethylene vinyl alcohol, etc. are highly hygroscopic, making it difficult to handle as the end surfaces of the rolled film become petal-like due to moisture absorption, and the gas barrier properties, which are the objective, are significantly reduced due to moisture absorption. It will drop.

[0004] Therefore, these films cannot be used alone as packaging material films;
Currently, these films with a thickness of about 0 to 40 μm are laminated together with the polypropylene film, polyester film, etc., and used. Moreover, these films are expensive even when used alone, and when multi-layered, not only do they become even more expensive, but the total layer thickness also becomes extremely thick, making it difficult to obtain a high degree of transparency. There are other problems. In addition, the level of gas barrier properties obtained by these films is still not sufficient compared to the previous aluminum laminated film, so we developed a new film with high transparency and high gas barrier properties.
The reality 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 coating oriented polypropylene, polyester, polyamide, etc. with a barrier resin such as polyvinyl alcohol, polyethylene vinyl alcohol, polyvinylidene chloride, etc. is also being considered. However, although polyvinyl alcohol and polyethylene vinyl alcohol have excellent gas barrier properties under low environmental humidity, they have the problem that their gas barrier properties are significantly lower than their hygroscopic properties under high environmental humidity. . Furthermore, although the gas barrier property of polyvinylidene chloride does not depend on environmental humidity, it cannot be said to be sufficient and is currently used by increasing the coating thickness. However, its level of gas barrier properties is still insufficient and is only far from the level of aluminum vapor deposition.

[0006]

[Problems to be Solved by the Invention] The present invention attempts to solve the above-mentioned conventional problems, and its purpose is to simultaneously provide a high degree of gas barrier property and a high degree of transparency that are not easily affected by humidity. The objective is to provide a plastic film that is satisfactory, does not require multi-layering such as lamination, and is excellent in handling and economy.

[0007]

[Means for Solving the Problems] That is, the gas barrier film of the present invention has a permacol value (
A composition consisting of a resin (A) having film-forming properties with π) of 75 cal/cc or more and kaolinite (B), the weight ratio of (B)/(A) being 1/99 to 90/ 1
This is a gas barrier film in which a layer is formed of a composition blended so that

The base film used in the gas barrier film of the present invention is not particularly limited as long as it is a thermoplastic resin that has the ability to form a transparent film, but polyolefin resins such as polyethylene and 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, polyamide resins such as polymethaxylylene adipamide, polystyrene, poly(
Vinyl resins such as meth)acrylic acid esters, polyacrylonitrile, polyvinyl acetate and their copolymers, polycarbonate resins, cellulose resins such as cellophane and acetate, and polyimides, Unstretched products made of simple substances, copolymers, mixtures, and laminates of polyetherimide, polyphenylene sulfide, polyethersulfone, polysulfone, polyetherketone, polyetherketoneketone, fluorine-containing polymers, and many other resins. Alternatively, an oriented film stretched in one axis or two orthogonal directions can be used. In particular, from the perspective of the present invention, the base film may be a biaxially stretched film of polypropylene, polyester, polyamide, etc. from the viewpoint of heat resistance to dimensional change, mechanical strength, moldability, and economical efficiency. suitable.

[0009] Although the thickness of the film is not particularly limited,
Normally it is 1 to 250 μm, and as a packaging material it is 3 to 5 μm.
Particularly preferred is 0 μm. This base film may be a single film or a composite multilayer film, and the combination method and number of layers in the multilayer film are arbitrary.

The essence of the present invention is that a layer of a specific composition is laminated on at least one side of such a thermoplastic resin film. Kaolinite (B) used in the compounded composition to be laminated on the surface is also called kaolin, and refers to an aluminosilicate as described in, for example, "Chemistry Dictionary" published by Kyoritsu Shuppansha. do. The basic chemical formula is Al2 Si2 O5 (OH)4, and the shape is generally hexagonal plate-like or irregular hexagonal, but special products such as spherical shapes may also be used. Further, a tubular hallosite type may also be used. The kaolinite (B) is
It may be a natural product or a synthetic product. Further, a fired product may also be used. The particle size of the kaolinite (B) is preferably one in which the average particle size measured with an electron microscope is 2 μm or less. If the average particle size exceeds 2 μm, the effect of improving gas barrier properties will be reduced, and transparency will also be reduced, which is not preferable.

It is extremely important that the kaolinite (B) has good dispersibility within the laminated layers. There are no particular limitations on the means to improve this dispersibility, but for example, it is effective to use kaolinite purified by a deionization method, or to use kaolinite that has been surface-treated to improve dispersibility. It is. Furthermore, in order to improve the dispersibility, it is preferable to use the material after dispersion treatment as a sol rather than using it directly as a powder. There is no limitation on the means for making the sol, and various dispersion means can be used as desired. Furthermore, there is no limit to the use of a dispersion aid such as a surfactant or a polymer dispersant at the time of sol formation.

The film-forming resin (A) used in the present invention has a permacol value [π
,M. Salame; Futur-Pack. '85
Refer to Proceedings P119 ('85)] must be 75 Cal/c.c or more. Preferably, it is 80 Cal/cc or more. 75Cal/c
- If it is less than c, the effect of imparting gas barrier properties will be reduced, which is not preferable. Examples of resins that satisfy these characteristics include polyvinylidene chloride resins, polyacrylonitrile resins, and polyvinyl alcohol resins. These resins may be used alone or in combination of two or more.

[0013] In the present invention, in the blended composition of the film-forming resin (A) and kaolinite (B),
The blending ratio is 1/99 to 90 (B)/(A) weight ratio
/10, and preferably 5/95 to 80/20. If the ratio is smaller than 1/99, the effect of improving gas barrier properties will not be sufficient, which is not preferable. On the other hand, if it exceeds 90/10, the effect of improving gas barrier properties will be saturated and the strength and flexibility of the film will decrease, which is not preferable. Although any known mixing method can be used to obtain the composition consisting of (A) and (B), it is possible to obtain the mixing effect of (A) and (B) most effectively. In order to achieve this, it is a preferred embodiment to mix a solution or a dispersion of (A) in a solvent and a sol, which is a dispersion of (B) in a solvent. The solvent is not particularly limited, but from the viewpoint of safety, an aqueous solvent is preferred. Also, (A)
A method of synthesizing (B) in a solution or dispersion of (B) or, conversely, polymerizing (A) in a sol of (B) is also recommended as a method of enhancing the effect of blending the two. The means for mixing is also not limited, and any known methods such as high-speed stirring, high-pressure dispersion, and ultrasonic dispersion can be used. A combination of these methods is also suitable. The blended composition includes:
In addition, other metal oxide particles, colorants,
Additives such as antistatic agents, antiblocking agents, lubricants made of inorganic or organic fine particles, and antioxidants may be included.

[0014] Methods for laminating the blended composition layer on the surface of the base film include a method in which the composition is made into a film in advance and laminated onto the base film, that is, a lamination method, and an extrusion coating method in which the composition is melt-extruded onto the base film. A known method may be used, such as a method or a coating method in which a solution or dispersion of the composition is applied to the surface of the base film. The most preferred method is to apply the coating onto the surface of the base film, followed by drying and heat treatment. As a coating method, a conventional method such as a roll coating method such as gravure or reverse, a doctor knife method, an air knife method, 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 base film, the desired level, etc., but is usually 10μ or less, preferably 5μ or less, and most preferably 3μ or less in dry thickness. It is desirable that there be. Although there is no particular lower limit, if it is 0.1 μ or less, it is difficult to obtain substantially sufficient effects. Note that, before performing 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.

[0015]

[Examples] The present invention will be described below with reference to Examples. In addition, unless otherwise specified, the concentration in the examples is based on weight, and the evaluation was performed according to the following method. (Oxygen permeability) Measured in accordance with ASTM-D-1003-61 at 25° C. dry and at 25° C. and 80% RH. (Haze) Based on ASTM-D-1003-61.

Example 1 A copolymerized polyester and a trifunctional isocyanate were coated with methyl ethyl ketone/toluene in a ratio of 4:1 on the corona-treated side of a biaxially stretched polypropylene film having a thickness of 25 μm that had been subjected to a corona discharge treatment. The coating amount after drying of the solution dissolved in an equal amount of mixed solvent is 0.
．． It was coated at a weight of 2 g/m2 and dried. The coated surface of the treated film has a polymerization degree of 300 and a saponification degree of 98.5.
% aqueous solution of polyvinyl alcohol and an aqueous sol of hexagonal plate-shaped natural kaolinite with an average particle size of 1.0 μm purified by deionization method at a weight ratio of kaolinite/polyvinyl alcohol of 0.1/0. The coating solution was mixed so as to have a coating weight of 2.5 μm after drying, and the coating solution was uniformly dispersed using a high-pressure homogenizing type dispersing machine using a roll coating method.
After coating and 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. The laminated film obtained in this example has excellent transparency and oxygen gas barrier properties.

Comparative Example 1 In the method of Example 1, the addition of kaolinite was stopped,
In addition to using only polyvinyl alcohol aqueous solution as the coating liquid,
Table 1 shows the properties of the laminated film obtained by the same method as in Example 1. Although the laminated film obtained in this comparative example has good transparency, it has poor oxygen gas barrier properties under high humidity. Comparative Example 2 Table 1 shows the properties of a laminated film obtained in the same manner as in Example 1, except that the blending of polyvinyl alcohol was stopped and only the kaolinite aqueous sol was used as the coating liquid.
Shown below. The laminated film obtained in this comparative example has poor oxygen gas barrier properties. Comparative Example 3 Table 1 shows the properties of the biaxially stretched polypropylene film used in the method of Example 1 before lamination. Although the film of this comparative example has good transparency, its oxygen gas barrier properties are significantly inferior.

Example 2 The same method as in Example 1 was used except that the average particle size of deionized and purified kaolinite and the blending ratio of kaolinite and polyvinyl alcohol were changed as shown in Table 1. Table 1 shows the properties of the obtained laminated film. The laminated film obtained in this example also has excellent transparency and oxygen gas barrier properties. Example 3 In the method of Example 1, a 12 μm biaxially stretched polyester film was used as the base film, a polyvinylidene chloride copolymer resin was used as the film-forming resin, and the composition ratio was as shown in Table 1. After drying, reduce the amount of application to 3.
．． Table 1 shows the properties of the laminated film obtained in the same manner as in Example 1 except that the thickness was changed to 5 μm. The laminated film obtained in this example also has excellent transparency and oxygen gas barrier properties.

Comparative Example 4 By the method of Example 3, the addition of kaolinite aqueous sol was stopped,
Table 1 shows the properties of a laminated film obtained in the same manner as in Example 3, except that only the aqueous dispersion of polyvinylidene chloride copolymer resin was used as the coating liquid. It can be seen that the laminated film obtained in this comparative example had inferior oxygen gas barrier properties under high humidity compared to the laminated film of Example 3, and that the effect of blending kaolinite was remarkable.

Example 4 In the method of Example 1, a copolymer resin of polyvinyl alcohol and polyvinylidene chloride (
Table 1 shows the properties of a laminated film obtained in the same manner as in Example 1, except that the ratio of polyvinyl alcohol units to polyvinylidene chloride units was 9/1 by weight. The laminated film obtained in this example also has excellent transparency and oxygen gas barrier properties.

Comparative Example 5 Table 1 shows the properties of a laminated film obtained in the same manner as in Example 3, except that the addition of the kaolinite aqueous sol was stopped. It can be seen that the laminated film obtained in this comparative example has inferior oxygen gas barrier properties under high humidity compared to the laminated film of Example 4, and that the effect of incorporating kaolinite is significant.

Example 5 In the method of Example 2, poly(ethylene vinyl alcohol) copolymer was used instead of polyvinyl alcohol as the film-forming resin, and the coating amount of the blended composition was changed to a thickness of 3.5 μm after drying. Table 1 shows the properties of the laminated film obtained in the same manner as in Example 2 except for the following changes. The laminated film obtained in this example also has excellent transparency and oxygen gas barrier properties. Comparative Example 6 Table 1 shows the properties of a laminated film obtained in the same manner as in Example 5 except that the addition of the kaolinite aqueous sol was stopped. It can be seen that the laminated film obtained in this comparative example has inferior oxygen gas barrier properties under high humidity compared to the laminated film of Example 5, and that the effect of incorporating kaolinite is significant.

Example 6 A 15 μm biaxially stretched nylon film was used as the base film, and a 1:1 mixture (weight ratio) of polyvinyl alcohol and polyvinylidene chloride copolymer was used as the film-forming resin.
Table 1 shows the properties of a laminated film obtained in the same manner as in Example 3, except that . The laminated film obtained in this example also has excellent transparency and oxygen gas barrier properties.

Comparative Example 7 Table 1 shows the properties of a laminated film obtained in the same manner as in Example 6, except that the addition of kaolinite was omitted. It can be seen that the laminated film obtained in this comparative example has inferior oxygen gas barrier properties under high humidity compared to the laminated film of Example 6, and that the effect of incorporating kaolinite is remarkable.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

Effects of the Invention As shown in the examples above, the method of the present invention provides a film that is transparent and has a high degree of gas barrier property, and can be used for food packaging, aseptic packaging for drugs and medical instruments, and for electrical appliances. It can be widely used for packaging machine parts, etc.

Claims (1)

[Claims] [Claim 1] A resin (A) having film-forming properties having a permacol value (π) defined by the following general formula of 75 cal/cc or more and kaolinite on at least one side of a base film made of a thermoplastic resin. (B) and a composition consisting of (B) and a composition consisting of (B)/(A) in a weight ratio of 1/99 to 90.
A gas barrier film formed with a layer made of a composition blended so as to have a ratio of 10 to 10. [Equation 1] (Here, δ is the cohesive force of the polymer chain, fv is the free volume)