JPS6341141A - Polyvinyl alcohol group resin film having excellent gas barrier property - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a polyvinyl alcohol-based U (fat film) having excellent gas barrier properties. The present invention relates to a transparent polyvinyl alcohol resin film with excellent properties.

``Conventional technology 1'' Plastic films used for packaging foods, pharmaceuticals, chemicals, etc. are made of materials with low permeability to gases such as water vapor and oxygen to prevent deterioration of the packaged contents. In the case of packaging materials that require even higher gas barrier properties, materials such as those made by laminating aluminum foil to a plastic film or those made by vapor-depositing aluminum on the surface of a plastic film have been used.

However, packaging materials using such metal foil are
Although it has excellent gas barrier properties against water vapor and oxygen, it has the disadvantage that it is opaque and the contents cannot be seen from the outside, making it unsuitable as a packaging material.

On the other hand, films of vinylidene chloride-based resins such as polyvinylidene chloride, copolymers containing vinylidene chloride as a main component and compounds copolymerizable with it, such as vinyl chloride, methyl acrylate, methyl methacrylate, acrylonitrile, etc.; Vinylidene chloride resin coated films, which are films made of polypropylene, polyester, polyamide, etc., coated with a copolymer, are also used as packaging materials with gas barrier properties. These polyvinyl chloride ↑j411? ? Although the film itself has gas barrier properties against water vapor and oxygen, these gas barrier properties are not sufficient and are unsuitable for packaging materials that require a high degree of gas barrier property. .

Furthermore, polyvinyl alcohol film, ethylene-
Polyvinyl alcohol based IIW films such as vinyl alcohol copolymer films have excellent oxygen barrier properties and are therefore widely used as packaging materials. However, this polyvinyl alcohol resin film has poor water vapor barrier properties6. Furthermore, under high humidity conditions, the oxygen barrier property also deteriorates. Therefore, when polyvinyl alcohol-based 1F* film is used as a packaging material, polypropylene film, polyethylene film, and polyester film are used.

A laminated film in which a film having a water vapor barrier property of 100% is laminated on a polyvinyl alcohol resin film is usually used. However, such laminated films cannot be used as packaging materials that require high gas barrier properties.
It has not been able to fully fulfill its function.

In addition, although the above laminated film has improved oxygen barrier properties to some extent under high humidity conditions, it is still not sufficient.

Therefore, in order to impart high gas barrier properties to such laminated films, the thickness of the laminated films must be increased. The disadvantage is that the properties of the material are impaired, and the preferred suitability as a packaging material is lost.

Several attempts have already been made to overcome the above drawbacks. For example, U.S. Patent No. 4.105,81
As shown in the specification of No. 8, it is known that a plastic film having a multilayer structure has improved gas barrier properties against carbon dioxide and carbon dioxide gas compared to the same film having the same thickness and -N structure. . however,
The films described herein are limited to multi-M films made of the same material, and their effect is merely to improve the barrier properties against oxygen and carbon dioxide gas.

The present inventors developed a transparent laminated film that improved the above drawbacks and filed a patent application (ulI 1986-222940
, patent application No. 6O-290246).

However, in order to impart excellent gas barrier properties to the transparent plastic films related to these applications, it is necessary to stretch them considerably, which not only increases the cost of manufacturing equipment but also requires advanced manufacturing technology. It had the disadvantage of becoming

``Problem 1 to be Solved by the Invention 1 In view of the current state of plastic film production, the present inventors have developed a plastic film that is transparent, has a high degree of spreadability, is inexpensive to produce, and has desirable performance as a packaging material. As a result of intensive studies, the present invention has been completed with the aim of providing the following.

[Means for Solving the Problems] Therefore, the gist of the fIS1 invention of the present invention is that a polyvinyl alcohol-based tH fat film containing 50 mol% or more of vinyl alcohol is used as a base film, and at least A polyvinyl alcohol fruit tree 111F film having excellent gas barrier properties is characterized in that one side is treated with an isocyanate compound or at least one side of the base film is coated with an isocyanate compound.

The gist of the second invention of the present invention is that the surface of the polyvinyl alcohol resin film according to the first invention that is treated with an isocyanate compound or the surface coated with an isocyanate compound has a transparent heat treatment film with excellent water vapor barrier properties. The present invention relates to a polyvinyl alcohol-based resin film with excellent gas barrier properties, characterized by being formed by laminating a plastic film.

The present invention will be explained in detail below.

In the film according to the present invention, a polyvinyl alcohol resin is used as a raw material resin.In the present invention, the polyvinyl alcohol resin film serving as a base material contains L (resin) containing polyvinyl alcohol in an amount of 50 mol% or more, preferably 70 mol% or more. Examples of such resins include polyvinyl alcohol 0, which is obtained by saponifying polyvinyl acetate, and ethylene-vinyl alcohol copolymer obtained by saponifying ethylene-vinyl acetate copolymer. can be given.

These base films may be manufactured from a raw resin by any known method such as a solution casting method, an extrusion method, and an inkjet method.

Polyvinyl alcohol fruit tree l11t that becomes the base film
The film may be an unstretched film, a pongee or a biaxially stretched film, but it is preferable to use a biaxially stretched film in the range of about 3×3 times in terms of film strength and gas barrier properties.

In the film of the first aspect of the present invention, at least one side of the base film is treated with an isocyanate compound, or at least one side of the base film is coated with an isocyanate compound.

The isocyanate compound refers to a compound containing an isocyanate group, and the isocyanate compound may be any of aliphatic isocyanates, aromatic isocyanates, monoisocyanates, diisocyanates, and triisocyanates. Preferred are aromatic diisocyanates.

To treat the surface of the base film with an isocyanate compound, the surface of the base film is exposed to an atmosphere of the isocyanate compound.

In order to apply the isocyanate compound to the surface of the base film, the isocyanate compound is used alone or mixed with other polymers or polyols in a solution, and the mixture is applied by roll coating or other known methods. Examples of solvents used in this case include ethyl acetate, alcohols, and carboxylic acids. These solvents are preferably dehydrated and do not contain water.

Examples of other polymers that can be mixed with the isocyanate compound include polybutanoene, polyisoprene, synthetic rubbers such as styrene-butadiene copolymers, polyvinyl chloride, polyvinylidene chloride, and the like.

Examples of polyols that can be mixed with isocyanate compounds include glycols such as ethylene glycol and butylene glycol, triols such as glycerin and trinotyolpropane, polyethylene glycol and polypropylene glycol, as well as relatively low molecular weight polyols having a hydroxyl group at the end. Examples include polyesters.

The isocyanate compound includes a base film and/*
It is preferable to add a small amount of tertiary amine such as N,N'-methylpiperazine, triethylamine, N-ethylmorpholine, etc. so as to quickly react with other compounds mixed with the isocyanate compound.

Base film surface treated with isocyanate compound,
Alternatively, a substrate film coated with an isocyanate compound surprisingly exhibits extremely excellent water vapor barrier properties.

Although the cause of this is unknown, it is thought to be due to the following mechanism. Polyvinyl alcohol type! The 14 Int film exhibits excellent gas barrier properties in a low-humidity atmosphere, but this deteriorates dramatically in a high-humidity atmosphere.

The reason for this is presumed to be that the 10H groups present in the polyvinyl alcohol resin film have a strong affinity for water or water vapor, causing a change in the molecular structure due to moisture absorption. When the surface of a base film of polyvinyl alcohol resin is treated with an isocyanate compound or coated with an isocyanate compound, the isocyanate compound reacts with the 10H groups present in the base film to form a urethane bond and release water or water vapor. This is thought to be because it reduces the chances of bonding.

When surface-treating a polyvinyl alcohol-based resin film as a base film with an isocyanate compound or applying an isocyanate compound thereto, the amount of the isocyanate compound should be sufficient for all of the base film cr and -OH groups to form urethane bonds. It is better to use quantity.

When treating the surface of the base film with an isocyanate compound or when applying the isocyanate compound to the surface of the base film, it is important to control the humidity of the atmosphere. This is because when the humidity of the atmosphere is high, inanate reacts with water in the atmosphere and does not react with the 10H groups on the surface of the base film. The preferred humidity of the atmosphere is 10%R.
H or less.

The object of the present invention is to produce a laminated M film in which a transparent thermoplastic resin film with excellent water vapor barrier properties is laminated on at least one side of a base film treated with an isocyanate compound or coated with an isocyanate compound as described above. The same can be achieved by

In the present invention, as another thermoplastic resin film that is transparent and has excellent water vapor barrier properties, based on ASTM F372 (temperature 40°C, relative humidity 90% (hereinafter referred to as 40°C x 90%
It is displayed as R1-1. ) The water vapor permeability (moisture permeability) under the conditions of 10g7m2・24hrs・20Jj or less, more preferably 2B/m2・24hrs・20
Examples of such films include polyvinylidene chloride, films made of vinylidene chloride iPSm resin such as vinylidene chloride-vinyl chloride copolymer,
Examples include films such as polytetrafluoroethylene, and vinylidene coated films coated with vinylidene chloride resin such as polyethylene film, polyethylene film, polyethylene terephthalate film, and nylon film.

When laminating other thermoplastic resin films onto the base polyvinyl alcohol-based #[It film, it is best to use an adhesive. Usable adhesives include urethane adhesives, acrylic adhesives, and polyester adhesives. Examples include adhesives. These adhesives are preferably used in a form dissolved in an organic solvent.The adhesives can be used on the surface of the base film treated with an isocyanate compound or on the surface coated with an isocyanate compound, or on the surface of other thermoplastic resin films to be laminated. Apply to either surface by roll coating, spraying, or other known methods. After the solvent component of the adhesive is volatilized, the film wound into a roll is unwound and stacked on the adhesive-coated surface, and the films are laminated while being pressed with a roll.

The thickness of the polyvinyl alcohol resin film according to the present invention can be selected depending on the application from the viewpoint of gas barrier properties, strength, flexibility, and economical efficiency, but is more preferably 10 to 500 μm. The thickness is preferably 12 to 100 μm, more preferably 12 to 100 μm.

The thickness of the thermoplastic #tFMy film having excellent water vapor barrier properties and the polyvinyl alcohol resin film serving as the base film may be appropriately selected so that the thickness of the polyvinyl alcohol resin film falls within the above range.

[Effect of the invention] The polyvinyl alcohol resin film according to the invention has the following properties:
It has excellent transparency, exhibits extremely high gas barrier properties, is flexible, and is excellent in terms of strength and economy.

Therefore, it can be used in a wide range of applications, including packaging materials for foods, medicines, chemicals, etc., and as packaging materials that require a high degree of elasticity, and its industrial utility value is extremely large.

“Example J The present invention will be explained in detail below based on Examples and in contrast with comparative examples, but the present invention is limited to the following Examples unless the gist of the invention is exceeded. isn't it.

In addition, in the following example, the water vapor permeability (moisture permeability) is A
Based on STM F372, it was measured under the conditions of 40°C x 90% RH, and the oxygen permeability was 30% using Modern Control's 0X-TRANloo.
It was measured under the conditions of ℃ x 80% RH.

In all examples, the lamination method was a dry lamination method using an acrylic adhesive.

The transparency of the f*M film was evaluated by observing the laminated film with the naked eye.

Example 1 Vinyl furfur content 99 mol%, 31 elongation (t13×
Polyvinyl alcohol (hereinafter referred to as PVA) with a thickness of 3 times and 18μ
That's what it means. ) prepared the film. R-
The solution was applied in an atmosphere at a temperature of 20° C. and a relative humidity of 50%, and the coated surface was heated at 80° C. for 3 minutes to volatilize the solvent to obtain a film coated with an isocyanate compound.

The water vapor permeability and oxygen permeability of the obtained film were measured. The results are shown in Table 1.

Comparative Example 1 In the example described in Example 1, no isocyanate compound was applied to the film surface.

The water vapor permeability and oxygen permeability of this film were measured. The results are shown in Table 1.

Example 2 According to the example described in Example 1, a film coated with triphenylmethane triisocyanate on one side was produced.

On the side of this film coated with the isocyanate compound,
An acrylic adhesive is applied to a thickness of 5μ, and on this adhesive layer, polyvinylidene chloride is applied to a thickness of 2μ on one side of a two-wheel stretched polypropylene film (this film is referred to as KOPP).

The total thickness is 20μ, and the water vapor transmission rate of this film is 2.0
11/m2・24hrs・20μ. ) were laminated to obtain a laminated polyvinyl alcohol resin film.
The water vapor permeability and oxygen permeability of this MtN polyvinyl alcohol resin film were measured. The results are shown in Table 1.

Example 3 A laminated polyvinyl alcohol resin film was obtained in the same manner as in Example 2, except that the isocyanate compound was replaced with di-7enylmethane diisocyanate.

The water vapor permeability and oxygen permeability of this film were measured. The results are shown in Table 1.

Comparative Example 2 A laminated polyvinyl alcohol lJf resin film was obtained in the same manner as in Example 2, except that no isocyanate compound was applied.

The water vapor permeability and oxygen permeability of this film were measured. The results are shown in Table 1.

Comparative Example 3 In the example described in Example 2, the base film was made of an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) having a vinyl alcohol content of 40 mol %, a stretching ratio of 3×3 times, and a thickness of 18 μm. A laminated film was obtained in the same manner as in the same example except that the film was replaced with a film.

Regarding this laminated film, water vapor permeability and Fi1
m transmittance was measured. The results are shown in Table 1.

Comparative Example 4 In the example described in Example 2, instead of KOPP, a thickness of 2
A multilayer N film was obtained in the same manner as in the same example except that a 0μ low density polyethylene film (the water vapor permeability of this film is 24 g/m 2 ·LI + rs · 20μ) was used.

The water vapor permeability and oxygen permeability of the second 81N film were measured. The results are shown in Table 1.

From Table 1, the following is clear.

(1) Polyvinyl alcohol films coated with an isocyanate compound have lower water vapor permeability and oxygen permeability than those without the coating.
It shows a low level value (see Example 1 and Comparative Example 1).

(2) When an isocyanate compound is coated on the surface of a polyvinyl alcohol film and a film with excellent water vapor barrier properties is laminated on this coated surface, the water vapor permeability,
Both oxygen permeability values are extremely low (Example 2,
(See Example 3).

(3) Laminated film in which no isocyanate compound is applied to the surface of the polyvinyl alcohol film (Comparative Example 2),
An 81-layer film based on EVOH film with a low vinyl alcohol content (Comparative Example 3) and a laminated film in which the water vapor barrier properties of the laminated films are not good even if an isocyanate compound is applied to the surface of the polyvinyl alcohol film (Comparative Example 3) 4) are both water vapor transmission rate,
It is not as good as the films of Examples 2 and 3 in terms of oxygen permeability.

Claims (3)

[Claims] (1) A polyvinyl alcohol resin film containing 50 mol% or more of vinyl alcohol is used as a base film,
A polyvinyl alcohol resin film having excellent gas barrier properties, characterized in that at least one side of the base film is treated with an isocyanate compound, or at least one side of the base film is coated with an isocyanate compound. (2) A polyvinyl alcohol resin film containing 50 mol% or more of vinyl alcohol is used as a base film,
At least one side of this base film is treated with an isocyanate compound, or at least one side of this base film is coated with an isocyanate compound, and the side treated with the isocyanate compound or the side coated with the isocyanate compound is made transparent. A polyvinyl alcohol resin film with excellent gas barrier properties, which is made by laminating thermoplastic resin films with excellent water vapor barrier properties. (3) A thermoplastic film that is transparent and has excellent water vapor barrier properties has a water vapor transmission rate of 10 g/m^2・24 hrs. at a temperature of 40°C and a relative humidity of 90%. The polyvinyl alcohol resin film having excellent gas barrier properties as set forth in claim (2), characterized in that the film is selected from those having a particle diameter of 20 μm or less.