JPS588985B2 - Curl-free gas barrier metallized film and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides gas barrier properties obtained by depositing metal on both sides of a specific saponified ethylene-vinyl acetate copolymer film.
This invention relates to a metal-deposited film that has excellent light-shielding properties and does not cause curling, and a method for producing the same.

In recent years, films made of saponified ethylene-vinyl acetate copolymers (hereinafter referred to as "saponified materials") with an ethylene content of 25 to 60 mol% and a saponification degree of 90% or more have been attracting attention as films with excellent gas barrier properties. However, since this single film does not have light-shielding properties, there is a risk that the contents may be deteriorated by light, especially when used for food packaging.

Furthermore, the gas barrier properties may be insufficient depending on the thickness, and gas barrier properties may also deteriorate due to moisture absorption, so it was urgent to take measures against these problems.

In view of these matters, the inventors of the present invention have conducted various studies and have focused on a technique of applying metal vapor deposition to a saponified material.

However, if only one side of the saponified film is metal vapor-deposited, a curl phenomenon will occur due to the hygroscopicity of the saponide, which poses a practical problem. As a result of intensive research to establish this technology, we have arrived at the present invention.

That is, the present invention provides a non-curling metallized film comprising a saponified ethylene-vinyl acetate copolymer film having an ethylene content of 25 to 60 mol% and a degree of saponification of 90% or more and a metallized layer provided on both sides, and the production thereof. In particular, this is a method for producing a metal-deposited film that does not curl, which is characterized by forming the saponified material into a film and then depositing metal on both sides of the film while maintaining a moisture-proof state.

The saponified product according to the present invention has an ethylene content of 25 to 60
mol%, preferably 30 to 50 mol%, saponification degree 90
% or more, preferably 95% or more.

Further, as the metal used for metal vapor deposition, aluminum is suitable, but other metals such as tin and zinc can also be used.

In the present invention, the moisture-proof state after forming the saponified material into a film must be such that the volatile content (water vapor) of the film is 1% or less, preferably 0.5% or less; Exposure to such temperature and humidity is undesirable because it causes uneven deposition, pinholes, bubbles, etc. in the metal deposition process.

In other words, when the saponified material enters the metal deposition process with moisture absorbed,
This is because moisture, moisture evaporation, etc. occur during the process and inhibit vapor deposition.

Regarding the maintenance of moisture-proof state, the degree of moisture absorption of saponified material is 2.
Since it is 0.3 to 0.5% at 0°C x 80% RH x 24H, it is sufficiently moisture-proof even if it is kept in a moisture-proof state after film formation and winding, and the moisture-proof state is removed when saponified material is attached to the feed roll before metal deposition. The moisture-proof state can be maintained and the effects of the present invention can be fully achieved.

Further, the moisture-proof state can be maintained in a preferable state by performing moisture-proof packaging, but it goes without saying that other appropriate methods can be applied.

In the present invention, the saponified film may be unstretched, or may be stretched in one or two axes, or it may be unstretched or uniaxially stretched, subjected to metal vapor deposition, and further stretched in one or two axes. It is also possible to produce stretched metallized films.

It can also be made heat-shrinkable, and its uses can be expanded depending on how these operations are performed.

In the present invention, the embodiments listed below may be adopted for the purpose of protecting the metal vapor deposited layer and improving the physical properties of the film such as strength and impact resistance.

(2) A metallized film in which a thermoplastic film is laminated on both sides of the metallized film of the present invention via an adhesive polyolefin resin layer.

The adhesive polyolefin resin used in this step 5 is a polyolefin such as polyethylene or ethylene-propylene copolymer, and an unsaturated carboxylic acid such as fumaric acid or maleic acid, or a derivative thereof, in an amount of 10-4 to 10% by weight, preferably. 1
Examples include modified polyolefin resins and ionomer resins obtained by graft copolymerization in a range of 0-3 to 5% by weight, and examples of thermoplastic resins include polyolefins such as polyethylene and polypropylene, polyamide resins, and the like.

Furthermore, when laminating, it is most preferable to carry out coextrusion and extrusion lamination.

Note that it is of course possible to use an appropriate adhesive instead of the adhesive polyolefin resin.

2) A metallized film obtained by laminating the thermoplastic resin on both sides of the metallized film of the present invention.

For this lamination, it is preferable to apply a melt extrusion lamination method.

In other words, the wetting tension of the metal (especially aluminum) vapor deposited surface is 40
It is about dynes/cm2 and can be directly extruded laminated without applying an anchor coat.

Incidentally, it is naturally possible to use the embodiments 1) and 2) above on each side of the metallized film, and to produce a metallized film using both methods in combination.

Furthermore, in order to improve the strength such as impact resistance and abrasion resistance of the saponified resin, the following embodiments may be adopted.

That is, it has two inner layers: a saponified layer and a polyamide resin layer such as nylon 6, nylon 6,6, or a copolymer thereof, and metal vapor deposited layers on both sides.

Note that the present invention is not limited to the above embodiments.

Next, examples of the present invention will be described.

Example 1 Ethylene content 40 mol%, saponification degree 90% or more, MI
:5.8, d:1.14 saponified ethylene-vinyl acetate copolymer A was extruded into a film with a thickness of 20μ at a T-die temperature of 240°C, and the film obtained by winding was made of polyethylene or the like. By using moisture-proof packaging sealed with a moisture-proof film, the volatile content (water vapor) of the saponified copolymer film was kept at 0.5% or less.

Immediately before carrying out the metal vapor deposition, the moisture-proof packaging was opened and a metal vapor deposited layer B of 0.03 μm thick made of aluminum was applied to both sides of the film A, thereby obtaining a metal vapor deposited film of the present invention.

Example 2 A laminated film obtained by coextruding nylon 6 resin and Admer resin (manufactured by Mitsui Petrochemical, adhesive polyolefin resin) on one side of the metallized film of Example 1, the Admer resin side was coextruded as described above. Then, a multilayer metal-deposited film was obtained by laminating the admer side of the film obtained by coextruding a polypropylene resin and an admer resin on the other side while carrying out the coextrusion.

This laminated structure is, from top to bottom, nylon 6-adhesive polyolefin-aluminum-saponified material-aluminum-adhesive polyolefin-polypropylene.

Example 3 Low density polyethylene (a:o.91s, MI:7)C was applied to both sides of the metallized film of Example 1 at a T-die temperature of 32
Extrusion lamination was carried out at 0° C. to a thickness of 20 μm, and the layers were immediately laminated under a Nippro roll pressure and a linear pressure of 10 kg/cm.

This metal vapor-deposited surface had a wetting tension of about 40 dynes/cm 2 and was sufficiently capable of extrusion lamination.

At this time, tensile speed 200mm/miA, 20℃
, the peel strength between B and C in the iso direction is 270g/
The value of 15 mm was practically satisfactory.

Comparative Example The saponified copolymer film in Example 1 was stored at 20° C. and 80% RH for one week without moisture-proof packaging, and one side of the film was subjected to aluminum metal deposition to obtain a metalized film.

The comparative data of Examples 1, 2.3 and Comparative Examples above are shown in the first section.
Shown in the table.

The methods for measuring the physical properties in the same table are as follows.

Measuring method Curl degree: How many times is it curled from one measurement to the other? Measure whether Lum is involved.

Oxygen permeability: ASTM-DI434.25℃, dry moisture permeability: JIS-Zo2o8 Impact resistance: Compliant with JIS-P8134 (23℃) Rub resistance Pull it out, release it, repeat this process, rub it with the corner of the cylinder, and measure the number of times until vacuum leaks.

As mentioned above, the metallized film of the present invention has oxygen permeability,
Since it has excellent moisture permeability, it is particularly suitable for use as a food packaging film.

In addition, since it has light-shielding properties, it not only prevents the contents from deteriorating due to light, but also prevents curling due to moisture absorption, making it convenient to handle and suitable for packaging, allowing for extremely beautiful packaging. .

Furthermore, no pinholes, bubbles, etc. were generated.

The metallized film of the present invention is particularly suitable for use in vacuum packaging, gas exchange packaging, fragrance packaging, spoilage prevention packaging for oil-based foods, oil-resistant packaging, deep drawing packaging, etc., and for BIB films, etc. It can be used for various purposes.

Note that although a film has been described above, even if the thickness is sheet-like, it naturally falls within the technical scope of the present invention.

Claims (1)

[Claims] 1. Ethylene content 25-60 mol%, saponification degree 90%
A non-curling, gas-barrier, metal-deposited film comprising a film made of the saponified ethylene-vinyl acetate copolymer and metal-deposited layers on both sides. 2 Ethylene content 25-60 mol%, saponification degree 90%
A method for producing a gas-barrier metal-deposited film that does not curl, characterized by forming a film of the saponified ethylene-vinyl acetate copolymer as described above, and applying metal vapor deposition on both sides of the film while maintaining a moisture-proof state after film formation.