JPH0774281B2 - Gas barrier film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas barrier film used as a packaging material for packaging foods and drinks, pharmaceuticals, and other various articles.

[Prior Art] There are many foods and drinks, medicines, and the like that do not like oxygen and water, and a packaging material made of a gas barrier film that does not easily pass oxygen and water is used for packaging such foods. Conventionally, polyvinylidene chloride, ethylene-modified polyvinyl alcohol, aromatic nylon and the like have been used as gas barrier films.

However, although polyvinylidene chloride is excellent in oxygen and water barrier properties, it is inferior in extrusion stability at the time of production and there is a risk of causing pollution. Although ethylene-modified polyvinyl alcohol has a high oxygen barrier property when dried, it has a poor oxygen barrier property when wet (100% relative humidity) and also has a low water barrier property. Furthermore, aromatic nylon has the same drawbacks as ethylene-modified polyvinyl alcohol.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to provide a gas barrier which has good oxygen barrier properties and water barrier properties not only when it is dried but also when it is wet, and which is excellent in extrusion stability during production. It is to provide a transparent film.

[Means for Solving the Problems] As a result of earnest research, the inventors of the present invention have found that a film containing a certain proportion of poly-1,4-cyclohexylene dimethylene terephthalate (hereinafter sometimes referred to as PCT) in a liquid crystal polyester. However, they have found that they have high oxygen barrier properties and water barrier properties even when wet, and completed the present invention.

That is, the present invention comprises a liquid crystal polyester and 0.1 to 20% by weight of the film of poly-1,4-cyclohexylene dimethylene terephthalate, 30 ° C, 100R
Provided is a gas barrier film having an oxygen transmission rate in H% of 0.8 cc / m ² / day / 100 μm or less.

[Effects of the Invention] The gas barrier film of the present invention has excellent oxygen barrier properties and water barrier properties not only when dried but also when wet.
Furthermore, the gas barrier film of the present invention has excellent extrusion stability during production, that is, there is no width variation or surging when a polymer is extruded. Furthermore, the film has excellent film-forming properties and stretchability, that is, it is unlikely that tearing or uneven thickness occurs during extrusion or stretching. Furthermore, the film of the present invention has good thinning property during manufacturing and can be manufactured as a very thin film having a thickness of about 1 μm. Such a thin gas barrier film emphasizes transparency and flexibility. It is advantageous when it is used for an application and further for an inexpensive application such as a manufacturing price.

[Detailed Description of the Invention] As the liquid crystal polyester used in the gas barrier film of the present invention, for example, known liquid crystal polyesters described in US Pat. No. 4,552,948 can be used. That is, phenylenedioxydiacetic acid and terephthalic acid are used as the acid component, hydridoquinone, phenylhydroquinone, resorcin, or an aliphatic or alicyclic dialcohol having 8 or less carbon atoms, that is, ethylene glycol, 1, 4 -Butanediol, 1,4-cyclohexanedimethanol, propylene glycol, diethylene glycol, 2,2,4-trimethyl-1,3-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,2-diethyl -1,3-propanediol, 2,2-diethyl-1,3-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol,
2,2-diethyl-1,3-propanediol, 2-methyl-
2-propyl-1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 2, Examples of the polyester include 2,4,4-tetramethyl-1,3-cyclobutanediol, o-, m- or p-xylenediol.
In the phenylenedioxydiacetic acid which is one of the acid components, the position of the substituent bonded to the benzene ring may be any of ortho, meta and para. Further, the ratio of phenylenedioxydiacetic acid and terephthalic acid, which constitutes the acid component, is 5: 5 in molar ratio.
95 to 50:50 is preferred. Further, diphenyldicarboxylic acid or the like may be used as an acid as a copolymerization component, and as the diol component, hydroquinone, phenylhydroquinone and resorcin are preferable among the above-mentioned components. The diol component may be the above-mentioned one alone or 2
It is possible to employ a combination of two or more species. Further, components other than the above-mentioned acid component and diol component may be copolymerized as long as the effects of the present invention are not impaired. Furthermore, a monomer having both an acid and an alcohol, for example, paraoxybenzoate, oxynaphthalenecarboxylic acid or the like may be used as a copolymerization component.

The PCT used in the gas barrier film of the present invention is a polyester mainly containing 1,4-cyclohexanedimethanol as a glycol component and mainly terephthalic acid as a dicarboxylic acid component. The molecular weight is not necessarily high, but may be as low as about 2000, and generally the molecular weight is preferably about 2000-200,000. It is preferable that 90% or more of the glycol component is 1,4-polycyclohexanedimethanol for improving the oxygen barrier property when wet, and the same reason that 80 mol% or more of the acid component is terephthalic acid. Is preferred. However, if it does not adversely affect the effect of the present invention, a small amount, preferably 10 mol%
The following other glycol components may be included. Further, it may contain a small amount, preferably 20 mol% or less of other acid components. An acid component composed of 80 mol% PCT and 20 mol% isophthalic acid can be preferably used.

The content of PCT in the gas barrier film of the present invention is 0.1 to 20% by weight, preferably 0.5 to 10% by weight. When the PCT content deviates from this range, the oxygen barrier property when wet is impaired.

The gas barrier film of the present invention has an oxygen permeability of 0.8 cc / m ² · day / 100 μm or less at 30 ° C. and 100 RH%. If this oxygen permeability is greater than 0.8cc / m ² · day / 100μm,
The oxygen barrier property when wet is insufficient.

The thickness of the gas barrier film of the present invention is not particularly limited, but is usually 0.5 μm to 400 μm, preferably about 3 μm to 200 μm.

The gas barrier film of the present invention may contain, if necessary, additives such as stabilizers, lubricants and antistatic agents that are usually added to polyesters, in addition to the above liquid crystal polyester and PCT. Further, other polymers may be blended within a range that does not adversely affect the effects of the present invention.

The gas barrier film of the present invention may be non-oriented, but is preferably uniaxially or biaxially stretched from the viewpoint of gas barrier properties and mechanical strength.

The gas barrier film of the present invention is a liquid crystal polyester and PCT and optionally mixed with inert particles, additives, etc., melt-extruded using a melt extruder such as an extruder, cooled, and stretched. The film can also be formed by. The conditions for drying the polymer chips are not particularly limited, but normally 170 ° C. and about 3 hours are suitable. The extrusion temperature is not particularly limited, but is usually about 200 ° C to 360 ° C, preferably about 250 ° C to 340 ° C. Casting is preferably performed by an electrostatic application method, and the temperature of the casting drum is not particularly limited, but is usually 5 ° C to 60 ° C, preferably 15 ° C.
To 40 ° C. Further, stretching after cooling may or may not be carried out, but in the case of stretching, it is usually 70
C. to 150.degree. C., preferably 85.degree. C. to 120.degree. C., and usually a draw ratio of 2.5 to 6.0. After stretching, the film is preferably heat set, which is usually carried out at a temperature of 150 ° C. to 280 ° C., preferably 165 ° C. to 250 ° C. for usually 1 to 20 seconds, preferably 5 seconds to 15 seconds.

In addition, when laminating a gas barrier film on a polyolefin film, it can also be produced by co-extruding with a polyolefin having an adhesive layer, casting in a water tank, and then stretching and heat fixing.

Next, a method of measuring physical property values relating to the present invention and a method of evaluating the effects performed in the following examples will be described.

(1) Oxygen permeability According to ASTM D-3985, it is measured by a measuring instrument of Modern Control Co.

(2) Water vapor barrier property The smaller the water vapor permeability, the better the water vapor barrier property. The water vapor permeability is measured by the cup method at 40 ° C and 90RH% according to JIS Z-208.

(3) Extrusion Stability The width variation and the presence or absence of surging during melt extrusion of the polymer were observed. The thickness of the film at this time was kept constant at 15 μm.

Evaluation criteria ○: When the film has no width variation or thickness variation and can be stably formed for a long time. Δ: When the film formation is apparently stable with no width variation, but there is thickness variation X : When the width and thickness of the film fluctuate significantly and a uniform film cannot be obtained. (4) Stretchability The presence or absence of breakage during film stretching and the thickness unevenness were observed.

Evaluation Criteria ○: When a film having a uniform thickness without breaking even when stretched 3 times in the transverse direction at 85 ° C. to 120 ° C. Δ: Even if stretched 3 times in the transverse direction at 85 ° C. to 120 ° C. When the thickness unevenness is large, X: When the film cannot be stretched 3 times in the transverse direction at 85 ° C to 120 ° C (5) Thinning property While polymer is melt extruded from the die and drafted.
Molded by closely cooling to a 25 ° C cast drum.

Evaluation Criteria ○: When the obtained lower limit film thickness is less than 5 μm Δ: When the obtained lower limit film thickness is 5 μm to 100 μm X: When the obtained lower limit film thickness exceeds 100 μm [Examples] Hereinafter, the present invention Will be described more specifically based on Examples.
However, the present invention is not limited to the following examples.

Example 1 60 mol% of terephthalic acid and 40 mol% of paraphenylenedioxydiacetic acid as an acid component, and hydroquinone as a diol component were reacted at 290 ° C. for 3 hours by a conventional method to produce a liquid crystal polyester. On the other hand, according to a conventional method, 80 mol% of dimethyl terephthalate and 20 mol% of dimethyl isophthalate as acid components, 1,4-cyclohexanedimethanol as a diol component, and 0.05 mol% of titanium oxide to the acid component as a catalyst were used. Transesterification was carried out by heating in an autoclave with stirring, and then polycondensation was performed to obtain PCT.

A blend consisting of 90% by weight of the liquid crystal polyester and 10% by weight of PCT was melt extruded at 340 ° C., and cooled on a casting drum kept at 40 ° C. while applying an electrostatic charge to obtain an unstretched film. This unstretched film was stretched 3.5 times in a tenter at a temperature of 120 ° C. Both ends of the obtained uniaxially stretched film were held by clips and heat-treated at 270 ° C. for 5 seconds to obtain a film having a thickness of 10 μm.

The oxygen permeability and the water permeability of the obtained film at 30 ° C. and 100 RH% were measured. Furthermore, the extrusion stability, stretchability, and thinning property during manufacturing were evaluated. The results are shown in the table below.

As is clear from the table below, the gas barrier film of the present invention produced as described above is excellent in oxygen barrier property and water barrier property when wet, and further, extrusion stability during production, stretchability and thin film. It was also excellent in chemical conversion.

Comparative Example 1 A film was produced in the same manner as in Example 1 except that liquid crystal polyester containing no PCT was used as a raw material, and oxygen permeability and water permeability and extrusion stability at the time of production were prepared in the same manner as in Example 1. The stretchability and thinning property were evaluated. The results are shown in the table below.

As is clear from the table below, this film is excellent in oxygen barrier property when wet, but is slightly inferior in water barrier property, and is inferior in extrusion stability, stretchability and thinning property during production.

Comparative Example 2 A film was produced in the same manner as in Example 1 except that PET having an intrinsic viscosity of 0.65 was used instead of PCT, and oxygen permeability and water permeability and extrusion stability at the time of production were produced as in Example 1. The stretchability and thinning property were evaluated. The results are shown in the table below.

As is clear from the table below, this film has poor oxygen barrier properties when wet, water barrier properties, extrusion stability during production,
It is inferior in thinning property and slightly inferior in stretchability.

Claims (2)

[Claims] 1. A liquid crystal polyester and poly-1,4-cyclohexylene dimethylene terephthalate in an amount of 0.1 to 20% by weight of the film, and has an oxygen permeability of 0.8 cc / m ^{2 at} 30 ° C. and 100 RH%.・ Gas barrier film with a day / 100 μm or less. 2. The gas barrier film according to claim 1, wherein the liquid crystal polyester contains phenylenedioxydiacetic acid and terephthalic acid as main components as an acid component and hydroquinone, phenylhydroquinone or resorcin as a main component as a diol component.