JP2001293833A - Gas barrier polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier polyester film which shows transparence, an excellent gas barrier porperty to steam and oxygen and excellent durability and is suitable for a packaging film for food, a medicine, a precision electronic component and the like. SOLUTION: A gas barrier polyester film with a coated layer is obtained by coating at least one surface of a polyester film with a coating liquid containing a crystalline polymer resin, drying, stretching and further heat- treating it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas barrier polyester film, and more particularly, it has transparency,
The present invention relates to a gas barrier polyester film which is excellent in gas barrier properties against water vapor and oxygen and has excellent durability and is suitable as a packaging film for foods, medicines, precision electronic parts and the like.

[0002]

2. Description of the Related Art Packaging films used for foods, pharmaceuticals, precision electronic parts, etc., are required to have high transparency for the visibility and aesthetics of the contents, and to deteriorate due to moisture absorption and oxidation of the contents. In order to prevent the intrusion of outside air, especially water vapor, oxygen, etc., a gas barrier property is required in order to prevent the occurrence of air and long-term storage.

As the packaging film, a film made of a resin having both a gas barrier property and a self-supporting property, a film provided with a resin having a gas barrier property having no self-supporting property on a base film, or a base material made of an inorganic compound is used. A film provided on a film by vapor deposition, sputtering, or the like has been studied or used.

[0004] A film made of a resin having both gas barrier properties and self-supporting properties requires a special raw material, so that the cost is high and there is a practical problem.

As a resin having a gas barrier property provided on a substrate film, for example, a laminate of polyvinylidene chloride having a good gas barrier property on a substrate film has been conventionally used in a large amount. There is a concern that harmful gas such as dioxin may be generated, so that a laminate of a saponified ethylene-vinyl acetate copolymer or a polyamide has come to be used as a substitute. However, these films are insufficient in gas barrier performance as compared with films using polyvinylidene chloride, and a solution is desired.

Further, a film in which an inorganic compound is provided on a base film by vapor deposition, sputtering, or the like requires complicated equipment and has a problem that productivity is low.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a gas barrier film having high gas barrier properties as a substitute for polyvinylidene chloride and having good productivity. is there.

[0008]

An object of the present invention is to provide a coating layer obtained by applying a coating solution containing a crystalline polymer resin on at least one side of a polyester film, drying, stretching, and further performing a heat treatment. The problem can be solved by using a gas barrier polyester film.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[Polyester] In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

Specific examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), and polyethylene-2,6-naphthalate. Among these, polyethylene terephthalate is preferred because of its good self-supporting property as a base film, and
Polyethylene-2,6-naphthalate is more preferred because it has good gas barrier properties in addition to the self-supporting properties of the base film.

The polyester in the present invention may be a copolymer of the above polyesters, or a mixture of polyesters or a mixture of polyester and a small proportion of another resin.

The polyester in the present invention contains an inorganic or organic lubricant such as silicon dioxide, calcium carbonate, kaolin, or silicone particles having a particle size of 0.1 to 5 μm in an amount of 0.0 to 5.0 μm.
It is preferably contained in an amount of 3 to 3.0% by weight, and 0.1% by weight.
More preferably, it is contained in an amount of 1.0 to 1.0% by weight. By adding these lubricants to the polyester, a polyester film having a surface center line roughness of 0.001 to 5 μm can be obtained. If the center line roughness of the film surface is smaller than 0.001 μm, sufficient slipperiness cannot be obtained, and the film cannot be wound up or the films adhere to each other, which is not preferable.
If the center line roughness of the surface is larger than 5 μm, when used as a packaging material, a logo of a product is printed on the surface, but it is not preferable because it cannot be printed clearly.

The polyester used in the present invention may contain a stabilizer, a colorant, an antioxidant, and other additives as needed, so long as the original performance is not impaired.

Further, in order to further enhance the gas barrier property, it is possible to laminate with another film material, for example, polyethylene, polypropylene, nylon or the like.

[Crystalline Polymer Resin] In the present invention, the crystalline polymer resin contained in the coating layer is a polymer resin whose molecules can have a crystal structure, and the temperature and the stretching temperature at the time of forming a polyester film. It is preferable that the polymer resin is a polymer resin in which at least some of the molecules crystallize under film forming conditions such as the above.

The crystalline polymer resin in the present invention is preferably a resin containing any one of polyvinyl alcohol, nylon, polyalkylene glycol, and polyalkylene, and particularly preferably a resin containing polyvinyl alcohol. These resins crystallize under the conditions for forming a polyester film, and have excellent gas barrier properties. In order to impart good gas barrier properties, the degree of crystallization of the crystalline polymer resin contained in the coating layer by stretching and heat treatment is preferably 10% or more in terms of crystallinity. The crystallinity is more preferably at least 20%, particularly preferably at least 50%.

The maximum crystallinity of the crystalline polymer resin in the coating layer can be maximized by stretching the coating layer at a temperature lower than the melting point of the crystalline polymer resin. For example, polyvinyl alcohol obtained as an industrial product has a melting point of about 2
By stretching at a temperature lower than 10 ° C., a high crystallinity can be obtained. If polyvinyl alcohol is used in the form of denatured or low tacticity,
Since the melting point is higher than 210 ° C., even when polyethylene-2,6-naphthalate, which has a high heat setting temperature, is used as the polyester, the polyvinyl alcohol in the coating layer can be processed to have a high crystallinity.

The resin containing polyvinyl alcohol is not particularly limited as long as it has a vinyl alcohol unit as a main component, but a resin having a vinyl alcohol unit content of 50 mol% or more is preferable. Examples of the component other than the vinyl alcohol unit of the resin containing polyvinyl alcohol include vinyl acetate, vinyl butyral, vinyl acetal, N-vinylacetamide, polyethylene, and polypropylene.

As the resin containing polyvinyl alcohol, an ethylene-vinyl alcohol copolymer is particularly preferred. The degree of saponification of the polyvinyl alcohol of this copolymer is preferably from 80 to 99.9 mol%, more preferably from 90 to 99.5 mol%. If the saponification degree is lower than the above range, the gas barrier property tends to deteriorate. The degree of polymerization of polyvinyl alcohol is preferably from 50 to 20,000, more preferably from 100 to 10,000 from the viewpoint of the degree of crystallization and handling during coating.

As the nylon used for the crystalline polymer resin, nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 6/66, nylon 66/610, nylon MXD6 and the like can be mentioned.

Examples of the resin containing a polyalkylene glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and a polyethylene glycol-polypropylene glycol copolymer. In addition, polyether dicarboxylic acids such as polyoxyethylene dicarboxylic acid and polyoxytetramethylene dicarboxylic acid whose terminals have been modified to carboxylic acids can also be mentioned. The molecular weight of the polyalkylene glycol is preferably from 50 to 10,000. A particularly preferred polyalkylene glycol is polyethylene glycol.

Examples of the resin containing polyalkylene include polyethylene, polymethylene and the like.

The crystalline polymer resin in the present invention may be a mixture of two or more of the above resins. Further, the resin may be a mixture of resins such as polyester, acrylic and urethane, or may be a copolymerized resin.

[Polyester Film] The gas-barrier polyester film of the present invention is obtained by applying a coating solution containing a crystalline polymer resin to at least one surface of the polyester film before the completion of the crystal orientation, drying, stretching and further heat-treating. It can be obtained by providing a coating layer obtained by the above method.

The polyester film used in the present invention can be obtained, for example, by the following method. The polyester is melt-extruded into a film, wound around a casting drum, cooled and solidified to form an unstretched film. This unstretched film is treated with Tg of polyester (Tg + 6
0) Heating in the range of ° C. (Tg is the secondary transition temperature of polyester) and stretching in the longitudinal direction once or twice or more, so that the total stretching ratio becomes 3 to 7 times. Then Tg
(Tg + 60) ° C., stretching is performed so that the stretching ratio in the width direction becomes 3 to 5 times, and then 0.1 to 1 at 200 to 250 ° C.
Heat treatment is performed for 0 second, and re-heat treatment is performed at a temperature lower by 10 to 20 ° C. than the heat treatment temperature while contracting or elongating 0 to 20% in the width direction.

The thickness of the polyester film used in the present invention is not particularly limited as long as it can be used for packaging, but is preferably 0.5 to 500 μm from the viewpoint of mechanical strength, handling properties, transparency and the like. Preferably, it is 1 to 400 μm. 50 film thickness
When the thickness is more than 0 μm, it is difficult to produce a film, and the productivity is poor. In addition, the handling property is deteriorated in the subsequent processing steps, which is not preferable.

[Coating Layer] In the present invention, a coating solution containing a crystalline polymer resin is applied to at least one surface of the polyester film before the completion of the crystal orientation, and dried, stretched and heat-set to form a coating layer. Is crystallized. Here, the polyester film before the completion of the crystal orientation is a non-stretched film obtained by melt-extruding a polyester into a film from a die, cooling and solidifying with a casting drum, and a uniaxially-stretched unstretched film. A stretchable biaxially stretched film obtained by stretching a stretched film, a uniaxially stretched film in another direction (sequential biaxially stretched film), or a further stretchable biaxially stretched film obtained by simultaneously biaxially stretching an unstretched film. It is an axially stretched film (simultaneous biaxially stretched film). As the polyester film before the completion of the crystal orientation, an unstretched film or a uniaxially stretched film is preferable.

In the present invention, the range of the thickness of the coating layer is 0.1.
It is preferably from 001 to 10 μm, more preferably from 0.01 to 5 μm. When the thickness of the coating layer is in the range of 0.001 to 10 μm, the adhesiveness with the polyester film becomes good, and when the film after coating the coating layer is wound into a roll, adhesion between the films occurs. It becomes difficult to do.
When the thickness of the coating layer is smaller than 0.001 μm, the gas barrier performance becomes insufficient.

[Coating Liquid] In the present invention, the coating liquid for forming the coating layer is preferably aqueous, but may contain some organic solvent as long as it does not affect the properties of the coating liquid. This coating liquid can be used by adding a required amount of a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant. As such surfactants, those capable of lowering the surface tension of the aqueous coating solution to 40 mN / m or less and promoting wetting to a polyester film are preferable. For example, polyoxyethylene-fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid esters, fatty acids Examples include metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts, alkylamine hydrochlorides, betaine surfactants, and the like. Further, other additives such as an antistatic agent, an ultraviolet absorber, a pigment, an organic filler, an inorganic filler, a lubricant, and an antiblocking agent can be used in combination as long as the effects of the present invention are not lost.

The solid content of the coating solution is usually 0.1 to 3
0% by weight, more preferably 1 to 10% by weight. Film 1 m ² per in coating amounts running from 0.5 to 50
g is preferred.

Known methods can be applied as a method for applying the coating liquid. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife method, an impregnation method, a curtain coating method, or the like may be applied alone or in combination.

[0033]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. Each characteristic value was measured by the following method. (1) Film thickness The weight of the film is measured and calculated from the density of the polyester.

(2) Thickness of coating layer The thickness of the coating layer is calculated from the coating amount per 1 m ² of the coating solution, the solid concentration of the coating solution, and the stretching ratio of the film.

(3) Crystallinity of coating layer The crystallinity (C) is calculated by X-ray diffraction analysis (manufactured by Rigaku Corporation). Create a dried product of the coating solution to prevent crystallization,
The scattering intensity (I _a ) was measured as _a completely amorphous material, and the scattering intensity (I) of the coating layer of the film after biaxial stretching was measured.
It was determined from the following equation.

[0036]

(Equation 1)

(4) Oxygen Permeability Coefficient Based on ASTM D-1434-75M method, a commercially available gas permeability measuring device (GTR tester MC manufactured by Toyo Seiki Seisaku-sho, Ltd.)
The oxygen transmission coefficient of the film was determined in 1). A pressure difference was applied to both sides of the film, and the oxygen permeability was calculated from the gradient of the change of the pressure at 25 ° C. with respect to time, and further converted into the oxygen permeability coefficient per unit thickness. The unit is [ml · cm /
cm ² · s · Pa].

(5) Secondary transition temperature (Tg) A film sample (10 mg) was subjected to DSC (Dupont, V.
4. After melting at 300 ° C. for 5 minutes using an OB2000 model), the mixture is rapidly cooled to room temperature or lower, and then heated at a rate of 20 ° C./min to measure the secondary transition temperature.

Example 1 Polyethylene terephthalate (Tg = 78 ° C., containing 0.07% by weight of porous silica particles) having an intrinsic viscosity of 0.60 dl / g measured in o-chlorophenol at 25 ° C. 280-300 ° C from die
And then rapidly cooled while applying static electricity on a rotating cooling drum maintained at about 30 ° C. to obtain an unstretched film. Next, the unstretched film was stretched 3.6 times in the longitudinal direction at 105 ° C. to obtain a uniaxially stretched film.
On one surface of the uniaxially stretched film, a coating solution having a solid content of 6% by weight (solid content: saponification degree 95%, polymerization degree 1000)
90 g of vinyl alcohol and 10 g of polyoxyethylene (n = 7) lauryl ether as a wetting agent) were applied at 10 g / m ² by a kiss coating method. Then 1
The film is stretched 4.0 times in the width direction at 20 ° C., subjected to a tension heat treatment at 220 ° C. with a fixed length, and re-heat treated at 210 ° C. while shrinking by 3% in the width direction to obtain a 12 μm-thick biaxially oriented film A polyester film was obtained. Table 1 shows the characteristic values of the obtained film.

Example 2 Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.62 dl / g measured in o-chlorophenol at 25 ° C. (Tg = 121 ° C., 0.07 weight of porous silica particles) %) From the T-die to 290
It was melt-extruded at a temperature of ３１０310 ° C. and rapidly cooled while being electrostatically applied on a rotating cooling drum maintained at about 30 ° C. to obtain an unstretched film. Next, this unstretched film is
The film was stretched 3.6 times in the longitudinal direction at 05 ° C to obtain a uniaxially stretched film. On one side of the uniaxially stretched film, a coating solution having a solid content of 6% by weight (solid content: 95% by weight of saponification degree, vinyl alcohol having a degree of polymerization of 1000), polyoxyethylene (n = 7) lauryl as a wetting agent (10% by weight of ether) was applied by a kiss coat method at 10 g / m ² . Then stretched 4.0 times in the width direction at 140 ° C and 230 ° C
Performs tensile heat treatment at a fixed length at 3% in the width direction at 220 ° C.
A re-heat treatment was performed while shrinking to obtain a biaxially oriented polyester film having a thickness of 12 μm. Table 1 shows the characteristic values of the obtained film.

[Comparative Example 1] The coating liquid contained an acrylic resin (MMA / EA / AA / N-MAA = 60 /
30/5/5) and 90% by weight, and 10% by weight of polyoxyethylene (n = 7) lauryl ether as a wetting agent.
A biaxially oriented polyester film of μm was obtained. Table 1 shows the characteristic values of the obtained film.

[Comparative Example 2] A film was formed in the same manner as in Example 1 except that the gas barrier layer was not coated in the film forming process, and then a coating solution having the same solid content composition as in Example 1 was dried. Was applied by a kiss coat method so that the coating thickness of Example 1 was the same as in Example 1, and dried at 120 ° C. to obtain a biaxially oriented polyester film. Table 1 shows the characteristic values of the obtained film.

Comparative Example 3 A film was formed in the same manner as in Example 1 except that the gas barrier layer was not coated to obtain a biaxially oriented polyester film. Table 1 shows the characteristic values of the obtained film.

[0044]

[Table 1]

[0045]

The gas barrier polyester film of the present invention has very good gas barrier properties and can be used for packaging materials and the like.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D075 BB07Z BB24Z CA42 DA04 DB48 DC36 EB39 4F006 AA35 AB20 AB32 AB38 BA05 CA07 DA04 EA05 EA06 4F100 AK01B AK21B AK41A AK42A AK48B AK54B BA02 J15 EJHJBJ01 J37

Claims (6)

[Claims] 1. A gas barrier polyester film provided with a coating layer obtained by applying a coating liquid containing a crystalline polymer resin to at least one surface of a polyester film, followed by drying, stretching and heat treatment. 2. The gas barrier polyester film according to claim 1, wherein the crystallinity of the crystalline polymer resin in the coating layer is 10% or more. 3. The gas barrier polyester film according to claim 1, wherein the crystalline polymer resin is a resin containing at least one selected from the group consisting of polyvinyl alcohol, nylon, polyalkylene glycol and polyalkylene. 4. The gas barrier polyester film according to claim 1, wherein the thickness of the coating layer is in the range of 0.001 to 10 μm. 5. The gas barrier polyester film according to claim 1, wherein the polyester is mainly composed of polyethylene terephthalate. 6. Polyester is polyethylene-2,6-
The gas barrier polyester film according to any one of claims 1 to 4, wherein the gas barrier polyester film is mainly composed of naphthalate.