JP2009202390A - Biaxially orientated polyester film for packaging and package using this film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially orientated polyester film for packaging with excellent piercing strength and a biaxially orientated polyester film for packaging with superior piercing pinhole resistance, as well as a package using these films. <P>SOLUTION: The biaxially orientated polyester film for packaging has an easy adhesive layer formed of a polyester resin and a melamine compound at least on one surface of the polyester film. In addition, this polyester film is characterized in that the coefficient of plane orientation (fn) of the biaxially orientated polyester film for packaging is not less than 0.167 to not more 0.175, the absolute value of birefringence rate (Δn) is less than 5, the piercing strength is not less than 7 N to not more than 15 N, the film thickness is not less than 7 μm to not more than 20 μm and the peel strength between the easy adhesive layer and the metal layer is not less than 1 N/15 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biaxially oriented polyester film for packaging. In particular, the present invention relates to a biaxially oriented polyester film for packaging excellent in puncture strength and a package using the same.

  Polyethylene terephthalate biaxially oriented film, which is a typical example of polyester film, has excellent mechanical strength, thermal characteristics, humidity characteristics, and many other excellent characteristics, so it can be used for industrial materials, magnetic recording materials, optical materials, information communication materials, and packaging. It is used in a wide range of fields such as materials. Furthermore, due to the diversification of consumer preferences in recent years, particularly in the food packaging field, hard snacks and the like are required from the market. Therefore, in applications where packaging pinhole resistance is increasingly important, polyethylene terephthalate has insufficient flexibility for pinpoint resistance due to the hardness that is the reverse of its toughness, and is an aliphatic polyamide with excellent flexibility. Many biaxially oriented films are used.

  However, aliphatic polyamides have high water absorption due to their high chemical structure, resulting in high water absorption, poor humidity dimensional stability, poor flatness, and changes in film properties over time due to moisture absorption. However, there is a problem that vapor deposition of a metal compound for improving the gas barrier property is difficult, and printing or adhesion with the laminate layer is reduced due to moisture absorption. On the other hand, although aromatic polyamide has an aromatic ring, hygroscopicity is improved, but melt film formation is difficult, and a special and high-risk solvent must be used even for solution film formation. However, there is a problem that it is difficult to use it as a packaging material in terms of productivity and economy, and a polyester film has been used.

  On the other hand, since polyester can be melt-formed and has poor hygroscopicity, problems such as polyamide do not occur, but it is inferior to the pin puncture resistance required for packaging materials as described above. The polyester film alone is rarely used as a packaging material, and is usually used by being deposited with metal or laminated with other films. However, if the peel strength from the metal vapor-deposited layer or other film is low, it has no value as a packaging material, so an easy-adhesion layer is provided between the polyester film and the metal vapor-deposited layer to bring the polyester film and metal vapor-deposited layer into close contact. A disclosed film is disclosed (for example, Patent Document 1). Further, in order to have heat sealability as a packaging material, a sealant layer is generally provided on the metal vapor-deposited layer, and a film that improves the pin puncture resistance by this sealant layer is disclosed (for example, Patent Document 2).

Furthermore, a film that defines a plane orientation coefficient (fn) and a refractive index of a polyester film and improves stab pinhole resistance as a package is also disclosed (for example, Patent Document 3). However, the techniques described in these documents have limitations in puncture strength and pin puncture resistance, and have not been able to meet recent demand.
Japanese Patent Application Laid-Open No. 08-311221 JP 2006-035646 A JP 2007-118476 A

  An object of the present invention is to eliminate the above-described problems of the prior art. That is, it is providing the biaxially-oriented polyester film for packaging excellent in puncture strength, the biaxially-oriented polyester film for packaging excellent in puncture pinhole resistance, and a package using the same.

  The above-mentioned problem is a biaxially oriented polyester film for packaging formed by forming an easy-adhesion layer using a polyester resin and a melamine compound on at least one side of a polyester film, and the plane orientation coefficient of the biaxially oriented polyester film for packaging (Fn) is 0.167 or more and 0.175 or less, the absolute value of birefringence (Δn) is less than 5, puncture strength is 7N or more and 15N or less, film thickness is 7 μm or more and 20 μm or less, and the easy adhesion layer It can be achieved by a biaxially oriented polyester film for packaging having a peel strength between the metal layer described later of 1 N / 15 mm or more and a package using the same.

As a more preferable aspect,
(1) The polyester resin constituting the easy-adhesion layer contains at least three acid components selected from the group consisting of terephthalic acid, isophthalic acid, trimellitic acid, and sebacic acid,
(2) the polyester resin constituting the easy-adhesion layer contains at least two or more glycol components selected from the group consisting of ethylene glycol, neopentyl glycol, and 1,4-butanediol;
(3) The amount of diethylene glycol in the biaxially oriented polyester film for packaging is 0.01 wt% or more and 1.2 wt% or less with respect to the entire biaxially oriented polyester film for packaging,
(4) A package in which a layer made of metal and / or metal oxide is laminated on the easy-adhesion layer of the biaxially oriented polyester film for packaging,
(5) A package in which a layer made of an olefin-based film is provided on a layer made of metal and / or metal oxide of the package of (4),
It is.

  The biaxially oriented polyester film for packaging according to the present invention is excellent in puncture pinhole resistance in various deformation modes required as a package laminated with other films, etc. can do. Furthermore, when it is used as a package having a layer made of metal and / or metal oxide, it has excellent peel strength between the polyester film and the layer made of metal and / or metal oxide. Can also maintain the puncture strength without causing delamination, so when a package is manufactured using the film of the present invention, even when packaging a hard snack, a heavy snack, etc. There is an excellent effect of improving pin puncture resistance during filling.

  In the present invention, an easy-adhesion layer is provided on at least one side of the polyester film to form a biaxially oriented polyester film for packaging. However, the polyester film as the base material must be made of a polyester resin using polyethylene terephthalate. is there. Here, the polyester resin using polyethylene terephthalate is a polyester resin in which 95 mol% or more of the dicarboxylic acid component constituting the polyester is a terephthalic acid component and 95 mol% or more of the glycol component is an ethylene glycol component. Means. Residue components other than terephthalic acid and ethylene glycol may be contained as a dicarboxylic acid component and a glycol component in a range of 5 mol% or less, and as a manner of inclusion, copolymerized polyethylene terephthalate may be used. A polyester resin may be blended and used. From the viewpoint of heat resistance and dimensional stability, it is preferable to use a polyethylene terephthalate resin itself which is not copolymerized or blended. Examples of acid components other than terephthalic acid include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and cyclohexanedicarboxylic acid. Alicyclic dicarboxylic acids, oxycarboxylic acids such as p-oxybenzoic acid, polyfunctional acids such as trimellitic acid and pyromellitic acid can be used.

  Examples of glycol components other than ethylene glycol include aliphatic diols such as diethylene glycol, butanediol, and hexanediol, alicyclic diols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and polyalkylene glycols. Can be used.

  Furthermore, polyethers such as polyethylene glycol and polytetramethylene glycol may be copolymerized. These dicarboxylic acid components and glycol components may be used in combination of two or more, or two or more polyesters may be blended and used. Further, two or more layers may be used as a co-extruded laminated film.

  Also known additives in this polyester resin, such as heat stabilizers, oxidation stabilizers, weathering stabilizers, UV absorbers, organic lubricants, pigments, dyes, fillers, antistatic agents, nucleating agents Etc. may be blended.

  When various particles are used as such additives, the diameter of the particles to be used is not particularly limited, but usually the number average particle diameter measured by a sedimentation method or a light scattering method is 0.05 to 8.0 μm, preferably 0. The particle | grains which are 0.1-4.0 micrometers can be mentioned as the representative.

  In the biaxially oriented polyester film for packaging of the present invention, the amount of diethylene glycol (hereinafter sometimes referred to as DEG) in the film using polyethylene terephthalate is from the viewpoint of puncture strength, pin puncture resistance and orientation. It is preferable that it is 0.01 to 1.2 weight% with respect to the biaxially oriented polyester film for use.

  Although diethylene glycol is generally produced as a by-product in the production of polyester, if the amount of diethylene glycol is less than 0.01% by weight, the polymerization process becomes complicated, which may increase the cost. Further, when the amount of diethylene glycol exceeds 1.2% by weight, the number of amorphous parts in the film increases, and the puncture strength and puncture pinhole resistance decrease, and the orientation becomes difficult during stretching. fn) and the birefringence index (Δn) are not preferable because it is necessary to set film-forming conditions in which film tearing is likely to occur. The smaller the amount of diethylene glycol, the better the puncture strength, pin puncture resistance and orientation, so more preferably 0.3 wt% to 1.0 wt%, still more preferably 0.35 wt% to 0.9 wt%. % Or less.

  To reduce the amount of diethylene glycol, shorten the polymerization time, limit the amount of antimony compound, germanium compound, titanium compound, etc. used as a polymerization catalyst, combine liquid layer polymerization and solid layer polymerization, alkaline components And the like.

  The biaxially oriented polyester film for packaging of the present invention needs to have a puncture strength of 7N or more and 15N or less. When the puncture strength is less than 7N, pinhole resistance is insufficient, and pinholes are likely to occur when filling contents such as snacks or during transportation. On the other hand, if the piercing strength exceeds 15 N, film tearing is likely to occur in the film forming process, and productivity may be reduced. In order to make the puncture strength 7N or more and 15N or less, the area magnification is 4 times or more and 25 times or less, preferably 6 times or more and 20 times or less, and the heat treatment temperature is 150 ° C. or more and 250 ° C. or less when the polyester film is formed. It can be achieved by. From the viewpoint of pinhole resistance and productivity, the puncture strength is more preferably 8N or more and 14N or less, and further preferably 9N or more and 13N or less.

  The biaxially oriented polyester film for packaging according to the present invention has a polyester resin and a melamine compound on at least one side of the polyester film from the viewpoints of peel strength and puncture strength from the metal and / or metal oxide layer, and pin puncture resistance. It is essential to have an easy-adhesion layer made of. By providing such an easy-adhesive layer, the adhesion between the metal and / or metal oxide layer provided when used as a package and the biaxially oriented polyester film for packaging is improved, and delamination is prevented. be able to. However, when either the polyester resin or the melamine compound is not contained in the easy-adhesion layer, the adhesion with the layer made of metal and / or metal oxide in high humidity, particularly in water, is insufficient, and delamination tends to occur. .

  Moreover, the biaxially oriented polyester film for packaging of the present invention needs to have a peel strength of 1 N / 15 mm or more between the easy-adhesion layer and a metal layer described later.

  The biaxially oriented polyester film for packaging according to the present invention is a packaging body in which a layer made of a metal and / or a metal oxide is laminated on the easy adhesion layer, and a layer made of an olefin film is further provided thereon. When it can be suitably used, the puncture pinhole resistance of the package is significantly deteriorated when the peel strength between the easy-adhesion layer and the metal layer described below is less than 1 N / 15 mm. This means that when the peel strength is outside the above range, when the contents are actually filled or transported, the delamination occurs between the metal and / or metal oxide layer and the biaxially oriented polyester film for packaging. When such delamination occurs, the puncture-resistant pinhole properties of the biaxially oriented polyester film for packaging and the olefinic film are divided, and the puncture-resistant pinhole properties as a package are significantly deteriorated. is there. In order to increase the peel strength to more than 10 N / 15 mm, an ion sputtering deposition method or the like that can apply a large energy to the metal and / or metal oxide when laminating a layer made of metal and / or metal oxide is used. Although it is necessary to adopt this, the production speed is slow, which may increase the cost. Further, in order to prevent delamination when filling heavy contents, the peel strength is more preferably 1.5 N / 15 mm or more and 10 N / 15 mm or less, and 2.0 N / 15 mm or more and 10 N / More preferably, it is 15 mm or less.

  The polyester resin constituting the easy-adhesion layer of the present invention has an ester bond consisting of an acid component and a glycol component in the main chain or side chain, and can be arbitrarily selected from conventionally known polyester resins. Examples of the acid component include sulfones represented by sulfoterephthalic acid, 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,6-dicarboxylic acid and the like from the viewpoint of adhesiveness. A dicarboxylic acid containing an acid group is preferred. The content of the sulfonic acid group is preferably 0.5 mol% or less when the total dicarboxylic acid component in the easy-adhesion layer is 100 mol%. If the sulfonic acid group is contained in an amount exceeding 0.5 mol%, not only the adhesion to the metal and / or metal oxide layer in high humidity or in water is lowered, but also the solvent resistance is lowered. As the carboxylic acid component not containing a sulfonic acid group, aromatic, aliphatic and alicyclic dicarboxylic acids and trivalent or higher polyvalent carboxylic acids can be used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid.

  These aromatic dicarboxylic acids are 30 mol% or more, preferably 35 mol% or more, more preferably 40 mol% or more of the total dicarboxylic acid component in the easy-adhesion layer. If it is less than 30 mol%, the mechanical strength and water resistance of the polyester copolymer are lowered. Aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexane And dicarboxylic acid. Examples of the polyvalent carboxylic acid include trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,2,3 , 4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl)- 3-methyl-3-cyclohexene-1,2-dicarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene-1,2-dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,3, 6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate, 2,2 , 3,3'-diphenyl tetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylene tetracarboxylic acid.

  Of these, trimellitic acid, pyromellitic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid and the like are preferably used. In particular, a polyester resin containing three or more acid components selected from the group consisting of terephthalic acid, isophthalic acid, trimellitic acid, and sebacic acid is used in terms of adhesion, water dispersibility, water solubility, heat resistance, and the like. More preferably, it is preferable to use a polyester resin containing four kinds of acid components of terephthalic acid, isophthalic acid, trimellitic acid and sebacic acid. When two or more kinds of acid components are used in the polyester resin, the easy adhesion layer of the present invention is an easy adhesion layer formed by using one or two or more polyester resins obtained by copolymerization of the two or more kinds of acid components. Alternatively, it may be an easy-adhesion layer using two or more polyester resins composed of one kind of acid component, or one or more polyester resins obtained by copolymerization of two or more kinds of acid components and 1 An easy-adhesion layer using one or more polyester resins composed of various acid components may be used.

  When using a polyester resin containing four types of acid components, terephthalic acid, isophthalic acid, trimellitic acid and sebacic acid, the content of terephthalic acid is preferably the highest, followed by trimellitic acid, isophthalic acid and sebacic acid in this order. It is preferable that the content is high.

  The terephthalic acid is preferably 10 mol% to 35 mol%, the isophthalic acid is 1 mol% to 15 mol%, the trimellitic acid is 5 mol% to 25 mol%, and the sebacic acid is 1 mol% to 10 mol%. The content is preferably not more than mol%. In addition, said "mol%" means the molar fraction of 100, when the acidic component of the polyester resin which comprises an easily bonding layer, and a glycol component are made into 100 mol% in total.

  Examples of the glycol component include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neo Pentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4- Trimethyl-1,6-hexanediol, 1,2-cyclohexanedimeta 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4 4,4'-methylenediphenol, 4,4 '-(2-norbornylidene) diphenol, 4,4'dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4'-isopropylidenephenol, 4, 4,4'-isopropylidenevindiol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, and the like.

  Among them, it is possible to use a polyester resin containing at least two glycol components selected from the group consisting of ethylene glycol, neopentyl glycol, and 1,4-butanediol, adhesion, water dispersibility, water solubility, heat resistance, etc. From the above point, it is preferable to use a polyester resin containing three glycol components of ethylene glycol, neopentyl glycol and 1,4-butanediol. When two or more glycol components are used in the polyester resin, the easy-adhesion layer of the present invention is an easy-adhesion layer using one or two or more polyester resins obtained by copolymerization of the two or more glycol components. Alternatively, it may be an easy-adhesion layer using two or more polyester resins composed of one kind of glycol component, or one or more polyester resins obtained by copolymerization of two or more kinds of glycol components and 1 An easy-adhesion layer using one or more polyester resins composed of various glycol components may be used.

  Moreover, when using the polyester resin containing three glycol components, ethylene glycol, neopentyl glycol, and 1, 4- butanediol, it is preferable that content of each glycol component is 5 mol% or more and 25 mol% or less. The “mol%” means a mole fraction when the acid content of the polyester resin constituting the easy-adhesion layer and the glycol component are totaled to 100 mol%.

  Examples of the melamine compound forming the easy-adhesion layer of the present invention include melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting a methylolated melamine with a lower alcohol, and these Of the mixture. The melamine resin may be a monomer or a condensate consisting of a dimer or higher polymer, or a mixture thereof. Examples of the lower alcohol used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like, and methyl alcohol is particularly preferable, but is not particularly limited.

  In the present invention, a compound obtained by partially etherifying a methylolated melamine derivative and a mixture thereof are preferable from the viewpoint of water solubility, reactivity, storage stability, moisture resistance, etc., and particularly 50% to 90% of the methylol group is etherified. The compounds are preferred but not particularly limited.

  The melamine compound of the present invention is preferably 0.01% by weight or more and 30% by weight or less, more preferably 0.05% by weight or more and 20% by weight or less with respect to the entire easy-adhesion layer. If it is less than 0.01% by weight, effects such as adhesiveness do not appear. When it exceeds 30% by weight, the stretchability of the easy-adhesion layer is lacking, and it becomes difficult to obtain a stable easy-adhesion layer.

  The polyester resin forming the easy-adhesion layer of the present invention is preferably 70% by weight or more and 99.99% by weight or less, more preferably 80% by weight or more and 99.95% by weight or less with respect to the whole easy-adhesion layer. If it is less than 70% by weight, the stretchability of the easy-adhesion layer is lacking, and if it exceeds 99.99% by weight, effects such as adhesion do not occur.

  In the present invention, when the easy-adhesion layer is composed of a polyester resin and a melamine compound, the polyester resin and the melamine compound can be mixed and applied at an arbitrary ratio, but preferably the polyester resin / melamine compound is 99/1 to 60 in a weight ratio. / 40 is preferable, more preferably 99/1 to 80/20, still more preferably 99/1 to 90/10. In this case, the polyester resin and the melamine compound may or may not react for a part or all of them.

  Examples of the method for laminating the easy adhesion layer on the polyester film include a hot melt coating method, an in-line coating method, and an offline coating method. When using the in-line coating method or offline coating method, create a coating solution in which the resin or compound constituting the easy-adhesion layer is dissolved and / or dispersed in water or an organic solvent, and apply the coating solution to the polyester film. It is preferable to do.

  Alternatively, an easy-adhesion layer may be provided by applying a coating solution on the biaxially oriented polyester after completion of orientation by an off-line coating method, etc., but the easy-adhesion layer on at least one side of the polyester film before orientation crystallization is completed An in-line coating method in which a coating liquid for forming a film is applied and heat-treated to complete orientation crystallization of the polyester film and form an easy-adhesion layer is preferable in that the easy-adhesion layer can be formed uniformly. The in-line coating method can be performed according to a known method. However, the crystal orientation is different in that it prevents ink or a pinhole in a vapor deposition film due to adhesion of dust in the process, or forms a thin and easy adhesion layer uniformly. Applying a coating solution that forms an easy-adhesion layer on the polyester film before completion, followed by drying, stretching, and heat treatment to complete the orientation crystal of polyester film, that is, easy-adhesion in the manufacturing process of biaxially oriented polyester film An in-line coating method for forming a layer is more preferable. In the case of forming an easy-adhesion layer by an in-line coating method, it is preferable to use a water-soluble and / or water-dispersible resin or compound that is advantageous in terms of the explosion-proof property of the device and environmental pollution. It is also preferable to use water-soluble and / or water-dispersible resins and compounds. Thereby, water can be used as a solvent for the coating agent, which is preferable.

  A water-soluble organic compound, a surfactant or the like may be added to the coating solution, and any coating material produced by a conventionally known method can be used. When an easy-adhesion layer is formed by an in-line coating method, the adhesion with a metal and / or metal oxide layer, the gloss of a coating film, and the adhesion with a printing ink are excellent.

  As for the polyester film of this invention, although an easily bonding layer is formed in the at least single side | surface, it is preferable that the surface free energy of the polyester film of the surface in which an easily bonding layer is formed is 45-60 mN / m. Also, on the surface where the easy-adhesion layer is not provided, the polyester on the surface can be easily applied to the film surface by bonding with other materials as a packaging material, coating with adhesives, printing or vapor deposition of metal compounds, etc. The surface free energy of the film is preferably 45 to 60 mN / m.

  Examples of the method for setting the surface free energy to such a preferable range include a method of performing a surface treatment by corona discharge or the like on the film surface in air or a nitrogen gas atmosphere, a method of performing a surface treatment by a flame, and the like.

  The thickness of the easy adhesion layer is not particularly limited, but is usually 0.001 μm or more and 1 μm or less, preferably 0.005 μm or more and 0.3 μm or less, more preferably 0.01 μm or more and 0.1 μm or less, and particularly preferably 0.02 μm or more. It is desirable that it is 0.07 μm or less. If the easy-adhesion layer is too thick, the deposited film may whiten and lose its gloss when it receives heat of about 200 ° C. If it is too thin, the adhesion between the metal and / or metal oxide layer and the easy-adhesion layer May be inferior. Moreover, the said thickness range is preferable also from the point of the collection | recovery point which uses a film by rechiping.

  In addition, various additives such as inorganic and organic particles, lubricants, antistatic agents, weathering agents, heat resistance agents, dyes, pigments and the like may be added to the easy-adhesion layer within the range that does not impair the effects of the present invention. Good.

  The biaxially oriented polyester film for packaging of the present invention needs to have a plane orientation coefficient (fn) of 0.167 or more and 0.175 or less from the viewpoints of puncture strength, peel strength described above, and dimensional stability. Furthermore, from the viewpoint of pin puncture resistance when used as a package, it is more preferably from 0.168 to 0.172. If the plane orientation coefficient (fn) is less than 0.167, the puncture strength is inferior. In addition, when the plane orientation coefficient (fn) exceeds 0.175, in a packaging material used by combining a polyester film and another material, cleavage and peeling occur in the polyester film, or the film is easily torn. For this reason, the pinhole resistance may be inferior.

  The film of the present invention needs to be a biaxially oriented polyester film, but in order to make the film biaxially oriented, for example, it can be achieved by stretching an unstretched (unoriented) film biaxially. it can.

  The method of biaxially stretching the polyester film of the present invention is not particularly limited as long as it is biaxially stretched, but as a known biaxial stretching method, for example, it is stretched in the longitudinal direction and then stretched in the width direction. And a method of stretching in the longitudinal direction after stretching in the width direction, a method of stretching in the longitudinal direction and stretching in the width direction in combination, and a method called simultaneous biaxial stretching in which stretching is performed simultaneously.

  As a method of setting the plane orientation coefficient (fn) of the biaxially oriented polyester film for packaging of the present invention in the range of 0.167 or more and 0.175 or less, for example, a sequential biaxial stretching method is adopted during the production of the polyester film. In this case, first, the birefringence (MD direction and width direction (hereinafter sometimes referred to as TD direction) of a uniaxially oriented film stretched in the film longitudinal direction (hereinafter sometimes referred to as MD direction). A method of multiplying the difference in refractive index by 1000) to 70 to 130 and then stretching in the TD direction is preferable. Here, when the birefringence of the uniaxially oriented film is less than 70, the orientation in the MD direction after stretching in the TD direction is insufficient, and the plane orientation coefficient (fn) may not be 0.167 or more. is there. On the other hand, if the birefringence of the uniaxially oriented film exceeds 130, the film is likely to be broken during stretching in the TD direction, and the film-forming stability is greatly reduced.

  The method of setting the birefringence of the uniaxially oriented film to 70 or more and 130 or less is not particularly limited. For example, the film may be stretched 2.3 to 7 times in the MD direction with a roll group heated to 40 to 130 ° C. A uniaxially oriented film having a birefringence (Δn) can be obtained. The birefringence of the uniaxially oriented film can be confirmed by taking out the uniaxially oriented film and measuring the refractive index once during the production of the biaxially oriented polyester film. In addition, it is preferable to perform heat treatment after stretching in the TD direction. However, when heat treatment is performed at a high temperature of 240 ° C. or higher, orientation relaxation of the polyester molecular chains in the film is likely to occur, and the plane orientation coefficient (fn) is increased. Since the temperature may decrease, the heat treatment temperature should be low as long as the dimensional stability is not deteriorated, more preferably 190 to 240 ° C, and particularly preferably 200 to 235 ° C.

  Since the biaxially oriented polyester film for packaging of the present invention has a characteristic that is particularly excellent in puncture strength, the absolute value of the birefringence index is required to be less than 5. When the absolute value of the birefringence is 5 or more, the high orientation direction and the low orientation direction exist in the plane of the film, so that the strength in the low orientation direction is lowered and the puncture strength is inferior. From the viewpoint of puncture strength, it is more preferable that the absolute value of the birefringence is less than 4. Moreover, if the maximum birefringence is less than 5, it is particularly preferable because the film is extremely excellent in puncture strength because of its extremely excellent alignment balance. Here, the maximum birefringence means a value obtained by multiplying 1000 by the difference between the maximum value and the minimum value of the refractive index in the film plane.

  The method for setting the absolute value of the birefringence to less than 5 can be adjusted by appropriately controlling the stretching temperature and the stretching ratio in the film TD direction. May progress to so-called necking stretching, resulting in a film whose orientation is biased in the TD direction. When the stretching temperature is less than 80 ° C., the film may be a film in which the heating is insufficient and the orientation is biased in the width direction. The draw ratio is preferably 3.5 to 5.5 times, but if the draw ratio is 4.5 times or more, film tearing is likely to occur, and therefore it is preferably 3.6 to 4.4 times. . Further, in the heat treatment step after biaxial stretching, if the heat treatment temperature is less than 190 ° C., the orientation may be biased in the film TD direction, so the heat treatment temperature is preferably 190 to 240 ° C., Particularly preferred is 235 ° C.

  The biaxially oriented polyester film for packaging of the present invention preferably has a refractive index in the thickness direction of 1.480 or more and 1.495 or less. If the refractive index in the thickness direction is less than 1.480, the orientation in the film surface direction may proceed too much and cleavage may occur easily. Conversely, if it exceeds 1.495, the pinhole resistance may be poor. is there. From the standpoint of pin puncture resistance and cleavage suppression, it is more preferably 1.485 or more and 1.492 or less. As a method for adjusting the refractive index in the thickness direction of the film to 1.480 or more and 1.495 or less, a method of further enhancing the plane orientation by heat-treating the film having a higher plane orientation by biaxial stretching is desirable. It is especially preferable to set it to -235 degreeC.

  The biaxially oriented polyester film for packaging of the present invention is required to have a film thickness of 7 μm or more and 20 μm or less from the viewpoint of puncture strength and puncture resistance when used as a package. When the film thickness is less than 7 μm, sufficient puncture strength cannot be obtained, and pinholes are likely to occur when filling the contents as a package. On the other hand, if the thickness exceeds 20 μm, it becomes difficult to handle, such as curling due to bonding with other materials, and it becomes over spec in strength, and the container recycling law increases the burden and waste weight Is not preferable from the viewpoint of the environment in that it increases. The thickness of the biaxially oriented polyester film for packaging is more preferably 8 μm or more and 18 μm or less, and particularly preferably 8 μm or more and 16 μm or less from the viewpoint of puncture strength, handleability, and economy.

  In addition, the biaxially oriented polyester film for packaging of the present invention is a film MD direction from the viewpoint of expressing the characteristics excellent in puncture strength and the characteristics excellent in puncture resistance when used as a package. The breaking strength in the TD direction is preferably 260 MPa or more and 400 MPa or less. Here, the breaking strength is the breaking strength in a tensile test at 25 ° C. When the breaking strength is less than 260 MPa, a direction with low strength exists, and pinholes may be easily generated in the puncture strength that simultaneously deforms the in-plane direction of the film. On the other hand, if the breaking strength exceeds 400 MPa, the cutability for taking out the contents in the case of a package may be deteriorated. In terms of achieving both pin puncture resistance and cut property, the breaking strength in the MD direction and the TD direction is more preferably 270 MPa or more and 350 MPa or less, and particularly preferably 280 MPa or more and 330 MPa or less. As a method for setting the tensile strength at break of the biaxially oriented polyester film for packaging to such a preferable range, the intrinsic viscosity of the polyester constituting the polyester film is preferably 0.60 or more and 0.70 or less. If the intrinsic viscosity of the polyester constituting the polyester film is less than 0.60, the molecular weight of the polyester resin is small, so that it becomes brittle. Conversely, if the intrinsic viscosity exceeds 0.70, the orientation balance in the film plane is adjusted. It becomes difficult.

  Although the manufacturing method of the biaxially-oriented polyester film for packaging of this invention is demonstrated concretely below, this invention is not limited to the following manufacturing methods. First, the polyester resin using the polyethylene terephthalate used in the polyester film of the present invention can be a commercially available polyethylene terephthalate resin as it is, but it is produced through a polycondensation reaction as follows. Also good.

  To a mixture of 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate and 0.03 parts by weight of antimony trioxide are added and gradually heated, finally at 220 ° C. Transesterification is performed while distilling methanol to synthesize a polyethylene terephthalate precursor. Next, 0.02 part by weight of an 85% aqueous solution of phosphoric acid is added to the precursor, and the mixture is transferred to a polycondensation reaction kettle. The reaction system is gradually depressurized while being heated and heated in a polycondensation reaction kettle, and a polycondensation reaction is performed at 290 ° C. under a reduced pressure of 1 hPa to obtain a polyethylene terephthalate resin having a desired molecular weight. In addition, when adding particles, it is preferable to add a slurry in which particles are dispersed in ethylene glycol to a polycondensation reaction kettle so as to have a predetermined particle concentration to perform a polycondensation reaction.

  To reduce the amount of diethylene glycol in the polyester resin, shorten the polymerization time or limit the amount of antimony compound, germanium compound, titanium compound, etc. used as a polymerization catalyst, and combine liquid phase polymerization and solid phase polymerization. Examples thereof include a method and a method of containing an alkali component, but are not particularly limited. For example, when the amount of DEG is adjusted by containing potassium hydroxide, the amount of DEG is 0.01 by adding 0.01 to 0.10 parts by weight with respect to 100 parts by weight of dimethyl terephthalate. A polyethylene terephthalate resin having a weight percent of 1.5% or less can be obtained.

  Next, although the manufacturing method of the polyester film which concerns on this invention is demonstrated, it is not limited to this example. The dried polyester resin chip is supplied to an extruder, heated to a temperature equal to or higher than the melting point of the polyester resin, and melted. Next, the molten polyester resin is extruded as a molten sheet from a T-die having slit-like discharge ports, and is tightly solidified on a cooling roll to obtain a cast film (unoriented film (unstretched film)). In order to improve the adhesion between the molten sheet and the cooling roll, it is usually preferable to employ an electrostatic application adhesion method and / or a liquid surface application adhesion method.

  The cast film is further stretched biaxially.

  First, it is preferably stretched 2.3 to 7 times in MD with a roll group heated to a glass transition temperature of the polyester resin or higher, for example, 40 to 130 ° C., to obtain a uniaxially oriented film (uniaxially stretched film).

Next, a coating liquid using a water-soluble and / or water-dispersible resin mainly composed of a polyester resin and a melamine compound that form an easy-adhesion layer is applied to at least one surface of the uniaxially oriented film.
Next, the film is stretched 3 to 7 times at 45 to 130 ° C. in the TD direction. In addition, although the method of extending | stretching one direction in two steps or more can be used, it is preferable that the final draw ratio also falls in the said range also in that case. The cast film can be simultaneously biaxially stretched so that the area magnification is 6 to 30 times. Here, the area ratio means a value obtained by multiplying the MD stretch ratio by the TD stretch ratio. In this case, it is preferable to apply the coating liquid for forming the easy-adhesion layer before simultaneous biaxial stretching (that is, to apply to a cast film).

  Thereby, the biaxially oriented polyester film for packaging (biaxially stretched film) of the present invention is obtained. Further, the film thus obtained may be subsequently heat-treated in-line and / or offline. Furthermore, you may extend | stretch in MD and / or TD direction again before or after performing heat processing as needed. The heat treatment temperature is 150 to 250 ° C., preferably 200 to 240 ° C., and the heat treatment time is usually 1 second to 5 minutes. The heat shrinkage characteristics can be adjusted under these heat treatment conditions. In addition, the cooling rate of the film after heat treatment also affects the heat shrink characteristics. For example, after the heat treatment, the heat shrinkage stress can be adjusted by providing the film with rapid cooling or slow cooling, or by providing an intermediate cooling zone. Further, in particular, in order to impart specific heat shrinkage characteristics, relaxation may be performed in the MD direction and / or TD direction during the heat treatment or in the subsequent slow cooling zone.

  In addition, the biaxially oriented polyester film for packaging according to the present invention is also one of preferred usage modes in which a layer made of a metal and / or a metal oxide is laminated on an easily adhesive layer and used as a gas barrier film for packaging. . Examples of metals or metal oxides include magnesium, calcium, barium, group 4, titanium, zirconium, group 13, aluminum, indium, group 14, silicon, germanium, tin, and oxides thereof, which are group 2 of the periodic table. Can be mentioned. Among these, aluminum, silicon and oxides thereof are particularly preferable. These metals and oxides thereof may be combined to form a layer made of metal and / or metal oxide.

  As a method for laminating a layer made of such a metal and / or metal oxide, a vacuum vapor deposition method, an EB vapor deposition method, a sputtering method, an ion plating method, a laminating method, or the like can be used, but is not limited thereto. However, vacuum deposition is preferably used from the viewpoint of layer thickness. Moreover, as thickness of the layer which consists of a metal and / or a metal oxide, 1-500 nm is preferable and if it is 3-300 nm, it is more preferable. From the viewpoint of productivity, the thickness is particularly preferably 3 to 200 nm.

  The biaxially oriented polyester film of the present invention preferably has a olefin-based film further laminated on a layer made of a metal and / or metal oxide as a structure suitable for use as a package. Here, the olefin-based film is, for example, an unstretched polypropylene film (hereinafter sometimes referred to as CPP), an unstretched low-density polyethylene film (hereinafter sometimes referred to as LDPE), an unstretched linear low Density polyethylene film (hereinafter sometimes referred to as LLDPE), unstretched high-density polyethylene film (hereinafter sometimes referred to as HDPE), ethylene-vinyl acetate copolymer unstretched film (hereinafter sometimes referred to as EVA) Examples thereof include, but are not particularly limited to, an unstretched film having heat sealing properties such as a biaxially stretched polypropylene film (hereinafter sometimes referred to as OPP). As a method for laminating these olefinic films and layers made of metal and / or metal oxides, it is possible to employ a laminating method using an adhesive such as an ester or a urethane or an extrusion laminating method of polyethylene. it can. Since the biaxially oriented polyester film for packaging of the present invention has excellent heat resistance, it has excellent characteristics that the pin puncture resistance does not change even after laminating with an olefin film, particularly by extrusion lamination. ing.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Birefringence (Δn), plane orientation coefficient (fn)
Using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting liquid, and using an Abbe refractometer at 25 ° C., MD, TD, and refractive index in the thickness direction of the biaxially oriented polyester film for packaging (respectively, _nMD , _nTD , _nZD ). The plane orientation coefficient (fn) and the birefringence index (Δn) were calculated from the obtained refractive index by the following formula. In addition, the measurement was performed on the surface side in close contact with the cooling drum after discharging from the T-die at the time of film formation, and the average of measured values at arbitrary three locations was evaluated.
fn = (n _MD + n _TD ) / 2-n _ZD
Δn = (n _MD −n _TD ) × 1000.

(2) The mass of 10 rectangular biaxially oriented polyester films for packaging cut into a film thickness of 300 × 200 mm was measured, and the specific gravity of the film was 1.4 × 10 ⁻³ (g / mm ³ ). The film thickness was determined as the mass average thickness according to the following formula.
T = W / (1.4 × 10 ⁻³ × 300 × 200 × 10)
However, T: Film thickness (mm), W: Mass of 10 films (g).

(3) Breaking strength By a method according to JIS C2151 (2006), a biaxially oriented polyester film for packaging was cut into a sample width of 10 mm and a length of 15 cm, and a micrometer (Digital Micrometer M manufactured by Sony Precision Technology Co., Ltd.) -30) is used to measure the film thickness of the packaging biaxially oriented polyester film. Then, it measured with the Instron type tensile tester (Orientec Co., Ltd. Tensilon RTC-1210A) with a chuck | zipper space | interval of 100 mm and a tensile speed of 10 mm / min. The load applied to the film immediately before the sample broke was read, and the value obtained by dividing the load by the cross-sectional area (film thickness x 10 mm) of the sample before the test was taken as the breaking strength. The measurement was performed at 25 ° C. and 65% RH.

(4) Intrinsic viscosity The intrinsic viscosity of the polyester resin used for forming the polyester film was dissolved in the polyester resin or the packaging biaxially oriented polyester film orthochlorophenol, and measured at 25 ° C using an Ostwald viscometer.

(5) Puncture strength By a method in accordance with JIS K1707 (1997), a biaxially oriented polyester film for packaging is stretched over a ring with a diameter of 40 mm so that the film does not loosen, the diameter is 1 mm, and the tip R is 0.5 mm. A semi-circular sapphire needle was used, the center of the circle was pierced at a speed of 50 mm / min, and the load (N) when the needle penetrated was defined as the piercing strength.

(6) Diethylene glycol amount Biaxially oriented polyester film (sample) for packaging 2.5 g of primary monoethanolamine is added to 1.0 g, heated at 280 ° C. for 40 minutes under total reflux, and then an internal standard solution (1,6 hexamethylene) Glycol / primary ethanol). Further, 40 g of special grade terephthalic acid and 5 ml of first grade ethanol are added to prepare a measurement sample. The sample for measurement was measured by Shimadzu Gas Chromatography-GC-9A (used column: Shimadzu C-R3A).

(7) Peel strength between easy-adhesion layer and metal layer Aluminum is vapor-deposited on the easy-adhesion layer side of the biaxially oriented polyester film for packaging with a continuous vacuum vapor deposition machine to a thickness of 25 nm. , “VM-PET”) and 20 μm thick biaxially stretched polypropylene film (OPP) (Torephane 2548 manufactured by Toray Film Processing Co., Ltd.), polyethylene (PE) at a resin temperature of 330 ° C. Extrusion lamination is performed on the aluminum vapor deposition layer side of VM-PET so as to have a thickness of 10 μm, and this is laminated as an adhesive to obtain a laminate 1 that becomes OPP (20 μm) / PE (10 μm) / VM-PET. It was. Next, the laminate 1 and an unstretched polypropylene film 1 (CPP1) having a thickness of 20 μm (Treffan NO 9160 manufactured by Toray Film Processing Co., Ltd.) and polyethylene on the biaxially oriented polyester film side are thickened at a resin temperature of 330 ° C. Extrusion lamination is performed so that the thickness becomes 10 μm, and this is laminated as an adhesive, and finally a laminate comprising OPP (20 μm) / PE (10 μm) / VM-PET / PE (10 μm) / CPP (20 μm) 2 was obtained. Using the polyurethane adhesive (AD503 / CAT-10 = 20 parts by weight / 1 part by weight, solvent: 20 parts by weight of ethyl acetate) manufactured by Toyo Morton Co., Ltd. CPP2) (Tray, Toray Synthetic Film Co., Ltd., T3501, 50 μm) was laminated and left standing at 40 ° C. for 48 hours, and then cut into strips of length 150 mm × width 15 mm. The CPP 2 and the component 2 are gripped so as to be bent at an acute angle, and a 180 ° peel test is performed at 25 ° C. and 50% using an Instron type tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.). The peel strength was measured by pulling in the direction of the arrow in FIG. 1 at a peel rate of 300 mm / min in an RH atmosphere. The average value of the strength between the measurement lengths of 50 mm and 100 mm was taken as the peel strength.

After the peel strength measurement was completed, the peel layer was visually confirmed and classified as follows.
A: Peeling between OPP / PE and VM-PET / PE / CPP B: Cleavage peeling of polyester film C: Peeling between aluminum deposited layer and biaxially oriented polyester film for packaging (adhesive layer) where When the peel location is A or B, it means that the peel strength between the easy-adhesion layer and the metal layer of the biaxially oriented polyester film for packaging is larger than the peel strength obtained at the peel location A or B. .

(8) Real package pinhole strength The laminate 2 created by the peel strength test of (7) above is cut into a rectangular shape with a size of 200 mm × 300 mm, the CPP surfaces are overlapped, and the three sides are 150. A bag-shaped sample for actual packaging test was obtained, which was heat-welded at 2 ° C. for 2 seconds and sealed on the three sides with a width of 10 mm from the side.
Insert 100 mm of the opening of the sample for actual packaging test into a plastic tube with a diameter of 100 mm and a length of 1 m fixed vertically, and use a ring-shaped jig with the bottom of the sample for actual packaging testing not touching anywhere. Secure the sample for the actual package test to the bottom of the tube. From the top of the cylinder, 40 regular triangular dropping chips each having a length of 65 mm, a thickness of 1.1 mm, and a vertex of 1 mm each made of high-density polyethylene (density: 0.96 g / cm ³ ). Drop all at once. After that, the chip for dropping is taken out, and a test solution (ageless seal check manufactured by Mitsubishi Gas Chemical Co., Ltd.) is sprayed inside the sample for actual packaging test to check the presence or absence and the number of pinholes.
Here, the actual package pinhole strength means a numerical value representing the pin puncture resistance in the actual package test sample, and the lower this value, the less likely the pinhole is generated during actual packaging.

[Production of polyester]
The polyester resin used for film formation was prepared as follows.

(1) Polyester resin A
To a mixture of 100 parts by weight of dimethyl terephthalate and 61 parts by weight of ethylene glycol, 0.04 parts by weight of magnesium acetate, 0.02 parts by weight of antimony trioxide and 0.001 parts by weight of potassium hydroxide were added, The temperature is gradually raised, and finally transesterification is performed while distilling methanol at 220 ° C. Next, 0.020 part by weight of an 85% aqueous solution of phosphoric acid is added to the transesterification reaction product, and then transferred to a polycondensation reaction kettle. Further, the reaction system was gradually depressurized while being heated, and a polycondensation reaction was performed at 290 ° C. under a reduced pressure of 1 hPa by a conventional method. The amount of diethylene glycol was 1.2% by weight and the intrinsic viscosity was 0.65. A polyethylene terephthalate resin A in which 95 mol% or more of the component was composed of terephthalic acid and 95 mol% or more of the glycol component was composed of ethylene glycol was produced.

(2) Particle master A
When the polyester of the above (1) is produced, a polycondensation reaction is performed after adding an ethylene glycol slurry of aggregated silica particles having an average particle size of 2.4 μm after the transesterification reaction, and a particle master A having a particle concentration of 2 mass% is obtained. Obtained.

  Next, the present invention will be described based on examples, but is not necessarily limited thereto.

Example 1
Polyethylene terephthalate resin A and particle master A were mixed and used at a mass ratio of 98: 2.
A mixture of polyethylene terephthalate resin A and particle master A is vacuum-dried, then supplied to an extruder, melt extruded at 280 ° C., filtered through an 8 μm cut stainless steel fiber sintered filter (FSS), and then from a T-shaped die. It was extruded into a sheet shape, and this was cooled and solidified on a cooling drum having a surface temperature of 25 ° C. by an electrostatic contact method. The unstretched (unoriented) PET film thus obtained was heated to 105 ° C. for 2 seconds and then stretched 4.1 times at 115 ° C. in the MD direction to obtain a uniaxially oriented film.
In order to perform corona discharge treatment in air on one side of the uniaxially oriented film and form an easy-adhesion layer, the following coating liquid was applied to the discharge treatment surface side with a rod coater. The coating thickness was set to 0.05 μm after completion of the oriented crystal of the polyester film, that is, after the heat treatment.

[Composition and formulation method of coating liquid]
1. Raw material (1) Aqueous dispersion / acid component of polyester resin
Terephthalic acid: 29 mol%
Isophthalic acid: 7 mol%
Trimellitic acid: 10 mol%
Sebacic acid: 3 mol%
・ As glycol component,
Ethylene glycol: 14 mol%
Neopentyl glycol: 19 mol%
1,4-butanediol: 18 mol%
A water dispersion of a polyester resin, which is a water-dispersible resin comprising: Here, the solid content concentration (polyester resin concentration) of the aqueous dispersion is 25% by weight, and the remaining 75% by weight is water. The acid value of the polyester resin is 41 KOHmg / g, and the glass transition temperature (Tg) is 20 ° C.
In addition, said "mol%" means the mol 100 fraction when the acid component and glycol component of the polyester resin which comprise an easily bonding layer are made into 100 mol% in total.
(2) As an aqueous dispersion of melamine compound / melamine compound,
An aqueous dispersion of an N-methylolated melamine compound (Nicalac MW-12LF (manufactured by Sanwa Chemical Co., Ltd.)), which is a water dispersible resin, was used. The solid content concentration (melamine compound concentration) of the aqueous dispersion is 70% by weight, and the remaining 30% by weight is water.

2. Preparation method of coating liquid It prepared with the following method using the aqueous dispersion of said polyester resin, the aqueous dispersion of a melamine compound, and pure water.
(1) It mix | blended so that 5 weight part of melamine compounds (solid content) might be added with respect to 95 weight part of polyester resins (solid content). That is, 380 parts by weight of an aqueous dispersion of polyester resin (of which solid content: 95 parts by weight, water: 285 parts) and 7.14 parts by weight of an aqueous dispersion of melamine compound (of which solid content: 5 parts by weight, water: 2. 14 parts by weight) was blended to obtain a stock solution.
(2) Pure water was blended so that the solid content of the stock solution (the total solid content of the polyester resin and the melamine compound) was 1.5% by weight, and this was used as the coating liquid.

This uniaxially oriented film was preheated at 105 ° C. for 2 seconds and then stretched 3.1 times in the TD direction while being heated to 115 ° C. This film was introduced into hot air at 233 ° C., heat-treated for 2 seconds without relaxing in the MD direction and TD direction, and then relaxed at 170 ° C. to 2.4% of the film width after TD stretching in the width direction. And cooled. After finally cooling to room temperature, a corona discharge treatment was performed on the surface opposite to the easy-adhesion layer with a treatment strength of 20 W · min / m ² , and this was guided to a winder and wound up to obtain a mill roll. In this way, a biaxially oriented polyester film for packaging having a thickness of 12 μm, which was finally provided with an easy adhesion layer having a thickness of 0.05 μm, was obtained. The characteristics of the resulting biaxially oriented polyester film for packaging are shown in Table 1 (Example 2)
The draw ratio in the MD direction was 4.3 times, the draw ratio in the TD direction was 3.3 times, and other conditions were the same as in Example 1, and a biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained. . The characteristics are shown in Table 1.

(Example 3)
The MD stretch ratio was 4.3 times, the TD stretch ratio was 2.9 times, and the other conditions were the same as in Example 1, and a biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained. The characteristics are shown in Table 1.

Example 4
A biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained under the same conditions as in Example 1 except that the MD stretch ratio was 3.9 times and the TD stretch ratio was 2.9 times. The characteristics are shown in Table 1.

(Example 5)
A biaxially oriented polyester film for packaging having a thickness of 7 μm was obtained under the same conditions as in Example 1 except that the amount of extrusion from the T-shaped die was adjusted. The characteristics are shown in Table 1.

(Example 6)
To a mixture of 100 parts by weight of dimethyl terephthalate and 61 parts by weight of ethylene glycol, 0.04 parts by weight of magnesium acetate, 0.02 parts by weight of antimony trioxide and 0.004 parts by weight of potassium hydroxide are gradually added. The ester exchange reaction is carried out while distilling methanol at 220 ° C. finally. Next, 0.020 part by weight of an 85% aqueous solution of phosphoric acid is added to the transesterification reaction product, and then transferred to a polycondensation reaction kettle. Furthermore, the reaction system was gradually depressurized while being heated and heated, and a polycondensation reaction was conducted at 290 ° C. under a reduced pressure of 1 hPa. The amount of diethylene glycol was 0.4% by weight, the intrinsic viscosity was 0.65, and the acid A polyethylene terephthalate resin B was prepared in which 95 mol% or more of the component was composed of terephthalic acid and 95 mol% or more of the glycol component was composed of ethylene glycol.
Further, when the polyethylene terephthalate resin B is produced, a polycondensation reaction is performed after adding an ethylene glycol slurry of agglomerated silica particles having an average particle size of 2.4 μm after the transesterification reaction, and a particle master B having a particle concentration of 2 mass%. Got. Polyethylene terephthalate resin B and particle master B were mixed and used at a mass ratio of 98: 2. Other conditions were the same as in Example 1, and a biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained. The characteristics are shown in Table 1.

(Example 7)
A biaxially oriented polyester film for packaging having a thickness of 20 μm was obtained under the same conditions as in Example 1 except that the amount of extrusion from the T-shaped die was adjusted. The characteristics are shown in Table 1.

(Comparative Example 1)
A biaxially oriented polyester film having a thickness of 12 μm was obtained under the same conditions as in Example 1 except that the coating liquid was not applied (the easy adhesion layer was not provided). The characteristics are shown in Table 2.

(Comparative Example 2)
A biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained under the same conditions as in Example 1 except that the MD stretch ratio was 3.6 times and the TD stretch ratio was 2.7 times. The characteristics are shown in Table 2.

(Comparative Example 3)
A biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained under the same conditions as in Example 1 except that the MD stretch ratio was 4.5 times and the TD stretch ratio was 3.5 times. The characteristics are shown in Table 2.

(Comparative Example 4)
A biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained under the same conditions as in Example 1 except that the MD stretch ratio was 4.5 times and the TD stretch ratio was 2.5 times. The characteristics are shown in Table 2.

(Comparative Example 5)
The heating temperature before MD stretching is 110 ° C., the MD stretching temperature is 120 ° C., the MD stretching ratio is 3.6 times, and the other conditions are the same as in Example 1, and the biaxially oriented polyester for packaging with a thickness of 12 μm. A film was obtained. The characteristics are shown in Table 2.

(Comparative Example 6)
A biaxially oriented polyester film for packaging having a thickness of 6 μm was obtained under the same conditions as in Example 1 except that the same polyester as in Example 1 was used and the amount of extrusion from the T-shaped die into a sheet was adjusted. The characteristics are shown in Table 2.

(Comparative Example 7)
To a mixture of 100 parts by weight of dimethyl terephthalate and 61 parts by weight of ethylene glycol, 0.04 part by weight of magnesium acetate and 0.02 part by weight of antimony trioxide are added, and the temperature is gradually raised. Transesterification is carried out while distilling methanol at 220 ° C. Next, 0.020 part by weight of an 85% aqueous solution of phosphoric acid is added to the transesterification reaction product, and then transferred to a polycondensation reaction kettle. Furthermore, the reaction system was gradually depressurized while being heated and heated, and a polycondensation reaction was performed at 290 ° C. under a reduced pressure of 1 hPa, and the amount of diethylene glycol was 2.0% by weight, the intrinsic viscosity was 0.65, and the acid A polyethylene terephthalate resin C was prepared in which 95 mol% or more of the components were composed of terephthalic acid and 95 mol% or more of the glycol components were composed of ethylene glycol.
Further, when the polyethylene terephthalate resin C is produced, a polycondensation reaction is performed after adding an ethylene glycol slurry of aggregated silica particles having an average particle diameter of 2.4 μm after the transesterification reaction, and a particle master C having a particle concentration of 2 mass%. Got. Polyethylene terephthalate resin C and particle master C were mixed and used at a mass ratio of 98: 2. Other conditions were the same as in Example 1, and a biaxially oriented polyester film for packaging having a thickness of 12 μm was obtained. The characteristics are shown in Table 2.

However, the abbreviations in the table are as follows.
Δn: Birefringence (a value obtained by multiplying the difference in refractive index between the film longitudinal direction and the width direction by 1000)
MD: Film longitudinal direction TD: Film width direction peeling part A: Peeling peeling part between OPP / PE and VM-PET / PE / CPP B: Polyester film cleaving peeling peeling part C: Aluminum evaporated film and biaxial for packaging Peeling between oriented polyester films From Tables 1 and 2, each film of the Examples was excellent in the resistance to actual package pinholes. On the other hand, each film of the comparative example is inferior in piercing strength because of poor orientation balance in the film longitudinal direction and in the width direction, or has low peel strength because there is no easy adhesion layer, and is inferior in actual package pinhole strength Since the plane orientation was too high, the polyester film was cleaved and peeled, and the actual resistance pinhole strength was inferior, which was insufficient as a packaging material.

  The biaxially oriented polyester film for packaging according to the present invention is excellent in puncture pinhole resistance in various deformation modes required as a package laminated with other films, etc. can do. Furthermore, when it is used as a package having a layer made of metal and / or metal oxide, it has excellent peel strength between the polyester film and the layer made of metal and / or metal oxide. Because the puncture strength can be maintained without causing delamination due to the above, when a package is manufactured using the present invention, even when packaging a hard snack or a heavy snack, etc. There is an excellent effect of improving pin puncture resistance.

It is the schematic of peel strength measurement.

Explanation of symbols

1: Constituent 2
2: Polyurethane adhesive 3: CPP2

Claims (7)

  A biaxially oriented polyester film for packaging in which an easy-adhesion layer using a polyester resin and a melamine compound is formed on at least one surface of the polyester film, and the plane orientation coefficient (fn) of the biaxially oriented polyester film for packaging is 0.167 or more and 0.175 or less, absolute value of birefringence (Δn) is less than 5, pin puncture strength is 7N or more and 15N or less, film thickness is 7 μm or more and 20 μm or less, and is defined in the specification as the easily adhesive layer A biaxially oriented polyester film for packaging having a peel strength between the metal layer of 1 N / 15 mm or more.   The biaxially oriented polyester film for packaging according to claim 1, wherein the polyester resin constituting the easy-adhesion layer contains at least three acid components selected from the group consisting of terephthalic acid, isophthalic acid, trimellitic acid, and sebacic acid. .   The biaxial packaging according to claim 1 or 2, wherein the polyester resin constituting the easy adhesion layer contains at least two glycol components selected from the group consisting of ethylene glycol, neopentyl glycol, and 1,4-butanediol. Oriented polyester film.   The amount of diethylene glycol in the biaxially oriented polyester film for packaging is 0.01 wt% or more and 1.2 wt% or less with respect to the entire biaxially oriented polyester film for packaging. Biaxially oriented polyester film.   The package which uses the biaxially-oriented polyester film for packaging in any one of Claims 1-4.   The package body in which the layer which consists of a metal and / or a metal oxide is laminated | stacked on the easily bonding layer of the biaxially-oriented polyester film for packaging in any one of Claims 1-4.   The package body in which the layer which consists of an olefin type film is provided on the layer which consists of a metal and / or a metal oxide of the package body of Claim 6.

Images