Polyester film and packaging

Abstract

To provide a polyester film which has high handleability in a process up to completion of lamination, and can impart high impact resistance and recyclability to a package.SOLUTION: A thickness T of a polyester film in which a plurality of layers are stacked is 30-70 μm. Each of the layers is a mixture of a polyester resin mainly containing polyethylene terephthalate. A copolymer component ratio that is the total of a product of copolymer component concentration of a monomer component other than the polyethylene terephthalate in a first layer, and a mass ratio of the polyester resin is 20-35 mol%. A copolymer component ratio of the whole film considering thicknesses of each of the layers with respect to the thickness of the whole film is 15% or less. The total of smaller blend ratios of the polyester resin having the same type of the component constituting the polyester resin in the two adjacent layers is 0.25-1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a polyester film laminated with a polyester resin, and to a packaging product using the polyester film. [Background technology]

[0002] The laminate materials used in pouch packaging are made of various materials, and a polyester film is sometimes used as the innermost layer, or so-called sealant layer (see, for example, Patent Document 1).

[0003] In the polyester film described in Patent Document 1, a mixed resin of a resin containing polyethylene terephthalate as a main component and polybutylene terephthalate is used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-165059 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a growing interest in "mono-material" packaging, which takes recycling into consideration as an environmentally friendly approach. .child Therefore, polyester films are required to be made of the same type of resin, taking into consideration the mono-materialization from the viewpoint of recyclability.

[0006] In pouch packaging, the heat-sealed layers of polyester film are bonded together by thermocompression to package the contents, so the heat-sealed areas must be highly impact resistant to prevent leakage of the contents.

[0007] Furthermore, if wrinkles occur in the polyester film during the production of the laminate material, the productivity of the polyester film decreases, and therefore a polyester film that is suppressed from wrinkling during the film transport and winding processes is desired.

[0008] Therefore, there is a demand for a polyester film that is made of a polyester resin having a polyethylene terephthalate skeleton, and that can be used to produce packaging materials that are highly impact resistant and that are easy to handle. [Means for solving the problem]

[0009] According to a first aspect of the present disclosure, there is provided a polyester film in which resins from a first layer to an nth layer are laminated in order, where n is a natural number of 2 or more. The polyester film has a thickness T of 30 μm to 70 μm. Each layer contains at least one polyester resin that is a polymer of an acid component and an alcohol component. The acid component contains a terephthalic acid component as a main component. The alcohol component contains an ethylene glycol component as a main component. At least one of the acid component and the alcohol component further contains a copolymer component other than the terephthalic acid component and the ethylene glycol component. The first layer is a mixture of a first polyester resin and a second polyester resin. In the first polyester resin, the acid component is a terephthalic acid component and an isophthalic acid component, and the alcohol component is an ethylene glycol component. In the second polyester resin, the acid component is a terephthalic acid component, and the alcohol component is the ethylene glycol component and a neopentyl glycol component. The sum of the proportion of copolymerization components relative to 100 mol% of the total amount of acid components in each polyester resin and the proportion of copolymerization components relative to 100 mol% of the total amount of alcohol components in each polyester resin is referred to as the copolymerization component concentration. The mass ratio of each polyester resin contained in each layer is referred to as the blend ratio. The sum of the values ​​obtained by multiplying the copolymerization component concentration of each polyester resin in each layer by the blend ratio is referred to as the copolymerization component ratio. The copolymerization component ratios of the first to nth layers are referred to as c1 to cn, respectively. The thicknesses of the first to nth layers are referred to as t1 to tn, respectively. In two adjacent layers, polyester resins in which the types of components constituting the polyester resin are the same are referred to as the same type of resin. The smaller blend ratio of the same type of resin in two adjacent layers is referred to as the minimum blend ratio. The sum of the minimum blend ratios in two adjacent layers is referred to as the same type of resin usage rate P. In this case, the following conditions (1) to (3) are satisfied. (1)c1=20mol%~35mol%; (2) c1×t1 / T+…+cn×tn / T≦15; and (3) P = 0.25 to 1.0. A second aspect of the present disclosure provides a polyester film in which resins from a first layer to an nth layer are laminated in order, where n is a natural number of 2 or greater. The polyester film has a thickness T of 30 μm to 70 μm. Each layer contains at least one polyester resin that is a polymer of an acid component and an alcohol component. The acid component contains a terephthalic acid component as a main component. The alcohol component contains an ethylene glycol component as a main component. At least one of the acid component and the alcohol component further contains a copolymer component other than the terephthalic acid component and the ethylene glycol component. The second layer adjacent to the first layer is a mixture of a third polyester resin and a fourth polyester resin. In the third polyester resin, the acid component is composed of a terephthalic acid component and an isophthalic acid component, and the alcohol component is composed of an ethylene glycol component. In the fourth polyester resin, the acid component is composed of a terephthalic acid component, and the alcohol component is composed of an ethylene glycol component and a neopentyl glycol component. The sum of the proportion of copolymerization components relative to 100 mol% of the total amount of acid components in each polyester resin and the proportion of copolymerization components relative to 100 mol% of the total amount of alcohol components in each polyester resin is referred to as the copolymerization component concentration. The mass ratio of each polyester resin contained in each layer is referred to as the blend ratio. The sum of the values ​​obtained by multiplying the copolymerization component concentration of each polyester resin in each layer by the blend ratio is referred to as the copolymerization component ratio. The copolymerization component ratios of the first layer to the nth layer are respectively referred to as c1 to cn. The thicknesses of the first layer to the nth layer are respectively referred to as t1 to tn. In two adjacent layers, polyester resins in which the types of components constituting the polyester resin are the same are referred to as the same type of resin. The smaller blend ratio of the same type of resin in two adjacent layers is referred to as the minimum blend ratio, and the sum of the minimum blend ratios in the two adjacent layers is referred to as the same type of resin usage rate P. In this case, the following conditions (1) to (3) are satisfied. (1)c1=20mol%~35mol%; (2) c1×t1 / T+…+cn×tn / T≦15; and (3)P=0.25~1.0。

[0010] The present disclosure 3 According to the viewpoint, the packaged item and the first viewpoint that packages the packaged item or second perspective and a packaging body comprising the polyester film according to claim 1, wherein the first layers are heat-fused together. [Effects of the Invention]

[0011] The first layers of polyester films of the present disclosure can form a highly impact resistant seal.

[0012] The polyester film of the present disclosure is suppressed from wrinkling during handling steps such as transportation, thereby improving the production efficiency of polyester films and packaging materials.

[0013] In the polyester film of the present disclosure, all layers are primarily made of polyethylene terephthalate, which makes the polyester film of the present disclosure highly recyclable.

[0014] The packaging of the present disclosure has high impact resistance. DETAILED DESCRIPTION OF THE INVENTION

[0015] According to a preferred embodiment of the first aspect, the copolymerization component is at least one selected from the group consisting of an isophthalic acid component and a neopentyl glycol component.

[0017] According to a preferred embodiment of the first aspect, the isophthalic acid component in the first polyester resin is 1 mol % to 30 mol % relative to the total amount of acid components in the first polyester resin, and the neopentyl glycol component in the second polyester resin is 20 mol % to 50 mol % relative to the total amount of alcohol components in the second polyester resin.

[0018] According to a preferred embodiment of the first aspect, the blend ratio of the first polyester resin is 0.08 to 0.5, and the blend ratio of the second polyester resin is 0.5 to 0.92.

[0019] According to a preferred mode of the first aspect, the thickness of the first layer is 5 μm to 25 μm.

[0020] According to a preferred embodiment of the first aspect, the second layer adjacent to the first layer is a mixture of a third polyester resin and a fourth polyester resin. In the third polyester resin, the acid component comprises a terephthalic acid component and an isophthalic acid component, and the alcohol component comprises an ethylene glycol component. In the fourth polyester resin, the acid component comprises a terephthalic acid component, and the alcohol component comprises an ethylene glycol component and a neopentyl glycol component.

[0021] According to a preferred embodiment of the first aspect, the isophthalic acid component in the third polyester resin is 2 mol % to 10 mol % relative to the total amount of acid components in the third polyester resin, and the neopentyl glycol component in the fourth polyester resin is 20 mol % to 40 mol % relative to the total amount of alcohol components in the fourth polyester resin.

[0022] According to a preferred embodiment of the first aspect, the blend ratio of the third polyester resin is 0.75 to 0.95, and the blend ratio of the fourth polyester resin is 0.05 to 0.25. According to a preferred embodiment of the second aspect, the isophthalic acid component in the third polyester resin is 2 mol % to 10 mol % relative to the total amount of acid components in the third polyester resin, and the neopentyl glycol component in the fourth polyester resin is 20 mol % to 40 mol % relative to the total amount of alcohol components in the fourth polyester resin. According to a preferred embodiment of the second aspect, the blend ratio of the third polyester resin is 0.75 to 0.95, and the blend ratio of the fourth polyester resin is 0.05 to 0.25. According to a preferred embodiment of the second aspect, the first layer has a thickness of 5 μm to 25 μm, and the second layer has a thickness of 22 μm to 50 μm.

[0023] The first viewpoint above or second perspective According to a preferred embodiment, n=2 or 3.

[0024] The first viewpoint above or second perspective According to a preferred embodiment of the present invention, the polyester film is for use as a sealant, and the first layer is a heat seal layer.

[0025] The first viewpoint above or second perspective According to a preferred embodiment, the ethylene glycol component is a component derived from biomass.

[0026] The above item 3 According to a preferred embodiment of the present invention, the packaged item is sealed with a polyester film.

[0027] In the present specification and claims, each acid component and each alcohol component may also include its derivatives. For example, an acid component may also include a derivative of the acid component (e.g., an ester).

[0028] The composition of the polyester resin may not necessarily be the same as the composition of the raw material monomers charged in the polyester resin. In the following, unless otherwise specified, the notation of mole percent (mol%) concentration indicating the composition refers to the mole percent concentration of the component in the produced resin, not the amount of raw material monomer charged in the polyester resin.

[0029] The polyester film according to the first embodiment of the present disclosure will be described.

[0030] The polyester film of the present disclosure is a film in which multiple polyester resins with different and / or identical compositions are laminated. Hereinafter, a polyester film in which a first layer to an nth layer (n is a natural number of 2 or more) are laminated in this order will be described. The number of layers (n) can be, for example, 2 to 5. n is preferably 2 or 3.

[0031] The polyester resin of each layer contains at least one polyester resin which is a polymer of an acid component and an alcohol component, and is preferably a mixture of two or three polyester resins with different compositions.

[0032] In this disclosure, the mass ratio of the polyester resins in each layer is referred to as the blend ratio. For example, if a first layer contains 20 mass% of a first polyester resin and 80 mass% of a second polyester resin, relative to the mass of the first layer, the blend ratio of the first polyester resin is 0.2 and the blend ratio of the second polyester resin is 0.8. In other words, the sum of the blend ratios in each layer is 1.

[0033] In the polyester resin of each layer, the acid component mainly contains a terephthalic acid component, the alcohol component mainly contains an ethylene glycol component, and the polyester resin of each layer has polyethylene terephthalate (PET) as the main skeleton.

[0034] The acid component is terephthalic acid componentThe alcohol component may further contain a component other than the ethylene glycol component. In the present disclosure, components other than the terephthalic acid component and the ethylene glycol component are referred to as copolymer components. An example of a copolymer component of the acid component is an isophthalic acid component. An example of a copolymer component of the alcohol component is a neopentyl glycol (2,2-dimethyl-1,3-propanediol) component. The polyester resin contained in each layer may contain at least one copolymer component selected from the group consisting of an isophthalic acid component and a neopentyl glycol component.

[0035] The acid component may contain other acid components as long as the essential properties of the polyester film of the present disclosure are not changed. Examples of other acid components include orthophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, succinic acid, dimer acid, 1,4-cyclohexadicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, or These derivatives Ingredients consisting of These other acid components may be added either alone or in any combination of two or more in any ratio.

[0036] The alcohol component may contain other alcohol components as long as the essential properties of the polyester film of the present disclosure are not altered. Examples of other alcohol components include 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, diethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, or These derivatives Ingredients consisting of These other alcohol components may be added either alone or in any combination of two or more in any proportion.

[0037] The monomer component of the polyester resin may be a component derived from a fossil fuel or a component derived from biomass.

[0038] Biomass-derived components can be detected, for example, by measuring the number of radioactive carbon atoms using accelerator mass spectrometry (AMS). 12 It is an isotope of C 14 C and 13 Measure the amount of C 14 C and 13 The amount of biomass-derived raw materials used can be measured from the amount of C.

[0039] The first layer will now be described. The first layer is the exposed end layer of the polyester film. When the polyester film of the present disclosure is used as a sealant material, the first layer can function as a heat-sealing layer.

[0040] The first layer may be a mixture of a first polyester resin and a second polyester resin, at least one of which may contain an isophthalic acid component as a copolymerization component, and at least the other of which may contain a neopentyl glycol component as a copolymerization component.

[0041] When the acid component does not contain an isophthalic acid component as a copolymerization component, the terephthalic acid component is preferably 90 mol% or more relative to the total amount of the acid components. The terephthalic acid component can be, for example, 93 mol% or more, 96 mol% or more, or 100 mol% relative to the total amount of the acid components. The terephthalic acid component can be, for example, 100 mol%, 97 mol% or less, or 94 mol% or less relative to the total amount of the acid components.

[0042] When the acid component contains an isophthalic acid component as a copolymerization component, the terephthalic acid component is preferably 70 mol% or more relative to the total amount of the acid components. The terephthalic acid component can be, for example, 73 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 93 mol% or more relative to the total amount of the acid components. The terephthalic acid component is preferably 99 mol% or less relative to the total amount of the acid components. The terephthalic acid component can be, for example, 98 mol% or less, 97 mol% or less, or 96 mol% or less relative to the total amount of the acid components.

[0043] When the acid component contains an isophthalic acid component as a copolymerization component, the isophthalic acid component is preferably 1 mol% or more relative to the total amount of the acid components. The isophthalic acid component can be, for example, 2 mol% or more, 3 mol% or more, or 4 mol% or more relative to the total amount of the acid components. If the isophthalic acid component is less than 1 mol%, it becomes difficult to obtain good heat-sealing properties. The isophthalic acid component is preferably 30 mol% or less relative to the total amount of the acid components. The isophthalic acid component can be, for example, 27 mol% or less, 25 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, or 7 mol% or less relative to the total amount of the acid components in the first polyester resin.

[0044] When the alcohol component does not contain a neopentyl glycol component as a copolymerization component, the ethylene glycol component is preferably, for example, 90 mol% or more relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 93 mol% or more, 96 mol% or more, or 100 mol% relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 100 mol%, 97 mol% or less, or 94 mol% or less relative to the total amount of the alcohol component.

[0045] When the alcohol component contains a neopentyl glycol component as a copolymerization component, the ethylene glycol component is preferably 50 mol% or more relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 55 mol% or more, 60 mol% or more, 65 mol% or more, or 70 mol% or more relative to the total amount of the alcohol component. For example, the ethylene glycol component is preferably 80 mol% or less relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 75 mol% or less, 70 mol% or less, or 65 mol% or less relative to the total amount of the alcohol component.

[0046] When the alcohol component contains a neopentyl glycol component as a copolymerization component, the neopentyl glycol component is preferably 20 mol% or more relative to the total amount of the alcohol component. The neopentyl glycol component can be, for example, 25 mol% or more, 30 mol% or more, or 35 mol% or more relative to the total amount of the alcohol component. If the neopentyl glycol component is less than 20 mol%, it becomes difficult to obtain good heat-sealing properties. The neopentyl glycol component is preferably 50 mol% or less relative to the total amount of the alcohol component. The neopentyl glycol component can be, for example, 45 mol% or less, 40 mol% or less, 35 mol% or less, or 30 mol% or less relative to the total amount of the alcohol component.

[0047] In the first polyester resin of the first layer, the acid component may be terephthalic acid and isophthalic acid, and the alcohol component may be ethylene glycol. In the second polyester resin, the acid component may be terephthalic acid, and the alcohol component may be ethylene glycol and neopentyl glycol.

[0048] For example, the first polyester resin in the first layer may contain 70 mol% to 99 mol% of a terephthalic acid component and 1 mol% to 30 mol% of an isophthalic acid component as the acid component, and 100 mol% of an ethylene glycol component as the alcohol component.

[0049] For example, in the second polyester resin of the first layer, the acid component can include 100 mol% of a terephthalic acid component, and in the second polyester resin of the first layer, the alcohol component can include 50 mol% to 80 mol% of an ethylene glycol component and 20 mol% to 50 mol% of a neopentyl glycol component.

[0050] The blend ratio of the first polyester resin in the first layer is preferably 0.08 or more. The blend ratio of the first polyester resin can be, for example, 0.1 or more, 0.12 or more, 0.18 or more, 0.25 or more, or 0.3 or more. The blend ratio of the first polyester resin is preferably 0.5 or less. The blend ratio of the first polyester resin can be, for example, 0.45 or less, 0.4 or less, 0.35 or less, 0.3 or less, 0.25 or less, 0.22 or less, or 0.18 or less.

[0051] The blend ratio of the second polyester resin in the first layer is preferably 0.5 or more. The blend ratio of the second polyester resin can be, for example, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, 0.78 or more, or 0.82 or more. The blend ratio of the second polyester resin is preferably 0.92 or less. The blend ratio of the second polyester resin can be, for example, 0.9 or less, 0.88 or less, 0.82 or less, 0.75 or less, or 0.7 or less.

[0052] In this disclosure, the sum of the proportion of copolymerization components relative to 100 mol% of the total amount of acid components and the proportion of copolymerization components relative to 100 mol% of the total amount of alcohol components in each polyester resin is referred to as the copolymerization component concentration. For example, if the isophthalic acid component is 5 mol% relative to the total amount of acid components and the neopentyl glycol component is 10 mol% relative to the total amount of alcohol components in a first polyester resin, the copolymerization component concentration of the first polyester resin is 15 mol%.

[0053] In this disclosure, the sum of the products of the copolymerization component concentrations and blend ratios of each polyester resin in a layer is referred to as the copolymerization component ratio. The copolymerization component ratios of the first to nth layers are denoted as c1 to cn, respectively. For example, if in the first layer the copolymerization component concentration of the first polyester resin is 10 mol%, the blend ratio of the first polyester resin is 0.3, the copolymerization component concentration of the second polyester resin is 20 mol%, and the blend ratio of the second polyester resin is 0.7, then the copolymerization component ratio c1 is 10 mol% × 0.3 + 20 mol% × 0.7 = 17 mol%.

[0054] The copolymerization component ratio c1 of the first layer is 20 mol% or more. do. The copolymerization component ratio c1 can be, for example, 22 mol% or more, 25 mol% or more, or 30 mol% or more. If the copolymerization component ratio c1 is less than 20 mol%, the bonding strength will be weak when the first layer is used as a heat seal layer. The copolymerization component ratio c1 of the first layer is 35 mol% or less. do. The copolymerization component ratio c1 can be, for example, 32 mol% or less, 30 mol% or less, 28 mol% or less, 26 mol% or less, or 24 mol% or less. If the copolymerization component ratio c1 exceeds 35 mol%, the degree of softening of the resin due to heat increases, and the thickness of the heat-sealed portion decreases due to the sealing pressure. This reduces the impact resistance of the sealed portion.

[0055] A second layer adjacent to the first layer is described.

[0056] The second layer may be a mixture of a third polyester resin and a fourth polyester resin, at least one of which may contain an isophthalic acid component as a copolymerization component, and at least the other of which may contain a neopentyl glycol component as a copolymerization component.

[0057] When the acid component does not contain an isophthalic acid component as a copolymerization component, the terephthalic acid component is preferably 90 mol% or more relative to the total amount of the acid components. The terephthalic acid component can be, for example, 93 mol% or more, 96 mol% or more, or 100 mol% relative to the total amount of the acid components. The terephthalic acid component can be, for example, 100 mol%, 97 mol% or less, or 94 mol% or less relative to the total amount of the acid components.

[0058] When the acid component contains an isophthalic acid component as a copolymerization component, the terephthalic acid component is preferably 70 mol% or more relative to the total amount of the acid components. The terephthalic acid component can be, for example, 73 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 93 mol% or more relative to the total amount of the acid components. The terephthalic acid component is preferably 99 mol% or less relative to the total amount of the acid components. The terephthalic acid component can be, for example, 98 mol% or less, 97 mol% or less, or 96 mol% or less relative to the total amount of the acid components.

[0059] When the acid component contains an isophthalic acid component as a copolymerization component, the isophthalic acid component is preferably 1 mol% or more relative to the total amount of the acid components. The isophthalic acid component can be, for example, 2 mol% or more, 3 mol% or more, or 4 mol% or more relative to the total amount of the acid components. The isophthalic acid component is preferably 30 mol% or less relative to the total amount of the acid components. The isophthalic acid component can be, for example, 27 mol% or less, 25 mol% or less, 20 mol% or less, 15 mol% or less, 10 mol% or less, or 7 mol% or less relative to the total amount of the acid components in the third polyester resin.

[0060] When the alcohol component does not contain a neopentyl glycol component as a copolymerization component, the ethylene glycol component is preferably, for example, 90 mol% or more relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 93 mol% or more, 96 mol% or more, or 100 mol% relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 100 mol%, 97 mol% or less, or 94 mol% or less relative to the total amount of the alcohol component.

[0061] When the alcohol component contains a neopentyl glycol component as a copolymerization component, the ethylene glycol component is preferably 50 mol% or more relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 55 mol% or more, 60 mol% or more, 65 mol% or more, or 70 mol% or more relative to the total amount of the alcohol component. For example, the ethylene glycol component is preferably 80 mol% or less relative to the total amount of the alcohol component. The ethylene glycol component can be, for example, 75 mol% or less, 70 mol% or less, or 65 mol% or less relative to the total amount of the alcohol component.

[0062] When the alcohol component contains a neopentyl glycol component as a copolymerization component, the neopentyl glycol component is preferably 20 mol% or more relative to the total amount of the alcohol component. The neopentyl glycol component can be, for example, 25 mol% or more, 30 mol% or more, or 35 mol% or more relative to the total amount of the alcohol component. The neopentyl glycol component is preferably 50 mol% or less relative to the total amount of the alcohol component. The neopentyl glycol component can be, for example, 45 mol% or less, 40 mol% or less, 35 mol% or less, or 30 mol% or less relative to the total amount of the alcohol component.

[0063] In the third polyester resin in the second layer, the acid component can be a terephthalic acid component and an isophthalic acid component, and the alcohol component can be an ethylene glycol component. In the fourth polyester resin, the acid component can be a terephthalic acid component, and the alcohol component can be an ethylene glycol component and a neopentyl glycol component.

[0064] For example, the acid component of the third polyester resin in the second layer may include 70 mol% to 99 mol% of a terephthalic acid component and 1 mol% to 30 mol% of an isophthalic acid component, and the alcohol component of the third polyester resin in the second layer may include 100 mol% of an ethylene glycol component.

[0065] For example, in the fourth polyester resin in the second layer, the acid component can include 100 mol% of a terephthalic acid component.In the fourth polyester resin in the second layer, the alcohol component can include 50 mol% to 80 mol% of an ethylene glycol component and 20 mol% to 50 mol% of a neopentyl glycol component.

[0066] The blend ratio of the third polyester resin in the second layer is preferably 0.5 or more. The blend ratio of the third polyester resin can be, for example, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, 0.78 or more, or 0.82 or more. The blend ratio of the third polyester resin is preferably 0.92 or less. The blend ratio of the third polyester resin can be, for example, 0.9 or less, 0.88 or less, 0.82 or less, 0.75 or less, or 0.7 or less.

[0067] The blend ratio of the fourth polyester resin in the second layer is preferably 0.08 or more. The blend ratio of the fourth polyester resin can be, for example, 0.1 or more, 0.12 or more, 0.18 or more, 0.25 or more, or 0.3 or more. The blend ratio of the fourth polyester resin is preferably 0.5 or less. The blend ratio of the fourth polyester resin can be, for example, 0.45 or less, 0.4 or less, 0.35 or less, 0.3 or less, 0.25 or less, 0.22 or less, or 0.18 or less.

[0068] The copolymerization component ratio c2 of the second layer is preferably 5 mol% or more. The copolymerization component ratio c2 can be, for example, 7 mol% or more, 8 mol% or more, or 9 mol% or more. If the copolymerization component ratio c2 is less than 5 mol%, the polyester resin with a high melting point will account for a large portion of the raw material, which will require maintaining a high temperature in the extruder during film formation, resulting in a high energy consumption rate. The copolymerization component ratio c2 of the second layer is preferably 20 mol% or less. The copolymerization component ratio c2 can be, for example, 18 mol% or less, 15 mol% or less, or 12 mol% or less. If the copolymerization component ratio c2 exceeds 20 mol%, the copolymerization component ratio will be high throughout the film, making it difficult to handle, such as in terms of transportability in the next process.

[0069] In the present disclosure, the total thickness of the polyester film of the present disclosure is represented as T. The thicknesses of the first to nth layers are represented as t1 to tn, respectively. For example, the thickness of the first layer is represented as t1. The total thickness T can be measured, for example, by actual measurement. The thickness of each layer can be measured, for example, by cross-sectional observation using a microscope.

[0070] The total thickness T of the polyester film of the present disclosure is 30 μm or more. do.The total thickness T of the polyester film of the present disclosure can be, for example, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 55 μm or more, 60 μm or more, or 70 μm or more. If the total thickness T of the polyester film of the present disclosure is less than 30 μm, the impact resistance of the entire film will be reduced. If the total thickness T of the polyester film of the present disclosure is 70 μm or less, do. The overall thickness T of the polyester film of the present disclosure can be, for example, 65 μm or less, 60 μm or less, 55 μm or less, or 50 μm or less. The total thickness T of the polyester film is When it exceeds 70 μm 、 Heat is not easily transferred to the heat seal layer, resulting in a decrease in seal strength.

[0071] The thickness t1 of the first layer is preferably 5 μm or more. The thickness t1 of the first layer can be, for example, 8 μm or more, 10 μm or more, 12 μm or more, or 15 μm or more. If the thickness t1 of the first layer is less than 5 μm, it becomes difficult to ensure the strength of the sealed portion. The thickness t1 of the first layer is preferably 25 μm or less. The thickness t1 of the first layer can be, for example, 22 μm or less, 20 μm or less, 18 μm or less, or 15 μm or less. If the thickness t1 of the first layer exceeds 25 μm, when the first layer is a heat-sealable layer, the copolymerization rate of the entire film will be high, resulting in a film that is difficult to handle, such as in terms of transportability in the next process.

[0072] In the present disclosure, the sum of the products of the ratio of the film thickness of each layer to the thickness of the entire film and the copolymerization component ratio of the corresponding layer is referred to as the copolymerization component ratio C of the entire film. That is, the copolymerization component ratio C of the entire film is expressed by the following formula. Overall copolymerization component ratio of film C=c1×t1 / T+…+cn×tn / T

[0073] The copolymerization component ratio C of the entire film in the polyester film of the present disclosure is preferably 5% or more. The copolymerization component ratio C of the entire film can be, for example, 8% or more, or 10% or more. If the copolymerization component ratio C of the entire film is less than 5%, polyester resins with high melting points will account for a large portion of the raw materials in layers other than the heat seal layer, and the temperature of the extruder during film production will need to be maintained at a high temperature, resulting in a high energy consumption rate. If the copolymerization component ratio C of the entire film is 15% or less, do. The copolymerization component ratio C of the entire film can be, for example, 14% or less, or 13% or less. If the copolymerization component ratio C of the entire film exceeds 15%, the copolymerization component (amorphous component) in the entire film increases, resulting in a film with low crystallinity. If the crystallinity is low, the film's lubricity decreases, and the film is more likely to wrinkle during the transport process.

[0074] In the present disclosure, polyester resins in which the types of components constituting the polyester resin are the same in two adjacent layers of a polyester film are referred to as "same type resins." The smaller blend ratio between the same type of resins is referred to as the minimum blend ratio. The sum of the minimum blend ratios in two adjacent layers is referred to as the same type resin usage rate P. When two adjacent layers contain one of the same type of resin, the minimum blend ratio is the same type of resin usage rate P. When two adjacent layers contain one of the same type of resin, the minimum blend ratio is the same type of resin usage rate P. The same resin When there are multiple resins, the sum of the minimum blend ratios is the same type resin usage rate P.

[0075] In the polyester film of the present disclosure, the same resin use ratio P is 0.25 or more. do. The homogeneous resin usage ratio P can be, for example, 0.28 or more, 0.33 or more, 0.38 or more, 0.43 or more, or 0.48 or more. If the homogeneous resin usage ratio P is less than 0.25, interlayer delamination is likely to occur. The homogeneous resin usage ratio P can be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0076] The ratio P of the same resins used in the first layer and the second layer is preferably 0.7 or less.

[0077] The polyester film of the present disclosure may have three or more layers. The description of the second layer above may be applied to the third and subsequent layers, and the description here will be omitted.

[0078] In the polyester film of the present disclosure, when adjacent layers have the same composition (when the proportion P of the same resin used is 1), they are considered to be the same layer.

[0079] There are cases where it is not possible or practical to directly identify the polyester films of the present disclosure by composition, structure, properties, etc. In such cases, it should be permitted to identify the polyester films of the present disclosure by their manufacturing method.

[0080] The polyester film of the present disclosure can be used as a sealant material. In this case, the first layer can be used as a heat-sealing layer. When the polyester film of the present disclosure is used as a sealant material, a seal with high impact resistance can be produced.

[0081] In the polyester film of the present disclosure, delamination between layers is suppressed, which increases the strength of the film itself and allows the production of packaging products with high impact resistance.

[0082] The polyester film of the present disclosure is prevented from wrinkling during processes such as conveyance, thereby improving yield and productivity.

[0083] All layers in the polyester film of the present disclosure have a polyethylene terephthalate backbone, which means that the polyester film of the present disclosure can be suitably used as a sealant film when producing mono-material packaging.

[0084] The method for producing the polyester resin of the present disclosure is not particularly limited and can be carried out by a known polymerization method using a known catalyst. The method for producing the polyester resin of the present disclosure may be either a method of directly esterifying an unsubstituted polycarboxylic acid as a starting material, or a method of carrying out a transesterification reaction using an esterified product such as a dimethyl ester as a starting material. In order to obtain a sufficient reaction rate when producing the polyester resin of the present disclosure, it is desirable to carry out a transesterification reaction under normal pressure using a known catalyst in the first step, and then a polycondensation reaction under reduced pressure using a known catalyst in the second step. After the polycondensation reaction, a solid-state polymerization reaction may be carried out. The solid-state polymerization reaction can increase the intrinsic viscosity of the polyester resin.

[0085] The polyester film of the present disclosure can be produced according to a typical polyester film production method. In the co-extrusion method, the raw resins for each layer are fed into extruders for each layer in a predetermined ratio and melted. The resulting mixture is then joined, for example, through a multi-manifold T-die, extruded into a sheet, and rapidly cooled by a roll to produce an unoriented polyester film. This unoriented film can be stretched in the running direction by utilizing the speed difference between rolls at a temperature above the glass transition temperature, or stretched in the width direction using a tenter to produce a stretched polyester film. In the test examples shown below, films were obtained using a uniaxial stretching method in which stretching is performed in only one direction. However, films can also be obtained using non-stretching or biaxial stretching methods by adjusting the conditions.

[0086] A packaging body according to a second embodiment of the present disclosure will now be described.

[0087] The package includes a packaged item and the polyester film according to the first embodiment that packages the packaged item. The package can be a laminate film formed by laminating the polyester film of the present disclosure with another film. The polyester film can function as a sealant layer. The package can be formed by thermally fusing first layers of polyester film together. A laminate formed by laminating the polyester film of the present disclosure with another material is generally used for processing the package. The other material used in the laminate is not particularly limited and can be selected according to the purpose. The lamination method is not particularly limited, and a dry lamination method is generally used in which an adhesive is applied, dried, and then pressed.

[0088] Examples of the form of the package include a four-sided seal in which two rectangular laminates of the same dimensions are placed so that the first layers of the polyester film of the present disclosure face each other and the four sides are heat-sealed, and a three-sided seal in which one rectangular laminate is folded in half so that the first layer of the polyester film of the present disclosure faces the inside and three sides are sealed; however, various forms can be appropriately selected depending on the purpose.

[0089] The packaged item may be anything that can be packaged (contained) with the polyester film of the present disclosure and / or a laminate film containing the polyester film of the present disclosure. The packaged item can be sealed with the polyester film and / or laminate film of the present disclosure. For example, the packaged item can be so-called pouch-packaged with the polyester film and / or laminate film of the present disclosure.

[0090] There are cases where it is not possible or practical to directly identify the packages of the present disclosure by their composition, structure, properties, etc. In such cases, it should be permitted to identify the packages of the present disclosure by their method of manufacture.

[0091] The packaging of the present disclosure has high impact resistance because the first layers are firmly bonded together and the film itself is strong, which prevents the packaged contents from leaking. [Example]

[0092] The polyester film and the method for producing the same according to the present disclosure will be described below with reference to examples. However, the polyester film and the method for producing the same according to the present disclosure are not limited to the following examples.

[0093] Tables 1 to 4 show the compositions of the polyester resins used in producing the polyester films.

[0094] The abbreviations used in the table below are as follows: Po: Polyester resin TPA: Terephthalic acid IPA: Isophthalic acid EG: Ethylene glycol NPG: Neopentyl glycol

[0095] [Production of polyester resin 1] The first polyester resin of Test Example 1 will be used as an example. Acid and The mixture was 95 mol % terephthalic acid and 5 mol % isophthalic acid, and alcohol Ru and Ethylene glycol 100 mol% (alcohol Lu's moles / Acid The mixture was charged with 1.12 moles of ethanol and esterified at 250°C and 250kPa. Then, triethyl phosphate and germanium dioxide were added and the mixture was heated at 275°C and 100Pa. pressure The resulting mixture was subjected to a polycondensation reaction at 100°C until the desired viscosity was reached. The mixture was extruded into cooling water and pelletized using a strand cutter. The intrinsic viscosity (IV) of the resulting polymer was 0.65 dL / g. The mixture was then dried in a drum dryer at 120°C (vacuum) and solid-state polymerized in a drum-type solid-state polymerizer under vacuum at 207°C. The IV of the solid-state polymerized product was 0.80. dl / g It was.

[0096] Similarly, PET copolymerized with 2 mol% isophthalic acid (IV 0.76 dL / g) was prepared, and PET copolymerized with 25 mol% isophthalic acid (IV 0.68 dL / g) was prepared by the melt polymerization alone.

[0097] [Production of polyester resin 2] The second polyester resin of Test Example 1 is used as an example for explanation. Acid and 100 mol% terephthalic acid and 100 mol% alcohol Ru and Ethylene glycol 75.7 mol%, neopentyl glycol 24.3 mol% (alcohol Lu's moles / Acid The mixture was charged with 1.48 moles of ethanol and esterified at 250°C and 250kPa. Then, triethyl phosphate and germanium dioxide were added and the mixture was heated at 275°C and 100Pa. pressure The resulting mixture was subjected to a polycondensation reaction at 1000 kJ / min until the viscosity reached a predetermined value. The mixture was extruded into cooling water and pelletized using a strand cutter. The IV of the resulting polymer was 0.69 dL / g.

[0098] Similarly, PET copolymerized with 20 mol % neopentyl glycol (IV 0.69 dl / g) and PET copolymerized with 40 mol % neopentyl glycol (IV 0.69 dl / g) were prepared.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] [Table 4]

[0103] Polyester films were produced using the polyester resins prepared. Tables 5 to 8 show the blend ratio, copolymerization component ratio, and film thickness of each layer, as well as the copolymerization component ratio, film thickness, and homogeneous resin usage rate of the entire polyester film. The terms used in Tables 5 to 8 are explained below. In Test Examples 4 and 9, the first to third layers were laminated in this order.

[0104] The first Po and the second Po refer to the first polyester resin and the second polyester resin shown in Tables 1 to 4, respectively.

[0105] The copolymerization component refers to a component other than the constituent components of polyethylene terephthalate. In other words, the copolymerization component is a component other than a terephthalic acid component and an ethylene glycol component. The copolymerization component concentration is the sum of the ratio of the copolymerization component to the total amount of acid components (100 mol%) in each polyester resin and the ratio of the copolymerization component to the total amount of alcohol components (100 mol%). Taking the first polyester resin in Test Example 1 shown in Table 1 as an example, the copolymerization component in the acid component is an isophthalic acid component, and no copolymerization component is added to the alcohol component. Therefore, the copolymerization component concentration of the first polyester resin in Test Example 1 is 5 mol%.

[0106] The blend ratio is the blending ratio of the polyester resin in each layer. For example, in the first layer of Test Example 1 shown in Table 5, the first layer contains 20% by mass of the first polyester resin and 80% by mass of the polyester resin, relative to the mass of the first layer. The blend ratio of the first polyester resin is 0.2, and the blend ratio of the second polyester resin is 0.8.

[0107] The copolymerization component ratio is the sum of the products of the copolymerization component concentration and the blend ratio of each polyester resin in each layer. Taking the first layer in Test Example 1 shown in Table 5 as an example, the product of the copolymerization component concentration and the blend ratio in the first polyester resin is 1, and the product of the copolymerization component concentration and the blend ratio in the second polyester resin is 24. Therefore, the copolymerization component ratio is 25 mol%. The copolymerization component ratio of the entire film is the sum of the product of the ratio of the film thickness of each layer to the total film thickness and the copolymerization component ratio of each layer. Taking Test Example 1 shown in Table 5 as an example, the total thickness of the polyester film in Test Example 1 is 50 μm, so the copolymerization component ratio of the entire film is 25 mol% × 15 μm / 50 μm + 10 mol% × 35 μm / 50 μm = 14.5 mol%.

[0108] The term "same resin" refers to polyester resins in which the types of components constituting the polyester resin are the same in two adjacent layers. Taking Test Example 1 shown in Tables 1 and 5 as an example, in adjacent first and second layers, the first polyester resin in the first layer and the third polyester resin in the second layer are the same resin, and the second polyester resin in the first layer and the fourth polyester resin in the second layer are the same resin. The same resin usage rate is the sum of the smallest blend ratios between the same resins. Taking Test Example 1 shown in Tables 1 and 5 as an example, the smallest blend ratio between the first polyester resin in the first layer and the third polyester resin in the second layer is 0.2, and the smallest blend ratio between the second polyester resin in the first layer and the fourth polyester resin in the second layer is also 0.2, so the same resin usage rate is 0.2 + 0.2 = 0.4.

[0109] Biomass-derived EG indicates whether or not ethylene glycol produced from biomass raw materials was used.

[0110] [Production of polyester film] The resins used as raw materials for each layer were fed into the extruder for each layer in the ratios shown below, melted, and then extruded into a sheet using a multi-manifold T-die. The resulting unoriented polyester film was then uniaxially stretched in one direction using the speed difference between the rolls to obtain a film.

[0111] [Table 5]

[0112] [Table 6]

[0113] [Table 7]

[0114] [Table 8]

[0115] The polyester films of Test Examples 1 to 21 obtained above were tested for dynamic friction coefficient, film conveyance property, heat seal strength, and impact resistance. The test results are shown in Tables 9 to 12. The "15 mm" in the unit of heat seal strength refers to the width of the measurement sample.

[0116] [Dynamic friction coefficient] Compliant with JISK7125, Co., Ltd. Toyo Seiki Factory Made of Using the friction tester TR-2, the friction of the front and back of the polyester film of each test example was measured. motion The coefficient of friction was measured using a 200g sled (weight).

[0117] [Film transportability] When film is transported at 350 m / min using film slitting equipment, the transport and winding the law of natureThe film was rated as A when it was in good condition, B when wrinkles were observed in the film during transport but it was well wound up, and C when wrinkles appeared in the film during winding.

[0118] [Heat seal strength] Tester Industry Co., Ltd. Made of Using the heat seal tester TP-701-B, the first layers (heat seal layers) of the same polyester film of the same test example were bonded together and sealed under the conditions of 130°C, 0.2 MPa, and 2 seconds. Department A tension and compression testing machine (MinebeaMitsumi) was manufactured. Co., Ltd. Made 、 The maximum load until the seal peeled or broke was measured using a Technograph TG-5KN.

[0119] [Impact resistance] The first layers of the same test polyester film were bonded together to create a four-sided sealed pouch containing 150 ml of water. Co., Ltd. Made of Heat Seal Tester TP-701 - B was used. Two 150mm x 150mm sheets of the same polyester film were sealed at the first layer to create pouches filled with water at 170-190°C, 0.2 MPa, and 2 seconds. The area containing the water measured approximately 130 x 130mm. After cooling the pouches at 5°C for 12 hours, each was subjected to an impact resistance test. In the impact resistance test, 10 samples were dropped repeatedly from a height of 1m onto a steel plate on the floor up to 10 times. The test was terminated when the bag broke or water leaked, and the number of drops was recorded as a score. If the sample survived the first 10 drops, it was given a score of 10 regardless of the result of the 10th drop. Ten samples were dropped, and impact resistance was evaluated based on the average score. A: The average score was 8 or more; B: The average score was 4 or more but less than 8 points; C: Average score 4 It was less than a point.

[0120] All of the polyester films of Test Examples 1 to 10 gave good results.

[0121] In Test Example 11, the overall thickness of the film was thin, and therefore fractures occurred in areas other than the sealed portions in the heat seal strength test and impact resistance test, resulting in unsatisfactory results. From this, it is considered that the overall thickness of the film should preferably be 30 μm or more.

[0122] In Test Example 12, the film was too thick and heat was not sufficiently conducted to the first layer (heat seal layer), which is thought to have reduced the heat seal strength. For this reason, it is thought that the overall film thickness should preferably be 70 μm or less.

[0123] In Test Examples 13, 14, and 19, the copolymerization component ratio in the first layer (heat seal layer) was low, which is thought to have reduced the bonding strength of the sealed portion. Therefore, it is thought that a copolymerization component ratio of 20 mol% or more is preferable for the first layer. On the other hand, in Test Example 15, the melting point of the film was low, and the film melted at the heat seal temperature. This is thought to have resulted in a reduction in the thickness of the sealed portion due to the heat seal pressure, reducing the impact resistance of the sealed portion. Therefore, it is thought that a copolymerization component ratio of 35 mol% or less is preferable for the first layer.

[0124] In Test Examples 16, 17, and 20, the crystallinity of the entire film was reduced due to the high copolymerization ratio of the entire film. This is thought to have increased the dynamic friction coefficient of the film, causing wrinkles during film transport. For this reason, it is thought that a copolymerization ratio of the entire film of 15% or less is preferable.

[0125] In Test Examples 18 and 21, the interlayer bonding strength was low, and both the heat seal strength and impact resistance were low. From this, it is considered preferable that the homogeneous resin usage ratio be 0.25 or more.

[0126] The polyester films of Test Examples 1 to 10, which have high impact resistance and a low coefficient of dynamic friction, have a basic structure of polyethylene terephthalate in all layers, and therefore can be used as sealant films for packaging with high recyclability.

[0127] [Table 9]

[0128] [Table 10]

[0129] [Table 11]

[0130] [Table 12]

[0131] The polyester film and its manufacturing method of the present disclosure have been described based on the above embodiments and examples, but are not limited to the above embodiments and examples, and may include various modifications, changes, and improvements to each disclosed element (including elements described in the claims, specification, and drawings) within the scope of the present invention and based on the basic technical concept of the present invention. Furthermore, various combinations, substitutions, and selections of each disclosed element are possible within the scope of the claims of the present invention.

[0132] Further objects, purposes and modes (including modifications) of the present invention will become apparent from the entire disclosure of the present invention including the claims.

[0133] With respect to numerical ranges set forth herein, unless otherwise specified, any numerical value or range falling within that range should be construed as being specifically set forth herein.

[0134] Some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes. Each supplementary note may be combined with each claim in the claims. [Appendix 1] A method of using the polyester film of the present disclosure as a sealant material. [Industrial Applicability]

[0135] The polyester film of the present disclosure can be used as a sealant material for pouch packaging, laminate packaging, and the like.

Claims

1. A polyester film in which resins from a first layer to an nth layer are laminated in order, where n is a natural number of 2 or more, The thickness T of the polyester film is 30 μm to 70 μm, Each layer contains at least one polyester resin which is a polymer of an acid component and an alcohol component, the acid component contains a terephthalic acid component as a main component, The alcohol component contains an ethylene glycol component as a main component, at least one of the acid component and the alcohol component further contains a copolymerization component other than the terephthalic acid component and the ethylene glycol component; the first layer is a mixture of a first polyester resin and a second polyester resin; In the first polyester resin, the acid component comprises the terephthalic acid component and the isophthalic acid component, and the alcohol component comprises the ethylene glycol component; In the second polyester resin, the acid component is the terephthalic acid component, and the alcohol component is the ethylene glycol component and the neopentyl glycol component, The sum of the ratio of the copolymerization component to 100 mol% of the total amount of the acid components in each polyester resin and the ratio of the copolymerization component to 100 mol% of the total amount of the alcohol components in each polyester resin is referred to as the copolymerization component concentration, The mass ratio of each polyester resin contained in each layer is referred to as the blend ratio. The sum of the values ​​obtained by multiplying the copolymerization component concentration of each polyester resin in each layer by the blend ratio is expressed as the copolymerization component ratio, The copolymerization component ratios of the first layer to the nth layer are denoted as c1 to cn, respectively. The thicknesses of the first layer to the nth layer are denoted as t1 to tn, respectively. In two adjacent layers, polyester resins in which the types of components constituting the polyester resin are the same are referred to as "same type resins," When the smaller blend ratio of the same resins in two adjacent layers is designated as the minimum blend ratio, and the sum of the minimum blend ratios in the two adjacent layers is designated as the same resin use rate P, A polyester film that satisfies the following conditions (1) to (3): (1) c1 = 20 mol% to 35 mol%; (2) c1 × t1 / T + ... + cn × tn / T ≤ 15; and (3) P=0.25-1.

0.

2. The polyester film according to claim 1 , wherein the copolymerization component is at least one selected from the group consisting of an isophthalic acid component and a neopentyl glycol component.

3. the isophthalic acid component in the first polyester resin is 1 mol % to 30 mol % based on the total amount of acid components in the first polyester resin; 3. The polyester film according to claim 1, wherein the neopentyl glycol component in the second polyester resin is 20 mol % to 50 mol % based on the total amount of alcohol components in the second polyester resin.

4. the blend ratio of the first polyester resin is 0.08 to 0.5; The polyester film according to any one of claims 1 to 3, wherein the blend ratio of the second polyester resin is 0.5 to 0.

92.

5. The polyester film according to any one of claims 1 to 4, wherein the first layer has a thickness of 5 µm to 25 µm.

6. a second layer adjacent to the first layer is a mixture of a third polyester resin and a fourth polyester resin; In the third polyester resin, the acid component comprises the terephthalic acid component and the isophthalic acid component, and the alcohol component comprises the ethylene glycol component; 6. The polyester film according to claim 1, wherein, in the fourth polyester resin, the acid component is the terephthalic acid component, and the alcohol component is the ethylene glycol component and the neopentyl glycol component.

7. the isophthalic acid component in the third polyester resin is 2 mol % to 10 mol % based on the total amount of acid components in the third polyester resin; The polyester film according to claim 6, wherein the neopentyl glycol component in the fourth polyester resin is 20 mol % to 40 mol % with respect to the total amount of the alcohol components of the fourth polyester resin.

8. the blend ratio of the third polyester resin is 0.75 to 0.95; The polyester film according to claim 6 or 7, wherein the blend ratio of the fourth polyester resin is 0.05 to 0.

25.

9. A polyester film in which resins from a first layer to an nth layer are laminated in order, where n is a natural number of 2 or more, The thickness T of the polyester film is 30 μm to 70 μm, Each layer contains at least one polyester resin which is a polymer of an acid component and an alcohol component, the acid component contains a terephthalic acid component as a main component, The alcohol component contains an ethylene glycol component as a main component, at least one of the acid component and the alcohol component further contains a copolymerization component other than the terephthalic acid component and the ethylene glycol component; a second layer adjacent to the first layer is a mixture of a third polyester resin and a fourth polyester resin; In the third polyester resin, the acid component comprises the terephthalic acid component and the isophthalic acid component, and the alcohol component comprises the ethylene glycol component; In the fourth polyester resin, the acid component is the terephthalic acid component, and the alcohol component is the ethylene glycol component and the neopentyl glycol component, The sum of the ratio of the copolymerization component to 100 mol% of the total amount of the acid components in each polyester resin and the ratio of the copolymerization component to 100 mol% of the total amount of the alcohol components in each polyester resin is referred to as the copolymerization component concentration, The mass ratio of each polyester resin contained in each layer is referred to as the blend ratio. The sum of the values ​​obtained by multiplying the copolymerization component concentration of each polyester resin in each layer by the blend ratio is expressed as the copolymerization component ratio, The copolymerization component ratios of the first layer to the nth layer are denoted as c1 to cn, respectively. The thicknesses of the first layer to the nth layer are denoted as t1 to tn, respectively. In two adjacent layers, polyester resins in which the types of components constituting the polyester resin are the same are referred to as "same type resins," When the smaller blend ratio of the same resins in two adjacent layers is designated as the minimum blend ratio, and the sum of the minimum blend ratios in the two adjacent layers is designated as the same resin use rate P, A polyester film that satisfies the following conditions (1) to (3): (1) c1 = 20 mol% to 35 mol%; (2) c1 × t1 / T + ... + cn × tn / T ≤ 15; and (3) P=0.25-1.

0.

10. The isophthalic acid component in the third polyester resin is 2 mol% to 10 mol% based on the total amount of acid components in the third polyester resin, 10. The polyester film according to claim 9, wherein the neopentyl glycol component in the fourth polyester resin is 20 mol % to 40 mol % with respect to the total amount of alcohol components in the fourth polyester resin.

11. The blend ratio of the third polyester resin is 0.75 to 0.95, The polyester film according to claim 9 or 10, wherein the blend ratio of the fourth polyester resin is 0.05 to 0.

25.

12. The thickness of the first layer is 5 μm to 25 μm, The polyester film according to any one of claims 9 to 11, wherein the second layer has a thickness of 22 µm to 50 µm.

13. The polyester film according to any one of claims 1 to 12, wherein n=2 or 3.

14. It is a polyester film for sealants, The polyester film according to any one of claims 1 to 13, wherein the first layer is a heat-sealable layer.

15. The polyester film according to any one of claims 1 to 14, wherein the ethylene glycol component is a component derived from biomass.

16. The packaged item, The polyester film according to any one of claims 1 to 15, which packages the packaged item, The first layers are heat-fused together.

17. 17. The package according to claim 16, wherein the packaged item is sealed by the polyester film.

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