sealant film

Abstract

To provide a polyester-based sealant film excellent in recyclability and also excellent in heat resistance.SOLUTION: The sealant film is a laminate film comprising at least two layers with a polyester layer X and a polyester layer Z. The polyester layer X contains a copolymerized polyester comprising a copolymer of a dicarboxylic acid component and a diol component. The dicarboxylic acid component contains terephthalic acid. The diol component contains an alicyclic diol. The polyester layer Z contains homopolyethylene terephthalate as a main component resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealant film having excellent heat seal strength and excellent heat resistance.

Background Art

[0002] A heat-sealable film is called a sealant film or the like, and is itself used as various packaging materials, or a laminated film in which the sealant film is laminated is used as various packaging materials. Conventional sealant films have generally been non-stretched films mainly made of linear low-density polyethylene (LLDPE) or non-stretched films (CPP) mainly made of polypropylene (PP). However, recently, various polyester-based sealant films mainly made of polyester have been developed because of their excellent aroma retention and heat resistance.

[0003] Polyester is excellent in properties such as heat resistance, weather resistance, mechanical strength, transparency, chemical resistance, and gas barrier properties, and is also easily available in terms of price. Therefore, it has high versatility and is currently widely used in resins such as containers and packaging materials for beverages and foods, molded products, and films.

[0004] Regarding sealant films mainly made of polyester, for example, in Patent Document 1 and Patent Document 2, etc., polyester-based films imparted with sealability to polyethylene terephthalate (PET) are disclosed. Patent Document 3 discloses a biaxially stretched polyester sealant film whose resin component is made of polybutylene terephthalate resin.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] Polyester-based sealant films, such as those disclosed in Patent Documents 1 to 3, have excellent heat-seal strength and the advantage of being less likely to adsorb components of the packaged contents due to their low affinity for various organic compounds. Furthermore, by laminating them onto other polyester-based substrate films such as transparent barrier-deposited PET, or by applying barrier deposition or printing processing technologies, packaging materials made from a single polyester material can be realized, thus offering the potential for high recyclability. On the other hand, polyester-based sealant films tend to have poor heat resistance, and have particular problems with heat resistance when boiled, such as in packaging materials for retort foods. The object of the present invention is to provide a polyester-based sealant film with excellent heat resistance, particularly heat resistance when boiled. [Means for solving the problem]

[0007] The sealant film proposed by the present invention has the following configuration in order to solve the above problems.

[0008] [1] A first aspect of the present invention is a sealant film comprising at least two layers, a polyester layer X and a polyester layer Z, wherein the polyester layer X comprises a copolymer polyester comprising a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component comprises terephthalic acid, and the diol component comprises an alicyclic diol, and the polyester layer Z comprises homopolyethylene terephthalate as the main component resin.

[0009] [2] A second aspect of the present invention is a sealant film in which, in the first aspect, the haze change rate after boiling in hot water at 95°C under atmospheric pressure for 10 minutes is 35% or less.

[0010] [3] A third aspect of the present invention is a sealant film in which, in the first or second aspect, the diol component of the copolymerized polyester further comprises ethylene glycol.

[0011] [4] A fourth aspect of the present invention is a sealant film in which, in any one of the first to third aspects, the alicyclic diol of the copolymer polyester is one or more selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, and 1,4-cyclohexanediol.

[0012] [5] A fifth aspect of the present invention is a sealant film having at least one polyester layer Y between the polyester layer X and the polyester layer Z, in any one of the first to fourth embodiments.

[0013] [6] A sixth aspect of the present invention is a sealant film in which the polyester layer Y is a single layer, in the fifth aspect.

[0014] [7] A seventh aspect of the present invention is a sealant film in which, in the fifth or sixth aspect, the polyester layer Y comprises a copolymer polyester consisting of a copolymer of a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component comprises terephthalic acid and the diol component comprises an alicyclic diol.

[0015] [8] An eighth aspect of the present invention is a sealant film in which, in the seventh aspect, the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer X is the same as or higher than the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer Y.

[0016] [9] The ninth aspect of the present invention is a sealant film in which, in the eighth aspect, the difference between the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in the polyester layer X and the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in the polyester layer Y is 7 to 20 mol%.

[0017]

[10] A tenth aspect of the present invention is a sealant film in any one of the seventh to nineth aspects, wherein the alicyclic diol of the copolymer polyester of the polyester layer Y is one or more selected from the group consisting of 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, and 1,4-cyclohexanediol.

[0018]

[11] An eleventh aspect of the present invention is a sealant film in any one of the fifth to ten embodiments, wherein the polyester layer Y comprises polyethylene terephthalate.

[0019]

[12] A twelfth aspect of the present invention is a sealant film in which the polyester layer Z comprises inorganic particles, in any one of the first to eleventh aspects.

[0020]

[13] The 13th aspect of the present invention is a sealant film in any one of the 1st to 12th aspects, wherein the seal strength when the polyester layers X of the laminated film are sealed under the conditions of 140°C, 0.2 MPa, and 2 seconds is 15 N / 15 mm or more.

[0021]

[14] The 14th aspect of the present invention is a sealant film in any one of the 1st to 13th aspects, which has a barrier layer on the polyester layer Z.

[0022]

[15] The 15th aspect of the present invention is a packaging material having the sealant film in any one of the 1st to 13th aspects.

[0023]

[16] The 16th aspect of the present invention is a laminate having at least one layer of the sealant film in any one of the 1st to 13th aspects.

[0024]

[17] The 17th aspect of the present invention is a packaging material having at least a part of the laminate in the 16th aspect.

Advantages of the Invention

[0025] In the sealant film of the present invention, since the polyester layer X functions as a seal layer, it can have excellent heat fusion properties, that is, heat sealability. Furthermore, since the sealant film of the present invention is excellent in heat resistance, particularly heat resistance when boiled, it can be suitably used as various packaging materials.

Embodiments for Carrying Out the Invention

[0026] Hereinafter, an example of an embodiment of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[0027] <<This Sealant Film>> A sealant film according to one embodiment of the present invention (hereinafter also referred to as "this sealant film") is a laminated film consisting of at least two layers, having a polyester layer X and a polyester layer Z.

[0028] This sealant film may also include "other layers" besides the polyester layer X and polyester layer Z. For example, as described later, an intermediate layer may be provided between the polyester layer X and the polyester layer Z, or a barrier layer may be provided on the outside of the polyester layer Z. However, it is not limited to these. Furthermore, if the "other layer" contains a resin component, from the viewpoint of recyclability, it is preferable that the resin component be polyester.

[0029] This sealant film may be an unstretched film (sheet) or a stretched film. In particular, a stretched film stretched uniaxially or biaxially is preferred. Among these, a biaxially stretched film is preferred due to its superior balance of mechanical properties and flatness.

[0030] <Polyester Layer X> The polyester layer X is a layer capable of functioning as a sealing layer and comprises copolymer polyester A-1 consisting of a copolymer of a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component comprises terephthalic acid and the diol component comprises an alicyclic diol.

[0031] The polyester layer X may consist solely of copolymerized polyester A-1, or it may contain resin B-1 other than copolymerized polyester A-1. From the viewpoint of film formation, it is preferable to include resin B-1 other than copolymerized polyester A.

[0032] (Copolymer Polyester A-1) The copolymer polyester A-1 is a copolymer of a dicarboxylic acid component containing at least terephthalic acid and a diol component containing at least an alicyclic diol.

[0033] The aforementioned dicarboxylic acid component may include "other dicarboxylic acid components" in addition to terephthalic acid. Examples of "other dicarboxylic acid components" include aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, and polyfunctional acids. Furthermore, "other dicarboxylic acid components" may be used individually or in combination of two or more. More specifically, aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, dodecanedioic acid, eicoic acid, and their derivatives; and alicyclic dicarboxylic acids or dimer acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, and cyclooctanedicarboxylic acid are preferred.

[0034] In copolymer polyester A-1 in polyester layer X, the proportion of "other dicarboxylic acid components" to the total of dicarboxylic acid components, i.e., terephthalic acid and "other dicarboxylic acid components," is preferably 0 to 15 mol%, more preferably 0 mol% to 7 mol%, and more preferably 0 mol% to 3 mol%. In copolymer polyester A-1 in polyester layer X, the proportion of terephthalic acid in the total of dicarboxylic acid components, i.e., terephthalic acid and "other dicarboxylic acid components," is preferably 100 to 85 mol%, more preferably 93 mol% or more, and more preferably 97 mol% or more. Note that if two or more "other dicarboxylic acid components" are used in combination, this refers to their total amount.

[0035] On the other hand, examples of the alicyclic diol in the diol component include 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, and 1,4-cyclohexanediol. Among these, 1,4-cyclohexanedimethanol, in which the methylol group is in the para position, is particularly preferred from the viewpoint of excellent stability. Because alicyclic diols, particularly esters copolymerized with cyclohexanedimethanol, have relatively high intrinsic viscosity (IV) and glass transition temperature (Tg), they can impart excellent heat resistance and high sealant strength to the polyester layer X and, consequently, to this sealant film. Furthermore, the inclusion of alicyclic diols, particularly cyclohexanedimethanol, as copolymer components results in relatively high film flexibility and contributes to high sealant strength.

[0036] Other diol components in the aforementioned diol component, that is, other diol components other than alicyclic diols, include, for example, aliphatic diols such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol. In addition to the above, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, trimethylene glycol, neopentyl glycol, bisphenol, and their derivatives may also be used. These diol components can be used individually or in combination of two or more, and among them, the combination of ethylene glycol and an alicyclic diol is particularly preferred from the viewpoint of ease of copolymerization and the glass transition temperature of the copolymer.

[0037] Normally, when polyester is manufactured (polycondensed) using ethylene glycol as one of the raw materials, a portion of the ethylene glycol is modified to become diethylene glycol and introduced into the polyester backbone. This diethylene glycol is called by-product diethylene glycol, and although the amount produced varies depending on the type of polycondensation (transesterification, direct polycondensation, etc.), it is approximately 1 to 5 mol% of the ethylene glycol. In this invention, the diethylene glycol produced as a by-product from ethylene glycol in this way is also included in "other diol components."

[0038] In copolymer polyester A-1 in polyester layer X, the total content of diol components, i.e., alicyclic diols and "other diol components", is preferably 15 to 70 mol%, more preferably 20 mol% or more or 50 mol% or less, and more preferably 25 mol% or more or 40 mol% or less.

[0039] Furthermore, in copolymer polyester A-1 in polyester layer X, the proportion of "other diol components" to the total of diol components, i.e., alicyclic diols and "other diol components," is preferably 85 to 30 mol%, more preferably 80 mol% or less or 50 mol% or more, and more preferably 75 mol% or less or 60 mol% or more. Note that if two or more "other diol components" are used in combination, this refers to their total amount.

[0040] (Resin B-1) As described above, the polyester layer X may be a layer comprising copolymerized polyester A-1 and resin B-1, which is another resin. Resin B-1 preferably contains one or more types of polyester. In particular, from the viewpoint of recyclability as mentioned above, it is preferable that resin B-1 is made of polyester.

[0041] When resin B-1 contains one or more types of polyester, the polyester may include terephthalic acid and "other dicarboxylic acid components" as dicarboxylic acid components, and a diol component, wherein the ratio of the total content of "other dicarboxylic acid components" to the total content of all dicarboxylic acid components (or the total content of dicarboxylic acid components contained in each polyester if more than two types of polyester are included) is 0 mol% or more and 15 mol% or less, more preferably 0 mol% or more and 10 mol% or less, and more preferably 0 mol% or more and 5 mol% or less.

[0042] Furthermore, if the polyester contains ethylene glycol and other diol components as diol components, it is preferable that the ratio of the total content of "other diol components" to the total content of the diol components (or the sum of the diol components contained in each polyester if two or more types of polyester are included) is 0 mol% or more and 5 mol% or less, more preferably 0 mol% or more and 3 mol% or less, and more preferably 0 mol% or more and 2 mol% or less. Furthermore, when two or more "other diol components" are used in combination, it refers to their total amount, and "other diol components" include by-product diethylene glycol, as described above.

[0043] Thus, the polyester constituting resin B-1 may be a copolymer polyester containing "other dicarboxylic acid components," or it may be a homopolyester that does not contain "other dicarboxylic acid components." In particular, from the viewpoint of heat resistance and film strength, resin B-1 is preferably homopolyethylene terephthalate (also simply referred to as "polyethylene terephthalate"). In this case, homopolyethylene terephthalate also contains 1-5 mol% of by-product diethylene glycol.

[0044] In the polyester layer X, the mass ratio of copolymer polyester A-1 to resin B-1 is preferably 30:70 to 100:0, more preferably 50:50 to 100:0, and among these, 69:31 to 100:0, and even more preferably 69:31 to 81:19.

[0045] When the polyester layer X contains one or more types of polyester (including copolymerized polyesters) as resin B-1, it is preferable that the total proportion of "other dicarboxylic acid components" in the total amount of polyester components contained in the polyester layer X is 0 mol% or more and 12 mol% or less in the total amount of dicarboxylic acid components. Note that if two or more "other dicarboxylic acid components" are used in combination, this refers to their total amount.

[0046] There are no particular restrictions on the content of the diol component, however, if the polyester contains ethylene glycol and other diol components as diol components, the proportion of the total content of "other diol components" to the total content of all diol components is preferably 0 mol% or more and 5 mol% or less, more preferably 1 mol% or more or 4 mol% or less, and even more preferably 2 mol% or more or 3 mol% or less. Furthermore, when two or more "other diol components" are used in combination, it refers to their total amount, and "other diol components" include by-product diethylene glycol, as described above.

[0047] (Inorganic particles C in polyester layer X) The polyester layer X can also contain inorganic particles C. By incorporating inorganic particles C into the polyester layer X, it is possible to provide slipperiness and prevent damage during each process.

[0048] Examples of the inorganic particles C include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, and the like. Furthermore, while the inorganic particle content is not particularly limited, it is preferable to include 0% to 0.5% by mass, particularly 0% to 0.4% by mass, and even more preferably 0% to 0.3% by mass in the polyester layer X.

[0049] <Polyester layer Z> As described above, this sealant film is a laminated film having a polyester layer Z on one side of a polyester layer X that can function as a sealing layer. The polyester layer Z is the layer that is on the opposite side from the contents, i.e., the outside, when this sealant film is used as a packaging material.

[0050] The polyester layer Z is a layer containing homopolyethylene terephthalate as the main component resin. By containing homopolyethylene terephthalate as the main component resin of the polyester layer Z, good heat resistance can be achieved. In this case, homopolyethylene terephthalate also contains 1-5 mol% of by-product diethylene glycol. The term "main component resin" refers to the resin that makes up the largest proportion of the resins constituting the polyester layer Z. This main component resin may account for 50% or more by mass of the resins constituting the polyester layer Z, of which 70% or more by mass is present, and of which 80% or more by mass is present (including 100% by mass).

[0051] The polyester layer Z may consist solely of homopolyethylene terephthalate, or it may contain resin B-2 other than homopolyethylene terephthalate. From the viewpoint of processability such as printing and lamination, it is preferable to include homopolyethylene terephthalate and resin B-2.

[0052] The resin B-2 contained in the polyester layer Z, other than homopolyethylene terephthalate, may be a copolymerized polyester (referred to as copolymerized polyester A-2), or it may be a homopolyester other than homopolyethylene terephthalate among the resin B-1. Furthermore, the resin B-2 contained in the polyester layer Z may be the same resin as the resin B-1 contained in the polyester layer X, or it may be a different resin. The copolymer polyester A-2 contained in polyester layer Z may be the same copolymer polyester as copolymer polyester A-1 contained in polyester layer X, or it may be a different copolymer polyester.

[0053] In the polyester layer Z, the mass ratio of homopolyethylene terephthalate to resin B-2 is preferably 100:0 to 50:50, more preferably 90:10 to 50:50, and even more preferably 70:30 to 50:50.

[0054] (Inorganic particles C in polyester layer Z) The polyester layer Z may contain inorganic particles C. By incorporating inorganic particles C into the polyester layer Z, it is possible to provide slipperiness and prevent damage during each process. The inorganic particles C can be those exemplified in the polyester layer X described above. Furthermore, the preferred range for the inorganic particle content is the same as that exemplified in the polyester layer X described above.

[0055] <Polyester layer Y> As described above, this sealant film may have an intermediate layer between the polyester layer X and the polyester layer Z, and from the viewpoint of recyclability as described above, it is preferable that the intermediate layer is at least one polyester layer Y. The polyester layer Y may be a single layer, or it may be a multi-layered layer such as two, three, or four layers. It is preferable that the polyester layer Y contains the copolymerized polyester A described above.

[0056] In this sealant film, the polyester layer Y may consist solely of copolymerized polyester A-3, or it may contain resin B-3 other than copolymerized polyester A-3. In particular, it is preferable that it contains resin B-3 other than copolymerized polyester A-3.

[0057] The copolymer polyester A-3 of polyester layer Y may be the same copolymer polyester as the copolymer polyester A-1 contained in polyester layer X, or it may be a different copolymer polyester. Furthermore, the resin B-3 contained in the polyester layer Y may be the same resin as the resin B-1 contained in the polyester layer X, or it may be a different resin.

[0058] In copolymer polyester A-3 in polyester layer Y, the proportion of "alicyclic diols" in the total of diol components, i.e., alicyclic diols and "other diol components," is preferably 10 to 70 mol%, more preferably 11 mol% or more or 50 mol% or less, and more preferably 12 mol% or more or 32 mol% or less.

[0059] Furthermore, in copolymer polyester A-3 in polyester layer Y, the proportion of "other diol components" to the total of diol components, i.e., alicyclic diols and "other diol components," is preferably 90 to 30 mol%, more preferably 89 mol% or less or 50 mol% or more, and more preferably 88 mol% or less or 68 mol% or more. Note that if two or more "other diol components" are used in combination, this refers to their total amount.

[0060] In copolymer polyester A-3 in polyester layer Y, the proportion of "other dicarboxylic acid components" to the total of dicarboxylic acid components, i.e., terephthalic acid and "other dicarboxylic acid components," is preferably 0 to 15 mol%, more preferably 5 mol% or less, and more preferably 3 mol% or less. In copolymer polyester A-3 in polyester layer Y, the proportion of terephthalic acid in the total of dicarboxylic acid components, i.e., terephthalic acid and "other dicarboxylic acid components," is preferably 100 to 85 mol%, more preferably 95 mol% or more, and more preferably 97 mol% or more. Note that if two or more "other dicarboxylic acid components" are used in combination, this refers to their total amount.

[0061] Furthermore, the polyester layer Y preferably contains one or more types of polyester as resin B-3. The polyester in question (including one or more types of polyester) includes terephthalic acid and "other dicarboxylic acid components" as dicarboxylic acid components, and a diol component, wherein the ratio of the total content of "other dicarboxylic acid components" to the total content of all dicarboxylic acid components (or the total content of dicarboxylic acid components contained in each polyester if more than one type of polyester is included) is 0 mol% or more and 15 mol% or less, more preferably 3 mol% or less, and more preferably 1 mol% or less.

[0062] Furthermore, if the polyester contains ethylene glycol and other diol components as diol components, it is preferable that the ratio of the total content of "other diol components" to the total content of the diol components (or the sum of the diol components contained in each polyester if two or more types of polyester are included) is 0 mol% or more and 5 mol% or less, more preferably 3 mol% or less, and more preferably 2 mol% or less. Furthermore, when two or more "other diol components" are used in combination, it refers to their total amount, and "other diol components" include by-product diethylene glycol, as described above.

[0063] Thus, the polyester constituting resin B-3 may be a copolymer polyester containing "other dicarboxylic acid components" or a homopolyester that does not contain "other dicarboxylic acid components". Among these, from the viewpoint of heat resistance and film strength, resin B-3 is preferably homopolyethylene terephthalate. In this case, homopolyethylene terephthalate also contains 1-5 mol% of by-product diethylene glycol.

[0064] In the polyester layer Y, the mass ratio of copolymerized polyester A-3 to resin B-3 is preferably 35:65 to 100:0, more preferably 35:65 to 80:20, and even more preferably 50:50 to 80:20.

[0065] When the polyester layer Y contains one or more types of polyester (including copolymerized polyester) as resin B-3, it is preferable that the total proportion of "other dicarboxylic acid components" to the total content of dicarboxylic acid components in the total amount of polyester components contained in the polyester layer Y is 0 mol% or more and 12 mol% or less. Note that if two or more "other dicarboxylic acid components" are used in combination, this refers to their total amount.

[0066] There are no particular restrictions on the content of the diol component, however, if the polyester contains ethylene glycol and other diol components as diol components, the proportion of the total content of "other diol components" to the total content of the diol components is preferably 0 mol% or more and 5 mol% or less, more preferably 1 mol% or more or 4 mol% or less, and even more preferably 1.5 mol% or more or 3 mol% or less. Furthermore, when two or more "other diol components" are used in combination, it refers to their total amount, and "other diol components" include by-product diethylene glycol, as described above.

[0067] <Particularly preferred form> The sealant film is preferably a laminated film having a structure in which polyester layer X, polyester layer Y, and polyester layer Z are laminated in this order.

[0068] As described above, it is preferable that both polyester layer X and polyester layer Y of this sealant film contain copolymer polyester (A-1 or A-2). In that case, from the viewpoint of having both excellent heat resistance and high sealant strength, it is preferable that the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in polyester layer X is the same as or higher than the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in polyester layer Y. In this case, the difference between the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer X and the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer Y (or, if there are multiple polyester layers Y, the polyester layer Y adjacent to polyester layer X) should be 7 to 20 mol%, and more preferably 9 mol% or more or 15 mol% or less, and more preferably 9 mol% or more or 12 mol% or less.

[0069] Furthermore, if polyester layer Z also contains copolymer polyester A, it is preferable that the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in polyester layer Y is higher than the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymer polyester) contained in polyester layer Z. In this case, the difference between the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer Z and the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in the polyester layer Y (or, if there are multiple polyester layers Y, the polyester layer Y adjacent to polyester layer Z) should be 7 to 20 mol%, and more preferably 8 mol% or more or 15 mol% or less, and more preferably 9 mol% or more or 12 mol% or less.

[0070] In this sealant film, it is particularly preferable, from the viewpoint of combining excellent heat resistance and high sealant strength, to have a laminated structure in which the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in each layer decreases sequentially from polyester layer X to polyester layer Z in the thickness direction of the film. That is, regarding the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in each layer, Polyester layer X ≥ Polyester layer Y ≥ Polyester layer Z It is preferable that this is the case, and among them Polyester layer X > Polyester layer Y > Polyester layer Z This is particularly preferable. If the relative proportions of alicyclic diol components in each layer are such that polyester layer X ≥ polyester layer Y ≥ polyester layer, then the force is transmitted more smoothly during the peeling process when measuring heat seal strength compared to cases where polyester layer X < polyester layer Y or polyester layer Y < polyester layer. As a result, this sealant film achieves extremely excellent heat seal strength.

[0071] In this sealant film, a method for creating a concentration gradient of the alicyclic diol component in the thickness direction of the film is to laminate two or more layers in the thickness direction, each having a different total content ratio (mol%) of all alicyclic diols relative to the total diol components of all polyesters (including copolymerized polyesters) contained in each layer. For example, if polyester layer X, polyester layer Y, and polyester layer Z are all composed of a mixed resin of copolymerized polyester (A-1, A-2, or A-3) and polyester B-4 that does not contain alicyclic diols, and the mixing ratio (including zero) of the two is adjusted so that the total content ratio (mol%) of all alicyclic diols relative to the total diol components of all polyesters (including copolymerized polyesters) contained in each layer is polyester layer X ≥ polyester layer Y ≥ polyester layer Z, then such a concentration gradient can be created. However, the method is not limited to this.

[0072] Furthermore, whether or not this sealant film has a concentration gradient of alicyclic diol components in the copolymerized polyester in the film thickness direction can be confirmed, for example, by checking for the presence or absence of an inflection point in the concentration gradient of alicyclic diol components in the film thickness direction. The inflection point can be investigated by preparing an obliquely cut surface of the film using SAICAS® and obtaining negative secondary ion peak intensity data using a time-of-flight secondary ion mass spectrometer (TOF-SIMS).

[0073] <Other layers> This sealant film may have a barrier layer on the side of the polyester layer Z opposite to the polyester layer X, i.e., on the outside of the polyester layer Z. It may also have other layers between the polyester layer Z and the barrier layer. A barrier layer is a layer that can enhance the property of suppressing gas permeation (also called "gas barrier properties"), particularly water vapor barrier properties.

[0074] Examples of inorganic materials that constitute the main component of this barrier layer include one or more inorganic compounds selected from the group consisting of silicon oxide, silicon nitride, silicon oxide-nitride, silicon oxide, silicon carbide oxide, aluminum oxide, aluminum nitride, aluminum oxide-nitride, and aluminum oxide-carbide.

[0075] The barrier layer is preferably, for example, a PVD inorganic layer formed by physical vapor deposition (PVD), a plasma-assisted vapor deposition inorganic layer formed by plasma-assisted vapor deposition, a CVD inorganic layer formed by chemical vapor deposition (CVD), or a coated inorganic layer formed by a method of dispersing inorganic particles in an organic polymer and applying it.

[0076] This barrier layer may be a single layer or a multi-layer structure of two or more layers. For example, one example of a multi-layer structure of two or more layers is to have one layer consisting only of inorganic materials, such as inorganic oxides, and the other layer being an inorganic-organic mixed layer consisting of inorganic materials, such as inorganic oxides, and organic materials. By mixing organic materials with inorganic materials, a relatively flexible layer can be created, and by providing such a flexible layer, the gas barrier properties can be improved. In other words, coarse protrusions on the base film can cause minute defects called pinholes on the surface of the inorganic layer, or raw materials may fly in clumps during heating and deposition and adhere to the inorganic layer, causing minute defects on the surface. Gas can pass through these voids caused by defects, which can reduce the gas barrier properties. Therefore, by layering a flexible layer as described above onto the surface, it is possible to fill these defects and improve the gas barrier properties.

[0077] The thickness of this barrier layer (or the total thickness of the inorganic layers if they are multilayered) is preferably 0.1 nm to 500 nm, more preferably 1 nm or more or 300 nm or less, and more preferably 5 nm or more or 100 nm or less. If the thickness of this barrier layer is within the above range, it is possible to ensure the desired gas barrier properties.

[0078] (Thickness of this sealant film) The thickness of this sealant film is not particularly limited, and an appropriate thickness can be selected depending on the application. From the viewpoint of ensuring high heat sealability and enabling barrier deposition and printing processes, the total thickness of this sealant film is preferably greater than 3 μm, more preferably 5 μm or more, and even more preferably 10 μm or more. On the other hand, there is no particular upper limit to the total thickness of this sealant film. It is preferably 200 μm or less, and more preferably 160 μm or less, of which 140 μm or less, and of which 120 μm or less.

[0079] In this sealant film, the thickness of the polyester layer X is preferably 10 to 30% of the total thickness of the sealant film, more preferably 18% or more or 25% or less, and more preferably 18% or more or 20% or less. The thickness of the polyester layer X is not particularly limited, but is preferably 1 μm to 15 μm, more preferably 3 μm or more or 12 μm or less, and even more preferably 5 μm or more or 10 μm or less.

[0080] In this sealant film, the thickness of the polyester layer Z is preferably 10 to 30% of the total thickness of the sealant film, more preferably 18% or more or 25% or less, and more preferably 18% or more or 20% or less. The thickness of the polyester layer Z is not particularly limited, but is preferably 1 μm to 15 μm, more preferably 3 μm or more or 12 μm or less, and even more preferably 5 μm or more or 10 μm or less.

[0081] In this sealant film, the thickness of the polyester layer Y is preferably 40 to 80% of the total thickness of the sealant film, more preferably 50% or more or 64% or less, and more preferably 60% or more or 64% or less. The total thickness of the polyester layer Y is not particularly limited, but is preferably 10 μm to 150 μm, more preferably 15 μm or more or 100 μm or less, and even more preferably 20 μm or more or 80 μm or less.

[0082] <Physical properties of this sealant film> (Haze change rate after boiling) If a sealant film has low heat resistance, it will whiten and increase in haze when heated, due to crystallization, water absorption leading to void formation, etc. Therefore, the heat resistance, especially the heat resistance when boiled, can be evaluated by the rate of change in haze after boiling. From the viewpoint of heat resistance, the sealant film preferably has a haze change rate of 35% or less, more preferably 30% or less, and most preferably 25% or less after being subjected to a boiling treatment in which it is immersed in hot water at a temperature of 95°C for 10 minutes under atmospheric pressure. Because this sealant film has a haze change rate of 35% or less, it can be suitably used in applications such as high-temperature filling, boiling sterilization at a temperature of around 95°C, and retort processing.

[0083] The haze change rate after boiling with hot water at 95°C, as described above, refers to the haze change rate after boiling, as measured by the method described in the examples below.

[0084] (Heat seal strength) The sealant film preferably has a seal strength of 15 N / 15 mm or more, more preferably 20 N / 15 mm or more, and most preferably 25 N / 15 mm or more, when the polyester layers X, i.e., the seal layers of two sealant films are sealed together under the conditions of 130°C, 0.1 MPa, and 2 seconds. Because this sealant film has a seal strength of 25 N / 15 mm or more at 130°C, it can contribute to improved low-temperature sealing and airtightness when used as a packaging material, for example, and can be suitably used for mass sealing, antibacterial purposes, and other applications.

[0085] Furthermore, it is preferable that the sealant film has a seal strength of 15 N / 15 mm or more, more preferably 20 N / 15 mm or more, and most preferably 25 N / 15 mm or more, when the polyester layers X, i.e., the seal layers of two sealant films are sealed together under the conditions of 140°C, 0.2 MPa, and 2 seconds. Because this sealant film has a seal strength of 25 N / 15 mm or more at 140°C, it can contribute to improved low-temperature sealing and airtightness when used as a packaging material, for example, and can be suitably used for mass sealing, antibacterial purposes, and other applications.

[0086] Furthermore, it is preferable that the sealant film has a seal strength of 15 N / 15 mm or more, more preferably 18 N / 15 mm or more, and most preferably 20 N / 15 mm or more, when the polyester layers X, i.e., the seal layers of two sealant films are sealed together under the conditions of 160°C, 0.2 MPa, and 2 seconds. Because this sealant film has a seal strength of 20 N / 15 mm or more at 160°C, it can contribute to improved airtightness when used as a packaging material, for example, and can be suitably used for mass sealing, antibacterial purposes, and other applications.

[0087] The heat seal strength of this sealant film can be measured by the method described in the examples below.

[0088] (Breaking strength) Preferably, the sealant film has a breaking strength of 50 MPa or more in both the longitudinal direction (MD) and the width direction (TD). A breaking strength of 50 MPa or more prevents breakage, for example, when used as a packaging material. From this viewpoint, it is preferable that the sealant film has a breaking strength of 50 MPa or more, more preferably 60 MPa or more, and even more preferably 65 MPa or more. While a higher breaking strength is preferable, a strength of 150 MPa or less is practically sufficient. The tensile strength of this sealant film can be measured, for example, by the method shown in the examples described later.

[0089] (Shrinkage rate) Preferably, the sealant film has a shrinkage rate of -5% to 5% in both the longitudinal direction (MD) and the width direction (TD). A shrinkage rate within the range of -5% to 5% allows the film to maintain its original shape even in high-temperature environments. From this viewpoint, it is preferable that the sealant film has a shrinkage rate of -4% to 4%, more preferably -3% to 3%, and even more preferably -2% to 2%. The shrinkage rate can be measured by the method shown in the examples described later.

[0090] (Hayes) The sealant film preferably has a haze of 1% to 15%. A haze of 1% to 15% allows for visibility of the contents, for example, when used as packaging material. Lower haze is preferable as it increases transparency, but with the current level of technology, 1% is the lower limit. From this viewpoint, the sealant film preferably has a haze of 1% to 15%, more preferably 1% to 13%, and even more preferably 1% to 10%. Furthermore, haze can be measured by the method shown in the examples described later.

[0091] <Method for manufacturing this sealant film> As an example of a manufacturing method for this sealant film, we will describe the case where the sealant film is a biaxially oriented film. However, the manufacturing method is not limited to the one described here. First, resin compositions constituting each layer are prepared by known methods, and each is separately supplied to a twin-screw molten extruder to melt the resin compositions. The discharge rate of the molten resin is adjusted so that the thickness of each layer is in a predetermined thickness ratio, and each layer is extruded from the die, i.e., co-extruded. This co-extruded sheet is cooled and solidified on a rotating cooling drum to a temperature below the glass transition point of the polymer, thereby obtaining a substantially amorphous, unoriented sheet. Next, the unoriented sheet is stretched in one direction using a roll or tenter type stretcher. At this time, the stretching temperature is usually 25 to 120°C, preferably 35 to 100°C, and the stretching ratio is usually 2.5 to 7 times, preferably 2.8 to 6 times. Next, the material is stretched in a direction perpendicular to the stretching direction of the first stage. At this stage, the stretching temperature is usually 50 to 140°C, and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. Then, by continuing the heat-fixation treatment at a temperature of 130-270°C under tension or under relaxation of 30% or less, the sealant film can be obtained as a biaxially oriented film. Furthermore, in the aforementioned extension, a method can be adopted in which the extension is carried out in two or more stages in one direction.

[0092] As described above, it is preferable to co-extrude the sealant film and then stretch and heat-set it as a single film. When the copolymer polyester A is crystalline, it is preferable to heat-set it at a temperature higher than the melting point of copolymer polyester A.

[0093] <Applications of this sealant film> This sealant film can be suitably used as a component of packaging materials and the like. The sealant film may be used as is as a packaging material, or it may be used as a laminate having at least one layer of this sealant film, with the laminate being at least a part of the packaging material.

[0094] <Explanation of terms and phrases> In this invention, the term "film" includes "sheets," and the term "sheet" includes "film." In the present invention, "polyester layer" means a layer in which the main component resin constituting the layer is polyester, and the main component resin means the resin that has the highest content proportion among the resins constituting each layer, and the main component resin may account for 50% by mass or more, of which 70% by mass or more, and of which 80% by mass or more (including 100% by mass) of the resins constituting each layer. Furthermore, in this invention, "sealant film" means a film that can exhibit heat-sealing properties.

[0095] In this invention, when "α~β" (where α and β are arbitrary numbers) is written, unless otherwise specified, it means "α or greater and β or less," and also includes the meaning of "preferably greater than α" or "preferably less than β." Furthermore, when written as "α or greater" or "α ≤" (where α is any number), unless otherwise specified, it includes the meaning of "preferably greater than α," and when written as "β or less" or "≤β" (where β is any number), unless otherwise specified, it also includes the meaning of "preferably less than β." [Examples]

[0096] The following describes an example of an embodiment of the present invention. However, the present invention is not limited to the embodiment described below.

[0097] <Materials used> [Adjustment of polyester raw materials] Table 1 shows the polymerization composition, i.e., the proportion of monomers, of each polyester used in this example and comparative example. In Table 1, TPA is terephthalic acid, IPA is isophthalic acid, EG is ethylene glycol, CHDM is 1,4-cyclohexanedimethanol, and DEG is diethylene glycol. The intrinsic viscosity (IV) of polyesters a to d was measured by dissolving the polyester in a 1:1 mixed solution of phenol and tetrachloroethane, and calculating IV from the elution time of this polyester solution. Furthermore, the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC). More specifically, a PerkinElmer "DSC8500" was used to heat 5.0 mg of polyester samples a to d to 300°C, followed by rapid cooling. Subsequently, measurements were performed while increasing the temperature at a heating rate of 10°C / min to obtain a DSC curve. The center value of the temperature range in which the DSC curve bends, based on the baseline shift of the obtained DSC curve, was defined as the glass transition temperature.

[0098] [Table 1]

[0099] (Example 1) As the raw material for polyester layer Z, polyester b and polyester c are mixed in a mass ratio of 50:50. As the raw material for the polyester layer Y, polyester a and polyester b are mixed in a mass ratio of 35:65. As raw materials for polyester layer X, polyester a, polyester b, and polyester c were mixed in a mass ratio of 69:24:7 to prepare the mixed raw materials for forming each layer. Each of the mixed raw materials for polyester layer Z, polyester layer Y, and polyester layer X was fed into separate twin-screw extruders. The mixed raw materials for polyester layer Z and polyester layer Y were heated to 280°C, and the mixed raw material for polyester layer X was heated to 270°C to melt. The discharge rate of the molten resin was adjusted so that each layer had a predetermined thickness, and each layer was extruded from the die. Each layer was then cooled and solidified on a cooling roll set to 15°C to obtain an unstretched laminated film consisting of three types and three layers (polyester layer Z / polyester layer Y / polyester layer X). Next, the obtained unstretched laminated film was stretched 3.3 times in the longitudinal direction (MD) at 85°C using a roll stretcher. Furthermore, after preheating in a tenter at 95°C, it was stretched 4.2 times in the width direction (TD) at 110°C. Finally, it was heat-treated at 225°C to obtain a laminated film (sample) with a thickness of 50 μm and consisting of three layers of three types (polyester layer Z: 9.3 μm, polyester layer Y: 31.4 μm, polyester layer X: 9.3 μm). The properties of the obtained laminated film were evaluated using the method described above. The evaluation results are shown in Table 3.

[0100] (Example 2) Polyester layer X was prepared by mixing polyester a, polyester b, and polyester c in a mass ratio of 81:12:7. The mass ratios of the raw materials for each layer other than polyester layer X and the film formation conditions were the same as in Example 1 to obtain a laminated film with a thickness of 50 μm. The evaluation results are shown in Table 3.

[0101] (Example 3) Polyester layer Y was prepared by mixing polyester a and polyester b in a mass ratio of 50:50, and polyester layer X was prepared by mixing polyester a, polyester b, and polyester c in a mass ratio of 81:12:7. The raw material mass ratio and film formation conditions for polyester layer Z were the same as in Example 1, and a laminated film with a thickness of 50 μm (polyester layer Z: 9.3 μm, polyester layer Y: 31.4 μm, polyester layer X: 9.3 μm) was obtained. The evaluation results are shown in Table 3.

[0102] (Comparative Example 1) Polyester layer Y was prepared by mixing polyester b and polyester d in a mass ratio of 52:48, and polyester layer X was prepared by mixing polyester b and polyester d in a mass ratio of 7:93. The raw material mass ratio and film formation conditions for polyester layer Z were the same as in Example 1, and a laminated film with a thickness of 50 μm (polyester layer Z: 9.3 μm, polyester layer Y: 31.4 μm, polyester layer X: 9.3 μm) was obtained. The evaluation results are shown in Table 3.

[0103] <Evaluation Method> The laminated films (samples) prepared in the examples and comparative examples were evaluated as follows.

[0104] (1) Heat seal strength measurement The heat seal strength of the laminated films (samples) prepared in the examples and comparative examples was measured in accordance with JIS Z1707. The sealing surfaces (polyester layer A) of the laminated films (samples) were placed together and heat-sealed by applying a pressure of 0.2 MPa for 2 seconds at 140°C or 160°C. The sealed portion was cut to a width of 15 mm, and the peel strength of the sealed portion was measured using a tensile testing machine at a tensile speed of 200 mm / min.

[0105] (2) Measurement of fracture strength The laminated films (samples) prepared in the examples and comparative examples were made into 1.5 cm x 15 cm sample films. Using a tensile testing machine, the sample films were pulled in the longitudinal direction (MD) or the width direction (TD) at a speed of 200 mm / min, and the strength at which the sample broke (ruptured) (the value obtained by dividing the tensile load value by the cross-sectional area of ​​the test piece) was defined as the breaking strength (MPa).

[0106] (3) Measurement of contraction rate The laminated films (samples) prepared in the examples and comparative examples were made into 1.5 cm x 15 cm sample films. The sample films were heat-treated for 5 minutes in a hot air oven maintained at a predetermined temperature (100°C) while in a tension-free state. The length of the sample films was measured before and after the treatment and calculated using the following formula (Equation 2). Measurements were taken in both the longitudinal direction (MD) and the width direction (TD) of the film. Shrinkage rate (%) = {(Sample length before heat treatment) - (Sample length after heat treatment)} ÷ (Sample length before heat treatment) × 100 ... (Equation 2)

[0107] (4) Hayes The haze of the laminated films (samples) prepared in the examples and comparative examples was measured using a haze meter DH-2000 manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS K7136.

[0108] (5) Rate of change in haze after boiling The laminated films (samples) prepared in the examples and comparative examples were immersed in water maintained at a predetermined temperature of 95°C under atmospheric pressure for 10 minutes in a tension-free state, and the haze of the laminated films (samples) was measured before and after the immersion. The haze was measured in accordance with JIS K7136 using a haze meter DH-2000 manufactured by Nippon Denshoku Industries Co., Ltd., and the rate of change in haze after boiling was calculated using the following formula (Equation 1). Haze change rate after boiling (%) = {(Sample haze after heat treatment) - (Sample haze before heat treatment)} ÷ (Sample haze before heat treatment) × 100 ... (Equation 1)

[0109] [Table 2]

[0110] [Table 3]

[0111] In Table 3, for example, the "Copolymer Content (mol%)" of polyester layer Z refers to the ratio (mol%) of the total CHDM content to the total diol components (100 mol%) contained in the total polyester (including copolymer polyester) that constitutes polyester layer Z. The same applies to the other layers.

[0112] (Consideration) From the above examples and comparative examples, as well as the test results conducted by the present inventors to date, it has been found that, in relation to a laminated film having a polyester layer X and a polyester layer Z, if the polyester layer X as a sealing layer contains a copolymerized polyester consisting of a copolymer of a dicarboxylic acid component and a diol component, the dicarboxylic acid component contains terephthalic acid, and the diol component contains an alicyclic diol, while the polyester layer Z contains homopolyethylene terephthalate as the main component resin, then it exhibits excellent heat resistance when boiled.

[0113] Furthermore, from the viewpoint of improving both heat resistance and sealant strength, it was found that in a configuration in which polyester layer X, polyester layer Y, and polyester layer Z are laminated in this order, it is particularly preferable that the total content ratio (mol%) of all alicyclic diols to the total diol components of all polyester (including copolymerized polyester) contained in each layer be such that polyester layer X ≥ polyester layer Y ≥ polyester layer Z.

[0114] Furthermore, since all the resin components constituting the sealant films of Examples 1 to 3 are polyester (including copolymerized polyester), it is possible to form packaging materials using a single material system made of polyester by laminating them onto other polyester-based substrate films such as transparent barrier-deposited PET, or by applying barrier deposition or printing processing technologies, thereby achieving high recyclability. [Industrial applicability]

[0115] The polyester-based sealant film of the present invention has excellent heat resistance and heat seal strength. Furthermore, the polyester sealant film of the present invention possesses sufficient mechanical properties such as low shrinkage and tensile strength necessary for sealant applications. Therefore, according to the present invention, by laminating other polyester-based substrate films, such as transparent barrier-deposited PET, or by combining high barrier deposition and printing processing technologies for polyester-based films, a packaging material made of a single material system consisting of polyester can be realized, thus providing a packaging material with excellent recyclability.

Claims

1. A laminated film comprising at least three layers, having a polyester layer X and a polyester layer Z, with at least one polyester layer Y between the polyester layer X and the polyester layer Z, The polyester layer X is a copolymer polyester comprising a copolymer of a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component contains terephthalic acid and the diol component contains 1,4-cyclohexanedimethanol. The polyester layer Y is a copolymer polyester comprising a copolymer of a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component contains terephthalic acid and the diol component contains 1,4-cyclohexanedimethanol. The polyester layer Z contains homopolyethylene terephthalate as the main component resin, The total content percentage (mol%) of 1,4-cyclohexanedimethanol relative to the total diol components in the total polyester (including copolymerized polyester) contained in the polyester layer X is 22.0 mol% or more. The difference between the total content percentage (mol%) of 1,4-cyclohexanedimethanol relative to the total diol components in the total polyester (including copolymerized polyester) contained in the polyester layer X and the total content percentage (mol%) of 1,4-cyclohexanedimethanol relative to the total diol components in the total polyester (including copolymerized polyester) contained in the polyester layer Y is 7 to 20 mol%, The total content percentage (mol%) of 1,4-cyclohexanedimethanol relative to the total diol components of all polyester in each layer is: polyester layer X > polyester layer Y > polyester layer Z. The thickness of the polyester layer X is 10 to 30% of the total thickness of the laminated film. The thickness of the polyester layer Y is 40 to 80% of the total thickness of the laminated film. The thickness of the polyester layer Z is 10 to 30% of the total thickness of the laminated film. A sealant film in which the thickness of the polyester layer X and the thickness of the polyester layer Z are the same.

2. The sealant film according to claim 1, wherein the polyester layer Z contains 80% by mass or more of homopolyethylene terephthalate as the resin constituting the layer.

3. The sealant film according to claim 1 or 2, wherein the polyester layer Z contains 100% by mass of homopolyethylene terephthalate as the resin constituting the layer.

4. A sealant film according to any one of claims 1 to 3, wherein the haze change rate after a boiling treatment in which the film is immersed in hot water at a temperature of 95°C for 10 minutes under atmospheric pressure is 35% or less.

5. The sealant film according to any one of claims 1 to 4, wherein the diol component of the copolymerized polyester contained in the polyester layer X further contains ethylene glycol.

6. The sealant film according to any one of claims 1 to 5, wherein the polyester layer Y is a single layer.

7. The polyester layer Y is a copolymer polyester comprising a copolymer of a dicarboxylic acid component and a diol component, wherein the dicarboxylic acid component is terephthalic acid and the diol component is 1,4-cyclohexanedimethanol, and the copolymer polyester A-3 comprises a resin B-3 other than the copolymer polyester A-3. The sealant film according to any one of claims 1 to 6, wherein the resin B-3 is a copolymer polyester containing terephthalic acid and other dicarboxylic acid components and a diol component, and the proportion of the other dicarboxylic acid components other than terephthalic acid to the total dicarboxylic acid components is 15 mol% or less.

8. The polyester layer X is a copolymer polyester comprising copolymer polyester A-1, which contains terephthalic acid as the dicarboxylic acid component and 1,4-cyclohexanedimethanol as the diol component, and resin B-1 other than copolymer polyester A-1. The sealant film according to any one of claims 1 to 7, wherein the resin B-1 is a copolymer polyester containing terephthalic acid and other dicarboxylic acid components and a diol component, and the proportion of the other dicarboxylic acid components other than terephthalic acid to the total dicarboxylic acid components is 15 mol% or less.

9. The sealant film according to claim 7 or 8, wherein the other dicarboxylic acid component of the copolymerized polyester contained in the polyester layer X and the polyester layer Y, other than terephthalic acid, is isophthalic acid.

10. A sealant film according to any one of claims 1 to 9, comprising a polyester layer X, a polyester layer Y, and a polyester layer Z laminated in that order, wherein the polyester layers X, Y, and Z are co-extruded and stretched together.

11. The sealant film according to any one of claims 1 to 10, wherein the polyester layer Y comprises polyethylene terephthalate.

12. The sealant film according to any one of claims 1 to 11, wherein the polyester layer Z contains inorganic particles.

13. The sealant film according to any one of claims 1 to 12, wherein the seal strength when the polyester layers X of the laminated film are sealed together under the conditions of 140°C, 0.2 MPa, and 2 seconds is 15 N / 15 mm or more.

14. A sealant film according to any one of claims 1 to 13, having a barrier layer on the polyester layer Z.

15. A packaging material having a sealant film according to any one of claims 1 to 13.

16. A laminate having at least one layer of sealant film according to any one of claims 1 to 13.

17. A packaging material having at least a portion of the laminate described in claim 16.

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