Sealant film, laminated film using same, packaging bag and packaging container, and method for manufacturing sealant film

Abstract

To maintain low adsorption of content and suppress deterioration of odor and flavor in sealant film using polyester resin.SOLUTION: A sealant film comprises a polyester layer containing polyester as main component. The polyester consists of structural units derived from ethylene glycol, structural units derived from terephthalic acid and structural units derived from isophthalic acid, the ratio of the isophthalic acid-derived structural unit is 3.0 mol% or more and 15 mol% or less with respect to the ratio of the terephthalic acid-derived structural unit and the isophthalic acid-derived structural unit constituting the polyester, the oligomer content in the polyester layer is less than 2.0% by weight.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sealant film, a laminated film using the same, a packaging bag and a packaging container, and a method for producing the sealant film. [Background technology]

[0002] Sealant films are widely used in packaging bags for foods, beverages, pharmaceuticals, etc. The sealant film is provided on the innermost layer of the packaging bag and is heat-sealed to seal the packaging bag. Polyolefin resins such as polyethylene and polypropylene, which have high sealing strength, have been used as sealant films.

[0003] However, such sealant films tend to adsorb organic compounds such as oils and fragrances, and therefore packaging bags with sealant films have the problem of adsorbing aromatic components and medicinal ingredients of the contents.

[0004] To address this issue, polyester resins, polyacrylonitrile copolymers (PAN), polyethylene terephthalate (PET), etc. are being used instead of polyolefin resins. Among these, polyester resins can be used with appropriate comonomer components, dibasic acids and glycols, to maintain low content adsorption while providing low-temperature sealing properties and controlling fluidity during sealing.

[0005] On the other hand, the presence of comonomer components results in the by-production of low molecular weight substances (oligomers) during the polymerization stage, which can cause problems such as a worsening of odor and flavor and a decrease in the adsorption ability of the contents.

[0006] Japanese Patent Laid-Open Publication No. 2006-305975 (Patent Document 1) discloses a sealant film made of an isophthalic acid-modified PET resin as a polyester resin, produced by a T-die casting method. It also discloses that the sealant film has low adsorption and excellent barrier properties, and is capable of stable heat sealing. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-305975 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the sealant film described in Patent Document 1 leaves room for improvement in terms of odor and flavor. Therefore, the present inventors focused on the dibasic acid and glycol, which are comonomer components of polyester resins, and discovered that by limiting the dibasic acid to terephthalic acid and isophthalic acid, and the glycol to ethylene glycol, respectively, copolymerizing terephthalic acid and isophthalic acid in specific ratios, and producing the film by inflation extrusion, it is possible to suppress the formation of oligomers. This makes it possible to suppress a decrease in adsorption of contents and a deterioration in odor and flavor.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to suppress deterioration of odor and flavor in a sealant film using a polyester resin while maintaining low adsorption of contents. [Means for solving the problem]

[0010] [1] A sealant film having a polyester layer containing polyester as a main component, the polyester comprises structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid; a ratio of the structural units derived from isophthalic acid to the structural units derived from terephthalic acid and isophthalic acid constituting the polyester is 3.0 mol % or more and 15 mol % or less, A sealant film, wherein the content of the oligomer in the polyester layer is less than 2.0% by mass.

[0011] [2] The sealant film according to [1], wherein the glass transition temperature of the polyester is 60°C or higher and 80°C or lower.

[0012] [3] A surface layer is provided, The sealant film according to [1] or [2], wherein the surface layer is at least one selected from the group consisting of polyethylene, ethylene-acrylic acid ester copolymer, and ethylene-methacrylic acid ester copolymer.

[0013] [4] an intermediate layer is further provided between the polyester layer and the surface layer; The sealant film according to [3], wherein the intermediate layer is at least one selected from the group consisting of acid anhydride-grafted polyethylene and ethylene-ester copolymer.

[0014] [5] The sealant film according to any one of [1] to [4], wherein the thickness of the polyester layer is 20 μm or more and 50 μm or less.

[0015] [6] A base film; [1] to [5]. A laminated film comprising the sealant film according to any one of the preceding claims.

[0016] [7] The laminate film according to [6], further comprising a gas barrier film between the base film and the sealant film.

[0017] [8] A packaging bag obtained by sealing the laminated film according to [6] or [7] so that the sealant films are fused together.

[0018] [9] A packaging container obtained by sealing the laminated film according to [6] or [7] so that the sealant films are fused together.

[0019]

[10] A method for producing a sealant film having a polyester layer containing polyester as a main component, The method for producing the sealant film includes an extrusion step of extruding a resin constituting the polyester layer by an inflation method, The temperature of the extrusion step is 180°C or higher and 260°C or lower, the polyester comprises structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid; a ratio of the structural units derived from isophthalic acid to the structural units derived from terephthalic acid and isophthalic acid constituting the polyester is 3.0 mol % or more and 15 mol % or less, The method for producing a sealant film, wherein the content of oligomer in the polyester layer is less than 2.0% by mass. [Effects of the Invention]

[0020] According to the present disclosure, a sealant film using a polyester resin can suppress deterioration of odor and flavor while maintaining low adsorption of contents. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the sealant film used in the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the sealant film used in the second embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an example of the sealant film used in the third embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of the sealant film used in the fourth embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an example of the sealant film used in the fifth embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an example of the sealant film used in the sixth embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an example of the laminated film of the seventh embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an example of the laminated film of the seventh embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view showing an example of the laminated film of the eighth embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an example of the laminated film of the eighth embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing an example of the laminated film of the ninth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or corresponding parts.

[0023] [Embodiment 1] <Sealant film> 1, the sealant film 1 of this embodiment is a sealant film consisting of two layers: a polyester layer 11 (sealing side) and a surface layer 12. Although the sealant film 1 of this embodiment consists of two layers, it may also consist of only the polyester layer 11.

[0024] (Polyester layer) The polyester layer 11 contains polyester as a main component. Here, "containing polyester as a main component" means, for example, that the polyester content is more than 50% by mass relative to the total amount of the polyester layer 11. The polyester content in the polyester layer 11 is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass. The polyester layer 11 may also contain other polymeric materials, various additives, and the like.

[0025] The polyester in this embodiment is composed of structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid, and has a number average molecular weight of 15,000 or more and 21,000 or less.

[0026] The ratio of structural units derived from isophthalic acid is 3.0 mol% or more and 15 mol% or less relative to the ratio of structural units derived from terephthalic acid and structural units derived from isophthalic acid that constitute the polyester. If the ratio of structural units derived from isophthalic acid is less than 3.0 mol%, the sealant film will have poor low-temperature sealing properties. If the ratio of structural units derived from isophthalic acid is more than 15 mol%, the polyester layer will be amorphous or low-crystalline, resulting in an increased amount of adsorption of contents. The ratio of structural units derived from isophthalic acid is preferably 8.0 mol% or more, more preferably 9.0 mol% or more, even more preferably 10 mol% or more, and may be 10.5 mol% or more, preferably 13 mol% or less, more preferably 12.5 mol% or less, and even more preferably 12 mol% or less, and may be 11.5 mol% or less.

[0027] The polyester layer 11 contains an oligomer. In this embodiment, the oligomer is a polymer having a smaller molecular weight than the polyester produced in the polyester polymerization stage, and includes both linear oligomers and cyclic oligomers. The oligomer causes problems such as a deterioration in odor and flavor and a decrease in adsorption of contents. The inventors have found that by using the above-mentioned components and ratios of polyester as the composition and producing it by the method described below, the oligomer content in the polyester layer 11 can be made less than 2.0% by mass. When the oligomer content in the polyester layer 11 is less than 2.0% by mass, the above problems are suppressed. The oligomer content in the polyester layer 11 is preferably 1.8% by mass or less.

[0028] The oligomer content in the polyester layer 11 can be measured by high performance liquid chromatography (HPLC). Specifically, the polyester layer to be measured is dissolved in hexafluoroisopropanol (HFIP), reprecipitated with acetonitrile, and the supernatant is filtered to prepare a sample solution, which is then measured by reverse-phase HPLC (Agilent 1260 Infinity II LC system) under the following conditions: [Measurement conditions] Detector: UV absorption photometer Measurement wavelength: 242nm Column: Reverse phase column C18 ODS 5μ (length: 250 mm, inner diameter: 4.6 mm) Column temperature: 25℃ Eluent: acetonitrile / water = 7 / 3 Flow rate: 1.5ml / min Injection volume: 20 μl In this embodiment, the oligomer refers to multiple peaks with elution times of 5 to 20 minutes in the molecular weight distribution measured by HPLC. In peak shape analysis of the chromatogram, the peak area is divided vertically by elution time, and the amount of each peak area is normalized using the weight of the measured polyester layer. The measurement is repeated three times, and the average value of each peak area is used as the value. It is sufficient if the peak area is less than 2%.

[0029] The thickness of the polyester layer 11 can be changed appropriately depending on the intended use, and is, for example, 20 μm or more and 50 μm or less. If the thickness of the polyester layer 11 is less than 20 μm, the amount of content adsorbed increases. If the thickness of the polyester layer 11 exceeds 50 μm, the discharge load during film formation is large, and film formation may not be possible. The thickness of the polyester layer 11 is preferably 25 μm or more and 45 μm or less.

[0030] The polyester layer 11 may contain an antiblocking agent. By containing an antiblocking agent, the slipperiness of the polyester layer 11 is improved, making blocking less likely to occur. Examples of antiblocking agents include silica, talc, and diatomaceous earth. The content of the antiblocking agent is, for example, from 0.1% to 3% by mass, and preferably from 0.5% to 1.5% by mass.

[0031] The glass transition temperature (Tg) of the polyester is preferably 60° C. or higher and 80° C. or lower, more preferably 70° C. or higher and 75° C. or lower. In this case, a sealant film 1 having appropriate sealing strength can be obtained. Tg can be measured in accordance with JIS K7121.

[0032] The crystallization temperature (Tc) of the polyester is preferably 130° C. or higher, and more preferably 135° C. or higher. In this case, a sealant film 1 having appropriate seal strength can be obtained. Tc can be measured in accordance with JIS K7121.

[0033] The melting temperature (Tm) of the polyester is preferably 200° C. or higher, and more preferably 210° C. or higher. In this case, a sealant film 1 having appropriate seal strength can be obtained. Tm can be measured in accordance with JIS K7121.

[0034] (Surface layer) The sealant film 1 may have a surface layer 12 .

[0035] Examples of the surface layer 12 include polyethylene (PE), ethylene-ester copolymers, etc. Examples of the ethylene-ester copolymers include ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid ester copolymers, etc.

[0036] The thickness of the sealant film 1 can be changed appropriately depending on the intended use, and is, for example, 30 μm or more and 80 μm or less.

[0037] The sealant film 1 of this embodiment is provided with the above-described layers, making it non-adsorbent and inhibiting adsorption or absorption of contents (fragrant components, medicinal components, etc.), and can also inhibit the liberation of oligomers. It also has sufficient sealing strength and low-temperature sealing properties.

[0038] Specifically, the sealant film preferably has a sealing initiation temperature of 130°C or lower at which a seal strength of 5 N / 15 mm width or more is achieved under sealing conditions of a sealing pressure of 0.1 MPa and a sealing time of 1.0 second. The sealing initiation temperature is measured according to JIS Z0238.

[0039] Specifically, the seal strength of the sealant film is preferably 30 N / 15 mm width or more under the following sealing conditions: sealing temperature: 160°C, sealing pressure: 0.1 MPa, sealing time: 1.0 second. The seal strength is measured according to JIS Z0238.

[0040] [Embodiment 2] Referring to FIG. 2, the sealant film 1 of this embodiment is the same as that of the first embodiment, except that a first intermediate layer 13 is provided between the polyester layer 11 and the surface layer 12.

[0041] The presence of the first intermediate layer 13 improves the adhesive strength between the polyester layer 11 and the surface layer 12, thereby improving the sealing strength of the sealant film 1. Examples of the first intermediate layer 13 include acid anhydride-grafted polyethylene (PE) and ethylene-ester copolymer. Examples of the acid anhydride-grafted PE include maleic anhydride-grafted PE and itaconic anhydride-grafted PE.

[0042] [Embodiment 3] 3, the sealant film 1 of this embodiment is a sealant film formed by laminating, in this order, a surface layer 12, a first intermediate layer 13, an intervening layer 14, a second intermediate layer 15, and a polyester layer 11. Except for the fact that the intervening layer 14 and the second intermediate layer 15 are further laminated, this embodiment is the same as the second embodiment.

[0043] The intermediate layer 14 can be made of the same material as the surface layer 12. The surface layer 12 and the intermediate layer 14 may be made of the same material or different materials.

[0044] The second intermediate layer 15 can be made of the same material as the first intermediate layer 13. The first intermediate layer 13 and the second intermediate layer 15 can be made of the same material or different materials.

[0045] [Embodiment 4] Referring to FIG. 4, the sealant film 1 of this embodiment is a sealant film made up of two layers: a polyester layer 11 and a back surface layer 16.

[0046] Normally, in the case of a sealant film structure such as that of the present embodiment, the polyester layer is not in contact with the contents, and therefore it is thought that the odor and flavor deterioration caused by the oligomers described above are unlikely to occur. However, when the contents are filled with, for example, alcoholic beverages, oily foods, or other foods and beverages, or pharmaceuticals such as patches, the driving force of these contents may cause the oligomers in the polyester layer to dissolve into the contents. The sealant film 1 of the present embodiment, by including the polyester layer 11, can be effective even in such cases.

[0047] The back surface layer 16 can be made of the same material as the above-mentioned front surface layer 12 . [Embodiment 5] Referring to FIG. 5, the sealant film 1 of this embodiment is the same as that of the fourth embodiment, except that a first intermediate layer 13 is provided between the polyester layer 11 and the back surface layer 16.

[0048] By including the first intermediate layer 13, the adhesive strength between the polyester layer 11 and the back surface layer 16 is improved, and the seal strength of the sealant film 1 is improved.

[0049] [Embodiment 6] 6, the sealant film 1 of this embodiment is a sealant film formed by laminating, in this order, a polyester layer 11, a first intermediate layer 13, an intervening layer 14, a second intermediate layer 15, and a back surface layer 16. Except for the fact that the intervening layer 14 and the second intermediate layer 15 are further laminated, this embodiment is the same as the fifth embodiment.

[0050] The backing layer 16 and the intermediate layer 14 may be made of the same material or different materials. [Embodiment 7] <Laminated film> Referring to Figures 7 and 8, the laminated film 2 (packaging material) of this embodiment is a laminated film formed by laminating a base film 31, an adhesive layer 51, a gas barrier film 4, an adhesive layer 52, and a sealant film 1 in this order.

[0051] The base film 31 is not particularly limited as long as it has mechanical strength and dimensional stability, and examples thereof include plastic film, paper, nonwoven fabric, etc. Examples of materials constituting the plastic film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as PE and polypropylene, polystyrene, polyamides such as 6-nylon, polycarbonate, polyacrylonitrile, polyimide, etc. The plastic film is preferably PET, PE, or paper.

[0052] The laminated film 2 of this embodiment may have a gas barrier film 4. The gas barrier film 4 can prevent deterioration of the contents due to oxygen gas, reduction of the contents due to external diffusion, and the like.

[0053] The gas barrier film 41 can be a metal foil such as aluminum foil, or a laminated film of a metal foil and a plastic film. The gas barrier film 42 can be a transparent vapor-deposited film having a vapor-deposited layer of an inorganic oxide or metal on a plastic film. Examples of plastic films include those described above, and examples of transparent vapor-deposited films include vapor-deposited films of metal oxides such as silicon oxide and aluminum oxide. Furthermore, films of ethylene-vinyl alcohol copolymers, polyamide resins, polyvinylidene chloride resins, polyacrylonitrile resins, and the like can also be used as gas barrier films. In this embodiment, when a transparent vapor-deposited film is used as the gas barrier film 4, the substrate film 31 and adhesive layer 51 may not be provided.

[0054] (adhesive layer) The laminate film 2 of the present embodiment may have an adhesive layer 51 between the base film 31 and the gas barrier film 41. The adhesive layer 51 can improve the adhesive strength between the base film 31 and the gas barrier film 41.

[0055] There are no particular limitations on the adhesive that constitutes the adhesive layer 51, but a dry laminating adhesive can be suitably used. Examples of dry laminating adhesives include two-component curing urethane adhesives, polyester urethane adhesives, polyether urethane adhesives, acrylic adhesives, polyester adhesives, polyamide adhesives, and epoxy adhesives.

[0056] Among the above adhesives, two-component curing adhesives are preferably used because they have excellent adhesive strength and are not easily weakened by the chemical components of the contents. Two-component curing adhesives are composed of a base agent and a curing agent, and examples thereof include two-component curing adhesives composed of polyester, polyol, and multifunctional polyisocyanate. A dry lamination method is one example of a method for bonding the substrate film 31 and the gas barrier film 41 using such an adhesive.

[0057] Furthermore, the laminated film 2 of this embodiment may have an adhesive layer 52 between the sealant film 1 and the gas barrier film 4. The adhesive constituting the adhesive layer 52 may be made of the same material as that of the adhesive layer 51 described above. The adhesive constituting the adhesive 51 and the adhesive constituting the adhesive layer 52 may be made of the same or different components. The sealant film 1 and the gas barrier film 4 may be bonded together by dry lamination.

[0058] The laminated film 2 of this embodiment is provided with the sealant film 1 of the above-described embodiment, making it non-adsorbent and inhibiting adsorption or absorption of contents (fragrant components, medicinal components, etc.), and can also inhibit the liberation of oligomers. It also has sufficient sealing strength and low-temperature sealing properties. Note that similar effects can be achieved in the following embodiments by providing the sealant film 1 of the above-described embodiment.

[0059] [Embodiment 8] 9 and 10, the laminate film 2 of this embodiment is a laminate film formed by laminating, in this order, a base film 31, an adhesive layer 51, a gas barrier film 4, an adhesive layer 52, a base film 32, an adhesive layer 53, and a sealant film 1. The laminate film 2 is the same as that of embodiment 7, except that the base film 32 and the adhesive layer 53 are further laminated.

[0060] The base film 32 can be made of the same material as the above-mentioned base film 31. The base film 31 and the base film 32 can be made of the same material or different materials.

[0061] The adhesive constituting adhesive layer 53 can be made of the same material as that of adhesive layer 51. The adhesive constituting adhesive 51, adhesive layer 52, and adhesive layer 53 may be made of the same or different components. The sealant film 1 and base film 32 can be bonded together by dry lamination.

[0062] [Embodiment 9] 11, the laminated film 2 of this embodiment is a laminated film formed by laminating, in this order, a base film 33, a base film 34, a base film 35, a gas barrier film 4, an adhesive layer 52, and a sealant film 1. In addition, the base film 32 and the adhesive layer 53 may be further laminated between the adhesive layer 52 and the sealant film 1.

[0063] [Embodiment 10] <Packaging bag> The laminated film formed as described above is used to form a packaging bag into a desired shape, such as a pillow-type packaging bag, a case-type packaging bag, or a free-standing packaging bag, depending on the purpose (design, capacity, ease of use, etc. of the packaging bag).

[0064] Examples of contents include food, beverages, medicines, quasi-drugs, etc. The packaging bag of this embodiment can be suitably used for contents containing, in particular, fragrance components, medicinal components, etc. (components that are easily adsorbed or absorbed by the packaging bag, or components that are problematic if adsorbed or absorbed by the packaging bag). Specifically, the packaging bag of this embodiment can be suitably used for storing, for example, alcoholic beverages, cosmetics containing fragrance components such as perfumes, patches or mouthwashes containing medicinal components, etc.

[0065] [Embodiment 11] <Packaging container> The laminated film formed as described above is used to form a bag in a desired shape to form a packaging container. For example, brick-type packaging containers, cup-type packaging containers, tray-type packaging containers, etc. may be produced depending on the purpose (design, capacity, ease of use, etc. of the packaging container). Examples of contents include those similar to those in the tenth embodiment described above.

[0066] [Embodiment 12] <Method of manufacturing sealant film> The sealant film in this embodiment is produced by an inflation method. The inflation method includes an extrusion step of extruding the resin that constitutes the polyester layer, and the temperature in the extrusion step is 180° C. or higher and 260° C. or lower. By producing the sealant film by such a method, it is possible to suppress the liberation of oligomers.

[0067] The inflation method in this embodiment is preferably an air-cooled inflation method. When a surface layer and an intermediate layer are provided, it is preferable to co-extrude the resins constituting the polyester layer, the resins constituting the surface layer, and the resins constituting the intermediate layer. Hereinafter, a method for producing a sealant film consisting of a polyester layer, a surface layer, and an intermediate layer by the air-cooled inflation method will be described.

[0068] The air-cooled inflation method includes a co-extrusion process in which the resins constituting the polyester layer, the resins constituting the surface layer, and the resins constituting the intermediate layer are melted in separate extruders and the molten resins are co-extruded through a die; an inflation cooling process in which air is supplied to the co-extruded molten resins to expand them into a tubular shape, while the air simultaneously air-cools and solidifies the molten resin to obtain a tubular film; and a take-up process in which the tubular film is taken up while the air inside is excluded.

[0069] There are no particular limitations on the inflation molding machine that can be used in this method, as long as it is capable of extruding two or more layers.

[0070] The temperature of the extruder in the co-extrusion process is 180°C or higher and 260°C or lower, and preferably 200°C or higher and 230°C or lower. If the extruder temperature is lower than 180°C, the resin used may not melt. If the extruder temperature exceeds 260°C, the amount of oligomer released may increase. In addition, the resin used may be thermally deteriorated.

[0071] The die shape of the inflation molding machine is usually circular. The die diameter is, for example, 100 mmΦ or more and 300 mmΦ or less, and preferably 200 mmΦ or more and 250 mmΦ or less. If the die diameter is less than 100 mmΦ, the film production efficiency may be poor. If the die diameter is more than 300 mmΦ, the valve shape of the sealant film will not be stable.

[0072] The degree of expansion in the inflation cooling process is determined by the blow ratio, which affects the seal strength, film formation stability, etc. The blow ratio is, for example, 1.5 to 2.5, and preferably 1.8 to 2.2. If the blow ratio is less than 1.5, the film formation efficiency may be poor. If the blow ratio is more than 2.5, the valve shape of the sealant film may be unstable.

[0073] The forming speed in the take-up step is, for example, 5.0 m / min to 25 m / min, preferably 10 m / min to 20 m / min. If the forming speed is less than 5.0 m / min, stable film formation may not be possible. If the forming speed is more than 25 m / min, film cracking may occur in the sealant film. [Example]

[0074] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0075] (Examples 1 to 4, Comparative Examples 1 to 3) In the sealant film of the laminated film having the layer structure shown in Figure 7(a), the polyester resins constituting the polyester layers were those with the compositions shown in Table 1. PE was used for the surface layer, and maleic anhydride-grafted PE was used for the intermediate layer.

[0076] In the "Polyester layer composition" column of Table 1, TPA stands for "terephthalic acid," IPA stands for "isophthalic acid," EG stands for "ethylene glycol," and other glycols stand for glycol components other than EG used in Comparative Examples 5 to 11 described below. For example, in Example 1, this means that the polyester layer contains 95 mol % TPA and 5 mol % IPA as dicarboxylic acids, and 100 mol % EG as diol.

[0077] A three-kind, three-layer inflation molding machine equipped with a 250 mm diameter extruder for the polyester layer, a 250 mm diameter extruder for the surface layer, and a 250 mm diameter extruder for the middle layer was used to produce sealant films under the following conditions to obtain sealant films of Examples 1 to 4 and Comparative Examples 1 to 3. In all of Examples 1 to 4 and Comparative Examples 1 to 3, the thickness of each layer of the produced sealant films was 40 μm for the polyester layer, 15 μm for the surface layer, and 5 μm for the middle layer. [Manufacturing conditions] Extruder temperature: 230℃ Die diameter: 250mmΦ Blow ratio: 2.0 Molding speed: 13m / min Separately from this sealant film, a substrate film and a gas barrier film were laminated by dry lamination with a two-component curing polyester urethane adhesive. Also, the sealant film prepared above was laminated on a gas barrier film with a two-component curing polyester urethane adhesive by dry lamination to obtain laminate films of Examples 1 to 4 and Comparative Examples 1 to 3.

[0078] The base film is polyethylene terephthalate (PET) and has a thickness of 12 μm, and the gas barrier film is aluminum foil and has a thickness of 9 μm.

[0079] Comparative Example 4 Except for the fact that the sealant film was formed by the T-die method, a laminated film was produced in the same manner as in Example 3. The temperature of the extruder in the T-die extrusion molding machine was 290°C.

[0080] (Comparative Examples 5 to 11) The laminated films were produced in the same manner as in Example 1, except that the glycol other than EG used to constitute the polyester layer was butanediol in Comparative Examples 5 and 6, neopentyl glycol in Comparative Example 7, hexanediol in Comparative Example 8, and cyclohexanedimethanol in Comparative Examples 9 to 11, in the proportions shown in Table 1.

[0081] <Evaluation> (Evaluation Test 1) In Evaluation Test 1, low-temperature sealing properties were evaluated. Specifically, each laminate film of the above-mentioned Examples and Comparative Examples was sealed with the sealant film facing inward. The sealing conditions were a sealing pressure of 0.1 MPa and a sealing time of 1.0 second, and the sealing temperature was varied. The temperature at which a seal strength of 5 N / 15 mm width or more was achieved was determined as the sealing initiation temperature in accordance with JIS Z0238. The results are shown in the "Sealing initiation temperature (°C)" column in Table 1. A temperature of 130°C or less was considered good.

[0082] (Evaluation Test 2) In Evaluation Test 2, the seal strength was evaluated. Specifically, each laminate film of the above-mentioned Examples and Comparative Examples was sealed with the sealant film facing inward. The sealing conditions were a sealing temperature of 160°C, a sealing pressure of 0.1 MPa, and a sealing time of 1.0 second. The seal strength (N / 15 mm) of the two sealed laminate films was measured based on JIS X0238 for laminate films cut into strips. The results are shown in the "Seal strength (N / 15 mm)" column in Table 1. A seal strength of 30 N / 15 mm or more was considered good.

[0083] (Evaluation Test 3) In Evaluation Test 3, the adsorption properties were evaluated. Specifically, each laminate film of the above-mentioned Examples and Comparative Examples was cut to a predetermined shape (length: 120 mm, width: 120 mm), and two laminate films were placed on a bag making machine with the sealant films in contact with each other. A predetermined area (periphery of the sealant film: within 10 mm from the peripheral edge) was sealed to create a three-sided bag-making type packaging bag. At this point, the top end of the packaging bag (top seal portion) was not yet sealed in order to fill the contents. The sealing conditions were a sealing temperature of 160°C, a sealing pressure of 0.1 MPa, and a sealing time of 1.0 second.

[0084] Next, sake ("Daiginjo" manufactured by Hakutsuru Sake Brewery Co., Ltd.) was filled into the packaging bag from the top under a nitrogen atmosphere, and the top end of the packaging bag (top seal) was sealed to hermetically seal the contents. Note that ethyl caprate, a component of the sake used here, is generally a component that is easily adsorbed by sealant films.

[0085] The packaging bag containing the contents as described above was stored for 3 months in a thermostatic chamber maintained at 40°C. After storage, the headspace in the packaging bag was concentrated using solid-phase microextraction (SPME), and quantitative analysis was performed using a gas chromatograph-mass spectrometer (GC-MS) based on the concentration of a standard sample of ethyl caprate used as an internal standard. The ratio of the amount remaining after the storage period to the initial amount was calculated as the residual rate (%) of ethyl caprate. The results are shown in the "Residual Rate (%)" column in Table 1. A value of 70% or higher was considered good.

[0086] (Evaluation Test 4) The amount of oligomers was evaluated in Evaluation Test 4. Specifically, each polyester layer of the above Examples and Comparative Examples was dissolved in hexafluoroisopropanol (HFIP), then reprecipitated with acetonitrile, and the supernatant was filtered to prepare a sample solution, which was then measured by reversed-phase HPLC (Agilent, 1260 Infinity II LC system) under the following conditions. [Measurement conditions] Detector: UV absorption photometer Measurement wavelength: 242nm Column: Reverse phase column C18 ODS 5μ (length: 250 mm, inner diameter: 4.6 mm) Column temperature: 25℃ Eluent: acetonitrile / water = 7 / 3 Flow rate: 1.5ml / min Injection volume: 20 μl In the molecular weight distribution obtained by HPLC as described above, the peak areas of the multiple peaks from 5 to 20 minutes in the elution time region were vertically divided by elution time, and the amount of each peak area was normalized using the weight of the polyester layer. Peak shape analysis was performed. The measurement was repeated three times, and the average value of each peak area was used as the value. The results are shown in the "Oligomer content (wt%)" column in Table 1. A content of less than 2.0 wt% was considered good.

[0087] Table 1 also shows the glass transition temperature, crystallization temperature, and melting temperature of each polyester layer of the sealant films used in Examples 1 to 4 and Comparative Examples 1 to 11, which were measured using a differential scanning calorimeter in accordance with JIS K7121.

[0088] [Table 1]

[0089] The results shown in Table 1 show that the laminated films of Examples 1 to 4, which use sealant films having a polyester layer containing a specific polyester as the main component, have a low oligomer content of less than 2.0 wt%, have excellent low adsorption properties for the contents, and can suppress deterioration of odor and flavor.

[0090] In contrast, in Comparative Examples 1 to 3, which used polyester with an IPA content exceeding the specified amount, the oligomer amount was 2.0 wt% or more, which showed high content adsorption and failure to suppress deterioration of odor and flavor. Furthermore, in Comparative Example 4, which was produced with the same composition as Example 3 except that the sealant film was produced by the T-die method, the oligomer amount was 2.0 wt%, which showed high content adsorption and failure to suppress deterioration of odor and flavor. Furthermore, Comparative Examples 5 to 11, which used glycols other than EG, showed high content adsorption.

[0091] The embodiments and examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0092] 1 sealant film, 11 polyester layer, 12 surface layer, 13 first intermediate layer, 14 intervening layer, 15 second intermediate layer, 16 back layer, 2 laminated film, 31, 32, 33, 34, 35 base film, 4, 41, 42 gas barrier film, 51, 52, 53 adhesive layer.

Claims

1. A sealant film comprising a polyester layer containing polyester as a main component and a surface layer, the polyester comprises structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid; a ratio of the structural units derived from isophthalic acid to the structural units derived from terephthalic acid and isophthalic acid constituting the polyester is 3.0 mol % or more and 15 mol % or less, the content of oligomer in the polyester layer is less than 2.0% by mass, The sealant film, wherein the surface layer is at least one selected from the group consisting of polyethylene, an ethylene-acrylic acid ester copolymer, and an ethylene-methacrylic acid ester copolymer.

2. The sealant film according to claim 1, wherein the glass transition temperature of the polyester is 60°C or higher and 80°C or lower.

3. an intermediate layer is further provided between the polyester layer and the surface layer; 3. The sealant film according to claim 1, wherein the intermediate layer is at least one selected from the group consisting of acid anhydride-grafted polyethylene and ethylene-ester copolymer.

4. The sealant film according to claim 1 , wherein the polyester layer has a thickness of 20 μm or more and 50 μm or less.

5. A base film; A laminated film comprising the sealant film according to any one of claims 1 to 4.

6. The laminate film according to claim 5 , further comprising a gas barrier film between the base film and the sealant film.

7. A packaging bag made by sealing the laminated film described in claim 5 or claim 6 so that the sealant films are fused together.

8. A packaging container formed by sealing the laminated film described in claim 5 or claim 6 so that the sealant films are fused together.

9. A method for producing a sealant film comprising a polyester layer containing polyester as a main component and a surface layer, The method for producing the sealant film includes an extrusion step of co-extruding resins constituting the polyester layer and the surface layer by an inflation method, The temperature in the extrusion step is 180°C or higher and 260°C or lower, the polyester comprises structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid; a ratio of the structural units derived from isophthalic acid to the structural units derived from terephthalic acid and isophthalic acid constituting the polyester is 3.0 mol % or more and 15 mol % or less, the content of oligomer in the polyester layer is less than 2.0% by mass, The method for producing a sealant film, wherein the surface layer is at least one selected from the group consisting of polyethylene, an ethylene-acrylic acid ester copolymer, and an ethylene-methacrylic acid ester copolymer.

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