Sealing film, laminated film using the same, packaging bag and packaging container, and method for manufacturing sealing film

Abstract

A sealing film (1) provided with a polyester layer (11) containing polyester as a main component, the polyester being composed of a structural unit derived from ethylene glycol, a structural unit derived from terephthalic acid, and a structural unit derived from isophthalic acid, the ratio of the structural unit derived from isophthalic acid being 3.0 mol% or more and 15 mol% or less relative to the ratio of the structural unit derived from terephthalic acid and the structural unit derived from isophthalic acid that constitute the polyester, and the content of oligomers in the polyester layer (11) being less than 2.0 mass%.

Description

Technical Field

[0001] This invention relates to sealing films, laminated films using the sealing films, packaging bags and packaging containers, and methods for manufacturing sealing films. Background Technology

[0002] Sealing films are widely used in the packaging of food, beverages, and pharmaceuticals. The sealing film is placed as the innermost layer of the packaging bag and is sealed by heat sealing. High-sealing-strength polyolefin resins such as polyethylene or polypropylene are used as sealing films.

[0003] However, because such sealing films easily absorb components composed of organic compounds such as oils or fragrances, packaging bags with sealing films have problems such as absorbing the aroma components or medicinal components of the contents.

[0004] As a countermeasure, polyester resins, polyacrylonitrile copolymers (PAN), and polyethylene terephthalate (PET) are used instead of polyolefin resins. Among them, polyester resins, by selectively choosing diacids and diols as comonomers, can control the imparting of low-temperature sealing properties and the flowability during sealing while maintaining low adsorption of contents.

[0005] On the other hand, due to the presence of comonomer components, low molecular weight substances (oligomers) are generated as byproducts during the polymerization stage, leading to problems such as odor and flavor degradation, and reduced adsorption of contents.

[0006] It should be noted that Japanese Patent Application Publication No. 2006-305975 (Patent Document 1) discloses a sealing film made of isophthalic acid-modified PET resin as a polyester resin, manufactured by T-die casting. The disclosure also states that this sealing film exhibits low adsorption and excellent barrier properties, enabling stable heat sealing.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-305975 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the sealing film described in Patent Document 1 has room for improvement in terms of odor and flavor. Therefore, the inventors discovered that by focusing on the comonomer components of the polyester resin, namely diacids and diols, limiting the diacids to terephthalic acid and isophthalic acid, and the diols to ethylene glycol, copolymerizing the terephthalic acid and isophthalic acid in a specific ratio, and manufacturing using an inflation method, the formation of oligomers can be suppressed. This suppresses the decrease in the absorbency of the contents and the deterioration of odor and flavor.

[0012] This disclosure was made in view of the above-mentioned issues, and its purpose is to suppress the deterioration of odor and flavor while maintaining low adsorption of contents in a sealing film using polyester resin.

[0013] Methods for solving problems [1]

[0015] A sealing film comprising a polyester layer containing polyester as the main component.

[0016] The polyester is composed of structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid.

[0017] The ratio of the structural units derived from isophthalic acid to the ratio of the structural units derived from terephthalic acid to the structural units derived from isophthalic acid constituting the polyester is more than 3.0 mol% and less than 15 mol%.

[0018] The oligomer content in the polyester layer is less than 2.0% by mass. [2]

[0020] According to the sealing film described in [1], the glass transition temperature of the polyester is 60°C.

[0021] Temperatures above ℃ and below 80℃. [3]

[0023] According to the sealing film described in [1] or [2],

[0024] It has a surface layer.

[0025] The surface layer is selected from at least one of polyethylene, ethylene-acrylate copolymer and ethylene-methacrylate copolymer. [4]

[0027] According to the sealing film described in [3],

[0028] An intermediate layer is further provided between the polyester layer and the surface layer.

[0029] The intermediate layer is selected from at least one of the groups consisting of anhydride-grafted polyethylene and ethylene-ester copolymers. [5]

[0031] The sealing film according to any one of [1] to [4], wherein the thickness of the polyester layer is more than 20 μm and less than 50 μm. [6]

[0033] A laminated membrane comprising:

[0034] Substrate film, and

[0035] The sealing membrane described in any one of [1] to [5]. [7]

[0037] According to the laminated film described in [6], an air barrier film is further included between the substrate film and the sealing film. [8]

[0039] A packaging bag is formed by sealing the laminated films described in [6] or [7] by fusing the sealing films together. [9]

[0041] A packaging container is formed by sealing the laminated films described in [6] or [7] by fusing the sealing films together.

[10]

[0043] A method for manufacturing a sealing film, comprising a polyester layer containing polyester as the main component.

[0044] The method for manufacturing the sealing film includes an extrusion step of extruding the resin constituting the polyester layer using a blow molding method.

[0045] The temperature of the extrusion process is above 180°C and below 260°C.

[0046] The polyester is composed of structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid.

[0047] The ratio of the structural units derived from isophthalic acid to the ratio of the structural units derived from terephthalic acid to the structural units derived from isophthalic acid constituting the polyester is more than 3.0 mol% and less than 15 mol%.

[0048] The oligomer content in the polyester layer is less than 2.0% by mass.

[0049] The effects of the invention

[0050] According to this disclosure, in a sealing film using polyester resin, odor and flavor degradation can be suppressed while maintaining low adsorption of the contents. Attached Figure Description

[0051] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 1.

[0052] [ Figure 2 ] Figure 2 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 2.

[0053] [ Figure 3 ] Figure 3 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 3.

[0054] [ Figure 4 ] Figure 4 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 4.

[0055] [ Figure 5 ] Figure 5 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 5.

[0056] [ Figure 6 ] Figure 6 This is a schematic cross-sectional view showing an example of the sealing membrane used in Embodiment 6.

[0057] [ Figure 7 ] Figure 7 This is a schematic cross-sectional view showing an example of the laminated film of Embodiment 7.

[0058] [ Figure 8 ] Figure 8 This is a schematic cross-sectional view showing an example of the laminated film of Embodiment 7.

[0059] [ Figure 9 ] Figure 9 This is a schematic cross-sectional view showing an example of the laminated film of Embodiment 8.

[0060] [ Figure 10 ] Figure 10 This is a schematic cross-sectional view showing an example of the laminated film of Embodiment 8.

[0061] [ Figure 11 ] Figure 11 This is a schematic cross-sectional view showing an example of the laminated film of Embodiment 9. Detailed Implementation

[0062] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that in the drawings, the same reference numerals denote the same or equivalent parts.

[0063] [Implementation Method 1]

[0064] <Sealing film>

[0065] Reference Figure 1 In this embodiment, the sealing film 1 is composed of two layers: a polyester layer 11 (sealing side) and a surface layer 12. It should be noted that the sealing film 1 in this embodiment is composed of two layers, but it may also be composed of only a polyester layer 11.

[0066] (Polyester layer)

[0067] The polyester layer 11 contains polyester as a main component. Here, "containing as a main component" means, for example, that the polyester content is greater 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. It should be noted that the polyester layer 11 may also be combined with other polymer materials, various additives, etc.

[0068] 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. The number-average molecular weight of this polyester is between 15,000 and 21,000.

[0069] The ratio of structural units derived from isophthalic acid is 3.0 mol% to 15 mol% relative to the ratio of structural units derived from terephthalic acid to structural units derived from isophthalic acid constituting the polyester. When the ratio of structural units derived from isophthalic acid is less than 3.0 mol%, it results in a sealing film with poor low-temperature sealing properties. When the ratio of structural units derived from isophthalic acid exceeds 15 mol%, it results in an amorphous or low-crystallinity polyester layer, increasing the adsorption capacity of the contents. The ratio of structural units derived from isophthalic acid is preferably 8.0 mol% or more, more preferably 9.0 mol% or more, further preferably 10 mol% or more, and may also be 10.5 mol% or more, preferably 13 mol% or less, more preferably 12.5 mol% or less, further preferably 12 mol% or less, and may also be 11.5 mol% or less.

[0070] The polyester layer 11 contains oligomers. In this embodiment, the oligomers are polymers with a molecular weight smaller than the polyester produced during the polymerization stage of the polyester, including both chain oligomers and cyclic oligomers. These oligomers cause problems such as deterioration of odor and flavor, and reduced adsorption of contents. The inventors have discovered that by setting the polyester composition to the above-described components and ratios, and manufacturing it using the method described later, the oligomer content in the polyester layer 11 can be less than 2.0% by mass. When the oligomer content in the polyester layer 11 is less than 2.0% by mass, the aforementioned problems can be suppressed. The oligomer content in the polyester layer 11 is preferably 1.8% by mass or less.

[0071] The content of oligomers in polyester layer 11 can be determined using high-performance liquid chromatography (HPLC). Specifically, the polyester layer to be measured is dissolved in hexafluoroisopropanol (HFIP), then precipitated with acetonitrile, and the supernatant is filtered to prepare a sample solution, which is then determined by reversed-phase HPLC (Agilent 1260 Infinity II LC system) under the following conditions.

[0072] [Measurement Conditions]

[0073] Detector: Ultraviolet Absorption Spectrophotometer

[0074] Measurement wavelength: 242nm

[0075] Column: Inverting column C18 ODS5μ (Length: 250mm, Inner Diameter: 4.6mm)

[0076] Column temperature: 25℃

[0077] Eluent: Acetonitrile / Water = 7 / 3

[0078] Flow rate: 1.5 ml / minute

[0079] Sample volume injected: 20 μl

[0080] In this embodiment, oligomers refer to multiple peak fractions with dissolution times ranging from 5 to 20 minutes in HPLC-based molecular weight distribution. In peak waveform processing of the chromatogram, the peak area is vertically segmented at each dissolution time, and normalized using the weight of the polyester layer with each peak area fraction determined. The measurement is repeated three times, and the average peak area is used as the value. This peak area only needs to be less than 2%.

[0081] The thickness of the polyester layer 11 can be appropriately varied depending on the application, for example, it can be 20 μm or more but less than 50 μm. When the thickness of the polyester layer 11 is less than 20 μm, the amount of contents adsorbed increases. When the thickness of the polyester layer 11 exceeds 50 μm, the discharge load during film formation is high, and film formation may not be possible. The thickness of the polyester layer 11 is preferably 25 μm or more but less than 45 μm.

[0082] The polyester layer 11 may contain an anti-blocking agent. This is because the presence of an anti-blocking agent improves the slip properties of the polyester layer 11, making it less prone to sticking. Examples of anti-blocking agents include silica, talc, and diatomaceous earth. The content of the anti-blocking agent is, for example, 0.1% by mass or more and 3% by mass or less, preferably 0.5% by mass or more and 1.5% by mass or less.

[0083] The glass transition temperature (Tg) of the polyester is preferably 60°C to 80°C, more preferably 70°C to 75°C. Under these conditions, a sealing film 1 with appropriate sealing strength can be obtained. Tg can be measured based on JIS K7121.

[0084] The crystallization temperature (Tc) of the polyester is preferably 130°C or higher, more preferably 135°C or higher. Under these conditions, a sealing film 1 with appropriate sealing strength can be obtained. Tc can be measured based on JIS K7121.

[0085] The melting temperature (Tm) of the polyester is preferably 200°C or higher, more preferably 210°C or higher. Under these conditions, a sealing film 1 with appropriate sealing strength can be obtained. Tm can be measured based on JIS K7121.

[0086] (Surface layer)

[0087] The sealing membrane 1 may also have a surface layer 12.

[0088] Examples of surface layer 12 include polyethylene (PE) and ethylene-ester copolymers. Examples of ethylene-ester copolymers include ethylene-acrylate copolymers and ethylene-methacrylate copolymers.

[0089] The thickness of the sealing membrane 1 can be appropriately changed according to the application, for example, from 30μm to 80μm.

[0090] The sealing film 1 of this embodiment, by having the layer described above, is a non-adsorbent film that inhibits the adsorption or absorption of contents (aroma components, medicinal components, etc.), and can suppress the release of oligomers. In addition, it also has sufficient sealing strength and low-temperature sealing performance.

[0091] Regarding low-temperature sealing performance, specifically, regarding the sealing start temperature of the sealing membrane, under sealing conditions of a sealing pressure of 0.1 MPa and a sealing time of 1.0 second, the temperature at which the sealing strength is greater than 5 N / 15 mm width is preferably below 130°C. It should be noted that the sealing start temperature is determined according to JIS Z0238.

[0092] Regarding sealing strength, specifically, under sealing conditions of 160℃, 0.1MPa, and 1.0 second, the sealing strength of the sealing membrane is preferably 30N / 15mm width or higher. It should be noted that the sealing strength is measured according to JIS Z0238.

[0093] [Implementation Method 2]

[0094] Reference Figure 2 Except for the fact that a first intermediate layer 13 is provided between the polyester layer 11 and the surface layer 12, the sealing film 1 of this embodiment is the same as that of embodiment 1.

[0095] By having a first intermediate layer 13, the adhesion between the polyester layer 11 and the surface layer 12 is improved, and the sealing strength of the sealing film 1 is enhanced. Examples of the first intermediate layer 13 include anhydride-grafted polyethylene (PE) and ethylene-ester copolymers. Examples of anhydride-grafted PE include maleic anhydride-grafted PE and itaconic anhydride-grafted PE.

[0096] [Implementation Method 3]

[0097] Reference Figure 3 The sealing film 1 in this embodiment is formed by sequentially stacking a surface layer 12, a first intermediate layer 13, an interlayer 14, a second intermediate layer 15, and a polyester layer 11. Except for the further stacking of the interlayer 14 and the second intermediate layer 15, it is the same as in embodiment 2.

[0098] As the intercalation layer 14, the same material as the surface layer 12 can be used. It should be noted that the surface layer 12 and the intercalation layer 14 can be made of the same material or different materials.

[0099] The second intermediate layer 15 can be made of the same material as the first intermediate layer 13. Alternatively, the first intermediate layer 13 and the second intermediate layer 15 can be made of the same material or different materials.

[0100] [Implementation Method 4]

[0101] Reference Figure 4 The sealing film 1 in this embodiment is a sealing film composed of two layers: a polyester layer 11 and a back layer 16.

[0102] It is generally believed that, in the case of a sealing film structure as described in this embodiment, the polyester layer does not come into contact with the contents, thus making it difficult for the aforementioned deterioration in odor and flavor caused by oligomers to occur. However, for example, when beverages or foods such as alcohols or oily foods, or pharmaceutical products such as patches, are used as contents, the oligomers in the polyester layer may sometimes dissolve into the contents due to the driving force of these contents. In the sealing film 1 of this embodiment, by providing the polyester layer 11, an effect can be achieved even in such cases.

[0103] The same material as the surface layer 12 described above can be used as the back layer 16.

[0104] [Implementation Method 5]

[0105] Reference Figure 5 Except for the fact that a first intermediate layer 13 is provided between the polyester layer 11 and the back layer 16, the sealing film 1 of this embodiment is the same as that of embodiment 4.

[0106] With the first intermediate layer 13, the adhesion between the polyester layer 11 and the back layer 16 is improved, and the sealing strength of the sealing film 1 is improved.

[0107] [Implementation Method 6]

[0108] Reference Figure 6 The sealing film 1 in this embodiment is formed by sequentially stacking a polyester layer 11, a first intermediate layer 13, an interlayer 14, a second intermediate layer 15, and a back layer 16. Except for the further stacking of the interlayer 14 and the second intermediate layer 15, it is the same as in embodiment 5.

[0109] The back layer 16 and the intercalation layer 14 can be made of the same material or different materials.

[0110] [Implementation Method 7]

[0111] <Laminated film>

[0112] Reference Figure 7 and Figure 8 In this embodiment, the laminated film 2 (packaging material) is a laminated film formed by sequentially laminating a substrate film 31, an adhesive layer 51, an air barrier film 4, an adhesive layer 52, and a sealing film 1.

[0113] As for the substrate film 31, any film with mechanical strength and dimensional stability is acceptable; there are no particular limitations, and plastic film, paper, non-woven fabric, etc., can be used. Examples of constituent materials for plastic films include: polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate; polyolefins such as PE and polypropylene; polystyrene; polyamides such as 6-nylon; polycarbonate; polyacrylonitrile; and polyimide. PET, PE, and paper are preferred for the plastic film.

[0114] The laminated membrane 2 in this embodiment may also have a gas barrier membrane 4. The gas barrier membrane 4 can suppress degradation caused by oxygen in the contents, reduction caused by external diffusion of the contents, etc.

[0115] As the gas barrier film 41, a laminated film of metal foil such as aluminum foil and a plastic film can be used. As the gas barrier film 42, a transparent vapor-deposited film having an inorganic oxide or metal vapor-deposited layer on a plastic film can be used. 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 or aluminum oxide. Additionally, films of ethylene / vinyl alcohol copolymers, polyamide resins, polyvinylidene chloride resins, and polyacrylonitrile resins can also be used as gas barrier films. It should be noted that in this embodiment, when a transparent vapor-deposited film is used as the gas barrier film 4, the substrate film 31 and the adhesive layer 51 may not be provided.

[0116] (Adhesive layer)

[0117] The laminated film 2 in this embodiment may also have an adhesive layer 51 between the substrate film 31 and the gas barrier film 41. The adhesive layer 51 can improve the adhesion strength between the substrate film 31 and the gas barrier film 41.

[0118] There are no particular limitations on the adhesive used to form the adhesive layer 51, but dry lamination adhesives are preferred. Examples of dry lamination adhesives include: two-component curing urethane adhesives, polyester urethane adhesives, polyether urethane adhesives, acrylic adhesives, polyester adhesives, polyamide adhesives, epoxy adhesives, etc.

[0119] Among the aforementioned adhesives, two-component curing adhesives with excellent adhesion and adhesion strength that is not easily reduced due to the chemical composition of the contents are preferred. Two-component curing adhesives consist of a base agent and a curing agent; examples include two-component curing adhesives composed of polyester, polyols, and polyfunctional polyisocyanates. It should be noted that dry lamination is an example of a method for bonding the substrate film 31 and the gas barrier film 41 using such an adhesive.

[0120] Furthermore, the laminated film 2 of this embodiment may also have an adhesive layer 52 between the sealing film 1 and the gas barrier film 4. The adhesive constituting the adhesive layer 52 can be the same material as that used in the adhesive layer 51 described above. It should be noted that the adhesive constituting the adhesive layer 51 and the adhesive constituting the adhesive layer 52 can be of the same composition or different compositions. It should also be noted that dry lamination can be used as a method for bonding the sealing film 1 and the gas barrier film 4.

[0121] The laminated membrane 2 of this embodiment, by incorporating the sealing membrane 1 of the above embodiment, is a non-adsorbent membrane that inhibits the adsorption or absorption of contents (aroma components, medicinal components, etc.), and can suppress the release of oligomers. Furthermore, it possesses sufficient sealing strength and low-temperature sealing performance. It should be noted that in the following embodiments, the same effect can be achieved by incorporating the sealing membrane 1 of the above embodiment.

[0122] [Implementation Method 8]

[0123] Reference Figure 9 and Figure 10 In this embodiment, the laminated film 2 is formed by sequentially laminating a substrate film 31, an adhesive layer 51, a gas barrier film 4, an adhesive layer 52, a substrate film 32, an adhesive layer 53, and a sealing film 1. Except for the further lamination of the substrate film 32 and the adhesive layer 53, it is the same as in embodiment 7.

[0124] As the substrate film 32, the same material as the substrate film 31 described above can be used. It should be noted that the substrate film 31 and the substrate film 32 can use the same material or different materials.

[0125] The adhesive constituting adhesive layer 53 can be the same material as that used in adhesive layer 51. It should be noted that the adhesives constituting adhesive layer 51, adhesive layer 52, and adhesive layer 53 can have the same composition or different compositions. It should also be noted that dry lamination can be used as a method for bonding the sealing film 1 and the substrate film 32.

[0126] [Implementation Method 9]

[0127] Reference Figure 11 In this embodiment, the laminated film 2 is formed by sequentially laminating a substrate film 33, a substrate film 34, a substrate film 35, a gas barrier film 4, an adhesive layer 52, and a sealing film 1. Alternatively, the substrate film 32 and the adhesive layer 53 may be further laminated between the adhesive layer 52 and the sealing film 1.

[0128] [Implementation Method 10]

[0129] <Packaging Bags>

[0130] Using the laminated film formed as described above, packaging bags are made into the desired shape. For example, pillow-shaped packaging bags, corner-supported packaging bags, stand-up pouches, etc., can be made according to the purpose (packaging bag design, content volume, ease of use, etc.).

[0131] Examples of contents that can be included include food, beverages, pharmaceuticals, and quasi-drugs. The packaging bag of this embodiment is particularly suitable for contents containing aroma components, medicinal ingredients, etc. (components that are easily absorbed or adsorbed by the packaging bag, or components whose absorption or adsorption by the packaging bag becomes problematic). Specifically, the packaging bag of this embodiment can be used, for example, to contain alcoholic beverages, cosmetics containing aroma components such as fragrances, patches containing medicinal ingredients, or mouthwash.

[0132] [Implementation Method 11]

[0133] <Packaging Containers>

[0134] Using the laminated film formed as described above, a packaging container is formed into the desired shape. For example, brick-shaped packaging containers, cup-shaped packaging containers, tray-shaped packaging containers, etc., can be made according to the purpose (packaging container design, content volume, ease of use, etc.). As for the contents, the same contents as those in Embodiment 10 described above can be listed.

[0135] [Implementation Method 12]

[0136] <Manufacturing Method of Sealing Membrane>

[0137] The sealing film in this embodiment is manufactured using a blow-blowing method. The blow-blowing method includes an extrusion step of extruding the resin constituting the polyester layer, with the extrusion temperature between 180°C and 260°C. Manufacturing in this way suppresses the release of oligomers.

[0138] In this embodiment, the blowing method is preferably an air-cooled blowing method. Furthermore, when a surface layer and an intermediate layer are provided, it is preferable to co-extrude the resin constituting the polyester layer, the resin constituting the surface layer, and the resin constituting the intermediate layer. Hereinafter, a method for manufacturing a sealing film composed of a polyester layer, a surface layer, and an intermediate layer using the air-cooled blowing method will be described.

[0139] The air-cooled blowing method includes: a co-extrusion step, in which the resin constituting the polyester layer, the resin constituting the surface layer, and the resin constituting the intermediate layer are melted by different extruders, and the molten resins are co-extruded from the mold; a blowing and cooling step, in which air is supplied to the molten resin after co-extrusion to expand it into a tubular shape, while the air cools and solidifies the molten resin to obtain a tubular film; and a pickup step, in which air is picked up while the air inside the tubular film is being extruded.

[0140] There are no particular restrictions on the blow molding machine that can be used in this method, as long as it can extrude more than two layers.

[0141] The extruder temperature in the co-extrusion process is between 180°C and 260°C, preferably between 200°C and 230°C. If the extruder temperature is below 180°C, the resin may not melt. If the extruder temperature exceeds 260°C, the amount of free oligomers may increase. Furthermore, the resin may also undergo thermal degradation.

[0142] The mold in a blow molding machine is typically circular. The mold diameter is, for example, 100 mmΦ to 300 mmΦ, preferably 200 mmΦ to 250 mmΦ. When the mold diameter is less than 100 mmΦ, the film-forming efficiency may deteriorate. When the mold diameter exceeds 300 mmΦ, the bulb shape of the sealing film becomes unstable.

[0143] The degree of expansion during the blow-up and cooling process is determined by the blow-up ratio, affecting sealing strength and film stability. This blow-up ratio is, for example, 1.5 to 2.5, preferably 1.8 to 2.2. When the blow-up ratio is less than 1.5, film formation efficiency may deteriorate. When the blow-up ratio exceeds 2.5, the tube shape of the sealing film becomes unstable.

[0144] The forming speed in the pick-up process 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, film formation may be unstable. If the forming speed exceeds 25 m / min, the sealing film may rupture.

[0145] Example

[0146] The present disclosure will be described in more detail below by way of examples, but the present disclosure is not limited thereto.

[0147] (Examples 1-4, Comparative Examples 1-3)

[0148] In having Figure 7 In the sealing film of the laminated film composed of (a) layers, the polyester resin constituting the polyester layer uses resins with the compositions shown in Table 1. Additionally, PE is used as the surface layer, and maleic anhydride-grafted PE is used as the intermediate layer.

[0149] It should be noted that in the "Polyester Layer Composition" column of Table 1, TPA refers to "terephthalic acid", IPA refers to "isophthalic acid", EG refers to "ethylene glycol", and other diols refer to the diol components other than EG used in Comparative Examples 5 to 11 described later. Furthermore, for example, for Example 1, this means a polyester layer containing 95 mol% TPA and 5 mol% IPA as dicarboxylic acids and 100 mol% EG as a diol.

[0150] The sealing films of Examples 1-4 and Comparative Examples 1-3 were obtained by manufacturing using three types of three-layer / multi-layer blow molding machines equipped with an extruder for the polyester layer (diameter 250 mm Φ), an extruder for the surface layer (diameter 250 mm Φ), and an extruder for the intermediate layer (diameter 250 mm Φ) under the following conditions. Regarding the thickness of each layer of the manufactured sealing film, in all Examples 1-4 and Comparative Examples 1-3, the polyester layer was 40 μm, the surface layer was 15 μm, and the intermediate layer was 5 μm.

[0151] [Manufacturing Conditions]

[0152] Extruder temperature: 230℃

[0153] Mold diameter: 250mmΦ

[0154] Inflation ratio: 2.0

[0155] Molding speed: 13m / min

[0156] In addition to the sealing film, a substrate film and a gas barrier film were laminated using a two-component curable polyester urethane adhesive via dry lamination. Furthermore, the sealing film prepared above was laminated onto the gas barrier film using a two-component curable polyester urethane adhesive via dry lamination, resulting in the laminated films of Examples 1-4 and Comparative Examples 1-3.

[0157] The substrate film is made of polyethylene terephthalate (PET) with a thickness of 12 μm. Additionally, the gas barrier film is made of aluminum foil with a thickness of 9 μm.

[0158] (Comparative Example 4)

[0159] Except for the fact that the sealing film was formed using the T-die method, a laminated film was produced in the same manner as in Example 3. It should be noted that the temperature of the extruder inside the T-die extrusion molding machine was 290°C.

[0160] (Comparative Examples 5-11)

[0161] As diols other than EG constituting the polyester layer, Comparative Examples 5 and 6 used butanediol in the proportions shown in Table 1, Comparative Example 7 used neopentyl glycol in the proportions shown in Table 1, Comparative Example 8 used hexanediol in the proportions shown in Table 1, and Comparative Examples 9 to 11 used cyclohexanediethanol in the proportions shown in Table 1. Except for this, the laminated films were prepared in the same manner as in Example 1.

[0162] <Evaluation>

[0163] (Evaluation Experiment 1)

[0164] As evaluation test 1, low-temperature sealing performance was evaluated. Specifically, the laminated films of the above-described embodiments and comparative examples were sealed with the sealing film as the inner side. The sealing conditions were: sealing pressure set to 0.1 MPa, sealing time set to 1.0 second, and the sealing temperature was varied. Based on JIS Z0238, the temperature at which the sealing strength was greater than 5 N / 15 mm width was determined as the sealing start temperature. The results are shown in the "Sealing Start Temperature (°C)" column of Table 1. Temperatures below 130°C were considered good.

[0165] (Evaluation Experiment 2)

[0166] As evaluation test 2, the sealing strength was evaluated. Specifically, each laminated film of the above-described examples and comparative examples was sealed with the sealing film as the inner side. The sealing conditions were: sealing temperature set at 160°C, sealing pressure set at 0.1 MPa, and sealing time set at 1.0 second. For laminated films cut into strips, the sealing strength (N / 15 mm) of the two laminated films was measured according to JIS X0238. The results are shown in the "Sealing Strength (N / 15 mm)" column of Table 1. A value of 30 N / 15 mm or higher was considered good.

[0167] (Evaluation Experiment 3)

[0168] As evaluation test 3, the absorbency was evaluated. Specifically, the laminated films of the above-described embodiments and comparative examples were cut into predetermined shapes (length: 120 mm, width: 120 mm). Two laminated films were placed on a bag-making machine with the sealing films in contact with each other, and a predetermined area (the periphery of the sealing film: the area 10 mm from the periphery) was sealed, thereby producing a three-sided bag-type packaging bag. It should be noted that at this time, the top end of the packaging bag (top seal) is not yet sealed for filling the contents. The sealing conditions were: sealing temperature set to 160°C, sealing pressure set to 0.1 MPa, and sealing time set to 1.0 second.

[0169] Next, under a nitrogen atmosphere, sake (manufactured by Hakutsuru Shuzo Co., Ltd., "Daiginjo") is filled into the top of the aforementioned packaging bag, and the top of the packaging bag (top seal) is sealed, thereby sealing the contents. It should be noted that the component of the sake used here, namely ethyl decanoate, is usually a component that is easily absorbed by the sealing film.

[0170] The packaging bags containing the contents, as described above, were stored in a constant temperature bath maintained at 40°C for 3 months. After storage, the headspace of the packaging bags was concentrated using solid-phase microextraction (SPME), and quantified by gas chromatography-mass spectrometry (GC-MS) based on the concentration of ethyl decanoate used as an internal standard. The ratio of the residual amount after storage to the initial amount was calculated as the ethyl decanoate residue percentage (%). The results are shown in the "Residue Percentage (%)" column of Table 1. A residue percentage of 70% or higher was considered good.

[0171] (Evaluation Experiment 4)

[0172] As evaluation test 4, the oligomer content was evaluated. Specifically, each polyester layer of the above examples and comparative examples was dissolved in hexafluoroisopropanol (HFIP), then precipitated with acetonitrile, and the supernatant was filtered to prepare a sample solution, which was then determined by reversed-phase HPLC (Agilent 1260 Infinity II LC system) under the following conditions.

[0173] [Measurement Conditions]

[0174] Detector: Ultraviolet Absorption Spectrophotometer

[0175] Measurement wavelength: 242nm

[0176] Column: Inverting column C18 ODS5μ (Length: 250mm, Inner Diameter: 4.6mm)

[0177] Column temperature: 25℃

[0178] Eluent: Acetonitrile / Water = 7 / 3

[0179] Flow rate: 1.5 ml / minute

[0180] Sample volume injected: 20 μl

[0181] In the HPLC-based molecular weight distribution obtained above, the peak areas of multiple peaks with dissolution times ranging from 5 to 20 minutes were vertically segmented at each dissolution time, and normalized using the weight of the polyester layer with the measured peak area components, thereby performing peak waveform processing. The measurements were repeated three times, and the average value of each peak area was used. The results are shown in the "Oligomer Content (wt%)" column of Table 1. Less than 2.0 wt% was considered good.

[0182] It should be noted that the glass transition temperature, crystallization temperature, and melting temperature of each polyester layer of the sealing film used in Examples 1-4 and Comparative Examples 1-11 are shown together in Table 1, measured using differential scanning calorimetry based on JIS K7121.

[0183] [Table 1]

[0184]

[0185] * The sealing layer is formed using the T-film method.

[0186] As shown in Table 1, the laminated films of Examples 1 to 4, which use a sealing film having a polyester layer containing a specific polyester as the main component, have low oligomer content (less than 2.0 wt%), excellent low adsorption of contents, and can suppress the deterioration of odor and flavor.

[0187] In contrast, Comparative Examples 1-3, which used polyester with an IPA content exceeding the specified amount, showed high adsorption of the contents due to oligomer content exceeding 2.0 wt%, failing to suppress odor and flavor degradation. Furthermore, Comparative Example 4, prepared with the same composition as Example 3 except for the T-molding method for sealing the film, also showed high adsorption of the contents due to oligomer content of 2.0 wt%, failing to suppress odor and flavor degradation. Additionally, Comparative Examples 5-11, which used diols other than EG, showed high adsorption of the contents.

[0188] It should be understood that the embodiments and examples disclosed herein are exemplary and not restrictive in all respects. The scope of this disclosure is defined by the claims rather than by the foregoing description and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0189] Explanation of symbols

[0190] 1. Sealing film; 11. Polyester layer; 12. Surface layer; 13. First intermediate layer; 14. Intercalation layer; 15. Second intermediate layer; 16. Back layer; 2-layer laminate; 31, 32, 33, 34, 35. Substrate film; 4. 41, 42. Gas barrier film; 51, 52, 53. Adhesive layer.

Claims

1. A sealing film comprising a polyester layer containing polyester as the main component, The polyester is composed of structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid. The ratio of the structural units derived from isophthalic acid to the ratio of the structural units derived from terephthalic acid to the structural units derived from isophthalic acid constituting the polyester is 3.0 mol% to 15 mol%. The oligomer content in the polyester layer is less than 2.0% by mass. The glass transition temperature of the polyester is above 60°C and below 80°C. The method for manufacturing the sealing film includes an extrusion step of extruding the resin constituting the polyester layer using a blow molding method. The temperature of the extrusion process is above 180°C and below 260°C.

2. The sealing membrane according to claim 1, It has a surface layer. The surface layer is selected from at least one of polyethylene, ethylene-acrylate copolymer and ethylene-methacrylate copolymer.

3. The sealing membrane according to claim 2, An intermediate layer is further provided between the polyester layer and the surface layer. The intermediate layer is selected from at least one of the groups consisting of anhydride-grafted polyethylene and ethylene-ester copolymers.

4. The sealing membrane according to claim 1, wherein, The thickness of the polyester layer is more than 20 μm and less than 50 μm.

5. A laminated film comprising: Substrate film, and The sealing film according to any one of claims 1 to 4.

6. The laminated film according to claim 5, An air barrier membrane is further included between the substrate film and the sealing film.

7. A packaging bag formed by sealing the laminated films of claim 5 by fusing the sealing films together.

8. A packaging container formed by sealing the laminated films of claim 5 by fusing the sealing films together.

9. A method for manufacturing a sealing film, comprising a polyester layer containing polyester as a main component. The method for manufacturing the sealing film includes an extrusion step of extruding the resin constituting the polyester layer using a blow molding method. The temperature of the extrusion process is above 180°C and below 260°C. The polyester is composed of structural units derived from ethylene glycol, structural units derived from terephthalic acid, and structural units derived from isophthalic acid. The ratio of the structural units derived from isophthalic acid to the ratio of the structural units derived from terephthalic acid to the structural units derived from isophthalic acid constituting the polyester is 3.0 mol% to 15 mol%. The oligomer content in the polyester layer is less than 2.0% by mass. The glass transition temperature of the polyester is above 60°C and below 80°C.

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