Sealant film, lid material, container and packaging bag

Abstract

To provide a sealant film which has easy peelability and can stably maintain peeling strength after heat sealing even when it is stored under a high-temperature environment, and a laminate, a lid material, a container, and a packaging bag which use the sealant film.SOLUTION: A sealant film has a seal layer composed of a mixture which contains at least component (A): a polyethylene terephthalate-based resin having a melting point of 190 to 270°C, component (B): a non-crystalline copolymerized polyester-based resin, and component (C): a polyolefin resin (C), and may contain component (D): a copolymerized polyester-based resin (D) having a melting point of 90 to 180°C, wherein with respect to the total mass of the component (A), the component (B), the component (C) and the component (D), a ratio of the component (A) is 25 to 65 mass%, a ratio of the component (B) is 4 to 40 mass%, a ratio of the component (C) is 28 to 38 mass%, and a ratio of the component (D) is 0 to 11 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealant film, a lid material, a container, and a packaging bag. [Background technology]

[0002] In the field of container packaging for food, medicine, etc., containers and packages equipped with easily peelable lids that facilitate opening of cup- or tray-shaped container bodies are widely used. In particular, for food and medicine containers, polyester-based resins, polycarbonate-based resins, etc. are used as materials for the container bodies and lids, and various easily peelable lids that can be easily peeled from the container bodies have been developed and commercialized.

[0003] For example, Patent Document 1 discloses a thermoplastic resin composition containing the following component (a) as a fusion component, the following component (b) as a peeling component, and the following component (c) as a moldability auxiliary component, and a lid material for an easily openable container having a sealing layer formed from the thermoplastic resin composition. Component (a): A polyester having a melting peak temperature of 110 to 150°C. (b) Component: Amine-modified styrene-based thermoplastic elastomer. (c) Component: amorphous polyester and / or polyolefin.

[0004] The film for the sealing layer used in the sealing layer described in Patent Document 1 is a single-layer film made of the thermoplastic composition and having a thickness of 2 to 100 μm, and the thickness of the film in the examples is 50 μm. However, since this film for the sealing layer contains a large amount of polyolefins (components (b) and (c)), it is not a single material made of polyester-based resin, and it is difficult to recycle.

[0005] Patent Document 2 discloses a polyester-based laminate film comprising a seal layer and a support layer. The seal layer contains 40 to 70 mass % of a polyethylene terephthalate resin having a melting point of 190 to 270°C and 5 to 30 mass % of a thermoplastic polymer polyester resin having a melting point of 90 to 180°C. The support layer contains 90 mass % or more of the polyethylene terephthalate resin. In this polyester-based laminate film, the thickness of the seal layer is, for example, 5 to 50% of the total thickness, and in the examples, the thickness ratio of the seal layer is 25%. The polyester laminate film and the lid material using the same described in Patent Document 2 are not made of a single material of polyester resin, but are formed from 90% by mass of polyester resin, and can be recycled. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-160398 [Patent Document 2] Japanese Patent Publication No. 2023-9803 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Documents 1 and 2 examine the ease of peeling after heat sealing of the film, but do not examine the change in peel strength over time. The polyester laminate film described in Patent Document 2 exhibits sufficient peelability immediately after film formation. However, the inventors of the present invention have found that, depending on the storage environment, a film stored for about a week may have a lower peel strength after heat sealing than a film immediately after film formation. In particular, when the film is stored at high temperatures, sufficient peel strength may not be ensured.

[0008] The main object of the present invention is to provide a sealant film that can be used as a packaging material primarily composed of a single material that is highly recyclable, that has easy peelability, and that can maintain a stable peel strength after heat sealing even when stored in a high-temperature environment, as well as a lid material, container, and packaging bag that use the sealant film. [Means for solving the problem]

[0009] The present invention includes the following aspects. [1] A sealant film having a sealing layer made of a mixture containing at least a polyethylene terephthalate resin (A) (hereinafter referred to as "component (A)") having a melting point of 190 to 270°C, a non-crystalline copolymer polyester resin (B) (hereinafter referred to as "component (B)"), and a polyolefin resin (C) (hereinafter referred to as "component (C)"), and which may also contain a copolymer polyester resin (D) (hereinafter referred to as "component (D)") having a melting point of 90 to 180°C, wherein the proportion of component (A) is 25 to 65% by mass, the proportion of component (B) is 4 to 40% by mass, the proportion of component (C) is 28 to 38% by mass, and the proportion of component (D) is 0 to 11% by mass, relative to the total mass of component (A), component (B), component (C), and component (D). [2] The sealant film according to [1], wherein the proportion of the component (D) relative to the total mass of the components (A), (B), (C), and (D) is 1 to 11 mass%. [3] The sealant film according to [1] or [2], wherein the component (C) is a linear low-density polyethylene resin. [4] The sealant film according to any one of [1] to [3], wherein the component (C) has a melt mass-flow rate at 190°C of 2.0 g / 10 min or less. [5] A sealant film according to any one of [1] to [4], which has, in addition to the sealing layer, a support layer whose main component is a polyethylene terephthalate resin. [6] A lid material using the sealant film according to any one of [1] to [5]. [7] A container having a lid material according to [6]. [8] A packaging bag using the sealant film described in any one of [1] to [5]. [Effects of the Invention]

[0010] According to the present invention, a sealant film is provided which can be used as a packaging material primarily composed of a single material that is highly recyclable, has easy peelability, and can maintain a stable peel strength after heat sealing even when stored in a high-temperature environment, as well as a lid material, container, and packaging bag using the sealant film. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Sealant film] The sealant film of the present invention has a sealing layer made of a mixture containing at least the following components (A) to (C) and may also contain component (D). Component (A): Polyethylene terephthalate resin (A) with a melting point of 190 to 270°C. Component (B): Amorphous copolymer polyester resin (B). Component (C): Polyolefin resin (C). Component (D): Copolymer polyester resin (D) with a melting point of 90 to 180°C.

[0012] The sealant film of the present invention may be a film consisting of a sealing layer alone, or may be a film having a support layer containing a polyethylene terephthalate resin as a main component in addition to the sealing layer. The sealant film of the present invention may be a film having another layer in addition to the sealing layer and the support layer, as long as the sealing layer is disposed as the outermost layer. The sealant film of the present invention can obtain a peel strength sufficient for easy peeling. The peel strength sufficient for easy peeling can be in the range of, for example, 7 to 18 N / 15 mm.

[0013] (Sealing layer) The sealing layer of the sealant film of the present invention is a layer that comes into direct contact with a container when the sealant film is used as a lid for the container. The mixture forming the sealing layer may contain components (A) to (C) and may not contain component (D), or may contain all of components (A) to (D). The mixture forming the sealing layer may further contain components other than components (A) to (D) within the range that does not impair the effects of the present invention. The "peel strength" used in the following description refers to the strength required to peel two sealant films of the present invention that have been heat-sealed together with their sealing layers facing each other. The peel strength when the sealant film of the present invention or a laminate using the sealant film of the present invention is heat-sealed to a container body made of a polyester resin and then peeled off is thought to have a similar tendency to that when sealant films are heat-sealed together.

[0014] <Component (A)> Component (A) is a crystalline polyethylene terephthalate resin having a melting point of 190 to 270°C. Component (A) is preferably a polyethylene terephthalate resin having a melting point of 190 to 270°C, which is a resin obtained by polycondensation of a polycarboxylic acid component and a polyol component, in which 90 mol % or more, preferably 95 mol % or more of the polycarboxylic acid component is a terephthalic acid component, and 90 mol % or more, preferably 95 mol % or more of the polyol component is ethylene glycol. The component (A) may be used alone or in combination of two or more.

[0015] The polycarboxylic acid component may be a derivative such as a free acid, a halide, an alkyl ester in which the alkyl group has 1 to 4 carbon atoms, an alkali metal salt, or an anhydride.

[0016] Examples of polycarboxylic acid components other than terephthalic acid components include aromatic dicarboxylic acids or derivatives thereof, such as phthalic acid, isophthalic acid, dibromoisophthalic acid, hydroxyisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids or derivatives thereof, such as hexahydroterephthalic acid and hexahydroisophthalic acid; aliphatic carboxylic acids or derivatives thereof, such as maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, and dodecadicarboxylic acid; and tri- or higher functional carboxylic acids, such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, and naphthalenetetracarboxylic acid.

[0017] Examples of polyol components other than the ethylene glycol component include aliphatic diols such as diethylene glycol, trimethylene glycol, tetramethylene glycol, 1,3-butanediol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, polyethylene glycol, and polytetramethylene ether glycol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, and 2,5-norbornanedimethylol; xylitol; aromatic diols such as ethylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid; alkylene oxide adducts of aromatic diol components such as an ethylene oxide adduct of 2,2-bis(4'-hydroxyphenyl)propane and a propylene oxide adduct of 2,2-bis(4'-hydroxyphenyl)propane; and tri- or higher functional polyols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, and sugar esters.

[0018] The polymerization components used in the polycondensation of component (A) may contain copolymerization components other than the polycarboxylic acid component and the polyol component. Examples of other copolymerization components include hydroxycarboxylic acids or alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, p-β-hydroxyethoxybenzoic acid, and gallic acid; monoalcohols such as stearyl alcohol, heneicosanol, octacosanol, and benzyl alcohol; and monocarboxylic acids such as stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid. These other copolymerization components may be used alone or in combination of two or more.

[0019] The melting point of component (A) is 190 to 270°C, preferably 200°C or higher, more preferably 240°C or higher, and preferably 265°C or lower. The melting point is the temperature of the endothermic peak with the greatest intensity detected during the second heating step, which is performed at a heating rate of 10°C / min, when a differential scanning calorimeter (DSC) measurement is performed in accordance with JIS K 7121. For commercially available products, the melting point listed in the catalog may be used.

[0020] The intrinsic viscosity of component (A) is not particularly limited. For example, it is 0.50 dL / g or more, preferably 0.60 dL / g or more, more preferably 0.70 dL / g or more, and for example, 0.95 dL / g or less, preferably 0.92 dL / g or less, more preferably 0.90 dL / g or less. If the intrinsic viscosity is equal to or greater than the lower limit, it is easy to suppress a decrease in melt viscosity during the film formation process, and it is easy to form tubular bubbles with a stable diameter, for example, during inflation film formation. If the intrinsic viscosity is equal to or less than the upper limit, it is possible to prevent the melt viscosity of the mixture from becoming too high. Therefore, for example, when film formation is performed using a multilayer cast film forming machine equipped with a feed block, the mixture is likely to spread to the ends of the die width direction. The intrinsic viscosity was measured by dissolving component (A) at an arbitrary concentration in a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and measuring the viscosity at 25°C using an Ubbelohde viscometer.

[0021] Commercially available products of component (A) include, for example, the "NEH series" manufactured by Unitika and the "S103" manufactured by Rikko.

[0022] The proportion of component (A) in the mixture that forms the seal layer is 25 to 65 mass % based on the total mass of components (A) to (D). When the proportion of component (A) is within this range, a sealant film that has peel strength suitable for easy peeling, a good appearance on the peeled surface, and excellent recyclability can be obtained at low cost.

[0023] <Ingredient (B)> Component (B) is a non-crystalline copolymer polyester resin. Component (B) imparts sealing properties to the sealing layer and also functions as a compatibilizer between components (A) and (C). Component (B) also has the function of suppressing a decrease in peel strength when heat-sealing is performed after a certain period of time has elapsed after the film is formed.

[0024] Component (B) can be obtained by polycondensation of a polycarboxylic acid component and a polyol component selected so as not to have a melting point. Commercially available copolymer polyester resins that are classified as "amorphous" by resin manufacturers can be used. The component (B) may be used alone or in combination of two or more.

[0025] The polycarboxylic acid component used in the polycondensation of component (B) is selected, for example, from the polycarboxylic acid components exemplified for component (A) so as to give a polyester resin having no melting point. The polyol component used in the polycondensation of component (B) is selected, for example, from the polyol components exemplified for component (A) so as to give a polyester resin having no melting point.

[0026] Commercially available products of component (B) include, for example, the "Vylon (registered trademark) series" manufactured by Toyobo.

[0027] The proportion of component (B) in the mixture forming the seal layer is 4% by mass or more, preferably 10% by mass or more, based on the total mass of components (A) to (D). When the content of component (B) is equal to or greater than the lower limit, even when the sealant film is heat-sealed some time after film formation, a decrease in peel strength is suppressed, deterioration of the easy peel function is suppressed, and the easy peel function can be stably maintained. This is thought to be because component (B) can suppress the crystallization of component (A) together with component (D) over time. Furthermore, the proportion of component (B) is 40% by mass or less, preferably 25% by mass or less. When the proportion of component (B) is equal to or less than the upper limit, the yield of components derived from terephthalic acid and ethylene glycol is increased when the sealant film is chemically recycled, resulting in excellent recyclability.

[0028] <Component (C)> Component (C) is a polyolefin resin. Component (C) is incompatible with component (A) and has the function of inhibiting heat sealing properties, thereby imparting easy peelability to the seal layer.

[0029] As component (C), a resin obtained by polymerizing one or more α-olefins having 2 to 20 carbon atoms is preferred. Examples of component (C) include low-density polyethylene resins, linear low-density polyethylene resins, medium-density polyethylene resins, high-density polyethylene resins, polypropylene resins, and copolymers of ethylene and an α-olefin having 3 to 20 carbon atoms. Component (C) is more preferably a polyethylene resin, and from the viewpoint of low-temperature sealing properties, an ethylene-α-olefin copolymer, which is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms and is also called a linear low-density polyethylene resin, is even more preferred. The component (C) may be used alone or in combination of two or more.

[0030] Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, and 1-dodecene. Of these, the α-olefin having 3 to 20 carbon atoms is preferably at least one selected from the group consisting of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene.

[0031] The catalyst used in producing a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms is not particularly limited, and examples thereof include Ziegler-Natta catalysts and metallocene catalysts. Metallocene catalysts are preferred as they can easily produce linear low-density polyethylene with a narrow molecular weight distribution and have excellent impact resistance.

[0032] The density of component (C) is not particularly limited, and may be, for example, 0.900 g / cm 3or more, preferably 0.913 g / cm 3 or more, and for example, 0.968 g / cm 3 or less, preferably 0.920 g / cm 3 or less, more preferably 0.917 g / cm 3 When the density of component (C) is equal to or greater than the lower limit, blocking of the sealant film or a laminate using the same is easily suppressed. When the density of component (C) is equal to or less than the upper limit, the transparency of the seal layer is good, making it easy to visually recognize the contents of the package, and the flexibility of the sealant film is improved, making it less likely to feel heavy when peeled off.

[0033] The density of low-density polyethylene resin is 0.900 g / cm 3 More than 0.930g / cm 3 The density of medium density polyethylene resin is preferably less than 0.930 g / cm 3 More than 0.942g / cm 3 The density of high density polyethylene resin is preferably less than 0.942 g / cm 3 More than 0.968g / cm 3 The following is preferred: The density of polypropylene resin is 0.90 g / cm 3 More than 0.91g / cm 3 Less than is preferred. The density is a value measured in accordance with the density gradient tube method in JIS K 7112. In the case of commercially available products, the density value listed in the catalog may be used.

[0034] The melt mass flow rate (MFR) of component (C) at 190°C is preferably 2.0 g / 10 min or less. If the MFR of component (C) is 2.0 g / 10 min or less, peel strength that allows easy peeling is easily obtained, and further, a good peel surface appearance in which the peel interface appears white without the occurrence of stringiness or the like is easily obtained. Furthermore, even when component (C) is a linear low-density polyethylene-based resin, if the MFR is higher than 2.0 g / 10 min, low-temperature sealability tends to be poor. Therefore, when low-temperature sealability is required, it is preferable to use a linear low-density polyethylene-based resin with an MFR of 2.0 g / 10 min or less as component (C). The MFR is a value measured in accordance with JIS K 7210-1 "Method for determining melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics." The MFR of the polyolefin resin in the present invention is a value measured at a cylinder temperature of 190°C and a weight of 2.16 kg, regardless of the type of polyolefin resin.

[0035] Commercially available polyethylene resins of component (C) include, for example, "Novatec" manufactured by Nippon Polyethylene and "Evolue (registered trademark)" manufactured by Prime Polymer. Commercially available polypropylene resins include, for example, "Prime Polypro (registered trademark)" manufactured by Prime Polymer.

[0036] The proportion of component (C) in the mixture forming the seal layer is 28% by mass or more, preferably 30% by mass or more, based on the total mass of components (A) to (D). When the proportion of component (C) is equal to or greater than the lower limit, excellent peel strength can be obtained. When the proportion of component (C) is less than the lower limit, the incompatibility with component (A) is insufficient, and the peel strength tends to be too high, resulting in insufficient peelability. Furthermore, the proportion of component (C) is 38% by mass or less, preferably 35% by mass or less. When the proportion of component (C) is equal to or less than the upper limit, the loss of heat sealability due to an excess of component (C) can be prevented, resulting in excellent peel strength. Furthermore, when a support layer is provided, excellent interlayer strength between the seal layer and the support layer is also achieved when the proportion of component (C) is equal to or less than the upper limit. When the proportion of component (C) exceeds the upper limit, heat sealability is impaired, making heat sealing impossible. Even if heat sealing is possible, the peel strength is extremely low and further, stringiness and other poor peel surface appearance tend to occur.

[0037] <Ingredient (D)> Component (D) is a crystalline copolymer polyester resin having a melting point of 90 to 180° C. Component (D) functions as a compatibilizer for components (A) and (C) to obtain film formability, good film appearance, and peel strength that indicates good peelability. Component (D) is obtained by polycondensing a polycarboxylic acid component and a polyol component selected so as to have a melting point of 90 to 180°C. The component (D) may be used alone or in combination of two or more.

[0038] The polycarboxylic acid component used in the polycondensation of component (D) is selected, for example, from the polycarboxylic acid components exemplified for component (A) so as to have a melting point of 90 to 180° C. Terephthalic acid is preferred as the polycarboxylic acid component used in the polycondensation of component (D). The polyol component used in the polycondensation of component (D) is selected from the polyol components exemplified for component (A) so as to have a melting point of 90 to 180° C. It is preferred that part of the ethylene glycol in the polyol component used in the polycondensation of component (D) is cyclohexanedimethanol.

[0039] The melting point of component (D) is 90 to 180°C, preferably 95°C or higher, more preferably 100°C or higher, and preferably 150°C or lower, more preferably 135°C or lower. The melting point of component (D) is a value measured by the method described for component (A).

[0040] Commercially available products of component (D) include, for example, the Vylon (registered trademark) series manufactured by Toyobo Co., Ltd. and the PETG (registered trademark) series manufactured by Eastman Chemical Company.

[0041] The proportion of component (D) in the mixture forming the seal layer, relative to the total mass of components (A) to (D), can impart easy peelability and a good peel surface appearance to the seal layer even at 0% by mass, but is preferably 1% by mass or more, more preferably 5% by mass or more, because it is easier to obtain better peel strength. Furthermore, if the proportion of component (D) is 1% by mass or more, the sealant film has excellent film formability and a better appearance. The proportion of component (D) is 11% by mass or less, preferably 8% by mass or less. Even if the proportion of component (D) exceeds the upper limit, good easy peelability can be obtained, but when heat-sealing is performed using a sealant film after a certain period of time has elapsed, the peel strength tends to decrease compared to a film immediately after film formation, and the easy peel function tends to be lost. If the proportion of component (D) is equal to or less than the upper limit, there is little change in peel strength even when heat-sealing is performed using a sealant film after a certain period of time has elapsed, and easy peelability can be stably maintained. When the proportion of the component (D) is 8% by mass or less, it is easy to suppress a decrease in peel strength even after the sealant film has been left at high temperatures for a certain period of time, and it is possible to maintain a stable peel strength that allows easy peeling.

[0042] The ratio of the total mass of components (B) and (D) to the total mass of components (A) to (D) in the mixture is preferably 50% by mass or less, more preferably 40% by mass or less. When the ratio of the total mass of components (B) and (D) is the upper limit value or more, the sealant film has excellent recyclability.

[0043] <Other ingredients> Examples of other components include various additives such as antistatic agents, antioxidants, lubricants, antiblocking agents, antifogging agents, colorants, ultraviolet absorbers, dispersants, and fillers. Examples of the anti-blocking agent include inorganic particles such as silica, zeolite, and talc, and organic resin particles such as silicone resin and (meth)acrylic resin. Examples of colorants include organic pigments and inorganic pigments. Examples of fillers include talc and calcium carbonate.

[0044] The sealing layer may contain other resins in addition to the components (A) to (D) as other components. The content of the other resins is preferably 3 parts by mass or less per 100 parts by mass of the total mass of the components (A) to (D) in the mixture of the sealing layer. Examples of other resins include polybutylene terephthalate resins. The other components may be used alone or in combination of two or more.

[0045] (support layer) The support layer is a layer having a surface to be bonded to another film, etc., when the sealant film is used to form a laminate. When the sealant film is produced by a co-extrusion method, the provision of the support layer allows the sealant film to be produced more stably.

[0046] The support layer is a layer containing a polyethylene terephthalate resin as a main component. Examples of the polyethylene terephthalate resin used in the support layer include the same polyethylene terephthalate resin as component (A). The polyethylene terephthalate resin contained in the support layer and the polyethylene terephthalate resin contained in the seal layer may be the same or different, but from the viewpoints of reducing production costs and recycling, it is preferable that the polyethylene terephthalate resins contained in the support layer and the seal layer are the same.

[0047] The support layer may contain components other than the polyethylene terephthalate-based resin. Examples of other components that can be contained in the support layer include resins other than the polyethylene terephthalate-based resin and additives.

[0048] Examples of resins other than polyethylene terephthalate resins include polyolefin resins, copolymer polyester resins, and polybutylene terephthalate resins. Examples of the additives include the same additives as those exemplified for the sealing layer. The other components contained in the support layer may be used alone or in combination of two or more.

[0049] The content of other components in the support layer is preferably less than 15 parts by mass relative to 100 parts by mass of the polyethylene terephthalate resin.

[0050] (Sealant film thickness) The thickness of the sealant film of the present invention is not particularly limited, and is, for example, 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, and is, for example, 200 μm or less, preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less. When the thickness of the sealant film is within the above range, it is easy to obtain a film that has a good balance between flexibility and rigidity. Furthermore, when the thickness of the sealant film is within the above range, it is easy to obtain peel strength that provides practical easy peelability, and it is easy to peel a lid material using the sealant film of the present invention from a package, and it is easy to ensure excellent easy peelability that allows a packaging bag using the sealant film of the present invention to be easily opened.

[0051] The ratio of the thickness of the seal layer to the total thickness of the sealant film of the present invention is not particularly limited, and is, for example, 5% or more, preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, and is, for example, 40% or less, preferably 30% or less. When the thickness ratio of the seal layer is equal to or greater than the above-mentioned lower limit, for example, the sealant film is easily extruded uniformly during film formation. As a result, when the sealant film is heat-sealed to a container body or the like, there are less areas where the support layer is directly welded to the container body or the like. Furthermore, when sealant films are heat-sealed to each other, there are less areas where the support layers are directly welded to each other. This makes it possible to prevent the weld strength from becoming too strong, resulting in a decrease in easy peelability.

[0052] The ratio of the thickness of the support layer to the total thickness of the sealant film of the present invention is not particularly limited and is, for example, 60% or more, preferably 70% or more, and for example, 95% or less, preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. If the thickness ratio of the support layer is equal to or greater than the lower limit, the sealant film can be easily formed stably, and subsequent handling such as winding will also be improved.

[0053] (Ratio of polyester resin in sealant film) In the seal layer of the sealant film of the present invention, components (A), (B), and (D) are polyester-based resins. That is, of the components (A) to (D) constituting the seal layer, 62 to 72 mass% is polyester-based resin, excluding 28 to 38 mass% of component (C). Furthermore, when the sealant film of the present invention has a support layer, the support layer is mainly composed of a polyethylene terephthalate-based resin. By adjusting the proportion of polyethylene terephthalate resin in the support layer and the thickness ratio of the support layer in the sealant film, the sealant film of the present invention can be made into a film in which 90% by mass or more of polyester resin is used, which allows it to be a packaging material whose main component is a single material with high recyclability, known as a "monomaterial," in accordance with the United Nations' Sustainable Development Goals (SDGs).

[0054] (Method of manufacturing sealant film) The method for producing the sealant film of the present invention is not particularly limited. For example, in the case of a sealant film having a seal layer and a support layer, a coextrusion method can be used in which the resin components constituting the seal layer and the support layer are fed into a multilayer T-die molding machine or a multilayer inflation molding machine and coextruded. The coextrusion method using a multilayer T-die molding machine or a multilayer inflation molding machine is preferred because it requires fewer steps, is simple, and can achieve sufficiently high adhesive strength between layers. Other methods that may be used include melt extrusion lamination, in which the resin components constituting the sealing layer are melt extrusion laminated onto at least one surface of the support layer, and dry lamination, in which the sealing layer and the support layer are formed separately and then dry laminated.

[0055] [Laminate] The sealant film of the present invention can be, for example, a laminate in which the sealant film serves as a sealant film layer and a substrate layer is provided on the surface of the support layer of the sealant film opposite to the sealing layer.

[0056] (base material layer) The base layer is a layer with high strength and does not deform even at a temperature at which the sealant film partially melts when the laminate is heat-sealed. Examples of the substrate layer include unstretched films, uniaxially stretched films, or biaxially stretched films of polyester resins, polyamide resins, polyolefin resins, etc.; gas barrier films obtained by depositing aluminum, silica, alumina, etc. on these films; paper; and metals such as aluminum foil. From the viewpoint of mono-materialization, a polyester resin film is preferred as the substrate layer. The laminate may have only one base layer, or may have two or more base layers that are the same as or different from each other. The base layer may be subjected to processing such as coloring and printing. By using these substrate layers, it is possible to obtain a laminate that is excellent in design, gas barrier properties, light blocking properties, pinhole resistance, curl resistance, and the like.

[0057] In the laminate, an intermediate layer may be provided between the sealant film layer made of a sealant film and the substrate layer, or between a plurality of substrate layers. Examples of intermediate layers include a printing layer, an adhesive layer, a primer layer, and a vapor-deposited layer. When the laminate of the present invention has an intermediate layer, the intermediate layer may be of only one type or of two or more types.

[0058] (Method of manufacturing laminate) Examples of methods for producing a laminate include a method of laminating a substrate layer onto a sealant film by dry lamination, a method of laminating a substrate layer onto a sealant film by sandwich lamination using molten polyethylene or the like, a method of laminating a sealant film onto a substrate layer by multilayer extrusion lamination, and a method of co-extruding all layers constituting the laminate. Dry lamination is preferred because it allows the substrate layer, etc. to be laminated via a thin adhesive and can increase the mono-material ratio.

[0059] [Lid materials, containers, packaging bags] The lid material of the present invention is a lid material using the sealant film of the present invention, and is constituted by the sealant film of the present invention or a laminate containing the sealant film of the present invention. The container of the present invention includes the lid of the present invention. Examples of the container of the present invention include a container that includes the lid of the present invention and a container body, the container body having a welding part such as a flange that can be tightly attached to the lid, and a storage part that stores contents such as food.

[0060] The shape of the container body is not particularly limited, and any shape such as a cup shape or a tray shape can be adopted. The position of the welded portion provided on the container is not particularly limited, and it can be provided, for example, on the top surface of the container body.

[0061] After the contents are placed in the storage section, the lid material and the container body can be welded together by heat-sealing the sealing layer of the lid material and the welded part of the container body while they are in contact. It is preferable to provide a gripping part called a "tab" that is not heat-sealed by making a part of the lid material protrude from the welded part of the container body or by providing an unsealed part as a peel-start part when opening.

[0062] The packaging bag of the present invention is a packaging bag using the sealant film of the present invention, and is constituted by the sealant film of the present invention or a laminate including the sealant film of the present invention. The shape of the packaging bag is not particularly limited, and examples thereof include palm-shaped bags, flat bags, side gusset bags, bottom gusset bags, and square-bottom packaging bags. The packaging bag may be provided with a mouth such as a spout or a zipper.

[0063] The sealant film of the present invention, and the laminate, lid, container, and packaging bag using the same described above, can maintain excellent peelability and have a good appearance on the peeled surface even when a sealant film that has been in use for a long time since film formation is used. Furthermore, the sealant film of the present invention, and the laminate, lid, container, and packaging bag using the same have a high proportion of polyester-based resin and are therefore highly recyclable. [Example]

[0064] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0065] [Sealing layer raw materials] Ingredient (A) A-1: Polyethylene terephthalate resin, Li-Peng "S103", intrinsic viscosity: 0.810 dl / g, melting point: 246°C. ·Component (B) B-1: Amorphous copolymer polyester resin, "Vylon (registered trademark) SI173" manufactured by Toyobo Co., Ltd., catalog softening point: 185°C. ·Component (C) C-1: Linear low-density polyethylene resin, "Novatec LL (registered trademark) UF420" manufactured by Japan Polyethylene Corporation, density: 0.924 g / cm 3 , MFR at 190°C: 0.9g / 10min. C-2: Block polypropylene resin, Prime Polypro (registered trademark) F703 manufactured by Prime Polymer Co., Ltd., density: 0.9 g / cm 3 , MFR at 190°C = 1.3 g / 10 min. C-3: Linear low-density polyethylene resin, "Evolue® SP1540" manufactured by Prime Polymer Co., Ltd., density: 0.913 g / cm 3 , MFR at 190°C: 3.8g / 10min. ·Component (D) D-1: Copolymer polyester resin, "Vylon (registered trademark) GM913" (manufactured by Toyobo Co., Ltd., catalog melting point: 126°C).

[0066] [Support layer materials] ·Component (E) E-1: Polyethylene terephthalate resin, "S103" (manufactured by Li-Peng, intrinsic viscosity: 0.810 dl / g, melting point: 246°C).

[0067] [glue] F-1: Urethane adhesive, "RU-40" manufactured by Rock Paint. [Film for base layer] H-1: Biaxially oriented polyethylene terephthalate film, "E5102" manufactured by Toyobo Co., Ltd., thickness 12 μm.

[0068] [Examples 1 to 12 and Comparative Examples 1 to 6] The components for forming the seal layer and the components for forming the support layer were prepared by mixing the components in a Henschel mixer according to the composition shown in Table 1. These components for forming the seal layer and the components for forming the support layer were placed in the hopper of a two-layer T-die molding machine and formed into a film at a die temperature of 285°C, yielding a two-layer sealant film having a seal layer and a support layer with the thicknesses shown in Table 1.

[0069] After corona treatment was performed on the surface of the support layer of the sealant film, adhesive F-1 was applied to the surface at an average solid content of 3.3 g / m 2 By the dry lamination method used in the above, film H-1 was laminated as a substrate layer on the support layer side of the sealant film, and aging was carried out at 40° C. for 3 days to obtain a laminate.

[0070] [Table 1]

[0071] <Evaluation of peel strength> [Peel strength (1)] The laminate obtained in each example was heat-sealed at 120°C over a 20 mm width at the overlapping seal layer, and both ends of the heat-sealed portion were cut off to obtain a 15 mm wide test piece for measuring peel strength. This test piece was left standing for 24 hours at 23°C and 50% relative humidity. Then, in accordance with JIS Z 0238, a T-peel test was performed at a peel rate of 300 mm / min using a tensile tester, and the peel strength per 15 mm width was measured. The measured peel strength was evaluated according to the following criteria. (Evaluation criteria) 1: Not heat sealable. 2: Heat sealable, but peel strength is less than 7N / 15mm. 3: Heat sealable, peel strength is 7 to 18 N / 15 mm, and easy peelability is good. 4: Heat sealable, but peel strength exceeds 18N / 15mm, making it difficult to peel. 5: Heat sealable but not peelable, breaks at seal edge.

[0072] [Peel strength (2)] The laminate obtained in each example was heat-sealed at 160°C over a 20 mm width at the overlapping seal layer, and both ends of the heat-sealed portion were cut off to obtain a 15 mm wide test piece for measuring peel strength. This test piece was left standing for 24 hours at 23°C and 50% relative humidity. Then, in accordance with JIS Z 0238, a T-peel test was performed at a peel rate of 300 mm / min using a tensile tester, and the peel strength per 15 mm width was measured. The measured peel strength was evaluated using the same criteria as for peel strength (1).

[0073] [Peel strength (3)] The laminate obtained in each example was aged in an oven at 40°C for 30 days, and then the peel strength per 15 mm width was measured in the same manner as in Peel Strength (2). The measured peel strength was evaluated according to the same criteria as in Peel Strength (1).

[0074] [Peel strength 4] The laminate obtained in each example was aged in an oven at 50°C for 30 days, and then the peel strength per 15 mm width was measured in the same manner as in Peel Strength (2). The measured peel strength was evaluated according to the same criteria as in Peel Strength (1).

[0075] <Recyclability evaluation> The recyclability of the sealant film of each example was evaluated according to the following criteria. (Evaluation criteria) A: The total weight of components (B) and (D) is 40% or less of the total weight of components (A) to (D). B: The ratio of the total mass of components (B) and (D) to the total mass of components (A) to (D) is more than 40% and 50% or less. C: The total mass of components (B) and (D) is greater than 50% of the total mass of components (A) to (D).

[0076] <Appearance of peeled surface> The peeled surface of the test piece for measuring peel strength after measuring peel strength (1) was visually observed and evaluated according to the following criteria. (Evaluation criteria) A: The peeled surface is uniformly whitened, and there is no stringiness or residual film. B: The peeled surface is uniformly whitened, but some stringiness occurs. C: Sealing is not possible, so the peeled surface cannot be observed. D: Peeling is not possible, so the peeled surface cannot be observed.

[0077] The evaluation results of Examples 1 to 12 and Comparative Examples 1 to 6 are shown in Table 2.

[0078] [Table 2]

[0079] As shown in Table 2, the laminates of Examples 1 to 11, in which the sealing layer contained components (A) to (D) in the ratios specified by the present invention, exhibited peel strength sufficient for easy peeling when heat-sealed at 160°C, and were able to maintain such peel strength even after 30 days of storage at 40°C. Furthermore, the laminate of Example 12, in which the sealing layer contained components (A) to (C) in the ratios specified by the present invention but did not contain component (D), exhibited peel strength sufficient for easy peeling when heat-sealed at 160°C, and was able to maintain such peel strength even after 30 days of storage at 40°C. A comparison of Example 1 with Examples 2 to 5, which contain the same types and proportions of component (C) and component (D), reveals that increasing the proportion of component (B) is highly effective in suppressing the decrease in peel strength after heat sealing, even when stored at 50°C for one month, and that a peel strength sufficient for easy peeling can be maintained. A comparison of Example 3 and Example 9, which have similar types and proportions of component (A) and component (C), shows that a lower proportion of component (D) is more effective in suppressing a decrease in peel strength after heat sealing, even after 30 days of storage at 50°C, and is able to maintain easy peelability. A comparison of Examples 4, 10, and 11, which differ only in the type of component (C), reveals that by using a linear low-density polyethylene resin with an MFR of 2.0 g / 10 min or less at 190°C, sufficient peel strength is easily obtained even with heat sealing at 120°C, and the low-temperature heat sealability is excellent, and it is easy to achieve both maintaining peel strength that allows easy peeling and a good peel surface appearance. Furthermore, although not shown in Table 2, the laminates of Examples 1 to 11 containing component (D) had excellent film formability and good film appearance compared to the laminate of Example 12 not containing component (D).

[0080] On the other hand, the laminate of Comparative Example 1, in which the sealing layer contained only the component (A) and did not contain the components (B) to (D), was strongly heat-sealed and did not exhibit easy peelability. In the laminate of Comparative Example 2, in which the sealing layer did not contain component (B), a peel strength was obtained that allowed easy peeling when heat-sealed at both 120°C and 160°C. However, after 30 days of storage at both 40°C and 50°C, the peel strength after heat-sealing decreased and the heat-sealability was lost. The laminate of Comparative Example 3, in which the proportion of component (B) contained in the sealing layer exceeds 40% by mass, can suppress the decrease in peel strength after heat sealing even after one month of storage at 40°C and 50°C, but has poor recyclability. The laminate of Comparative Example 4, in which the proportion of component (C) contained in the sealing layer was less than 28% by mass, exhibited high peel strength when heat-sealed at both 120°C and 160°C, and did not exhibit easy peelability. The laminate of Comparative Example 5, in which the proportion of component (C) contained in the seal layer exceeded 38% by mass, was unable to be heat-sealed. The laminate of Comparative Example 6, in which the proportion of component (D) contained in the sealing layer exceeded 11% by mass, was heat-sealable immediately after film formation, but was unable to be heat-sealed after 30 days of storage at either 40°C or 50°C.

Claims

1. a sealing layer made of a mixture containing at least a polyethylene terephthalate resin (A) (hereinafter referred to as "component (A)") having a melting point of 190 to 270°C, a non-crystalline copolymer polyester resin (B) (hereinafter referred to as "component (B)"), and a polyolefin resin (C) (hereinafter referred to as "component (C)"), and optionally containing a copolymer polyester resin (D) (hereinafter referred to as "component (D)") having a melting point of 90 to 180°C; A sealant film, wherein, relative to the total mass of the components (A), (B), (C), and (D), a proportion of the component (A) is 25 to 65 mass%, a proportion of the component (B) is 4 to 40 mass%, a proportion of the component (C) is 28 to 38 mass%, and a proportion of the component (D) is 0 to 11 mass%.

2. The sealant film according to claim 1, wherein the proportion of the component (D) relative to the total mass of the components (A), (B), (C), and (D) is 1 to 11 mass%.

3. The sealant film according to claim 1 , wherein the component (C) is a linear low-density polyethylene resin.

4. 2. The sealant film according to claim 1, wherein the component (C) has a melt mass-flow rate at 190°C of 2.0 g / 10 min or less.

5. The sealant film according to claim 1 , further comprising a support layer containing a polyethylene terephthalate resin as a main component in addition to the sealing layer.

6. A lid material using the sealant film according to any one of claims 1 to 5.

7. A container comprising the lid material according to claim 6.

8. A packaging bag using the sealant film according to any one of claims 1 to 5.

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