Film for heat sealing and packaging material

Abstract

To provide a heat-sealing film that has excellent recyclability and can reduce an environmental burden, and that can provide a strong heat-sealing strength in a short crimping time and has heat resistance to withstand retort processing at a high temperature, and to provide a packaging material.SOLUTION: There is provided heat-sealing films 10 and 10', in which thermoplastic polyester resin layers 12 and 12' including a thermoplastic polyester resin containing poly-oxyalkylene glycol as a diol component are provided on one side or both sides of base material layers 11 and 11', and the thermoplastic polyester resin is a material in which after the material is melted and then quenched to -50°C at a speed of 200°C / min, a glass transition temperature (Tg) observed when the temperature is raised at 10°C / min is 50°C or less, a melting point (Tm) is 150°C or higher, and a heat of fusion ΔH exceeds 0 J / g and is 20 J / g or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat-sealing film for a packaging bag formed in a bag shape or a lid material used by being melt-bonded to a container body, and a packaging material.

Background Art

[0002] Conventionally, as a packaging material for foods, pharmaceuticals, etc., a laminated film (heat-sealing film) in which a heat-sealing layer is provided on a film base material has been used. And these packaging materials are melt-bonded (heat-sealed) by crimping and heating the heat-sealing layers to form a bag shape or a container shape with an opening left, and after putting the contents through the opening, the heat-sealing layers of the opening are further crimped and heated to melt and bond the heat-sealing layers, thereby sealing the contents.

[0003] As this film base material, a polyester-based film is widely used from the viewpoints of strength, heat resistance, gas barrier property, etc. On the other hand, as the heat-sealing layer, a layer made of a polyolefin-based resin such as polyethylene or polypropylene, or a copolymer resin such as ionomer or EMMA is used. It is known that these resins can achieve high adhesion strength by heat-sealing.

[0004] On the other hand, in recent years, environmental pollution by plastic waste has become a social problem, as represented by the problem of marine plastic waste. For this reason, the recycling of plastic products is being promoted. Plastic packaging materials are manufactured by combining a plurality of plastic materials according to the required performance and functions. In order to recycle plastic products into high-quality products, it is preferable that the packaging material is made of a single plastic material. Since it is difficult to separate a product made of a plurality of plastic materials into the plastic materials constituting it, it can only be recycled into a low-quality plastic product or incinerated.

[0005] Therefore, even in the case of heat-sealing films, in order to enhance recyclability, it is desired that the film base material and the heat-sealing layer use the same type of resin as each other.

[0006] Generally, heat sealing is performed by overlapping the heat-sealing layer of a heat-sealing film and the heat-sealing layer or the film base material surface of another heat-sealing film and subjecting them to pressure bonding and heating with a heat sealer. The temperature of the heat sealer at this time is lower than the melting point of the material forming the film base material and higher than the melting point of the material forming the heat-sealing layer, and the pressure bonding time is short, ranging from 0.1 second to several seconds. In recent years, particular importance has been attached to production efficiency, and there is a demand for a heat-sealing film that can obtain strong heat-sealing strength with a short pressure bonding time.

[0007] Furthermore, heat-sealing films are also used for retort pouches and the like used for packaging retort foods. For this reason, heat-sealing films are required to have heat resistance that can withstand retort processing (120 to 135°C), and the resin forming the heat-sealing layer is required to have a melting point of 150°C or higher.

[0008] Polyethylene terephthalate (PET) resin, which is generally used as a material for polyester-based films, has a high glass transition temperature (Tg) of 70°C and a melting point (Tm) of 250°C, and furthermore, since the heat of fusion ΔH is large, high-temperature and long-time heating is required to melt it, so it is not suitable as a material for forming the heat-sealing layer. Also, polybutylene terephthalate (PBT) resin, which is widely used as an engineering plastic, has a glass transition temperature (Tg) of 40°C and a melting point (Tm) lower than that of PET resin. Therefore, although it is not impossible to adopt it as a material for the heat-sealing layer when using a PET film as the film base material, it is difficult to put it into practical use as the heat-sealing layer because the heat of fusion ΔH is large.

[0009] Therefore, a heat-sealing film used for a heat-sealing layer made of a polyester resin obtained by copolymerizing isophthalic acid, adipic acid, sebacic acid, dimer acid, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. with PET or PBT has been proposed (see, for example, Patent Documents 1 and 2). Further, among these, as conditions for increasing the heat-sealing strength during heat-sealing, it has been proposed to design the glass transition temperature (Tg) and the heat of crystal melting within a specific range. For example, Patent Document 1 discloses a heat-sealing layer made of a copolymer resin having a melting temperature of 125°C or higher, a glass transition temperature (Tg) of 40°C or lower, and a heat of crystal melting of 4 cal / g or lower. Also, Patent Document 2 proposes a laminated polyester film in which a polyester film made of an amorphous polyester copolymer or a low-crystalline polyester copolymer having a heat of crystallization (ΔH) of less than 10 J / g is laminated.

[0010] In addition, a film in which a resin layer made of a polyester resin copolymerized with polyoxyalkylene glycol as a copolymer component is laminated is also known (see, for example, Patent Documents 3 and 4). This polyester resin is a block copolymer composed of a high-melting-point crystalline segment and a low-melting-point amorphous segment as disclosed in Patent Documents 3 and 4, and has a melting point of 180°C or higher. The heat-sealing film laminated on the film base material can withstand the retort temperature.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0012] However, for example, as disclosed in Patent Document 1, a resin obtained by copolymerizing isophthalic acid, adipic acid, sebacic acid, or dimer acid with PET or PBT and having a heat of fusion of crystallization of 4 cal / g or less has a melting point of less than 132°C. Therefore, a packaging bag (pouch) made from a heat-sealing film using this as a heat-sealing layer cannot withstand retort processing. In order to improve the heat resistance of the heat-sealing film, when the copolymerization ratio of isophthalic acid, adipic acid, etc. in the resin forming the heat-sealing layer is decreased, although the melting point of the resin increases, the heat of fusion of crystallization also increases. As a result, the heat-sealing layer cannot be sufficiently melted in a short crimping time, and thus there is a problem that a high heat-sealing strength cannot be exhibited. Also, in a heat-sealing layer using a polyester copolymerized with polyoxyalkylene glycol as a copolymerization component as described above, since a melting point of 180°C or higher can be obtained, a heat-sealing film laminated on a film base material can withstand retort temperatures. However, a strong heat-sealing strength cannot be obtained even with a short crimping time.

[0013] The present invention solves the above problems, and provides a heat-sealing film excellent in recyclability and capable of reducing environmental load, which can obtain a strong heat-sealing strength in a short crimping time, and further has heat resistance to withstand retort processing at high temperatures, and also provides a packaging material.

Means for Solving the Problems

[0014] The heat-sealing film of the present invention is a heat-sealing film provided with a thermoplastic polyester resin layer containing a thermoplastic polyester resin containing polyoxyalkylene glycol as a diol component on one or both sides of a base material layer. The base material layer is an unstretched polybutylene terephthalate-based film, the content of the polytetramethylene glycol component in the thermoplastic polyester-based resin is 30% by mass or more and the content of the isophthalic acid component is 0 mol%, The thermoplastic polyester resin is characterized in that, after melting, when it is rapidly cooled to -50°C at 200°C / min and then heated at 10°C / min, the glass transition temperature (Tg) observed is 50°C or less, the melting point (Tm) is 150°C or more, and the heat of fusion ΔH exceeds 0 J / g and is 20 J / g or less.

[0015] In the heat-sealing film of the present invention, it is preferable that the thermoplastic polyester resin contains terephthalic acid as the main dicarboxylic acid component and contains ethylene glycol and / or 1,4-tetramethylene glycol as the main diol component. Also, in the heat-sealing film of the present invention, it is preferable that the heat of fusion ΔH exceeds 0 J / g and is 10 J / g or less. Also, in the heat-sealing film of the present invention, it is more preferable that the heat of fusion ΔH exceeds 0 J / g and is 5 J / g or less. Also, in the heat-sealing film of the present invention, it is preferable that the thermoplastic polyester resin contains terephthalic acid as the main dicarboxylic acid component, contains 1,4-tetramethylene glycol as the main diol component, and is a thermoplastic polyester resin containing polytetramethylene glycol as the diol component as the polyoxyalkylene glycol. 。

[0016] The packaging material of the present invention is characterized by including the above heat-sealing film. The packaging material of the present invention can be configured as a packaging bag or a lid material for a sealed container.

Advantages of the Invention

[0017] According to the heat-sealing film and packaging material of the present invention, since the thermoplastic polyester resin layer is provided as a heat-sealing layer on one side or both sides of the base material layer, if the base material layer is formed of a polyester resin, the entire heat-sealing film will be composed mainly of a polyester resin. Therefore, it can be easily recycled into high-quality polyester materials and polyester products, obtaining excellent recyclability, and as a result, the environmental load can be reduced. Moreover, since the above-mentioned thermoplastic polyester resin contains polyoxyalkylene glycol as a diol component and exhibits specific glass transition temperature (Tg), melting point (Tm), and heat of fusion ΔH, strong heat-sealing strength can be obtained with a short crimping time, and heat resistance to withstand retort processing at high temperatures can be obtained. As a result, the occurrence of leakage of the contents can be prevented in the packaging material.

Brief Description of the Drawings

[0018]

Figure 1

Embodiments for Carrying Out the Invention

[0019] 〔Heat-sealing film〕 The heat-sealing film according to an embodiment of the present invention is a laminated film in which a heat-sealing layer (thermoplastic polyester resin layer) 12 containing a thermoplastic polyester resin containing polyoxyalkylene glycol as a diol component is provided on one side of a base material layer 11, as shown in FIG. 1.

[0020] 〔Heat-sealing layer〕 The heat-sealing layer 12 contains a polyoxyalkylene glycol as a diol component, and when observed after melting, quenched to -50°C at 200°C / min, and then heated at 10°C / min, it has a glass transition temperature (Tg) of 50°C or less, a melting point (Tm) of 150°C or more, and a heat of fusion ΔH exceeding 0 J / g and being 20 J / g or less. It contains a thermoplastic polyester resin (hereinafter also referred to as "specific thermoplastic polyester resin").

[0021] 〔Specific thermoplastic polyester resin〕 The specific thermoplastic polyester resin is generally obtained by subjecting a dicarboxylic acid component such as terephthalic acid, a diol component such as ethylene glycol and 1,4-tetramethylene glycol, and other components used as necessary to an esterification reaction and / or transesterification reaction, and then performing a polycondensation reaction. The polyoxyalkylene glycol contained as a diol component in the specific thermoplastic polyester resin is a polyether in which ethylene, propylene, tetramethylene (butylene), etc. are connected by ether bonds. Specifically, polyethylene glycol, polypropylene glycol, polytetramethylene glycol (polytetramethylene ether glycol), etc. can be mentioned. Among these, it is preferable that polytetramethylene glycol is contained as a diol component. As the polyoxyalkylene glycol, those having an average molecular weight of 500 to 2,000 are preferable, and particularly preferably those having an average molecular weight of 500 to 1,000. When the average molecular weight of the polyoxyalkylene glycol is less than 500, the melting point of the thermoplastic polyester resin may be lowered and the heat resistance may be reduced. On the other hand, when the average molecular weight of the polyoxyalkylene glycol exceeds 2,000, the melting point of the thermoplastic polyester resin becomes high and it is difficult to obtain sufficient heat-sealing strength in a short crimping time.

[0022] When a specific thermoplastic polyester resin is melted, rapidly cooled to -50°C at 200°C / min, and then heated at 10°C / min, the glass transition temperature (Tg) observed is 50°C or lower, the melting point (Tm) is 150°C or higher, and the heat of fusion ΔH exceeds 0 J / g and is 20 J / g or lower. Preferably, the heat of fusion ΔH is 10 J / g or lower, more preferably 5 J / g or lower. When the glass transition temperature (Tg) exceeds 50°C, the thermoplastic polyester resin becomes difficult to soften, and it becomes difficult to obtain sufficient heat seal strength with a short crimping time. Also, when no melting point (Tm) is observed, that is, when the heat of fusion ΔH is 0 J / g, or when the melting point (Tm) is less than 150°C, there is a possibility that a pouch made from a heat seal film using this thermoplastic polyester resin as a heat seal layer may not have sufficient heat resistance and may not withstand retort processing. Furthermore, when the heat of fusion ΔH exceeds 20 J / g, it takes time for the thermoplastic polyester resin to melt, so it becomes difficult to obtain sufficient heat seal strength with a short crimping time.

[0023] As the dicarboxylic acid component and diol component for forming a specific thermoplastic polyester resin, components other than the polyoxyalkylene glycol component are not particularly limited as long as the thermoplastic polyester resin has the above glass transition temperature (Tg), melting point (Tm), and heat of fusion ΔH within the range. However, those containing terephthalic acid as the main dicarboxylic acid component and ethylene glycol and / or 1,4-tetramethylene glycol as the main diol component are preferred. The content of the terephthalic acid component is preferably 50 mol% or more, particularly preferably 70 mol% or more, based on the total dicarboxylic acid components of the thermoplastic polyester resin. When the content of the terephthalic acid component is less than 50 mol%, the melting point (Tm) of the thermoplastic polyester resin decreases, and the pouch obtained by heat-sealing the heat-sealing film laminated with this resin cannot withstand retort processing. Also, for the same reason, when the total diol components of the thermoplastic polyester resin are taken as 100 mol% and the proportion of the polyoxyalkylene glycol is x mol%, the content ratio of ethylene glycol and 1,4-tetramethylene glycol is preferably 70% or more of (100 - x) mol%. Furthermore, ethylene glycol and 1,4-tetramethylene glycol may coexist, but their proportions are set within the range where the resulting thermoplastic polyester resin satisfies the above glass transition temperature (Tg), melting point (Tm), and heat of fusion ΔH ranges.

[0024] Examples of components other than the above-mentioned polyoxyalkylene glycol, terephthalic acid, ethylene glycol, and / or 1,4-tetramethylene glycol for forming a specific thermoplastic polyester resin include aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, phthalic acid, etc.; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, etc.; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, etc. (dicarboxylic acid components); aliphatic glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, etc.; aromatic glycols such as bisphenol A, bisphenol S, etc.; alicyclic glycols such as 1,4-cyclohexanedimethanol, etc. (diol components); polyfunctional compound components such as trimellitic acid, pentaerythritol, etc. These components may be used alone or in combination of two or more, and by copolymerizing them, the melting point, crystallinity, and flexibility of the resulting thermoplastic polyester resin can be adjusted. Also, a specific thermoplastic polyester resin may be modified with maleic anhydride or the like in order to improve the adhesiveness with other resins.

[0025] As a preferred resin composition of a specific thermoplastic polyester resin, terephthalic acid is used as the main dicarboxylic acid component, 1,4-tetramethylene glycol is used as the main diol component, and the content of the polytetramethylene glycol component contained as the diol component is 30% by mass or more, or the content of the polytetramethylene glycol component is 10% by mass or more and the content of the isophthalic acid component is 20 mol% or more. When the isophthalic acid component is not contained and the content of the polytetramethylene glycol component is less than 30% by mass, or when the isophthalic acid component is contained at 20 mol% or more and the content of the polytetramethylene glycol component is less than 10% by mass, and further when the content of the polytetramethylene glycol component is 10% by mass or more and less than 30% by mass and the content of the isophthalic acid component is less than 20 mol%, in any case, the thermoplastic polyester resin has a heat of fusion ΔH exceeding 20 J / g, so it takes time until the resin melts, and it is difficult to obtain sufficient heat seal strength with a short crimping time.

[0026] The specific thermoplastic polyester resin preferably has a polystyrene-reduced weight average molecular weight (Mw) of 50,000 to 200,000, more preferably 70,000 to 150,000, as determined by size exclusion chromatography (SEC).

[0027] To the specific thermoplastic polyester resin, a lubricant, other resins, a light stabilizer, a compatibilizer, a plasticizer, an antistatic agent, a reaction catalyst, an anti-coloring agent, a radical inhibitor, an antistatic agent, a terminal blocking agent, an antioxidant, a heat stabilizer, a release agent, a flame retardant, an antibacterial agent, an antifungal agent, etc. may be added to prevent the films from sticking to each other when the films made of the specific thermoplastic polyester resin are overlapped.

[0028] The heat-sealing layer (thermoplastic polyester resin layer) 12 may consist only of the above-specified thermoplastic polyester resin, or may consist of a mixture of the specific thermoplastic polyester resin and other resins. As the other resins, thermoplastic polyester resins such as polybutylene terephthalate (PBT) resin are preferably used. Further, the other resins may be mixed resins mixed with hydrophilic silica or the like.

[0029] 〔Base material layer〕 As the base material layer 11 constituting the heat-sealing film 10 together with the heat-sealing layer 12, it is not particularly limited as long as it satisfies mechanical properties such as tensile strength and puncture strength, heat resistance, chemical resistance, etc. required for the obtained heat-sealing film 10. For example, those made of materials such as stretched nylon, stretched polyethylene terephthalate, other resins, metals, and paper can be mentioned. Further, from the viewpoint of enhancing recyclability, it is preferable to use polyester films such as polyethylene terephthalate-based films and polybutylene terephthalate-based films, and more preferably unstretched polybutylene terephthalate-based films. Further, from the viewpoints of mechanical properties and heat resistance, these polyester films are preferably made of homopolymers (polyethylene terephthalate, polybutylene terephthalate), and the content of copolymerization components such as dicarboxylic acids such as isophthalic acid, diols such as 1,4-cyclohexanedimethanol and neopentyl glycol, and polyfunctional compounds such as trimellitic acid and pentaerythritol is desirably minimized. Further, the base material layer 11 preferably consists of a material having a melting point of 200 °C or higher so as not to melt when heat-sealed.

[0030] A light stabilizer, an impact resistance improver, a compatibilizer, a lubricant, a plasticizer, an antistatic agent, a reaction catalyst, an anti-coloring agent, a radical inhibitor, an antistatic agent, a terminal blocking agent, an antioxidant, a heat stabilizer, a release agent, a flame retardant, an antibacterial agent, an antifungal agent, etc. may be added to the base material layer 11.

[0031] The method for manufacturing the heat-sealing film 10 by laminating the base material layer 11 and the heat-sealing layer 12 is not particularly limited, and examples include a method of applying a solution obtained by dissolving a specific thermoplastic polyester resin in a solvent to one or both sides of the base material layer 11 and then drying it; a method of forming a specific thermoplastic polyester resin into a film shape and laminating it to the base material layer 11 using an adhesive or the like; and a method of supplying the specific thermoplastic polyester resin and the resin for forming the base material layer 11 to separate extruders, melting them, and then co-extruding and laminating them from a T-die. Among these, the co-extrusion method that does not require a solvent or an adhesive and also does not require a step of laminating films is particularly preferable from the viewpoints of low environmental impact and high production efficiency. Further, when using the co-extrusion method, if a polybutylene terephthalate resin is used as the material for forming the base material layer 11, after co-extruding with a specific thermoplastic polyester resin for forming the heat-sealing layer 12 and then cooling and winding it up as it is, the base material layer 11 crystallizes, resulting in a film having excellent heat resistance and mechanical strength, which is even more preferable.

[0032] 〔Packaging Material〕 The packaging material of the present invention is a packaging material including the above heat-sealing film 10. Specifically, examples include a packaging bag such as a retort pouch, and a lid material for closing the opening of the container body for forming a sealed container. As shown in FIG. 1, for example, the packaging bag is formed by overlapping the heat-sealing film 10 and another heat-sealing film 10' such that the heat-sealing layers 12 and 12' face each other, and then heat-sealing and pressing the periphery from the outside (the base material layer 11 and the base material layer 11' side) to form a bag shape using a heat sealer 13. As a result, the heat-sealing layers 12 and 12' are melt-bonded (heat-sealed). By adhering the peripheries of the two heat-sealing films 10 and 10' in this way, a packaging material for sealing the contents can be produced. The heating temperature by the heat sealer 13 is, for example, 160 to 210°C, the pressure for heat-sealing and pressing is, for example, 0.1 to 1 MPa, and the heat-sealing and pressing time is, for example, 0.1 to 3 seconds. The sealed container using the heat-sealing film 10 as a lid material houses the contents in the container body, and the heat-sealing film 10 is arranged on the edge flange of the opening of the container body with the heat-sealing layer 12 in contact with this edge flange and heat-pressed. As a result, the heat-sealing film 10 is heat-sealed, and thereby the contents can be sealed. From the viewpoint of recyclability, the container body of such a sealed container is preferably made of a polyester resin such as PET, for example.

[0033] As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. For example, the heat-sealing film of the present invention is not limited to a configuration in which the sealant layer is provided only on one side of the base material layer, and may have a configuration in which the sealant layers are provided on both sides of the base material layer. Also, for example, the heat-sealing film of the present invention may have an intermediate layer such as an appropriate barrier layer interposed between the heat-sealing layer and the base material layer. Furthermore, the heat-sealing film of the present invention may have a configuration in which the heat-sealing layer is provided on one side of the base material layer, and a printing layer, a barrier layer, or the like is provided on the opposite side.

Examples

[0034] Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto. The following examples , Reference Example And in the comparative examples, the analysis method of the resin composition of the thermoplastic polyester resin, the measurement methods of the glass transition temperature (Tg), the melting point (Tm), the heat of fusion (ΔH), the measurement method of the heat-sealing strength of the heat-sealing film, and the measurement method of the heat resistance of the packaging material are as follows.

[0035] <Resin composition of thermoplastic polyester resin> The thermoplastic polyester resin was dissolved in heavy trifluoroacetic acid and further diluted with heavy chloroform (containing 0.1% by mass of trimethylsilane). The resin composition was analyzed and calculated by measuring the proton NMR spectrum using a nuclear magnetic resonance analyzer (trade name "JNM-ECZ400S", manufactured by JEOL Ltd.).

[0036] <Glass transition temperature (Tg), melting point (Tm), and heat of fusion ΔH of the thermoplastic polyester resin> Using a differential scanning calorimeter (trade name "DSC8500", manufactured by PerkinElmer), after melting at a temperature exceeding the melting point of the thermoplastic polyester resin (200 - 250 °C), it was cooled to -50 °C at 200 °C / min. Then, when heating from -50 °C to a temperature exceeding the melting point of the thermoplastic polyester resin (200 - 250) °C at 10 °C / min, the extrapolated onset temperature of the glass transition observed was taken as the glass transition temperature (Tg), the temperature at the peak top of the melting peak was taken as the melting point (Tm), and the heat of fusion ΔH was determined from the area of the portion surrounded by the melting peak and the baseline.

[0037] <Heat seal strength of the heat-sealing film> Two pieces cut out from the heat-sealing film to 20 mm × 80 mm were overlapped in a state where the resin layers containing the thermoplastic polyester resin faced each other. Then, they were heat-sealed by crimping at a seal width of 10 mm, a seal temperature of 210 °C (one side), and a seal pressure of 0.3 MPa for 1 second using a heat sealer. Next, based on JIS Z1707 (General Rules for Plastic Films for Food Packaging 7.5 Heat Seal Strength Test), a test piece with a length of 80 mm and a width of 15 mm, consisting of a heat-sealed part (length 10 mm) and a non-sealed part (length 70 mm) that was not heat-sealed, was cut out from the heat-sealed heat-sealing film. Then, with the heat-sealed part at the center, this test piece was opened to 180°, and its both ends were attached to the two jaws of a tensile testing machine, and the maximum load when pulling until the heat-sealed part broke at a speed of 300 mm / min was determined.

[0038] <Heat resistance> Two pieces cut out from the heat-sealing film to a size of 140 mm × 170 mm were overlapped in a state where the resin layers containing the thermoplastic polyester-based resin faced each other. Then, three sides were heat-sealed by a heat sealer at a seal width of 5 mm, a seal temperature of 210 °C (one side), and a seal pressure of 0.3 MPa for 1 second to produce a packaging bag. After putting 200 g of water through the opening of this packaging bag, the opening was heat-sealed and sealed in the same manner, and then retort treatment was performed at 127 °C for 30 minutes in a retort kettle. At this time, the presence or absence of leakage of the contents (water) due to peeling of the heat-sealed part and the appearance were evaluated according to the following evaluation criteria. - Evaluation Criteria - 〇: No leakage of contents, no change in appearance △: No leakage of contents, there is a change in appearance ×: There is leakage of contents -: Evaluation cannot be performed

[0039] 〔 Reference Example 1〕 The thermoplastic polyester-based resin [P1] (trade name "Hytrel 2551", manufactured by Toray DuPont Co., Ltd.) was supplied from the hopper of a twin-screw extruder, melted at 270 °C, extruded into a film shape by a T-die, and cooled and solidified by a cast roll to produce a film with a thickness of 40 μm. After applying an adhesive (main agent: Takelac A-315, curing agent: Takenate A-50, both manufactured by Mitsui Chemicals, Inc.) to this film, it was adhered to a biaxially stretched polyethylene terephthalate (PET) film with a thickness of 34 μm and left standing at 37 °C for 5 days or more to be cured, thereby producing a heat-sealing film. The thermoplastic polyester-based resin [P1] contained a polytetramethylene glycol component which is a polyoxyalkylene glycol, had a glass transition temperature (Tg) of -3 °C, a melting point (Tm) of 158 °C, and a heat of fusion ΔH of 0.3 J / g. The resin composition of this thermoplastic polyester-based resin [P1] was as described in Table 1. The heat-sealing strength of this heat-sealing film was 44.8 (N / 15 mm), which was good. Also, the packaging bag produced using this heat-sealing film had no leakage of the contents after retort treatment and good heat resistance was obtained.

[0040] Reference Example 2, Example 1 Reference Example In 1, instead of the thermoplastic polyester resin [P1], the thermoplastic polyester resin [P2] (trade name "Hytrel 4057N", manufactured by Toray DuPont Co., Ltd.) or the thermoplastic polyester resin [P3] (trade name "Modic GQ430", manufactured by Mitsubishi Chemical Corporation) was used. In each case, except that the melting temperature during extrusion into a film shape by a T-die was 200 °C Reference Example Heat-sealing films were produced in the same manner as in 1. The resin compositions of these thermoplastic polyester resins [P2] and [P3] contained a polytetramethylene glycol component as shown in Table 1, had a glass transition temperature (Tg) of 50 °C or lower, a melting point (Tm) of 150 °C or higher, and a heat of fusion ΔH of 20 J / g or lower. Further, as shown in Table 1, the heat-sealing strengths of these heat-sealing films all showed high values, and it was confirmed that good heat-sealing strength could be obtained. Furthermore, the packaging bags produced using these heat-sealing films all had good heat resistance without leakage of the contents after retort treatment.

[0041] [Comparative Examples 1 and 2] Reference Example In 1, instead of the thermoplastic polyester resin [P1], the thermoplastic polyester resin [P4] (trade name "Hytrel 7247", manufactured by Toray DuPont Co., Ltd.) or the thermoplastic polyester resin [P5] (trade name "Novaduran 5510S", manufactured by Mitsubishi Engineering Plastics Corporation) was used Reference Example Heat-sealing films were produced in the same manner as in 1. The resin compositions of these thermoplastic polyester resins [P4] and [P5] contained a polytetramethylene glycol component as shown in Table 1, had a glass transition temperature (Tg) of 50 °C or lower, and a melting point (Tm) of 150 °C or higher was observed, but the heat of fusion ΔH exceeded 20 J / g. Further, as shown in Table 1, the heat-sealing strengths of these heat-sealing films all showed extremely low values, and it was confirmed that good heat-sealing strength could not be obtained.

[0042] ​​ [Comparative Example 3] Reference Example In 2, except that the thermoplastic polyester resin [P6] (trade name "600LP", manufactured by Mitsubishi Chemical Corporation) was used instead of the thermoplastic polyester resin [P2], Reference Example A heat-sealing film was produced in the same manner as in 2. The resin composition of this thermoplastic polyester resin [P6] was a copolybutylene terephthalate (PBT) containing no polytetramethylene glycol component and containing 30 mol% of an isophthalic acid component, as shown in Table 1. The heat of fusion ΔH of this thermoplastic polyester resin [P6] was 30 J / g, which exceeded 20 J / g. Also, as shown in Table 1, the heat-sealing strength of the heat-sealing film showed a low value, and it was confirmed that good heat-sealing strength could not be obtained.

[0043] [Comparative Example 4] Reference Example In 1, except that the thermoplastic polyester resin [P1] was replaced with the thermoplastic polyester resin [P7] (trade name "PETG", manufactured by Eastman Chemical Company), Reference Example A heat-sealing film was produced in the same manner as in 1. The resin composition of this thermoplastic polyester resin [P7] was a copolyethylene terephthalate (PET) containing no polytetramethylene glycol component and containing 33 mol% of 1,4-cyclohexanedimethanol (CHDM), as shown in Table 1. The glass transition temperature (Tg) of this thermoplastic polyester resin [P7] was 70°C, which exceeded 50°C, the melting point (Tm) was not observed, and the heat of fusion ΔH was 0 J / g. Also, as shown in Table 1, the heat-sealing strength of the heat-sealing film showed a low value, and it was confirmed that good heat-sealing strength could not be obtained. Furthermore, it was confirmed that the packaging bag produced using this heat-sealing film had leakage of the contents after retort treatment and good heat resistance could not be obtained.

[0044] [Example 2 ​80 parts by mass of a thermoplastic polyester resin [P3] and 20 parts by mass of a mixed resin [B1] obtained by mixing 5% by mass of hydrophilic silica into a polybutylene terephthalate (PBT) resin were supplied from the hopper of a twin-screw extruder A and melted at 245 - 240°C. Further, a PBT resin [C1] (trade name "1100-211S", manufactured by Changchun Co., Ltd.) was supplied from the hopper of a twin-screw extruder B and melt-kneaded at 270 - 260°C. The resins extruded from these twin-screw extruders A and B were supplied to a multi-manifold T die, extruded into a film shape, and cooled and solidified by a cast roll to produce a heat-sealing film with a thickness of 75 μm. The thickness ratio of the resin layer (thermoplastic polyester resin layer) in which the thermoplastic polyester resin [P3] and the mixed resin [B1] mixed with hydrophilic silica were blended and the layer (base material layer) made of the PBT resin [C1] of this heat-sealing film was 1:2. The heat-sealing strength of this heat-sealing film showed a high value as shown in Table 2, and it was confirmed that good heat-sealing strength was obtained. Further, the packaging bags produced using these heat-sealing films had no leakage of the contents after retort treatment and good heat resistance was obtained.

[0045] 〔Example 3 〕 80 parts by mass of a thermoplastic polyester resin [P3] and 20 parts by mass of a mixed resin [B1] obtained by mixing 5% by mass of hydrophilic silica with a polybutylene terephthalate (PBT) resin were supplied from the hopper of a twin-screw extruder A and melted at 245 - 240°C. Further, a PET resin [C2] (trade name "BK6180", manufactured by Mitsubishi Chemical Corporation) copolymerized with 2 mol% of isophthalic acid was supplied from the hopper of a twin-screw extruder B and melt-kneaded at 270°C. The resins extruded from these twin-screw extruders A and B were supplied to a multi-manifold T-die, extruded into a film shape, and cooled and solidified with a cast roll to produce a heat-sealing film with a thickness of 75 μm. The thickness ratio of the resin layer (thermoplastic polyester resin layer) in which the thermoplastic polyester resin [P3] and the mixed resin [B1] mixed with hydrophilic silica were blended and the layer (base material layer) made of the PET resin [C2] of this heat-sealing film was 1:2. The heat-sealing strength of this heat-sealing film showed a high value as shown in Table 2, and it was confirmed that good heat-sealing strength was obtained. Furthermore, the packaging bags produced using these heat-sealing films had no leakage of the contents after retort treatment and had no problem in practical use, but a change (film deformation) was observed in the appearance.

[0046] In Table 1 below, "TA" represents terephthalic acid, "IA" represents isophthalic acid, "EG" represents ethylene glycol, "BG" represents 1,4-tetramethylene glycol, "CHDM" represents 1,4-cyclohexanedimethanol, and "PTMG" represents polytetramethylene glycol.

[0047]

Table 1

[0048]

Table 2

Explanation of symbols

[0049] 10, 10’ ··· Heat-sealing film 11, 11’... Substrate layer 12, 12’... Heat-sealing layer (thermoplastic polyester resin layer) 13... Heat sealer

Claims

1. A heat-sealing film provided with a thermoplastic polyester resin layer containing a thermoplastic polyester resin containing polyoxyalkylene glycol as a diol component on one or both sides of a base material layer, wherein the base material layer is an unstretched polybutylene terephthalate film, the content of the polytetramethylene glycol component in the thermoplastic polyester resin is 30% by mass or more and the content of the isophthalic acid component is 0 mol%, when the thermoplastic polyester resin is melted, rapidly cooled to -50°C at 200°C / min, and then heated at 10°C / min, the glass transition temperature (Tg) observed is 50°C or lower, and the melting point (Tm) of 150°C or higher is observed, and the heat of fusion ΔH exceeds 0 J / g and is 20 J / g or lower. A heat-sealing film characterized by the above.

2. The heat-sealing film according to claim 1, wherein the thermoplastic polyester resin contains terephthalic acid as a main dicarboxylic acid component and contains ethylene glycol and / or 1,4-tetramethylene glycol as a main diol component.

3. The heat-sealing film according to claim 1 or claim 2, wherein the heat of fusion ΔH exceeds 0 J / g and is 10 J / g or lower.

4. The heat-sealing film according to claim 3, wherein the heat of fusion ΔH exceeds 0 J / g and is 5 J / g or lower.

5. The heat-sealing film according to any one of claims 1 to 4, wherein the thermoplastic polyester resin contains terephthalic acid as a main dicarboxylic acid component, contains 1,4-tetramethylene glycol as a main diol component, and contains polytetramethylene glycol as a diol component as the polyoxyalkylene glycol.

6. A packaging material characterized by including the heat-sealing film according to any one of claims 1 to 5.

7. The packaging material according to claim 6, which is a packaging bag or a lid material for a sealed container.

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