Low-adsorption sealant films, laminates, and packaging bags

Abstract

To provide a sealant film that is resistant to the adsorption of various organic compounds, has excellent heat-sealing properties at 140°C, but has low heat-sealing strength at 100°C, and prevents the heat-seal layers from sticking together when used as a packaging bag and attempting to heat the contents by boiling them in hot water. [Solution] A low-adsorption sealant film having a heat-seal layer made of at least one polyester-based component, and satisfying the following conditions (1) to (3). (1) When heat-seal layers are sealed together at 120°C, 0.2 MPa, and for 2 seconds, the seal strength is 4N / 15mm or more and 15N / 15mm or less. (2) When heat-seal layers are sealed together at 140°C, 0.2 MPa, and for 2 seconds, the seal strength is 8 N / 15 mm or more and 30 N / 15 mm or less. (3) In the heat seal layer, the oxygen atom abundance determined by X-ray electron spectroscopy (ESCA) is between 26.6% and 31.0%.

Description

[Technical Field]

[0001] This invention relates to a sealant film that achieves both excellent low adsorption and heat-sealing properties, as well as laminates and packaging bags using the same. [Background technology]

[0002] Traditionally, sealant films have been used as packaging materials for many distributed goods, such as food, pharmaceuticals, and industrial products. The innermost layer of packaging materials, such as packaging bags and lids, is provided with a heat-seal layer made of polyolefin resins such as polyethylene and polypropylene, or copolymer resins such as ionomers and EMMA, which exhibit high heat-seal strength. These resins are known to achieve high adhesion strength through heat sealing. However, unstretched sealant films made of polyolefin resin, as described in Patent Document 1, readily adsorb components made of organic compounds such as oils and fragrances. Therefore, packaging materials that use a sealant film as the innermost layer, i.e., the layer in contact with the contents, have the disadvantage of easily altering the aroma and taste of the contents. When using a sealant layer made of polyolefin resin as the innermost layer of packaging bags for chemical products, pharmaceuticals, food products, etc., measures such as pre-adding a larger amount of the active ingredients of the contents are necessary, making it unsuitable for use in many cases.

[0003] On the other hand, sealant films made of polyacrylonitrile resin, such as those described in Patent Document 2, have the characteristic of being less adsorbent of organic compounds contained in chemical products, pharmaceuticals, foods, etc. However, polyacrylonitrile films have poor heat sealability at 140°C, and good seal strength could not be obtained in some cases. In light of these problems, Patent Document 3 discloses a polyester film for sealant applications that is non-adsorbent to organic compounds. However, because the polyester film of Patent Document 3 has high heat seal strength at 100°C, when used as a packaging bag and attempting to heat the contents by boiling them in hot water, the innermost heat seal layers tend to stick together, making it difficult to open the packaging bag.

[0004] Furthermore, the applicant disclosed in Patent Document 4 a polyester film for sealant applications that has non-adsorbent properties for organic compounds. However, in recent years, there has been a trend towards faster automated filling and packaging to increase productivity, but it has been found that the polyester film in Patent Document 4 is not suitable for high-speed automated filling and packaging. In the case of high-speed automated filling and packaging, even if the heat seal bar temperature is set to 140°C, the temperature of the sealant film only rises to around 120°C due to the short heating time. However, the polyester film in Patent Document 4 does not have sufficient heat seal strength at 120°C, resulting in the problem of peeling of the sealed portion after heat sealing. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 3817846 [Patent Document 2] Japanese Patent Application Publication No. 7-132946 [Patent Document 3] International Publication No. 2014 / 175313 [Patent Document 4] Japanese Patent Publication No. 2017-165059 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention aims to solve the problems of the prior art described above. Specifically, it provides a sealant film (A) that is less susceptible to adsorption of various organic compounds and exhibits excellent heat sealability at 140°C. The present invention provides the sealant film (A) described above, which has low heat seal strength at 100°C and whose heat seal layers do not easily adhere to each other when used as a packaging bag and the contents are heated by boiling in hot water. The second invention of this application provides the sealant film (A) described above, which also has excellent heat sealability at low temperatures of 120°C, and therefore has sufficient heat seal strength even in high-speed automated filling and packaging. Furthermore, the present invention aims to provide a laminate comprising at least one layer of the sealant film of the first or second invention of this application, and a packaging bag using the same. [Means for solving the problem]

[0007] Hereinafter, the sealant film described in item 1 below will be referred to as the first invention of this application, and the sealant film described in item 2 below will be referred to as the second invention of this application. Unless otherwise specified, the matters of the present invention are common to both inventions. The present invention consists of the following configuration. 1. A low-adsorption sealant film having at least one heat-seal layer made of polyester components, and characterized in that it satisfies the following conditions (1) to (3). (1) When heat-seal layers are sealed together at 100°C, 0.2 MPa, and for 2 seconds, the seal strength is 0 N / 15 mm or more and 5 N / 15 mm or less. (2) When heat-seal layers are sealed together at 140°C, 0.2 MPa, and for 2 seconds, the seal strength is 8 N / 15 mm or more and 30 N / 15 mm or less. (3) The density of the film including all layers is 1.20 or more and less than 1.39 2. A low-adsorption sealant film having a heat-seal layer consisting of at least one polyester-based component, and characterized in that it satisfies the following conditions (4) to (6). (4) When heat-seal layers are sealed together at 120°C, 0.2 MPa, and for 2 seconds, the seal strength is 4N / 15mm or more and 15N / 15mm or less. (5) When heat-seal layers are sealed together at 140°C, 0.2 MPa, and for 2 seconds, the seal strength is 8 N / 15 mm or more and 30 N / 15 mm or less. (6) In the heat seal layer, the oxygen atom abundance determined by X-ray electron spectroscopy (ESCA) is between 26.6% and 31.0%. 3. A low-adsorption sealant film according to either 1. or 2., wherein the average length RSm of the surface roughness elements determined by a three-dimensional roughness meter is 18 μm or more and 29 μm or less. 4. A low-adsorption sealant film according to any one of 1 to 3, wherein the coefficient of dynamic friction between the heat-sealed surfaces is 0.30 or more and 0.80 or less. 5. A low-adsorption sealant film according to any of 1 to 4, wherein the components constituting the film are polyester, with ethylene terephthalate as the main component. 6. A low-adsorption sealant film according to any one of 1 to 5, wherein the monomers constituting the polyester components constituting the heat seal layer contain diol monomer components other than ethylene glycol, and the diol monomer component is one or more of neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-butanediol, and diethylene glycol. A low-adsorption sealant film according to any of 1 to 6, wherein the thermal shrinkage rate when treated in 7.80°C hot water for 10 seconds is 0% or more and 10% or less in both the longitudinal and width directions. 8. A laminate characterized by comprising at least one layer of the sealant film described in any of items 1 to 7 above. 9. A packaging bag characterized by using at least a portion of the sealant film described in any of 1. to 7. above, or the laminate described in 8. above. [Effects of the Invention]

[0008] The sealant film of the present invention is less likely to adsorb various organic compounds, allowing for hygienic packaging of items containing oils and fragrances, such as chemical products, pharmaceuticals, and food products, while also exhibiting excellent heat sealability at 140°C. The sealant film of the first invention of this application has low heat seal strength at 100°C, so when used as a packaging bag and attempting to heat the contents by boiling them in hot water, the innermost heat seal layers do not easily adhere to each other. The second invention of this application exhibits excellent heat sealability at 140°C and also has excellent heat sealability at a lower temperature of 120°C, thus providing a sealant film with sufficient heat seal strength even in high-speed automated filling and packaging. Furthermore, a laminate including at least one layer of the sealant film of the first invention or the second invention of the present application, and a packaging bag using the same can be provided.

Embodiments for Carrying out the Invention

[0009] The sealant film of the first invention of the present application has a heat-sealing layer made of at least one layer of polyester-based components, and is a low-adsorption sealant film characterized by satisfying the following (1) to (3). (1) When the heat-sealing layers are sealed at 100 ° C, 0.2 MPa, and for 2 seconds, the seal strength is 0 N / 15 mm or more and 5 N / 15 mm or less. (2) When the heat-sealing layers are sealed at 140 ° C, 0.2 MPa, and for 2 seconds, the seal strength is 8 N / 15 mm or more and 30 N / 15 mm or less. (3) The density of the film including all layers is 1.20 or more and less than 1.39. Hereinafter, the characteristics of the sealant film of the present invention, the layer structure, the layer ratio, the raw materials constituting the sealant film, the manufacturing method of the sealant film, the type of the content, and the structure of the package and the bag-making method will be described in detail.

[0010] 1. Characteristics of the sealant film 1.1. 100 °C heat-seal strength The sealant film of the first invention of the present application needs to have a heat-seal strength of 0 N / 15 mm or more and 5 N / 15 mm or less when the heat-sealing layers are heat-sealed at a temperature of 100 °C, a seal bar pressure of 0.2 MPa, and a seal time of 2 seconds. When the 100 °C heat-seal strength exceeds 5 N / 15 mm, when trying to warm the contents using it as a packaging bag, the heat-sealing layers of the innermost layer are likely to stick to each other, and the peelability is impaired, so it is not suitable as a packaging bag. The 100 °C heat-seal strength is more preferably 4.5 N / 15 mm or less, and even more preferably 4.0 N / 15 mm or less.

[0011] 1.2. 120 °C heat-seal strength The sealant film of the second invention of this application must have a heat seal strength of 4N / 15mm or more and 15N / 15mm or less when heat-sealed together at a temperature of 120°C, a seal bar pressure of 0.2 MPa, and a sealing time of 2 seconds. If the heat seal strength at 120°C is less than 4N / 15mm, the heat seal strength will be insufficient during high-speed automated filling and packaging, making it impossible to increase the productivity of the packaging bags. A high heat seal strength at 120°C is preferable, but with the current state of the present invention, the upper limit that can be obtained is about 15N / 15mm, which is sufficient for practical purposes. A heat seal strength of 5N / 15mm or higher at 120°C is more preferable, and 6N / 15mm or higher is even more preferable.

[0012] 1.3. Heat seal strength at 140℃ The sealant film of the present invention must have a heat seal strength of 8N / 15mm or more and 30N / 15mm or less when heat-sealed between heat-seal layers at a temperature of 140°C, a seal bar pressure of 0.2MPa, and a sealing time of 2 seconds. If the heat seal strength at 140°C is less than 8N / 15mm, the sealed portion will easily peel off, making it difficult to use as a packaging bag. A high heat seal strength at 140°C is preferable, but with the current state of the art, the upper limit that can be obtained is about 30N / 15mm. A heat seal strength of 9N / 15mm or higher at 140°C is more preferable, and even more preferable is 10N / 15mm or higher.

[0013] 1.4. Density The sealant film of the first invention of this application must have a film density of 1.20 or more and less than 1.39, including all layers. The density of the film including all layers correlates with its adsorption, heat resistance, and 140°C heat seal strength. The higher the density, the better the sealant film has in terms of low adsorption and heat resistance. This is because higher density tends to result in higher crystallinity, and higher crystallinity leads to higher chemical resistance and heat resistance. Therefore, if the density of the film including all layers is less than 1.20, the chemical resistance will be poor, the adsorption will be high, and the heat resistance will be low, making the film prone to punctures during heat sealing, thus making it unsuitable as a packaging bag. Furthermore, while a density of 1.39 or higher offers excellent low adsorption and heat resistance, it compromises heat sealability at 140°C, making it unsuitable as a sealant film. A density range of 1.25 to 1.38 is more preferable, and 1.30 to 1.37 is even more preferable.

[0014] 1.5. Average length RSm of the surface roughness elements of the heat seal layer The sealant film of the present invention has a cutoff of 0.250 mm and a measurement speed of 0.2 mm / second. The average length RSm of the surface roughness elements of the heat seal layer measured under the following conditions is 18 μm or greater. It is preferable that the thickness be 9 μm or less. The average length RSm of the surface roughness elements of the heat seal layer correlates with the 100°C heat seal strength and the coefficient of dynamic friction between the heat seal surfaces. The longer the average length RSm of the surface roughness elements of the heat seal layer, the less unevenness there is on the heat seal surface, resulting in a smoother surface, a larger contact area, higher 100°C heat seal strength, and a higher coefficient of dynamic friction between the heat seal surfaces. If the average length RSm of the surface roughness elements of the heat seal layer is 29 μm or more, the 100°C heat seal strength will be high, and when attempting to heat the contents using it as a packaging bag, the innermost heat seal layers will easily stick together, impairing the ease of opening, making it unsuitable as a packaging bag. On the other hand, if the average length RSm of the surface roughness elements is less than 18 μm, the contact area between the heat seal surfaces will be extremely small, resulting in a low 140°C seal strength, making it unsuitable as a sealant film. The range of the average length RSm of the surface roughness elements of the heat seal layer is more preferably 19 μm to 28 μm, and even more preferably 20 μm to 27 μm.

[0015] 1.6. Dynamic friction coefficient of the heat seal layer The sealant film of the present invention preferably has a coefficient of dynamic friction between heat-sealed surfaces of 0.30 or more and 0.80 or less. If the coefficient of dynamic friction is less than 0.30, the film will slip too much, resulting in poor handling. On the other hand, if the coefficient of dynamic friction exceeds 0.80, the poor slipperiness may cause wrinkles to form when winding the film onto a roll, potentially reducing winding quality. The range of the coefficient of dynamic friction of the heat seal layer is more preferably 0.35 to 0.75, and even more preferably 0.40 to 0.70.

[0016] 1.7. Abundance ratio of oxygen atoms on the surface of the heat seal layer The sealant film of the second invention of this application requires that the oxygen atom abundance ratio in the heat seal layer, as determined by X-ray electron spectroscopy (ESCA), be between 26.6% and 31.0%. Non-patent document 1 describes how introducing oxygen-containing groups through surface treatment can increase the unevenness of charge density, strengthen intermolecular forces, and improve adhesive strength. This is because adhesion, especially to plastics, is believed to occur through bonding by intermolecular forces. In the sealant film of the present invention, the higher the oxygen atom abundance ratio on the surface of the heat seal layer, the greater the unevenness of charge density, and therefore the stronger the 120°C heat seal strength. For this reason, if the oxygen atom abundance ratio on the surface of the heat seal layer is less than 26.6%, the 120°C heat seal strength will be low, resulting in insufficient heat seal strength during high-speed automatic filling and packaging. Furthermore, if the oxygen atom abundance ratio on the surface of the heat seal layer exceeds 31.0%, the unevenness of charge density becomes large, making it easier for the films to adhere to each other at room temperature, causing the films wound on the roll to block each other and making it difficult to unwind the film smoothly. The oxygen atom content on the surface of the heat seal layer is more preferably in the range of 26.7% to 30.5%, and even more preferably in the range of 26.8% to 30.0%.

[0017] 1.8. Wetting tension of the heat seal layer surface The sealant film of the second invention of this application preferably has a wetting tension of 38 mN / m or more and 55 mN / m or less on the surface of the heat seal layer. The higher the proportion of oxygen atoms on the surface of the heat seal layer, the higher the wetting tension of the surface of the heat seal layer and the greater the 120°C heat seal strength. If the wetting tension of the surface of the heat seal layer is less than 38 mN / m, the 120°C heat seal strength will be low, resulting in insufficient heat seal strength during high-speed automatic filling and packaging. On the other hand, if the wetting tension of the surface of the heat seal layer exceeds 55 mN / m, the films wound on the roll will block each other, making it impossible to unwind the film smoothly. The range of the wetting tension of the surface of the heat seal layer is more preferably 39 mN / m or more and 54 mN / m or less, and even more preferably 40 mN / m or more and 53 mN / m or less.

[0018] 1.9. Thermal shrinkage rate The sealant film of the present invention preferably has a thermal shrinkage rate in both the width direction and the longitudinal direction of 0% or more and 10% or less when treated in 80°C hot water for 10 seconds. If the heat shrinkage rate exceeds 10%, the film shrinks significantly when heat-sealed, resulting in poor flatness after sealing. On the other hand, if the heat shrinkage rate is below zero, it means the film stretches, which is undesirable as it makes it difficult for the film to maintain its original shape, similar to the case of a high shrinkage rate. The upper limit of the heat shrinkage rate is more preferably 9% or less, and even more preferably 8% or less.

[0019] 1.10. Haze The sealant film of the present invention preferably has a haze of 0% or more and less than 10%. A haze of 10% or more is undesirable because transparency is impaired, making it difficult to see the contents when used as a packaging bag. The upper limit of the haze is more preferably 9% or less, and even more preferably 8% or less.

[0020] 1.11. Film Thickness The thickness of the sealant film of the present invention is not particularly limited, but is preferably 3 μm or more and 200 μm or less. A film thickness of less than 3 μm is undesirable because it may result in insufficient heat seal strength and difficulties in processing such as printing. While a film thickness greater than 200 μm is acceptable, it is undesirable because it increases the weight of the film used and thus the chemical costs. A film thickness of 5 μm to 160 μm is more preferable, and 7 μm to 120 μm is even more preferable.

[0021] 2. Composition of sealant film 2.1. Layer composition and heat seal layer ratio of sealant film The sealant film of the present invention may be a single layer consisting only of a heat seal layer, or it may be a laminated structure of two or more layers. However, since heat sealability and heat resistance are mutually exclusive, in the first invention of this application, a laminated structure is preferred because it is possible to maintain the 140°C heat sealability of the heat seal layer while increasing the heat resistance with layers other than the heat seal layer (hereinafter sometimes referred to as the heat-resistant layer). In the second invention of this application, a laminated structure is preferred because it is possible to maintain the 120°C heat sealability of the heat seal layer while increasing the heat resistance with layers other than the heat seal layer. A preferred lamination configuration is one in which a heat seal layer is present on the surface of at least one side of the film. Examples include a two-layer configuration of a heat seal layer / heat-resistant layer, a three-layer configuration of a heat seal layer / heat-resistant layer / heat seal layer, etc., but a two-layer configuration of a heat seal layer / heat-resistant layer is more preferred. When the sealant film of the present invention is constructed in a laminated form, the layer ratio of the heat seal layer is preferably 20% or more and 80% or less. If the layer ratio of the heat seal layer is less than 20%, the heat seal strength of the film will decrease, which is undesirable. If the layer ratio of the heat seal layer is higher than 80%, the heat sealability of the film will improve, but the heat resistance will decrease, which is undesirable. A layer ratio of 30% or more and 70% or less is more preferable.

[0022] 2.2. Lamination Method When the sealant film of the present invention is constructed in a laminated form, the heat-seal layer must be on at least one of the surface layers of the film. To laminate the film with a layer whose raw material is resin (resin layer), various methods can be used, such as in-line film formation by co-extrusion or lamination by bonding after film formation. The former method includes co-extrusion by multi-manifold T-die or inflation method, while the latter method includes extrusion lamination, wet or dry lamination, and hot-melt bonding. In the case of dry lamination, commercially available dry lamination adhesives can be used. Representative examples include DIC Dry® LX-703VL and DIC KR-90 from DIC Corporation, and Takenate® A-4 and Takelac® A-905 from Mitsui Chemicals Corporation. The heat seal layer may be unstretched, uniaxially oriented, or biaxially oriented, but from the viewpoint of strength, it is preferable that it is stretched in at least one direction (uniaxially oriented), and more preferably biaxially oriented. A preferred manufacturing method for biaxially oriented material will be described later.

[0023] 2.3. Surface treatment of the heat seal layer The sealant film of the first invention of this application may have layers that have been treated with coating or flame treatment, regardless of whether they are heat-seal layers or other layers, and inorganic material deposition may also be performed. However, corona treatment and plasma treatment are preferable not to be performed on the heat-seal layer because there is a concern that the heat-seal strength at 100°C will be 5N / 15mm or more. The sealant film of the second invention of this application may have layers that have been treated with corona treatment, plasma treatment, coating treatment, flame treatment, etc., regardless of whether they are a heat-seal layer or other layers, and inorganic material deposition may also be performed. Corona treatment and plasma treatment can increase the proportion of oxygen atoms on the surface, so it is preferable to perform them on the surface of the heat-seal layer. Corona treatment is particularly preferred.

[0024] 2.4. Other layer configurations and layer ratios The sealant film of the present invention may have a three-layer or more configuration, including at least one inorganic thin film layer in addition to the heat seal layer and heat-resistant layer, for the purpose of improving barrier properties. The presence of the inorganic thin film layer can provide gas barrier properties. The inorganic thin film layer and the heat-resistant layer can be in any position, but in order to achieve the required heat seal strength, the heat seal layer must be the outermost layer. A preferred layer order is a configuration in which the outermost layers are the seal layer and the inorganic thin film layer, with the heat-resistant layer in the middle. Furthermore, the layer structure of the laminate may include one or more layers other than the heat seal layer, heat-resistant layer, and inorganic thin film layer. Specifically, these may include an anchor coat layer placed beneath the inorganic thin film layer, an overcoat layer placed on top of the inorganic thin film layer, or resin layers (films) other than the resin layer constituting the sealant film of the present invention.

[0025] The thickness of the inorganic thin film layer is preferably between 2 nm and 100 nm (the ratio of the thickness of the inorganic thin film layer to the total thickness of the laminate is negligibly small). A thickness of less than 2 nm in the inorganic thin film layer is undesirable because it becomes difficult to satisfy the gas barrier properties. On the other hand, a thickness exceeding 100 nm in the inorganic thin film layer is also undesirable because it does not provide a corresponding improvement in gas barrier properties and increases manufacturing costs. A thickness of 5 nm to 97 nm in the inorganic thin film layer is more preferable, and a thickness of 8 nm to 94 nm is even more preferable.

[0026] 3. Raw materials that make up sealant film 3.1. Types of raw materials that make up sealant The sealant film of the present invention must have at least one heat-seal layer made of polyester components, and it is preferable that the polyester components of the heat-seal layer have 2 to 6 oxygen atoms per ester unit. Polyester raw materials mainly composed of ethylene terephthalate are particularly preferred. Here, "main component" means that it contains 50 mol% or more when the total amount of components is 100 mol%. It is preferable that the polyester used in the present invention contains one or more monomer components that can be amorphous components (hereinafter simply referred to as amorphous components) as components other than ethylene terephthalate units. This is because the heat-seal strength is improved by the presence of amorphous components. Examples of monomers that can be amorphous dicarboxylic acid components include isophthalic acid, 1,4-cyclohexanedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid.

[0027] Furthermore, examples of monomers for diol components that can become amorphous components include neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, and hexanediol. Of these amorphous dicarboxylic acid and diol components, isophthalic acid, neopentyl glycol, 1,4-cyclohexanedimethanol, and diethylene glycol are preferred. Using these components increases the amorphousness of the film, making it easier to improve the heat seal strength.

[0028] In the present invention, components other than ethylene terephthalate and amorphous components may be included. Examples of dicarboxylic acid components constituting the polyester include aromatic dicarboxylic acids such as orthophthalic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids. However, it is preferable not to include polycarboxylic acids with a valency of 3 or higher (for example, trimellitic acid, pyromellitic acid, and their anhydrides) in the polyester.

[0029] In addition to the above, other components that make up polyester include long-chain diols such as 1,4-butanediol, aliphatic diols such as hexanediol, and aromatic diols such as bisphenol A. Among these, the inclusion of 1,4-butanediol is preferred. Furthermore, the polyester may also contain polyester elastomers containing ε-caprolactone or tetramethylene glycol as components. These components are preferred as components of the heat seal layer because they have the effect of lowering the melting point of the film. However, it is preferable not to include diols with 8 or more carbon atoms (e.g., octanediol) or polyhydric alcohols with a valency of 3 or higher (e.g., trimethylolpropane, trimethylolethane, glycerin, diglycerin) in polyester, as these significantly reduce the strength of the film.

[0030] The sealant film of the present invention may contain various additives as needed, such as waxes, antioxidants, antistatic agents, nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, and UV absorbers. Furthermore, it is preferable to add fine particles as lubricants to at least the surface layer of the film to improve its slipperiness. Any fine particles can be selected. For example, inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate, while organic fine particles include acrylic resin particles, melamine resin particles, silicone resin particles, and cross-linked polystyrene particles. The average particle size of the fine particles can be appropriately selected within the range of 0.05 to 3.0 μm when measured with a Coulter counter. Among these fine particles, silica and calcium carbonate are preferred to achieve both slipperiness and transparency in the film, with silica being particularly preferred. The preferred amount of additive varies depending on the type of fine particles added and cannot be uniquely determined. However, for example, when silica is used, the preferred amount is 200 ppm to 1000 ppm, more preferably 300 ppm to 900 ppm, and even more preferably 400 ppm to 800 ppm. If the amount of silica added is less than 200 ppm, the slipperiness cannot be sufficiently improved. Also, if the amount of silica added exceeds 1000 ppm, the haze becomes high, which is undesirable.

[0031] As a method for incorporating particles into the sealant film of the present invention, for example, they can be added at any stage in the production of the polyester resin, but it is preferable to add them as a slurry dispersed in ethylene glycol or the like at the esterification stage, or after the completion of the transesterification reaction but before the start of the polycondensation reaction, in order to proceed with the polycondensation reaction. Other methods include blending a slurry of particles dispersed in ethylene glycol, water, or other solvents with the polyester resin raw material using a vented kneading extruder, or blending dried particles with the polyester resin raw material using a kneading extruder.

[0032] When the sealant film of the present invention is constructed in a laminated form, the raw material used for layers other than the heat-seal layer can be the same polyester as that used for the heat-seal layer. For example, a polyester made of components suitable for the aforementioned heat-seal layer can be used to provide a polyester layer with a different composition from the heat-seal layer.

[0033] 3.2. Amount of raw materials in the heat seal layer The polyester used in the heat seal layer of the present invention preferably contains 20 mol% or more of dicarboxylic acid monomers and / or diol monomers other than terephthalic acid and ethylene glycol that constitute ethylene terephthalate, more preferably 25 mol% or more, and particularly preferably 30 mol% or more. The higher the amount of amorphous components, the lower the density, which makes it easier to improve the heat seal strength. Furthermore, the upper limit of the monomer content other than ethylene terephthalate is 50 mol%.

[0034] If the amount of monomers other than ethylene terephthalate in the heat seal layer is less than 30 mol%, even if the molten resin is rapidly cooled and solidified after being extruded from the die, crystallization will occur during the subsequent stretching and heat setting process, making it difficult to achieve a heat seal strength of 8 N / 15 mm or more at 140°C, which is undesirable.

[0035] On the other hand, if the amount of monomers other than ethylene terephthalate in the heat seal layer is 50 mol% or more, the heat resistance of the heat seal layer becomes extremely low. As a result, when heat sealing, blocking occurs around the sealed area (a phenomenon in which a wider area than intended is sealed due to heat conduction from the heating element), making proper heat sealing difficult. It is more preferable that the amount of monomers other than ethylene terephthalate be 48 mol% or less, and particularly preferable that be 46% or less.

[0036] 3.3. Amount of components of the heat-resistant layer In the sealant film of the present invention, when a heat-resistant layer is provided, the polyester used in the heat-resistant layer preferably contains 9 mol% or more of dicarboxylic acid monomers and / or diol monomers that are components other than terephthalic acid and ethylene glycol, which constitute ethylene terephthalate, more preferably 10 mol% or more, and particularly preferably 11 mol% or more. Furthermore, the upper limit of the monomer content other than ethylene terephthalate is 20 mol%.

[0037] If the amount of monomers other than ethylene terephthalate in the heat-resistant layer is less than 9 mol%, the difference in thermal shrinkage rate between it and the seal layer becomes large, which is undesirable because it causes the laminate to curl more. When the difference in the amount of monomers other than ethylene terephthalate in the heat-resistant layer and the seal layer becomes large, the difference in thermal shrinkage rate between each layer during heat setting becomes large, and even if cooling after heat setting is strengthened, shrinkage toward the seal layer becomes large, resulting in a large curl.

[0038] On the other hand, if the amount of monomers other than ethylene terephthalate in the heat-resistant layer is 20 mol% or more, it is undesirable because the heat resistance of the laminate will decrease, such as causing holes to form due to the heat applied during heat sealing. It is more preferable that the amount of monomers other than ethylene terephthalate be 19 mol% or less, and particularly preferable that be 18% or less. Furthermore, the monomer content of components other than ethylene terephthalate for controlling curl is more preferably 10 mol% to 45 mol% and even more preferably 11 mol% to 44 mol% in difference between the amount of each layer individually and the amount of the sealing layer and the heat-resistant layer.

[0039] 3.4. Raw material types and composition of inorganic thin film layers In the sealant film of the present invention, when an inorganic thin film layer is provided, the raw material for the inorganic thin film layer is not particularly limited, and conventionally known materials can be used, and can be appropriately selected according to the purpose in order to satisfy the desired gas barrier properties, etc. Examples of raw material for the inorganic thin film layer include metals such as silicon, aluminum, tin, zinc, iron, and manganese, and inorganic compounds containing one or more of these metals. Examples of applicable inorganic compounds include oxides, nitrides, carbides, and fluorides. These inorganic substances or inorganic compounds may be used individually or in combination. In particular, using silicon oxide and aluminum oxide individually (as a single element) or in combination (as a binary element) is preferable because it can improve the transparency of the laminate. When the inorganic compound consists of a binary of silicon oxide and aluminum oxide, the aluminum oxide content is preferably 20% by mass or more and 80% by mass or less, and more preferably 25% by mass or more and 70% by mass or less. If the aluminum oxide content is 20% by mass or less, the density of the inorganic thin film layer decreases, which may reduce the gas barrier properties, so this is undesirable. Furthermore, if the aluminum oxide content exceeds 80% by mass, the flexibility of the inorganic thin film layer decreases, making it more prone to cracking, which may result in a decrease in gas barrier properties and is therefore undesirable.

[0040] For metal oxides used in inorganic thin film layers, an oxygen / metal elemental ratio of 1.3 or higher and less than 1.8 is preferable because it minimizes variations in gas barrier properties and consistently provides excellent gas barrier performance. The oxygen / metal elemental ratio can be determined by measuring the amounts of each element, oxygen and metal, using X-ray photoelectron spectroscopy (XPS) and calculating the oxygen / metal elemental ratio.

[0041] 4. Method for manufacturing sealant film 4.1. Molten Extrusion The sealant film of the present invention can be obtained by melt-extruding the polyester raw material described in 3. "Raw materials constituting the sealant film" above using an extruder to form an unstretched laminated film, and then uniaxially stretching or biaxially stretching it by the predetermined method shown below. Film obtained by biaxial stretching is more preferable. The polyester can be obtained by polycondensing selected dicarboxylic acid and diol components so as to contain appropriate amounts of monomers other than ethylene terephthalate, as described above. Alternatively, two or more types of chip-shaped polyester can be mixed and used as raw materials for the film.

[0042] When melt-extruding the raw resin, it is preferable to dry each layer of polyester raw material using a dryer such as a hopper dryer or paddle dryer, or a vacuum dryer. After drying each layer of polyester raw material in this way, it is melted at a temperature of 200-300°C using an extruder and extruded as a film. Any existing method such as the T-die method or tubular method can be used for extrusion.

[0043] Subsequently, an unstretched film can be obtained by rapidly cooling the film melted by extrusion. A suitable method for rapidly cooling the molten resin is to cast the molten resin from a die onto a rotating drum and rapidly cool and solidify it to obtain a substantially unoriented resin sheet. The film is preferably stretched in at least one direction, either the longitudinal (longitudinal) direction or the transverse (width) direction, i.e., uniaxial stretching or biaxial stretching. The following describes a sequential biaxial stretching method using longitudinal stretching followed by transverse stretching; however, reversing the order (transverse stretching followed by longitudinal stretching) is also acceptable, as only the primary orientation direction changes. Simultaneous biaxial stretching is also acceptable.

[0044] 4.2. Longitudinal extension For longitudinal stretching, it is preferable to introduce the unstretched film into a longitudinal stretching machine that has multiple rolls arranged in a continuous pattern. When performing longitudinal stretching, it is preferable to preheat the film using a preheating roll until the film temperature reaches 65°C to 90°C. If the film temperature is lower than 65°C, it becomes difficult to stretch in the longitudinal direction and is prone to breakage, which is undesirable. Also, if the temperature is higher than 90°C, the film tends to stick to the rolls, which is undesirable as it can lead to the film wrapping around the rolls and the rolls becoming easily soiled during continuous production. When the film temperature reaches 65°C to 90°C, perform longitudinal stretching. The longitudinal stretching ratio should be between 1x and 5x. 1x means no longitudinal stretching has been performed, so to obtain a transversely oriented film, the longitudinal stretching ratio should be 1x, and to obtain a biaxially oriented film, the longitudinal stretching ratio should be 1.1x or higher. While there is no upper limit to the longitudinal stretching ratio, excessively high ratios make transverse stretching difficult and increase the likelihood of breakage, so it is preferable to keep it at 5x or less.

[0045] Furthermore, by relaxing the film in the longitudinal direction after longitudinal stretching (relaxation in the longitudinal direction), the longitudinal shrinkage rate of the film caused by longitudinal stretching can be reduced. In addition, relaxation in the longitudinal direction can reduce bowing (strain) that occurs in the tenter. This is because in subsequent processes such as transverse stretching and final heat treatment, both ends of the film in the width direction are held while heating, so only the central part of the film shrinks in the longitudinal direction. The relaxation rate in the longitudinal direction is preferably 0% to 70% (a relaxation rate of 0% means no relaxation is performed). The upper limit of the relaxation rate in the longitudinal direction is determined by the raw materials used and the longitudinal stretching conditions, so relaxation cannot be performed beyond this limit. In the sealant film of the present invention, the upper limit of the relaxation rate in the longitudinal direction is 70%. Relaxation in the longitudinal direction can be performed by heating the film after longitudinal stretching at a temperature of 65°C to 100°C or lower and adjusting the speed difference of the rolls. Any of the heating means can be used, such as rolls, near-infrared rays, far-infrared rays, or hot air heaters. Furthermore, longitudinal relaxation can be performed not only immediately after longitudinal stretching, but also, for example, during transverse stretching (including the preheating zone) or the final heat treatment by narrowing the clipping interval in the longitudinal direction (in this case, both ends in the film width direction are also relaxed in the longitudinal direction, thus reducing bowing distortion), and can be performed at any desired timing.

[0046] After relaxing the film in the longitudinal direction (or stretching it longitudinally if relaxation is not performed), it is preferable to cool the film, preferably using a cooling roll with a surface temperature of 20-40°C.

[0047] 4.3. Lateral stretching After longitudinal stretching, it is preferable to perform transverse stretching at a stretching ratio of 3 to 5 times at 65°C to 110°C while holding both ends of the film in the width direction with clips inside the tenter. It is preferable to preheat the film before performing transverse stretching, and preheating should be carried out until the film surface temperature reaches 75°C to 120°C.

[0048] After transverse stretching, it is preferable to pass the film through an intermediate zone where no active heating is performed. Because the temperature in the final heat treatment zone is higher than in the transverse stretching zone of the tenter, without an intermediate zone, heat from the final heat treatment zone (both hot air and radiant heat) will flow into the transverse stretching process. In this case, the temperature in the transverse stretching zone will not be stable, leading not only to a deterioration in the film's thickness accuracy but also to variations in physical properties such as heat seal strength and shrinkage rate. Therefore, it is preferable to pass the transversely stretched film through an intermediate zone for a predetermined time before performing the final heat treatment. In this intermediate zone, it is important to block the accompanying flow associated with the film's movement and the hot air from the transverse stretching zone and the final heat treatment zone so that when a strip of paper is dropped without the film passing through, the strip hangs almost completely vertically. A passage time of 1 to 5 seconds through the intermediate zone is sufficient. Shorter than 1 second results in an insufficient intermediate zone length and inadequate heat blocking effect. On the other hand, a longer intermediate zone is preferable, but if it's too long, the equipment will become too large, so about 5 seconds is sufficient.

[0049] 4.4. Final Heat Treatment After passing through the intermediate zone, it is preferable to perform heat treatment in the final heat treatment zone at a temperature between the stretching temperature and 250°C. Heat treatment can reduce the thermal shrinkage rate of the film, but it will not be effective unless the temperature is above the stretching temperature. In this case, the 80°C hot water shrinkage rate of the film will be higher than 10%, which is undesirable because it will easily wrinkle when heat sealing is performed. The higher the heat treatment temperature, the lower the shrinkage rate of the film, but if it is higher than 250°C, the film haze will be higher than 15%, or the film may melt and fall into the tenter during the final heat treatment process, which is undesirable. The range of the heat treatment temperature is more preferably between 120°C and 240°C, and particularly preferably between 150°C and 220°C.

[0050] Furthermore, while the 140°C heat seal strength increases with higher heat treatment temperatures, the melting of the heat seal layer smooths the surface, increasing the average length RSm of the surface roughness element of the heat seal layer. Therefore, the 100°C heat seal strength increases with higher heat treatment temperatures, and the slipperiness deteriorates. The 140°C heat seal strength and the average length RSm of the surface roughness element of the heat seal layer are determined not only by the heat treatment temperature but also by the component amounts of the raw materials of the heat seal layer, the longitudinal stretching conditions, and the transverse stretching conditions. For this reason, it is not possible to uniquely determine a preferred range of heat treatment temperatures, but in the case of the raw material composition and film formation conditions of the examples described later, the heat treatment temperature is preferably 170°C to 210°C, and more preferably 180°C to 200°C. A heat treatment temperature below 170°C is undesirable because the 140°C heat seal strength is insufficient. Also, a heat treatment temperature exceeding 210°C is undesirable because the 100°C heat seal strength increases and the slipperiness deteriorates.

[0051] During the final heat treatment, the shrinkage rate in the width direction can be reduced by shortening the distance between tenter clips by an arbitrary factor (relaxation in the width direction). Therefore, it is preferable to perform relaxation in the width direction within the range of 0% to 10% during the final heat treatment (a relaxation rate of 0% means no relaxation is performed). Although the shrinkage rate in the width direction decreases as the relaxation rate in the width direction increases, the upper limit of the relaxation rate (the shrinkage rate in the width direction of the film immediately after transverse stretching) is determined by the raw materials used, the stretching conditions in the width direction, and the heat treatment temperature, so relaxation cannot be performed beyond this limit. In the sealant film of the present invention, the upper limit of the relaxation rate in the width direction is 10%.

[0052] Furthermore, the passage time through the final heat treatment zone is preferably between 2 seconds and 20 seconds. If the passage time is less than 2 seconds, the film will pass through the heat treatment zone before its surface temperature reaches the set temperature, rendering the heat treatment ineffective. The longer the passage time, the more effective the heat treatment becomes, so a passage time of 2 seconds or more is preferable, and 5 seconds or more is even preferable. However, increasing the passage time would require larger equipment, so for practical purposes, 20 seconds or less is sufficient.

[0053] 4.5. Cooling After the final heat treatment, it is preferable to cool the film in a cooling zone with cooling air at a temperature of 10°C to 30°C. At this time, it is preferable to improve the cooling efficiency by lowering the temperature of the cooling air or increasing the airflow speed so that the actual temperature of the film at the tenter exit is lower than the glass transition temperature of the heat seal layer. The actual temperature refers to the film surface temperature measured with a non-contact radiation thermometer. If the actual temperature of the film at the tenter exit exceeds the glass transition temperature, it is undesirable because the film will shrink due to heat when both ends of the film, which were held by clips, are released.

[0054] The passage time through the cooling zone is preferably between 2 seconds and 20 seconds. If the passage time is less than 2 seconds, the film will pass through the cooling zone before its surface temperature reaches the glass transition temperature. The longer the passage time, the greater the cooling effect, so a passage time of 2 seconds or more is preferable, and 5 seconds or more is even preferable. However, increasing the passage time would require larger equipment, so for practical purposes, 20 seconds or less is sufficient. Finally, by cutting and removing the ends of the film while winding it up, a roll of sealant film is obtained.

[0055] 4.6. Corona treatment In the second invention of this application, it is preferable to corona treat the surface of the heat seal layer with a corona treatment device after cooling. The degree of corona treatment is determined by the line speed of the sealant film, the corona treatment voltage, and the roll temperature. Therefore, it is not possible to uniquely determine these preferred ranges of conditions, but by making the wetting tension of the heat seal layer surface after corona treatment 38 mN / m or higher, the abundance ratio of oxygen atoms on the heat seal layer surface can be made higher than 26.5%. Furthermore, it is preferable to perform the corona treatment in air.

[0056] 5. Types of contents The sealant film of the present invention has the characteristic of being less adsorbent of organic compounds contained in chemical products, pharmaceuticals, foods, etc., and is preferable for packaging the contents described below. Examples of the contents include d-limonene, citral, citronellal, p-menthane, pinene, terpinene, myrcene, carene, geraniol, nerol, citronellal, terpineol, l-menthol, nerolidol, borneol, dl-camphor, lycopene, carotene, trans-2- Hexenal, cis-3-hexenol, β-ionone, selinen, 1-octen-3-ol, Examples of aromatic and medicinal components include benzyl alcohol, octartulobuterol hydrochloride, and tocopherol acetate.

[0057] However, the sealant film of the present invention has a heat-seal layer made of polyester components, and the polyester components of the heat-seal layer contain 2 to 6 oxygen atoms per ester unit. Therefore, the adsorption tends to increase for contents with a similar chemical structure that contains many oxygen atoms. The ratio of oxygen atoms to carbon atoms in the contents is proportional to the amount of adsorption by the sealant film of the present invention. The sealant film of the present invention is not suitable for packaging contents with an oxygen atom to carbon atom ratio of 0.2 or higher, such as eugenol or methyl salicylate. When the amount of adsorption is measured by the method described in the examples below, the preferred range of adsorption is 10 μg / cm³. 2 The following is the case: 6 μg / cm³ 2 The following is more preferable: 2 μg / cm³ 2 The following are even more preferable.

[0058] 6. Packaging composition and bag-making method The sealant film of the present invention can be suitably used as a packaging material. The sealant of the present invention can be used to form a bag on its own, or it can be used as a laminate by laminating other materials. Examples of other layers constituting the sealant include, but are not limited to, an unoriented film containing polyethylene terephthalate as a component, an unoriented, uniaxially oriented, or biaxially oriented film containing other amorphous polyesters as a component, an unoriented, uniaxially oriented, or biaxially oriented film containing nylon as a component, or an unoriented, uniaxially oriented, or biaxially oriented film containing polypropylene as a component. The method of using the sealant in the packaging material is not particularly limited, and conventionally known manufacturing methods such as coating, lamination, and heat sealing can be employed.

[0059] The packaging body may be composed of at least a portion of the sealant according to the present invention, but it is preferable that the entire packaging body is composed of the sealant described above. Furthermore, the sealant of the present invention may be in any layer of the packaging body, but considering non-adsorption to the contents and seal strength when forming the bag, it is preferable that the heat-sealed layer of the sealant of the present invention be the innermost layer of the bag.

[0060] The method for forming a packaging body having the sealant of the present invention is not particularly limited, and conventionally known manufacturing methods such as heat sealing using a heat bar (heat jaw), bonding using hot melt, and center sealing with a solvent can be employed. The packaging material having the sealant of the present invention can be suitably used as a packaging material for various articles such as food, pharmaceuticals, and industrial products. [Examples]

[0061] Next, the present invention will be specifically described using examples and comparative examples. However, the present invention is not limited in any way to the embodiments of these examples, and can be modified as appropriate without departing from the spirit of the invention. The method for evaluating the film is as follows. If the length and width directions cannot be immediately determined due to the small area of ​​the film, for example, it is acceptable to tentatively define the length and width directions and take measurements accordingly. There is no particular problem if the tentatively defined length and width directions are 90 degrees different from the true directions.

[0062] <Film Evaluation Methods> [density] The density was determined by immersing the film in a density gradient solution (calcium nitrate aqueous solution) in accordance with JIS K7112.

[0063] [Average length of surface roughness elements in the heat seal layer (RSm)] In accordance with JIS B0601:2013, the heat-sealed surface was measured using the "ET4000A" three-dimensional micro-shape measuring instrument manufactured by Kosaka Laboratory Co., Ltd., under conditions of a measurement speed of 0.2 mm / second and a cutoff of 0.25 mm.

[0064] [Heat seal strength at 100℃] The heat seal strength was measured in accordance with JIS Z1707. The specific procedure is briefly described below. The heat-sealed surfaces of samples that had not undergone any coating treatment were bonded together using a heat sealer. The heat-sealing conditions were: heat-seal width 10 mm, upper bar temperature 100°C, lower bar temperature 30°C, pressure 0.2 MPa, and time 2 seconds. The bonded samples were cut to have a seal width of 15 mm. The peel strength was measured using a Shimadzu Corporation universal tensile testing machine "DSS-100" at a tensile speed of 200 mm / min. The peel strength is expressed as strength per 15 mm (N / 15 mm).

[0065] [Heat seal strength at 120℃] The evaluation was performed in the same manner as the 100°C heat seal strength evaluation method, except that the upper bar temperature was changed to 120°C.

[0066] [Heat seal strength at 140℃] The evaluation was performed in the same manner as the 100°C heat seal strength evaluation method, except that the upper bar temperature was changed to 140°C.

[0067] [Coefficient of dynamic friction of the heat seal layer] In accordance with JIS K7125, a tensile testing machine (ORIENTEC Tensilon) was used. The coefficient of dynamic friction μd was determined when two heat-sealed surfaces were joined together under conditions of 23°C and 65% RH. The weight of the thread (weight) to which the upper film was wrapped was 1.5 kg, and the base area of ​​the thread was 63 mm x 63 mm. The tensile speed during friction measurement was 200 mm / min.

[0068] [Oxygen atom abundance ratio on the heat seal layer surface] Using a Thermo Fisher Scientific K-Alpha+ XPS spectrometer, narrow scans of carbon, nitrogen, oxygen, and silicon were performed to evaluate the relative abundance of oxygen atoms on the surface of the heat seal layer. Monochromatic AlKα was used as the excitation X-ray, and the evaluation was performed with an X-ray output of 12kV, 6mA, a photoemission angle of 90°, a spot size of 400μmφ, a pass energy of 50eV (narrow scan), and a step of 0.1eV (narrow scan).

[0069] [Wetting tension of the heat-sealed layer surface] The wetting tension of the heat seal layer surface was evaluated in accordance with JIS K6768:1999.

[0070] [Hayes] Measurements were taken in accordance with JIS-K-7136 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., 300A). Two measurements were taken, and the average value was calculated.

[0071] [80℃ Hot Water Heat Contraction Rate] The film was cut into 10cm x 10cm squares, immersed in 80±0.5℃ warm water for 10 seconds without load to shrink it, and then immersed in 25℃±0.5℃ water for 10 seconds before being removed from the water. Afterward, the lengthwise and widthwise dimensions of the film were measured, and the shrinkage rate in each direction was calculated according to Equation 1 below. The measurement was performed twice, and the average value was calculated. Shrinkage rate = { (Length before shrinkage - Length after shrinkage) / Length before shrinkage} × 100 (%) Formula 1

[0072] [Adsorption amount] The film was cut into a 10 cm × 10 cm square, and two pieces were overlapped with the heat-sealing surface facing inward. A bag was created by heat-sealing at a position 1 cm from the film edge. An aluminum cup containing 0.5 ml of the contents was placed in the bag, and the bag was closed and sealed by heat-sealing at a position 1 cm from the film edge. For the said contents, D-limonene (manufactured by Tokyo Chemical Industry Co., Ltd.) and D-camphor (manufactured by Nacalai Tesque, Inc.) were used. After holding for 20 hours in a 30 °C environment, a 5 cm × 5 cm square was cut from the surface of the film bag that contacts the mouth of the aluminum cup. The cut film was immersed in 4 ml of the extraction solvent and extracted with ultrasonic waves for 30 minutes. For the extraction solvent of D-limonene, 99.8% ethanol (manufactured by Fujifilm Wako Pure Chemical Corporation) was used, and for the extraction solvent of D-camphor, 99.8% methanol (manufactured by Fujifilm Wako Pure Chemical Corporation) was used. The concentration of the contents in the extraction solution was quantified using a gas chromatograph "GC-14B" manufactured by Shimadzu Corporation. For the gas chromatograph, "GC-14A Glass I.D.2.6φx1.1m PET-HT 5% Uniport HP 80 / 100 (manufactured by GL Sciences Inc.)" was used for the column, FID was used for the detector, N2 was used for the carrier gas, and quantification was performed by the area percentage method at a carrier gas flow rate of 35 ml / min and an injection volume of 1 μl. The adsorption amount is the adsorption amount per 1 cm 2 of the heat-sealing surface (μg / cm 2 ), and low adsorption was determined as follows. Judgment ○ 0 μg / cm 2 or more and less than 2 μg / cm 2 Judgment △ 2 μg / cm<于 2 or more and less than 10 μg / cm<于 2 Judgment × 10 μg / cm<于 2 or more

[0073] [Blocking evaluation] ​​The film was cut into 10cm x 10cm squares, and five pieces were stacked with the heat-sealed side and the non-heat-sealed side in contact. A 5kg weight was placed on top, and the stack was left undisturbed in a 40°C environment for 2 hours. After standing, the weight was removed, and the condition of the film was determined as follows when the film was picked up one by one by hand. Verification: No blocking marks or tears on any of the 5 films. Judgment: × One or more of the 5 films have blocking marks or tears.

[0074] [Suitability for boiling in packaging bags] The film was cut into 12cm x 12cm squares, and two pieces were stacked with the heat-seal side facing inward. The bags were then heat-sealed to create a bag with an inner diameter of 10cm x 10cm. The heat-sealing conditions were: heat-seal width 10mm, upper bar temperature 140℃, lower bar temperature 30℃, pressure 0.2MPa, and time 2 seconds. The created bags were heated in 100℃ boiling water for 30 minutes and then cooled. One side of the bag was cut with scissors to check the condition of the inside of the bag and the following judgment was made. Verdict: ○ There is no sticking between the inner surfaces of the bags, and the bags can be easily opened. Judgment: × The inside surfaces of the bags are stuck together, making it impossible to open them.

[0075] [Loss of the bag evaluation] A bag was created by cutting the film into a 20cm x 20cm square, stacking two pieces with the heat-seal side facing inward, and heat-sealing 1cm from the edge of the film. The heat-sealing conditions were: heat-seal width 10mm, upper bar temperature 120℃, lower bar temperature 30℃, pressure 0.2MPa, and time 2 seconds. Two rolled Kimtowels (manufactured by Nippon Paper Crecia), which had been soaked in water to adjust their weight to 100g, were placed in the bag, and the bag was sealed by heat-sealing 1cm from the edge of the opening using the same heat-sealing conditions as when the bag was made. The prepared sealed bags were repeatedly dropped from a height of 1 meter five times, and the number of drops until the bag broke was calculated as the bag drop score, as shown below. The bag drop score was calculated as the sum after five trials (maximum 4 points x 5 times = 20 points). Bag torn on the first try. 0 points. The bag broke on the second try. 1 point. The bag broke on the third try. 2 points. The bag broke on the fourth try. 3 points. The bag broke on the 5th try. 4 points. Furthermore, the following judgments were made based on the score of the lost bags. Judgment: ○ Bag drop score: 10 points or higher Judgment: × Lost bag score: 9 points or less

[0076] <Preparation of polyester raw materials> [Synthesis Example 1] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 100 mol% dimethyl terephthalate (DMT) as the dicarboxylic acid component and 100 mol% ethylene glycol (EG) as the polyhydric alcohol component were charged so that the molar ratio of ethylene glycol was 2.2 times that of dimethyl terephthalate. Using 0.05 mol% zinc acetate (relative to the acid component) as a transesterification catalyst, the transesterification reaction was carried out while distilling off the resulting methanol. Subsequently, 0.225 mol% antimony trioxide (relative to the acid component) was added as a polycondensation catalyst, and the polycondensation reaction was carried out at 280°C under reduced pressure of 26.7 Pa to obtain polyester (A) with an intrinsic viscosity of 0.75 dl / g. This polyester (A) is polyethylene terephthalate. The composition of polyester (A) is shown in Table 1.

[0077] [Synthesis Example 2] Polyesters (B) to (G) were obtained by changing the monomer using the same procedure as in Synthesis Example 1. The composition of each polyester is shown in Table 1. In Table 1, TPA is terephthalic acid, IPA is isophthalic acid, EG is ethylene glycol, BD is 1,4-butanediol, NPG is neopentyl glycol, CHDM is 1,4-cyclohexanedimethanol, and DEG is diethylene glycol. When producing polyester (G), SiO2 (Silysia 266, manufactured by Fuji Silysia Co., Ltd.) was added as a lubricant at a ratio of 7,000 ppm relative to the polyester. Each polyester was made into chips as appropriate. The intrinsic viscosities of each polyester were B: 0.73 dl / g, C: 0.69 dl / g, D: 0.73 dl / g, E: 0.74 dl / g, F: 0.80 dl / g, and G: 0.75 dl / g, respectively. The composition of polyesters (B) to (G) is shown in Table 1.

[0078] [Table 1]

[0079] [Examples 1, 7] Polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 10:60:24:6 as the raw material for the heat seal layer, and polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 51:37:6:6 as the raw material for the heat-resistant layer. The mixed raw materials for the heat-seal layer and the heat-resistant layer were fed into separate twin-screw extruders and melted at 270°C. The molten resins were joined together by a feed block midway through the flow path and extruded from a T-die, where they were cooled on a chill roll set to a surface temperature of 30°C to obtain an unstretched laminated film. The flow path of the molten resin was set so that one side of the laminated film was the heat-seal layer and the other side was the heat-resistant layer (a two-layer structure of two types: heat-seal layer / heat-resistant layer), and the extrusion rate was adjusted so that the thickness ratio of the heat-seal layer to the heat-resistant layer was 50:50. The unstretched laminated film obtained by cooling and solidifying was guided to a longitudinal stretcher with multiple rolls arranged in a series. After preheating on a preheating roll until the film temperature reached 80°C, it was stretched to 4.1 times its original length. Immediately after longitudinal stretching, the film was passed through a heating furnace set to 90°C with a hot air heater, and a 20% relaxation treatment was performed in the longitudinal direction using the speed difference between the rolls at the inlet and outlet of the heating furnace. Subsequently, the longitudinally stretched film was forcibly cooled by a cooling roll set to a surface temperature of 25°C.

[0080] After the relaxation treatment, the film was guided to a tenter and preheated for 5 seconds until the surface temperature reached 95°C, and then stretched 4.0 times in the width direction (lateral direction). The stretched film was then guided to an intermediate zone and passed through for 1.0 second. In the intermediate zone of the tenter, the hot air from the final heat treatment zone and the hot air from the lateral stretching zone were blocked so that when a strip of paper was hung down without the film passing through, the strip of paper would hang almost completely vertically. Subsequently, the film that had passed through the intermediate zone was guided to the final heat treatment zone and heat-treated at 180°C for 5 seconds. At the same time as the heat treatment, the clip spacing in the width direction of the film was narrowed, thereby performing a 3% relaxation treatment in the width direction. After passing through the final heat treatment zone, the film was cooled, and both edges were cut off and wound into a roll with a width of 500 mm, thereby continuously producing a biaxially oriented film with a thickness of 30 μm over a predetermined length. This film was designated as Example 1.

[0081] Furthermore, the film after passing through the final heat treatment zone was cooled, and corona discharge treatment was performed at room temperature using an in-line corona treatment device (manufactured by Kasuga Electric Co., Ltd.) to achieve a wetting tension of 38 mN / m or more on the surface of the heat seal layer. The corona treatment power used at that time was 1.8 kW. Subsequently, both edges were cut off and the film was wound into a roll with a width of 500 mm to continuously produce a biaxially oriented film with a thickness of 30 μm over a predetermined length. This film was designated as Example 7. The properties of the obtained film were evaluated using the method described above. The manufacturing conditions and evaluation results are shown in Tables 2 and 3.

[0082] [Examples 2-5, Comparative Examples 1 and 2] Examples 2-5 and Comparative Examples 1 and 2 were prepared by laminating a heat-seal layer and a heat-resistant layer in the same manner as in Example 1. Polyester-based sealants were then fabricated and evaluated by varying the raw material mixing ratios and final heat treatment conditions. Table 2 shows the film manufacturing conditions and evaluation results for each example and comparative example.

[0083] [Examples 8-11, Comparative Examples 8 and 9] Examples 8-11 and Comparative Example 8 were prepared by laminating a heat-seal layer and a heat-resistant layer in the same manner as in Example 7. Polyester-based sealants were then fabricated and evaluated by varying the raw material mixing ratio, final heat treatment conditions, and corona treatment conditions (comparative example 8 did not undergo corona treatment). The film manufacturing conditions and evaluation results for each example and comparative example are shown in Table 3.

[0084] [Example 6] As raw materials for the heat seal layer, polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 10:60:24:6. The subsequent steps were carried out in the same manner as in Example 1, with only the final heat treatment temperature changed to 200°C to produce a polyester sealant film consisting only of layer A with a thickness of 15 μm. In addition, as raw materials for the heat-resistant layer, polyester A and polyester G were mixed in a mass ratio of 94:6. The subsequent steps were carried out in the same manner as in Example 1, with only the final heat treatment temperature changed to 230°C to produce a polyester film consisting only of layer B with a thickness of 45 μm. The polyester sealant film consisting only of layer A was used as the heat seal layer, and the polyester film consisting only of layer B was used as the heat-resistant layer. The two films were bonded together with a dry lamination adhesive (Takelac® A-950, manufactured by Mitsui Chemicals, Inc.). The manufacturing conditions and evaluation results are shown in Table 2.

[0085] [Example 12] As raw materials for the heat seal layer, polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 10:60:24:6. The subsequent steps were carried out in the same manner as in Example 1, with the final heat treatment temperature changed to 200°C and the corona treatment power to 2.7kW to produce a polyester sealant film consisting only of layer A. In addition, as raw materials for the heat-resistant layer, polyester A and polyester G were mixed in a mass ratio of 94:6. The subsequent steps were carried out in the same manner as in Example 1, with the final heat treatment temperature changed to 230°C to produce a polyester film consisting only of layer B. The polyester sealant film consisting only of layer A was used as the heat seal layer, and the polyester film consisting only of layer B was used as the heat-resistant layer. The two films were bonded together with a dry lamination adhesive (Takelac® A-950, manufactured by Mitsui Chemicals, Inc.). The manufacturing conditions and evaluation results are shown in Table 3.

[0086] [Comparative Example 3] Polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 5:66:24:5 as the raw materials for the heat seal layer. The subsequent steps were carried out in the same manner as in Example 1, with only the final heat treatment temperature changed to 170°C to produce a polyester-based sealant consisting only of layer A, which was then evaluated. The manufacturing conditions and evaluation results are shown in Table 2.

[0087] [Comparative Example 4] Polyester A and polyester G were mixed in a mass ratio of 94:6 as the raw materials for the heat seal layer. The subsequent steps were carried out in the same manner as in Example 1, with only the final heat treatment temperature changed to 230°C to produce a polyester-based sealant consisting only of layer A, which was then evaluated. The manufacturing conditions and evaluation results are shown in Table 2.

[0088] [Comparative Example 5] Comparative Example 4 used Rixfilm® L4102-25μm manufactured by Toyobo Co., Ltd. The evaluation results are shown in Table 2.

[0089] [Comparative Example 6] Comparative Example 5 used Pyrene Film-CT(registered trademark) P1128-25μm manufactured by Toyobo Co., Ltd. The evaluation results are shown in Table 2.

[0090] [Comparative Example 7] Polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 9:75:10:6 as the raw material for the heat seal layer, and polyester A, polyester B, polyester F, and polyester G were mixed in a mass ratio of 47:37:10:6 as the raw material for the heat-resistant layer. The flow path of the molten resin was set so that the laminated film had a heat seal layer on the surface and a heat-resistant layer on the inside (a 2-type, 3-layer structure of heat seal layer / heat-resistant layer / heat seal layer). The discharge amount was adjusted so that the thickness ratio of each layer was 25:50:25, and the final heat treatment temperature was changed to 115°C. A polyester-based sealant was manufactured and evaluated in the same manner as in Example 1, except that corona treatment was not performed. The manufacturing conditions and evaluation results are shown in Table 3.

[0091] [Comparative Example 10] Comparative Example 10 used Rixfilm® L4102-25μm manufactured by Toyobo Co., Ltd. The evaluation results are shown in Table 3.

[0092] [Comparative Example 11] Comparative Example 11 used Pyrene Film-CT(registered trademark) P1128-25μm manufactured by Toyobo Co., Ltd. The evaluation results are shown in Table 3.

[0093] [Table 2]

[0094] [Table 3]

[0095] [Film evaluation results] As shown in Table 2, the films from Examples 1 to 6 all had average lengths RSm of density and surface roughness of the heat seal layer within the specified range, and exhibited excellent performance in 100°C heat seal strength and 140°C heat seal strength, dynamic friction coefficient of the heat seal layer, haze, 80°C hot water shrinkage rate, low adsorption, and boilability in packaging bags, resulting in favorable evaluation results. On the other hand, the film of Comparative Example 1 had excellent heat seal strength at 100°C, dynamic friction coefficient of the heat seal layer, haze, 80°C hot water shrinkage rate, low adsorption, and suitability for boiling in packaging bags, but its heat seal strength at 140°C was low due to the low final heat treatment temperature.

[0096] Furthermore, in Comparative Examples 2 and 3, the heat seal layer melts during the final heat treatment, resulting in a smoother surface and a longer average length RSm of the surface roughness element of the heat seal layer. Therefore, the 100°C seal strength is high, but the suitability for boiling in packaging bags is poor. In addition, the coefficient of dynamic friction of the heat seal layer is high, which may cause wrinkles to form when winding the film onto a roll, potentially reducing winding quality. The film in Comparative Example 4 has a high density of 1.394 and low heat seal strength at 140°C, making it unsuitable as a sealant film. The films of Comparative Examples 5 and 6 use olefin-based films, and therefore have poor low-adsorption properties. In addition, the film of Comparative Example 5 also has low heat seal strength at 140°C.

[0097] As shown in Table 3, the films from Examples 7 to 12 all had an oxygen atom ratio within the specified range on the surface of the heat seal layer, exhibited excellent 120°C and 140°C heat seal strength, dynamic friction coefficient of the heat seal layer, haze, 80°C hot water shrinkage rate, and low adsorption, and the blocking evaluation and bag drop evaluation results were also good. On the other hand, while the film of Comparative Example 7 exhibited excellent 140°C heat seal strength, dynamic friction coefficient of the heat seal layer, haze, 80°C hot water shrinkage rate, low adsorption, and boilability in packaging bags, its 120°C heat seal strength was low due to the oxygen atom content on the surface of the heat seal layer being 26.5% or less, resulting in a tendency to tear during bag drop evaluation.

[0098] Furthermore, the film of Comparative Example 8 is unsuitable as a sealant film because the oxygen atom content on the surface of the heat seal layer is 26.5% or less, resulting in low heat seal strength at 120°C and also low heat seal strength at 140°C. The film of Comparative Example 9 had an oxygen atom content of 31.0% or more on the surface of the heat seal layer, resulting in excellent heat seal strength at 120°C, but the films blocked each other.

[0099] Because the films of Comparative Examples 10 and 11 use olefin-based films, they have poor low-adsorption properties. In addition, the film of Comparative Example 10 has low heat seal strength at 140°C, and the film of Comparative Example 11 has low heat seal strength at 120°C. [Industrial applicability]

[0100] The first invention of this application provides a sealant film that is resistant to the adsorption of various organic compounds, has excellent heat-sealing properties at 140°C, and has low heat-sealing strength at 100°C, making it difficult for the heat-sealing layers to stick together when used as a packaging bag and the contents are heated by boiling in hot water. The second invention of this application provides a sealant film that is less likely to adsorb various organic compounds, has excellent heat sealability at 140°C, and also has excellent heat sealability at a lower temperature of 120°C, thus providing sufficient heat seal strength even in high-speed automated filling and packaging. Furthermore, the present invention can also be a laminate containing at least one layer of the sealant film, and a packaging bag can be made from such a laminate.

Claims

1. A low-adsorption sealant film comprising at least one polyester-based component and having a corona-treated heat-sealed layer, wherein the average length RSm of the surface roughness elements determined by a three-dimensional roughness meter is 18 μm or more and 29 μm or less, and satisfying the following conditions (1) to (3). (1) When heat-seal layers are sealed together at 120°C, 0.2 MPa, and for 2 seconds, the seal strength is 4 N / 15 mm or more and 15 N / 15 mm or less. (2) When heat-seal layers are sealed together at 140°C, 0.2 MPa, and for 2 seconds, the seal strength is 8 N / 15 mm or more and 30 N / 15 mm or less. (3) In the heat seal layer, the oxygen atom abundance determined by X-ray electron spectroscopy (ESCA) is 26.6% or more and 31.0% or less. (4) The wetting tension of the heat seal layer surface is 38 mN / m or more.

2. The low-adsorption sealant film according to claim 1, wherein the coefficient of dynamic friction between the heat-sealed surfaces is 0.30 or more and 0.80 or less.

3. The low-adsorption sealant film according to claim 1 or 2, wherein the components constituting the film are polyester mainly composed of ethylene terephthalate.

4. A low-adsorption sealant film according to any one of claims 1 to 3, wherein the polyester-based components constituting the heat-seal layer contain a diol monomer component other than ethylene glycol, and the diol monomer component is one or more of neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4-butanediol, and diethylene glycol.

5. A low-adsorption sealant film according to any one of claims 1 to 4, wherein the thermal shrinkage rate when treated in 80°C hot water for 10 seconds is 0% or more and 10% or less in both the longitudinal and width directions.

6. A laminate characterized by comprising at least one layer of sealant film according to any one of claims 1 to 5.

7. A packaging bag characterized by using at least a portion of the sealant film according to any one of claims 1 to 5, or the laminate according to claim 6.

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