Polyester film, vacuum formed body or pressure formed body, laminate for vacuum forming or laminate for pressure forming, and use thereof

Abstract

The present invention addresses the problem of providing a polyester film and the like having excellent vacuum formability and / or pressure formability. To solve this problem, the polyester film contains: a first polyester resin that is a polymer of a first acid unit including a terephthalic acid unit and a first alcohol unit including a 1,4-butanediol unit; and a second polyester resin that is a polymer of a second acid unit including a terephthalic acid unit and a second alcohol unit including an ethylene glycol unit. The mass ratio (A / B) of the content A of the first polyester resin to the content B of the second polyester resin is 0.8-10. When differential scanning calorimetry is performed at a temperature increase rate of 10 °C / minute and a measurement temperature range of 0-300 °C, there is a cold crystallization peak indicating a cold crystallization heat quantity, the area of the cold crystallization peak is 10 J / g or more, and the peak top temperature is 50-105 °C.

Description

Polyester film, vacuum-formed or pressure-formed body, and laminate for vacuum forming or pressure forming, and uses thereof Related Applications

[0001] This application claims priority from Japanese Patent Application No. 2024-154679, filed on September 9, 2024, and incorporates by reference all the contents of that Japanese patent application.

[0002] The present invention relates to a polyester film, a vacuum-formed or pressure-formed article, a laminate for vacuum forming or a laminate for pressure forming, and a food and drink package, a pharmaceutical package, a medical instrument package, and an electric or electronic component package.

[0003] Conventionally, a vacuum-formed or pressure-formed body has been used, which is produced by using a polyester film to form a base material having a storage recess by vacuum forming and / or pressure forming, filling the storage recess with an item to be stored, such as processed meat products such as ham and sausage, processed seafood products, prepared foods, retort pouch foods, infusion packs, medicines, medical equipment, electronic components, or semiconductors, and then heat-sealing a film that serves as a lid to the base material.

[0004] As such a polyester film, for example, a polyester film for use in thermoforming or vacuum forming has been proposed, which is made of a polyester resin composition containing 10% to 90% by mass of a polyethylene terephthalate resin and 90% to 10% by mass of a polybutylene terephthalate resin and has a planar orientation coefficient of 0.155 or more (see, for example, Patent Document 1). Here, the planar orientation coefficient is a value calculated from the refractive index in the longitudinal stretching direction, the refractive index in the transverse stretching direction, and the refractive index in the thickness direction, and the polyester film of Patent Document 1 having a planar orientation coefficient of 0.155 or more is a stretched film.

[0005] Furthermore, a longitudinally uniaxially stretched film has been proposed, which is made of a polyester resin composition comprising 50% by mass to 70% by mass of a polyester (a) whose dicarboxylic acid component is terephthalic acid and whose glycol component is 1,4-butanediol, and 50% by mass to 30% by mass of a polyester (b) whose dicarboxylic acid component is terephthalic acid and whose glycol component is ethylene glycol (see, for example, Patent Document 2).

[0006] Furthermore, a deep drawing film containing 80% by mass or more of polybutylene terephthalate has been proposed (see, for example, Patent Document 3). The deep drawing film in Patent Document 3 may be a non-stretched film or a uniaxially or biaxially stretched film, but it is described that a biaxially stretched film is preferable from the viewpoint of improving dimensional stability, heat resistance, and mechanical strength (see paragraph

[0029] ). Furthermore, Example 1 of Patent Document 3 uses biaxially stretched PBT, and the Reference Example uses biaxially stretched PET.

[0007] Japanese Patent Application Laid-Open No. 2005-60617 Japanese Patent No. 5348944 Japanese Patent Application Laid-Open No. 2018-203273

[0008] The polyester films described in the above prior art documents are stretched films containing polybutylene terephthalate resin and / or polyethylene terephthalate resin and subjected to a stretching treatment. Therefore, when the polyester films are vacuum-formed and / or pressure-formed using a mold with a drawing ratio of, for example, 0.6 to 1, there are problems in that breaks and / or pinholes occur in the polyester film, and the polyester film cannot be molded neatly by conforming it to the entire surface of the mold, including the corners.

[0009] Here, the drawing ratio of the mold is calculated by dividing the diameter of the mold bottom by the diameter of the mold opening. A mold with a drawing ratio of 1 (maximum) is most difficult to vacuum and / or pressure form. Furthermore, a mold with a drawing ratio of 0.6 or more but less than 1 has a large drawing ratio, making it difficult to vacuum and / or pressure form. The diameter of the mold bottom and the diameter of the mold opening refer to the largest linear distance between any two points on the outer periphery of the mold bottom and the mold opening.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a polyester film, a vacuum-formed body or a pressure-formed body, a laminate for vacuum forming or a laminate for pressure forming, and a food and beverage package, a pharmaceutical package, a medical device package, and an electrical component package or an electronic component package, each having excellent vacuum formability and / or pressure formability.

[0011] The polyester film of the present invention contains a first polyester resin which is a polymer of first acid units containing terephthalic acid units and first alcohol units containing 1,4-butanediol units, and a second polyester resin which is a polymer of second acid units containing terephthalic acid units and second alcohol units containing ethylene glycol units. The mass ratio (A / B) of the content A of the first polyester resin to the content B of the second polyester resin is 0.8 to 10. When the polyester film is subjected to differential scanning calorimetry at a heating rate of 10°C / min within a measurement temperature range of 0°C to 300°C, the film has a cold crystallization peak indicating the heat of cold crystallization, the area of ​​the cold crystallization peak being 10 J / g or more, and the peak top temperature being 50°C to 105°C.

[0012] In one embodiment of the polyester film of the present invention, the crystallinity calculated from the following mathematical formula A is preferably 28% or less. [Formula A] Crystallinity={(total endothermic amounts of all endothermic peaks within the measurement range)−(heat of cold crystallization)} / [{(heat of fusion of first perfectly crystalline polybutylene terephthalate)×(content of first polyester resin) / 100}+{(heat of fusion of second perfectly crystalline polyethylene terephthalate)×(content of second polyester resin) / 100}]×100 Heat of fusion of first perfectly crystalline polybutylene terephthalate: 145.3 J / g (literature value) Heat of fusion of second perfectly crystalline polyethylene terephthalate: 140.0 J / g (literature value) The total endothermic amounts of all endothermic peaks within the measurement range is calculated by summing the endothermic amounts of all endothermic peaks in a DSC chart obtained by measurement using a differential scanning calorimeter at a heating rate of 10°C / min in a temperature range of 0°C to 300°C. The calorific value of cold crystallization is calculated by summing the calorific values ​​of all exothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a temperature rise rate of 10°C / min in a temperature range of 0°C to 300°C.

[0013] In one embodiment of the polyester film of the present invention, it is preferred that the tensile elongation at break in the longitudinal direction and the width direction at 23°C is 500% or more, and the tensile strength at break in the longitudinal direction and the width direction at 23°C is 100 MPa or less.

[0014] In one embodiment of the polyester film of the present invention, it is preferably an unstretched film of a single layer structure having a thickness of 25 μm or more.

[0015] In one embodiment of the polyester film of the present invention, the content of the first polyester resin is preferably 50% by mass to 80% by mass.

[0016] In one embodiment of the polyester film of the present invention, the content of 1,4-butanediol units is preferably 90 mol % or more based on the total amount of the first alcohol units.

[0017] In one embodiment of the polyester film of the present invention, the content of ethylene glycol units is preferably 90 mol % or more based on the total amount of the second alcohol units.

[0018] In one embodiment of the polyester film of the present invention, the second acid unit preferably further contains an isophthalic acid unit.

[0019] In one embodiment of the polyester film of the present invention, the intrinsic viscosity at 20° C. is preferably 0.8 dl / g or more.

[0020] The vacuum-formed or pressure-formed article of the present invention comprises the polyester film of the present invention.

[0021] In one embodiment of the vacuum-formed or pressure-formed article of the present invention, it is preferable that the article is vacuum-formed and / or pressure-formed using a mold having a molding section with a depth of 10 mm, a diameter of the mold bottom of 90 mm, and a drawing ratio of 0.6 or more and 1 or less.

[0022] The laminate for vacuum forming or the laminate for pressure forming of the present invention comprises the polyester film of the present invention.

[0023] A first food and beverage package of the present invention comprises the vacuum-formed or pressure-formed product of the present invention and a food or beverage covered with the formed product. A second food and beverage package of the present invention comprises the vacuum-forming laminate or pressure-forming laminate of the present invention and a food or beverage covered with the laminate.

[0024] A first pharmaceutical package of the present invention comprises the vacuum-formed or pressure-formed product of the present invention and a pharmaceutical product covered with the product. A second pharmaceutical package of the present invention comprises the vacuum-formed or pressure-formed laminate of the present invention and a pharmaceutical product covered with the laminate.

[0025] A first medical instrument package of the present invention comprises the vacuum-formed or pressure-formed article of the present invention and a medical instrument covered with the article. A second medical instrument package of the present invention comprises the vacuum-forming or pressure-forming laminate of the present invention and a medical instrument covered with the laminate.

[0026] The first electric component packaging body or electronic component packaging body of the present invention comprises the vacuum-formed body or pressure-formed body of the present invention and an electric component or electronic component covered with the formed body.The second electric component packaging body or electronic component packaging body of the present invention comprises the vacuum-formed or pressure-formed laminate of the present invention and an electric component or electronic component covered with the laminate.

[0027] According to the present invention, it is possible to provide a polyester film having excellent vacuum formability and / or pressure formability, a vacuum-formed body or pressure-formed body, a laminate for vacuum forming or a laminate for pressure forming, as well as a food and beverage package, a pharmaceutical package, a medical device package, and an electrical component package or an electronic component package.

[0028] FIG. 1 is a schematic diagram showing an example of a polyester film of the present invention. FIG. 2 is a schematic diagram showing an example of a laminate for vacuum forming or a laminate for pressure forming of the present invention. FIG. 3 is a schematic diagram showing another example of a laminate for vacuum forming or a laminate for pressure forming of the present invention. FIG. 4 is a schematic diagram showing an example of a mold used in a test example, where (A) is a schematic plan view of the mold and (B) is a schematic side view of the mold. FIG. 5 is a DSC chart of the polyester film of Test Example 1. FIG. 6 is a DSC chart of the polyester film of Test Example 9. FIG. 7 is a DSC chart of the polyester film of Test Example 11. FIG. 8 is a DSC chart of the polyester film of Test Example 14. FIG. 9 is a DSC chart of the polyester film of Test Example 20. FIG. 10 is a DSC chart of the polyester film of Test Example 21.

[0029] (Polyester Film) The polyester film of the present invention contains a first polyester resin which is a polymer of a first acid unit containing a terephthalic acid unit and a first alcohol unit containing a 1,4-butanediol unit, and a second polyester resin which is a polymer of a second acid unit containing a terephthalic acid unit and a second alcohol unit containing an ethylene glycol unit, and may contain a third polyester resin, and further contains other components as necessary.

[0030] In the polyester film of the present invention, the mass ratio (A / B) of the content A of the first polyester resin to the content B of the second polyester resin is 0.8 to 10, preferably 1 to 5, more preferably 1 to 2, and even more preferably 1.2 to 1.8. If the mass ratio (A / B) is less than 0.8 or more than 10, vacuum forming and / or pressure forming using a mold with a drawing ratio of, for example, 0.6 to 1 may result in breakage and / or pinholes in the polyester film, or the polyester film may not be able to conform neatly to the entire surface of the mold, including the corners.

[0031] The polyester film of the present invention has a cold crystallization peak indicating the heat of cold crystallization when the polyester film is subjected to differential scanning calorimetry at a heating rate of 10°C / min within a measurement temperature range of 0°C to 300°C. The area of ​​the cold crystallization peak is 10 J / g or more, preferably 15 J / g or more, and more preferably 15 J / g to 20 J / g. If the area of ​​the cold crystallization peak is less than 10 J / g, when vacuum forming and / or pressure forming is performed using a mold having a drawing ratio of, for example, 0.6 to 1, the polyester film may suffer from breaks and / or pinholes, or the polyester film may not be able to conform cleanly to the entire surface of the mold, including the corners.

[0032] The peak-top temperature of the cold crystallization peak is 50°C to 105°C, preferably 50°C to 100°C, more preferably 55°C to 90°C, even more preferably 55°C to 80°C, and particularly preferably 60°C to 75°C. If the peak-top temperature of the cold crystallization peak is less than 50°C or more than 105°C, when vacuum forming and / or pressure forming is performed using a mold with a drawing ratio of, for example, 0.6 to 1, breaks and / or pinholes may occur in the polyester film, or the polyester film may not be able to conform to the entire surface of the mold, including the corners, and may not be able to be formed cleanly. The crystallization peak area and peak-top temperature can be determined from a DSC chart obtained by measuring using a differential scanning calorimeter under conditions of a heating rate of 10°C / min and a temperature range of 0°C to 300°C.

[0033] The polyester film of the present invention preferably has a crystallinity of 28% or less, more preferably 27% or less, even more preferably 20% to 26%, and particularly preferably 21% to 24%, as calculated by the following mathematical formula A. If the crystallinity exceeds 28%, the polyester film may suffer from breakage and / or pinholes when vacuum-molded and / or pressure-molded using a mold having a drawing ratio of, for example, 0.6 to 1, or the polyester film may not be able to conform neatly to the entire surface of the mold, including the corners. [Formula A] Crystallinity = {(total endothermic amounts of all endothermic peaks within the measurement range) - (heat of cold crystallization)} / [{(heat of fusion of the first perfectly crystalline polybutylene terephthalate) x (content of the first polyester resin) / 100} + {(heat of fusion of the second perfectly crystalline polyethylene terephthalate) x (content of the second polyester resin) / 100}] x 100 Heat of fusion of the first perfectly crystalline polybutylene terephthalate: 145.3 J / g (literature value) Heat of fusion of the second perfectly crystalline polyethylene terephthalate: 140.0 J / g (literature value) The total endothermic amounts of all endothermic peaks within the measurement range can be calculated by summing the endothermic amounts of all endothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a heating rate of 10 ° C. / min in a temperature range of 0 ° C. to 300 ° C. The calorific value of cold crystallization can be calculated by summing the calorific values ​​of all exothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a temperature rise rate of 10°C / min in a temperature range of 0°C to 300°C.

[0034] The polyester film of the present invention preferably has a tensile elongation at break of 500% or more, more preferably 600% or more, even more preferably 600% to 1000%, particularly preferably 600% to 800%, and even more particularly preferably 650% to 750% in the longitudinal and transverse directions at 23° C. If the tensile elongation at break is less than 500%, when vacuum forming and / or pressure forming is performed using a mold having a drawing ratio of, for example, 0.6 to 1, the polyester film may suffer from breaks and / or pinholes, or the polyester film may not be able to conform cleanly to the entire surface of the mold including the corners.

[0035] The polyester film of the present invention preferably has a tensile break strength at 23°C in the longitudinal and width directions of 100 MPa or less, more preferably 90 MPa or less, even more preferably 50 MPa to 90 MPa, and particularly preferably 60 MPa to 85 MPa. If the tensile break strength exceeds 100 MPa, when vacuum forming and / or pressure forming is performed using a mold with a drawing ratio of, for example, 0.6 to 1, the polyester film may suffer from breaks and / or pinholes, or the polyester film may not be able to conform cleanly to the entire surface of the mold, including the corners. The longitudinal direction is sometimes referred to as the machine direction (MD direction). The width direction is sometimes referred to as the transverse direction (TD direction). The tensile breaking elongation and tensile breaking strength can be measured in accordance with ISO (International Organization for Standardization) 527, for example.

[0036] The polyester film of the present invention preferably has a thickness of 25 μm or more. The thickness of the polyester film can be 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, or 55 μm or more. The thickness of the polyester film can be 3 mm (3,000 μm) or less, 1 mm (1,000 μm) or less, 500 μm or less, 100 μm or less, 75 μm or less, 60 μm or less, 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, or 35 μm or less. If the thickness of the polyester film is less than 25 μm, the polyester film may break and / or have pinholes when vacuum-molded and / or pressure-molded using a mold with a drawing ratio of, for example, 0.6 to 1. If the thickness of the polyester film exceeds 75 μm, the preheating time for vacuum forming and / or pressure forming must be extended, otherwise the polyester film will not be able to conform to the entire surface of the mold, including the corners, and the production efficiency of vacuum forming and / or pressure forming will decrease. The thickness of the polyester film can be measured, for example, using a micrometer.

[0037] The polyester film of the present invention is preferably a single-layer unstretched product, which means a polyester film that has not been subjected to a stretching treatment during the production process.

[0038] The composition of the polyester resin in the polyester film of the present invention, other components, physical properties, and a method for producing the polyester resin will be described in detail below.

[0039] The composition of a polyester resin may not necessarily be the same as the composition of the raw material monomers. For example, when ethylene glycol is used as the alcohol component, diethylene glycol may be included as a by-product. Hereinafter, unless otherwise specified, the notation of mole percent (mol%) concentration indicating the composition refers to the mole percent concentration of the component in the produced resin, not the amount of raw material monomer charged.

[0040] <First Polyester Resin> The first polyester resin is a polymer of first acid units containing terephthalic acid units and first alcohol units containing 1,4-butanediol units. The first polyester resin preferably contains polybutylene terephthalate (PBT) units as its main structural unit. Here, the term "main structural unit" generally refers to a structural unit contained in the first polyester resin at 70% by mass or more. The content of the main structural unit is preferably 80% by mass or more, more preferably 90% by mass or more. The first polyester resin may also contain no structural units other than the main structural unit (100% by mass).

[0041] -First Acid Units- The first acid units mainly contain terephthalic acid units. In addition to terephthalic acid, the terephthalic acid units may be units derived from terephthalic acid derivatives such as alkyl esters of terephthalic acid and terephthalic anhydride. Examples of alkyl esters of terephthalic acid include dimethyl terephthalate (DMT) and diethyl terephthalate. The content of terephthalic acid units is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 98 mol% or more, relative to the total amount of the first acid units, and may be 100 mol%.

[0042] The first acid unit may contain other acid units as long as the essential properties of the first polyester resin are not altered. Examples of other acid units include units of isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, succinic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, and derivatives thereof. These may be used alone or in combination of two or more.

[0043] —First Alcohol Units—The first alcohol units mainly contain 1,4-butanediol units. The content of 1,4-butanediol units is preferably 90 mol % or more, more preferably 95 mol % or more, and even more preferably 98 mol % or more, relative to the total amount of the first alcohol units, and may be 100 mol %.

[0044] The first alcohol unit may contain other alcohol units as long as the essential properties of the first polyester resin are not altered. Examples of other alcohol units include units consisting of ethylene glycol, 2,2-dimethyl-1,3-propanediol ("neopentyl glycol"), 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, or derivatives thereof. These may be used alone or in combination of two or more.

[0045] The first polyester resin may be appropriately synthesized or may be a commercially available product. A method for synthesizing the first polyester resin will be described later in the polyester resin manufacturing method. Scraps generated during film production or the like can be used as the first polyester resin. This allows for efficient use of resources and reduction in manufacturing costs. The first polyester resin may be derived from recycled polyester resin or biomass.

[0046] The content A of the first polyester resin in the polyester film is preferably 50% to 80% by mass. This content range allows for excellent vacuum formability and / or pressure formability. The content A of the first polyester resin can be 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, or 75% by mass or more, relative to the mass of the polyester film. Furthermore, the content of the first polyester resin can be 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, or 55% by mass or less, relative to the mass of the polyester film.

[0047] <Second Polyester Resin> The second polyester resin is a polymer of a second acid unit containing a terephthalic acid unit and a second alcohol unit containing an ethylene glycol unit. The second polyester resin preferably has a polyethylene terephthalate (PET) unit as a main structural unit. Here, the "main structural unit" generally refers to a structural unit contained in the second polyester resin at 70% by mass or more, and the content of the main structural unit is preferably 80% by mass or more, more preferably 90% by mass or more. It is also possible for the second polyester resin to contain no structural units other than the main structural unit (100% by mass).

[0048] - Second Acid Units - The second acid units mainly contain terephthalic acid units. The terephthalic acid units may be units derived from terephthalic acid or terephthalic acid derivatives such as alkyl esters of terephthalic acid and terephthalic anhydride, in addition to terephthalic acid. Examples of alkyl esters of terephthalic acid include dimethyl terephthalate (DMT) and diethyl terephthalate. The content of terephthalic acid units is preferably 80 mol% or more relative to the total amount of second acid units. The content of terephthalic acid units in the second acid units can be, for example, 85 mol% or more, 90 mol% or more, or 95 mol% or more relative to the total amount of second acid units. The content of terephthalic acid in the second acid component is preferably 95 mol% or less relative to the total amount of second acid components, and the content of terephthalic acid units in the second acid units can be 90 mol% or less, or 85 mol% or less relative to the total amount of second acid units.

[0049] The second acid unit preferably contains an aromatic dicarboxylic acid unit other than a terephthalic acid unit. Examples of aromatic dicarboxylic acid units other than a terephthalic acid unit include units formed of isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, dimethyl terephthalate, dimethyl isophthalate, or derivatives thereof. These may be used alone or in combination of two or more. Among these, an isophthalic acid unit is preferred.

[0050] The content of aromatic dicarboxylic acid units other than terephthalic unit acids in the second acid units is preferably 20 mol % or less, more preferably 15 mol % or less, even more preferably 10 mol % or less, and particularly preferably 5 mol % or less, relative to the total amount of the second acid units.

[0051] The second acid unit may contain other acid units as long as the essential properties of the second polyester resin are not changed. Examples of other acid units include units of adipic acid, sebacic acid, succinic acid, dimer acid, 1,4-cyclohexanedicarboxylic acid, or derivatives thereof. These may be used alone or in combination of two or more.

[0052] —Second Alcohol Units— The second alcohol units mainly contain ethylene glycol units. The content of ethylene glycol units is preferably 90 mol % or more, more preferably 95 mol % or more, even more preferably 97 mol % or more, and particularly preferably 98 mol % or more, relative to the total amount of the second alcohol units, and may be 100 mol %.

[0053] The second alcohol units preferably contain diethylene glycol units by-produced from ethylene glycol units during melt polymerization. The content of the diethylene glycol units is preferably 1 mol % to 5 mol %, more preferably 1 mol % to 3 mol %, and even more preferably 2 mol % to 3 mol %, based on the total amount of the second alcohol units.

[0054] The second alcohol unit may contain other alcohol units as long as the essential properties of the second polyester resin are not altered. Examples of other alcohol units include units consisting of 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, or derivatives thereof. These may be used alone or in combination of two or more.

[0055] The second polyester resin may be appropriately synthesized or may be a commercially available product. The synthesis method of the second polyester resin will be described later in the polyester resin production method. Scraps generated during film production or the like can be used as the second polyester resin. This allows for efficient use of resources and reduction in production costs. The second polyester resin may be derived from recycled polyester resin or biomass.

[0056] The content B of the second polyester resin in the polyester film is preferably 15% by mass to 50% by mass. This content range allows for excellent vacuum formability and / or pressure formability. The content B of the second polyester resin can be 20% by mass or more, 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, relative to the mass of the polyester film. Furthermore, the content of the second polyester resin can be 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, or 20% by mass or less, relative to the mass of the polyester film.

[0057] <Third Polyester Resin> The polyester film of the present invention may contain a third polyester resin in addition to the first polyester resin and the second polyester resin, as long as the properties of the present invention are not impaired. Examples of the third polyester resin include polybutylene terephthalate (PBT) other than the first polyester resin, copolymerized polybutylene terephthalate (copolymerized PBT) other than the first polyester resin, polyethylene terephthalate (PET) other than the second polyester resin, and copolymerized polyethylene terephthalate (copolymerized PET) other than the second polyester resin. The content of the third polyester resin is preferably 5% by mass or less, more preferably 3% by mass or less, relative to the mass of the polyester film. When the third polyester resin is PBT or copolymerized PBT, the total content of the first polyester resin and the third polyester resin is preferably 50% by mass to 80% by mass.

[0058] <Other Components> The polyester film of the present invention may further contain other components as necessary. The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components include various additives such as antiblocking agents, lubricants, antioxidants, heat stabilizers, antistatic agents, plasticizers, UV absorbers, release agents, pigments, and dyes.

[0059] As the antiblocking agent, organic or inorganic fine particles can be used. Examples of the fine particles include inorganic particles such as calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, lithium phosphate, magnesium phosphate, calcium phosphate, lithium fluoride, aluminum oxide (alumina), silicon oxide (silica), and kaolin, organic particles such as acrylic resin and guanamine resin, and precipitated particles obtained by granulating catalyst residues. The content of the antiblocking agent is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, based on the mass of the polyester film. Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.

[0060] The first polyester resin and the second polyester resin in the polyester film of the present invention can be produced by a known method using the above-mentioned monomers of the acid unit and the alcohol unit and other components. For example, an ester prepolymer may be produced by direct esterification using an unsubstituted polycarboxylic acid as a starting material, or an ester prepolymer may be produced by transesterification using an esterified product such as a dimethyl ester as a starting material.

[0061] The ratio of the monomers added may be the ratios indicated above in the description of the first polyester resin and the second polyester resin.

[0062] The direct esterification reaction or the transesterification reaction can be carried out, for example, by charging the raw materials into a reaction vessel equipped with a heater, a stirrer, and a distillation tube, adding a reaction catalyst, and raising the temperature while stirring under an inert gas atmosphere at atmospheric pressure, and allowing the reaction to proceed while distilling off by-products such as methanol and water produced by the reaction.

[0063] At least one metal compound can be used as a catalyst for the transesterification reaction. Examples of metal compounds include sodium, potassium, calcium, titanium, lithium, magnesium, manganese, zinc, tin, and cobalt. Of these, titanium and manganese compounds are preferred because they have high reactivity and produce a good color tone for the resulting resin. The amount of transesterification catalyst added is usually preferably 5 ppm to 1,000 ppm, and more preferably 10 ppm to 100 ppm, based on the polyester resin produced.

[0064] In the case of a direct esterification reaction, it is preferable to reduce the amount of ethylene glycol in the reaction system in order to suppress the production of the by-product diethylene glycol, for example, by setting the molar ratio of the amount of alcohol unit monomer to the amount of acid unit monomer (alcohol unit monomer / acid unit monomer) to 1.3 or less.

[0065] Alternatively, a phosphorus compound may be added after the completion of the direct esterification reaction or the transesterification reaction to further promote the esterification reaction. Examples of the phosphorus compound include phosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, trimethyl phosphite, triethyl phosphite, and tributyl phosphite. The amount of the phosphorus compound added is preferably 5 ppm to 1,000 ppm, and more preferably 300 ppm to 600 ppm, based on the mass of the polyester resin produced.

[0066] Following the transesterification and esterification reactions, a polymerization catalyst can be added to the ester prepolymer, and a polycondensation reaction can be further carried out until the desired molecular weight is achieved. Examples of catalysts that can be used in the polycondensation reaction include germanium dioxide. The amount of catalyst added can be, for example, 150 ppm to 250 ppm relative to the amount of resin produced. The polycondensation reaction can be carried out, for example, by gradually increasing the temperature and reducing the pressure inside the reaction vessel after adding the polymerization catalyst. The pressure inside the vessel is preferably reduced to, for example, 0.4 kPa or less, preferably 0.2 kPa or less. The temperature inside the vessel is preferably increased to, for example, 250°C to 290°C. The polymerization reaction can be carried out, for example, under reduced pressure until the final vessel pressure is 150 Pa or less, until the desired melt viscosity is achieved. The vessel pressure can then be increased to, for example, 0.5 MPa, and the reaction product can be extruded and recovered from the bottom of the vessel. For example, the reaction product can be extruded into water in the form of strands, cooled, and cut to obtain pelletized polyester resin. If necessary, the pelletized polyester resin may be subjected to a solid-state polymerization reaction until the desired molecular weight is achieved. The solid-state polymerization reaction may be carried out, for example, by heating the pelletized polyester resin under reduced pressure or in a nitrogen gas flow. The reaction temperature is, for example, preferably 160°C to 220°C, and more preferably 180°C to 200°C.

[0067] As the polymerization catalyst, catalysts other than germanium dioxide can also be used. For example, tetra-n-butoxytitanium, antimony trioxide, etc. can be used. When tetra-n-butoxytitanium is used, the amount of the polymerization catalyst added can be, for example, 350 ppm to 700 ppm relative to the amount of polyester resin produced.

[0068] The first polyester resin and the second polyester resin may be appropriately blended with various additives depending on the application and molding purpose, such as an antiblocking agent, a lubricant, an antioxidant, a heat stabilizer, an antistatic agent, a plasticizer, an ultraviolet absorber, a mold release agent, a pigment, a dye, etc. These additives may be blended in either the polymerization reaction step or the molding step.

[0069] <Method for Producing Polyester Film> The method for producing the polyester film of the present invention is not particularly limited and can be appropriately selected depending on the purpose. For example, a polyester film (unstretched product) can be produced by mixing the first polyester resin, the second polyester resin, and optionally the third polyester resin, and other components, feeding the mixture into an extruder equipped with a T-die, melting the mixture, extruding it through the T-die, bringing it into contact with a cooling roll by electrostatic adhesion or the like, and cooling it to solidify it. In this case, the temperature of the extruder is preferably 250°C to 280°C.

[0070] <Physical Properties> The intrinsic viscosity (IV) of the polyester film of the present invention at 20°C is preferably 0.8 dl / g or more, more preferably 0.8 dl / g to 1.2 dl / g, and even more preferably 0.9 dl / g to 1.1 dl / g. If the intrinsic viscosity is less than 0.8 dl / g, sufficient mechanical properties may not be obtained. The intrinsic viscosity is a value measured at 20°C by dissolving 0.5000±0.0005 g of polyester film in a mixed solvent of phenol:tetrachloroethane = 60:40 (mass ratio) using an automatic viscosity measuring device equipped with an Ubbelohde viscometer.

[0071] 1 is a schematic diagram showing an example of the polyester film of the present invention. The polyester film 1 preferably has a single-layer (one-layer) structure, but may have a multi-layer structure of two or more layers, if necessary.

[0072] (Vacuum-formed or pressure-formed article) The vacuum-formed or pressure-formed article of the present invention has the polyester film of the present invention described above. The vacuum-formed or pressure-formed article is vacuum-formed and / or pressure-formed using a mold having a molding section with a depth of 10 mm, a mold bottom diameter of 90 mm, and a drawing ratio of 0.6 to 1. Note that vacuum-formed and / or pressure-formed means vacuum forming, pressure forming, or vacuum-pressure forming.

[0073] The method for producing a vacuum-formed or pressure-formed body includes the steps of placing a polyester film and an adherend in a chamber box, reducing and / or pressurizing the chamber box, and covering the adherend with the film, and may further include other steps as necessary.

[0074] In the step of reducing the pressure inside the chamber box, the pressure inside the chamber box is preferably 0.1 kPa to 20 kPa, and more preferably 0.1 kPa to 10 kPa. In the step of pressurizing the chamber box, the pressure inside the chamber box is preferably 180 kPa to 200 kPa, and more preferably 190 kPa to 200 kPa. In the step of covering the adherend with a polyester film, the film temperature of the polyester film is preferably in the range of the glass transition temperature Tg of the polyester film to Tg + 50°C.

[0075] By using the polyester film of the present invention, the vacuum-formed or pressure-formed article of the present invention can be formed without breaks and / or pinholes, even when a mold has a drawing ratio of, for example, 0.6 to 1, and the film can be molded neatly by conforming to the entire surface of the mold, including the corners. The drawing ratio is calculated by dividing the diameter of the mold bottom by the diameter of the mold opening. The diameters of the mold bottom and the mold opening refer to the largest linear distance between any two points on the periphery of the mold bottom and the mold opening. For example, even when vacuum forming and / or pressure forming are performed using a mold having a circular molding portion 5 in plan view, with a depth of 10 mm, a mold bottom diameter of 90 mm, and a mold opening diameter of 90 mm, with a drawing ratio of 90 mm divided by 90 mm = 1, as shown in Figure 4, the article can be formed neatly without breaks and / or pinholes, and by conforming to the entire surface of the mold, including the corners. The mold 10 in Figure 4 has a drawing ratio of 1 (maximum), making it the most difficult mold to perform vacuum forming and / or pressure forming. The shape of the molded portion 5 in plan view is not particularly limited, and examples thereof include a circle, an ellipse, a triangle, a square, a pentagon, a hexagon, a heptagon, an octagon, a rectangle, a square, a star, and a heart.

[0076] (Laminate for Vacuum Forming or Laminate for Pressure Forming) The laminate for vacuum forming or laminate for pressure forming of the present invention comprises the polyester film of the present invention, and preferably comprises a heat seal layer, and further comprises other layers as necessary. Examples of the other layers include a barrier layer and an adhesive layer.

[0077] Fig. 2 is a schematic diagram showing an example of the vacuum forming laminate or pressure forming laminate 2 of the present invention. The vacuum forming laminate or pressure forming laminate 2 of Fig. 2 comprises a polyester film 1 and a heat seal layer 3. As shown in Fig. 3, a barrier layer 4 may further be provided between the polyester film 1 and the heat seal layer 3.

[0078] The heat seal layer can be formed using a resin having heat sealability, such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-propylene copolymer, polyethylene terephthalate, and copolymer polyester.

[0079] The heat seal layer may further contain additives such as plasticizers, UV stabilizers, color inhibitors, matting agents, deodorants, flame retardants, weather resistance agents, antistatic agents, friction reducers, slip agents, antiblocking agents, mold release agents, antioxidants, ion exchange agents, dispersants, UV absorbers, and color pigments. The thickness of the heat seal layer is preferably 25 μm to 150 μm.

[0080] The presence of a barrier layer can improve the gas barrier properties that prevent the permeation of oxygen gas, water vapor, etc. Examples of the barrier layer include metal foils or vapor-deposited films of inorganic substances or inorganic oxides.

[0081] The polyester film, vacuum-formed or pressure-formed article, and laminate for vacuum forming or laminate for pressure forming of the present invention can be widely used in various technical fields by utilizing vacuum forming and / or pressure forming, taking advantage of the heat resistance, impact resistance, and crystallization properties of the polyester film. Among these, as described below, they are preferably used for packaging for food and beverages, packaging for pharmaceuticals, packaging for medical devices, packaging for electrical components, or packaging for electronic components.

[0082] - Food and beverage packaging - A first food and beverage packaging of the present invention comprises the vacuum-formed or pressure-formed product of the present invention and a food or beverage covered with the formed product. A second food and beverage packaging of the present invention comprises the vacuum-forming or pressure-forming laminate of the present invention and a food or beverage covered with the laminate.

[0083] Depending on the application, only a portion of the food and beverage package may be made of a packaging material (the vacuum-formed or pressure-formed article of the present invention, or the laminate for vacuum forming or the laminate for pressure forming of the present invention), or substantially the entire food and beverage package may be made of a packaging material. Examples of the shape of the food and beverage package include a bag, tray, pack, pouch, container, etc. The food and beverage package is used to package various foods and beverages. Examples of foods and beverages include, but are not limited to, beverages such as soft drinks, carbonated drinks, nutritional drinks, fruit drinks, and lactic acid drinks (including concentrated concentrates and powders for adjusting these beverages); frozen desserts such as ice cream, ice sherbet, and shaved ice; noodles such as soba, udon, vermicelli, gyoza wrappers, shumai wrappers, Chinese noodles, and instant noodles; sweets such as candy, chewing gum, candies, gum, chocolate, candy tablets, snacks, biscuits, jelly, jam, cream, and baked goods; processed seafood or livestock foods such as kamaboko, ham, and sausage; dairy products such as processed milk and fermented milk; oils and fats and oil-based foods such as seafood, salad oil, tempura oil, margarine, mayonnaise, shortening, whipped cream, and dressing; condiments such as sauces and dressings; soups, stews, salads, side dishes, and pickles; various other forms of supplementary foods; and energy drinks.

[0084] - Pharmaceutical Package - A first pharmaceutical package of the present invention comprises the vacuum-formed or pressure-formed product of the present invention and a pharmaceutical product covered with the formed product. A second pharmaceutical package of the present invention comprises the vacuum-formed or pressure-formed laminate of the present invention and a pharmaceutical product covered with the laminate.

[0085] Depending on the application, only a portion of the pharmaceutical package may be composed of a packaging material (the vacuum-formed or pressure-formed article of the present invention, or the laminate for vacuum forming or the laminate for pressure forming of the present invention), or substantially the entire pharmaceutical package may be composed of a packaging material. Examples of the pharmaceutical package form include blister packs, bags, trays, packs, and containers. Pharmaceutical packages are used to package various pharmaceuticals. Pharmaceuticals are pharmaceuticals and quasi-drugs as defined in Article 2, Paragraphs 1 and 2 of the Pharmaceutical and Medical Device Act, and may be in the form of oral dosage forms such as liquids, suspensions, tablets, capsules, powders, etc., or parenteral dosage forms such as ointments and patches.

[0086] - Medical instrument package - A first medical instrument package of the present invention comprises the vacuum-formed or pressure-formed article of the present invention and a medical instrument covered with the formed article. A second medical instrument package of the present invention comprises the vacuum-forming or pressure-forming laminate of the present invention and a medical instrument covered with the laminate.

[0087] Depending on the application, only a portion of the medical instrument package may be made of a packaging material (the vacuum-formed or pressure-formed article of the present invention, or the vacuum-forming or pressure-forming laminate of the present invention), or substantially the entire medical instrument package may be made of a packaging material. Examples of the form of the medical instrument package include a bag, a tray, a pack, and a container. The medical instrument package is used to package various medical instruments. Examples of medical instruments include, but are not limited to, tubes, bottles, chambers, casings, connectors, hubs, needle tubes, autoinjectors, syringes, prefilled syringes, injection needles, blood bags, blood collection needles, blood filters, blood collection tubes, infusion bags containing medicinal solutions, cartridges containing medicinal solutions, catheters, and endoscopic treatment tools.

[0088] -Electric component packaging body or electronic component packaging body-A first electric component packaging body or electronic component packaging body of the present invention comprises the vacuum-formed body or pressure-formed body of the present invention and an electric component or electronic component covered with the formed body.A second electric component packaging body or electronic component packaging body of the present invention comprises the vacuum-forming or pressure-forming laminate of the present invention and an electric component or electronic component covered with the laminate.

[0089] Depending on the application, only a portion of the electrical component packaging or electronic component packaging may be made of a packaging material (the vacuum-formed or pressure-formed body of the present invention, or the laminate for vacuum forming or laminate for pressure forming of the present invention), or substantially the entire electrical component packaging or electronic component packaging may be made of a packaging material. Examples of the shape of the electrical component packaging or electronic component packaging include a bag, a tray, a pack, and a container. The electrical component packaging or electronic component packaging is used to package various electrical components or electronic components. Examples of electrical components or electronic components include, but are not limited to, switches, touch panels, sensors, connectors, batteries, semiconductors, ICs, transistors, diodes, capacitors, LEDs, RFID tags, and substrates.

[0090] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0091] Synthesis Example 1 - Synthesis of First Polyester Resin - 100 parts by mass of dimethyl terephthalate and 100 parts by mass of 1,4-butanediol were charged into a stainless steel (registered trademark) autoclave equipped with a stirrer and a distillation column and melted at 150°C. 0.009 parts by mass of tetra-n-butoxytitanium was added to the resulting melt, and a transesterification reaction was carried out while the resulting methanol was distilled out of the system. Thereafter, 0.045 parts by mass of tetra-n-butoxytitanium was added as a polycondensation catalyst, and a polycondensation reaction was carried out at 240°C under a reduced pressure of 100 Pa until a predetermined viscosity was reached. Next, the resulting polycondensate was extruded into cooling water, pelletized using a strand cutter, and then solid-phase polymerized at 180°C under a nitrogen stream until a predetermined viscosity was reached. In this manner, a first polyester resin (PBT) was synthesized.

[0092] (Synthesis Example 2) - Synthesis of Second Polyester Resin - 95 parts by mass of terephthalic acid, 5 parts by mass of isophthalic acid (IPA), and 42 parts by mass of ethylene glycol were charged into a Stainless Steel (registered trademark) autoclave equipped with a stirrer and a distillation column, and an esterification reaction was carried out under conditions of 250°C and 250 kPa. Thereafter, 0.061 parts by mass of triethyl phosphate and 0.023 parts by mass of germanium dioxide were charged, and a polycondensation reaction was carried out at 275°C and a reduced pressure of 100 Pa until a predetermined viscosity was reached. Next, the obtained polycondensate was extruded into cooling water and pelletized using a strand cutter, and then solid-phase polymerized at 200°C under a nitrogen stream until a predetermined viscosity was reached. In this manner, a second polyester resin (PET containing 5 mol% IPA) was synthesized.

[0093] (Synthesis Example 3) - Synthesis of third polyester resin - 100 parts by mass of terephthalic acid and 42 parts by mass of ethylene glycol were charged into a Stainless Steel (registered trademark) autoclave equipped with a stirrer and a rectification column, and an esterification reaction was carried out under conditions of 250°C and 250 kPa. Thereafter, 0.061 parts by mass of triethyl phosphate and 0.023 parts by mass of germanium dioxide were charged, and a polycondensation reaction was carried out at 275°C and a reduced pressure of 100 Pa until a predetermined viscosity was achieved. Next, the obtained polycondensate was extruded into cooling water and pelletized using a strand cutter. In this manner, a third polyester resin (PET) was synthesized.

[0094] (Test Examples 1 to 12 and Test Examples 15 to 19) - Preparation of Polyester Films - The first polyester resin, second polyester resin, third polyester resin, and silica (SYLYSIA530, manufactured by Fuji Silysia Chemical Ltd.) shown in Table 1-1 were vacuum-dried at 120°C for 6 hours. Thereafter, the mixture was mixed to the mass ratio (A / B) shown in Table 1-1, and charged into an extruder equipped with a T-die, where it was heated and melted at 280°C. The silica was mixed in a state where it had been pre-mixed with a portion of the polyester resin (polyester resin / silica = 94 / 6 (mass ratio)). The resulting melt was then fed into a T-die, formed into a sheet, extruded from a nozzle, and cooled and solidified on a cast roll to obtain polyester films of Test Examples 1 to 12 and Test Examples 15 to 19 having the thicknesses shown in Table 1-1 (unstretched products).

[0095] (Test Example 13) A polyester film obtained in the same manner as in Test Example 1 was uniaxially stretched in the machine direction at a temperature of 90°C at a stretching ratio of 4 to obtain a stretched polyester film of Test Example 13 having a thickness of 30 µm.

[0096] (Test Example 14) A polyester film obtained in the same manner as in Test Example 1 was biaxially stretched in the longitudinal direction by 3 times at a temperature of 80°C and in the transverse direction by 3 times at a temperature of 95°C, and then heat-set at a temperature of 180°C to obtain a stretched polyester film of Test Example 14 having a thickness of 30 μm.

[0097] (Test Example 20) A polyester film (PET) obtained in the same manner as in Test Example 8 was biaxially stretched in the machine direction at a stretching ratio of 3 at a temperature of 95°C and in the transverse direction at a stretching ratio of 3 at a temperature of 110°C, and then heat-set at a temperature of 210°C to obtain a stretched polyester film of Test Example 20 having a thickness of 30 μm.

[0098] (Test Example 21) A polyester film (PBT) obtained in the same manner as in Test Example 12 was biaxially stretched in the machine direction at a stretching ratio of 3 at a temperature of 80°C and in the transverse direction at a stretching ratio of 3 at a temperature of 95°C, and then heat-set at a temperature of 180°C to obtain a stretched polyester film of Test Example 21 having a thickness of 30 μm.

[0099] Next, the properties of the obtained polyester films of Test Examples 1 to 21 were evaluated as follows, and the results are shown in Tables 1-2 and 1-3.

[0100] <Vacuum formability 1> Each polyester film was preheated at 300°C for 4 seconds, and then vacuum formed (chamber box internal pressure 5 kPa, forming time 2.5 seconds) using a mold 10 having a circular forming portion 5 in a plan view as shown in Figure 4, and the vacuum formability was evaluated based on the following criteria. The mold 10 in Figure 4 has a drawing ratio = (diameter of mold bottom) ÷ (diameter of mold opening) = 90 mm ÷ 90 mm = 1, and since the drawing ratio is 1 (maximum), it is the most difficult mold for vacuum forming. [Evaluation criteria] A: No breaks and / or pinholes occurred in the film, and the entire surface of the mold, including the corners, was vacuum-formed cleanly (the film conformed to the entire surface of the mold, including the corners, during molding). B: No breaks and / or pinholes occurred in the film, and some of the corners of the mold could not be vacuum-formed (the film did not conform to some of the corners of the mold during molding). C: No breaks and / or pinholes occurred, but the film did not deform, and vacuum-forming was not possible. D: Breaks and / or pinholes occurred during molding, and vacuum-forming was not possible.

[0101] <Vacuum formability 2> Each polyester film was preheated at 300°C for 5 seconds, and then vacuum formed (chamber box internal pressure 5 kPa, forming time 2.5 seconds) using a mold 10 having a circular forming portion 5 in a plan view as shown in Figure 4, and the vacuum formability was evaluated based on the following criteria. The mold 10 in Figure 4 has a drawing ratio = (diameter of mold bottom) ÷ (diameter of mold opening) = 90 mm ÷ 90 mm = 1, and since the drawing ratio is 1 (maximum), it is the most difficult mold to vacuum form. [Evaluation criteria] A: No breaks and / or pinholes occurred in the film, and the entire surface of the mold, including the corners, was vacuum-formed cleanly (the film conformed to the entire surface of the mold, including the corners, during molding). B: No breaks and / or pinholes occurred in the film, and some of the corners of the mold could not be vacuum-formed (the film did not conform to some of the corners of the mold during molding). C: No breaks and / or pinholes occurred, but the film did not deform, and vacuum-forming was not possible. D: Breaks and / or pinholes occurred during molding, and vacuum-forming was not possible.

[0102] <Vacuum formability 3> The polyester films of Test Examples 8 to 15 and Test Examples 18 to 21 were preheated at a temperature of 300°C for 15 seconds, and then vacuum formed (chamber box internal pressure 5 kPa, forming time 2.5 seconds) using a mold 10 having a circular forming portion 5 in a plan view as shown in Figure 4, and the vacuum formability was evaluated based on the following criteria. For the mold 10 of Figure 4, the drawing ratio = (diameter of the mold bottom) ÷ (diameter of the mold opening) = 90 mm ÷ 90 mm = 1, and since the drawing ratio is 1 (maximum), it is the most difficult mold for vacuum forming. [Evaluation criteria] A: No breaks and / or pinholes occurred in the film, and the entire surface of the mold, including the corners, was vacuum-formed cleanly (the film conformed to the entire surface of the mold, including the corners, during molding). B: No breaks and / or pinholes occurred in the film, and some of the corners of the mold could not be vacuum-formed (the film did not conform to some of the corners of the mold during molding). C: No breaks and / or pinholes occurred, but the film did not deform, and vacuum-forming was not possible. D: Breaks and / or pinholes occurred during molding, and vacuum-forming was not possible.

[0103] <Overall evaluation of vacuum formability> From the results of vacuum formability 1 to 3 above, an overall evaluation of vacuum formability was performed based on the following criteria. An overall evaluation of A is a pass level. [Evaluation criteria] A: Vacuum formability 1 and 2 were rated A B: Vacuum formability 1 was rated B to D, and vacuum formability 2 was rated A C: Vacuum formability 1 and 2 were rated B to D, and vacuum formability 3 was rated A D: Vacuum formability 1 and 2 were rated B to D, and vacuum formability 3 was rated B E: Vacuum formability 1 and 2 were rated B to D, and vacuum formability 3 was rated C to D

[0104] <Crystallization degree> Differential scanning calorimetry was performed on each polyester film using a differential scanning calorimeter (DSC2500, manufactured by TA Instruments Japan Co., Ltd.) at a temperature rise rate of 10°C / min within a measurement temperature range of 0°C to 300°C, and the crystallinity was calculated from the obtained DSC chart according to the following mathematical formula A. Figures 5 to 10 show the DSC charts of the polyester films of Test Examples 1, 9, 11, 14, 20, and 21, respectively. [Formula A] Crystallinity = {(total endothermic amounts of all endothermic peaks within the measurement range) - (heat of cold crystallization)} / [{(heat of fusion of the first perfectly crystalline polybutylene terephthalate) x (content of the first polyester resin) / 100} + {(heat of fusion of the second perfectly crystalline polyethylene terephthalate) x (content of the second polyester resin) / 100}] x 100 Heat of fusion of the first perfectly crystalline polybutylene terephthalate: 145.3 J / g (literature value) Heat of fusion of the second perfectly crystalline polyethylene terephthalate: 140.0 J / g (literature value) The total endothermic amounts of all endothermic peaks within the measurement range can be calculated by summing the endothermic amounts of all endothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a heating rate of 10 ° C. / min in a temperature range of 0 ° C. to 300 ° C. The calorific value of cold crystallization can be calculated by summing the calorific values ​​of all exothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a temperature rise rate of 10°C / min in a temperature range of 0°C to 300°C.

[0105] <Crystallization Peak Area and Peak-Top Temperature> Each polyester film was subjected to differential scanning calorimetry using a differential scanning calorimeter (DSC2500, manufactured by TA Instruments Japan Co., Ltd.) at a heating rate of 10°C / min over a measurement temperature range of 0°C to 300°C, and the cold crystallization peak area and peak-top temperature were determined from the obtained DSC chart. DSC charts of the polyester films of Test Examples 1, 9, 11, 14, 20, and 21 are shown in Figures 5 to 10.

[0106] <Intrinsic Viscosity (IV)> 0.5000±0.0005 g of each polyester film was dissolved in a mixed solvent of phenol:tetrachloroethane = 60:40 (mass ratio), and the intrinsic viscosity (IV) of the polyester film at 20°C was measured using an automatic viscosity measuring device (ALC-6C, manufactured by Sun Electronics Industries Co., Ltd.) equipped with an Ubbelohde viscosity tube.

[0107] <Tensile Breaking Elongation and Tensile Breaking Strength> Each polyester film was cut into a strip shape with a long side of 150 mm and a short side of 10 mm, and a tensile test was performed in the machine direction (MD) or the width direction (TD) in accordance with JIS C-2151 using a tensile tester (Tensilon UCT-500, manufactured by Orientec Co., Ltd.) at a temperature of 23°C and a speed of 100 mm / min. The strength (the value obtained by dividing the maximum tensile load during the test by the cross-sectional area of ​​the test specimen before the test) and elongation at the time the test specimen broke (fractured) were determined. The tensile elongation was calculated using the following formula: Tensile elongation (%) = 100 × (L - Lo) ÷ Lo, where Lo is the length of the test specimen before the test, and L is the length of the test specimen at break.

[0108]

[0109]

[0110]

[0111] The results in Tables 1-1 to 1-3 show that Test Examples 1 to 7 satisfied all of the requirements (1) to (5) below. As a result, it was found that even when vacuum forming was performed using a mold with a drawing ratio of 1 and a short preheating time (e.g., 300°C x 4 to 5 seconds), no breaks and / or pinholes occurred in the polyester film, and the polyester film could be molded cleanly by conforming to the entire surface of the mold, including the corners. (1) The polyester resin contains a first polyester resin which is a polymer of first acid units containing terephthalic acid units and first alcohol units containing 1,4-butanediol units, and a second polyester resin which is a polymer of second acid units containing terephthalic acid units and second alcohol units containing ethylene glycol units. (2) The mass ratio (A / B) of the content A of the first polyester resin to the content B of the second polyester resin is 0.8 to 10. (3) When the polyester film is subjected to differential scanning calorimetry at a heating rate of 10°C / min within a measurement temperature range of 0°C to 300°C, it has a cold crystallization peak indicating the heat of cold crystallization, the area of ​​the cold crystallization peak being 10 J / g or more, and the peak top temperature being 50°C to 105°C. (4) It has a tensile breaking elongation of 500% or more at 23°C in the longitudinal direction and the width direction, and a tensile breaking strength of 100 MPa or less at 23°C in the longitudinal direction and the width direction. (5) It is an unstretched product of a single layer structure having a thickness of 25 μm or more.

[0112] In contrast, Test Example 8 did not satisfy the requirements (1), (2), and (3) above, and therefore failed to vacuum form when vacuum formed using a mold with a drawing ratio of 1, due to the occurrence of breaks and / or pinholes in the polyester film. Furthermore, when the preheating time for vacuum forming was longer than 4 seconds, Test Example 8 failed to vacuum form due to the occurrence of breaks and / or pinholes in the polyester film.

[0113] Furthermore, Test Example 9 did not satisfy the requirements (2) and (3) above, and therefore, when vacuum-molded using a mold with a drawing ratio of 1, breaks and / or pinholes occurred in the polyester film, making vacuum-molding impossible. Furthermore, when the preheating time for vacuum-molding was longer than 4 seconds, breaks and / or pinholes occurred in the polyester film, making vacuum-molding impossible.

[0114] Furthermore, Test Example 10 did not satisfy the requirement (2) above, and therefore, when vacuum-molded using a mold with a drawing ratio of 1, no breaks and / or pinholes occurred in the polyester film, but the polyester film did not conform to some of the corners of the mold during molding, and some of the corners of the mold could not be vacuum-molded. Furthermore, when the preheating time for vacuum molding was longer than 4 seconds in Test Example 10, breaks and / or pinholes occurred in the polyester film, and vacuum molding was not possible.

[0115] Furthermore, Test Example 11 did not satisfy the requirements (2) and (3) above, and therefore, when vacuum-molded using a mold with a drawing ratio of 1, no breaks and / or pinholes occurred in the polyester film, but the polyester film did not conform to some of the corners of the mold during molding, and some of the corners of the mold could not be vacuum-molded. Furthermore, in Test Example 11, when the preheating time for vacuum molding was longer than 4 seconds, breaks and / or pinholes occurred in the polyester film, and vacuum-molding was not possible.

[0116] Furthermore, Test Example 12 did not satisfy the above requirements (1), (2), and (3), and therefore, when vacuum-molded using a mold with a drawing ratio of 1, no breaks and / or pinholes occurred in the polyester film, but the polyester film did not conform to some of the corners of the mold during molding, and some of the corners of the mold could not be vacuum-molded. Furthermore, in Test Example 12, when the preheating time for vacuum molding was longer than 4 seconds, breaks and / or pinholes occurred in the polyester film, and vacuum molding was not possible.

[0117] Furthermore, Test Examples 13 and 14 did not satisfy the requirements (3), (4), and (5) above, and therefore, when vacuum-molded using a mold with a drawing ratio of 1, breaks and / or pinholes occurred in the polyester film, making vacuum-molding impossible. Furthermore, when the preheating time for vacuum molding was longer than 4 seconds, breaks and / or pinholes occurred in the polyester film, making vacuum-molding impossible for Test Examples 13 and 14.

[0118] Furthermore, Test Example 15 was an unstretched product with a single-layer structure having a thickness of 20 μm, which did not satisfy the requirement (5) above, and therefore failed to vacuum form when vacuum formed using a mold with a drawing ratio of 1, due to the occurrence of breaks and / or pinholes in the polyester film. Furthermore, Test Example 15 failed to vacuum form when the preheating time for vacuum forming was longer than 4 seconds, due to the occurrence of breaks and / or pinholes in the polyester film.

[0119] Furthermore, Test Examples 16 to 19 were unstretched products with a single-layer structure having a thickness exceeding 75 μm, and satisfied all of the requirements (1) to (5) above. Even when vacuum-molded using a mold with a drawing ratio of 1, no breaks and / or pinholes occurred in the polyester film, and the polyester film was able to conform to the entire surface of the mold, including the corners, and was molded cleanly. However, because the polyester film thickness exceeded 75 μm, the preheating time for vacuum molding had to be extended to 5 seconds or more for Test Examples 16 and 17, and 15 seconds or more for Test Examples 18 and 19, which may reduce the productivity of vacuum molding.

[0120] Furthermore, Test Example 20 reproduces the biaxially stretched PBT film of Example 1 of Patent Document 3 (JP 2018-203273 A), and Test Example 21 reproduces the biaxially stretched PET film of the Reference Example of Patent Document 3 (JP 2018-203273 A). Test Examples 20 and 21 do not satisfy the requirements (1), (2), (3), (4), and (5) above. Therefore, when vacuum-molded using a mold with a drawing ratio of 1, breaks and / or pinholes occurred in the polyester film, making vacuum molding impossible. Furthermore, in Test Examples 20 and 21, when the preheating time for vacuum molding was longer than 4 seconds, breaks and / or pinholes occurred in the polyester film, making vacuum molding impossible.

[0121] The polyester film of the present invention, the vacuum-formed or pressure-formed article of the present invention, and the laminate for vacuum forming or laminate for pressure forming of the present invention can be widely used in various technical fields by utilizing vacuum forming and / or pressure forming, and are particularly suitable for use as food and beverage packaging, pharmaceutical packaging, medical device packaging, electrical component packaging, or electronic component packaging.

[0122] REFERENCE SIGNS LIST 1 Polyester film 2 Vacuum forming laminate or pressure forming laminate 3 Heat seal layer 4 Barrier layer 5 Molding section 10 Mold

Claims

1. A polyester film comprising: a first polyester resin which is a polymer of first acid units containing terephthalic acid units and first alcohol units containing 1,4-butanediol units; and a second polyester resin which is a polymer of second acid units containing terephthalic acid units and second alcohol units containing ethylene glycol units, wherein the mass ratio (A / B) of the content A of the first polyester resin to the content B of the second polyester resin is 0.8 to 10; and when the polyester film is subjected to differential scanning calorimetry at a heating rate of 10°C / min within a measurement temperature range of 0°C to 300°C, the polyester film has a cold crystallization peak indicating the heat of cold crystallization, the area of ​​the cold crystallization peak being 10 J / g or more, and the peak top temperature being 50°C to 105°C.

2. The polyester film according to claim 1, having a crystallinity of 28% or less as calculated by the following formula A: [Formula A] Crystallinity={(total endothermic amounts of all endothermic peaks within the measurement range)−(heat of cold crystallization)}÷[{(heat of fusion of first perfectly crystalline polybutylene terephthalate)×(content of first polyester resin)÷100}+{(heat of fusion of second perfectly crystalline polyethylene terephthalate)×(content of second polyester resin)÷100}]×100 Heat of fusion of first perfectly crystalline polybutylene terephthalate: 145.3 J / g (literature value) Heat of fusion of second perfectly crystalline polyethylene terephthalate: 140.0 J / g (literature value) The total endothermic amounts of all endothermic peaks within the measurement range is calculated by summing the endothermic amounts of all endothermic peaks in a DSC chart obtained by measurement using a differential scanning calorimeter at a heating rate of 10°C / min in a temperature range of 0°C to 300°C. The calorific value of cold crystallization is calculated by summing the calorific values ​​of all exothermic peaks in a DSC chart obtained by measuring using a differential scanning calorimeter at a temperature rise rate of 10°C / min in a temperature range of 0°C to 300°C.

3. The polyester film according to claim 1, having a tensile elongation at break of 500% or more in the longitudinal and transverse directions at 23°C, and a tensile strength at break of 100 MPa or less in the longitudinal and transverse directions at 23°C.

4. The polyester film according to claim 1, which is an unstretched single-layer film having a thickness of 25 μm or more.

5. The polyester film according to claim 1, wherein the content of the first polyester resin is 50% by mass to 80% by mass.

6. The polyester film according to claim 1, wherein the content of the 1,4-butanediol units is 90 mol % or more based on the total amount of the first alcohol units.

7. The polyester film according to claim 1, wherein the content of the ethylene glycol units is 90 mol % or more based on the total amount of the second alcohol units.

8. The polyester film of claim 1, wherein the second acid units further comprise isophthalic acid units.

9. The polyester film according to claim 1, having an intrinsic viscosity at 20°C of 0.8 dl / g or more.

10. A vacuum-formed product, a pressure-formed product, a laminate for vacuum forming, or a laminate for pressure forming, comprising the polyester film according to any one of claims 1 to 9.

11. The molded article or laminate according to claim 10, which is vacuum-formed and / or pressure-formed using a mold having a molding section with a depth of 10 mm, a mold bottom diameter of 90 mm, and a drawing ratio of 0.6 or more and 1 or less.

12. A food and beverage packaging body comprising the vacuum-formed body, pressure-formed body, laminate for vacuum forming, or laminate for pressure forming described in claim 10, and food and beverage covered with the formed body or laminate.

13. A pharmaceutical package comprising the vacuum-formed body, pressure-formed body, laminate for vacuum forming, or laminate for pressure forming according to claim 10, and a pharmaceutical product covered with the formed body or laminate.

14. A medical instrument package comprising the vacuum-formed body, pressure-formed body, laminate for vacuum forming, or laminate for pressure forming according to claim 10, and a medical instrument covered with the formed body or laminate.

15. An electrical component packaging body or electronic component packaging body, characterized by comprising the vacuum formed body, pressure formed body, laminate for vacuum forming, or laminate for pressure forming described in claim 10, and an electrical component or electronic component covered with the formed body or laminate.

Images