Polyester film, method for producing polyester film, laminated metal plate, method for producing laminated metal plate, and laminated metal container

Abstract

Provided is a polyester film or the like which can be stably manufactured in an energy-saving manner at any of the manufacturing stages of a film, a laminated metal plate, and a laminated metal container. Also provided is a polyester film or the like having sufficient corrosion resistance even when molding a two-piece can or the like is performed, for example. The polyester film contains a polyester containing polyethylene terephthalate as a component. The net intensity of the polyester film in a positive electrode diagram, which is obtained by X-ray diffraction and represents crystal orientation distribution, satisfies predetermined conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a polyester film for a laminated metal plate, a method for manufacturing a polyester film, a laminated metal plate, a method for manufacturing a laminated metal plate, and a laminated metal container. BACKGROUND

[0002] A metal container such as a food can, a beverage can, and an 18L can uses a metal plate of tin-free steel (TFS), aluminum, or the like as a material. The metal plate is coated and baked to impart corrosion resistance, durability, weather resistance, and the like.

[0003] Baking of the metal plate is complicated and requires a large amount of processing time. In addition, a large amount of solvent is discharged when the metal plate is subjected to coating. Therefore, as an alternative to the metal plate subjected to coating, a laminated metal plate in which a thermoplastic resin film is laminated on a metal plate is used.

[0004] For the thermoplastic resin film for the laminated metal plate, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or the like is used.

[0005] For these thermoplastic resin films, adhesion of the thermoplastic resin film to the metal plate when the laminated metal plate is formed, corrosion resistance, container formability when the laminated metal plate is formed into a container, and the like are required.

[0006] Metal containers are roughly classified into two-piece cans and three-piece cans. The two-piece can is composed of two members of a can body formed into a bottomed cylindrical shape and a lid body that closes an opening formed on one end side of the can body in the axial direction. The three-piece can is composed of three members of a can body formed into a cylindrical shape, an upper lid that closes an opening formed on one end side of the can body, and a bottom lid that closes an opening formed on the other end side of the can body.

[0007] The main body member of the three-piece can is mostly formed by cylindrical forming and welding. In addition, since the thermoplastic resin film covering the laminated metal plate is usually an insulator, the technique of welding is difficult. Therefore, in the case of the three-piece can, the laminated metal plate is mostly used for the bottom member or the lid member. In addition, in the case of the two-piece can, the laminated metal plate is also used for the main body member.

[0008] As a forming method of the main body member of the two-piece can, there are various forming methods such as Draw and Redraw (DRD) forming, Draw and Ironing (DI) forming, Draw and Thin Redraw (DTR) forming, and the like. These forming methods all apply draw processing and, as needed, thin draw processing. Therefore, the processability of the laminated metal plate is strongly required.

[0009] In particular, in the laminated metal plate for the body member of a two-piece can, a polyester film mainly using PET (Polyethylene terephthalate) is used as the thermoplastic resin film thereof.

[0010] However, from the viewpoint of the stretching method, the manufacturing method of the polyester film can be classified into non-stretching, longitudinal monoaxial stretching, transverse monoaxial stretching, sequential biaxial stretching, simultaneous biaxial stretching, and multi-stage stretching including re- longitudinal stretching.

[0011] As an advantage of the non-stretching method, the price of the equipment can be cited as being low compared to other stretching methods. As a disadvantage of the non-stretching method, the productivity and the accuracy of the thickness of the generated polyester film can be cited as being inferior to those of other stretching methods.

[0012] As an advantage of the longitudinal monoaxial stretching, the price of the equipment can be cited as being relatively low compared to other stretching methods. As a disadvantage of the longitudinal monoaxial stretching, anisotropy can be cited as being generated in the formation into a laminated metal container due to the monoaxial orientation.

[0013] As an advantage of the transverse monoaxial stretching, no advantage peculiar to the laminated metal container can be cited. As a disadvantage of the transverse monoaxial stretching, the price of the equipment can be cited as being relatively expensive compared to other stretching methods, and anisotropy can be cited as being generated in the formation into a laminated metal container due to the monoaxial orientation.

[0014] As an advantage of the sequential biaxial stretching, the productivity, the accuracy of the thickness of the generated polyester film, and the in-plane isotropy of the generated polyester film can be cited as being superior to those of other stretching methods. As a disadvantage of the sequential biaxial stretching, the price of the equipment can be cited as being expensive compared to other stretching methods.

[0015] As an advantage of the simultaneous biaxial stretching, the in-plane isotropy of the generated polyester film can be cited as being superior to that of other stretching methods. As a disadvantage of the simultaneous biaxial stretching, the price of the equipment can be cited as being very expensive compared to other stretching methods.

[0016] As an advantage of the multi-stage stretching including the re- longitudinal stretching, no advantage peculiar to the laminated metal container can be cited. As a disadvantage of the multi-stage stretching, the price of the equipment can be cited as being expensive compared to other stretching methods. In view of the orientation of the polyester film, the film of the multi-stage stretching is not suitable for the polyester film for the laminated metal container.

[0017] In view of the above advantages and disadvantages, the thermoplastic resin film used in the laminated metal container is mostly generated by the sequential biaxial stretching. However, the sequential biaxial stretching requires a large-scale heating furnace for the transverse stretching and heat fixation.

[0018] Therefore, polyester films are also produced using an unstretched method, longitudinal uniaxial stretching, which not only reduces equipment costs but also eliminates the need for large-scale heating furnaces. For example, patent document 1 discloses the use of an unstretched polyester film. For example, patent document 2 discloses the use of a longitudinally uniaxially stretched polyester film.

[0019] Existing technical documents

[0020] Patent documents

[0021] Patent Document 1: International Publication No. 2015 / 012222

[0022] Patent Document 2: Japanese Patent Publication No. 2014-518781 Summary of the Invention

[0023] The problem that the invention aims to solve

[0024] As mentioned above, requirements for thermoplastic resin films include good adhesion between the thermoplastic resin film and the metal sheet when formed into laminated metal sheets, corrosion resistance, and container formability when the laminated metal sheets are formed into containers. Furthermore, as energy-efficient polyester films that meet these requirements without requiring large-scale heating furnaces, unstretched films and longitudinally uniaxially stretched films have been proposed.

[0025] However, in the unstretched polyester film disclosed in Patent Document 1, as an example, only an extrusion coating method is described, in which the film extruded by the T-die of an extruder is directly heat-pressed onto a metal plate. Furthermore, Patent Document 1 states that when the extruded film is temporarily wound up and then laminated separately, it is inferior from the viewpoints of thin film production, productivity, and operability. Based on these descriptions, one issue that is practically impossible to carry out industrial production of polyester films using methods other than extrusion coating can be identified.

[0026] Furthermore, in extrusion coating, the production volume of polyester film is limited by the extrusion volume from the T-die because the laminating equipment and extruder are produced simultaneously. Therefore, extrusion coating suffers from lower productivity compared to methods that cut and then laminate films extruded or laterally stretched from wide dies. Additionally, for the same reason, in extrusion coating, changing the resin type requires both the extruder and the laminating equipment to be stopped.

[0027] Patent Document 2 describes a laminated metal sheet with a polyester film that has been stretched uniaxially in the longitudinal direction. This laminated metal sheet is manufactured by laminating the polyester film onto a preheated metal sheet and then post-heating the laminated metal sheet. Therefore, the manufacturing of the laminated metal sheet described in Patent Document 2 requires two heating processes, resulting in a high energy consumption during manufacturing.

[0028] Furthermore, the longitudinal uniaxial stretching described in Patent Document 2 requires trimming the edges of the film before stretching. Patent Document 2 also describes trimming the edges of the longitudinally uniaxially stretched film as needed. Considering variations in the width of the longitudinally uniaxially stretched film and yield rates, the probability of trimming the film after longitudinal uniaxial stretching is high. Therefore, the longitudinal uniaxial stretching method described in Patent Document 2 requires two trimming processes, necessitating energy efficiency in the manufacturing process.

[0029] The present invention was made in view of the above-mentioned problems, and its object is to provide polyester films, etc., that can be manufactured energy-efficiently and stably at any stage of the manufacturing process of membranes, laminated metal sheets, and laminated metal containers. Furthermore, the object of the present invention is to provide polyester films, etc., that also possess sufficient corrosion resistance during, for example, the forming process of two-piece cans.

[0030] Methods for solving problems

[0031] To address the above problems, the present invention has the following features. [1]

[0033] A polyester film containing a polyester comprising polyethylene terephthalate as a component, wherein the net intensity of the positive polarimetric pattern representing the crystal orientation distribution obtained by X-ray diffraction satisfies the following equations (1) and (2).

[0034] 0.30≤I 100 (60,0) / I 100 (60,90) ≤0.63 …(1)

[0035] 0.42≤I 1-10 (60,0) / I 1-10 (60,90) ≤0.60 …(2)

[0036] In the X-ray diffraction measurements using CuKα rays, the diffraction peak appearing at 2θ = 26.5 ± 1.0° was designated as the 100 diffraction, and the diffraction peak appearing at 2θ = 23.0 ± 0.5° was designated as the 1-10 diffraction. The positive electrode diagram is determined by setting the elevation angle of the bisecting line between the incident and reflected X-rays, which is parallel to the film surface, to α = 0°. The in-plane rotation angle at which the maximum diffraction intensity is achieved when α=60° in the positive polarimetric pattern of 100 diffraction is set to β=90°. I 100 (60,0) The net intensity at α=60° and β=0° in the positive polarimetric plot of the 100 diffraction intensity is... I 100(60,90) The net intensity at α=60° and β=90° in the positive polarimetric plot of the 100 diffraction intensity is... I 1-10 (60,0) The net intensity at α=60° and β=0° in the positive polarimetric plot of the diffraction intensities of 1-10 is the net intensity at α=60° and β=0°. I 1-10 (60,90) The net intensity at α=60° and β=90° is the positive polarimetric value of the diffraction intensity of 1-10. [2]

[0038] According to the polyester film described in [1], the standard deviation of the sample thickness measured along the incident X-ray direction at β=0° in the positive electrode pattern is less than 10% of the average of the measured thickness. [3]

[0040] The polyester film according to [1] or [2] comprises: The first layer contains a polyester comprising polyethylene terephthalate; and The second layer is stacked on top of the first layer and contains a polyester comprising polyethylene terephthalate and a lubricant. [4]

[0042] According to the polyester film described in [3], the first layer contains pigment. [5]

[0044] A method for manufacturing a polyester film, comprising a polyester film containing polyethylene terephthalate as a component, wherein the method comprises: An unstretched film manufacturing process, wherein the polyester is extruded from a T-die using an extruder to obtain an unstretched film; and The process of producing a longitudinally uniaxially stretched film includes obtaining a longitudinally uniaxially stretched film by longitudinally stretching the unstretched film using a longitudinally uniaxial stretching machine equipped with preheating rollers and stretching rollers. The longitudinal uniaxial stretching film manufacturing process is carried out under the conditions that the longitudinal stretching stretching ratio is more than 3.3 times and less than 7.5 times, and the final preheating roller temperature of the longitudinal stretching is more than 75°C and less than 110°C. [6]

[0046] A laminated metal sheet having a polyester film, as described in any one of [1] to [4], bonded to at least one of the surface and the back surface of a metal sheet having a surface and a back surface. [7]

[0048] According to the laminated metal plate described in [6], its wide-angle X-ray diffraction pattern satisfies the following equation (3).

[0049] I 100 (90,0) / I 非晶 (90,0) ≤1.5 …(3)

[0050] The wide-angle X-ray diffraction pattern was determined using the θ-2θ method with sample angles of α=90° and β=0° in the positive polarimetric diagram. I 100 (90,0) The net intensity of the 100 diffraction peak appearing at 2θ = 26.5 ± 1.0° is given. I 非晶 (90,0) The net intensity of the amorphous halo that appears at 2θ = 20.0 ± 5.0°. [8]

[0052] A method for manufacturing a laminated metal sheet, which is the method for manufacturing a laminated metal sheet as described in [6] or [7], comprising: The hot pressing process includes using laminating rollers to hot press a preheated metal plate and the polyester film to form a hot-pressed body; and The water cooling process involves water cooling the hot-pressed joint within 7 seconds of the hot-pressing connection. In the hot pressing process, the polyester film and the metal plate are preheated within the range of -5°C to +50°C of the melting point of the polyester film before being hot pressed together. [9]

[0054] A laminated metal container comprising, as described in [6] or [7], a laminated metal sheet as a material.

[0055] Invention Effects

[0056] According to the present invention, energy-efficient and stable manufacturing is possible at any stage of the production of the membrane, laminated metal sheet, or laminated metal container. Furthermore, the polyester film of the present invention exhibits sufficient corrosion resistance, for example, when performing forming processes such as two-piece cans. Attached Figure Description

[0057] Figure 1 This is an explanatory diagram of a laminated metal container.

[0058] Figure 2 This is a cross-sectional view of a polyester film consisting of two layers.

[0059] Figure 3 This is a cross-sectional view of a polyester film consisting of three layers.

[0060] Figure 4 This is the positive electrode diagram of a polyester film with a diffraction intensity of 100.

[0061] Figure 5 This is the positive electrode diagram of a polyester film with diffraction intensities of 1-10.

[0062] Figure 6 This is a flowchart illustrating a method for manufacturing polyester film.

[0063] Figure 7 This is a flowchart illustrating a method for manufacturing laminated metal sheets. Detailed Implementation

[0064] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This illustrates the structure of a laminated metal container. (For example...) Figure 1 As shown, the laminated metal container 100 is formed into a container shape with a bottom and has a lid to close the container. The laminated metal container 100 is used, for example, as a food can, beverage can, 18L can, etc. Figure 1 The right side shows an enlarged cross-section of the wall of the laminated metal container 100.

[0065] The laminated metal container 100 is not particularly limited and can be either a three-piece can formed by joining a lid member, a main body member, and a bottom member, or a two-piece can formed by joining a lid member and a main body member. It should be noted that the laminated metal container 100 is not limited to cans; for example, an opening may be provided at one end of the main body member.

[0066] like Figure 1 As shown in the enlarged cross-sectional view, the laminated metal container 100 includes a laminated metal sheet 10 as material. The laminated metal sheet 10 comprises a metal plate 20 having a surface 21 serving as the outer surface of the laminated metal container 100 and a back surface 22 serving as the inner surface of the laminated metal container 100. The laminated metal sheet 10 has a polyester film 30 bonded to at least one of the surface 21 and the back surface 22 of the metal sheet 20. Figure 1 In this case, the polyester film 30 is arranged to cover the surface 21 of the metal plate 20.

[0067] The metal sheet 20 is not particularly limited and can be made of aluminum or steel, which are widely used as materials for metal containers, or metal sheets that have undergone various surface treatments. In particular, it is preferred to use a surface-treated steel sheet (TFS: Tin Free Steel) with a film formed of metallic chromium and hydrated chromium oxide.

[0068] The steel sheet with a TFS-like steel base is not particularly limited as long as it can be formed into a shape corresponding to the laminated metal container 100. Preferably, it is a steel sheet obtained by recrystallization annealing and tempering rolling of low-carbon steel or IF (Interstitial Free) steel. The steel sheet with a TFS-like steel base can be a steel sheet that has undergone aging treatment as needed. Additionally, the steel sheet with a TFS-like steel base can be a steel sheet that has undergone secondary cold rolling.

[0069] As a low-carbon steel, for example, a low-carbon steel with a carbon content of 0.010% by mass or more and 0.100% by mass or less can be used. Furthermore, as an IF steel, for example, an IF steel obtained by adding Nb, Ti, etc., to an extremely low-carbon steel with a carbon content of 0.003% by mass or less can be used. As for recrystallization annealing, examples include continuous annealing, close-fitting annealing, and open-face annealing.

[0070] The mechanical properties of the steel plate corresponding to the TFS steel base are not particularly limited as long as it can be formed into a shape corresponding to the laminated metal container 100. For example, the yield point of the steel plate is preferably in the range of 220 to 580 MPa, the Lankford value is preferably 0.8 or higher, and the absolute value of the in-plane anisotropy of the Lankford value is preferably 0.7 or lower. Regarding the amount of chromium layer and chromium hydrate oxide layer adhered to the TFS, there are no particular limitations. From the viewpoint of film adhesion and corrosion resistance, based on Cr conversion, the chromium layer is preferably 50 to 200 mg / m³. 2 The preferred range for the chromium hydrate oxide layer is 3–30 mg / m³. 2 The range.

[0071] The thickness of the metal sheet is not particularly limited, but from the viewpoint of the formability of the laminated metal container and the strength of the metal container, it is preferably in the range of 0.10 to 0.60 mm.

[0072] The polyester film 30 contains polyester, including polyethylene terephthalate as a component. The content of polyethylene terephthalate in the polyester film 30 is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0073] The polyester can be polyethylene terephthalate, or a copolymer of polyethylene terephthalate and a copolymer component. When the polyester is a polyethylene terephthalate copolymer, the content of the copolymer component is preferably 20 mol% or less, more preferably 2 to 16 mol%.

[0074] Among the copolymer components of polyester, acidic components can include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and sodium isophthalate-5-sulfonate, as well as aliphatic dicarboxylic acids or their ester derivatives such as oxalic acid, succinic acid, adipic acid, octanoic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, dodecanoic acid, and cyclohexane dicarboxylic acid.

[0075] Among the copolymer components of polyester, alcohols can include propylene glycol, butanediol, pentanediol, hexanediol, neopentanediol, cyclohexanediol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbide (1,4:3,6-didehydroglucanol, 1,4:3,6-didehydro-D-sorbitol), spirocyclic glycol, bisphenol A, bisphenol S, etc.

[0076] The copolymer component of the polyester can be one of the above-mentioned components, or two or more components.

[0077] From the viewpoint of ease of forming the polyester film 30 and its adhesion to the metal plate, isophthalic acid is preferably used as the copolymer component. When isophthalic acid is used as the copolymer component, the content of isophthalic acid in the copolymer is preferably 1 to 20 mol%, more preferably 2 to 16 mol%.

[0078] The intrinsic viscosity of the polyester is preferably in the range of 0.62–1.10 dL / g. When the intrinsic viscosity is less than 0.62 dL / g, there is a tendency for the formability of the laminated metal sheet to decrease. When the intrinsic viscosity is greater than 1.10 dL / g, there is a tendency for the energy consumption in the polymerization and extrusion processes to increase.

[0079] In addition to polyester, the polyester film 30 may also contain additives such as lubricants, pigments, dyes, antioxidants, nucleating agents, heat stabilizers, and antistatic agents. In particular, to improve operability, the polyester film 30 preferably contains 0.01 to 1.00% by mass of lubricant.

[0080] As a lubricant, there are no particular limitations; inorganic lubricants such as silica, diatomaceous earth, and talc, as well as organic lubricants such as PMMA, carnauba wax, polyolefin wax, and modified polyolefin wax can be used.

[0081] Furthermore, two or more types of lubricants, including inorganic and organic lubricants, can be used in combination. By including inorganic and organic lubricants in the polyester film 30, it is possible to achieve improved conveyability of the polyester film 30 and the laminated metal plate 10 due to the inorganic lubricant, and improved formability of the two-piece tank body component due to the organic lubricant.

[0082] There are no particular limitations on the pigment used; for example, white pigment or yellow pigment can be used. By containing pigment in the polyester film 30, it can be coated onto the metal plate 20, which serves as the substrate, thus improving design flexibility and printability.

[0083] In addition to oxide ceramics such as alumina, titanium dioxide, and zinc oxide, talc, calcium carbonate, and barium sulfate can also be used as white pigments. In particular, from the viewpoint of dispersibility and whiteness, titanium dioxide is preferred as a white pigment, and rutile titanium dioxide is even more preferred.

[0084] As a yellow pigment, isoindolinone yellow, diazo yellow, etc. can be used, for example. From the viewpoint of heat resistance, diazo yellow is preferred as a yellow pigment.

[0085] The polyester film 30 may contain 0.0001% by mass and less than 1.0000% by mass of an antioxidant. There are no particular limitations on the antioxidant; known antioxidants classified as hindered phenols, hydrazines, phosphites, etc., can be used. The presence of an antioxidant in the polyester film 30 improves its heat resistance.

[0086] Polyester film 30 can also be composed of two or more layers. Figure 2 The cross-section of a polyester film 30 consisting of two layers is shown. (Example) Figure 2 As shown, the polyester film 30 comprises a first layer 31 disposed on the surface 21 of the metal plate 20 and a second layer 32 stacked on the first layer 31.

[0087] The first layer 31 contains polyester and pigments, including polyethylene terephthalate. The second layer 32 contains polyester and lubricant, including polyethylene terephthalate.

[0088] In this way, when the polyester film 30 is composed of two or more layers, the second layer 32, which is the outermost layer and the layer furthest from the laminated metal plate 10, can contain lubricant. Figure 2 In the example of the polyester film 30 shown, for instance, the first layer 31 may contain less than 0.02% by mass of lubricant. Furthermore, the second layer 32 may contain 0.01 to 1.00% by mass of lubricant.

[0089] Furthermore, the outermost layer of the polyester film 30 can be formed without the addition of pigments. By forming the polyester film 30 in this way, it is possible to prevent pigments from adhering to the operator's hands or from flowing into the contents.

[0090] The polyester film 30 is not limited to a 2-layer structure, but can also consist of 3 or more layers. Figure 3 The cross-section of a polyester film 30 consisting of three layers is shown. (Example) Figure 3 As shown, a second layer 32 can be provided in the lamination direction of the polyester film 30 in such a way as to sandwich the first layer 31.

[0091] In this configuration of the polyester film 30, additives can be added to the layers from which the benefits can be enjoyed. For example, a lubricant can be added to the second layer 32 at a rate of 0.01 to 1.00% by mass. In this case, the lubricant may not be added to the first layer 31. Thus, by selectively adding lubricant to the second layer 32, the effectiveness of the lubricant can be maintained and manufacturing costs can be reduced. It should be noted that the lubricant only needs to be included in the outermost layer, and preferably not in other layers.

[0092] Alternatively, for example, pigment can be added to the first layer 31. In this case, the pigment may not be added to the second layer 32. In this way, by selectively adding pigment to the first layer 31, the effect of the pigment can be maintained and manufacturing costs can be reduced. Furthermore, since the first layer 31 is covered by the second layer 32 as the outermost layer, it is possible to prevent pigment from flowing into the contents and causing hygiene problems.

[0093] It should be noted that, as a lamination method for the polyester film 30, known methods such as co-extrusion using a feed block or manifold, lamination with other films, and lamination by directly laminating molten resin onto the film can be used. From the viewpoint of productivity and energy saving, co-extrusion is the preferred lamination method for the polyester film 30.

[0094] Figure 4 This is the positive electrode diagram of polyester film 30 with a diffraction intensity of 100. Figure 5 This is the positive electrode plot of polyester film 30 with diffraction intensities of 1-10. Figure 4 and Figure 5 In the diagram, the positive pole figure is obtained by X-ray diffraction and represents the crystal orientation distribution. Additionally, in... Figure 4 and Figure 5 The diagram shows 10 contour lines dividing the net intensity from minimum to maximum into 11 parts. Figure 4 and Figure 5 The numbers marked on the contour lines shown are net strength expressed as a percentage relative to the maximum value. Polyester film 30 Figure 4 and 5 The net strength of the positive electrode diagram shown satisfies the following equations (1) and (2).

[0095] 0.30≤I 100 (60,0) / I 100 (60,90) ≤0.63 …(1)

[0096] 0.42≤I 1-10 (60,0) / I 1-10 (60,90) ≤0.60 …(2)

[0097] In X-ray diffraction measurements using CuKα rays, the diffraction peak appearing at 2θ = 26.5 ± 1.0° is designated as the 100 diffraction, and the diffraction peak appearing at 2θ = 23.0 ± 0.5° is designated as the 1-10 diffraction. The positive polarimetric diagram is determined by setting the elevation angle α = 0°, where the bisecting line of the incident and reflected X-rays is parallel to the film surface. The in-plane rotation angle at which α = 60° achieves the maximum diffraction intensity in the positive polarimetric diagram of the 100 diffraction is set as β = 90°.

[0098] I 100 (60,0) The net intensity at α=60° and β=0° in the positive electrode plot of a diffraction intensity of 100. 100 (60,0) exist Figure 4 The middle part is represented by a black dot.

[0099] I 100 (60,90) The net intensity at α=60° and β=90° in the positive polarimetric plot of a 100 diffraction intensity. 100 (60,90) exist Figure 4 The middle part is represented by a slash dot.

[0100] I 1-10 (60,0) The net intensity at α=60° and β=0° is shown in the positive polarimetric plot of diffraction intensities from 1 to 10. 1-10 (60,0) exist Figure 5 The middle part is represented by a black dot.

[0101] I 1-10 (60,90) The net intensity at α=60° and β=90° is shown in the positive polarimetric plot of diffraction intensities from 1 to 10. 1-10 (60,90) exist Figure 5 The middle part is represented by a slash dot.

[0102] The net strength of the positive pole figure is the sum of the strengths of each positive pole figure ( Figure 4 , 5 The diffraction intensity is obtained by subtracting the diffraction intensity of the point with the lowest diffraction intensity when α=15° from the diffraction intensity of each point.

[0103] I 100 (60,0) I 100 (60,90) The ratio of the (100) facet, i.e. the aromatic ring facet, of the polyester polyethylene terephthalate to the directions of β=0° and 90°, respectively.

[0104] I 100 (60,0) / I 100 (60,90)The value is 0.30 or higher and 0.63 or lower, preferably 0.35 or higher and 0.50 or lower. By making I... 100 (60,0) / I 100 (60,90) A value between 0.30 and 0.63 can improve the uniformity of the thickness of the polyester film 30. Furthermore, it can suppress thermal shrinkage in the width direction of the polyester film 30 when it is laminated onto the metal plate 20, and improve the tensile stability in the length direction of the polyester film 30.

[0105] On the other hand, in I 100 (60,0) / I 100 (60,90) When the value is less than 0.30, the polyester film 30 tends to shrink in the width direction of the metal plate 20 when it is laminated onto the metal plate 20. Therefore, the tension of the polyester film 30 in the length direction of the metal plate 20 tends to become unstable.

[0106] In addition, I 100 (60,0) / I 100 (60,90) When the value is greater than 0.63, the stretch ratio of polyester film 30 is small, thus there is a tendency for the uniformity of the thickness of polyester film 30 to be compromised.

[0107] I 1-10 (60,0) I 1-10 (60,90) This represents the ratio of the (1-10) faces of the polyethylene terephthalate (PET) polyester to the directions β=0° and 90°, respectively. 1-10 (60,0) / I 1-10 (60,90) The value is 0.42 or higher and 0.60 or lower, preferably 0.45 or higher and 0.55 or lower. By making I... 1-10 (60,0) / I 1-10 (60,90) A value between 0.42 and 0.60 improves the uniformity of the polyester film 30's thickness. Furthermore, when the polyester film 30 is laminated onto the metal plate 20, thermal shrinkage of the polyester film 30 in the width direction of the metal plate 20 can be suppressed. Therefore, the instability of the tension of the polyester film 30 in the length direction of the metal plate 20 can be prevented.

[0108] I 1-10 (60,0) / I 1-10 (60,90)When the value is less than 0.42, when the polyester film 30 is laminated onto the metal plate 20, the polyester film 30 tends to shrink easily in the width direction of the metal plate 20. In addition, when the polyester film 30 is laminated onto the metal plate 20, the tension of the polyester film 30 tends to become unstable in the length direction of the metal plate 20.

[0109] In addition, I 1-10 (60,0) / I 1-10 (60,90) When the stretch ratio is greater than 0.60, the stretch ratio is small, thus reducing the uniformity of the thickness of the polyester film 30.

[0110] The standard deviation of the sample thickness of the polyester film of the present invention, measured along the incident X-ray direction at β=0° in the positive electrode pattern, is preferably less than 10% of the average film thickness, and more preferably less than 5%.

[0111] The thickness of polyester film 30 is the value obtained by calculating the standard deviation and average of the sample thickness measured at 1000 points along the direction of β=0° at 1mm intervals using a constant pressure thickness gauge.

[0112] The direction where β=0° corresponds to the stretching direction of the polyester film 30. When the sample standard deviation of the thickness of the polyester film 30 is less than 10% of the average thickness of the polyester film 30, the polyester film 30 is stretched to a degree exceeding the neck stretch range during stretching.

[0113] By imparting rigidity to the polyester film 30 at such a thickness, the operability of the polyester film 30 is improved. Furthermore, when the polyester film 30 is laminated onto the metal plate 20, the tensile stability of the polyester film 30 along the length of the metal plate 20 can be improved.

[0114] In addition, it can suppress the breakage of the polyester film 30, or the polyester film 30 and the metal plate 20, when the laminated metal plate 10 is formed into the laminated metal container 100.

[0115] The average thickness of the polyester film 30 can be 8 to 50 μm, preferably 10 to 30 μm.

[0116] When the average thickness of the polyester film 30 is less than 8 μm, the reduced thickness of the polyester film 30 may compromise corrosion resistance when the laminated metal sheet 10 is formed into a laminated metal container 100.

[0117] Even if the average thickness of the polyester film 30 is greater than 50 μm, it is difficult to obtain the aforementioned effects of corrosion resistance and improved operability resulting from the rigidity imparted to the polyester film 30. Furthermore, if the average thickness of the polyester film 30 is greater than 50 μm, it becomes difficult to manufacture the polyester film 30 energy-efficiently.

[0118] (Manufacturing method of polyester film)

[0119] Next, the manufacturing method of polyester film 30 will be described. Figure 6 The manufacturing process of polyester film 30 is shown. For example... Figure 6 As shown, in the method for manufacturing polyester film 30, an unstretched film production step (step S101) is performed, in which polyester is extruded from a T-die using an extruder to obtain an unstretched film. Next, a longitudinal uniaxial stretching film production step (step S102) is performed, in which the unstretched film is longitudinally stretched to obtain a longitudinally uniaxial stretching film. Then, a heat-fixing step (step S103) is performed, in which the longitudinally uniaxial stretching film is heated to perform heat-fixing, thereby manufacturing polyester film 30.

[0120] In the unstretched film production process of step S101, the aforementioned polyester is an essential raw material. Additives such as lubricants, pigments, dyes, antioxidants, nucleating agents, heat stabilizers, and antistatic agents can be added to the raw material.

[0121] The masterbatch, consisting of these raw materials and additives such as lubricants dispersed in a resin, is mixed in granule form, for example, by dry mixing, to produce a resin mixture. The resin mixture is then dried under hot air or vacuum as needed and fed to an extruder.

[0122] The polyester is heated above its melting point in an extruder and melted. After impurities and modified resins are removed by a filter, the molten resin composition is fed to a T-die via a gear pump and extruded from the T-die. The resin composition is formed into a sheet during extrusion through the T-die.

[0123] In the case where the polyester film 30 is formed from two or more layers, for example, a co-extrusion method can be used to laminate the two or more layers to form a single polyester film 30. In this case, multiple extruders can be used, along with feed blocks and multi-manifold dies that melt-extrude resin compositions, which serve as the forming materials of each layer.

[0124] The molten resin composition discharged from the T-die is cooled and solidified by a cooling device such as a casting roller to become an unstretched polyester film (hereinafter also referred to as unstretched film). During the cooling and solidification of the molten resin composition, it is preferable to use an electrostatic pinning device, a vacuum chamber, or the like. By using these devices, the adhesion between the casting roller and the resin composition can be improved, resulting in a homogeneous unstretched film.

[0125] The longitudinal uniaxial stretching film production process in step S102 is performed by longitudinal stretching using a longitudinal uniaxial stretching machine equipped with a preheating roller and a stretching roller. Specifically, the unstretched film is heated to a specified temperature as it passes through the preheating roller. The difference in circumferential speed between the preheating roller and the previous roller is preferably less than 2%.

[0126] The unstretched film, heated to a specified temperature by a preheating roller, is stretched along its length between a stretching roller and a final preheating roller preceding it. It should be noted that the circumferential speed difference between the stretching roller and the preceding roller is greater than 50%.

[0127] In heating the unstretched film, an infrared heater can be used in addition to the preheating roller. For example, an infrared heater can be installed between the final preheating roller and the stretching roller, located on the side closest to the stretching roller. By using an infrared heater to heat the unstretched film, the temperature of the final preheating roller can be kept low.

[0128] By maintaining a low final preheating roller temperature, adhesion of the unstretched film to the preheating roller can be suppressed. It should be noted that longitudinal uniaxial stretching can be performed using multiple stretching rollers in a multi-segment longitudinal stretching manner.

[0129] The stretching ratio of the longitudinal stretching is 3.3 times or more and 7.5 times or less. Preferably, the stretching ratio of the longitudinal stretching is 3.9 times or more and 6.5 times or less. It should be noted that the stretching ratio of the longitudinal stretching can be expressed as the ratio of the conveying speed on the outlet side to the conveying speed on the inlet side of the longitudinal stretching machine.

[0130] When the stretch ratio is less than 3.3 times, I 1-10 (60,0) / I 1-10 (60,90) It may be greater than 0.60. When the stretch ratio is greater than 7.5 times, I 1-10 (60,0) / I 1-10 (60,90) It may be less than 0.42. In addition, when the stretch ratio is greater than 7.5 times, there is a tendency for the film to break easily during stretching.

[0131] The longitudinal uniaxial stretching film production process is carried out under conditions where the temperature of the final preheating roller is 75°C or higher and 110°C or lower. Preferably, it is carried out under conditions where the temperature of the final preheating roller is 80°C or higher and 105°C or lower. When the temperature of the final preheating roller is lower than 75°C, it is possible to be stretched below the glass transition temperature of the polyester film, and there is a tendency for the film of the resin composition to easily break during stretching.

[0132] It should be noted that, for example, the glass transition temperature of the polyester film 30 can be the temperature at which the baseline displacement of the heat flow is generated when the temperature is increased from -50°C to 280°C at a rate of 10°C / min in a DSC.

[0133] When the temperature of the final preheating roller exceeds 110°C, the longitudinally uniaxially stretched film adheres to the roller, which tends to reduce productivity and decrease the thickness accuracy of the longitudinally uniaxially stretched film.

[0134] The heat-fixing process in step S103 is optional. Heat-fixing is preferably performed by heating the polyester film 30 at a temperature at least 5°C higher than the final preheating roller temperature during stretching and at least 50°C lower than the melting point of the polyester film 30.

[0135] It should be noted that the melting point of the polyester film 30 can be, for example, the peak temperature of the endothermic peak on the highest temperature side when heated from -50°C to 280°C at a rate of 10°C / min in differential scanning calorimetry (DSC).

[0136] Alternatively, the longitudinally uniaxially stretched film can be heated using rollers that are heated in the same way as those used for preheating during longitudinal stretching. In this case, it is preferable to preheat the rollers to a temperature at least 5°C higher than the final preheated roller temperature during stretching but less than 150°C. This helps to suppress adhesion of the longitudinally uniaxially stretched film to the rollers.

[0137] During heat curing, the longitudinally uniaxially stretched film can be relaxed along its length. The relaxation rate of the longitudinally uniaxially stretched film is preferably 0.5% or more and 5% or less. The relaxation of the longitudinally uniaxially stretched film can be performed using a pair of rollers with a difference in circumferential speed, but it is more preferable to use multiple pairs of rollers in multiple stages.

[0138] By performing the heat-fixing process in step S103, the residual stress caused by stretching can be mitigated, and the longitudinal uniaxial stretched film can be given rigidity through thermal crystallization.

[0139] The longitudinally uniaxially stretched film preferably has its edges trimmed to form a predetermined width. If the heat-curing process in step S103 is performed, this trimming can be performed subsequently. It should be noted that this trimming is an optional process.

[0140] The trimmed longitudinally stretched uniaxial film is used as a polyester film after being wound into rolls and stored. By trimming the edges of the longitudinally stretched film, its thickness in the width direction can be controlled to the desired size. As a result, wrinkles and stretching in the longitudinally stretched film can be suppressed.

[0141] Furthermore, by performing the longitudinal uniaxial stretching film production process in step S102 at the aforementioned stretch ratio and final preheating roll temperature, polyester film can be manufactured stably. As a result, even if the edges of the film are not trimmed between the unstretched film production process in step S101 and the longitudinal uniaxial stretching film production process in step S102, the desired dimensions can be controlled.

[0142] (Manufacturing method of laminated metal sheets)

[0143] The manufacturing method of the laminated metal sheet 10 is described. Figure 7 The manufacturing process of the laminated metal sheet 10 is shown. For example... Figure 7As shown, the metal plate 20 and the polyester film 30 are thermally pressed together using the lamination rollers of the lamination equipment to generate a thermally pressed body (step S201).

[0144] In the hot pressing process of step S201, a polyester film 30 is laminated onto at least one of the surface 21 and the back surface 22 of the metal plate 20. It should be noted that the metal plate 20 is a metal plate that has been cast, rolled to a specified thickness and width, and then subjected to surface treatments such as annealing, tempering and rolling, and plating as needed.

[0145] The hot pressing process in step S201 is performed by placing a polyester film 30 between a preheated metal plate 20 and a laminating roller, and then pressing the polyester film 30 onto the metal plate 20 using the laminating roller. At this time, the polyester film 30 melts due to the heat of the metal plate 20 and is pressed onto the metal plate 20.

[0146] The preheating of the metal plate 20 is carried out at a temperature between -5°C and +50°C from the melting point of the polyester film 30. Preferably, the preheating of the metal plate 20 is carried out at a temperature between the melting point of the polyester film 30 and that melting point +30°C.

[0147] If the preheating temperature of the metal plate 20 is lower than the melting point of the polyester film 30 by -5°C, the polyester film 30 may not melt and therefore cannot adhere tightly to the metal plate 20. If the preheating temperature of the metal plate 20 is higher than the melting point of the polyester film 30 by +50°C, the polyester film 30 in contact with the laminating roller may melt, resulting in a deteriorated appearance. Additionally, the polyester film 30 may adhere to the laminating roller, reducing productivity.

[0148] The polyester film 30 used in the hot pressing process of step S201 can be a preheated polyester film 30. The heating temperature of the polyester film 30 can be set to below 150°C. By heating the polyester film 30 in such a temperature range, the polyester film 30 can be transported smoothly, and the preheating temperature of the metal plate 20 can be reduced.

[0149] The pressure applied by the laminating roller is preferably 0.35 to 1.50 MPa. By setting the pressure applied by the laminating roller to 0.35 MPa or more, air bubbles that are rolled into the interface between the metal sheet 20 and the polyester film 30 can be eliminated more effectively, thereby improving the adhesion between the metal sheet 20 and the polyester film 30. In addition, by eliminating these air bubbles, damage to the appearance of the laminated metal sheet 10 can be suppressed.

[0150] By setting the pressure applied to the laminating roller to 1.50 MPa or less, excessive heat migration from the metal sheet 20 to the laminating roller can be suppressed, thereby efficiently reducing the energy consumed during manufacturing. Furthermore, under these conditions, wear on the laminating roller can be suppressed.

[0151] The laminating roller is preferably heated at a temperature above -30°C to below +40°C of the glass transition temperature of the polyester film 30. Heating the laminating roller can mitigate the spontaneous temperature rise caused by heat input from the metal plate and control the amount of crystallization on the surface of the polyester film 30.

[0152] The hot-pressed metal sheet, after hot pressing, is cooled by water within 7 seconds of the hot pressing in step 201 (step S202). In the water cooling process of step S202, water is sprayed onto the hot-pressed sheet or the hot-pressed sheet is immersed in water.

[0153] For operational stability, the cooling water used in the water cooling process of step S202 can also be heated. The temperature of the cooling water is preferably below the glass transition temperature of the polyester film 30 + 40°C. It should be noted that the water used for water cooling is not limited to water; for example, oil bath oils such as silicone oil can also be used.

[0154] After water cooling, the hot-pressed body uses extrusion rollers to remove the cooling water. The hot-pressed body undergoes post-heating and oiling treatments as needed. After inspecting for surface defects, internal defects, and thickness, the hot-pressed body is wound into rolls, for example, using a tension winding machine. The hot-pressed body can be cut and sheared to produce sheet products.

[0155] The laminated metal plate 10 thus generated preferably has a wide-angle X-ray diffraction pattern that satisfies the following equation (3).

[0156] I 100 (90,0) / I 非晶 (90,0) ≤1.5 …(3)

[0157] Among them, the wide-angle X-ray diffraction pattern was determined using the θ-2θ method with sample angles of α=90° and β=0° in the positive polarimetric diagram, and by using CuK α-rays. 100 (90,0) I represents the net intensity of the 100 diffraction peak appearing at 2θ = 26.5 ± 1.0°. 非晶 (90,0) The net intensity of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

[0158] It should be noted that, in the absence of a clear peak at 2θ = 26.5 ± 1.0°, the maximum net intensity within the range of 2θ = 25.5–27.5° is taken as I. 100 (90,0) The net intensity of a wide-angle X-ray diffraction pattern is obtained by subtracting the background intensity, represented by the straight line connecting the diffraction intensities at 2θ=10.0° and 2θ=30.0°, from the diffraction intensities at each 2θ.

[0159] I 100 (90,0) / I 非晶 (90,0) Preferably, the value is 1.5 or less, and more preferably 1.3 or less. When the wide-angle X-ray diffraction pattern of the laminated metal plate 10 satisfies equation (3), the oriented crystals generated by stretching are amorphized by the heat during lamination, thus improving the formability of the polyester film 30. As a result, it is possible to suppress the breakage of the polyester film and the deterioration of the corrosion resistance of the polyester film when forming the laminated metal container 100. By manufacturing the laminated metal plate 10 in this way, the laminated metal container 100 can be manufactured more energy-efficiently and more stably.

[0160] It should be noted that the thermal crystallization of the polyester film 30 occurs without air cooling of the hot-pressed body in step S202 (water cooling process). Therefore, it is difficult to control the wide-angle X-ray diffraction pattern of the laminated metal plate 10 within the range specified in this invention.

[0161] Furthermore, in the water cooling process of step S202, water cooling needs to be performed within 7 seconds of the hot pressing connection, and more preferably within 3 seconds of the hot pressing connection. By performing water cooling in this manner, the thermal crystallization of the polyester film can be suppressed, and the control can be achieved by ensuring that the wide-angle X-ray diffraction pattern of the laminated metal plate 10 satisfies the above-mentioned equation (3).

[0162] As described above, by using the hot-pressing lamination method described above for the hot-pressing process in step S201, the adhesion between the polyester film 30 and the metal plate 20 can be improved, and the laminated metal plate 10 can be manufactured in an energy-efficient manner. Specifically, it can satisfy the performance requirements of the polyester film 30 and the metal plate 20 when formed into the laminated metal plate 10, such as adhesion, corrosion resistance, and container formability when the laminated metal plate 10 is formed into a container.

[0163] Furthermore, the laminated metal sheet 10 obtained by laminating the polyester film 30 with a wide-angle X-ray diffraction pattern that corresponds to the aforementioned diffraction intensity distribution improves the processability of the resin layer. Therefore, when forming the laminated metal sheet 10 into a laminated metal container 100, energy-efficient and stable forming can be performed. Thus, the laminated metal sheet 10 is more suitable for use as a laminated metal container 100.

[0164] It should be noted that the laminating equipment for the hot pressing process in step S201 can be located after the continuous annealing line, plating line, etc. Positioning the laminating equipment in this way improves productivity. Alternatively, the laminating equipment can be a minimal setup comprising an uncoiler, a tension winding machine, and a laminating section.

[0165] Alternatively, a thermoplastic resin film different from the polyester film 30 can be provided on the back side 22 of the metal plate 20, for example, or a coating can be applied. When a thermoplastic resin film different from the polyester film 30 is provided on the back side 22 of the metal plate 20, it can be provided at any time; for example, it can be provided at the same time as the polyester film 30 by lamination.

[0166] Furthermore, the polyester film 30 can be attached to the metal plate 20 using an adhesive (not shown). By attaching the polyester film 30 with an adhesive in this way, the heat-pressing temperature can be reduced, and the adhesion between the polyester film 30 and the metal plate 20 can be improved.

[0167] Examples of adhesives include polyester resins, alkyd resins, epoxy resins, acrylic resins, phenolic resins, polyurethane resins, polyamine resins, polyamide-amine resins, and polyamide resins. One or more of these resins may be used. Additives may be added to the adhesive as needed.

[0168] (Manufacturing method of laminated metal containers)

[0169] The laminated metal container 100 is formed by using a laminated metal sheet 10 in at least one of two or more components constituting the laminated metal container 100. As described above, examples of laminated metal containers 100 include a three-piece can consisting of three components and a two-piece can consisting of two components.

[0170] For example, the main body of a two-piece can is formed by various forming methods such as draw and redraw (DRD), draw and ironing (DI), and draw and thin redraw (DTR).

[0171] DI forming and DTR forming are forming methods that involve thinning and deep drawing, and require high machinability. Laminated metal sheets 10, even with such machinability requirements, possess high formability, thus any of the aforementioned forming methods can be used.

[0172] It should be noted that the laminated metal container 100 can also be coated or printed. The lamination of the laminated metal container 100 can be performed by known methods. For example, the laminated metal container 100 can be formed using a can-making machine.

[0173] Laminated metal container 100 is particularly suitable for use as a container exposed to cooking sterilization treatment.

[0174] It should be noted that in the above embodiments, an example is described where the laminated metal plate 10 has a surface 21 serving as the outer surface of the laminated metal container 100 and a back surface 22 serving as the inner surface. The laminated metal plate 10 can be freely configured according to the embodiments. For example, the surface 21 of the metal plate 20 may be configured as the inner surface of the laminated metal container 100, and the back surface 22 may be configured as the outer surface of the laminated metal container 100. In this case, the polyester film 30 may be provided only on the surface 21 that serves as the inner surface of the laminated metal container 100.

[0175] Example

[0176] The present invention will now be described in more detail by way of examples, but is not necessarily limited thereto. Polyester films of Examples 1 to 6 and Comparative Examples 1 to 4 were prepared.

[0177] (Example 1)

[0178] As a raw material resin for polyester film, granules of copolymer of polyethylene terephthalate (PET) and granules of lubricant masterbatch are prepared.

[0179] The copolymer of polyethylene terephthalate (PET) contains 5 mol% isophthalic acid and 2 mol% diethylene glycol as copolymer components, and has a melting point of 245°C.

[0180] The lubricant masterbatch granules use silica as an inorganic lubricant. The lubricant masterbatch granules are made by dispersing the lubricant in PET with a melting point of 254°C.

[0181] The two types of raw resin granules were blended with silica at a concentration of 0.04% by mass of the total resin mixture. Then, to remove moisture from the granules, they were heated to 150°C under vacuum and held for 3 hours to dry them. The dried granules were then fed into a single-screw extruder and melt-blended at 275°C.

[0182] Next, after foreign matter is removed by a sintering filter with a 25μm cutoff, the film is discharged from the T-die and cooled and solidified on a casting roller with a surface temperature controlled at 30°C to obtain an unstretched film.

[0183] Next, the film is preheated using a ceramic roller heated to 90°C and stretched longitudinally by 5.0 times along the length of the unstretched film. Then, it is slowly cooled to room temperature without heat fixation or relaxation in the stretching direction. The film with the ends removed is then wound up using a winding machine to obtain a polyester film with a thickness of 18 μm.

[0184] (Examples 2-5)

[0185] As shown in Table 1, polyester films of Examples 2-5 were prepared by varying the copolymer composition of PET, the type and amount of additives, the stretching ratio of longitudinal stretching, and the final preheating roller temperature. Table 1 shows the copolymer composition of PET, the type and amount of additives, the stretching ratio of longitudinal stretching, and the final preheating roller temperature of the polyester films of Examples 2-5. Other aspects are the same as in Example 1, so descriptions are omitted. It should be noted that the unit of copolymer composition shown in Table 1 is mol%. In addition, the polyester films of Examples 1-5 are constructed as a single layer, so they are listed as the first layer in Table 1.

[0186] (Example 6)

[0187] The polyester film of Example 6 consists of three layers: a first layer and a second layer disposed on both sides of the first layer. As the raw material resin for the polyester film of Example 6, the first layer is prepared from granules of copolymerized PET and granules of pigment masterbatch. The copolymerized PET of the first layer contains 2 mol% isophthalic acid and 2 mol% diethylene glycol. The pigment masterbatch is a substance obtained by dispersing rutile titanium dioxide as an inorganic pigment in PET with a melting point of 254°C.

[0188] The second layer consists of granules of copolymerized PET and granules of lubricant masterbatch. The copolymerized PET used in the second layer contains 2 mol% isophthalic acid and 3 mol% diethylene glycol. The lubricant masterbatch is a substance made by dispersing silica, an inorganic lubricant, in PET with a melting point of 254°C.

[0189] The raw materials for the first layer are blended such that titanium dioxide accounts for 15% by mass of the first layer. The raw materials for the second layer are blended such that silicon dioxide accounts for 0.04% by mass of the second layer.

[0190] Then, the vacuum-dried first and second layer raw materials were fed into different single-screw extruders and melt-blended. The melt-blended resin composition was co-extruded using the feed block method to obtain an unstretched film. Regarding longitudinal stretching, the stretch ratio and final preheating roll temperature were changed as shown in Table 1. Otherwise, the polyester film of Example 6 was obtained in the same manner as in Example 1.

[0191] (Comparative Examples 1-3)

[0192] As shown in Table 1, polyester films of Comparative Examples 1 to 3 were prepared by varying the copolymer composition of PET, the type and amount of additives, the stretching ratio of longitudinal stretching, and the final preheating roller temperature. Table 1 shows the copolymer composition of PET, the type and amount of additives, the stretching ratio of longitudinal stretching, and the final preheating roller temperature of the polyester films of Comparative Examples 1 to 3. Other methods are the same as in Example 1, so descriptions are omitted. It should be noted that the unit of copolymer composition shown in Table 1 is mol%.

[0193] (Comparative Example 4)

[0194] The polyester film of Comparative Example 4, like that of Example 6, consists of three layers: a first layer and a second layer disposed on both sides of the first layer. The only difference between the polyester film of Comparative Example 4 and that of Example 6 is the stretch ratio.

[0195] (evaluate)

[0196] Positive electrode diagrams were prepared, the thickness of the polyester films was measured, and the melting point was determined for the polyester films of Examples 1-6 and Comparative Examples 1-4.

[0197] (Positive electrode diagram)

[0198] The measurements were performed using a wide-angle goniometer RINT-2000 manufactured by Rigaku Corporation and a multi-purpose sample stage for poles, under the following conditions, by the Schulz reflection method.

[0199] X-ray source: CuK α rays; tube voltage: 40kV; tube current: 50mA; divergence slit: 0.5°; scattering slit: 4mm; receiving slit: 3mm; longitudinal divergence restriction slit: 1.2mm; filter: CuK β ray filter; α: 15~90° (5° / step); β: 0~360° (5° / step continuous scan); β scan speed: 360° / minute

[0200] Regarding the sample orientation, the elevation angle of the bisecting line of the incident X-ray and the reflected X-ray parallel to the film surface is set to α=0°, and the in-plane rotation angle that achieves the maximum diffraction intensity at α=60° in the positive polarimetric pattern of 100° is set to β=90°.

[0201] Based on the wide-angle X-ray diffraction pattern obtained by rotating the β-axis while setting the sample at α=90°, the diffraction peak appearing at 2θ=26.5° is attributed to the 100 diffraction.

[0202] Furthermore, regarding 1-10 diffraction, no diffraction peak was observed at 2θ = 23.0 ± 0.5° in the θ-2θ method. Therefore, the laminated metal plate of Example 1 was heat-treated at 150°C for 15 minutes, and the wide-angle X-ray diffraction pattern was measured again, so that the diffraction peak appearing at 2θ = 23.0° was attributed to 1-10 diffraction. In addition, other polyester films were measured based on the diffraction angle 2θ = 23.0° obtained for Example 1.

[0203] Therefore, the positive polarimetric pattern is determined by 100 diffraction at 2θ = 26.5°, and by 1-10 diffraction at 2θ = 23.0°. The net intensity in the positive polarimetric pattern is set as the diffraction intensity obtained by subtracting the diffraction intensity at the point with the lowest diffraction intensity at α = 15° from the diffraction intensity at each point in each positive polarimetric pattern.

[0204] Based on the obtained positive polarimetric diagram, the net intensity at α=60° and β=0° in the positive polarimetric diagram of 100 diffraction is set as I. 100 (60,0) Let the net intensity at α=60° and β=90° in the positive polarimetric pattern of the 100 diffraction be I. 100 (60,90) Let the net intensity at α=60° and β=0° in the positive polarimetric pattern of the 1-10 diffraction be I. 1-10 (60,0) Let the net intensity at α=60° and β=90° in the positive polarimetric pattern of the 1-10 diffraction be I. 1-10 (60,90) Verify equations (1) and (2) below.

[0205] 0.30≤I 100 (60,0) / I 100 (60,90) ≤0.63 …(1)

[0206] 0.42≤I 1-10 (60,0) / I 1-10 (60,90) ≤0.60 …(2)

[0207] (Measurement of polyester film thickness)

[0208] The thickness of the polyester film was measured using a continuous thickness gauge FT-A100 manufactured by FUJIWORK Co., Ltd., which is equipped with a Millimar1301 micrometer probe manufactured by Maer Nippon Co., Ltd.

[0209] A 1000 mm section of polyester film was cut along the β=0° direction, and measurements were taken 1000 times at a rate of 1 mm / step. The thickness t at each point was recorded. i (i=1~1000), the values ​​expressed by the following formulas are respectively used as the average thickness μ and the sample standard deviation σ.

[0210]

[0211] (Determination of the melting peak temperature of polyester film)

[0212] The thermal properties of polyester film were determined using a DSCQ100 differential scanning calorimeter manufactured by TA Instruments, Ltd., Japan. A 5 mg sample of polyester film was cut and placed in an aluminum dish. The sample was cooled to -50°C under a nitrogen atmosphere, then heated to 290°C at a rate of 10°C / min, during which the first run (1st Run) was measured. After holding at 290°C for 5 minutes, the sample was rapidly cooled with liquid nitrogen. Then, the sample was again heated from -50°C to 290°C at a rate of 10°C / min, during which the second run (2nd Run) was measured. The endothermic peak observed in the first run (1st Run), excluding the enthalpy relaxation peak near the glass transition temperature, was identified as the melting point.

[0213] The evaluation results of the polyester films obtained in Examples 1-6 and Comparative Examples 1-4 are shown in Table 1. Additionally, the positive polarity of the 100 diffraction intensity of the polyester film of Example 1 is plotted in Table 1. Figure 4 The positive polarity of diffraction intensities from 1 to 10 is plotted on... Figure 5 .

[0214]

[0215] IA: Isophthalic acid

[0216] DEG: Diethylene glycol

[0217] WAX: Acid-modified polyethylene wax

[0218] (Evaluation results of polyester film)

[0219] In Comparative Example 3, the stretching ratio was too high during the longitudinal stretching process in the manufacture of the polyester film, resulting in breakage and making it impossible to stably cut samples. In contrast, in Examples 1-6 and Comparative Examples 1, 2, and 4, polyester films were stably manufactured. However, the stretching ratios in Comparative Examples 2 and 4 were too low. Therefore, I 100(60,0) / I 100 (60,90) and I 1-10(60,0) / I 1-10 (60,90) The values ​​are greater than the upper limits of equations (1) and (2). In addition, the sample standard deviation of the film thickness in Comparative Examples 2 and 4 is more than 10% of the average.

[0220] In contrast, in Examples 1-6 and Comparative Example 1, the membrane was produced stably. In Examples 1-6 and Comparative Example 1, the aforementioned drawbacks were not observed, and stable production was confirmed.

[0221] (Fabrication of laminated metal sheets)

[0222] Laminated metal sheets were made using the polyester films of Examples 1-6 and Comparative Examples 1-4.

[0223] TFS was used as the metal sheet. The base metal for TFS was low-carbon steel with a temper grade of T3CA and a thickness of 0.22 mm, which underwent cold rolling, annealing, and tempering. TFS was obtained by degreasing and pickling the base metal followed by chromium plating. It should be noted that the chromium coating of TFS, calculated based on Cr, is 120 mg / m². 2 The chromium hydrate oxide layer is 10 mg / m². 2 .

[0224] (Lamination of metal sheets using hot pressing lamination method)

[0225] The polyester films of Examples 1-6 and Comparative Examples 1-4 were applied to the back of a metal plate using a hot-press lamination method. A biaxially stretched PET film with a melting point of 248°C and a thickness of 20 μm was applied to the surface. The pressure applied by the laminating roller was set to 0.60 MPa. The temperature of the laminating roller was set to 80°C.

[0226] A pair of laminating rollers are arranged to hold the front and back sides of a metal sheet. Polyester films of Examples 1-6 and Comparative Examples 1-4 are placed between the metal sheet and the laminating rollers, allowing the metal sheet to pass through the rollers. After applying pressure to the metal sheet using the laminating rollers for 1 second, it is water-cooled to obtain a laminated metal sheet with polyester films bonded to both sides of the metal sheet.

[0227] It should be noted that the lamination inlet side panel temperature was set to 240°C, and the metal plate was hot-pressed. In addition, in Examples 2 to 6 and Comparative Examples 1 to 4, except for changing the lamination inlet side panel temperature as shown in Table 2, the above-mentioned polyester film was made in the same manner as in Example 1.

[0228] Wide-angle X-ray diffraction patterns were measured for laminated metal plates using the polyester films of Examples 1-6 and Comparative Examples 1-4.

[0229] (Wide-angle X-ray diffraction pattern of laminated metal sheet)

[0230] The measurements were performed using the SmartLab wide-angle goniometer manufactured by Rigaku Corporation under the following conditions via the θ-2θ method.

[0231] X-ray source: CuKα rays; tube voltage: 40kV; tube current: 40mA; entrance slit: 0.5°; entrance parallel slit: 5.0°; receiving slit: 0.6mm; receiving parallel slit: 5.0°; monochromator slit: BBM; length limiting slit: 10.0mm; 2θ = 10~30° (0.1° / step); counting time: 8 seconds / step.

[0232] Regarding the sample orientation, measurements were performed in the same direction as α=90° and β=0° in the positive pole figure. For the obtained wide-angle X-ray diffraction pattern, the background intensity, represented by the straight line connecting the diffraction intensities at 2θ=10.0° and 2θ=30°, was subtracted from the diffraction intensities at each 2θ point to obtain the net intensity. The peak appearing at 2θ=26.5° in the net intensity spectrum was assigned to the 100° diffraction, and its intensity was set as I. 100 (90,0) .

[0233] It should be noted that, in the absence of a clear peak at 2θ = 26.5° ± 1.0°, the maximum intensity within the range of 2θ = 25.5° to 27.5° is taken as I. 100 (90,0) Additionally, the intensity of the amorphous halo appearing at 2θ = 20.4° in the net intensity spectrum will be used as I. 非晶 (90,0) Verify the following equation (3).

[0234] I 100 (90,0) / I 非晶 (90,0) ≤1.5 …(3)

[0235] In addition, for the laminated metal sheets obtained using the polyester films of Examples 1-6 and Comparative Examples 1-4, the initial sealing performance, the sealing performance after retort sterilization, and the appearance after retort sterilization were evaluated. Furthermore, laminated metal containers were formed using these laminated metal sheets, and the formability of the laminated metal sheets was evaluated by measuring the degree of defects in the film.

[0236] (One-time sealing)

[0237] From the laminated metal sheets obtained using the polyester films of Examples 1-6 and Comparative Examples 1-4, samples with a conveying direction of 120 mm and a width of 15 mm were cut. A portion of the polyester film was peeled off from the long side end of the cut sample. The peeled polyester film was opened in the opposite direction to the peeling direction (angle: 180°), and a peel test was performed using a tensile testing machine at a tensile speed of 30 mm / min. The adhesion force per 15 mm width was evaluated according to the following scoring.

[0238] ◎:15.0N / 15mm or more

[0239] ○: 10.0N / 15mm or more but less than 15.0N / 15mm

[0240] △: 5.0N / 15mm or more and less than 10.0N / 15mm

[0241] ×: Less than 5.0N / 15mm

[0242] (Sealing properties after steam sterilization)

[0243] From the laminated metal sheets obtained using the polyester films of Examples 1-6 and Comparative Examples 1-4, samples with a length of 100 mm in the conveying direction and 30 mm in the width direction were cut out. A portion of the film was peeled off from the long side end of the cut sample. The peeled film was opened in the opposite direction to the peeling direction (angle: 180°), a 100 g weight was fixed, and the film was subjected to sterilization treatment under pressurized steam at 125°C for 25 minutes. The peel length of the film after sterilization treatment was measured, and the results were evaluated according to the following scoring.

[0244] ◎: Less than 2mm

[0245] ○: 2mm or more but less than 5mm

[0246] △: 5mm or more and less than 10mm

[0247] ×: 10mm or more

[0248] (Formability of laminated metal sheets)

[0249] After coating the laminated metal plate obtained using the polyester films of Examples 1-6 and Comparative Examples 1-4 with paraffin wax, it was punched into a Φ123 round plate and deep-drawn with the film of the evaluation object located on the inner side to obtain a shallow deep-drawn metal container with an inner diameter of Φ71 and a height of 36mm.

[0250] The shallow-drawn can was placed into a DI forming apparatus and formed using a punch speed of 200 mm / s, a stroke of 560 mm, a further drawing process, and a three-stage thinning stretching process, with a total thinning rate of 50%. The final product was a laminated metal container with an inner diameter of 52 mm and a height of 90 mm. It should be noted that tap water was circulated at 50°C during DI forming. After can formation, a 1% NaCl aqueous solution was injected into the can, filling it to a height of 60 mm. Then, the current value when a voltage of 6 V was applied between the can body and the electrolyte was measured, which is the Enamel Rating Value (ERV value). The formability of the laminated metal sheet was evaluated according to the following rating: the integrity of the formed film as determined by the ERV test was used to evaluate the formability of the laminated metal sheet.

[0251] ◎: Less than 0.01mA

[0252] ○: Above 0.01mA and below 0.1mA

[0253] △: Above 0.1mA and below 1mA

[0254] ×: 1mA or more

[0255] The evaluation of the laminated metal sheets and laminated metal containers obtained using the polyester films of Examples 1-6 and Comparative Examples 1-4 is shown in Table 2.

[0256]

[0257] (Evaluation results of laminated metal sheets)

[0258] Comparative Example 1: Due to the low temperature of the laminated inlet side panel, therefore I 100 (90,0) / I 非晶 (90,0) The value is greater than the upper limit of equation (3). In Comparative Example 1, no good results were obtained regarding the airtightness of the first-time sealing and the airtightness during the cooking sterilization treatment.

[0259] Furthermore, the thickness deviations of the polyester films in Comparative Examples 2 and 4 were large. Therefore, in Comparative Examples 2 and 4, the formability of the laminated metal sheets did not yield satisfactory results.

[0260] The stretch ratio of Comparative Example 3 was too high. Therefore, the I of the polyester film of Comparative Example 3 was... 100(60,0) / I 100 (60,90) and I 1-10(60,0) / I 1-10 (60,90) Below the lower limits of equations (1) and (2). In Comparative Example 3, due to excessive orientation of the polyester film, I in the laminated metal plate 100 (90,0) / I 非晶 (90,0) The value is greater than the upper limit of equation (3). Therefore, in Comparative Example 3, no good results were obtained regarding the airtightness during steam sterilization and the formability of the laminated metal sheet.

[0261] In Examples 1-6, good results were obtained in any evaluation of primary sealing, sealing during sterilization treatment, and formability of the laminated metal sheet. Furthermore, regarding Examples 1-6, stable production was achieved at any stage of the manufacturing process for the laminated metal sheet and the laminated metal container.

[0262] As confirmed above, Examples 1-6 meet the performance requirements of laminated metal sheets and polyester films, and can be manufactured energy-efficiently and stably at any stage of the manufacturing process of polyester films and laminated metal sheets.

[0263] Symbol Explanation

[0264] 100 laminated metal containers

[0265] 10-Layer Metal Sheet

[0266] 20 metal plates

[0267] 21 Surface

[0268] 22 Back

[0269] 30 Polyester film

Claims

1. A polyester film containing a polyester comprising polyethylene terephthalate as a component, wherein the net intensity of the positive pole figure representing the crystal orientation distribution obtained by X-ray diffraction satisfies the following equations (1) and (2). 0.30≤I 100 (60,0) / I 100 (60,90) ≤0.63 …(1) 0.42≤I 1-10 (60,0) / I 1-10 (60,90) ≤0.60 …(2) in, In X-ray diffraction measurements using CuKα rays, the diffraction peak appearing at 2θ = 26.5 ± 1.0° is designated as the 100 diffraction, and the diffraction peak appearing at 2θ = 23.0 ± 0.5° is designated as the 1-10 diffraction. The positive electrode diagram is determined by setting the elevation angle of the bisecting line between the incident and reflected X-rays, which is parallel to the film surface, to α = 0°. The in-plane rotation angle at which the maximum diffraction intensity is achieved when α=60° in the positive polarimetric pattern of 100 diffraction is set to β=90°. I 100 (60,0) The net intensity at α=60° and β=0° in the positive polarimetric plot of the 100 diffraction intensity is... I 100 (60,90) The net intensity at α=60° and β=90° in the positive polarimetric plot of the 100 diffraction intensity is... I 1-10 (60,0) The net intensity at α=60° and β=0° in the positive polarimetric plot of the diffraction intensities of 1-10 is the net intensity at α=60° and β=0°. I 1-10 (60,90) The net intensity at α=60° and β=90° is the positive polarimetric value of the diffraction intensity of 1-10.

2. The polyester film according to claim 1, wherein, The standard deviation of the sample thickness measured along the incident X-ray direction at β=0° in the positive polarimetric diagram is less than 10% of the average of the measured thicknesses.

3. The polyester film according to claim 1 or 2, comprising: The first layer contains a polyester comprising polyethylene terephthalate; and The second layer is stacked on top of the first layer and contains a polyester comprising polyethylene terephthalate and a lubricant.

4. The polyester film according to claim 3, wherein, The first layer contains pigment.

5. A method for manufacturing a polyester film, comprising a polyester film containing polyethylene terephthalate as a component. It has the following characteristics: The unstretched film manufacturing process includes, The polyester is extruded from a T-die using an extruder to obtain an unstretched film; and The process of producing a longitudinally uniaxially stretched film includes obtaining a longitudinally uniaxially stretched film by longitudinally stretching the unstretched film using a longitudinally uniaxial stretching machine equipped with preheating rollers and stretching rollers. The longitudinal uniaxial stretching film manufacturing process is carried out under the conditions that the longitudinal stretching stretching ratio is more than 3.3 times and less than 7.5 times, and the final preheating roller temperature of the longitudinal stretching is more than 75°C and less than 110°C.

6. A laminated metal sheet having a polyester film of any one of claims 1 to 4 bonded on at least one of the surface and the back surface of a metal sheet having a surface and a back surface.

7. The laminated metal sheet according to claim 6, wherein its wide-angle X-ray diffraction pattern satisfies the following equation (3), I 100 (90,0) / I 非晶 (90,0) ≤1.5 …(3) in, Wide-angle X-ray diffraction patterns were determined using the θ-2θ method with sample angles of α=90° and β=0° in the aforementioned positive polarimetric diagram. I 100 (90,0) The net intensity of the 100 diffraction peak appearing at 2θ = 26.5 ± 1.0° is given. I 非晶 (90,0) The net intensity of the amorphous halo that appears at 2θ = 20.0 ± 5.0°.

8. A method for manufacturing a laminated metal sheet, which is the method for manufacturing a laminated metal sheet according to claim 6 or 7, comprising: The hot pressing process, in which... A heat-pressed body is formed by hot-pressing a preheated metal plate and the polyester film using a laminating roller; and The water cooling process involves water cooling the hot-pressed joint within 7 seconds of the hot-pressing connection. In the hot pressing process, the polyester film and the metal plate are preheated within the range of -5°C to +50°C of the melting point of the polyester film before being hot pressed together.

9. A laminated metal container comprising the laminated metal sheet of claim 6 or 7 as a material.

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