Laminated metal sheet, method for manufacturing laminated metal sheet, and laminated metal container

Abstract

Provided are an inexpensive and low environmental load laminated metal plate and a laminated metal container that have basic properties such as workability, adhesion between the film and the metal plate, and corrosion resistance, and do not cause deterioration of appearance due to whitening even after retort sterilization treatment. 【Solution means】A laminated metal plate 10 in which a first film 31 is laminated on at least one of the front surface 21 and the back surface 22 of a metal plate 20, the first film 31 is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, and the first film 31 is a laminated metal plate in which w(x) obtained from linear polarization laser Raman spectroscopic analysis with respect to its cross section satisfies the following formulas (1) and (2). w 1730 ID (1.0) ≦ 20cm -1 ···(1) w 1730 ND (1.0) ≦ 20cm -1 ···(2)

Description

[Technical Field]

[0001] This invention relates to laminated metal sheets, methods for manufacturing laminated metal sheets, and laminated metal containers. [Background technology]

[0002] Metal containers such as food cans, beverage cans, and 18L cans utilize metal sheets made of materials such as tin-free steel (TFS) or aluminum. These metal sheets are painted and baked to provide corrosion resistance, durability, and weather resistance. However, baking metal sheets is a complex process that requires considerable processing time. Furthermore, painting metal sheets generates a large amount of solvent. Therefore, laminated metal sheets, in which a thermoplastic resin film is laminated onto the metal sheet, have been proposed as an alternative to painted metal sheets.

[0003] Thermoplastic resin films used for laminated metal sheets are required to have basic properties such as processability, adhesion to the metal sheet, and corrosion resistance.

[0004] Incidentally, canned food products are often subjected to retort sterilization, a process that involves heating with high-temperature steam for sterilization. In thermoplastic resin films, retort sterilization can sometimes cause the formation of tiny air bubbles inside the film. Because these air bubbles have the property of scattering light, thermoplastic resin films that have become filled with air bubbles due to retort sterilization appear cloudy and whitish, which spoils the appearance of canned food products. This problem is called retort whitening.

[0005] Attempts to suppress retort whitening have been made as follows. For example, Patent Document 1 discloses a film made of a polyester composition which is a blend of a polyester whose main repeating unit is ethylene terephthalate and a polyester whose main repeating unit is butylene terephthalate, wherein the crystallization temperature of the polyester composition is 65 to 120°C, the secondary transition point is 40°C or higher, and the melting point is 260°C or higher.

[0006] Patent Document 2 describes a resin-coated metal plate having polyester resin layers mainly composed of polyethylene terephthalate on both sides, wherein the full width at half maximum of the C=O stretching vibration peak, as determined by laser Raman spectroscopy in the thickness direction of the polyester resin layer, is 16.0 cm. -1 More than 24.0cm -1 The following resin-coated metal plate is disclosed.

[0007] Patent Document 3 discloses a polyester resin-coated metal sheet having an unstretched polyester resin layer on at least one surface of a metal material, wherein the polyester resin layer has a first region on the interface side with the metal material where a specific peak determined by laser Raman spectroscopy is within a specific half-width range, and a second region on the surface side opposite to the metal material where the specific peak is within a specific half-width range. Furthermore, a method for manufacturing a polyester resin-coated metal sheet having the above characteristics is disclosed, which involves heating and pressing an unstretched polyester resin film onto a metal material, rapidly cooling the polyester resin film after heating and pressing to form a polyester resin layer on the metal material, and then performing a post-heat treatment after rapid cooling.

[0008] Patent Document 4 describes a resin-coated metal plate having a polyester resin coating layer in which 90 mol% or more of the constituent units are ethylene terephthalate units, wherein the full width at half maximum of the C=O stretching vibration peak, determined by laser Raman spectroscopy in the thickness-direction cross-section of the polyester resin coating layer, is 18.5 cm at a position 1.0 μm from the metal plate side of the polyester resin coating layer in the thickness direction. -1 22.0cm or more -1 The following is true, and also, at a position 1.0 μm from the surface in the thickness direction, 17.0 cm -1 Over 18.5cm -1 The following resin-coated metal plate is disclosed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 5-331302 [Patent Document 2] Japanese Patent Publication No. 2010-105263 [Patent Document 3] Japanese Patent Publication No. 2017-213884 [Patent Document 4] International Publication No. 2021 / 020549 [Overview of the project] [Problems that the invention aims to solve]

[0010] As mentioned above, laminated metal sheets are sometimes required to have not only basic properties such as processability, adhesion between the thermoplastic resin film and the metal sheet, and corrosion resistance, but also resistance to retort whitening. Furthermore, as a thermoplastic film that achieves resistance to retort whitening, a film mainly composed of polyethylene terephthalate and polybutylene terephthalate has been proposed. It is thought that this film can suppress retort whitening by generating a large number of microcrystals in the resin film during retort sterilization treatment. In addition, a method has been proposed in which the crystalline structure in the thickness direction of the resin layer is controlled by heat treatment of the polyester resin layer on the laminated metal sheet.

[0011] However, the method described in Patent Document 1 had the problem of being inferior in corrosion resistance compared to conventional polyester resins and requiring the inclusion of expensive polybutylene terephthalate. Furthermore, although the methods described in Patent Documents 2 to 4 could suppress retort whitening, they required heat treatment after lamination, resulting in a higher environmental impact compared to conventional methods for manufacturing laminated metal sheets.

[0012] This invention has been made in view of the above-mentioned problems. Specifically, the objective is to provide inexpensive and environmentally friendly laminated metal sheets and laminated metal containers that have basic properties such as processability, adhesion between the film and the metal sheet, and corrosion resistance, and that do not deteriorate in appearance due to whitening even after retort sterilization treatment. [Means for solving the problem]

[0013] The inventors of the present invention have conducted intensive studies to solve the above problems. As a result, it has been found that in the film cross-section (thickness-direction cross-section) on a laminated metal plate, a laminated metal plate in which the full width at half maximum of a specific peak in the linearly polarized laser Raman spectroscopic analysis spectrum shows a specific distribution does not cause deterioration in appearance due to whitening even when subjected to retort sterilization treatment. Further, in order to manufacture a laminated metal plate showing the above-described distribution of the full width at half maximum, it has been found that it is preferable that the elapsed time from the thermocompression bonding step to the rapid cooling step during lamination and the surface temperature of the thermocompression bonded body immediately before being rapidly cooled in the rapid cooling step satisfy a specific relationship. Based on such findings, the present invention has been further studied and completed, and the gist of the present invention is as follows.

[0014] 1. A laminated metal plate in which a first film is laminated on at least one of the front and back surfaces of a metal plate, where the first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, where the first film satisfies the following formulas (1) and (2) for w(x) obtained from linearly polarized laser Raman spectroscopic analysis of its cross-section, a laminated metal plate. w 1730 ID (1.0) ≦ 20 cm -1 ···(1) w 1730 ND (1.0) ≦ 20 cm -1 ···(2) However, w 1730 ID (x) is the full width at half maximum of the peak caused by the C=O stretching vibration in the vicinity of 1730 cm when linearly polarized laser light is incident parallel to the film surface direction at a position x μm in the thickness direction from the metal plate side with respect to the cross-section of the first film, -1 and w 1730 ND(x) is the value obtained when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film at a position x μm in the thickness direction from the metal plate side, parallel to the film thickness direction, at 1730 cm². -1 This is the full width at half maximum of the peak caused by the nearby C=O stretching vibration.

[0015] 2. In the laminated metal sheet described in item 1 above, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies the following equations (3) and (4). Laminated metal plate. 14cm -1 ≤ w 1730 ID (3.0) ≤ 20cm -1 ...(3) 14cm -1 ≤ w 1730 ND (3.0) ≤ 20cm -1 ...(4)

[0016] 3. In the laminated metal sheet described in 1 or 2 above, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies equations (5) and (6) below. Laminated metal plate. w 1730 ID (5.0) ≤ 16cm -1 ...(5) 20cm -1 ≤ w 1730 ND (5.0) ···(6)

[0017] 4. A method for manufacturing laminated metal sheets, A heat-pressing process to create a heat-pressed body by heat-pressing a preheated metal plate and a first film using a laminating roll, The process includes a rapid cooling step for rapidly cooling the heat-sealed body, The first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate. The elapsed time tq from the end of the heat-pressing process to the start of the rapid cooling process, and the surface temperature Tq of the first film side of the heat-pressed body 0.2 seconds after the end of the heat-pressing process, satisfy the following equation (7): A method for manufacturing laminated metal sheets. 0.38×Tq-tq-72 ≦ 0.0 (7)

[0018] 5. In the method for manufacturing a laminated metal sheet as described in item 4 above, The preheating temperature of the metal plate in the heat-compression bonding process is 250°C or higher. A method for manufacturing laminated metal sheets.

[0019] 6. A laminated metal container comprising a laminated metal plate as described in any one of items 1 to 3 above as a material. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide inexpensive laminated metal sheets and laminated metal containers that have basic properties such as processability, adhesion between the film and the metal sheet, and corrosion resistance, and that do not deteriorate in appearance due to whitening even after retort sterilization treatment. [Brief explanation of the drawing]

[0021] [Figure 1] (a) is a diagram showing the configuration of an example of a laminated metal container according to the present invention, and (b) is an enlarged cross-sectional view of the lid of the laminated metal container shown in (a). [Modes for carrying out the invention]

[0022] The present invention will be described in more detail below with reference to the drawings, but is not necessarily limited thereto.

[0023] (Laminated metal container) Figure 1(a) shows the configuration of an example of a laminated metal container according to the present invention. As shown in Figure 1(a), the laminated metal container 100 comprises a bottomed cylindrical container body 11 and further comprises a lid portion 12 that closes the container body 11 as needed. The laminated metal container 100 is used, for example, for canned food, beverage cans, 18L cans, etc. Figure 1(b) shows an enlarged cross-sectional view of the lid portion 12 of the laminated metal container 100.

[0024] The laminated metal container 100 may be a three-piece can formed by joining three components: a lid material constituting the lid portion 12, and a body material and bottom material constituting the container body 11. Alternatively, it may be a two-piece can formed by joining two components: a lid material constituting the lid portion 12, and a bottomed body material constituting the container body 11. The laminated metal container 100 may also have an opening in the container body 11, for example, by omitting the lid portion 12.

[0025] (Laminated metal plate) As shown in Figure 1(b), the laminated metal container 100 includes a laminated metal sheet 10 as a material. The laminated metal container 100 does not need to have one or more of its components, such as the lid, body, and bottom, made of laminated metal sheet 10. For example, the body may be made of an unlaminated metal sheet, and the lid may be made of laminated metal sheet 10.

[0026] The laminated metal plate 10 has a surface 21 which is the outer surface of the laminated metal container 100 and a back surface 22 which is the inner surface of the laminated metal container 100. The laminated metal plate 10 has a first film 31 bonded to at least one of the surface 21 and back surface 22 of the metal plate 20. Alternatively, the laminated metal plate 10 may have the first film 31 on one of the surface 21 and back surface 22 of the metal plate 20 and a second film 32 on the other surface. In Figure 1, the first film 31 is provided so as to cover the surface 21 of the metal plate 20. The second film 32 is provided so as to cover the back surface 22 of the metal plate 20.

[0027] The metal plate 20 is not particularly limited, but can be aluminum plate or steel plate, which are widely used as materials for metal containers, or these that have undergone various surface treatments. In particular, it is preferable to use a surface-treated steel plate (TFS: Tin Free Steel) on which a film made of metallic chromium and chromium hydrate oxide has been formed as the metal plate 20.

[0028] The steel sheet that forms the base of TFS is not particularly limited, but it is preferably obtained by recrystallizing and annealing low-carbon steel or IF (Interstitial Free) steel and then rolling it, such as by temper rolling. The steel sheet that forms the base of TFS may also be subjected to overaging treatment as needed. Furthermore, the steel sheet that forms the base of TFS may also be subjected to secondary cold rolling.

[0029] As low-carbon steel, for example, steel with a carbon content of 0.010% by mass or more and 0.10% by mass or less can be used. As IF steel, for example, extremely low-carbon steel with a carbon content of 0.003% by mass or less to which niobium (Nb), titanium (Ti), etc., have been added can be used. As for recrystallization annealing, examples include continuous annealing, tight annealing, and open annealing.

[0030] The mechanical properties of the steel sheet forming the base of the TFS are not particularly limited, as long as they can be formed into a shape corresponding to the laminated metal container 100. For example, the yield point of the steel sheet is preferably 220 MPa or more and 580 MPa or less. The Rankford value is preferably 0.8 or more, and the absolute value of the in-plane anisotropy of the Rankford value is preferably 0.7 or less. The amount of metallic chromium layer and chromium hydrated oxide layer attached to the TFS is not particularly limited, but in terms of chromium equivalent, the metallic chromium layer is 50 to 200 mg / m². 2 The chromium hydrated oxide layer contains 3-30 mg / m². 2 A range of this magnitude is preferable. If the amount of metal chromium layer and chromium hydrated oxide layer attached is within the aforementioned range, the film and TFS will adhere more easily, and corrosion resistance will be improved.

[0031] The thickness of the metal plate 20 is not particularly limited, but is preferably 0.10 mm or more. Furthermore, the thickness of the metal plate 20 is preferably 0.35 mm or less. If the thickness of the metal plate 20 is 0.10 mm or more, the rigidity of the laminated metal container 100 is improved. Also, if the thickness of the metal plate 20 is 0.35 mm or less, the laminated metal container 100 can be made lighter, reducing the energy consumed during the molding process and during transportation.

[0032] (First film) Copolymerized polyethylene terephthalate can be suitably used as the resin constituting the first film 31, but homopolyethylene terephthalate can be more suitably used. With homopolyethylene terephthalate, the crystallization rate of the first film 31 is faster, and retort whitening resistance can be expressed more effectively.

[0033] The copolymer components of copolymerized polyethylene terephthalate include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenyl etherdicarboxylic acid, diphenyl sulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodium sulfisophthalic acid, as well as aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, dodecanedionic acid, and cyclohexanedicarboxylic acid, and their ester derivatives.

[0034] The copolymer components of copolymerized polyethylene terephthalate include, as alcohol components, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbide (1,4:3,6-dianhydroglucitol, 1,4:3,6-dianhydro-D-sorbitol), spiroglycol, bisphenol A, bisphenol S, etc.

[0035] The copolymer of copolymerized polyethylene terephthalate may use only one of the aforementioned copolymers or two or more. It is preferable to use isophthalic acid (IA) as the copolymer of the copolymerized polyethylene terephthalate. When isophthalic acid is used as the copolymer of the first polyester, the content is preferably 1 mol% to 15 mol%, more preferably 2 mol% to 13 mol%, and even more preferably 3 mol% to 7 mol%. When isophthalic acid is included as a copolymer of 1 mol% or more, the first film 31 and the metal plate 20 adhere well to each other. Furthermore, when isophthalic acid is included as a copolymer of 15 mol% or less, the cooling crystallization temperature of the first film 31 is high, and retort whitening resistance can be achieved even with a short elapsed time from the heat-sealing process to the rapid cooling process during lamination.

[0036] The intrinsic viscosity of the first film 31 is preferably 0.65 dL / g or more and 1.00 dL / g or less, and more preferably 0.70 dL / g or more and 0.90 dL / g or less. If the intrinsic viscosity of the first film 31 is 0.65 dL / g or more, the moldability of the laminated metal sheet 10 is improved. If the intrinsic viscosity of the first film 31 is 1.00 dL / g or less, energy consumption in the polymerization and extrusion processes can be suppressed.

[0037] The first film 31 preferably has a cooling crystallization peak temperature (Tcc) of 185°C to 205°C, and more preferably 190°C to 200°C. The cooling crystallization peak temperature is the peak temperature of the exothermic peak when the film is cooled from 290°C at a rate of 10°C / min using differential scanning thermal analysis (DSC). If the cooling crystallization peak temperature of the first film 31 is 185°C or higher, crystallization will proceed even at high temperatures, making it easier to obtain good resistance to retort whitening. Furthermore, if the cooling crystallization peak temperature of the first film 31 is 205°C or lower, a decrease in processability due to excessive crystallization can be suppressed.

[0038] The first film 31 may contain additives such as antioxidants, inorganic lubricants, organic lubricants, nucleating agents, heat stabilizers, antistatic agents, and coloring pigments, in addition to homopolyethylene terephthalate or copolymerized polyethylene terephthalate.

[0039] The first film 31 preferably contains an antioxidant in an amount of 0.0001% by mass or more and 1.0000% by mass or less. The heat resistance of the first film 31 is improved if the antioxidant is contained in an amount of 0.0001% by mass or more and 1.0000% by mass or less. The antioxidant is not particularly limited, but known antioxidants classified as hindered phenols, hydrazines, phosphites, etc., can be used.

[0040] Furthermore, it is preferable that the first film 31 contains an inorganic lubricant in an amount of 0.01% by mass or more and 0.50% by mass or less. If the first film 31 contains an inorganic lubricant in an amount of 0.01% by mass or more and 0.50% by mass or less, the handling properties of the first film are improved. The inorganic lubricant is not particularly limited, but known inorganic lubricants such as silicon dioxide, diatomaceous earth, and talc can be used.

[0041] Incidentally, the first film 31 can also be composed of multiple layers laminated in the thickness direction. Known methods can be used for laminating the multiple layers, such as co-extrusion using a feed block or multi-manifold, laminating multiple films together, or directly laminating molten resin onto a film. In order to increase productivity and suppress energy consumption, it is preferable to use co-extrusion for laminating the first film 31.

[0042] As described above, when the first film 31 is composed of multiple layers, it is preferable to include an inorganic lubricant in an amount of 0.01% by mass or more and 0.50% by mass or less relative to the outermost layer. Furthermore, it is preferable that the layers other than the outermost layer do not contain an inorganic lubricant, or that they contain an amount of 0.01% by mass or less relative to the layers other than the outermost layer. For example, when the first film 31 is composed of three layers: an air-side surface layer, a core layer, and a metal plate-side surface layer, an example configuration can be given in which the air-side surface layer and the metal plate-side surface layer contain an inorganic lubricant, while the core layer does not. By including an inorganic lubricant only in the outermost layer, the amount of inorganic lubricant used can be reduced, making it economical.

[0043] Furthermore, the first film 31 preferably contains an organic lubricant in an amount of 0.01% by mass or more and 1.00% by mass or less. If the first film 31 contains an organic lubricant in an amount of 0.01% by mass or more and 1.00% by mass or less, the moldability of the laminated metal sheet 10 is improved. If the first film 31 is composed of multiple layers, it is preferable to include the organic lubricant in an amount of 0.01% by mass or more and 1.00% by mass or less relative to the outermost layer. The organic lubricant is not particularly limited, but known organic lubricants such as carnauba wax, polyolefin wax, and modified polyolefin wax can be used.

[0044] The average thickness of the first film 31 is preferably 7 μm or more, and preferably 50 μm or less. The average thickness of the first film 31 is more preferably 8 μm or more and 30 μm or less, and even more preferably 10 μm or more and 22 μm or less. If the average thickness of the first film 31 is 7 μm or more, better corrosion resistance can be ensured when the laminated metal plate 10 is formed into a laminated metal container 100. If the average thickness of the first film 31 is 50 μm or less, the energy consumption required for heating during the manufacturing of the first film 31 and the laminated metal plate 10 can be suppressed.

[0045] The sample standard deviation of the thickness of the first film 31 is preferably 10% or less of the average thickness of the first film 31, and more preferably 5% or less. If the sample standard deviation of the thickness of the first film 31 is 10% or less of the average thickness of the first film 31, it is possible to suppress the breakage of the first film 31 or the metal plate 20 when forming the laminated metal plate 10 into a laminated metal container 100.

[0046] The average thickness and sample standard deviation of the first film 31 are calculated from the sample standard deviation and average of 1,000 thickness points measured at 1 mm intervals over 1,000 mm along the longitudinal direction of the first film 31 using a constant-pressure thickness gauge.

[0047] The first film 31 in the laminated metal plate 10 satisfies equations (1) and (2) below, as obtained from linearly polarized laser Raman spectroscopy of its cross-section. w 1730 ID (1.0) ≤ 20cm -1 ...(1) w 1730 ND (1.0) ≤ 20cm -1 ...(2) However, w 1730 ID (x) is the value obtained when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film 31 from the metal plate 20 side at a position x μm in the thickness direction, parallel to the direction in the film plane, at 1730 cm². -1 This is the full width at half maximum of the peak caused by the nearby C=O stretching vibration. 1730 ND (x) is the value obtained when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film 31 from the metal plate 20 side at a position x μm in the thickness direction, parallel to the film thickness direction, at 1730 cm². -1 This is the full width at half maximum of the peak caused by the nearby C=O stretching vibration.

[0048] Wave number 1730cm -1The nearby Raman peak is due to C=O stretching vibrations in the ester group of polyethylene terephthalate, and the full width at half maximum of this peak narrows as the crystallinity of polyethylene terephthalate increases. Furthermore, by using linearly polarized laser light as the light source for Raman spectroscopy, it is possible to obtain information only about C=O bonds oriented in the same direction as the polarization direction.

[0049] Also, w 1730 ID (1.0) is 20cm -1 The following is 19cm -1 The following is preferable. Also, w 1730 ID (1.0) is 13cm -1 Preferably, it should be 15 cm or more. -1 It is more preferable that it be as above. 1730 ND (1.0) is 20cm -1 The following is 19cm -1 The following is preferable. Also, w 1730 ND (1.0) is 14cm -1 Preferably, it should be 15 cm or more. -1 It is more preferable that the above conditions are met.

[0050] The wavenumber of the first film 31 at a position 1.0 μm in the thickness direction from the metal plate 20 side is 1730 cm². -1 The full width at half maximum of the nearby Raman peak is 20 cm in both the in-plane and thickness directions. -1 If the following conditions are met, the polyethylene terephthalate forms isotropic crystals in the first film 31 at a position close to the metal plate 20. Thus, the formation of isotropic crystals of polyethylene terephthalate at a position close to the metal plate 20 is effective in suppressing retort whitening.

[0051] The mechanism of retort whitening is presumed to be as follows: Water vapor that permeates the first film 31 in the initial stages of retort sterilization is cooled by the low-temperature contents near the interface between the metal plate 20 and the first film 31, causing it to condense. As the temperature of the contents rises, bubbles are formed when the vaporized water vapor appears, making it appear white. Therefore, when the temperature of the contents rises, if the crystallinity of the first film 31 is high near the metal plate 20, that is, if equations (1) and (2) are satisfied, retort whitening can be suppressed.

[0052] Furthermore, when the first film 31 is a biaxially oriented polyethylene terephthalate film, the C=O bonds of the ester groups of the oriented and crystallized polyethylene terephthalate are oriented in the direction in the film plane. That is, the C=O bonds oriented outward from the film plane originate from amorphous polyethylene terephthalate that has not undergone oriented crystallization. Therefore, equation (2) is not satisfied. Also, in the method for manufacturing a laminated metal plate according to the present invention, which will be described later, if a biaxially oriented polyethylene terephthalate film is laminated at a preheating temperature lower than the range of the present invention, the amorphous state of polyethylene terephthalate does not proceed, and equation (2) is not satisfied.

[0053] In the laminated metal plate 10, it is preferable that the first film 31, when analyzed by linearly polarized laser Raman spectroscopy of its cross-section, satisfies the following equations (3) and (4). 14cm -1 ≤ w 1730 ID (3.0) ≤ 20cm -1 ...(3) 14cm -1 ≤ w 1730 ND (3.0) ≤ 20cm -1 ...(4)

[0054] w 1730 ID (3.0) is 20cm -1 The following is preferable: 19cm -1 The following is more preferable. Also, w 1730 ID(3.0) is preferably 14 cm or more, more preferably 15 cm or more. w -1 It is preferably 14 cm or more, more preferably 15 cm or more. w -1 It is preferably 14 cm or more, more preferably 15 cm or more. w 1730 ND (3.0) is preferably 20 cm or less, more preferably 19 cm or less. Also, w -1 It is preferably 20 cm or less, more preferably 19 cm or less. Also, w -1 It is preferably 20 cm or less, more preferably 19 cm or less. Also, w 1730 ND (3.0) is preferably 14 cm or more, more preferably 16 cm or more. -1 It is preferably 14 cm or more, more preferably at least 16 cm. <00> -1 It is preferably 14 cm or more, more preferably 16 cm or more.

[0055] At a position 3.0 μm in the thickness direction from the metal plate 20 side, the full width at half maximum of the Raman peak near the wave number 1730 cm of the first film 31 is 20 cm in both the in-plane direction and the thickness direction. -1 If it is 20 cm or less in both the in-plane direction and the thickness direction, it is sufficiently crystallized and retort whitening can be effectively suppressed. Also, at a position 3.0 μm in the thickness direction from the metal plate 20 side, the full width at half maximum of the Raman peak near the wave number 1730 cm of the first film 31 is 14 cm in both the in-plane direction and the thickness direction. -1 If it is 20 cm or less in both the in-plane direction and the thickness direction, it is sufficiently crystallized and retort whitening can be effectively suppressed. Also, at a position 3.0 μm in the thickness direction from the metal plate 20 side, the full width at half maximum of the Raman peak near the wave number 1730 cm of the first film 31 is 14 cm in both the in-plane direction and the thickness direction. -1 If it is 14 cm or more in both the in-plane direction and the thickness direction, it indicates that the polyethylene terephthalate has been once amorphized during lamination. In such a case, the first film 31 and the metal plate 20 are sufficiently adhered, and it is possible to suppress the peeling of the first film 31 from the metal plate 20 during the retort sterilization treatment. -1 If it is 14 cm or more in both the in-plane direction and the thickness direction, it indicates that the polyethylene terephthalate has been once amorphized during lamination. In such a case, the first film 31 and the metal plate are sufficiently adhered, and it is possible to suppress the peeling of the first film 31 from the metal plate 20 during the retort sterilization treatment.

[0056] For the first film 31 in the laminated metal plate 10, it is preferable that w(x) obtained from the linearly polarized laser Raman spectroscopic analysis of its cross-section satisfies the following equations (5) and (6). w 1730 ID (5.0) ≤ 16 cm -1 ···(5) 20 cm -1 ≤ w 1730 ND (5.0) ···(6)<00> <>

[0057] w 1730ID (5.0) is 16cm -1 Preferably, it is 15 cm -1 The following is more preferable. Also, w 1730 ID (5.0) is 13cm -1 It is more preferable that it be as above. 1730 ND (5.0) is 20cm -1 Preferably, it should be 22 cm or more. -1 It is more preferable that it be the above. Also, w 1730 ND (5.0) is 26cm -1 The following is more preferable:

[0058] At a position 5.0 μm in the thickness direction from the metal plate 20 side, the wavenumber of the first film 31 is 1730 cm². -1 The full width at half maximum of the nearby Raman peak is 16 cm in the in-plane direction. -1 The following applies, and in the thickness direction, 20cm -1 If the above conditions are met, the benzene rings are oriented in a substantially in-plane manner, indicating that oriented crystallization has occurred. In other words, the oriented crystals of the stretched polyethylene terephthalate film roll before lamination remain. When oriented crystals of the roll remain at a position of 5.0 μm in the thickness direction in this way, no excess amorphous formation occurs during lamination beyond what is necessary to ensure adhesion, and the preheating temperature of the metal plate can be reduced, making it economical.

[0059] (First method of manufacturing film) The first film 31 can be manufactured using various known methods. When manufacturing a laminated metal sheet 10 by laminating the first film 31 onto a metal sheet 20, an extrusion coating method may be used in which the molten first film extruded from the T-die of an extruder is directly heat-pressed onto the metal sheet 20. Alternatively, the first film 31 may be manufactured on a separate film manufacturing line from the laminated metal sheet manufacturing line, and then the first film 31 and the metal sheet 20 may be laminated on the laminated metal sheet manufacturing line.

[0060] The following describes a method for manufacturing the first film 31 on a film production line. However, the present invention is not limited to the following description.

[0061] An example of a production line for the first film 31 is a production line consisting of an unstretched film production step in which an unstretched film is obtained from a resin composition using an extruder, a stretched film production step in which the unstretched film is stretched, and a winding step in which the film is wound into a roll.

[0062] In the process of producing unstretched film, a raw material resin of homopolyethylene terephthalate or copolymerized polyethylene terephthalate is used, along with additives such as antioxidants, inorganic lubricants, organic lubricants, nucleating agents, heat stabilizers, antistatic agents, and coloring pigments as needed. The raw material resin is preferably in the form of pellets. From the viewpoint of handling, the additives are preferably in the form of masterbatch pellets in which the additives are dispersed in the resin. From the viewpoint of economy, homopolyethylene terephthalate is preferred as the resin in which the additives are dispersed in the masterbatch pellets. The pellets of the raw material resin and additives can be mixed by dry blending to form a resin mixture. The resin mixture is dried under hot air or vacuum as needed before being supplied to an extruder.

[0063] The raw resin supplied to the extruder is heated above its melting point and melted. The additives and the molten raw resin are kneaded in the extruder to form a resin composition in which the additives are dispersed in polyethylene terephthalate. After foreign matter and modified resin are removed by filtering, the resin composition is extruded from a T-die and formed into a molten resin sheet. To improve the metering accuracy of the extrusion, it is preferable to install a feeder and a gear pump in the extruder. To omit the drying process of the resin mixture and to suppress hydrolysis during extrusion, it is preferable to install vacuum piping to reduce the pressure inside the extruder.

[0064] In this case, if the first film 31 is to be formed from multiple layers, for example, multiple layers can be laminated using a co-extrusion method to form a single first film 31. In this case, several extruders can be used, and feed blocks and multi-manifold dies can be used to melt-extrude the resin composition and other materials that will form each layer.

[0065] The molten resin sheet discharged from the T-die is cooled and solidified by a cooling device such as a cast roll to form an unstretched film. When cooling and solidifying the molten resin sheet, it is preferable to use electrostatic pinning or a vacuum chamber. By using these devices, the adhesion between the cast roll and the molten resin sheet can be improved, and a homogeneous unstretched film can be obtained.

[0066] In the stretched film manufacturing process, the unstretched film is stretched in the film transport direction and / or the film width direction. Stretching in the film transport direction is called longitudinal stretching, and stretching in the film width direction is called transverse stretching. In the stretched film manufacturing process, either longitudinal stretching or transverse stretching alone may be performed, but sequential biaxial stretching, where longitudinal and transverse stretching are performed consecutively, or simultaneous biaxial stretching, where longitudinal and transverse stretching are performed simultaneously, may also be performed. Furthermore, the stretched film manufacturing process may be omitted.

[0067] Longitudinal stretching is performed, for example, in a longitudinal stretching machine equipped with a preheating roll and a stretching roll. The film before stretching is heated to a predetermined temperature as it passes through the preheating roll while being conveyed in the longitudinal direction. The film before stretching, heated to the predetermined temperature by the preheating roll, is stretched in the longitudinal direction by a stretching roll that rotates at a faster conveying speed than the preceding roll. In addition to the preheating roll, an infrared heater may also be used to heat the film. It is preferable to install the infrared heater between the stretching roll and the roll immediately preceding it. By installing the infrared heater in this position, it is possible to suppress adhesion of the film to the preheating roll and reduce the torque during stretching.

[0068] Transverse stretching is performed, for example, by gripping the widthwise ends of the film with clips and widening the clip spacing in the film widthwise direction in a heating furnace. Preferably, the heating furnace is divided into several temperature zones from the inlet to the outlet.

[0069] Sequential biaxial stretching can be performed by carrying out the longitudinal stretching and the transverse stretching consecutively. The order in which the longitudinal and transverse stretching are performed can be determined as appropriate, and for example, longitudinal stretching can be performed once each, followed by another longitudinal stretching.

[0070] Simultaneous biaxial stretching can be performed, for example, by widening the clip spacing in the film's longitudinal direction at the same time as widening the clip spacing in the film's width direction during the transverse stretching process.

[0071] In any of the stretching methods—longitudinal stretching, transverse stretching, sequential biaxial stretching, or simultaneous biaxial stretching—it is preferable that the maximum temperature of the film is equal to or greater than the glass transition temperature of the unstretched film. Furthermore, the ratio of the length of the film in the stretching direction before and after stretching is called the stretching ratio, and it is preferable that the stretching ratio is between 2.0 and 9.0 times.

[0072] In the stretched film manufacturing process, a heat-setting treatment may be performed. This treatment can be carried out, for example, by sequentially biaxial stretching the film, then raising its temperature to a level higher than the film's highest temperature during stretching, and loosening the tension of the film as needed. Heat-setting treatment can improve the film's heat resistance and suppress dimensional changes over time.

[0073] In the winding process, the unstretched or stretched film is wound into a roll to obtain a film roll.

[0074] Before winding the film into a roll, it is preferable to use quality inspection equipment such as a thickness gauge or defect detector to inspect the film's quality. While this quality inspection equipment may be installed in the unstretched film manufacturing process or the stretched film manufacturing process, it is more effective to install it in the winding process, which is the final step in the film manufacturing line.

[0075] Furthermore, it is preferable to use a trimmer to remove the widthwise edges of the film before winding it into a roll. Applying a trimmer helps to standardize the width of the film, contributes to the stable manufacturing of laminated metal sheets, and suppresses fold defects at the widthwise edges of the film. In trimmers, the application of oscillation rolling, which causes the film to pass through while oscillating in the width direction, is preferable. Oscillation rolling can suppress gauge band defects, which occur when thickness variations in the width direction of the film accumulate, resulting in unevenness in the width direction of the film roll.

[0076] (Second film) The resin of the second film 32 is preferably homopolybutylene terephthalate or copolymerized polyethylene terephthalate. If the resin of the second film 32 is homopolybutylene terephthalate or copolymerized polyethylene terephthalate, the melting point of the second film 32 will be close to that of the first film 31. Therefore, when the first film 31 and the second film 32 are heat-pressed onto a metal plate at the same time, both the first film 31 and the second film 32 tend to exhibit good adhesion.

[0077] The copolymer components of copolymerized polyethylene terephthalate can preferably be the same as those of the first film 31. The copolymer components of copolymerized polyethylene terephthalate may be one type only, or two or more types may be used.

[0078] The copolymer component is preferably isophthalic acid. When isophthalic acid is used as the copolymer component of the second polyester, the content is preferably 1 mol% to 20 mol%, more preferably 3 mol% to 18 mol%, and even more preferably 4 mol% to 15 mol%. When isophthalic acid is contained in an amount of 1 mol% or more as a copolymer component, the second film 31 and the metal plate 20 adhere well to each other. Furthermore, when the isophthalic acid content as a copolymer component is 20 mol% or less, the strength of the film is high and handling properties are improved.

[0079] The intrinsic viscosity of the second film 32 is preferably 0.60 dL / g or more and 1.00 dL / g or less, and more preferably 0.65 dL / g or more and 0.90 dL / g or less. If the intrinsic viscosity of the second film 32 is 0.60 dL / g or more, the moldability of the laminated metal sheet 10 is improved. If the intrinsic viscosity of the second film 32 is 1.00 dL / g or less, energy consumption in the polymerization and extrusion processes can be suppressed.

[0080] The second film 32 may contain the same additives as the first film 31. The second film 32 can also be composed of multiple layers in the thickness direction. When the second film 32 is composed of multiple layers, it is preferable to change the additive content for each layer. By changing the additive content for each layer, it is possible to design layers and additive content that allow the additive to exert its effect most effectively, which is economical.

[0081] The average thickness of the second film 32 is preferably 7 μm or more, and preferably 50 μm or less. The average thickness of the second film 32 is more preferably 8 μm or more and 30 μm or less, and even more preferably 10 μm or more and 22 μm or less. If the average thickness of the second film 32 is 7 μm or more, better corrosion resistance can be ensured when the laminated metal plate 10 is formed into a laminated metal container 100. If the average thickness of the second film 32 is 50 μm or less, the energy consumption required for heating during the manufacturing of the second film 32 and the laminated metal plate 10 can be suppressed.

[0082] The sample standard deviation of the thickness of the second film 32 is preferably 10% or less of the average thickness of the second film 32, and more preferably 5% or less. If the sample standard deviation of the thickness of the second film 32 is 10% or less of the average thickness of the second film 32, it is possible to suppress the breakage of the second film 32 or the metal plate 20 when forming the laminated metal plate 10 into a laminated metal container 100. The average thickness and sample standard deviation of the second film 32 are calculated in the same manner as the average thickness and sample standard deviation of the first film 31.

[0083] (Second method of manufacturing film) The second film 32 can be manufactured using various known methods, similar to the first film 31 described above.

[0084] (Method of manufacturing laminated metal sheets) The method for manufacturing the laminated metal sheet 10 is described below. The method for manufacturing the laminated metal sheet 10 according to the present invention comprises a heat-compression bonding step and a rapid cooling step.

[0085] In the thermocompression bonding process, a preheated metal plate 20 and a first film 31 are thermocompressed together using a laminating roll to produce a thermocompressed body. In the thermocompression bonding process, the first film 31 is thermocompressed to at least one of the front surface 21 and back surface 22 of the metal plate 20. The metal plate 20 is cast and rolled to a predetermined thickness and width, and then subjected to surface treatments such as annealing, temper rolling, and plating as needed.

[0086] The heat-pressing process is performed by placing a first film 31 between a metal plate 20, which has been preheated to a predetermined temperature, and a laminating roll, and then pressing the first film 31 against the metal plate 20 with the laminating roll. At this time, the first film 31 melts due to the heat of the metal plate 20 and is pressed against the metal plate 20.

[0087] In this specification, the surface temperature of the metal plate 20 0.5 seconds before it comes into contact with the first film 31 is referred to as the preheating temperature of the metal plate 20. The preheating temperature of the metal plate 20 is preferably 250°C or higher, and more preferably 260°C to 285°C. If the preheating temperature of the metal plate 20 is 250°C or higher, amorphization of the first film 31 progresses in a region of 3.0 μm or less in the thickness direction from the metal plate 20 side, and the metal plate 20 and the first film 31 adhere to each other with sufficient strength. If the preheating temperature of the metal plate 20 is 285°C or lower, it is possible to suppress the first film 31 from completely melting and adhering to the laminating roll while it is in contact with the laminating roll.

[0088] Alternatively, in the heat-pressing process, the first film 31, the preheated metal plate 20, and the second film 32 may be heat-pressed together in this order to produce a heat-pressed body. In this case, in the heat-pressing process, the first film 31 is heat-pressed to one side of the metal plate 20 (front surface 21 and back surface 22), and the second film 32 is heat-pressed to the other side.

[0089] When the first film 31 and the second film 32 are heat-pressed onto the metal plate 20, the first film 31 and the second film 32 may be heat-pressed onto the metal plate 20 sequentially, but it is preferable to heat-press them onto the metal plate 20 simultaneously. When the first film 31 and the second film 32 are heat-pressed onto the metal plate 20 simultaneously, the energy consumption required to raise the temperature of the metal plate 20 can be suppressed, and the equipment configuration can also be simplified.

[0090] In the heat-sealing process, the first film 31 and the second film 32 may be preheated. In this case, it is preferable that the heating temperature be 180°C or lower. By heating the first film 31 and / or the second film 32 in this temperature range, the first film 31 and / or the second film 32 can be transported smoothly, and the preheating temperature of the metal plate 20 can also be reduced.

[0091] The pressure applied by the laminating roll is preferably 0.35 MPa or higher. Furthermore, the pressure applied by the laminating roll is preferably 1.50 MPa or lower. More preferably, the pressure applied by the laminating roll is between 0.40 MPa and 1.40 MPa. If the pressure applied by the laminating roll is 0.35 MPa or higher, it is possible to suppress the entrapment of air bubbles at the interface between the metal plate 20 and the first film 31 or the second film 32, thereby improving the adhesion between the metal plate 20 and the first film 31 or the second film 32. If the pressure applied by the laminating roll is 1.50 MPa or lower, the amount of heat transferred from the metal plate 20 through the first film 31 or the second film 32 to the laminating roll can be suppressed, thereby reducing energy consumption. In addition, wear on the laminating roll can also be suppressed.

[0092] The laminating roll is preferably heated to a temperature in the range of -20°C to +60°C relative to the glass transition temperature of the first film 31. Heating the laminating roll mitigates spontaneous temperature rise due to heat input from the metal plate 20, thereby suppressing variations in the properties of the first film 31 in the longitudinal direction. The glass transition temperature of the first film 31 is determined by differential scanning thermal analysis, which measures the temperature of the first film 31 after heating it from -50°C to 290°C at a rate of 10°C / min. The glass transition temperature is defined as the average temperature of the two intersection points (glass transition start temperature and glass transition end temperature) of the baseline before and after the shift and the tangent line at the inflection point during the shift.

[0093] Furthermore, it is preferable that the laminating roll in contact with the second film 32 be heated to a temperature in the range of -20°C to +60°C relative to the glass transition temperature of the second film 32. By heating the laminating roll in contact with the second film 32 in this manner, spontaneous temperature rise due to heat input from the metal plate 20 can be mitigated, and variations in the properties of the second film 32 in the longitudinal direction can be suppressed. The glass transition temperature of the second film 32 can be determined in the same manner as the glass transition temperature of the first film 31.

[0094] In the rapid cooling process, the heat-sealed body produced in the heat-sealing process is rapidly cooled. Examples of rapid cooling methods include spraying a refrigerant onto the heat-sealed body or immersing the heat-sealed body in a refrigerant.

[0095] Let tq be the elapsed time from the end of the heat-sealing process to the start of the rapid cooling process, that is, the elapsed time from when the surface of the heat-sealed body facing the first film 31 is separated from the laminating roll until it comes into contact with the refrigerant, etc. Also, let Tq be the surface temperature of the heat-sealed body facing the first film 31 0.2 seconds after the end of the heat-sealing process. The temperature Tq can be measured by applying a radiation thermometer to the surface of the first film 31. The elapsed time tq to the start of the rapid cooling process and the temperature Tq immediately after heat-sealing satisfy equation (7) below. 0.38×Tq-tq-72 ≦ 0.0 (7)

[0096] In the heat-sealing process, amorphization progresses, particularly on the metal plate 20 side of the first film 31. However, if the elapsed time tq from the end of the heat-sealing process to the start of the rapid cooling process is long, the amorphized polyethylene terephthalate will recrystallize. When the polyethylene terephthalate on the metal plate 20 side of the first film 31 recrystallizes, a function to suppress retort whitening is activated. The higher the temperature Tq immediately after heat-sealing, the more amorphized polyethylene terephthalate is produced during the heat-sealing process, and therefore the longer the elapsed time tq until rapid cooling, which is necessary to suppress retort whitening, becomes. To control the elapsed time tq until the start of the rapid cooling process, the distance from the laminating roll to the refrigerant, the diameter of the laminating roll and the pressure applied by the laminating roll, and the line speed should be controlled. To control the temperature Tq immediately after thermocompression bonding, the elapsed time tq until the start of the rapid cooling process, the preheating temperature and thickness of the metal plate, the film thickness of the first and second films, the diameter of the laminating roll and the material of the laminating roll and the pressure applied by the laminating roll, and the temperature of the laminating roll should be controlled.

[0097] Furthermore, the surface temperature of the first film 31 side of the heat-sealed body immediately before rapid cooling is preferably 160°C to 205°C, more preferably 170°C to 195°C, and even more preferably 180°C to 190°C. The surface temperature of the first film 31 side of the heat-sealed body immediately before rapid cooling is expressed by the temperature measurement taken 0.2 seconds before the start of the rapid cooling process.

[0098] If the surface temperature of the first film 31 side of the heat-sealed body immediately before rapid cooling is 205°C or lower, it is within a temperature range where crystallization is likely to occur, minimizing the elapsed time tq until the start of the rapid cooling process and thus reducing the size of the equipment. If the surface temperature of the first film 31 side of the heat-sealed body immediately before rapid cooling is 160°C or higher, the first film 31 and the metal plate 20 will adhere sufficiently, and the elapsed time tq until the start of the rapid cooling process will not be excessively long, making it economical.

[0099] The elapsed time tq from the end of the heat-sealing process to the start of the rapid cooling process is preferably 1.0 second or more and 10 seconds or less, more preferably 2.0 seconds or more and 8.0 seconds or less, and even more preferably 2.5 seconds or more and 5.0 seconds or less. If the elapsed time tq to the start of the rapid cooling process is 1.0 second or more, the temperature Tq immediately after heat-sealing can be set to 193°C or higher, allowing the first film 31 to be sufficiently amorphous during the heat-sealing process and the first film 31 to be sufficiently adhered to the metal plate 20. If the elapsed time tq to the start of the rapid cooling process is 10 seconds or less, for example, when laminating at a line speed of 60 m / min, the time between the end of the heat-sealing process and the start of the rapid cooling process can be set to 10 m or less, thereby reducing the size of the equipment.

[0100] In the rapid cooling process, water, oils such as silicone oil, and organic solvents can be used as refrigerants, but water is preferred, and ion-exchanged water or distilled water is preferred. When water is used as a refrigerant, ion-exchanged water or distilled water is used as a refrigerant, the amount of impurities such as minerals is low, so the precipitation of impurities can be suppressed even when drying is performed after the rapid cooling process. When industrial water or tap water is used as a refrigerant, it is preferable to rinse with ion-exchanged water or distilled water after rapid cooling to prevent appearance defects due to the precipitation of impurities.

[0101] The refrigerant used in the rapid cooling process may be heated for operational stability. The temperature of the refrigerant is preferably 10°C or higher. Furthermore, the temperature of the refrigerant is preferably +40°C or less above the glass transition temperature of the first film 31. If the temperature of the refrigerant is 10°C or higher, freezing in the refrigerant tank and contamination due to condensation in the refrigerant piping can be effectively suppressed. If the temperature of the refrigerant is +40°C or less above the glass transition temperature of the first film 31, the first film 31 can be smoothly conveyed to the pass line roll installed after the rapid cooling process without sticking.

[0102] After rapid cooling, the heat-sealed body is preferably defrosted using a squeezing roll. The heat-sealed body is subjected to post-heating and oiling treatments as needed. After the heat-sealed body is inspected for surface defects, internal defects, thickness, etc., as needed, it is wound into a coil shape using, for example, a tension reel to become a laminated metal sheet 10. The heat-sealed body may also be formed into a sheet-like laminated metal sheet 10 by slitting or shearing.

[0103] (Manufacturing method for laminated metal containers) The laminated metal container 100 is formed using a laminated metal sheet 10 as the material for at least one of the components that make up the laminated metal container 100. As described above, the laminated metal container 100 can be, for example, a three-piece can made of three components, or a two-piece can made of two components. The laminated metal container 100 is formed by known methods. The laminated metal container 100 can be efficiently formed, for example, by using a can-making machine.

[0104] The laminated metal container 100 may be painted, printed, or wrapped in paper. The laminated metal container 100 is particularly suitable for use as a container that will be subjected to retort sterilization.

[0105] In the above-described embodiment, an example was described in which the laminated metal plate 10 has a metal plate 20 having a surface 21 which is the outer surface of the laminated metal container 100 and a back surface 22 which is the inner surface. The laminated metal plate 10 can be freely provided according to the mode of implementation. For example, the surface 21 of the metal plate 20 may be provided as the inner surface of the laminated metal container 100, and the back surface 22 may be provided as the outer surface of the laminated metal container 100. In this case, the first film 31 may be provided only on the surface 21 which is the inner surface of the laminated metal container 100.

[0106] As described above, the laminated metal sheet 10 and laminated metal container 100 according to the present invention possess basic characteristics such as processability, adhesion between the film and the metal sheet, and corrosion resistance, and can suppress deterioration of appearance due to whitening even after retort sterilization treatment. According to the manufacturing method of the present invention, it is possible to manufacture a laminated metal sheet 10 that suppresses retort whitening by utilizing existing laminating equipment, without the need to use expensive polybutylene terephthalate or to perform further post-heat treatment after lamination. [Examples]

[0107] The present invention will be described in more detail below with reference to examples, but is not necessarily limited thereto.

[0108] The method for manufacturing the laminated metal plate and the method for measuring the characteristic values ​​in the example invention and comparative example are as follows.

[0109] (Fabrication of laminated metal sheets) TFS was used as the metal sheet 20. As the base metal for the TFS, a low-carbon steel with a temper grade of T3CA and a thickness of 0.22 mm was used, which had undergone cold rolling, annealing, and temper rolling. The TFS was manufactured by degreasing, pickling, and then chromium plating the low-carbon steel. The amount of chromium plating on the TFS was 120 mg / m² in terms of metallic chromium (Cr equivalent). 2 Chromium hydrated oxide is 10 mg / m³ 2 That was the case. Biaxially oriented polyethylene terephthalate film was used as the first film 31 laminated on the surface 21 of the metal plate 20 and the second film 32 laminated on the back surface 22 of the metal plate 20.

[0110] Next, the TFS, the first film 31, and the second film 32 were laminated using a thermocompression lamination method. Specifically, a pair of laminating rolls were positioned to sandwich the metal plate 20, the first film 31 was placed between the surface 21 of the metal plate 20 and the laminating roll on the surface side, and the second film 32 was placed between the back surface 22 of the metal plate 20 and the laminating roll on the back side. Then, the preheated metal plate 20 was passed between the laminating rolls and thermocompressed.

[0111] After the TFS passed through the laminating roll and the first film 31 separated from the laminating roll on the surface side, the TFS was immersed in tap water and rapidly cooled for a certain period of time to obtain a laminated metal plate 10 in which the first film 31 and the second film 32 were laminated on both sides of the TFS. The resin composition of the first film 31 and the second film 32, the conditions for heat bonding, and the conditions for rapid cooling are shown in Table 1.

[0112] [Table 1]

[0113] (Linear polarized laser Raman spectroscopy) Linearly polarized laser Raman spectroscopy analysis was performed on the MD cross-section of a laminated metal plate using the LabRAM HR Evolution micro-laser Raman spectroscopy system manufactured by Horiba, Ltd. The fabricated laminated metal plates were embedded in resin and polished to create MD cross-sections, which were then used as samples for observation. The laser wavelength was 532 nm, the aperture diameter was 25 μm, and two exposures were performed with an exposure time of 5 seconds. The diffraction grating was 300 gr / mm, the focal length was 800 mm, and the objective lens was 100x. When linearly polarized laser light, polarized in the MD direction, is incident on the metal plate at a position x μm in the thickness direction, the response time is 1730 cm². -1 The full width at half maximum of the nearby C=O stretching vibration peak is w 1730 ID (x) was used. Also, when linearly polarized laser light polarized in the ZD direction was incident, 1730 cm-1 The full width at half maximum of the nearby C=O stretching vibration peak is w 1730 ND Let (x) be the value. We verified equations (1) to (6) below. w 1730 ID (1.0) ≤ 20cm -1 ...(1) w 1730 ND (1.0) ≤ 20cm -1 ...(2) 14cm -1 ≤ w 1730 ID (3.0) ≤ 20cm -1 ...(3) 14cm -1 ≤ w 1730 ND (3.0) ≤ 20cm -1 ...(4) w 1730 ID (5.0) ≤ 16cm -1 ...(5) 20cm -1 ≤ w 1730 ND (5.0) ···(6)

[0114] (Evaluation of adhesion) A sample measuring 100 mm in the transport direction and 30 mm in the width direction was cut from a laminated metal sheet. A portion of the film was peeled off from the long edge 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 in place, and the sample was retort sterilized for 25 minutes under pressurized steam at 125°C. The peeled length of the film after retort sterilization was measured and evaluated according to the following scoring system. A: Less than 2mm B: 2mm or more, less than 10mm C: 10mm or more

[0115] (Evaluation of whitening in retort pouches) A φ48 sample was punched out from a laminated metal plate. The sample was attached to the bottom of a commercially available 350 mL negative-pressure steel can (φ66, height 122.2 mm) using a donut-shaped magnet with an outer diameter of φ50 and an inner diameter of φ30. The steel can with the attached sample was retort sterilized under pressurized steam at 130°C for 10 minutes. After retort sterilization, the sample was removed from the steel can, and the changes in appearance were observed visually and evaluated according to the following scoring system. A: No change in appearance B: Slight whitening on the exterior (less than 5% of the area) C: The appearance is cloudy (more than 5% by area).

[0116] (Evaluation of processability) After applying paraffin wax to a laminated metal sheet, a φ200 sample was punched out. The first film was pressed into a cup with a drawing ratio of 2.00 using a cupping press so that it faced the outside of the can. Next, the resulting cup was subjected to two stages of re-drawing to achieve drawing ratios of 2.20 and 2.50, and a panel was applied to the bottom of the can. The panelized bottom of the resulting can was observed and evaluated according to the following criteria. A: No damage to the film after molding. B: Partial damage is observed in the molded film. No practical problems. C: Minor damage is observed all around the film after molding. This poses a practical problem.

[0117] (Evaluation results) Table 2 shows the evaluation results of the laminated metal plates obtained for Invention Examples 1-5 and Comparative Examples 1-2. Comparative Examples 1 and 2 showed deterioration in appearance after retort sterilization. Furthermore, Comparative Example 2 did not yield satisfactory results in evaluating the adhesion and processability of the laminated metal sheet. Invention Examples 1 to 4 yielded satisfactory results in all evaluations of the appearance, adhesion, retort whitening, and processability of the laminated metal sheet. Invention Example 3 yielded satisfactory results in adhesion, retort whitening, and processability, but the appearance of the laminated metal sheet was somewhat inferior. Invention Example 5 yielded satisfactory results in appearance, retort whitening, and processability of the laminated metal sheet, but the adhesion was somewhat inferior. Therefore, it has been confirmed that the present invention provides inexpensive and environmentally friendly laminated metal sheets and laminated metal containers that possess basic characteristics such as processability, adhesion between the film and the metal sheet, and corrosion resistance, and that do not deteriorate in appearance due to whitening even after retort sterilization.

[0118] [Table 2] [Industrial applicability]

[0119] According to the present invention, it is possible to provide inexpensive laminated metal sheets and laminated metal containers that have basic properties such as processability, adhesion between the film and the metal sheet, and corrosion resistance, and that do not deteriorate in appearance due to whitening even after retort sterilization treatment. [Explanation of symbols]

[0120] 10 Laminated metal plate 11 Container body 12 Lid 20 metal plate 21 Surface 22 Back side 31 The first film 32 The second film 100 Laminated metal containers

Claims

1. A laminated metal plate in which a first film is laminated on at least one of the front and back surfaces of a metal plate. The first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies the following equations (1) and (2). Laminated metal plate. w １７３０ ＩＤ (1.0) ≦ 20cm －１ ・・・(1) w １７３０ ＮＤ (1.0) ≦ 20cm －１ ・・・(2) However, w １７３０ ＩＤ (x) is the full width at half maximum of the peak caused by the C=O stretching vibration in the vicinity of 1730 cm －１ when linearly polarized laser light with its polarization plane parallel to the film plane direction is incident on the cross section of the first film at a position x μm in the thickness direction from the metal plate side, and lol １７３０ ＮＤ (x) is the value obtained when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film at a position x μm in the thickness direction from the metal plate side, parallel to the film thickness direction, at 1730 cm². －１ This is the full width at half maximum of the peak caused by the nearby C=O stretching vibration.

2. In the laminated metal plate according to claim 1, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies the following equations (3) and (4). Laminated metal plate. 14cm －１ ≦ w １７３０ ＩＤ (3.0) ≦ 20cm －１ ・・・(3) 14cm －１ ≦ w １７３０ ＮＤ (3.0) ≦ 20cm －１ ・・・(4)

3. In the laminated metal plate according to claim 1 or 2, The first film is such that w(x), obtained from linearly polarized laser Raman spectroscopy of its cross-section, satisfies equations (5) and (6) below. Laminated metal plate. w １７３０ ＩＤ (5.0) ≦ 16cm －１ ・・・(5) 20cm －１ ≦ w １７３０ ＮＤ (5.0) ・・・(6)

4. A method for manufacturing laminated metal sheets, A heat-pressing process to create a heat-pressed body by heat-pressing a preheated metal plate and a first film using a laminating roll, The process includes a rapid cooling step for rapidly cooling the heat-sealed body, The first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, The elapsed time tq from the end of the heat-pressing process to the start of the rapid cooling process, and the surface temperature Tq of the first film side of the heat-pressed body 0.2 seconds after the end of the heat-pressing process, satisfy the following equation (7): A method for manufacturing laminated metal sheets. 0.38×Tq-tq-72 ≦ 0.0 (7)

5. In the method for manufacturing a laminated metal plate according to claim 4, The preheating temperature of the metal plate in the heat-compression bonding process is 250°C or higher. A method for manufacturing laminated metal sheets.

6. A laminated metal container comprising the laminated metal plate described in claim 1 or 2 as a material.

7. A laminated metal container comprising the laminated metal plate described in claim 3 as a material.

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