Resin-coated metal sheet for containers, metal container, and method for producing resin-coated metal sheet for containers

Abstract

Provided is a resin-coated metal plate for a container, said plate having excellent processability, film adhesion, and feathering resistance. This resin-coated metal plate 1 for a container has a prescribed resin coating layer 3. The half-value width of a peak in the vicinity of 1730 cm−1, measured by making linearly polarized laser light be incident on a thickness-direction cross-section of the resin coating layer 3 so that the plane of polarization is perpendicular to the thickness direction of the resin coating layer 3, is within a prescribed range. A value A / B determined by dividing the half-value width A of the peak in the vicinity of 1730 cm−1, measured by making the linearly polarized laser light incident so that the plane of polarization is parallel with the thickness direction of the resin coating layer 3, at a position 1.0 μm from an interface of the resin coating layer 3 with a metal plate 2, by the half-value width B at a position one-half the thickness of the resin coating layer 3, is 0.80–1.10. The ratio I100 / I110 of the diffraction peak intensity I100 at the (100) plane and the diffraction peak intensity I110 at the (110) plane, based on X-ray diffraction, of the resin coating layer 3, is at least 2.00 and no greater than 6.00.

Description

[Technical field]

[0001] The present invention relates to a resin-coated metal sheet for containers having a polyester resin coating layer on at least one surface of a metal sheet, a metal container using the resin-coated metal sheet for containers, and a method for producing the resin-coated metal sheet for containers. [Background technology]

[0002] Conventionally, metal sheets, such as tin free steel (TFS) and aluminum, used as materials for metal containers, have been painted to improve corrosion resistance and weather resistance. However, this painting technology requires a long processing time for complex painting and baking processes, and further has the problem of discharging a large amount of solvent. Therefore, resin-coated metal sheets for containers, in which the surface of the metal sheet is covered with a thermoplastic film, have been developed and are currently widely used industrially, mainly as materials for beverage cans.

[0003] Resin-coated metal sheets for metal containers are required to have performance such as workability and coating adhesion, as well as design and color stability. In particular, when the surface having the resin coating layer is used as the inner surface of a container such as a food can, when the food can is opened with a can opener, a phenomenon called feathering may occur in which the film on the inner surface is not cut along the mouth of the can and remains like a feather. When this feathering occurs, it is a problem not only in terms of the design of the container but also in terms of hygiene.

[0004] To address this problem of feathering, Patent Document 1 proposes a polyester resin-coated aluminum alloy sheet in which the surface of an aluminum alloy sheet is coated with a co-extruded biaxially oriented polyester resin film having a two-layer structure consisting of an adhesive layer on the side in contact with the aluminum alloy sheet and an orientation layer on the side not in contact with the aluminum alloy sheet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-122577 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, a two-layer film is disposed on the resin coating layer to improve the breakability of the film and reduce feathering. For this reason, when forming a two-layer film, it is necessary to control the composition and thickness of each layer to be appropriate, which raises concerns about increased costs and manufacturing burdens, and there is room for improvement.

[0007] In view of the above problems, the present invention has an object to provide a resin-coated metal sheet for containers which has excellent processability, coating adhesion, and feathering resistance, a method for producing the same, and a metallic container using the metal sheet. [Means for solving the problem]

[0008] The present inventors have conducted intensive studies to solve the above problems, and have come to the following findings. When the resin coating layer has a layer having a suitable degree of crystallinity and orientation near the metal plate side and a layer having an orientation perpendicular to the thickness direction near the surface side, the resin coating layer has excellent processability, coating adhesion, and feathering resistance. At this time, the metal plate side of the resin coating layer is a molten resin layer with low crystallinity in order to obtain coating adhesion with the metal plate, but by strictly controlling the crystallinity and orientation, excellent coating adhesion and feathering resistance can be obtained. In addition, by having an orientation perpendicular to the thickness direction near the surface side of the resin coating layer, a resin coating layer with excellent processability can be obtained. The appropriate index of crystallinity and orientation can be expressed by the peak half-width by laser Raman spectroscopy.

[0009] The gist and configuration of the present invention, which has been completed based on the above findings, are as follows.

[0010] [1] A resin-coated metal sheet for containers having a polyester resin coating layer on at least one side of the metal sheet, the polyester resin coating layer being 90 mol % or more of the constituent units being ethylene terephthalate units, A laser Raman spectroscopy method in which linearly polarized laser light is incident on a cross section of the polyester resin coating layer in the thickness direction such that the polarization plane is perpendicular to the thickness direction of the polyester resin coating layer, and the thickness direction of the polyester resin coating layer is measured. -1 The half-width of the peak due to the nearby C=O stretching vibration is (I) A distance of 14.0 cm from the interface of the polyester resin coating layer with the metal plate at a thickness of 1.0 μm -1 Over 18.5cm -1 is equal to or less than the above, and (II) 14.0 cm from the surface of the polyester resin coating layer at a depth of 1.0 μm -1 More than 18.0cm -1 is as follows: A laser Raman spectroscopy method in which linearly polarized laser light is incident on a cross section of the polyester resin coating layer in the thickness direction so that the polarization plane is parallel to the thickness direction of the polyester resin coating layer, and the thickness direction of the polyester resin coating layer is measured. -1 a value A / B obtained by dividing a half-value width A at a position 1.0 μm thick from the interface between the polyester resin coating layer and the metal sheet, of a peak due to C═O stretching vibration in the vicinity of the metal sheet, by a half-value width B at a position 1 / 2 the thickness of the polyester resin coating layer, is 0.80 or more and 1.10 or less; The polyester resin coating layer has a diffraction peak intensity I 100 and (110) diffraction peak intensity I 110 Comparison with I 100 / I 110 is between 2.00 and 6.00, Resin-coated metal sheet for containers.

[0011] [2] A metal container formed from the resin-coated metal sheet for containers described in [1] above, wherein the polyester resin coating layer is located on the inner surface side of the container.

[0012] [3] A lamination process in which a stretched polyester resin coating film, the constituent units of which are 90 mol% or more of ethylene terephthalate units, is heat-pressed onto a metal plate using a lamination roll to obtain a resin-coated metal plate in which a polyester resin coating layer is formed on at least one side of the metal plate; and a heat treatment step of holding the resin-coated metal sheet at 80° C. or higher and 165° C. or lower for 10 minutes or longer to obtain a resin-coated metal sheet for containers. The method for producing a resin-coated metal sheet for containers, wherein in the laminating step, the temperature of the metal sheet during thermocompression bonding is 265°C or higher and 279°C or lower. Effect of the Invention

[0013] According to the present invention, it is possible to provide a resin-coated metal sheet for containers having excellent workability, coating adhesion and feathering resistance, a method for producing the same, and a metallic container using the metal sheet. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing a configuration of a resin-coated metal sheet for containers according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the polarization direction of a laser in laser Raman spectroscopy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a resin-coated metal sheet for containers according to one embodiment of the present invention will be described. Note that the embodiment described below is an example of the present invention, and the configuration of the present invention is not limited to this specific example. In addition, hereinafter, "%" indicates "mass %" unless otherwise specified.

[0016] Fig. 1 shows a cross-sectional view of a resin-coated metal sheet for containers according to one embodiment of the present invention. The resin-coated metal sheet for containers 1 comprises a metal sheet 2 and a polyester resin coating layer 3 (hereinafter also referred to as "resin coating layer"). Note that Fig. 1 shows an example in which the resin-coated metal sheet for containers 1 has the resin coating layer 3 on one side of the metal sheet 2, but the resin coating layer 3 may be provided on both sides of the metal sheet 2.

[0017] [Metal plate] As the metal sheet of the resin-coated metal sheet, a steel sheet such as tinplate or tin-free steel (TFS) can be used. Tinplate has a plating weight of 0.5 g / m 2 More than 15g / m 2 The following range is preferable: Tin-free steel has a coating weight of 50 mg / m 2 More than 200g / m 2 A metal Cr layer with a coating weight of 3mg / m2 or less in terms of a metal Cr layer. 2 More than 30g / m 2 It is preferable that the surface of the alloy has a Cr oxide layer having the following properties:

[0018] The type of metal sheet is not particularly limited as long as it can be formed into a desired shape, but a steel sheet having the component composition and manufacturing method described below is preferred. (1) Steel plate obtained by using low-carbon steel with a C (carbon) content of 0.010% or more and 0.10% or less and recrystallizing it through continuous annealing. (2) A steel plate obtained by using low carbon steel with a C content of 0.010% or more and 0.10% or less, and by subjecting the steel to recrystallization annealing and overaging treatment by continuous annealing. (3) A steel sheet obtained by using low-carbon steel with a C content of 0.010% or more and 0.10% or less and recrystallizing annealing by box annealing. (4) A steel sheet obtained by using low carbon steel with a C content of 0.010% or more and 0.10% or less, recrystallization annealing by continuous annealing or box annealing, and then secondary cold rolling (DR (Double Reduced) rolling). (5) A steel sheet obtained by recrystallization annealing using IF (Interstitial Free) steel, which is made by adding elements that fix the dissolved C, such as Nb and Ti, to ultra-low carbon steel with a C content of 0.003% or less, and then performing recrystallization annealing by continuous annealing.

[0019] The mechanical properties of the metal sheet are not particularly limited as long as it can be formed into a desired shape. In order to maintain workability and sufficient can body strength, it is preferable to use a metal sheet having a yield point (YP) of 220 MPa or more and 580 MPa or less. In addition, the Lankford value (r value), which is an index of plastic anisotropy, is preferably 0.8 or more. Furthermore, it is preferable that the absolute value of the in-plane anisotropy Δr of the r value is 0.7 or less.

[0020] The composition of the metal plate is not particularly limited, but a steel plate containing, for example, Si, Mn, P, S, Al, and N may be used. The Si content is preferably 0.001% or more, and preferably 0.1% or less. The Mn content is preferably 0.01% or more, and preferably 0.6% or less. The P content is preferably 0.002% or more, and preferably 0.05% or less. The S content is preferably 0.002% or more, and preferably 0.05% or less. The Al content is preferably 0.005% or more, and preferably 0.100% or less. The N content is preferably 0.0005% or more, and preferably 0.020% or less. The composition may further contain Ti, Nb, B, Cu, Ni, Cr, Mo, V, and other components. The total content of these component elements is preferably 1.0% or less.

[0021] The thickness of the metal plate is not particularly limited, but may be, for example, 0.01 mm or more and 0.35 mm or less.

[0022] [Resin coating layer] The resin coating layer is a polyester resin coating layer in which 90 mol% or more of the polyester structural units are ethylene terephthalate units. The polyester structural units are preferably 95 mol% or more of ethylene terephthalate units. When the proportion of ethylene terephthalate units in the structural units is less than 100 mol%, the remainder may be various dicarboxylic acid units or glycol units as shown below.

[0023] As the dicarboxylic acid unit, units derived from aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfoisophthalic acid, and phthalic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, and fumaric acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and oxycarboxylic acids such as p-oxybenzoic acid can be used.

[0024] As the glycol unit, units derived from aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol; alicyclic glycols such as cyclohexanedimethanol; aromatic glycols such as bisphenol A and bisphenol S; and diethylene glycol can be used.

[0025] The above dicarboxylic acids and glycols may be used in combination in two or more amounts as long as the processability is not impaired.

[0026] The resin material forming the resin coating layer is not limited by the manufacturing method. In addition, in the manufacturing of the polyester resin coating, additives such as fluorescent whitening agents, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents, and lubricants may be appropriately added as necessary.

[0027] The thickness of the resin coating layer is not particularly limited, but may be, for example, 0.01 mm or more and 0.10 mm or less.

[0028] The inventors have discovered that by setting the crystallinity and orientation of the resin coating layer within appropriate ranges, excellent processability, coating adhesion, and feathering resistance can be obtained.

[0029] The crystallinity and orientation of the resin coating layer are determined by laser Raman spectroscopy. -1 The half-width of the peak due to the nearby C=O stretching vibration can be used as an index for evaluation. -1 It is known that the half-width of the peak due to the nearby C=O stretching vibration correlates with the density of polyester resin (AJ Melverger, "Laser-Raman Study of Crystallinity Changes in Poly(ethylene terephthalate)", Journal of Polymer Science Part A2 (Polymer Physics) vol. 10, published February 1972, pp. 317-322). It is also known that there is a correlation between the density of resin and the volume fraction crystallinity (edited by the Polymer Experimental Studies Editorial Committee of the Society of Polymer Science, "Solid Structure of Polymers II", Kyoritsu Shuppan Co., Ltd., published 1984). Therefore, the half-width of the peak due to the nearby C=O stretching vibration correlates with the density of polyester resin (AJ Melverger, "Laser-Raman Study of Crystallinity Changes in Poly(ethylene terephthalate)", Journal of Polymer Science Part A2 (Polymer Physics) vol. 10, published February 1972, pp. 317-322). It is also known that there is a correlation between the density of resin and the volume fraction crystallinity (edited by the Polymer Experimental Studies Editorial Committee of the Society of Polymer Science, "Solid Structure of Polymers II", Kyoritsu Shuppan Co., Ltd., published 1984). -1 By measuring the half-width of the peak due to the nearby C=O stretching vibration, the crystallinity of the polyester resin can be determined through the density of the polyester resin.

[0030] FIG. 2 shows a direction 4 perpendicular to the thickness direction of the resin coating layer 3 and a direction 5 parallel to the thickness direction. Conventionally, values ​​obtained by laser Raman spectroscopy by irradiating a linearly polarized laser beam to a cross section in the thickness direction of the resin coating layer with a polarization plane in the direction 5 have been used. However, such average values ​​in the thickness direction of the resin coating layer 3 alone cannot strictly evaluate the crystallinity near the metal plate side and the orientation state near the surface side. Therefore, in the present invention, the half-width of the peak obtained by irradiating a linearly polarized laser beam to a cross section in the thickness direction of the resin coating layer 3 with a polarization plane in the direction 4 (i.e., a direction parallel to the surface of the metal plate 2) is also used. This allows the degree of crystallinity of the resin coating layer 3 near the metal plate side and near the surface side to be evaluated.

[0031] A linearly polarized laser beam is incident on a cross section of the polyester resin coating layer in the thickness direction so that the polarization plane is perpendicular to the thickness direction of the polyester resin coating layer, and the measured laser Raman spectroscopy is performed. -1 The half-width of the peak due to the nearby C=O stretching vibration was 14.0 cm at a position 1.0 μm thick from the interface between the polyester resin coating layer and the metal plate. -1 Over 18.5cm -1 The half-width of the above peak is 14.0 cm or less. -1 If the half-width of the peak is less than 18.5 cm, the crystallinity of the resin coating layer in the vicinity of the metal sheet interface is too high, and the coating adhesion is deteriorated. -1 If it exceeds 15.0 cm, the feathering resistance is poor. -1 The peak half width is preferably 16.5 cm or more. -1 The half width of the peak is preferably 15.0 cm or less. -1 More than 16.5cm -1 It is more preferable that:

[0032] A linearly polarized laser beam is incident on a cross section of the polyester resin coating layer in the thickness direction so that the polarization plane is perpendicular to the thickness direction of the polyester resin coating layer, and the measured laser Raman spectroscopy is performed. -1 The half-width of the peak due to the nearby C=O stretching vibration is 14.0 cm at a depth of 1.0 μm from the surface of the polyester resin coating layer. -1 More than 18.0cm -1 The half-width of the above peak is 14.0 cm or less. -1 If the half width of the peak is less than 18.0 cm, the crystallization proceeds excessively, resulting in embrittlement and poor processability. -1 If it exceeds 15.0 cm, the feathering resistance is poor. -1 The peak half width is preferably 17.0 cm or more. -1 The half width of the peak is preferably 15.0 cm or less. -1More than 17.0cm -1 It is more preferable that:

[0033] A linearly polarized laser beam is incident on a cross section of the polyester resin coating layer in the thickness direction so that the polarization plane is parallel to the thickness direction of the polyester resin coating layer, and the measured wavelength is 1730 cm -1 The value A / B obtained by dividing the half-width A at a position 1.0 μm thick from the interface of the polyester resin coating layer with the metal sheet of the peak due to the nearby C=O stretching vibration by the half-width B at a position 1 / 2 the thickness of the polyester resin coating layer is 0.80 or more and 1.10 or less. If A / B exceeds 1.10, the adhesion between the metal sheet and the resin coating layer is impaired, and processability is not obtained. On the other hand, if A / B is less than 0.80, the coating adhesion is excellent, but feathering resistance is not obtained. A / B is preferably 1.05 or less, and more preferably 1.03 or less. Also, A / B is preferably 0.85 or more, and more preferably 0.90 or more. A / B is more preferably 0.85 or more and 1.05 or less, and particularly preferably 0.90 or more and 1.03 or less. Furthermore, from the viewpoint of suppressing bubble expansion, the half-width value A is 20.5 cm -1 It is preferable that:

[0034] The half-width of the peak and A / B can be measured as follows. A linearly polarized laser beam is incident on the thickness-direction cross section of the resin coating layer to be measured so that the polarization plane is perpendicular to the thickness-direction cross section of the resin coating layer, and laser Raman spectroscopy is performed. -1 The half-width of the peak due to the C=O stretching vibration in the vicinity of the resin coating layer is obtained. The measurement positions are a position 1.0 μm thick from the interface between the resin coating layer and the metal sheet, and a position 1.0 μm thick from the surface of the resin coating layer. Similarly, a linearly polarized laser beam is incident on the thickness-wise cross section of the manufactured resin-coated metal sheet for containers so that the polarization plane is parallel to the thickness-wise cross section of the resin coating layer, and laser Raman spectroscopy is performed. As a result, -1The half-width of the peak due to the nearby C=O stretching vibration is obtained. The half-width measured at a position 1.0 μm thick from the interface of the resin coating layer with the metal plate is A, and the half-width measured at a position 1 / 2 the thickness of the resin coating layer is B, and the half-width ratio A / B is calculated. Note that Nanophoton's RAMAN force can be used for the laser Raman spectroscopy analysis. In addition, the laser wavelength is 532 nm, and a 100x objective lens is used, with an aperture diameter of 25 μm and a diffraction grating of 600 gr / mm.

[0035] The resin coating layer has a diffraction peak intensity of I 100 and (110) diffraction peak intensity I 110 Comparison with I 100 / I 110 shall be between 2.00 and 6.00 inclusive. 100 / I 110 By having the above range, it is possible to suppress the phenomenon of feathering, in which the film does not cut but remains like a feather along the mouth of the can when the can is opened with a can opener. The feathering phenomenon can deteriorate the design after opening the can and can cause the film to be mixed into the food after opening, which is also a hygiene problem. In order to make the resin coating layer easier to cut when opening the can, it is necessary to increase the crystallinity of the entire resin coating layer. 100 / I 110 If the strength ratio I is less than 2.00, the crystallinity is low, so that the resin coating does not break but stretches when the can is opened, causing feathering. 100 / I 110 If the intensity ratio exceeds 6.00, the overall crystallinity becomes excessively high, which may cause the coating adhesion to deteriorate and allow the contents to permeate the film and reach the interface between the metal plate and the film, resulting in corrosion of the metal plate. 100 / I 110 is preferably 4.00 or less. 100 / I 110 It is more preferable that the ratio is 2.00 or more and 4.00 or less.

[0036] The diffraction peak intensity in each direction can be measured as follows. X-ray diffraction is performed on the resin-coated metal sheet for containers to be measured using a Smart Lab manufactured by Rigaku Corporation. The X-ray tube is CuKα, the measurement angle range is 2θ=10° to 30°, and the scan speed is 80 seconds / degree. The peaks present at measurement angles of 24° to 29° are regarded as the peaks of the (100) plane, and the intensity I 100 The peaks at measurement angles of 22° to 24° are regarded as the peaks of the (110) plane, and the intensity I 110 From the obtained intensities, the peak intensity ratio I 100 / I 110 Request.

[0037] [Metal container] By using the resin-coated metal sheet for containers described above, it is possible to provide a metal container having excellent processability, coating adhesion, and feathering resistance. In one example, the metal container has a member formed by molding the resin-coated metal sheet for containers, and the member has a polyester resin coating layer on the inner surface side of the container. The metal container and the member can be manufactured by a conventional method.

[0038] [Manufacturing method] Next, a method for producing a resin-coated metal sheet for containers will be described. The resin coating layer having the above-mentioned properties can be achieved by a two-step process: (1) controlling the thermal history to thermocompress an oriented polyester resin coating onto a metal sheet (lamination process), and then (2) heating and aging the metal sheet (heat treatment process).

[0039] First, a non-stretched polyester resin coating is produced using a polyester resin in which 90 mol % or more of the constituent units are ethylene terephthalate units. As described above in the description of the resin coating layer, a polyester resin in which 90 mol % or more of the constituent units are ethylene terephthalate units can be used as the polyester resin constituting the polyester resin coating. Additives and the like are also as described above in the description of the resin coating layer.

[0040] The method for producing the polyester resin coating is not particularly limited, but in one example, it can be produced as follows. First, the polyester resin is heated and dried under vacuum as necessary, and then charged into an extruder, where the polyester resin is heated and melted. The heated and melted polyester resin is extruded through a filter or the like. At that time, foreign matter and denatured resin can be removed by the filter. The extruded polyester resin is formed into a sheet shape using a T-die, discharged, and extruded onto a cooling body such as a cast drum. The extruded sheet is cooled and solidified to obtain a non-stretched polyester resin coating.

[0041] Next, the unstretched polyester resin coating is stretched to obtain a stretched polyester resin coating. As a method for obtaining a stretched polyester resin coating, a sequential biaxial stretching method in which the polyester resin is stretched in one of the longitudinal direction and the width direction and then stretched in the other direction, or a simultaneous biaxial stretching method in which the polyester resin is stretched in the longitudinal direction and the width direction at the same time, etc. are preferably used. The stretched polyester resin coating is preferably a biaxially stretched polyester resin coating.

[0042] Next, a lamination step is performed in which the stretched polyester resin film is thermocompressed to a metal plate. The stretched polyester resin film is heated to a temperature equal to or higher than the melting start temperature, and thermocompressed to the metal plate using a lamination roll (thermocompression film lamination method). In order to control the properties of the resin coating layer, it is preferable that the resin coating layer after thermocompression is melted near the interface with the metal plate and oriented near the surface on the opposite side.

[0043] In addition, the temperature of the metal plate during thermocompression bonding is set to 279°C or less in order to control the X-ray diffraction intensity ratio. If the temperature of the metal plate during thermocompression bonding is 279°C or less, the diffraction peak intensity I 100 and (110) diffraction peak intensity I 110 Comparison with I 100 / I 110 On the other hand, when the temperature of the metal plate during the thermocompression bonding is 265° C. or higher, the wettability between the stretched polyester resin film and the metal plate can be favorably obtained, and the strength ratio I 100 / I 110can be 6.00 or less. Therefore, the temperature of the metal plate during thermocompression bonding is 265° C. or more, and preferably 268° C. or more. The temperature of the metal plate during thermocompression bonding is more preferably 265° C. or more and 279° C. or less, and even more preferably 268° C. or more and 279° C. or less.

[0044] In order to control the surface side vicinity of the resin coating layer to an appropriate orientation, it is preferable to maintain the orientation formed during the production of the stretched polyester resin coating without melting the surface side vicinity of the stretched polyester resin coating. For this purpose, it is preferable to set the temperature of the laminating roll that presses the stretched polyester resin coating onto the metal plate during thermocompression bonding to (melting point of the resin coating layer - 100) ° C or less. This makes it possible to suitably prevent the surface of the stretched polyester resin coating from being heated to the melting point or higher during thermocompression bonding, and to maintain the orientation state of the stretched polyester resin coating. It is more preferable to set the temperature of the laminating roll to (melting point of the resin coating layer - 120 ° C) or less, and even more preferable to set the temperature of (melting point of the resin coating layer - 140 ° C) or less. In addition, it is preferable to set the temperature of the laminating roll to (melting point of the resin coating layer - 200 ° C) or more. The temperature of the laminate roll is preferably at least (melting point of the resin coating layer - 200°C) but not exceeding (melting point of the resin coating layer - 100)°C, more preferably at least (melting point of the resin coating layer - 200°C) but not exceeding (melting point of the resin coating layer - 120)°C, and even more preferably at least (melting point of the resin coating layer - 200°C) but not exceeding (melting point of the resin coating layer - 140)°C.

[0045] The time during which the stretched polyester resin film is thermocompressed to the metal plate by the laminating roll (hereinafter referred to as the thermocompression time) is preferably short in order to maintain the oriented state. The thermocompression time is preferably 5 msec or more, and more preferably 40 msec or less. By setting the thermocompression time to 5 msec or more, the time for the stretched polyester resin film to thermally flow is sufficiently secured, and the wetting to the metal plate is improved, thereby further improving the coating adhesion. Furthermore, by setting the thermocompression time to 40 msec or less, it is more preferable that the oriented state remains. The thermocompression time is more preferably 5 msec or more and 40 msec or less.

[0046] Next, the metal plate after the lamination process is subjected to a heat treatment (heat treatment process). In the heat treatment process, the metal plate side of the resin coating layer is appropriately crystallized, and the crystallinity of the resin coating layer is adjusted to within the range specified in the present invention. The heat treatment method is not particularly limited, and for example, a method in which the atmospheric temperature is raised to a high temperature by heating with a hot air oven and heating from the surface side of the resin coating layer may be used. Also, a method of heating with an induction heater or near infrared rays may be used.

[0047] The heat treatment temperature is 80°C or higher and 165°C or lower. This temperature range is the glass transition temperature to cold crystallization peak temperature range of a polyester resin in which 90 mol% or more of the constituent units are ethylene terephthalate units. The heat treatment temperature is preferably 90°C or higher. The heat treatment temperature is preferably 120°C or lower. The heat treatment temperature is more preferably 90°C or higher and 120°C or lower. By setting the heat treatment temperature to 90°C or higher and 120°C or lower, it is possible to preferably obtain anti-feathering properties while suppressing a decrease in coating adhesion due to excessive crystallization. After reaching a predetermined temperature, the temperature is controlled so as to be maintained within this temperature range. The heat treatment temperature is based on the temperature of the metal plate.

[0048] The heat treatment time is 10 minutes or more. If the treatment time is less than 10 minutes, the crystallization of the resin coating layer near the metal plate side is insufficient, making it difficult to obtain feathering resistance. On the other hand, the heat treatment time is preferably 48 hours or less. If the treatment time is 48 hours or less, crystallization of the resin coating layer near the metal plate side is favorable, and adhesion between the metal plate and the resin coating layer is favorably obtained. The heat treatment time is preferably 5 hours or more. In addition, the heat treatment time is more preferably 24 hours or less. The heat treatment time is preferably 1 hour or more and 48 hours or less, and more preferably 5 hours or more and 24 hours or less.

[0049] The production conditions other than those mentioned above can be the same as those in the ordinary methods. EXAMPLES

[0050] The metal plate was a 0.22 mm thick TFS (metal Cr layer: 120 mg / m 2 Cr oxide layer: 10mg / m2 in terms of metallic Cr 2 The polyester resin (ethylene terephthalate unit ratio: 100 mol%) shown in Table 1 was fed into an extruder, heated and melted, extruded through a filter, and cooled and solidified to obtain a polyester resin coating. The polyester resin coating was stretched in the longitudinal direction and then in the transverse direction to obtain a biaxially stretched polyester resin coating. Note that No. 55 was not stretched and was subjected to the next process.

[0051] A biaxially oriented polyester resin coating (non-oriented polyester resin coating in the case of No. 55) was coated on a metal plate by the film lamination method (film thermocompression method). The metal plate was heated at the temperature shown in Table 1, and the biaxially oriented polyester resin coating (non-oriented polyester resin coating in the case of No. 55) was thermocompressed to the metal plate by a laminating roll. The melting point of the resin coating layer (PET) was about 260°C. The temperature of the laminating roll was 160°C or less, and the thermocompression bonding time was within the range of 5 msec to 40 msec. A resin-coated metal plate in which both sides of the metal plate were coated with a resin coating layer was produced by water cooling 1 second after thermocompression bonding. Next, the resin-coated metal plate was subjected to a heat treatment under the conditions shown in Table 1 to obtain a resin-coated metal plate for containers.

[0052] Laser Raman spectroscopy and X-ray diffraction were performed by the methods described above. The results of each measurement are shown in Table 1. In Table 1, the direction of the polarization plane is described as "horizontally polarized" when it is perpendicular to the cross section of the resin coating layer in the thickness direction, based on the direction of the metal plate surface, and as "vertically polarized" when it is parallel to the cross section of the resin coating layer in the thickness direction.

[0053] The resin-coated metal sheets of the invention and comparative examples were evaluated for coating adhesion, processability, and feathering resistance by the methods described below. Table 1 shows the results of each evaluation.

[0054] (1) Evaluation of coating adhesion Paraffin wax was applied to a resin-coated metal plate for containers. A disk with a diameter of 200 mm was then punched out. The disk was drawn into a cup with a drawing ratio of 2.00 using a cupping press so that the resin coating layer to be evaluated was on the outer surface of the can. The resulting cup was then subjected to a two-stage redrawing process so that drawing ratios were 2.20 and 2.50. The can flange was trimmed to obtain a redrawn can. The resulting can body was subjected to a retort sterilization treatment at 125°C for 90 minutes in a retort device. The trimmed portion of the can body after the retort sterilization treatment was observed over the entire circumference and evaluated according to the following criteria. Rating "4": No peeling. Rating "3": Peeling of up to 1 mm was observed. No practical problems were observed. Rating "2": Peeling of more than 1 mm and less than 3 mm is observed. No practical problems. Rating "1": Peeling of more than 3 mm at maximum is observed. Problems in practical use.

[0055] (2) Evaluation of workability Paraffin wax was applied to a resin-coated metal plate for containers. A disk with a diameter of 200 mm was then punched out. The disk was drawn into a cup with a drawing ratio of 2.00 using a cupping press so that the resin coating layer to be evaluated was on the outer surface of the can. The resulting cup was then subjected to a two-stage redrawing process so that drawing ratios were 2.20 and 2.50. Panel processing was applied to the bottom of the can. The bottom panel processing part of the resulting can body was observed and evaluated according to the following criteria. Rating "4": No damage to the polyester resin coating layer after molding. Rating "3": Fine damage was observed in some parts of the polyester resin coating layer after molding. No practical problems. Rating "2": Partial damage was observed in the polyester resin coating layer after molding. No practical problems. Rating "1": Slight damage was observed all around the polyester resin coating layer after molding. Problems in practical use.

[0056] (3) Evaluation of feathering resistance Paraffin wax was applied to a resin-coated metal sheet for containers. Then, a disk having a diameter of 200 mm was punched out. The disk was drawn into a cup with a drawing ratio of 2.00 using a cupping press so that the resin coating layer to be evaluated was on the inner surface side of the can. The obtained cup was then subjected to a two-stage redrawing process so that the drawing ratios were 2.20 and 2.50. A lid was also made by a lid-making process so that the resin coating layer to be evaluated was on the inner surface side of the can, and this lid was then seamed around the redrawn can to make a can. The obtained can was opened using a can opener. After opening, the opening of the can was observed under an optical microscope, the length of feathering was measured, and evaluation was performed according to the following criteria. Rating "4": Feathering after opening is 0 mm to 4 mm. No practical problems. Rating "3": Feathering after opening is greater than 4 mm and less than 8 mm. No practical problems. Rating "2": Feathering after opening is greater than 8 mm and less than 10 mm. No practical problems. Rating "1": Feathering occurred after opening the can exceeding 10 mm. Practical problems exist.

[0057] [Table 1] TIFF0007673878000002.tif223118TIFF0007673878000003.tif223119TIFF0007673878000004.tif223114

[0058] In the resin-coated metal sheets for containers of the invention, the coating adhesion, workability, and feathering resistance were all good (evaluated as "2" or higher). On the other hand, in the comparative examples, the evaluation results of any one of the coating adhesion, workability, and feathering resistance were insufficient (evaluated as "1").

[0059] Nos. 1, 2, 35, and 49 have poor feathering resistance because the peak intensity ratio by X-ray diffraction of the resin coating layer is outside the range of the invention. Nos. 3 and 4 have a large half-width of the C=O peak at a position 1.0 μm from the surface of the resin coating layer, and poor processability. No. 5 has a large half-width of the C=O peak at a position 1.0 μm from the interface between the resin coating layer and the metal sheet, and a small amount of crystals, and therefore poor feathering resistance. Nos. 53 and 54 have a high heat treatment temperature, and although crystallization is sufficient at a position 1.0 μm from the interface between the resin coating layer and the metal sheet, crystallization is excessive, so the half-width ratio A / B becomes excessive, and the coating adhesion and processability are poor. No. 55 is a non-stretched film, and therefore the amount of crystals at a position 1.0 μm from the surface of the resin coating layer is small, so impact resistance is deteriorated and processability is poor. Furthermore, Nos. 55 to 58 have poor feathering resistance because the peak intensity ratios of the resin coating layer by X-ray diffraction are outside the range of the present invention. [Industrial Applicability]

[0060] According to the present invention, it is possible to provide a resin-coated metal sheet for containers having excellent workability, coating adhesion and feathering resistance, a method for producing the same, and a metallic container using the metal sheet. [Explanation of symbols]

[0061] 1 Resin-coated metal sheets for containers 2 metal plate 3 Resin coating layer 4. Direction perpendicular to the thickness direction of the resin coating layer 5. Parallel to the thickness direction of the resin coating layer

Claims

1. A resin-coated metal sheet for containers, comprising a polyester resin coating layer on at least one surface of the metal sheet, the polyester resin coating layer comprising 90 mol % or more of ethylene terephthalate units, A laser Raman spectroscopy method in which linearly polarized laser light is incident on a cross section of the polyester resin coating layer in the thickness direction such that the polarization plane is perpendicular to the thickness direction of the polyester resin coating layer, and the thickness direction of the polyester resin coating layer is measured. －１ The half width of the peak due to the nearby C═O stretching vibration is (I) 14.0 cm at a position 1.0 μm thick from the interface between the polyester resin coating layer and the metal plate －１ 18.5cm or more －１ and (II) 14.0 cm at a position 1.0 μm thick from the surface of the polyester resin coating layer －１ 18.0cm or more －１ is as follows: A laser Raman spectroscopy method in which linearly polarized laser light is incident on a cross section of the polyester resin coating layer in the thickness direction so that the polarization plane is parallel to the thickness direction of the polyester resin coating layer, and the thickness direction of the polyester resin coating layer is measured. －１ a value A / B obtained by dividing a half-value width A at a position 1.0 μm thick from the interface between the polyester resin coating layer and the metal sheet, of a peak due to C═O stretching vibration in the vicinity of the metal sheet, by a half-value width B at a position 1 / 2 the thickness of the polyester resin coating layer, is 0.80 or more and 1.10 or less; The polyester resin coating layer has a diffraction peak intensity I １００ and the diffraction peak intensity of the (110) plane I １１０ Comparison with I １００ / I １１０ is 2.00 or more and 6.00 or less, Resin-coated metal sheet for containers.

2. 2. A metal container formed from the resin-coated metal sheet for containers according to claim 1, wherein the polyester resin coating layer is located on the inner surface side of the container.

3. a lamination step of thermocompressing an oriented polyester resin coating film, the constituent units of which are 90 mol % or more of ethylene terephthalate units, onto a metal sheet using a lamination roll to obtain a resin-coated metal sheet having a polyester resin coating layer formed on at least one surface of the metal sheet; and a heat treatment step of holding the resin-coated metal sheet at 80° C. or higher and 165° C. or lower for 10 minutes or longer to obtain a resin-coated metal sheet for containers.

2. A method for producing a resin-coated metal plate for containers, comprising the steps of: in the laminating step, setting the temperature of the metal plate during thermocompression bonding to 265° C. or more and 279° C. or less to produce the resin-coated metal plate for containers according to claim 1.

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