Resin-coated metal sheet for containers and method for producing same

Abstract

Provided is a resin-coated metal plate for a container, in which breakage of a resin coating layer in can making, and planing of the resin coating layer due to insufficient ability to slide during can making can be suppressed, and the plate has excellent adhesion to printing paint after can making.　A resin-coated metal plate 1 for a container comprises a polyester resin coating layer 3 on at least one surface of a metal plate 2, the polyester resin coating layer 3 containing 0.010-1.0 mass% of an organic lubricant in which the half-value width of a peak due to C=O stretching vibration in the vicinity of 1730 cm-1 is 24 cm-1 to 28 cm -1, determined by laser Raman spectroscopy analysis from measurement with linearly polarized laser light having a wavelength of 532 nm incident on the surface of the polyester resin coating layer 3 with the plane of polarization of the laser light parallel to the rolling direction of the metal plate, and the contact angle of diiodomethane on the surface of the polyester resin coating layer after heat treatment for two minutes from room temperature to 240°C being 23-40°.

Description

[Technical field]

[0001] The present invention relates to a resin-coated metal sheet for containers, which has a polyester resin coating layer on at least one surface of a metal sheet. [Background technology]

[0002] Generally, metal containers are roughly divided into two-piece cans and three-piece cans. A two-piece can is a metal container that is composed of two parts: a can body that is integrated with the can bottom, and a lid. On the other hand, a three-piece can is a metal container that is composed of three parts: a can body, a top lid, and a bottom lid. A two-piece can has a beautiful appearance because there are no welds on the can body, but generally requires a high degree of processing.

[0003] Conventionally, metal sheets, such as tin-free steel (TFS) and aluminum, used as materials for metal containers, have been painted to improve their corrosion resistance. However, this painting technology requires a long processing time for the complicated painting and baking processes, and has the problem of emitting a large amount of solvents and carbon dioxide, which places a heavy burden on the environment. As a means of solving these problems, resin-coated metal sheets for containers, which have a thermoplastic film on the metal surface, have been developed and are currently widely used industrially, mainly as materials for beverage cans.

[0004] Patent documents 1 to 3 disclose techniques for manufacturing two-piece cans by drawing or DI (Draw & Ironing) using a resin-coated metal sheet, which has resin coating layers on both sides of the metal sheet. Patent documents 4 and 5 disclose techniques for adding a white pigment to the resin coating layer located on the outer surface side of the metal container after can-making, in order to enable processing such as printing to improve the design of the can body.

[0005] In recent years, with the diversification of can body shapes, there is an increasing need for a high degree of processing of can bodies. By reducing the can diameter and increasing the can height, the number of can bodies that can be stored per unit area can be increased. On the other hand, with the high degree of processing, the resin coating layer located on the outer surface side of the can body of the resin-coated metal sheet for containers may break or be scraped, making processing impossible. Patent Document 6 proposes a technology of adding a lubricant component to the resin coating layer as a technology for suppressing scraping of the resin coating layer when manufacturing highly processed two-piece cans. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-303634 [Patent Document 2] Japanese Patent Application Publication No. 4-91825 [Patent Document 3] JP 2004-148324 A [Patent Document 4] Japanese Patent Application Publication No. 8-169098 [Patent Document 5] JP 2004-130536 A [Patent Document 6] JP 2017-30210 A Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, in order to suppress scraping of the resin coating layer during the production of highly processed two-piece cans, it is necessary to increase the sliding properties of the surface of the resin coating layer by, for example, adding a lubricant component to the resin coating layer.

[0008] On the other hand, the lubricant component may hinder adhesion with the printing paint used in the printing process, causing poor adhesion of the printing paint. Therefore, it is necessary to prevent the lubricant component from bleeding out excessively onto the surface of the resin coating layer (the phenomenon in which additives in the polymer rise to the surface). If the lubricant component rises to the surface of the resin coating layer excessively due to bleeding out, the lubricant component present on the surface of the resin coating layer will repel the printing paint, reducing the adhesion of the printing paint.

[0009] Furthermore, the resin coating layer is also required to have flexibility so that it can withstand a high degree of can forming processing and, as a result, breakage of the resin coating layer can be suppressed.

[0010] In view of these characteristics, conventional technology has not been able to obtain a resin-coated metal sheet for containers that achieves all of the following: suppression of breakage and scraping of the resin coating layer during high-intensity can manufacturing, and improved paint adhesion.

[0011] The present invention has been made in consideration of the above problems, and aims to provide a resin-coated metal sheet for containers that can suppress breakage and scraping of the resin coating layer that accompanies can making processes and has excellent adhesion of printing paint after can making processes. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have obtained the following findings.

[0013] In order to prevent the resin coating layer from breaking during high-process can-making, it is necessary to ensure the flexibility of the resin coating layer surface. It has been found that in order to ensure the flexibility of the resin coating layer surface, it is necessary to reduce the crystallinity of the resin coating layer surface. The crystallinity of the resin coating layer surface is measured using a laser Raman spectroscopy method. -1 We focused on the half-width of the peak due to the nearby C=O stretching vibration. By setting this within a specific range, it is possible to suppress breakage of the resin coating layer during can manufacturing.

[0014] In addition, in order to suppress scraping of the resin coating layer during can processing, it is necessary to improve the sliding property. In order to improve the sliding property, it is necessary to add an organic lubricant. On the other hand, as described above, the lubricant component may inhibit adhesion with the printing paint and cause poor adhesion of the printing paint. Therefore, it is necessary to suppress excessive bleeding out of the lubricant component onto the surface of the resin coating layer. The present inventors have found that the bleeding out of the organic lubricant onto the surface of the resin coating layer is further promoted when the crystallinity of the surface of the resin coating layer is high. That is, in the present invention, it has been found that by reducing the crystallinity of the surface of the resin coating layer, it is possible to ensure the flexibility of the resin coating layer and suppress excessive bleeding out of the organic lubricant onto the surface of the resin coating layer.

[0015] Furthermore, it has been found that it is important to control the affinity with non-polar liquids for the adhesion of the printing paint on the surface of the resin coating layer. The resin coating layer and the printing paint are adhered to each other by van der Waals force, and the adhesion with the printing paint can be increased by increasing the van der Waals force component of the surface tension of the resin coating layer. The van der Waals force component of the surface tension can be evaluated by the contact angle with a non-polar liquid, and the larger the van der Waals force component of the surface tension, the smaller the contact angle with the non-polar liquid. The present inventors have found that it is possible to obtain a resin-coated metal plate for containers that has excellent adhesion with printing paint by controlling the contact angle of diiodomethane on the resin coating layer after heat treatment from room temperature to 240 ° C. in 2 minutes to a specific value.

[0016] The present invention has been made based on the above findings, and the gist of the present invention is as follows. [1] A resin-coated metal sheet for containers having a polyester resin coating layer on at least one surface of a metal sheet, The polyester resin coating layer is A laser Raman spectroscopy analysis was performed by irradiating the surface of the polyester resin coating layer with a linearly polarized laser beam having a wavelength of 532 nm in parallel with the rolling direction of the metal plate to measure a wavelength of 1730 cm -1 The half-width of the peak due to the nearby C=O stretching vibration is 24 cm-1 More than 28cm -1 is as follows: Contains 0.010% by mass or more and 1.0% by mass or less of an organic lubricant, and A resin-coated metal sheet for containers, in which the contact angle of diiodomethane on the surface of the polyester resin coating layer after heat treatment from room temperature to 240°C in 2 minutes is 23° or more and 40° or less. [2] The resin-coated metal sheet for containers according to [1], wherein the polyester resin coating layer contains 30% by mass or less of titanium oxide. [3] A resin-coated metal sheet for containers having a polyester resin coating layer on at least one surface of a metal sheet, The polyester resin coating layer is It has a structure consisting of at least three layers: a top surface layer, an intermediate layer, and a bottom layer, A laser Raman spectroscopy analysis was performed by irradiating the surface of the outermost layer with a linearly polarized laser beam having a wavelength of 532 nm in parallel with the rolling direction of the metal plate, and the polarization plane of the laser beam was measured. -1 The half-width of the peak due to the nearby C=O stretching vibration is 24 cm -1 More than 28cm -1 is as follows: the contact angle of diiodomethane on the surface of the outermost layer after heat treatment from room temperature to 240° C. in 2 minutes is 23° or more and 40° or less; The outermost layer contains 0.010% by mass or more and 1.0% by mass or less of an organic lubricant, the outermost layer and the bottom layer each contain 0% by mass or more and 2.0% by mass or less of titanium oxide, and the intermediate layer contains 10% by mass or more and 30% by mass or less of titanium oxide, The resin-coated metal sheet for containers, wherein the outermost layer and the lowermost layer each have a thickness of 1.0 μm or more and 5.0 μm or less, and the intermediate layer has a thickness of 6.0 μm or more and 30 μm or less. [4] The resin-coated metal sheet for containers according to any one of [1] to [3], wherein the polyester resin coating layer is made of a resin material containing 90 mol % or more of ethylene terephthalate units. [5] The resin-coated metal sheet for containers according to any one of [1] to [4], wherein the organic lubricant contains an acid-modified polyolefin or an oxidized polyolefin having an acid value of 1.0 mgKOH / g or more and 100 mgKOH / g or less. [6] A method for producing a resin-coated metal sheet for containers according to the above [1] or [2], A polyester resin coating layer containing 0.010% by mass or more and 1.0% by mass or less of an organic lubricant is pressure-bonded to a metal plate, and then A method for producing a resin-coated metal sheet for containers, comprising: holding the surface of the polyester resin coating layer at a temperature equal to or higher than the melting start temperature of the polyester resin coating layer for 0.50 seconds or more, and then cooling at a cooling rate of 150°C / second or more. [7] The method for producing a resin-coated metal sheet for containers according to [6], wherein the polyester resin coating layer contains 30 mass % or less of titanium oxide. [8] A method for producing a resin-coated metal sheet for containers according to the above [3], A polyester resin coating layer having a structure consisting of at least three layers, a surface layer, an intermediate layer, and a bottom layer, is bonded to a metal plate, the surface layer containing 0.010% by mass or more and 1.0% by mass or less of an organic lubricant, the surface layer and the bottom layer each containing 0% by mass or more and 2.0% by mass or less of titanium oxide, and the intermediate layer containing 10% by mass or more and 30% by mass or less of titanium oxide, A method for producing a resin-coated metal sheet for containers, comprising: holding the surface of the outermost layer at a temperature equal to or higher than the melting start temperature of the outermost layer for 0.50 seconds or more, and then cooling at a cooling rate of 150°C / second or more. [9] The method for producing a resin-coated metal sheet for containers according to any one of [6] to [8], wherein the polyester resin coating layer is made of a resin material containing 90 mol % or more of ethylene terephthalate units.

[10] The method for producing a resin-coated metal sheet for containers according to any one of [6] to [9], wherein the organic lubricant contains an acid-modified polyolefin or an oxidized polyolefin having an acid value of 1.0 mgKOH / g or more and 100 mgKOH / g or less. Effect of the Invention

[0017] According to the present invention, it is possible to provide a resin-coated metal sheet for containers which can suppress breakage and scraping of the resin coating layer that accompanies can-making processing and has excellent adhesion of printing paint after can-making processing. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of a resin-coated metal sheet for containers according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a resin-coated metal sheet for containers, which is another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a resin-coated metal sheet for containers according to one embodiment of the present invention will be described.

[0020] Fig. 1 is a cross-sectional view showing the configuration of a resin-coated metal sheet for containers according to one embodiment of the present invention. As shown in Fig. 1, a resin-coated metal sheet for containers 1 according to one embodiment of the present invention includes a metal sheet 2, a polyester resin coating layer 3 (hereinafter sometimes simply referred to as resin coating layer 3) formed on the front side of the metal sheet 2, and a resin coating layer 4 formed on the back side of the metal sheet 2. The resin coating layers 3 and 4 respectively become the outer and inner sides of the metal container after can forming.

[0021] In this embodiment, the metal plate 2 is formed of a steel plate such as tinplate or tin-free steel. 2 More than 15g / m 2 It is recommended to use the following: Tin-free steel with a coating weight of 50 mg / m 2 More than 200g / m 2 The following metal chrome layer and the metal chrome equivalent coating weight are 3mg / m 2 More than 30g / m 2 It is preferable that the steel sheet has a chromium oxide layer on its surface as described below. There is no particular restriction on the type of steel sheet as long as it can be formed into a desired shape, but it is preferable that the steel sheet has the following composition and is manufactured by the following method.

[0022] (1) Made of low-carbon steel with a C (carbon) content in the range of more than 0.003 mass% and not more than 0.10 mass%, and recrystallized by continuous annealing. (2) Made of low-carbon steel with a C content in the range of more than 0.003 mass% and not more than 0.10 mass%, and subjected to recrystallization annealing and overaging treatment by continuous annealing. (3) Made of low-carbon steel with a C content in the range of more than 0.003 mass% and not more than 0.10 mass%, and recrystallized by box annealing. (4) Made from low-carbon steel with a C content in the range of more than 0.003% by mass and not more than 0.10% by mass, the steel is recrystallized by continuous annealing or box annealing, and then subjected to secondary cold rolling (DR (Double Reduced) rolling). (5) An IF (Interstitial Free) steel made by adding elements that fix the dissolved C, such as Nb and Ti, to ultra-low carbon steel with a C content of approximately 0.003 mass% or less, and then recrystallizing and annealing the steel by continuous annealing.

[0023] The mechanical properties of the steel sheet are not particularly limited as long as they can be formed into the desired shape. In order to maintain the workability and sufficient can body strength, it is preferable to use a steel sheet with 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.

[0024] The steel components for achieving the above characteristics are not particularly limited, but may contain, for example, Si, Mn, P, S, Al, N, and other components. The Si content is preferably 0.001% by mass or more and 0.1% by mass or less, the Mn content is 0.01% by mass or more and 0.6% by mass or less, the P content is 0.002% by mass or more and 0.05% by mass or less, the S content is 0.002% by mass or more and 0.05% by mass or less, the Al content is 0.005% by mass or more and 0.100% by mass or less, and the N content is 0.0005% by mass or more and 0.020% by mass or less. The balance may be Fe and unavoidable impurities. In addition, other components such as Ti, Nb, B, Cu, Ni, Cr, Mo, and V may be contained, but from the viewpoint of ensuring corrosion resistance, etc., it is preferable that the total content of these components is 0.02% by mass or less.

[0025] In the present invention, the surface of at least one of the polyester resin coating layers 3 (the resin coating layer that will become the outer surface of the container by molding) has a wavelength of 1730 cm as determined by laser Raman spectroscopy, which is measured by irradiating the plane of polarization of a linearly polarized laser beam having a wavelength of 532 nm parallel to the rolling direction of the metal plate (steel plate). -1 The half-width of the peak due to the nearby C=O stretching vibration is 24 cm -1 More than 28cm -1 The following is the result.

[0026] The Raman shift determined by laser Raman spectroscopy is 1730 cm -1 It is known that the half-width of the peak due to the C=O stretching vibration in the vicinity correlates with the density of the polyester resin (J. Polymer Science 10.317.1972.). It is also known that there is a correlation between the density of the resin and the volume fraction crystallinity (Solid Structure of Polymers II (Kyoritsu Shuppan, 1984)). Therefore, the 1730 cm -1 By measuring the half-width of the peak due to the C=O stretching vibration in the vicinity, it is possible to determine the crystallinity of the polyester through the density of the polyester. Therefore, in the present invention, the crystallinity of the polyester is determined by the 1730 cm peak determined by laser Raman spectroscopy. -1The half-width of the peak due to the nearby C=O stretching vibration is used as an index of the crystallinity of the resin coating layer surface.

[0027] 1730cm -1 The half-width of the peak due to the nearby C=O stretching vibration (hereinafter simply referred to as the half-width of the peak) is 24 cm -1 More than 28cm -1 When the half width of the peak is 24 cm or less, the crystallinity of the surface of the resin coating layer 3 is low, and a resin coating layer having high flexibility is obtained. -1 If the peak width is less than 22 cm, the bleeding out of the organic lubricant cannot be suppressed, and the adhesion of the printing paint is poor. -1 If it is less than this, the flexibility of the surface of the resin coating layer 3 will be poor, and the resin coating layer 3 will not be able to follow the deformation that occurs during can forming, causing the resin coating layer 3 to break.

[0028] In addition, a low degree of crystallinity on the surface of the resin coating layer 3 is very important from the viewpoint of suppressing excessive bleeding out of the organic lubricant onto the surface of the resin coating layer 3. If the degree of crystallinity of the resin coating layer 3 becomes high, bleeding out of the organic lubricant present in the resin coating layer 3 is promoted, and the contact angle of diiodomethane described below cannot be controlled within the range specified in the present invention, which reduces the adhesion of the printing paint. Therefore, from the viewpoint of adhesion of the printing paint, it is preferable to set the crystallinity of the surface of the resin coating layer 3 so that the contact angle of diiodomethane described below cannot be controlled within the range specified in the present invention, which reduces the adhesion of the printing paint. -1 The half-width of the peak due to the nearby C=O stretching vibration is 24 cm -1 More than 28cm -1 The half-width of the peak should preferably be 25 cm or less. -1 More than 28cm -1 Here, the 1730 cm when no crystals remain is -1 The half-width of the peak due to the nearby C=O stretching vibration is 28 cm -1 Therefore, the upper limit of the half-width in the present invention is 28 cm -1 The half-width of the peak can be measured in detail by the method described in the Examples.

[0029] The resin-coated metal sheet for containers 1 is produced by pressing the resin coating layers 3 and 4 with a laminating roll onto the front and back surfaces of a metal sheet 2 heated to or above the melting points of the resin coating layers 3 and 4, respectively, and then cooling. The crystallinity of the surface of the resin coating layer 3 can be adjusted by changing the surface temperature of the resin coating layer 3 after pressing and the time during which the surface temperature of the resin coating layer 3 after pressing is maintained at or above the melting start temperature of the resin coating layer 3.

[0030] In order to control the crystallinity of the surface of the resin coating layer 3 within the range specified in the present invention, after the resin coating layer 3 is pressed onto the metal plate 2, the surface of the resin coating layer 3 must be held at a temperature equal to or higher than the melting start temperature of the resin coating layer 3 for 0.50 seconds or more, and then quenched. If the time during which the surface of the resin coating layer 3 is held at a temperature equal to or higher than the melting start temperature of the resin coating layer 3 after the resin coating layer 3 is pressed onto the metal plate 2 is less than 0.50 seconds, the melting of the surface of the resin coating layer 3 is insufficient, and the crystallinity of the surface specified in the present invention cannot be obtained. On the other hand, if the time during which the surface of the resin coating layer 3 is held at a temperature equal to or higher than the melting start temperature of the resin coating layer 3 after the resin coating layer 3 is pressed onto the metal plate 2 exceeds 3.0 seconds, the production line becomes longer, and the productivity is significantly reduced. Therefore, the time during which the surface of the resin coating layer 3 is held at a temperature equal to or higher than the melting start temperature of the resin coating layer 3 after the resin coating layer 3 is pressed onto the metal plate 2 is preferably 3.0 seconds or less.

[0031] Here, rapid cooling means that the surface of the resin coating layer 3 is cooled from the melting start temperature of the resin coating layer 3 to 120°C at a cooling rate of 150°C / sec or more. Preferably, the cooling rate is 200°C / sec or more. If the surface of the resin coating layer 3 is held at a temperature equal to or higher than the melting start temperature of the resin coating layer 3 and then cooled to below the melting start temperature by natural cooling or the like, crystallization of the surface of the resin coating layer 3 will proceed, and the degree of crystallization of the present invention will not be obtained.

[0032] Furthermore, after the resin coating layer 3 is pressure-bonded to the metal plate 2, the resin coating layer 3 must not come into contact with rolls or the like until it is rapidly cooled. If the resin coating layer 3 comes into contact with rolls or the like having a temperature lower than the melting start temperature of the resin coating layer 3, the surface of the resin coating layer 3 is cooled and the temperature drops below the melting start temperature of the resin coating layer 3, and the crystallinity of the surface of the resin coating layer 3 cannot be controlled to the range specified in the present invention. Furthermore, if the resin coating layer 3 comes into contact with rolls or the like having a temperature higher than the melting point of the resin coating layer 3, welding to the roll occurs. Therefore, after the resin coating layer 3 is pressure-bonded to the metal plate 2, the resin coating layer 3 must not come into contact with rolls or the like until it is rapidly cooled.

[0033] In order to increase the surface temperature of the resin coating layer 3 after it is bonded to the metal plate 2, there are methods such as increasing the heating temperature of the metal plate 2 before bonding, decreasing the pressure of the laminating roll during bonding, and increasing the temperature of the laminating roll during bonding. In order to achieve the crystallinity targeted by the present invention, it is preferable that the heating temperature of the metal plate 2 is about 20°C to 50°C higher than the melting point of the resin coating layer 3. In addition, by decreasing the pressing pressure of the roll during bonding, it is possible to reduce the cooling effect of the roll during bonding and keep the surface temperature of the resin coating layer 3 after bonding high. In addition, the higher the temperature of the laminating roll, the smaller the cooling effect of the roll during bonding and the higher the surface temperature of the resin coating layer 3 after bonding can be kept. However, when the temperature of the laminating roll is higher than the glass transition point + 60°C of the resin coating layer 3, the roughness of the laminating roll is transferred as the resin coating layer 3 softens, resulting in appearance defects. Therefore, the temperature of the laminating roll needs to be the glass transition point of the resin coating layer 3 + 60° C. or lower.

[0034] In order to improve the sliding property during can forming, the resin coating layer 3 contains an organic lubricant in the range of 0.010% by mass or more and 1.0% by mass or less. If the content of the organic lubricant is less than 0.010% by mass, sufficient sliding property cannot be ensured during can forming, and scraping of the resin coating layer 3 occurs. If the content of the organic lubricant exceeds 1.0% by mass, the proportion of the organic lubricant in the resin coating layer 3 increases, causing embrittlement of the resin coating layer 3 and causing scraping during can forming. The content of the organic lubricant is preferably 0.020% by mass or more. The content of the organic lubricant is preferably 0.90% by mass or less, more preferably 0.80% by mass or less.

[0035] The organic lubricant contained in the resin coating layer 3 desirably contains an acid-modified polyolefin having an acid value of 1.0 mgKOH / g to 100 mgKOH / g, or an oxidized polyolefin having an acid value of 1.0 mgKOH / g to 100 mgKOH / g. By controlling the acid value of the organic lubricant, it is possible to adjust the bleeding behavior of the organic lubricant onto the surface of the resin coating layer 3. The lower the acid value of the organic lubricant, the easier it is to bleed out onto the surface of the resin coating layer 3 during heat treatment, and the higher the acid value of the organic lubricant, the less likely it is to bleed out onto the surface of the resin coating layer 3 during heat treatment. If the acid value of the organic lubricant contained in the resin coating layer 3 is 1.0 mgKOH / g or more, excessive bleeding out onto the surface of the resin coating layer 3 due to heat treatment can be more effectively suppressed. Also, if the acid value of the organic lubricant contained in the resin coating layer 3 is 100 mgKOH / g or less, a more appropriate amount of bleeding out onto the surface of the resin coating layer 3 can be obtained, and scraping during can manufacturing can be more effectively suppressed. The acid value of the organic lubricant is more preferably 2.0 mgKOH / g or more, and even more preferably 10 mgKOH / g or more. The acid value of the organic lubricant is more preferably 80 mgKOH / g or less, and even more preferably 60 mgKOH / g or less. The acid value of the organic lubricant can be measured according to JIS K5902.

[0036] In addition, the melting point of the organic lubricant is preferably 80°C or higher and 230°C or lower. If the melting point of the organic lubricant is 80°C or higher, the bleeding out of the organic lubricant to the surface of the resin coating layer 3 can be more effectively suppressed. On the other hand, if the melting point of the organic lubricant is 230°C or lower, better sliding properties can be obtained during processing. The melting point of the organic lubricant is more preferably 90°C or higher, and even more preferably 100°C or higher. In addition, the melting point of the organic lubricant is more preferably 200°C or lower, and even more preferably 180°C or lower.

[0037] In the present invention, the resin coating layer 3 has a contact angle of diiodomethane on the surface of the resin coating layer 3 after heat treatment from room temperature (normal temperature) to 240° C. in 2 minutes, which is 23° or more and 40° or less. Here, the heat treatment from room temperature to 240° C. in 2 minutes means a heat treatment in which the temperature of the resin-coated metal sheet for containers 1 becomes 240° C. (reaches 240° C.) in 2 minutes from the start of the heat treatment (room temperature). The room temperature is not particularly limited, but is 20° C.±15° C. as an example. This heat treatment simulates a heat treatment performed after processing for the purpose of increasing the adhesion between the resin coating layer and the metal sheet when manufacturing a can body on a can manufacturing line. The contact angle of diiodomethane correlates with the van der Waals force component of the surface tension of the resin coating layer 3, and the larger the contact angle of diiodomethane, the smaller the van der Waals force component of the surface tension of the resin coating layer 3. Therefore, when the contact angle of diiodomethane exceeds 40°, the adhesive force due to van der Waals force between diiodomethane and the printing paint is reduced, and the printing paint peels off. When the contact angle of diiodomethane is smaller than 23°, the organic lubricant is hardly present on the surface of the resin coating layer 3, and scraping during can manufacturing cannot be suppressed. Therefore, the contact angle of diiodomethane on the surface of the resin coating layer 3 after the heat treatment needs to be 23° or more and 40° or less. The contact angle is preferably 25° or more, more preferably 27° or more. The contact angle is preferably 38° or less, more preferably 36° or less, and even more preferably 29° or less. The contact angle of diiodomethane can be measured in detail by the method described in the Examples. In the present invention, the half-width of the peak (crystallinity) and the organic lubricant content can be controlled to obtain the desired contact angle of diiodomethane. If the resin coating layer 3 does not contain an organic lubricant, even if the crystallinity is controlled, the contact angle of diiodomethane on the surface of the resin coating layer 3 becomes small because no organic lubricant is present on the surface of the resin coating layer 3, and scraping of the resin coating layer 3 occurs.

[0038] The resin coating layer 3 is desirably formed from a resin material containing 90 mol% or more of ethylene terephthalate units. Specifically, the resin coating layer 3 is desirably a polyester containing 90 mol% or more of ethylene terephthalate units constituting polyethylene terephthalate, which is composed of terephthalic acid as a carboxylic acid component and ethylene glycol as a glycol component. The resin coating layer 3 is more desirably formed from a resin material containing 92 mol% or more of ethylene terephthalate units. More desirably, the resin coating layer 3 is formed from a resin material containing 92 mol% or more and 97 mol% or less of ethylene terephthalate units. If the ethylene terephthalate units are 90 mol% or more, the resin coating layer 3 can withstand higher heat generated during continuous can forming processing.

[0039] Various dicarboxylic acid components and glycol components may be used as raw materials for the polyester resin. In addition, multiple dicarboxylic acid components and glycol components may be copolymerized within a range that does not impair heat resistance or processability. Examples of dicarboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic 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. Examples of glycol components include 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.

[0040] The resin material forming the resin coating layer 3 is not limited by its manufacturing method. For example, the resin material can be formed by a method of esterifying terephthalic acid, ethylene glycol, and a copolymerization component, and then polycondensing the resulting reaction product to form a copolymer polyester. Alternatively, the resin material can be formed by a method of transesterifying dimethyl terephthalate, ethylene glycol, and a copolymerization component, and then polycondensing the resulting reaction product to form a copolymer polyester. In addition, in the production of polyester, additives such as fluorescent whitening agents, antioxidants, heat stabilizers, ultraviolet absorbers, and antistatic agents may be added as necessary.

[0041] The resin coating layer 3 may be required to be white in order to improve the design after printing. In this case, the resin coating layer 3 may contain 30% by mass or less of titanium oxide as an optional component. The content of titanium oxide is preferably 10% by mass or more, more preferably 12% by mass or more. The content of titanium oxide is more preferably 25% by mass or less, and even more preferably 20% by mass or less. If the titanium oxide content is 10% by mass or more, a better whiteness after processing can be obtained. If the titanium oxide content is 30% by mass or less, better adhesion between the metal plate 2 and the resin coating layer 3 and better processability of the resin coating layer 3 can be obtained even during forming with a high degree of processing.

[0042] The titanium oxide added to the resin coating layer 3 is not particularly limited, but rutile-type titanium oxide with a purity of 90% or more is preferred because it has better dispersibility when mixed with a resin material.

[0043] The resin material forming the resin coating layer 4 (the resin coating layer that becomes the inner surface of the container by molding) may be the same as the resin material forming the above-mentioned resin coating layer 3. In particular, polyester containing 90 mol % or more of ethylene terephthalate units constituting polyethylene terephthalate composed of terephthalic acid as the carboxylic acid component and ethylene glycol as the glycol component is preferred. The resin coating layer 4 may have the same structure as the resin coating layer 3, or may have a different structure.

[0044] An example of a suitable manufacturing method for the resin-coated metal sheet for containers of this embodiment is a manufacturing method in which a polyester resin coating layer (a resin material forming a polyester resin coating layer) is pressure-bonded to a metal sheet, and then the surface of the polyester resin coating layer is held at a temperature equal to or higher than the melting start temperature of the polyester resin coating layer for 0.50 seconds or more, and then cooled at a cooling rate of 150°C / second or more. The polyester resin coating layer contains an organic lubricant in an amount of 0.010 mass% or more and 1.0 mass% or less. In addition, the polyester resin coating layer is preferably made of a resin material having 90 mol% or more of ethylene terephthalate units. The organic lubricant preferably contains an acid-modified polyolefin or an oxidized polyolefin having an acid value of 1.0 mgKOH / g or more and 100 mgKOH / g or less.

[0045] Next, a resin-coated metal sheet for containers according to another embodiment of the present invention will be described. The resin-coated metal sheet for containers of this embodiment has a polyester resin coating layer on at least one side of a metal sheet, and the polyester resin coating layer has at least three layers, namely, an outermost layer, an intermediate layer, and a lowermost layer.

[0046] 2 is a cross-sectional view showing the configuration of a resin-coated metal sheet for containers 10, which is one example of this embodiment. In this embodiment, components corresponding to those in the resin-coated metal sheet for containers 1 described above are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0047] The resin-coated metal plate 10 for containers shown in Figure 2 differs from the above-mentioned resin-coated metal plate 1 for containers in that the polyester resin coating layer 30 (hereinafter sometimes simply referred to as resin coating layer 30) formed on the surface side of the metal plate 2 is composed of multiple polyester resin coating layers (outermost layer 30a, intermediate layer 30b, and bottom layer 30c).

[0048] In the resin-coated metal sheet for containers 10, the configurations of the metal sheet 2 and the resin coating layer 4 are similar to the configurations of the metal sheet 2 and the resin coating layer 4 of the resin-coated metal sheet for containers 1 described above, respectively.

[0049] At least one of the resin coating layers 30 on the resin-coated metal sheet 10 for containers (the resin coating layer that will become the outer surface of the container after molding) has a surface (i.e., the surface of the outermost surface layer 30a) of 1730 cm determined by laser Raman spectroscopy, which is measured by irradiating the polarization plane of linearly polarized laser light having a wavelength of 532 nm parallel to the rolling direction of the metal sheet. -1 The half-value width of the peak due to the C=O stretching vibration in the vicinity is the same as that of the resin coating layer 3 of the resin-coated metal sheet for containers 1 described above. That is, the half-value width of the peak is 24 cm -1 More than 28cm -1 The following is the result.

[0050] In addition, the resin coating layer 30 has a contact angle of diiodomethane on its surface (i.e., the surface of the outermost layer 30a) after heat treatment from room temperature (normal temperature) to 240°C in 2 minutes, which is the same as that of the resin coating layer 3 of the resin-coated metal sheet for containers 1 described above. That is, the contact angle is 23° or more and 40° or less.

[0051] The outermost surface layer 30a has the same configuration as the above-mentioned resin coating layer 3. That is, the outermost surface layer 30a is made of the same resin material as the resin coating layer 3, and contains 0.010 mass % to 1.0 mass % of an organic lubricant.

[0052] The resin materials forming the intermediate layer 30b and the bottom layer 30c may be the same as the resin materials forming the resin coating layer 3 described above.

[0053] In the resin-coated metal sheet for containers 10, the thickness of each of the outermost layer 30a and the bottom layer 30c is preferably 1.0 μm or more and 5.0 μm or less. The thickness of each of the outermost layer 30a and the bottom layer 30c is more preferably 1.5 μm or more, and even more preferably 2.0 μm or more. The thickness of each of the outermost layer 30a and the bottom layer 30c is more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. The thickness of the intermediate layer 30b is preferably 6.0 μm or more and 30 μm or less. The thickness of the intermediate layer 30b is more preferably 8.0 μm or more, and even more preferably 10 μm or more. The thickness of the intermediate layer 30b is more preferably 25 μm or less, and even more preferably 20 μm or less. When titanium oxide is added to the resin coating layer 30, the amount of titanium oxide contained in the outermost layer 30a is preferably 0% by mass or more and 2.0% by mass or less with respect to the outermost layer 30a from the viewpoint of suppressing embrittlement of the outermost layer 30a. Moreover, the amount of titanium oxide contained in the lowermost layer 30c is preferably 0% by mass or more and 2.0% by mass or less with respect to the innermost layer 30c from the viewpoint of suppressing a decrease in adhesion between the lowermost layer 30c and the metal plate 2. Moreover, the amount of titanium oxide contained in the intermediate layer 30b is preferably 10% by mass or more and 30% by mass or less with respect to the intermediate layer 30b from the viewpoint of ensuring whiteness after processing.

[0054] The resin-coated metal plate 10 for containers can be produced in the same manner as the resin-coated metal plate 1 for containers. That is, the resin coating layer 30 consisting of the outermost layer 30a, the intermediate layer 30b, and the bottom layer 30c is formed in advance by a known means. For example, the same or different polyester resins are melted in a plurality of extruders (single-screw or twin-screw extruders), and then the molten resin films (30a-c) are co-extruded from a T-die to be laminated into three layers. Then, the resin layer can be either an unstretched film solidified by a cooling roll and wound up, or a film (longitudinal uniaxially stretched film, transverse uniaxially stretched film, sequential biaxially stretched film, simultaneous biaxially stretched film, etc.) obtained by stretching the cooled and solidified film. The resin coating layers 30 and 4 are pressed by a laminating roll onto the front and back surfaces of the metal plate 2 heated to above the melting points of the resin coating layers 30 and 4, respectively, and then cooled to produce the resin coating layer. In this case, the crystallinity of the surface of the resin coating layer 30 (that is, the surface of the outermost layer 30a) can be adjusted in the same manner as in the resin-coated metal sheet 1 for containers described above.

[0055] An example of a suitable manufacturing method for the resin-coated metal sheet for containers of this embodiment is a manufacturing method in which a polyester resin coating layer (a resin layer forming a polyester resin coating layer) having a structure consisting of at least three layers, an outermost layer, an intermediate layer, and a bottom layer, is pressure-bonded to a metal sheet, and then the surface of the outermost layer is held at a temperature equal to or higher than the melting start temperature of the outermost layer for 0.50 seconds or more, and then cooled at a cooling rate of 150°C / second or more. The outermost layer contains an organic lubricant of 0.010 mass% to 1.0 mass%. In addition, it is preferable that the outermost layer and the bottom layer each contain titanium oxide of 0 mass% to 2.0 mass%, and the intermediate layer contains titanium oxide of 10 mass% to 30 mass%. It is preferable that the polyester resin coating layer is made of a resin material having an ethylene terephthalate unit of 90 mol% or more. It is preferable that the organic lubricant contains an acid-modified polyolefin or an oxidized polyolefin with an acid value of 1.0 mgKOH / g to 100 mgKOH / g.

[0056] The resin-coated metal sheet for containers of this embodiment also provides the same effects as those of the resin-coated metal sheet for containers 1 described above. EXAMPLES

[0057] The metal plate is TFS (Tin Free Steel) with a thickness of 0.22 mm, and the metal Cr layer is 120 mg / m 2 Cr oxide layer: 10mg / m2 in terms of metallic Cr 2 A resin coating layer shown in Tables 1 to 4 was formed by a film lamination method (film heat fusion method) using a resin coating layer (tempering grade: T3CA) as shown in Tables 1 to 4. For Examples 1 to 24 and Comparative Examples 1, 6, and 9, resin-coated metal sheets for containers in which both sides of a metal sheet were coated with a resin coating layer were manufactured by the following method. The metal sheet was heated to a temperature 20 to 40°C higher than the melting point of the resin coating layer, and a film-like resin coating layer manufactured by a biaxial stretching method was thermocompressed to the metal sheet using a lamination roll. Thereafter, the surface of the resin coating layer (the outermost layer in the case of a multi-layered sheet) located on the outer surface side of the container after can forming was held at a temperature equal to or higher than the melting start temperature of the resin coating layer (the outermost layer in the case of a multi-layered sheet) for 0.50 to 3.0 seconds, and then quenched (cooled with water). For Comparative Examples 2 to 5, 7, and 8, resin-coated metal sheets for containers in which both sides of a metal sheet were coated with a resin coating layer were manufactured by the following method. After the film was thermocompressed, the surface of the resin coating layer (the outermost layer in the case of a multi-layer) located on the outer surface of the container after can processing was held at a temperature equal to or higher than the melting initiation temperature of the resin coating layer (the outermost layer in the case of a multi-layer) for less than 0.50 seconds, and then rapidly cooled (water-cooled).

[0058] The resin-coated metal sheet for containers thus obtained was subjected to laser Raman spectroscopy analysis by the method described below to determine the 1730 cm -1 The half-width of the peak due to the nearby C=O stretching vibration and the contact angle of diiodomethane were measured.

[0059] <1730cm determined by laser Raman spectroscopy -1 Half-width of the peak due to nearby C=O stretching vibration> The surface of the resin coating layer that will be the outer surface of the container after can-making of the resin-coated metal sheet for containers was the object of measurement, and measurements were carried out by laser Raman spectroscopy using linearly polarized laser light. The polarization direction of the laser light was set parallel to the rolling direction of the metal sheet (steel sheet). The peak targeted for half-width measurement had a Raman shift of 1730 cm -1 This peak is due to the stretching vibration of C=O in the vicinity. A laser Raman spectrometer (RAMA force manufactured by Nanophoton Corporation) was used for the measurement. A laser with a wavelength of 532 nm was used as the incident light, and the measurement conditions were a laser intensity of 6.0 mW, a slit width of 50 μm, a diffraction grating of 600 gr / mm, and one accumulation. A total of 100 points (10 points x 10 points) were measured at 5 μm pitch, and the 1730 cm peak was obtained from the average spectrum. -1 The half-width of the peak due to the nearby C=O stretching vibration was calculated. -1 A pseudo-Voigt function was used for curve fitting when calculating the half-width of the peak due to nearby C=O stretching vibration.

[0060] <Contact angle of diiodomethane> The resin-coated metal plate for containers was heat-treated in a hot air drying oven so that the temperature rose from room temperature to 240°C in 2 minutes, and then cooled to room temperature. After that, the contact angle of diiodomethane was measured on the surface of the resin coating layer that would become the outer surface of the container after can processing. Using a contact angle meter of the CA-DT type manufactured by Kyowa Interface Science Co., Ltd., a 2 μL droplet of diiodomethane was deposited on the surface of the resin coating layer in an environment of 20°C, and the static contact angle 1 second after the droplet was deposited was calculated using the θ / 2 method.

[0061] Moreover, the obtained resin-coated metal sheets for containers were evaluated for processability (break resistance), abrasion resistance, and printing paint adhesion by the methods described below.

[0062] (1) Processability After applying paraffin wax to a resin-coated metal plate for containers, a disk with a diameter of 180 mm was punched out. This disk was drawn in a cupping press, then redrawn in two stages and ironed in one stage to form a can with an inner diameter of 52 mm and a can height of 163 mm. After forming, the surface of the resin coating layer on the outside of the can was visually observed, and the processability was evaluated according to the following criteria. In the following evaluation, a "○" was given as a pass, as it was judged that the breakage of the resin coating layer during the can-making process could be suppressed. Evaluation: "◯": No breakage of the resin coating layer was observed. No practical problems. Evaluation "x": Breakage of the resin coating layer was observed, or breakage occurred. Problems in practical use.

[0063] (2) Abrasion resistance After applying paraffin wax to a resin-coated metal plate for containers, a disk with a diameter of 180 mm was punched out. This disk was drawn using a cupping press, then redrawn in two stages and ironed in one stage to form a can with an inner diameter of 52 mm and a can height of 163 mm. The formed can was heated from room temperature to 240°C in two minutes, and then forcibly cooled with cold air. After cooling, the surface of the resin coating layer on the outer side of the can was visually observed, and the abrasion resistance was evaluated according to the following criteria. In the evaluation below, "◎" and "○" were judged to be acceptable, as they were able to suppress abrasion of the resin coating layer during can-making. Evaluation: "A": No scraping was observed. Evaluation: "○": Scraping occurred within 5 mm from the can flange. No practical problems. Evaluation: △: Scraping occurred at a height of more than 5 mm and less than 20 mm from the can flange. Problematic for practical use. Evaluation "x": Scraping or breakage occurred reaching a height of more than 20 mm from the can flange. Problematic for practical use. Evaluation "-": The resin coating layer was broken or the barrel was broken during can manufacturing, making it impossible to evaluate the abrasion resistance. Problems in practical use.

[0064] (3) Adhesion of printing paint The resin-coated metal plate for containers was heat-treated from room temperature to 240°C in 2 minutes using a hot air drying oven, and cooled to room temperature. Then, a polyester-based printing paint was printed on the resin coating layer on the outer surface of the container of each sample, and heat-treated to 185°C in 90 seconds using a hot air drying oven, and cooled to room temperature. The surface on which the printing paint was printed of the obtained sample was scanned from the printing end at a speed of 10 mm / min. under a load of 500 g using a scratch-type coating hardness tester, and the maximum pencil hardness at which the printing paint did not peel off was measured. The adhesion of the printing paint was evaluated according to the following criteria based on this pencil hardness. In the following evaluation, "◎" and "○" were judged to be excellent in adhesion of the printing paint after can processing, and were passed. Rating: ◎: Pencil hardness 3H or higher. Evaluation: Good: Pencil hardness 2H. No practical problems. Evaluation "△": Pencil hardness H. Problems in practical use. Evaluation "x": Pencil hardness is F or less. Problematic in practical use.

[0065] Table 5 shows the evaluation results.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] [Table 4]

[0070] [Table 5]

[0071] As shown in Table 5, in each Example, the workability (break resistance), abrasion resistance, and printed paint adhesion were all good. In addition, the breakage of the resin coating layer and the abrasion of the resin coating layer that accompanies the can forming process could be suppressed, and a resin-coated metal sheet for containers having excellent adhesion of the printed paint after the can forming process was obtained. In contrast, the evaluation results of any one of the workability, abrasion resistance, and printed paint adhesion were insufficient in each Comparative Example. [Explanation of symbols]

[0072] 1, 10 Resin-coated metal sheet for containers 2 metal plate 3, 30 (polyester) resin coating layer 4 Resin coating layer 30a Top layer 30b middle class 30c bottom layer

Claims

1. A resin-coated metal sheet for containers comprising a polyester resin coating layer on at least one surface of a metal sheet, The polyester resin coating layer is A laser Raman spectroscopy analysis was performed by irradiating the surface of the polyester resin coating layer with a linearly polarized laser beam having a wavelength of 532 nm in parallel with the rolling direction of the metal plate to measure a wavelength of 1730 cm －１ The half-width of the peak due to the nearby C=O stretching vibration is 25 cm －１ 28cm or more －１ is as follows: Contains 0.010% by mass or more and 1.0% by mass or less of an organic lubricant, and the contact angle of diiodomethane on the surface of the polyester resin coating layer after heat treatment from room temperature to 240° C. in 2 minutes is 27° or more and 29° or less; the organic lubricant contains an acid-modified polyolefin or an oxidized polyolefin having an acid value of 10 mgKOH / g or more and 60 mgKOH / g or less, The polyester resin coating layer is made of a resin material containing 90 mol % or more of ethylene terephthalate units.

2. 2. The resin-coated metal sheet for containers according to claim 1, wherein the polyester resin coating layer contains 30% by mass or less of titanium oxide.

3. A resin-coated metal sheet for containers comprising a polyester resin coating layer on at least one surface of a metal sheet, The polyester resin coating layer is The structure has at least three layers, which are a top surface layer, an intermediate layer, and a bottom layer, A laser Raman spectroscopy analysis was performed by irradiating the surface of the outermost layer with a linearly polarized laser beam having a wavelength of 532 nm in parallel with the rolling direction of the metal plate. －１ The half-width of the peak due to the nearby C=O stretching vibration is 25 cm －１ 28cm or more －１ is as follows: the contact angle of diiodomethane on the surface of the outermost layer after heat treatment from room temperature to 240° C. in 2 minutes is 27° or more and 29° or less; The outermost layer contains 0.010% by mass or more and 1.0% by mass or less of an organic lubricant, the organic lubricant contains an acid-modified polyolefin or an oxidized polyolefin having an acid value of 10 mgKOH / g or more and 60 mgKOH / g or less, the polyester resin coating layer is made of a resin material containing 90 mol % or more of ethylene terephthalate units, the outermost layer and the lowermost layer each contain 0% by mass or more and 2.0% by mass or less of titanium oxide, and the intermediate layer contains 10% by mass or more and 30% by mass or less of titanium oxide, The resin-coated metal sheet for containers, wherein the outermost layer and the lowermost layer each have a thickness of 1.0 μm or more and 5.0 μm or less, and the intermediate layer has a thickness of 6.0 μm or more and 30 μm or less.

4. A method for producing the resin-coated metal sheet for containers according to claim 1 or 2, A polyester resin coating layer made of a resin material containing 90 mol % or more of ethylene terephthalate units and containing an organic lubricant containing an acid-modified polyolefin or an oxidized polyolefin having an acid value of 0.010 mass % or more and 1.0 mass % or less of 10 mg KOH / g or more and 60 mg KOH / g or less, is pressure-bonded to a metal plate, and thereafter, A method for producing a resin-coated metal sheet for containers, comprising: holding the surface of the polyester resin coating layer at a temperature equal to or higher than the melting start temperature of the polyester resin coating layer for 0.50 seconds or more, and then cooling at a cooling rate of 150°C / second or more.

5. The method for producing a resin-coated metal sheet for containers according to claim 4, wherein the polyester resin coating layer contains 30% by mass or less of titanium oxide.

6. A method for producing the resin-coated metal sheet for containers according to claim 3, A polyester resin coating layer made of a resin material containing 90 mol% or more of ethylene terephthalate units is pressure-bonded to a metal plate, the polyester resin coating layer having a structure consisting of at least three layers, namely, an outermost layer, an intermediate layer, and a bottom layer, the outermost layer containing an organic lubricant containing an acid-modified polyolefin or an oxidized polyolefin having an acid value of 10 mgKOH / g to 60 mgKOH / g at 0.010 mass% to 1.0 mass%, the outermost layer and the bottom layer each containing 0 mass% to 2.0 mass% of titanium oxide, and the intermediate layer containing 10 mass% to 30 mass% of titanium oxide, and thereafter A method for producing a resin-coated metal sheet for containers, comprising: holding the surface of the outermost layer at a temperature equal to or higher than a melting start temperature of the outermost layer for 0.50 seconds or more, and then cooling at a cooling rate of 150° C. / second or more.

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