Resin-coated metal plate and method for producing same

Abstract

Provided are: a resin-coated metal plate having excellent moldability and adhesiveness of a resin layer, and excellent ink adhesiveness; and a method for producing the resin-coated metal plate. This resin-coated metal plate is provided with a metal plate layer (2) and a resin layer (3) containing a polyester resin and covering the plate surface of the metal plate layer (2), the resin layer (3) having a melting point of 225-255 DEG C or less, and having a surface layer (31) disposed on the surface on the opposite side from the side facing the metal plate layer (2), a lower layer (33) facing the metal plate layer (2), and an intermediate layer (32) between the surface layer (31) and the lower layer (33). The surface layer (31) contains a lubricating component comprising a polyolefin having a melting point of 75-140 DEG C, and the coating rate of the lubricating component exposed on the surface of the surface layer (31) is 0.040-0.80% as determined by peak intensity ratio analysis of Raman spectrum data obtained when the surface layer (31) is subjected to Raman measurement using a confocal Raman device.

Description

Technical Field

[0001] The present invention relates to a resin-coated metal plate and a method for manufacturing the same. Background Art

[0002] As described in Patent Document 1, in order to improve corrosion resistance and weather resistance, metal plates such as TFS (tin-free steel) and aluminum used as blanks for metal containers are coated. In this coating, there are problems that the processes of coating and sintering require a huge processing time. In addition, since a large amount of solvent is discharged, there are problems in terms of environmental load. Therefore, in order to solve these problems, the use of laminated steel plates in which a thermoplastic resin film is coated on the surface of a metal plate to form a resin layer is gradually increasing. Laminated steel plates are widely used in, for example, the fields of beverage cans and food cans that require high processing degrees of forming. For the resin layer on the outer surface side of the container, printing is sometimes performed in order to improve the designability.

[0003] In recent years, from the viewpoints of resource saving and material cost reduction, the thinning of materials used for metal containers, particularly metal plates and resin layers, has been promoted. Therefore, the processing degree during can making becomes higher, and in particular, after forming, there is a possibility that the resin layer on the outer surface side of the container is broken or scratched. Therefore, in order to suppress breakage and scratching of the resin layer during can making, a lubricating component is sometimes added to the resin layer (for example, refer to Patent Document 1).

[0004] Patent Document 1 discloses a resin-coated metal plate for a container. This resin-coated metal plate for a container has resin coating layers on both sides of the metal plate. In this resin-coated metal plate for a container, the resin coating layer on the outer surface side of the container after forming is mainly composed of a polyester resin having a melting point in the range of 230°C to 254°C and contains a lubricating component, the melting point of the lubricating component is 80°C to 230°C, and the average particle diameter of the lubricating component present on the surface of the resin coating layer is 17.0 nm or less.

[0005] In addition, Patent Document 1 also discloses that a deep drawing method or a DI (draw and iron) processing method is sometimes used as the processing of the resin-coated metal plate for a container. It is also described that in order to improve the designability and aesthetics of the can body after printing, a white pigment is sometimes added to the resin coating layer on the outer surface side of the container after forming.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: International Publication No. 2019 / 116706 Summary of the Invention

[0009] If a lubricating component is added to the resin layer of the metal-clad sheet, the breakage and scratching of the resin layer are suppressed, and good moldability is ensured. However, the lubricating component sometimes reduces the adhesion between the resin layer and the metal sheet, which sometimes causes the resin layer to peel off from the metal sheet during can manufacturing. This peeling causes poor molding during can manufacturing and subsequent reduction in corrosion resistance and weather resistance, resulting in problems. In addition, the lubricating component reduces the adhesion between the printing ink for printing and the resin layer, sometimes causing ink peeling during can manufacturing. The ink peeling damages the design and aesthetics of the can body, resulting in problems. Therefore, it is desired to provide a resin-clad metal sheet having excellent moldability, adhesion, and ink adhesion of the resin layer.

[0010] The present invention has been completed in view of this actual situation, and an object thereof is to provide a resin-clad metal sheet having excellent moldability, adhesion, and ink adhesion of the resin layer and a method for manufacturing the same.

[0011] In order to achieve the above object, the resin-clad metal sheet according to the present invention is as follows.

[0012] [1] A resin-clad metal sheet, comprising:

[0013] a metal plate layer, and

[0014] a resin layer containing a polyester resin that coats the surface of the metal plate layer,

[0015] The melting point of the resin layer is 225°C to 255°C, and it has:

[0016] a surface layer disposed on the surface on the opposite side of the side opposite to the metal plate layer,

[0017] a lower layer opposite to the metal plate layer, and

[0018] an intermediate layer located between the surface layer and the lower layer,

[0019] The surface layer contains a lubricating component composed of a polyolefin having a melting point of 75°C to 140°C,

[0020] The coating rate of the lubricating component exposed on the surface of the surface layer is 0.040% to 0.80%, and this coating rate is obtained by analyzing the peak intensity ratio of the Raman spectrum data obtained by performing Raman measurement on the surface layer using a confocal Raman apparatus.

[0021] The resin-clad metal sheet according to the present invention may also be as follows.

[0022] [2] The resin-clad metal sheet according to the above [1], wherein the resin layer is formed of a resin material containing 90 mol% or more of ethylene terephthalate units.

[0023] [3]The resin-coated metal plate according to [1] or [2] above, wherein the surface layer contains 0.10% to 1.0% by mass of the above lubricating component.

[0024] [4]The resin-coated metal plate according to any one of [1] to [3] above, wherein the lubricating component contains an acid-modified polyolefin or an oxidized polyolefin.

[0025] [5]The resin-coated metal plate according to [4] above, wherein the acid value of the lubricating component is 1.0 mgKOH / g to 80 mgKOH / g.

[0026] [6]The resin-coated metal plate according to any one of [1] to [5] above, wherein the intermediate layer contains 10% to 30% by mass of inorganic particles.

[0027] [7]The resin-coated metal plate according to any one of [1] to [6] above, wherein

[0028] the layer thickness of the surface layer is 1.0 μm to 5.0 μm,

[0029] the layer thickness of the intermediate layer is 6.0 μm to 30 μm,

[0030] the layer thickness of the lower layer is 1.0 μm to 5.0 μm.

[0031] The resin-coated metal plate according to any one of [1] to [7] above can be manufactured by the following manufacturing method.

[0032] [8]A manufacturing method of a resin-coated metal plate, wherein

[0033] masterbatch particles are produced with a polyester resin having a melting point of 230 °C to 254 °C and an intrinsic viscosity of 0.45 to 0.88 as a matrix and the above lubricating component dispersed therein,

[0034] the masterbatch particles are kneaded with polyester resin particles, extruded at a specified extrusion temperature, and stretched by a biaxial stretching method to produce a film,

[0035] the film is thermocompression bonded to a metal plate by a laminating roll.

[0036] [9]The manufacturing method of a resin-coated metal plate according to [8] above, wherein the specified extrusion temperature is 255 °C to 285 °C.

[0037]

[10] The manufacturing method of a resin-coated metal plate according to [8] or [9] above, wherein the stretching ratio of the film is set to 2.0 times to 5.0 times.

[0038] According to the invention of the present application, a resin-coated metal plate excellent in moldability, adhesion, and ink adhesion of a resin layer and a manufacturing method thereof can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a cross-sectional view for explaining the structure of the resin-coated metal plate according to an embodiment of the present invention.

[0040] Figure 2 It is a cross-sectional view for explaining the structure of the resin-coated metal plate according to another embodiment of the present invention.

[0041] Figure 3 It is a cross-sectional view for explaining the structure of the resin-coated metal plate according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] Based on the drawings, the resin-coated metal plate and the manufacturing method thereof according to the embodiments of the present invention will be described.

[0043] Figure 1 A cross-sectional view of the resin-coated metal plate 100 (hereinafter referred to as the plate 100) according to the present embodiment is shown.

[0044] The outline of the plate 100 will be described. The plate 100 includes a metal plate layer 2 and a resin layer 3 containing a polyester resin that coats the surface of the metal plate layer 2. The resin layer 3 has a surface layer 31 disposed on the surface opposite to the side facing the metal plate layer 2, a lower layer 33 facing the metal plate layer 2, and an intermediate layer 32 located between the surface layer 31 and the lower layer 33. The melting point of the resin layer 3 is 225°C to 255°C. The surface layer 31 contains a lubricating component composed of a polyolefin having a melting point of 75°C to 140°C. The coating rate of the lubricating component exposed on the surface of the surface layer 31 is 0.040% to 0.80%. This coating rate is obtained by analyzing the peak intensity ratio of the Raman spectrum data obtained by performing Raman measurement on the surface layer 31 using a confocal Raman device.

[0045] It should be noted that Figure 1 A case where the plate 100 further includes a resin layer 4 is shown. Hereinafter, the plate 100 will be described in detail.

[0046] The metal plate layer 2 is a layer of a metal plate. The metal plate layer 2 is, for example, a steel plate such as tinplate or TFS. As the tinplate, it is preferable to use tinplate in the range of a plating amount of 0.5 g / m 2 to 15 g / m 2 As the TFS, it is preferable that the amount of chromium metal attached to the surface is 50 mg / m 2 to 200 g / m 2The chromium metal layer and the amount of chromium oxide adhered in terms of chromium metal is 3 mg / m 2 ~30 g / m 2 chromium oxide layer. The above steel plate may have a coating or a chromium oxide layer on both sides, only one side, or only a part thereof. When only a part such as one side of the steel plate has a coating or a chromium oxide layer, it is preferable to provide a resin layer 3 at least on the surface portion of the steel plate where there is no coating or chromium oxide layer.

[0047] When using the steel plate as the metal plate layer 2, the type of the steel plate is not particularly limited as long as it can be formed into the target shape, and it is preferably a steel plate made by the following composition and manufacturing method.

[0048] It is preferable to use a low-carbon steel with the C content (carbon content) of the steel plate in the range of about 0.010 mass% to 0.10 mass%, and perform recrystallization annealing by continuous annealing.

[0049] In addition, it is preferable to use a low-carbon steel with the C content of the steel plate in the range of about 0.010 mass% to 0.10 mass%, and perform recrystallization annealing and overaging treatment by continuous annealing.

[0050] In addition, it is preferable to use a low-carbon steel with the C content in the range of about 0.010 mass% to 0.10 mass%, and perform recrystallization annealing by box annealing.

[0051] In addition, it is preferable to use a low-carbon steel with the C content in the range of about 0.010 mass% to 0.10 mass%, and perform secondary cold rolling after recrystallization annealing by continuous annealing or box annealing.

[0052] In addition, it is preferable to use an IF (Interstitial Free) steel added with elements such as Nb and Ti that fix the C dissolved in a super low-carbon steel with a C content of about 0.003 mass% or less, and perform recrystallization annealing by continuous annealing.

[0053] The mechanical properties of the steel plate are not particularly limited as long as it can be formed into the target shape. For the mechanical properties of the steel plate, in order not to impair the workability and maintain sufficient tank strength, it is preferable to use a steel plate with a yield point (YP) in the range of about 220 MPa to 580 MPa. In addition, as the Lankford value (r value) which is an index of plastic anisotropy, it is preferably 0.8 or more. In addition, for the in-plane anisotropy Δr of the r value, the absolute value is preferably 0.7 or less.

[0054] Regarding the steel plate, the composition of the steel for satisfying the above mechanical properties is not particularly limited. For example, it may contain components such as Si, Mn, P, S, Al, N, etc. Preferably, the Si content is 0.001% by mass to 0.1% by mass, the Mn content is 0.01% by mass to 0.6% by mass, the P content is 0.002% by mass to 0.05% by mass, the S content is 0.002% by mass to 0.05% by mass, the Al content is 0.005% by mass to 0.100% by mass, and the N content is 0.0005% by mass to 0.020% by mass. In addition, other components such as Ti, Nb, B, Cu, Ni, Cr, Mo, V, etc. may also be contained, but from the viewpoint of ensuring corrosion resistance, etc., the total amount of the contents of these components is preferably 0.02% by mass or less.

[0055] As described above, the resin layer 3 has a surface layer 31, an intermediate layer 32, and a lower layer 33. In the present embodiment, when the surface layer 31 is the outermost layer, the lower layer 33 is the lowermost layer of the resin layer 3.

[0056] The melting point of the resin layer 3 is 225°C to 255°C and contains a polyester resin as the main component. Preferably, the melting point of the resin layer 3 is 232°C to 252°C. More preferably, the melting point of the resin layer 3 is 238°C to 250°C. When the melting point of the resin layer 3 is less than 225°C, the resin softens due to the heat applied to the resin during molding, the resin layer 3 breaks or is scratched, and the moldability decreases. On the other hand, when the melting point of the resin layer 3 exceeds 255°C, since the crystallinity of the polyester resin becomes high, breaks or scratches are likely to occur in the resin layer 3 during molding, and the moldability decreases.

[0057] As raw materials for the polyester resin, various dicarboxylic acid components and glycol components can be used. In addition, within a range not impairing heat resistance and processability, a plurality of dicarboxylic acid components and glycol components can also be copolymerized. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfonate isophthalic acid, phthalic acid, etc., aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid, etc., alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and hydroxycarboxylic acids such as p-hydroxybenzoic acid. Examples of the glycol component include aliphatic glycols such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, neopentyl glycol, etc., alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A, bisphenol S, and diethylene glycol.

[0058] In order to ensure excellent slidability and scratch resistance during the forming of the can body during can manufacturing, a lubricating component can be added at least in the outermost surface layer 31 among the three layers constituting the resin layer 3. When forming the resin layer 3 into a film, the surface layer 31 and the lower layer 33 can be formed of resins extruded by the same extruder. In this case, the surface layer 31 and the lower layer 33 have the same composition, and not only the outermost surface layer 31 but also the lower layer 33 located at the lowermost layer contains a lubricating component. Of course, the surface layer 31 and the lower layer 33 can also be formed of resins with the same or different compositions extruded by two different extruders.

[0059] As the lubricating component, a lubricating component composed of a polyolefin having a melting point of 75°C to 140°C is used because of its excellent film-forming property and dispersibility. In order to ensure sufficient affinity with the polyester resin which is the main component of the resin layer 3, the above polyolefin preferably has a polar group. Examples of polyolefins having a polar group include acid-modified polyolefins such as ethylene maleic anhydride copolymer, oxidized polyolefins such as oxidized polyethylene, and ethylene acrylic acid copolymer, and one of them can be used alone or two or more of them can be used in combination. The affinity of the lubricating component with the resin layer 3 varies with the acid value etc. of the polyolefin constituting the lubricating component. For example, the higher the acid value of the polyolefin constituting the lubricating component, the higher the affinity of the lubricating component with the resin layer 3 becomes. If the above affinity becomes high, the dispersed particle diameter of the lubricating component on the surface of the resin layer 3 becomes small, and the coverage rate of the lubricating component obtained by analyzing the peak intensity ratio of Raman spectroscopic data tends to decrease.

[0060] The melting point of the above lubricating component is preferably 90°C to 130°C, more preferably 100°C to 120°C. When the melting point of the lubricating component is less than 75°C, due to the process of coating the resin layer 3 on the metal plate layer 2 and the heat treatment carried out during the forming process of the resin-coated metal plate, the lubricating component is likely to accumulate on the surface of the resin layer 3. In addition, due to the heat during processing, most of the lubricating component is likely to dissolve. Therefore, scratches may be generated in the resin layer 3 due to processing in the mold, and the formability may be reduced. In addition, since the affinity of the lubricating component with the printing ink is low, the adhesion of the printing ink is hindered, and peeling of the printing ink may occur during the forming process. Furthermore, when the melting point of the lubricating component exceeds 140°C, sufficient slidability and scratch resistance cannot be ensured, fractures or scratches are generated in the resin layer 3 during the forming process, and the formability is reduced.

[0061] The coverage rate (hereinafter, simply referred to as "coverage rate") of the lubricating component exposed on the surface of the outermost surface of the resin layer 3, that is, the surface layer 31, is 0.040% to 0.80%. It is preferably 0.060% to 0.70%, more preferably 0.070% to 0.65%, and further preferably 0.080% to 0.50%.

[0062] The above-mentioned coverage rate is obtained by analyzing the peak intensity ratio of the Raman spectrum data obtained by performing Raman measurement on the surface layer 31 using a confocal Raman apparatus (hereinafter, simply referred to as "this measurement method"). With this measurement method, it is possible to calculate the dispersion state of the lubricating component non-destructively and with high resolution, and it is possible to capture minute lubricating components on the surface of the surface layer 31 that cannot be captured by other analysis methods.

[0063] It should be noted that there is also a method of evaluating the hydrophilic and hydrophobic states of the surface of the surface layer 31 by measuring the contact angle using water or the like. However, since the contact angle measurement is greatly affected by the surface roughness, it is difficult to capture only the influence of the lubricating component. On the other hand, in the case of Raman measurement, it is not affected by the surface roughness, can capture the dispersion state of the lubricating component, and can evaluate the influence of the lubricating component on the surface of the surface layer 31 with higher accuracy.

[0064] When the coverage rate of the lubricating component exposed on the outermost surface of the resin layer 3 is extremely low, less than 0.040%, it is impossible to ensure the slidability and scratch resistance sufficient to withstand the processing during can manufacturing, and fractures and scratches may occur during the forming process, resulting in a decrease in formability. In addition, when the coverage rate of the lubricating component exposed on the outermost surface of the resin layer 3 exceeds 0.80% and is excessive, the lubricating component hinders the adhesion of the printing ink, and peeling of the printing ink may occur during the forming process.

[0065] The coverage rate is affected by the content, dispersion state, or dispersibility of the lubricating component in the surface layer 31. Therefore, in order to improve the dispersion state of the lubricating component in the surface layer 31, it is preferable to use a masterbatch when manufacturing the film constituting the surface layer 31 or the resin layer 3.

[0066] The above-mentioned masterbatch is obtained by dispersing the lubricating component at a high concentration in a polyester resin. The melting point of the polyester resin as the matrix of the masterbatch is preferably 230°C to 254°C, more preferably 234°C to 252°C, and further preferably 238°C to 250°C.

[0067] In addition, the intrinsic viscosity of the polyester resin as the matrix of the above-mentioned masterbatch is preferably 0.45 to 0.88, more preferably 0.50 to 0.85, and further preferably 0.55 to 0.80.

[0068] As described above, the melting point of the lubricating component used in the above-mentioned masterbatch is 75°C to 140°C, preferably 90°C to 130°C, and further preferably 100°C to 120°C.

[0069] The acid value of the lubricating component used in the above masterbatch is preferably 1.0 mgKOH / g to 80 mgKOH / g, more preferably 1.0 mgKOH / g to 60 mgKOH / g, and further preferably 2.0 mgKOH / g to 45 mgKOH / g. By controlling the melting point, intrinsic viscosity of the polyester resin and the melting point, acid value of the lubricating component within the above ranges, the coverage rate of the lubricating component exposed on the outermost surface of the resin layer 3 (i.e., the surface of the surface layer 31) can be controlled to 0.040% to 0.80%. Moreover, by controlling the coverage rate instead of the content of the lubricating component, a resin-coated metal plate with more excellent moldability and ink adhesion of the resin layer 3 can be provided.

[0070] The resin layer 3 is preferably formed of a resin material containing 90 mol% or more of ethylene terephthalate units. The content of ethylene terephthalate units in the above resin material is more preferably 92 mol% or more, and further preferably 95 mol% or more. When the ethylene terephthalate units are 90 mol% or more, the melting point of the resin layer 3 is high enough. Therefore, thermal degradation of the resin material caused by the process of coating the resin layer 3 on the metal plate layer 2 and the heat treatment performed during the molding process of the resin-coated metal plate can be suppressed, and the moldability of the resin layer 3 is good. As long as the entire resin layer 3 satisfies the content of the ethylene terephthalate units as described above, the surface layer 31, the intermediate layer 32, and the lower layer 33 may be formed of a polyester resin material having the same composition, or may be formed of polyester resin materials having different compositions.

[0071] The lubricating component contained in the surface layer 31 of the resin layer 3 is preferably 0.10% by mass to 1.0% by mass, more preferably 0.20% by mass to 0.90% by mass, and further preferably 0.40% by mass to 0.80% by mass. When the content of the lubricating component is within the above range, the coverage rate of the lubricating component exposed on the surface of the surface layer 31 is within an appropriate range. Therefore, sufficient slidability and scratch resistance can be ensured during the molding process, and no breakage or scratches occur in the resin layer 3. In addition, in order to ensure sufficient ink adhesion, no peeling of the ink occurs during the molding process. The lower layer 33 may optionally contain the lubricating component in the same content range as the surface layer 31. If the content of the lubricating component is within the above range, the adhesion between the lower layer 33 and the metal plate layer 2 can be sufficiently ensured, and peeling of the resin layer 3 is not likely to occur during the molding process. The intermediate layer 32 may contain the lubricating component in the content range as described above, but from the viewpoint of cost, it is preferably free of the lubricating component.

[0072] The acid value of the lubricating component is preferably 1.0 mgKOH / g to 80 mgKOH / g, more preferably 1.0 mgKOH / g to 60 mgKOH / g, and still more preferably 2.0 mgKOH / g to 45 mgKOH / g. When the acid value of the lubricating component is within the above range, the affinity between the resin layer 3 and the printing ink can be sufficiently ensured, and the adhesion of the printing ink can be improved. Furthermore, since the lubricating component is incompatible with the polyester resin forming the resin layer 3, softening and deterioration of the resin layer 3 can be suppressed. Therefore, sufficient slidability and scratch resistance can be ensured during molding processing, no fracture or scratch occurs in the resin layer 3, and the moldability is good.

[0073] In order to improve the design and aesthetics of the appearance of the can body after printing, the resin layer 3 is sometimes required to be white. When the resin layer 3 is to be white, it is preferred that the intermediate layer 32 contains 10% to 30% by mass of inorganic particles. The content of the inorganic particles in the intermediate layer 32 is more preferably 10% to 25% by mass, and still more preferably 15% to 20% by mass. When the content of the inorganic particles in the intermediate layer 32 is within the above range, the resin layer 3 can ensure sufficient whiteness and hiding power. In addition, fracture and scratch of the resin layer 3 are not likely to occur during the processing of can making, and the moldability is good. Here, the above content of the inorganic particles is based on 100% by mass of the resin composition (including the polyester resin material and the inorganic particles) used to form the intermediate layer 32.

[0074] The inorganic particles contained in the intermediate layer 32 are not particularly limited, and rutile-type titanium dioxide (TiO2) with a purity of 90% or more is preferably used. When the inorganic particles are the above-specified titanium dioxide, good dispersibility is exhibited during the mixing of the resin material and titanium dioxide, uniform whiteness can be obtained, and the design and aesthetics of the appearance are improved.

[0075] The resin layer 3 only needs to have the surface layer 31, the lower layer 33, and the intermediate layer 32, and is not limited to a three-layer structure, and can also be a laminated structure of four or more layers. By forming two or more layers of any one of the above three layers (for example, the intermediate layer 32), the resin layer 3 can be made into a laminated structure of four or more layers. If the case where the resin layer 3 is a three-layer structure of the surface layer 31, the intermediate layer 32, and the lower layer 33 is exemplified, the layer thickness (film thickness) of the surface layer 31, the intermediate layer 32, and the lower layer 33 is as follows.

[0076] The layer thickness of the surface layer 31 is preferably 1.0 μm to 5.0 μm, more preferably 1.5 μm to 4.0 μm, and still more preferably 2.0 μm to 3.0 μm. When the layer thickness of the surface layer 31 is within the above range, sufficient slidability and scratch resistance can be ensured during molding processing, fracture or scratch is not likely to occur in the resin layer 3, and the moldability is good. In addition, sufficient whiteness can be ensured, and the design and aesthetics of the appearance are improved.

[0077] The layer thickness of the surface layer 33 is preferably 1.0 μm to 5.0 μm, more preferably 1.5 μm to 4.0 μm, and still more preferably 2.0 μm to 3.0 μm. When the layer thickness of the lower layer 33 is within the above range, since the overall thickness of the resin layer 3 is within an appropriate range, sufficient scratch resistance can be ensured during molding. In addition, when the lower layer 33 contains a lubricating component, since the absolute amount of the lubricating component dispersed on the surface side of the metal plate layer 2 is within an appropriate range, the adhesion between the resin layer 3 and the metal plate layer 2 is improved.

[0078] The layer thickness of the intermediate layer 32 is preferably 6.0 μm to 30 μm, more preferably 8.0 μm to 25 μm, and still more preferably 10 μm to 20 μm. When the layer thickness of the intermediate layer 32 is within the above range, without changing the layer thicknesses of the surface layer 31 and the lower layer 33, the increase and decrease of the absolute amount of the lubricating component can be suppressed. Therefore, the coverage rate of the lubricating component is easily within an appropriate range, and no peeling, cracking or scratching occurs in the resin layer 3 during molding, and the adhesion between the printing ink and the resin layer 3 can be improved.

[0079] The manufacturing method of the film for forming the resin layer 3 can use ordinary laminated film manufacturing techniques, such as co-extrusion, film lamination, etc. From the viewpoint of simplifying the manufacturing process, it is preferable to manufacture the film by co-extrusion. The film can be manufactured by co-extrusion as follows. A multilayer die can be used to co-extrude the resin compositions for each layer from the extruders for each layer to produce an unstretched laminated film, and then it is stretched to form a film. The film formation is preferably carried out by biaxial stretching, that is, stretching the unstretched laminated film once in the film formation direction and then once in the direction perpendicular to the film formation direction. When the surface layer 31 and the lower layer 33 have the same composition, the resin compositions can be co-extruded from the extruder for the intermediate layer 32 and the extruders for the surface layer 31 and the lower layer 33 to produce an unstretched laminated film.

[0080] The method for making the surface layer 31 contain a lubricating component is not particularly limited. As an example, the addition can be carried out as follows. As described above, first, a masterbatch (masterbatch particles) in which the lubricating component is highly dispersed in a polyester resin is produced using a kneading extruder. Then, when making the above-mentioned film, the polyester resin particles as the main component of the resin layer 3 can be kneaded with the masterbatch, and the obtained resin composition is introduced into the extruder for the surface layer 31 and extruded at a specified extrusion temperature to form the surface layer 31, thereby carrying out the addition. The same applies to the case where the lower layer 33 contains a lubricating component. It should be noted that the above-mentioned specified extrusion temperature is preferably adjusted to 255 °C to 285 °C, which is 30 °C higher than the melting point of the resin particles.

[0081] In order to improve the dispersion state of the lubricating component in the layer containing the lubricating component in the resin layer 3, at least in the surface layer 31, it is preferable to adjust the extrusion temperature to a higher temperature within the above temperature range.

[0082] In addition, in order to improve the dispersion state of the lubricating component in the above layer, the draw ratio after producing the non-stretched laminated film is preferably 2.0 to 5.0 times in both the long side direction and the width direction, and more preferably 3.0 to 4.5 times.

[0083] In addition, in order to improve the dispersion state of the lubricating component in the above layer, the temperature of kneading and extrusion during masterbatch production and the screw rotation speed of the extruder can be adjusted.

[0084] It should be noted that the covering of the metal plate layer 2 with the film of the resin layer 3 (the lamination of the film with respect to the metal plate layer 2) can be carried out by a method of thermocompression bonding the film to the metal plate layer 2 using a laminating roll.

[0085] The resin layer 4 is a layer formed on the surface of the sheet material 100 opposite to the resin layer 3. The resin layer 4 is, for example, a layer containing a polyester resin. In the sheet material 100, the resin layer 4 is not essential, as Figure 2 shown, the sheet material 100 sometimes does not have the resin layer 4. The resin layer 4 can be formed as Figure 1 shown as a single layer, or can be a multi-layer of two or more layers. In the sheet material 100, the resin layer 4 does not have to be a layer having a different structure from the resin layer 3, as Figure 3 shown, the resin layer 3 can also be formed on both sides of the sheet material 100. That is, in the sheet material 100, the resin layer 3 (refer to Figure 3 ) can also be provided as the resin layer 4 (refer to Figure 1 ).

[0086] Examples

[0087] The resin-coated metal plates related to Manufacturing Examples 1 to 28 and Comparative Examples 1 to 8 were manufactured as follows.

[0088] As the metal plate serving as the metal plate layer, a TFS with a thickness of 0.22 mm, a metal chromium layer of 120 mg / m 2 , a chromium oxide layer of 10 mg / m in terms of metal chromium 2 , and a temper degree of T3CA was prepared.

[0089] Next, a resin layer having a three-layer structure of a surface layer, an intermediate layer, and a lower layer was formed under the formulations and conditions shown in Tables 1 to 3 as follows. First, a resin layer film was produced under the condition that the extrusion temperature during the kneading of resin particles and masterbatch was 275°C according to the formulations shown in Tables 1 to 3. The stretching of the film was carried out using a biaxial stretching method and was produced with a 4.0-fold stretch in both the long side direction and the width direction. Then, a metal plate was heated, and the film was thermocompression bonded to the metal plate using a laminating roller. After 1.5 seconds of thermocompression bonding, water cooling was carried out in a water cooling box, thereby producing a resin-coated metal plate in which both sides of the metal plate were coated with a resin layer. Table 1 shows the formulations and manufacturing conditions of the resin-coated metal plates related to Examples 1 to 13, and Table 2 shows the formulations and manufacturing conditions of the resin-coated metal plates related to Examples 14 to 24. Table 3 shows the formulations and manufacturing conditions of the resin-coated metal plates related to Examples 25 to 28 and Comparative Examples 1 to 8. It should be noted that in Tables 1 to 3, descriptions such as "ethylene glycol terephthalate 90 ethylene glycol isophthalate 10" (in the case of citing Example 1) in the "resin composition [mol%]" column mean that the content of ethylene glycol terephthalate units in the resin material forming the resin layer is 90 mol%, and the content of ethylene glycol isophthalate units is 10 mol%.

[0090]

[0091]

[0092]

[0093] Regarding the resin-coated metal plates related to the examples and comparative examples, the melting point of the resin layer, the melting point of the lubricating component, the coating rate of the lubricating component exposed on the outermost surface (surface layer surface) of the resin layer, the resin composition of the resin layer, the acid value of the lubricating component, and the film thickness of the resin layer were measured using the methods shown below.

[0094] (1) Melting point of the resin layer

[0095] The melting point of the resin layer was determined as follows. First, the resin-coated metal plate was immersed in a mixed solution of concentrated hydrochloric acid (30 wt%) : distilled water = 1 : 1 at room temperature (20°C) to dissolve the metal plate and peel off the resin layer. Then, using a differential scanning calorimeter: DSC Q100 manufactured by TA Instruments, the peeled resin layer was measured under the conditions that the atmosphere gas was N2, the flow rate was 50 ml / min, the temperature range was from room temperature to 290°C, and the heating rate was 10°C / min. Based on the obtained heat flow, the peak temperature of the endothermic peak in the range of 200°C to 280°C was taken as the melting point.

[0096] (2) Melting point of the lubricating component

[0097] The melting point of the lubricating component is determined as follows. As described in (1) above, the resin layer is peeled off from the resin-coated metal plate, and the resin layer is dissolved in hexafluoro-2-propanol as a solvent. After centrifuging the dissolved solution, it is pressure-filtered successively through filters with pore sizes of 1 μm and 0.1 μm, thereby extracting the lubricating components contained in the surface layer and the lower layer. Furthermore, Soxhlet extraction is performed using xylene as a solvent in the above filters, and the lubricating components are additionally extracted by concentration, reprecipitation, and centrifugation. For the lubricating components extracted above, a differential scanning calorimeter: DSC Q100 manufactured by TA Instruments is used, and the measurement is carried out under the conditions that the atmosphere gas is N2, the flow rate is 50 ml / min, the temperature range is from room temperature to 290 °C, and the heating rate is 10 °C / min. The peak temperature of the endothermic peak in the range of 50 °C to 170 °C of the obtained heat flow is taken as the melting point.

[0098] (3) Coating rate of the lubricating component

[0099] The coating rate of the lubricating component exposed on the outermost surface (surface layer surface) of the resin layer is determined as follows. Raman measurement is performed on the outermost surface of the resin-coated metal plate using a microscopic Raman device: LabRAM HR VIS-NIR manufactured by Horiba, Ltd. The measurement conditions are set as follows: confocal laser is used, the laser wavelength is 532 nm, the laser power is 10%, the aperture is 25 μm, the exposure time is 0.08 sec, the number of exposures is 1 time, the grating is 300 lines / mm, the objective lens is 100 times, and the wavenumber range is 310 cm -1 ~3400 cm -1 . It should be noted that the measurement range is set to 50 μm (the lamination direction of the resin-coated metal plate) × 50 μm (the direction orthogonal to the lamination direction in the plane of the resin-coated metal plate). The measurement pitch is 0.5 μm in both the lamination direction and the direction orthogonal to the lamination direction in the plane of the plate.

[0100] Based on the Raman spectral data obtained in the above measurement, the intensity ratio of the CH stretching vibration peak (2850 cm -1 ) of polyethylene, which is the main component of the lubricating component, and the CH stretching vibration peak (2960 cm -1 ) of polyester, which is the main component of the resin layer, is calculated, and the coating rate of the lubricating component is calculated through mapping analysis. The measurement is carried out for 3 fields of view randomly selected from each resin-coated metal plate, and all the lubricating components in the measurement field of view are taken as the calculation objects.

[0101] (4) Resin composition of the resin layer

[0102] The resin composition of the resin layer is calculated as follows. After peeling the resin layer from the resin-coated metal plate by the same method as in (1) above, the resin layer is dissolved in a solvent obtained by adding an appropriate amount of trifluoroacetic acid-d to chloroform-d. At this time, in order to remove the insoluble components generated during the dissolution process, centrifugation is performed, and the soluble components are used for measurement. The measurement is performed using a nuclear magnetic resonance apparatus manufactured by Bruker-BioSpin Corporation: AVANCE NEO cryo-500 type, under the conditions that the measurement nuclide is 1 H (500 MHz) and the number of accumulations is 16 times. The resin composition ratio is calculated based on the integral intensity of each signal in the obtained spectrum.

[0103] (5) Acid value of the lubricating component

[0104] The acid value of the lubricating component is calculated as follows. The lubricating component extracted by the same method as in (2) above is weighed in a beaker in an amount corresponding to the inferred acid value according to JIS K5902 and dissolved in 100 mL of a neutral solvent. As the neutral solvent, a solution obtained by mixing diethyl ether and ethanol (purity 99.5 or higher) specified in JIS K8101 in a volume ratio of 1:1 or 2:1 as specified in JIS K8103 is used. Using phenolphthalein as an indicator, the dissolved solution is titrated with a 0.1 mol / L potassium hydroxide standard solution, and the end point of neutralization is taken as the point when the color change of the indicator persists for 30 seconds, and the acid value is calculated according to the following formula. It should be noted that in the following formula (I), α represents the amount (mL) of the 0.1 mol / L potassium hydroxide standard solution used, β represents the sample taken amount (g), and F represents the factor of the 0.1 mol / L potassium hydroxide standard solution.

[0105] Acid value (mgKOH / g) = 5.611 × α × F / β (I)

[0106] (6) Thickness of each layer of the resin layer

[0107] The thickness of each layer of the resin layer is obtained as follows. After peeling the resin layer from the resin-coated metal plate by the same method as in (1) above, Pt coating is applied to the outermost surface of the resin layer, and cross-section preparation is performed using an ion milling apparatus manufactured by Leica Microsystems GmbH: EM TIC 3X. Then, a scanning electron microscope (SEM) manufactured by Hitachi High-Technologies Corporation: Regulus8220 is used to observe the backscattered electron image under two conditions of observation magnifications of 2500 times and 8000 times, and the thickness of each layer of the surface layer, intermediate layer, and lower layer of the resin layer is calculated based on the observed image.

[0108] Regarding the resin-coated metal plates of Examples 1 to 28 and Comparative Examples 1 to 8 above, the film adhesion, formability, and ink adhesion of the resin layer were further evaluated by the methods shown below. The evaluation results are shown in Table 4.

[0109] [Table 4]

[0110] Film adhesion Moldability Ink adhesion Example 1 A A A Example 2 A A A Example 3 A A A Example 4 A A A Example 5 A A A Example 6 A A A Example 7 A A A Example 8 A A A Example 9 A A A Example 10 A A A Example 11 A B A Example 12 A A A Example 13 A A B Example 14 A B A Example 15 A B A Example 16 B A B Example 17 A A B Example 18 A A A Example 19 A A A Example 20 A B A Example 21 A B A Example 22 A A A Example 23 A A A Example 24 A B B Example 25 A A B Example 26 A A A Example 27 A A B Example 28 A A A Comparative Example 1 A D C Comparative Example 2 A D A Comparative Example 3 A D A Comparative Example 4 D D D Comparative Example 5 C D D Comparative Example 6 C D D Comparative Example 7 A D A Comparative Example 8 D A D

[0111] (7) Film adhesion

[0112] The evaluation of film adhesion was carried out as follows. After forming the resin-coated metal plates of Examples 1 to 28 and Comparative Examples 1 to 8 into a can body (formed into a cylindrical shape with a diameter of 50 mm and a height of 160 mm), a T-shaped test piece was cut out from the upper position of the can body. Next, a cut was made on the resin layer and the metal plate, which was not the target surface, with a cutter to separate them. Using a Tensilon universal testing machine manufactured by Orientech Co., Ltd., the resin layer, which was the target surface, was stretched by 15 mm in the direction opposite to the separated metal plate (180° direction), and thus the strength of peeling from the resin layer was measured. Two plates were cut out from each can for measurement, and it was evaluated whether the resin layer was still sufficiently adhered to the metal plate after undergoing strong processing.

[0113] It should be noted that the film adhesion was evaluated in four grades from "A" (the best) to "D" (the worst), and the evaluation criteria were specified as follows.

[0114] Evaluation "A": The average maximum load for two pieces per can was 2.5 N / 15 mm or more.

[0115] Evaluation "B": The average maximum load for two pieces per can was 2.0 N / 15 mm or more and less than 2.5 N / 15 mm.

[0116] Evaluation "C": The average maximum load for two pieces per can was 1.5 N / 15 mm or more and less than 2.0 N / 15 mm.

[0117] Evaluation "D": The average maximum load for two pieces per can was less than 1.5 N / 15 mm.

[0118] (8) Formability

[0119] The evaluation of formability was carried out as follows. After applying wax to the resin-coated metal plates of Examples 1 to 28 and Comparative Examples 1 to 8, they were stamped into a circular plate shape with a diameter of 123 mm, and then drawn and formed into a cup shape with a drawing ratio of 1.7 using a deep drawing press. The obtained cup was inserted into a DI forming device, and redrawing and DI processing were carried out with a drawing ratio of 1.3 to form a can with an inner diameter of 52 mm and a can height of 90 mm. For the formed can, the surface of the resin layer was visually observed to evaluate the workability.

[0120] It should be noted that the evaluation of formability was in four grades from "A" (the best) to "D" (the worst), and the evaluation criteria were specified as follows.

[0121] Evaluation "A": No scratches can be observed visually at all.

[0122] Evaluation "B": Scratches are observed visually at a height within 10 mm from the flange part of the can.

[0123] Evaluation "C": Scratches are observed visually at a height exceeding 10 mm and within 30 mm from the flange part of the can.

[0124] Evaluation "D": Scratches or can body rupture is observed visually at a height exceeding 30 mm from the flange part of the can.

[0125] (9) Ink adhesion

[0126] The evaluation of ink adhesion is carried out as follows. The resin-coated metal plates of Examples 1 to 28 and Comparative Examples 1 to 8 are subjected to heat treatment in a hot air drying furnace to reach 240 °C in 2 minutes and then cooled to room temperature. Then, for each of the above heat-treated resin-coated metal plates, polyester-based printing ink (red) is printed on the resin layer on the outer surface side of the container after forming using a universal printing test machine manufactured by Kumagai Riki Kogyo Co., Ltd. Heat treatment is carried out in a hot air drying furnace to reach 185 °C in 1 minute and then cooled to room temperature. Taking the ink-printed surface of the cooled resin-coated metal plate as the object, a scratch test is carried out in the lamination direction of the resin layer. Using a load-variable friction and wear test machine manufactured by Shinto Kagaku Co., Ltd.: HHS2000, the test conditions are as follows: the continuous load from the printing end is from 10 gf to 1000 gf, the moving speed is 0.5 mm / sec, the moving distance is 30 mm, and a sapphire indenter (diameter 0.6 mm). 10 tests (2 pieces × 5 tests) are carried out for each resin-coated metal plate respectively, and the ink peeling load is calculated based on the obtained peeling length of the ink, and the ink adhesion is evaluated.

[0127] It should be noted that the evaluation of ink adhesion is a four-grade evaluation from Evaluation "A" (the best) to Evaluation "D" (the worst), and the respective evaluation criteria are specified as follows.

[0128] Evaluation "A": In 10 tests, the peeling loads of all 10 (all) are above the lower limit value of the material without added lubricating component.

[0129] Evaluation "B": In 10 tests, the peeling loads of 7 to 9 are above the lower limit value of the material without added lubricating component.

[0130] Evaluation "C": In 10 tests, the peeling loads of 5 to 6 are above the lower limit value of the material without added lubricating component.

[0131] Evaluation "D": In 10 tests, more than 6 peeling loads are less than the lower limit value of the material without added lubricating component.

[0132] As shown in Table 4, for the evaluation of the film adhesion, formability, and ink adhesion of the resin-coated metal plates involved in the examples, favorable evaluations of B or higher (evaluation A or B) were all obtained. In contrast, for the evaluation of the film adhesion, formability, or ink adhesion of the resin-coated metal plates involved in the comparative examples, including evaluations of C or lower (evaluation C or D), the evaluations were not good and were inferior to the resin-coated metal plates involved in the examples.

[0133] If each resin-coated metal plate involved in the examples is observed individually, the following trends can be grasped. Even if the lubricating component on the surface layer is less than 0.10% by mass (Example 15), good film adhesion, formability, and ink adhesion can be achieved. However, if it is 0.40% by mass or more, it is even better, especially the formability is improved. In addition, even if the lubricating component on the surface layer is 1.0% by mass (Example 13), good film adhesion, formability, and ink adhesion can be achieved. However, if it is 0.90% by mass or less, it is even better, especially the ink adhesion is improved.

[0134] If the coverage rate of the lubricating component in Examples 11, 13, 15 - 17, and 24 is focused on, as long as the coverage rate is 0.040% - 0.80%, sufficient slidability and scratch resistance for the processing during can manufacturing can be ensured, and it is difficult to generate fractures or scratches during the forming process, and the formability is improved. If the balance with the ink adhesion is considered (Examples 13, 17, 18, and 24), when the coverage rate is 0.50% or less, the formability and ink adhesion are better balanced.

[0135] Regarding the addition of titanium dioxide (TiO2) as inorganic fine particles to the intermediate layer, in order to ensure sufficient whiteness and hiding power, it is important to add a specified amount in the resin layer. In this regard, when adding titanium dioxide as inorganic fine particles, the addition amount (TiO2 amount) can exceed 30% by mass (Example 20), but 10% - 30% is appropriate and the formability becomes better.

[0136] If the melting point of the resin layer is 238°C or higher, the formability is better.

[0137] As described above, a resin-coated metal plate and a method for manufacturing the same can be provided.

[0138] It should be noted that the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately changed without departing from the purpose of the present invention.

[0139] Industrial Applicability

[0140] The present invention can be applied to a resin-coated metal plate and a method for manufacturing the same.

[0141] Symbol Explanation

[0142] 100: Sheet material (resin-coated metal sheet)

[0143] 2: Metal plate layer

[0144] 3: Resin layer

[0145] 31: Surface layer

[0146] 32: Intermediate layer

[0147] 33: Lower layer

[0148] 4: Resin layer

Claims

1. A resin-coated metal plate includes a metal plate layer and a resin layer. The resin layer coats the plate surface of the metal plate layer and contains a polyester resin. The resin layer has a melting point of 225°C to 255°C and has: a surface layer disposed on the surface opposite to the side opposite to the metal plate layer, a lower layer opposite to the metal plate layer, and an intermediate layer located between the surface layer and the lower layer, wherein the surface layer contains a lubricating component composed of a polyolefin having a melting point of 75°C to 140°C, the coverage rate of the lubricating component exposed on the surface of the surface layer is 0.040% to 0.80%, and this coverage rate is obtained by analyzing the peak intensity ratio of Raman spectrum data obtained by performing Raman measurement on the surface layer using a confocal Raman device.

2. The resin-coated metal plate according to claim 1, wherein The resin layer is formed of a resin material in which the ethylene terephthalate unit is 90 mol% or more.

3. The resin-coated metal plate according to claim 1 or 2, wherein The surface layer contains 0.10% by mass to 1.0% by mass of the lubricating component.

4. The resin-coated metal plate according to any one of claims 1 to 3, wherein, The lubricating component includes an acid-modified polyolefin or an oxidized polyolefin.

5. The resin-coated metal plate according to claim 4, wherein, The acid value of the lubricating component is 1.0 mgKOH / g to 80 mgKOH / g.

6. The resin-coated metal plate according to any one of claims 1 to 5, wherein, The intermediate layer contains 10% by mass to 30% by mass of inorganic particles.

7. The resin-coated metal plate according to any one of claims 1 to 6, wherein the layer thickness of the surface layer is 1.0 μm to 5.0 μm, the layer thickness of the intermediate layer is 6.0 μm to 30 μm, the layer thickness of the lower layer is 1.0 μm to 5.0 μm.

8. A method for manufacturing a resin-coated metal plate, which is a method for manufacturing the resin-coated metal plate according to any one of claims 1 to 7, producing masterbatch particles using a polyester resin having a melting point of 230°C to 254°C and an intrinsic viscosity of 0.45 to 0.88 as a matrix and dispersing the lubricating component therein, kneading the masterbatch particles with polyester resin particles, extruding at a specified extrusion temperature, and stretching by a biaxial stretching method to produce a film, thermocompression bonding the film to a metal plate using a laminating roll.

9. The manufacturing method of the resin-coated metal plate according to claim 8, wherein, The specified extrusion temperature is 255°C to 285°C.

10. The method for manufacturing a resin-coated metal plate according to claim 8 or 9, wherein, The stretching ratio of the film is set to 2.0 times to 5.0 times.

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