Resin-coated aluminum seamless can, resin-coated aluminum plate, drawn and ironed can

Abstract

[Problem] To provide a resin-coated seamless aluminum can that has both resin adhesiveness and a color tone. [Solution] This resin-coated seamless aluminum can is characterized by comprising an aluminum base material, a surface treatment layer formed on at least one surface of the aluminum base material, and a resin layer formed on the surface treatment layer, and is characterized in that the surface treatment layer contains aluminum hydroxide, and exhibits, in an infrared absorption spectrum thereof measured by FT-IR, a Pa / Pb value of 0.13-3.00 when the height of an absorbance peak at a wave number of 850-1000 cm-1 is defined as Pa and the height of an absorbance peak at a wave number of 1000-1200 cm-1 is defined as Pb.

Description

Technical Field

[0001] The present disclosure relates to a resin-coated aluminum seamless can, a resin-coated aluminum plate, and a drawn and ironed can.

Background Art

[0002] Conventionally, as a metal material applied to containers such as food cans and beverage cans, an aluminum plate that is rich in lightness and easy to form has been preferably used. In addition, a resin-coated aluminum plate in which an aluminum plate is coated with a resin has been known for a long time as a can-making material. It is also well known that this resin-coated aluminum plate is subjected to a drawing process or a drawn and ironed process to form a seamless can for filling beverages and the like. For example, a resin-coated aluminum plate having a thermoplastic resin film made of a crystalline polyester resin mainly composed of ethylene terephthalate units as a resin layer is used as a can-making material for seamless cans.

[0003] In addition, as an aluminum plate used for such a resin-coated aluminum plate for seamless can applications, generally, a surface-treated aluminum plate subjected to a surface treatment such as a chemical conversion treatment is used for the purpose of ensuring corrosion resistance and adhesion to the resin layer. Such a surface treatment includes, for example, a phosphoric acid chromate treatment. The surface-treated aluminum plate subjected to the phosphoric acid chromate treatment has excellent adhesion to the resin layer and has been widely used. However, from the perspective of environmental protection, the demand for a chromium-free surface treatment is increasing. For example, Patent Documents 1 to 4 below disclose a treatment for forming aluminum hydroxide on the surface of an aluminum substrate as a chromium-free surface treatment. And it is disclosed that a container or the like is formed using an aluminum substrate subjected to these treatments.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] The aluminum hydroxide film formed on the surface of the aluminum substrate is considered to be a film mainly composed of alumina monohydrate (AlO(OH)) called boehmite. Boehmite is mainly used for the sealing treatment of the aluminate film and is known as a corrosion-resistant substance. It is also known as a needle-like structure with unevenness on the surface, and it is considered that this needle-like structure exerts an anchor effect on resin layers such as coating films and films, improving the resin adhesion.

[0006] However, when this aluminum hydroxide film treatment is applied to a resin-coated aluminum plate for seamless cans formed by severe forming processes such as ironing and squeezing, there are the following problems. That is, depending on the film formation treatment conditions, when the seamless can is subjected to sterilization treatments such as retort treatment after forming and filling the contents, the resin layer may peel off due to insufficient adhesion between the aluminum hydroxide film layer and the resin layer (hereinafter also referred to as "resin adhesion"). Also, on the inner surface of the seamless can, the corrosion resistance against the contents may be insufficient due to the above-mentioned insufficient resin adhesion.

[0007] On the one hand, when forming a container such as a seamless can using an aluminum plate, a design that takes advantage of the excellent color tone of the aluminum base material, such as a beautiful silver-white color and metallic luster, is often applied. However, when severe forming processes such as ironing are applied to the resin-coated aluminum plate treated with the aluminum hydroxide film as described above, depending on the film formation treatment conditions, the silver-white color and metallic luster inherent in the aluminum base material are mainly lost in the processed part, resulting in a dull white appearance and a damaged color tone in some cases.

[0008] The above-mentioned patent documents do not fully consider the resin adhesion during sterilization treatment such as retort treatment as described above, and there is no knowledge about the deterioration of the color tone of the aluminum base material caused by the aluminum hydroxide film, and they do not solve such problems.

[0009] The present disclosure has been made in view of solving such problems, and an object thereof is to provide a resin-coated aluminum seamless can having both resin adhesion and color tone. Another object is to provide a resin-coated aluminum plate for manufacturing a resin-coated aluminum seamless can having both resin adhesion and color tone.

Means for Solving the Problems

[0010] In order to solve the problems exemplified above, a resin-coated aluminum seamless can according to an embodiment of the present invention includes an aluminum base material, a surface treatment layer formed on at least one surface of the aluminum base material, and a resin layer formed on the surface treatment layer, the surface treatment layer contains aluminum hydroxide, and in the infrared absorption spectrum measured by FT-IR, when the height of the absorbance peak at a wave number of 850 to 1000 cm -1 is defined as Pa, and the height of the absorbance peak at a wave number of 1000 to 1200 cm -1 is defined as Pb, the value of Pa / Pb is 0.13 to 3.00.

[0011] Also, in order to solve the problems exemplified above, a resin-coated aluminum plate according to an embodiment of the present invention includes an aluminum substrate, a surface treatment layer formed on at least one surface of the aluminum substrate, and a resin layer formed on the surface treatment layer, wherein the surface treatment layer contains aluminum hydroxide, and in the infrared absorption spectrum measured by FT-IR, the height of the absorbance peak at a wave number of 850 to 1000 cm -1 is defined as Pa, and when the height of the absorbance peak at a wave number of 1000 to 1200 cm -1 is defined as Pb, the value of Pa / Pb is 0.13 to 3.00.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide a resin-coated aluminum seamless can having both resin adhesion and color tone.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the resin-coated aluminum seamless can of the present disclosure will be described with reference to the drawings. In the present disclosure, "resin adhesion" generally refers to the adhesion between the surface treatment layer and the resin layer after the retort treatment after the forming process as described above. Also, "color tone" refers to the color difference (ΔE) and lightness (L *shall include the value).

[0015] <Resin-coated aluminum seamless can 100> FIG. 1 is a diagram schematically showing an embodiment of a resin-coated aluminum seamless can. As shown in FIG. 1, the resin-coated aluminum seamless can 100 has a bottomed cylindrical shape in which the can body and the can bottom are integrated. However, the shape of the resin-coated aluminum seamless can 100 of the present embodiment is not limited to the shape shown in FIG. 1, and can be a known shape applicable to beverage cans, food cans, etc.

[0016] More specifically, the shape of the resin-coated aluminum seamless can 100 may be a so-called tapered container 120 in which the diameters of the can bottom and the can top (opening) are different and the side wall is an inclined surface (see FIG. 2). There may be a step in the tapered portion (not shown). Further, the shape of the resin-coated aluminum seamless can 100 may be a substantially rectangular shape with rounded corners and a shallow bottom can body (for example, the shape of canned seafood such as sardines), or a square shape (not shown).

[0017] Also, the height of the resin-coated aluminum seamless can 100 can be appropriately adjusted according to its use.

[0018] The resin-coated aluminum seamless can 100 includes an aluminum base material 10, a surface treatment layer 20 formed on at least one surface of the aluminum base material 10, and a resin layer 30 formed on the surface treatment layer 20.

[0019] Note that the resin-coated aluminum seamless can 100 shown in Fig. 1a has a surface treatment layer 20 and a resin layer 30 on the outer surface side of the can, but it is not limited thereto. That is, the resin-coated aluminum seamless can 100 may be provided with a surface treatment layer 20 and a resin layer 30 on the inner surface side of the can (not shown). Further, as shown in Fig. 1b, in the present embodiment, a resin-coated aluminum seamless can 110 provided with a surface treatment layer 20 and a resin layer 30 in order from the aluminum base material 10 on both the inner surface side and the outer surface side may be used. In this case, the surface treatment layers 20 and resin layers 30 on the inner surface side and the outer surface side of the can may be the same or different in type and thickness. Further, in the tapered container 120 of Fig. 2, the display of the surface treatment layer 20 and the resin layer 30 is omitted, but as in Fig. 1, the surface treatment layer 20 and the resin layer 30 are formed on at least one of the inner surface and the outer surface of the container.

[0020] <aluminum base material 10> In the resin-coated aluminum seamless can 100, as the aluminum base material 10, a pure aluminum plate and an aluminum alloy plate can be used. The thickness of the aluminum base material 10 generally preferably has a thickness of 0.10 mm to 1.00 mm, and particularly preferably has a thickness of 0.15 mm to 0.40 mm. The alloy type of the aluminum base material 10 is selected according to the application. For example, from the viewpoints of workability, strength, and corrosion resistance, an aluminum alloy plate of the 3000 series or 5000 series of JIS standards is used.

[0021] <surface treatment layer 20> The surface treatment layer 20 contains aluminum hydroxide. Aluminum hydroxide contains aluminum oxide monohydrate (AlO(OH)), aluminum oxide trihydrate (Al(OH)3), and the like. By containing these substances, the corrosion resistance and the resin adhesion can be improved. The aluminum hydroxide in the surface treatment layer 20 appears as a peak in the infrared absorption spectrum measured by FT-IR in the range of a wave number of 1000 to 1200 cm (more specifically, 1070 cm -1 in the range) -1can be confirmed by the nearby peak). The peak appearing in the range of this wavenumber 1000 to 1200 cm -1 is known to be the absorbance peak of the Al-OH bending vibration derived from aluminum hydroxide.

[0022] In addition, the surface treatment layer 20 may contain amorphous alumina (Al2O3). The amorphous alumina in the surface treatment layer 20 can be confirmed by the peak (more specifically, the peak near 950 cm -1 ) appearing in the range of wavenumber 850 to 1000 cm -1 in the infrared absorption spectrum measured by FT-IR. The peak appearing in the range of this wavenumber 850 to 1000 cm -1 is known to be the absorbance peak derived from the Al-O stretching vibration of amorphous alumina.

[0023] Note that the above infrared absorption spectrum measured by FT-IR can be more specifically measured by the high-sensitivity reflection method (Reflection Absorption Spectroscopy (RAS) method) using a known Fourier transform infrared spectrophotometer (FT-IR).

[0024] As a method for measuring the absorbance peak, first, connect the absorbance at a wavenumber of 1200 cm -1 and the absorbance at a wavenumber of 850 cm -1 with a straight line and use it as the baseline. Then, as the peak derived from the Al-O stretching vibration of amorphous alumina, within the range of wavenumber 850 to 1000 cm -1 (near 950 cm -1 ), take the highest point from the baseline as the absorbance peak height Pa. Also, as the peak derived from the Al-OH bending vibration of aluminum hydroxide, within the range of wavenumber 1000 to 1200 cm -1 (near 1070 cm -1 ), take the highest point from the baseline as the absorbance peak height Pb. Calculate the peak ratio "Pa / Pb" from the obtained values.

[0025] Thus, in the resin-coated aluminum seamless can 100 of the present embodiment, in the infrared absorption spectrum measured by FT-IR of the surface treatment layer 20, the wavenumber is 850 to 1000 cm -1 The height of the absorbance peak derived from amorphous alumina of is defined as "Pa", and the wavenumber is 1000 to 1200 cm -1 When the height of the absorbance peak derived from aluminum hydroxide of is defined as "Pb", the value of the peak ratio "Pa / Pb" is characterized by being 0.13 to 3.00.

[0026] In the infrared absorption spectrum measured by FT-IR, it is considered that the absorbance of the surface treatment layer is in a proportional relationship with the amount of infrared-active chemical species present in the surface treatment layer. Therefore, the peak ratio "Pa / Pb" of the height of the absorbance peak "Pa" derived from amorphous alumina and the height of the absorbance peak "Pb" derived from aluminum hydroxide is a measure representing the quantitative ratio of amorphous alumina and aluminum hydroxide. The larger this value is, the larger the abundance ratio of amorphous alumina / smaller the abundance ratio of aluminum hydroxide. Conversely, the smaller this value is, the smaller the abundance ratio of amorphous alumina / larger the abundance ratio of aluminum hydroxide.

[0027] The reason why the inventors focused on the peak ratio "Pa / Pb" in the surface treatment layer 20, that is, the abundance ratio of amorphous alumina and aluminum hydroxide, in order to obtain the resin-coated aluminum seamless can they aimed for is as follows.

[0028] First, an explanation will be given from the perspective of resin adhesion. Aluminum hydroxide films such as boehmite contain amorphous alumina (Al2O3) depending on the film formation treatment conditions. However, it is known that amorphous alumina, unlike poorly soluble aluminum hydroxide, dissolves in hot water in a short time.

[0029] Therefore, if water-soluble amorphous alumina is contained in a high proportion in the aluminum hydroxide film present between the aluminum substrate and the resin layer, the insoluble or hardly soluble property of the film cannot be maintained, and the adhesion surface with the resin layer will dissolve due to heat water treatment such as retort treatment, so it is considered that sufficient resin adhesion cannot be obtained. Therefore, the inventors earnestly studied and considered that it is necessary to control the ratio of amorphous alumina in the film in order to obtain resin adhesion. As a result, it was found that by setting the peak ratio "Pa / Pb" to 3.00 or less, the insoluble or hardly soluble property of the film in hot water can be maintained, and sufficient resin adhesion can be obtained.

[0030] Next, an explanation will be given from the viewpoint of color tone. When an aluminum hydroxide film is formed on an aluminum substrate by the method described later, as the growth of acicular structures such as boehmite progresses, light is more likely to be scattered by the unevenness of the film. It is considered that when the acicular structure is in an overgrown state, it approaches a white color due to light scattering. Furthermore, when forming a seamless can from a resin-coated aluminum plate by ironing or other processes, it is presumed that the film is likely to aggregate and break during processing when the acicular structure is in an overgrown state. As a result, gaps (voids) are generated in the film, and light is scattered by this, which is considered to increase the white color tone, lose the metallic luster, and lead to deterioration of the color tone. Therefore, the inventors earnestly studied and considered that it is necessary to control the degree of growth of the acicular structure in order to suppress color tone changes from the viewpoints of light scattering and aggregation and breakage of the film during processing. As a result, it was found that by setting the peak ratio "Pa / Pb" to 0.13 or more, a state where the acicular structure grows moderately can be realized, and a good color tone can be obtained even after processing.

[0031] From the above, in this embodiment, it is important that the peak ratio "Pa / Pb" of the above surface treatment layer (aluminum hydroxide film) is within the range of 0.13 to 3.00. Thereby, it becomes possible to obtain a resin-coated aluminum seamless can having both required resin adhesion and color tone.

[0032] In the surface treatment layer of the present embodiment, it is desirable that the value of the aforementioned peak ratio "Pa / Pb" is in the range of 0.13 to 3.00, preferably 0.14 to 2.50, more preferably 0.20 to 2.00, and particularly preferably 0.30 to 1.50. When the value of the peak ratio "Pa / Pb" is greater than the above range, the resin adhesion will be inferior. When it is small, the color tone will be inferior.

[0033] Also, in the surface treatment layer formed on the outer surface side of the can, it is desirable that the value of the aforementioned peak ratio "Pa / Pb" is in the range of 0.13 to 3.00, preferably 0.14 to 2.50, more preferably 0.20 to 2.00, and particularly preferably 0.30 to 1.50. When the value of the peak ratio "Pa / Pb" is greater than the above range, the resin adhesion will be inferior. When it is small, the color tone will be inferior.

[0034] On the other hand, in the surface treatment layer formed on the inner surface side of the can, from the viewpoints of resin adhesion and corrosion resistance, it is desirable that the value of the aforementioned peak ratio "Pa / Pb" is in the range of 0.30 to 3.00, preferably 0.35 to 2.00. When the value of the peak ratio "Pa / Pb" is greater than the above range, the resin adhesion will be inferior, and as a result, the corrosion resistance against the contents will also be inferior. On the other hand, when the value of the peak ratio "Pa / Pb" is smaller than the above range, since the acicular structure is in an overgrown state, when a seamless can is formed by drawing and ironing from a resin-coated aluminum sheet, it is presumed that the film is likely to aggregate and break during processing. As a result, gaps (voids) are generated in the film, and when the content liquid penetrates thereinto, corrosion under the resin layer called under-film corrosion (UFC) is likely to occur, and the corrosion resistance becomes inferior.

[0035] In this embodiment, from the viewpoint of the resin adhesion of the resin-coated aluminum seamless can 100, the thickness (film thickness) of the surface treatment layer 20 is preferably 2 nm or more in the case of a seamless can. On the other hand, from the viewpoints of color tone and corrosion resistance, the upper limit of the thickness of the surface treatment layer 20 is preferably less than 100 nm. The optimum thickness of the surface treatment layer 20 depends on the target can shape and the like, but is more preferably 5 nm or more and less than 100 nm, still more preferably 8 to 90 nm, particularly preferably 10 to 80 nm, and most preferably 12 to 45 nm. If the film thickness is larger than the above range, the color tone and corrosion resistance may deteriorate, and if it is smaller, the resin adhesion may deteriorate.

[0036] When the seamless can is a drawn and ironed can, as will be described later, since it is formed from a resin-coated aluminum plate by a drawing and ironing process, the thickness of the surface treatment layer located on the can body is thinned in the same manner as the aluminum base material by the processing. The thickness of the surface treatment layer at the center of the can body (the thinnest part near the center in the height direction) is 20 to 85% of the thickness of the surface treatment layer at the center of the can bottom, preferably 20 to 75%, more preferably 20 to 60%, still more preferably 20 to 50%, particularly preferably 30 to 45%, and most preferably 30% or more and less than 40%. The thickness of the surface treatment layer at the center of the can bottom is more preferably 5 nm or more and less than 100 nm, still more preferably 8 to 90 nm, particularly preferably 10 to 80 nm, and most preferably 12 to 45 nm.

[0037] In this embodiment, as a method for measuring the thickness of the surface treatment layer 20, a known method can be applied. As an example of the method for measuring the thickness of the surface treatment layer 20, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), etc. can be applied, but TOF-SIMS is particularly desirable.

[0038] TOF-SIMS is a method of irradiating the surface of a solid sample to be analyzed with a primary ion beam from a primary ion gun, mass-separating the secondary ions sputtered and emitted from the sample surface using the difference in their flight times (the flight time is proportional to the square root of the weight), and performing mass spectrometry. Here, by detecting the secondary ion intensity while the sputtering is proceeding, the concentration distribution of the detectable element in the depth direction of the sample surface can be obtained by converting the transition time into depth data for the ion intensity of the secondary ions, i.e., the ions of the detectable element or molecular ions bonded to the detectable element.

[0039] In the present disclosure, etching is performed using TOF-SIMS from the surface side of the surface treatment layer 20 (the surface side opposite to the aluminum base material) until the aluminum base material is reached, and the secondary ion intensity of metallic aluminum derived from the aluminum base material is the maximum intensity (at the aluminum base material reach). The depth at which the secondary ion intensity of metallic aluminum at the time of reaching the surface treatment layer is half that of the surface treatment layer. The depth was defined as the thickness of the film. Note that the depth was calculated based on Al2O3.

[0040] As described above, the surface treatment layer 20 of this embodiment contains alumina monohydrate and alumina trihydrate as aluminum hydroxide. In addition, it may contain aluminum oxide (Al2O3) as another compound. In addition, the surface treatment layer 20 of this embodiment may contain trace amounts of compounds present in the treatment liquid, such as silicon dioxide (SiO2), magnesium oxide (MgO), manganese oxide (MnO), iron oxide (FeO), calcium oxide (CaO), phosphoric acid, etc., to the extent that performance is not impaired.

[0041] <Resin layer 30> The resin layer 30 is formed directly or indirectly on the surface treatment layer 20 on the side opposite to the aluminum base material 10. In this embodiment, a known adhesive layer (adhesive primer layer) or the like may be present between the surface treatment layer 20 and the resin layer 30.

[0042] In this embodiment, as the material of the resin layer 30, it is possible to apply a known thermoplastic resin or thermosetting resin coated on a metal substrate. Exemplifying thermoplastic resins, it is possible to preferably apply one or more resins such as polyolefin resins, polyester resins, polycarbonate resins, acrylic resins, polystyrene resins, ABS resins, polyamide resins, fluororesins, polyvinyl chloride resins, etc. Also, exemplifying thermosetting resins, it is possible to preferably apply one or more resins such as acrylic resins, unsaturated polyester resins, phenol resins, urea resins, polyurethane resins, silicone resins, polyimide resins, melamine resins, epoxy resins, etc. As the material of the resin layer 30, a thermoplastic resin is more preferable.

[0043] Among thermoplastic resins, polyolefin resins or polyester resins, and mixtures thereof can be more preferably applied.

[0044] Exemplifying polyolefin resins, it is possible to preferably apply one or more resins such as polyethylene resins, polypropylene resins, ethylene-propylene copolymer resins, ethylene-acrylic acid ester copolymer resins, ethylene-methacrylic acid ester copolymer resins, unsaturated carboxylic acid-modified polyolefin resins such as ethylene-methacrylic acid copolymer resins, ionomer resins, etc.

[0045] As an example of the polyester resin, a polyester resin mainly composed of ethylene terephthalate units is preferred. Specifically, it may be a polyethylene terephthalate resin, but a copolymerized polyester monomer or a blend thereof containing an acid component other than terephthalic acid in an amount of 35 mol% or less based on the acid component and an alcohol component other than ethylene glycol in an amount of 35 mol% or less based on the alcohol component may also be used. Examples of the acid component other than terephthalic acid include isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, P-β-oxyethoxybenzoic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, trimellitic acid, pyromellitic acid, and the like. Examples of the alcohol component other than ethylene glycol include glycol components such as propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, trimethylolpropane, and pentaerythritol. Examples of polyester resins other than those mainly composed of ethylene terephthalate units include polyester resins mainly composed of butylene terephthalate units or polyester resins mainly composed of ethylene naphthalate units, and blends of these polyester resins may also be used.

[0046] As the resin layer 30, a polyester resin can be more preferably applied. One or more crystalline polyester resins such as polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene terephthalate resin copolymerized with isophthalic acid, and polybutylene terephthalate resin copolymerized with isophthalic acid can be particularly preferably applied, and polyethylene terephthalate resin copolymerized with isophthalic acid is most preferred. More specifically, it is desirable that the resin layer 30 is a crystalline polyester resin mainly composed of ethylene terephthalate units containing 2 mol% to 25 mol% of isophthalic acid.

[0047] The resin layer 30 may be a multilayer resin layer. For example, a multilayer polyester resin layer having two or more layers in which isophthalic acid is copolymerized at different ratios can be used. More specifically, the resin layer 30 may include a lower layer with a relatively high copolymerization of isophthalic acid and a surface layer with a relatively low copolymerization of isophthalic acid. Even more specifically, the lower layer is a polyester resin mainly composed of ethylene terephthalate units containing isophthalic acid in an amount of 1 mol% to 20 mol%, the surface layer is a polyethylene terephthalate resin, or a polyester resin mainly composed of ethylene terephthalate units containing isophthalic acid in an amount of 15 mol% or less, preferably 1 mol% to 10 mol%. In this case, the lower layer is the layer closer to the aluminum base material 10, and the surface layer is the layer relatively farthest from the aluminum base material 10 compared to the lower layer. Also in this case, the thickness ratio (layer ratio) of the surface layer to the lower layer is preferably in the range of surface layer:lower layer = 20:1 to 1:20, and more preferably in the range of surface layer:lower layer = 10:1 to 1:10.

[0048] Also, the resin layer 30 may be a resin layer in which a plurality of different resins are blended. For example, a resin layer in which an ionomer resin, an ethylene-propylene copolymer resin, or an unsaturated carboxylic acid-modified polyolefin resin is blended with a polyethylene terephthalate resin, or a resin layer in which a polyethylene terephthalate resin or a polyethylene terephthalate resin copolymerized with isophthalic acid and a polybutylene terephthalate resin are blended can be applied. In the case of a resin in which a polyethylene terephthalate resin or a polyethylene terephthalate resin copolymerized with isophthalic acid and a polybutylene terephthalate resin are blended, it is preferable that the polybutylene terephthalate resin is blended in the range of 10 to 50% with respect to the polyethylene terephthalate resin or the polyethylene terephthalate resin copolymerized with isophthalic acid.

[0049] The thermoplastic resin such as the above-mentioned crystalline polyester resin may be laminated on the aluminum substrate after forming a film, or may be by direct lamination in which the heat-melted thermoplastic resin is extruded into a film shape by a slit with a narrow extrusion width of an extrusion molding machine and directly laminated on the aluminum substrate. When laminating after forming the above film, the film is not particularly limited, and for example, it may be an unstretched film, a uniaxially stretched film, or a biaxially stretched film.

[0050] Known compounding agents for resins can be compounded into the resin layer 30 according to known methods, such as anti-blocking agents such as amorphous silica, inorganic fillers such as calcium carbonate, magnesium carbonate, talc, and glass, various fibers such as glass fibers, carbon fibers, and aramid fibers, antistatic agents, antioxidants such as tocopherol, and ultraviolet absorbers.

[0051] Further, the resin layer 30 made of a thermoplastic resin may be formed on the surface treatment layer 20 via a conventionally known adhesive primer layer such as an epoxy phenol type or a polyester phenol type. The adhesive primer layer exhibits excellent adhesiveness to both the surface treatment layer and the resin layer. By providing the adhesive primer layer on the inner surface side of the seamless can, even when the can body is dented (dented) due to an external impact such as dropping and a defect (crack) occurs in the resin layer, the occurrence of metal exposure can be suppressed, and excellent impact resistance (dent resistance) can be exhibited. Thereby, even when the content to be filled is a highly corrosive acidic beverage or the like, it is possible to prevent the occurrence of corrosion at the dented portion. As the epoxy phenol type adhesive primer, it is particularly preferably formed from a paint containing an epoxy resin and a phenol resin in a weight ratio of 50:50 to 99:1, particularly 60:40 to 95:5, from the viewpoints of adhesion and dent resistance. As the polyester phenol type adhesive primer, it is particularly preferably formed from a paint containing a polyester resin and a phenol resin in a weight ratio of 50:50 to 99:1, particularly 60:40 to 95:5, from the viewpoints of adhesion and dent resistance. The above adhesive primer layer is generally preferably provided with a thickness of 0.1 to 10 μm.

[0052] When the resin layer 30 is a crystalline resin such as polyethylene terephthalate, it is preferable to have oriented crystals inside, but it is not necessary to have them. That is, when the resin-coated aluminum seamless can 100 is a drawn and ironed can, the resin layer 30 in the can body is given processing orientation in the process of drawn and ironed processing, and oriented crystals are formed inside the resin layer 30. On the other hand, the resin layer 30 at the bottom of the can has a lower degree of processing orientation imparted in the process of drawn and ironed processing, so the amount of oriented crystals is relatively less compared to the can body.

[0053] When the resin-coated aluminum seamless can 100 is a drawn and ironed can in this way, the amount of oriented crystals contained in the resin layer 30 is preferably larger in the can body than in the can bottom. Note that the presence or absence and amount of oriented crystals inside the resin layer 30 can be confirmed by a known method such as peak intensity using X-ray diffraction. When a resin layer composed of a crystalline resin such as polyethylene terephthalate is formed on the inner surface side of the resin-coated seamless can of the present embodiment, the X-ray diffraction intensity I by the (100) plane parallel to the surface of the resin layer 30 on the inner surface side ( 100) and the X-ray diffraction intensity I by the parallel (1-10) plane (1-10) The X-ray diffraction intensity ratio (R) between them = I (100) / I (1-10) is preferably 1.8 or more in the can body and less than 1.8 in the can bottom. That is, regarding this point, the X-ray diffraction intensity ratio (R) of the resin layer of the crystalline resin such as polyethylene terephthalate on the inner surface of the can body indicates the orientation structure of the crystal on the film surface, and the larger the X-ray diffraction intensity of the (100) plane is compared to the X-ray diffraction intensity of the (1-10) plane, the more surface orientation to the film surface is shown

[0054] When the resin-coated seamless can of the present embodiment is a drawn and ironed can, the X-ray diffraction intensity ratio (R) of the resin layer of the crystalline resin such as polyethylene terephthalate on the inner surface of the can body is 1.8 or more, more preferably 2.2 or more, still more preferably 2.4 or more, and particularly preferably 2.6 or more, and it is desirable that the (100) plane is preferentially surface-oriented. As a result, by drawing, thinning drawing forming and / or ironing, in the resin layer, in the can height direction By forming an oriented crystal to a certain degree or more, corrosion under the resin layer called under-film corrosion (UFC) is suppressed when filling the seamless can with an acidic content, and the impact resistance (dent resistance) of the resin layer can be enhanced. Further, when stored as a canned product, it is possible to prevent the flavor components of the content from adsorbing to the resin layer and suppress the change in the flavor of the content. On the other hand, when the X-ray diffraction intensity ratio (R) of the can body part is less than 1.8, UFC is likely to occur and the corrosion resistance deteriorates. Further, the impact resistance (dent resistance) also deteriorates, which is not preferable.

[0055] When the resin-coated seamless can of the present embodiment is a drawn and ironed can, it is desirable that the X-ray diffraction intensity ratio (R) of the resin layer at the bottom of the can is less than 1.8. That is, since the orientation state of the resin layer at the bottom of the can shows the same orientation state as the resin layer before processing, in order to follow the severe processing of the can body part, it is desirable that the orientation state of the resin layer at the bottom of the can is substantially in an unoriented state. At the bottom of the can, the degree of processing is not severe, and it is substantially retained in the form of the resin-coated aluminum plate before processing. Therefore, even in a state close to unorientation, the corrosion resistance and impact resistance can be satisfied.

[0056] On the other hand, when the resin-coated aluminum seamless can 100 is a drawn can, the degree of processing orientation imparted to the resin layer 30 does not differ significantly between the can body part and the bottom of the can. Therefore, the amount of oriented crystals contained in the resin layer 30 is generally the same between the can body part and the bottom of the can.

[0057] The thickness of the resin layer 30 is not particularly limited and can be the same as that of a known seamless can. More specifically, the thickness of the resin layer 30 preferably ranges from 0.5 to 200 μm, more preferably from 1 to 40 μm, still more preferably from 2 to 30 μm, and particularly preferably from 5 to 20 μm. When the seamless can is a drawn and ironed can, the thickness of the resin layer at the center of the can body (near the center in the can height direction, the thinnest part) is 20 to 85%, preferably 20 to 75%, more preferably 20 to 60%, still more preferably 20 to 50%, particularly preferably 30 to 45%, and most preferably more than 30% and less than 40% of the thickness of the resin layer at the center of the can bottom. Note that the thickness of the resin layer 30 at the center of the can bottom preferably ranges from 0.5 to 200 μm, more preferably from 1 to 40 μm, still more preferably from 2 to 30 μm, and particularly preferably from 5 to 20 μm.

[0058] On the other hand, regarding the thickness of the resin layer 30, when the resin-coated aluminum seamless can 100 is a drawn and ironed can, the thickness of the resin layer 30 in the can body is relatively thinner than the thickness of the resin layer 30 at the can bottom. This is because the side wall of the can is thinned overall in the process of drawn and ironed processing.

[0059] On the other hand, when the resin-coated aluminum seamless can 100 is a drawn can, the resin layer 30 in the can body is compressed in the thickness direction by the mold in the process of drawing. Therefore, when the resin-coated aluminum seamless can 100 is a drawn can, the thickness of the resin layer 30 is relatively thicker in the can body than at the can bottom.

[0060] In the present embodiment, the resin-coated aluminum seamless can 100 preferably has a lightness L* value of the outer surface of the can of 85 or more. Also, in the present embodiment, the lightness L* value can be measured using a spectrophotometer in accordance with JIS Z 8781-4:2013. When measuring the lightness L* value, a cut-out of the can body of the resin-coated aluminum seamless can 100 Flatten it, and it can be measured and evaluated at a can height of 60 mm and at a rolling 0° portion. In this embodiment, when printing is performed on the resin layer on the outer surface of the seamless can, or when the resin layer itself is colored or has low transparency, the lightness L* value of the outer surface of the can is the resin layer 30 It is desirable to remove it by a known method and measure it in a state where only the aluminum base material and the surface treatment layer remain.

[0061] The lightness L* value of the outer surface of the can is preferably 85 or more, more preferably 86 or more, and even more preferably in the range of 87 to 9 2. Also, when the resin layer 30 is removed by a known method and the lightness L* value of the outer surface of the can is measured in a state where only the aluminum base material and the surface treatment layer remain, it is preferably 86 or more, more preferably 87 or more Preferably, it is in the range of 88 to 93.

[0062] The chromaticity a* value and b* value of the resin-coated aluminum seamless can 100 on the outer surface of the can are not particularly limited, but are preferably in the range of -5 or more and 5 or less, and more preferably in the range of -3 or more and 3 or less, respectively.

[0063] In this embodiment, the resin-coated aluminum seamless can 100 preferably has a color difference (ΔE) of less than 5, more preferably less than 4, and even more preferably less than 3 from a reference can without the surface treatment layer 20 on the outer surface side.

[0064] The color difference (ΔE) is an index indicated using the L*a*b* color system defined in JIS Z8730:2009, and is an index calculated by the following formula based on the difference in CIE lightness L* and the differences in chromaticity a* and b* between two object colors. Lightness, chromaticity, and color difference can be measured using a colorimeter or the like.

[0065] An example of a specific method for calculating the color difference (ΔE) in this embodiment is as follows. Cut out the can body portion of the resin-coated aluminum seamless can 100 and flatten it. On the outer surface side, at a position near a can height of 60 mm and at a rolling 0° portion, the lightness (L* value) and chromaticity (a * value and b * value) are measured. Also, for a can (reference product) manufactured in the same manner except that it does not have the surface treatment layer 20, the lightness (L * value) and chromaticity (a * value and b * value) are measured. Then, using the following formula (1), the color difference (ΔE) between the resin-coated aluminum seamless can 100 and the reference product is calculated. ΔE = ((ΔL*) 2 +(Δa*) 2 +(Δb*) 2 ) 1 / 2 ···(1) ΔL* = L*1 - L*0, Δa* = a*1 - a*0, Δb* = b*1 - b*0 ΔL*: Change in L* value, L*0: L* value of the reference product, L*1: L* value of the present embodiment Δa*: Change in a* value, a*0: a* value of the reference product, a*1: a* value of the present embodiment Δb*: Change in b* value, b*0: b* value of the reference product, b*1: b* value of the present embodiment

[0066] <Method for manufacturing a resin-coated aluminum seamless can> The method for manufacturing the resin-coated aluminum seamless can 100 is described below. Note that the manufacturing method shown here is only an example in the present embodiment and is not limited to this method.

[0067] The method for manufacturing the resin-coated aluminum seamless can 100 includes at least (I) a manufacturing process of a resin-coated aluminum plate, and (II) a can manufacturing process of forming the obtained resin-coated aluminum plate into a seamless can.

[0068] (II) The can manufacturing process for forming seamless cans will be described in detail below. Note that the manufacturing process of the resin-coated aluminum sheet in (I) will be described later. As the forming method applied in the can manufacturing process, known forming methods can be applied. To give an example below, the resin-coated aluminum sheet is punched into a predetermined shape and dimensions, and then formed into various containers using a press die. As the forming process, conventionally known processing means such as drawing, redrawing, ironing, deep drawing, stretch bending ironing, and ironing can be applied. In this embodiment, ironing is particularly preferred. Since the resin-coated aluminum sheet used in this embodiment has excellent adhesion between the resin layer and the surface treatment layer, seamless cans formed by severe processing such as drawing, deep drawing, ironing, and stretch bending ironing can be formed without causing breakage of the can body or peeling of the resin layer at the flange forming part. Also, in this embodiment, by using a resin-coated aluminum sheet with a resin layer 30 previously formed on the surface, it becomes possible to reduce the surface friction coefficient with respect to the processing tool, and processing can be performed under dry conditions without using a coolant (cooling and lubricant). In addition, low environmental impact can manufacturing can be achieved, such as reducing the amount of washing water used in the container manufacturing process and omitting the painting and baking processes performed after container forming.

[0069] In the can manufacturing process for forming the seamless can of this embodiment, the can body of the seamless can is thinned by stretch bending by redrawing or ironing of the resin-coated aluminum sheet, etc., so that the thickness at the center of the can body is 20 to 85%, preferably 20 to 75%, more preferably 20 to 60%, still more preferably 20 to 50%, even more preferably 25 to 45%, and most preferably 30 to 40% of the thickness of the can bottom. When it is thicker than the above range, it cannot be sufficiently thinned and is not sufficiently satisfactory in terms of economy. On the other hand, when it is thinner than the above range, the resin layer cannot follow the processing and there is a risk of metal exposure.

[0070] In the can manufacturing process for forming the seamless can of the present embodiment, it is desirable to remove the residual stress of the resin layer generated by processing by subjecting the obtained seamless can to at least one stage of heat treatment. By removing the residual stress of the resin layer, it becomes possible to improve the adhesion between the resin layer after processing and the surface treatment layer. Also, when the resin layer is a crystalline resin such as polyethylene terephthalate, it is possible to thermally fix the oriented crystals in the can body. This heat treatment is preferably performed generally in the temperature range of Tg + 50°C or higher, particularly Tg + 100°C to the melting point (Tm) - 5°C, based on the glass transition point (Tg) of the resin layer. If the temperature is lower than this temperature range, the relaxation of the residual stress in the resin layer becomes insufficient, and the workability of post-processing such as neck-in processing tends to deteriorate. On the other hand, if the temperature is higher than this temperature range, the oriented crystals formed during can forming tend to dissolve, and problems such as a decrease in the corrosion resistance and impact resistance (dent resistance) of the can body occur. In the case where the resin layer is a multi-layer of two or more layers, it is preferable to perform the heat treatment so that the lowermost resin layer is within the above temperature range. By this heat treatment, the heat resistance of the resin layer is improved, the adhesion to the aluminum base material is also improved, and further, the workability for post-processing such as neck-in processing and flange processing, or the corrosion resistance, impact resistance (dent resistance), and flavorability are improved. On the lower temperature side than this temperature range, the relaxation of the residual stress in the resin layer becomes insufficient, and the workability of post-processing such as neck-in processing tends to deteriorate. On the other hand, on the higher temperature side than this temperature range, the oriented crystals formed during can forming tend to dissolve, and problems such as a decrease in the corrosion resistance and impact resistance (dent resistance) of the can body occur. In the case where the resin layer is a multi-layer of two or more layers, it is preferable to perform the heat treatment so that the lowermost resin layer is within the above temperature range. By this heat treatment, the heat resistance of the resin layer is improved, the adhesion to the aluminum base material is also improved, and further, the workability for post-processing such as neck-in processing and flange processing, or the corrosion resistance, impact resistance (dent resistance), and flavorability are improved.

[0071] <Resin-coated aluminum plate> The resin-coated aluminum plate 300 that can be used in the production of the resin-coated aluminum seamless can 100 will be described below. FIG. 3 is a diagram schematically showing the resin-coated aluminum plate 300 according to the present embodiment. As shown in FIG. 3, the resin-coated aluminum plate 300 includes an aluminum base material 10', a surface treatment layer 20' formed on at least one surface of the aluminum base material 10', and a resin layer 30' formed on the surface treatment layer 20'. The resin-coated aluminum plate 300 shown in FIG. 3a has the surface treatment layer 20' and the resin layer 30' on one side thereof, but the present disclosure is not limited thereto, and as shown in FIG. 3b, a resin-coated aluminum plate 310 having the surface treatment layer 20' and the resin layer 30' on both surfaces of the aluminum base material 10' may be used. The aluminum base material 10', the surface treatment layer 20', and the resin layer 30' respectively correspond to the aluminum base material 10, the surface treatment layer 20, and the resin layer 30 included in the resin-coated aluminum seamless can 100 described above. Therefore, only the differences will be described below, and the description of the common configuration will be omitted.

[0072] In the present embodiment, the thickness of the surface treatment layer 20' is preferably 2 nm or more from the viewpoint of resin adhesion. On the other hand, the upper limit of the thickness of the surface treatment layer 20' is preferably less than 100 nm from the viewpoints of color tone and corrosion resistance. The optimum thickness of the surface treatment layer 20' depends on the target can shape and the like, but is more preferably 5 nm or more and less than 100 nm, still more preferably 8 to 90 nm, particularly preferably 10 to 80 nm, and most preferably 12 to 45 nm.

[0073] Also, in the present embodiment, the thickness of the resin layer 30' is not particularly limited, but a range of 0.5 to 200 μm is preferable, a range of 1 to 40 μm is more preferable, and a range of 2 to 20 μm is still more preferable. Generally, the corrosion resistance improves as the resin layer becomes thicker, but the resin adhesion decreases, so there is an optimum thickness range depending on the application.

[0074] Note that the above Pa / Pb ratio does not change due to forming processes such as drawing and ironing. Therefore, the Pa / Pb ratio of the surface treatment layer 20' on the resin-coated aluminum plate 300 is characterized by being 0.13 to 3.00, similar to that of the resin-coated seamless aluminum can 100.

[0075] In this embodiment, when the resin layer 30' of the resin-coated aluminum plate 300 is a crystalline resin such as polyethylene terephthalate, it is preferably unoriented from the viewpoint of processing followability. Thereby, it is excellent in draw and ironing formability for thinning, and the body part of the can can be highly thinned, and it is also easy to increase the height of the seamless can.

[0076] <Manufacturing Method of Resin-Coated Aluminum Plate> Next, the manufacturing method of the resin-coated aluminum plate 300 in this embodiment (the above-mentioned (I) manufacturing process of the resin-coated aluminum plate) will be described below. Note that the manufacturing method shown here in this embodiment is only an example and is not limited to this method.

[0077] The manufacturing method of the resin-coated aluminum plate in this embodiment includes a surface treatment step of forming a surface treatment layer 20' containing aluminum hydroxide on the aluminum base material 10', and a resin coating step of forming a resin layer 30'. Note that in the surface treatment step, in the infrared absorption spectrum measured by FT-IR, when the height of the absorbance peak at a wave number of 850 to 1000 cm -1 mainly derived from the Al-O stretching vibration of amorphous alumina is defined as Pa, and the height of the absorbance peak at a wave number of 1000 to 1200 cm -1 mainly derived from the Al-OH bending vibration of aluminum hydroxide is defined as Pb, the surface treatment layer 20' is formed so that the value of Pa / Pb becomes 0.13 to 3.00.

[0078] As the surface treatment step, there is no particular limitation as long as the step can set the value of the peak ratio Pa / Pb to 0.13 to 3.00. For example, there are methods of immersing the aluminum substrate 10’ in a solution (treatment agent) at 20 to 100 °C and pH 6 to 13 for contact for 0.1 second to 30 seconds, or contacting with steam (treatment agent) at 100 °C to 140 °C for 0.1 second to 120 seconds.

[0079] That is, as the treatment agent for the surface treatment, a solution at 20 °C to 100 °C or steam at 100 °C to 140 °C can be used. The higher the temperature of the treatment agent, the shorter the time required to form the surface treatment layer 20’.

[0080] When the aluminum substrate 10’ is immersed in a solution (treatment agent) for treatment, as the pH of the treatment agent, those within the range of pH 6 to 13 can be applied. Aluminum hydroxide is hardly formed in an acidic solution with a pH less than 6, and a stable film can be formed in water with a pH of 7 or higher, or in an alkaline solution with a pH of 8 to 13.

[0081] The reason for using an alkali in the surface treatment solution is to dissolve the naturally formed oxide film present on the surface of the aluminum substrate before treatment in an extremely short time. Generally, the natural oxide film of the aluminum substrate is a film mainly composed of aluminum oxide and can be dissolved in an alkaline solution in an extremely short time. However, as the pH of the solution increases, the ratio of amorphous alumina in the surface treatment layer 20’ increases, so the more preferable pH range is pH 8 to 10.

[0082] In the surface treatment liquid used in the above surface treatment step, preferably, pure water can be used. Also, ion-exchanged water with an electric conductivity of 10 μS / cm or less may be used. The reason why pure water and ion-exchanged water are preferred is that as the phosphorus concentration, calcium concentration, silicon concentration, magnesium concentration, and iron concentration in the surface treatment liquid increase, the ratio of amorphous alumina contained in the surface treatment layer 20' becomes larger. When any of the phosphoric acid concentration, calcium concentration, silicon concentration, magnesium concentration, and iron concentration exceeds 1 ppm, the ratio of amorphous alumina contained in the surface treatment layer 20' rapidly increases. Therefore, it is preferable to control these element concentrations to 1 ppm or less. More preferably, it is 0.1 ppm or less.

[0083] When the surface treatment liquid used in the above surface treatment step is alkaline (pH 8 to 13), an aqueous sodium carbonate solution, an aqueous sodium aluminate solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, etc. are preferably used. Regarding the water used in the alkaline solution, the above-mentioned pure water and ion-exchanged water are preferred.

[0084] As a specific example when using a gas as the treatment agent, steam or superheated steam can be applied. In this case, the temperature of the steam is preferably 100°C to 140°C. Also, the temperature of the superheated steam is preferably 120°C to 350°C. The higher the temperature, the shorter the treatment time required to form a surface treatment layer 20' according to the application. In the case of superheated steam, a process is required in which the surface of the aluminum base material gets wet with dew condensation immediately after being put into the superheated steam furnace, or the aluminum base material 10' in a state of being previously wetted with water is put into the superheated steam furnace and dried. This is because the film containing aluminum hydroxide is rapidly formed at the timing when the moisture on the surface of the aluminum base material vaporizes.

[0085] In the manufacturing method according to this embodiment, a pretreatment step may be included before the surface treatment step. The pretreatment step is performed as a step of removing the natural oxide film present on the surface of the aluminum substrate 10'. Specifically, as the pretreatment step, dipping treatment using an alkaline solution or cathodic electrolysis treatment can be performed. As a specific example of the dipping treatment conditions, the alkaline solution can have a pH of 8 to 13, a liquid temperature of 20°C to 90°C, and a dipping time of 0.1 second to 10 seconds. Also, as a specific example of the cathodic electrolysis treatment conditions, the alkaline solution can have a pH of 8 to 13, a liquid temperature of 20°C to 90°C, a cathodic electrolysis time of 0.1 second to 10 seconds, and a current density of 1 to 10 A / dm 2 can be used. By the above pretreatment step, the natural oxide film present on the surface of the aluminum substrate is removed, and local dissolution of the aluminum substrate is suppressed, so that a more homogeneous surface treatment layer 20' containing aluminum hydroxide can be formed. Particularly from the viewpoint of homogenizing the surface treatment layer 20', cathodic electrolysis treatment is preferable because it can remove the natural oxide film more uniformly than dipping treatment. Also, if necessary, before the pretreatment step, a known degreasing treatment may be performed as surface cleaning for removing rolling oil, rust preventive oil, etc. The degreasing agent is not particularly limited, and known degreasing agents such as organic solvent-based degreasing agents and acidic or alkaline aqueous degreasing agents can be used.

[0086] Next, examples of the resin coating process include methods of forming the resin layer 30' on the surface treatment layer 20' formed as described above. The formation of the resin layer 30' can be performed by any method. For example, when the resin layer 30' is a thermoplastic resin, the resin in a molten state can be directly laminated onto the surface-treated aluminum plate, or a film processed in another line can be thermocompression-bonded onto the surface-treated aluminum plate heated in a laminating line. As described above, an adhesion primer layer may be formed between the surface treatment layer 20' and the resin layer 30' for the purpose of enhancing dent resistance. The adhesion primer layer may be provided in advance on the surface treatment layer on the surface-treated aluminum plate, or may be provided in advance on a resin layer such as a thermoplastic resin film. When the resin layer 30' is a thermosetting resin, there are methods such as coating with a roll coater and then drying in an oven, or coating with a spray and then drying in an oven.

[0087] <Example> Hereinafter, the present disclosure will be described more specifically with reference to examples. First, the measurement methods in the examples will be described.

[0088] [Calculation of absorbance peak ratio (Pa / Pb)] The absorbance in the infrared absorption spectrum of the surface treatment layer 20 of the resin-coated aluminum seamless can 100 was measured from the surface-treated aluminum plate using a Fourier transform infrared spectrophotometer (FT-IR) by the high-sensitivity reflection method (Reflection Absorption Spectroscopy (RAS) method) under the following conditions. A gold-deposited mirror was used for the background. A polarizer was used to detect only parallel polarized light.

[0089] Equipment: FTIR-6600 typeA manufactured by JASCO Corporation Measurement conditions Measurement method: RAS method Accessory used: Advanced Grazing Angle manufactured by PIKE Detector: MCT Wavenumber resolution: 4 cm -1 Integration count: 64 Measured temperature: Room temperature Measured atmosphere: Air Measured wavenumber range: 4000 - 500 cm -1

[0090] The measurement of the absorbance peak was performed on the surface - treated aluminum plate. First, as shown in Fig. 4, the absorbance at a wavenumber of 1200 cm -1 and the absorbance at a wavenumber of 850 cm -1 of the infrared absorption spectrum were connected by a straight line, and this was used as the baseline. Then, as the peak derived from the Al - O stretching vibration of amorphous alumina, within the range of 850 - 1000 cm -1 wavenumber, the highest point from the baseline was taken as the absorbance peak height Pa. Also, as the peak derived from the Al - OH bending vibration of aluminum hydroxide, within the range of 1000 - 1200 cm -1 wavenumber, the highest point from the baseline was taken as the absorbance peak height Pb. The absorbance peak ratio (Pa / Pb) was calculated from the measured Pa and Pb. The calculated absorbance peak ratio (Pa / Pb) was shown in Table 1. Note that the value of the absorbance peak ratio obtained by the above - mentioned measurement method matches the value of the absorbance peak ratio obtained by measuring after removing the resin layer 30 from the resin - coated aluminum seamless can 100 by a known method. Hereinafter, an example of measuring the value of the absorbance peak ratio from the resin - coated aluminum seamless can 100 is shown.

[0091] In a 350 - mL drawn and ironed can (resin - coated aluminum seamless can) obtained from the resin - coated aluminum plate of Example 4 prepared by the method (ii) described later, using an oven heat treatment was performed at 200°C for 90 seconds. Then, a can wall portion with a height of 60 mm was cut out into a 6 cm×6 cm size, and the resin layers 30 on the inner and outer surfaces were removed by a known method to make it in a state with only the aluminum substrate 10 and the surface - treatment layer 20. After that, as a result of measuring the absorbance peak and the absorbance peak ratio by the above - mentioned method, Pa was 0.0045, Pb was 0.030, and Pa / Pb was 0.15.

[0092] [Calculation of the film thickness of the surface - treatment layer] The thickness of the surface treatment layer was calculated from the surface-treated aluminum plate using a time-of-flight secondary ion mass spectrometer (TOF-SIMS) under the following conditions: Soft etching was repeated at a constant speed from the surface side of the surface treatment layer of the surface-treated aluminum plate using a Cs (cesium) ion gun, while mass analysis was performed on the components that make up the film. Etching was continued until the aluminum base material was reached, and the secondary ion intensity of metallic aluminum derived from the aluminum base material was measured. is half of the maximum intensity (secondary ion intensity of metallic aluminum when it reaches the aluminum substrate). The depth at which the surface was removed was taken as the film thickness of the surface treatment layer. Note that the depth is calculated as the alumina equivalent.

[0093] Equipment: ION TOF, TOF.SIMS5 Measurement conditions Primary ion type: Bi Etching gun type: Cs Measurement area: 50μm × 50μm

[0094] [Retort adhesion evaluation] Regarding the resin adhesion in a humid environment, the resin-coated aluminum prepared by the method (i) described below was The drawn and ironed cans (resin-coated seamless aluminum cans) obtained from the miniature plates were used for testing and evaluation in the following manner. First, a cut was made in the film (resin layer) on the outer surface of the 350 mL drawn and ironed can at a height of 90 mm from the bottom of the can with a cutter. The can was placed in a retort oven while immersed in tap water, and retorted at 125°C for 45 minutes. The maximum film peeling length below the cut with the cutter of the removed can was measured, and the can was evaluated as follows. ◎: Film peel length 10mm or less ○: Film peel length is over 10mm and 20mm or less △: Film peel length over 20mm and 30mm or less ×: Film peel length >30mm

[0095] [Color Tone Evaluation] 350 mL of drawn and ironed cans (resin-coated aluminum seamless cans) obtained from the resin-coated aluminum plates produced by the method (ii) described below were cut out from the can body and flattened. On the outer surface side, the color tone was measured at around 60 mm of the can height and at the rolling 0° portion. As the measuring instrument, a portable integrating sphere spectrocolorimeter Ci64 manufactured by X-Rite was used. Specifically, first, the lightness (L * value) and chromaticity (a * value and b * value) were measured, and then the color difference (ΔE) from the reference product (Comparative Example 1) was calculated using the following formula (1).

[0096] ΔE = ((ΔL*) 2 + (Δa*) 2 + (Δb*) 2 ) 1 / 2 ···(1) ΔL* = L*1 - L*0, Δa* = a*1 - a*0, Δb* = b*1 - b*0 ΔL*: Change in L* value, L*0: L* value of Comparative Example 1, L*1: L* value of the Example Δa*: Change in a* value, a*0: a* value of Comparative Example 1, a*1: a* value of the Example Δb*: Change in b* value, b*0: b* value of Comparative Example 1, b*1: b* value of the Example Based on the obtained ΔE, the judgment was made as follows. ◎: ΔE is less than 3 〇: ΔE is 3 or more and less than 4 △: ΔE is 4 or more and less than 5 ×: ΔE is 5 or more

[0097] In the 350 mL of drawn and ironed cans (resin-coated aluminum seamless cans) obtained from the resin-coated aluminum plates of Examples 3, 4, and 5 produced by the method (ii) described below, a 6 cm × 6 cm portion of the can wall at around 6 0 mm of the can height and at the rolling 0° portion was cut out and flattened. Next, the resin layer 30 on the outer surface was removed by a known method to leave only the aluminum base material 10 and the surface treatment layer 20, and then the lightness (L * value) at around 60 mm of the can height and at the rolling 0° portion was measured by the above method. The results are shown below. L of the drawn and ironed can of Example 3* Value: 90.31 L of the drawn and ironed can of Example 4 * Value: 88.29 L of the drawn and ironed can of Example 5 * Value: 86.97

[0098] [Corrosion Resistance Evaluation] First, in a 350 mL drawn and ironed can (resin-coated aluminum seamless can) obtained from the resin-coated aluminum plate prepared by the method (ii) described below, heat treatment was performed at 200 °C for 90 seconds using an oven. Next, on the inner surface side of the can body, a portion at a height of 60 mm from the bottom of the can and at 90° with respect to the rolling direction was cut out into a 4 cm × 4 cm test piece. The test piece was provided with two cross-cut scratches reaching the base material with a cutter in a direction 45 degrees with respect to the rolling direction, and immersed in a corrosion model solution (an aqueous solution with mass concentrations of 1.0% and 0.5% of sodium chloride and anhydrous citric acid, respectively) for 2 weeks at 37 °C. After that, the test piece was taken out from the model solution, and the state of discoloration due to peeling of the film (resin layer) or generation of corrosion products around the cross-cut part and its periphery was observed by visual evaluation. Around the cross-cut part, evaluation was performed as follows based on the maximum width of discoloration or film peeling. ◎: Those with a maximum width of less than 1 mm per side ○: Those with a maximum width of 1 mm or more and less than 2 mm per side △: Those with a maximum width of 2 mm or more and less than 3 mm per side ×: Those with a maximum width of 3 mm or more per side

[0099] [Dent Resistance Evaluation] The resin-coated aluminum plate prepared by the method (ii) described below, and the method (iii) described below Using 350 mL drawn and ironed cans (resin-coated aluminum seamless cans) obtained from resin-coated aluminum plates prepared with an adhesion primer, the evaluation was carried out by the following method. As the surface-treated aluminum plate, the surface-treated aluminum plate of Example 2 was used. First, after trimming the opening edge of the drawn and ironed can, heat treatment was performed at 200 °C for 90 seconds using an oven. Next, after necking and flanging the opening end, 350 g of the content Coca-Cola (trademark) was filled, and the lid was tightened according to the conventional method. Then, the can was placed horizontally and a 1 kg metal weight was vertically dropped from a height of 30 mm onto the lower surface of the side wall of the can (near the bottom) to give a dent. After that, after storing for 1.5 months at 37 °C with the lid facing upward, the corrosion state of the dented part on the inner surface side of the can was visually observed to evaluate the dent resistance. The results are shown below. Drawn and ironed can of Example 2 (without adhesion primer): Corrosion occurred Drawn and ironed can of Example 2 (with adhesion primer): No corrosion

[0100] [Calculation of X-ray diffraction intensity ratio (R)] In a 350 mL drawn and ironed can (resin-coated aluminum seamless can) obtained from a resin-coated aluminum plate prepared by the method of (ii) described later, heat treatment was performed at 200 °C for 90 seconds using an oven. Next, the center of the bottom of the can was cut out to 3 cm × 3 cm, the aluminum substrate was dissolved by a known method to obtain only the inner resin layer, and then it was fixed on a flat aluminum alloy plate with double-sided tape to obtain a measurement sample. Also, a 3 cm × 3 cm portion of the can wall at a height of 60 mm from the bottom of the can was cut out, the aluminum substrate was dissolved by a known method to obtain only the inner resin layer, and then it was fixed on a flat aluminum alloy plate with double-sided tape to obtain a measurement sample. The X-ray diffraction intensities of the (100) plane and the (1-10) plane were measured under the following measurement conditions, and the X-ray diffraction intensity ratio (R) = I (100) / I (1-10) was calculated.

[0101] X-ray diffractometer: RINT-2500 manufactured by Rigaku Corporation X-ray: CuKα X-ray (wavelength λ = 0.1542 nm) Tube voltage: 45 kV Tube current: 200 mA Divergence slit: 1 / 2° Receiving slit: 0.15 mm

[0102] (100) plane X-ray diffraction intensity: The maximum value confirmed within the range of 2θ = 25.0 to 27.0° was used. Also, for the (1-10) plane X-ray diffraction intensity, the maximum value confirmed within the range of 2θ = 22.0° to 24.0° was used. The background removal was performed by the Sonneveld-Visser method.

[0103] In the drawn and ironed can of Example 1 using the resin-coated aluminum plate prepared by the method of (ii) above, after heat treatment at 200 °C for 90 seconds, the X-ray diffraction intensity ratio (R) = I (100) / I (1-10) was calculated. As a result, the X-ray diffraction intensity ratio (R) at the bottom of the can was 1.7, and the X-ray diffraction intensity ratio (R) at the wall of the can was 2.9.

[0104] (Example 1) An aluminum base material of alloy type A3104, quality H19, and plate thickness 0.27 mm was prepared. After degreasing the rolling oil of the aluminum base material by a known method, it was immersed in a treatment liquid (ion-exchanged water at 95 °C) (surface treatment step). The treatment time was 8 seconds. Water was drained with a roller and dried with a dryer to obtain a surface-treated aluminum plate with a surface treatment layer containing aluminum hydroxide formed on both sides in the same manner. The film thickness and absorbance peak ratio (Pa / Pb) in the surface treatment layer of the obtained surface-treated aluminum plate were calculated and shown in Table 1.

[0105] Next, a resin layer was thermocompression-bonded onto the surface treatment layer of the obtained surface-treated aluminum plate to produce a resin laminate plate (resin-coated aluminum plate). Specifically, the resin laminate plate was created by the following three methods of (i) to (iii).

[0106] (i) On both sides of a heated surface-treated aluminum plate, an unstretched two-layer polyethylene terephthalate film (thickness 20 μm) was laminated, and it was placed in water and rapidly cooled to obtain a resin laminate plate. The two-layer polyethylene terephthalate film used was a film in which two layers, polyethylene terephthalate copolymerized with 2 mol% isophthalic acid (IA) as the surface layer and polyethylene terephthalate copolymerized with 15 mol% isophthalic acid (IA) as the lower layer, were laminated at a layer ratio of surface layer 4: lower layer 1.

[0107] (ii) On both sides of a heated surface-treated aluminum plate, a stretched polyethylene terephthalate film was laminated, and it was placed in water and rapidly cooled to obtain a resin laminate plate. For the surface on the inner side of the can, a polyethylene terephthalate film (thickness 19 μm) copolymerized with 11 mol% isophthalic acid (IA) was used. Also, for the surface on the outer side of the can, a stretched two-layer polyethylene terephthalate film (thickness 1 2 μm) in which two layers, polyethylene terephthalate copolymerized with 7.5 mol% isophthalic acid (IA) as the surface layer and polyethylene terephthalate copolymerized with 15 mol% isophthalic acid (IA) as the lower layer, were laminated at a layer ratio of surface layer 1: lower layer 5 was used. It was confirmed by X-ray diffraction that the inner and outer films after lamination were in an unoriented state.

[0108] (iii) On both sides of a heated surface-treated aluminum plate, a stretched polyethylene terephthalate film was laminated, and it was placed in water and rapidly cooled to obtain a resin laminate plate. For the surface on the inner side of the can, a polyethylene terephthalate film (thickness 19 μm) copolymerized with 11 mol% isophthalic acid (IA) was pre-laminated with polyester phenol on the laminated surface side. An adhesion primer was applied to a thickness of 1 μm and used. On the surface on the outside of the can, a two-layer structure of polyethylene terephthalate copolymerized with 7.5 mol% isophthalic acid (IA) as the surface layer and polyethylene terephthalate copolymerized with 15 mol% isophthalic acid (IA) as the lower layer was laminated at a layer ratio of surface layer 1: lower layer 5. A stretched two-layer polyethylene terephthalate film (thickness 12 μm) was used. In addition, it was confirmed by X-ray diffraction that the inner and outer surface films after lamination were in an unoriented state.

[0109] Paraffin wax of 50 mg / m was applied to both sides of the obtained resin laminate plate, punched out with a blank diameter of 142 mm, and a 1st cup was produced. Next, this 1st cup was processed into a drawn and ironed can with a reduction rate of 65% and a volume of 350 mL using a can-making machine (BodyMaker). 2 Can body diameter: about 66 mm Can body height: about 130 mm Thickness near the center of the can body with respect to the thickness of the original plate (bottom of the can): about 35%

[0110] In the obtained drawn and ironed can, retort adhesion evaluation on the outside of the can, color tone evaluation on the outside of the can, and corrosion resistance evaluation on the inside of the can were performed. The results of each evaluation were as shown in Table 1.

[0111] (Examples 2 to 5) The immersion time (treatment time) in the treatment liquid in the surface treatment step was as shown in Table 1. Otherwise, the same procedure as in Example 1 was performed. The results are shown in Table 1.

[0112] (Comparative Example 1) An aluminum substrate of alloy type A3104, quality H19, and plate thickness 0.27 mm was prepared. After degreasing the rolling oil of the aluminum substrate by a known method, the same evaluation as in Example 1 was performed without surface treatment. The results are shown in Table 1. The film naturally formed after degreasing was a film mainly composed of amorphous alumina, and the absorbance peak ratio (Pa / Pb) was 13.98. The results are shown in Table 1.​

[0113] (Comparative Examples 2 - 5) The immersion time (treatment time) in the treatment liquid in the surface treatment step was made as shown in Table 1. Otherwise, it was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0114] (Reference Example) Using an aluminum alloy plate having a phosphoric acid chromate treatment film, drawing and ironing can forming and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0115]

Table 1

[0116] From the above Examples and Comparative Examples, it was confirmed that by setting the Pa / Pb value of the surface treatment layer to 0.13 - 3.00, a resin-coated aluminum seamless can having both resin adhesion after retort treatment and color tone on the outer surface of the can can be obtained. Further, it was confirmed that by setting the Pa / Pb value to 0.30 - 3.00, a resin-coated aluminum seamless can having excellent corrosion resistance on the inner surface of the can can be obtained.

Industrial Applicability

[0117] The resin-coated aluminum seamless can of the present disclosure is suitable for applications such as beverage cans and beverage cups.

Explanation of Reference Numerals

[0118] 100 Resin-coated aluminum seamless can 10 Aluminum base material 20 Surface treatment layer 30 Resin layer

Claims

1. An aluminum substrate; a surface treatment layer formed on at least one surface of the aluminum base; a resin layer formed directly or indirectly on the surface treatment layer; Including, The surface treatment layer contains aluminum hydroxide, and in an infrared absorption spectrum measured by FT-IR, the wave number is 850 to 1000 cm －１ The height of the absorbance peak is defined as Pa, and the wave number is 1000 to 1200 cm －１ When the height of the absorbance peak is defined as Pb, the value of Pa / Pb is 0.13 to 3.

00. A resin-coated aluminum seamless can.

2. 2. The resin-coated aluminum seamless can according to claim 1, wherein the surface treatment layer has a thickness of 2 nm or more and less than 100 nm.

3. 3. The resin-coated aluminum seamless can according to claim 1, wherein the L* value in the can body is 85 or more.

4. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the resin layer contains a crystalline polyester resin.

5. 3. The resin-coated aluminum seamless can according to claim 1, which is a drawn and ironed can.

6. 6. The resin-coated aluminum seamless can according to claim 5, wherein the thickness of the central part of the can body is 20 to 85% of the thickness of the central part of the can bottom.

7. 3. The resin-coated aluminum seamless can according to claim 1, wherein the amount of oriented crystals contained in the resin layer is greater in a can body portion than in a can bottom portion.

8. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the resin layer contains a crystalline polyester resin, and the crystalline polyester resin is a polyester resin mainly composed of ethylene terephthalate units containing 2 mol% to 25 mol% of isophthalic acid.

9. X-ray diffraction intensity I from the (100) plane parallel to the surface of the resin layer （１００） and the X-ray diffraction intensity I from the parallel (1-10) plane （１－１０） X-ray diffraction intensity ratio (R) = I （１００） / I （１－１０） 3. The resin-coated aluminum seamless can according to claim 1, wherein the can body has a viscosity of at least 1.8 and the can bottom has a viscosity of less than 1.

8.

10. 3. The resin-coated aluminum seamless can according to claim 1, wherein the resin layer is a multi-layer resin layer, and a thickness ratio of the surface layer to the lower layer is surface layer:lower layer=20:1 to 1:

20.

11. the can has the surface treatment layer and the resin layer on the outer surface side, and the Pa / Pb value of the surface treatment layer is 0.13 to 3.00; The resin-coated aluminum seamless can according to claim 1 or 2.

12. The can has the surface treatment layer and the resin layer on the inner surface side, and the Pa / Pb value of the surface treatment layer is 0.30 to 3.

00. The resin-coated aluminum seamless can according to claim 1 or 2.

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