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EP-4741530-A1 - RESIN-COATED SEAMLESS ALUMINUM CAN, RESIN-COATED ALUMINUM SHEET, AND DRAWN-IRONED CAN

EP4741530A1EP 4741530 A1EP4741530 A1EP 4741530A1EP-4741530-A1

Abstract

[Object] To provide a resin-coated aluminum seamless can having both resin adhesiveness and a color tone. [Solving Means] A resin-coated aluminum seamless can includes an aluminum base material, a surface treatment layer formed on at least one side of the aluminum base material, and a resin layer formed on the surface treatment layer. The surface treatment layer contains aluminum hydroxide, and has a Pa/Pb value of 0.13 to 3.00 when, in an infrared absorption spectrum measured by an FT-IR, a height of an absorbance peak at wavenumbers of 850 to 1000 cm -1 is defined as Pa and a height of an absorbance peak at wavenumbers of 1000 to 1200 cm -1 is defined as Pb.

Inventors

  • KASHIWAKURA, Takuya
  • NISHIDA, KAZUHIRO
  • KANAZAWA, SEITARO
  • TAKENAGA, Tomoyasu
  • TAKEGUCHI, SHOTA
  • IKEBUCHI, MASASHI

Assignees

  • Toyo Kohan Co., Ltd.
  • Toyo Seikan Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240705

Claims (14)

  1. A resin-coated aluminum seamless can comprising: an aluminum base material; a surface treatment layer formed on at least one side of the aluminum base material; and a resin layer directly or indirectly formed on the surface treatment layer, wherein the surface treatment layer contains aluminum hydroxide, and has a Pa/Pb value of 0.13 to 3.00 when, in an infrared absorption spectrum measured by a Fourier transform infrared spectrophotometer, a height of an absorbance peak at wavenumbers of 850 to 1000 cm -1 is defined as Pa and a height of an absorbance peak at wavenumbers of 1000 to 1200 cm -1 is defined as Pb.
  2. The resin-coated aluminum seamless can according to claim 1, wherein the surface treatment layer has a thickness of 2 nm or greater but smaller than 100 nm.
  3. The resin-coated aluminum seamless can according to claim 1 or 2, wherein an L* value at a can barrel portion is 85 or greater.
  4. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the resin layer contains a crystalline polyester resin.
  5. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the resin-coated aluminum seamless can is a drawn and ironed can.
  6. The resin-coated aluminum seamless can according to claim 5, wherein a central portion of a can barrel has a thickness that is 20% to 85% of a thickness of a central portion of a can bottom.
  7. The resin-coated aluminum seamless can according to claim 1 or 2, wherein, in an amount of oriented crystals contained in the resin layer, a can barrel portion is greater than 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 that contains 2 to 25 mol% of isophthalic acid and that is composed primarily of ethylene terephthalate unis.
  9. The resin-coated aluminum seamless can according to claim 1 or 2, wherein an X-ray diffraction intensity ratio (R) = I (100) /I (1-10) of an X-ray diffraction intensity I (100) from (100) planes parallel to a surface of the resin layer to an X-ray diffraction intensity I (1-10) from (1-10) planes parallel to the surface of the resin layer is 1.8 or greater at a can barrel portion but smaller than 1.8 at a can bottom portion.
  10. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the resin layer is a multilayer resin layer, and a thickness ratio of a surface layer to a bottom layer is surface layer:bottom layer = 20:1 to 1:20.
  11. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the surface treatment layer and the resin layer are on a side of an outer surface of the can, and the Pa/Pb value of the surface treatment layer is 0.13 to 3.00.
  12. The resin-coated aluminum seamless can according to claim 1 or 2, wherein the surface treatment layer and the resin layer are on a side of an inner surface of the can, and the Pa/Pb value of the surface treatment layer is 0.30 to 3.00.
  13. A resin-coated aluminum sheet comprising: an aluminum base material; a surface treatment layer formed on at least one side of the aluminum base material; and a resin layer formed on the surface treatment layer, wherein the surface treatment layer contains aluminum hydroxide, and has a Pa/Pb value of 0.13 to 3.00 when, in an infrared absorption spectrum measured by a Fourier transform infrared spectrophotometer, a height of an absorbance peak at wavenumbers of 850 to 1000 cm -1 is defined as Pa and a height of an absorbance peak at wavenumbers of 1000 to 1200 cm -1 is defined as Pb.
  14. A resin-coated aluminum seamless can made of the resin-coated aluminum sheet according to claim 13.

Description

[Technical Field] This disclosure relates to a resin-coated aluminum seamless can, a resin-coated aluminum sheet, and a drawn and ironed can. [Background Art] Conventionally, as a metal material for application to containers such as food cans and beverage cans, aluminum sheets have suitably been used for their excellent lightweight property and readily forming processability. Further, resin-coated aluminum sheets obtained by coating aluminum sheets with resin have long been known as a canmaking material, and the manufacture of seamless cans, which are to be filled with a beverage or the like, by subjecting such resin-coated aluminum sheets to drawing or to drawing and ironing are also well known. For example, resin-coated aluminum sheets each having as a resin layer a thermoplastic resin film formed of a crystalline polyester resin composed primarily of ethylene terephthalate units are used as a canmaking material for seamless cans. On the other hand, as aluminum sheets for use in resin-coated aluminum sheets for such seamless cans, surface-treated aluminum sheets to which surface treatment such as chemical treatment has been applied are used in general to secure corrosion resistance and adhesion with resin layers. As such surface treatment, there is, for example, chromate phosphate treatment, and surface-treated aluminum sheets to which chromate phosphate treatment has been applied have widely been used for their excellent adhesion with resin layers. From the viewpoint of environment protection, however, there is an increasing demand for chromium-free surface treatment. For example, in PTL 1 to PTL 4 described below, treatment that forms aluminum hydroxide on surfaces of an aluminum base material is disclosed as chromium-free surface treatment. It is also disclosed that containers and the like are formed using aluminum base materials subjected to such treatment. [Citation List] [Patent Literature] [PTL 1] JP 2003-013253A[PTL 2] JP 2004-216801A[PTL 3] JP 2007-176072A[PTL 4] JP H11-012762A [Summary] [Technical Problems] An aluminum hydroxide film formed on a surface of an aluminum base material is considered to be a film composed primarily of alumina monohydrate (AlO(OH)) called boehmite. Boehmite is mainly used in sealing treatment for anodized aluminum films, and is known as a material having corrosion resistance. Boehmite is also known for its acicular texture having roughness on the surface. This acicular texture is considered to exhibit an anchoring effect to a resin layer such as a coating film or a film and hence improve resin adhesiveness. If this aluminum hydroxide coating treatment is applied to a resin-coated aluminum sheet for seamless cans to be formed by severe forming processing such as drawing and ironing, however, there are such problems as will be described hereinafter. Described specifically, there were some cases where, when sterilization treatment such as retort treatment after forming of a seamless can and filling of contents was applied to a can body, a resin layer was peeled off due to lack of adhesiveness (hereinafter also called "resin adhesiveness") between an aluminum hydroxide film layer and the resin layer, depending on forming and treatment conditions for the film. Further, there were some other cases where, on an inner surface of a seamless can, corrosion resistance to contents was insufficient due to such lack of resin adhesiveness as described above. If containers such as seamless cans are formed using an aluminum sheet, on the other hand, there are many cases where a design is applied making use of an excellent color tone, such as a beautiful silver white shade and a metallic gloss, which an aluminum base material has. If severe forming processing such as drawing and ironing was applied to a resin-coated aluminum sheet subjected to aluminum hydroxide coating treatment as described above, however, there were cases where the silver white shade and metallic gloss, which an aluminum base material inherently had, were lost mainly at a processed potion, depending on forming and treatment conditions for the film, leading to a dull white appearance and an impairment in color tone. The above-mentioned pieces of patent literature do not make sufficient consideration regarding resin adhesiveness upon application of sterilization treatment such as retort treatment as described above, by no means include any finding regarding the deterioration of a color tone of an aluminum base material attributable to an aluminum hydroxide film, and therefore do not solve such problems. This disclosure has been made with a view to solve such problems, and has as an object thereof the provision of a resin-coated aluminum seamless can having both resin adhesiveness and a color tone. Further, this disclosure also has as another object thereof the provision of a resin-coated aluminum sheet for manufacturing the resin-coated aluminum seamless can having the resin adhesiveness and the color tone. [Solution