Search

EP-4741531-A1 - RESIN-COATED ALUMINUM CAN LID AND RESIN-COATED ALUMINUM PLATE

EP4741531A1EP 4741531 A1EP4741531 A1EP 4741531A1EP-4741531-A1

Abstract

[Object] To provide a resin-coated aluminum can lid having resin adhesiveness, corrosion resistance, and a color tone in combination. [Solving Means] A resin-coated aluminum can lid 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 0.14 to 3.50 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
  • TAKEGUCHI, SHOTA
  • TAKENAGA, Tomoyasu
  • IKEBUCHI, MASASHI

Assignees

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

Dates

Publication Date
20260513
Application Date
20240705

Claims (11)

  1. A resin-coated aluminum can lid 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 0.14 to 3.50 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 can lid 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 can lid according to claim 1 or 2, wherein an L* value at a can lid outer surface is 85.5 or greater.
  4. The resin-coated aluminum can lid according to claim 1 or 2, wherein specular glossiness on a can lid outer surface is 85 or greater in terms of 60° gloss value in accordance with JIS Z 8741:1997.
  5. The resin-coated aluminum can lid according to claim 1 or 2, wherein the resin layer is a coating film.
  6. The resin-coated aluminum can lid according to claim 5, wherein the coating film is at least one selected from an epoxy acrylic-based coating film, a polyester phenol-based coating film, a polyester amino-based coating film, and a vinyl chloride organosol-based coating film.
  7. The resin-coated aluminum can lid according to claim 1 or 2, wherein the resin layer is a thermoplastic resin film.
  8. The resin-coated aluminum can lid according to claim 7, wherein the thermoplastic resin film is crystalline polyester.
  9. The resin-coated aluminum can lid according to claim 7 or 8, wherein the thermoplastic resin film is formed on the surface treatment layer via an adhesion primer layer.
  10. 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 coating film formed on the surface treatment layer, wherein the surface treatment layer contains aluminum hydroxide, and has a Pa/Pb value of 0.14 to 3.50 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.
  11. A resin-coated aluminum can lid made of the resin-coated aluminum sheet according to claim 10.

Description

[Technical Field] This disclosure relates to a resin-coated aluminum can lid and a resin-coated aluminum sheet. [Background Art] Conventionally, as a metal material for application to food cans, beverage cans, and the like, aluminum sheets have suitably been used for their excellent lightweight property and readily forming processability. Further, resin-coated aluminum sheets obtained by forming a resin layer such as a coating film or a thermoplastic resin film on aluminum sheets have long been known as a material for cans, and the formation into can lids, which are to be applied to beverage cans or the like, by subjecting these resin-coated aluminum sheets to processing is also well known. As aluminum sheets for use in resin-coated aluminum sheets for such can lids, surface-treated aluminum sheets to which surface treatment such as chemical treatment has been applied are used in general to secure corrosion resistance and adhesiveness after formation of 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 adhesiveness and corrosion resistance after the formation of 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 surface-treated aluminum sheet for use in can lids, however, there are such problems as will be described hereinafter. Described specifically, surface-treated aluminum sheets to be applied for use in can lids are used, depending on the use, in combinations with wide varieties of coating films and thermoplastic resin films. However, there were some cases where, when aluminum hydroxide coating treatment was combined with specific coating films or thermoplastic resin films, corrosion resistance and/or resin adhesiveness was deteriorated, and therefore, aluminum hydroxide coating treatment was not usable for a wide variety of use, unlike chromate phosphate treatment. On the other hand, many of can lids made of aluminum sheets have an appearance making use of an excellent color tone, such as a beautiful silver white shade and a metallic gloss, of the aluminum base material. If the above-described aluminum hydroxide coating treatment is applied, however, there were cases where silver white shade and metallic gloss, which the aluminum base material inherently had, were lost, leading to an impairment in color tone. The above-mentioned pieces of patent literature do not make sufficient consideration regarding adhesiveness with such a wide variety of coating films and thermoplastic resin films as described above and corrosion resistance after the formation of resin layers, 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 can lid that ensures adhesiveness and corrosion resistance even when combined with a wide variety of coating films and thermoplastic resin films and that also has an excellent color tone. Further, this disclosure also has as another object thereof the provision of a resin-coated aluminum sheet for manufacturing the above-described resin-coated aluminum can lid. [Solution to Problems] To solve the problems exemplified above, a resin-coated aluminum can lid according to an embodiment of the present invention 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 0.14 to 3.50 when, in an infrared absorption spectrum measured by a