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JP-2026075587-A - Laminated metal sheet, method for manufacturing laminated metal sheet, and laminated metal container

JP2026075587AJP 2026075587 AJP2026075587 AJP 2026075587AJP-2026075587-A

Abstract

[Problem] To provide inexpensive and environmentally friendly laminated metal sheets and laminated metal containers that possess basic characteristics such as processability, adhesion between film and metal sheet, and corrosion resistance, and that do not deteriorate in appearance due to whitening even after retort sterilization. [Solution] A laminated metal plate 10 in which a first film 31 is laminated on at least one surface of the front surface 21 and back surface 22 of a metal plate 20, wherein the first film 31 is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, and the first film 31 satisfies the following equations (1) and (2) when w(x) obtained from linearly polarized laser Raman spectroscopy analysis of its cross-section. w 1730 ID (1.0) ≦ 20cm -1 ...(1) w 1730 ND (1.0) ≦ 20cm -1 ...(2) [Selection Diagram] Figure 1

Inventors

  • 稲盛 樹
  • 平口 智也
  • 山中 洋一郎

Assignees

  • ＪＦＥスチール株式会社

Dates

Publication Date
20260508
Application Date
20250624
Priority Date
20241022

Claims (7)

  1. A laminated metal plate in which a first film is laminated on at least one of the front and back surfaces of a metal plate. The first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies the following equations (1) and (2). Laminated metal plate. w 1730 ID (1.0) ≦ 20cm -1 ...(1) w 1730 ND (1.0) ≦ 20cm -1 ...(2) However, w 1730 ID (x) is the full width at half maximum of the peak caused by the C=O stretching vibration near 1730 cm⁻¹ when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film from the metal plate side at a position x μm in the thickness direction, parallel to the direction in the film plane. w 1730 ND (x) is the full width at half maximum of the peak caused by C=O stretching vibration near 1730 cm⁻¹ when the polarization plane of a linearly polarized laser beam is incident on the cross-section of the first film from the metal plate side at a position x μm in the thickness direction, parallel to the film thickness direction.
  2. In the laminated metal plate according to claim 1, The first film is such that the w(x) obtained from linearly polarized laser Raman spectroscopy of its cross-section satisfies the following equations (3) and (4). Laminated metal plate. 14cm -1 ≦ w 1730 ID (3.0) ≦ 20cm -1 ... (3) 14cm -1 ≦ w 1730 ND (3.0) ≦ 20cm -1 ... (4)
  3. In the laminated metal plate according to claim 1 or 2, The first film is such that w(x), obtained from linearly polarized laser Raman spectroscopy of its cross-section, satisfies equations (5) and (6) below. Laminated metal plate. w 1730 ID (5.0) ≦ 16cm -1 ...(5) 20cm -1 ≦ w 1730 ND (5.0) ... (6)
  4. A method for manufacturing laminated metal sheets, A heat-pressing process to create a heat-pressed body by heat-pressing a preheated metal plate and a first film using a laminating roll, The process includes a rapid cooling step for rapidly cooling the heat-sealed body, The first film is homopolyethylene terephthalate or copolymerized polyethylene terephthalate, The elapsed time tq from the end of the heat-pressing process to the start of the rapid cooling process, and the surface temperature Tq of the first film side of the heat-pressed body 0.2 seconds after the end of the heat-pressing process, satisfy the following equation (7): A method for manufacturing laminated metal sheets. 0.38×Tq-tq-72 ≦ 0.0 (7)
  5. In the method for manufacturing a laminated metal plate according to claim 4, The preheating temperature of the metal plate in the heat-compression bonding process is 250°C or higher. A method for manufacturing laminated metal sheets.
  6. A laminated metal container comprising the laminated metal plate described in claim 1 or 2 as a material.
  7. A laminated metal container comprising the laminated metal plate described in claim 3 as a material.

Description

This invention relates to laminated metal sheets, a method for manufacturing laminated metal sheets, and laminated metal containers. Metal containers such as food cans, beverage cans, and 18L cans utilize metal sheets made of materials such as tin-free steel (TFS) and aluminum. These metal sheets are painted and baked to provide corrosion resistance, durability, and weather resistance. However, baking metal sheets is a complex process requiring considerable processing time. Furthermore, painting metal sheets generates large amounts of solvents. Therefore, laminated metal sheets, in which a thermoplastic resin film is laminated to the metal sheet, have been proposed as an alternative to painted metal sheets. Thermoplastic resin films used for laminated metal sheets require basic properties such as processability, adhesion to the metal sheet, and corrosion resistance. Incidentally, in the case of canned food, retort sterilization, which involves heating with high-temperature steam, is often used for sterilization. Thermoplastic resin films can develop tiny air bubbles inside during retort sterilization. Because these bubbles scatter light, thermoplastic resin films that have developed these bubbles after retort sterilization appear cloudy and whitish, impairing the appearance of the canned food. This problem is known as retort whitening. Attempts to suppress retort whitening are being made as follows. For example, Patent Document 1 discloses a film made of a polyester composition blended with a polyester whose main repeating unit is ethylene terephthalate and a polyester whose main repeating unit is butylene terephthalate, wherein the crystallization temperature of the polyester composition is 65 to 120°C, the secondary transition temperature is 40°C or higher, and the melting point is 260°C or higher. Patent Document 2 discloses a resin-coated metal plate having polyester resin layers mainly composed of polyethylene terephthalate on both sides, wherein the full width at half maximum of the C=O stretching vibration peak, as determined by laser Raman spectroscopy in a cross-section in the thickness direction of the polyester resin layer, is 16.0 cm⁻¹ or more and 24.0 cm⁻¹ or less. Patent Document 3 discloses a polyester resin-coated metal sheet having an unstretched polyester resin layer on at least one surface of a metal material, wherein the polyester resin layer has a first region on the interface side with the metal material where a specific peak determined by laser Raman spectroscopy is within a specific half-width range, and a second region on the surface side opposite to the metal material where the same specific peak is within a specific half-width range. Furthermore, a method for manufacturing a polyester resin-coated metal sheet having the above characteristics is disclosed, which involves heat-pressing an unstretched polyester resin film onto a metal material, rapidly cooling the polyester resin film after heat-pressing to form a polyester resin layer on the metal material, and then performing a post-heat treatment after rapid cooling. Patent Document 4 discloses a resin-coated metal plate having a polyester resin coating layer in which 90 mol% or more of the constituent units are ethylene terephthalate units, wherein the full width at half maximum of the C=O stretching vibration peak, as determined by laser Raman spectroscopy in the thickness direction cross section of the polyester resin coating layer, is 18.5 cm⁻¹ to 22.0 cm⁻¹ at a position 1.0 μm from the metal plate side in the thickness direction of the polyester resin coating layer, and 17.0 cm⁻¹ to 18.5 cm⁻¹ at a position 1.0 μm from the surface side in the thickness direction. Japanese Patent Application Publication No. 5-331302Japanese Patent Publication No. 2010-105263Japanese Patent Publication No. 2017-213884International Publication No. 2021/020549 (a) is a diagram showing the configuration of an example of a laminated metal container according to the present invention, and (b) is an enlarged cross-sectional view of the lid of the laminated metal container shown in (a). The present invention will be described in more detail below with reference to the drawings, but is not necessarily limited thereto. (Laminated metal container) Figure 1(a) shows the configuration of an example of a laminated metal container according to the present invention. As shown in Figure 1(a), the laminated metal container 100 comprises a bottomed cylindrical container body 11 and further comprises a lid portion 12 that closes the container body 11 as needed. The laminated metal container 100 is used, for example, for canned food, beverage cans, 18L cans, etc. Figure 1(b) shows an enlarged cross-sectional view of the lid portion 12 of the laminated metal container 100. The laminated metal container 100 may be a three-piece can formed by joining three components: a lid material constituting the lid portion 12, and a body material and bottom material constituting