| 摘要 |
<p>PROBLEM TO BE SOLVED: To make it hard to generate defects during processing of a metal sheet coated on its both sides with polyester by a method wherein the birefringence of the polyester coating layer at a side wall part has a specified value, while the intrinsic viscosity thereof is at least a specified value. SOLUTION: In a drawn-ironed can body, birefringence of a polyester coating layer at the side wall part is 0.05-0.150. In the case where the value is below 0.050, the strength of the polyester coating layer becomes insufficient to incur defects easily and at the same time water-vapor permeability becomes lower to increase the possibility of corrosion of the base metal. In the case where the birefringence is above 0.150, the molecular orientation becomes too high, cracks occur easily in the direction of the height of the can. The intrinsic viscosity is at least 0.60 d1/g/. If the value is below that value, the toughness becomes insufficient, cracks occur easily when being impacted to the polyester coating layer at the can bottom where the molecular orientation is not processed. In the standpoint of characteristics, the intrinsic viscosity has no upper limit, but it is desirable that the intrinsic viscosity is at most 1.00 d1/g in the standpoint of formability in the case the polyester coating layer is to be formed.</p> |
