Laminate steel sheet for two-piece can, method for production of two-piece can, and two-piece laminate can

Abstract

A laminated steel sheet for a two-piece can body with a high strain level satisfying the following formulae, the polyester resin layer composing the laminated steel sheet having a center line surface roughness (Ra) of 0.2 μm to 1.8 μm:r1≦r, 0.1≦r1 / R≦0.25, and 1.5≦h / (R−r)≦4wherein h is the height of the two-piece can body, r is the maximum radius, r1 is the minimum radius, and R is the radius of the circular laminated steel sheet before forming having the same weight as the can body.

Description

TECHNICAL FIELD[0001]The present invention relates to a laminated steel sheet for a two-piece can body, a method for making a two-piece can body, and a two-piece can body made of the laminated steel sheet, and specifically to a laminated steel sheet for making a two-piece can body having a high strain level such as those for containing aerosols, a method for making a two-piece can body, and a two-piece can body made of the laminated steel sheet.BACKGROUND ART[0002]Metal cans are broadly divided into two-piece and three-piece cans. A two-piece can is made of two sections, namely a can end and a can body integrated with a can bottom. A three-piece can is made of three sections, namely a can body, a can end, and a can bottom. A two-piece can body has no seam (weld) and thus looks good, but is usually required to endure a high strain level. A three-piece can has seams in its can body and thus is inferior to a two-piece can in the appearance, but is usually not required to endure a high ...

AI Technical Summary

Benefits of technology

[0015]The present invention is intended to provide a laminated steel sheet suitable for a two-piece can body which will not cause delamination or fracture of the resin layer, a method for making a two-piece can body, and a two-piece can body made of the laminated steel sheet.

[0018]For example, when a common rubber roll having a surface roughness (Ra) of 0.5 μm is used for lamination, bumps of several tens to hundreds of nanometers are formed in the film surface direction. In addition, the surface roughness can be controlled within a range of 0.2 to 1.8 in terms of the center line surface roughness (Ra). As a result of research, it has been found that a laminated steel sheet with bumps on its surface exhibits a markedly reduced surface friction, which results in the reduction of the processing stress and marked improvement of the processability.

[0019]A laminated steel sheet having the surface shape will not cause delamination or fracture even subjected to forming at a high strain level to make a two-piece aerosol can or the like. The laminated steel sheet favorably restored its adhesion through the heat treatment following the processing, indicating that it provides good film adhesion in the form of a can. The heat treatment temperature for sufficiently recovering the adhesion was lower and the heat treatment time was shorter in comparison with the case using a resin having a lower copolymerization ratio. In addition, crystallization hardly occurred during cooling, suggesting that sufficient performance is maintained even at a low cooling rate.

Problems solved by technology

Two-piece can bodies are usually made of a thick and expensive aluminum sheet, and are rarely made of a thin and low-cost tin or tin-free steel sheet.

The reason for this is that a steel sheet is not suitable for making a two-piece can body for containing an aerosol which is produced through drawing or DI processing at high strain levels, while a soft metal material such as an aluminum endures impact forming.

However, there has been no study on the use of the laminated steel sheet for the production of a can body produced through drawing and subsequent diametral reduction with a high strain level, such as a two-piece can for containing an aerosol.

However, according to the main text and examples of the description, the strain level of the can body thus obtained is still low.

More specifically there has been no disclosed method for producing a two-piece can body with a high strain level, such as those for containing an aerosol, from a laminated steel sheet.

As a result of this, the resin layer caused delamination and fracture.

However, it is known that these problems cannot be sufficiently solved by heat treatment before or after the forming, and delamination of the resin layer cannot be avoided at such a high strain level.

Therefore, the delamination of the resin layer during the production of a two-piece can body with a high strain level cannot be prevented by the simple use of the prior art.

In addition, the processability of the resin layer deteriorated during or after the heat treatment.

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