Laminated steel sheet for two-piece can body, two-piece can body made of laminated steel sheet, and method of producing the two-piece can body

Abstract

Provided is a laminated steel sheet for a can body of a two-piece can, containing a copolyethylene terephthalate resin layer containing at least one member selected from the group consisting of isophthalic acid and cyclohexane dimethanol as a copolymer component in a proportion of 5 to 20 mol % and having a crystallization temperature of 120° C. to 140° C. on at least one side of a steel sheet; and satisfying the following relationships: r 1 ≦r, 0.1≦r 1 /R≦0.25, and 1.5≦h/(R−r)≦4, wherein r 1 represents the minimum radius of the can body, r represents the maximum radius of the can body, h represents the height of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body. The laminated steel sheet is suitable for a can body of a two-piece can having a high strain level, and can provide a two-piece can body which is free from delamination and breakage of the resin layer.

1 . A laminated steel sheet for a can body of a two-piece can, comprising:
 a copolyethylene terephthalate resin layer containing at least one member selected from the group consisting of isophthalic acid and cyclohexane dimethanol as a copolymer component in a proportion of 5 to 20 mol % and having a crystallization temperature of 120° C. to 140° C. on at least one side of a steel sheet; and   satisfying the following relationships:   r 1 ≦r, 0.1≦r 1 /R≦0.25, and 1.5≦h/(R−r)≦4, wherein r 1  represents the minimum radius of the can body, r represents the maximum radius of the can body, h represents the height of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body.   
   
   
       2 . The laminated steel sheet according to  claim 1 , wherein a plane orientation coefficient of the copolyethylene terephthalate resin layer is 0.04 or lower. 
   
   
       3 . A method of producing a can body of a two-piece can, comprising:
 a step of shaping, in multiple steps, a circular sheet of the laminated steel sheet according to  claim 1  into a formed body satisfying the following relationships:   r 1 ≦r, 0.1≦r 1 /R≦0.25, and 1.5≦h/(R−r)≦4, wherein r 1  represents the minimum radius of the can body, r represents the maximum radius of the can body, h represents the height of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body.   
   
   
       4 . The production method of the can body according to  claim 3 , wherein a formed body obtained in the middle of the multiple steps is heated at least once at a temperature ranging from 150° C. or higher to a melting point of the copolyethylene terephthalate resin or lower. 
   
   
       5 . The production method of the can body according to  claim 4 , wherein, the heat treatment is performed when the formed body obtained in the middle of the multiple steps satisfies the following relationships:
 r 1 ≦r, 0.2≦r 1 /R≦0.5, and 1.5≦h/(R−r)≦2.5, wherein r 1  represents the minimum radius of the can body, r represents the maximum radius of the can body, h represents the height of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body.   
   
   
       6 . A can body of a two-piece can, which is produced by the production method according to  claim 3 . 
   
   
       7 . A laminated steel sheet for a two-piece can body, satisfying the following relationships:
 r 1 ≦r, 0.1≦r 1 /R≦0.25, and 1.5≦h/(R−r)≦4, wherein h represents the height of the can body, r represents the maximum radius of the can body, r 1  represents the minimum radius of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body,   the laminated steel sheet comprising a polyester resin layer on at least one side, and   the polyester resin layer comprising terephthalic acid and ethylene glycol as a main polymer component and at least one member of isophthalic acid and cyclohexane dimethanol as a copolymer component in a proportion of 5 to 20 mol %, and having a crystallization temperature of 120 to 140° C.   
   
   
       8 . A can body of a two-piece can, which is produced by the production method according to  claim 4 . 
   
   
       9 . A can body of a two-piece can, which is produced by the production method according to  claim 5 .