Laminated steel sheet for two-piece can, method for manufacturing two-piece can, and two-piece laminated can

Abstract

A laminated steel sheet including a polyester resin layer arranged on at least one face of the steel sheet, polyester resin forming the polyester resin layer is obtained by polycondensation of dicarboxylic acid and diol components, the dicarboxylic component contains terephthalic acid as the main ingredient and a copolymerizing ingredient, the diol component comprises ethylene and/or butylene glycol as a main ingredient and a copolymerizing ingredient, the sum of the copolymerizing ingredient in the dicarboxylic acid and the copolymerizing ingredient in the diol component is 8 to 16% by mole in the polyester resin, and the polyester resin layer has 0.06 or less of plane orientation factor.

1 . A method for manufacturing a two-piece can comprising multi-stage forming a circular disk of the laminated steel sheet comprising:
 a polyester resin layer arranged on at least one face of the steel sheet,   polyester resin forming the polyester resin layer is obtained by polycondensation of a dicarboxylic acid component and a diol component,   the dicarboxylic component contains terephthalic acid as the main ingredient and a copolymerizing ingredient,   the diol component comprises ethylene glycol and/or butylene glycol as a main ingredient and a copolymerizing ingredient, the sum of the copolymerizing ingredient in the dicarboxylic acid and the copolymerizing ingredient in the diol component ranges from 8 to 16% by mole in the polyester resin, and the polyester resin layer has 0.06 or less of plane orientation factor into a final formed body which satisfies the following relations:
   0.1 ≦d/R ≦0.25
 
   1.5 ≦h /( R−r )≦4
 
   
       wherein
 h is a height of a final formed body, 
 r is a maximum radius of the final formed body, 
 d is a minimum radius of the final formed body (including when r and d are equal), 
 R is a radius of a circular disk, before forming, having the same weight as that of the final formed body. 
 
     
     
         2 . A method for manufacturing a two-piece can comprising producing the final formed body according to  claim 1 , wherein heat treatment is applied as an interim stage of forming so that the formed body is heated to a temperature of from 150° C. to the melting point of the polyester resin. 
     
     
         3 . The method according to  claim 2 , wherein the heat treatment is carried out two or more times during forming. 
     
     
         4 . The method according to  claim 2 , wherein the heat treatment is applied at an interim stage that satisfies the following relations:
   0.1 ≦d/R ≦0.25
     1.5 ≦h /( R−r )≦4
   
       wherein
 h is a height of the formed body in the interim stage, 
 r is a maximum radius of the formed body in the interim stage, 
 d is a minimum radius d of the formed body in the interim stage (including when r and d are equal), 
 R is a radius R of the circular disk, before forming, having the same weight as that of the final formed body.