Development of amorphous layer of biaxially oriented polyester film on laminated steel in the laminating process

Polyester film laminated steel for can container will gradually replace lac quer coated steel sheet from environmental concern and cost consideration. The process of lamination is characterized by partial melting of the film o n the surface of steel during lamination by pressing the supplied films bet ween both sides of heated steel and a couple of cooled rubber rolls. Variou s characteristics of film laminated steel for can use are strongly influenc ed by the degree of biaxial orientation and the thickness of amorphous laye r of the laminated film, and the characteristics are greatly influenced by several laminating conditions. Therefore, this report deals with the result of numerical analysis applied to characterize heat transfer in laminating process, in order to estimate t he variation of orientation of the laminated film. From the result of numer ical analysis, we found that the cross-sectional temperature distribution i n roll nip greatly changes within extremely short time, and the distributio n contributes to the formation of double layered structure of amorphous and biaxially oriented layers. Moreover, it was found important to form the double layered structure of th e laminated film by keeping an appropriate temperature profile of film in r oll nip. The thickness of amorphous layer with the numerical analysis obtai ned by the cross-sectional variation of maximum temperature of film in the roll nip agrees well with the one observed by polarizing microscope. The es timation of the thickness of amorphous layer was found possible by this met hod with a good accuracy.