Metal sheet for containers and method for manufacturing same

1. A metal sheet for containers, comprising:

a metal sheet; and

a polyester film which is scheduled to be an inner surface side of containers and which is laminated on a surface of the metal sheet, wherein the polyester film is a stacked laminate film comprising at least a first layer and a second layer, the first layer being on a metal sheet side of the polyester film, and the second layer being on top of the first layer on a side opposite to the metal sheet side,

wherein the second layer of the polyester film contains a wax in an amount of 0.010 to 2.000 mass %,

wherein the first layer of the polyester film contains isophthalic acid-modified polyethylene terephthalate,

wherein a total amount of polyethylene terephthalate and polyethylene naphthalate in the second layer is 80 mol % or more of the polyester included in said second layer,

wherein an amount of polybutylene terephthalate in the first layer is 5 to 80 mol % of the polyester included in said first layer, and

wherein the second layer of the polyester film has a dipole-dipole force of 20 mN/m to 40 mN/m.

2. The metal sheet for containers according to claim 1 ,

wherein the wax is any or a plurality of a polyethylene wax, a polypropylene wax, and sodium stearate.

3. The metal sheet for containers according to claim 1 ,

wherein a polyester film having a crystallization temperature of 120° C. or lower is laminated on a surface of the metal sheet ,which is scheduled to be an outer surface side of containers.

4. A method for manufacturing a metal sheet for containers, comprising:

a laminating step of passing a metal sheet and a polyester film comprising at least a first layer and a second layer, the first layer being on a metal sheet side of the polyester film, and the second layer being on top of the first layer on a side opposite to the metal sheet side and containing polyester and 0.010 to 2.000 mass % of a wax through a pair of lamination rolls in a sandwiched state to laminate the polyester film on a surface of the metal sheet which is scheduled to be an inner surface side of containers; and

a cooling step of cooling the metal sheet having the polyester film laminated on the surface after the laminating step,

wherein Tr (unit: ° C.) that is a temperature of the pair of lamination rolls is equal to or higher than Tg (unit: ° C.) that is a glass transition temperature of the polyester film and equal to or lower than Tm (unit: ° C.) that is a melting point of the wax,

t (unit: seconds) that is a time taken from an end of the laminating step to a start of the cooling step satisfies Expression (1):

0.9−{0.4/(Tm−Tg)}×(Tr−Tg)≤t≤2.6−{0.4/(Tm−Tg)}×(Tr−Tg)   (1)

and

the second layer after the cooling step has a dipole-dipole force of 20 mN/m to 40 mN/m.

5. A metal sheet for containers manufactured using the method for manufacturing a metal sheet for containers according to claim 4 , the metal sheet for containers comprising:

a metal sheet; and

a polyester film which is scheduled to be an inner surface side of containers and which is laminated on a surface of the metal sheet, wherein the polyester film is a stacked laminate film comprising at least a first layer and a second layer, the first layer being on a metal sheet side of the polyester film, and the second layer being on top of the first layer on a side opposite to the metal sheet side,

wherein the second layer of the polyester film contains a wax in an amount of 0.010 to 2.000 mass %,

wherein the first layer of the polyester film contains isophthalic acid-modified polyethylene terephthalate,

wherein a total amount of polyethylene terephthalate and polyethylene naphthalate in the second layer is 80 mol % or more of the polyester included in said second layer,

wherein an amount of polybutylene terephthalate in the first layer is 5 to 80 mol % of the polyester included in said first layer, and

wherein the second layer of the polyester film has a dipole-dipole force of 20 mN/m to 40 mN/m.

6. The metal sheet for containers according to claim 5 ,

wherein the wax is any or a plurality of a polyethylene wax, a polypropylene wax, and sodium stearate.

7. The metal sheet for containers according to claim 5 ,

wherein a polyester film having a crystallization temperature of 120° C. or lower is laminated on a surface of the metal sheet, which is scheduled to be an outer surface side of containers.