Cover material for packaging container for retort sterilization

A cover material for a packaging container for retort sterilization, comprising a multilayer laminate obtained by laminating a base layer, interlayer and sealing layer in that order,

• the base layer comprising a laminated film obtained by laminating a polyethylene terephthalate film or polybutylene terephthalate film on an aluminum foil,
• the interlayer comprising an ethylene/propylene block copolymer, an ethylene/propylene random copolymer or high-density polyethylene,
• the sealing layer comprising a mixture of high-density polyethylene and an ethylene/propylene random copolymer,
• the base layer being laminated with the aluminum foil side facing the interlayer,
• the aluminum foil and interlayer in the base layer being laminated using a polyurethane-based adhesive or a polyester-based adhesive,
• the interlayer is laminated on the sealing layer such that the interlayer is in contact with the sealing layer, and
• the thickness of the aluminum foil being 5 to 40 μm, the thickness of the polyethylene terephthalate film or polybutylene terephthalate film being 6 to 18 μm, the thickness of the interlayer being 10 to 100 μm and the thickness of the sealing layer being 3 to 20 μm.