Laminated packaging material, and a method for manufacturing

A method of manufacturing a laminated packaging material for packaging of liquid food products, comprising:

• providing a bulk layer of paper or paperboard or other cellulose-based material with at least one through-going hole,
• laminating barrier film or sheet to said bulk layer such that the barrier film or sheet forms a membrane part covering the at least one through-going hole of the bulk layer, said barrier film or sheet is a non-metal barrier film or sheet, or a barrier film or sheet having a metal content of 5 mass percent or less,
• providing the barrier film or sheet of the membrane part with at least one slit, and
• laminating a first outermost liquid tight layer on the outside of the bulk layer to constitute the outside of a packaging container formed from the packaging material, and
• laminating a second innermost liquid tight layer on the inside of the barrier film or sheet to be in direct contact with the filled food product, such that the first liquid tight layer, the second liquid tight layer, and the barrier film or sheet together form a laminated membrane at the area of the at least one through-going hole.