Method of producing packaging container comprising a valve

A method of producing a packaging container for bulk solids, the packaging container comprising an inner compartment and a transport closure closing the inner compartment, the transport closure comprising a top layer and a bottom layer, the bottom layer facing the inner compartment, the top layer being provided with an opening, the transport closure being provided, on a first side of the transport closure, with a one-way pressure relief valve for allowing gas in the inner compartment of the packaging container to exit therefrom, the valve being arranged within the opening and on a side of the bottom layer facing away from the inner compartment, a surface area of the opening being greater than a surface area of the valve, the transport closure being provided with at least one through perforation covered by the valve on the first side of the transport closure, the method comprises the steps of:

• a) forming a tubular container body, the container body having an upper end with an upper body opening and a bottom end with a bottom body opening and a container body wall extending in a height direction of the packaging container between the upper body opening and the bottom body opening, the container body wall having an inner surface and an outer surface, an upper end edge and a bottom end edge;
• b) presenting the container body to an upper body opening sealing station comprising a plunger piston comprising a bottom plate, the bottom plate having a through hole extending from a first side of the bottom plate to a second side of the bottom plate, the first and second sides being opposing sides;
• c) applying the first side of the bottom plate against the first side of the transport closure such that the through hole of the bottom plate is arranged to at least partially overlap the opening of the top layer and closing the upper body opening by pressing the transport closure with the plunger piston comprising the bottom plate into the upper body opening such that a pressure above an ambient pressure is produced within the tubular container body on a second side of the transport closure, allowing gas to exit the valve and the valve to be pre-conditioned;
• and
• d) attaching the transport closure to the inner surface of the container body wall.