Blank for forming a packaging container and a packaging container

A blank for forming a packaging container, the blank comprising:

• a sheet defining an internal side and an external side of the packaging container;
• wherein the sheet comprises:
• a plurality of side panels separated from one another by side crease lines;
• a plurality of flaps, each one of the flaps extending from one of the side panels and being joined to the respective side panel by a flap crease line, each pair of adjacent flaps defining an inner flap and an outer flap;
• a sealant film disposed on the internal side of the sheet and having areas which are bonded to a portion of each one of the side panels and to a portion of each one of the flaps;
• wherein the sealant film comprises an unbonded area between the areas bonded to adjacent inner and outer flaps to allow the inner flap to first be folded inwards before the outer flap is folded onto the inner flap to form an end panel of the packaging container, with the sealant film forming a seal between the flaps, wherein the unbonded area extends across a portion of the outer flap, the inward folding movement of the inner flap draws the outer flap inward to form the packaging container, and the unbonded area extends across the outer flap by a distance which is greater than or equal to a length of the inner flap from the flap crease line so that the outer flap can lie directly against the inner flap;
• wherein the sealant film is bonded to a triangular area of the outer flap which has its base located along the flap crease line, wherein the base of the bonded triangular area is shorter than a length of the flap crease line;
• and
• wherein the sealant film is a water-soluble synthetic polymer.