Heat-sealable biodegradable packaging material, a method for its manufacture, and a product package made from the material

The invention relates to a heat-sealable biodegradable packaging material, its manufacturing method and a product package formed thereof. The packaging material comprises a fibre substrate (1 ), an inner polymeric coating layer (2) against the same, which contains polylactide and a biodegradable polyester that is blended therewith to improve the adhesion between the layer and the fibre substrate, and an outer coating layer (3) that constitutes the outer surface of the material and contains polylactide and a biodegradable polyester that is blended therewith to improve the heat sealing ability of the layer, the portion of polylactide in the inner layer (2) being higher than that in the outer layer (3). The inner and/or outer coating layers (2, 3) can further have blended therewith a small amount of acrylic copolymer that improves the adhesion and/or heat sealing ability. The coating layers can be introduced onto the fibre substrate by extrusion or coextrusion.