Heat-sealable biodegradable packaging material, a package made thereof, and use of a resin in extrusion coating
The invention concerns a heat-sealable biodegradable packaging material, which comprises a fibrous substrate and one or more polymer coating layers extruded onto said substrate. According to the invention the packaging material includes at least one polymer coating layer containing polylactide and at least about 1 weight-% of terpene phenolic resin blended therewith. The invention further concerns a heat-sealed product package made from the packaging material, as well as uses of the resin as blends with polylactide in extrusion coating, for improving line speed and neck-in in extrusion, adhesivity of the coating to the fibrous substrate, and heat-sealability of the coating.
1. A method of manufacturing a heat-sealed biodegradable container or package, comprising the steps of
(a) extruding a polymer blend consisting of polylactide and at least about 1 weight-% and at most 10 weight-% of terpene phenolic resin as a melt onto a fibrous board base having a basis weight of 170 to 350 g/m 2 on a moving line, to produce a heat-sealable board comprising a coating layer of said polymer blend on said board base, wherein said coating layer of said polymer blend is a monolayer having a basis weight of 10 to 30 g/m 2 , and
(b) forming the container or package from the polymer coated board thus obtained by introduction of heat to melt said polymer coating and by heat sealing the board sides or surfaces together.
2. The method of claim 1 , wherein said polymer coating layer contains polylactide and at least about 2 weight-% of terpene phenolic resin blended therewith.
3. The method of claim 1 , wherein said polymer coating layer contains at least 4 weight-% of terpene phenolic resin blended with polylactide.
4. The method of claim 1 , wherein said polymer coating layer contains at least 10 weight-% of terpene phenolic resin blended with polylactide.
5. The method of claim 1 , wherein said polymer coating layer contains at most 20 weight-% of terpene phenolic resin blended with polylactide.
6. The method of claim 1 , wherein said polymer coating layer is in a direct contact with the fibrous board base.
7. The method of claim 1 , wherein said polymer coating layer is the uppermost surface layer of a multilayer coating coextruded at step (a) onto the fibrous board base.
8. The method of claim 1 , wherein the terpene phenolic resin is made from α-pinene and phenol.
9. The method of claim 1 , wherein the heat sealability of said polymer coating layer is improved by blending the minor share of terpene phenolic resin with a share of at least 80 wt-% of polylactide.
10. The method of claim 1 , wherein the line speed in extrusion of said polymer coating layer is increased by blending the minor share of terpene phenolic resin with a share of at least 80 wt-% of polylactide.
11. The method of claim 1 , wherein the neck-in in extrusion of said polymer coating layer is reduced by blending the minor share of terpene phenolic resin with a share of at least 80 wt-% of polylactide.
12. The method of claim 1 , wherein adhesion of said polymer coating layer to the fibrous board base is improved by blending the minor share of terpene phenolic resin with a share of at least 80 wt-% of polylactide.
13. The method of claim 1 , wherein said package is a heat-sealed product package.
14. The method of claim 1 , wherein said container is a disposable drinking cup.
15. The method of claim 1 , wherein the polymer coating is heat sealed by use of hot air.