Synergistic biopolymer blown film extrusion system and method
View Patent ↗A biopolymer blown film extrusion system comprising an extruder receiving polymer pellets and at least two additives, and generating a molten mass having at least one layer; a die receiving the molten extrudates and generating a bubble having at least one layer from a die orifice; an internal bubble blower operably connected to maintain air inside the bubble; a bubble collapsing frame receiving the bubble and generating a biopolymer film having at least one layer, the film having a selected elongation at break of 180% or more in one direction and heat sealing at 195° F. or less; a nip roller operably connected to draw the biopolymer film from the bubble collapsing frame; a turning bar operably connected to change a travel angle of the biopolymer film; and a travel roller operably connected to direct travel of the biopolymer film.
1. A method of forming a biopolymer blown film comprising:
extruding at least one biopolymer having at least two additives to form a feed;
passing the feed through a die orifice to form a bubble;
collapsing the bubble to form a biopolymer film having at least one of a selected elongation at break of 180% or more in one direction and heat sealing at 195° F. or less;
drawing the biopolymer film through a nip roller;
changing travel angle of the biopolymer film with a turning bar;
separating the turning bar from the biopolymer film with a heated air stream from the turning bar; and
directing travel of the biopolymer film with a travel roller.
2. The method of claim 1 wherein the passing the feed through a die orifice further comprises maintaining heated air inside the bubble.
3. The method of claim 1 further comprising centering the bubble before the collapsing.
4. The method of claim 1 wherein collapsing the bubble further comprises frictionally heating the bubble.
5. The method of claim 1 further comprising heating the nip roller.
6. The method of claim 1 wherein the die orifice is less than or equal to 0.070 inches wide.
7. The method of claim 1 further comprising maintaining pressure in the die orifice at greater than or equal to 2000 psi.
8. The method of claim 1 wherein the travel roller includes a concavity of about 0.060 inches.
9. The method of claim 1 wherein the biopolymer comprises at least one of an amorphous polylactic acid polymer (PLA) and a semicrystalline polylactic acid polymer (PLA).
10. The method of claim 9 wherein the amorphous polylactic acid polymer (PLA) is 17% or more of the total weight of the biopolymer film.
11. The method of claim 9 wherein the amorphous polylactic acid polymer (PLA) is 65% or more of the total weight of the biopolymer film.
12. The method of claim 1 wherein at least one of the two additives is selected from the group consisting of an crosslinker, a polycaprolactone resin, an impact modifier such as ethylene acrylate copolymer, a melt strength improver, a slip modifier, an antistat, an anti-block modifier, a surface appearance modifier, and a processing aid.
13. The method of claim 12 wherein at least one of the two additives is 1% or more of the total weight of the biopolymer film.
14. The method of claim 12 wherein the at least one of the two additives is 2% or more of the total weight of the biopolymer film.
15. A method of forming a biopolymer blown film comprising:
layering a plurality of extruded polymers to form a layered feed, at least one of the plurality of extruded polymers being a biopolymer having at least two additives;
passing the layered feed through a die orifice to form a multilayered bubble;
collapsing the multilayered bubble to form a biopolymer film having at least one layer having a selected elongation at break of 180% or more in one direction and heat sealing at 195° F. or less;
drawing the biopolymer film through a nip roller;
changing travel angle of the biopolymer film with a turning bar;
separating the turning bar from the biopolymer film with a heated air stream from the turning bar; and
directing travel of the biopolymer film with a concave travel roller.