EXTRUSION OF HIGH MOISTURE PHA
The present disclosure provides a method for extruding high moisture polyhydroxyalkanoates. The method includes a step of mixing at least one polyhydroxyalkanoate in powder form and having an initial moisture content of at least 0.10 weight percent, with at least one resin additive at a temperature from about 120 to about 190° C. to form an extrusion mixture. This mixture is then extruded through an extrusion die to form a resin extrudate comprising the at least one polyhydroxyalkanoate and the at least one resin additive.
1 . A method for extruding a resin which includes polyhydroxyalkanoates, the method comprising the steps of:
mixing at least one polyhydroxyalkanoate in powder form with at least one resin additive at a temperature from 120 to 190° C. to form an extrusion mixture; and
extruding the mixture through an extrusion die to form a resin extrudate comprising the at least one polyhydroxyalkanoate and the at least one resin additive,
wherein the least one polyhydroxyalkanoate in powder form has an initial moisture content of at least 0.1 weight percent, as determined in accordance with ASTM D7191-05, when mixed with the at least one resin additive.
2 . The method of claim 1 , wherein the least one polyhydroxyalkanoate in powder form has an initial moisture content of at least 1 weight percent, as determined in accordance with ASTM D7191-05 when mixed with the at least one resin additive.
3 . The method of claim 1 , wherein the least one polyhydroxyalkanoate in powder form has an initial moisture content of at least 5 weight percent, as determined in accordance with ASTM D7191-05 when mixed with the at least one resin additive.
4 . The method of claim 1 , wherein the mixing step and the extruding steps are carried out in different devices or in different chambers of the same device.
5 . The method of claim 1 , wherein the mixing step is carried out in a continuous mixer.
6 . The method of claim 1 , wherein the extruding step is carried out in a screw extruder.
7 . The method of claim 1 , wherein the least one polyhydroxyalkanoate has an initial weight average molecular weight before the mixing step and a final weight average molecular weight after the extruding step, which is at least 40 percent of the initial weight average molecular weight, wherein all weight average molecular weights are determined in accordance with ASTM D5296-05.
8 . The method of claim 1 , wherein the at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (“P(3HB-co-3HHx)”).
9 . The method of claim 8 , wherein the P(3HB-co-3HHx) comprises from 75 to 99 mole percent hydroxybutyrate and from 1 to 25 mole percent hydroxyhexanoate.
10 . The method of claim 1 , wherein the at least one poly(hydroxyalkanoate) comprises from 1 to 25 weight percent of at least one polyhydroxyalkanoate comprising from 25 to 50 mole percent of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and/or hydroxydecanoate.
11 . The method of claim 1 , wherein the at least one poly(hydroxyalkanoate) comprises a terpolymer made up from 75 to 99.9 mole percent monomer residues of 3-hydroxybutyrate, from 0.1 to 25 mole percent monomer residues of 3-hydroxyhexanoate, and from 0.1 to 25 mole percent monomer residues of a third 3-hydroxyalkanoate having from 5 to 12 carbon atoms.
12 . The method of claim 1 , wherein the at least one poly(hydroxyalkanoate) has an initial weight average molecular weight from 50,000 Daltons to 2.5 million Daltons, as determined by ASTM D5296-05.
13 . The method of claim 1 , wherein the at least one resin additive comprises at least one rheology modifier selected from the group consisting of vinyl acetate homopolymers or copolymers, peroxides, epoxides, isocyanates, carbodiimides, and mixtures thereof.
14 . The method of claim 1 , wherein the at least one resin additive comprises at least one nucleating agent selected from the group consisting of pentaerythritol, boron nitride, poly(hydroxybutyrate), inositol, clays, dipentaerythritol, sorbitol, and mixtures thereof.
15 . The method of claim 1 , wherein the at least one resin additive comprises at least one filler selected from the group consisting of aragonite, clays, calcium carbonate, cellulose, nano-cellulose, talc, kaolinite, montmorillonite, bentonite, silica, chitin, starches, diatomaceous earth, titanium dioxide, nano clay, mica, and mixtures thereof.
16 . The method of claim 1 , wherein the mixing step further comprises mixing the at least one polyhydroxyalkanoate in powder form with at least one biopolymer selected from the group consisting of biodegradable polymer selected from the group consisting of polybutylene succinate, polycaprolactone, polybutylene succinate-co-butylene adipate, polybutylene adipate-co-terephthalate, polylactic acid, cellulose acetate, and mixtures thereof.