Extrusion of high moisture PHA

Abstract

The present disclosure provides a method for extruding a high-moisture polyhydroxyalkanoate. The method includes mixing at least one powdered polyhydroxyalkanoate having an initial moisture content of at least 0.10 weight percent with at least one resin additive at a temperature of about 120 to about 190° C. to form an extrusion mixture. Thereafter, the mixture is extruded through an extrusion die to form a resin extrudate containing the at least one polyhydroxyalkanoate and the at least one resin additive.

Description

[Technical Field]

[0001] The present disclosure relates to biodegradable polymer compositions. More specifically, the present disclosure relates to the extrusion of biodegradable polymers, such as polyhydroxyalkanoates, extruded under conditions of elevated moisture. [Background technology]

[0002] Many polymeric materials, including biodegradable polymers such as polyhydroxyalkanoates, are conventionally extruded to form final products or intermediate pellets that are subsequently remelted and shaped into the final product.

[0003] Conventionally, it is necessary to thoroughly dry the polymer before heating and extruding it. This process is particularly applicable to polyhydroxyalkanoates. Typically, if the polyhydroxyalkanoate is not dried to a very low moisture level before heating and extruding, significant degradation of the polyhydroxyalkanoate due to hydrolysis (with accompanying loss of molecular weight) is observed.

[0004] However, such drying of polyhydroxyalkanoates is an energy- and time-consuming process. Therefore, it would be desirable to melt extrude polyhydroxyalkanoates at a higher initial moisture content, thus reducing the need for a lengthy drying process prior to melt extrusion. At the same time, the polyhydroxyalkanoates should not exhibit significant hydrolysis or loss of molecular weight of the polymer. Summary of the Invention

[0005] According to the present disclosure, these and other needs are met by a method for extruding a high moisture polyhydroxyalkanoate. In one embodiment, the method of the present disclosure includes mixing at least one powdered polyhydroxyalkanoate with at least one resin additive at a temperature of about 120 to about 190° C. to form an extrusion mixture. The mixture is then extruded through an extrusion die to form a resin extrudate containing the at least one polyhydroxyalkanoate and the at least one resin additive.

[0006] According to the present disclosure, at least one powdered polyhydroxyalkanoate, when mixed with at least one resin additive, has an initial (i.e., pre-mixing) moisture content of at least 0.10 weight percent, as determined in accordance with ASTM D7191-05. In certain embodiments, the polyhydroxyalkanoate powder may have an even higher moisture content. In some cases, at least one powdered polyhydroxyalkanoate, when mixed with at least one resin additive, may have an initial moisture content of at least 1 weight percent, at least 5 weight percent, at least 10 weight percent, at least 15 weight percent, or even higher, as determined in accordance with ASTM D7191-05.

[0007] According to certain embodiments, the mixing and extrusion steps are preferably carried out in different devices or in different chambers of the same device. In some cases, the mixing step is preferably carried out in a low-shear continuous mixer. In some embodiments, it is also preferred that the extrusion step be carried out in a screw extruder.

[0008] In some cases, the at least one polyhydroxyalkanoate preferably has an initial weight average molecular weight before the mixing step and a final weight average molecular weight after the extrusion step, the final weight average molecular weight being at least 40 percent of the initial weight average molecular weight, all weight average molecular weights being determined in accordance with ASTM D5296-05. More preferably, the final weight average molecular weight of the at least one polyhydroxyalkanoate is at least 70 percent of the initial weight average molecular weight, even more preferably at least 80 percent of the initial weight average molecular weight, and even more preferably at least 85 percent of the initial weight average molecular weight.

[0009] A variety of different forms of polyhydroxyalkanoates can be used in the methods of the present disclosure. In certain embodiments, at least one polyhydroxyalkanoate is composed of poly-3-hydroxybutyrate-co-3-hydroxyhexanoate ("P(3HB-co-3HHx)"). In some embodiments, the P(3HB-co-3HHx) is preferably composed of about 75 to about 99 mole percent hydroxybutyrate and about 1 to about 25 mole percent hydroxyhexanoate.

[0010] In other embodiments, the at least one polyhydroxyalkanoate is preferably comprised of from about 1 to about 25 weight percent of at least one polyhydroxyalkanoate, including from about 25 to about 50 mole percent of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate. In some embodiments, the at least one polyhydroxyalkanoate preferably comprises a terpolymer comprised of from about 75 to about 99.9 mole percent monomeric residues of 3-hydroxybutyrate, from about 0.1 to about 25 mole percent monomeric residues of 3-hydroxyhexanoate, and from about 0.1 to about 25 mole percent monomeric residues of a third 3-hydroxyalkanoate having from 5 to 12 carbon atoms.

[0011] In some cases, the at least one poly(hydroxyalkanoate) preferably has an initial weight average molecular weight of from about 50,000 Daltons to about 2.5 million Daltons as determined by ASTM D5296-05.

[0012] According to certain embodiments, the at least one resin additive preferably comprises at least one rheology modifier selected from the group consisting of vinyl acetate homopolymers or copolymers, peroxides, epoxides, isocyanates, carbodiimides, and mixtures thereof.

[0013] In some embodiments, the at least one resin additive preferably comprises at least one nucleating agent from the group consisting of pentaerythritol, boron nitride, poly(hydroxybutyrate), inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.

[0014] In some cases, the at least one resin additive preferably comprises at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolinite, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.

[0015] Furthermore, in certain embodiments, the mixing step may also include mixing at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from the group consisting of biodegradable polymers 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. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present disclosure provides a method for extruding high moisture polyhydroxyalkanoates. Conventionally, to prevent hydrolysis of polyhydroxyalkanoates, the polyhydroxyalkanoates must be dried to a very low moisture content before extrusion.

[0017] However, according to the methods of the present disclosure, the inventors have discovered that polyhydroxyalkanoates having substantially higher moisture contents can be extruded without substantial polymer degradation due to hydrolysis.

[0018] Generally, the disclosed method comprises a first step of mixing at least one polyhydroxyalkanoate in powder form with at least one resin additive to form an extrusion mixture at a temperature of about 120 to about 190° C. The 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.

[0019] As described above, the at least one polyhydroxyalkanoate in powder form has an unusually high initial moisture content before the mixing step. Typically, the at least one polyhydroxyalkanoate has an initial (before mixing) moisture content of at least 0.1 weight percent when mixed with the at least one resin additive, as determined according to ASTM D7191-05. In some cases, the polyhydroxyalkanoate powder may have an even higher moisture content. For example, the at least one polyhydroxyalkanoate in powder form may have an initial moisture content of at least 1 weight percent, at least 5 weight percent, at least 10 weight percent, or even at least 15 weight percent when mixed with the at least one resin additive, as determined according to ASTM D7191-05.

[0020] The methods of the present disclosure can be practiced using a wide variety of forms of polyhydroxyalkanoates, including homopolymers, copolymers, terpolymers, and blends of the foregoing.

[0021] Thus, in some embodiments, the polyhydroxyalkanoate can include a homopolymer such as poly(hydroxybutyrate).

[0022] In other cases, the polyhydroxyalkanoate may comprise a copolymer or terpolymer. For example, in some embodiments, at least one polyhydroxyalkanoate comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate ("P(3HB-co-3HHx)"). In some embodiments, the P(3HB-co-3HHx) is preferably composed of about 75 to about 99 mole percent hydroxybutyrate and about 1 to about 25 mole percent hydroxyhexanoate.

[0023] In another embodiment, the at least one polyhydroxyalkanoate preferably comprises from about 1 to about 25 weight percent of at least one polyhydroxyalkanoate, including from about 25 to about 50 mole percent of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate. In yet another embodiment, the at least one polyhydroxyalkanoate preferably comprises a terpolymer composed of from about 75 to about 99.9 mole percent monomer residues of 3-hydroxybutyrate, from about 0.1 to about 25 mole percent monomer residues of 3-hydroxyhexanoate, and from about 0.1 to about 25 mole percent monomer residues of a third 3-hydroxyalkanoate having from 5 to 12 carbon atoms.

[0024] At least one resin additive is mixed with the polyhydroxyalkanoate to form an extrusion mixture. Examples of resin additives that can be mixed with the polyhydroxyalkanoate include rheology modifiers, nucleating agents, organic fillers, inorganic fillers, polyesters, and impact modifiers.

[0025] For example, in certain embodiments, the at least one resin additive preferably comprises at least one rheology modifier selected from the group consisting of vinyl acetate homopolymers or copolymers, peroxides, epoxides, isocyanates, carbodiimides, and mixtures thereof.

[0026] In some embodiments, the at least one resin additive preferably comprises at least one nucleating agent from the group consisting of pentaerythritol, boron nitride, poly(hydroxybutyrate), inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.

[0027] In some cases, the at least one resin additive preferably comprises at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolinite, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.

[0028] Furthermore, in certain embodiments, the mixing step can also include mixing at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from the group consisting of biodegradable polymers 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. In such embodiments, the additional biopolymer can be added to the mixture in a weight ratio of about 1 to about 75 parts by weight of biopolymer per 100 parts by weight of the at least one polyhydroxyalkanoate.

[0029] According to the present disclosure, the mixing and extruding steps are performed separately. In some cases, the mixing and extruding steps are performed in separate devices. In other cases, the mixing and extruding steps are performed in separate chambers of a single device.

[0030] For example, according to certain embodiments of the present disclosure, the mixing step is preferably carried out in a continuous mixer, which typically operates under relatively low shear mixing conditions. One example of a suitable mixing system is the Farrel continuous mixer available from Farrel Pomini.

[0031] Typically, continuous mixers, such as the aforementioned Farrel mixer, have a mixing chamber with two non-intermeshing, counter-rotating rotors (i.e., screws) for mixing materials. As noted, the lobes of the two rotors do not intermesh, and the rotors are sized to provide a relatively large free volume within the mixing chamber. This large free volume within the mixing chamber is due to the non-intermeshing rotor lobes as well as the relatively large gap between the screw lobes and the wall of the extrusion chamber. In conventional screw extruders, this gap is extremely small, and the material is subjected to extreme shear as it passes through this narrow gap. The larger the gap in a continuous mixer, the less shear the material is subjected to as it passes through the gap. This reduction in shear is believed to reduce the amount of degradation in the material.

[0032] Additionally, the continuous mixer also allows for internal water cooling to be applied to the extruder screw. Preferably, the extruder screw is cooled to maintain the material in the mixer at a temperature of about 120°C to about 190°C.

[0033] After initial mixing under the aforementioned conditions, the extrusion mixer can be transferred to a conventional screw extruder for the final extrusion step.

[0034] As discussed above, it has been surprisingly observed that polyhydroxyalkanoates mixed and extruded in accordance with the present disclosure do not exhibit a high degree of polymer degradation due to hydrolysis, despite the elevated moisture content of the primary polyhydroxyalkanoate.

[0035] For example, in some cases, the at least one poly(hydroxyalkanoate) preferably has an initial (i.e., before mixing with the resin additive) weight average molecular weight, as determined by ASTM D5296-05, of about 50,000 daltons to about 2.5 million daltons. More preferably, the at least one poly(hydroxyalkanoate) preferably has an initial weight average molecular weight, as determined by ASTM D5296-05, of about 300,000 daltons to about 2.5 million daltons.

[0036] Advantageously, according to the present disclosure, the at least one polyhydroxyalkanoate preferably has an initial weight average molecular weight before the mixing step and a final weight average molecular weight after the extrusion step, the final weight average molecular weight being at least 40 percent of the initial weight average molecular weight, all weight average molecular weights being determined in accordance with ASTM D5296-05. More preferably, the final weight average molecular weight of the at least one polyhydroxyalkanoate is at least 70 percent of the initial weight average molecular weight, even more preferably at least 80 percent of the initial weight average molecular weight, and even more preferably at least 85 percent of the initial weight average molecular weight. [Example]

[0037] The following non-limiting examples illustrate various additional aspects of the present invention. Unless otherwise specified, temperatures are in degrees Celsius and percentages are by weight based on the dry weight of the formulation.

[0038] Examples 1 to 24 For these examples, a series of polyhydroxyalkanoate (PHA) samples were prepared in accordance with the present disclosure, each having a different initial moisture content ranging from 0.15 weight percent to about 15 weight percent. For each sample, the PHA was a poly-3-hydroxybutyrate-co-3-hydroxyhexanoate copolymer containing about 6 mole percent 3-hydroxyhexanoate monomer repeat units. The initial weight average molecular weight of the PHA copolymer was about 1,032,000, as determined by ASTM D5296.

[0039] The PHA was initially provided as a substantially dry powder. For each sample, the powder was mixed with a known amount of water in a bucket and stirred using a paint stirrer to obtain a PHA sample with a known initial moisture content.

[0040] Each PHA sample was then mixed using a Farrel C-PEX lab-scale continuous mixer. The PHA material was fed through the continuous mixer at a rate of approximately 12 kilograms per hour. For simplicity in these examples, the PHA was mixed alone in the continuous mixer without any additives. The temperature profile within the continuous mixer was set at 140°C. The mixing screw within the continuous mixer was also internally cooled using cold water.

[0041] After feeding through the continuous mixer, the material was dropped into a conveying screw, which steadily fed the material into the extrusion die for extrusion and pelletization. The conveying screw was a single screw extruder set at a temperature range of 120-140°C.

[0042] After extrusion and pelletization, the pellets of each PHA sample were tested to determine the final weight average molecular weight of the PHA and the final melt flow index of the PHA. The molecular weight was determined by gel permeation chromatography according to ASTM D5296. The melt flow index was determined according to ASTM D1238 at 175°C with a 10 kg load. The results are reported in Table 1 below. [Table 1-1] [Table 1-2] [Table 1-3]

[0043] From this, it can be seen that when PHAs were first processed in a continuous mixer according to the present disclosure and then extruded, the PHAs in nearly all cases retained at least 80% of their initial weight average molecular weight. In many cases, the PHAs retained at least 85% of their initial weight average molecular weight. Furthermore, the final melt flow index of the PHAs was less than 6.0 in nearly all cases, and less than 5.0 g / 10 min in many cases. Because melt flow index generally increases with decreasing molecular weight, these melt flow index values ​​also indicate that degradation of the PHAs and loss of weight average molecular weight were relatively small.

[0044] These results are quite surprising considering the high initial amount of moisture in the PHA samples prior to processing in the continuous mixer and subsequent extrusion.

[0045] As noted above, no additives were mixed with the PHA in the preceding examples. However, one skilled in the art would understand that the presence or absence of additives such as rheology modifiers, nucleating agents, organic fillers, inorganic fillers, polyesters, and impact modifiers will not affect the molecular weight of the PHA. Therefore, the molecular weight values ​​for the PHA after mixing and extrusion would be expected to be similar whether or not additional resin additives were used.

[0046] Comparative Examples 35 to 38 For comparative purposes, an additional series of PHA samples was also prepared. As with the previous samples, the PHA was a poly-3-hydroxybutyrate-co-3-hydroxyhexanoate copolymer containing approximately 6 mole percent 3-hydroxyhexanoate monomer repeat units. The initial weight average molecular weight of the PHA copolymers varied from approximately 600,000 to approximately 1,100,000 g / mol, as shown in the table below.

[0047] As with previous samples, the PHA was initially provided as a substantially dry powder. For each sample, the powder was mixed with a known amount of water in a bucket and stirred using a paint stirrer to obtain a PHA sample with a known initial moisture content.

[0048] Unlike previous samples, these control samples were prepared using an Entek 27mm twin-screw lab-scale extruder for comparative purposes. In the extruder, the PHA was heated to a temperature of approximately 120-140°C and then extruded through a two-hole die into a water bath set at 150-160°F (65-71°C). The extruded PHA was then chopped into pellets.

[0049] As in the previous examples, after extrusion and pelletization, the pellets of each PHA sample were tested to determine the final weight average molecular weight of the PHA and the final melt flow index of the PHA. The molecular weight was determined by gel permeation chromatography according to ASTM D5296. The melt flow index was determined according to ASTM D1238 at 175°C with a 10 kg load. The results are reported in Table 2 below. [Table 2]

[0050] These results are in stark contrast to the results described above using a continuous mixer. Four of the five comparative examples exhibited molecular weight losses of more than 35% when starting with a PHA having an initial moisture content of only 0.10-0.15 wt. %. Again, for these examples, in accordance with the present disclosure, substantially lower weight average molecular weight losses were observed even when the initial moisture content of the PHA was more than an order of magnitude higher than in the comparative examples.

[0051] Additionally, the melt flow index observed for the comparative example was also substantially higher than that of the previous example using a continuous mixer.

[0052] The present disclosure is further illustrated by the following embodiments.

[0053] Embodiment 1. 1. A method for extruding a resin comprising a polyhydroxyalkanoate, said method comprising: mixing at least one powdered polyhydroxyalkanoate with at least one resin additive at a temperature of about 120 to about 190°C to form an extrusion mixture; 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; Including, The method wherein the at least one powdered polyhydroxyalkanoate, upon mixing with the at least one resin additive, has an initial moisture content of at least 0.10 weight percent as determined in accordance with ASTM D7191-05.

[0054] Embodiment 2. 2. The method of claim 1, wherein the at least one powdered polyhydroxyalkanoate, upon mixing with the at least one resin additive, has an initial moisture content of at least 1 percent by weight as determined according to ASTM D7191-05.

[0055] Embodiment 3. 3. The method of claim 1 or 2, wherein the at least one powdered polyhydroxyalkanoate, upon mixing with the at least one resin additive, has an initial moisture content of at least 5 weight percent, more preferably at least 10 weight percent, and even more preferably at least 15 weight percent, as determined according to ASTM D7191-05.

[0056] Embodiment 4. 10. The method of any preceding embodiment, wherein the mixing and extruding steps are performed in different devices or in different chambers of the same device.

[0057] Embodiment 5. 10. The method of any preceding embodiment, wherein the mixing step is carried out in a continuous mixer.

[0058] Embodiment 6. 10. The method of any preceding embodiment, wherein the extruding step is carried out in a screw extruder.

[0059] Embodiment 7. The method of any preceding embodiment, wherein the at least one polyhydroxyalkanoate has an initial weight average molecular weight before the mixing step and a final weight average molecular weight after the extrusion step, wherein the final weight average molecular weight is at least 40 percent, at least 70 percent, at least 80 percent, or at least 85 percent of the initial weight average molecular weight, all weight average molecular weights determined according to ASTM D5296-05.

[0060] Embodiment 8. The method of any preceding embodiment, wherein the at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (“P(3HB-co-3HHx)”).

[0061] Embodiment 9. 9. The method of embodiment 8, wherein the P(3HB-co-3HHx) comprises from about 75 to about 99 mole percent hydroxybutyrate and from about 1 to about 25 mole percent hydroxyhexanoate.

[0062] Embodiment 10. The method of any preceding embodiment, wherein the at least one poly(hydroxyalkanoate) comprises from about 1 to about 25 weight percent of at least one polyhydroxyalkanoate comprising from about 25 to about 50 mole percent hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate.

[0063] Embodiment 11. The method of any preceding embodiment, wherein the at least one poly(hydroxyalkanoate) comprises a terpolymer composed of from about 75 to about 99.9 mole percent monomer residues of 3-hydroxybutyrate, from about 0.1 to about 25 mole percent monomer residues of 3-hydroxyhexanoate, and from about 0.1 to about 25 mole percent monomer residues of a third 3-hydroxyalkanoate having from 5 to 12 carbon atoms.

[0064] Embodiment 12. 10. The method of any preceding embodiment, wherein the at least one poly(hydroxyalkanoate) has an initial weight average molecular weight of from about 50,000 Daltons to about 2.5 million Daltons, as determined by ASTM D5296-05.

[0065] Embodiment 13. 10. The method of any of the preceding embodiments, 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.

[0066] Embodiment 14. 10. The method of any preceding embodiment, wherein the at least one resin additive comprises at least one nucleating agent from the group consisting of pentaerythritol, boron nitride, poly(hydroxybutyrate), inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.

[0067] Embodiment 15. 10. The method of any preceding embodiment, wherein the at least one resin additive comprises at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolinite, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.

[0068] Embodiment 16. 10. The method of any preceding embodiment, wherein the mixing step further comprises mixing the at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from the group consisting of biodegradable polymers 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.

[0069] The foregoing description of preferred embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications and variations are possible in light of the above teachings. The embodiments have been chosen and described in an effort to provide the best illustration of the principles of the invention and its practical application, thereby enabling others skilled in the art to utilize the invention in various embodiments, with various modifications made to suit the particular uses contemplated. All such modifications and variations are within the scope of the invention, as determined by the appended claims, when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

1. 1. A method for extruding a resin comprising a polyhydroxyalkanoate, said method comprising: mixing at least one powdered polyhydroxyalkanoate with at least one resin additive at a temperature of 120-190°C to form an extrusion mixture; 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; Including, The process wherein the at least one powdered polyhydroxyalkanoate, when mixed with the at least one resin additive, has an initial moisture content of at least 0.1 weight percent as determined according to ASTM D7191-05.

2. 10. The method of claim 1, wherein the at least one powdered polyhydroxyalkanoate, upon mixing with the at least one resin additive, has an initial moisture content of at least 1 weight percent as determined according to ASTM D7191-05.

3. 10. The method of claim 1, wherein the at least one powdered polyhydroxyalkanoate, upon mixing with the at least one resin additive, has an initial moisture content of at least 5 percent by weight as determined according to ASTM D7191-05.

4. 10. The method of claim 1, wherein the mixing and extruding steps are performed in different devices or in different chambers of the same device.

5. 10. The method of claim 1, wherein the mixing step is carried out in a continuous mixer.

6. 10. The method of claim 1, wherein the extruding step is carried out in a screw extruder.

7. 10. The method of claim 1, wherein the at least one polyhydroxyalkanoate has an initial weight average molecular weight before the mixing step and a final weight average molecular weight after the extrusion step, the final weight average molecular weight being at least 40 percent of the initial weight average molecular weight, all weight average molecular weights determined in accordance with ASTM D5296-05.

8. 2. The method of claim 1, wherein the at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate ("P(3HB-co-3HHx)").

9. 9. The method of claim 8, wherein the P(3HB-co-3HHx) comprises 75 to 99 mole percent hydroxybutyrate and 1 to 25 mole percent hydroxyhexanoate.

10. 10. The method of claim 1, wherein the at least one poly(hydroxyalkanoate) comprises 1 to 25 weight percent of at least one polyhydroxyalkanoate comprising 25 to 50 mole percent hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate.

11. 10. The method of claim 1, wherein the at least one poly(hydroxyalkanoate) comprises a terpolymer composed of 75 to 99.9 mole percent monomer residues of 3-hydroxybutyrate, 0.1 to 25 mole percent monomer residues of 3-hydroxyhexanoate, and 0.1 to 25 mole percent monomer residues of a third 3-hydroxyalkanoate having 5 to 12 carbon atoms.

12. 10. The method of claim 1, wherein the at least one poly(hydroxyalkanoate) has an initial weight average molecular weight of from 50,000 Daltons to 2.5 million Daltons as determined by ASTM D5296-05.

13. 10. 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. 10. 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, clay, dipentaerythritol, sorbitol, and mixtures thereof.

15. 10. The method of claim 1, wherein the at least one resin additive comprises at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolinite, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.

16. 10. The method of claim 1, wherein the mixing step further comprises mixing the at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from the group consisting of biodegradable polymers 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.

Images