Extrusion of high moisture phas
By mixing polyhydroxyalkanoates with resin additives under high humidity and utilizing a combination of a low-shear continuous mixer and a screw extruder, the hydrolytic degradation problem of polyhydroxyalkanoates during extrusion under high moisture conditions was solved, achieving efficient polymer processing and molecular weight maintenance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 丹尼米尔知识产权有限责任公司
- Filing Date
- 2023-10-02
- Publication Date
- 2026-07-03
AI Technical Summary
Under high humidity conditions, polyhydroxyalkanoates need to be thoroughly dried before heating and extrusion to avoid hydrolytic degradation. However, this drying process is energy- and time-intensive, and existing technologies make it difficult to extrude under high moisture content without causing significant polymer degradation.
Powdered polyhydroxy fatty acid esters are mixed with resin additives at temperatures ranging from approximately 120°C to 190°C to form an extrusion mixture, which is then extruded through an extrusion die. The mixture is processed using a combination of a low-shear continuous mixer and a screw extruder to reduce shear forces and thus minimize degradation.
The extrusion of polyhydroxy fatty acid esters under high moisture conditions effectively maintains a high molecular weight, significantly reduces the risk of hydrolytic degradation, and improves processing efficiency.
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Figure BDA0005323639780000071
Abstract
Description
Technical Field
[0001] This disclosure relates to biodegradable polymer compositions. More specifically, this disclosure relates to biodegradable polymers, such as polyhydroxyalkanoates, extruded under high humidity conditions. Background Technology
[0002] Many polymer materials, including biodegradable polymers (such as polyhydroxyalkanoates), are typically extruded to form the final product or intermediate pellets (which are then remelted to form the final product).
[0003] Typically, it is necessary to thoroughly dry the polymer before heating and extruding it. This process is especially true for polyhydroxyalkanoates (PHA). Generally, if PHAs are not dried to a very low moisture content before heating and extrusion, significant degradation due to hydrolysis (accompanied by a decrease in molecular weight) will be observed.
[0004] However, this drying process for polyhydroxyalkanoates is energy- and time-intensive. Therefore, it is desirable to melt extrude polyhydroxyalkanoates with a high initial moisture content, thereby reducing the need for a long drying process before melt extrusion. Simultaneously, the polyhydroxyalkanoates should not exhibit significant hydrolytic degradation or molecular weight loss. Summary of the Invention
[0005] According to this disclosure, the method of extruding high-moisture polyhydroxyalkanoates satisfies the above and other requirements. In one embodiment, the method of this disclosure includes the following steps: mixing at least one powdered polyhydroxyalkanoate with at least one resin additive at a temperature of about 120°C to about 190°C to form an extrusion mixture. The mixture is then extruded through an extrusion die to form a resin extruder comprising at least one polyhydroxyalkanoate and at least one resin additive.
[0006] According to this disclosure, when mixed with at least one resin additive, at least one powdered polyhydroxyalkanoate has an initial (i.e., before mixing) moisture content of at least 0.10% by weight, as determined by ASTM D7191-05. In some embodiments, the polyhydroxyalkanoate powder has an even higher moisture content. In some cases, when mixed with at least one resin additive, at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 1% by weight, at least 5% by weight, at least 10% by weight, at least 15% by weight, or even higher, as determined by ASTM D7191-05.
[0007] According to some embodiments, the mixing and extrusion steps are preferably carried out in different devices or 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, the extrusion step is preferably carried out in a screw extruder.
[0008] In some cases, preferably, 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% of the initial weight-average molecular weight, and wherein all weight-average molecular weights are determined according to ASTM D5296-05. More preferably, the final weight-average molecular weight of at least one polyhydroxyalkanoate is at least 70% of the initial weight-average molecular weight, more preferably at least 80% of the initial weight-average molecular weight, and even more preferably at least 85% of the initial weight-average molecular weight.
[0009] Various forms of polyhydroxy fatty acid esters can be used in the methods of this disclosure. In some embodiments, at least one polyhydroxy fatty acid ester is made of poly(3-hydroxybutyrate-3-hydroxyhexanoate) (“P(3HB-co-3HHx)”). In some embodiments, P(3HB-co-3HHx) is preferably made of about 75 to about 99 mol% of hydroxybutyrate and about 1 to about 25 mol% of hydroxyhexanoate.
[0010] In other embodiments, preferably, at least one polyhydroxyalkanoate is made from about 1 to about 25 wt% of at least one polyhydroxyalkanoate, said polyhydroxyalkanoate comprising about 25 to about 50 mol% of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate. In some embodiments, preferably, at least one polyhydroxyalkanoate comprises a ternary polymer made from about 75 to about 99.9 mol% of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mol% of 3-hydroxyhexanoate monomer residues, and about 0.1 to about 25 mol% of a third 3-hydroxyalkanoate monomer residue having 5 to 12 carbon atoms.
[0011] In some cases, preferably, at least one polyhydroxyalkanoate has an initial weight-average molecular weight of about 50,000 Daltons to about 2.5 million Daltons, as determined by ASTM D5296-05.
[0012] According to certain embodiments, preferably, at least one resin additive includes 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, preferably, at least one resin additive includes at least one nucleating agent selected from the group consisting of pentaerythritol, boron nitride, polyhydroxybutyrate, inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.
[0014] In some cases, preferably, at least one resin additive includes at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolin, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.
[0015] In addition, in some embodiments, the mixing step may further include mixing at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from biodegradable polymers, wherein the biodegradable polymer is 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 Implementation
[0016] This disclosure provides a method for extruding high-moisture polyhydroxyalkanoates. Typically, polyhydroxyalkanoates must be dried to a very low moisture content before extrusion to prevent hydrolytic degradation.
[0017] However, according to the method of this disclosure, the inventors have discovered that polyhydroxyalkanoates with significantly higher moisture content can be extruded without significant polymer degradation due to hydrolysis.
[0018] Generally, the method disclosed herein includes a first step of mixing at least one powdered polyhydroxyalkanoate with at least one resin additive at a temperature of about 120°C to about 190°C to form an extrusion mixture. The mixture is then extruded through an extrusion die to form a resin extruder comprising at least one polyhydroxyalkanoate and at least one resin additive.
[0019] As described above, prior to the mixing step, at least one powdered polyhydroxyalkanoate has an unusually high initial moisture content. Generally, when mixed with at least one resin additive, at least one polyhydroxyalkanoate has an initial (before mixing) moisture content of at least 0.1% by weight, as determined by ASTM D7191-05. In some cases, the polyhydroxyalkanoate powder has even higher moisture content. For example, when mixed with at least one resin additive, at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 1% by weight, at least 5% by weight, at least 10% by weight, or even at least 15% by weight, as determined by ASTM D7191-05.
[0020] The methods disclosed herein can be implemented using various forms of polyhydroxyalkanoates, including homopolymers, copolymers, terpolymers, and mixtures thereof.
[0021] Therefore, in some embodiments, polyhydroxy fatty acid esters include homopolymers, such as polyhydroxybutyrate.
[0022] In other cases, polyhydroxyalkanoates include copolymers or terpolymers. For example, in some embodiments, at least one polyhydroxyalkanoate includes poly(3-hydroxybutyrate-3-hydroxyhexanoate) (“P(3HB-co-3HHx)”). In some embodiments, the P(3HB-co-3HHx) is preferably made of about 75 to about 99 mol% of hydroxybutyrate and about 1 to about 25 mol% of hydroxyhexanoate.
[0023] In other embodiments, preferably, at least one polyhydroxyalkanoate comprises about 1 to about 25 wt% of at least one polyhydroxyalkanoate, said polyhydroxyalkanoate comprising about 25 to about 50 mol% of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate, and / or hydroxydecanoate. In other embodiments, preferably, at least one polyhydroxyalkanoate comprises a ternary polymer made of about 75 to about 99.9 mol% of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mol% of 3-hydroxyhexanoate monomer residues, and about 0.1 to about 25 mol% of a third 3-hydroxyalkanoate monomer residue having 5 to 12 carbon atoms.
[0024] At least one resin additive is mixed with a polyhydroxyalkanoate to form an extrusion mixture. Examples of resin additives that can be mixed with a polyhydroxyalkanoate include rheology modifiers, nucleating agents, organic fillers, inorganic fillers, polyesters, and impact modifiers.
[0025] For example, in some embodiments, preferably, 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.
[0026] In some embodiments, preferably, at least one resin additive comprises at least one nucleating agent selected from the group consisting of pentaerythritol, boron nitride, polyhydroxybutyrate, inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.
[0027] In some cases, preferably, at least one resin additive comprises at least one filler selected from the group consisting of aragonite, clay, calcium carbonate, cellulose, nanocellulose, talc, kaolin, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.
[0028] Furthermore, in some embodiments, the mixing step further includes mixing at least one powdered polyhydroxyalkanoate with at least one biopolymer selected from biodegradable polymers, said biodegradable polymer being selected from the group consisting of polybutylene succinate, polycaprolactone, polybutylene succinate-butylene adipate, polybutylene adipate-terephthalate, polylactic acid, cellulose acetate, and mixtures thereof. In these embodiments, additional biopolymer may be added to the mixture at a weight ratio of about 1 to about 75 parts by weight of biopolymer per 100 parts by weight of at least one polyhydroxyalkanoate.
[0029] According to this disclosure, the mixing step and the extrusion step are performed separately. In some cases, the mixing step and the extrusion step are performed in different devices. In other cases, the mixing step and the extrusion step are performed in different chambers of a single device.
[0030] For example, according to certain embodiments of this disclosure, the mixing step is preferably carried out in a continuous mixer, typically operating under relatively low shear mixing conditions. An example of a suitable mixing system is the Farrel continuous mixer, available from Farrel Pomini.
[0031] Generally, continuous mixers (such as the Farrel mixer mentioned above) have a mixing chamber with two counter-rotating, non-meshing rotors (i.e., screws) for mixing materials. As described above, the threads of the two rotors do not mesh, 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 lack of meshing between the rotor threads and also to the relatively large gap between the screw threads and the wall of the extrusion chamber. In conventional screw extruders, this gap is quite small, and when the material passes through this tight gap, a very large shear force is applied to the material. Because of the larger gap in the continuous mixer, the shear force applied to the material is reduced when it passes through this gap. This lower shear force is believed to reduce the amount of material degradation.
[0032] Furthermore, the continuous mixer allows for internal water cooling of 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 above conditions, the extrusion mixer can then be transferred to a conventional screw extruder for the final extrusion step.
[0034] As described above, it was unexpectedly observed that, despite the increased moisture content of the starting polyhydroxyalkanoate, the polyhydroxyalkanoate mixed and extruded according to this disclosure did not exhibit significant polymer degradation due to hydrolysis.
[0035] For example, in some cases, preferably, at least one polyhydroxyalkanoate has an initial (i.e., before being mixed with resin additives) weight-average molecular weight of about 50,000 Daltons to about 2.5 million Daltons, as determined by ASTM D5296-05. More preferably, at least one polyhydroxyalkanoate preferably has an initial weight-average molecular weight of about 300,000 Daltons to about 2.5 million Daltons, as determined by ASTM D5296-05.
[0036] Advantageously, according to this disclosure, preferably, 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% of the initial weight-average molecular weight, wherein all weight-average molecular weights are determined according to ASTM D5296-05. More preferably, the final weight-average molecular weight of at least one polyhydroxyalkanoate is at least 70% of the initial weight-average molecular weight, more preferably at least 80% of the initial weight-average molecular weight, and even more preferably at least 85% of the initial weight-average molecular weight.
[0037] Example
[0038] The following non-limiting examples illustrate various additional aspects of the invention. Unless otherwise stated, temperatures are in degrees Celsius, and percentages are weight percentages based on the dry weight of the formulation.
[0039] Examples 1-24
[0040] For these embodiments, according to this disclosure, a series of polyhydroxyalkanoate (PHA) samples were prepared, each having a different initial moisture content of 0.15 wt% to about 15 wt%. For each sample, the PHA is a poly(3-hydroxybutyrate-3-hydroxyhexanoate) copolymer containing about 6 mol% of repeating 3-hydroxyhexanoate monomer units. The initial weight-average molecular weight of the PHA copolymer was about 1,032,000, as determined by ASTM D5296.
[0041] PHA is initially supplied in a substantially dry powder form. For each sample, the powder is mixed with a known amount of water in a container and stirred with a paint mixer to provide a PHA sample with a known initial moisture content.
[0042] Each sample of PHA was then mixed using a Farrel C-PEX laboratory-scale continuous mixer. The PHA material was fed through the continuous mixer at a rate of approximately 12 kg / h. For convenience, in these embodiments, the PHA was mixed individually in the continuous mixer without any additives. The temperature profile within the continuous mixer was set to 140°C. Furthermore, the mixing screw within the continuous mixer was internally cooled using cooling water.
[0043] After being fed through a continuous mixer, the material falls into a delivery screw, which steadily pumps the material to the extrusion die to allow for extrusion and granulation. The delivery screw is a single-screw extruder set within a temperature range of 120-140°C.
[0044] After extrusion and granulation, the pellets of each PHA sample were tested to determine the final weight-average molecular weight (Mw) and final melt flow index (MFR) of the PHA. Molecular weight was determined by gel permeation chromatography according to ASTM D5296. Melt flow index was determined at 175°C and a 10 kg load according to ASTM D1238. The results are reported in Table 1 below:
[0045] Table 1
[0046] Example Initial moisture content (wt%) Final MFR (g / 10min) Final Mw (g / mol) Mw decreased by % 1 0.15 4.7 848,946 17.74 2 0.19 4.6 802,536 22.23 3 0.23 4.51 879,750 14.75 4 0.23 6.11 811,246 21.39 5 0.4 4.56 827,916 19.78 6 0.41 5.3 862,950 16.38 7 0.65 4.77 890,776 13.68 8 0.68 5.1 837,293 18.87 9 0.89 5.61 848,470 17.78 10 0.93 5.08 839,212 18.68 11 0.97 5.05 865,231 16.16 12 1.24 4.87 906,173 12.19 13 1.6 4.38 961,481 6.83 14 2.47 4.6 877,781 14.94 15 2.53 4.88 793,130 23.15 16 3.1 4.4 875,546 15.16 17 3.27 4.9 864,512 16.23 18 3.72 5.4 824,430 20.11 19 5.76 4.33 847,274 17.90 20 6.23 4.46 863,577 16.32 21 6.64 4.63 797,797 22.69 22 8.37 4.6 815,008 21.03 23 8.56 4.65 824,207 20.13 24 9.11 4.8 832,601 19.32 25 9.11 5.9 863,808 16.30 26 9.38 4.76 902,910 12.51 27 10.02 4.52 865,384 16.14 28 10.27 4.72 901,443 12.65 29 10.29 7.1 917,349 11.11 30 12.12 6.37 887,559 14.00 31 14.08 5.33 897,974 12.99 32 14.5 5.6 892,237 13.54 33 14.85 5.71 884,850 14.26 34 15.04 5.11 904,070 12.40
[0047] Therefore, when PHA is first processed in a continuous mixer according to this disclosure and then extruded, in almost all cases, PHA retains at least 80% of its initial weight-average molecular weight. In many cases, PHA retains at least 85% of its initial weight-average molecular weight. Furthermore, the final melt flow index of PHA is less than 6.0 in almost all cases, and less than 5.0 g / 10 min in many cases. Since the melt flow index generally increases with decreasing molecular weight, these melt flow index values also indicate relatively small degradation and reduction in weight-average molecular weight of PHA.
[0048] These results are quite surprising, considering the high initial moisture content in the PHA samples before processing in a continuous mixer and subsequent extrusion.
[0049] As described above, in the foregoing embodiments, no additives were mixed with PHA. However, those skilled in the art will understand that the presence or absence of additives (e.g., rheology modifiers, nucleating agents, organic fillers, inorganic fillers, polyesters, and impact modifiers) does not affect the molecular weight of PHA. Therefore, after mixing and extrusion, the molecular weight value of PHA is similar with or without further resin additives.
[0050] Comparative examples 35-38
[0051] For comparison, another series of PHA samples were prepared. Like the previous samples, PHA is a poly(3-hydroxybutyrate-3-hydroxyhexanoate) copolymer containing approximately 6 mol% of repeating 3-hydroxyhexanoate monomer units. The initial weight-average molecular weight of the PHA copolymers was approximately 600,000 to approximately 1,100,000 g / mol, as shown in the table below.
[0052] As with previous samples, PHA was initially provided in a substantially dry powder form. For each sample, the powder was mixed with a known amount of water in a container and stirred with a paint mixer to provide a PHA sample with a known initial moisture content.
[0053] Unlike the aforementioned samples, these control samples were prepared using an Entek 27mm twin-screw laboratory-scale extruder for comparative purposes. In the extruder, PHA was heated to approximately 120–140°C and then extruded through a dual-die into a water bath set at 150–160°C (65°C–71°C). The extruded PHA was then cut into pellets.
[0054] As in the previous embodiments, after extrusion and granulation, the pellets of each PHA sample were tested to determine the final weight-average molecular weight and final melt flow index of the PHA. Molecular weight was determined by gel permeation chromatography according to ASTM D5296. Melt flow index was determined at 175°C and a 10 kg load according to ASTM D1238. The results are reported in Table 2 below.
[0055] Table 2
[0056]
[0057] These results contrast sharply with those obtained using a continuous mixer. In four of the five comparative examples, a molecular weight loss of over 35% was observed when starting with PHA containing only 0.10-0.15% by weight of initial moisture content. Again, for the foregoing embodiments, according to this disclosure, a significantly lower loss of weight-average molecular weight was observed even when the initial moisture content of the PHA was more than an order of magnitude higher than that of the comparative examples.
[0058] Furthermore, the melt flow index of the comparative example was observed to be significantly higher than that of the aforementioned embodiment using a continuous mixer.
[0059] The following implementation plan further illustrates this disclosure:
[0060] Implementation Scheme 1. A method for extruding a resin, the resin comprising a polyhydroxyalkanoate, the method comprising the following steps:
[0061] At a temperature of about 120°C to about 190°C, at least one powdered polyhydroxyalkanoate is mixed with at least one resin additive to form an extrusion mixture; and
[0062] The mixture is extruded through an extrusion die to form a resin extruder containing at least one polyhydroxy fatty acid ester and at least one resin additive.
[0063] When mixed with at least one resin additive, the at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 0.10% by weight, as determined by ASTM D7191-05.
[0064] Implementation Scheme 2. The method according to Implementation Scheme 1, wherein when mixed with the at least one resin additive, the at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 1% by weight, as determined by ASTM D7191-05.
[0065] Implementation Scheme 3. The method according to Implementation Scheme 1 or 2, wherein when mixed with the at least one resin additive, the at least one powdered polyhydroxyalkanoate has an initial moisture content of at least % by weight, more preferably at least 10% by weight, and even more preferably at least 15% by weight, as determined by ASTM D7191-05.
[0066] Implementation Scheme 4. The method according to any one of the foregoing implementation schemes, wherein the mixing step and the extrusion step are carried out in different devices or different chambers of the same device.
[0067] Implementation Scheme 5. The method according to any one of the foregoing embodiments, wherein the mixing step is carried out in a continuous mixer.
[0068] Implementation Scheme 6. The method according to any one of the foregoing implementation schemes, wherein the extrusion step is carried out in a screw extruder.
[0069] Implementation Scheme 7. The method according to any one of the preceding embodiments, 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%, at least 70%, at least 80%, or at least 85% of the initial weight-average molecular weight, wherein all weight-average molecular weights are determined according to ASTM D5296-05.
[0070] Implementation Scheme 8. The method according to any one of the preceding embodiments, wherein the at least one polyhydroxy fatty acid ester comprises poly(3-hydroxybutyrate-3-hydroxyhexanoate) (“P(3HB-co-3HHx)”).
[0071] Implementation Scheme 9. The method according to Implementation Scheme 8, wherein P(3HB-co-3HHx) comprises about 75 to about 99 mol% of hydroxybutyrate and about 1 to about 25 mol% of hydroxyhexanoate.
[0072] Implementation Scheme 10. The method according to any one of the preceding embodiments, wherein the at least one polyhydroxy fatty acid ester comprises about 1 to about 25% by weight of at least one polyhydroxy fatty acid ester, wherein the polyhydroxy fatty acid ester comprises about 25 to about 50 mol% of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate and / or hydroxydecanoate.
[0073] Implementation Scheme 11. The method according to any one of the preceding embodiments, wherein the at least one polyhydroxy fatty acid ester comprises a ternary polymer made of about 75 to about 99.9 mol% of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mol% of 3-hydroxyhexanoate monomer residues and about 0.1 to about 25 mol% of a third 3-hydroxyalkanoate monomer residue having 5 to 12 carbon atoms.
[0074] Implementation Scheme 12. The method according to any one of the preceding embodiments, wherein the initial weight-average molecular weight of the at least one polyhydroxyalkanoate is about 50,000 Daltons to about 2.5 million Daltons, as determined by ASTM D5296-05.
[0075] Implementation Scheme 13. The method according to any one 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 homopolymer or copolymer, peroxide, epoxide, isocyanate, carbodiimide and mixtures thereof.
[0076] Implementation Scheme 14. The method according to any one of the preceding embodiments, wherein the at least one resin additive comprises at least one nucleating agent selected from the group consisting of pentaerythritol, boron nitride, polyhydroxybutyrate, inositol, clay, dipentaerythritol, sorbitol, and mixtures thereof.
[0077] Implementation Scheme 15. The method according to any one of the preceding implementation schemes, 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, kaolin, montmorillonite, bentonite, silica, chitin, starch, diatomaceous earth, titanium dioxide, nanoclay, mica, and mixtures thereof.
[0078] Implementation Scheme 16. The method according to any one of the preceding embodiments, wherein the mixing step further comprises mixing the at least one powdered polyhydroxy fatty acid ester with at least one biopolymer selected from biodegradable polymers, said biodegradable polymer being selected from the group consisting of polybutylene succinate, polycaprolactone, polybutylene succinate-butylene adipate, polybutylene adipate-terephthalate, polylactic acid, cellulose acetate and mixtures thereof.
[0079] The foregoing description of preferred embodiments of the invention is intended to be illustrative and descriptive. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in accordance with the foregoing teachings. The embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application, thereby enabling those skilled in the art to utilize the invention in various embodiments and make various modifications to suit the particular intended use. All such modifications and variations fall within the scope of the invention as defined by the appended claims when interpreted in accordance with the scope of a fair, legal, and just authorization.
Claims
1. A method for extruding a resin, said resin comprising a polyhydroxyalkanoate, said method comprising the following steps: At a temperature of 120 °C to 190 °C, at least one polyhydroxyalkanoate in powder form is processed to form at least one processed polyhydroxyalkanoate; and The processed at least one polyhydroxyalkanoate is extruded through an extrusion die to form a resin extrudate composed of the processed at least one polyhydroxyalkanoate. When processed, the at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 1% by weight prior to processing, as determined by ASTM D7191-05. The at least one polyhydroxyalkanoate has an initial weight-average molecular weight before the processing step and a final weight-average molecular weight after the extrusion step, wherein the final weight-average molecular weight is at least 80% of the initial weight-average molecular weight, and all weight-average molecular weights are determined according to ASTM D5296-05.
2. The method of claim 1, wherein, during processing, the at least one powdered polyhydroxyalkanoate has an initial moisture content of at least 5% by weight, as determined by ASTM D7191-05.
3. The method according to claim 1, wherein the processing step and the extrusion step are performed in different devices or different chambers of the same device.
4. The method of claim 1, wherein the processing steps are carried out in a continuous mixer.
5. The method of claim 1, wherein the extrusion step is performed in a screw extruder.
6. The method of claim 1, wherein the at least one polyhydroxy fatty acid ester comprises poly(3-hydroxybutyrate-3-hydroxyhexanoate).
7. The method of claim 6, wherein the poly(3-hydroxybutyrate-3-hydroxyhexanoate) comprises 75 mol% to 99 mol% of hydroxybutyrate and 1 mol% to 25 mol% of hydroxyhexanoate.
8. The method of claim 1, wherein the at least one polyhydroxy fatty acid ester comprises 1% to 25% by weight of at least one polyhydroxy fatty acid ester, wherein the polyhydroxy fatty acid ester comprises 25% to 50% by weight of hydroxyvalerate, hydroxyhexanoate, hydroxyoctanoate and / or hydroxydecanoate.
9. The method according to claim 1, wherein the at least one polyhydroxyalkanoate comprises a ternary polymer made of 75 mol% to 99.9 mol% of 3-hydroxybutyrate monomer residues, 0.1 mol% to 25 mol% of 3-hydroxyhexanoate monomer residues and 0.1 mol% to 25 mol% of a third 3-hydroxyalkanoate monomer residue having 5 to 12 carbon atoms.
10. The method of claim 1, wherein the initial weight-average molecular weight of the at least one polyhydroxyalkanoate is from 50,000 Daltons to 2.5 million Daltons, as determined by ASTM D5296-05.