METHOD FOR MITIGATING POLYMER DEGRADATION IN POLY(HYDROXYALKANOATE) AND POLYMERIC COMPOSITIONS

Description

1 / 21 “METHOD FOR MITIGATING POLYMER DEGRADATION IN POLY(HYDROXYALKANOATE) AND POLYMERIC COMPOSITIONS” FIELD

[001] The present invention relates to biodegradable polymeric compositions. More particularly, this description relates to biodegradable polymeric compositions comprising poly(hydroxyalkanoates), in which the degradation of the poly(hydroxyalkanoate) is mitigated. BACKGROUND

[002] Poly(hydroxyalkanoates) (PHAs) are a class of polymers that are desirably biodegradable and / or compostable. Thus, products made from poly(hydroxyalkanoates) will degrade when the product has reached the end of its life cycle. However, poly(hydroxyalkanoates) are also susceptible to degradation through heat, shear, and hydrolysis under other circumstances outside of end-of-life disposal. When this occurs, the material degrades to form the monomeric components of the polymers. This degradation can cause loss of material properties, organoleptic problems, and regulatory issues.

[003] Consequently, it would be desirable and an objective of the present invention to provide poly(hydroxyalkanoate) compositions in which the degradation of the poly(hydroxyalkanoate) due to heat, shear and hydrolysis is mitigated or even eliminated.

[004] US9328239B2 describes biodegradable compositions of polylactic acid (PLA) combined with polyhydroxyalkanoates (PHA) to increase the toughness, flexibility and mechanical strength of PLA, while maintaining its biodegradable and industrial processing properties.

[005] CN105879111A discloses a method for obtaining biodegradable porous structures based on PHBV / PPC composites, des Petition 870260051913, dated 05 / 29 / 2026, page 11 / 86 2 / 21 primarily intended for tissue engineering and biomedical applications, providing high porosity, biocompatibility and suitable mechanical properties.

[006] EP2291429B1 discloses compositions of branched polyhydroxyalkanoates (PHAs), as well as methods for their production, aiming to improve processability, thermal stability, mechanical properties and industrial applicability of biodegradable materials. SUMMARY OF THE INVENTION

[007] According to the present invention, the above and other needs are satisfied by a method for mitigating the degradation of polymers into poly(hydroxyalkanoates).

[008] In a first aspect, the present invention provides a method for mitigating the degradation of polymers into poly(hydroxyalkanoates). According to one embodiment, the method includes a first step of combining at least one poly(hydroxyalkanoate) with a terminating agent, at least one acid anhydride, and a peroxide to form a reaction mixture comprising at least 50 percent by weight of the at least one poly(hydroxyalkanoate), from about 0.01 to about 15 percent by weight of the terminating agent, from about 0.01 to about 15 percent by weight of the cyclic acid anhydride, and from about 0.01 to about 0.5 percent by weight of the peroxide. The at least one poly(hydroxyalkanoate) in this mixture includes carboxylic acid terminal groups and repeating monomeric units, which are susceptible to degradation to form unsaturated carboxylic acid byproducts.

[009] The method includes a reaction step of the terminating agent with the terminal groups of carboxylic acids to form termination groups in at least one poly(hydroxyalkanoate). The method also includes a reaction step of at least one acid anhydride. Petition 870260051913, dated 05 / 29 / 2026, page 12 / 86 3 / 21 and the peroxide with at least one poly(hydroxyalkanoate) to graft side chains formed from the acid anhydride onto at least one poly(hydroxyalkanoate). According to the present invention, the terminating agent consists of at least one compound selected from the group consisting of carbodiimides, diisocyanates, epoxides and mixtures thereof, and the at least one acid anhydride consists of a cyclic or non-cyclic acid anhydride having from 3 to 40 carbon atoms.

[0010] According to certain embodiments, the at least one poly(hydroxyalkanoate), in a preferred embodiment, has an initial weight-average molecular weight, before combining with the terminating agent and the acid anhydride, of at least 10,000 Daltons, as determined by ASTM 5296-19. In a more preferred embodiment, the at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight, before combining with the terminating agent and the acid anhydride, of about 20,000 Daltons to about 2,500,000 Daltons, as determined by ASTM 5296-19.

[0011] In certain embodiments, the at least one poly(hydroxyalkanoate), preferably, includes repeating monomeric units of 3-hydroxybutyrate, which are susceptible to degradation to form crotonic acid. In some embodiments, the at least one poly(hydroxyalkanoate), preferably, includes repeating monomeric units of 3-hydroxyhexanoate, which are susceptible to degradation to form hexenoic acid. In other embodiments, the at least one poly(hydroxyalkanoate), preferably, includes repeating monomeric units of 3-hydroxypropionate, which are susceptible to degradation to form acrylic acid. In further embodiments, the at least one poly(hydroxyalkanoate), preferably, includes repeating monomeric units of 4-hydroxybutyrate, which are susceptible to degradation to form 4-hydroxybutyric acid. Petition 870260051913, dated 05 / 29 / 2026, page 13 / 86 4 / 21

[0012] In certain modes

[0013] es, the monomer units

[0014] Repeating poly(hydroxyalkanoate) compounds susceptible to degradation to form unsaturated carboxylic acid byproducts include, for example: • 3-hydroxybutyrate units, which can form crotonic acid; • 3-hydroxyhexanoate units, which can form hexenoic acid; • 3-hydroxypropionate units, which can form acrylic acid; • 4-hydroxybutyrate units, which can form 4-hydroxybutyric acid.

[0015] In some cases, at least one poly(hydroxyalkanoate) includes a polyhydroxybutyrate homopolymer. In other embodiments, at least one poly(hydroxyalkanoate) includes poly-3-hydroxybutyrate-co-3-hydroxyvalerate. In further embodiments, at least one poly(hydroxyalkanoate) includes poly-3-hydroxybutyrate-co-3-hydroxyvalerate.

[0016] According to certain embodiments, at least one poly(hydroxyalkanoate), in a preferred embodiment, includes from about 0.1 to about 25 mole percent of monomer residues of a 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0017] In some embodiments, at least one poly(hydroxyalkanoate), preferably, includes a polyhydroxyalkanoate terpolymer consisting of about 75 to about 99.9 mole percent of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mole percent of 3-hydroxyhexanoate monomer residues, and about 0.1 to about 25 mole percent Petition 870260051913, dated 05 / 29 / 2026, page 14 / 86 5 / 21 of monomer residues of a third 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0018] In some embodiments, the terminating agent preferably includes at least one carbodiimide according to Formula (I) R1 - N = C = N - R2(I), where R1 and R2 independently comprise an aliphatic or aromatic group, optionally substituted by one or more heteroatoms selected from the group consisting of N, O, S, and P.

[0019] In accordance with some embodiments, the terminating agent, in a preferred manner, includes at least one polymeric carbodiimide having a molecular weight of about 20 to about 2,000 Daltons, as determined by ASTM 5296-19.

[0020] In other embodiments, the terminating agent, in a preferred mode, includes at least one diisocyanate according to Formula (II) O = c = n - R3- N = C = O (II) in which R3 comprises an aliphatic or aromatic group containing from 1 to 20 carbon atoms.

[0021] In some embodiments, the terminating agent, in a preferred manner, includes at least one aliphatic or aromatic epoxide having from 2 to 200 carbon atoms.

[0022] In some cases, the terminating agent, preferably, includes at least one poly(epoxide) having a molecular weight of about 40 to about 5,000 Daltons as determined by ASTM 5296-19. Petition 870260051913, dated 05 / 29 / 2026, p. 15 / 86 6 / 21

[0023] In accordance with certain embodiments of the present invention, the at least one acid anhydride, in a preferred manner, includes an aliphatic cyclic acid anhydride having from 3 to 40 carbon atoms. In some embodiments, the at least one acid anhydride, in a preferred manner, includes at least one cyclic anhydride selected from the group consisting of maleic anhydride, succinic anhydride, octadecenyl succinic anhydride and mixtures thereof.

[0024] In some embodiments, the peroxide is preferably an organic peroxide. More preferably, the peroxide is selected from the group consisting of lauryl peroxide, dicumyl peroxide and 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane.

[0025] According to certain embodiments, the reaction step is preferably carried out in an extruder. In other embodiments, the reaction step is preferably carried out in a continuous mixer. In some embodiments, the reaction step is preferably carried out at a temperature of about 120 °C to about 200 °C.

[0026] In another embodiment, the present invention provides a polymer composition, which consists of at least 50 percent by weight of terminated and grafted poly(hydroxyalkanoate), formed according to the method mentioned above.

[0027] In some embodiments, the reaction of carbodiimide with poly(hydroxyalkanoate) is distinguished by an increase in molecular weight as measured by ASTM 5296-19, a reduction in acid value as measured by titration with potassium hydroxide (KOH) solution, and the formation of new carbon-nitrogen bonds as observed by FT-IR spectroscopy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The additional advantages of the description are evident by reference to the detailed description when considered as a whole. Petition 870260051913, dated 05 / 29 / 2026, page 16 / 86 7 / 21 with the figure, where: FIG. 1 is a set of FT-IR spectra of poly(hydroxyalkanoate) with and without the reaction with a carbodiimide capping at the end according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides methods for preparing biodegradable polymeric compositions comprising poly(hydroxyalkanoates) wherein the poly(hydroxyalkanoates) have improved resistance to unwanted degradation. The present invention also provides biodegradable polymeric compositions prepared in accordance with such methods.

[0030] Poly(hydroxyalkanoates) are susceptible to degradation through heat, shear, and hydrolysis, leading to the degradation of the material into monomeric components of the polymers. For example, if the poly(hydroxyalkanoates) comprise repeating monomeric units of 3-hydroxybutyrate, these repeating units are susceptible to degradation to form crotonic acid. If the poly(hydroxyalkanoates) comprise repeating monomeric units of 3-hydroxyhexanoate, these repeating units are susceptible to degradation to form hexenoic acid. If the poly(hydroxyalkanoates) comprise repeating monomeric units of 3-hydroxypropionate, these repeating units are susceptible to degradation to form acrylic acid. If poly(hydroxyalkanoates) comprise repeating monomeric units of 4-hydroxybutyrate, these repeating units are susceptible to degradation to form 4-hydroxybutyric acid.

[0031] The formation of such degradation products can cause the loss of material properties (such as strength and molecular weight), organoleptic problems, and regulatory issues due to Petition 870260051913, dated 05 / 29 / 2026, page 17 / 86 8 / 21 presence of materials such as crotonic acid in the composition of polymers.

[0032] In response to these difficulties, the present invention first provides a method for mitigating the degradation of polymers in poly(hydroxyalkanoates) using termination and grafting. According to one embodiment, the method comprises at least a first step of combining at least one poly(hydroxyalkanoate) with a terminating agent, at least one acid anhydride and a peroxide to form a reaction mixture comprising at least 50 percent by weight of the at least one poly(hydroxyalkanoate), from about 0.01 to about 15 percent by weight of the terminating agent, from about 0.01 to about 15 percent by weight of the cyclic acid anhydride and from about 0.01 to about 0.5 percent by weight of the peroxide.

[0033] In certain embodiments of the present invention, the method is carried out in sequential steps, so that the

[0034] terminating agent reacts preferentially with the carboxylic acid terminal groups of the poly(hydroxyalkanoate) before the graft reaction with the acid anhydride.

[0035] In a representative embodiment, the poly(hydroxyalkanoate) is initially mixed with the terminating agent under temperature conditions between 120 °C and 170 °C, allowing the reaction of the terminal carboxylic acid groups to form capping groups.

[0036] Subsequently, acid anhydride and peroxide are added to the mixture to promote the grafting reaction of acid anhydride-derived side chains onto poly(hydroxyalkanoate).

[0037] This sequence can be carried out, for example, in a twin-screw extruder or continuous mixer, by sequential feeding of the reagents or by reaction zones distinct from the equipment. Petition 870260051913, dated 05 / 29 / 2026, page 18 / 86 9 / 21 payment.

[0038] The method includes a reaction step of the terminating agent with the terminal carboxylic acid groups to form termination groups on at least one poly(hydroxyalkanoate). The method also includes a reaction step of at least one acid anhydride and peroxide with at least one poly(hydroxyalkanoate) to graft side chains formed from the acid anhydride onto at least one poly(hydroxyalkanoate). According to the present invention, the terminating agent consists of at least one compound selected from the group consisting of carbodiimides, diisocyanates, epoxides and mixtures thereof, and at least one acid anhydride consists of a cyclic or non-cyclic acid anhydride having from 3 to 40 carbon atoms.

[0039] A variety of poly(hydroxyalkanoates) can be capped at the end according to the present invention, including homopolymers, copolymers and terpolymers.

[0040] For example, in certain embodiments, at least one poly(hydroxyalkanoate) may comprise a polyhydroxybutyrate homopolymer.

[0041] In other embodiments, at least one poly(hydroxyalkanoate) may comprise a copolymer such as poly-3-hydroxybutyrate-co-3-hydroxyvalerate or poly-3-hydroxybutyrate-co-3-hydroxyvalerate. More generally, the poly(hydroxyalkanoate) copolymer, in some embodiments, may comprise from about 0.1 to about 25 mole percent of monomer residues of a 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0042] In other embodiments, at least one poly(hydroxyalkanoate) may comprise a poly terpolymer Petition 870260051913, dated 05 / 29 / 2026, page 19 / 86 10 / 21 hydroxyalkanoate consisting of about 75 to about 99.9 mole percent of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mole percent of 3-hydroxyhexanoate monomer residues, and about 0.1 to about 25 mole percent of monomer residues of a third 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0043] A mixture of two or more of the above poly(hydroxyalkanoates) can also be capped at the end according to the present method.

[0044] The at least one poly(hydroxyalkanoate) typically has an initial weight-average molecular weight, before combining with the terminating agent, acid anhydride and peroxide, of at least 10,000 Daltons, as determined by ASTM 5296-19. More preferably, the at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight of about 20,000 Daltons to about 2,500,000 Daltons, as determined by ASTM 5296-19, before combining with the terminating agent, acid anhydride and peroxide.

[0045] As for the terminating agent, the terminating agent comprises at least one compound selected from the group consisting of carbodi-imides, di-isocyanates, epoxides and mixtures thereof.

[0046] For example, in certain embodiments, the terminating agent may comprise at least one carbodiimide according to Formula (I) R1- N = C = N - R2Formula (I)

[0047] In this carbodiimide, each of R1 and R2 independently comprises an aliphatic or aromatic group, optionally Petition 870260051913, dated 05 / 29 / 2026, p. 20 / 86 11 / 21 replaced by one or more heteroatoms selected from the group consisting of N, O, S, and P. Although the overall size of this carbodiimide may vary, the carbodiimide is, in some embodiments, a polymeric carbodiimide having a molecular weight of about 20 to about 5,000 Daltons, more preferably from about 300 to about 2,000 Daltons, as determined by ASTM 5296-19.

[0048] In some embodiments, each of R1 and R2, more preferably, comprises an aromatic group. An example of a suitable carbodiimide is STABAXOL P, available from Lanxess AG of Germany. Although the exact composition of STABAXOL P is not known, it is believed to comprise an aromatic carbodiimide, in which the aromatic groups are replaced by isopropyl groups.

[0049] In other embodiments, the terminating agent may comprise at least one diisocyanate according to Formula (II) O = C = N - R3- N = C = O Formula (II) where R3 comprises an aliphatic or aromatic group having from 1 to 20 carbon atoms.

[0050] In some embodiments, this terminating agent preferably comprises at least one aliphatic or aromatic epoxide having from 2 to 200 carbon atoms.

[0051] In other embodiments, the terminating agent may comprise at least one poly(epoxide) having a molecular weight of about 40 to about 5,000 Daltons, more preferably from about 500 to about 3,000 Daltons, as determined by ASTM 5296-19.

[0052] As noted above, the graft is performed with a Petition 870260051913, dated 05 / 29 / 2026, p. 21 / 86 12 / 21 acid anhydride and a peroxide. In general, the acid anhydride may be a cyclic or non-cyclic acid anhydride with 3 to 40 carbon atoms. In some cases, the at least one acid anhydride, preferably, comprises at least one cyclic anhydride selected from the group consisting of maleic anhydride, succinic anhydride, octadecenyl succinic anhydride, and mixtures thereof.

[0053] In some embodiments, the peroxide is preferably an organic peroxide. More preferably, the peroxide is selected from the group consisting of lauryl peroxide, dicumyl peroxide and 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane.

[0054] Both the termination reaction and the acid anhydride graft reaction are preferably carried out at a temperature of about 120 °C to about 200 °C, more preferably from about 130 °C to about 170 °C.

[0055] According to certain embodiments, one or both of these reaction steps are preferably carried out in an extruder. In other embodiments, one or both of these reaction steps are preferably carried out in a continuous mixer.

[0056] In another embodiment, the present invention provides a polymer composition consisting of at least 50 percent by weight of terminated and grafted poly(hydroxyalkanoate), formed according to the method mentioned above.

[0057] In certain embodiments, the grafting reaction step of the grafting method is preferably carried out in an extruder. In other embodiments, the grafting reaction step is preferably carried out in a continuous mixer. In some embodiments, the reaction step is preferably carried out at a temperature of about 120 °C to about 200 °C, more preferably from about 130 °C to about 170 °C. Petition 870260051913, dated 05 / 29 / 2026, page 22 / 86 13 / 21

[0058] In some embodiments, the polymer and other reactive components also include other additives, including, but not limited to, nucleators, lubricants, other biodegradable polymers, processing aids, fillers, antioxidants and mixtures thereof.

[0059] In other embodiments, the extent of degradation prevention / acidity mitigation is identified by changes in the percent molecular weight change as determined by ASTM 5296-19, by Hunter color determined by ASTM E1347, by changes in FTIR spectra by ASTM E168-16, and by determining acidity indices by ASTM D7253-16.

[0060] The present invention is also further illustrated by the following embodiments:

[0061] Embodiment 1. A method for mitigating the degradation of polymers into poly(hydroxyalkanoates), the method comprising: combining at least one poly(hydroxyalkanoate) with a terminating agent, at least one acid anhydride and a peroxide to form a reaction mixture comprising at least 50 percent by weight of the at least one poly(hydroxyalkanoate), from about 0.01 to about 15 percent by weight of the terminating agent, from about 0.01 to about 15 percent by weight of the cyclic acid anhydride, and from about 0.01 to about 0.5 percent by weight of the peroxide, wherein the at least one poly(hydroxyalkanoate) comprises carboxylic acid terminal groups and repeating monomeric units that are susceptible to degradation to form unsaturated carboxylic acid byproducts; react the terminating agent with the terminal carboxylic acid groups to form the terminating groups in at least one poly(hydroxyalkanoate); and Petition 870260051913, dated 05 / 29 / 2026, page 23 / 86 14 / 21 reacting at least one acid anhydride and peroxide with at least one poly(hydroxyalkanoate) to graft side chains formed from the acid anhydride onto at least one poly(hydroxyalkanoate), wherein the terminating agent comprises at least one compound selected from the group consisting of carbodiimides, diisocyanates, epoxides and mixtures thereof, and wherein the at least one acid anhydride comprises a cyclic or non-cyclic acid anhydride having from 3 to 40 carbon atoms.

[0062] Embodiment 2. The method of Embodiment 1, wherein at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight, before combining with the terminating agent and the acid anhydride, of at least 10,000 Daltons, as determined by ASTM 5296-19.

[0063] Modality 3. The method of Modality 1 or 2, wherein at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight before combining with a terminating agent and the acid anhydride, of about 20,000 Daltons to about 2,500,000 Daltons, as determined by ASTM 5296-19.

[0064] Embodiment 4. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 3-hydroxybutyrate that are susceptible to degradation to form crotonic acid.

[0065] Embodiment 5. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 3-hydroxyhexanoate that are susceptible to degradation to form hexenoic acid.

[0066] Embodiment 6. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises the repeating monomeric units of 3-hydroxypropionate which are Petition 870260051913, dated 05 / 29 / 2026, page 24 / 86 15 / 21 susceptible to degradation to form acrylic acid.

[0067] Embodiment 7. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 4-hydroxybutyrate that are susceptible to degradation to form 4-hydroxybutyric acid.

[0068] Embodiment 8. The method of any of the preceding embodiments, in which at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P3HB-co-P3HHx).

[0069] Embodiment 9. The method of any of the preceding embodiments, in which at least one poly(hydroxyalkanoate) comprises a polyhydroxybutyrate homopolymer.

[0070] Embodiment 10. The method of any of the preceding embodiments, in which at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyvalerate.

[0071] Embodiment 11. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises from about 0.1 to about 25 mole percent of monomer residues of a 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0072] Embodiment 12. The method of any of the preceding embodiments, wherein at least one poly(hydroxyalkanoate) comprises a polyhydroxyalkanoate terpolymer consisting of about 75 to about 99.9 mole percent of 3-hydroxybutyrate monomer residues, about 0.1 to about 25 mole percent of 3-hydroxyhexanoate monomer residues, and about 0.1 to about 25 mole percent of monomer residues of a third 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

[0073] Modality 13. The method of any of the modalities Petition 870260051913, dated 05 / 29 / 2026, page 25 / 86 16 / 21 of the preceding ones, wherein the terminating agent comprises at least one carbodiimide according to Formula (I) R1- N = C = N - R2Formula (I) wherein R1 and R2 independently comprise an aliphatic or aromatic group, optionally replaced by one or more heteroatoms selected from the group consisting of N, O, S and P.

[0074] Embodiment 14. The method of any of the above embodiments, wherein the terminating agent comprises at least one polymeric carbodiimide having a molecular weight of about 20 to about 5,000 Daltons, as determined by ASTM 5296-19.

[0075] Embodiment 15. The method of any of the above embodiments, wherein the terminating agent comprises at least one diisocyanate according to Formula (II) O = c = n - R3 - N = C = O Formula (II) where R3 comprises an aliphatic or aromatic group having from 1 to 20 carbon atoms.

[0076] Embodiment 16. The method of any of the above embodiments, in which the terminating agent comprises at least one aliphatic or aromatic epoxide having from 2 to 200 carbon atoms.

[0077] Embodiment 17. The method of any of the above embodiments, wherein the terminating agent comprises at least one poly(epoxide) having a molecular weight of about 40 to about 5,000 Daltons, as determined by ASTM 5296-19.

[0078] Modality 18. The method of any of the modalities Petition 870260051913, dated 05 / 29 / 2026, p. 26 / 86 17 / 21 of the previous ones, in which at least one acid anhydride is an aliphatic cyclic acid anhydride having from 3 to 40 carbon atoms.

[0079] Embodiment 19. The method of any of the preceding embodiments, in which at least one acid anhydride comprises at least one cyclic anhydride selected from the group consisting of maleic anhydride, succinic anhydride, octadecenylsuccinic anhydride and mixtures thereof.

[0080] Modality 20. The method of any of the previous modalities, in which the reaction step is carried out at a temperature of about 120 °C to about 200 °C.

[0081] Modality 21. The method of any of the above embodiments, in which the peroxide is an organic peroxide.

[0082] Embodiment 22. The method of any of the above embodiments, wherein the peroxide is selected from the group consisting of lauryl peroxide, dicumyl peroxide and 2,5-Bis(tert-butylperoxy)2,5-dimethylhexane

[0083] Modality 23. The method of any of the previous modalities, in which the reaction step is carried out in an extruder.

[0084] Modality 24. The method of any of the previous modalities, in which the reaction step is carried out in a continuous mixer.

[0085] Modality 25. The method of any of the previous modalities, in which the reaction step is carried out at a temperature of about 120 °C to about 200 °C.

[0086] Embodiment 26. A polymer composition comprising at least 50 percent by weight of terminated and grafted poly(hydroxyalkanoate), formed in accordance with any of the preceding embodiments. EXAMPLES

[0087] The following non-limiting examples illustrate several as Petition 870260051913, dated 05 / 29 / 2026, page 27 / 86 18 / 21 additional aspects of the invention. Unless otherwise indicated, temperatures are in degrees Celsius and percentages are by weight based on the dry weight of the formulation.

[0088] Example 1. A poly(hydroxyalkanoate) consisting of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% of a nucleator (pentaerythritol) and compounded at a melting temperature of approximately 182 °C. The resulting pellets were analyzed for molecular weight according to ASTM 5296-19. The pellets were then converted into molded plates by injection molding and measured for Hunter color and molecular weight according to ASTM E1347 and ASTM 5296-19, respectively. The percent change in molecular weight after molding was calculated, and this value, along with the Hunter color, was used as a control for comparison in Table 1.

[0089] Example 2. A poly(hydroxyalkanoate), which consists of A pellet composed of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% nucleator (pentaerythritol) and 2% Stabaxol P, a commercially available carbodiimide, and compounded at a melting temperature of approximately 182 °C. The resulting pellets were analyzed for molecular weight according to ASTM 5296-19. The pellets were then converted into molded plates by injection molding and measured for yellowness index using Hunter color and molecular weight, according to ASTM E1347 and ASTM 5296-19 standards, respectively. The percentage change in molecular weight after molding was calculated, and this value and Hunter color were compared to the control (Example 1) in Table 1. The sample shows a smaller percentage change in molecular weight and a lower yellowness index compared to Petition 870260051913, dated 05 / 29 / 2026, page 28 / 86 19 / 21 control, indicating successful mitigation of acid / degradation.

[0090] Example 3. A poly(hydroxyalkanoate) consisting of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% nucleator (pentaerythritol) and 0.1% dicumyl peroxide, and compounded at a melting temperature of approximately 182 °C. The resulting pellets were analyzed for molecular weight according to ASTM 5296-19. The pellets were then converted into molded plates by injection molding and measured for yellowness index using the Hunter color and molecular weight according to ASTM E1347 and ASTM 5296-19 standards, respectively. The percentage change in molecular weight after molding was calculated, and this value, along with the Hunter color, was compared to the control in Table 1. The sample shows a smaller percentage change in molecular weight and a lower yellowing index compared to the control, indicating successful mitigation of acid / degradation.

[0091] Example 4. A poly(hydroxyalkanoate) consisting of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% nucleator (pentaerythritol), 0.1% dicumyl peroxide, and 2.0% succinic anhydride and compounded at a melting temperature of approximately 182 °C. The resulting pellets were analyzed for molecular weight according to ASTM 5296-19. The pellets were then converted into molded plates by injection molding and measured for yellowness index using the Hunter color and molecular weight according to ASTM E1347 and ASTM 5296-19 standards, respectively. The percentage change in molecular weight after molding was calculated, and this value, along with the Hunter shade, was compared to the control in Table 1. The sample showed Petition 870260051913, dated 05 / 29 / 2026, page 29 / 86 20 / 21 shows a smaller percentage change in molecular weight and a lower yellowing index compared to the control, indicating successful mitigation of acid / degradation.

[0092] Example 5. A poly(hydroxyalkanoate) consisting of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% nucleator (pentaerythritol), 0.1% dicumyl peroxide, and 1.0% maleic anhydride and compounded at a melting temperature of approximately 182 °C. The resulting pellets were analyzed for molecular weight according to ASTM 5296-19. The pellets were then converted into molded plates by injection molding and measured for yellowness index using Hunter color and molecular weight according to ASTM E1347 and ASTM 5296-19 standards, respectively. The percent change in molecular weight after molding was calculated, and this value, along with the Hunter color, was compared to the control in Table 1.The sample shows a smaller percentage change in molecular weight and a lower yellowing index compared to the control, indicating successful mitigation of acid / degradation. Table 1 Sample Percentage change in weight-average molecular weight Hunter color yellowing index Example 1 65.97% 55.32 Example 2 17.16% 26.12 Example 3 10.78% 27.45 Example 4 9.28% 27.29 Example 5 11.92% 32.33

[0093] Example 6. A poly(hydroxyalkanoate) consisting of 94% repeating units of hydroxybutyrate and 6% repeating units of hydroxyhexanoate was loaded into a twin-screw extruder with 1% nucleator (pentaerythritol) and 2.0% of a carbodiimide. Petition 870260051913, dated 05 / 29 / 2026, page 30 / 86 21 / 21 limeric, and compound at a melting temperature of approximately 182 °C. Compared to a control sample (Example 1), this reaction with the polymeric carbodiimide is distinguished by an increase in molecular weight as measured by ASTM 5296-19 and a reduction in acid value from approximately 0.7 to 0.2 as measured by titration with a potassium hydroxide (KOH) solution, as shown in Table 2 below. Additionally, the termination reaction is confirmed by the formation of new carbon-nitrogen (CN) bonds as captured by FT-IR spectroscopy, as illustrated in FIG. 1. In the FT-IR spectrum of the terminated 2% poly(hydroxyalkanoate), a new CN stretch also appears around 1250 cm⁻¹, and N=C=N stretches around 2120 cm⁻¹, indicating unreacted residual carbodiimide. Table 2 Example 1 (Control) Example 6 Weight-average molecular weight (Mw) (kilodaltons) 392 646 Number-average molecular weight (Mn) (kilodaltons) 193 246 Polydispersity Index (PDI) 2.0 2.6 Acidity Index 0.7 0.2

[0094] The preceding description of the preferred modalities for this description has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the description to the precise form revealed. Obvious modifications or variations are possible in light of the above teachings. The modalities are chosen and described in an effort to provide the best illustrations of the principles of description and their practical application, and thereby enable someone skilled in the art to utilize the description in various modalities and with various modifications as appropriate to the particular use contemplated. Petition 870260051913, dated 05 / 29 / 2026, page 31 / 86

Claims

1 / 6 CLAIMS 1. A method for mitigating the degradation of polymers into poly(hydroxyalkanoates), characterized in that it comprises: combining at least one poly(hydroxyalkanoate) with a terminating agent, at least one acid anhydride and a peroxide to form a reaction mixture comprising at least 50 percent by weight of the at least one poly(hydroxyalkanoate), from 0.01 to 15 percent by weight of the terminating agent, from 0.01 to 15 percent by weight of the acid anhydride and from 0.01 to 0.5 percent by weight of the peroxide, wherein the at least one poly(hydroxyalkanoate) comprises carboxylic acid terminal groups and repeating monomeric units that are susceptible to degradation to form unsaturated carboxylic acid byproducts; react the terminating agent with the terminal carboxylic acid groups to form terminating groups in at least one poly(hydroxyalkanoate);and reacting at least one acid anhydride and peroxide with at least one poly(hydroxyalkanoate) to graft side chains formed from the acid anhydride onto at least one poly(hydroxyalkanoate), wherein the terminating agent comprises at least one compound selected from the group consisting of carbodiimides, diisocyanates, epoxides and mixtures thereof, and wherein the at least one acid anhydride comprises a cyclic or non-cyclic acid anhydride having from 3 to 40 carbon atoms.

2. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight, before combining with the terminating agent and the acid anhydride, of at least 10,000 Daltons, Petition 870260051913, dated 05 / 29 / 2026, page 32 / 86 2 / 6 as determined by ASTM 5296-19.

3. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) has an initial weight-average molecular weight before combining with a terminating agent and the acid anhydride, of 20,000 Daltons to 2,500,000 Daltons, as determined by ASTM 5296-19.

4. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 3-hydroxybutyrate, which are susceptible to degradation to form crotonic acid.

5. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 3-hydroxyhexanoate, which are susceptible to degradation to form hexenoic acid.

6. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 3-hydroxypropionate, which are susceptible to degradation to form acrylic acid.

7. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises repeating monomeric units of 4-hydroxybutyrate, which are susceptible to degradation to form 4-hydroxybutyric acid.

8. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P3HB-co-P3HHx).

9. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises the polyhydroxybutyrate homopolymer.

10. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises Petition 870260051913, dated 05 / 29 / 2026, page 33 / 86 3 / 6 poly-3-hydroxybutyrate-co-3-hydroxyvalerate.

11. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises from 0.1 to 25 mole percent of monomer residues of a 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

12. Method according to claim 1, characterized in that at least one poly(hydroxyalkanoate) comprises a polyhydroxyalkanoate terpolymer consisting of 75 to 99.9 mole percent of 3-hydroxybutyrate monomer residues, 0.1 to 25 mole percent of 3-hydroxyhexanoate monomer residues and 0.1 to 25 mole percent of monomer residues of a third 3-hydroxyalkanoate selected from the group consisting of 3-hydroxyoctanoate, 3-hydroxydecanoate and mixtures thereof.

13. Method according to claim 1, characterized in that the terminating agent comprises at least one carbodiimide according to Formula (I) R1 - N = C = N - R2 (I), wherein R1 and R2 independently comprise an aliphatic or aromatic group, optionally substituted by one or more heteroatoms selected from the group consisting of N, O, S and P.

14. Method according to claim 1, characterized in that the terminating agent comprises at least one polymeric carbodiimide having a molecular weight of 20 to 5,000 Daltons, as determined by ASTM 5296-19.

15. Method according to claim 1, characterized in that the terminating agent comprises at least one diisocyanate according to Formula (II) Petition 870260051913, dated 29 / 05 / 2026, page 34 / 86 4 / 6 O = c = N - R3 - N = C = O (II), wherein R3 comprises an aliphatic or aromatic group having from 1 to 20 carbon atoms.

16. Method according to claim 1, characterized in that the terminating agent comprises at least one aliphatic or aromatic epoxide having from 2 to 200 carbon atoms.

17. Method according to claim 1, characterized in that the terminating agent comprises at least one poly(epoxide) having a molecular weight of 40 to 5,000 Daltons, as determined by ASTM 5296-19.

18. Method according to claim 1, characterized in that at least one acid anhydride is an aliphatic cyclic acid anhydride having from 3 to 40 carbon atoms.

19. Method according to claim 1, characterized in that at least one acid anhydride comprises at least one cyclic anhydride selected from the group consisting of maleic anhydride, succinic anhydride, octadecenyl succinic anhydride and mixtures thereof.

20. Method according to claim 1, characterized in that the reaction step is carried out at a temperature of 120 °C to 200 °C.

21. Method according to claim 1, characterized in that the peroxide is an organic peroxide.

22. Method according to claim 1, characterized in that the peroxide is selected from the group consisting of lauryl peroxide, dicumyl peroxide and 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane.

23. Method, according to claim 1, characterized by the fact that the reaction step is carried out in an extruder.

24. Method according to claim 1, characterized in that the reaction step is carried out in a continuous mixer.

25. Method according to claim 1, characterized in that the reaction step is carried out at a temperature of 120 °C to 200 °C.

26. A method according to any one of claims 1 to 25, characterized in that it comprises: (a) combining at least one poly(hydroxyalkanoate) with a terminating agent, at least one acid anhydride and a peroxide to form a reaction mixture; (b) reacting the terminating agent with the carboxylic acid terminal groups of at least one poly(hydroxyalkanoate) to form terminating groups; (c) subsequently adding at least one acid anhydride and a peroxide to the reaction mixture; and (d) reacting the at least one acid anhydride and the peroxide with the at least one poly(hydroxyalkanoate) to graft side chains formed from the acid anhydride onto the at least one poly(hydroxyalkanoate); wherein the terminating agent comprises at least one compound selected from the group consisting of carbodiimides, diisocyanates, epoxides and mixtures thereof;wherein at least one acid anhydride comprises a cyclic or non-cyclic acid anhydride having from 3 to 40 carbon atoms; wherein the mixture comprises: • at least 50 percent by weight of poly(hydroxyalkanoate); Petition 870260051913, dated 05 / 29 / 2026, page 36 / 86 6 / 6 • 0.01 to 15 percent by weight of the capping agent; • 0.01 to 15 percent by weight of the acid anhydride; • 0.01 to 0.5 percent by weight of the peroxide.

27. Method according to claim 26, characterized in that the steps are performed in a twin-screw extruder with sequential feeding of the reagents.

28. Method according to claim 26 or 27, characterized in that the poly(hydroxyalkanoate) comprises repeating monomeric units selected from: • 3-hydroxybutyrate; • 3-hydroxyhexanoate; • 3-hydroxypropionate; • 4-hydroxybutyrate.

29. Polymeric composition, characterized in that it comprises at least 50 percent by weight of terminated and grafted poly(hydroxyalkanoate), formed according to the method as defined in any one of claims 1 to 28. Petition 870260051913, dated 05 / 29 / 2026, p. 37 / 86

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