Aging-resistant PHA degradable material and preparation method and application thereof

Abstract

The application relates to the field of degradable materials, and particularly relates to an anti-aging PHA degradable material and a preparation method and application thereof, which comprises the following raw materials in parts by weight: PHA 70-85 parts, PBAT 15-30 parts, nucleating agent 0.1-0.5 parts, hindered phenolic antioxidant 0.1-0.5 parts, modified lignin 5-10 parts, montan wax 0.5-1.5 parts and chain extender 0.3-1 part. The application improves the flexibility by introducing PBAT, and then the nucleating agent and the modified lignin are added, on one hand, a large number of small and uniform crystal nuclei are induced to form and rapid crystallization is realized, and on the other hand, the migration path and nucleation condition required for the rearrangement of PHA molecular chains at room temperature to form secondary crystallization are blocked, the probability of secondary crystallization of the PHA material at room temperature is obviously reduced, and the anti-aging property of the PHA degradable material is improved.

Description

Technical Field

[0001] This application relates to the field of biodegradable materials, and in particular to an aging-resistant PHA biodegradable material and its preparation method. Background Technology

[0002] With the full implementation of global policies to limit and ban plastics, environmentally friendly alternatives to single-use plastic straws have become a core development direction in the packaging and food contact materials sector. Polyhydroxyalkanoates (PHA), as a natural high-molecular-weight polyester synthesized by microorganisms, possess complete biodegradability, excellent biocompatibility, and environmental friendliness, giving them unique advantages in the application of single-use straws.

[0003] However, PHA is a typical semi-crystalline polymer that is prone to secondary crystallization at room temperature. After 3-6 months of storage at room temperature, the resulting PHA straws suffer from severe performance degradation and quality failure, such as breaking easily when bent or cracking under pressure. This makes it impossible to meet the usage requirements and shelf life regulations for straw products, making it difficult for PHA straws to adapt to the industry needs of large-scale production and omni-channel distribution. Summary of the Invention

[0004] To improve the aging resistance of PHA materials, this application provides an aging-resistant PHA biodegradable material, its preparation method, and its application.

[0005] Firstly, this application provides an aging-resistant PHA biodegradable material, which adopts the following technical solution: An aging-resistant PHA biodegradable material comprises the following raw materials in parts by weight: 70-85 parts PHA, 15-30 parts PBAT, 0.1-0.5 parts nucleating agent, 0.1-0.5 parts hindered phenolic antioxidant, 5-10 parts modified lignin, 0.5-1.5 parts montan wax, and 0.3-1 parts chain extender.

[0006] By adopting the above technical solution, the introduction of PBAT allows PBAT molecular chains to interpenetrate within PHA molecular chains in the blend system, thereby increasing the resistance to PHA chain rearrangement and limiting the space required for long-range migration and orderly arrangement of PHA molecular chains at room temperature. Furthermore, the addition of nucleating agents and modified lignin allows the nucleating agents to induce the formation of numerous fine, uniform crystal nuclei in PHA during the melting and cooling stage, leading to rapid crystallization. Lignin itself possesses a three-dimensional network structure; modification enhances its compatibility with PHA, thus creating steric hindrance and topological constraints on the PHA molecular chains. Furthermore, the modified lignin… The phenolic hydroxyl groups in lignin can form intermolecular hydrogen bonds with the ester carbonyl groups or terminal hydroxyl groups of PHA, anchoring some segments of PHA onto lignin. At the same time, the aromatic rings in lignin can interact with the methylene segments in the PHA backbone through hydrophobic interactions and weak π-H polarization, further enhancing the interfacial bonding strength between lignin and PHA. This effectively blocks the migration path and nucleation conditions required for the rearrangement of PHA molecular chains to form secondary crystals at room temperature, significantly reducing the probability of secondary crystallization of PHA biodegradable materials at room temperature and improving the aging resistance of PHA biodegradable materials.

[0007] This application improves flexibility by introducing PBAT, and by adding nucleating agents and modified lignin, it induces the formation of a large number of small and uniform crystal nuclei and achieves rapid crystallization. On the other hand, it can block the migration path and nucleation conditions required for the rearrangement of PHA molecular chains to form secondary crystallization at room temperature, significantly reducing the probability of secondary crystallization of PHA materials at room temperature and improving the aging resistance of PHA degradable materials.

[0008] Preferably, the modified lignin is phytic acid-modified lignin, and the preparation method of the phytic acid-modified lignin includes the following steps: Step 1: Disperse lignin in deionized water and adjust the pH to 12, stirring to obtain the first mixture; Step 2: Dissolve sodium phytate hydrate in deionized water, stir well, add to the first mixture, adjust the pH to 11, stir in a water bath at 20-30℃ for 15-30 minutes, adjust the pH to 7, purify and dry to obtain phytate modified lignin.

[0009] By adopting the above technical solution, lignin is modified with phytic acid, and a large number of phosphate groups are introduced on the surface of lignin. This not only effectively improves the compatibility between lignin and the PHA matrix and promotes the uniform dispersion of lignin in the matrix, but the presence of phosphate groups can also form hydrogen bonds with multiple ester carbonyl groups and terminal hydroxyl groups on the PHA molecular chain, forming a multi-point network anchoring structure. Its anchoring effect is much higher than that of hydrogen bond anchoring between lignin and PHA, thereby restricting the movement and rearrangement of PHA at room temperature and further reducing the probability of secondary crystallization of PHA degradable materials at room temperature.

[0010] Furthermore, the phosphate group can preferentially capture free metal ions in the system and fix them on the surface of lignin. The complexed metal ions lose their activity and cannot catalyze ester bond exchange reactions or induce rearrangement of PHA segments, thus inhibiting the secondary crystallization of PHA degradable materials.

[0011] Meanwhile, since phosphate contains phosphate ester groups, the P=O bonds in the phosphate ester groups are polar and can undergo addition reactions with free radicals to generate relatively stable phosphorus-oxygen free radical adducts. The phenolic hydroxyl groups in lignin can quench free radicals to generate phenoxy free radicals. The phosphate groups can further stabilize phenoxy free radicals and inhibit them from initiating new chain reactions, forming a phenol-phosphorus synergistic antioxidant cycle.

[0012] Preferably, the molar ratio of lignin to phytic acid is 1:0.2-0.6.

[0013] By adopting the above technical solution, when the proportion of lignin is too high, the amount of phytic acid is insufficient, resulting in the incomplete occupation of effective grafting sites on the lignin surface. The modified lignin obtained has a low degree of modification, few phosphate groups on the surface, and poor compatibility with the matrix. It is prone to agglomeration, which reduces the toughness of the PHA biodegradable material and decreases the anchoring ability of PHA segments. It cannot effectively inhibit the rearrangement of PHA segments, making the PHA biodegradable material prone to secondary crystallization at room temperature, resulting in increased brittleness of the PHA biodegradable material.

[0014] When the proportion of lignin is too low, the amount of phytic acid added is too high, causing excessive cross-linking of lignin molecules, forming large-particle aggregates. Furthermore, excessive phytic acid grafting introduces too many phosphate groups onto the lignin surface, resulting in a significant increase in the hydrophilicity and polarity of the modified lignin surface, which worsens its compatibility with the PHA matrix and reduces the elongation at break of the resulting aging-resistant PHA biodegradable material.

[0015] Preferably, the lignin is sulfate lignin.

[0016] By adopting the above technical solution, sulfate lignin exhibits high thermal stability and superior compatibility with the matrix, making it less prone to aggregation. Furthermore, the high phenolic hydroxyl content in sulfate lignin allows for better dissociation and dispersion at pH 12, exposing more reaction sites. This facilitates more complete and uniform esterification or ionic bonding reactions with the phosphate groups in sodium phytate, ensuring a high and stable grafting rate for phytate-modified lignin.

[0017] Furthermore, the rigid aromatic ring structure of sulfate lignin can serve as an effective heterogeneous nucleation site. During the processing and cooling stage, it helps to form a finer crystal network. During room temperature storage, the phytic acid groups on its surface can stabilize these crystals and inhibit secondary crystallization, thereby effectively maintaining the toughness of PHA biodegradable materials.

[0018] Preferably, the nucleating agent is at least one of calcium lactate, cyclodextrin, and zinc stearate.

[0019] Preferably, the nucleating agent is calcium lactate.

[0020] By adopting the above technical solution, calcium lactate is an organic calcium salt that can be uniformly dispersed in the PHA melt in the form of micro-nano-scale crystalline particles, providing a heterogeneous nucleation surface and inducing rapid nucleation of PHA. Furthermore, the calcium ions in calcium lactate can undergo weak coordination with the ester carbonyl group or terminal hydroxyl group of PHA, forming a locally ordered structure at the nucleation interface and promoting the growth of crystal nuclei.

[0021] Cyclodextrin is a cyclic oligosaccharide composed of glucose units. It has a cavity structure that is "hydrophilic on the outside and hydrophobic on the inside". In the PHA melt, the hydrophobic cavity of cyclodextrin can encapsulate the alkyl segments of PHA or other additive molecules through host-guest interactions, forming local physical cross-linking points. In addition, the surface of cyclodextrin has abundant hydroxyl groups, which can form hydrogen bonds with the ester groups of PHA, providing a heterogeneous nucleation surface.

[0022] Zinc stearate is a metal soap nucleating agent. The zinc ions in it can form complexes with the polar groups of PHA, thereby promoting the nucleation of PHA. The stearate ions can provide hydrophobic lubrication. In the PHA melt, zinc stearate can partially dissolve in the amorphous region of PHA and precipitate out during cooling to form fine crystals, inducing heterogeneous nucleation of PHA.

[0023] Calcium lactate contains a lactate group structure, similar to the structure of PHA segments, which can form efficient heterogeneous nucleation centers, promoting rapid and complete crystallization of PHA. Simultaneously, the calcium ions in calcium lactate can also coordinate and crosslink with the phosphate groups in modified lignin, forming "lignin-Ca..." 2+ The lignin-PHA complex, with its multi-layered network structure, exhibits a degree of dynamic reversibility in its coordination. Under processing conditions, it can moderately dissociate to facilitate dispersion, and under cooling and storage conditions, it can reform stable coordination. Calcium ions act as "bridging points," strengthening the connection between lignin and PHA molecular chains. This not only improves the interfacial bonding between lignin and the PHA matrix but also further restricts the movement of PHA amorphous chain segments. The calcium-phosphorus complex on the lignin surface serves as a more efficient heterogeneous nucleation site, synergistically promoting crystallization with free calcium lactate. Therefore, calcium lactate is preferred as the nucleating agent.

[0024] Preferred, aging-resistant, PHA-degradable materials also contain added vitamin E.

[0025] By adopting the above technical solution, vitamin E is a natural and highly efficient chain-terminating antioxidant. Its molecular structure contains a benzodihydropyran ring and a phenolic hydroxyl group. The phenolic hydroxyl group can provide hydrogen ions for active free radicals to generate stable tocopherol free radicals, thereby terminating the free radical chain reaction. Furthermore, the tocopherol free radicals can synergistically interact with hindered phenolic antioxidants to achieve reduction and regeneration, further extending the antioxidant lifespan.

[0026] Vitamin E can also form a ternary synergy of "phenol-phosphorus-tocopherol" with phytic acid-modified lignin. After capturing free radicals through the phenolic hydroxyl groups of lignin, phenoxy free radicals are generated, which can be reduced and regenerated by vitamin E. Phosphorus-centered free radical adducts of phytate can undergo electron transfer with vitamin E, thereby restoring the activity of the phosphorus center. The three form a cyclic regeneration system, which significantly prolongs the antioxidant effect.

[0027] Secondly, this application provides a method for preparing an aging-resistant PHA biodegradable material, which adopts the following technical solution: A method for preparing an aging-resistant PHA biodegradable material includes the following steps: S1. Dry PHA, PBAT and modified lignin at 60-80℃ for 4-6 hours. Then, stir and mix the formulated amounts of PHA, PBAT, nucleating agent, hindered phenolic antioxidant, modified lignin, montan wax and chain extender to obtain a mixture. S2. The mixture is melt-blended, extruded, and granulated to obtain an aging-resistant PHA biodegradable material.

[0028] By adopting the above technical solution, the probability of PHA undergoing hydrolysis and degradation during the melt processing is first reduced by drying. Then, the raw materials are initially mixed, melt-blended and granulated to achieve uniform dispersion and coordination between components, resulting in an aging-resistant PHA biodegradable material.

[0029] Preferably, in S1, the formulated amounts of vitamin E, PHA, PBAT, nucleating agent, hindered phenolic antioxidant, modified lignin, montan wax, and chain extender are added and mixed to obtain a mixture.

[0030] By adopting the above technical solution, vitamin E is added to S1, which enables vitamin E to be uniformly adsorbed on the surface of PHA, PBAT and modified lignin, ensuring that vitamin E can capture free radicals in time during subsequent melt blending and work synergistically with hindered phenolic antioxidants to ensure the antioxidant capacity of PHA degradable materials.

[0031] Thirdly, the application of the aging-resistant PHA biodegradable material provided in this application in the preparation of aging-resistant PHA biodegradable straws adopts the following technical solution: The above-mentioned method for preparing aging-resistant PHA biodegradable straws includes the following steps: extruding and drawing the aging-resistant PHA biodegradable material, cooling and shaping it with cooling water at 15-30℃, keeping it at 80-100℃ for 20-30 minutes, cooling it to room temperature, and then cutting it to obtain the aging-resistant PHA biodegradable straw.

[0032] By adopting the above technical solution, through extrusion, traction, and cooling shaping, the aging-resistant PHA biodegradable material forms fine and uniform microcrystals under the action of nucleating agent. The subsequent heat preservation treatment allows the material to complete residual and possible secondary crystallization under controlled conditions, so that the material reaches a stable crystallization state, thereby obtaining an aging-resistant PHA biodegradable straw.

[0033] The straw is cooled and shaped using cooling water at 15-30℃. When the water temperature is too high, the cooling rate of the material is too slow, giving the PHA molecular chains ample time to align and migrate. This provides a large space and driving force for subsequent secondary crystallization at room temperature, leading to increased brittleness of the PHA biodegradable material during storage. When the water temperature is too low, a large number of molecular chain segments do not have time to align and enter the crystal lattice, and are "frozen" in a disordered amorphous state. At this time, the material is in a highly thermodynamically metastable state. During subsequent heat preservation treatment or room temperature storage, these frozen chain segments and fine crystals have a very strong tendency to rearrange and undergo secondary crystallization, which increases the brittleness of the PHA biodegradable material.

[0034] In summary, this application includes at least one of the following beneficial technical effects: 1. This application improves flexibility by introducing PBAT, and then induces the formation of a large number of small and uniform crystal nuclei and achieves rapid crystallization by adding nucleating agents and modified lignin. On the other hand, it can block the migration path and nucleation conditions required for the rearrangement of PHA molecular chains to form secondary crystals at room temperature, significantly reducing the probability of secondary crystallization of PHA materials at room temperature and improving the aging resistance of PHA degradable materials. 2. This application selects lactate as a nucleating agent. Calcium lactate contains a lactate structure, which is similar to the structure of PHA segments, enabling the formation of highly efficient heterogeneous nucleation centers and promoting rapid and complete crystallization of PHA. Simultaneously, the calcium ions in calcium lactate can also coordinate and crosslink with the phosphate groups in modified lignin, forming "lignin-Ca..." 2+The multi-network structure of "-lactic acid ion / PHA" allows calcium ions to act as "bridging points" to connect lignin and PHA molecular chains more firmly. This not only improves the interfacial bonding between lignin and the PHA matrix but also further restricts the movement of PHA amorphous chain segments. The calcium-phosphorus complex on the lignin surface can serve as a more efficient heterogeneous nucleation point, synergistically promoting crystallization with free calcium lactate. 3. This application incorporates vitamin E, a natural and highly effective chain-terminating antioxidant. Its molecular structure contains a benzodihydropyran ring and a phenolic hydroxyl group. The phenolic hydroxyl group can provide hydrogen ions to active free radicals to generate stable tocopherol free radicals, thereby terminating the free radical chain reaction. Furthermore, the tocopherol free radicals can synergistically interact with hindered phenolic antioxidants to achieve reduction and regeneration, further extending the antioxidant lifespan. Detailed Implementation

[0035] The raw materials in this application include the following: PHA: Uses product brand Blue Crystal from Blue Crystal Biotechnology Co., Ltd. TM Commercially available products of PHA BH2-ES004; PBAT: Uses commercially available product with brand name BX7011 from Suzhou Guoyao New Materials Co., Ltd.; Calcium lactate: Food-grade calcium lactate from Zhengzhou Ruipu Bioengineering Co., Ltd. is used; Cyclodextrin: Food-grade β-cyclodextrin from Sichuan Huayuan Shengtai Biotechnology Co., Ltd. Zinc stearate: Food-grade zinc stearate from Jiangsu Jiujia Biotechnology Co., Ltd. Hindered phenolic antioxidants: This application uses antioxidant 1010, catalog number S67391, from Shanghai Yuanye Biotechnology Co., Ltd. Sulfate lignin: The product used is MDH, a commercially available product from Hubei Maidehao Biotechnology Co., Ltd. Sodium phytate hydrate: The product used is a commercially available product from Huangshan Shengfeng Technology Co., Ltd. Montana wax: The product used is the commercially available product with model number LicowaxE from Guangzhou Yinuo Chemical Technology Co., Ltd. Chain extender: This application uses Relysorb™ 4400, a commercially available product from Yantai Ruilaien New Materials Co., Ltd.; Vitamin E: Food-grade Vitamin E from Leshengyuan Biotechnology (Nanjing) Co., Ltd.

[0036] Preparation Example 1 A method for preparing silane-modified lignin includes the following steps: A1. KH-560 and anhydrous ethanol are mixed at a mass ratio of 1:2. After stirring and dissolving, deionized water is added to obtain a silane hydrolysate. The mass ratio of deionized water to KH-560 is 25:1. A2. After drying sulfate lignin at 70℃ for 60 min, silane hydrolysate is sprayed onto the surface of the dried sulfate lignin while stirring at 700 r / min. After spraying, the mixture is stirred at 1200 r / min and 70℃ for 3 h. After drying, it is dried in an oven at 90℃ for 6 h to obtain silane-modified lignin. The amount of KH-560 used accounts for 3% of the mass of sulfate lignin.

[0037] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0038] Example 1

[0039] A method for preparing an age-resistant, PHA-degradable straw includes the following steps: S1. Dry PHA, PBAT and modified lignin at 70℃ for 5h. Then add 80kg PHA, 20kg PBAT and 8kg phytic acid modified lignin and stir at 300r / min for 3min. Then add 0.3kg calcium lactate (nucleating agent), 0.3kg hindered phenolic antioxidant, 1kg montmorillonite wax and 0.6kg chain extender in sequence and stir at 1000r / min until uniform to obtain the mixture. S2. The mixture is fed into a twin-screw extruder for melt blending, extrusion, and granulation to obtain an aging-resistant PHA biodegradable material. The temperature of the twin-screw extruder is 165℃ in zone 1, 167℃ in zone 2, 172℃ in zone 3, 173℃ in zone 4, 167℃ in zone 5, and 167℃ in zone 6. The screw speed is 250 r / min. S3. The aging-resistant PHA biodegradable material is fed into a single-screw extruder for extrusion and pulled by a traction machine at a speed of 10m / min. It is then cooled and shaped by passing through a 6m long quench water tank with a water temperature of 25℃. Subsequently, it is kept at 90℃ for 25min. After cooling to room temperature, it is cut into 200mm pieces to obtain the aging-resistant PHA biodegradable straw. The temperature of the single-screw extruder is 158℃ in zone one, 165℃ in zone two, 168℃ in zone three, 167℃ in the die head, 166℃ in the die opening, and the wall thickness is 1mm.

[0040] The preparation method of phytic acid-modified lignin includes the following steps: Step 1: Disperse sulfate lignin in deionized water, adjust the pH to 12 with 1M sodium hydroxide, and stir at 500r / min for 60min in a 25℃ constant temperature water bath to obtain the first mixture; Step 2: Dissolve sodium phytate hydrate in deionized water at a solid content of 18%, stir evenly at 300 r / min at 25℃, add to the first mixture, adjust the pH to 11, stir in a water bath at 25℃ for 25 min, then adjust the pH to 7 with 1M sulfuric acid, then dialyze the neutralized product in deionized water for 48 h, and dry in an oven at 60℃ until the moisture content is ≤2% to obtain phytate modified lignin, wherein the molar ratio of lignin to phytate is 1:0.4.

[0041] Example 2-3 Examples 2-3 are based on the preparation method of Example 1, with adjustments made to the components of the aging-resistant PHA biodegradable straw, as shown in Table 1.

[0042] Comparative Examples 1-3 Comparative Examples 1-3 were prepared based on the method in Example 1, with adjustments made to the components of the aging-resistant PHA biodegradable straws, as shown in Table 1.

[0043] Performance testing The aging-resistant PHA biodegradable pipettes of Examples 1-3 and Comparative Examples 1-3 were analyzed using the following specific testing methods: 1. Physical aging The elongation at break of the aging-resistant PHA biodegradable straw was tested according to the standard test method specified in GB / T1040-2006 to obtain the elongation at break before storage. Then, the elongation at break of the aging-resistant PHA biodegradable straw was tested again after being stored at 30±5℃ for half a year to obtain the elongation at break after storage, thus obtaining the physical aging resistance retention rate of the aging-resistant PHA biodegradable straw.

[0044] Based on the above detection method, the test results of Examples 1-3 and Comparative Examples 1-3 were obtained, as shown in Table 1 below.

[0045] Table 1. Components and performance test results of the aging-resistant PHA biodegradable straws of Examples 1-3 and Comparative Examples 1-3.

[0046] Referring to Table 1, a comparison of Examples 1-3 and Comparative Examples 1-3 shows that the performance of the aging-resistant PHA biodegradable straws of Examples 1-3 is better than that of the aging-resistant PHA biodegradable straws of Comparative Examples 1-3. This may be because the introduction of PBAT improves flexibility, and the addition of nucleating agents and modified lignin induces the formation of a large number of small and uniform crystal nuclei and achieves rapid crystallization. On the other hand, it can block the migration path and nucleation conditions required for the rearrangement of PHA molecular chains to form secondary crystals at room temperature, significantly reducing the probability of secondary crystallization of PHA straws at room temperature and improving the aging resistance of PHA biodegradable straws.

[0047] Example 4 Example 4 is based on the preparation method of Example 1, but the phytic acid modified lignin is replaced in equal amounts with the silane modified coupling agent prepared in Preparation Example 1, and the other conditions remain unchanged.

[0048] Performance testing The aging-resistant PHA biodegradable pipettes from Examples 1 and 4 were analyzed using the following specific testing methods: 1. Resistant to thermal oxidation The PHA biodegradable straw samples were placed in a thermal aging test chamber and exposed at 80°C for 7 days. The samples were then removed, and the elongation at break of the aging-resistant PHA biodegradable straws was tested according to the standard test method specified in GB / T1040-2006 to obtain the thermal oxidation retention rate.

[0049] Based on the above detection method, the test results of Examples 1 and 4 were obtained, as shown in Table 2 below.

[0050] Table 2 Performance test results for Examples 1 and 4

[0051] Referring to Table 2, a comparison of Examples 1 and 4 shows that the performance of the aging-resistant PHA biodegradable straw obtained in Example 1 is superior to that of the aging-resistant PHA biodegradable straw material obtained in Example 4. This may be because the modification of lignin with phytic acid introduces a large number of phosphate groups on the surface of lignin, which can form hydrogen bonds with multiple ester carbonyl groups and terminal hydroxyl groups on the PHA molecular chain, forming a multi-point network anchoring structure, restricting the movement and rearrangement of PHA at room temperature. Furthermore, the phosphate groups can preferentially capture free metal ions in the system and fix them on the surface of lignin. The complexed metal ions lose their activity and cannot catalyze ester bond exchange reactions or induce rearrangement of PHA chain segments, thus inhibiting the secondary crystallization of the PHA biodegradable straw. At the same time, since phosphate contains phosphate ester groups, the P=O bonds in the phosphate ester groups are polar and can undergo addition reactions with free radicals to generate relatively stable phosphorus-oxygen free radical adducts. The phenolic hydroxyl groups in lignin can quench free radicals to generate phenoxy free radicals, and the phosphate groups can further stabilize phenoxy free radicals, inhibiting them from initiating new chain reactions, forming a phenol-phosphorus synergistic antioxidant cycle.

[0052] Examples 5-8 Examples 5-8 are based on the preparation method of Example 1, but the molar ratio of lignin to phytic acid is adjusted as shown in Table 3.

[0053] Performance testing The aging-resistant PHA biodegradable pipettes from Examples 1 and 5-8 were analyzed using the following specific testing methods: 1. Water absorption rate The water absorption test of the straw material was carried out according to the standard test method specified in GB / T 1034-2008. Deionized water at 23℃ was used as the reagent, the soaking time was 24 hours, and the material was weighed after draining for 30 minutes to calculate the water absorption rate.

[0054] Based on the above detection method, the test results of Examples 1 and 5-8 were obtained, as shown in Table 3 below.

[0055] Table 3. Molar ratio of lignin to phytic acid and its performance test results in Examples 1 and 5-8.

[0056] Referring to Table 3, comparing Examples 1 and 5-8, it can be seen that when the molar ratio of lignin to phytic acid is between 1:0.2 and 0.6, especially when the molar ratio of lignin to phytic acid is 1:0.4, the resulting aging-resistant PHA biodegradable straw exhibits the best performance. This may be because when the proportion of lignin is too high, the effective grafting sites on the lignin surface are not fully occupied, resulting in a low degree of modification of the obtained modified lignin and poor compatibility with the matrix. This leads to a decrease in the toughness of the PHA biodegradable straw material and a decrease in the anchoring ability of PHA segments. The PHA biodegradable straw is prone to secondary crystallization at room temperature, resulting in an increase in the brittleness of the PHA biodegradable straw. When the proportion of lignin is too low, the amount of phytic acid added is too high, causing excessive cross-linking of lignin molecules and the introduction of too many phosphate groups on the lignin surface. This significantly increases the hydrophilicity and polarity of the modified lignin surface, worsens the compatibility with the PHA matrix, and reduces the elongation at break of the resulting aging-resistant PHA biodegradable straw.

[0057] Examples 9-10 Examples 9-10 are based on the preparation method of Example 1, but the components of the nucleating agent are adjusted as shown in Table 4.

[0058] The aging-resistant PHA biodegradable straws of Examples 9-10 were subjected to the above performance tests, and the test results are shown in Table 4.

[0059] Table 4. Nucleating agents and their performance test results for Examples 1 and 9-10

[0060] Referring to Table 4, a comparison of Examples 1 and 9-10 shows that the performance of the PHA-resistant biodegradable straw obtained in Example 1 is superior to that obtained in Examples 9-10. This may be because calcium lactate contains lactate groups, which are similar in structure to PHA segments, enabling the formation of efficient heterogeneous nucleation centers that promote rapid and complete crystallization of PHA. Simultaneously, the calcium ions in calcium lactate can coordinate and crosslink with the phosphate groups in the modified lignin, forming "lignin-Ca..." 2+ The multi-network structure of "-lactic acid ion / PHA" allows calcium ions to act as "bridging points," connecting lignin and PHA molecular chains more firmly. This not only improves the interfacial bonding between lignin and the PHA matrix but also further restricts the movement of PHA amorphous chain segments. The calcium-phosphorus complex on the lignin surface can serve as a more efficient heterogeneous nucleation site, synergistically promoting crystallization with free calcium lactate.

[0061] Example 11 In Example 11, based on the preparation method of Example 1, 0.6 kg of vitamin E, PHA, PBAT, nucleating agent, hindered phenolic antioxidant, modified lignin, montan wax and chain extender were added to S1 and stirred to obtain a mixture, with the other conditions remaining unchanged.

[0062] The aging-resistant PHA biodegradable straws of Example 11 were subjected to the above performance tests, and the test results are shown in Table 5.

[0063] Table 5 Performance test results for Examples 1 and 11

[0064] Referring to Table 5, a comparison of Example 1 and Example 11 shows that the addition of vitamin E significantly improved the performance of the aging-resistant PHA biodegradable straw. This may be because the vitamin E molecule contains a benzodihydropyran ring and a phenolic hydroxyl group. The phenolic hydroxyl group can provide hydrogen ions to active free radicals to generate stable tocopherol free radicals, thereby terminating the free radical chain reaction. Furthermore, the tocopherol free radicals can synergistically interact with hindered phenolic antioxidants to achieve reduction and regeneration, further extending the antioxidant lifespan. At the same time, vitamin E can also form a "phenol-phosphorus-tocopherol" ternary synergy with phytic acid-modified lignin. After capturing free radicals through the phenolic hydroxyl group of lignin, phenoxy free radicals are generated, which vitamin E can reduce and regenerate. The phosphorus-centered free radical adduct of phytate can undergo electron transfer with vitamin E, restoring the activity of the phosphorus center. The three form a cyclic regeneration system, significantly extending the antioxidant duration.

[0065] Examples 12-15 Examples 12-15 are based on the preparation method of Example 1, but the temperature of the cooling water is adjusted as shown in Table 6.

[0066] The aging-resistant PHA biodegradable straws from Examples 12-15 were subjected to the above performance tests, and the test results are shown in Table 6.

[0067] Table 6. Water temperature and performance test results of the quenching tanks in Examples 1 and 12-15.

[0068] Referring to Table 6, a comparison of Examples 1 and 12-15 shows that the aging-resistant PHA biodegradable straws exhibit the best performance when the water temperature in the quenching bath is in the range of 15-30℃, especially when the water temperature is 25℃. This may be because when the water temperature is too high, the material cools too slowly, allowing sufficient time for the PHA molecular chains to arrange and migrate, leaving ample space and driving force for subsequent secondary crystallization at room temperature, resulting in increased brittleness of the PHA biodegradable straws during storage. When the water temperature is too low, a large number of molecular chain segments do not have time to arrange themselves neatly into the crystal lattice and are "frozen" in a disordered amorphous state. During subsequent heat preservation treatment or room temperature storage, these frozen chain segments and fine crystals have a very strong tendency to rearrange and undergo secondary crystallization, increasing the brittleness of the PHA biodegradable straw material.

[0069] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A PHA-resistant biodegradable material, characterized in that, The raw materials include the following parts by weight: 70-85 parts PHA, 15-30 parts PBAT, 0.1-0.5 parts nucleating agent, 0.1-0.5 parts hindered phenolic antioxidant, 5-10 parts modified lignin, 0.5-1.5 parts montan wax, and 0.3-1 parts chain extender.

2. The aging-resistant PHA biodegradable material according to claim 1, characterized in that, The modified lignin is phytic acid-modified lignin, and the preparation method of the phytic acid-modified lignin includes the following steps: Step 1: Disperse lignin in deionized water and adjust the pH to 12, stirring to obtain the first mixture; Step 2: Dissolve sodium phytate hydrate in deionized water, stir well, add to the first mixture, adjust the pH to 11, stir in a water bath at 20-30℃ for 15-30 minutes, adjust the pH to 7, purify and dry to obtain phytate modified lignin.

3. The aging-resistant PHA biodegradable material according to claim 2, characterized in that, The molar ratio of lignin to phytic acid is 1:0.2-0.

6.

4. The aging-resistant PHA biodegradable material according to claim 3, characterized in that, The lignin is sulfate lignin.

5. The aging-resistant PHA biodegradable material according to claim 2, characterized in that, The nucleating agent is at least one of calcium lactate, cyclodextrin, and zinc stearate.

6. The aging-resistant PHA biodegradable material according to claim 5, characterized in that, The nucleating agent is calcium lactate.

7. The aging-resistant PHA biodegradable material according to claim 2, characterized in that, It also contains added vitamin E.

8. A method for preparing an aging-resistant PHA biodegradable material according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Dry PHA, PBAT and modified lignin at 60-80℃ for 4-6 hours. Then, stir and mix the formulated amounts of PHA, PBAT, nucleating agent, hindered phenolic antioxidant, modified lignin, montan wax and chain extender to obtain a mixture. S2. The mixture is melt-blended, extruded, and granulated to obtain an aging-resistant PHA biodegradable material.

9. The method for preparing an aging-resistant PHA biodegradable material according to claim 8, characterized in that, In S1, the prescribed amounts of vitamin E, PHA, PBAT, nucleating agent, hindered phenolic antioxidant, modified lignin, montan wax, and chain extender are added and mixed to obtain a mixture.

10. The application of the aging-resistant PHA biodegradable material according to any one of claims 1-7 in the preparation of aging-resistant PHA biodegradable straws, characterized in that, The preparation method of the aging-resistant PHA biodegradable straw includes the following steps: extruding and drawing the aging-resistant PHA biodegradable material, cooling and shaping it with cooling water at 15-30℃, keeping it at 80-100℃ for 20-30 minutes, cooling it to room temperature, and then cutting it to obtain the aging-resistant PHA biodegradable straw.

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