Low-temperature resistant crystalline straw and preparation method thereof

Abstract

The application relates to the field of straw technology, in particular to a low-temperature-resistant crystallization straw and a preparation method thereof, the low-temperature-resistant crystallization straw comprises the following components in parts by weight: PLA, 5-15 parts of PBS, 5-10 parts of PBAT, 1-35 parts of inorganic mineral powder, 0.1-0.6 parts of an alcoholysis agent, 1-3 parts of a compatilizer, 0.1-0.5 parts of an antioxidant and 0.1-1 parts of a nucleating agent; the compatilizer is a biodegradable polyester containing an epoxy functional group. The brittleness of PLA is offset by the introduction of PBA and PBAT, then the PLA is cut and the short-chain end of the PLA rich in hydroxyl and carboxyl is formed by adding the alcoholysis agent, the epoxy group of the compatilizer is opened, the originally incompatible PLA phase and the PBA / PBAT phase are chemically bonded, finally the crystallization rate and the crystallinity of the PLA are improved by the cooperation between the nucleating agent and the inorganic mineral powder, the low-temperature resistance of the crystallization straw is effectively improved, and the raw materials of the application are various degradable materials, which are helpful to realize the degradability of the low-temperature-resistant crystallization straw.

Description

Technical Field

[0001] This application relates to the field of straw technology, and in particular to a low-temperature crystallization resistant straw and its preparation method. Background Technology

[0002] In the field of plastic products, straws are a common and widely used product, widely used in the catering industry, providing convenience for people to drink liquids.

[0003] Polylactic acid (PLA), a bio-based polyester derived from renewable resources such as corn and sugarcane, is widely recognized as one of the ideal materials for making environmentally friendly straws due to its excellent biodegradability, good transparency and gloss, and compliance with food contact safety standards. However, PLA is prone to crystallization at low temperatures. This not only makes the straws easily brittle and prone to breakage when bent or compressed, but also makes them susceptible to damage from slight impacts during low-temperature distribution processes such as filling, storage, and transportation, seriously affecting the product's performance. Summary of the Invention

[0004] To improve the low-temperature resistance of straws, this application provides a low-temperature resistant crystallization straw and its preparation method.

[0005] Firstly, this application provides a low-temperature crystallization pipette, which adopts the following technical solution: A low-temperature resistant crystallization pipette comprises the following components in parts by weight: PLA 90-110 parts, PBS 5-15 parts, PBAT 5-10 parts, inorganic mineral powder 1-35 parts, alcoholysis agent 0.1-0.6 parts, compatibilizer 1-3 parts, antioxidant 0.1-0.5 parts, and nucleating agent 0.1-1 parts; The compatibilizer is a biodegradable polyester containing epoxy functional groups.

[0006] By adopting the above technical solution, PLA, as the main component, can provide basic rigidity, but its brittleness at low temperatures is significant. Therefore, PBS and PBAT, both of which are flexible aliphatic polyesters, are introduced to impart excellent toughness to the blend system, offsetting the brittleness of PLA. This allows the material to maintain chain segment mobility at low temperatures. The addition of the alcoholysis agent breaks the long molecular chains of PLA, generating more terminal hydroxyl and carboxyl groups, thereby "activating" PLA. The resulting short chain ends of PLA will undergo ring-opening reactions with the epoxy groups of the compatibilizer, causing the originally incompatible PLA phase to chemically bond with the PBS / PBAT phase, greatly enhancing the adhesion between the phase interfaces and effectively improving low-temperature toughness. Finally, through the combined action of the nucleating agent and inorganic mineral powder, the crystallization rate and crystallinity of PLA are improved. The regular and fine crystal structure can effectively prevent crack propagation. Through the combination of the above multi-components, a crystallization straw with ideal low-temperature resistance is obtained.

[0007] This application counteracts the brittleness of PLA by introducing PBA and PBAT, and then uses the addition of an alcoholysis agent to cleave PLA and form short chain ends rich in hydroxyl and carboxyl groups. These chains open with the epoxy groups of the compatibilizer, causing the originally incompatible PLA phase to chemically bond with the PBA / PBAT phase. Finally, through the combination of nucleating agent and inorganic mineral powder, the crystallization rate and crystallinity of PLA are improved, effectively enhancing the low-temperature resistance of the crystallization pipette. Furthermore, the raw materials used in this application are a variety of biodegradable materials, which helps to achieve the biodegradability of the low-temperature resistant crystallization pipette.

[0008] Preferably, the alcoholysis agent is at least one selected from ethylene glycol, propylene glycol, and glycerol.

[0009] By adopting the above technical solution, the hydroxyl groups on the alcoholysis agent molecule can undergo an "alcohololysis reaction" with the molecular chains of polyesters such as PLA, PBS, and PBAT, "cutting" the long polyester chains and generating more shorter molecular chains with active groups at the ends.

[0010] Ethylene glycol has small molecules and good fluidity. Its two terminal hydroxyl groups are highly reactive and have no steric hindrance, which can "cut" polyester chains very efficiently, making it a powerful viscosity reducer.

[0011] The methyl side chain in the propylene glycol molecule can produce a slight steric hindrance effect, making the attack between its hydroxyl pairs less "rapid" than that of ethylene glycol. This allows it to effectively improve the flowability of the material during processing and makes it easier to stabilize the reduction in molecular weight within an ideal range, thus better maintaining the final mechanical properties of the product.

[0012] Glycerol has three active hydroxyl groups. In addition to "cutting" the molecular chains of polyester, these hydroxyl groups may also form a small number of branch points between the molecular chains, which may further improve the toughness of the crystallization straw at low temperatures.

[0013] Preferably, the compatibilizer is at least one of GMA-PLA, GMA-PBS, and GMA-PBAT.

[0014] By adopting the above technical solution, GMA-PLA uses PLA as the main chain and grafts GMA epoxy functional groups, which can be compatible with PLA in the matrix. The epoxy end of GMA can react with the active ends of PLA produced by alcoholysis, and can also react with the ends of PBS / PBAT. While strengthening the PLA matrix itself, it firmly captures the flexible phase particles of PBS / PBAT.

[0015] GMA-PBS uses PBS as the main chain and grafts GMA epoxy functional groups, which can be well entangled into the interior of PBS flexible phase particles, strongly anchored in the PBS phase, and establish chemical connections with the PLA matrix from the inside of the PBS phase outward, effectively transferring and dissipating the stress between the PBS phase and the PLA phase.

[0016] GMA-PBAT uses PBAT as the main chain and grafts GMA epoxy functional groups, which can be well integrated into the PBAT phase, ensuring that the PBAT phase and PLA phase matrix achieve optimal chemical adhesion, fully leveraging the toughening potential of PBAT, and preventing PBAT particles from separating from PLA under impact.

[0017] Preferably, the mass ratio of the compatibilizer to the alcoholysis agent is 1:0.1-0.3.

[0018] By adopting the above technical solution, when the amount of compatibilizer added is too large, the excessive epoxy groups may compete with or over-react with the alcoholysis agent, interfering with the normal regulation of polyester molecular weight by the alcoholysis agent, and may even cause local cross-linking, leading to an increase in the brittleness of the crystallization straw. Furthermore, the excess compatibilizer may form self-polymerized "micelles" in a certain phase, becoming a new stress defect point and damaging the mechanical strength of the crystallization straw.

[0019] When the amount of compatibilizer added is too small, the compatibilizer cannot fully "stitch" the interface between PLA and flexible phases such as PBS / PBAT, resulting in weak phase interface bonding and coarse dispersed phase particles. This makes it impossible to effectively transfer stress, causing the crystallizer to easily crack at the interface at low temperatures, resulting in a decrease in the low-temperature toughness of the crystallizer.

[0020] Preferably, cyclic lactide is also added.

[0021] By employing the above technical solution, cyclic lactide can undergo in-situ ring-opening polymerization under the initiation of hydroxyl groups generated from residual alcoholysis in the system during processing and molten state. This generates new PLA segments with narrower molecular weights. These newly formed PLA segments are highly active and can repair PLA molecular chains that may have been excessively cleaved by the alcoholysis agent, preventing excessive loss of matrix strength. Simultaneously, they can form new entanglements with the flexible phase, improving toughness. Furthermore, the ends of the newly formed PLA segments still contain active hydroxyl or carboxyl groups, allowing them to continue reacting with compatibilizers containing epoxy functional groups. This adds more and denser "chemical anchoring points" between the PLA phase and the PBS / PBAT phase, making the "molecular bridge" network constructed by the compatibilizer more complete and robust, effectively improving the low-temperature toughness of the crystallization pipette.

[0022] Preferably, the inorganic mineral powder is aminosilane-modified calcium carbonate.

[0023] By adopting the above technical solution, calcium carbonate itself is non-toxic and odorless, meeting the environmental protection requirements for food contact and biodegradable products. Furthermore, an appropriate amount of calcium carbonate can improve the rigidity and dimensional stability of polymers. Modifying the surface of calcium carbonate with an aminosilane coupling agent effectively solves the problems of easy aggregation and poor compatibility with polymers caused by the large number of hydroxyl groups on the surface of calcium carbonate. Moreover, aminosilane-modified calcium carbonate can act as a highly efficient heterogeneous nucleating agent, significantly improving the crystallization rate and crystallinity of PLA and preventing crack propagation. The epoxy groups of the compatibilizer can also react simultaneously with the amino groups on the surface of aminosilane-modified calcium carbonate and the terminal groups of PBA / PBAT, forming a strong and tough interface of "calcium carbonate-compatible-flexible phase," ensuring the effective transfer and dissipation of impact energy.

[0024] The amino groups on the surface of aminosilane-modified calcium carbonate can also initiate the ring-opening polymerization of cyclic lactide. This can promote the ring-opening polymerization of cyclic lactide on and near the surface of calcium carbonate particles, generating new PLA segments. These newly formed PLA segments can be tightly "anchored" to the calcium carbonate particles through physical entanglement or interaction with unreacted amino groups on the calcium carbonate surface. Furthermore, the newly formed PLA segments can work together with the matrix PLA to synergistically promote PLA crystallization at the nucleation sites provided by the calcium carbonate particles, thereby increasing the crystallization rate and crystallinity of the composite material. It tends to form a microcrystalline structure with smaller crystal size and more uniform distribution. This dense and fine crystal network is the key to the material's resistance to brittle fracture and maintenance of toughness at low temperatures.

[0025] Preferably, the mass ratio of the cyclic lactide to the aminosilane-modified calcium carbonate is 1:5-10.

[0026] By adopting the above technical solution, when the amount of cyclic lactide added is too small, the cyclic lactide cannot form a sufficiently thick and continuous PLA organic coating layer on the surface of aminosilane-modified calcium carbonate, which greatly reduces the heterogeneous nucleation effect of calcium carbonate and has limited effect on improving the crystallization rate and crystallinity of PLA, resulting in an insignificant improvement in the low-temperature toughness of the crystallization pipette. When the amount of cyclic lactide added is too large, the excess cyclic lactide cannot be effectively anchored on the aminosilane-modified calcium carbonate. A large number of free PLA short chains will act as a strong plasticizer, seriously interfering with the regular arrangement of PLA molecular chains, resulting in a decrease in the crystallinity of the matrix and a reduction in the structural strength of the material.

[0027] Preferably, the nucleating agent is at least one of inorganic nucleating agents, amide nucleating agents, acylhydrazine nucleating agents, and organophosphate nucleating agents.

[0028] By adopting the above technical solution, the inorganic nucleating agent mainly relies on its huge specific surface area and regular surface crystal structure. Its surface can serve as a template to reduce the nucleation free energy of PLA through the interface effect, thereby inducing the molecular chains to adsorb and arrange in an orderly manner on the surface.

[0029] The amide groups in amide nucleating agents can form hydrogen bonds or dipole interactions with the ester groups of PLA, which can more effectively induce and "fix" PLA segments, aligning them in a specific direction, greatly reducing the nucleation energy barrier and effectively refining the grains.

[0030] Acylhydrazide nucleating agents contain multiple acylhydrazide groups in their molecules, which can form a dense hydrogen bond network with PLA, providing a large number of nucleation sites. Their molecular structure is usually symmetrical and rigid, which can provide a more stable and regular arrangement template for PLA chain segments, resulting in extremely high nucleation efficiency.

[0031] The role of organophosphate nucleating agents depends not only on hydrogen bonding but also on their unique self-assembly behavior. In PLA melt, they can aggregate into nanoscale fibrous or sheet-like structures. These supramolecular assemblies have a huge specific surface area and abundant ionic / polar sites, enabling them to adsorb and induce PLA molecular chain nucleation with ultra-high efficiency, significantly improving the PLA crystallization rate and crystallinity.

[0032] Secondly, the method for preparing a low-temperature resistant crystallization pipette provided in this application adopts the following technical solution: A method for preparing a low-temperature resistant crystallization pipette includes the following steps: S1. The formulated amounts of PLA, PBS, PBAT, inorganic mineral powder, alcoholysis agent, compatibilizer, antioxidant and nucleating agent are blended together to obtain a mixture; S2. The mixture is melted, extruded, and granulated to obtain straw material; S3. Extrude the straw material, and after cooling and setting, cut it into a preset length and heat-treat it at 80-110℃ to obtain a low-temperature resistant crystallization straw.

[0033] By adopting the above technical solution, multiple components are mixed to achieve complementary and enhanced performance. Then, through the process of "extrusion molding + low temperature heat treatment", the PLA molecular chains that did not have time to crystallize or were incompletely crystallized during the rapid extrusion cooling process can obtain sufficient energy in the solid state to undergo secondary rearrangement and crystallization, which further greatly improves the overall crystallinity of the straw, thereby producing a high-performance low temperature crystallization straw.

[0034] Preferably, in S2, the formulated amount of cyclic lactide is added and mixed with the mixture, then melted, extruded, and granulated to obtain the straw material.

[0035] By adopting the above technical solution, cyclic lactide is added to S2 and melted with the mixture. Under the high temperature and shear action of the melt extrusion section, the existing alcoholysis agent, water or residual catalyst in the system can initiate the ring-opening polymerization of cyclic lactide, effectively "stitching" the phase interface and playing the role of a highly efficient "reactive compatibilizer".

[0036] In summary, this application includes at least one of the following beneficial technical effects: 1. This application counteracts the brittleness of PLA by introducing PBA and PBAT, and then the addition of an alcoholysis agent causes PLA to be cleaved and form short chain ends rich in hydroxyl and carboxyl groups, which open the ring with the epoxy group of the compatibilizer, so that the originally incompatible PLA phase is chemically bonded to the PBA / PBAT phase. Finally, through the combination of nucleating agent and inorganic mineral powder, the crystallization rate and crystallinity of PLA are improved, effectively improving the low temperature resistance of the crystallization pipette. In addition, the raw materials used in this application are a variety of biodegradable materials, which helps to achieve the biodegradability of the low temperature resistant crystallization pipette. 2. This application utilizes the addition of cyclic lactide. In the molten state during processing, the cyclic lactide undergoes in-situ ring-opening polymerization initiated by hydroxyl groups generated from residual alcoholysis in the system, generating new PLA segments with narrower molecular weights. These newly formed PLA segments possess high activity, capable of repairing PLA molecular chains that may have been excessively cleaved by the alcoholysis agent, preventing excessive loss of matrix strength. Simultaneously, they can form new entanglements with the flexible phase, enhancing toughness. Furthermore, the ends of the newly formed PLA segments still contain active hydroxyl or carboxyl groups, allowing them to continue reacting with compatibilizers containing epoxy functional groups. This adds more and denser "chemical anchoring points" between the PLA phase and the PBS / PBAT phase, making the "molecular bridge" network constructed by the compatibilizer more complete and robust, effectively improving the low-temperature toughness of the crystallization pipette. 3. This application selects aminosilane-modified calcium carbonate as the inorganic mineral powder. The amino groups on the surface of aminosilane-modified calcium carbonate can also initiate the ring-opening polymerization of cyclic lactide, which can promote the ring-opening polymerization of cyclic lactide on and near the surface of calcium carbonate particles to generate new PLA segments. These newly generated PLA segments can be tightly "anchored" to the calcium carbonate particles through physical entanglement or interaction with unreacted amino groups on the surface of calcium carbonate. Furthermore, the newly generated PLA segments can work together with the matrix PLA to synergistically promote PLA crystallization at the nucleation sites provided by the calcium carbonate particles, thereby improving the crystallization rate and crystallinity of the composite material and tending to form a microcrystalline structure with smaller crystal size and more uniform distribution. This dense and fine crystal network is the key to the material resisting brittle fracture and maintaining toughness at low temperatures. Detailed Implementation

[0037] The raw materials in this application include the following: PLA: The product used is REVODE190, a commercially available product from Zhejiang Hisun Biomaterials Co., Ltd. PBS: The product used is commercially available from Dongguan Caihua Plastics Technology Co., Ltd., with the brand name FZ91PM. PBAT: Uses commercially available product with brand name BX7011 from Suzhou Guoyao New Materials Co., Ltd.; Calcium carbonate: Calcium carbonate with a particle size of 300-800 nm is selected. This application takes calcium carbonate with a particle size of 500 nm as an example. Aminosilane coupling agents: This application takes KH-550 with CAS number 919-30-2 as an example; Propylene glycol: Uses commercially available product with CAS number 57-55-6; GMA-PLA: GMA-PLA from Dongguan Zhangmutou Hengtai Plastic Raw Materials Business Department; GMA-PBAT: GMA-PBAT from Dongguan Zhangmutou Hengtai Plastic Raw Materials Business Department; GMA: Uses commercially available products with CAS number 106-91-2; Antioxidants: Antioxidant 1010, antioxidant 168 and antioxidant 1076 can be selected. This application uses antioxidant 1010 with CAS number 6683-19-8. Inorganic nucleating agents: talc, kaolin, halloysite nanotubes, etc. can be selected. This application takes 1250 mesh talc as an example. Amide nucleating agent: TMC-300 from Hubei Langbowan Biomedical Co., Ltd. was used; Acylhydrazide nucleating agent: NA300 from Hubei Zhonglong Kangcheng Fine Chemical Co., Ltd. was used; Organophosphate nucleating agent: Nucleating agent NA11 from Hubei Hongxin Ruiyu Fine Chemical Co., Ltd. was used; Cyclic lactide: The commercially available product with CAS number 4511-42-6 is used.

[0038] Preparation Example 1 The preparation method of aminosilane-modified calcium carbonate includes the following steps: Step 1: Mix aminosilane coupling agent with anhydrous ethanol at a mass ratio of 1:15, add deionized water, and adjust the pH to 5 with acetic acid to obtain a silane solution, wherein the molar ratio of aminosilane coupling agent to water is 1:4. Step 2: Disperse the dried calcium carbonate in anhydrous ethanol at a solid-liquid ratio of 1:8, and sonicate for 20 minutes to obtain a calcium carbonate suspension. Step 3: Slowly add the silane solution dropwise to the calcium carbonate suspension and stir in a water bath at 70°C for 3 hours. After centrifugation, wash three times with anhydrous ethanol and dry at 100°C for 10 hours to obtain aminosilane-modified calcium carbonate.

[0039] Preparation Example 2 The preparation method of GMA-PBS includes the following steps: PBS, GMA and BPO are mixed evenly in a mass ratio of 100:10:1 to obtain a mixture. The mixture is fed into a twin-screw extruder and melt-blended, extruded and granulated at 150°C and 100 r / min to obtain GMA-PBS.

[0040] The present application will be further described in detail below with reference to embodiments and comparative examples. Example 1

[0041] A method for preparing a low-temperature resistant crystallization pipette includes the following steps: S1. 100 kg PLA, 10 kg PBS, 8 kg PBAT, 20 kg aminosilane-modified calcium carbonate, 0.4 kg propylene glycol, 2 kg GMA-PLA, 0.3 kg antioxidant, and 0.5 kg organophosphate nucleating agent are blended to obtain a mixture. S2. The mixture is fed into a twin-screw extruder for melting, extrusion, and granulation to obtain straw material. The temperature of the twin-screw extruder is 180℃ and the screw speed is 300r / min. S3. Extrude the straw material, and after cooling and setting, cut it into a preset length. Then, heat-treat it at 100°C for 4 hours to obtain a low-temperature resistant crystallization straw.

[0042] Example 2-3 Examples 2-3 are based on the preparation method of Example 1, but the components of the low-temperature crystallization pipette are adjusted, as shown in Table 1.

[0043] Comparative Examples 1-2 Comparative Examples 1-2 are based on the preparation method of Example 1, but the components of the low-temperature crystallization pipette are adjusted as shown in Table 1.

[0044] Performance testing The low-temperature crystallization pipettes of Examples 1-3 and Comparative Examples 1-2 were analyzed using the following specific testing methods: 1. Freezing crack rate The low-temperature crystallization pipettes were placed in a refrigerator with a pre-set constant temperature of -15°C and frozen for 4 hours. Then, they were immediately squeezed by hand, and the freezing crack rate of the pipettes was recorded. Fifty low-temperature crystallization pipettes were taken from each of the embodiments and comparative examples and frozen.

[0045] 2. Degradation rate Low-temperature crystallization pipettes were placed in a natural environment for natural degradation, and the degradation rate of each group of low-temperature crystallization pipettes was recorded after 3 months.

[0046] Based on the above detection method, the test results of Examples 1-3 and Comparative Examples 1-2 were obtained, as shown in Table 1 below.

[0047] Table 1. Components and performance test results of the low-temperature crystallization pipettes of Examples 1-3 and Comparative Examples 1-2.

[0048] Referring to Table 1, comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that the performance of the low-temperature crystallization pipettes of Examples 1-3 is significantly better than that of the low-temperature crystallization pipettes of Comparative Examples 1-2. This may be because the addition of the alcoholysis agent breaks the long molecular chain of PLA, generating more terminal hydroxyl and carboxyl groups, thereby "activating" PLA. The short chain ends of the generated PLA will undergo ring-opening reaction with the epoxy groups of the compatibilizer, so that the originally incompatible PLA phase and PBS / PBAT phase are chemically bonded together, greatly enhancing the adhesion between the phase interfaces and effectively improving the low-temperature toughness.

[0049] Examples 4-5 Examples 4-5 are based on the preparation method of Example 1, but the type of alcoholysis agent is adjusted, as shown in Table 2.

[0050] The low-temperature crystallization pipettes of Examples 4-5 were subjected to the above-mentioned performance tests, and the test results are shown in Table 2.

[0051] Table 2. Alcohololysis agents and their performance test results in Examples 1 and 4-5.

[0052] Referring to Table 2, a comparison of Examples 1 and 4-5 shows that propylene glycol, ethylene glycol, and glycerol can all be used as alcoholysis agents to improve the performance of low-temperature crystallization pipettes. Among them, Example 1 has the best performance. This may be because propylene glycol has a methyl side chain in its molecule, which can produce a slight steric hindrance effect, making its hydroxyl group attack less "rapid" than that of ethylene glycol. This allows it to effectively improve the material's processing fluidity while more easily stabilizing the degree of molecular weight reduction within an ideal range, thus better maintaining the final mechanical properties of the product.

[0053] Examples 6-7 Examples 6-7 are based on the preparation method of Example 1, but the types of compatibilizers are adjusted, as shown in Table 3.

[0054] The low-temperature crystallization pipettes of Examples 6-7 were subjected to the above-mentioned performance tests, and the test results are shown in Table 3.

[0055] Table 3. Compatibilizers and their performance test results in Examples 1 and 6-7

[0056] Referring to Table 3, a comparison of Examples 1 and 6-7 shows that GMA-PLA, GMA-PBS, and GMA-PBAT, as compatibilizers, can all improve the performance of low-temperature crystallization pipettes. Among them, Example 1 has the best performance. This may be because GMA-PLA has PLA as the main chain and grafts GMA epoxy functional groups, which can be compatible with PLA in the matrix. The epoxy end of its GMA can react with the active ends of PLA produced by alcoholysis, as well as with the ends of PBS / PBAT. While strengthening the PLA matrix itself, it firmly grasps the flexible phase particles of PBS / PBAT.

[0057] Examples 8-11 Examples 8-11 are based on the preparation method of Example 1, but with the amount of compatibilizer added remaining unchanged, the mixing mass ratio of compatibilizer and alcoholysis agent is adjusted as shown in Table 4.

[0058] The low-temperature crystallization pipettes of Examples 8-11 were subjected to the above-mentioned performance tests, and the test results are shown in Table 4.

[0059] Table 4. Mixing mass ratio of compatibilizer and alcoholysis agent and their performance test results in Examples 1 and 8-11.

[0060] Referring to Table 4, a comparison of Examples 1 and 8-11 shows that when the mass ratio of compatibilizer to alcoholysis agent is in the range of 1:0.1-0.3, especially when the mass ratio of compatibilizer to alcoholysis agent is 1:0.2, the resulting low-temperature resistant crystallization pipette exhibits the best performance. This may be because when the amount of compatibilizer added is too large, the excessive epoxy groups may compete with or over-react with the alcoholysis agent, interfering with the normal regulation of polyester molecular weight by the alcoholysis agent, leading to an increase in the brittleness of the crystallization pipette. Furthermore, excess compatibilizer may form self-polymerized "micelles" in a certain phase, becoming new stress defect points and damaging the mechanical strength of the crystallization pipette. When the amount of compatibilizer added is too small, the compatibilizer cannot fully "stitch" the interface between PLA and flexible phases such as PBS / PBAT, resulting in weak phase interface bonding and coarse dispersed phase particles, making it impossible to effectively transfer stress. This makes the crystallization pipette prone to cracking at the interface at low temperatures, leading to a decrease in the low-temperature toughness of the crystallization pipette.

[0061] Example 12 Example 12 is based on the preparation method of Example 1. In S2, cyclic lactide is added and mixed with the mixture, then melted, extruded and granulated to obtain the straw material. The other conditions remain unchanged. The mass ratio of cyclic lactide to aminosilane modified calcium carbonate is 1:8.

[0062] Examples 13-16 Examples 13-16 are based on the preparation method of Example 12, but with the mass of aminosilane-modified calcium carbonate remaining unchanged, the mixing mass ratio of cyclic lactide and aminosilane-modified calcium carbonate is adjusted as shown in Table 5.

[0063] The low-temperature crystallization pipettes of Examples 12-16 were subjected to the above-mentioned performance tests, and the test results are shown in Table 5.

[0064] Table 5. Mixing mass ratio and performance test results of cyclic lactide and aminosilane-modified calcium carbonate in Examples 1 and 12-16.

[0065] Referring to Table 5, a comparison of Examples 1 and 12 shows that the addition of cyclic lactide significantly improves the performance of the low-temperature crystallization pipette. This is likely because, in the molten state during processing, cyclic lactide can undergo in-situ ring-opening polymerization initiated by the hydroxyl groups generated from residual alcoholysis in the system, generating new PLA segments with narrower molecular weights. These newly formed PLA segments have high activity and can repair PLA molecular chains that may have been excessively cleaved due to the action of the alcoholysis agent, preventing excessive loss of matrix strength. At the same time, they can also form new entanglements with the flexible phase, improving toughness. Furthermore, the ends of the newly formed PLA segments still contain active hydroxyl or carboxyl groups, which can continue to react with compatibilizers containing epoxy functional groups, adding more and denser "chemical anchoring points" between the PLA phase and the PBS / PBAT phase. This makes the "molecular bridge" network constructed by the compatibilizer more complete and robust, effectively improving the low-temperature toughness of the crystallization pipette.

[0066] Comparative examples 12-16 show that when the mass ratio of cyclic lactide to aminosilane-modified calcium carbonate is in the range of 1:5-10, especially when the mass ratio is 1:8, the resulting low-temperature crystallization pipette exhibits the best performance. This may be because when the amount of cyclic lactide added is too small, it cannot form a sufficiently thick and continuous PLA organic coating layer on the surface of aminosilane-modified calcium carbonate, which greatly reduces the heterogeneous nucleation effect of calcium carbonate and has limited effect on improving the crystallization rate and crystallinity of PLA, resulting in an insignificant improvement in the low-temperature toughness of the crystallization pipette. When the amount of cyclic lactide added is too large, the excess cyclic lactide cannot be effectively anchored on the aminosilane-modified calcium carbonate, and a large number of free PLA short chains will act as a strong plasticizer, seriously interfering with the regular arrangement of PLA molecular chains, leading to a decrease in the crystallinity of the matrix and a reduction in the structural strength of the material.

[0067] Examples 17-19 Examples 17-19 are based on the preparation method of Example 1, but the types of nucleating agents are adjusted, as shown in Table 6.

[0068] The low-temperature crystallization pipettes of Examples 17-19 were subjected to the above-mentioned performance tests, and the test results are shown in Table 6.

[0069] Table 6. Nucleating agents and their performance test results for Examples 1 and 17-19

[0070] Referring to Table 6, a comparison of Examples 1 and 17-19 shows that organophosphate nucleating agents, inorganic nucleating agents, amide nucleating agents, and hydrazide nucleating agents all provide ideal performance for low-temperature crystallization pipettes. Among them, Example 1 exhibits the best performance. This may be because the effect of organophosphate nucleating agents depends not only on hydrogen bonding but also on their unique self-assembly behavior. In PLA melt, they can aggregate into nanoscale fibrous or sheet-like structures. These supramolecular assemblies possess a huge specific surface area and abundant ionic / polar sites, enabling ultra-efficient adsorption and induction of PLA molecular chain nucleation, significantly improving the PLA crystallization rate and crystallinity.

[0071] 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 low-temperature resistant crystallization pipette, characterized in that, It includes the following components in parts by weight: PLA 90-110 parts, PBS 5-15 parts, PBAT 5-10 parts, inorganic mineral powder 1-35 parts, alcoholysis agent 0.1-0.6 parts, compatibilizer 1-3 parts, antioxidant 0.1-0.5 parts, nucleating agent 0.1-1 parts; The compatibilizer is a biodegradable polyester containing epoxy functional groups.

2. The low-temperature crystallization resistant pipette according to claim 1, characterized in that, The alcoholysis agent is at least one of ethylene glycol, propylene glycol, and glycerol.

3. A low-temperature crystallization resistant pipette according to claim 2, characterized in that, The compatibilizer is at least one of GMA-PLA, GMA-PBS, and GMA-PBAT.

4. A low-temperature crystallization resistant pipette according to claim 3, characterized in that, The mass ratio of the compatibilizer to the alcoholysis agent is 1:0.1-0.

3.

5. A low-temperature crystallization resistant pipette according to claim 1, characterized in that, It also contains cyclic lactide.

6. A low-temperature crystallization resistant pipette according to claim 5, characterized in that, The inorganic mineral powder is aminosilane-modified calcium carbonate.

7. A low-temperature crystallization resistant pipette according to claim 6, characterized in that, The mass ratio of the cyclic lactide to the aminosilane-modified calcium carbonate is 1:5-10.

8. A low-temperature crystallization resistant pipette according to claim 1, characterized in that, The nucleating agent is at least one of inorganic nucleating agents, amide nucleating agents, acylhydrazine nucleating agents, and organophosphate nucleating agents.

9. A method for preparing a low-temperature resistant crystallization pipette according to any one of claims 1-8, characterized in that, Includes the following steps: S1. The formulated amounts of PLA, PBS, PBAT, inorganic mineral powder, alcoholysis agent, compatibilizer, antioxidant, and nucleating agent are blended together to obtain a mixture; S2. The mixture is melted, extruded, and granulated to obtain straw material; S3. Extrude the straw material, and after cooling and setting, cut it into a preset length and heat-treat it at 80-110℃ to obtain a low-temperature resistant crystallization straw.

10. The method for preparing a low-temperature resistant crystallization pipette according to claim 9, characterized in that, In S2, the formulated amount of cyclic lactide is added to the mixture, which is then melted, extruded, and granulated to obtain the straw material.

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