Highly flexible crystalline straw material and method of making

Abstract

The application relates to the field of degradable straw production technology, in particular to a high-flexibility crystalline straw material and a preparation method thereof, which comprises the following raw materials in parts by weight: PLA 70-85 parts, a toughening agent 10-20 parts, an antioxidant 0.2-0.5 parts, a lubricant 0.3-0.8 parts and a crystallization regulator 0.5-1 part; the toughening agent is at least one of PCL, TBC and a PLA-PEG block copolymer. According to the application, the selection of PLA as a matrix not only guarantees the core biodegradability of the material, but also provides the basic structural rigidity of the straw material; the addition of the toughening agent effectively absorbs external force impact, reduces the brittleness of PLA, and makes the straw not prone to breakage when being bent; the addition of a trace amount of the crystallization regulator can improve the crystallinity of the straw material and form complementation with the flexible chain segment of the toughening agent, so that the high-flexibility crystalline straw material with ideal performance is prepared.

Description

Technical Field

[0001] This application relates to the field of biodegradable straw production technology, and in particular to a highly flexible crystalline straw material and its preparation method. Background Technology

[0002] Polylactic acid (PLA), as a biodegradable material, has become an ideal alternative to plastic straws due to its renewable and environmentally friendly properties. However, PLA itself has a linear polyester structure with strong molecular chain rigidity and insufficient toughness. With a glass transition temperature of approximately 55°C, it is prone to bending and deformation during extrusion, tube forming, and cooling due to stress concentration and uneven molecular chain orientation. This makes it susceptible to breakage and damage during use, failing to meet consumers' requirements for straw durability and reliability. This limits the further promotion and application of biodegradable straws. Summary of the Invention

[0003] To improve the flexibility of PLA straw materials, this application provides a highly flexible crystalline straw material and its preparation method.

[0004] Firstly, this application provides a highly flexible crystallizing straw material, which adopts the following technical solution: A highly flexible crystallizing straw material comprises the following raw materials in parts by weight: 70-85 parts PLA, 10-20 parts toughening agent, 0.2-0.5 parts antioxidant, 0.3-0.8 parts lubricant, and 0.5-1 parts crystallization regulator; The toughening agent is at least one of PCL, TBC, and PLA-PEG block copolymer.

[0005] By adopting the above technical solution, PLA is used as the matrix to provide basic structural rigidity for the straw material. The addition of toughening agent effectively absorbs external impact and reduces the brittleness of PLA, making the straw less prone to breakage when bent. The addition of trace crystallization regulator can act as crystal nuclei for PLA crystallization, inducing the PLA molecular chains to arrange themselves rapidly and orderly during processing and cooling, thereby improving the crystallinity of the straw material. This complements the flexible segments of the toughening agent, enabling the straw material to have ideal flexibility while reducing the probability of excessive degradation of mechanical properties due to toughening, thus producing a high-flexibility crystalline straw material with ideal performance.

[0006] Among them, PCL, TBC, and PLA-PEG block copolymers are all flexible materials with good compatibility with PLA. PCL is a flexible aliphatic polyester, and its flexible segments can be embedded between PLA molecular chains. After blending with PCL, a co-continuous phase is formed, which alleviates the entanglement of rigid PLA molecular chains and thus improves the flexibility of the straw material. TBC, as a food-grade toughening agent, can effectively reduce the intermolecular forces of PLA and increase the mobility of molecular chains, thereby improving the flexibility of the straw material. The presence of PLA segments in the PLA-PEG block copolymer enables it to have ideal compatibility with the matrix, and the PEG segments introduce hydrophilicity and flexibility, forming a flexible phase region in the PLA matrix. When the straw material is subjected to external bending force, it can absorb energy and reduce the probability of straw material breakage.

[0007] This application not only ensures the core biodegradability of the material by using PLA as the matrix, but also provides basic structural rigidity for the straw material. Furthermore, the addition of toughening agents effectively absorbs external impacts and reduces the brittleness of PLA, making the straw less prone to breakage when bent. The addition of trace amounts of crystallization regulators can improve the crystallinity of the straw material and complement the flexible segments of the toughening agent, thereby obtaining a high-flexibility crystalline straw material with ideal performance.

[0008] Preferably, the toughening agent is a mixture of PCL, TBC, and PLA-PEG block copolymer.

[0009] By adopting the above technical solution, the PLA-PEG block copolymer, containing PLA segments, is completely compatible with the PLA matrix and can act as an "interface bridging agent" distributed at the interface between the PLA molecular chain and other toughening agents. PCL is partially compatible with PLA, and its flexible long chains can be embedded between PLA molecular chains. TBC, as a small molecule plasticizer, can be evenly distributed between PLA molecular chains. Through the cooperation of the three toughening agents, the plasticizer can be evenly distributed in the PLA matrix and jointly improve the brittleness of PLA, significantly improving the flexibility of the straw material.

[0010] Preferably, the mixing mass ratio of the PCL, TBC, and PLA-PEG block copolymer is 2-4:1-3:1.

[0011] By adopting the above technical solution, when the proportion of PCL is too high, since PCL is a flexible polymer, excessive PCL will form a large number of flexible phase regions in the PLA matrix, which will offset the structural rigidity provided by the PLA matrix and PLA-PEG, making the straw material too flexible and lacking in support, resulting in a significant decrease in the tensile strength of the straw material.

[0012] When the proportion of TBC is too high, the binding force of PLA molecular chains is greatly reduced, causing the straw material to change from a "tough and hard" state to a sticky and soft state. Furthermore, TBC will migrate to the surface of the straw material over time and with temperature changes, causing the straw material to rapidly lose its flexibility.

[0013] When the proportion of PLA-PEG block copolymer is too high, the excessive amount of PLA-PEG block copolymer will soften the PLA matrix excessively, resulting in a decrease in the rigidity and strength of the straw material. In addition, PEG is a strongly hydrophilic group, and excessive PLA-PEG block copolymer will cause the water absorption rate of the straw material to increase significantly.

[0014] Preferably, the raw materials also contain flax fiber.

[0015] By adopting the above technical solution, since the addition of toughening agent will inevitably reduce the rigidity of straw material, flax fiber, as a high modulus natural plant fiber, has excellent mechanical rigidity and deformation resistance. When it is dispersed in PLA matrix, it can form a three-dimensional physical reinforcement skeleton, which can make up for the dilution of the rigidity of PLA matrix by toughening agent, so that straw material has high flexibility and can improve the tensile strength of straw material.

[0016] Furthermore, the surface of flax fibers contains a large number of polar groups such as hydroxyl and carboxyl groups, which can act as auxiliary nuclei for PLA crystallization. Combined with crystallization regulators, this further induces the effective arrangement of PLA molecular chains, increasing the crystallinity of the straw material. The polar groups in flax fibers can form hydrogen bonds with the ester groups of the PLA matrix, complementing the interfacial bridging effect of the PLA-PEG block copolymer, achieving interfacial bonding between flax fibers and the PLA matrix, and inhibiting the surface migration of toughening agents. The crystalline regions of flax fibers have a hydrophobic structure, which can further reduce the water absorption rate of the straw material.

[0017] Preferably, the flax fiber is flax fiber modified with epoxy silane.

[0018] By employing the above technical solution, the hydrophobic organic segments of the epoxy silane-modified flax fibers can cover the surface of the flax fibers, making the surface of the flax fibers oleophilic and allowing the flax fibers to be uniformly dispersed in the PLA matrix. Furthermore, the presence of epoxy groups can undergo ring-opening reactions with the terminal hydroxyl / ester groups of the PLA matrix and the ether / ester groups of the PLA-PEG block copolymer to form CO bonds, making the bond between the flax fibers and the PLA matrix a covalent bond, thus fully leveraging the reinforcing effect of the flax fibers.

[0019] Furthermore, the formation of a siloxane hydrophobic layer on the surface of flax fibers after epoxy silane grafting can reduce the adsorption of water on flax fibers, and the covalently closed interface structure can also eliminate the hydrophilic channels between flax fibers and PLA matrix, further reducing the water absorption rate of straw material.

[0020] Preferably, the PLA-PEG block copolymer is PLA-PEG-NH2.

[0021] By employing the above technical solution, the amino group at the end of PLA-PEG-NH2 can undergo a ring-opening addition reaction with the epoxy groups of flax fibers modified with epoxysilane to form stable CN bonds. Simultaneously, the PLA segments of PLA-PEG-NH2 are closely compatible with the matrix, achieving covalent bonding among the matrix, toughening agent, and modified flax fibers, constructing a three-dimensional interfacial cross-linked network for the entire material, significantly improving the tensile strength of the straw material. Furthermore, the amino group of PLA-PEG-NH2 is a strongly polar group, capable of forming various hydrogen bonds with the ester groups on the PLA matrix molecular chain, effectively reducing the probability of phase separation or local aggregation of the toughening agent in the PLA matrix. The chemically bonded network of PLA-PEG-NH2 can also encapsulate and immobilize small molecules such as TBC, inhibiting TBC migration and precipitation.

[0022] Preferably, the crystallization regulator is DBS.

[0023] By adopting the above technical solution, DBS is a food-grade nucleating agent. Its molecules can self-assemble through hydrogen bonds to form a nanoscale crystal nucleus structure. During the cooling process of PLA melt, a large number of uniformly distributed heterogeneous crystal nuclei are formed, reducing the crystallization activation energy, thereby promoting the rapid and orderly arrangement of PLA molecular chains and inducing PLA to form a stable α crystal form.

[0024] The hydroxyl and ether bonds in the DBS molecule can form weak hydrogen bonds with the ester groups of PLA, allowing DBS to be uniformly distributed in the PLA matrix. Furthermore, the microcrystalline regions induced by DBS can form complementary structures with the flexible segments of the toughening agent. The microcrystalline regions can provide rigid support, while the toughening agent regions absorb impact energy, thereby achieving a balance between rigidity and toughness in the straw material.

[0025] Secondly, this application provides a method for preparing a highly flexible crystallizing straw material, which adopts the following technical solution: A method for preparing a highly flexible crystallizing straw material includes the following steps: S1. After mixing PLA, toughening agent, antioxidant, lubricant and crystallization regulator according to the formula, a mixture is obtained; S2. The mixture is melted, extruded, and granulated to obtain modified PLA particles; S3. The modified PLA particles are extruded and drawn, cooled and shaped, and then kept at 50-60℃ for 20-30 minutes. After cooling to room temperature, they are cut to obtain a highly flexible crystallized straw material.

[0026] By adopting the above technical solution, the raw materials are first initially mixed, and then melt-blended and granulated to achieve uniform dispersion and coordination between components. Finally, through extrusion molding and cooling and shaping processes, the straw material can improve its crystallinity and uniformity under the induction of crystallization regulator, thereby achieving a balance between the flexibility and rigidity of the straw material and producing a high-performance, highly flexible, crystalline straw material.

[0027] Preferably, in S3, cooling and shaping are performed by a water-cooling tank, and the water temperature of the water-cooling tank is 30-40℃.

[0028] By adopting the above technical solution, when the water temperature in the cold water tank is too low, the cooling rate after the straw is extruded is too fast, causing the PLA molecular chains and other components to be frozen instantly. This results in the inability to complete the initial relaxation and orderly arrangement of the molecular chains, leading to insufficient crystallinity. Consequently, the resulting straw material has high rigidity but reduced flexibility. When the water temperature in the cold water tank is too high, the cooling rate after the straw is extruded is too low, allowing sufficient time for the PLA molecular chains and toughening agent phase regions to undergo phase separation and rearrangement during the cooling process. This may lead to local aggregation of the toughening agent and coarse crystal grains, resulting in a decrease in the rigidity of the straw material.

[0029] Preferably, in S1, the formulated amount of flax fiber is mixed with PLA, toughening agent, antioxidant, lubricant and crystallization regulator to obtain a mixture.

[0030] By adopting the above technical solution, the addition of flax fiber to S1 allows the flax fiber to be initially and uniformly mixed with the PLA matrix and other components before melt blending, laying the foundation for the uniform dispersion, interfacial chemical bonding, and effective distribution of the fiber as an auxiliary crystal nucleus during the subsequent melt extrusion process in S2.

[0031] In summary, this application includes at least one of the following beneficial technical effects: 1. By using PLA as the matrix, this application not only ensures the core biodegradability of the material, but also provides basic structural rigidity for the straw material. Furthermore, the addition of toughening agent effectively absorbs external impact and reduces the brittleness of PLA, making the straw less prone to breakage when bent. The addition of trace crystallization regulator can improve the crystallinity of the straw material and complement the flexible segments of the toughening agent, thereby obtaining a high-flexibility crystalline straw material with ideal performance. 2. This application uses PCL, TBC, and PLA-PEG block copolymer to form a toughening agent. Because the PLA-PEG block copolymer contains PLA segments, it is completely compatible with the PLA matrix and can act as an "interfacial bridger" distributed at the interface between the PLA molecular chain and the other toughening agents. PCL is partially compatible with PLA, and its flexible long chains can be embedded between the PLA molecular chains. TBC, as a small molecule plasticizer, can be evenly distributed between the PLA molecular chains. Through the combination of the three toughening agents, the plasticizer can be evenly distributed in the PLA matrix and jointly improve the brittleness of PLA, significantly improving the flexibility of the straw material. 3. By adding flax fibers, this application can form a three-dimensional physical reinforcement skeleton in the PLA matrix, which can make up for the dilution of the rigidity of the PLA matrix by the toughening agent, so that the straw material has high flexibility while improving the tensile strength of the straw material. Detailed Implementation

[0032] The raw materials in this application include the following: PLA: PLA with optical purity ≥99% and melt index 5-10g / 10min (190℃ / 2.16kg) is selected. This application takes PLA with melt index 8g / 10min (190℃ / 2.16kg) as an example. PCL: PCL with a number average molecular weight of 10,000-20,000 is selected. This application takes PCL with a number average molecular weight of 15,000 as an example. TBC: Select TBC with an ester content ≥99%. PLA-PEG-NH2: PLA-PEG-NH2 with a weight average molecular weight of 8000-12000 is selected. This application takes PLA-PEG-NH2 with a weight average molecular weight of 10000 from Meiluo Technology Co., Ltd. as an example. PLA-PEG-PLA: This application takes PLA-PEG-PLA with a weight-average molecular weight of 10,000 from Meiluo Technology Co., Ltd. as an example; Antioxidant: This application takes antioxidant 1010 with CAS number 6683-19-8 as an example; Lubricant: This application takes calcium stearate with CAS number 1592-23-0 as an example; DBS: Uses commercially available products with CAS number 32647-67-9; Flax fiber: Flax fiber with a length of 0.1-0.5 mm and a diameter of 10-30 μm is selected. This application takes flax fiber with a length of 0.3 mm and a diameter of 20 μm as an example. Epoxysilane: This application takes KH-560 with CAS number 2530-83-8 as an example.

[0033] Preparation Example 1 A method for preparing flax fiber modified with epoxy silane includes the following steps: Step 1: Add flax fiber to a 2wt% sodium hydroxide solution, stir and acid wash at 65℃ for 30 min, wash with deionized water until the filtrate is neutral, and dry until the moisture content of the flax fiber is less than or equal to 1% to obtain activated flax fiber. The bath ratio of flax fiber to sodium hydroxide solution is 1g:30mL. Step 2: Mix ethanol and deionized water at a volume ratio of 3:1, stir at 250 rpm in a 40°C water bath to obtain an ethanol-water solution, adjust the pH to 4, add KH-560, and continue stirring for 45 min to obtain an epoxy silane hydrolysate, with KH-560 accounting for 3 wt% of the total solution mass. Step 3: Add the activated flax fiber to the epoxy silane hydrolysate, stir at 350 r / min, stir for 3 h at 55℃ and pH 4, wash, dry at 85℃ for 4 h, gently break apart to obtain epoxy silane modified flax fiber, wherein the bath ratio of activated flax fiber to epoxy silane hydrolysate is 1 g: 25 mL.

[0034] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0035] Example 1

[0036] A highly flexible crystallizing straw material comprises the following components: PLA 80kg, toughening agent 15kg, antioxidant 0.3kg, lubricant 0.6kg, and crystallization regulator 0.8kg.

[0037] A method for preparing a highly flexible crystallizing straw material includes the following steps: S1. PCL, TBC, PLA-PEG-NH2 are added to a high-speed mixer at a mass ratio of 3:2:1 and mixed at 75℃ and 350r / min for 10min to obtain a toughening agent. After drying PLA in an oven at 65℃ for 5h, it is mixed with toughening agent, antioxidant, lubricant and crystallization regulator DBS according to the formula to obtain a mixture. S2. The mixture is fed into a twin-screw extruder for melting, extrusion, and granulation to obtain modified PLA particles. The temperature of the first barrel zone of the twin-screw extruder is 155℃, the temperature of the second barrel zone is 170℃, the temperature of the third barrel zone is 175℃, the die head temperature is 170℃, and the screw speed is 250r / min. S3. The modified PLA granules are fed into a single-screw extruder for extrusion and uniformly pulled by a traction machine at a speed of 8m / min. After cooling and shaping in a water-cooling tank at a water temperature of 35℃, they are kept at 55℃ for 25min. After cooling to room temperature, they are cut into 200mm pieces to obtain a high-flexibility crystalline straw material. The barrel temperature of the single-screw extruder is 165℃ in zone 1, 180℃ in zone 2, 185℃ in zone 3, and 180℃ in the die head. The die inner diameter is 7mm and the wall thickness is 1mm.

[0038] Example 2-3 Examples 2-3 are based on the preparation method of Example 1, but the composition of the high-flexibility crystallization straw material is adjusted, as shown in Table 1.

[0039] Comparative Examples 1-2 Comparative Examples 1-2 were prepared based on the method in Example 1, but the composition of the high-flexibility crystallization straw material was adjusted as shown in Table 1.

[0040] Performance testing The components of the highly flexible crystallizing straw materials of Examples 1-3 and Comparative Examples 1-2 were analyzed, and the specific detection methods are as follows: 1. Mechanical properties The tensile strength and elongation at break of the high-flexibility crystallization straw material were tested according to the standard test methods specified in GB / T1040-2006.

[0041] 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.

[0042] Table 1. Composition and performance test results of the high-flexibility crystallization straw materials of Examples 1-3 and Comparative Examples 1-2

[0043] Referring to Table 1, comparing Examples 1-3 and Comparative Example 1, it can be seen that the addition of toughening agent can effectively improve the flexibility of straw material. This may be because toughening agent can effectively absorb the impact of external force and reduce the brittleness of PLA.

[0044] Comparing Examples 1-3 and Comparative Example 2, it can be seen that the addition of crystallization regulator can improve the performance of straw material. This may be because the addition of crystallization regulator can act as crystal nuclei for PLA crystallization, inducing PLA molecular chains to arrange themselves rapidly and orderly during processing and cooling, thereby improving the crystallinity of straw material and complementing the flexible segments of toughening agent. This allows straw material to have ideal flexibility while reducing the probability of excessive degradation of mechanical properties due to toughening.

[0045] Examples 4-6 Examples 4-6 are based on the preparation method of Example 1, but the toughening agent components are adjusted as shown in Table 2.

[0046] The high-flexibility crystallization straw materials of Examples 4-6 were subjected to the above-mentioned performance tests, and the test results are shown in Table 2.

[0047] Table 2. Toughening agents and their performance test results in Examples 1 and 4-6.

[0048] Referring to Table 2, a comparison of Examples 1 and 4-6 shows that the high-flexibility crystalline straw material obtained by compounding PCL, TBC, and PLA-PEG block copolymers as toughening agents exhibits the best performance. This may be because the PLA-PEG block copolymer, containing PLA segments, is completely compatible with the PLA matrix and can act as an "interfacial bridger" distributed at the interface between the PLA molecular chains and the other toughening agents. PCL is partially compatible with PLA, and its flexible long chains can be embedded between PLA molecular chains. TBC, as a small molecule plasticizer, can be uniformly distributed between PLA molecular chains. Through the synergy of the three toughening agents, the plasticizers can be uniformly distributed in the PLA matrix and jointly improve the brittleness of PLA, significantly enhancing the flexibility of the straw material.

[0049] Examples 7-10 Examples 7-10 are based on the preparation method of Example 1, but the mixing mass ratio of PCL, TBC, PLA-PEG-NH2 is adjusted as shown in Table 3.

[0050] Performance testing The components of the highly flexible crystallizing straw materials of Examples 1 and 7-10 were analyzed, and the specific detection methods are as follows: 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.

[0051] Based on the above detection method, the test results of Examples 1 and 7-10 were obtained, as shown in Table 3 below.

[0052] Table 3. Mixing mass ratios and performance test results of PCL, TBC, PLA-PEG-NH2 in Examples 1 and 7-10.

[0053] Referring to Table 3, a comparison of Examples 1 and 7-10 shows that when the mass ratio of PCL, TBC, and PLA-PEG-NH2 is in the range of 2-4:1-3:1, especially when the mass ratio of PCL, TBC, and PLA-PEG-NH2 is 3:2:1, the resulting highly flexible crystalline straw material exhibits the best performance. This may be because when the proportion of PCL is too high, since PCL is a flexible polymer, excessive PCL will form a large number of flexible phase regions in the PLA matrix, offsetting the structural rigidity provided by the PLA matrix and PLA-PEG, making the straw material too flexible and lacking in support. This leads to a significant decrease in the tensile strength of the straw material. When the proportion of TBC is too high, the binding force of the PLA molecular chains is greatly reduced, causing the straw material to change from a "tough and hard" state to a sticky and soft state. Furthermore, TBC will migrate to the surface of the straw material with time and temperature changes, causing the straw material's flexibility to rapidly decrease. When the proportion of PLA-PEG block copolymer is too high, the excessive amount of PLA-PEG block copolymer will excessively soften the PLA matrix, leading to a decrease in the rigidity and strength of the straw material. In addition, PEG is a strongly hydrophilic group, and excessive PLA-PEG block copolymer will cause the water absorption rate of the straw material to increase significantly.

[0054] Example 11 Example 11: Based on the preparation method of Example 1, in S1, 7 kg of flax fiber was added and mixed with PLA, toughening agent, antioxidant, lubricant and crystallization regulator to obtain a mixture, while the other conditions remained unchanged.

[0055] Example 12 Example 12 is based on the preparation method of Example 11, but the flax fiber is replaced in equal amounts with the epoxy silane modified flax fiber obtained in Preparation Example 1, and the other conditions remain unchanged.

[0056] Example 13 Example 13 is based on the preparation method of Example 12, except that PLA-PEG-NH2 is replaced with PLA-PEG-PLA in equal amounts, while the other conditions remain unchanged.

[0057] The high-flexibility crystallization straw materials of Examples 11-13 were subjected to the above-mentioned performance tests, and the test results are shown in Table 4.

[0058] Table 4 Performance test results for Examples 1 and 11-13

[0059] Referring to Table 4, a comparison of Example 1 and Examples 11-12 shows that the addition of flax fiber can compensate for the loss of rigidity due to the addition of toughening agent. The flax fiber modified with epoxy silane can undergo ring-opening reaction with the terminal hydroxyl / ester groups of PLA matrix and the ether / ester groups of PLA-PEG block copolymer to form CO bonds, making the bond between flax fiber and PLA matrix covalent, so that the reinforcing effect of flax fiber can be fully exerted. At the same time, the addition of flax fiber also helps to reduce the water absorption rate of straw material.

[0060] Comparative examples 12-13 show that the straw material obtained when the PLA-PEG block copolymer is PLA-PEG-NH2 exhibits the best performance. This is likely because the amino groups at the ends of PLA-PEG-NH2 can undergo ring-opening addition reactions with the epoxy groups of the epoxy-modified flax fibers to form stable CN bonds. Simultaneously, the PLA segments of PLA-PEG-NH2 are closely compatible with the matrix, achieving covalent bonds between the matrix, toughening agent, and modified flax fibers, constructing a three-dimensional interfacial cross-linked network for the entire material, significantly improving the tensile strength of the straw material. Furthermore, the amino groups of PLA-PEG-NH2 are highly polar groups, capable of forming various hydrogen bonds with the ester groups on the PLA matrix molecular chain, effectively reducing the probability of phase separation or local aggregation of the toughening agent in the PLA matrix. The chemically bonded network of PLA-PEG-NH2 can also encapsulate and immobilize small molecules such as TBC, inhibiting TBC migration and precipitation.

[0061] Examples 14-17 Examples 14-17 are based on the preparation method of Example 1, but the water temperature of the water cooling tank is adjusted, as shown in Table 5.

[0062] The high-flexibility crystallization straw materials of Examples 14-17 were subjected to the above-mentioned performance tests, and the test results are shown in Table 5.

[0063] Table 5. Water temperature and performance test results of the water-cooled tanks in Examples 1 and 14-17.

[0064] Referring to Table 5, a comparison of Examples 1 and 14-17 shows that the high-flexibility crystalline straw material exhibits the best performance when the water temperature in the cold water bath is in the range of 30-40℃, especially when the water temperature is 35℃. This may be because when the water temperature in the cold water bath is too low, the cooling rate after the straw is extruded is too fast, causing the PLA molecular chains and other components to be frozen instantly. This prevents the initial relaxation and orderly arrangement of the molecular chains from being completed, resulting in insufficient crystallinity. Consequently, the straw material has high rigidity but reduced flexibility. When the water temperature in the cold water bath is too high, the cooling rate after the straw is extruded is too low, allowing sufficient time for the PLA molecular chains and toughening agent phase regions to undergo phase separation and rearrangement during the cooling process. This may lead to local aggregation of the toughening agent and coarse crystal grains, resulting in a decrease in the rigidity of the straw material.

[0065] 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 highly flexible crystallizing straw material, characterized in that, The raw materials include the following parts by weight: PLA 70-85 parts, toughening agent 10-20 parts, antioxidant 0.2-0.5 parts, lubricant 0.3-0.8 parts, and crystallization regulator 0.5-1 parts; The toughening agent is at least one of PCL, TBC, and PLA-PEG block copolymer.

2. The highly flexible crystallizing straw material according to claim 1, characterized in that, The toughening agent is a mixture of PCL, TBC, and PLA-PEG block copolymer.

3. The highly flexible crystallizing straw material according to claim 2, characterized in that, The mass ratio of the PCL, TBC, and PLA-PEG block copolymers is 2-4:1-3:

1.

4. The highly flexible crystallizing straw material according to claim 1, characterized in that, The ingredients also include flax fiber.

5. The highly flexible crystallizing straw material according to claim 4, characterized in that, The flax fiber is flax fiber modified with epoxy silane.

6. The highly flexible crystallizing straw material according to claim 5, characterized in that, The PLA-PEG block copolymer is PLA-PEG-NH2.

7. The highly flexible crystallizing straw material according to claim 1, characterized in that, The crystallization regulator is DBS.

8. A method for preparing a highly flexible crystallizing straw material according to claims 1-7, characterized in that, Includes the following steps: S1. After mixing PLA, toughening agent, antioxidant, lubricant and crystallization regulator according to the formula, a mixture is obtained; S2. The mixture is melted, extruded, and granulated to obtain modified PLA particles; S3. The modified PLA particles are extruded and drawn, cooled and shaped, and then kept at 50-60℃ for 20-30 minutes. After cooling to room temperature, they are cut to obtain a highly flexible crystallized straw material.

9. The method for preparing a highly flexible crystallizing straw material according to claim 8, characterized in that, In S3, cooling and shaping are carried out through a water-cooled tank with a water temperature of 30-40℃.

10. The method for preparing a highly flexible crystallizing straw material according to claim 8, characterized in that, In S1, the formulated amount of flax fiber is mixed with PLA, toughening agent, antioxidant, lubricant and crystallization regulator to obtain a mixture.

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