Environment-friendly degradable polylactic acid straw and preparation process thereof

Abstract

The application relates to the technical field of degradable materials, and discloses an environment-friendly degradable polylactic acid straw and a preparation process thereof; the process comprises the following operation steps: step 1: chitosan is added into a mixed solution, uniformly mixed, amino-wood fiber-water solution and glutaraldehyde water solution are added, uniformly mixed, the pH is adjusted to 6.5-7, reaction is carried out at 40-45 DEG C for 2.5-3 hours, and then washing, drying and modification wood fiber are obtained; step 2: (1) modified polylactic acid, polyhydroxyalkanoate, modified wood fiber, tributyl citrate and triglyceride are uniformly mixed, and then dense mixing, discharging and crushing are carried out to obtain a composite master batch; (2) the composite master batch is sequentially subjected to extrusion forming, cooling and shaping and cutting to obtain the degradable polylactic acid straw.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, specifically an environmentally friendly biodegradable polylactic acid straw and its preparation process. Background Technology

[0002] Straws are an essential part of daily life; however, traditional plastic straws are difficult to recycle and cannot be quickly degraded. Extensive use leads to white pollution, harming the ecological environment and marine life, thus impacting people's living environment. Therefore, there is an urgent need for biodegradable alternative materials. Polylactic acid (PLA) is typically made from renewable resources such as corn and sugarcane. Lactic acid is produced through hydrolysis and bio-fermentation, and then polymerized. It is a biodegradable thermoplastic polyester with good biocompatibility, biodegradability, excellent gloss, and barrier properties. After use and disposal, it degrades into carbon dioxide and water in the natural environment, making it a green and environmentally friendly polymer material that aligns with the concept of sustainable development.

[0003] The larger the molecular weight of polylactic acid (PLA), the slower its degradation rate is generally. However, if the molecular weight of PLA is too low, the intermolecular forces are weak, which will result in insufficient straw strength. When used to hold hot drinks, the straw may soften and deform at relatively low temperatures. Simply increasing the molecular weight of PLA can enhance the strength of the straw, but it will significantly slow down the degradation rate, making it difficult to degrade quickly in the natural environment, thus placing a continuous burden on the environment and hindering sustainable development.

[0004] In conclusion, the development of an environmentally friendly and biodegradable polylactic acid straw is of great significance in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an environmentally friendly and biodegradable polylactic acid straw and its preparation process to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A process for preparing an environmentally friendly and biodegradable polylactic acid straw includes the following steps:

[0008] Step 1: Add chitosan to the mixture and mix evenly. Add aminated lignocellulose-water solution and glutaraldehyde-water solution and mix evenly. Adjust the pH to 6.5-7 and react at 40-45℃ for 2.5-3 hours. Wash and dry to obtain modified lignocellulose.

[0009] Step 2: (1) Mix the modified polylactic acid, polyhydroxy fatty acid ester, modified wood fiber, tributyl citrate and triglyceride evenly, knead, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch in sequence, cool and shape it and cut it to obtain biodegradable polylactic acid straws.

[0010] In a more optimized form, the raw materials of the masterbatch include the following components: by mass parts, 65-80 parts modified polylactic acid, 17-25 parts polyhydroxy fatty acid ester, 8-12 parts modified lignocellulose, 2-5 parts tributyl citrate, and 2-4 parts triglycerides.

[0011] In a more optimized configuration, the mass ratio of the aminated lignocellulose-aqueous solution, chitosan, and glutaraldehyde-aqueous solution is (2-3):1:1; the concentration of the glutaraldehyde-aqueous solution is 45-50 wt%; the concentration of the aminated lignocellulose-aqueous solution is 6-10 wt%; the mixture includes a hydrochloric acid solution and an acetic acid solution in a mass ratio of (3-4):1; and the concentrations of both the hydrochloric acid solution and the acetic acid solution are 2-3 wt%.

[0012] A more optimized method for preparing the modified polylactic acid is as follows: (1) Thiol-nano titanium dioxide is ultrasonically dispersed in tetrahydrofuran, hydroxyethyl acrylate and AIBN are added and mixed evenly, and the mixture is irradiated under ultraviolet light at 90-100W for 1.5-2 hours to obtain modified nano titanium dioxide; (2) L-lactide and catalyst are added to xylene and mixed evenly at 50-60℃, polyethylene glycol and modified nano titanium dioxide-xylene solution are added, and the mixture is heated to 140-150℃ for 8-12 hours under nitrogen protection, and then distilled under reduced pressure, purified and dried to obtain modified polylactic acid.

[0013] In a more optimized form, the raw material for the modified nano-titanium dioxide comprises the following components: by mass parts, 1-2 parts hydroxyethyl acrylate, 0.3-0.5 parts mercapto-nano-titanium dioxide, 0.002-0.0025 parts AIBN, and 20-30 parts tetrahydrofuran.

[0014] In a more optimized form, the raw materials for the modified polylactic acid include the following components: by mass parts, 7-10 parts of L-lactide, 0.25-0.35 parts of polyethylene glycol, 0.15-0.22 parts of modified nano-titanium dioxide, 0.01-0.02 parts of catalyst, and 50-60 parts of xylene; wherein the polyethylene glycol has a molecular weight of 600-1200.

[0015] For optimal results, the mixing temperature is 160–180℃ and the mixing time is 10–15 minutes; the extrusion molding temperature is 170–185℃.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] This invention involves mixing polylactic acid, polyhydroxyalkanoate, lignocellulose, tributyl citrate, and triglycerides to form a composite masterbatch, which is then extruded, cooled, shaped, and cut to obtain a biodegradable polylactic acid straw.

[0018] The action of sunlight accelerates the secretion of esterases by microorganisms, causing the ester bonds to break and thus increasing the degradation rate of straws. The porous structure and large specific surface area of ​​lignocellulose provide attachment sites for microorganisms, while chitosan has good biocompatibility and can regulate the growth environment of microorganisms. The synergistic effect of polyhydroxyalkanoates and modified lignocellulose provides a suitable habitat for microorganisms and attracts more microorganisms to attach. The enzymes secreted by microorganisms can act on the ester bonds of polylactic acid, accelerating its degradation. Triglycerides (plasticizers), as plasticizers from natural fat sources, help improve molding efficiency because they themselves have good biodegradability, thus promoting the biodegradation rate of polylactic acid. Tributyl citrate (compatibilizer) can interact with other components, thereby improving interfacial compatibility. At the same time, tributyl citrate can be decomposed into carbon dioxide and water by microorganisms in the natural environment.

[0019] In the proposed solution, polylactic acid (PLA) is also a biodegradable material. However, the rate of degradation is related to its molecular weight. High molecular weight PLA has a regular and compact molecular chain arrangement and low porosity, so it degrades more slowly. However, low molecular weight PLA has weaker intermolecular forces, which makes the straw less strong.

[0020] To address the issue of slow degradation of high molecular weight polylactic acid (PLA), the proposed method involves adding polyethylene glycol and modified nano-titanium dioxide during the ring-opening polymerization of L-lactide to obtain modified PLA. Polyethylene glycol enhances the hydrophilicity of PLA and reduces its brittleness. Increased hydrophilicity facilitates the entry of water molecules into the material, causing the ester bonds in the PLA backbone to break, thus improving PLA degradation. Modification with nano-titanium dioxide improves its dispersibility within PLA, thereby increasing PLA porosity and providing attachment sites for bacteria, thus accelerating PLA degradation.

[0021] However, lignocellulose and polylactic acid (PLA) have poor compatibility. Introducing polyethylene glycol (PEG) into PLA can improve the interfacial compatibility between PLA and PEG. Further mixing can enhance the interfacial compatibility between the two. Introducing more hydrophilic sites into the PLA matrix significantly improves the overall hydrophilicity of the material. It also works synergistically with PEG to accelerate the hydrolytic breakage of ester bonds on the PLA backbone, thereby improving the degradation rate of PLA. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] In the following specific embodiments, "parts" refers to parts by weight. In this embodiment, it should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: lignocellulose (TE40, average particle size 40μm, purchased from Hubei Xinrunde Chemical Co., Ltd.); chitosan (26520, purchased from Hubei Shiteng Chemical Technology Co., Ltd.); glutaraldehyde (CAS number 111-30-8); nano-titanium dioxide (HBWS-1339, average particle size 90nm, purchased from Hubei Weideli Chemical Technology Co., Ltd.); hydroxyethyl acrylate (CAS number 818-61-1); and AIBN (azo dye). The CAS number for diisobutyronitrile (DII) is 78-67-1; the product number for L-lactide is GA0317, purchased from Hubei Guangao Biotechnology Co., Ltd.; the molecular weight of polyethylene glycol is 600, purchased from Nanjing Kerunjiang Chemical Co., Ltd.; the model number for polyhydroxyalkanoate is Z312, purchased from Guangzhou Zhenshun Plastic Raw Materials Co., Ltd.; the CAS number for tributyl citrate is 77-94-1; the CAS number for triglycerides is 538-24-9; the CAS number for KH550 (3-aminopropyltriethoxysilane) is 919-30-2; and the CAS number for KH590 (3-mercaptopropyltriethoxysilane) is 14814-09-6.

[0024] The preparation method of aminated lignocellulose is as follows: 0.4 parts of KH550 are added to 30 parts of ethanol aqueous solution (70wt%), mixed evenly, 3 parts of lignocellulose are added, and the mixture is stirred at 75℃ for 5.5 hours. After washing and drying, aminated lignocellulose is obtained.

[0025] The preparation method of thiolized nano-titanium dioxide is as follows: 0.32 parts of KH590 are added to 30 parts of ethanol aqueous solution (70wt%), mixed evenly, 2.5 parts of nano-titanium dioxide are added, stirred at 75℃ for 6 hours, washed and dried to obtain thiolized nano-titanium dioxide.

[0026] Example 1: A preparation process for an environmentally friendly and biodegradable polylactic acid straw, comprising the following steps:

[0027] Step 1: (1) Weigh the aminated lignocellulose-water solution (7wt%), chitosan, and glutaraldehyde-water solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid-water solution and 2.5wt% acetic acid-water solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-water solution and glutaraldehyde-water solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0028] (2) 0.4 parts of mercapto-nano titanium dioxide were ultrasonically dispersed in 30 parts of tetrahydrofuran, 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN were added and mixed evenly. The mixture was irradiated under 100W ultraviolet light for 2 hours, washed and dried to obtain modified nano titanium dioxide; (3) 9 parts of L-lactide and 0.013 parts of catalyst were added to 40 parts of xylene and mixed evenly at 50-60℃. 0.25 parts of polyethylene glycol and modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide were added to 10 parts of xylene) were added. Under nitrogen protection, the mixture was heated to 140℃ and reacted for 10 hours. The mixture was then distilled under reduced pressure, added to chloroform, precipitated with methanol, filtered and dried to obtain modified polylactic acid;

[0029] Step 2: (1) Mix 65 parts of modified polylactic acid, 17 parts of polyhydroxy fatty acid ester, 8 parts of modified lignocellulose, 3 parts of tributyl citrate, and 3 parts of triglycerides evenly, and knead at 165°C for 15 minutes. Discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape it, and cut it to obtain biodegradable polylactic acid straws.

[0030] Example 2: A preparation process for an environmentally friendly and biodegradable polylactic acid straw, comprising the following steps:

[0031] Step 1: (1) Weigh the aminated lignocellulose-water solution (7wt%), chitosan, and glutaraldehyde-water solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid-water solution and 2.5wt% acetic acid-water solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-water solution and glutaraldehyde-water solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0032] (2) 0.4 parts of mercapto-nano titanium dioxide were ultrasonically dispersed in 30 parts of tetrahydrofuran, 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN were added and mixed evenly. The mixture was irradiated under 100W ultraviolet light for 2 hours, washed and dried to obtain modified nano titanium dioxide; (3) 9 parts of L-lactide and 0.013 parts of catalyst were added to 40 parts of xylene and mixed evenly at 50-60℃. 0.25 parts of polyethylene glycol and modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide were added to 10 parts of xylene) were added. Under nitrogen protection, the mixture was heated to 140℃ and reacted for 10 hours. The mixture was then distilled under reduced pressure, added to chloroform, precipitated with methanol, filtered and dried to obtain modified polylactic acid;

[0033] Step 2: (1) Mix 70 parts of modified polylactic acid, 20 parts of polyhydroxy fatty acid ester, 12 parts of modified lignocellulose, 4 parts of tributyl citrate and 3.2 parts of triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0034] Example 3: A preparation process for an environmentally friendly and biodegradable polylactic acid straw, comprising the following steps:

[0035] Step 1: (1) Weigh the aminated lignocellulose-water solution (7wt%), chitosan, and glutaraldehyde-water solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid-water solution and 2.5wt% acetic acid-water solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-water solution and glutaraldehyde-water solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0036] (2) 0.4 parts of mercapto-nano titanium dioxide were ultrasonically dispersed in 30 parts of tetrahydrofuran, 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN were added and mixed evenly. The mixture was irradiated under 100W ultraviolet light for 2 hours, washed and dried to obtain modified nano titanium dioxide; (3) 9 parts of L-lactide and 0.013 parts of catalyst were added to 40 parts of xylene and mixed evenly at 50-60℃. 0.25 parts of polyethylene glycol and modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide were added to 10 parts of xylene) were added. Under nitrogen protection, the mixture was heated to 140℃ and reacted for 10 hours. The mixture was then distilled under reduced pressure, added to chloroform, precipitated with methanol, filtered and dried to obtain modified polylactic acid;

[0037] Step 2: (1) Mix 80 parts of modified polylactic acid, 20 parts of polyhydroxy fatty acid ester, 12 parts of modified lignocellulose, 4.3 parts of tributyl citrate and 3.5 parts of triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0038] Comparative Example 1 is based on Example 2, but without the introduction of nano-titanium dioxide into the modified polylactic acid;

[0039] Step 1: (1) Weigh the aminated lignocellulose-water solution (7wt%), chitosan, and glutaraldehyde-water solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid-water solution and 2.5wt% acetic acid-water solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-water solution and glutaraldehyde-water solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0040] (2) Add 9 parts of L-lactide and 0.013 parts of catalyst to 50 parts of xylene, mix them evenly at 50-60℃, add 0.25 parts of polyethylene glycol, and react at 140℃ for 10 hours under nitrogen protection. Distill under reduced pressure, add to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid.

[0041] Step 2: (1) Mix 70 parts of modified polylactic acid, 20 parts of polyhydroxy fatty acid ester, 15 parts of modified lignocellulose, 4 parts of tributyl citrate and 3.2 parts of triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0042] Comparative Example 2 is based on Example 2, but without the introduction of polyethylene glycol into the modified polylactic acid;

[0043] Step 1: (1) Weigh the aminated lignocellulose-water solution (7wt%), chitosan, and glutaraldehyde-water solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid-water solution and 2.5wt% acetic acid-water solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-water solution and glutaraldehyde-water solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0044] (2) 0.4 parts of mercapto-nano titanium dioxide were ultrasonically dispersed in 30 parts of tetrahydrofuran, 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN were added and mixed evenly. The mixture was irradiated under 100W ultraviolet light for 2 hours, washed and dried to obtain modified nano titanium dioxide; (3) 9 parts of L-lactide and 0.013 parts of catalyst were added to 40 parts of xylene and mixed evenly at 50-60℃ to obtain a modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide were added to 10 parts of xylene). Under nitrogen protection, the temperature was raised to 140℃ and reacted for 10 hours. The mixture was then distilled under reduced pressure, added to chloroform, precipitated with methanol, filtered and dried to obtain modified polylactic acid;

[0045] Step 2: (1) Mix 70 parts of modified polylactic acid, 20 parts of polyhydroxy fatty acid ester, 12 parts of modified lignocellulose, 4 parts of tributyl citrate and 3.2 parts of triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0046] Comparative Example 3 is based on Example 2, with chitosan and lignocellulose added directly;

[0047] Step 1: (1) Disperse 0.4 parts of mercapto-nano titanium dioxide ultrasonically in 30 parts of tetrahydrofuran, add 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN and mix evenly. Irradiate under 100W UV light for 2 hours, wash and dry to obtain modified nano titanium dioxide; (2) Add 9 parts of L-lactide and 0.013 parts of catalyst to 40 parts of xylene and mix evenly at 50-60℃. Add 0.25 parts of polyethylene glycol and modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide added to 10 parts of xylene). Under nitrogen protection, heat to 140℃ and react for 10 hours. Distill under reduced pressure, add to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid;

[0048] Step 2: (1) Mix 70 parts of modified polylactic acid, 20 parts of polyhydroxy fatty acid ester, 9 parts of lignocellulose, 3 parts of chitosan, 4 parts of tributyl citrate and 3.2 parts of triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0049] Comparative Example 4 is based on Example 2, except that the modified polylactic acid is replaced with conventional polylactic acid (molecular weight 50,000);

[0050] Step 1: Weigh out the aminated lignocellulose-aqueous solution (7wt%), chitosan, and glutaraldehyde-aqueous solution (45wt%) in a mass ratio of 3:1:1; add the chitosan to the mixture (2.5wt% hydrochloric acid aqueous solution and 2.5wt% acetic acid aqueous solution in a mass ratio of (3-4):1), mix evenly, add the aminated lignocellulose-aqueous solution and glutaraldehyde-aqueous solution, mix evenly, adjust the pH to 6.5, react at 42℃ for 3 hours, wash and dry to obtain modified lignocellulose;

[0051] Step 2: (1) Mix 70 parts polylactic acid, 20 parts polyhydroxy fatty acid ester, 12 parts modified lignocellulose, 4 parts tributyl citrate and 3.2 parts triglycerides evenly, knead at 165°C for 15 minutes, discharge and crush to obtain composite masterbatch; (2) Extrude the composite masterbatch at 175°C, cool and shape, and cut to obtain biodegradable polylactic acid straws.

[0052] Test: (1) Take 6 biodegradable polylactic acid straws from Examples 1-3 and Comparative Examples 1-4 respectively, and perform tensile tests according to GB / T1040.2-2022 standard. Record the values ​​and calculate the tensile strength by taking the average value.

[0053] (2) Take 6 biodegradable polylactic acid straws from Examples 1-3 and Comparative Examples 1-4, weigh them separately, bury them in humus soil for 180 days (adjust the moisture content to 40% and the burial depth to 5cm), take them out, remove surface impurities, weigh them, calculate the mass loss rate, and record it as the degradation rate (%).

[0054]

[0055]

[0056] Table 1

[0057] Conclusions: Comparative Example 1, based on Example 2, did not introduce nano-titanium dioxide into the modified polylactic acid (PLA), resulting in a decrease in the performance of the biodegradable PLA straw. Comparative Example 2, based on Example 2, did not introduce polyethylene glycol into the modified PLA, leading to a decrease in the hydrophilicity of PLA, which hinders water molecules from entering the material and affects the breaking of ester bonds, thus reducing the degradation of the biodegradable PLA straw. Comparative Example 3, based on Example 2, directly added chitosan and lignocellulose, affecting the dispersibility of lignin and chitosan in the PLA matrix, thus affecting the performance of the biodegradable PLA straw. Comparative Example 4, based on Example 2, replaced the modified PLA with conventional PLA (molecular weight 50,000), resulting in reduced interfacial compatibility between components, decreased hydrophilicity of PLA, and reduced bacterial attachment points, leading to a decrease in the performance of the biodegradable PLA straw.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A preparation process for an environmentally friendly and biodegradable polylactic acid straw, characterized in that: The preparation process comprises the following steps: Step 1: chitosan is added into a mixed solution, and then amino-wood fiber-water solution and glutaraldehyde solution are added and uniformly mixed; the pH value is adjusted to 6.5-7, and the mixture is reacted at 40-45℃ for 2.5-3 hours; then the mixture is washed and dried to obtain modified wood fiber; Step 2: (1) modified polylactic acid, polyhydroxyalkanoate, modified wood fiber, tributyl citrate and triglyceride are uniformly mixed, and then are subjected to mixing, discharging and crushing to obtain a composite master batch; (2) the composite master batch is subjected to extrusion forming, cooling and shaping and cutting to obtain a degradable polylactic acid straw; The raw materials of the master batch comprise the following components: 65-80 parts of modified polylactic acid, 17-25 parts of polyhydroxyalkanoate, 8-12 parts of modified wood fiber, 2-5 parts of tributyl citrate and 2-4 parts of triglyceride by mass fraction; The preparation method of the modified polylactic acid comprises the following steps: (1) mercapto-nano titanium dioxide is ultrasonically dispersed in tetrahydrofuran, and then hydroxyethyl acrylate and AIBN are added and uniformly mixed; the mixture is irradiated under ultraviolet light at 90-100W for 1.5-2 hours to obtain modified nano titanium dioxide; (2) L-lactide and a catalyst are added into dimethylbenzene, and then the mixture is uniformly mixed at 50-60℃; polyethylene glycol and modified nano titanium dioxide-dimethylbenzene solution are added, and the mixture is reacted at 140-150℃ for 8-12 hours under nitrogen protection; the mixture is subjected to reduced-pressure distillation, purification and drying to obtain modified polylactic acid; The mass ratio of the amino-wood fiber-water solution, chitosan and glutaraldehyde solution is (2-3):1:1; the concentration of the glutaraldehyde solution is 45-50wt%; the concentration of the amino-wood fiber-water solution is 6-10wt%; the mixed solution comprises hydrochloric acid solution and acetic acid solution at a mass ratio of (3-4):1; the concentration of the hydrochloric acid solution and the acetic acid solution is 2-3wt%.

2. The preparation process of the environment-friendly degradable polylactic acid straw according to claim 1, characterized in that: The raw materials of the modified nano titanium dioxide comprise the following components: 1-2 parts of hydroxyethyl acrylate, 0.3-0.5 parts of mercapto-nano titanium dioxide, 0.002-0.0025 parts of AIBN and 20-30 parts of tetrahydrofuran by mass fraction.

3. The preparation process of the environment-friendly degradable polylactic acid straw according to claim 1, characterized in that: The raw materials of the modified polylactic acid comprise the following components: 7-10 parts of L-lactide, 0.25-0.35 parts of polyethylene glycol, 0.15-0.22 parts of modified nano titanium dioxide, 0.01-0.02 parts of a catalyst and 50-60 parts of dimethylbenzene by mass fraction; the molecular weight of the polyethylene glycol is 600-1200.

4. The preparation process of the environment-friendly degradable polylactic acid straw according to claim 1, characterized in that: The temperature of the mixing is 160-180℃, and the mixing time is 10-15 minutes; the temperature of the extrusion forming is 170-185℃.

5. A degradable polylactic acid straw prepared by the preparation process of the degradable polylactic acid straw according to any one of claims 1-4.

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