Environment-friendly degradable polylactic acid straw and preparation process thereof

Abstract

The invention relates to the technical field of degradable materials, and discloses an environment-friendly degradable polylactic acid straw and a preparation process thereof. Comprising the following operation steps: step 1, adding chitosan into a mixed solution, uniformly mixing, adding an aminated lignocellulose-aqueous solution and a glutaraldehyde aqueous solution, uniformly mixing, adjusting the pH value to 6.5-7, reacting at 40-45 DEG C for 2.5-3 hours, washing and drying to obtain modified lignocellulose; step 2: (1) uniformly mixing modified polylactic acid, polyhydroxyalkanoate, modified wood fiber, tributyl citrate and triglyceride, banburying, discharging and crushing to obtain composite master batch; and (2) sequentially carrying out extrusion molding, cooling shaping and cutting on the composite master batch to obtain the degradable polylactic acid straw.

Description

Technical Field

[0001] The invention relates to the technical field of degradable materials, and in particular to an environmentally friendly degradable polylactic acid straw and a preparation process thereof. Background Art

[0002] Straws are indispensable in people's daily lives; however, traditional plastic straws are difficult to recycle and cannot be quickly degraded. Extensive use will cause white pollution, harm the ecological environment, marine life, etc., thus affecting people's living environment. Therefore, degradable alternative materials are urgently needed; and the raw materials of polylactic acid usually come from renewable resources such as corn and sugarcane. Lactic acid is prepared through hydrolysis and biological fermentation, and then polymerized; it is a biodegradable thermoplastic polyester with good biocompatibility, biodegradability, excellent gloss and barrier properties; after use and disposal, it can be degraded into carbon dioxide and water in the natural environment. It is a green and environmentally friendly polymer material that conforms to the concept of sustainable development.

[0003] The larger the molecular weight of polylactic acid, the slower its degradation rate is generally; however, if the molecular weight of polylactic acid is too low, the intermolecular force is weak, which will cause the straw to be insufficiently strong; when used to hold hot drinks, the straw may soften and deform at a relatively low temperature; if the molecular weight of polylactic acid is simply increased, although the strength of the straw can be enhanced, the degradation rate will be significantly slowed down, and it will be difficult to degrade quickly in the natural environment, thereby bringing a continuous burden to the environment and being unfavorable to sustainable development.

[0004] In summary, in order to solve the above problems, it is of great significance to prepare an environmentally friendly and degradable polylactic acid straw. Summary of the invention

[0005] The purpose of the present invention is to provide an environmentally friendly and degradable polylactic acid straw and a preparation process thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation process of an environmentally friendly and degradable polylactic acid straw comprises the following steps:

[0008] Step 1: chitosan is added to the mixed solution, mixed evenly, an amination lignocellulose aqueous solution and a glutaraldehyde aqueous solution are added, mixed evenly, the pH is adjusted to 6.5-7, reacted at 40-45° C. for 2.5-3 hours, washed and dried to obtain modified lignocellulose;

[0009] Step 2: (1) Uniformly mix modified polylactic acid, polyhydroxyalkanoate, modified wood fiber, tributyl citrate, and triglyceride, conduct internal mixing, discharge the material, and crush it to obtain a composite masterbatch; (2) Extrude the composite masterbatch successively, cool and shape it, and cut it to obtain a degradable polylactic acid straw.

[0010] More preferably, the raw materials of the masterbatch include the following components: by mass, 65 - 80 parts of modified polylactic acid, 17 - 25 parts of polyhydroxyalkanoate, 8 - 12 parts of modified wood cellulose, 2 - 5 parts of tributyl citrate, and 2 - 4 parts of triglyceride.

[0011] More preferably, the mass ratio of the amino - modified wood cellulose - 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 amino - modified wood cellulose - aqueous solution is 6 - 10 wt%; the mixed solution includes a hydrochloric acid solution and an acetic acid solution with a mass ratio of (3 - 4):1; the concentrations of the hydrochloric acid solution and the acetic acid solution are both 2 - 3 wt%.

[0012] More preferably, the preparation method of the modified polylactic acid is: (1) Ultrasonically disperse mercapto - nano - titanium dioxide in tetrahydrofuran, add hydroxyethyl acrylate and AIBN, mix them uniformly, and irradiate under ultraviolet light of 90 - 100 W for 1.5 - 2 hours to obtain modified nano - titanium dioxide; (2) Add L - lactide and a catalyst to xylene, mix them uniformly at 50 - 60 °C, add polyethylene glycol and the modified nano - titanium dioxide - xylene solution, and under nitrogen protection, raise the temperature to 140 - 150 °C and react for 8 - 12 hours, then conduct vacuum distillation, purification, and drying to obtain modified polylactic acid.

[0013] More preferably, the raw materials of the modified nano - titanium dioxide include the following components: by mass, 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.

[0014] More preferably, the raw materials of the modified polylactic acid include the following components: by mass, 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 xylene; the molecular weight of the polyethylene glycol is 600 - 1200.

[0015] More preferably, the temperature of internal mixing is 160 - 180 °C, the time of internal mixing is 10 - 15 minutes; the temperature of extrusion molding is 170 - 185 °C.

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

[0017] In the present invention, polylactic acid, polyhydroxyalkanoates, lignocellulose, tributyl citrate, and triglyceride are kneaded and mixed to form a composite masterbatch, and then extruded, cooled and shaped, and cut to obtain a degradable polylactic acid straw.

[0018] Under the action of sunlight, polyhydroxyalkanoates will accelerate the secretion of esterase by microorganisms, causing the ester bonds to break, thereby increasing the degradation rate of the straw; the porous structure and large specific surface area of lignocellulose provide attachment sites for microorganisms, and chitosan has good biocompatibility and can regulate the growth environment of microorganisms; the synergistic effect of polyhydroxyalkanoates and modified lignocellulose not only provides a suitable habitat for microorganisms but also attracts more microorganisms to attach. The enzymes secreted by microorganisms can act on the ester bonds of polylactic acid to accelerate its degradation; triglycerides (plasticizers), as plasticizers derived from natural fats, help improve the molding efficiency because they themselves have good biodegradability, thus promoting the biodegradation rate of polylactic acid; tributyl citrate (compatibilizer) can interact with other components to improve the interfacial compatibility; at the same time, tributyl citrate can be decomposed by microorganisms into carbon dioxide and water in the natural environment.

[0019] In the solution, polylactic acid is also a biodegradable material, but its degradation rate is related to the molecular weight. The molecular chains of high-molecular-weight polylactic acid are arranged regularly and tightly, with a low porosity, so the degradation time is slower; however, for low-molecular-weight polylactic acid, the intermolecular force is weak, which results in insufficient strength of the straw.

[0020] To solve the problem of the slower degradation time of high-molecular-weight polylactic acid; in the solution, polyethylene glycol and modified nano-titanium dioxide are added during the ring-opening polymerization of L-lactide to obtain modified polylactic acid; among them, polyethylene glycol can improve the hydrophilicity of polylactic acid and reduce its brittleness; the increased hydrophilicity is conducive to water molecules entering the interior of the material, causing the ester bonds on the main chain of polylactic acid to break, thereby improving the degradation of polylactic acid; after modifying nano-titanium dioxide, its dispersibility in polylactic acid is improved, thereby increasing the porosity of polylactic acid and providing attachment sites for bacteria, thus improving the degradation rate of polylactic acid.

[0021] However, the compatibility between lignocellulose and polylactic acid is poor. The polylactic acid after introducing polyethylene glycol can improve the interfacial compatibility between it and polylactic acid, and through kneading, the interfacial compatibility between the two can be further improved; more hydrophilic sites are introduced into the polylactic acid matrix, significantly increasing the hydrophilicity of the whole material; through synergistic action with polyethylene glycol, the hydrolysis and breakage of the ester bonds on the main chain of polylactic acid are accelerated, thereby improving the degradation rate of polylactic acid. Specific embodiments

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0023] In the following specific embodiments, the parts are parts by mass. In this embodiment, it should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in the present invention. Exemplarily, they include: the model of wood cellulose is TE40, with an average particle size of 40 μm, purchased from Hubei Xinrunde Chemical Co., Ltd.; the model of chitosan is 26520, purchased from Hubei Shiteng Chemical Technology Co., Ltd.; the CAS number of glutaraldehyde is 111-30-8; the product number of nano-titanium dioxide is HBWS-1339, with an average particle size of 90 nm, purchased from Hubei Widely Chemical Technology Co., Ltd.; the CAS number of hydroxyethyl acrylate is 818-61-1; the CAS number of AIBN (azobisisobutyronitrile) is 78-67-1; the product number of 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 of polyhydroxyalkanoate is Z312, purchased from Guangzhou Zhenshun Plastic Raw Materials Co., Ltd.; the CAS number of tributyl citrate is 77-94-1; the CAS number of triglyceride is 538-24-9; the CAS number of KH550 (3-aminopropyltriethoxysilane) is 919-30-2; the CAS number of KH590 (3-mercaptopropyltriethoxysilane) is 14814-09-6.

[0024] The preparation method of amino-functionalized wood cellulose is as follows: Add 0.4 parts of KH550 to 30 parts of ethanol aqueous solution (70 wt%), mix evenly, add 3 parts of wood cellulose, stir at 75 °C for 5.5 hours, wash and dry to obtain amino-functionalized wood cellulose.

[0025] The preparation method of mercapto-functionalized nano-titanium dioxide is as follows: Add 0.32 parts of KH590 to 30 parts of ethanol aqueous solution (70 wt%), mix evenly, add 2.5 parts of nano-titanium dioxide, stir at 75 °C for 6 hours, wash and dry to obtain mercapto-functionalized nano-titanium dioxide.

[0026] Example 1: A preparation process of an environmentally friendly and degradable polylactic acid straw, including the following operating steps:

[0027] Step 1: (1) Weigh the aminated cellulose - aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1. Add chitosan to the mixed solution (a mixed solution of 2.5 wt% hydrochloric acid aqueous solution and 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix evenly, add the aminated cellulose - aqueous solution and glutaraldehyde aqueous solution, mix evenly, adjust the pH to 6.5, react at 42 °C for 3 hours, wash and dry to obtain modified cellulose.

[0028] (2) Ultrasonically disperse 0.4 parts of mercapto - nano - titanium dioxide in 30 parts of tetrahydrofuran, add 1.7 parts of 2 - hydroxyethyl acrylate and 0.002 parts of AIBN, mix evenly, irradiate under ultraviolet light of 100 W for 2 hours, wash and dry to obtain modified nano - titanium dioxide. (3) Add 9 parts of L - lactide and 0.013 parts of catalyst to 40 parts of xylene, mix evenly at 50 - 60 °C, add 0.25 parts of polyethylene glycol and the modified nano - titanium dioxide - xylene solution (0.17 parts of modified nano - titanium dioxide added to 10 parts of xylene), under nitrogen protection, heat up to 140 °C and react for 10 hours, carry out vacuum distillation, add it to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid.

[0029] Step 2: (1) Mix 65 parts of modified polylactic acid, 17 parts of polyhydroxyalkanoate, 8 parts of modified cellulose, 3 parts of tributyl citrate, and 3 parts of triglyceride evenly, carry out internal mixing at 165 °C for 15 minutes, discharge and crush to obtain composite masterbatch. (2) Extrude and mold the composite masterbatch at 175 °C, cool and shape, and cut to obtain a degradable polylactic acid straw.

[0030] Example 2: A preparation process of an environmentally friendly degradable polylactic acid straw, including the following operating steps:

[0031] Step 1: (1) Weigh the aminated cellulose - aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1. Add chitosan to the mixed solution (a mixed solution of 2.5 wt% hydrochloric acid aqueous solution and 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix evenly, add the aminated cellulose - aqueous solution and glutaraldehyde aqueous solution, mix evenly, adjust the pH to 6.5, react at 42 °C for 3 hours, wash and dry to obtain modified cellulose.

[0032] (2) Ultrasonically disperse 0.4 parts of mercapto-nano titanium dioxide in 30 parts of tetrahydrofuran, add 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN, mix evenly, irradiate with ultraviolet light at 100 W for 2 hours, wash and dry to obtain modified nano titanium dioxide; (3) Add 9 parts of L-lactide and 0.013 parts of catalyst to 40 parts of xylene, mix evenly at 50 - 60 °C, add 0.25 parts of polyethylene glycol and the modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide added to 10 parts of xylene), under nitrogen protection, raise the temperature to 140 °C and react for 10 hours, carry out vacuum distillation, add to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid;

[0033] Step 2: (1) Uniformly mix 70 parts of modified polylactic acid, 20 parts of polyhydroxyalkanoate, 12 parts of modified lignocellulose, 4 parts of tributyl citrate, and 3.2 parts of triglyceride, carry out internal mixing at 165 °C for 15 minutes, discharge and pulverize to obtain a composite masterbatch; (2) Extrude and mold the composite masterbatch at 175 °C, cool and shape, and cut to obtain a degradable polylactic acid straw.

[0034] Example 3: A preparation process of an environmentally friendly degradable polylactic acid straw, comprising the following operating steps:

[0035] Step 1: (1) Weigh amino-functionalized lignocellulose-aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1; add chitosan to the mixed solution (2.5 wt% hydrochloric acid aqueous solution and 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix evenly, add amino-functionalized lignocellulose-aqueous solution and glutaraldehyde aqueous solution, mix evenly, adjust the pH to 6.5, react at 42 °C for 3 hours, wash and dry to obtain modified lignocellulose;

[0036] (2) Ultrasonically disperse 0.4 parts of mercapto-nano titanium dioxide in 30 parts of tetrahydrofuran, add 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN, mix evenly, irradiate with ultraviolet light at 100 W for 2 hours, wash and dry to obtain modified nano titanium dioxide; (3) Add 9 parts of L-lactide and 0.013 parts of catalyst to 40 parts of xylene, mix evenly at 50 - 60 °C, add 0.25 parts of polyethylene glycol and the modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide added to 10 parts of xylene), under nitrogen protection, raise the temperature to 140 °C and react for 10 hours, carry out vacuum distillation, add to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid;

[0037] Step 2: (1) Uniformly mix 80 parts of modified polylactic acid, 20 parts of polyhydroxyalkanoate, 12 parts of modified lignocellulose, 4.3 parts of tributyl citrate, and 3.5 parts of triglyceride, carry out internal mixing at 165 °C for 15 minutes, discharge and pulverize to obtain composite masterbatch; (2) Extrude and mold the composite masterbatch at 175 °C, cool and shape, and cut to obtain a degradable polylactic acid straw.

[0038] Comparative Example 1 is based on Example 2, and nano-titanium dioxide is not introduced into the modified polylactic acid;

[0039] Step 1: (1) Weigh amino-functionalized lignocellulose-aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1; add chitosan to the mixed solution (2.5 wt% hydrochloric acid aqueous solution and 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix uniformly, add amino-functionalized lignocellulose-aqueous solution and glutaraldehyde aqueous solution, mix uniformly, adjust the pH to 6.5, react at 42 °C 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 uniformly at 50 - 60 °C, add 0.25 parts of polyethylene glycol, under nitrogen protection, heat up to 140 °C and react for 10 hours, carry out vacuum distillation, add to chloroform, precipitate with methanol, filter and dry to obtain modified polylactic acid;

[0041] Step 2: (1) Uniformly mix 70 parts of modified polylactic acid, 20 parts of polyhydroxyalkanoate, 15 parts of modified lignocellulose, 4 parts of tributyl citrate, and 3.2 parts of triglyceride, carry out internal mixing at 165 °C for 15 minutes, discharge and pulverize to obtain composite masterbatch; (2) Extrude and mold the composite masterbatch at 175 °C, cool and shape, and cut to obtain a degradable polylactic acid straw.

[0042] Comparative Example 2 is based on Example 2, and polyethylene glycol is not introduced into the modified polylactic acid;

[0043] Step 1: (1) Weigh amino-functionalized lignocellulose-aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1; add chitosan to the mixed solution (2.5 wt% hydrochloric acid aqueous solution and 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix uniformly, add amino-functionalized lignocellulose-aqueous solution and glutaraldehyde aqueous solution, mix uniformly, adjust the pH to 6.5, react at 42 °C for 3 hours, wash and dry to obtain modified lignocellulose;

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

[0045] Step 2: (1) 70 parts of modified polylactic acid, 20 parts of polyhydroxyalkanoate, 12 parts of modified lignocellulose, 4 parts of tributyl citrate, and 3.2 parts of triglyceride were mixed evenly, kneaded at 165 °C for 15 minutes, discharged and crushed to obtain a composite masterbatch; (2) The composite masterbatch was extruded at 175 °C, cooled and shaped, and cut to obtain a degradable polylactic acid straw.

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

[0047] Step 1: (1) 0.4 parts of mercapto-nano titanium dioxide was ultrasonically dispersed in 30 parts of tetrahydrofuran, 1.7 parts of hydroxyethyl acrylate and 0.002 parts of AIBN were added and mixed evenly, irradiated under ultraviolet light of 100 W for 2 hours, washed and dried to obtain modified nano titanium dioxide; (2) 9 parts of L-lactide and 0.013 parts of catalyst were added to 40 parts of xylene, mixed evenly at 50 - 60 °C, 0.25 parts of polyethylene glycol and a modified nano titanium dioxide-xylene solution (0.17 parts of modified nano titanium dioxide was added to 10 parts of xylene) were added. Under nitrogen protection, the temperature was raised to 140 °C and reacted for 10 hours, then distilled under reduced pressure, added to chloroform, precipitated with methanol, filtered and dried to obtain modified polylactic acid;

[0048] Step 2: (1) 70 parts of modified polylactic acid, 20 parts of polyhydroxyalkanoate, 9 parts of lignocellulose, 3 parts of chitosan, 4 parts of tributyl citrate, and 3.2 parts of triglyceride were mixed evenly, kneaded at 165 °C for 15 minutes, discharged and crushed to obtain a composite masterbatch; (2) The composite masterbatch was extruded at 175 °C, cooled and shaped, and cut to obtain a degradable polylactic acid straw.

[0049] Comparative Example 4 was based on Example 2, and the modified polylactic acid was replaced with conventional polylactic acid (molecular weight 50000);

[0050] Step 1: Weigh the aminated cellulose - aqueous solution (7 wt%), chitosan, and glutaraldehyde aqueous solution (45 wt%) according to a mass ratio of 3:1:1. Add chitosan to the mixed solution (a 2.5 wt% hydrochloric acid aqueous solution and a 2.5 wt% acetic acid aqueous solution with a mass ratio of (3 - 4):1), mix evenly, add the aminated cellulose - aqueous solution and the glutaraldehyde aqueous solution, mix evenly, adjust the pH to 6.5, react at 42 °C for 3 hours, wash and dry to obtain modified cellulose.

[0051] Step 2: (1) Uniformly mix 70 parts of polylactic acid, 20 parts of polyhydroxyalkanoate, 12 parts of modified cellulose, 4 parts of tributyl citrate, and 3.2 parts of triglyceride, knead at 165 °C for 15 minutes, discharge and crush to obtain a composite masterbatch. (2) Extrude and mold the composite masterbatch at 175 °C, cool and shape, and cut to obtain a degradable polylactic acid straw.

[0052] Detection test: (1) Take 6 degradable polylactic acid straws from Examples 1 - 3 and Comparative Examples 1 - 4 respectively, conduct a tensile test with reference to the GB / T1040.2 - 2022 standard, record the values, and calculate the average tensile strength.

[0053] (2) Take 6 degradable polylactic acid straws from Examples 1 - 3 and Comparative Examples 1 - 4 respectively, weigh them, bury them in humus soil for 180 days (control the moisture content at 40% and the burial depth at 5 cm), take them out, remove the surface impurities, weigh them, and calculate the mass loss rate, which is recorded as the degradation rate (%).

[0054]

[0055]

[0056] Table 1

[0057] Conclusion: Based on Example 2, in Comparative Example 1, nano - titanium dioxide was not introduced into the modified polylactic acid, resulting in a decline in the performance of the degradable polylactic acid straw. Based on Example 2, in Comparative Example 2, polyethylene glycol was not introduced into the modified polylactic acid, leading to a decrease in the hydrophilicity of polylactic acid, which is not conducive to water molecules entering the material interior and affects the cleavage of ester bonds, thus reducing the degradation of the degradable polylactic acid straw. Based on Example 2, in Comparative Example 3, chitosan and cellulose were directly added, affecting the dispersion of lignin and chitosan in the polylactic acid matrix, and thus affecting the performance of the degradable polylactic acid straw. Based on Example 2, in Comparative Example 4, the modified polylactic acid was replaced with conventional polylactic acid (molecular weight 50000), resulting in a decrease in the interfacial compatibility between components, a decrease in the hydrophilicity and bacterial attachment points of polylactic acid, and a decline in the performance of the degradable polylactic acid straw.

[0058] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A process for preparing an environmentally friendly and degradable polylactic acid straw, characterized in that: The steps include: Step 1: chitosan is added to the mixed solution, mixed evenly, an amination lignocellulose aqueous solution and a glutaraldehyde aqueous solution are added, mixed evenly, the pH is adjusted to 6.5-7, reacted at 40-45° C. for 2.5-3 hours, washed and dried to obtain modified lignocellulose; Step 2: (1) uniformly mixing modified polylactic acid, polyhydroxyalkanoate, modified wood fiber, tributyl citrate and triglyceride, mixing, discharging and crushing to obtain composite masterbatch; (2) sequentially extruding the composite masterbatch, cooling and shaping, and cutting to obtain degradable polylactic acid straws.

2. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 1, characterized in that: The raw materials of the masterbatch include the following components: by weight, 65 to 80 parts of modified polylactic acid, 17 to 25 parts of polyhydroxyalkanoate, 8 to 12 parts of modified wood cellulose, 2 to 5 parts of tributyl citrate, and 2 to 4 parts of triglyceride.

3. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 1, characterized in that: The mass ratio of the aminated lignocellulose-water solution, chitosan and glutaraldehyde aqueous solution is (2-3):1:1; the concentration of the glutaraldehyde aqueous solution is 45-50wt%; the concentration of the aminated lignocellulose-water solution is 6-10wt%; the mixed solution includes a hydrochloric acid solution and an acetic acid solution in a mass ratio of (3-4):1; the concentrations of the hydrochloric acid solution and the acetic acid solution are both 2-3wt%.

4. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 2, characterized in that: The preparation method of the modified polylactic acid is as follows: (1) mercapto-nano titanium dioxide is ultrasonically dispersed in tetrahydrofuran, hydroxyethyl acrylate and AIBN are added and uniformly mixed, and the mixture is irradiated under ultraviolet light of 90 to 100 W for 1.5 to 2 hours to obtain modified nano titanium dioxide; (2) L-lactide and a catalyst are added into xylene, the mixture is uniformly mixed at 50 to 60° C., polyethylene glycol and modified nano titanium dioxide-xylene solution are added, the mixture is heated to 140 to 150° C. under nitrogen protection, the mixture is reacted for 8 to 12 hours, and the mixture is distilled under reduced pressure, purified, and dried to obtain modified polylactic acid.

5. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 4, characterized in that: The raw materials of the modified nano titanium dioxide include the following components: by mass, 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.

6. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 4, characterized in that: The raw materials of the modified polylactic acid include the following components: by weight, 7 to 10 parts of L-lactide, 0.25 to 0.35 parts of polyethylene glycol, 0.15 to 0.22 parts of modified nano titanium dioxide, 0.01 to 0.02 parts of a catalyst, and 50 to 60 parts of xylene; the molecular weight of the polyethylene glycol is 600 to 1200.

7. The process for preparing an environmentally friendly and degradable polylactic acid straw according to claim 1, characterized in that: The mixing temperature is 160-180°C, and the mixing time is 10-15 minutes; the extrusion molding temperature is 170-185°C.

8. A degradable polylactic acid straw is prepared according to the process for preparing an environmentally friendly degradable polylactic acid straw according to any one of claims 1 to 7.

Images