Antistatic polylactic acid plastic particles and preparation method thereof

Abstract

The invention discloses antistatic polylactic acid plastic particles and a preparation method thereof, and relates to the technical field of plastics. The preparation method comprises the following steps: firstly, taking lignin as a biomass precursor, and preparing sulfonated biochar through a gas-phase sulfonation process; meanwhile, modifying the graphene oxide by adopting polyethyleneimine to construct hybridized graphene with positive electricity; the two phases are efficiently compounded, and a dual mechanism of pi-pi accumulation and electrostatic adsorption is combined to form the composite filler. Secondly, the hydroxyl-terminated polylactic acid is combined with the composite filler to be foamed into porous plastic particles, and the porous plastic particles and residual amino groups on the surface of the hybridized graphene are subjected to a condensation reaction to form chemical grafting; the hydroxyl groups and sulfonic groups generated by proton dissociation of the sulfonated biochar form dynamic crosslinking through a hydrogen bond network; and finally, introducing choline ionic liquid into the porous polylactic acid skeleton through an impregnation method to form a three-dimensional ionic conductive network penetrating through a polylactic acid body-filler interface. The polylactic acid plastic prepared by the invention has antistatic and environment-friendly effects.

Description

Technical Field

[0001] The present invention relates to the technical field of plastics, in particular to antistatic polylactic acid plastic particles and a preparation method thereof. Background Art

[0002] As a typical bio-based degradable polymer material, polylactic acid is considered an ideal substitute for traditional petroleum-based plastics because its raw materials are derived from renewable resources such as corn and sugarcane, and it can be decomposed into carbon dioxide and water by microorganisms in the natural environment. It is widely used in packaging, textiles, medical devices, 3D printing and other fields. However, traditional PLA plastics have significant defects in actual applications: high surface resistivity, easy accumulation of static electricity, which can lead to dust absorption, damage to electronic components, and even increase the risk of flammable and explosive environments, seriously limiting its application in precision electronic packaging, anti-static industrial products and other fields. In the existing technology, the main methods to improve the antistatic properties of PLA include surface coating with antistatic agents, blending with conductive fillers and adding ionic antistatic agents, but these solutions all have obvious shortcomings. For example, the antistatic effect of surface coating is short-lived and easy to wear; although blended conductive fillers can provide long-term antistatic effect, they will significantly reduce the transparency and mechanical properties of PLA, and high addition amounts may increase processing difficulty; and although ionic antistatic agents can migrate to the surface of the material to absorb moisture to form a conductive layer, they are easily affected by environmental humidity and have poor dispersion in the PLA matrix, and long-term use may lead to precipitation and contamination of the product.

[0003] With the urgent global demand for environmentally friendly materials and the increasing demand for antistatic performance in the electronics and medical industries, the development of PLA particles that combine biodegradability with long-lasting antistatic properties has become a key research direction. Static electricity in traditional PLA not only affects product appearance and functionality but can also lead to bacterial adsorption in medical devices or electronic component failure, directly threatening application safety. Therefore, innovative preparation processes are urgently needed to achieve intrinsic optimization of antistatic properties while retaining PLA's inherent advantages. Summary of the Invention

[0004] The purpose of the present invention is to provide an antistatic polylactic acid plastic particle and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: an antistatic polylactic acid plastic particle, comprising the following preparation steps: (1) The biochar was transferred to a gas-phase sulfonation reactor, and sulfuric acid vapor was introduced at a flow rate of 20-30 mL / min. The reaction temperature was controlled to be 160-180 ° C and the pressure was 0.3 MPa, and the sulfonation treatment was carried out for 3-4 hours. After the treatment, the product was washed with deionized water for 3 times, and then vacuum-dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar. 10 parts by weight of graphene oxide was dispersed in deionized water and ultrasonically treated for 30 minutes at a power of 600 W and a frequency of 40 kHz to disperse the product. Then, 80-100 parts by weight of polyethyleneimine solution was added, and the reaction was stirred at 60 ° C under nitrogen protection for 24 hours with a stirring speed of 120 rpm. The product was centrifuged at a speed of 10,000 rpm for 15 minutes to remove the ungrafted polyethyleneimine, and then vacuum-dried at 80 ° C with a vacuum degree of 0.085 MPa to obtain amino-hybrid graphene. (2) Sulfonated biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, and ethanol was added to prepare a solution with a concentration of 50 mg / mL. The mixture was then ultrasonically dispersed at a power of 800 W for 1 h. After the dispersion was completed, the ethanol was evaporated by stirring at 60 ° C at a stirring speed of 240 rpm for 4 h. The mixture was then vacuum dried at 80 ° C for 24 h with a vacuum degree of 0.085 MPa to obtain a composite filler. (3) 100 parts by weight of end-hydroxy polylactic acid and 6-10 parts of composite fillers were melt-blended in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120 rpm, and pelletized to obtain master batches; the master batches were placed in a supercritical foaming device, injected with carbon dioxide, and saturated at a temperature of 130-140°C for 2 hours; after the reaction was completed, the pressure was released to obtain porous particles; (2-hydroxyethyl)trimethylammonium chloride was dissolved in ethanol, and then added to the porous particles, and the porous particles were soaked at a temperature of 50°C and a vacuum degree of -0.08 MPa for 4 hours; finally, vacuum dried at 60°C for 24 hours with a vacuum degree of 0.0085 MPa to remove the residual solvent and obtain antistatic polylactic acid plastic particles.

[0006] Furthermore, the preparation method of biochar in step (1) is as follows: 100 parts by weight of lignin powder with a particle size of 60-80 μm is placed in a quartz boat of a tubular furnace, heated to 550-650° C. at 5° C. / min under a nitrogen atmosphere, and carbonized for 2 h to obtain biochar.

[0007] Furthermore, in step (1), the sulfuric acid vapor is generated by evaporating 98% concentrated sulfuric acid at 200°C.

[0008] Furthermore, the concentration of graphene oxide in step (1) is 1 mg / mL.

[0009] Furthermore, in step (1), the diameter of the graphene oxide sheet is 5-20 μm.

[0010] Furthermore, the concentration of the polyethyleneimine solution in step (1) is 10 wt%.

[0011] Furthermore, when carbon dioxide is injected in step (3), the pressure reaches 25 MPa.

[0012] Furthermore, the pressure relief rate in step (3) is 50-100 MPa / s.

[0013] Furthermore, the concentration of (2-hydroxyethyl)trimethylammonium chloride in step (3) is 20 wt%.

[0014] Furthermore, in step (3), the mass ratio of the porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention takes bio-based functional fillers and multi-level composite structure design as the core to achieve the antistatic and environmentally friendly effects of polylactic acid plastic.

[0016] First, sulfonated biochar was prepared via a vapor-phase sulfonation process using lignin as a biomass precursor. Its surface is rich in sulfonic acid groups, which form a dynamic ion-conducting network through proton dissociation of the sulfonic acid groups in a humid environment. Graphene oxide was then modified with polyethyleneimine. A positively charged hybrid graphene was constructed through covalent grafting and physical coating of amino groups onto the epoxy groups on the graphene oxide surface. The amino groups in the hybrid graphene enhanced the hygroscopicity of the polylactic acid surface, creating continuous water molecule channels. Combined with the graphene permeation network, this enabled rapid charge dissipation in the bulk. To achieve efficient two-phase composites, a dual mechanism of π-π stacking and electrostatic adsorption was employed. The lignin-derived polycyclic aromatic hydrocarbon structure and the sp² carbon layers of the hybrid graphene were tightly stacked through π-π interactions. The sulfonated biochar and amino groups were then electrostatically attracted to form a composite filler with a synergistic "chemical bond-physical interaction" interface.

[0017] Secondly, the hydroxy-terminated polylactic acid is combined with composite fillers to foam into porous plastic particles, which are then impregnated with ionic liquid to improve conductivity. The hydroxyl groups at the end of the hydroxyl-terminated polylactic acid (PLA) molecular chains provide unique reactive sites for functional modification. They react with residual amino groups on the hybrid graphene surface through a condensation reaction, forming chemical grafts. The graphene's sp² carbon layers generate dipole-π interactions with the ester groups of the PLA backbone, significantly improving the filler's interfacial compatibility. The two-dimensional barrier effect of graphene sheets refines the pore size during supercritical CO2 foaming. Hydroxyl groups form dynamic crosslinks through a hydrogen-bonding network with sulfonic acid groups generated by proton dissociation of sulfonated biochar. This not only inhibits cell collapse but also serves as anchor points for an ionic "highway," providing active sites for subsequent ionic liquid loading. Finally, a choline-based ionic liquid is introduced into the porous PLA backbone via an impregnation method. The choline cations form stable ion pairs with the sulfonic acid through strong electrostatic interactions, while the anions of the ionic liquid bind to the residual amino groups of the hybrid graphene through hydrogen bonds and ion-dipole interactions, forming a three-dimensional ionic conductive network throughout the PLA-filler interface. This synergistic effect of the three components creates an "electron-ion" dual-mechanism for conductivity, endowing the material with excellent antistatic properties. And the material still maintains its environmentally friendly characteristics and has an excellent biodegradability rate. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the antistatic polylactic acid plastic particles prepared in the following examples. Volume resistivity: measured according to GB / T15662-1995; Surface resistivity: measured according to GB / T31838.3-2019; Degradation rate: Refer to GB / T16716.7-2012 standard to test the compost degradation rate of degradable plastics after 3 months (%) Example 1

[0020] (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm was placed in a tubular furnace quartz boat, and the temperature was raised to 550-650 ° C at 5 ° C / min in a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; the biochar was transferred to a gas phase sulfonation reactor, and sulfuric acid vapor was introduced at a flow rate of 20-30 mL / min. The sulfuric acid vapor was generated by evaporating 98% concentrated sulfuric acid at 200 ° C. The reaction temperature was controlled to be 160-180 ° C and the pressure was 0.3 MPa. The sulfonation treatment was carried out for 3-4 hours; the product after the treatment was washed with deionized water for 3 times, and then vacuum dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar; 10 parts by weight of graphene oxide with a flake size of 5-20 μm was dispersed in deionized water with a graphene oxide concentration of 1 mg / mL. The power was 600 W and the frequency was 40 kHz ultrasonic treatment for 30 minutes to disperse; adding 80-100 parts by weight of a 10 wt% polyethyleneimine solution, stirring and reacting at 60°C under nitrogen protection for 24 hours at a stirring speed of 120 rpm; centrifuging at a speed of 10000 rpm for 15 minutes to remove ungrafted polyethyleneimine, and vacuum drying at 80°C with a vacuum degree of 0.085 MPa to obtain amino hybrid graphene; (2) Sulfonated biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, and ethanol was added to prepare a solution with a concentration of 50 mg / mL. The mixture was then ultrasonically dispersed at a power of 800 W for 1 h. After the dispersion was completed, the ethanol was evaporated by stirring at 60 ° C at a stirring speed of 240 rpm for 4 h. The mixture was then vacuum dried at 80 ° C for 24 h with a vacuum degree of 0.085 MPa to obtain a composite filler. (3) Add 100 parts of lactic acid monomer to the reactor, evacuate the reaction system at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6 hours, remove the moisture generated in the reaction to obtain polylactic acid prepolymer; then add 1-35 parts of polyol and 0.5-5 parts of tetrabutyl titanate to the reaction system, heat it to 140-200°C, evacuate the reaction system to control the pressure to be maintained at 50-5KPa, react for 4-12 hours to obtain end-hydroxy polylactic acid; melt-blend 100 parts by weight of end-hydroxy polylactic acid with 6-10 parts of composite filler in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120rpm, and cut into pellets to obtain masterbatch The masterbatch is placed in a supercritical foaming device, and carbon dioxide is injected to a pressure of 25 MPa, and saturated at a temperature of 130-140°C for 2 hours. After the reaction is completed, the pressure is released at a rate of 50-100 MPa / s to obtain porous particles. (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol, and the concentration of (2-hydroxyethyl)trimethylammonium chloride is 20wt%. Then, porous particles are added, and the mass ratio of porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1. The porous particles are soaked at a temperature of 50°C and a vacuum degree of -0.08MPa for 4 hours. Finally, vacuum drying is carried out at 60°C for 24 hours, and the vacuum degree is 0.0085MPa to remove the residual solvent to obtain antistatic polylactic acid plastic particles. Example 2

[0021] (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm was placed in a tubular furnace quartz boat, and the temperature was raised to 550-650 ° C at 5 ° C / min in a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; the biochar was transferred to a gas phase sulfonation reactor, and sulfuric acid vapor was introduced at a flow rate of 20-30 mL / min. The sulfuric acid vapor was generated by evaporating 98% concentrated sulfuric acid at 200 ° C. The reaction temperature was controlled to be 160-180 ° C and the pressure was 0.3 MPa. The sulfonation treatment was carried out for 3-4 hours; the product after the treatment was washed with deionized water for 3 times, and then vacuum dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar; 10 parts by weight of graphene oxide with a flake size of 5-20 μm was dispersed in deionized water with a graphene oxide concentration of 1 mg / mL. The power was 600 W and the frequency was 40 kHz ultrasonic treatment for 30 minutes to disperse; adding 80-100 parts by weight of a 10 wt% polyethyleneimine solution, stirring and reacting at 60°C under nitrogen protection for 24 hours at a stirring speed of 120 rpm; centrifuging at a speed of 10000 rpm for 15 minutes to remove ungrafted polyethyleneimine, and vacuum drying at 80°C with a vacuum degree of 0.085 MPa to obtain amino hybrid graphene; (2) Sulfonated biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, and ethanol was added to prepare a solution with a concentration of 50 mg / mL. The mixture was then ultrasonically dispersed at a power of 800 W for 1 h. After the dispersion was completed, the ethanol was evaporated by stirring at 60 ° C at a stirring speed of 240 rpm for 4 h. The mixture was then vacuum dried at 80 ° C for 24 h with a vacuum degree of 0.085 MPa to obtain a composite filler. (3) Add 100 parts of lactic acid monomer to the reactor, evacuate the reaction system at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6 hours, remove the moisture generated in the reaction to obtain polylactic acid prepolymer; then add 1-35 parts of polyol and 0.5-5 parts of tetrabutyl titanate to the reaction system, heat it to 140-200°C, evacuate the reaction system to control the pressure to be maintained at 50-5KPa, react for 4-12 hours to obtain end-hydroxy polylactic acid; melt-blend 100 parts by weight of end-hydroxy polylactic acid with 6-10 parts of composite filler in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120rpm, and cut into pellets to obtain masterbatch The masterbatch is placed in a supercritical foaming device, and carbon dioxide is injected to a pressure of 25 MPa, and saturated at a temperature of 130-140°C for 2 hours. After the reaction is completed, the pressure is released at a rate of 50-100 MPa / s to obtain porous particles. (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol, and the concentration of (2-hydroxyethyl)trimethylammonium chloride is 20wt%. Then, porous particles are added, and the mass ratio of porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1. The porous particles are soaked at a temperature of 50°C and a vacuum degree of -0.08MPa for 4 hours. Finally, vacuum drying is carried out at 60°C for 24 hours, and the vacuum degree is 0.0085MPa to remove the residual solvent to obtain antistatic polylactic acid plastic particles. Example 3

[0022] (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm was placed in a tubular furnace quartz boat, and the temperature was raised to 550-650 ° C at 5 ° C / min in a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; the biochar was transferred to a gas phase sulfonation reactor, and sulfuric acid vapor was introduced at a flow rate of 20-30 mL / min. The sulfuric acid vapor was generated by evaporating 98% concentrated sulfuric acid at 200 ° C. The reaction temperature was controlled to be 160-180 ° C and the pressure was 0.3 MPa. The sulfonation treatment was carried out for 3-4 hours; the product after the treatment was washed with deionized water for 3 times, and then vacuum dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar; 10 parts by weight of graphene oxide with a flake size of 5-20 μm was dispersed in deionized water with a graphene oxide concentration of 1 mg / mL. The power was 600 W and the frequency was 40 kHz ultrasonic treatment for 30 minutes to disperse; adding 80-100 parts by weight of a 10 wt% polyethyleneimine solution, stirring and reacting at 60°C under nitrogen protection for 24 hours at a stirring speed of 120 rpm; centrifuging at a speed of 10000 rpm for 15 minutes to remove ungrafted polyethyleneimine, and vacuum drying at 80°C with a vacuum degree of 0.085 MPa to obtain amino hybrid graphene; (2) Sulfonated biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, and ethanol was added to prepare a solution with a concentration of 50 mg / mL. The mixture was then ultrasonically dispersed at a power of 800 W for 1 h. After the dispersion was completed, the ethanol was evaporated by stirring at 60 ° C at a stirring speed of 240 rpm for 4 h. The mixture was then vacuum dried at 80 ° C for 24 h with a vacuum degree of 0.085 MPa to obtain a composite filler. (3) Add 100 parts of lactic acid monomer to the reactor, evacuate the reaction system at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6 hours, remove the moisture generated in the reaction to obtain polylactic acid prepolymer; then add 1-35 parts of polyol and 0.5-5 parts of tetrabutyl titanate to the reaction system, heat it to 140-200°C, evacuate the reaction system to control the pressure to be maintained at 50-5KPa, react for 4-12 hours to obtain end-hydroxy polylactic acid; melt-blend 100 parts by weight of end-hydroxy polylactic acid with 6-10 parts of composite filler in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120rpm, and cut into pellets to obtain masterbatch The masterbatch is placed in a supercritical foaming device, and carbon dioxide is injected to a pressure of 25 MPa, and saturated at a temperature of 130-140°C for 2 hours. After the reaction is completed, the pressure is released at a rate of 50-100 MPa / s to obtain porous particles. (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol, and the concentration of (2-hydroxyethyl)trimethylammonium chloride is 20wt%. Then, porous particles are added, and the mass ratio of porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1. The porous particles are soaked at a temperature of 50°C and a vacuum degree of -0.08MPa for 4 hours. Finally, vacuum drying is carried out at 60°C for 24 hours, and the vacuum degree is 0.0085MPa to remove the residual solvent to obtain antistatic polylactic acid plastic particles.

[0023] Comparative Example 1 The difference between Comparative Example 1 and Example 2 lies in the difference in steps (1) and (2). Steps (1) and (2) are changed to: (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm is placed in a tubular furnace quartz boat, heated to 550-650°C at 5°C / min under a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; 10 parts by weight of graphene oxide with a flake size of 5-20 μm is dispersed in deionized water, the graphene oxide concentration is 1 mg / mL, and ultrasonically treated for 30 minutes at a power of 600 W and a frequency of 40 kHz for dispersion; 80-100 parts by weight of a 10 wt% polyethyleneimine solution is added, and the mixture is stirred and reacted at 60°C under nitrogen protection for 24 hours at a stirring speed of 120 rpm; the mixture is centrifuged at a speed of 10,000 rpm for 15 minutes to remove ungrafted polyethyleneimine, and the mixture is vacuum dried at 80°C with a vacuum degree of 0.085 MPa to obtain amino hybrid graphene; (2) Biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, ethanol was added to prepare a solution with a concentration of 50 mg / mL, and then ultrasonically dispersed at a power of 800 W for 1 hour; after the dispersion was completed, the ethanol was evaporated by stirring at 60°C at a stirring speed of 240 rpm for 4 hours; then vacuum dried at 80°C for 24 hours with a vacuum degree of 0.085 MPa to obtain a composite filler; the remaining steps were the same as in Example 2.

[0024] Comparative Example 2 The difference between Comparative Example 2 and Example 2 lies in the difference in steps (1) and (2). Steps (1) and (2) are changed to: (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm is placed in a quartz boat of a tubular furnace, and the temperature is raised to 550-650°C at 5°C / min under a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; the biochar is transferred to a gas-phase sulfonation reactor, and sulfuric acid vapor is introduced at a flow rate of 20-30 mL / min, and the sulfuric acid vapor is increased from 98 % concentrated sulfuric acid is evaporated at 200 ° C, the reaction temperature is controlled to be 160-180 ° C, the pressure is 0.3 MPa, and the sulfonation treatment is carried out for 3-4 hours; the product after the treatment is washed with deionized water for 3 times, and then vacuum dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar; 10 parts by weight of graphene oxide with a sheet diameter of 5-20 μm is dispersed in deionized water, and the graphene oxide concentration is 1 mg / mL. It is dispersed by ultrasonic treatment at a power of 600 W and a frequency of 40 kHz for 30 minutes; 80-100 parts by weight of a 10wt% polyethyleneimine solution is added, and the reaction is stirred at 60 ° C under nitrogen protection for 24 hours with a stirring speed of 120 rpm; the rotation speed is 10000 rpm for 15 minutes to remove the ungrafted polyethyleneimine, and the product is vacuum dried at 80 ° C with a vacuum degree of 0.085 MPa to obtain amino hybrid graphene; (2) Sulfonated biochar and graphene oxide with a sheet diameter of 5-20 μm were mixed in a mass ratio of 7:2-4, ethanol was added to prepare a solution with a concentration of 50 mg / mL, and then ultrasonically dispersed at a power of 800 W for 1 hour; after the dispersion was completed, the ethanol was evaporated by stirring at 60°C at a stirring speed of 240 rpm for 4 hours; then vacuum dried at 80°C for 24 hours with a vacuum degree of 0.085 MPa to obtain a composite filler; the remaining steps were the same as in Example 2.

[0025] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that there is no step (2), and steps (1) and (3) are changed to: (1) 100 parts by weight of lignin powder with a particle size of 60-80 μm is placed in a tubular furnace quartz boat, and the temperature is raised to 550-650°C at 5°C / min under a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar; the biochar is transferred to a gas-phase sulfonation reactor, and sulfuric acid vapor is introduced at a flow rate of 20-30 mL / min. The sulfuric acid vapor is generated by evaporating 98% concentrated sulfuric acid at 200°C. The reaction temperature is controlled to be 160-180°C and the pressure is 0.3 MPa. The sulfonation treatment is carried out for 3-4 hours; the product after the treatment is washed with deionized water for 3 times, and then vacuum-dried at 80°C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar; (3) Add 100 parts of lactic acid monomer to the reactor, evacuate the reaction system at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6 hours, remove the water generated in the reaction to obtain polylactic acid prepolymer; then add 1-35 parts of polyol and 0.5-5 parts of tetrabutyl titanate to the reaction system, heat it to 140-200°C, evacuate the reaction system to control the pressure to be maintained at 50-5KPa, react for 4-12 hours to obtain end-hydroxy polylactic acid; melt-blend 100 parts by weight of end-hydroxy polylactic acid with 6-10 parts of sulfonated biochar in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120rpm, and cut into pellets to obtain master batches; the master batches are placed In a supercritical foaming device, carbon dioxide is injected to a pressure of 25 MPa, and saturated at a temperature of 130-140° C. for 2 hours; after the reaction is completed, the pressure is released at a rate of 50-100 MPa / s to obtain porous particles; (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol to a concentration of 20 wt % of (2-hydroxyethyl)trimethylammonium chloride, and then the porous particles are added, with a mass ratio of the porous particles to (2-hydroxyethyl)trimethylammonium chloride being 3-5:1; the porous particles are soaked at a temperature of 50° C. and a vacuum degree of -0.08 MPa for 4 hours; finally, vacuum drying is performed at 60° C. for 24 hours to a vacuum degree of 0.0085 MPa to remove residual solvent to obtain antistatic polylactic acid plastic particles; and the remaining steps are the same as those in Example 2.

[0026] Comparative Example 4 The difference between Comparative Example 4 and Example 2 lies in the difference in step (3). Step (3) is changed to: add 100 parts of lactic acid monomer to the reactor, evacuate the reaction system at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6h, remove the moisture generated in the reaction to obtain polylactic acid prepolymer; then add 0.5-5 parts of tetrabutyl titanate to the reaction system, heat it to 140-200°C, evacuate the reaction system to control the pressure to be maintained at 50-5KPa, react for 4-12h to obtain polylactic acid; melt blend 100 parts by weight of polylactic acid with 6-10 parts of composite filler in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120rpm, and pelletize to obtain The masterbatch is placed in a supercritical foaming device, and carbon dioxide is injected to a pressure of 25 MPa, and saturated at a temperature of 130-140° C. for 2 hours; after the reaction is completed, the pressure is released at a rate of 50-100 MPa / s to obtain porous particles; (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol, and the concentration of (2-hydroxyethyl)trimethylammonium chloride is 20wt%, and then the porous particles are added, and the mass ratio of the porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1, and the porous particles are soaked at a temperature of 50° C. and a vacuum degree of -0.08 MPa for 4 hours; finally, vacuum drying is performed at 60° C. for 24 hours, and the vacuum degree is 0.0085 MPa, and the residual solvent is removed to obtain antistatic polylactic acid plastic particles; the remaining steps are the same as those in Example 2.

[0027] Comparative Example 5 The difference between Comparative Example 5 and Example 2 lies in the difference in step (3). Step (3) is changed to: add 100 parts of lactic acid monomer to the reactor, evacuate at 120°C, control the pressure of the reaction system to be maintained at 70-30KPa, react for 2-6 hours, remove the moisture generated in the reaction to obtain polylactic acid prepolymer; then add 1-35 parts of polyol and 0.5-5 parts of tetrabutyl titanate to the reaction system, heat to 140-200°C, evacuate and control the pressure of the reaction system to be maintained at 50-5KPa, react for 4-12 hours to obtain end-hydroxy polylactic acid; 100 parts by weight of end-hydroxy polylactic acid and 6-10 parts of compound The filler is melt-blended in a twin-screw extruder at a melting temperature of 170-180° C. and a rotation speed of 80-120 rpm, and pelletized to obtain a masterbatch; (2-hydroxyethyl)trimethylammonium chloride is dissolved in ethanol at a concentration of 20 wt %; the masterbatch is added, and the mass ratio of the porous particles to the (2-hydroxyethyl)trimethylammonium chloride is 3-5:1; the porous particles are soaked at a temperature of 50° C. and a vacuum degree of -0.08 MPa for 4 hours; and finally, vacuum drying is performed at 60° C. for 24 hours at a vacuum degree of 0.0085 MPa to remove residual solvent to obtain antistatic polylactic acid plastic particles; and the remaining steps are the same as those in Example 2.

[0028] Effect Examples Table 1 below shows the performance analysis results of antistatic polylactic acid plastic particles using Examples 1 to 3 of the present invention and Comparative Examples 1 to 5.

[0029] Table 1

[0030] Comparison of the experimental data for volume and surface resistivity in the examples and comparative examples reveals that the present invention utilizes lignin as a biomass precursor and produces sulfonated biochar via a vapor-phase sulfonation process. The biochar's surface is rich in sulfonic acid groups, which form a dynamic ionic conductive network through proton dissociation of the sulfonic acid groups in a humid environment. Graphene oxide is modified with polyethyleneimine, and positively charged hybrid graphene is constructed through covalent grafting and physical coating of amino groups with epoxy groups on the graphene oxide surface. The amino groups in the hybrid graphene enhance the hygroscopicity of the polylactic acid surface, creating continuous water molecule channels. Combined with the graphene permeation network, this allows for rapid bulk charge dissipation. To achieve efficient two-phase composites, a dual mechanism of π-π stacking and electrostatic adsorption is employed. The lignin-derived polycyclic aromatic hydrocarbon structure and the sp² carbon layers of the hybrid graphene are tightly stacked through π-π interactions, while the sulfonated biochar and amino groups are electrostatically attracted to form a composite filler with a synergistic "chemical bond-physical interaction" interface. Furthermore, the hydroxyl-terminated polylactic acid is combined with the composite filler to form porous plastic particles, which are then impregnated with an ionic liquid to improve conductivity. The hydroxyl groups at the end of the hydroxyl-terminated polylactic acid (PLA) molecular chains provide unique reactive sites for functional modification. They react with residual amino groups on the hybrid graphene surface through a condensation reaction, forming chemical grafts. The graphene's sp² carbon layers generate dipole-π interactions with the ester groups of the PLA backbone, significantly improving the filler's interfacial compatibility. The two-dimensional barrier effect of graphene sheets refines the pore size during supercritical CO2 foaming. Hydroxyl groups form dynamic crosslinks through a hydrogen-bonding network with sulfonic acid groups generated by proton dissociation of sulfonated biochar. This not only inhibits cell collapse but also serves as anchor points for an ionic "highway," providing active sites for subsequent ionic liquid loading. Finally, a choline-based ionic liquid is introduced into the porous PLA backbone via an impregnation method. The choline cations form stable ion pairs with the sulfonic acid through strong electrostatic interactions, while the anions of the ionic liquid bind to the residual amino groups of the hybrid graphene through hydrogen bonds and ion-dipole interactions, forming a three-dimensional ionic conductive network throughout the PLA-filler interface. This synergistic effect of the three components creates an "electron-ion" dual-mechanism for conductivity, endowing the material with excellent antistatic properties. From the comparison of the experimental data of the degradation rates of the embodiment and the comparative example, it can be found that the material used in the present invention still maintains the environmental protection characteristics and has an excellent biodegradation rate.

[0031] 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 embodied 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 illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. An antistatic polylactic acid plastic particle, characterized in that: The method comprises the following preparation steps: (1) The biochar was transferred to a gas-phase sulfonation reactor, and sulfuric acid vapor was introduced at a flow rate of 20-30 mL / min. The reaction temperature was controlled to be 160-180 ° C and the pressure was 0.3 MPa, and the sulfonation treatment was carried out for 3-4 hours. After the treatment, the product was washed with deionized water for 3 times, and then vacuum-dried at 80 ° C for 12 hours with a vacuum degree of 0.085 MPa to obtain sulfonated biochar. 10 parts by weight of graphene oxide was dispersed in deionized water and ultrasonically treated for 30 minutes at a power of 600 W and a frequency of 40 kHz to disperse the product. Then, 80-100 parts by weight of polyethyleneimine solution was added, and the reaction was stirred at 60 ° C under nitrogen protection for 24 hours with a stirring speed of 120 rpm. The product was centrifuged at a speed of 10,000 rpm for 15 minutes to remove the ungrafted polyethyleneimine, and then vacuum-dried at 80 ° C with a vacuum degree of 0.085 MPa to obtain amino-hybrid graphene. (2) Sulfonated biochar and amino-modified hybrid graphene were mixed in a mass ratio of 7:2-4, and ethanol was added to prepare a solution with a concentration of 50 mg / mL. The mixture was then ultrasonically dispersed at a power of 800 W for 1 h. After the dispersion was completed, the ethanol was evaporated by stirring at 60 ° C at a stirring speed of 240 rpm for 4 h. The mixture was then vacuum dried at 80 ° C for 24 h with a vacuum degree of 0.085 MPa to obtain a composite filler. (3) 100 parts by weight of end-hydroxy polylactic acid and 6-10 parts of composite fillers were melt-blended in a twin-screw extruder at a melting temperature of 170-180°C and a rotation speed of 80-120 rpm, and pelletized to obtain master batches; the master batches were placed in a supercritical foaming device, injected with carbon dioxide, and saturated at a temperature of 130-140°C for 2 hours; after the reaction was completed, the pressure was released to obtain porous particles; (2-hydroxyethyl)trimethylammonium chloride was dissolved in ethanol, and then added to the porous particles, and the porous particles were soaked at a temperature of 50°C and a vacuum degree of -0.08 MPa for 4 hours; finally, vacuum dried at 60°C for 24 hours with a vacuum degree of 0.0085 MPa to remove the residual solvent and obtain antistatic polylactic acid plastic particles.

2. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: The preparation method of biochar in step (1) is as follows: 100 parts by weight of lignin powder with a particle size of 60-80 μm is placed in a tubular furnace quartz boat, the temperature is raised to 550-650° C. at 5° C. / min under a nitrogen atmosphere, and carbonized for 2 hours to obtain biochar.

3. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: In step (1), the sulfuric acid vapor is generated by evaporating 98% concentrated sulfuric acid at 200°C.

4. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: The concentration of graphene oxide in step (1) is 1 mg / mL.

5. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: In the step (1), the diameter of the graphene oxide sheet is 5-20 μm.

6. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: The concentration of the polyethyleneimine solution in step (1) is 10 wt%.

7. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: When carbon dioxide is injected in step (3), the pressure reaches 25 MPa.

8. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: The pressure relief rate in step (3) is 50-100 MPa / s.

9. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: The concentration of (2-hydroxyethyl)trimethylammonium chloride in step (3) is 20 wt %.

10. The antistatic polylactic acid plastic particles according to claim 1, characterized in that: In step (3), the mass ratio of the porous particles to (2-hydroxyethyl)trimethylammonium chloride is 3-5:1.

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