Wear-resistant environment-friendly plastic for children's toys and preparation method of wear-resistant environment-friendly plastic

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a wear-resistant environment-friendly plastic for children's toys and a preparation method of the wear-resistant environment-friendly plastic for children's toys, and the wear-resistant environment-friendly plastic for children's toys comprises the following components: 100 parts of polylactic acid; 15 to 40 parts of polycaprolactone; 6-25 parts of a composite wear-resistant agent; 5 to 15 parts of a reactive compatibilizer; 0.2 to 1 part of an antioxidant; and 0.2 to 1 part of a lubricant. The preparation method of the wear-resistant environment-friendly plastic for the children's toys comprises the following steps: mixing the weighed materials at a high speed to obtain a uniform premix; the premix is subjected to melt blending extrusion, and the extruded material is subjected to water cooling, bracing, pelletizing and drying to obtain the wear-resistant environment-friendly plastic for the children's toys. The plastic disclosed by the invention can form a chemical bonding network in a polylactic acid and polycaprolactone blending system, and meanwhile, excellent wear resistance and impact resistance are realized.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a wear-resistant and environmentally friendly plastic for children's toys and its preparation method. Background Technology

[0002] In the children's toy industry, plastic has become the dominant material for manufacturing various toys due to its ease of processing and molding, high design freedom, and relatively low production cost. From rattles and teething toys for infants to building blocks and model cars for preschoolers, and even outdoor playground equipment, plastic is ubiquitous. With socio-economic development and parents' increasing attention to children's growth environment, modern toy design not only pursues fun and educational functions but also prioritizes the environmental safety and durability of materials.

[0003] In real-world use, children's toys face wear and tear issues in many ways. Take interlocking building blocks as an example: the connecting posts and slots in these toys experience significant friction and pressure during repeated insertion and removal. One toy company, while producing a particular building block set, discovered that in laboratory simulations of insertion and removal, the connecting posts showed noticeable white wear marks after 300 cycles, with the insertion and removal force decreasing by over 40%, leading to loosening of the blocks and affecting assembly stability. Even more seriously, when the blocks fall onto outdoor gravel surfaces, the surface is scratched deeply by the sand and gravel. These micro-grooves not only trap dirt but also provide a breeding ground for bacteria.

[0004] Another typical product is the wheels of children's scooters and strollers. After children's wheels have been driven continuously for 10 kilometers on concrete roads, the wear depth of the wheel surface can reach 0.3 to 0.5 millimeters. The fine dust generated by the wear not only pollutes the environment, but more importantly, the roughened wheel surface increases rolling resistance, significantly reducing the ease of riding for children. In addition, the curved surface of the base of some rocking horse toys is also prone to wear through when repeatedly rubbing against the ground, exposing the internal filling and posing a safety hazard.

[0005] To address these issues, existing technologies have explored various approaches. One approach involves adding inorganic rigid fillers to the matrix resin to improve surface hardness, such as silica, alumina, or diatomaceous earth. Studies have shown that adding less than 10% diatomaceous earth to polypropylene can improve the impact strength and flexural properties of the composite material. However, when the addition exceeds 10%, voids easily form between the diatomaceous earth particles, which actually reduces the material's impact strength. Furthermore, these inorganic fillers have poor interfacial compatibility with organic resins, requiring surface treatment with silane coupling agents or titanate coupling agents. However, if these coupling agents remain or migrate, they may introduce volatile organic compounds, posing an environmental risk for infant and toddler toys.

[0006] Another technical approach involves fiber reinforcement, such as adding glass fibers or carbon fibers. Studies have shown that adding modified carbon nanotubes to polylactic acid can achieve reinforcement and toughening, but the adhesion and dispersion between the filler and the matrix remain significant challenges. Glass fiber reinforced materials also suffer from fiber floating, resulting in rough and uneven toy surfaces that may irritate children's skin. Furthermore, the anisotropy of these materials increases the difficulty of dimensional control for precision components.

[0007] In recent years, researchers have begun to focus on the development of novel wear-resistant fillers. Some patents use polyoxymethylene powder as a wear-resistant agent, utilizing its self-lubricating properties to improve the wear resistance of materials. Other studies have explored introducing fullerenes as wear-resistant fillers into polymer matrices, utilizing their spherical molecular structure and excellent mechanical properties to enhance the material's wear resistance. In addition, some naturally derived materials, such as microfibers and layered double hydroxides, have also been explored for polymer modification. Nano-hydroxyapatite, due to its good biocompatibility and mechanical properties, has been widely used in the field of biomedical materials in recent years, but its application in toy materials has not yet been systematically studied.

[0008] However, most of the aforementioned studies employ single-filler modification, resulting in weak interfacial bonding between the filler and the matrix, making it difficult to simultaneously meet the dual requirements of wear resistance and impact resistance. Even more challenging is the fact that children's toys need to withstand both frictional contact and dynamic impact. While high-hardness fillers can improve surface wear resistance, they reduce the material's impact toughness; flexible components, while improving toughness, often come at the cost of sacrificing surface hardness. For example, Shantou Chenghai Qunlong Plastic Products Co., Ltd., in producing a children's toy car, experimented with various formulations and found that when the material's wear resistance met the standards, its impact resistance was often insufficient, causing the product to easily break when dropped from a height of 1 meter; conversely, when the impact resistance met the standards, the wear resistance was insufficient for long-term use. This dilemma of compromise plagues the entire toy industry.

[0009] Furthermore, existing technologies commonly employ commercially available general-purpose compatibilizers such as tributyl acetylacetonate and epoxidized soybean oil. While these compatibilizers can improve the compatibility of polylactic acid (PLA) and polycaprolactone (PVC) to some extent, their molecular chain structure lacks specific interaction with the matrix resin, making it difficult to simultaneously achieve interfacial bonding with inorganic fillers. Some studies have attempted to use copolymers of PLA and PVC as compatibilizers, but these compatibilizers have limited functionality, cannot form chemical bonds with fillers, and thus offer limited improvement to the overall performance of the composite material.

[0010] Therefore, there is a need to design a wear-resistant and environmentally friendly plastic for children's toys and its preparation method. Summary of the Invention

[0011] To overcome the shortcomings of existing technologies, this paper provides a wear-resistant and environmentally friendly plastic for children's toys and a method for preparing the same.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A wear-resistant and environmentally friendly plastic for use in children's toys, comprising the following components by parts by weight:

[0014] 100 parts of polylactic acid;

[0015] 15 to 40 parts of polycaprolactone;

[0016] 6 to 25 parts of composite wear-resistant agent;

[0017] 5 to 15 parts of reactive compatibilizer;

[0018] Antioxidant 0.2 to 1 part;

[0019] Lubricant 0.2 to 1 part;

[0020] The composite wear-resistant agent is a composite formed by the coordination of polyoxymethylene whiskers, fullerene, and phytic acid-modified hydroxyapatite through calcium ion coordination; the reactive compatibilizer is a triblock copolymer of polylactic acid, polycaprolactone, and glycidyl methacrylate.

[0021] The preparation process of the composite wear-resistant agent includes the following steps: dispersing polyoxymethylene whiskers and fullerene in anhydrous ethanol and ultrasonically dispersing for 30 to 60 minutes to obtain a mixed dispersion; dispersing phytic acid-modified hydroxyapatite in anhydrous ethanol and ultrasonically dispersing for 20 to 40 minutes to obtain a hydroxyapatite dispersion; slowly adding the hydroxyapatite dispersion dropwise to the mixed dispersion, while simultaneously adding a calcium chloride ethanol solution, wherein the amount of calcium chloride added is 1% to 5% of the mass of the phytic acid-modified hydroxyapatite; stirring and reacting at a temperature of 50 to 70°C for 3 to 6 hours; after the reaction is completed, centrifuging is performed, and the product is washed 3 to 5 times with anhydrous ethanol. The solid product is collected and vacuum dried at 60 to 80°C for 8 to 12 hours to obtain the composite wear-resistant agent.

[0022] The mass ratio of polyoxymethylene whiskers to fullerene is 1:0.3-0.6; the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 0.5-2:1.

[0023] The polyoxymethylene whiskers have an aspect ratio of 20:1 to 50:1, a diameter of 0.5 to 2 micrometers, and a length of 10 to 100 micrometers; the fullerene is C60, with an average particle size of 10 to 100 nanometers.

[0024] The phytic acid-modified hydroxyapatite is obtained by the following steps: dispersing nano-hydroxyapatite in water to prepare a suspension with a mass concentration of 5% to 10%, adding phytic acid, stirring and reacting at a temperature of 40 to 60°C for 2 to 4 hours, then centrifuging, washing with deionized water 2 to 4 times, collecting the solid product and vacuum drying at 50 to 70°C for 6 to 10 hours to obtain phytic acid-modified hydroxyapatite.

[0025] The amount of phytic acid added is 2% to 8% of the nano-hydroxyapatite.

[0026] In the actual use of children's toys, plastic materials need to withstand repeated friction and dynamic impacts simultaneously, posing a dual challenge to their wear resistance and impact resistance. Polylactic acid (PLA), as a biodegradable material, possesses high mechanical strength and good environmental friendliness, but its inherent brittleness limits its application. Polycaprolactone (PVC), while exhibiting excellent toughness, lacks sufficient strength when used alone. Although blending the two can be complementary, poor compatibility and easy phase separation are problems. Existing technologies attempt to add inorganic rigid fillers such as silica or diatomaceous earth to improve wear resistance, but the interfacial bonding between the filler and the matrix is ​​weak and easily leads to a decrease in impact toughness. Adding glass fiber or carbon fiber can provide reinforcement, but fiber floating and dimensional control problems exist. General-purpose compatibilizers such as tributyl acetylacetonate can improve compatibility, but they cannot form chemical bonds with fillers, thus having limited improvement on the overall performance of the composite material. Therefore, how to construct a structure in a PLA and PVC blend system that can effectively transfer stress and synergistically dissipate energy has become the key to resolving the contradiction between wear resistance and impact resistance.

[0027] This invention begins with the structural design of composite wear-resistant agents. Polyoxymethylene whiskers are highly crystalline micron-sized fibers with self-lubricating properties. During friction, they can form a transfer film on the surface to reduce the coefficient of friction; however, when used alone, their interfacial bonding with the matrix is ​​weak. Fullerene C60 has a unique spherical molecular structure and delocalized π-electron cloud, which can act like molecular balls at the friction interface, converting sliding friction into rolling friction; however, fullerene molecules are prone to aggregation. Nano-hydroxyapatite has high hardness and can provide wear-resistant support points, but its interfacial compatibility with organic polymers is poor.

[0028] To combine the advantages of the three materials, this invention employs phytic acid to modify the surface of nano-hydroxyapatite. Phytic acid molecules contain six phosphate groups, which coordinate with calcium ions on the surface of hydroxyapatite, introducing a large number of active phosphate groups onto the hydroxyapatite surface, resulting in phytic acid-modified hydroxyapatite. When polyoxymethylene whiskers and fullerenes are ultrasonically dispersed in anhydrous ethanol, the fullerenes interact with the ether oxygen atoms on the surface of the polyoxymethylene whiskers through delocalized π-electron clouds, forming a fullerene-coated whisker structure. Subsequently, a calcium chloride ethanol solution is added. Calcium ions coordinate with the phosphate groups on the surface of the phytic acid-modified hydroxyapatite, and also interact with the fullerene molecules through cation-π interactions. Simultaneously, they also exhibit weak coordination with the ether oxygen atoms on the surface of the polyoxymethylene whiskers, thereby bridging the three components together through calcium ions to form a composite wear-resistant agent. This ternary composite formed through chemical coordination has clear chemical bonds within it. When dispersed in polylactic acid and polycaprolactone, it can maintain structural integrity, avoiding the problem of filler agglomeration. At the same time, it allows stress to be effectively transferred between the three components, laying the foundation for subsequent chemical bonding with the matrix.

[0029] The reactive compatibilizer is obtained by the following steps: adding polylactic acid monomer and polycaprolactone monomer in a mass ratio of 1:0.3-1 to a reaction vessel, adding stannous octoate as a catalyst, wherein the amount of catalyst added is 0.1% to 0.5% of the total mass of the monomers, and reacting for 4 to 8 hours at a temperature of 130 to 150°C and a gauge pressure of -0.08 to -0.1 MPa to obtain a polylactic acid-polycaprolactone diblock prepolymer;

[0030] The polylactic acid-polycaprolactone diblock prepolymer was dissolved in toluene, and glycidyl methacrylate and azobisisobutyronitrile were added. The reaction was carried out at 70 to 90°C under nitrogen protection for 6 to 10 hours. After the reaction was completed, the mixture was cooled to room temperature and precipitated with anhydrous methanol. The precipitate was collected and vacuum dried at 40 to 60°C for 12 to 24 hours to obtain a polylactic acid-polycaprolactone-glycidyl methacrylate triblock copolymer.

[0031] The catalyst is added at a rate of 0.1% to 0.5% of the total mass of polylactic acid monomer and polycaprolactone monomer; the glycidyl methacrylate is added at a rate of 5% to 15% of the diblock prepolymer; and the azobisisobutyronitrile is added at a rate of 1% to 3% of the glycidyl methacrylate.

[0032] However, even if the composite wear-resistant agent itself has a synergistic reinforcing effect, if its interfacial bond with the polylactic acid and polycaprolactone matrix is ​​weak, it may still be pulled out or peeled off during friction, leading to performance degradation.

[0033] To address this problem, this invention designs a reactive compatibilizer, namely a triblock copolymer of polylactic acid (PLA), polycaprolactone (PCL), and glycidyl methacrylate (GAMA). This compatibilizer is prepared via a two-step method: first, PLA monomers and PCL monomers are reacted under stannous octoate catalysis to generate a PLA-PCL diblock prepolymer; then, this prepolymer is dissolved in toluene, and GAMA and azobisisobutyronitrile (AIBN) are added for grafting. The resulting molecular chain consists of three functional segments: the PLA segment exhibits good compatibility with PLA in the matrix and can entangle with the PLA molecular chain; the PCL segment is compatible with PCL in the matrix, enhancing the interfacial bonding of the flexible phase; and the terminal GAMA segment contains epoxy groups, exhibiting high reactivity.

[0034] During melt blending, the epoxy groups at the ends of the reactive compatibilizer molecular chains undergo a ring-opening reaction with the phosphate groups on the surface of the phytic acid-modified hydroxyapatite in the composite wear-resistant agent, forming stable chemical bonds. This anchors the composite wear-resistant agent within the polylactic acid and polycaprolactone blend system via chemical bonds. Compared to commonly used compatibilizers in the prior art, the reactive compatibilizer of this invention not only improves the compatibility between the polylactic acid and polycaprolactone phases and reduces the interfacial tension, but more importantly, it can form chemical bonds with the composite wear-resistant agent, avoiding the problem of weak filler-matrix interfaces in traditional blend systems.

[0035] The antioxidant includes hindered phenolic antioxidants and phosphite antioxidants; the hindered phenolic antioxidant is antioxidant 1010; the phosphite antioxidant is antioxidant 168; and the mass ratio of antioxidant 1010 to antioxidant 168 is 1-3:1.

[0036] The lubricant is calcium stearate.

[0037] A method for preparing wear-resistant and environmentally friendly plastic for children's toys includes the following steps: weighing polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant, mixing the above materials at high speed to obtain a uniform premix; performing melt blending extrusion on the premix, and then water-cooling, pelletizing and drying the extruded material to obtain the wear-resistant and environmentally friendly plastic for children's toys.

[0038] The specific parameters for the high-speed mixing are as follows: polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant are mixed at a temperature of 25 to 40°C and a rotation speed of 500 to 1500 revolutions per minute for 5 to 15 minutes.

[0039] The specific parameters for the melt blending extrusion are as follows: the premix is ​​added to a twin-screw extruder at a screw speed of 200 to 400 rpm and a feed speed of 20 to 40 rpm; the gauge pressure during extrusion is -0.06 to -0.1 MPa.

[0040] The drying process involves collecting the extruded material after it has been water-cooled and pelletized, and then maintaining the resulting pellets at a temperature of 60 to 80°C for 2 to 4 hours.

[0041] Building upon the above, the composite wear-resistant agent and reactive compatibilizer of this invention also exhibit a synergistic effect, forming a chemically bonded network spanning both phases in polylactic acid and polycaprolactone. When the material is subjected to friction, the polyoxymethylene whiskers in the composite wear-resistant agent provide skeletal support and self-lubricating properties, forming a transfer film on the friction surface to reduce the coefficient of friction; fullerene molecules act like molecular ball bearings at the friction interface, converting some sliding friction into rolling friction; and phytic acid-modified hydroxyapatite provides high-hardness support points to resist the cutting action of abrasive particles.

[0042] Because the composite wear-resistant agent is linked to the reactive compatibilizer via chemical bonds, and the reactive compatibilizer is entangled with the two phases in the matrix through its polylactic acid and polycaprolactone segments respectively, the composite wear-resistant agent will not be easily pulled out or peeled off during friction, thus maintaining its wear-resistant performance for a long time. When the material is subjected to impact, polyoxymethylene whiskers absorb impact energy through pull-out and bridging effects, fullerene molecules initiate and terminate crazing through their spherical structure, and phytic acid-modified hydroxyapatite particles hinder crack propagation through pinning effects. Simultaneously, the reactive compatibilizer molecular chains deform during impact through their flexible block structure, further absorbing impact energy. This synergistic effect of multiple energy dissipation mechanisms allows the material to maintain high surface hardness while possessing excellent toughness, thereby achieving a simultaneous improvement in wear resistance and impact resistance.

[0043] All components and their preparation methods used in this invention exhibit excellent environmental safety. Polylactic acid and polycaprolactone are both biodegradable materials, phytic acid is widely found in plant seeds, and polyoxymethylene whiskers, fullerenes, and nano-hydroxyapatite are all biocompatible materials. The entire preparation process avoids the use of toxic reagents that may introduce volatile organic compounds, such as silane coupling agents or titanate coupling agents, and the synthesis of reactive compatibilizers does not use toxic catalysts or solvents. Therefore, the wear-resistant and environmentally friendly plastic prepared by this invention fully meets the stringent environmental safety requirements for children's toys and is suitable for manufacturing various toy parts that need to withstand both frictional contact and dynamic impact.

[0044] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0045] 1. The composite wear-resistant agent of this invention organically combines polyoxymethylene whiskers, fullerene, and phytic acid-modified hydroxyapatite through calcium ion coordination to form a ternary composite. The phytic acid-modified hydroxyapatite is obtained through a coordination reaction between the phosphate groups in the phytic acid molecules and calcium ions on the surface of nano-hydroxyapatite. This modification process introduces a large number of active phosphate groups onto the surface of the hydroxyapatite, providing reaction sites for subsequent coordination assembly. When polyoxymethylene whiskers and fullerene are ultrasonically dispersed in anhydrous ethanol, the fullerene molecules interact with the ether oxygen atoms on the surface of the polyoxymethylene whiskers through their delocalized π-electron clouds, forming a fullerene-coated whisker structure. Subsequently, during the addition of calcium chloride ethanol solution, calcium ions coordinate with the phosphate groups on the surface of the phytic acid-modified hydroxyapatite and also generate cation-π interactions with the fullerene molecules. Simultaneously, they also exhibit weak coordination with the ether oxygen atoms on the surface of the polyoxymethylene whiskers, thereby bridging the three components together through calcium ions. The components in the composite wear-resistant agent are linked by chemical bonds. When dispersed in a matrix resin composed of polylactic acid and polycaprolactone, the structural integrity is maintained, avoiding the problem of filler agglomeration. At the same time, stress can be effectively transferred between the three components.

[0046] 2. The reactive compatibilizer used in this invention is a triblock copolymer of polylactic acid, polycaprolactone, and glycidyl methacrylate. Its molecular chain consists of three functional segments. The polylactic acid segment has good compatibility with the polylactic acid phase in the matrix and can entangle with the polylactic acid molecular chain. The polycaprolactone segment is compatible with the polycaprolactone phase in the matrix, enhancing the interfacial bonding of the flexible phase. The terminal glycidyl methacrylate segment contains epoxy groups and has high reactivity. During melt blending, the epoxy groups at the end of the reactive compatibilizer molecular chain undergo a ring-opening reaction with the phosphate groups on the surface of the phytic acid-modified hydroxyapatite in the composite wear-resistant agent, forming stable chemical bonds. This anchors the composite wear-resistant agent to the matrix resin through chemical bonds. Compared with common compatibilizers such as tributyl acetylglucose or epoxidized soybean oil used in the prior art, the reactive compatibilizer of the present invention can not only improve the compatibility between polylactic acid and polycaprolactone and reduce the interfacial tension between the two phases, but also form chemical bonds with composite wear-resistant agents, thus avoiding the problem of weak interface between filler and matrix in traditional blending systems.

[0047] 3. This invention establishes a chemically bonded network spanning both phases of polylactic acid (PLA) and polycaprolactone (PCL) through a composite wear-resistant agent and a reactive compatibilizer. When the material is subjected to friction, the polyoxymethylene (POM) whiskers in the composite wear-resistant agent provide skeletal support and self-lubricating properties, forming a transfer film on the friction surface and reducing the coefficient of friction. Fullerene molecules act like molecular ball bearings at the friction interface, converting some sliding friction into rolling friction. Phytic acid-modified hydroxyapatite provides high-hardness support points to resist the cutting action of abrasive particles. Because the composite wear-resistant agent is connected to the reactive compatibilizer through chemical bonds, and the reactive compatibilizer is entangled with both phases in the matrix through its PLA and PCL segments respectively, the composite wear-resistant agent will not be easily pulled out or peeled off during friction, thus maintaining its wear-resistant effect for a long time. When the material is subjected to impact, polyoxymethylene whiskers absorb impact energy through pull-out and bridging effects, fullerene molecules initiate and terminate craze propagation through their spherical structure, phytic acid-modified hydroxyapatite particles hinder crack propagation through pinning effects, and reactive compatibilizer molecular chains deform during impact through their flexible block structure, further absorbing impact energy, thereby achieving a simultaneous improvement in wear resistance and impact resistance. Detailed Implementation

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows:

[0050] Polylactic acid was purchased from Zhejiang Hisun Biomaterials Co., Ltd., CAS No. 9051-89-2, grade REVODE290 transparent injection molding grade.

[0051] Polycaprolactone was purchased from Wuhan Haishan Technology Co., Ltd., CAS No. 24980-41-4, grade PCL-8w white granules.

[0052] The polyoxymethylene whiskers were purchased from Suzhou Haicai Plastics Co., Ltd., under the brand name Mitsubishi Engineering Plastics, and the grade name IupitalFT2020.

[0053] The fullerene C60 was purchased from Suzhou CarbonFeng Graphene Technology Co., Ltd., CAS number 99685-96-8, brand name CarbonFeng Technology Fullerene C60.

[0054] The nano-hydroxyapatite was purchased from Zhejiang Yamei Nanotechnology Co., Ltd., with CAS number 1306-06-5 and grade AM-HAP-001-1.

[0055] Phytic acid was purchased from Jinjinle Chemical Co., Ltd., CAS No. 83-86-3.

[0056] Stannous octanoate was purchased from Baoji Funuokang Industrial Co., Ltd., CAS No. 301-10-0.

[0057] Glycidyl methacrylate was purchased from Ningbo Yinuo Chemical Co., Ltd., CAS No. 106-91-2.

[0058] Azobisisobutyronitrile (AIBN) was purchased from Zouping Mingxing Chemical Co., Ltd., CAS No. 78-67-1.

[0059] The technical solution of this application is as follows:

[0060] A wear-resistant and environmentally friendly plastic for use in children's toys, comprising the following components by parts by weight:

[0061] 100 parts of polylactic acid;

[0062] 15 to 40 parts of polycaprolactone;

[0063] 6 to 25 parts of composite wear-resistant agent;

[0064] 5 to 15 parts of reactive compatibilizer;

[0065] Antioxidant 0.2 to 1 part;

[0066] Lubricant 0.2 to 1 part;

[0067] The composite wear-resistant agent is a composite formed by the coordination of polyoxymethylene whiskers, fullerene, and phytic acid-modified hydroxyapatite through calcium ion coordination; the reactive compatibilizer is a triblock copolymer of polylactic acid, polycaprolactone, and glycidyl methacrylate.

[0068] The preparation process of the composite wear-resistant agent includes the following steps: dispersing polyoxymethylene whiskers and fullerene in anhydrous ethanol and ultrasonically dispersing for 30 to 60 minutes to obtain a mixed dispersion; dispersing phytic acid-modified hydroxyapatite in anhydrous ethanol and ultrasonically dispersing for 20 to 40 minutes to obtain a hydroxyapatite dispersion; slowly adding the hydroxyapatite dispersion dropwise to the mixed dispersion, while simultaneously adding a calcium chloride ethanol solution, wherein the amount of calcium chloride added is 1% to 5% of the mass of the phytic acid-modified hydroxyapatite; stirring and reacting at a temperature of 50 to 70°C for 3 to 6 hours; after the reaction is completed, centrifuging is performed, and the product is washed 3 to 5 times with anhydrous ethanol. The solid product is collected and vacuum dried at 60 to 80°C for 8 to 12 hours to obtain the composite wear-resistant agent.

[0069] The mass ratio of polyoxymethylene whiskers to fullerene is 1:0.3-0.6; the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 0.5-2:1.

[0070] The polyoxymethylene whiskers have an aspect ratio of 20:1 to 50:1, a diameter of 0.5 to 2 micrometers, and a length of 10 to 100 micrometers; the fullerene is C60, with an average particle size of 10 to 100 nanometers.

[0071] The phytic acid-modified hydroxyapatite is obtained by the following steps: dispersing nano-hydroxyapatite in water to prepare a suspension with a mass concentration of 5% to 10%, adding phytic acid, stirring and reacting at a temperature of 40 to 60°C for 2 to 4 hours, then centrifuging, washing with deionized water 2 to 4 times, collecting the solid product and vacuum drying at 50 to 70°C for 6 to 10 hours to obtain phytic acid-modified hydroxyapatite.

[0072] The amount of phytic acid added is 2% to 8% of the nano-hydroxyapatite.

[0073] The reactive compatibilizer is obtained by the following steps: adding polylactic acid monomer and polycaprolactone monomer in a mass ratio of 1:0.3-1 to a reaction vessel, adding stannous octoate as a catalyst, wherein the amount of catalyst added is 0.1% to 0.5% of the total mass of the monomers, and reacting for 4 to 8 hours at a temperature of 130 to 150°C and a gauge pressure of -0.08 to -0.1 MPa to obtain a polylactic acid-polycaprolactone diblock prepolymer;

[0074] The polylactic acid-polycaprolactone diblock prepolymer was dissolved in toluene, and glycidyl methacrylate and azobisisobutyronitrile were added. The reaction was carried out at 70 to 90°C under nitrogen protection for 6 to 10 hours. After the reaction was completed, the mixture was cooled to room temperature and precipitated with anhydrous methanol. The precipitate was collected and vacuum dried at 40 to 60°C for 12 to 24 hours to obtain a polylactic acid-polycaprolactone-glycidyl methacrylate triblock copolymer.

[0075] The catalyst is added at a rate of 0.1% to 0.5% of the total mass of polylactic acid monomer and polycaprolactone monomer; the glycidyl methacrylate is added at a rate of 5% to 15% of the diblock prepolymer; and the azobisisobutyronitrile is added at a rate of 1% to 3% of the glycidyl methacrylate.

[0076] The antioxidant includes hindered phenolic antioxidants and phosphite antioxidants; the hindered phenolic antioxidant is antioxidant 1010; the phosphite antioxidant is antioxidant 168; and the mass ratio of antioxidant 1010 to antioxidant 168 is 1-3:1.

[0077] The lubricant is calcium stearate.

[0078] A method for preparing wear-resistant and environmentally friendly plastic for children's toys includes the following steps: weighing polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant, mixing the above materials at high speed to obtain a uniform premix; performing melt blending extrusion on the premix, and then water-cooling, pelletizing and drying the extruded material to obtain the wear-resistant and environmentally friendly plastic for children's toys.

[0079] The specific parameters for the high-speed mixing are as follows: polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant are mixed at a temperature of 25 to 40°C and a rotation speed of 500 to 1500 revolutions per minute for 5 to 15 minutes.

[0080] The specific parameters for the melt blending extrusion are as follows: the premix is ​​added to a twin-screw extruder at a screw speed of 200 to 400 rpm and a feed speed of 20 to 40 rpm; the gauge pressure during extrusion is -0.06 to -0.1 MPa.

[0081] The drying process involves collecting the extruded material after it has been water-cooled and pelletized, and then maintaining the resulting pellets at a temperature of 60 to 80°C for 2 to 4 hours.

[0082] This invention utilizes the chemical bonding between composite wear-resistant agents and reactive compatibilizers to construct a three-dimensional network structure that spans both phases in a polylactic acid and polycaprolactone blend system, thereby achieving simultaneous improvement in wear resistance and impact resistance.

[0083] The present invention will be described in detail below through examples and comparative examples, but the scope of protection of the present invention is not limited to these examples. Unless otherwise specified, the chemical reagents and raw materials used in the following examples and comparative examples are all conventional commercially available products.

[0084] Example 1

[0085] Weigh out 100 parts of polylactic acid, 40 parts of polycaprolactone, 25 parts of composite wear-resistant agent, 15 parts of reactive compatibilizer, 1 part of antioxidant, and 1 part of lubricant by weight.

[0086] In the preparation of the composite wear-resistant agent, the mass ratio of polyoxymethylene whiskers to fullerene is 1:0.6, the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 2:1, the aspect ratio of polyoxymethylene whiskers is 50:1, the diameter is 2 micrometers and the length is 100 micrometers, the fullerene is C60 with an average particle size of 100 nanometers, the amount of calcium chloride added is 5% of the mass of phytic acid-modified hydroxyapatite, the reaction temperature is 70℃, the reaction time is 6 hours, the number of washings is 5, and the vacuum drying temperature is 80℃ for 12 hours.

[0087] In the preparation of phytic acid modified hydroxyapatite, the mass concentration of nano-hydroxyapatite suspension is 10%, the amount of phytic acid added is 8% of the nano-hydroxyapatite, the reaction temperature is 60℃, the reaction time is 4 hours, the washing is performed 4 times, and the vacuum drying temperature is 70℃ for 10 hours.

[0088] In the preparation of the reactive compatibilizer, the mass ratio of polylactic acid monomer to polycaprolactone monomer is 1:0.3, the amount of stannous octoate catalyst added is 0.5% of the total mass of monomers, the reaction temperature is 150℃, the gauge pressure is -0.08 MPa, the reaction time is 4 hours, the amount of glycidyl methacrylate added is 15% of the diblock prepolymer, the amount of azobisisobutyronitrile added is 3% of the glycidyl methacrylate, the reaction temperature is 90℃, the reaction time is 10 hours, and the vacuum drying temperature is 60℃ for 24 hours.

[0089] The antioxidant consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 3:1, and the lubricant is calcium stearate.

[0090] The above materials are mixed at 40°C and 1500 rpm for 5 minutes to obtain a premix. The premix is ​​added to a twin-screw extruder and melt-blended and extruded under the conditions of screw speed of 400 rpm, feed speed of 40 rpm, and gauge pressure of -0.06 MPa. The extruded material is water-cooled, granulated, and dried at 80°C for 2 hours to obtain wear-resistant and environmentally friendly plastic for children's toys.

[0091] Example 2

[0092] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0093] Weigh out 100 parts of polylactic acid, 15 parts of polycaprolactone, 6 parts of composite wear-resistant agent, 5 parts of reactive compatibilizer, 0.2 parts of antioxidant, and 0.2 parts of lubricant by weight.

[0094] In the preparation of the composite wear-resistant agent, the mass ratio of polyoxymethylene whiskers to fullerene is 1:0.3, the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 0.5:1, the aspect ratio of polyoxymethylene whiskers is 20:1, the diameter is 0.5 μm and the length is 10 μm, the fullerene is C60 with an average particle size of 10 nm, the amount of calcium chloride added is 1% of the mass of phytic acid-modified hydroxyapatite, the reaction temperature is 50℃, the reaction time is 3 hours, the washing is performed 3 times, and the vacuum drying temperature is 60℃ for 8 hours.

[0095] In the preparation of phytic acid modified hydroxyapatite, the mass concentration of nano-hydroxyapatite suspension is 5%, the amount of phytic acid added is 2% of the nano-hydroxyapatite, the reaction temperature is 40℃, the reaction time is 2 hours, the washing is performed twice, and the vacuum drying temperature is 50℃ and the time is 6 hours.

[0096] In the preparation of the reactive compatibilizer, the mass ratio of polylactic acid monomer to polycaprolactone monomer is 1:1, the amount of stannous octoate catalyst added is 0.1% of the total mass of monomers, the reaction temperature is 130℃, the gauge pressure is -0.1 MPa, the reaction time is 8 hours, the amount of glycidyl methacrylate added is 5% of the diblock prepolymer, the amount of azobisisobutyronitrile added is 1% of glycidyl methacrylate, the reaction temperature is 70℃, the reaction time is 6 hours, and the vacuum drying temperature is 40℃ for 12 hours.

[0097] The antioxidant consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, and the lubricant is calcium stearate.

[0098] The above materials are mixed at 25°C and 500 rpm for 15 minutes to obtain a premix. The premix is ​​added to a twin-screw extruder and melt-blended and extruded under the conditions of screw speed of 200 rpm, feed speed of 20 rpm, and gauge pressure of -0.1 MPa. The extruded material is water-cooled, granulated, and dried at 60°C for 4 hours to obtain wear-resistant and environmentally friendly plastic for children's toys.

[0099] Example 3

[0100] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0101] Weigh out 100 parts of polylactic acid, 25 parts of polycaprolactone, 15 parts of composite wear-resistant agent, 10 parts of reactive compatibilizer, 0.5 parts of antioxidant, and 0.5 parts of lubricant by weight.

[0102] In the preparation of the composite wear-resistant agent, the mass ratio of polyoxymethylene whiskers to fullerene is 1:0.45, the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 1.2:1, the aspect ratio of polyoxymethylene whiskers is 35:1, the diameter is 1.2 micrometers and the length is 55 micrometers, the fullerene is C60 with an average particle size of 55 nanometers, the amount of calcium chloride added is 3% of the mass of phytic acid-modified hydroxyapatite, the reaction temperature is 60℃, the reaction time is 4.5 hours, the washing is performed 4 times, and the vacuum drying temperature is 70℃ for 10 hours.

[0103] In the preparation of phytic acid modified hydroxyapatite, the mass concentration of nano-hydroxyapatite suspension is 7%, the amount of phytic acid added is 5% of the nano-hydroxyapatite, the reaction temperature is 50℃, the reaction time is 3 hours, the washing is performed 3 times, and the vacuum drying temperature is 60℃ for 8 hours.

[0104] In the preparation of the reactive compatibilizer, the mass ratio of polylactic acid monomer to polycaprolactone monomer is 1:0.65, the amount of stannous octoate catalyst added is 0.3% of the total mass of monomers, the reaction temperature is 140℃, the gauge pressure is -0.09 MPa, the reaction time is 6 hours, the amount of glycidyl methacrylate added is 10% of the diblock prepolymer, the amount of azobisisobutyronitrile added is 2% of glycidyl methacrylate, the reaction temperature is 80℃, the reaction time is 8 hours, and the vacuum drying temperature is 50℃ for 18 hours.

[0105] The antioxidant consists of antioxidant 1010 and antioxidant 168 in a mass ratio of 2:1, and the lubricant is calcium stearate.

[0106] The above materials were mixed at 32°C and 1000 rpm for 10 minutes to obtain a premix. The premix was added to a twin-screw extruder and melt-blended and extruded under the conditions of screw speed of 300 rpm, feed speed of 30 rpm, and gauge pressure of -0.08 MPa. The extruded material was water-cooled, stretched, and pelletized, and then dried at 70°C for 3 hours to obtain wear-resistant and environmentally friendly plastic for children's toys.

[0107] Comparative Example 1

[0108] The difference between this comparative example and Example 3 is that calcium chloride ethanol solution is not added during the preparation of the composite wear-resistant agent. That is, polyoxymethylene whiskers, fullerene and phytic acid modified hydroxyapatite are only physically mixed and do not form a composite through calcium ion coordination. The remaining components and preparation methods are the same as in Example 3.

[0109] Comparative Example 2

[0110] The difference between this comparative example and Example 3 is that the phytic acid-modified hydroxyapatite in the composite wear-resistant agent is replaced by an equal mass of unmodified nano-hydroxyapatite, while the remaining components and preparation methods are the same as in Example 3.

[0111] Comparative Example 3

[0112] The difference between this comparative example and Example 3 is that the reactive compatibilizer is replaced with an equal mass of commercially available acetylthiocitrate tributyl ester, while the remaining components and preparation methods are the same as in Example 3.

[0113] Comparative Example 4

[0114] The difference between this comparative example and Example 3 is that glycidyl methacrylate is not added during the preparation of the reactive compatibilizer; that is, the compatibilizer is polylactic acid-polycaprolactone diblock copolymer. The remaining components and preparation methods are the same as in Example 3.

[0115] Comparative Example 5

[0116] The difference between this comparative example and Example 3 is that the amount of polycaprolactone added is 10 parts, which is lower than the range of 15 to 40 parts limited by the present invention. The other components and preparation methods are the same as those in Example 3.

[0117] Comparative Example 6

[0118] The difference between this comparative example and Example 3 is that the amount of composite wear-resistant agent added is 4 parts, which is lower than the range of 6 to 25 parts limited by the present invention. The other components and preparation methods are the same as those in Example 3.

[0119] Comparative Example 7

[0120] The difference between this comparative example and Example 3 is that the amount of reactive compatibilizer added is 3 parts, which is lower than the range of 5 to 15 parts limited by the present invention. The other components and preparation methods are the same as those in Example 3.

[0121] Performance Test Results and Analysis

[0122] Plastic particles prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were subjected to performance tests after being conditioned for 24 hours at a temperature of 23°C and a relative humidity of 50%.

[0123] The wear test was conducted in accordance with ASTM D1044 standard, using a Taber abrasion tester with an H-22 type grinding wheel, a load of 1000 grams, a test speed of 60 revolutions per minute, and the mass loss after 2000 revolutions was recorded. The test results are in milligrams.

[0124] The notched impact strength of the cantilever beam was tested according to ASTM D256 standard using an impact testing machine. The specimen size was 80 mm x 10 mm x 4 mm, with a notch depth of 2 mm. The test results are expressed in kilojoules per square meter. The melt flow rate was tested according to ASTM D1238 standard at a test temperature of 190°C and a load of 2.16 kg. The test results are expressed in grams per 10 minutes. The specific test results are shown in Table 1.

[0125] As shown in Table 1, the wear-resistant and environmentally friendly plastics for children's toys prepared in Examples 1 to 3 all exhibit good comprehensive performance. Example 1 had an abrasion loss of 9.2 mg and a notched cantilever beam impact strength of 12.8 kJ / m²; Example 2 had an abrasion loss of 8.9 mg and a notched cantilever beam impact strength of 13.1 kJ / m²; and Example 3 had an abrasion loss of 8.4 mg and a notched cantilever beam impact strength of 13.6 kJ / m². This demonstrates that the technical solution of this invention can achieve a synergistic improvement in abrasion resistance and impact resistance in a polylactic acid and polycaprolactone blend system.

[0126] Table 1 Analysis of Test Results

[0127] Sample number Wear amount (mg) Impact strength of cantilever beam with notch (kJ / m²) Melt flow rate (grams per 10 minutes) Example 1 9.2 12.8 8.5 Example 2 8.9 13.1 8.2 Example 3 8.4 13.6 8.7 Comparative Example 1 15.3 9.6 9.2 Comparative Example 2 18.5 7.8 9.5 Comparative Example 3 14.6 10.2 10.3 Comparative Example 4 15.8 9.3 9.7 Comparative Example 5 11.2 11.6 9.8 Comparative Example 6 13.5 10.8 8.9 Comparative Example 7 12.4 11.2 9.3

[0128] In-depth analysis of the test results reveals that the overall performance of Example 3 is superior to that of Examples 1 and 2, indicating that the synergistic effect of each component in Example 3 is more fully realized. When the mass ratio of polyoxymethylene whiskers to fullerene is 1:0.45, the fullerene can form a uniform coating layer on the surface of the polyoxymethylene whiskers, providing a molecular ball-bead effect, without affecting the skeletal support of the whiskers due to excessive amounts. When the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 1.2:1, the hardness support provided by hydroxyapatite and the fiber reinforcement effect of the whiskers are balanced, ensuring surface wear resistance without reducing toughness due to excessive rigid particles.

[0129] Analysis of the test results from Example 3 shows that, in Comparative Example 1, which did not use calcium chloride for calcium ion coordination crosslinking, the polyoxymethylene whiskers, fullerene, and phytic acid-modified hydroxyapatite in the composite wear-resistant agent were only physically mixed. This resulted in an increase in wear loss to 15.3 mg and a decrease in impact strength to 9.6 kJ / m². This is because the lack of calcium ion bridging prevents the formation of a chemically bonded composite structure among the three components. When dispersed in polylactic acid and polycaprolactone, they act independently, failing to form an effective stress transfer network. The skeletal support of polyoxymethylene whiskers, the molecular ball-bead effect of fullerene, and the hardness support of hydroxyapatite cannot work synergistically. When the material is subjected to friction, localized stress concentration leads to increased wear loss, and the weak interface during impact results in decreased toughness.

[0130] Comparative Example 2, using unmodified nano-hydroxyapatite instead of phytate-modified hydroxyapatite, showed the worst performance among all comparative examples, with an abrasion loss of 18.5 mg and an impact strength of only 7.8 kJ / m². This is because the surface of unmodified hydroxyapatite lacks active phosphate groups, making it unable to effectively coordinate with calcium ions or undergo ring-opening reactions with the epoxy groups of the reactive compatibilizer. During phytate modification, the phosphate groups in the phytate molecules coordinate with calcium ions on the surface of hydroxyapatite, introducing a large number of active phosphate groups onto the surface of hydroxyapatite. This step is fundamental to the subsequent formation of a chemical bond network. Without phytate modification, the interfacial bonding between hydroxyapatite and polylactic acid and polycaprolactone is weak, and it cannot form chemical bonds with reactive compatibilizers. Under stress, this makes it prone to becoming a stress concentration point, inducing crack formation and leading to a severe performance degradation.

[0131] Comparative Example 3 used commercially available tributyl acetylglucosamine instead of the reactive compatibilizer of this invention. The wear loss was 14.6 mg, and the impact strength was 10.2 kJ / m², indicating a significant decrease in performance. As a common compatibilizer, tributyl acetylglucosamine lacks active groups in its molecular chain that can chemically react with the composite wear-resistant agent. Although it can improve the compatibility between polylactic acid and polycaprolactone phases to some extent and reduce the interfacial tension, it cannot form chemical bonds with the composite wear-resistant agent. This results in the composite wear-resistant agent being dispersed in the matrix only through physical action, with weak interfacial bonding. During friction, it is easily pulled out or peeled off, failing to provide sustained wear resistance.

[0132] Comparative Example 4, which replaced the triblock copolymer with a polylactic acid-polycaprolactone diblock copolymer, showed an abrasion loss of 15.8 mg and an impact strength of 9.3 kJ / m², performance also lower than Example 3. Although the polylactic acid-polycaprolactone diblock copolymer can improve compatibility by having polylactic acid and polycaprolactone segments entangle with the two-phase matrix respectively, its molecular chain ends lack epoxy groups, preventing it from undergoing a ring-opening reaction with the phosphate groups on the surface of the phytic acid-modified hydroxyapatite in the composite wear-resistant agent. Comparing Comparative Examples 3 and 4, it can be seen that although neither can form chemical bonds with the composite wear-resistant agent, the compatibilizer in Comparative Example 4 has the same segmental structure as the matrix, exhibiting better compatibility with the matrix than tributyl acetylacetic acid. Therefore, its impact strength is slightly higher than Comparative Example 3, but still significantly lower than Example 3.

[0133] Comparative Example 5 adjusted the amount of polycaprolactone to 10 parts, lower than the 15 to 40 parts range specified in this invention. The abrasion loss was 11.2 mg, and the impact strength was 11.6 kJ / m². Polycaprolactone, as a flexible component, provides toughening for polylactic acid. When the amount of polycaprolactone is too low, the toughening effect is insufficient, the material becomes brittle overall, and the impact strength decreases. Simultaneously, due to the increased rigidity of the matrix, the abrasion loss increased slightly compared to Example 3, indicating that the amount of polycaprolactone has a relatively small impact on abrasion resistance but a significant impact on impact toughness.

[0134] Comparative Example 6 adjusted the amount of composite wear-resistant agent to 4 parts, lower than the 6 to 25 parts range specified in this invention. The wear loss was 13.5 mg, and the impact strength was 10.8 kJ / m². In the composite wear-resistant agent, polyoxymethylene whiskers provide skeletal support and self-lubricating properties, fullerene provides a molecular ball-bearing effect, and phytic acid-modified hydroxyapatite provides hardness support. These three components work synergistically to form a wear-resistant reinforcing network. When the amount of composite wear-resistant agent is too low, there are insufficient reinforcing nodes in the network, making it impossible to form a complete stress transmission path, resulting in a significant decrease in both wear resistance and impact resistance.

[0135] Comparative Example 7 adjusted the reactive compatibilizer dosage to 3 parts, lower than the 5 to 15 parts range specified in this invention. The wear loss was 12.4 mg, and the impact strength was 11.2 kJ / m². The reactive compatibilizer functions to improve the compatibility between polylactic acid and polycaprolactone and to form chemical bonds with the composite wear-resistant agent through epoxy groups. When the reactive compatibilizer dosage is too low, on the one hand, it cannot adequately cover the interface between the two phases, resulting in incomplete improvement in compatibility; on the other hand, there are insufficient active sites to form chemical bonds with the composite wear-resistant agent, and some of the composite wear-resistant agent cannot be anchored in the matrix, leading to a decrease in interfacial bonding strength.

[0136] Test results show that the present invention, through the ternary composite formed by the calcium ion coordination of polyoxymethylene whiskers, fullerene, and phytate-modified hydroxyapatite in the composite wear-resistant agent, and combined with polylactic acid-polycaprolactone-glycidyl methacrylate triblock copolymer as a reactive compatibilizer, can form a chemically bonded network in the polylactic acid and polycaprolactone blend system. In this network, polyoxymethylene whiskers provide support as a skeleton, fullerene acts as molecular balls to reduce friction, and phytate-modified hydroxyapatite acts as hard nodes to resist abrasive cutting. The three are bridged by calcium ions to form a composite. The reactive compatibilizer anchors the composite wear-resistant agent in the matrix through the ring-opening reaction of epoxy groups with the phosphate groups, while simultaneously entangled with the two phases of the matrix through polylactic acid segments and polycaprolactone segments, respectively. When the material is subjected to friction, the stress is effectively dispersed and transmitted through the chemical bonding network, and the components work together to play a wear-resistant role. When the material is subjected to impact, whisker pull-out, fullerene initiation and termination of crazing, hydroxyapatite pinning cracks, and compatibilizer molecular chain deformation jointly absorb the impact energy.

[0137] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A wear-resistant and environmentally friendly plastic for children's toys, characterized in that, The plastic comprises the following components by parts by weight: 100 parts of polylactic acid; 15 to 40 parts of polycaprolactone; 6 to 25 parts of composite wear-resistant agent; 5 to 15 parts of reactive compatibilizer; Antioxidant 0.2 to 1 part; Lubricant 0.2 to 1 part; The composite wear-resistant agent is a composite formed by the coordination of polyoxymethylene whiskers, fullerene, and phytic acid-modified hydroxyapatite through calcium ion coordination; the reactive compatibilizer is a triblock copolymer of polylactic acid, polycaprolactone, and glycidyl methacrylate.

2. The wear-resistant and environmentally friendly plastic for children's toys according to claim 1, characterized in that, The preparation process of the composite wear-resistant agent includes the following steps: dispersing polyoxymethylene whiskers and fullerene in anhydrous ethanol and ultrasonically dispersing for 30 to 60 minutes to obtain a mixed dispersion; dispersing phytic acid-modified hydroxyapatite in anhydrous ethanol and ultrasonically dispersing for 20 to 40 minutes to obtain a hydroxyapatite dispersion; slowly adding the hydroxyapatite dispersion dropwise to the mixed dispersion, while simultaneously adding a calcium chloride ethanol solution, wherein the amount of calcium chloride added is 1% to 5% of the mass of the phytic acid-modified hydroxyapatite; stirring and reacting at a temperature of 50 to 70°C for 3 to 6 hours; after the reaction is completed, centrifuging is performed, and the product is washed 3 to 5 times with anhydrous ethanol. The solid product is collected and vacuum dried at 60 to 80°C for 8 to 12 hours to obtain the composite wear-resistant agent.

3. The wear-resistant and environmentally friendly plastic for children's toys according to claim 2, characterized in that, The mass ratio of polyoxymethylene whiskers to fullerene is 1:0.3-0.6; the mass ratio of phytic acid-modified hydroxyapatite to polyoxymethylene whiskers is 0.5-2:

1. The polyoxymethylene whiskers have an aspect ratio of 20:1 to 50:1, a diameter of 0.5 to 2 micrometers, and a length of 10 to 100 micrometers; the fullerene is C60, with an average particle size of 10 to 100 nanometers.

4. The wear-resistant and environmentally friendly plastic for children's toys according to claim 2, characterized in that, The phytic acid-modified hydroxyapatite is obtained by the following steps: dispersing nano-hydroxyapatite in water to prepare a suspension with a mass concentration of 5% to 10%, adding phytic acid, stirring and reacting at a temperature of 40 to 60°C for 2 to 4 hours, then centrifuging, washing with deionized water 2 to 4 times, collecting the solid product and vacuum drying at 50 to 70°C for 6 to 10 hours to obtain phytic acid-modified hydroxyapatite.

5. The wear-resistant and environmentally friendly plastic for children's toys according to claim 4, characterized in that, The amount of phytic acid added is 2% to 8% of the nano-hydroxyapatite.

6. The wear-resistant and environmentally friendly plastic for children's toys according to claim 1, characterized in that, The reactive compatibilizer is obtained by the following steps: adding polylactic acid monomer and polycaprolactone monomer in a mass ratio of 1:0.3-1 to a reaction vessel, adding stannous octoate as a catalyst, wherein the amount of catalyst added is 0.1% to 0.5% of the total mass of the monomers, and reacting for 4 to 8 hours at a temperature of 130 to 150°C and a gauge pressure of -0.08 to -0.1 MPa to obtain a polylactic acid-polycaprolactone diblock prepolymer; The polylactic acid-polycaprolactone diblock prepolymer was dissolved in toluene, and glycidyl methacrylate and azobisisobutyronitrile were added. The reaction was carried out at 70 to 90°C under nitrogen protection for 6 to 10 hours. After the reaction was completed, the mixture was cooled to room temperature and precipitated with anhydrous methanol. The precipitate was collected and vacuum dried at 40 to 60°C for 12 to 24 hours to obtain a polylactic acid-polycaprolactone-glycidyl methacrylate triblock copolymer.

7. The wear-resistant and environmentally friendly plastic for children's toys according to claim 6, characterized in that, The catalyst is added at a rate of 0.1% to 0.5% of the total mass of polylactic acid monomer and polycaprolactone monomer; the glycidyl methacrylate is added at a rate of 5% to 15% of the diblock prepolymer; and the azobisisobutyronitrile is added at a rate of 1% to 3% of the glycidyl methacrylate.

8. The wear-resistant and environmentally friendly plastic for children's toys according to claim 1, characterized in that, The antioxidant includes hindered phenolic antioxidants and phosphite antioxidants; the hindered phenolic antioxidant is antioxidant 1010; the phosphite antioxidant is antioxidant 168; and the mass ratio of antioxidant 1010 to antioxidant 168 is 1-3:

1. The lubricant is calcium stearate.

9. A method for preparing a wear-resistant and environmentally friendly plastic for children's toys as described in any one of claims 1-8, characterized in that, The method includes the following steps: weighing polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant, mixing the above materials at high speed to obtain a uniform premix; performing melt blending extrusion on the premix, and then water-cooling, pelletizing and drying the extruded material to obtain the wear-resistant and environmentally friendly plastic for children's toys.

10. A method for preparing a wear-resistant and environmentally friendly plastic for children's toys according to claim 9, characterized in that, The specific parameters for the high-speed mixing are as follows: polylactic acid, polycaprolactone, reactive compatibilizer, composite wear-resistant agent, antioxidant and lubricant are mixed at a temperature of 25 to 40°C and a rotation speed of 500 to 1500 revolutions per minute for 5 to 15 minutes. The specific parameters for the melt blending extrusion are as follows: the premix is ​​added to a twin-screw extruder at a screw speed of 200 to 400 rpm and a feed speed of 20 to 40 rpm; the gauge pressure during extrusion is -0.06 to -0.1 MPa. The drying process involves collecting the extruded material after it has been water-cooled and pelletized, and then maintaining the resulting pellets at a temperature of 60 to 80°C for 2 to 4 hours.