High flowability regenerated POM precision injection molding plastic and preparation method thereof

Abstract

This invention discloses a high-flowability recycled POM precision injection molding plastic and its preparation method in the field of polymer materials technology. The material comprises recycled POM resin, polyoxymethylene homopolymer, polyoxymethylene copolymer, multimetal-oxygen cluster ionic liquid hybrid material, hyperbranched polyacetal block polyester synergist, and additives. The multimetal-oxygen cluster ionic liquid hybrid material is prepared by ion exchange of phosphomolybdic acid and an ionic liquid, followed by redox-initiated polymerization and crosslinking. The hyperbranched polyacetal block polyester synergist is prepared through melt polycondensation, ring-opening polymerization, and block copolymerization. This invention significantly improves the thermal stability and melt flowability of the recycled POM material through the synergistic effect of two novel modified compounds, while maintaining good mechanical properties. It solves the key technical problem of insufficient flowability of recycled POM in precision injection molding, making it suitable for injection molding of thin-walled precision parts.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a high-flowability recycled POM precision injection molding plastic and its preparation method. Background Technology

[0002] Polyoxymethylene (POM), as a high-performance polymer material, holds an irreplaceable position in industrial manufacturing. Its regular molecular structure and high crystallinity exhibit excellent mechanical strength, rigidity, fatigue resistance, and dimensional stability, making it widely used in key sectors such as the automotive industry, electronics, precision machinery, and consumer goods. With the deepening of sustainable development concepts and the advancement of circular economy policies, the recycling of POM products has become a focus of industry attention. However, the amount of waste generated during the processing and use of POM materials is enormous. Traditional treatment methods not only waste resources but also put pressure on the environment. Therefore, developing efficient POM recycling and reuse technologies to achieve high-value utilization of waste resources not only meets the requirements of green manufacturing but also has significant economic and social benefits.

[0003] Currently, the recycling of polyoxymethylene (POM) faces numerous technical bottlenecks. POM resin is extremely sensitive to heat, easily undergoing depolymerization during melt processing, releasing formaldehyde gas, leading to a decrease in molecular weight and performance degradation. This thermal instability narrows the processing window for recycled POM, requiring extremely high process control. While conventional physical recycling methods are simple to operate, they only achieve downgrading, significantly reducing the mechanical properties and thermal stability of the recycled material, failing to meet the demands of high-end applications. Existing technologies typically use stabilizers and compatibilizers to improve the performance of recycled POM, but these traditional additives often only address single issues and cannot simultaneously improve the material's flowability, thermal stability, and mechanical properties. Some studies have attempted to improve the rigidity of recycled materials through fiber reinforcement, but this further impairs the material's flowability, making it difficult to meet the processing requirements of precision injection molding. These technical limitations severely restrict the application of recycled POM in high-quality products.

[0004] To address the aforementioned technical challenges, the industry urgently needs to develop a novel modification system and preparation method that can simultaneously solve key problems such as insufficient flowability, poor thermal stability, and decreased mechanical properties of recycled polyoxymethylene (POM). An ideal solution should involve molecular design to develop modifiers with unique structures, achieving a comprehensive improvement in the performance of recycled POM through the synergistic effect of multiple mechanisms. This innovative technology not only needs to significantly increase the melt flow rate of recycled materials to meet the process requirements of precision injection molding of thin-walled products, but also needs to effectively suppress thermal degradation during processing to maintain the material's fundamental mechanical properties. Simultaneously, the technology should be feasible for industrial production, with a simple and efficient process route, controllable costs, and the ability to drive the POM recycling industry towards high quality and high added value, providing a new technological path for the green recycling of engineering plastics. Summary of the Invention

[0005] The purpose of this invention is to provide a high-flowability recycled POM precision injection molding plastic and its preparation method, which solves the technical problems of poor thermal stability, insufficient melt flowability and significant decline in mechanical properties of existing recycled polyoxymethylene materials during recycling.

[0006] The present invention achieves the above objectives through the following technical solutions: A high-flowability recycled POM precision injection molding plastic comprises the following raw materials in parts by weight: Recycled POM resin: 40-70 parts by weight; POM homopolymer: 10-25 parts by weight; POM copolymer: 5-15 parts by weight; Polymetallic oxygen cluster-ionic liquid hybrid material: 0.5-3 parts by weight; Hyperbranched polyacetal-block-polyester synergist: 1-5 parts by weight; Polyethylene wax: 0.1-1 parts by weight; Calcium stearate: 0.1-0.5 parts by weight; Antioxidant 1010: 0.1-0.3 parts by weight; Antioxidant 168: 0.1-0.3 parts by weight; The preparation method of the polymetallic oxygen cluster-ionic liquid hybrid material includes: A1, dissolving phosphomolybdic acid in deionized water to prepare a clear solution and stirring; then adding 1-vinyl-3-ethylimidazolium bromide ionic liquid, and heating the reaction system to 74-76℃ under nitrogen protection, stirring and controlling the pH value at 2-3 during the reaction; A2, after the reaction is completed, adding potassium persulfate and adding ascorbic acid aqueous solution dropwise, and reacting at 35-45℃; finally, centrifuging the reaction mixture, washing the precipitate with ethanol, and drying it in a vacuum oven at 60-64℃.

[0007] In this invention, the preparation process of the polyoxometalate cluster-ionic liquid hybrid material is a carefully designed organic-inorganic hybrid reaction system, and its reaction mechanism involves several key steps such as ion exchange, coordination, and in-situ polymerization. In the initial stage, phosphomolybdic acid dissociates in aqueous solution to form polyoxometalate anion clusters. These nanoclusters with abundant surface charges initially bind to the ionic liquid monomer through electrostatic interactions. The imidazole cations in the ionic liquid monomer generate strong ion-pair interactions with the polyoxometalate anions, which not only promotes their tight bonding but also lays the foundation for subsequent polymerization. During the heating of the reaction system under nitrogen protection, the vinyl groups in the ionic liquid monomer coordinate with the active sites on the surface of the polyoxometalate clusters, forming a preliminary organic-inorganic hybrid structure. The reaction temperature in this stage is controlled within a specific range to ensure a sufficient reaction rate while avoiding premature polymerization of the ionic liquid monomer. The subsequent redox-initiated polymerization is the key step in the entire preparation process. Potassium persulfate, as an oxidant, generates sulfate radicals under the reduction of ascorbic acid. These radicals attack the vinyl groups in the ionic liquid monomer, initiating the polymerization reaction. Since the ionic liquid monomers are already anchored to the surface of the polyoxometalate clusters through ion exchange and coordination, the polymerization reaction mainly occurs in the interface region of the hybrid material, forming a core-shell structure with the polyoxometalate cluster as the core and the polyionic liquid as the shell. This special structural design allows the hybrid material to maintain the thermal stability and catalytic performance of the polyoxometalate clusters while possessing the good compatibility and interface modification capabilities of the ionic liquid. During the polymerization process, a certain degree of cross-linking reaction also occurs between the polyionic liquid segments, forming a three-dimensional network structure, further enhancing the stability of the hybrid material. The resulting hybrid material has unique performance advantages. The polyoxometalate cluster core can effectively capture formaldehyde molecules produced by the degradation of polyoxymethylene (POM) and convert them into harmless substances through redox reactions, thereby inhibiting the thermal degradation process of POM. At the same time, the ionic liquid shell has good compatibility with the POM matrix and can be uniformly dispersed in the matrix to form a nanoscale reinforcing phase. This hybrid material not only acts as a stabilizer in the POM regeneration process but also as a nucleating agent to promote the crystallization of POM, improving the mechanical properties and dimensional stability of the material. In addition, the ionic liquid component also has an internal lubricating effect, which can reduce the melt viscosity and improve the processing fluidity of the material.

[0008] According to a preferred embodiment of the present invention, in step A1, the reaction time is 12-15 hours after the temperature is raised to 74-76°C.

[0009] According to a preferred embodiment of the present invention, in step A2, the reaction time is 2-4 hours at 35-45°C.

[0010] According to a preferred embodiment of the present invention, the preparation method of the hyperbranched polyacetal-block-polyester synergist includes: B1, mixing pentaerythritol with 2,2-dimethylolpropionic acid and heating to 158-162°C under nitrogen protection to carry out melt polycondensation reaction to synthesize hyperbranched polyester; then adding ε-caprolactone and stannous octoate catalysts and carrying out ring-opening polymerization at 138-142°C; B2, finally adding trioxymethylene and carrying out block copolymerization reaction at 58-62°C under boron trifluoride diethyl ether catalysis; after the reaction, dissolving the product in acetone, purifying it by recrystallization using n-hexane, filtering, washing, and drying in a vacuum environment at 48-52°C.

[0011] In this invention, the preparation of the hyperbranched polyacetal-block-polyester synergist is a multi-step synthetic process, with its reaction mechanism involving several important stages such as polycondensation, ring-opening polymerization, and block copolymerization. The first stage is the synthesis of the hyperbranched polyester with pentaerythritol as the core, following a typical melt polycondensation reaction mechanism. The four hydroxyl groups of pentaerythritol undergo esterification with the carboxyl groups of dimethylolpropionic acid. By precisely controlling the molar ratio of reactants and reaction conditions, a hyperbranched polymer with a regular branched structure can be synthesized. In this stage, temperature control is crucial, ensuring a sufficient reaction rate while avoiding side reactions. Nitrogen protection not only prevents oxidative degradation of the raw materials but also facilitates the removal of water molecules generated during the reaction, promoting the forward esterification reaction. The subsequent ring-opening polymerization stage is another key step in the entire preparation process. The terminal hydroxyl groups of the hyperbranched polyester undergo ring-opening polymerization with caprolactone monomers under the action of a catalyst; the mechanism of this process involves a coordination-intercalation mechanism. The catalyst first coordinates with the carbonyl oxygen of the caprolactone monomer, activating the monomer molecule. Then, the hydroxyl groups at the ends of the hyperbranched polyester nucleophilically attack the acyl carbon atom of the caprolactone, causing the lactone ring to cleave and form a new ester bond. The reaction temperature in this stage needs precise control; too low a temperature will result in a slow reaction rate, while too high a temperature may cause side reactions. Through this ring-opening polymerization process, polyester segments are introduced at the ends of the hyperbranched polyester, significantly increasing the polymer's molecular weight and segment length. The final block copolymerization reaction is the highlight of the entire synthesis process. The hyperbranched polymer with polyester segments undergoes a block copolymerization reaction with trioxymethylene under Lewis acid catalysis. The mechanism of this process involves cationic polymerization. The catalyst first activates the trioxymethylene molecule, forming an oxonium ion active species. Then, the hydroxyl groups at the ends of the hyperbranched polyester act as nucleophiles to attack the oxonium ions, achieving a chain growth reaction. By precisely controlling the reaction conditions, polyoxymethylene segments can be introduced at the ends of the hyperbranched polymer, forming a unique hyperbranched polyacetal-block-polyester structure. This unique molecular structure endows the synergist with superior performance: the hyperbranched core provides a large number of terminal functional groups, enabling strong interactions with the recycled polyoxymethylene (POM) molecular chains; the polyester segments improve compatibility with the POM matrix; and the POM segments have the same chemical structure as the matrix molecules, enabling molecular-level fusion. This multi-layered structural design allows the synergist to simultaneously perform multiple functions such as compatibilization, toughening, and improved flowability.

[0012] According to a preferred embodiment of the present invention, in step B1, the melt polycondensation reaction is carried out at 158-162°C for 4-6 hours; and the ring-opening polymerization is carried out at 138-142°C for 5-10 hours.

[0013] According to a preferred embodiment of the present invention, in step B2, the drying time in a vacuum environment at 48-52°C is 48-50 hours.

[0014] This invention also provides a method for preparing the high-flowability recycled POM precision injection molded plastic, comprising the following steps: S1. After removing surface stains from waste POM products with alkaline cleaning solution, crush them into granules and dry them in a vacuum oven at 78-82℃. S2. The pretreated recycled POM material, POM homopolymer, POM copolymer, polyoxometalate cluster-ionic liquid hybrid material, hyperbranched polyacetal-block-polyester synergist, polyethylene wax, calcium stearate, antioxidant 1010 and antioxidant 168 are put into a high-speed mixer and mixed. S3. The mixture is melt-blended in a twin-screw extruder. The screw temperatures are set at 185℃, 190℃, 195℃, and 200℃ from the feeding section to the die head, respectively, and the melt pressure is maintained at 12-15MPa. The extruded melt is granulated underwater, cooled, and dried to obtain granular products. The final granular products are precision injection molded at an injection temperature of 190-210℃ and a mold temperature of 80-90℃.

[0015] In this invention, the preparation of high-flowability recycled POM precision injection molding plastic is a complex physicochemical process, and its reaction mechanism involves the interaction and synergistic effect between multiple components. In the pretreatment stage, waste polyoxymethylene products are washed and crushed, then dried at a specific temperature. This process primarily involves physical changes. Moisture removal not only avoids hydrolysis reactions that may occur during subsequent processing but also ensures that the components can be fully mixed and interact. The selection of the drying temperature requires comprehensive consideration of the glass transition temperature and thermal stability of polyoxymethylene, ensuring sufficient moisture removal while preventing thermal degradation of the material. In the melt blending stage, the various components undergo a complex multiphase system evolution process in a twin-screw extruder. Recycled polyoxymethylene resin, as the matrix material, melts first to form a continuous phase. The subsequently added polyoxometalate cluster-ionic liquid hybrid material is dispersed in the matrix under shear force. These nanoscale hybrid materials interact with the polyoxymethylene (POM) molecular chains in multiple ways: on the one hand, the ionic liquid component has good compatibility with the POM segments and can be uniformly dispersed in the matrix; on the other hand, the polyoxometalate cluster component can coordinate with the hemiacetal groups at the ends of the POM chains to form physical cross-linking points. This interaction improves the mechanical properties of the material and inhibits the thermal motion of the chain segments, thereby enhancing thermal stability. The hyperbranched polyacetal-block-polyester synergist plays a key role in this stage. Its hyperbranched structure acts like a "molecular ball bearing" in the melt, greatly reducing the melt viscosity. At the same time, the POM segments at the ends of the synergist undergo co-crystallization with the matrix molecular chains, forming a strong interfacial bond; while the polyester segments provide the necessary flexibility and compatibility. This special structural design allows the synergist to simultaneously improve the material's flowability, toughness, and interfacial bond strength. The addition of lubricant further reduces friction between the melt and the metal surface of the equipment, ensuring smooth processing. The antioxidant system provides crucial stabilizing protection during processing. The primary antioxidant terminates free radicals generated by POM degradation by providing hydrogen atoms, while the secondary antioxidant prevents chain reactions by decomposing hydrogen peroxide. These two antioxidants work synergistically to form a complete stabilization system, effectively inhibiting the degradation reaction of POM under high-temperature processing conditions. Temperature control throughout the preparation process is critical. The gradually increasing temperature profile from the feeding section to the die head ensures sufficient melting and mixing of the material while avoiding degradation reactions caused by localized overheating. Control of screw speed and melt pressure optimizes the residence time and shear history of the material in the barrel, ultimately yielding recycled POM material with a uniform structure and excellent performance. This precise preparation process allows the recycled material to not only maintain good mechanical properties but also achieve flowability and thermal stability far superior to conventional recycled materials, fully meeting the stringent requirements of precision injection molding.

[0016] According to a preferred embodiment of the present invention, in step S1, the drying time in a vacuum oven at 78-82°C is 12-15 hours.

[0017] According to a preferred embodiment of the present invention, in step S2, the mixing time in the high-speed mixer is 15-20 min.

[0018] According to a preferred embodiment of the present invention, in step S3, the screw speed of the twin-screw extruder is 350-400 rpm.

[0019] The beneficial effects of this invention are as follows: The technical solution provided by this invention significantly improves the overall performance of recycled polyoxymethylene (POM) materials, particularly achieving breakthroughs in thermal stability and processing flowability. By introducing a multi-metal-oxygen cluster ionic liquid hybrid material, the thermal degradation of POM during processing is effectively suppressed. The special structure of this hybrid material captures and neutralizes the formaldehyde gas produced during degradation, blocking the autocatalytic degradation reaction and maintaining a stable chemical structure under high-temperature processing conditions. Simultaneously, the three-dimensional structure of the hyperbranched polyacetal block polyester synergist acts as a molecular lubricant in the melt, significantly reducing melt viscosity and giving the recycled material excellent flow characteristics, fully meeting the process requirements for precision injection molding of thin-walled products. The synergistic effect of these two modifiers enables the recycled POM material to achieve a qualitative leap in flowability while maintaining good mechanical properties.

[0020] In terms of mechanical properties, this invention achieves optimal performance of recycled materials through a unique formulation design. The multi-metal-oxygen cluster ionic liquid hybrid material forms a nanoscale reinforcing network in the matrix, effectively improving the material's rigidity and heat distortion temperature. Meanwhile, the hyperbranched polyacetal block polyester synergist, through its abundant end groups, forms a strong interaction with the polyoxymethylene molecular chains, improving interfacial compatibility, preventing stress concentration, and significantly improving the material's impact toughness. The modified recycled polyoxymethylene not only maintains mechanical strength comparable to virgin materials, but its fatigue resistance and dimensional stability are even superior to ordinary virgin materials, making the application of recycled materials in the field of precision structural components possible.

[0021] From the perspectives of production technology and practical value, the preparation method provided by this invention has significant industrialization advantages. The entire process is simple and efficient, with low equipment requirements, making it suitable for large-scale continuous production. Precise control of temperature parameters and process conditions ensures the stability and consistency of product quality. The recycled polyoxymethylene precision injection molded plastic produced using this invention not only solves the problem of recycling waste polyoxymethylene materials and reduces production costs, but also reduces environmental pollution and achieves resource recycling. This material can be widely used in high-end fields such as automotive parts, electronic and electrical components, and precision mechanical components, yielding significant economic and social benefits. Detailed Implementation

[0022] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0023] The following is information on domestic suppliers of key related equipment and materials: The POM homopolymer was purchased from Shenma Industry Co., Ltd.

[0024] The POM copolymer was purchased from Kaifeng Longyu Chemical Co., Ltd.

[0025] The polyethylene wax was purchased from Shanghai Petrochemical Wax Industry Co., Ltd.

[0026] The calcium stearate was purchased from Hangzhou Haihong Fine Chemical Co., Ltd.

[0027] The antioxidant 1010 was purchased from Yingkou Fengguang Chemical Co., Ltd.

[0028] The antioxidant 168 was purchased from Linyi Sanfeng Chemical Co., Ltd.

[0029] The phosphomolybdic acid was purchased from Beijing Bailingwei Technology Co., Ltd.

[0030] The 1-vinyl-3-ethylimidazolium bromide ionic liquid was purchased from Linzhou Keneng Materials Technology Co., Ltd.

[0031] The potassium persulfate was purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0032] The ascorbic acid was purchased from Shijiazhuang Weisheng Pharmaceutical Co., Ltd.

[0033] The ethanol was purchased from Jiangsu Youpu Biochemical Technology Co., Ltd.

[0034] The pentaerythritol was purchased from Hubei Yihua Chemical Co., Ltd.

[0035] The 2,2-dihydroxymethylpropionic acid was purchased from Guangzhou Qiyun Biotechnology Co., Ltd.

[0036] The ε-caprolactone was purchased from Zhejiang Huanyi Resource Utilization Co., Ltd.

[0037] The stannous octoate catalyst was purchased from Shenzhen Yoshida Chemical Co., Ltd.

[0038] The trioxymethylene was purchased from Jiangsu Jincheng Reagent Co., Ltd.

[0039] The boron trifluoride ether was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0040] The vacuum oven was purchased from Shanghai Yiheng Scientific Instruments Co., Ltd.

[0041] The twin-screw extruder was purchased from Nanjing Keya Chemical Equipment Co., Ltd.

[0042] Example 1 The raw material ratio for high-flowability recycled POM precision injection molding plastic is as follows: 700g recycled POM resin, 150g POM homopolymer, 100g POM copolymer, 15g polyoxometalate-ionic liquid hybrid material, 30g hyperbranched polyacetal-block-polyester synergist, 5g polyethylene wax, 3g calcium stearate, 10102g antioxidant, and 1682g antioxidant. Preparation of the polyoxometalate-ionic liquid hybrid material: First, prepare a 500ml three-necked flask, install a mechanical stirrer, thermometer, and nitrogen inlet tube; add 200ml deionized water to the flask, start stirring and slowly add 10.0g phosphomolybdic acid, maintaining a stirring speed of 300rpm for 30 minutes until completely dissolved to obtain a clear solution; add 15.0g... 1-Vinyl-3-ethylimidazolium bromide ionic liquid was added in three portions, 10 minutes apart. Nitrogen gas was introduced to purge air, and the temperature was increased to 75°C at a rate of 2°C / min. The pH was adjusted to 2.5, and the reaction was maintained for 13 hours under a nitrogen atmosphere throughout. After the reaction was completed, the temperature was lowered to 40°C, and 0.5 g of potassium persulfate was added at once. Then, 20 ml of an aqueous solution containing 0.3 g of ascorbic acid was slowly added dropwise over 30 minutes using a constant-pressure dropping funnel. After the addition was complete, the reaction was maintained at 40°C for 3 hours. The reaction solution was transferred to a centrifuge tube and centrifuged at 8000 rpm for 15 minutes. The supernatant was discarded. The precipitate was washed three times with 100 ml of ethanol, centrifuged under the same conditions after each wash. Finally, the solid product was spread evenly in a petri dish and dried in a vacuum oven at 62°C for 24 hours to obtain a pale yellow powdery hybrid material. Preparation of hyperbranched polyacetal-block-polyester synergist: A 250ml four-necked flask was fitted with a mechanical stirrer, thermometer, nitrogen protection, and distillation apparatus. 20.0g pentaerythritol and 80.0g 2,2-dimethylolpropionic acid were added sequentially. Under nitrogen protection, the mixture was heated in an oil bath to 160℃, and the stirring speed was maintained at 200rpm for melt polycondensation reaction for 5 hours, during which the generated water was removed using a water separator. The system was then cooled to 140℃, and 50.0g of… ε-caprolactone and 0.5 g stannous octoate catalyst were reacted at 140 °C for 8 hours; the temperature was then lowered to 60 °C, and 30.0 g trioxymethylene and 1.0 g boron trifluoride diethyl ether catalyst were added, and the reaction was continued at 60 °C for 6 hours; after the reaction was completed, the product was dissolved in 200 ml acetone, slowly poured into 500 ml n-hexane to precipitate, and the white precipitate was collected by filtration; after washing three times with n-hexane, the product was placed in a vacuum drying oven at 50 °C and dried for 48 hours to obtain a white solid synergist.Preparation of high-flowability recycled POM precision injection molding plastic: First, 800g of waste POM product is ultrasonically cleaned for 30 minutes at 60℃ with a cleaning solution containing 5% sodium hydroxide, then rinsed three times with deionized water and crushed into 3mm particles; the crushed material is spread evenly in a tray and dried in an 80℃ vacuum oven for 13 hours until the moisture content is below 0.1%; 700g of pretreated recycled POM material and 150g of... POM homopolymer, 100g POM copolymer, 15g polyoxometalate-ionic liquid hybrid material, 30g hyperbranched polyacetal-block-polyester synergist, 5g polyethylene wax, 3g calcium stearate, 2g antioxidant 1010 and 2g antioxidant 168 were added to a high-speed mixer and mixed at 800 rpm for 18 minutes. The mixture was then melt-blended in a twin-screw extruder with the screw zone temperatures set at 185℃, 190℃, 195℃ and 200℃, the die temperature at 205℃, the melt pressure maintained at 13MPa, and the screw speed at 380 rpm. The extruded melt was granulated by an underwater pelletizer, and the pellets were dried in an 80℃ circulating oven for 4 hours. The final pellet product was precision injection molded at an injection temperature of 200℃ and a mold temperature of 85℃, with a holding pressure of 80MPa and a cooling time of 25 seconds.

[0043] Example 2 The specific implementation method is the same as in Example 1, except that the raw material ratio of the high-flowability recycled POM precision injection molding plastic is as follows: 600g recycled POM resin, 200g POM homopolymer, 80g POM copolymer, 10g polymetallic oxy-ionic liquid hybrid material, 20g hyperbranched polyacetal-block-polyester synergist, 3g polyethylene wax, 2g calcium stearate, 10101g antioxidant, and 1681g antioxidant. Preparation of polyoxometalate cluster-ionic liquid hybrid materials: 8.0 g of phosphomolybdic acid was dissolved in 150 ml of deionized water and stirred until clear; 12.0 g of 1-vinyl-3-ethylimidazolium bromide ionic liquid was added, and the mixture was heated to 74 °C and reacted for 12 hours under nitrogen protection, with the pH controlled at 2.0; after the reaction was completed, 0.4 g of potassium persulfate was added, and 15 ml of an aqueous solution containing 0.2 g of ascorbic acid was added dropwise, and the mixture was reacted at 35 °C for 2 hours; finally, the reaction mixture was centrifuged, the precipitate was washed three times with 80 ml of ethanol, and dried in a vacuum oven at 60 °C for 24 hours. Preparation of hyperbranched polyacetal-block-polyester synergist: 15.0 g pentaerythritol and 70.0 g 2,2-dimethylolpropionic acid were mixed and heated to 158 °C under nitrogen protection for melt polycondensation reaction for 4 hours; then 40.0 g ε-caprolactone and 0.4 g stannous octoate catalyst were added, and ring-opening polymerization reaction was carried out at 138 °C for 5 hours; finally, 25.0 g trioxymethylene and 0.8 g boron trifluoride ether were added, and block copolymerization reaction was carried out at 58 °C for 5 hours; after the reaction, the product was dissolved in 150 ml acetone, and purified by recrystallization using 400 ml n-hexane. After filtration and washing, it was dried in a vacuum environment at 48 °C for 48 hours. Preparation of high-flowability recycled POM precision injection molding plastic: 700g of waste POM products were washed with alkaline cleaning solution and crushed into granules, then dried in a vacuum oven at 78℃ for 12 hours; 600g of pretreated recycled POM material, 200g of POM homopolymer, and 80g of... POM copolymer, 10g polyoxometalate-ionic liquid hybrid material, 20g hyperbranched polyacetal-block-polyester synergist, 3g polyethylene wax, 2g calcium stearate, 1g antioxidant 1010 and 1g antioxidant 168 are added to a high-speed mixer and mixed for 15 minutes. The mixture is then melt-blended in a twin-screw extruder with screw temperatures set at 185℃, 190℃, 195℃ and 200℃ from the feed section to the die head, respectively, melt pressure maintained at 12MPa and screw speed at 350rpm. The extruded melt is then underwater pelletized, cooled and dried to obtain granules. The final granules are then precision injection molded at an injection temperature of 190℃ and a mold temperature of 80℃.

[0044] Example 3 The specific implementation method is the same as in Example 1, except that the raw material ratio of the high-flowability recycled POM precision injection molding plastic is as follows: 500g recycled POM resin, 250g POM homopolymer, 120g POM copolymer, 20g polymetallic oxy-ionic liquid hybrid material, 40g hyperbranched polyacetal-block-polyester synergist, 8g polyethylene wax, 4g calcium stearate, 10103g antioxidant, and 1683g antioxidant. Preparation of polyoxometalate cluster-ionic liquid hybrid materials: 12.0 g of phosphomolybdic acid was dissolved in 250 ml of deionized water and stirred until clear; 18.0 g of 1-vinyl-3-ethylimidazolium bromide ionic liquid was added, and the mixture was heated to 76 °C for 15 hours under nitrogen protection, with the pH controlled at 3.0; after the reaction was completed, 0.6 g of potassium persulfate was added, and 25 ml of an aqueous solution containing 0.4 g of ascorbic acid was added dropwise, and the mixture was reacted at 45 °C for 4 hours; finally, the reaction mixture was centrifuged, the precipitate was washed three times with 120 ml of ethanol, and dried in a vacuum oven at 64 °C for 24 hours. Preparation of hyperbranched polyacetal-block-polyester synergist: 25.0 g pentaerythritol and 90.0 g 2,2-dimethylolpropionic acid were mixed and heated to 162 °C under nitrogen protection for melt polycondensation reaction for 6 hours; then 60.0 g ε-caprolactone and 0.6 g stannous octoate catalyst were added, and ring-opening polymerization reaction was carried out at 142 °C for 10 hours; finally, 35.0 g trioxymethylene and 1.2 g boron trifluoride ether were added, and block copolymerization reaction was carried out at 62 °C for 7 hours; after the reaction, the product was dissolved in 250 ml acetone, and purified by recrystallization using 600 ml n-hexane. After filtration and washing, it was dried in a vacuum environment at 52 °C for 50 hours. Preparation of high-flowability recycled POM precision injection molding plastic: 900g of waste POM products were washed with alkaline cleaning solution and crushed into granules, then dried in a vacuum oven at 82℃ for 15 hours; 500g of pretreated recycled POM material, 250g of POM homopolymer, and 120g of... POM copolymer, 20g of polyoxometalate cluster-ionic liquid hybrid material, 40g of hyperbranched polyacetal-block-polyester synergist, 8g of polyethylene wax, 4g of calcium stearate, 3g of antioxidant 1010 and 3g of antioxidant 168 were added to a high-speed mixer and mixed for 20 minutes. The mixture was then melt-blended in a twin-screw extruder with screw temperatures set at 185℃, 190℃, 195℃ and 200℃ from the feed section to the die head, respectively, melt pressure maintained at 15MPa and screw speed at 400rpm. The extruded melt was then underwater pelletized, cooled and dried to obtain granules. The final granules were precision injection molded at an injection temperature of 210℃ and a mold temperature of 90℃.

[0045] Comparative Example 1 The specific implementation method is the same as in Example 1, except that the raw material ratio for the high-flowability recycled POM precision injection molding plastic is as follows: 700g recycled POM resin, 150g POM homopolymer, 100g POM copolymer, 30g hyperbranched polyacetal-block-polyester synergist, 5g polyethylene wax, 3g calcium stearate, 10102g antioxidant, and 1682g antioxidant. The preparation method is the same as in Example 1, but without the addition of polymetallic oxy-ionic liquid hybrid materials.

[0046] Comparative Example 2 The specific implementation method is the same as in Example 1, except that the raw material ratio for the high-flowability recycled POM precision injection molding plastic is as follows: 700g recycled POM resin, 150g POM homopolymer, 100g POM copolymer, 15g polyoxometalate-ionic liquid hybrid material, 5g polyethylene wax, 3g calcium stearate, 10102g antioxidant, and 1682g antioxidant. The preparation method is the same as in Example 1, but without the addition of hyperbranched polyacetal-block-polyester synergist.

[0047] Comparative Example 3 The specific implementation method is the same as in Example 1, except that the raw material ratio for the high-flowability recycled POM precision injection molding plastic is: 700g recycled POM resin, 150g POM homopolymer, 100g POM copolymer, 5g polyethylene wax, 3g calcium stearate, 10102g antioxidant, and 1682g antioxidant. The preparation method is the same as in Example 1, but without the addition of polyoxometalate cluster-ionic liquid hybrid materials and hyperbranched polyacetal-block-polyester synergists.

[0048] Performance testing The high-flowability recycled POM precision injection molding plastics were prepared according to Examples 1-3 and Comparative Examples 1-3. All granular products prepared in the examples and comparative examples were conditioned for 24 hours in a standard laboratory environment (temperature 23±2℃, relative humidity 50±5%) before performance testing. Melt index testing was conducted according to GB / T 3682.1-2018 standard using a ZRX-400 melt indexer at 190℃ and a load of 2.16 kg. The preheating time was 5 minutes, the cutting interval was 30 seconds, and the average of 5 cuts was taken as the final result. The instrument die inner diameter was 2.095 mm, and the length was 8.000 mm. Tensile property testing was conducted according to GB / T 1040.2-2006 standard, using a UTM-4204 electronic universal testing machine. A type 1B dumbbell-shaped specimen with a thickness of 4 mm was used. The tensile speed was 50 mm / min, and the gauge length was 50 mm. Five specimens were tested, and the average value was taken. During the test, the load-displacement curve was automatically recorded, and the tensile strength and elongation at break were calculated. Impact strength testing was conducted according to GB / T 1843-2008 standard, using an XJC-50 cantilever beam impact testing machine. The specimen size was 80 mm × 10 mm × 4 mm, the notch depth was 2.7 mm, the radius of the notch bottom arc was 0.25 mm, and the impact energy was 5.5 J. Ten specimens were tested for each sample, and the average value was taken. The notch needed to be precisely machined with a milling cutter before testing. The heat distortion temperature test was conducted according to GB / T 1634.2-2019 standard using an XRW-300A heat distortion temperature testing machine. The sample size was 80mm × 10mm × 4mm, the load was 1.82MPa, the heating rate was 120℃ / h, and a three-point bending loading method was used with a span of 64mm. The temperature recorded when the sample bending deformation reached 0.34mm was the heat distortion temperature. For the heat aging resistance test, the samples were placed in a 401A heat aging chamber and aged continuously at 120℃ for 168 hours. After aging, the samples were removed and conditioned in a standard laboratory environment for 24 hours. Then, the tensile strength was tested according to the tensile test method described above, and the retention rate was calculated. For the flow performance test, a CJ-300 spiral flow tester was used. The mold cavity thickness was 1mm and the width was 10mm. Injection molding was performed at an injection temperature of 200℃ and an injection pressure of 80MPa. The length of the spiral flow channel filled by the melt was measured. Each sample was tested three times, and the average value was taken. All testing equipment has been calibrated by a legal metrology institution and is within its validity period.

[0049] Performance test results: Table 1: Performance test results of each embodiment and comparative example ; As shown in Table 1, Examples 1-3 effectively solved the three major technical problems existing in the recycling process of recycled polyoxymethylene materials by introducing the synergistic effect of polyoxymethylene cluster-ionic liquid hybrid materials and hyperbranched polyacetal-block-polyester synergists. Regarding thermal stability, the heat distortion temperature of Examples 1-3 reached 122-126℃, significantly higher than the 105-115℃ of Comparative Examples 1-3. Furthermore, after 168 hours of thermal aging, the tensile strength retention rate was as high as 90-93%, far exceeding the 70-82% level of the Comparative Examples. This is mainly due to the synergistic stabilizing effect of the phosphomolybdic acid component in the polyoxymethylene cluster-ionic liquid hybrid material and the ionic liquid, which can effectively capture and neutralize free radicals generated during degradation, inhibiting the thermo-oxidative aging process. Regarding melt flowability, Examples 1-3 exhibited melt flow indices of 25.7-30.2 g / 10 min and flow lengths of 65.2-70.1 cm, significantly improved compared to Comparative Examples 1-3 (12.3-18.6 g / 10 min and 41.3-52.4 cm). This is primarily attributed to the branched structure of the hyperbranched polyacetal-block-polyester synergist acting as a molecular chain lubricant during melting, while the ionic liquid hybrid material further improved processing rheology by reducing melt viscosity. In terms of mechanical properties, Examples 1-3 maintained tensile strengths of 60.8-63.1 MPa and impact strengths of 9.5-10.1 kJ / m². 2 The elongation at break remained at 42-47%, which was significantly better than the 48.5-55.2 MPa and 5.9-7.2 kJ / m of comparative examples 1-3. 2 The results showed a 22-32% increase, indicating that the hyperbranched synergist, through its unique core-shell structure, forms physical entanglement and hydrogen bonds with the recycled POM molecular chains, effectively restoring the molecular network structure damaged by multiple processing steps. Simultaneously, the hybrid material enhances the compatibility between the filler and the matrix at the phase interface. Comparative Example 1, lacking the hybrid material, resulted in limited improvement in thermal stability and flowability; Comparative Example 2, lacking the hyperbranched synergist, led to insufficient recovery of mechanical properties; and Comparative Example 3, lacking both modifiers, exhibited the worst performance across all properties, fully demonstrating the synergistic effect and necessity of the two modifiers in solving key problems of recycled POM materials.

[0050] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A high-flowability recycled POM precision injection molding plastic, characterized in that, Including the following parts by weight of raw materials: Recycled POM resin: 40-70 parts by weight; POM homopolymer: 10-25 parts by weight; POM copolymer: 5-15 parts by weight; Polymetallic oxygen cluster-ionic liquid hybrid material: 0.5-3 parts by weight; Hyperbranched polyacetal-block-polyester synergist: 1-5 parts by weight; Polyethylene wax: 0.1-1 parts by weight; Calcium stearate: 0.1-0.5 parts by weight; Antioxidant 1010: 0.1-0.3 parts by weight; Antioxidant 168: 0.1-0.3 parts by weight; The preparation method of the polymetallic oxygen cluster-ionic liquid hybrid material includes: A1, dissolving phosphomolybdic acid in deionized water to prepare a clear solution and stirring; then adding 1-vinyl-3-ethylimidazolium bromide ionic liquid, and heating the reaction system to 74-76℃ under nitrogen protection, stirring and controlling the pH value at 2-3 during the reaction; A2, after the reaction is completed, adding potassium persulfate and adding ascorbic acid aqueous solution dropwise, and reacting at 35-45℃; finally, centrifuging the reaction mixture, washing the precipitate with ethanol, and drying it in a vacuum oven at 60-64℃.

2. The high-flowability recycled POM precision injection molding plastic according to claim 1, characterized in that, In step A1, the temperature is raised to 74-76℃ and the reaction time is 12-15 hours.

3. The high-flowability recycled POM precision injection molding plastic according to claim 1, characterized in that, In step A2, the reaction time is 2-4 hours at 35-45℃.

4. The high-flowability recycled POM precision injection molding plastic according to claim 1, characterized in that, The preparation method of the hyperbranched polyacetal-block-polyester synergist includes: B1, mixing pentaerythritol with 2,2-dimethylolpropionic acid and heating to 158-162℃ under nitrogen protection to carry out melt polycondensation reaction to synthesize hyperbranched polyester; then adding ε-caprolactone and stannous octoate catalysts and carrying out ring-opening polymerization at 138-142℃; B2, finally adding trioxymethylene and carrying out block copolymerization reaction at 58-62℃ under boron trifluoride diethyl ether catalysis; after the reaction, dissolving the product in acetone, purifying it by recrystallization with n-hexane, filtering, washing, and drying in a vacuum environment at 48-52℃.

5. The high-flowability recycled POM precision injection molding plastic according to claim 4, characterized in that, In step B1, the melt polycondensation reaction is carried out at 158-162℃ for 4-6 hours; the ring-opening polymerization is carried out at 138-142℃ for 5-10 hours.

6. The high-flowability recycled POM precision injection molding plastic according to claim 4, characterized in that, In step B2, the drying time in a vacuum environment at 48-52℃ is 48-50 hours.

7. A method for preparing high-flowability recycled POM precision injection molded plastic according to any one of claims 1-6, characterized in that, step include: S1. After removing surface stains from waste POM products with alkaline cleaning solution, crush them into granules and dry them in a vacuum oven at 78-82℃. S2. The pretreated recycled POM material, POM homopolymer, POM copolymer, polyoxometalate cluster-ionic liquid hybrid material, hyperbranched polyacetal-block-polyester synergist, polyethylene wax, calcium stearate, antioxidant 1010 and antioxidant 168 are put into a high-speed mixer and mixed. S3. The mixture is melt-blended in a twin-screw extruder. The screw temperatures are set at 185℃, 190℃, 195℃, and 200℃ from the feeding section to the die head, respectively, and the melt pressure is maintained at 12-15MPa. The extruded melt is granulated underwater, cooled, and dried to obtain granular products. The final granular products are precision injection molded at an injection temperature of 190-210℃ and a mold temperature of 80-90℃.

8. The preparation method according to claim 7, characterized in that, In step S1, the drying time in a vacuum oven at 78-82℃ is 12-15 hours.

9. The preparation method according to claim 7, characterized in that, In step S2, the mixing time in the high-speed mixer is 15-20 minutes.

10. The preparation method according to claim 7, characterized in that, In step S3, the screw speed of the twin-screw extruder is 350-400 rpm.