Recycled modified polypropylene composite material preparation system and method

Abstract

The invention discloses a recycled modified polypropylene composite material preparation system and a resource recovery method, and relates to the technical field of high polymer material science and engineering. The raw material pretreatment module adopts near infrared spectrum classification, multi-stage cleaning, drying and crushing, and the moisture content is controlled to be less than 0.5%; the melt blending module melts the materials at 180-220 DEG C, modifiers and additives are added, and vacuum degassing is performed to remove impurities; adding a reinforcing agent into the modification reinforcing module, and performing ultrasonic dispersion and dynamic vulcanization; the molding processing module is used for manufacturing a product through extrusion, injection molding or calendaring; the quality detection module is used for detecting mechanical and thermal properties; the waste recovery module is used for crushing and melting granulation to realize a closed loop; the intelligent control module uses a PLC to coordinate each module. Integrated treatment of waste polypropylene is achieved, the purity of raw materials and the performance of a composite material are improved, the resource utilization rate is increased through closed-loop recycling, manual intervention is reduced through intelligent control, product stability is guaranteed, economic and environment-friendly benefits are achieved, and high-valued circulation of waste plastic is promoted.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material science and engineering technology, and particularly relates to a modified polypropylene composite material preparation system and method for recycling. BACKGROUND

[0002] With the rapid development of the plastic industry, polypropylene, as one of the most widely used general-purpose plastics, is widely used in packaging, automobiles, building materials and other fields. The amount of waste polypropylene generated has also increased year by year. At present, the simple melt regranulation process is used for recycling waste polypropylene, and there is a lack of systematic pretreatment and modification and enhancement links, which leads to problems such as low purity and serious performance degradation of the recycled material, making it difficult to meet the use requirements of high value-added products. For example, during the recycling process, waste polypropylene is often mixed with other plastics, metals, sand and other impurities. The traditional manual sorting has low efficiency and an accuracy rate of less than 80%, and cannot be classified and processed according to the molecular weight difference of polypropylene. During melt blending, uneven melting of the material often occurs, affecting the quality of the final product.

[0003] The existing modified polypropylene preparation system has obvious shortcomings in the recycling link. On the one hand, the pretreatment of raw materials only stays in simple cleaning and crushing, and does not detect and control the degradation characteristics of waste polypropylene. The problems such as reduction of molecular weight and increase of carbonyl content of the recycled material due to long-term use or aging will lead to a significant decrease in the mechanical properties of the composite material, and the tensile strength and impact strength are usually reduced by more than 30% compared with new materials. On the other hand, the compatibility between the reinforcing agent and the polypropylene matrix is poor, and the reinforcing agent is prone to agglomeration under the traditional adding method, with a dispersion uniformity of less than 70%. The reinforcing effect cannot be fully played, and the generated edge scraps and unqualified products during the preparation process are mostly discarded without forming a closed-loop recycling, and the resource utilization rate is only 60%-70%, causing secondary waste. In addition, the existing system has low automation degree, relies on manual adjustment of process parameters, and has large fluctuations in product qualification rate, which is difficult to meet the needs of large-scale and high-quality recycling.

[0004] From an industry development perspective, increasingly stringent environmental policies and resource shortages are driving the upgrading of waste plastic recycling technologies. However, current technologies still face several challenges: First, there is a lack of integrated preparation systems, with each stage of equipment operating independently and lacking coordination. For example, pre-treated raw materials need to be manually transferred to melt blending equipment, which is inefficient and prone to secondary pollution. Second, quality inspection is lagging behind, mostly relying on offline sampling and testing, which cannot provide real-time feedback for adjusting process parameters, resulting in a high rate of defective products during mass production. Third, the level of intelligent control is insufficient, failing to adaptively optimize parameters based on raw material characteristics and product requirements, making it difficult to guarantee the stability of product performance across different batches. These problems not only limit the high-value utilization of waste polypropylene but also hinder the development of the circular economy. There is an urgent need for a modified polypropylene composite material preparation system that integrates efficient pretreatment, precise modification, closed-loop recycling, and intelligent control to address the pain points of existing technologies and promote the efficient recycling of waste polypropylene resources. Summary of the Invention

[0005] The present invention provides a recycling system and method for preparing modified polypropylene composite materials to solve the problems mentioned in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a recyclable modified polypropylene composite material preparation system, comprising:

[0007] The raw material pretreatment module is used for sorting, cleaning, drying, and crushing recycled waste polypropylene. It includes a sorting unit, a cleaning unit, a drying unit, and a crushing unit. The sorting unit uses near-infrared spectroscopy to identify the material composition of the waste polypropylene using a near-infrared spectrometer with a wavelength of 900-1700nm. The identification accuracy is no less than 98%. Polypropylene is graded according to its molecular weight (50,000-300,000), into low molecular weight (50,000-100,000), medium molecular weight (100,000-200,000), and high molecular weight (200,000-300,000). The cleaning unit includes a coarse washing device, a fine washing device, and a rinsing device connected in sequence. The coarse washing device uses a high-pressure water gun (pressure 0.3-0.5MPa) to remove surface-adhered mud and other impurities. The fine washing device... The polypropylene is soaked in an alkaline cleaning agent (sodium hydroxide and sodium carbonate mixed at a mass ratio of 2:1) at 50-60℃ for 20-30 minutes to remove oil and other organic impurities. The rinsing device uses deionized water to rinse until the pH of the rinsing water is 6.5-7.5. The drying unit uses a hot air circulating dryer with a drying temperature of 80-100℃ and a drying time of 2-4 hours to ensure the moisture content of the treated polypropylene is below 0.5%. The crushing unit uses a combination of a twin-shaft shredder and a high-speed crusher. The twin-shaft shredder first crushes large pieces of waste polypropylene to 50-100mm, and then the high-speed crusher crushes them to 5-10mm particles. During the crushing process, the temperature is controlled to not exceed 60℃ through a cooling water circuit to prevent thermal degradation of the polypropylene.

[0008] The melt blending module is used to melt blend pretreated polypropylene granules with modifiers and additives. It includes a blending kettle, a heating device, a stirring device, and a vacuum degassing device. The blending kettle has a volume of 500-1000L and is made of stainless steel (304 stainless steel). The kettle body is equipped with a jacketed heating structure. The heating device includes an electric heating element and a temperature sensor. The electric heating element has a power of 15-20kW and can control the temperature inside the blending kettle at 180-220℃, with a temperature fluctuation range not exceeding ±2℃. The stirring device adopts a combination structure of an anchor-type stirring paddle and a dispersing disc. The stirring paddle speed is 50-200r / min, and the dispersing disc speed is 500-1500r / min. The different speeds are coordinated... The same action achieves uniform mixing of materials; the vacuum degassing device is connected to the mixing vessel, which can control the vacuum degree inside the vessel at -0.08 to -0.09 MPa, and the degassing time is 10-20 min to remove air bubbles and volatiles from the materials; during the mixing process, polypropylene granules are first added to the mixing vessel and heated to a molten state (melt index of 5-20 g / 10 min, 190℃, 2.16 kg), and then modifiers (such as maleic anhydride grafted polypropylene, the amount added is 1%-5% of the mass of polypropylene) and additives (such as antioxidant 1010, the amount added is 0.1%-0.5%; lubricant calcium stearate, the amount added is 0.2%-1%) are added in proportion, and stirring is continued for 15-30 min.

[0009] The modification and reinforcement module is used to reinforce and modify the melt-blended material to improve the mechanical properties of the composite material. It includes a reinforcement addition unit, an ultrasonic dispersion unit, and a dynamic vulcanization unit. The reinforcement addition unit can accurately meter and add reinforcement, which can be glass fiber (3-10 mm in length, 10-20 μm in diameter) or carbon fiber (5-15 mm in length, 5-10 μm in diameter), at a rate of 10%-30% of the total mass of the composite material. The ultrasonic dispersion unit uses an ultrasonic generator with a power of 1-3 kW and an ultrasonic frequency of 2... The ultrasonic treatment unit, operating at 0-40 kHz, treats the material with added reinforcing agents for 5-15 minutes to ensure uniform dispersion of the reinforcing agents in the polypropylene matrix, with a dispersion uniformity of not less than 90%. The dynamic vulcanization unit is used to vulcanize composite materials containing elastomers (such as EPDM rubber, with an addition amount of 5%-15%). The vulcanization temperature is 170-190℃, and the vulcanization time is 5-15 minutes. During the vulcanization process, a kneader with a rotation speed of 30-80 r / min is used for shearing action to form a micro-crosslinked structure in the elastomer, thereby improving the toughness of the composite material.

[0010] The molding and processing module is used to process modified and reinforced materials into products of the required shapes, including an extrusion molding unit, an injection molding unit, and a calendering unit. The extrusion molding unit uses a single-screw extruder with a screw diameter of 30-65mm, a length-to-diameter ratio of 20-30:1, an extrusion temperature of 180-220℃, and a screw speed of 30-100 r / min. It can produce sheets, pipes, and other products with dimensional accuracy controlled within ±0.5mm. The injection molding unit uses a clamping force of 500-20... The injection molding machine has a capacity of 00kN, an injection temperature of 180-230℃, an injection pressure of 50-150MPa, a holding pressure of 30-100MPa, and a holding time of 5-30s. It can produce injection molded products of various complex shapes. The calendering unit includes a multi-roll calender with a roll temperature of 160-190℃, a roll speed of 10-30r / min, and a calendering speed of 1-5m / min. It can produce films or sheets with a thickness of 0.1-5mm and a thickness deviation of no more than ±0.05mm.

[0011] The quality inspection module is used to test various properties of the prepared modified polypropylene composite material, including mechanical property testing, thermal property testing, aging resistance testing, and appearance inspection. The mechanical property testing unit uses a universal testing machine to test tensile strength (testing speed 50 mm / min) and elongation at break according to GB / T1040.1-2018 standard, flexural strength (testing speed 2 mm / min) and flexural modulus according to GB / T9341-2008 standard, and according to GB / T1843-2 standard. The 008 standard test was used to measure the impact strength of a simply supported beam (notch type A); the thermal performance testing unit used a differential scanning calorimeter (DSC) to test the melting point and crystallinity at a heating rate of 10℃ / min under a nitrogen atmosphere; the heat distortion temperature tester tested the heat distortion temperature (load 1.82MPa) according to GB / T1634.2-2004 standard; the aging resistance testing unit used an ultraviolet aging test chamber to conduct ultraviolet aging tests according to GB / T16422.3-2014 standard (wavelength 340nm, irradiance 0.71W / m²). 2 The mechanical properties retention rate after aging is tested at 60℃ for 1000 hours. The appearance inspection unit uses an industrial camera (resolution not less than 20 million pixels) in conjunction with an image recognition system to detect defects such as scratches, bubbles, and impurities on the surface of the product, with a defect recognition accuracy rate of not less than 95%.

[0012] The waste recycling module is used to recycle and reuse waste generated during the preparation process (such as scraps and defective products). It includes a waste collection unit, a crushing unit, a melting unit, and a granulation unit. The waste collection unit collects waste generated by each module via a conveyor belt, with a collection efficiency of no less than 98%. The crushing unit uses a high-speed crusher to crush the waste into particles of 3-8mm. The melting unit uses a screw extruder to heat and melt the crushed waste at a melting temperature of 180-210℃. The granulation unit granulates the molten material using an underwater pelletizer, with a particle diameter of 2-5mm and a length of 2-5mm. The granulated particles can be fed back into the melt blending module for reuse, achieving a closed-loop cycle.

[0013] The intelligent control module is used for automated control and parameter optimization of the entire preparation system. It includes a central controller, sensor group, actuator group, and human-machine interface. The central controller uses a Siemens S7-1200 PLC (Programmable Logic Controller) to coordinate the control of each module. The sensor group includes a temperature sensor (measurement range 0-300℃, accuracy ±1℃), a pressure sensor (measurement range 0-200MPa, accuracy ±0.5%FS), a flow sensor (measurement range 0-1000L / h, accuracy ±1%FS), a level sensor (measurement range 0-2m, accuracy ±1mm), and a mass sensor. (Measurement range 0-500kg, accuracy ±0.1kg), real-time acquisition of operating parameters of each module; the actuator group includes various solenoid valves, motors, heating devices, etc., which receive instructions from the central controller and execute corresponding actions; the human-machine interface adopts a touch screen (size 10-15 inches), which can display the system operating status, parameter curves and alarm information in real time. Operators can set parameters, start / stop the system and handle alarms through the touch screen; the intelligent control module also has an adaptive control function, which can automatically adjust parameters such as melt blending temperature, stirring speed and reinforcing agent addition amount according to the detection results of the quality detection module, so that the product qualification rate is maintained above 95%.

[0014] Furthermore, it also includes: a reinforcing agent surface treatment unit, located before the reinforcing agent addition unit of the modified reinforcing module, used to perform surface modification treatment on the reinforcing agent to improve the compatibility between the reinforcing agent and the polypropylene matrix; the reinforcing agent surface treatment unit includes a coupling agent solution preparation tank, an impregnation device, and a drying device; the coupling agent solution preparation tank is used to prepare the coupling agent solution, the coupling agent is a silane coupling agent (such as KH550), the mass fraction of the coupling agent solution is 0.5%-2%, and the solvent is a mixture of ethanol and water (volume ratio 1:1); the impregnation device impregnates the reinforcing agent in the coupling agent solution for 5-10 minutes, and ultrasonic assistance is used during the impregnation process (power 500-1000W, frequency 30kHz); the drying device uses hot air drying, the drying temperature is 80-100℃, and the drying time is 1-2 hours, so that the moisture content of the treated reinforcing agent is less than 0.3%; the interfacial bonding strength between the surface-treated reinforcing agent and the polypropylene matrix can be evaluated by the following formula: Where σ is the interfacial bonding strength (MPa), F is the force required for the reinforcing agent to be pulled out of the matrix (N), and A is the contact area between the reinforcing agent and the matrix (m²). 2 ).

[0015] Furthermore, it also includes a degradation degree detection unit, located between the raw material pretreatment module and the melt blending module, used to detect the degradation degree of waste polypropylene to determine the optimal blending process parameters; the degradation degree detection unit uses gel permeation chromatography (GPC) to determine the molecular weight distribution index (PDI) of waste polypropylene and Fourier transform infrared spectroscopy (FTIR) to detect the carbonyl index (CI); when the molecular weight distribution index is greater than 3.5 or the carbonyl index is greater than 0.2, the polypropylene is considered to be severely degraded, and a molecular weight regulator (such as dicumyl peroxide, added at a rate of 0.05%-0.2%) needs to be added during the melt blending process; the optimal amount of molecular weight regulator can be calculated by the following formula: m=k×(PDI-3.0)×M where m is the amount of molecular weight regulator added (kg), k is a correction coefficient (range 0.001-0.005), PDI is the measured molecular weight distribution index, and M is the mass of waste polypropylene (kg).

[0016] Furthermore, the stirring device of the melt blending module also includes a torque sensor for real-time monitoring of the torque value during the stirring process. The torque sensor has a measurement range of 0-500 N·m and an accuracy of ±1% FS. The central controller automatically adjusts the stirring speed and heating temperature according to the changes in the torque value. When the torque value exceeds the set upper limit (300 N·m), it automatically reduces the stirring speed (by 5-10 r / min) and increases the heating temperature (by 5-10 °C). When the torque value is lower than the set lower limit (100 N·m), it automatically increases the stirring speed (by 5-10 r / min) and decreases the heating temperature (by 5-10 °C) to ensure the melt blending effect of the material and keep the torque value stable within the range of 150-250 N·m.

[0017] Furthermore, the molding and processing module also includes an online thickness detection unit for real-time thickness detection and feedback control of extruded or calendered products. The online thickness detection unit uses a laser thickness gauge with a measurement range of 0-10mm, an accuracy of ±0.01mm, and a measurement frequency of 100-500Hz. The laser thickness gauge is installed at the mold exit, with 5-10 measurement points evenly set along the width of the product. The central controller compares the measured thickness with the set thickness. When the deviation exceeds ±0.05mm, it automatically adjusts the extruder screw speed or the calender roller clearance, with an adjustment range of 0.01-0.1mm / time, until the product thickness meets the requirements.

[0018] Furthermore, the quality inspection module also includes a density detection unit for detecting the density of the modified polypropylene composite material. The density is measured using the water displacement method, with a measurement accuracy of ±0.001 g / cm³. 3 The density detection unit includes an electronic balance (accuracy 0.001g), a constant temperature water bath (temperature controlled at 23±1℃), and a suspended basket. During measurement, the mass of the sample in air is first weighed, followed by the mass of the sample submerged in water. The density is calculated based on Archimedes' principle. When the detected density is close to the set value (1.0-1.5g / cm³), the density is measured. 3 The deviation exceeds ±0.05 g / cm 3 If the product is deemed unqualified, the information is fed back to the intelligent control module, which then adjusts the amount of reinforcing agent added to correct the density.

[0019] Furthermore, the waste recycling module also includes an impurity separation unit for removing impurities such as metals and stones from the waste. The impurity separation unit includes a magnetic separator and a screening device. The magnetic separator uses a high-strength magnetic drum (magnetic field strength 5000-8000Gs) to remove ferromagnetic impurities with a removal efficiency of not less than 99%. The screening device uses a multi-layer vibrating screen (2-3 layers) with screen apertures of 8mm, 3mm and 1mm, which can separate impurities and particles of different sizes with a screening efficiency of not less than 95%. The purity of the waste after impurity separation can be increased to over 99%, ensuring the quality of the recycled material.

[0020] A method for preparing resource recovery from the aforementioned recyclable modified polypropylene composite material includes:

[0021] The raw material pretreatment steps involve classifying, cleaning, drying, and crushing the recycled waste polypropylene. Specifically, near-infrared spectroscopy is used to identify the material composition and molecular weight of the waste polypropylene. Impurities are removed by coarse washing, fine washing, and rinsing, with the fine washing temperature controlled at 50-60℃ and the pH value after rinsing at 6.5-7.5. The material is then dried at 80-100℃ for 2-4 hours to reduce the moisture content to below 0.5%. The material is first crushed to 50-100mm, then further crushed to 5-10mm particles, with the crushing temperature not exceeding 60℃.

[0022] The melt blending step involves melt blending the pretreated polypropylene granules with modifiers and additives. Specifically, the polypropylene granules are added to a blending vessel and heated to 180-220℃ to melt. Modifiers (1%-5%) and additives (antioxidant 0.1%-0.5%, lubricant 0.2%-1%) are added in proportion. The mixture is stirred for 15-30 minutes at a stirring speed of 50-200 r / min and a dispersing disc speed of 500-1500 r / min. The mixture is then degassed for 10-20 minutes under a vacuum of -0.08 to -0.09 MPa to remove bubbles and volatiles.

[0023] The modification and reinforcement step involves modifying the melt-blended material. Specifically, this includes adding glass fiber or carbon fiber at 10%-30% of the total mass of the composite material; ultrasonically treating the material at 1-3kW and 20-40kHz for 5-15 minutes to ensure that the uniformity of the reinforcing agent dispersion is not less than 90%; if 5%-15% elastomer is added, kneading and vulcanizing the mixture at 170-190℃ and 30-80r / min for 5-15 minutes to form a micro-crosslinked structure.

[0024] The molding and processing steps involve processing the modified and reinforced material into the desired product. Specifically: if extrusion molding is used, the screw diameter is 30-65mm, the length-to-diameter ratio is 20-30:1, the temperature is 180-220℃, and the rotation speed is 30-100r / min to produce sheets or pipes; if injection molding is used, the clamping force is 500-2000kN, the temperature is 180-230℃, the pressure is 50-150MPa, the holding pressure is 30-100MPa, and the time is 5-30s; if calendering is used, the roller temperature is 160-190℃, the rotation speed is 10-30r / min, and the speed is 1-5m / min to produce films or sheets.

[0025] The quality inspection steps involve testing the properties of the prepared composite material; specifically: testing tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength; testing melting point, crystallinity, and heat distortion temperature; conducting ultraviolet aging tests and testing performance retention rate; inspecting for surface defects in the product; all properties must meet preset standards, and unqualified products are sent to the waste recycling module.

[0026] The waste recycling step involves recycling and reusing the waste generated during the preparation process. Specifically, the waste is collected by a conveyor belt with a collection efficiency of not less than 98%; crushed into 3-8mm particles; melted at 180-210℃; granulated by an underwater pelletizer (diameter 2-5mm, length 2-5mm); and the granulated particles are then fed back into the melt blending step to achieve a closed-loop cycle.

[0027] The intelligent control process automates and optimizes parameters throughout the entire recycling process. Specifically, it coordinates and controls each step through a PLC controller; uses a sensor array to collect parameters such as temperature, pressure, and flow rate in real time; executes control actions through an actuator array; operators monitor the system operation and set parameters via a touchscreen; and automatically adjusts process parameters based on quality inspection results to maintain a product qualification rate of over 95%.

[0028] Furthermore, in the modification and reinforcement step, surface treatment is required before adding the reinforcing agent. Specifically, this includes: preparing a silane coupling agent solution with a mass fraction of 0.5%-2% (ethanol to water volume ratio 1:1); immersing the reinforcing agent in the coupling agent solution for 5-10 minutes while simultaneously subjecting it to ultrasonic treatment at 500-1000W and 30kHz; and drying it at 80-100℃ for 1-2 hours to reduce the moisture content to below 0.3%. After surface treatment, the interfacial bonding effect between the reinforcing agent and the polypropylene matrix can be evaluated by the interfacial bonding strength. The higher the interfacial bonding strength, the better the mechanical properties of the composite material.

[0029] Furthermore, between the raw material pretreatment step and the melt blending step, a degradation degree detection step is also included. Specifically, the molecular weight distribution index (PDI) of waste polypropylene is determined using gel permeation chromatography; the carbonyl index (CI) is detected using Fourier transform infrared spectroscopy; when the PDI is greater than 3.5 or the CI is greater than 0.2, the polypropylene is considered severely degraded; the amount of molecular weight regulator to be added is calculated according to the following formula: Where C is the actual concentration (mass fraction, %) of the molecular weight regulator, c0 is the basic concentration (value 0.05%), and CI is the measured carbonyl index; the calculated molecular weight regulator is added to the melt blend system to improve the molecular weight distribution of polypropylene and enhance the performance stability of the composite material.

[0030] Compared with existing technologies, the beneficial effects of this invention are:

[0031] This invention breaks through existing technological bottlenecks from the dual dimensions of resource recycling and product quality improvement, providing a comprehensive solution for the high-value recycling of waste polypropylene. In the raw material processing stage, near-infrared spectroscopy identification and multi-stage cleaning and drying achieve precise classification and deep purification of waste polypropylene, effectively removing impurities and grading it according to molecular weight. This avoids performance fluctuations caused by mixing raw materials of different qualities, laying the foundation for the subsequent preparation of high-quality composite materials. The degradation detection function can identify the degradation status of polypropylene in advance, and the addition of molecular weight regulators can improve the performance of the raw materials, solving the problem of performance degradation in traditional recycled materials and ensuring the basic performance of the composite materials.

[0032] In the modification, reinforcement, and molding processes, this invention significantly improves the compatibility between the reinforcing agent and the polypropylene matrix through surface treatment and ultrasonic dispersion of the reinforcing agent, preventing reinforcing agent agglomeration, fully leveraging its reinforcing effect, and significantly improving the mechanical properties and thermal stability of the composite material. Multiple molding methods are available to meet the needs of different products, and online detection and feedback control ensure dimensional accuracy and appearance quality, reducing the generation of defective products. Simultaneously, a closed-loop waste recycling system enables the efficient recycling and reuse of scraps and defective products from the manufacturing process, greatly improving resource utilization, reducing waste, and aligning with the concept of a circular economy.

[0033] In terms of system intelligence and stability, the intelligent control module, through the collaboration of PLC and multiple sensors, achieves real-time acquisition and adaptive adjustment of parameters at each stage. This ensures stable system operation without extensive manual intervention, effectively improving product qualification rate and batch consistency. The user interface is convenient and intuitive, facilitating monitoring and management by operators and reducing operational difficulty. Overall, this invention achieves integrated and intelligent processing of waste polypropylene from recycling and modification to molding. It not only improves the performance and quality of modified polypropylene composite materials but also significantly increases resource utilization and production efficiency, reduces production costs and environmental pressure, and combines economic, environmental, and social benefits, promoting the waste plastic recycling industry towards high-value, large-scale, and green development. Attached Figure Description

[0034] Figure 1 This is a schematic block diagram of the recycling-modified polypropylene composite material preparation system proposed in this invention;

[0035] Figure 2 Comparison of impurity removal effects of different pretreatment processes on waste polypropylene;

[0036] Figure 3 A comparison chart showing the effects of reinforcing agent surface treatment on the mechanical properties of composite materials;

[0037] Figure 4 A comparison chart showing the performance degradation of polypropylene composites after different recycling cycles;

[0038] Figure 5 This is a comparison chart of the stability of process parameters between intelligent control and manual control. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The invention will now be described in further detail with reference to the accompanying drawings.

[0042] Reference Figures 1 to 5 A system for preparing recyclable modified polypropylene composite materials, comprising:

[0043] The raw material pretreatment module is used for sorting, cleaning, drying, and crushing recycled waste polypropylene. It includes a sorting unit, a cleaning unit, a drying unit, and a crushing unit. The sorting unit uses near-infrared spectroscopy to identify the material composition of the waste polypropylene using a near-infrared spectrometer with a wavelength of 900-1700nm. The identification accuracy is no less than 98%. Polypropylene is graded according to its molecular weight (50,000-300,000), into low molecular weight (50,000-100,000), medium molecular weight (100,000-200,000), and high molecular weight (200,000-300,000). The cleaning unit includes a coarse washing device, a fine washing device, and a rinsing device connected in sequence. The coarse washing device uses a high-pressure water gun (pressure 0.3-0.5MPa) to remove surface-adhered mud and other impurities. The fine washing device... The polypropylene is soaked in an alkaline cleaning agent (sodium hydroxide and sodium carbonate mixed at a mass ratio of 2:1) at 50-60℃ for 20-30 minutes to remove oil and other organic impurities. The rinsing device uses deionized water to rinse until the pH of the rinsing water is 6.5-7.5. The drying unit uses a hot air circulating dryer with a drying temperature of 80-100℃ and a drying time of 2-4 hours to ensure the moisture content of the treated polypropylene is below 0.5%. The crushing unit uses a combination of a twin-shaft shredder and a high-speed crusher. The twin-shaft shredder first crushes large pieces of waste polypropylene to 50-100mm, and then the high-speed crusher crushes them to 5-10mm particles. During the crushing process, the temperature is controlled to not exceed 60℃ through a cooling water circuit to prevent thermal degradation of the polypropylene.

[0044] The melt blending module is used to melt blend pretreated polypropylene granules with modifiers and additives. It includes a blending kettle, a heating device, a stirring device, and a vacuum degassing device. The blending kettle has a volume of 500-1000L and is made of stainless steel (304 stainless steel). The kettle body is equipped with a jacketed heating structure. The heating device includes an electric heating element and a temperature sensor. The electric heating element has a power of 15-20kW and can control the temperature inside the blending kettle at 180-220℃, with a temperature fluctuation range not exceeding ±2℃. The stirring device adopts a combination structure of an anchor-type stirring paddle and a dispersing disc. The stirring paddle speed is 50-200r / min, and the dispersing disc speed is 500-1500r / min. The different speeds are coordinated... The same action achieves uniform mixing of materials; the vacuum degassing device is connected to the mixing vessel, which can control the vacuum degree inside the vessel at -0.08 to -0.09 MPa, and the degassing time is 10-20 min to remove air bubbles and volatiles from the materials; during the mixing process, polypropylene granules are first added to the mixing vessel and heated to a molten state (melt index of 5-20 g / 10 min, 190℃, 2.16 kg), and then modifiers (such as maleic anhydride grafted polypropylene, the amount added is 1%-5% of the mass of polypropylene) and additives (such as antioxidant 1010, the amount added is 0.1%-0.5%; lubricant calcium stearate, the amount added is 0.2%-1%) are added in proportion, and stirring is continued for 15-30 min.

[0045] The modification and reinforcement module is used to reinforce and modify the melt-blended material to improve the mechanical properties of the composite material. It includes a reinforcement addition unit, an ultrasonic dispersion unit, and a dynamic vulcanization unit. The reinforcement addition unit can accurately meter and add reinforcement, which can be glass fiber (3-10 mm in length, 10-20 μm in diameter) or carbon fiber (5-15 mm in length, 5-10 μm in diameter), at a rate of 10%-30% of the total mass of the composite material. The ultrasonic dispersion unit uses an ultrasonic generator with a power of 1-3 kW and an ultrasonic frequency of 2... The ultrasonic treatment unit, operating at 0-40 kHz, treats the material with added reinforcing agents for 5-15 minutes to ensure uniform dispersion of the reinforcing agents in the polypropylene matrix, with a dispersion uniformity of not less than 90%. The dynamic vulcanization unit is used to vulcanize composite materials containing elastomers (such as EPDM rubber, with an addition amount of 5%-15%). The vulcanization temperature is 170-190℃, and the vulcanization time is 5-15 minutes. During the vulcanization process, a kneader with a rotation speed of 30-80 r / min is used for shearing action to form a micro-crosslinked structure in the elastomer, thereby improving the toughness of the composite material.

[0046] The molding and processing module is used to process modified and reinforced materials into products of the required shapes, including an extrusion molding unit, an injection molding unit, and a calendering unit. The extrusion molding unit uses a single-screw extruder with a screw diameter of 30-65mm, a length-to-diameter ratio of 20-30:1, an extrusion temperature of 180-220℃, and a screw speed of 30-100 r / min. It can produce sheets, pipes, and other products with dimensional accuracy controlled within ±0.5mm. The injection molding unit uses a clamping force of 500-20... The injection molding machine has a capacity of 00kN, an injection temperature of 180-230℃, an injection pressure of 50-150MPa, a holding pressure of 30-100MPa, and a holding time of 5-30s. It can produce injection molded products of various complex shapes. The calendering unit includes a multi-roll calender with a roll temperature of 160-190℃, a roll speed of 10-30r / min, and a calendering speed of 1-5m / min. It can produce films or sheets with a thickness of 0.1-5mm and a thickness deviation of no more than ±0.05mm.

[0047] The quality inspection module is used to test various properties of the prepared modified polypropylene composite material, including mechanical property testing, thermal property testing, aging resistance testing, and appearance inspection. The mechanical property testing unit uses a universal testing machine to test tensile strength (testing speed 50 mm / min) and elongation at break according to GB / T1040.1-2018 standard, flexural strength (testing speed 2 mm / min) and flexural modulus according to GB / T9341-2008 standard, and according to GB / T1843-2 standard. The 008 standard test was used to measure the impact strength of a simply supported beam (notch type A); the thermal performance testing unit used a differential scanning calorimeter (DSC) to test the melting point and crystallinity at a heating rate of 10℃ / min under a nitrogen atmosphere; the heat distortion temperature tester tested the heat distortion temperature (load 1.82MPa) according to GB / T1634.2-2004 standard; the aging resistance testing unit used an ultraviolet aging test chamber to conduct ultraviolet aging tests according to GB / T16422.3-2014 standard (wavelength 340nm, irradiance 0.71W / m²). 2 The mechanical properties retention rate after aging is tested at 60℃ for 1000 hours. The appearance inspection unit uses an industrial camera (resolution not less than 20 million pixels) in conjunction with an image recognition system to detect defects such as scratches, bubbles, and impurities on the surface of the product, with a defect recognition accuracy rate of not less than 95%.

[0048] The waste recycling module is used to recycle and reuse waste generated during the preparation process (such as scraps and defective products). It includes a waste collection unit, a crushing unit, a melting unit, and a granulation unit. The waste collection unit collects waste generated by each module via a conveyor belt, with a collection efficiency of no less than 98%. The crushing unit uses a high-speed crusher to crush the waste into particles of 3-8mm. The melting unit uses a screw extruder to heat and melt the crushed waste at a melting temperature of 180-210℃. The granulation unit granulates the molten material using an underwater pelletizer, with a particle diameter of 2-5mm and a length of 2-5mm. The granulated particles can be fed back into the melt blending module for reuse, achieving a closed-loop cycle.

[0049] The intelligent control module is used for automated control and parameter optimization of the entire preparation system. It includes a central controller, sensor group, actuator group, and human-machine interface. The central controller uses a Siemens S7-1200 PLC (Programmable Logic Controller) to coordinate the control of each module. The sensor group includes a temperature sensor (measurement range 0-300℃, accuracy ±1℃), a pressure sensor (measurement range 0-200MPa, accuracy ±0.5%FS), a flow sensor (measurement range 0-1000L / h, accuracy ±1%FS), a level sensor (measurement range 0-2m, accuracy ±1mm), and a mass sensor. (Measurement range 0-500kg, accuracy ±0.1kg), real-time acquisition of operating parameters of each module; the actuator group includes various solenoid valves, motors, heating devices, etc., which receive instructions from the central controller and execute corresponding actions; the human-machine interface adopts a touch screen (size 10-15 inches), which can display the system operating status, parameter curves and alarm information in real time. Operators can set parameters, start / stop the system and handle alarms through the touch screen; the intelligent control module also has an adaptive control function, which can automatically adjust parameters such as melt blending temperature, stirring speed and reinforcing agent addition amount according to the detection results of the quality detection module, so that the product qualification rate is maintained above 95%.

[0050] This invention further includes: a reinforcing agent surface treatment unit, located before the reinforcing agent addition unit of the modified reinforcing module, used to perform surface modification treatment on the reinforcing agent to improve the compatibility between the reinforcing agent and the polypropylene matrix; the reinforcing agent surface treatment unit includes a coupling agent solution preparation tank, an impregnation device, and a drying device; the coupling agent solution preparation tank is used to prepare the coupling agent solution, the coupling agent is a silane coupling agent (such as KH550), the mass fraction of the coupling agent solution is 0.5%-2%, and the solvent is a mixture of ethanol and water (volume ratio 1:1); the impregnation device impregnates the reinforcing agent in the coupling agent solution for 5-10 minutes, and ultrasonic assistance is used during the impregnation process (power 500-1000W, frequency 30kHz); the drying device uses hot air drying, the drying temperature is 80-100℃, and the drying time is 1-2 hours, so that the moisture content of the treated reinforcing agent is less than 0.3%; the interfacial bonding strength between the surface-treated reinforcing agent and the polypropylene matrix can be evaluated by the following formula: Where σ is the interfacial bonding strength (MPa), F is the force required for the reinforcing agent to be pulled out of the matrix (N), and A is the contact area between the reinforcing agent and the matrix (m²). 2 ).

[0051] This invention also includes: a degradation degree detection unit, located between the raw material pretreatment module and the melt blending module, used to detect the degradation degree of waste polypropylene to determine the optimal blending process parameters; the degradation degree detection unit uses gel permeation chromatography (GPC) to determine the molecular weight distribution index (PDI) of waste polypropylene and Fourier transform infrared spectroscopy (FTIR) to detect the carbonyl index (CI); when the molecular weight distribution index is greater than 3.5 or the carbonyl index is greater than 0.2, the polypropylene is determined to be severely degraded, and a molecular weight regulator (such as dicumyl peroxide, added at a rate of 0.05%-0.2%) needs to be added during the melt blending process; the optimal amount of molecular weight regulator can be calculated by the following formula: m = k × (PDI - 3.0) × M where m is the amount of molecular weight regulator added (kg), k is a correction coefficient (range 0.001-0.005), PDI is the measured molecular weight distribution index, and M is the mass of waste polypropylene (kg).

[0052] In this invention, the stirring device of the melt blending module also includes a torque sensor for real-time monitoring of the torque value during the stirring process. The torque sensor has a measurement range of 0-500 N·m and an accuracy of ±1% FS. The central controller automatically adjusts the stirring speed and heating temperature according to the changes in the torque value. When the torque value exceeds the set upper limit (300 N·m), it automatically reduces the stirring speed (by 5-10 r / min) and increases the heating temperature (by 5-10 °C). When the torque value is lower than the set lower limit (100 N·m), it automatically increases the stirring speed (by 5-10 r / min) and decreases the heating temperature (by 5-10 °C) to ensure the melt blending effect of the material and keep the torque value stable within the range of 150-250 N·m.

[0053] In this invention, the molding and processing module also includes an online thickness detection unit for real-time thickness detection and feedback control of extruded or calendered products. The online thickness detection unit uses a laser thickness gauge with a measurement range of 0-10 mm, an accuracy of ±0.01 mm, and a measurement frequency of 100-500 Hz. The laser thickness gauge is installed at the exit of the molding die, with 5-10 measurement points evenly set along the width direction of the product. The central controller compares the measured thickness with the set thickness. When the deviation exceeds ±0.05 mm, it automatically adjusts the extruder screw speed or the calender roller clearance, with an adjustment range of 0.01-0.1 mm / time, until the product thickness meets the requirements.

[0054] In this invention, the quality inspection module further includes a density detection unit for detecting the density of the modified polypropylene composite material. The density is measured using the water displacement method, with a measurement accuracy of ±0.001 g / cm³. 3 The density detection unit includes an electronic balance (accuracy 0.001g), a constant temperature water bath (temperature controlled at 23±1℃), and a suspended basket. During measurement, the mass of the sample in air is first weighed, followed by the mass of the sample submerged in water. The density is calculated based on Archimedes' principle. When the detected density is close to the set value (1.0-1.5g / cm³), the density is measured. 3 The deviation exceeds ±0.05 g / cm 3 If the product is deemed unqualified, the information is fed back to the intelligent control module, which then adjusts the amount of reinforcing agent added to correct the density.

[0055] In this invention, the waste recycling module also includes an impurity separation unit for removing impurities such as metals and stones from the waste. The impurity separation unit includes a magnetic separator and a screening device. The magnetic separator uses a high-strength magnetic drum (magnetic field strength 5000-8000Gs) to remove ferromagnetic impurities with a removal efficiency of not less than 99%. The screening device uses a multi-layer vibrating screen (2-3 layers) with screen apertures of 8mm, 3mm and 1mm, which can separate impurities and particles of different sizes with a screening efficiency of not less than 95%. The purity of the waste after impurity separation can be increased to over 99%, ensuring the quality of the recycled material.

[0056] A method for preparing resource recovery from the aforementioned recyclable modified polypropylene composite material includes:

[0057] The raw material pretreatment steps involve classifying, cleaning, drying, and crushing the recycled waste polypropylene. Specifically, near-infrared spectroscopy is used to identify the material composition and molecular weight of the waste polypropylene. Impurities are removed by coarse washing, fine washing, and rinsing, with the fine washing temperature controlled at 50-60℃ and the pH value after rinsing at 6.5-7.5. The material is then dried at 80-100℃ for 2-4 hours to reduce the moisture content to below 0.5%. The material is first crushed to 50-100mm, then further crushed to 5-10mm particles, with the crushing temperature not exceeding 60℃.

[0058] The melt blending step involves melt blending the pretreated polypropylene granules with modifiers and additives. Specifically, the polypropylene granules are added to a blending vessel and heated to 180-220℃ to melt. Modifiers (1%-5%) and additives (antioxidant 0.1%-0.5%, lubricant 0.2%-1%) are added in proportion. The mixture is stirred for 15-30 minutes at a stirring speed of 50-200 r / min and a dispersing disc speed of 500-1500 r / min. The mixture is then degassed for 10-20 minutes under a vacuum of -0.08 to -0.09 MPa to remove bubbles and volatiles.

[0059] The modification and reinforcement step involves modifying the melt-blended material. Specifically, this includes adding glass fiber or carbon fiber at 10%-30% of the total mass of the composite material; ultrasonically treating the material at 1-3kW and 20-40kHz for 5-15 minutes to ensure that the uniformity of the reinforcing agent dispersion is not less than 90%; if 5%-15% elastomer is added, kneading and vulcanizing the mixture at 170-190℃ and 30-80r / min for 5-15 minutes to form a micro-crosslinked structure.

[0060] The molding and processing steps involve processing the modified and reinforced material into the desired product. Specifically: if extrusion molding is used, the screw diameter is 30-65mm, the length-to-diameter ratio is 20-30:1, the temperature is 180-220℃, and the rotation speed is 30-100r / min to produce sheets or pipes; if injection molding is used, the clamping force is 500-2000kN, the temperature is 180-230℃, the pressure is 50-150MPa, the holding pressure is 30-100MPa, and the time is 5-30s; if calendering is used, the roller temperature is 160-190℃, the rotation speed is 10-30r / min, and the speed is 1-5m / min to produce films or sheets.

[0061] The quality inspection steps involve testing the properties of the prepared composite material; specifically: testing tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength; testing melting point, crystallinity, and heat distortion temperature; conducting ultraviolet aging tests and testing performance retention rate; inspecting for surface defects in the product; all properties must meet preset standards, and unqualified products are sent to the waste recycling module.

[0062] The waste recycling step involves recycling and reusing the waste generated during the preparation process. Specifically, the waste is collected by a conveyor belt with a collection efficiency of not less than 98%; crushed into 3-8mm particles; melted at 180-210℃; granulated by an underwater pelletizer (diameter 2-5mm, length 2-5mm); and the granulated particles are then fed back into the melt blending step to achieve a closed-loop cycle.

[0063] The intelligent control process automates and optimizes parameters throughout the entire recycling process. Specifically, it coordinates and controls each step through a PLC controller; uses a sensor array to collect parameters such as temperature, pressure, and flow rate in real time; executes control actions through an actuator array; operators monitor the system operation and set parameters via a touchscreen; and automatically adjusts process parameters based on quality inspection results to maintain a product qualification rate of over 95%.

[0064] In this invention, before adding the reinforcing agent, surface treatment is required in the modification and reinforcement step. Specifically, this includes: preparing a silane coupling agent solution with a mass fraction of 0.5%-2% (ethanol to water volume ratio 1:1); immersing the reinforcing agent in the coupling agent solution for 5-10 minutes while simultaneously subjecting it to ultrasonic treatment at 500-1000W and 30kHz; and drying it at 80-100℃ for 1-2 hours to reduce the moisture content to below 0.3%. After surface treatment, the interfacial bonding effect between the reinforcing agent and the polypropylene matrix can be evaluated by the interfacial bonding strength. The higher the interfacial bonding strength, the better the mechanical properties of the composite material.

[0065] In this invention, a degradation degree detection step is included between the raw material pretreatment step and the melt blending step. Specifically, this involves: determining the molecular weight distribution index (PDI) of waste polypropylene using gel permeation chromatography; detecting the carbonyl index (CI) using Fourier transform infrared spectroscopy; determining that the polypropylene is severely degraded when the PDI is greater than 3.5 or the CI is greater than 0.2; and calculating the amount of molecular weight regulator to be added according to the following formula: Where C is the actual concentration (mass fraction, %) of the molecular weight regulator, c0 is the basic concentration (value 0.05%), and CI is the measured carbonyl index; the calculated molecular weight regulator is added to the melt blend system to improve the molecular weight distribution of polypropylene and enhance the performance stability of the composite material.

[0066] Specific implementation methods for the preparation system and method of recyclable modified polypropylene composite materials:

[0067] Example 1

[0068] Preparation of Modified Polypropylene Composite Material for Automobile Bumpers (Based on Waste Polypropylene Recycling) This embodiment focuses on the preparation of modified polypropylene composite material for automobile bumpers. A recycled modified polypropylene composite material preparation system is used to process recycled waste polypropylene bumper fragments (initial impurity content of about 15%, molecular weight distribution of 100,000-250,000). The key focus is on verifying the synergistic effect of raw material pretreatment, modification and reinforcement, and waste recycling, solving the problems of insufficient mechanical properties and low molding accuracy of traditional recycled materials.

[0069] I. System Deployment and Parameter Configuration

[0070] Raw material pretreatment module: A Bruker MPAII near-infrared spectrometer with a wavelength range of 900-1700nm was used to separate waste polypropylene into medium molecular weight grade (100,000-200,000, accounting for 70%) and high molecular weight grade (200,000-250,000, accounting for 30%). The coarse washing device used three high-pressure water guns (pressure 0.4MPa, flow rate 50L / min). The fine washing device was a 500L stainless steel tank (with built-in heating tube, power 10kW), with 2% by mass of alkaline cleaning agent (NaOH and Na2CO3 mixed in a 2:1 ratio) added, temperature controlled at 55℃, and soaking for 25 minutes. The rinsing device was a three-stage countercurrent rinsing tank, with each stage having a volume of 300L. The deionized water flow rate is 20L / min, and a pH sensor (accuracy ±0.1) is installed at the outlet to ensure that the pH after rinsing is 7.0±0.2. The drying unit is a hot air circulating dryer (model CT-C, volume 1000L), with a temperature of 90℃, an air velocity of 1.5m / s, and a drying time of 3h. The crushing unit first crushes the material to 80±10mm using a twin-shaft shredder (model DSJ-600, blade shaft speed 30r / min), and then crushes it to 8±2mm using a high-speed crusher (model PC-800, blade speed 1500r / min). Cooling water (water temperature 25℃, flow rate 10L / min) is circulated through the crushing chamber jacket to control the crushing temperature ≤55℃.

[0071] Melt blending module: The blending vessel is an 800L 304 stainless steel vessel (jacketed heating power 18kW), with electric heating elements controlling the temperature in three zones (zone 1 180℃, zone 2 200℃, zone 3 210℃), monitored in real time by a temperature sensor (model PT100, accuracy ±0.5℃); the stirring device uses an anchor-type stirring paddle (500mm diameter, 100r / min) combined with a dispersion disc (200mm diameter, 1000r / min), and a torque sensor (model HBMT40B, range 0-500). The N·m) is installed on the stirring shaft; the vacuum degassing device is a rotary vane vacuum pump (model 2XZ-4, ultimate vacuum -0.095MPa), and the degassing time is 15min; when blending, first add 500kg of pretreated polypropylene granules, heat and melt (melt index 12g / 10min, 190℃, 2.16kg), then add 20kg of maleic anhydride grafted polypropylene (modifier, content 4%), 1.5kg of antioxidant 1010 (0.3%), and 2.5kg of calcium stearate (0.5%), and stir for 20min.

[0072] Modified reinforcement module: The reinforcing agent is alkali-free glass fiber (model ER13-2400-988A) with a length of 6mm and a diameter of 15μm, with an addition amount of 120kg (20%); in the surface treatment unit of the reinforcing agent, a 1.5% KH550 solution (ethanol:water = 1:1) is prepared in a 200L coupling agent solution preparation tank, and the impregnation device is an ultrasonic mesh belt conveyor (ultrasonic power 800W, frequency 30kHz, conveying speed 0.5m / min), and the drying device... The material was placed in a belt dryer (temperature 90℃, drying time 1.5h); the ultrasonic dispersion unit used a 2kW ultrasonic generator (model JY-J2000, frequency 28kHz), the ultrasonic probe was inserted into the material in the mixing vessel, and the processing time was 10min; in the dynamic vulcanization unit, because the bumper material required high toughness, 50kg of EPDM rubber (10%) was added, and the kneader (model NHZ-1000, speed 50r / min) was used at a temperature of 180℃ for a vulcanization time of 10min.

[0073] Molding and Quality Inspection Module: Molding uses an injection molding unit (model HTF1200X, clamping force 1200kN), injection temperature 190-220℃ (nozzle 220℃, front section 210℃, middle section 200℃, rear section 190℃), injection pressure 80MPa, holding pressure 60MPa, holding time 15s, cooling time 20s; In the quality inspection module, a universal testing machine (model CMT6104) is used to test tensile strength (speed 50m). Impact strength was tested using an impact testing machine (model XJUD-5.5) with a speed of 2 mm / min for bending strength and a speed of 2 mm / min for bending strength; a DSC (model DSC214) was used with a heating rate of 10℃ / min and a nitrogen flow rate of 50 mL / min; a heat distortion temperature tester (model XRW-300) was used with a load of 1.82 MPa and a heating rate of 2℃ / min; and an ultraviolet aging test chamber (model UV2000) was used with a wavelength of 340 nm and an irradiance of 0.71 W / m². 2 Temperature 60℃, time 1000h; industrial camera (model Baslerac A2500-14gm, resolution 2592×1944) with Halcon software to inspect appearance; density detection unit electronic balance (model FA2004) with accuracy 0.001g, constant temperature water bath temperature 23℃.

[0074] Waste recycling and intelligent control module: The waste recycling module collects injection molding gates and defective products (approximately 50kg), removes iron through a magnetic separator (magnetic field strength 6000Gs, drum speed 20r / min), screens them through a three-layer vibrating screen (sieve apertures 8mm, 3mm, and 1mm, vibration frequency 50Hz), crushes them to 5mm in size using a high-speed pulverizer (model PC-600), melts them using a screw extruder (model SJ-65, length-to-diameter ratio 25:1) (temperature 200℃), and granulates them (diameter 3mm, length 3mm) using an underwater pelletizer (model SLJ-80). The intelligent control module uses a Siemens S7-1200 PLC, with a sensor group containing 10 temperature sensors, 5 pressure sensors, and 3 flow sensors. A touch screen (model Kunlun Tongtai TPC1262H) displays parameter curves, and the adaptive control function adjusts the glass fiber addition amount based on the impact strength test results (for strength below 15kJ / m). 2 (Increase the amount by 2%).

[0075] II. Performance Verification Form

[0076]

[0077] The data in the table is based on statistical analysis of three batches of automotive bumper manufacturing tests. Traditional methods, due to high levels of impurities in raw materials and poor dispersion of reinforcing agents, result in tensile strengths below 28 MPa and impact strengths below 10 kJ / m². 2 The previous method failed to meet the requirements for use in automotive bumpers. This invention, through precise pretreatment to remove impurities (purity up to 99.5%), surface treatment of the reinforcing agent, and ultrasonic dispersion (dispersion uniformity 92%), significantly improves mechanical properties, achieving an impact strength exceeding 18 kJ / m². 2 With a heat distortion temperature exceeding 110℃ and a strength retention rate of over 85% after aging, it fully complies with the GB / T2411-2008 automotive plastic parts standard. The product qualification rate has increased from 80% to over 95%, the resource utilization rate exceeds 95%, and all gate waste is recycled and reused, solving the pain points of traditional solutions such as "poor performance, low qualification rate, and large waste," and meeting the high requirements of the automotive industry.

[0078] Example 2

[0079] Preparation of modified polypropylene film for packaging (based on recycling waste polypropylene woven bags)

[0080] This embodiment focuses on the preparation of modified polypropylene film (thickness 0.5±0.05mm) for packaging. It processes recycled waste polypropylene woven bags (initial impurity content 20%, molecular weight 50,000-180,000) to verify the system's effectiveness in film forming, online detection, and degradation control, solving the problems of easy breakage and uneven thickness of traditional films.

[0081] I. System Deployment and Parameter Configuration Raw Material Pretreatment and Degradation Detection: Near-infrared spectroscopy separates the woven bag polypropylene into low molecular weight (50,000-100,000, accounting for 40%) and medium molecular weight (100,000-180,000, accounting for 60%) grades; the coarse washing device is a drum washing machine (model GX-1000, speed 20r / min), with a high-pressure water gun pressure of 0.3MPa; 1.5% alkaline cleaning agent is added to the fine washing tank, temperature 50℃, soaking for 20min; the pH of the rinsing tank outlet is controlled at 6.8±0.2; the dryer temperature is 85℃, time 2.5h, moisture content controlled ≤0.4%; crushed to 6mm particles; The degradation degree detection unit used a gel permeation chromatograph (Waters 1515) to measure PDI (PDI = 3.8 for low molecular weight grade and PDI = 3.2 for medium molecular weight grade), and a Fourier transform infrared spectrometer (Nicoleti S50) to measure CI (CI = 0.22 for low molecular weight grade and CI = 0.18 for medium molecular weight grade). For low molecular weight grade, a molecular weight regulator needs to be added. According to the formula m = k × (PDI - 3.0) × M (k = 0.003, M = 200 kg), we get m = 0.003 × (3.8 - 3.0) × 200 = 0.48 kg of dicumyl peroxide. Melt blending and modification reinforcement: The blending vessel volume was 600L, the temperature was 180-200℃, the stirring speed was 80r / min, and the dispersion disc speed was 800r / min. 400kg of polypropylene granules (200kg low molecular weight + 200kg medium molecular weight), 0.48kg of molecular weight regulator, 1.2kg of antioxidant 1010 (0.3%), 1.6kg of calcium stearate (0.4%), and 10kg of maleic anhydride-grafted polypropylene (2.5%) were added. The mixture was stirred for 25min and then vacuum degassed for 12min. The reinforcing agent was 3mm long and 12μm diameter glass fiber, added at 80kg (16%). Surface treatment was performed with 1% KH550 solution, followed by ultrasonic impregnation for 8min and drying for 1h. Ultrasonic dispersion power was 1.5kW for 8min, achieving a dispersion uniformity of 90%. Forming and Online Inspection: Forming is carried out using a calendering unit (model YJ-4S, four-roll calender), with roll temperatures of 170-185℃ (roll 1: 170℃, roll 2: 180℃, roll 3: 185℃, roll 4: 180℃), roll speed of 20r / min, and calendering speed of 3m / min; the online thickness inspection unit uses a laser thickness gauge (model KEYENCEIL-600, accuracy ±0.005mm), with 8 measuring points (100mm spacing) along the film width direction. The central controller compares the measured thickness with the set value (0.5mm), and adjusts the roll gap when the deviation exceeds 0.03mm (adjustment increment 0.01mm / time); in quality inspection, the tensile strength of the film is tested according to GB / T1040.3-2006 (speed 100mm / min), and the light transmittance is tested according to GB / T2410-2008 (wavelength 550nm).Waste recycling and intelligent control: The waste material is calender scrap (about 30kg), which is magnetically separated (magnetic field strength 5500Gs), screened (sieve holes 5mm and 2mm), crushed to 4mm, melted in an extruder (temperature 190℃), and granulated (diameter 2mm); the intelligent control module adjusts the roller speed according to the data of the laser thickness gauge (increases by 0.5r / min when the thickness is too thick), and adjusts the amount of glass fiber added according to the light transmittance test results (reduces the amount of glass fiber added by 1% when the light transmittance is less than 85%).

[0082] II. Performance Verification Form

[0083]

[0084]

[0085] The data in the table is based on statistical analysis of three batches of film preparation tests. Traditional calendering methods result in film thickness deviations exceeding 0.1mm, leading to wrinkles, damage, longitudinal tensile strength below 23MPa, and low light transmittance. This invention, through online laser thickness measurement and real-time adjustment of roller gap, controls thickness deviations within 0.03mm, ensuring a smooth, defect-free surface. Uniform dispersion of reinforcing agents and the addition of molecular weight regulators result in tensile strength exceeding 32MPa, elongation at break exceeding 450%, and heat shrinkage below 5%, meeting the GB4806.7-2016 standard for food packaging films. The waste recycling cycle is shortened from 30 minutes to within 15 minutes. The performance of recycled materials is close to that of virgin materials, allowing direct use in film production. Resource utilization exceeds 96%, solving the problems of uneven thickness, poor performance, and slow recycling in traditional packaging films, thus meeting the large-scale needs of the packaging industry.

[0086] Figure 2 This invention focuses on the core pain points of raw material pretreatment—incomplete impurity removal and low efficiency. Traditional processes rely on manual sorting, achieving an impurity removal rate of less than 53%, and require 8.5 hours to process one ton of raw material, making it unsuitable for waste polypropylene from mixed sources (such as a mixture of car bumpers and woven bags). This invention utilizes near-infrared spectroscopy for precise classification (98% accuracy) and three-stage cleaning (coarse washing to remove mud and sand, fine washing to remove oil and dirt, and rinsing to adjust pH), combined with hot air drying to control moisture content. This increases the impurity removal rate to over 97% and reduces processing time to within 3 hours. For example, for a mixture with an initial impurity content of 18%, traditional processes still leave 8.5% impurities, while this invention leaves only 0.5%, significantly reducing material unevenness during subsequent melt blending. This lays the foundation for preparing high-quality composite materials and solves the problems of "difficult sorting, poor cleaning, and long processing time" inherent in traditional processes.

[0087] Figure 3This study verifies the crucial role of surface treatment of the reinforcing agent in the modified reinforcement module—solving the problem of poor compatibility between the reinforcing agent and the polypropylene matrix. Traditionally, untreated glass fiber, due to its smooth surface and weak bonding with the matrix, results in an interfacial bonding strength of only 8 MPa, leading to a composite material tensile strength of less than 26 MPa and an impact strength of 9 kJ / m². 2 This method cannot meet the high-strength requirements of automotive parts, etc.; the present invention uses a 1.5% silane coupling agent solution for impregnation (ethanol:water = 1:1), combined with 800W ultrasonic assistance (30kHz), to ensure that the coupling agent uniformly coats the surface of the reinforcing agent, increasing the interfacial bonding strength to 28MPa, and comprehensively improving the mechanical properties (tensile strength 37MPa, impact strength 21kJ / m). 2 Even with the addition amount reduced to 10%, the reinforcing agent treated in this invention can still achieve an impact strength of 16 kJ / m. 2 It improves performance by 128% compared to the untreated group, ensuring performance while reducing the amount of reinforcing agent used, thus lowering costs. It is suitable for products with different strength requirements (from films to automotive parts), solving the pain points of traditional reinforcement methods such as "weak performance and large amount of agent used".

[0088] Figure 4 Focusing on the core advantages of the waste recycling module—reduced performance degradation and extended cycle life. Traditional recycling processes, lacking degradation control and impurity separation, result in a melt index that rises from 12 to 18 after one recycling cycle (an abnormal increase in fluidity, indicating a decrease in molecular weight), and an impact strength retention rate of only 75%. After three recycling cycles, performance drops below the 70% critical value, rendering the material unusable. This invention, through degradation degree detection (GPC PDI measurement, FTIR CI measurement) and the addition of molecular weight regulators, combined with magnetic separation and sieving to remove impurities, stabilizes the melt index at 13 after one recycling cycle, maintaining a performance retention rate of over 92%. After three recycling cycles, it still maintains over 80%, increasing the number of recyclables from 3 to 5. For example, after three recycling cycles, the tensile strength of traditional processes is only 65%, while this invention reaches 88%, still usable for medium-requirement products (such as packaging pallets), significantly improving resource utilization, reducing waste from "discarding after 1-2 recycling cycles," aligning with the circular economy concept, and solving the pain points of traditional recycling: "rapid performance degradation and few recycling cycles."

[0089] Figure 5The core value of the intelligent control module is to improve parameter stability and production efficiency. Traditional fully manual control relies on operator experience, resulting in melt temperature fluctuations of ±5℃ and reinforcer dosage deviations of ±2.5%, leading to product thickness deviations exceeding 0.1mm and a product qualification rate of only 78%. Batch changeover debugging requires one hour, making it unsuitable for mass production. This invention uses a PLC (Siemens S7-1200) to collect data from 10+ sensors (temperature, pressure, flow rate) in real time, adaptively adjusting heating temperature, stirring speed, and dosage. Parameter fluctuations are controlled within ±1.5℃ / ±0.8% / ±0.03mm, increasing the product qualification rate to over 95%, and batch changeover debugging takes only 15 minutes. For example, during batch changeover, the qualification rate under manual control drops sharply to 65%, while this invention maintains 95%, solving the pain points of traditional control's "large fluctuations, low qualification rate, and slow batch changeover." It is particularly suitable for scenarios with high parameter stability requirements, such as automotive parts and high-precision films, enabling large-scale, high-quality production.

[0090] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A system for preparing recyclable modified polypropylene composite materials, characterized in that, include: The raw material pretreatment module is used to classify, clean, dry and crush waste polypropylene; The classification unit uses a near-infrared spectrometer to classify molecules; the cleaning unit includes coarse washing, fine washing, and rinsing devices to remove mud, sand, and oil, and to adjust the pH; the crushing unit obtains particles through biaxial shredding and high-speed crushing, and the temperature is controlled. The melt blending module is used to blend polypropylene granules with modifiers and additives; the blending kettle is equipped with a jacketed heating and stirring device to control the temperature and vacuum; the polypropylene is melted first, and then the modifiers and additives are added and mixed. The modified reinforcement module is used to enhance the mechanical properties of materials, including the addition of reinforcing agents, ultrasonic dispersion, and dynamic vulcanization units; the reinforcing agents are glass fibers or carbon fibers, which are uniformly dispersed through ultrasonic treatment; the dynamic vulcanization units cause micro-crosslinking of the elastomer under shear. The molding and processing module is used to process materials into products, including extrusion, injection molding and calendering units, which control the corresponding process parameters to produce different products; The quality inspection module is used to test the performance of composite materials, including mechanical properties, thermal properties, aging resistance properties, and appearance inspection units. It tests various indicators according to national standards and detects appearance defects through image recognition. The waste recycling module is used to recycle scraps and defective products, including collection, crushing, melting and granulation units. After granulation, the granules are sent back to the melting and blending module to achieve recycling. The intelligent control module is used for automatic system control and optimization, including a central controller, sensor group, actuator group and human-machine interface; it adaptively adjusts process parameters based on quality inspection results.

2. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, Also includes: The reinforcing agent surface treatment unit is located before the reinforcing agent addition unit of the modification and reinforcement module, and is used to perform surface modification treatment on the reinforcing agent; The reinforcing agent surface treatment unit includes a coupling agent solution preparation tank, an impregnation device, and a drying device; The coupling agent solution preparation tank is used to prepare the coupling agent solution. The coupling agent is a silane coupling agent, and the solvent is a mixture of ethanol and water. The impregnation device impregnates the reinforcing agent in the coupling agent solution for 5-10 minutes, and ultrasonic assistance is used during the impregnation process. The drying device uses hot air drying. The interfacial bonding strength between the surface-treated reinforcing agent and the polypropylene matrix is ​​evaluated using the following formula: Where σ is the interfacial bonding strength, F is the force required for the reinforcing agent to be pulled out of the matrix, and A is the contact area between the reinforcing agent and the matrix.

3. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, Also includes: It also includes a degradation degree detection unit, which is set between the raw material pretreatment module and the melt blending module, and is used to detect the degradation degree of waste polypropylene; The degradation degree detection unit uses gel permeation chromatography to determine the molecular weight distribution index of waste polypropylene and Fourier transform infrared spectroscopy to detect the carbonyl index. When the molecular weight distribution index is greater than 3.5 or the carbonyl index is greater than 0.2, the polypropylene is considered to be severely degraded, and a molecular weight regulator needs to be added during the melt blending process. The optimal amount of molecular weight regulator can be calculated by the following formula: m = k × (PDI - 3.0) × m, where m is the amount of molecular weight regulator added, k is the correction coefficient, PDI is the measured molecular weight distribution index, and M is the mass of waste polypropylene.

4. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, The stirring device of the melt blending module also includes a torque sensor to monitor the torque value during the stirring process in real time. The central controller automatically adjusts the stirring speed and heating temperature according to the change of torque value. When the torque value exceeds the set upper limit, the stirring speed is automatically reduced and the heating temperature is increased. When the torque value is lower than the set lower limit, the stirring speed is automatically increased and the heating temperature is decreased.

5. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, The molding and processing module also includes an online thickness detection unit, which is used to perform real-time thickness detection and feedback control on extruded or calendered products. The online thickness detection unit uses a laser thickness gauge. The laser thickness gauge is installed at the exit of the molding die, with 5-10 measuring points evenly set along the width of the product. The central controller compares the measured thickness with the set thickness. When the deviation exceeds ±0.05mm, it automatically adjusts the extruder screw speed or the calender roller gap until the product thickness meets the requirements.

6. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, The quality inspection module also includes a density detection unit for detecting the density of the modified polypropylene composite material. The density is measured using the water displacement method, with a measurement accuracy of ±0.001 g / cm³. 3 The density detection unit includes an electronic balance, a constant temperature water bath, and a suspended basket. During measurement, the mass of the sample in air is first measured, followed by the mass of the sample submerged in water. The density is then calculated based on Archimedes' principle. If the detected density deviates from the set value by more than ±0.05 g / cm³, the measurement is complete. 3 If the product is deemed defective, the information is sent to the intelligent control module.

7. The recycling-modified polypropylene composite material preparation system according to claim 1, characterized in that, The waste recycling module also includes an impurity separation unit, which is used to remove metal and stone impurities from the waste. The impurity separation unit includes a magnetic separator and a screening device. The magnetic separator uses a strong magnetic drum to remove ferromagnetic impurities, and the screening device uses a multi-layer vibrating screen to separate impurities and particles of different sizes.

8. A method for preparing resource recovery using the recyclable modified polypropylene composite material according to any one of claims 1-7, characterized in that, include: The raw material pretreatment step involves sorting, cleaning, drying, and crushing the recycled waste polypropylene. Specifically, the waste polypropylene is identified and classified by molecular weight using a near-infrared spectrometer; impurities are removed by coarse washing, fine washing, and rinsing in sequence, with the fine washing temperature controlled at 50-60℃ and the pH value after rinsing at 6.5-7.5; it is then dried at 80-100℃ for 2-4 hours to reduce the moisture content to below 0.5%; it is first crushed to 50-100mm, then further crushed to 5-10mm particles, with the crushing temperature not exceeding 60℃. The melt blending step involves melt blending the pretreated polypropylene granules with modifiers and additives. Specifically, the polypropylene granules are added to a blending vessel and heated to 180-220℃ to melt. Modifiers and additives are added in proportion. The mixture is then stirred for 15-30 minutes at a stirring speed of 50-200 r / min and a dispersing disc speed of 500-1500 r / min. Degas under a vacuum of -0.08 to -0.09 MPa for 10-20 minutes to remove bubbles and volatiles; The modification and reinforcement step involves modifying the melt-blended material. Specifically, this includes adding glass fiber or carbon fiber at 10%-30% of the total mass of the composite material; ultrasonically treating the material at 1-3kW and 20-40kHz for 5-15 minutes to ensure that the uniformity of the reinforcing agent dispersion is not less than 90%; if 5%-15% elastomer is added, kneading and vulcanizing the mixture at 170-190℃ and 30-80r / min for 5-15 minutes to form a micro-crosslinked structure. The molding and processing steps involve processing the modified and reinforced material into the desired product. Specifically: If extrusion molding is used, the screw diameter is 30-65mm, the length-to-diameter ratio is 20-30:1, the temperature is 180-220℃, and the rotation speed is 30-100r / min to produce sheets or tubes; if injection molding is used, the clamping force is 500-2000kN, the temperature is 180-230℃, the pressure is 50-150MPa, the holding pressure is 30-100MPa, and the time is 5-30s; if calendering is used, the roller temperature is 160-190℃, the rotation speed is 10-30r / min, and the speed is 1-5m / min to produce films or sheets. The quality inspection steps involve testing the properties of the prepared composite material; specifically: testing tensile strength, elongation at break, flexural strength, flexural modulus, and impact strength; testing melting point, crystallinity, and heat distortion temperature; conducting ultraviolet aging tests and testing performance retention rate; inspecting for surface defects in the product; all properties must meet preset standards, and unqualified products are sent to the waste recycling module; The waste recycling step involves recycling and reusing the waste generated during the preparation process. Specifically, the waste is collected via a conveyor belt, crushed into 3-8mm particles, melted at 180-210℃, granulated using an underwater pelletizer, and then fed back into the melt blending step. The intelligent control process automates and optimizes parameters throughout the entire recycling process. Specifically, it coordinates and controls each step through a PLC controller; uses a sensor array to collect temperature, pressure, and flow parameters in real time; executes control actions through an actuator array; operators monitor the system operation and set parameters via a touchscreen; and automatically adjusts process parameters based on quality inspection results.

9. The method for recycling modified polypropylene composite materials according to claim 8, characterized in that, In the modification and reinforcement step, surface treatment is required before adding the reinforcing agent. Specifically, this includes: preparing a silane coupling agent solution with a mass fraction of 0.5%-2%; immersing the reinforcing agent in the coupling agent solution for 5-10 minutes while simultaneously subjecting it to ultrasonic treatment at 500-1000W and 30kHz; drying it at 80-100℃ for 1-2 hours to reduce the moisture content to below 0.3%; and evaluating the interfacial bonding effect between the reinforcing agent and the polypropylene matrix after surface treatment by assessing the interfacial bonding strength.

10. The method for recycling modified polypropylene composite materials according to claim 8, characterized in that, Between the raw material pretreatment step and the melt blending step, there is also a degradation degree detection step, specifically: the molecular weight distribution index of waste polypropylene is determined by gel permeation chromatography. The carbonyl index was detected using Fourier transform infrared spectroscopy; when the PDI was greater than 3.5 or the CI was greater than 0.2, polypropylene was considered to be severely degraded; the amount of molecular weight regulator to be added was calculated according to the following formula: Where C is the actual concentration of the molecular weight regulator, c0 is the basic concentration, and CI is the measured carbonyl index; the calculated molecular weight regulator is added to the melt blend system.

Images