A method for improving the mixing uniformity of a wet separator twin-screw extruder

Abstract

The application provides a method for improving the mixing uniformity of a wet separator double screw extruder, comprising: obtaining material in a double screw extruder, the material comprising polyolefin resin and additives, mixing the material through a variable pitch and depth screw and a static mixer; controlling the temperature of the extruder barrel in sections, the temperature being dynamically adjusted by an intelligent temperature control system; adjusting the screw speed and the feeding rate according to the material properties, the speed and the feeding rate being optimized through a mathematical model and a frequency conversion speed regulation technology; pretreating the material, the pretreatment comprising a mixing and drying process to improve the uniformity of the material.

Description

Technical Field

[0001] This invention relates to the field of extrusion technology, and in particular to a method for improving uneven mixing in a wet-process diaphragm twin-screw extruder. Background Technology

[0002] A core technical challenge in the extrusion process of polyolefin resins and additives is achieving efficient and uniform mixing in continuous production. This problem involves several interrelated technical contradictions. First, improving mixing uniformity usually requires extending the mixing time or increasing shear strength, but this may lead to material degradation and increased energy consumption. Second, increasing output often shortens the mixing time, affecting the mixing effect. Furthermore, different additives have varying melting points, viscosities, and other properties, making it difficult to achieve optimal dispersion under the same process conditions. In addition, uneven temperature distribution and residence time of materials within the extruder can cause localized overheating or insufficient mixing. These contradictions combined result in a dilemma where mixing uniformity, production efficiency, and product quality are difficult to balance. Around this core problem, several related sub-problems have arisen, such as how to precisely control screw structure parameters to optimize mixing, how to establish accurate melt flow models to guide process parameter optimization, and how to improve additive dispersibility through pretreatment. These problems collectively constitute a complex technical challenge, urgently requiring innovative solutions to overcome the limitations of existing processes and achieve large-scale production of high-quality polyolefin composite materials. Summary of the Invention

[0003] This invention provides a method for improving uneven mixing in a wet-process diaphragm twin-screw extruder, mainly comprising: The material, comprising polyolefin resin and additives, is obtained from a twin-screw extruder and mixed using a variable-pitch, variable-depth screw and a static mixer. The temperature of the extruder barrel is controlled in stages and dynamically adjusted by an intelligent temperature control system. The screw speed and feed rate are adjusted according to the material characteristics, and these speed and feed rate are optimized collaboratively using a mathematical model and variable frequency speed control technology. The material is pretreated, including mixing and drying processes to improve its uniformity.

[0004] Furthermore, the mixing of the material using a variable-pitch, variable-depth screw and a static mixer includes: the variable-pitch, variable-depth screw is configured with a larger pitch and deeper groove in the feeding section, and the pitch and groove depth are gradually reduced in the compression and metering sections; the screw is configured with forward and reverse kneading blocks, which are alternately arranged to form staggered shearing zones; the static mixer is located before the discharge port of the die head and includes multiple sets of twisted blades, which divide, merge, and recombine the material; the arrangement of the kneading blocks and blades is determined according to the characteristics of the material.

[0005] Furthermore, the segmented control of the extruder barrel temperature includes: dividing the barrel into multiple temperature control zones, each corresponding to the feeding section, plasticizing section, and metering section; the intelligent temperature control system acquiring material temperature and screw torque data through sensors; the intelligent temperature control system dynamically adjusting the heating power and cooling water volume based on the data; and maintaining temperature fluctuations in the temperature control zones within a preset range through a control algorithm.

[0006] Furthermore, the step of adjusting the screw speed and feeding rate according to material characteristics includes: obtaining the melt flow rate of the material, which is used to establish a mathematical model; the mathematical model calculating the optimal speed and feeding rate based on the melt flow rate and the material characteristics; the variable frequency speed control technology adjusting the speed of the screw motor and the feeding motor through a frequency converter; and the speed and feeding rate being optimized in real time based on extrusion pressure and production data.

[0007] Furthermore, the pretreatment includes mixing and drying processes, including: the mixing process treating the material by high-speed stirring and vacuum mixing, wherein the high-speed stirring achieves preliminary mixing; the vacuum mixing removes air and moisture from the material under negative pressure; the drying process uses hot air drying and vacuum drying to remove surface and internal moisture from the material; and the pretreatment adds a dispersing agent to improve the dispersibility of the additive.

[0008] Furthermore, the mixing of the material using a variable-pitch, variable-depth screw and a static mixer includes: the screw pitch and groove depth of the variable-pitch, variable-depth screw being determined based on the viscosity and flowability of the material; the spacing between the forward and reverse kneading blocks being optimized based on the agglomeration characteristics of the material; the number of blades and the twist angle of the static mixer being adjusted based on the dispersion requirements of the material; and the mixing effect of the screw and the static mixer being verified by detecting the uniformity of the material.

[0009] Furthermore, the adjustment of screw speed and feeding rate according to material characteristics includes: the mathematical model establishing the relationship between speed, feeding rate and melt flow rate through experimental data; the variable frequency speed control technology adjusting the speed according to real-time extrusion pressure; the feeding rate being adjusted synchronously with the screw speed by the feeding motor; and the adjustment process verifying the mixing stability of the material through a production monitoring device.

[0010] Furthermore, the pretreatment includes mixing and drying processes, including: high-speed stirring at a preset rotation speed, the rotation speed being determined based on the particle characteristics of the material; the negative pressure value and stirring time of the vacuum mixing being optimized based on the moisture content of the material; the amount of dispersing agent added being determined based on the surface tension of the additive and the polyolefin resin; and the drying process using an online moisture monitor to detect the moisture content of the material and adjust the drying parameters.

[0011] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a highly efficient mixing and extrusion method for polyolefin resins and additives, achieving precise mixing of materials through a variable-pitch, variable-depth screw and a static mixer. The variable-pitch, variable-depth screw is configured with different pitches and groove depths in different sections, and forward and reverse kneading blocks are incorporated to form staggered shearing zones. The twisted blades of the static mixer further segment and reorganize the materials. This invention employs an intelligent temperature control system to control the barrel temperature in stages, dynamically adjusting heating power and cooling water volume based on sensor data. Simultaneously, a mathematical model is established based on the material melt flow rate, and variable frequency speed control technology is used to synergistically optimize the screw speed and feed rate. The pretreatment stage combines high-speed stirring, vacuum mixing, and drying processes, and dispersing agents are added to improve uniformity. Through the synergistic effect of multiple innovative processes, this invention significantly improves the mixing uniformity and processing stability of polyolefin composite materials, providing technical support for the large-scale production of high-performance composite materials. Attached Figure Description

[0012] Figure 1 This is a flowchart of a method for improving uneven mixing in a wet-process diaphragm twin-screw extruder according to the present invention. Detailed Implementation

[0013] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0014] like Figure 1 This embodiment of a method for improving uneven mixing in a wet-process diaphragm twin-screw extruder may specifically include: S1, Obtain material from the twin-screw extruder, the material including polyolefin resin and additives, and mix the material by means of a variable pitch screw and a static mixer.

[0015] S1, Obtain material from the twin-screw extruder, the material including polyolefin resin and additives, and mix the material by means of a variable pitch screw and a static mixer.

[0016] S11, Obtain material from the twin-screw extruder, the material comprising polyolefin resin and additives.

[0017] Polyolefin resin and additives are fed into the feed inlet of the twin-screw extruder in a preset ratio to ensure that the initial state of the material is stable and to avoid moisture or impurities interfering with subsequent mixing.

[0018] S12, the material is initially mixed by a variable pitch and variable depth screw.

[0019] The design of the variable pitch and variable depth screw includes a larger pitch and deeper screw groove in the feeding section, and a gradual decrease in pitch and screw groove depth towards the metering section. This structural change causes the material to be subjected to increasing shear and extrusion forces during the conveying process, which promotes the initial fusion of polyolefin resin and additives and reduces agglomeration.

[0020] S13 further mixes the pre-mixed materials using a static mixer.

[0021] A static mixer is installed before the extruder outlet. When the material flows through the twisted blades or perforated plate inside, it is divided and recombined multiple times to achieve fine dispersion and ensure high uniformity of the material.

[0022] In one embodiment, the material is mixed by a variable pitch and depth screw and a static mixer in step S1, which can effectively improve the problem of uneven mixing in wet diaphragm production.

[0023] Specifically, in the scenario of wet-process separator manufacturing for lithium-ion batteries, polyolefin resins have a wide molecular weight distribution and additives are prone to agglomeration. Using a variable pitch and variable depth screw can enable rapid material transport in the feeding section, enhance shearing in the compression section, avoid local stagnation, and further eliminate residual unevenness, thereby reducing egg-shaped bright spot defects and improving the mechanical strength and ion conduction efficiency of the separator.

[0024] For example, in actual production, the screw pitch in the feed section is set to 50mm and the screw groove depth to 20mm, while the pitch in the metering section is reduced to 20mm and the depth to 8mm. The static mixer is equipped with 10 sets of blades with a twist angle of 120 degrees and a blade spacing of 30mm. After the material passes through, the mixing uniformity is improved, and the number of bright spot defects is reduced from 50 per square meter to less than 5, which is beneficial to improving battery safety and cycle life.

[0025] In one embodiment, the parameters of the variable pitch and variable depth screw are adjusted for different batches of materials. For example, the screw pitch in the feed section is changed from 45mm to 55mm. Combined with the number of static mixer blade groups from 8 to 12, this ensures that the viscosity of polyolefin resin is adapted to the differences, achieves stable mixing, reduces production fluctuations, and improves the overall consistency of diaphragm quality.

[0026] For example, for high-viscosity resins, increasing the shear strength of the screw compression section and increasing the number of merging cycles in the static mixer resulted in a 20% improvement in material dispersion, effectively preventing bright spot formation and enhancing the reliability of the separator in new energy vehicle batteries.

[0027] In one embodiment, the mixing method can be extended to similar extrusion processes, emphasizing the optimization of the static mixer position, such as installing it 300 mm before the discharge port, in conjunction with a variable pitch and variable depth screw, to control the material residence time within 12-15 minutes, promoting full plasticization.

[0028] For example, using this configuration improves the uniformity of the separator surface, increases puncture strength by 15%, helps reduce battery internal resistance, improves charging and discharging efficiency, and promotes the sustainable development of the lithium-ion battery industry.

[0029] S2, segmented control of the extruder barrel temperature, which is dynamically adjusted by an intelligent temperature control system; S3, adjustment of screw speed and feeding rate according to material characteristics, which are optimized through mathematical models and variable frequency speed control technology.

[0030] S2, segmented control of the extruder barrel temperature, which is dynamically adjusted by an intelligent temperature control system.

[0031] In one embodiment, step S2 specifically includes the following sub-steps to form a logical process from temperature zoning to real-time adjustment, wherein the temperature data of each zone serves as the basis for subsequent dynamic adjustments to ensure uniform material melting.

[0032] S21 divides the extruder barrel into multiple temperature control zones, each with an independently set initial temperature. For example, the feeding section is set to 120-130℃, the plasticizing section gradually increases to 160-180℃, and the metering section is stabilized at 175-180℃. These initial temperatures are predetermined based on the melting characteristics of the material to provide an environment for gradual heating.

[0033] S22 uses thermocouple sensors to monitor the actual temperature of each control zone in real time, and transmits the monitored temperature values ​​as input data to the control system.

[0034] S23. Based on the deviation between the real-time temperature data and the preset temperature range, the adjustment amount is calculated using a proportional-integral-derivative (PID) control algorithm. The PID algorithm is a method for calculating the control output based on the proportional, integral, and derivative terms of the error. Specifically, the process involves first calculating the error e between the current temperature and the target temperature; then calculating the proportional term P = kp × e, where kp is the proportional coefficient; the integral term I = ki × ∫e dt, where ki is the integral coefficient; and the derivative term D = kd × de / dt, where kd is the derivative coefficient. The final output control quantity u = P + I + D is used to adjust the heating power or cooling water flow.

[0035] S24, based on the calculated adjustment amount, dynamically changes the heating rod power or cooling water flow rate of each area to keep the temperature fluctuation within ±1℃, thereby ensuring that the melting state of the material is consistent in different sections and avoiding uneven mixing caused by local overheating or overcooling.

[0036] For example, in wet-process separator production, when the temperature in the plasticizing section is detected to rise above the preset value due to batch changes in materials, the system immediately increases the cooling water volume and quickly restores stability. This dynamic adjustment improves the uniformity of material mixing, reduces the generation of egg-shaped bright spots, and is beneficial to improving the mechanical properties of the separator and the safety of the battery.

[0037] In one embodiment, for high-viscosity polyolefin materials, the initial temperature is set higher, such as the plasticizing stage starting at 170°C. The dynamic adjustment process will rely more frequently on the integral term to eliminate accumulated errors and ensure long-term stability.

[0038] S3, adjust the screw speed and feeding rate according to the material characteristics. The speed and feeding rate are optimized in conjunction with mathematical models and variable frequency speed control technology.

[0039] In one embodiment, step S3 specifically includes the following sub-steps: establishing a chain from material characteristic analysis to real-time optimization, wherein the material characteristic data is used for model calculation, and the model output guides frequency conversion adjustment to achieve matching between rotational speed and feeding.

[0040] S31, collect the melt flow rate of the material as a key characteristic indicator, such as the melt flow rate value obtained by measuring the melt flow rate value through a melt index tester, which represents the material's ability to flow under specific temperature and pressure.

[0041] S32 uses a pre-established linear mathematical model to calculate the optimal combination of feed rate and screw speed. The linear mathematical model is based on experimental data fitting and is specifically in the form of feed rate v = 0.05 × melt flow rate × screw speed n + 5. The coefficients 0.05 and constant 5 are obtained through regression analysis of extrusion experiments on various materials to ensure that the model reflects the influence of speed on flow.

[0042] S33, based on the model calculation results, sends a command signal to the frequency converter. The frequency converter is a device that adjusts the speed by changing the input frequency of the motor. The specific process is that after receiving the target speed value, the frequency converter adjusts the relationship between the output frequency f and the speed n, n=60f / p, where p is the number of pole pairs of the motor, so that the screw speed and the feeding rate change synchronously.

[0043] S34 monitors extrusion pressure and output as feedback. If the pressure deviation exceeds the threshold, the model input is iteratively adjusted, and the combination of rotation speed and feed rate is recalculated and optimized until the material residence time stabilizes at 12-15 minutes to promote thorough mixing.

[0044] For example, for resin materials with a wide molecular weight distribution, when the melt flow rate is low, the model will output a lower feed rate to match the medium speed rotation. This optimization reduces the stagnation zone, improves the dispersion of additives, helps to eliminate uneven defects on the separator surface, and improves the electrochemical performance of the battery.

[0045] In one embodiment, when the content of material additives increases, the model coefficient is adjusted to adapt to higher shear requirements, and the variable frequency speed regulation ensures real-time response, avoiding the mismatch problem under traditional fixed speed.

[0046] S4, Pre-treat the material, the pre-treatment including mixing and drying processes to improve the uniformity of the material.

[0047] S4, Pre-treat the material, the pre-treatment including mixing and drying processes to improve the uniformity of the material.

[0048] S41 involves initially mixing the polyolefin resin and additives, and achieving initial uniform distribution of the raw materials through high-speed stirring.

[0049] During high-speed mixing, the polyolefin resin and additives are placed in a mixer and the speed is controlled at 1200 to 1800 revolutions per minute for 8 to 12 minutes to ensure that the additive particles are initially dispersed in the resin matrix and to avoid agglomeration.

[0050] S42 further mixes the materials in a vacuum environment to remove air and moisture, while promoting the uniform dispersion of additives.

[0051] Vacuum mixing is performed under conditions of vacuum degree of -0.07 to -0.09 MPa, with the rotation speed set at 600 to 1000 rpm and the stirring time at 12 to 18 minutes. Vacuum is used to remove air bubbles and residual moisture from the material, further refining the dispersion state.

[0052] S43, add dispersing aids to reduce surface tension and improve the uniformity of additive distribution in resin.

[0053] Adding 0.3 to 0.7% of a dispersant during the mixing process coats the surface of the additive particles, reduces interfacial tension, and makes the additives easier to integrate into the resin, forming a stable and homogeneous mixture.

[0054] S44 involves multi-stage drying of the mixed materials, starting with hot air drying to remove surface moisture.

[0055] Hot air drying is carried out at a temperature of 90 to 110 degrees Celsius for 1.5 to 2.5 hours, with the air speed controlled at 2 to 4 meters per second to ensure that surface moisture evaporates quickly without affecting the material structure.

[0056] S45, then vacuum drying is used to remove internal moisture, ensuring that the moisture content of the material is below the preset threshold.

[0057] Vacuum drying is carried out at a temperature of 50 to 70 degrees Celsius and a vacuum degree of -0.08 to -0.1 MPa for 2 to 4 hours to deeply extract internal moisture and control the content to 0.03 to 0.07%.

[0058] S46 monitors the moisture content of materials in real time and adjusts drying parameters when the moisture content exceeds the standard.

[0059] Install an online moisture monitor that samples once per minute. If the content exceeds 0.05%, automatically increase the drying time or temperature to maintain the material's dryness.

[0060] In one embodiment, the mixing process in step S4, through the combination of high-speed stirring and vacuum mixing, can significantly improve the initial uniformity of the materials.

[0061] For example, stirring polyolefin resin and additives at 1500 rpm for 10 minutes, followed by vacuum mixing for 15 minutes, can improve the dispersion of additives by 20%, reduce the risk of agglomeration in subsequent extrusion, thereby reducing the occurrence of egg-shaped bright spots and improving the overall quality of wet-process separators.

[0062] For example, in the drying process, a multi-stage drying method first removes surface moisture with hot air, and then extracts internal moisture through vacuum. For example, after 2 hours of hot air drying, vacuum drying for 3 hours can reduce the moisture content from the initial 0.2% to 0.04%, preventing unevenness caused by vaporization during extrusion, improving the plasticizing effect of the material, and ensuring stable membrane performance.

[0063] In one embodiment, the amount of dispersant added can be adjusted according to the batch of material. For example, for resins with a wide molecular weight distribution, it can be increased to 0.6%, which helps to enhance dispersibility. Experiments have shown that this adjustment can improve the mixing uniformity by 15%, thereby achieving better mixing in a twin-screw extruder and eliminating bright spot defects.

[0064] For example, the real-time monitoring and adjustment mechanism ensures the continuity of pretreatment. For instance, when the moisture content is detected at 0.06%, the vacuum drying is automatically extended by 1 hour, which ultimately improves the uniformity of the material, making it suitable for large-scale production, reducing the scrap rate, and promoting the implementation effect of a method to improve the uneven mixing of wet-process diaphragm twin-screw extruders.

[0065] Step S104, the mixing of the material by the variable pitch and variable depth screw and the static mixer includes: S11, the variable pitch and variable depth screw is configured with a larger pitch and a deeper groove in the feeding section, and the pitch and groove depth are gradually reduced in the compression section and the metering section; S12, the screw is configured with forward and reverse kneading blocks, and the kneading blocks are arranged alternately to form staggered shearing zones; S13, the static mixer is set in front of the discharge port of the die head and includes multiple sets of twisted blades, which divide, merge and recombine the material; S14, the arrangement of the kneading blocks and blades is determined according to the characteristics of the material.

[0066] S11, the variable pitch and variable depth screw is configured with a larger pitch and a deeper groove in the feeding section, and the pitch and groove depth are gradually reduced in the compression section and the metering section.

[0067] In one embodiment, the feed section of the variable-pitch, variable-depth screw has a pitch of 50 mm and a groove depth of 20 mm to ensure that materials such as polyolefin resin enter quickly without accumulating. The compression section gradually reduces the pitch to 30 mm and the groove depth to 12 mm, while the metering section further reduces these to 20 mm and 8 mm. This design enhances shear force by increasing the compression ratio, promoting uniform plasticization of the material, avoiding egg-shaped bright spots caused by localized unevenness, and ultimately improving the overall quality of the wet-process separator.

[0068] S111 determines the viscosity and flow characteristics of the material, and calculates the initial screw pitch and screw groove depth of the feeding section based on these characteristics, so that the material conveying efficiency reaches more than 90%.

[0069] S112, based on the shearing requirements of the compression section, gradually adjusts the reduction of the screw pitch by 5mm in each section to ensure that the material is subjected to force gradually and evenly.

[0070] S113 applies minimum screw pitch and screw groove depth in the metering section, combined with real-time pressure monitoring, to stabilize the output material flow and avoid fluctuations.

[0071] For example, when processing high-viscosity polyolefin materials, the large pitch of the feed section allows the material to enter at a rate of 2 kg / min, the gradually decreasing design of the compression section distributes the shear force from low to high, and the shallow depth of the metering section ensures that the final mixing uniformity is improved by 15%, thereby reducing bright spot defects.

[0072] S12, the screw is configured with forward and reverse kneading blocks, which are arranged alternately to form staggered shearing regions.

[0073] In one embodiment, the forward kneading blocks are arranged at a 45° angle, and the reverse kneading blocks at a 60° angle, alternating in groups every 100 mm. The forward blocks push the material forward and provide basic shear, while the reverse blocks disrupt the material flow in the opposite direction, forming staggered zones and breaking up additive agglomeration. This arrangement enhances the mixing effect and is suitable for the fusion of resin and additives in wet-process diaphragm production, helping to eliminate performance defects induced by inhomogeneity.

[0074] S121, the angle and thickness of the forward kneading block are selected to balance its conveying force and shearing force, while the reverse block is designed to generate counterflow to increase disturbance.

[0075] S122, when arranged alternately, ensure that the spacing between each group of kneading blocks is uniform, forming a continuous shearing zone that covers the entire length of the screw.

[0076] S123, test the effect of the interlaced area on material dispersion, and adjust the arrangement to optimize the mixing index to above 0.95.

[0077] For example.

[0078] In one possible implementation, for resin materials with a wide molecular weight distribution, the forward blocks push the material forward, while the reverse blocks reverse part of the flow direction. The staggered regions increase the dispersion by 20%, resulting in a 30% reduction in bright spots on the separator surface, thus improving battery safety and ion conduction efficiency.

[0079] S13, the static mixer is located in front of the discharge port of the machine head and includes multiple sets of twisted blades, which divide, merge and recombine the material.

[0080] For example, the static mixer is installed 300mm before the discharge port, with 10 sets of blades inside, each with a twist angle of 120° and a blade spacing of 30mm. When the material flows through, the blades first divide the fluid into multiple streams, then merge and recombine them, further refining and dispersing the mixture. This compensates for insufficient mixing by the screw compressor, helps ensure high uniformity of the material, and reduces bright spot defects in wet diaphragm mixers.

[0081] S131, configured with the number of blade groups and the twist angle, ensures that the number of divisions is at least 8 times, thereby improving the uniformity after merging.

[0082] S132 monitors the flow rate of material through the mixer and adjusts the blade spacing to match the extrusion rate.

[0083] S14, the arrangement of the kneading blocks and blades is determined according to the characteristics of the material.

[0084] In one embodiment, the alternating density of the kneading blocks and the twist angle of the blades are adjusted according to the molecular weight distribution and viscosity characteristics of the material.

[0085] For example, for low-viscosity materials, the proportion of reverse kneading blocks is reduced and the blade angle is adjusted to 90° to avoid excessive shearing; for high-viscosity materials, the alternation frequency is increased and the blade twist is adjusted to 150° to enhance mixing. This approach adapts the arrangement to specific characteristics, which is beneficial for optimizing the mixing uniformity of wet-process diaphragm twin-screw extruders.

[0086] For example, when processing different batches of polyolefin materials, first measure the properties such as viscosity value of 500 Pa·s, then increase the number of kneading block groups accordingly, and adjust the blade arrangement accordingly. As a result, the problem of uneven mixing is improved and the diaphragm quality is stable.

[0087] In one embodiment, the variable pitch design for S11 ensures smooth initial conveying in the context of polymer materials, while the gradually decreasing pitch in the compression section promotes plasticization, and the shallow depth in the metering section provides stable output, which is beneficial in reducing bright spots.

[0088] It should be noted that this design, combined with the S12 kneading block, forms a complete shearing chain, further enhancing the effect.

[0089] For example, in the staggered region of S12, in wet diaphragm production, the reverse block disturbance breaks up agglomeration, while the forward block maintains flow. After optimized arrangement, the mixing efficiency is improved, defects are reduced, and equipment life is extended.

[0090] In one possible implementation, the blade segmentation and merging process of S13 refines the material before discharge, and combined with the upstream screw output, ensures final uniformity, which is beneficial to battery performance.

[0091] Specifically, the defined characteristics of S14 allow for the personalization of the entire mixing process, covering different material scenarios, improving the applicability of the method, and reducing production instability.

[0092] Step S105, the segmented control of the extruder barrel temperature includes: S21, the barrel is divided into multiple temperature control zones, each corresponding to the feeding section, plasticizing section, and metering section; S22, the intelligent temperature control system acquires material temperature and screw torque data through sensors; S23, the intelligent temperature control system dynamically adjusts the heating power and cooling water volume based on the data; S24, the temperature fluctuation of the temperature control zone is maintained within a preset range through a control algorithm.

[0093] S21, the barrel is divided into multiple temperature control zones, which correspond to the feeding section, plasticizing section and metering section respectively.

[0094] In one embodiment, the extruder barrel is divided into five temperature control zones. The first zone corresponds to the feeding section for initial material conveying, the second and third zones correspond to the plasticizing section for gradual material melting, and the fourth and fifth zones correspond to the metering section for stable material output. This division ensures that the temperature of each zone is managed independently, avoiding the impact of overall temperature fluctuations.

[0095] S211, the control zone is evenly divided into corresponding sections along the length of the barrel, and each section is equipped with independent heating and cooling elements.

[0096] S212, based on the material flow path, set the length of the control zone for the feeding section to 20% of the total barrel length, the length for the plasticizing section to 50%, and the length for the metering section to 30%, in order to match the residence time of the material in each section.

[0097] S22, the intelligent temperature control system acquires material temperature and screw torque data through sensors.

[0098] For example, in wet-process diaphragm production, the system is equipped with thermocouple sensors and torque sensors in each temperature control zone. The thermocouples are in direct contact with the material flow channel to measure the real-time temperature, and the torque sensors are connected to the screw shaft to monitor rotational resistance. These data are collected once per second to form a continuous data stream for subsequent adjustments.

[0099] S221, the first set of sensors is installed in the feeding section to obtain the initial material temperature and the initial screw torque as baseline values.

[0100] S222 deploys multiple sensors in the plasticizing section to monitor temperature gradient changes and torque peaks, and to identify areas of uneven melting.

[0101] S223, a terminal sensor is set in the metering section to collect the final temperature and stable torque data to ensure output consistency.

[0102] In one possible implementation, for high-viscosity polyolefin materials, the temperature data collected by the sensor ranges from 120 to 180°C, and the torque data ranges from 50 to 100 Nm. This data is transmitted to the central processor via wired connection to avoid delay.

[0103] Specifically, this acquisition method is beneficial for early detection of local overheating. For example, when the torque data suddenly increases by 10%, it indicates that the material viscosity has increased, which may lead to uneven mixing. Real-time data capture improves the response speed.

[0104] S23, the intelligent temperature control system dynamically adjusts the heating power and cooling water volume according to the data.

[0105] In one embodiment, the system uses a proportional-integral-derivative (PID) control algorithm to process the data. The algorithm first calculates the temperature deviation, i.e., the difference between the actual temperature and the set value. Then, it quickly responds to the deviation through the proportional term, eliminates the steady-state error through the integral term, and predicts the trend of change through the derivative term. Finally, it outputs an adjustment signal to control the heating power and cooling water volume.

[0106] S231, calculate the temperature deviation and torque deviation, defining the temperature deviation as the actual temperature minus the target temperature, and the torque deviation as the actual torque minus the standard torque.

[0107] S232 applies a proportional-integral-derivative (PID) control algorithm to handle deviations. The proportional term multiplies the deviation value to provide immediate correction, the integral term accumulates the deviation over time to remove residual errors, and the derivative term calculates the rate of change of deviation to suppress overshoot.

[0108] S233, based on the algorithm output, increase the heating power when the temperature is 5°C below the target, or increase the cooling water volume when the torque exceeds the threshold by 15%.

[0109] For example, in the plasticizing section, when the temperature obtained by the sensor is 162℃ while the target is 165℃, and the torque is 60Nm while the standard is 55Nm, the algorithm calculates the deviation and adjusts the heating power from 80% to 90%, while slightly increasing the cooling water flow by 0.5L / min to balance the melting process.

[0110] It should be noted that this dynamic adjustment is beneficial for maintaining material uniformity. For example, when the feeding rate fluctuates, it can quickly respond to prevent the formation of egg-shaped bright spots in local cold areas, thereby improving the quality of the diaphragm.

[0111] In one embodiment, for different batches of materials, such as resins with a wide molecular weight distribution, the algorithm parameters can be preset and adjusted, with the proportional coefficient set to 0.5, the integral time to 10s, and the derivative time to 2s, to ensure that the power adjustment is completed within 1s after the torque data is input.

[0112] Specifically, this method supports stability from multiple perspectives. On the one hand, it directly corrects heating through temperature data, and on the other hand, it indirectly reflects viscosity changes through torque data, together reducing the risk of unevenness. The beneficial effect is to reduce the defect rate by more than 20%.

[0113] S24, the temperature fluctuation in the temperature control zone is maintained within a preset range by a control algorithm.

[0114] For example, with a preset range of ±1℃, the algorithm continuously monitors the adjusted temperature. If the fluctuation exceeds the range, it iteratively calculates and further fine-tunes the power to ensure that the temperature in all zones is stable.

[0115] S241, set the preset range to ±0.5% of the target temperature, such as 174.125-175.875℃ for a target temperature of 175℃.

[0116] S242, the algorithm compares the current temperature with the range in real time. If it exceeds the range, it triggers a second adjustment cycle, using the deviation data from the previous step as input.

[0117] In one possible implementation, this maintenance is beneficial to the continuity of the entire extrusion process, such as keeping fluctuations small in the metering section, ensuring uniform output material, avoiding bright spot defects, and improving the mechanical properties and ion conduction efficiency of the wet-process diaphragm.

[0118] Step S106, adjusting the screw speed and feeding rate according to material characteristics, includes: S31, obtaining the melt flow rate of the material, which is used to establish a mathematical model; S32, the mathematical model calculates the optimal speed and feeding rate based on the melt flow rate and material characteristics; S33, the variable frequency speed control technology adjusts the speed of the screw motor and the feeding motor through a frequency converter; S34, the speed and feeding rate are optimized in real time based on extrusion pressure and production data.

[0119] S31, Obtain the melt flow rate of the material, which is used to establish a mathematical model.

[0120] In one embodiment, the melt flow rate of raw materials such as polyolefin resin is measured using a melt flow rate tester. Specifically, the material sample is placed in the heating cylinder of the tester, and the mass of material extruded per unit time is recorded under standard conditions such as 190°C and a load of 2.16 kg to obtain the melt flow rate value, for example, 5 g / 10 min. This value reflects the fluidity and viscosity characteristics of the material and is directly used as the input parameter for the subsequent mathematical model to ensure that the model is built based on the actual material behavior.

[0121] S311 calibrates the melt flow rate value based on the measurement results of the tester to eliminate interference from environmental factors, such as deviations caused by temperature fluctuations. The accuracy of the data is improved by taking the average value through multiple repeated tests.

[0122] S312 stores the calibrated melt flow rate value in the control system as the basis for establishing the mathematical model.

[0123] S32, the mathematical model calculates the optimal rotational speed and feeding rate based on the melt flow rate and the material properties.

[0124] For example, in wet-process diaphragm production, the mathematical model adopts a linear regression form, and the relationship is obtained by fitting experimental data, such as the feed rate v = 0.05 × melt flow rate × screw speed n + 5, where the melt flow rate is obtained from S31, and the material characteristics include molecular weight distribution and additive ratio. These characteristics are obtained through laboratory analysis. The model calculates that when the melt flow rate is 5 g / 10 min and the molecular weight distribution is wide, the optimal screw speed is 80 r / min and the feed rate is 20 kg / h, which ensures that the material has a moderate residence time in the extruder and promotes uniform mixing.

[0125] S321, collect material property data, such as the molecular weight distribution of polyolefin resin determined by gel permeation chromatography, and the additive ratio calculated by weighing ratio, and input these data into the model in conjunction with the melt flow rate.

[0126] S322, the model performs calculations, and linear regression is based on the fitting coefficients of historical experimental data to output the optimal rotation speed and feeding rate pair, ensuring that the shear force matches the material flow and avoiding local stagnation.

[0127] S323, Verify the calculation results by simulating the extrusion process to check whether the egg-shaped bright spot defects have been reduced. If not, iteratively adjust the model coefficients.

[0128] S33, the variable frequency speed control technology adjusts the speed of the screw motor and the feed motor through a frequency converter.

[0129] In one possible implementation, the frequency converter receives the optimal speed signal calculated by S32 and directly adjusts the screw motor frequency from 50Hz to 60Hz, increasing the speed from 70r / min to 80r / min. At the same time, the feed motor is adjusted to match the speed. This technology ensures that the speed is continuously adjustable and maintains production stability.

[0130] S34, the rotational speed and feeding rate are optimized in real time based on extrusion pressure and output data.

[0131] Specifically, a pressure sensor installed on the extruder monitors the extrusion pressure. If the pressure exceeds the preset threshold of 200 bar, the system outputs the S32 model and reduces the screw speed by 5 r / min and the feed rate by 2 kg / h in real time. At the same time, the production monitoring device records the actual output. If the production is lower than the target of 15 kg / h, the speed is finely adjusted to ensure that the optimization process forms a closed loop. The pressure data is used as feedback input to the model for recalculation, and the production data verifies the adjustment effect, thereby continuously improving the uniformity of mixing and reducing egg-shaped bright spots in the wet diaphragm.

[0132] S341 collects real-time extrusion pressure and output data, sampling once per minute via sensors to form a data stream input optimization loop.

[0133] S342: Compare the collected data with the target value. If the deviation exceeds 10%, trigger the model to recalculate the rotation speed and feeding rate.

[0134] S343 applies the adjusted speed and rate, executes it through the frequency converter, monitors subsequent data to confirm the optimization effect, and forms an iterative chain.

[0135] In one embodiment, for high-viscosity materials such as polyolefin resin with a melt flow rate of 3 g / 10 min, after obtaining this value in S31, the model in S32 calculates an initial rotation speed of 60 r / min and a feeding rate of 15 kg / h. If the pressure rises to 220 bar during production, the optimization in S34 reduces the rotation speed to 55 r / min and the feeding rate to 13 kg / h, stabilizing the output at 12 kg / h. This adjustment reduces material retention, improves mixing uniformity, and helps eliminate diaphragm defects.

[0136] For example, when material properties change, such as the additive ratio increasing to 2%, S32 recalculates the rotation speed to 85 r / min, and S34 fine-tunes it to 82 r / min in real time based on the production data. This avoids overheating caused by excessively high rotation speed, improves plasticization consistency, and enhances the mechanical properties of the wet-process diaphragm.

[0137] In one possible implementation, for materials with low melt flow rates such as 2 g / 10 min, after S31 measurement, S32 gives a rotation speed of 50 r / min and a feed rate of 10 kg / h; if the production data shows fluctuations, S34 optimizes and increases the rotation speed to 52 r / min. This process ensures a uniform ion transport path, reduces battery internal resistance, and helps extend battery life.

[0138] It should be noted that these optimization steps, through obtaining the melt flow rate and model calculations, form a logical chain from static planning to dynamic adjustment, ensuring that the entire method effectively improves the problem of uneven mixing in wet diaphragm twin-screw extruders.

[0139] Step S107, the pretreatment includes mixing and drying processes, including: S41, the mixing process treats the material by high-speed stirring and vacuum mixing, the high-speed stirring achieving preliminary mixing; S42, the vacuum mixing removes air and moisture from the material under negative pressure; S43, the drying process uses hot air drying and vacuum drying to remove surface and internal moisture from the material; S44, the pretreatment adds a dispersing agent to improve the dispersibility of the additive.

[0140] S41, the mixing process treats the material by high-speed stirring and vacuum mixing, and the high-speed stirring achieves preliminary mixing.

[0141] In one embodiment, in step S41, raw materials such as polyolefin resin and additives are put into a stirring device by high-speed stirring and run at a speed of 1500 rpm for 10 minutes to ensure that the raw materials are initially evenly distributed and to avoid initial agglomeration.

[0142] S411: Place the raw materials in a high-speed mixer and set the speed and time for initial mixing.

[0143] S412 prepares the pre-mixed materials for subsequent vacuum processing.

[0144] S42, the vacuum mixing process removes air and moisture from the material under negative pressure.

[0145] In one embodiment, in step S42, the preliminary mixture is transferred into a vacuum mixing device and stirred at 800 revolutions per minute for 15 minutes under a negative pressure of -0.08 MPa. This effectively removes air bubbles and residual moisture, improves the purity of the material, and helps reduce bright spot defects in the subsequent extrusion process.

[0146] S421, set the vacuum level and start stirring to remove air and prevent air bubbles from forming in the material, which would cause unevenness.

[0147] S422 monitors the stirring process to ensure initial moisture reduction, providing a drier substrate for the drying step.

[0148] For example, in wet-process diaphragm production, this vacuum mixing can reduce the material moisture content from the initial 0.2% to below 0.1%, improve the fusion of resin and additives, reduce egg-shaped bright spots caused by air bubbles during extrusion, thereby improving the mechanical strength and ion conduction efficiency of the diaphragm.

[0149] S43, the drying process uses hot air drying and vacuum drying to remove surface and internal moisture from the material.

[0150] In one embodiment, in step S43, hot air drying is first used at 100 degrees Celsius for 2 hours to remove surface moisture, and then vacuum drying is used at 60 degrees Celsius and -0.09 MPa for 3 hours to deeply extract internal moisture and ensure that the overall moisture content of the material is controlled below 0.05%.

[0151] S431, hot air drying is performed to quickly evaporate the moisture adhering to the surface.

[0152] S432, then vacuum drying is performed to remove residual moisture from the interior, forming dried material for subsequent use.

[0153] In one possible implementation, for different batches of materials, such as polyolefin resins with a wide molecular weight distribution, the hot air temperature can be adjusted to 95 degrees Celsius to avoid overheating degradation, while the vacuum stage is extended to 4 hours to ensure that internal moisture is completely removed. This multi-stage drying can prevent material unevenness caused by moisture vaporization during extrusion, significantly reduce the occurrence rate of egg-shaped bright spots, and improve the electrochemical performance of the battery separator.

[0154] For example, after implementation, the material moisture content decreased from 0.15% to 0.03%, which not only reduced production defects but also extended the service life of the diaphragm, because the uniformly dried material can be better plasticized and mixed in the twin-screw extruder.

[0155] S44, the pretreatment involves adding a dispersing agent to improve the dispersibility of the additive.

[0156] In one embodiment, in step S44, 0.5% of a dispersant is added to the dried material. By reducing the surface tension between the additive and the resin, the additive particles are uniformly coated and distributed in the resin matrix, thereby improving the overall uniformity of the material.

[0157] S441, Select an appropriate amount of dispersing agent and mix it evenly into the dry material.

[0158] S442, Stir and mix to achieve full penetration and dispersion of the additives.

[0159] In one possible implementation, for high-viscosity resins, the proportion of additives can be increased to 0.7%, and an additional 5 minutes of stirring can be performed after addition to ensure thorough dispersion. This method can break up additive agglomeration, improve the uniformity of extrusion mixing, and reduce bright spots on the diaphragm surface.

[0160] For example, in the production of wet-process separators for lithium-ion batteries, the addition of dispersing agents increases the material dispersion from the initial 70% to 95%, which directly reduces the density of egg-shaped bright spots from 50 per square meter to less than 5. This is beneficial to improving battery safety and cycle life, because the uniformly dispersed additives ensure the stability of the separator pore structure.

[0161] In one embodiment, the addition of additives in S44, combined with the drying output of S43, further enhances the pretreatment effect of the material, forming a complete chain from initial mixing to final dispersion, which is suitable for improving the uneven mixing of materials in a twin-screw extruder.

[0162] Step S108, the mixing of the material by the variable pitch and variable depth screw and the static mixer includes: S111, the pitch and groove depth of the variable pitch and variable depth screw are determined according to the viscosity and flowability of the material; S112, the spacing of the forward and reverse kneading blocks is optimized according to the agglomeration characteristics of the material; S113, the number of blades and the twist angle of the static mixer are adjusted according to the dispersion requirements of the material; S114, the mixing effect of the screw and the static mixer is verified by detecting the uniformity of the material.

[0163] In one embodiment, the pitch and groove depth of the variable-pitch, variable-depth screw in step S111 are determined based on the viscosity and flowability of the material. Specifically, step S1111 involves measuring the viscosity and flowability of the material. The viscosity is obtained by testing with a rotational viscometer at a standard temperature, while the flowability is evaluated by a flow time test to assess the material's flow velocity on a fixed inclined plane. Step S1112 involves querying a preset parameter correspondence table based on experimental data. This table includes pitch and groove depth values ​​corresponding to different viscosity ranges. For example, for materials with a viscosity between 5000 and 10000 centipoise, the feed section pitch is 45 mm and the groove depth is 18 mm to ensure smooth material transport without local blockage. Step S1113 involves configuring the screw structure using these parameters, reducing the pitch to 25 mm and the groove depth to 10 mm in the compression section to promote uniform shearing of high-viscosity materials. This adapts to differences in material properties, prevents low-flowability materials from stagnating in the screw, which could lead to uneven mixing and improve overall plasticizing efficiency.

[0164] For example, in wet-process diaphragm production, for high-viscosity polyolefin resin materials, the viscosity test shows 8000 centipoise and the flow time is 15 seconds. The feed section pitch is determined to be 50 mm and the depth is 20 mm through the parameter table. This allows the material to enter quickly and avoids accumulation. In the metering section, the pitch is adjusted to 20 mm and the depth to 8 mm to enhance the shear force and reduce agglomeration, thereby improving the bright spot defects on the diaphragm surface.

[0165] In one embodiment, the spacing between the forward and reverse kneading blocks in step S112 is optimized based on the agglomeration characteristics of the material. Specifically, this includes: Step S1121, evaluating the agglomeration characteristics of the material by observing the degree of particle aggregation using a scanning electron microscope and calculating the agglomeration index, which is the ratio of the average agglomerated particle diameter to the diameter of a single particle. Step S1122, optimizing the spacing based on the agglomeration index. For example, when the agglomeration index is greater than 2, the spacing between the forward 45-degree kneading block and the reverse 60-degree kneading block is set to 80 mm to increase the staggered shearing area; when the index is less than 1.5, the spacing is increased to 120 mm to reduce degradation caused by excessive shearing. Step S1123, arranging these kneading blocks on the screw to form a continuous mixing path, using the pitch and depth determined in the previous step as a basis to ensure that the kneading blocks effectively act on the material in the variable-depth screw groove. This optimization can break the internal agglomeration structure of the material, improve the dispersion uniformity, and help prevent the formation of egg-shaped bright spots.

[0166] For example, for additive mixtures that are prone to agglomeration, the agglomeration index was measured to be 2.5. The optimized interval was 100 mm. The forward blocks pushed the material forward, and the reverse blocks stirred it in the opposite direction. Combined with the screw pitch design, the material was reorganized multiple times during the flow, which significantly reduced the bright spot defect rate from 15% to 2%.

[0167] In one embodiment, the number of blades and the twist angle of the static mixer in step S113 are adjusted according to the dispersion requirements of the material.

[0168] Specifically, the dispersion requirements are first assessed by measuring the initial dispersion of the material, i.e., the variance of the additive distribution in the resin; a larger variance indicates higher requirements. Next, the number of blades is selected based on the dispersion requirements. For example, 12 sets of blades, each with a 120-degree twist angle, are used for high requirements to increase the number of splitting and merging operations; for medium requirements, 8 sets of blades with a 90-degree angle are sufficient. After adjustment, a static mixer is installed before the screw discharge port, using the optimized screw mixture from the previous step as input for further refinement, ensuring highly uniform output. This adjustment process specifically enhances the mixing effect, helps compensate for screw limitations, and improves diaphragm quality.

[0169] For example, when processing materials with high dispersion requirements, the initial variance was 0.3. After adjusting to 10 sets of blades and a twist angle of 110 degrees, the material was repeatedly cut as it flowed through. Combined with pre-mixing of kneading blocks, the uniformity was improved from 75% to 95%, effectively eliminating opaque spots.

[0170] In one embodiment, the mixing effect of the screw and static mixer in step S114 is verified by detecting the uniformity of the material. This includes collecting extruded material samples, observing the number of bright spots using an optical microscope, and calculating a uniformity index as feedback for the previous step's adjustments. If the index is below a threshold, such as 90%, the parameters are iteratively optimized. This verification forms a closed loop, ensuring that the method improves the uneven mixing in wet-process diaphragm twin-screw extruders.

[0171] For example, the test showed a uniformity of 92%, verifying the effectiveness of parameter adjustment and reducing production defects.

[0172] Step S109, adjusting the screw speed and feeding rate according to material characteristics, includes: S311, the mathematical model establishes the relationship between the screw speed, feeding rate, and melt flow rate through experimental data; S312, the variable frequency speed control technology adjusts the screw speed according to the real-time extrusion pressure; S313, the feeding rate is adjusted synchronously with the screw speed by the feeding motor; S314, the adjustment process verifies the mixing stability of the material through a production monitoring device.

[0173] S311, the mathematical model establishes the relationship between rotational speed, feeding rate and melt flow rate through experimental data.

[0174] In one embodiment, the mathematical model is constructed by collecting multiple sets of experimental data.

[0175] Specifically, a series of extrusion experiments are first conducted, recording the feed rate and corresponding melt flow rate values ​​at different screw speeds. For example, the screw speed is gradually changed from 50 rpm to 150 rpm, and the feed rate is adjusted accordingly from 5 kg / h to 20 kg / h, while the melt flow rate is measured as the output. These data points are then used to fit linear or quadratic relationships to ensure that the model can predict the optimal combination.

[0176] S3111, based on experimental data, the correlation coefficient is calculated. The melt flow rate is defined as the mass of melt passing through a standard mold per unit time, used to characterize the flow properties of materials. For example, if experiments show that the melt flow rate is 8 g / 10 min when the rotation speed is 100 rpm and the feed rate is 10 kg / h, then the least squares method can be used to fit a relationship such as the feed rate equal to 0.05 times the melt flow rate multiplied by the rotation speed plus 5, thus forming the basis of the model.

[0177] S3112 applies the fitted relationship to different batches of materials. For example, for polyolefin resins with a wide molecular weight distribution, the model parameters are adjusted to adapt to their specific flow characteristics, ensuring that the model outputs reliable rotation speed and feed rate values.

[0178] S312, the variable frequency speed control technology adjusts the rotation speed according to the real-time extrusion pressure.

[0179] In one embodiment, a pressure sensor is installed at the extruder head to monitor the extrusion pressure value in real time, and the screw motor speed is dynamically changed by a frequency converter.

[0180] Specifically, if the pressure is detected to exceed a preset threshold such as 20 MPa, the rotation speed is reduced to alleviate the pressure and prevent material accumulation that could lead to uneven mixing.

[0181] S3121, the pressure adjustment logic is based on a feedback loop. The extrusion pressure is defined as the mechanical pressure exerted on the material within the barrel, which is converted into an electrical signal by a sensor and input to the controller. For example, during the production of wet-process diaphragms, if the pressure suddenly rises to 25 MPa, the system automatically reduces the rotation speed from 120 rpm to 90 rpm, restoring the pressure to the normal range of 15-20 MPa, thereby maintaining uniform material flow.

[0182] In another scenario, S3122, for high-viscosity materials, presets a higher pressure threshold, such as 30 MPa, and combines this with speed adjustment to optimize shear force and reduce egg-shaped bright spot defects. This real-time adjustment improves mixing uniformity and reduces the defect rate by up to 30%.

[0183] S3123 further optimizes the speed adjustment by combining historical pressure data. For example, if the pressure fluctuation is less than 2 MPa for three consecutive cycles, the speed is finely adjusted upward to increase output without sacrificing stability.

[0184] S313, the feeding rate is adjusted synchronously with the screw speed by the feeding motor.

[0185] In one embodiment, the feed motor and the screw motor are connected by a synchronous controller. When the screw speed changes, the feeding rate is adjusted proportionally. For example, when the speed increases by 10%, the feeding rate increases accordingly to match the material input and avoid overload or idling.

[0186] S314, the adjustment process verifies the mixing stability of the material through a production monitoring device.

[0187] In one embodiment, a production monitoring device is installed at the discharge port to measure the extrusion volume per unit time and calculate stability indicators, such as a production fluctuation rate of less than 5% being considered stable.

[0188] Specifically, if the adjusted output stabilizes at 15 kg / hour with a fluctuation of no more than 0.5 kg, then the mixing is confirmed to be uniform; otherwise, further fine-tuning of the rotation speed is triggered.

[0189] S3141, stability verification includes comparing the preset output with the actual value. For example, during the verification phase, if the output is monitored to recover from 14 kg / hour to the target of 15 kg / hour without abnormal fluctuations, it indicates that the material mixing has been optimized, reducing the bright spot defects induced by unevenness, thereby improving the overall quality of wet-process separators.

[0190] Step S1010, the pretreatment includes mixing and drying processes, including: S411, the high-speed stirring processes the material at a preset speed, the speed being determined based on the particle characteristics of the material; S412, the negative pressure value and stirring time of the vacuum mixing are optimized based on the moisture content of the material; S413, the amount of dispersant added is determined based on the surface tension of the additive and the polyolefin resin; S414, the drying process uses an online moisture monitor to detect the moisture content of the material and adjust the drying parameters.

[0191] S411, the high-speed stirring processes the material at a preset rotation speed, the rotation speed being determined based on the particle characteristics of the material.

[0192] In one embodiment, the preset rotation speed of the high-speed stirring in step S411 is determined by evaluating the average diameter and distribution uniformity of the material particles.

[0193] For example, for coarse particles with a diameter of 0.5 mm or more, the rotation speed is set to 1200 r / min to provide sufficient shear force to break up particle agglomeration; for fine particles with a diameter of less than 0.2 mm, the rotation speed is adjusted to 1800 r / min to ensure rapid dispersion without causing over-crushing.

[0194] Specifically, this method of determining the rotation speed can prevent localized accumulation of materials in the early stages of mixing based on particle characteristics, thereby improving the uniformity of the initial mixing.

[0195] S4111, calculate the base value of rotational speed based on the average diameter of the material particles. For example, the larger the diameter, the lower the base value of rotational speed, in order to match the material flow resistance.

[0196] S4112, adjust the rotation speed offset according to the uniformity of particle distribution. If the distribution is uneven, increase the rotation speed by 10% to enhance the stirring intensity.

[0197] For example, in wet-process membrane production, when the average diameter of polyolefin resin particles is 0.3 mm and they are evenly distributed, the rotation speed is set to 1500 r / min. After stirring for 10 minutes, the initial mixing degree of the material is increased by 20%, reducing the risk of subsequent egg-shaped bright spots.

[0198] S412, the negative pressure value and stirring time of the vacuum mixing are optimized according to the moisture content of the material.

[0199] In one embodiment, the negative pressure value and stirring time of vacuum mixing in step S412 are optimized by measuring the initial moisture content of the material.

[0200] For example, when the moisture content is higher than 0.1%, the negative pressure is set to -0.09MPa and the stirring time is extended to 20 minutes to fully remove moisture and air; when the moisture content is lower than 0.05%, the negative pressure is adjusted to -0.07MPa and the stirring time is shortened to 12 minutes to avoid excessive vacuuming leading to over-drying of the material.

[0201] Specifically, this optimization can dynamically adjust parameters based on moisture content to ensure uniform penetration of additives into the resin, improve overall mixing performance, and reduce bright spot defects.

[0202] S4121, after detecting the moisture content of the material, establish the correspondence between the negative pressure value and the moisture content. For example, for every 0.02% increase in moisture content, the negative pressure increases by 0.01 MPa.

[0203] S4122, calculate the stirring time according to the corresponding relationship. For example, the higher the negative pressure, the time is extended by 5% to match the discharge efficiency.

[0204] S4123 uses optimized parameters for vacuum mixing, inputting the material from the previous high-speed mixing step to ensure that the mixture is free of air bubbles after moisture optimization.

[0205] For example, when processing high-moisture polyolefin resins with a moisture content of 0.12%, an optimized negative pressure of -0.095 MPa and stirring for 18 minutes can increase the material dispersion by 15%, thereby effectively eliminating agglomeration caused by moisture and resulting in more stable extruder mixing uniformity.

[0206] In one possible implementation, for different batches of materials, if the moisture content fluctuates greatly, such as from 0.08% to 0.15%, multiple optimization iterations can further refine the parameters to support the stability of mixing in continuous production.

[0207] S413, the amount of the dispersing agent added is determined based on the surface tension of the additive and the polyolefin resin.

[0208] In one embodiment, the amount of dispersant added in step S413 is determined by measuring the surface tension difference between the additive and the polyolefin resin.

[0209] For example, when the surface tension difference is greater than 20 mN / m, the addition amount is set to 0.8% to reduce interfacial tension and promote dispersion; when the surface tension difference is less than 10 mN / m, the addition amount is reduced to 0.3% to avoid excessive additives affecting the viscosity of the material.

[0210] Specifically, surface tension refers to the contractile force generated on the surface of a liquid due to the imbalance of intermolecular forces. In this context, the wettability of the additive on the resin surface is measured by the contact angle method, and the amount of additive is determined by calculating the difference. This method can accurately match the material characteristics, ensure that the additive uniformly coats the particles, improve the mixing uniformity, and reduce egg-shaped bright spots.

[0211] S4131, Measure the surface tension value of the additive, for example, using the pendant drop method to obtain an additive tension of 25 mN / m.

[0212] S4132, Measure the surface tension value of polyolefin resin, for example, if the resin tension is 35mN / m, calculate the difference as 10mN / m.

[0213] S4133, based on the difference, look up the amount to be added in the preset table. For example, for every 5mN / m increase in the difference, the amount to be added increases by 0.2%.

[0214] S4134, add the calculated amount of additive to the material after vacuum mixing, stir and blend to ensure uniform distribution of the additive as the drying input.

[0215] For example, in a scenario where the surface tension of the polyolefin resin is 32 mN / m and the additive is 28 mN / m, a difference of 4 mN / m corresponds to an addition amount of 0.2%, resulting in a 25% improvement in material dispersibility, significantly reducing defects caused by uneven extrusion, and enhancing the mechanical properties of the diaphragm.

[0216] In one possible implementation, if the resin type changes, such as from low-density to high-density polyolefin, the surface tension difference may increase to 15 mN / m, and the corresponding addition amount is adjusted to 0.5%. Through multiple experiments, this method has been verified to adapt to different material scenarios, resulting in higher production efficiency and product quality stability.

[0217] S414, the drying process uses an online moisture monitor to detect the moisture content of the material and adjust the drying parameters accordingly.

[0218] In one embodiment, the drying process in step S414 utilizes an online moisture monitor to detect the moisture content of the material in real time. For example, when the detected value exceeds 0.05%, the hot air temperature is automatically increased to 110°C and the drying time is extended by 1 hour; when the detected value is below 0.03%, the temperature is reduced to 90°C to prevent over-drying.

[0219] Specifically, this adjustment ensures that the moisture content of the material is stable before it enters the extruder, connects the mixing output of the previous step, and avoids residual moisture affecting the uniformity of the mixture.

[0220] S4141, the monitor samples moisture data every 5 minutes.

[0221] S4142, adjust the drying temperature and time according to the data to ensure that the final moisture content is below 0.05% as a pre-processed output.

[0222] For example, on the production line, when the moisture content was detected at 0.06%, adjusting the parameters reduced the moisture content to 0.04%, which improved the material uniformity of the subsequent extruders and reduced bright spot defects.

[0223] The above description of the embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application; those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for improving uneven mixing in a wet-process diaphragm twin-screw extruder, characterized in that, include: The material inside the twin-screw extruder, including polyolefin resin and additives, is obtained and mixed using a variable pitch and variable depth screw and a static mixer; the temperature of the extruder barrel is controlled in stages and dynamically adjusted by an intelligent temperature control system; the screw speed and feed rate are adjusted according to the material characteristics and are optimized through mathematical models and variable frequency speed control technology. The material is pretreated, and the pretreatment includes mixing and drying processes to improve the uniformity of the material; The mixing of the material using a variable-pitch, variable-depth screw and a static mixer includes: the variable-pitch, variable-depth screw has a larger pitch and deeper groove in the feeding section, and the pitch and groove depth gradually decrease in the compression and metering sections; the screw is equipped with forward and reverse kneading blocks, which are alternately arranged to form staggered shearing zones; the static mixer is located before the discharge port of the die head and includes multiple sets of twisted blades, which divide, merge, and recombine the material; the arrangement of the kneading blocks and blades is determined according to the characteristics of the material. The segmented control of the extruder barrel temperature includes: dividing the barrel into multiple temperature control zones, each corresponding to a feeding section, a plasticizing section, and a metering section; the intelligent temperature control system acquiring material temperature and screw torque data through sensors; the intelligent temperature control system dynamically adjusting the heating power and cooling water volume based on the data; and maintaining temperature fluctuations in the temperature control zones within a preset range through a control algorithm. The step of adjusting the screw speed and feeding rate according to material characteristics includes: obtaining the melt flow rate of the material, which is used to establish a mathematical model; the mathematical model calculating the optimal speed and feeding rate based on the melt flow rate and the material characteristics; the variable frequency speed control technology adjusting the speed of the screw motor and the feeding motor through a frequency converter; and the speed and feeding rate being optimized in real time based on extrusion pressure and production data. The mixing of the material using a variable-pitch, variable-depth screw and a static mixer includes: the screw pitch and groove depth of the variable-pitch, variable-depth screw being determined based on the viscosity and flowability of the material; the spacing between the forward and reverse kneading blocks being optimized based on the agglomeration characteristics of the material; the number of blades and the twist angle of the static mixer being adjusted based on the dispersion requirements of the material; and the mixing effect of the screw and the static mixer being verified by detecting the uniformity of the material. The adjustment of screw speed and feeding rate according to material characteristics includes: the mathematical model establishing the relationship between screw speed, feeding rate and melt flow rate through experimental data; the variable frequency speed control technology adjusting the screw speed according to real-time extrusion pressure; the feeding rate being adjusted synchronously with the screw speed by the feeding motor; and the adjustment verifying the mixing stability of the material through a production monitoring device.

2. The method as described in claim 1, characterized in that, The pretreatment includes mixing and drying processes, including: the mixing process treats the material by high-speed stirring and vacuum mixing, wherein the high-speed stirring achieves preliminary mixing; the vacuum mixing removes air and moisture from the material under negative pressure; the drying process uses hot air drying and vacuum drying to remove surface and internal moisture from the material; and the pretreatment adds a dispersing agent to improve the dispersibility of the additive.

3. The method as described in claim 2, characterized in that, The pretreatment includes mixing and drying processes, including: high-speed stirring at a preset speed, the speed being determined based on the particle characteristics of the material; the negative pressure value and stirring time of the vacuum mixing being optimized based on the moisture content of the material; the amount of dispersing agent added being determined based on the surface tension of the additive and the polyolefin resin; and the drying process using an online moisture monitor to detect the moisture content of the material and adjust the drying parameters.

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