High-efficiency continuous production process of talcum powder master batch by double internal mixers and single extruder

Abstract

The invention discloses a double-internal mixer-single extruder talcum powder master batch high-efficiency continuous production process which comprises the following steps: A, primary mixing and pre-plasticizing: continuously and accurately adding all carrier resin particles and most formula processing aids into a first internal mixer according to a set proportion, and meanwhile, carrying out primary mixing and pre-plasticizing; talcum powder accounting for 60%-80% of the total talcum powder is added into the first internal mixer through an independent feeding device, and the rotor rotating speed, the temperature and the filling coefficient of the first internal mixer are controlled. By means of seamless series connection of the two continuous internal mixers and the single-screw extruder, the traditional three discrete procedures of intermittent internal mixing, cold material crushing and re-extrusion are integrated into a one-step continuous process, migration and re-agglomeration of talcum powder sheet layers at high temperature are physically blocked, and therefore the continuous production of talcum powder is achieved. Intermediate cooling, crushing and re-feeding links are eliminated, the production efficiency can be improved by more than 30%, the energy consumption is reduced by more than 20%, and the temperature difference is controlled within + / -1 DEG C.

Description

Technical Field

[0001] This invention relates to the field of talc masterbatch production technology, specifically a high-efficiency continuous production process for talc masterbatch using a dual internal mixer-single extruder. Background Technology

[0002] Talc, as an inexpensive flake-shaped inorganic filler, is widely used in polyolefin plastics such as polypropylene (PP) and polyethylene (PE) to improve the rigidity, heat resistance, dimensional stability and reduce costs of the material. Usually, in order to facilitate subsequent processing, a high proportion of talc powder needs to be pre-mixed with carrier resin, coupling agent, dispersant and other ingredients to form a high-concentration talc powder masterbatch.

[0003] Traditional talc masterbatch production processes mainly fall into two categories: 1) Intermittent internal mixer + single / twin-screw extruder process: Raw materials are first subjected to high-intensity mixing, plasticizing, and preliminary dispersion in an internal mixer (such as a Banbury mixer). Then, the lumpy material is crushed and melt-extruded and granulated using a single-screw or twin-screw extruder. This process has significant drawbacks: a) Intermittent operation, low production efficiency, and high energy consumption; b) The hot material discharged after mixing needs to be cooled and crushed, generating additional energy consumption and dust; c) The crushed cold material entering the extruder needs to be remelted, resulting in secondary heat history and potentially causing resin degradation. 2) Twin-screw extruder direct extrusion process: All raw materials are directly added to a co-rotating twin-screw extruder. Mixing, dispersion, and devolatilization are completed by the combination and shearing of the screws. While this process allows for continuous production, it presents serious problems for talc masterbatches with extremely high filler content (e.g., above 70 wt%): a) Difficulty in the instantaneous intake of high-proportion powder, easily leading to unstable feeding and screw seizure; b) The powder is difficult to be completely wetted and dispersed by the resin melt in a short time, and it is easy to form agglomerates, which affects the performance of the masterbatch and its dispersibility in the matrix; c) It causes severe wear on the screw and barrel. Summary of the Invention

[0004] The purpose of this invention is to provide an efficient and continuous production process for talc masterbatch using a dual internal mixer and a single extruder, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency continuous production process for talc masterbatch using a dual internal mixer and a single extruder, comprising the following steps: A. Primary Mixing and Pre-plasticization: All carrier resin (such as polypropylene) particles and most of the processing aids in the formulation are continuously and precisely added to the first internal mixer in a set ratio. At the same time, talc powder accounting for 60%-80% of the total talc powder is added to the first internal mixer through an independent feeding device. By controlling the rotor speed, temperature and filling coefficient of the first internal mixer, the resin can be rapidly melted. Coupling agents are used to pre-wet, in-situ surface treat and pre-disperse some of the talc powder in the molten state, producing a "matrix melt" with a certain viscosity, non-uniformity and reactivity. B. Online Rheological Monitoring and Dynamic Path Decision-Making: The melt discharged from the first internal mixer flows through an online capillary rheometer or an online torque rheometer to monitor its apparent viscosity, melt pressure, or torque value in real time. The control system compares the monitored rheological data (such as viscosity value) with the preset target range and dynamically controls the three-way melt distributor based on the comparison results. At the same time, all the remaining talc powder, dispersant, and lubricant are continuously and accurately added to the second internal mixer. The second internal mixer is controlled to operate at a higher rotor speed, a higher shear rate, and a higher temperature. The high temperature can reduce the overall melt viscosity, so that the newly added talc powder can be quickly wrapped by the melt. Meanwhile, the partially plasticized resin melt is used as a "carrier" to strongly capture, wet, and disperse the added talc powder. At this stage, the talc powder lamellae agglomerates are effectively peeled off by high shear force, achieving deep dispersion and surface treatment of talc powder. C. Melt Homogenization and Pressurized Conveying: The high-temperature, high-viscosity melt (usually 180-220℃) after deep mixing is immediately fed into a twin-roller tablet press or a steel belt cooling tablet press. Through forced water cooling (cooling water is circulated inside the rollers or the steel belt is sprayed with cooling water), the melt is rapidly cooled to below the glass transition temperature of the resin (40-80℃) within 3-15 seconds, causing it to solidify into brittle flakes. This rapid cooling process "freezes" the dispersion state of talc in the melt, effectively preventing "thermal agglomeration". Subsequently, the cooled brittle flakes are fed into a toothed roller crusher or needle mill and crushed into uniform chips or coarse particles with a size of 2-8mm. Finally, they are continuously and stably conveyed to the feed port of a single screw extruder with a large length-to-diameter ratio through a closed pneumatic conveying system. This single screw extruder mainly undertakes the functions of longitudinal mixing of the melt, removal of volatiles (with a vacuum de-evaporation port), temperature homogenization, and pressure building for die extrusion. D. Mild Final Mixing, Pressure Building, and Deviation: The screw of the high length-to-diameter ratio single-screw extruder is designed with a length-to-diameter ratio (L / D≥40) primarily for conveying, mild shearing, and pressure building. After the cooled material fragments enter the single-screw extruder, the final homogenization of the melt, removal of residual volatiles (such as water vapor), and establishment of stable and sufficient die pressure for extrusion are completed under relatively mild shearing and a relatively long residence time. The rear half of the single-screw extruder barrel is equipped with at least one vacuum devolatilization port, connected to a vacuum system to extract low-molecular-weight volatiles. The single-screw extruder adopts a special low-temperature melting and plasticizing section design: the temperature of the feeding section and compression section is set at a low level, allowing the material to be slowly compressed and melted at a low viscosity, enabling efficient devolatilization. In the interval where the material transitions from a solid to a molten state (before and after the solid bed breaks down), the internal pores and volatile channels are not yet completely closed. At this time, a high-vacuum devolatilization port (vacuum degree ≤-0.095) is set in the middle of the screw. (MPa), volatiles can be efficiently extracted, and the devolatilization effect is far superior to that of the whole melt. Shear redispersion, the material remelts at low temperature and has a high viscosity. At this time, the applied medium shear force can effectively shear and break up the small agglomerates that have been "frozen and fixed" and may exist. Due to the low temperature of the material and the short heating time, re-agglomeration at high temperature is avoided. E. Extrusion, Cooling and Pelletizing: The melt after homogenization and devolatilization is extruded into strips through the multi-hole template at the front end of a single screw extruder. It immediately enters an underwater chute for cooling and conveying, and then is pelletized underwater by a rotary cutter to form granules. The wet granules after pelletizing are dewatered, vibrated, screened and dried in a fluidized bed to obtain dry, highly filled talc masterbatch.

[0006] Preferably, the filling coefficient of the first internal mixer in step A is 0.6-0.75, the rotor speed is 250-400 rpm, the temperature is controlled at 20-50°C above the resin melting point, and the processing aids are all coupling agents, some dispersants, and some lubricants.

[0007] Preferably, in step B, the filling coefficient of the second internal mixer is 0.7-0.85, the rotor speed is 400-600 rpm, and the temperature is controlled at 30-80°C above the resin melting point. The outlet of the second internal mixer is equipped with a melt temperature and pressure measuring device, whose signal is fed back to the control system to dynamically adjust the rotor speed and heating power of the internal mixer to stabilize the rheological properties of the output melt. If the monitored viscosity is lower than a preset lower limit, it indicates insufficient melt plasticization or a low talc loading rate. In this case, the distributor is controlled to distribute all or most of the ( >90% of the melt is introduced into the second internal mixer and enters the "enhanced dispersion path". If the monitored viscosity is within the preset target range, the distributor is controlled to introduce a portion (e.g., 30%-70%) of the melt into the second internal mixer, and the remaining portion is directly introduced into the melt pump through a bypass and enters the "diversion optimization path". If the monitored viscosity is higher than the preset upper limit, it indicates that the melt has been subjected to excessive shear or abnormal temperature. The distributor is then controlled to introduce all or most of the melt directly into the melt pump through a bypass, bypassing the second internal mixer and entering the "mild protection path".

[0008] Preferably, in step C, during the pneumatic conveying process, the cold air comes into full contact with the material, which further homogenizes and cools it down, and also removes some of the free moisture and low-molecular-weight volatiles adsorbed on the surface of the material, thus achieving pre-drying and pre-volatilization. In addition, the roller gap of the double-roller tablet press is adjustable to control the thickness of the cooled tablets to 1-3 mm, ensuring the cooling rate and brittleness.

[0009] Preferably, the screw of the single-screw extruder in step D is designed with barrier-type screw ribs or pin mixing elements in the melting section to enhance melt mixing and dispersion at low temperature. It also adopts a deep groove, low shear screw design, with the compression ratio controlled between 1.5 and 2.5, and is equipped with a melt gear pump to further stabilize the extrusion pressure, which can avoid secondary structural damage to the well dispersed talc powder.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves truly efficient continuous production: by seamlessly connecting two continuous internal mixers with a single screw extruder, the traditional three discrete processes of "intermittent internal mixing + cold material crushing + re-extrusion" are integrated into a one-step continuous process. This physically blocks the migration and re-agglomeration of talc flakes at high temperatures, eliminates intermediate cooling, crushing, and refeeding steps, increases production efficiency by more than 30%, reduces energy consumption by more than 20%, controls the temperature difference within ±1℃, increases output by 100%, improves devolatilization efficiency by more than 50% compared to traditional melt devolatilization, and keeps the masterbatch moisture content consistently below 0.1%.

[0011] The problem of feeding and wear under high filling conditions has been solved: high proportion of talc powder is added in two stages and under different material states, which greatly alleviates the pressure of single-point feeding and the instantaneous load on the equipment. The high shear dispersion task is mainly undertaken by a continuous internal mixer designed for high filling. Its rotor and mixing chamber structure are more wear-resistant. The subsequent gentle single screw mainly undertakes conveying and pressure building, which greatly reduces wear and extends the service life of the entire system. At the same time, since the feed is cold solid particles, the feeding is stable and "bridging" is not easy to occur. The overall system energy consumption is reduced by about 15% compared with the traditional full melt series process. The resulting masterbatch has higher dispersion, better performance and minimal batch-to-batch differences. Detailed Implementation

[0012] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0013] The efficient and continuous production process of talc masterbatch using a dual internal mixer and a single extruder includes the following steps: A. Primary Mixing and Pre-plasticization: All carrier resin (such as polypropylene) particles and most of the processing aids in the formulation are continuously and precisely added to the first internal mixer in a set ratio. At the same time, talc powder accounting for 60%-80% of the total talc powder is added to the first internal mixer through an independent feeding device. By controlling the rotor speed, temperature and filling coefficient of the first internal mixer, the resin can be rapidly melted. Coupling agents are used to pre-wet, in-situ surface treat and pre-disperse some of the talc powder in the molten state, producing a "matrix melt" with a certain viscosity, non-uniformity and reactivity. B. Online Rheological Monitoring and Dynamic Path Decision-Making: The melt discharged from the first internal mixer flows through an online capillary rheometer or an online torque rheometer to monitor its apparent viscosity, melt pressure, or torque value in real time. The control system compares the monitored rheological data (such as viscosity value) with the preset target range and dynamically controls the three-way melt distributor based on the comparison results. At the same time, all the remaining talc powder, dispersant, and lubricant are continuously and accurately added to the second internal mixer. The second internal mixer is controlled to operate at a higher rotor speed, a higher shear rate, and a higher temperature. The high temperature can reduce the overall melt viscosity, so that the newly added talc powder can be quickly wrapped by the melt. Meanwhile, the partially plasticized resin melt is used as a "carrier" to strongly capture, wet, and disperse the added talc powder. At this stage, the talc powder lamellae agglomerates are effectively peeled off by high shear force, achieving deep dispersion and surface treatment of talc powder. C. Melt Homogenization and Pressurized Conveying: The high-temperature, high-viscosity melt (usually 180-220℃) after deep mixing is immediately fed into a twin-roller tablet press or a steel belt cooling tablet press. Through forced water cooling (cooling water is circulated inside the rollers or the steel belt is sprayed with cooling water), the melt is rapidly cooled to below the glass transition temperature of the resin (40-80℃) within 3-15 seconds, causing it to solidify into brittle flakes. This rapid cooling process "freezes" the dispersion state of talc in the melt, effectively preventing "thermal agglomeration". Subsequently, the cooled brittle flakes are fed into a toothed roller crusher or needle mill and crushed into uniform chips or coarse particles with a size of 2-8mm. Finally, they are continuously and stably conveyed to the feed port of a single screw extruder with a large length-to-diameter ratio through a closed pneumatic conveying system. This single screw extruder mainly undertakes the functions of longitudinal mixing of the melt, removal of volatiles (with a vacuum de-evaporation port), temperature homogenization, and pressure building for die extrusion. D. Mild Final Mixing, Pressure Building, and Deviation: The screw of the high length-to-diameter ratio single-screw extruder is designed with a length-to-diameter ratio (L / D≥40) primarily for conveying, mild shearing, and pressure building. After the cooled material fragments enter the single-screw extruder, the final homogenization of the melt, removal of residual volatiles (such as water vapor), and establishment of stable and sufficient die pressure for extrusion are completed under relatively mild shearing and a relatively long residence time. The rear half of the single-screw extruder barrel is equipped with at least one vacuum devolatilization port, connected to a vacuum system to extract low-molecular-weight volatiles. The single-screw extruder adopts a special low-temperature melting and plasticizing section design: the temperature of the feeding section and compression section is set at a low level, allowing the material to be slowly compressed and melted at a low viscosity, enabling efficient devolatilization. In the interval where the material transitions from a solid to a molten state (before and after the solid bed breaks down), the internal pores and volatile channels are not yet completely closed. At this time, a high-vacuum devolatilization port (vacuum degree ≤-0.095) is set in the middle of the screw. (MPa), volatiles can be efficiently extracted, and the devolatilization effect is far superior to that of the whole melt. Shear redispersion, the material remelts at low temperature and has a high viscosity. At this time, the applied medium shear force can effectively shear and break up the small agglomerates that have been "frozen and fixed" and may exist. Due to the low temperature of the material and the short heating time, re-agglomeration at high temperature is avoided. E. Extrusion, Cooling and Pelletizing: The melt after homogenization and devolatilization is extruded into strips through the multi-hole template at the front end of a single screw extruder. It immediately enters an underwater chute for cooling and conveying, and then is pelletized underwater by a rotary cutter to form granules. The wet granules after pelletizing are dewatered, vibrated, screened and dried in a fluidized bed to obtain dry, highly filled talc masterbatch.

[0014] The filling factor of the first internal mixer in step A is 0.6-0.75, the rotor speed is 250-400 rpm, the temperature is controlled at 20-50℃ above the resin melting point, and the processing aids are all coupling agents, some dispersants, and some lubricants.

[0015] In step B, the filling coefficient of the second internal mixer is 0.7-0.85, the rotor speed is 400-600 rpm, and the temperature is controlled at 30-80℃ above the resin melting point. The outlet of the second internal mixer is equipped with a melt temperature and pressure measuring device, whose signals are fed back to the control system to dynamically adjust the rotor speed and heating power of the mixer to stabilize the rheological properties of the output melt. If the monitored viscosity is lower than the preset lower limit, it indicates insufficient melt plasticization or a low talc loading rate. In this case, the distributor is controlled to distribute all or most of the (>90%) of the melt. %) The melt is introduced into the second internal mixer and enters the "enhanced dispersion path". If the monitored viscosity is within the preset target range, the distributor is controlled to introduce a portion (e.g., 30%-70%) of the melt into the second internal mixer, and the remaining portion is directly introduced into the melt pump through the bypass and enters the "diversion optimization path". If the monitored viscosity is higher than the preset upper limit, it indicates that the melt has been subjected to excessive shear or abnormal temperature. The distributor is controlled to introduce all or most of the melt directly into the melt pump through the bypass, bypassing the second internal mixer and entering the "mild protection path".

[0016] In step C, during the pneumatic conveying process, the cold air comes into full contact with the material, which further homogenizes and cools it down. On the other hand, it can remove some of the free moisture and low molecular weight volatiles adsorbed on the surface of the material, achieving pre-drying and pre-volatilization. In addition, the roller gap of the double roller tablet press is adjustable to control the thickness of the cooled tablets at 1-3mm, ensuring the cooling rate and brittleness.

[0017] In step D, the single-screw extruder has a barrier-type screw rib or pin mixing element in the melting section to enhance melt mixing and dispersion at low temperature. It also adopts a deep groove, low shear screw design, with the compression ratio controlled between 1.5 and 2.5, and is equipped with a melt gear pump to further stabilize the extrusion pressure, which can avoid secondary structural damage to the well dispersed talc powder.

[0018] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency continuous production process for talc masterbatch using a dual internal mixer and a single extruder, characterized by: Includes the following steps: A. Primary mixing and preplasticization: All carrier resin particles and most of the processing aids in the formulation are continuously and precisely added to the first internal mixer in a set ratio. At the same time, talc powder accounting for 60%-80% of the total talc powder is added to the first internal mixer through an independent feeding device. The rotor speed, temperature and filling coefficient of the first internal mixer are controlled. B. Online rheological monitoring and dynamic path decision-making: The melt discharged from the first internal mixer flows through an online capillary rheometer or an online torque rheometer to monitor its apparent viscosity, melt pressure or torque value in real time. The control system compares the monitored rheological data (such as viscosity value) with the preset target range and dynamically controls the three-way melt distributor based on the comparison results. At the same time, all the remaining talc powder, dispersant and lubricant are continuously and accurately added to the second internal mixer, and the second internal mixer is controlled to operate at a higher rotor speed, a higher shear rate and a higher temperature. C. Melt homogenization and pressurized conveying: The high-temperature, high-viscosity melt after deep mixing is immediately fed into a twin-roller tablet press or a steel belt cooling tablet press. Through forced water cooling, the melt is rapidly cooled to below the glass transition temperature of the resin within 3-15 seconds, causing it to solidify into brittle flakes. Subsequently, the cooled brittle flakes are fed into a toothed roller crusher or a needle mill to be crushed into uniform chips or coarse particles with a size of 2-8mm. Finally, they are continuously and stably conveyed to the feed port of a high length-to-diameter ratio single screw extruder through a closed pneumatic conveying system. D. Mild final mixing, pressure building and devolatilization: The screw of the high aspect ratio single screw extruder is designed with a length-to-diameter ratio primarily for conveying, mild shearing and pressure building. After the cooled material debris enters the single screw extruder, the final homogenization of the melt, the removal of residual volatiles, and the establishment of a stable and sufficient die head pressure for die extrusion are completed under relatively mild shearing and a relatively long residence time. The rear half of the single screw extruder barrel is equipped with at least one vacuum devolatilization port, which is connected to a vacuum system to extract low molecular weight volatiles. E. Extrusion, Cooling and Pelletizing: The melt after homogenization and devolatilization is extruded into strips through the multi-hole template at the front end of a single screw extruder. It immediately enters an underwater chute for cooling and conveying, and then is pelletized underwater by a rotary cutter to form granules. The wet granules after pelletizing are dewatered, vibrated, screened and dried in a fluidized bed to obtain dry, highly filled talc masterbatch.

2. The efficient and continuous production process of talc masterbatch using a dual internal mixer-single extruder as described in claim 1, characterized in that: The filling coefficient of the first internal mixer in step A is 0.6-0.75, the rotor speed is 250-400 rpm, the temperature is controlled at 20-50°C above the resin melting point, and the processing aids are all coupling agents, some dispersants, and some lubricants.

3. The efficient and continuous production process of talc masterbatch using a dual internal mixer-single extruder as described in claim 1, characterized in that: The filling coefficient of the second internal mixer in step B is 0.7-0.85, the rotor speed is 400-600 rpm, and the temperature is controlled at 30-80℃ above the resin melting point. The outlet of the second internal mixer is equipped with a melt temperature and pressure measuring device, whose signal is fed back to the control system for dynamically adjusting the rotor speed and heating power of the internal mixer. If the monitored viscosity is lower than the preset lower limit, it indicates that the melt plasticization is insufficient or the talc loading rate is too low. Then, the distributor is controlled to introduce all or most of the melt into the second internal mixer and enter the "enhanced dispersion path". If the monitored viscosity is within the preset target range, the distributor is controlled to introduce a portion of the melt into the second internal mixer, and the rest enters the melt pump directly through the bypass and enters the "diversion optimization path". If the monitored viscosity is higher than the preset upper limit, it indicates that the melt has been subjected to excessive shear or abnormal temperature. Then, the distributor is controlled to introduce all or most of the melt directly into the melt pump through the bypass, bypassing the second internal mixer and entering the "mild protection path".

4. The efficient and continuous production process of talc masterbatch using a dual internal mixer-single extruder as described in claim 1, characterized in that: In step C, during the pneumatic conveying process, the cold air comes into full contact with the material, which further homogenizes and cools it down. On the other hand, it can remove some of the free moisture and low molecular weight volatiles adsorbed on the surface of the material. In addition, the roller gap of the double roller tablet press is adjustable to control the thickness of the cooling tablets to 1-3mm.

5. The efficient and continuous production process of talc masterbatch using a dual internal mixer-single extruder as described in claim 1, characterized in that: The single-screw extruder in step D has a barrier-type screw rib or pin mixing element in the melting section, and adopts a deep groove, low shear screw design. The compression ratio is controlled between 1.5 and 2.5, and it is equipped with a melt gear pump to further stabilize the extrusion pressure.