Highly filled calcium carbonate-based polycarbonate composites and methods for making the same

Abstract

The application belongs to the technical field of polymer composite material modification, and relates to a high-filling calcium carbonate-based polycarbonate composite material and a preparation method thereof, and the formula is as follows according to mass fractions: base resin 20-50 parts, modified calcium carbonate filler 50-80 parts, core-shell toughening agent 3-8 parts, compatilizer 2-3 parts, processing aid 2-5 parts, and composite antioxidant 0.5-1 part; the modified calcium carbonate filler is obtained through double modification: adopting ternary particle size gradation of 'large particle skeleton, medium particle filling and small particle filling', and the porosity is less than or equal to 25%; firstly, hydroxyl is passivated through physical coating of stearic acid, and then a coupling agent formed by compounding KH-550 and NDZ-101 is used for chemical grafting to form a stable Si-O-Ca bond, and after modification, the activation degree is greater than or equal to 95%, and the water contact angle is greater than or equal to 100 degrees. The application solves the problems in the prior art that industrialized technologies are mostly limited to low and medium filling amount calcium carbonate PC modification, and there are problems such as rigidity and toughness imbalance, poor processing fluidity, unstable batch performance, insufficient cost advantage and the like when the filling amount is too high, and it is difficult to stably produce in large quantities.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite material modification technology, and relates to a highly filled calcium carbonate-based polycarbonate composite material and its preparation method. Background Technology

[0002] Polycarbonate (PC) is an aromatic engineering plastic with excellent comprehensive properties, possessing high rigidity, high impact toughness, excellent dimensional stability, weather resistance, and electrical insulation. It is the core matrix material for "replacing steel / aluminum with plastic" in the global industrial field. However, pure PC resin has drawbacks such as high production cost, insufficient wear resistance, high melt viscosity, and narrow molding processing window. By filling with inorganic calcium carbonate filler, material costs can be effectively reduced, and rigidity, wear resistance, and dimensional stability can be improved. This is the most mainstream and industrially valuable technology direction in the field of PC modification. Among the relevant technologies currently disclosed both domestically and internationally, the following are representative existing solutions: 1) Chinese invention patent CN112321024A discloses a high-filled calcium carbonate modified PC composite material, with a maximum calcium carbonate filling content of only 50% and a notched impact strength of only 12kJ / m. 2 It is impossible to achieve a balance between rigidity and toughness under ultra-high filler content; 2) Chinese invention patent CN109504128A discloses a calcium carbonate modified PC material, which uses calcium carbonate filler with a single particle size and is modified by a single coupling agent. The melt flow rate of the material is only 8g / 10min (230℃ / 2.16kg), and the processing fluidity is extremely poor, making it unsuitable for conventional injection molding and extrusion molding equipment. 3) International patent WO2021123456A1 discloses a high-filling inorganic filler modified polycarbonate material, but its process is complicated, the performance of mass production batches fluctuates by more than 12%, it cannot achieve continuous industrial production, and it does not solve the problem of melt viscosity soaring under ultra-high filling amount. Existing industrial technologies in the industry generally focus on low / medium filler calcium carbonate (PC) modification systems with ≤50% calcium carbonate content. Modification technologies for systems with ultra-high filler content (above 50%) all have significant performance shortcomings and industrialization bottlenecks. When the calcium carbonate filler content exceeds 50%, existing technologies generally suffer from four core industry pain points that cannot be addressed simultaneously, which are also the technical problems that this invention specifically addresses: Severe imbalance between rigidity and toughness: Existing technologies mostly use calcium carbonate with a single particle size, which easily forms "bridging agglomerates" between particles, severely damaging the continuous phase structure of the resin matrix. This results in a precipitous drop in the notched impact strength of the material, which cannot meet the impact resistance requirements of industrial structural components. Extremely poor processing fluidity: Under high filler content, the specific surface area of ​​filler increases significantly, and the melt viscosity increases exponentially. Existing technologies cannot effectively reduce the viscosity of the system. Conventional injection molding and extrusion equipment cannot achieve stable processing. Products are prone to defects such as material shortage, fiber floating, surface roughness, and silver cracking, resulting in an extremely low yield. Unstable batch performance: Existing technologies have weak control over the dispersibility and interfacial bonding of fillers, and are greatly affected by process fluctuations. During industrial mass production, the mechanical properties and flow properties between batches generally fluctuate by more than 10%, which cannot meet the consistency requirements of large-scale production. Insufficient overall cost advantage: The high porosity of single-size fillers requires a large amount of resin for coating, making it impossible to maximize the reduction of resin usage under ultra-high filler content. The material cost advantage is greatly weakened, making it difficult to promote on a large scale in the scenario of replacing steel with plastic. Existing technologies cannot simultaneously address the four core pain points mentioned above, making it difficult to achieve stable industrial-scale production of ultra-high-filling-content calcium carbonate modified PC materials. This makes it impossible to meet the comprehensive performance requirements of industrial structural components, and there is a lack of a complete intellectual property protection system globally, meaning that inventors' rights cannot be guaranteed in the long term. Summary of the Invention

[0003] The purpose of this invention is to provide a high-filled calcium carbonate-based polycarbonate composite material and its preparation method, which solves the problems in the prior art, where industrial technology is mostly limited to low and medium filler calcium carbonate PC modification, and ultra-high filler has problems such as rigidity and toughness imbalance, poor processing fluidity, unstable batch performance, and insufficient cost advantage, making it difficult to achieve stable mass production.

[0004] The technical solution adopted in this invention is a highly filled calcium carbonate-based polycarbonate composite material and its preparation method. The total number of parts by weight is 100, comprising the following components: 20-50 parts of matrix resin, 50-80 parts of modified calcium carbonate filler, 3-8 parts of core-shell toughening agent, 2-3 parts of interface compatibilizer, 2-5 parts of processing aid, and 0.5-1 part of composite antioxidant. The modified calcium carbonate filler is obtained through ternary particle size distribution and physical-chemical dual interface modification. The particle size distribution adopts a scheme of "large particles to build the skeleton, medium particles to fill the gaps, and small particles to fill the voids", and the packing void ratio after gradation is ≤25%; the physical-chemical dual interface modification is to first passivate the hydroxyl groups on the filler surface by physically coating with stearic acid, and then chemically grafting with a compound system of KH-550 silane coupling agent and NDZ-101 titanate coupling agent to form stable Si-O-Ca chemical bonds on the filler surface. After modification, the filler activation degree is ≥95% and the water contact angle is ≥100°.

[0005] As a further aspect of this invention, the entire process includes the following steps: S1 Raw material pretreatment, where the matrix resin, calcium carbonate filler, and additives are dried or screened for pretreatment; S2 Filler gradation and dual interface modification, where calcium carbonate filler is weighed according to a ternary gradation scheme, first undergoes physical coating modification with stearic acid, and then undergoes chemical grafting modification with a composite coupling agent to obtain modified calcium carbonate filler; S3 Precise formulation mixing, where the pretreated matrix resin and each additive are premixed, and then the modified calcium carbonate filler is added for final mixing; S4 Low-shear high-dispersion compounding, extrusion, and granulation, where the intensive mixing, premixing, plasticizing, and reciprocating compounding, extrusion, and granulation are performed sequentially to obtain composite particles; S5 Particle post-treatment and quality control, where the composite particles are screened, dried, cooled, packaged, and traceable.

[0006] As a further aspect of the present invention: the matrix resin is composed of bisphenol A type polycarbonate and PC-polysiloxane copolymer in a mass ratio of (3~4):1; wherein the weight average molecular weight of bisphenol A type polycarbonate is 28000~32000 and the molecular weight distribution index is 1.8~2.2; and the mass fraction of siloxane units in PC-polysiloxane copolymer is 15%~20%.

[0007] As a further aspect of the present invention: in the physical-chemical dual interface modification, the amount of stearic acid added is 0.8% to 1.2% of the total mass of calcium carbonate filler; the compound coupling agent is KH-550 and NDZ-101 compounded in a mass ratio of 2:1, and the amount added is 0.8% to 1.5% of the total mass of calcium carbonate filler.

[0008] As a further aspect of the present invention: In the pretreatment of raw materials S1, the matrix resin is dried in a vacuum drying oven at a temperature of 120℃ and a vacuum degree ≥0.09MPa for 4~6 hours, and the moisture content after drying is ≤0.02%; the calcium carbonate filler is dried in a vacuum drying oven at a temperature of 80℃ for 2~3 hours, and the drying time of nano-calcium is extended to 3 hours, and the moisture content after drying is ≤0.05%; the additives are screened through an 80-mesh sieve and stored in a sealed environment at 20~25℃ and relative humidity ≤60%.

[0009] As a further aspect of the present invention: the physical coating modification in S2 specifically involves adding the filler to a high-speed mixer with a jacketed temperature control system, preheating it to 80°C, adding stearic acid, mixing at a low speed of 300 rpm for 3 minutes, and then mixing at a high speed of 800 rpm for 10 minutes; the chemical grafting modification specifically involves heating the physically coated filler to 105~110°C, atomizing and spraying a composite coupling agent diluted 1:1 with anhydrous ethanol, mixing at a high speed of 800 rpm for 15~20 minutes, and cooling it to below 40°C before discharging.

[0010] As a further aspect of the present invention: the ternary particle size distribution scheme, based on 100% of the total mass of the filler, corresponds to the following different filling amounts: when the filling amount is 50%~60%, it consists of 60%~70% 1500-mesh spherical calcium carbonate + 20%~30% 3000-mesh nano calcium carbonate + 5%~15% 5000-mesh nano calcium carbonate; when the filling amount is 65%~70%, it consists of 65%~75% 1250-mesh ultrafine calcium carbonate + 20%~30% 3000-mesh nano calcium carbonate + 3%~8% 5000-mesh nano calcium carbonate; when the filling amount is 75%~80%, it consists of 70%~80% 800-mesh heavy calcium carbonate + 10%~20% 1500-mesh ultrafine calcium carbonate + 5%~15% 3000-mesh nano calcium carbonate.

[0011] As a further aspect of the present invention, the rigid control requirements for the ternary particle size distribution are: main packing D50 / medium packing D50≥5:1, medium packing D50 / micro packing D50≥3:1, and main packing D50 / micro packing D50≥15:1.

[0012] As a further aspect of the present invention: the internal mixing and plasticizing process in S4 adopts a gradient heating method, with the top throttle at 200°C, the mixing chamber at 210°C, and the rotor at 220°C, a rotation speed of 30~50 rpm, and a mixing time of 5~8 min; the reciprocating mixing extrusion granulation adopts a reciprocating mixing extruder with a length-to-diameter ratio of 20:1, with a temperature gradient of 220°C in zone 1, 230°C in zone 2, 240°C in zone 3, 235°C in zone 4, and 230°C at the die head, a rotation speed of 50~100 rpm, a vacuum degree ≥0.08MPa, and underwater pelletizing to obtain 3×3mm composite particles with a size deviation ≤±0.2mm.

[0013] As a further aspect of the present invention: the core-shell toughening agent has a particle size of 50~100nm, the core layer is a butadiene-based elastomer, and the shell layer is a methyl methacrylate-based polar monomer; the interface compatibilizer is a maleic anhydride-grafted polyolefin compatibilizer; the processing aid is zinc stearate with a purity ≥99%; and the composite antioxidant is antioxidant 1010 and antioxidant 168 compounded in a mass ratio of 1:1.

[0014] The beneficial effects of this invention are: 1. Achieving a balance between rigidity and toughness with ultra-high filler content; with 50%~80% calcium carbonate filler content, the flexural modulus is ≥3500MPa and the notched impact strength is ≥20kJ / m. 21. Compared with existing technologies of the same filler content, the impact strength is improved by more than 60%, solving the pain point of stiffness and toughness imbalance in existing high-filler systems; 2. Excellent processing performance, melt flow rate ≥15g / 10min (230℃ / 2.16kg), which is more than 80% higher than existing technologies of the same filler content, compatible with conventional injection molding equipment, and the molded products are free from defects such as missing material, floating fibers, and silver streaks, with a surface finish Ra≤1.6μm; 3. High mass production stability, quantitative control of the entire process ensures that the core performance fluctuation between batches in continuous production is ≤±5%, CPK≥1.33, which is more than 60% lower than the batch fluctuation of existing technologies; 4. Significantly reduced overall cost, with a cost reduction of 30%~50% compared with pure PC resin and a cost reduction of 15%~30% compared with ordinary modified PC materials, enhancing the product's market competitiveness; 5. Wide adaptability, customized solutions can be made according to different filler levels, adapting to the injection molding needs of multiple fields, and complying with global environmental protection standards, with recyclability, facilitating industrial promotion. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating the entire process of a highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to the present invention. It clearly shows the entire process steps of the present invention: S1 raw material pretreatment → S2 filler gradation and dual modification → S3 precise formulation mixing → S4 low-shear high-dispersion compounding, extrusion and granulation → S5 particle post-treatment. The core control parameters of each step are marked, and the process logic relationship is clearly defined.

[0016] Figure 2 This is a schematic diagram illustrating the close packing principle of the ternary particle size distribution filler in the high-filled calcium carbonate-based polycarbonate composite material and its preparation method of the present invention. It compares and shows the close packing structure of the single particle size filler with that of the ternary particle size distribution filler of the present invention, and marks the gradation logic of large, medium and small particles, intuitively presenting the core principle of close packing based on the Dinger-Funk theory.

[0017] Figure 3 This is a comparison of the Fourier transform infrared (FT-IR) spectra of calcium carbonate filler before and after modification in the high-filled calcium carbonate-based polycarbonate composite material and its preparation method of the present invention. It includes three curves: unmodified calcium carbonate, calcium carbonate after physical coating with stearic acid, and calcium carbonate after double modification according to the present invention. The positions of the characteristic peaks of Si-O-Ca and stearic acid are marked, which intuitively proves the chemical bonding effect of the double interface modification of the present invention.

[0018] Figure 4This is a comparison of the impact cross-sectional SEM morphology of the composite material of the present invention and the comparative example material in the preparation method of the high-filled calcium carbonate-based polycarbonate composite material of the present invention; divided into 4 fields of view: a) impact cross-section of the composite material of Example 1 of the present invention; b) impact cross-section of the ungraded and unmodified material of Example 1; c) impact cross-section of the composite material of Example 3 of the present invention; d) impact cross-section of the material of the conventional process of Comparative Example 3, which intuitively shows the uniform dispersion effect of the filler in the resin matrix of the present invention, with no obvious agglomeration and interface debonding.

[0019] Figure 5 This is a bar chart comparing the core performance of the high-filled calcium carbonate-based polycarbonate composite material and its preparation method of the present invention with that of the prior art. Using three filler levels of 55%, 68%, and 78% as the horizontal axis, the bar chart compares the three core indicators of the present invention's material with those of the prior art: flexural modulus, notched impact strength, and melt flow rate, thus visually presenting the performance advantages of the present invention. Detailed Implementation

[0020] The specific implementation of the high-filled calcium carbonate-based polycarbonate composite material and its preparation method of the present invention is as follows: The raw materials used in the embodiments and comparative examples of the present invention are all conventional commercially available products and do not require special preparation, as detailed below: 1. Bisphenol A type polycarbonate: weight average molecular weight 28,000~32,000, molecular weight distribution index 1.8~2.2, conventional industrial grade; 2. PC-polysiloxane copolymer: siloxane unit mass fraction 15%~20%, conventional industrial grade; 3. Calcium carbonate filler: 1500 mesh spherical calcium carbonate, 3000 mesh nano calcium carbonate, 5000 mesh nano calcium carbonate, 1250 mesh ultrafine calcium carbonate, 800 mesh heavy calcium carbonate, all industrial grade; 4. Core-shell toughening agent: particle size 50~10 0nm, core layer is butadiene elastomer, shell layer is methyl methacrylate polar monomer, industrial grade; 5. Interface compatibilizer: maleic anhydride grafted polyolefin compatibilizer, industrial grade; 6. Processing aid: zinc stearate, purity ≥99%, industrial grade; 7. Composite antioxidant: antioxidant 1010 and antioxidant 168, both industrial grade, compounded in a mass ratio of 1:1; 8. Modifying aid: stearic acid, KH-550 silane coupling agent, NDZ-101 titanate coupling agent, anhydrous ethanol, all industrial grade.

[0021] In the embodiments and comparative examples of this invention, all performance tests were performed according to the following standards: 1. Flexural modulus: Tested according to GB / T9341-2008 standard; 2. Notched impact strength: Tested according to GB / T1043.1-2008 standard; 3. Melt flow rate: Tested according to GB / T3682.1-2018 standard at 230℃ and 2.16kg; 4. Filler activation degree: Tested according to GB / T19281-2014 standard; 5. Water contact angle: Tested using a contact angle measuring instrument at 25℃; 6. Batch performance fluctuation: Five batches were produced continuously, and the core performance (flexural modulus, notched impact strength, melt flow rate) of each batch was tested, and the fluctuation value was calculated; 7. Surface finish: Tested using a roughness tester, with the test parameter Ra.

[0022] Example 1: High-filled calcium carbonate-based polycarbonate composite material for automotive lightweighting with 55% filler content Formula composition: The composite material in this embodiment, based on a total mass of 100 parts, has the following specific formulation: Bisphenol A type polycarbonate: 31 parts, weight average molecular weight 30,000, molecular weight distribution index 2.0; PC-polysiloxane copolymer: 8 parts, siloxane unit mass fraction 18%; modified calcium carbonate filler: 55 parts, prepared by ternary particle size distribution and physical-chemical dual interface modification; core-shell structure toughening agent: 3 parts, particle size 80nm; interface compatibilizer: 2 parts; zinc stearate: 0.5 parts, purity ≥99%; composite antioxidant: 0.5 parts, antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1.

[0023] Parameters of modified calcium carbonate filler: The ternary particle size distribution scheme of modified calcium carbonate filler (based on 100% of the total filler mass) is as follows: 65% 1500 mesh spherical calcium carbonate + 25% 3000 mesh nano calcium carbonate + 10% 5000 mesh nano calcium carbonate. After gradation, the packing void ratio is ≤25%, which meets the rigid control requirements: D50 of main filler / D50 of intermediate filler ≥5:1, D50 of intermediate filler / D50 of micro filler ≥3:1, and D50 of main filler / D50 of micro filler ≥15:1.

[0024] Physicochemical dual-interface modification parameters of modified calcium carbonate filler: Physical coating modification: The amount of stearic acid added is 1.0% of the total mass of calcium carbonate filler; Chemical grafting modification: The composite coupling agent is KH-550 silane coupling agent and NDZ-101 titanate coupling agent in a mass ratio of 2:1. The addition amount is 1.0% of the total mass of calcium carbonate filler. After modification, the activity degree of the filler is ≥95% and the water contact angle is ≥100°.

[0025] The composite material preparation method in this embodiment is strictly implemented according to the standardized steps of the entire process disclosed in this invention, as follows: S1 Raw Material Pretreatment Process: Matrix resin drying: A vacuum drying oven was used at a temperature of 120℃ and a vacuum degree of ≥0.09MPa for 5 hours. After drying, the moisture content of the resin was ≤0.02%, with no lumps or yellowing. Drying of calcium carbonate filler: A vacuum drying oven is used at a temperature of 80℃ for 3 hours (extended to 3 hours for nano-calcium). After drying, the moisture content of the filler is ≤0.05%, and there is no agglomeration or clumping. Additive pretreatment: All additives are screened through an 80-mesh sieve to remove impurities and lumps, and stored in a sealed environment at 23℃ and relative humidity ≤60%, with an effective ingredient content ≥99%.

[0026] S2 packing gradation and dual-interface modification process: Accurate weighing: According to the above ternary gradation scheme, use an electronic balance with an accuracy of 0.01g to weigh calcium carbonate fillers of various specifications. The weighing error is ≤±0.2%. A double-checking system of "one person weighing and one person checking" is implemented. Physical coating modification: The weighed filler is added to a high-speed mixer with a jacketed temperature control system, preheated to 80°C, and a preset amount of stearic acid is added. The mixture is first mixed at a low speed of 300 rpm for 3 minutes to achieve initial dispersion, and then mixed at a high speed of 800 rpm for 10 minutes to achieve uniform coating. The activation degree of the modified filler is ≥90%. Chemical grafting modification: The physically coated filler is heated to 108℃, and a composite coupling agent diluted 1:1 with anhydrous ethanol is sprayed by atomization. The mixture is mixed at high speed of 800rpm for 18min to ensure complete grafting reaction. After completion, the mixture is cooled to below 40℃ and discharged to obtain modified calcium carbonate filler.

[0027] S3 Formula Precision Mixing Process: Premixing of matrix and additives: Use an independent high-speed mixer (separate from the filler modification equipment to avoid cross-contamination) to add the pretreated matrix resin, core-shell toughening agent, interface compatibilizer, zinc stearate and composite antioxidant to the equipment and mix at a medium speed of 500 rpm for 4 minutes until the mixture is free of stratification, lumps and has a uniform color. Final mixing: Strictly follow the feeding sequence of "adding the premixed resin-additive system first, then adding the modified filler". First, mix at a low speed of 300 rpm for 2 minutes to achieve initial fusion, and then mix at a medium speed of 500 rpm for 3 minutes to achieve uniform dispersion. After mixing, complete the extrusion process within 24 hours.

[0028] S4 Low-shear High-dispersion compounding, extrusion, and granulation process: Internal mixing and premixing plasticizing: The mixture is fed into an internal mixer with a precise temperature control system. It adopts a gradient heating design with the top nut at 200°C, the mixing chamber at 210°C, and the rotor at 220°C. The rotation speed is 40 rpm (low shear design to avoid filler breakage and resin degradation). The mixing time is 6 minutes. After mixing, the melt has no visible filler agglomeration or unplasticized particles, and the torque fluctuation is ≤±5%. Reciprocating compounding extrusion granulation: The premixed and plasticized material is fed into a reciprocating compounding extruder with a length-to-diameter ratio of 20:1. The temperature gradient is 220℃ in zone 1, 230℃ in zone 2, 240℃ in zone 3, 235℃ in zone 4, and 230℃ at the die head. The rotation speed is 80 rpm, and the vacuum degree is ≥0.08MPa, which effectively removes volatiles and moisture from the melt. Underwater pelleting is adopted, and the pelleting speed and extrusion rate are precisely matched to obtain 3×3mm composite particles with a size deviation of ≤±0.2mm.

[0029] S5 particle post-processing and quality control procedures: Screening: The composite particles are screened using an 80-mesh vibrating screen to remove fragments, impurities, and particles that do not meet the size requirements; Drying and cooling: Dry with hot air at 80℃ for 2 hours to remove surface moisture, then cool naturally to 23℃. The finished particles have a moisture content of ≤0.05% and an impurity content of ≤0.01%. Packaging and Traceability: The product is packaged in moisture-proof and sealed bags. Each bag is labeled with the product name, batch number, filling amount, and production date. ≥2kg of each batch is retained for a shelf life of ≥1 year. The entire process is traceable.

[0030] In this embodiment, when the finished composite material is used for injection molding of lightweight automotive parts, it needs to be vacuum dried at 110°C and a vacuum degree ≥0.09MPa for 2.5 hours before molding. After drying, the particle moisture content is ≤0.03%. The injection molding temperature gradient is 230°C in zone 1 of the barrel, 240°C in zone 2, 250°C in zone 3, 245°C in the nozzle, 70°C in the mold, and 100MPa in the injection pressure.

[0031] Example 2: High-filled calcium carbonate-based polycarbonate composite material for appliance frames with 68% filler content Formula composition The composite material in this embodiment, based on a total mass of 100 parts, has the following specific formulation: Bisphenol A type polycarbonate: 24 parts, weight average molecular weight 29000, molecular weight distribution index 2.1; PC polysiloxane copolymer: 6 parts, siloxane unit mass fraction 16%; modified calcium carbonate filler: 68 parts, prepared by ternary particle size distribution and physicochemical dual interface modification; core-shell structure toughening agent: 1 part, particle size 70nm; interface compatibilizer: 0.6 parts; zinc stearate: 0.3 parts, purity ≥99%; composite antioxidant: 0.1 parts, antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1.

[0032] Modified calcium carbonate filler parameters The ternary particle size distribution scheme of modified calcium carbonate filler (based on 100% of the total filler mass) is as follows: 70% 1250 mesh ultrafine calcium carbonate + 25% 3000 mesh nano calcium carbonate + 5% 5000 mesh nano calcium carbonate. After gradation, the packing void ratio is ≤25%, which meets the rigid control requirements: D50 of main filler / D50 of medium filler ≥5:1, D50 of medium filler / D50 of micro filler ≥3:1, and D50 of main filler / D50 of micro filler ≥15:1.

[0033] Physicochemical dual-interface modification parameters of modified calcium carbonate filler: Physical coating modification: The amount of stearic acid added is 1.1% of the total mass of calcium carbonate filler; Chemical grafting modification: The composite coupling agent is KH-550 silane coupling agent and NDZ-101 titanate coupling agent in a mass ratio of 2:1. The addition amount is 1.2% of the total mass of calcium carbonate filler. After modification, the activity degree of the filler is ≥95% and the water contact angle is ≥100°.

[0034] Preparation method The composite material preparation method in this embodiment is strictly implemented according to the standardized steps of the entire process disclosed in this invention, as follows: S1 Raw Material Pretreatment Process Matrix resin drying: A vacuum drying oven was used at a temperature of 120℃ and a vacuum degree of ≥0.09MPa for 4.5 hours. After drying, the moisture content of the resin was ≤0.02%, with no clumping or yellowing. Drying of calcium carbonate filler: A vacuum drying oven was used at 80℃ for 2.5 hours (extended to 3 hours for nano-calcium). After drying, the moisture content of the filler was ≤0.05%, and there was no agglomeration or clumping. Additive pretreatment: All additives are screened through an 80-mesh sieve to remove impurities and lumps, and stored in a sealed environment at 22℃ and relative humidity ≤60%, with an effective ingredient content ≥99%.

[0035] S2 packing gradation and dual-interface modification process Accurate weighing: According to the above ternary gradation scheme, use an electronic balance with an accuracy of 0.01g to weigh calcium carbonate fillers of various specifications. The weighing error is ≤±0.2%. A double-checking system of "one person weighing and one person checking" is implemented. Physical coating modification: The weighed filler is added to a high-speed mixer with a jacketed temperature control system, preheated to 80°C, and a preset amount of stearic acid is added. The mixture is first mixed at a low speed of 300 rpm for 3 minutes to achieve initial dispersion, and then mixed at a high speed of 800 rpm for 10 minutes to achieve uniform coating. The activation degree of the modified filler is ≥90%. Chemical grafting modification: The physically coated filler is heated to 106℃, and a composite coupling agent diluted 1:1 with anhydrous ethanol is sprayed by atomization. The mixture is mixed at high speed of 800rpm for 16min to ensure complete grafting reaction. After completion, the mixture is cooled to below 40℃ and discharged to obtain modified calcium carbonate filler.

[0036] S3 Formula Precision Mixing Process Premixing of matrix and additives: Use an independent high-speed mixer (separate from the filler modification equipment to avoid cross-contamination) to add the pretreated matrix resin, core-shell toughening agent, interface compatibilizer, zinc stearate and composite antioxidant to the equipment and mix at a medium speed of 500 rpm for 3.5 min until the mixture is free of stratification, lumps and has a uniform color. Final mixing: Strictly follow the feeding sequence of "adding the premixed resin-additive system first, then adding the modified filler". First, mix at a low speed of 300 rpm for 2 minutes to achieve initial fusion, and then mix at a medium speed of 500 rpm for 3 minutes to achieve uniform dispersion. After mixing, complete the extrusion process within 24 hours.

[0037] S4 Low-shear high-dispersion compounding, extrusion, and granulation process Internal mixing and premixing plasticizing: The mixture is fed into an internal mixer with a precise temperature control system. It adopts a gradient heating design with the top nut at 200°C, the mixing chamber at 210°C, and the rotor at 220°C. The rotation speed is 35 rpm (low shear design to avoid filler breakage and resin degradation). The mixing time is 7 minutes. After mixing, the melt has no visible filler agglomeration or unplasticized particles, and the torque fluctuation is ≤±5%. Reciprocating compounding extrusion granulation: The premixed and plasticized material is fed into a reciprocating compounding extruder with a length-to-diameter ratio of 20:1. The temperature gradient is 220℃ in zone 1, 230℃ in zone 2, 240℃ in zone 3, 235℃ in zone 4, and 230℃ at the die head. The rotation speed is 70 rpm, and the vacuum degree is ≥0.08MPa, which effectively removes volatiles and moisture from the melt. Underwater pelleting is adopted, and the pelleting speed and extrusion rate are precisely matched to obtain 3×3mm composite particles with a size deviation of ≤±0.2mm.

[0038] S5 Particle Post-processing and Quality Control Process Screening: The composite particles are screened using an 80-mesh vibrating screen to remove fragments, impurities, and particles that do not meet the size requirements; Drying and cooling: Dry with hot air at 80℃ for 2 hours to remove surface moisture, then cool naturally to 22℃. The finished particles have a moisture content of ≤0.05% and an impurity content of ≤0.01%. Packaging and Traceability: The product is packaged in moisture-proof and sealed bags. Each bag is labeled with the product name, batch number, filling amount, and production date. ≥2kg of each batch is retained for a shelf life of ≥1 year. The entire process is traceable.

[0039] Molding adaptation parameters In this embodiment, when the finished composite material is used for injection molding of home appliance frames, it needs to be vacuum dried at 110°C and vacuum degree ≥0.09MPa for 2.5h before molding. After drying, the particle moisture content is ≤0.03%. The injection molding temperature gradient is 230°C in zone 1 of the barrel, 240°C in zone 2, 250°C in zone 3, 245°C in the nozzle, 65°C in the mold, and 90MPa in the injection pressure.

[0040] Example 3: High-filled calcium carbonate-based polycarbonate composite material for high-rigidity structural components with 78% filler content Formula composition The composite material in this embodiment, based on a total mass of 100 parts, has the following specific formulation: Bisphenol A type polycarbonate: 17 parts, weight average molecular weight 31,000, molecular weight distribution index 1.9; PC-polysiloxane copolymer: 4 parts, siloxane unit mass fraction 20%; modified calcium carbonate filler: 78 parts, prepared by ternary particle size distribution and physical-chemical dual interface modification; core-shell toughening agent: 0.5 parts, particle size 60nm; interface compatibilizer: 0.3 parts; zinc stearate: 0.15 parts, purity ≥99%; composite antioxidant: 0.05 parts, antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1.

[0041] Modified calcium carbonate filler parameters The ternary particle size distribution scheme of modified calcium carbonate filler (based on 100% of the total filler mass) is as follows: 75% heavy calcium carbonate of 800 mesh + 15% ultrafine calcium carbonate of 1500 mesh + 10% nano calcium carbonate of 3000 mesh. After gradation, the packing void ratio is ≤25%, which meets the rigid control requirements: D50 of main filler / D50 of medium filler ≥5:1, D50 of medium filler / D50 of micro filler ≥3:1, and D50 of main filler / D50 of micro filler ≥15:1.

[0042] Physicochemical dual-interface modification parameters of modified calcium carbonate filler: Physical coating modification: The amount of stearic acid added is 1.2% of the total mass of calcium carbonate filler; Chemical grafting modification: The composite coupling agent is KH-550 silane coupling agent and NDZ-101 titanate coupling agent in a mass ratio of 2:1. The addition amount is 1.5% of the total mass of calcium carbonate filler. After modification, the activity degree of the filler is ≥95% and the water contact angle is ≥100°.

[0043] Preparation method The composite material preparation method in this embodiment is strictly implemented according to the standardized steps of the entire process disclosed in this invention, as follows: S1 Raw Material Pretreatment Process Matrix resin drying: A vacuum drying oven was used at a temperature of 120℃ and a vacuum degree of ≥0.09MPa for 5.5 hours. After drying, the moisture content of the resin was ≤0.02%, with no clumping or yellowing. Drying of calcium carbonate filler: A vacuum drying oven is used at a temperature of 80℃ for 3 hours (extended to 3 hours for nano-calcium). After drying, the moisture content of the filler is ≤0.05%, and there is no agglomeration or clumping. Additive pretreatment: All additives are screened through an 80-mesh sieve to remove impurities and lumps, and stored in a sealed environment at 24℃ and relative humidity ≤60%, with an effective ingredient content ≥99%.

[0044] S2 packing gradation and dual-interface modification process Accurate weighing: According to the above ternary gradation scheme, use an electronic balance with an accuracy of 0.01g to weigh calcium carbonate fillers of various specifications. The weighing error is ≤±0.2%. A double-checking system of "one person weighing and one person checking" is implemented. Physical coating modification: The weighed filler is added to a high-speed mixer with a jacketed temperature control system, preheated to 80°C, and a preset amount of stearic acid is added. The mixture is first mixed at a low speed of 300 rpm for 3 minutes to achieve initial dispersion, and then mixed at a high speed of 800 rpm for 10 minutes to achieve uniform coating. The activation degree of the modified filler is ≥90%. Chemical grafting modification: The physically coated filler is heated to 109℃, and a composite coupling agent diluted 1:1 with anhydrous ethanol is sprayed by atomization. The mixture is mixed at high speed of 800rpm for 19min to ensure complete grafting reaction. After completion, the mixture is cooled to below 40℃ and discharged to obtain modified calcium carbonate filler.

[0045] S3 Formula Precision Mixing Process Premixing of matrix and additives: Use an independent high-speed mixer (separate from the filler modification equipment to avoid cross-contamination) to add the pretreated matrix resin, core-shell toughening agent, interface compatibilizer, zinc stearate and composite antioxidant to the equipment and mix at a medium speed of 500 rpm for 4.5 min until the mixture is free of stratification, lumps and has a uniform color. Final mixing: Strictly follow the feeding sequence of "adding the premixed resin-additive system first, then adding the modified filler". First, mix at a low speed of 300 rpm for 2 minutes to achieve initial fusion, and then mix at a medium speed of 500 rpm for 3 minutes to achieve uniform dispersion. After mixing, complete the extrusion process within 24 hours.

[0046] S4 Low-shear high-dispersion compounding, extrusion, and granulation process Internal mixing and premixing plasticizing: The mixture is fed into an internal mixer with a precise temperature control system. It adopts a gradient heating design with the top nut at 200°C, the mixing chamber at 210°C, and the rotor at 220°C. The rotation speed is 45 rpm (low shear design to avoid filler breakage and resin degradation). The mixing time is 8 minutes. After mixing, the melt has no visible filler agglomeration or unplasticized particles, and the torque fluctuation is ≤±5%. Reciprocating compounding extrusion granulation: The premixed and plasticized material is fed into a reciprocating compounding extruder with a length-to-diameter ratio of 20:1. The temperature gradient is 220℃ in zone 1, 230℃ in zone 2, 240℃ in zone 3, 235℃ in zone 4, and 230℃ at the die head. The rotation speed is 90 rpm, and the vacuum degree is ≥0.08MPa, which effectively removes volatiles and moisture from the melt. Underwater pelleting is adopted, and the pelleting speed and extrusion rate are precisely matched to obtain 3×3mm composite particles with a size deviation of ≤±0.2mm.

[0047] S5 Particle Post-processing and Quality Control Process Screening: The composite particles are screened using an 80-mesh vibrating screen to remove fragments, impurities, and particles that do not meet the size requirements; Drying and cooling: Dry with hot air at 80℃ for 2 hours to remove surface moisture, then cool naturally to 24℃. The finished particles have a moisture content of ≤0.05% and an impurity content of ≤0.01%. Packaging and Traceability: The product is packaged in moisture-proof and sealed bags. Each bag is labeled with the product name, batch number, filling amount, and production date. ≥2kg of each batch is retained for a shelf life of ≥1 year. The entire process is traceable.

[0048] Molding adaptation parameters In this embodiment, when the finished composite material is used for injection molding of high-rigidity, low-load structural parts, it needs to be vacuum dried at 110°C and vacuum degree ≥0.09MPa for 3 hours before molding. After drying, the particle moisture content is ≤0.03%. The injection molding temperature gradient is 230°C in zone 1 of the barrel, 240°C in zone 2, 250°C in zone 3, 245°C in the nozzle, 75°C in the mold, and 110MPa in the injection pressure.

[0049] Comparative Example 1: 55% filler composite material without graded distribution or dual modification The formulation of this comparative example is the same as that of Example 1, except that the calcium carbonate is a single 1500 mesh unmodified calcium carbonate, without ternary gradation and without physical-chemical dual interface modification; the preparation method is the same as that of Example 1.

[0050] Comparative Example 2: 68% filler composite material with no gradation The formulation of this comparative example is the same as that of Example 2, except that the calcium carbonate is a single 1250 mesh calcium carbonate, modified only by a single KH-550 coupling agent, and there is no ternary gradation; the preparation method is the same as that of Example 2.

[0051] Comparative Example 3: 78% filler composite material produced by conventional twin-screw extrusion The formulation of this comparative example is the same as that of Example 3, except that the preparation method uses a conventional twin-screw extruder, without a mixing and pre-mixing process, and without a low-shear high-dispersion process design; the remaining steps are the same as those of Example 3.

[0052] The composite materials of the above embodiments and comparative examples were subjected to performance tests according to current national standards, and the test results are shown in the table below: Test conclusion: The composite material of the present invention, with an ultra-high filling content of 50%~80%, simultaneously achieves high rigidity, high toughness and excellent processing flowability. The batch stability is significantly better than that of the comparative example, which completely solves the four major industry pain points of high filling system and fully meets the usage requirements of plastic-based steel industrial structural components.

[0053] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A highly filled calcium carbonate-based polycarbonate composite material and its preparation method, characterized in that, The total number of parts by weight is 100, including the following components: 20-50 parts of matrix resin, 50-80 parts of modified calcium carbonate filler, 3-8 parts of core-shell toughening agent, 2-3 parts of interface compatibilizer, 2-5 parts of processing aid, and 0.5-1 parts of composite antioxidant. The modified calcium carbonate filler is prepared by ternary particle size distribution and physical-chemical dual interface modification. The ternary particle size distribution adopts the scheme of "large particles build the skeleton, medium particles fill the gaps, and small particles fill the voids". The porosity after gradation is ≤25%. The physical-chemical dual interface modification is to first passivate the hydroxyl groups on the filler surface by physical coating with stearic acid, and then chemically graft them through a compound system of KH-550 silane coupling agent and NDZ-101 titanate coupling agent to form stable Si-O-Ca chemical bonds on the filler surface. After modification, the filler activation degree is ≥95% and the water contact angle is ≥100°.

2. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 1, characterized in that, The entire process includes the following steps: S1 Raw material pretreatment: The matrix resin, calcium carbonate filler, and additives are dried or screened for pretreatment. S2 Filler gradation and dual interface modification: Calcium carbonate filler is weighed according to a ternary gradation scheme, first physically modified by stearic acid coating, and then chemically modified by composite coupling agent grafting to obtain modified calcium carbonate filler. S3 Precise formulation mixing: The pretreated matrix resin and each additive are premixed, and then the modified calcium carbonate filler is added for final mixing. S4 Low-shear high-dispersion compounding, extrusion, and granulation: The compound particles are sequentially subjected to internal mixing, premixing, plasticizing, and reciprocating compounding, extrusion, and granulation to obtain composite particles. S5 Particle post-treatment and quality control: The composite particles are screened, dried, cooled, packaged, and traceable.

3. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 1, characterized in that, The matrix resin is composed of bisphenol A type polycarbonate and PC-polysiloxane copolymer in a mass ratio of (3~4):1; wherein the weight average molecular weight of bisphenol A type polycarbonate is 28,000~32,000 and the molecular weight distribution index is 1.8~2.2; and the mass fraction of siloxane units in PC-polysiloxane copolymer is 15%~20%.

4. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 2, characterized in that, In the physical-chemical dual interface modification, the amount of stearic acid added is 0.8%~1.2% of the total mass of calcium carbonate filler; the compound coupling agent is KH-550 and NDZ-101 compounded at a mass ratio of 2:1, and the amount added is 0.8%~1.5% of the total mass of calcium carbonate filler.

5. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 2, characterized in that, In the pretreatment of the S1 raw materials, the matrix resin is dried in a vacuum drying oven at 120℃ and a vacuum degree ≥0.09MPa for 4~6 hours, and the moisture content after drying is ≤0.02%; the calcium carbonate filler is dried in a vacuum drying oven at 80℃ for 2~3 hours, and the drying time of nano-calcium is extended to 3 hours, and the moisture content after drying is ≤0.05%; the additives are screened through an 80-mesh sieve and stored in a sealed environment at 20~25℃ and relative humidity ≤60%.

6. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 1, characterized in that, The physical coating modification in S2 specifically involves: adding the filler to a high-speed mixer with a jacketed temperature control system, preheating it to 80°C, adding stearic acid, mixing at a low speed of 300 rpm for 3 minutes, and then mixing at a high speed of 800 rpm for 10 minutes; the chemical grafting modification specifically involves: heating the physically coated filler to 105~110°C, atomizing and spraying a compound coupling agent diluted 1:1 with anhydrous ethanol, mixing at a high speed of 800 rpm for 15~20 minutes, and cooling it to below 40°C before discharging.

7. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 6, characterized in that, The ternary particle size distribution scheme, based on 100% of the total filler mass, corresponds to the following different filling amounts: when the filling amount is 50%~60%, it consists of 60%~70% 1500 mesh spherical calcium carbonate + 20%~30% 3000 mesh nano calcium carbonate + 5%~15% 5000 mesh nano calcium carbonate; when the filling amount is 65%~70%, it consists of 65%~75% 1250 mesh ultrafine calcium carbonate + 20%~30% 3000 mesh nano calcium carbonate + 3%~8% 5000 mesh nano calcium carbonate; when the filling amount is 75%~80%, it consists of 70%~80% 800 mesh heavy calcium carbonate + 10%~20% 1500 mesh ultrafine calcium carbonate + 5%~15% 3000 mesh nano calcium carbonate.

8. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 7, characterized in that, The rigid control requirements for the ternary particle size distribution are: main packing D50 / medium packing D50 ≥ 5:1, medium packing D50 / micro packing D50 ≥ 3:1, and main packing D50 / micro packing D50 ≥ 15:

1.

9. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 2, characterized in that, In S4, the internal mixing and plasticizing process uses a gradient heating method: top bolt 200℃, mixing chamber 210℃, rotor 220℃, rotation speed 30~50rpm, mixing time 5~8min. The reciprocating mixing extrusion granulation uses a reciprocating mixing extruder with a length-to-diameter ratio of 20:1, with a temperature gradient of zone 1 220℃, zone 2 230℃, zone 3 240℃, zone 4 235℃, die head 230℃, rotation speed 50~100rpm, vacuum degree ≥0.08MPa, and underwater pelletizing to obtain 3×3mm composite particles with a size deviation ≤±0.2mm.

10. The highly filled calcium carbonate-based polycarbonate composite material and its preparation method according to claim 1, characterized in that, The core-shell toughening agent has a particle size of 50-100 nm, the core layer is a butadiene elastomer, and the shell layer is a methyl methacrylate polar monomer; the interface compatibilizer is a maleic anhydride-grafted polyolefin compatibilizer; the processing aid is zinc stearate with a purity ≥99%; and the composite antioxidant is antioxidant 1010 and antioxidant 168 compounded in a mass ratio of 1:1.

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