Method for preparing high aspect ratio wollastonite reinforcing filler powder in an oriented flow field and applications thereof

Abstract

The application belongs to the technical field of inorganic filler materials, and particularly relates to a directional flow field preparation method of high-aspect-ratio wollastonite reinforced filler powder and application thereof. The directional flow field preparation method of high-aspect-ratio wollastonite reinforced filler powder comprises the following steps: S1, turning on a heater to control the temperature to be 100-110 DEG C and preheating for 5-10 min; S2, opening an outlet valve of a steam generator and adjusting the medium pressure to be 0.5-0.6 MPa for 100-120 s; S3, uniformly feeding 0.2-0.3 kg of wollastonite raw materials within 8-10 min, and performing directional flow field crushing treatment through a steam kinetic energy mill to obtain high-aspect-ratio wollastonite reinforced filler powder. The high-aspect-ratio wollastonite reinforced filler powder is prepared through the directional flow field, and is added into a PP matrix as a reinforced filler to effectively improve the mechanical properties of the composite material.

Description

Technical Field

[0001] This invention belongs to the field of inorganic filler materials technology, specifically relating to a method for preparing directional flow field of high aspect ratio wollastonite reinforced filler powder and its application. Background Technology

[0002] Wollastonite, as a functional inorganic filler, exhibits significant reinforcing and toughening effects in polypropylene composites. Its application effectiveness largely depends on the particle size, particle size distribution, and particle morphology of the wollastonite powder. Ultrafine grinding of wollastonite aims to control particle size while maintaining long fibrous structures. Based on different grinding principles, it can be divided into three main categories: mechanical impact grinding, stirred mill grinding, and air jet milling. Mechanical impact grinding and stirred mill grinding rely on high-speed impact between the medium and particles, which easily leads to radial fracture of needle-like crystals and a significant decrease in the aspect ratio, making them only suitable for preparing wollastonite with low aspect ratios. Fluidized bed air jet milling, on the other hand, relies on self-grinding collisions between particles to achieve grinding, with a gentler impact that maximizes the protection of the needle-like crystal structure, making it the mainstream equipment for preparing wollastonite with high aspect ratios.

[0003] Wollastonite crystals exhibit significant anisotropy. Axial impact crushing readily induces dissociation along cleavage planes, maintaining or even increasing the aspect ratio; conversely, radial impact crushing tends to cause transverse fracture, drastically reducing the aspect ratio. Therefore, to achieve high aspect ratio wollastonite, particles must primarily undergo axial collisions and friction within the flow field, minimizing high-speed radial impacts. Steam kinetic energy milling technology, using superheated steam as the pulverizing medium, has become a research hotspot in recent years, attracting widespread attention from both academia and industry. The basic principle of this technology is similar to that of traditional air jet mills, both utilizing high-speed airflow to cause material collisions and shearing for pulverization. However, the unique feature of steam kinetic energy mills lies in using high-temperature, high-pressure superheated steam as the power source. Under the same pressure conditions, superheated steam can generate higher airflow velocities and stronger pulverizing energy, significantly improving the pulverization efficiency of materials.

[0004] Therefore, how to prepare high aspect ratio wollastonite reinforcing filler powder through directional flow field and add it as a reinforcing filler to PP matrix, thereby improving the mechanical properties of polypropylene composites by means of the high aspect ratio of the filler, has become a key research direction. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing high aspect ratio wollastonite reinforced filler powder using a directional flow field and its application. The method comprises the following steps: S1, System preheating: The heater is turned on, the temperature is controlled at 100-110℃, and preheating is performed for 5-10 minutes; S2, Operating condition control: The outlet valve of the steam generator is opened, and the medium pressure is adjusted to 0.5-0.6 MPa and maintained for 100-120 seconds; S3, Filler pulverization: 0.2-0.3 kg of wollastonite raw material is uniformly added within 8-10 minutes, and directional flow field pulverization is performed using a steam kinetic energy mill to obtain high aspect ratio wollastonite reinforced filler powder. This invention, through the control of airflow pressure, steam temperature, and classification frequency, combined with the jet flow, ensures that the prepared wollastonite reinforced filler powder has an aspect ratio ≥20, enabling its effective application in polypropylene composite materials.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for preparing a directional flow field of wollastonite-reinforced filler powder with a high aspect ratio, comprising the following steps: S1. System preheating: Turn on the heater and control the temperature to 100~110℃ and preheat for 5~10 minutes; S2, Operating Condition Control: Open the steam generator outlet valve and adjust the medium pressure to 0.5~0.6MPa and maintain it for 100~120s; S3. Filler crushing: 0.2-0.3 kg of wollastonite raw material is uniformly added within 8-10 min and crushed by directional flow field through a steam kinetic energy mill to obtain wollastonite reinforced filler powder with high aspect ratio. S4. Powder testing: The particle size distribution and microstructure of the high aspect ratio wollastonite reinforced filler powder described in step S3 are tested.

[0007] As a preferred technical solution of the present invention, the heater mentioned in step S1 is model DXGD-15, rated voltage 380V, and rated power 15kW.

[0008] In this invention, a cryogenic fluid enters the heater through a delivery pipeline under pressure. The fluid flows orderly along a customized heat exchange channel, continuously absorbing heat generated by the heating element to raise its own temperature, ultimately bringing the fluid medium at the heater outlet to the specified process temperature. Temperature sensors in the system collect the medium temperature signal in real time and transmit it to the control system. The control system automatically adjusts the output power of the heating unit based on the feedback data, thereby achieving precise control of the medium temperature and ensuring uniform and stable temperature throughout the process.

[0009] As a preferred embodiment of the present invention, the steam generator in step S2 has a nominal steam production capacity of 50 kg / h, a rated water storage capacity of 14 L, a nominal power of 36 kW, a rated working pressure of 0.7 MPa, and a steam temperature of 220 °C.

[0010] The steam generator of this invention is equipped with a built-in electrode probe, which can automatically control the start and stop of the water supply pump, thereby adjusting the heating water volume and working time. An electric heating tube is installed inside the inner tank to continuously heat and generate steam; a pressure gauge at the top of the equipment provides real-time feedback of the steam pressure value, and the overall operating status of the machine is simultaneously displayed by indicator lights on the outside of the housing.

[0011] As a preferred embodiment of the present invention, the steam kinetic mill in step S3 is composed of a grinding chamber and a classifying mechanism; the nozzle inlet pressure of the grinding chamber is 0.55 MPa, and the frequency of the classifying mechanism is 60 Hz.

[0012] This invention utilizes a high-speed airflow generated by supersonic nozzles to pulverize powder particles through collisions. The pulverized material then ascends into a forced vortex classifier for sorting. Qualified powder is collected by a dust collector, while unqualified material is returned to the pulverizer for further pulverization. The classified and collected particles are discharged from the discharge port via a pulse jet cleaning mechanism. This invention employs a metal cartridge dust collector.

[0013] As a preferred technical solution of the present invention, the steam kinetic energy mill in step S3 adopts a two-jet flow or a three-jet flow.

[0014] As an inorganic filler, wollastonite's influence on composite material properties is not solely determined by particle size; the aspect ratio is a more critical control factor. Different grinding processes can significantly alter the aspect ratio of wollastonite, thereby affecting its synergistic effect in the matrix. Even with finer particle size, a substantial decrease in the aspect ratio will result in the loss of the core advantages of fiber reinforcement.

[0015] As a preferred embodiment of the present invention, the steam kinetic energy mill preferably employs a jet flow.

[0016] The steam-powered mill of this invention preferably uses a counter-jet flow. Under the action of the counter-jet flow, the particle size is refined through crushing. The wollastonite particles mainly exhibit long columnar and needle-like morphologies with significantly higher aspect ratios and clear crystal cleavage planes. Some particles show fibrous extension structural features. This indicates that the flow field of the counter-jet flow tends to selectively break up wollastonite along its cleavage planes, effectively preserving its intrinsic morphology of high aspect ratio while achieving particle refinement. Under the action of a triple-jet flow, the wollastonite particle size is further reduced, the aspect ratio is significantly decreased, the needle-like / fibrous structures are shorter, the proportion of high aspect ratio particles is greatly reduced, and more irregularly broken particle fragments are visible. This is because the triple-jet flow constructs a stronger and more complex turbulent field in the crushing chamber, significantly increasing the collision frequency and shear intensity between particles and jets, and between particles. This leads to more complete cleavage fracture of the wollastonite crystals, and the long columnar structure is excessively broken into short rod-shaped or irregular particles, sacrificing the key morphological feature of aspect ratio.

[0017] As a preferred embodiment of the present invention, the particle size range of the wollastonite raw material in step S3 is 2~100μm, D 10 4~8μm, D 50 20~30μm, D 90 Its size is 80~90μm, and its density is 2840~2860kg / m³. 3 .

[0018] This invention selects wollastonite raw materials with a particle size range of 2~100μm. The feed particle size of commonly used large air jet mills is below 500μm. However, in small air jet mills, when the particle size is too large, the acceleration and fluidization effect is poor, which affects the grinding efficiency. Therefore, the acceleration effect of particles larger than 100μm is not good.

[0019] As a preferred technical solution of the present invention, in the particle size distribution test of the high aspect ratio wollastonite reinforced filler powder in step S4, the aspect ratio of the wollastonite reinforced filler powder is ≥20.

[0020] The second aspect of the present invention provides the application of high aspect ratio wollastonite reinforcing filler powder prepared by the method described in the first aspect in polypropylene composite materials. The preparation method of the polypropylene composite material includes the following steps: by weight, 77-88 parts of polypropylene, 10-20 parts of high aspect ratio wollastonite reinforcing filler powder and 2-3 parts of maleic anhydride-grafted polypropylene are added to an internal mixer and mixed at 500-600 r / min for 15-25 min at 200-210°C. Then, the mixture is transferred to a flat vulcanizing press and hot-pressed at 180-185°C for 10-12 min to obtain the polypropylene composite material.

[0021] As a preferred embodiment of the present invention, the tensile strength of the polypropylene composite material is ≥37MPa and the flexural strength is ≥55MPa.

[0022] This invention prepares high aspect ratio wollastonite reinforcing filler powder through directional flow field. When applied to polypropylene composites, the high aspect ratio wollastonite easily forms a three-dimensional needle-like network structure in the PP matrix, transferring interfacial stress. Moreover, it has a large specific surface area and a large contact area with the PP matrix, effectively dispersing and dissipating external loads, significantly improving the mechanical properties of polypropylene composites, and providing a new technical approach for the development of high-performance polypropylene materials.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The preferred steam temperature of the present invention is 220°C, at which the aspect ratio reaches its peak. When the steam temperature is 180°C, the steam kinetic energy is weak and it is difficult to achieve sufficient cleavage and dispersion of wollastonite. When the temperature rises to 260°C, although the crushing power is significantly improved, wollastonite will be excessively crushed by high-speed impact. 220°C can balance the steam kinetic energy output and the thermal stability of wollastonite.

[0024] (2) The preferred nozzle inlet pressure of this invention is 0.55 MPa, under which the aspect ratio of wollastonite reaches its peak. When the pressure drops to 0.45 MPa, the steam kinetic energy is insufficient, the wollastonite cleavage is incomplete, and the aspect ratio is too small. When the pressure rises to 0.65 MPa, the impact load is too large, the needle-like crystals break, and the aspect ratio decreases accordingly. The classifier frequency is the core factor in maintaining the needle-like structure of wollastonite. The aspect ratio of the product under 60 Hz is much better than that under 30 Hz. This is because increasing the classifier frequency can enhance the sorting effect and effectively reduce the phenomenon of over-crushing of materials.

[0025] (3) The jet flow center region of the present invention is a concentrated collision and rapid diffusion mode. The collision trajectory is simple and the residence time is short, avoiding repeated friction and shearing. The direct collision of the jet flow is more inclined to disintegrate the aggregates of wollastonite rather than destroy the needle-shaped crystals themselves, reducing the risk of crystal bending and breakage, and better maintaining the original needle-shaped morphology and high aspect ratio of wollastonite. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a physical diagram of the directional flow field processing system of the present invention.

[0028] Figure 2 This is a SEM image of wollastonite-reinforced filler powder prepared by jet flow in Example 1 of the present invention.

[0029] Figure 3 This is a SEM image of the wollastonite raw material of Comparative Example 1 of the present invention.

[0030] Figure 4 This is a SEM image of the wollastonite-reinforced filler powder prepared by the three-jet flow method in Comparative Example 2 of the present invention.

[0031] Figure 5 The aspect ratios of the wollastonite reinforced filler powder prepared by jet flow in Example 1 of the present invention, the wollastonite raw material in Comparative Example 1, and the wollastonite reinforced filler powder prepared by three jet flow in Comparative Example 2 are shown. Detailed Implementation

[0032] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0033] Example 1 This embodiment provides a method for preparing a directional flow field of wollastonite-reinforced filler powder with high aspect ratio, including the following steps: S1. System preheating: Turn on the heater (model DXGD-15, rated voltage 380V, rated power 15kW), control the temperature to 100℃ and preheat for 10 minutes.

[0034] S2. Operating Condition Control: Open the outlet valve of the steam generator (nominal steam output of 50kg / h, rated water storage of 14L, nominal power of 36kW, and rated working pressure of 0.7MPa) and adjust the medium pressure to 0.6MPa and maintain it for 100s; control the steam temperature to 220℃.

[0035] S3. Filler crushing: Evenly add 0.3 kg of wollastonite raw material (D) within 10 minutes. 10 It is 4.55μm, D 50 It is 27.86 μm, D 90 Its diameter is 83.53 μm and its density is 2850 kg / m³. 3 The powder is pulverized by a steam-powered mill in a directional flow field to obtain wollastonite-reinforced filler powder with a high aspect ratio. The steam-powered mill consists of a pulverizing chamber and a classifying mechanism. The nozzle inlet pressure of the pulverizing chamber is 0.55 MPa, and the frequency of the classifier is 60 Hz. The steam-powered mill adopts a jet flow.

[0036] S4. Powder testing: The particle size distribution of the high aspect ratio wollastonite reinforced filler powder described in step S3 was tested. The aspect ratio of the wollastonite reinforced filler powder was 21.15.

[0037] Example 2 This embodiment provides a method for preparing a directional flow field of wollastonite-reinforced filler powder with high aspect ratio, including the following steps: S1. System preheating: Turn on the heater (model DXGD-15, rated voltage 380V, rated power 15kW), control the temperature to 110℃ and preheat for 5 minutes.

[0038] S2. Operating Condition Control: Open the outlet valve of the steam generator (nominal steam output of 50kg / h, rated water storage of 14L, nominal power of 36kW, and rated working pressure of 0.7MPa) and adjust the medium pressure to 0.5MPa and maintain it for 120s; control the steam temperature to 220℃.

[0039] S3. Filler crushing: Evenly add 0.2 kg of wollastonite raw material (D) within 8 minutes. 10 It is 4.55μm, D 50 It is 27.86 μm, D 90 Its diameter is 83.53 μm and its density is 2850 kg / m³. 3 The powder is pulverized by a steam-powered mill in a directional flow field to obtain wollastonite-reinforced filler powder with a high aspect ratio. The steam-powered mill consists of a pulverizing chamber and a classifying mechanism. The nozzle inlet pressure of the pulverizing chamber is 0.55 MPa, and the frequency of the classifier is 60 Hz. The steam-powered mill adopts a jet flow.

[0040] S4. Powder testing: The particle size distribution of the high aspect ratio wollastonite reinforced filler powder described in step S3 was tested. The aspect ratio of the wollastonite reinforced filler powder was 20.08.

[0041] Example 3 This embodiment provides a method for preparing a directional flow field of wollastonite-reinforced filler powder with high aspect ratio, including the following steps: S1. System preheating: Turn on the heater (model DXGD-15, rated voltage 380V, rated power 15kW), control the temperature to 105℃ and preheat for 8 minutes.

[0042] S2. Operating Condition Control: Open the outlet valve of the steam generator (nominal steam output of 50kg / h, rated water storage of 14L, nominal power of 36kW, and rated working pressure of 0.7MPa) and adjust the medium pressure to 0.55MPa and maintain it for 110s; control the steam temperature to 220℃.

[0043] S3, Filler Crushing: 0.25 kg of wollastonite raw material (D) is uniformly added within 9 minutes. 10 It is 4.55μm, D 50 It is 27.86 μm, D 90 Its diameter is 83.53 μm and its density is 2850 kg / m³. 3The powder is pulverized by a steam-powered mill in a directional flow field to obtain wollastonite-reinforced filler powder with a high aspect ratio. The steam-powered mill consists of a pulverizing chamber and a classifying mechanism. The nozzle inlet pressure of the pulverizing chamber is 0.55 MPa, and the frequency of the classifier is 60 Hz. The steam-powered mill adopts a jet flow.

[0044] S4. Powder testing: The particle size distribution of the high aspect ratio wollastonite reinforced filler powder described in step S3 was tested. The aspect ratio of the wollastonite reinforced filler powder was 20.11.

[0045] Comparative Example 1 This comparative example uses wollastonite raw material with a minimum aspect ratio of 4.34.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that a three-jet stream is used instead of the jet stream. Comparative Example 3 The difference between this comparative example and Example 1 is that the frequency of the classifier is changed to 30Hz.

[0047] Comparative Example 4 The difference between this comparative example and Example 1 is that the nozzle inlet pressure of the pulverizing chamber is changed to 0.45 MPa.

[0048] Comparative Example 5 The difference between this comparative example and Example 1 is that the nozzle inlet pressure of the pulverizing chamber is changed to 0.65 MPa.

[0049] Comparative Example 6 The difference between this comparative example and Example 1 is that the steam temperature of the steam generator is 180°C.

[0050] Comparative Example 7 The difference between this comparative example and Example 1 is that the steam temperature of the steam generator is 260°C.

[0051] The performance of the wollastonite powder provided in the above embodiments and comparative examples was tested. The particle samples were imaged and scanned using a ZEISS Sigma 300. The scanned images were processed and dimensionally calibrated using Nano Measurer software, and the aspect ratio of each particle was measured and calculated.

[0052] The performance test data are shown in Table 1.

[0053] Table 1 Performance test results of wollastonite powder

[0054] Compared to Example 1, Comparative Example 1 used wollastonite as raw material, which had the lowest aspect ratio of 4.34 (Comparative Example 1); compared to Example 1, a three-jet flow was used instead of a single-jet flow. Because the three-jet flow resulted in more complete wollastonite crystal fragmentation, the aspect ratio of the filler powder decreased to a minimum (Comparative Example 2); compared to Example 1, the classifier frequency was changed to 30Hz. Because the low frequency caused over-grinding of the wollastonite, the aspect ratio of the filler powder decreased to a minimum (Comparative Example 3); compared to Example 1, the nozzle inlet pressure of the grinding chamber was changed to 0.45MPa. Because insufficient steam kinetic energy led to insufficient wollastonite cleavage and a low aspect ratio, the filler powder... The length-to-diameter ratio decreased to the lowest level in Comparative Example 4; compared with Example 1, the nozzle inlet pressure of the pulverizing chamber was changed to 0.65 MPa, and the length-to-diameter ratio of the filler powder decreased to the lowest level due to the excessive impact strength causing the needle-like structure to break (Comparative Example 5); compared with Example 1, the steam temperature of the steam generator was 180°C, and the length-to-diameter ratio of the filler powder decreased to the lowest level due to the insufficient steam kinetic energy preventing the cleavage dispersion of wollastonite (Comparative Example 6); compared with Example 1, the steam temperature of the steam generator was 260°C, and the length-to-diameter ratio of the filler powder decreased to the lowest level due to the greater pulverizing power provided by the high temperature causing excessive breakage (Comparative Example 7).

[0055] Application Example 1 This application example provides a polypropylene composite material prepared according to the following steps: 88 parts by weight of polypropylene, 10 parts by weight of the high aspect ratio wollastonite reinforcing filler powder prepared in Example 1, and 2 parts by weight of maleic anhydride-grafted polypropylene are added to a mixer and mixed at 600 r / min for 15 min at 210°C. Then, the mixture is transferred to a flat vulcanizing machine and hot-pressed at 185°C for 10 min to obtain the polypropylene composite material.

[0056] Application Example 2 This application example uses pure polypropylene material.

[0057] Application Example 3 This application example provides a polypropylene composite material prepared according to the following steps: 88 parts by weight of polypropylene, 10 parts by weight of the high aspect ratio wollastonite reinforcing filler powder prepared in Comparative Example 2, and 2 parts by weight of maleic anhydride-grafted polypropylene are added to a mixer and mixed at 600 r / min for 15 min at 210°C. Then, the mixture is transferred to a flat vulcanizing press and hot-pressed at 185°C for 10 min to obtain the polypropylene composite material.

[0058] The polypropylene material provided in the above application example was subjected to performance tests. The tensile test was conducted in accordance with the requirements of GB / T 1040.2-2022 Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics. The flexural test was conducted in accordance with the requirements of GB / T 9341-2008 Determination of flexural properties of plastics.

[0059] The performance test data above are shown in Table 2.

[0060] Table 2 Test Results of Polypropylene Material Properties

[0061] Application Example 1 incorporates wollastonite reinforcing filler powder with an aspect ratio of 21.15, as described in Embodiment 1 of the present invention. The high aspect ratio wollastonite reinforcing filler powder forms a three-dimensional needle-like network structure in the PP matrix, which transmits stress through the interface. Furthermore, it has a large specific surface area and a large contact area with the PP matrix, which effectively disperses and dissipates the applied load, significantly improving the mechanical properties of the polypropylene composite material.

Claims

1. A method for preparing directional flow field of high aspect ratio wollastonite reinforced filler powder, characterized in that, Includes the following steps: S1. System preheating: Turn on the heater and control the temperature to 100~110℃ and preheat for 5~10 minutes; S2, Operating Condition Control: Open the steam generator outlet valve and adjust the medium pressure to 0.5~0.6MPa and maintain it for 100~120s; S3. Filler crushing: 0.2-0.3 kg of wollastonite raw material is uniformly added within 8-10 min and crushed by directional flow field through a steam kinetic energy mill to obtain wollastonite reinforced filler powder with high aspect ratio. S4. Powder testing: The particle size distribution and microstructure of the high aspect ratio wollastonite reinforced filler powder described in step S3 are tested.

2. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, The heater mentioned in step S1 is model DXGD-15, rated voltage 380V, and rated power 15kW.

3. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, The steam generator described in step S2 has a nominal steam production capacity of 50 kg / h, a rated water storage capacity of 14 L, a nominal power of 36 kW, a rated working pressure of 0.7 MPa, and a steam temperature of 220 °C.

4. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, The steam-powered mill in step S3 consists of a grinding chamber and a classifying mechanism; the nozzle inlet pressure of the grinding chamber is 0.55 MPa, and the frequency of the classifying mechanism is 60 Hz.

5. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, The steam kinetic mill described in step S3 uses either a two-jet or a three-jet flow.

6. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 5, characterized in that, The steam-powered mill preferably employs a jet flow.

7. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, The particle size range of the wollastonite raw material in step S3 is 2~100μm, D 10 4~8μm, D 50 20~30μm, D 90 Its size is 80~90μm, and its density is 2840~2860kg / m³. 3 .

8. The method for preparing a directional flow field of high aspect ratio wollastonite reinforced filler powder according to claim 1, characterized in that, In step S4, the aspect ratio of the high aspect ratio wollastonite-reinforced filler powder in the particle size distribution test is ≥20.

9. The application of a high aspect ratio wollastonite reinforcing filler powder prepared by the method according to any one of claims 1 to 8 in polypropylene composite materials, characterized in that, The preparation method of the polypropylene composite material includes the following steps: by weight, 77-88 parts of polypropylene, 10-20 parts of high aspect ratio wollastonite reinforcing filler powder and 2-3 parts of maleic anhydride-grafted polypropylene are added to an internal mixer and mixed at 500-600 r / min for 15-25 min at 200-210℃. Then, the mixture is transferred to a flat vulcanizing machine and hot-pressed at 180-185℃ for 10-12 min to obtain the polypropylene composite material.

10. The application of the high aspect ratio wollastonite reinforcing filler powder according to claim 9 in polypropylene composite materials, characterized in that, The tensile strength of the polypropylene composite material is ≥37MPa, and the flexural strength is ≥55MPa.

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