Preparation process of polypropylene microplastics

Abstract

The application provides a preparation process of polypropylene microplastics and belongs to the field of organic synthesis. The application induces the conversion of polypropylene to beta crystal polypropylene by using N,N'-dicyclohexyl terephthalamide nucleating agent, and the beta crystal has excellent toughness. Secondly, the nano-silicon dioxide is modified by 3-(methacryloyloxy) propyl trimethoxysilane. The methoxy group in the 3-(methacryloyloxy) propyl trimethoxysilane molecule is hydrolyzed to generate a hydroxyl group, which undergoes a dehydration condensation reaction with the silicon hydroxyl group on the surface of the nano-silicon dioxide, thereby reducing the surface polarity of the nano-silicon dioxide and facilitating the uniform dispersion of the nano-silicon dioxide in the polypropylene. The nano-silicon dioxide further strengthens the toughness of the polypropylene microplastics through the mode of interfacial interaction. Finally, the compatibility of carbon black and polypropylene is increased by modifying the carbon black with maleic anhydride, thereby improving the anti-aging ability of the polypropylene microplastics.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis and relates to a preparation process of polypropylene, specifically a preparation process of polypropylene microplastics. Background Technology

[0002] Polypropylene (PP) is a thermoplastic resin, one of the five major general-purpose plastics. It is widely used in various fields due to its advantages such as being non-toxic, odorless, lightweight (0.90 g / cm³, the lightest general-purpose plastic), easy to process, high impact strength, strong flexural strength, and good electrical insulation. Microplastic forms of polypropylene also have multiple applications. Polypropylene microplastics are food-grade plastics, commonly used to make food containers and packaging materials such as lunch boxes, water bottles, baby bottles, foam boxes, and PP plastic cups. Polypropylene microplastics can also be used to make woven plastic products, such as bulk bags, woven bags, food bags, and transparent bags. These products are widely used in the packaging of grains, fertilizers, and cement. Due to the non-toxic and high-temperature resistant properties of polypropylene microplastics, they are widely used in the manufacture of pipes for water supply and heating systems. Compared with PE pipes, PP pipes are lighter, easier to transport, and have better environmental performance and are recyclable. This makes PP pipes highly competitive in the market. Besides the main applications mentioned above, polypropylene microplastics are also used to manufacture various other products, such as medical devices, stationery, and sporting goods. These products also utilize the excellent properties of polypropylene, such as chemical resistance and ease of processing. In summary, polypropylene microplastics are widely used in various fields due to their many superior properties. However, polypropylene materials have poor toughness, aging resistance, and impact resistance, making the products prone to breakage and damage when subjected to external impacts. Therefore, improving the toughness of polypropylene microplastics can help expand their applications. Summary of the Invention

[0003] To address the above problems, this invention presents a process for preparing polypropylene microplastics, which specifically includes the following steps:

[0004] S1. Weigh 70-100g of polypropylene granules and 0.1-0.4g of N,N'-dicyclohexyl terephthalamide, melt-mix and blend evenly, then extrude into crude masterbatch using a single-screw extruder. The extrusion temperature and pressure are 200-260℃ and 10-16 MPa, respectively. The β-nucleation effect of N,N'-dicyclohexyl terephthalamide regulates the crystal form of polypropylene, thereby enhancing the toughness of polypropylene.

[0005] S2. Modified Nanoscale Silica: Anhydrous ethanol, deionized water, 3-(methacryloyloxy)propyltrimethoxysilane, and nanoscale silica were added to a three-necked flask in a mass ratio of 10:10:5:1. The mixture was stirred at room temperature to ensure uniform dispersion of the silica. The mixture was then microwaved to 50-80°C while simultaneously refluxing for 2-5 hours. After the reaction, the mixture was filtered through anhydrous ethanol to obtain a filter cake. The filter cake was then dried in a vacuum drying oven at 50-80°C for 8-14 hours. The dried filter cake was then ground to obtain modified silica powder. The mechanism of this step is that the methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of the nanoscale silica. This reduces the surface polarity of the nanoscale silica, decreases its agglomeration, and improves the compatibility between the nanoscale silica and polypropylene, thereby enhancing the dispersibility of the nanoscale silica in polypropylene. Nano-silica further enhances the toughness of polypropylene microplastics through interfacial interactions.

[0006] S3. Modified Carbon Black: Weigh 2-8g of carbon black and 6-12g of maleic anhydride and dissolve them in 100ml of acetone. Stir with a magnetic stirrer at room temperature for 1-2 hours. After stirring, vacuum filter the carbon black and dry it in an oven for 2-8 hours. Then, transfer the carbon black into a ceramic boat and place it in a muffle furnace at 160-220℃ for 1.5-3 hours to obtain maleic anhydride-grafted carbon black. Under high temperature, the anhydride groups in maleic anhydride react with the hydroxyl and carboxyl groups on the surface of carbon black to form ester bonds, thereby increasing the compatibility of carbon black with polypropylene.

[0007] S4. The masterbatch obtained in step S1, the modified nano-silica obtained in step S2, and the modified carbon black obtained in step S3 are mixed evenly in a ratio of 2:1:1, and then melt-extruded into granules on a twin-screw extruder at 200-350 rpm and 190-220℃. After the granules cool to room temperature, they are poured into a crusher and crushed at 600-900 rpm for 1-4 hours, using a 5 mm sieve aperture to ensure that they reach the microplastic level.

[0008] Preferably, 90g of polypropylene granules are weighed in step S1;

[0009] Preferably, the extrusion temperature in step S1 is 220°C;

[0010] Preferably, the extrusion pressure in step S1 is 12 MPa;

[0011] Preferably, the reflux reaction in step S2 lasts for 4 hours;

[0012] Preferably, 6g of carbon black is weighed in step S3;

[0013] Preferably, the heat preservation temperature in step S3 is 180°C;

[0014] Preferably, the twin-screw extruder rotates at 300 rpm in step S4;

[0015] Preferably, the extrusion temperature in step S4 is 200°C;

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention uses N,N'-dicyclohexyl terephthalamide nucleating agent to induce the transformation of polypropylene to β-crystalline polypropylene, which has excellent toughness.

[0018] This invention modifies nano-silica using 3-(methacryloyloxy)propyltrimethoxysilane. The methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of nano-silica. This reduces the surface polarity of the nano-silica, thus facilitating the uniform dispersion of nano-silica into polypropylene. The nano-silica further enhances the toughness of the polypropylene microplastics through interfacial interactions.

[0019] Maleic anhydride-modified carbon black increases the compatibility of carbon black with polypropylene, and its synergistic effect with modified nano-silica improves the anti-aging ability of polypropylene microplastics. Attached Figure Description

[0020] Figure 1 The tensile yield strength diagrams are for the polypropylene microplastic strips in Embodiment 1 and Comparative Examples 1-3 of the present invention.

[0021] Figure 2 This is a cross-sectional scanning electron microscope image of the polypropylene microplastic particles in Comparative Example 6 of the present invention.

[0022] Figure 3 This is a cross-sectional scanning electron microscope image of the polypropylene microplastic particles in Example 3 of the present invention.

[0023] Figure 4 The impact strength diagrams are for the polypropylene microplastic strips in Example 4 and Comparative Examples 7-9 of this invention. Detailed Implementation

[0024] The exemplary embodiments, features, and performance aspects of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] In this invention, the polypropylene particles are from Qingdao Juli New Energy Technology Co., Ltd., N,N'-dicyclohexyl terephthalamide is from Hubei Shuaiyan Ligao Biomedical Co., Ltd., 3-(methacryloyloxy)propyltrimethoxysilane is from Hubei Hengjingrui Chemical Co., Ltd., nano-sized silica is from Fujian Xinhe Nano Silicon Industry Co., Ltd., carbon black is from Jiangxi Black Cat Carbon Black Co., Ltd., and maleic anhydride is from Hubei Kewode Chemical Co., Ltd.

[0026] Example 1

[0027] S1. Weigh 70g of polypropylene granules and 0.1g of N,N'-dicyclohexyl terephthalamide, melt-mix and blend evenly, then extrude into crude masterbatch using a single-screw extruder. The extrusion temperature and pressure are 200℃ and 10MPa, respectively. The β-nucleation effect of N,N'-dicyclohexyl terephthalamide regulates the crystal form of polypropylene, thereby enhancing the toughness of polypropylene.

[0028] S2. Modified Nanoscale Silica: Anhydrous ethanol, deionized water, 3-(methacryloyloxy)propyltrimethoxysilane, and nanoscale silica were added to a three-necked flask in a mass ratio of 10:10:5:1. The mixture was stirred at room temperature to ensure uniform dispersion of the silica. The mixture was then microwaved to 50°C and refluxed for 2 hours. After the reaction, the mixture was filtered through anhydrous ethanol to obtain a filter cake. The filter cake was then dried in a vacuum drying oven at 50°C for 8 hours. The dried filter cake was then ground to obtain modified silica powder. The mechanism of this step is that the methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of nanoscale silica. This reduces the surface polarity of the nanoscale silica, decreases its agglomeration, and improves the compatibility between the nanoscale silica and polypropylene, thereby enhancing the dispersibility of the nanoscale silica in polypropylene. The nanoscale silica further strengthens the toughness of the polypropylene microplastics through interfacial interactions.

[0029] S3. Modified carbon black: Weigh 2g of carbon black and 6g of maleic anhydride and dissolve them in 100ml of acetone. Stir with a magnetic stirrer at room temperature for 1h. After stirring, vacuum filter the carbon black and dry it in an oven for 2h. Then transfer the carbon black into a ceramic boat and place it in a muffle furnace at 160℃ for 1.5h to obtain maleic anhydride-grafted carbon black.

[0030] S4. The masterbatch obtained in step S1, the modified nano-silica obtained in step S2, and the modified carbon black obtained in step S3 are mixed evenly in a ratio of 2:1:1 and then melt-extruded into granules on a twin-screw extruder at 200 rpm and 190°C. After the granules cool to room temperature, they are poured into a crusher and crushed at 600 rpm for 1 hour, using a 5 mm sieve aperture to ensure that they reach the microplastic level.

[0031] Comparative Example 1: Except for step S1, in which calcium carbonate was used instead of N,N'-dicyclohexyl terephthalamide, all other steps were the same as in Example 1.

[0032] Comparative Example 2: Except for step S1, in which calcium pimecronate was used instead of N,N'-dicyclohexyl terephthalamide, all other steps were the same as in Example 1.

[0033] Comparative Example 3: Except for step S1, in which sodium carboxylate was used instead of N,N'-dicyclohexyl terephthalamide, all other steps were the same as in Example 1.

[0034] The polypropylene microplastics prepared in Examples 1, 1, 2, and 3 were melt-extruded into strips with dimensions of 60mm*10mm*1mm. Tensile yield strength tests were conducted using a universal testing machine at room temperature and a traction rate of 1mm / min. The results are as follows: Figure 1 As shown, Figure 1 The main reason why the tensile yield strength of Comparative Example 1 is lower than that of Example 1 is that the β-nucleation induction efficiency of calcium carbonate is lower and it is not easy to disperse in polypropylene. The tensile strength of the polypropylene strips prepared in Comparative Examples 2 and 3 is lower than that of Example 1. The fundamental reason is that there is a hydrogen bonding interaction between N,N'-dicyclohexyl terephthalamide and the modified nano-silica, which further reduces the surface energy of nano-silica. The two work synergistically to promote the dispersion of nano-silica in polypropylene microplastics and improve the toughness of polypropylene microplastics.

[0035] Example 2

[0036] S1. Weigh 80g of polypropylene granules and 0.2g of N,N'-dicyclohexyl terephthalamide, melt-mix and blend evenly, then extrude into crude masterbatch using a single-screw extruder. The extrusion temperature and pressure are 220℃ and 12MPa, respectively. The β-nucleation effect of N,N'-dicyclohexyl terephthalamide regulates the crystal form of polypropylene, thereby enhancing the toughness of polypropylene.

[0037] S2. Modified Nanoscale Silica: Anhydrous ethanol, deionized water, 3-(methacryloyloxy)propyltrimethoxysilane, and nanoscale silica were added to a three-necked flask in a mass ratio of 10:10:5:1. The mixture was stirred at room temperature to ensure uniform dispersion of the silica. The mixture was then microwaved to 60°C and refluxed for 3 hours. After the reaction, the mixture was filtered through anhydrous ethanol to obtain a filter cake. The filter cake was then dried in a vacuum drying oven at 60°C for 10 hours. The dried filter cake was then ground to obtain modified silica powder. The mechanism of this step is that the methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of nanoscale silica. This reduces the surface polarity of the nanoscale silica, decreases its agglomeration, and improves the compatibility between the nanoscale silica and polypropylene, thereby enhancing the dispersibility of the nanoscale silica in polypropylene. The nanoscale silica further strengthens the toughness of the polypropylene microplastics through interfacial interactions.

[0038] S3. Modified carbon black: Weigh 4g of carbon black and 8g of maleic anhydride and dissolve them in 100ml of acetone. Stir with a magnetic stirrer at room temperature for 1.5h. After stirring, vacuum filter the carbon black and put it in an oven to dry for 4h. Then, transfer the carbon black into a porcelain boat and place it in a muffle furnace at 180℃ for 2h to obtain maleic anhydride-grafted carbon black.

[0039] S4. The masterbatch obtained in step S1, the modified nano-silica obtained in step S2, and the modified carbon black obtained in step S3 are mixed evenly in a ratio of 2:1:1 and then melt-extruded into granules on a twin-screw extruder at 250 rpm and 200°C. After the granules cool to room temperature, they are poured into a crusher and crushed at 700 rpm for 2 hours, using a 5 mm sieve aperture to ensure that they reach the microplastic level.

[0040] Comparative Example 4: Except for step S2, in which 3-(methacryloyloxy)propyltrimethoxysilane was not added, all other steps were the same as in Example 2.

[0041] Comparative Example 5: Except for step S2, in which ethylene glycol was used instead of 3-(methacryloyloxy)propyltrimethoxysilane, all other steps were the same as in Example 2.

[0042] The polypropylene microplastic particles prepared in Example 2, Comparative Example 4, and Comparative Example 5 were subjected to flattening tests. During the flattening test, the polypropylene microplastic particles were placed between two parallel plates and pressed down evenly with a press to observe whether they deformed. The press power was 2.5KW, the pressing speed was 50um / s, and the fixed load was 20N. The results are shown in Table 1.

[0043] Table 1

[0044]

[0045] Table 1 shows that in the pressure test under fixed load, Comparative Example 4, which did not use 3-(methacryloyloxy)propyltrimethoxysilane, experienced uneven dispersion of nano-silica in the polypropylene microplastics due to its polarity, leading to particle breakage. Comparative Example 5 in Table 1 shows that ethylene glycol has a certain effect on reducing the polarity of nano-silica, with a significant improvement compared to Comparative Example 4. Example 2 demonstrates that the polypropylene microplastic particles modified with 3-(methacryloyloxy)propyltrimethoxysilane still maintain a good spherical shape. This is mainly because 3-(methacryloyloxy)propyltrimethoxysilane enhances the interfacial bonding between nano-silica and polypropylene, thereby improving the particle toughness.

[0046] Example 3

[0047] S1. Weigh 90g of polypropylene granules and 0.3g of N,N'-dicyclohexyl terephthalamide, melt-mix them evenly, and then extrude them into crude masterbatch through a single-screw extruder. The extrusion temperature and pressure are 240℃ and 14MPa, respectively. The β-nucleation effect of N,N'-dicyclohexyl terephthalamide regulates the crystal form of polypropylene, thereby enhancing the toughness of polypropylene.

[0048] S2. Modified Nanoscale Silica: Anhydrous ethanol, deionized water, 3-(methacryloyloxy)propyltrimethoxysilane, and nanoscale silica were added to a three-necked flask in a mass ratio of 10:10:5:1. The mixture was stirred at room temperature to ensure uniform dispersion of the silica. The mixture was then microwaved to 70°C and refluxed for 4 hours. After the reaction, the mixture was filtered through anhydrous ethanol to obtain a filter cake. The filter cake was then dried in a vacuum drying oven at 70°C for 12 hours. The dried filter cake was then ground to obtain modified silica powder. The mechanism of this step is that the methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of nanoscale silica. This reduces the surface polarity of the nanoscale silica, decreases its agglomeration, and improves the compatibility between the nanoscale silica and polypropylene, thereby enhancing the dispersibility of the nanoscale silica in polypropylene. The nanoscale silica further strengthens the toughness of the polypropylene microplastics through interfacial interactions.

[0049] S3. Modified carbon black: Weigh 6g of carbon black and 10g of maleic anhydride and dissolve them in 100ml of acetone. Stir with a magnetic stirrer at room temperature for 1.5h. After stirring, vacuum filter the carbon black and dry it in an oven for 6h. Then transfer the carbon black into a porcelain boat and place it in a muffle furnace at 200℃ for 2.5h to obtain maleic anhydride-grafted carbon black.

[0050] S4. The masterbatch obtained in step S1, the modified nano-silica obtained in step S2, and the modified carbon black obtained in step S3 are mixed evenly in a ratio of 2:1:1 and then melt-extruded into granules on a twin-screw extruder at 300 rpm and 210°C. After the granules cool to room temperature, they are poured into a crusher and crushed at 800 rpm for 3 hours, using a 5 mm sieve aperture to ensure that they reach the microplastic level.

[0051] Comparative Example 6: Except for step S1, which did not include N,N'-dicyclohexyl terephthalamide, all other steps were the same as in Example 3.

[0052] Figure 2 A cross-sectional view of the polypropylene microplastics prepared in Comparative Example 6 shows that the cross-section is relatively smooth and exhibits brittle fracture. Figure 3 This is a cross-sectional view of the polypropylene microplastics prepared in Example 3. A large number of banded structures can be seen in the figure. This is mainly because N,N'-dicyclohexyl terephthalamide hinders the relaxation of the polypropylene molecular chains, thereby generating a large number of banded structures. This structure further improves the toughness of the material.

[0053] Example 4

[0054] S1. Weigh 100g of polypropylene granules and 0.4g of N,N'-dicyclohexyl terephthalamide, melt-mix and blend evenly, then extrude into crude masterbatch using a single-screw extruder. The extrusion temperature and pressure are 260℃ and 16MPa, respectively. The β-nucleation effect of N,N'-dicyclohexyl terephthalamide regulates the crystal form of polypropylene, thereby enhancing the toughness of polypropylene.

[0055] S2. Modified Nanoscale Silica: Anhydrous ethanol, deionized water, 3-(methacryloyloxy)propyltrimethoxysilane, and nanoscale silica were added to a three-necked flask in a mass ratio of 10:10:5:1. The mixture was stirred at room temperature to ensure uniform dispersion of the silica. The mixture was then microwaved to 80°C and refluxed for 5 hours. After the reaction, the mixture was filtered through anhydrous ethanol to obtain a filter cake. The filter cake was then dried in a vacuum drying oven at 80°C for 14 hours. The dried filter cake was then ground to obtain modified silica powder. The mechanism of this step is that the methoxy group in the 3-(methacryloyloxy)propyltrimethoxysilane molecule undergoes hydrolysis to generate hydroxyl groups, which then undergo a dehydration condensation reaction with the silanol groups on the surface of nanoscale silica. This reduces the surface polarity of the nanoscale silica, decreases its agglomeration, and improves the compatibility between the nanoscale silica and polypropylene, thereby enhancing the dispersibility of the nanoscale silica in polypropylene. The nanoscale silica further strengthens the toughness of the polypropylene microplastics through interfacial interactions.

[0056] S3. Modified carbon black: Weigh 8g of carbon black and 12g of maleic anhydride and dissolve them in 100ml of acetone. Stir with a magnetic stirrer at room temperature for 2 hours. After stirring, vacuum filter the carbon black and put it in an oven to dry for 8 hours. Then, transfer the carbon black into a porcelain boat and place it in a muffle furnace at 220℃ for 3 hours to obtain maleic anhydride-grafted carbon black.

[0057] S4. The masterbatch obtained in step S1, the modified nano-silica obtained in step S2, and the modified carbon black obtained in step S3 are mixed evenly in a ratio of 2:1:1 and then melt-extruded into granules on a twin-screw extruder at 350 rpm and 220°C. After the granules cool to room temperature, they are poured into a crusher and crushed at 900 rpm for 4 hours, using a 5 mm sieve aperture to ensure that they reach the microplastic level.

[0058] Comparative Example 7: Except for step S3, which does not involve the addition of maleic anhydride, all other steps are the same as in Example 4.

[0059] Comparative Example 8: Except for the carbon black dried in step S3 not being calcined in a muffle furnace, all other steps are the same as in Example 4.

[0060] Comparative Example 9: Except for step S4, in which the modified nano-silica obtained in step S2 is replaced with unmodified nano-silica, all other steps are the same as in Example 4.

[0061] The polypropylene microplastics prepared in Examples 4, 7, 8, and 9 were melt-extruded into strips with dimensions of 80mm*10mm*4mm and a type A notch. After irradiation in a xenon lamp aging chamber for 960 hours, the strips were removed and subjected to a cantilever beam notched impact strength test with an impact hammer energy of 22J. The results are as follows... Figure 4 As shown, Comparative Example 7, without the addition of maleic anhydride, suffers from a significant reduction in impact strength due to the poor compatibility of carbon black in polypropylene. Comparative Example 8, lacking muffle furnace calcination of the carbon black, exhibits a significantly reduced maleic anhydride grafting effect, resulting in impact strength similar to Comparative Example 7. However, Example 4, modified with maleic anhydride, demonstrates significantly superior impact strength compared to Comparative Examples 7 and 8. Comparative Example 9 indicates that the modified nano-silica also makes a significant contribution to the material's anti-aging ability, primarily due to the enhanced UV absorption capacity of the modified nano-silica. Benefiting from the synergistic effect of modified carbon black and modified nano-silica on the surface of polypropylene microplastic particles, the material's anti-aging performance is improved, thus resulting in higher impact strength.

[0062] Finally, it should be noted that the above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of polypropylene microplastics, characterized in that: The specific preparation method is as follows: S1, 70-100 g of polypropylene particles and 0.1-0.4 g of N,N'-dicyclohexyl terephthalamide are weighed and uniformly mixed by melting and blending, and then a crude master batch is prepared by a single screw extruder, and the extrusion temperature and pressure are 200-260 DEG C and 10-16 MPa respectively; S2, modified nano-sized silicon dioxide: anhydrous ethanol, deionized water, 3-(methacryloyloxy) propyl trimethoxysilane, nano-sized silicon dioxide are added into a three-necked flask in a mass ratio of 10:10:5:1, and stirred at room temperature to uniformly disperse the silicon dioxide; then heated to 50-80 DEG C by microwave, and simultaneously refluxed and condensed for 2-5 h; after the reaction is completed, the filter cake is obtained by filtering with anhydrous ethanol, and the filter cake is dried in a vacuum drying oven at 50-80 DEG C for 8-14 h, and the modified silicon dioxide powder is obtained after grinding the dried filter cake; S3, modified carbon black: 2-8 g of carbon black and 6-12 g of maleic anhydride are dissolved in 100 ml of acetone, and stirred at room temperature for 1-2 h by a magnetic stirrer, and the obtained carbon black is dried in an oven for 2-8 h, and then transferred into a porcelain boat and placed in a muffle furnace at 160-220 DEG C for 1.5-3 h to obtain maleic anhydride grafted carbon black; S4, the master batch obtained in step S1, the modified nano-sized silicon dioxide obtained in step S2 and the modified carbon black obtained in step S3 are uniformly mixed in a ratio of 2:1:1, and then melt-extruded and granulated on a twin-screw extruder at 200-350 rpm and 190-220 DEG C; after the particles are cooled to room temperature, they are poured into a crusher, and crushed at 600-900 rpm for 1-4 h, and a screen aperture of 5 mm is used to ensure that the micro-plastic level is reached.

2. The process for the preparation of polypropylene microplastics according to claim 1, characterized in that: In the step S1, 90 g of polypropylene particles are weighed.

3. The process for the preparation of polypropylene microplastics according to claim 1, characterized in that: In the step S1, the extrusion pressure is 12 MPa.

4. The process for preparing polypropylene microplastics according to claim 1, characterized in that: In the step S2, the microwave is heated to 60 DEG C.

5. The process for the preparation of polypropylene microplastics as claimed in claim 1, wherein: In the step S2, the reflux reaction is condensed for 4 h.

6. The process for the preparation of polypropylene microplastics according to claim 1, characterized in that: In the step S3, 6 g of carbon black is weighed.

7. The process for the preparation of polypropylene microplastics as claimed in claim 1, wherein: In the step S3, the temperature is 180 DEG C.

8. The process for the preparation of polypropylene microplastics as claimed in claim 1, wherein: In the step S4, the rotating speed of the twin-screw extruder is 300 rpm.

9. The process for the preparation of polypropylene microplastics as claimed in claim 1, wherein: In the step S4, the extrusion temperature is 200 DEG C.

10. A polypropylene micro-plastic prepared by the preparation process of the polypropylene micro-plastic according to any one of claims 1-9.

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