Polypropylene composite material for automobile side guards and preparation method thereof

Abstract

The application discloses a polypropylene composite material for automobile side guards and a preparation method thereof, and relates to the technical field of high-performance polypropylene.The application discloses a preparation method of a polypropylene composite material for automobile side guards, and comprises the following steps: loading antioxidants and light stabilizers in a synergist through a liquid-phase loading process to obtain a loaded synergist; blending copolymerized polypropylene resin, a compatibilizer, a toughening agent and dicumyl peroxide, adding magnesium sulfate whiskers, talcum powder, a lubricant and the loaded synergist for blending, extruding, granulating, injection molding and annealing treatment to obtain the polypropylene composite material for automobile side guards; and the synergist is obtained by bonding modified mesoporous silicon dioxide with double bonds after modifying hydroxyl-terminated hyperbranched polyester with maleic anhydride.The polypropylene composite material prepared in the application meets multiple use requirements of high rigidity, high low-temperature toughness, long-acting weather resistance, scratch resistance, dimensional stability and good molding appearance.

Description

Technical Field

[0001] This invention relates to the field of high-performance polypropylene technology, specifically to polypropylene composite materials for automotive side panels and their preparation methods. Background Technology

[0002] Automotive side skirts are external protective accessories installed under the doors of vehicle bodies. They are constantly exposed to complex outdoor conditions, enduring impacts from gravel, road scratches, mud and water erosion, and alternating high and low temperatures and UV aging. This places stringent requirements on the material's rigidity, low-temperature impact resistance, weather resistance, dimensional stability, and molded appearance. Polypropylene, with its advantages of light weight, low cost, good processability, and corrosion resistance, has become the core matrix material for manufacturing automotive side skirts. However, pure polypropylene has high crystallinity, poor toughness, and large molding shrinkage, which cannot directly meet the application requirements. Therefore, the industry generally adopts modified methods such as filler filling and elastomer blending to prepare PP composite materials.

[0003] Currently, most commercially available PP composite materials for automotive side skirts are modified systems filled with talc and compounded with polyolefin elastomers. Inorganic fillers enhance material rigidity and dimensional stability, while elastomers such as POE and EPDM improve matrix toughness, balancing performance and production costs. Some high-end products utilize glass fiber reinforcement to enhance mechanical strength. However, existing modified PP composite materials still have significant technical shortcomings, making them unsuitable for the long-term service requirements of side skirts. First, it is difficult to balance material rigidity and low-temperature toughness. Fillers can easily cause stress concentration, reducing low-temperature impact resistance and making the material susceptible to stone impact cracking in low-temperature environments. Increasing the amount of elastomer can increase toughness, but this leads to a decrease in material rigidity and heat resistance, making the product prone to high-temperature creep deformation. Second, the material lacks sufficient weather resistance and durability. Polypropylene molecules are easily degraded in ultraviolet and humid environments, and conventional additive systems have limited anti-aging effects. Long-term use can easily result in yellowing, loss of gloss, and chalking, leading to a significant decline in mechanical properties. Meanwhile, traditional modified materials have low surface hardness, poor scratch resistance and stone impact resistance, and are prone to whitening scratches after being scratched, affecting the overall appearance quality of the vehicle. In addition, the filler has poor interfacial compatibility with the PP matrix, and is prone to agglomeration and uneven dispersion, resulting in product warping, large performance fluctuations and low yield.

[0004] To address the aforementioned shortcomings, existing technologies have undergone several improvements and optimizations. The mainstream approaches include: using multi-elastomer blends to achieve synergistic toughening; using coupling agents and stearic acid to modify the surface of inorganic fillers and improve interfacial bonding; adding nucleating agents to optimize crystallization behavior and reduce molding shrinkage; using blends of antioxidants and light stabilizers to construct an aging-resistant system; and using hybrid filler blends and small-molecule scratch-resistant additives to optimize overall performance.

[0005] However, the aforementioned improvement methods all have significant limitations and cannot achieve synergistic optimization of multiple properties. Single toughening modification has performance trade-offs and cannot simultaneously address both rigidity and toughness; filler modification and nucleating agent optimization have limited improvement effects and cannot solve core pain points; aging-resistant additives are prone to migration and loss, resulting in insufficient long-term protection; scratch-resistant additives can easily affect the adhesion of the product coating and have poor durability; mixed fillers and glass fiber modification are prone to problems such as poor dispersion and poor surface texture, failing to meet the appearance requirements of exposed side panels. Overall, existing modified PP materials generally suffer from prominent performance shortcomings and poor comprehensive adaptability, making it difficult to simultaneously meet the multiple usage requirements of automotive side panels, including high rigidity, high and low temperature toughness, long-term weather resistance, scratch resistance, dimensional stability, and good molding appearance, severely restricting the product's service life and quality upgrades. Summary of the Invention

[0006] The purpose of this invention is to provide a polypropylene composite material for automotive side skirts and its preparation method, thereby solving the following technical problems: Existing polypropylene composite materials are difficult to simultaneously meet the multiple application requirements of high rigidity, high and low temperature toughness, long-term weather resistance, scratch resistance, dimensional stability and good molding appearance.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing polypropylene composite material for automotive side skirts includes the following steps: Antioxidants and light stabilizers are loaded into synergists using a liquid-phase loading process to obtain loaded synergists; Polypropylene resin, compatibilizer, toughening agent, and dicumyl peroxide are blended together, and magnesium sulfate whiskers, talc, lubricant, and load enhancer are added and blended together. The mixture is then extruded, granulated, injection molded, and annealed to obtain a polypropylene composite material for automotive side panels. The synergist is prepared by modifying hydroxyl-terminated hyperbranched polyester with maleic anhydride and then bonding it with double-bond modified mesoporous silica.

[0008] As a further aspect of the present invention, the preparation method of the loaded synergist includes the following steps: mixing the synergist, anhydrous ethanol, antioxidant, and light stabilizer, controlling the temperature at 40-50℃, impregnating for 4-6 hours, and removing the anhydrous ethanol by rotary evaporation to obtain the loaded synergist.

[0009] The specific annealing process is as follows: control the temperature at 120-130℃ and process for 2 hours.

[0010] As a further aspect of the present invention: the polypropylene composite material comprises the following raw materials in parts by weight: 100 parts by weight of polypropylene resin, 5-15 parts by weight of compatibilizer, 8-12 parts by weight of toughening agent, 8-15 parts by weight of synergist, 15-25 parts by weight of magnesium sulfate whiskers, 10-20 parts by weight of talc, 0.3-0.6 parts by weight of antioxidant, 0.4-0.6 parts by weight of light stabilizer, 0.4-0.8 parts by weight of lubricant, and 0.03-0.08 parts by weight of dicumyl peroxide.

[0011] As a further aspect of the present invention, the preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, pentaerythritol and 2,2-dimethylolpropionic acid are added to a reaction vessel and melted at a controlled temperature of 130-140℃. P-toluenesulfonic acid is added and the reaction is maintained at this temperature for 1.5-3 hours. The generated water is removed through a water separator. The temperature is raised to 145-155℃ and the reaction is carried out under vacuum for 3-4 hours. Heating is stopped, the vacuum is turned off, and nitrogen is introduced to atmospheric pressure. The crude product is dissolved in acetone, deionized water is added to precipitate, the precipitate is collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product is then refluxed and washed to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, hydroxyl-terminated hyperbranched polyester and anhydrous toluene were added to a reaction flask and stirred at 60-70℃ to dissolve. Maleic anhydride, p-toluenesulfonic acid, and hydroquinone were added and dispersed. The reaction was refluxed at 110-125℃ for 4-6 hours. After cooling to room temperature, cold methanol was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: Under a nitrogen atmosphere, maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and N,N-dimethylformamide were added to a reaction flask and dispersed. The temperature was controlled at 60-70℃. Double bond-modified mesoporous silica was added and dispersed. p-Toluenesulfonic acid was added and the temperature was controlled at 90-105℃. The reaction was carried out under stirring for 6-9 hours. After cooling to room temperature, cold methanol was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain the synergist.

[0012] As a further aspect of the present invention: the mass ratio of pentaerythritol, 2,2-dimethylolpropionic acid, and p-toluenesulfonic acid in A1 is 6.8-13.6:40-68:0.47-0.81.

[0013] As a further embodiment of the present invention: the addition ratio of A2 hydroxyl-terminated hyperbranched polyester, anhydrous toluene, maleic anhydride, p-toluenesulfonic acid, and hydroquinone is 25g: 100-150mL: 4.9-9.8g: 0.17-0.28g: 0.025-0.05g.

[0014] As a further embodiment of the present invention: the addition ratio of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester, N,N-dimethylformamide, double bond-modified mesoporous silica, and p-toluenesulfonic acid in A3 is 20g: 80-150mL: 3-7.5g: 0.015-0.03g.

[0015] As a further embodiment of the present invention, the preparation method of double bond modified mesoporous silica includes the following steps: hexadecyltrimethylammonium bromide, anhydrous ethanol, and deionized water are added to a reaction flask for dispersion, the pH is adjusted to 10-11, tetraethyl orthosilicate and KH570 are mixed and added to the reaction flask for dispersion, the temperature is controlled at 25-35℃ and the reaction is kept at a temperature of 25-35℃ for 2-4 hours under stirring, and then placed in an oven at 60-80℃ for static aging for 12-24 hours, centrifuged, the precipitate is taken and washed to remove hexadecyltrimethylammonium bromide, washed and dried to obtain double bond modified mesoporous silica; The addition ratio of hexadecyltrimethylammonium bromide, anhydrous ethanol, deionized water, tetraethyl orthosilicate, and KH570 is 3.65-7.3g: 100-200mL: 50-100mL: 20g: 2.5-6.25g.

[0016] As a further aspect of the present invention, the method for removing hexadecyltrimethylammonium bromide includes the following steps: the washed precipitate is placed in an ethanol solution containing NH4NO3 and refluxed at 60-80°C for 2-3 hours, and repeated 2-3 times.

[0017] As a further aspect of the present invention: the polypropylene resin is one or both of copolymer polypropylene and homopolymer polypropylene; The compatibilizer is PP-g-MAH compatibilizer; The toughening agent is POE-g-MAH toughening agent; The antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 0.1-0.3:0.1-0.3. The light stabilizer is a hindered amine light stabilizer; The lubricating dispersant is ethylene bis-stearamide.

[0018] As a further aspect of the present invention: magnesium sulfate whiskers are dried at 80-100℃ for 2-4 hours before use to remove surface free water and promote in-situ dehydration condensation esterification reaction with carboxyl groups on the synergist molecular chain during melt blending to form a chemical bonding interface.

[0019] As a further aspect of the present invention: the melting temperature of the extrusion granulation is 190-220℃; The injection temperature for injection molding is 210-220℃, the mold temperature is 50-60℃, and the pressure is 55-65MPa.

[0020] The polypropylene composite material for automotive side panels is prepared by any of the above-mentioned methods.

[0021] The beneficial effects of this invention are: This application uses pentaerythritol as the core and 2,2-dimethylolpropionic acid as the monomer to synthesize a highly reactive hyperbranched polyester with a large number of terminal hydroxyl groups and internal cavities via melt polycondensation. This application also utilizes maleic anhydride to react with the hyperbranched polyester, esterifying some of the terminal hydroxyl groups and introducing reactive double bonds and anhydride groups to obtain maleic anhydride-modified hyperbranched polyester. Subsequently, under the action of a catalyst, double-bond modified mesoporous silica is chemically bonded to the residual hydroxyl groups or hydrolyzed carboxyl groups of the maleic anhydride-modified hyperbranched polyester via a sol-gel method to obtain a synergist.

[0022] (1) Achieving a balance between rigidity and toughness through reactive compatibilization and interfacial strengthening. In the melt blending stage of preparing polypropylene composite materials, the added dicumyl peroxide decomposes upon heating to generate free radicals, forming macromolecular free radicals on the polypropylene molecular chain. These macromolecular free radicals undergo a free radical addition reaction with the carbon-carbon double bonds in the maleic anhydride groups of the synergist, covalently binding the synergist and polypropylene resin to form long-chain PP, thus achieving chemical anchoring of the synergist in the polypropylene matrix. Simultaneously, the residual carboxyl / anhydride groups on the synergist molecular chain undergo an in-situ esterification reaction with the maleic anhydride groups of the toughening agent POE-g-MAH side chain at high temperature, integrating the flexible POE chain segments of the toughening agent into the rigid PP main chain network. The flexible segments of the toughening agent efficiently absorb impact energy through the crazing shear band mechanism, while the mesoporous silica covalently bonded to the synergist molecular chain acts as a local reinforcing network node. Under external impact, it further dissipates impact energy and restricts molecular chain slippage through the minute elastic deformation of the mesoporous pore walls. Thus, it significantly improves low-temperature impact toughness without sacrificing rigidity, overcoming the performance trade-off of traditional toughening inevitably reducing rigidity. Simultaneously, the interfacial bonding strength of the mesoporous silica bonded to the synergist is significantly enhanced due to the in-situ introduction of high-density double bonds during the preparation process.

[0023] (2) Free radical scavenging and long-lasting weather resistance The toughening agent prepared in this application utilizes the internal cavities and numerous end groups of its terminal hydroxyl hyperbranched polyester molecular chains to act as free radical quenchers, terminating the degradation chain reaction of polypropylene resin. The mesoporous silica bonded to the toughening agent molecular chains possesses a high specific surface area and ordered channels, which not only scatter and reflect some ultraviolet light but also serve as a nano-reservoir for antioxidants and light stabilizers. During the service life of the composite material, the small molecule additives are slowly and continuously released from the channels, maintaining an effective concentration on the material surface. This overcomes the short-term protective failure problem caused by the volatilization and migration of conventional additives during high-temperature processing, achieving long-term weather-resistant protection.

[0024] (3) In-situ hardening and self-healing properties enable scratch resistance. The toughening agent prepared in this application possesses high polarity and surface energy. During injection molding, the toughening agent tends to migrate and accumulate on the surface of the product, forming a dense, hardened layer composed of hyperbranched polymers and mesoporous silica. The pore structure of the mesoporous silica increases the microscopic roughness and specific surface area of ​​the surface layer, which helps to form a denser physical cross-linked network, further improving surface hardness. The three-dimensional network structure of the hyperbranched polymer exhibits an elastic memory effect. Slight scratches only disrupt the van der Waals forces and hydrogen bonds between the surface molecular chains. After heating (such as exposure to summer sun) or being left for a period of time, the molecular chains reorient and associate, causing the scratches to become shallower or disappear completely. The mesoporous structure of the mesoporous silica provides more free volume and space for molecular chain rearrangement, effectively improving self-healing efficiency.

[0025] (4) Dimensional stability The synergist molecular chain prepared in this application is bonded with mesoporous silica. The mesoporous silica acts as a multi-arm crosslinking center, restricting the unwinding and slippage of the PP macromolecular chain at high temperatures through the entanglement of the hyperbranched polyester molecular chain, thereby reducing the coefficient of thermal expansion. Furthermore, the high specific surface area and abundant silanol groups of the mesoporous structure form a stronger hydrogen bond network with the polypropylene matrix and the hyperbranched polyester molecular chain of the synergist, inhibiting warpage deformation of the product and ensuring the dimensional accuracy of the side panel during large-size thin-wall molding.

[0026] (5) In-situ chemical anchoring of inorganic fillers and synergistic dispersion of multiple components The synergist molecular chain prepared in this application contains a large number of carboxyl and anhydride groups. Under high temperature and high shear during melt blending, the carboxyl groups in the synergist undergo in-situ dehydration condensation esterification with the active hydroxyl groups on the surface of magnesium sulfate whiskers, covalently connecting the rigid whiskers to the hyperbranched polymer network. This eliminates the defects of whisker debonding and stress concentration at the interface between the whiskers and the PP matrix in traditional physical blending. At the same time, the hyperbranched three-dimensional structure on the synergist molecular chain and the abundant silanol groups on the surface of mesoporous silica provide good wetting and physical anchoring effects on the talc flakes. Combined with the lubricating dispersion of ethylene bis-stearamide, uniform distribution of talc powder in the matrix is ​​achieved. The synergist, acting as a "molecular bridge," connects the polypropylene matrix, the POE-g-MAH flexible toughening phase, the magnesium sulfate whisker reinforcing phase, and the talc functional filler into an integrated synergistic network through chemical bonds / strong hydrogen bonds. This fundamentally solves the industry pain points of filler agglomeration, interface debonding, and large performance fluctuations in traditional modified systems, ensuring batch-to-batch performance stability and high yield of injection molded products. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, 6.8 g pentaerythritol and 40 g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 130 °C. 0.47 g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 1.5 h. The generated water was removed through a water separator. The temperature was raised to 145 °C and the vacuum was drawn to 0.08 MPa for 3 h. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 50 mL of acetone and 500 mL of deionized water was added to precipitate. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 h to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, 25g of hydroxyl-terminated hyperbranched polyester and 100mL of anhydrous toluene were added to a reaction flask and stirred at 60℃ to dissolve. Then, 4.9g of maleic anhydride, 0.17g of p-toluenesulfonic acid, and 0.025g of hydroquinone were added and dispersed. The mixture was refluxed at 110℃ for 4h and cooled to room temperature. 300mL of cold methanol at 0℃ was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: 3.65g of hexadecyltrimethylammonium bromide, 100mL of anhydrous ethanol, and 50mL of deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 10. 20g of tetraethyl orthosilicate and 2.5g of KH570 were mixed and added to the reaction flask for dispersion. The reaction was carried out at 25℃ with stirring for 2 hours. The mixture was then placed in an oven at 60℃ and allowed to stand for 12 hours. After centrifugation, the precipitate was washed and placed in 200mL of 0.03g / mL NH4NO3 ethanol solution and refluxed at 60℃ for 2 hours. This process was repeated twice to remove hexadecyltrimethylammonium bromide. The mixture was then washed and dried to obtain double-bond modified mesoporous silica. A4: Under a nitrogen atmosphere, 20g of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and 80mL of N,N-dimethylformamide were added to a reaction flask for dispersion. The temperature was controlled at 60℃. 3g of double-bond modified mesoporous silica was added for dispersion. 0.015g of p-toluenesulfonic acid was added. The temperature was controlled at 90℃ and the reaction was maintained at this temperature for 6h under stirring. After cooling to room temperature, 400mL of cold methanol at 0℃ was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain the synergist.

[0029] A method for preparing polypropylene composite material for automotive side skirts includes the following steps: S1: 11.5 parts by weight of the synergist prepared in Example 1, 50 mL of anhydrous ethanol, 0.2 parts by weight of antioxidant 1010, 0.2 parts by weight of antioxidant 168, and 0.5 parts by weight of light stabilizer (Tinuvin 770 purchased from BASF) were mixed, and the mixture was impregnated at a controlled temperature of 45°C for 5 h. The anhydrous ethanol was then removed by rotary evaporation to obtain the loaded synergist. S2: 100 parts by weight of polypropylene resin (K7726 copolymer polypropylene resin purchased from Sinopec), 10 parts by weight of PP-g-MAH compatibilizer (OREVAC CA100 purchased from Arkema), 10 parts by weight of POE-g-MAH toughening agent (UF-MOE purchased from Guangzhou Yuanfeng New Energy Co., Ltd.), and 0.05 parts by weight of dicumyl peroxide were blended together, and 20 parts by weight of magnesium sulfate whiskers (WS-1 basic magnesium sulfate whiskers purchased from Yingkou Wesker Chemical Co., Ltd.), 15 parts by weight of talc powder (particle size 10μm), 0.6 parts by weight of ethylene bis-stearamide, and a loading synergist were added and blended together. The mixture was then extruded, granulated, injection molded, and annealed at 120℃ for 2 hours to obtain a polypropylene composite material for automotive side guards.

[0030] Example 2: The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, 10g pentaerythritol and 54g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 135℃. 0.65g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 2 hours. The generated water was removed through a water separator. The temperature was raised to 150℃ and the vacuum was drawn to 0.08MPa for 3.5 hours. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 70mL acetone and precipitated with 700mL deionized water. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 hours to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, 25g of hydroxyl-terminated hyperbranched polyester and 120mL of anhydrous toluene were added to a reaction flask and stirred at 65℃ to dissolve. 7.4g of maleic anhydride, 0.22g of p-toluenesulfonic acid, and 0.04g of hydroquinone were added for dispersion. The mixture was refluxed at 120℃ for 5h and cooled to room temperature. 400mL of cold methanol at 0℃ was added and stirred to precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: 5.5g hexadecyltrimethylammonium bromide, 150mL anhydrous ethanol, and 50mL deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 11. 20g tetraethyl orthosilicate and 4.2g KH570 were mixed and added to the reaction flask for dispersion. The reaction was carried out at 30℃ with stirring for 3h. The mixture was then placed in an oven at 70℃ and allowed to stand for 18h. After centrifugation, the precipitate was washed and placed in 200mL of 0.03g / mL NH4NO3 ethanol solution and refluxed at 70℃ for 3h. This process was repeated twice to remove hexadecyltrimethylammonium bromide. The precipitate was then washed and dried to obtain double-bond modified mesoporous silica. A4: Under a nitrogen atmosphere, 20g of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and 120mL of N,N-dimethylformamide were added to a reaction flask and dispersed. The temperature was controlled at 65℃. 5.5g of double-bond modified mesoporous silica was added and dispersed. 0.02g of p-toluenesulfonic acid was added. The temperature was controlled at 100℃ and the reaction was maintained at this temperature for 7.5h under stirring. After cooling to room temperature, 500mL of cold methanol at 0℃ was added and stirred to precipitate the product. The precipitate was collected, washed, and dried to obtain the synergist.

[0031] The preparation method of polypropylene composite material for automobile side guards is the same as that of Example 1, except that the synergist prepared in Example 1 is replaced in equal amounts with the synergist prepared in Example 2. The remaining components and preparation methods are completely consistent with those of Example 1.

[0032] Example 3: The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, 13.6 g pentaerythritol and 68 g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 140 °C. 0.81 g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 3 h. The generated water was removed through a water separator. The temperature was raised to 155 °C and the vacuum was drawn to 0.08 MPa for 4 h. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 80 mL of acetone and precipitated with 800 mL of deionized water. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 h to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, 25g of hydroxyl-terminated hyperbranched polyester and 150mL of anhydrous toluene were added to a reaction flask and stirred at 70℃ to dissolve. Then, 9.8g of maleic anhydride, 0.28g of p-toluenesulfonic acid, and 0.05g of hydroquinone were added to disperse the mixture. The mixture was refluxed at 125℃ for 6 hours and cooled to room temperature. 500mL of cold methanol at 0℃ was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: 7.3g hexadecyltrimethylammonium bromide, 200mL anhydrous ethanol, and 100mL deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 11. 20g tetraethyl orthosilicate and 6.25g KH570 were mixed and added to the reaction flask for dispersion. The reaction was carried out at 35℃ with stirring for 4 hours. The mixture was then placed in an oven at 80℃ and allowed to stand for 24 hours. After centrifugation, the precipitate was washed and placed in 200mL of 0.03g / mL NH4NO3 ethanol solution and refluxed at 80℃ for 3 hours. This process was repeated 3 times to remove hexadecyltrimethylammonium bromide. The mixture was then washed and dried to obtain double-bond modified mesoporous silica. A4: Under a nitrogen atmosphere, 20g of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and 150mL of N,N-dimethylformamide were added to a reaction flask for dispersion. The temperature was controlled at 70℃. 7.5g of double-bond modified mesoporous silica was added for dispersion. 0.03g of p-toluenesulfonic acid was added. The temperature was controlled at 105℃ and the reaction was maintained at this temperature for 9h under stirring. After cooling to room temperature, 600mL of cold methanol at 0℃ was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain the synergist.

[0033] The preparation method of polypropylene composite material for automobile side guards is the same as that of Example 1, except that the synergist prepared in Example 1 is replaced in equal amounts with the synergist prepared in Example 3. The other components and preparation methods are completely consistent with those of Example 1.

[0034] Comparative Example 1: The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, 10g pentaerythritol and 54g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 135℃. 0.65g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 2 hours. The generated water was removed through a water separator. The temperature was raised to 150℃ and the vacuum was drawn to 0.08MPa for 3.5 hours. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 70mL acetone and precipitated with 700mL deionized water. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 hours to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, 25g of hydroxyl-terminated hyperbranched polyester and 120mL of anhydrous toluene were added to a reaction flask and stirred at 65℃ to dissolve. 7.4g of maleic anhydride, 0.22g of p-toluenesulfonic acid, and 0.04g of hydroquinone were added for dispersion. The mixture was refluxed at 120℃ for 5h and cooled to room temperature. 400mL of cold methanol at 0℃ was added and stirred to precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: 5.77g of nano silica, 150mL of anhydrous ethanol and 50mL of deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 11. 4.2g of KH570 was added for dispersion. The reaction was carried out at 30℃ with stirring for 3h. After centrifugation, washing and drying, double bond modified silica was obtained. A4: Under a nitrogen atmosphere, 20g of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and 120mL of N,N-dimethylformamide were added to a reaction flask and dispersed. The temperature was controlled at 65℃. 5.5g of double-bond modified silica was added and dispersed. 0.02g of p-toluenesulfonic acid was added, and the temperature was controlled at 100℃. The reaction was carried out under stirring for 7.5h. After cooling to room temperature, 500mL of cold methanol at 0℃ was added and stirred to precipitate. The precipitate was collected, washed, and dried to obtain the synergist.

[0035] The preparation method of polypropylene composite material for automobile side guards is the same as that of Example 1, except that the synergist prepared in Example 1 is replaced in equal amounts with the synergist prepared in Comparative Example 1. The remaining components and preparation methods are completely consistent with those of Example 1.

[0036] Comparative Example 2: The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, 10g pentaerythritol and 54g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 135℃. 0.65g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 2 hours. The generated water was removed through a water separator. The temperature was raised to 150℃ and the vacuum was drawn to 0.08MPa for 3.5 hours. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 70mL acetone and precipitated with 700mL deionized water. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 hours to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, 25g of hydroxyl-terminated hyperbranched polyester and 120mL of anhydrous toluene were added to a reaction flask and stirred at 65℃ to dissolve. 7.4g of maleic anhydride, 0.22g of p-toluenesulfonic acid, and 0.04g of hydroquinone were added for dispersion. The mixture was refluxed at 120℃ for 5h and cooled to room temperature. 400mL of cold methanol at 0℃ was added and stirred to precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: 5.5g hexadecyltrimethylammonium bromide, 150mL anhydrous ethanol, and 50mL deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 11. 20g tetraethyl orthosilicate and 4.2g KH570 were mixed and added to the reaction flask for dispersion. The reaction was carried out at 30℃ with stirring for 3h. The mixture was then placed in an oven at 70℃ and allowed to stand for 18h. After centrifugation, the precipitate was washed and placed in 200mL of 0.03g / mL NH4NO3 ethanol solution and refluxed at 70℃ for 3h. This process was repeated twice to remove hexadecyltrimethylammonium bromide. The precipitate was then washed and dried to obtain double-bond modified mesoporous silica. A4: 20g of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and 5.5g of double bond-modified mesoporous silica were blended to obtain a synergist.

[0037] The preparation method of polypropylene composite material for automobile side guards is the same as that of Example 1, except that the synergist prepared in Example 1 is replaced in equal amounts with the synergist prepared in Comparative Example 2. The remaining components and preparation methods are completely consistent with those of Example 1.

[0038] The preparation method of the synergist in Comparative Example 3 includes the following steps: A1: Under a nitrogen atmosphere, 10g pentaerythritol and 54g 2,2-dimethylolpropionic acid were added to a reaction vessel and melted at 135℃. 0.65g p-toluenesulfonic acid was added and the reaction was maintained at this temperature for 2 hours. The generated water was removed through a water separator. The temperature was raised to 150℃ and the vacuum was drawn to 0.08MPa for 3.5 hours. Heating was stopped, the vacuum was turned off, and nitrogen was introduced to atmospheric pressure. The crude product was dissolved in 70mL acetone and precipitated with 700mL deionized water. The precipitate was collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product was then refluxed and washed for 8 hours to obtain a hydroxyl-terminated hyperbranched polyester. A2: 5.5g hexadecyltrimethylammonium bromide, 150mL anhydrous ethanol, and 50mL deionized water were added to a reaction flask for dispersion. Ammonia was added to adjust the pH to 11. 20g tetraethyl orthosilicate and 4.2g KH570 were mixed and added to the reaction flask for dispersion. The reaction was carried out at 30℃ with stirring for 3h. The mixture was then placed in an oven at 70℃ and allowed to stand for 18h. After centrifugation, the precipitate was washed and placed in 200mL of 0.03g / mL NH4NO3 ethanol solution and refluxed at 70℃ for 3h. This process was repeated twice to remove hexadecyltrimethylammonium bromide. The precipitate was then washed and dried to obtain double-bond modified mesoporous silica. A3: 20g of hydroxyl-terminated hyperbranched polyester and 5.5g of double-bond modified mesoporous silica were blended to obtain a synergist.

[0039] The preparation method of polypropylene composite material for automobile side guards is the same as that of Example 1, except that the synergist prepared in Example 1 is replaced in equal amounts with the synergist prepared in Comparative Example 3. The remaining components and preparation methods are completely consistent with those of Example 1.

[0040] Comparative Example 4: A method for preparing polypropylene composite material for automotive side skirts, comprising the following steps: S1: 11.5 parts by weight of the synergist prepared in Example 2, 50 mL of anhydrous ethanol, 0.2 parts by weight of antioxidant 1010, 0.2 parts by weight of antioxidant 168, and 0.5 parts by weight of light stabilizer (Tinuvin 770 purchased from BASF) were mixed, and the mixture was impregnated at a controlled temperature of 45°C for 5 h. The anhydrous ethanol was then removed by rotary evaporation to obtain the loaded synergist. S2: 100 parts by weight of polypropylene resin (K7726 copolymer polypropylene resin purchased from Sinopec), 10 parts by weight of PP-g-MAH compatibilizer (OREVAC CA100 purchased from Arkema), 10 parts by weight of POE-g-MAH toughening agent (UF-MOE purchased from Guangzhou Yuanfeng New Energy Co., Ltd.), and 0.05 parts by weight of dicumyl peroxide were blended together, and 20 parts by weight of magnesium sulfate whiskers (WS-1 basic magnesium sulfate whiskers purchased from Yingkou Wesker Chemical Co., Ltd.), 15 parts by weight of talc powder (particle size 10μm), 0.6 parts by weight of ethylene bis-stearamide, and a loading synergist were added and blended together. The mixture was then extruded, granulated, and injection molded to obtain a polypropylene composite material for automotive side guards.

[0041] Comparative Example 5: A method for preparing polypropylene composite material for automotive side skirts, comprising the following steps: 100 parts by weight of polypropylene resin (K7726 copolymer polypropylene resin purchased from Sinopec), 10 parts by weight of PP-g-MAH compatibilizer (OREVAC CA100 purchased from Arkema), 10 parts by weight of POE-g-MAH toughening agent (UF-MOE purchased from Guangzhou Yuanfeng New Energy Co., Ltd.), 0.05 parts by weight of dicumyl peroxide are blended, and 20 parts by weight of magnesium sulfate whiskers (WS-1 basic magnesium sulfate whiskers purchased from Yingkou Wesker Chemical Co., Ltd.), 15 parts by weight of talc powder (particle size 10 μm), 0.6 parts by weight of ethylene bis-stearamide, 11.5 parts by weight of the synergist prepared in Example 2, 0.2 parts by weight of antioxidant 1010, 0.2 parts by weight of antioxidant 168, and 0.5 parts by weight of light stabilizer (Tinuvin purchased from BASF) are added. 770) Blending, extrusion granulation, injection molding, and annealing at 120℃ for 2 hours yielded a polypropylene composite material for automotive side guards.

[0042] Comparative Example 6: A method for preparing polypropylene composite material for automotive side skirts, comprising the following steps: S1: 11.5 parts by weight of the synergist prepared in Example 1, 50 mL of anhydrous ethanol, 0.2 parts by weight of antioxidant 1010, 0.2 parts by weight of antioxidant 168, and 0.5 parts by weight of light stabilizer (Tinuvin 770 purchased from BASF) were mixed, and the mixture was impregnated at a controlled temperature of 45°C for 5 h. The anhydrous ethanol was then removed by rotary evaporation to obtain the loaded synergist. S2: 100 parts by weight of polypropylene resin (K7726 copolymer polypropylene resin purchased from Sinopec), 10 parts by weight of PP-g-MAH compatibilizer (OREVAC CA100 purchased from Arkema), 10 parts by weight of POE-g-MAH toughening agent (UF-MOE purchased from Guangzhou Yuanfeng New Energy Co., Ltd.) were blended together, and 20 parts by weight of magnesium sulfate whiskers (WS-1 basic magnesium sulfate whiskers purchased from Yingkou Wesker Chemical Co., Ltd.), 15 parts by weight of talc powder (particle size 10μm), 0.6 parts by weight of ethylene bis-stearamide, and a loading synergist were added and blended together. The mixture was then extruded, granulated, injection molded, and annealed at 120℃ for 2 hours to obtain a polypropylene composite material for automotive side guards.

[0043] Comparative Example 7: A method for preparing polypropylene composite material for automotive side panels, comprising the following steps: 100 parts by weight of polypropylene resin (K7726 copolymer polypropylene resin purchased from Sinopec), 10 parts by weight of PP-g-MAH compatibilizer (OREVAC CA100 purchased from Arkema), 10 parts by weight of POE-g-MAH toughening agent (UF-MOE purchased from Guangzhou Yuanfeng New Energy Co., Ltd.), and 0.05 parts by weight of dicumyl peroxide are blended together. 20 parts by weight of magnesium sulfate whiskers (WS-1 basic magnesium sulfate whiskers purchased from Yingkou Wesker Chemical Co., Ltd.), 15 parts by weight of talc powder (particle size 10 μm), 0.6 parts by weight of ethylene bis-stearamide, 0.2 parts by weight of antioxidant 1010, 0.2 parts by weight of antioxidant 168, and 0.5 parts by weight of light stabilizer (Tinuvin 770 purchased from BASF) are then blended together. The mixture is extruded and granulated, injection molded, and annealed at 120°C for 2 hours to obtain the polypropylene composite material for automotive side panels.

[0044] Performance testing (1) Mechanical properties Tensile properties: Tensile strength and tensile modulus were tested according to GB / T 1040-2006 "Test Method for Tensile Properties of Plastics". The test results are shown in Table 1. Bending performance: Bending strength and bending modulus were tested according to GB / T 9341-2000 "Plastics - Test Method for Bending Performance". The test results are shown in Table 1. Cantilever beam notched impact strength: The cantilever beam notched impact strength of the specimens prepared in Examples 1-3 and Comparative Examples 1-7 at 23℃ and -30℃ was tested according to GB / T 1843-1996 "Plastic Cantilever Beam Impact Test Method". The test results are shown in Table 1. Unnotched impact strength of simply supported beams: The impact strength of the specimens prepared in Examples 1-3 and Comparative Examples 1-7 at 23℃ was tested according to GB / T 1043-2008 "Impact Test Method for Simply Supported Beams of Rigid Plastics". The test results are shown in Table 1. Table 1: Statistical Table of Mechanical Property Test Data for Examples 1-3 and Comparative Examples 1-7

[0045] As shown in Table 1, the samples prepared in this application have both rigidity and toughness.

[0046] (2) Heat resistance and aging resistance Melt mass flow rate (MFR): The MFR of the samples prepared in Examples 1-3 and Comparative Examples 1-7 at 230℃ / 2.16kg was tested according to GB / T 3682-2000 "Determination of melt mass flow rate and melt volume flow rate of thermoplastic plastics". The test results are shown in Table 2. Heat distortion temperature: Tested according to GB / T 1634.2-2019 "Determination of heat distortion temperature of plastics under load - Part 2: Plastics and hard rubber" at 1.82 MPa. The test results are shown in Table 2. Xenon lamp artificial accelerated aging: After exposure for 1000h according to GB / T 16422.2-2022 "Laboratory Light Sources for Plastics - Exposure Test Methods - Part 2: Xenon Arc Lamps", the impact strength retention rate and color difference ΔE were measured. The test results are shown in Table 2. Thermo-oxidative aging: Tensile strength retention rate was measured after aging at 150℃ for 168h according to GB / T 7141-2008 "Plastics Thermal Aging Test Method". The test results are shown in Table 2. Table 2: Statistical Table of Heat Resistance and Aging Resistance Test Data for Examples 1-3 and Comparative Examples 1-7

[0047] As shown in Table 2, the samples prepared in this application have good processability, heat resistance, and aging resistance.

[0048] (3) Appearance and surface properties Molding shrinkage: The test was conducted according to GB / T 15585-1995 "Determination of shrinkage of injection molding of thermoplastic plastics", and the test results are shown in Table 3; Surface gloss (60°): Tested according to GB / T 8807-1988 "Test Method for Mirror Gloss of Plastics", and the test results are shown in Table 3; Shore hardness (Type D): The test was conducted according to GB / T 2411-2008 "Plastics and hard rubber - Determination of indentation hardness (Shore hardness) using a hardness tester". The test results are shown in Table 3. Scratch performance test: The test was conducted according to GB / T 44303-2024 "Quantitative assessment of scratch damage and scratch visibility in plastics", and the test results are shown in Table 3; Table 3: Statistical table of surface performance test data for Examples 1-3 and Comparative Examples 1-7

[0049] As shown in Table 3, the samples prepared in this application have good surface gloss, low molding shrinkage, are not prone to warping, and have high surface hardness and good scratch resistance.

[0050] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing polypropylene composite material for automotive side panels, characterized in that, Includes the following steps: Antioxidants and light stabilizers are loaded into synergists using a liquid-phase loading process to obtain loaded synergists; Polypropylene resin, compatibilizer, toughening agent, and dicumyl peroxide are blended together, and magnesium sulfate whiskers, talc, lubricant, and load enhancer are added and blended together. The mixture is then extruded, granulated, injection molded, and annealed to obtain a polypropylene composite material for automotive side panels. The synergist is prepared by modifying a hydroxyl-terminated hyperbranched polyester with maleic anhydride and then bonding it with double-bond modified mesoporous silica.

2. The method for preparing polypropylene composite material for automotive side panels according to claim 1, characterized in that, The polypropylene composite material comprises the following raw materials in parts by weight: 100 parts polypropylene resin, 5-15 parts compatibilizer, 8-12 parts toughening agent, 8-15 parts synergist, 15-25 parts magnesium sulfate whiskers, 10-20 parts talc, 0.3-0.6 parts antioxidant, 0.4-0.6 parts light stabilizer, 0.4-0.8 parts lubricant, and 0.03-0.08 parts dicumyl peroxide.

3. The method for preparing polypropylene composite material for automotive side panels according to claim 1, characterized in that, The preparation method of the synergist includes the following steps: A1: Under a nitrogen atmosphere, pentaerythritol and 2,2-dimethylolpropionic acid are added to a reaction vessel and melted at a controlled temperature of 130-140℃. P-toluenesulfonic acid is added and the reaction is maintained at this temperature for 1.5-3 hours. The generated water is removed through a water separator. The temperature is raised to 145-155℃ and the reaction is carried out under vacuum for 3-4 hours. Heating is stopped, the vacuum is turned off, and nitrogen is introduced to atmospheric pressure. The crude product is dissolved in acetone, deionized water is added to precipitate, the precipitate is collected, washed with water, dried, ground, and then extracted with acetone using a Soxhlet extractor. The product is then refluxed and washed to obtain a hydroxyl-terminated hyperbranched polyester. A2: Under a nitrogen atmosphere, hydroxyl-terminated hyperbranched polyester and anhydrous toluene were added to a reaction flask and stirred at 60-70℃ to dissolve. Maleic anhydride, p-toluenesulfonic acid, and hydroquinone were added and dispersed. The reaction was refluxed at 110-125℃ for 4-6 hours. After cooling to room temperature, cold methanol was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain maleic anhydride-modified hydroxyl-terminated hyperbranched polyester. A3: Under a nitrogen atmosphere, maleic anhydride-modified hydroxyl-terminated hyperbranched polyester and N,N-dimethylformamide were added to a reaction flask and dispersed. The temperature was controlled at 60-70℃. Double bond-modified mesoporous silica was added and dispersed. p-Toluenesulfonic acid was added and the temperature was controlled at 90-105℃. The reaction was carried out under stirring for 6-9 hours. After cooling to room temperature, cold methanol was added and stirred to precipitate the precipitate. The precipitate was collected, washed, and dried to obtain the synergist.

4. The method for preparing polypropylene composite material for automotive side panels according to claim 3, characterized in that, The mass ratio of pentaerythritol, 2,2-dimethylolpropionic acid, and p-toluenesulfonic acid in A1 is 6.8-13.6:40-68:0.47-0.

81.

5. The method for preparing polypropylene composite material for automotive side panels according to claim 3, characterized in that, The addition ratio of A2 hydroxyl-terminated hyperbranched polyester, anhydrous toluene, maleic anhydride, p-toluenesulfonic acid, and hydroquinone is 25g: 100-150mL: 4.9-9.8g: 0.17-0.28g: 0.025-0.05g.

6. The method for preparing polypropylene composite material for automotive side panels according to claim 3, characterized in that, The addition ratio of maleic anhydride-modified hydroxyl-terminated hyperbranched polyester, N,N-dimethylformamide, double bond-modified mesoporous silica, and p-toluenesulfonic acid in A3 is 20g: 80-150mL: 3-7.5g: 0.015-0.03g.

7. The method for preparing polypropylene composite material for automotive side panels according to claim 3, characterized in that, The preparation method of the double bond modified mesoporous silica includes the following steps: hexadecyltrimethylammonium bromide, anhydrous ethanol, and deionized water are added to a reaction flask for dispersion, the pH is adjusted to 10-11, tetraethyl orthosilicate and KH570 are mixed and added to the reaction flask for dispersion, the temperature is controlled at 25-35℃ and the reaction is kept at this temperature for 2-4 hours under stirring, then placed in an oven at 60-80℃ and allowed to stand for aging for 12-24 hours, centrifuged, the precipitate is taken, washed to remove hexadecyltrimethylammonium bromide, washed and dried to obtain double bond modified mesoporous silica; The addition ratio of hexadecyltrimethylammonium bromide, anhydrous ethanol, deionized water, tetraethyl orthosilicate, and KH570 is 3.65-7.3g: 100-200mL: 50-100mL: 20g: 2.5-6.25g.

8. The method for preparing polypropylene composite material for automotive side panels according to claim 1, characterized in that, The polypropylene resin is one or both of copolymer polypropylene and homopolymer polypropylene. The compatibilizer is a PP-g-MAH compatibilizer; The toughening agent is POE-g-MAH toughening agent; The antioxidant is composed of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 0.1-0.3:0.1-0.

3. The light stabilizer is a hindered amine light stabilizer; The lubricating dispersant is ethylene bis-stearamide.

9. The method for preparing polypropylene composite material for automotive side panels according to claim 1, characterized in that, The melt temperature for extrusion granulation is 190-220℃; The injection temperature for injection molding is 210-220℃, the mold temperature is 50-60℃, and the pressure is 55-65MPa.

10. A polypropylene composite material for automobile side guards, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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