Polypropylene composition, process for its preparation and use thereof

Abstract

This invention discloses a polypropylene composition, its preparation method, and its application, belonging to the field of polymer materials technology. This product introduces long-chain branched polypropylene and modified rod-shaped particles with a core-shell structure into a glass fiber reinforced polypropylene resin system. Through the synergistic effect of the two and the matrix resin, it can not only effectively overcome the problem of low strength in the weld line area of ​​existing products, but also ensure high dimensional stability, low warpage, good processing effect, and high reliability of the finished product.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a polypropylene composition, its preparation method, and its application. Background Technology

[0002] Polypropylene materials, especially glass fiber reinforced polypropylene composites, are often used in fields such as automobiles and home appliances due to their good rigidity, strength, and heat resistance. However, the strength of glass fiber reinforced polypropylene composites in the weld line area during injection molding is extremely low. This is because when two or more resin melts meet in the mold cavity, the glass fibers in the melt tend to align parallel to the weld line rather than overlapping through it. This results in the fiber reinforcement effect in the weld line area being almost completely lost. At the same time, the molecular chains of the polymer matrix itself are difficult to diffuse and entangle fully due to cooling and orientation. As a result, the strength of this area on the prepared part is only 30% to 50% of that in the non-weld line area, with low strength uniformity and low reliability. However, if the glass fiber content is removed or reduced, it is not only difficult to achieve the rigidity reinforcement effect, but the warpage of the finished product will also increase during processing, resulting in a low yield and unreliable reliability. Summary of the Invention

[0003] Based on the deficiencies of existing technologies, the present invention aims to provide a polypropylene composition that, by introducing long-chain branched polypropylene and modified rod-shaped particles with a core-shell structure into a glass fiber reinforced polypropylene resin, can effectively overcome the problem of low strength in the weld line area of ​​existing products through the synergistic effect of the two and the matrix resin. At the same time, it can also ensure high dimensional stability, low warpage, good processing effect, and high reliability of the finished product during processing.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A polypropylene composition comprising the following components in parts by weight: 30-90 parts polypropylene resin, 8-50 parts glass fiber, 1-8 parts long-chain branched polypropylene, 1-10 parts compatibilizer, and 1-8 parts modified rod-shaped particles. The modified rod-shaped particles include inorganic rod-shaped particles and an organic shell layer disposed on the surface of the inorganic rod-shaped particles.

[0005] Preferably, the inorganic rod-shaped particles include at least one of rod-shaped silica, rod-shaped zinc oxide, halloysite nanotubes, magnesium sulfate whiskers, and attapulgite.

[0006] More preferably, the inorganic rod-shaped particles include at least one of rod-shaped silicon dioxide and rod-shaped zinc oxide.

[0007] The inventors discovered that after introducing modified rod-shaped particles, when the inorganic rod-shaped particles inside are selected from the above-mentioned preferred types, the effect on improving the strength of the weld line area and the dimensional stability of the product is even better.

[0008] Preferably, the organic shell layer comprises at least one of styrene polymers, acrylate polymers, and methacrylate polymers.

[0009] More preferably, the organic shell layer includes at least one of polystyrene, polymethyl acrylate, and polymethyl methacrylate.

[0010] Preferably, the organic shell content in the modified rod-shaped particles is 10-40% by mass.

[0011] Preferably, the mass percentage of the organic shell in the modified rod-shaped particles is one or any two of the following: 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, and 40%.

[0012] It should be noted that the mass percentage of the organic shell in the modified rod-shaped particles of the present invention can be confirmed in the following way: The test method is based on ASTM E1131-20. Using thermogravimetric analysis (TGA), the temperature range is set from 150℃ to 800℃. A 0.3 mg sample is placed in an aluminum crucible, and the temperature is maintained at 150℃ for 30 minutes at a rate of 10℃ / min. The temperature is then increased to 800℃, and the data is recorded. The formula for calculating the mass percentage (GP) of the organic shell in the modified rod-shaped particles is as follows: ; in, It is the mass of the sample at the end of the isothermal treatment at 150℃. It is the residual mass of the sample at 800℃.

[0013] To overcome the contradiction between insufficient strength in the weld line region of existing glass fiber reinforced polypropylene composites after injection molding and the difficulty in achieving dimensional stability through traditional modification methods, this invention introduces long-chain branched polypropylene (LCB-PP) and organic-shell modified inorganic rod-shaped particles into a glass fiber reinforced rigid polypropylene resin matrix. The long-chain branched polypropylene, due to its long-chain structure, can reduce interfacial porosity during injection molding by cross-interfacial diffusion entanglement based on molecular weight after merging with the glass fiber reinforced polypropylene resin matrix, and suppress the necking effect at the melt front. The organic-shell modified inorganic rod-shaped particles can further enhance the composite product's melt properties. The glass fiber, based on its anisotropic rod-like structure, acts as a turbulent, bridging, and stitching agent. This turbulence and bridging effect reduces the isotropic nature of the melt in the weld line region during injection molding, allowing for rapid connection between the two melts. This improves the uniformity of the molded product. The glass fiber also works synergistically to achieve spatial complementarity of rigid particles in the weld line region, realizing intra-component "stitching" and enhancing the dispersion of the glass fiber in the weld line region, thus improving the uniformity of stress transfer. Simultaneously, the long-chain branched polypropylene and the matrix polypropylene resin can form an inter-molecular structure based on molecular chain interlacing, further enhancing the intermolecular forces at the melt interface, significantly improving the strength of the weld line region. On the other hand, long-chain branched polypropylene, after being compounded, can make the product flow more smoothly during injection molding, avoiding excessive anisotropy caused by unstable flow of glass fiber and modified rod particles. In addition, the molecular chain entanglement of this component is high, so the stress relaxation rate of the product during cooling is faster after compounding, effectively releasing the stress during molding. The modified rod particles can also act as a nucleating agent of polypropylene resin to a certain extent, refining the spherulite size. Through the synergistic effect of the two, the product can have high dimensional stability during injection molding and cooling, and is not prone to warping.

[0014] However, the inventors' experiments revealed that the modified rod-shaped particles need to be paired with an organic shell to achieve better interfacial compatibility in the product composition and to achieve uniform dispersion with the rigid glass fiber skeleton and fill the gaps between the glass fibers. Without the introduction of an organic shell, even if compatibilizer components are present, significant agglomeration and surface migration will occur due to the large contact area and the functional groups on the surface, which is not conducive to improving product performance.

[0015] In some embodiments, the polypropylene resin is in the range of one or any two of the following weight parts: 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, and 90 parts; and the glass fiber is in the range of one or any two of the following weight parts: 8 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, and 50 parts. The weight parts of the long-chain branched polypropylene are 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, and 8 parts, or any two of these values; the weight parts of the compatibilizer are 1 part, 3 parts, 4 parts, 5 parts, 6 parts, 8 parts, and 10 parts, or any two of these values; and the weight parts of the modified rod-shaped particles are 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, and 8 parts, or any two of these values.

[0016] Preferably, the polypropylene composition comprises the following components in parts by weight: 40-60 parts polypropylene resin, 30-40 parts glass fiber, 2-6 parts long-chain branched polypropylene, 4-6 parts compatibilizer, and 2-6 parts modified rod-shaped particles.

[0017] Preferably, in the polypropylene composition, the mass percentage of polypropylene resin is ≥30wt%.

[0018] Preferably, the polypropylene composition contains glass fiber at a mass percentage of ≥10 wt%.

[0019] Preferably, in the polypropylene composition, the mass percentage of modified rod-shaped particles is ≥1wt% and ≤10wt%.

[0020] Preferably, the polypropylene resin includes at least one of copolymer polypropylene and homopolymer polypropylene.

[0021] Preferably, the polypropylene resin has a melt flow rate of 10~50g / 10min at 230℃ and 2.16kg load, according to GB / T 3682.1-2018.

[0022] In some embodiments, the polypropylene resin has a melt flow rate of 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 28 g / 10 min, 30 g / 10 min, 40 g / 10 min, or 50 g / 10 min, according to GB / T 3682.1-2018 at 230°C and 2.16 kg load, based on any one or both of these ranges.

[0023] The type of polypropylene resin described in this invention is not specifically limited. Homopolymer polypropylene or other types can be used, as long as they can achieve the expected high weld line strength and high dimensional stability in a glass fiber reinforced system by combining long-chain branched polypropylene and modified rod particles.

[0024] Preferably, the long-chain branched polypropylene has a melt flow rate of 0.5~15g / 10min at 230℃ and 2.16kg load according to GB / T 3682.1-2018.

[0025] Preferably, the long-chain branched polypropylene, referring to section

[0064] of the specification CN108137834B, is extruded from an orifice with a diameter of 2 mm and a length of 40 mm at 230°C using a capillary rheometer at a pushing speed of 20 mm / min. When the base resin is rolled at a speed of 4 m / min, the melt strength detected by the pulley is ≥5 g.

[0026] Preferably, the long-chain branched polypropylene has a melt strength of 5~36g at 230°C.

[0027] Preferably, the melt strength of the long-chain branched polypropylene at 230°C is a value within the range of one or any two of the following: 5g, 6g, 8g, 10g, 15g, 17g, 25g, 28g, and 36g.

[0028] More preferably, the long-chain branched polypropylene has a melt strength of 15~28g at 230°C.

[0029] The melt strength of long-chain branched polypropylene is related to its dispersibility in the product and the degree of molecular chain entanglement. When long-chain branched polypropylene is at the above-mentioned preferred melt strength, its synergistic effect with glass fiber and modified rod particles is better, the degree of improvement of the weld line strength of the product is better, the uniformity of the components is better, and the dimensional stability of the product is also better.

[0030] Preferably, the modified rod-shaped particles can be commercially available products or self-made products. Further, the modified rod-shaped particles can be prepared by the following method: Inorganic rod-shaped particles were washed, purified, and dried sequentially. They were then placed in organic solvent I, and an aminosilane coupling agent was added under a protective atmosphere. The mixture was then heated to 80-120°C and stirred for 6-48 hours. The solid was filtered, washed, and dried. The resulting pre-modified inorganic rod-shaped particles were then subjected to a pre-loading reaction. The resulting pre-loaded initiator-containing inorganic rod-shaped particles were then placed in organic solvent II, and a catalyst, catalyst ligand, and monomer of the modified organic shell were added. The mixture was heated to 50-110°C and stirred for 2-24 hours. The mixture was then cooled, and the solid and liquid were separated. The resulting solid was washed and dried to obtain the modified rod-shaped particles.

[0031] It should be noted that the monomer stirring reaction time mentioned in the above scheme can be determined by sampling tests at interval stages, such as at intervals of 1h, 2h, 12h, etc., or at equal time intervals (e.g., 30min intervals). When sampling, the temperature is lowered or a polymerization inhibitor is added to stop the polymerization. Subsequently, the concentration of the remaining monomer in the reaction mother liquor is analyzed by gas chromatography (GC) or nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), and the conversion rate of the monomer is tested and calculated. The solid product is tested by the above thermogravimetric analysis (TGA) to determine the content of polymer that has formed an organic shell. The data is used to determine whether the expected reaction node has been reached.

[0032] Preferably, the organic solvent I includes at least one of toluene and xylene.

[0033] More preferably, the concentration of the inorganic rod-shaped particles after dispersion in organic solvent I is 30~80 g / L.

[0034] Preferably, the silane coupling agent comprises at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane (APTMS), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602).

[0035] More preferably, the mass ratio of the inorganic rod-shaped particles to the aminosilane coupling agent is 1:(0.05~0.3).

[0036] Preferably, the step of pre-loading the pre-modified inorganic rod-shaped particles at low temperature is as follows: The pre-modified inorganic rod-shaped particles were dispersed in dichloromethane at a mass content of 3-8 wt%. Triethylamine and 2-bromoisobutyryl bromide at a mass content of 0.2-0.6 wt% and 2-bromoisobutyryl bromide were added at 0-5 °C and reacted for 0.5-3 h. Then the temperature was raised to 20-30 °C and reacted for a second time for 10-15 h.

[0037] Preferably, the organic solvent II includes at least one of toluene, anisole, and N,N-dimethylformamide.

[0038] More preferably, the concentration of the inorganic rod-shaped particles of the preloaded initiator in organic solvent II is 30~80 g / L.

[0039] Preferably, the catalyst includes at least one of cuprous bromide and cuprous chloride.

[0040] Preferably, the catalyst ligand comprises at least one of N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) and 2,2'-bipyridine.

[0041] Preferably, the monomer of the modified organic shell includes at least one of styrene monomer, methyl acrylate monomer, and methacrylate monomer.

[0042] More preferably, the monomer content of the modified organic shell is 0.5 to 1.5 wt% based on the mass of the inorganic rod-shaped particles supporting the initiator.

[0043] Preferably, the inorganic rod-shaped particles have an average retention diameter of 0.03~2μm and an average retention length of 1~30μm.

[0044] Preferably, the inorganic rod-shaped particles retain an average aspect ratio of 2 to 1100. More preferably, the inorganic rod-shaped particles retain an average aspect ratio of 5 to 19.

[0045] More preferably, the retained average aspect ratio of the inorganic rod-shaped particles is a range of one or both of 5, 6, 7, 8, 9, 10, 12, 15, 18, and 19.

[0046] More preferably, the inorganic rod-shaped particles retain an average aspect ratio of 5 to 10.

[0047] When the aspect ratio of inorganic rod-shaped particles in the product is further optimized within the above range, their filling effect on the glass fiber skeleton in the product is better, their dispersion is better, they are less prone to agglomeration, their control effect on the anisotropy of glass fiber in the weld line area is better, their weld line strength is higher, and their nucleating agent effect is better, which can also improve the dimensional stability of the product and reduce warpage.

[0048] It should be noted that the average retained diameter, average retained length, and average retained aspect ratio of the inorganic rod-shaped particles in the polypropylene composition described in this invention refer to the average values ​​of the final retained diameter, the final retained length, and the final retained aspect ratio of the inorganic rod-shaped particles in the product after they have been compounded with other components and processed into a polypropylene composition. These values ​​are not the same as the original average diameter, the original average length, and the original average aspect ratio of the inorganic rod-shaped particles. Those skilled in the art can use raw material inorganic rod-shaped particles of different sizes to obtain different average retained diameters, average retained lengths, and average retained aspect ratios in the product according to actual needs. Alternatively, they can use the same raw material but adjust the processing parameters during processing. No specific limitation is made in this regard.

[0049] The original average length and original average diameter of the inorganic rod-shaped particles described in this invention were measured using a two-dimensional microscope. The inorganic rod-shaped particles not used in the preparation of the product were dispersed in ethanol, and then 200 inorganic rod-shaped particles were observed and selected to statistically analyze their length and diameter. The average value was calculated, which is the original average length and original average diameter of the inorganic rod-shaped particles.

[0050] It should be noted that the average retained diameter, average retained length, and average retained aspect ratio of the inorganic rod-shaped particles in the polypropylene composition of the present invention can be confirmed by, but is not limited to, the following methods: First, the polypropylene composition was calcined at 650℃ for 30 minutes to remove resin and retain inorganic matter. Inorganic rod-shaped particles and glass fibers were then separated from the light ash by ultrasonic sedimentation. These were then uniformly dispersed in water. Two hundred intact inorganic rod-shaped particles were selected for observation and testing using a two-dimensional microscope. The average retained diameter and length of each inorganic rod-shaped particle were measured (the diameter was measured at the middle of the inorganic rod-shaped particle). The aspect ratio (retained length / retained diameter) was calculated based on the average retained diameter and length.

[0051] Preferably, the glass fiber has an average retained diameter of 10-17 μm and an average retained length of 100-500 μm.

[0052] The methods for testing the retained average diameter and retained average length of the glass fiber described in this application are the same as those for testing the retained average diameter and retained average length of inorganic rod-shaped particles, and will not be repeated here.

[0053] Preferably, the compatibilizer includes at least one of maleic anhydride-grafted polypropylene, glycidyl methacrylate-grafted polypropylene, and glycidyl methacrylate-grafted polyolefin elastomer.

[0054] More preferably, the grafting rate of the compatibilizer is 0.01~2wt%.

[0055] The grafting rate of the compatibilizer described in this invention was confirmed by titration: For example, when the grafting material is maleic anhydride, weigh 0.5g of the analyte and dissolve it completely in 50mL of hot xylene. Add V1mL of C1mol / L NaOH-ethanol solution and reflux at 140℃ for 10min to allow the maleic anhydride groups in the analyte to react fully with the alkali. Then, add an appropriate amount of deionized water to promote the hydrolysis of the anhydride to carboxylic acid. At the same time, add 3 drops of phenolphthalein indicator and titrate with hydrochloric acid / isopropanol to the endpoint. The concentration of hydrochloric acid / isopropanol is C2 (mol / L). When M (g) of sample is titrated, V2 (mL) of solution is consumed. The grafting rate G is then calculated using the following formula: ; As mentioned above, V1 is the volume of excess KOH-ethanol solution, V2 is the volume of HCl-isopropanol solution in the back titration, C1 is the concentration of KOH-ethanol standard solution, C2 is the concentration of HCl-isopropanol solution, and m is the mass of the analyte, i.e., 0.5g.

[0056] If the grafting compound is glycidyl methacrylate, weigh 0.5 g of the test substance and dissolve it in 50 mL of hot toluene under reflux. Cool to below 60 °C, add 20 mL of 0.1 mol / L trichloroacetic acid / toluene solution and reflux for 4 h. Use phenolphthalein as an indicator and back-titrate with NaOH / ethanol standard solution to the endpoint. Perform a blank test (i.e., without adding the test sample) in the same manner as above. The grafting rate G is calculated using the following formula: G = 100% × N × (V0 - V) × M （甲基丙烯酸缩水甘油酯） / (1000 × W); Where N is the concentration of NaOH / ethanol standard solution (mol / L), V0 is the volume of NaOH / ethanol standard solution consumed in the blank test (mL), V is the volume of NaOH / ethanol standard solution consumed by the test sample (mL), W is the mass of the test sample (0.5g), and M... （甲基丙烯酸缩水甘油酯） The molar mass of glycidyl methacrylate is 142.15 g / mol.

[0057] Based on actual needs, those skilled in the art can introduce compatibilizer components with compatibility effects into the product components of the product to ensure that the glass fiber in the product can achieve good compatibility. There are no specific restrictions on the selection of compatibilizers. They can be the types mentioned above, or other types of compatibilizers commonly used in polypropylene products. As long as it does not affect the performance of other components and ensures that the product can achieve the expected technical effect, it is acceptable.

[0058] More preferably, the polypropylene composition further includes 0.2 to 2 parts of processing aids.

[0059] More preferably, the processing aid includes at least one of antioxidants and lubricants.

[0060] More preferably, the antioxidant includes at least one of hindered phenolic antioxidants, hindered amine antioxidants, and phosphite antioxidants.

[0061] More preferably, the antioxidant includes tris(2,4-di-tert-butylphenyl) phosphite, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 2,5-di-tert-butyl-4-hydroxybenzyl dimethylamine, diethyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate, stearyl-3,5-di-tert-butyl-4-hydroxybenzyl phosphate; 3,5-di-tert-butyl-4-hydroxyphenyl-3,5-distearate-thiotriazolylamine, 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,4-di-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylglycerol allyl ether)-1,3,5-triazine. At least one of N,N'-hexamethylene di(3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamamide), N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl ester, triethylene glycol di[3-(3,5-dimethyl-4-hydroxyphenyl)propionate], triethylene glycol di[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 2,2'-thiodiethyl-di[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0062] More preferably, the lubricant includes at least one of stearic acid lubricants, amide lubricants, silicone lubricants, and polyethylene wax lubricants.

[0063] Based on actual needs, other types of processing aids can also be introduced into the polypropylene composition of the present invention, such as antioxidants, lubricants, etc., as listed above. These aids can provide additional performance enhancements that are not expected to achieve the technical effects of the product during product processing and use. For example, the use of lubricants can improve the demolding efficiency of the product, while the use of antioxidants can improve the product's resistance to easy oxidation. As long as it does not affect the normal function of the key components of the product of the present invention and enable them to achieve the expected results, there are no restrictions.

[0064] Another object of the present invention is to provide a method for preparing the polypropylene composition, comprising the following steps: After the components are mixed evenly, they are melt-extruded and granulated in a screw extruder to obtain the polypropylene composition.

[0065] The preparation method of the polypropylene composition of the present invention has simple operation steps and can achieve industrial-scale production.

[0066] Preferably, the glass fiber is added from the side feed port.

[0067] Preferably, the temperature range of the screw extruder is set to 80~260℃, the screw speed is 300~500r / min, and the screw length-to-diameter ratio is 40~52:1.

[0068] Another object of the present invention is to provide the use of the polypropylene composition in the manufacture of automotive or electrical components.

[0069] Another object of the present invention is to provide an automotive component comprising the polypropylene composition described herein.

[0070] Another object of the present invention is to provide an electrical component comprising the polypropylene composition described herein.

[0071] The polypropylene composition described in this invention is designed with specific components, which can not only effectively ensure that the strength of the weld line area during injection molding is maintained at a high level, resulting in high product reliability and long service life, but also ensure high dimensional stability and low warpage during part processing, making it applicable to various processing scenarios.

[0072] The beneficial effects of the present invention are that it provides a polypropylene composition, which introduces long-chain branched polypropylene and modified rod-shaped particles with a core-shell structure into the polypropylene resin of the glass fiber reinforced system. Through the synergistic effect of the two and the matrix resin, it can not only effectively overcome the problem of low strength in the weld line area of ​​existing products, but also take into account the high dimensional stability of the product during processing, low warpage, good processing effect, and high reliability of the finished product. Detailed Implementation

[0073] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0074] Examples 1-14 Examples of the polypropylene composition, its preparation method, and its application according to the present invention are shown in Table 1.

[0075] The preparation method of the product includes the following steps: The components are mixed evenly and then placed in a screw extruder for melt extrusion granulation, wherein glass fiber is fed in from the side feed port to obtain the polypropylene composition.

[0076] The temperature zones of the screw extruder are set as follows: Zone 1: 100℃, Zone 2: 230℃, Zone 3: 240℃, Zone 4: 240℃, Zone 5: 250℃, Zone 6: 250℃, Zone 7: 260℃, Zone 8: 260℃, Zone 9: 260℃, the screw speed is 300 r / min, and the length-to-diameter ratio is 40:1.

[0077] Comparative Examples 1-8 The only difference between each comparative example and the embodiment is the type and ratio of components, as shown in Table 2.

[0078] In the components described in each embodiment and comparative example, Polypropylene resin 1 is PP 1124 produced by Yongjia Chemical Co., Ltd., a homopolymer polypropylene, with a melt flow rate of 15.0 g / 10 min at 230℃ and 2.16 kg load; Polypropylene resin 2 is PP KF-Z30S produced by Ningbo Kingfa New Materials Co., Ltd., a homopolymer polypropylene with a melt flow rate of 27.0 g / 10 min at 230℃ and 2.16 kg load. The glass fiber is ECS13-04-508A produced by China Jushi Co., Ltd., with an average diameter of 13μm and an average length of 4.0mm. Long-chain branched polypropylene 1 is produced by Nippon Polypropylene Co., Ltd. as MFX3, with a melt strength of 6g at 230°C. Long-chain branched polypropylene 2 is MFX6 produced by Nippon Polypropylene Co., Ltd., with a melt strength of 17g at 230°C. Long-chain branched polypropylene 3 is MFX8 produced by Nippon Polypropylene Co., Ltd., with a melt strength of 25g at 230°C. The long-chain branched polypropylene 4 is SABIC® PP-UMS 561P, with a melt strength of >65g at 230°C and a traction speed of 3.14 m / min; Compatibilizer 1: LEP-1A, produced by Shenyang Ketong Plastics Co., Ltd., is maleic anhydride-grafted polypropylene with a grafting rate of 0.8%. Compatibilizer 2: SPG-02, produced by Jiayirong Compatibilizer Jiangsu Co., Ltd., is made of glycidyl methacrylate grafted polypropylene with a grafting rate of 1%. Modified rod-shaped particles 1 are self-made products. The preparation method is as follows: (1) The inorganic rod-shaped particles 1, which are washed and dried after pretreatment with water, are dispersed in anhydrous toluene at a concentration of 50 g / L. The aminosilane coupling agent 3-aminopropyltriethoxysilane (the mass ratio of inorganic rod-shaped particles to aminosilane coupling agent is 1:0.1) is added, and the reaction is carried out at 80°C under nitrogen protection for 6 h; (2) After the reaction is completed, the solid is filtered, washed with anhydrous toluene, dried, and then the obtained pre-modified inorganic rod-shaped particles are dispersed in anhydrous dichloromethane at a mass content of 5 wt%. At 0°C, 0.45 wt% of triethylamine and 1.5 wt% of 2-bromoisobutyryl bromide are added and reacted for 1 h. Then the temperature is raised to 25°C and reacted for 12 h; (3) After the reaction is completed, the inorganic rod-shaped particles 1 are dispersed in anhydrous dichloromethane at a mass content of 5 wt%. The reaction is carried out at 0°C. The inorganic rod-shaped particles 1 are prepared by washing and drying with water and then dispersing them in anhydrous toluene at a concentration of 5 wt%. ... After the reaction, the solid was filtered, washed with anhydrous dichloromethane, and dried. The resulting inorganic rod-shaped particles with pre-loaded initiator were dispersed in anisole at a concentration of 40 g / L. Styrene monomer and CuBr / PMDETA catalyst with a mass content of 0.9 wt% based on the mass of the inorganic rod-shaped particles with initiator were added, wherein the molar ratio of styrene monomer:CuBr:PMDETA was 100:1:1.5. The resulting mixture was heated to 90 °C and stirred for polymerization reaction for 10 h. (4) After the reaction was completed, the mixture was filtered, cooled, and the solid and liquid were separated. The resulting solid was washed three times each with toluene and ethanol, and then dried under vacuum at 60 °C for 24 h to obtain modified rod-shaped particles 1. The mass percentage of its organic shell was determined to be 21.3 wt% by thermogravimetric analysis.

[0079] Modified rod-shaped particles 2 are self-made products, and the preparation method is basically the same as that of modified inorganic rod-shaped particles 1. The difference is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 2, the styrene monomer in step (3) is replaced with methyl acrylate monomer, the amount added is 1.5 wt% based on the mass of the inorganic rod-shaped particles with pre-loaded initiator, and the stirring polymerization reaction temperature is adjusted to 80℃ and the stirring polymerization time is adjusted to 13h. The organic shell mass percentage of modified rod-shaped particles 2 is 36.5 wt% as determined by thermogravimetric analysis.

[0080] The modified rod-shaped particles 3 are self-made products. The only difference between them and the modified inorganic rod-shaped particles 1 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 3.

[0081] The modified rod-shaped particles 4 are self-made products. The only difference between the preparation method and steps of the modified inorganic rod-shaped particles 1 and the modified inorganic rod-shaped particles 4 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 4.

[0082] The modified rod-shaped particles 5 are self-made products. The only difference between the preparation method and steps of the modified inorganic rod-shaped particles 1 and the modified inorganic rod-shaped particles 5 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 5.

[0083] The modified rod-shaped particles 6 are self-made products, and the only difference between them and the modified inorganic rod-shaped particles 1 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 6.

[0084] The modified rod-shaped particles 7 are self-made products, and the only difference between them and the modified inorganic rod-shaped particles 1 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 7.

[0085] The modified rod-shaped particles 8 are self-made products. The only difference between the preparation method and steps of the modified inorganic rod-shaped particles 1 and the modified inorganic rod-shaped particles 8 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 8.

[0086] The modified rod-shaped particles 9 are self-made products. The only difference between the preparation method and steps of the modified inorganic rod-shaped particles 1 and the modified inorganic rod-shaped particles 9 is that the inorganic rod-shaped particles 1 are replaced with inorganic rod-shaped particles 9.

[0087] Modified particle 1 is a self-made product. The only difference between it and modified inorganic rod-shaped particles 1 is that the inorganic rod-shaped particles 1 are replaced with inorganic particulate particles.

[0088] Modified particle 2 is a self-made product. The only difference between it and modified inorganic rod-shaped particles 1 is that the inorganic rod-shaped particles 1 are replaced with inorganic sheet-shaped particles.

[0089] Among them, the aforementioned inorganic rod-shaped particles 1 are XFI18 series products produced by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., rod-shaped zinc oxide, with an average diameter of 1μm and an average length of 5.5μm after screening; Inorganic rod-shaped particles 2 are produced by Jingkang Biotechnology Co., Ltd., JK-R0769, rod-shaped zinc oxide, with an average diameter of 0.050μm and an average length of 30μm after screening; Inorganic rod-shaped particles 3 are XFI18 series products produced by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., rod-shaped zinc oxide, with an average diameter of 0.9μm and an average length of 3μm after screening; Inorganic rod-shaped particles 4 are XFI18 series products produced by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., rod-shaped zinc oxide, with an average diameter of 1.5μm and an average length of 9μm after screening; Inorganic rod-shaped particles 5 are XFJ53-1 products produced by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., rod-shaped zinc oxide, with an average diameter of 0.2μm and an average length of 4μm after screening; Inorganic rod-shaped particles 6 are WS-1 produced by Wesker Chemicals Ltd., rod-shaped magnesium sulfate whiskers, with an average diameter of 0.5 μm and an average length of 25 μm after screening; Inorganic rod-shaped particles 7 are XFI18 series products manufactured by Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., rod-shaped zinc oxide, with an average diameter of 0.4μm and an average length of 1μm after grinding and screening; The inorganic rod-shaped particles 8 are rod-shaped silica prepared by the method described in Example 6 of CN112194139B, with an average diameter of 1.2 μm and an average length of 6 μm. Inorganic rod-shaped particles 9 are produced by Hubei Shuaiyan Ligao Biomedical Co., Ltd. (sylglsmjx-14145), rod-shaped magnesium sulfate whiskers, with an average diameter of 1.1μm and an average length of 5.2μm after grinding and crushing. The inorganic particles are commercially available granular zinc oxide, with an average diameter of 1.2 μm after screening; The inorganic flake particles are zinc oxide flakes produced by Guangzhou Guangna Huichuan Technology Co., Ltd., with an average flake diameter of 2μm.

[0090] Polystyrene was a self-made product, prepared as follows: styrene monomer was dissolved in toluene to prepare a reaction solution with a styrene mass fraction of 30 wt%. Azobisisobutyronitrile (AIB) with a mass content of 0.8 wt% (based on the mass of styrene monomer) was added, and the mixture was heated to 90°C and reacted for 10 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to 25°C, and the resulting reaction solution was slowly added dropwise to methanol, causing a solid to precipitate. The solid was allowed to stand, filtered, and washed three times with methanol. It was then dried under vacuum at 60°C for 16 hours to obtain the polystyrene.

[0091] The antioxidant is a mixture of commercially available hindered phenolic antioxidants, commercially available phosphite antioxidants, antioxidant 168 and antioxidant 1010 in a mass ratio of 1:1.

[0092] The lubricant is commercially available calcium stearate.

[0093] Unless otherwise specified, the antioxidants, lubricants and other processing aids and anti-dripping agents used in the embodiments and comparative examples of this invention are all commercially available raw materials, and the raw materials used in each parallel experiment are all the same.

[0094] Table 1 Table 2 Example of effect 1 To verify the performance of the product described in this invention, the following performance tests were conducted on the products of each embodiment and comparative example, with the specific steps as follows: (1) Weld line strength test: Referring to ISO 527-1:2019, two types of standard tensile specimens were prepared by injection molding using the examples and comparative products: (A) bulk strength specimen (without weld line) and (B) weld line strength specimen. The mold was made by two-end injection, and the weld line was located in the middle of the specimen. Then, a universal testing machine was used, and the tensile speed of the testing machine was set to 5 mm / min. Five (A) type bulk strength specimens were taken for tensile testing. The maximum tensile stress (i.e., tensile strength) at the time of fracture of each specimen was recorded, and its average value was calculated and recorded as σbulk. Five (B) type weld line strength specimens were taken for tensile testing, ensuring that the weld line was located in the middle of the fixture. The maximum tensile stress at the time of fracture of each specimen was recorded, and its average value was calculated and recorded as σweld. It was observed and recorded that all (B) type specimens underwent brittle fracture at the weld line location. The weld line strength retention (WLSR) can be calculated and confirmed by the following formula: ; (2) Injection molding warpage test: The products of each embodiment and comparative example were injection molded into flat samples of 100mm × 100mm × 2mm. The injection molding parameters were: melt temperature 220~240℃, mold temperature 70℃, holding pressure 50 MPa, and cooling time 30s. After injection molding, the flat sample is placed on a flat surface and allowed to cool naturally to room temperature. Referring to ISO 291-2008 standard, it is left to stand for 48 hours in a standard environment of 23±2℃ and 50% relative humidity. The flat sample to be tested is placed on a reference platform, allowing it to naturally adhere to the three corners (lower left, lower right, and upper left) of the sample under gravity, ensuring stable contact with the reference platform. These three points constitute the measurement zero plane. Then, the height of the fourth corner (i.e., the upper right corner) relative to the reference platform is measured. This height is taken as the maximum warpage value of the sample. Ten parallel samples are prepared for each product and measured. The average of the maximum warpage values ​​of the ten parallel samples is the warpage of the product.

[0095] The test results are shown in Tables 3 and 4.

[0096] Table 3 Table 4 As can be seen from Tables 3 and 4, the products of this invention, based on the selection of specific component combinations, not only achieve ideal weld line strength, but also achieve a weld line strength retention rate of 75% or higher in each embodiment. Furthermore, they exhibit good dimensional stability during processing. For example, the warpage of a 2mm thin-layer flat plate can be controlled within 1.1mm. This is mainly due to the introduction of long-chain branched polypropylene and organic shell-modified inorganic rod-shaped particles into the glass fiber-reinforced polypropylene resin matrix. The former effectively fills and diffuses into the interfacial micropores of the product components, suppressing melt necking and improving the flow stability during injection molding. The latter acts as a turbulent, bridging, and sealing agent. Therefore, when either of these is lacking, as shown in Comparative Examples 1 and 2 and Comparative Examples 7 and 8, neither the weld line strength nor the dimensional stability during processing can be guaranteed, resulting in high warpage. In Comparative Example 3, the inorganic rod-shaped particles and modified polystyrene were introduced into the product separately. Although the polystyrene also had a certain compatibilizing effect between the inorganic rod-shaped particles and the matrix resin, the effect was not significant. At this time, due to the aggregation and migration of the inorganic rod-shaped particles, the performance of the product was almost not significantly improved compared to Comparative Example 2, which did not introduce rod-shaped particles. The modified particles introduced in Comparative Examples 4 and 5 also had an organic shell layer, but their shape was not the rod shape defined in this invention. Obviously, these particles could not play the expected role of turbulence, bridging, and stitching. The weld line area strength retention rate of the product was low and the warpage was high. In Comparative Example 6, the amount of modified rod-shaped particles added was too much, which obviously seriously affected the fluidity of the resin in the product during processing. Moreover, the aggregation and migration phenomena were too serious. The weld line area strength retention rate of the product decreased significantly and the warpage was high.

[0097] Meanwhile, based on the comparison of products in Examples 1 and 4-6, it can be seen that the melt strength of long-chain branched polypropylene is related to its dispersibility in the product and the degree of molecular chain entanglement. When the long-chain branched polypropylene is preferably in the melt strength range of 15-28g, its synergistic effect with glass fiber and modified rod particles is better, the degree of improvement in weld line strength is better, the uniformity of components is better, and the dimensional stability of the product is also better.

[0098] Furthermore, a comparison of Examples 1 and 7-14 shows that, in the final product, when the aspect ratio of the modified inorganic rod-shaped particles coated with the organic shell is further optimized to be between 5 and 19, it is more conducive to their filling effect in the glass fiber skeleton, resulting in stronger dispersion of inorganic components in the organic resin, better control of the anisotropy of glass fibers, and better nucleation effect of the particles. If the inorganic rod-shaped particles are selected as rod-shaped zinc oxide and rod-shaped silica, the performance of the product can also be further improved.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polypropylene composition, characterized in that, The components include the following parts by weight: 30-90 parts polypropylene resin, 8-50 parts glass fiber, 1-8 parts long-chain branched polypropylene, 1-10 parts compatibilizer, and 1-8 parts modified rod-shaped particles. The modified rod-shaped particles include inorganic rod-shaped particles and an organic shell layer disposed on the surface of the inorganic rod-shaped particles.

2. The polypropylene composition according to claim 1, characterized in that, The inorganic rod-shaped particles include at least one of rod-shaped silica, rod-shaped zinc oxide, halloysite nanotubes, magnesium sulfate whiskers, and attapulgite, and / or the organic shell includes at least one of styrene polymers, acrylate polymers, and methacrylate polymers.

3. The polypropylene composition according to claim 1, characterized in that, The long-chain branched polypropylene has a melt strength of ≥5g at 230℃; preferably, the melt strength of the long-chain branched polypropylene at 230℃ is 5~36g.

4. The polypropylene composition according to claim 1, characterized in that, The inorganic rod-shaped particles have an average retention diameter of 0.03~2μm and an average retention length of 1~30μm.

5. The polypropylene composition according to claim 4, characterized in that, The inorganic rod-shaped particles retain an average aspect ratio of 2 to 1100; preferably, the inorganic rod-shaped particles retain an average aspect ratio of 5 to 19.

6. The polypropylene composition according to claim 1, characterized in that, Includes at least one of the following (1) to (3): (1) The melt flow rate of the polypropylene resin at 230℃ and 2.16kg load is 10~50g / 10min; (2) The compatibilizer includes at least one of maleic anhydride-grafted polypropylene, glycidyl methacrylate-grafted polypropylene, and glycidyl methacrylate-grafted polyolefin elastomer. (3) The polypropylene composition further includes 0.2 to 2 parts of processing aids; preferably, the processing aids include at least one of antioxidants and lubricants.

7. The method for preparing the polypropylene composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: After the components are mixed evenly, they are melt-extruded and granulated in a screw extruder to obtain the polypropylene composition.

8. The use of the polypropylene composition according to any one of claims 1 to 6 in the preparation of automotive parts or electrical parts.

9. An automotive component, characterized in that, Includes the polypropylene composition according to any one of claims 1 to 6.

10. An electrical component, characterized in that, Includes the polypropylene composition according to any one of claims 1 to 6.

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