A polypropylene composite material, its preparation method and application

Abstract

The present invention discloses a polypropylene composite material, its preparation method and application, relating to the technical field of polymer material modification. The polypropylene composite material of the present invention is compounded with polypropylene resin and ethylene-based copolymer elastomer, and at the same time specific primary antioxidant and auxiliary antioxidant and other components are introduced. It not only has high mechanical properties, light transmittance and light transmittance retention rate after aging, but also has a low yellowness coefficient after aging, and has good appearance performance when applied to the preparation of a light-transmitting automotive bumper. The present invention also provides a preparation method of the low-yellowness light-transmitting polypropylene composite material and its application in the preparation of a light-transmitting automotive bumper.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material modification, and specifically relates to a polypropylene composite material, a preparation method thereof, and an application thereof. Background Art

[0002] At present, new energy vehicles have gradually become an important choice for people when purchasing cars due to their advantages such as low power price and environmental protection. With the popularization of new energy vehicles, new energy vehicles pay more attention to a sense of technology in appearance design. Among them, the bumper, which is in the core position outside the vehicle body, has attracted the attention of new energy vehicle manufacturers. More and more vehicle manufacturers put forward new appearance requirements for the bumper, that is, by designing a pattern on the bumper with light transmittance and placing a lighting component behind the bumper, presenting a specific decorative effect, enhancing the sense of technology and high-class feeling. Therefore, it is necessary to provide a polypropylene composite material with high transparency function and meeting the application requirements of the bumper. Although the existing modified polypropylene can achieve the light transmittance effect and the basic functions of the bumper, the problem is that after experiencing sunlight and high temperature exposure, there will be a certain degree of yellowing and color change, affecting the light transmittance effect and appearance. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a low-yellowing light-transmitting polypropylene composite material, a preparation method thereof, and an application thereof.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: providing a polypropylene composite material, comprising the following components in parts by weight: 48-79 parts of polypropylene resin, 10-30 parts of ethylene copolymerized elastomer, 0.2-0.5 part of main antioxidant, and 0.2-0.5 part of auxiliary antioxidant;

[0005] Among them, the polypropylene resin is homopolypropylene; the ethylene copolymerized elastomer is at least one of ethylene-butene copolymer and ethylene-octene copolymer; the crystallinity of the ethylene copolymerized elastomer ≥ 13%; the main antioxidant is at least one of antioxidant 1076 and antioxidant 1790; the auxiliary antioxidant is bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite.

[0006] As a preferred embodiment of the polypropylene composite material of the present invention, the crystallinity of the ethylene copolymerized elastomer is 18-40%; preferably, the crystallinity of the ethylene copolymerized elastomer is 20-30%; more preferably, the crystallinity of the ethylene copolymerized elastomer is 25-29%.

[0007] The test method for the crystallinity of the ethylene copolymerized elastomer is measured by differential scanning calorimetry (DSC) according to the standard ISO 11357-2016.

[0008] The polypropylene composite material prepared by the present invention has the following characteristics: ① After aging for 1000 h at 100 °C, the yellowing coefficient △Yi ≤ 3.0, and the light transmittance retention rate ≥ 90%; ② After xenon lamp aging test with an energy radiation of 2500 KJ / m 2 of irradiation dose, the yellowing coefficient △Yi ≤ 3.0, and the light transmittance retention rate ≥ 90%. This composite material solves the problem of poor appearance and light transmittance caused by yellowing of the existing light-transmitting polypropylene bumper material.

[0009] In the components of the polypropylene composite material of the present invention, homopolypropylene is used as the matrix resin, and an ethylene copolymer type elastomer is added for compounding, which can effectively reduce the yellowing coefficient of the product after aging, and at the same time improve the mechanical properties, light transmittance and light transmittance retention rate of the product after aging; the reason may be that there is good compatibility between ethylene-butene copolymer and ethylene-octene copolymer and the polypropylene resin matrix, and a better dispersion effect can be achieved in the matrix resin. The crystallinity of the ethylene copolymer type elastomer has a greater influence on the product. If the crystallinity of the ethylene copolymer type elastomer is too low, the light transmittance of the product decreases, the yellowing coefficient of the product after aging increases, and the light transmittance retention rate decreases. Therefore, the present invention preferably selects the crystallinity of the ethylene copolymer type elastomer to improve the light transmittance of the product, the light transmittance retention rate after product aging, and reduce the yellowing coefficient of the product after aging.

[0010] In the raw materials for light-transmitting automobile bumpers, a main antioxidant is generally added to improve the antioxidant property of the product. However, the most commonly used main antioxidant is antioxidant 1010. Although it has good light transmittance, because it contains a hindered phenol structure that is converted into quinone, the yellowing coefficient of the product after aging increases, and the light transmittance retention rate decreases. After optimization by the inventor, in the product of the present invention, antioxidant 1076 and / or antioxidant 1790 is used instead of antioxidant 1010, which can not only reduce the increase in the yellowing coefficient of the product after aging, improve the light transmittance retention rate of the product after aging, but also will not weaken the mechanical properties and light transmittance of the product.

[0011] As an example, the melt flow rate of the polypropylene resin is 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 60 g / 10 min, 70 g / 10 min, 80 g / 10 min, 90 g / 10 min, 100 g / 10 min, 110 g / 10 min, 120 g / 10 min, 130 g / 10 min, 140 g / 10 min, 150 g / 10 min, etc.; it can also be a range composed of any two of the above values.

[0012] As a preferred embodiment of the polypropylene composite material of the present invention, the melt flow rate of the polypropylene resin ≥ 10 g / 10 min; preferably, the melt flow rate of the polypropylene resin is 20 - 150 g / 10 min; more preferably, the melt flow rate of the polypropylene resin is 25 - 60 g / 10 min.

[0013] The melt flow rate of the polypropylene resin is measured by a melt flow rate tester according to the standard: GB / T 3682 - 2000, with a test load of 2.16 kg, a test temperature of 230 °C, and a sample cutting interval of 120 s.

[0014] The melt flow rate of the polypropylene resin has an impact on the mechanical properties, light transmittance, yellowing coefficient after aging, and light transmittance retention rate after aging of the product. If the melt flow rate of the polypropylene resin is too low, the mechanical properties, light transmittance, and light transmittance retention rate after aging of the product will all decrease, while increasing the yellowing coefficient of the product after aging. After optimization, the product prepared from the polypropylene resin within the above range has better mechanical properties, light transmittance, and low yellowing properties.

[0015] As a preferred embodiment of the polypropylene composite material of the present invention, the mass ratio of the main antioxidant to the auxiliary antioxidant is (1:3) - (3:1); preferably, the mass ratio of the main antioxidant to the auxiliary antioxidant is 1:1.

[0016] As a preferred embodiment of the polypropylene composite material of the present invention, the polypropylene composite material further comprises 10 - 20 parts by weight of one-dimensional inorganic filler and 0.3 - 0.5 parts by weight of light stabilizer; the one-dimensional inorganic filler is magnesium sulfate whisker; the light stabilizer is a hindered amine light stabilizer.

[0017] Another object of the present invention is to provide a method for preparing the polypropylene composite material, comprising the following steps:

[0018] S1: Mix the polypropylene resin, main antioxidant, auxiliary antioxidant, and light stabilizer uniformly in a high-speed mixer to obtain premix 1;

[0019] S2: Add premix 1 into a twin-screw extruder, mix uniformly and melt-extrude, and pelletize and dry to obtain mixture A;

[0020] S3: Mix mixture A, ethylene copolymer elastomer, and one-dimensional inorganic filler uniformly in a high-speed mixer to obtain premix 2;

[0021] S4: Add premix 2 into a twin-screw extruder, mix uniformly and melt-extrude, and pelletize and dry to obtain the low yellowing and light-transmitting polypropylene composite material.

[0022] Through the two-step extrusion method, the present invention can make the primary antioxidant, secondary antioxidant, and light stabilizer more distributed in the resin matrix, reduce their distribution in the ethylene copolymer elastomer, further improve the mechanical properties, light transmittance, and light transmittance retention rate after aging of the product, and at the same time reduce the yellowing coefficient of the product after aging.

[0023] As a preferred embodiment of the preparation method of the polypropylene composite material of the present invention, in the steps S2 and S4, when melt-extruding in the twin-screw extruder, the set temperatures of the twin-screw extruder from the feeding port to the head are as follows: the temperature of the first zone is 80 - 120 °C, the temperature of the second zone is 190 - 210 °C, the temperature of the third zone is 210 - 230 °C, the temperature of the fourth zone is 210 - 230 °C, the temperature of the fifth zone is 210 - 230 °C, the temperature of the sixth zone is 210 - 230 °C, the temperature of the seventh zone is 210 - 230 °C, the temperature of the eighth zone is 210 - 230 °C, the temperature of the ninth zone is 210 - 230 °C, and the main machine speed is 200 - 800 revolutions per minute; the length-diameter ratio of the twin-screw extruder is 36:1 - 56:1.

[0024] As a preferred embodiment of the preparation method of the polypropylene composite material of the present invention, in the steps S1 and S2, the rotation speed of the high-speed mixer is set to 700 - 900 rpm, and the time is 1 - 3 min.

[0025] Another object of the present invention is to provide the application of the polypropylene composite material in a light-transmitting automotive bumper.

[0026] The polypropylene composite material of the present invention has high mechanical properties and light transmittance, and at the same time has a high light transmittance retention rate and a low yellowing coefficient after aging. When applied to a light-transmitting automotive bumper, it has a good appearance and excellent use performance.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: The polypropylene composite material of the present invention is compounded with polypropylene resin and ethylene-based copolymer elastomer, and at the same time specific primary antioxidants and auxiliary antioxidants and other components are introduced. It not only has high mechanical properties, light transmittance, and light transmittance retention rate after aging, but also has a low yellowing coefficient after aging, and has good appearance performance when applied to the preparation of a light-transmitting automotive bumper. The polypropylene composite material prepared by the present invention has the following characteristics: ① It meets that after aging at 100 °C for 1000 h, the yellowing coefficient △Yi ≤ 3.0, and the light transmittance retention rate ≥ 90%; ② It meets that after xenon lamp aging test with an energy radiation of 2500 KJ / m 2 of energy radiation, the yellowing coefficient △Yi ≤ 3.0, and the light transmittance retention rate ≥ 90%. The present invention also provides a preparation method of the polypropylene composite material and its application in the preparation of a light-transmitting automotive bumper. Specific Embodiments

[0028] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0029] In the embodiments, unless otherwise specified, the experimental methods used are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels. The light stabilizers and one-dimensional inorganic fillers used in the embodiments and comparative examples are the same.

[0030] The raw materials used in the embodiments and comparative examples are described as follows, but are not limited to these materials:

[0031] Polypropylene resin 1: PP BX3950, SK Chemical Co., Ltd., South Korea, homopolypropylene, melt flow rate of 150 g / 10 min;

[0032] Polypropylene resin 2: PP BX3920, SK Chemical Co., Ltd., South Korea, homopolypropylene, melt flow rate of 100 g / 10 min;

[0033] Polypropylene resin 3: PP H9018, PetroChina Lanzhou Petrochemical Company, homopolypropylene, melt flow rate of 50 g / 10 min;

[0034] Polypropylene resin 4: PP 320 powder, Sinopec Baling Company, homopolypropylene, melt flow rate of 32 g / 10 min;

[0035] Polypropylene resin 5: PP SZ30S, PetroChina Wuhan Petrochemical Company, homopolypropylene, melt flow rate of 25 g / 10 min;

[0036] Polypropylene resin 6: PP 1100N, Shenhua Ningxia Coal Industry Group Coal Chemical Industry Branch, homopolypropylene, melt flow rate of 12 g / 10 min;

[0037] Polypropylene resin 7: PP EP648U, CNOOC and Shell Petrochemical Company Limited, copolymerized polypropylene, melt flow rate of 65 g / 10 min;

[0038] Ethylene copolymerized elastomer 1: POE 8848, Dow Chemical China Co., Ltd., ethylene-butene copolymer, crystallinity of 29%;

[0039] Ethylene copolymerized elastomer 2: POE 8876, Dow Chemical China Co., Ltd., ethylene-butene copolymer, crystallinity of 25%;

[0040] Ethylene copolymerized elastomer 3: POE 8886, Dow Chemical China Co., Ltd., ethylene-butene copolymer, crystallinity of 19%;

[0041] Ethylene copolymerized elastomer 4: POE 8892, Dow Chemical China Co., Ltd., ethylene-octene copolymer,

[0042] The crystallinity is 25%;

[0043] Ethylene copolymerized elastomer 5: POE 8896, Dow Chemical China Co., Ltd., ethylene-hexene copolymer, the crystallinity is 25%;

[0044] Ethylene copolymerized elastomer 6: POE 8838, Dow Chemical China Co., Ltd., ethylene-butene copolymer, the crystallinity is 13%;

[0045] Primary antioxidant 1: Antioxidant 1076, Ciba Specialty Chemicals China Co., Ltd.;

[0046] Primary antioxidant 2: Antioxidant 1790, Ciba Specialty Chemicals China Co., Ltd.;

[0047] Primary antioxidant 3: Antioxidant 1010, Shandong Linyi Sanfeng Chemical Co., Ltd.;

[0048] Secondary antioxidant 1: Bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, Shandong Linyi Sanfeng Chemical Co., Ltd.;

[0049] Secondary antioxidant 2: Antioxidant 168, Shandong Linyi Sanfeng Chemical Co., Ltd.;

[0050] Light stabilizer: LA-402AF, Adeka;

[0051] One-dimensional inorganic filler: Magnesium sulfate whisker, Chongqing Baozhuan New Material Technology Co., Ltd.

[0052] Examples 1-15 and Comparative Examples 1-6

[0053] The components and weight parts of the polypropylene composites in the examples and comparative examples are selected as shown in Table 1-2.

[0054] Preparation method of low-yellowing light-transmitting polypropylene composites in Examples 1-15 and Comparative Examples 1-5, including the following steps:

[0055] S1: Mix the polypropylene resin, primary antioxidant, secondary antioxidant, and light stabilizer in a high-speed mixer for 3 min until uniform to obtain premix 1; the rotation speed of the high-speed mixer is set to 800 rpm;

[0056] S2: Add premix 1 to a twin-screw extruder, mix evenly and melt-extrude, and pelletize and dry to obtain mixture A;

[0057] S3: Mix mixture A, ethylene copolymerized elastomer, and one-dimensional inorganic filler in a high-speed mixer for 3 min until uniform to obtain premix 2; the rotation speed of the high-speed mixer is set to 800 rpm;

[0058] S4: Add the premix 2 into a twin-screw extruder, mix evenly and melt-extrude, then pelletize and dry to obtain a polypropylene composite material;

[0059] Among them, in steps S2 and S4, when melt-extruding in the twin-screw extruder, the set temperatures of the twin-screw extruder from the feeding port to the head are respectively: the temperature of zone 1 is 80 - 120 °C, the temperature of zone 2 is 190 - 210 °C, the temperature of zone 3 is 210 - 230 °C, the temperature of zone 4 is 210 - 230 °C, the temperature of zone 5 is 210 - 230 °C, the temperature of zone 6 is 210 - 230 °C, the temperature of zone 7 is 210 - 230 °C, the temperature of zone 8 is 210 - 230 °C, the temperature of zone 9 is 210 - 230 °C, and the main machine speed is 500 revolutions per minute; the length-diameter ratio of the twin-screw extruder is 46:1.

[0060] The preparation method of the polypropylene composite material of Comparative Example 6 includes the following steps:

[0061] S1: Mix polypropylene resin, ethylene copolymer elastomer, one-dimensional inorganic filler, primary antioxidant, secondary antioxidant, and light stabilizer in a high-speed mixer for 3 minutes until uniform to obtain a premix; the rotation speed of the high-speed mixer is set to 800 rpm;

[0062] S2: Add the premix into a twin-screw extruder, mix evenly and melt-extrude, then pelletize and dry to obtain a polypropylene composite material; among them, when melt-extruding in the twin-screw extruder, the set temperatures of the twin-screw extruder from the feeding port to the head are respectively: the temperature of zone 1 is 80 - 120 °C, the temperature of zone 2 is 190 - 210 °C, the temperature of zone 3 is 210 - 230 °C, the temperature of zone 4 is 210 - 230 °C, the temperature of zone 5 is 210 - 230 °C, the temperature of zone 6 is 210 - 230 °C, the temperature of zone 7 is 210 - 230 °C, the temperature of zone 8 is 210 - 230 °C, the temperature of zone 9 is 210 - 230 °C, and the main machine speed is 500 revolutions per minute; the length-diameter ratio of the twin-screw extruder is 46:1.

[0063] Table 1

[0064]

[0065] Table 2

[0066]

[0067]

[0068] Performance test:

[0069] Perform performance tests on the polypropylene composite materials prepared in the examples and comparative examples according to the following method;

[0070] (1) Light transmittance (2.5 mm thick plate): Tested in accordance with the test method for haze and light transmittance of transparent plastics GBT 2410-2008;

[0071] (2) Yellowing △Yi after thermal aging: Tested in accordance with the test method for the determination of the yellow index and its change value of plastics GBT 39822-2021, and calculate the difference in yellowing coefficients before and after aging for 1000 h at 100 °C;

[0072] (3) Light transmittance retention rate after thermal aging: Tested in accordance with the test method for haze and light transmittance of transparent plastics GBT 2410-2008, and calculate the ratio of light transmittance before and after aging for 1000 h at 100 °C;

[0073] (4) Yellowing △Yi after xenon lamp aging: Tested in accordance with the test method for the determination of the yellow index and its change value of plastics GBT 39822-2021, and calculate the difference in yellowing coefficients before and after xenon lamp aging test under the energy of irradiation dose of 2500 KJ / m 2 ;

[0074] (5) Light transmittance retention rate after xenon lamp aging: Tested in accordance with the test method for haze and light transmittance of transparent plastics GBT 2410-2008, and calculate the ratio of light transmittance before and after xenon lamp aging test under the energy of irradiation dose of 2500 KJ / m 2 ;

[0075] The test results are shown in Table 3 and Table 4;

[0076] Table 3

[0077]

[0078]

[0079] Table 4

[0080]

[0081] From the experimental data in Table 3 and Table 4, it can be seen that the polypropylene composite materials of each embodiment of the present invention, while maintaining the mechanical properties, also have the following characteristics: ① Meet the requirement that after aging for 1000 h at 100 °C, the yellowing coefficient △Yi ≤ 3.0 and the light transmittance retention rate ≥ 90%; ② Meet the requirement that after xenon lamp aging test under the energy of irradiation dose of 2500 KJ / m 2 ; the yellowing coefficient △Yi ≤ 3.0 and the light transmittance retention rate ≥ 90%.

[0082] Comparing the experimental data of Comparative Examples 1-6 and Comparative Example 3, it can be seen that the type of polypropylene resin and the melt flow rate of the polypropylene resin will affect the yellowing coefficient and light transmittance retention rate of the product; when the melt flow rate of the polypropylene resin is 25-60 g / 10 min, the yellowing coefficient of the product is relatively low and the light transmittance retention rate is relatively high. This may be because when the melt flow rate of the polypropylene resin is too low, the viscosity of the melt is large, there are many entanglements of molecular chains, and the light transmittance of the product is relatively low. When the melt flow rate of the polypropylene resin is too high, air entrapment is likely to occur during the product molding process, resulting in a higher yellowing coefficient of the material; when the polypropylene resin is copolymerized polypropylene, the yellowing coefficient of the polypropylene composite material increases significantly, and at the same time the light transmittance retention rate decreases significantly.

[0083] Comparing the experimental data of Example 1, Examples 7-9 and Comparative Examples 1-2, it can be seen that the crystallinity and type of the ethylene co-clustered elastomer are one of the key factors affecting the yellowing performance and light transmittance performance of the product. When the crystallinity of the ethylene co-clustered elastomer is too low, both the yellowing performance and the light transmittance performance of the obtained product will decrease significantly, as shown in Comparative Example 2; when the crystallinity of the ethylene co-clustered elastomer is 20-30%, the yellowing performance and the light transmittance performance of the obtained product will increase significantly; when ethylene-hexene copolymer is selected as the ethylene co-clustered elastomer, the yellowing performance and the light transmittance performance of the obtained product are significantly reduced.

[0084] Comparing the experimental data of Example 1, Example 10 and Comparative Examples 4-5, it can be seen that the compounding of the primary antioxidant and the secondary antioxidant selected in the present invention can effectively reduce the yellowing coefficient of the product and improve the light transmittance retention rate of the product; in addition, the contents of the primary antioxidant and the secondary antioxidant can also affect the yellowing performance and light transmittance performance of the product. When the contents of the primary antioxidant and the secondary antioxidant are too low or too high, the yellowing coefficient of the product increases significantly, and the light transmittance retention rate decreases significantly.

[0085] Comparing Example 1 and Examples 13-15, it can be seen that the mass ratio of the primary antioxidant and the secondary antioxidant will affect the yellowing performance and light transmittance performance of the product. When the mass ratio of the primary antioxidant and the secondary antioxidant is (1:3)-(3:1), the yellowing coefficient of the product is relatively low and the light transmittance retention rate is relatively high.

[0086] Comparing Example 1 and Comparative Example 6, it can be seen that the preparation method of the two-step extrusion method adopted in this application is superior to the preparation method of the one-step extrusion method. This may be because the two-step extrusion method enables the primary antioxidant, the secondary antioxidant, and the light stabilizer to be selectively distributed more in the resin matrix, reducing the distribution in the ethylene co-clustered elastomer, and enabling the polypropylene composite material to obtain better effects.

[0087] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A polypropylene composite material, characterized in that, Comprising the following components in parts by weight: 48 - 79 parts of polypropylene resin, 10 - 30 parts of ethylene copolymer elastomer, 0.2 - 0.5 part of primary antioxidant, 0.2 - 0.5 part of secondary antioxidant, 10 - 20 parts of one-dimensional inorganic filler, 0.3 - 0.5 part of light stabilizer; Among them, the polypropylene resin is homopolypropylene, and the melt flow rate of the polypropylene resin under the test conditions of 230 °C and 2.16 kg is 10 - 150 g / 10 min; the ethylene copolymer elastomer is at least one of ethylene-butene copolymer and ethylene-octene copolymer; the crystallinity of the ethylene copolymer elastomer is 18 - 40%; the primary antioxidant is at least one of antioxidant 1076 and antioxidant 1790; the secondary antioxidant is bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate; The preparation method of the polypropylene composite material comprises the following steps: S1: Mix the polypropylene resin, primary antioxidant, secondary antioxidant, and light stabilizer evenly in a high-speed mixer to obtain premix 1; S2: Add premix 1 into a twin-screw extruder, mix evenly and melt-extrude, pelletize and dry to obtain mixture A; S3: Mix mixture A, ethylene copolymer elastomer, and one-dimensional inorganic filler evenly in a high-speed mixer to obtain premix 2; S4: Add premix 2 into a twin-screw extruder, mix evenly and melt-extrude, pelletize and dry to obtain a low-yellowing and light-transmitting polypropylene composite material.

2. The polypropylene composite material according to claim 1, characterized in that, The crystallinity of the ethylene copolymer elastomer is 20 - 30%.

3. The polypropylene composite material according to claim 1, characterized in that, The melt flow rate of the polypropylene resin is 20 - 150 g / 10 min.

4. The polypropylene composite material according to claim 3, characterized in that, The melt flow rate of the polypropylene resin is 25 - 60 g / 10 min.

5. The polypropylene composite material according to claim 1, wherein The mass ratio of the primary antioxidant to the secondary antioxidant is (1:3) - (3:1).

6. The polypropylene composite material according to claim 1, wherein The one-dimensional inorganic filler is magnesium sulfate whisker; the light stabilizer is a hindered amine light stabilizer.

7. The preparation method of the polypropylene composite material according to any one of claims 1-6, characterized in that, Comprising the following steps: S1: Mix the polypropylene resin, primary antioxidant, secondary antioxidant, and light stabilizer evenly in a high-speed mixer to obtain premix 1; S2: Add premix 1 into a twin-screw extruder, mix evenly and melt-extrude, pelletize and dry to obtain mixture A; S3: Mix mixture A, ethylene copolymer elastomer, and one-dimensional inorganic filler evenly in a high-speed mixer to obtain premix 2; S4: Add premix 2 into a twin-screw extruder, mix evenly and melt-extrude, pelletize and dry to obtain a low-yellowing and light-transmitting polypropylene composite material.

8. The preparation method according to claim 7, characterized in that, In steps S2 and S4, when melt-extruding in the twin-screw extruder, the set temperatures of the twin-screw extruder from the feed port to the head are as follows: the temperature of zone 1 is 80 - 120 °C, the temperature of zone 2 is 190 - 210 °C, the temperature of zone 3 is 210 - 230 °C, the temperature of zone 4 is 210 - 230 °C, the temperature of zone 5 is 210 - 230 °C, the temperature of zone 6 is 210 - 230 °C, the temperature of zone 7 is 210 - 230 °C, the temperature of zone 8 is 210 - 230 °C, the temperature of zone 9 is 210 - 230 °C, and the main machine speed is 200 - 800 revolutions per minute; the length-diameter ratio of the twin-screw extruder is 36:1 - 56:

1.

9. The preparation method according to claim 7, characterized in that In the said step S1 and step S3, the rotation speed of the high-speed mixer is set at 700 - 900 rpm, and the time is 1 - 3 min.

10. Application of the polypropylene composite material according to any one of claims 1 - 6 in a light-transmitting automotive bumper.

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