High-strength low-shrinkage low-warpage polypropylene material and preparation method thereof

Abstract

The invention provides a high-strength low-shrinkage low-warpage polypropylene material and a preparation method thereof. The high-strength low-shrinkage low-warpage polypropylene material is prepared from propylene under the combined action of a main catalyst, a cocatalyst and an external electron donor by adopting ethylene as a comonomer and hydrogen as a molecular weight regulator by adopting a gas-phase polymerization process. According to the polypropylene material, the ethylene unit content is 11-15 wt%, the melt flow rate is 28-42 g / 10 min under the conditions that the temperature is 230 DEG C and the load is 2.16 kg, the simply supported beam notch impact strength at the room temperature is larger than or equal to 8 kJ / m < 2 >, the bending modulus is larger than or equal to 1000 MPa, the transverse shrinkage rate is smaller than or equal to 1.0%, the longitudinal shrinkage rate is smaller than or equal to 1.0%, the warping degree is smaller than or equal to 5, and the requirement for light weight of automobiles is met.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a high-strength, low-shrinkage, low-warpage polypropylene material and a preparation method thereof. Background Art

[0002] With the rapid development of the modern automobile industry, in order to cope with the world energy crisis and meet the requirements of energy conservation and emission reduction, automobile lightweighting has become one of the effective measures to reduce emissions and improve fuel efficiency. In particular, the development of new energy vehicles in recent years has put forward higher requirements for automobile lightweighting. Using plastic instead of steel as the main implementation technology is in line with the trend and trend of automobile lightweight development, and its usage has become one of the important indicators to measure the development level of the modern automobile industry.

[0003] Automotive plastics can be divided into polypropylene, polyurethane, polyvinyl chloride, thermosetting composite materials, acrylonitrile-butadiene-styrene, nylon, etc., and are mainly used in three parts: automotive exterior parts, interior parts and functional structural parts. Different grades of cars have different choices for materials. In comparison, polypropylene is more lightweight, cheap, easy to recycle and has excellent heat resistance. It is currently the most used type of automotive plastics, accounting for about 33% of the total automotive plastics.

[0004] As a highly crystalline polymer material, polypropylene often shrinks during the injection molding, storage and use of products, causing warping of the products. Therefore, reducing the shrinkage rate of polypropylene has become an important direction for improving the performance of polypropylene, and it is also a development need for the aesthetic design of automotive plastic parts. Auto parts need to be assembled with the car body without gaps to achieve beautiful and safe effects. Zero assembly gap depends on the shrinkage rate of the material. The smaller the shrinkage rate, the closer the product size is to the actual size of the mold, and the better the fit with the car body. From the actual effect of product design and application, the molding shrinkage rate of the material needs to be less than 1%. In order to achieve this effect, automotive modification manufacturers add a large amount of inorganic fillers in the process of polypropylene modification. Therefore, reducing the shrinkage rate of polypropylene and reducing the addition of inorganic fillers are the development requirements of lightweight automobiles.

[0005] In recent years, the domestic automotive impact-resistant polypropylene has developed rapidly. However, in the process of market promotion, it was found that the shrinkage rate of domestic impact-resistant polypropylene products is generally large. The shrinkage rate of the matrix itself is generally more than 1.5%, while the automotive modified products generally require the shrinkage rate to be controlled within 1.0%. Therefore, a large amount of inorganic fillers need to be added to solve the shrinkage problem, which is not conducive to the requirements of lightweight automobiles. Even after the optimization and adjustment of the polymerization process, the shrinkage problem has been improved, but there is still a significant gap compared with imported high-end products. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a high-strength, low-shrinkage, low-warpage polypropylene material and a preparation method thereof. The present invention can ensure that the polypropylene resin has high fluidity, excellent mechanical properties, low shrinkage, and low warpage, and can significantly reduce the addition of inorganic fillers in automobile modification, meeting the development needs of automobile lightweighting.

[0007] In a first aspect, the present invention provides a high-strength, low-shrinkage, low-warpage polypropylene material, the polypropylene material comprising the following components in parts by weight: 99.1 to 99.8 parts of polypropylene powder, 0.05 to 0.3 parts of a nucleating agent, 0.05 to 0.2 parts of a primary antioxidant, 0.05 to 0.2 parts of an auxiliary antioxidant, and 0.05 to 0.2 parts of a halogen absorber;

[0008] The raw materials for preparing the polypropylene powder include polypropylene, propylene, ethylene and hydrogen;

[0009] The ethylene unit content in the polypropylene material is 11-15 wt%.

[0010] As a specific embodiment of the present invention, the polypropylene material has a melt flow rate of 28 to 42 g / 10 min at a temperature of 230° C. and a load of 2.16 kg, and a simply supported beam notched impact strength of ≥8 kJ / m at room temperature. 2 , flexural modulus ≥1000MPa, transverse shrinkage ≤1.0%, longitudinal shrinkage ≤1.0%, warpage ≤5.

[0011] In a second aspect, the present invention provides a method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, comprising the following steps:

[0012] S1: Propylene undergoes polymerization reaction in the first reactor under the combined action of the main catalyst, the co-catalyst and the external electron donor to obtain polypropylene;

[0013] S2: adding the polypropylene, propylene, ethylene and hydrogen obtained in step S1 into a second reactor to continue polymerization reaction;

[0014] S3: The polymerization product obtained in step S2 is passed through a flash drying system to obtain polypropylene powder;

[0015] S4: the polypropylene powder obtained in step S3, the antioxidant, the auxiliary antioxidant, the halogen absorber and the nucleating agent are uniformly mixed, and then extruded and granulated to obtain a polypropylene material.

[0016] As a specific embodiment of the present invention, in the step S1, the polymerization reaction in the step S1 is carried out in the presence of hydrogen. Preferably, the hydrogen concentration of the first reactor is 0.2v% to 0.8v%.

[0017] As a specific embodiment of the present invention, the temperature of the polymerization reaction in step S1 is 62-70°C.

[0018] As a specific embodiment of the present invention, in step S1, the main catalyst is CDi; the co-catalyst is triethylaluminum; and the external electron donor is isobutyltriethoxysilane.

[0019] As a specific embodiment of the present invention, in step S2, the hydrogen concentration of the second reactor is 0.07v% to 0.4v%, the ethylene concentration is 20v% to 40v%, and the temperature is 62 to 70°C.

[0020] As a specific embodiment of the present invention, in step S4, the polypropylene material includes the following components in parts by weight: 99.1 to 99.8 parts of polypropylene powder, 0.05 to 0.3 parts of nucleating agent, 0.05 to 0.2 parts of primary antioxidant, 0.05 to 0.2 parts of auxiliary antioxidant, and 0.05 to 0.2 parts of halogen absorber.

[0021] As a specific embodiment of the present invention, in step S4, the nucleating agent is an organic carboxylate nucleating agent, the halogen absorber is calcium stearate, the primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], and the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

[0022] As a specific embodiment of the present invention, the extrusion granulation in step S4 includes: extrusion by an extruder, cooling with cooling water and pelletizing. Preferably, the extrusion barrel temperature of the extruder is 180-230°C, and the cooling water temperature is 55-80°C.

[0023] The above raw materials in the present invention can be prepared in-house or commercially available, and the present invention is not particularly limited thereto.

[0024] In a third aspect, the present invention provides application of the high-strength, low-shrinkage, low-warpage polypropylene material in the automotive field.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention adopts a gas phase polymerization process. Propylene is subjected to the combined action of a main catalyst, a co-catalyst and an external electron donor. During the polymerization process, the temperature of the reactor is controlled at 62-70° C., ethylene is used as a comonomer, hydrogen is used as a molecular weight regulator, and the hydrogen concentration is further optimized to obtain a suitable polypropylene base resin. After being uniformly mixed with an antioxidant, an auxiliary antioxidant, a halogen absorber and a nucleating agent, the resin is extruded and granulated to prepare a high-strength, low-shrinkage polypropylene material. The preparation method can ensure that the polypropylene resin has high fluidity, excellent mechanical properties, low shrinkage and low warpage.

[0027] 2. The melt mass flow rate of the polypropylene material obtained by the present invention is 28-42 g / 10 min, and the simply supported beam notched impact strength at room temperature is ≥8 kJ / m 2 , bending modulus ≥1000MPa, lateral shrinkage ≤1.0%, longitudinal shrinkage ≤1.0%, warpage ≤5. This polypropylene resin not only has good fluidity and mechanical properties, excellent rigidity-toughness balance, but also has the characteristics of low shrinkage and low warpage, meeting the development needs of lightweight automobiles.

[0028] 3. The present invention can ensure that the polypropylene resin has high fluidity, excellent mechanical properties, low shrinkage, and low warpage. It can significantly reduce the addition of inorganic fillers in automobile modification, which meets the development needs of automobile lightweighting. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0030] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] In the following Examples 1-5 and Comparative Examples, unless otherwise specified: the primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite; the halogen absorber is calcium stearate; and the nucleating agent is an organic carboxylate nucleating agent, specifically Milliken's nucleating agent HPN-20E.

[0032] Example 1

[0033] This embodiment provides a method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, the specific details of which are as follows:

[0034] A method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material comprises the following steps:

[0035] (1) Propylene is polymerized in a first reactor under the combined action of a main catalyst CDi, a co-catalyst triethylaluminum and an external electron donor diisobutyltriethoxysilane, wherein the hydrogen concentration in the first reactor is 0.5% by volume and the temperature is 64° C.;

[0036] (2) the polypropylene, propylene, ethylene and hydrogen obtained in step (1) are added to a second reactor to continue polymerization reaction, the hydrogen concentration in the second reactor is 0.2% by volume, the ethylene concentration is 30% by volume, and the temperature is 64° C.;

[0037] (3) The polymerization product obtained in step (2) is subjected to flash evaporation to remove liquid propylene, and then enters a steaming and drying system to obtain a polypropylene powder having a melt mass flow rate of 31.2 g / 10 min and an ethylene content of 12.3 wt %;

[0038] (4) The polypropylene powder, antioxidant, auxiliary antioxidant, halogen absorber and nucleating agent obtained in step (3) are uniformly mixed and then extruded into granules to prepare a polypropylene material having a melt mass flow rate of 30.8 g / 10 min and an ethylene content of 12.3 wt %.

[0039] The polypropylene material comprises the following components in parts by weight: 99.54 parts of polypropylene powder, 0.15 parts of a nucleating agent, 0.15 parts of a primary antioxidant, 0.1 parts of an auxiliary antioxidant, and 0.06 parts of a halogen absorber;

[0040] The extruder barrel temperatures were controlled at 180°C, 190°C, 200°C, 200°C, and 200°C, respectively; the die head temperature was 255°C; and the pelletizing water temperature was 66°C.

[0041] Example 2

[0042] This embodiment provides a method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, the specific details of which are as follows:

[0043] (1) Propylene is polymerized in a first reactor under the combined action of a main catalyst CDi, a co-catalyst triethylaluminum and an external electron donor diisobutyltriethoxysilane, wherein the hydrogen concentration in the first reactor is 0.6% by volume and the temperature is 64° C.;

[0044] (2) the polypropylene, propylene, ethylene and hydrogen obtained in step (1) are added to a second reactor to continue polymerization reaction, the hydrogen concentration in the second reactor is 0.3% by volume, the ethylene concentration is 32% by volume, and the temperature is 64° C.;

[0045] (3) The polymerization product obtained in step (2) is subjected to flash evaporation to remove liquid propylene, and then enters a steaming and drying system to obtain a polypropylene powder having a melt mass flow rate of 32.4 g / 10 min and an ethylene content of 12.8 wt %;

[0046] (4) The polypropylene powder, antioxidant, auxiliary antioxidant, halogen absorber and nucleating agent obtained in step (3) are uniformly mixed and then extruded and granulated to prepare a polypropylene material having a melt mass flow rate of 31.9 g / 10 min and an ethylene content of 12.8 wt %.

[0047] The polypropylene material comprises the following components in parts by weight: 99.52 parts of polypropylene powder, 0.12 parts of a nucleating agent, 0.15 parts of a primary antioxidant, 0.16 parts of an auxiliary antioxidant, and 0.06 parts of a halogen absorber;

[0048] The extruder barrel temperatures were controlled at 180°C, 190°C, 200°C, 200°C, and 200°C, respectively; the die head temperature was 255°C; and the pelletizing water temperature was 66°C.

[0049] Example 3

[0050] This embodiment provides a method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, the specific details of which are as follows:

[0051] (1) Propylene is polymerized in a first reactor under the combined action of a main catalyst CDi, a co-catalyst triethylaluminum and an external electron donor diisobutyltriethoxysilane, wherein the hydrogen concentration in the first reactor is 0.5% by volume and the temperature is 68° C.;

[0052] (2) the polypropylene, propylene, ethylene and hydrogen obtained in step (1) are added to a second reactor to continue polymerization reaction, the hydrogen concentration in the second reactor is 0.2% by volume, the ethylene concentration is 30% by volume, and the temperature is 64° C.;

[0053] (3) The polymerization product obtained in step (2) is subjected to flash evaporation to remove liquid propylene, and then enters a steaming and drying system to obtain a polypropylene powder having a melt mass flow rate of 33.1 g / 10 min and an ethylene content of 12.2 wt %;

[0054] (4) The polypropylene powder, antioxidant, auxiliary antioxidant, halogen absorber and nucleating agent obtained in step (3) are uniformly mixed and then extruded into granules to prepare a polypropylene material having a melt mass flow rate of 29.6 g / 10 min and an ethylene content of 12.2 wt %.

[0055] The polypropylene material comprises the following components in parts by weight: 99.53 parts of polypropylene powder, 0.16 parts of a nucleating agent, 0.15 parts of a primary antioxidant, 0.1 parts of an auxiliary antioxidant, and 0.06 parts of a halogen absorber;

[0056] The extruder barrel temperatures were controlled at 180°C, 190°C, 200°C, 200°C, and 200°C, respectively; the die head temperature was 255°C; and the pelletizing water temperature was 66°C.

[0057] Example 4

[0058] This embodiment provides a method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, the specific details of which are as follows:

[0059] 1) Propylene is polymerized in a first reactor under the combined action of main catalyst CDi, co-catalyst triethylaluminum and external electron donor diisobutyltriethoxysilane, wherein the hydrogen concentration in the first reactor is 0.6% by volume and the temperature is 65° C.;

[0060] (2) the polypropylene, propylene, ethylene and hydrogen obtained in step (1) are added to a second reactor to continue the polymerization reaction, the hydrogen concentration in the second reactor is 0.35% by volume, the ethylene concentration is 38% by volume, and the temperature is 65° C.;

[0061] (3) The polymerization product obtained in step (2) is subjected to flash evaporation to remove liquid propylene, and then enters a steaming and drying system to obtain a polypropylene powder having a melt mass flow rate of 34.9 g / 10 min and an ethylene content of 13.6 wt %;

[0062] (4) The polypropylene powder, antioxidant, auxiliary antioxidant, halogen absorber and nucleating agent obtained in step (3) are uniformly mixed, and then extruded and granulated to prepare a polypropylene material with a melt mass flow rate of 32.7 g / 10 min and an ethylene content of 13.6 wt %.

[0063] The polypropylene material includes the following components in parts by weight: 99.44 parts of polypropylene powder, 0.23 parts of a nucleating agent, 0.17 parts of a primary antioxidant, 0.1 parts of an auxiliary antioxidant, and 0.06 parts of a halogen absorber;

[0064] The extruder barrel temperatures were controlled at 180°C, 190°C, 200°C, 200°C, and 200°C, respectively; the die head temperature was 255°C; and the pelletizing water temperature was 66°C.

[0065] Example 5

[0066] (1) Propylene is polymerized in a first reactor under the combined action of a main catalyst CDi, a co-catalyst triethylaluminum and an external electron donor diisobutyltriethoxysilane, wherein the hydrogen concentration in the first reactor is 0.7% by volume and the temperature is 68° C.;

[0067] (2) the polypropylene, propylene, ethylene and hydrogen obtained in step (1) are added to a second reactor to continue the polymerization reaction, the hydrogen concentration in the second reactor is 0.4% by volume, the ethylene concentration is 28% by volume, and the temperature is 65° C.;

[0068] (3) The polymerization product obtained in step (2) is subjected to flash evaporation to remove liquid propylene, and then enters a steaming and drying system to obtain a polypropylene powder having a melt mass flow rate of 37.5 g / 10 min and an ethylene content of 11.2 wt %;

[0069] (4) The polypropylene powder, antioxidant, auxiliary antioxidant, halogen absorber and nucleating agent obtained in step (3) are uniformly mixed and then extruded into granules to prepare a polypropylene material having a melt mass flow rate of 35.7 g / 10 min and an ethylene content of 11.2 wt %.

[0070] The polypropylene material includes the following components in parts by weight: 99.56 parts of polypropylene powder, 0.12 parts of a nucleating agent, 0.1 parts of a primary antioxidant, 0.17 parts of an auxiliary antioxidant, and 0.05 parts of a halogen absorber;

[0071] The extruder barrel temperatures were controlled at 180°C, 190°C, 200°C, 200°C, and 200°C, respectively; the die head temperature was 255°C; and the pelletizing water temperature was 66°C.

[0072] Comparative Example 1

[0073] The polypropylene material was prepared in the same manner as in Example 1, except that an α-crystalline benzoate nucleating agent was used as the nucleating agent. A polypropylene material having a melt mass flow rate of 30.9 g / 10 min was prepared, and its various indicators are shown in Table 1.

[0074] Comparative Example 2

[0075] The polypropylene material was prepared in the same manner as in Example 1, except that the hydrogen concentration in the first reactor was 0.1v%. A polypropylene material having a melt mass flow rate of 25.4 g / 10 min was prepared, and its various indicators are shown in Table 1.

[0076] Comparative Example 3

[0077] The polypropylene material was prepared in the same manner as in Example 1, except that the hydrogen concentration in the first reactor was 0.9v%. A polypropylene material having a melt mass flow rate of 50.3 g / 10 min was prepared, and its various indicators are shown in Table 1.

[0078] Comparative Example 4

[0079] The polypropylene material was prepared in the same manner as in Example 1, except that the hydrogen concentration in the second reactor was 0.05 vol%. A polypropylene material having a melt mass flow rate of 23.8 g / 10 min was prepared, and its various indices are shown in Table 1.

[0080] Comparative Example 5

[0081] The polypropylene material was prepared in the same manner as in Example 1, except that the hydrogen concentration in the second reactor was 0.5 vol%. A polypropylene material having a melt mass flow rate of 46.5 g / 10 min was prepared, and its various indices are shown in Table 1.

[0082] Comparative Example 6

[0083] The polypropylene material was prepared in the same manner as in Example 1, except that the ethylene concentration in the second reactor was 10% by volume. A polypropylene material having a melt mass flow rate of 31.5 g / 10 min was prepared, and its various indices are shown in Table 1.

[0084] The reactor conditions and granulation conditions in the above Examples 1-5 and Comparative Examples 1-6 are shown in Table 1, Table 2 and Table 3.

[0085] Table 1 Conditions of the first reactor

[0086]

[0087]

[0088] Table 2 Second reactor conditions

[0089]

[0090] Table 3 Granulation conditions

[0091]

[0092]

[0093] The performance results of the polypropylene materials prepared in the above Examples 1-5 and Comparative Examples 1-6 are shown in Table 4:

[0094] Table 4 Performance test of polypropylene materials prepared in Examples 1-5 and Comparative Examples 1-6

[0095]

[0096]

[0097] The results in the table above show that Examples 1-5 directly use a high-efficiency nucleating agent, an antioxidant, a halogen absorber and polypropylene powder, and extrude a high-strength, low-shrinkage, and low-warpage polypropylene material through an extruder. The material has high fluidity, excellent mechanical properties, good rigidity-toughness balance, low shrinkage, and low warpage. As a base resin for automobile modification, it meets the development needs of automobile lightweighting.

[0098] According to the comparison between Examples 1-5 and Comparative Example 1, it can be seen that by changing the type of nucleating agent, the shrinkage performance of the polypropylene material in the same direction becomes worse, resulting in a larger warpage of the product. It can be seen from Examples 1-5 and Comparative Examples 2-6 that by changing the hydrogen concentration or the amount of ethylene added, the melt flow rate, mechanical properties and shrinkage rate of the material change greatly, resulting in a worse rigidity-toughness balance of the material, a larger shrinkage and an increased warpage.

[0099] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A high-strength, low-shrinkage, low-warpage polypropylene material, characterized in that: The polypropylene material comprises the following components in parts by weight: 99.1 to 99.8 parts of polypropylene powder, 0.05 to 0.3 parts of a nucleating agent, 0.05 to 0.2 parts of a primary antioxidant, 0.05 to 0.2 parts of an auxiliary antioxidant, and 0.05 to 0.2 parts of a halogen absorber; The raw materials for preparing the polypropylene powder include polypropylene, propylene, ethylene and hydrogen; The ethylene unit content in the polypropylene material is 11-15 wt%.

2. The high-strength, low-shrinkage, low-warpage polypropylene material according to claim 1, characterized in that: The polypropylene material has a melt flow rate of 28-42 g / 10 min at a temperature of 230° C. and a load of 2.16 kg, and a simply supported beam notched impact strength of ≥8 kJ / m at room temperature. 2 , flexural modulus ≥1000MPa, transverse shrinkage ≤1.0%, longitudinal shrinkage ≤1.0%, warpage ≤5.

3. A method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material, characterized in that: The following steps are involved: S1: Propylene undergoes polymerization reaction in the first reactor under the combined action of the main catalyst, the co-catalyst and the external electron donor to obtain polypropylene; S2: adding the polypropylene, propylene, ethylene and hydrogen obtained in step S1 into a second reactor to continue polymerization reaction; S3: The polymerization product obtained in step S2 is passed through a flash drying system to obtain polypropylene powder; S4: the polypropylene powder obtained in step S3, the antioxidant, the auxiliary antioxidant, the halogen absorber and the nucleating agent are uniformly mixed, and then extruded and granulated to obtain a polypropylene material.

4. The method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material according to claim 3, characterized in that: The polymerization reaction in step S1 is carried out in the presence of hydrogen, and preferably, the hydrogen concentration in the first reactor is 0.2v% to 0.8v%; And / or the temperature of the polymerization reaction in step S1 is 62-70°C.

5. The method for preparing the high-strength, low-shrinkage, low-warpage polypropylene material according to claim 3 or 4, characterized in that: In the step S1, the main catalyst is CDi; the co-catalyst is triethylaluminum; and the external electron donor is isobutyltriethoxysilane.

6. The method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material according to any one of claims 3 to 5, characterized in that: In the step S2, the hydrogen concentration of the second reactor is 0.07v% to 0.4v%, the ethylene concentration is 20v% to 40v%, and the temperature is 62 to 70°C.

7. The method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material according to any one of claims 3 to 6, characterized in that: In step S4, the polypropylene material includes the following components in parts by weight: 99.1 to 99.8 parts of polypropylene powder, 0.05 to 0.3 parts of nucleating agent, 0.05 to 0.2 parts of primary antioxidant, 0.05 to 0.2 parts of auxiliary antioxidant, and 0.05 to 0.2 parts of halogen absorbent.

8. The method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material according to any one of claims 3 to 7, characterized in that: In step S4, the nucleating agent is an organic carboxylate nucleating agent, the halogen absorber is calcium stearate, the primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], and the auxiliary antioxidant is tris(2,4-di-tert-butylphenyl) phosphite.

9. The method for preparing a high-strength, low-shrinkage, low-warpage polypropylene material according to any one of claims 3 to 8, characterized in that: The extrusion granulation in step S4 includes: extrusion by an extruder, cooling by cooling water and pelletizing. Preferably, the extrusion barrel temperature of the extruder is 180-230°C, and the cooling water temperature is 55-80°C.

10. Use of the high-strength, low-shrinkage, low-warpage polypropylene material according to claim 1 or 2 or the high-strength, low-shrinkage, low-warpage polypropylene material prepared by the preparation method according to any one of claims 3 to 9 in the automotive field.

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