Polypropylene material with improved low-temperature brittleness and preparation method thereof

Abstract

The invention belongs to the technical field of polypropylene reinforced composite materials, and particularly relates to a polypropylene material with improved low-temperature brittleness and a preparation method thereof. Aiming at the problems in the prior art, the invention provides a polypropylene material with improved low-temperature brittleness and a preparation method thereof, the polypropylene material comprises the following components in parts by mass: 100 parts of polypropylene, 10-40 parts of glass fiber, 5-20 parts of modified needle-like wollastonite treated by treating fluid, 4-10 parts of compatilizer and 0.5-2 parts of anti-aging master batch, the treating fluid is prepared from 1 to 3 parts of silane coupling agent and 0.01 to 0.2 part of beta nucleating agent. The beta nucleating agent is used for modifying polypropylene to form a beta crystal form with better performance, and wollastonite is used for replacing part of glass fibers, so that the low-temperature brittleness of the glass fiber reinforced polypropylene composite material can be greatly improved, and the pressure resistance at high temperature is not influenced.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene reinforced composite materials technology, and particularly relates to a polypropylene material with improved low-temperature brittleness and its preparation method. Background Technology

[0002] The addition of glass fibers or mineral powder can enhance the performance of polypropylene resin. Glass fiber reinforced polypropylene, with glass fibers parallel to the axial and radial directions of the granules, and longer glass fibers, provides increased rigidity and strength within the PP. F-PPR pipes, made with glass fiber reinforced random copolymer polypropylene (PPR) as the interlayer, exhibit significantly improved strength due to the glass fiber reinforcement in the PP-R interlayer. Furthermore, the coefficient of linear expansion is reduced to 1 / 3-1 / 5 of the original value, greatly preventing bending damage caused by linear expansion under prolonged hot water use. With my country's rapid economic development, F-PPR, as an upgraded version of PPR pipes, has seen a substantial increase in usage, experiencing rapid growth in recent years.

[0003] However, since polypropylene has a glass transition temperature of around 0°C and exhibits some low-temperature brittleness below 5°C, and F-PPR uses glass fiber reinforcement, its toughness is further reduced. At low temperatures, it is more susceptible to damage from external forces, which brings inconvenience to winter construction and transportation in cold northern regions. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a polypropylene material with improved low-temperature brittleness and a method for preparing the same.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions: A polypropylene material for improving low-temperature brittleness comprises 100 parts by weight of polypropylene, 10-40 parts by weight of glass fiber, 5-20 parts by weight of modified needle-like wollastonite treated with a treatment solution, 4-10 parts by weight of compatibilizer, and 0.5-2 parts by weight of antioxidant masterbatch, wherein the treatment solution contains 1-3 parts by weight of silane coupling agent and 0.01-0.2 parts by weight of β-nucleating agent.

[0006] In the aforementioned polypropylene material for improving low-temperature brittleness, the polypropylene material comprises 100 parts by weight of polypropylene, 25 parts by weight of glass fiber, 10 parts by weight of modified needle-shaped wollastonite treated with a treatment liquid, 5 parts by weight of compatibilizer, and 1 part by weight of anti-aging masterbatch, wherein the treatment liquid contains 2 parts by weight of silane coupling agent and 0.15 parts by weight of β-nucleating agent.

[0007] In the aforementioned polypropylene material for improving low-temperature brittleness, the modified acicular wollastonite is obtained by the following method: A solvent was obtained by mixing anhydrous ethanol and water at a volume ratio of 9:1. The silane coupling agent and β-nucleating agent were dissolved in the solvent to obtain a treatment solution. The needle-shaped wollastonite was immersed in the treatment solution and mechanically stirred at 75-85℃ for 1-3 hours. The solvent was removed by vacuum distillation and then dried.

[0008] In the aforementioned polypropylene material for improving low-temperature brittleness, the dried acicular wollastonite is further subjected to a stearic acid coating process: the dried acicular wollastonite and stearic acid are added to a high-speed mixer and mixed at 80-100°C for 5-10 minutes. The heating is then stopped, the material is discharged and cooled to room temperature to obtain modified acicular wollastonite.

[0009] The addition of anti-aging masterbatch prevents oxidative degradation of polypropylene molecular chains, ensuring modification effects and improving the heat resistance and aging resistance of polypropylene materials. After soaking in the treatment solution, the active groups on the surface of needle-like wollastonite are grafted with silane coupling agents, which improves the compatibility between wollastonite and the matrix resin, promotes uniform dispersion, and increases material strength. Some of these agents can also adsorb β-nucleating agents, achieving uniform dispersion even with low amounts, thus better facilitating heterogeneous nucleation and making it easier for polypropylene to form β-crystals. This also replaces some glass fiber, reducing costs without affecting the pipe's coefficient of linear expansion. The formation of needle-like wollastonite and β-crystals significantly improves the low-temperature brittleness of glass fiber reinforced polypropylene materials without affecting their strength or high-temperature pressure resistance. Furthermore, it is easy to process and has a low material cost. Annealing improves the crystal structure and increases the mobility of composite material chains, further enhancing low-temperature toughness. Pipes produced using the material of this invention show significantly improved low-temperature brittleness without affecting mechanical properties.

[0010] In the aforementioned polypropylene material for improving low-temperature brittleness, the pH value of the treatment solution is 4.5-5.5.

[0011] In the aforementioned polypropylene material for improving low-temperature brittleness, the glass fiber is a continuous glass fiber with a diameter of 6-20 μm.

[0012] In the aforementioned polypropylene material for improving low-temperature brittleness, the antioxidant masterbatch is a blend of polypropylene and antioxidant in a mass ratio of 8:2, and the antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 1330, and antioxidant DSTDP.

[0013] In the aforementioned polypropylene material for improving low-temperature brittleness, the silane coupling agent is one or more of methoxysilane coupling agents.

[0014] A method for preparing a polypropylene material with improved low-temperature brittleness includes the following steps: Step 1: Prepare the treatment solution by mixing anhydrous ethanol and water to prepare the solvent, dissolving the β-nucleating agent and silane coupling agent in the solvent, and adjusting the pH value to 4.5-5.5 to obtain the treatment solution; Step 2: Processing acicular wollastonite. Immerse the acicular wollastonite in the processing solution prepared in Step 1. After mechanical stirring at 75-85℃ for 1-3 hours, remove the solvent by vacuum distillation and dry it. Then add the dried acicular wollastonite and stearic acid into a high-speed mixer and mix at 80-100℃ for 5-10 minutes. Then stop heating, discharge the material and cool it to room temperature to obtain modified acicular wollastonite. Step 3: Granulation. Polypropylene, anti-aging masterbatch, compatibilizer and modified needle-shaped wollastonite obtained in step 2 are thoroughly mixed at high speed and fed into a twin-screw extruder for melting through the main feed port. Glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling and pelletizing, polypropylene granules are obtained. Step 4: Annealing. The polypropylene granules obtained in Step 3 are annealed in an oven for 1-3 hours to obtain a polypropylene material with improved low-temperature brittleness.

[0015] In the above preparation method, the processing temperature in step three is 170-220℃; the annealing temperature in step four is 110-130℃.

[0016] Compared with existing technologies, the advantages of this invention are: 1. The present invention uses the same material as the inner and outer layers of the pipe, namely polypropylene, as the base resin. This ensures that when the reinforcing material to be prepared is used as the middle reinforcing layer of the composite pipe, it can be fully integrated with the inner and outer layers, so that the inner and outer layers are firmly bonded.

[0017] 2. This invention utilizes a β-nucleating agent to modify polypropylene, forming a β-crystal form with better performance. At the same time, replacing part of the glass fiber with wollastonite can greatly improve the low-temperature brittleness of glass fiber reinforced polypropylene composites without affecting the pressure resistance at high temperatures.

[0018] 3. The needle-shaped wollastonite of the present invention, after modification treatment, can promote the uniform dispersion of glass fiber and β-nucleating agent in polypropylene matrix through the action of treatment liquid, so as to give full play to its role. The carboxyl end of stearic acid is combined with the surface of wollastonite through ionic bonds or hydrogen bonds, while its long alkyl chain has good compatibility with polypropylene. The stearic acid coating film effectively reduces the polarity of the wollastonite surface, reduces the agglomeration between particles, and further improves the dispersibility.

[0019] 4. The present invention uses needle-shaped wollastonite instead of glass fiber, which can further reduce the cost of materials.

[0020] 5. The annealing treatment of this invention can improve crystallinity, improve crystal structure and increase the mobility of composite material chain segments, and further improve low-temperature brittleness. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments.

[0022] In the examples and comparative examples, the polypropylene used was YPR-503 from Yangzi Petrochemical. The glass fiber was 960A reinforced polypropylene from Zhejiang Jushi Group; alternatively, other glass fibers from Jushi Group with a polypropylene-friendly impregnating agent could be used. The silane coupling agent was KH570 from Chenguang Chemical. The compatibilizer was JX-01 from Nanjing Juxing. The wollastonite was KT-acicular wollastonite powder from Jiangxi Kete; antioxidant 1010 and auxiliary antioxidant 168 were products of Ciba, Switzerland. The β-nucleating agent was WBG-Ⅱ from Guangdong Weilinna.

[0023] Example 1 This embodiment provides a polypropylene material with improved low-temperature brittleness and its preparation method. The raw materials used include: continuous glass fiber, polypropylene, needle-like wollastonite, β-nucleating agent, compatibilizer, antioxidant 1010, antioxidant 168, water, anhydrous ethanol, and stearic acid.

[0024] The preparation steps used are as follows: Step 1: Prepare the treatment solution. Mix anhydrous ethanol and water at a volume ratio of 9:1 to obtain a solvent. Take 1500ml of the solvent and dissolve 0.5g of β-nucleating agent and 50g of KH570 in the solvent in sequence. Adjust the pH of the treatment solution to 4.5-5.5 to obtain the treatment solution. Step 2: Processing acicular wollastonite. Immerse 500g of acicular wollastonite in the processing solution prepared in Step 1, mechanically stir at 80℃ for 2h, remove the solvent by vacuum distillation, and dry at 110℃. Then add the dried acicular wollastonite and stearic acid into a high-speed mixer, mix at 90℃ for 8min, then stop heating, discharge the material and cool to room temperature to obtain modified acicular wollastonite. Step 3: Granulation. 5000g of polypropylene, 50g of antioxidant masterbatch, 250g of compatibilizer, and the modified needle-shaped wollastonite obtained in Step 2 are thoroughly mixed at high speed and fed into a twin-screw extruder through the main feed port for melting. 1250g of glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling, and pelletizing, polypropylene granules are obtained. The processing temperature is controlled at 200℃. Step 4: Annealing. The polypropylene granules obtained in Step 3 are annealed in an oven at 110°C for 2 hours to obtain a polypropylene material with improved low-temperature brittleness.

[0025] Example 2 This embodiment is basically the same as Embodiment 1, except for the amount of β-nucleating agent used. Specifically, in this embodiment, the amount of β-nucleating agent added is 2.5g.

[0026] Example 3 This embodiment is basically the same as Embodiment 1, except for the amount of β-nucleating agent used. Specifically, in this embodiment, the amount of β-nucleating agent added is 5g.

[0027] Example 4 This embodiment is basically the same as Embodiment 1, except for the amount of β-nucleating agent used. Specifically, in this embodiment, the amount of β-nucleating agent added is 7.5g.

[0028] Example 5 This embodiment is basically the same as Embodiment 1, except for the amount of β-nucleating agent used. Specifically, in this embodiment, the amount of β-nucleating agent added is 10g.

[0029] Example 6 This embodiment is basically the same as Embodiment 1, except for the amount of β nucleating agent and silane coupling agent. Specifically, in this embodiment, the amount of β nucleating agent added is 7.5g and the amount of silane coupling agent added is 100g.

[0030] Example 7 This embodiment is basically the same as Embodiment 1, except for the amount of β nucleating agent and silane coupling agent. Specifically, in this embodiment, the amount of β nucleating agent added is 7.5g and the amount of silane coupling agent added is 150g.

[0031] Example 8 This embodiment is basically the same as Embodiment 1, except for the amount of β nucleating agent and silane coupling agent and the annealing temperature. Specifically, in this embodiment, the amount of β nucleating agent added is 7.5g, the amount of silane coupling agent added is 100g, and the annealing temperature is 120℃.

[0032] Example 9 This embodiment is basically the same as Embodiment 1, except for the amount of β nucleating agent and silane coupling agent and the annealing temperature. Specifically, in this embodiment, the amount of β nucleating agent added is 7.5g, the amount of silane coupling agent added is 100g, and the annealing temperature is 130℃.

[0033] Example 10 This embodiment is basically the same as Embodiment 1, except for the amount of β nucleating agent and silane coupling agent and the annealing temperature. Specifically, in this embodiment, the amount of β nucleating agent added is 7.5g, the amount of silane coupling agent added is 100g, and the annealing temperature is 140℃.

[0034] Comparative Example 1 This comparative example provides a polypropylene material and its preparation method, including the following steps: Step 1: Granulation. 5000g of polypropylene, 50g of antioxidant masterbatch and 250g of compatibilizer are thoroughly mixed at high speed and fed into a twin-screw extruder through the main feed port for melting. 1750g of glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling and pelletizing, polypropylene granules are obtained. The processing temperature is controlled at 200℃. Step 2: Annealing. The polypropylene granules obtained in Step 1 are annealed in an oven at 110°C for 2 hours to obtain polypropylene material.

[0035] Comparative Example 2 This comparative example provides a polypropylene material and its preparation method, including the following steps: Step 1: Granulation. 5000g of polypropylene, 50g of antioxidant masterbatch, 250g of compatibilizer and 500g of wollastonite are thoroughly mixed at high speed and fed into a twin-screw extruder through the main feed port for melting. 1250g of glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling and pelletizing, polypropylene granules are obtained. The processing temperature is controlled at 200℃. Step 2: Annealing. The polypropylene granules obtained in Step 1 are annealed in an oven at 110°C for 2 hours to obtain polypropylene material.

[0036] Comparative Example 3 This comparative example provides a polypropylene material and its preparation method, including the following steps: Step 1: Prepare the treatment solution by mixing anhydrous ethanol and water in a volume ratio of 9:1. Take 1500ml of the solvent, dissolve 7.5g of β-nucleating agent in the solvent, and adjust the pH of the treatment solution to 4.5-5.5 to obtain the treatment solution. Step 2: Processing acicular wollastonite. Immerse 500g of acicular wollastonite in the processing solution prepared in Step 1, mechanically stir at 80℃ for 2h, remove the solvent by vacuum distillation, and dry at 110℃. Then add the dried acicular wollastonite and stearic acid into a high-speed mixer, mix at 90℃ for 8min, then stop heating, discharge the material and cool to room temperature to obtain modified acicular wollastonite. Step 3: Granulation. 5000g of polypropylene, 50g of antioxidant masterbatch, 250g of compatibilizer, and the modified needle-shaped wollastonite obtained in Step 2 are thoroughly mixed at high speed and fed into a twin-screw extruder through the main feed port for melting. 1250g of glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling, and pelletizing, polypropylene granules are obtained. The processing temperature is controlled at 200℃. Step 4: Annealing. The polypropylene granules obtained in Step 3 are annealed in an oven at 110°C for 2 hours to obtain polypropylene material.

[0037] Comparative Example 4 This comparative example provides a polypropylene material and its preparation method, including the following steps: Step 1: Prepare the treatment solution by mixing anhydrous ethanol and water in a volume ratio of 9:1. Take 1500ml of the solvent, dissolve 100g of KH570 in the solvent, and adjust the pH of the treatment solution to 4.5-5.5 to obtain the treatment solution. Step 2: Processing acicular wollastonite. Immerse 500g of acicular wollastonite in the processing solution prepared in Step 1, mechanically stir at 80℃ for 2h, remove the solvent by vacuum distillation, and dry at 110℃. Then add the dried acicular wollastonite and stearic acid into a high-speed mixer, mix at 90℃ for 8min, then stop heating, discharge the material and cool to room temperature to obtain modified acicular wollastonite. Step 3: Granulation. 5000g of polypropylene, 50g of antioxidant masterbatch, 250g of compatibilizer, and the modified needle-shaped wollastonite obtained in Step 2 are thoroughly mixed at high speed and fed into a twin-screw extruder through the main feed port for melting. 1250g of glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling, and pelletizing, polypropylene granules are obtained. The processing temperature is controlled at 200℃. Step 4: Annealing. The polypropylene granules obtained in Step 3 are annealed in an oven at 110°C for 2 hours to obtain polypropylene material.

[0038] Application Example 1 The mechanical properties of the polypropylene materials prepared in Examples 1-10 and Comparative Examples 1-4 were tested, and the results are shown in the table below: Serial Number Flexural strength MPa Flexural modulus (MPa) <![CDATA[Izod impact strength at 0 °C, KJ / m 2 > Relative content of β crystals (%) Example 1 61.99 2312 12.96 11 Example 2 62.22 2358 14.13 26 Example 3 61.23 2331 15.66 32 Example 4 61.40 2403 17.31 37 Example 5 62.67 2482 17.15 40 Example 6 64.75 2486 17.75 37 Example 7 65.43 2510 17.88 36 Example 8 65.88 2594 18.78 38 Example 9 64.40 2416 20.96 39 Example 10 65.17 2673 16.68 21 Comparative Example 1 66.02 2686 10.10 0 Comparative Example 2 59.26 2139 12.54 0 Comparative Example 3 58.37 2127 14.30 38 Comparative Example 4 63.85 2587 13.23 0 Comparing Examples 1-5 and Comparative Examples 1-4, it can be seen that the formation of β crystals slightly reduces the bending strength because the stiffness of β crystals is lower than that of α crystals with interlocking structures. However, the low-temperature toughness of β crystals is higher than that of α crystals. Therefore, with the increase of nucleating agent content, its low-temperature notched impact strength is further improved. The effect is most pronounced when 1.5 parts are added, and further addition has little effect.

[0039] Meanwhile, comparing Examples 4, 6, and 7, it is evident that wollastonite's stiffening effect on PPR is not as strong as that of glass fiber composites. Compared to Comparative Example 1 without wollastonite, the flexural strength is lower, but it does not affect the toughness of the composite material at low temperatures. In fact, because it replaces some glass fiber, its low-temperature notched impact strength is improved to some extent. With the addition of coupling agent, the stiffening effect of acicular wollastonite is enhanced, gradually approaching that of glass fiber. The effect is significant when 2 parts are added, and further addition has little effect.

[0040] Furthermore, Examples 4 and 8-10 demonstrate that annealing temperature also has a significant impact on the low-temperature brittleness of the material. As the annealing temperature gradually increases to 130°C, its low-temperature notched impact strength also gradually increases. However, when the annealing temperature further reaches 140°C, the notched impact strength decreases rapidly. This is because β-α recrystallization occurs at this temperature, resulting in a decrease in β crystal content and an increase in α crystal content.

[0041] The data above demonstrate that the synergistic effect of wollastonite, β-nucleating agent, and annealing process can greatly improve the low-temperature brittleness of polypropylene materials.

[0042] Application Example 2 The polypropylene materials obtained in Examples 1-10 and Comparative Examples 1-4 were used to produce S3.2Dn25*3.5 F-PPR pipes, and the hydrostatic strength of the pipes in hot water at 95℃ was tested. The results are shown in the table below: Serial Number Circumferential stress 3.8 MPa 165 h / h 4.5MPa 165h / h 95℃, hoop stress 3.5MPa, 1000h / h 4.2MPa 1000h / h Example 1 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 2 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 3 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 4 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 5 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 6 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 7 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 8 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 9 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Example 10 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Comparative Example 1 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Comparative Example 2 No cracks or leaks 122h leakage 846h leakage 410h leakage Comparative Example 3 No cracks or leaks No cracks or leaks No cracks or leaks No cracks or leaks Comparative Example 4 No cracks or leaks No cracks or leaks No cracks or leaks 787h leakage Therefore, it can be seen that by replacing part of the glass fiber with wollastonite, the present invention improves the low-temperature brittleness of glass fiber reinforced polypropylene composites without affecting the high-temperature compressive strength of polypropylene composites.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A polypropylene material for improving low-temperature brittleness, characterized in that: It comprises 100 parts by weight of polypropylene, 10-40 parts of glass fiber, 5-20 parts of modified needle-shaped wollastonite treated with a treatment solution, 4-10 parts of compatibilizer, and 0.5-2 parts of anti-aging masterbatch, wherein the treatment solution contains 1-3 parts of silane coupling agent and 0.01-0.2 parts of β-nucleating agent.

2. The polypropylene material for improving low-temperature brittleness as described in claim 1, characterized in that: The polypropylene material comprises 100 parts by weight of polypropylene, 25 parts by weight of glass fiber, 10 parts by weight of modified needle-shaped wollastonite treated with a treatment solution, 5 parts by weight of compatibilizer and 1 part by weight of anti-aging masterbatch, wherein the treatment solution contains 2 parts by weight of silane coupling agent and 0.15 parts by weight of β-nucleating agent.

3. The polypropylene material for improving low-temperature brittleness as described in claim 1, characterized in that: The modified acicular wollastonite was prepared by the following method: A solvent was obtained by mixing anhydrous ethanol and water at a volume ratio of 9:

1. The silane coupling agent and β-nucleating agent were dissolved in the solvent to obtain a treatment solution. The needle-shaped wollastonite was immersed in the treatment solution and mechanically stirred at 75-85℃ for 1-3 hours. The solvent was removed by vacuum distillation and then dried.

4. The polypropylene material for improving low-temperature brittleness as described in claim 3, characterized in that: After the acicular wollastonite is dried, a stearic acid coating treatment step is also included: the dried acicular wollastonite and stearic acid are added to a high-speed mixer and mixed at 80-100℃ for 5-10 minutes, then heating is stopped, the material is discharged and cooled to room temperature to obtain modified acicular wollastonite.

5. The polypropylene material for improving low-temperature brittleness as described in claim 3, characterized in that: The pH value of the treatment solution is 4.5-5.

5.

6. The polypropylene material for improving low-temperature brittleness as described in claim 1, characterized in that: The glass fiber is a continuous glass fiber with a diameter of 6-20 μm.

7. The polypropylene material for improving low-temperature brittleness as described in claim 1, characterized in that: The anti-aging masterbatch is a blend of polypropylene and antioxidant in a mass ratio of 8:

2. The antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant 1330 and antioxidant DSTDP.

8. The polypropylene material for improving low-temperature brittleness as described in claim 1, characterized in that: The silane coupling agent is one or more of the methoxysilane coupling agents.

9. A method for preparing a polypropylene material with improved low-temperature brittleness as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Prepare the treatment solution by mixing anhydrous ethanol and water to prepare the solvent, dissolving the β-nucleating agent and silane coupling agent in the solvent, and adjusting the pH value to 4.5-5.5 to obtain the treatment solution; Step 2: Processing acicular wollastonite. Immerse the acicular wollastonite in the processing solution prepared in Step 1. After mechanical stirring at 75-85℃ for 1-3 hours, remove the solvent by vacuum distillation and dry it. Then add the dried acicular wollastonite and stearic acid into a high-speed mixer and mix at 80-100℃ for 5-10 minutes. Then stop heating, discharge the material and cool it to room temperature to obtain modified acicular wollastonite. Step 3: Granulation. Polypropylene, anti-aging masterbatch, compatibilizer and modified needle-shaped wollastonite obtained in step 2 are thoroughly mixed at high speed and fed into a twin-screw extruder for melting through the main feed port. Glass fiber is fed into the twin-screw extruder through the side feed port. After melt blending, stretching, extrusion, cooling and pelletizing, polypropylene granules are obtained. Step 4: Annealing. The polypropylene granules obtained in Step 3 are annealed in an oven for 1-3 hours to obtain a polypropylene material with improved low-temperature brittleness.

10. The preparation method according to claim 9, characterized in that: The processing temperature in step three is 170-220℃; the annealing temperature in step four is 110-130℃.