Impact-resistant low-temperature-resistant polypropylene material, preparation method and application thereof

Abstract

The application relates to the technical field of cold chain transportation, in particular to an impact-resistant and low-temperature-resistant polypropylene material and a preparation method and application thereof. According to weight parts, the raw materials of the impact-resistant and low-temperature-resistant polypropylene material include the following components: 65-80 parts of a polypropylene matrix, 5-12 parts of a grafted modified elastomer, 2-5 parts of a beta nucleating agent master batch, 0.5-2 parts of a silane coupling agent, 3-8 parts of a cold-resistant additive, 1-3 parts of an antioxidant, and 2-6 parts of nano-enhanced fillers. The polypropylene matrix provides rigidity and load-carrying capacity, the grafted modified elastomer is uniformly distributed in the polypropylene matrix in the form of a dispersed phase, can absorb impact energy as a stress buffering point, inhibits crack conversion and expansion, the nucleating agent master batch can further strengthen the low-temperature resistance, the silane coupling agent can improve the activity of molecular chains at low temperatures, and the nano-enhanced fillers can fill matrix defects, disperse stress, hinder crack expansion, and further synergistically enhance the impact resistance of the material.

Description

Technical Field

[0001] This application relates to the field of cold chain transportation technology, and in particular to an impact-resistant and low-temperature resistant polypropylene material, its preparation method, and its application. Background Technology

[0002] As a core load-bearing component in cold chain logistics, cold chain equipment pallets must operate for extended periods in environments with fluctuating temperatures ranging from -40°C to ambient temperature, enduring impact loads from stacking and frequent loading and unloading. Therefore, the requirements for the material's impact resistance, low-temperature stability, and load-bearing capacity are stringent. While polypropylene materials are widely used due to their lightweight and ease of processing, they are prone to embrittlement at low temperatures, resulting in a significant decrease in notched impact strength. Furthermore, after long-term low-temperature service or high-low temperature cycling, they are susceptible to cracking and deformation, failing to meet the stringent requirements of cold chain scenarios. Existing modified polypropylene technologies primarily improve performance through toughening with a single elastomer or modification with nucleating agents, but these methods suffer from poor synergy between low-temperature resistance and impact resistance, insufficient interfacial compatibility, and unsatisfactory long-term service stability. Therefore, developing a polypropylene material that combines excellent low-temperature impact resistance, stable load-bearing capacity, and long-term low-temperature resistance has become an urgent need in the cold chain equipment pallet field. Summary of the Invention

[0003] The technical problem to be solved by this application is to solve at least one of the technical problems mentioned above.

[0004] The solution to the technical problem in this application is: In a first aspect, this application provides an impact-resistant and low-temperature-resistant polypropylene material, wherein, by weight parts, the raw material comprises the following components: The composition includes 65-80 parts of polypropylene matrix, 5-12 parts of grafted modified elastomer, 2-5 parts of β-nucleating agent masterbatch, 0.5-2 parts of silane coupling agent, 3-8 parts of cold-resistant agent, 1-3 parts of antioxidant, and 2-6 parts of nano-reinforcing filler.

[0005] Furthermore, the grafted modified elastomer is a combination of maleic anhydride-grafted POE and acrylic acid-grafted SEBS, with a weight ratio of maleic anhydride-grafted POE to acrylic acid-grafted SEBS of 1:3-4.

[0006] Furthermore, the preparation method of the cold-resistant agent includes the following steps: Methyl ricinoleate and urea were added to methanol and stirred in a water bath at 0°C for 3-5 hours. After crystallization at 0-5°C for 14-20 hours, the mixture was filtered under vacuum. The filtrate was extracted with petroleum ether, washed twice with deionized water, and then distilled under reduced pressure at 60-70°C and 0.09 MPa to remove the solvent, thus obtaining the pretreated product. The pretreated material and dimethyl ethyl silane were mixed, a platinum-carbon catalyst was added, and the mixture was refluxed and stirred at 110-120℃ for 6-7 hours. The catalyst was removed by centrifugation, and the remaining dimethyl ethyl silane was removed by vacuum distillation at 80-85℃ and 0.06MPa. The weight ratio of methyl ricinoleate, urea, and methanol is 1:3:4.8-5.2; The weight ratio of the pretreatment material, dimethylethylsilane, and platinum-carbon catalyst is 2:2-3:0.02-0.03.

[0007] Furthermore, the preparation method of the β-nucleating agent masterbatch includes the following steps: Rare earth β crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and second polypropylene matrix were granulated by twin screw extruder and kept at a constant temperature of 120-125℃ for 2 hours. The weight ratio of rare earth β-crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and the second polypropylene matrix is ​​2:1:1:0.1:40-44.

[0008] Furthermore, the silane coupling agent is a combination of γ-glycidoxypropyltrimethoxysilane and vinyltriethoxysilane, with a weight ratio of γ-glycidoxypropyltrimethoxysilane to vinyltriethoxysilane of 1:1-2.

[0009] Furthermore, the antioxidant is a combination of antioxidant 1076 and tris(2,4-di-tert-butylphenyl) phosphite, with a weight ratio of antioxidant 1076 to tris(2,4-di-tert-butylphenyl) phosphite of 3-5:2.

[0010] Furthermore, the particle size of the nano-reinforced filler is 50-200 nm; The nano-reinforcing filler is a combination of modified wollastonite, nano-calcium carbonate and montmorillonite, with a weight ratio of 4-6:1:1. The modified wollastonite is obtained by modifying wollastonite with chitosan and titanate coupling agent.

[0011] Secondly, this application provides a method for preparing an impact-resistant and low-temperature resistant polypropylene material as described in the first aspect, comprising the following steps: Mix the polypropylene matrix, grafted modified elastomer, β nucleating agent masterbatch and silane coupling agent at 115-125℃ and 5000-5500rpm for 30-40min, stirring every 10min and then letting stand for 4-5min. Introduce nitrogen gas and cool to 70-80℃, then add β-nucleating agent masterbatch and continue mixing for 15-20 minutes; Then add nano-reinforced fillers and antioxidants, mix at 70-80℃ and 4000-4500rpm for 25-30 minutes, and then cool to room temperature; Add the cold-resistant additive and stir at 600-800 rpm for 7 minutes to obtain the mixture; The mixture is fed into a twin-screw extruder and plasticized with nitrogen at a flow rate of 7L / min at 360-380℃ for 50 minutes. It is then extruded according to the temperature gradient of 182-186℃ in the feed section, 188-192℃ in the first section, 195-199℃ in the second section, 202-206℃ in the third section, and 210-214℃ in the die section. The screw speed is 170-180rpm. The extrudate is cooled in a 40℃ water cooling tank for 45 seconds and then pelletized.

[0012] Furthermore, the process after pelleting includes the following steps: Place at -10~-15℃ for aging for 48-60 hours, then raise to 23-25℃ for 2-3 hours to recover.

[0013] Thirdly, this application provides the application of an impact-resistant and low-temperature resistant polypropylene material, as described in the first aspect, in the preparation of cold chain equipment pallets.

[0014] The beneficial effects of this application are as follows: the polypropylene matrix can provide rigidity and load-bearing capacity as a matrix structure to meet the requirements of stacked pressure resistance; the grafted modified elastomer is uniformly distributed in the polypropylene matrix in the form of a dispersed phase, playing an anchoring role; its flexible chain segments can still maintain good mobility in low-temperature environments; when the material is impacted, the elastomer particles can act as stress buffer points to absorb impact energy, inhibit crack transformation and propagation, effectively alleviate the low-temperature brittleness of the polypropylene matrix, and significantly improve the impact resistance of the material; the nucleating agent masterbatch can refine the grain size, reduce stress concentration between grains, and enable the material to maintain structural stability during low-temperature cycling, further enhancing low-temperature resistance; the silane coupling agent can reduce interfacial tension and improve the bonding force between components; the cold-resistant additive can weaken the interaction force between polypropylene molecular chains, improve the mobility of molecular chains at low temperatures, and avoid increased brittleness caused by chain segment freezing; the nano-reinforcing filler can fill matrix defects, disperse stress, and hinder crack propagation, further synergistically enhancing the impact resistance of the material. Detailed Implementation

[0015] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application. The various technical features in this application can be combined interactively without contradicting each other.

[0016] This application provides an impact-resistant and low-temperature resistant polypropylene material, wherein the raw material comprises the following components by weight: The composition includes 65-80 parts of polypropylene matrix, 5-12 parts of grafted modified elastomer, 2-5 parts of β-nucleating agent masterbatch, 0.5-2 parts of silane coupling agent, 3-8 parts of cold-resistant agent, 1-3 parts of antioxidant, and 2-6 parts of nano-reinforcing filler.

[0017] In this application, the polypropylene matrix provides rigidity and load-bearing capacity as a matrix structure, meeting the requirements for stacked pressure resistance. The grafted modified elastomer is uniformly distributed in the polypropylene matrix in the form of a dispersed phase, playing an anchoring role. Its flexible chain segments can still maintain good mobility in low-temperature environments. When the material is impacted, the elastomer particles can act as stress buffer points to absorb impact energy, inhibit crack transformation and propagation, effectively alleviate the low-temperature brittleness of the polypropylene matrix, and significantly improve the impact resistance of the material. The nucleating agent masterbatch can refine the grain size, reduce stress concentration between grains, and maintain structural stability of the material during low-temperature cycling, further enhancing its low-temperature resistance. The silane coupling agent can reduce interfacial tension and improve the bonding force between components. The cold-resistant additive can weaken the interaction force between polypropylene molecular chains, improve the mobility of molecular chains at low temperatures, and avoid increased brittleness caused by chain segment freezing. The nano-reinforcing filler can fill matrix defects, disperse stress, and hinder crack propagation, further synergistically enhancing the impact resistance of the material.

[0018] The weight-average molecular weight of the polypropylene matrix can be 200,000-240,000. This molecular weight range can ensure the entanglement density between molecular chains, improve the load-bearing capacity, and avoid the increase in melt viscosity caused by excessively high molecular weight, thus ensuring processability and providing a stable matrix support for the synergistic effect of various functional components.

[0019] Furthermore, the grafted modified elastomer is a combination of maleic anhydride-grafted POE and acrylic acid-grafted SEBS, with a weight ratio of maleic anhydride-grafted POE to acrylic acid-grafted SEBS of 1:3-4.

[0020] In this application, the polar groups of maleic anhydride grafted with POE can form a strong interaction with the polypropylene matrix, improving interfacial compatibility. Its flexible segments can absorb impact energy through segment movement at low temperatures (-40℃). At the same time, the styrene blocks of acrylic acid grafted with SEBS can serve as physical crosslinking points, enhancing the load-bearing capacity of the elastomer network. The low glass transition temperature of the polybutadiene blocks can endow the material with good low-temperature flexibility. The uniform distribution of the elastomer in the matrix can provide a certain anchoring effect for the whole, effectively inhibiting crack propagation and inducing a certain crazing effect during impact, absorbing impact energy and improving overall toughness, thus significantly improving the impact resistance of the material.

[0021] Furthermore, the preparation method of the cold-resistant agent includes the following steps: Methyl ricinoleate and urea were added to methanol and stirred in a water bath at 0°C for 3-5 hours. After crystallization at 0-5°C for 14-20 hours, the mixture was filtered under vacuum. The filtrate was extracted with petroleum ether, washed twice with deionized water, and then distilled under reduced pressure at 60-70°C and 0.09 MPa to remove the solvent, thus obtaining the pretreated product. The pretreated material and dimethyl ethyl silane were mixed, a platinum-carbon catalyst was added, and the mixture was refluxed and stirred at 110-120℃ for 6-7 hours. The catalyst was removed by centrifugation, and the remaining dimethyl ethyl silane was removed by vacuum distillation at 80-85℃ and 0.06MPa.

[0022] In this application, the cold-resistant additive is prepared by inclusion purification of methyl ricinoleate and urea, followed by catalytic addition reaction with dimethyl ethyl silane. Its molecular structure contains both polar hydroxyl groups and low surface energy silane groups. The polar hydroxyl groups can form hydrogen bonds with the polypropylene matrix and nano-reinforcing fillers, improving the dispersion stability of the additive. The silane groups can improve lubrication performance, while weakening the intermolecular forces of polypropylene molecules, improving the chain segment mobility at low temperatures, and avoiding the increase in brittleness of the molecular chains due to low-temperature freezing. Its carbon chain structure can promote the formation of flexible interfaces at low temperatures, further buffering impact stress and enhancing low-temperature impact resistance.

[0023] Furthermore, the weight ratio of methyl ricinoleate, urea, and methanol is 1:3:4.8-5.2; The weight ratio of the pretreatment material, dimethylethylsilane, and platinum-carbon catalyst is 2:2-3:0.02-0.03.

[0024] In this application, if the amount of urea is too low, the selective coating of unsaturated components in methyl castor oil ester will be insufficient, leading to a decrease in the purity of unsaturated fatty acid methyl esters in the pretreated product. This reduces the subsequent addition reaction sites with silane compounds, affecting the low-temperature toughening efficiency. If the amount of urea is too high, it is easy to leave residues, which can lead to uneven dispersion of the prepared cold-resistant additive in the matrix. If the amount of dimethyl ethyl silane is too low, the silane groups provided will be insufficient, the proportion of low surface energy groups will be reduced, and the improvement of chain segment activity at low temperatures will be limited. If the amount is too high, residues will form free components, which are prone to agglomeration in the matrix after preparation, forming stress concentration points. This application prepares the cold-resistant additive by appropriate proportions, ensuring its good low-temperature performance and dispersibility, which is beneficial to improving the impact resistance and low-temperature stability of the polypropylene material matrix.

[0025] Furthermore, the preparation method of the β-nucleating agent masterbatch includes the following steps: Rare earth β crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and second polypropylene matrix were granulated by twin screw extruder and kept at a constant temperature of 120-125℃ for 2 hours. The weight ratio of rare earth β-crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and the second polypropylene matrix is ​​2:1:1:0.1:40-44.

[0026] The rare earth β-crystal nucleating agent is a rare earth β-crystal nucleating agent for polypropylene. The second polypropylene matrix is ​​made of the same material as the polypropylene matrix and is not included in the amount of polypropylene material used.

[0027] In this application, rare earth β-crystal nucleating agent, hydrotalcite, and montmorillonite are compounded in a specific ratio and subjected to twin-screw granulation and isothermal activation treatment at 120-125℃. The rare earth β-crystal nucleating agent, as a highly efficient crystal nucleation site, can induce polypropylene molecular chains to preferentially form β-crystals. Compared with conventional α-crystals, β-crystals have stronger interlayer bonding and higher elongation at break. Furthermore, the lamellar structure of hydrotalcite and montmorillonite can further refine the grain size and reduce stress concentration points. At the same time, the β-nucleating agent masterbatch has good compatibility with the polypropylene matrix and can prevent rigid aggregation of molecular chains at low temperatures, thus maintaining good toughness and preventing brittleness.

[0028] Furthermore, the silane coupling agent is a combination of γ-glycidoxypropyltrimethoxysilane and vinyltriethoxysilane, with a weight ratio of γ-glycidoxypropyltrimethoxysilane to vinyltriethoxysilane of 1:1-2.

[0029] In this application, the silane coupling agent is a compound of γ-glycidoxypropyltrimethoxysilane and vinyltriethoxysilane in a ratio of 1:1-2. Its siloxane groups can undergo hydrolysis and condensation reaction with the hydroxyl groups on the surface of the nano-reinforced filler, thereby improving the interfacial bonding force between the nano-reinforced filler and the matrix and avoiding interfacial peeling at low temperatures.

[0030] Furthermore, the antioxidant is a combination of antioxidant 1076 and tris(2,4-di-tert-butylphenyl) phosphite, with a weight ratio of antioxidant 1076 to tris(2,4-di-tert-butylphenyl) phosphite of 3-5:2.

[0031] In this application, antioxidant 1076 and tris(2,4-di-tert-butylphenyl) phosphite are compounded in a 2:1 ratio, which can respectively capture free radicals and decompose hydrogen peroxide, synergistically inhibiting the thermal oxidative aging of polypropylene during processing and use, and ensuring the long-term low-temperature resistance of the material.

[0032] Furthermore, the particle size of the nano-reinforced filler is 50-200 nm; The nano-reinforcing filler is a combination of modified wollastonite, nano-calcium carbonate and montmorillonite, with a weight ratio of 4-6:1:1. The modified wollastonite is obtained by modifying wollastonite with chitosan and titanate coupling agent.

[0033] In this application, the nano-reinforced filler is a compound of modified wollastonite, nano-calcium carbonate and montmorillonite in a weight ratio of 4-6:1:1. The modified wollastonite is modified by both chitosan and titanate coupling agent. The amino and hydroxyl groups of chitosan can improve the compatibility between the filler and the matrix, while the titanate coupling agent reduces the surface energy of the filler and avoids agglomeration. The layered structure of nano-calcium carbonate and montmorillonite can fill matrix defects and improve the load-bearing strength of the material under impact. At the same time, the nanoscale effect refines the grains and disperses stress, avoiding material failure caused by stress concentration at low temperatures.

[0034] The preparation method of modified wollastonite includes the following steps: Chitosan is dissolved in deionized water, and the pH is adjusted to 5.0-6.0 to obtain a chitosan solution; Add wollastonite to the chitosan solution, heat to 60-70℃, and stir at 1200-1500 rpm for 60 minutes; The titanate coupling agent was diluted in anhydrous ethanol to obtain a titanate coupling agent solution, which was then added dropwise to the system. The mixture was stirred at 60-70℃ and 1200-1500rpm for 40-50 minutes. After filtration and collection, the mixture was washed 2-3 times with anhydrous ethanol and dried in a vacuum drying oven at 90℃ for 3 hours. After cooling to room temperature, the mixture was pulverized and passed through a 200-mesh sieve to obtain modified wollastonite. The weight ratio of chitosan, deionized water, wollastonite, titanate coupling agent, and anhydrous ethanol is 2-3:5-8:10:1-1.5:5. Chitosan can be uniformly adsorbed onto the surface of wollastonite powder through hydrogen bonding to form a coating layer. The alkoxy groups of the titanate coupling agent react with the hydroxyl groups on the surface of wollastonite powder and the amino groups of chitosan to form chemical bonds, improving compatibility with the polypropylene matrix.

[0035] This application also provides a method for preparing the impact-resistant and low-temperature resistant polypropylene material as described above, comprising the following steps: Mix the polypropylene matrix, grafted modified elastomer, β nucleating agent masterbatch and silane coupling agent at 115-125℃ and 5000-5500rpm for 30-40min, stirring every 10min and then letting stand for 4-5min. Introduce nitrogen gas and cool to 70-80℃, then add β-nucleating agent masterbatch and continue mixing for 15-20 minutes; Then add nano-reinforced fillers and antioxidants, mix at 70-80℃ and 4000-4500rpm for 25-30 minutes, and then cool to room temperature; Add the cold-resistant additive and stir at 600-800 rpm for 7 minutes to obtain the mixture; The mixture is fed into a twin-screw extruder and plasticized with nitrogen at a flow rate of 7L / min at 360-380℃ for 50 minutes. It is then extruded according to the temperature gradient of 182-186℃ in the feed section, 188-192℃ in the first section, 195-199℃ in the second section, 202-206℃ in the third section, and 210-214℃ in the die section. The screw speed is 170-180rpm. The extrudate is cooled in a 40℃ water cooling tank for 45 seconds and then pelletized.

[0036] In this application, the internal stress generated during the mixing process is released by stirring and allowing the mixture to stand, thus avoiding stress residue that could lead to subsequent material brittleness. The cold-resistant additive is mixed at room temperature and low speed to ensure its structural integrity. Plasticization under nitrogen gas is used to prevent thermal oxidation degradation of the polypropylene matrix and elastomer. Finally, the mixture is sheared, mixed, and extruded and granulated using a twin-screw extruder to obtain an impact-resistant and low-temperature resistant polypropylene material.

[0037] Furthermore, the process after pelleting includes the following steps: Place at -10~-15℃ for aging for 48-60 hours, then raise to 23-25℃ for 2-3 hours to recover.

[0038] In this application, by performing an aging treatment after pelleting, the residual thermal stress and phase separation stress after pelleting are slowly released, preventing these internal stresses from concentrating and erupting during subsequent cold chain use, which could lead to material cracking and brittle fracture. After low-temperature aging, a recovery at 23-25℃ for 2-3 hours allows the internal molecular chains of the material to rearrange under mild conditions, further optimizing the crystal structure and phase distribution, making the β-crystal form more stable, the interfaces between components more tightly bonded, and improving the uniformity of the material structure.

[0039] This application also provides the application of the impact-resistant and low-temperature-resistant polypropylene material described above in the preparation of cold chain equipment pallets. The polypropylene material obtained by this application has good impact resistance and low-temperature resistance, effectively meeting the stacking and load-bearing requirements of cold chain transportation.

[0040] The following specific examples provide further details.

[0041] The preparation method of the cold-resistant additive used in the embodiments and comparative examples of this application includes the following steps: Methyl ricinoleate and urea were added to methanol, stirred in a water bath at 0°C for 4 hours, and then crystallized at 2°C for 16 hours. After vacuum filtration, the filtrate was extracted with petroleum ether, washed twice with deionized water, and the solvent was removed by vacuum distillation at 70°C and 0.09 MPa to obtain the pretreated product. The pretreated material and dimethyl ethyl silane were mixed, a platinum-carbon catalyst was added, and the mixture was refluxed and stirred at 110-120℃ for 6-7 hours. The catalyst was removed by centrifugation, and the remaining dimethyl ethyl silane was removed by vacuum distillation at 80-85℃ and 0.06MPa. The weight ratio of methyl ricinoleate, urea, and methanol was 1:3:5; the weight ratio of pretreatment material, dimethyl ethyl silane, and platinum-carbon catalyst was 2:2.5:0.03.

[0042] The preparation method of the β-nucleating agent masterbatch used in the embodiments and comparative examples of this application includes the following steps: Rare earth β crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and second polypropylene matrix were granulated by twin screw extruder and kept at a constant temperature of 120-125℃ for 2 hours. The weight ratio of rare earth β-crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and the second polypropylene matrix is ​​2:1:1:0.1:40.

[0043] The preparation method of the modified wollastonite used in the embodiments and comparative examples of this application includes the following steps: Chitosan was dissolved in deionized water, and the pH was adjusted to 5.5 to obtain a chitosan solution. Add wollastonite to the chitosan solution, heat to 65°C, and stir at 1250 rpm for 60 min; The titanate coupling agent was diluted in anhydrous ethanol to obtain a titanate coupling agent solution, which was then added dropwise to the system. The mixture was stirred at 35°C and 1250 rpm for 45 min. After filtration and collection, the solution was washed 2-3 times with anhydrous ethanol and placed in a vacuum drying oven at 90°C for 3 h. After cooling to room temperature, the solution was pulverized and passed through a 200-mesh sieve to obtain modified wollastonite.

[0044] The weight ratio of chitosan, deionized water, wollastonite, titanate coupling agent and anhydrous ethanol is 2-3:5-8:10:1-1.5:5.

[0045] The preparation method of the polypropylene material in the embodiments and comparative examples of this application includes the following steps: The polypropylene matrix, grafted modified elastomer, β nucleating agent masterbatch and silane coupling agent were mixed at 115-125℃ and 5300rpm for 35min, with stirring every 10min and then standing for 4min. Nitrogen gas was introduced and the temperature was lowered to 75°C. β-nucleating agent masterbatch was added and mixing was continued for 20 min. Then add nano-reinforced fillers and antioxidants, mix at 75°C and 4200 rpm for 25 minutes, and then cool to room temperature; Add the cold-resistant additive and stir at 700 rpm for 7 minutes to obtain the mixture; The mixture is fed into a twin-screw extruder and plasticized with nitrogen at 370°C for 50 minutes at a flow rate of 7 L / min. It is then extruded according to the temperature gradient of 184°C in the feed section, 190°C in the first section, 197°C in the second section, 204°C in the third section, and 212°C in the die section. The screw speed is 180 rpm. The extrudate is cooled in a 40°C water cooling tank for 45 seconds and then pelletized. It was then aged at -15℃ for 50 hours, followed by recovery at 24℃ for 3 hours. The weight-average molecular weight of the polypropylene matrix was 240,000.

[0046] The raw material components of Examples 1-3 are shown in Table 1: Table 1 The raw material components of Comparative Examples 1-5 are shown in Table 2: Table 2 Performance tests were conducted on the embodiments and comparative examples. The performance test items are as follows: (1) Low temperature impact strength at -40℃: A simple beam impact tester was used. The sample size was 80mm×10mm×4mm with a V-notch (notch depth 2mm, angle 45°). Before the test, the sample was placed in a -40℃ constant temperature chamber for 24h to ensure uniform sample temperature. The impact speed was 3.5m / s. Five parallel samples were tested in each group, and the average value was taken to characterize the low temperature impact resistance of the material. (2) Tensile strength at room temperature: The sample was made into a dumbbell-shaped standard specimen (Type I) using a universal testing machine. The tensile rate was 50 mm / min. The test environment temperature was 23℃ and the humidity was 50%±5%. Five parallel samples were tested in each group, and the average value was taken to characterize the material's load-bearing and deformation resistance. (3) Tensile strength retention rate after being placed at -40℃ for 72 hours: First, test the tensile strength of the sample at room temperature (referred to as S0). Then, place the same batch of samples in a constant temperature chamber at -40℃ for 72 hours. After taking them out, restore them in an environment at 23℃ for 2 hours and test the tensile strength at this time (referred to as S1). Retention rate = (S1 / S0) × 100%, which characterizes the long-term low-temperature service stability of the material. (4) Low temperature bending strength (-40℃): A universal testing machine was used. The sample size was 80mm×10mm×4mm, the span of the simply supported beam was 64mm, the bending rate was 2mm / min, and the sample was kept at -40℃ for 24h before the test. Five parallel samples were tested in each group, and the average value was taken to characterize the bending bearing capacity of the material under low temperature stacked pressure.

[0047] The performance test results of Examples 1-3 and Comparative Examples 1-5 are shown in Table 3: Table 3 Observations reveal that the polypropylene prepared in Examples 1-3 of this application exhibits good impact resistance and low-temperature resistance. Comparative Example 1, lacking grafted elastomer, suffers from a significant decrease in low-temperature impact strength and low-temperature flexural strength due to the absence of stress absorption and crazing-inducing effects. It is prone to brittle fracture after high and low temperature cycling and cannot withstand stress impacts caused by low temperatures and temperature fluctuations. Comparative Example 2, with its increased proportion of maleic anhydride-grafted POE, weakens the synergistic toughening effect of the elastomer, resulting in a decrease in the retention rates of low-temperature impact, flexural, and tensile strength, making it prone to edge microcracks during use. Comparative Example 3 demonstrates better interfacial bonding strength. The strength of polypropylene materials decreased, and interfacial delamination was exacerbated at low temperatures. This resulted in decreased tensile and flexural strength, and the presence of minor cracks and deformations after high and low temperature cycling. In Comparative Example 4, the amount of silane coupling agent was insufficient, leading to even worse interfacial compatibility. The tensile and flexural strengths at both room temperature and low temperature were the lowest, and the deformation was more pronounced after high and low temperature cycling. In Comparative Example 5, the amount of cold-resistant additive was insufficient, resulting in inadequate improvement in molecular chain mobility at low temperatures. The low-temperature impact strength, flexural strength, and retention rate all decreased, and surface microcracks appeared after high and low temperature cycling. This demonstrates that the cold-resistant additive has a strengthening effect on the low-temperature adaptability of polypropylene materials.

[0048] The preferred embodiments of this application have been described in detail above, but the invention of this application is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A polypropylene material that is impact-resistant and resistant to low temperatures, characterized in that, The raw materials consist of the following components, calculated by weight: The composition includes 65-80 parts of polypropylene matrix, 5-12 parts of grafted modified elastomer, 2-5 parts of β-nucleating agent masterbatch, 0.5-2 parts of silane coupling agent, 3-8 parts of cold-resistant agent, 1-3 parts of antioxidant, and 2-6 parts of nano-reinforcing filler.

2. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The grafted modified elastomer is a combination of maleic anhydride-grafted POE and acrylic acid-grafted SEBS, with a weight ratio of maleic anhydride-grafted POE to acrylic acid-grafted SEBS of 1:3-4.

3. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The preparation method of the cold-resistant agent includes the following steps: Methyl ricinoleate and urea were added to methanol and stirred in a water bath at 0°C for 3-5 hours. After crystallization at 0-5°C for 14-20 hours, the mixture was filtered under vacuum. The filtrate was extracted with petroleum ether, washed twice with deionized water, and then distilled under reduced pressure at 60-70°C and 0.09 MPa to remove the solvent, thus obtaining the pretreated product. The pretreated material and dimethyl ethyl silane were mixed, a platinum-carbon catalyst was added, and the mixture was refluxed and stirred at 110-120°C for 6-7 hours. The catalyst was removed by centrifugation, and the remaining dimethyl ethyl silane was removed by vacuum distillation at 80-85°C and 0.06 MPa. The weight ratio of methyl ricinoleate, urea, and methanol is 1:3:4.8-5.2; The weight ratio of the pretreated material, the dimethylethylsilane, and the platinum-carbon catalyst is 2:2-3:0.02-0.

03.

4. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The preparation method of the β-nucleating agent masterbatch includes the following steps: Rare earth β crystal nucleating agent, hydrotalcite, montmorillonite, antioxidant 1010, and second polypropylene matrix were granulated by twin screw extruder and kept at a constant temperature of 120-125℃ for 2 hours. The weight ratio of the rare earth β-crystal nucleating agent, the hydrotalcite, the montmorillonite, the antioxidant 1010, and the second polypropylene matrix is ​​2:1:1:0.1:40-44.

5. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The silane coupling agent is a combination of γ-glycidoxypropyltrimethoxysilane and vinyltriethoxysilane, wherein the weight ratio of γ-glycidoxypropyltrimethoxysilane to vinyltriethoxysilane is 1:1-2.

6. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The antioxidant is a combination of antioxidant 1076 and tris(2,4-di-tert-butylphenyl) phosphite, wherein the weight ratio of antioxidant 1076 to tris(2,4-di-tert-butylphenyl) phosphite is 3-5:

2.

7. The impact-resistant and low-temperature resistant polypropylene material according to claim 1, characterized in that, The particle size of the nano-reinforced filler is 50-200 nm; The nano-reinforcing filler is a combination of modified wollastonite, nano-calcium carbonate, and montmorillonite, with a weight ratio of 4-6:1:1 for the modified wollastonite, nano-calcium carbonate, and montmorillonite. The modified wollastonite is obtained by modifying wollastonite with chitosan and titanate coupling agent.

8. A method for preparing an impact-resistant and low-temperature resistant polypropylene material as described in any one of claims 1-7, characterized in that, Includes the following steps: The polypropylene matrix, the grafted modified elastomer, the β nucleating agent masterbatch and the silane coupling agent are mixed at 115-125℃ and 5000-5500rpm for 30-40min, with stirring every 10min and then standing for 4-5min. Introduce nitrogen gas and cool to 70-80℃, then add the β-nucleating agent masterbatch and continue mixing for 15-20 minutes. Then add the nano-reinforced filler and the antioxidant, mix at 70-80℃ and 4000-4500rpm for 25-30 minutes, and then cool to room temperature; Add the aforementioned cold-resistant additive and stir at 600-800 rpm for 7 minutes to obtain the mixture; The mixture is fed into a twin-screw extruder and plasticized with nitrogen at a flow rate of 7 L / min at 360-380℃ for 50 min. It is then extruded according to the temperature gradient of 182-186℃ in the feed section, 188-192℃ in the first section, 195-199℃ in the second section, 202-206℃ in the third section, and 210-214℃ in the die section. The screw speed is 170-180 rpm. The extrudate is cooled in a 40℃ water cooling tank for 45 seconds and then pelletized.

9. The method for preparing polypropylene material according to claim 8, characterized in that, The pelletizing process also includes the following steps: Place at -10~-15℃ for aging for 48-60 hours, then raise to 23-25℃ for 2-3 hours to recover.

10. The application of the impact-resistant and low-temperature resistant polypropylene material as described in any one of claims 1-7 in the preparation of cold chain equipment pallets.

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