High-rubber-impact-resistance co-polypropylene and preparation method thereof

Abstract

The invention discloses high-rubber-impact-resistance co-polypropylene and a preparation method thereof. The preparation method comprises the following steps: propylene is subjected to a homopolymerization reaction in a catalytic system; and adding the long-chain substituted diene mixed with the solvent in a copolymerization stage, and introducing mixed gas of propylene and other monoene for reaction to obtain the high-rubber anti-impact co-polypropylene. The long-chain substituted diene mixed with the solvent is added in the copolymerization stage, the crosslinking degree and the product uniformity of the high-rubber-impact-resistance co-polypropylene prepared by the method disclosed by the invention are remarkably improved, the introduction amount of the long-chain substituted diene is reduced, the cost is reduced, and the production efficiency is improved. In addition, the content of a rubber phase is broken through, the particle surface is not sticky, the viscosity index change is small after heating, the distribution and fluidity of the propylene copolymer are effectively controlled, and the low-temperature impact toughness is higher.

Description

Technical Field

[0001] This invention relates to the field of olefin polymerization, and more specifically to a high-rubber-impact copolymer polypropylene and its preparation method. Background Technology

[0002] Impact copolymer polypropylene (IPC), as an important modified polypropylene material, effectively balances the rigidity and toughness of the material by introducing an ethylene propylene rubber phase into the homopolymer polypropylene matrix, and is widely used in automotive parts, appliance housings, packaging materials, and other fields. With the continuous improvement of downstream application requirements for material performance, the development of impact copolymer polypropylene with high rubber content, excellent low-temperature impact toughness, and a non-sticky surface has become a research hotspot in the industry.

[0003] Currently, the low-temperature impact toughness of impact-resistant copolymer polypropylene is closely related to its rubber phase (ethylene-propylene random copolymer) content; generally, the higher the rubber phase content, the better the low-temperature impact resistance of the material. However, at high rubber content, the rubber phase is prone to problems such as phase agglomeration, excessively large phase region size, and weak interfacial bonding. Furthermore, the rubber phase is prone to migration, aggregation, and phase separation during polymerization and processing, often migrating to the particle surface and increasing the particle surface viscosity index, leading to problems such as stickiness and agglomeration on the particle surface. Therefore, the current core approach is to introduce crosslinking aids during the ethylene-propylene copolymerization stage. By controlling the degree of crosslinking and dispersion state of the rubber phase, the migration rate and distribution of the rubber phase can be limited, optimizing the microstructure of the material to improve the performance of impact-resistant polypropylene.

[0004] In recent years, crosslinking aids with different structures have been continuously applied to the research on optimizing the structure and improving the performance of olefin polymerization. Some researchers have introduced α,w-diene monomers into the ethylene-propylene copolymerization stage, making them the third monomer in the ethylene-propylene copolymerization process. Through their double bonds, they crosslink the molecular chains, thereby limiting the migration rate and distribution of the rubber phase, inhibiting the increase in the size of ethylene-propylene rubber and its migration to the particle surface, thus achieving a slight reduction in the surface viscosity and improvement in the mechanical properties of high-impact polypropylene. On this basis, the carbon number of the crosslinking agent was also optimized (CN102838701A). Liu Ming et al. compared the crosslinking efficiency of α,w-diene monomers and w-olefin methyl dichlorosilane on polyolefin elastomers (POE), and found that using w-olefin methyl dichlorosilane as a crosslinking aid has a higher efficiency in generating long-chain branched structures. This is mainly because the electron-withdrawing effect of silicon element increases the electron cloud density near the double bond and the insertion rate (Liu Ming, Yang Xiaojun, Chen Fengtao, et al. Synthesis, structure and performance study of long-chain branched polyolefin elastomers [J]. Acta Polymerica Sinica, 2025, 56(09):1480-1492.). However, existing technologies still have many problems in practical applications: Crosslinking aids, designed to effectively inhibit the migration of ethylene-propylene rubber (EPR), often possess long-chain structures, resulting in high boiling points. Crosslinking aids added during the EPR copolymerization stage are difficult to vaporize, leading to uneven distribution of the crosslinking agent in the polymerization system, forming localized over-crosslinked and uncrosslinked regions. Furthermore, crosslinking aids with high boiling points often exist in liquid column form, limiting their contact area with the monomer and resulting in low crosslinking efficiency. Increased crosslinking agent dosage also raises production costs.

[0005] Crosslinking aids, due to the steric hindrance effect of their long-chain structure and the electron-withdrawing effect of some elements such as silicon, significantly inhibit catalyst activity, leading to a decrease in monomer polymerization rate, a longer reaction cycle, and affecting the growth and dispersion of the rubber phase. This makes it difficult to achieve the preparation target of high rubber content (such as more than 40%) and further improve its mechanical properties.

[0006] Therefore, developing a preparation method that can solve the above-mentioned technical bottlenecks, and achieving a synergistic balance of high rubber content, excellent low-temperature impact toughness and low surface viscosity by optimizing the use of crosslinking aids, improving dispersion uniformity and compensating for catalyst activity loss, has become an urgent technical problem to be solved in the field of impact copolymer polypropylene. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing high-rubber impact-resistant copolymer polypropylene. This impact-resistant copolymer polypropylene introduces a mixture of long-chain substituted dienes and solvents as crosslinking aid monomers and solvents during the copolymerization stage, achieving the preparation of impact-resistant polypropylene with high rubber content and a non-sticky surface. This promotes the degree of crosslinking of the propylene copolymer in the impact-resistant copolymer polypropylene, significantly improving its low-temperature impact toughness and product uniformity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a high rubber impact-resistant copolymer polypropylene prepared by the method described above, wherein the high rubber impact-resistant copolymer polypropylene comprises: homopolymer polypropylene as the matrix and propylene copolymer as the mobile phase.

[0009] Based on a specific embodiment of the present invention, the NMR quantitative long-chain substituted diene insertion rate in the high-rubber impact-resistant copolymer polypropylene is 0.01 mol%-10 mol%; preferably 3 mol%-10 mol%; more preferably 5 mol%-10 mol%. The rubber content of the high-rubber impact-resistant copolymer polypropylene is preferably 50%-70%.

[0010] Furthermore, the surface viscosity index of the high rubber impact-resistant copolymer polypropylene (defined as the ratio of the time required for 100g of sieved high rubber impact-resistant copolymer polypropylene sample to pass through a cross-sectional funnel at room temperature (25°C) to the time required for 100g of sieved homopolymer polypropylene sample with the same particle size range to pass through a cross-sectional funnel, wherein the size of the sieved polypropylene particles is 1200-1300μm) is 1.1-1.4, preferably 1.1-1.3, and the change in surface viscosity index before and after heat treatment (heating to 90°C and maintaining for 2 hours) is preferably 1%-5%.

[0011] Furthermore, the high-impact copolymer polypropylene preferably has an impact strength of 60-70 KJ / m at -20℃. 2 .

[0012] On the other hand, the present invention provides a method for preparing impact-resistant copolymer polypropylene with high rubber content, the method being used to prepare the aforementioned impact-resistant copolymer polypropylene.

[0013] The preparation method includes the following steps: Propylene undergoes homopolymerization under a catalytic system; after homopolymerization, the solvent in the reactor is extracted. After the solvent is completely removed, a long-chain substituted diene mixed with the solvent is added at the copolymerization reaction temperature, and a mixed gas of propylene and other monoenes is introduced to carry out copolymerization to obtain the high rubber impact-resistant copolymer polypropylene.

[0014] This invention, through in-depth research, has discovered that adding long-chain substituted dienes mixed with solvent before the copolymerization stage allows the solvent, with its low boiling point and easy vaporization, to effectively disperse the long-chain substituted dienes, which have a high boiling point and are difficult to vaporize. This helps ensure the uniformity of crosslinking during the copolymerization stage. Furthermore, this method changes the form in which the long-chain substituted dienes enter the reactor from a liquid column to droplets, significantly increasing the surface area for the crosslinking reaction, improving crosslinking efficiency, and reducing the amount of long-chain substituted dienes used, thus saving costs. Finally, during the copolymerization stage, the solvent, through co-solvent interaction, promotes the diffusion of monomers to the catalyst's active sites, increasing the monomer concentration at these sites. This compensates for the decrease in catalyst activity caused by the electronic effects of silicon, aromatics, etc., and the steric hindrance effect of the long-chain substituted dienes. Moreover, by altering the radial distribution and migration rate of the propylene copolymer within the homopolymer polypropylene particles, the resulting high-rubber impact-resistant copolymer polypropylene exhibits high rubber content, good low-temperature impact toughness, and no significant increase in viscosity index.

[0015] According to a specific embodiment of the present invention, the step of extracting residual solvent from the reactor includes: after homopolymerization, controlling the temperature and pressure to vaporize and extract the residual solvent from the reactor. For example, after homopolymerization, the temperature inside the reactor can be maintained at the homopolymerization reaction temperature, and a vacuum pump or air pump can be used to change the pressure inside the reactor to vaporize and extract the residual solvent. Preferably, the temperature of the solvent extraction step is 60-70°C, and the solvent is extracted to a pressure gauge reading of -1 bar.

[0016] Based on specific embodiments of the present invention, when adding the long-chain substituted diene mixed with the solvent, the temperature inside the reactor is controlled at the copolymerization reaction temperature. Typically, but not limited to, the temperature is controlled at 60-90°C when adding the long-chain substituted diene mixed with the solvent. Preferably, the long-chain substituted diene mixed with the solvent is added to the reactor under slight positive pressure.

[0017] According to a preferred embodiment of the present invention, a prepolymerization step may be further included before the homopolymerization reaction.

[0018] Based on specific embodiments of the present invention, the other monoenes are one or more of the C2-C10 linear α-olefins other than propylene, preferably one of ethylene, 1-butene or a mixture thereof.

[0019] Based on a specific embodiment of the present invention, the solvent has a molecular weight of 58 g / mol to 101 g / mol, and the solvent is one or a mixture of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, cyclopentane, n-butane, and isobutane. Preferably, it is one or a mixture of n-hexane, isopentane, and n-heptane, and more preferably, it is n-hexane.

[0020] Based on specific embodiments of the present invention, the catalytic system comprises a solid catalyst component, a co-catalyst component, and at least one external electron donor; the solid catalyst component is one or a mixture of metallocene catalysts, Ziegler-Natta catalysts, chromium-based catalysts, and post-transition metal catalysts; the co-catalyst component is one or a mixture of alkylaluminum, alkylaluminoxane, and modified alkylaluminoxane. The external electron donor is one or a mixture of dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, and diisopropyldimethoxysilane.

[0021] Based on specific embodiments of the present invention, the substituents of the long-chain substituted diene include halogens, halosilanes, methoxy groups, methoxysilanes, aromatic groups, or combinations thereof. Further, the main chain carbon number in the long-chain substituted diene is C8-C20.

[0022] Based on specific embodiments of the present invention, the olefinic alkoxysilane preferably includes one or a mixture of: di(5-hexenyl)dimethoxysilane, di(6-heptenyl)dimethoxysilane, di(6-heptenyl)dichlorosilane, di(7-octenyl)dichlorosilane, and benzohexadiene. Preferably, it is an olefinic siloxane, such as di(5-hexenyl)dimethoxysilane or di(6-heptenyl)dimethoxysilane.

[0023] Based on a specific embodiment of the present invention, in the copolymerization reaction, the molar ratio of propylene to other monoenes is preferably 1:1.

[0024] Based on a specific embodiment of the present invention, in the copolymerization reaction stage, the solvent is added in an amount of 1-50 parts by weight per 100 parts of the mixed gas, and the long-chain substituted diene is added in an amount of 0.001-5 parts by weight. Further, the solvent is preferably added in an amount of 7-9 parts by weight per 100 parts of the mixed gas, and the long-chain substituted diene is preferably added in an amount of 0.01-0.8 parts by weight.

[0025] The homopolymerization reaction temperature of the propylene is 50-80℃, the polymerization pressure is 4-40 bar, and the polymerization time is 20-120 min; the copolymerization reaction temperature is 50-90℃, the polymerization pressure is 4-40 bar, and the polymerization time is 20-120 min.

[0026] Based on a specific embodiment of the present invention, the homopolymerization temperature is preferably 60-70℃, and the polymerization pressure is preferably 4-18 bar; the copolymerization reaction temperature is preferably 60-80℃, and the polymerization pressure is preferably 4-20 bar.

[0027] Through in-depth research, this invention has found that the high rubber impact copolymer polypropylene prepared by the above preparation method has significantly improved crosslinking degree and product uniformity, reduced the amount of long-chain substituted diene introduced, reduced costs, and achieved a new high rubber phase content with non-sticky particle surface and minimal change in viscosity index after heating. This effectively controls the distribution and flowability of propylene copolymer and provides higher low-temperature impact toughness.

[0028] The present invention also provides the application of the aforementioned high-impact copolymer polypropylene in the preparation of automotive parts, appliance housings, or packaging materials.

[0029] Compared with the prior art, the beneficial effects of the present invention include: (1) In the preparation method of the present invention, the copolymerization reaction is carried out in the presence of long-chain substituted dienes mixed with solvent, which can improve the degree of crosslinking of the rubber phase and the uniformity of the product in the obtained impact-resistant copolymer polypropylene, reduce the amount of long-chain substituted dienes used, and thus reduce costs. This is mainly because the solvent has a low boiling point and is easy to vaporize. The energy released by its instantaneous vaporization will effectively disperse the long-chain substituted dienes with high boiling points and are not easy to vaporize, changing their form into "liquid column" into "liquid droplets" in the reactor, which significantly increases the surface area of ​​the crosslinking reaction and improves the crosslinking efficiency.

[0030] (2) The high rubber impact copolymer polypropylene prepared by the above preparation method in this invention has a new high rubber phase content and the particle surface is not sticky. The viscosity index changes little after heating, which effectively controls the distribution and flowability of propylene copolymer and has higher low-temperature impact toughness. This is mainly because the co-solvent effect of the solvent promotes the diffusion of monomer to the catalyst active center, increases the monomer concentration at the catalyst active center, and makes up for the decrease in catalyst activity caused by the electronic effect of silicon, aromatics, etc. and the steric hindrance effect of long-chain substituted diene. In addition, the solvent and long-chain substituted diene respectively change the radial distribution and migration rate of propylene copolymer in homopolymer polypropylene particles, which greatly utilizes the utilization rate of the "loading" capacity of propylene copolymer in the pores of homopolymer polypropylene. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be described in complete and clear form below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0032] Example 1 This embodiment prepares a high-impact rubber copolymer polypropylene, specifically including: Catalyst feeding was performed on a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added through the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas was added at 0.4 bar, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain the pressure inside the reactor at 6 bar. Homopolymerization was carried out for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g of hexane and 0.02 g of bis(6-heptenyl)dimethoxysilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 60 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0033] Example 2 This embodiment prepares a high-impact rubber copolymer polypropylene, specifically including: Catalyst feeding was performed in a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added via the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas at 0.4 bar was added, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain a pressure of 6 bar inside the reactor for homopolymerization for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g of hexane and 0.02 g of bis(6-heptenyl)dichlorosilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 65 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0034] Example 3 Catalyst feeding was performed in a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added via the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas at 0.4 bar was added, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain a pressure of 6 bar inside the reactor for homopolymerization for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g isopentane and 0.02 g di(6-heptenyl)dimethoxysilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 70 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0035] Example 4 Catalyst feeding was performed in a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added via the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas at 0.4 bar was added, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain a pressure of 6 bar inside the reactor for homopolymerization for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g of heptane and 0.02 g of bis(6-heptenyl)dimethoxysilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 50 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0036] Example 5 Catalyst feeding was performed in a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added via the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas at 0.4 bar was added, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain a pressure of 6 bar inside the reactor for homopolymerization for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g of hexane and 0.01 g of bis(6-heptenyl)dimethoxysilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 55 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0037] Example 6 Catalyst feeding was performed in a 1.1L stirred tank reactor under vacuum conditions at an initial temperature of 30℃. The catalyst was Ziegler-Natta catalyst, with a dosage of 35-40 mg each time. Simultaneously, 0.10-0.13 ml of the external electron donor dicyclopentyldimethoxysilane (Ddonor) and 0.60-0.75 ml of the co-catalyst triethylaluminum (TEA) were added through the external electron donor line. 100-150 ml of n-heptane was added via the solvent line, and the catalyst was added to the stirred tank reactor through the catalyst line. Hydrogen gas at 0.4 bar was added, and propylene was introduced until the total pressure inside the reactor reached 1 bar. Stirring was started at 500 rpm and maintained for 15 min. The temperature was then raised to 70℃, and propylene was introduced to maintain a pressure of 6 bar inside the reactor for homopolymerization for 30 min. Heptane was extracted using a vacuum pump connected to a cold trap. A mixture of 0.9 g of hexane and 0.03 g of bis(6-heptenyl)dimethoxysilane was added at 70°C and under slight positive pressure. Then, a 1:1 ethylene-propylene mixture was introduced to maintain a pressure of 6 bar inside the reactor, initiating the copolymerization reaction. The reaction time was 70 minutes, consuming 10 g of the ethylene-propylene mixture. After the polymerization reaction was complete, the resulting polymer was dried in a vacuum oven at 65°C to obtain the high-impact, rubber-resistant copolymer polypropylene.

[0038] Comparative Example 1 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 1, except that the solvent n-hexane is not added in the ethylene-propylene copolymerization reaction, the copolymerization reaction time is 80 min, and 10g of ethylene-propylene mixed gas is consumed.

[0039] Comparative Example 2 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 2, except that the solvent n-hexane is not added in the ethylene-propylene copolymerization reaction, the copolymerization reaction time is 85 min, and 10g of ethylene-propylene mixed gas is consumed.

[0040] Comparative Example 3 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 1. The difference is that the solvent and long-chain substituted diene are added in sequence before the ethylene-propylene copolymerization reaction. Specifically, 0.9g of n-hexane is added first, and after waiting for 5 minutes, 0.02g of bis(6-heptenyl)dimethoxysilane is added. The copolymerization reaction time is 80 minutes, and 10g of ethylene-propylene mixed gas is consumed.

[0041] Comparative Example 4 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 2. The difference is that the solvent and long-chain substituted diene are added in sequence before the ethylene-propylene copolymerization reaction. Specifically, 0.9g of n-hexane is added first, and after waiting for 5 minutes, 0.02g of bis(6-heptenyl)dichlorosilane is added. The copolymerization reaction time is 85 minutes, and 10g of ethylene-propylene mixed gas is consumed.

[0042] Comparative Example 5 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 5, except that the solvent n-hexane is not added in the ethylene-propylene copolymerization reaction, the copolymerization reaction time is 70 min, and 10g of ethylene-propylene mixed gas is consumed.

[0043] Comparative Example 6 This comparative example prepares a high-impact rubber copolymer polypropylene, which is basically carried out according to the method of Example 6, except that the solvent n-hexane is not added in the ethylene-propylene copolymerization reaction, the copolymerization reaction time is 100 min, and 10g of ethylene-propylene mixed gas is consumed.

[0044] Test case This test example examines the insertion amount, mechanical properties, viscosity index, and thermal viscosity index of the long-chain substituted diene in the high-impact copolymer polypropylene obtained in the above examples and comparative examples.

[0045] After long-chain substituted dienes are introduced during the ethylene-propylene copolymerization stage, they will form two structural types depending on the number of inserted double bonds: dangling double bonds and cross-linked structures. The amount of long-chain substituted diene inserted is the sum of the two, and the two are quantified by H-NMR and C-NMR, respectively.

[0046] Low-temperature impact performance testing method: The impact specimen is machined with a 45° V-shaped notch using a notching machine, with a notch depth of 2 mm. Before impact testing, the specimen is stored in a 23 ℃ constant temperature chamber for at least 48 hours. The impact strength of the material is obtained by repeating the test five times at -20 ℃ using a pendulum impact tester.

[0047] Test methods for viscosity index and heat-induced viscosity index change: The viscosity index is the ratio of the time required for 100g of sieved high-impact copolymer polypropylene sample to pass through a cross-sectional funnel at room temperature (25℃) to the time required for 100g of sieved homopolymer polypropylene sample of the same particle size range to pass through a cross-sectional funnel. The heat-induced viscosity index change is the viscosity index of the high-impact copolymer polypropylene sample powder after heat treatment at 90℃ for 2 hours. Comparing Examples 1, 2, and 3 with Comparative Example 1 in Table 1, it can be seen that the high-impact copolymer polypropylene prepared by the solvent-premixed method with long-chain substituted dienes in the examples exhibits significantly improved low-temperature impact toughness, and significantly reduced changes in viscosity index and viscosity index after heating. On one hand, the low boiling point of the solvent allows for rapid vaporization, and the energy released during vaporization disperses the long-chain substituted dienes from a liquid column into droplets, resulting in more uniform dispersion and increased contact area. This improves crosslinking efficiency and product uniformity, thus significantly increasing low-temperature impact toughness. On the other hand, the solvent co-solvent effect promotes monomer diffusion, reversing the radial distribution of ethylene propylene rubber from a shell-heavy to a shell-heavy distribution. This reduces the size of the ethylene propylene rubber and enhances molecular chain entanglement through the bridging crosslinking effect of the long-chain substituted dienes, restricting its flowability. This makes it difficult for the ethylene propylene rubber to flow to the surface after heating, resulting in an increase in particle viscosity index. Meanwhile, hexane is superior to isopentane and heptane as a solvent. This is because hexane has a stronger co-solvent effect on the polymer monomers than isopentane, resulting in better radial distribution of ethylene propylene rubber. Furthermore, hexane has a lower boiling point than heptane, leading to more significant vaporization and better dispersion of long-chain substituted dienes.

[0048] Comparing Examples 1 and 2 and Comparative Examples 1 and 2 in Table 1, it can be seen that the effect of using olefin-based siloxanes is better than that of olefin-based chlorosilanes. This is mainly because the electronegativity of oxygen atoms is stronger than that of chlorine atoms. Through the inductive effect, electrons are withdrawn, thereby increasing the electron cloud density of the olefin double bond connected to Si, which is more conducive to the occurrence of double bond insertion reaction in coordination polymerization.

[0049] Comparing Examples 1, 5, and 6 with Comparative Examples 1, 5, and 6 in Table 1, it can be seen that as the amount of long-chain substituted diene introduced increases, the flowability of ethylene propylene rubber is significantly suppressed, leading to a slower change in the viscosity index before and after heating. Furthermore, the low-temperature impact toughness of the high-impact copolymer polypropylene prepared with long-chain substituted diene mixed with solvent shows a trend of first increasing and then decreasing with increasing long-chain substituted diene introduction, while the low-temperature impact toughness of the high-impact copolymer polypropylene with only olefin-based siloxanes added shows a gradual increasing trend, but the absolute value is much smaller than the former. This indicates that the solvent rapidly vaporizes, and the energy released by its vaporization disperses the long-chain substituted diene from a liquid column into droplets, resulting in more uniform dispersion and increased contact area, thus improving crosslinking efficiency and product uniformity. From a process perspective, this reduces the amount of expensive olefin-based siloxanes used to achieve superior mechanical properties and lowers production costs.

[0050] Comparing Examples 1 and 2 and Comparative Examples 3 and 4 in Table 1, it can be seen that adding hexane first and then the long-chain substituted diene does not significantly improve the low-temperature impact toughness of the product. Furthermore, although the viscosity index is low at room temperature (25°C), it increases sharply after heat treatment, exhibiting a high rate of change. This is mainly because adding hexane first only utilizes its co-solvent effect to promote monomer diffusion and alter the radial distribution of the propylene copolymer within the homopolymer polypropylene particles, resulting in a trend of fewer shells and more cores in the propylene copolymer, thus reducing the surface viscosity index. However, it does not change the form of subsequent addition of the long-chain substituted diene. Therefore, the amount of long-chain substituted diene inserted and its improvement on product performance are relatively limited.

[0051] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A high-impact rubber copolymer polypropylene, characterized in that, The high-rubber impact-resistant copolymer polypropylene includes: homopolymer polypropylene as the matrix and propylene copolymer as the mobile phase; The long-chain substituted diene insertion rate, quantitatively determined by NMR, in the high-rubber impact-resistant copolymer polypropylene is 0.01 mol%-10 mol%, and the rubber content of the high-rubber impact-resistant polypropylene is 30%-70%. The surface viscosity index is defined as the ratio of the time required for 100g of sieved high-impact copolymer polypropylene sample to pass through a cross-sectional funnel to the time required for 100g of sieved homopolymer polypropylene sample with the same particle size range to pass through a cross-sectional funnel at 25℃. The size of the sieved polypropylene particles is 1200-1300μm, the surface viscosity index of the high-impact copolymer polypropylene is 1.1-1.4, and the change in surface viscosity index before and after heat treatment is 0%-9%. The heat treatment is heating to 90℃ and maintaining it for 2 hours. The high-impact rubber copolymer polypropylene has an impact strength of 50-70 KJ / m at -20℃. 2 .

2. A method for preparing a high-impact copolymer polypropylene, characterized in that, Includes the following steps: Propylene undergoes homopolymerization in a catalytic system. After homopolymerization, the solvent is removed from the reactor. Once the solvent is completely removed, a long-chain substituted diene mixed with the solvent is added at the copolymerization reaction temperature. A mixed gas of propylene and other monoenes is then introduced to carry out a copolymerization reaction, yielding the high-rubber impact-resistant copolymer polypropylene. In the copolymerization reaction stage, the amount of solvent added is 1-50 parts by weight per 100 parts by weight of the mixed gas, and the amount of the long-chain substituted diene added is 0.001-5 parts by weight.

3. The method according to claim 2, characterized in that, The other monoenes are one or more of the C2-C10 linear α-olefins other than propylene; wherein the mass fraction of propylene is 10%-90%, and the mass fraction of the other monoenes is 10%-90%.

4. The method according to claim 2, characterized in that, The catalytic system comprises a solid catalyst component, a co-catalyst component, and at least one external electron donor; the solid catalyst component is one or a mixture of metallocene catalysts, Ziegler-Natta catalysts, chromium-based catalysts, and post-transition metal catalysts; the co-catalyst component is one or a mixture of alkylaluminum, alkylaluminoxane, and modified alkylaluminoxane.

5. The method according to claim 2, characterized in that, The homopolymerization reaction temperature of the propylene is 50-80℃, the polymerization pressure is 4-40 bar, and the polymerization time is 20-120 min; the copolymerization reaction temperature is 50-90℃, the polymerization pressure is 4-40 bar, and the polymerization time is 20-120 min.

6. The method according to claim 2, characterized in that, The step of extracting the residual solvent from the reactor includes: after homopolymerization is completed, controlling the temperature and pressure to vaporize and extract the residual solvent from the reactor.

7. The method according to claim 2, characterized in that, The solvent has a molecular weight of 58 g / mol to 101 g / mol and is one or a mixture of n-pentane, isopentane, n-hexane, cyclohexane, n-heptane, cyclopentane, n-butane, and isobutane.

8. The method according to claim 2, characterized in that, The substituents of the long-chain substituted diene include halogens, halosilanes, methoxy groups, methoxysilanes, aromatics, or a combination thereof.

9. The method according to claim 2, characterized in that, The main chain carbon number in the long-chain substituted diene is C8-C20.

10. The application of the high rubber impact copolymer polypropylene of claim 1 in the preparation of automotive parts, appliance housings or packaging materials.

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