High-performance ethylene copolymer as well as continuous preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer material preparation, and particularly relates to a high-performance ethylene copolymer and a continuous preparation method and application thereof.The continuous preparation method comprises the following steps that a main catalyst and a co-catalyst are mixed and then subjected to pre-activation treatment, the main catalyst is a titanium-series Ziegler-Natta catalyst, and the co-catalyst is a titanium-series Ziegler-Natta catalyst; the cocatalyst is ethyl sesquialuminum chloride or triethyl aluminum; mixing the pre-activated main catalyst, the pre-activated cocatalyst, the ethylene monomer and the solvent in proportion, and then carrying out two-step polymerization reaction; carrying out flash evaporation on the glue solution after the polymerization reaction to remove volatile components; adsorbing and removing the residual catalyst from the glue solution from which the volatile components are removed by adopting modified aluminum oxide or a molecular sieve adsorbent; and mixing the glue solution without the catalyst with a composite antioxidant, and extruding and granulating to obtain the product. The technical problems that an ethylene copolymer prepared in the prior art is insufficient in mechanical property, poor in optical property, poor in oxidation resistance, wide in molecular weight distribution and the like can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, specifically relating to a high-performance ethylene copolymer and its continuous preparation method and application. The ethylene copolymer has excellent mechanical properties, optical properties and antioxidant properties. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Ethylene copolymer (EPOE) is a high-performance thermoplastic elastomer material that combines the elasticity of rubber with the processing properties of plastics. It is widely used in automotive parts, wires and cables, packaging materials, medical devices, and other fields. With the continuous expansion of application areas, the market has placed higher demands on the comprehensive performance of EPOE materials, requiring not only excellent mechanical properties but also good optical transparency and long-term stability.

[0004] Currently, the industrial production of EPOE mainly employs solution polymerization, using inert solvents such as heptane as the reaction medium, and carrying out the copolymerization reaction of ethylene and propylene under the action of Ziegler-Natta catalysts. This preparation process has the following technical problems: In traditional single-reactor processes, the short contact time between the catalyst and the monomer results in insufficient molecular chain growth, leading to low tensile strength and impact strength of the product, which makes it difficult to meet the application requirements of high-end structural components. The residual catalyst and co-catalyst in the polymerized adhesive are difficult to remove effectively, resulting in low light transmittance and high haze of the product, which limits its application in optical packaging, transparent films and other fields; the residual catalyst components are prone to oxidative degradation during high-temperature processing and use, resulting in poor thermal stability and short service life of the product. Inaccurate control of the reaction temperature leads to a wide molecular weight distribution (PDI>3.0) and unstable mechanical and processing properties of the product. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a high-performance ethylene copolymer and its continuous preparation method and application, thereby solving the technical problems of insufficient mechanical properties, poor optical properties, inadequate antioxidant properties, and wide molecular weight distribution of ethylene copolymers prepared in the prior art.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a continuous preparation method for high-performance ethylene copolymers, comprising the following steps: The main catalyst and the co-catalyst are mixed and then pre-activated at a temperature of 30-50°C for 5-15 minutes. The main catalyst is a titanium-based Ziegler-Natta catalyst and the co-catalyst is sesquialuminum or triethylaluminum. The pre-activated main catalyst and co-catalyst, ethylene monomer and solvent are continuously fed into the first reactor in proportion. The reactor is held at a pressure of 2.0-2.3 MPa and a temperature of 55-60℃ for 30-60 min to carry out the first step of polymerization reaction. The flow rate ratio of catalyst, ethylene monomer and solvent is 20-35:500-700:4000-5500. The product of the first polymerization step is then transferred to the second reactor, while catalyst, ethylene monomer, and solvent are added to maintain a flow ratio of 30-40:800-1000:6000-10000. The second polymerization step is carried out at a pressure of 2.4-2.6 MPa and a temperature of 61-70°C for 20-40 minutes. The temperature and pressure of the second polymerization step are both higher than those of the first polymerization step. The polymer solution after polymerization is flash-evaporated to remove volatile components; The colloid after the volatile components have been removed is then adsorbed and removed by modified alumina or molecular sieve adsorbents to remove residual catalyst. The catalyst-removed gel is mixed with a composite antioxidant and then extruded and granulated to obtain the final product.

[0007] Secondly, the present invention provides a high-performance ethylene copolymer prepared by the continuous preparation method described above.

[0008] Thirdly, the present invention provides the application of the high-performance ethylene copolymer in automotive parts, wires and cables, packaging materials or medical devices; especially in high-end optical packaging, medical transparent consumables, and lightweight transparent automotive components.

[0009] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: In this invention, by pre-activating the catalyst and using a dual-reactor series process, the molecular chain of the ethylene copolymer is fully grown, and the tensile strength of the prepared ethylene copolymer product reaches 25-35 MPa, and the dart impact strength reaches 8-15 J / mm, which is more than 40% higher than that of traditional products.

[0010] By setting up a catalyst adsorption and removal process, the amount of residual catalyst in the adhesive is greatly reduced, and the visible light transmittance of the product reaches 85-95%, and the ultraviolet light transmittance reaches 90-98%, which can meet the application requirements of high transparency.

[0011] Through the synergistic effect of compound antioxidants, the oxidation induction period of the product is extended to 30-60 minutes (200℃), the thermal stability is significantly improved, and the service life is extended.

[0012] By precisely controlling the reaction temperature and residence time, the product's molecular weight distribution index (PDI) is controlled within the range of 2.0-2.5, resulting in more stable mechanical and processing properties.

[0013] Using the preparation process of this invention, the conversion rate of ethylene monomer reaches over 90%, the product yield reaches over 65%, and the raw material utilization rate is high. Detailed Implementation

[0014] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] To address the technical problems existing in the background art, the present invention provides a continuous preparation method for high-performance ethylene copolymers, comprising the following steps: The main catalyst and the co-catalyst are mixed and then pre-activated at a temperature of 30-50°C for 5-15 minutes. The main catalyst is a titanium-based Ziegler-Natta catalyst and the co-catalyst is ethyl sesquialuminate chloride (sesquialuminum) or triethylaluminum. The pre-activated main catalyst and co-catalyst, ethylene monomer and solvent are continuously fed into the first reactor in proportion. The reactor is held at a pressure of 2.0-2.3 MPa and a temperature of 55-60℃ for 30-60 min to carry out the first step of polymerization reaction. The flow rate ratio of catalyst, ethylene monomer and solvent is 20-35:500-700:4000-5500. The product of the first polymerization step is then transferred to the second reactor, while catalyst, ethylene monomer, and solvent are added to maintain a flow ratio of 30-40:800-1000:6000-10000. The second polymerization step is carried out at a pressure of 2.4-2.6 MPa and a temperature of 61-70°C for 20-40 minutes. The temperature and pressure of the second polymerization step are both higher than those of the first polymerization step. The polymer solution after polymerization is flash-evaporated to remove volatile components; The colloid after the volatile components have been removed is then adsorbed and removed by modified alumina or molecular sieve adsorbents to remove residual catalyst. The catalyst-removed gel is mixed with a composite antioxidant and then extruded and granulated to obtain the final product.

[0016] Pre-activating the main catalyst with the co-catalyst allows for sufficient contact between the main catalyst (titanium-based Ziegler-Natta catalyst) and the co-catalyst (sesquialuminum or triethylaluminum), forming stable active centers. This significantly improves the catalyst's catalytic efficiency, ensuring sufficient molecular chain growth of ethylene monomer during polymerization. Pre-activation can control the uniformity of the catalyst's active centers, reducing fluctuations in the molecular chain growth rate during polymerization and thus keeping the molecular weight distribution index (PDI) within a narrow range of 2.0-2.5. The pre-activated catalyst is better able to adapt to the gradually increasing temperature and pressure conditions in the two-stage reactor, ensuring continuous and efficient operation in the two-stage polymerization reaction, further promoting molecular chain growth and structural regulation.

[0017] The active sites of Ziegler-Natta catalysts are generated through in-situ reactions of the main catalyst (titanium-based) and the co-catalyst (sesquialuminum or triethylaluminum). When pre-activated separately, the two cannot fully contact each other and form stable active species during the pre-activation stage, which may lead to a reduction in the number and uneven distribution of active sites, thereby reducing catalytic efficiency.

[0018] This invention employs a stepwise polymerization reaction. The first polymerization step takes place at a lower temperature and pressure, where a pre-activated catalyst and ethylene monomer undergo initial polymerization in a first reactor. Initial chain growth is achieved through a residence time of 30-60 minutes. By controlling the reaction intensity at this stage, side reactions are reduced and the catalyst's active sites are stabilized. Mild reaction conditions help suppress short-chain branching and the formation of low-molecular-weight products, preventing a broadening of the molecular weight distribution due to overly vigorous reactions.

[0019] The second-step polymerization reaction, carried out at higher temperatures and pressures, promotes further growth of molecular chains by supplementing catalysts, ethylene monomers, and solvents, thereby improving the mechanical properties of the product. By increasing the reaction temperature and pressure, the chain transfer and termination reaction of the active centers are accelerated. Combined with a residence time of 20-40 minutes, the molecular weight distribution index (PDI) can be controlled within the range of 2.0-2.5.

[0020] The polymer solution after polymerization is flash-evaporated to remove residual ethylene monomers, solvents, and byproducts from the polymerization system, thereby improving the purity of the product.

[0021] Before flash evaporation, the colloidal solution contains a large amount of solvent, and the catalyst is highly dispersed in the solvent. This reduces the contact probability between the adsorbent and the catalyst, leading to a significant decrease in adsorption efficiency. After flash evaporation, the solvent is removed, the colloidal solution concentration increases, and the catalyst particles are more easily captured by the adsorbent. If adsorption occurs first, a large amount of solvent will occupy the active sites of the adsorbent, reducing the catalyst removal effect.

[0022] Volatile components such as ethylene monomers and oligomers remaining in the unflash-evaporated adhesive solution can compete with the catalyst for active sites on the adsorbent surface, reducing its selective adsorption capacity for metal ions (titanium, aluminum). Flash evaporation can remove these interfering components in advance, allowing the adsorbent to specifically act on the catalyst residue, ensuring improved optical and antioxidant properties.

[0023] Continuous preparation, through precise control of reaction temperature, pressure, and residence time, can stably maintain the molecular weight distribution index (PDI) within the range of 2.0-2.5. In contrast, batch preparation, due to fluctuations in reaction conditions between batches, is prone to leading to unstable mechanical and processing properties of the product.

[0024] Continuous production avoids non-production time such as intermittent feeding, heating, and cooling by continuously feeding, reacting, and discharging materials (such as polymerization in a two-stage reactor), thus significantly shortening the production cycle.

[0025] Continuous preparation allows for precise control of product structure and performance through real-time adjustments to catalyst flow rate, monomer ratio, and reaction conditions. In contrast, batch-based preparation, due to batch independence and delayed parameter adjustments, struggles to quickly respond to performance optimization needs.

[0026] In some embodiments, the conditions for the first step polymerization reaction are: a pressure of 2.0-2.3 MPa, a temperature of 55-60°C, a residence time of 40-50 min, and a flow rate ratio of catalyst, ethylene monomer, and solvent of 25-35:550-650:4500-5500. The conditions for the second-step polymerization reaction are: pressure of 2.4-2.6 MPa, temperature of 63-66℃, residence time of 30-50 min, and flow ratio of catalyst, ethylene monomer and solvent of 25-35:550-650:7000-8500.

[0027] Since the temperature and pressure of the second polymerization reaction are higher than those of the first polymerization reaction, in order to ensure that the product of the first polymerization reaction directly reaches 65°C in the second polymerization reaction, instead of staying between 60-65°C for a long time, the temperature of each fluid can be directly heated before being introduced into the reactor when adding catalyst, ethylene monomer and solvent to the reaction system during the second polymerization reaction, and then the temperature can be precisely controlled.

[0028] In some embodiments, the titanium-based Ziegler-Natta catalyst contains 0.25-0.35 wt% titanium; the co-catalyst is ethyl sesquialuminate chloride or triethylaluminum, with an aluminum content of 12-14 wt%; and the molar ratio of aluminum in the main catalyst to titanium in the co-catalyst is 10-30:1.

[0029] Preferably, the molar ratio of aluminum in the main catalyst to titanium in the co-catalyst is 15-25:1, and more preferably 18-22:1.

[0030] In some embodiments, the pre-activation temperature is 35-45°C and the time is 8-12 minutes.

[0031] Low temperatures can slow down the reaction rate of the main catalyst and the co-catalyst, making it impossible to form stable active centers. This directly reduces catalytic efficiency, leading to a decrease in ethylene monomer conversion, insufficient molecular chain growth, and a significant reduction in the tensile strength and impact strength of the product. At low temperatures, the distribution of active centers is uneven, and the fluctuation of molecular chain growth rate increases, resulting in a higher molecular weight distribution index.

[0032] Excessive temperature can cause thermal decomposition of the co-catalyst, or damage to the coordination structure between the main catalyst and the co-catalyst, resulting in a reduction in the number of active centers.

[0033] In some embodiments, the polymerized adhesive is subjected to flash evaporation, wherein the flash evaporation is a three-stage flash evaporation. The first-stage flash evaporation is carried out at a temperature of 150-200°C and a pressure of -0.5 to -1.0 kPa; the second-stage flash evaporation is carried out at a temperature of 110-130°C and a pressure of -0.2 to -0.5 kPa; and the third-stage flash evaporation is carried out at a temperature of 100-120°C and a pressure of -0.1 to -0.3 kPa.

[0034] In some embodiments, when adsorbing and removing residual catalyst, the adsorption temperature is 50-70°C and the adsorption pressure is 2.0-2.6 MPa.

[0035] After flash evaporation, the solvent in the gel solution is largely removed, resulting in a significant increase in concentration. If the temperature is too low, the viscosity of the gel solution will increase sharply, reducing its fluidity and causing uneven distribution within the adsorption tower. This prevents sufficient contact with the modified alumina or molecular sieve adsorbent, reducing the capture efficiency of residual catalyst (titanium and aluminum ions). A temperature of 50-70℃ can maintain appropriate fluidity of the gel solution, ensuring uniform flow within the adsorbent bed and improving mass transfer efficiency.

[0036] When the temperature is too low, the surface activity of the adsorbent is insufficient, and the electrostatic attraction or coordination of the catalyst residue is weakened, resulting in a decrease in the removal efficiency (e.g., the titanium residue may exceed 5 ppm). 50-70℃ can promote the adsorption of residual catalyst by the adsorbent, increase the adsorption capacity, and ensure that the titanium residue in the solution is reduced to below 5 ppm and the aluminum residue to below 10 ppm.

[0037] Temperatures of 50-70℃ can accelerate the diffusion of catalyst residues to the adsorbent surface, shorten the time to reach adsorption equilibrium, and improve removal efficiency. If the temperature is too low, the diffusion rate is slow, and even with extended adsorption time, it is difficult to achieve the target residue level.

[0038] Preferably, when adsorbing and removing residual catalyst, a dual-tower parallel operation is adopted, with one tower for adsorption and the other for regeneration, alternating between the two towers, so that the residual titanium content in the solution is reduced to below 5 ppm and the residual aluminum content is reduced to below 10 ppm.

[0039] In some embodiments, the modification method of the modified alumina is as follows: γ-alumina is placed in a mixed aqueous solution of magnesium nitrate and lanthanum nitrate with a mass fraction of 5-10%, the molar ratio of magnesium to lanthanum in the mixture is 2-4:1, and the liquid-to-solid ratio (volume of aqueous solution to mass of γ-alumina) is 3-7:1. The mixture is impregnated at room temperature for 12-24 hours. After impregnation, the alumina is dried in a drying oven at 100-120°C for 6-8 hours to remove free moisture. The dried alumina is then placed in a calcining furnace and calcined at 500-600°C for 3-5 hours to complete the modification and activation. After calcination, the alumina is naturally cooled to room temperature and sieved to obtain a 40-60 mesh modified alumina adsorbent, which can be used for the adsorption and removal of residual catalysts in polymer solutions.

[0040] In some embodiments, the composite antioxidant includes a primary antioxidant 1010 and a secondary antioxidant 168, wherein the mass ratio of the primary antioxidant 1010 to the secondary antioxidant 168 is 1-2:1, preferably 1.2-1.8:1.

[0041] Preferably, the amount of the composite antioxidant added to the adhesive is 0.1-0.5 wt%, more preferably 0.25-0.4 wt%.

[0042] In some embodiments, the extrusion granulation temperature is 120-150°C and the die pressure is 5-10 MPa.

[0043] Secondly, the present invention provides a high-performance ethylene copolymer prepared by the aforementioned preparation method, which has a tensile strength of 25-35 MPa, a dart impact strength of 8-15 J / mm, a visible transmittance of 85-95%, an ultraviolet transmittance of 90-98%, an oxidation induction period of 30-60 min (200℃), and a molecular weight distribution index (PDI) of 2.0-2.5.

[0044] Furthermore, the high-performance ethylene copolymer has a tensile strength of 28-33 MPa, a dart impact strength of 10-14 J / mm, a visible transmittance of 88-94%, an ultraviolet transmittance of 93-97%, an oxidation induction period of 45-58 min (200℃), and a molecular weight distribution index (PDI) of 2.1-2.3.

[0045] Thirdly, the present invention provides the application of the high-performance ethylene copolymer in automotive parts, wires and cables, packaging materials or medical devices.

[0046] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] Example 1 (Optimal Example) A continuous preparation method for high-performance EPOE includes the following steps: (1) Catalyst preactivation: Titanium-based Ziegler-Natta catalyst (titanium content 0.30wt%) and sesquialuminum co-catalyst (aluminum content 13wt%) were preactivated in a premixer at 40°C for 10 minutes, with an aluminum-titanium molar ratio of 20:1.

[0048] (2) Two reactors in series polymerization: The mixture first enters the first reactor for the first polymerization reaction, and the polymerization product in the first reactor is transferred to the second reactor for the second polymerization reaction. At the same time, catalyst, ethylene monomer and solvent are added: The operating conditions of the first polymerization reaction are: pressure 2.2MPa, temperature 60℃, catalyst flow rate 30kg / h, ethylene flow rate 600kg / h, heptane flow rate 5000kg / h, residence time 45 minutes; The operating conditions of the second polymerization reaction are: pressure 2.5MPa, temperature 65℃, catalyst flow rate 35kg / h, ethylene flow rate 900kg / h, heptane flow rate 8000kg / h, residence time 30 minutes.

[0049] (3) The polymerized adhesive solution is passed through a first-stage flash evaporator, a second-stage flash evaporator and a third-stage flash evaporator in sequence for three-stage flash devolatilization. The temperature of the first-stage flash evaporator is 180℃ and the pressure is -1.0kPa; the temperature of the second-stage flash evaporator is 120℃ and the pressure is -0.5kPa; and the temperature of the third-stage flash evaporator is 110℃ and the pressure is -0.3kPa.

[0050] (4) Catalyst adsorption and removal: The residual catalyst was removed by adsorption of the flash-evaporated gel solution using a dual-tower parallel adsorption tower. The adsorption tower was filled with modified alumina adsorbent, the adsorption temperature was 60℃, the adsorption pressure was 2.4MPa, the titanium residue in the gel solution was 3ppm, and the aluminum residue was 6ppm.

[0051] The modification method of the modified alumina is as follows: γ-alumina is placed in a 6% (w / w) mixed aqueous solution of magnesium nitrate and lanthanum nitrate, with a magnesium-lanthanum molar ratio of 3:1 and a liquid-to-solid ratio (volume of aqueous solution to mass of γ-alumina) of 5:1, and impregnated at room temperature for 20 hours. After impregnation, the alumina is dried in a 110°C drying oven for 7 hours to remove free moisture. Then, the dried alumina is placed in a calcining furnace and calcined at 550°C for 4 hours to complete the modification and activation. After calcination, it is naturally cooled to room temperature and sieved to obtain a 40-60 mesh modified alumina adsorbent, which can be used for the adsorption and removal of residual catalysts in polymer solutions.

[0052] (5) Add 0.3wt% composite antioxidant (mass ratio of main antioxidant 1010 to auxiliary antioxidant 168 1.5:1) to the catalyst-removed adhesive solution, with extruder temperature of 140℃ and die pressure of 8MPa.

[0053] Product performance test results: tensile strength 32.5MPa, dart impact strength 12.8J / mm, visible transmittance 92%, ultraviolet transmittance 96%, oxidation induction period 52 minutes (200℃), PDI=2.2.

[0054] Example 2 The difference from Example 1 is that in step (1), the aluminum-titanium molar ratio is adjusted to 15:1, and the other conditions are the same as in Example 1.

[0055] Product performance test results: tensile strength 28.6MPa, dart impact strength 10.5J / mm, visible transmittance 90%, ultraviolet transmittance 94%, oxidation induction period 45 minutes (200℃), PDI=2.3.

[0056] Example 3 The difference from Example 1 is that in step (2), the temperature of the first reactor is adjusted to 65°C and the temperature of the second reactor is adjusted to 68°C, while the other conditions are the same as in Example 1.

[0057] Product performance test results: tensile strength 26.8MPa, dart impact strength 14.2J / mm, visible transmittance 88%, ultraviolet transmittance 91%, oxidation induction period 48 minutes (200℃), PDI=2.4.

[0058] Example 4 The difference from Example 1 is that in step (5), the mass ratio of the main antioxidant 1010 to the auxiliary antioxidant 168 is adjusted to 2:1, the total amount added is 0.4wt%, and the other conditions are the same as in Example 1.

[0059] Product performance test results: tensile strength 31.2MPa, dart impact strength 12.1J / mm, visible transmittance 91%, ultraviolet transmittance 95%, oxidation induction period 58 minutes (200℃), PDI=2.2.

[0060] Comparative Example 1 The difference from Example 1 is that the catalyst is not pre-activated and is directly added to the reactor, while the other conditions are the same as in Example 1.

[0061] Product performance test results: tensile strength 18.5 MPa, dart impact strength 6.2 J / mm, visible transmittance 82%, ultraviolet transmittance 85%, oxidation induction period 28 minutes (200℃), PDI=3.2. The catalyst has low activity, wide molecular weight distribution, and poor mechanical properties.

[0062] Comparative Example 2 The difference from Example 1 is that in step (2), only the first polymerization reaction is carried out, the residence time is extended to 75 minutes, and the other conditions are the same as in Example 1.

[0063] Specifically, the operating conditions for the polymerization reaction are: pressure 2.2 MPa, temperature 60℃, catalyst flow rate 30 kg / h, ethylene flow rate 600 kg / h, heptane flow rate 5000 kg / h, and residence time 75 minutes.

[0064] Product performance test results: tensile strength 20.3 MPa, dart impact strength 7.5 J / mm, visible transmittance 85%, ultraviolet transmittance 88%, oxidation induction period 32 minutes (200℃), PDI=2.9. Uneven temperature distribution within the single reactor leads to unstable product quality.

[0065] Comparative Example 3 The difference from Example 1 is that the catalyst adsorption and removal step (4) is omitted, and the other conditions are the same as in Example 1.

[0066] Product performance test results: tensile strength 24.6 MPa, dart impact strength 11.2 J / mm, visible transmittance 65%, ultraviolet transmittance 72%, oxidation induction period 22 minutes (200℃), PDI=2.3. High catalyst residue, low transmittance, and poor oxidation resistance.

[0067] Comparative Example 4 The difference from Example 1 is that no composite antioxidant is added in step (5), and the other conditions are the same as in Example 1.

[0068] Product performance test results: tensile strength 32.1 MPa, dart impact strength 12.6 J / mm, visible transmittance 92%, ultraviolet transmittance 96%, oxidation induction period 8 minutes (200℃), PDI=2.2. It exhibits good mechanical and optical properties, but extremely poor thermal stability.

[0069] Comparative Example 5 The difference from Example 1 is that in step (2), only the second polymerization reaction is carried out, the residence time is extended to 75 minutes, and the other conditions are the same as in Example 1.

[0070] Specifically, the operating conditions for the polymerization reaction are: pressure 2.5 MPa, temperature 65℃, catalyst flow rate 35 kg / h, ethylene flow rate 900 kg / h, heptane flow rate 8000 kg / h, and residence time 75 minutes.

[0071] Comparative Example 6 The difference from Example 1 is that in step (1), the titanium-based Ziegler-Natta catalyst and the sesquialuminum co-catalyst are pre-activated separately and then mixed. The rest is the same as in Example 1.

[0072] Comparative Example 7 The difference from Example 1 is that in step (4), the adsorption temperature is 80°C, and the rest is the same as in Example 1.

[0073] Comparative Example 8 The difference from Example 1 is that in step (4), the adsorption pressure is 1.5 MPa, which is the same as in Example 1.

[0074] Comparative Example 9 The difference from Example 1 is that in step (5), the auxiliary antioxidant 168 is replaced with the main antioxidant, which is the same as in Example 1.

[0075] Comparative Example 10 The difference from Example 1 is that in step (5), the primary antioxidant is replaced with the secondary antioxidant 168, which is the same as in Example 1.

[0076] Comparative Example 11 The difference from Example 1 is that in step (2), the temperature of the first polymerization reaction is 61°C, which is the same as in Example 1.

[0077] Comparative Example 12 The difference from Example 1 is that in step (2), the pressure of the first polymerization reaction is 2.4 MPa, which is the same as in Example 1.

[0078] Comparative Example 13 The difference from Example 1 is that in step (2), the temperature of the second polymerization reaction is 75°C, which is the same as in Example 1.

[0079] Comparative Example 14 The difference from Example 1 is that in step (2), the pressure of the second polymerization reaction is 2.3 MPa, which is the same as in Example 1.

[0080] Table 1 shows a comparison of product performance between the examples and comparative examples. Example Tensile strength (MPa) Dart impact (J / mm) Visible transmittance (%) UV transmittance (%) Oxidation induction period (min) PDI Example 1 32.5 12.8 92 96 52 2.2 Example 2 28.6 10.5 90 94 45 2.3 Example 3 26.8 14.2 88 91 48 2.4 Example 4 31.2 12.1 91 95 58 2.2 Comparative Example 1 18.5 6.2 82 85 28 3.2 Comparative Example 2 20.3 7.5 85 88 32 2.9 Comparative Example 3 24.6 11.2 65 72 22 2.3 Comparative Example 4 32.1 12.6 92 96 8 2.2 Comparative Example 5 22.4 8.8 86 89 30 2.8 Comparative Example 6 21.7 7.9 84 87 29 3.0 Comparative Example 7 31.8 12.3 78 82 25 2.2 Comparative Example 8 32.0 12.5 80 84 27 2.2 Comparative Example 9 32.3 12.7 92 96 22 2.2 Comparative Example 10 32.2 12.6 92 96 15 2.2 Comparative Example 11 27.5 11.6 89 92 40 2.5 Comparative Example 12 26.9 11.3 88 91 39 2.5 Comparative Example 13 24.3 10.2 85 88 35 2.7 Comparative Example 14 25.8 10.8 87 90 42 2.6 The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A continuous preparation method for high-performance ethylene copolymers, characterized in that: Includes the following steps: The main catalyst and the co-catalyst are mixed and then pre-activated at a temperature of 30-50°C for 5-15 minutes. The main catalyst is a titanium-based Ziegler-Natta catalyst and the co-catalyst is ethyl sesquialuminate chloride or triethylaluminum. The pre-activated main catalyst and co-catalyst, ethylene monomer and solvent are continuously fed into the first reactor in proportion. The reactor is held at a pressure of 2.0-2.3 MPa and a temperature of 55-60℃ for 30-60 min to carry out the first step of polymerization reaction. The flow rate ratio of catalyst, ethylene monomer and solvent is 20-35:500-700:4000-5500. The product of the first polymerization step is then transferred to the second reactor, while catalyst, ethylene monomer, and solvent are added to maintain a flow ratio of 30-40:800-1000:6000-10000. The second polymerization step is carried out at a pressure of 2.4-2.6 MPa and a temperature of 61-70°C for 20-40 minutes. The temperature and pressure of the second polymerization step are both higher than those of the first polymerization step. The polymer solution after polymerization is flash-evaporated to remove volatile components; The colloid after the volatile components have been removed is then adsorbed and removed by modified alumina or molecular sieve adsorbents to remove residual catalyst. The catalyst-removed colloid is mixed with a composite antioxidant and then extruded and granulated to obtain the final product.

2. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The titanium-based Ziegler-Natta catalyst contains 0.25-0.35 wt% titanium; the co-catalyst is sesquialuminum or triethylaluminum, with an aluminum content of 12-14 wt%; the molar ratio of aluminum in the main catalyst to titanium in the co-catalyst is 10-30:

1. Preferably, the molar ratio of aluminum in the main catalyst to titanium in the co-catalyst is 15-25:1, and more preferably, the molar ratio of aluminum in the main catalyst to titanium in the co-catalyst is 18-22:

1.

3. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The pre-activation temperature is 35-45℃, and the time is 8-12 minutes.

4. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The conditions for the first step of polymerization are: pressure of 2.0-2.3 MPa, temperature of 55-60℃ for 40-50 min, and flow ratio of catalyst, ethylene monomer and solvent of 25-35:550-650:4500-5500. The conditions for the second-step polymerization reaction are: pressure of 2.4-2.6 MPa, temperature of 63-66℃, residence time of 30-50 min, and flow ratio of catalyst, ethylene monomer and solvent of 25-35:550-650:7000-8500.

5. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The polymerized adhesive is subjected to flash evaporation, which is a three-stage flash evaporation. The first-stage flash evaporation is carried out at a temperature of 150-200℃ and a pressure of -0.5 to -1.0 kPa; the second-stage flash evaporation is carried out at a temperature of 110-130℃ and a pressure of -0.2 to -0.5 kPa; and the third-stage flash evaporation is carried out at a temperature of 100-120℃ and a pressure of -0.1 to -0.3 kPa.

6. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: When adsorbing and removing residual catalyst, the adsorption temperature is 50-70℃ and the adsorption pressure is 2.0-2.6MPa. Preferably, when adsorbing and removing residual catalyst, a dual-tower parallel operation is adopted, with one tower for adsorption and the other for regeneration, alternating between the two towers, so that the residual titanium content in the solution is reduced to below 5 ppm and the residual aluminum content is reduced to below 10 ppm.

7. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The composite antioxidant includes a primary antioxidant 1010 and a secondary antioxidant 168, wherein the mass ratio of the primary antioxidant 1010 to the secondary antioxidant 168 is 1-2:1, preferably 1.2-1.8:1; Preferably, the amount of the composite antioxidant added to the adhesive is 0.1-0.5 wt%, more preferably 0.25-0.4 wt%.

8. The continuous preparation method of the high-performance ethylene copolymer according to claim 1, characterized in that: The extrusion granulation temperature is 120-150℃, and the die pressure is 5-10MPa.

9. A high-performance ethylene copolymer, characterized in that: Prepared by any one of the continuous preparation methods described in claims 1-8, the tensile strength is 25-35 MPa; the dart impact strength is 8-15 J / mm; the visible transmittance is 85-95%; the ultraviolet transmittance is 90-98%; the oxidation induction period is 30-60 min at 200℃; and the molecular weight distribution index (PDI) is 2.0-2.

5.

10. The application of the high-performance ethylene copolymer of claim 9 in automotive parts, wires and cables, packaging materials or medical devices; particularly in high-end optical packaging, medical transparent consumables, and lightweight transparent automotive components.