Vinyl elastomer and preparation method thereof

Abstract

The preparation method comprises the following steps: adding a solvent (a solvent A or a combined solvent of the solvent A and a solvent B), an olefin monomer (ethylene or a combination of ethylene and alpha-olefin), an antistatic agent, a metallocene catalyst and a co-catalyst into a first reactor, and carrying out a first polymerization reaction; the obtained slurry containing polymer particles is conveyed to a mixing tank, a solvent B is added into the mixing tank, materials in the mixing tank are injected into a second reactor, ethylene, alpha-olefin, a solvent C, an antistatic agent and hydrogen are introduced into the second reactor according to the proportion for a second polymerization reaction, devolatilization and extrusion granulation treatment are sequentially carried out, and the polymer particles are obtained. The vinyl elastomer product has the characteristics of low density, high light transmittance, high volume resistivity and excellent processability.

Description

Technical Field

[0001] This invention relates to the field of polyolefin elastomer technology, and more specifically to a vinyl elastomer and its preparation method. Background Technology

[0002] Polyolefin elastomers (POEs), as high-performance polyolefin materials, successfully combine the high elasticity of rubber with the easy processability of plastics through their unique two-phase microstructure. They possess excellent flexibility, impact resistance, tear resistance, high temperature resistance, corrosion resistance, and high light transmittance. POE has a very broad application prospect, capable of replacing a range of general-purpose polymers such as EPM, EPDM, EVA, SBC, TPU, PVC, LDPE, and EMA. Due to its high light transmittance, excellent resistance to PID (potential-induced degradation), and strong moisture barrier properties, POE can effectively protect fragile solar cells and ensure long-term module power generation efficiency. POE is currently the preferred material for encapsulation films of double-glass photovoltaic modules and N-type high-efficiency modules, and it also has important applications in medical packaging materials, new energy vehicles, cables and wires, daily necessities, and toys.

[0003] Current POE production all employs solution polymerization, a process where monomers and metallocene catalysts are completely dissolved in an inert solvent (such as hexane, cyclohexane, or cyclopentane). This process requires a large amount of solvent, necessitating multi-stage flash evaporation and devolatilization to separate the polymer from the solvent and recover the solvent. The heating, separation, cooling, and recycling of the solvent consume significant energy, resulting in high operating costs and a complex and cumbersome process. In contrast, gas-phase polymerization involves the polymerization of olefin monomers in a gaseous form within a suspension of solid particles. Because it eliminates the use of organic solvents, it offers advantages such as low energy consumption, a shorter process, lower investment, environmental friendliness and safety, and strong applicability. Its cost advantage is significant, making it a valuable and promising area for POE development. Summary of the Invention

[0004] The main objective of this invention is to provide a vinyl elastomer and a method for preparing the same.

[0005] The first aspect of this invention provides a method for preparing a vinyl elastomer, the technical solution of which mainly includes the following steps: a) A solvent, olefin monomer, antistatic agent, metallocene catalyst, and co-catalyst are added to a first reactor to carry out a first polymerization reaction, and the resulting slurry containing polymer particles is conveyed to a mixing tank; wherein, the viscosity of the solvent added to the first reactor meets the requirement of 2 mPa·s-100 mPa·s (25°C); the olefin monomer added to the first reactor is ethylene, or a combination of ethylene and α-olefin; the average particle size D50 of the polymer particles in the slurry discharged from the first reactor is 40 μm ~ 140 μm, the particle size distribution Span value is 0.7 ~ 1.8, and the specific surface area (BET) is 0.5 m². 2 / g ~ 100 m 2 / g, with an average pore size of 5 ~ 40 nm and a pore volume of 0.0001 ~ 25 cm³. 3 / g; b) Add solvent B to the mixing tank; c) Inject the material in the mixing tank into the second reactor, and introduce ethylene, α-olefin, solvent C, antistatic agent and hydrogen into the second reactor in proportion to carry out the second polymerization reaction; d) After the second polymerization reaction is completed, the mixture discharged from the second reactor is separated. Unreacted ethylene, α-olefin, solvent C and hydrogen are recycled. The vinyl elastomer in the mixture is subjected to devolatilization and extrusion granulation treatment in sequence to obtain vinyl elastomer products.

[0006] In this invention, solvent B may be selected from solvents suitable for homopolymerization or copolymerization of ethylene in the art, or may be selected from substances capable of dissolving, dispersing, or transporting vinyl polymerization products. Typically, but not limited to, solvent B may be selected from one or more of cyclopentane, n-heptane, n-pentane, isopentane, n-hexane, benzene, toluene, and xylene.

[0007] The viscosity requirement of the solvent added to the first reactor is 2 mPa·s-100 mPa·s (25°C). It can be solvent A or a combination of solvent A and solvent B. In this invention, solvent A refers to a substance with a significantly higher viscosity than solvent B that can be used for ethylene homopolymerization or copolymerization. Typically, but not limited to, solvent A is selected from one or more of white oil, paraffin oil, diesel oil, silicone oil, and petrolatum. In this invention, because the viscosity of solvent A is higher than that of solvent B, solvent A is also referred to as a high-viscosity solvent, and solvent B is referred to as a low-viscosity solvent. Preferably, when a combination of solvent A and solvent B is used in step a), the mass ratio of solvent B to solvent A is 0.1:1 to 1:1.

[0008] Preferably, the α-olefin is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, or 1-octene.

[0009] Preferably, the metallocene catalyst is a supported catalyst, wherein the support is selected from one or more of silica, magnesium chloride, and alkoxymagnesium, and the metal element of the catalyst active center is selected from one or more of titanium, zirconium, hafnium, and vanadium; wherein the average particle size D50 of the metallocene catalyst is 30 μm to 49 μm, and the particle size distribution Span value is 0.9 to 2.0; the co-catalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, dichloroethylaluminum, methylaluminoxane, and modified methylaluminoxane.

[0010] Preferably, the first reactor is selected from a batch reactor or a tubular reactor.

[0011] Preferably, the operating parameters of the first polymerization reaction satisfy: (1) The reaction temperature is 0~50℃; (2) The reaction pressure is 0.1~0.5 MPa; (3) The reaction time is 10 ~ 600 min; (4) The mass ratio of solvent to metallocene catalyst is 5:1 to 150:1; (5) When using a batch reactor, the rotation speed is 50 ~ 400 rpm / min; when using a tubular reactor, the flow rate is 0.2 ~ 1.0 m / s; (6) The Al / M molar ratio of the co-catalyst to the metallocene catalyst is 10 ~ 500 (M is the metal element in the metallocene catalyst). (7) The molar ratio of α-olefin to ethylene is 0:1 ~ 0.3:1 (8) The amount of antistatic agent added is 0.05wt‰ ~ 0.05wt% of the amount of ethylene added.

[0012] Preferably, the mass ratio of solvent B to solvent A added to the mixing tank in step b) is 0.3:1 to 1:1; Preferably, the second reactor is selected from one of a batch reactor, a tubular reactor, and a fluidized bed reactor; In this invention, solvent C can be any solvent suitable for ethylene copolymerization. Preferably, solvent C in step c) is selected from one or more of n-hexane, n-pentane, cyclopentane, isopentane, n-butane, isobutane, propane, etc. The amount of solvent C added accounts for 0% to 30% of the total mass of the circulating gas, where 0% means no solvent C is added.

[0013] Preferably, the operating parameters of the second polymerization reaction satisfy: (1) The reaction temperature is 40 ~ 70℃; (2) The reaction pressure is 1.5 ~ 3.0 MPa; (3) The reaction time is 4 ~ 20 h; (4) The molar ratio of α-olefin to ethylene is 0.1:1 ~ 0.5:1; (5) The molar ratio of hydrogen to ethylene is 0:1 ~ 0.1:1; (6) When using a batch reactor, the rotation speed is 50 ~ 400 rpm / min; when using a tubular reactor, the flow rate is 0.5 ~ 1.2 m / s; when using a fluidized bed reactor, the gas velocity is 0.2 ~ 1.5 m / s. (7) The amount of antistatic agent added is 0.00wt‰~0.05wt% of the amount of ethylene added.

[0014] A second aspect of the present invention provides a vinyl elastomer obtained by the preparation method described above.

[0015] Preferably, the density of the vinyl elastomer is 0.865 ~ 0.890 g / cm³. 3 The melt flow index is 0.3-30.0 g / 10min, the transmittance is 90-94%, and the volume resistivity is 1.0 × 10⁻⁶. 15 Ω·cm ~ 9.0 × 10 18 Ω·cm.

[0016] Compared with existing technical solutions, the present invention has the following advantages: (1) The present invention regulates the internal pore structure (pore volume, pore size and specific surface area, etc.) of the catalyst through the polymerization reaction in the first reactor, which improves the uniformity of temperature and concentration of α-olefin insertion into the ethylene backbone in the early stage of polymerization, avoids the generation of hot spots, improves the uniformity of α-olefin insertion into the ethylene backbone, and further reduces the product density and further improves the light transmittance.

[0017] (2) In the first polymerization reaction, this invention uses a high-viscosity solvent or a mixture of a high-viscosity solvent and a low-viscosity solvent as the dispersant. This helps to keep the catalyst particles in suspension during the first polymerization reaction, so as to generate a polymer layer with uniform thickness and loose texture on the outer surface of the catalyst particles, thereby simultaneously improving particle size distribution and mechanical strength, enhancing the stability of the process operation, and improving the polymerization performance of the catalyst in the second reactor. At the same time, adding an antistatic agent to the first reactor allows the antistatic agent to be uniformly embedded into the growing polymer particles. In the subsequent second reactor, these antistatic agents will continuously and slowly migrate from the inside of the particles to the surface. Compared to adding it in the second reactor, this provides durable and uniform antistatic protection, requires less antistatic dosage, and is more economical.

[0018] (3) When the polymerization reaction in the first reactor is the copolymerization of ethylene and α-olefin monomers, it can also suppress the generation of high-melting-point components in POE products. On the one hand, it optimizes processing performance: high-melting-point components may not melt completely during processing (such as blown film and extrusion), resulting in "crystal points", "fish eyes" or gel particles in the product, affecting surface smoothness and transparency. The first polymerization reaction effectively reduces such defects. On the other hand, it improves the uniformity and stability of mechanical properties: high-melting-point components, as "hard points", will destroy the uniform, amorphous or low-crystallinity phase structure that POE, as an elastomer, strives for. After eliminating these hard points, the tensile properties, elastic recovery, tear resistance and other mechanical properties of the product are more stable, and the batch-to-batch stability is greatly improved. On the other hand, it improves optical properties: for POE used in packaging or special films, high-melting-point microcrystals will cause light scattering, resulting in increased haze and decreased transparency. The first polymerization reaction helps to produce products with higher transparency and lower haze. On the one hand, it enhances the reliability of downstream products: In high-end applications such as photovoltaic encapsulants, any uneven composition can lead to performance degradation after long-term aging (such as potential-induced degradation, PID). More uniform POE raw materials are a prerequisite for manufacturing high-reliability photovoltaic encapsulants. In wire and cable insulation or sheathing materials, a more uniform structure means more stable electrical properties and resistance to environmental stress cracking. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of a method for preparing a vinyl elastomer according to the present invention.

[0020] Figure 2 This is a comparison of the process conditions and product performance of Examples 1-5 and Comparative Examples 1-4 (first polymerization reaction).

[0021] Figure 3 This is a comparison of the process conditions and product performance of Examples 1-5 and Comparative Examples 1-4 (second polymerization reaction). Detailed Implementation

[0022] The technical solution of the present invention will be fully and clearly described below with reference to the embodiments of the present invention, so as to fully understand the purpose, technical solution and effects of the present invention. Obviously, the described embodiments are some embodiments of this application, but not all embodiments. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

[0023] The following methods are used to test the properties of the vinyl elastomers produced in the embodiments described above: Laser particle size analyzers are used to test the average particle size and particle size distribution of catalysts and polymer particles; Gradient density meters are used to test the density of vinyl elastomers; Melt flow rate testers are used to test the melt index of vinyl elastomers; A haze meter is used to test the light transmittance of vinyl elastomers; An insulation resistance tester is used to test the volume resistivity of vinyl elastomers.

[0024] Example 1 like Figure 1 As shown, in the first polymerization reaction, under nitrogen protection, white oil was added as a solvent to the first reactor (stirred reactor). The solvent viscosity was 98 mPa·s (25 °C). A metallocene catalyst was added, with a white oil to metallocene catalyst mass ratio of 30:1. The average particle size D50 of the metallocene catalyst was 42 μm, and the particle size distribution Span value was 1.5. Ethylene was then introduced as an olefin monomer, and an antistatic agent was added at an amount of 0.01 wt% of the ethylene. Triisobutylaluminum was added as a co-catalyst to make the Al / M (molar ratio) 50. The first polymerization reaction was controlled at 30 °C, a reaction pressure of 0.5 MPa, a stirring speed of 400 rpm, and a reaction time of 20 min, resulting in a slurry containing polymer particles, which was then transferred to a mixing tank.

[0025] Hexane was added to the mixing tank for dilution, with a hexane to white oil mass ratio of 1:1. The resulting polymer particles had an average particle size D50 of 45 μm, a particle size distribution Span of 1.1, and a specific surface area (BET) of 0.6 m². 2 / g, average pore size 15nm, pore volume 0.21 cm³ 3 / g.

[0026] In the second polymerization reaction, the material in the mixing tank is injected into the second reactor (fluidized bed reactor), and ethylene, 1-butene, n-hexane (as solvent C, added at 15% of the total mass of the circulating gas), and hydrogen are introduced into it in proportion, wherein the molar ratio of 1-butene to ethylene is 0.25, and the molar ratio of hydrogen to ethylene is 0.03. The temperature of the second polymerization reaction is controlled at 50 °C, the reaction pressure at 2.2 MPa, the fluidized bed gas velocity at 0.4 m / s, and the reaction time at 6 h. After the reaction, the mixture discharged from the second reactor is separated, devolatilized, and extruded and granulated to obtain the vinyl elastomer product. The polymerization activity of the catalyst is 25071 g. 聚合物 / g cat The density of the vinyl elastomer product is 0.878 g / cm³. 3 The melt flow index is 6.5 g / 10 min, the transmittance is 92%, and the volume resistivity is 3.2 × 10⁻⁶. 17 Ω·cm.

[0027] Example 2 Except for the following differences, the other conditions are the same as in Example 1.

[0028] In the first polymerization reaction, the mass ratio of white oil to metallocene catalyst was 100:1; n-heptane was added simultaneously, with a mass ratio of n-heptane to white oil of 1:1, and the solvent viscosity was 29 mPa·s; the average particle size D50 of the metallocene catalyst was 48 μm, and the particle size distribution Span value was 1.8; the olefin monomers selected were ethylene and 1-butene, with a molar ratio of 1-butene to ethylene of 0.25:1 and an Al / M (molar ratio) of 300; the amount of antistatic agent added was 0.05 wt% of ethylene. The first polymerization reaction temperature was 10 ℃, the reaction pressure was 0.3 MPa, the stirring speed was 200 rpm, and the reaction time was 300 min. Heptane was added to a mixing tank at a mass ratio of 0.3:1 to white oil. The resulting polymer particles had an average particle size (D50) of 92 μm, a particle size distribution (Span) of 0.9, and a specific surface area (BET) of 55 m². 2 / g, average pore size is 6 nm, average pore volume is 0.03 cm³. 3 / g.

[0029] In the second polymerization reaction, a batch reactor was used as the second reactor. Cyclopentane was selected as solvent C, and its addition amount was 5% of the total mass of the circulating gas. The molar ratio of 1-butene to ethylene was 0.2:1, and the molar ratio of hydrogen to ethylene was 0.01:1. The temperature of the second polymerization reaction was controlled at 40 °C, the reaction pressure at 1.6 MPa, the reactor rotation speed at 80 rpm, and the reaction time at 12 h. The final polymerization activity of the catalyst was 14903 g. 聚合物 / g catThe resulting vinyl elastomer had a density of 0.870 g / cm³. 3 The melt index is 18.0 g / 10 min, the transmittance is 93%, and the volume resistivity is 6.5 × 10⁻⁶. 17 Ω·cm.

[0030] Example 3 Except for the following differences, the other conditions are the same as in Example 1.

[0031] In the first polymerization reaction, the first reactor is a tubular reactor. Solvent A is paraffin oil, with a mass ratio of paraffin oil to metallocene catalyst of 140:1. Toluene is added simultaneously, with a mass ratio of toluene to paraffin oil of 0.5:1. The solvent viscosity is 45 mPa·s. The average particle size D50 of the metallocene catalyst is 40 μm, and the particle size distribution Span value is 1.0. The olefin monomers are ethylene and 1-hexene, with a molar ratio of 1-hexene to ethylene of 0.1:1. Triethylaluminum is used as a co-catalyst, with an Al / M (molar ratio) of 100. The linear velocity of the material in the tubular reactor is 0.6 m / s. The temperature of the first polymerization reaction is 25 ℃, the reaction pressure is 0.1 MPa, and the reaction time is 600 min.

[0032] Toluene was added to a mixing tank at a mass ratio of 0.5:1 to paraffin oil. The resulting polymer particles had a D50 of 110 μm, a Span value of 0.7, and a specific surface area (BET) of 96 m². 2 / g, average pore size is 9 nm, average pore volume is 0.0003 cm³ 3 / g.

[0033] In the second polymerization reaction, isopentane was selected as solvent C, and its addition amount was 5% of the total mass of the circulating gas. The molar ratio of 1-butene to ethylene was 0.3:1, and the molar ratio of hydrogen to ethylene was 0.04:1. The temperature of the second polymerization reaction was controlled at 60 °C, the reaction pressure at 2.5 MPa, the material flow rate at 0.4 m / s, and the reaction time at 18 h. The final polymerization activity of the catalyst was 19876 g. 聚合物 / g cat The resulting vinyl elastomer product had a density of 0.885 g / cm³. 3 The melt flow index is 2.5 g / 10 min, the transmittance is 90%, and the volume resistivity is 8.1 × 10⁻⁶. 18 Ω·cm.

[0034] Example 4 Except for the following differences, the other conditions are the same as in Example 1.

[0035] In the first polymerization reaction, the first reactor is a tubular reactor; solvent A is silicone oil, with a mass ratio of silicone oil to metallocene catalyst of 20:1, and n-hexane is added simultaneously, with a mass ratio of n-hexane to silicone oil of 0.1:1, and the solvent viscosity is 82 mPa·s; the average particle size D50 of the metallocene catalyst is 33 μm, and the particle size distribution Span value is 1.1; the olefin monomers are ethylene and 1-octene, with a molar ratio of 1-octene to ethylene of 0.01:1; methylaluminoxane is used as a co-catalyst, with an Al / M (molar ratio) of 120, and the amount of antistatic agent added is 0.03 wt% of ethylene; the material linear velocity in the tubular reactor is 0.9 m / s; the temperature of the first polymerization reaction is 45 ℃, the reaction pressure is 0.3 MPa, and the reaction time is 60 min.

[0036] The resulting polymer particles had a D50 of 75 μm, a Span value of 1.1, and a specific surface area (BET) of 18 m². 2 / g, with an average pore size of 13 nm and an average pore volume of 0.006 cm³. 3 / g.

[0037] In the second polymerization reaction, the molar ratio of 1-butene to ethylene was 0.22:1, and the molar ratio of hydrogen to ethylene was 0.02:1. The temperature of the second polymerization reaction was controlled at 52℃, the reaction pressure at 2.0 MPa, the fluidized bed gas velocity at 0.8 m / s, and the reaction time at 9 h. The final polymerization activity of the catalyst was 27567 g. 聚合物 / g cat The resulting vinyl elastomer product had a density of 0.868 g / cm³. 3 The melt flow index is 24.0 g / 10 min, the transmittance is 94%, and the volume resistivity is 1.5 × 10⁻⁶. 16 Ω·cm.

[0038] Example 5 Except for the following differences, the other conditions are the same as in Example 1.

[0039] In the first polymerization reaction, diesel oil was selected as solvent A, with a mass ratio of diesel oil to metallocene catalyst of 80:1 and a solvent viscosity of 2.8 mPa·s. The metallocene catalyst was a hafnium-based metallocene catalyst supported on magnesium chloride, with an average particle size D50 of 38 and a particle size distribution Span value of 1.7. The amount of antistatic agent added was 0.03 wt% of ethylene. Dichloroethylaluminum was used as a co-catalyst, with an Al / M (molar ratio) of 400. The first polymerization reaction temperature was 5 ℃, the reaction pressure was 0.2 MPa, the stirring speed was 60 rpm, and the reaction time was 240 min.

[0040] The resulting polymer particles had a D50 of 95 μm, a Span value of 1.4, and a specific surface area (BET) of 10 m².2 / g, average pore size is 9 nm, average pore volume is 0.06 cm³. 3 / g.

[0041] In the second polymerization reaction, solvent C was n-pentane, added at 5% of the total mass of the circulating gas; the molar ratio of 1-butene to ethylene was 0.35:1, and the molar ratio of hydrogen to ethylene was 0.05:1; the temperature of the second polymerization reaction was controlled at 65 °C, the reaction pressure at 2.8 MPa, the fluidized bed gas velocity at 1.2 m / s, and the reaction time at 18 h. The final polymerization activity of the catalyst was 13289 g. 聚合物 / g cat The resulting vinyl elastomer product had a density of 0.890 g / cm³. 3 The melt flow index is 0.8 g / 10 min, the transmittance is 91%, and the volume resistivity is 5.0 × 10⁻⁶. 18 Ω·cm.

[0042] Comparative Example 1 In the first reactor, solvent A was not added; instead, cyclopentane was used as the reaction medium instead of solvent A, and the other conditions were the same as in Example 1.

[0043] The polymer particles obtained from the first reactor had a D50 of 335 μm, exhibiting extremely uneven particle size distribution (Span value > 3.0) and a specific surface area (BET) of 1.5 m². 2 / g, with an average pore size of 19 nm and an average pore volume of 0.4 cm³. 3 / g. During the first polymerization reaction, the polymer severely adhered to the walls and agglomerated, making it impossible to stably transport to the second reactor; the final polymerization activity of the catalyst was 6798g. 聚合物 / g cat The density of the obtained vinyl elastomer product was tested to be 0.900 g / cm³. 3 The melt flow index was 5.9 g / 10 min, the transmittance was only 86%, and the volume resistivity decreased to 5.0 × 10⁻⁶. 13 Ω·cm.

[0044] Comparative Example 2 In this comparative example, no first reactor and mixing tank are included.

[0045] Specifically, under nitrogen protection, ethylene, 1-butene, and hydrogen were directly introduced into the second reactor (fluidized bed reactor), with n-hexane added as solvent C, accounting for 15% of the total mass of the circulating gas; the molar ratio of 1-butene to ethylene was 0.25:1, and the molar ratio of hydrogen to ethylene was 0.03:1. Subsequently, the same supported metallocene catalyst as in Example 1 was directly added to the second reactor, along with an antistatic agent at 0.01 wt% of ethylene. The reaction temperature was controlled at 50 °C, the reaction pressure at 2.2 MPa, the fluidized bed gas velocity at 0.4 m / s, and the reaction time at 6 h to allow polymerization. After the reaction, the product was separated, devolatilized, and extruded into granules. The resulting vinyl elastomer product had an extremely wide particle size distribution, a significantly increased content of fine powder, and uneven distribution of comonomers. The final polymerization activity of the catalyst was 16981 g. 聚合物 / g cat The product's density was tested and found to be 0.901 g / cm³. 3 The melt flow index is 5.8 g / 10 min, the transmittance is only 84%, and the volume resistivity is 6.1 × 10⁻⁶. 14 Ω·cm.

[0046] Comparative Example 3 Except for the following differences, the remaining steps are the same as in Example 2.

[0047] The first polymerization reaction was controlled at 60°C, 0.6 MPa, 600 rpm, and 800 min.

[0048] The polymer particles obtained from the first reactor had an average particle size D50 of approximately 130 μm, a particle size distribution Span value of 2.3, and a specific surface area (BET) of 0.2 m². 2 / g, average pore size 0.5 nm, pore volume 0.0001 cm³ 3 / g.

[0049] After the second polymerization reaction, the catalyst underwent separation, devolatilization, and extrusion granulation. The final polymerization activity of the catalyst was 16341 g. 聚合物 / g cat The density of this vinyl elastomer product was tested to be 0.896 g / cm³. 3 The melt flow index is 3.2 g / 10 min, the transmittance is only 86%, and the volume resistivity is 9.6 × 10⁻⁶. 14 Ω·cm.

[0050] Comparative Example 4 The first reactor used an unsupported homogeneous metallocene catalyst, and the other conditions were the same as in Example 1.

[0051] The polymer particles obtained from the first reactor had an average particle size D50 of <10 μm, a particle size distribution Span of 2.8, and a specific surface area (BET) of 120 m². 2 / g, average pore size is 6 nm, pore volume is 0.33 cm³. 3 / g. Due to the extremely small particle size of the polymer particles generated in the first polymerization reaction (D50 < 10 μm), severe entrainment and electrostatic problems occurred in the subsequent second polymerization reaction (fluidized bed reaction), resulting in poor reaction stability. The final polymerization activity of the catalyst was 8855 g. 聚合物 / g cat The density of this vinyl elastomer product was tested and found to be 0.892 g / cm³. 3 It has a melt index of 5.0 g / 10 min, a light transmittance of only 80%, and a volume resistivity of only 1.0 × 10⁻⁶. 14 Ω·cm.

[0052] Figure 2 and Figure 3 The process conditions and product performance of Examples 1-5 and Comparative Examples 1-4 are shown in comparison.

[0053] Based on the above embodiments and comparative examples, the present invention reduces the density of vinyl elastomers and improves light transmittance by using a first-stage controlled polymerization induced by a high-viscosity solvent or a mixture of a high-viscosity solvent and a low-viscosity solvent, designing polymer particles with specific particle size and pore structure, and synergistic control of the segmented polymerization process. This significantly improves the electrical properties and processing performance of vinyl elastomers.

Claims

1. A method for preparing a vinyl elastomer, characterized in that, Includes the following steps: a) A solvent, olefin monomer, antistatic agent, metallocene catalyst, and co-catalyst are added to a first reactor to carry out a first polymerization reaction, and the resulting slurry containing polymer particles is conveyed to a mixing tank; wherein, the viscosity of the solvent is 2 mPa·s ~ 100 mPa·s (25°C); the olefin monomer added to the first reactor is ethylene, or a combination of ethylene and α-olefin; the average particle size D50 of the polymer particles in the slurry discharged from the first reactor is 40 μm ~ 140 μm, the particle size distribution Span value is 0.7 ~ 1.8, and the specific surface area (BET) is 0.5 m². 2 / g ~ 100 m 2 / g, with an average pore size of 5 ~ 40 nm and a pore volume of 0.0001 ~ 25 cm³. 3 / g; b) Add solvent B to the mixing tank; c) Inject the material in the mixing tank into the second reactor, and introduce ethylene, α-olefin, solvent C, antistatic agent and hydrogen into the second reactor in proportion to carry out the second polymerization reaction; d) After the second polymerization reaction is completed, the mixture discharged from the second reactor is separated. Unreacted ethylene, α-olefin, solvent C and hydrogen are recycled. The vinyl elastomer in the mixture is subjected to devolatilization and extrusion granulation treatment in sequence to obtain vinyl elastomer products.

2. The method according to claim 1, characterized in that, The solvent mentioned in step a) is solvent A, or a combination of solvent A and solvent B. Solvent A is selected from one or more of white oil, paraffin oil, diesel oil, silicone oil and petrolatum.

3. The method according to claim 1, characterized in that, The α-olefin is selected from one or more of propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene.

4. The method according to claim 1, characterized in that, The metallocene catalyst is a supported metallocene catalyst, and its support is selected from one or more of silica, magnesium chloride, and alkoxymagnesium, and the metal element of the catalyst active center is selected from one or more of titanium, zirconium, hafnium, and vanadium. Among them, the average particle size D50 of the metallocene catalyst is 30 μm ~ 49 μm, and the particle size distribution Span value is 0.9 ~ 2.0; The co-catalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum, diethylaluminum chloride, dichloroethylaluminum, methylaluminoxane, and modified methylaluminoxane.

5. The method according to claim 1, characterized in that, The first reactor is selected from a batch reactor or a tubular reactor; the second reactor is selected from one of a batch reactor, a tubular reactor, or a fluidized bed reactor.

6. The method according to claim 1, characterized in that, The operating parameters of the first polymerization reaction satisfy: (1) The reaction temperature is 0 ~ 50℃; (2) The reaction pressure is 0.1 ~ 0.5 MPa; (3) The reaction time is 10 ~ 600 min; (4) The mass ratio of solvent to metallocene catalyst is 5:1 to 150:1; (5) When using a batch reactor, the rotation speed is 50 ~ 400 rpm / min; when using a tubular reactor, the flow rate is 0.2 ~ 1.0 m / s; (6) The Al / M molar ratio of the co-catalyst to the metallocene catalyst is 10 ~ 500, where M is the metal element in the metallocene catalyst; (7) The molar ratio of α-olefin to ethylene is 0:1 ~ 0.3:1; (8) The amount of antistatic agent added is 0.05wt‰~0.05wt% of the amount of ethylene added.

7. The method according to claim 1, characterized in that, Solvent B is selected from one or more of cyclopentane, n-heptane, n-pentane, isopentane, n-hexane, benzene, toluene, and xylene; When a combination of solvent A and solvent B is used in step a), the mass ratio of solvent B to solvent A is 0.1:1 to 1:1; the mass ratio of solvent B added to the mixing tank in step b) to solvent A used in step a) is 0.3:1 to 1:1; the solvent C mentioned in step c) is selected from one or more of n-hexane, n-pentane, cyclopentane, isopentane, n-butane, isobutane, and propane, and the amount of solvent C added accounts for 0% to 30% of the total mass of the circulating gas, where 0% means no solvent C is added.

8. The method according to claim 1, characterized in that, The operating parameters of the second polymerization reaction satisfy: (1) The reaction temperature is 40 ~ 70℃; (2) The reaction pressure is 1.5 ~ 3.0 MPa; (3) The reaction time is 4 ~ 20 h; (4) The molar ratio of α-olefin to ethylene is 0.1:1 ~ 0.5:1; (5) The molar ratio of hydrogen to ethylene is 0:1 ~ 0.1:1; (6) When using a batch reactor, the rotation speed is 50 ~ 400 rpm; when using a tubular reactor, the flow rate is 0.5 ~ 1.2 m / s; When a fluidized bed reactor is used, the gas velocity is 0.2 ~ 1.5 m / s; (7) The amount of antistatic agent added is 0.00wt‰~0.05wt% of the amount of ethylene added, where 0.00wt‰ means no antistatic agent is added.

9. The method according to claim 1, characterized in that, The polymerization activity of metallocene catalysts is 10,000 ~ 30,000 g. 聚合物 / g cat .

10. A vinyl elastomer, characterized in that, The vinyl elastomer is obtained by the preparation method according to any one of claims 1 to 9, and the density of the vinyl elastomer is 0.865 to 0.890 g / cm³. 3 The melt flow index is 0.3 ~ 30.0 g / 10 min, the transmittance is 90 ~ 94%, and the volume resistivity is 1.0 × 10⁻⁶. 15 Ω·cm ~ 9.0 × 10 18 Ω·cm.

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