An ethylene-α-olefin random copolymer, its preparation method and application

Abstract

This invention belongs to the field of olefin polymerization technology, specifically relating to an olefin copolymer, particularly an ethylene-α-olefin random copolymer, and further disclosing its preparation method and application. The ethylene-α-olefin random copolymer of this invention provides a random copolymer composed of ethylene and α-olefins, especially α-olefins with 3 to 8 carbon atoms. During gradient temperature rinsing, the copolymer is leached at temperatures ranging from 25 to 40°C and 45 to 120°C, wherein the leached component accounts for 0.5 to 5 wt% of the mass within the 25 to 40°C temperature range. This copolymer can be used in photovoltaic film applications, exhibiting improved crosslinking and electrical insulation properties.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization technology, specifically relating to an olefin copolymer, particularly an ethylene-α-olefin random copolymer, and further disclosing its preparation method and application. Background Technology

[0002] Polyolefin elastomers (POEs) are the lightest polymer materials, characterized by low cost, light weight, and ease of molding and processing, and are widely used in many fields such as industry, agriculture, military, and medicine. Polyethylene is a very important product in the polyolefin industry and is currently the largest-volume general-purpose synthetic resin. Copolymers obtained by copolymerizing ethylene and α-olefins possess the plasticity of plastics and the high elasticity of rubber, and are one of the main directions for the development of high-end polyolefin materials.

[0003] Random copolymers of ethylene and α-olefins are semi-crystalline polymers typically containing more than 55 wt% ethylene monomer and less than 45 wt% α-olefin. While the random insertion of α-olefin into the ethylene methylene chain disrupts the regularity of the polymer chain, reducing its crystallinity and consequently increasing its light transmittance, the polymer chain structure, composed of nonpolar C and H atoms with very few unsaturated double bonds, gives random copolymers of ethylene and α-olefins excellent insulation, moisture barrier properties, weather resistance, and UV aging resistance. These properties make them widely used in photovoltaic films.

[0004] However, despite its excellent overall performance in photovoltaic encapsulant applications, POE's inherent characteristics as a semi-crystalline, random copolymer elastomer result in low heat resistance and insufficient mechanical properties. This prevents its direct and long-term use in the natural environment where photovoltaic modules are located. Even with excellent electrical insulation and moisture barrier properties, insufficient mechanical properties still reduce its sealing performance, allowing moisture to penetrate the photovoltaic modules, causing potential decay and impacting module lifespan and power generation efficiency. For these reasons, POE typically requires cross-linking treatment in photovoltaic encapsulant applications to maintain its excellent insulation, transparency, weather resistance, mechanical strength, and sealing properties. Furthermore, during photovoltaic encapsulant processing, POE is directly cross-linked with the solar cells and glass during the lamination and bonding process after film formation, through the addition of cross-linking agents and a heating cross-linking process. However, due to the non-polar composition of POE, the compatibility between the polar crosslinking agent and POE is usually very poor, which affects the processing efficiency, sealing performance and anti-induced potential decay (PID) performance of POE in photovoltaic film application processing.

[0005] Therefore, the art expects to develop an olefin copolymer with improved crosslinking and resistance to induced potential decay (PID) properties, which is of great significance for the development and promotion of encapsulation materials in the photovoltaic field. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide an ethylene-α-olefin random copolymer, wherein the copolymer contains only two components with leaching temperatures of 25-40°C and 45-120°C, and the proportion of the leaching component in the low temperature range is low, and the polymer composition is uniform. The copolymer has improved crosslinking and electrical insulation properties, and has the advantages of fast crosslinking speed and excellent resistance to induced potential decay (PID) in the field of photovoltaic film application.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing and applying the above-mentioned ethylene-α-olefin random copolymer.

[0008] To solve the above-mentioned technical problems, the present invention provides an ethylene-α-olefin random copolymer, wherein the ethylene-α-olefin random copolymer comprises:

[0009] (1) Soluble fractions with a temperature range of 25–40 °C leached out during a 1,2,4-trichlorobenzene gradient leaching process; and,

[0010] (2) Soluble fractions with a temperature range of 45 to 120 °C were leached out during the 1,2,4-trichlorobenzene gradient rinsing process.

[0011] The soluble fraction at 25-40℃ accounts for 0.5-5 wt% of the total mass.

[0012] Specifically, the ethylene-α-olefin random copolymer comprises α-olefin monomers and ethylene monomers as polymerization raw materials; wherein,

[0013] The α-olefin monomer is based on the mass content of the ethylene-α-olefin random copolymer of 20-45 wt%;

[0014] The ethylene monomer is based on the mass content of the ethylene-α-olefin random copolymer of 55-80 wt%;

[0015] Preferably, the α-olefin monomer comprises an α-olefin having 3 to 8 carbon atoms, and more preferably, the α-olefin monomer comprises at least one selected from propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, or 1-octene.

[0016] Specifically, the ethylene-α-olefin random copolymer has a melt flow rate of 0.5–30 g / 10 min (2.16 kg, 190 °C) and a density of 0.860–0.910 g / cm³. 3 .

[0017] The present invention also discloses a method for preparing the ethylene-α-olefin random copolymer, comprising the steps of performing a polymerization reaction on ethylene monomer, α-olefin monomer, impurity remover, dispersant and polymerization catalyst.

[0018] Specifically, the preparation method of the ethylene-α-olefin random copolymer is as follows:

[0019] The amount of ethylene monomer added is 5-20 wt%, based on the total feed amount of the ethylene-α-olefin random copolymer; and / or,

[0020] Based on the total feed amount of the ethylene-α-olefin random copolymer, the amount of α-olefin monomer added is 10-35 wt%; and / or,

[0021] The impurity remover includes at least one of alkylaluminum or alkylaluminoxane; preferably at least one of alkylaluminum, methylaluminoxane, or modified methylaluminoxane; preferably triisobutylaluminum or n-octyl modified methylaluminoxane; preferably, the amount of the impurity remover added is 5-90 ppm based on the total feed amount of the ethylene-α-olefin random copolymer; and / or,

[0022] The dispersant comprises at least one of C6-C10 aliphatic hydrocarbons, such as one or more of C6-C10 straight-chain alkanes, C6-C10 isoalkanes, and C6-C10 cycloalkanes, preferably at least one of C6, C7, C8, C9, or C10 isoalkanes, for example, one or more of n-hexane, cyclohexane, methylcyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, toluene, and xylene; preferably, the amount of the dispersant added is 55-80 wt% based on the total feed amount of the ethylene-α-olefin random copolymer; and / or,

[0023] The polymerization catalyst includes a main catalyst and a co-catalyst;

[0024] Preferably, the main catalyst comprises a group IVB-IIB transition metal compound, preferably bis(methylcyclopentadienyl)zirconium dichloride, bis(cyclopentadienyl)dimethylzirconium, dimethicylbis(2-methylindenyl)zirconium dichloride, dimethicyl(N-tert-butylamino)(cyclopentadienyl)titanium dichloride, dimethicyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium, dimethicyl(N-tert-butylamino)(2,7-di-tert-butylfluorenyl)titanium dichloride, dimethicyl(N-tert-butylamino)(3-pyrrolidinyl)titanium dichloride, diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, diphenylmethylene(cyclopentadienyl)(2,7-di-... One or more of the following: tert-butylfluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(dibenzo[a]fluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(2-dimethylamino-fluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(octamethyloctahydrobenzo[a]fluorenyl)zirconia dichloride, bis(tetramethylcyclopentadienyl)hafnium dichloride, dimethylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride, and diphenylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride; the amount of the main catalyst added is 0.3-5 ppm based on the total feed amount of the ethylene-α-olefin random copolymer; and / or,

[0025] Preferably, the co-catalyst comprises fluoroborane or fluoroborate; preferably, it is one or more of tripentafluorophenylborane, triphenylcarbazone (pentafluorophenyl)borate, and N,N-dimethylphenylamine tetra(pentafluorophenyl)borate; preferably, the amount of co-catalyst added is 0.5 to 7 ppm based on the total feed amount of the ethylene-α-olefin random copolymer.

[0026] Specifically, in the preparation method of the ethylene-α-olefin random copolymer, the polymerization reaction temperature is 120-220℃, the reaction pressure is 3-10MPa, and the reaction time is 2-20min;

[0027] Preferably, the polymerization reaction includes the step of continuously feeding selected reactants into a polymerization reactor; preferably, the polymerization reactor is a stirred tank reactor or a tubular reactor with a circulating pump.

[0028] Specifically, the method for preparing the ethylene-α-olefin random copolymer further includes a step of premixing the ethylene monomer, α-olefin monomer, impurity remover, and dispersant before the polymerization reaction;

[0029] Preferably, the temperature of the premixing step is -10 to 150°C, the pressure is 3 to 10 MPa, and the time is 0.2 to 2 min;

[0030] Preferably, the premixing step includes the step of introducing the ethylene monomer, α-olefin monomer, impurity remover and dispersant into the mixing reactor; preferably, the mixing reactor is a tubular reactor with a static mixer.

[0031] Specifically, the method for preparing the ethylene-α-olefin random copolymer further includes a step of terminating the reaction by adding a quencher and a stabilizer to the polymer reactants of the polymerization reaction;

[0032] Preferably, the quenching agent comprises water or a C1-C15 long-chain alcohol; preferably water or a C1-C15 long-chain fatty alcohol; preferably at least one of water, undecyl alcohol or dodecanol; preferably, the amount of the quenching agent added is 1 to 40 ppm based on the total amount of raw material fed into the ethylene-α-olefin random copolymer.

[0033] Preferably, the stabilizer includes at least one of antioxidants, anti-aging agents, or stearates; preferably, the amount of stabilizer added is 5 to 50 ppm based on the total amount of raw material fed into the ethylene-α-olefin random copolymer.

[0034] Preferably, the temperature for terminating the reaction is 120–220°C, the pressure is 3–10 MPa, and the time is 0.5–5 min.

[0035] Preferably, the termination reaction includes the step of introducing the polymerization reactants, quencher, and stabilizer into a termination reactor; preferably, the termination reactor is a batch reactor equipped with a stirrer.

[0036] Specifically, the method for preparing the ethylene-α-olefin random copolymer further includes a step of collecting the polymer after the termination reaction for post-processing;

[0037] Preferably, the post-processing step includes separating unreacted ethylene, α-olefins and dispersant light components from the polymer by depressurization flash evaporation, and collecting the polymer melt heavy components by extrusion and pelletizing to obtain polymer particles;

[0038] Preferably, the post-processing step further includes the step of reusing the separated unreacted ethylene, α-olefin, and dispersant light components as raw materials.

[0039] The present invention also discloses the application of the ethylene-α-olefin random copolymer or the ethylene-α-olefin random copolymer prepared by the method in the field of photovoltaic encapsulation, especially its application in the preparation of photovoltaic encapsulation films.

[0040] In some embodiments, the specific steps for applying the ethylene-α-olefin random copolymer to the field of photovoltaic encapsulation films can be conventional operations in the art. For example, the ethylene-α-olefin random copolymer can be mixed with additives to form a photovoltaic encapsulation film composition, and then the composition can be processed into a photovoltaic encapsulation film using conventional processing techniques in the art. The additives can be commonly used types of additives in the art, such as crosslinking agents, crosslinking aids, antioxidants, etc.

[0041] The present invention provides an ethylene-α-olefin random copolymer, which is a random copolymer composed of ethylene and α-olefins, especially α-olefins with 3 to 8 carbon atoms. During gradient temperature rinsing, the copolymer is leached at temperatures ranging from 25 to 40°C and 45 to 120°C, wherein the molar percentage of the leached component is 0.5 to 5% within the temperature range of 25 to 40°C. This copolymer can be used in photovoltaic film applications with improved crosslinking and electrical insulation properties.

[0042] The ethylene-α-olefin random copolymer of the present invention, after being graded by a gradient temperature rinsing system, contains only two components with rinsing temperatures ranging from 25 to 40°C and 45 to 120°C, respectively. The proportion of the rinsing component in the low temperature range is low, and the polymer composition is uniform. This polymer has improved crosslinking and electrical insulation properties, and is characterized by fast crosslinking speed and excellent resistance to induced potential decay (PID) when used in photovoltaic films.

[0043] The method for preparing the ethylene-α-olefin random copolymer of the present invention, based on the optimization and proportioning of raw materials in the entire specific system, can prepare an olefin copolymer with a low proportion of leaching components and a uniform two-component composition in the low-temperature range. When used as a photovoltaic film, this copolymer has a fast crosslinking speed and excellent anti-PID performance. Attached Figure Description

[0044] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0045] Figure 1 The results show the eluent composition distribution of the copolymer described in Example 5. Detailed Implementation

[0046] This invention provides an ethylene-α-olefin random copolymer with improved crosslinking and electrical insulation properties for use in photovoltaic encapsulant film applications, wherein the ethylene-α-olefin random copolymer comprises:

[0047] (1) Soluble fractions with a temperature range of 25–40 °C leached out during a 1,2,4-trichlorobenzene gradient leaching process; and,

[0048] (2) Soluble fractions with a temperature range of 45 to 120 °C were leached out during the 1,2,4-trichlorobenzene gradient rinsing process.

[0049] The soluble fraction at 25-40℃ accounts for 0.5-5 wt% of the total mass.

[0050] Specifically, the ethylene-α-olefin random copolymer comprises α-olefin monomers and ethylene monomers as polymerization raw materials; wherein,

[0051] As an feasible option, the mass content of the α-olefin monomer is 20 to 45 wt% based on the mass of the ethylene-α-olefin random copolymer;

[0052] As an feasible option, the mass content of the ethylene monomer is 55-80 wt% based on the mass of the ethylene-α-olefin random copolymer;

[0053] As an feasible option, the α-olefin monomer includes at least one selected from propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, or 1-octene.

[0054] Specifically, the ethylene-α-olefin random copolymer described in this application has a melt flow rate of 0.5–30 g / 10 min (2.16 kg, 190 °C) and a density of 0.860–0.910 g / cm³. 3 .

[0055] The present invention also provides a method for preparing the ethylene-α-olefin random copolymer, which includes the steps of carrying out a polymerization reaction of ethylene monomer, α-olefin monomer, impurity remover, dispersant and polymerization catalyst.

[0056] As an exemplary implementation, the amount of ethylene monomer added is 5 to 20 wt%, based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of ethylene monomer added can be controlled to be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 wt%, or any range between the above values.

[0057] As an exemplary embodiment, the amount of α-olefin monomer added is 10 to 35 wt% based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of α-olefin monomer added can be controlled to be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 wt%, or any range between the above values.

[0058] The impurity remover includes at least one of alkylaluminum or alkylaluminoxane; preferably at least one of alkylaluminum, methylaluminoxane, or modified methylaluminoxane, and more preferably triisobutylaluminum or octyl-modified methylaluminoxane. Preferably, the amount of the impurity remover added is 5–90 ppm, based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of the impurity remover added can be adjusted to 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 ppm, or any range between the above values.

[0059] As an exemplary embodiment, the dispersant includes at least one of C6-C10 aliphatic hydrocarbons, such as one or more of C6-C10 straight-chain alkanes, C6-C10 isoalkanes, and C6-C10 cycloalkanes, preferably at least one of C6, C7, C8, C9, or C10 isoalkanes, for example, one or more of n-hexane, cyclohexane, methylcyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, toluene, and xylene. Preferably, the amount of dispersant added is 55-80 wt% based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of the dispersant added can be adjusted to 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 wt%, or any range between the above values.

[0060] As an feasible option, the polymerization catalyst includes a main catalyst and a co-catalyst.

[0061] As an exemplary embodiment, the catalyst comprises a group IVB-IIB transition metal compound, preferably bis(methylcyclopentadiene)zirconium dichloride, bis(cyclopentadiene)dimethylzirconium, dimethicylbis(2-methylindenyl)zirconium dichloride, dimethicyl(N-tert-butylamino)(cyclopentadienyl)titanium dichloride, dimethicyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium, dimethicyl(N-tert-butylamino)(2,7-di-tert-butylfluorenyl)titanium dichloride, dimethicyl(N-tert-butylamino)(3-pyrrolidinyl)titanium dichloride, diphenylmethylene(cyclopentadiene)(9 One or more of the following: diphenylmethylene(cyclopentadienyl)(2,7-di-tert-butylfluorenyl)zirconia, diphenylmethylene(cyclopentadienyl)(dibenzo[a]fluorenyl)zirconia, diphenylmethylene(cyclopentadienyl)(2-dimethylamino-fluorenyl)zirconia, diphenylmethylene(cyclopentadienyl)(octamethyloctahydrobenzo[a]fluorenyl)zirconia, bis(tetramethylcyclopentadienyl)hafnium dichloride, dimethylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride, and diphenylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride. Preferably, the amount of the main catalyst added is 0.3 to 5 ppm based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of the main catalyst added can be adjusted to 0.3, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 ppm, or any range between the above values.

[0062] As an exemplary embodiment, the co-catalyst comprises fluoroborane or fluoroborate; preferably, one or more of tripentafluorophenylborane, triphenylcarbazone (pentafluorophenyl)borate, and N,N-dimethylphenylammonium tetra(pentafluorophenyl)borate. Preferably, the amount of co-catalyst added is 0.5 to 7 ppm based on the total feed amount of the ethylene-α-olefin random copolymer. For example, the amount of co-catalyst added can be adjusted to 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 ppm, or any range between the above values.

[0063] As an exemplary embodiment, the polymerization reaction is carried out at a temperature of 120–220°C, a pressure of 3–10 MPa, and a time of 2–20 min.

[0064] For example, the reaction temperature of the polymerization reaction can be controlled to be 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220°C, or any range between the above values.

[0065] For example, the reaction pressure of the polymerization reaction can be controlled to be 3, 4, 5, 6, 7, 8, 9, 10 MPa, or any range between the above values.

[0066] For example, the reaction time of the polymerization reaction can be controlled to be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 min, or any range between the above values.

[0067] As an exemplary embodiment, the polymerization reaction includes the step of continuously feeding selected reactants into a polymerization reactor; preferably, the polymerization reactor is a stirred tank reactor or a tubular reactor with a circulating pump.

[0068] As an feasible option, the method further includes a step of premixing the ethylene monomer, α-olefin monomer, impurity remover and dispersant before the polymerization reaction;

[0069] Preferably, the temperature of the premixing step is -10 to 150°C, the pressure is 3 to 10 MPa, and the time is 0.2 to 2 min.

[0070] For example, the temperature of the premixing step can be controlled to be -10, -5, 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150°C, or any range between the above values.

[0071] For example, the pressure of the premixing step can be controlled to be 3, 4, 5, 6, 7, 8, 9, 10 MPa, or any range between the above values.

[0072] For example, the time for the premixing step can be controlled to be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 min, or any range between the above values.

[0073] As an exemplary embodiment, the premixing step includes the step of introducing the ethylene monomer, α-olefin monomer, impurity remover and dispersant into a mixing reactor; preferably, the mixing reactor is a tubular reactor with a static mixer.

[0074] As an feasible option, the method further includes the step of terminating the reaction by adding a quencher and a stabilizer to the polymer reactants of the polymerization reaction;

[0075] As an exemplary embodiment, the quencher comprises water or a C1-C15 long-chain alcohol; preferably water or a C1-C15 long-chain fatty alcohol; preferably at least one of water, undecyl alcohol, or dodecayl alcohol; for example, conventional alcohol reagents such as water, 1-undecyl alcohol, 2-undecyl alcohol, 1-dodecayl alcohol, and 2-dodecayl alcohol. Preferably, the amount of the quencher added is 1 to 40 ppm based on the total amount of raw material fed into the ethylene-α-olefin random copolymer. For example, the amount of the quencher added can be adjusted to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 ppm, or any range between the above values.

[0076] Preferably, the stabilizer includes at least one of antioxidants, anti-aging agents, or stearates. For example, antioxidant 168, antioxidant CA, anti-aging agent DNP, zinc stearate, calcium stearate, and magnesium stearate are all stabilizers with good performance. Preferably, the amount of stabilizer added is 5 to 50 ppm based on the total amount of raw material fed into the ethylene-α-olefin random copolymer. For example, the amount of quenching agent added can be adjusted to 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 ppm, or any range between the above values.

[0077] As an feasible approach, the inactivation reaction is carried out at a temperature of 120–220°C, a pressure of 3–10 MPa, and a time of 0.5–5 min.

[0078] For example, the reaction temperature of the inactivation reaction can be controlled to be 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220°C, or any range between the above values.

[0079] For example, the reaction pressure of the inactivation reaction can be controlled to be 3, 4, 5, 6, 7, 8, 9, 10 MPa, or any range between the above values.

[0080] For example, the reaction time of the inactivation reaction can be controlled to be 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8, 4.0, 4.2, 4.5, 4.8, 5.0 min, or any range between the above values.

[0081] As an exemplary embodiment, the termination reaction includes the step of introducing the polymerization reactants and quenching agent into a termination reactor; preferably, the termination reactor is a batch reactor equipped with a stirrer.

[0082] As an feasible option, the method for preparing the ethylene-α-olefin random copolymer further includes a step of collecting the polymer after the termination reaction for post-processing;

[0083] As an exemplary implementation, the post-processing steps include separating unreacted ethylene, α-olefins, and dispersant light components from the polymer by depressurization flash evaporation, and collecting the polymer melt heavy components by extrusion and pelletizing to obtain polymer particles.

[0084] The present invention is further illustrated by the following embodiments, but the present invention is not limited to these embodiments.

[0085] In the following embodiments of the present invention, the sources and specifications of some of the raw materials involved are shown in Tables 1-2 below.

[0086] Table 1 Partial Raw Material Information

[0087]

[0088]

[0089] Table 2 Catalyst Types

[0090] Catalyst number Catalyst name A Dimethicylbis(2-methylindenyl)zirconium dichloride B Dimethicone (N-tert-butylamino)(2,7-di-tert-butylfluorenyl)titanium dichloride C Dimethylsilyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium D Dimethicone (N-tert-butylamino)(3-pyrrolidinylindenyl)titanium dichloride E Dimethicone (N-tert-butylamino) (cyclopentadienyl) titanium dichloride F Diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconium dichloride G Diphenylmethylene(cyclopentadienyl)(octamethyloctahydrobenzofluorenyl)zirconium dichloride H Dimethylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride I Hafnium dichloride (9-fluorenyl)(3-tert-butylcyclopentadienyl) J Diphenylmethylene(cyclopentadienyl)(dibenzofluorenyl)zirconium dichloride a Tri-pentafluorophenylborane b Triphenylcarbazone (pentafluorophenyl) borate c N,N-Dimethylphenylamine tetra(pentafluorophenyl)borate

[0091] In the following embodiments of the present invention, the polymerization method for the ethylene-α-olefin random copolymer is a continuous solution polymerization method carried out in a high-pressure stirred reactor with PLC control.

[0092] After thorough mixing of dehydrated and deoxygenated purified ethylene, α-olefins, impurity removers, and dispersants, the mixture is continuously fed into a 2.0-liter reactor equipped with a jacket for temperature control and internal thermocouples. The ethylene feed rate is metered using a gas mass flow controller, while the flow rates of the α-olefins, impurity removers, and dispersants are controlled by diaphragm metering pumps. Before entering the reactor, the temperature of the ethylene, α-olefins, impurity remover, and dispersant solution is controlled using a heat exchanger and added to the bottom of the reactor. Separately, the main catalyst and co-catalyst are prepared into solutions using a dispersant and fed separately to the bottom of the reactor via a diaphragm metering pump. The quencher and stabilizer are also prepared into solutions using a dispersant and fed separately to the bottom of the termination reactor via a diaphragm metering pump. The polymerization temperature is stably controlled by the feed temperature and the reactor jacket temperature. The reactor is operated with full liquid under stirring speed of 500-1000 rpm. The reaction liquid flows out through the outlet pipeline at the top of the reactor and enters the termination reactor to mix with the quencher and stabilizer. After mixing and reacting, the mixture enters the heat exchanger and is heated to 260°C. The reactor pressure (3.5 MPa) is controlled by the heat exchanger outlet pressure regulating valve. After the high-temperature reaction liquid is depressurized by the pressure control valve, it enters the three-stage low-pressure flash evaporation system in sequence. The small amount of ethylene removed is discharged, while the α-olefin and solvent are recycled. The polymer melt is extruded and pelletized to obtain polymer particles.

[0093] The selection, proportioning, and reaction condition control parameters of the polymerization raw materials involved in the following embodiments of the present invention are shown in Table 3.

[0094] Table 3 Continuous polymerization reaction conditions of the example schemes

[0095]

[0096]

[0097] Comparative Example 1

[0098] The raw material system and preparation method of the ethylene-α-olefin random copolymer described in this comparative example are the same as those in Example 1, except that the quencher is not added.

[0099] Comparative Example 2

[0100] The raw material system and preparation method of the ethylene-α-olefin random copolymer described in this comparative example are the same as those in Example 1, except that the stabilizer is not added.

[0101] Comparative Example 3

[0102] The raw material system and preparation method of the ethylene-α-olefin random copolymer described in this comparative example are the same as those in Example 1, except that the quencher and stabilizer are not added.

[0103] Experimental Example

[0104] 1. Reactivity

[0105] This experimental example measures the polymerization activity of the reaction based on the above-mentioned examples and comparative schemes. The calculation method is the ratio of the weight of the dried polymer product obtained by the polymerization reaction to the number of moles of the transition metal compound (catalyst) added during the reaction process. The results are shown in Table 4 below.

[0106] Table 4 Polymerization activity results

[0107]

[0108]

[0109] It is evident that the polymerization reaction described in this invention has a suitable reactivity.

[0110] 2. Polymer composition

[0111] The copolymer prepared in Example 5 was used, and a gradient temperature elution system was employed with polymer soluble fractionation (SF) using 1,2,4-trichlorobenzene as the mobile phase. The elution temperature ranged from 10 to 150 °C, and the heating rate was 5 °C / min. The eluted composition distribution was analyzed, and the results are shown in the appendix. Figure 1 .

[0112] As can be seen, the ethylene-α-olefin random copolymer of the present invention contains only two components with leaching temperatures of 25-40°C and 45-120°C, and the proportion of the leaching component in the low temperature range is low, resulting in a uniform polymer composition.

[0113] Other embodiments of the present invention have similar composition distribution results. After being graded by the gradient temperature rinsing system, they only contain two components with rinsing temperatures ranging from 25 to 40°C and 50 to 120°C, and the proportion of the rinsing component in the low temperature range is low.

[0114] 3. Polymer properties

[0115] In this experimental example, the processing properties of the ethylene-α-olefin random copolymers prepared by the above-mentioned examples and comparative schemes were tested.

[0116] (1) The polymer soluble fraction (SF) adopts a gradient temperature rinsing system with 1,2,4-trichlorobenzene as the mobile phase, the rinsing temperature is 10-150℃ and the heating rate is 5℃ / min.

[0117] (2) Polymer melt index (MFR) is tested using a melt indexer (MI-4). Under test conditions of 190℃ and 2.16kg load, the weight of molten polymer extruded through a die with a length of 8mm and an inner diameter of 2.095mm for a specified time is the MFR, and the unit is g / 10min.

[0118] (3) The polymer density was tested using a densitometer (impregnation method). The mass of the sample suspended by a metal wire with a diameter not greater than 0.5 mm was weighed in air. The sample mass was not greater than 10 g, accurate to 0.1 mg, and the mass of the sample was recorded. The sample suspended by the thin metal wire was then immersed in a beaker filled with impregnation liquid placed on a fixed support. The temperature of the impregnation liquid should be 23℃±2℃. Air bubbles adhering to the sample were removed with the thin metal wire. The mass of the sample in the impregnation liquid was weighed, accurate to 0.1 mg.

[0119] The results of the above processing performance tests in this experimental example are shown in Table 5 below.

[0120] Table 5 Performance Indicators of Copolymers

[0121]

[0122] It is evident that the addition of a quencher during the polymerization reaction can terminate the reaction in a timely manner, thereby ensuring that the polymerization reaction is carried out under relatively constant ethylene / α-olefin reaction feedstock ratio conditions, and reducing the low molecular weight low-temperature leaching components generated in the later stages of the reaction under reaction conditions where the concentration of ethylene monomer is lower than that of α-olefin monomer.

[0123] Furthermore, the addition of stabilizers effectively prevents the high molecular weight, high-temperature leaching components in the polymer from degrading into low molecular weight, low-temperature leaching components during subsequent high-temperature post-processing. The combined effect of these two factors ensures a low proportion of low-temperature leaching components in the polymer product composition and maintains good light transmittance.

[0124] Therefore, compared with the comparative example, the ethylene-α-olefin random copolymer prepared in the embodiments of the present invention has a lower content of leaching components in the low-temperature range, and a higher starting temperature value in the leaching temperature range. When applied to photovoltaic films, it exhibits less PID attenuation after 96 hours and a higher degree of crosslinking under the same conditions.

[0125] 4. Copolymer film

[0126] This experimental example is based on the copolymers prepared in the above examples and comparative examples, and the film properties were tested after film formation.

[0127] The anti-PID degradation performance test was conducted using a power test environment chamber. First, copolymer particles and dicumyl peroxide were mixed and processed into a photovoltaic film with a thickness of 500-700 μm by a casting machine. Then, the film was pressed for 5 minutes under negative pressure at 70°C by a laminator. The prepared double-glass photovoltaic module was then subjected to anti-PID performance testing under the conditions of 96h-85°C / 85RH / -1500V.

[0128] Crosslinking degree: The xylene soluble matter test method was adopted. First, the copolymer particles and dicumyl peroxide were mixed and processed into a photovoltaic film with a thickness of 500-700 μm by a casting machine. Then, the film was pressed for 5 min under negative pressure at 70℃ by a laminator. Finally, the crosslinked photovoltaic film was taken to test the crosslinking degree and peel strength.

[0129] Transmittance: The transmittance was measured using a projection spectrometer. A clean film sample was placed on a transparent substrate, and the transmission spectrum was automatically scanned and recorded by the spectrometer. The transmittance percentage at different wavelengths was then calculated.

[0130] The test results of the copolymer film in this experimental example are shown in Table 6 below.

[0131] Table 6 Properties of Copolymer Films

[0132]

[0133] As can be seen, the ethylene-α-olefin random copolymer described in this invention, when used in the field of photovoltaic films, has the advantage of high crosslinking degree while maintaining high light transmittance.

[0134] In summary, the ethylene-α-olefin random copolymer described in this invention has improved crosslinking and electrical insulation properties, and exhibits excellent performance in photovoltaic film applications, including fast crosslinking speed and superior resistance to induced potential decay (PID).

[0135] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An ethylene-α-olefin random copolymer, characterized in that, The ethylene-α-olefin random copolymer includes: (1) Soluble fractions with a temperature range of 25~40℃ leached out during the 1,2,4-trichlorobenzene gradient leaching process; and, (2) Soluble fractions with a temperature range of 45~120℃ were leached out during the 1,2,4-trichlorobenzene gradient rinsing process; The soluble fraction at 25-40℃ accounts for 0.5-5 wt% by mass. The preparation method of the ethylene-α-olefin random copolymer includes the following steps: The ethylene monomer, α-olefin monomer, impurity remover, dispersant and polymerization catalyst are subjected to polymerization reaction; the reaction temperature of the polymerization reaction is 120~220℃, the reaction pressure is 3~10MPa, and the reaction time is 2~20min. A quencher and a stabilizer are added to the polymer reactants of the polymerization reaction to terminate the reaction; the temperature for terminating the reaction is 120~220℃, the pressure is 3~10MPa, and the time is 0.5~5min.

2. The ethylene-α-olefin random copolymer according to claim 1, characterized in that, The polymerization raw materials for the ethylene-α-olefin random copolymer include α-olefin monomers and ethylene monomers; wherein, The α-olefin monomer has a mass content of 20-45 wt% based on the ethylene-α-olefin random copolymer. The ethylene monomer has a mass content of 55-80 wt% based on the ethylene-α-olefin random copolymer. And / or, the α-olefin monomer comprises an α-olefin having 3 to 8 carbon atoms.

3. The ethylene-α-olefin random copolymer according to claim 1 or 2, characterized in that, The ethylene-α-olefin random copolymer has a melt flow rate of 0.5~30 g / 10 min at 190℃ and a density of 0.860~0.910 g / cm³. 3 ; And / or, the α-olefin monomer includes at least one selected from propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, or 1-octene.

4. A method for preparing the ethylene-α-olefin random copolymer as described in any one of claims 1-3, characterized in that, It includes the steps of polymerizing ethylene monomers, α-olefin monomers, impurity removers, dispersants, and polymerization catalysts.

5. The method for preparing the ethylene-α-olefin random copolymer according to claim 4, characterized in that: Based on the total feed amount of the ethylene-α-olefin random copolymer, the amount of ethylene monomer added is 5~20wt%; and / or, Based on the total feed amount of the ethylene-α-olefin random copolymer, the amount of α-olefin monomer added is 10~35wt%; and / or, The impurity remover includes at least one of alkylaluminum, alkylaluminoxane, or modified methylaluminoxane; and / or, The amount of the impurity remover added is 5-90 ppm, based on the total feed amount of the ethylene-α-olefin random copolymer; and / or, The dispersant includes at least one of C6-C10 aliphatic hydrocarbons; and / or, The amount of dispersant added is 55-80 wt% based on the total feed amount of the ethylene-α-olefin random copolymer; and / or, The polymerization catalyst includes a main catalyst and a co-catalyst.

6. The method for preparing the ethylene-α-olefin random copolymer according to claim 5, characterized in that, The impurity remover includes at least one of alkylaluminum, methylaluminoxane, or modified methylaluminoxane; and / or, The dispersant includes at least one of C6, C7, C8, C9, or C10 isoalkane; and / or, The main catalyst comprises group IVB-IIB transition metal compounds; and / or, Based on the total feed amount of the ethylene-α-olefin random copolymer, the amount of the main catalyst added is 0.3~5 ppm; and / or, The cocatalyst comprises fluoroboranes or fluoroborates; and / or, The amount of the co-catalyst added is 0.5~7 ppm, based on the total feed amount of the ethylene-α-olefin random copolymer; and / or, The polymerization reaction is carried out at a temperature of 120-220°C, a pressure of 3-10 MPa, and a time of 2-20 min; and / or, The polymerization reaction includes the step of continuously feeding selected reactants into the polymerization reactor.

7. The method for preparing the ethylene-α-olefin random copolymer according to claim 6, characterized in that, The impurity remover includes triisobutylaluminum or n-octyl-modified methylaluminoxane; and / or, The main catalyst includes bis(methylcyclopentadiene)zirconia dichloride, bis(cyclopentadiene)dimethylzirconia, dimethicylbis(2-methylindenyl)zirconia dichloride, dimethicyl(N-tert-butylamino)(cyclopentadienyl)titanium dichloride, dimethicyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium, dimethicyl(N-tert-butylamino)(2,7-di-tert-butylfluorenyl)titanium dichloride, dimethicyl(N-tert-butylamino)(3-pyrrolidinyl)titanium dichloride, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconia dichloride, and diphenylmethylene( One or more of the following: cyclopentadienyl(2,7-di-tert-butylfluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(dibenzo[2]fluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(2-dimethylamino-fluorenyl)zirconia dichloride, diphenylmethylene(cyclopentadienyl)(octamethyloctahydrobenzo[2]fluorenyl)zirconia dichloride, bis(tetramethylcyclopentadienyl)hafnium dichloride, dimethylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride, and diphenylsilyl(9-fluorenyl)(3-tert-butylcyclopentadienyl)hafnium dichloride; and / or, The cocatalyst comprises one or more of triphenylphenylborane, triphenylcarbazone (pentafluorophenyl)borate, and N,N-dimethylphenylamine tetra(pentafluorophenyl)borate; and / or, The polymerization reactor is a stirred tank reactor or a tubular reactor with a circulating pump; and / or, The method further includes a step of premixing the ethylene monomer, α-olefin monomer, impurity remover, and dispersant before the polymerization reaction.

8. The method for preparing the ethylene-α-olefin random copolymer according to claim 7, characterized in that, The premixing step is performed at a temperature of -10 to 150°C, a pressure of 3 to 10 MPa, and a time of 0.2 to 2 min; and / or, The premixing step includes passing the ethylene monomer, α-olefin monomer, impurity remover, and dispersant into a mixing reactor; the mixing reactor is a tubular reactor equipped with a static mixer; and / or, The method further includes the step of terminating the reaction by adding a quencher and a stabilizer to the polymer reactants of the polymerization reaction.

9. The method for preparing the ethylene-α-olefin random copolymer according to claim 8, characterized in that, The quenching agent comprises water or a C1-C15 long-chain alcohol; and / or, The amount of quencher added is 1~40 ppm, based on the total feed amount of the ethylene-α-olefin random copolymer; and / or, The stabilizer includes at least one of antioxidants, anti-aging agents, or stearates; and / or, The stabilizer addition amount is 5-50 ppm, based on the total feed amount of the ethylene-α-olefin random copolymer; and / or, The termination reaction is carried out at a temperature of 120-220°C, a pressure of 3-10 MPa, and a time of 0.5-5 min; and / or, The termination reaction includes the step of introducing the polymer reactant, quencher, and stabilizer into the termination reactor; and / or, The method further includes a step of collecting the polymer after the termination reaction for post-processing.

10. The method for preparing the ethylene-α-olefin random copolymer according to claim 9, characterized in that, The post-processing steps include separating unreacted ethylene, α-olefins, and dispersant light components from the polymer by depressurized flash evaporation, and collecting the polymer melt heavy components for extrusion and pelletizing to obtain polymer particles; and / or, The quenching agent comprises water or a C1-C15 long-chain fatty alcohol; and / or, The termination reactor is a batch reactor equipped with a stirrer.

11. The method for preparing the ethylene-α-olefin random copolymer according to claim 10, characterized in that, The post-processing step further includes the step of reusing the separated unreacted ethylene, α-olefins, and dispersant light components as raw materials; and / or, The quenching agent includes at least one of water, undecyl alcohol, or dodecayl alcohol.

12. The application of the ethylene-α-olefin random copolymer according to any one of claims 1-3 or the ethylene-α-olefin random copolymer prepared by the method according to any one of claims 4-11 in the field of photovoltaic encapsulation.

13. The application according to claim 12, characterized in that, Applications in the preparation of photovoltaic encapsulating films.

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