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KR-20260066176-A - Ethylene/α-olefin random copolymer for solar encapsulant films and uses thereof

KR20260066176AKR 20260066176 AKR20260066176 AKR 20260066176AKR-20260066176-A

Abstract

The present application belongs to the field of solar encapsulant film technology, and in particular relates to an ethylene/α-olefin random copolymer and its uses. The ethylene/α-olefin random copolymer satisfies the following characteristics: (i) the molar content of the soluble fraction (SF) at 35°C or lower, measured by a gradient heating elution method, is 0.5% to 3%, and the weight-average molecular weight of the soluble fraction is 20,000 g/mol or less; and (ii) the total number of branched chains per 1,000 carbon atoms in the chain structure of the copolymer is 25 to 85, and a highly linear fitting relationship is formed between the number of branched chains per 1,000 carbon atoms of chain segments of different molecular weights and the logarithm of the molecular weight of the copolymer chain segments. When applied to a solar encapsulant film, the copolymer of the present application has a fast crosslinking rate and a high degree of crosslinking, and possesses improved processing performance; furthermore, the obtained solar encapsulant film has high light transmittance and excellent sealing performance.

Inventors

  • 린, 샤오지에
  • 장, 옌위
  • 왕, 진창
  • 황, 링옌
  • 티안, 진
  • 지아오, 동
  • 왕, 달린
  • 왕, 레이

Assignees

  • 완후아 케미컬 그룹 코., 엘티디

Dates

Publication Date
20260512
Application Date
20240511
Priority Date
20240115

Claims (15)

  1. As an ethylene/α-olefin random copolymer for solar encapsulant films, It has ethylene monomer units and C3–C8 α-olefin monomer units, and (i) a molar content of the soluble fraction at 35°C or lower measured by the gradient heating elution method of 0.5% to 3%, and a weight-average molecular weight of the soluble fraction of 20,000 g/mol or less; and (ii) a total number of branched chains per 1,000 carbon atoms in the chain structure of the copolymer is 25 to 85, and also a good linear fitting relationship is formed between the number of branched chains per 1,000 carbon atoms of each molecular weight chain segment, which is the dependent variable y, and the log value of the molecular weight of each copolymer chain segment, which is the independent variable x, with a fitting coefficient of determination R² of 0.75 or higher; an ethylene/α-olefin random copolymer satisfying these characteristics.
  2. In paragraph 1, (iii) Characteristics of the copolymer having a melt flow index of 4–35 g/10 min (190℃, 2.16 kg) and a density of 0.865–0.890 g/ cm³ ; (iv) an ethylene/α-olefin random copolymer satisfying the characteristics of having a weight-average molecular weight of 45,000 to 80,000 g/mol and a molecular weight distribution (Mw/Mn) of 3 or less.
  3. In paragraph 1 or 2, The above α-olefin monomer is an ethylene/α-olefin random copolymer, one or more selected from the group consisting of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene.
  4. In any one of paragraphs 1 through 3, An ethylene/α-olefin random copolymer, which is a product obtained by a solution polymerization reaction in which an alkane solvent, an ethylene monomer, an α-olefin monomer, and a polymerization catalyst are continuously fed into a polymerization reactor and mixed in contact.
  5. In paragraph 4, The above alkane solvent is an ethylene/α-olefin random copolymer selected from the group consisting of C6-C10 straight-chain alkanes, C6-C10 isoparaffins, C6-C10 cycloparaffins, and C6-C10 aromatic alkanes.
  6. In paragraph 5, The above alkane solvent is an ethylene/α-olefin random copolymer, one or more selected from the group consisting of n-hexane, cyclohexane, methylcyclohexane, n-heptane, isoheptane, n-octane, isooctane, n-decane, toluene, and xylene.
  7. In paragraph 4, The above polymerization catalyst is an ethylene/α-olefin random copolymer comprising a main catalyst and a co-catalyst.
  8. In Paragraph 7, The above main catalyst is a group IVB-IIB transition metal compound; The above co-catalyst is an ethylene/α-olefin random copolymer, which is an alkylaluminoxane.
  9. In paragraph 8, The above main catalyst is dimethylsilylene-bis(indenyl)zirconium dichloride, dimethylsilylene-bis(2-methyl-indenyl)zirconium dichloride, bis(2-methyl-4-phenyl-indenyl)zirconium dichloride, dimethylsilylene-bis(2-methyl-4-phenyl-indenyl)zirconium dichloride, dimethylsilylene-bis(2-methyl-4-phenyl-indenyl)dimethylzirconium, dimethylsilylene-bis[2-methyl-4-(3,5-dimethylphenyl)-indenyl]dimethylzirconium, isopropylene-bis(2-methyl-4-phenyl-indenyl)dimethylhafnium, isopropylene-bis[2-methyl-4-(3,5-dimethylphenyl)-indenyl]dimethylhafnium, bis(cyclopentadienyl)dimethylhafnium, Dimethylsilylene-bis(tetramethylcyclopentadienyl)dimethyltitanium, dimethylsilylene(cyclopentadienyl-fluorenyl)zirconium dichloride, isopropylene(cyclopentadienyl-fluorenyl)zirconium dichloride, isopropylene[cyclopentadienyl-(3,6-di-tert-butyl-fluorenyl)]zirconium dichloride, isopropylene(fluorenyl-tert-butylamino)titanium dichloride, dimethylsilylene(3,6-di-tert-butylfluorenyl-tert-butylamino)dimethyltitanium, isopropylene(tetramethylcyclopentadienyl-tert-butylamino)dimethyltitanium, dimethylsilylene(3-pyrrolidenyl-tert-butylamino)dimethyltitanium, An ethylene/α-olefin random copolymer, at least one selected from the group consisting of bis(3-methylsalicylidene-pentafluorophenylimino)titanium dichloride and bis(salicylidene-phenylimino)titanium dichloride.
  10. In paragraph 8, The above co-catalyst is an ethylene/α-olefin random copolymer, at least one selected from the group consisting of methylaluminoxane and modified methylaluminoxane.
  11. In any one of paragraphs 4 through 10, The process conditions of the above solution polymerization reaction include a reaction temperature of 110 to 180°C and a reaction pressure of 3 to 10 MPaG, for an ethylene/α-olefin random copolymer.
  12. In any one of paragraphs 4 through 11, The polymer reaction solution obtained by the above solution polymerization reaction is subjected to inactivation treatment through an inactivator; said inactivator is an ethylene/α-olefin random copolymer, which is a C6-C8 long-chain alcohol.
  13. In Paragraph 12, An ethylene/α-olefin random copolymer, wherein the product stream after the above inactivation treatment is heated, and the resulting high-temperature reaction solution is subjected to instantaneous evaporation treatment through an instantaneous evaporation system to remove volatile components, solvent, and unreacted monomers therein.
  14. In Paragraph 13, The obtained unreacted monomer and the solvent are recycled as raw materials, and the obtained polymer product stream is melt-extruded and pelletized to obtain copolymer particles, an ethylene/α-olefin random copolymer.
  15. Use of an ethylene/α-olefin random copolymer according to any one of claims 1 to 14 in the field of photovoltaic encapsulation films.

Description

Ethylene/α-olefin random copolymer for solar encapsulant films and uses thereof The present application relates to the field of solar encapsulation film technology, for example, to ethylene/α-olefin random copolymers and their uses. Polyolefin elastomers (POE) are random copolymers of ethylene and α-olefins, and common α-olefin comonomers include 1-butene and 1-octene. Generally, α-olefin comonomers account for at least 20 wt% by mass of the random copolymer. In ethylene-based copolymers, the insertion of α-olefin comonomers disrupts the orderliness of the methylene sequence, introduces a short-chain branched structure, and reduces the degree of crystallinity of the polymer. This allows the polymer to possess excellent transparency while simultaneously achieving the elasticity of rubber and the processability of plastic. Polyolefin elastomers have a non-polar hydrocarbon backbone structure and a low number of tertiary carbon atoms. Due to their excellent weather resistance, UV aging performance, as well as superior insulation and water vapor barrier properties, they are widely applied in the field of solar encapsulation films, accounting for approximately 30% of the total solar encapsulation film market. In recent years, the solar industry has developed rapidly, and solar installation capacity is increasing year by year. As a sealing material for solar modules, POE holds broad market prospects in the solar industry. Currently, EVA holds a significant market share in the solar encapsulant film sector due to its superior cost competitiveness. However, as the service life lengthens, the polar components contained in EVA are prone to hydrolysis reactions under external humid environments, generating acidic substances. This not only corrodes the transparent glass of solar modules but also generates easily ionized sodium ions, causing leakage current and degrading the performance of preventing PID (potential-induced degradation). Although POE materials with a non-polar hydrocarbon backbone structure can largely avoid the aforementioned problems due to their excellent aging resistance and electrical insulation performance, it is generally necessary to add polar auxiliaries, such as crosslinking agents, during the processing stage to further enhance the mechanical strength and aging resistance of the encapsulant film. Due to its inherent non-polar nature, POE has low compatibility with polar auxiliaries, which affects the crosslinking rate during processing and, consequently, impacts the sealing performance of the encapsulant film for solar cell modules. This, in turn, leads to water vapor penetration and a decrease in the power generation efficiency of the cell modules. Therefore, for POE films, the negative impact on processing efficiency caused by insufficient compatibility with crosslinking auxiliaries, auxiliary migration issues, and low crosslinking rates has long remained a challenge in the solar encapsulant film industry. Due to changes in solar module structures and trends toward thinner and larger cells, the demand for electrical insulation and processability of solar encapsulation films is increasing. Therefore, in this technical field, it is urgent to obtain olefin copolymers with improved processability that are applicable to solar encapsulation films. The following is a brief description of the subjects mentioned in the detailed description of this specification. However, the scope of protection of the present invention is not limited thereto. To solve the above technical problem, the present application provides an ethylene/α-olefin random copolymer for solar encapsulant films and its uses. The ethylene/α-olefin random copolymer according to the present application has a low content of the soluble fraction (SF) at 35°C or lower and a uniform branched chain distribution. As a result, when applied to a solar encapsulant film, it has a fast crosslinking rate and a high degree of crosslinking, and has improved processing performance. Furthermore, the obtained solar encapsulant film has high light transmittance and excellent sealing performance. An ethylene/α-olefin random copolymer for a solar encapsulant film provided in the first aspect, having ethylene monomer units and C3-C8 α-olefin monomer units, (i) a molar content (molar percentage) of the soluble fraction (SF) at 35°C or lower, measured by a gradient heating elution method, of 0.5% to 3% (e.g., 0.55%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.5%, 2.8%), optionally 0.5% to 1.5%, and a weight-average molecular weight of the soluble fraction of 20,000 g/mol or less (e.g., 18,000 g/mol, 15,000 g/mol, 12,000 g/mol, 10,000 g/mol, 8,000 g/mol, 6,000 g/mol, 5,000 g/mol, 4,000 g/mol, 2,000 g/mol, 1,000 g/mol, 500 g/mol); and (ii) The total number of branched chains per 1,000 carbon atoms in the copolymer chain structure is 25 to 85 (e.g., 26, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, 55, 60, 65, 70, 75, 80, 82, 84), and additionally, the fitting coefficient of