High light transmittance ethylene / α-olefin copolymer

Abstract

The ethylene / α-olefin copolymer of the present invention has a low glass transition temperature and high light transmittance, and can be used as a photovoltaic encapsulant. The present invention relates to an ethylene / α-olefin copolymer with high light transmittance that satisfies the following conditions (a) to (d): (a) a density of 0.855 g / cm 3 ~0.885g / cm 3 (b) the molecular weight distribution is 1.8 to 3.2; (c) the melt index under the conditions of 190°C and a load of 2.16 kg is 0.3 g / 10 min to 40 g / 10 min; (d) the high-temperature nuclear magnetic resonance carbon spectrum ( 13 The proportion of ethylene ternary sequences EEE<70% and the proportion of EXE+XEX>10% as measured by C-NMR, where E represents an ethylene unit and X represents an α-olefin unit.

Description

[Technical Field]

[0001] The present invention relates to ethylene / α-olefin copolymers with low glass transition temperatures and high light transmittance, and methods for preparing the same. [Background technology]

[0002] Influenced by factors such as global warming and the continuous consumption of non-renewable energy, the global energy consumption structure is accelerating its transition to a low-carbon society. Photovoltaic power generation, which is clean and sustainable, has already become an important new energy development trend and is rapidly emerging in countries and regions around the world. As the market share of twin-glass and N-type batteries increases, demand for polyolefin elastomer particles is experiencing rapid growth. Polyolefin elastomer POE is a thermoplastic elastomer obtained by in-situ polymerization of ethylene and α-olefin using a metallocene or non-metallocene catalyst. It has excellent water vapor barrier properties, weather resistance, and high volume resistivity, ensuring the safety and long-term aging resistance of photovoltaic modules in high-temperature and high-humidity environments. It is therefore widely used as an encapsulating and adhesive film material for photovoltaic modules.

[0003] While the continued improvement of photovoltaic module power generation efficiency requires more advanced cell technology, various auxiliary materials within the module must also ensure better encapsulation and aging resistance. As the encapsulant for modules, polyolefin elastomers directly determine the amount of solar light transmitted through the encapsulant and absorbed by the cell strips, so light transmittance is an important performance factor for the encapsulant. For polymer materials, light transmittance is closely related to factors such as crystallization performance. Increasing the light transmittance of polymers is crucial while ensuring that other performance factors, such as volume resistivity and yellowness index, meet requirements. At the same time, the encapsulant requires the addition of several small molecule additives when subsequently processed into an adhesive film. These additives are prone to decomposition and further affect the light transmittance of the adhesive film. Therefore, to improve module power generation performance, it is necessary to develop polyolefin elastomers with high light transmittance on the polymer particle side. Summary of the Invention

[0004] An object of the present invention is to provide an ethylene / α-olefin copolymer having a low glass transition temperature and high light transmittance, which is applicable to sealing adhesive film materials for photovoltaic modules.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows. An ethylene / α-olefin copolymer that satisfies the following conditions (a) to (d): (a) Density is 0.855 g / cm 3 ~0.885g / cm 3 and (b) the molecular weight distribution is 1.8 to 3.2; (c) A melt index of 0.3 g / 10 min to 40 g / 10 min under the conditions of 190 ° C and a load of 2.16 kg; (d) Nuclear magnetic resonance carbon spectrum ( 13 The percentage of ethylene ternary sequence EEE measured by C-NMR is less than 70%, and the percentage of EXE+XEX is more than 10%. Here, E represents an ethylene unit, and X represents an α-olefin unit.

[0006] In the present invention, the melt index of the ethylene / α-olefin copolymer is preferably 0.5 g / 10 min to 30 g / 10 min.

[0007] In the present invention, the ethylene / α-olefin copolymer preferably has an ethylene ternary sequence EEE ratio of 60.3% to 69.5%, an EXE ratio of 9.5% to 11.8%, and an XEX ratio of 1.2% to 1.82%.

[0008] In the present invention, the ethylene / α-olefin copolymer preferably has an ethylene ternary sequence EEE ratio of 63.5% to 69.5%, an EXE ratio of 9.5% to 11.8%, and an XEX ratio of 1.2% to 1.8%.

[0009] In the present invention, the melting temperature of the ethylene / α-olefin copolymer is 75° C. or less. Specifically, the melting temperature may be 50° C. or more, 55° C. or more, or 60° C. or more, and may be 70° C. or less, 68° C. or less, or 65° C. or less.

[0010] In the present invention, the glass transition temperature (Tg) of the ethylene / α-olefin copolymer is −45° C. or lower. Specifically, the glass transition temperature is −50° C. or lower, −55° C. or lower, or −60° C. or lower.

[0011] In the present invention, the weight average molecular weight Mw of the ethylene / α-olefin copolymer is 40,000 g / mol to 150,000 g / mol. Specifically, the weight average molecular weight may be 45,000 g / mol or more, 60,000 g / mol or more, or 70,000 g / mol or more, and may be 150,000 g / mol or less, or 80,000 g / mol or less.

[0012] In the present invention, the number average molecular weight Mn of the ethylene / α-olefin copolymer is 20,000 g / mol to 80,000 g / mol. Specifically, the number average molecular weight may be 25,000 g / mol or more, 30,000 g / mol or more, or 40,000 g / mol or more, and may be 80,000 g / mol or less, 60,000 g / mol or less, or 50,000 g / mol or less.

[0013] The weight average molecular weight (Mw) and number average molecular weight (Mn) are polystyrene-equivalent molecular weights analyzed by gel permeation chromatography (GPC), and the molecular weight distribution can be calculated from the ratio of Mw / Mn.

[0014] In the present invention, the α-olefin of the ethylene / α-olefin copolymer is an olefin having 3 to 20 carbon atoms, and includes one or more of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

[0015] In the present invention, the molar insertion rate of the α-olefin comonomer in the ethylene / α-olefin copolymer is 5% to 50%. Specifically, the molar insertion rate may be 10% or more, 15% or more, or 20% or more, and may be 50% or less, 45% or less, or 40% or less.

[0016] The present invention further relates to a method for preparing the above ethylene / α-olefin copolymers.

[0017] The process for preparing the ethylene / α-olefin copolymer of the present invention comprises polymerizing ethylene and an α-olefin in the presence of a catalyst composition comprising Compound A and Compound B.

[0018] The catalysts used to prepare the ethylene / α-olefin copolymer of the present invention include transition metal compounds represented by Compound A and Compound B. Since Compound A and Compound B have different polymerization activity and temperature resistance for α-olefin monomers, when these two compounds are used in combination, different process parameters can be controlled as needed to develop different copolymers.

[0019] In the present invention, the molar ratio of the transition metal compound represented by Compound A to Compound B may be, but is not limited to, 1:1 to 1:10, for example, 1:1.5 to 1:9, 1:2 to 1:5, or 1:2 to 1:4. The total amount of catalyst used can be determined by those skilled in the art depending on the catalytic activity and the weight of the target product.

[0020] As a result of research, it was found that the following three methods can be used to prepare copolymers with excellent light transmission performance. First, transition metal compound A and compound B with different copolymerization abilities with comonomers are used. Second, the flow rate ratio of ethylene to comonomer and the flow rate ratio with the mixed transition metal compound are adjusted and changed multiple times to make the comonomer insertion rate more uniform. Third, multiple types of comonomers are polymerized simultaneously, and the flow rate ratios of different comonomers are controlled so that different comonomers cause different degrees of destruction of ethylene crystal segments. In the present invention, the above three methods are used comprehensively to prepare copolymers with excellent transmission performance.

[0021] In the present invention, since the compound A and / or compound B has high polymerization activity, it is more preferable to use a co-catalyst in the catalyst composition, and the co-catalysts are broadly classified into two types: alkylaluminum or alkylaluminoxane compounds, and borate compounds. Specifically, the alkylaluminum or alkylaluminoxane compounds include trimethylaluminum, triethylaluminum, triisobutylaluminum, tripropylaluminum, tributylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO), ethylaluminoxane, isobutylaluminoxane, or t-butylaluminoxane, and the borate compounds include trimethylammonium tetraphenylborate, methylbisoctadecylammonium tetraphenylborate, triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tris(n-butyl)ammonium tetraphenylborate, methyltetradecyloctadecylammonium tetraphenylborate, N,N-dimethylanilinium tetraphenylborate, N,N-diethylanilinium tetraphenylborate, N,N-dimethyl(2,4,6-trimethylanilinium)tetraphenylborate, trimethyl N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-diethylanilinium tetrakis(pentafluorophenyl)borate, N,N-dimethyl(2,4,6-trimethylanilinium)tetrakis(pentafluorophenyl)borate, N,N-dimethyl(2,4,6-trimethylanilinium)tetrakis(pentafluorophenyl)borate, N,N-dimethyl(2,4,6-trimethylanilinium)tetrakis(pentafluorophenyl)borate, N,N-dimethyl(2,3 ...tetrakis(2,3,4,6-tetrafluorophenyl)borate, tripropylammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate, tris(n-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate, dimethyl(t-butyl)ammonium tetrakis(2,3,4,6-tetrafluorophenyl)borate, N,N-dimethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate, N,N-diethylanilinium tetrakis(2,3,4,6-tetrafluorophenyl)borate, or N,N-dimethyl-(2,4,6-trimethylanilinium)tetrakis(2,3,4,6-tetrafluorophenyl)borate. tri-substituted ammonium salt-type borate compounds such as bisoctadecylammonium tetrakis(pentafluorophenyl)borate, dialkylammonium salt-type borate compounds such as bistetradecylammonium tetrakis(pentafluorophenyl)borate, or dicyclohexylammonium tetrakis(pentafluorophenyl)borate, tri-substituted phosphate-type borate compounds such as triphenylphosphonium tetrakis(pentafluorophenyl)borate, methylbisoctadecylphosphonium tetrakis(pentafluorophenyl)borate, or tris(2,6-dimethylphenyl)phosphonium tetrakis(pentafluorophenyl)borate, etc., but are not limited to these.

[0022] The use of an appropriate amount of these cocatalysts results in a more uniform molecular weight distribution of the prepared ethylene / α-olefin copolymer and higher polymerization activity. In some specific embodiments, the ratio of the cocatalyst feed rate to the catalyst feed rate is 5 to 1000, preferably 10 to 100, in terms of metal molar ratio.

[0023] In the present invention, under the conditions of the catalyst composition, 3 / min~80cm 3 The polymerization reaction was suppressed by continuously introducing hydrogen gas at a rate of 1 cm / min. 3 / min or more or 5cm 3 / min or more or 10cm3 / min or more or 20cm 3 / min or more or 30cm 3 / min or more and 80cm 3 / min or less or 60cm 3 / min or less or 50cm 3 / min or less or 40cm 3 / min or less.

[0024] In the present invention, the polymerization reaction can be carried out at a temperature of 100 to 200°C, ensuring that the catalyst composition maintains high polymerization activity at an appropriate temperature. Specifically, the polymerization reaction temperature may be, but is not limited to, 100°C, 120°C, 140°C, 160°C, 180°C, or 200°C.

[0025] In the present invention, the polymerization reaction can be carried out at a pressure of 1 MPa to 7 MPa, ensuring that the catalyst composition maintains high polymerization activity at an appropriate pressure. Specifically, the polymerization reaction pressure may be, but is not limited to, 1 MPa, 3 MPa, 5 MPa, 6 MPa, or 7 MPa.

[0026] In the present invention, compound A is further described in Chinese Patent CN111484574A, which is incorporated herein by reference, and has the structure of Formula I below: [ka] In the formula I, R1 and R2 are the same or different and are each independently selected from hydrogen, a methyl group, an isopropyl group, and a t-butyl group. Preferably, R1 is selected from a methyl group, an isopropyl group, and a t-butyl group, and R2 is selected from hydrogen, a methyl group, and a t-butyl group. M is selected from titanium, zirconium, or hafnium, and is preferably zirconium.

[0027] Preferably, compound A according to the present invention has the following structure: [ka] Compound B is further described in Chinese Patent CN111909196B, which is incorporated herein by reference, and has the structure of Formula II: [ka] In the formula II, R3 is any one selected from a C3-10 cycloalkyl group, a C3-10 cycloalkyloxy group, a C3-10 dicycloalkylamino group, a C6-14 aryl group, a C6-14 aryloxy group, a C6-14 arylamino group, a dicyclohexanemethyl group, a dibenzocycloheptene group, an anthracene group, and a dicyclohexanophenyl group; R4 is hydrogen, halogen, or a C1-6 alkyl group, a C1-6 alkoxy group, a C3-10 cycloa T1 and T2 are the same or different, and both T1 and T2 are 1,2-ethylene, 1,3-propanediyl, 1,4-butanediyl, or 2,4-pentanediyl groups; X is a halogen, methyl, benzyl, or dimethylamino group; and M is selected from titanium, zirconium, or hafnium, preferably zirconium.

[0028] Preferably, compound B according to the present invention has the following structure: [ka] A large amount of α-olefin comonomer is inserted into the molecular chain of the ethylene / α-olefin copolymer of the present invention prepared using these mixed compounds as a catalyst, and the α-olefin comonomer is distributed in high-density regions of similar polyethylene segments, but also in large amounts among the ethylene monomers. This distribution destroys the crystals of the polyethylene segments, thereby reducing the lamella size of the copolymer and making it more uniform, resulting in better light transmission performance.

[0029] Typically, when two or more non-polar monomers are polymerized using solution polymerization, the molecular weight distribution becomes broad, which contributes to the processability of the polymer, but at the same time, some mechanical properties are lost. The molecular weight distribution is affected by the copolymerization performance of the catalyst for different monomers, and when two or more catalysts are used to prepare a copolymer, if the polymerization properties of the various catalysts differ significantly, the molecular weight distribution of the polymer will become broad.

[0030] To control the molecular weight of the polymer and maintain its good processability, it is necessary to introduce a certain amount of hydrogen gas at an appropriate time during the polymer reaction process to prevent the occurrence of β-hydrogen elimination reactions in the polymer chain and terminate the polymerization reaction, which results in a decrease in the molecular weight of the polymer and an increase in the melt index. Therefore, it is necessary to determine the appropriate catalyst type and amount of hydrogen gas introduced within a range that simultaneously satisfies the inherent characteristics of the catalyst structure that affect the molecular weight and molecular weight distribution and the molecular weight reduction effect of the introduction of hydrogen gas.

[0031] Generally, when the crystallinity distribution of a copolymer is high, the light transmittance decreases and the glass transition temperature increases due to the high crystal content. On the contrary, the copolymer of the present invention has a narrower lamellar size distribution index and a more uniform lamellar distribution, so it has excellent light transmittance and low-temperature resistance.

[0032] The present invention further relates to the use of the above ethylene / α-olefin copolymers.

[0033] The ethylene / α-olefin copolymer of the present invention can be used to form a resin composition together with auxiliary agents such as a crosslinking agent, a crosslinking aid, a silane coupling agent, a light stabilizer, an ultraviolet absorber, a precipitation prevention aid, and an anti-PID aid. In addition to the above components, various other additives known in the art can be appropriately contained depending on the application of the resin component to be applied.

[0034] In addition, the resin composition can be used to produce a photovoltaic sealing material by a molding method such as casting extrusion or twin-screw extrusion, and can be used, for example, to produce a sealing adhesive film for a photovoltaic module, thereby ensuring stable power generation performance of the battery chip for a long period of time.

[0035] beneficial effects The ethylene / α-olefin copolymer of the present invention has a low EEE ternary structure and a more uniform α-olefin distribution. The uniform insertion of α-olefin increases the breakage of ethylene crystalline segments and weakens the crystalline performance of the polymer. The copolymer has a thinner lamellar thickness, a narrower lamellar size distribution index, and a more uniform lamellar distribution, resulting in a low crystallinity. The low-crystallinity polymer has high transparency, which can enhance the strength of solar light incident on the surface of the cell strips in photovoltaic encapsulation adhesive films and further improve the power generation efficiency of the cell strips. At the same time, the low-crystallinity polymer has a low glass transition temperature, which allows the product to maintain excellent deformation resistance even at lower temperatures, ensuring that the battery module can be used for a long time in colder environments. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following provides a clear and complete description of the technical solutions in the embodiments of the present invention, but of course, the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without any creative effort fall within the scope of protection of the present invention.

[0037] Catalysts used in the examples and comparative examples [ka] [ka] Modified methylaluminoxane (MMAO): concentration 7 wt% Al, Isopar E solvent, Nouryon Chemicals (Ningbo) Co., Ltd.

[0038] Example 1 The solution polymerization reaction was carried out in a 10L continuous reactor, with the feed from the bottom and the discharge from the top. The solvent Isopar E was introduced at a rate of 40 kg / h, and the comonomers (octene, hexene, butene) and ethylene were deoxidized and dehydrated in a fixed bed, and then continuously fed to the reactor at the feed rate shown in Table 1. The catalyst and cocatalyst MMAO were prepared into a solution, which was then transported to the reactor at the feed rate shown in Table 1, with the catalyst concentration being 400 ppm (dissolved in Isopar E solvent). The reaction was controlled to occur at a predetermined temperature using a heat exchanger in front of the reactor and the reactor jacket, and the pressure was controlled by an air pressure proportional control valve at the reactor outlet. After the polymerization reaction is completed, the melt is devolatilized and granulated, and then sampled and analyzed. Other parameters are shown in Table 1. In Examples 2 to 4, copolymers with different performance were prepared by changing parameters such as the type of comonomer to be inserted, flow rate ratio, and amount of catalyst introduced. However, the catalyst flow rate is in μmol min -1 , The cocatalyst flow rate unit is mmol·min -1 is.

[0039] Comparative Examples 1 to 4 The copolymer was prepared by solution polymerization using essentially the same method as in the examples, with the difference being the adjustment of each process parameter, except for rac-ethylenebis(1-indenyl)dichlorozirconium (catalyst C), 99%.

[0040] [Table 1]

[0041] Performance analysis of ethylene / α-olefin copolymers The properties of the ethylene / α-olefin copolymers prepared in the above examples and comparative examples were measured by the following methods, and the results are shown in Table 2. (1) Density (g / cm 3 ) was measured according to ASTM D-792. (2) Melt index (g / 10 min) was measured in accordance with ASTM D-1238 (conditions: 190°C, 2.16 kg load). (3) The glass transition temperature (°C) can be measured using a PerkinElmer Differential Scanning Calorimeter (DSC 6000). Specifically, the copolymer is heated to 150°C under a nitrogen atmosphere using DSC, maintained at this temperature for 5 minutes, cooled to -100°C, and then heated again, followed by observation of the DSC curve. The heating and cooling rates are 10°C / min, respectively. (4) Molecular weight (MW), molecular weight distribution (MWD), and comonomer insertion rate can be obtained using gel permeation chromatography (GPC). Specifically, column: Agilent Olexis; solvent: trichlorobenzene; flow rate: 1.0 ml / min; sample concentration: 1.0 mg / ml; injection volume: 200 μl; column temperature: 160 °C; detector: Agilent High Temperature RI detector; standard: Polystyrene (corrected by a cubic function). (5) Comonomer distribution is 13C NMR can be used to test and obtain data. Specifically, 2.74 g of sample and 0.025 M Cr(AcAc)3 in tetrachloroethane-d2 were added to a Nore II 1001-7 10 mm NMR tube. The tube was manually purged with nitrogen gas using a Pasteur pipette for 1 minute to remove oxygen. The tube and its contents were heated to 150 °C using a heat plate, preferably without a heat gun, to dissolve and homogenize the sample. Therefore, the sample must be thoroughly mixed immediately before analysis and not cooled until inserted into the heated NMR probe. This is necessary to ensure that the sample is homogeneous and representative of the entire sample. Data collection was performed using a Bruker 400 MHz spectrometer equipped with a Bruker cryoprobe. Data were collected using 160 scans, a 6-second pulse delay, and a sample temperature of 120 °C. All measurements were performed on unspun samples in locked mode. The sample was allowed to thermally equilibrate for 7 minutes before data collection. 13 The C NMR chemical shifts corresponded to the EEE ternary sequence segment absorption peak at 30.0 ppm. For the butene comonomer, the chemical shifts corresponded to the EBE ternary sequence segment absorption peak at 39.7 ppm, 26.7 ppm, and 11.2 ppm, and the BEB ternary sequence segment absorption peak at 34.7 ppm. For the hexene comonomer, the chemical shifts corresponded to the EHE ternary sequence segment absorption peak at 38.1 ppm, 34.1 ppm, 29.5 ppm, 23.4 ppm, and 14.1 ppm, and the HEH ternary sequence segment absorption peak at 35.0 ppm. For the octene comonomer, the chemical shifts corresponded to the EOE ternary sequence segment absorption peak at 38.5 ppm, 32.4 ppm, 22.9 ppm, and 14.1 ppm, and the OEO ternary sequence segment absorption peak at 35.1 ppm. The proportion of the sum of the EBE, EHE, and EOE ternary sequences in the molecular chain is defined as the EXE proportion, and the proportion of the sum of the BEB, HEH, and OEO ternary sequences in the molecular chain is defined as the XEX proportion.

[0042] [Table 2]

[0043] Preparation of sealing adhesive film A certain amount of the ethylene / α-olefin copolymer prepared in each of the examples and comparative examples was weighed and thoroughly mixed with a crosslinking agent, crosslinking coagent, silane coupling agent, light stabilizer, UV absorber, antioxidant, anti-PID coagent, etc., and then added to a single-screw extruder. The mixed material was melt-plasticized and then injected into a T-die. Photovoltaic sealing adhesive films were produced through processes such as melt extrusion, casting, cooling, slitting, and winding. The components of the sealing adhesive films are listed in Table 3.

[0044] [Table 3]

[0045] The light transmittance was tested according to the spectrophotometer method of GB / T 2410-2008, and the average values ​​in the band ranges of 290 nm to 380 nm and 380 nm to 1100 nm were calculated, respectively, and the results are shown in Table 4.

[0046] [Table 4]

[0047] The results show that the light transmittance is closely related to the comonomer insertion rate and the proportion of ternary monomer.The present invention uses multiple methods to adjust the preparation of ethylene-alpha olefins, so that the polymer has high light transmittance and the photovoltaic module maintains high power generation efficiency.

Claims

1. The proportion of ethylene ternary sequences EEE<70% and the proportion of EXE+XEX>10% as measured by nuclear magnetic resonance carbon spectroscopy; wherein E represents an ethylene unit and X represents an α-olefin unit.

2. 2. The ethylene / α-olefin copolymer according to claim 1, wherein the proportion of ethylene ternary sequences EEE is 63.5% to 69.5%, the proportion of EXE is 9.5% to 11.8%, and the proportion of XEX is 1.2% to 1.8%.

3. 3. The ethylene / α-olefin copolymer according to claim 1, wherein the proportion of ethylene ternary sequences EEE is 60.3% to 69.5%, the proportion of EXE is 9.5% to 11.8%, and the proportion of XEX is 1.2% to 1.82%.

4. moreover, (a) Density is 0.855 g / cm ３ ~0.885g / cm ３ and (b) a molecular weight distribution of 1.8 to 3.2; (c) a melt index of 0.3 g / 10 min to 40 g / 10 min, preferably 0.5 g / 10 min to 30 g / 10 min, at 190°C under a load of 2.16 kg; The ethylene / α-olefin copolymer according to any one of claims 1 to 3, characterized in that it comprises the condition:

5. 5. The ethylene / α-olefin copolymer according to claim 1, wherein the melting temperature is 75° C. or less.

6. 6. The ethylene / α-olefin copolymer according to claim 1, wherein the glass transition temperature is −45° C. or lower.

7. 7. The ethylene / α-olefin copolymer according to claim 1, wherein the weight average molecular weight Mw is from 40,000 g / mol to 150,000 g / mol.

8. 8. Ethylene / α-olefin copolymer according to any one of claims 1 to 7, characterized in that it has a number average molecular weight Mn of from 20,000 g / mol to 80,000 g / mol.

9. 9. The ethylene / α-olefin copolymer according to claim 1, wherein the α-olefin is an olefin having from 3 to 20 carbon atoms.

10. 10. The ethylene / α-olefin copolymer of claim 1, wherein the α-olefin comprises at least one of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene.

11. 11. The ethylene / α-olefin copolymer according to any one of claims 1 to 10, wherein the molar insertion rate of the α-olefin comonomer is from 5% to 50%.

12. 12. The ethylene / α-olefin copolymer according to any one of claims 1 to 11, wherein the molar insertion rate of the α-olefin comonomer is from 10% to 20%.

13. A photovoltaic encapsulant material comprising the ethylene / α-olefin copolymer of any one of claims 1 to 12.

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