Ethylene-α-olefin copolymer, and encapsulant composition containing same

Abstract

The present application relates to the field of olefin polymerization. Provided are an ethylene-α-olefin copolymer, a preparation method therefor, an encapsulant composition comprising the ethylene-α-olefin copolymer, and an encapsulant film formed by using the encapsulant composition. The ethylene-α-olefin copolymer has the following properties: the density is 0.860-0.905 g / cm3; according to a GPC test, the weight-average molecular weight is 20000-200000 g / mol with a unimodal distribution, and the molecular weight distribution polydispersity index (PDI) range is 2.3-3; and according to a TGIC test, said copolymer has two elution peaks, the temperature difference between the two peaks being 5-30 ℃, and the highest elution temperature in an obtained TGIC curve is not higher than 125 ℃. The ethylene-α-olefin copolymer is used for encapsulating solar cells, has relatively high mechanical properties, can shorten the mixing time of auxiliaries or improve the degree of crosslinking during processing, and exhibits a good performance in casting for film formation, thus effectively reducing the generation of fisheyes.

Description

An ethylene-α-olefin copolymer and an encapsulating composition comprising the thereof Technical Field

[0001] This application relates to the field of olefin polymerization, such as an ethylene-α-olefin copolymer that improves crosslinking degree or shortens additive mixing time and has high mechanical strength, a method for preparing the copolymer, an encapsulating composition including the copolymer, and a solar cell encapsulation film formed using the encapsulating composition. Background Technology

[0002] In the field of polymer materials, polyolefins occupy a pivotal position, accounting for the largest share of production. They possess significant characteristics such as low cost, low density, and ease of molding and processing, leading to their widespread application in various fields including industry, agriculture, military, and medicine. Polyethylene, in particular, holds a crucial position in the polyolefin industry, currently being the most widely produced general-purpose synthetic resin globally.

[0003] Furthermore, through the copolymerization reaction of ethylene and α-olefins, we can prepare a copolymer that combines the excellent plasticity of plastics with the high elasticity of rubber. This copolymer plays an important role in the development of cutting-edge polyolefin materials and is considered one of the mainstream trends for future development.

[0004] With the increasing severity of global environmental problems and the energy crisis, solar cells have received growing attention due to their environmentally friendly, pollution-free, and inexhaustible energy characteristics. Modular solar cells have become the preferred choice, especially in outdoor applications such as building rooftops. These modules typically employ a multi-layered stacking structure, consisting of a front glass layer, a solar cell encapsulant layer, crystalline solar cell units, another layer of solar cell encapsulant, and finally a rear glass layer (or rear protective sheet).

[0005] In the encapsulation process of solar cells, ethylene / vinyl acetate copolymers or ethylene-α-olefin copolymers, which possess good transparency, flexibility, and adhesion properties, are typically chosen as key encapsulation materials. In particular, ethylene-α-olefin copolymers, due to their excellent anti-PID properties, are gradually becoming dominant in photovoltaic cell encapsulation technology and foreshadow future development trends. However, when fabricating photovoltaic films from these copolymers, sufficient mechanical strength must be ensured; therefore, the fundamental mechanical properties of this material are crucial.

[0006] To improve its mechanical strength and heat resistance, the conventional approach is to add crosslinking agents. However, the problem is that commonly used crosslinking agents and additives have low affinity with ethylene-α-olefin copolymers, which may lead to insufficient crosslinking or a long mixing process, thus affecting the overall processing efficiency. This, to some extent, restricts the widespread application of ethylene-α-olefins in photovoltaic encapsulation. Furthermore, in the photovoltaic encapsulant film production process, polar additives must first be uniformly dispersed into the particles, and then the film is prepared using a casting machine at a temperature below the decomposition temperature of the crosslinking agent. Due to the relatively low processing temperature, grain aggregation may occur during film formation, affecting the lifespan of the final encapsulated photovoltaic cell.

[0007] Therefore, in response to this challenge, the industry urgently needs to continuously develop new ethylene-α-olefin copolymer materials with special properties, especially those ethylene-α-olefin copolymers with high strength and excellent casting properties to reduce crystal point formation, so as to promote their further application and development in the field of photovoltaic packaging.

[0008] Summary of the Invention

[0009] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0010] This application provides an ethylene-α-olefin copolymer, its preparation method, an encapsulating agent composition including the ethylene-α-olefin copolymer, and an encapsulating film formed using the encapsulating agent composition. The polymer exhibits specific properties, having a content of 0.860–0.905 g / cm³. 3 The density is as follows: the weight-average molecular weight is between 20,000 and 200,000 g / mol as measured by GPC, the molecular weight distribution curve is single-peaked and the molecular weight distribution width (PDI) ranges from 2.3 to 3; the elution peak measured by TGIC is double-peaked and the temperature difference between the two peaks is about 5 to 30℃, which meets the application requirements of photovoltaic films, has high mechanical properties, can shorten the mixing time of additives during processing or improve the degree of crosslinking, and has good casting film performance, effectively reducing the formation of crystal points.

[0011] According to a first aspect of this application, an ethylene-α-olefin copolymer is provided, which has the following properties:

[0012] (a) 0.860~0.905g / cm 3 The density; for example, it could be 0.860 g / cm³. 3 0.865g / cm 3 0.870 g / cm 3 0.875g / cm 3 0.880 g / cm 3 0.885g / cm3 0.890 g / cm 3 0.895g / cm 3 0.900g / cm 3 Or 0.905g / cm 3 g / cm 3 ;

[0013] (b) The weight-average molecular weight, as determined by GPC, is 20,000–200,000 g / mol, is unimodal, and has a molecular weight distribution width (PDI) range of 2.3–3; for example, it can be 20,000 g / mol, 30,000 g / mol, 40,000 g / mol, 50,000 g / mol, 60,000 g / mol, 70,000 g / mol, 80,000 g / mol, 90,000 g / mol, 100,000 g / mol, 110,000 g / mol, 120,000 g / mol, 130,000 g / mol, 140,000 g / mol, 150,000 g / mol, 160,000 g / mol, 170,000 g / mol, 180,000 g / mol, 190,000 g / mol, or 200,000 g / mol;

[0014] (c) The elution peaks measured by TGIC are bimodal, and the temperature difference between the two peaks is approximately 5–30 °C; for example, these can be 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 15 °C, 17 °C, 18 °C, 19 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, or 30 °C; the highest elution temperature in the obtained TGIC curve is not higher than 125 °C, for example, these can be 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, or 125 °C.

[0015] In one embodiment, the α-olefin comonomer insertion rate in the ethylene-α-olefin copolymer is 20 to 40 wt%, for example, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, or 40 wt%.

[0016] In one embodiment, the melt index MFR2 (190°C, 2.16 kg load) of the ethylene-α-olefin copolymer is 1–30 g / 10 min.

[0017] In one embodiment, the melting peak temperature Tm of the ethylene-α-olefin copolymer is 30–90°C.

[0018] In one embodiment, the α-olefin is a C3 to 20 olefin or a mixture thereof, more preferably selected from 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.

[0019] According to a second aspect of this application, a method for preparing the ethylene-α-olefin copolymer described in this application is provided, comprising the following steps:

[0020] Ethylene is solution polymerized with one or more α-olefins in the presence of a catalyst and optional chain transfer agent in a continuous reaction platform, wherein the continuous reaction platform comprises at least two reactors arranged in parallel and at least one reactor arranged in series with the at least two reactors arranged in parallel, and in the direction of travel of the reactants, the at least two reactors arranged in parallel are in front and the at least one reactor arranged in series is behind.

[0021] In one embodiment, reactors arranged in parallel use the same catalyst and independently carry out solution polymerization under different polymerization conditions to obtain ethylene-α-olefin copolymer reaction streams, which then enter reactors arranged in series for mixing and further reaction of the ethylene-α-olefin copolymer.

[0022] In one embodiment, the conditions for solution polymerization in each reactor of the continuous reaction platform are independently a temperature of 120–200°C and a pressure of 2–10 MPa, more preferably a temperature of 120–190°C and a pressure of 2–9 MPa.

[0023] In one embodiment, the pressure in each reactor of the continuous reaction platform is the same, the reaction temperature in each reactor connected in parallel is different, and the temperature of the reactors connected in series is the temperature after the streams in the parallel reactors merge.

[0024] In one embodiment, the continuous reaction platform includes two reactors arranged in parallel and one reactor arranged in series.

[0025] Suitable reactors are unstirred or stirred cylindrical and tank-like vessels, as well as circulating loop reactors or combinations thereof. The volume ratio of any two reactors in this continuous reaction platform is 1:5 to 5:1, for example, 1:5, 2:5, 3:5, 4:5, 1:1, 1:2, 1:3, 1:4, or 1:5.

[0026] The catalysts used in this application are homogeneous catalysts conventionally used in the art, such as metallocene catalysts and metallocene catalysts. Preferred catalysts include silyl(N-tert-butylamino)(tetramethylcyclopentadienyl)titanium chloride, dimethyl(N-tert-butylamino)(tetramethylcyclopentadienyl)dimethyltitanium, dimethyl(N-tert-butylamino)(fluorenyl)titanium chloride, (pentamethylcyclopentadienyl)trimethoxytitanium, diphenylmethylene(cyclopentadiene)(9-fluorenyl)zirconium chloride, dimethyldimethsilylbis(2-methyl-4-phenyl-1-indenyl)zirconium chloride, mesodimethylmethsilylbis(1-indenyl)zirconium chloride, (bis(methylcyclopentadiene)zirconium chloride), (bis(1,3-dimethylcyclopentadienyl)zirconium chloride). Zirconium chloride, (cyclopentadienyl)(1,2-dimethoxyethane)zirconium trichloride, diphenylsilyl(cyclopentadiene)(9-fluorenyl)zirconium dichloride, racemic dimethylsilylbis(2-methyl-1-indene)zirconium dichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, di-p-tolymethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, dimethylbis(propylcyclopentadienyl)hafnium, bis(n-butylcyclopentadiene)hafnium dichloride, dimethylsilylbis(2-methyl-4-phenylindene)zirconium dichloride, and compounds represented by the following formula.

[0027] In solution polymerization, the solvent is in a liquid or supercritical state under the polymerization conditions. The solvent is typically and preferably a hydrocarbon solvent. The liquid hydrocarbon solvent used is preferably a C5-12 alkane, which may be an unsubstituted or C1-4 alkyl-substituted alkane (e.g., pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, and hydrogenated naphtha), more preferably hexane, C6 mixed alkanes, methylcyclohexane, or IsoparE, etc.

[0028] The chain transfer agent can be a chain transfer agent commonly used in the art, such as hydrogen.

[0029] In the polymerization process described in this application, a co-catalyst may also be added. The co-catalyst is a combination of one or more of aluminoxane, alkylaluminum compound, and alkylaluminum chloride, or a combination of one or more of aluminoxane, alkylaluminum compound, and alkylaluminum chloride with one or more organoborides.

[0030] In one embodiment, the aluminum oxane includes methylaluminoxane (MAO) and modified methylaluminoxane (MMAO); the alkylaluminum compound includes triethylaluminum, triisobutylaluminum, and trioctylaluminum, etc.; the alkylaluminum chloride includes monochloroethylaluminum, sesquiethylaluminum, and dichloroethylaluminum, etc.; and the organoboronide is triphenylmethyltetra(pentafluorophenyl)borate, tri(pentafluorophenyl)boron, N,N-dimethylanilinetetra(pentafluorophenyl)borate, bis(octadecylmethyl)tertiaryaminetetra(pentafluorophenyl)borate, and dihydrotallowylmethyl)tertiaryaminetetra(pentafluorophenyl)borate.

[0031] In one embodiment, the molar ratio Al / M of aluminum in the co-catalyst to transition metal M in the main catalyst is 5 to 1000, for example, it can be 5, 10, 20, 50, 80, 100, 120, 140, 160, 180, 200, 300, 400, 500, 600, 700, 800 or 1000, more preferably 10 to 100.

[0032] In one embodiment, the molar ratio B / M of the organoboride to the transition metal M in the main catalyst is 0 to 10, for example, it can be 0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9 or 10, preferably 1 to 3.

[0033] According to another aspect of this application, an encapsulating agent composition comprising the ethylene-α-olefin copolymer is provided. By using the encapsulating agent composition, modified resin compositions, such as silane-modified resin compositions or aminosilane-modified resin compositions, can be prepared.

[0034] In one embodiment, the encapsulating agent composition is used to encapsulate a solar cell.

[0035] The encapsulating agent composition according to this application can improve the degree of crosslinking or shorten the mixing time of the additives and copolymers.

[0036] The encapsulating agent composition may also include other components conventionally added in the art, specifically, for example, one or more of crosslinking agents, antioxidants, coupling agents, and co-crosslinking agents. Of course, other additional components permitted in the art may also be included.

[0037] For example, the crosslinking agent can be a peroxide-based crosslinking agent, comprising, but not limited to, one or more combinations of the following compounds: tert-butyl peroxycarbonate isopropyl ester, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane, tert-butyl peroxycarbonate-2-ethylhexyl ester, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-pentylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxycarbonate, tert-pentyl peroxycarbonate, tert-pentyl peroxycarbonate, and tert-butyl peroxycarbonate of 3,3,5-trimethylhexanoate. The amount of crosslinking agent can be conventionally set by those skilled in the art as needed.

[0038] For example, the antioxidant may be one or more combinations of hindered phenolic antioxidants and phosphate ester antioxidants, including but not limited to compositions of one or more of the following compounds: β-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate n-octadecyl alcohol ester, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis(3,5-di-tert-butyl-4-hydroxypropionyl)hydrazine, 2,2'-oxamido-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate, N,N'-hexamethylenebis( 3,5-Di-tert-butyl-4-hydroxyphenylpropionamide), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)trione, triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 4,6-bis(octylthiomethyl)o-cresol, tris[2,4-di-tert-butylphenyl]phosphite, bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate. Based on 100 parts by weight of the ethylene-α-olefin copolymer, the amount of antioxidant can be 0.01-1 parts by weight, preferably 0.05-0.5 parts by weight.

[0039] For example, the coupling agent can be a silane coupling agent, including but not limited to one or more combinations of the following compounds: γ-methacryloyloxypropyltrimethoxysilane, γ-chloropropylmethoxysilane, vinylethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate, anilinemethyltriethoxysilane, and octyltrimethoxysilane. The amount of the coupling agent can be conventionally set by those skilled in the art as needed.

[0040] For example, the co-crosslinking agent can be one or more acrylate substances with multifunctional groups. Including but not limited to one or more combinations of the following substances: triallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated trimethylolpropane triacrylate, propionylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propionylated glycerol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, bis(trimethylolpropane tetraacrylate), bis(trimethylolpropane tetramethacrylate), propionylated pentaerythritol tetraacrylate, tricyclodecanediethanol diacrylate, propionylated neopentyl glycol diacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate. The amount of the crosslinking agent can be conventionally set by those skilled in the art as needed.

[0041] In some embodiments, based on 100 parts by weight of the ethylene-α-olefin copolymer, the encapsulating agent composition comprises: 100 parts by weight of the ethylene-α-olefin copolymer; 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight of a crosslinking agent; 0.01 to 1 part by weight, preferably 0.05 to 0.5 parts by weight of an antioxidant; 0.1 to 3 parts by weight, preferably 0.1 to 0.6 parts by weight of a coupling agent; and 0.1 to 5 parts by weight, preferably 0.1 to 2 parts by weight of a co-crosslinking agent.

[0042] According to another aspect of this application, an encapsulating film is provided, which is prepared using the encapsulating agent composition described in this application.

[0043] In one embodiment, the encapsulating film is a solar cell encapsulating film.

[0044] According to another aspect of this application, a method for preparing the encapsulating film described above is also provided, comprising the following steps: mixing and melting the components of the composition, extruding and casting them into a film, and then cooling and slitting the film. Specifically, a winding step may also be included. The specific process operations and process conditions of this preparation method can be performed with reference to conventional methods in the art, and there are no particular limitations thereto.

[0045] The present application will be described in more detail below with reference to embodiments. The embodiments provided are for illustrative purposes only and should not be construed as limiting the scope of the present application to this.

[0046] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0047] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0048] Figure 1 is a schematic diagram of the continuous reaction platform 1 used in Example 1;

[0049] Figure 2 is a schematic diagram of the continuous reaction platform 2 used in Example 2;

[0050] Figure 3 is a schematic diagram of the continuous reaction platform 3 used in Example 3;

[0051] Figure 4 is a schematic diagram of the continuous reaction platform 4 used in Example 4. Detailed Implementation

[0052] To help researchers in the field better understand this application, specific examples will be used to further describe this application below, but this is only for further detailed description and is not intended to limit the scope of this application.

[0053] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0054] The materials and reagents used in the following examples are all commercially available, as detailed below:

[0055] IsoparE, 100% hydrogenated naphtha, Mobil;

[0056] C6 mixed alkanes, 100% alkanes, Jingbo;

[0057] 1-Octenene, 98%, INEOS;

[0058] 1-Hexene, 99%, Leading Research Biotechnology;

[0059] Ethylene, polymerization grade, produced by Air Liquide;

[0060] 1-Butene, 99%, light source;

[0061] MMAO, a 7% aluminum solution, Noryon;

[0062] 8200, ethylene-octene copolymer, Dow;

[0063] LF675, ethylene-butene copolymer, LG;

[0064] Dimethicone (N-tert-butylamino) (tetramethylcyclopentadienyl)dimethyltitanium, 99%, Xinnoco is M1;

[0065] Dimethicone (N-tert-butylamino) (fluorenyl) titanium dichloride, 99%, strem, denoted as M2;

[0066] Triisobutylaluminum hexane solution, 1 mol / L, Inokai;

[0067] NN dimethylaniline tetrapentafluorophenyl borate, 99%, Inokai, soluble in toluene, designated as B1;

[0068] Diphenylmethylenecyclopentadiene (2,7-dimethyl-fluorenyl)zirconium dichloride, Yaodexin Chemical, 98%, designated as M3;

[0069] Compound (M4) was synthesized according to Example 15 of patent CN 114315883 A;

[0070] 2-Ethylhexyl carbonate tert-butyl peroxide, Akzo Corporation, purity >95%;

[0071] Triallyl isocyanurate, Acros, 98% purity;

[0072] γ-Methacryloxypropyltrimethoxysilane, Aladdin, purity 95%;

[0073] γ-(2,3-epoxypropoxy)propyltrimethoxysilane, Aladdin, 95% purity;

[0074] Bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite, Acros, purity 95%;

[0075] β-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate n-octadecyl alcohol ester, ark, purity 95%;

[0076] 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, Acros, 95% purity;

[0077] Amyl peroxide carbonate, Ark, purity 95%;

[0078] Trimethylolpropane triacrylate, Aladdin, 98% purity;

[0079] Antioxidant 1076, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester, Lianlong New Materials Co., Ltd., industrial grade;

[0080] Antioxidant 1010, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], Lianlong New Materials Co., Ltd., industrial grade;

[0081] The melting peak temperature T of the polymers obtained in the following examples and comparative examples m The enthalpy of fusion was measured using DSC, with data obtained from the second heating cycle at a rate of 10℃ / min. The specific testing procedure involved cutting the sample granules and performing DSC analysis on a Mettler DSC 3 differential scanning calorimeter using an FRS6+ sensor. Programmed temperature control was employed: initial temperature 25℃, increased to 160℃ at 10℃ / min, then decreased to -100℃ at 10℃ / min, held for 3 minutes, and then increased to 160℃ at 10℃ / min. Nitrogen flow rate was 50 mL / min, and sample volume was 5-10 mg. Calibration was performed using In and Zn standards.

[0082] The TGIC elution temperature of the samples was analyzed using a PolymerChart TGIC instrument: the samples were dissolved in trichlorobenzene at 165℃ and passed through a TGIC column. The temperature was then programmed to decrease to 40℃ (20℃ / min). Some polyolefin structures adhered to the column due to adsorption and crystallization with the graphite column. The soluble fraction was washed at a flow rate of 0.5 ml / min and detected by detector IR5. The temperature was then increased to 165℃ at a rate of 2℃ / min. The molecules attached to the column were eluted sequentially according to their crystallization ability and the number of short branches.

[0083] In the examples and comparative examples, the polymer density was measured using a densitometer. Samples cut from the compression plates were tested for density using a Mettler XS204 densitometer via an impregnation method with anhydrous ethanol (AR) as the impregnation solution. The testing environment temperature was 23℃±2℃; the testing temperature required internal calibration. The sample mass was greater than 1g and free of air bubbles. The mass of the sample in air and in the impregnation solution were weighed separately, and the sample density was calculated using Archimedes' principle.

[0084] The molecular weight, molecular weight distribution, and comonomer insertion rate of the polymers obtained in the examples and comparative examples were analyzed using a GPC-IR instrument from PolymerChart. This instrument has three tandem MIXED columns, each 300*7.5mm in size, and is equipped with infrared, viscosity, and laser detectors. The IR5 MCT infrared detector specifically designed for polyolefins was commonly used for detection. 8 ml of trichlorobenzene solvent was automatically injected into the high-temperature zone (160°C) of the instrument's autosampler. After shaking and dissolving for one hour, 200 μL was extracted for testing. The infrared detector temperature was 150°C. The molecular weight standard used was PS, and the monomer calibration lines were established using a series of POEs with different monomer content gradients.

[0085] The entire embodiment is carried out in the continuous reaction platforms shown in Figures 1-4. Continuous reaction platform 1, as shown in Figure 1, consists of two 25L stirred tank reactors connected in parallel, and then connected in series with one other 25L stirred tank reactor. Continuous reaction platform 2, as shown in Figure 2, consists of one 25L circulating tubular reactor and one 5L stirred tank reactor connected in parallel, and then connected in series with one other 25L stirred tank reactor. Continuous reaction platform 3, as shown in Figure 3, consists of one 15L circulating tubular reactor and one 25L stirred tank reactor connected in parallel, and then connected in series with one other 25L circulating tubular reactor. Continuous reaction platform 4, as shown in Figure 4, consists of two 25L circulating tubular reactors connected in parallel, and then connected in series with one other 25L circulating tubular reactor.

[0086] Examples 1 to 4

[0087] The polymerization of ethylene and α-olefins was carried out on the polymerization platform shown in Figures 1 to 4. The solvent, α-olefin comonomers (octene, hexene, or butene), and ethylene were continuously fed into their respective reactors at the feed rates shown in Table 1 after deoxygenation and dehydration in a fixed bed. Simultaneously, the catalyst and co-catalyst were prepared into solutions and fed into their respective reactors. The reaction liquids from the two parallel reactors were mixed in a series reactor, then devolatilized and granulated to obtain the product, which was then sampled for analysis. The heat exchanger and reaction jacket before the reactors controlled the reaction at a specified temperature. The pressure was controlled by a pneumatic proportional control valve at the outlet of the series reactor; the pressure was hydraulic, meaning the pressure in the series reactor was the same as the pressure in the other two reactors. The temperature was the temperature after the streams from the two reactors were mixed and was not specially controlled. The relevant product characteristics are shown in Table 2.

[0088] Example 5

[0089] To 1000g of the ethylene-α-olefin copolymer obtained in Example 1, add 8g of 2-ethylhexyl tert-butyl peroxide, 4.5g of triallyl isocyanurate, 2g of γ-methacryloyloxypropyltrimethoxysilane, 1g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 1g of bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite and 1g of β-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate n-octadecyl alcohol ester.

[0090] The above raw materials were heated to 50°C and mixed uniformly for 3 hours. The extruder parameters were adjusted so that the temperature from the feed port to the die head was 80°C, 90°C, 90°C, 90°C, 90°C, 95°C, 95°C, 95°C, 95°C, the screw speed was 45 rpm, the traction speed was 0.7 rpm, and the winding speed was 1.3 rpm. After extrusion, casting, cooling, slitting, and winding processes, a solar cell encapsulation film with a thickness of 0.6 mm was prepared.

[0091] Example 6

[0092] To 1000g of the ethylene-α-olefin copolymer obtained in Example 2, add 6g of 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1.5g of tert-amyl peroxycarbonate, 3.8g of trimethylolpropane triacrylate, 2g of γ-methacryloyloxypropyltrimethoxysilane, 1g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1g of antioxidant 1076 and 1g of antioxidant 1010.

[0093] The above raw materials were heated to 50°C and mixed uniformly for 3 hours. The extruder parameters were adjusted so that the temperature from the feed port to the die head was 80°C, 90°C, 90°C, 90°C, 90°C, 95°C, 95°C, 95°C, 95°C, the screw speed was 45 rpm, the traction speed was 0.7 rpm, and the winding speed was 1.3 rpm. After extrusion, casting, cooling, slitting, and winding processes, a solar cell encapsulation film with a thickness of 0.6 mm was prepared.

[0094] Example 7

[0095] Except that the ethylene-α-olefin copolymer obtained in Example 3 was used to replace the ethylene-α-olefin copolymer obtained in Example 1, the solar cell encapsulation film was prepared in the same manner as in Example 5.

[0096] Example 8

[0097] The solar cell encapsulating film was prepared in the same manner as in Example 5, except that the ethylene-α-olefin copolymer obtained in Example 4 was used to replace the ethylene-α-olefin copolymer obtained in Example 1.

[0098] Comparative Example 4

[0099] The solar cell encapsulation film was prepared in the same manner as in Example 5, except that the ethylene-α-olefin copolymer obtained in Comparative Example 1 was used instead of the ethylene-α-olefin copolymer obtained in Comparative Example 1.

[0100] Comparative Example 5

[0101] The solar cell encapsulation film was prepared in the same manner as in Example 5, except that the ethylene-α-olefin copolymer obtained in Comparative Example 2 was used to replace the ethylene-α-olefin copolymer obtained in Example 1.

[0102] Comparative Example 6

[0103] Except that the ethylene-α-olefin copolymer obtained in Comparative Example 3 was used to replace the ethylene-α-olefin copolymer obtained in Example 1, the solar cell encapsulation film was prepared in the same manner as in Example 5.

[0104] Example 9

[0105] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Example 5.

[0106] Example 10

[0107] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Example 6.

[0108] Example 11

[0109] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Example 7.

[0110] Example 12

[0111] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Example 8.

[0112] Comparative Example 7

[0113] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Comparative Example 4.

[0114] Comparative Example 8

[0115] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Comparative Example 5.

[0116] Comparative Example 9

[0117] Except for heating the raw materials to 50°C and mixing them uniformly for only 2 hours, the solar cell encapsulation film was prepared in the same manner as in Comparative Example 6.

[0118] Table 3 Number of crystal points after ethylene-α-olefin copolymer is cast into film

[0119] The crystal points in Table 3 were tested according to the ASTM D3351 standard.

[0120] As shown in Table 3, the number of crystal points of the ethylene-α-olefin copolymer described in this application after casting into a film is significantly reduced compared to the number of crystal points of the copolymer in Comparative Example 1.

[0121] Crosslinking degree was evaluated according to the standards of the China Photovoltaic Industry Association (CPIA) and ASTM D2765. The obtained solar cell encapsulation film was cut into 10cm×10cm pieces and vacuum-laminated at 150°C for 20 minutes (5 minutes of vacuum / 1 minute of pressure / 14 minutes of decompression) to obtain crosslinked samples.

[0122] The crosslinked samples were cut into appropriate sizes, and 0.5 g was weighed onto a 200-mesh wire mesh cage and dissolved in xylene under reflux for 5 hours. Afterward, the samples were dried in a vacuum oven, and the weights before and after reflux were compared to measure the degree of crosslinking for each sample. The degree of crosslinking information obtained from each example and comparative example is shown in Table 4.

[0123] Table 4. Crosslinking degree data for different embodiments and comparative examples.

[0124] As shown in Table 4, referring to Examples 5-8 and Comparative Examples 5-6, the ethylene-α-olefin copolymer described in this application can improve the crosslinking degree of photovoltaic encapsulant films. Referring to Examples 9-12 and Comparative Examples 7-9, the ethylene-α-olefin copolymer described in this application can maintain a high degree of crosslinking, exceeding the 85% required for photovoltaic encapsulant films, even with a shorter mixing time with additives during film formation. This is superior to the ethylene-α-olefin copolymers described in the comparative examples, thus shortening the mixing time and improving processing efficiency. Because the ethylene-α-olefin described in this application facilitates the migration of additives from the particle surface to the particle interior, it achieves a higher degree of crosslinking at the same mixing time, or in other words, it can still meet the crosslinking requirements at a shorter mixing time.

[0125] The embodiments of this application have been described in detail above, but this application is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An ethylene-α-olefin copolymer, wherein, The ethylene-α-olefin copolymer has the following properties: (a) 0.860~0.905g / cm 3 The density; (b) The weight-average molecular weight, as determined by GPC, is 20,000–200,000 g / mol, and the molecular weight distribution curve exhibits a single peak with a molecular weight distribution width (PDI) ranging from 2.3 to 3; and (c) The elution peaks measured by TGIC are double peaks, and the temperature difference between the two peaks is 5 to 30 °C; the highest elution temperature in the obtained TGIC curve is not higher than 125 °C.

2. The ethylene-α-olefin copolymer according to claim 1, wherein, In the ethylene-α-olefin copolymer, the α-olefin comonomer insertion rate is 20 wt% to 40 wt%; and / or The temperature difference between the two elution peaks, as measured by TGIC, was 8–29 °C; and / or The α-olefin is a C3 to C20 olefin or a mixture thereof.

3. The ethylene-α-olefin copolymer according to claim 1 or 2, wherein, The ethylene-α-olefin copolymer has a melt flow index (MFR2) of 1–30 g / 10 min at 190 °C and under a load of 2.16 kg; and / or The highest elution temperature in the TGIC curve should not exceed 124°C; and / or The melting peak temperature Tm of the ethylene-α-olefin copolymer is 30–90 °C; and / or The α-olefin is selected from 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.

4. A method for preparing the ethylene-α-olefin copolymer according to any one of claims 1 to 3, wherein, It includes the following steps: Ethylene is solution polymerized with one or more α-olefins in a continuous reaction platform in the presence of a catalyst and optionally a chain transfer agent, wherein the continuous reaction platform comprises at least two reactors arranged in parallel and at least one reactor arranged in series with the at least two parallel reactors, and in accordance with the direction of travel of the reactants, the at least two parallel reactors are in front, and the at least one reactor arranged in series is behind; and / or Reactors arranged in parallel use the same catalyst and undergo solution polymerization independently under different polymerization conditions to obtain ethylene-α-olefin copolymer reaction streams. These streams then enter reactors arranged in series for mixing and further reaction of the ethylene-α-olefin copolymer; and / or The conditions for solution polymerization in each reactor of the continuous reaction platform are independently: a temperature of 120–200°C and a pressure of 2–10 MPa.

5. The method for preparing ethylene-α-olefin copolymer according to claim 4, wherein, The pressure is the same in each reactor of the continuous reaction platform, the reaction temperature is different in each reactor connected in parallel, and the temperature of the reactors connected in series is the temperature after the streams in the parallel reactors merge. Degree; and / or The volume ratio of any two reactors in the continuous reaction platform is 1:5 to 5:1; and / or The solution polymerization reaction in each reactor of the continuous reaction platform is carried out independently under the following conditions: a temperature of 120–190°C and a pressure of 2–9 MPa; and / or The catalyst is a metallocene catalyst or a metallocene catalyst; and / or The solvent used in solution polymerization is a hydrocarbon solvent; and / or A co-catalyst is used in the solution polymerization.

6. The method for preparing ethylene-α-olefin copolymer according to claim 5, wherein, The hydrocarbon flux is a C5-12 alkane; and / or The cocatalyst is a combination of one or more selected from aluminum oxanes, alkyl aluminum compounds, and alkyl aluminum chlorides, or a combination of one or more selected from aluminum oxanes, alkyl aluminum compounds, and alkyl aluminum chlorides with one or more organoborides.

7. An encapsulating agent composition, wherein, It comprises an ethylene-α-olefin copolymer according to any one of claims 1 to 3 or an ethylene-α-olefin copolymer obtained by the method for preparing an ethylene-α-olefin copolymer according to claim 4 or 5; and optionally the following components: It is selected from one or more components of crosslinking agents, antioxidants, coupling agents and co-crosslinking agents.

8. The encapsulating composition according to claim 7, wherein, The encapsulating agent composition comprises: 100 parts by weight of ethylene-α-olefin copolymer; 0.1 to 5 parts by weight of crosslinking agent; 0.01 to 1 part by weight of antioxidant; 0.1 to 3 parts by weight of coupling agent; and 0.1 to 5 parts by weight of crosslinking agent.

9. The encapsulating composition according to claim 7 or 8, wherein, The crosslinking agent is a peroxide-based crosslinking agent; and / or The antioxidant is one or more selected from hindered phenolic antioxidants and phosphate ester antioxidants; The coupling agent is a silane-based coupling agent; and / or The crosslinking agent is one or more acrylates with multifunctional groups.

10. An encapsulating film, wherein, The encapsulating film is prepared by using the encapsulating agent composition according to any one of claims 7 to 9.

11. The encapsulating film according to claim 10, wherein, The encapsulating film is a solar cell encapsulating film.

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