Ethylene / α-olefin copolymer and application thereof, and packaging adhesive film composition

Abstract

The present application relates to the technical field of olefin polymerization, and in particular to an ethylene / α-olefin copolymer and an application thereof, and a packaging adhesive film composition. The ethylene / α-olefin copolymer has the following characteristics: (a) the melting peak temperature measured by means of a differential scanning calorimeter (DSC) is 30-90°C, and the melting range width measured by means of the DSC is 75-90°C; and (b) dH(90) and dH(100) continuously measured by using the DSC and from nucleation / annealing (SSA), wherein 0≤dH(90)≤2J / g, and dH(100)=0. The ethylene / α-olefin copolymer of the present application has specific property characteristics, and when the polymer is used in an adhesive film processing process, a high degree of crosslinking is still maintained while the mixing time of the polymer and an auxiliary agent is shortened.

Description

Ethylene / α-olefin copolymer and its application, packaging film composition Technical Field

[0001] The present application relates to the technical field of olefin polymerization, for example, an ethylene / α-olefin copolymer and its application, and an encapsulating film composition. Background Art

[0002] Polyolefins are the product with the largest proportion among polymer materials. They have the characteristics of low cost, light weight, and easy molding and processing. Among them, ethylene / α-olefin copolymers have the plasticity of plastics and the high elasticity of rubber, and are one of the main directions of development of high-end polyolefin materials.

[0003] As global environmental problems, energy problems and the like are becoming increasingly serious, and solar cells have attracted attention as a means of generating energy without having to worry about environmental pollution and depletion. If solar cells are used outside (such as on the roof of a building), modular solar cells are generally used. When manufacturing a solar cell module, in order to obtain a crystalline solar cell module, it is necessary to stack the front glass / solar cell encapsulant / crystalline solar cell device / solar cell encapsulant / back glass (or back protective sheet) in sequence. As an encapsulant for a solar cell, ethylene / vinyl acetate copolymer or ethylene / α-olefin copolymer having excellent transparency, flexibility, adhesion, etc. is generally used.

[0004] Due to their excellent PID resistance, ethylene / α-olefin copolymers are becoming a mainstream and future development direction for photovoltaic cell encapsulation. However, when preparing ethylene / α-olefin copolymers into photovoltaic films, crosslinking aids are generally required to enhance their mechanical strength and heat resistance. However, the polar materials used for crosslinking (e.g., crosslinking agents, crosslinking aids) have low affinity with the ethylene / α-olefin copolymers, which can easily result in insufficient crosslinking or prolonged mixing time during additive addition, thus affecting processing efficiency and limiting the application of ethylene / α-olefins in photovoltaic encapsulation.

[0005] Therefore, there is a need to continuously develop ethylene / α-olefin copolymers with special properties in order to meet the application requirements in the photovoltaic encapsulation field.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In order to solve some problems existing in the application of ethylene / α-olefin copolymers in the field of photovoltaic encapsulation, the present application provides an ethylene / α-olefin copolymer and its application, and an encapsulation film composition. The ethylene / α-olefin copolymer has specific performance characteristics, can meet the application requirements of photovoltaic films, can solve the problems of long mixing time or insufficient cross-linking degree of additives added during the film processing process, and has good industrial prospects.

[0009] In a first aspect, an ethylene / α-olefin copolymer is provided, wherein the ethylene / α-olefin copolymer has the following characteristics:

[0010] (a) a melting peak temperature of 30 to 90°C (e.g., 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C) and a melting range of 75 to 90°C (e.g., 78°C, 80°C, 82°C, 84°C, 85°C, 88°C, 89°C) as measured by DSC;

[0011] (b) dH(90) and dH(100) measured using a differential scanning calorimeter sequentially from nucleation / annealing (SSA), where 0≤dH(90)≤2 J / g (e.g., 0.01 J / g, 0.05 J / g, 0.1 J / g, 0.2 J / g, 0.4 J / g, 0.5 J / g, 0.8 J / g, 1.0 J / g, 1.2 J / g, 1.5 J / g, 1.8 J / g), and dH(100)=0.

[0012] The melting range of a polymer is a temperature range called the melting range. The two limits are called the initial melting temperature and the final melting temperature. The initial melting temperature is the temperature at which the substance begins to melt, and the final melting temperature is the temperature at which the substance is completely melted. In this text, the melting range width is the difference between the temperature at which the polymer is completely melted and the temperature at which it begins to melt, that is, T endset With T onset The difference.

[0013] In this text, in the results of SSA measurements using a differential scanning calorimeter, when the heat capacity of each segment is graded relative to the total heat capacity by integrating the temperature-heat capacity curve of each segment, dH(90) represents the sum of the melting enthalpies above 90°C, and dH(100) represents the sum of the melting enthalpies above 100°C.

[0014] According to the ethylene / α-olefin copolymer provided herein, in some embodiments, the ethylene / α-olefin copolymer further has the following characteristics:

[0015] (c) Density 0.850 to 0.905 g / cm 3 , for example, 0.852 g / cm 3 , 0.855g / cm3 , 0.86g / cm 3 , 0.87g / cm 3 、0.88g / cm 3 , 0.89g / cm 3 , 0.90g / cm 3 、0.904g / cm 3 ;

[0016] (d) a weight average molecular weight of 20,000 to 150,000 g / mol (e.g., 25,000 g / mol, 30,000 g / mol, 50,000 g / mol, 60,000 g / mol, 80,000 g / mol, 100,000 g / mol, 120,000 g / mol, 140,000 g / mol), and a molecular weight distribution width (PDI) of 2.3 to 3 (e.g., 2.35, 2.4, 2.5, 2.6, 2.8, 2.9, 2.95).

[0017] In some embodiments, the ethylene / α-olefin copolymer has a melting enthalpy of 20 to 100 J / g, for example, 22 J / g, 25 J / g, 30 J / g, 40 J / g, 50 J / g, 60 J / g, 80 J / g, 90 J / g, or 95 J / g.

[0018] In some embodiments, the ethylene / α-olefin copolymer has a melt index (MI) of 0.1 to 30 g / 10 min at 190° C. and a load of 2.16 kg, for example, 0.2 g / 10 min, 0.5 g / 10 min, 1.0 g / 10 min, 2.0 g / 10 min, 5.0 g / 10 min, 8.0 g / 10 min, 10 g / 10 min, 12 g / 10 min, 15 g / 10 min, or 18 g / 10 min.

[0019] In some embodiments, the glass transition temperature Tg of the ethylene / α-olefin copolymer is -65°C to -30°C, for example, -62°C, -60°C, -55°C, -50°C, -45°C, -40°C, -38°C, -35°C, or -32°C.

[0020] In some embodiments, in the ethylene / α-olefin copolymer, the α-olefin is a C3-C20 olefin or a mixture thereof.

[0021] In some embodiments, 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.

[0022] In some embodiments, the ethylene / α-olefin copolymer is a product obtained by solution polymerization of ethylene and one or more α-olefins in the presence of a catalyst and, optionally, hydrogen as a chain transfer agent.

[0023] In some embodiments, the solution polymerization reaction is carried out in one or more polymerization reactors.

[0024] In some embodiments, the polymerization reactor is one or more of a non-stirred or stirred cylindrical vessel, a tank vessel, and a circulating loop reactor.

[0025] In some embodiments, (when the polymerization reactor is a cylindrical container) the length-to-diameter ratio of the cylindrical container is 2:1 to 3:1 (e.g., 2.1:1, 2.2:1, 2.4:1, 2.5:1, 2.8:1), (when the polymerization reactor is a canister container) the length-to-diameter ratio of the canister container is 2:1 to 3:1 (e.g., 2.1:1, 2.2:1, 2.4:1, 2.5:1, 2.8:1), (when the polymerization reactor is a circulating loop reactor) the circulation ratio of the circulating loop reactor is 20 to 40 (e.g., 22, 24, 25, 26, 28, 30, 32, 35, 38).

[0026] In a polymerization reaction, the aspect ratio or circulation ratio of the reactor will cause the material entering the reactor to have a temperature distribution and a concentration distribution. Then, the relevant characteristics of the polymer obtained can be regulated by regulating the aspect ratio or circulation ratio of the reactor. Of course, it is not ruled out that there are other means to achieve the regulation of the relevant characteristics of the polymer obtained. For example, by controlling the aspect ratio and circulation ratio of the reactor, the temperature distribution and concentration distribution inside the reaction system can be adjusted, thereby achieving the regulation of the ethylene amount, comonomer amount and temperature in the microscopic region, further achieving the adjustment of the catalyst reactivity ratio in different temperature regions of the microscopic region, and ultimately achieving the generation of polymers with specific properties (such as melting range width, dH(90), dH(100)).

[0027] In the solution polymerization process, a solvent is also present. The solvent is in a liquid or supercritical state under the polymerization conditions. The solvent can be a hydrocarbon solvent. The liquid hydrocarbon solvent used can be, for example, a C5-C12 hydrocarbon compound, for example, selected from hydrocarbons that are unsubstituted or substituted with a C1-C4 alkyl group (e.g., pentane, methylpentane, hexane, C6 mixed alkanes, cyclohexane, methylcyclohexane, heptane, octane, hydrogenated naphtha), optionally, selected from one or more of hexane, C6 mixed alkanes, methylcyclohexane and Isopar E.

[0028] In some embodiments, in a solution polymerization reaction, the catalyst includes a main catalyst and a co-catalyst.

[0029] In some embodiments, the main catalyst is a homogeneous catalyst selected from a metallocene catalyst or a non-metallocene catalyst.

[0030] In some embodiments, the main catalyst can be selected from, but not limited to, methylsilyl (N-tert-butylamino) (tetramethylcyclopentadienyl) titanium dichloride, dimethylsilyl (N-tert-butylamino) (tetramethylcyclopentadienyl) dimethyl titanium, dimethylsilyl (N-tert-butylamino) (fluorenyl) titanium dichloride, (pentamethylcyclopentadienyl) trimethoxytitanium, dibenzylidene (cyclopentadienyl) (9-fluorenyl) zirconium dichloride, dimethyldisilyl bis (2-methyl-4-phenyl-1-indenyl) zirconium dichloride, mesodimethylsilyl bis (1-indenyl) zirconium dichloride, bis (methylcyclopentadienyl) zirconium dichloride, bis (1,3-dimethylcyclopentadienyl) Zirconium dichloride, (cyclopentadienyl)(1,2-dimethoxyethane)zirconium trichloride, diphenylsilyl(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, racemic dimethylsilylbis(2-methyl-1-indenyl)zirconium dichloride, dibenzylidenecyclopentadienyl(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, di-p-tolylidenecyclopentadienyl(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, dimethylbis(propylcyclopentadienyl)hafnium, bis(n-butylcyclopentadienyl)hafnium dichloride, dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, and one or more compounds represented by the following formulas (I) to (VIII);

[0031] From left to right and from top to bottom, they are Formula (IV) to Formula (VIII).

[0032] In some embodiments, the cocatalyst is one or more of aluminoxane, alkylaluminum compound and alkylaluminum chloride, or a combination of one or more of aluminoxane, alkylaluminum compound, alkylaluminum chloride and one or more organic boron compounds; for example, the cocatalyst is a combination of aluminoxane and organic boron compound, a combination of alkylaluminum compound and organic boron compound, or a combination of alkylaluminum chloride and organic boron compound.

[0033] In some embodiments, the aluminoxane is selected from methylaluminoxane (MAO) and modified methylaluminoxane (MMAO).

[0034] In some embodiments, the alkyl aluminum compound is selected from triethylaluminum, triisobutylaluminum, and trioctylaluminum.

[0035] In some embodiments, the alkylaluminum chloride is selected from ethylaluminum monochloride, ethylaluminum sesquichloride, and ethylaluminum dichloride.

[0036] In some embodiments, the organic boron compound is selected from trityltetrakis(pentafluorophenyl)borate, tris(pentafluorophenyl)boron, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, dioctadecylmethyltertiaryaminetetrakis(pentafluorophenyl)borate, and dihydrogenated tallow methyltertiaryaminetetrakis(pentafluorophenyl)borate.

[0037] Furthermore, the molar ratio Al / M of the metal aluminum in the co-catalyst to the metal M in the main catalyst is 3-1000, for example, 5, 10, 20, 50, 80, 100, 120, 140, 160, 180, 200, 300, 400, 500, 600, 700, 800, 900, and can be optionally 10-100.

[0038] Furthermore, the molar ratio B / M of the organic boron compound (measured in boron) in the co-catalyst to the 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, 9.5, etc., and can be optionally 1 to 3.

[0039] In some embodiments, the solution polymerization reaction is carried out at 2 to 10 MPa (e.g., 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 5.5 MPa, 6.0 MPa, 7.0 MPa, 8.0 MPa, 9.0 MPa), optionally 2 to 5 MPa.

[0040] In some embodiments, the reaction temperature of the solution polymerization reaction is 100-220°C, for example, 110°C, 120°C, 140°C, 150°C, 180°C, 200°C, or 210°C.

[0041] Herein, the ethylene / α-olefin copolymer can be prepared by conventional polymerization processes in the art. For example, in solution polymerization, the relevant process conditions and equipment can also be conventionally selected in the art and will not be described in detail here.

[0042] In a second aspect, a use of the ethylene / α-olefin copolymer described above in the field of photovoltaic encapsulation films is provided.

[0043] The application of the ethylene / α-olefin copolymer in the field of photovoltaic films can be achieved through conventional operations in this field, which will not be described in detail here.

[0044] For example, the ethylene / α-olefin copolymer can be used to prepare a cast film in the field of photovoltaic films through a casting process.

[0045] For example, the present application provides an encapsulant film composition comprising the ethylene / α-olefin copolymer, and a cast photovoltaic film can be obtained by subjecting the encapsulant film composition to a casting process; or the encapsulant film composition can also be used to prepare a modified resin composition (for example, a silane-modified resin composition or an aminosilane-modified resin composition).

[0046] In a third aspect, a solar cell encapsulation film composition is provided, comprising: the ethylene / α-olefin copolymer as described above and an optional auxiliary agent.

[0047] According to the composition provided herein, in some embodiments, the ethylene / α-olefin copolymer has the following characteristics:

[0048] (a) The melting peak temperature measured by DSC is 30-90°C, and the melting range width is 75-90°C;

[0049] (b) dH(90) and dH(100) measured using differential scanning calorimetry with continuous self-nucleation / annealing (SSA), where 0≤dH(90)≤2 J / g and dH(100)=0.

[0050] The ethylene / α-olefin copolymer also has the following characteristics:

[0051] (c) Density 0.850 to 0.905 g / cm 3 ;

[0052] (d) The weight average molecular weight is 20,000 to 150,000 g / mol, and the molecular weight distribution width PDI is 2.3 to 3.

[0053] The ethylene / α-olefin copolymer has a melting enthalpy of 20 to 100 J / g; a melt index (MI) of 0.1 to 30 g / 10 min at 190° C. and a load of 2.16 kg; and a glass transition temperature Tg of -65° C. to -30° C.

[0054] Of course, the solar cell encapsulation film composition provided in the present application may also include other additional components allowed in the art.

[0055] According to the composition provided herein, in some embodiments, the auxiliary agent is selected from one or more of a cross-linking agent, a co-cross-linking agent, a coupling agent and an antioxidant.

[0056] Further, the cross-linking agent can be a peroxide cross-linking agent, including but not limited to one or more combinations of the following compounds: tert-butyl peroxy isopropyl carbonate, 2,5-dimethyl-2,5-(bis-tert-butylperoxy)hexane, tert-butyl peroxy-2-ethylhexyl carbonate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)butane, tert-butyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxy carbonate, tert-butyl peroxy-3,3,5-trimethylhexanoate. Based on 100 parts by weight of the ethylene / α-olefin copolymer, the amount of the crosslinking agent can be 0.1-5 parts by weight (for example, 0.15 parts by weight, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 1.0 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 3.0 parts by weight, 4.0 parts by weight), and can optionally be 0.5-2 parts by weight.

[0057] Furthermore, the auxiliary cross-linking agent can be a combination of one or more multifunctional acrylate substances, including but not limited to a combination of one or more of the following substances: triallyl isocyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, tris(2-hydroxyethyl)isocyanuric acid triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, pentaerythritol tetrapropylene glycol, propylene glycol triacrylate ... Acrylates, ethoxylated pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, ditrimethylolpropane tetraacrylate, ditrimethylolpropane tetramethacrylate, propoxylated pentaerythritol tetraacrylate, tricyclodecane dimethanol diacrylate, propoxylated 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. Based on 100 parts by weight of the ethylene / α-olefin copolymer, the amount of the co-crosslinking agent can be 0.1-5 parts by weight (for example, 0.15 parts by weight, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 1.0 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 3.0 parts by weight, 4.0 parts by weight), and can optionally be 0.1-2 parts by weight.

[0058] Furthermore, the coupling agent can be a silane coupling agent, including but not limited to a combination of one or more of the following compounds: γ-methacryloxypropyltrimethoxysilane, γ-chloropropylmethoxysilane, vinylethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, 3-(trimethoxysilyl)propyl-2-methyl-2-acrylate, anilinemethyltriethoxysilane, and octyltrimethoxysilane. Based on 100 parts by weight of the ethylene / α-olefin copolymer, the amount of the coupling agent can be 0.1-3 parts by weight (for example, 0.15 parts by weight, 0.2 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 1.0 parts by weight, 1.5 parts by weight, 1.8 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 2.8 parts by weight), and can optionally be 0.1-0.6 parts by weight.

[0059] Furthermore, the antioxidant can be a combination of one or more of a hindered phenol antioxidant and a phosphate antioxidant, including but not limited to a combination of one or more of the following compounds: β-[3,5-di-tert-butyl-4-hydroxyphenyl] propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, bis(3,5-di-tert-butyl-4-hydroxypropionyl)hydrazine, 2,2'-oxalyl-bis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)] propionate, N,N'-hexamethylenebis[ethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)] propionate, (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 the antioxidant can be 0.01-1 part by weight (for example, 0.015 parts by weight, 0.02 parts by weight, 0.04 parts by weight, 0.05 parts by weight, 0.1 parts by weight, 0.15 parts by weight, 0.18 parts by weight, 0.2 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.55 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 0.9 parts by weight), and can optionally be 0.05-0.5 parts by weight.

[0060] In some embodiments, based on 100 parts by weight of the ethylene / α-olefin copolymer, the encapsulation film composition for solar cells includes the following components:

[0061] 100 parts by weight of ethylene / α-olefin copolymer,

[0062] The cross-linking agent is 0.1-5 parts by weight, and can be optionally 0.5-2 parts by weight;

[0063] The auxiliary cross-linking agent is 0.1-5 parts by weight, and can be optionally 0.1-2 parts by weight;

[0064] The coupling agent is 0.1-3 parts by weight, and can be optionally 0.1-0.6 parts by weight;

[0065] The antioxidant is 0.01-1 parts by weight, and can be optionally 0.05-0.5 parts by weight.

[0066] This application also provides a method for preparing the aforementioned solar cell encapsulation film, comprising the following steps: weighing the raw material components of the composition according to a formula, mixing and melting them, extruding and granulating them through an extruder, casting them into a film, and then cooling and slitting them. This method may also include a winding step. The specific operations, equipment, and process conditions of this method can be carried out in accordance with conventional methods in the art and are not particularly limited.

[0067] The ethylene / α-olefin copolymer described herein has a wide melting range, 0≤dH(90)≤2J / g, dH(100)=0, and a greater presence of rubber phase (amorphous phase) in the system. Therefore, when melt-mixed with other additives, additives such as crosslinking agents are more likely to enter the interior of the particles. Consequently, at the same additive absorption time, more additives migrate into the interior of the particles, making it easier to absorb the additives when processing the composition comprising the ethylene / α-olefin copolymer and the additives. Furthermore, when the composition is further cross-linked, the resulting polymer / composition has a higher degree of crosslinking, thereby exhibiting stronger mechanical properties. Furthermore, when controlling for the same degree of crosslinking, the particles of the composition described herein require a shorter additive absorption time.

[0068] Compared with the related art, the excellent effects of the technical solution of this application are at least:

[0069] The ethylene / α-olefin copolymer described in the present application has special performance characteristics such as a wide melting range, 0≤dH(90)≤2J / g and dH(100)=0. When the composition comprising the ethylene / α-olefin copolymer and the additive is processed, it is easier to absorb the additive, and the additive absorption time required for the composition particles is shorter. At the same time, the cross-linking degree of the obtained product is higher when further cross-linked; the composition comprising the ethylene / α-olefin copolymer and the additive can meet the application requirements of photovoltaic films, can solve the problems of long mixing time or insufficient cross-linking degree of the additives added during the film processing, and has good industrial prospects.

[0070] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0071] In order to understand the technical features and content of the present application in detail, the optional embodiments of the present application will be described in more detail below. Although the optional embodiments of the present application are described in the embodiments, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein.

[0072] Unless otherwise specified, the experimental procedures used in the following examples are conventional methods.

[0073] The materials and reagents used in the following examples can all be obtained from commercial sources. The specific information of some raw materials is as follows:

[0074] 8660, ethylene / octene copolymer, available from Dow;

[0075] 8688, ethylene / butene copolymer, available from Dow;

[0076] Isopar E, 100% hydrogenated naphtha, purchased from Mobil;

[0077] Ethylene, polymerization grade, was purchased from Air Liquide;

[0078] 1-Octene, 98%, purchased from INEOS;

[0079] 1-Hexene, 99%, purchased from Lingyan Biotechnology;

[0080] 1-Butene, 99%, purchased from Mingju;

[0081] Dimethylsilyl(N-tert-butylamino)(fluorenyl)titanium dichloride, 99%, strem, labeled M1;

[0082] Dimethylsilyl(N-tert-butylamino)(tetramethylcyclopentadienyl)titanium dimethyl, 99%, purchased from Sinotec and marked as M2;

[0083] Dibenzylidenecyclopentadienyl (2,7-di-tert-butyl-fluorenyl) zirconium dichloride, 98%, purchased from Yaodexin Chemical, marked as M3;

[0084] The compound (labeled as M4) was synthesized according to Example 6 in patent document CN 114315883 A, and its chemical structure is shown below:

[0085] The compound (labeled as M5) was synthesized according to Example 4 in patent document CN202010793023.8 (CN111909196B), and its chemical structure is shown below:

[0086] MMAO, 7% aluminum solution, purchased from Nouryon;

[0087] Triisobutylaluminum hexane solution, concentration 1 mol / L, purchased from Inokai;

[0088] N,N-Dimethylanilinium tetrakis(pentafluorophenyl)borate, 99%, was purchased from Inochem and dissolved in toluene and marked as B1.

[0089] Tert-butyl peroxy-2-ethylhexyl carbonate, purchased from Aksu Company, purity >95%;

[0090] Triallyl isocyanurate, purchased from Acros, 98% purity;

[0091] γ-Methacryloxypropyltrimethoxysilane, purchased from Aladdin, purity 95%;

[0092] γ-(2,3-Epoxypropyloxy)propyltrimethoxysilane, purchased from Aladdin, purity 95%;

[0093] Bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite, purchased from Acros, purity 95%;

[0094] 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, purchased from Acros, purity 95%;

[0095] Trimethylolpropane triacrylate, purchased from Aladdin, 98% purity;

[0096] Tert-amyl peroxycarbonate, purchased from ark, purity 95%;

[0097] Antioxidant 1076, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, purchased from Li'anlong New Materials Co., Ltd., industrial grade;

[0098] Antioxidant 1010, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, purchased from Li'anlong New Materials Co., Ltd., industrial grade.

[0099] <Test Method>

[0100] (1) In the following examples and comparative examples, the melting peak temperature T m The melting enthalpy and melting enthalpy are measured by DSC, using the data obtained from the second heating, with a heating and cooling rate of 10℃ / min. The melting range width is the difference between the temperature at which the polymer is completely melted and the temperature at which it begins to melt, that is, T endset With T onset The difference.

[0101] (2) In the following examples and comparative examples, the SSA of the obtained polymers was measured by DSC. Specifically, in the first cycle, the temperature was raised to 150°C, held for 1 minute, and then lowered to -50°C; in the second cycle, the temperature was raised to 120°C, held for 5 minutes, and then lowered to -50°C; in the third cycle, the temperature was raised to 112.5°C, held for 5 minutes, and then lowered to -50°C; the temperature was raised and held for 5 minutes and then lowered according to the above cyclic operation, and the fourth cycle (i.e., in the fourth cycle, the temperature was raised to a maximum of 105°C at intervals of 7.5°C and held for 5 minutes before lowering the temperature to -50°C), the fifth cycle (i.e., in the fifth cycle, the temperature was raised to a maximum of 97.5°C at intervals of 7.5°C and held for 5 minutes before lowering the temperature to -50°C), the sixth cycle, etc., until the rising temperature reached -40°C, thereby crystallizing in each temperature interval. In the final cycle, the temperature was raised to 150°C at 10°C / min and the heat capacity was measured, dH(90) representing the sum of the melting enthalpies above 90°C and dH(100) representing the sum of the melting enthalpies above 100°C.

[0102] (3) In the following examples and comparative examples, the density of the obtained polymer was tested using a densitometer; the sample to be tested was cut from a tabletting plate and the density was tested using a densitometer Mettler XS204, using an immersion method with anhydrous ethanol AR as the immersion liquid; the test ambient temperature was 23°C ± 2°C, and the test temperature required internal calibration; the mass of the sample to be tested was > 1g and free of bubbles; the mass of the sample in air and the mass in the immersion liquid were weighed separately, and the sample density was calculated and derived using the Archimedean principle.

[0103] (4) In the following examples and comparative examples, the molecular weight, molecular weight distribution and insertion rate of α-olefin (such as 1-octene) of the obtained polymers were obtained by GPC-IR testing of polymer char at a test temperature of 150°C, and the product recovery rate exceeded 95%.

[0104] (5) In the following examples and comparative examples, the melt index (MI) of the obtained polymers was tested at 190°C and a load of 2.16 kg: 4-8 g of the pellets to be tested were taken, the temperature was set to 190°C, the load was 2.16 kg, and the inner diameter of the standard die was 2.095 mm. After the pellets were melted in the barrel for 5 minutes, they flowed out of the die under the action of a pressure load, and the time taken for the displacement point to be 46 mm to 20.6 mm was measured and recorded. The specimens were automatically cut and the mass of the specimens was weighed on a balance. The MFR or MVR was calculated in units of g / 10 min and cm 3 / 10min.

[0105] The ethylene / α-olefin copolymers in the various examples and comparative examples were prepared in a continuous reaction platform equipped with reactors of different volumes and types, and the operation steps were as follows:

[0106] The dried solvent is continuously introduced into the reactor for 2 days to remove impurities from the reactor, and then an α-olefin comonomer, a solvent, a primary catalyst, and a co-catalyst are introduced into the reactor in sequence, stirring and mixing is started, the system is heated, and ethylene monomer at 3 to 9 MPa is introduced to carry out a polymerization reaction; wherein:

[0107] The polymerization reaction conditions shown in Tables 1 and 2 are respectively carried out (e.g., a specific solvent, ethylene, α-olefin comonomer, primary catalyst and co-catalyst are delivered to the reactor at a certain feed rate, a certain reaction pressure and temperature are controlled, and the aspect ratio or reflux ratio is adjusted according to the selected reactor type);

[0108] The obtained reaction solution is subjected to subsequent steps (removal of volatile components, drying, extrusion and granulation) to obtain specific ethylene / α-olefin copolymer product particles.

[0109] The volatile components in the reaction liquid are removed by flash evaporation; extrusion and granulation are carried out by a twin-screw extruder, the extrusion temperature is 80-260° C., and the screw speed is 30-150 rpm.

[0110] The characteristic test results of the products prepared in various embodiments and comparative examples are shown in Tables 3 and 4.

[0111] Table 1 Polymerization conditions of each embodiment and comparative example

[0112] Table 2 Polymerization conditions of each embodiment and comparative example

[0113] Table 3 Characteristic test results of polymers obtained in various examples and comparative examples

[0114] Table 4 Characteristic test results of polymers obtained in various examples and comparative examples

[0115] Preparation of encapsulating film

[0116] Example 7

[0117] 1000 g of the ethylene / α-olefin copolymer prepared in Example 1 was weighed and 6 g of tert-butyl peroxy-2-ethylhexyl carbonate, 4.5 g of triallyl isocyanurate, 2 g of γ-methacryloyloxypropyltrimethoxysilane, 1 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 1 g of bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite and 1 g of β-[3,5-di-tert-butyl-4-hydroxyphenyl]propionic acid n-octadecyl ester were added thereto;

[0118] The above raw materials were heated to 50° C. and uniformly mixed for 3 hours to obtain an encapsulation film composition; the obtained composition was then subjected to extrusion granulation, cast film formation, and re-cooling, slitting, and winding processes in a screw extruder; the extruder parameters were adjusted, wherein the temperature from the feed port to the die head was 80° C., 90° C., 90° C., 90° C., 95° C., 95° C., 95° C., the screw speed was 45 rpm, the pulling speed was 0.7 rpm, and the winding speed was 1.3 rpm; and a solar cell encapsulation film was prepared, wherein the film thickness was 0.6 mm.

[0119] Example 8

[0120] 1000 g of the ethylene / α-olefin copolymer prepared in Example 2 was weighed and added with 9 g of 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2 g of tert-amyl peroxycarbonate, 4 g of trimethylolpropane triacrylate, 2 g of γ-methacryloxypropyltrimethoxysilane, 1 g of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 g of antioxidant 1076 and 1 g of antioxidant 1010;

[0121] The above raw materials were heated to 50° C. and uniformly mixed for 3 hours to obtain an encapsulation film composition; the obtained mixture was then subjected to extrusion granulation, cast film formation, and re-cooling, slitting, and winding processes in a screw extruder; the extruder parameters were adjusted, wherein the temperature from the feed port to the die head was 80° C., 90° C., 90° C., 90° C., 95° C., 95° C., 95° C., the screw speed was 45 rpm, the pulling speed was 0.7 rpm, and the winding speed was 1.3 rpm; and a solar cell encapsulation film was prepared, wherein the film thickness was 0.6 mm.

[0122] Example 9

[0123] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Example 3. The remaining operations were the same as those in Example 7.

[0124] Example 10

[0125] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Example 4. The remaining operations were the same as those in Example 7.

[0126] Example 11

[0127] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Example 5. The remaining operations were the same as those in Example 7.

[0128] Example 12

[0129] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Example 6. The remaining operations were the same as those in Example 7.

[0130] Comparative Example 5

[0131] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Comparative Example 1. The remaining operations were the same as those of Example 7.

[0132] The experiment found that when the film was rolled up, the number of crystal points on the film increased significantly, making it difficult to form a film and not meeting the requirements for use.

[0133] Comparative Example 6

[0134] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer prepared in Comparative Example 2. The remaining operations were the same as those of Example 7.

[0135] Comparative Example 7

[0136] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer used was the ethylene / α-olefin copolymer of Comparative Example 3. The remaining operations were the same as those of Example 7.

[0137] Comparative Example 8

[0138] The preparation process of the solar cell encapsulation film was similar to that of Example 7, except that the ethylene / α-olefin copolymer weighed was the ethylene / α-olefin copolymer of Comparative Example 4. The remaining operations were the same as those of Example 7.

[0139] Example 13

[0140] The preparation process of the solar cell encapsulation film is similar to that of Example 7, except that the raw materials are heated to 50° C. and uniformly mixed for 2 h. The rest of the operation process is the same as that of Example 7.

[0141] Example 14

[0142] The preparation process of the solar cell encapsulation film is similar to that of Example 8, except that the raw materials are heated to 50° C. and uniformly mixed for 2 hours. The rest of the operation process is the same as that of Example 7.

[0143] Example 15

[0144] The preparation process of the solar cell encapsulation film is similar to that of Example 9, except that the raw materials are heated to 50° C. and uniformly mixed for 2 hours. The rest of the operation process is the same as that of Example 7.

[0145] Example 16

[0146] The preparation process of the solar cell encapsulation film is similar to that of Example 10, except that the raw materials are heated to 50° C. and uniformly mixed for 2 hours. The rest of the operation process is the same as that of Example 7.

[0147] Example 17

[0148] The preparation process of the solar cell encapsulation film is similar to that of Example 11, except that the raw materials are heated to 50° C. and uniformly mixed for 2 hours. The rest of the operation process is the same as that of Example 7.

[0149] Example 18

[0150] The preparation process of the solar cell encapsulation film is similar to that of Example 12, except that the raw materials are heated to 50° C. and uniformly mixed for 2 hours. The rest of the operation process is the same as that of Example 7.

[0151] Comparative Example 9

[0152] The preparation process of the solar cell encapsulation film is similar to that of Comparative Example 5, except that the raw materials are heated to 50° C. and uniformly mixed for 2 h.

[0153] During the experiment, it was found that when the film was rolled up, the number of crystal points on the film increased significantly, making it difficult to form a film and not meeting the requirements for use.

[0154] Comparative Example 10

[0155] The preparation process of the solar cell encapsulation film is similar to that of Comparative Example 6, except that the raw materials are heated to 50° C. and uniformly mixed for 2 h.

[0156] Comparative Example 11

[0157] The preparation process of the solar cell encapsulation film is similar to that of Comparative Example 7, except that the raw materials are heated to 50° C. and uniformly mixed for 2 h.

[0158] Comparative Example 12

[0159] The preparation process of the solar cell encapsulation film is similar to that of Comparative Example 8, except that the raw materials are heated to 50° C. and uniformly mixed for 2 h.

[0160] The crosslinking degree of the encapsulation film prepared as above was evaluated according to the China Photovoltaic Industry Association (CPIA) standard and ASTM D2765.

[0161] The encapsulant films (solar cell encapsulation films) obtained in the above examples and comparative examples were cut into a size of 10 cm×10 cm and vacuum laminated at 150° C. for 20 minutes (maintaining vacuum for 5 minutes / pressurizing for 1 minute / decompressing for 14 minutes) to obtain cross-linked samples to be tested.

[0162] The cross-linked samples to be tested were cut into appropriate sizes, 0.5 g of which was weighed onto a 200-mesh wire cage and dissolved in xylene under reflux for 5 hours. The samples were then dried in a vacuum oven, and the weights before and after reflux were compared to measure the degree of cross-linking of each test sample. The cross-linking degrees of the solar cell encapsulation films obtained in the Examples and Comparative Examples are shown in Table 5.

[0163] Table 5 Crosslinking degree data of the encapsulation films of various embodiments and comparative examples

[0164] As shown in Table 5, compared with Comparative Examples 5 to 8, the mixing time of the ethylene / α-olefin copolymer and the auxiliary agent during the film formation process of Examples 7 to 12 is under the same conditions. The ethylene / α-olefin copolymer described in the present application can improve the crosslinking degree of the photovoltaic film product; compared with Comparative Examples 9 to 12, the mixing time of the ethylene / α-olefin copolymer and the auxiliary agent during the film formation process of Examples 13 to 18 is under the same conditions. The ethylene / α-olefin copolymer described in the present application shortens the mixing time with the auxiliary agent during the film formation process and can still maintain a high crosslinking degree, which is greater than 85% of the requirement for photovoltaic films, and is better than the ethylene / α-olefin copolymer of the comparative example.

[0165] Therefore, the ethylene / α-olefin copolymers described herein can shorten mixing time with additives, improving processing efficiency while maintaining a high degree of crosslinking. This is because the ethylene / α-olefin copolymers described herein have a wide melting range, which facilitates the migration of additives from the particle surface to the particle interior at lower temperatures. This results in a higher degree of crosslinking at the same mixing time, or in other words, can still meet crosslinking requirements with shorter mixing times.

[0166] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those skilled in the art without departing from the spirit of the present invention.

Claims

1. An ethylene / α-olefin copolymer, wherein, the ethylene / α-olefin copolymer has the following characteristics: (a) The melting peak temperature measured by DSC is 30 - 90 °C, and the melting range width is 75 - 90 °C; (b) dH(90) and dH(100) measured by differential scanning calorimeter through continuous self-nucleation / annealing (SSA), wherein 0 ≤ dH(90) ≤ 2 J / g, and dH(100) = 0.

2. The ethylene / α-olefin copolymer according to claim 1, wherein, the ethylene / α-olefin copolymer further has the following characteristics: (c) The density is 0.850 to 0.905 g / cm 3 ; (d) The weight-average molecular weight is 20,000 - 150,000 g / mol, and the molecular weight distribution width PDI is 2.3 - 3.

3. The ethylene / α-olefin copolymer according to claim 1, wherein, the melting enthalpy of the ethylene / α-olefin copolymer is 20 - 100 J / g.

4. The ethylene / α-olefin copolymer according to claim 1, wherein, the melt index (MI) of the ethylene / α-olefin copolymer under the conditions of 190 °C and 2.16 kg load is 0.1 - 30 g / 10 min.

5. The ethylene / α-olefin copolymer according to claim 1, wherein, the glass transition temperature Tg of the ethylene / α-olefin copolymer is -65 °C to -30 °C.

6. The ethylene / α-olefin copolymer according to claim 1, wherein, in the ethylene / α-olefin copolymer, the α-olefin is an olefin of C3 - C20 or a mixture thereof.

7. The ethylene / α-olefin copolymer according to claim 6, wherein, 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.

8. The ethylene / α-olefin copolymer according to claim 1, wherein, the ethylene / α-olefin copolymer is a product obtained by solution polymerization of ethylene with one or more α-olefins in the presence of a catalyst and optionally a chain transfer agent hydrogen.

9. The ethylene / α-olefin copolymer according to claim 8, wherein, the solution polymerization reaction is carried out in one or more polymerization reactors; Optionally, the polymerization reactor is one or more of a non-stirred or stirred cylindrical container, a tank-shaped container, and a circulation loop reactor; Optionally, the aspect ratio of the cylindrical container is 2:1 - 3:1, the aspect ratio of the tank-shaped container is 2:1 - 3:1, and the circulation ratio of the circulation loop reactor is 20 - 40.

10. The ethylene / α-olefin copolymer according to claim 9, wherein, in the solution polymerization reaction, the catalyst includes a main catalyst and a co-catalyst.

11. The ethylene / α-olefin copolymer according to claim 10, wherein, the main catalyst is a homogeneous catalyst, selected from metallocene catalysts or non-metallocene catalysts.

12. The ethylene / α-olefin copolymer according to claim 10, wherein, The cocatalyst is one or more of aluminoxane, alkylaluminum compound, and alkylaluminum chloride, or a composition of one or more of aluminoxane, alkylaluminum compound, and alkylaluminum chloride and one or more organoboron compounds; Optionally, the aluminoxane is selected from methylaluminoxane and modified methylaluminoxane; Optionally, the alkylaluminum compound is selected from triethylaluminum, triisobutylaluminum, and trioctylaluminum; Optionally, the alkylaluminum chloride is selected from chloroethylaluminum, sesquialethylaluminum, and dichloroethylaluminum; Optionally, the organoboron compound is selected from trityl tetrakis(pentafluorophenyl)borate, tris(pentafluorophenyl)boron, N,N-dimethylaniline tetrakis(pentafluorophenyl)borate, bis(octadecyl)methylamine tetrakis(pentafluorophenyl)borate, and bis(hydrogenated tallow)methylamine tetrakis(pentafluorophenyl)borate.

13. The ethylene / α-olefin copolymer according to claim 8, wherein, the solution polymerization reaction is carried out at 2 to 10 MPa, optionally 2 to 5 MPa.

14. Use of the ethylene / α-olefin copolymer according to any one of claims 1-13 in the field of photovoltaic encapsulation films.

15. An encapsulation film composition for a solar cell, wherein, it comprises: the ethylene / α-olefin copolymer according to any one of claims 1-13 and optionally an auxiliary agent; Optionally, the auxiliary agent is selected from one or more of a crosslinking agent, a co-crosslinking agent, a coupling agent, and an antioxidant.

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