Ethylene / alpha-olefin copolymer as well as preparation method and application thereof

Abstract

The invention relates to an ethylene / alpha-olefin copolymer as well as a preparation method and application thereof. The ethylene / alpha-olefin copolymer has the following characteristics: a) the melt index (MI) is 1-30g / min under the conditions of 190 DEG C and 2.16 kg; b) a density of from 0.850 to 0.910 g / cm; c) a molecular weight distribution index (PDI, Mw / Mn) of from 2.0 to 2.8; d) the SEF value is less than 6%; the SEF value is equal to a + b, the value a is the content (wt%) of soluble substances in the ethylene / alpha-olefin copolymer measured by temperature gradient cross-chromatography (TGIC), and the value b is the content (wt%) of soluble substances in the ethylene / alpha-olefin copolymer measured by temperature gradient cross-chromatography (TGIC); the value b is the content (wt%) of a soluble substance obtained by extracting the ethylene / alpha-olefin copolymer for 6 hours at the temperature of 20-30 DEG C by using an isoparaffin solvent. The olefin-based polymer according to the present invention, as a low-density olefin-based polymer, exhibits excellent anti-blocking properties due to having an improved SEF value.

Description

Technical Field

[0001] The present invention belongs to the field of olefin polymers, and relates to an ethylene / α-olefin copolymer, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing depletion of traditional energy resources and the intensification of global warming, the transformation of the global energy pattern is accelerating. Clean and renewable energy has gradually become the dominant direction of the global energy transformation. In recent years, with the reform of photovoltaic technology, the photovoltaic power generation efficiency has increased rapidly, and the cost has decreased rapidly. Coupled with the cleanliness and sustainability of its energy source, the development of the photovoltaic industry has witnessed explosive growth. With the development of photovoltaic technology, the demand for high-performance polyolefin elastomer particles in the photovoltaic industry is increasing, and the performance requirements are also getting higher and higher. Polyolefin elastomer POE is a thermoplastic polyolefin elastomer obtained by copolymerizing ethylene and α-olefin through a solution polymerization process. It has excellent anti-PID performance (anti-potential-induced degradation effect), water vapor barrier performance, weather resistance, and light transmittance, and is widely used in the encapsulation film of photovoltaic modules.

[0003] The reduction of photovoltaic power generation cost depends on the progress of battery technology on the one hand and the improvement of the production efficiency and stability of photovoltaic modules on the other hand. The adhesion of polyolefin elastomer particles will, on the one hand, cause poor or no feeding during the film casting process of the encapsulation film, seriously affecting the processing efficiency of the photovoltaic encapsulation film. On the other hand, the particle adhesion will directly affect the absorption effect of additives during the film processing, resulting in a decrease in the finished product rate of the film and affecting the service life of the photovoltaic module. In patent CN111491960A, the anti-adhesion property of the polyolefin elastomer is improved by increasing the melting temperature and hardness, but the adhesion performance between the POE film and the photovoltaic glass is sacrificed, and the production efficiency and finished product rate of the photovoltaic module are also reduced.

[0004] Therefore, it is necessary to develop a polyolefin elastomer to improve the particle stickiness performance without sacrificing hardness, so as to improve the processing efficiency and finished product rate of the module. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide an ethylene / α-olefin copolymer, which has a narrow molecular weight distribution index, improved anti-adhesion property, and low density, can be widely used in the encapsulation film of photovoltaic modules, and has improved processing efficiency and finished product rate of the module.

[0006] The present invention also aims to provide a preparation method of the above ethylene / α-olefin copolymer. By screening catalysts or regulating reaction conditions, the ethylene / α-olefin copolymer of the present invention can be prepared, and the method is simple and efficient.

[0007] In the research of ethylene / α-olefin copolymers, the present inventors found that when polymerizing two or more monomers, the molecular weight distribution increases, the impact strength and mechanical properties may decrease, and phenomena such as adhesion may occur. Therefore, in the present invention, the molecular weight and molecular weight distribution of the ethylene / α-olefin copolymer are reduced, and under the condition of similar insertion rates, the mechanical properties, particle anti-adhesion properties, etc. are improved. At the same time, by controlling the introduction amount of the comonomer, the copolymer has a lower density. And the ethylene / α-olefin copolymer that meets the characteristics of the present invention can also maintain excellent mechanical properties, show improved particle stickiness and thus show improved processability.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides an ethylene / α-olefin copolymer having the following characteristics:

[0010] a) The melt index (MI) at 190 °C and 2.16 kg is 1-30 g / min, such as 1, 3, 5, 7, 10, 13, 15, 17, 20, 23, 25, 27, 30 g / min, preferably 1.5-24 g / min, more preferably 3-22 g / min;

[0011] b) The density is 0.850-0.910 g / cm 3 , such as 0.850, 0.860, 0.870, 0.880, 0.890, 0.900, 0.910 g / cm 3 , preferably 0.855-0.900 g / cm 3 , more preferably 0.860-0.890 g / cm 3 ;

[0012] c) The molecular weight distribution index (PDI, Mw / Mn) is 2.0-2.8, such as 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, preferably 2.1-2.7, more preferably 2.2-2.6;

[0013] d) The SEF value < 6%, such as 5.9, 5.7, 5.5, 5.3, 5.0, 4.7, 4.5, 4.3, 4.0, 3.7, 3.5, 3.3, 2.0, etc.;

[0014] The SEF value = a + b,

[0015] wherein, the a value is the content of the soluble matter in the ethylene / α-olefin copolymer measured by temperature gradient cross chromatography (TGIC), (wt%); the b value is the content of the soluble matter obtained by extracting the ethylene / α-olefin copolymer with an isoparaffin solvent at 20-30 °C for 6 h, (wt%).

[0016] In the present invention, when the temperature gradient intersection chromatography (TGIC) is used to test the soluble content in the ethylene / α-olefin copolymer of the present invention, the separation of different components of the polyolefin is achieved under a certain solvent flow rate and temperature change by the combined action of the interaction between the polyolefin chain and the TGIC column (graphite column), adsorption and desorption, and crystallization performance. Specifically, a conventional type of instrument such as Polymer Char can be used for testing, and the solvent can be selected from trichlorobenzene, etc., and the separation and characterization of different components of the polyolefin are achieved by temperature rising elution. Those skilled in the art can determine the specific test conditions with reference to the content disclosed in the prior art according to actual needs. For example, the test method mentioned in the examples of the present invention can be adopted. In one test method, the sample is dissolved in trichlorobenzene at 165°C and passed through the TGIC chromatographic column, and the temperature is programmed to drop to 40°C (20°C / min). Part of the polyolefin structure adheres to the chromatographic column due to adsorption and crystallization with the graphite column, and is rinsed at a flow rate of 0.5 ml / min. The soluble part is flushed to the detector IR5 for detection, and the temperature is raised for elution, and the temperature is raised to 165°C at a rate of 2°C / min. The molecules attached to the column are eluted in turn according to the difference in their crystallization ability and the number of short branches.

[0017] In the present invention, the soluble matter obtained by extracting the ethylene / α-olefin copolymer with an isoparaffin solvent at 20 - 30°C for 6 h has a weight average molecular weight Mw < 25000, such as 24900, 24000, 23000, 22000, 21000, 20000, 18000, 15000, 13000, 10000, etc.

[0018] Preferably, the isoparaffin is selected from at least one of C8 - C10 isoparaffins, preferably at least one of 2,4-dimethylhexane, 2,5-dimethylhexane, 2,3,3-trimethylpentane, 2,3,4-trimethylpentane, 2-methylheptane, 2,2,4-trimethylhexane, 2,3,5-trimethylhexane, 2,5-dimethylheptane, 2,3-dimethylheptane, 2,2,4-trimethylheptane, 2,3,6-trimethylheptane, and mixed alkane IsoparE.

[0019] In the present invention, the ethylene / α-olefin copolymer is a copolymer of an ethylene monomer and a C3 - C12 α-olefin monomer;

[0020] Preferably, the α-olefin monomer is selected from at least one of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, and 1-dodecene.

[0021] In the present invention, in the ethylene / α-olefin copolymer, based on the total mass of the copolymer, the α-olefin content is 20 - 38%.

[0022] In the present invention, the ethylene / α-olefin copolymer has a weight-average molecular weight (Mw) of 40,000 - 150,000, such as 40000, 60000, 80000, 100000, 130000, 150000, preferably 45,000 - 130,000, and more preferably 46,000 - 90,000.

[0023] In a second aspect, the present invention provides a method for preparing the above-mentioned ethylene / α-olefin copolymer. It is prepared from an ethylene monomer and an α-olefin monomer through a conventional copolymerization reaction type. In some specific examples, by selecting a suitable catalyst or injecting an appropriate amount of a chain transfer agent such as hydrogen during the polymerization process to obtain a copolymer that simultaneously meets characteristics (a) to (d), the physical properties of the ethylene / α-olefin copolymer, especially the anti-blocking performance of the ethylene / α-olefin copolymer, can be greatly improved. Those skilled in the art should understand that this preparation method is only an exemplary illustration of the source mode of the ethylene / α-olefin copolymer product with the above characteristics in the present invention, but does not constitute any limitation.

[0024] In a preferred embodiment, the present invention provides a method for preparing the ethylene / α-olefin copolymer, the steps including:

[0025] Mixing ethylene, an α-olefin, a catalyst, a cocatalyst, an optional chain transfer agent, and a solvent and adding them to a reaction kettle for solution polymerization to obtain the ethylene / α-olefin copolymer.

[0026] In the present invention, the catalyst is selected from conventional olefin copolymerization catalysts in the art. For example, a homogeneous catalyst is used, preferably at least one of a metallocene catalyst and a non-metallocene catalyst; both the metallocene catalyst and the non-metallocene catalyst can be conventionally selected in the art, but can also be screened according to actual needs. By controlling the addition ratio of the α-olefin and ethylene, the introduction amount of the comonomer can be regulated, so that the copolymer has a lower density and hardness while showing excellent processability;

[0027] Preferably, the metallocene catalyst is selected from at least one of dimethylsilyl(N-tert-butylamido)(tetramethylcyclopentadienyl)titanium dichloride, dimethylsilyl(N-tert-butylamido)(tetramethylcyclopentadienyl)dimethyltitanium, dimethylsilyl(N-tert-butylamido)(fluorenyl)titanium dichloride, (pentamethylcyclopentadienyl)trimethoxytitanium, diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, dimethyldimethylsilylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride, meso-dimethyldisilylbis(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-dimethyldisilylbis(2-methyl-1-indenyl)zirconium dichloride, diphenylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, di-p-tolylmethylenecyclopentadiene(2,7-di-tert-butyl-fluorenyl)zirconium dichloride, dimethylbis(propylcyclopentadienyl)hafnium, bis(n-butylcyclopentadienyl)hafnium dichloride, dimethylsilylbis(2-methyl-4-phenylindenylidene)zirconium dichloride; preferably at least one of dimethylsilyl(N-tert-butylamido)(tetramethylcyclopentadienyl)titanium dichloride, dimethylsilyl(N-tert-butylamido)(tetramethylcyclopentadienyl)dimethyltitanium, dimethylsilyl(N-tert-butylamido)(fluorenyl)titanium dichloride, (pentamethylcyclopentadienyl)trimethoxytitanium, diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride, dimethyldimethylsilylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride;

[0028] Preferably, the non-metallocene catalyst is selected from the products disclosed in the prior art and can be prepared based on the prior art. For example, the catalysts disclosed in patents CN111747977B, CN115710326A, CN111592562B, and CN112142775B are used. Preferably, the non-metallocene catalyst disclosed in CN111747977B is used.

[0029] In the present invention, the cocatalyst is selected from the conventional olefin copolymerization cocatalysts in the art, such as at least one of aluminoxane, alkylaluminum compounds, alkylaluminum chlorides, and organoborides; the aluminoxane, alkylaluminum compounds, alkylaluminum chlorides, and organoborides can all be the conventional selections in the art, but can also be screened according to actual needs;

[0030] Preferably, the aluminoxane is selected from at least one of methylaluminoxane (MAO) and modified methylaluminoxane (MMAO); the alkylaluminum compound is selected from at least one of triethylaluminum, triisobutylaluminum, trioctylaluminum, etc.; the chloroalkylaluminum includes at least one of chloroethylaluminum, sesquialethylaluminum, dichloroethylaluminum, etc.; the organic boride is at least one of trityl tetrakis(pentafluorophenyl)borate, tris(pentafluorophenyl)boron, N,N-dimethylaniline tetrakis(pentafluorophenyl)borate, bis(octadecyl)methyl tertiary amine tetrakis(pentafluorophenyl)borate, bis(hydrogenated tallow)methyl tertiary amine tetrakis(pentafluorophenyl)borate.

[0031] In the present invention, the solvent is selected from conventional olefin copolymerization solvents in the art, for example, aliphatic hydrocarbon solvents and / or aromatic hydrocarbon solvents are used;

[0032] Preferably, the aliphatic hydrocarbon solvent is selected from at least one of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylenecyclopentane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, n-heptane, n-octane, n-nonane or IsoparE; the aromatic hydrocarbon solvent is selected from at least one of benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, dichlorotoluene, IsoparE.

[0033] In the present invention, the chain transfer agent is selected from at least one of hydrogen, methane, ethane, propane, and preferably hydrogen.

[0034] In the present invention, the mass ratio of ethylene to α-olefin is 1:0.2 - 1:5, such as 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, and preferably 1:1 - 1:3.

[0035] In the present invention, the addition amount of the catalyst is 1 / 100000 - 1 / 100000000 of the total molar amount of ethylene and α-olefin monomers, such as 1 / 100000, 1 / 500000, 1 / 1000000, 1 / 5000000, 1 / 10000000, 1 / 50000000, 1 / 100000000, and preferably 1 / 300000 - 1 / 80000000.

[0036] In the present invention, the addition amount of the cocatalyst is 1 / 100 - 1 / 100000000 of the total molar amount of ethylene and α-olefin monomers, such as 1 / 100, 1 / 500、1 / 1000、1 / 5000、 1 / 10000, 1 / 50000, 1 / 100000, 1 / 500000, 1 / 1000000, 1 / 5000000, 1 / 10000000, 1 / 50000000, 1 / 100000000, and preferably 1 / 1000 - 1 / 8000000.

[0037] In the present invention, the addition amount of the solvent is 2 to 10 times the total mass of ethylene and the α-olefin monomer, such as 2, 4, 6, 8, 10 times, preferably 2.5 to 8 times.

[0038] In the present invention, the addition amount of the chain transfer agent is 1 / 1000000 to 1 / 100000 of the total mass of ethylene and the α-olefin monomer, such as 1 / 1000000, 1 / 800000, 1 / 600000, 1 / 400000, 1 / 100000;

[0039] Preferably, when the chain transfer agent is hydrogen, the hydrogen feed rate controls the system pressure to be 2 - 10 MPaG, such as 2, 4, 6, 8, 10 MPa, preferably 2 - 5 MPaG.

[0040] In the present invention, for the solution polymerization reaction, the reaction temperature is 100 - 250 °C, such as 100, 150, 200, 250 °C, preferably 120 - 190 °C; the reaction time is 3 - 20 minutes, such as 3, 5, 10, 15, 20 minutes, preferably 4 - 12 minutes.

[0041] In the present invention, for the polymerization reaction, one or more polymerization reactors can be used. Suitable reactors are selected from non-stirred or stirred spherical, cylindrical and tank-shaped containers, as well as loop reactors and tubular reactors. When mixing is carried out by stirring or a circulation pump respectively, the Reynolds number Re is controlled to be 6000 - 20000, for example, it can be 6000, 6500, 7000, 7500, 8000, 8500, 9000, 9500, 10000, 12000, 15000, 18000, 20000, preferably 6000 - 10000.

[0042] After the polymerization reaction of the present invention is completed, it also includes quenching, devolatilization, desolvation, and subsequent operations such as extrusion granulation, which are all conventional operations in the art and there are no special requirements in the present invention.

[0043] In the third aspect, the present invention provides the use of the ethylene / α-olefin copolymer described above, which is mainly used in the field of photovoltaic encapsulation films.

[0044] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0045] The ethylene / α-olefin copolymer of the present invention, at the same α-olefin content, has a low density, a narrower molecular weight distribution index, a lower SEF value, and improved anti-blocking properties. Detailed Embodiments

[0046] The following examples will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples and should also include any other well-known changes within the scope of the claims of the present invention. The specific applications of the present invention are not limited to those described in the examples, and any simple changes made to the present invention by those familiar with the art using the concept of the present invention are within the scope of protection of the present invention.

[0047] In the examples and comparative examples of the present invention, the sources of the main raw materials are as follows. Unless otherwise specified, other raw materials and reagents are obtained through commercial channels:

[0048] Ethylene: Purchased from Air Liquide, purity 99.95% V;

[0049] 1-Octene, 98%, Ineos;

[0050] 1-Hexene, 99%, Lingyan Bio;

[0051] 1-Butene, 99%, Mingju;

[0052] Solvent isoparaffin IosparE, purchased from ExxonMobil;

[0053] Methylaluminoxane, AkzoNobel, 10% toluene solution;

[0054] Modified methylaluminoxane, Nouryon;

[0055] Triisobutylaluminum: InnoChem;

[0056] Dimethylanilinium tetrakis(pentafluorophenyl)borate: InnoChem;

[0057] Catalyst A: The catalyst prepared in Example 1 of Patent CN111747977B;

[0058] Catalyst B: Dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, Yaodexin Chemical Industry;

[0059] Catalyst C: Dimethylsilyl(tert-butylamino)tetramethylcyclopentadienyl dimethyltitanium, Xin Nuoke.

[0060] The main test instruments and methods used in the examples and comparative examples of the present invention:

[0061] Melt index tester: Zwick Mflow, test standard ASTM D1238;

[0062] The extruder is a single-screw extruder (L / D = 35), screw diameter 30 mm;

[0063] Molecular weight and incorporation rate tester: Polymer Char, GPC-IR;

[0064] Soluble matter analysis: Polymer Char, TGIC, solvent trichlorobenzene.

[0065] TGIC realizes the separation and characterization of different components of polyolefins by temperature - rising elution. The sample is dissolved in trichlorobenzene at 165 °C and passed through the TGIC chromatographic column. The temperature is programmed to drop to 40 °C (20 °C / min). Some polyolefin structures adhere to the chromatographic column due to adsorption and crystallization with the graphite column. It is rinsed at a flow rate of 0.5 ml / min, and the soluble part is flushed to the detector IR5 for detection. Then, it is eluted with temperature rising, and the temperature is raised to 165 °C at a rate of 2 °C / min. The molecules attached to the column are eluted successively according to their crystallization ability differences and the number of short - chain branches.

[0066] Example 1

[0067] Preparation of ethylene / α - olefin copolymer:

[0068] n - hexane solvent (5 kg / h) and 1 - butene (1.2 kg / h, 21.4 mol / h) are added to a 1.5 L high - pressure continuous reactor, and then the temperature at the top of the reactor is pre - heated to 150 °C. Meanwhile, the main catalyst A (0.3 μmol / min), the co - catalyst methylaluminoxane (0.9 mmol / min), and dimethylanilinium tetrakis(pentafluorophenyl)borate (0.70 μmol / min) are introduced into the reactor. Subsequently, ethylene (0.87 kg / h, 31.1 mol / h) and hydrogen (0.012 g / h) are added to the high - pressure reactor, and the copolymerization reaction is continuously carried out at 150 °C under a pressure of 3.5 Mpa for more than 15 minutes to obtain a polymer solution. The Reynolds number in the reaction kettle is controlled to be 8000 by stirring. After adding 1.8 mmol / min of methanol for quenching, it enters a three - stage devolatilization tank for devolatilization. After removing unreacted hexane, 1 - butene, and ethylene in the devolatilization tank, polymer particles are obtained by extrusion granulation, and their properties are tested.

[0069] Examples 2 - 5

[0070] A copolymer is prepared in the same manner as in Example 1, except that catalyst B is used instead of catalyst A, MMAO is used as the co - catalyst instead of MAO, and the amount of each substance is changed as shown in Table 2 below.

[0071] Examples 6 - 10

[0072] A copolymer is prepared in the same manner as in Example 1, except that catalyst C is used instead of catalyst A, triisobutylaluminum is used as the co - catalyst, and the amount of each substance is changed as shown in Table 2 below.

[0073] Comparative Examples 1 - 3

[0074] A catalyst A was used, and the cocatalyst was MAO. A copolymer was prepared in the same manner as in Example 1 except that the amount of each substance was changed as shown in Table 2 below.

[0075] Comparative Example 4

[0076] In Comparative Example 4, LC170 of LG Chem Ltd. was purchased and used, which is a copolymer of ethylene and 1-octene.

[0077] Comparative Example 5

[0078] In Comparative Example 5, 7447 of Dow Chemical Company was purchased and used, which is a copolymer of ethylene and 1-butene.

[0079] [Table 2]

[0080]

[0081] Experimental Example 11

[0082] The physical properties of the copolymers of Examples 1-10 and Comparative Examples 1-5 were evaluated according to the following methods, and the results are shown in Table 3 below.

[0083] 1) Density of the polymer

[0084] Measurement was carried out according to ASTM D-792.

[0085] 2) Melt index (MI) of the polymer

[0086] Measurement was carried out according to ASTM D-1238 [Condition E, (190 °C, load 2.16 kg)].

[0087] 3) Melting temperature (Tm) of the polymer

[0088] The melting temperature was obtained using a differential scanning calorimeter (DSC) 6000 manufactured by PerkinElmer. That is, after raising the temperature to 200 °C, the temperature was held at this temperature for 1 minute, then lowered to -100 °C, and the temperature was raised again to obtain the top of the DSC curve as the melting point. At this time, the rate of temperature rise and fall was 10 °C / min, and the melting point was obtained during the second temperature rise.

[0089] 4) Weight - average molecular weight (Mw, g / mol) and molecular weight distribution (MWD)

[0090] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured separately by gel permeation chromatography (GPC), and the molecular weight distribution was calculated by dividing the weight-average molecular weight by the number-average molecular weight.

[0091] Chromatographic column: PL Olexis

[0092] Solvent: Trichlorobenzene (TCB)

[0093] Flow rate: 1.0 ml / min

[0094] Sample concentration: 1.0 mg / ml

[0095] Injection volume: 200 μl

[0096] Column temperature: 160 °C

[0097] Detector: Agilent high-temperature RI detector

[0098] Standard: Polystyrene (calibrated using a cubic function)

[0099] Value of a: For the determination of the soluble content (wt%) in the TGIC test of ethylene / α-olefin copolymer, the sample is dissolved in trichlorobenzene at 165 °C and passed through the TGIC chromatographic column. The temperature is programmed to decrease to 40 °C (20 °C / min). Due to adsorption and crystallization with the graphite column, part of the polyolefin structure adheres to the chromatographic column and is rinsed at a flow rate of 0.5 ml / min. The soluble part is flushed to the detector IR5 for detection. Then, temperature programming elution is carried out, and the temperature is increased to 165 °C at a rate of 2 °C / min. The molecules adhering to the column are eluted successively according to their crystallization ability differences and the number of short side chains.

[0100] Value of b: The soluble content (wt%) obtained by extracting the ethylene / α-olefin copolymer with the mixed isoparaffin solvent IsoparE at 20 - 30 °C for 6 h.

[0101] [Table 3]

[0102]

[0103] The olefin-based polymer according to the present invention is a low-density olefin-based polymer and shows improved anti-blocking performance due to having a reduced SEF value at the same density as conventional olefin-based polymers.

[0104] It can be seen that when comparing the olefin-based polymers of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3 in Table 3 that exhibit the same or similar density, the olefin-based polymers (ethylene and 1-butene copolymers) of Examples 1 - 3 having the same or similar density as the corresponding olefin-based polymers (ethylene and 1-butene copolymers) of Comparative Examples 1 - 3 show lower SEF values.

[0105] Similarly, it can be seen that when Example 10 and Example 7 are respectively compared with Comparative Example 4 and Comparative Example 5, lower SEF values are exhibited under similar melt index and density conditions.

[0106] Example 12

[0107] Take 50 g of each copolymer in Examples 1-10 and Comparative Examples 1-5 and put them into an 8 cm × 10 cm zip bag. Pierce the zip bag with a needle to remove air and squeeze. Place the zip bag in the central part away from the bottom of the chamber and apply a load of two 2 kg weights on it. Run the chamber temperature program and let it stand at 35°C for 7 hours, at -5°C for 5 hours, at 0°C for 5 hours, and maintain at 0°C. Thereafter, confirm the degree of adhesion.

[0108] The evaluation criteria are shown in Table 4 below, and the experimental results are shown in Table 5 below.

[0109] [Table 4]

[0110] Rating Status 0 Pour out when the zipper bag is opened and turned over 1 Disintegrate during removal of the zipper bag 2 The mass of the removed zipper bag disintegrates within 20 seconds 3 Disintegrate when pressed by hand 4 Disintegrate when pressed strongly 5 Do not disintegrate when pressed by hand

[0111] [Table 5]

[0112]

[0113]

[0114] Referring to Table 5, it can be seen that samples showing higher SEF values at the same or similar densities have higher adhesion grades, indicating poorer anti-adhesion properties.

Claims

1. An ethylene / α-olefin copolymer, which has the following characteristics: a) The melt index (MI) at 190 °C and 2.16 kg is 1 - 30 g / min, preferably 1.5 - 24 g / min, more preferably 3 - 22 g / min; b) The density is 0.850 - 0.910 g / cm 3 , preferably 0.855 - 0.900 g / cm 3 , more preferably 0.860 - 0.890 g / cm 3 ; c) The polydispersity index (PDI, Mw / Mn) is 2.0 - 2.8, preferably 2.1 - 2.7, more preferably 2.2 - 2.6; d) The SEF value < 6%; The SEF value = a + b, Among them, The a value is the soluble content in the ethylene / α-olefin copolymer measured by temperature gradient cross chromatography (TGIC), (wt%); the b value is the soluble content obtained by extracting the ethylene / α-olefin copolymer with an isoparaffin solvent at 20 - 30 °C for 6 h, (wt%).

2. The ethylene / α-olefin copolymer according to claim 1, wherein The soluble matter obtained by extracting an ethylene / α-olefin copolymer with an isoparaffin solvent at 20 - 30°C for 6 h, having a weight average molecular weight Mw< 25,000; and / or The isoparaffin is selected from at least one of C8 - C10 isoparaffins, preferably at least one of 2,4-dimethylhexane, 2,5-dimethylhexane, 2,3,3-trimethylpentane, 2,3,4-trimethylpentane, 2-methylheptane, 2,2,4-trimethylhexane, 2,3,5-trimethylhexane, 2,5-dimethylheptane, 2,3-dimethylheptane, 2,2,4-trimethylheptane, 2,3,6-trimethylheptane, and mixed alkane IsoparE.

3. The ethylene / α-olefin copolymer according to claim 1, wherein The ethylene / α-olefin copolymer is a copolymer of an ethylene monomer and a C3 - C12 α-olefin monomer; Preferably, the α-olefin monomer is selected from at least one of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, and 1-dodecene; Preferably, in the ethylene / α-olefin copolymer, based on the total mass of the copolymer, the α-olefin content is 20 - 38%; and / or The ethylene / α-olefin copolymer has a weight-average molecular weight (Mw) of 40,000 - 150,000, preferably 45,000 - 130,000, more preferably 46,000 - 90,000.

4. A method for preparing the ethylene / α-olefin copolymer according to any one of claims 1-3, characterized in that the step Comprising: Mixing ethylene, α-olefin, catalyst, cocatalyst, optional chain transfer agent, and solvent and adding them to a reaction kettle for solution polymerization reaction to obtain an ethylene / α-olefin copolymer.

5. The preparation method according to claim 4, wherein The catalyst is selected from homogeneous catalysts, preferably at least one of metallocene catalysts and non-metallocene catalysts; and / or The cocatalyst is selected from at least one of aluminoxane, alkyl aluminum compounds, alkyl aluminum chlorides, and organic borides.

6. The preparation method according to claim 4, characterized in that, The solvent is selected from aliphatic hydrocarbon solvents and / or aromatic hydrocarbon solvents; Preferably, the aliphatic hydrocarbon solvent is selected from at least one of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylene cyclopentane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, n-heptane, n-octane, n-nonane, or IsoparE; the aromatic hydrocarbon solvent is selected from at least one of benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, dichlorotoluene, and IsoparE.

7. The preparation method according to claim 4, characterized in that, The chain transfer agent is selected from at least one of hydrogen, methane, ethane, and propane, preferably hydrogen; Preferably, when the chain transfer agent is hydrogen, the hydrogen feed rate controls the system pressure to be 2 - 10 MPaG, preferably 2 - 5 MPaG.

8. The preparation method according to claim 4, characterized in that, The mass ratio of the ethylene to the α-olefin is 1:0.2 - 1:5, preferably 1:1 - 1:3; and / or The addition amount of the catalyst is 1 / 100,000 - 1 / 100,000,000 of the total molar amount of the ethylene and the α-olefin monomers, preferably 1 / 300,000 - 1 / 80,000,000; and / or The addition amount of the cocatalyst is 1 / 100 - 1 / 10,000,000 of the total molar amount of the ethylene and the α-olefin monomers, preferably 1 / 1,000 - 1 / 8,000,000; and / or The addition amount of the solvent is 2 - 10 times the total mass of the ethylene and the α-olefin monomers, preferably 2.5 - 8 times; and / or The addition amount of the chain transfer agent is 1 / 1,000,000 - 1 / 100,000 of the total mass of the ethylene and the α-olefin monomers.

9. The preparation method according to claim 4, characterized in that, For the solution polymerization reaction, the reaction temperature is 100 - 250 °C, preferably 120 - 190 °C; the reaction time is 3 - 20 minutes, preferably 4 - 12 minutes; and / or For the polymerization reaction, the Reynolds number Re is controlled to be 6,000 - 20,000, preferably 6,000 - 10,000.

10. Use of the ethylene / α-olefin copolymer according to any one of claims 1 - 3 or the ethylene / α-olefin copolymer prepared by the method according to any one of claims 4 - 9 in the field of photovoltaic encapsulation films.

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