Polyolefin elastomer for photovoltaic packaging film, preparation method and application

Abstract

The invention discloses a polyolefin elastomer for a photovoltaic packaging film as well as a preparation method and application of the polyolefin elastomer. The polyolefin elastomer simultaneously meets the following requirements: a) the residual amount of metal elements is less than 100 ppm, and b) the total content of crystal grains with the crystal grain thickness Lc being greater than 4 nm, measured by continuous self-nucleation / annealing (SSA) by using a differential scanning calorimeter, is less than 2%. When the polyolefin elastomer provided by the invention is applied to the preparation of a photovoltaic packaging film, the polyolefin elastomer still has the advantage of few film-forming crystal points at a relatively high casting linear speed, is beneficial to reducing the absorption time of an auxiliary agent, and shows the advantages of production cost and product performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of photovoltaic encapsulant film materials, especially a kind of photovoltaic encapsulant film polyolefin elastomer, preparation method and application. BACKGROUND

[0002] With the rapid development of photovoltaic industry, photovoltaic encapsulant film as the key material of photovoltaic module, its performance directly affects the power generation efficiency and service life of photovoltaic module. Polyolefin elastomer (POE) has become the main raw material of photovoltaic encapsulant film due to its excellent light transmittance, weather resistance and electrical insulation performance.

[0003] Currently, the polyolefin elastomer for photovoltaic encapsulant film is mainly composed of ethylene and α-olefin copolymer, and its molecular structure, molecular weight and molecular weight distribution have important influence on the performance of the final encapsulant film. Existing researches have proposed many improvement schemes for its application by adjusting POE product indicators and process, such as the patent application with publication number CN120365466A, which solves the problem of uneven dispersion and failure of photovoltaic adhesive film light transmittance improvement by preparing bimodal distribution of ethylene and α-olefin random or block polymer, combined with crosslinking agent, realizes high light transmittance and high efficiency of photovoltaic cell; the patent application with publication number WO2025043950A1 solves the problem of photovoltaic adhesive film attenuation under PID effect by preparing POE particles with special microstructure and optimizing the content of soluble matter, realizes photovoltaic composition with high light transmittance and high PID resistance, improves the stability and service life of photovoltaic module; the patent application with publication number WO2025043950A1 solves the problem of complex preparation process and poor performance control of dynamic crosslinking polyolefin elastomer by double-kettle series solution polymerization process, combined with dynamic chemical crosslinking agent and initiator, optimizes the catalyst ratio, realizes the preparation of high-performance dynamic crosslinking polyolefin elastomer.

[0004] However, the polyolefin elastomer in the prior art still has some problems when applied to photovoltaic encapsulant film. First, in the processing of photovoltaic adhesive film, crystal point problem seriously affects the product quality and performance. Although the patent application with publication number CN119410295A realizes high light transmittance and high crosslinking degree of photovoltaic encapsulant film by adjusting the molecular weight, molecular weight distribution and long chain branch content of polyolefin elastomer, it fails to effectively solve the problem of crystal point. These crystal points will reduce the light transmittance of the adhesive film, and then affect the absorption and conversion efficiency of photovoltaic module to sunlight.

[0005] Secondly, with the increasing demand of photovoltaic industry for production efficiency, adhesive film processing enterprises need to increase the production line speed to reduce unit energy consumption and production cost. However, the processing performance bottleneck of existing materials seriously restricts the breakthrough of production efficiency, especially under high line speed processing conditions, it is more prone to produce crystal point defects, and it is difficult to adapt to ultra-high speed casting process (such as line speed > 15 m / min). SUMMARY

[0006] To solve the above technical problems, the present application proposes a polyolefin elastomer for photovoltaic encapsulation film, a preparation method and application.

[0007] To achieve the above object, the technical solution adopted by the present application is as follows: Based on the first aspect of the present application, a polyolefin elastomer for photovoltaic encapsulation film is first proposed, characterized in that the polyolefin elastomer simultaneously satisfies the following requirements: a) residual amount of metal elements < 100 ppm, b) total content of crystal grains with grain thickness Lc > 4 nm measured by differential scanning calorimeter continuous self-nucleation / annealing (SSA) < 2%.

[0008] As a preferred embodiment, the molecular weight Mw of the polyolefin elastomer is 40000-100000, the PDI is 2-2.5, and the density is 0.87-0.878 g / cm 3 .

[0009] As a preferred embodiment, the polyolefin elastomer is prepared from ethylene and α-olefin by solution polymerization method. Preferably, the α-olefin is an olefin with carbon atom number 3-13, preferably one or more of propylene, butene, hexene, octene, nonene, decene.

[0010] The present inventors have unexpectedly found, through continuous research, that by adjusting the residual amount of metal elements and the total content of crystal grains with Lc > 4 nm in the polyolefin elastomer within a certain range, the processing performance and crystal point level of the photovoltaic encapsulation film can be improved, especially when the casting line speed during the processing of the photovoltaic encapsulation film is increased, the low crystal point characteristics can still be maintained, further showing that the absorption speed of POE particles to the auxiliary agent is accelerated, and significant application performance advantages are exhibited.

[0011] In the present application, the grain thickness Lc of the polyolefin elastomer is obtained by SSA thermal fractionation measurement, specifically, DSC is applied to SSA treatment of the sample, so that copolymer chain segments with different sequence structures form lamellae with different thicknesses based on the difference in crystallization properties, and then the lamellae with different thicknesses exhibit multiple melting peaks in the last heating scan process of DSC. According to the Thomson-Gibbs equation, the grain thickness of each component is calculated from the peak temperature of the multiple melting peaks, thereby characterizing the crystallization sequence distribution of the copolymer chain.

[0012] The mass fraction of each component corresponding to different crystal grain thicknesses is obtained by multiplying the corresponding melting peak area fraction by 293 / AHm(T) and normalizing, wherein AHm(T) is the melting enthalpy corresponding to each component. The mass fraction of components with a crystal grain thickness Lc>4nm is added, which is the total content of crystal grains with a crystal grain thickness Lc>4nm measured using SSA.

[0013] Based on the second aspect of the present application, a method for preparing the polyolefin elastomer as described above is also proposed, characterized in that the organic solvent and the alpha-olefin are added to a reaction kettle, ethylene gas is introduced to the reaction pressure, the main catalyst and the cocatalyst are added and stirred to react; After the reaction is completed, the reaction solution is inactivated, and after the volatile components are removed, the solution is granulated in an aqueous solution containing a nucleating agent, dried, and the polyolefin elastomer particles are obtained; Preferably, the nucleating agent is one or more of sodium benzoate, sodium adipate, and sodium phenolate. Preferably, in the aqueous solution, the mass ratio of the nucleating agent to water is (0.5-3):1000.

[0014] In order to obtain the polyolefin elastomer with a residual amount of metal elements <100ppm as defined above, the actual addition amount of the main catalyst or the cocatalyst can be reduced by increasing the activity of the main catalyst, or the post-treatment method such as chelation adsorption can be used, and the present application does not make any limitation on this.

[0015] As a feasible method for increasing the activity of the main catalyst, for example, a metallocene catalyst or a post-metallocene catalyst with high copolymerization activity is selected, or a metallocene catalyst or a post-metallocene catalyst with good high-temperature stability is selected in combination with a high-temperature polymerization process, or the addition amount of metal elements is reduced in combination with the cocatalyst, especially the use of organoborides with the cocatalyst to significantly reduce the use amount of the main catalyst and the cocatalyst containing metal elements, which is easy to adjust for industry technicians.

[0016] As a feasible post-treatment method, for example, the chelation adsorption disclosed in CN114950368B and CN114989331B can advantageously control the residual amount of metal elements to be less than 100ppm.

[0017] In order to control the total content of large crystal grains to be less than 2%, the present application preferably introduces a nucleating agent in the granulation process after the polymerization reaction based on the consideration of simple and convenient operation, so that the nucleating agent provides a crystallization core in the particle forming process, the polymer forms fine and dense crystals, the generation of large-size crystal grains is reduced, and the product structure is controllable.

[0018] As a preferred embodiment of the above preparation method, the procatalyst is one or more of metallocene catalysts or post-metallocene catalysts, preferably one or more of bis(silyl)(N-tert-butylamido) (tetramethylcyclopentadienyl) titanium dichloride, bis(silyl)(N-tert-butylamido)(tetramethylcyclopentadienyl) titanium dimethyl, bis(silyl)(N-tert-butylamido)(fluorenyl) titanium dichloride, (pentamethylcyclopentadienyl) titanium trimethoxide, bis(phenylmethylene)(cyclopentadienyl)(9-fluorenyl) zirconium dichloride, dimethylsilyl bis(2-methyl-4-phenyl-1-indenyl) zirconium dichloride, meso-dimethylsilyl 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, rac-dimethylsilyl bis(2-methyl-1-indenyl) zirconium dichloride, bisphenylmethylene cyclopentadienyl(2,7-di-tert-butyl-fluorenyl) zirconium dichloride, bis(p-tolylmethylene cyclopentadienyl)(2,7-di-tert-butyl-fluorenyl) zirconium dichloride, dimethylbis(propylcyclopentadienyl) hafnium, bis(n-butylcyclopentadienyl) hafnium dichloride, dimethylsilyl bis(2-methyl-4-phenylindenyl) zirconium dichloride, dimethylsilyl(tert-butylamido)tetramethylcyclopentadienyl titanium dimethyl. Generally, the procatalyst can be added in an amount ranging from 0.1 to 10 ppm by weight of the polymer.

[0019] As a preferred embodiment of the above preparation method, the cocatalyst comprises one or more of aluminoxane, alkylaluminum and their modifications, preferably one or more of methylaluminoxane, modified methylaluminoxane, triethylaluminum, triisobutylaluminum, trioctylaluminum, mono-chloroethylaluminum, sesqui-ethylaluminum, di-chloroethylaluminum; Preferably, the cocatalyst further optionally comprises one or more of organoborides, preferably one or more of triphenylmethyl tetra(pentafluorophenyl) borate, tris(pentafluorophenyl) boron, N,N-dimethylanilinium tetra(pentafluorophenyl) borate, dioctadecylmethyl tertiary amine tetra(pentafluorophenyl) borate, dihydrogenated tallowmethyl tertiary amine tetra(pentafluorophenyl) borate.

[0020] Generally, the molar ratio of aluminum metal in the cocatalyst to the metal elements in the procatalyst (denoted as Al / M) can be 1 to 2000, preferably 1 to 800; when the cocatalyst contains organoborides, the amount of aluminum metal can be further reduced.

[0021] Generally, the molar ratio of boron in the organoborides to the metal elements in the procatalyst (denoted as B / M) can be 0 to 8, preferably 1 to 5.

[0022] As a preferred solution of the above preparation method, the reaction temperature is 140-200°C, and the reaction pressure is 3-8 MPa.

[0023] As a preferred solution of the above preparation method, the temperature condition of the granulation is 0-20°C.

[0024] As a preferred solution of the above preparation method, the organic solvent is selected from aliphatic hydrocarbon solvents and / or aromatic hydrocarbon solvents; Preferably, the aliphatic hydrocarbon solvent is selected from one or more of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylenecyclopentane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, n-heptane, n-octane, n-nonane, Isopar E; and the aromatic hydrocarbon solvent is selected from one or more of benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, dichlorotoluene.

[0025] Based on the third aspect of the present application, there is also provided a use of the polyolefin elastomer as described above or the polyolefin elastomer prepared by the method as described above in a photovoltaic encapsulant film.

[0026] As a specific example, a photovoltaic encapsulant film is characterized in that it comprises the following components in parts by weight: polyolefin elastomer, 100 parts, crosslinking agent, 0.1-5 parts, preferably 0.5-2 parts, coagent, 0.1-3 parts, preferably 0.1-0.6 parts, coagent, 0.1-3 parts, preferably 0.1-0.6 parts, wherein the polyolefin elastomer is the polyolefin elastomer for photovoltaic encapsulant film as provided above or the polyolefin elastomer prepared by the method as described above.

[0027] Preferably, the crosslinking agent is a peroxide crosslinking agent, including but not limited to one or more of the following: tert-butyl peroxy isopropyl carbonate, 2,5-dimethyl-2,5-(bis-tert-butyl peroxy) hexane, tert-butyl peroxy-2-ethylhexyl carbonate, 1,1-bis(tert-butyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amyl peroxy)cyclohexane, 1,1-bis(tert-butyl peroxy)cyclohexane, 2,2-bis(tert-butyl peroxy)butane, tert-butyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxy-(2-ethylhexyl) carbonate, tert-butyl peroxy-3,3,5-trimethylhexanoate; Further, the co-coupling agent is a silane coupling agent, including but not limited to one or more of the following: gamma-chloropropyl methoxysilane, dimethyl vinyl ethoxysilane, vinyl tri (beta-methoxyethoxy) silane, gamma-methacryloyloxypropyl trimethoxysilane, vinyl triacetoxy silane, gamma-glycidoxypropyl trimethoxysilane, 3- (trimethoxysilyl) propyl-2-methyl-2-acrylate, aniline methyl triethoxysilane, octyl trimethoxysilane. Further, the co-coupling agent is a silane coupling agent, including but not limited to one or more of the following: gamma-chloropropyl methoxysilane, dimethyl vinyl ethoxysilane, vinyl tri (beta-methoxyethoxy) silane, gamma-methacryloyloxypropyl trimethoxysilane, vinyl triacetoxy silane, gamma-glycidoxypropyl trimethoxysilane, 3- (trimethoxysilyl) propyl-2-methyl-2-acrylate, aniline methyl triethoxysilane, octyl trimethoxysilane.

[0028] In the present application, the preparation of the photovoltaic packaging film can adopt conventional methods in the art, for example, including the following steps: raw material high temperature pre-mixing, melt extrusion, film casting, cooling and slitting, and winding process.

[0029] The present application has the following advantages: The polyolefin elastomer prepared by the present application has the advantages of less crystallization points at a higher casting line speed when applied to prepare photovoltaic packaging films, which helps to reduce the additive absorption time, and shows production cost advantage and product performance advantage. DETAILED DESCRIPTION

[0030] The present application will be further described below by specific examples, and the examples described in the present application are only used to illustrate the present application, and do not limit the scope of the present application.

[0031] In the present application, "parts" and "%" are by weight, unless otherwise specified.

[0032] The raw materials and reagents in the following examples and comparative examples of the present application can be obtained by commercial channels, unless otherwise specified. Among them, the information of the main raw materials is as follows: Methylaluminoxane, Aksu, 10% toluene solution; Modified methylaluminoxane, Norsolite; Dimethylsilyl bis(2-methyl-4-phenylindenyl) zirconium dichloride, Yaodeshixin Chemical Industry; Di-p-tolylmethylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride, Yafen Technology; Dimethylsilyl (N-tert-butylamido) (tetramethylcyclopentadienyl) titanium dimethyl, Jiangsu Xinnuo Catalyst Co., Ltd.; Dimethyl bis(propylcyclopentadienyl) hafnium, Yafen Technology; Diphenylmethylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride, Yaodeshixin Chemical Industry; Dimethylsilyl (tert-butylamido) tetramethylcyclopentadienyl titanium dimethyl, Xinnuo.

[0033] The main performance test methods and devices involved in the following examples and comparative examples of the present application are as follows: (1) Melt index: tester uses Zwick Mflow, test standard ASTM D1238; (2) Extruder: single screw extruder (L / D=35), screw diameter 30mm; (3) Molecular weight and insertion rate: tester uses Polymer Char, GPC-IR; (4) Metal residual amount: after wet decomposition of the polyolefin elastomer, use pure water to constant volume, and use inductively coupled plasma emission spectrometer (ICP)-Agilent, USA, to quantitatively determine the metal elements, and the total amount of these elements is taken as the metal residual amount, unit ppm; (5) Crystal grain content: use DSC tester to measure the SSA thermal classification of the polyolefin elastomer, the specific method is: in the first cycle, raise the temperature to 150℃, keep for 1 minute, and reduce to-50℃; in the second cycle, raise the temperature to 120℃, keep for 5 minutes, and reduce to-50℃; in the third cycle, raise the temperature to 112.5℃, keep for 5 minutes, and reduce to-50℃; according to the above cycle operation, raise the temperature and keep for 5 minutes, and then reduce the temperature, the fourth cycle (i.e. in the fourth cycle, raise the temperature to the highest point 105℃ at an interval of 7.5℃ and keep for 5 minutes, and then reduce the temperature to-50℃), the fifth cycle (i.e. in the fifth cycle, raise the temperature to the highest point 97.5℃ at an interval of 7.5℃ and keep for 5 minutes, and then reduce the temperature to-50℃), the sixth cycle……, until the temperature reaches-40℃ in the last time of temperature scanning, to obtain multiple melting peaks corresponding to different thickness of lamellar crystals.

[0034] According to the Thomson-Gibbs equation, the crystal grain thickness of each component is calculated from the melting point of the multiple melting peaks:

[0035] where Tm is the melting point of the melting peak, T 0 m is the equilibrium melting point of polyethylene lamellae (418.5 K), σ is the lateral surface free energy of infinite polyethylene lamellae (90 x 10 -3 J / m 2 ), and ΔHv is the enthalpy of fusion of infinite polyethylene lamellae (293 x 10 6 J / m 3 ).

[0036] At the same time, the mass fraction of the component with a lamellar thickness Lc > 4 nm is obtained by multiplying the area fraction of the corresponding melting peak of the component by 293 / ΔHm(T) and normalizing, wherein ΔHm(T) is the enthalpy of fusion of the corresponding component. The total content of the lamellar thickness Lc > 4 nm is obtained by adding the mass fraction of the component with a lamellar thickness Lc > 4 nm.

[0037] The following Examples 1-8 and Comparative Examples 1-3 are used to prepare different polyolefin elastomers: Example 1 Preparation of polyolefin elastomer A: using a solution polymerization method, 2.8 kg of octene is added to 4.2 kg of n-butane solvent to form a solution, which is then added to a reaction kettle, the temperature is raised to 150°C, ethylene gas is introduced, and the pressure in the kettle is controlled at 3 MPa. 1 mg of the main catalyst dimethyl silicon-based bis(2-methyl-4-phenyl indenyl) zirconium dichloride is added to the reaction kettle, and the co-catalyst (1.5 mol / L methylaluminoxane toluene solution) is added according to Al / Zr=20, and tris(pentafluorophenyl) boron is added at the same time. The molar ratio of boron in the organoboron compound to the metal element in the main catalyst (denoted as B / Zr) is 2. After stirring for 8 minutes, 30 g of water is mixed with the reaction liquid for inactivation, and after the volatile matter is removed, underwater granulation is performed. The granulation solution is a sodium benzoate aqueous solution, the mass ratio of water to sodium benzoate is 1000:0.5, and the water temperature is 10°C. After granulation and drying, the polymer, i.e., polyolefin elastomer A (Mw is 69000, PDI is 2.5, density is 0.8712 g / cm 3 , the total content of the lamellar thickness Lc (nm) > 4 nm is 1.7%, the metal residual amount is 75 ppm).

[0038] Example 2 Preparation of polyolefin elastomer B: using solution polymerization method, 2.6 kg of octene was added into 5 kg of Isopar E to form a solution, which was then added into a reaction kettle, and the temperature was raised to 148 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled to be 5 MPa. 4.88 mg of the main catalyst bis-p-tolylmethylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride was added into the reaction kettle, and the cocatalyst (methylaluminoxane toluene solution with an Al concentration of 1.5 mol / L) was added according to Al / Zr = 40, and tris(pentafluorophenyl) boron was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Zr) of 1.3, and after stirring for 10 minutes, 30 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, and the granulation solution was a sodium adipate aqueous solution, and the mass ratio of water to sodium adipate was 1000:1, and the water temperature was 15 ℃, and after granulation, the polymer was dried to obtain polyolefin elastomer B (Mw was 57000, PDI was 2.2, density was 0.8750 g / cm 3 , the metal residual amount was 90 ppm, and the total content of the crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 1.9%).

[0039] Example 3 Preparation of polyolefin elastomer C: using solution polymerization method, 1.9 kg of butene was added into 5.7 kg of Isopar E to form a solution, which was then added into a reaction kettle, and the temperature was raised to 155 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled to be 3 MPa. 18.4 mg of the main catalyst dimethylsilyl (N-tert-butylamine) (tetramethylcyclopentadienyl) titanium dichloride was added into the reaction kettle, and the cocatalyst (7 wt% Al modified methylaluminoxane Isopar E solution) was added according to Al / Ti = 30, and tris(pentafluorophenyl) boron was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Ti) of 4, and after stirring for 8 minutes, 30 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, and the granulation solution was a sodium benzoate aqueous solution, and the mass ratio of water to sodium benzoate was 1000:2.5, and the water temperature was 8 ℃, and after granulation, the polymer was dried to obtain polyolefin elastomer C (Mw was 51000, PDI was 2.15, density was 0.8731 g / cm 3 , the metal residual amount was 48 ppm, and the total content of the crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 0.5%).

[0040] Example 4 Preparation of polyolefin elastomer D: using solution polymerization method, 3.3 kg of hexene was added into 8.9 kg of Isopar E solvent to form a solution, which was then added into a reaction kettle, the temperature was raised to 140 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled at 4 MPa. 25.2 mg of dimethyl bis (propyl cyclopentadienyl) hafnium was added into the reaction kettle, and the co-catalyst (methylaluminoxane toluene solution with an Al concentration of 1.5 mol / L) was added according to Al / Hf=45, and tris (pentafluorophenyl) boron was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Hf) of 2, and after stirring for 7 minutes, 30 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, the water solution was a sodium phenate aqueous solution, the mass ratio of water to sodium phenate was 1000:1.5, and the water temperature was 5 ℃, and after granulation, drying was performed to obtain the polymer, i.e., polyolefin elastomer D (Mw is 58000, PDI is 2.25, density is 0.8725 g / cm 3 , metal residual amount is 93 ppm, and the total content of crystal grains with a crystal grain thickness Lc (nm) > 4 nm is 0.2%).

[0041] Example 5 Preparation of polyolefin elastomer E: using solution polymerization method, 2.35 kg of octene was added into 4.68 kg of Isopar E solvent to form a solution, which was then added into a reaction kettle, the temperature was raised to 160 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled at 3.5 MPa. 20.4 mg of diphenyl methylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride was added into the reaction kettle, and the co-catalyst (7% Al Isopar E modified methylaluminoxane solution) was added according to Al / Zr=10, and tris (pentafluorophenyl) boron was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Zr) of 1.5, and after stirring for 6 minutes, 30 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, the granulation solution was a sodium benzoate aqueous solution, the mass ratio of water to sodium benzoate was 1000:1, and the water temperature was 1 ℃, and after granulation, drying was performed to obtain the polymer, i.e., polyolefin elastomer E (Mw is 64000, PDI is 2.34, density is 0.8720 g / cm 3 , metal residual amount is 41 ppm, and the total content of crystal grains with a crystal grain thickness Lc (nm) > 4 nm is 1.1%).

[0042] Example 6 Preparation of polyolefin elastomer F: Preparation of polyolefin elastomer F: using solution polymerization method, 3.2 kg of octene was added into 4.8 kg of Isopar E to form a solution, which was then added into a reaction kettle, the temperature was raised to 145 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled at 4.5 MPa. 5.12 mg of main catalyst bis-p-tolylmethylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride was added into the reaction kettle, and the cocatalyst (methylaluminoxane toluene solution with Al concentration of 1.5 mol / L) was added according to Al / Zr=20, and triphenylmethyl tetrakis (pentafluorophenyl) borate was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Zr) of 3, and after stirring for 8 minutes, 50 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, the granulation solution was sodium adipate aqueous solution, the mass ratio of water to sodium adipate was 1000:1.5, and the water temperature was 12 ℃, and after granulation and drying, the polymer, i.e., polyolefin elastomer B (Mw was 49000, PDI was 2.3, density was 0.8720 g / cm 3 , the metal residual amount was 58 ppm, and the total content of crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 1.7%).

[0043] Example 7 Preparation of polyolefin elastomer G: Preparation of polyolefin elastomer G: using solution polymerization method, 2.1 kg of octene was added into 5.1 kg of n-butane solvent to form a solution, which was then added into a reaction kettle, the temperature was raised to 140 ℃, and ethylene gas was introduced, and the pressure in the kettle was controlled at 5 MPa. 1.4 mg of main catalyst bis-p-tolylmethylene cyclopentadiene (9-fluorenyl) zirconium dichloride was added into the reaction kettle, and the cocatalyst (methylaluminoxane toluene solution with Al concentration of 1.5 mol / L) was added according to Al / Zr=45, and triphenylmethyl tetrakis (pentafluorophenyl) borate was added at the same time, the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Zr) was 3, and after stirring for 6 minutes, 60 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, the granulation solution was sodium benzoate aqueous solution, the mass ratio of water to sodium benzoate was 1000:2, and the water temperature was 13 ℃, and after granulation and drying, the polymer, i.e., polyolefin elastomer A (Mw was 61000, PDI was 2.35, density was 0.8732 g / cm 3 , the metal residual amount was 75 ppm, and the total content of crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 1.5%).

[0044] Example 8 Preparation of polyolefin elastomer H: Preparation of polyolefin elastomer D: using solution polymerization method, hexene 2.8 kg was added to 8 kg of Isopar E solvent to form a solution, which was then added to a reaction kettle, and the temperature was raised to 150°C. Ethylene gas was introduced, and the pressure in the kettle was controlled at 3.5 MPa. The main catalyst dimethyl bis (propyl cyclopentadienyl) hafnium 20.1 mg was added to the reaction kettle, and the cocatalyst (methylaluminoxane toluene solution with Al concentration of 1.5 mol / L) was added according to Al / Hf=35. The tris (pentafluorophenyl) boron was added according to the molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Hf) of 2. After stirring for 8 minutes, 50 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was carried out. The water solution was a sodium benzoate aqueous solution, the mass ratio of water to sodium benzoate was 1000:2.5, and the water temperature was 8°C. After granulation and drying, the polymer, i.e. polyolefin elastomer D (Mw 55000, PDI 2.35, density 0.8735 g / cm 3 , metal residual amount 93 ppm, total content of crystal grains with crystal grain thickness Lc (nm) > 4 nm 1.6%).

[0045] Comparative Example 1 Preparation of polyolefin elastomer D-1: using solution polymerization method, octene 4 kg was added to 7 kg of n-butane solvent to form a solution, which was then added to a reaction kettle, and the temperature was raised to 150°C. Ethylene gas was introduced, and the pressure in the kettle was controlled at 4 MPa. The main catalyst dimethyl silyl (tert-butyl amino) tetramethyl cyclopentadienyl dimethyl titanium 20.5 mg (about 10 ppm) was added to the reaction kettle, and the cocatalyst (methylaluminoxane toluene solution with Al concentration of 1.5 mol / L) was added according to Al / Zr=1800. The reaction solution was obtained after stirring for 16 min; 30 g of water was mixed with the reaction solution, and after the volatile matter was removed, underwater granulation was carried out. The water temperature was 25°C. After granulation and drying, the polymer, i.e. polyolefin elastomer D-1, was obtained. Mw 68000, PDI 2.5, density 0.8720 g / cm 3 , metal residual amount 169 ppm, total content of crystal grains with crystal grain thickness Lc (nm) > 4 nm 2.4%.

[0046] Comparative Example 2 Preparation of polyolefin elastomer D-2: using solution polymerization method, 2.95 kg of octene was added into 4.92 kg of Isopar E solvent to form a solution, which was then added into a reaction kettle, and the temperature was raised to 150°C, and ethylene gas was introduced, and the pressure in the kettle was controlled at 4 MPa. 26.2 mg of the main catalyst diphenyl methylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride was added into the reaction kettle, and the cocatalyst (7% Al Isopar E modified methylaluminoxane solution) was added according to Al / Zr=2000, and after 10 minutes of stirring reaction, 50 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, and the granulation solution was a sodium benzoate aqueous solution, and the mass ratio of water to sodium benzoate was 1000:1.5, and the water temperature was 6°C, and after granulation, drying was performed to obtain the polymer, i.e., polyolefin elastomer E (Mw was 62000, PDI was 2.25, density was 0.8710 g / cm 3 , the metal residual amount was 225 ppm, and the total content of the crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 1.4%).

[0047] Comparative Example 3 Preparation of polyolefin elastomer D-3: using solution polymerization method, 4.15 kg of octene was added into 5.8 kg of Isopar E to form a solution, which was then added into a reaction kettle, and the temperature was raised to 145°C, and ethylene gas was introduced, and the pressure in the kettle was controlled at 5 MPa. 5.12 mg of the main catalyst diphenyl methylene cyclopentadiene (2,7-di-tert-butyl-fluorenyl) zirconium dichloride was added into the reaction kettle, and the cocatalyst (Aluminum methylaluminoxane toluene solution with an Al concentration of 1.5 mol / L) was added according to Al / Zr=60, and tris(pentafluorophenyl)boron was added according to a molar ratio of boron in the organoboron compound to the metal elements in the main catalyst (denoted as B / Zr) of 5, and after 15 minutes of stirring reaction, 60 g of water was mixed with the reaction solution for inactivation, and after the volatile matter was removed, underwater granulation was performed, and the water temperature was 11°C, and after granulation, drying was performed to obtain the polymer, i.e., polyolefin elastomer B (Mw was 54000, PDI was 2.28, density was 0.8726 g / cm 3 , the metal residual amount was 59 ppm, and the total content of the crystal grains with a crystal grain thickness Lc (nm) > 4 nm was 2.87%).

[0048] Application Examples 1-8 and Application Comparative Examples 1-3 Using polyolefin elastomers A-H and polyolefin elastomers D-1, D-2, and D-3 prepared above as raw materials, photovoltaic packaging adhesive films were prepared according to the following method to prepare Application Examples 1-10 and Application Comparative Examples 1-3, and the specific method was as follows: To 1000g polyolefin elastomer, 9g tert-butyl peroxy-2-ethylhexyl carbonate, 5g triallyl isocyanurate, 2g γ-methacryloyloxypropyl trimethoxysilane, 1g γ-(2, 3-epoxypropoxy) propyl trimethoxysilane are added. The above raw materials are heated to 50°C and mixed uniformly, and the extruder parameters are adjusted, the temperature of the discharge port to the die is 80°C, 90°C, 90°C, 90°C, 90°C, 95°C, 95°C, 95°C, the screw speed is adjusted to 28r / min, the pulling speed is 1.4r / min, and the winding is driven. Through the processes of extrusion, flow casting, cooling, slitting and winding, a packaging film for photovoltaic modules is prepared, and the film thickness is 0.55mm. (The process corresponds to a flow casting line speed of 13m / min) In addition, the raw materials are mixed and extruded in the same way as described above, and the difference is only that the screw speed of the extruder is adjusted to 21r / min, the pulling speed is 1.2r / min, and the winding is driven. Through the processes of extrusion, flow casting, cooling, slitting and winding, a packaging film for photovoltaic modules is prepared, and the film thickness is 0.55mm. (The process corresponds to a flow casting line speed of 10m / min) The additive absorption time during the production of the photovoltaic packaging film in the above application examples 1-10 and application comparative examples 1-3 is tested, and the quantitative evaluation method in the patent application with publication number CN118746677A is referred to.

[0049] In addition, the different photovoltaic packaging films prepared in the above application examples 1-10 and application comparative examples 1-3 are tested for crystal point defect rate, and the test method is as follows: the crystal points are counted according to the ASTM D 3351 standard, an LED backlight detection platform is used, the illumination is not less than 1000lux, and the number of crystal points within 2 square meters is detected online, and finally the number of defects is counted.

[0050] Table 1

[0051] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and supplements without departing from the method of the present application, and these improvements and supplements should also be considered as the protection scope of the present application.

Claims

1. A polyolefin elastomer for a photovoltaic encapsulant film, characterized by, The polyolefin elastomer simultaneously satisfies the following requirements: a) residual amount of metal elements < 100 ppm, b) total content of crystal grains with grain thickness Lc > 4 nm measured by using a differential scanning calorimeter for continuous self-nucleation / annealing (SSA) < 2%.

2. The polyolefin elastomer for photovoltaic encapsulating films according to claim 1, characterized by, The polyolefin elastomer has a molecular weight Mw of 40,000-100,000, a PDI of 2-2.5, and a density of 0.87-0.878 g / cm 3 .

3. The polyolefin elastomer for photovoltaic encapsulating films according to claim 2, characterized by, The olefin elastomer is prepared from ethylene and an α-olefin by a solution polymerization method; The α-olefin is an olefin with 3-13 carbon atoms; or The α-olefin is one or more of propylene, butene, hexene, octene, nonene, decene.

4. A method for producing a polyolefin elastomer for a photovoltaic encapsulant film according to any one of claims 1 to 3, characterized by, An organic solvent and an α-olefin are added into a reaction kettle, ethylene gas is introduced to a reaction pressure, a main catalyst and a cocatalyst are added and stirred to react; After the reaction is completed, inactivation is performed to obtain a reaction solution, which is then removed of volatile components and granulated in an aqueous solution containing a nucleating agent, dried to obtain polyolefin elastomer particles; The nucleating agent is one or more of sodium benzoate, sodium adipate, sodium phenate; In the aqueous solution, the mass ratio of the nucleating agent to water is (0.5-3):1000.

5. The method for preparing the polyolefin elastomer for photovoltaic encapsulation film according to claim 4, characterized in that, The main catalyst is a metallocene catalyst or a post-metallocene catalyst; or The main catalyst is one or more of dimethylsilyl(N-tert-butylamido) (tetramethylcyclopentadienyl) titanium dichloride, dimethylsilyl(N-tert-butylamido) (tetramethylcyclopentadienyl) titanium dimethyl, dimethylsilyl(N-tert-butylamido) (fluorenyl) titanium dichloride, (pentamethylcyclopentadienyl) titanium trimethoxide, bis (methylene) (cyclopentadienyl) (9-fluorenyl) zirconium dichloride, dimethylsilyl bis(2-methyl-4-phenyl-1-indenyl) zirconium dichloride, meso-dimethylsilyl 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, rac-dimethylsilyl bis(2-methyl-1-indenyl) zirconium dichloride, bis(methylene) cyclopentadienyl (2,7-di-tert-butyl-fluorenyl) zirconium dichloride, bis(p-methyl-methylene) cyclopentadienyl (2,7-di-tert-butyl-fluorenyl) zirconium dichloride, dimethyl bis(propylcyclopentadienyl) hafnium, bis(n-butylcyclopentadienyl) hafnium dichloride, dimethylsilyl bis(2-methyl-4-phenylindenyl) zirconium dichloride, dimethylsilyl (tert-butylamido) tetramethylcyclopentadienyl titanium dimethyl.

6. The method for preparing the polyolefin elastomer for photovoltaic encapsulation film according to claim 4, characterized in that, The cocatalyst includes one or more of aluminoxane, aluminum alkyl and modified products thereof; and / or The cocatalyst is one or more of methyl aluminoxane, modified methyl aluminoxane, triethyl aluminum, triisobutyl aluminum, trioctyl aluminum, mono-chloroethyl aluminum, sesqui-ethyl aluminum, di-chloroethyl aluminum; and / or The cocatalyst optionally further comprises an organic boron compound.

7. The method of producing a polyolefin elastomer for a photovoltaic encapsulant film according to any one of claims 4 to 6, characterized in that, The reaction temperature is 140-200°C, and the reaction pressure is 3-8 MPa.

8. The method of producing a polyolefin elastomer for a photovoltaic encapsulant film according to any one of claims 4 to 6, characterized in that, The temperature condition for the granulation is 0-20°C.

9. The method of producing a polyolefin elastomer for a photovoltaic encapsulant film according to any one of claims 4 to 6, characterized in that, The organic solvent is selected from aliphatic hydrocarbon solvents and / or aromatic hydrocarbon solvents.

10. Use of a polyolefin elastomer according to any one of claims 1 to 3 or a polyolefin elastomer produced according to the method of any one of claims 4 to 9 in a photovoltaic encapsulant film.

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