Modified Catalyst and Its Preparation Method, Polyolefin Elastomer and Its Preparation Method and Application

Abstract

The present invention provides a modified catalyst and a preparation method thereof, a polyolefin elastomer and a preparation method and application thereof. The modified catalyst comprises a catalyst matrix and a coating layer coated on the outer surface of the catalyst matrix. Among them, the catalyst matrix is a metallocene catalyst, and the metallocene catalyst comprises a dichlorodicyclopentadienylzirconium main catalyst and a butylaluminoxane cocatalyst, and the coating layer material is a low-carbon olefin homopolymer. The polyolefin elastomer prepared by the present invention has improved uniformity of comonomer insertion into the molecular chain segment and enhanced light transmittance of the product, making its industrial application prospect broader.

Description

Technical Field

[0001] The present application relates to the technical field of polyolefin elastomers, and particularly relates to a modified catalyst and a preparation method thereof, a polyolefin elastomer and a preparation method and application thereof. Background Art

[0002] Polyolefin elastomer (POE), in its preparation process, a large amount of comonomer, i.e., α-olefin, is introduced into the ethylene main chain, disrupting the original crystalline state and forming more short branches, making the polymer tend to the "plasticizing effect". Thereby reducing the crystallinity of ethylene on the branches and enabling the material to have better optical properties. Moreover, POE has advantages such as low volume resistivity, low water vapor transmission rate, good aging resistance, and small potential induced degradation (PID). Generally, it is used to produce EPE structure (EVA-POE-EVA) film or pure POE film by the three-layer coextrusion casting method with EVA (ethylene-vinyl acetate copolymer).

[0003] Currently, the proportion of POE in the raw materials of photovoltaic module encapsulation films is 20 - 30%, and there is still room for further improvement. With the progress of photovoltaic technology, N-type batteries will dominate in future photovoltaic modules, and the module type will develop from single-glass single-sided power generation to double-glass double-sided power generation. Different battery and module types require corresponding encapsulation materials. EPE films and POE films are indispensable encapsulation materials for future new batteries. The continuous growth of the global demand for photovoltaic modules will lead to a substantial increase in the demand for EVA and POE encapsulation materials.

[0004] From the perspective of application, to ensure a high photoelectric conversion efficiency of photovoltaic power generation modules, the photovoltaic film must have a high light transmittance. Referring to the energy industry standard "NB / T10200 - 2019 Polyolefin Elastomer (POE) Encapsulation Insulating Film for Crystalline Silicon Solar Cell Modules", the light transmittance requirements for POE films are ≥70% in the range of 290 - 380 nm and ≥90% in the range of 380 - 1100 nm. However, the actual procurement quality requirement of POE for photovoltaic films by photovoltaic film enterprises is that the light transmittance is ≥85% in the range of 290 - 380 nm and ≥90% in the range of 380 - 1100 nm. Currently, POE for photovoltaic films is produced by two processes: solution polymerization and gas-phase polymerization. Generally, the stable and mature POE for photovoltaic films in the market has a relatively high light transmittance, while there may be problems of insufficient light transmittance for solution-process POE with poor quality stability or gas-phase POE with a relatively high density. With a density of 0.8750 - 0.8880 g / cm 3Taking gas-phase POE within a certain range as an example, affected by factors such as microstructure, the total light transmittance (0.5-mm sample) is generally 84-88%, seriously affecting its application proportion in photovoltaic POE films and failing to give full play to the advantages of low production cost and low product odor of gas-phase POE. In addition, gas-phase POE with lower light transmittance may contain microcomponents with high melting points, which cannot be effectively plasticized within the processing temperature range of photovoltaic films, resulting in holes or an excessive number of crystal points in the prepared photovoltaic films and quality issues.

[0005] In the prior art, Chinese Patent Publication No.: CN118221858A discloses a preparation method of a polyolefin elastomer POE for photovoltaic encapsulation. Under anhydrous and anaerobic conditions, ethylene, comonomer, organic solvent, main catalyst and cocatalyst are added into a polymerization stirring reactor for reaction to obtain elastomer POE, which is produced by a solution process. Chinese Patent Publication No.: CN116789883A discloses a polyolefin elastomer and its application in a photovoltaic encapsulation film. In the elastomer preparation step, it is clearly stated that the solvent and α-olefin are mixed and then injected into the reactor, which is a solution polymerization process; the composition prepared from the elastomer has more excellent optical properties, electrical insulation properties and anti-PID properties for photovoltaic encapsulation films. Chinese Patent Publication No.: CN116041598A discloses an olefin polymer for a photovoltaic film and its solution polymerization method, and this method obtains an olefin polymer for a photovoltaic film with improved anti-PID properties. Chinese Patent Publication No.: CN115746746A discloses a polyolefin elastomer composition for a photovoltaic encapsulation film, and its polyolefin elastomer is obtained by solution polymerization. By analysis, the relationship between the POE structure and the properties of the polyolefin elastomer composition is found, thus ensuring that the properties such as light transmittance, water vapor transmission rate, and volume resistivity of the polyolefin elastomer composition are maintained at a relatively high level. Chinese Patent Publication No.: CN117567961B discloses an ethylene / α-olefin random copolymer for a photovoltaic film and its application. The copolymer has a fast crosslinking speed and a high crosslinking degree in the application of a photovoltaic film, and the photovoltaic film has a high light transmittance; it is clearly stated that the copolymer is prepared by a kettle reactor and a solution polymerization process.

[0006] Based on this, in the above prior art content, the POE for photovoltaic films is mainly produced by a solution polymerization process, and the solution process is relatively complex and cumbersome. However, the POE produced by a gas-phase polymerization process has the defect of low light transmittance. There is an urgent need to provide a modified catalyst and its preparation method, a polyolefin elastomer and its preparation method to improve the above problems. Summary of the Invention

[0007] The main object of the present invention is to provide a modified catalyst and its preparation method, a polyolefin elastomer and its preparation method and application, so as to solve the technical problem that the polyolefin elastomer in the existing gas-phase polymerization process technology has a relatively low light transmittance.

[0008] To achieve the above object, according to one aspect of the present invention, there is provided a modified catalyst, which includes a catalyst matrix and a coating layer coated on the outer surface of the catalyst matrix. Among them, the catalyst matrix is a metallocene catalyst, and the metallocene catalyst includes a dichlorodicyclopentadienylzirconium main catalyst and a butylaluminoxane cocatalyst, and the coating layer material is a low-carbon olefin homopolymer.

[0009] Further, the thickness of the coating layer is 40-140 μm, the modified catalyst is granular, and its particle size D50 is 130-330 μm.

[0010] To achieve the above object, according to one aspect of the present invention, there is provided a preparation method of a modified catalyst, and the preparation method includes: carrying out a micro-polymerization reaction on the catalyst matrix, olefins, nitrogen and a solvent to form a coating layer on the outer surface of the catalyst matrix to obtain a modified catalyst.

[0011] Further, the olefins are selected from one or more of ethylene, propylene or 1-butene; preferably, the solvent is selected from one or more of cyclopentane, propane, butane, pentane or hexane; preferably, the temperature of the micro-polymerization reaction is 25-45 °C, the reaction pressure is 0.2-0.5 MPa, and the reaction time is 20-50 min.

[0012] According to another aspect of the present invention, there is provided a preparation method of a polyolefin elastomer, including the step of using a modified catalyst, and the modified catalyst is the modified catalyst obtained by the above preparation method of the modified catalyst. The preparation method of the polyolefin elastomer includes: mixing the modified catalyst, ethylene, 1-butene, hydrogen, nitrogen, and a condensing agent in a gas-phase fluidized bed reactor, and then carrying out a polymerization reaction on the modified catalyst and an antistatic agent in the fluidized bed layer of the gas-phase fluidized bed reactor to obtain a polyolefin elastomer.

[0013] Further, the condensing agent is selected from one or more of propane, pentane or cyclopentane, and the addition amount of the antistatic agent accounts for 0.001-0.010% of the addition amount of ethylene.

[0014] Further, the polymerization reaction temperature is 40-70 °C, the polymerization reaction pressure is 1.5-5.5 MPa, the polymerization reaction time is 12-18 h, and the yield of the modified catalyst is 6000-9900 g of product / g of catalyst.

[0015] According to another aspect of the present invention, there is provided a polyolefin elastomer which is obtained by the preparation method of the above polyolefin elastomer.

[0016] Further, the density of the polyolefin elastomer is 0.8750 - 0.8880 g / cm 3 , the melt mass flow rate is 4 - 14 g / 10 min, the molecular weight distribution width PDI is 2.0 - 2.3. When the thickness of the polyolefin elastomer is 0.5 mm, the light transmittance at a wavelength of 290 - 380 nm is 85 - 90%, and the light transmittance at a wavelength of 380 - 1100 nm is 90 - 93.5%.

[0017] According to another aspect of the present invention, there is provided an application of the polyolefin elastomer in the field of POE pure gum film or EPE structure photovoltaic gum film, and the polyolefin elastomer is the above polyolefin elastomer.

[0018] By applying the polyolefin elastomer prepared by the present invention, the uniformity of the comonomer inserted into the molecular chain segment is improved, and the light transmittance of the product is increased, making its industrial application prospect wider. Specific Embodiments

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0020] As described in the background art section of the present invention, the polyolefin elastomer in the existing gas-phase polymerization process technology has the technical problem of low light transmittance. Based on this, the present invention provides a modified catalyst, which includes a catalyst matrix and a coating layer coated on the outer surface of the catalyst matrix. Among them, the catalyst matrix is a metallocene catalyst, and the metallocene catalyst includes a dichlorodicyclopentadienyl zirconium main catalyst and a butylaluminoxane cocatalyst, and the coating layer material is a low-carbon olefin homopolymer.

[0021] Currently, the main microstructure factors affecting the light transmittance of polyolefins are the crystallinity of the comonomer α-olefin, the grain size, and the uniformity of its distribution. When the comonomer α-olefin is inserted more uniformly into the ethylene molecular chain, its distribution uniformity is higher, the grain size it exhibits is more uniform, and thus its light transmittance is higher. However, when the comonomer α-olefin is inserted more unevenly into the ethylene molecular chain, its distribution is uneven, with a higher content of large grains or more fine fragmented grains, and the grain size is uneven, resulting in a poorer light transmittance. The present invention uses a novel modified catalyst to reduce the activity of the original catalyst and slow down the degree of instantaneous explosive polymerization during the polymerization reaction with the addition of the catalyst, so that the comonomer can be more orderly and uniformly distributed onto the main chain of the ethylene molecule, thereby improving the light transmittance. Specifically, the modified catalyst provided by the present invention is obtained by further coating on the basis of the catalyst matrix metallocene catalyst, and the coating material is a low-carbon olefin homopolymer, which can further improve the structural stability of the catalyst. This modified catalyst solves the problem that in the gas-phase preparation process of polyolefin elastomers, there is an instantaneous explosive polymerization phenomenon when the ethylene and α-olefin raw materials encounter the unmodified catalyst, resulting in uneven insertion and distribution of the comonomer on the ethylene molecular chain.

[0022] In a preferred embodiment, the thickness of the coating layer is 40 - 140 μm, the weight-average molecular weight of the coating layer material is 100 - 2000 g / mol, the modified catalyst is granular, and its particle size D50 is 130 - 330 μm, thereby further improving the light transmittance of the polyolefin elastomer. Preferably, the metallocene catalyst is a commercially available metallocene catalyst, the main catalyst component is zirconocene dichloride, and the cocatalyst is butylaluminoxane. Among them, in the metallocene catalyst, the mass fraction of zirconium element is 0.48%, and the mass fraction of aluminum element is 19.2%.

[0023] The metallocene catalyst is used as the catalyst matrix to further improve the catalytic performance of the modified catalyst.

[0024] On the other hand, the present invention also provides a preparation method of the modified catalyst, which includes: performing a micro-polymerization reaction on the catalyst matrix, olefin, nitrogen, and solvent to form a coating layer on the outer surface of the catalyst matrix to obtain the modified catalyst.

[0025] Those skilled in the art first perform a micro-polymerization reaction on the catalyst matrix, olefin, nitrogen, and solvent to form a coating layer on the outer surface of the catalyst matrix to obtain the modified catalyst. This modified catalyst can moderately inhibit its initial activity during the subsequent polymerization reaction in the reactor, thereby further improving the light transmittance of the product.

[0026] In a preferred embodiment, the olefin is selected from one or more of ethylene, propylene or 1-butene; the solvent is selected from one or more of cyclopentane, propane, butane, pentane or hexane; the temperature of the micro-polymerization reaction is 25-45 °C, preferably 35-40 °C, the reaction pressure is 0.2-0.5 MPa, the reaction time is 20-50 min, preferably 30-40 min.

[0027] On the other hand, the present invention also provides a method for preparing a polyolefin elastomer, which includes the step of using a modified catalyst, and the modified catalyst is the modified catalyst obtained by the above-mentioned method for preparing a modified catalyst. The method for preparing a polyolefin elastomer includes: mixing the modified catalyst, ethylene, 1-butene, hydrogen, nitrogen and a condensing agent in a gas-phase fluidized bed reactor, and then carrying out a polymerization reaction on the fluidized bed layer of the gas-phase fluidized bed reactor with the modified catalyst and an antistatic agent to obtain a polyolefin elastomer.

[0028] Those skilled in the art first mix the modified catalyst, ethylene, 1-butene, hydrogen, nitrogen and a condensing agent in a gas-phase fluidized bed reactor, and then carry out a polymerization reaction on the fluidized bed layer of the gas-phase fluidized bed reactor with the modified catalyst and an antistatic agent to obtain a polyolefin elastomer. The polyolefin elastomer has better optical properties and a higher light transmittance.

[0029] In a preferred embodiment, the polymerization reaction temperature is 40-70 °C, the polymerization reaction pressure is 1.5-5.5 MPa, the polymerization reaction time is 12-18 h, and the yield of the modified catalyst is 6000-9900 g of product / g of catalyst, so as to prepare a polyolefin elastomer product with better performance.

[0030] On the other hand, the present invention also provides a polyolefin elastomer, and the polyolefin elastomer is the polyolefin elastomer obtained by the above-mentioned method for preparing a polyolefin elastomer. Its density is 0.8750-0.8880 g / cm 3 , the melt mass flow rate is 4-14 g / 10 min, the molecular weight distribution width PDI is 2.0-2.3, and when the thickness of the polyolefin elastomer is 0.5 mm, its light transmittance at a wavelength of 290-380 nm is 85-90%, and its light transmittance at a wavelength of 380-1100 nm is 90-93.5%.

[0031] The polyolefin elastomer prepared in the present invention has the following microstructure:

[0032] a) The content of the comonomer 1-butene is 11.0-15.0 mol%;

[0033] b) Ternary sequence distribution of molecular chain segments: [EEE] = 0.600 - 0.700, [EEB] = 0.170 - 0.180, [EBE] = 0.110 - 0.160, [BEB] = 0.012 - 0.024, [BBE] = 0.005 - 0.045, [BBB] = 0 - 0.003;

[0034] c) Average sequence length of ethylene nE = 8.7 - 9.4;

[0035] d) Average sequence length of 1 - butene nB = 1.05 - 1.12;

[0036] Among them, [EEE] represents the fraction of ethylene triple - sequence; [EEB] represents the fraction of ethylene double - sequence; [EBE] represents the fraction of ethylene meta - sequence; [BEB] represents the fraction of 1 - butene meta - sequence; [BBE] represents the fraction of 1 - butene double - sequence; [BBB] represents the fraction of 1 - butene triple - sequence. The above - mentioned microstructure of the polyolefin elastomer characterizes the uniformity of the inserted molecular chain segments of 1 - butene.

[0037] On the other hand, the present invention also provides an application of the polyolefin elastomer in the fields of POE pure gum film or EPE - structured photovoltaic gum film, and the polyolefin elastomer is the above - mentioned polyolefin elastomer.

[0038] The following further describes the present application in detail with specific embodiments, and these embodiments should not be construed as limiting the scope claimed by the present application.

[0039] Example 1

[0040] A micro - polymerization reaction is carried out on a catalyst matrix, olefins, nitrogen, and a solvent to form a coating layer on the outer surface of the catalyst matrix, obtaining a modified catalyst. Among them, the catalyst matrix is a metallocene catalyst, the olefin is propylene, the solvent is cyclopentane, the micro - polymerization reaction is carried out in a tubular container with a capacity of 10 L, the micro - polymerization reaction temperature is 40 °C, the pressure is 0.35 MPa, and the reaction time is 30 min. The coating layer material is a low - carbon olefin homopolymer with a weight - average molecular weight of 2000 g / mol, the coating layer thickness is 140 μm, and the modified catalyst is granular with a particle size D50 of 330 μm.

[0041] Mix the modified catalyst, ethylene, 1-butene, hydrogen, nitrogen and the condensing agent in a gas-phase fluidized bed reactor, and then take the modified catalyst and the antistatic agent into the fluidized bed layer of the gas-phase fluidized bed reactor to carry out the polymerization reaction to obtain a polyolefin elastomer. Among them, the polymerization temperature is 68 °C, the polymerization pressure is 1.55 MPa, the catalyst yield is 9300 g of product / g of catalyst, the addition amount of the antistatic agent accounts for 0.0012% of the ethylene addition amount, the condensing agent is cyclopentane, the polymerization time is 12 h, and a polyolefin product is obtained. The density of the polyolefin elastomer product is 0.8870 g / cm 3 , the melt mass flow rate MFR (190 °C, 2.16 kg) is 4.9 g / 10 min, and the molecular weight distribution width PDI is 2.25; the content of the comonomer 1-butene in the product is 11.0 mol%, and the molecular chain segment ternary sequence distribution: [EEE]=0.699, [EEB]=0.173, [EBE]=0.111, [BEB]=0.012, [BBE]=0.007, [BBB]=0.002; the average sequence length of ethylene nE = 9.3, and the average sequence length of 1-butene nB = 1.07. Among them, [EEE] represents the fraction of ethylene triple sequences; [EEB] represents the fraction of ethylene double sequences; [EBE] represents the fraction of ethylene meta sequences; [BEB] represents the fraction of butene-1 meta sequences; [BBE] represents the fraction of 1-butene double sequences; [BBB] represents the fraction of 1-butene triple sequences. The product is made into a sample by pressing, and a polyolefin product with a thickness of 0.5 mm is obtained. The light transmittance at wavelengths of 290-380 nm is measured to be 87.2%, and the light transmittance at wavelengths of 380-1100 nm is 90.1%. The product is used for blending applications in the raw materials of photovoltaic encapsulation adhesive films POE, and the blending ratio is 20%.

[0042] Example 2

[0043] The difference from Example 1 is only that: the micro-polymerization reaction temperature is 38 °C and the pressure is 0.20 MPa. The coating material is a low-carbon olefin homopolymer with a weight average molecular weight of 1400 g / mol, the coating thickness is 105 μm, the modified catalyst is granular, and its particle size D50 is 260 μm.

[0044] The polymerization temperature is 58 °C, the polymerization pressure is 2.05 MPa, the catalyst yield is 8400 g of product / g of catalyst, the addition amount of the antistatic agent accounts for 0.0045% of the ethylene addition amount, the condensing agent is pentane, and the polymerization time is 14 h. The density of the polyolefin elastomer product is 0.8826 g / cm 3, the melt mass flow rate MFR (at 190 °C, 2.16 kg) is 9.7 g / 10 min, the molecular weight distribution breadth PDI is 2.12; the content of comonomer 1-butene in the product is 12.23 mol%, and the ternary sequence distribution of molecular chain segments: [EEE]=0.675, [EEB]=0.171, [EBE]=0.121, [BEB]=0.017, [BBE]=0.014, [BBB]=0.002; the average sequence length of ethylene n E =9.1, the average sequence length of 1-butene n B =1.09. Among them, [EEE] represents the fraction of ethylene triple sequences; [EEB] represents the fraction of ethylene double sequences; [EBE] represents the fraction of ethylene meta sequences; [BEB] represents the fraction of 1-butene meta sequences; [BBE] represents the fraction of 1-butene double sequences; [BBB] represents the fraction of 1-butene triple sequences. The product is made into a sample with a thickness of 0.5 mm by pressing. The light transmittance at wavelengths of 290 - 380 nm is measured to be 87.7%, and the light transmittance at wavelengths of 380 - 1100 nm is 90.9%. The product is used for blending in the raw material of photovoltaic encapsulation film POE, and the blending ratio is 30%.

[0045] Example 3

[0046] The difference from Example 1 is only that: the micro-polymerization reaction temperature is 35 °C and the reaction time is 40 min. The coating material is a low-carbon olefin homopolymer with a weight-average molecular weight of 800 g / mol, the coating thickness is 75 μm, the modified catalyst is granular with a particle size D50 of 200 μm.

[0047] The polymerization temperature is 45 °C, the polymerization pressure is 4.5 MPa, the catalyst yield is 6000 g of product / g of catalyst, the addition amount of the antistatic agent accounts for 0.009% of the ethylene addition amount, the condensing agent is propane, and the polymerization time is 18 h. The density of the polyolefin elastomer product is 0.8785 g / cm 3 , the melt mass flow rate MFR (at 190 °C, 2.16 kg) is 13.9 g / 10 min, the molecular weight distribution breadth PDI is 2.10; the content of comonomer 1-butene in the product is 14.40 mol%, and the ternary sequence distribution of molecular chain segments: [EEE]=0.607, [EEB]=0.170, [EBE]=0.159, [BEB]=0.022, [BBE]=0.042, [BBB]=0; the average sequence length of ethylene n E =8.8, the average sequence length of 1-butene n B= 1.11. Wherein, [EEE] represents the fraction of ethylene triad sequences; [EEB] represents the fraction of ethylene dyad sequences; [EBE] represents the fraction of ethylene meta sequences; [BEB] represents the fraction of 1-butene meta sequences; [BBE] represents the fraction of 1-butene dyad sequences; [BBB] represents the fraction of 1-butene triad sequences. The product was made into a tablet sample, and the thickness of the polyolefin elastomer was 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm was measured to be 89.3%, and the light transmittance at wavelengths of 380 - 1100 nm was 92.8%. The product is used for blending applications in the raw material of the photovoltaic encapsulation film POE, and the blending ratio is 35%.

[0048] Example 4

[0049] The difference from Example 2 is only that: the micro-polymerization reaction olefin is 1-butene, and the reaction time is 40 min. The coating material is a low-carbon olefin homopolymer with a weight-average molecular weight of 1200 g / mol, the coating thickness is 110 μm, and the modified catalyst is granular with a particle size D50 of 270 μm.

[0050] The catalyst yield is 7500 g of product / g of catalyst, and the polymerization time is 16 h. The density of the polyolefin elastomer product is 0.8854 g / cm 3 , the melt mass flow rate MFR (190 °C, 2.16 kg) is 10.0 g / 10 min, and the molecular weight distribution width PDI is 2.18; the content of the comonomer 1-butene in the product is 11.83 mol%. The product was made into a tablet sample, and the thickness of the polyolefin elastomer was 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm was measured to be 88.2%, and the light transmittance at wavelengths of 380 - 1100 nm was 91.5%. The product is used for blending applications in the raw material of the photovoltaic encapsulation film POE, and the blending ratio is 25%.

[0051] Example 5

[0052] The difference from Example 3 is only that: the micro-polymerization reaction olefin is ethylene, and the reaction time is 35 min. The coating material is a low-carbon olefin homopolymer with a weight-average molecular weight of 500 g / mol, the coating thickness is 40 μm, and the modified catalyst is granular with a particle size D50 of 130 μm.

[0053] The polymerization pressure is 5.05 MPa, the catalyst yield is 6800 g of product / g of catalyst, and the density of the polyolefin elastomer product is 0.8755 g / cm 3, the melt mass flow rate MFR (at 190°C, 2.16 kg) is 14.0 g / 10 min, the molecular weight distribution width PDI is 2.02; the content of comonomer 1-butene in the product is 14.93 mol%. The product is made into a tablet sample, and the thickness of the polyolefin elastomer obtained is 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm is measured to be 89.4%, and the light transmittance at wavelengths of 380 - 1100 nm is 93.3%. The product is used for blending in the raw material of photovoltaic encapsulation film POE, and the blending ratio is 45%.

[0054] Comparative Example 1

[0055] The difference from Example 1 is only that: the micro-polymerization reaction temperature is 60°C, and the feeding ratio of propylene is increased. The coating material is a low-carbon olefin homopolymer with a weight-average molecular weight of 4300 g / mol, the coating thickness is 260 μm, the modified catalyst is granular, and its particle size D50 is 570 μm.

[0056] The catalyst yield is 8200 g of product / g of catalyst, the addition amount of the antistatic agent to the mass of ethylene is 0.0030%, and the polymerization time is 16 h. The density of the obtained polyolefin elastomer product is 0.8848 g / cm 3 , the melt mass flow rate MFR (at 190°C, 2.16 kg) is 4.90 g / 10 min, the molecular weight distribution width PDI is 2.56; the content of comonomer 1-butene in the product is 12.04 mol%, and the molecular chain segment ternary sequence distribution: [EEE]=0.693, [EEB]=0.175, [EBE]=0.093, [BEB]=0.014, [BBE]=0.013, [BBB]=0.012; the average sequence length of ethylene n E = 9.5, the average sequence length of 1-butene n B = 1.11, where, [EEE] represents the fraction of ethylene triple sequence; [EEB] represents the fraction of ethylene double sequence; [EBE] represents the fraction of ethylene meta sequence; [BEB] represents the fraction of 1-butene meta sequence; [BBE] represents the fraction of 1-butene double sequence; [BBB] represents the fraction of 1-butene triple sequence. The average sequence length of ethylene is too large, and the distribution uniformity of 1-butene in the molecular chain segment is poor. The product is made into a tablet sample, and the thickness of the polyolefin elastomer obtained is 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm is measured to be 84.0%, and the light transmittance at wavelengths of 380 - 1100 nm is 87.6%; the product is blended at 10% in the raw material of photovoltaic encapsulation film POE, and the light transmittance of the obtained photovoltaic film at wavelengths of 380 - 1100 nm is 88.8%, which cannot meet the standard requirement of 90%.

[0057] Comparative Example 2

[0058] The difference from Example 1 is only that: an unmodified catalyst is used for the polymerization reaction, the catalyst yield is 13200 g of product / g of catalyst, the mass ratio of the antistatic agent added to ethylene is 0.0010%, and the polymerization reaction time is 9 h. The density of the polyolefin elastomer product is 0.8905 g / cm 3 , the melt mass flow rate MFR (190 °C, 2.16 kg) is 5.0 g / 10 min, and the molecular weight distribution width PDI is 2.72; the content of the comonomer 1-butene in the product is 10.2 mol%, and the molecular chain segment ternary sequence distribution: [EEE]=0.772, [EEB]=0.123, [EBE]=0.081, [BEB]=0.007, [BBE]=0.011, [BBB]=0.006; the average sequence length of ethylene n E = 9.9, and the average sequence length of butene-1 n B = 1.02, where, [EEE] represents the fraction of ethylene triple sequences; [EEB] represents the fraction of ethylene double sequences; [EBE] represents the fraction of ethylene meta sequences; [BEB] represents the fraction of 1-butene meta sequences; [BBE] represents the fraction of 1-butene double sequences; [BBB] represents the fraction of 1-butene triple sequences. The product is made into a tablet sample, and the thickness of the polyolefin elastomer is 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm is measured to be 82.6%, and the light transmittance at wavelengths of 380 - 1100 nm is 85.3%. The light transmittance of the product at wavelengths of 380 - 1100 nm is much lower than the index requirement of 90% for the photovoltaic adhesive film and cannot be used for its blending application.

[0059] Comparative Example 3

[0060] The difference from Example 3 is only that: an unmodified catalyst is used for the polymerization reaction, the catalyst yield is 10500 g of product / g of catalyst, the mass ratio of the antistatic agent added to ethylene is 0.0010%, and the polymerization reaction time is 12 h. The molecular weight distribution width PDI of the polyolefin elastomer product is 2.44; the content of the comonomer butene-1 in the product is 14.20 mol%, and the molecular chain segment ternary sequence distribution: [EEE]=0.607, [EEB]=0.173, [EBE]=0.143, [BEB]=0.023, [BBE]=0.044, [BBB]=0.010; the average sequence length of ethylene n E = 8.4, and the average sequence length of 1-butene n B= 1.17, where [EEE] represents the fraction of ethylene triad sequences; [EEB] represents the fraction of ethylene dyad sequences; [EBE] represents the fraction of ethylene meso sequences; [BEB] represents the fraction of 1-butene meso sequences; [BBE] represents the fraction of 1-butene dyad sequences; [BBB] represents the fraction of 1-butene triad sequences. When the average sequence length of 1-butene is too large, the distribution uniformity of 1-butene in the molecular chain segments is poor. After the product is made into a tablet sample, the thickness of the polyolefin elastomer is 0.5 mm. The light transmittance at wavelengths of 290 - 380 nm is measured to be 84.7%, and the light transmittance at wavelengths of 380 - 1100 nm is 88.9%. The product is used for blending in the raw material of the photovoltaic encapsulation adhesive film POE, with a blending ratio of 10%, and its application value is low.

[0061] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0062] From the test results of the above embodiments and comparative examples, it can be found that in the gas-phase polymerization process, by using a modified catalyst, the uniformity of the comonomer inserted into the molecular chain segments is improved, thereby increasing the light transmittance of POE; through process optimization, the product quality is improved, and the application ratio of gas-phase POE in photovoltaic adhesive films is increased, making its application prospect wider.

[0063] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of what is claimed, but are mainly used to describe the characteristics of specific embodiments of a particular invention. Certain features described in multiple embodiments within this specification can also be implemented in combination in a single embodiment. On the other hand, various features described in a single embodiment can also be implemented separately in multiple embodiments or in any suitable sub-combination. In addition, although features may function in certain combinations as described above and are even initially claimed as such, one or more features from the claimed combination can in some cases be removed from the combination, and the claimed combination can be directed to a sub-combination or a variant of the sub-combination.

[0064] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the acts recited in the claims can be performed in a different order and still achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.

[0065] It should be noted that in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0066] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a polyolefin elastomer, comprising the step of using a modified catalyst, characterized in that, The preparation method of the polyolefin elastomer is as follows: mixing a modified catalyst, ethylene, 1-butene, hydrogen, nitrogen and a condensing agent in a gas-phase fluidized bed reactor, and then carrying out a polymerization reaction on the fluidized bed layer of the gas-phase fluidized bed reactor with the modified catalyst and an antistatic agent to obtain the polyolefin elastomer; The polymerization reaction temperature is 40-70 °C, the polymerization reaction pressure is 1.5-5.5 MPa, and the polymerization reaction time is 12-18 h; The modified catalyst is composed of a catalyst matrix and a coating layer coated on the outer surface of the catalyst matrix. Among them, the catalyst matrix is a metallocene catalyst, the metallocene catalyst is composed of a dichlorodicyclopentadienyl zirconium main catalyst and a butylaluminoxane cocatalyst, the coating layer material is a low-carbon olefin homopolymer, the thickness of the coating layer is 40-140 μm, and the weight-average molecular weight of the coating layer material is 100-2000 g / mol; the modified catalyst is granular, and its particle size D50 is 130-330 μm; The preparation method of the modified catalyst is as follows: carrying out a micro-polymerization reaction on the catalyst matrix, olefin, nitrogen and a solvent to form a coating layer on the outer surface of the catalyst matrix to obtain the modified catalyst; the temperature of the micro-polymerization reaction is 25-45 °C, the reaction pressure is 0.2-0.5 MPa, and the reaction time is 20-50 min; the olefin is selected from one or more of ethylene, propylene or 1-butene; the solvent is selected from one or more of cyclopentane, propane, butane, pentane or hexane; The polyolefin elastomer has the following microstructure: a) the content of the comonomer 1-butene is 11.0-15.0 mol%; b) the molecular chain segment ternary sequence distribution: [EEE]=0.600-0.700, [EEB]=0.170-0.180, [EBE]=0.110-0.160, [BEB]=0.012-0.024, [BBE]=0.005-0.045, [BBB]=0-0.003; c) the average sequence length of ethylene nE = 8.7-9.4; d) the average sequence length of 1-butene nB = 1.05-1.

12.

2. The preparation method of the polyolefin elastomer according to claim 1, wherein, The condensing agent is selected from one or more of propane, pentane or cyclopentane, and the addition amount of the antistatic agent accounts for 0.001-0.01% of the addition amount of ethylene.

3. The method for preparing a polyolefin elastomer according to claim 1 or 2, characterized in that, The yield of the modified catalyst is 6000-9900 g product / g catalyst.

4. A polyolefin elastomer, characterized in that, The polyolefin elastomer is the polyolefin elastomer obtained by the preparation method of the polyolefin elastomer according to any one of claims 1-3.

5. The polyolefin elastomer according to claim 4, wherein The density of the polyolefin elastomer is 0.8750 - 0.8880 g / cm 3 , the melt mass flow rate is 4 - 14 g / 10 min, the molecular weight distribution width PDI is 2.0 - 2.

3. When the thickness of the polyolefin elastomer is 0.5 mm, the light transmittance at a wavelength of 290 - 380 nm is 85 - 90%, and the light transmittance at a wavelength of 380 - 1100 nm is 90 - 93.5%.

6. An application of a polyolefin elastomer in the field of POE pure gum film or EPE structure photovoltaic gum film, characterized in that, The polyolefin elastomer is the polyolefin elastomer according to claim 4 or 5.