Polyolefin elastomer and its preparation method and application

Abstract

The present invention provides a novel polyolefin elastomer, its preparation method and applications, including: subjecting ethylene, an α-olefin and a condensing agent to refining treatment, and carrying out a low-temperature polymerization reaction on the reaction raw materials, hydrogen, nitrogen, a metallocene catalyst and an antistatic agent obtained after the refining treatment in a reactor to obtain a polyolefin elastomer powder, and successively carrying out degassing treatment and extrusion granulation treatment on the polyolefin elastomer powder to obtain the novel polyolefin elastomer. Among them, in the polyolefin elastomer powder, the particle contents of powder particles with particle sizes D50 of 1 μm to 300 μm, 300 μm to 1000 μm, and 1600 μm to 4000 μm are 0.1% to 0.3%, 3.0% to 9.6%, and 33.4% to 58.9% respectively. The polyolefin elastomer of the present invention has excellent properties, avoids agglomeration during the preparation process, improves production efficiency and quality, and has excellent industrial application prospects.

Description

Technical Field

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

[0002] Polyolefin elastomer (POE) refers to a random copolymer obtained by polymerizing ethylene with α-olefins (1-butene, 1-hexene, 1-octene, etc.), with a comonomer content of 20-45% and a density of 0.860-0.890 g / cm 3 , and the polymer crystallinity <20%. Polyolefin elastomers have excellent water vapor permeability resistance, aging resistance, corrosion resistance, and heat resistance, and can be widely used in fields such as automotive plastic modification, photovoltaic encapsulation films, foamed shoe materials, packaging, household appliances, wire and cable, medical devices, hot melt adhesives, etc.

[0003] Due to the existence of many technical difficulties in the production of polyolefin elastomers, solution polymerization processes are used for production both at home and abroad. Generally, the polymerization process of ethylene and α-olefins has three processes: gas-phase polymerization, slurry polymerization, and solution polymerization. As the α-olefin insertion rate increases, the polymer transitions from linear low-density polyethylene to polyolefin plastomer and polyolefin elastomer, the degree of molecular structure branching increases, and the density, crystallinity, softening point, and melting point gradually decrease. When the α-olefin insertion rate increases to 10% to 20%, the polymer concentration is too high, resulting in too high a polymer viscosity, and it is difficult for the polymer to flow in the slurry reactor in granular form to achieve homogeneous polymerization. In addition, the low-melting-point polymer is easily swollen by the solvent and agglomerates and adheres, becoming sticky and clogging the pipeline, resulting in the problem of kettle wall sticking and blocking, and it cannot be produced by the gas-phase polymerization process. Therefore, in recent years, domestic efforts have been increased in the development of solution polymerization processes for polyolefin elastomers, and no polyolefin elastomer products have been developed on industrial devices using the gas-phase fluidized bed process. Compared with the gas-phase polymerization process, the solution polymerization process overcomes the problem that polyolefin elastomers have a low melting point and are prone to softening and blocking. However, the solution polymerization process requires the use of a large amount of organic solvents, and the energy consumption and cost for solvent separation and recovery are high. Moreover, as the polymer concentration in the solvent increases, the mass transfer and heat transfer resistances increase, easily causing fouling and even blocking in the reaction kettle. Based on the above problems, in the prior art, the Chinese patent document with the authorization publication number CN103221439B discloses a polyethylene polymerization in a gas-phase reactor, and the product density range is 0.900 g / cm 3 to 0.912 g / cm 3 , and the product is actually very low-density polyethylene according to the density division, and the density is much higher than the range of polyolefin elastomers.

[0004] The Chinese patent document with the authorization announcement number CN105199031B discloses a method and device for olefin polymerization. The method includes: introducing a liquid material and a catalyst into a first reactor, where the olefin in the liquid material contacts the catalyst to undergo a polymerization reaction to form a polyolefin; introducing the liquid material and the polyolefin drawn from the outlet of the first reactor into a second reactor, and at the same time introducing the catalyst, a gas material, and a liquid material into the second reactor; maintaining a dense-phase fluidized bed inside the second reactor, where the gas material, the liquid material, and the catalyst contact to generate a polyolefin; discharging the unreacted gas material from the outlet of the second reactor, subjecting it to compression, condensation, and gas-liquid separation, transporting the liquid material obtained from the gas-liquid separation to the first reactor to form a circulation loop, and transporting the remaining liquid material and the gas material to the second reactor to form a circulation loop; continuously or intermittently discharging the polyolefin from the second reactor. The addition of the first reactor with a stirring kettle makes the product density higher than 0.90 g / cm 3 , and the series connection of the two reactors is beneficial to the production of polyolefin products with a wide molecular weight distribution and improves the operation stability of the reactors.

[0005] The Chinese patent document with the authorization announcement number CN108948248B discloses a method, device, and application of polyolefin elastomer produced by a gas phase method. The method is to carry out a reaction in a reactor with polyethylene particles as a seed bed, introducing a raw material mixed gas including ethylene, hydrogen, and nitrogen into the reactor to make the polyethylene particles in the seed bed flow and reach a fluidized state, and then adding a catalyst and introducing an atomized droplet-shaped comonomer into the reactor for reaction. The comonomer is a long-chain olefin with 6 to 18 carbon atoms, and the density of the prepared polymerization product is 0.865 g / cm 3 to 0.910 g / cm 3 , and the content of the long-chain olefin is 6 wt% to 40 wt%. The invention purpose of this patent is to solve the problems that the liquid long-chain α-olefin with a high comonomer content is unevenly distributed in the gas phase seed bed and has poor copolymerization performance during the preparation process of the polyolefin elastomer. The invention method and device of this patent must atomize the comonomer and require a test device with structural transformation, specifically a reactor with a special structural form. The polymerization temperature adopted is generally higher than the melting point of the product, there is a risk of polymer sticking and blocking the reactor and pipelines, and a series of problems such as blockage and caking in the system after polymerization are not considered.

[0006] Based on this, in the face of the problem of polymer sticking and caking in the polymerization process of the existing polyolefin elastomer, there is an urgent need to provide 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 polyolefin elastomer, a preparation method and an application thereof, so as to solve the technical problem of polymer agglomeration in the polymerization process of polyolefin elastomers in the prior art.

[0008] To achieve the above object, according to one aspect of the present invention, a preparation method of a polyolefin elastomer is provided. The preparation method includes: Step S1, refining ethylene, an α-olefin and a condensing agent to obtain the reaction raw materials after refining; Step S2, performing a low-temperature polymerization reaction on the reaction raw materials after refining, hydrogen, nitrogen, a metallocene catalyst and an antistatic agent in a reactor to obtain polyolefin elastomer powder; Step S3, performing degassing treatment and extrusion granulation treatment on the polyolefin elastomer powder in sequence to obtain a polyolefin elastomer; wherein, in the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.1% to 0.3%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 3.0% to 9.6%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 33.4% to 58.9%.

[0009] Further, in Step S1, the refining treatment includes: refining ethylene, an α-olefin and a condensing agent in a fixed-bed reactor. In the obtained reaction raw materials after refining, the mass percentage of water is independently 0 to 1 μg / g, the mass percentage of oxygen is independently 0 to 0.5 μg / g, and the volume percentage of the sum of carbon monoxide and carbon dioxide is independently 0 to 0.5 μg / g.

[0010] Further, the active component of the metallocene catalyst is selected from one or more of zirconocene dichloride, methylaluminoxane, butylaluminoxane and hexylaluminoxane. The particle size D50 of the metallocene catalyst is 45 μm to 54 μm, and the metallocene catalyst yield is 6000 g product / g catalyst to 15000 g product / g catalyst.

[0011] Further, in Step S2, the low-temperature polymerization reaction is carried out in a gas-phase fluidized bed reactor. The gas-phase fluidization rate is 0.3 m / s to 0.8 m / s, more preferably 0.40 m / s to 0.70 m / s; preferably, the bed pressure difference of the gas-phase fluidized bed reactor is 10 kPa to 80 kPa, more preferably 20 kPa to 45 kPa; preferably, the temperature of the low-temperature polymerization reaction is 35°C to 65°C, the reaction pressure is 1.5 MPa to 3.0 MPa, and the reaction time is 7 h to 12 h.

[0012] Further, in step S3, the degassing treatment includes a primary degassing treatment and a secondary degassing treatment. The gas volume removed in the primary degassing treatment is 30 to 60 times the volume of the polyolefin elastomer powder, the temperature of the primary degassing treatment is 35°C to 55°C, the gas volume removed in the secondary degassing treatment is 60 to 120 times the volume of the polyolefin elastomer powder, the temperature of the secondary degassing treatment is 45°C to 65°C, and the time of the secondary degassing treatment is 12h to 15h. Preferably, during the extrusion granulation process, additives are added to the polyolefin elastomer powder. The additives include talcum powder and antioxidants, and the addition amount of the additives is 80ppm to 350ppm, wherein the addition amount of talcum powder is 0 to 100ppm, and the temperature of the pelletizing water for extrusion granulation is 13°C to 45°C.

[0013] Further, when the gas-phase fluidized bed reactor is in a polymerization reaction equilibrium state, the molar percentage content of ethylene is 30% to 40%, the molar percentage content of α-olefin is 1.0% to 8.5%, the molar percentage content of hydrogen is 0.005% to 0.06%, the molar percentage content of the condensing agent is 0.5% to 5%, and the balance is nitrogen. Preferably, the α-olefin is 1-butene and / or 1-hexene, and the condensing agent is selected from one or more of propane, pentane, cyclopentane, hexane, and cyclohexane, more preferably one or more of propane, pentane, and / or cyclohexane.

[0014] Further, the addition amount of the antistatic agent accounts for 0.002wt% to 0.005wt% of ethylene. The antistatic agent includes poly(sulfonic acid) betaine, alkylbenzene sulfonic acid, α-olefin homopolymer, and organic solvent. The weight percentages of the components in the antistatic agent are: 2% to 5% of poly(sulfonic acid) betaine, 4% to 10% of alkylbenzene sulfonic acid, 10% to 15% of α-olefin homopolymer, and 71% to 81% of organic solvent.

[0015] To achieve the above object, according to one aspect of the present invention, a polyolefin elastomer is provided, and the polyolefin elastomer is obtained by the above-mentioned preparation method of the polyolefin elastomer.

[0016] Further, the density of the polyolefin elastomer is 0.870g / cm 3 to 0.890g / cm 3 , the melt mass flow rate is 0.8g / 10min to 18g / 10min, and the volatile content is 30ppm to 150ppm.

[0017] According to another aspect of the present invention, an application of the polyolefin elastomer in the fields of photovoltaic encapsulation film, automotive plastic modification, wire and cable, and film packaging is provided, and the polyolefin elastomer is the above-mentioned polyolefin elastomer.

[0018] The polyolefin elastomer obtained by applying the technical solution of the present invention has excellent properties. During its preparation process, the problem of adhesion and caking is reduced, the production process efficiency and quality are improved, and it has broad industrial application prospects. Detailed 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, there is a technical problem of polymer adhesion and caking in the polymerization process of polyolefin elastomers in the prior art. Based on this, the present invention provides a method for preparing a polyolefin elastomer. The preparation method includes: Step S1, refining ethylene, α-olefin, and a condensing agent to obtain reaction raw materials after refining; Step S2, performing a low-temperature polymerization reaction on the reaction raw materials after refining, hydrogen, nitrogen, a metallocene catalyst, and an antistatic agent in a reactor to obtain polyolefin elastomer powder; Step S3, sequentially performing degassing treatment and extrusion granulation treatment on the polyolefin elastomer powder to obtain a polyolefin elastomer; wherein, in the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.1% to 0.3%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 3.0% to 9.6%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 33.4% to 58.9%.

[0021] Based on the technical problem of adhesion and caking existing in polyolefin elastomers in the prior art, in the present invention, ethylene, α-olefin, and a condensing agent are respectively refined before entering the reactor. The purpose of refining is to reduce the influence of the material on the catalyst activity. The refined materials, hydrogen, nitrogen, a metallocene catalyst, and an antistatic agent are subjected to a low-temperature polymerization reaction in the reactor to obtain polyolefin elastomer powder. Then, degassing and extrusion granulation processing are carried out again to reduce the temperature during the processing to prevent the material from softening and blocking in the pipeline, and finally a polyolefin elastomer product is obtained. In particular, in the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.1% to 0.3%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 3.0% to 9.6%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 33.4% to 58.9%.

[0022] The above-mentioned gas-phase fluidized bed process in the present invention does not require a major transformation of the production equipment. Compared with the solution polymerization process, it has the characteristics of short operation process, low production cost, low product odor, etc. The production of polyolefin elastomers by this method has a better industrial application prospect. Moreover, in the gas-phase fluidized bed process of a single reactor, a large-particle-size, high-activity metallocene catalyst is used, and by optimizing the polymerization reaction temperature, regulating the pressure in the reactor, the molar percentage of α-olefin and ethylene, and the gas-phase fluidization rate at the bottom of the reactor, injecting an antistatic agent, preventing and controlling polymerization stickiness, and reducing the generation of polymer fine powder, the problem of softening, agglomeration, and fouling blockage of polyolefin elastomers is effectively prevented, and the technical difficulties in the production of polyolefin elastomers in the gas-phase polymerization process are eliminated.

[0023] In a preferred embodiment, in step S1, the refining treatment includes: refining ethylene, α-olefin and condensing agent in a fixed bed reactor, so that the mass percentage of water in the reaction raw materials after the refining treatment is independently 0 to 1 μg / g, the mass percentage of oxygen is independently 0 to 0.5 μg / g, and the volume percentage of the sum of carbon monoxide and carbon dioxide is independently 0 to 0.5 μg / g, so as to further reduce the influence of the materials on the catalyst activity and minimize the phenomenon of product agglomeration.

[0024] In order to further improve the performance of polyolefin elastomers, the active components of the metallocene catalyst are preferably selected from one or more of zirconocene chloride, methylaluminoxane, butylaluminoxane and hexylaluminoxane, the particle size D50 of the metallocene catalyst is 45μm to 54μm, and the yield of the metallocene catalyst is 6000g product / g catalyst to 15000g product / g catalyst.

[0025] In a preferred embodiment, in step S2, the low-temperature polymerization reaction is carried out in a gas-phase fluidized bed reactor, and the gas-phase fluidization rate is 0.3 m / s to 0.8 m / s, more preferably 0.40 m / s to 0.70 m / s. Thus, the material in the gas-phase reactor is in a fluidized state, a homogeneous reaction is achieved under the action of the catalyst, and the generation of fine powder in the polymerization system is suppressed by a lower gas-phase fluidization rate.

[0026] In a preferred embodiment, it is further preferred that the bed pressure difference of the gas-phase fluidized bed reactor is 10 kPa to 80 kPa, more preferably 20 kPa to 45 kPa; the temperature of the low-temperature polymerization reaction is 35 °C to 65 °C, the reaction pressure is 1.5 MPa to 3.0 MPa, and the reaction time is 7 h to 12 h. Too low polymerization pressure or polymerization temperature is not conducive to the release of catalyst activity, nor is it conducive to the improvement of the α-olefin insertion rate in the polyolefin elastomer; too high polymerization pressure increases the content of fines in the polyolefin elastomer powder, and the fines enter the reactor to soften, scale and block; too high polymerization temperature will cause the polymer to stick and block in the reactor.

[0027] In order to further remove light components, small molecule substances, volatile components, etc. in the polyolefin elastomer powder, low-temperature control is adopted to prevent the polyolefin elastomer powder from softening and blocking in the pipeline, and the degassing effect of the powder is improved by increasing the degassing volume. Preferably, in step S3, the degassing treatment includes primary degassing treatment and secondary degassing treatment. The degassing volume of the primary degassing treatment is 30 to 60 times the volume of the polyolefin elastomer powder, the temperature of the primary degassing treatment is 35 °C to 55 °C, the degassing volume of the secondary degassing treatment is 60 to 120 times the volume of the polyolefin elastomer powder, the temperature of the secondary degassing treatment is 45 °C to 65 °C, and the time of the secondary degassing treatment is 12 h to 15 h.

[0028] In a preferred embodiment, during the extrusion granulation process, additives are added to the polyolefin elastomer powder. The additives include talcum powder and antioxidants. Further preferably, the antioxidants include antioxidant 1076 and antioxidant 1010. The addition amount of the additives is 80 ppm to 350 ppm, wherein the addition amount of talcum powder is 0 to 100 ppm, and the temperature of the pelletizing water for extrusion granulation is 13 °C to 45 °C. The addition of a small amount of talcum powder can reduce the adhesion between product particles and prevent caking during storage and transportation of the product; the number of sticky particles of the polyolefin elastomer pellets is controlled by the low temperature of the pelletizing water to meet the requirements of the particle appearance.

[0029] In order to further adjust the molar percentage of α-olefin and ethylene to increase the insertion rate of α-olefin in the polyolefin elastomer, the melt mass flow rate of the polyolefin elastomer powder is adjusted by adjusting the molar percentage of hydrogen and ethylene, and the heat removal effect of the heat generated by polymerization in the reactor is enhanced by the flow of the condensing agent in the polymerization system. When the gas-phase fluidized bed reactor is in a polymerization reaction equilibrium state, preferably, the molar percentage of ethylene in the reactor is 30% to 40%, the molar percentage of α-olefin is 1.0% to 8.5%, the molar percentage of hydrogen is 0.005% to 0.06%, the molar percentage of the condensing agent is 0.5% to 5%, and the balance is nitrogen. More preferably, the α-olefin is 1-butene and / or 1-hexene, and the condensing agent is selected from one or more of propane, pentane, cyclopentane, hexane, and cyclohexane, and more preferably one or more of propane, pentane, and / or cyclohexane.

[0030] In a preferred embodiment, the addition amount of the antistatic agent accounts for 0.002 wt% to 0.005 wt% of ethylene; the antistatic agent includes polysulfobetaine, alkylbenzenesulfonic acid, α-olefin homopolymer, and organic solvent. The weight percentages of the components in the antistatic agent are as follows: 2% to 5% of polysulfobetaine, 4% to 10% of alkylbenzenesulfonic acid, 10% to 15% of α-olefin homopolymer, and 71% to 81% of organic solvent. A uniform conductive layer is formed on the polymer surface by polysulfobetaine, enabling the static electricity generated by the polymer powder to dissipate and transfer quickly; alkylbenzenesulfonic acid is an anionic surfactant, and a small amount of its addition can promote the formation of an easily conductive thin layer on the surface of the polymer powder, and cooperate with polysulfobetaine to reduce the accumulation of static electricity.

[0031] On the other hand, the present invention also provides a polyolefin elastomer, which is obtained by the preparation method of the above polyolefin elastomer. The density of the polyolefin elastomer is 0.870 g / cm 3 to 0.890 g / cm 3 , the melt mass flow rate is 0.8 g / 10 min to 18 g / 10 min, and the volatile content is 30 ppm to 150 ppm.

[0032] On the other hand, the present invention also provides an application of the polyolefin elastomer in the fields of photovoltaic encapsulation film, automotive plastic modification, wire and cable, and film packaging, and the polyolefin elastomer is the above polyolefin elastomer.

[0033] The following further describes the present application in detail with specific examples, and these examples should not be construed as limiting the scope claimed by the present application.

[0034] Example 1

[0035] Ethylene, α-olefin (1-butene), and a condensing agent (cyclohexane) are taken in a fixed-bed reactor for refining treatment to obtain a reaction raw material after refining treatment. Among them, in the reaction raw material after refining treatment, the mass percentage of water is independently 0.7 μg / g, the mass percentage of oxygen is independently 0.3 μg / g, and the total volume percentage of carbon monoxide and carbon dioxide is independently 0.3 μg / g.

[0036] The reaction raw material after refining treatment, hydrogen, nitrogen, a metallocene catalyst, and an antistatic agent are taken in a gas-phase fluidized-bed reactor for low-temperature polymerization reaction to obtain a polyolefin elastomer powder. Among them, when the gas-phase fluidized-bed reactor is in a polymerization reaction equilibrium state, the molar percentage of ethylene is 39.3%, the molar percentage of α-olefin is 6.7%, the molar percentage of hydrogen is 0.0071%, the molar percentage of the condensing agent is 1.3%, and the balance is nitrogen. The active components of the metallocene catalyst are zirconocene dichloride and butylaluminoxane. The particle size D50 of the metallocene catalyst is 48 μm, and the metallocene catalyst yield is 11000 g of product / g of catalyst. The gas-phase fluidization rate is 0.58 m / s, the bed pressure difference of the gas-phase fluidized-bed reactor is 23.5 kPa, the temperature of the low-temperature polymerization reaction is 62 °C, the reaction pressure is 1.55 MPa, the reaction time is 7.5 h, and the addition amount of the antistatic agent accounts for 0.0022 wt% of ethylene. The antistatic agent includes polysulfobetaine, alkylbenzene sulfonic acid, α-olefin homopolymer, and an organic solvent. By weight percentage, the antistatic agent includes the following components: 2.8% of polysulfobetaine, 4.4% of alkylbenzene sulfonic acid, 12% of α-olefin homopolymer, and 80.8% of the organic solvent cyclohexane.

[0037] Finally, the above polyolefin elastomer powder is subjected to degassing treatment and extrusion granulation treatment in sequence to obtain a polyolefin elastomer. Among them, in the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.1%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 3.8%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 58.0%. Among them, the degassing treatment includes a primary degassing treatment and a secondary degassing treatment. The degassing amount of the primary degassing treatment is 33 times the volume of the polyolefin elastomer powder, and the temperature of the primary degassing treatment is 45 °C. The degassing amount of the secondary degassing treatment is 65 times the volume of the polyolefin elastomer powder, the temperature of the secondary degassing treatment is 50 °C, and the time of the secondary degassing treatment is 12.0 h. During the extrusion granulation treatment, additives are added to the polyolefin elastomer powder. The additives include talcum powder and an antioxidant. The antioxidant model is 1076, and the addition amount of the additives is 100 ppm. Among them, the addition amount of talcum powder is 0 ppm, the granulation water temperature for extrusion granulation is 42 °C, and the appearance of the product particles is normal.

[0038] Finally, the density of the polyolefin elastomer product obtained is 0.8848 g / cm 3 , the melt mass flow rate is 1.06 g / 10 min, and the volatile content is 41 ppm.

[0039] Example 2

[0040] The difference from Example 1 is only that: the coolant is pentane, the molar percentage content of ethylene in the gas-phase fluidized bed reactor is 37.6%, the molar percentage content of α-olefin is 4.6%, the molar percentage content of hydrogen is 0.033%, the molar percentage content of the coolant is 5.3%, the yield of the metallocene catalyst is 12500 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 28.2 kPa. In the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.12%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 4.5%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 52.2%.

[0041] Finally, the density of the polyolefin elastomer product obtained is 0.8854 g / cm 3 , the melt mass flow rate is 5.1 g / 10 min, and the volatile content is 69 ppm.

[0042] Example 3

[0043] The difference from Example 1 is only that: the coolant is pentane, the fluidization rate of the gas-phase fluidized bed is 0.63 m / s, the polymerization reaction temperature is 58 °C, the molar percentage content of ethylene in the gas-phase fluidized bed reactor is 35.6%, the molar percentage content of α-olefin is 3.6%, the molar percentage content of hydrogen is 0.047%, the molar percentage content of the coolant is 2.1%, the yield of the metallocene catalyst is 14600 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 42.6 kPa. In the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 0.2%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 6.7%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 44.3%. During the extrusion granulation process, the temperature of the granulation water for extrusion granulation is 29 °C.

[0044] Finally, the density of the polyolefin elastomer product obtained is 0.8850 g / cm 3 , the melt mass flow rate is 13.6 g / 10 min, and the volatile content is 100 ppm.

[0045] Example 4

[0046] The differences from Example 1 are only as follows: the α-olefin is 1-hexene, the condensing agent is propane, the active component of the metallocene catalyst is zirconocene dichloride and hexylaluminoxane, the particle size D50 of the metallocene catalyst is 52 μm, the antistatic agent comprises the following components: 4% of polysulfobetaine, 8.9% of alkylbenzene sulfonic acid, 12% of α-olefin homopolymer and 75.1% of the organic solvent heptane. The fluidization rate of the gas-phase fluidized bed is 0.42 m / s, the polymerization reaction temperature is 55 °C, the reaction pressure is 2.15 MPa, the reaction time is 9.0 h, the addition amount of the antistatic agent accounts for 0.0048 wt% of ethylene, the molar percentage content of ethylene in the gas-phase fluidized bed reactor is 33.9%, the molar percentage content of α-olefin is 2.2%, the molar percentage content of hydrogen is 0.0056%, the molar percentage content of the condensing agent is 4.1%, the yield of the metallocene catalyst is 6400 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 26 kPa. In the polyolefin elastomer powder, the content of particles with a particle size D50 of 1 μm to 300 μm is 0.15%, the content of particles with a particle size D50 of 300 μm to 1000 μm is 3.0%, and the content of particles with a particle size D50 of 1600 μm to 4000 μm is 50.0%. The degassing amount of the primary degassing treatment of the polyolefin elastomer powder is 50 times the volume of the polyolefin elastomer powder, and the primary degassing treatment temperature is 55 °C; the degassing amount of the secondary degassing treatment is 110 times the volume of the polyolefin elastomer powder, the secondary degassing treatment temperature is 63 °C, and the secondary degassing treatment time is 15.0 h. During the extrusion granulation treatment process, the temperature of the pelletizing water for extrusion granulation is 22 °C.

[0047] Finally, the density of the polyolefin elastomer product obtained is 0.8855 g / cm 3 , the melt mass flow rate is 0.98 g / 10 min, and the volatile content is 112 ppm.

[0048] Example 5

[0049] The differences from Example 4 are only as follows: the molar percentage content of ethylene in the gas-phase fluidized bed reactor is 31.9%, the molar percentage content of α-olefin is 1.2%, the molar percentage content of hydrogen is 0.03%, the molar percentage content of the condensing agent is 4.1%, the yield of the metallocene catalyst is 8900 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 33.5 kPa.

[0050] Finally, the density of the polyolefin elastomer product obtained is 0.8855 g / cm 3 , the melt mass flow rate is 4.8 g / 10 min, and the volatile content is 125 ppm.

[0051] Example 6

[0052] The differences from Example 1 are only as follows: The coolant is propane. In the reaction raw materials after refining treatment, the mass percentage of water is independently 0.3 μg / g, the mass percentage of oxygen is independently 0.1 μg / g, and the total volume percentage of carbon monoxide and carbon dioxide is independently 0.1 μg / g. The active components of the metallocene catalyst are zirconocene dichloride and hexylaluminoxane. The particle size D50 of the metallocene catalyst is 52 μm. The antistatic agent includes the following components: 5% of polysulfobetaine, 8.9% of alkylbenzenesulfonic acid, 14.5% of α-olefin homopolymer, and 71.6% of the organic solvent heptane. The fluidization rate of the gas-phase fluidized bed is 0.67 m / s, the polymerization reaction temperature is 42 °C, the reaction pressure is 3.0 MPa, the reaction time is 12.0 h, the addition amount of the antistatic agent accounts for 0.0033 wt% of ethylene, the molar percentage of ethylene in the gas-phase fluidized bed reactor is 35.2%, the molar percentage of α-olefin is 7.2%, the molar percentage of hydrogen is 0.031%, the coolant is propane, and its molar percentage is 4.1%. The metallocene catalyst yield is 7000 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 32.2 kPa. In the polyolefin elastomer powder, the content of particles with a particle size D50 of 1 μm to 300 μm is 0.3%, the content of particles with a particle size D50 of 300 μm to 1000 μm is 9.6%, and the content of particles with a particle size D50 of 1600 μm to 4000 μm is 33.4%. The degassing amount of the primary degassing treatment of the polyolefin elastomer powder is 60 times the volume of the polyolefin elastomer powder, and the primary degassing treatment temperature is 35 °C; the degassing amount of the secondary degassing treatment is 120 times the volume of the polyolefin elastomer powder, the secondary degassing treatment temperature is 48 °C, and the secondary degassing treatment time is 12.0 h. During the extrusion granulation treatment process, the temperature of the pelletizing water for extrusion granulation is 13 °C.

[0053] Finally, the density of the polyolefin elastomer product obtained is 0.8735 g / cm 3 , the melt mass flow rate is 4.87 g / 10 min, and the volatile content is 110 ppm.

[0054] Example 7

[0055] The differences from Example 6 are only as follows: The polymerization reaction temperature is 38 °C, the molar percentage of ethylene in the gas-phase fluidized bed reactor is 36.0%, the molar percentage of α-olefin is 8.2%, the molar percentage of hydrogen is 0.057%, the molar percentage of the coolant is 1.7%, the metallocene catalyst yield is 9300 g of product / g of catalyst, and the bed pressure difference of the gas-phase fluidized bed reactor is 41.3 kPa.

[0056] Finally, the density of the polyolefin elastomer product obtained is 0.8742 g / cm 3, melt mass flow rate is 14.2 g / 10 min, and volatile content is 147 ppm.

[0057] Comparative Example 1

[0058] The difference from Example 1 is only that: the catalyst used is a general catalyst, the active component of which is an organometallic mixture containing titanium, the particle size D50 is 37 μm, the antistatic agent is a mixture of quaternary ammonium salt and organic solvent, and the commercial brand is AS1200. The fluidization rate of the gas-phase fluidized bed is 0.72 m / s, the polymerization reaction temperature is 85 °C, the reaction pressure is 2.15 MPa, the molar percentage of ethylene in the gas-phase fluidized bed reactor is 37.8%, the molar percentage of α-olefin is 2.2%, the molar percentage of hydrogen is 0.055%, the molar percentage of the condensing agent is 1.7%, the bed pressure difference of the gas-phase fluidized bed reactor is 17.5 kPa, and the addition amount of the antistatic agent accounts for 0.0033 wt% of ethylene. During the process of reducing the polymerization temperature to 75 °C and increasing the molar concentration of 1-butene to 3.2%, the bed pressure difference of the reactor rapidly rises to 142 kPa, the distributor plate in the reactor is blocked, belt-shaped lumps are discharged from the hopper at the bottom of the reactor, and the polymerization reaction is forced to stop. In the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 5.5%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 35.0%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 18.2%. Finally, the density of the obtained linear low-density polyethylene product is 0.9193 g / cm 3 , melt mass flow rate is 1.0 g / 10 min, and volatile content is 349 ppm.

[0059] Comparative Example 2

[0060] The difference from Example 1 is only that: the catalyst used is a general catalyst, the active component of which is a compound composed of vanadium and metallocene, the particle size D50 is 30 μm, the antistatic agent is a mixture containing quaternary ammonium salt, alkylbenzene sulfonic acid and organic solvent, and the commercial brand is Statsafe 6000. The fluidization rate of the gas-phase fluidized bed is 0.55 m / s, the polymerization reaction temperature is 66 °C, the reaction pressure is 2.15 MPa, the molar percentage content of ethylene in the gas-phase fluidized bed reactor is 34.3%, the molar percentage content of α-olefin is 3.4%, the molar percentage content of hydrogen is 0.031%, the condensing agent is propane, and its molar percentage content is 4.1%. The bed pressure difference of the gas-phase fluidized bed reactor is 37.1 kPa, and the addition amount of the antistatic agent accounts for 0.0055 wt% of ethylene. The bed pressure difference of the reactor rises slowly, and a high alarm appears in the monitoring of the reactor wall temperature. It is analyzed that the polymer in the reactor becomes sticky and caking and the reactor wall is caked. To ensure safe production, the polymerization reaction is forced to stop. In the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 7.5%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 16.0%, and the content of particles with a powder particle size D50 of 1600 μm to 4000 μm is 30.0%.

[0061] Comparative Example 3

[0062] The difference from Example 1 is only that: ethylene, α-olefin, hydrogen, nitrogen and the condensing agent are not refined. The addition amount of the antistatic agent accounts for 0.008 wt% of ethylene, and the yield of the metallocene catalyst is 4400 g product / g catalyst. The harmful substances not removed by refining in the reaction raw materials cause a significant decrease in the catalyst yield. In the polyolefin elastomer powder, the content of particles with a powder particle size D50 of 1 μm to 300 μm is 2.2%, the content of particles with a powder particle size D50 of 300 μm to 1000 μm is 10.2%. The temperature of the first-stage degassing treatment for powder degassing is 60 °C, and the temperature of the second-stage degassing treatment is 60 °C. After the polymerization reaction proceeds for 30 hours, the pipeline between the second-stage degassing bin and the extrusion granulator is blocked, and the pneumatic conveying system loses the function of conveying the polyolefin elastomer powder. The pressure of the gas flow in the pipeline continuously increases, and the polymerization reaction is forced to stop. After shutdown and maintenance verification, it is found that the metal pipeline with a diameter of 30 cm is blocked, and the blockage is a sticky polymer.

[0063] Comparative Example 4

[0064] The difference from Example 1 is only that: the polymerization reaction temperature is 35 °C, the pressure is 1.2 MPa, the addition amount of the antistatic agent accounts for 0.004 wt% of ethylene, and the yield of the metallocene catalyst is 1500 g of product / g of catalyst. The process parameters such as temperature and pressure are too low, resulting in the yield of the catalyst falling short of expectations. The too low polymerization temperature requires an increase in the heat withdrawal amount in the reactor, resulting in an increase in the energy consumption for the production of polyolefin elastomers.

[0065] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0066] From the test results of the examples and comparative examples, it can be found that factors such as the types of catalysts and antistatic agents, the indicators after raw material refining treatment, the polymerization temperature, polymerization pressure, fluidization gas velocity, raw material composition in the reactor, the amount of degassing in the degassing bin, and the regulation of degassing temperature are the necessary conditions for preparing polyolefin elastomer products by the gas-phase fluidized bed process. The effective combination of the process methods provided by the present invention can achieve the efficient and stable production of qualified polyolefin elastomer products in a gas-phase polyethylene plant.

[0067] Adopting the above gas-phase fluidized bed process in the present invention does not require major modifications to the production device. Compared with the solution polymerization process, it has the characteristics of a short operation process, low production cost, and low product odor. Applying this method to produce polyolefin elastomers has a better industrial application prospect. Moreover, in the gas-phase fluidized bed process of a single reactor, by using a large-particle-size and highly active metallocene catalyst, optimizing the polymerization reaction temperature, regulating the pressure in the reactor, the molar percentage of α-olefin to ethylene, and the gas-phase fluidization rate at the lower part of the reactor, injecting an antistatic agent, preventing polymerization from sticking, reducing the generation of polymer fines, effectively preventing the problems of softening and caking blockage and fouling blockage of polyolefin elastomers, and eliminating the technical difficulties in the production of polyolefin elastomers in the gas-phase polymerization process.

[0068] Although this specification contains many specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claimed invention, but are mainly used to describe the characteristics of specific embodiments of a particular invention. Certain features described in multiple embodiments in this specification can also be combined and implemented in a single embodiment. On the other hand, the various features described in a single embodiment can also be separately implemented in multiple embodiments or implemented in any suitable sub-combination. In addition, although features can function in certain combinations as 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 refer to a sub-combination or a variant of the sub-combination.

[0069] Accordingly, 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.

[0070] 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 term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or apparatus 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 apparatus. Without further limitation, an element defined by the statement "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the element.

[0071] 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 to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a polyolefin elastomer, characterized in that, The preparation method includes: Step S1: Refine ethylene, α-olefin and a condensing agent to obtain the reaction raw materials after refining treatment. Step S2: Conduct a low-temperature polymerization reaction on the reaction raw materials after refining treatment, hydrogen, nitrogen, a metallocene catalyst and an antistatic agent in a reactor to obtain a polyolefin elastomer powder. Among them, the addition amount of the antistatic agent accounts for 0.002 wt% to 0.005 wt% of ethylene; the antistatic agent includes polysulfobetaine, alkylbenzene sulfonic acid, α-olefin homopolymer and an organic solvent. The weight percentages of each component in the antistatic agent are: 2% to 5% of polysulfobetaine, 4% to 10% of alkylbenzene sulfonic acid, 10% to 15% of α-olefin homopolymer and 71% to 81% of organic solvent. The active component of the metallocene catalyst is selected from one or more of zirconocene dichloride, methylaluminoxane, butylaluminoxane and hexylaluminoxane. The particle size D50 of the metallocene catalyst is 45 μm to 54 μm, and the yield of the metallocene catalyst is 6000 g product / g catalyst to 15000 g product / g catalyst. Step S3: Conduct degassing treatment and extrusion granulation treatment on the polyolefin elastomer powder in sequence to obtain a polyolefin elastomer, where In the polyolefin elastomer powder, the content of particles with a particle size D50 of 1 μm to 300 μm is 0.1% to 0.3%, the content of particles with a particle size D50 of 300 μm to 1000 μm is 3.0% to 9.6%, and the content of particles with a particle size D50 of 1600 μm to 4000 μm is 33.4% to 58.9%. When the gas-phase fluidized bed reactor is in a polymerization reaction equilibrium state, the molar percentage of ethylene is 30% to 40%, the molar percentage of α-olefin is 1.0% to 8.5%, the molar percentage of hydrogen is 0.005% to 0.06%, the molar percentage of the condensing agent is 0.5% to 5% and the balance is nitrogen. The α-olefin is 1-butene and / or 1-hexene, and the condensing agent is selected from one or more of propane, pentane, cyclopentane, hexane and cyclohexane. In step S1, the refining treatment includes: refining ethylene, α-olefin and the condensing agent in a fixed-bed reactor. In the reaction raw materials after refining treatment, the mass percentage of water is independently 0 to 1 μg / g, the mass percentage of oxygen is independently 0 to 0.5 μg / g, and the total volume percentage of carbon monoxide and carbon dioxide is independently 0 to 0.5 μg / g. In step S2, the low-temperature polymerization reaction is carried out in a gas-phase fluidized bed reactor. The gas-phase fluidization rate is 0.3 m / s to 0.8 m / s, the bed pressure difference of the gas-phase fluidized bed reactor is 10 kPa to 80 kPa, the temperature of the low-temperature polymerization reaction is 35 °C to 65 °C, the reaction pressure is 1.5 MPa to 3.0 MPa, and the reaction time is 7 h to 12 h. In step S3, the degassing treatment includes a primary degassing treatment and a secondary degassing treatment. The gas removal volume of the primary degassing treatment is 30 to 60 times the volume of the polyolefin elastomer powder, the temperature of the primary degassing treatment is 35°C to 55°C, the gas removal volume of the secondary degassing treatment is 60 to 120 times the volume of the polyolefin elastomer powder, the temperature of the secondary degassing treatment is 45°C to 65°C, and the time of the secondary degassing treatment is 12h to 15h.

2. The preparation method of the polyolefin elastomer according to claim 1, characterized in that, In step S3, during the extrusion granulation treatment, additives are added to the polyolefin elastomer powder. The additives include talcum powder and antioxidant, and the addition amount of the additives is 80ppm to 350ppm. Among them, the addition amount of talcum powder is 0 to 100ppm, and the temperature of the cutting water for extrusion granulation is 13°C to 45°C.

3. A polyolefin elastomer, characterized in that, The polyolefin elastomer is prepared by the method for preparing a polyolefin elastomer according to claim 1 or 2.

4. The polyolefin elastomer according to claim 3, wherein The density of the polyolefin elastomer is 0.870 g / cm 3 to 0.890 g / cm 3 , the melt mass flow rate is from 0.8 g / 10 min to 18 g / 10 min, and the volatile content is from 30 ppm to 150 ppm.

5. The application of a polyolefin elastomer in the fields of photovoltaic encapsulation film, automotive plastic modification, wire and cable, and film packaging, characterized in that, The polyolefin elastomer is the polyolefin elastomer according to claim 3 or 4.