Solution polymerization method of polyolefin elastomer

Abstract

The invention discloses a solution polymerization method of a polyolefin elastomer, which comprises the following steps: carrying out continuous solution polymerization on a polymerization monomer in a reaction device provided with a stirrer under the action of C16-C20 long-chain alkane and a catalyst to obtain a polyolefin elastomer product, a gas phase evaporated in the polymerization process is cooled and then circulated into the reaction device; the content of C16-C20 long-chain alkane in the polymerization system is 0.5 wt%-10 wt%; and the structure of the stirrer is limited. Through mutual cooperation of long-chain alkane addition, evaporation heat removal and a specific stirrer structure, polymerization heat is removed in time, meanwhile, large bubbles are avoided, meanwhile, the viscosity of a system is reduced, and when it is ensured that the mass fraction of the polyolefin elastomer in the reaction device is 20% or above, the reaction time is shortened. The stability of the product property of the polyolefin elastomer and the efficient continuous production of the polyolefin elastomer are beneficial to industrial large-scale continuous production.

Description

Technical Field

[0001] The invention relates to the field of solution polymerization, and in particular to a solution polymerization method for a polyolefin elastomer. Background Art

[0002] Polyolefin elastomers are typically produced using a solution process, in which the heat load of the polymerization reactor is closely related to the mass fraction of the polyolefin elastomer in the reaction mixture. When the mass fraction of the polyolefin elastomer in the reaction mixture is less than 10%, the heat of reaction can generally be removed by simply feeding the reactants. When the mass fraction of the polyolefin elastomer in the reaction mixture is between 10% and 20%, other methods are required to remove the polymerization heat, such as the most common jacket heat removal, internal cooling coils, and external solution circulation. However, these heat removal methods have their own significant limitations. For example, the heat removal capacity of the jacket is very limited and cannot be removed entirely by the jacket alone; internal cooling coils can easily lead to poor fluid mixing; and the high viscosity of the external solution after cooling can easily cause polymer adhesion to the pipe wall. Therefore, absorbing heat by evaporating the solution and cooling the evaporated gas mixture and recycling it back to the reactor is currently the most commonly used method. Removing polymerization reaction heat by evaporating the solution is also widely used in industry. For example, Chinese patent documents CN1597706 and CN115141301A both disclose methods for removing reaction heat by evaporating the solution. The CX process of Japan's Mitsui Petrochemical and the Hostalen process of BASELL also use methods for removing reaction heat by evaporating the solution.

[0003] While the aforementioned solution evaporation technology for removing heat from solution polymerization reactions has achieved promising results in industrial applications, it is only applicable when the mass fraction of polyolefin elastomer in the polymerization reactor is less than 20%. However, to improve production efficiency, the mass fraction of polyolefin elastomer needs to be further increased to within the range of 20%-45%. At this point, the efficient and continuous production of polyolefin elastomers using solution evaporation to remove heat faces significant challenges: This process struggles to simultaneously achieve both efficient heat removal and adequate mixing of the reaction mixture. This is because increasing the mass fraction of polyolefin elastomer increases the reactor heat load dramatically, requiring the evaporation of a large amount of solvent, while also significantly increasing the viscosity of the system. These multiple negative factors ultimately lead to instability in the polyolefin elastomer production process and the inability to sustain efficient production.

[0004] In response to the above-mentioned problems, Chinese patent document CN109261101A discloses a stirring structure and method for enhancing olefin polymerization. The stirring structure for enhancing olefin polymerization includes a reactor body and an inner and outer double-layered agitator disposed within the reactor body. The inner and outer double-layered agitator is composed of an inner paddle and an outer paddle disposed outside the inner paddle. The inner and outer paddles are coaxially mounted in the reactor body and, as needed, rotate at different speeds and directions. The outer paddle is a plate-and-frame paddle or an anchor paddle. Although the inner and outer double-layered agitator can improve heat transfer efficiency and thereby promote uniform mixing of materials within the reactor, when the mass fraction of the polyolefin elastomer is greater than 20%, a large amount of solvent needs to be evaporated, and the viscosity of the system will also increase significantly, ultimately leading to instability in the polyolefin elastomer production process and the inability to sustain efficient production. Summary of the Invention

[0005] In view of this, the present invention provides a solution polymerization method for polyolefin elastomers. This method comprises adding a certain amount of long-chain alkanes to the reaction mixture, adopting a reaction apparatus with a special stirring structure, and combining conventional solution evaporation to remove heat. The polyolefin elastomer product finally obtained has stable performance and can be continuously and efficiently produced industrially.

[0006] To achieve the above object, the present invention provides a solution polymerization method for a polyolefin elastomer, comprising the following steps:

[0007] The polymerization monomer is continuously solution polymerized in a reaction device equipped with a stirrer under the action of C16-C20 long-chain alkanes and a catalyst to obtain a polyolefin elastomer product;

[0008] Wherein, the gas phase evaporated during the polymerization process is cooled and then circulated into the reaction device;

[0009] The content of the C16-C20 long-chain alkane in the polymerization system is 0.5wt%-10wt%, that is, in the polymerization system consisting of the polymerization monomer, the C16-C20 long-chain alkane, the catalyst and the solvent, the content of the C16-C20 long-chain alkane is 0.5wt%-10wt%, such as 0.55wt%, 0.65wt%, 0.75wt%, 0.80wt%, 0.95wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, 6.5wt%, 7.0wt%, 7.5wt%, 8.0wt%, 8.5wt%, 9.0wt%, 9.5wt% and the like;

[0010] The agitator includes a stirring shaft, an inner paddle and an outer paddle; the stirring shaft is arranged at the center of the reaction device, the inner paddle is arranged on the stirring shaft, and the inner paddles include a first inner paddle, a second inner paddle and a third inner paddle from top to bottom; the first inner paddle is a lower inclined blade paddle, the second inner paddle is a multi-layer inclined blade paddle, and an upper inclined blade paddle is provided between two adjacent inclined blade paddles, and the third inner paddle is a straight blade paddle or a turbine paddle;

[0011] The ratio of the diameter of the outer slurry to the diameter of the reaction device is 0.85-0.95, such as 0.85, 0.88, 0.89, 0.90, 0.92, 0.93, 0.94, etc.

[0012] The solution polymerization method for polyolefin elastomers provided by the present invention fully utilizes the regulating effect of specific long-chain alkanes on the physical property parameters of the solution polymerization system, and the control effect of a specially structured agitator on the flow field distribution and bubble size distribution. Combined with the solution evaporation heat transfer mode, the synergistic effect of these two methods ensures that the solution preparation method for polyolefin elastomers can still operate efficiently when the polyolefin elastomer content is greater than 20%, thereby improving the efficiency of the polyolefin elastomer while ensuring the product performance of the polyolefin elastomer and the stability of continuous production.

[0013] Optionally, in the solution polymerization method of the polyolefin elastomer, the C16-C20 long-chain alkane is selected from at least one of n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane and n-eicosane.

[0014] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the number of layers of the inclined blade pulp is not specifically limited and can be set and adjusted according to actual conditions and needs. For example, it can be limited to 3-8 layers, such as 4 layers, 5 layers, 6 layers, 7 layers, etc.; each of the inclined blade pulps is composed of 2-4 evenly distributed blades, such as 2, 3, and 4.

[0015] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the diameters of the inclined blade pulps are the same or different.

[0016] Optionally, in the solution polymerization method for polyolefin elastomers, the upper inclined blade refers to an upwardly inclined blade that forms a certain angle with the stirring shaft; the lower inclined blade refers to a downwardly inclined blade that forms a certain angle with the stirring shaft. The angle between the upper inclined blade and the stirring shaft is 15°-45°, such as 15°, 20°, 25°, 30°, 35°, 40°, 45°, etc.; each of the upper inclined blades is composed of 2-4 evenly distributed blades, such as 2, 3, or 4; and the diameter of each upper inclined blade is smaller than the diameter of the inclined blade.

[0017] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the angle between the downward inclined blade paddle and the stirring shaft is 15°-45°, such as 15°, 20°, 25°, 30°, 35°, 40°, 45°, etc.; the downward inclined blade paddle is composed of 2-4 evenly distributed blades, such as 2, 3, or 4; and the diameter of the downward inclined blade paddle is smaller than the diameter of the inclined blade paddle.

[0018] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the angle between the inclined blade paddle and the stirring shaft is 30°-60°, such as 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc.

[0019] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the inclined blades are distributed at equal intervals.

[0020] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the upper inclined blades are distributed at equal intervals.

[0021] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the ratio of the diameter of the inclined blade paddle to the diameter of the reaction device is 0.25-0.65, such as 0.30, 0.35, 0.40, 0.45, 0.55, 0.60, etc.

[0022] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the ratio of the diameter of the upper inclined blade to the diameter of the reaction device is 0.1-0.35, such as 0.15, 0.20, 0.25, 0.30, etc.

[0023] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the ratio of the diameter of the downward inclined blade to the diameter of the reaction device is 0.1-0.35, such as 0.15, 0.20, 0.25, 0.30, etc.

[0024] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the ratio of the diameter of the third inner paste to the diameter of the reaction device is 0.1-0.35, such as 0.15, 0.20, 0.25, 0.30, etc.

[0025] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the external propeller is selected from a propeller, an anchor propeller or a frame propeller;

[0026] Preferably, the outer propeller is an external anchor propeller comprising a plurality of evenly distributed upward inclined blades, and the angle between each upward inclined blade and the vertical direction of the reaction device is 15°-45°, such as 15°, 20°, 25°, 30°, 35°, 40°, 45°, etc.

[0027] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the number of the upward inclined blades is 4-8, such as 4, 5, 6, 7, or 8.

[0028] Optionally, in the solution polymerization method of the above-mentioned polyolefin elastomer, the ratio of the rotational speed of the inner paddle to the outer paddle is 3-20, such as 4, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, etc.; the specific rotational speeds of the inner and outer paddles are not limited and can be adjusted according to actual conditions. For example, the rotational speed of the inner paddle can be limited to 150-350 rpm, such as 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, etc., and the rotational speed of the outer paddle is 10-50 rpm, such as 15, 20, 25, 30, 35, 40, 45, 50, etc.

[0029] The inner propeller and the outer propeller have the same or opposite rotation directions, and preferably the inner propeller and the outer propeller have opposite rotation directions.

[0030] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the ratio of the gas phase flow evaporated in the reaction device to the feed flow (referring to the total feed flow, including the total feed flow of polymerization monomers, solvents, catalysts and long-chain alkanes, etc.) is 0.1-1.5, such as 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3, 1.5 and the like.

[0031] Optionally, in the solution polymerization method of the above-mentioned polyolefin elastomer, the polymerization temperature can be adjusted according to actual conditions and is not specifically limited. The reaction temperature of the continuous solution polymerization recommended by the present invention is 60-280°C, such as 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 275°C and the like.

[0032] Optionally, in the solution polymerization method of the above-mentioned polyolefin elastomer, the polymerization pressure can be adjusted according to actual conditions without specific limitation. The reaction pressure of the continuous solution polymerization recommended by the present invention is 2.0-8.0 MPa, such as 2.2 MPa, 2.5 MPa, 2.8 MPa, 3.0 MPa, 3.2 MPa, 3.5 MPa, 3.7 MPa, 4.0 MPa, 4.2 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa, 6.0 MPa, 6.5 MPa, 7.0 MPa, 7.5 MPa and the like.

[0033] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the content of polyolefin elastomer in the reaction device is 10%-45%; such as 15%, 20%, 25%, 30%, 35%, 40% and the like; preferably, the content of polyolefin elastomer is 20%-40%, such as 22%, 27%, 32%, 35%, 36%, 38% and the like.

[0034] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, the reaction apparatus is a vertical stirred reactor, and the height-to-diameter ratio of the vertical stirred reactor is not specifically limited, and can be limited according to actual conditions and renewal. For example, the height-to-diameter ratio of the vertical stirred reactor can be limited to 0.9-2.5, specifically 1.0, 1.2, 1.5, 1.8, 2.0, 2.2, 2.3, etc.

[0035] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, an overflow port is provided on the upper side wall of the reaction device for the outflow of the polyolefin elastomer product, and a raw material inlet and a long-chain alkane inlet are provided at the bottom for the addition of raw materials such as long-chain alkanes, polymerization monomers, solvents and catalysts.

[0036] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, a gas phase outlet is provided on the top of the reaction device, and the gas phase evaporated during the polymerization process is cooled by a cooling device and circulated into the reaction device through a circulation inlet provided at the bottom of the reaction device. Preferably, the circulation inlet includes a gas phase circulation inlet and a liquid phase circulation inlet, and the cooling device is connected to the gas phase circulation inlet and the liquid phase circulation inlet respectively through a gas-liquid separation device.

[0037] Optionally, in the above-mentioned solution polymerization method of polyolefin elastomer, a conventional jacket heat removal accessory is further provided on the outside of the reaction device, which can be used in conjunction with the solution evaporation heat removal method to remove polymerization heat.

[0038] Optionally, in the solution polymerization method of the polyolefin elastomer, the polymerization monomers are selected from at least two C2-C10 olefins, such as ethylene, propylene, butene, isopentene, 1-hexene, 1-heptene, 1-octene, etc.;

[0039] The solvent used in the continuous solution polymerization is selected from at least one of C4-C20 alkanes, such as butane, n-pentane, n-hexane, cyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, etc.;

[0040] The catalyst is a conventional Zignata catalyst or a metallocene catalyst in the industry.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] To improve the efficiency of preparing polyolefin elastomers by the solution process, it is necessary to increase the polyolefin elastomer content in the polyolefin elastomer product. However, as the content increases, the heat load in the reaction unit will inevitably increase sharply, requiring the evaporation of a large amount of gas for heat removal. The inventors have discovered that, on the one hand, the evaporation of a large amount of gas significantly increases the number of bubbles in the reaction unit. This increase in the number of bubbles promotes the continuous aggregation of bubbles and the generation of larger bubbles, seriously hindering the efficient mixing of materials in the reaction unit, increasing the temperature gradient and concentration gradient within the reaction unit, and making the properties of the polyolefin elastomer product difficult to control. On the other hand, the increase in the polyolefin elastomer content also leads to an increase in the viscosity and surface tension of the reaction system. The increase in viscosity does not facilitate the effective mixing of the reaction mixture, while the increase in surface tension further hinders the breakage of bubbles, resulting in an increasing number of large bubbles in the reaction unit and making the polymerization process difficult to control. This is the root cause of the instability and inability to sustain efficient production of polyolefin elastomer production processes after increasing the polyolefin elastomer content.

[0043] On the basis of the above research, the inventors provide a solution polymerization method for polyolefin elastomers. By adding a specific amount of C16-C20 long-chain alkanes that are not easy to evaporate to the polymerization system, the viscosity and surface tension of the polymerization system at a high mass fraction of polyolefin elastomer can be effectively reduced. If short-chain alkanes with a carbon number of less than 16 or long-chain alkanes with a carbon number greater than 20 are used, the polymerization reaction efficiency will be low or the properties of the polyolefin elastomer product will be unstable. By adopting a stirrer with a special structure, the specific inner and outer paddles cooperate with each other, not only can efficient mixing of the fluid in the reaction device be achieved, but also the distribution of bubbles can be controlled, large bubbles can be broken into multiple small bubbles, and the average size and size distribution of the bubbles can be regulated. The heat of polymerization is removed by evaporating the solution to remove heat (the evaporated gas phase during the polymerization process is cooled and circulated to the reaction device). The above three measures work together synergistically to remove the polymerization heat of the system in a timely manner without the formation of large bubbles, regulate the average diameter and size distribution of the bubbles, and at the same time reduce the viscosity of the system to ensure that the mass fraction of the polyolefin elastomer in the reaction device is above 20%. The stability of the properties of the polyolefin elastomer product and the efficient continuous production of the polyolefin elastomer are beneficial to industrial large-scale continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of a reaction device used in a solution polymerization method for a polyolefin elastomer provided by the present invention;

[0045] Figure 2 A schematic diagram of a reaction device used in another solution polymerization method for polyolefin elastomer provided by the present invention;

[0046] Figure 3This is a schematic diagram of the reaction apparatus used in the conventional solution polymerization method adopted in Comparative Example 1 of the present invention.

[0047] Among them, 1. Raw material inlet pipeline, 2. Long-chain alkane inlet pipeline, 3. Jacket cooling medium inlet, 4. Jacket cooling medium outlet, 5. Cooling jacket, 6. External anchor paddle, 7. Upward inclined blade, 8. Inclined blade paddle, 9. Agitator shaft, 10. Straight paddle, 11. Upward inclined blade, 12. Downward inclined blade paddle, 13. Overflow port, 14. Gas phase pipeline, 15. Cooler, 16. Gas-liquid separator, 17. Cooling liquid phase pipeline, 18. Delivery pump, 19. Cooling gas pipeline, 20. Gas compressor. DETAILED DESCRIPTION

[0048] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above disclosure.

[0049] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0050] The solution polymerization method for polyolefin elastomers provided herein is applicable to the preparation of any existing polyolefin elastomer. For ease of comparison, the following examples and comparative examples all use ethylene and octene as monomers, n-hexane as the solvent, a metallocene catalyst (constrained configuration catalyst GCG, relative molecular weight 383) as the primary catalyst, and triethylaluminum as the co-catalyst. The polymerization reactors used all had an aspect ratio of 1.2, a volume of 530 L, and were made of stainless steel.

[0051] Example 1

[0052] This embodiment provides a solution polymerization method for polyolefin elastomer, using Figure 1 The polymerization reaction device shown comprises the following steps:

[0053] After ethylene, octene, n-hexane, catalyst and co-catalyst are uniformly mixed, they continuously enter the polymerization reactor through the raw material inlet pipe 1 (wherein, the ethylene feed rate is 240 kg / h, the octene feed rate is 240 kg / h, the n-hexane feed rate is 600 kg / h, and the catalyst feed rate is Cv). Long-chain alkanes continuously enter the polymerization reactor through the long-chain alkane inlet pipe 2 at a feed rate of Fc. The mixture of ethylene, octene, n-hexane, catalyst and co-catalyst is mixed with the long-chain alkanes by stirring the inner slurry on the stirring shaft 9 located at the center of the polymerization reactor and the outer slurry located near the inner wall of the polymerization reactor and undergoes continuous polymerization reaction. The clockwise stirring speed of the inner slurry is 250 rpm, and the clockwise stirring speed of the outer slurry is 40 rpm (the ratio of the rotation speeds of the inner paddle and the outer paddle is 6.25). The average temperature of the polymerization reaction is 157°C and the pressure is 7.0 MPa.

[0054] During the polymerization process, the gas phase (primarily consisting of unreacted ethylene and n-hexane, as well as a small amount of octene) evaporates from the top of the polymerization reactor and is discharged through the gas phase outlet at the top at an evaporation rate of Ev. It is then transported via gas phase pipeline 14 to cooler 15 for cooling, and then separated into gas and liquid phases by gas-liquid separator 16. The gas phase is transported via cooling gas pipeline 19 to gas compressor 20 for compression, and then circulated back into the polymerization reactor via the gas phase circulation inlet located at the bottom of the polymerization reactor. The liquid phase is circulated back into the polymerization reactor via the liquid phase circulation inlet located at the bottom of the polymerization reactor via cooling liquid phase pipeline 17 with the aid of a delivery pump 18. The generated product continuously flows out through overflow port 13 located on the upper sidewall of the polymerization reactor, and the entire polymerization process operates continuously.

[0055] The inner paddles include, from top to bottom, a first inner paddle (a lower inclined blade paddle 12 is used in this embodiment, and the lower inclined blade paddle 12 is composed of 4 evenly distributed blades, and the angle between the lower inclined blade paddle 12 and the stirring shaft 9 is 30°), 4 layers of equally spaced inclined blade paddles 8 (each composed of 4 evenly distributed blades), and a straight blade paddle 10 (composed of 4 evenly distributed blades). An upper inclined blade paddle 11 is provided between each adjacent inclined blade paddle 8 (each upper inclined blade paddle 11 is composed of 4 evenly distributed blades, and the angle between each upper inclined blade paddle 11 and the stirring shaft 9 is 30°). The ratio of the diameter of each inclined blade paddle 8 to the diameter of the polymerization reactor is 0.4; the ratio of the diameter of each upper inclined blade paddle 11 to the diameter of the polymerization reactor is 0.10; and the ratio of the diameter of the lower inclined blade paddle 12 to the diameter of the polymerization reactor is 0.15.

[0056] The outer paddle is an external anchor paddle 6 comprising four evenly distributed upwardly inclined blades 7, each upwardly inclined blade 7 forming an angle of 30° with the vertical direction of the polymerization reactor; the ratio of the diameter of the outer paddle to the diameter of the polymerization reactor is 0.90.

[0057] During the stirring and mixing process, the outer anchor paddle 6 in the outer paddle is mainly used to enhance the fluid mixing in the wall area of ​​the polymerization reactor, avoiding wall sticking and the aggregation of large bubbles on the wall; the four layers of equally spaced inclined blade paddles 8 are mainly used to enhance the radial mixing of the fluid in the central area of ​​the polymerization reactor; the straight blade paddle 10 is mainly responsible for enhancing the fluid mixing at the bottom of the polymerization reactor, avoiding the appearance of dead zones in the bottom area; the upper inclined blade 7 of the outer paddle has the function of, first, enhancing the fluid turbulence intensity between the outer paddle and the inner paddle, and secondly, quickly breaking up large bubbles in the solution; the upper inclined blade paddle 11 arranged between the two adjacent inclined blade paddles 8 mainly plays the role of enhancing the fluid mixing effect in the area between the inclined blade paddles 8 and breaking up large bubbles; the lower inclined blade paddle 12 is mainly used to avoid the formation of obvious central vortex phenomenon due to high-speed centrifugal motion of the fluid, and at the same time enhance the fragmentation rate of rising bubbles in the central area.

[0058] Example 2

[0059] This embodiment is similar to embodiment 1, with the only difference being that:

[0060] 1. The polymerization reactor used is different. The polymerization reactor used in this embodiment is provided with a cooling jacket on the outer wall of the polymerization reactor used in Example 1. The specific schematic diagram is shown in FIG. Figure 2 As shown; During the polymerization process, cooling water enters the cooling jacket 5 from the jacket cooling medium inlet 3 and then flows out from the jacket cooling medium outlet 4; the jacket cooling water feed flow rate is 500kg / h, and the jacket heat exchange area is 2.7m 2 , the cooling water inlet temperature is 18℃.

[0061] 2. Some process parameters are different; the specific parameters are shown in Table 1 below.

[0062] Examples 3-6

[0063] Examples 3-6 are similar to Example 2, except that some process parameters are different, as shown in Table 1.

[0064] Comparative Example 1

[0065] This comparative example provides a solution polymerization method for polyolefins, using Figure 3 The polymerization reactor specifically comprises the following steps:

[0066] After ethylene, octene and n-hexane are uniformly mixed, they are continuously fed into the polymerization reactor through the raw material inlet pipe 1 (wherein, the ethylene feed rate is 240 kg / h, the octene feed rate is 240 kg / h, and the n-hexane feed rate is 600 kg / h). After the catalyst and co-catalyst are uniformly mixed, they are continuously fed into the polymerization reactor through the long-chain alkane inlet pipe 2. The ethylene, octene, n-hexane, catalyst and co-catalyst are mixed and continuously polymerized by stirring the inner slurry on the stirring shaft 9 located at the center of the polymerization reactor and the outer slurry located near the inner wall of the polymerization reactor. The clockwise stirring speed of the inner slurry is 250 rpm, and the clockwise stirring speed of the outer slurry is 30 rpm (the ratio of the rotation speeds of the inner paddle to the outer paddle is 8.33). The average temperature of the polymerization reaction is 157° C. and the pressure is 7.0 MPa.

[0067] During the polymerization process, the vapor phase (unreacted ethylene and n-hexane) formed by evaporation from the top of the polymerization reactor is discharged through the vapor phase outlet located at the top at an evaporation rate of Ev. It is then transported to cooler 15 via gas phase pipeline 14 for cooling. It is then separated into gas and liquid phases by gas-liquid separator 16. The vapor phase is transported to gas compressor 20 via cooling gas pipeline 19 for compression, and then circulated back into the polymerization reactor via the vapor phase circulation inlet located at the bottom of the polymerization reactor. The liquid phase is circulated back into the polymerization reactor via the liquid phase circulation inlet located at the bottom of the polymerization reactor via cooling liquid phase pipeline 17 with the aid of a delivery pump 18. The generated product continuously flows out through overflow port 13 located on the upper sidewall of the polymerization reactor, and the entire polymerization process operates continuously.

[0068] The inner paddle is composed of four layers of equally spaced inclined blade paddles 8, and the ratio of the diameter of each inclined blade paddle 8 to the diameter of the polymerization reactor is 0.4; the outer paddle is an external anchor paddle 6, and the ratio of the diameter of the outer paddle to the diameter of the polymerization reactor is 0.90. During the stirring and mixing process, the inner paddle strengthens the mixing of the fluid in the central area, and the outer paddle improves the mixing of the fluid in the wall area. However, when the viscosity is high, this combination of inner and outer diameters cannot achieve effective mixing of the fluid in (1) the area between the center and the side wall and (2) the area between adjacent inner blades, resulting in poor fluid flow conditions in these areas and inability to effectively break up large bubbles in these areas. In addition, when using this type of agitator, when the rotation speed of the inner and outer blades is high and the rotation direction is consistent, the fluid flows to the side wall area under strong centrifugal action, forming a vortex phenomenon in the central area.

[0069] A cooling jacket is provided outside the polymerization reactor. During the polymerization process, cooling water enters the cooling jacket 5 from the jacket cooling medium inlet 3 and flows out from the jacket cooling medium outlet 4. The jacket cooling water feed rate is 500 kg / h and the jacket heat exchange area is 2.7 m 2 , the cooling water inlet temperature is 18℃.

[0070] Comparative Example 2

[0071] This comparative example is similar to comparative example 1, except that a long-chain alkane is added to this comparative example. The polymerization reactor used in the solution polymerization method of polyolefin provided in this comparative example is as follows: Figure 3 As shown, the specific steps include:

[0072] After ethylene, octene, n-hexane, catalyst and co-catalyst are uniformly mixed, they continuously enter the polymerization reactor through the raw material inlet pipe 1 (wherein, the ethylene feed rate is 240 kg / h, the octene feed rate is 240 kg / h, the n-hexane feed rate is 600 kg / h, and the catalyst feed rate is Cv). Long-chain alkanes continuously enter the polymerization reactor through the long-chain alkane inlet pipe 2 at a feed rate of Fc. The mixture of ethylene, octene, n-hexane, catalyst and co-catalyst is mixed with the long-chain alkanes by stirring the inner slurry on the stirring shaft 9 located at the center of the polymerization reactor and the outer slurry located near the inner wall of the polymerization reactor and undergoes continuous polymerization reaction. The clockwise stirring speed of the inner slurry is 250 rpm, and the clockwise stirring speed of the outer slurry is 30 rpm (the ratio of the rotation speeds of the inner paddle and the outer paddle is 8.33). The average temperature of the polymerization reaction is 157°C and the pressure is 7.0 MPa.

[0073] During the polymerization process, the vapor phase (unreacted ethylene and n-hexane) formed by evaporation from the top of the polymerization reactor is discharged through the vapor phase outlet located at the top at an evaporation rate of Ev. It is then transported to cooler 15 via gas phase pipeline 14 for cooling. It is then separated into gas and liquid phases by gas-liquid separator 16. The vapor phase is transported to gas compressor 20 via cooling gas pipeline 19 for compression, and then circulated back into the polymerization reactor via the vapor phase circulation inlet located at the bottom of the polymerization reactor. The liquid phase is circulated back into the polymerization reactor via the liquid phase circulation inlet located at the bottom of the polymerization reactor via cooling liquid phase pipeline 17 with the aid of a delivery pump 18. The generated product continuously flows out through overflow port 13 located on the upper sidewall of the polymerization reactor, and the entire polymerization process operates continuously.

[0074] The inner paddle is composed of four layers of equally spaced inclined blade paddles 8, with the ratio of the diameter of each inclined blade paddle 8 to the diameter of the polymerization reactor being 0.4. The outer paddle is an external anchor paddle 6, with the ratio of the diameter of the outer paddle to the diameter of the polymerization reactor being 0.90.

[0075] A cooling jacket is provided outside the polymerization reactor. During the polymerization process, cooling water enters the cooling jacket 5 from the jacket cooling medium inlet 3 and flows out from the jacket cooling medium outlet 4. The jacket cooling water feed rate is 500 kg / h and the jacket heat exchange area is 2.7 m 2 , the cooling water inlet temperature is 18℃.

[0076] Comparative Example 3

[0077] This comparative example is similar to Example 2. Figure 2The apparatus shown differs only in that no long-chain alkane is added during the polymerization.

[0078] Comparative Example 4

[0079] This comparative example is similar to Example 2. Figure 2 The devices shown in the figure differ only in the long-chain alkane used in the polymerization process: in this comparative example, the long-chain alkane added in the polymerization process is n-dodecane.

[0080] Table 1

[0081]

[0082]

[0083] Wherein, Pv, Wt, Mw and PDI represent the production rate of polyolefin elastomer, the comonomer content in polyolefin elastomer, the weight average molecular weight of polyolefin elastomer and the dispersed phase index of polyolefin elastomer, respectively.

[0084] From the results of Examples 1-6 in the above table, it can be seen that by adopting a reaction device containing the agitator provided by the present invention and adding long-chain alkanes, the two can play a synergistic role: not only can the production rate of polyolefin elastomers be increased, but the obtained polyolefin elastomer products fully meet the product property requirements of general polyolefin elastomers. Specifically, the difference in the results of Example 1 and Example 2 shows that the use of an external jacket to transfer heat can slightly improve the production efficiency of polyolefin elastomers, slightly increase the comonomer content and weight-average molecular weight, and slightly reduce PDI. The difference in the results of Example 3 and Example 4 shows that when a turbine propeller is used as the third inner propeller and the outer propeller rotates counterclockwise, by appropriately increasing the number of layers of the inclined blade propeller, the angle between the upper inclined blade propeller and the stirring shaft, and the angle between the lower inclined blade propeller and the stirring shaft, the production rate of polyolefin elastomer can be further improved, the comonomer content and weight-average molecular weight of the product can be increased, and the PDI can be reduced. The difference between the results of Example 5 and Example 6 shows that by increasing the number of layers of the inclined blade pulp and the carbon number of the long-chain alkane, the production rate and comonomer content of the polyolefin elastomer can be further increased, but the weight average molecular weight and PDI will be slightly reduced.

[0085] Comparative Example 1, compared to Example 2, utilizes a different apparatus and does not add long-chain alkanes. The differences in the results indicate that the conventional solution polymerization method (Comparative Example 1) for continuous polyolefin production not only results in a slower polyolefin production rate, but also yields a polyolefin product with a comonomer content of only 17.8%, a weight-average molecular weight of 381,977, and a PDI of 4.42, which do not meet the required properties for polyolefin elastomers (typical polyolefin elastomers have a comonomer content of 25%-35%, a weight-average molecular weight of 80,000-140,000, and a PDI range of 2.0-3.0). Comparative Example 2, compared to Comparative Example 1, adds long-chain alkanes. While this increases the polyolefin production rate and comonomer content, and reduces the weight-average molecular weight and PDI, the resulting product still meets the required properties for typical polyolefin elastomers. Comparative Example 3 also yielded similar results. Compared to Example 2, Comparative Example 3 omitted the long-chain alkane. While the resulting polyolefin properties were closer to the product property requirements for polyolefin elastomers than those in Comparative Example 2, there was still a significant gap. Compared to Example 2, Comparative Example 4, when using n-dodecane with a carbon number of less than 16, exhibited lower polyolefin production rates and comonomer content, while exhibiting higher weight-average molecular weight and PDI. In summary, the solution polymerization method provided by the present invention can ensure efficient and continuous production of polyolefin elastomers, effectively improving polyolefin production efficiency while maintaining product properties.

[0086] Of course, the present invention may have many other embodiments and variations thereof. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and variations based on the present invention, but these corresponding changes and variations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A solution polymerization method for a polyolefin elastomer, characterized in that: The steps include: The polymerization monomer is continuously solution polymerized in a reaction device equipped with a stirrer under the action of C16-C20 long-chain alkanes and a catalyst to obtain a polyolefin elastomer product; Wherein, the gas phase evaporated during the polymerization process is cooled and then circulated into the reaction device; The content of the C16-C20 long-chain alkane in the polymerization system is 0.5wt%-10wt%; The agitator includes a stirring shaft, an inner paddle and an outer paddle. The stirring shaft is arranged at the center of the reaction device. The inner paddle is arranged on the stirring shaft. The inner paddles include a first inner paddle, a second inner paddle and a third inner paddle from top to bottom. The first inner paddle is a lower inclined blade paddle, the second inner paddle is a multi-layer inclined blade paddle, and an upper inclined blade paddle is provided between two adjacent inclined blade paddles. The third inner paddle is a straight blade paddle or a turbine paddle. The ratio of the diameter of the outer pulp to the diameter of the reaction device is 0.85-0.

95.

2. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein The C16-C20 long-chain alkane is selected from any one of n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane and n-eicosane.

3. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein The inclined blade pulp has 3-8 layers; and / or The angle between the upper inclined blade and the stirring shaft is 15°-45°, and the diameter of each of the upper inclined blades is smaller than the diameter of the inclined blade; and / or The angle between the downward-sloping blade and the stirring shaft is 15°-45°, and the diameter of the downward-sloping blade is smaller than the diameter of the inclined blade; and / or The angle between the inclined blade paddle and the stirring shaft is 30°-60°.

4. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein The inclined blades are equally spaced; and / or The upward inclined blades are equally spaced; and / or The ratio of the diameter of each of the inclined blades to the diameter of the reaction device is 0.25-0.65; and / or The ratio of the diameter of the upward inclined blade to the diameter of the reaction device is 0.1-0.35; and / or The ratio of the diameter of the downwardly inclined blade to the diameter of the reaction device is 0.1-0.35; and / or The ratio of the diameter of the third inner slurry to the diameter of the reaction device is 0.1-0.

35.

5. The solution polymerization method of polyolefin elastomer according to claim 1, wherein The outer propeller is selected from a propeller, an anchor propeller or a frame propeller; The outer propeller is an external anchor propeller comprising a plurality of evenly distributed upwardly inclined blades, and the angle between each upwardly inclined blade and the vertical direction of the reaction device is 15°-45°; There are 4 to 8 upward inclined blades.

6. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein The ratio of the rotational speed of the inner propeller to the rotational speed of the outer propeller is 3-20; and / or The inner propeller and the outer propeller rotate in the same direction or in opposite directions.

7. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein: The ratio of the vapor phase flow rate to the feed flow rate in the reaction device is 0.1-1.5; and / or The reaction temperature of the continuous solution polymerization is 60-280° C.; and / or The reaction pressure of the continuous solution polymerization is 2.0-8.0 MPa; and / or In the reaction device, the content of the polyolefin elastomer is 10%-45%, preferably 20%-40%.

8. The solution polymerization method of a polyolefin elastomer according to claim 1, wherein: The reaction apparatus is a vertical stirring reactor, and the height-to-diameter ratio of the vertical stirring reactor is 0.9-2.5; and / or The upper side wall of the reaction device is provided with an overflow port, and the bottom is provided with a raw material inlet and a long-chain alkane inlet; and / or A gas phase outlet is provided on the top of the reaction device. The gas phase evaporated during the polymerization process is cooled by a cooling device and then circulated into the reaction device through a circulation inlet provided at the bottom of the reaction device.

9. The solution polymerization method for a polyolefin elastomer according to claim 8, wherein: The circulation inlet includes a gas phase circulation inlet and a liquid phase circulation inlet, and the cooling device is connected to the gas phase circulation inlet and the liquid phase circulation inlet respectively through a gas-liquid separation device.

10. The solution polymerization method of polyolefin elastomer according to claim 1, wherein The polymerizable monomers are selected from at least two C2-C10 olefins; and / or The solvent used in the continuous solution polymerization is selected from at least one of C4-C20 alkanes.

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