Production method for reducing transition material in polyolefin elastomer produced from titanium polyethylene

Abstract

The invention relates to a production method for reducing a transition material in a polyolefin elastomer produced from titanium polyethylene, and belongs to the technical field of petrochemical engineering. The production method comprises the following steps: 1) controlling the pressure difference of a distribution plate of a to-be-converted gas phase reactor, and increasing the discharging frequency of a discharging system; 2) cutting off the injection of the cocatalyst, and then stopping the injection of the main catalyst in the titanium catalyst; 3) injecting a terminating agent; 4) replacing the to-be-converted gas phase reactor; (5) injecting a pretreating agent, and re-establishing a gas-phase component for producing POE (Polyolefin Elastomer); 6) injecting a POE catalyst to initiate a polymerization reaction of POE production, and meanwhile, carrying out bed replacement; the production method provided by the invention adopts a production mode without exiting from a condensation state, the pentane concentration does not need to be adjusted, the generation of a transition material is reduced, in addition, water is not added in the production method, and the risks of caking in the gas phase reactor to be converted and pipeline blockage are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry and relates to a production method for reducing transition materials in converting titanium-based polyethylene into polyolefin elastomer. Background Art

[0002] Polyolefin elastomer (POE) is an elastomer polymerized by ethylene and α-olefin under the action of a homogeneous metal catalyst. It has a wide range of uses. It can be used as a rubber, a thermoplastic elastomer, and a plastic impact modifier and toughening agent. It has been well applied in the toughening modification of a variety of plastics and has posed a strong competition to traditional toughening agents.

[0003] POE can replace general polymers such as EPM, EPDM, EVA, SBC (styrene bulk copolymer), TPU, PVC, LDPE and EMA, and is widely used in medical packaging materials, auto parts, wires and cables, daily necessities and toys. Since it can omit vulcanization and other processing steps during use, it can save 25% to 40% of energy consumption and improve processing efficiency by 10 to 20 times.

[0004] At present, the most commercialized POE is ethylene-octene copolymer and vinyl copolymer with octene mass fraction greater than 35% (octene mass fraction is less than 20% is a plastomer). Dow Chemical, Mitsui, and ExxonMobil, which have a relatively high market share, all use the solution method to produce. Although the performance of POE products prepared by the solution method has advantages, the solution method has the following disadvantages: ① High cost of solvent recovery: A large amount of organic solvents are required in the production process, and the recovery and treatment of these solvents require high costs and energy; ② Complex process flow: It involves multiple steps such as solvent addition, separation and recovery, making the entire production process more cumbersome; ③Great environmental impact: The use and discharge of solvents may cause certain pollution and harm to the environment; ④ Relatively low production efficiency: Compared with conventional polyolefin production methods, the solution method has a slower production speed and limited production capacity; ⑤ Large equipment investment: Due to the complexity of the process and the requirements for solvent treatment, more expensive and complex production equipment is required.

[0005] It is precisely because of the many shortcomings in the above-mentioned process methods and equipment facilities that the price of POE remains high.

[0006] In order to solve the complex process and equipment of the solution-based POE production method, some researchers have also studied the method of using titanium catalysts to convert to metallocene catalysts, but there are still disadvantages such as complex conversion process, long material qualification time, large amount of transition materials, easy pipeline blockage, and short production cycle. The following are examples.

[0007] Patent CN 117567676 B discloses a production method of converting titanium-based polyethylene to metallocene polyethylene, including: adjusting the gas phase reactor to be converted from the condensed state production mode to the dry state operation mode; in the dry state operation mode, reducing the discharge frequency of the discharge system of the gas phase reactor to be converted; reducing the catalyst injection amount to half of the original injection amount, and cutting off the co-catalyst at the same time, and gradually reducing the catalyst to zero when the co-catalyst is consumed; injecting a terminator into the gas phase reactor to be converted; reducing the pressure of the gas phase reactor to be converted, and injecting steam; replacing the gas phase reactor to be converted, and then injecting a pretreatment agent; re-establishing the gas phase component concentration according to the initiation conditions of the metallocene polyethylene, and then injecting the metallocene catalyst to complete the conversion. The whole process of this method can complete the start-up of metallocene polyethylene without using a metallocene polyethylene seed bed, and at the same time, it reduces the start-up time of metallocene polyethylene.

[0008] Patent CN 117567675 B relates to a production method for converting chromium-based polyethylene to metallocene polyethylene, which belongs to the field of petrochemical technology; the method includes: adjusting the gas phase reactor to be converted to the conversion state, and then injecting a terminator; replacing the gas phase reactor to be converted, and then injecting a pretreatment agent; re-establishing the gas phase component concentration according to the initiation conditions of the metallocene polyethylene, and then injecting a metallocene catalyst to initiate the reaction and complete the conversion; wherein the pretreatment agent includes an antistatic agent. The entire process of this method can complete the start-up of metallocene polyethylene without using a metallocene polyethylene seed bed, which minimizes the cost of extracting and filling the seed bed, and avoids the construction cost of adding a metallocene polyethylene seed silo; at the same time, it reduces the start-up time of metallocene polyethylene.

[0009] Patent CN 108948248 B discloses a method and device for producing polyolefin elastomers by gas phase method and the application of polyolefin elastomers. The method comprises the following steps: reacting in a reactor with polyethylene particles as a seed bed, introducing a raw material mixed gas including ethylene, hydrogen and nitrogen into the reactor, causing the polyethylene particles in the seed bed to flow and reach a fluidized state, then adding a catalyst into the reactor and introducing atomized droplet-shaped comonomers to react, wherein the comonomers are long-chain olefins with 6 to 18 carbon atoms, and the prepared polymer product has a density of 0.865-0.910 g / cm 3 , the long-chain olefin content is 6-40 wt%.

[0010] However, the above patent adopts the gas phase method to produce POE products. Although it can solve the problems of high solvent recovery cost, complex process flow, large environmental impact, relatively low production efficiency and large equipment investment when preparing POE products by solution method, the above patent only involves the method of switching different catalyst systems when preparing polyethylene by gas phase method, and does not solve the problems of complex POE conversion process, large amount of transition materials and easy pipeline blockage. Summary of the invention

[0011] In order to solve the problems existing in the prior art, the present invention provides a production method for reducing transition materials in the conversion of titanium-based polyethylene to polyolefin elastomers. The method can greatly reduce the POE conversion time, reduce the amount of transition materials, make the material pipeline unobstructed, and extend the POE production operation cycle.

[0012] In a first aspect, the present invention provides a method for reducing transition material in titanium-based polyethylene production of polyolefin elastomers, the method comprising the following steps: 1) Controlling the pressure difference of the distribution plate of the gas phase reactor to be converted to make the pores of the distribution plate of the gas phase reactor to be converted to be unobstructed; increasing the discharge frequency of the discharge system of the gas phase reactor to be converted to reduce the bed height of the titanium polyethylene product powder, so that the titanium polyethylene product powder to be replaced is at the lowest bed height (or material level); 2) Cut off the injection of the co-catalyst. After the co-catalyst in the gas phase reactor to be converted is consumed, stop injecting the main catalyst in the titanium catalyst, so that the residual titanium catalyst is consumed naturally and the reaction load is reduced; 3) maintaining the reaction temperature, reaction pressure and fluidized state in the gas phase reactor to be converted, and injecting a terminator into the gas phase reactor to be converted, so as to completely terminate the reaction in the gas phase reactor to be converted; 4) After the reaction is completely terminated, the partial pressures and total pressure of the components in the gas phase reactor to be converted to the product are kept unchanged, the reaction temperature is maintained, and the gas phase reactor to be converted to the product is replaced; 5) Inject pretreatment agent to pretreat the bed powder in the gas phase reactor to be converted (i.e., inject pretreatment agent for preloading (or adding in advance) so that the POE catalyst can release activity quickly and smoothly after injection), and re-establish the gas phase components for producing POE according to the polymerization initiation conditions of POE; 6) After the gas phase components are established, the POE catalyst is injected to initiate the polymerization reaction of POE production, and the bed is replaced at the same time; 7) After the bed replacement is completed, the bed height is raised to the gas phase fluidized bed expansion section, the bed height is maintained, and the polymerization reaction is continued to complete the conversion.

[0013] In the present invention, titanium-based polyethylene products refer to polyethylene products produced using titanium-based catalysts, such as polyethylene plastics and polyethylene-α-olefin copolymers.

[0014] As an optional embodiment, the polyolefin elastomer is obtained by polymerization of ethylene and α-olefin using a metallocene catalyst, wherein the α-olefin includes at least one of octene, hexene and butene; the density of the polyolefin elastomer is less than 0.89 g / cm 3 .

[0015] As an optional embodiment, the gas phase reactor to be converted includes a gas phase fluidized bed, and the gas phase fluidized bed includes a straight section and an expanded section.

[0016] There are numerous small holes on the distribution plate of the gas-phase reactor to be converted, which may be clogged by powder or sticky materials. By adjusting the operating conditions of the gas-phase reactor to be converted, such as increasing the fluidizing gas velocity, or / and increasing the condensate concentration, the clogged materials in the small holes can be flushed away, thereby ensuring that the pores on the distribution plate of the gas-phase reactor to be converted are in an unobstructed state.

[0017] As an optional embodiment, the pressure difference of the distribution plate is controlled in the lowest range, and the lowest range is 15-45 kPa. Preferably, the pressure difference of the distribution plate is controlled in the range of 18-24 kPa.

[0018] In the present invention, when the pressure difference of the distribution plate is too large, many small holes on the distribution plate are blocked by polymers, and the fluidization circuit is blocked, which leads to untimely heat removal and easy occurrence of implosion.

[0019] As an optional implementation, in the step 1), the titanium-based polyethylene product powder to be replaced is placed at a minimum bed height, and the minimum bed height is 7.5-9.5 m.

[0020] As an optional implementation, the bed height of the titanium-based polyethylene powder to be replaced is 75% to 90% of the straight section of the gas-phase fluidized bed.

[0021] As an optional embodiment, the titanium-based catalyst adopts a conventional titanium-based catalyst in the art, including any one of a silica-supported titanium-based catalyst and a magnesium chloride-supported titanium-based catalyst.

[0022] As an optional embodiment, the activity of the titanium-based catalyst is 3 to 5 times that of the POE catalyst. Optionally, the POE catalyst uses a conventional metallocene catalyst in the art, including a dichlorozirconocene (Cp2ZrCl2) catalyst and a bridged metallocene catalyst, wherein Cp represents a cyclopentadienyl group; the bridging group can be an alkylene group (such as -CH2-), a silane group (such as -SiMe2-, Me represents a methyl group).

[0023] As an optional embodiment, the co-catalyst includes at least one of diethylaluminum monochloride and tri-n-hexylaluminum.

[0024] As an optional embodiment, the pretreatment agent has a mass concentration of 10 ppm to 80 ppm of the ethylene feed.

[0025] As an optional embodiment, the pretreatment agent circulates in the gas phase reactor to be converted for 0.5 h to 8 h.

[0026] As an optional embodiment, the pretreatment agent includes at least one of a stearate pretreatment agent, a composite stearate pretreatment agent and dodecylbenzene sulfonic acid.

[0027] In the present invention, the main components of the stearate pretreatment agent are aluminum stearate, oil-soluble alkyl alcohol amine and mineral oil solvent, and the ratio is 10% to 30%: 15% to 25%: 65% to 90%. The main components of the composite stearate pretreatment agent are aluminum stearate, oil-soluble alkanolamide, mineral oil solvent, and stearate, and the ratio is 10% to 30%: 15% to 25%: 65% to 90%: 1% to 3%.

[0028] As an optional embodiment, the terminator comprises at least one of ethanol and toluidine. Preferably, the terminator comprises toluidine.

[0029] As an optional embodiment, the replacement is terminated when the ethanol in the gas phase reactor to be converted is less than 10 ppm and the toluidine is less than 15 ppm.

[0030] As an optional implementation, in step 4), the replacement adopts a boost-and-drop pressure method, wherein the low pressure of the boost-and-drop pressure method is 600 kPa to 900 kPa, and the high pressure of the boost-and-drop pressure method is 1100 kPa to 1400 kPa.

[0031] As an optional implementation, in step 7), after the bed replacement is completed, the bed height is rapidly raised to the gas phase fluidized bed expansion section, the bed height (or material level) is maintained at 11.5-15.5 m, and the polymerization reaction is continued to complete the conversion.

[0032] As an optional implementation, the method produces 90-130 t of transition material.

[0033] The production method provided by the present invention adopts a production mode without exiting the condensed state, cuts off the co-catalyst in advance, and after the co-catalyst is almost completely consumed, cuts off the injection of the high-activity catalyst to naturally deactivate the catalyst and reduce the load. The activity of the main catalyst is consumed until the reaction heat load is reduced to the target value. Without emptying the bed powder or cleaning the reactor, after the replacement is qualified, a pretreatment agent is added to eliminate the influence of residual components in the bed on the POE catalyst, and then a gas phase is established, and the POE catalyst is injected to initiate the reaction to complete the production conversion.

[0034] The whole process does not require the use of water to eliminate the co-catalyst in the gas phase reactor to be converted. The co-catalyst can be consumed cleanly by using the original high-activity titanium catalyst, avoiding the use of excess water to replace a large amount of transition material generated by the gas phase reactor to be converted, thereby reducing the transition material during POE production. After the water is added in the prior art, since the water is in liquid form in the reactor, the water will be adsorbed by the powder, so the water will be unevenly distributed in the reactor, and the poison will be unevenly distributed, which will inevitably lead to uneven release of catalyst activity, and will increase the risk of agglomeration and pipeline blockage in the gas phase reactor to be converted. The present invention avoids the above risks, thereby improving the operating efficiency of the device.

[0035] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0036] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: (1) The production method provided by the present invention adopts a production mode without exiting the condensed state. Compared with the production mode of exiting the condensed state in the prior art, there is no need to adjust the pentane concentration, thereby reducing the amount of transition material produced; (2) The production method provided by the present invention does not require the use of water to eliminate the co-catalyst in the gas phase reactor to be converted during the entire process. The co-catalyst in the gas phase reactor to be converted is completely consumed by the main catalyst with higher activity, thereby avoiding the use of excess water to replace a large amount of transition material generated by the reactor, thereby reducing the transition material during POE production; (3) The production method provided by the present invention does not add water during the transfer process, thereby avoiding uneven distribution of powder and poisons in the gas phase reactor to be transferred, which leads to uneven release of catalyst activity, and avoiding the risk of agglomeration and pipeline blockage in the gas phase reactor to be transferred, thereby improving the operating efficiency of the device and extending the operating cycle. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] The catalysts commonly used in POE production are mainly constrained geometry metallocene catalysts (CGC), which are generally formed by the interaction of transition metal elements (such as Group IVB elements Ti, Zr, Hf, etc.) or rare earth metal elements and at least one cyclopentadienyl or its derivatives through covalent bonds or coordination bonds. The catalysts currently used in commercial POE production are bridged dicyclopentadienyl catalysts and CGC catalysts, which are very different from the components of traditional Ziegler-Natta catalysts and chromium-based catalyst systems and are more sensitive to impurity components in the raw materials. Therefore, in the process of converting titanium-based catalysts to metallocene catalysts to produce POE in the gas phase polymerization process, water is mainly used as an alkyl aluminum deactivator for deactivation treatment in China, but this production method has the following disadvantages: ① After excessive water is injected into the gas phase reactor to be converted, it is adsorbed on the surface of the powder and is difficult to be displaced out of the gas phase reactor to be converted, resulting in a large amount of conversion transition material; ② The activity of the titanium-based main catalyst (generally alkyl aluminum) is not high enough. The alkyl aluminum that has not been completely ineffective will become a poison for the metallocene catalyst, which will affect the gelation and crystal point of subsequent metallocene products (for example, POE products); ③ The excess water is unevenly distributed in the gas phase reactor to be converted, resulting in uneven release of catalyst activity, easy agglomeration and crusting, and blockage of system pipelines.

[0039] To this end, the inventor intends to provide a method for reducing transition materials for converting titanium-based polyethylene copolymers to polyolefin elastomer POE. When the pores of the distribution plate of the gas phase reactor to be converted are in an unobstructed state, the powder bed height is lowered, the co-catalyst is first cut off, and the co-catalyst in the gas phase to be converted is almost completely consumed, and then the injection of the high-activity catalyst is cut off to deactivate the catalyst naturally and reduce the load. The activity of the main catalyst is consumed until the reaction heat load is reduced to the target value (11.5±2 t / h). Without emptying the bed powder and cleaning the gas phase reactor to be converted, after the replacement is qualified, a pretreatment agent is added to eliminate the influence of residual components in the bed on the metallocene catalyst for producing POE, and then a gas phase is established, and a metallocene catalyst is injected to initiate the reaction. After the bed replacement is completed, the bed height is raised to 13.5±2 m, the bed height is maintained, and the polymerization reaction is continued to complete the conversion. The whole process does not require the use of water to eliminate the co-catalyst in the gas phase reactor to be converted. The co-catalyst is completely consumed by the chemical reaction between the high-activity titanium catalyst (i.e., the main catalyst added in advance) and the co-catalyst, avoiding the need to use water to eliminate the co-catalyst to replace the excess water in the gas phase reactor to be converted, thereby reducing the transition material during POE production. In addition, since no water is added, there is no problem of uneven catalyst activity due to the adsorption of water on the powder, thereby avoiding the risk of agglomeration and pipeline blockage in the gas phase reactor to be converted, and the operation cycle can be extended.

[0040] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0041] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0042] Example 1 A production method for reducing transition materials in converting titanium-based polyethylene to polyolefin elastomers comprises the following steps: S1: Make the pores of the distribution plate of the gas phase reactor to be converted unobstructed, and control the pressure difference of the distribution plate at 23 kPa; increase the discharge frequency of the discharge system of the gas phase reactor to be converted to reduce the height of the titanium polyethylene product powder bed to 85% of the height of the straight section. Through the height of the titanium polyethylene product powder bed, the powder of the original product in the gas phase reactor to be converted is reduced, thereby reducing the product powder that needs to be replaced, so that the indicators of bed replacement can quickly meet the qualified requirements, accelerate the conversion process, and reduce the conversion time.

[0043] S2: Cut off the injection of the co-catalyst diethylaluminum chloride. After the co-catalyst is consumed in the reactor, gradually reduce the main catalyst in the titanium catalyst to 0, so that the residual catalyst is naturally consumed and the reaction load is reduced; the activity of the main catalyst is 4.5 times that of the subsequent POE catalyst. Among them, the main catalyst includes: silicon dioxide>70, titanium tetrachloride less than<11, tetraoxysilane<11, magnesium chloride<8.

[0044] S3: Maintain the reaction temperature, reaction pressure and fluidization state in the reactor, inject terminator ethanol, gradually reduce the ethylene feed rate according to the deactivation rate of ethanol on the catalyst, increase the nitrogen injection rate, keep the total pressure in the reactor unchanged, and avoid the adverse effects of pressure changes on the catalyst activity.

[0045] S4: After the reaction is completely terminated, keep the partial pressure and total pressure of each component in the reactor unchanged, maintain the reaction temperature, use nitrogen to replace the impurities in the reactor, and the replacement standard is 0.8 ppm of ethanol content in the reactor.

[0046] S5: Pretreat the bed powder in the reactor to re-establish the gas phase components; wherein, a composite stearate pretreatment agent is selected as the bed pretreatment agent to treat the residual catalyst and impurities in the bed to avoid their influence on the activity of the subsequently added metallocene catalyst, so that the activity of the subsequent POE catalyst can be released quickly and stably; the injection amount of the bed pretreatment agent is 76 ppm of the ethylene mass concentration, and it is circulated for 2 hours after injection.

[0047] S6: After the gas phase components are established, the metallocene catalyst is injected to initiate the polymerization reaction of POE production. Usually, the reactor is stable within 10 minutes and an upward trend can be seen. At the same time, the transition material produced during the polymerization reaction is replaced; S7: After 3 hours of polymerization, the titanium powder in the reactor has been completely replaced, and the bed height is raised to the junction of the expansion section and the straight section, and the bed height is kept unchanged to complete the production conversion.

[0048] Example 2 A production method for reducing transition materials in converting titanium-based polyethylene to polyolefin elastomers comprises the following steps: S1: Make sure the pores of the distribution plate of the gas phase reactor to be converted are unobstructed, and control the pressure difference of the distribution plate to the lowest range of 22 kPa; increase the discharge frequency of the reactor discharge system, and reduce the height of the powder bed to 80% of the height of the straight cylinder section.

[0049] S2: Cut off the injection of the co-catalyst tri-n-hexyl aluminum. After the co-catalyst is consumed in the reactor, gradually reduce the main catalyst to 0, so that the residual catalyst is naturally consumed and the reaction load is reduced. The activity of the main catalyst is 4 times that of the subsequent POE catalyst. Among them, the main catalyst uses the co-catalyst in Example 1.

[0050] S3: Maintain the reaction temperature, reaction pressure and fluidized state in the reactor, inject the terminator toluidine, gradually reduce the ethylene feed rate according to the deactivation rate of the catalyst by toluidine, increase the nitrogen injection rate, and keep the total pressure in the reactor unchanged.

[0051] S4: After the reaction is completely terminated, keep the partial pressure and total pressure of each component in the reactor unchanged, maintain the reaction temperature, use nitrogen to replace the impurities in the reactor, and the replacement standard is that the toluidine content in the reactor is 0.4 ppm.

[0052] S5: Pre-treat the bed powder in the reactor and re-establish the gas phase components; among them, stearate pre-treating agent is selected as the bed pre-treating agent to quickly release the activity of the subsequent POE catalyst and stabilize the activity. The injection amount of the bed pre-treating agent is 45 ppm of the ethylene mass concentration, and it circulates for 3.5 hours after injection.

[0053] S6: After the gas phase components are in place, the POE catalyst is injected to initiate the polymerization reaction of POE production. Usually, the reactor is stable within 15 minutes and an upward trend can be seen; at the same time, the transition material produced during the polymerization reaction is replaced.

[0054] S7: After 4.5 hours of polymerization reaction, the titanium powder in the reactor is completely replaced, and the bed height is raised to the junction of the expansion section and the straight cylinder section, and the bed height is kept unchanged to complete the production conversion.

[0055] Example 3 A production method for reducing transition materials in converting titanium-based polyethylene to polyolefin elastomers comprises the following steps: S1: Make sure the pores of the distribution plate of the gas phase reactor to be converted are unobstructed, and control the pressure difference of the distribution plate to the lowest range of 19 kPa; increase the discharge frequency of the reactor discharge system, and reduce the height of the powder bed to 70% of the height of the straight cylinder section.

[0056] S2: Cut off the injection of the co-catalyst diethylaluminum chloride. After the co-catalyst is consumed in the reactor, gradually reduce the main catalyst to 0, so that the residual catalyst is naturally consumed and the reaction load is reduced. The activity of the main catalyst is 3.5 times that of the subsequent POE catalyst. Among them, the main catalyst uses the co-catalyst in Example 1.

[0057] S3: Maintain the reaction temperature, reaction pressure and fluidized state in the reactor, inject terminator ethanol, gradually reduce the ethylene feed rate according to the deactivation rate of ethanol on the catalyst, increase the nitrogen injection rate, and keep the total pressure in the reactor unchanged.

[0058] S4: After the reaction is completely terminated, keep the partial pressure and total pressure of each component in the reactor unchanged, maintain the reaction temperature, use nitrogen to replace the impurities in the reactor, and the replacement standard is that the ethanol content in the reactor is 0.6 ppm.

[0059] S5: Pre-treat the bed powder in the reactor and re-establish the gas phase components; among them, dodecylbenzene sulfonic acid is selected as the bed pre-treatment agent to enable the subsequent POE catalyst to release the activity quickly and stably. The injection amount of the bed pre-treatment agent is 18 ppm of the ethylene mass concentration, and it circulates for 6 hours after injection.

[0060] S6: After the gas phase components are in place, the POE catalyst is injected to initiate the polymerization reaction of POE production. Usually, the reactor is stable within 20 minutes and an upward trend can be seen; at the same time, the transition material produced during the polymerization reaction is replaced.

[0061] S7: After 4 hours of polymerization, the titanium powder in the reactor is completely replaced, and the bed height is raised to the junction of the expansion section and the straight cylinder section, keeping the bed height unchanged to complete the production conversion.

[0062] Comparative Example 1 This comparative example provides a production method for reducing transition materials in the conversion of titanium-based polyethylene to polyolefin elastomers. The difference between this method and Example 1 is only that step S1 is different, and the other processes and conditions are the same as those in Example 1. Specifically, Step S1: Make the pores of the distribution plate of the gas phase reactor to be converted to an unobstructed state, and control the pressure difference of the distribution plate to the lowest range of 26 kPa; the discharge frequency of the reactor discharge system remains unchanged, and the reactor powder bed height is still maintained at the highest position, located at the expansion section of the reactor.

[0063] Comparative Example 2 This comparative example provides a production method of polyolefin elastomer POE using a titanium catalyst, which differs from Example 2 only in that step S2 is different, and other processes and conditions are the same as those in Example 2. Specifically, Step S2: Cut off the injection of the main catalyst and the co-catalyst at the same time, and when the co-catalyst tri-n-hexyl aluminum in the reactor is completely consumed, inject steam into the reactor to consume the residual catalyst naturally and reduce the reaction load.

[0064] Comparative Example 3 This comparative example provides a production method for reducing transition materials in the conversion of titanium-based polyethylene to polyolefin elastomers, which differs from Example 3 only in: Step S3 and Step S4, and other processes and conditions are the same as those in Example 3. Specifically, S3: Maintain the reaction temperature, reaction pressure and fluidized state in the reactor, inject the terminator carbon monoxide, gradually reduce the ethylene feed amount according to the deactivation rate of carbon monoxide on the catalyst, increase the nitrogen injection amount, and keep the total pressure in the reactor unchanged.

[0065] S4: After the reaction is completely terminated, keep the partial pressure and total pressure of each component in the reactor unchanged, maintain the reaction temperature, use nitrogen to replace the impurities in the reactor, and the replacement standard is 0.5 ppm of carbon monoxide content in the reactor.

[0066] Table 1 shows the conversion time of titanium-based polyethylene to polyolefin elastomer in Examples 1 to 3 and Comparative Examples 1 to 3, the weight of transition material and the block weight of the degassing system every 8 hours.

[0067] Table 1:

[0068] It can be seen from Table 1 that, relative to Comparative Examples 1 to 3, the production method for reducing transition materials in converting titanium-based polyethylene to polyolefin elastomer provided by Examples 1 to 3 of the present invention has a shorter conversion time for converting titanium-based polyethylene to POE, less transition materials, less block materials generated by the system, and a lower risk of pipeline blockage.

[0069] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0070] In the present invention, the terms "include", "comprises", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items.

[0071] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for reducing transition material in the production of polyolefin elastomers from titanium-based polyethylene, characterized in that: The production method comprises the following steps: 1) Controlling the pressure difference of the distribution plate of the gas phase reactor to be converted to make the pores of the distribution plate of the gas phase reactor to be converted to be in an unobstructed state; increasing the discharge frequency of the discharge system of the gas phase reactor to be converted to reduce the bed height of the titanium polyethylene product powder so that the titanium polyethylene product powder to be replaced is at the lowest bed height; the gas phase reactor to be converted to include a gas phase fluidized bed, and the gas phase fluidized bed includes a straight section and an expansion section; 2) Cutting off the injection of the co-catalyst, and stopping the injection of the main catalyst in the titanium-based catalyst after the co-catalyst in the gas phase reactor to be converted is consumed; 3) maintaining the reaction temperature, reaction pressure and fluidization state in the gas-phase reactor to be converted, and injecting a terminator into the gas-phase reactor to be converted; 4) After the reaction is completely terminated, the partial pressures of the components and the total pressure in the gas-phase reactor to be converted to the product are kept unchanged, the reaction temperature is maintained, and the gas-phase reactor to be converted to the product is replaced; 5) injecting a pretreatment agent to pretreat the bed powder in the gas phase reactor to be converted to production, and re-establishing the gas phase components for producing POE according to the polymerization initiation conditions of POE; 6) After the gas phase components are established, the POE catalyst is injected to initiate the polymerization reaction of POE production, and the bed is replaced at the same time; 7) After the bed replacement is completed, the bed height is raised to the expansion section of the gas phase fluidized bed, the bed height is maintained, and the polymerization reaction is continued to complete the production conversion.

2. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: The polyolefin elastomer is obtained by polymerization reaction of ethylene and α-olefin using a metallocene catalyst, wherein the α-olefin includes at least one of octene, hexene and butene.

3. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 2, characterized in that: The density of the polyolefin elastomer is less than 0.89 g / cm 3 .

4. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: The POE catalyst is a metallocene catalyst; the activity of the titanium-based catalyst is 3 to 5 times that of the POE catalyst.

5. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 1), the pressure difference range is 15-45 kPa.

6. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 1), the bed height of the titanium-based polyethylene powder to be replaced is 75% to 90% of the straight section of the gas-phase fluidized bed.

7. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 1), the minimum bed height is 7.5-9.5 m.

8. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 2), the co-catalyst includes at least one of diethylaluminum monochloride and tri-n-hexylaluminum; The terminator includes at least one of ethanol and toluidine.

9. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 4), the replacement is terminated when the ethanol in the gas phase reactor to be converted is less than 10 ppm and the toluidine is less than 15 ppm.

10. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 4), the replacement adopts the lifting and lowering pressure method, the low pressure of the lifting and lowering pressure method is 600 kPa to 900 kPa; the high pressure of the lifting and lowering pressure method is 1100 kPa to 1400 kPa.

11. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 5), the mass concentration of the pretreatment agent is 10 ppm to 80 ppm of the ethylene feed.

12. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 5), the pretreatment agent is circulated in the gas phase reactor to be converted for 0.5 h to 8 h.

13. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 5), the pretreatment agent includes at least one of a stearate pretreatment agent, a composite stearate pretreatment agent and dodecylbenzene sulfonic acid.

14. The method for reducing transition material in converting titanium-based polyethylene into polyolefin elastomer according to claim 1, characterized in that: In the step 7), after the bed replacement is completed, the bed height is rapidly raised to the expansion section of the gas phase fluidized bed, the bed height is maintained at 11.5-15.5 m, and the polymerization reaction is continued to complete the conversion.

15. The method for producing transition material in converting titanium-based polyethylene to polyolefin elastomer according to any one of claims 1 to 14, characterized in that: The transition material produced by the production method is 90-130 t.

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