Anti-caking polyolefin production method

Abstract

The invention belongs to the technical field of polyolefin production, and particularly relates to an anti-caking polyolefin production method, which comprises the following steps: in an olefin polymerization process, pre-contacting an active control agent StatsafeTM 6000 with an active solid catalyst component in a polymerization catalyst system outside a polymerization reactor under anhydrous and anaerobic conditions, then metering and adding a mixture obtained by pre-contact into a polymerization reactor; and the mass ratio of the active inhibitor to the active center metal is (0.01: 1)-(100: 1) based on the active center metal element contained in the active solid catalyst component. According to the method, after the active inhibitor and the active solid catalyst component are in pre-contact, the self-extinguishing effect of the active control agent is obviously better than that of the active solid catalyst component which is not in pre-contact (the self-extinguishing effect is improved by at least 20%), and the anti-caking effect is obvious.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin production, and in particular relates to an anti-caking polyolefin production method. Background Art

[0002] Olefin gas phase polymerization reactors mainly include vertical fluidized bed, vertical stirred tank, horizontal stirred tank and other types. The problem of polyolefin material agglomeration has existed for a long time in their production process.

[0003] With the recent rise of polyolefins from coal-to-chemical processes in China, more and more manufacturers are opting for the UNIPOL gas-phase polyethylene process. Currently, the annual production capacity of UNIPOL gas-phase polyethylene production plants in China has reached nearly 7.5 million tons. Because it utilizes a gas-phase fluidized bed reactor, the circulating reaction gas drives the polyethylene powder particles through high-speed flow and collisions. This process is extremely sensitive to impurities in the system, prone to friction-induced static electricity and agglomeration due to poor fluidization. From the 60,000-ton / year polymerization plants introduced in the late 1970s to the current 450,000-ton / year large-scale polymerization plants, agglomeration has been a persistent problem. For example, a 300,000-ton / year UNIPOL polyethylene plant in China experiences agglomeration during the production of LLDPE or HDPE. In severe cases, the reactor generates as much as 4 to 6 tons of agglomerated material per day. These agglomerates destabilize production control and product quality, creating additional workload for skilled workers to separate the agglomerates, and these agglomerates can only be sold at a low price as landfill, impacting economic efficiency. A more serious potential hazard is that if the block size is too large (>40cm) and blocks the discharge pipeline, it will cause unplanned shutdown of the polyethylene unit, thereby affecting the material balance of the entire plant upstream and downstream, with huge potential risks and losses.

[0004] It is generally believed that the main factors that cause agglomeration in gas-phase reactors include: electrostatic adsorption, the special design of the reactor expansion section that leads to retained materials, dead zones in the inherent double-circulation flow of the fluidized bed, and drastic fluctuations in process conditions. Due to the low heat transfer efficiency between the gas and solid phases, when the local concentration in the reactor fluctuates, the polyolefin resin particles adhere, aggregate, and continue to react. The reaction heat cannot be removed in time, resulting in hot spots, which in turn lead to the formation of agglomerates. The generated agglomerates continue to react and release heat, and the reaction heat cannot be effectively removed, causing the polyolefin agglomerates to soften or melt, and continue to adhere to more resin, causing the agglomerates to grow. The fundamental reason for the formation and growth of agglomerates is that the polymerization heat cannot be removed in time, resulting in the softening, melting, and agglomeration of the powder. If the agglomerates deactivate or reduce the activity of the catalyst active centers during or after the formation process, forcing the polymerization reaction to stop or weaken, and stopping or reducing the continued heat release, the continued formation and growth of the agglomerates can be inhibited.

[0005] The agglomeration problem of gas phase reactors is highly valued in this field, and efforts are being made to alleviate or resolve the agglomeration problem by reducing the static electricity level of the reaction system, improving raw material quality control, and optimizing the process.

[0006] Du Pont's patent document US3917466 proposes that adding a small amount of olefin-sulfur dioxide copolymer and polyamine substances to hydrocarbon fuel can significantly reduce the static electricity of the system. This type of antistatic agent can significantly improve the anti-knock property of the fuel.

[0007] Union Carbide Corporation's patent US4532311 discloses a process for reducing caking in polyolefin production. This process uses a Ti-based catalyst and coats the reactor's inner surface with chromocene to eliminate static electricity, maintaining the charge level below the critical caking potential. While this method is commonly used in UNIPOL gas-phase polyethylene fluidized-bed reactors for static elimination, caking still occurs frequently and remains unresolved.

[0008] Equistar Chemicals' patent document US6884749B2 discloses a method of anchoring a monofunctional hydrophobic compound (i.e., a C14-C18 alkyl chromium salicylate) on a catalyst support to reduce agglomeration and flaking in gas-phase polymerization reactors. Furthermore, if used in a slurry polymerization process to produce polyolefins, agglomeration can be reduced and product morphology and bulk density can be improved.

[0009] Univation Technologies' patent document US8420733B2 discloses a method of continuously adding a certain amount of a mixture of an aqueous solution of aluminum stearate or aluminum distearate and a scavenger such as an alkyl aluminum to a polymerization reactor using a metallocene catalyst. This method can not only prevent static electricity and reduce agglomeration, but also increase activity by at least 20%.

[0010] Univation Technologies' patent document US8722820B2 discloses a method for reducing the initial electrostatic level of a catalyst by at least 75% through prepolymerization. By prepolymerizing the catalyst with ethylene or hexene, the initial charge level of the metallocene catalyst is reduced, thereby reducing reactor electrostatics and controlling agglomeration.

[0011] Patent documents CN101835813A, CN102186889A, and CN101945897A from Dow Global Technologies, Inc., and patent document CN103214601A from Grace Corporation, disclose a self-extinguishing polypropylene catalyst. The catalyst comprises a Ziegler-Natta catalyst, an alkyl aluminum cocatalyst, and a selectivity control agent (SCA). The SCA is a mixture of an activity limiting agent (ALA) and a selectivity determining agent (SDA, such as a non-silane component). The SCA extinguishes the polymerization process or reaction at high temperatures (e.g., 100°C), effectively preventing polypropylene agglomeration. Examples of the catalysts describe adding a predetermined amount of SCA to a high-throughput PPR reactor after the reactor reaches a set temperature, achieving high-temperature self-extinguishing properties. Prior to entering the reactor, the SCA does not come into contact with the catalyst.

[0012] The various methods mentioned above for eliminating or inhibiting agglomeration in polyolefin production processes, on the one hand, have relatively low self-extinguishing temperatures (around 100°C), making them suitable for propylene polymerization (65-75°C). However, they are inappropriate for ethylene polymerization (85-110°C), which has higher polymerization temperatures. This is because the gap between the self-extinguishing temperature and the polymerization control temperature is too small, resulting in a narrow operating control window. Consequently, a large portion of the catalyst self-extinguishes and becomes inactive at the polymerization temperature, affecting normal operation of the device. On the other hand, existing selectivity control agents are continuously added to the reactor during the polymerization process, requiring a relatively large amount, which can affect the performance of the final polymer product. Furthermore, their self-extinguishing effect needs to be improved.

[0013] In view of this, it is necessary to continue to study how to more effectively eliminate or inhibit agglomeration in the polyolefin production process. Summary of the Invention

[0014] In order to overcome the shortcomings of the existing olefin gas phase polymerization method, the purpose of the present invention is to provide an anti-caking polyolefin production method using a small amount of Statsafe TM 6000 (abbreviated as S6000) is used as an activity control agent and pre-contacted with an ethylene polymerization Ziegler-Natta (ZN) catalyst to form a mixture, which is then added to the reaction device for polymerization reaction. It was unexpectedly found that after pre-contact, the self-extinguishing effect of the activity control agent was significantly improved (the self-extinguishing effect was increased by at least 20%), and the anti-caking effect was significantly better than the existing technology.

[0015] In order to achieve the above object, the present invention provides the following technical solutions:

[0016] A method for producing anti-caking polyolefins, wherein the active control agent Statsafe is added during the olefin polymerization process. TM6000 is pre-contacted with the active solid catalyst component (i.e., the main catalyst component) in the polymerization catalyst system outside the polymerization reactor under anhydrous and oxygen-free conditions, and then the pre-contacted mixture (measured) is added to the polymerization reactor, wherein:

[0017] The mass ratio of the activity inhibitor to the active center metal in the polymerization catalyst system (e.g., calculated as the metal element Ti), calculated based on the active center metal element contained in the active solid catalyst component, is 0.01:1 to 100:1 (for example, 0.02:1, 0.04:1, 0.05:1, 0.08:1, 0.1:1, 0.2:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 2:1, 4:1, 5:1, 6:1, 8:1, 10:1, 15:1, 20:1, 25:1, 30:1, 40:1, 50:1, 60:1, 80:1).

[0018] In the present invention, the active control agent used is the commercial Statsafe TM 6000, which can be purchased commercially.

[0019] In the present invention, the amount of the activity inhibitor can be controlled to be 1 / 100 to 1 / 10 of the amount used in a polymerization method without pre-contact to achieve a comparable anti-agglomeration effect in the polymerization reaction.

[0020] According to the polyolefin production method provided by the present invention, in some embodiments, the activity control agent Statsafe is calculated based on the active center metal element contained in the active solid catalyst component. TM The mass ratio of TiO2 6000 to the active center metal (calculated as metal element Ti) is 0.05:1 to 100:1, preferably 0.1:1 to 50:1.

[0021] In the present invention, the activity control agent is pre-contacted with the active solid catalyst component in the polymerization catalyst system before being added to the polymerization system to achieve the desired improved technical effect. In some embodiments, the time for the activity control agent to be pre-contacted with the active solid catalyst component in the polymerization catalyst system is ≥ 0.01 s (e.g., 0.05 s, 0.1 s, 0.2 s, 0.5 s, 1 s, 5 s, 10 s, 30 s, 60 s, 2 min, 5 min, 10 min, 30 min, 60 min, 2 h, 4 h, 5 h, 10 h, 20 h, 40 h, 50 h, 80 h, 100 h, 200 h, 500 h), preferably 0.01 s to 1000 h.

[0022] In some embodiments, the time for the pre-contact between the activity control agent and the active solid catalyst component in the polymerization catalyst system is 0.5 minutes to 6000 minutes.

[0023] In some embodiments, the activity control agent is pre-contacted with the active solid catalyst component in the polymerization catalyst system by intermittent pre-contact or continuous pre-contact.

[0024] In the present invention, the catalyst used for ethylene polymerization or copolymerization is a Ziegler-Natta (ZN) catalyst. In some embodiments, the polymerization catalyst system is a Ziegler-Natta catalyst, comprising: (a) an active solid catalyst component as a main catalyst; (b) an organoaluminum compound as a co-catalyst; and, optionally, (c) an internal electron donor component.

[0025] In some embodiments, the active solid catalyst component is a titanium-containing solid catalyst active component, preferably one or more selected from UCAT-J series catalysts, XY series catalysts, and BSG series catalysts.

[0026] In some embodiments, the organoaluminum compound is an alkylaluminum compound, preferably a trialkylaluminum, more preferably one or more selected from diethylaluminum monochloride, ethylaluminum dichloride, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, and tri-n-hexylaluminum. The organoaluminum compound as a cocatalyst can be added separately to the polymerization system. For example, the activity control agent and the active solid catalyst component are first pre-contacted to form a mixture, and then the mixture and the organoaluminum compound are separately added to the polymerization system.

[0027] In some embodiments, the ratio of the active solid catalyst component to the organoaluminum compound (in terms of Ti / Al molar ratio) is 1:25 to 1:400, for example, 1:26, 1:30, 1:35, 1:40, 1:50, 1:60, 1:80, 1:90, 1:100, 1:120, 1:150, 1:170, 1:200, 1:250, 1:300, 1:350.

[0028] If an internal electron donor is required, the internal electron donor can be a monocoordinate compound or a compound containing only one O, S, or P atom, preferably a dialkyl ether compound or a cyclic ether compound. The type and amount of the internal electron donor are conventional in the art and will not be described in detail here.

[0029] In some embodiments, the polyolefin production process is a polyethylene production process.

[0030] The inventors of the present invention unexpectedly discovered that by pre-contacting a small amount of S6000 as an activity control agent with the main catalyst component of a Ziegler-Natta (ZN) catalyst to form a mixture, and then adding the mixture to a reactor for ethylene polymerization, the main catalyst and the activity control agent undergo in-situ complexation during the pre-contact, resulting in a significantly better self-extinguishing effect (at least 20% improvement) than in the absence of pre-contact. The activity control agent selected in the present invention can achieve a satisfactory self-extinguishing effect even at a relatively low dosage, significantly improving anti-caking performance. Furthermore, the activity control agent selected in the present invention has a high self-extinguishing temperature (110°C and above), making it suitable for anti-caking applications in ethylene polymerization (copolymerization) applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The relationship between the relative activity of polymerization and the polymerization temperature is shown. DETAILED DESCRIPTION

[0032] In order to understand the technical features and content of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items.

[0034] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be followed. Reagents or instruments used without manufacturer specified are all commercially available conventional products.

[0035] Commercially available Statsafe TM 6000 (S6000), wherein the mass percentage concentration of the active component is 30%, and the balance is 70% heptane; its density is 0.805 g / ml; the preparation method of the S6000 solution used in the present invention is as follows:

[0036] Take 0.15 ml of the commercial S6000, then add 73.1 ml of n-heptane, shake well and set aside. The mass volume concentration of the prepared solution is 0.495 mg / ml.

[0037] Commercially available isopropyl myristate (IPM) has a density of 0.85 g / ml and a purity of 98%. The preparation method of the IPM solution is as follows:

[0038] 0.10 ml of the isopropyl myristate (IPM) was mixed with 42.5 ml of n-heptane, and the mixture was shaken for later use. The mass volume concentration of the prepared solution was 1.96 mg / mL.

[0039] Catalyst A: prepared according to the catalyst preparation section on pages 13-14 of WO2015073221A1, wherein the mass content of Ti is 2.8 wt%.

[0040] Example 1

[0041] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0042] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 85°C;

[0043] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0044] Step 3: 2.0 ml of a heptane solution of Catalyst A at a concentration of 8.5 mg / ml and 1.0 ml of a prepared S6000 solution were pre-contacted outside the reactor in an oxygen-free and water-free environment for 20 minutes. The pre-contacted mixture was then added to the reactor. 3.4 ml of a 0.5 M triethylaluminum heptane solution (Al / Ti = 170) was then added to the reactor.

[0045] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0046] Example 2

[0047] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0048] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 110°C;

[0049] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0050] Step 3: 2.0 ml of a heptane solution of Catalyst A at a concentration of 8.5 mg / ml and 1.0 ml of a prepared S6000 solution were pre-contacted outside the reactor in an oxygen-free and water-free environment for 20 minutes. The pre-contacted mixture was then added to the reactor. 3.4 ml of a 0.5 M triethylaluminum heptane solution (Al / Ti = 170) was then added to the reactor.

[0051] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0052] Example 3

[0053] The polymerization process was carried out according to the experimental steps of Example 1, except that, in step 3, 0.6 ml of S6000 solution was used for pre-contact for 20 minutes.

[0054] Example 4

[0055] The polymerization process was carried out according to the experimental steps of Example 1, except that, in step 3, 2.1 ml of S6000 solution was used for pre-contact for 20 minutes.

[0056] Example 5

[0057] The polymerization process was carried out according to the experimental steps of Example 1, except that, in step 3, 5.5 ml of S6000 solution was used for pre-contact for 20 minutes.

[0058] Example 6

[0059] The polymerization process was carried out according to the experimental steps of Example 1, except that, in step 3, 33.7 ml of S6000 solution was used for pre-contact for 20 minutes.

[0060] Example 7

[0061] The polymerization process was carried out according to the experimental steps of Example 2, except that, in step 3, 0.6 ml of S6000 solution was used for pre-contact for 20 minutes.

[0062] Example 8

[0063] The polymerization process was carried out according to the experimental steps of Example 2, except that, in step 3, 2.1 ml of S6000 solution was used for pre-contact for 20 minutes.

[0064] Example 9

[0065] The polymerization process was carried out according to the experimental steps of Example 2, except that, in step 3, 5.5 ml of S6000 solution was used for pre-contact for 20 minutes.

[0066] Example 10

[0067] The polymerization process was carried out according to the experimental steps of Example 2, except that, in step 3, 33.7 ml of S6000 solution was used for pre-contact for 20 minutes.

[0068] Example 11

[0069] The polymerization process was carried out according to the experimental steps of Example 1, except that in step 3, the pre-contact time of the S6000 solution was changed to 10 minutes.

[0070] Comparative Example 1

[0071] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0072] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to 85°C;

[0073] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0074] Step 3: 2.0 ml of a heptane solution of catalyst A with a concentration of 8.5 mg / ml and 3.4 ml of a 0.5 M triethylaluminum heptane solution were added to the reactor, wherein Al / Ti=170;

[0075] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0076] Comparative Example 2

[0077] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0078] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 110°C;

[0079] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0080] Step 3: 2.0 ml of a heptane solution of catalyst A with a concentration of 8.5 mg / ml and 3.4 ml of a 0.5 M triethylaluminum heptane solution were added to the reactor, wherein Al / Ti=170;

[0081] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0082] Comparative Example 3

[0083] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0084] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 85°C;

[0085] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0086] Step 3: 2.0 ml of a heptane solution of catalyst A (8.5 mg / ml), 3.4 ml of a 0.5 M triethylaluminum heptane solution, and 1.0 ml of a prepared S6000 solution were added to the reactor, wherein Al / Ti=170.

[0087] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0088] Comparative Example 4

[0089] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0090] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 110°C;

[0091] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0092] Step 3: 2.0 ml of a heptane solution of catalyst A (8.5 mg / ml), 3.4 ml of a 0.5 M triethylaluminum heptane solution, and 1.0 ml of a prepared S6000 solution were added to the reactor, wherein Al / Ti=170.

[0093] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0094] Table 1 Polymerization reaction conditions and results

[0095]

[0096] Compared with Comparative Example 1 in which no S6000 was added, when polymerization was carried out at 85°C, Comparative Example 3 in which S6000 was added and the S6000 / Ti mass ratio was 1.04, and S6000 was not pre-contacted with Catalyst A, had a polymerization activity attenuation ratio of only 16%; in Example 1 in which S6000 was added and the S6000 / Ti mass ratio was 1.04, and S6000 was pre-contacted with Catalyst A for 20 minutes, the polymerization activity attenuation ratio was increased to 26%.

[0097] Compared with Comparative Example 2 in which no S6000 was added, when polymerization was carried out at 110°C, Comparative Example 4 in which S6000 was added and the S6000 / Ti mass ratio was 1.04, and S6000 was not pre-contacted with Catalyst A, had a polymerization activity attenuation ratio of 47%; in Example 2 in which S6000 was added and the S6000 / Ti mass ratio was 1.04, and S6000 was pre-contacted with Catalyst A for 20 minutes, the polymerization activity attenuation ratio increased to 67%.

[0098] It can be seen that after adding a certain amount of S6000 to the polymerization system and pre-contacting it with Catalyst A, the polymerization activity is significantly suppressed; the higher the polymerization temperature, the greater the degree of activity suppression and the better the anti-agglomeration effect; and the anti-agglomeration effect of pre-contacting S6000 with Catalyst A is significantly better than that without pre-contact treatment.

[0099] Table 2 Polymerization reaction conditions and results

[0100]

[0101]

[0102] Compared to Example 1, with the same polymerization conditions of 85°C and a 20-minute pre-contact of S6000 with Catalyst A, different amounts of S6000 resulted in different polymerization activity decay rates. In Example 3, where the amount of S6000 was less than that in Example 1, the polymerization activity (12,175 times) was higher than that in Example 1 (10,704 times), and the corresponding polymerization activity decay rate was 18%, less than the 26% in Example 1. As the amount of S6000 increased, the S6000 / Ti mass ratio increased from 2.18 in Example 4 to 35.05 in Example 6, and the corresponding polymerization activity decreased from 9,502 times in Example 4 to 4,170 times in Example 6, both lower than that in Example 1. Compared to Example 1, the corresponding polymerization activity decay rate gradually increased, from 34% to 71%. This indicates that the magnitude of activity decay increases with increasing S6000 dosage.

[0103] Compared to Example 2, under the same polymerization conditions of 110°C and with a 20-minute pre-contact of S6000 with Catalyst A, different amounts of S6000 resulted in different polymerization activity decay rates. In Example 7, where the amount of S6000 was less than that in Example 2, the polymerization activity (1003 times) was higher than that in Example 1 (723 times), and the corresponding polymerization activity decay rate was 54%, lower than the 67% in Example 2. As the amount of S6000 continued to increase, the S6000 / Ti mass ratio increased from 2.18 in Example 8 to 35.05 in Example 10, and the corresponding polymerization activity decreased from 825 times in Example 8 to 178 times in Example 10, both lower than that in Example 2. Compared to Example 2, the corresponding polymerization activity decay rate gradually increased, from 62% to 92%. This indicates that the magnitude of activity decay increases with increasing S6000 dosage.

[0104] In Example 11, the pre-contact time between S6000 and the catalyst is 10 minutes, and the corresponding polymerization activity attenuation ratio is 23%; in Example 1, the pre-contact time between S6000 and the catalyst is 20 minutes, and the corresponding polymerization activity attenuation ratio is 26%; that is, the polymerization activity attenuation ratio of Example 11 is not much different from that of Example 1, and their effects on preventing agglomeration are basically the same.

[0105] In addition, the polymerization reaction of S6000 solution was studied with the same addition amount and different polymerization temperature conditions. The specific process was referred to Example 1 and Comparative Example 3, with the only difference being that the polymerization temperature was 90°C and 100°C, respectively. The relationship between the relative activity of polymerization and the polymerization temperature is shown in Figure 1. Figure 1 As shown, the relative activity of polymerization can be defined as the ratio of the activity with the addition of activity control agent to the activity without the addition of activity control agent. Figure 1 It can be seen from the changes in that: when the activity control agent is added or not, the relative activity of the polymerization decreases with the increase of the reaction temperature; after the activity control agent is added, the relative activity of the polymerization is reduced compared with the case without the activity control agent, and the relative activity of the polymerization decreases the most under the condition of pre-contact between the activity control agent and the catalyst, indicating that the self-extinguishing effect under this condition is the most significant at different polymerization temperatures.

[0106] Comparative Example 5

[0107] The polymerization process was carried out on a 2L stainless steel polymerization reactor in the laboratory:

[0108] Step 1: First, purge the reactor with purified nitrogen (water <1 ppm, oxygen <1 ppm); then add 1.0 L of liquid hexane solvent at room temperature and heat to the set temperature of 85°C;

[0109] Step 2: When the reactor reaches the set temperature, hydrogen is introduced to increase the pressure to 0.28 MPa, and then ethylene is introduced to increase the pressure to 0.75 MPa and maintain the pressure;

[0110] Step 3: 2.0 ml of a heptane solution of Catalyst A (8.5 mg / ml), 3.4 ml of a 0.5 M triethylaluminum heptane solution, and 1.7 ml of the prepared IPM solution were pre-contacted for 20 minutes. The pre-contacted mixture was then added to the reactor, with an Al / Ti ratio of 170.

[0111] Step 4: After 60 minutes of reaction, stop the reaction, take out the polymer sample, dry it, and weigh it to calculate the catalyst activity.

[0112] Comparative Example 6

[0113] The polymerization process refers to the experimental steps of Comparative Example 5, except that in step 3, 3.4 ml of IPM solution was used for pre-contact for 20 minutes.

[0114] Comparative Example 7

[0115] The polymerization process refers to the experimental steps of Comparative Example 5, except that in step 3, 6.8 ml of IPM solution was used for pre-contact for 20 minutes.

[0116] Comparative Example 8

[0117] The polymerization process refers to the experimental steps of Comparative Example 5, except that in step 1, the polymerization temperature is set to 110°C.

[0118] Comparative Example 9

[0119] The polymerization process refers to the experimental steps of Comparative Example 6, except that in step 1, the polymerization temperature is set to 110°C.

[0120] Comparative Example 10

[0121] The polymerization process refers to the experimental steps of Comparative Example 7, except that in step 1, the polymerization temperature is set to 110°C.

[0122] Table 3 Polymerization reaction conditions and results

[0123]

[0124]

[0125] Table 4 Polymerization reaction conditions and results

[0126]

[0127] Relative to Comparative Example 1, polymerization was carried out under the same conditions of 85°C, and IPM was added to Comparative Examples 5-7, with IPM / Ti mass ratios of 7:1, 14:1, and 28:1, respectively, and IPM was pre-contacted with Catalyst A for 20 minutes. The corresponding polymerization activity decay ratios were 12%, 18%, and 20%, respectively, all less than Example 1. Relative to Comparative Example 2, polymerization was carried out under the same conditions of 110°C, and IPM was added to Comparative Examples 8-10, with IPM / Ti mass ratios of 7:1, 14:1, and 28:1, respectively, and IPM was pre-contacted with Catalyst A for 20 minutes. The corresponding polymerization activity decay ratios increased to 35%, 45%, and 51%, respectively, all less than Example 2.

[0128] It can be seen from this that after IPM is selected as the activity control agent and added to the system, although the catalyst polymerization activity is inhibited to a certain extent, compared with the system with S6000 added, only a smaller amount of S6000 (S6000 / Ti mass ratio is 1.04:1) is needed to achieve a better activity inhibition effect than adding a larger amount of IPM. Therefore, the anti-caking effect is better in the polymerization system using S6000 as the activity control agent.

[0129] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A method for producing anti-caking polyolefins, characterized in that: In the olefin polymerization process, the activity control agent Statsafe TM 6000 is pre-contacted with the active solid catalyst component in the polymerization catalyst system outside the polymerization reactor under anhydrous and oxygen-free conditions, and then the pre-contacted mixture is added to the polymerization reactor, wherein: Calculated based on the active center metal element contained in the active solid catalyst component, the mass ratio of the activity inhibitor to the active center metal in the polymerization catalyst system is 0.01:1 to 100:

1.

2. The polyolefin production method according to claim 1, characterized in that Calculated based on the active center metal elements contained in the active solid catalyst component, the activity control agent Statsafe TM The mass ratio of 6000 to the active center metal is 0.05:1 to 100:1, preferably 0.1:1 to 50:

1.

3. The polyolefin production method according to claim 1, characterized in that The pre-contact time between the activity control agent and the active solid catalyst component in the polymerization catalyst system is ≥0.01s, preferably 0.01s to 1000h.

4. The polyolefin production method according to claim 3, characterized in that The time for the activity control agent to be in pre-contact with the active solid catalyst component in the polymerization catalyst system is 0.5 minute to 6000 minutes.

5. The polyolefin production method according to claim 1, characterized in that The activity control agent is pre-contacted with the active solid catalyst component in the polymerization catalyst system by intermittent pre-contact or continuous pre-contact.

6. The polyolefin production method according to any one of claims 1 to 5, characterized in that The polymerization catalyst system is a Ziegler-Natta type catalyst comprising: (a) an active solid catalyst component as a main catalyst; (b) an organoaluminum compound as a cocatalyst; and, optionally, (c) an internal electron donor component.

7. The polyolefin production method according to claim 6, characterized in that The active solid catalyst component is a titanium-containing solid catalyst active component, preferably selected from one or more of UCAT-J series catalysts, XY series catalysts and BSG series catalysts.

8. The polyolefin production method according to claim 6, characterized in that The organoaluminum compound is an alkylaluminum compound, preferably a trialkylaluminum, more preferably one or more selected from diethylaluminum monochloride, ethylaluminum dichloride, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum and tri-n-hexylaluminum.

9. The polyolefin production method according to any one of claims 6 to 8, characterized in that The dosage ratio of the active solid catalyst component to the organic aluminum compound (calculated as Ti / Al molar ratio) is 1:25 to 1:

400.

10. The polyolefin production method according to claim 6, which is a polyethylene production method.

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