A stabilizer composition and its preparation method

Abstract

This invention provides a stabilizer composition and its preparation method. The stabilizer composition comprises, by mass percentage: 50%–99.9% alkane oil solvent, 0.01%–40% fatty acid salt compound, and 0.01%–20% modified fumed silica; wherein the modified fumed silica is fumed silica surface-treated with organohalosilanes. The stabilizer composition of this invention exhibits high dispersibility and low impurities, and can meet the stringent requirements of metallocene catalysts.

Description

Technical Field

[0001] This invention relates to the field of additives for olefin polymerization processes, and more specifically to a stabilizer composition and its preparation method. Background Technology

[0002] Since metallocene catalysts were first used on a large scale in the industrial production of polyethylene in 1991, their preparation and related processes have become one of the most eye-catching technological directions in the polyolefin field. Compared with traditional Ziegler-Natta or chromium-based catalysts, metallocene catalysts possess ideal single active centers, enabling precise control over the molecular weight and distribution of the polymerization product, the content and sequence arrangement of comonomers, and the crystallinity and structural regularity of the polymerization product. Therefore, the resulting metallocene polyolefins often exhibit high stereoregularity, narrow molecular weight distribution, uniform comonomer distribution, and low catalyst residue, thus endowing the polymerization product with excellent impact resistance, puncture resistance, low-temperature heat sealing, and resistance to environmental stress cracking. At the application level, by designing and optimizing key parameters such as the main catalyst ligand, cocatalyst, type of silica support, and loading process, the physical and processing properties of the polymerization product can be selectively controlled.

[0003] However, the extremely high initial reactivity of metallocene catalysts also brings significant technical challenges. During polymerization, the intense exothermic reaction can easily lead to localized overheating areas ("hot spots") within the reactor, causing the polymerization system to run out of control. Polymer particles deteriorate from highly fluid granules to low-fluidity clumps. Failure to remove heat in a timely manner exacerbates the tendency of the polymer products to agglomerate, causing blockages in the reactor's pipelines and significantly increasing the difficulty of process control. Specifically, in slurry polymerization, the thermal convection of the solvent and the thermal conduction of the reactor wall are the main heat removal pathways. When these two are inefficient, fine polymer particles agglomerate and gradually adhere to the reactor's inner wall. As the reaction proceeds, the polymer scale layer on the wall continuously accumulates, not only affecting the performance of the polyolefin product but also potentially causing premature shutdown of the reactor. In gas-phase polymerization, due to the anhydrous and oxygen-free reaction environment, the friction and collision between insulating particles cause continuous accumulation of static electricity. Under electrostatic attraction, particles easily adhere to the wall, forming flakes or agglomerates, severely affecting heat and mass transfer within the reactor. In extreme cases, this can even trigger explosive polymerization, leading to non-polar shutdown.

[0004] Unstable polymerization states degrade the quality of polymerization products, hinder long-term operation of the equipment, and increase operating costs. In existing technologies, adding stabilizers (or stabilizer compositions) is a widely used and effective measure to prevent agglomeration. However, in actual production processes, reactor agglomeration is complex, with various influencing factors not existing independently but rather overlapping and coupled, mutually affecting each other. This complexity of multi-factor coupling, coupled with a lack of effective laboratory research methods, presents a severe challenge to stabilizer research. Directly introducing large amounts of stabilizers into the metallocene catalyst system not only makes stable polymerization difficult but may also lead to a sharp drop in catalyst activity and polymerization instability. Therefore, in practice, stabilizers and catalysts are generally injected separately into the reactor. When the stabilizer is a heterogeneous suspension system, i.e., simultaneously containing suspended solid particles and continuous liquid solvent, the inherent dispersion instability of this heterogeneous suspension system will further weaken its uniformity during adsorption and contact with the catalyst. The prior art (CN 118702849 B) discloses a scheme to improve the dispersion stability of the system by using surfactants as emulsifiers. However, as amphiphilic compounds containing polar groups, surfactants naturally have a significant negative impact on the activity of metallocene catalysts. Higher addition amounts can even lead to a more severe deterioration of the reactor's operating condition.

[0005] Besides the inherent dispersion stability of stabilizers, the dilution and separation of slurry solvents or gas phase gases in both slurry and gas-phase polymerization reactors reduce the probability of adsorption contact between stabilizers and metallocene catalysts, thus limiting their actual effectiveness in stabilizing olefin polymerization. Furthermore, the use of stabilizers as additives in the preparation of polyolefin products for food contact is often subject to regulations such as those of the European Commission and the US Food and Drug Administration, which restrict the use of conventional additives including ethoxyamines, alkylbenzene sulfonic acids, and random ethylene oxide / propylene oxide copolymers.

[0006] Therefore, developing a highly dispersible, low-impurity stabilizer to meet the stringent requirements of metallocene catalysts has become a research hotspot in this field. Summary of the Invention

[0007] This invention provides a stabilizer composition and its preparation method. The stabilizer composition is suitable for olefin polymerization processes under metallocene catalysis, and has high dispersibility and low impurities, thus meeting the stringent requirements of metallocene catalysts.

[0008] The present invention provides a stabilizer composition comprising, by weight percentage: 50%–99.9% alkane oil solvent, 0.01%–40% fatty acid salt compound, and 0.01%–20% modified fumed silica; wherein the modified fumed silica is fumed silica surface-treated with organohalosilane.

[0009] Optionally, the organohalosilane includes chlorosilanes, which include one or more of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and diphenyldichlorosilane.

[0010] Optionally, the surface treatment process specifically includes: (1) dehydrating fumed silica by vacuum drying at 150 ℃~200 ℃ for 2~6 h to obtain dehydrated fumed silica; (2) reacting the dehydrated fumed silica with the organohalosilane at 200 ℃~350 ℃ for 2~6 h; (3) maintaining the above reaction temperature while continuously purging with an inert gas stream for at least 2 h to obtain the modified fumed silica.

[0011] Optionally, the particle size of the modified fumed silica is 5 to 500 nm.

[0012] Optionally, the particle size of the modified fumed silica is 100–400 nm.

[0013] Optionally, the alkane oil solvent includes one or more of the following: pentane, hexane, cyclohexane, heptane, benzene, toluene, xylene, chlorinated hydrocarbons, chloroform, diethyl ether, carbon tetrachloride, carbon disulfide, amyl acetate, turpentine, vegetable oil, petroleum ether, lubricating oil, white oil, mineral oil, base oil, and liquid paraffin.

[0014] Optionally, the alkane oil solvent includes one or more of lubricating oil, white oil, mineral oil, base oil, and liquid paraffin.

[0015] Optionally, the alkane oil solvent is pre-treated by vacuum distillation at a pressure of 10. -10 ~101325 Pa; and / or, the temperature of the vacuum distillation treatment is 20 ℃~400 ℃.

[0016] Optionally, the alkane oil solvent is pre-treated by vacuum distillation at a pressure of 10. -1 ~101325 Pa; and / or, the temperature of the vacuum distillation treatment is 20 ℃~200 ℃.

[0017] Optionally, the fatty acid salt compound includes one or more of monovalent fatty acid salts, divalent fatty acid salts, and trivalent or higher fatty acid salts.

[0018] Optionally, the divalent fatty acid salt includes one or more of magnesium fatty acid, calcium fatty acid, strontium fatty acid, barium fatty acid, copper fatty acid, zinc fatty acid, and lead fatty acid, wherein the calcium fatty acid includes calcium octadecanoate and the zinc fatty acid includes zinc octadecanoate.

[0019] Optionally, the trivalent fatty acid salt includes one or more of aluminum fatty acid and iron fatty acid, wherein the aluminum fatty acid includes aluminum octadecanoate.

[0020] Optionally, the fatty acid salt compound is pre-washed, and the washing process includes: (1) washing with water at least twice; (2) washing with a mixed solvent including alcohol and water at least twice; and (3) drying.

[0021] Optionally, the alcohol includes one or more of methanol, ethanol, n-propanol, isopropanol, and allyl alcohol; in the mixed solvent comprising alcohol and water, the mass of the alcohol accounts for X% to Y% of the total mass of the mixed solvent, wherein the values ​​of X and Y are selected from any of the following five ranges: (1) X=0.01, Y=99.99; (2) X=0.1, Y=99.9; (3) X=1, Y=99; (4) X=10, Y=90; (5) X=15, Y=85.

[0022] Optionally, the drying method includes one or more of the following: natural evaporation, forced-air evaporation, heating drying, vacuum drying, and freeze sublimation.

[0023] The present invention also provides a method for preparing a stabilizer composition, comprising: adding a raw material system including the fatty acid salt compound and the modified fumed silica to the alkane oil solvent to obtain the stabilizer composition.

[0024] This invention provides a stabilizer composition and its preparation method, which has at least the following beneficial effects: The stabilizer composition of this invention adopts an alkane oil solvent + fatty acid salt compound + modified fumed silica system. The three components work synergistically to improve the dispersibility and purity of the stabilizer. The alkane oil solvent, as the basic dispersion medium of the stabilizer composition, provides an inert environment for the entire system. The fatty acid salt compound can effectively promote the initial dispersion of modified fumed silica in the alkane oil solvent and inhibit the formation of precipitation. The fumed silica can form a three-dimensional network structure to firmly lock the fatty acid salt compound and itself in the system, greatly enhancing the stability of the entire dispersion system. By optimizing the electrostatic adsorption capacity of fumed silica through surface modification, particle agglomeration during the olefin polymerization reaction is inhibited, and the dispersion stability of the olefin polymerization reaction system is improved. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is the clumping situation of the slurry in the small-scale reactor provided in Test Example 4 of the present invention without the addition of a stabilizer;

[0027] Figure 2 This is the agglomeration situation of the slurry in the small-scale reactor after adding the stabilizer composition provided in Test Example 4 of the present invention;

[0028] Figure 3 This describes the agglomeration situation in the gas-phase pilot reactor provided in Experimental Example 6 of the present invention. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a stabilizer composition comprising, by mass percentage: 50%–99.9% alkane oil solvent, 0.01%–40% fatty acid salt compound, and 0.01%–20% modified fumed silica; the modified fumed silica is fumed silica surface-treated with organohalosilanes.

[0031] Based on research and analysis, the stabilizer composition of this invention employs an alkane oil solvent + fatty acid salt compound + modified fumed silica system. These three components work synergistically to improve the dispersibility and purity of the stabilizer composition. Specifically, the alkane oil solvent, as the basic dispersion medium, provides an inert environment for the entire system. The fatty acid salt compound effectively promotes the initial dispersion of modified fumed silica in the alkane oil solvent and inhibits precipitation. The fumed silica forms a three-dimensional network structure that firmly locks the fatty acid salt compound and itself within the system, greatly enhancing the stability of the entire dispersion system. Furthermore, surface modification optimizes the electrostatic adsorption capacity of the fumed silica, thereby inhibiting particle agglomeration during olefin polymerization and improving the dispersion stability of the olefin polymerization system.

[0032] Metallocene catalysts generally refer to catalytic systems composed of metallocene complexes as both the main catalyst and co-catalyst. Metallocene complexes are typically organometallic complexes composed of transition metal elements (such as group IVB elements titanium, zirconium, and hafnium) or rare earth metal elements and at least one cyclopentadiene or cyclopentadiene derivative as a ligand. These are compounds formed when cyclopentadiene or its derivative bonds to a metal or metal halide via planar conjugated π bonds. The "magnesium" in metallocene comes from the "pentane" in cyclopentadiene, indicating that the ligand is an aromatic cyclopentadienyl anion. Based on the ligand structure, metallocene catalysts can be classified into monometallocene catalysts, non-bridged bismetallocene catalysts, and bridged bismetallocene catalysts. The range of ligands can be further expanded to include indene or fluorene rings.

[0033] The stabilizer composition comprises, by weight percentage: 50%–99.9% alkane oil solvent, 0.01%–40% fatty acid salt compound, and 0.01%–20% modified fumed silica.

[0034] The stabilizer composition may be in the form of a solid, gel, or fluid. When the stabilizer composition is in fluid form, it may be one or more of the following forms: pure liquid, solid suspension, and slurry.

[0035] In some embodiments, the alkane oil solvent includes one or more of the following: pentane, hexane, cyclohexane, heptane, benzene, toluene, xylene, chlorinated hydrocarbons, chloroform, diethyl ether, carbon tetrachloride, carbon disulfide, amyl acetate, turpentine, vegetable oil, petroleum ether, lubricating oil, white oil, mineral oil, base oil, and liquid paraffin.

[0036] Since pentane, hexane, cyclohexane, heptane, benzene, toluene, xylene, chlorinated hydrocarbons, chloroform, diethyl ether, carbon tetrachloride, carbon disulfide, amyl acetate, turpentine, vegetable oil, and petroleum ether are mostly low-boiling-point and highly volatile solvents used as solvents for alkane oils, these light solvents are extremely prone to vaporization and volatilization in high-temperature polymerization reaction systems catalyzed by metallocene. This not only changes the composition and viscosity of the stabilizer system, but may also lead to its failure, making it unable to meet the long-term stability requirements under high-temperature conditions.

[0037] Preferably, the alkane oil solvent includes one or more of lubricating oil, white oil, mineral oil, base oil, and liquid paraffin.

[0038] The alkane oil solvents in the embodiments of the present invention meet the above-mentioned requirements, and can improve the dispersibility of suspended solid particles contained in the heterogeneous suspension system during metallocene catalysis. Furthermore, the preferred alkane oil solvents have high viscosity, which can improve the suspension properties of the system.

[0039] Furthermore, liquid paraffin (CAS No.: 8042-47-5) is preferred. Liquid paraffin is a highly refined mixture of saturated alkanes with stable chemical properties. It can serve as a continuous phase and the basic dispersion medium for the composition, providing an inert environment for the entire system. At the same time, liquid paraffin has been included in the pharmacopoeias of many countries, including the Chinese Pharmacopoeia, the United States Pharmacopeia (USP), and the European Pharmacopoeia (EP). It is widely used as a pharmaceutical excipient in injections, creams, ointments, and oral medications. In addition, it is also a base oil for cosmetics (such as skin creams and baby oils) and some food processing lubricants. These applications are based on its recognized low toxicity, non-irritation, and chemical inertness.

[0040] In the stabilizer composition, the alkane oil solvent has a mass percentage of 50% to 99.9%, for example, a range of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99.9%, or any two of these, preferably 70% to 95%.

[0041] The alkane oil solvent has a mass percentage content within the above range, which can encapsulate and isolate fatty acid salt compounds and modified fumed silica solid particles, preventing them from agglomerating, settling or caking due to van der Waals forces (weak electrical attraction between molecules or atoms), electrostatics, etc., thereby improving the stability of the stabilizer composition.

[0042] The aforementioned liquid paraffins include various categories with different grades, viscosities, boiling ranges, and molecular weights. They are mainly mixtures of refined liquid hydrocarbons such as saturated cycloalkanes and alkanes, and are generally obtained from crude oil through atmospheric and vacuum distillation, solvent extraction and dewaxing, and hydrogenation refining.

[0043] Preferably, the alkane oil solvent can be pre-treated by vacuum distillation at a pressure of 10. -10 ~101325 Pa, for example 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 -1 10 2 500, 10 3 10 4 10 5 The range of 101325 Pa or any two thereof, preferably 10 Pa. -6~101325 Pa, more preferably 10 -1 ~101325 Pa, further preferred 10 2 ~101325 Pa.

[0044] 10 of them -10 Pa is extremely high vacuum; 101325 Pa is one standard atmosphere, i.e., normal pressure; 10 -6 Pa represents the ultra-high vacuum level; 10 -1 Pa is the high vacuum level; 10 2 Pa is at the medium vacuum level; greater than the medium vacuum level (10 2 A vacuum level of 101325 Pa (Pa) and less than the standard atmospheric pressure (101325 Pa) is considered a rough vacuum level.

[0045] The pressure of vacuum distillation within the above range can reduce processing difficulty and cost, remove trace amounts of water and light alkanes from alkane oil solvents, and reduce the impurity content in alkane oil solvents.

[0046] The temperature for vacuum distillation can be selected from any of the following ranges: 20 ℃~400 ℃, 20 ℃~200 ℃, 20 ℃~150 ℃, 40 ℃~150 ℃, or 40 ℃~120 ℃.

[0047] The temperature for vacuum distillation can range from 20℃ to 400℃, for example, 20℃, 25℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, and 400℃. The temperature range is ℃ or any combination thereof, preferably 20℃~200℃, more preferably 20℃~150℃, further preferably 40℃~150℃, and most preferably 40℃~120℃.

[0048] The temperature of vacuum distillation meets the above range, which is beneficial for removing trace amounts of water and light alkanes from alkane oil solvents and reducing the impurity content in alkane oil solvents.

[0049] Fatty acid salts are a class of stabilizer compositions that can be used in olefin polymerization reactions and have multiple functions. Specific uses include: (1) acid neutralizers in olefin polymerization reactions, usually used to neutralize acid catalyst residues caused by Ziegler-Natta catalysts. (2) antioxidants, used to improve color stability and corrosion resistance in olefin polymerization reactions. In ethylene polymerization (polyethylene), the most widely used fatty acid salts are calcium octadecanoate and zinc octadecanoate, while in propylene polymerization (polypropylene), calcium octadecanoate is the most widely used. (3) lubricants, used to provide processability of polyolefins in extrusion molding (such as films, fibers, spinning, etc.) and compression molding. (4) release agents. For example, in thermosetting products, fatty acid salts will gradually migrate to the surface of the part as curing progresses, precipitating into a gel-like substance, thereby forming a highly releaseable film at the mold cavity interface. In addition to being used as additives in stabilizer compositions for the post-processing of olefin polymerization, fatty acid salts are also ideal raw materials in the daily chemical industry due to their low biotoxicity and high food contact safety, and are widely used in the manufacture of soaps and other products.

[0050] In some embodiments, the fatty acid salt compound includes one or more of monovalent fatty acid salts, divalent fatty acid salts, and trivalent or higher fatty acid salts, preferably one or more of divalent and trivalent fatty acid salts.

[0051] Fatty acid salts include compounds containing carboxylate ions (COO). - Based on the degree of carbon chain saturation, fatty acid components can be classified into saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. It is understood that saturated fatty acids do not contain C=C (unsaturated bonds) in their main chain; monounsaturated fatty acids contain one C=C (such as palmitoleic acid, oleic acid, and ricinoleic acid) in their main chain; and polyunsaturated fatty acids contain two or more C=C (such as linoleic acid, linolenic acid, and arachidonic acid) in their main chain.

[0052] The fatty acid components described above preferably include one or more of saturated fatty acids and monounsaturated fatty acids, wherein the monounsaturated fatty acids preferably include oleic acid.

[0053] Depending on the number of carbon atoms in the fatty acid salt compound, the fatty acid salt compound may include fatty acid salts containing 6-36 carbon atoms, preferably fatty acid salts containing 12-22 carbon atoms, more preferably fatty acid salts containing 16-18 carbon atoms, and more preferably one or more of fatty acid salts containing 16 carbon atoms and 18 carbon atoms.

[0054] Depending on the number of carboxylate ions, fatty acid salts can include monovalent fatty acid salts, divalent fatty acid salts, and trivalent or higher fatty acid salts.

[0055] The fatty acid salt compounds preferably include one or more of divalent and trivalent fatty acid salts.

[0056] Preferably, the monovalent fatty acid salt includes one or more of sodium fatty acid, potassium fatty acid, and ammonium fatty acid.

[0057] Preferably, the divalent fatty acid salt includes one or more of magnesium fatty acid, calcium fatty acid, strontium fatty acid, barium fatty acid, copper fatty acid, zinc fatty acid, and lead fatty acid, wherein calcium fatty acid includes calcium octadecanoate and zinc fatty acid includes zinc octadecanoate.

[0058] Preferably, the trivalent fatty acid salt includes one or more of aluminum fatty acid and iron fatty acid, and more preferably includes aluminum fatty acid. Aluminum fatty acid can effectively promote the initial dispersion of modified fumed silica in liquid paraffin and prevent the modified fumed silica from forming a hard precipitate that is difficult to depolymerize.

[0059] Aluminum fatty acid compounds include those with COO - fatty acid components and Al 3+ The aluminum component, wherein the mass percentage of aluminum in the fatty acid aluminum compound is 0.1% to 15%, preferably 1% to 10%, more preferably 2% to 8%, and even more preferably 2.5% to 8%.

[0060] Furthermore, the aforementioned aluminum fatty acid more preferably includes aluminum octadecanoate (since the aluminum component is in the trivalent state and the carboxyl group on the fatty acid component is in the monovalent state, the missing valence position will be filled by hydroxide ions, which are also in the monovalent state. Since hydroxide ions often exhibit basicity, aluminum octadecanoate is often called basic aluminum octadecanoate).

[0061] Fatty acid salt compounds satisfy the above-mentioned categories, enabling the stabilizer composition to be better compatible with metallocene catalysts, thereby improving the stability and dispersibility of the metallocene catalyst reaction system in olefin polymerization (polyolefin) reaction.

[0062] The fatty acid salt compound has a mass percentage of 0.01% to 40% in the stabilizer composition, for example, 0.01%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any combination thereof, preferably 5% to 30%.

[0063] The amount of fatty acid salt compounds used within the above range is beneficial for the stabilizer composition to be better compatible with the metallocene catalyst, thereby improving the stability and dispersibility of the metallocene catalyst reaction system in olefin polymerization (polyolefin).

[0064] When used to improve the stability of olefin polymerization processes, especially when paired with metallocene catalysts that are extremely sensitive to impurities, it is crucial to further enhance the applicability of fatty acid salts and improve the operability of the methods.

[0065] In some embodiments, the fatty acid salt compounds are pre-washed, and the washing process includes: (1) washing with water at least twice; (2) washing with a mixed solvent including alcohol and water at least twice; and (3) drying.

[0066] The washing (purification) process satisfies the above operations, enabling fatty acid salt compounds to be fully mixed with solvents (water or mixed solvents including alcohol and water) to remove impurities that affect the dispersion stability of the product and the activity of metallocene catalysts, thereby improving the applicability of fatty acid salt compounds and improving the preparation method and operability of stabilizer compositions.

[0067] The specific operations of the above washing process may include one or more of the following: washing, emulsification, ultrasonication, dispersion, stirring, shaking, rinsing, wetting, mixing, homogenization, extraction, demulsification, filtration, and centrifugation.

[0068] Using water as a solvent for washing (purification) can remove water-soluble impurities. Divalent or trivalent fatty acid salts are not easily dispersed or dissolved in water due to their low hydrophilicity, thus obtaining fatty acid salts with high purity and no impurities, which can further enhance the dispersing stabilizer in olefin polymerization reactions.

[0069] In some embodiments, the alcohol includes one or more of methanol, ethanol, n-propanol, isopropanol, and allyl alcohol, preferably one or more of methanol and ethanol.

[0070] In a mixed solvent including alcohol and water, the mass of alcohol accounts for X% to Y% of the total mass of the mixed solvent, where the values ​​of X and Y are selected from any of the following five ranges: (1) X=0.01, Y=99.99; (2) X=0.1, Y=99.9; (3) X=1, Y=99; (4) X=10, Y=90; (5) X=15, Y=85.

[0071] Specifically, the mass ratio of alcohol to the total mass of the mixed solvent can be 0.01% to 99.99%, for example, 0.01%, 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, 99.9%, 99.99%, or any combination thereof, preferably 0.1% to 99.9%, more preferably 1% to 99%, further preferably 5% to 99%, even more preferably 10% to 90%, and most preferably 15% to 85%.

[0072] Washing (purification) with a mixed solvent including alcohol and water can not only further remove impurities, but also improve the drying efficiency and degree of the third drying process.

[0073] In some embodiments, the drying method includes one or more of natural evaporation, forced-air evaporation, heating drying, vacuum drying, and freeze sublimation, with vacuum drying being preferred.

[0074] The drying method described above can ensure that fatty acid salt compounds are completely dried, thereby improving the purity of the stabilizer.

[0075] The modified fumed silica is present in the stabilizer composition at a mass percentage of 0.01% to 20%, for example, 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or any combination thereof, preferably 0.01% to 10%.

[0076] The modified fumed silica in the stabilizer composition meets the above-mentioned range by mass percentage, which enables the stabilizer composition to better suppress particle agglomeration during the polymerization reaction and improve the dispersion stability of the olefin polymerization system.

[0077] In some specific embodiments, the modified fumed silica is fumed silica that has undergone surface modification and particle size screening.

[0078] In the prior art, the surface modification of fumed silica can use inorganic substances (such as hydrofluoric acid and water vapor), siloxanes (such as hexamethylethylsiloxane, hexamethyldisiloxane, polydimethylsiloxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane), alcohols (butanol, pentanol, heptanol, octanol, linear dodecanol), and silane coupling agents (such as trimethylethoxysilane, methyltrimethoxysilane, vinylethoxysilane, and tetrabutoxysilane).

[0079] Inorganic compounds, siloxanes, and alcohols primarily adjust surface properties through physical or weak chemical interactions, making it difficult to provide a stable organic protective layer for metallocene catalysts and potentially introducing acidic sites. Therefore, silane coupling agents and organohalosilanes are preferred. However, although silane coupling agents are widely used, their reactions are mild, and residual alkoxy groups or unreacted hydroxyl groups may pose potential risks (e.g., vinyltriethoxysilane can introduce reactive vinyl groups that participate in subsequent ethylene gas-phase polymerization, leading to uncertain byproducts).

[0080] In some embodiments, the surface modification of fumed silica may use organohalosilanes, including chlorosilanes, which include one or more of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and diphenyldichlorosilane.

[0081] Organohalosilanes, especially chlorosilanes, can be used to remove hydrogen halides, which then firmly bond organic groups to the surface of fumed silica via Si-C bonds. This process efficiently and extensively replaces the silanol groups on the fumed silica surface, significantly reducing its polarity and hydrophilicity, thus transforming it into a hydrophobic surface.

[0082] Of the aforementioned chlorosilanes, dimethyldichlorosilane is further preferred. Dimethyldichlorosilane is a bifunctional modifier that, after reaction, forms a monolayer primarily composed of dimethylsiloxane on the surface of fumed silica, providing moderate steric hindrance and good hydrophobicity. The organic layer formed by dimethyldichlorosilane effectively shields the internal silanol groups, greatly reducing electron-rich sites that interact with metallocene catalysts, thus providing excellent chemical inertness protection. Simultaneously, the organic groups introduced by dimethyldichlorosilane improve the dispersibility of silica in hydrocarbon solvents.

[0083] In some embodiments, the process of surface treatment of fumed silica with dimethyldichlorosilane specifically includes: (1) dehydrating fumed silica by vacuum drying at 150℃~200℃ for 2~6 h to obtain dehydrated fumed silica; (2) reacting the dehydrated fumed silica with an organohalosilane at 200℃~350℃ for 2~6 h; (3) maintaining the above reaction temperature while continuously purging with an inert gas stream for at least 2 h to obtain modified fumed silica.

[0084] Modified fumed silica can be prepared using the surface treatment method described above.

[0085] The above-mentioned surface treatment method for fumed silica is a post-processing modification. The specific steps of the post-processing modification method include dehydration, reaction, and purification.

[0086] (1) The fumed silica was dehydrated by vacuum drying at 150 ℃~200 ℃ for 2~6 h to obtain dehydrated fumed silica.

[0087] The aforementioned fumed silica can be conventional hydrophilic fumed silica.

[0088] The temperature for vacuum drying can be 150 ℃ to 200 ℃, for example, 150, 160, 170, 180, 190, 200 ℃ or any combination thereof.

[0089] The vacuum drying time can be 2 to 6 hours, for example, 2, 3, 4, 5, 6 hours or any combination thereof.

[0090] (2) The dehydrated fumed silica was reacted with organohalosilane at 200 ℃~350 ℃ for 2~6 h.

[0091] Specifically, under the protection of an inert gas, the dehydrated fumed silica is fluidized at 200 ℃ to 350 ℃, and an organohalosilane (surface modifier, preferably dimethyldichlorosilane) vapor is introduced and reacted for 2 to 6 h.

[0092] The reaction temperature can be 200 ℃ to 350 ℃, for example 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350 ℃ or any combination thereof.

[0093] The reaction time can be 2 to 6 hours, for example, 2, 3, 4, 5, 6 hours or any combination thereof.

[0094] (3) Next, maintain the above reaction temperature and continuously purge with an inert gas stream for at least 2 hours to obtain modified fumed silica.

[0095] Specifically, step (3) is used to purify the modified fumed silica. The modified fumed silica prepared in step (2) is purged with an inert gas at 200 ℃~350 ℃ to remove byproducts and residual reagents. After cooling, the modified fumed silica is obtained.

[0096] Inert gases include nitrogen.

[0097] In addition to post-processing modification, modified fumed silica can also be prepared by integrated in-situ modification. Both methods can achieve surface treatment of fumed silica.

[0098] The integrated in-situ modification method includes synthesis and introduction, in-situ reaction and collection and purification. The specific process includes: (1) hydrolyzing the silicon source in an oxyhydrogen flame at high temperature, the temperature of which can be selected from 400 ℃ to 800 ℃, to obtain highly active fumed silica particles, and introducing the surface modifier (preferably dimethyldichlorosilane) directly into the reaction system in the form of vapor; (2) the highly active fumed silica particles and the modifier vapor undergo an instantaneous chemical reaction to complete the surface grafting modification, and obtain a gas-solid mixture including fumed silica particles and modifier vapor; (3) collecting the gas-solid mixture including fumed silica particles and modifier vapor, separating it by cyclone separation, bag filtration, purging it with high temperature inert gas to remove byproducts and residual reagents, and then cooling it to obtain modified fumed silica.

[0099] The temperature at which the aforementioned silicon source is hydrolyzed at high temperature in an oxyhydrogen flame can be 400℃~800℃, for example, 400, 500, 600, 700, 800℃ or any combination thereof.

[0100] Regardless of whether post-processing modification or integrated in-situ modification is used, the modified fumed silica obtained with the specific surface and physical properties of this invention falls within the protection scope of this invention.

[0101] After surface modification, the polar silanol groups on the surface of fumed silica are shielded by the inert dimethylsiloxane structure, reducing surface energy and reactivity, thus greatly improving its biocompatibility. This type of hydrophobic fumed silica is commonly used in the pharmaceutical industry as a thixotropic agent in ointments and a suspending agent in oily preparations, and its safety and efficacy have been verified in relevant fields.

[0102] It should be specifically noted that the protection of modified fumed silica in this invention lies in its role as a component of a stabilizer composition and its specific product properties (such as the hydrophobicity, low hydroxyl content, and dispersion stability exhibited by surface modification with dimethyldichlorosilane), rather than the specific modification process. The core of this invention lies in the stabilizer composition itself, which contains modified fumed silica products with specific properties (surface chemistry, particle size). Any stabilizer composition employing modified fumed silica possessing these specific properties, regardless of the details of the method for preparing the modified fumed silica, should fall within the scope of protection of this invention.

[0103] It should be understood that the term "gas phase" in this article refers to the method of preparing silica and the resulting specific physical morphology (such as small particle size, low packing density, high purity, amorphous, chain structure, etc.), which has a generally accepted meaning in the art. Therefore, any silica material having the same or similar chemical composition and physical properties as described below, regardless of whether its name contains the word "gas phase," should be considered equivalent to the "modified fumed silica" of this invention and fall within the protection scope of this invention, as long as it achieves the purpose of this invention.

[0104] Typically, the particle size of modified fumed silica can include the primary particle size of the fumed silica (i.e., the primary particle size) and / or the particle size of the aggregates of fumed silica in the dispersion system.

[0105] The particle size distribution range of modified fumed silica can be determined using D. 50 The distribution range is represented by D. 50 Median particle size, also known as median diameter, is a statistical value. It represents the percentage of particles with a diameter less than or equal to this value in a powder or particle sample, accounting for 50% of the total sample mass. 50 It is a value, not a range. D 50 The distribution range represents D 50 The value can take any range of values ​​consisting of two numbers of different sizes.

[0106] In some embodiments, the particle size (native particle size D) of the modified fumed silica 50 The nm range is 5–500 nm, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500 nm or any combination thereof, preferably 10–400 nm, more preferably 100–400 nm, and even more preferably 150–350 nm.

[0107] The particle size of modified fumed silica within the above range enables a better balance between the specific surface area and steric hindrance of the modified fumed silica. This allows the modified fumed silica to perform both space-filling and rheological control functions, while avoiding excessive agglomeration or excessively high surface energy caused by excessively small particle size. This, in turn, helps to improve the anti-agglomeration performance of the stabilizer composition.

[0108] Modified fumed silica actually exists and functions in a certain degree of agglomeration in the alkane oil solvent of the stabilizer composition, and the particle size D of the dispersed agglomerates is... 50 Crucially, the particle size D of the modified fumed silica agglomerates in the composition system is... 50 The distribution range is 0.1 μm to 50 μm (100 nm to 50000 nm).

[0109] In the alkane oil solvent of the stabilizer composition, modified fumed silica forms a three-dimensional network aggregate with a certain structural strength through van der Waals forces and other interactions. This structure is key to achieving polymerization stabilization. The three-dimensional network structure formed by modified fumed silica can firmly lock fatty acid salt compounds and themselves within the system, greatly enhancing the stability of the entire stabilizer composition dispersion system, preventing stratification and sedimentation during storage and transportation, and ensuring the consistency of the stabilizer composition's performance.

[0110] The particle size of agglomerates dynamically changes within a certain range depending on external forces such as settling time, stirring duration, stirring rate, and swelling / melting. Therefore, the core of the protection of modified fumed silica in this invention lies in its inherent, stable primary particle size characteristics and the surface chemical properties obtained after specific modification, rather than its dynamic agglomerate size affected by external conditions. Any fumed silica possessing the aforementioned primary particle size range and the surface modification characteristics of this invention, whose naturally formed three-dimensional network structure in the application system provides a stabilizing effect, falls within the scope of protection of this invention.

[0111] Fatty acid salt compounds and modified fumed silica can exist in alkane oil solvents in the form of particles, partial swelling, partial dissolution, or complete dissolution. When fatty acid salt compounds and modified fumed silica exist in alkane oil solvents in the form of particles, partial swelling, or partial dissolution, they can exhibit dispersion forms including floating, suspension, settling, bottom settling, stratification, emulsification, and their combinations.

[0112] Alkane oil solvents (e.g., liquid paraffin), fatty acid salt compounds (e.g., aluminum stearate), and modified fumed alumina (e.g., fumed silica with surface modified by dimethyl dichlorosilane) all possess good biocompatibility and can promote and support each other functionally to produce a synergistic effect of 1+1+1>3. This synergistic effect is beneficial to improving the dispersion stability of the stabilizer composition and enhancing the anti-agglomeration ability of the stabilizer composition.

[0113] The aforementioned aluminum stearate is a classic metal soap with a long history of safe application in the pharmaceutical and cosmetic industries. It is widely used as a lubricant for tablets, a thickener for creams, and a stabilizer for drugs. Its safety has been recognized by multiple drug regulatory agencies worldwide, including China. As an excipient in topical and oral formulations, it has demonstrated reliable tissue compatibility and low biotoxicity, improving the safety of stabilizer compositions in food contact (food compliance).

[0114] By optimizing the types of alkane oil solvents and fatty acid salt compounds, catalyst poisoning is reduced, acidic impurities are neutralized, the lubrication function of the solvent is improved, and the compatibility with metallocene catalysts is enhanced, making the stabilizer more suitable for metallocene catalysts that are extremely sensitive to impurities.

[0115] This invention also provides a method for preparing a stabilizer composition, comprising: adding a raw material system including fatty acid salt compounds and modified fumed silica to an alkane oil solvent to obtain a stabilizer composition.

[0116] The above-mentioned method for preparing stabilizer compositions can produce stabilizer compositions simply and quickly.

[0117] The above-mentioned raw material system, including fatty acid salt compounds and modified fumed silica, is added to an alkane oil solvent and then mixed by stirring.

[0118] The mixing method can include one or more of the following: mechanical mixing, high-speed shearing, and homogenization.

[0119] The above stirring method enables the alkane oil solvent, fatty acid salt compound and modified fumed silica to be fully mixed and uniformly dispersed to form a stable suspension system, i.e., a stabilizer composition.

[0120] The stirring (preparation) and storage of the stabilizer composition can be carried out in a protective gas atmosphere, which may include one or more of nitrogen, argon, carbon dioxide, deoxygenated air, dehydrated air, dehydrated oxygenated air, helium, and neon, preferably one or more of nitrogen and argon.

[0121] In the olefin polymerization process, metallocene catalyst particles are the active centers of the polymerization reaction and the core of the newly formed olefin particles. The long-chain alkane structure of fatty acid salt compounds (aluminum stearate) allows them to be effectively physically adsorbed onto the surface of the catalyst and polyolefin particles through van der Waals forces. Modified fumed silica nanoparticles, with their large specific surface area and surface energy, fill the voids between particles and between fatty acid salt compounds (aluminum stearate) and particles, enhancing the steric hindrance effect and preventing direct contact between polymer particles, thereby effectively preventing, reducing, or inhibiting particle aggregation and agglomeration.

[0122] It is particularly important to emphasize that the core of protection under this invention lies in the stabilizer composition itself, namely the composition of each specific component, its physicochemical properties (such as the surface properties and primary particle size of modified fumed silica), and the synergistic effect between the three, rather than its specific preparation process. The aforementioned stirring and mixing steps are existing technical means that can be conventionally selected and implemented by those skilled in the art after learning the composition formulation of this invention, without creative effort, and should not be considered a factor limiting the implementation and protection of this invention.

[0123] The stabilizer composition of this invention can be used in different olefin polymerization methods, specifically including solution polymerization, gas-phase polymerization, slurry polymerization, high-pressure polymerization, etc.

[0124] Olefin polymerization can include ethylene polymerization, propylene polymerization, butene polymerization, pentene polymerization, hexene polymerization, octene polymerization, α-olefin polymerization, cycloolefin polymerization, ethylene-α-olefin copolymerization, propylene-α-olefin copolymerization, and other combined polymerizations.

[0125] α-Alkenes are monoalkenes with double bonds at the ends of the molecular chain, with the molecular formula R-CH=CH2, where R is an alkyl group. The carbon number range of α-alkenes is selected from C3 to C4. 40 Preferably C4~C 20 Preferably C4~C 10 Preferably, the compounds are C4, C5, C6, or C8, namely 1-butene, 1-pentene, 1-hexene, or 1-octene.

[0126] The polymerization reactors used in the polymerization process include one or more of the following: stirred tank reactor, gas phase reactor, fluidized bed reactor, loop reactor, loop slurry reactor, or slurry reactor.

[0127] The amount of stabilizer composition introduced is 0.01 ppm to 10,000 ppm of the mass of the slurry solvent or the mass of the polymerization product in the polymerization reactor, for example, 0.01, 0.1, 1, 5, 10, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000 ppm or any combination thereof, preferably 0.1 ppm to 1,000 ppm, more preferably 1 ppm to 500 ppm, and even more preferably 10 ppm to 200 ppm.

[0128] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0129] The metallocene catalyst in the examples is a metallocene polyethylene catalyst product with the trade name MEG 0001HA from PetroChina (Shanghai) New Materials Research Institute Co., Ltd.

[0130] Those skilled in the art may use other metallocene catalysts, or combinations of metallocene catalysts with other catalysts. Other catalysts may be selected from Ziegler-Natta catalysts, chromium-based catalysts, bimetallic catalysts, metallocene catalysts and combinations thereof.

[0131] Experimental Example 1: Washing and Purification Experiment

[0132] Example 1

[0133] Basic aluminum octadecanoate (commercially available, a fatty acid salt compound) was first washed (purified) twice with a water solvent, and then washed (purified) twice with a mixed solvent including ethanol and water in a ratio of 25:75. It was then dried in a vacuum drying oven at 60 °C for 24 h.

[0134] Comparative Example 1

[0135] It is basically the same as Example 1, except that it is not washed (purified) with water solvent and mixed solvent including ethanol and water, and is not dried.

[0136] Comparative Example 2

[0137] The procedure is basically the same as in Example 1, except that a mixed solvent including ethanol and water is not used for washing (purification), while the other steps are the same.

[0138] Comparative Example 3

[0139] It is basically the same as Example 1, except that water solvent is not used for washing (purification), and the other steps are the same.

[0140] The ICP elemental analysis results of Example 1 and Comparative Examples 1-3 are shown in Table 1.

[0141] Table 1. Results of ICP elemental analysis

[0142]

[0143] As shown in Table 1, the ICP elemental analysis results indicate that basic aluminum octadecanoate contains a significant amount of Na and S impurities when it is not washed (Comparative Example 1). Washing and purification with water solvent only (Comparative Example 2) can reduce the impurity content to some extent. Washing and purification with ethanol solvent only (Comparative Example 3) is not very effective in reducing the impurity content. However, a two-step washing and purification process (Example 1), which involves washing and purification with water solvent first, followed by washing and purification with a mixed ethanol / water solvent, can effectively reduce the impurity content by more than an order of magnitude.

[0144] Test Example 2: Dehydration and Drying Test

[0145] Example 2

[0146] This embodiment provides a method for preparing a stabilizer composition.

[0147] Liquid paraffin vacuum distillation: Liquid paraffin is added to a stirred reactor, vacuum is first applied to about 40 kPa, then the temperature is gradually increased to 80 °C, and vacuum distillation is carried out for 12 h before being cooled to room temperature.

[0148] Washing and purification: The basic aluminum octadecanoate (commercially available) was first washed (purified) twice with a water solvent, and then washed (purified) twice with a mixed solvent including ethanol and water, wherein the ratio of ethanol to water was 25:75. It was then dried in a vacuum drying oven at 60 °C for 24 h.

[0149] Surface treatment of fumed silica: (1) Place hydrophilic fumed silica in a vacuum oven, set the temperature to 180 °C, and dry for 4 h; (2) At 280 °C and under nitrogen flow, introduce vaporized dimethyl dichlorosilane into a fluidized bed and react for 4 h; (3) Maintain the temperature and nitrogen flow, purge for 2 hours to remove byproducts and residual reagents, and finally cool.

[0150] A mixture of 19% (by mass) of washed, alkaline aluminum octadecanoate (a fatty acid salt compound), 80% liquid paraffin (distilled under reduced pressure, CAS No. 8042-47-5, alkane oil solvent), and 1% fumed silica (native particle size D) surface-treated with dimethyl dichlorosilane was prepared.50 The stabilizer composition was obtained by mixing 255 nm modified fumed silica with nitrogen atmosphere and stirring until homogeneous.

[0151] Example 3

[0152] The process is basically the same as in Example 2, except that the alkaline aluminum octadecanoate after washing is dried at 60 °C for 24 h in a normal pressure forced-air heating oven, while the other steps are the same.

[0153] Example 4

[0154] The process is basically the same as in Example 2, except that no protective gas is used during the mixing and stirring of alkaline aluminum octadecanoate with liquid paraffin and dimethyl dichlorosilane; the mixture is directly exposed to air. The remaining steps are the same.

[0155] The moisture content of the stabilizer composition was tested using a volumetric Karl Fischer moisture analyzer. The moisture content results for Comparative Examples 4, 5 and Example 2 are shown in Table 2.

[0156] Table 2 Moisture Content Results

[0157]

[0158] As can be seen from the moisture content results in Table 2, compared with Examples 3 and 4, the drying method of Example 2, which uses vacuum drying and nitrogen as the protective gas, can significantly reduce the moisture content of the stabilizer composition. The moisture content of the final product is only 209 ppm.

[0159] Experimental Example 3: Sedimentation Separation Test

[0160] Comparative Example 4

[0161] This is essentially the same as Example 2, except that the fumed silica used was not surface-treated and the original particle size D... 50 The wavelength is 245 nm, and the remaining steps are the same.

[0162] Example 5

[0163] The example is basically the same as Example 2, except that the native particle size D of the fumed silica used is... 50 The wavelength is 1600 nm, and the remaining steps are the same.

[0164] The basic properties and sedimentation separation times of Examples 2-5 and Comparative Example 4 are shown in Table 3.

[0165] Table 3 Sedimentation Separation Results

[0166]

[0167] As shown in Table 3, the sedimentation separation results indicate that the water content, silica surface modification method, and original particle size D in the stabilizer composition are all factors that affect the sedimentation separation process. 50 All factors affect the dispersion stability, with moisture content having the greatest impact. As shown in Example 2, Example 3 had the highest moisture content, resulting in the fastest sedimentation. Example 4 followed suit. A longer sedimentation time indicates better dispersion stability. The sedimentation time of Example 2 was greater than 10 days, higher than Comparative Example 4 and Examples 3-5. The results indicate that vacuum drying, nitrogen as the protective gas, dimethyldichlorosilane as the surface modification method for silica, and the original particle size D of silica are all suitable for effective dispersion. 50 Using 255 nm can significantly improve the dispersion stability of the stabilizer composition.

[0168] Experimental Example 4: Small-scale homopolymerization test of ethylene slurry

[0169] Small-scale homopolymerization test of ethylene slurry polymerization: 350 g of n-hexane, 2 mM triethylaluminum, 100 mg of stabilizer composition, and 100 mg of metallocene catalyst MEG 0001HA were added to the slurry polymerization reactor. The stirring rate was 400 rpm, the pressure was 1 MPa, the temperature was 80 ℃, and the reaction time was 1 h. Ethylene was automatically fed using a gas mass flow meter. Triethylaluminum is a commonly used solvent for removing impurities from n-hexane and the reactor. Before adding to the reactor, the stabilizer composition and metallocene catalyst were dispersed in a glass vial containing 5 g of hexane and mixed uniformly for 1 h (premixing). The results of the small-scale slurry polymerization were evaluated by catalyst activity and agglomeration level. Catalyst activity was measured in gPE / gCat•h, defined as the mass of target product obtained per unit mass of catalyst per unit time. Agglomeration level was determined by the amount of fouling on the agitator and reactor walls, and was characterized by A, B, C, D, and E, where A represents little agglomeration and E represents severe agglomeration.

[0170] Example 6

[0171] The procedure is basically the same as in Example 2, except that the fatty acid salt compound used is aluminum oleate, and the other steps are the same.

[0172] Example 7

[0173] The procedure is basically the same as in Example 2, except that the fatty acid salt compound used is aluminum hexadecanoate, and the other steps are the same.

[0174] Example 8

[0175] The procedure is basically the same as in Example 2, except that the fatty acid salt compound used is calcium octadecanoate, while the other steps are the same.

[0176] Comparative Example 5

[0177] No stabilizer composition was added during the experiment.

[0178] The basic conditions and slurry homopolymerization results of Comparative Example 5, Example 2, and Examples 6-8 are shown in Table 4.

[0179] Table 4 Results of small-scale homopolymerization of ethylene slurry

[0180]

[0181] As shown in Table 4, the slurry copolymerization results indicate that without the addition of a stabilizer composition (i.e., without fatty acid salt compounds, Comparative Example 5), the activity of the metallocene catalyst is 512 gPE / gCat•h, and the agglomeration grade is D. This indicates that the polymerization in the reactor is unstable, resulting in the formation of a large amount of agglomerated fouling. The agglomerated fouling during unstable polymerization is as follows: Figure 1 As shown. After adding stabilizer compositions containing different fatty acid salts (Examples 2 and 6-8), the activity of the metallocene catalyst showed a decreasing trend, while the agglomeration level increased, indicating improved homopolymerization stability and reduced agglomeration fouling within the reactor. Among these, the addition of a stabilizer composition containing basic aluminum octadecanoate (Example 2) resulted in the smallest decrease in metallocene catalyst activity and achieved the optimal agglomeration level (A), indicating improved polymerization stability and a significant reduction in agglomeration fouling within the reactor. This demonstrates that the stabilizer compositions can effectively promote the homopolymerization stability of the metallocene catalyst in the slurry reactor. The agglomeration situation within the reactor under stable polymerization conditions is shown in the figure. Figure 2 As shown.

[0182] Experimental Example 5: Small-scale copolymerization test of ethylene-hexene slurry method

[0183] Small-scale copolymerization experiment of ethylene-hexene slurry polymerization: 350 g of n-hexane, 2 mM triethylaluminum, 40 mL of 1-hexene, 100 mg of stabilizer composition, and 100 mg of metallocene catalyst MEG 0001HA were added to the slurry polymerization reactor. The stirring rate was 400 rpm, the pressure was 1 MPa, the temperature was 80 ℃, and the reaction time was 1 h. Ethylene was automatically fed using a gas mass flow meter. Before adding it to the reactor, the stabilizer composition and metallocene catalyst were dispersed in a glass vial containing 5 g of hexane and mixed uniformly for 1 h (premixing). The results of the small-scale ethylene-hexene slurry polymerization were evaluated by catalyst activity and agglomeration level. The agglomeration level was determined by the amount of adhesion and fouling on the agitator and reactor wall, and was characterized by A, B, C, D, and E, where A represents little agglomeration and E represents severe agglomeration.

[0184] The basic conditions and the results of the small-scale copolymerization test of ethylene-hexene slurry method for Example 2 and Comparative Example 5 are shown in Table 5.

[0185] Table 5 Results of small-scale copolymerization of slurry

[0186]

[0187] As shown in Table 5, the results of the ethylene-hexene slurry copolymerization test indicate that without the addition of the stabilizer composition (Comparative Example 5), the activity of the metallocene catalyst was 710 gPE / gCat•h, and the agglomeration grade was C, indicating that the polymerization in the reactor was unstable and formed a lot of agglomerate fouling. After adding the stabilizer composition (Example 2), although the activity of the metallocene catalyst showed a decreasing trend, the agglomeration grade increased to A. This is because the metallocene catalyst has high reactivity in the early stage of the catalytic reaction, resulting in a more vigorous reaction, making the reaction system unstable and prone to agglomeration. Appropriately reducing the activity of the metallocene catalyst in the early stage of the catalytic reaction can improve the stability of the copolymerization reaction in the reactor and reduce agglomerate fouling. This result proves that the stabilizer composition can effectively promote the copolymerization stability of the metallocene catalyst in the slurry reactor.

[0188] Experimental Example 6: Gas-phase pilot-scale polymerization experiment

[0189] Gas-phase pilot-scale polymerization experiment: A 50 kg / h gas-phase full-density polyethylene pilot-scale unit was used to evaluate the metallocene catalyst and stabilizer composition. The fluidized bed reactor height was approximately 2.7-2.8 m, including a 2.1 m straight section and a 0.6-0.7 m enlarged section. The reaction pressure was 2.0 MPa, the reaction temperature was 85 ℃, the bed weight was 200-210 kg, the discharge mass per batch was 4 kg, the metallocene catalyst injection rate was 3.99 g / h, the ethylene injection rate was 50.98 kg / h, and the 1-hexene injection rate was 4.20 kg / h.

[0190] In Example 2, the stabilizer composition was injected at a rate of 150 ppm, resulting in an approximately 18% decrease in activity compared to before injection. During the reaction, the bed temperature and electrostatic level remained very stable, with electrostatic discharge maintained at ±0.015 kV without significant fluctuations, indicating that the stabilizer composition can promote the stable polymerization of the metallocene catalyst in the gas phase. Without the stabilizer composition (Comparative Example 5), only the metallocene catalyst MEG 0001HA was injected. After a period of operation, significant fluctuations in bed temperature and electrostatic level occurred, leading to a runaway temperature in the reactor (a rapid and uncontrollable rise in reaction temperature within a short period). The polymerization became unstable and eventually stopped. After stopping, the reactor was transferred to a gas-phase pilot reactor, where obvious agglomerates were observed forming on the reactor walls and probes. Figure 3 As shown.

[0191] Compared with Comparative Examples 1-5, Examples 1-8 effectively reduce the impurity salt content and water content in the stabilizer composition, exhibiting higher dispersion stability and compatibility with metallocene catalysts, and effectively preventing, reducing, or inhibiting the agglomeration and clumping of polyolefin particles during polymerization. Through the above-mentioned washing and purification tests, dehydration and drying tests, sedimentation and separation tests, small-scale homopolymerization tests of ethylene slurry, small-scale copolymerization tests of ethylene-hexene slurry, and pilot-scale gas-phase polymerization tests, it is evident that this invention provides a more suitable stabilizer composition formulation and raw material improvement method for metallocene catalysts.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A stabilizer composition, characterized in that, The stabilizer composition comprises, by weight percentage: 50%–99.9% alkane oil solvent, 0.01%–40% fatty acid salt compound, and 0.01%–20% modified fumed silica; the fatty acid salt compound and the modified fumed silica are added to the alkane oil solvent and stirred evenly under a nitrogen atmosphere to obtain the stabilizer composition; the fatty acid salt compound is pre-washed, and the washing process includes: (1) washing with water at least twice; (2) washing with a mixed solvent including alcohol and water at least twice; and vacuum drying. The modified fumed silica is fumed silica that has undergone surface treatment with organohalosilanes; The alkane oil solvent includes one or more of lubricating oil, mineral oil, and base oil; the mineral oil includes white oil and liquid paraffin. The fatty acid salt compound is selected from aluminum fatty acid or calcium fatty acid; The particle size of the modified fumed silica is 5–500 nm. The organohalosilanes include chlorosilanes, and the chlorosilanes include one or more of methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and diphenyldichlorosilane; The surface treatment process specifically includes: (1) The fumed silica was dehydrated by vacuum drying at 150 ℃~200 ℃ for 2~6 h to obtain dehydrated fumed silica; (2) The dehydrated fumed silica is reacted with the organosilane at 200 °C to 350 °C for 2 to 6 h; (3) Next, maintain the above reaction temperature and continuously purge with an inert gas stream for at least 2 hours to obtain the modified fumed silica.

2. The stabilizer composition according to claim 1, characterized in that, The modified fumed silica has a particle size of 100–400 nm.

3. The stabilizer composition according to claim 1, characterized in that, The alkane oil solvent is previously subjected to a reduced pressure distillation treatment at a pressure of 10 -10 Pa, less than 101325 Pa; And / or, the temperature of the vacuum distillation treatment is 20 ℃ to 400 ℃.

4. The stabilizer composition according to claim 3, characterized in that, The alkane oil solvent is pre-treated by vacuum distillation at a pressure greater than or equal to 10. -1 Pa, less than 101325 Pa; And / or, the temperature of the vacuum distillation treatment is 20 ℃ to 200 ℃.

5. The stabilizer composition according to claim 1, characterized in that, The alcohol includes one or more of methanol, ethanol, n-propanol, isopropanol, and allyl alcohol; And / or, in the mixed solvent comprising alcohol and water, the mass percentage of the alcohol to the total mass of the mixed solvent is X% to Y%, wherein the values ​​of X and Y are selected from any of the following five ranges: (1) X=0.01, Y=99.99; (2) X=0.1, Y=99.9; (3) X=1, Y=99; (4) X=10, Y=90; (5) X=15, Y=85.

6. A method for preparing the stabilizer composition according to any one of claims 1-5, characterized in that, include: The fatty acid salt compound and the modified fumed silica are added to the alkane oil solvent and stirred evenly under a nitrogen atmosphere to obtain the stabilizer composition.

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