Supported metallocene catalysts for ethylene polymerization and in situ grafting, and methods of making and using the same

Abstract

The present application relates to a kind of supported metallocene catalyst for ethylene polymerization and in situ grafting and its preparation method and application.Free radical initiator is added in the supporting process, and the supported metallocene catalyst particles are obtained by spray drying, the particle size is adjustable, the particle shape is good, the particle size distribution is narrower, it is easier to control, so as to prepare smaller polyethylene particles, and then it is beneficial to improve grafting reaction rate.Metallocene catalyst can make free radicals uniformly dispersed in polyethylene after initiating ethylene polymerization, and then initiate in-situ polar monomer grafting, the metallocene catalyst obtains narrow polymer molecular weight distribution, so that the performance of final product is more uniform.The catalyst and polymerization method can directly obtain grafted polyethylene by one-step method, and do not need drying and separation, simplify the preparation process of grafted polyethylene, the amount of initiator and polar monomer is less, grafting reaction is more uniform, grafting rate is higher, and side reaction is less.Powder has good particle morphology, and the bulk density is high.

Description

Technical Field

[0001] This invention relates to the field of polyolefin catalysts, specifically to a supported metallocene catalyst for olefin polymerization and in-situ grafting, its preparation method, and its application. Background Technology

[0002] Polyethylene is the most common general-purpose plastic, but its application is limited due to its complete lack of polarity. In order to expand its application range and improve its processing and performance deficiencies, it is usually necessary to carry out processing modification to introduce polar groups into its molecular chain.

[0003] Catalysts are the core technology of the polyolefin industry. Metallocene catalysts are the next generation of olefin polymerization catalysts after Zigeler-Natta catalysts. Compared with multi-active-site catalysts, this single-active-site catalyst has the advantages of high polymerization activity, hydrogen sensitivity, and uniform distribution of comonomers [Chem.Rev.,2000.100(4):1253]. After loading, it can not only maintain its catalytic characteristics, improve polymer morphology, and increase bulk density, but also adapt to existing slurry polymerization process equipment.

[0004] Currently, the commonly used methods for grafting polyethylene are mainly: 1. Melt grafting. This is the most commonly used and most studied chemical grafting method. Molten polyethylene reacts with grafting monomers in an extruder under the action of an initiator; 2. Solution grafting. This refers to dissolving polyethylene, polar monomers, and initiators in a reaction medium to carry out the grafting reaction; 3. Solid-phase grafting. This involves placing polyethylene powder directly with initiators, grafting monomers, surfactants, etc., for direct contact and reaction; 4. Radiation grafting. This method uses high-energy γ-rays or ultraviolet rays as radiation energy. Irradiated polyethylene generates free radicals, which are then polymerized with grafting monomers to obtain grafted free radical initiators (Plastics Technology, 2005(2): 42-46). All of the above methods involve secondary reactions of finished polyethylene to finally obtain grafted polyethylene.

[0005] The melt grafting method requires significant equipment investment and, due to the high preparation temperature, results in a high gel content. The solid-phase grafting method offers numerous advantages, including simple operation, short reaction time, low investment due to the lack of large equipment, and the elimination of the need for a reaction medium and solvent recovery, making it highly practical. However, this method also has drawbacks: the reaction is a heterogeneous system, a localized modification method, which easily leads to uneven grafting and low grafting rates, similar to the problems encountered with the radiation method. While the solution method is a homogeneous system and can yield uniform grafted products, the products require drying and separation, resulting in numerous operations and an unfriendly environment. Summary of the Invention

[0006] Based on this, the present invention provides a metallocene catalyst for ethylene polymerization and in-situ grafting, and a method for preparing the same. The catalyst incorporates a free radical initiator during preparation, resulting in a relatively simple process. First, the supported metallocene catalyst catalyzes ethylene polymerization, while the free radical initiator is uniformly dispersed in polyethylene powder. Then, the free radical initiator initiates the grafting of polar monomers onto the polyethylene, leading to a more uniform grafting reaction, lower free radical initiator dosage, higher grafting efficiency, and a narrower molecular weight distribution of the polymer obtained from the metallocene catalyst, resulting in more uniform final product performance. Furthermore, the use of spray drying ensures the catalyst has a good particle shape and allows for adjustment of particle size according to application requirements, improving grafting efficiency. Using this catalyst, grafted polyethylene can be obtained directly in one step, producing polymer particles with good morphology and high bulk density, eliminating the need for drying and separation, thus simplifying the grafted polyethylene preparation process.

[0007] A first aspect of the present invention is to provide a supported metallocene catalyst, comprising a support, and a blend of a metallocene catalyst, an activator and a radical initiator supported on the support and / or a reaction product, wherein the activator is an organoaluminum compound.

[0008] According to an embodiment of the present invention, the metallocene catalyst has the structural formula Cp A Cp B MX n ;

[0009] Among them, Cp A and Cp B It is independently selected from one of substituted or unsubstituted cyclopentadiene, substituted or unsubstituted indenyl, or substituted or unsubstituted fluorenyl;

[0010] M is selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni, and is preferably selected from at least one of Ti, Zr, and Hf;

[0011] X is at least one of halogen, substituted or unsubstituted hydrocarbon group, preferably selected from chlorine, substituted or unsubstituted hydrocarbon group having 1-10 carbon atoms; n = 1 or 2.

[0012] The metallocene catalyst of this invention can be obtained by commercially available methods or methods described in the prior art.

[0013] According to an embodiment of the present invention, the free radical initiator is selected from at least one of azo and peroxide initiators, preferably from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl peroxide, diisobutyl percarbonate, azobisisobutyronitrile, and azobisisoheptanenitrile.

[0014] According to an embodiment of the present invention, the organoaluminum compound is AlR n X (3-n) or contains A compound with the structure R, wherein R is an alkyl group having 1-10 carbon atoms, X is a halogen, and n is an integer from 1 to 3; preferably,

[0015] The organoaluminum compound is selected from at least one of trimethylaluminum, triethylaluminum, methylaluminoxane, diethylaluminum chloride, diethylaluminum chloride, tri-n-butylaluminum, triisobutylaluminum, sesquimethylaluminum chloride, and sesquiethylaluminum chloride.

[0016] According to embodiments of the present invention, the carrier is selected from inorganic oxides, preferably from silicon oxides and / or aluminum oxides, more preferably from silicon dioxide; and / or,

[0017] The particle size of the carrier is 0.01-5μm, preferably 0.01-2μm.

[0018] According to a preferred embodiment of the present invention, based on a total weight of 100 wt% of the supported metallocene catalyst, the mass content of metallocene M in the supported metallocene catalyst is 0.1-5 wt%, for example, it can be any value or a range between any two values ​​from 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, preferably 0.3-2.5 wt%; and / or, the content of the free radical initiator is 10-60 wt%, for example, it can be any value or a range between any two values ​​from 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, preferably 20-40 wt%; and / or,

[0019] The molar ratio of aluminum to metallocene M in the organoaluminum compound is (5-1000):1, for example, it can be any ratio or a range between any two ratios of 5:1, 10:1, 50:1, 100:1, 300:1, 500:1, 800:1, 1000:1, preferably (20-300):1.

[0020] According to a preferred embodiment of the present invention, the average particle size of the supported metallocene catalyst is 7-100 μm. The inventors have discovered that, based on the catalyst formulation of the present invention (i.e., support, metallocene catalyst, activator, and free radical initiator, wherein the activator is an organoaluminum compound), the grafting rate of grafted polyethylene can be adjusted by further regulating the average particle size of the supported metallocene catalyst. Within the preferred average particle size range of the present invention, grafted polyethylene with a high grafting rate can be obtained while maintaining a certain polymerization activity. More preferably, the average particle size of the supported metallocene catalyst is 8-30 μm, which can further improve the grafting rate. Even more preferably, the average particle size of the supported metallocene catalyst is 8-20 μm; most preferably, the average particle size of the supported metallocene catalyst is 8-16 μm. Under further lower average particle size conditions, grafted polyethylene exhibits an even higher grafting rate.

[0021] According to the present invention, in order to further improve the uniformity of the particle size of the obtained grafted polyethylene and make the particle size distribution narrower, the particle size distribution of the supported metallocene catalyst is less than 2, preferably less than 1.5.

[0022] In this invention, particle size refers to the average particle size, which is the equivalent diameter of the largest particle when the cumulative distribution in the particle size distribution curve is 50%, i.e., (d). 50 Particle size distribution refers to the radial distance, i.e., (d). 90 -d 10 ) / d 50 ), which describes the breadth of particle distribution.

[0023] A second aspect of the present invention is to provide a method for preparing the supported metallocene catalyst described in the first aspect, comprising the following steps:

[0024] (1) The components including the metallocene catalyst, activator, support, and free radical initiator are dispersed in an organic solvent to form a slurry;

[0025] (2) After spray drying the slurry obtained in step (1), the supported metallocene catalyst is obtained; preferably,

[0026] The preparation of the slurry in step (1) includes: dissolving the free radical initiator, metallocene catalyst, and activator in an organic solvent and then adding the carrier; more preferably, dissolving the free radical initiator, metallocene catalyst, and activator in an organic solvent first, and then adding the carrier at 20-45°C and mixing for 2-12 hours; more preferably, the dissolution conditions are constant temperature at 20-40°C for 0.5-3 hours.

[0027] The spray drying conditions in step (2) are: inlet temperature 50-200℃, outlet temperature 30-150℃; and / or,

[0028] According to the present invention, the particle size of the obtained catalyst can be adjusted by the air inlet flow rate of the spray drying nozzle. In a preferred embodiment of the present invention, the air inlet flow rate of the spray drying nozzle in step (2) is 10-50 m³ / h. 3 / h; more preferably 21-50m 3 / h, and even more preferably 26-50m 3 / h.

[0029] According to embodiments of the present invention, the organic solvent is selected from at least one of alkanes, haloalkanes, aromatics, heterocyclic compounds, ethers, ketones, and esters, preferably from at least one of pentane, hexane, heptane, dichloromethane, trichloromethane, benzene, toluene, chlorobenzene, chlorotoluene, tetrahydrofuran, acetone, diethyl ether, and ethyl acetate; and / or,

[0030] In a preferred embodiment of the present invention, the amount of organic solvent used is 5-100 mL, preferably 10-50 mL, relative to 1 g of carrier.

[0031] According to a preferred embodiment of the present invention, based on parts by mass, the amount of metallocene catalyst is 0.01-1 part, the amount of activator is 0.1-30 parts, and the amount of free radical initiator is 0.02-10 parts relative to 1 part of the support; more preferably, the amount of metallocene catalyst is 0.05-0.5 parts, the amount of activator is 0.3-10 parts, and the amount of free radical initiator is 0.1-3 parts relative to 1 part of the support.

[0032] A third aspect of the present invention is to provide the application of the supported metallocene catalyst described in the first aspect or the supported metallocene catalyst prepared by the preparation method described in the second aspect in olefin polymerization.

[0033] According to a preferred embodiment of the present invention, the application of the supported metallocene catalyst in olefin polymerization includes the application of the supported metallocene catalyst in olefin polymerization for ethylene polymerization and in-situ grafting (i.e., the method of ethylene polymerization and in-situ grafting):

[0034] 1) Ethylene is contacted with the supported metallocene catalyst to carry out ethylene polymerization reaction, thereby obtaining polyethylene powder containing a free radical initiator;

[0035] 2) The polar monomer is contacted with the polyethylene powder containing the free radical initiator obtained in 1), so that the free radical initiator initiates in-situ grafting of the polar monomer onto the polyethylene; more preferably,

[0036] The polar monomer is a compound containing a double bond and a polar group, preferably at least one of acrylic acid and its derivatives or esters, maleic anhydride or esters, maleate salts, alkenyl bisphenol A ether, acrylonitrile, styrene and its homologues, and glycidyl methacrylate.

[0037] The methods for ethylene polymerization and in-situ grafting in this invention include, but are not limited to, ethylene slurry polymerization and grafting reaction.

[0038] For example, during ethylene slurry polymerization and grafting reactions, the conditions for the ethylene polymerization reaction include:

[0039] The temperature is 50-10℃, the reaction time is 0.5-3h, the pressure is 0.1-5MPa, and the amount of supported metallocene catalyst is 20-500mg; preferably, the reaction is carried out in the presence of alkylaluminum or methylaluminoxane.

[0040] Alkyl aluminum can be selected from at least one of sesquiethylaluminum chloride, triethylaluminum, tri-n-hexylaluminum, triisobutylaluminum, and tri-n-octylaluminum, and / or, relative to the metal content of 1 mol of the supported metallocene catalyst, the amount of alkyl aluminum or methylaluminoxane is 5-1000 mol. The role of alkyl aluminum or methylaluminoxane is to (1) act as a purifying agent to remove water and oxygen during the reaction process to avoid interference with the polymerization reaction; and (2) activate the catalyst to carry out the polymerization reaction.

[0041] The conditions for the ethylene polymerization reaction are such that the content of the free radical initiator in the resulting polyethylene powder containing the free radical initiator is 0.1-10 wt%.

[0042] As an example, in ethylene slurry polymerization and grafting reactions, the conditions for in-situ grafting reactions include:

[0043] The temperature is 80-150℃, the reaction time is 2-8h, the pressure is 1-5MPa, and the mass ratio of polyethylene powder containing free radical initiator to polar monomer is 100-3:1.

[0044] This invention provides a catalyst for ethylene polymerization and in-situ grafting of metallocene and its preparation method. The catalyst preparation process introduces a free radical initiator. First, the metallocene catalyst catalyzes ethylene polymerization. After the reaction, the free radical initiator is uniformly dispersed in polyethylene powder. Then, the free radical initiator initiates in-situ grafting of polar monomers onto the polyethylene. This results in a more uniform grafting reaction, a higher grafting rate, and a lower gel content. Furthermore, the wide variety of metallocenes allows for adjustment of catalytic properties based on the ligand and metal type, leading to easier polar grafting of polyethylene, reducing side reactions, and high adjustability. The metallocene catalyst produces a polymer with a narrow molecular weight distribution, resulting in more uniform final product performance. On the other hand, the catalyst is prepared using a spray drying method, resulting in a catalyst with good particle shape and narrow particle size distribution. The catalyst particle size can be adjusted according to application requirements, reducing the polyethylene powder particle size and thus improving the further grafting rate. Using this catalyst, grafted polyethylene with good flowability can be obtained directly in a one-step process, eliminating the need for drying and separation, thus simplifying the grafted polyethylene preparation process.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] (1) The metallocene catalyst for ethylene polymerization and in-situ grafting provided by the present invention adds a free radical initiator during the loading process. After initiating ethylene polymerization, the free radicals can be uniformly dispersed in the polyethylene, thereby initiating in-situ grafting of polar monomers, and polar grafted polyethylene can be obtained directly in one step.

[0047] (2) The metallocene catalyst for ethylene polymerization and in-situ grafting supported by the present invention has a smaller amount of initiator used in the preparation of grafted polyethylene, resulting in a more uniform grafting reaction, a higher grafting rate, and a lower gel content. Furthermore, the metallocene catalyst produces a polymer with a narrow molecular weight distribution, which makes the final product more uniform in performance.

[0048] (3) The supported metallocene catalyst provided by the present invention has good particle morphology and high bulk density when used for olefin polymerization to obtain resin powder. The product does not need to be dried and separated and can be used in slurry polymerization process.

[0049] (4) The preparation method of the catalyst for ethylene polymerization and in-situ grafted supported metallocene provided by the present invention is simple, the catalyst particles have good morphology, the particle size is adjustable in a large range, the particle size distribution is narrow, and the catalyst particle size can be adjusted according to the application requirements, so as to reduce the particle size of polyethylene powder and thus improve the grafting rate. Detailed Implementation

[0050] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0051] The testing instruments and conditions used in this embodiment are as follows:

[0052] Grafting rate (DG) determination: Take 0.5 g of grafted sample, heat under reflux, dissolve in 70 mL xylene, add 15 mL of KOH-methanol standard solution while hot, continue reflux for 2 h, add 2 drops of phenolphthalein reagent, and titrate with standard HCl-isopropanol solution. Titrate the blank sample simultaneously, and calculate the grafting rate. The result is calculated based on the mass of maleic anhydride contained in 100 g of sample.

[0053] Determination of gel content (DC): A small amount of grafted sample was placed in a filter cloth bag and put into a Soxhlet extractor. The sample was refluxed with xylene for more than 12 hours. Then the filter cloth bag was removed and dried in an oven at 80°C until the mass was constant. DC was calculated as the mass (g) of gel in 100g of sample, as shown in formula (1).

[0054] DC = (m3-m2) / (m1-m2) (1)

[0055] Where: m1 is the mass of the filter cloth bag after the sample is loaded, g; m2 is the mass of the filter cloth bag, g; m3 is the total mass after extraction and drying, g;

[0056] Particle size and particle size distribution: The particle size and particle size distribution of the catalyst were tested using a Malvern MS3000 laser particle size analyzer.

[0057] Metal content: The metal content in the catalyst was determined using inductively coupled plasma mass spectrometry (ICP-MS) (Agilent 7500CX).

[0058] Initiator content determination in catalyst: Liquid NMR (Bruker AVANCE 300) was used, with hydroquinone as an internal standard for determination.

[0059] The molecular weight distribution was determined by high-temperature gel permeation chromatography (Polymer Char GPC-IR) using trichlorobenzene as the solvent.

[0060] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0061] Example 1

[0062] 1. Preparation of the supported catalyst: Under nitrogen protection, 6.0 g of dicumyl peroxide, 0.40 g of bis(n-butylcyclopentadienyl)zirconia dichloride, and 40 mL of 10% MAO (methylaluminoxane) toluene solution were dissolved in 100 mL of toluene solution at room temperature. After dissolution, 6 g of silica (particle size 0.01-2 μm) was added, and the mixture was stirred for 2 h. Subsequently, it was spray-dried using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature: 110℃, inlet nitrogen flow rate controlled at 31.0 m³ / s. 3 / h, 11.2g of catalyst was obtained. Some of its physical properties are shown in Table 1.

[0063] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane was added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Simultaneously, 1mL of triethylaluminum (1M) and 100mg of dry powder catalyst were added, and ethylene was added to a pressure of 1.03MPa. The temperature was raised to 50℃, and the reaction was maintained at 50℃ and constant pressure for 1 hour. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. Then, 6.0g of methyl methacrylate was added, the temperature was raised to 130℃, and the reaction was carried out for 5 hours before cooling and discharging. The evaluation results are shown in Table 2.

[0064] Example 2

[0065] 1. Preparation of the supported catalyst: Under nitrogen protection, 3.0 g of dicumyl peroxide, 0.36 g of bis(n-ethylcyclopentadienyl)zirconia dichloride, and 40 mL of 10% MAO toluene solution were dissolved in 100 mL of toluene solution at room temperature. After dissolution, 3.0 g of silica (particle size 0.01-2 μm) was added, and the mixture was stirred for 2 h. Subsequently, it was spray-dried using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature: 110℃, inlet nitrogen flow rate controlled at 25.0 m³ / s. 3 / h, yielding 6.2g of catalyst. Some of its physical properties are shown in Table 1.

[0066] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane was added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Simultaneously, 1mL of triethylaluminum (1M) and 100mg of dry powder catalyst were added, and ethylene was added to a pressure of 1.03MPa. The temperature was raised to 50℃, and the reaction was maintained at 50℃ and constant pressure for 45min. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. Then, 8.0g of acrylic acid was added, the temperature was raised to 130℃, and the reaction was carried out for 5h before cooling and discharging. The evaluation results are shown in Table 2.

[0067] Example 3

[0068] 1. Preparation of the supported catalyst: Under nitrogen protection, 6.0 g of tert-butyl hydroperoxide, 0.80 g of bis(n-butylcyclopentadienyl)zirconia dichloride, and 60 mL of 10% MAO (methylaluminoxane) toluene solution were dissolved in 100 mL of toluene solution at room temperature. After dissolution, 6.0 g of silica (particle size 0.01-2 μm) was added, and the mixture was stirred for 2 h. Subsequently, it was spray-dried using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature: 110℃, inlet nitrogen flow rate controlled at 25.0 m³ / s. 3 / h, yielding 12.7g of catalyst.

[0069] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane was added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Simultaneously, 1mL of triethylaluminum (1M) and 100mg of dry powder catalyst were added, and ethylene was added to a pressure of 1.03MPa. The temperature was raised to 50℃, and the reaction was carried out at a constant temperature and pressure of 50℃ for 40min. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. Then, 6.0g of methyl acrylate was added, the temperature was raised to 130℃, and the reaction was carried out for 5h before cooling and discharging. The evaluation results are shown in Table 2.

[0070] Example 4

[0071] 1. Preparation of the supported catalyst: Under nitrogen protection, 6.0 g of tert-butyl hydroperoxide, 0.36 g of bis(n-ethylcyclopentadienyl)zirconia dichloride, and 40 mL of 10% MAO toluene solution were dissolved in 100 mL of toluene solution at room temperature. After dissolution, 6.0 g of silica (particle size 0.01-2 μm) was added, and the reaction was stirred for 2 h. Subsequently, spray drying was performed using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature: 110℃, inlet nitrogen flow rate controlled at 31.0 m³ / s. 3 / h, yielding 12.5g of catalyst.

[0072] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane was added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Simultaneously, 1mL of triethylaluminum (1M) and 100mg of dry powder catalyst were added, and ethylene was added to a pressure of 1.03MPa. The temperature was raised to 50℃, and the reaction was maintained at 50℃ and constant pressure for 1 hour. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. Then, 8.0g of methyl acrylate was added, the temperature was raised to 130℃, and the reaction was carried out for 5 hours before cooling and discharging. The evaluation results are shown in Table 2.

[0073] Example 5

[0074] The catalyst was prepared according to the method of Example 1, except that the inlet nitrogen flow rate was controlled at 20.0 m³ / s during spray drying. 3 / h, 8.5g of catalyst was obtained, and some of its physical properties are shown in Table 1.

[0075] Ethylene slurry polymerization and grafting reaction were carried out according to the method of Example 1 to obtain product samples. The evaluation results are shown in Table 2.

[0076] Comparative Example 1

[0077] In a stainless steel jacketed heating and stirring reactor, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of dicumyl peroxide and an appropriate amount of interface wetting agent were added. The reaction temperature was set to 120℃. After reacting for 3 hours, the product was discharged. Then, it was washed with xylene and anhydrous ethanol, filtered and dried to obtain the product sample. Its physical properties are shown in Table 2.

[0078] Comparative Example 2

[0079] In a stainless steel jacketed heating and stirring reactor, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of tert-butyl hydrogen peroxide and an appropriate amount of interface wetting agent were added. The reaction temperature was set to 120℃. After reacting for 3 hours, the product was discharged. Then, it was washed with xylene and anhydrous ethanol, filtered, and dried to obtain the product sample. Its physical properties are shown in Table 2.

[0080] Comparative Example 3

[0081] The catalyst was prepared according to the method in Example 1, except that benzoyl peroxide was not added during the preparation process, resulting in 12.6 g of supported metallocene catalyst. Some of its physical properties are shown in Table 1.

[0082] Ethylene slurry polymerization and grafting reaction were carried out according to the method of Example 1, except that the polymerization reaction time was 45 min, and 6 g of dicumyl peroxide was added at the same time as methyl methacrylate during the grafting reaction to obtain product samples. The evaluation results are shown in Table 2.

[0083] Table 1. Physical parameters of supported metallocene catalysts

[0084]

[0085] Table 2. Some physical properties of grafted polyethylene

[0086]

[0087]

[0088] As can be seen from the data in Table 1, the metal loading and free radical content of the supported metallocene catalysts for ethylene polymerization and in-situ grafting obtained in Examples 1-4 of the present invention can be adjusted according to the formulation, and the particle size can be controlled by the slurry formulation and process conditions, which can yield smaller polyethylene particles, which is more conducive to improving the grafting reaction rate and has a narrower particle size distribution.

[0089] Example 5 shows that by changing the spray drying conditions, the catalyst size is increased (Table 1). The polymer particle size obtained by this catalyst is also increased. Compared with Example 1, it can be seen that Example 5 reduces the grafting efficiency, which shows the controllability of the catalyst particle size.

[0090] As can be seen from the data in Table 2, the initiator content in Examples 1-4 is much lower than that in the comparative example, resulting in a lower gel content in the product. Furthermore, the polyethylene prepared by the metallocene catalyst has a narrow molecular weight distribution and more uniform product performance. Under conditions of less initiator and polar monomer dosage, a one-step method can be used to directly obtain polar grafted polyethylene with higher grafting rate and lower gel rate. The obtained polymer does not require drying and separation, the preparation process is short, and due to the advantages of the catalyst and polymer preparation method, the polymer bulk density is higher.

[0091] The other conditions of Comparative Example 3 were the same as those of Comparative Example 1, but the initiator was not in the catalyst but added during the grafting reaction. This meant that the initiator could not be uniformly introduced into the polymer during the first polymerization reaction, resulting in low grafting efficiency (Table 2). This shows that adding the initiator to the catalyst and dispersing it uniformly in the polymer through the polymerization reaction achieved unexpected technical effects.

[0092] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0093] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0094] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0095] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0096] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0097] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A supported metallocene catalyst, comprising a support, and a blend of a metallocene catalyst, an activator, and a free radical initiator supported on the support, and / or a reaction product, wherein the activator is an organoaluminum compound; and the support is selected from inorganic oxides; Based on a total weight of 100 wt% for the supported metallocene catalyst, the content of the free radical initiator is 10-60 wt%. The free radical initiator is used to initiate in-situ grafting of polar monomers onto polyethylene.

2. The supported metallocene catalyst according to claim 1, characterized in that, The metallocene catalyst has the structural formula Cp A Cp B MX n ; Among them, Cp A and Cp B It is independently selected from one of substituted or unsubstituted cyclopentadiene, substituted or unsubstituted indenyl, or substituted or unsubstituted fluorenyl; M is selected from at least one of Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni; X is at least one of halogen, substituted or unsubstituted hydrocarbon group; n = 1 or 2.

3. The supported metallocene catalyst according to claim 2, characterized in that, M is selected from at least one of Ti, Zr, and Hf.

4. The supported metallocene catalyst according to claim 2, characterized in that, X is selected from at least one of chlorine and substituted or unsubstituted hydrocarbon groups having 1-10 carbon atoms.

5. The supported metallocene catalyst according to claim 1, characterized in that, The free radical initiator is selected from at least one of azo and peroxide initiators.

6. The supported metallocene catalyst according to claim 1, characterized in that, The free radical initiator is selected from at least one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl peroxide, diisobutyl percarbonate, azobisisobutyronitrile, and azobisisoheptanenitrile.

7. The supported metallocene catalyst according to claim 1, characterized in that, The organoaluminum compound is AlR n X (3-n) or contains Compounds with the structure R, where R is an alkyl group having 1-10 carbon atoms, X is a halogen, and n is an integer from 1 to 3.

8. The supported metallocene catalyst according to claim 1, characterized in that, The organoaluminum compound is selected from at least one of trimethylaluminum, triethylaluminum, methylaluminoxane, diethylaluminum chloride, diethylaluminum chloride, tri-n-butylaluminum, triisobutylaluminum, sesquimethylaluminum chloride, and sesquiethylaluminum chloride.

9. The supported metallocene catalyst according to claim 1, characterized in that, The particle size of the carrier is 0.01-5µm.

10. The supported metallocene catalyst according to claim 1, characterized in that, The carrier is selected from silicon oxide and / or aluminum oxide; and / or, The particle size of the carrier is 0.01-2µm.

11. The supported metallocene catalyst according to any one of claims 1-10, characterized in that, Based on a total weight of 100 wt% for the supported metallocene catalyst, the mass content of metallocene M in the supported metallocene catalyst is 0.1-5 wt%; and / or, The molar ratio of aluminum to metallocene M in the organoaluminum compound is (5-1000):1; and / or, The supported metallocene catalyst has an average particle size of 7-100 µm; and / or, The particle size distribution of the supported metallocene catalyst is less than 2.

12. The supported metallocene catalyst according to any one of claims 1-10, characterized in that, Based on a total weight of 100 wt% for the supported metallocene catalyst, the supported metallocene catalyst contains 0.3-2.5 wt% metallocene M; and / or 20-40 wt% free radical initiator; and / or The molar ratio of aluminum to metallocene M in the organoaluminum compound is (20-300):1; and / or, The supported metallocene catalyst has an average particle size of 8-30 µm; and / or, The supported metallocene catalyst has a particle size distribution of less than 1.

5.

13. A method for preparing a supported metallocene catalyst according to any one of claims 1-12, comprising the following steps: (1) Disperse the components including the metallocene catalyst, activator, support, and free radical initiator in an organic solvent to form a slurry; (2) After spray drying the slurry obtained in step (1), the supported metallocene catalyst is obtained.

14. The preparation method according to claim 13, characterized in that, The preparation of the slurry in step (1) includes: dissolving the free radical initiator, metallocene catalyst, and activator in an organic solvent and then adding the carrier.

15. The preparation method according to claim 13, characterized in that, The preparation of the slurry in step (1) includes: First, dissolve the free radical initiator, metallocene catalyst, and activator in an organic solvent, then add the support at 20-45℃ and mix for 2-12 hours.

16. The preparation method according to claim 13, characterized in that, The spray drying conditions in step (2) are: inlet temperature 50-200℃, outlet temperature 30-150℃; and / or, In step (2), the air inlet flow rate of the spray drying nozzle is 10-50 m³ / h. 3 / h.

17. The preparation method according to claim 13, characterized in that, The organic solvent is selected from at least one of alkanes, haloalkanes, aromatics, heterocyclic compounds, ethers, ketones, and esters; and / or, The amount of organic solvent used is 5-100 mL relative to 1 g of carrier.

18. The preparation method according to claim 13, characterized in that, The organic solvent is selected from at least one of pentane, hexane, heptane, dichloromethane, chloroform, benzene, toluene, chlorobenzene, chlorotoluene, tetrahydrofuran, acetone, diethyl ether, and ethyl acetate; and / or, The amount of organic solvent used is 10-50 mL relative to 1 g of carrier.

19. The preparation method according to any one of claims 13-18, characterized in that, By mass, relative to 1 part of the support, the amount of metallocene catalyst is 0.01-1 part, the amount of activator is 0.1-30 parts, and the amount of free radical initiator is 0.02-10 parts.

20. The preparation method according to any one of claims 13-18, characterized in that, By mass, relative to 1 part of the support, the amount of metallocene catalyst is 0.05-0.5 parts, the amount of activator is 0.3-10 parts, and the amount of free radical initiator is 0.1-3 parts.

21. The use of a supported metallocene catalyst according to any one of claims 1-12 or a supported metallocene catalyst prepared by the preparation method according to any one of claims 13-20 in olefin polymerization.

22. The application according to claim 21, characterized in that, The applications of the supported metallocene catalysts in olefin polymerization include: 1) Ethylene is contacted with the supported metallocene catalyst to carry out ethylene polymerization reaction, thereby obtaining polyethylene powder containing a free radical initiator; 2) Contact the polar monomer with the polyethylene powder containing the free radical initiator obtained in 1), so that the free radical initiator initiates the in-situ grafting of the polar monomer onto the polyethylene.

23. The application according to claim 22, characterized in that, The polar monomer is a compound containing a double bond and a polar group.

24. The application according to claim 22, characterized in that, The polar monomer is at least one of acrylic acid and its derivatives or esters, maleic anhydride or esters, maleate, alkenyl bisphenol A ether, acrylonitrile, styrene and its homologues, and glycidyl methacrylate.

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