Supported metallocene catalyst for ethylene polymerization and in-situ grafting as well as preparation method and application of supported metallocene catalyst

Abstract

The invention relates to a supported metallocene catalyst for ethylene polymerization and in-situ grafting as well as a preparation method and application of the supported metallocene catalyst. The free radical initiator is added in the loading process, the loaded metallocene catalyst particles are obtained through spray drying forming, the particle size is adjustable, the particle shape is good, the particle size distribution is narrow, regulation and control are easier, polyethylene particles with the smaller particle size are prepared, and then the grafting reaction rate is increased. After ethylene polymerization is initiated by the metallocene catalyst, free radicals can be uniformly dispersed in polyethylene, then in-situ polar monomer grafting is initiated, the molecular weight distribution of a polymer obtained by the metallocene catalyst is narrow, and the performance of a final product is more uniform. According to the catalyst and the polymerization method, the grafted polyethylene can be directly obtained by adopting a one-step method, drying separation is not needed, the preparation process of the grafted polyethylene is simplified, the dosage of the initiator and the polar monomer is small, the grafting reaction is more uniform, the grafting rate is higher, and the side reaction is less. The powder has good particle morphology and high bulk density.

Description

Technical Field

[0001] The invention relates to the field of polyolefin catalysts, and in particular to a supported metallocene catalyst for olefin polymerization and in-situ grafting, and a preparation method and application thereof. Background Art

[0002] Polyethylene is the most common general-purpose plastic, but due to its complete lack of polarity, its application is subject to certain restrictions. In order to expand its scope of application 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 a new generation of olefin polymerization catalysts after Zigeler-Natta catalysts. Compared with multi-active center catalysts, this single-active center catalyst has the advantages of high polymerization activity, hydrogen sensitivity, and uniform distribution of comonomers [Chem. Rev., 2000.100(4):1253]. After being loaded, it can not only maintain its catalytic properties, improve polymer morphology, and increase bulk density, but also adapt to existing slurry polymerization process equipment.

[0004] The commonly used polyethylene grafting methods are: 1. Melt grafting. This is the most commonly used and most researched chemical grafting method. The polyethylene in a molten state is grafted with the grafting monomer 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 for grafting reaction; 3. Solid phase grafting. This is to place polyethylene powder directly with initiators, grafting monomers, surfactants, etc. for contact reaction; 4. Radiation grafting. This method uses high-energy gamma rays or ultraviolet rays as radiation energy. The irradiated polyethylene produces free radicals, which are then polymerized with the grafting monomer to obtain a grafted free radical initiator (Plastics Science and Technology, 2005 (2): 42-46). The above methods all involve secondary reactions of the finished polyethylene to obtain grafted polyethylene.

[0005] Among them, the melting method requires large equipment investment, and the gel content is high due to the high preparation temperature; the solid phase grafting method has many advantages such as simple operation, short reaction time, no need for large equipment and therefore low investment, no need for reaction medium and therefore no need for solvent recovery and other operation steps, and has high practical value. However, this method also has disadvantages: the reaction is a heterogeneous system and a local modification method, so it is prone to problems such as uneven grafting and low grafting rate. The radiation method also has such problems; and although the solution method is a homogeneous system and can obtain uniform grafted products, the products need to be dried and separated, which requires many operations and is not environmentally friendly. Summary of the invention

[0006] Based on this, the present invention provides a metallocene catalyst for ethylene polymerization and in-situ grafting and a preparation method thereof. A free radical initiator is introduced into the catalyst during the preparation process, and the preparation process is relatively simple. First, the supported metallocene catalyst is responsible for catalyzing ethylene polymerization, and at this time, the free radical initiator is evenly dispersed in polyethylene powder, and then the free radical initiator initiates the polar monomer to be grafted on the polyethylene, the grafting reaction is more uniform, the amount of free radical initiator used is small, the grafting rate efficiency is higher, and the metallocene catalyst obtains a polymer with a narrow molecular weight distribution, so that the performance of the final product is more uniform; on the other hand, the catalyst is prepared by a spray drying method, and not only has a good particle shape, but also the catalyst particle size can be adjusted according to the use requirements, thereby improving the grafting efficiency. The catalyst can be used to directly obtain grafted polyethylene by a one-step method, and the obtained polymer particles have a good morphology and a high bulk density, and do not need to be dried and separated, thereby simplifying the preparation process of the grafted polyethylene.

[0007] The first aspect of the present invention is to provide a supported metallocene catalyst, including a carrier, and a blended component and / or reaction product containing a metallocene catalyst, an activator and a free radical initiator supported on the carrier, wherein the activator is an organic aluminum compound.

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

[0009] Among them, Cp A and Cp B Independently selected from substituted or unsubstituted cyclopentadiene, substituted or unsubstituted indenyl, 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, 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 at least one of chlorine, substituted or unsubstituted hydrocarbon group having 1 to 10 carbon atoms; n=1 or 2.

[0012] The metallocene catalyst in the present invention can be obtained by commercially available catalysts 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 selected from at least one of benzoyl peroxide, diisopropylbenzene peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, diisobutyl peroxydicarbonate, azobisisobutyronitrile and azobisisoheptylonitrile.

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

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

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

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

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

[0019] The molar ratio of aluminum in the organic aluminum compound to the metallocene M is (5-1000):1, for example, it can be any ratio of 5:1, 10:1, 50:1, 100:1, 300:1, 500:1, 800:1, 1000:1 or a range between any two ratios, 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 inventor of the present invention has found through research that on the basis of the catalyst formula of the present invention (i.e., carrier, metallocene catalyst, activator and free radical initiator, the activator is an organic aluminum compound), by further adjusting the average particle size of the supported metallocene catalyst, the grafting rate of the grafted polyethylene can be adjusted. Within the preferred average particle size range of the present invention, a grafted polyethylene with a high grafting rate can be obtained under the condition of 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. Further 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, and under the condition of a further lower average particle size, the grafted polyethylene has a further 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 the present invention, the particle size refers to the average particle size, that is, the equivalent diameter of the largest particle when the cumulative distribution is 50% in the particle size distribution curve (d 50 ). Particle size distribution refers to the diameter distance, that is, (d 90 -d 10 ) / d 50 ), which describes how broad the particle distribution is.

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

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

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

[0026] The preparation of the slurry in step (1) comprises: dissolving the free radical initiator, the metallocene catalyst and the activator in an organic solvent and then adding the carrier. More preferably, the free radical initiator, the metallocene catalyst and the activator are first dissolved in an organic solvent, and the carrier is added at 20-45° C. and mixed for 2-12 hours. More preferably, the dissolution condition is a constant temperature of 20-40° C. for 0.5-3 hours.

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

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

[0029] According to an embodiment of the present invention, the organic solvent is selected from at least one of alkanes, halogenated alkanes, aromatic hydrocarbons, heterocyclic compounds, ethers, ketones, and esters, preferably selected from at least one of pentane, hexane, heptane, dichloromethane, chloroform, benzene, toluene, chlorobenzene, chlorotoluene, tetrahydrofuran, acetone, ether, and ethyl acetate; and / or,

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

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

[0032] The third aspect of the present invention is to provide an 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 technical solution of the present invention, the application of the supported metallocene catalyst in olefin polymerization is the application of the supported metallocene catalyst in olefin polymerization for ethylene polymerization and in-situ grafting (i.e., the method for ethylene polymerization and in-situ grafting) comprising:

[0034] 1) contacting ethylene with the supported metallocene catalyst to carry out ethylene polymerization reaction to obtain polyethylene powder containing a free radical initiator;

[0035] 2) contacting the polar monomer 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 on 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, alkenyl bisphenol A ether, acrylonitrile, styrene and its homologues, and glycidyl methacrylate.

[0037] The methods of ethylene polymerization and in-situ grafting in the present invention include but are not limited to ethylene slurry polymerization and grafting reaction.

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

[0039] The temperature is 50-10° C., the reaction time is 0.5-3 hours, the pressure is 0.1-5 MPa, and the amount of supported metallocene catalyst is 20-500 mg; preferably, the reaction is carried out in the presence of alkyl aluminum or methyl aluminoxane.

[0040] The alkyl aluminum can be selected from at least one of sesquiethylaluminum chloride, triethylaluminum, tri-n-hexylaluminum, tri-isobutylaluminum, and tri-n-octylaluminum, and / or the amount of the alkyl aluminum or methylaluminoxane is 5-1000 mol relative to 1 mol of the metal content in the supported metallocene catalyst. The alkyl aluminum or methylaluminoxane has the following functions: (1) as an impurity remover, removing water and oxygen in the reaction process to avoid interference with the polymerization reaction; and (2) stimulating the catalyst to carry out the polymerization reaction.

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

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

[0043] The temperature is 80-150°C, 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] The present invention provides a metallocene catalyst for ethylene polymerization and in-situ grafting and a preparation method thereof. The catalyst introduces a free radical initiator during the preparation process. First, the metallocene catalyst catalyzes ethylene polymerization. After the reaction, the free radical initiator is evenly dispersed in the polyethylene powder. Then, the free radical initiator initiates the in-situ grafting of polar monomers on the polyethylene, which makes the grafting reaction more uniform, the grafting rate is higher, and the gel content is lower. Moreover, there are many types of metallocenes, and the catalytic properties can be adjusted according to the types of ligands and metals, so that the polymerization obtains polyethylene that is easier to polar graft, reduces the occurrence of side reactions, has high adjustability, and the metallocene catalyst obtains a narrow molecular weight distribution of the polymer, so that the performance of the final product is more uniform; on the other hand, the catalyst is prepared by a spray drying method, and the catalyst not only has a good particle shape and a narrow particle size distribution, but also can adjust the catalyst particle size according to the use requirements, so that the polyethylene powder particle size is reduced, thereby improving the further grafting rate. The use of the catalyst can directly obtain a grafted polyethylene by a one-step method to obtain a polymer powder with good fluidity, without the need for drying and separation, and simplifies the preparation process of the grafted polyethylene.

[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 is added with a free radical initiator during the loading process, and after initiating ethylene polymerization, the free radicals can be evenly dispersed in the polyethylene, thereby initiating in-situ polar monomer grafting, and polar grafted polyethylene can be directly obtained in one step;

[0047] (2) The metallocene catalyst for ethylene polymerization and in-situ grafting provided by the present invention has a small amount of initiator used in the preparation process of grafted polyethylene, a more uniform grafting reaction, a higher grafting rate, a lower gel content, and a narrow molecular weight distribution of the polymer obtained by the metallocene catalyst, so that the performance of the final product is more uniform;

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

[0049] (4) The preparation method of the supported metallocene catalyst for ethylene polymerization and in-situ grafting provided by the present invention is simple, the catalyst particles have good morphology, the particle size can be adjusted within a large range, the particle size distribution is narrow, and the catalyst particle size can be adjusted according to the use requirements, so that the particle size of the polyethylene powder is reduced, thereby improving the grafting rate. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0051] The test instruments and test conditions used in the examples are as follows:

[0052] Determination of grafting rate (DG): Take 0.5g grafted sample, heat to reflux, dissolve in 70mL xylene, add 15mL KOH-methanol standard solution while hot, continue to reflux for 2h, add 2 drops of phenolphthalein reagent, titrate with standard HCl-isopropanol solution, and titrate the blank sample at the same time to calculate the grafting rate. It is calculated as the mass of maleic anhydride per 100g sample.

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

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

[0055] Where: m1 is the mass of the filter cloth bag after loading the sample, 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 distribution analyzer;

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

[0058] Determination of initiator content in the catalyst: Liquid nuclear magnetic resonance (Bruker AVANCE 300) was used for determination with hydroquinone as the internal standard.

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

[0060] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0061] Example 1

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

[0063] 2. Ethylene slurry polymerization and grafting reaction: 1L hexane was added to a 2L polymerization kettle that was purged with nitrogen first and then hydrogen, and 1mL triethylaluminum (1M) and 100mg dry powder catalyst were added at the same time. Ethylene was added to 1.03MPa, and the temperature was raised to 50°C. After reacting at 50°C for 1h, the ethylene in the kettle was replaced with nitrogen and the pressure was raised to 2MPa. Then 6.0g methyl methacrylate was added, the temperature was raised to 130°C, and the reaction was continued for 5h before cooling and discharging. The assessment results are shown in Table 2.

[0064] Example 2

[0065] 1. Preparation of supported catalyst: Under nitrogen protection, 3.0g diisopropylbenzene peroxide, 0.36g bis(n-ethylcyclopentadienyl)zirconium dichloride and 40mL 10% MAO toluene solution were dissolved in 100mL toluene solution at room temperature. After dissolution, 3.0g silica (particle size 0.01-2μm) was added and stirred for 2h. Then spray drying was performed using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature 110℃, control the inlet nitrogen flow rate at 25.0m 3 / h, and 6.2g of catalyst was obtained. Some of its physical property parameters are shown in Table 1.

[0066] 2. Ethylene slurry polymerization and grafting reaction: 1L hexane was added to a 2L polymerization kettle that was purged with nitrogen first and then hydrogen, and 1mL triethylaluminum (1M) and 100mg dry powder catalyst were added at the same time. Ethylene was added to 1.03MPa, and the temperature was raised to 50°C. After reacting at 50°C for 45 minutes, the ethylene in the kettle was replaced with nitrogen and the pressure was raised to 2MPa. Then 8.0g acrylic acid was added, the temperature was raised to 130°C, and the reaction was continued for 5 hours before cooling and discharging. The assessment results are shown in Table 2.

[0067] Example 3

[0068] 1. Preparation of supported catalyst: Under nitrogen protection, 6.0g of tert-butyl hydroperoxide, 0.80g of bis(n-butylcyclopentadienyl)zirconium dichloride and 60mL of 10% mass concentration of MAO (methylaluminoxane) toluene solution were dissolved in 100mL toluene solution at room temperature. After dissolution, 6.0g of silicon dioxide (particle size of 0.01-2μm) was added and stirred for 2h. Then spray drying was performed using a spray dryer. Spray conditions: inlet temperature: 150℃, outlet temperature 110℃, control the inlet nitrogen flow rate at 25.0m 3 / h, obtaining 12.7 g of catalyst.

[0069] 2. Ethylene slurry polymerization and grafting reaction: 1L hexane was added to a 2L polymerization kettle that was purged with nitrogen first and then hydrogen, and 1mL triethylaluminum (1M) and 100mg dry powder catalyst were added at the same time. Ethylene was added to 1.03MPa, and the temperature was raised to 50°C. After reacting at 50°C for 40 minutes, the ethylene in the kettle was replaced with nitrogen and the pressure was raised to 2MPa. Then 6.0g methyl acrylate was added, the temperature was raised to 130°C, and the reaction was continued for 5 hours before cooling and discharging. The assessment results are shown in Table 2.

[0070] Example 4

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

[0072] 2. Ethylene slurry polymerization and grafting reaction: 1L hexane was added to a 2L polymerization kettle that was purged with nitrogen first and then hydrogen, and 1mL triethylaluminum (1M) and 100mg dry powder catalyst were added at the same time. Ethylene was added to 1.03MPa, and the temperature was raised to 50°C. After reacting at 50°C for 1h, the ethylene in the kettle was replaced with nitrogen and the pressure was raised to 2MPa. Then 8.0g methyl acrylate was added, the temperature was raised to 130°C, and the reaction was continued for 5h before cooling and discharging. The assessment results are shown in Table 2.

[0073] Example 5

[0074] The catalyst was prepared according to the method of Example 1, except that during spray drying, the inlet nitrogen flow rate was controlled at 20.0 m 3 / h, and 8.5g of catalyst was obtained. Some of its physical property parameters 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 belt stirring reactor, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of diisopropylbenzene peroxide and an appropriate amount of interfacial wetting agent were added, the reaction temperature was set to 120°C, and the material was discharged after reacting for 3h, and then washed with xylene and anhydrous ethanol, filtered and dried to obtain a product sample. Its physical properties are shown in Table 2.

[0078] Comparative Example 2

[0079] In a stainless steel jacketed heating belt stirring reactor, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of tert-butyl hydroperoxide and an appropriate amount of interfacial wetting agent were added, the reaction temperature was set to 120°C, and the material was discharged after reacting for 3h, and then washed with xylene and anhydrous ethanol, filtered and dried to obtain a product sample. Its physical properties are shown in Table 2.

[0080] Comparative Example 3

[0081] The catalyst was prepared according to the method of Example 1, except that benzoyl peroxide was not added during the preparation process, and 12.6 g of supported metallocene catalyst was obtained. Some of its physical property parameters 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 minutes. During the grafting reaction, 6 g of diisopropylbenzene peroxide was added at the same time as methyl methacrylate to obtain a product sample. 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] It can be seen from the data in Table 1 that 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 formula, and the particle size can be regulated by the slurry formula and process conditions, so that smaller polyethylene particles can be obtained, which is more conducive to improving the grafting reaction rate and has a narrower particle size distribution.

[0089] In Example 5, the catalyst size becomes larger by changing the spray drying conditions (Table 1), and the polymer particle size obtained by such a catalyst also becomes larger. Compared with Example 1, it can be seen that Example 5 reduces the grafting efficiency, indicating the controllability of the catalyst particle size.

[0090] It can be seen from the data in Table 2 that the initiator content in Examples 1-4 is much lower than that in the comparative example, so the gel content of the obtained product is lower; and the polyethylene prepared by the metallocene catalyst has a narrow molecular weight distribution and more uniform product performance; under the condition of less initiator and polar monomer dosage, a polar grafted polyethylene with a higher grafting rate and a lower gel rate can be directly obtained by a one-step method; the obtained polymer does not need to be dried and separated, the preparation process is short, and due to the advantages of the catalyst and the polymer preparation method, the polymer has a higher bulk density.

[0091] The other conditions of Comparative Example 3 are the same as those of Comparative Example 1, but the initiator is not in the catalyst but added during the grafting reaction. Thus, the initiator cannot be uniformly introduced into the polymer during the first polymerization reaction, resulting in low grafting efficiency (Table 2), indicating that adding the initiator to the catalyst and uniformly dispersing it in the polymer through the polymerization reaction achieves an unexpected technical effect.

[0092] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[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 conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0094] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0095] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0096] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0097] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A supported metallocene catalyst, comprising a carrier, and a blended component and / or a reaction product containing a metallocene catalyst, an activator and a free radical initiator supported on the carrier, wherein the activator is an organic aluminum compound.

2. The supported metallocene catalyst according to claim 1, characterized in that The structural formula of the metallocene catalyst is Cp A Cp B MX n ; Among them, Cp A and Cp B Independently selected from substituted or unsubstituted cyclopentadiene, substituted or unsubstituted indenyl, 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, preferably selected from at least one of Ti, Zr, and Hf; X is at least one of halogen, substituted or unsubstituted hydrocarbon group, preferably at least one of chlorine, substituted or unsubstituted hydrocarbon group having 1 to 10 carbon atoms; n=1 or 2.

3. 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, preferably selected from at least one of benzoyl peroxide, diisopropylbenzene peroxide, di-tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl perbenzoate, diisobutyl peroxydicarbonate, azobisisobutyronitrile and azobisisoheptylonitrile.

4. The supported metallocene catalyst according to claim 1, characterized in that The organoaluminum compound is AlR n X (3-n) or contains A compound of the structure, wherein R is an alkyl group having 1 to 10 carbon atoms, X is a halogen, and n is an integer of 1 to 3; preferably, The organoaluminum compound is at least one selected from trimethylaluminum, triethylaluminum, methylaluminoxane, diethylaluminum monochloride, ethylaluminum dichloride, tri-n-butylaluminum, triisobutylaluminum, sesquimethylaluminum chloride, and sesquiethylaluminum chloride.

5. The supported metallocene catalyst according to claim 1, characterized in that The carrier is selected from inorganic oxides, preferably silicon oxide and / or aluminum oxide, more preferably silicon dioxide; and / or, The particle size of the carrier is 0.01-5 μm, preferably 0.01-2 μm.

6. The supported metallocene catalyst according to any one of claims 1 to 5, characterized in that Based on the total weight of the supported metallocene catalyst as 100wt%, the weight content of metallocene M in the supported metallocene catalyst is 0.1-5wt%, preferably 0.3-2.5wt%; and / or, the content of free radical initiator is 10-60wt%, preferably 20-40wt%; and / or, The molar ratio of aluminum in the organoaluminum compound to the metallocene M is (5-1000):1, preferably (20-300):1; and / or, The average particle size of the supported metallocene catalyst is 7-100 μm, preferably 8-30 μm; and / or, The particle size distribution of the supported metallocene catalyst is less than 2, preferably less than 1.

5.

7. A method for preparing the supported metallocene catalyst according to any one of claims 1 to 6, comprising the following steps: (1) dispersing the components including the metallocene catalyst, activator, carrier, and free radical initiator in an organic solvent to form a slurry; (2) spray drying the slurry obtained in step (1) to obtain the supported metallocene catalyst; preferably, The preparation of the slurry in step (1) comprises: dissolving a free radical initiator, a metallocene catalyst, and an activator in an organic solvent and then adding a carrier. More preferably, the free radical initiator, the metallocene catalyst, and the activator are first dissolved in an organic solvent, and then the carrier is added and mixed at 20-45° C. for 2-12 hours; and / or, The spray drying conditions in step (2) are: inlet temperature 50-200°C, outlet temperature 30-150°C; and / or, The air flow rate of the spray drying nozzle in step (2) is 10-50m 3 / h.

8. The preparation method according to claim 7, characterized in that: The organic solvent is selected from at least one of alkanes, halogenated alkanes, aromatic hydrocarbons, heterocyclic compounds, ethers, ketones, and esters, preferably selected from at least one of pentane, hexane, heptane, dichloromethane, chloroform, benzene, toluene, chlorobenzene, chlorotoluene, tetrahydrofuran, acetone, ether, and ethyl acetate; and / or, Relative to 1 g of the carrier, the amount of the organic solvent used is 5-100 mL, preferably 10-50 mL.

9. The preparation method according to claim 7 or 8, characterized in that: In parts by mass, relative to 1 part of the carrier, the amount of the metallocene catalyst is 0.01-1 part, the amount of the activator is 0.1-30 parts, and the amount of the free radical initiator is 0.02-10 parts; Preferably, relative to 1 part of the carrier, the amount of the metallocene catalyst is 0.05-0.5 parts, the amount of the activator is 0.3-10 parts, and the amount of the free radical initiator is 0.1-3 parts.

10. Use of the supported metallocene catalyst according to any one of claims 1 to 6 or the supported metallocene catalyst prepared by the preparation method according to any one of claims 7 to 9 in olefin polymerization.

11. The use according to claim 10, characterized in that: The application of the supported metallocene catalyst in olefin polymerization includes: 1) contacting ethylene with the supported metallocene catalyst to carry out ethylene polymerization reaction to obtain polyethylene powder containing a free radical initiator; 2) contacting the polar monomer 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 on the polyethylene; preferably, 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, alkenyl bisphenol A ether, acrylonitrile, styrene and its homologues, and glycidyl methacrylate.

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