A ziegler-natta catalyst for ethylene polymerization and in situ grafting, its preparation method and application

Abstract

The present application relates to the field of polyolefin catalysts, in particular to a Ziegler-Natta catalyst for olefin polymerization and in-situ grafting, and a preparation method and application thereof. The Ziegler-Natta catalyst comprises the following blending components and / or reaction products: a carrier, a titanium element source, a magnesium element source, an electron donor and a free radical initiator. The free radical initiator is introduced during the preparation process of the catalyst, the preparation process is relatively simple, the grafting of the polar monomer on the polyethylene is initiated, the grafting reaction is more uniform, the amount of the free radical initiator is less, the grafting efficiency is higher, and the gel content is lower; the particle size of the catalyst can be adjusted according to the use requirement, thereby the particle size of the polymer is controlled, and the grafting efficiency is improved; the grafted polyethylene can be directly obtained by using the catalyst through a one-step method, the grafted product does not need to be dried and separated, and the preparation process of the grafted polyethylene is simplified.

Description

A Ziegler-Natta catalyst for ethylene polymerization and in-situ grafting, its preparation method and application Technical Field

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

[0002] Polyethylene is one of the world's most produced plastic products and is therefore widely used in various fields. However, its complete lack of polarity and low surface energy limit its wider application. To address this issue, polyethylene is grafted to introduce polar groups into the molecular chain. The polarity and functionality of these polar groups can improve its performance shortcomings.

[0003] Catalysts are a key technology in the polyolefin industry. Among them, Ziegler-Natta catalyst is the most mature system. Its high activity, high hydrogen sensitivity and controllable molecular weight distribution make it dominant in the polyethylene industry (Polymer Bulletin 2021, (6): 15-24).

[0004] Currently, the commonly used methods for grafting polyethylene are: 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 contact 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. All of the above methods involve secondary reactions of finished polyethylene to finally obtain grafted polyethylene (Plastics Technology, 2005(2): 42-46).

[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 Ziegler-Natta catalyst for ethylene polymerization and in-situ grafting, and its preparation method. This catalyst incorporates a free radical initiator during preparation, resulting in a relatively simple process. First, the Ziegler-Natta catalyst catalyzes ethylene polymerization, with the free radical initiator 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 lower gel content. Furthermore, the use of spray drying ensures the catalyst has a good particle shape and allows for adjustment of the catalyst particle size according to application requirements, thereby controlling the polymer particle size and improving grafting efficiency. Using this catalyst, grafted polyethylene can be obtained directly in one step, eliminating the need for drying and separation of the grafted product, thus simplifying the grafted polyethylene preparation process.

[0007] A first aspect of the present invention is to provide a Ziegler-Natta catalyst comprising a blend of the following raw materials and / or reaction products:

[0008] Support, titanium source, magnesium source, electron donor and free radical initiator.

[0009] According to a preferred embodiment of the present invention, the carrier is selected from inorganic oxide carriers, preferably from silicon oxide and / or aluminum oxide, and more preferably from silicon dioxide.

[0010] According to a preferred embodiment of the present invention, the particle size of the inorganic oxide support is 0.01–5 μm, preferably 0.01–2 μm.

[0011] According to an embodiment of the present invention, the free radical initiator is selected from at least one of azo and peroxide initiators. According to a preferred embodiment of the present invention, the free radical initiator is preferably 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.

[0012] According to an embodiment of the present invention, the titanium source is a titanium-containing compound; preferably, the titanium-containing compound is selected from at least one of titanium halide, the product of aluminum reduction of titanium halide, and the product of magnesium reduction of titanium halide.

[0013] The general formula of the titanium-containing compound is Ti(OR). 4 ) a X b Ti(OR) 4 ) a X b Chinese R 4 For C1-C 10The aliphatic or aromatic hydrocarbon group, where X is a halogen, preferably fluorine, chlorine, or bromine, a is 0, 1, or 2, b is an integer from 1 to 4, and a + b = 3 or 4; preferably, R 4 Selected from C1-C6 alkyl, C2-C6 alkenyl, C3-C 10 cycloalkyl or C6-C 10 Aromatic hydrocarbon groups; preferably, R 4 It is selected from methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, cyclopropyl, methylcyclopropyl, n-pentyl, methylcyclopentyl, cyclohexyl, phenyl, benzyl or xylylyl.

[0014] According to an embodiment of the present invention, the magnesium source is magnesium halide; preferably, the magnesium halide is selected from at least one of magnesium fluoride, magnesium chloride, magnesium bromide and magnesium iodide.

[0015] According to embodiments of the present invention, the electron donor is selected from at least one of the following: alkyl esters of C1-C4 saturated fatty carboxylic acids, alkyl esters of C7-C8 aromatic carboxylic acids, C2-C6 fatty ethers, C3-C4 cyclic ethers, and C3-C6 saturated fatty ketones. Preferably, it is at least one of methyl formate, ethyl acetate, butyl acetate, diethyl ether, hexyl ether, tetrahydrofuran, acetone, and methyl isobutyl ketone, etc., and these electron donor compounds can be used alone or in combination.

[0016] According to a preferred embodiment of the present invention, the Ziegler-Natta catalyst comprises, based on a total weight of 100 wt%, the following components: titanium: 0.5-4 wt%; magnesium: 2-8 wt%; electron donor: 10-35 wt%; radical initiator: 10-60 wt%; and support: 10-60 wt%.

[0017] According to a preferred embodiment of the present invention, the average particle size of the Ziegler-Natta catalyst is 7 to 100 μm, preferably 8 to 50 μm.

[0018] In a preferred embodiment of the present invention, the average particle size of the supported transition metal catalyst is 7–100 μm. The inventors have discovered that, based on the catalyst formulation of the present invention, the grafting rate of grafted polyethylene can be adjusted by further regulating the average particle size of the 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 catalyst is 8–50 μm, which can further improve the grafting rate. Even more preferably, the average particle size of the catalyst is 8–30 μm; even more preferably, the average particle size of the supported transition metal catalyst is 8–20 μm. Under further lower average particle size conditions, the grafted polyethylene has an even higher grafting rate; preferably, it is 8–15 μm.

[0019] 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, in a preferred embodiment of the present invention, the particle size distribution of the Ziegler-Natta catalyst is less than 2, preferably less than 1.5.

[0020] 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.

[0021] A second aspect of the present invention is to provide a method for preparing the Ziegler-Natta catalyst described in the first aspect, comprising the following steps:

[0022] (1) Mix the raw materials including titanium source, magnesium source, electron donor, free radical initiator, carrier and optional organic solvent to obtain slurry suspension;

[0023] (2) The slurry suspension obtained in step (1) is spray-dried to obtain the Ziegler-Natta catalyst.

[0024] According to a preferred embodiment of the present invention, the preparation of the slurry suspension in step (1) includes: first mixing a titanium source, a magnesium source and an electron donor, and treating at 20-85°C for 0.5-3 hours to obtain a mother liquor; adding a carrier and a free radical initiator during or after the preparation of the mother liquor, and mixing for 2-12 hours.

[0025] According to a preferred embodiment of the present invention, the spray drying conditions in step (2) are: inlet temperature 50-200°C and outlet temperature 30-150°C.

[0026] 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.

[0027] According to a preferred embodiment of the present invention, in step (1), the amount of the electron donor relative to 1g of carrier is 5-100mL, preferably 10-50mL, for example, 10mL, 20mL, 30mL, 40mL, 50mL, and any two values ​​or any range of any two values; and / or, the mass ratio of the carrier to the free radical initiator is (0.1-50):1, preferably (0.3-10):1, for example, 0.3:1, 0.5:1, 1:1, 1.5:1, 2:1, 4:1, 6:1, 8... The ratios are: 1, 10:1; and any two values ​​or any range of two values; and / or, the molar ratio of titanium in the titanium source to magnesium in the magnesium source is (0.1-0.5):1, for example, 0.1, 0.2, 0.3, 0.4, 0.5, and any two values ​​or any range of two values ​​compared to 1; and / or, the mass ratio of the carrier to the magnesium source is (0.5-6):1, for example, 0.5, 1, 2, 3, 4, 5, 6, and any two values ​​or any range of two values ​​compared to 1.

[0028] According to a more preferred embodiment of the present invention, in step (1), the amount of the electron donor relative to 1g of carrier is 5-100mL, preferably 10-50mL; the mass ratio of the carrier to the free radical initiator is (0.1-50):1, preferably (0.3-10):1; the molar ratio of titanium in the titanium source to magnesium in the magnesium source is (0.1-0.5):1; and the mass ratio of the carrier to the magnesium source is (0.5-6):1.

[0029] According to a preferred embodiment of the present invention, the molar ratio of the electron donor to the magnesium element in the magnesium source is (10-45):1, for example, 10, 20, 30, 40, 45, and any two values ​​or any interval of any two values ​​to 1.

[0030] In step (1), an organic solvent is optionally added to form a homogeneous slurry. The organic solvent used can be a commonly used organic solvent in the art, preferably selected from at least one of alkanes, haloalkanes, aromatics, heterocyclic compounds, ethers, ketones, and esters, and more preferably from at least one of pentane, hexane, heptane, dichloromethane, trichloromethane, benzene, toluene, chlorobenzene, chlorotoluene, tetrahydrofuran, acetone, diethyl ether, and ethyl acetate. The amount of the organic solvent used is 5 to 100 mL, preferably 10 to 50 mL, based on 1 g of carrier. The organic solvent and electron donor can be added simultaneously. When the electron donor can also act as an organic solvent to dissolve raw materials such as magnesium element sources, only the electron donor can be added. For example, in the embodiments of the present invention, tetrahydrofuran is both an electron donor and an organic solvent, and no other organic solvent needs to be added.

[0031] A third aspect of the present invention is to provide a catalyst for olefin polymerization, comprising:

[0032] (A) The Ziegler-Natta catalyst described in the first aspect or the Ziegler-Natta catalyst prepared by the method described in the second aspect;

[0033] (B) The general formula is A1R b X' 3b Organoaluminum compounds, wherein R is a hydrogen or hydrocarbon group with 120 carbon atoms; X' is a halogen; 0 < b ≤ 3.

[0034] According to a preferred embodiment of the present invention, the organoaluminum compound is selected from at least one of triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, and diethylaluminum chloride.

[0035] According to a preferred embodiment of the present invention, the molar ratio of titanium in the organoaluminum compound and the Ziegler-Natta catalyst is (5-1000):1.

[0036] The fourth aspect of the present invention is to provide the application of the Ziegler-Natta catalyst described in the first aspect, or the Ziegler-Natta catalyst prepared by the preparation method described in the second aspect, or the catalyst described in the third aspect, in olefin polymerization.

[0037] According to a preferred embodiment of the present invention, the application of the Zigler-Natta catalyst in olefin polymerization includes:

[0038] 1) Ethylene is reacted with a Ziegler-Natta catalyst and a catalyst of general formula A1R. b X' 3bContacting the organoaluminum compound with ethylene and / or contacting the catalyst described in the third aspect to carry out an ethylene polymerization reaction, thereby obtaining a polyethylene powder containing a free radical initiator;

[0039] 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; preferably,

[0040] 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.

[0041] The methods for ethylene polymerization and in-situ grafting in this invention include, but are not limited to, ethylene slurry polymerization and grafting reaction.

[0042] For example, during ethylene slurry polymerization and grafting reactions, the conditions for the ethylene polymerization reaction include:

[0043] The temperature is 40-100℃, the reaction time is 0.5-3h, the pressure is 0.5-3MPa, and the amount of Zigler-Natta catalyst is 20-500mg. It is preferably carried out in the presence of alkylaluminum.

[0044] Alkyl aluminum may be selected from at least one of sesquiethylaluminum chloride, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, etc., and / or the amount of alkyl aluminum used is 10-1000 mol relative to 1 mol of titanium content in the catalyst.

[0045] 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%.

[0046] The role of alkylaluminum or methylchlorooxyalkane is to (1) act as a purifier 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.

[0047] As an example, in ethylene slurry polymerization and grafting reactions, the conditions for in-situ grafting reactions include:

[0048] The temperature is 80-150℃, the reaction time is 2-8 hours, and the pressure is 1-5 MPa.

[0049] The mass ratio of polyethylene powder containing free radical initiators to polar monomers is 500-50:1.

[0050] This invention provides a Ziegler-Natta catalyst for ethylene polymerization and in-situ grafting, and its preparation method. The catalyst preparation process introduces a free radical initiator. First, the Ziegler-Natta catalyst catalyzes ethylene polymerization. After the reaction, the free radical initiator is uniformly dispersed in polyethylene powder. Then, the free radical initiator initiates the in-situ grafting of polar monomers onto the polyethylene, resulting in a more uniform grafting reaction, a higher grafting rate, and a lower gel content. Furthermore, the catalyst is prepared using a spray drying method, which not only produces catalysts with good particle shape and narrow particle size distribution, but also allows for adjustment of the catalyst particle size according to application requirements, thereby reducing the polyethylene powder particle size and improving the grafting rate. Using this catalyst, grafted polyethylene can be obtained directly in one step, yielding a polymer powder with good flowability, eliminating the need for drying and separation, and simplifying the grafted polyethylene preparation process.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] (1) The Ziegler-Natta 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.

[0053] (2) The Ziegler-Natta catalyst for ethylene polymerization and in-situ grafting provided by the present invention has a lower initiator dosage, more uniform grafting reaction, higher grafting rate and lower gel content in the process of preparing grafted polyethylene.

[0054] (3) The Ziegler-Natta catalyst provided by the present invention is used to obtain resin powder with good particle morphology and high bulk density for olefin polymerization. The product does not need to be dried and separated and can be used in slurry polymerization process.

[0055] (4) The preparation method of the catalyst for ethylene polymerization and in-situ grafting Ziegler-Natta 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

[0056] 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.

[0057] The testing instruments and conditions used in this embodiment are as follows:

[0058] 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.

[0059] 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).

[0060] DC=(m3-m2) / (m1-m2) (1)

[0061] In the formula: 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.

[0062] 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.

[0063] Metal content in catalyst: The metal content in the catalyst was determined using inductively coupled plasma mass spectrometry (ICP-MS) (Agilent 7500CX).

[0064] Initiator content determination in catalyst: Liquid NMR (Bruker AVANCE 300) was used, with hydroquinone as an internal standard for determination.

[0065] Example 1

[0066] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 120 mL of tetrahydrofuran (THF), 4.2 g of magnesium chloride, and 1.0 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours with constant temperature to obtain a mother liquor. Then, 5.5 g of silica gel and 5.0 g of benzoyl peroxide were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, with an outlet temperature of 95 °C and an inlet nitrogen flow rate controlled at 31.0 m³ / s. 3 / h, the solid catalyst composition was obtained, and some of its physical properties are shown in Table 1.

[0067] 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 (i.e., solid catalyst component) were added. Hydrogen was added to a pressure of 0.28MPa. After hydrogenation, 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 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 6.0g of methyl methacrylate was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0068] Example 2

[0069] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 120 mL of tetrahydrofuran (THF), 4.2 g of magnesium chloride, and 1.0 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours to obtain a mother liquor. Then, 5.5 g of silica gel and 7.0 g of benzoyl peroxide were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, with an outlet temperature of 95 °C and an inlet nitrogen flow rate controlled at 31.0 m³ / s. 3 The solid catalyst composition was obtained at / h, and some of its physical properties are shown in Table 1.

[0070] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane, 1mL of triethylaluminum (1M), and 100mg of dry powder catalyst were added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Hydrogen was added to a pressure of 0.28MPa, and after hydrogenation, 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 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 8.0g of methacrylic acid was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0071] Example 3

[0072] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 120 mL of tetrahydrofuran (THF), 4.2 g of magnesium chloride, and 1.0 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours to obtain a mother liquor. Then, 3.0 g of silica gel and 6.0 g of azobisisobutyronitrile (AIBN) were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, with an outlet temperature of 95 °C and an inlet nitrogen flow rate controlled at 25.4 m³ / s. 3 The solid catalyst composition was obtained at / h, and some of its physical properties are shown in Table 1.

[0073] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane, 1mL of triethylaluminum (1M), and 100mg of dry powder catalyst were added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Hydrogen was added to a pressure of 0.28MPa, followed by the addition of ethylene to a pressure of 1.03MPa. The temperature was raised to 50℃, and the reaction was maintained at 50℃ and constant pressure for 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 10g of diethyl maleic anhydride was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0074] Example 4

[0075] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 120 mL of tetrahydrofuran (THF), 4.2 g of magnesium chloride, and 1.0 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours to obtain a mother liquor. Then, 3.0 g of silica gel and 8.0 g of azobisisobutyronitrile (AIBN) were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, with an outlet temperature of 95 °C and an inlet nitrogen flow rate controlled at 25.4 m³ / s. 3 The solid catalyst composition was obtained at / h, and some of its physical properties are shown in Table 1.

[0076] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane, 1mL of triethylaluminum (1M), and 100mg of dry powder catalyst were added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Hydrogen was added to a pressure of 0.28MPa, and after hydrogenation, 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 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 12g of methacrylic acid was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0077] Example 5

[0078] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 80 mL of tetrahydrofuran (THF), 2.1 g of magnesium chloride, and 0.5 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours to obtain a mother liquor. Then, 5.0 g of silica gel and 5.0 g of benzoyl peroxide were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, the outlet temperature was 95 °C, and the inlet nitrogen flow rate was controlled at 32.5 m³ / s. 3 The solid catalyst composition was obtained at / h, and some of its physical properties are shown in Table 1.

[0079] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane, 1mL of triethylaluminum (1M), and 100mg of dry powder catalyst were added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Hydrogen was added to a pressure of 0.28MPa, and after hydrogenation, 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 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 12g of methyl methacrylate was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0080] Example 6

[0081] 1. Catalyst Preparation: In a 250 mL four-necked flask equipped with a temperature controller, stirrer, reflux condenser, and protected by nitrogen purging, 80 mL of tetrahydrofuran (THF), 2.1 g of magnesium chloride, and 0.5 mL of TiCl4 were added sequentially with stirring. The mixture was heated to 65 °C and refluxed for 4 hours to obtain a mother liquor. Then, 3.0 g of silica gel and 6.0 g of benzoyl peroxide were added, and the mixture was refluxed and stirred at 65 °C for another 2 hours to ensure complete dispersion of the silica gel in the mother liquor, resulting in a slurry suspension. Nitrogen gas at an inlet temperature of 140 °C was introduced into a closed-loop circulating spray dryer. The resulting slurry suspension was added to the dryer, with an outlet temperature of 95 °C and an inlet nitrogen flow rate controlled at 32.5 m³ / s. 3 The solid catalyst composition was obtained at / h, and some of its physical properties are shown in Table 1.

[0082] 2. Ethylene slurry polymerization and grafting reaction: 1L of hexane, 1mL of triethylaluminum (1M), and 100mg of dry powder catalyst were added to a 2L polymerization reactor that had been purged with nitrogen followed by hydrogen. Hydrogen was added to a pressure of 0.28MPa, and after hydrogenation, 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 0.5h. The ethylene in the reactor was then replaced with nitrogen, and the pressure was increased to 2MPa. 6g of methyl methacrylate was then added, and the temperature was raised to 125℃. After reacting for 5h, the mixture was cooled and discharged. The evaluation results are shown in Table 2.

[0083] Example 7

[0084] The catalyst was prepared according to the method in Example 5, except that the inlet nitrogen flow rate was controlled at 20.0 m³ / s during spray drying. 3 / h, some of its physical properties are shown in Table 1.

[0085] Ethylene slurry polymerization and grafting reaction were carried out according to the method in Example 5.

[0086] Comparative Example 1

[0087] In a 1L reactor with a stainless steel jacket heating and stirring, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of benzoyl peroxide and an appropriate amount of interface wetting agent were added. The reaction temperature was set to 100℃. 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.

[0088] Comparative Example 2

[0089] In a 1L reactor with a stainless steel jacket heating and stirring, 50g of high-density polyethylene, 4g of methacrylic acid, 4g of azobisisobutyronitrile and an appropriate amount of interface wetting agent were added. The reaction temperature was set to 100℃. 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.

[0090] Comparative Example 3

[0091] The catalyst was prepared according to the method in Example 5, except that benzoyl peroxide was not added during the preparation process. Some of its physical properties are shown in Table 1.

[0092] Ethylene slurry polymerization and grafting reaction were carried out according to the method of Example 1, except that 5g of benzoyl peroxide was added at the same time as methyl methacrylate to obtain product samples. The evaluation results are shown in Table 2.

[0093] Table 1. Partial physical parameters of the catalyst

[0094]

[0095]

[0096] Table 2. Some physical properties of grafted polyethylene

[0097]

[0098] As can be seen from the data in Table 1, the metal loading and free radical content of the Ziegler-Natta catalysts obtained in Examples 1-7 of this invention for ethylene polymerization and in-situ grafting can be adjusted according to the formulation, and the particle size can be controlled by the slurry formulation and process conditions, resulting in smaller polyethylene particles, which is more conducive to improving the grafting reaction rate and has a narrower particle size distribution.

[0099] Example 7 shows that by changing the spray drying conditions, the catalyst size is larger than that of Example 5 (Table 1). The resulting polymer particle size is also larger, which reduces the grafting efficiency, demonstrating the controllability of the catalyst particle size.

[0100] As can be seen from the data in Table 2, the initiator content in Examples 1-7 is much lower than that in the comparative example, resulting in a lower gel content in the product. Under the condition of using less initiator and polar monomer, the present invention can directly obtain polar grafted polyethylene with higher grafting rate and lower gel rate in one step. Moreover, due to the advantages of the catalyst and polymer preparation method, the obtained polymer does not require drying and separation, the process is short, and the polymer has a higher bulk density, achieving unexpected technical effects.

[0101] The other conditions of Comparative Example 3 were the same as those of Example 5, 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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 Ziegler-Natta catalyst comprising a blend of the following raw materials and / or reaction products: a support, a titanium source, a magnesium source, an electron donor, and a radical initiator; wherein, based on a total weight of 100 wt% of the Ziegler-Natta catalyst, the catalyst comprises: a radical initiator of 10-60 wt%; the radical initiator is used to initiate in-situ grafting of polar monomers onto polyethylene.

2. The Ziegler-Natta catalyst according to claim 1, characterized in that, The support is selected from inorganic oxide supports; and / or the particle size of the support is 0.01~5µm; and / or the free radical initiator is selected from at least one of azo and peroxide initiators.

3. The Ziegler-Natta catalyst according to claim 1, characterized in that, The support is selected from silicon oxide and / or aluminum oxide; and / or, the particle size of the support is 0.01~2µm; and / or, 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.

4. The Ziegler-Natta catalyst according to claim 1, characterized in that, The titanium source is a titanium-containing compound; and / or, the magnesium source is magnesium halide; and / or, the electron donor is selected from at least one of the following: alkyl esters of C1-C4 saturated aliphatic carboxylic acids, alkyl esters of C7-C8 aromatic carboxylic acids, C2-C6 aliphatic ethers, C3-C4 cyclic ethers, and C3-C6 saturated aliphatic ketones.

5. The Ziegler-Natta catalyst according to claim 1, characterized in that, The titanium source is a titanium-containing compound; the titanium-containing compound is selected from at least one of titanium halide, the product of aluminum reduction of titanium halide, and the product of magnesium reduction of titanium halide; and / or, the magnesium source is magnesium halide; the magnesium halide is selected from at least one of magnesium fluoride, magnesium chloride, magnesium bromide, and magnesium iodide.

6. The Ziegler-Natta catalyst according to any one of claims 1-5, characterized in that, Based on a total weight of 100 wt% for the Ziegler-Natta catalyst, the catalyst comprises: titanium: 0.5-4 wt%; magnesium: 2-8 wt%; electron donor: 10-35 wt%; free radical initiator: 10-60 wt%. Support: 10-60 wt%; and / or, the average particle size of the Ziegler-Natta catalyst is 7-100 µm; and / or, the particle size distribution of the Ziegler-Natta catalyst is less than 2.

7. The Ziegler-Natta catalyst according to any one of claims 1-5, characterized in that, The average particle size of the Ziegler-Natta catalyst is 8~50µm; and / or, the particle size distribution of the Ziegler-Natta catalyst is less than 1.

5.

8. A method for preparing the Ziegler-Natta catalyst according to any one of claims 1 to 7, comprising the following steps: (1) Mix the raw materials including titanium source, magnesium source, electron donor, free radical initiator, support and optional organic solvent to obtain a slurry suspension; (2) Spray dry the slurry suspension obtained in step (1) to obtain the Ziegler-Natta catalyst.

9. The preparation method according to claim 8, characterized in that, The preparation of the slurry suspension in step (1) includes: first mixing the titanium source, magnesium source and electron donor, and treating at 20-85℃ for 0.5-3h to obtain the mother liquor; adding the carrier and free radical initiator during or after the preparation of the mother liquor, and mixing for 2-12h; and / or, the spray drying conditions in step (2) are: inlet temperature 50-200℃, outlet temperature 30-150℃; and / or, the air inlet flow rate of the spray drying nozzle in step (2) is 10-50 m³ / h. 3 / h.

10. The preparation method according to claim 8 or 9, characterized in that, In step (1), the amount of electron donor used is 5 to 100 mL relative to 1 g of carrier; and / or, the mass ratio of carrier to free radical initiator is (0.1 to 50): 1; and / or, the molar ratio of titanium in the titanium source to magnesium in the magnesium source is (0.1 to 0.5): 1; and / or, the mass ratio of carrier to magnesium source is (0.5 to 6):

1.

11. The preparation method according to claim 8 or 9, characterized in that, In step (1), the amount of electron donor used is 10 to 50 mL relative to 1 g of carrier; and / or, the mass ratio of carrier to free radical initiator is (0.3 to 10):

1.

12. A catalyst for olefin polymerization, comprising: (A) The Ziegler-Natta catalyst according to any one of claims 1 to 7 or the Ziegler-Natta catalyst obtained by the preparation method according to any one of claims 8 to 11; (B) A catalyst of the general formula AlR b X'3 b Organoaluminum compounds, wherein R is a hydrogen atom or a carbon atom with 1 carbon atom. 20 is a hydrocarbon group; X' is a halogen; 0 < b ≤ 3.

13. The catalyst according to claim 12, characterized in that, The organoaluminum compound is selected from at least one of triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, and diethylaluminum chloride; and / or, the molar ratio of the organoaluminum compound to titanium in the Ziegler-Natta catalyst is (5~1000):

1.

14. The use of a Ziegler-Natta catalyst according to any one of claims 1 to 7, or a Ziegler-Natta catalyst prepared by the preparation method according to any one of claims 8 to 11, or a catalyst according to claim 12 or 13, in olefin polymerization.

15. The application according to claim 14, characterized in that, The application of the Zigler-Natta catalyst in olefin polymerization includes: 1) reacting ethylene with a Zigler-Natta catalyst and a general formula AlR b X'3 b 1) Contacting an organoaluminum compound with ethylene and / or contacting ethylene with the catalyst of claim 12 or 13 to carry out an ethylene polymerization reaction to obtain a polyethylene powder containing a free radical initiator; 2) Contacting a polar monomer with the polyethylene powder containing a free radical initiator obtained in 1) such that the free radical initiator initiates in-situ grafting of the polar monomer onto the polyethylene.

16. The application according to claim 15, characterized in that: The polar monomer is a compound containing a double bond and a polar group.

17. The application according to claim 15, 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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