Main catalyst component for olefin polymerization, preparation method and application

Abstract

The invention discloses a main catalyst component for olefin polymerization, a preparation method and application. The main catalyst component for ethylene polymerization comprises at least one solid magnesium compound, at least one silicon chloride compound, at least one zinc alkyl chloride compound and at least one titanium compound. The main catalytic component is combined with the cocatalyst of the alkoxy organic aluminum compound, so that a branched structure can be formed when ethylene polymerization is catalyzed, and the melt strength is obviously improved.

Description

Technical Field

[0001] The present invention relates to a catalyst component and a catalytic system for ethylene polymerization or copolymerization, a preparation method and use of the catalyst component, and the catalytic system is particularly suitable for preparing high melt strength polyethylene for the preparation of hollow container products. Background Art

[0002] Since the successful development of highly efficient polyethylene catalysts in the 1970s, the world's polyethylene industry has undergone great changes. In the past 20 years or more, along with the development of ethylene polymerization processes, the catalysts matching the polymerization processes have also made great progress. Among them, highly efficient catalysts still occupy an important position in the field of polyethylene catalysts due to their excellent polymerization performance and mature application technologies. After years of exploration and research, many highly efficient Z-N catalysts have been prepared, such as the technical solutions disclosed in CN1158136A, CN1127760A, CN1129709A, CN1085569A, US4109071, US3901863, US4617360, EP1760096, US4508843, US4921920, and US5124296, etc. Among the catalysts disclosed in the above patent applications, many patents are used to prepare high-density polyethylene.

[0003] High-density polyethylene (HDPE) has a high density, good balance between rigidity and toughness, excellent chemical resistance, does not absorb moisture and has good waterproof properties, and can be used to produce various hollow containers such as large shipping containers, 200L barrels, automotive fuel tanks, and fruit milk bottles. At present, large hollow container products made of high-density polyethylene have been widely used for the storage of various hazardous and non-hazardous chemicals, oils, and other liquids, and are gradually replacing metal containers and will become the main form of liquid packaging in some industries.

[0004] High-density polyethylene for hollow container products is mainly produced using chromium-based catalysts. Chromium-based catalysts can produce high-density polyethylene with a wide relative molecular mass distribution, and such polyethylene contains a certain amount of high relative molecular mass components, thus meeting the requirements for melt strength and environmental stress cracking resistance (ESCR) of the products during the blow molding process of hollow containers. In addition, a small amount of long-chain branches can be formed online during the catalytic ethylene polymerization process of chromium-based catalysts, and the presence of these long-chain branches is beneficial to both the blow molding process of hollow containers and the final mechanical properties of the products. From the current situation, domestic polyethylene manufacturers basically use chromium-based catalysts to produce special materials for large hollow containers.

[0005] Compared with chromium-based catalysts, titanium-based catalysts cannot produce polyethylene with a broad molecular weight distribution. To achieve the purpose of broadening the molecular weight distribution, a tandem double-reactor method is generally used for the production of bimodal polyethylene. The low molecular weight part is produced in the first reactor, and the high molecular weight part is produced in the second reactor, so as to meet the requirement of the hollow container for a broad molecular weight distribution. However, conventional titanium-based catalysts cannot form long chain branches, and the melt strength of polyethylene produced by titanium-based catalysts is often low, and the melt tensile strength is insufficient, so it cannot be well used in the blow molding process to produce hollow blow molded products.

[0006] Chinese Patent CN 201780069713.5 provides a polymerization process control method for preparing polyethylene. The process control method includes carrying out a polymerization reaction in a polymerization reactor to prepare the polyethylene, wherein ethylene and optionally one or more comonomers in the polymerization reaction are catalyzed by a Ziegler-Natta catalyst without an electron donor and an alkylaluminum cocatalyst. Measuring the melt flow ratio (I 21 / I2) of the polyethylene removed from the polymerization reactor and controlling the amount of long chain branching (LCB) of the polyethylene in the polymerization reactor by adjusting the weight concentration of the alkylaluminum cocatalyst present in the polymerization reactor. In addition, measuring the productivity of the Ziegler-Natta catalyst without an electron donor of the polyethylene produced in the polymerization reactor, wherein the amount of LCB of the polyethylene in the polymerization reactor is determined using the measured productivity of the Ziegler-Natta catalyst without an electron donor and a predetermined relationship between the productivity of the Ziegler-Natta catalyst without an electron donor and the LCB.

[0007] Chinese Patent CN 201710725365.4 discloses a main catalyst component for solution-phase ethylene polymerization, which is prepared by reacting at least one alkyl magnesium compound, at least one chloroalkane compound, at least one titanium compound and at least one silicon chloride compound; wherein, the general formula of the alkyl magnesium compound is MgR 1 n Cl 2-n (Ⅰ), in the formula R 1 is the same or different C2-C 20 saturated or unsaturated straight-chain, branched-chain or cyclic hydrocarbon group, 0 < n ≤ 2; the general formula of the chloroalkane compound is R 2 Cl(Ⅱ), in the formula R 2 is a C2-C 20 saturated or unsaturated straight-chain, branched-chain or cyclic hydrocarbon group; the general formula of the silicon chloride compound is Si(OR 3 ) nCl 4-n (Ⅲ), where R 3 It is C2~C 20 Saturated or unsaturated straight-chain, branched, or cyclic hydrocarbon groups, 0 ≤ n < 4; the general formula for titanium compounds is Ti(OR). 4 ) n Cl 4-n (Ⅳ), where R 4 It consists of C2 to C20 saturated or unsaturated straight-chain, branched, or cyclic hydrocarbon groups, where 0 ≤ n < 4. However, the polymers produced by this catalyst have low melt strength. Summary of the Invention

[0008] The purpose of this invention is to provide a main catalyst component for ethylene polymerization and its preparation method, a catalyst containing the main catalyst and its application, and the catalyst system can significantly improve the melt strength of the polymer.

[0009] To achieve the above objectives, the present invention provides a main catalyst component for ethylene polymerization, the main catalyst component comprising: at least one solid magnesium compound, at least one silicon chloride compound, at least one alkyl zinc chloride compound, and at least one titanium compound.

[0010] The main catalyst component for ethylene polymerization of the present invention, wherein the solid magnesium compound is of general formula (I)Mg(OR) 1 As shown in Figure 2, R 1 It is C2~C 20 The hydrocarbon group can be a saturated or unsaturated straight chain, branched chain, or cyclic chain.

[0011] Preferably, the solid magnesium compound includes at least one of magnesium diethoxy, magnesium dibutoxy, magnesium dipropoxy, and magnesium chloride alcohol, and the solid magnesium compound is spherical or near-spherical particles with an average particle size ranging from 2 to 20 micrometers, preferably 5 to 15 micrometers.

[0012] The main catalyst component for ethylene polymerization of the present invention, wherein the silicon chloride compound is such as general formula (II)Si(OR) 2 ) n Cl 2-n As shown in the formula, R 2 It is C2~C 20 The hydrocarbon group can be a saturated or unsaturated straight chain, branched chain, or cyclic chain, and 0 < n ≤ 2.

[0013] Preferably, the silicon chloride compound includes the reaction product of silicon tetrachloride and a fatty alcohol. When silicon tetrachloride and a fatty alcohol are used in the reaction, the molar ratio of the fatty alcohol to silicon tetrachloride should be less than 4.0, the reaction temperature is generally controlled between room temperature and 50°C, and the reaction time is controlled between 0.5 and 5 hours.

[0014] The main catalyst component for ethylene polymerization of the present invention, wherein the chloroalkyl zinc compound is such as general formula (Ⅲ)ZnR 3 As shown in Cl, R 3 It is C2~C 20 The hydrocarbon group can be a saturated or unsaturated straight chain, branched chain, or cyclic chain.

[0015] Preferably, the chloroalkyl zinc compound includes at least one of methyl zinc chloride, ethyl zinc chloride, butyl zinc chloride, propyl zinc chloride, tert-butyl zinc chloride, and benzyl zinc chloride.

[0016] The main catalyst component for ethylene polymerization of the present invention, wherein the titanium compound is of general formula (Ⅳ)Ti(OR) 4 ) n Cl 4-n As shown in the formula, R 4 It is C2~C 20 The hydrocarbon group can be a saturated or unsaturated straight chain, branched chain, or cyclic chain, and 0 ≤ n < 4.

[0017] Preferably, the titanium compound comprises titanium tetrachloride or the reaction product of titanium tetrachloride and a fatty alcohol. When titanium tetrachloride and a fatty alcohol are used in the reaction, the molar ratio of the fatty alcohol to titanium tetrachloride should be less than 4.0, the reaction temperature is generally controlled between room temperature and 100°C, and the reaction time is controlled between 0.5 and 5 hours.

[0018] This invention also provides a method for preparing a main catalyst component for ethylene polymerization, the method comprising the following steps:

[0019] (1) Mix solid magnesium compounds and silicon chloride compounds to form reaction products;

[0020] (2) The reaction product obtained in step (1) is reacted with a chloroalkyl zinc compound;

[0021] (3) The reaction product obtained in step (2) is reacted with a titanium compound to obtain the main catalyst component.

[0022] The method for preparing the main catalyst component for ethylene polymerization of the present invention comprises the following proportions: per mole of solid magnesium compound, the silicon chloride compound is 0.1 to 10 moles, preferably 0.5 to 5 moles; the chloroalkyl zinc compound is 0.05 to 3 moles, preferably 0.1 to 2 moles; and the titanium compound is 0.05 to 3 moles, preferably 0.1 to 2 moles.

[0023] The method for preparing the main catalyst component of ethylene polymerization according to the present invention wherein the solid magnesium compound has a spherical or hemispherical particle morphology with an average particle size ranging from 2 to 20 micrometers, preferably 5 to 15 micrometers. If the solid magnesium compound is an alkoxymagnesium compound, it can be prepared by reacting magnesium powder with a fatty alcohol under certain conditions; if the solid magnesium compound is a magnesium chloride alcohol, it is obtained by dissolving magnesium chloride in a fatty alcohol, then transferring it to hexane at low temperature, stirring, dispersing, melting, and solidifying.

[0024] To facilitate the reaction of solid magnesium compounds, an inert dispersant can be added. The inert dispersant does not participate in the reaction process; its purpose is simply to enhance the dispersion of the solid components. Suitable solvents for use as inert dispersants include at least one of hexane, heptane, octane, toluene, xylene, 1,2-dichloroethane, chlorocyclohexane, chlorobenzene, and other hydrocarbons or halogenated hydrocarbons. Generally, inert solvents such as pentane, hexane, heptane, or toluene are required.

[0025] In the preparation method of the above-mentioned main catalyst component, the solid magnesium compound is reacted with a silicon chloride compound and a zinc chloroalkyl compound, respectively. The order of addition of the silicon chloride and zinc chloroalkyl compounds is not particularly required; the silicon chloride compound can be added first, followed by the zinc chloroalkyl compound, or vice versa. This step mainly involves the chlorination of the solid magnesium compound, while simultaneously removing other substituent groups. Experiments have shown that the feeding temperature and rate of the silicon chloride and zinc chloroalkyl compounds are crucial for controlling the morphology of the solid particles. Higher feeding temperatures and faster feeding rates will damage the particle morphology of the solid magnesium compound. Therefore, in this step, the reaction temperature is selected to be between -10℃ and 100℃, and the addition time is between 30 minutes and 5 hours.

[0026] Similarly, the reaction process of the titanium compound also requires precise control after the addition of silicon chloride and zinc chloroalkyl chloride compounds. Typically, the feeding temperature of the titanium compound is controlled between -10°C and 20°C, and the feeding time is between 30 minutes and 5 hours. After the feeding is complete, it is preferable to slowly raise the system temperature to 80-100°C and stir the reaction for a period of time; this reaction is called catalyst ripening. Ripening is beneficial to the catalyst particle shape, narrowing the particle size distribution and increasing the strength of the catalyst particles, thereby reducing particle breakage during the catalytic polymerization of ethylene. The ripening temperature is generally equal to or higher than the feeding temperature of the titanium compound, and the ripening time can be controlled between 0.5 and 15 hours, preferably between 2 and 5 hours.

[0027] After the ripening reaction, the ripened main catalyst suspension is generally washed to remove excess reactants and by-products formed during the preparation process. Any inert solvent can be used for this washing step, such as a combination of one or more of isobutane, pentane, hexane, heptane, cyclohexane, etc. Usually, hexane is selected as the inert solvent for washing. After washing, the main catalyst suspension needs to go through a drying step to obtain a solid main catalyst, and this drying step can be completed by purging the main catalyst suspension with high-temperature nitrogen under heating conditions.

[0028] The present invention further provides a catalyst for ethylene polymerization, which catalyst for ethylene polymerization comprises the following components:

[0029] (a) The above-mentioned main catalyst component;

[0030] (b) An organoaluminum compound with a general formula of AlR' n (OR”) 3-n where R' and R” are the same or different alkyl groups having 1 to 20 carbon atoms, and n is a number where 1 < n < 3.

[0031] For the catalyst for ethylene polymerization of the present invention, the organoaluminum compound includes at least one of Al(OEt)Et2, (EtO)Al(iso-Bu)2, (EtO)Al(n-C6H 13 )2, (EtO)Al(n-C8H 17 )2. The organoaluminum compound can be obtained by reacting an alkylaluminum compound with a fatty alcohol. The molar ratio of the organoaluminum compound to titanium in the main catalyst component is 1 to 500.

[0032] The present invention further provides an application of the above catalyst in a slurry-phase ethylene polymerization reaction. The catalyst catalyzes the polymerization of ethylene or the copolymerization of ethylene and an α-olefin, where the α-olefin can be at least one of propylene, butene, pentene, hexene, octene, 4-methylpentene-1.

[0033] Experimental findings show that when using the catalyst of the present invention to catalyze the copolymerization of ethylene, polyethylene containing long-chain branching can be obtained, and the melt strength of the polyethylene is relatively high, which is suitable for the hollow blow molding processing method.

[0034] During the research process, the inventors unexpectedly discovered a Ziegler-Natta type titanium-based main catalyst component. When this main catalyst component is combined with a co-catalyst of an alkoxy-containing organoaluminum compound, a branched structure can be formed during the catalysis of ethylene polymerization, which has an obvious effect on improving the melt strength. Detailed embodiments

[0035] The present invention will be further described below through specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are all conventional reagents, which can be purchased commercially or synthesized according to conventional methods in the art; the experimental methods, unless otherwise specified, are all conventional methods.

[0036] Melt strength test

[0037] The experimental setup for melt strength testing consists of a single-screw extruder equipped with a capillary tube and a melt strength tester. First, the polyethylene resin melt to be tested is extruded from the extruder die. Then, the resulting extruded melt bundle is pulled by two rollers moving in opposite directions on a balance beam. The rollers accelerate uniformly until the melt bundle breaks. The force experienced when the melt bundle breaks is defined as the melt strength.

[0038] Example 1

[0039] (1) Preparation of the main catalyst component

[0040] The 500mL reactor was dried and fully purged with nitrogen. Then, 200mL of anhydrous hexane and 10g of magnesium diethoxy were added. The temperature was lowered to -10℃, and 10mL of a mixture of silicon tetrachloride and ethanol (molar ratio of silicon tetrachloride to ethanol 1:2) was added. The mixture was stirred for 0.5 hours. Then, 10mL of methyl zinc chloride was added, and the mixture was stirred for 0.5 hours. Next, 20mL of titanium tetrachloride was added, and the mixture was reacted for 0.5 hours. Finally, the temperature was raised to 100℃, and the mixture was stirred for 60 minutes. Stirring was then stopped, and the supernatant was collected after the solid particles settled. Another 200mL of anhydrous hexane was added, and the mixture was stirred for 0.5 hours. Stirring was then stopped, and the supernatant was collected after the solid particles settled. This process was repeated three times. Finally, the mixture was heated to 80℃ and dried under vacuum.

[0041] (2) Catalytic ethylene polymerization reaction

[0042] In a 2L polymerization reactor, 1L of hexane and 2.3mL of diethylethoxyaluminum solution (1M) were added, followed by about 10mg of main catalyst powder. The temperature was raised to 80℃, and ethylene was continuously introduced to carry out the polymerization reaction of ethylene. The total polymerization pressure was maintained at 1.0MPa. After the polymerization reaction was carried out for 2 hours, the temperature was lowered, the pressure was released, the material was discharged, and after drying, polyethylene powder was obtained. The activity of the catalyst was calculated after weighing.

[0043] The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0044] Example 2

[0045] The 10g magnesium diethoxy in the preparation of the main catalyst component was adjusted to 11g dibutylmagnesium, the silicon tetrachloride was adjusted to a mixture of silicon tetrachloride and ethanol in a 1:3 molar ratio, and the amount added was adjusted to 12mL. Other conditions were the same as in Example 1.

[0046] The 2.3 mL diethylethoxyaluminum solution (1 M) in the catalytic ethylene polymerization reaction was adjusted to 3.0 mL di-tert-butylethoxyaluminum solution (1 M), and other conditions were the same as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0047] Example 3

[0048] The 10 mL of methyl zinc chloride used in the preparation of the main catalyst component was changed to 20 mL of butyl zinc chloride, and other conditions were the same as in Example 1.

[0049] The 2.3 mL diethylethoxyaluminum solution (1 M) in the catalytic ethylene polymerization reaction was adjusted to 3.5 mL dipropylethoxyaluminum solution (1 M), and other conditions were the same as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0050] Example 4

[0051] The titanium tetrachloride in the preparation of the main catalyst component was adjusted from 20 mL to 30 mL, the silicon tetrachloride was adjusted to a mixture of silicon tetrachloride and isopropanol in a 1:3 molar ratio, and the methyl zinc chloride was adjusted from 10 mL to propyl zinc chloride 8 mL. Other conditions were the same as in Example 1.

[0052] The 2.3 mL diethylethoxyaluminum solution (1 M) in the catalytic ethylene polymerization reaction was adjusted to 3.0 mL dihexylethoxyaluminum solution (1 M), and other conditions were the same as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0053] Example 5

[0054] The 10 mL of methyl zinc chloride used in the preparation of the main catalyst component was adjusted to 10 mL of a mixture of diethyl zinc and zinc chloride in a 1:1 ratio, with other conditions the same as in Example 1.

[0055] The 2.3 mL diethylethoxyaluminum solution (1 M) in the catalytic ethylene polymerization reaction was adjusted to 5.0 mL dioctylethoxyaluminum solution (1 M), and other conditions were the same as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0056] Example 6

[0057] The 20 mL of titanium tetrachloride in the preparation of the main catalyst component was adjusted to 25 mL of a mixture of titanium tetrachloride and isooctyl alcohol in a 1:2 ratio, and the 10 mL of methyl zinc chloride was adjusted to 16 mL of tert-butyl zinc chloride. Other conditions were the same as in Example 1.

[0058] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0059] Example 7

[0060] The 10 mL of methyl zinc chloride used in the preparation of the main catalyst component was adjusted to 12 mL of a mixture of dipropyl zinc and zinc chloride in a 1:3 ratio, with other conditions the same as in Example 1.

[0061] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0062] Example 8

[0063] The 10 mL of methyl zinc chloride used in the preparation of the main catalyst component was adjusted to 15 mL of a mixture of di-tert-butyl zinc and zinc chloride in a 1:2 ratio, with other conditions the same as in Example 1.

[0064] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0065] Example 9

[0066] The 10g diethoxymagnesium in the preparation of the main catalyst component was adjusted to 10g magnesium chloride alcohol (MgCl2·2.5CH3CH2OH), and the 10mL methyl zinc chloride was adjusted to 15mL of a mixture of diethyl zinc and zinc chloride in a 1:2 ratio. Other conditions were the same as in Example 1.

[0067] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0068] Example 10

[0069] The 10g diethoxymagnesium in the preparation of the main catalyst component was adjusted to 10g magnesium chloride alcohol (MgCl2·2.0CH3CH2OH), and the 20mL titanium tetrachloride was adjusted to 25mL of a mixture of titanium tetrachloride and isooctyl alcohol in a 1:2 ratio. Other conditions were the same as in Example 1.

[0070] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0071] Example 11

[0072] The 10g diethoxymagnesium in the preparation of the main catalyst component was adjusted to 10g magnesium chloride alcohol (MgCl2·1.8CH3CH2OH), and the 10mL methyl zinc chloride was adjusted to 12mL of a mixture of di-tert-butyl zinc and zinc chloride in a 1:3 ratio. Other conditions were the same as in Example 1.

[0073] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0074] Comparative Example 1

[0075] The catalyst main component was prepared according to the method disclosed in patent CN201210402234. The specific preparation method is shown below.

[0076] (1) Preparation of the main catalyst component

[0077] A 500 mL reactor was dried and fully purged with nitrogen. Then, 4.0 g magnesium chloride, 50 mL toluene, 2.0 mL epichlorohydrin, and 3.0 mL tributyl phosphate were added sequentially. The mixture was heated to 50 °C with stirring and maintained at this temperature for 15 minutes. 6.0 mL ethanol was added, and the reaction was continued with stirring for another 15 minutes. The solution was cooled to -5 to 0 °C, and 30 mL titanium tetrachloride was added dropwise. Then, 10 mL of 1,2-dichlorohexane was added, and the solution was heated to 80 °C. The mother liquor was removed. Another 40 mL of 1,2-dichlorohexane was added, and the reaction was carried out at 60 °C for 30 minutes. After filtration, the mixture was washed four times with hexane and dried under vacuum to obtain the solid main catalyst component.

[0078] (2) Evaluation of ethylene polymerization

[0079] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0080] Comparative Example 2

[0081] The catalyst main component was prepared according to the method disclosed in patent US20090203857. The specific preparation method is shown below.

[0082] (1) Preparation of the main catalyst component

[0083] The 500 mL reactor was dried and fully purged with nitrogen. Then, 150 g of magnesium ethoxylate, 350 mL of hexane, 4.9 mL of silicon tetrachloride, and 4.9 mL of isopropanol were added sequentially. The mixture was heated to 70 °C with stirring and maintained for 2 hours. Then, 36 mL of titanium tetrachloride was added dropwise and the reaction was continued for 6 hours. After filtration, the mixture was washed four times with hexane and dried under vacuum to obtain the solid main catalyst component.

[0084] (2) Evaluation of ethylene polymerization

[0085] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0086] Comparative Example 3

[0087] The main catalyst component was prepared by referring to the method disclosed in patent CN201710725365.4 and making appropriate adjustments. The specific preparation method is shown below.

[0088] (1) Preparation of the main catalyst component

[0089] The 500 mL reactor was dried and fully purged with nitrogen. Then, 200 mL of anhydrous cyclohexane, 5 mL of dibutylmagnesium solution (Aldrich product, 1 M hexane solution containing 12 mol% triethylaluminum) and 1.1 mL of anhydrous tert-butane chloride were added. The temperature was raised to 50 °C, and then 0.05 mL of silicon tetrachloride was added. After reacting for 5 minutes, 0.1 mL of titanium tetrachloride was added. Finally, the temperature was raised to 100 °C, and the reaction was stirred for 5 minutes. After filtration, the mixture was washed four times with hexane and dried under vacuum to obtain the solid main catalyst component.

[0090] (2) Evaluation of ethylene polymerization

[0091] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0092] Comparative Example 4

[0093] The main catalyst component was prepared according to the method disclosed in patent CN201110332403.2. The specific preparation method is shown below.

[0094] (1) Preparation of the main catalyst component

[0095] In a reactor fully purged with high-purity N2, 0.042 mol anhydrous MgCl2, 0.0014 mol zinc powder, and 0.39 mol n-decane were added sequentially. 0.14 mol 2-ethylhexanol was added with stirring, the temperature was raised to 130°C and maintained for 1 hour. The solution was then cooled to -10°C, and 0.27 mol titanium tetrachloride was added dropwise, maintaining the temperature for 1 hour. The temperature was then raised to 110°C and maintained for 1 hour. After filtration, the solution was washed four times with hexane and dried under vacuum to obtain the solid catalyst component.

[0096] (2) Evaluation of ethylene polymerization

[0097] The catalytic ethylene polymerization reaction was carried out in the same manner as in Example 1. The melt strength and melt index of the polymer powder were tested, and the results are shown in Table 1.

[0098] Table 1

[0099]

[0100] As can be seen from the data in Table 1, the catalyst of this invention has high activity, and the polyethylene resin prepared under the same conditions has a larger melt index, indicating that the catalyst also has good hydrogen regulation performance. More importantly, the polyethylene prepared by the catalyst of this invention has significantly higher melt strength, making it more suitable for polyethylene processing methods such as blow molding.

[0101] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A main catalyst component for ethylene polymerization, characterized in that, include: At least one solid magnesium compound, at least one silicon chloride compound, at least one alkyl zinc chloride compound, and at least one titanium compound.

2. The main catalyst component for ethylene polymerization according to claim 1, characterized in that, The solid magnesium compound is such as general formula (Ⅰ)Mg(OR) 1 As shown in Figure 2, R 1 It is C2~C 20 The hydrocarbon group is a saturated or unsaturated straight chain, branched chain, or cyclic chain; Preferably, the solid magnesium compound includes at least one of magnesium diethoxy, magnesium dibutoxy, magnesium dipropoxy, and magnesium chloride alcohols.

3. The main catalyst component for ethylene polymerization according to claim 1, characterized in that, The silicon chloride compound is such as general formula (II)Si(OR) 2 ) n Cl 2-n As shown in the formula, R 2 It is C2~C 20 The hydrocarbon group is a saturated or unsaturated straight chain, branched chain, or cyclic chain, where 0 < n ≤ 2; Preferably, the silicon chloride compound includes the reaction product of silicon tetrachloride and a fatty alcohol; the molar ratio of the fatty alcohol to silicon tetrachloride is less than 4.0, the reaction temperature is between room temperature and 50°C, and the reaction time is 0.5-5 hours.

4. The main catalyst component for ethylene polymerization according to claim 1, characterized in that, The chloroalkyl zinc compound, such as general formula (Ⅲ)ZnR 3 As shown in Cl, R 3 It is C2~C 20 The hydrocarbon group is a saturated or unsaturated straight chain, branched chain, or cyclic chain; Preferably, the chloroalkyl zinc compound includes at least one of methyl zinc chloride, ethyl zinc chloride, butyl zinc chloride, propyl zinc chloride, tert-butyl zinc chloride, and benzyl zinc chloride.

5. The main catalyst component for ethylene polymerization according to claim 1, characterized in that, The titanium compound, such as general formula (Ⅳ)Ti(OR) 4 ) n Cl 4-n As shown in the formula, R 4 It is C2~C 20 The hydrocarbon group is a saturated or unsaturated straight chain, branched chain, or cyclic chain, and 0 ≤ n < 4; Preferably, the titanium compound comprises titanium tetrachloride or the reaction product of titanium tetrachloride and a fatty alcohol; the molar ratio of the fatty alcohol to titanium tetrachloride is less than 4.0, the reaction temperature is between room temperature and 100°C, and the reaction time is 0.5-5 hours.

6. A method for preparing the main catalyst component for ethylene polymerization according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Mix solid magnesium compounds and silicon chloride compounds to form reaction products; (2) The reaction product obtained in step (1) is reacted with a chloroalkyl zinc compound; (3) The reaction product obtained in step (2) is reacted with a titanium compound to obtain the main catalyst component.

7. The preparation method according to claim 6, characterized in that, The proportions of the components are such that, per mole of solid magnesium compound, the silicon chloride compound is 0.1 to 10 moles, preferably 0.5 to 5 moles, the chloroalkyl zinc compound is 0.05 to 3 moles, preferably 0.1 to 2 moles, and the titanium compound is 0.05 to 3 moles, preferably 0.1 to 2 moles.

8. The preparation method according to claim 6, characterized in that, The solid magnesium compound is at least one of alkoxy magnesium compound and magnesium chloride alcohol; The alkoxy magnesium compound is prepared by reacting magnesium powder with fatty alcohol; The preparation process of the magnesium chloride alcohol complex includes: dissolving magnesium chloride in a fatty alcohol, then transferring it to low-temperature hexane, stirring, dispersing, melting and solidifying to obtain the product; Preferably, an inert dispersant is added during the preparation of the solid magnesium compound. The inert dispersant is selected from at least one of hexaane, heptane, octane, toluene, xylene, 1,2-dichloroethane, chlorocyclohexane, chlorobenzene, and other hydrocarbons or halogenated hydrocarbons.

9. A catalyst for ethylene polymerization, characterized in that, It contains the following components: (a) The main catalyst component according to any one of claims 1-5; (b) An organoaluminum compound with the general formula AlR' n (OR”) 3-n wherein R' and R” are the same or different alkyl groups having 1 to 20 carbon atoms, and n is a number such that 1 < n < 3.

10. The catalyst for ethylene polymerization according to claim 9, characterized in that, The organoaluminum compounds include Al(OEt)Et2, (EtO)Al(iso-Bu)2, and (EtO)Al(n-C6H 13 2. (EtO)Al(n-C8H) 17 At least one of the following: )2; the molar ratio of the organoaluminum compound to titanium in the main catalyst component is 1 to 500.

11. The application of the catalyst according to any one of claims 9-10 in the slurry polymerization of ethylene, characterized in that, The catalyst catalyzes the polymerization of ethylene or the copolymerization of ethylene with α-olefins, wherein the α-olefin is at least one selected from olefin, butene, pentene, hexene, octene, and 4-methylpentene-1.

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