A metallocene catalyst

Abstract

The application discloses a metallocene catalyst, which comprises an inorganic carrier, polyethylene polycarboxylic acid ester and a cocatalyst methylaluminoxane (MAO) adsorbed on the inorganic carrier, and a metallocene compound combined with the MAO. The metallocene catalyst of the application can catalyze a polymerization reaction at a higher temperature, has high catalytic activity, and does not cause a stuck kettle in the polymerization reaction, and can produce ultrahigh melt flow rate polyethylene through hydrogen regulation in the polymerization process.

Description

Technical Field

[0001] This invention belongs to the field of metallocene catalyst technology, specifically relating to a supported metallocene catalyst for the preparation of meltblown polyethylene. Background Technology

[0002] Metallocene catalysts represent another major breakthrough following the Ziegler-Natta catalyst. Since Professor Kaminsky of the University of Hamburg, Germany, first discovered the high activity of the metallocene / MAO catalyst system for olefin polymerization in the early 1980s, this catalytic system has been a hot topic of research for scientists and is currently gradually replacing Zn catalysts. Metallocene compounds offer many advantages as catalysts for olefin polymerization. They exhibit higher activity, and the polymers produced have better homogeneity, tensile and tear strength, and impact resistance. Furthermore, the resulting polymers have uniform comonomer distribution, low soluble content, and good transparency. However, the polymers produced by directly using these metallocene compounds for olefin polymerization often have poor morphology, severe reactant adhesion to the reactor, and difficult product handling. These problems limit the industrial application of metallocene catalysts. A solution is to load metallocene catalysts onto inert porous particulate supports. Common supports include inorganic supports such as silica gel, magnesium chloride, alumina, clay, and molecular sieves, as well as polymer supports and inorganic / organic composite supports.

[0003] Metallocene catalysts, compared to traditional Ziegler-Natta catalysts, exhibit better hydrogen regulation performance and are more effective in preparing low-molecular-weight, high-melt-flow-rate polyolefins. Meltblown polypropylene can be used to produce ultrafine fibers, which are already widely used in masks and protective clothing. Polyethylene fibers, compared to polypropylene fibers, have better flexibility and thermal conductivity, making them more comfortable for use in masks and protective clothing. However, to date, there is no suitable preparation method for meltblown polyethylene resin, and no commercially available meltblown polyethylene resin products exist.

[0004] Meltblown polyethylene processing requires polyethylene with ultra-high melt flow rates. Current polymerization processes using Ziegler-Natta catalysts to produce ultra-high melt flow rate polyethylene require the addition of large amounts of hydrogen during polymerization, employing a hydrogen-modified method. However, large amounts of hydrogen lead to reduced catalyst activity and increased fine powder content in the polymer. Therefore, to produce ultra-high melt flow rate polyethylene products, it is essential to develop highly hydrogen-sensitive catalyst systems and corresponding polymerization processes.

[0005] Chinese Patent 201610393399.3 discloses a modified silica gel support, a supported metallocene catalyst, a preparation method, and a metallocene catalyst system. The metallocene loading process of this patent is as follows: (1) In the presence of a first solvent, manganese chloride is reacted with silica gel to obtain a manganese chloride / silica gel support; (2) In the presence of a second solvent, the manganese chloride / silica gel is reacted with an alkylaluminoxane; (3) In the presence of a third solvent, the modified silica gel support described in (2) is reacted with a metallocene complex. However, introducing manganese into the supported catalyst is a harmful substance in many application fields. Manganese chloride cannot react with or chemically adsorb MAO, and therefore does not increase the metallocene loading.

[0006] Chinese Patent 201710399926.6 discloses a metallocene polyethylene catalyst and its preparation method. The metallocene loading process of this patent is as follows: (1) SiO2 or modified SiO2 is in a fluidized state under nitrogen purging, heated and kept at a constant temperature, and then cooled to room temperature using a gradient cooling method to obtain a SiO2 support; (2) Under nitrogen protection, the SiO2 support is mixed and dispersed with a hydrocarbon solvent; (3) A co-catalyst is added and reacted with the SiO2 support at -20 to 200°C for 0.1 to 48 h; (4) A metallocene compound is added and reacted at -20 to 200°C for 0.1 to 48 h; (5) The reactants are washed with a solvent and dried at a higher temperature to obtain the product. However, the most conventional loading method has limited reaction capacity between MAO and silica gel due to the small number of reactive groups on the silica gel surface, resulting in limited ability of silica gel to support MAO and a relatively small ability to support metallocene, leading to low catalytic activity of the support.

[0007] Chinese Patent 201810800963.8 discloses a method for preparing a polypropylene catalyst. The metallocene-supported process in this patent is as follows: a heat-treated silica gel support is dispersed in a solvent, then alkylaluminum, boric acid, and water are added to react. After the reaction, a metallocene complex is added to continue the reaction. After the reaction is complete, the catalyst is washed and dried to obtain the supported catalyst. However, this process uses boric acid, water, and alkylaluminum to treat the silica gel, generating alkylaluminum in situ, which is then supported on the silica gel. Since the reaction between alkylaluminum and water is a vigorous and rapid reaction, the product structure is strongly dependent on the reaction rate. The MAO structure prepared by this method is poor, with excessive gelation, which is detrimental to loading.

[0008] Chinese Patent 99801772.8 discloses a polyethylene nonwoven fabric and a nonwoven laminate made therefrom. It is prepared by melt-blowing using a resin composition containing polyethylene (A) with a weight-average molecular weight of 21,000-45,000 and a melt flow rate of 15-250 g / 10 min measured according to ASTM D1238 at 190°C and a load of 2.16 kg, and polyethylene wax (B) with a weight-average molecular weight below 15,000. The weight ratio of polyethylene (A) to polyethylene wax (B) is 30 / 70-70 / 30, and the fiber fineness of the polyethylene nonwoven fabric is below 5 μm. However, by mixing high melt flow rate polyethylene and polyethylene wax, a resin with lower viscosity is obtained for melt-blowing processing, but the preparation method of high melt flow rate polyethylene is not clearly defined.

[0009] Generally, the metallocene supported process uses MAO to treat silica gel and then chemically adsorbs metallocene compounds. The supported catalyst prepared by this process has a low content of metallocene compounds and low catalytic activity. Summary of the Invention

[0010] The purpose of this invention is to provide a metallocene catalyst that can catalyze polymerization reactions at higher temperatures, has high catalytic activity, does not stick to the reactor during polymerization, and can produce polyethylene with ultra-high melt flow rate by hydrogen adjustment during the polymerization process.

[0011] To achieve the above objectives, the present invention provides a metallocene catalyst comprising: an inorganic support, a polyethylene polycarboxylic acid ester adsorbed on the inorganic support and a cocatalyst methylaluminoxane (MAO), and a metallocene compound bound to MAO.

[0012] In the metallocene catalyst of the present invention, the inorganic support accounts for 70%-90% by weight.

[0013] In the metallocene catalyst of the present invention, the polyethylene polycarboxylic acid ester accounts for 0.05-1.5% by weight.

[0014] In the metallocene catalyst of the present invention, the MAO accounts for 10%-25% by weight.

[0015] The metallocene catalyst of the present invention comprises a metallocene compound in an amount of 1.3%-4.2% by weight.

[0016] The metallocene catalyst of the present invention uses at least one inorganic support selected from silica gel, alumina, and molecular sieves, preferably silica gel. The particle size range of the inorganic support is 15-120 μm.

[0017] The metallocene catalyst of the present invention comprises a polyethylene polycarboxylic acid ester with the general formula -(CH2CH2)n-(CH2CHCOOR)m-, a molecular weight of 1000-20000 g / mol, wherein the molar content of the carboxylic acid ester is 2-15%, R is a C1-C4 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n is an integer greater than or equal to 1, and m is an integer greater than or equal to 1.

[0018] The metallocene catalyst of the present invention comprises a substituted dicenocene compound of a Group 4 metal, having the following structure:

[0019]

[0020] R1 to R5 may be the same or different, and are independently selected from H or C1-C4 alkyl groups; M is titanium, zirconium or hafnium.

[0021] Typically, the metallocene compound is at least one of titanium dichlorodicyclopentadiene, zirconium dichlorodicyclopentadiene, hafnium dichlorodicyclopentadiene, di(n-butylcendichloride), and di(n-propylcendichloride).

[0022] This invention also discloses a method for preparing a metallocene catalyst, which includes the following steps:

[0023] (1) The inorganic carrier is subjected to high-temperature treatment under nitrogen protection;

[0024] (2) The inorganic carrier after high temperature treatment in step (1) is reacted with polyethylene polycarboxylate and MAO under solvent stirring conditions, and then washed, filtered and dried to obtain a supported carrier loaded with polyethylene polycarboxylate and MAO.

[0025] (3) The supporting support and homogeneous metallocene catalyst from step (2) are reacted and loaded in a solvent under stirring, and then washed, filtered and dried to obtain the metallocene catalyst.

[0026] In the preparation method of the metallocene catalyst of the present invention, in step (1), the high temperature treatment is 400℃-600℃ and the treatment time is 4-6h.

[0027] In the preparation method of the metallocene catalyst of the present invention, in step (2), the reaction temperature is 20℃-120℃ and the reaction time is 2-4h.

[0028] In the preparation method of the metallocene catalyst of the present invention, in step (3), the temperature of the reaction loading is 40-80℃ and the time is 2-4h.

[0029] The present invention also provides a method for preparing polyethylene resin, the method comprising the following steps: adding a metallocene catalyst and activator, ethylene and comonomer, and a molecular weight regulator to a polymerization reactor to carry out a polymerization reaction to obtain a polyethylene copolymer; and degassing and granulating the polyethylene copolymer to obtain a polyethylene resin.

[0030] The method for preparing polyethylene resin of the present invention includes an activator that is at least one of alkylaluminum and methylaluminoxane; wherein the molar ratio of aluminum in the activator to the metal in the metallocene catalyst is 50-2000.

[0031] The method for preparing polyethylene resin of the present invention wherein the comonomer is at least one of propylene, butene, and hexene; and the comonomer accounts for less than 20% of the total molar proportion of polymeric monomers (ethylene plus comonomer).

[0032] In the method for preparing polyethylene resin of the present invention, the molecular weight regulator is hydrogen, and the molar proportion of hydrogen to ethylene does not exceed 20 mol%.

[0033] The method for preparing polyethylene resin of the present invention wherein the polymerization reaction temperature is 70-100℃, preferably 70-90℃, the reaction time is 30-150 min, and the reaction pressure is 0.5-2.0 MPa.

[0034] In the preparation method of polyethylene resin of the present invention, antioxidants and other components may be added as needed during the granulation process.

[0035] The present invention further provides a polyethylene resin, wherein the melt flow rate of the polyethylene resin is 200-950 g / 10 min and the melting point is 115-135 °C.

[0036] When the metallocene catalyst of the present invention is used for ethylene polymerization, the melt flow rate of the resulting polyethylene resin can reach up to 950 g / 10 min when the amount of hydrogen added is less than 10% of the ethylene content.

[0037] The metallocene catalyst of this invention features high catalytic activity and high sensitivity to hydrogen regulation. Polymers prepared using this catalyst exhibit adjustable melt flow rates and non-stick properties. The metallocene catalyst of this invention incorporates polyethylene polycarboxylic acid esters as modifiers, allowing the inorganic support to load more MAO, and consequently more metallocene compounds, thus improving catalytic activity. The preparation temperature of the metallocene catalyst of this invention is close to the polymerization temperature. During polymerization, the metallocene catalyst is resistant to desorption and will not revert to a homogeneous catalyst due to the detachment of the metallocene from the inorganic support. During the catalytic polymerization reaction, the metallocene catalyst of this invention allows for wide-range controllable adjustment of the polymer melt flow rate through hydrogen regulation, resulting in polyethylene with ultra-high melt flow rates. Polyethylene with ultra-high melt flow rates can be used for meltblown processing to prepare meltblown fibers. The metallocene catalyst of this invention can prepare polyethylene with ultra-high melt flow rates by adding a small amount of hydrogen during the catalytic polymerization reaction. Detailed Implementation

[0038] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0039] Source of raw materials or equipment:

[0040] Toluene: Analytical grade, produced by Beijing Chemical Industry, dehydrated and filtered through 3A molecular sieve, with a water content of less than 10 ppm;

[0041] n-Hexane: Analytical grade, produced by Beijing Chemical Industry, dehydrated and filtered through 3A molecular sieve, with a water content of less than 10 ppm;

[0042] Ethylene: Polymer grade, supplied by Beijing Huatong Precision Gas & Chemical Co., Ltd.

[0043] Propylene: Polymer grade, supplied by Beijing Huatong Precision Gas Chemical Co., Ltd.

[0044] 1-Hexene: 99%, Aladdin Chemical Reagents Website;

[0045] Hydrogen: 99.999%, Beijing Huatong Precision Gas & Chemical Co., Ltd.

[0046] Polyethylene polycarboxylate: Industrial grade, DuPont, USA;

[0047] Methylaluminoxane (MAO): 1.5 mol / L toluene solution, manufactured by Arbemarle;

[0048] SiO2 (955 / 2408) silicone: Imported from the USA;

[0049] Alumina: 99.9%, Beijing Innocare Technology Co., Ltd.

[0050] Bis(n-butylcyclopentadienyl)zirconium dichloride: laboratory synthesis.

[0051] Evaluation and analysis methods:

[0052] Polyethylene thermal properties testing: Performed on a TA Q2000 differential scanning calorimeter (DSC) from the USA. Sample preparation: Weigh approximately 2-5 mg of sample using an electronic balance. Under nitrogen protection, heat the sample from 10°C to 200°C at a rate of 10°C / min, hold at 200°C for 5 min, then cool to 30°C at a rate of 10°C / min, hold at 30°C for 5 min, and finally heat to 200°C at a rate of 10°C / min. The results of the melting and crystallization processes are then derived.

[0053] Melt flow rate (MFR) test: The test was conducted using a melt flow rate tester from Jinjian Company. The experimental conditions were 2.16 kg and 190 °C.

[0054] Example 1:

[0055] Take 20g of 955 silica gel (90% of the particles have a particle size range of 20-70 micrometers), calcine it at 500℃ for 4 hours in a tube furnace under N2 atmosphere, cool it under nitrogen atmosphere, transfer it to a desiccator, dry it and store it separately under nitrogen.

[0056] 2g of heat-treated silica gel (type 955) was mixed with 20mL of MAO toluene solution (10wt%) and 0.2g of polyethylene polycarboxylic acid ester (molecular weight 4000g / mol) with a methyl acrylate content of 3mol%. The mixture was magnetically stirred at 500rpm and refluxed at room temperature for 3h. After cooling to room temperature, excess MAO was washed with dehydrated toluene at a ratio of 10 (1g silica gel to 10g toluene) twice. Excess toluene was then washed with dehydrated n-hexane at a ratio of 10 (1g silica gel to 10g n-hexane) twice. The mixture was then vacuum dried at room temperature for 4h to obtain MAO-supported silica gel sMAO.

[0057] Take 80 mg of metallocene catalyst monomer (bis(n-butylcyclopentadienyl)zirconium dichloride) at a ratio of 4 mol% (1 g silica gel 40 mg metallocene monomer), mix it with 20 mL of toluene at 80 °C for 2 h, and stir magnetically at 500 rpm to obtain solution B;

[0058] 2g of loaded silica gel sMAO and solution B were thoroughly mixed at 80°C under a nitrogen atmosphere for 3 hours, and then cooled to room temperature.

[0059] Excess catalyst monomer was washed twice with dehydrated toluene at a ratio of 10 (1g silica gel to 10g toluene). Then, excess toluene was washed twice with dehydrated n-hexane at a ratio of 10 (1g silica gel to 10g n-hexane). The mixture was then vacuum dried at room temperature for 4 hours to obtain the supported metallocene catalyst SMS-1.

[0060] Example 2:

[0061] Take 20g of type 2408 silica gel (90% of the particles have a particle size range of 30-70μm), calcine it at 500℃ for 4h in a tube furnace under N2 atmosphere, cool it under nitrogen atmosphere, transfer it to a desiccator, dry it and store it separately under nitrogen.

[0062] 1 g of heat-treated silica gel was mixed with 20 mL of MAO toluene solution (10 wt%) and 0.1 g of polyethylene polycarboxylic acid ester (molecular weight 3000 g / mol) with a methyl acrylate content of 5 mol%. The mixture was magnetically stirred at 500 rpm and refluxed at 50 °C for 4 h. After cooling to room temperature, excess MAO was washed with dehydrated toluene at a ratio of 10 (1 g silica gel 10 g toluene) twice. Excess toluene was then washed with dehydrated n-hexane at a ratio of 10 (1 g silica gel 10 g n-hexane) twice. The mixture was then vacuum dried at room temperature for 4 h to obtain MAO-supported silica gel sMAO.

[0063] Take 40 mg of metallocene catalyst monomer (bis(n-butylcyclopentadienyl)zirconium dichloride) at a ratio of 4% (1 g silica gel 40 mg metallocene monomer), and dissolve and mix it with 20 mL of toluene at 50 °C and 500 rpm with magnetic stirring to obtain solution B;

[0064] sMAO and B were magnetically stirred at 500 rpm in a N2 atmosphere at 50°C for 4 hours to ensure thorough mixing, and then cooled to room temperature.

[0065] Excess catalyst monomer was washed twice with dehydrated toluene at a ratio of 10 (1g silica gel 10g toluene). Then, excess toluene was washed twice with dehydrated n-hexane at a ratio of 10 (1g silica gel 10g n-hexane). The mixture was then vacuum dried at room temperature for 4 hours to obtain the supported metallocene catalyst SMS-2.

[0066] Comparative Example 3:

[0067] Take 20g of aluminum oxide (specific surface area 300m²) 2 / g), calcined at 500℃ for 4h in a tube furnace under N2 atmosphere, cooled under nitrogen atmosphere, transferred to a desiccator, dried and stored separately under nitrogen;

[0068] Take 1g of heat-treated alumina and mix it with 20mL of MAO toluene solution (10wt%). Stir magnetically at 500rpm and reflux at 50℃ for 4h. Cool to room temperature and wash the excess MAO with dehydrated toluene at a ratio of 10 (1g alumina to 10g toluene). Wash twice consecutively. Then wash the excess toluene with dehydrated n-hexane at a ratio of 10 (1g alumina to 10g n-hexane). Wash twice consecutively. Dry under vacuum at room temperature for 4h to obtain MAO-supported alumina aMAO.

[0069] Take 40 mg of metallocene catalyst monomer (bis(n-butylcyclopentadienyl)zirconia) at a ratio of 4% (1 g alumina 40 mg metallocene monomer), and dissolve and mix it with 20 mL of toluene at 500 rpm under magnetic stirring at 50 °C to obtain solution B;

[0070] aMAO and B were magnetically stirred at 500 rpm in a N2 atmosphere at 50°C for 4 hours to ensure thorough mixing, and then cooled to room temperature.

[0071] Excess catalyst monomer was washed twice with dehydrated toluene at a ratio of 10 (1g alumina to 10g toluene). Then, excess toluene was washed twice with dehydrated n-hexane at a ratio of 10 (1g alumina to 10g n-hexane). The catalyst was then dried under vacuum at room temperature for 4 hours to obtain the supported metallocene catalyst SMS-3.

[0072] Example 4:

[0073] Take 20g of aluminum oxide (specific surface area 350m²) 2 / g), calcined at 500℃ for 4h in a tube furnace under N2 atmosphere, cooled under nitrogen atmosphere, transferred to a desiccator, dried and stored separately under nitrogen;

[0074] Take 1g of heat-treated alumina and mix it with 20mL of MAO toluene solution (10wt%) and 0.1g of polyethylene polycarboxylic acid ester (molecular weight 3200g / mol) with 7% methyl acrylate content. Stir magnetically at 500rpm and reflux at 50℃ for 4h. Cool to room temperature and wash the excess MAO with dehydrated toluene at a ratio of 10 (1g alumina 10g toluene). Wash twice consecutively. Then wash the excess toluene with dehydrated n-hexane at a ratio of 10 (1g alumina 10g n-hexane). Wash twice consecutively. Vacuum dry at room temperature for 4h to obtain MAO-supported alumina aMAO.

[0075] Take 40 mg of metallocene catalyst monomer (bis(n-butylcyclopentadienyl)zirconia) at a ratio of 4% (1 g alumina 40 mg metallocene monomer), and dissolve and mix it with 20 mL of toluene at 500 rpm under magnetic stirring at 50 °C to obtain solution B;

[0076] aMAO and B were magnetically stirred at 500 rpm in a N2 atmosphere at 50°C for 4 hours to ensure thorough mixing, and then cooled to room temperature.

[0077] Excess catalyst monomer was washed twice with dehydrated toluene at a ratio of 10 (1g alumina to 10g toluene). Then, excess toluene was washed twice with dehydrated n-hexane at a ratio of 10 (1g alumina to 10g n-hexane). The catalyst was then dried under vacuum at room temperature for 4 hours to obtain the supported metallocene catalyst SMS-4.

[0078] Comparative Example 5:

[0079] Weigh 80 mg of catalyst (SMS-3) into a catalyst tube under nitrogen protection.

[0080] Add 250 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0081] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 0.94%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0082] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0083] The catalyst activity was 1500 g PE / g cat, the resulting polymer had a melting point of 135.2 °C, and a melt flow rate of 110 g / 10 min (190 °C / 2.16 kg).

[0084] Example 6:

[0085] Weigh 80 mg of catalyst (SMS-1) into a catalyst tube under nitrogen protection.

[0086] Add 250 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0087] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 0.94%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0088] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0089] The catalyst activity was 3800 gPE / gcat, the resulting polymer had a melting point of 128.4℃, and a melt flow rate of 230 g / 10 min (190℃ / 2.16 kg).

[0090] Example 7:

[0091] Weigh 80 mg of catalyst (SMS-2) into a catalyst tube under nitrogen protection.

[0092] Add 250 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0093] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 0.94%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0094] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0095] The catalyst activity was 4000 gPE / gcat, the resulting polymer had a melting point of 125.2℃, and a melt flow rate of 370 g / 10 min (190℃ / 2.16 kg).

[0096] Example 8:

[0097] Weigh 80 mg of catalyst (SMS-2) into a catalyst tube under nitrogen protection.

[0098] Add 250 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0099] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 1.9%, polymerization was carried out at 90℃ with mechanical stirring at 500 rpm, and the polymerization time was 1 hour.

[0100] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0101] The catalyst activity was 3500 gPE / gcat, the resulting polymer had a melting point of 126℃, and a melt flow rate of 540 g / 10 min (190℃ / 2.16 kg).

[0102] Example 9:

[0103] Weigh 80 mg of catalyst (SMS-2) into a catalyst tube under nitrogen protection.

[0104] Add 250 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0105] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 2.54%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0106] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0107] The catalyst activity was 2300 gPE / gcat, the resulting polymer had a melting point of 126.5℃, and a melt flow rate of 720 g / 10 min (190℃ / 2.16 kg).

[0108] Example 10:

[0109] Weigh 150 mg of catalyst (SMS-4) into a catalyst tube under nitrogen protection.

[0110] Add 650 mL of n-hexane, 15 mL of 1-hexene, and 5 mL of MAO toluene solution (1.5 M) to a 1 L glass reactor. Stir mechanically at 500 rpm and heat to 90 °C.

[0111] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 0.94%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0112] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0113] The catalyst activity was 3450 gPE / gcat, the resulting polymer had a melting point of 121.6℃, and a melt flow rate of 510 g / 10 min (190℃ / 2.16 kg).

[0114] Example 11:

[0115] Weigh 150 mg of catalyst (SMS-3) into a catalyst tube under nitrogen protection.

[0116] Add 650 mL of n-hexane, 25 mL of 1-hexene, and 5 mL of MAO toluene solution (1.5 M) to a 1 L glass reactor. Stir mechanically at 500 rpm and heat to 90 °C.

[0117] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 0.94%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0118] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0119] The catalyst activity was 3900 gPE / gcat, the resulting polymer had a melting point of 118.7℃, and a melt flow rate of 660 g / 10 min (190℃ / 2.16 kg).

[0120] Example 12:

[0121] Weigh 150 mg of catalyst (SMS-4) into a catalyst tube under nitrogen protection.

[0122] Add 650 mL of n-hexane, 25 mL of 1-hexene, and 5 mL of MAO toluene solution (1.5 M) to a 1 L glass reactor. Stir mechanically at 500 rpm and heat to 90 °C.

[0123] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 1.9%, polymerization was carried out at 90℃ with mechanical stirring at 500 rpm, and the polymerization time was 1 hour.

[0124] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0125] The catalyst activity was 3300 gPE / gcat, the resulting polymer had a melting point of 117℃, and a melt flow rate of 830 g / 10 min (190℃ / 2.16 kg).

[0126] Example 13:

[0127] Weigh 150 mg of catalyst (SMS-4) into a catalyst tube under nitrogen protection.

[0128] Add 650 mL of n-hexane, 25 mL of 1-hexene, and 5 mL of MAO toluene solution (1.5 M) to a 1 L glass reactor. Stir mechanically at 500 rpm and heat to 90 °C.

[0129] A catalyst was added, a certain amount of hydrogen gas was introduced, and ethylene gas was introduced. The pressure in the reactor reached 0.5 MPa, the hydrogen / ethylene partial pressure ratio was 2.54%, and polymerization was carried out at 90℃ with mechanical stirring at 500 rpm for 1 hour.

[0130] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0131] The catalyst activity was 2700 gPE / gcat, the resulting polymer had a melting point of 115℃, and a melt flow rate of 950 g / 10 min (190℃ / 2.16 kg).

[0132] Example 14:

[0133] Weigh 150 mg of catalyst (SMS-4) into a catalyst tube under nitrogen protection.

[0134] Ethylene and propylene are mixed evenly in a mixing tank at a volume ratio of ethylene / propylene = 5 / 95.

[0135] Add 650 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0136] A catalyst was added, a certain amount of hydrogen was introduced, and an ethylene / propylene mixed gas was introduced. The pressure in the reactor reached 0.5 MPa, the partial pressure ratio of hydrogen to ethylene / propylene mixed gas was 1.9%, polymerization was carried out at 90℃ with mechanical stirring at 500 rpm, and the polymerization time was 1 hour.

[0137] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0138] The catalyst activity was 2900 gPE / gcat, the resulting polymer had a melting point of 120.2℃, and a melt flow rate of 580 g / 10 min (190℃ / 2.16 kg).

[0139] Example 15:

[0140] Weigh 150 mg of catalyst (SMS-4) into a catalyst tube under nitrogen protection.

[0141] Ethylene and propylene are mixed evenly in a mixing tank at a volume ratio of ethylene / propylene = 15 / 85.

[0142] Add 650 mL of n-hexane to a 1 L glass reactor, add 5 mL of MAO toluene solution (1.5 M), stir mechanically at 500 rpm, and heat to 90 °C.

[0143] A catalyst was added, a certain amount of hydrogen was introduced, and an ethylene / propylene mixed gas was introduced. The pressure in the reactor reached 0.5 MPa, the partial pressure ratio of hydrogen to ethylene / propylene mixed gas was 1.9%, polymerization was carried out at 90℃ with mechanical stirring at 500 rpm, and the polymerization time was 1 hour.

[0144] The polymerization reactor is cooled to room temperature and depressurized to atmospheric pressure. The polymer and hexane solvent are then poured out, filtered, and dried to obtain the polymer.

[0145] The catalyst activity was 3600 gPE / gcat, the resulting polymer had a melting point of 117.9℃, and a melt flow rate of 650 g / 10 min (190℃ / 2.16 kg).

[0146] Comparative Example 5 is a comparative example of catalyst polymerization, and Examples 6-15 are examples of catalyst polymerization. A summary is shown in Table 1.

[0147] Table 1 Results of catalyst polymerization experiments

[0148]

[0149]

[0150] As shown in Table 1, the above examples demonstrate that adding polyethylene polycarboxylate to the metallocene catalyst of the present invention during the loading process can improve the catalyst activity. The metallocene catalyst can achieve a wide range of controllable adjustment of the polyethylene melt index by adjusting the hydrogen / ethylene partial pressure ratio within a very small range while ensuring high catalyst activity. The metallocene catalyst prepared by polyethylene polycarboxylate can achieve controllable adjustment of the polymer's melting point and melt flow rate (melt index) by adjusting the hydrogen partial pressure ratio, the type of comonomer, and the proportion of comonomers, so as to meet the requirements of the meltblown process for polymer raw materials.

[0151] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A metallocene catalyst, characterized in that, include: Inorganic carrier, polyethylene polycarboxylic acid ester and cocatalyst methylaluminoxane (MAO) adsorbed on inorganic carrier, and metallocene compounds combined with MAO; The general formula of the polyethylene polycarboxylic acid ester is -(CH2CH2)n-(CH2CHCOOR)m-, and its molecular weight is 1000-20000 g / mol, wherein the molar content of the carboxylic acid ester is 2-15%, R is a C1-C4 alkyl group, n is an integer greater than or equal to 1, and m is an integer greater than or equal to 1. The inorganic carrier accounts for 70%-90% by weight; The polyethylene polycarboxylic acid ester comprises 0.05-1.5% by weight; The MAO content is 10%-25% by weight. The metallocene compound comprises 1.3%-4.2% by weight.

2. The metallocene catalyst according to claim 1, characterized in that, The inorganic carrier is at least one of silica gel, alumina, and molecular sieve; the particle size range of the inorganic carrier is 15-120 μm.

3. The metallocene catalyst according to claim 1, characterized in that, R is one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl.

4. The metallocene catalyst according to claim 1, characterized in that, The metallocene compound is a substituted dicenocene compound of a Group 4 metal, having the following structure: R1 to R5 may be the same or different, and are independently selected from H or C1-C4 alkyl groups; M is titanium, zirconium or hafnium.

5. The metallocene catalyst according to claim 4, characterized in that, The metallocene compound is at least one of titanium dichlorodicyclopentadiene, zirconium dichlorodicyclopentadiene, hafnium dichlorodicyclopentadiene, di(n-butylcendichloride), and di(n-propylcendichloride).

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