Catalyst of polypropylene for lithium battery diaphragm, propylene polymer and preparation method of propylene polymer

Abstract

The invention discloses a polypropylene catalyst for a lithium battery diaphragm, a propylene polymer and a preparation method of the propylene polymer. The catalyst comprises a titanium-containing main catalyst and a co-catalyst, the main catalyst comprises a magnesium halide alcohol adduct carrier, titanium halide and an internal electron donor, the internal electron donor is a diphosphine compound with a molecular skeleton of a thiophene structure as shown in a general formula (I): # imgabs0 #, R1, R2, R3 and R4 are the same or different and are independently selected from a hydrogen atom, a C1-C20 straight chain or branched chain alkyl group, a C3-C20 cycloalkyl group, a C6-C20 aryl group, a C7-C20 aralkyl group and a C7-C20 alkoxy aryl group, and R1, R2, R3 and R4 are selected from hydrogen atoms, C1-C20 straight chain or branched chain alkyl groups, C3-C20 cycloalkyl groups, C6-C20 aryl groups and C7-C20 alkoxy aryl groups. The cocatalyst is a mixture of alkyl halide or halogenated naphthenic modified aluminoxane and an alkyl aluminum compound. The catalyst provided by the invention shows relatively high catalytic activity under a high-temperature polymerization condition, and meanwhile, polypropylene with a certain beta crystal content is generated in situ.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to a catalyst for polypropylene for lithium battery diaphragm, a propylene polymer and a preparation method thereof. Background Art

[0002] Lithium battery separator is a thin film material with a microporous structure, generally 8 to 40 μm thick. Its main function in the battery is to isolate the positive and negative electrodes of the battery to prevent short circuits, while ensuring that lithium ions pass through the microporous channels normally during the charging and discharging process to ensure the normal operation of the battery. The core process for preparing lithium battery separators is microporous preparation technology. The production process of polyolefin-based separators is mainly divided into dry process and wet process. Different processes use different raw materials. The raw material corresponding to the dry process is mainly polypropylene.

[0003] The dry process for preparing diaphragms is also called the melt-stretching (MSCS) process. Its preparation principle is that the polymer melt crystallizes under a high stress field to form a lamellar structure perpendicular to the extrusion direction and arranged in parallel, and then undergoes heat treatment to obtain a hard elastic material. After being stretched again, the lamellar crystals are separated to form a large number of microporous structures, and then the microporous membrane is obtained by heat setting. According to the different stretching directions, the dry process is divided into two processes: dry uniaxial stretching and dry biaxial stretching. The dry biaxial stretching process is a process with independent intellectual property rights developed by the Institute of Chemistry of the Chinese Academy of Sciences in the early 1990s. The dry biaxial stretching process is to add a β-nucleating agent with a nucleating effect to polypropylene, and utilize the density difference between different phases of polypropylene to form micropores through crystal transformation during the stretching process. Compared with dry uniaxial stretching, dry biaxial stretching improves the strength of the diaphragm in the transverse direction, and has the characteristics of good air permeability, high permeability and absorbency. In addition, the production process of the dry biaxial stretching process is continuous, the process is simple, and the production cost is lower than that of dry uniaxial stretching and wet process.

[0004] The dry biaxial stretching process requires the addition of a β-nucleating agent to the raw material polypropylene to achieve microporous forming during the stretching process. For example, Chinese patent document CN108346764A discloses a method for preparing a dry biaxially stretched lithium battery microporous diaphragm, in which homopolymer polypropylene and a β-crystal nucleating agent are mixed and extruded at high temperature through a twin-screw extruder, and a casting is obtained by casting. The casting is subjected to biaxial synchronous stretching and then heat-setting treatment to form a diaphragm with a microporous structure. However, the addition of a β-nucleating agent to homopolymer polypropylene not only increases the production cost, but also increases the ash introduced by the β-nucleating agent. Excessive ash content in the raw material will cause many problems such as easy film breakage, easy aging, and increased surface crystal points during the production process.

[0005] Supported Ziegler-Natta (ZN) catalyst is one of the most important industrial catalysts for synthesizing propylene polymers. In the polymerization process, ZN catalyst is usually used as the main catalyst, alkyl aluminum (such as Et3AL, etc.) is used as the co-catalyst, and propylene polymerization is carried out at a temperature of 70-80°C, which can obtain a higher polymerization activity, and the resulting polymer has a higher isotactic index. However, there are two problems: 1. When the polypropylene produced by the existing ZN catalyst is used to prepare lithium battery separators, it is still necessary to add a β-nucleating agent to the polypropylene; 2. After increasing the polymerization temperature, the above conventional reaction will cause the polymerization activity of the catalyst, the isotactic index of the polymer, and the molecular weight to drop sharply. This is because the main function of the co-catalyst alkyl aluminum is to alkylate the active center, but a reduction reaction will also occur at the same time as the alkylation. The increase in polymerization temperature will promote the reduction reaction, and more active centers Ti 3+ Over-reduced to Ti 2+ , the deactivation of the active center of the catalyst is accelerated, thereby reducing the polymerization reaction rate, resulting in a decrease in the polymerization activity of the system, an increase in the amount of oligomers generated, and a low isotactic index of the final polymer.

[0006] For example, Chinese patent document CN1887918A discloses a catalyst, which introduces a mixture of aluminoxane and alkyl aluminum as a cocatalyst during the polymerization process. When the propylene polymerization temperature is 100°C, the catalyst system has high activity and stereospecificity, and the isotactic index of the polymer reaches up to 95%. However, when the polypropylene prepared by the catalyst is used to prepare lithium battery separators, a β-nucleating agent still needs to be added, and the polymerization activity and stereospecificity of the catalyst need to be further improved.

[0007] Chinese patent document CN109517099A discloses an external electron donor, an olefin polymerization catalyst system and its application, wherein the olefin polymerization catalyst system comprises a titanium catalyst, an alkyl aluminum compound and an external electron donor, wherein the external electron donor composition comprises halogenated hydrocarbons, aliphatic carboxylates and alkoxysilanes. In this scheme, halogenated hydrocarbons, aliphatic carboxylates and alkoxysilanes are combined to form a composite external electron donor composition, which can greatly improve the polymerization activity of propylene at conventional polymerization temperatures while ensuring low grayness of olefin polymerization. However, its polymerization activity is low under the condition of a temperature higher than 80°C, and the normalized activity at 100°C in its embodiment is <10.0kgPP / gCat.h; moreover, when the polypropylene prepared by the catalyst is used to prepare lithium battery separators, a β-nucleating agent still needs to be added. Summary of the invention

[0008] In view of the problems existing in the prior art and the direction to be improved, the present invention provides a catalyst for polypropylene for lithium battery separators, wherein the catalyst composition contains a bisphosphine compound with a thiophene molecular skeleton and a functional group, and the co-catalyst is a mixture of aluminoxane modified with a haloalkane and an alkyl aluminum compound. The catalyst is used for high-temperature polymerization or copolymerization of propylene, which can ensure the catalytic activity and stereoregularity of the catalyst system on the one hand, and can generate polypropylene with a certain β crystal content in situ on the other hand, which is used for preparing dry biaxially stretched lithium battery separators, solving the problem that a β nucleating agent needs to be added to the raw material polypropylene during the production process of the existing dry biaxially stretched lithium battery separators, which not only reduces the introduction of separator ash, but also reduces the production cost.

[0009] To achieve the above object, the present invention provides a catalyst for polypropylene for lithium battery separator, the catalyst comprising a titanium-containing main catalyst and a co-catalyst, wherein:

[0010] The main catalyst is a titanium catalyst supported by a magnesium halide alcoholate carrier, comprising a magnesium halide alcoholate carrier, a titanium halide and an internal electron donor, wherein the internal electron donor is a diphosphine compound having a molecular skeleton of a thiophene structure and having a general formula (I):

[0011]

[0012]

[0013] wherein R1, R2, R3 and R4 are the same or different and are independently selected from a hydrogen atom, a C1-C20 straight or branched alkyl group, a C3-C20 cycloalkyl group, a C6-C20 aryl group, a C7-C20 aralkyl group and a C7-C20 alkoxyaryl group; P is phosphorus; S is sulfur;

[0014] The cocatalyst is a mixture of aluminoxane modified by alkyl halide or cyclohalide and an alkyl aluminum compound.

[0015] The present invention does not particularly limit the magnesium halide alcoholate carrier, and the magnesium halide alcoholate carrier is selected from at least one of a magnesium chloride ethanol adduct carrier, a magnesium bromide ethanol adduct carrier, a magnesium chloride isopropanol adduct carrier, a magnesium chloride n-butanol adduct carrier, and a magnesium chloroethoxymethanol adduct carrier, preferably a magnesium chloride ethanol adduct carrier.

[0016] The present invention does not particularly limit the titanium halide, which is a liquid compound completely soluble in a non-polar solvent at an application temperature (e.g., -50 to 130° C.), selected from at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, triethoxytitanium monochloride, diethoxytitanium dichloride, triethoxytitanium trichloride, and titanium trichloride, preferably titanium tetrachloride.

[0017] Optionally, in the catalyst of polypropylene for lithium battery separator provided by the present invention, the internal electron donor is selected from 3,4-bis(dimethylphosphino)-thiophene, 3,4-bis(diethylphosphino)-thiophene, 3,4-bis(di-n-propylphosphino)-thiophene, 3,4-bis(diisopropylphosphino)-thiophene, 3,4-bis(dimethylphosphino)-2-(4-ethylphenyl)thiophene, 3,4-bis(di-n-butylphosphino)-thiophene, 3,4-bis(diisobutylphosphino)-thiophene, 3,4-bis(di-n-pentylphosphino)-thiophene, 3,4-bis(dicyclopentylphosphino)-thiophene, 3,4-bis(di-n-hexylphosphino)-thiophene, 3,4-bis(dicyclohexylphosphino)-thiophene, 3,4-bis(diphenylphosphino)- ...-n-pentylphosphino)-thiophene, 3,4-bis(di-n-hexylphosphino)-thiophene, 3,4-bis( 4-bis(di-p-tolylphosphino)-thiophene, 3,4-bis(di-m-tolylphosphino)-thiophene, 3,4-bis(di-p-methoxyphenylphosphino)-thiophene, 3,4-bis(di-m-methoxyphenylphosphino)-thiophene, 3,4-bis(di-o-methoxyphenylphosphino)-thiophene, 3,4-bis(dimethylphosphino)-2-methylthiophene, 3,4-bis(diethylphosphino)-2-methylthiophene, 3,4-bis(di-n-propylphosphino)-2-methylthiophene, 3,4-bis(diisopropylphosphino)-2-methylthiophene, 3,4-bis(di-n-butylphosphino)-2-methylthiophene, 3,4-bis(diisobutylphosphino)-2-methylthiophene, 3,4-bis(di-n-pentylphosphino)-2-methylthiophene, 3,4-bis(di- 3,4-bis(di-p-tolylphosphino)-2-methylthiophene, 3,4-bis(di-m-tolylphosphino)-2-methylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(di-m-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(di-o-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(dimethylphosphino)-2-ethylthiophene, 3,4-bis(diethylphosphino)-2-ethylthiophene, 3,4-bis(di-n-propylphosphino)- 2-ethylthiophene, 3,4-bis(diisobutylphosphino)-2-ethylthiophene, 3,4-bis(dicyclopentylphosphino)-2-ethylthiophene, 3,4-bis(dicyclohexylphosphino)-2-ethylthiophene, 3,4-bis(diphenylphosphino)-2-ethylthiophene, 3,4-bis(di-p-tolylphosphino)-2-ethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-ethylthiophene, 3,4-bis(dimethylphosphino)-2-isopropylthiophene, 3,4-bis(diethylphosphino)-2-isopropylthiophene, 3,4-bis(di-n-propylphosphino)-2-isopropylthiophene, 3,4-bis(diisobutylphosphino)-2-isopropylthiophene, 3,4-bis(dicyclopentylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-ethylthiophene,4-bis(dicyclohexylphosphino)-2-isopropylthiophene, 3,4-bis(diphenylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-tolylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-isopropylthiophene, 3,4-bis(dimethylphosphino)-2-cyclopentylthiophene, 3,4-bis(diethylphosphino)-2-cyclopentylthiophene, 3,4-bis(di-n-propylphosphino)-2-cyclopentylthiophene, 3,4-bis(diisobutylphosphino)-2-cyclopentylthiophene, 3,4-bis(dicyclopentylphosphino)-2-cyclopentylthiophene, 3,4-bis(dicyclohexylphosphino)-2-cyclopentylthiophene, 3,4-bis(diphenylphosphino)-2-cyclopentylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-cyclopentylthiophene, 3,4-bis(dimethylphosphino)-2-phenylthiophene, 3,4-bis(diethylphosphino)-2-phenylthiophene, 3,4-bis(di-n-propylphosphino)-2-phenylthiophene, 3,4-bis(diisobutylphosphino)-2-phenylthiophene, 3,4-bis(dicyclopentylphosphino)-2-phenylthiophene, 3,4-bis(dicyclohexylphosphino)-2-phenylthiophene, 3,4-bis(diphenylphosphino)-2-phenylthiophene, 3,4-bis(di-p-tolylphosphino)-2-phenylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-phenylthiophene, 3,4-bis(dimethylphosphino)-2-phenylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-phenylthiophene, 3,4-bis(dimethylphosphino)-2-phenylthiophene 3,4-bis(diphenylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diethylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(di-n-propylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diisobutylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dicyclopentylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dicyclohexylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diphenylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(di-p-tolylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dimethylphosphino)-2,5 -dimethylthiophene, 3,4-bis(diethylphosphino)-2,5-dimethylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-dimethylthiophene, 3,4-bis(diisobutylphosphino)-2,5-dimethylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-dimethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene, 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-dimethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2,5-diethylthiophene, 3,4-bis(diethylphosphino)-2,5-diethylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diethylthiophene, 3,4-bis(diisobutylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diethylthiophene, 3,4-bis(diphenylphosphino)-2,5-diethylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diethylthiophene, 3,4-bis(dimethylphosphino)-2,5-diisopropylthiophene, 3,4-bis(diethylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diethylthiophene 3,4-bis(diisobutylphosphino)-2,5-diisopropylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-diisopropylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diisopropylthiophene, 3,4-bis(diphenylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diisopropylthiophene, 3,4-bis(dimethylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diethylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diisobutylphosphino)-2,5-di-n-butylthiophene, 4-bis(dicyclopentylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diphenylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(dimethylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(diethylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(diisobutylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-dicyclohexylthiophene , 3,4-bis(dicyclohexylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(diphenylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(dimethylphosphino)-2,5-diphenylthiophene, 3,4-bis(diethylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diphenylthiophene, 3,4-bis(diisobutylphosphino)-2,5-diphenylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-diphenylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diphenylthiophene, 3,4-bis(diphenylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diphenylthiophene, 3,4-bis(dimethylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diethylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diisopropylphosphino)-2,5-di-p-tolylthiophene At least one of 3,4-bis(diphenylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diphenylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-di-p-tolylthiophene and 3,4-bis(di-p-methoxyphenylphosphino)-2,5-di-p-tolylthiophene.

[0018] Preferably, the internal electron donor is selected from at least one of 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2-isopropylthiophene, 3,4-bis(diphenylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2-(4-methoxyphenyl)thiophene and 3,4-bis(dimethylphosphino)-2-(4-ethylphenyl)thiophene.

[0019] In the catalyst of polypropylene for lithium battery separator of the present invention, the main catalyst includes the following components in weight percentage:

[0020]

[0021] The present invention does not particularly limit the preparation method of the main catalyst, and the following method can be adopted: a magnesium halide alcoholate carrier (calculated as magnesium) and a titanium halide (calculated as titanium) are mixed in a molar ratio of 1:15 to 60, an internal electron donor of a diphosphine compound containing a thiophene molecular skeleton and a functional group is added, the mixture is heated and then filtered, the titanium halide is added again, the mixture is heated, filtered, washed and dried to obtain a catalyst product. The specific steps are as follows: (1) adding spherical magnesium halide alcohol compound particles to titanium halide liquid at -50 to 20°C, reacting for 10 minutes to 5 hours, wherein the molar ratio of magnesium to titanium is 1:5 to 1:100; (2) raising the temperature to 0 to 90°C, adding an internal electron donor compound, wherein the molar ratio of magnesium to the internal electron donor compound is 2:1 to 20:1; (3) raising the temperature to 100 to 130°C, reacting for 1 to 6 hours; (4) after filtering, adding the same amount of titanium halide liquid as in step 1, reacting at 110 to 130°C for 1 to 4 hours, and then filtering, washing, and drying to obtain a supported main catalyst.

[0022] In the catalyst for polypropylene for lithium battery separator of the present invention, the aluminoxane is a compound having a structure shown in general formula (II):

[0023]

[0024] Where Y is C1-C 12 A hydrocarbon group, Y2 is 2 Y groups, a is an integer of 4 to 30, Al is aluminum, and O is oxygen; the aluminoxane is, for example but not limited to, at least one of methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane, and butylaluminoxane, preferably, the aluminoxane is methylaluminoxane.

[0025] The present invention does not particularly limit the operation method of modifying aluminoxane with alkyl halides or cyclohalides. The operation method of the modification treatment is, for example but not limited to: evacuating a dry polymerization bottle and replacing it with nitrogen three times, adding a certain amount of toluene solution of aluminoxane into the bottle, and obtaining dry powder of aluminoxane by reduced pressure distillation; then mixing the obtained dry powder of aluminoxane with alkyl halides or cyclohalides to form a solution or suspension of a certain concentration, and using it for propylene polymerization reaction.

[0026] Optionally, in the catalyst of polypropylene for lithium battery separator described in the present invention, the haloalkane or halocycloalkane modified aluminoxane is a solution or suspension formed by mixing aluminoxane dry powder with the haloalkane or halocycloalkane; preferably, the molar ratio of the aluminoxane dry powder (calculated as aluminum) to the haloalkane or halocycloalkane is 1:1 to 20, preferably 1:4 to 10.

[0027] Optionally, in the catalyst of polypropylene for lithium battery separator described in the present invention, the ratio of aluminoxane modified by alkyl halide or cyclohalide to the alkyl aluminum compound is 1:1 to 50, preferably 1:1 to 30, and more preferably 1:1 to 10, calculated as the molar ratio of aluminum to aluminum.

[0028] Optionally, in the catalyst of polypropylene for lithium battery separator of the present invention, in the aluminoxane modified by alkyl halide or cyclohalide, the alkyl halide is a compound containing at least one halogen atom and 1-20 carbon atoms; preferably at least one of monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, 1,2-dichloroethane, monochloropropane, monochlorobutane, monochlorosec-butane, monochlorotert-butane, chlorobenzene, monobromomethane, monobromopropane, monobromobutane and monoiodomethane;

[0029] The halogenated cycloalkane is monochlorocyclohexane or monochlorocyclopentane.

[0030] Optionally, in the catalyst for polypropylene for lithium battery separator of the present invention, the general formula of the alkyl aluminum compound is AlZ n X (3-n) ; Among them, Z is C1~C20 The alkyl group is an alkyl group of C6-C20, an aryl group of C6-C20, or an aralkyl group of C7-C20; X is a halogen (fluorine, chlorine, bromine, iodine), preferably chlorine; n is an integer of 0-3, and Al is aluminum. The alkyl aluminum compound is, for example but not limited to, at least one of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum, diethyl aluminum monochloride, and diisobutyl aluminum monochloride, preferably triethyl aluminum or triisobutyl aluminum.

[0031] Optionally, in the catalyst of polypropylene for lithium battery separator described in the present invention, the catalyst also contains an organic external electron donor, and the organic external electron donor is an alkoxysilane compound, selected from at least one of cyclohexylmethyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane or dimethoxydiphenylsilane, preferably cyclohexylmethyldimethoxysilane.

[0032] In the catalyst for polypropylene for lithium battery separator described in the present invention, the main catalyst is calculated in titanium, the co-catalyst is calculated in aluminum, and the organic external electron donor is calculated in silicon. The molar ratio of the main catalyst, the co-catalyst and the organic external electron donor is 1:5-1000:1-500; when applied to propylene polymerization, preferably, the molar ratio of the main catalyst, the co-catalyst and the organic external electron donor is preferably 1:10-50:1-5.

[0033] Another object of the present invention is to provide a method for preparing a propylene polymer, which uses the above-mentioned catalyst for polypropylene for lithium battery separators for propylene polymerization or copolymerization under high temperature polymerization conditions, can exhibit high catalytic activity and stereoregularity, and at the same time in situ generate polypropylene with a certain content of β crystals for the preparation of dry-process biaxially stretched lithium battery separators.

[0034] To achieve the above-mentioned purpose, the present invention provides a method for preparing a propylene polymer, using the above-mentioned catalyst for polypropylene for lithium battery separator to catalyze the high-temperature polymerization or copolymerization of propylene; preferably, at 85 to 120°C, the catalyst for polypropylene for lithium battery separator is used to homopolymerize or copolymerize propylene in a liquid phase (liquid phase monomer or monomer in an inert solvent) or gas phase medium for 0.5 to 2 hours.

[0035] In the specific preparation process, the main catalyst, co-catalyst and organic external electron donor can be directly added to the polymerization reactor, or they can be added to the polymerization reactor after pre-complexation and / or pre-polymerization as known in the art. Whether to pre-complex or pre-polymerize can be selected according to actual needs.

[0036] Optionally, in the preparation method of the propylene polymer provided by the present invention, the preparation method of the propylene polymer includes a catalyst pre-complexation step; preferably, the catalyst pre-complexation temperature is -10 to 40°C, more preferably 5 to 30°C, and the catalyst pre-complexation time is 1 to 10 min.

[0037] Optionally, in the method for preparing the propylene polymer provided by the present invention, the method for preparing the propylene polymer includes a prepolymerization step; preferably, the prepolymerization temperature is -10 to 60°C, more preferably 20 to 50°C, and the prepolymerization time is 5 to 20 minutes.

[0038] The present invention also provides a propylene polymer prepared by the above-mentioned preparation method of propylene polymer. The isotactic index of the propylene polymer prepared by the method is ≥96.5%, the β crystal content in the propylene polymer is ≥3.5%, and the ash content of the propylene polymer is ≤40ppm.

[0039] The present invention also provides an application of the propylene polymer prepared by the above-mentioned preparation method of the propylene polymer in the preparation of lithium battery separators; preferably, the application in the preparation of lithium battery separators by a dry biaxial stretching method.

[0040] Beneficial effects of the present invention:

[0041] 1. In the prior art, in the dry biaxial stretching process of polypropylene lithium battery separator, the introduction of β-crystal nucleating agent into polypropylene not only increases the production cost, but also introduces ash, which affects the performance of the lithium battery separator. The catalyst system for polypropylene for lithium battery separator provided by the present invention can in-situ catalytically produce native β-crystal polypropylene with a certain content, which can be directly used as a raw material for the dry biaxial stretching process of lithium battery separator, avoiding the introduction of β-crystal nucleating agent, while ensuring its catalytic activity and stereoregularity.

[0042] 2. The catalyst for polypropylene for lithium battery separator provided by the present invention adopts a diphosphine compound containing a thiophene structure. The lone pair electrons of the phosphorus atom and the sulfur atom in the diphosphine compound can stabilize the central metal titanium, so that the catalyst has high activity during propylene polymerization. The phosphorus atom and the sulfur atom in the diphosphine compound containing a thiophene structure provide two different chemical environments. At the same time, relying on the spatial structure provided by the thiophene skeleton, the problem of low isotactic index in the prepared polymer is solved.

[0043] 3. The present invention adopts halogenated alkanes or halogenated cycloalkanes to modify aluminoxane, and then mixes it with alkyl aluminum compounds as a co-catalyst, and combines it with other catalytic components to solve the problem of low isotactic index of prepared polymers while ensuring the polymerization activity of the catalyst system under high-temperature polymerization or copolymerization conditions of propylene (85-120°C). The reason why the isotacticity of polymers obtained by high-temperature polymerization in existing catalyst systems is low may be that under high-temperature polymerization conditions, the titanium active center of the catalyst is over-reduced, thereby reducing the polymerization activity of the catalyst and increasing the amount of oligomers generated. In the present invention, after introducing halogenated alkanes or halogenated cycloalkanes to modify aluminoxane, the polarity of the halogenated hydrocarbons can further oxidize the titanium active center of the catalyst, thereby improving the polymerization activity of the catalyst and the isotacticity of the polymer. DETAILED DESCRIPTION

[0044] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and process are given, but the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments without specifying specific conditions are usually carried out under conventional conditions.

[0045] Test Method

[0046] Isotactic index of polymer: It is determined by heptane extraction method (heptane boiling extraction for 6 hours), that is, 1 gram of dry polymer sample is extracted with boiling heptane in a Soxhlet extractor for 6 hours, and the residue is dried to constant weight. The ratio of the obtained polymer weight (g) to 1 is the isotactic index.

[0047] Polymer β-crystal content: An injection molding specimen of 60 mm × 60 mm × 1 mm was prepared using a D1 mold in the GB / T 17037.3-2003 standard, and XRD test was performed. The XRD spectrum was analyzed and the β-crystal content was calculated using the Turner-Jones formula.

[0048] Polymer ash determination: The ash content of the polymer was tested according to GB / T 9345.1-2008 standard.

[0049] Synthesis of internal electron donors

[0050] The present invention does not particularly limit the preparation method of the internal electron donor. For the convenience of description, taking 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene as an example, the preparation method of the internal electron donor can adopt the following steps:

[0051] 1.0 g of 2,5-dimethylthiophene and 1.9 g of NaOAc were added to 50 mL of CH2Cl2 and reacted at room temperature in the dark for 5 min. Then the temperature was lowered to 0°C and 0.96 mL of Br2 was gradually added dropwise. After the addition was completed, the temperature was raised to room temperature. After reacting for 2 h, 10% Na2S2O3 solution was added, the liquids were separated, the aqueous phase was extracted with CH2Cl2, the organic phases were combined, washed with water, the organic phases were dried over anhydrous MgSO4, and separated by column chromatography using petroleum ether as eluent to obtain 1.87 g of colorless solid 3,4-dibromo-2,5-dimethylthiophene with a yield of 75%.

[0052] 6 g of 3,4-dibromo-2,5-dimethylthiophene was added to 70 mL of THF under a nitrogen atmosphere, cooled to -78°C, and 18.8 mL of n-butyllithium in n-hexane was slowly added dropwise, maintaining the temperature at -78°C. After stirring for 1 h, 8.41 mL of diphenylphosphine chloride was added, the temperature was raised to room temperature, and the reaction was quenched with water after 5 h of reaction. The organic phase was extracted with CH2Cl2, dried, evaporated the organic solvent, and subjected to column chromatography to obtain 7.42 g of a white solid with a yield of 69%.

[0053] 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene: molecular formula, C 30 H 26 P2S; molecular weight, 480.12; elemental analysis, C, 74.98; H, 5.45; P, 12.89; S, 6.67. 31 PNMR(CDCl3,120MHz)δ:-21.45.

[0054] The internal electron donors used in the following examples can all be synthesized according to this method, and the corresponding raw materials for preparing the internal electron donors in each example can all be obtained commercially.

[0055] Example 1

[0056] Preparation of magnesium halide alcoholate carrier: white oil and methyl silicone oil are used as dispersion medium, magnesium chloride and ethanol are added, and the temperature is raised to melt for 7 hours, and then the molten alcoholate is quickly stirred and transferred to a hexane medium at -35°C to prepare microspherical magnesium chloride alcoholate particles. The average particle size of the magnesium chloride alcoholate carrier is 30-60 μm, and the specific surface area is 150-230 m 2 / g, the molar ratio of alcohol to magnesium chloride is 2.85:1, and the molecular formula is MgCl2·2.85CH3CH2OH.

[0057] Preparation of the main catalyst: Under anhydrous and oxygen-free conditions, add 5.0 grams of the above-mentioned microspherical magnesium chloride alcoholate carrier to 140 mL of titanium tetrachloride liquid at -20°C, react for 1 hour, and gradually heat to 60°C; add 1.2 g of 3,4-di(diphenylphosphino)-2,5-dimethylthiophene, gradually heat to 120°C, react for 2 hours, and filter; add 140 mL of titanium tetrachloride again, react at 120°C for 2 hours and filter. Wash with 50 mL of hexane at 50°C for 4 times, wash with 50 mL of hexane at room temperature for 2 times, and obtain the main catalyst after vacuum drying.

[0058] Preparation of modified aluminoxane: vacuum-nitrogen replacement three times in a dry 1L polymerization bottle, add 500mL of MAO (0.5mol / L MAO toluene solution) produced by Shanghai Yabao under nitrogen protection, distill the solvent toluene under reduced pressure, and when the methyl aluminoxane in the polymerization bottle is white dry powder, it indicates that the free trimethyl aluminum has been removed, stop the reaction, and mark the compound as MMAO. Take 5 grams of MMAO dry powder in a glove box and mix it with 34.8mL of chloroform to form a solution, in which the molar ratio of aluminum to chloroform in MMAO is 1:5, and set aside.

[0059] Catalyst system pre-complexation: under nitrogen protection, in a 100-mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 0°C.

[0060] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add 1kg propylene and the pre-complexed catalyst system, flush the catalyst addition line with 0.5kg propylene, add 0.2g hydrogen, keep stirring, and prepolymerize at 25°C for 10min.

[0061] High temperature polymerization of propylene: The temperature of the polymerization kettle was rapidly raised to 93°C. After polymerization for 1 hour, the remaining propylene was discharged to obtain a high temperature polymer.

[0062] The polymerization results are shown in Table 1.

[0063] Example 2

[0064] The preparation of the magnesium halide alcoholate carrier, the main catalyst, the modified aluminoxane, and the high-temperature polymerization of propylene are the same as in Example 1, except that the pre-complexation temperature of the catalyst system is increased to 10°C and the pre-polymerization temperature is increased to 40°C.

[0065] The polymerization results are shown in Table 1.

[0066] Example 3

[0067] The preparation of the magnesium halide alcoholate support, the main catalyst, the modified aluminoxane, the catalyst system pre-complexation, the prepolymerization and the high temperature polymerization are the same as in Example 1, except that the pre-complexation temperature is 20°C and the prepolymerization is carried out at 50°C for 15 minutes.

[0068] The polymerization results are shown in Table 1.

[0069] Example 4

[0070] The preparation of the magnesium halide alcoholate carrier, the main catalyst, the modified aluminoxane, and the amount of catalyst system added are the same as those in Example 1, except that the catalyst system has no pre-complexation and no pre-polymerization.

[0071] Propylene high temperature polymerization: In a 5L propylene high temperature polymerization kettle that had been vacuum dried and replaced with nitrogen-propylene three times, 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane were added, and the catalyst addition line was flushed with 0.5 kg of propylene, 0.2 g of hydrogen was added, stirring was maintained, and the temperature was rapidly raised to 93°C. After polymerization for 1 hour, the remaining propylene was vented to obtain a high temperature polymer.

[0072] The polymerization results are shown in Table 1.

[0073] Example 5

[0074] The preparation of magnesium halide alcoholate carrier, main catalyst and modified aluminoxane is the same as in Example 1.

[0075] Catalyst system pre-complexation: under nitrogen protection, in a 100-mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 8 mL of triethylaluminum hexane solution (1 mol / L), 2 mL of the above-mentioned MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0076] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add 1kg propylene and the pre-complexed catalyst system, flush the catalyst addition line with 0.5kg propylene, add 0.2g hydrogen, keep stirring, and prepolymerize at 45°C for 15min.

[0077] Example 1 of high temperature polymerization of propylene.

[0078] The polymerization results are shown in Table 1.

[0079] Example 6

[0080] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1.

[0081] Preparation of modified aluminoxane: Take 2 g of MMAO dry powder in a glove box and mix it with 49.5 mL of chloroform to form a solution, wherein the molar ratio of aluminum in MMAO to chloroform is 1:18, and set aside.

[0082] Catalyst system pre-complexation: under nitrogen protection, in a 100-mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 0.5 mL of the above-mentioned MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 10°C.

[0083] Propylene high temperature polymerization: In a 5L propylene high temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add 1kg propylene and the pre-complexed catalyst system, flush the catalyst addition line with 0.5kg propylene, add 0.2g hydrogen, keep stirring, and quickly heat to 93°C. After polymerizing for 1 hour, vent the remaining propylene to obtain a high temperature polymer.

[0084] The polymerization results are shown in Table 1.

[0085] Example 7

[0086] The preparation of the magnesium halide alcoholate carrier, the main catalyst and the modified aluminoxane is the same as in Example 1, except that the catalyst system is not pre-complexed.

[0087] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that had been vacuum dried and replaced with nitrogen-propylene three times, 30mg of the main catalyst, 10mL of triethylaluminum hexane solution (1mol / L), 0.5mL of MMAO chloroform solution (wherein the molar ratio of aluminum to chloroform in MMAO is 1:5), 0.1mL of cyclohexylmethyldimethoxysilane, 1.5kg of propylene, and 0.2g of hydrogen were added. Stirring was maintained and the temperature was quickly raised to 45°C for prepolymerization for 20min.

[0088] Example 1 of high temperature polymerization of propylene.

[0089] The polymerization results are shown in Table 1.

[0090] Example 8

[0091] The preparation of the magnesium halide alcoholate carrier, the main catalyst and the modified aluminoxane is the same as in Example 1, except that the catalyst system is not pre-complexed;

[0092] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that had been vacuum dried and replaced with nitrogen-propylene three times, 30mg of the main catalyst, 10mL of triisobutylaluminum hexane solution (1mol / L), 1mL of MMAO chloroform solution (wherein the molar ratio of aluminum to chloroform in MMAO is 1:5), 0.2mL of cyclohexylmethyldimethoxysilane, 1.5kg of propylene, and 0.2g of hydrogen were added. The mixture was stirred and the temperature was quickly raised to 45°C for prepolymerization for 15min.

[0093] Example 1 of high temperature polymerization of propylene.

[0094] The polymerization results are shown in Table 1.

[0095] Example 9

[0096] The steps of preparing the magnesium halide alcoholate carrier, the main catalyst, the modified aluminoxane and the pre-complexation of the catalyst system were the same as those in Example 1, except that the pre-complexation temperature was 25°C.

[0097] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add the pre-complexed catalyst system, 0.5kg propylene, and 0.2g hydrogen, keep stirring, and quickly heat to 45°C for prepolymerization for 15 minutes.

[0098] High-temperature copolymerization of ethylene and propylene: The temperature of the polymerization kettle was rapidly raised to 93°C, and a mixture of ethylene and propylene (in which the volume fraction of ethylene was 3%) was introduced. After polymerization for 1 hour, the unreacted mixture of ethylene and propylene was vented to obtain a high-temperature ethylene-propylene copolymer.

[0099] The polymerization results are shown in Table 1.

[0100] Example 10

[0101] The preparation of the magnesium halide alcoholate carrier and the modified aluminoxane is the same as in Example 1, except that the internal electron donor used in the preparation of the main catalyst is different, and the main catalyst prepared in this example is used in the propylene high temperature polymerization step. The preparation steps of the main catalyst in this example are as follows:

[0102] The preparation method of 3,4-bis(dimethylphosphino)-2-isopropylthiophene is similar to the preparation method of 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene in Example 1. 3,4-bis(dimethylphosphino)-2-isopropylthiophene: Molecular formula, C 11 H 20 P2S; molecular weight, 246.29; elemental analysis, C, 53.64; H, 8.19; P, 25.15; S, 13.02.

[0103] Under anhydrous and oxygen-free conditions, 5.0 grams of the above-mentioned microspherical magnesium chloride alcoholate particles were added to 140 mL of titanium tetrachloride liquid at -20°C, reacted for 1 hour, and then gradually heated to 60°C; 0.6 g of 3,4-di(dimethylphosphino)-2-isopropylthiophene was added, and the temperature was gradually raised to 120°C, reacted for 2 hours, and filtered; 140 mL of titanium tetrachloride was added, reacted at 120°C for 2 hours and filtered. Washed with 50 mL of hexane at 40-60°C for 4 times, washed with 50 mL of hexane at room temperature for 2 times, and vacuum dried to obtain the main catalyst.

[0104] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0105] The propylene prepolymerization is similar to that in Example 5, except that the temperature of the propylene prepolymerization in this example is 40° C. and the prepolymerization time is 10 min.

[0106] Example 5 of high temperature polymerization of propylene.

[0107] The polymerization results are shown in Table 1.

[0108] Embodiment 11

[0109] The preparation of the magnesium halide alcoholate carrier and the modified aluminoxane is the same as in Example 1, except that the internal electron donor used in the preparation of the main catalyst is different, and the main catalyst prepared in this example is used in the propylene high temperature polymerization step. The preparation steps of the main catalyst in this example are as follows:

[0110] The preparation method of 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene is similar to the preparation method of 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene in Example 1. 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene: Molecular formula, C 30 H 38 P2S; molecular weight, 492.64; elemental analysis, C, 73.14; H, 7.78; P, 12.57; S, 6.51.

[0111] Under anhydrous and oxygen-free conditions, 5.0 grams of the above-mentioned microspherical magnesium chloride alcoholate particles were added to 140 mL of titanium tetrachloride liquid at -20°C, reacted for 1 hour, and then gradually heated to 60°C; 1.2 g of 3,4-di(dicyclohexylphosphino)-2,5-dimethylthiophene was added, and the temperature was gradually raised to 120°C, reacted for 2 hours, and filtered; 140 mL of titanium tetrachloride was added, reacted at 120°C for 2 hours and filtered. Washed with 50 mL of hexane at 40-60°C for 4 times, washed with 50 mL of hexane at room temperature for 2 times, and vacuum dried to obtain the main catalyst.

[0112] Example 5 of catalyst system pre-complexation, prepolymerization and propylene high temperature polymerization.

[0113] The polymerization results are shown in Table 1.

[0114] Example 12

[0115] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1, except that the ratio of MMAO dry powder to chloroform is different in the preparation process of the modified aluminoxane, and the modified aluminoxane prepared in this example is used in the propylene high temperature polymerization step. The specific preparation steps of the modified aluminoxane in this example are as follows:

[0116] In a glove box, take 2.5 g of MMAO dry powder and mix it with 34.8 mL of chloroform to form a solution, wherein the molar ratio of aluminum in MMAO to chloroform is 1:10, and set aside.

[0117] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO chloroform solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0118] Example 5 of propylene prepolymerization and propylene high temperature polymerization.

[0119] The polymerization results are shown in Table 1.

[0120] Example 13

[0121] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1, except that the alkyl halide used in the preparation of the modified aluminoxane is different, and the modified aluminoxane prepared in this example is used in the propylene high temperature polymerization step. The specific preparation steps of the modified aluminoxane in this example are as follows:

[0122] In a glove box, take 5 g of MMAO dry powder and mix it with 27.6 mL of dichloromethane to form a solution, wherein the molar ratio of aluminum in MMAO to dichloromethane is 1:5, and set aside.

[0123] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO dichloromethane solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0124] Example 5 of propylene prepolymerization and propylene high temperature polymerization.

[0125] The polymerization results are shown in Table 1.

[0126] Embodiment 14

[0127] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1, except that the alkyl halide used in the preparation process of the modified aluminoxane is different, and the modified aluminoxane prepared in this example is used in the propylene high temperature polymerization step. The specific preparation steps of the modified aluminoxane in this example are as follows:

[0128] In a glove box, take 5 g of MMAO dry powder and mix it with 31.2 mL of monochloroethane to form a solution, wherein the molar ratio of aluminum in MMAO to monochloroethane is 1:5, and set aside.

[0129] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO monochloroethane solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0130] Example 5 of propylene prepolymerization and propylene high temperature polymerization.

[0131] The polymerization results are shown in Table 1.

[0132] Embodiment 15

[0133] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1, except that the alkyl halide used in the preparation process of the modified aluminoxane is different, and the modified aluminoxane prepared in this example is used in the propylene high temperature polymerization step. The specific preparation steps of the modified aluminoxane in this example are as follows:

[0134] In a glove box, take 5 g of MMAO dry powder and mix it with 51 mL of monochlorocyclohexane to form a solution, wherein the molar ratio of aluminum in MMAO to monochlorocyclohexane is 1:4.3, and set aside.

[0135] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO monochlorocyclohexane solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0136] Example 5 of propylene prepolymerization and propylene high temperature polymerization.

[0137] The polymerization results are shown in Table 1.

[0138] Example 16

[0139] The preparation of the magnesium halide alcoholate carrier and the main catalyst is the same as in Example 1, except that the alkyl halide used in the preparation process of the modified aluminoxane is different, and the modified aluminoxane prepared in this example is used in the propylene high temperature polymerization step. The specific preparation steps of the modified aluminoxane in this example are as follows:

[0140] In a glove box, take 5 g of MMAO dry powder and mix it with 39.2 mL of monobromopropane to form a solution, wherein the molar ratio of aluminum in MMAO to monobromopropane is 1:5, and set aside.

[0141] Catalyst pre-complexation: under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, add 30 mg of the main catalyst, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of the above-mentioned MMAO monobromopropane solution and 0.2 mL of cyclohexylmethyldimethoxysilane, and pre-complex for 5 min at 25°C.

[0142] Example 5 of propylene prepolymerization and propylene high temperature polymerization.

[0143] The polymerization results are shown in Table 1.

[0144] Embodiment 17

[0145] The preparation of the magnesium halide alcoholate carrier, the main catalyst, the modified aluminoxane, the catalyst system pre-complexation and the pre-polymerization are the same as those in Example 13, except that the polymerization temperature is replaced by 85°C instead of 93°C.

[0146] The polymerization results are shown in Table 1.

[0147] Embodiment 18

[0148] The preparation of the magnesium halide alcoholate carrier, the main catalyst, the preparation of the modified aluminoxane, and the amount of the co-catalyst are the same as in Example 1, except that the catalyst system pre-complexation, prepolymerization and propylene polymerization methods are the same as in Example 5, except that the high-temperature polymerization temperature is replaced by 120°C instead of 93°C.

[0149] The polymerization results are shown in Table 1.

[0150] Comparative Example 1

[0151] The preparation of the magnesium halide alcoholate carrier is the same as in Example 1, and the preparation of the main catalyst is similar to that in Example 1, except that diisobutyl phthalate is used instead of 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene in the preparation of the main catalyst in this comparative example. The preparation steps of the main catalyst in this comparative example are as follows:

[0152] Under anhydrous and oxygen-free conditions, 5.0 grams of the above-mentioned microspherical magnesium chloride alcoholate particles were added to 140 mL of titanium tetrachloride liquid at -20°C, reacted for 1 hour, and then gradually heated to 60°C; 0.7 mL of diisobutyl phthalate was added, and the temperature was gradually raised to 120°C, reacted for 2 hours, and filtered; 140 mL of titanium tetrachloride was added, reacted at 120°C for 2 hours and filtered. The catalyst was washed with 50 mL of hexane at 40-60°C for 4 times, washed with 50 mL of hexane at room temperature for 2 times, and vacuum dried to obtain the main catalyst.

[0153] High-temperature polymerization of propylene: In a 5L propylene high-temperature polymerization kettle that had been vacuum dried and replaced with nitrogen-propylene three times, 1kg propylene, 30mg of the above-mentioned main catalyst, 10mL of triethylaluminum hexane solution (1mol / L), and 0.2mL of cyclohexylmethyldimethoxysilane were added, the temperature of the polymerization kettle was quickly raised to 93°C, the polymerization reaction was carried out for 1 hour, and the unreacted propylene was vented to obtain a 93°C prepared polymer.

[0154] The polymerization results are shown in Table 1.

[0155] Comparative Example 2

[0156] The preparation of the magnesium halide alcoholate carrier and the main catalyst are the same as those in Comparative Example 1.

[0157] The co-catalysts are triethylaluminum in hexane and MMAO in toluene.

[0158] Pre-complexation of the catalyst system: Under nitrogen protection, in a 100-mL vacuum-dried polymerization bottle, 30 mg of the main catalyst of Comparative Example 1, 10 mL of a hexane solution of triethylaluminum (1 mol / L), 10 mL of a toluene solution of MAO (0.5 mol / L) and 0.2 mL of cyclohexylmethyldimethoxysilane were added, and pre-complexed at 0°C for 5 min.

[0159] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add 1kg propylene and the pre-complexed catalyst system, flush the catalyst addition line with 0.5kg propylene, add 0.2g hydrogen, keep stirring, and prepolymerize at 25°C for 10min.

[0160] High temperature polymerization of propylene: The temperature of the polymerization kettle was rapidly raised to 93°C, the polymerization reaction was carried out for 1 hour, and the unreacted propylene was discharged to obtain a high temperature polymer.

[0161] The polymerization results are shown in Table 1.

[0162] Comparative Example 3

[0163] The preparation of the magnesium halide alcoholate carrier and the main catalyst are the same as those in Comparative Example 1; the preparation of the modified aluminoxane is the same as that in Example 1.

[0164] Catalyst system pre-complexation: Under nitrogen protection, in a 100 mL vacuum-dried polymerization bottle, 30 mg of the main catalyst of Comparative Example 1, 10 mL of triethylaluminum hexane solution (1 mol / L), 1 mL of MMAO chloroform solution (wherein the molar ratio of aluminum to chloroform in MMAO is 1:5) and 0.2 mL of cyclohexylmethyldimethoxysilane were added, and pre-complexed at 25°C for 5 min.

[0165] Propylene prepolymerization: In a 5L propylene high-temperature polymerization kettle that has been vacuum dried and replaced with nitrogen-propylene three times, add 1kg propylene and the pre-complexed catalyst system, flush the catalyst addition line with 0.5kg propylene, add 0.2g hydrogen, keep stirring, and prepolymerize at 45°C for 15min.

[0166] Example 1 of high temperature polymerization of propylene.

[0167] The polymerization results are shown in Table 1.

[0168] Comparative Example 4

[0169] The preparation of the main catalyst is the same as in Example 1.

[0170] Preparation of co-catalyst: vacuum-purify and replace with nitrogen in a dry 50mL polymerization bottle three times. Under nitrogen protection, add 20mL of MAO (0.5mol / L MAO toluene solution) produced by Shanghai Yabao into the polymerization bottle, and add 10mL of BF3 ether solution (0.5mol / L BF3 ether solution) dropwise. The molar ratio of BF3:MAO is 1:2. After a certain reaction time, a complex solution of BF3 and MAO is obtained, which is recorded as BMAO and set aside.

[0171] Catalyst system pre-complexation: under nitrogen protection, add 30 mg of the main catalyst, 1.25 mL of triethylaluminum (1 mol / L hexane solution), 2.5 mL of BMAO mixed solution and 0.1 mL of cyclohexylmethyldimethoxysilane into a 100 mL glass bottle at room temperature, and pre-complex the catalyst system in the glass bottle at room temperature for 5 min;

[0172] Propylene prepolymerization: add 1 kg of propylene to a 10L high-temperature polymerization kettle that has been vacuum dried and fully replaced with nitrogen and propylene gas, then add the above pre-complexed catalyst system under nitrogen protection, continue to add 0.5 kg of propylene, keep stirring, and prepolymerize at 10°C for 10 minutes;

[0173] High temperature polymerization of propylene: same as in Example 1.

[0174] The polymerization results are shown in Table 1.

[0175] Table 1 Polymerization results of embodiments and comparative examples

[0176]

[0177]

[0178] It can be seen from the results of the embodiments and comparative examples that the present invention uses a diphosphine compound containing a thiophene structure as a main catalyst and a mixture of aluminoxane modified with a halide and alkyl aluminum as a composite co-catalyst. Under high-temperature propylene homopolymerization and ethylene-propylene copolymerization conditions, a propylene polymer with a certain β-crystal content is obtained, and the β-crystal content of the polymer is as high as 17.8%; at the same time, a high catalytic activity of the catalyst system is ensured, the high-temperature homopolymerization activity of propylene reaches 63.5kgPP / gCat·h, and the high-temperature copolymerization activity of ethylene-propylene reaches 65.5kgPP / gCat·h, and the prepared high-temperature polymer has a high isotactic index.

[0179] The above embodiments are typical examples listed to illustrate the technical solutions of the present invention in detail. The present invention is subject to the protection scope of the claims and the content of the invention and is not limited by the implementation scheme. Simple replacement or modification of the present invention is still within the protection scope of the present invention.

Claims

1. A catalyst for polypropylene for lithium battery separator, characterized in that: include: Titanium-containing main catalyst and co-catalyst; The main catalyst comprises a magnesium halide alcoholate carrier, a titanium halide and an internal electron donor, wherein the internal electron donor is a diphosphine compound having a molecular skeleton of a thiophene structure and having a general formula (I): wherein R1, R2, R3 and R4 are the same or different and are independently selected from a hydrogen atom, a C1-C20 straight or branched alkyl group, a C3-C20 cycloalkyl group, a C6-C20 aryl group, a C7-C20 aralkyl group and a C7-C20 alkoxyaryl group; P is phosphorus; S is sulfur; The cocatalyst is a mixture of aluminoxane modified by alkyl halide or cyclohalide and an alkyl aluminum compound.

2. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The internal electron donor is selected from 3,4-bis(dimethylphosphino)-thiophene, 3,4-bis(diethylphosphino)-thiophene, 3,4-bis(di-n-propylphosphino)-thiophene, 3,4-bis(diisopropylphosphino)-thiophene, 3,4-bis(dimethylphosphino)-2-(4-ethylphenyl)thiophene, 3,4-bis(di-n-butylphosphino)-thiophene, 3,4-bis(diisobutylphosphino)-thiophene, 3,4-bis(di-n-pentylphosphino)-thiophene, 3,4-bis(dicyclopentylphosphino)-thiophene, 3,4-bis(di-n-hexylphosphino)-thiophene, 3,4-bis(dicyclohexylphosphino)-thiophene, 3,4-bis(diphenylphosphino)-thiophene, 3,4-bis(di-p-tolylphosphino)-thiophene, 3,4-bis(di-p-tolylphosphino)-thiophene, 3,4-bis(di-p-methoxyphenylphosphino)-thiophene, 3,4-bis(di-m-methoxyphenylphosphino)-thiophene, 3,4-bis(di-o-methoxyphenylphosphino)-thiophene, 3,4-bis(dimethylphosphino)-2-methylthiophene, 3,4-bis(diethylphosphino)-2-methylthiophene, 3,4-bis(di-n-propylphosphino)-2-methylthiophene, 3,4-bis(diisopropylphosphino)-2-methylthiophene, 3,4-bis(di-n-butylphosphino)-2-methylthiophene, 3,4-bis(diisobutylphosphino)-2-methylthiophene, 3,4-bis(di-n-pentylphosphino)-2-methylthiophene, 3,4-bis(dicyclopentylphosphino)-2-methylthiophene, 3,4-bis(di-n-hexylphosphino)-2-methylthiophene 3,4-bis(dimethylphosphino)-2-methylthiophene, 3,4-bis(dicyclohexylphosphino)-2-methylthiophene, 3,4-bis(diphenylphosphino)-2-methylthiophene, 3,4-bis(di-p-tolylphosphino)-2-methylthiophene, 3,4-bis(di-m-tolylphosphino)-2-methylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(di-m-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(di-o-methoxyphenylphosphino)-2-methylthiophene, 3,4-bis(dimethylphosphino)-2-ethylthiophene, 3,4-bis(diethylphosphino)-2-ethylthiophene, 3,4-bis(di-n-propylphosphino)-2-ethylthiophene, 3,4-bis(diisobutylphosphino)-2 3,4-bis(dimethylphosphino)-2-isopropylthiophene, 3,4-bis(diethylphosphino)-2-isopropylthiophene, 3,4-bis(di-n-propylphosphino)-2-isopropylthiophene, 3,4-bis(diisobutylphosphino)-2-isopropylthiophene, 3,4-bis(dicyclopentylphosphino)-2-isopropylthiophene, 3,4-bis(dicyclohexylphosphino)-2-ethylthiophene, 3,4-bis(diphenylphosphino)-2-ethylthiophene, 3,4-bis(di-p-tolylphosphino)-2-ethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-ethylthiophene, 3,4-bis(dimethylphosphino)-2-isopropylthiophene, 3,4-bis(diethylphosphino)-2-isopropylthiophene, 3,4-bis(di-n-propylphosphino)-2-isopropylthiophene, 3,4-bis(diisobutylphosphino)-2-isopropylthiophene, 3,4-bis(dicyclopentylphosphino)-2-isopropylthiophene, 3,4-bis(dicyclohexylphosphino)-2-isopropylthiophene, 3,4-bis(diphenylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-tolylphosphino)-2-isopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-isopropylthiophene, 3,4-bis(dimethylphosphino)-2-cyclopentylthiophene, 3,4-bis(diethylphosphino)-2-cyclopentylthiophene, 3,4-bis(di-n-propylphosphino)-2-cyclopentylthiophene, 3,4-bis(diisobutylphosphino)-2-cyclopentylthiophene, 3,4-bis(dicyclopentylphosphino)-2-cyclopentylthiophene, 3,4-bis(dicyclohexylphosphino)-2-cyclopentylthiophene, 3,4-bis(diphenylphosphino)-2-cyclopentylthiophene, 3,4-bis(di-p-tolylphosphino)-2-cyclopentylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-isopropylthiophene, 3,4-bis(dimethylphosphino)-2-phenylthiophene, 3,4-bis(diethylphosphino)-2-phenylthiophene, 3,4-bis(di-n-propylphosphino)-2-phenylthiophene, 3,4-bis(diisobutylphosphino)-2-phenylthiophene, 3,4-bis(dicyclopentylphosphino)-2-phenylthiophene, 3,4-bis(dicyclohexylphosphino)-2-phenylthiophene, 3,4-bis(diphenylphosphino)-2-phenylthiophene, 3,4-bis(di-p-tolylphosphino)-2-phenylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-phenylthiophene, 3,4-bis(dimethylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diethylphosphino)-2-( 4-methoxyphenyl)thiophene, 3,4-bis(di-n-propylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diisobutylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dicyclopentylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dicyclohexylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(diphenylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(di-p-tolylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2-(4-methoxyphenyl)thiophene, 3,4-bis(dimethylphosphino)-2,5-dimethylthiophene, 3,4-bis(diethylphosphino)-2,5 -dimethylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-dimethylthiophene, 3,4-bis(diisobutylphosphino)-2,5-dimethylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-dimethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene, 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-dimethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2,5-diethylthiophene, 3,4-bis(diethylphosphino)-2,5-diethylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diethylthiophene, 3,4-bis(diisobutylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diethylthiophene, 3,4-bis(diphenylphosphino)-2,5-diethylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diethylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diethylthiophene, 3,4-bis(dimethylphosphino)-2,5-diisopropylthiophene, 3,4-bis(diethylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diisopropylthiophene, 3,4-bis(diisobutylphosphino)-2,5-diisopropylthiophene, 3,4- bis(dicyclopentylphosphino)-2,5-diisopropylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diisopropylthiophene, 3,4-bis(diphenylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diisopropylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diisopropylthiophene, 3,4-bis(dimethylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diethylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diisobutylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-di-n-butylthiophene, ,4-bis(dicyclohexylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(diphenylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-di-n-butylthiophene, 3,4-bis(dimethylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(diethylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(diisobutylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-dicyclohexylthiophene Thiophene, 3,4-bis(diphenylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-dicyclohexylthiophene, 3,4-bis(dimethylphosphino)-2,5-diphenylthiophene, 3,4-bis(diethylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-diphenylthiophene, 3,4-bis(diisobutylphosphino)-2,5-diphenylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-diphenylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-diphenylthiophene, 3,4-bis(diphenylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-p-tolylphosphino)-2,5-diphenylthiophene, 3,4-bis(di-p-methoxyphenylphosphino)-2,5-diphenylthiophene, 3,4-bis(dimethylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diethylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(di-n-propylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diisobutylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(dicyclopentylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-di-p-tolylthiophene, 3,4-bis(diphenylphosphino)-2,5-di-p-tolylthiophene phene, 3,4-bis(di-p-tolylphosphino)-2,5-di-p-tolylthiophene and 3,4-bis(di-p-methoxyphenylphosphino)-2,5-di-p-tolylthiophene; preferably, the internal electron donor is selected from at least one of 3,4-bis(diphenylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2-isopropylthiophene, 3,4-bis(diphenylphosphino)-2,5-diethylthiophene, 3,4-bis(dicyclohexylphosphino)-2,5-dimethylthiophene, 3,4-bis(dimethylphosphino)-2-(4-methoxyphenyl)thiophene and 3,4-bis(dimethylphosphino)-2-(4-ethylphenyl)thiophene. , 3. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The main catalyst includes the following components in weight percentage:

4. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The haloalkane or halocycloalkane modified aluminoxane is a solution or suspension formed by mixing aluminoxane dry powder with the haloalkane or halocycloalkane; preferably, the molar ratio of the aluminoxane dry powder to the haloalkane or halocycloalkane is 1:1-20, preferably 1:4-10, calculated on the basis of aluminum.

5. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The ratio of the aluminoxane modified with the alkyl halide or cyclohalide to the alkyl aluminum compound is 1:1 to 50, preferably 1:1 to 30, and more preferably 1:1 to 10, in terms of the molar ratio of aluminum to aluminum.

6. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The aluminoxane is a compound having a structure shown in the following general formula (II): General formula (II); Wherein, Y is a C1-C12 hydrocarbon group, Y2 is two Y groups, Al is aluminum, O is oxygen, and a is an integer of 4 to 30; preferably, the aluminoxane is at least one of methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane and butylaluminoxane, and more preferably, the aluminoxane is methylaluminoxane.

7. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The halogenated alkane is a compound containing at least one halogen atom and 1 to 20 carbon atoms; preferably at least one of monochloromethane, dichloromethane, trichloromethane, tetrachloromethane, monochloroethane, 1,2-dichloroethane, monochloropropane, monochlorobutane, monochlorosec-butane, monochlorotert-butane, chlorobenzene, monobromomethane, monobromopropane, monobromobutane and monoiodomethane; the halogenated cycloalkane is monochlorocyclohexane or monochlorocyclopentane.

8. The catalyst for polypropylene for lithium battery separator according to claim 1, characterized in that: The general formula of the alkyl aluminum compound is AlZ n X (3-n) ; wherein Al is aluminum; Z is an alkyl group of C1 to C20, an aryl group of C6 to C20, or an arylalkyl group of C7 to C20; X is a halogen, preferably chlorine; n is an integer from 0 to 3; preferably, the alkyl aluminum compound is at least one of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-hexylaluminum, diethyl aluminum monochloride, and diisobutyl aluminum monochloride, preferably triethyl aluminum or triisobutyl aluminum.

9. The catalyst for polypropylene for lithium battery separator according to any one of claims 1 to 8, characterized in that: The catalyst also contains an organic external electron donor, which is an alkoxysilane compound, selected from at least one of cyclohexylmethyldimethoxysilane, dicyclopentyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane and dimethoxydiphenylsilane, preferably cyclohexylmethyldimethoxysilane.

10. The catalyst for polypropylene for lithium battery separator according to claim 9, characterized in that: The molar ratio of the main catalyst to the co-catalyst is 1:5-1000:1-500, preferably 1:10-50:1-5, calculated based on titanium, the co-catalyst to the organic external electron donor, calculated based on silicon.

11. A method for preparing a propylene polymer, characterized in that: The catalyst for polypropylene for lithium battery separator according to any one of claims 1 to 10 is used to catalyze the high-temperature polymerization or copolymerization of propylene; preferably, at 85 to 120° C., the catalyst for polypropylene for lithium battery separator causes propylene to homopolymerize or copolymerize in a liquid or gas medium.

12. The preparation method according to claim 11, characterized in that: The method for preparing the propylene polymer comprises a catalyst pre-complexation step; preferably, the catalyst pre-complexation temperature is -10 to 40°C, more preferably 5 to 30°C, and the catalyst pre-complexation time is 1 to 10 minutes; and / or The method for preparing the propylene polymer comprises a prepolymerization step; preferably, the prepolymerization temperature is -10 to 60°C, more preferably 20 to 50°C, and the prepolymerization time is 5 to 20 minutes.

13. The propylene polymer obtained by the method for preparing a propylene polymer according to claim 11 or 12, characterized in that: The isotactic index of the propylene polymer is ≥96.5%, the content of β crystals in the propylene polymer is ≥3.5%, and the ash content of the propylene polymer is ≤40ppm.

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