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CN-121975042-A - Polypropylene catalyst active center environment regulation and control method and polypropylene preparation method

CN121975042ACN 121975042 ACN121975042 ACN 121975042ACN-121975042-A

Abstract

The invention belongs to the field of olefin polymerization, and discloses an environment regulation method for an active center of a polypropylene catalyst and a polypropylene preparation method. According to the invention, the additive is introduced into the existing magnesium-titanium polypropylene catalyst to increase the distance between adjacent active centers, or the additive is used for removing part of active centers of the polypropylene catalyst, and the electron donor and the titanium-containing compound are loaded on the surface of the polypropylene catalyst again, so that the Ti content of the active centers of the surface of the polypropylene catalyst and the distance between adjacent active centers are regulated and controlled. The polypropylene catalyst regulated by the active center is used for propylene bulk polymerization or slurry polymerization to prepare the ultra-high molecular weight polypropylene with the characteristics of high isotacticity, low entanglement, easy processing, high strength and high toughness.

Inventors

  • LI WEI
  • LIU YANG
  • CHEN YUMING
  • MA JUNPENG
  • WANG JINGDAI
  • WANG MAOLI
  • YANG YONGRONG
  • AN YANJUN
  • BAI JIN
  • MA SHUAI

Assignees

  • 浙江大学
  • 中煤鄂尔多斯能源化工有限公司

Dates

Publication Date
20260505
Application Date
20260128

Claims (10)

  1. 1. A method for regulating and controlling the environment of an active center of a polypropylene catalyst, which is characterized by comprising one of the following steps: Step combination 1: a) Adding a polypropylene catalyst and an alkane solvent into a reactor and stirring; b) Dissolving the additive in an alkane solvent, adding the alkane solvent into a reactor, and stirring for reaction; c) Removing the supernatant after the reaction is finished, washing with alkane solvent, and drying to obtain the polypropylene catalyst with the regulated active center; step combination 2: a) Adding a polypropylene catalyst and an alkane solvent into a reactor and stirring; b) Dissolving the additive in an alkane solvent, adding the alkane solvent into a reactor, and stirring for reaction; c) Removing supernatant after the reaction is finished, and washing the supernatant with an alkane solvent for later use; d) Adding an alkane solvent, an electron donor and a titanium-containing compound into the reactor in the step c), stirring for reaction, standing for layering, removing supernatant after standing for layering, washing with the alkane solvent for several times, and drying to obtain a polypropylene catalyst with an adjustable active center; Wherein the polypropylene catalyst is a magnesium-titanium catalyst, and the components at least comprise two or more of MgCl 2 、MgO、Mg(OEt) 2 、TiCl 4 、TiCl 3 , titanate compound and electron donor, and at least one of magnesium compound and titanium compound.
  2. 2. The method according to claim 1, wherein the alkane solvent is selected from one or more of pentane, isopentane, n-hexane, cyclohexane, 2-methylpentane, n-heptane, 2-methylhexane, methylcyclohexane, perfluoro-n-pentane, perfluoro-isopentane, perfluoro-n-hexane, perfluoro-cyclohexane, perfluoro-n-heptane, and the weight ratio of alkane solvent to polypropylene catalyst in step a) is in the range of 5:1 to 100:1.
  3. 3. The method according to claim 1, wherein the additive is selected from one or more of siloxane organic compounds, silazane organic compounds, ether compounds, fluorosilane organic compounds, fluorosilicone organic compounds, fluorosilazane organic compounds, fluorosilicone ether organic compounds, and fluorosilicone ether organic compounds, the main structure of the additive is one or more of cage type, half cage type, and star type structures, and the weight ratio of the additive to the polypropylene catalyst in the step b) is 0.03:1-0.5:1.
  4. 4. The method of claim 1, wherein the temperature of step a) and step b) of step combination 1 is-40-40 ℃, the reaction time of step b) is 0.1-10.0 h, the temperature of step a) and step b) of step combination 2 is-40-90 ℃, and the reaction time of step b) is 0.1-10.0 h.
  5. 5. The method according to claim 1, wherein the electron donor in the step d) is selected from one or more of diisobutyl phthalate, di-n-butyl phthalate, diisobutyl 2, 3-diisopropylsuccinate, 1, 3-diol ester, 1, 2-benzenediol ester, 9-bis (methoxymethyl) fluorene, alkyl substituted 1, 3-diether and tributyl maleate, and the weight ratio of the electron donor to the polypropylene catalyst is 0.005:1-0.4:1.
  6. 6. The process according to claim 1, wherein the weight ratio of titanium-containing compound added to polypropylene catalyst in step d) is from 0.001:1 to 1:1.
  7. 7. The method according to claim 1, wherein the stirring time in step d) is 0.5-5 h, and the electron donor is added first and then the titanium-containing compound is added.
  8. 8. A propylene polymerization method is characterized in that propylene, triethylaluminum, an active center-regulated polypropylene catalyst obtained by the method of any one of claims 1 to 7 and an external electron donor are added into a reaction kettle after anhydrous and anaerobic treatment, the temperature is raised to 50 to 100 ℃ and reacts for 0.2 to 8h, and a polypropylene product is obtained after stopping the reaction and drying.
  9. 9. The polymerization method according to claim 8, wherein the external electron donor is selected from one or more of dicyclopentyl dimethoxy silane, cyclohexylmethyl dimethoxy silane, diisopropyl dimethoxy silane, diisobutyl dimethoxy silane, and the molar ratio of Si in the external electron donor to the surface active center Ti of the polypropylene catalyst is 2:1-20:1.
  10. 10. The polypropylene product prepared by the polymerization method of claim 8, wherein the polypropylene product has an average molecular weight of 0.8-6 x 10 6 g/mol, an isotacticity of 95% or more, an initial storage modulus of 50000-150000 Pa in a rheological test of the polypropylene product, and a storage modulus of 150% or more of the initial storage modulus after the rheological test of 24 h.

Description

Polypropylene catalyst active center environment regulation and control method and polypropylene preparation method Technical Field The invention belongs to the field of polyolefin catalysts and polyolefin products, and particularly relates to a polypropylene catalyst active center environment regulation method and a polypropylene preparation method. Background Polypropylene is the second most general synthetic resin worldwide, accounting for about 30% of the total consumption of the synthetic resin, and has wide application in the fields of automobile industry, household appliances, electronics, packaging, building material furniture and the like, and in recent years, the yield and the demand of polypropylene are continuously increased. The existing propylene polymerization process mostly adopts a propylene bulk polymerization method to prepare a polypropylene product, so that the concentration of propylene monomers around the active center of the catalyst is extremely high, and the chain transfer behavior is remarkable, thereby limiting the molecular weight of the polypropylene product. The molecular weight of the polypropylene commercial material is concentrated at 10-60 ten thousand g/mol, and the lower molecular weight causes the outstanding problems of lower mechanical property, lower heat resistance, seriously insufficient melt strength, poor creep resistance and environmental stress cracking resistance, lower long-term reliability and the like of polypropylene. Increasing the molecular weight of polypropylene products is critical to solving the above problems. In addition, increasing the molecular weight of polypropylene causes problems such as an increase in viscosity, a decrease in processability, and the like. It is a very challenging problem how to increase the molecular weight while at the same time improving the processability of polypropylene. The existing methods for improving the processability of polyolefin materials mainly comprise molecular chain structure design, catalyst regulation and control, blending modification and processing technology optimization. Reducing the entanglement of high molecular weight polypropylene is one of the reliable ways to solve the above problems, and reducing entanglement can improve processability and also significantly improve the problem of low melt viscosity of polypropylene, resulting in polypropylene having both excellent service performance and processability. At present, research on domestic ultra-high molecular weight polypropylene (UHMWPP) is mainly focused on the field of catalysts, and the prepared ultra-high molecular weight polypropylene has not yet shown the characteristic of low entanglement. The invention patent CN115353575A discloses a main catalyst, a preparation method and application for preparing ultra-high molecular weight polypropylene, wherein the catalyst consists of a main catalyst component and an alkyl aluminum cocatalyst, the main catalyst component is formed by reacting a magnesium-and titanium-containing catalyst precursor compound, an internal electron donor and a titanium compound, and the catalyst precursor compound is formed by reacting an alkoxy magnesium compound, a titanate compound, an alcohol compound, a chlorosilane compound and a phosphite compound in an alkane/halogenated aromatic hydrocarbon mixed solvent and then performing controlled precipitation. The catalyst system can polymerize and produce UHMWPP with viscosity average molecular weight M v =100-600 ten thousand adjustable at a wider temperature range (55-105 ℃), and high polymerization efficiency is maintained in the temperature range, so that key technical characteristics such as isotacticity and molecular weight distribution of the obtained ultra-high molecular weight polypropylene resin cannot fluctuate due to polymerization temperature change. The invention patent CN118265731a discloses a method for producing ultra-high molecular weight polypropylene, which has a lower inorganic content with a viscosity average molecular weight of more than 100 ten thousand g/mol and less than 30 ppm. Disclosure of Invention The invention aims to overcome the defects in the prior art, and provides an environment regulating and controlling method for an active center of a polypropylene catalyst and a polypropylene preparation method, which can reduce entanglement degree and improve processability while meeting the preparation of ultra-high molecular weight polypropylene. The aim of the invention can be achieved by the following technical scheme: The first object of the present invention is to provide a method for preparing a polypropylene catalyst, comprising one of the following combinations of steps: Step combination 1: a) Adding a polypropylene catalyst and an alkane solvent into a reactor and stirring; b) Dissolving the additive in an alkane solvent, adding the alkane solvent into a reactor, and stirring for reaction; c) Removing the supernatant after the reaction i