Phosphine-Substituted Vinyl Metallocene Catalyst for Olefin Polymerization
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Solution Overview
Problem
Current metallocene catalysts for olefin polymerization, particularly those with pyrrole ring ligands, exhibit low catalytic activity and limited molecular weight distribution control, necessitating the development of more active and structure-controllable catalysts for polyolefin production.
Innovation Solution
A phosphine-substituted vinyl containing metallocene catalyst with the general formula Cp2(CR1=CR2(P(R3)2)MX is developed, where Cp is a cyclopentadiene ligand with 1-5 substitutions, R1-2 are selected from various alkyl or aryl groups, and M is titanium or zirconium, along with a specific preparation process involving dihalide dicyclopentadienyl compounds, alkaline compounds, and dialkyl phosphorus halides to enhance catalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pyrrole ring containing transition metal catalysts are used for olefin polymerization, then the catalyst structure provides coordination capability, but the catalytic activity is low
Solution Approach 1:
The patent changes the ligand type from pyrrole ring to phosphine-substituted vinyl group, altering the electronic and steric parameters of the coordinating ligand. This parameter change enhances the catalytic activity while maintaining the coordination capability through the phosphine group and cyclopentadienyl ligands.
Solution Approach 2:
The catalyst combines multiple ligand types (cyclopentadienyl, phosphine, vinyl) with a transition metal center to create a composite catalyst system. This composite structure integrates the coordination stability of cyclopentadienyl with the electronic modulation of phosphine and the structural flexibility of vinyl groups, achieving high activity.
2Productivity
If conventional metallocene catalysts are used, then the polymerization activity is high, but the molecular weight distribution control is limited
Solution Approach 1:
The patent introduces local structural features through the phosphine-substituted vinyl group that create specific local electronic and steric environments around the metal center. This local quality modification enables better control over polymer chain growth and termination, achieving broader molecular weight distribution control while maintaining high activity.
Solution Approach 2:
The vinyl-containing ligand structure provides dynamic flexibility that allows the catalyst to adapt its coordination geometry during the polymerization process. This dynamic behavior enables the catalyst to accommodate different chain lengths and structures, improving molecular weight distribution control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The phosphine-substituted vinyl metallocene catalyst demonstrates high catalytic activity for homopolymerization and copolymerization of alpha-olefins, producing polymers with high molecular weight and broad molecular weight distribution, outperforming existing catalysts in terms of activity and polymer properties.
Implementation Method 1
A phosphine-substituted vinyl containing metallocene catalyst with the general formula Cp2(CR1=CR2(P(R3)2)MX is developed... demonstrates high catalytic activity for homopolymerization and copolymerization of alpha-olefins
Data Source
AI summary
The invention relates to a phosphine-substituted vinyl containing metallocene catalyst, and also to the preparation process of the same as well as to the application of the catalyst. The catalyst has the general formula of Cp2(CR1=CR2(P(R32))MX, wherein Cp is a ligand containing cyclopentadiene having 1~5 substitutions, of which two neighbors connecting to each other to form fused rings having more than two members; R1-R3 is selected from the groups consisting of hydrogen, C1~C18 alkyl or perfluoro-alkyl, C6~C24 aralkyl or alkaryl; M is selected from the groups consisting of metals of the IVB group; and X is selected from the groups consisting of halogens, C1~C24 alkyl, alkoxyl, silicone or alkaryl. With aluminoxane or modified aluminoxane, aluminum alkyl, halogenated aluminum alkyl or their mixture as the catalyst promoter, the phosphine-substituted vinyl containing metallocene catalyst may be employed as the major catalyst for the polymerization or copolymerization of alpha-olefin, Due to its high activity, the polymerization may occur at both high and low temperatures with the polymer having higher molecular weight and broader molecular weight distribution.