Half-Metallocene Titanium Phosphinimide Catalyst Molecular Weight Control
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Solution Overview
Problem
Current catalyst systems for producing polyolefins, such as HDPE and LLDPE, primarily control molecular weight and distribution through the transition metal component, limiting the ability to adjust these properties effectively using alkylaluminum compounds or co-catalysts.
Innovation Solution
The process involves precontacting a half-metallocene titanium phosphinimide compound with an alkylaluminum compound, followed by activation with an activator and optional co-catalyst, to form a catalyst composition that is then used in olefin polymerization, allowing for increased molecular weight and controlled molecular weight distribution of the resulting polymer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transition metal component of the catalyst system is used to control molecular weight and molecular weight distribution, then the polymerization process can produce ethylene polymers with specific MWD characteristics, but the ability to adjust these properties using alkylaluminum compounds or co-catalysts is limited
Solution Approach 1:
The patent changes the chemical parameters of the alkylaluminum compound (specifically the alkyl group structure) to control molecular weight and distribution. By selecting different alkyl groups (methyl, ethyl, propyl, butyl, etc.), the catalyst system can adjust polymer properties without changing the transition metal component, thereby improving adaptability while maintaining system simplicity
Solution Approach 2:
The patent performs preliminary action by pre-contacting the alkylaluminum compound with the transition metal catalyst before polymerization. This pre-contacting step allows the alkylaluminum compound to modify the catalyst structure in advance, creating a more versatile catalyst system that can control molecular weight and distribution through the alkyl group selection rather than requiring complex post-catalyst adjustments
2Weight of moving object
If a standard catalyst system is used for polymerization, then the process is straightforward, but the molecular weight of the polymer cannot be significantly increased
Solution Approach 1:
The patent applies preliminary action by pre-contacting the alkylaluminum compound with the transition metal catalyst before polymerization. This pre-contacting step modifies the catalyst structure in advance, enabling significantly higher molecular weights in the resulting polymer while maintaining ease of manufacture through a simple additional preparation step
Solution Approach 2:
The patent changes the chemical parameters of the alkylaluminum compound (molar ratio, alkyl group structure, pre-contacting time) to achieve significantly higher molecular weights. By optimizing these parameters, the patent increases polymer molecular weight while keeping the manufacturing process straightforward and manageable
3Weight of moving object
If the alkylaluminum compound is precontacted with the half-metallocene titanium phosphinimide compound, then the molecular weight of the polymer increases, but the catalyst preparation process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-contacting the alkylaluminum compound with the half-metallocene titanium phosphinimide compound. This pre-contacting step, while adding a process step, creates a modified catalyst that significantly increases polymer molecular weight. The complexity is managed by making this a standardized preparation step rather than a complex multi-variable process
Solution Approach 2:
The patent changes the chemical parameters of the pre-contacting process (molar ratios of alkylaluminum to catalyst, pre-contacting time, temperature) to optimize molecular weight increase while minimizing process complexity. By establishing optimal parameter ranges, the patent achieves high molecular weights with a relatively simple and controllable preparation process
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
This approach significantly increases the molecular weight of the polymer and allows for precise control of the molecular weight distribution, enhancing the properties of the produced polyolefins.
Implementation Method 1
contacting a half-metallocene titanium phosphinimide compound and an alkylaluminum compound for a first period of time to form a precontacted mixture
Data Source
AI summary
Methods for controlling or adjusting the molecular weight and molecular weight distribution of an olefin polymer, such as an ethylene polymer, using an alkylaluminum compound are disclosed. In addition to the alkylaluminum compound, the catalyst systems contain a half-metallocene titanium phosphinimide compound and an activator.