Ziegler-Natta Catalyst for Ultra-High Molecular Weight Polyethylene
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Solution Overview
Problem
Current Ziegler-Natta catalyst compositions struggle to produce polyethylene with desired properties, particularly ultra-high molecular weight polyethylene (UHMWPE), in a cost-effective manner, while maintaining uniform shape and morphology.
Innovation Solution
A Ziegler-Natta catalyst composition comprising a magnesium-titanium procatalyst, an organo-aluminum co-catalyst, and external electron donors such as substituted silanediyl diacetate, trialkyl borate, or tetraalkoxysilane, which supports uniform polymerization and prevents chain termination, resulting in UHMWPE with molecular weights between 4 million and 12 million g/mol and improved crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional Ziegler-Natta catalyst compositions are used, then polyethylene can be produced, but the molecular weight is limited and uniform shape control is difficult
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by introducing specific external electron donors (substituted silanediyl diacetates, trialkyl borates, or tetraalkoxysilanes) and adjusting their ratios with the organo-aluminum co-catalyst. This parameter modification enables simultaneous achievement of ultra-high molecular weight (4-12 million g/mol) and uniform resin shape, resolving the contradiction between molecular weight enhancement and shape control.
2Quantity of substance
If catalyst compositions are optimized for high molecular weight, then UHMWPE is produced, but production cost increases
Solution Approach 1:
The patent optimizes the concentration parameters of catalyst components, specifically using external electron donors at ratios of 0.01-10 times relative to the organo-aluminum co-catalyst. This parameter optimization achieves ultra-high molecular weight polyethylene (4-12 million g/mol) while maintaining cost-effective production, directly resolving the contradiction between high molecular weight achievement and manufacturing cost.
3Productivity
If chain transfer agents are present, then polymerization proceeds, but molecular weight decreases
Solution Approach 1:
The patent introduces external electron donors as intermediary substances that mediate between the organo-aluminum co-catalyst and the polymerization process. These intermediaries modify the catalyst's electronic properties to reduce chain transfer reactions, thereby maintaining ultra-high molecular weight (4-12 million g/mol) even when chain transfer agents are present, resolving the contradiction between polymerization productivity and molecular weight retention.
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 catalyst composition achieves polyethylene with uniform shape and desired molecular weight, enhancing flowability and productivity while reducing downstream costs, and maintaining high crystallinity and molecular weight, even in the presence of chain transfer agents.
Implementation Method 1
at least one external electron donor selected from the group consisting of substituted silanediyl diacetate, trialkyl borate and tetraalkoxysilane
Implementation Method 2
a pro-catalyst comprising a magnesium component and a titanium component
Implementation Method 3
polymerization of ethylene in the presence of a Ziegler-Natta catalyst composition
Data Source
AI summary
The Zigler-Natta catalyst composition of the present disclosure provides uniform polyethylene having a molecular weight in the range from 1 million g/mol to 12 million g/mol. The Zigler-Natta catalyst composition of the present disclosure comprises external electron donor selected from the group consisting of substituted silanediyl diacetate, trialkyl borate and tetraalkoxysilane.