Ethylene Polymer Blends with Controlled Long-Chain Branching
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Solution Overview
Problem
The high-temperature solution process for making ethylene polymers lacks the ability to introduce controlled long-chain branching, which is desirable for applications like shrink-film, and existing catalysts such as metallocenes are prone to deactivation by trace impurities and have low thermal stability.
Innovation Solution
A high-temperature solution process using a Ziegler-Natta catalyst comprising titanium, magnesium, and aluminum, in the absence of hydrogen, produces a first ethylene polymer component with substantial long-chain branching, while a second component with little or no long-chain branching is produced under different conditions, allowing the blend's long-chain branching to be controlled by adjusting the relative amounts of these components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metallocene catalysts are used to introduce long-chain branching, then long-chain branching is achieved, but the catalyst is easily poisoned by trace impurities and has low thermal stability
Solution Approach 1:
The patent changes the catalyst system parameters from metallocene to Ziegler-Natta catalysts (Ti/Mg/Al combination), and changes the reaction condition parameter by introducing hydrogen to suppress long-chain branching in one reactor while allowing it in another, thereby achieving controlled long-chain branching without catalyst deactivation issues
Solution Approach 2:
The patent divides the polymerization process into two separate reaction zones with different catalyst systems and hydrogen conditions. The first zone produces polymer with minimal long-chain branching using Ziegler-Natta catalyst with hydrogen, while the second zone produces polymer with controlled long-chain branching using Ziegler-Natta catalyst without hydrogen, allowing independent optimization of each zone
2Productivity
If Ziegler-Natta catalysts are used to produce linear ethylene polymers, then high activity and comonomer incorporation are achieved, but long-chain branching cannot be introduced
Solution Approach 1:
The patent segments the polymerization process into two reaction zones with different hydrogen conditions. The first zone uses Ziegler-Natta catalyst with hydrogen to produce high-activity linear polymer, while the second zone uses the same catalyst type without hydrogen to produce polymer with long-chain branching, thereby maintaining catalyst activity while achieving branching control
Solution Approach 2:
The patent changes the hydrogen parameter in the reaction conditions. By removing hydrogen in the second reaction zone while maintaining the Ziegler-Natta catalyst system, the process enables long-chain branching formation without sacrificing catalyst activity or comonomer incorporation capabilities
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 process enables the production of ethylene polymer blends with a predetermined degree of long-chain branching using readily available Ziegler-Natta catalysts and conventional equipment, improving the polymer's properties and processability without requiring new catalysts or extensive equipment modifications.
Implementation Method 1
ethylene is polymerized in the presence of a first Ziegler-Natta catalyst comprising titanium, magnesium, and aluminum
Data Source
AI summary
A high-temperature solution process for making an ethylene polymer blend having a controlled degree of long-chain branching is disclosed. Ethylene is polymerized in the presence of a first Ziegler-Natta catalyst comprising titanium, magnesium, and aluminum in the absence of hydrogen to produce a first ethylene polymer component having substantial long-chain branching. A second ethylene polymer component having little or no long-chain branching is also prepared. Both polymerizations are performed at a temperature from 140° C. to 250° C. The first and second ethylene polymer components are combined to give a polymer blend. The degree of long-chain branching in the blend is controlled by adjusting the relative amounts of the first and second ethylene polymer components. The invention enables the preparation of valuable products having a pre-determined degree of long-chain branching using readily available Zeigler-Natta catalysts, commercially practiced techniques, and conventional equipment.