Polyethylene Long Chain Branching Control via Alkyl Aluminum Co-Catalyst
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Solution Overview
Problem
There is a need to control the amount of long-chain branching in polyethylene resins produced using Ziegler-Natta catalysts, as existing methods do not effectively manage this parameter, affecting polymer melt behavior and processing properties.
Innovation Solution
Adjusting the concentration of alkyl aluminum co-catalyst with an electron donor-free Ziegler-Natta catalyst during polymerization to manipulate and control long-chain branching, using methods such as measuring melt flow ratio (MFR) and catalyst productivity as indicators for process control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the concentration of alkyl aluminum co-catalyst is increased to improve catalyst productivity, then the long-chain branching amount increases, but the melt flow ratio decreases
Solution Approach 1:
The patent applies parameter changes by systematically varying the alkyl aluminum co-catalyst concentration to establish quantitative relationships between co-catalyst amount, long-chain branching content, and melt flow ratio. This enables precise control of processing properties through parameter optimization.
Solution Approach 2:
The patent implements feedback control by using melt flow ratio measurements as an indicator to monitor and adjust the long-chain branching amount. By measuring MFR and correlating it with LCB content, the system can automatically adjust co-catalyst concentration to maintain desired processing properties.
2Ease of operation
If the concentration of alkyl aluminum co-catalyst is adjusted to control long-chain branching, then the processing properties improve, but the process complexity increases
Solution Approach 1:
The patent applies self-service by establishing predetermined relationships between melt flow ratio and long-chain branching content. These pre-established correlations allow the system to determine LCB from routine MFR measurements without requiring additional complex analysis equipment or procedures.
3Manufacturing precision
If the alkyl aluminum co-catalyst concentration is reduced to decrease long-chain branching, then the melt flow ratio increases, but the catalyst productivity decreases
Solution Approach 1:
The patent optimizes the alkyl aluminum co-catalyst concentration within specific ranges (e.g., 0.5-5 mmol per mmol of titanium) to achieve the desired balance between productivity and processing properties. This quantitative parameter optimization allows simultaneous improvement of multiple conflicting parameters.
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 allows for precise control of long-chain branching in polyethylene, enhancing processing properties and productivity by correlating alkyl aluminum co-catalyst concentration with MFR and catalyst productivity, thereby improving polymer properties like melt strength and extrusion processibility.
Implementation Method 1
ethylene, and optionally one or more comonomers, in the polymerization reaction is catalyzed by an electron donor-free Ziegler-Natta catalyst and an alkyl aluminum co-catalyst
Implementation Method 2
the amount of LCB in the polyethylene is controlled by adjusting an amount of an alkyl aluminum co-catalyst used with an electron donor-free Ziegler-Natta catalyst during the production of the polyethylene
Data Source
AI summary
Polymerization process control methods for making polyethylene are provided. The process control methods include performing a polymerization reaction in a polymerization reactor to produce the polyethylene, where ethylene, and optionally one or more comonomers, in the polymerization reaction is catalyzed by an electron donor-free Ziegler-Natta catalyst and an alkyl aluminum co-catalyst. A melt flow ratio (I21/I2) of the polyethylene removed from the polymerization reactor is measured and an amount of long chain branching (LCB) of the polyethylene from the polymerization reactor is controlled by adjusting a weight concentration of the alkyl aluminum co-catalyst present in the polymerization reactor. In addition, an electron donor-free Ziegler-Natta catalyst productivity of the polyethylene being produced in the polymerization reactor is measured from which the amount of LCB of the polyethylene from the polymerization reactor is determined using the measured electron donor-free Ziegler-Natta catalyst productivity and a predetermined relationship between the electron donor-free Ziegler-Natta catalyst productivity and the LCB.