Ziegler Catalyst Particle Sizing for Loop-Slurry Polyethylene
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Solution Overview
Problem
Existing Ziegler catalysts for olefin polymerization struggle to balance polyolefin particle size and catalyst efficiency, leading to the production of fine particles unsuitable for slurry processes and gas-phase polymerizations, particularly in loop-slurry reactors, which limits their application in producing high-density polyethylene for demanding end-use applications like injection molding.
Innovation Solution
A Ziegler catalyst with a particle size between 5-20 micrometers is used in a loop-slurry reactor to produce polyethylene with specific properties, including a density of 0.930 g/cm3 to 0.970 g/cm3, a melt flow rate of 0 to 50 g/10 min, and a particle size distribution of 50 to 850 micrometers, achieving a balance between particle size and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional Ziegler catalysts are used to increase catalyst efficiency, then polymerization activity improves, but polyolefin particle size decreases producing fine particles unsuitable for slurry processes
Solution Approach 1:
The patent applies parameter changes by carefully controlling the particle size of the catalyst support (5-20 micrometers) and adjusting the halogen to magnesium ratio in the catalyst preparation. These parameter modifications enable the catalyst to achieve high efficiency while producing polyolefin particles within the acceptable size range for slurry processes, resolving the contradiction between catalyst efficiency and particle size.
2Manufacturing precision
If catalyst efficiency is increased to produce high-density polyethylene, then polymer properties improve, but fine particles are produced that are unsuitable for injection molding applications
Solution Approach 1:
The patent uses parameter changes by optimizing the catalyst composition (halogen to magnesium ratio) and support particle size (5-20 micrometers) to achieve the desired polyethylene density (0.930-0.970 g/cm³) while maintaining particle size within the acceptable range (50-850 micrometers) for injection molding applications.
3Productivity
If conventional catalysts are used in loop-slurry processes, then polymerization occurs, but the produced polyethylene does not meet the requirements for demanding end-use applications
Solution Approach 1:
The patent applies parameter changes by optimizing catalyst composition (using specific halogen to magnesium ratios) and support characteristics (5-20 micrometer particle size) to produce polyethylene with improved properties including density (0.930-0.970 g/cm³), melt flow rate (0-50 g/10 min), and particle size distribution (50-850 micrometers), making it suitable for demanding end-use applications like injection molding.
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 achieves high catalyst mileage, producing polyethylene with improved properties suitable for injection molding, such as crates, pallets, and other applications, while minimizing fine particles and maintaining high polymerization activity.
Implementation Method 1
A Ziegler catalyst with a particle size between 5-20 micrometers is used in a loop-slurry reactor to produce polyethylene with specific properties
Data Source
AI summary
A polyethylene composition produced by a loop-slurry process. The process includes contacting a feedstock comprising ethylene with a solid catalyst having a particle size (D50) of about 5 to about 20 micrometers and comprising a magnesium dihalide support containing a predominantly titanium trichloride species on its crystalline lattice derived by the reaction of magnesium alcoholates with tetravalent, halogen-containing compounds and one or more aluminum alkyl or aluminum alkyl halide components at a temperature of between about 90 to about 105° C. and a residence time of between about 30 to about 60 min. The resulting polyethylene composition has a particle size (D50) of about 200 to 400 micrometers, with less than 0.05 wt. % of particles being less than 45 micrometers in diameter. A loop-slurry process and a catalyst component are also provided.