Ziegler-Natta Catalyst Grain Size Control for Polyolefin Homogenization
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Solution Overview
Problem
Ziegler-Natta-type catalysts used in olefin polymerization processes often result in defects such as dots, specks, and rough patches in polyolefin products, particularly in pipes, due to homogenization issues during extrusion, which affect the strength and flow properties of the final product.
Innovation Solution
A Ziegler-Natta catalyst system with a particle size distribution of d50 between 5 μm and 20 μm is used in a two-loop reactor system, allowing for the production of polyolefins with improved homogenization and reduced defects, leading to enhanced resin particle size distribution and increased productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Ziegler-Natta catalysts are used in olefin polymerization, then polymerization activity is achieved, but defects such as dots, specks, and rough patches appear in the final polyolefin products
Solution Approach 1:
The invention changes the particle size parameter of the Ziegler-Natta catalyst from conventional sizes to a specific range of 5-20 μm (with d50 between 8-15 μm). This parameter change in catalyst morphology improves homogenization during extrusion and eliminates defects in the final polyolefin products while maintaining polymerization activity.
2Ease of operation
If larger catalyst particles are used, then catalyst handling is easier, but homogenization problems occur during extrusion leading to defects in the final product
Solution Approach 1:
The invention optimizes the catalyst particle size parameter to a specific range (5-20 μm) that balances handling ease with extrusion homogenization. The d50 value between 8-15 μm provides sufficient particle size for stable handling while being small enough to achieve complete homogenization during extrusion, eliminating the trade-off between these two requirements.
3Manufacturing precision
If catalyst particle size is reduced to improve homogenization, then defects are reduced, but catalyst productivity may decrease
Solution Approach 1:
The invention identifies an optimal particle size range (5-20 μm) that maintains high catalyst productivity while achieving superior homogenization. The specific d50 range of 8-15 μm ensures particles are small enough for complete extrusion homogenization but large enough to maintain adequate catalyst activity and productivity, resolving the contradiction between these two 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
The process results in improved homogenization, higher unit throughput, increased catalyst productivity, and reduced defects in polyolefin products, with smaller resin particles facilitating easier extrusion and higher bulk density, resulting in more efficient production and lower catalyst costs.
Implementation Method 1
a Ziegler-Natta catalyst system... In any olefin polymerisation process, the polyolefin is produced in the reactor in the presence of an olefin polymerisation catalyst
Implementation Method 2
The flow of ethylene polymer obtained in the first reactor is transferred into the second reactor by means of one or more settling legs of the first reactor, for example by using two settling legs (each being filled independently with the suspension coming from the reactor, the solids being concentrated by gravity settling and discharge)
Data Source
AI summary
The present invention discloses an olefin polymerisation process carried out in the presence of a Ziegler-Natta catalyst in two liquid full loop reactors connected in series wherein different molecular weight fractions are produced to form a polyolefin, said process being characterized in that the Ziegler-Natta catalyst has a particle size distribution d50 of less than 20 μm and greater that 5 μm.