Procatalyst Composition Halogenation for Polymer Selectivity
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Solution Overview
Problem
Current Ziegler-Natta catalyst compositions for olefin-based polymers lack variability in molecular weight distribution and selectivity, and there is a need for higher bulk density and phthalate-free alternatives.
Innovation Solution
A process involving halogenation of a procatalyst precursor in the presence of a substituted phenylene aromatic diester at controlled temperatures to form a procatalyst composition with enhanced selectivity and bulk density, using magnesium and titanium moieties with a substituted phenylene aromatic diester as an internal electron donor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Ziegler-Natta catalyst compositions are used, then polymerization can proceed, but the molecular weight distribution remains narrow and selectivity is limited
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by introducing substituted phenylene aromatic diesters with specific structural variations (different substituents at positions 3 and 5 of the phenylene ring). This modifies the electronic and steric properties of the internal electron donor, thereby changing the catalyst's selectivity and the polymer's molecular weight distribution without fundamentally altering the Ziegler-Natta catalyst structure
Solution Approach 2:
The patent creates a composite catalyst system combining magnesium halide support, titanium halide active sites, organoaluminum cocatalyst, and substituted phenylene aromatic diester internal electron donor. The synergistic interaction between these components produces the desired broad molecular weight distribution and enhanced selectivity
2Volume of stationary object
If conventional procatalyst preparation methods are used, then catalyst can be formed, but bulk density of the polymer is insufficient
Solution Approach 1:
The patent optimizes the particle size parameter of the procatalyst precursor to a specific range (5-25 μm, preferably 8-18 μm). This size control, combined with controlled halogenation conditions, produces catalyst particles that generate polymers with improved bulk density while maintaining compositional precision
3Reliability
If conventional halogenation temperature is used (≥115°C), then reaction proceeds efficiently, but selectivity index is poor (≥2.5)
Solution Approach 1:
The patent inverts the conventional temperature approach by conducting halogenation at lower temperatures (25-115°C, preferably 40-100°C). This counterintuitive parameter change improves selectivity index to below 2.5 by controlling the reaction kinetics and preventing side reactions that occur at higher temperatures
Solution Approach 2:
The patent employs a two-stage halogenation process: first stage at lower temperature (25-115°C) to establish high selectivity, and second stage at higher temperature to complete the halogenation. This periodic temperature variation achieves both high selectivity and complete reaction
4Object-affected harmful factors
If conventional internal electron donors are used, then catalyst can function, but phthalate derivatives are present which are undesirable
Solution Approach 1:
The patent extracts and replaces conventional phthalate-based internal electron donors with substituted phenylene aromatic diesters. This substitution removes the harmful phthalate derivatives from the catalyst system while maintaining the essential internal electron donor function for catalyst performance
Solution Approach 2:
The patent incorporates substituted phenylene aromatic diesters as non-phthalate internal electron donors in the catalyst composite. These alternative compounds provide the necessary electron donation functionality without introducing phthalate derivatives, achieving both environmental compliance and catalytic performance
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 improves the selectivity and bulk density of olefin-based polymers, achieving a broader molecular weight distribution and higher isotacticity while eliminating phthalate derivatives, resulting in a phthalate-free catalyst composition and polymer.
Implementation Method 1
halogenating a procatalyst precursor in the presence of a substituted phenylene aromatic diester at a temperature less than 115°C
Implementation Method 2
The internal electron donor includes a substituted phenylene aromatic diester
Data Source
AI summary
Disclosed herein are processes for preparing procatalyst compositions and polymers, i.e., propylene-based polymers, produced therefrom. The present procatalyst compositions improve catalyst selectivity and also increase the bulk density of the formant polymer.