Nitrogen External Donor for Propylene Polymerization Kinetics
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Solution Overview
Problem
Current propylene polymerization catalyst systems, particularly diester and monoester based Ziegler Natta systems, face challenges in achieving broad molecular weight distribution and controlled kinetics, leading to issues like lump formation and narrow molecular weight distribution, which are undesirable for applications like BOPP and injection molding.
Innovation Solution
A catalyst system incorporating a nitrogen-containing external donor, such as pentamethyldiethyltriamine (PMDETA) in combination with alkoxy silane, is used with a titanium-supported magnesium dichloride procatalyst and organoaluminium co-catalyst to control polymerization kinetics and stereo regularity, thereby achieving broad molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If diester catalyst system is used with silane as external donor, then polymerization activity is high, but molecular weight distribution becomes narrow and lump formation occurs
Solution Approach 1:
The patent applies parameter changes by switching from silane (oxygen-containing) to PMDETA (nitrogen-containing) as the external donor. This chemical parameter change fundamentally alters the catalyst system's behavior, transforming it from non-self-extinguishing with narrow molecular weight distribution to self-extinguishing with broad molecular weight distribution, while maintaining high polymerization activity.
Solution Approach 2:
PMDETA acts as an intermediary substance that mediates between the diester catalyst system and the polymerization process. It controls the kinetics by interacting with the catalyst active sites, providing self-extinguishing characteristics and broadening molecular weight distribution without sacrificing productivity.
2Reliability
If oxygen containing external donors are used with diester catalyst, then kinetics control is improved, but molecular weight distribution remains narrow
Solution Approach 1:
The patent employs parameter changes by transitioning from oxygen-containing external donors to nitrogen-containing PMDETA. This chemical composition change enables simultaneous achievement of reliable kinetics control and broad molecular weight distribution, resolving the contradiction between these two features.
3Reliability
If monoester catalyst system is used, then self extinguishing characteristics are achieved, but polymerization activity decreases
Solution Approach 1:
The patent applies universality by making the diester catalyst system exhibit properties traditionally associated with monoester systems. PMDETA enables the diester system to achieve self-extinguishing characteristics while maintaining high polymerization activity, making the catalyst system multi-functional and adaptable.
Solution Approach 2:
PMDETA serves as an intermediary that imparts self-extinguishing characteristics to the diester catalyst system without compromising its inherent high activity. The nitrogen-containing donor mediates the interaction between catalyst and monomer to achieve both reliability and productivity.
4Productivity
If silane is used as external donor with diester catalyst, then activity control is achieved, but stereo regularity and molecular weight distribution are compromised
Solution Approach 1:
The patent uses parameter changes by replacing silane with PMDETA, which has different steric and electronic properties. This change optimizes the interaction with the catalyst active sites, simultaneously improving activity control, stereo regularity, and molecular weight distribution.
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 use of PMDETA with silane as external donors results in controlled polymerization kinetics and broad molecular weight distribution, preventing lump formation and enhancing polymer properties for film and injection molding grades, while maintaining stereregularity and melt flow index levels.
Implementation Method 1
polymerization of propylene is carried out in presence of catalyst system consisting of titanium supported on magnesium dichloride (Ziegler Natta) carrying internal donor, an organo aluminium co-catalyst and an external electron donor
Implementation Method 2
external donor comprising pentamethyldiethyltriamine and an alkoxy silane
Data Source
AI summary
The present invention discloses new class of nitrogen containing external donor systems. These donor systems are used in titanium supported on magnesium dichloride pro-catalyst system for polymerization of propylene. The external donor systems of the present invention in combination with silane show the kinetics control for diester catalyst polymerization process along with stereo regularity control of product. The polypropylene produced using nitrogen containing external donor systems of the present invention have broad molecular weight distribution.