Ethylene Polymerization CTA Distribution for Melt Strength
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Solution Overview
Problem
Conventional processes for producing low density polyethylene (LDPE) struggle to achieve high melt strength and increased G' values in film and extrusion coating applications, often resulting in issues like gel formation and process fouling, especially when using multifunctional components.
Innovation Solution
A process involving the polymerization of ethylene with a monomeric Chain Transfer Agent (mCTA) and a Chain Transfer Agent system in a reactor configuration with multiple zones, where the CTA activity is strategically distributed to enhance T-branch formation and reduce inter- and intramolecular branching, thereby improving melt strength without causing cross-linking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multifunctional components are used to increase long chain branching and melt strength, then melt strength and G' are improved, but gel formation and process fouling occur
Solution Approach 1:
The patent segments the branching function into two separate components: a monomeric CTA (mCTA) that forms T-branches and a polyene that forms H-branches. This segmentation prevents the gel formation caused by multifunctional components while achieving the desired long chain branching and melt strength improvement through controlled T- and H-branch formation.
Solution Approach 2:
The patent introduces an asymmetrical polyene as an intermediary component that facilitates H-branch formation without causing cross-linking. The polyene acts as a mediator between the mCTA and the polymer chains, enabling controlled branching while preventing the harmful gelation effects associated with direct use of multifunctional crosslinking agents.
2Strength
If multifunctional components are used to increase long chain branching, then melt strength is improved, but consumption of components and polymer residuals increase
Solution Approach 1:
By dividing the branching function between mCTA and polyene components, each component can be used at lower concentrations while achieving the same overall branching effect. The mCTA efficiently forms T-branches at low levels, and the polyene supplements H-branch formation, reducing total component consumption compared to using high levels of multifunctional agents.
Solution Approach 2:
The patent changes the functional parameters of the branching agents by selecting specific mCTA and asymmetrical polyene structures with optimized reactivity and branching efficiency. This parameter optimization allows achieving target melt strength with lower component concentrations, reducing both consumption and residuals.
3Ease of operation
If conventional processes are used to produce LDPE, then processability is maintained, but melt strength and G' values are insufficient for film and extrusion coating applications
Solution Approach 1:
The patent creates a composite polymer structure containing both T-branches from mCTA and H-branches from polyene within the LDPE matrix. This composite branching architecture maintains the good processability of conventional LDPE while significantly enhancing melt strength and G' values, making the material suitable for demanding film and extrusion coating applications.
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 the production of ethylene-based polymers with increased melt strength and reduced gel formation, achieving the desired properties while minimizing the consumption of mCTA and polymer residuals, thus optimizing the polymerization process.
Implementation Method 1
the polymerization takes place in the presence of at least one free-radical initiator
Implementation Method 2
a Chain Transfer Agent (mCTA) and a Chain Transfer Agent system
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A process to form an ethylene-based polymer comprises polymerizing a reaction mixture comprising ethylene, at least one monomeric chain transier agent, and at least one chain transfer agent system comprising at least one chain transfer agent (C'l'A) in the presence of at least one free-radical initiator and in a reactor configuration comprising at least two reaction zones, reaction zone 1 and reaction zone i (i≥2), wherein the reaction zone i is downstream from reaction zone 1. The ratio of "the activity of the CTA system of the feed to the first reaction zone" to the "activity of the CTA system of the cumulative feed to the reaction zone i," (Ζ1/Zi), is less than or equal to (0.8-0.2*log(Cs)), wherein Cs is from 0.0001 to 10.