Polyethylene Cable Insulation via Mixed Chain Transfer Agents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polymerization processes for producing low density polyethylene (LDPE) struggle to achieve optimal electrical properties, particularly low dielectric losses and space charge management, which are crucial for demanding applications like wire and cable insulation, where high temperatures and electric stresses are involved.
Innovation Solution
A high-pressure polymerization process using a combination of polar and non-polar chain transfer agents, such as methyl ethyl ketone and propylene, to produce polyethylene with significantly reduced tan δ values across a wide temperature and electric stress range, ensuring low dielectric losses and minimal space charges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polar CTA is used alone for polymerization, then the polymer can be produced with controlled molecular weight, but the dielectric losses (tan δ) increase especially at high temperatures and high electric stresses
Solution Approach 1:
The patent combines a polar chain transfer agent (such as propionaldehyde) with a non-polar chain transfer agent (such as propylene or methyl ethyl ketone) in a mixed CTA system. This merging of opposite polarity agents creates a synergistic effect where the non-polar CTA compensates for the high dielectric losses introduced by the polar CTA, while the polar CTA maintains its effectiveness in controlling molecular weight and stabilizing the polymerization process at high temperatures and electric stresses.
Solution Approach 2:
The patent optimizes the ratio of polar to non-polar CTA in the mixed system, typically using a non-polar CTA in excess (e.g., 90-99 mol% non-polar CTA and 1-10 mol% polar CTA). This parameter adjustment allows the system to maintain the molecular weight control benefits of polar CTA while minimizing dielectric losses through the dominant non-polar CTA component.
2Loss of energy
If a non-polar CTA is used alone for polymerization, then the polymer exhibits low dielectric losses, but the molecular weight control and stability at high temperatures deteriorate
Solution Approach 1:
The patent merges the advantages of both polar and non-polar CTAs by using them in combination. The non-polar CTA provides low dielectric losses and good electrical properties, while the polar CTA contributes molecular weight control and thermal stability. The synergistic interaction between the two types of agents allows the polymer to simultaneously achieve low dielectric losses and high stability under demanding electrical and thermal conditions.
3Productivity
If high pressure polymerization is used to produce LDPE, then the polymer can be produced with desired molecular weight distribution, but the dielectric losses increase at high temperatures and high electric stresses
Solution Approach 1:
The patent modifies the CTA composition parameter in high pressure polymerization by introducing a mixed CTA system with predominantly non-polar agents (90-99 mol%). This parameter change allows the process to maintain high productivity through efficient radical chain transfer while producing polymer with significantly reduced dielectric losses, especially at elevated temperatures and high electric field strengths.
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 polyethylene with exceptionally low dielectric losses and reduced space charges, enhancing the stability and reliability of cable insulation by maintaining low dielectric losses and preventing thermal runaway, thus meeting stringent requirements for wire and cable applications.
Implementation Method 1
Chain Transfer Agents (CTA) are used during high pressure polymerisation of ethylene to low density polyethylene (LDPE) to control the molecular weight and thus indirectly melt flow rate (MFR) of the formed polymer. The mechanism is based on hydrogen atoms that are easy to abstract.
Implementation Method 2
high pressure polymerisation of ethylene to low density polyethylene (LDPE)
Data Source
AI summary
The invention relates to a process for polymerizing a polymer in the presence of a mixture of at least two chain transfer agents, which mixture comprises: a polar chain transfer agent (polar CTA), and a non-polar (non-polar CTA).