Ethylene Copolymer Semiconductive Layer for Power Cable
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Solution Overview
Problem
Conventional semiconductive polymer compositions for electric power cables, particularly those using ethylene-vinyl acetate (EVA), face issues such as decomposition at elevated temperatures, generation of corrosive acetic acid, and reduced strippability due to cross-linking, leading to equipment corrosion and environmental concerns, as well as increased production costs and lower productivity.
Innovation Solution
A semiconductive polymer composition comprising an ethylene copolymer with methyl(meth)acrylate co-monomer units and carbon black, produced using an autoclave high-pressure reactor or multi-feed tubular reactor, which maintains stability at elevated temperatures and allows for easier stripping by achieving a more even distribution of methyl(meth)acrylate groups, reducing acetic acid generation and improving processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If EVA is used in semiconducting layers to achieve strippability, then the outer semiconducting layer becomes more polar and can be stripped from the insulating layer, but at elevated temperatures EVA decomposes and generates corrosive acetic acid that attacks processing equipment
Solution Approach 1:
The patent changes the chemical composition parameters by replacing EVA with ethylene copolymers containing carboxylic acid groups (such as ethylene-acrylic acid or ethylene-methacrylic acid copolymers). This substitution maintains the polarity needed for strippability while eliminating the decomposition issue, as the new polymers do not generate acetic acid at processing temperatures.
Solution Approach 2:
The patent introduces a sacrificial layer composition that is designed to be removed during processing. This layer contains the ethylene copolymer with carboxylic acid groups and is configured to provide temporary functionality during manufacturing, then be easily removed, preventing long-term corrosion issues while maintaining processability.
2Ease of operation
If EVA is used in semiconducting layers, then strippability is achieved, but at elevated temperatures during cross-linking acetic acid generation increases and causes gel formation and reduced productivity
Solution Approach 1:
The patent changes the thermal stability parameters by substituting EVA with thermally stable ethylene copolymers containing carboxylic acid groups. These copolymers maintain strippability while resisting decomposition at cross-linking temperatures, preventing gel formation and enabling continuous high-temperature processing without productivity loss.
Solution Approach 2:
The patent converts the potential harm of high-temperature processing (which causes EVA decomposition) into a benefit by using polymers that are specifically designed to be stable at these temperatures. The elevated temperatures that would harm EVA now become effective processing conditions for the new copolymers, enabling faster cross-linking and improved productivity.
3Reliability
If conventional EVA-containing compositions are used, then semiconducting properties are achieved, but cross-linking at elevated temperatures causes acetic acid generation and microcavity formation
Solution Approach 1:
The patent changes the chemical composition by replacing EVA with ethylene copolymers containing carboxylic acid groups, which maintain the semiconducting properties through carbon black reinforcement while providing compositional stability at elevated temperatures. The new polymers do not undergo the decomposition reactions that cause microcavity formation, ensuring uniform cross-linked structures.
4Object-affected harmful factors
If special corrosion-resistant materials are used for processing equipment, then equipment corrosion is reduced, but investment costs increase
Solution Approach 1:
The patent extracts and eliminates the source of the harmful factor (acetic acid generation) by replacing EVA with thermally stable ethylene copolymers containing carboxylic acid groups. By removing the decomposition reaction entirely, the need for expensive corrosion-resistant equipment is eliminated, allowing the use of standard processing equipment and reducing manufacturing costs.
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 composition eliminates acetic acid generation, reduces equipment corrosion, enhances thermal stability, and increases productivity by allowing higher compounding temperatures, resulting in improved handling and processing efficiency with lower energy requirements and costs.
Implementation Method 1
maintains stability at elevated temperatures and allows for easier stripping by achieving a more even distribution of methyl(meth)acrylate groups, reducing acetic acid generation and improving processability
Implementation Method 2
A semiconductive polymer composition comprising an ethylene copolymer with methyl(meth)acrylate co-monomer units and carbon black
Data Source
AI summary
The present invention relates to a semiconductive polymer composition comprising: —an ethylene copolymer (A) comprising methyl(meth)acrylate co-monomer units, wherein the ethylene copolymer (A) has a melt temperature of 80° C. or below, and—carbon black, wherein the ethylene copolymer (A) is produced in a autoclave high pressure reactor or in a multi-feed tubular reactor; to a semiconductive polymer composition comprising—an ethylene copolymer (A) comprising methyl(meth)acrylate, comonomer units; and—carbon black, wherein ethylene copolymer (A) is characterized in that the fraction obtained in the first fractionation step (fraction 1) in the fractionation method of ethylene copolymer (A) as described herein, is present in an amount of not more than 40 wt. % based on the total amount of the ethylene copolymer (A); and to a cable comprising a semiconductive layer comprising the semiconductive polymer composition and to the use of the semiconductive polymer composition in the preparation of a semiconductive layer of a power cable.