Strippable Semiconductive Polyolefin Cable Composition
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Solution Overview
Problem
Existing semiconductive layers in electric power cables face challenges with strippability, thermo-oxidative stability, and handling issues, particularly due to the use of acrylonitrile-butadiene rubber (NBR), which is inconvenient to process and leads to degradation.
Innovation Solution
A semiconductive polymer composition comprising an ethylene copolymer with 10% or more polar co-monomer units, an olefin copolymer with propylene and ethylene monomer units prepared using a metallocene catalyst, and carbon black, which allows for easy stripping and improved processing properties without the need for NBR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acrylonitrile-butadiene rubber (NBR) is added to increase polarity for strippability, then stripping characteristics are improved, but handling properties deteriorate and thermo-oxidative stability decreases
Solution Approach 1:
The invention extracts NBR from the composition entirely and replaces it with an ethylene copolymer containing polar comonomer units (such as vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate). This extraction eliminates the handling problems and thermo-oxidative instability associated with NBR while maintaining the necessary polarity for strippability through the alternative polar comonomers.
Solution Approach 2:
The invention changes the chemical composition parameters by specifying that the ethylene copolymer must contain 10-60 weight percent polar comonomer units. This parameter range ensures sufficient polarity for strippability while avoiding the drawbacks of NBR. The composition also specifies 5-40 weight percent of the olefin copolymer with controlled melting point and 10-50 weight percent carbon black to achieve the desired balance of properties.
2Ease of operation
If NBR is used to achieve strippability, then stripping characteristics are improved, but thermo-oxidative stability worsens
Solution Approach 1:
The invention removes NBR from the composition, which is prone to thermo-oxidative degradation due to its unsaturated bonds. The replacement ethylene copolymer with polar comonomers provides similar polarity for strippability but with superior thermo-oxidative stability, as evidenced by the patent's emphasis on improved handling and stability characteristics.
3Ease of manufacture
If conventional semiconductive composition is used, then processing is simplified, but stripping characteristics are insufficient
Solution Approach 1:
The invention creates a composite material system combining three key components: (A) ethylene copolymer with polar comonomer units (10-60 wt%), (B) olefin copolymer with propylene and ethylene units (5-40 wt%, melting point 110°C or less), and (C) carbon black (10-50 wt%). This composite provides both the polarity needed for strippability and the processing advantages of polyolefin-based systems.
4Productivity
If high processing temperatures are applied to improve productivity, then production rate increases, but material degradation occurs with NBR-containing compositions
Solution Approach 1:
The invention changes the thermal stability parameter of the composition by replacing NBR with thermally stable polyolefin-based materials. The ethylene copolymer and olefin copolymer combination allows processing at higher temperatures without degradation, enabling increased production rates and line speeds as explicitly stated in the patent's technical effects.
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 enables easy adjustment of stripping characteristics, enhanced thermo-oxidative stability, and improved handling, allowing for higher processing temperatures and reduced stickiness, resulting in superior mechanical and processing properties compared to conventional compositions.
Implementation Method 1
an olefin copolymer comprising propylene monomer units and ethylene monomer units, wherein the olefin copolymer has a melting point of 110° C. or less
Data Source
AI summary
The present invention relates to a semiconductive polymer composition having easily controllable stripping characteristics, especially for an electric power cable. The semiconductive polymer composition has an ethylene copolymer having polar co-monomer units, wherein the amount of the polar co-monomer units in the ethylene copolymer is 10 wt. % or more, based on the total weight of the ethylene copolymer; an olefin copolymer having propylene monomer units and ethylene monomer units, wherein the olefin copolymer has a melting point of 110° C. or less, and carbon black in an amount of from 10 to 50 wt. %, based on the total weight of the semiconductive polymer composition, wherein the olefin copolymer (B) is prepared by using a metallocene polymerization catalyst.