Cable Insulation Antioxidant Blend for Peroxide Stability
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Solution Overview
Problem
Peroxide crosslinkable insulation compounds for extra high voltage (EHV) cables suffer from peroxide instability during storage and rapid pressure development due to screen fouling during extrusion, leading to reduced run lengths and yields.
Innovation Solution
A cable insulation composition comprising a sulfur-containing first antioxidant with a -S(CH2)2CO2R group and a sulfur-containing second antioxidant without this group, in specific weight percentages, along with an ethylene-based polymer and peroxide, optionally including an organic nitrogenous base and a phenolic antioxidant, to enhance stability and prevent screen fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sulfur-containing first antioxidant with -S(CH2)2CO2R group is used in high amount, then peroxide stability is improved, but screen fouling occurs during extrusion
Solution Approach 1:
The patent combines two different sulfur-containing antioxidants (first antioxidant with -S(CH2)2CO2R group and second antioxidant without this group) in specific proportions. The first antioxidant (0.01-0.5 wt%) provides peroxide stability while the second antioxidant (0.001-0.009 wt%) prevents screen fouling. This synergistic combination resolves the contradiction by having each component address a different aspect of the problem.
Solution Approach 2:
The patent optimizes the concentration parameters of the antioxidants to resolve the contradiction. By controlling the first antioxidant at 0.01-0.5 wt% and the second antioxidant at 0.001-0.009 wt%, the formulation achieves both peroxide stability and screen cleanliness. The specific parameter ranges prevent excessive antioxidant concentration that would cause screen fouling while maintaining sufficient stability.
2Reliability
If amine bases are included to mitigate peroxide instability, then storage stability is improved, but rapid pressure development occurs due to screen fouling
Solution Approach 1:
The patent merges the function of amine bases (for stability) with sulfur-containing antioxidants (for fouling prevention) in a balanced formulation. The specific combination of 0.01-0.5 wt% first antioxidant, 0.001-0.009 wt% second antioxidant, and controlled amine base (0.1-1 wt%) creates a synergistic effect that achieves storage stability without the rapid pressure development caused by screen fouling.
Solution Approach 2:
The patent adjusts the parameter ranges of all additives to achieve optimal balance. The amine base is limited to 0.1-1 wt% while sulfur-containing antioxidants are precisely controlled at 0.01-0.5 wt% and 0.001-0.009 wt% respectively. This parameter optimization prevents excessive pressure development during extrusion while maintaining storage stability.
3Manufacturing precision
If fine screens (less than 50 μm) are used to achieve EHV cleanliness, then cable quality is improved, but run length is reduced due to screen fouling
Solution Approach 1:
The patent applies preliminary action by incorporating antioxidants and stabilizers into the insulation compound formulation before extrusion. The sulfur-containing antioxidants (0.01-0.5 wt% first antioxidant and 0.001-0.009 wt% second antioxidant) are pre-mixed into the polymer matrix, providing proactive protection against screen fouling during the extrusion process through fine screens (less than 50 μm), thereby maintaining EHV cleanliness while extending run length.
Data Source
AI summary
The process for making extra high voltage cable insulation is improved by using a composition comprising in weight percent based on the weight of the composition: (A) 95 to 99.9% of an ethylene-based polymer; (B) 0.2 to 2.5% peroxide; (C) 0.01 to 0.5% of a sulfur-containing first antioxidant having at least one -S(CH2)2C02R group, wherein R is C6 to C20 alkyl; (D) 0.001 to 0.009%) of a sulfur-containing second antioxidant that does not contain a -S(CH2)2C02R group, wherein R is a C6 to C20 alkyl; (E) Optionally, an organic nitrogenous base; and (F) Optionally, a phenolic third antioxidant that does not contain a -S(CH2)2C02R group, wherein R is a C6 to C20 alkyl.