Crosslinkable Polyolefin Blend for Power Cable Layering
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Solution Overview
Problem
Current methods for preparing crosslinkable polymer compositions for power cables face challenges such as premature crosslinking, uneven distribution of crosslinking agents, and high production costs, which affect the quality and efficiency of the crosslinking process, leading to issues like scorch and uneven layer formation.
Innovation Solution
A process involving a blend of an unsaturated first polyolefin and a crosslinking agent, with optional unsaturated low molecular weight compounds, is used, where the components are blended in specific ratios and forms to optimize crosslinking efficiency and flexibility, ensuring high-quality layer formation in power cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peroxide is added to polymeric material prior to extrusion, then crosslinking can be effected, but premature decomposition of peroxide occurs during extrusion causing scorch and inhomogeneity
Solution Approach 1:
The patent divides the peroxide addition process into two separate stages: first adding peroxide to the polymer melt in the extruder (Stage 1), then adding more peroxide during the cable manufacturing process (Stage 2). This segmentation prevents premature decomposition by controlling the timing and amount of peroxide addition, thereby avoiding scorch while ensuring complete crosslinking.
Solution Approach 2:
The patent performs preliminary mixing of peroxide with polymer in the extruder at controlled conditions, then maintains this mixture during extrusion. This preliminary action prepares the polymer for crosslinking without causing premature reaction, as the extrusion temperature is kept below the peroxide decomposition threshold.
2Reliability
If peroxide is added during cable manufacturing process, then crosslinking can be completed, but control over peroxide injection becomes complex and costly
Solution Approach 1:
The patent combines the peroxide addition steps with the existing extrusion and cable manufacturing processes. The peroxide is mixed with polymer in the extruder and then injected during cable manufacturing using the existing equipment and control systems, thereby achieving complete crosslinking without adding complex injection control systems.
Solution Approach 2:
The patent uses the existing extrusion and cable manufacturing processes to facilitate peroxide addition and crosslinking. The process leverages the current equipment and control mechanisms to achieve peroxide injection and mixing, eliminating the need for separate complex injection control systems.
3Manufacturing precision
If peroxide is mixed into polymer melt, then crosslinking agent distribution can be achieved, but peroxide flows away and lubricates polymer resulting in non-uniform distribution
Solution Approach 1:
The patent adds peroxide in controlled amounts during extrusion and then adds additional peroxide during cable manufacturing. This partial action approach ensures sufficient peroxide distribution without causing excessive peroxide that would flow away and lubricate the polymer, thereby maintaining uniform distribution while achieving complete crosslinking.
4Ease of manufacture
If extrusion temperature is increased to ensure proper melting and homogenisation, then mixing improves, but peroxide decomposition increases causing scorch
Solution Approach 1:
The patent performs peroxide addition and mixing during extrusion at controlled temperatures, then maintains the mixture during cable manufacturing. This periodic action allows the peroxide to be introduced and mixed without causing premature decomposition, as the temperature is kept below the decomposition threshold during the critical mixing phase.
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 achieves a high degree of crosslinking with improved wet ageing resistance and reduced scorch, resulting in power cables with enhanced mechanical and thermal properties, meeting stringent hot set elongation and permanent deformation requirements.
Implementation Method 1
the crosslinking agent should decompose in a subsequent cross-linking step at elevated temperature
Implementation Method 2
Cross-linking can be effected by adding free-radical forming agents like peroxides to the polymeric material
Implementation Method 3
extrusion performed at a temperature low enough to minimize the early decomposition of the peroxide but high enough to obtain proper melting and homogenisation
Data Source
AI summary
The present invention relates to a process for the preparation of an article, comprising the following steps: (a) providing a component (i) which comprises a blend of (a1) an unsaturated first polyolefin having a certain total amount m1 of carbon-carbon double bonds/1000 carbon atoms, (a2) a crosslinking agent, (a3) optionally an unsaturated low molecular weight compound having a certain total amount m2 carbon-carbon double bonds/1000 carbon atoms, (b) providing a component (ii) which comprises a second polymer having a certain total amount m3 of carbon-carbon double bonds/1000 carbon atoms, wherein m1, m2 and m3 satisfy a certain relationship, (c) forming a blend of component (i) and component (ii) wherein the weight ratio of the component (i) to the component (ii) is within the range of 10:90 to 99:1, (d) applying one or more layers of the blend onto a substrate.