Crosslinkable Polyethylene Compounding With Low-Scorch Peroxide Injection
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Solution Overview
Problem
Conventional methods for making crosslinkable compound compositions for cable insulation require soaking towers and result in high costs, energy consumption, and contamination risks, with challenges in incorporating free radical initiators due to decomposition under compounding conditions, leading to premature crosslinking and defects in manufactured articles.
Innovation Solution
A method involving melt compounding a thermoplastic polyolefin with antioxidants but lacking curative additives, followed by injecting organic peroxides and crosslinking coagents into the melt at controlled temperatures to create a homogeneous crosslinkable compound without the need for soaking, ensuring high temperature and low scorch properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional soaking methods are used to incorporate free radical initiators, then crosslinkable compound compositions can be made, but the process requires massive and expensive soaking towers, leading to high costs and limited feasibility of multiple compounding sites
Solution Approach 1:
The patent extracts the free radical initiator incorporation step from the traditional soaking tower process and integrates it into the extruder. The extruder is modified to include a barrel with a temperature gradient and a screw design that allows for initiator addition and in-situ crosslinking, eliminating the need for separate soaking tower equipment.
Solution Approach 2:
The patent merges multiple functions into the extruder: melting, mixing, initiator incorporation, and crosslinking all occur within a single extruder unit. This consolidation eliminates the need for separate soaking towers and reduces equipment complexity while maintaining the crosslinking functionality.
2Productivity
If free radical initiators are incorporated during melt compounding at high temperatures, then production efficiency is improved, but the initiators decompose under compounding conditions, causing premature crosslinking and defects
Solution Approach 1:
The patent implements a temperature gradient in the extruder barrel, with lower temperatures in the initial zones and progressively higher temperatures toward the discharge zone. This parameter change allows the free radical initiator to be incorporated and gradually activated without premature decomposition, maintaining crosslinking stability while enabling continuous production.
Solution Approach 2:
The free radical initiator is incorporated into the polymer melt during the extrusion process before the material reaches high temperatures. The initiator is added in a cooler zone and protected during transport through the extruder, allowing it to remain stable until the intended crosslinking point, thus preventing premature activation.
3Stability of the object's composition
If soaking towers are used for incorporating free radical initiators, then uniform distribution can be achieved, but the process consumes large amounts of energy and increases contamination risks
Solution Approach 1:
The extruder's screw design creates self-mixing action through its geometry and rotation, which automatically distributes the free radical initiator uniformly throughout the polymer melt without requiring additional soaking or external mixing equipment. The system uses its own mechanical energy to achieve uniform distribution.
Solution Approach 2:
The patent replaces the thermal soaking process with a mechanical mixing approach. The extruder screw mechanically incorporates and distributes the initiator through shear and compressive forces during extrusion, eliminating the need for thermal energy-intensive soaking towers while achieving uniform distribution.
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
This approach eliminates the need for soaking towers, reduces costs and contamination risks, and achieves stable, high-temperature, low-scorch crosslinkable compositions with improved mechanical properties and production efficiency, preventing defects in manufactured articles.
Implementation Method 1
injecting into the compounded melt a combination of curative additives comprising one or more organic peroxides and one or more crosslinking coagents
Implementation Method 2
curatives, which are compounds that initiate free-radical crosslinking or increase concentration of crosslinks made thereby
Implementation Method 3
crosslinking coagents... compounds that initiate free-radical crosslinking or increase concentration of crosslinks made thereby
Implementation Method 4
melt compounding a primary stream at a temperature of from 120.0° to 150.0° C.... injecting into the compounded melt a combination of curative additives
Data Source
AI summary
Provided are high temperature, low scorch, including no scorch, which is defined herein, methods of making crosslinkable compound compositions, the method comprising melt compounding a primary stream at a temperature of from 120.0° to 150.0° C., wherein the primary stream comprises one or more thermoplastic polyolefins and one or more antioxidants, but lacks curative additives selected from the group consisting of: peroxides and crosslinking coagents; and injecting into the compounded melt a combination of curative additives comprising one or more organic peroxides and one or more crosslinking coagents, and homogeneously mixing the one or more thermoplastic polyolefins, one or more antioxidants, one or more organic peroxides, and one or more crosslinking coagents by melt compounding them together. Also provided are methods of making crosslinked compound compositions and manufactured articles.