Crosslinked Polyolefin Separator With Silane-Bound Inorganic Particles
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Solution Overview
Problem
Existing methods for manufacturing crosslinked polyolefin separators face challenges such as side reactions between diluting agents and initiators, difficulty in handling silane crosslinking agents, and increased extruder pressure, leading to non-homogeneous crosslinking and die-drooling phenomena.
Innovation Solution
A method involving the use of inorganic particles surface-treated with alkoxysilane containing a carbon-carbon double bonded group, which are chemically bound to polyolefin through Si—O—Si crosslinking bonds, preventing side reactions and evaporation of unreacted alkoxysilane, and allowing for improved heat resistance and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diluting agent and initiator are introduced to extruder at once, then crosslinking reaction occurs, but side reaction between diluting agent and initiator occurs
Solution Approach 1:
The patent divides the crosslinking process into two separate stages: first introducing the diluting agent and silane crosslinking agent to the extruder, then separately introducing the initiator in a subsequent step. This segmentation prevents the diluting agent and initiator from contacting each other simultaneously, thereby eliminating side reactions while ensuring the crosslinking reaction proceeds efficiently.
Solution Approach 2:
The patent performs preliminary mixing of the diluting agent and silane crosslinking agent in the extruder before adding the initiator. This preliminary action prepares the reaction system in advance, ensuring proper distribution of crosslinking agents throughout the polyolefin matrix, while delaying initiator introduction until conditions are optimal to prevent premature or side reactions.
2Manufacturing precision
If silane crosslinking agent is introduced in combination with diluting agent, then handling difficulty occurs, but crosslinking uniformity can be achieved
Solution Approach 1:
The patent uses the extruder as an intermediary device to mix the silane crosslinking agent with the diluting agent and polyolefin under controlled conditions. The extruder's mechanical mixing action ensures uniform distribution of the crosslinking agent throughout the material matrix, achieving homogeneous crosslinking while the controlled feeding process maintains ease of operation.
Solution Approach 2:
The patent controls the feeding rate and mixing parameters of the extruder to optimize the incorporation of silane crosslinking agent. By adjusting extrusion temperature, screw speed, and feeding rate, the patent achieves uniform crosslinking distribution while maintaining manageable processing conditions and avoiding handling difficulties.
3Productivity
If crosslinking is performed in extruder, then productivity increases, but extruder pressure increases causing non-homogeneous crosslinking
Solution Approach 1:
The patent performs preliminary mixing and distribution of crosslinking agents in the extruder before the actual crosslinking reaction is triggered by initiator addition. This preliminary action occurs at lower pressure, ensuring uniform agent distribution throughout the material. When the initiator is subsequently added and crosslinking begins, the reaction proceeds more uniformly without excessive pressure buildup.
Solution Approach 2:
The patent segments the crosslinking process into distinct phases: (1) mixing phase where diluting agent and silane crosslinking agent are incorporated at moderate pressure, and (2) reaction phase where initiator is added and crosslinking occurs. This segmentation allows pressure management during mixing while maintaining productivity, as the subsequent crosslinking reaction proceeds in a controlled manner with more uniform pressure distribution.
4Productivity
If crosslinking is performed in extruder, then manufacturing efficiency improves, but die-drooling phenomenon occurs
Solution Approach 1:
The patent segments the material flow into two streams: one containing the polyolefin and silane crosslinking agent (without initiator), and another containing the initiator. By keeping the initiator separate until the extrusion die, the patent prevents premature crosslinking that would cause die-drooling, while still enabling efficient crosslinked separator production through subsequent reaction in the extruder.
Solution Approach 2:
The patent uses a separate feeding system or sequential feeding mechanism as an intermediary to introduce the initiator at the optimal location and timing. This ensures that crosslinking occurs after the material has been properly formed and extruded, preventing die-drooling while maintaining high manufacturing efficiency through continuous processing.
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 method results in a crosslinked polyolefin separator with reduced die-drooling, enhanced heat resistance, and improved air permeability, suitable for lithium secondary batteries with a broad safety margin between shutdown and meltdown temperatures.
Implementation Method 1
crosslinked polyolefin having Si—O—Si crosslinking bonds
Implementation Method 2
silicon (Si) atoms of the Si—O—Si crosslinking bonds are chemically bound to the inorganic particles by means of oxygen (O) atoms
Data Source
AI summary
A crosslinked polyolefin separator and a method of making the same are disclosed herein. The method includes mixing a polyolefin, a diluting agent, an initiator, a crosslinking catalyst, and inorganic particles surface treated with an alkoxysilane containing a carbon-carbon double bonded group in an extruder to obtain a mixture, and then reactively extruding the mixture to form an extruded silane-grafted polyolefin composition; molding and orienting the extruded silane-grafted polyolefin composition in the form of an oriented sheet; extracting the diluting agent from the oriented sheet to obtain a porous membrane; thermally fixing the porous membrane to obtain a thermally fixed porous membrane; and crosslinking the thermally fixed porous membrane in the presence of moisture.