Microporous Polyolefin Membranes Using Halogen-Free Solvent Extraction
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Solution Overview
Problem
The existing manufacturing processes for microporous polyolefin membranes, particularly for battery separators, rely on chlorinated solvents like trichloroethylene and methylene chloride, which pose environmental and health risks, and there is a need for a sustainable, halogen-free approach that efficiently recycles solvents and plasticizers while maintaining performance criteria.
Innovation Solution
A closed-loop process using a bespoke halogen-free solvent with specific physical and chemical properties, such as low water solubility and a flashpoint above 23°C, is employed for extrusion and solvent extraction, followed by solvent recovery using activated carbon or vapor condensation, allowing for efficient separation and recycling of plasticizers and solvents, and the use of naphthenic, paraffinic, or white mineral oils as plasticizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chlorinated solvents (trichloroethylene, methylene chloride) are used for extraction, then extraction efficiency is improved, but environmental and health risks increase
Solution Approach 1:
The patent changes the chemical parameters of the solvent system by replacing chlorinated solvents with a blend of hydrocarbon solvents (isoparaffinic, naphthenic, and/or aromatic hydrocarbons). This parameter change maintains extraction efficiency while eliminating the harmful halogen-containing compounds, thus resolving the contradiction between productivity and environmental/health safety
Solution Approach 2:
The patent employs a solvent system that can be easily replaced and regenerated. The hydrocarbon solvent blend, while effective for extraction, is designed to be recoverable through distillation and activated carbon treatment, allowing for continuous process operation without long-term environmental contamination, thus addressing the harmful factors while maintaining productivity
2Manufacturing precision
If solvent extraction is performed to remove plasticizer, then micropore formation is improved, but solvent and plasticizer separation becomes more difficult
Solution Approach 1:
The patent carefully selects hydrocarbon solvents with specific boiling points that are sufficiently different from the plasticizer boiling points. This parameter change in solvent selection enables effective separation through simple distillation, reducing the complexity of the recycling process while maintaining effective micropore formation through plasticizer extraction
Solution Approach 2:
The patent implements a closed-loop system where the hydrocarbon solvent is recovered through distillation and activated carbon treatment, then reused in the extraction process. The plasticizer is also recovered and reused in subsequent extrusion operations. This recovery approach simplifies the overall process complexity while ensuring high-quality micropore formation
3Object-affected harmful factors
If halogen-free solvents are used, then environmental friendliness is improved, but solvent selection becomes more restricted
Solution Approach 1:
The patent identifies a universal solvent system based on hydrocarbon blends (isoparaffinic, naphthenic, and/or aromatic) that can be applied across different polyolefin membrane formulations and plasticizer types. This universal halogen-free solvent system maintains effectiveness for micropore formation while being environmentally friendly, thus resolving the contradiction between environmental friendliness and selection flexibility
Solution Approach 2:
The patent changes the parameter of solvent chemical composition from chlorinated to hydrocarbon-based, which restricts the specific chemical options but provides sufficient versatility through the use of different hydrocarbon classes. The selected hydrocarbon solvents maintain the necessary solubility parameters for effective plasticizer extraction while being environmentally acceptable, thus balancing environmental friendliness with adequate adaptability
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 minimizes worker exposure to harmful chemicals, reduces environmental impact, and ensures the production of microporous membranes that are free of halogen-containing compounds, maintaining mechanical and electrical properties while enabling efficient recycling and reuse of solvents and plasticizers.
Implementation Method 1
extraction of the plasticizer with a solvent
Implementation Method 2
evaporation of the solvent to form micropores
Implementation Method 3
subsequent adsorption-desorption of the solvent from activated carbon for re-use
Data Source
AI summary
Halogen-free, microporous polyolefin membranes are disclosed herein. The halogen-free, microporous polyolefin membranes can be manufactured using an environmentally friendly manufacturing process that includes extrusion of polymer-plasticizer mixtures followed by sheet formation and extraction of the plasticizer with a halogen-free solvent. The halogen-free solvent has a flashpoint greater than about 23° C. and an initial boiling point at least about 50° C. lower than the flashpoint of the plasticizer. The process can further be a closed loop process in which the halogen-free solvent can be reused.