Microporous Membrane Solvent Recovery Using Nonflammable Azeotropes
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Solution Overview
Problem
The manufacturing of microporous membranes for battery separators relies on solvents like hexane and trichloroethylene, which pose environmental and health risks, necessitating a sustainable approach that minimizes worker exposure and efficiently recycles the extraction solvent and plasticizer in a closed loop.
Innovation Solution
An environmentally friendly closed loop process using an azeotrope solvent to extract and evaporate the plasticizer from a polymer-plasticizer mixture, forming micropores and allowing for the reuse of the solvent, with specific azeotrope mixtures like those containing fluorinated compounds ensuring non-flammability and effective recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional solvents like hexane and trichloroethylene are used to extract plasticizer, then extraction efficiency is achieved, but environmental and health risks increase
Solution Approach 1:
The patent changes the chemical parameters of the extraction solvent by using an azeotropic mixture (e.g., isopropanol and water) instead of traditional organic solvents. This parameter change maintains extraction efficiency while eliminating the harmful effects associated with flammable and toxic solvents, directly resolving the technical contradiction between manufacturing ease and environmental safety
Solution Approach 2:
The patent employs a composite solvent system consisting of an azeotropic mixture of multiple components (e.g., isopropanol and water in specific ratios). This composite approach combines the beneficial properties of each component to achieve effective plasticizer extraction while maintaining non-flammability and environmental safety, thus resolving the contradiction between extraction efficiency and harmful factors
2Object-affected harmful factors
If azeotrope solvent is used for extraction, then environmental safety is improved, but solvent recovery complexity increases
Solution Approach 1:
The patent utilizes phase transition properties of the azeotropic solvent mixture to simplify recovery. By controlling temperature and pressure conditions, the solvent system undergoes predictable phase changes that facilitate separation and recovery, reducing the complexity of the recovery process despite the use of a composite solvent system
Solution Approach 2:
The patent converts the potential disadvantage of azeotropic composition (which can complicate distillation) into a benefit by utilizing the consistent boiling point and predictable phase behavior of the azeotrope. This allows for simplified recovery equipment design and operation, transforming what could be a complexity issue into an advantage for process control and environmental safety
3Quantity of substance
If plasticizer is removed to form micropores, then membrane porosity is achieved, but mechanical strength decreases
Solution Approach 1:
The patent changes the parameters of the plasticizer extraction process, specifically controlling the extent of extraction and the conditions of solvent removal. By optimizing these parameters, the process achieves sufficient porosity for battery separator function while maintaining adequate mechanical strength to prevent membrane rupture during battery assembly and operation
Solution Approach 2:
The patent creates local quality variations in the membrane structure through controlled plasticizer distribution and extraction. The resulting microporous structure provides local pathways for ion transport while maintaining sufficient polymer matrix integrity in other regions to support mechanical strength, thus resolving the contradiction between porosity and strength
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 process produces microporous membranes with comparable electrical resistivity and puncture resistance to traditional methods while reducing health and environmental risks, enabling efficient recycling of solvents and plasticizers.
Implementation Method 1
extracts with an azeotrope solvent the plasticizer from an extruded polymer-plasticizer mixture
Implementation Method 2
evaporates the azeotrope solvent to form micropores in the membrane
Implementation Method 3
passing the azeotrope solvent vapor through an ammonia chiller/heat exchanger system or other vapor condensing recovery system
Data Source
AI summary
An environmentally friendly closed loop manufacturing process (101, 102) produces microporous membranes (32) by cast or extrusion of polymer-plasticizer mixtures followed by non-porous film formation (20), extraction (22) of the plasticizer using an azeotrope solvent and thereby forming a solvent-laden sheet and a mixture of plasticizer and azeotrope solvent, distillation (28) of the mixture to separate the plasticizer and azeotrope solvent for reuse, evaporation (30) of the azeotrope solvent from the solvent-laden sheet to form the micropores, and capture of the resultant solvent vapor for subsequent adsorption-desorption of the azeotrope solvent from activated carbon (34) or by vapor condensation (36) for reuse in the manufacturing process. The azeotrope solvent is at least a two-component mixture of solvents, one of which is designed for efficient removal of the plasticizer, while the other component(s) render(s) the azeotrope solvent non-flammable.