Composite Hollow Fiber Membrane with Woven Braid Reinforcement
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Solution Overview
Problem
Existing methods for producing porous hollow fiber membranes, such as non-solvent induced phase separation (NIPS) and thermal induced phase separation (TIPS), face challenges with mechanical strength, filtration accuracy, water flux, and contamination resistance, often resulting in poor adhesion between layers and reduced porosity.
Innovation Solution
A composite multilayer porous hollow fiber membrane is fabricated using a combination of the NIPS and TIPS techniques, involving a thermoplastic macromolecule polymer resin, organic and inorganic pore-forming agents, and a coating solution to create a sturdy inner layer with large pores and an ultra-thin outer layer with fine pores, enhancing mechanical strength and filtration accuracy while preventing peeling between layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-solvent induced phase separation (NIPS) technique is used to produce hollow fiber membranes, then porosity is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a polyvinylidene fluoride (PVDF) hollow fiber membrane combined with a woven braid made of polyacrylonitrile (PAN) or polyethylene terephthalate (PET). The PVDF membrane provides high porosity (50-80%) and filtration performance, while the woven braid reinforcement layer provides tensile strength (8-25 MPa) and mechanical stability. This composite structure resolves the contradiction by combining materials with complementary properties.
2Strength
If embedding technique is used to strengthen supporting structure, then mechanical strength is improved, but fluid flowing resistance increases
Solution Approach 1:
The patent applies local quality by strategically placing the woven braid reinforcement only in specific locations where mechanical strength is needed (circumferential and longitudinal directions), while keeping the membrane wall thickness optimized (0.1-1.0 mm) to maintain low fluid resistance. The braid is embedded within grooves or channels of the hollow fiber membrane, providing strength without creating excessive flow resistance pathways.
3Ease of manufacture
If coating technique is used to produce composite hollow fiber membrane, then separation membrane and supporting material can be separated, but binding force between layers deteriorates
Solution Approach 1:
The patent segments the membrane structure into distinct functional layers: a PVDF hollow fiber membrane layer for separation and a woven braid layer for reinforcement. These layers are connected through mechanical interlocking where the braid is embedded in grooves or channels of the membrane, rather than through chemical coating bonds. This segmentation allows ease of manufacture while maintaining strong binding force through physical interlocking.
4Strength
If thermal induced phase separation (TIPS) technique is used, then mechanical strength is improved, but porosity deteriorates
Solution Approach 1:
The patent merges two different phase separation techniques: TIPS is used to form the PVDF hollow fiber membrane structure with good mechanical properties, while NIPS is used to create the porous structure with high porosity (50-80%). The combination of these two techniques in sequence allows the membrane to achieve both high mechanical strength and high porosity, resolving the contradiction between these two parameters.
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 resulting membrane exhibits high mechanical strength, improved filtration accuracy, increased water flux, and enhanced contamination resistance, with no peeling observed between layers, and maintains performance in alkaline conditions.
Implementation Method 1
non-solvent induced phase separation (NIPS) technique... the good solvents and pore forming agents in the polymer solution are extracted into the coagulated phase, and the polymers are due to phase transfer so as to precipitate and form polymeric hollow fiber membranes
Implementation Method 2
thermal induced phase separation (TIPS) technique... polyvinylidene fluoride resin and organic pore-forming agents are mixed and heated under partial vacuum at 220° C. to form a melted polymeric dope; then the polymeric dope is extruded through a spinning nozzle to form a hollow fiber membrane
Implementation Method 3
the good solvents and pore forming agents in the polymer solution are extracted into the coagulated phase... extracting to obtain the composite multilayer hollow fiber membrane
Data Source
AI summary
A method for preparing a composite multilayer porous hollow fiber membrane and the device and product thereof. The method comprises preparing uncured porous hollow fibers with larger pore diameters as the inner supporter of the membrane from thermoplastic macromolecule polymer resins by thermal induced phase separation method and then bonding a superthin coating layer with microfiltration or nanofiltration function and small pore diameter prepared on the outer surface of the hollow fibers from a solution of the thermoplastic macromolecule polymer resins by a coating process using non-solvent induced phase separation method. The composite multilayer porous hollow fiber membrane has such excellent mechanical strength and high water flux as the membranes prepared by thermal induced phase separation method, such high precision filter effect and high contamination resistance as the membranes prepared by non-solvent induced phase separation method, and high binding force of the membrane prepared by the above method.