Cellulose Ester Separation Film Strength and Elongation
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Solution Overview
Problem
Conventional separation membranes are prone to thread breakage during the scrubbing process, which is necessary for removing soil from the membrane surface over time, due to insufficient strength and elongation.
Innovation Solution
A separation membrane with a cellulose ester as the main component, featuring a structure with an average pore diameter of 0.001 μm to 6 μm and a breakage parameter of 40 or more, along with a degree of elongation of 10% or more, is developed to enhance membrane strength and resistance to breakage during scrubbing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional separation membranes are used, then the membrane structure provides basic separation function, but thread breakage occurs frequently during scrubbing due to insufficient strength and elongation
Solution Approach 1:
The patent applies parameter changes by optimizing the molecular weight distribution of the cellulose ester polymer. Specifically, it controls the weight average molecular weight (Mw) to be 50,000-250,000 and the number average molecular weight ( Mn) to be 5,000-25,000, achieving a polydispersity index (Mw/Mn) of 2.0-10.0. This molecular weight parameter optimization enables the membrane to achieve both high strength and high elongation, preventing breakage during scrubbing while maintaining separation performance
Solution Approach 2:
The patent uses composite materials by combining cellulose ester with specific additives including plasticizers (in 5-40 wt% range), pore-forming agents (in 10-70 wt% range), and lubricants (in 1-20 wt% range). This composite formulation creates a membrane that achieves both mechanical strength and flexibility, allowing it to withstand scrubbing forces without breaking while maintaining its separation function
2Strength
If the membrane has high strength to withstand scrubbing, then breakage is suppressed, but the membrane structure may become less flexible
Solution Approach 1:
The patent resolves this contradiction through precise parameter control of molecular weight distribution. By setting Mw at 50,000-250,000 and Mn at 5,000-25,000 with Mw/Mn between 2.0-10.0, the membrane achieves breaking strength of 10-30 MPa while simultaneously achieving degree of elongation of 10-60%. This parameter optimization allows the membrane to be both strong and flexible, withstanding scrubbing forces while maintaining operational flexibility
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 membrane exhibits high strength and elongation, enabling effective use in various applications, including water treatment, medical, and food-beverage industries, while preventing thread breakage during washing processes.
Implementation Method 1
PTLs 1 and 2 and NPL 1 disclose the technique of obtaining a separation membrane by dissolving a resin composition including a cellulose ester and a pore-forming agent in an organic solvent and immersing the solution into a coagulation liquid including immersion water, to undergo phase separation.
Data Source
AI summary
The purpose of the present invention is to provide: a separation film that consists primarily of a cellulose ester and has a high membrane strength and a high elongation degree; and a production method therefor. Provided is a separation film which has a structure comprising a cellulose ester phase and pores, wherein the average pore diameter R is 0.001-6 μm, the value obtained from the expression: breaking strength (MPa)÷(100−porosity (%))×100 is 40 or greater, and the elongation degree is 10% or greater.