Dissolvable Polymer Coating for Thin Film Composite Membrane Storage
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Solution Overview
Problem
Thin film composite membranes designed for high flux applications face challenges in maintaining performance characteristics when stored dry, particularly experiencing changes when re-wetted after extended periods, which is exacerbated for membranes with high A-values, as existing coatings either reduce flux or fail to mitigate storage issues effectively.
Innovation Solution
A thin film composite membrane with a polyamide layer formed by interfacial polycondensation between m-phenylene diamine and trimesoyl chloride, coated with a humectant and a dissolvable cellulose polymer, maintaining a water content less than 5 g/m² and an A-value of at least 8 l/m² hr/bar, where the dissolvable polymer substantially dissolves within one hour of water cross-flow, preserving membrane performance upon re-wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer coating is applied to the membrane surface to improve fouling resistance, then fouling resistance is improved, but flux is reduced
Solution Approach 1:
The patent applies a water-soluble polymer coating that is intentionally designed to dissolve after a short period (e.g., first rinse or first few hours of operation). This temporary coating provides fouling resistance during storage and initial use, then disappears to restore high flux, effectively using a disposable protective layer that serves its purpose and then is discarded.
2Reliability
If the membrane is stored in a wet state to maintain performance, then performance characteristics are maintained, but storage stability deteriorates due to bacterial growth and chemical degradation
Solution Approach 1:
The water-soluble polymer coating acts as an intermediary protective layer during storage. It allows the membrane to be stored in a wet state with the coating providing protection against fouling and degradation, while the coating itself prevents direct contact between the membrane surface and environmental contaminants. The coating can be removed by rinsing when the membrane is put into service.
3Stability of the object's composition
If the membrane is stored in a dry state to improve storage stability, then storage stability is improved, but performance characteristics change when re-wetted
Solution Approach 1:
The patent applies a water-soluble polymer coating to the membrane surface before storage. This preliminary action ensures that when the membrane is stored dry, the coating prevents adverse changes to the membrane performance. Upon re-wetting, the coating dissolves to reveal the membrane in its original high-performance state, effectively pre-preparing the membrane for optimal performance after storage.
4Stability of the object's composition
If a coating is applied to mitigate storage issues, then storage stability is improved, but flux is reduced due to the coating
Solution Approach 1:
The water-soluble polymer coating is designed as a temporary measure that provides protection during storage but automatically disappears during operation. The coating is applied before storage to maintain stability, then dissolves upon contact with water during use, restoring high flux without permanent flux reduction.
Solution Approach 2:
The patent utilizes the parameter change of the coating's solubility state. The coating transitions from a solid protective layer during storage to a dissolved state during operation. This parameter change (from insoluble to soluble) allows the same coating to provide different functions at different times: protection during storage and transparency to flow during operation.
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 maintains its original performance characteristics and high A-value even after days or weeks of dry storage, with the dissolvable polymer coating preventing swelling and adverse effects during dry storage, ensuring minimal increase in B-value and maintaining high flux capabilities.
Implementation Method 1
a dissolvable polymer provided at coverage of at least 10 mg/m2 that substantially dissolves from the membrane after one hour of continuous cross-flow of water
Implementation Method 2
The membrane maintains much of its original performance characteristics, even when re-wetted after days or weeks of dry storage... The outer coating includes a dissolvable polymer... and a humectant
Implementation Method 3
The thin film layer may be formed by an interfacial polycondensation reaction between polyfunctional amine (e.g. m-phenylenediamine) and polyfunctional acyl halide (e.g. trimesoyl chloride) monomers
Data Source
AI summary
A thin film composite membrane including a thin film polyamide layer positioned between a porous support and an outer coating, and a humectant; wherein the membrane has an A-value of at least 8 l/m2 hr/bar when tested at 25 l/m2 hr with pure water at 25° C. for one hour, and wherein the outer coating comprises a dissolvable cellulose polymer provided at coverage of at least 10 mg/m2 that substantially dissolves from the membrane after one hour of continuous cross-flow of water at 25 l/m2 hr and 25° C.