PPSU Filtration Membrane Chemical Stability

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Solution Overview

Problem

Water filtration membranes, particularly those used in micro- or ultrafiltration, nanofiltration, or reverse osmosis, face chemical degradation issues due to exposure to oxidizing agents during cleaning processes, leading to reduced mechanical properties and permeability, resulting in shorter membrane lifetimes and increased maintenance costs.

Innovation Solution

Incorporating polyphenylsulfone (PPSU) into the membrane material, either as a main component or in combination with polyethersulfone (PESU), to enhance chemical resistance and stability against oxidizing agents, thereby improving the membrane's durability and performance during chemical backwash processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If membranes are regularly cleaned with oxidizing solutions (chemical backwash), then fouling and blockages are removed maintaining flux, but the membrane material undergoes degradation (chain scission, embrittlement) reducing lifetime

Engineering Contradiction:

Improveflux maintenanceVSAvoidmembrane lifetime

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies this principle by selecting a polymer material (PPSU or PPSU-containing copolymer) that can withstand and resist the harmful oxidizing cleaning agents. The polymer's inherent chemical stability converts the harmful oxidizing environment into a benign condition, allowing regular chemical cleaning to maintain flux without causing degradation, thus transforming the harmful effect into a beneficial operational capability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the chemical parameter of the membrane material by selecting PPSU or copolymers containing it, which have superior resistance to oxidizing agents compared to conventional polymers. This parameter change in material composition enables the membrane to withstand chemical backwash without degradation, resolving the contradiction between cleaning effectiveness and lifetime

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If polymer chains undergo scission due to hydroxyl radicals from bleach solutions, then mechanical properties deteriorate and membrane breaks, but the cleaning process is necessary for operational continuity

Engineering Contradiction:

Improvecleaning capabilityVSAvoidmechanical property

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The patent selects a polymer material with inherent resistance to hydroxyl radical attack, converting the harmful oxidizing environment into a benign condition. The PPSU-based polymer maintains mechanical integrity during chemical cleaning, allowing easy operation through regular cleaning without strength deterioration

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs composite material strategy by using copolymers that combine PPSU units with other polymer units. This composite structure leverages the superior chemical stability of PPSU while maintaining appropriate mechanical and functional properties, achieving both cleaning capability and strength retention

Inventive Principle:

Principle #40Composite materials

3Productivity

If membranes are made from conventional polymers (cellulose acetate, PSU, PESU, PVDF), then good initial performance is achieved, but chemical resistance to oxidizing agents is insufficient leading to premature failure

Engineering Contradiction:

Improveinitial performanceVSAvoidchemical stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the chemical composition parameter by introducing PPSU or copolymers containing PPSU units, which have superior resistance to oxidizing agents compared to conventional polymers. This parameter change maintains good initial performance while dramatically improving chemical stability and longevity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material approach with copolymers combining PPSU units with other polymer units, achieving a balance between initial performance characteristics and enhanced chemical resistance to oxidizing agents, thus resolving the contradiction between productivity and reliability

Inventive Principle:

Principle #40Composite materials

Data Source

PatentEP3057688B1Improving the chemical stability of filtration membranes

Publication Date: 2022.01.05 BASF SE

AI summary

Polyethers (A), whose main chain essentially consists of repeating units of the formulae (1 ) and (2) in alternating order, are useful as an additive to a porous polymer membrane, or as the main polymer constituent of a porous polymer membrane, for stabilizing said membrane against detrimental effects of oxidizing agents and/or for improving the stability of a filtration module comprising said membrane against detrimental effects of oxidizing agents.