Cellulose Hydrate Ultrafiltration Membrane Saponification Control

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Solution Overview

Problem

Cellulose hydrate ultrafiltration membranes face challenges in achieving reliable porosity adjustment and favorable flux:rejection ratios, particularly for small-pored membranes, due to the unpredictable nature of saponification processes and high production costs associated with cellulose acetate membranes.

Innovation Solution

A process involving tempering of cellulose ester ultrafiltration membranes in a medium with additives like acetic acid followed by saponification, which allows for improved control over the membrane's flux and rejection characteristics, enabling the production of cellulose hydrate ultrafiltration membranes with superior flux:rejection ratios across various molecular weight cut-off classes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If saponification is used to convert cellulose ester membranes to cellulose hydrate membranes, then solvent resistance and temperature stability are improved, but production cost increases

Engineering Contradiction:

Improvesolvent resistanceVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by treating the cellulose ester membrane with a swelling agent (such as water, alcohol, or their mixtures) before saponification. This pre-swelling step modifies the membrane structure in advance to control the saponification process, enabling better porosity adjustment and reduced production costs while maintaining the solvent resistance benefits of cellulose hydrate membranes

Inventive Principle:

Principle #10Preliminary action

2Temperature

If saponification is used to convert cellulose ester membranes to cellulose hydrate membranes, then temperature stability is improved, but production cost increases

Engineering Contradiction:

Improvetemperature stabilityVSAvoidproduction cost

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by treating the cellulose ester membrane with a swelling agent (such as water, alcohol, or their mixtures) before saponification. This pre-swelling step modifies the membrane structure in advance to control the saponification process, enabling better porosity adjustment and reduced production costs while maintaining the temperature stability benefits of cellulose hydrate membranes

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If very high polymer concentration and smaller amount of swelling agent are used in casting solution, then porosity adjustment reliability is improved, but flux:rejection ratio becomes unfavorable

Engineering Contradiction:

Improveporosity adjustment reliabilityVSAvoidflux:rejection ratio

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies parameter changes by introducing a controlled swelling step before saponification. The swelling agent concentration, type, and treatment conditions are adjusted as parameters to achieve reliable porosity control without requiring very high polymer concentrations in the casting solution, thereby maintaining favorable flux:rejection ratios

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a swelling agent as an intermediary substance between the cellulose ester membrane and the saponification process. This intermediary enables controlled structural modification that improves porosity adjustment reliability while preserving the membrane's flux:rejection characteristics

Inventive Principle:

Principle #24Intermediary (Mediator)

4Stability of the object's composition

If crosslinking is performed after saponification, then chemical stability is improved, but flux:retention ratio does not improve

Engineering Contradiction:

Improvechemical stabilityVSAvoidflux:retention ratio

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent applies preliminary action by performing the swelling treatment before saponification rather than relying on post-saponification crosslinking. This preliminary structural modification achieves both chemical stability and improved flux:retention ratio by controlling the saponification process itself to create the desired membrane properties

Inventive Principle:

Principle #10Preliminary action

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 process results in cellulose hydrate ultrafiltration membranes with significantly enhanced flux and rejection performance, achieving higher flux rates while maintaining low non-specific adsorption and solvent resistance, surpassing the performance of existing membranes in the same cut-off classes.

Implementation Method 1

saponification of the cellulose ester ultrafiltration membrane

Methodology Applied

Scientific EffectSaponification: Hydrolysis

Implementation Method 2

tempering of cellulose ester ultrafiltration membranes in a medium with additives like acetic acid

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS7422686B2Cellulose hydrate ultrafiltration membranes and method for their production

Publication Date: 2008.09.09 SARTORIUS STEDIM BIOTECH GMBH

AI summary

There is disclosed a process for the production of cellulose hydrate ultrafiltration membranes having improved filtration performance and the ultrafiltration membranes produced by the process.