Fluoropolymer Dispersion Surfactant Removal via pH-Dependent Stabilization
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Solution Overview
Problem
Existing methods for reducing fluorinated emulsifiers in fluoropolymer dispersions using non-ionic surfactants hinder phase separation and result in fluoropolymer coatings with poor physical properties due to residual surfactants, leading to issues like water absorption and compromised surface hardness.
Innovation Solution
A process involving anion exchange resins in the presence of pH-dependent surfactants, which stabilizes the dispersion in its non-ionic form, allowing for effective removal of fluorinated emulsifiers and subsequent phase separation of fluoropolymers, reducing the amount of residual surfactants and improving coating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-ionic surfactants are added to stabilize fluoropolymer dispersion during anion exchange, then fluorinated emulsifier removal is achieved, but phase separation is hindered and residual surfactants compromise coating properties
Solution Approach 1:
A pH-dependent surfactant acts as an intermediary that stabilizes the fluoropolymer dispersion during anion exchange at alkaline pH, then undergoes phase separation at acidic pH to eliminate residual surfactant harm. The pH-dependent surfactant mediates between the need for dispersion stability and the need for complete phase separation.
Solution Approach 2:
The patent changes the pH parameter to control the state of the surfactant. At alkaline pH, the surfactant is in ionic form providing electrostatic stabilization during anion exchange. At acidic pH, the surfactant transitions to non-ionic form enabling phase separation and removal of residuals.
2Object-generated harmful factors
If fluorinated emulsifiers are removed from fluoropolymer dispersions, then coating quality improves, but dispersion stability deteriorates
Solution Approach 1:
The pH-dependent surfactant serves as a temporary intermediary stabilizer that replaces fluorinated emulsifiers during anion exchange. It provides sufficient stabilization during the process, then allows complete phase separation upon pH change, achieving both goals.
Solution Approach 2:
The patent extracts fluorinated emulsifiers from the dispersion through anion exchange while introducing a pH-dependent surfactant as a temporary replacement. The extracted emulsifier is removed, and the replacement surfactant is subsequently eliminated through pH-induced phase separation.
3Object-generated harmful factors
If pH-dependent surfactants are used instead of non-ionic surfactants, then phase separation is enabled, but process complexity increases
Solution Approach 1:
The patent uses pH as a control parameter to switch the surfactant between ionic and non-ionic states. This single parameter change enables both dispersion stabilization and phase separation functions, simplifying the overall process despite the surfactant's dual nature.
Solution Approach 2:
The surfactant's properties are made dynamic through pH adjustment. It transitions from a stabilizing ionic state during anion exchange to a phase-separating non-ionic state upon acidification, allowing one surfactant to perform multiple functions at different process stages.
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
This approach enables the production of fluoropolymer dispersions with low or no fluorinated surfactants, facilitating complete coagulation and enhancing the physical properties of fluoropolymer coatings by minimizing residual surfactant impact, resulting in improved surface hardness and water resistance.
Implementation Method 1
contacting the dispersion with an anion exchange resin in the presence of one or more pH-dependent surfactants
Implementation Method 2
The pH-dependent surfactant is capable of stabilising the dispersion when the surfactant is in its non-ionic form
Implementation Method 3
it may be desirable to avoid or at least to reduce the presence of non-ionic surfactants. In these applications the fluoropolymer is separated from the dispersion prior to application to the substrate which is typically done by destabilising the dispersion and separating the fluoropolymer from the aqueous medium (also referred to as phase-separation or coagulation)
Data Source
AI summary
A process of reducing the amount of fluorinated emulsifiers in fluoropolymer dispersions by contacting the fluoropolymer dispersion with an anion exchange resin in the presence of a pH-dependent surfactant, and fluoropolymer dispersions containing the pH-dependent surfactant and uses thereof.