PVDF Emulsion Polymerization Using PVOH Without Fluorinated Surfactants
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Solution Overview
Problem
Existing emulsion polymerization processes for poly(vinylidene fluoride) (PVDF) require fluorinated surfactants for stabilization, which are not environmentally friendly and can lead to reactor fouling, and there is a need for a process that can produce stable PVDF latex with high solid content without these surfactants.
Innovation Solution
The use of poly(vinyl alcohol) (PVOH) as a sole stabilizer in the emulsion polymerization of vinylidene fluoride (VDF), with a degree of hydrolysis ranging from 70 to 99 mol%, to stabilize PVDF particles without fluorinated or low molar mass surfactants, allowing for high solid content latex production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorinated surfactants are used for stabilization in VDF emulsion polymerization, then stable PVDF particles can be obtained, but environmental friendliness deteriorates and reactor fouling occurs
Solution Approach 1:
The patent removes fluorinated surfactants from the polymerization system entirely, extracting the harmful stabilization agents while maintaining particle stability through alternative means (water-soluble polymers and in-situ formed stabilizing structures), thereby eliminating reactor fouling and environmental harm
Solution Approach 2:
The patent introduces water-soluble polymers as intermediary substances that mediate between the hydrophobic PVDF particles and the aqueous phase, providing stabilization without the harmful effects of fluorinated surfactants, thus resolving the contradiction between stability and environmental friendliness
2Reliability
If conventional emulsion polymerization with surfactants is used, then stable dispersion is achieved, but solid content is limited and productivity decreases
Solution Approach 1:
The patent changes the stabilization mechanism from surfactant-based to polymer-based stabilization, allowing for higher solid content latexes (up to 60% or more) while maintaining dispersion stability, thereby improving productivity without sacrificing reliability
Solution Approach 2:
The patent creates a composite stabilization system using water-soluble polymers combined with in-situ formed stabilizing structures on particle surfaces, achieving both high dispersion stability and high solid content that enables improved productivity
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 achieves stable PVDF latex with high solid content (up to 60% by weight) and small particle size (less than 500 nm) using PVOH, which is biodegradable and thermally stable, overcoming reactor fouling issues and improving production efficiency.
Implementation Method 1
These polymers are able to provide a good colloidal stability by combination of adsorption to hydrophobic surfaces and grafting to the polymer
Implementation Method 2
combination of adsorption to hydrophobic surfaces and grafting to the polymer (chemical bond linking the WSP to the particle)
Implementation Method 3
Hydrophobic vinyl acetate units give strong adsorption on the hydrophobic particles
Implementation Method 4
hydrophilic hydroxyl units act as stabilizing moieties
Implementation Method 5
aqueous free-radical emulsion or suspension polymerization of vinylidene fluoride
Data Source
AI summary
A process for producing a stable PVDF latex by emulsion polymerization in the absence of fluorinated surfactant, said latex being stabilized by poly(vinyl alcohol) (PVOH). The process including the steps of charging a polymerization reactor with deionized water and a stabilizer, raising the temperature to 50 to 120° C., feeding VDF to the reactor until the pressure reaches from 100 kPa to 10 MPa, adding an initiator to start the polymerization, continuously feeding VDF to maintain said pressure, and stopping the VDF feed when the desired amount of polymer conversion has been reached.