Fluoropolymer Processing Additive for Melt Fracture Reduction
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Solution Overview
Problem
Melt-processable thermoplastic polymers face challenges with surface roughening and gel defects due to high shear rates, leading to inefficiencies in extrusion and moldability, particularly with high viscosity fluoropolymers which are poorly dispersible and cause die build-up.
Innovation Solution
A processing additive comprising a fluoropolymer with an acid value of not lower than 0.5 KOH mg/g, which reduces melt fracture time and inhibits gel defects, even at low viscosity, allowing for increased extrusion rates and reduced additive levels, by adhering to dies and screws for improved coating and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high viscosity fluoropolymer is used as a processing additive, then the critical shear rate is improved and melt fracture is reduced, but dispersibility in resin deteriorates and gel defects or die build-up occur
Solution Approach 1:
The patent changes the key parameter of fluoropolymer from high viscosity to low viscosity, while compensating for the potential loss of moldability improvement through the introduction of acidic terminal groups. This parameter change resolves the contradiction by eliminating gel defects and die build-up associated with high viscosity fluoropolymers while maintaining effective processing additive functionality through acid-value-driven mechanisms.
Solution Approach 2:
The patent converts the typically harmful acidic terminal groups into a beneficial feature. Instead of reducing acid value to improve dispersibility, the invention utilizes high acid value to enhance adhesion to dies and screws, thereby preventing die build-up and improving processing performance. This transforms a previously undesirable characteristic into a useful property for resolving the technical contradiction.
2Object-generated harmful factors
If a low viscosity fluoropolymer is used as a processing additive, then dispersibility in resin is improved, but moldability improvement is insufficient
Solution Approach 1:
The patent introduces acidic terminal groups as an intermediary mechanism that mediates between the fluoropolymer and the processing system. These acidic groups act as adhesion promoters that compensate for the low viscosity and poor dispersibility characteristics, enabling low viscosity fluoropolymers to effectively improve moldability by adhering to dies and screws during processing.
3Productivity
If high Mooney viscosity fluoroelastomer is used to shorten melt fracture disappearance time, then extrusion rate is improved, but dispersibility deteriorates and gel defects appear
Solution Approach 1:
The patent changes the viscosity parameter from high to low, eliminating gel defect formation while maintaining the ability to shorten melt fracture disappearance time through the acid-value-driven adhesion mechanism. This parameter change enables high extrusion rates without the harmful gel defects associated with high viscosity fluoropolymers.
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 fluoropolymer processing additive effectively shortens melt fracture disappearance time, reduces extrusion pressure, and enhances moldability and productivity by improving dispersibility and reducing the need for high viscosity fluoropolymers, thus addressing the limitations of existing technologies.
Implementation Method 1
a fluoropolymer increased in acid value can display excellent characteristics required of a processing additive... such fluoropolymer exhibits excellent processing additive performance characteristics... it provides a melt-processable resin with improved moldability
Data Source
AI summary
The present invention provides a processing additive which can bring about improvements in moldability at Mooney viscosity levels at which the dispersibility in a melt-processable resin is high and which further can work at reduced addition levels. The present invention is a processing additive comprising a fluoropolymer having an acid value of not lower than 0.5 KOH mg/g.