Slot-Die Porous Web Coating With Web Positioning for Uniform Thickness
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Solution Overview
Problem
Current methods for double-sidedly coating porous webs with a dope struggle to maintain consistent coating thickness, especially for high open area and thin porous webs, leading to increased ionic resistance and reduced mechanical strength, which limits their effectiveness in intensified electrochemical processes.
Innovation Solution
A coating apparatus with a single slot-die coating head and a web positioning element that steadies one side of the porous web, ensuring constant coating thickness on that side while absorbing thickness variations on the other side, allowing for efficient coating of high open area and thin porous webs with reduced ionic resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional double-sided coating methods are used with two opposing dies, then both sides of the porous web can be coated, but consistent coating thickness cannot be maintained especially for high open area and thin porous webs
Solution Approach 1:
The invention extracts the web positioning function from the coating process by introducing a dedicated positioning element that steadies one side of the porous web. This separate positioning function allows the coating head to focus on depositing uniform layers without the complexity of simultaneously controlling web position and coating application.
Solution Approach 2:
The positioning element acts as an intermediary between the porous web and the coating head. It provides a stable reference surface that enables consistent coating thickness by absorbing web thickness variations, thereby mediating between the variable web structure and the requirement for uniform coating.
2Reliability
If the porous web has high open area and thin thickness to reduce ionic resistance, then ion permeability improves, but mechanical strength decreases
Solution Approach 1:
The invention changes the coating parameters by using a single coating head with controlled dope flow rate instead of two opposing dies. This allows for optimized coating thickness and distribution that compensates for the reduced mechanical strength of high open area, thin porous webs, thereby maintaining reliability while improving ion permeability.
3Manufacturing precision
If flow rate of dope is controlled to make coated wet layer thickness depend on flow rate rather than clearance, then coating thickness becomes independent from clearance, but control precision requirements increase
Solution Approach 1:
The positioning element provides a stable reference that enables feedback control of the coating process. By steadying one side of the web against the positioning element, the system can monitor and adjust dope flow rate to maintain consistent coating thickness, making the process more controllable despite the increased precision requirements.
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 solution enables the production of ion-permeable web-reinforced diaphragms with low ionic resistance, suitable for intensified electrochemical processes, by maintaining consistent coating thickness and enhancing mechanical strength, thereby improving efficiency and durability.
Implementation Method 1
providing the dope through the slot of the slot-die coating head into the slit, thereby coating a first side of the porous web facing the slot
Implementation Method 2
The web positioning element is the upper lip of the slot-die coating head, the upper lip protruding up to the reference plane so that there is an offset between the upper lip and the lower lip
Data Source
AI summary
A coating apparatus for double-sidedly coating a porous web with a dope, includes: (i) a slot-die coating head comprising an upper lip, a lower lip and a slot between the upper lip and the lower lip, (ii) a counter element arranged opposite the lower lip across a reference plane, (iii) a slit defined between the lower lip and the counter element for passing a porous web therebetween, the slot opening up towards the slit, and (iv) a web positioning element. The web positioning element is the upper lip of the slot-die coating head. The upper lip protrudes up to the reference plane so that there is an offset between the upper lip and the lower lip, or a spacing structure on the counter element. The spacing structure protrudes up to the reference plane so that there is an offset between the spacing structure and the counter element.