Multi-Layer Web Curl Control via Stretching During Curing
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Solution Overview
Problem
Multi-layer webs tend to curl due to strain induced by curing coatings, leading to handling difficulties and potential delamination issues, with existing solutions either compromising coating functionality or increasing web thickness, which is costly and not always desirable.
Innovation Solution
A method involving stretching the web during coating curing to counteract the strain caused by the curing process, resulting in a multi-layer web with a desired curvature, either flat or slightly curled, by synchronizing the web stretching section with the curing section to induce matching strains in the web.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the coating is cured to form a multi-layer web, then the coating achieves its functional properties, but strain is induced causing the web to curl
Solution Approach 1:
The web is stretched in advance before curing to induce tensile strain that counteracts the compressive strain that will develop during coating curing. This preliminary opposing action prevents the web from curling after curing, allowing the coating to achieve its functional properties without causing unwanted curvature.
Solution Approach 2:
The physical state of the web is changed by applying controlled tensile strain during the curing process. By modifying the strain parameters of the web substrate, the internal stresses generated by coating curing are balanced, maintaining the web in a flat state while the coating cures to its functional state.
2Shape
If the web is stretched to counteract curing strain, then curl is reduced, but the web thickness may be compromised
Solution Approach 1:
The web is stretched to a degree that exactly counteracts the curing strain without over-stretching. This partial action approach applies just enough tensile strain to balance the compressive curing forces, maintaining web flatness while preserving the original web thickness and avoiding excessive deformation.
3Ease of operation
If existing solutions are used to reduce curl, then handling is improved, but coating functionality is compromised or web thickness increases
Solution Approach 1:
Instead of applying post-curing treatments that might compromise coating properties, the web is pre-stretched before curing to counteract the expected curing strain. This preliminary action achieves good web handling characteristics while preserving the full functionality of the cured coating.
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 method effectively reduces curling issues, minimizing stress between layers, enhancing product lifespan and adhesion, while maintaining the web's thickness, thus improving product quality and handling efficiency.
Implementation Method 1
the coating being characterized by at least partially shrinking when cured
Implementation Method 2
stretching the web during curing of the coating, wherein stretching the web substantially cancels the strain induced by curing
Data Source
AI summary
A system and method for controlling curl in multi-layer webs. The method can include providing a coated web, curing the coating to form a multi-layer web, and stretching the web during curing of the coating. Some coatings shrink at least partially when cured such that curing the coating induces a strain in the multi-layer web. Stretching the web occurs during curing to induce an opposing strain that at least partially counteracts the strain induced by curing to form a multi-layer web having a desired curvature. The system can include a curing section configured to cure the coating, and can further include a web stretching section, which can be located proximate the curing section and can be substantially coincident with the curing section, such that the web is stretched while the coating is cured.