Substrate Web CoF Control via Varnish Transfer
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Solution Overview
Problem
The packaging industry faces challenges in achieving a low coefficient of friction (CoF) on both sides of substrate webs, particularly with aluminum foils, as existing methods require separate coatings on both sides, which is inefficient and often unnecessary.
Innovation Solution
Applying a varnish to one side of a flexible substrate web, allowing it to transfer and modify the CoF on the opposite side during rewinding, using a combination of wax materials and binders like polyamide resin or nitrocellulose, which can be oxidatively, ultraviolet, or electron beam curing, to achieve the desired CoF without additional coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate coatings are applied to both sides of the substrate web to achieve low CoF, then the desired CoF on both sides is achieved, but the process complexity and time increase
Solution Approach 1:
The patent combines the coating operations for both sides of the substrate into a single operation by applying varnish to one side only. The varnish transfers to the opposite side during rewinding, merging two separate coating processes into one, thereby reducing process complexity while maintaining CoF control on both sides.
Solution Approach 2:
The varnish is applied in advance to one side of the substrate web before rewinding. This preliminary action allows the varnish to transfer to the opposite side during the rewinding process, achieving CoF modification on both sides without requiring a separate coating operation for the second side.
2Reliability
If separate coatings are applied to both sides of the substrate web, then proper CoF is achieved on both sides, but the production time increases
Solution Approach 1:
The patent merges two separate coating operations into a single varnish application step. By applying varnish to one side and utilizing the rewinding process to transfer it to the other side, the production time is reduced while maintaining proper CoF control on both sides of the substrate web.
Solution Approach 2:
The substrate web itself serves as the transfer medium for the varnish. During the normal rewinding operation, the varnish on one side automatically transfers to the opposite side through contact, eliminating the need for additional coating equipment or operations and thereby improving productivity.
3Ease of manufacture
If varnish is applied to only one side of the substrate web, then the coating process is simplified, but the CoF on the opposite side remains high
Solution Approach 1:
The rewinding process acts as an intermediary mechanism that facilitates the transfer of varnish from one side of the substrate web to the opposite side. This intermediary action allows the varnish applied to one side to reach the other side, thereby achieving CoF control on both sides while maintaining manufacturing simplicity.
Solution Approach 2:
The substrate web transfers the varnish to its own opposite side through the natural rewinding process. This self-service mechanism eliminates the need for additional coating operations on the opposite side while still achieving the desired CoF, thereby resolving the contradiction between manufacturing ease and CoF control reliability.
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 method effectively reduces the CoF on both sides of the substrate web to the desired range of 0.20-0.40, enhancing processing efficiency in packaging lines without the need for separate coatings, while ensuring acceptable adhesion and slip resistance.
Implementation Method 1
the coefficient of friction (CoF) is often too high on both the front side and the back side of the substrate web
Implementation Method 2
using a combination of wax materials and binders like polyamide resin or nitrocellulose, which can be oxidatively, ultraviolet, or electron beam curing
Data Source
AI summary
The present invention provides a method for printing and coating a flexible substrate web so as to attain a specified coefficient of friction on both sides of the substrate web which employs the use of controlled set-off of coated and/or printed material from the front side to the back side side of the web. Furthermore the method provides a substrate web produced therefrom and the method is useful for packaging substrate webs and, in particular, foil substrate webs.