Gluing Nozzle Relaxation Volume for Adhesive Stability
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Solution Overview
Problem
The existing continuous gluing processes for flexible packaging materials face limitations in speed and fineness due to the sensitivity of adhesive compositions to shearing, leading to instability and tearing, especially at high speeds and thin adhesive layers.
Innovation Solution
A gluing process utilizing a gluing nozzle with an extrusion die featuring a concave relaxation volume that allows the adhesive composition to regain cohesiveness before extrusion, with adjustable lip spacing and chromium-plated surfaces to reduce shear-induced degradation, enabling higher gluing speeds and finer coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate film is run at high speed through the gluing nozzle, then productivity is improved, but the adhesive composition becomes unstable and tears due to high shearing
Solution Approach 1:
The patent introduces a relaxation volume upstream of the extrusion die that allows the adhesive composition to regain cohesiveness before being extruded at high speed. This preliminary recovery action prevents the adhesive from tearing during high-speed application by restoring its structural integrity before the high-shear extrusion process.
Solution Approach 2:
The patent employs a dynamic balance between the relaxation time of the adhesive composition and the residence time in the relaxation volume. By adjusting the volume and flow rate, the system dynamically adapts to maintain adhesive stability across varying production speeds, allowing high productivity while preventing adhesive failure.
2Manufacturing precision
If the adhesive layer is made thinner to achieve finer coating, then manufacturing precision is improved, but the adhesive becomes more prone to tearing and instability
Solution Approach 1:
The relaxation volume provides a preliminary recovery zone where thin adhesive layers can regain cohesiveness before extrusion. This pre-conditioning allows the adhesive to maintain integrity even when applied as a thin layer, enabling fine coating precision without sacrificing reliability.
Solution Approach 2:
The patent changes the rheological parameters of the adhesive flow by providing a relaxation period. This parameter change allows the adhesive to transition from a high-shear state to a recovered state, maintaining cohesion in thin layers while achieving the desired fine coating precision.
3Manufacturing precision
If the extrusion die channel is made narrower to control adhesive flow, then manufacturing precision is improved, but the adhesive composition undergoes higher shearing and loses cohesion
Solution Approach 1:
The relaxation volume acts as a preliminary recovery chamber upstream of the narrow extrusion die channel. The adhesive regains cohesiveness in this volume before entering the narrow channel, allowing precise flow control during extrusion without the adhesive tearing from excessive shearing.
Solution Approach 2:
The patent segments the flow path into two distinct zones: a relaxation volume for adhesive recovery and a narrow extrusion die channel for precise flow control. This segmentation allows each zone to perform its specific function without compromising the other, maintaining both precision and cohesion.
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 gluing speeds up to 600 m/min and grammage as low as 2 g/m2 with improved adhesive cohesion, reducing instability and tearing, and maintaining high appearance quality.
Implementation Method 1
the transverse channel comprising a concave volume for relaxation of the adhesive composition
Implementation Method 2
chromium-plated surfaces to reduce shear-induced degradation
Data Source
AI summary
The invention relates to a gluing process of an adhesive composition with the use of a gluing nozzle having an extrusion die for continuous extrusion of an adhesive composition over a predetermined width, the extrusion die (20) comprising a lower lip (22) and an upper lip (24), the upper and lower lips (24, 22) extending parallel to one another so as to form a transverse channel (28) for the longitudinal flow of the adhesive composition, the transverse channel extending longitudinally between: a supply opening (30) for supplying the adhesive composition; and an extrusion outlet (34) for extrusion of the adhesive composition (34); the channel (28) comprising a concave volume (32) for relaxation of the adhesive composition between the supply opening (30) and the gluing outlet (34).