Soft Rubber Roller Reduces Shear Hardening in Acrylic Adhesive Coating
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Solution Overview
Problem
Existing methods for coating acrylic adhesive on labels, such as direct and indirect coating, face challenges like adhesive absorption in direct coating and shear hardening in indirect coating, leading to inefficiencies and increased costs.
Innovation Solution
The use of a soft rubber roller between a reverse anilox cylinder and an anvil cylinder in a flexo print station, combined with air knives for drying, to reduce shear hardening and ensure a smooth adhesive transfer onto a silicone liner, allowing for controlled coating thickness and efficient adhesive application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If indirect coating is used to reduce adhesive absorption, then adhesive cost is reduced, but shear hardening occurs in the coating process
Solution Approach 1:
A soft rubber roller is introduced as an intermediary component between the anilox cylinder and the silicone liner. This roller acts as a mediator that transfers adhesive from the anilox cylinder to the liner while reducing shear hardening. The soft rubber material allows for gentler adhesive transfer, preventing premature hardening and separation that occurs with traditional reverse roll systems.
Solution Approach 2:
The invention changes the physical parameters of the coating system by using a soft rubber roller with specific surface properties and flexibility. This alters the shear forces and contact mechanics during adhesive transfer, enabling controlled coating thickness while preventing shear hardening. The soft rubber roller modifies the adhesive flow and distribution characteristics compared to traditional rigid roller systems.
2Reliability
If reverse roll coating is used to coat adhesive on silicone liner, then adhesive transfer is improved, but coating thickness control becomes difficult
Solution Approach 1:
The soft rubber roller serves as an intermediary that improves adhesive transfer reliability while enabling better thickness control. Its flexible nature allows it to conform to the silicone liner surface, ensuring uniform adhesive distribution and consistent coating thickness, whereas traditional reverse roll systems struggle with thickness uniformity.
3Ease of manufacture
If traditional reverse gravure coating is used, then adhesive coating is achieved, but work or shear hardening issues occur
Solution Approach 1:
The soft rubber roller replaces the traditional gravure cylinder in the coating process. This intermediary component enables adhesive coating while eliminating shear hardening issues. The soft rubber material allows for gentle, controlled adhesive transfer without the premature hardening and separation that plague gravure-based systems.
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 approach reduces shear hardening, enables smoother adhesive coating, and facilitates inline production, resulting in cost savings and improved efficiency in label manufacturing.
Implementation Method 1
air knives are used to speed up the drying of the adhesive on the silicone liner
Data Source
AI summary
In an indirect process, acrylic adhesive is coated on a silicone liner. A soft rubber roller is employed between a reverse anilox cylinder and an anvil cylinder in a flexo print station to reduce shear hardening in the coating process and prevent or reduce shear hardening on the print rollers. Once the coated silicone liner passes the rollers, air knives are used to speed up the drying of the adhesive on the silicone liner before the coated liner is laminated to a face stock.