Polymer-Coated Cellulosic Release Liner with Extruded Primer
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Solution Overview
Problem
Polyolefin-coated cellulosic substrates for release liners face issues with unstable silicone anchorage due to weak interactions and the formation of pinholes, leading to poor release stability and silicone transfer, which are exacerbated by corona treatment and thermal processing.
Innovation Solution
A polymer-coated cellulosic substrate is developed with an extruded primer layer comprising a thermoplastic polymer covalently bonded to functional vinyl groups, which enhances silicone anchorage through covalent bonding and reduces pinhole formation by eliminating water and solvent, allowing for a more stable and efficient silicone coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If corona treatment is applied to polyolefin-coated cellulosic substrates to improve silicone anchorage, then adhesion is improved, but polymer chain scission and pinholes are formed causing anchorage problems
Solution Approach 1:
The patent applies preliminary action by incorporating polar groups into the polymer coating during the extrusion process itself, before the silicone coating is applied. This pre-modification of the polymer surface creates ready-to-bond sites for silicone anchorage without requiring subsequent corona treatment that would cause damage.
Solution Approach 2:
The patent uses an intermediary approach by introducing a polymer coating layer with incorporated polar groups as a mediator between the cellulosic substrate and the silicone coating. This intermediate layer provides the necessary polarity for anchorage while maintaining the protective function of the polyolefin coating.
2Strength
If weak interactions are used for silicone anchorage on polyolefin coatings, then adhesion is achieved, but anchorage becomes unstable over time causing silicone transfer
Solution Approach 1:
The patent applies parameter changes by modifying the chemical parameters of the polymer coating to incorporate polar groups (such as carboxyl, hydroxyl, or amine groups) that enable strong chemical bonding with silicone. This changes the bonding mechanism from weak physical interactions to strong chemical bonds, ensuring long-term stability.
3Shape
If polyolefin coating is applied to cellulosic substrate to prevent silicone penetration, then smooth finish is achieved, but pinholes form during thermal processing causing contamination
Solution Approach 1:
The patent uses composite materials by creating a multi-layer structure combining polyolefin coating with incorporated polar groups. This composite approach maintains the smooth finish and barrier properties of polyolefin while adding the chemical bonding capability through the integrated polar groups, eliminating the need for corona treatment that causes pinholes.
4Strength
If corona treatment is applied to improve surface energy, then adhesion is improved, but manufacturing complexity and process time increase
Solution Approach 1:
The patent extracts and eliminates the corona treatment step from the manufacturing process by incorporating the polarity modification directly into the polymer coating extrusion process. This removes the need for separate corona treatment equipment and process steps while achieving the same adhesion improvement.
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 provides improved adherence and stability of the silicone coating, reduces the risk of silicone contamination, and decreases the amount of silicone required, resulting in cost-efficient and consistent release properties with enhanced surface coverage and reduced defects.
Implementation Method 1
an extruded primer layer comprising a second composition containing a thermoplastic polymer covalently bonded to functional vinyl groups
Implementation Method 2
the extruded primer layer has excellent adherence to the underlying first coating layer, as the thermoplastic melt sticks firmly to the first coating layer after solidifying
Data Source
AI summary
The invention relates to a polymer-coated cellulosic substrate (S2) for a release liner (REL1), comprising a cellulosic support layer (PAP1), a first coating layer (PO1), comprising a first composition containing polyolefin, and an extruded primer layer (PRIM1) comprising a second composition containing a thermoplastic polymer covalently bonded to functional vinyl groups: wherein the first coating layer (POI) is situated between the cellulosic support layer (PAP1) and the extruded primer layer (PRIM1).