Silicone Release Coating Anchorage Additive for Polymer Film Adhesion
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Solution Overview
Problem
Current curable silicone release coating compositions face challenges in achieving reliable adhesion to polymer film substrates, particularly unprimed polyester films, leading to premature silicone rub-off over time.
Innovation Solution
A release coating composition comprising a polyorganosiloxane with alkenyl groups, an organohydrogensiloxane crosslinking agent, a hydrosilylation catalyst, and an anchorage additive formed by reacting a fluid polyorganosiloxane with alkenyl and silanol groups with a hydrolysable silane containing an epoxide group, enhancing adhesion to polymer films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a silicone based release coating composition is applied to polymer film substrates such as unprimed polyester film, then the smooth surface provides reduced transfer of adhesive patterns to the label, but the silicone layer becomes easily removed from the polymeric film by rubbing after a few days at room temperature
Solution Approach 1:
The patent introduces an intermediary substance - a silane crosslinking agent - that mediates between the silicone release coating and the polymer film substrate. This crosslinking agent forms chemical bonds with both the silicone coating and the polymer substrate, creating a strong anchorage that prevents rub-off while maintaining the smooth surface properties that prevent adhesive pattern transfer.
Solution Approach 2:
The patent creates a composite coating system consisting of multiple components: the silicone release coating, the silane crosslinking agent, and the polymer film substrate. This composite structure combines the non-adhesive properties of silicone with the bonding capabilities of crosslinked silane networks, achieving both smooth surface protection and durable anchorage simultaneously.
2Strength
If the silicone release coating is designed to adhere well to the liner substrate, then the label can be retained without affecting adhesive properties, but the silicone layer shows greater tendency to rub off over time on polymer substrates
Solution Approach 1:
The patent applies preliminary action by incorporating the silane crosslinking agent into the coating composition before application to the substrate. This pre-formulated crosslinking system activates during or after coating to create durable chemical bonds, ensuring long-term rub-off resistance while maintaining initial adhesion strength to the liner substrate.
Solution Approach 2:
The patent utilizes parameter changes by modifying the chemical structure and crosslinking density of the silicone coating through the addition of silane agents. This changes the physical and chemical parameters of the coating, creating a crosslinked network that resists rub-off while maintaining appropriate adhesion characteristics for label retention.
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 and consistent anchorage to polymer film substrates, reducing the tendency of silicone rub-off, even on unprimed polyester films, and maintaining adhesion over extended periods.
Implementation Method 1
The preferred curing mechanism is thermally initiated hydrosilylation, which can readily be modified to vary the adhesive force between the release coating and the adhesive label.
Data Source
AI summary
A release coating composition is prepared comprising a polyorganosiloxane (A) having alkenyl groups, a crosslinking agent (B) having organohydrogensiloxane groups, a catalyst for the hydrosilylation reaction between (A) and (B), and an anchorage additive for enhancing the adhesion of the composition to a polymer film substrate. The anchorage additive is the reaction product of a fluid polyorganosiloxane (C) containing at least one alkenyl group and at least one silanol group with a hydrolysable silane (D) containing at least one epoxide group. The curable silicone release coating composition can be applied to a substrate known as a ‘liner’ retaining a label, which liner can for example be paper or a polymer film, and cured.