Photocurable Silicone Adhesive Resolves Viscosity and Curing Trade-offs
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Solution Overview
Problem
The production of pressure-sensitive adhesives using crosslinkable silicon group-containing organic polymers is challenged by the issue of increased viscosity when an adhesion-imparting resin is added, and the risk of premature curing during high-temperature processing, which can lead to instability and reduced productivity.
Innovation Solution
A photocurable composition comprising a crosslinkable silicon group-containing organic polymer, an adhesion-imparting resin, a Si—F bond-containing silicon compound, and a photobase generator, which remains stable under heat but undergoes rapid curing upon light irradiation, ensuring stability during processing and efficient crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a crosslinkable silicon group-containing organic polymer is heated to high temperature during coating, then the viscosity decreases and coating becomes easier, but the crosslinkable silicon group reacts and cures prematurely
Solution Approach 1:
The patent applies preliminary action by adding a silane coupling agent and catalyst before coating, which remain dormant during heating and only activate after coating to initiate crosslinking. This allows the composition to be heated for easy coating without premature curing, as the crosslinking reaction is triggered in advance by the pre-added catalyst system rather than by heat alone.
Solution Approach 2:
The patent changes the chemical parameters by introducing specific catalysts (tin octoate, dibutyltin dilaurate) and silane coupling agents that alter the reaction conditions. The crosslinking is controlled to occur at specific temperature ranges and times after coating, rather than immediately upon heating, thus separating the coating temperature from the curing trigger temperature.
2Strength
If an adhesion-imparting resin is added to improve adhesion, then adhesion performance increases, but the curable composition viscosity increases
Solution Approach 1:
The patent changes the viscosity parameter by controlling the molecular weight and structure of the adhesion-imparting resin, and by adjusting the composition ratio of crosslinkable silicon group-containing polymer to adhesion resin. The catalyst system is also optimized to ensure rapid crosslinking at appropriate times, balancing the need for low coating viscosity with adequate adhesion performance.
3Productivity
If a roll coater is used to improve productivity, then coating efficiency increases, but the curable composition cures by moisture in the air during coating
Solution Approach 1:
The patent introduces a catalyst system (tin octoate, dibutyltin dilaurate) as an intermediary that mediates the crosslinking reaction. Instead of relying on moisture from air to trigger curing (which causes problems in roll coating), the catalyst provides a controlled pathway for crosslinking that can be activated at specific times and temperatures, enabling the use of roll coaters without premature curing issues.
Solution Approach 2:
The patent changes the curing mechanism from moisture-dependent to catalyst-dependent, altering the reaction kinetics and triggering conditions. This allows the composition to remain stable during high-speed roll coating while still achieving complete crosslinking afterward, thus resolving the contradiction between productivity and curing stability.
Data Source
AI summary
Provided is a method of producing a pressure-sensitive adhesive containing a cured product of a curable composition containing a crosslinkable silicon group-containing organic polymer and an adhesion-imparting resin as a pressure-sensitive adhesive layer; curing of the curable composition does not proceed when heated during production, i.e., the curable composition has excellent stability when heated, and the crosslinking reaction of the curable composition proceeds by some sort of trigger. The pressure-sensitive adhesive contains, as a pressure-sensitive adhesive layer, a cured product of a curable composition containing (A) a crosslinkable silicon group-containing organic polymer, (B) an adhesion-imparting resin, (C) a Si—F bond-containing silicon compound, and (D) a photobase generator.