Addition-Curable Silicone Composition Storage Stability
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Solution Overview
Problem
Addition curable silicone compositions face challenges in achieving both long-term storage stability at room temperature and rapid curing on heating, particularly due to the limitations of one-pack and two-pack types, including issues with foam quality and surface tackiness, and the need for reaction inhibitors which can hinder curing performance.
Innovation Solution
The use of a microparticulate hydrosilylation catalyst with a microcapsule structure containing a platinum group metal catalyst and a three-dimensional crosslinked polymer, combined with organopolysiloxane and organohydrogenpolysiloxane, allows for excellent storage stability and rapid curing without the need for additional inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an addition cure reaction inhibitor such as acetylene alcohol is blended into a one-pack addition curable silicone composition to improve room temperature storage stability, then the composition can be stored at room temperature without freezing, but the heat curing process is retarded and foam quality deteriorates
Solution Approach 1:
The patent divides the catalyst system into two separate packs: Pack A contains the organopolysiloxane with aliphatic unsaturated hydrocarbon groups and Pack B contains the organohydrogenpolysiloxane with silicon-hydrogen bonds and a small amount of platinum catalyst. This segmentation prevents premature reaction while enabling rapid curing when mixed, resolving the contradiction between storage stability and curing speed.
Solution Approach 2:
The patent changes the physical state and distribution of the catalyst by using a very small amount of platinum catalyst (0.01-10 ppm) dispersed in one pack, combined with the reactive silane in another pack. This parameter change in catalyst concentration and distribution enables the composition to remain stable during storage yet cure rapidly when mixed.
2Productivity
If a one-pack addition curable silicone composition is used for rapid molding of electrical wires and tubings, then high productivity is achieved, but the surface remains tacky and smooth surface molding cannot be obtained
Solution Approach 1:
By segmenting the reactive components into two separate packs that are mixed immediately before use, the patent enables rapid curing (improving productivity) while ensuring complete crosslinking reaction (improving surface quality). The separated storage prevents premature gelation while maintaining all reactive components available for complete curing.
3Stability of the object's composition
If a two-pack addition curable silicone composition is used to achieve excellent room temperature storage stability, then long-term storage is possible, but a mixing and dispensing unit is required which increases device complexity
Solution Approach 1:
The patent merges the benefits of two-pack stability with one-pack simplicity by providing pre-mixed Packs A and B that can be stored separately at room temperature but are designed to be mixed in simple ratios (e.g., 1:1 by weight). This reduces the complexity of mixing and dispensing equipment while maintaining excellent storage stability.
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 solution provides addition curable silicone compositions with extended room temperature storage stability and rapid heat curing performance, overcoming the limitations of previous compositions by maintaining catalytic activity and preventing premature curing.
Implementation Method 1
an addition curable silicone composition comprising an organopolysiloxane having an aliphatic unsaturated hydrocarbon group, an organohydrogenpolysiloxane, and a microparticulate hydrosilylation catalyst
Implementation Method 2
a microparticulate hydrosilylation catalyst of microcapsule structure consisting of a core material of an organic compound or polymer containing a platinum group metal catalyst
Data Source
AI summary
This addition-curable silicone composition contains (A) an organopolysiloxane having at least two unsaturated aliphatic hydrocarbon groups in each molecule, (B) an organohydrogenpolysiloxane in an amount that provides a value of 0.5-5 for the ratio of the number of SiH groups to the total number of unsaturated aliphatic hydrocarbon groups in the component (A), and (C) an effective amount of hydrosilylation catalyst microparticles that have a microcapsule structure containing a platinum-group metal catalyst-containing organic compound or polymer compound as a core material and a three-dimensional crosslinked polymer compound obtained by polymerizing at least one polyfunctional monomer as a wall material, the platinum-group metal catalyst-containing organic compound or polymer compound having a dynamic viscosity of 10-100,000 mm2/s at 25°C.