Moisture Curable Silicone Catalyst Package Stability
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Solution Overview
Problem
Two-part moisture cure organopolysiloxane compositions face issues with phase separation during storage, leading to reduced storage stability and increased safety hazards due to flammable catalysts, while fast-curing compositions compromise tooling time and productivity.
Innovation Solution
A two-part moisture curing silicone composition using a silicon-free, linear or branched polyether as the carrier fluid in the catalyst package, along with a cross-linker, aminosilane, tin-based catalyst, and optionally reinforcing or non-reinforcing fillers, which maintains compatibility and stability without sacrificing adhesion or cure rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high concentrations of primary amine and tin catalyst are used in the catalyst package to induce fast curing, then cure speed is improved, but phase separation occurs during storage reducing stability
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst package by incorporating specific additives (silane-modified polyether, amino silane, alkoxy silane) that modify the interaction between the catalyst and carrier fluid. This allows the system to maintain fast cure speed through high catalyst concentration while preventing phase separation during storage, effectively changing the stability parameters of the composition.
2Productivity
If tin catalyst and aminosilane levels are increased to achieve quick bulk mechanical property development, then productivity is improved, but tooling time and tack-free time are reduced
Solution Approach 1:
The patent applies local quality by using silane-modified polyether as a carrier fluid that specifically enhances bulk cure characteristics without uniformly affecting surface cure behavior. This allows accelerated bulk mechanical property development through increased catalyst levels while maintaining adequate tooling time for surface operations, as the polyether modifies the local cure kinetics in the bulk material.
3Productivity
If fast-curing two-part compositions are used to reduce work in progress, then productivity is improved, but static mixer life is reduced and base purges are increased
Solution Approach 1:
The silane-modified polyether acts as an intermediary substance that mediates between the catalyst and the silicone base polymer. It facilitates faster bulk cure to reduce work in progress and increase productivity, while its stabilizing effect on the catalyst package extends static mixer life and reduces the frequency of base purges, thereby minimizing material waste.
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 achieves a shelf-stable continuous phase with improved storage stability and faster bulk durometer build, enabling quicker mechanical property development without impacting cure speed or adhesion, thus enhancing productivity and safety.
Implementation Method 1
a tin based catalyst
Implementation Method 2
hydrolysable groups per molecule
Implementation Method 3
condensation curable organosiloxane compositions
Implementation Method 4
utilizing a silicon-free polyether as the carrier fluid, enabling the catalyst package to be stored and function as a shelf stable continuous phase
Data Source
AI summary
A two-part moisture cure organopolysiloxane composition comprising a base part and a catalyst package part is provided. The catalyst package part, despite comprising amino silane(s), alkoxy silane(s), and tin catalyst(s) and optionally reinforcing filler(s) and/or extending filler(s) in a carrier fluid, undergoes minimal phase separation during storage. This is achieved by utilizing silicon-free linear or branched polyethers comprising repeating units having the average formula (—CnH2n—O—)y wherein n is an integer from 3 to 6 inclusive and y is at least four, comprising one or more —OH terminal groups, —OR10 terminal groups or —OH and —OR10 terminal groups where R10 is an optionally functionalised hydrocarbon group having from 1 to 12 carbons; as the carrier fluid, enabling the catalyst package part to function as a shelf stable continuous phase.