Silicone Resin Emulsion Shelf Stability and Adhesion
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Solution Overview
Problem
Silicone resin emulsions face challenges with poor shelf stability due to resin hydrolysis and condensation, leading to emulsion breaking or gelling, and post-curing issues that result in weak adhesion and binding ability, especially when reactive groups are lost over time, and the use of catalysts limits immediate application and storage stability.
Innovation Solution
An aqueous emulsion comprising 1-70 weight percent of a silicone resin with specific empirical formula and viscosity, combined with hydroxy terminated polydiorganosiloxane, polyvinyl alcohol as an emulsifier, and a water-soluble salt, which provides a solid coating upon water removal without the need for catalysts, ensuring stability and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silicone resin emulsion contains reactive groups for post-curing, then film adhesion and strength are improved, but shelf stability deteriorates due to hydrolysis and condensation
Solution Approach 1:
The patent controls the water content parameter within specific ranges (0.5-20% emulsifier, 0.001-5% water-soluble salt) to prevent hydrolysis of reactive groups while maintaining emulsion stability. This parameter optimization allows the resin to retain reactive functionality for post-curing without premature reaction during storage
Solution Approach 2:
The patent introduces water-soluble salts as intermediary substances that regulate the chemical environment in the emulsion. These salts act as buffers to control pH and ionic strength, preventing premature hydrolysis of the silicone resin's reactive groups while allowing post-curing to proceed after application
2Speed
If catalyst is added to accelerate post-curing, then film formation speed is improved, but storage stability deteriorates due to premature reaction
Solution Approach 1:
The patent removes the catalyst from the emulsion formulation entirely, eliminating the source of premature reaction during storage. Instead, the emulsion relies on ambient moisture and controlled environmental conditions to enable gradual post-curing after application, thus maintaining storage stability while achieving adequate film formation speed
3Area of stationary object
If emulsion droplets are made smaller for better coverage, then surface coverage is improved, but emulsion stability deteriorates due to increased surface area for hydrolysis
Solution Approach 1:
The patent optimizes the emulsion droplet size parameter and controls the water content within specific ranges to balance surface coverage and stability. By controlling the concentration of emulsifier and water-soluble salts, the patent prevents excessive hydrolysis even in smaller droplets while maintaining adequate coverage
Data Source
AI summary
Aqueous emulsions of a silicone resin are disclosed that provide a solid silicone resineous coating upon removing water from a film of the emulsion. The silicone resin emulsions are useful for treating various substrates for imparting water resistance/repellence and improving wear/weather protective properties. In particular, they are useful for rendering mineral-based building materials water-resistant, and also as binders in paints.