Radiation-Curable Alkoxysilane Coatings With Controlled Partial Hydrolysis
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Solution Overview
Problem
Existing radiation-curable hard coating compositions for optical articles require full or partial hydrolysis of epoxy-functional alkoxysilanes to achieve acceptable performance, leading to unstable silanol groups that spontaneously condense, limiting the formation of improved coatings.
Innovation Solution
A curable composition comprising unhydrolyzed and partially hydrolyzed alkoxysilanes, along with an ethylenically unsaturated monomer, is developed, with controlled hydrolysis conditions to minimize spontaneous condensation, ensuring a higher monomeric content and improved coating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy-functional alkoxysilanes are fully or partially hydrolyzed to enable formation of condensed oligomers, then coating adhesion to ophthalmic lens materials is achieved, but the silanol groups become unstable and spontaneously condense, limiting improved coating performance
Solution Approach 1:
The patent changes the hydrolysis parameter from complete or extensive hydrolysis to controlled partial hydrolysis (less than 50% hydrolysis). This parameter change prevents spontaneous condensation of silanol groups while still enabling sufficient adhesion through the remaining hydrolyzable groups, resolving the contradiction between adhesion and stability.
Solution Approach 2:
The patent applies partial action by using alkoxysilanes with less than 50% hydrolysis rather than complete hydrolysis. This partial hydrolysis provides enough reactivity for adhesion while preventing the instability that arises from extensive hydrolysis and subsequent spontaneous condensation.
2Productivity
If alkoxysilane is reacted with stoichiometrically sufficient quantity of water to hydrolyze at least 50% of the alkoxy groups, then condensed oligomers are formed, but the composition requires extended mixing time (at least 16 hours) and achieves acceptable performance only with limited unhydrolyzed content below 50 weight percent
Solution Approach 1:
The patent uses partial hydrolysis (less than 50% hydrolysis) instead of complete hydrolysis, which dramatically reduces the required mixing time from at least 16 hours to a much shorter duration. This partial action approach maintains sufficient adhesion performance while eliminating the need for extended mixing.
Solution Approach 2:
The patent changes the hydrolysis extent parameter from ≥50% to <50%, which fundamentally alters the reaction kinetics and eliminates the need for prolonged mixing. This parameter change enables faster coating formation while maintaining performance through the controlled presence of unhydrolyzed alkoxysilane.
3Stability of the object's composition
If unhydrolyzed alkoxysilane is used to maintain stability and prevent spontaneous condensation, then coating performance is improved, but adhesion to the substrate may be compromised
Solution Approach 1:
The patent optimizes the hydrolysis parameter to less than 50% hydrolysis, which provides the right balance between stability and adhesion. This parameter change ensures sufficient unhydrolyzed alkoxysilane remains to prevent spontaneous condensation while enough hydrolyzed groups are present to provide adequate adhesion to ophthalmic lens materials.
Solution Approach 2:
The patent creates a composite system containing both unhydrolyzed and partially hydrolyzed alkoxysilane species in controlled proportions. This composite approach allows the unhydrolyzed portions to provide stability and the hydrolyzed portions to provide adhesion, resolving the contradiction between these two properties.
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 composition achieves enhanced coating performance with improved scratch resistance and stability, providing a more effective coating solution for optical articles.
Implementation Method 1
Hydrolysis of the alkoxy groups liberates the associated alcohol to form silanol groups
Implementation Method 2
Self-condensation of the hydrolyzed alkoxysilane species yields a mixture of primarily oligomeric and polymeric products
Implementation Method 3
an ethylenically unsaturated monomer
Data Source
AI summary
Provided is a curable composition including the following components: (i) a first alkoxysilane which is unhydrolyzed; (ii) a second alkoxysilane which is 5 to 45 percent hydrolyzed; and (iii) an ethylenically unsaturated monomer. The invention also provides coatings formed from the curable composition and articles coated with the curable composition.