Thermolatent Catalyst Polyurethane Composition for Optical Lenses
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Solution Overview
Problem
Conventional polyurethane-based elastomers for optical lenses have a short pot life due to catalyst acceleration of the NCO-OH reaction and high adhesion to molds, making demolding difficult.
Innovation Solution
A composition comprising a cycloaliphatic or araliphatic diisocyanate, a polyol with an OH number of 80 to 1000 mg KOH/g, an internal mold release agent with 8 to 12 carbon atoms, and a thermolatent catalyst with a specific reaction rate quotient, which extends pot life and improves demolding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a catalyst is used to accelerate the NCO-OH reaction, then the curing speed is improved, but the pot life is reduced
Solution Approach 1:
The patent uses thermolatent catalysts that change their catalytic activity based on temperature parameters. At low temperatures (e.g., 20°C), the catalyst remains inactive or has very low activity, preserving pot life. When heated to elevated temperatures (e.g., 60°C or above), the catalyst becomes highly active, accelerating the curing reaction. This temperature-dependent parameter change resolves the contradiction between curing speed and pot life.
2Strength
If conventional polyurethane-based elastomers are used, then the material strength is improved, but the adhesion to mold is increased making demolding difficult
Solution Approach 1:
The patent introduces a mold release agent as an intermediary substance between the polyurethane elastomer and the mold surface. This mold release agent prevents direct adhesion between the elastomer and mold, allowing easy demolding while preserving the material strength of the cured elastomer. The mold release agent acts as a mediating layer that eliminates the harmful adhesion effect.
3Loss of time
If the NCO-OH reaction is accelerated by catalyst, then the processing time is reduced, but the processing window is narrowed
Solution Approach 1:
The patent employs thermolatent catalysts that dynamically adjust their catalytic activity based on temperature conditions. During storage and low-temperature processing, the catalyst remains inactive, providing a wide processing window and extended pot life. When the mixture is heated during the molding process, the catalyst becomes active and accelerates the reaction, reducing processing time. This dynamic behavior allows the system to adapt to different processing conditions, resolving the contradiction between processing time and processing window.
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 an extended pot life and easier demolding of transparent moldings, such as optical lenses, with improved processing window and reduced adhesion to molds.
Implementation Method 1
the use of catalysts to accelerate curing is already known to experts... so-called thermolatent catalysts have been developed. These compounds are characterized by having little to no activity at low temperatures and only developing their catalytic activity at elevated temperatures
Implementation Method 2
an internal mold release agent, wherein the mold release agent is at least one mono- and/or dialkyl phosphate having 8 to 12 carbon atoms in the alkyl radical... very good demolding properties
Data Source
Figure 1~2
AI summary
A composition comprising an isocyanate component A) comprising at least one cycloaliphatic or araliphatic diisocyanate, a polyol component B) comprising at least one polyol having an OH number of 80 to 1000 mg KOH/g, an additive component C) comprising at least one internal demoulding agent, and a catalyst component D) comprising at least one inorganic metal complex as thermally latent catalyst, characterized in that the thermally latent catalyst has a quotient of reaction rates between catalysed reaction and uncatalysed reaction at 30°C of ≤ 5.0 and at 60°C of ≥ 1.1. The present invention further provides a process for producing an elastomer and for the use of the composition for production of transparent shaped bodies.