High Water Contact Lens Crosslinking via Carbamate Agents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High water content ophthalmic devices, such as contact lenses, face challenges with dimensional stability and manufacturability due to the use of allyl methacrylate as a cross-linking agent, which causes physical distortions and edge curling issues.
Innovation Solution
A polymerization product of a monomeric mixture comprising non-silicone-containing hydrophilic monomers, hydrophobic monomers, and a crosslinking agent mixture of di-, tri-, or tetra(meth)acrylate-containing and di-, tri-, or tetracarbamate-containing crosslinking agents, achieving an equilibrium water content of at least 65 weight percent without using allyl methacrylate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If allyl methacrylate (AMA) is used as a crosslinking agent to achieve high water content in ophthalmic devices, then the water content can be maintained at high levels, but dimensional stability deteriorates due to physical distortion and edge curling during manufacturing
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by replacing AMA with a specific combination of crosslinking agents (first crosslinking agent with methacrylate groups and second crosslinking agent with carbamate groups) in controlled weight ratios (0.01-5% first agent, 0.01-2% second agent). This parameter change maintains high water content while eliminating the dimensional instability caused by AMA volatility and reactivity issues.
Solution Approach 2:
The patent employs a composite crosslinking system using two different types of crosslinking agents with distinct chemical functionalities (methacrylate and carbamate groups). This composite approach combines the benefits of both agents to achieve superior dimensional stability and mechanical properties while maintaining high water content, overcoming the limitations of using a single crosslinking agent like AMA.
2Quantity of substance
If allyl methacrylate (AMA) is used as a crosslinking agent, then high water content can be achieved, but manufacturing precision deteriorates due to physical distortion and edge curling during post-fill-stand-down and purging processes
Solution Approach 1:
The patent modifies the chemical reactivity parameters by selecting crosslinking agents with appropriate functional groups and concentrations. The use of methacrylate and carbamate crosslinking agents in specific weight ranges (0.01-5% and 0.01-2% respectively) provides controlled crosslinking that prevents excessive shrinkage and distortion during manufacturing processes, thereby maintaining dimensional accuracy while achieving high water content.
Solution Approach 2:
The patent replaces the volatile and problematic AMA monomer with more stable crosslinking agents that do not require aggressive purging processes. This substitution eliminates the need for extended stand-down times and intensive purging, reducing manufacturing complexity and improving dimensional consistency without compromising water content.
3Stability of the object's composition
If a crosslinking agent mixture is used to improve dimensional stability and avoid AMA, then manufacturing complexity increases due to the need to mix and control multiple crosslinking agents
Solution Approach 1:
The patent establishes specific parameter ranges for the crosslinking agents (first agent: 0.01-5% by weight, second agent: 0.01-2% by weight) that optimize both dimensional stability and ease of manufacture. These defined parameters provide clear formulation guidelines that simplify the mixing and control processes, reducing the perceived complexity while maintaining superior performance.
Solution Approach 2:
The patent creates a synergistic composite crosslinking system where the combination of methacrylate and carbamate crosslinking agents produces enhanced dimensional stability and mechanical properties. This composite approach, while using multiple agents, results in improved overall performance that justifies the formulation complexity through superior product quality and manufacturing reliability.
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 provides improved modulus, dimensional stability, lower extractables, and enhanced tear resistance for high water content ophthalmic devices, addressing the issues associated with allyl methacrylate while maintaining high water content.
Implementation Method 1
subjecting the monomeric mixture to polymerizing conditions to provide a polymerized device
Data Source
AI summary
An ophthalmic device is disclosed which is a polymerization product of a monomeric mixture comprising: (a) a major amount of one or more first non-silicone- containing hydrophilic monomers; (b) one or more hydrophobic monomers; and (c) a crosslinking agent mixture comprising (i) one or more di-, tri-or tetra(meth)acrylate- containing crosslinking agents and (ii) one or more di-, tri-or tetracarbamate-containing crosslinking agents, wherein the ophthalmic device has an equilibrium water content of at least about 65 weight percent.