Dual Crosslink Agents for Ophthalmic Lens Copolymerization
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Solution Overview
Problem
Conventional polymer formulations with two monomers having different reactivity ratios and a single crosslinking agent often result in inefficient production, mechanical property deterioration, and difficulty in maintaining design specifications due to phase separation and unreacted monomer extraction, especially when copolymerizing N-vinyl-2-pyrrolidone with alkyl acrylates or methacrylates for ophthalmic lenses.
Innovation Solution
The use of dual crosslink agents, each selectively reacting with a respective monomer, ensures compatibility and reduces unreacted monomer extraction, allowing for better control of the polymer's chemical, physical, and structural characteristics by matching the reactivity ratios of the hydrophilic and lens monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single crosslinking agent is used with two monomers having very different reactivity ratios, then the polymerization reaction can proceed, but the two monomers coexist as essentially two homopolymers with phase separation, resulting in decreased transparency and deteriorated mechanical properties
Solution Approach 1:
The invention divides the crosslinking function into two separate crosslinking agents, each optimized for one of the two monomers with different reactivity ratios. This segmentation allows each monomer to react preferentially with its matched crosslinking agent, preventing phase separation and ensuring homogeneous copolymer formation while maintaining transparency and mechanical properties.
Solution Approach 2:
The invention introduces two different crosslinking agents as intermediaries that mediate the polymerization between two monomers with very different reactivity ratios. Each crosslinking agent acts as a specialized mediator for its corresponding monomer, enabling controlled copolymerization and preventing the formation of separate homopolymer phases.
2Productivity
If one monomer preferentially reacts with the crosslinking agent during initial stages, then that monomer is consumed first, but the second monomer remains unreacted or forms oligomers that must be extracted, reducing production efficiency and yielding unreacted monomer
Solution Approach 1:
The invention segments the crosslinking function into two specialized agents, each with matched reactivity ratios for its corresponding monomer. This prevents one monomer from being consumed preferentially, as each monomer-crosslinking agent pair reacts at comparable rates, eliminating the need to extract unreacted monomer and improving production efficiency.
Solution Approach 2:
The invention changes the reactivity ratio parameters by selecting crosslinking agents with matched reactivity ratios for each monomer. This parameter matching ensures that both monomers react at similar rates during polymerization, preventing the formation of unreacted monomer or oligomers that would require extraction.
3Productivity
If conventional polymer formulations are used with variable reaction conditions, then production can proceed, but it is difficult to maintain design specifications from one production batch to another
Solution Approach 1:
The invention segments the crosslinking system into two matched pairs, which creates a more balanced and controllable polymerization reaction. This segmentation reduces sensitivity to variable reaction conditions, enabling consistent production that maintains design specifications across batches while preserving production continuity.
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
This approach enhances the production efficiency and material properties of ophthalmic lenses by minimizing unreacted monomer extraction and maintaining design specifications, resulting in improved mechanical properties and hydrophilic character.
Implementation Method 1
The polymer comprises monomeric units of two or more monomers and two or more crosslink agents... NVP is often copolymerized with an alkyl acrylate or methacrylate... N-methyl-3-methylene-2-pyrrolidone (NMMP)... has a polymerization reaction rate more in-line with the other acrylate/methacrylate monomers
Data Source
AI summary
A compound of general formula I wherein R1, R2, R3, R4, R7 and R8 are independently selected from hydrogen, C1-C4alkyl, C1-C2alkanol or hydroxyl; A is O, O(CH2CH2O)v or [SiR5R6O]wSiR5R6, wherein R5 and R6 are independently selected from C1-4alkyl or phenyl, and v is from 1-20 and w is from 0 to 60; m and n are integers independently selected from 1 to 10; p is 0 or 1; and q is an integer from 0 to 6; and X and Y are independently selected from O or NR9, wherein R9 is hydrogen, C1-C4alkyl or C1-C2alkanol.