Optical Article Polymer Composition Shrinkage Control
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Solution Overview
Problem
Conventional diethylene glycol bis(allyl carbonate) monomer compositions exhibit high shrinkage during polymerization, leading to commercially unacceptable products in optical applications like ophthalmic lenses, and existing low-shrinkage compositions often result in soft polymers with increased cross-link length.
Innovation Solution
A polymerizable composition comprising diethyleneglycol bischloroformate, allyl alcohol, a cyclic polyol, and optionally ethyleneglycol bischloroformate and a linear or branched aliphatic polyol, which reduces shrinkage while maintaining the rigidity necessary for optical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional diethylene glycol bis(allyl carbonate) monomer compositions are used for polymerization, then the polymerization process is simple and straightforward, but the shrinkage exceeds 13 percent leading to commercially unacceptable products
Solution Approach 1:
The patent modifies the chemical composition parameters by introducing cyclic polyols (such as 1,4-cyclohexanediol, isosorbide) and aliphatic polyols into the monomer system. This changes the molecular structure and cross-linking density, reducing polymerization shrinkage from over 13% to acceptable levels while maintaining product quality and yield
Solution Approach 2:
The patent creates a composite monomer system combining diethylene glycol bis(allyl carbonate) with cyclic polyols and aliphatic polyols. This composite approach allows the synergistic effects of different molecular structures to reduce shrinkage while maintaining the desired mechanical properties and optical clarity for commercially viable products
2Manufacturing precision
If a large number of polymerizable ethylenic double bonds are used during partial polymerization to produce prepolymer, then shrinkage in the mold is reduced, but the viscosity increases making the prepolymer difficult to flow into the mold
Solution Approach 1:
The patent optimizes the degree of partial polymerization and the ratio of polyols to control the balance between viscosity and shrinkage reduction. By adjusting these parameters, the prepolymer achieves sufficient flowability for mold filling while still providing the desired shrinkage control during final polymerization
3Manufacturing precision
If pre-polymerization is performed to consume polymerizable ethylenic double bonds, then shrinkage is reduced, but processing difficulties such as potential gelling of the reactor occur and production costs increase
Solution Approach 1:
The patent employs controlled partial polymerization rather than full pre-polymerization. This partial action approach consumes enough double bonds to reduce shrinkage but stops before reaching the gel point, avoiding reactor gelling and complex processing steps while still achieving acceptable shrinkage control
Solution Approach 2:
The patent adjusts the extent of partial polymerization and monomer composition to optimize the balance between shrinkage reduction and processing simplicity, eliminating the need for complex pre-polymerization steps and associated costs
4Manufacturing precision
If conventional low shrinkage compositions are used, then shrinkage is reduced, but the length between cross-links increases producing soft polymers with insufficient rigidity
Solution Approach 1:
The patent modifies the cross-linking parameters by incorporating cyclic polyols with specific molecular structures that provide appropriate cross-link density. This maintains short cross-link lengths for rigidity while controlling shrinkage through the unique molecular architecture of the cyclic and aliphatic polyol components
Solution Approach 2:
The composite monomer system combines different polyol types to achieve synergistic effects where the cyclic polyols provide structural rigidity and appropriate cross-link density, while the aliphatic polyols contribute to shrinkage control, resulting in polymers that are both rigid and have acceptable shrinkage
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 reduced shrinkage and improved mechanical properties, such as increased Fischer microhardness and storage modulus, resulting in solid, transparent optical articles suitable for various optical applications.
Implementation Method 1
Allyl carbonate monomer compositions can be polymerized to use as transparent coatings, optical lenses, and other optical elements
Data Source
AI summary
An exemplary polymerizable composition includes the reaction product of (a) diethyleneglycol bischloroformate; (b) allyl alcohol; (c) a cyclic polyol selected from the group consisting of a cycloaliphatic polyol having at least one secondary hydroxyl group, a heterocyclic polyol having primary and/or secondary hydroxyl groups, and mixtures thereof; (d) optionally, ethyleneglycol bischloroformate; and (e) optionally, at least one linear or branched aliphatic polyol having two to six hydroxyl groups. Another exemplary polymerizable composition includes the reaction product of (a) allyl alcohol; (b) a cyclic polyol selected from the group consisting of a cycloaliphatic polyol having at least one secondary hydroxyl group, a heterocyclic polyol having primary and/or secondary hydroxyl groups, and mixtures thereof; (c) ethyleneglycol bischloroformate; and (d) optionally, at least one linear or branched aliphatic polyol having two to six hydroxyl groups is also described. A reaction product, a polymerizate including the polymerizable composition, and an optical article including the polymerizable composition are also provided.