Silicone Polyurethane Xerogel Contact Lens
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Solution Overview
Problem
Current contact lens materials face challenges in providing sufficient oxygen permeability and comfort during daily wear, with issues such as lipid binding and dryness, despite advancements in silicone-containing polymers, which can lead to surface wettability problems.
Innovation Solution
Development of silicone-containing polyurethane xerogels and hydrogels prepared from a mixture of polyethylene glycol, di-isocyanate, polydialkyl siloxane diol, and a specific diol, reacted under substantially anhydrous conditions to minimize urea group formation, resulting in thermoplastic materials suitable for injection molding and offering high oxygen permeability and wearer comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone-containing polymers are used to increase oxygen permeability, then DK value is improved, but surface wettability deteriorates
Solution Approach 1:
The patent combines silicone units with polyurethane and polyether units to create a composite polymer system. The silicone segments provide high oxygen permeability (DK values up to 100-150), while the polyurethane/polyether matrix maintains surface wettability and comfort, resolving the contradiction between oxygen transmission and surface properties
Solution Approach 2:
The invention creates localized silicone-rich domains within a polyurethane/polyether matrix, allowing different regions of the material to perform different functions: silicone units provide oxygen permeability while the surrounding polyurethane/polyether regions maintain surface wettability and comfort
2Reliability
If hydrophilic comonomers are incorporated to increase oxygen permeability, then DK value is improved, but protein and lipid deposition increases
Solution Approach 1:
The patent replaces traditional hydrophilic comonomer systems with a silicone-polyurethane-polyether composite system. This composite structure achieves high oxygen permeability through silicone units while the polyurethane/polyether framework resists protein and lipid deposition, eliminating the harmful effects associated with conventional hydrophilic comonomers
3Strength
If water is added to the reaction mixture to form urea groups, then modulus increases, but thermal stability deteriorates
Solution Approach 1:
The patent modifies the reaction parameters by conducting polymerization under substantially anhydrous conditions (water content <0.1%), which prevents urea group formation. This parameter change maintains thermal stability while achieving adequate modulus values through the polyurethane-hard segment structure without urea crosslinking
4Ease of manufacture
If conventional contact lens materials are used, then manufacturing is simplified, but comfort during daily wear deteriorates
Solution Approach 1:
The patent employs a silicone-polyurethane-polyether composite system that can be processed using conventional contact lens manufacturing techniques. The composite material provides superior comfort properties (high oxygen permeability, good wettability, resistance to deposition) while remaining compatible with existing manufacturing processes, thus improving comfort without sacrificing ease of manufacture
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 resulting materials exhibit improved modulus values, thermal stability, and resistance to oxidative degradation, enabling high oxygen flux and enhanced wearer comfort with high DK values and light transmissibility, suitable for large-scale cost-effective production of contact lenses.
Implementation Method 1
a polyurethane xerogel prepared from a mixture comprising: (a) at least one polyethylene glycol; (b) at least one di-isocyanate; (c) at least one polydialkyl siloxane diol (d) at least one diol of formula I
Implementation Method 2
A second aspect of the invention relates to a polyurethane hydrogel which comprises the polyurethane xerogel as described above in hydrated form
Implementation Method 3
The lenses produced from these materials were originally designed for extended wear... These materials are based on the copolymerisation of silicone methacylates with hydrophilic comonomers... further increasing the level of oxygen
Data Source
AI summary
The present invention relates to a polyurethane prepared from a mixture comprising: (a) at least one polyethylene glycol; (b) at least one di-isocyanate; (c) at least one polydialkyl siloxane diol; and (d) at least one diol of formula (I) wherein n is an integer from 1 to 25; wherein the polyethylene glycol, di-isocyanate, polydialkyl siloxane diol and diol are reacted under substantially anhydrous conditions. Further aspects of the invention relate to a process for preparing a polyurethane. The invention also relates to a process for preparing a polyurethane xerogel in the form of a molded article, said process comprising the steps of: (i) preparing a reaction mixture comprising at least one polyethylene glycol, at least one di-isocyanate, at least one polydialkyl siloxane diol and at least one diol of formula I as described above; (ii) reacting the reaction mixture formed in step (i) under substantially anhydrous conditions to form a polyurethane xerogel; and (iii) injection molding the polyurethane xerogel to form a molded article.