Water-Soluble Crosslinkable Polyurea Prepolymers for Contact Lenses
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Solution Overview
Problem
Current water-soluble photo-crosslinkable prepolymers for contact lenses often fail to achieve the desired combination of physical/mechanical properties such as tensile strength, elongation, and biocompatibility, leading to suboptimal performance and durability.
Innovation Solution
A water-soluble crosslinkable polyurea prepolymer is developed, formed by reacting an amine- or isocyanate-capped polyurea with a multifunctional compound containing ethylenically unsaturated groups, which is then actinically crosslinked to produce a soft contact lens with enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-soluble photo-crosslinkable prepolymers are used for contact lenses, then biocompatibility and wearing comfort are improved, but tensile properties and mechanical strength deteriorate
Solution Approach 1:
The patent uses composite materials by combining polyurea prepolymer chains with crosslinking agents containing ethylenically unsaturated groups. This creates a hybrid network structure where the polyurea provides biocompatibility and the crosslinking agent provides mechanical strength, resolving the contradiction between softness and tensile properties
Solution Approach 2:
The patent changes the chemical parameters of the prepolymer by introducing crosslinkable functional groups (ethylenically unsaturated groups) that can form covalent bonds upon photoirradiation. This parameter change transforms the material from a simple hydrogel to a crosslinked network, improving mechanical strength while maintaining the water-soluble nature for biocompatibility
2Ease of manufacture
If water-soluble crosslinkable prepolymers are used, then ease of manufacture and mold cleaning are improved, but mechanical durability and elasticity deteriorate
Solution Approach 1:
The patent applies preliminary action by incorporating crosslinkable functional groups into the prepolymer structure before molding. This allows the material to be easily processed and cleaned during manufacturing, while the crosslinking reaction during or after molding provides the necessary mechanical durability for the final product
Solution Approach 2:
The patent changes the physical state parameter of the material during processing - the prepolymer is water-soluble and flexible during manufacturing for easy handling and cleaning, but undergoes crosslinking to become mechanically durable in the final lens product
3Strength
If conventional polyurea prepolymers are used, then mechanical strength is improved, but biocompatibility and wearing comfort deteriorate
Solution Approach 1:
The patent applies local quality by making the prepolymer water-soluble in the bulk phase for biocompatibility, while introducing localized crosslinking sites through ethylenically unsaturated groups. This creates different properties in different regions - the bulk remains soft and biocompatible, while crosslinked regions provide mechanical strength
4Strength
If crosslinking is performed to improve mechanical properties, then tensile strength and elasticity are improved, but water content and softness may deteriorate
Solution Approach 1:
The patent carefully controls the crosslinking degree by adjusting the ratio of crosslinking agent to prepolymer and the photoirradiation conditions. This parameter control allows achieving sufficient tensile strength while maintaining adequate water content and softness for contact lens comfort
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 contact lenses exhibit improved tensile properties, biocompatibility, and durability, with a balanced water content and mechanical strength, ensuring comfort and stability, including resistance to autoclave-induced changes and thermal stability.
Implementation Method 1
a water-soluble crosslinkable polyurea prepolymer, which is the reaction product of an amine- or isocyanate-capped polyurea and a multifunctional compound having at least one ethylenically unsaturated group and a function group coreactive with capping amine or isocyanate groups
Implementation Method 2
a lens-forming material (a prepolymer solution) is introduced into a mold consisting of two mold halves... The crosslinking of the lens-forming material in the mold cavity is carried out by means of actinic irradiation, in particular UV light
Data Source
AI summary
The present invention provides a water-soluble crosslinkable polyurea prepolymer. The crosslinkable polyurea prepolymer of the invention is prepared by reacting an amine- or isocyanate-capped polyurea with a multifunctional compound having at least one one ethylenically unsaturated group and a function group coreactive with the capping amine or isocyanate groups of the amine- or isocyanate-capped polyurea. The amine- or isocyanate-capped polyurea is a copolymerization production of: (a) at least one poly(oxyalkylene)diamine, (b) optionally at least one organic di- or poly-amine, (c) optionally at least one diisocyanate, and (d) at least one polyisocyanate. The crosslinkable polyurea prepolymer of the invention can find use in economically producing contact lenses which have durable, highly elastic soft contact lenses with desired physical properties. In addition, the present invention provides method for making a medical device, preferably an ophthalmic device, more preferably a contact lens.