Polymerizable Materials for Soft Contact Lenses
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Solution Overview
Problem
Current methods for producing soft contact lenses using water-soluble photo-crosslinkable polyvinyl alcohol often result in defects such as cracks, flaws, or breakage during mold removal, leading to reduced production yield and suboptimal physical properties like elasticity and durability.
Innovation Solution
A polymerizable composition comprising water-soluble polyvinyl alcohol with crosslinkable groups and a modifier, such as nanoparticles or copolymers, is used to enhance physical properties like stress at break, elongation at break, toughness, and susceptibility to fracture, which are improved through radiation-crosslinking and the presence of additional vinylic monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water-soluble photo-crosslinkable polyvinyl alcohol is used for contact lens production, then manufacturing cost is reduced and production speed is improved, but lens durability and elasticity deteriorate
Solution Approach 1:
The patent combines water-soluble polyvinyl alcohol with hydrophilic monomers (N-vinyl-2-pyrrolidone, hydroxyethyl methacrylate) and crosslinking agents to create a composite hydrogel material. This composite structure maintains the ease of manufacturing and water solubility of PVA while adding the mechanical strength, elasticity, and durability properties of the hydrogel network, thereby resolving the contradiction between production efficiency and lens strength.
Solution Approach 2:
The patent modifies the chemical and physical parameters of the base polymer by incorporating functional monomers and crosslinking agents. The crosslinking degree, monomer composition ratios, and molecular weight parameters are optimized to achieve the desired balance between manufacturing processability and final product mechanical properties, allowing simultaneous improvement in both productivity and durability.
2Ease of manufacture
If water-soluble photo-crosslinkable polyvinyl alcohol is used, then manufacturing cost is reduced, but lens elasticity and toughness deteriorate
Solution Approach 1:
The invention creates a composite hydrogel system where hydrophilic monomers form a three-dimensional network within the polyvinyl alcohol matrix. This network structure provides the necessary elasticity and toughness while maintaining the cost-effectiveness of the PVA base material, resolving the contradiction between manufacturing economy and material stability.
Solution Approach 2:
The patent introduces functional monomers at specific concentrations and locations within the polymer matrix to locally enhance elastic properties. The hydroxyethyl methacrylate and N-vinyl-2-pyrrolidone are incorporated in optimized amounts to provide localized flexibility and toughness without compromising the overall manufacturing cost structure.
3Productivity
If conventional molding process is used, then production yield is reduced due to lens breakage during mold removal, but process complexity is minimized
Solution Approach 1:
The patent optimizes the mechanical parameters of the lens material through controlled crosslinking and monomer selection, adjusting the glass transition temperature and crosslinking density to achieve optimal flexibility during mold removal. This allows lenses to be released from molds without breaking, significantly improving production yield while maintaining relatively simple processing equipment.
Solution Approach 2:
The patent incorporates mold-release agents and optimizes the curing sequence in advance to prevent lens-mold adhesion before removal. By pre-configuring the material properties and mold surface characteristics, the process avoids lens breakage during ejection, improving yield without requiring complex additional equipment or post-processing steps.
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 modified composition allows for the production of soft contact lenses with improved durability and elasticity, reducing defects and enhancing mechanical properties, thereby increasing production yield and quality.
Implementation Method 1
a water-soluble polyvinyl alcohol having crosslinkable groups; and a modifier in an amount sufficient to improve one or more physical properties of a polymeric article made from the polymerizable material
Implementation Method 2
which are improved through radiation-crosslinking and the presence of additional vinylic monomers
Data Source
AI summary
The present invention provides a polymerizable material for making a polymeric article, the polymerizable material comprising: a water-soluble polyvinyl alcohol having crosslinkable groups; and a modifier in an amount sufficient to improve one or more physical properties of a polymeric article made from the polymerizable material, wherein the one or more physical properties are selected from the group consisting of stress at break (N/mm2), percentage of elongation at break, toughness or energy to break (N·mm), and susceptibility to fracture. The modifier is selected from the group consisting of nanoparticles having a hydrophilic surface, a copolymer having hydrophobic groups or units for imparting at least one desired physical property to said ophthalmic device and hydrophilic groups or units in an amount sufficient to render the copolymer miscible with the polyvinyl alcohol, and mixtures thereof. In addition, the present invention provides a polymeric article obtained by polymerization of a polymerizable material of the invention and also a method for modifying one or more physical properties of a hydrogel article obtained from the polymerization of a crosslinkable polymer.