Butylated Polyvinylpyrrolidone Mold Release for Contact Lens Cast Molding
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Solution Overview
Problem
The existing methods for producing contact lenses using cast-molding processes face challenges with mold separation, leading to defects such as cracks, flaws, and reduced yield due to strong adhesion between the lens and the mold, which is exacerbated by the limitations of surfactants and non-polymerizable polymers as mold releasing agents, especially under high-speed automated operations.
Innovation Solution
Incorporating Butylated Polyvinylpyrrolidone into the lens-forming composition as a mold releasing agent, which forms an interfacial film reducing the averaged mold separation force by at least 20%, thereby facilitating easier lens removal and improving product quality and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cast-molding process is used without mold releasing agents, then manufacturing simplicity is maintained, but lens adhesion to mold increases causing cracks and defects
Solution Approach 1:
The patent introduces Butylated Polyvinylpyrrolidone as an intermediary substance between the mold surface and the lens-forming composition. This intermediary forms an interfacial film that reduces adhesion between the lens and mold, facilitating easy separation without causing cracks or defects, while maintaining process simplicity.
Solution Approach 2:
The patent changes the chemical composition parameter of the lens-forming composition by incorporating Butylated Polyvinylpyrrolidone. This parameter change modifies the interfacial properties between the composition and mold, reducing separation force and preventing lens damage during mold opening.
2Force
If surfactants are used as internal mold releasing agents, then lens-mold adhesion is reduced, but surfactant exhaustion occurs with repeated mold use
Solution Approach 1:
The patent replaces surfactants with Butylated Polyvinylpyrrolidone, changing the chemical parameter from surface-active compounds to a polymeric releasing agent. This polymer provides consistent mold release performance across multiple production cycles without exhaustion, maintaining reliable low separation force.
Solution Approach 2:
The patent moves away from reusable surfactants that get exhausted toward a polymer-based system that provides durable, long-lasting mold release capability throughout the mold's service life, eliminating the need for frequent reapplication or replacement.
3Force
If external mold releasing agents are applied to mold surfaces, then lens-mold adhesion is reduced, but lens surface uniformity and clarity deteriorate due to agent migration
Solution Approach 1:
The patent incorporates the mold releasing agent Butylated Polyvinylpyrrolidone directly into the lens-forming composition as an internal intermediary. This ensures the releasing agent remains within the lens matrix and does not migrate to the surface, preventing turbidity and surface non-uniformity while still reducing mold separation force.
Solution Approach 2:
The patent applies the mold releasing agent specifically at the mold-lens interface within the composition, creating localized release functionality at the critical separation zone without affecting the overall lens material properties or surface quality.
4Productivity
If high-speed automated operations are used, then productivity increases, but mold separation becomes more difficult due to short processing time
Solution Approach 1:
The patent incorporates Butylated Polyvinylpyrrolidone into the lens-forming composition before molding, performing preliminary preparation of the mold-lens interface. This pre-established interfacial film reduces separation force even under the short processing times of high-speed automated operations, enabling fast production without increasing separation difficulty.
Solution Approach 2:
The patent modifies the rheological and interfacial parameters of the lens-forming composition by adding Butylated Polyvinylpyrrolidone, which optimizes the material's behavior during rapid molding and separation cycles, maintaining low separation force despite reduced processing time.
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 use of Butylated Polyvinylpyrrolidone significantly reduces the mold separation force, minimizing defects and increasing the production yield of contact lenses by forming an effective interfacial film that reduces adhesion, thus enhancing the quality and efficiency of the lens production process.
Implementation Method 1
wherein the Butylated forms an interfacial film at interface between the mold and the fluid composition therein
Implementation Method 2
wherein the lens-forming material is crosslinkable and/or polymerizable by actinic radiation
Data Source
AI summary
The instant invention pertains to a method and a fluid composition for producing contact lenses with improved lens quality and with increased product yield. The method of the invention involves adding a Butylated Polyvinylpyrrolidone into a fluid composition including a lens-forming material in an amount sufficient to reduce an averaged mold separation force by at least about 20% in comparison with that without the Butylated Polyvinylpyrrolidone.