Isocyanate-Free Polyurethane Film Crosslinking During Solvent Drying
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Solution Overview
Problem
Existing polyurethane synthesis methods, such as extrusion, water-based, and solvent-based processes, face challenges including the need for expensive equipment, lack of versatility, use of hazardous solvents, and impact on film properties due to surfactants and emulsifiers, as well as high viscosity issues.
Innovation Solution
A method involving the deposition of a prepolymer composition onto a substrate without isocyanate, which includes carboxyl and/or silane moieties, and crosslinking occurs simultaneously with solvent drying, using a polyaziridine crosslinking agent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If water-based processes are used to form polyurethane films, then versatility is enhanced, but surfactants and emulsifiers must be added which impact film properties such as printability and make the final film sensitive to water
Solution Approach 1:
The invention extracts and eliminates the need for surfactants, emulsifiers, and wetting agents from the formulation by using a solvent-based system instead of water-based. This removal of harmful additives directly resolves the contradiction by maintaining versatility while preserving film properties like printability and water sensitivity.
Solution Approach 2:
The invention changes the fundamental parameter of the base medium from water to an organic solvent system. This parameter change allows the formulation to achieve versatility without requiring surfactants and emulsifiers, thereby maintaining film properties that are compromised in water-based systems.
2Adaptability or versatility
If solvent-based processes are used to form polyurethane films, then versatility is achieved, but hazardous solvents are used which are environmentally damaging
Solution Approach 1:
The invention changes the chemical composition parameter of the solvent system to use less hazardous organic solvents. This parameter change maintains the versatility of solvent-based processing while reducing the environmental harm associated with traditional solvent-based processes.
Solution Approach 2:
The invention converts the potential harm of solvent usage into a benefit by carefully selecting solvents that provide the necessary processing versatility while having reduced environmental impact compared to conventional solvents. The formulation achieves versatility without the severe environmental drawbacks of traditional solvent-based systems.
3Reliability
If isocyanate-containing prepolymers are used in polyurethane synthesis, then crosslinking and film formation are achieved, but hazardous materials are used which require special handling and pose safety risks
Solution Approach 1:
The invention extracts and removes isocyanate groups from the prepolymer formulation entirely. Instead of using traditional isocyanate-based crosslinking chemistry, the invention employs alternative crosslinking mechanisms that do not require hazardous isocyanates, thereby maintaining reliable crosslinking and film formation while eliminating safety hazards.
Solution Approach 2:
The invention introduces intermediary functional groups (such as carboxyl or hydroxyl groups) that serve as safe alternatives to isocyanates for achieving crosslinking. These intermediary groups enable the same crosslinking function without the hazardous properties of isocyanates, resolving the contradiction between reliability and safety.
4Productivity
If extrusion processes are used to form polyurethane films, then production is achieved, but expensive equipment is required and the processes lack versatility
Solution Approach 1:
The invention extracts the polyurethane formation process from complex extrusion equipment and transfers it to simpler coating and curing operations. By using preformed prepolymers that cure on the substrate, the invention eliminates the need for expensive extrusion machinery while maintaining production capability and adding versatility.
Solution Approach 2:
The invention replaces the mechanical extrusion system with a chemical curing system. Instead of using complex mechanical extrusion equipment to form and process polyurethane, the invention uses simpler deposition methods followed by chemical crosslinking, thereby reducing device complexity while maintaining productivity.
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
Produces polyurethane films with improved properties like long-term weatherability, conformability, printability, and chemical resistance, while eliminating the use of hazardous isocyanates and reducing environmental impact.
Implementation Method 1
crosslinking the prepolymer
Implementation Method 2
drying of the solvent
Data Source
AI summary
A method is disclosed for producing a polyurethane film including the steps of depositing a prepolymer composition, drying the prepolymer composition, and crosslinking the prepolymer composition.