Solventless Polyurethane Adhesive Crystalline Oxygen Barrier
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Solution Overview
Problem
Current polymeric film laminates lack effective oxygen barrier properties, and existing adhesives often pose environmental and workplace hazards or require significant energy for solvent removal, with complex structures and high energy expenditure.
Innovation Solution
A method involving a solvent-based adhesive mixture of polyisocyanate and hydroxyl-terminated polyester, forming crystalline polyester domains to enhance oxygen barrier properties, which is applied between polymeric films and cured at a temperature of 50°C or higher to create a laminate with improved barrier performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If solvent-based adhesives are used to bond polymeric films, then the adhesive can be applied easily and bonds films effectively, but the solvent or residual adhesive represents workplace and environmental danger and requires additional energy for solvent removal
Solution Approach 1:
The patent extracts and removes the solvent component from the adhesive system entirely, transitioning from solvent-based to solventless formulations. This eliminates the harmful factors associated with solvent evaporation and residual adhesive while maintaining the bonding functionality through alternative adhesive chemistries that cure without solvents.
Solution Approach 2:
The patent changes the fundamental parameter of adhesive formulation from solvent-based to solventless, altering the chemical composition and curing mechanism. This parameter change eliminates the harmful solvent-related effects while preserving adhesive performance through modified chemical pathways.
2Temperature
If water-borne EVOH formulations are used to adhere polymeric films, then films with low melt temperatures can be bonded without melting, but significant energy must be expended to remove the water
Solution Approach 1:
The patent extracts and removes the water component from the EVOH adhesive formulation, transitioning to a solventless system. This eliminates the energy-intensive water removal step while maintaining the ability to bond heat-sensitive films through controlled curing mechanisms that do not require high temperatures.
Solution Approach 2:
The patent changes the formulation parameter from water-borne to solventless, fundamentally altering how the adhesive is applied and cured. This parameter change eliminates the need for energy-intensive drying while preserving film integrity during bonding.
3Reliability
If coextrusion is used to apply EVOH, then the laminate performs well in high humidity conditions, but the structure becomes relatively complex
Solution Approach 1:
The patent merges the adhesive and barrier functions into a single integrated layer by applying EVOH as a coating rather than requiring separate coextruded layers. This consolidation simplifies the overall laminate structure while maintaining the oxygen barrier performance needed for humidity resistance.
Solution Approach 2:
The patent creates a multi-functional EVOH layer that simultaneously serves as both the adhesive bonding agent and the oxygen barrier layer. This universal layer eliminates the need for complex multi-layer coextrusion structures while providing both bonding and barrier functions.
4Reliability
If multiple layers of polymeric materials are used to enhance oxygen barrier properties, then the oxygen barrier capability is improved, but the laminate structure becomes more complex and manufacturing becomes more difficult
Solution Approach 1:
The patent merges multiple functional layers into fewer integrated layers by using adhesive formulations that provide both bonding and barrier functions simultaneously. This reduces the total number of layers needed while maintaining oxygen barrier capability.
Solution Approach 2:
The patent creates adhesive layers with multi-functionality, where a single layer provides both the bonding function and the oxygen barrier function. This universal approach eliminates the need for separate dedicated barrier layers, simplifying the overall structure.
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 method results in a laminate with significantly improved oxygen barrier properties, convenient application, and reduced environmental impact, maintaining crystalline domains for enhanced barrier performance and flexibility, even after flex-cracking tests.
Implementation Method 1
cure under conditions such that crystalline polyester domains are formed prior to completion of cure
Data Source
AI summary
Laminates of polymeric films and solvent-based polyurethane adhesive formulations for preparing them are provided. The adhesive formulations include a hydroxyl-terminated polyester that forms crystalline polyester domains after reaction with an appropriate polyisocyanate, but prior to completion of cure. The result is an adhesive layer that substantially enhances the oxygen barrier properties of the adhesive and, therefore, of the laminate as a whole, while offering desirable convenience of application even at relatively low temperatures. The laminates may also exhibit desirable retention of barrier properties following flex-cracking.