Solvent-Free Urethane Adhesive Viscosity and Bond Strength
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Solution Overview
Problem
Existing solvent-free urethane adhesives face challenges in achieving low viscosity for mixing and application, rapid 'green tack' formation, and high ultimate bond strength that withstands thermal cycles and chemical exposure.
Innovation Solution
A solvent-free adhesive composition comprising polyisocyanate and polymeric polyol, where the polymeric polyol is a reaction product of a dihydroxy tertiary amine and a polyhydroxy alcohol, combined with an epoxide or glycidyl ether compound, maintaining low viscosity for extended mixing and application time while forming a strong, thermally stable bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the adhesive composition uses conventional polyols, then the viscosity decreases, but the green tack formation and bond strength are insufficient
Solution Approach 1:
The patent changes the chemical parameters of the polyol by using a polymeric polyol with specific molecular weight (2,000-10,000) and hydroxyl number (30-200), which optimizes the balance between viscosity and reactivity. This parameter optimization enables both low viscosity for easy application and rapid green tack formation for strong bonding.
Solution Approach 2:
The patent creates a composite adhesive system by combining polyisocyanate with a specifically designed polymeric polyol that contains both tertiary amine groups and hydroxyl groups. This composite material approach allows the adhesive to exhibit multiple desirable properties simultaneously: low viscosity, rapid green tack formation, and high ultimate bond strength.
2Strength
If the adhesive composition is designed for rapid green tack formation, then the bond strength improves, but the mixing and application time is reduced
Solution Approach 1:
The patent creates a dynamic viscosity profile where the adhesive maintains low viscosity during the mixing and application phase, then rapidly increases viscosity to form green tack. The polymeric polyol's specific molecular structure enables this time-dependent behavior, providing a long open time for application followed by rapid bond formation.
Solution Approach 2:
The patent optimizes the hydroxyl number (30-200) and molecular weight (2,000-10,000) parameters of the polymeric polyol to control the reaction kinetics. These parameter changes enable the adhesive to maintain stability during mixing, then rapidly cure to form green tack within minutes, resolving the contradiction between application time and bond formation speed.
3Speed
If the adhesive composition uses high reactivity components, then the green tack forms rapidly, but the viscosity increases too quickly for application
Solution Approach 1:
The patent carefully selects the molecular weight (2,000-10,000) and hydroxyl number (30-200) parameters of the polymeric polyol to achieve optimal reactivity. This parameter optimization ensures that the adhesive has sufficiently low viscosity for easy application while maintaining the capability for rapid green tack formation, resolving the contradiction between application ease and cure speed.
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 adhesive composition achieves rapid 'green tack' formation and high ultimate bond strength, maintaining integrity under thermal cycles and chemical exposure, with controlled viscosity for efficient application and curing.
Implementation Method 1
the polyisocyanate and the polyol react with each other to form a cured composition
Implementation Method 2
said polymeric polyol is a reaction product of (I) a polyol initiator, wherein said polyol initiator is a reaction product of (a) one or more dihydroxy tertiary amine compound... and (b) one or more glycidyl ether compound
Data Source
AI summary
Provided is an adhesive composition comprising (A) one or more polyisocyanate and (B) one or more polymeric polyol, wherein said polymeric polyol is a reaction product of (I) a polyol initiator, wherein said polyol initiator is a reaction product of (a) one or more dihydroxy tertiary amine compound, and (b) a polyhydroxy alcohol, and (II) one or more epoxide compound or one or more glycidyl ether compound or a mixture thereof; wherein said adhesive composition contains solvent in an amount of 0 to 5% by weight based on the weight of said adhesive composition. Also provided is a method of bonding substrates using such an adhesive composition.