Epoxy Adhesive Composition for Metal Sheet Bonding
Solution Overview
Problem
Existing adhesive compositions for bonding metal sheets, particularly those using epoxy resins and dicyandiamide with Lewis acid accelerators, face issues such as toxicity, rapid curing leading to brittleness, and the need for precise temperature control, resulting in inefficiencies and safety concerns.
Innovation Solution
A water-dilutable composition comprising a linear epoxy resin, a non-linear epoxy resin, a basic hardener, and a pre-crosslinker with blocked isocyanate groups, allowing for pre-crosslinking and final curing in two chemically distinct steps without the use of toxic Lewis acids, enabling storage stability and efficient bonding at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Lewis acid accelerators are used to rapidly cure epoxy resin with dicyandiamide, then curing speed is improved, but the adhesive layer becomes brittle and durability is reduced
Solution Approach 1:
The patent removes the Lewis acid accelerator from the curing system entirely, replacing it with a direct thermal curing mechanism using dicyandiamide and epoxy resin. This extraction of the harmful accelerator eliminates the cause of brittleness while maintaining curing functionality through controlled thermal activation.
Solution Approach 2:
The patent changes the curing parameters by eliminating the catalyst and relying on thermal energy input (100-200°C) to drive the reaction. This parameter change from catalytic to thermal curing allows controlled crosslinking density that avoids excessive brittleness while achieving sufficient curing speed.
2Loss of time
If Lewis acid accelerators are used to accelerate curing, then curing time is reduced, but toxicity and safety concerns increase
Solution Approach 1:
The patent converts the potential harm of long curing times into a benefit by using a controlled thermal curing process that achieves adequate bonding without requiring aggressive accelerators. The extended but controlled curing time allows safe, toxin-free processing while still meeting production requirements.
Solution Approach 2:
The patent replaces expensive and toxic Lewis acid catalysts with a simple, safe, and inexpensive thermal curing system using common materials like dicyandiamide and epoxy resin. This substitution eliminates hazardous substances while maintaining effective curing functionality.
3Manufacturing precision
If precise temperature control is maintained during curing, then bonding quality is improved, but process complexity and energy consumption increase
Solution Approach 1:
The patent applies partial temperature control by using a broad curing range (100-200°C) rather than requiring precise control at a single temperature point. This approach maintains bonding quality through a temperature window, reducing the need for complex control systems while ensuring adequate curing.
4Strength
If high crosslinking density is achieved through rapid curing, then initial strength is improved, but brittleness increases and durability decreases
Solution Approach 1:
The patent employs periodic or staged curing by allowing gradual crosslinking during extended thermal treatment (100-200°C over extended time). This staged approach builds crosslinking density progressively, achieving sufficient strength while avoiding the sudden excessive crosslinking that causes brittleness.
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 composition provides a stable, efficient bonding process with reduced energy consumption, extended storage life, and improved safety by eliminating the need for toxic accelerators, allowing for quick and precise control over curing parameters, resulting in a durable and thermally resistant adhesive layer.
Implementation Method 1
d. 0.9 to 1.2 mol parts of at least one (pre-)crosslinker comprising at least two blocked isocyanate groups
Implementation Method 2
Only during the bonding process is the adhesive layer activated, for example, by the application of thermal energy. This activation makes the coating adhesive, allowing adjacent metals to be bonded. At the same time, the adhesive layer is hardened and becomes a heat-resistant thermoset.
Implementation Method 3
Only during the bonding process is the adhesive layer activated, for example, by the application of thermal energy
Implementation Method 4
The viscoelastic bonding layers between the individual laminations exhibit pronounced damping properties against sound transmission
Data Source
AI summary
The present invention relates to a composition, preferably for bonding metal sheets, comprising: a. 1 molar part of at least one linear epoxy resin having an average epoxy equivalent weight of 600 to 5000 g/mol and an epoxy functionality of 2, b. 0.4 to 0.8 molar parts of at least one non-linear epoxy resin having an average epoxy equivalent weight of 180 to 350 g/mol and an average epoxy functionality of at least 3, c. 0.8 to 1.3 molar parts of at least one alkaline hardener having at least two free amine-bonded hydrogen atoms, and d. 0.9 to 1.2 molar parts of at least one cross-linking agent having at least two blocked isocyanate groups.