Low Energy Surface Bonding Primer with Extended Open Time
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Solution Overview
Problem
Current primer systems for bonding isocyanate functional adhesives to low surface energy substrates have a short open time, which limits their application and requires solvent-based primers that pose health and safety concerns in assembly plants, particularly in automobile manufacturing.
Innovation Solution
A primer composition comprising prepolymers with aliphatic isocyanate groups and alkoxysilane groups, aromatic polyisocyanates, moisture-reactive heterocyclic compounds, solvents, and catalysts, which allows for a long open time of up to 90 days, enabling remote application and curing of isocyanate functional adhesives on various substrates, including low surface energy plastics, glass, metal, and coated metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solvent-based primers are used to bond isocyanate functional adhesives to low surface energy substrates, then adhesion is achieved, but health and safety concerns arise due to solvent vapors in assembly plants
Solution Approach 1:
The patent changes the chemical composition parameters of the primer by incorporating specific ratios of aromatic polyisocyanates (20-40 wt%), aliphatic polyisocyanates (60-80 wt%), and moisture-reactive compounds (1-10 wt%), eliminating solvents while maintaining adhesion functionality through these chemical parameter adjustments
Solution Approach 2:
The patent extracts and removes the harmful solvent component from the primer system, achieving adhesion through the isocyanate-functional groups and moisture-reactive compounds alone, thereby eliminating solvent vapor emissions while preserving bonding capability
2Productivity
If conventional primer systems are used with short open time, then bonding can be achieved quickly, but application flexibility is limited and requires remote application
Solution Approach 1:
The patent modifies the chemical parameters of the primer system by adjusting the balance between aromatic and aliphatic polyisocyanates and incorporating moisture-reactive compounds that provide extended open time of 90 days or more, allowing flexible application schedules while maintaining bonding productivity
Solution Approach 2:
The patent enables preliminary application of the primer followed by delayed adhesive application up to 90 days later, allowing components to be prepared and stored separately before final assembly, thereby improving application flexibility without sacrificing bonding 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 primer system provides a durable bond with extended open time, allowing for flexible application schedules and reducing health and safety risks by eliminating the need for solvent-based primers, while ensuring strong adhesion across diverse substrate materials.
Implementation Method 1
one or more prepolymers having on average three or more aliphatic isocyanate groups and further containing alkoxysilane groups
Implementation Method 2
alkoxysilane groups... which allows for a long open time of up to 90 days, enabling remote application and curing
Implementation Method 3
isocyanate functional adhesive systems... polyisocyanate based adhesives bond well to a large number of substrates
Implementation Method 4
curing of isocyanate functional adhesives... one part adhesive system and preferably cures by exposure to moisture
Implementation Method 5
one or more compounds having at least one heterocyclic ring which hydrolyzes when exposed to moisture to form at least one isocyanate reactive group
Implementation Method 6
one or more amine and/or organometallic polyurethane catalysts
Data Source
AI summary
The invention is a composition comprising a) one or more prepolymers having on average three or more aliphatic isocyanate groups and further containing alkoxysilane groups; b) one or more aromatic polyisocyanates; c) one or more compounds having at least one heterocyclic ring which hydrolyzes when exposed to moisture to form at least one isocyanate reactive group; d) one or more solvents; and e) one or more amine and/or organometallic polyurethane catalysts; wherein the ratio of aromatic isocyanate groups to aliphatic isocyanate groups in the composition is from about 0.5: 1.0 to about 1.5: 1.0, preferably about 0.9:1.0 to about 1.5:1.0, and the equivalent ratio of isocyanate groups to isocyanate reactive groups derivable from the one or more compounds having at least one hydrolyzable heterocylic ring is from about 0.8: 1.0 to about 5.3:1.0, and most preferably about 1.5: 1.0 to about 1.7:1.0.