Silane-Modified Hot Melt Adhesive for Zero Diisocyanate Emission
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Solution Overview
Problem
Conventional reactive polyurethane hot melt adhesives emit toxic and irritating monomeric diisocyanates during application, posing health risks and requiring costly precautionary measures due to their carcinogenic potential, necessitating the development of adhesives with reduced or zero monomeric diisocyanate content.
Innovation Solution
Formulation of non-MDI emitting reactive hot melt adhesives using high and low modulus silane modified liquid polymers, tackifiers, and catalysts, which upon curing, form a strong and durable adhesive film with reduced vapor pressure of isocyanate vapors, thereby minimizing health hazards and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional reactive polyurethane hot melt adhesives are used, then strong adhesive performance and durability are achieved, but toxic monomeric diisocyanates are emitted during application posing health risks
Solution Approach 1:
The patent changes the chemical composition parameters by replacing conventional polyisocyanate-based polymers with silane-modified liquid polymers containing reactive silane groups. This parameter change eliminates monomeric diisocyanate emissions while maintaining adhesive performance through alternative crosslinking chemistry between silane groups and moisture.
Solution Approach 2:
The invention extracts and removes the harmful monomeric diisocyanate component from the adhesive formulation. By using silane-modified polymers instead of polyisocyanates, the toxic substance is completely taken out of the system, eliminating vapor pressure and health hazards while preserving the crosslinking function through silane hydrolysis and condensation reactions.
2Productivity
If conventional reactive hot melt adhesives are applied at elevated temperatures, then rapid setting and adhesive strength build-up occur, but monomeric diisocyanates are expelled in gaseous form requiring costly precautionary measures
Solution Approach 1:
The patent converts the harmful high-temperature application process that previously caused diisocyanate emission into a beneficial process. The silane-modified polymers utilize the application temperature to enhance moisture reactivity and accelerate crosslinking, while the absence of monomeric diisocyanates eliminates vapor pressure. The heat that previously caused harm now benefits rapid curing without toxic emissions.
Solution Approach 2:
The invention changes the chemical composition to silane-modified polymers with different thermal and reactivity characteristics. These polymers are designed to react with moisture at application temperatures without generating toxic vapors, transforming the thermal processing parameter from a hazard source to a curing accelerator.
3Ease of manufacture
If the content of monomeric diisocyanates is reduced to less than 0.1 wt.%, then hazardous substance labeling is no longer required, but achieving this level while maintaining adhesive performance is highly desirable and challenging
Solution Approach 1:
Rather than merely reducing monomeric diisocyanate content to below 0.1 wt.%, the invention completely extracts and eliminates diisocyanate monomers from the formulation. The adhesive uses silane-modified polymers that crosslink through moisture reaction, achieving zero monomeric diisocyanate content and thereby eliminating hazardous substance labeling requirements entirely.
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 resulting adhesives exhibit similar or superior performance to conventional hot melt adhesives with significantly reduced monomeric diisocyanate content, ensuring safety and cost-effectiveness in packaging and bookbinding applications while maintaining high modulus and elongation properties.
Implementation Method 1
the chemical reaction of the isocyanate groups still present with moisture from the environment to form a crosslinked infusible adhesive
Implementation Method 2
reaction of the isocyanate groups with moisture
Implementation Method 3
followed by the chemical reaction of the isocyanate groups still present with moisture from the environment to form a crosslinked infusible adhesive
Data Source
AI summary
The present invention relates to new improved adhesives for binding books and related articles and the production of such adhesives. In particular, the adhesives have reduced content of monomeric diisocyanates or no monomeric diisocyanate content.