Moisture-Curable Hot Melt Adhesive Suppressing Bubble Formation
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Solution Overview
Problem
Conventional moisture-curable hot melt adhesives for lighting appliances face issues with volume expansion and sagging due to the reaction of isocyanate and moisture, leading to long curing times and bubble generation when heated, which is undesirable for inspection and shipment processes.
Innovation Solution
A moisture-curable hot melt adhesive is developed by blending a thermoplastic polyacrylic resin, an oxazolidine compound, and a urethane prepolymer, specifically using compounds like 2-isopropyl-3-(2-hydroxyethyl)oxazolidine and 4,4'-diphenylmethane diisocyanate, to prevent volume expansion and sagging while improving thermal stability and initial adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional moisture-curable urethane-based hot melt adhesive is used for sealing application, then adhesive properties and flexibility are improved, but volume expansion and bubble generation occur due to decarboxylation reaction when heated
Solution Approach 1:
The patent extracts and removes the carboxyl groups from the adhesive composition through reaction with isocyanate compounds. The adhesive composition reacts isocyanate groups with carboxyl groups to form urea linkages, thereby eliminating the source of carbon dioxide generation and bubble formation while preserving the adhesive properties
Solution Approach 2:
The patent converts the harmful decarboxylation reaction into a beneficial process by using the carboxyl groups to react with isocyanate groups. The reaction that would otherwise produce harmful carbon dioxide is redirected to form useful urea crosslinks that enhance adhesive strength and eliminate the harmful gas generation
2Reliability
If a conventional moisture-curable hot melt adhesive is used, then sealing properties are achieved, but long curing time is required which hinders inspection and shipment
Solution Approach 1:
The patent changes the chemical parameters of the adhesive system by introducing a two-component formulation with specific isocyanate compounds. This chemical parameter change accelerates the curing reaction kinetics, reducing the curing time from conventional long durations to just 1 hour while maintaining reliable sealing properties
Solution Approach 2:
The patent performs preliminary preparation by pre-mixing the adhesive components and preparing the substrate surfaces before the actual bonding operation. This preliminary action ensures that when the adhesive is applied and cured, the reaction proceeds efficiently and rapidly, reducing the overall curing time required
3Strength
If a conventional hot melt adhesive is used for sealing application, then adhesion is achieved, but the adhesive sags and effuses when heated to high temperatures
Solution Approach 1:
The patent creates a composite adhesive system combining polyacrylic resin base polymer with reactive isocyanate compounds and carboxyl-containing additives. This composite formulation provides both the adhesion properties of the base polymer and the thermal stability of the crosslinked network, preventing sagging and effusion at high temperatures
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 solution effectively suppresses volume expansion, sagging, and effusion when the adhesive is heated, enhancing thermal stability and initial adhesive strength, allowing for faster inspection and shipment without bubble formation.
Implementation Method 1
an oxazolidine compound (C) which is selected from a urethane bond-containing oxazolidine compound obtained by using a compound having hydroxy group and an oxazolidine ring and an organic isocyanate compound
Implementation Method 2
a hot melt adhesive for sealing application is required to develop strength by solidification after coating
Implementation Method 3
the moisture-curable hot melt adhesive for lighting appliances is prevented from volume expansion, sagging, and effusion when the uncured adhesive is heated
Data Source
AI summary
An object of the present invention is to provide a moisture-curable hot melt adhesive which can substantially suppress generation of carbon dioxide bubbles by a reaction of an isocyanate compound and moisture as well as volume expansion when an uncured adhesive is heated. The present invention relates to a moisture -curable hot melt adhesive for lighting appliances comprising: an urethane prepolymer obtained by mixing a polyol compound and an isocyanate compound, a thermoplastic polyacrylic resin and an oxazolidine compound.