High-Isocyanate Urethane Adhesive With Zeolite Foaming Control
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Solution Overview
Problem
Conventional two-part urethane adhesive compositions with high isocyanate group content suffer from foaming due to moisture-induced reactions, leading to delayed adhesion development and reduced effectiveness.
Innovation Solution
Incorporating an organic tin catalyst and a specific amine catalyst, along with zeolite, into a urethane adhesive composition with a high isocyanate group content to facilitate rapid adhesion development while minimizing foaming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the amount of isocyanate groups in the main agent is increased to achieve high adhesion strength and high elastic modulus, then adhesion strength and elastic modulus are improved, but air is incorporated into the mixture and moisture causes rapid carbon dioxide generation leading to foaming in the cured product
Solution Approach 1:
A dehydrating agent is introduced as an intermediary substance that selectively removes water from the mixture before isocyanate groups can react with moisture. This mediator prevents the harmful reaction between isocyanate and water that causes foaming, while allowing the isocyanate groups to remain available for achieving high adhesion strength and elastic modulus in the cured product.
Solution Approach 2:
Water is extracted or removed from the mixture using a dehydrating agent before the isocyanate groups can react with moisture. By taking out the water component that causes the harmful foaming reaction, the system maintains high isocyanate group content for strength development without suffering from carbon dioxide generation and foaming issues.
2Object-generated harmful factors
If a dehydrating agent is added to prevent foaming caused by moisture reaction, then foaming is minimized, but it takes a longer period of time for high adhesion strength to develop
Solution Approach 1:
The molecular structure and properties of the dehydrating agent are optimized to enhance its water-removal efficiency while minimizing its impact on the main urethanization reaction. By changing the parameters of the dehydrating agent (such as its reactivity, molecular weight, or functional groups), the system achieves effective moisture control without significantly delaying adhesion strength development.
Solution Approach 2:
The adhesive composition is formulated as a composite system containing multiple components including the main agent with high isocyanate content, curing agent, dehydrating agent, and potentially other additives. This composite formulation allows the dehydrating agent to perform its moisture-removal function while the other components maintain rapid adhesion development, balancing foaming prevention with speed of cure.
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 achieves rapid adhesion strength development and minimizes foaming in the cured product, ensuring high adhesion and elastic modulus.
Implementation Method 1
the urethanization reaction catalyst contains an organic tin catalyst, and an amine catalyst represented by Formula (1) or a blocked amine catalyst in which the amine catalyst is blocked with an acid
Implementation Method 2
using zeolite in combination therewith in a two-part urethane adhesive composition whose main agent has a high isocyanate group content, excellent adhesion strength can rapidly develop, while foaming in a cured product can be minimized
Data Source
AI summary
A two-part urethane adhesive composition includes a main agent containing a filler and a urethane prepolymer having an isocyanate group and formed from a polyisocyanate A and a polyol 1 with two to three hydroxy groups per molecule and a number-average molecular weight of ≥1800. Isocyanate group content in the main agent is ≥5 mass % of a main agent total content. The composition includes a curing agent containing a polyoxyalkylene polyol, a polyol 2, a urethanization reaction catalyst, a filler, and zeolite, the polyoxyalkylene polyol having two to three hydroxy groups per molecule and having a number-average molecular weight of ≥1800, the polyol 2 having two or more hydroxy groups per molecule and having a number-average molecular weight of ≤200. The urethanization reaction catalyst contains an organic tin catalyst, and an amine catalyst represented by Formula (1) or an amine catalyst blocked with an acid.