Two-Part Curable Adhesive Composition with Composite Curing Agent
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Solution Overview
Problem
Two-part curable polyurethane adhesive compositions face challenges in achieving high tensile properties and low temperature dependence of viscoelastic properties, while also preventing foaming, particularly when using polyol compounds with high crystallinity as the skeleton.
Innovation Solution
A two-part curable adhesive composition comprising a main agent with a urethane prepolymer obtained from reacting a raw polyisocyanate and a crystalline polyol, and a curing agent containing a non-crystalline polyol and polyamine, with specific equivalent ratios of isocyanate to hydroxyl groups and amino groups to control the curing reaction and reduce temperature dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyol compound having high crystallinity is used as a skeleton of polyurethane, then tensile properties (strength at break and elongation at break) are improved, but temperature dependence of viscoelastic properties becomes extremely high
Solution Approach 1:
The patent uses a composite curing agent system combining non-crystalline polyol (providing low temperature dependence) and crystalline polyol (providing high tensile properties) in specific ratios. This composite approach allows the cured product to simultaneously achieve excellent tensile properties and low temperature dependence of viscoelastic properties, resolving the contradiction between strength and stability.
2Productivity
If the equivalent ratio of isocyanate group to hydroxyl group is adjusted to approximately 1, then the curing rate becomes extremely slow, but using a catalyst to accelerate curing causes foaming which diminishes tensile properties
Solution Approach 1:
The patent changes the equivalent ratio parameter from the conventional approximately 1 to a specific range of 0.8 to 1.2, and combines this with a dual-curing agent system (non-crystalline polyol + crystalline polyol). This parameter adjustment, together with the composite curing agent, enables accelerated curing without foaming, maintaining excellent tensile properties while improving productivity.
3Productivity
If a catalyst is used to accelerate the curing rate of urethane prepolymer, then productivity is improved, but foaming occurs which leads to diminished tensile properties
Solution Approach 1:
The patent adjusts the equivalent ratio of isocyanate to hydroxyl groups to 0.8-1.2 and uses a composite curing agent system, which inherently accelerates curing without requiring additional catalysts. This parameter change eliminates the need for catalysts that cause foaming, thereby maintaining tensile properties while improving curing rate and productivity.
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 excellent tensile properties such as strength at break and elongation at break, while minimizing foaming and temperature dependence of viscoelastic properties, resulting in a cured product suitable for structural bonding applications.
Implementation Method 1
the urethane prepolymer (a1) being obtained by reacting a raw polyisocyanate and a crystalline polyol compound
Implementation Method 2
the main agent (A) further containing, in addition to the urethane prepolymer (a1), a remaining polyisocyanate (a2) that is a remainder of the raw polyisocyanate
Implementation Method 3
the curing agent (B) containing a non-crystalline polyol compound (b1) and a polyamine compound (b2)
Data Source
Figure 1(a)~1(c)
AI summary
A two-part curable adhesive composition includes a main agent (A) containing a urethane prepolymer (a1) and a remaining polyisocyanate (a2), and a curing agent (B) containing a non-crystalline polyol compound (b1) and a polyamine compound (b2). An equivalent ratio of an isocyanate group in a raw polyisocyanate to a hydroxyl group in the polyol compound is from 2.05 to 12. The equivalent ratio of the isocyanate group in the main agent (A) to an amino group in the polyamine compound (b2) is from 1.2 to 6. The equivalent ratio of the isocyanate group in the main agent (A) to the hydroxyl group in the non-crystalline polyol compound (b1) is from 2 to 12.