Two-Stage Epoxy Adhesive Composition for Fast Fixation and Oil Absorption

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Solution Overview

Problem

Existing epoxy adhesives in the automotive industry face challenges in achieving a balance between fast fixation, curing speed, mechanical performance, durability, and oil absorption, with 1K adhesives lacking mechanical strength before curing and 2K adhesives having poor oil absorption at room temperature.

Innovation Solution

A method involving a two-step application of an epoxy adhesive composition comprising epoxy resin, reactive urethane or urea group-containing polymers with capped isocyanate, an epoxy curing catalyst, and dicyandiamide, with optional hardener, to achieve rapid curing and high mechanical strength while maintaining good oil absorption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If 1K structural epoxy adhesives are cured at high temperature for fast fixation, then curing speed is improved, but mechanical strength before curing is insufficient requiring additional fixation methods

Engineering Contradiction:

Improvecuring speedVSAvoidmechanical strength before curing

Core Design Contradiction:

SpeedVSStrength

Solution Approach 1:

The patent segments the adhesive system into two separate compositions applied in sequence. The first composition (without hardener) provides initial bonding and dimensional stability, while the second composition (with hardener) delivers full mechanical strength and oil absorption properties. This segmentation allows each composition to be optimized for its specific function without compromise.

Inventive Principle:

Principle #1Segmentation

2Strength

If 2K structural adhesives are used to achieve fast cure and dimensional stability, then mechanical strength before curing is improved, but oil absorption capability deteriorates

Engineering Contradiction:

Improvemechanical strength before curingVSAvoidoil absorption

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent separates the adhesive system into two compositions where the first applies the cured adhesive composition without hardener provides fast initial set and dimensional stability, while the second applies the cured adhesive composition with hardener ensures oil absorption and long-term durability. This segmentation resolves the contradiction by assigning different functions to different application stages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first epoxy adhesive composition is applied and allowed to partially cure before applying the second composition. This preliminary action establishes dimensional stability and prevents part movement during the initial phase, creating optimal conditions for the subsequent application that provides full mechanical properties and oil absorption.

Inventive Principle:

Principle #10Preliminary action

3Speed

If 2K adhesive network formation progresses too far at room temperature, then fast fixation is achieved, but oil absorption capability is lost due to excessive cross-linking

Engineering Contradiction:

Improvefixation speedVSAvoidoil absorption

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent divides the adhesive application into two distinct compositions: the first without hardener allows rapid initial set without extensive network formation, preserving oil absorption pathways; the second with hardener completes the curing process to achieve full mechanical strength. This segmentation prevents premature network formation that would block oil absorption.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the chemical composition parameter between the two applications. The first composition lacks the hardener component, limiting network formation and maintaining oil absorption capability. The second composition introduces the hardener to complete cross-linking and achieve full mechanical properties. This parameter change resolves the contradiction between fixation speed and oil absorption.

Inventive Principle:

Principle #35Parameter changes

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 method results in an adhesive with lap shear strength greater than 15 MPa after curing, combining the benefits of both 1K and 2K technologies, ensuring dimensional stability and oil absorption.

Implementation Method 1

an epoxy curing catalyst

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

epoxy resin, a reactive urethane group- and/or urea group-containing polymer having capped isocyanate

Methodology Applied

Scientific EffectChemical Bonding: Chemical Bonding

Implementation Method 3

allow for the oil to diffuse and dissolve in the epoxy adhesive

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentEP3973011B1Epoxy adhesive composition and method of use

Publication Date: 2025.08.20 DDP SPECIALTY ELECTRONICS MATERIALS US LLC

AI summary

Disclosed is epoxy adhesive composition that combine the benefits of both 1K and 2K technologies in one system which demonstrates a good balance of fast fixation, curing speed, desirable mechanical performance, durability, and good oil adsorption once cured. Said epoxy adhesive composition comprising an epoxy resin, a reactive urethane group- and/or urea group-containing polymer having capped isocyanate, an epoxy curing catalyst, a dicyandiamide, and a hardener.