Epoxy-Terminated Impact Modifier for Tough Low-Viscosity Adhesives

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Solution Overview

Problem

Conventional epoxy adhesives are too brittle and fail to meet the requirements for high impact resistance, lap shear strength, and peel strength, especially at low temperatures, making them unsuitable for automotive applications under crash conditions.

Innovation Solution

An epoxy group-terminated impact modifier is prepared by reacting polyisocyanates with polyols, including polyetherpolyol and OH-terminated rubber, at a specific molar ratio, followed by reacting the isocyanate-terminated prepolymer with a polyepoxide in the presence of an ionic liquid to enhance impact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional epoxy adhesives are used to achieve high mechanical strength and tensile strength, then bonding strength is improved, but impact resistance and flexibility deteriorate due to brittleness

Engineering Contradiction:

Improvetensile strengthVSAvoidimpact resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent uses composite materials by combining epoxy resin with polyol components (polyester polyol, polyether polyol, and hydroxyl-terminated rubber) in specific ratios. This creates a hybrid adhesive system that maintains the high tensile strength of epoxy while incorporating the flexibility and impact resistance of the polyol components, resolving the contradiction between strength and impact resistance

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the chemical composition parameters of the epoxy adhesive by controlling the ratio of epoxy resin to polyol components and adjusting the molecular weight and functionality of each component. This parameter optimization allows the adhesive to achieve both high tensile strength and improved impact resistance by balancing the rigid epoxy matrix with flexible polyol segments

Inventive Principle:

Principle #35Parameter changes

2Strength

If epoxy adhesives are formulated for high strength bonding, then lap shear strength is improved, but peel strength and flexibility deteriorate under crash conditions

Engineering Contradiction:

Improvelap shear strengthVSAvoidflexibility under stress

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The adhesive combines epoxy resin with multiple polyol components including hydroxyl-terminated rubber, which provides elasticity and flexibility. This composite formulation allows the adhesive to maintain lap shear strength while exhibiting sufficient flexibility to withstand peel stresses and deformation during crash conditions

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent creates local quality differences within the adhesive structure by incorporating polyol components with different molecular weights and functionalities. The hydroxyl-terminated rubber provides flexibility in regions subjected to peel stress, while the epoxy matrix maintains strength in regions subjected to shear load, optimizing performance for different stress types

Inventive Principle:

Principle #3Local quality

3Reliability

If impact modifiers are added to epoxy adhesives to improve impact resistance, then flexibility is improved, but viscosity and processing characteristics may deteriorate

Engineering Contradiction:

Improveimpact resistanceVSAvoidviscosity control

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent controls the viscosity and processing characteristics by optimizing the molecular weight and concentration of impact modifier components. By selecting polyols with appropriate molecular weights and controlling their ratio in the formulation, the adhesive achieves improved impact resistance while maintaining acceptable viscosity for processing and application

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 resulting impact modifier improves the impact resistance, lap shear strength, and peel strength of epoxy resin matrices while maintaining low viscosity and glass transition temperature, suitable for automotive applications.

Implementation Method 1

reacting the isocyanate-terminated prepolymer with a polyepoxide (c) in the presence of an ionic liquid to give the epoxy group-terminated impact modifier

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS20250382408A1Epoxy-terminated isocyanate prepolymers, and process for the preparation thereof

Publication Date: 2025.12.18 BASF SE

AI summary

The present invention relates to processes for preparing an epoxy group-terminated impact modifier, by mixing one or more polyisocyanates (a) with two or more polyols (b), comprising at least one polyetherpolyol (b1) and at least one OH-terminated rubber (b2), at a molar ratio of isocyanate groups to OH groups of 10:1 to 1.5:1, and reacting the mixture to give an isocyanate-terminated prepolymer, and reacting the isocyanate-terminated prepolymer with a polyepoxide (c) in the presence of an ionic liquid to give the epoxy group-terminated impact modifier. Further, the present invention relates to an epoxy group-terminated impact modifier obtainable by a process of the invention, to the use of an epoxy group-terminated impact modifier in a one-component or two-component epoxy resin composition, preferably in a one-component or two-component epoxy resin adhesive, for increasing the impact resistance of the cured epoxy resin matrix, and to a one-component or two-component epoxy resin composition comprising at least one epoxy group-terminated impact modifier of the invention.