Quaternary Ammonium Catalyst for Low-Temperature Epoxy Curing

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Solution Overview

Problem

Low curing temperatures for one-component epoxy adhesives require higher reactive hardeners, which often lack sufficient storage stability, necessitating a catalyst composition that is effective at low temperatures while maintaining high storage stability and adhesion.

Innovation Solution

A catalyst composition comprising a base and a quaternary ammonium salt, specifically represented by certain formulas, which rearranges upon heating to cure epoxy resins cationically, either directly or as an accelerator for common hardening agents like dicyandiamide, reducing curing temperatures and enhancing storage stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If higher reactive hardeners are used to achieve low curing temperatures, then curing temperature is reduced, but storage stability deteriorates

Engineering Contradiction:

Improvecuring temperatureVSAvoidstorage stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The invention divides the curing system into two separate components: a stable quaternary ammonium salt that provides low-temperature curing capability and a base that is added separately before application. This segmentation allows the reactive hardener to remain stable in storage while still enabling low-temperature curing when activated by the base.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The quaternary ammonium salt is pre-formulated and stored separately in a stable state. The curing action is preliminarily prepared but not activated until the base is added shortly before application, ensuring storage stability while maintaining the capability for low-temperature curing.

Inventive Principle:

Principle #10Preliminary action

2Temperature

If higher reactive hardeners are used to achieve low curing temperatures, then curing temperature is reduced, but adhesion deteriorates

Engineering Contradiction:

Improvecuring temperatureVSAvoidadhesion

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The invention changes the chemical parameters of the hardener system by using a quaternary ammonium salt with specific structural characteristics (Formula I) that enable effective curing at lower temperatures while maintaining adhesion properties. The molecular structure parameters are optimized to balance reactivity and adhesion.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If common hardening agents are used, then storage stability is maintained, but curing temperature remains high

Engineering Contradiction:

Improvestorage stabilityVSAvoidcuring temperature

Core Design Contradiction:

Stability of the object's compositionVSTemperature

Solution Approach 1:

The invention creates a composite curing system combining a quaternary ammonium salt (with specific R1-R7 groups as defined in Formula I) and a base. This composite material exhibits both storage stability of common hardening agents and the low-temperature curing capability of reactive hardeners.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The quaternary ammonium salt acts as an intermediary that bridges the gap between stable common hardening agents and reactive low-temperature hardeners. When combined with the base, it mediates the curing process to achieve low temperatures while maintaining stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Stability of the object's composition

If common hardening agents are used, then storage stability is maintained, but curing time is extended

Engineering Contradiction:

Improvestorage stabilityVSAvoidcuring time

Core Design Contradiction:

Stability of the object's compositionVSLoss of time

Solution Approach 1:

The invention changes the kinetic parameters of the curing reaction by introducing the quaternary ammonium salt/base system, which accelerates the curing process at lower temperatures, thereby reducing the time required to achieve full cure while maintaining storage stability.

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 quaternary ammonium salt/base system achieves faster curing and better adhesion at low temperatures compared to industry standards, with improved storage stability and reduced curing times, specifically lowering curing temperatures by 30°C or shortening curing time at 120°C, while maintaining stability in unmodified epoxy resins.

Implementation Method 1

quaternary ammonium salts bearing a nitro, carbonyl or vinyl group in the β-position relative to the ammonium nitrogen rearrange upon heating to yield NH-ammonium salts

Methodology Applied

Scientific EffectThermal rearrangement: Thermolysis

Implementation Method 2

these salts are able to cure epoxy cationically

Methodology Applied

Scientific EffectCationic curing: Chemical Bonding

Implementation Method 3

These amines can either directly cure epoxy resins themselves or function as accelerators for common hardening agents

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentUS10179832B2Storage stable heat activated quaternary ammonium catalysts for epoxy cure

Publication Date: 2019.01.15 HENKEL KGAA

AI summary

The present invention relates to a catalyst composition for curing epoxy group containing compounds comprising a base and a quaternary ammonium salt, of Formula (I):with R1, R2, R3, R4, R5, Y, A and X being as defined herein. Also encompassed are adhesive compositions containing said catalyst composition and the use of the catalyst composition.