Polyurethane Adhesive Debonding With Lactic Acid for Substrate Recycling

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Solution Overview

Problem

Existing methods for detaching substrates bonded with polyurethane adhesive, particularly in high-demanding applications like shoes, face challenges such as increased cost, insufficient bonding strength, and impact resistance, and require costly special heating equipment, making them unsuitable for industrial-scale recycling.

Innovation Solution

A debonding agent comprising lactic acid, water, and non-ionic surfactants is used to treat polyurethane adhesive bonds at temperatures between 40°C to 90°C, facilitating the detachment of substrates by immersing, spraying, or brushing, with treatment durations ranging from 0.5 to 240 hours.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If polyurethane adhesive bonding is used to bond substrates, then bonding strength and adhesion are improved, but the bonds become permanent and difficult to detach without destroying substrates

Engineering Contradiction:

Improvebonding strengthVSAvoidease of detachment

Core Design Contradiction:

StrengthVSEase of repair

Solution Approach 1:

The patent introduces a debonding agent as an intermediary substance that facilitates the separation of bonded substrates. The debonding agent penetrates the adhesive bond line and weakens the polyurethane adhesive through chemical interaction, allowing substrates to be detached without damage. This mediator enables the reversal of the permanent bond while maintaining substrate integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical parameters of the adhesive system by introducing a debonding agent that alters the adhesive's properties. The debonding agent modifies the chemical structure or physical state of the polyurethane adhesive, transforming it from a permanent bonding state to a detachable state, thereby enabling easy separation of substrates.

Inventive Principle:

Principle #35Parameter changes

2Ease of repair

If special heating equipment and methods are used to detach substrates, then detachment capability is improved, but cost and energy consumption increase

Engineering Contradiction:

Improvedetachment capabilityVSAvoidenergy consumption

Core Design Contradiction:

Ease of repairVSUse of energy by stationary object

Solution Approach 1:

The patent replaces complex mechanical/thermal systems (heating equipment, microwave generators) with a simple chemical system (debonding agent). Instead of using external energy fields or sophisticated heating apparatus, the invention uses a chemical substance that naturally penetrates and weakens the adhesive bond, eliminating the need for expensive and energy-intensive equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs a simple, inexpensive debonding agent that can be easily applied and discarded after use. This disposable chemical solution replaces expensive, complex heating equipment, providing a cost-effective and energy-efficient method for substrate detachment without requiring sophisticated infrastructure.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Strength

If polyurethane adhesive is used for bonding, then adhesion portfolio and bonding strength are improved, but recyclability and ease of material separation deteriorate

Engineering Contradiction:

Improveadhesion portfolioVSAvoidrecyclability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The debonding agent serves as a mediator that enables recycling by facilitating the separation of bonded materials. It penetrates the adhesive layer and selectively weakens the bond between substrates and adhesive, allowing for complete material separation and recovery. This intermediary enables the recycling process to proceed efficiently while maintaining high adhesion performance during the product's service life.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical parameters of the adhesive system by introducing a debonding agent that reverses the curing or bonding process. This parameter change transforms the permanently bonded state into a separable state, enabling material recovery and recycling while preserving the strong bonding characteristics needed during product usage.

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 effectively detaches substrates without damage, enabling efficient recycling and reducing environmental impact by maintaining the quality of materials for reuse, suitable for industrial-scale shoe recycling.

Implementation Method 1

treating a first substrate and a second substrate bonded by a polyurethane adhesive with a debonding agent comprising lactic acid at a temperature from 40°C to 90°C

Methodology Applied

Scientific EffectChemical degradation:

Implementation Method 2

treating a first substrate and a second substrate bonded by a polyurethane adhesive with a debonding agent comprising lactic acid at a temperature from 40°C to 90°C

Methodology Applied

Scientific EffectThermal activation: Heating

Data Source

PatentEP4140679B1Method for detaching substrates bonded by polyurethane adhesive

Publication Date: 2026.05.13 HENKEL KGAA

AI summary

Method for detaching two substrates bonded by a polyurethane adhesive, comprising the steps of: (1) treating a first substrate and a second substrate bonded by a polyurethane adhesive with a debonding agent comprising lactic acid at a temperature from 40°C to 90°C, and (2) separating the first substrate and the second substrate from the polyurethane adhesive.