Boronic Ester Elastomer Decrosslinking for Reversible Rubber Reuse

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Solution Overview

Problem

Existing methods for recycling crosslinked elastomers do not effectively address the decrosslinking and recrosslinking of elastomers, particularly those crosslinked by methods other than vulcanization, limiting their versatile utilization.

Innovation Solution

A method involving the use of a crosslinked elastomer with a diboronic acid ester skeleton unit, treated with a monoboronic acid compound in a specific organic solvent, facilitates decrosslinking and subsequent recrosslinking, utilizing an exchange reaction to return the crosslinking site to a non-crosslinked state.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If devulcanization is used to recycle vulcanized rubber, then rubber content can be recovered, but energy efficiency is poor due to extremely high temperature required

Engineering Contradiction:

Improveenergy efficiencyVSAvoidreaction temperature

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The patent changes the chemical parameters of the crosslinking system by using boronic ester bonds instead of traditional sulfur crosslinks. This allows the crosslinking and decrosslinking reactions to proceed at much lower temperatures (room temperature to moderate heating), dramatically improving energy efficiency while eliminating the need for extremely high temperature devulcanization processes

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If traditional vulcanization methods are used to crosslink rubber, then crosslinking strength is achieved, but decrosslinking and recrosslinking capability is lost

Engineering Contradiction:

Improvereversible crosslinkabilityVSAvoidcrosslinking stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent introduces dynamic reversibility to the crosslinking system by using boronic ester bonds that can dynamically form and break under controlled conditions. The crosslinks are stable during use but can be reversibly broken by adding compounds like 1,3- or 1,2-diols, enabling multiple cycles of crosslinking and decrosslinking for recycling and reprocessing

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses boronic ester groups as intermediary crosslinking sites that mediate between the polymer chains. These boronic ester crosslinks serve as reversible connection points that can be selectively formed and broken, allowing the material to transition between crosslinked and non-crosslinked states while maintaining structural integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

3Temperature

If decomposition methods other than devulcanization are used, then decomposition temperature is reduced, but the method does not effectively address decrosslinking and recrosslinking of elastomers

Engineering Contradiction:

Improvedecomposition temperatureVSAvoidcrosslinking reversibility

Core Design Contradiction:

TemperatureVSAdaptability or versatility

Solution Approach 1:

The patent fundamentally changes the chemical nature of the crosslinking bonds from irreversible sulfur crosslinks to reversible boronic ester crosslinks. This parameter change enables the material to be processed at lower temperatures while maintaining the capability for controlled decrosslinking and recrosslinking, achieving both energy efficiency and material versatility

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

This method enables easy decrosslinking and recrosslinking of crosslinked elastomers, allowing for their versatile reuse in various rubber articles.

Implementation Method 1

utilizing an exchange reaction to return the crosslinking site to a non-crosslinked state

Methodology Applied

Scientific EffectExchange reaction: Chemical Bonding

Data Source

PatentEP4382553B1Method of returning crosslinking site of crosslinked elastomer to non-crosslinked state

Publication Date: 2026.03.18 BRIDGESTONE CORP

AI summary

Provided is a method by which a crosslinking site of a crosslinked elastomer can easily be returned to a non-crosslinked state. The method of returning a crosslinking site of a crosslinked elastomer to a non-crosslinked state includes a step of causing contact of a crosslinked elastomer including a diboronic acid ester skeleton unit represented by a specific general formula (1) at a crosslinking site with a monoboronic acid compound represented by a specific general formula (3) in the presence of an organic solvent having an SP value (solubility parameter) of not less than 7 (cal/cm3)1/2 and not more than 10 (cal/cm3)1/2. In this step, a molar abundance ratio of the monoboronic acid compound relative to the diboronic acid ester skeleton unit (monoboronic acid compound/diboronic acid ester skeleton unit) is set as more than 2 and not more than 5.