Rubber-Modified Bitumen With Polysulfide Pretreatment for Hot Stability

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Solution Overview

Problem

Existing rubber-modified bitumen exhibits unsatisfactory elastic properties at temperatures above 60°C, particularly when using sulfur-crosslinked rubber, which is insoluble in bitumen and leads to quality issues in road construction due to settling during storage and varying performance.

Innovation Solution

A mixture of vulcanized rubber and C1-C18-dialkyl polysulfides is heat treated at 130-150°C for less than 20 minutes under mechanical stress, then mixed with bitumen to enhance solubility and improve elastic properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If sulfur-crosslinked rubber is used to modify bitumen, then the material is readily available and cost-effective, but the rubber is relatively insoluble in bitumen and settles out during storage

Engineering Contradiction:

Improveavailability of rubber materialVSAvoidhomogeneity of bitumen mixture

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary devulcanization treatment to the sulfur-crosslinked rubber before mixing with bitumen. This pre-treatment breaks down some of the sulfur crosslinks, making the rubber more soluble and preventing settling during storage, while still allowing the rubber to be readily available from waste tire sources.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the chemical parameters of the rubber by controlling the devulcanization process - using specific temperatures (140-200°C), sulfur compounds (0.5-5% by weight), and treatment times to achieve optimal solubility in bitumen while maintaining elastic properties.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If devulcanization is performed to enhance solubility of rubber in bitumen, then the rubber becomes more soluble, but the elastic properties of the modified bitumen at road temperatures above 60°C remain unsatisfactory

Engineering Contradiction:

Improvesolubility of rubber in bitumenVSAvoidelastic properties at elevated temperatures

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent optimizes the devulcanization parameters - using moderate temperatures (140-200°C), controlled sulfur content (0.5-5% by weight), and specific treatment durations - to achieve the right balance between solubility enhancement and preservation of elastic properties at road temperatures above 60°C.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses sulfur compounds as intermediaries during the devulcanization process. These sulfur compounds facilitate the controlled breakdown of crosslinks while maintaining the elastic network structure, acting as a mediator between solubility requirements and elastic property preservation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If uncrosslinked elastomer is used and subsequent crosslinking with sulfur or polysulfides is performed, then the elastic properties are improved, but the production cost increases significantly

Engineering Contradiction:

Improveelastic properties of modified bitumenVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses waste rubber from tires as a cheap, readily available starting material. By applying devulcanization treatment, this waste material can be effectively reused in bitumen modification, significantly reducing material costs compared to using virgin uncrosslinked elastomers.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent converts the harmful aspect of sulfur crosslinking (which causes insolubility and settling) into a benefit by using controlled devulcanization. The same sulfur that creates the problematic crosslinked structure is used in controlled amounts during devulcanization to break down the network to an optimal degree, improving solubility while maintaining elasticity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 process significantly improves the elastic properties of bitumen at elevated temperatures, demonstrated by enhanced recovery and reduced compliance in Multiple Stress Creep and Recovery tests, indicating better performance under stress conditions.

Implementation Method 1

sulfur-crosslinked rubber as a source of substituted material

Methodology Applied

Scientific EffectVulcanization: Chemical Bonding

Implementation Method 2

enhance the solubility of rubber in hot bitumen

Methodology Applied

Scientific EffectSolubility enhancement: Solvation

Implementation Method 3

the reaction product from a) is heat treated at 130-150° C. for less than 20 minutes

Methodology Applied

Scientific EffectHeat treatment: Heating

Implementation Method 4

enhanced recovery and reduced compliance in Multiple Stress Creep and Recovery tests

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Data Source

PatentUS12516193B2Rubber-modified bitumen, process for production thereof and use thereof in asphalt

Publication Date: 2026.01.06 LANXESS DEUTSCHLAND GMBH

AI summary

The present invention relates to novel rubber-modified bitumen, to improved processes for producing rubber-modified bitumen using vulcanized rubber and to the use thereof in asphalt.