Bitumen Polymer Crosslinking Reducing Hydrogen Sulfide Emissions
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Solution Overview
Problem
The crosslinking of bitumen/polymer compositions with sulfur results in significant emissions of hydrogen sulfide, a toxic gas, which poses environmental concerns and necessitates the development of a process to reduce or eliminate these emissions while maintaining satisfactory rheological characteristics.
Innovation Solution
A process involving the use of crosslinking agents with the general formula HS-R-SH, where R is a hydrocarbon group, saturated or unsaturated, linear or branched, and optionally containing heteroatoms, is employed at temperatures between 100° C and 230° C with stirring for at least ten minutes, to create crosslinked bitumen/polymer compositions with reduced hydrogen sulfide emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sulfur is used as a crosslinking agent for bitumen/polymer compositions, then the rheological properties (elasticity and consistency) are improved, but hydrogen sulfide emissions increase significantly
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking agent by using compounds with specific molecular structures (formulae I and II with defined R groups) instead of elemental sulfur. This parameter change maintains the crosslinking effectiveness and rheological improvement while eliminating the harmful hydrogen sulfide emissions that occur with sulfur crosslinking.
Solution Approach 2:
The patent employs alternative crosslinking agents that serve the same functional purpose as sulfur but without the harmful byproducts. These alternative agents are used in specific quantities (0.05-5% by weight) to achieve the desired crosslinking effect temporarily during processing, after which they decompose or remain as harmless residues, unlike sulfur which generates persistent hydrogen sulfide emissions.
2Object-generated harmful factors
If crosslinking agents of formula HS-R-SH are used, then hydrogen sulfide emissions are reduced by up to 97%, but the process requires specific temperature control (100-230°C) and stirring for at least ten minutes
Solution Approach 1:
The patent specifies precise parameter ranges for the crosslinking process including temperature (100-230°C), time (at least 10 minutes), and stirring conditions. These parameter changes are optimized to enable the alternative crosslinking agents to function effectively while minimizing harmful emissions, trading some process control complexity for environmental benefit.
3Object-generated harmful factors
If crosslinking agents with specific hydrocarbon groups (2-40 carbon atoms) are used, then emissions are reduced, but the selection of suitable agents becomes more restricted
Solution Approach 1:
The patent defines specific structural parameters for the crosslinking agents including the hydrocarbon group R with 2-40 carbon atoms, optional heteroatoms (0-5), and exclusion of certain functional groups (C=O, O-C=O). These parameter specifications narrow down the suitable agent options but ensure effective crosslinking with reduced emissions, balancing versatility with environmental performance.
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 effectively reduces hydrogen sulfide emissions by up to 97% during the crosslinking of bitumen/polymer compositions while maintaining rheological characteristics equivalent to sulfur-crosslinked compositions, such as elasticity and consistency, without the disadvantage of hydrogen sulfide release.
Implementation Method 1
crosslinking agent being represented by the general formula HS-R-SH where R represents a hydrocarbon group... to create crosslinked bitumen/polymer compositions
Implementation Method 2
contact is made, operating at temperatures between 100° C. and 230° C. and with stirring, for a period at least ten minutes
Data Source
AI summary
The invention relates to a method of preparing crosslinked bitumen/polymer compositions having reduced emissions of hydrogen sulphide, in which, while operating at temperatures between 100°C and 230°C and with stirring, for a duration of at least ten minutes, at least one bitumen or mixture of bitumens is brought into contact with at least one polymer and at least one crosslinking agent, said crosslinking agent being represented by the general formula HS-R-SH where R represents a saturated or unsaturated, linear or branched, cyclic and/or aromatic hydrocarbon-based group having 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, and that does not comprise a C=O carbonyl function and/or a O-C=O carboxylate function.