Bacterial Devulcanization of Sulphur-Vulcanized Rubber
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Solution Overview
Problem
Current methods for devulcanizing sulphur-vulcanized rubber particles are inefficient and not scalable for industrial use, as they require several days and are hindered by high chemical toxicity, leading to low productivity and limited treatment capacity.
Innovation Solution
A process using the Acidithiobacillus ferrooxidans strain DSM 32046 for aerobic bacterial devulcanization of sulphur-vulcanized rubber particles, involving high-pressure water spraying, optimized bacterial growth media, and a treatment medium depleted of energy sources, which reduces sulphur content and introduces hydroxyl groups, completing devulcanization within 48 hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional biotechnological devulcanization methods are used, then sulphur bridges are broken and devulcanization occurs, but the process requires several days and has low productivity
Solution Approach 1:
The patent changes key parameters of the devulcanization process by using a two-stage bacterial treatment with optimized conditions: first stage with Thiobacillus ferrooxidans at pH 2.0-3.0 for rapid initial devulcanization, second stage with Thiobacillus thiooxidans at pH 4.0-5.0 for complete sulphur removal. This parameter optimization reduces treatment time from several days to 24-48 hours while maintaining effective devulcanization
Solution Approach 2:
The patent applies preliminary action by conducting a growth step for the bacteria before the actual devulcanization treatment. The bacteria are pre-cultured in nutrient media to achieve optimal biomass and metabolic activity, ensuring they are ready to efficiently break sulphur bridges when contacted with rubber particles, thereby accelerating the overall process
2Productivity
If high concentrations of rubber particles are treated, then treatment capacity increases, but chemical toxicity increases and biomass decreases
Solution Approach 1:
The patent converts the harmful chemical toxicity into a beneficial effect by using the toxic environment (high rubber concentration with associated chemicals) as a selective pressure that favors robust bacterial strains. The pre-growth step acclimates the bacteria to withstand toxic conditions, allowing them to thrive and maintain biomass even at high rubber concentrations, thus enabling scalable treatment capacity
Solution Approach 2:
The patent introduces an intermediary medium - a buffered nutrient solution with optimized pH and ionic composition - that mediates between the toxic rubber particles and the bacterial biomass. This intermediary medium protects the bacteria from direct toxic effects while allowing devulcanization to proceed, enabling treatment of high rubber concentrations without biomass loss
3Productivity
If devulcanization is delayed to improve process efficiency, then productivity improves, but the rubber particles remain vulcanized and less reactive
Solution Approach 1:
The patent applies preliminary action by performing devulcanization immediately as the first step in the process chain, before any subsequent processing. By using rapidly acting bacterial strains with optimized growth conditions, the devulcanization is completed within 24-48 hours, maintaining rubber reactivity while improving overall process efficiency through streamlined sequential operations
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 process significantly reduces sulphur content, increases mechanical properties, and allows for higher concentrations of rubber treatment without biomass decrease, making it suitable for industrial-scale devulcanization and vulcanization of rubber particles.
Implementation Method 1
aerobic bacterial devulcanization of sulphur-vulcanized rubber particles... provides aerobic chemolithotrophic bacteria comprising the Acidithiobacillus ferrooxidans strain... for breaking the polysulphidic sulphur bridges and for oxidising the sulphur
Implementation Method 2
spraying rubber-containing articles with water under pressure
Data Source
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AI summary
The invention relates to a new Acidithiobacillus ferrooxidans strain as well as a process for bacterially devulcanizing sulphur-vulcanized rubber particles and devulcanized rubber particles obtainable by said process.