Devulcanization Methods in Tire Recycling

Manufacturing devulcanized rubber that can be used as a viable substitute to virgin rubber in different types of applications, such as in tyres and general rubber goods such as conveyor belts, sheeting, extrusion profiles and moulded products. The process includes introducing tyre rubber particles to a mill; introducing a gaseous flow in the mill for generating a field of high turbulence, strong eddies and high energy impact between the tyre rubber particles which causes micronization and rupture of the tyre rubber particles due to extreme hysteresis and mechanical forces sufficient to at least partially devulcanize the tyre rubber particles; and fast dissipation of the heat generated into the gaseous flow.

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Devulcanization of rubber products like tires to recycle them by breaking the sulfur crosslinks without melting the rubber. The process involves mixing the vulcanized rubber particles with a high-boiling swelling agent and heating them in oxygen. The high-boiling swelling agent causes the rubber to swell, making it easier to break the sulfur bonds. The oxygen oxidizes the sulfur and devulcanizes the rubber. After devulcanization, the rubber chains can be separated from the swelling agent. This allows recycling of the devulcanized rubber by reusing it in new products rather than disposing of it.

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A process to produce rubber granules from end-of-life tires suitable for devulcanization and recycling. The process involves shredding the tires, sieving the shreds to separate the rubber, and then grinding the rubber to the desired particle size. The ground rubber is then subjected to a thermal-mechanical reactor treatment to devulcanize and soften the rubber. This step involves heating and agitating the rubber to break the crosslinks and restore the polymer chains. The resulting devulcanized rubber granules can be used in new tire production or other applications. The process allows recycling of tires by converting the rubber into a reusable form without requiring extensive processing steps like vulcanization.

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Recycling used tires into reusable components by breaking down the vulcanized rubber and extracting the steel belts. The process involves heating the tires in the presence of a supercritical hydrocarbon reactant like butene to pyrolyze the rubber. This breaks the carbon bonds and crosslinks to release hydrocarbons. A caustic agent removes contaminants like heavy metals and carcinogens. Induction heating the steel belts provides additional energy. Rapid depressurization tears the tire apart. This complete and rapid recycling eliminates hazardous tire waste.

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Mechanochemical method of devulcanizing rubber from waste tires using a catalyst containing nickel and cyclooctadiene ligands. The method involves grinding the tire rubber into chips, heating it in the presence of hydrogen gas, and using the catalyst to break the sulfur bonds in the vulcanized rubber. The catalyst activates in the hydrogen atmosphere and facilitates hydrogen transfer to the rubber, causing devulcanization. The process allows regeneration of the rubber for reuse instead of landfilling or incineration.

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A method to convert vulcanized rubber into a product that can be used to replace virgin rubber in new products without degrading properties. The conversion involves heating the vulcanized rubber in a solvent like water below the solvent's critical temperature, while maintaining a higher-than-normal pressure. This breaks some of the crosslinks in the rubber without degrading the polymer chains. The lower temperature and higher pressure prevent chain scission that occurs at higher temperatures. The converted rubber has similar rheological properties to unvulcanized rubber.

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A process for recovering carbon black from waste vulcanized rubber, like used tires, by microwaving the rubber granules at specific conditions to selectively devulcanize the rubber without crystallizing the carbon black. The process involves forming the rubber into small granules, microwaving at reduced power levels to initiate devulcanization, and monitoring temperature and gas evolution. The microwaving breaks the rubber bonds without overheating, allowing selective recovery of amorphous carbon black.

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Desulfurization process for recycling waste tires by grinding them to remove sulfur and other harmful elements. The process involves pulverizing the waste tires to prepare rubber chips, then grinding and compressing the chips at high temperature and pressure with air injection. This removes the sulfur and desulfurizes the rubber. The desulfurized rubber chips can then be used in new tire applications instead of virgin rubber. The grinding/compressing step is done at high temperatures to volatilize and remove the sulfur.

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Devulcanization and modification of waste tire rubber using mechanical treatment to convert cured rubber into a form that can be reused. The process involves kneading and extruding the waste rubber with a thermoplastic polymer as a swelling agent and bearing fluid. This is done at higher screw speeds and temperatures to selectively break the crosslinks in the cured rubber network. The resulting devulcanized rubber can then be further processed into useful forms like sheets or ground into filler for new rubber products.

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Reducing the amount of 2-butanol needed for devulcanizing cured rubber by using carbon dioxide as a co-solvent. The process involves heating the rubber to 150-300°C under high pressure in a mixture of 2-butanol and carbon dioxide. This allows selectively devulcanizing just the surface of the rubber particles without fully devulcanizing the core. The carbon dioxide reduces the required 2-butanol concentration. After devulcanization, the surface-devulcanized rubber can be recompounded and recycled into high performance rubber products.

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Easily and economically recycling waste rubber from products like tires into high-quality recycled rubber. The method involves devulcanizing the waste rubber by contact-reacting it with high-temperature steam. The vulcanization bonds are broken without adding chemicals. The devulcanized rubber is then recovered and reused as a new rubber material. The steam devulcanization temperatures and pressures are tailored for specific rubber compositions like natural rubber vs styrene-butadiene rubber.

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Reducing rubber using subcritical water extraction to mitigate disadvantages of existing rubber reduction methods. The method involves heating rubber, including synthetic rubber, in the presence of water below its critical temperature and pressure. This subcritical water extraction allows devulcanization without significant depolymerization, producing a solid reaction product with larger molecular weight hydrocarbons compared to oil. This avoids completely depolymerizing the rubber, preserving more of its original value compared to supercritical processing.

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Recovering high-purity high-molecular-weight rubber and high-quality carbon black from vulcanized rubber waste like tires and scraps. The method involves pretreating the rubber with shearing forces, then extracting it with organic solvents to separate the rubber and extraction residue. The residue is further processed by heating or dissolving in rubber dissolving agents to decompose the rubber and recover the carbon black. The extracted rubber can also be purified by removing the solvent. This allows reusing the recovered rubber and carbon black as raw materials for new rubber products instead of waste disposal.

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Recycling waste vulcanized rubber from tires and improving its properties for effective recycling applications. The recycled rubber has controlled desulfurization levels to maintain rubber properties while enhancing adhesion. The recycled rubber can be used in elastic molded products like paving materials to replace virgin rubber. The desulfurization treatment involves targeted removal of sulfur compounds from the vulcanized rubber to balance desulfurization with retention of rubber properties. This allows the recycled rubber to have desirable characteristics like elasticity and adhesion for recycled applications without fully desulfurizing it. The recycled rubber can be used as an elastic aggregate in paving materials and pavements to replace some of the natural rubber or other elastomers. This enables utilizing waste tires and other vulcanized rubber in recycled products while avoiding issues like low adhesion.

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Recycling of hardened rubber articles like tires by selectively devulcanizing the surface of ground-up recycled rubber pieces to enable reblending and reusing in high performance rubber products. The technique involves grinding the recycled rubber to a specific particle size range, then devulcanizing only the surface under pressure with solvents like alcohols or ketones. This allows co-curing the devulcanized recycled rubber pieces with virgin rubber to create composite rubber blends suitable for making tires, belts, etc. By selectively devulcanizing just the surface, it reduces the overall devulcanization cost compared to fully devulcanizing the entire recycled rubber.

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A commercially viable technique for recycling large quantities of cured rubber from reclaimed rubber articles. The technique involves grinding the reclaimed rubber to a particle size within 325 mesh to 20 mesh, then devulcanizing the surface of the reclaimed rubber crumb using alcohol and pressure. This allows blending and curing the surface-devulcanized crumb with virgin rubber to make high-performance products like tires. By just devulcanizing the surface, it reduces the cost compared to fully devulcanizing.

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A method for producing thermoplastic rubber using devulcanized rubber and thermoplastics. The method involves blending devulcanized rubber (from scrap tires or overruns) with thermoplastics, without further vulcanization. This allows reusing scrap rubber in a thermoplastic form, avoiding the need for virgin thermoplastic materials. The blended mixture can be processed like regular thermoplastics for applications like making heels and soles. The thermoplastic nature allows reprocessing without vulcanization, unlike conventional rubber.

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