Tire Rubber Bitumen Solubilization with Staged Heating

The patent applies nitrogen gas purging to create an inert atmosphere during the heating and dissolution process. This prevents oxidation of the asphalt at elevated temperatures while allowing the tire rubber to dissolve completely. The nitrogen atmosphere eliminates oxygen contact, thereby preventing oxidative degradation even when temperatures exceed 475°F, resolving the contradiction between achieving complete dissolution and preventing asphalt degradation.

The patent employs a multi-stage temperature protocol that dynamically adjusts heating parameters. The process begins at moderate temperatures (275-325°F) for wetting, then increases to intermediate temperatures (325-350°F) for devulcanization, and finally reaches high temperatures (500-700°F) for complete dissolution. This staged parameter change optimizes dissolution efficiency at each phase, achieving >99% solubility while minimizing total energy consumption and preventing excessive asphalt aging that would result from prolonged heating at a single high temperature.

The patent implements a dynamic mixing strategy that adapts shear intensity to the processing stage. Low shear mixing (50-200 RPM) is used during the wetting phase to avoid premature fragmentation. Moderate shear mixing (200-500 RPM) is applied during devulcanization to facilitate chemical breakdown without excessive mechanical stress. High shear mixing (500-1500 RPM) is employed only during the final dissolution phase when the rubber is already softened and more susceptible to complete dissolution. This dynamic adjustment of mixing intensity optimizes dissolution efficiency while maintaining viscosity stability.