Binder Production Binder Production. There are several options of bitumen-polymer binder production, but almost all methods include heating and mixing.
The most efficient methods known today employ dispersers (colloid mills) which evolved from regular agitators in bitumen tanks. In theory, bitumen-polymer binder can be made in any bitumen tank with a certain amount of polymer added. The mixture is stirred until the modifier fully dissolves. The total time needed for the production is determined by the temperature of bitumen and the efficiency of the agitator.
The essence of the process is that polymer particles swell when dissolved in malthene fraction, forming a shell over the unsolved part of the substance. The main function of the agitator is to remove the shell. The dry polymer particle can then continue to dissolve in bitumen.
For efficiency of the process, the bitumen-polymer mixture must be cycled through the disperser until the polymer is fully dissolved in bitumen.
There is an alternative technique, sometimes referred to as inline technology. It does not involve multiple passes of the material through a disperser, instead, the mix passes through the mill only once. It enters the disperser with the bitumen in solid state. The small size is achieved by passing the substance through the gap between the rotor and the stator of the mill. To complete the process of solving the polymer, the mixture is then stirred for two hours.
The process is essentially the transition of polymer from solid to liquid state by extrusion and mixing of the plasticized modifier with bitumen heated to a certain temperature.
As the components are moved, several processes occur:
- polymer extrusion;
- mixing of the anomalously viscous liquid with a certain amount of bitumen and production of polymer binding with high or superhigh polymer content;
- consequent mixing of the polymer bitumen concentrate with main bitumen stream in the proportions to achieve the required polymer concentration in the finished product.