Polymer modified bitumen
Polymer modified bitumen is one of the specially designed and engineered bitumen grades that is used in making pavement, roads for heavy duty traffic and home roofing solutions to withstand extreme weather conditions. Polymer modified bitumen is a normal bitumen with added polymer, which gives it extra strength, high cohesiveness and resistance to fatigue, stripping and deformations, making it a favorable material for infrastructure.
When a polymer is added to regular bitumen, it becomes more elastomeric, which provides it with additional elasticity. The polymer that is added is styrene butadiene styrene, which acts as a binder modification agent. The primary objective of styrene butadiene styrene polymer modified bitumen is to provide extra life to pavement, roads and construction designs.
Some of the qualities exhibited by Polymer Modified Bitumen are:
Increased resistance to deformations
Increased resistance to cracks and stripping
Better water resistance properties
Application of Polymer Modified Bitumen:
The development of very stressed pavement
Roads for high and heavy traffic
High temperature amplitude
More durable pavement
Process for preparing of polymer modified bitumen:Process for preparing a polymer modified bitumen binder composition in the substantial absence of cross linking agents by heating a bitumen component in a stirred tank to a temperature from 185° C. to 221° C.; adding a block co polymer composition to the bitumen component while the bitumen component is being stirred to form a homogeneous mixture of the bitumen component and the block co polymer composition; and continuing to stir the homogeneous mixture while maintaining the temperature from 185° C. to 221° C. for a period of time from 4 hours to 30 hours thereby forming a cured polymer modified bitumen binder composition.
The block co polymer composition utilized in the process comprises a diblock co polymer comprising one block of a Monovinyl aromatic hydrocarbon and one block of a conjugated diene having a peak molecular weight from 30,000 to 78,000 and a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, and optionally one or more block co polymers comprising at least two blocks of monovinyl aromatic hydrocarbon and at least one block of conjugated diene, the block co polymer selected from linear tri block co polymers having a peak molecular weight that is 1.5 to 3.0 times the peak molecular weight of the diblock co polymer, multiarm coupled block co polymers having a peak molecular weight that is 1.5 to 9.0 times the peak molecular weight of the diblock co polymer, and mixtures thereof, wherein each block co polymer has a vinyl content from 35 to 80 mol percent based on the number of repeat monomer units in the conjugated diene block, wherein when both (i) and (ii) are present in the block co polymer composition, the ratio of (i) to (ii) is greater than 1:1.
The present invention is further related to an alternative to this process, a specific class of bituminous binder compositions and concentrates and a specific class of block co polymer compositions.