Patent attributes
The present invention is directed to a process for preparing a polymer modified bituminous binder composition in the substantial absence of crosslinking agents by heating a bitumen component in a stirred tank to a temperature from 160° C. to 221° C.; adding a block copolymer composition to the bitumen component while the bitumen component is being stirred to form a homogeneous mixture of the bitumen component and the block copolymer composition; and continuing to stir the homogeneous mixture while maintaining the temperature from 180° C. to 221° C. for a total period of time from 4 hours to 30 hours thereby forming a cured polymer modified bituminous binder composition. The block copolymer composition utilized in the process comprises one or more block copolymers having at least one monovinylaromatic block and either (I) at least one polybutadiene block having a vinyl content of less than 15 mol percent and at least one polybutadiene block having a vinyl content of greater than 25 mol percent or (II) at least one polybutadiene block having a vinyl content that tapers from a vinyl content of less than 15 mol percent at the first end adjacent to the monovinylaromatic block to a vinyl content that is greater than 25 mol percent at the second end which is furthest from the monovinylaromatic block and optionally at least one polybutadiene block having a vinyl content of less than 15 mol percent.
