Method for obtaining polymer/bitumen blends with improved stability and polymer efficiency

Abstract

The present invention is an improvement in a process for producing a blend of bitumen and a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene comprising mixing from 88 to 99.5 weight percent of bitumen with 0.5 to 12 weight percent copolymer at 135° to 250° C., agitating the mixture for at least 30 minutes, adding 0.01 to 2 weight percent sulfur and maintaining the mixture under agitation for at least 30 minutes. The improvement comprises utilizing high shear mixing at a shear rate of at least 10,000 second -1 to provide said agitation.

I claim: 
     
       1. In a process for producing a blend of bitumen and a block copolymer of a vinyl aromatic hydrocarbon and a conjugated diene comprising mixing from 88 to 99.5 weight percent of bitumen with 0.5 to 12 weight percent copolymer at 135° to 250° C., agitating the mixture for at least 30 minutes, adding 0.01 to 2 weight percent sulfur and maintaining the mixture under agitation for at least 30 minutes, the improvement which comprises utilizing high shear mixing at a shear rate of at least 10,000 second -1  to provide said agitation. 
     
     
       2. The product of the process of claim 1. 
     
     
       3. The process of claim 1 wherein the bitumen concentration is 92 to 99 weight percent and the polymer concentration is 1 to 8 weight percent. 
     
     
       4. The product of the process of claim 3.