Process for mixing modified bitumen by extrusion
Provided is a method of mixing a modified bitumen composition and feeding one or more polymeric materials to an extruder, together with asphalt fed at more than one location along a length of the extruder. Improved mixing and elimination of asphalt melting in the production of rolled goods and other products is improved.
1. A method of mixing a modified bitumen composition, the method comprising:
feeding one or more polymeric materials to an extruder;
feeding asphalt to the extruder at more than one location along a length of the extruder; and
extruding a mixture comprising the one or more polymeric materials and asphalt from the extruder.
2. The method of claim 1 , wherein the extruder is a twin screw extruder.
3. The method of claim 2 , comprising co-rotating the twin screws.
4. The method of claim 1 , wherein the extruder has a length to diameter ratio of at least 60.
5. The method of claim 1 , wherein the one or more polymeric materials comprise styrene-butadiene-styrene.
6. The method of claim 1 , wherein the one or more polymeric materials comprise atactic polypropylene.
7. The method of claim 1 , further comprising feeding one or more additional materials selected from the group consisting of fillers, flame retardant materials, and mixtures thereof, to the extruder.
8. The method of claim 1 , wherein the one or more polymeric materials comprise about 3-80% of the mixture extruded from the extruder.
9. The method of claim 1 , further comprising using at least two extruders.
10. The method of claim 9 , wherein the at least two extruders have different diameters.
11. The method of claim 9 , wherein the at least two extruders have different length to diameter ratios.
12. The method of claim 9 , comprising running different screw speeds in the at least two extruders.
13. A method of forming a reinforced modified bitumen composition, the method comprising:
feeding one or more polymeric materials to an extruder;
feeding asphalt to the extruder at more than one location along a length of the extruder;
feeding fiber to the extruder; and
extruding a mixture comprising the one or more polymeric materials, asphalt, and discontinuous glass fiber from the extruder.
14. The method of claim 13 wherein the fibers are discontinuous fibers.
15. The method of claim 14 wherein the discontinuous fibers are glass.
16. The method of claim 13 wherein the fibers are synthetic polymer fibers.