Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-08-13
2000-08-08
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 68, 524 59, 525 545, C08L 9500
Patent
active
061003174
DESCRIPTION:
BRIEF SUMMARY
REFERENCE TO RELATED APPLICATIONS
This application is a U.S. National Phase filing under 35 USC 371 from PCT/CA94/00174 filed Mar. 28, 1994.
The present invention relates to the provision of stable dispersions of polymeric materials in bitumen for a variety of applications and methods of producing the same.
BACKGROUND TO THE INVENTION
The combination of two or more polymer types into bitumen is considered desirable from the standpoint of obtaining improvements in properties that may not be possible with a single modifier. By providing a blend of the two or more types of polymers, it is conceivable that improvement in properties can be achieved over a greater range of expected pavement-service conditions.
While this goal is highly desirable, heretofore it has been difficult to achieve this result because of the inherent incompatibility of bitumen and the polymeric materials to be incorporated therein. In addition, different polymers, which, when used independently, are compatible with the bitumen, in combination, interfere with the compatibility of each other and/or the final system.
Various procedures have been attempted to improve the compatibility of bitumen and polymers, for example, by the use of low molecular weight copolymers, process oils, and by the use of specific processing conditions to promote chemical reactions, such as cross-linking.
In International patent application no. WO 93/07219 (corresponding to U.S. Ser. No. 863,734 filed Apr. 6, 1992), assigned to The University of Toronto Innovations Foundation, there is described the stabilization of dispersed polyethylene and other olefin polymers in bitumen for imparting improved properties to such asphalt. The polyethylene is maintained in a dispersed state by using a steric stabilizer which is anchored to the dispersed particles and which is compatible with the liquid medium. Such an arrangement maintains the dispersed polyethylene particles spaced from each other in the bitumen, and inhibits separation of the particulate phase from the liquid phase by the progressive coalescence of dispersed particles.
In particular, a stable dispersion of polyolefin particles in bitumen may be formed by employing a functionalized diene rubber which is covalently bonded to a functionalized polyethylene, with or without liquid polybutadiene. Cross-linking of the unsaturated structure in the functionalized butadiene molecular chain to the bitumen forms an extended polybutadiene-based network with a partially cross-linked structure anchored to each of the polymer particles by compatibility of the functionalized polyethylene with the polymer particles and swollen by the bitumen phase, to provide a gel envelope about the polymer particles, which prevents coalescence of the polymer particles.
SUMMARY OF INVENTION
It has now been surprisingly found that a wide range of copolymers may be incorporated into the bitumen composition containing stabilized polyethylene or other polyolefin described in WO 93/07219 and such copolymer resists separation from the bitumen. The present invention, therefore, permits two or more different polymeric materials to be incorporated into bitumen and to remain stably dispersed therein.
Accordingly, in one aspect of the present invention, there is provided a bitumen composition, comprising bitumen, at least one polyolefin sterically stabilized in the bitumen, and at least one additional polymeric material stably incorporated into the composition.
These stable novel bituminous compositions permit improved performance and a versatility of formulation design which has not previously been possible, while also providing for compositions from which the polymer components do not separate.
In addition, it has been found that a wide variety of properties may be achieved, independent of the formulation utilized, depending on the sequence of addition of the polyolefin, copolymer and stabilizer to the bitumen and variations in other processing parameters, such as mixing time, temperature and rate of shear.
In accordance with a further aspect of
REFERENCES:
patent: 4282127 (1981-08-01), Desgouilles
patent: 5278207 (1994-01-01), Kluttz
patent: 5280064 (1994-01-01), Hesp et al.
Liang Zhi-Zhong
Smith James W.
Woodhams Raymond T.
Asinovsky Olga
Polyphalt L.L.C.
Seidleck James J.
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