Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1993-08-23
1994-12-20
Szekely, Peter
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 68, 524 69, 524 71, 524 59, 422258, 422259, C08L 9500
Patent
active
053746724
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing an aqueous asphalt binder emulsion which makes it possible to control the viscosity and breaking properties of the emulsion.
The use of aqueous asphalt binder emulsions in the construction and repair of roads, for the paving of roadways, soil stabilization, for leakproofing in civil engineering or in buildings or for analogous applications is well known. The aqueous emulsions which are suitable for these applications are emulsions of the "oil-in-water" type, which consist of a dispersion of an organic phase formed of fine globules of asphalt binder in a continuous aqueous phase, the aqueous phase containing an emulsifying system, which favours the dispersion of the globules of the asphalt binder in the aqueous phase and consists of one or a number of emulsifying agents, and optionally a pH-regulating agent, which can be, depending on the case, an acid, a water-soluble salt or a base. Such emulsions, whose organic phase content is commonly between 60 and 75% by weight, are commonly classified according to the nature of the emulsifying system used to provide dispersion of the asphalt binder in the aqueous phase and depending on whether the emulsifying system consists of one or a number of anionic, cationic, nonionic or amphoteric emulsifying agents, the corresponding emulsions will be respectively called anionic, cationic, nonionic or amphoteric.
The aqueous emulsion of the asphalt binder is regarded as a convenient means for making it possible to reduce the apparent viscosity of the binder during operations of use of this asphalt binder. After breaking, the emulsion restores the asphalt binder, containing a part of the emulsifying system and other additives present in the aqueous phase.
The aqueous asphalt binder emulsions used for the production of impregnation layers, of holding-down layers or yet again of sealing coats require entirely different viscosity levels depending upon the use concerned. For impregnation layers, the emulsion must have a sufficiently low viscosity to be able to enter as deeply as possible into the structure to be stabilized before breaking of the emulsion takes place which brings about release of the binder. In the case of a holding-down layer or of a sealing coat, the emulsion must, on the other hand, have a sufficiently high viscosity for the slope of the ground, on which this emulsion is spread, not to bring about the formation of run-outs, which have the double disadvantage of simultaneously bringing about local underchargings of asphalt binder and an overcharging or smears at other spots.
The increase in the viscosity of the emulsions is the solution generally adopted for minimizing the run-out problems. The viscosity increase can be achieved either by addition of thickening substances to the aqueous phase, or by adjustment of the manufacturing parameters of the emulsion in order to control the mean size and the particle-size distribution of the globules of asphalt binder which it contains or yet again by the expedient of an increase in the binder content of the emulsion. In particular, the aqueous emulsion containing 80% by weight or more of asphalt binder should make it possible to solve the problems of run-outs at conventional proportions and for uses requiring a greater emulsion proportion as is the case, for example, for monolayer coats. Parallel to this technical aspect, the aqueous emulsion containing 80% by weight or more of asphalt binder also has an advantage at the economic level, because it makes it possible to transport more active material (asphalt binder) for the same amount of emulsion, this aspect acting favourably to reduce the transportation costs as far as the building site.
The emulsification of hydrocarbon binders is generally carried out by conveying, to an emulsifying chamber of colloid mill or turbine type, on the one hand, an asphalt binder in the form of a molten mass having a temperature between 80.degree. C. and 180.degree. C., and preferably between 110.degree. C. and 160.degree. C., and, on the oth
REFERENCES:
patent: 3127367 (1964-03-01), Endres et al.
patent: 4314921 (1982-02-01), Biegenzein
patent: 4722953 (1988-02-01), DeRuiter et al.
Chaverot Pierre
Demangeon Francis
Vincent Regis
Koch Materials Company
Szekely Peter
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