Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-15
2002-04-30
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S068000, C524S069000, C524S070000, C524S071000
Reexamination Certificate
active
06380284
ABSTRACT:
This invention pertains to a process for continuous production of sulfur crosslinked polymer asphalts, whereby said process makes it possible to produce all kinds of modified binders, from conventional binders such as are used today to highly concentrated polymer binders that do not yet exist.
Improving the properties of asphalts is today an absolute necessity in order to guarantee improved quality for the materials that use asphalts and to thus help to create and develop new applications. This goal is achieved by increasing the polymer concentration that said materials must assimilate. Unfortunately, few asphalts are truly compatible with polymers, and this incompatibility worsens as the quantity to be introduced into them is increased!
Today two families of polymer asphalts are available on the market:
a) physical mixtures that are produced by simple dissolution of polymers;
b) media that are transformed by a chemical reaction that is induced between components of the asphalts and polymer(s).
If these two discontinuous batch production processes are identical, the properties of the binders that are obtained by a chemical sulfur reaction, at equivalent polymer contents, are superior to those of binders that are produced from simple mixtures, both in terms of elastic performance and in terms of stability or storage under hot conditions. Nevertheless, for various reasons these two concepts do not make it possible to obtain highly modified binders. For no particular reason, where the dissolved-polymer contents can reach 9-10 percent for the majority of asphalts and, in the case of physical mixtures, from 5 to 6 percent polymer, solubility is quickly limited, and these mixtures decant in different phases under the action of an unavoidable phenomenon, which sets in more or less quickly over time. With sulfur-crosslinked asphalts, the polymer content also limits the ability to produce concentrated binders because in the liquid state, i.e., under storage conditions, several hours or several days after vulcanization complete and unstoppable polymerization takes place, leading to a gelatinous state, whereby this happens starting at 6 percent dissolved polymer. Thus, there are many new applications which these types of binders could offer but which have yet to see the light of day for the reasons cited above!
There is tremendous interest in this new process. These new, heavily modified binders will be very useful to the road-building industry, as well as to the field of sealants, and will make it possible to produce materials and coated materials that have very high levels of performance. The same will be true for the production of emulsions from these same binders: no such materials exist today.
Moreover, certain recovered plastics, rubber from discarded tires, and waste oils of mineral, vegetable, or synthetic origin can also be recycled within the framework of the binders produced by the invention.
These new innovative materials will be intended especially to be used to regenerate old coated materials on roads within the framework of the hot-recycling technique. Said innovative materials will promote the recovery, i.e., enhancement of the value, of old asphalt materials on roads and will keep them from being discarded.
From the economic standpoint, the advantages offered to road builders and sealant makers are numerous and can be mainly summarized as follows:
having binders whose performance is much better than that of the binders that are known today;
opening new avenues for techniques for building or maintaining roads at lower cost which, owing to their improved mechanical properties and exceptional fatigue strength, will help to improve the behavior and service life of roads significantly;
contributing to the practicability of emulsions and of the binders produced by the invention by the immediate and direct injection of product onto the feed heads of colloid emulsion mills, thereby opening the way to many new applications that can be provided by these truly special emulsions!
enhancing the value, in road and sealant applications, of certain waste products that today are for the most part destroyed, such as plastics, tire rubber, and lubricants, owing to the advantages offered by the vulcanization reaction that is employed in the invention;
recycling of all kinds of used asphalt materials by regenerating the contained asphalts through the incorporation of certain binders that are the direct result of the invention. The use of some of these crosslinked asphalts that have high polymer concentrations as a way to regenerate old coated materials may be done at a permanent coating facility or at a mobile facility that is outfitted in advance with the process. Depending on the characteristics of the materials that are to be recycled, just about 100 percent of them can be regenerated. This is due to the nature of the regeneration process that is employed within the heart of the old asphalt itself: the addition of plasticizing materials and polymers to the old asphalt structure which, under the crosslinking action of sulfur, will help, on the one hand, to reformulate a rejuvenated asphalt and, on the other, to create a polymer mesh that brings together all of the components. This will therefore be a modified-binder coated material that is obtained by this kind of recycling operation. This accounts for the bright prospects for obtaining, by using these products, recycled coated materials whose levels of performance are at least equivalent to, if not better than, the characteristics that they had at the time when they were first used.
STATE OF THE ART
For more than 25 years now, asphalts have been modified by the addition of polymers in order to improve their rheological properties and also to curb their ability to age. Two main effects are sought. The first is to increase the plasticity range in such a way that, under conditions of elevated temperature, the asphalt remains viscous enough that coated materials, as well as sheets of sealant complexes, are kept from deforming. The second effect, especially at low temperatures, is to reduce the rigidity of the material and to impart to it a great capacity for plastic deformation so that it will be able to withstand great stress.
Many families of polymers are currently used to add this type of modification to asphalt. Among these, the following can be cited: polyolefins, polyvinyl acetates or polyvinyl chlorides, elastomers, etc.. Of all these materials, it is elastomers that are best suited for imparting elasticity and, optionally, plasticity. As a matter of practicality, introduction of these polymers into asphalts is no simple matter. Specifically it is the morphological composition of the base asphalt, i.e., its groups of chemical components: saturated, aromatic, polar, and asphaltene, that dictate the choice of the polymer or polymers and limit-its or their solubility. For a particular type of asphalt, the level of modification that one can hope to achieve is more or less predetermined in advance.
With the exception of the sealant industries, which purchase so-called “special” asphalts, whereby they require that the materials delivered that they use be of an unvarying nature and composition in order to keep the quality of the plastic mixtures that are produced stable, refiners supply only so-called “run-of-the-mill” asphalts in conformity with specifications. This is due to the organization of the petroleum markets and the technical and economic constraints imposed on refining. It is impossible for this industry to continuously produce a special type of asphalt. Because of the risks of segregation, attempts to introduce significant quantities of polymers have not succeeded in producing stable binders that are adapted to industrial use.
Chemically transformed asphalts obtained from styrene-butadiene (SB) of the statistical or stereo regulated block type, or tri-sequence styrene-butadiene-styrene (SBS), or styrene-isoprene (SI), or styrene-isoprene-styrene (SIS), or ethylene-propylene-diene (EPDM), or other types of polymers
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