Compositions: coating or plastic – Coating or plastic compositions – Bituminous material or tarry residue
Reexamination Certificate
2003-05-29
2004-07-20
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Bituminous material or tarry residue
C106S279000, C106S280000
Reexamination Certificate
active
06764542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to “cutback asphalts” and asphalt emulsions made with biodiesel.
2. Description of the Prior Art
A good discussion of asphalt roads, cutback asphalt and asphalt emulsions is contained in http://www.epa.gov/ttn/chief/ap42/ch04/final/c4s05.pdf, which is incorporated herein by reference.
Although a considerable oversimplification, asphalt road products could be broadly grouped in three categories:
Neat-asphalt obtained by distillation for making roads, e.g., asphalt cement.
Cutback asphalts-an asphalt softened with petroleum solvent, e.g., asphalt cement with gasoline or diesel fuel, for patching.
Asphalt emulsions-solid particles of asphalt in water, usually with an emulsifying agent.
Neat asphalt is used to make new roads and is usually applied hot. Cutback asphalts are used for patching and some types of new road construction or resurfacing, though primarily in cooler months. Asphalt emulsions are used in a variety of thickness and applications, ranging from surface sealers to patching material to new road construction, though primarily in warmer climates.
The present invention focuses on cutback asphalt and asphalt emulsions and problems of repairing and restoring road surfaces.
One of the most common problems encountered in maintaining asphalt roads is potholes or chuck holes. These usually start off small, in areas where there has been freeze/thaw damage or poor surface preparation or some assault on the road surface. Once started, they usually grow progressively worse, due to accumulation of water and pounding. Conventionally, cutback asphalt is used for patching, especially in cooler climates and/or winter months. To make the asphalt soft enough to work with, and/or reduce or eliminate the amount of heating needed to make the material workable, a petroleum solvent is dissolved in the asphalt. Such “cold patch” materials are frequently made in advance and stockpiled to provide a source of material for patching.
Another method of making a high softening point asphalt fluid enough to process at ambient, or relatively low, temperature, is to form an emulsion of asphalt in water with an emulsifier. The asphalt retains its high melting point, but is ground finely enough, to particles on the order of 5-10 microns, that a relatively stable emulsion of asphalt in water is formed which behaves as a liquid with a much lower viscosity than the asphalt particles. The emulsion sets or breaks when the water evaporates and/or it reacts with particles of aggregate.
In some instances roads are made with cutback asphalt or asphalt emulsions.
All cutback asphalts contain solvent. The solvent eventually evaporates, quickly or slowly, depending on the nature of the solvent, local weather conditions and the amount of heating. When used to construct a parking lot or road, the amounts of solvent used, and discharged into the air are enormous—from about 2 tons of hydrocarbon per acre of parking lot up to 10-20 tons of hydrocarbon per acre of road.
Modern cars, with catalytic converters burning clean fuels, generate relatively low levels of HC emissions per mile of travel, an order of magnitude less emissions as compared to pre-catalytic converter cars. In contrast, modern road building and repair methods have changed little and the amount of volatile organic compounds released by making or repairing roads using cutback asphalt or asphalt emulsion has not changed significantly. About the only accommodation to the polluting effect of modern roads is legislation in many areas banning use of cutback asphalts, except in winter months.
Another problem with cutback asphalts, especially the quick setting variety, is that the large amounts of petroleum hydrocarbon solvent added, and the volatility of the fractions used, create a fire hazard and subject workers, and those near the road, to exposure to toxic chemicals.
We discovered that it was possible to use a natural oil, derived from vegetable, oils or animal fats, as part of a cutback asphalt or asphalt emulsion. So far as is know, biodiesel has never been used in this way, though use of biodiesel as a release agent has been reported as follows:
http:/www.soygold.com/many uses.htm teaches use of biodiesel as a release agent for
Effective Release Agent
Tool Cleaning
Drag chains in plants
Paving equipment clean up. http://www.apexnorth.com/applications/teaches similar uses (e.g., asphalt release agent).
Biodiesel, is now well known and widely available commercially and extensively studied, as shown by 100+papers included in the report, Biodiesel Research Progress, discussed above. Biodiesels are attractive for fuels, and some other uses, because they have a low vapor pressure, are non-toxic and are stable, as per HMIS regulation and do not deteriorate or detonate upon mild heating.
Although these benefits (safety, toxicity) may seem to be an obvious part of biodiesel, it was by no means obvious to look on biodiesel as suitable for either an asphalt cutback solvent or for use in forming an asphalt emulsion. Asphalt has a high molecular weight and is highly aromatic. Biodiesel is aliphatic, contains no sulfur, has no ring structures or aromatics, and is relatively low molecular weight, as compared to asphalt. Biodiesel also contains large amounts of oxygen, approaching 10%. It could be argued that a linear, relatively low molecular weight, aliphatic molecule such as biodiesel would be a good release agent but not suitable as a solvent (in cutback asphalt) nor for forming a stable emulsion (in asphalt emulsions).
SUMMARY OF THE INVENTION
1. General Statement of the Invention
One embodiment of the present invention provides cutback asphalt comprising asphalt obtained from petroleum by distillation and/or extraction and a cutter solvent comprising an ester derived from vegetable oils or animal fats, such as biodiesel.
Despite the discussed above concerns, the aliphatic biodiesel cutback asphalts and asphalt emulsions worked well and had some very unexpected benefits.
The cutback asphalts of the present invention, which have been tested extensively as a patch material, stay in the pothole and have met with the customer approval. For instance, some benefits to using biodiesel include fire hazard safety and low toxicity in preparing the materials also the biodiesel is a very nice material to work with; it has no unpleasant odor, and although it will burn, it has such a low volatility that it will not form an explosive mixture in air under normal processing conditions. The biodiesel is essentially free of aromatics and considered non-toxic for skin contact and is readily biodegradable, should any spills occur. In addition, there were some very unexpected benefits to using biodiesel in cutback asphalts.
The biodiesel cutback asphalt is stable in storage, even when simply left in a pile in a storage yard, which is the usual method of storing such cold patch material. There is no observable run-off, which can occur when liquid petroleum solvents are used as a diluent. There is little or no loss of material due to evaporation, or perhaps drainage, in that a pile of patch material retained a pleasing shiny appearance and was readily worked, after two months in storage while a competitor's product lost its “luster” after about 1 month of storage. Further surprisingly, it is now possible to make a satisfactory cutback asphalt with relatively low amounts of biodiesel, much less than was necessary, or at least customary, for the prior art, liquid petroleum solvent cutback materials.
In another embodiment, the present invention provides an asphalt emulsion comprising emulsifiable particles of asphalt obtained from petroleum by distillation and/or extraction, water and an oil phase comprising an ester derived from vegetable oils or animal fats.
In yet another embodiment, the present invention provides a pavement or paving composition comprising aggregate and from 1.0% to 10.0% of an asphalt composition comprising a cutback asphalt containing biodiesel or an asphalt emulsion comprising biod
Alcorn, II James R.
Lackey Kenneth R.
Brunsman David
Emch, Schaffer, Schaub & Porcello & Co., L.P.A.
Marathon Ashland Petroleum LLC
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