Compositions: coating or plastic – Coating or plastic compositions – Carbohydrate or derivative containing
Reexamination Certificate
2001-03-06
2003-05-13
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Carbohydrate or derivative containing
C106S282000
Reexamination Certificate
active
06562118
ABSTRACT:
BACKGROUND OF THE INVENTION
Asphaltic products are produced in various forms, with the primary application being in paving and construction products. Some asphalt products have improved properties as a result of chemical processing, or the inclusion of various additives. One of the more important class of materials included in asphaltic compositions are fibers of various types, which are known to improve the tensile strength and integrity of the final product. Asphalt-fiber combinations play an important role in the manufacture of various products useful for construction including water resistant building papers, felts and roofing materials such as shingles. An extensive field of use for fiber modified asphalt (FMA) in road paving applications is also known, such fibrated products having improved strength and wear resistance compared to other road pavements. It has been reported that flex and durability have been substantially improved with respect to paving and sealing compositions by including reinforcing fiber materials. An important aspect of FMA is the fact that fibers increase the viscosity of the asphalt thus providing a product which can be retained on vertical surfaces at elevated temperatures.
One of the serious weaknesses of fibrated asphaltic materials used for construction is that the fibers degrade over time. This occurs as a result of various chemical reactions which occur as a result of the exposure of the fibers to heat and light. The problem is particularly acute when catalytically hardened, or oxidized asphalt is used in that it has been found that the chemicals present are particularly damaging to cellulosic fibers. As a consequence cellulosic fibers are often replaced by more stable, but more expensive, synthetic fibers in areas where high ambient temperatures demand the use of harder asphalt;
One of the most promising commercial applications for FMA stems from the popularity of new types of road paving which require high viscosity fibrated asphalt widespread use of fibrated asphalt in road construction has, however, been hindered by the practical difficulties of incorporating the fibers into the composition. All known paving applications of FMA thus involve incorporation of the fibers at the construction plant where the composition is prepared immediately prior to compaction on the roadbed. Although there are numerous disadvantages to this approach, no method of simplifying the process by premixing the asphalt and fiber has yet been described. Such a process would require both a method of manufacturing an FMA premix with defined performance specifications, and also of stabilizing the dispersion so that its properties would be retained in transit and during storage at the job site. These activities frequently take as many as 10 days, during which time the FMA is held at temperatures up to 160° C.
The present invention is principally directed to a method for chemically modifying asphalt to protect cellulose fibers from degradation at high temperatures. A particular embodiment of this invention relates to the manufacture of roofing materials such as shingles and another particular embodiment to the manufacture of FMAs of superior properties and stability, particularly for the construction of roads.
BRIEF REVIEW OF THE PRIOR ART
Fibrated Liquid Asphalt Compositions
Many asphaltic compositions employing organic and inorganic fibers are known. Inorganic fibers include fiberglass, mineral wool asbestos etc., while organic fibrous compositions include synthetic rubbers and polymers of various types, as well as natural cellulosic fibers. Numerous examples of the benefits of incorporating fibers in both aqueous and non-aqueous asphalt compositions have been described. Thus U.S. patents issued to Frizzell U.S. Pat. No. 4,738,723, Borger U.S. Pat. No. 5,897,950, German Patent 39 30 59 and French Patent 26 76 436-A1 disclose ways of improving hot melt asphaltic compositions using inorganic or organic fibers. References to the incorporation of fibers into asphaltic emulsions include the U.S. Patents of Draper U.S. Pat. No. 3,474,625, Bresson U.S. Pat. No. 3,993,496, Buse U.S. Pat. No. 4,302,370, Duszak U.S. Pat. No. 4,492,781 and Marvel et. al. U.S. Pat. No. 4,663,370.
In spite of these numerous examples of admixing fibers and asphalt, no reference is to be found to the preparation of stable FMA premixes. Unlike asphalt emulsions which are usually produced far from the point of sale, hot melt FMA is always prepared at the point of use (E. R. Brown et. al., “Designing Stone Matrix Asphalt Mixtures”, National Center of Asphalt Technology Publication, July 1998 and L. A. Cooley and E. R. Brown, “Evaluation of Asphalt Binders Containing Fibers and Fillers.” Transportation Research Board Meeting, Washington D.C. January 1999). In this process, bags of fiber are usually added manually to the mixer, while on other occasions expensive specialized feeding equipment is employed. Both methods are less than satisfactory in that they require a significant investment of time and energy or equipment to achieve a satisfactory blend of the various ingredients. Manual addition is slow and subject to variability, and the poor workability of the resulting composition often results in an unacceptable increase in processing temperature. Addition of fiber at the work site thus adds significantly to the cost of paving construction due to the special attention required, and many of the disclosures are directed to improving this application.
In an attempt to improve the efficiency of this operation Mleczewski (U.S. Pat. Nos. 5,407,139 and 5,529,247) disclosed a method by which fibers are discharged into a chamber containing hot asphalt and aggregate. The bulky equipment described is, however, unsuitable for most operations similarly the method invented by Brocious (U.S. Pat. No. 4,820,078) for dispensing a mixture of asphalt and fiber would significantly add to the cost of the process, as would that of Strassman (U.S. Pat. No. 5,460,649). Rettenmaier (U.S. Pat. No. 5,028,266) has described another complex process which requires the fibers to be first encapsulated into pellets, and then packaged and shipped to the job site where they are introduced by means of a calibrated conveyor. Fry (U.S. Pat. No. 4,422,878) attempted to solve some of the process problems encountered by admixing polypropylene fibers with fatty acids, but this is not applicable to cellulosic fibers which are destroyed by acids at elevated temperatures.
Although other attempted solutions have also been disclosed in U.S. Patents (e.g. Roberts, U.S. Pat. No. 4,316,829; Marzocchi U.S. Pat. No. 4,166,752; Loftus et. al. U.S. Pat. No. 5,468,546; Gallagher et. al. U.S. Pat. Nos. 5,718,787, 5,869,413, 5,897,951) none of these considered the possibility of preparing a stable premix of fibers in asphalt.
Asphaltic compositions, as for use in paving, are frequently stored for several days at temperatures of up to 160°-170° C. Hitherto, the difficulty of preparing an asphalt dispersion of fibers of acceptable stability under these conditions has seemed unsurmountable. To some extent at least, this is attributable to a general poor understanding of the relationship which exists between processing conditions and the properties of FMAs.
Asphalt Treated Fibrous Mats
Good thermal stability of cellulosic fibers in contact with hot asphalt is also important in a very different industrial application, that of construction papers such as roofing shingles. In this case the actual temperature of exposure is lower, but the duration is considerably longer in that the strength of the fibrous mat after years of exposure to beat and sunlight is a major concern. In shingle production the problems associated with loss of fibers strength differ from those encountered in road construction where the short term fiber integrity is more important. It is therefore of some significance that we have discovered that the decomposition of cellulosic fibers in roofing shingles and hot melt road compositions appears to be due to the same chemical reaction, and thus bo
Brunsman David
Dinesh Agarwal, P.C.
Lafarge Materials & Construction Inc.
LandOfFree
Asphaltic compositions containing fibrous materials with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Asphaltic compositions containing fibrous materials with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Asphaltic compositions containing fibrous materials with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3072950