Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-08-22
2002-06-04
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S062000, C524S069000, C525S054500
Reexamination Certificate
active
06399680
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to acid-reacted polymer-modified asphalt compositions. More particularly, this invention relates to modified asphalt compositions comprising an asphalt, an acid, and a polymer selected from (a) certain specific ethylene-carbon monoxide polymers containing epoxy functional groups or (b) a curable blend of these polymers with an organic thermosetting resin. The novel asphalt compositions of this invention, when tested with a dynamic shear rheometer at temperatures ranging from 42° to 82° C., exhibits G*/sin (&dgr;) stiffness values which are at least about 2 times greater than the asphalt without polymer or acid, at least about 1.5 times greater than the asphalt/polymer compositions without acid both when tested according to AASHTO TP5, exhibits G″ viscous component of complex modulus values about the same as the asphalt/polymer composition without acid when tested according to AASHTO TP5 at temperatures ranging from 4° C. to 40° C., and exhibit low temperature creep stiffness and “m” values about the same as those exhibited by the asphalt without polymer or acid when tested at low temperatures ranging from −42° C. to 0° C. according to the SHRP Bending Beam Creep Stiffness test, AASHTO TP 1.
BACKGROUND OF THE INVENTION
It has long been known that a wide variety of polymeric additives can be used to produce asphalt and bitumen containing compositions (generally referred to as “polymer modified asphalt” compositions—PMA compositions) having certain enhanced properties. All types of asphalt, both naturally occurring and synthetically manufactured, are suitable for use in this invention. According to the present invention, the term “asphalt” is meant to also be inclusive of materials designated by the term “bitumen” and no distinction is made herein between the two terms. Naturally occurring asphalt is inclusive of native rock asphalt, lake asphalt, etc. Synthetically manufactured asphalt is often a by-product of petroleum refining operations and includes air-blown asphalt, blended asphalt, cracked or residual asphalt, petroleum asphalt, propane asphalt, straight-run asphalt, thermal asphalt, etc.
Asphalt has both viscous properties, which allow it to flow, and elastic properties, which resist flow. At high temperatures, the viscous properties dominate and the asphalt tends to flow or deform. At low temperature, the elastic properties dominate and the asphalt tends to resist flow. By adding certain polymers, these natural characteristics of asphalt can be modified. The properties improved by the addition of polymers are resistance to high temperature thermal deformation (“creep” or “rutting”), as well as resistance to cracking or deforming under repeated loadings, and, perhaps, the ability to use reduced amounts of asphalt in asphaltic aggregate compositions without loss of desired properties.
Goodrich, U.S. Pat. No. 5,331,028, issued Jul. 19, 1994, and assigned to Chevron, relates to a PMA composition comprising asphalt, a glycidyl-containing ethylene copolymer and a styrene/conjugated diene block copolymer. The Goodrich PMA composition can be used in preparation of asphalt concrete and is said to have enhanced resistance to thermal and pressure induced deformation.
Another Goodrich patent, U.S. Pat. No. 5,306,750, issued Apr. 26, 1994, and assigned jointly to Chevron and Du Pont, relates to a thermoplastic polymer-linked-asphalt product said to evidence enhanced performance properties even at low polymer concentrations. Among the polymers which can be used in the PMA compositions of both Goodrich patents are reactant polymers containing an epoxide moiety which is said to react with the asphalt. Preferred polymers for both Goodrich compositions are of the generalized formula:
E—X—Y
E symbolizes an ethylene copolymer unit. X symbolizes a polymer unit of the formula:
—CH
2
—C(R
1
)(R
2
)—
wherein R
1
is hydrogen, methyl or ethyl, and R
2
is —C(O)OR
3
, —OC(O)R
3
, or —OR
3
, and wherein R
3
is a lower alkyl group. Y symbolizes a copolymer unit of the formula:
—CH
2
—C(R
4
)(R
5
)—
wherein R
4
is hydrogen or methyl, and R
5
is an epoxide-containing moiety of the formula
The polymers used in the PMA compositions of these two Goodrich patents are said to be well known in the art and are described, for example, in U.S. Pat. No. 4,070,532, issued Jan. 24, 1978 and in U.S. Pat. No. 4,157,428, issued Jun. 5, 1979, both by Clarence F. Hammer and both assigned to Du Pont. The polymers described in the Hammer patents and incorporated into the PMA compositions of the Goodrich patents include a polymer modifier known by the trade name, ELVALOY™ AM, available from Du Pont. ELVALOY™ AM is characterized by Du Pont as a polymer modifier to extend asphalt pavement life and to provide improvements in asphalt compatibility, mix stability, handling characteristics and product performance. Chevron makes available a PMA composition which contains the Du Pont ELVALOY™ AM, typically at polymer levels of about 1-3% by weight of the PMA composition.
Other processes for forming asphaltic products have been known to utilize acid treatment in conjunction with the addition of certain other earlier known polymers. For example, Benjamin S. Santos, U.S. Pat. No. 5,288,392, issued Feb. 22, 1994, relates to a process for converting acid sludge from waste oil refineries into an intermediate for production of asphaltic mixtures. The acid sludge is described as containing such non-specifically defined components as resinous and asphaltic materials and undefined hydrocarbon polymers. However, the unidentifiable polymers contained in this acid sludge are not related structurally or chemically to the polymers described by the Goodrich and Hammer patents or to the specific polymers used according to the present invention.
Three patents have issued to Lyle E. Moran, U.S. Pat. No. 4,882,373, issued Nov. 21, 1989 (Moran I), U.S. Pat. No. 5,070,123, issued Dec. 3, 1991 (Moran II), and U.S. Pat. No. 5,095,055, issued Mar. 10, 1992 (Moran III), which all relate to premodification of asphalt with an acid, such as HCl and H
3
PO
4
, and then subsequent addition of a thermoplastic block copolymer.
Specifically, Moran I is said to improve the tensile properties of asphalt compositions by contacting asphalt with a mineral acid, bubbling an oxygen-containing gas through the acid treated asphalt, adding a thermoplastic elastomer to the treated asphalt and finally adding an unsaturated functional monomer to the polymer modified asphalt. Moran II and III dispense with the use of oxygen-containing gas and elaborate on a variety of acids and polymers which may be added to the asphalt composition to improve its storage stability. The processes of the Moran II and III patents are said to yield a more highly stabilized PMA composition by adding the acid simultaneously with or subsequent to the addition of the polymer.
In addition, Moran III acknowledges an earlier German Offen. 2 255 173 by Shell, published May 16, 1974, which relates to the addition of styrenic thermoplastic elastomers and small amounts of phosphoric acid or hydrochloric acid to asphalt to produce stabilized PMA compositions.
Other patent disclosures contain further descriptions of various acid and polymer treatments of bituminous or asphaltic materials. According to U.S. Pat. No. 4,368,228 of Romolo Gorgati, issued Jan. 11, 1983, bitumen obtained from acid sludge produced by concentrated sulfuric acid treatment of heavy distillates of asphalt-based petroleum is mixed with certain thermoplastic polymers to prepare prefabricated waterproofing membrane for roofing materials. U.S. Pat. No. 3,915,730 of Jean Lehureau, et al., issued Oct. 28, 1974, describes a surface paving material which is a composition of matter comprising 2,2-bis (4-cyclohexanol) propane diglycidyl ether, and a curing agent with a bituminous material derived from treatment of petroleum with boiling sulfuric acid.
Processes for acidic treatment of asphaltic or bituminous materials without the additional presence of polymers are related by two pat
Engber Steven L.
Reinke Gerald H.
Mathy Construction Company
Wilson D. R.
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