Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-05-08
2002-07-02
Cain, Edward J. (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
06414056
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to modified asphalt paving binder compositions.
BACKGROUND OF THE INVENTION
Asphalt is a visoelastic semi-solid bituminous material derived from the distillation residue of crude petroleum. Because it has good adhesive and weathering characteristics, it is widely used as a binder or cement for stone or rock aggregate in pavement construction. If, because of the nature of the crude oil distilled, the asphalt is too soft at ambient temperature, a harder product may be manufactured, for example, by extraction of the lighter components with liquid propane or other solvents, or by oxidizing by air blowing at an elevated temperature. However, these manufacturing processes can produce asphalts that are too brittle at low temperature, and result in excessive cracking in cold weather. Another means of stiffening soft asphalt to extend its useful temperature range is by blending with suitable polymers. Polymers can reduce the tendency of an asphalt pavement to creep and rut in warm weather by increasing its high temperature viscoelastic stiffness. Thus, polymers have been added which permit the use of, in some instances, softer grades of asphalt to reduce cracking in cold weather without risking excessive softening in hot weather.
Other components have been added to asphalts and polymer modified asphalts to improve their physical properties such as storage stability and viscoelastic properties. U.S. Pat. No. 5,348,994 teaches the preparation of storage stable pavement binder having improved viscoelastic properties inter alia by cosulfonation followed by neutralization of a blend of asphalt and polymer having some unsaturated bonds. U.S. Pat. No. 5,070,123 discloses a method of improving storage stability by first adding an inorganic acid such as hydrochloric acid, phosphorus pentoxide and preferably, phosphoric acid to an asphalt then adding from about 1.0 to about 15 wt % polymer to the blend. The patent does not teach or suggest the use of superphosphoric or polyphosphoric acid. U.S. Pat. No. 4,882,373 discloses an asphaltic composition having improved tensile properties produced by the process of contacting an asphalt with a mineral acid to form an acid modified asphalt, oxidizing the resulting material to form an acid/oxygen modified asphalt, contacting it with a thermoplastic elastomer and then with specified unsaturated functional monomers. Phosphoric acid is disclosed as one of the mineral acids. U.S. Pat. No. 5,565,510 discloses the addition of polyphosphoric acid to bitumen then blending with that product a polymer containing a propylene homo- or co-polymer, a xylene soluble co-polymer fraction and optionally a xylene insoluble ethylene co-polymer fraction. U.S. Pat. No. 3,751,278 discloses treatment of an asphalt with a phosphoric acid mixture having a H
3
PO
4
equivalent of greater than 100% concentration and including ortho-, pyro-, and poly-phosphoric acids. However, polymer addition is not taught or suggested. German patent DE 2255173 C3 teaches the use of 85% o-phosphoric acid, i.e., the addition of low molecular weight phosphoric acid. None of the above patents teach or suggest the addition of superphosphoric or polyphosphoric acid to the asphalt which contains polymer enabling a cross-linking between asphalt and polymer moieties.
Thus, there is a continuing need for new compositions having both enhanced low and high temperature service properties that minimizing the amount of costly additional materials such as monomers and polymers and process steps such as air blowing when making polymer modified asphalt binders. Applicants' invention addresses these needs.
SUMMARY OF THE INVENTION
The present invention provides for modified asphalt binder compositions and the method of making the compositions including phosphonated polymer modified asphalt binder composition having enhanced viscoelastic properties, over a wide temperature range, comprising a storage stable blend of:
an admixture of phosphoric acid having an H
3
PO
4
equivalent of at least 100%; a major amount of an asphalt having a flash point of at least 230° C.; and a minor amount of a polymer selected from polymers having at least one diene monomer or unsaturated bond. Polymer is present in the range of 0.5-7 wt %, preferably 0.5-3 wt % polymer to total composition. The phosphoric acid is admixed in the range of 0.05-2 wt %, preferably not more than 0.7 wt % based on the weight of the total composition. Typically, the starting asphalt has a penetration of 50-600 dmm.
The invention also includes combination of the novel binder compositions with aggregate.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed herein and includes the products produced by the processes disclosed herein.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides for novel polymer modified asphalt binder and paving compositions, and their methods of preparation and use. The compositions possess enhanced viscoelastic properties at both low and high temperatures. Desirably, these performance characteristics can be achieved at lower amounts of added polymer (typically 30-70% less) than are currently used for a given grade of polymer modified asphalt.
It has been discovered that storage stable polymer modified asphalt binders having low temperature performance (equivalent to base/unmodified asphalt) and having enhanced rutting resistance can be produced by combining a blend of asphalt and polymer with a phosphonating agent having H
3
PO
4
equivalent concentration of greater than 100%, such as superphosphoric acid (i.e., having H
3
PO
4
equivalent concentration of 105%) and polyphosphoric acid (i.e., having H
3
PO
4
equivalent concentration of 115-117%). Typically the foregoing acids will have a viscosity at 100° C. of from 36 to 1,010 cP. An amount of 0.05-2 wt %, preferably 0.05-0.7 wt %, of the phosphonating agent is added to the asphalt and polymer mixture.
Superphosphoric acid is represented by a formula of H
3.3
P
1.3
O
5
and a molecular weight of approximately 125 and polyphosphoric acid is represented by a molecular formula of approximately H
5.5
P
3.5
O
11.5
and a molecular weight of approximately 296. Typically grades include 105% for superphosphoric acid (designated herein as SP 105), and 115% and 117% (designated herein as PP 115 and PP 117) for polyphosphoric acid.
Superphosphoric acid having a H
3
PO
4
equivalent concentration of 105% typically has an orthophosphoric content of about 49%, pyrophosphoric content of about 42%, triphosphoric content of about 8%, tetraphosphoric content of about 1%. Polyphosphoric acid having H
3
PO
4
equivalent concentration of 115% contains typically about 5% orthophosphoric content, about 16% pyrophosphoric, about 17% triphosphoric, about 16% tetraphosphoric and 46% higher acids. Polyphosphoric acid having H
3
PO
4
equivalent concentration of 117% contains typically about 2% orthophosphoric content, about 7% pyrophosphoric, about 8% triphosphoric, about 11% tetraphosphoric and 72% higher acids, as known in the art (see, e.g., FMC Technical Data Sheet, CAS No. 8017-16-1).
Super- and poly-phosphoric acids provide an advantage over phosphoric acid (i.e., acid having H
3
PO
4
equivalent of less than 100%) in that the super- and poly-phosphoric acids are not water-based and range from very low to no corrosivity while phosphoric acid is water-based and highly corrosive. H
3
PO
4
contains water that can cause a violent reaction when contacted with hot asphalt under typical blending conditions (120-200° C.). High water evaporation rates can result in foaming and splattering, which was not recognized in the art. Applicants have discovered that superphosphoric and polyphosphoric acids, by contrast, readily can be incorporated into hot polymer modified asphalt, while minimizing foaming or undesirable byproducts.
Storage stability means that the polymer and asphalt phases do not segregate on standing for a specified period of time, usually 2-3 days, at a specified elevated temperature, u
Puzic Olga
Williamson Kenneth Edward
Cain Edward J.
ExxonMobil Research and Engineering Company
Scuorzo Linda M.
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