Low softening point petroleum pitch and sealer

Details Low softening point petroleum pitch and sealer Low softening point petroleum pitch and sealer

1999-11-16

2002-05-07

Griffin, Walter D. (Department: 1764)

Mineral oils: processes and products

Products and compositions

Asphalts, tars, pitches and resins

C208S022000, C208S044000, C208S045000

Reexamination Certificate

active

06383365

ABSTRACT:

BACKGROUND OF THE INVENTION
I. Field of the Invention
The invention relates to a low softening point petroleum pitch and sealer made from this pitch for asphalt pavement or metal surfaces.
II. Description of the Prior Art
There are two basic types of driveway or pavement sealer—coal tar based and asphalt based. These materials are primarily used to seal driveways and other pavement surfaces, but can also be used to seal or coat metal, wood, or cementitious surfaces, e.g., pipe coatings.
Coal tar is the premier product and has the largest market share. Driveway sealer made from coal tar is an emulsion of water, coal tar pitch, clay and water, perhaps with emulsifier and optional ingredients such as sand. These materials are long lasting, have a pleasing black color and resistance to gasoline and kerosene spills but have an objectionable odor during application and contain aromatic compounds.
Asphalt based materials are made from distilled petroleum fractions, typically vacuum tower bottoms or perhaps atmospheric tower bottoms. These heavy hydrocarbon fractions are sometimes oxidized or “blown” to change the asphalt properties. Asphalt based sealers do not smell as much as the coal tar based materials and are able to withstand a wider range of temperatures. The asphalt sealers are not as toxic and in some areas only asphalt-based sealers are sold. Asphalt sealers do not have the black color desired by many users. Asphalt sealers do not last as long, and frequently must be reapplied every year or every two years.
The goal of the present invention is to provide a low softening point pitch product similar to coal tar sealer base with similar physical properties such as viscosity and softening point. This material is intended to be a complete, or at least partial, replacement of coal tar, so that sealer base and driveway sealers with acceptable properties can be made with less, or no, coal tar pitch. With that goal in mind, some of the closest art known is reviewed hereafter. The art review can be arbitrarily grouped into four areas:
A. Coal tar driveway sealer
B. Blends of coal tar pitch/petroleum
C. Control of pitch production
D. Low softening point pitches
Coal Tar Driveway Sealer Art
U.S. Pat. No. 4,222,916, Hergenrother, RUBBERIZED COAL TAR PITCH EMULSION, discloses a coal tar based sealer with acrylate emulsion.
U.S. Pat. No. 4,537,635 Bart et al, teaches driveways sealers from oxidized coal tar.
As stated previously, most driveway sealer is either a premium product based on coal tar or a coal tar free, asphalt based product, which lasts for a year. Blends of coal tar and asphalt based products are not sold commercially. An additional concern is that coal tar based driveway sealers comply with the specifications for coal tar based sealers disclosed in ASTM D3320, Emulsified Coal Tar Pitch (Mineral Colloidal Type), and Federal Specification R-P=355e, Pitch, Coal Tar Emulsion (Coating for Bituminous Pavements), which specify use of coal tar pitch. Although coal tar/petroleum pitch blends are not used commercially in driveway sealers, there have been reports of pitch blends for other uses, reviewed next.
Blends of Coal Tar Pitch/Petroleum
Commercial blends of coal tar pitch and a minor amount of petroleum pitch have probably been made. For Aluminum anode binder pitch, reviewed in greater length hereafter, it has been common to “extend” the coal tar pitch by blending in up to 10% petroleum pitch, so that the pitch used was a 90:10 blend of coal tar:petroleum pitch. Some uses of petroleum pitch as an extender for driveway sealer may have occurred but they have not been reported in the literature.
Blends of coal tar with petroleum pitch are known in the art, but not for driveway sealer. This art, reviewed hereafter, is believed to be the closest to the low softening point petroleum pitch of the present invention.
U.S. Pat. No. 5,746,906 McHenry, et. al. May 5, 1998, disclosed a coal tar pitch/petroleum pitch blend and method of making it. A crude coal tar material is selected according to specific properties including QI, specific gravity, water and ash content. A petroleum pitch material is also selected according to its softening point, QI, coking value and sulfur content. The coal tar pitch is distilled to an uncharacteristically high softening point then mixed with a lower softening point petroleum pitch to a desired softening end point. The material retains significant QI and coking value characteristics of pure coal tar pitch particularly for use in Soderberg-type anodes for aluminum smelting as well as electric arc furnace electrodes. PAH emissions, and more specifically B(a)P equivalent emissions, are all reduced by approximately 40%.
The petroleum pitch used in '906 had a softening point of 80° C. nominal. This was mixed with coal tar pitch distilled to have a softening point of 130-175° C.
Control of Pitch Production
Control of coal tar pitch fractionation is described in U.S. Pat. No. 4,066,159.
Control of petroleum pitch fractionation is straightforward distillation.
It is easy to run any pitch fractionation process to produce a product with the desired softening point and this is the norm for most pitches, both coal tar and petroleum.
Low Softening Point Pitch
Some coal tar pitch materials are made with a relatively low softening point. For driveway sealer use, the coal tar pitch will typically have a softening point of around 40° C., as discussed in the driveway sealer art.
Some lower softening point petroleum pitches, which are solids at room temperature have been made by producing a high softening point material, e.g., A240, and blending this with cutter stock such as aromatic oil. It is possible to take A-240 pitch and cut it back with aromatic cutter oil to produce a nominally “solid” pitch specialty product having a low softening point. Some physical properties of various commercial petroleum pitch products are summarized in the following section.
TABLE 1
Specifications and Typical Properties of
Marathon Ashland Petroleum Pitch
CAS Number 68334-31-6
Test
A170
A240
A225
Analysis
Method
Pitch
Pitch
Pitch
Specification Points
Limits
Softening Point, Mettler
ASTM
79.4-82.6
118-124
105-110
° C.
D3104
Softening Point, Ring
ASTM
166-171
235-248
212-221
& Ball ° F.
D36
Flash, Cleveland Open
ASTM
200 
270
260
Cup, ° C. minimum
D92
Coking Value, Modified
ASTM
NA
49
46
Conradson Carbon, wt
D2416
%, minimum
Sulfur Content, wt %,
ASTM
NA
3.0
1.5
maximum
D1552 or
D4294
Typical Properties
Values
Specific Gravity, Helium
ASTM
  1.18
1.22
1.22
Pycnometer, g/cc,
D71
minimum
Moisture, wt %,
—
—
0.5
-
maximum
Toluene Insolubles, wt
ASTM
—
2.10
2.10
%, minimum
D4072
Quinoline Insolubles, wt
ASTM D
0
0.5
0.5
% maximum
2318
In addition to these high softening point materials, blends of A240 and #6 fuel oil have been made to produce specialty products ranging from thick liquids to materials having a softening point of 80° C.
“A 500” pitch is a viscous liquid, a blend of 35% A 240 pitch and 65% aromatic oil. The product has a viscosity specification of 230-300 centipoise at 160° F. This material is unsuitable for use as a driveway sealer.
“A 120” pitch is a blend of 37% A 240 pitch and 63% fuel oil. The semi-solid blend has a softening point of about 111° F. It has never been used in a driveway sealer formulation.
ART SUMMARY
This voluminous art could be summarized as follows. Driveway sealers are made from coal tar pitch (premium products) or asphalt, but not both. It is easy to control fractionation of pitch products to produce a pitch product with any desired softening point. Blends of coal tar pitch and petroleum pitch are used for making anodes for aluminum production. Blends of high softening point petroleum pitch with fuel oil or other cutter stock are known, but the blends produced to date have either been too thick or too thin for use as driveway sealer.
There is no commercially available petroleum pitch which can be used directly and without further modification in driveway sealer or for other sealer applications heretofore using coal tar pitch

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