Note: Descriptions are shown in the official language in which they were submitted.
CA 02509284 2011-02-18
IMPROVED RUBBER MODIFIED ASPHALT CEMENT COMPOSITIONS AND
METHODS
FIELD OF THE INVENTION
The present invention generally relates to methods of making improved rubber
modified asphalt cement compositions, and compositions made by the method,
where
the compositions are useful in paving, roofing, coating and other sealing
applications.
BACKGROUND OF THE INVENTION
Ever since the first United States patent was issued in 1930 to Samuel Sadtler
(United States Patent No. 1,758,913) for a rubber and asphalt mixture for use
as a
road surface product, the asphalt industry has continued to devise new methods
for
the production of rubber modified asphalt cement (RMAC).
To date, some of the processes for producing RMAC include the addition of
solubilized rubber crumb (United States Patent No. 5,798,394, Meyers et al.)
gelled
crumb rubber (United States Patent No. 3,891,585, McDonald), melted crumb
rubber
(U.S. Pat No. 5,492,561, Flanigan I) (United States Patent No. 5,334,641,
Rouse),
mechanically sheared (United States Patent No. 6,66,676, Rouse et al.), and/or
acid
treated asphalt (United States Patent No. 5,095,055, Moran) for incorporating
vulcanized rubber into asphalt. Memon (United States Patent No. 6,444,731)
teaches
addition of a dispersion agent, such as furfural and/or vegetable oil) to the
crumb
rubber material, which is then heated at elevated temperatures that can be as
high as
1500 C, to ensure the rubber is fully treated with the dispersion agent. The
treated
rubber is then added to hot asphalt, after which an activator (a Lewis acid
that contains
a trace of sulfur) and a micro-activator (phenyl formaldehyde resin) are added
and
mixed, to achieve a modified asphalt.
Although prior art processes have made some inroads in improved production
of RMAC, the hurdle remains to find a way to devulcanize recycled vulcanized
particulate rubber (RVPR) and incorporate it into the asphalt in a single step
process.
Such a process should not degrade the asphalt or the rubber through the use of
high
temperatures, require highly sophisticated equipment or release harmful toxins
into the
air.
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CA 02509284 2011-02-18
SUMMARY OF THE INVENTION
The present invention provides a method for devulcanizing recycled vulcanized
particulate rubber (RVPR) and incorporating it into the asphalt in a process,
such as a
single step process. The method does not degrade the asphalt or the rubber
through
the use of high temperatures, does not require highly sophisticated equipment
and
does not release harmful toxins into the air. The invention also discloses
improved
RMAC products made by the method of the invention.
In one aspect, a method of the invention comprises the step of combining
asphalt, rubber and at least one dodecyl or tridecylbenzene sulfonic acid
(AS), which
can be linear (LAS) or branched (BAS), in the presence of moderate heat and/or
mixing to form rubber modified asphalt. The components may be combined in
various
orders. In some applications, the asphalt may be initially combined with the
dodecyl or
tridecylbenzene sulfonic acid (e.g., DDBSA) and the rubber may then be added
with
heat and/or mixing. Although any suitable temperature may be used, the
temperatures
used are preferably in the range of about 225 to about 450 F (ca. 107 C to
about
232 C), most preferably at about 350 F (ca. 177 C). Although any type of
rubber may
be used, one type of rubber that may be preferable is crumb rubber obtained
form
recycled vehicle tires. Rubber particles of any suitable size may be used. In
some
applications, crumb rubber particles sized to pass through a U.S. series sieve
as large
as a #9 mesh may be employed.
The asphalt may be initially combined with at least one dodecyl or
tridecylbenzene sulfonic acid with heat and/or mixing and then subsequently
adding
recycled vulcanized particulate rubber to the mixture.
The asphalt may be from about 65 to about 98 percent, the recycled vulcanized
particulate rubber may be from about 1 to about 25 percent, and the at least
one
dodecyl or tridecylbenzene sulfonic acid may be from about 1 to about 10
percent,
based on weight.
The recycled vulcanized particulate rubber may pass through a #4 mesh US
Series sieve.
Further in accordance with the invention, there is provided a method for
making
rubber modified asphalt wherein asphalt is combined with rubber or RVPR (or a
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blended mixture of asphalt and RVPR) and at least one dodecyl or
tridecylbenzene
sulfonic acid (AS), which can be linear (LAS) or branched (BAS), in the
presence of
moderate heat. Preferably, the mixture of asphalt, rubber or RVPR and the
SA(s) are
heated at temperatures of about 225 to about 450 F. (ca. 107 C. to about
232 C.),
most preferably at about 350 F. (ca.177 C.). The mixture is heated,
preferably for
about 1 - 2 hours, or until the resultant RMAC mixture exhibits at least one
of the
following: (1) an increase in softening point, (2) an increase in hardness, or
(3)
improved recovery from deformation. For paving compositions, the resultant
RMAC
mixture is mixed with an appropriate grade of aggregate composition, and other
paving
materials as desired. The resultant RMAC may also be emulsified in an aqueous
solution to form a seal coat.
According to ,the another teaching of the present invention, sulfonic acids of
dodecylbenzene and tridecylbenzene may also be added to previously
manufactured
RMAC to accomplish at least one of the following in the resultant improved
RMAC: (1)
an increase in the softening point, (2) an increase in the hardness, or (3) an
improvement in the recovery from deformation, of the resulting improved RMAC
compositions. This aspect of the invention includes a method for improving at
least one
of (1) the softening point, (2) the hardness, or (3) the recovery from
deformation of a
RMAC composition comprising adding at least one dodecyl or tridecylbenzene
sulfonic
acid (SA), in the amount of from about 1 to about 10 percent, WNV, to the RMAC
in the
presence of moderate heat (about 225 to about 450 F. (ca. 107 C. to about
232
C.)) for about 1 -4 hours, and improved RMAC compositions made by this method.
In preferred form, for use in the present invention, the sulfonic acid is a
linear
dodecylbenzene sulfonic acid with from about 1 to about 18 alkyl groups.
Especially
preferred is dodecylbenzene sulfonic acid (or DDBSA, which is also known as
DBSA).
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram of the experimental apparatus used in Example 4 below.
DETAILED DESCRIPTION AND EXAMPLES
The following detailed description with examples, and the accompanying
drawings and tables to which it refers, are provided for the purpose of
describing and
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illustrating certain examples or specific embodiments of the invention only
and not for
the purpose of exhaustively describing all possible embodiments and examples
of the
invention. Thus, this detailed description with examples does not in any way
limit the
scope of the inventions claimed in this patent application or in any patent(s)
issuing
form this or any related application.
Example I
Method
A. 400 grams of asphalt (AR4000, San Joaquin Refining, Bakersfield,
CA), with a softening point of 118 F. (ca. 48 C.) and a penetration of
33 at 77 F. (25 C.) was heated for about 60 minutes at about 350 F.
(ca. 177 C.) until it was free flowing and then mixed with 59.77 grams
of 80 mesh crumb rubber (BAS Recycling, Inc., San Bernardino, CA).
B. A portion of the mixture was then drawn off and tested.
C. 18.39 grams of DDBSA (Pilot Chemical, Inc., Santa Fe Springs, CA)
was then added all at once to the non-drawn off and remaining portion
of the rubber/asphalt mixture, which was then continuously blended
with a simple propellor mixer for a period of about 2 hours at a
temperature of about 350 F. (ca.177 C.).
Result
The addition of the DDBSA increased the softening point and hardness of the
compositions. The test results are set forth in the following table.
Composition Penetration Softening Point
A Asphalt Alone 33 118 F. (ca. 48 C.)
B Asphalt/Rubber 29 141 F. (ca. 61 C.)
C Asphalt/Rubber/DDBSA 22 153 F. (ca. 67 C.)
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Example 2
Method
604.7 grams of asphalt (AR4000, Paramount Petroleum Company, Paramount,
CA), with a softening point of 117 F. (ca. 47 C.) and a penetration of 47 at
77 F. (25
C.) was heated at about 350 F. (ca.177 C.) for about 60 minutes until it was
free
flowing and then mixed with 66 .52grams of 20 mesh crumb rubber (BAS
Recycling,
Inc., San Bernardino, CA) together with 24.188 grams of DDBSA (Pilot Chemical,
Inc.
Santa Fe Springs, CA). The rubber/asphalt/DDBSA mixture was heated to a
temperature of about 350 F. (ca. 177 C.) and mixed with a simple propellor
mixer.
Samples were drawn and tested at elapsed times of 0.5 hours, 1 hour,2 hours
and 3
hours. The changes occurring in the mixture as exhibited by the corresponding
test are
included in the table below.
Heat Time and Sample Penetration Softening Point
No heat, Original Mixture (OM) 47 117 F. (ca. 47 C.)
0.5 hour heat + OM + DDBSA 27 152 F. (ca. 67 C.)
1.0 hour heat + OM + DDBSA 26 150 F. (ca. 66 C.)
2.0 hour heat + OM + DDBSA 26 150 F. (ca. 66 C.)
3.0 hour heat + OM + DDBSA 26 147 F. (ca. 64 C.)
Example 3
Method.
A blended and homogenous mixture of RMAC containing approximately 13.25%
crumb rubber from recycled tires (MAC10- TR) was reacted with increasing
percentages
(by weight) of DDBSA. The mixtures were mixed with a simple propeller mixer
and
heated at a temperature of about 350 F. (ca.177 C.) for about 60 minutes.
Results
These tests demonstrate that the greater the amount of DDBSA, the higher the
softening point and the greater the penetration. Results are summarized in the
table
below.
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Sample Penetration @ Softening Point
DDBSA 77 F. (25 C.)
MAC 10-TR, W/O DDBSA 0 46 124 F. (ca. 51 C.)
MAC 10-TR, W/2% DDBSA 2 33 150 F. (ca. 66 C.)
MAC 10-TR, W/4% DDBSA 4 20 152 F. (ca. 67 C.)
MAC 10-TR, W/6% DDBSA 6 23 163 F. (ca. 73 C.)
Example 4
DDBSA (which is also known as DBSA) Reactions with Asphalt and Crumb Rubber.
Summary:
Several experiments were carried out to determine the nature of gases evolved
(if any) when asphalt was heated to about 300 F. (ca.149 C.) by itself, when
DBSA
was heated to the same temperature by itself, then with asphalt, with crumb
rubber, and
finally with both asphalt and rubber crumb. Gasses evolved were trapped in
tedlar bags
attached to the closed system being heated. Figure 1 is a diagram of the
experimental
set up 10 which comprised a hot plate/magnetic stirrer base 12, a sealed flask
14, a
thermometer 16, a sealed bag 18 (i.e., a Tedlar bag) and a tube 20 connecting
the
interior of the flask 14 to the interior of the bag 18. Asphalt and DDBSA were
combined
in the flask and heated to about 300 F. (ca. 149 C.). Foaming occurred in
flask 14
and elemental sulfur was deposited on the cooled glassware, but no gasses were
observed to collect in the bag 18. When a mixture of crumb rubber and DDBSA
were
placed in the flask 14 and heated to around 300 F. (ca. 149 C.), elemental
sulphur
and gases containing hydrocarbons and sulfur compounds were evolved and
collected
in the bag 18. When crumb rubber, asphalt and DDBSA were combined in the flask
and heated to a temperature of about 300 F. (ca.149 C.), foaming occurred in
the
flask and*evidence of formation of elemental sulphur and evolved gases were
observed
to collect in the bag 18. These major hydrocarbon gases and sulphur containing
gasses
were identified by gas chromatography/and mass spectrometry (GC/MS). This
involves
separating the gases from each other (GC), then identifying the gas after it
had been
bombarded with electrons (MS) with the help of a computerized catalogue
containing
spectra of about 80,000 compounds.
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These preliminary experiments revealed that the role of DBSA in the reaction
involving crumb rubber and asphalt appears to be de-vulcanization of the
rubber
crumb. DBSA also has the capability to catalyze reactions of the de-vulcanized
rubber
with molecules present in asphalt (particularly any molecules with double
bonds.) This
catalytic role can apparently continue even after the rubber asphalt has been
emulsified (i.e., carbon to carbon bond formation can continue even in the
presence of
water). As a strong surfactant, DBSA would stabilize the asphaltenes (and
hence the
entire system) in an asphalt-rubber system. The presence of DDBSA when the
asphalt-rubber mixture is emulsified may provide additional emulsion
stability. There
was no evidence of gas evolution when duplicate samples of DBSA (50 grams of
material provided by Ram Technologies) were heated for 45 minutes at
temperatures
ranging between 138 C (280 F) and 175 C (347 F). In other words, the tedlar
bag d
not become inflated during that time.
Similarly, there was no evidence of gases being evolved and trapped by the
attached tedlar bag when asphalt (50 grams PG58-28 from McAsphalt Industries
in
Winnipeg) was heated alone at 149 152 C (300-306 F) for 15 minutes.
Experimental:
Asphalt Heated with DBSA
DBSA was added to asphalt (500 grams of PG58-28 from McAsphalt Industries
in Winnipeg) that had been heated in a flask to 149 C (300 F), and the system
rapidly
closed again to allow the bubbling gases to enter the tedlar bag. The asphalt-
DBSA
mixture continued to be stirred for 43 minutes (as long as some foam bubbles
were still
being formed on the surface of the asphalt) at temperatures that ranged
between 147
and 155 C (297-311 F). In spite of all the bubbling and foaming that was
taking place
in the flask, there was no evidence of gas being collected--the tedlar bags
remained
uninflated. This was true whether 8.5 grams or 26.1 grams of DBSA had been
added
to the flask containing 500 grams asphalt. However, there was evidence of some
milky
liquid condensing on the walls of the flask.
Peak area is generally proportional to concentration. Approximate
concentrations were calculated assuming that the peak areas were directly
proportional to mass.
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Table 1
Identity and Normalized Approximate % Concentration* of the 10-12 Largest
Peaks in the
Sample as Detected by a Capillary Gas Chromatograph-Mass Selective Detector
Compound Reactants
PG58-28 Asphalt + PG58-28 Asphalt +
Rubber Crumb + Rubber Crumb +
Rubber Crumb + Rubber Crumb +
DBSA DBSA
(t = 0-12 minutes at (t = 12-195 min. DBSA, Run 1 DBSA,
Run 2
140 -199 C or at 149 -210 C or (t = 130 minutes
at (t = 126 minutes at
144-168 C or 141-158 C or
284-390 F) 300-410 F)
291-334 P) 286-316 P)
_
2-methyl propane 9.33 32.81 0.92 0.30
2-methyl-1-propene 6.28 18.41 0.44 0.46
2-methyl butane 1.97 2.51 3.19 0.24
butane - _ 4.76 0.34
2-methyl-l-butene 0.94 3.56 0.45 -
pentane _ - 0.98 -
2-pentene - - 0.41 -
2-methyl pentane - 1.78 0.87 0.26
2-methyl-2-pentene 0.65 2.06 - -
2,4,4-trimrthy1-1-
0.75 1.91 - .
pentene
2,3,4-trimrthy1-2-
1.36 2.59 . -
pentene
. _
2,2-dimethyl hexane - - - 0.22
3,4-dimethyl hexane_ - 0.51 ..
2,5-dimethy1-2-hexane 0.83 2.13 - -
2-methyl-2- 0.57
propanethiol
- - _
Carbon disulfide - 0.21
Hydrogen sulfide - 4.74 1.67 2.88
Sulfur dioxide 5.31- - _
Air (oxygen, nitrogen,
carbon dioxide + 72.02 27.49 85.80 95.07
argon)
*Peak area is generally proportional to concentration. Approximate
concentrations were calculated assuming
that the peak areas were directly proportional to mass
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CA 02509284 2011-02-18
From the results in Table 1, it appears that air (displaced from the rubber
crumb surface) made up most of the gas filling the bag 18 in the first 12
minutes of the
reaction. After that, pyrolysis gases like 2 methyl propane and 2-methyl
propene from
the decomposition of rubber crumb in the presence DBSA began to dominate the
gases evolved. In the presence of asphalt, however, it appears that while some
of
these molecules are still evolved from the rubber crumb, many appear to have
been
either absorbed into the asphalt or reacted with molecules in the asphalt. It
must be
noted, however, that temperatures of mixtures in asphalt were much easier to
control
than temperatures of the DBSA-rubber crumb mixture, which rose uncontrollably
high,
leading to significant pyrolysis of the rubber crumb.
Since no gases had been evolved when DBSA was heated with asphalt alone,
the gases collected when DBSA was heated with asphalt and rubber crumb would
likely have come from the rubber crumb.
In the flask 12 containing 500 g asphalt and 26.1 g DBSA, an attempt was
made to encourage evolving gaseous (or liquid) materials to enter the tedlar
bags
instead of condensing on the flask walls. The top and neck of the flask were
wrapped
to insulate the area in the flask above the hot asphalt and heating was
continued for a
further two hours. This resulted in the deposition of a thin cream coloured
solid layer in
the glass side arm of the adapter and in the glass tubing acting as an adapter
to
connect the side arm to the flexible tubing connected to the tedlar bag. This
cream-
coloured solid sublimed off the glass surfaces within a day at room
temperature. This
is strong evidence that sulfur present in asphalt had been released when
asphalt was
heated in the presence of the DBSA. However, there was no evidence of bag 18
inflation even after of two hours and 42 minutes of heating asphalt with DBSA
at
temperatures that ranged between 141 and 155 C (286-311 F).
Rubber Crumb Heated with DBSA
When rubber crumb (80 mesh, 66 grams) was combined with DBSA (31.1
grams), not all the rubber crumb was wetted by DBSA, resulting in uneven heat
transfer within the mass inside the flask 12. Temperature control was
difficult. As
heating progressed, some small areas of wetness and bubbling appeared in a few
areas of the rubber mass. As each bubble broke, a puff of smoke issued forth.
Within
an eight minute period, the measured temperature in one area of the rubber
mass
9
CA 02509284 2011-02-18
rose from 140 C (284 F) to 199 C (390 F). The first bag 18 rapidly filled
w was
replaced with a second bag 18 after twelve minutes. The measured temperatures
ranged between 149 C (300 F) and 210 C (410 F) over the next three hours
and 3
minutes as gases were collected in the second bag 18.
The top part of the flask 12 had been insulated to allow evolving gases to
pass
into the second bag 18. When the heating was ended and insulation removed, a
creamy colored condensate was observed moving down the neck of the flask 12. A
sulfurous smell came forth when the adapter was removed from the flask 12 to
expose
the flask contents to the air.
Heating Asphalt with Rubber Crumb and DBSA Rubber crumb (80 mesh, 66
grams) was mixed with DBSA (29.3 and 32.7 grams respectively added to Flasks 1
and 2) and then added to flasks of pre-heated asphalt (430 grams of PG58-28,
preheated to 120 C [248 F], in each of Flasks 1 and 2). The system was
rapidly
closed and connected to tedlar bags that were opened immediately to collect
any
evolving gases produced. Occasional gentle manual flask shaking was needed to
supplement the magnetic stirring to incorporate the rubber crumb into the
asphalt.
Foaming and bubbling increased as the mixture was heated and stirred. Heating
in
Flask 1 continued for 130 minutes, maintaining temperatures between 144.5 and
168
C (292-334 F). Heating in Flask 2 continued for 126 minutes, with
temperatures
ranging between 141 and 158 C Both tedlar bags showed evidence of some gas
having been collected. A cream coloured condensate was observed on the upper
(cooler) parts of the flask.
ANALYSES OF VOLATILE REACTION PRODUCTS:
The four bags 18 that showed evidence of having collected gases were
analyzed for volatile organic compounds and for sulfur compounds by GC/MS as
mentioned earlier. The results of these analyses are shown in Tables 1 and 2.
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Table 2-Sulfer Compound Gas Analysis
Identity and Normalized % Concentration of Sulfur Compounds in Gasses Evolved
Compound Reactants
PG58-28 Asphalt + PG58-28
Asphalt +
Rubber Crumb + Rubber Crumb +
Rubber Crumb + Rubber
Crumb +
DBSA DBSA
DBSA, Run 1 DBSA, Run 2
(t = 0-12 minutes at (t = 12-195 min. at
140 -199 C or 149 -210 C or (t = 130 minutes at 144- (t =
126 minutes at
168 C or 141-158 C or
284-390 F) 300-410 F)
291-334 P) 286-316 P)
Carbon disulfide 13.6 6.21 1.79 1.14
Hydrogen sulfide 55.2 82.3 96.96 97.80
Sulfur dioxide -* - - -
Methyl mercaptan 0.30 0.27 0.15 0.22
Ethyl mercaptan 1.43 0.08 0.15 0.06
n-propyl mercaptan - 0.02- -
i-propyl mercaptan 0.39 0.19- 0.04
n-butvl mercaptan 1.67 1.26- 0.03
Sec-butyl
0.23 0.06- 0.03
mercaptan
t-butyl mercaptan 26,85 9.22 0.95 0.64
Dimethyl sulfide 0.14 0.26 - 0.03
Methylethyl sulfide - 0.08 - -
,
Diethyl sulfide 0.25 0.07 - 0.01
* Inconsistent with the findings of major peaks for this sample as shown in
Table 1
=
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From Table 2, it is apparent that the reaction of rubber crumb with either
rubber
crumb or with asphalt in the presence of DBSA produces a number of
sulfur-containing compounds, with hydrogen sulfide being by far the most
dominant
species. Since only solid sulfur but no gases had been evolved during the
heating of
asphalt alone with DBSA, it appears that that the sulfur-containing gases
evolved
during the heating of asphalt, rubber crumb and DBSA would have originated
from the
rubber crumb.
Crumb rubber consists of vulcanized polymers obtained from the treads of
tires.
Tire rubber vulcanization involves using sulfur to cross-link the polymers,
which are
mainly a blend of butadiene and styrenebutadiene-styrene polymers. The
presence
of hydrogen sulfide and other sulfur-containing compounds in the gases evolved
when
rubber crumb was heated in asphalt in the presence of DBSA is a strong
indicator that
rubber crumb is being de-vulcanized - the sulfur cross-links are being
eliminated -
during the process.
CONCLUSION
The role of DBSA in the reaction involving rubber crumb and asphalt appears
to be de-vulcanization of the rubber crumb. DBSA also has the capability to
catalyze
reactions of the de-vulcanized rubber with molecules present in asphalt
(particularly
any molecules with double bonds). This catalytic role can apparently continue
even
after the rubber asphalt has been emulsified (i.e. carbon to carbon bond
formation can
continue even in the presence of water). As a strong surfactant, DBSA would be
effective in stabilizing the asphaltenes (and hence the asphalt) within the
rubber-asphalt mixture. Furthermore, in an emulsion, DBSA can then play the
role of
an additional emulsifier, which may be important in maintaining emulsion
stability.
Example 5
Tables 3 and 4 below list various aggregates Aggregate Compositions That
May Be Mixed With the Improved Rubber Modified Asphalt Cement Compositions of
the Present Invention.
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Table 3
Dense Graded Aggregate '
_
, I
V I I
19-mm Maximum, Coarse 12.5-mm Maximum, Medium
Limits of Limits of
Proposed Operating Proposed Operating
Sieve Sizes Gradation Range Sieve Size; Gradation Range
25-mm - 100 19-rnm ' - 100
19-mm , - 90-100 , 12.5-mm ' - ¨ 95-
100
-
9,5-mm - 60-75 9.5-mm - 00-95
475-mm 45-50 X+/-5 4,75-mm 59-66 X+/-5
2,36-mm r 32-36 X+/-5 2.36-mm 43-49 X+1-5
600-urn 15-18 k+/-5 , 600-urn 22-27 X+1-5 .
75-urn ' - 3-7 75-um - 1 3-6
. 1.
19-mm Maximum, Medium 9.5-rnm Maximum
-
,
' Limits of ' Limits of
Proposed Operating Proposed Operatng
Sieve Sizes Gradation Range Sieve Sizes,Gradation, Range
25-rrm - 100 . 12.5-mm - 100
19-Mm - 5-100 2,5-mm - 95-100
9.5-mm - 65-80 4,75-mm 73-77 X4-1-6
- 4.76-mm 49-54 X+/-5 2,36-mm 55.63 X+1-6
, -
, 2,36-mm 36-40 , X44-5 600-urn 29-34
600-um 16-21 X41-5 - 75-urn - 3-10
75-urn 1 - 3-8 I
1 I
1 . 1 .
12.5-mm Maximum, Coarse 4.75-mm Maximum
Omits of . Limits of
Proposed Operating - Proposed Operating
Sieve Sizes Gradation Range Sieve Sizes Gradation Range
...
19-mm - 100 9.6-mm - 100
12.5-mm - 95-100 ,.. 4.75-rnm - 95-100
- , ,
9.5-mm - 75-90 2.36-rrm 72-77 X+1-6
,
4.75-mm 55-61 '-- X+/-5 600-urn 37-43 X-1-7
2.36-mm 36-40 X+/-5 . 75-urn - 93 3-12
..
600-urn 18-21 X+/-5
. . ___________________
75-urn - 3-7 1 ____ .
. . . I .
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Table 4
Min
IIIIIMIIIII
IMNIMIIIIIIIIIWIIIIIIIIIIIIIIMIIIIIIIIII
Open Graded Aggregate
1 = ;
9.5-mm Maximum
125 mm Maximum
Limits of Tisof
Proposed Operating PrOposed
Operating
Sieve Sizes Gradation Range SieVe Sizes Gradation Range
19.mm , - 100 EOM - 100
12.6-mm - 95-100 9.6-min - 90.100
95 ram 7849 X14-4 4.76-mm 29-36 X-14-4
475 mm 28-31 ' *14 236 mm 748
X+i,4
236 mm 12-18 X+/4 600 urn - 0-10
600 urn - 0-10 75-uin . 0-3
75-urn - 0-3 MEE
i
T as A and B Asphalt Concrete Base
Ell ________________________________________________________ 1111=11111=
Ferrante 00 Passing
Li MINI
mits of Mil
Proposed Operating _______________________ l
Sieve Sizes Gradation Range s I --
31 -5 -mm - 100 ilL111111111¨ mos
29-mm MUM 95-100
111111111111111111111111111
1 9-rnin - i0-100
9.5-mm 55-60 IMP IIIIIIIIII
4J5-mm 40-45 X+1-5 IIIIIIINUIIIIIIIMIIIIIIIIIMIIIIIIIIII
800 urn- 14.19 R475
7s-urn
DEFINITIONS
The following terms of art used in the present specification and claims are
defined as follows:
As used herein, "asphalt" includes bitumen, as well as naturally occurring
asphalt, synthetically manufactured asphalt as the by-product of the petroleum
refining process, blown asphalts, blended asphalt, residual asphalt, aged
asphalt,
petroleum asphalt, straight- run asphalt, thermal asphalt, paving grade-
asphalt, and
the like.
As used herein, "blended asphalt rubber" means RVPR and asphalt blends that
have been prepared by methods such as those disclosed in US Patents No.
5,492,561 (Flanigan I), No. 5,583,168 (Flanigan II), and No. 5,496,400 (Doyle
and
Stevens) which disclose so-called , "TRMAC" processes for blending RVPR and
asphalt. In the TRMAC process, RVPR and asphalt are heated to temperatures in
14
CA 02509284 2011-02-18
excess of 400 F (205 C) under carefully controlled conditions that require
sophisticated equipment and environmental controls. Flanigan I requires the
introduction of oxygen into the mix during admixing and heating; Flanigan II
requires
that the mixing and heating occur in a vacuum. The Doyle/Stevens process, used
by
Doyle-Ellis, uses a process in which the PVPR is pretreated with a cross
linking agent
consisting of tall oil, a strong base, an anhydrous organic solvent and fatty
amines
prior to being incorporated into hot liquid asphalt. Commercial forms of
blended
asphalt rubber are available as MAC 10- TR from Paramount Petroleum Company,
Paramount, Calif. or Doyle-Ellis, LLC, Bakersfield, Calif.) or AC5-15 TR (also
available
from Paramount Petroleum Company). The teaching of the present invention
includes
post addition of sulfonic acids of dodecylbenzene and tridecylbenzene to
previously
manufactured RMAC to accomplish at least one of the following: (1) an increase
the
softening point, (2) an increase the hardness, or (3) an increase in recovery
from
deformation, in the resultant RMAC compositions.
As used herein, "RMAC" means rubber modified asphalt cement. TRMAC
means tire rubber modified asphalt cement. RAC means rubberized asphalt
cement.
The terms RMAC, TRMAC and RAC are used interchangeably.
As used herein, "RVPR" means recycled vulcanizate (or vulcanized) particulate
rubber. The term "crumb rubber" or "rubber crumb" are used interchangeably
with
RVPR. RVPR is classified by particle size and grade (based on the polymer type
of the
parent compound from which the RVPR is derived). The RVPR classifications are
the
those published in the American Society for Testing and Materials publication
"Standard Classification for Rubber Compounding Materials--Recycled
Vulcanizate
Particulate Rubber", Designation: D 5603-96, published January, 1997. In sum,
"coarse rubber powders" are products with designations of 425.about.m (40
mesh) or
larger. Coarse powders typically range in particle size from 2000.about.m (10
mesh) to
425.about.m (40 mesh) regardless of polymer type or method of processing.
"Fine
rubber powders" are products with designations of 425 µm (40 mesh) or
smaller.
These materials typically range in particle size from 300 µm (50 mesh) to
less than
75 µm (200 mesh) regardless of polymer type or method of processing. Grades
of
RVPR are based on polymer/compound types of the parent compounds, with Grades
1, 2 and 3 being the most common, Grades 4, 5 and 6 less common. Grade 1
designates whole tire RVPR prepared from passenger car, truck, and bus tires
from
which the fiber and metal have been removed. The rubber is then
CA 02509284 2005-06-10
WO 2004/055115 PCT/US2003/039570
process to the desired particle size. Grade 2 designates RVPR made from so-
called
"peel rubber", while Grade 3 designates RVPR made from retread buffings only.
As used herein the words "vulcanizate" and "vulcanized" are used
interchangeably. As used herein, "cured rubber" means a composition consisting
of
thermoplastic polymer resins having no epoxy groups.
As used herein, "DDBSA" means dodecylbenzene sulfonic acid. DBSA is used
interchangeably with DDBSA.
As used herein, the term "sulfonic acids of dodecylbenzenes and
tridecylbenzenes" 15 refers to members of the group of chemical compounds also
known as alkylbenzene sulfonics (AS). For use in the invention, the
alkylbenzene
sulfonics can be linear (LAS) or branched (BAS). Preferred LAS and BAS
compounds
for use in the present invention will have from C-1 to about C-20 alkyl
derivatives.
Dodecylbenzene has the chemical formula C12H25-C6F15. Tridecylbenzene has
the chemical formula C13H27-C6H5. For use in the present invention, the
sulfonic group
can be placed on the benzene ring on the carbon atom either next to the
dodecyl or
tridecyl group (at the "ortho" position), or on the second carbon atom over
from the
dodecyl or tridecyl group (at the "meta" position), or on the third carbon
atom over
from the dodecyl or tridecyl group (at the "pare" position), to give molecules
with the
formula C12H25-C6H4 - SO 3H (o-, m - or p-dodecylbenzene sulfonic acid) or
C13H27-
C6H5 - SO 3H (o-, m - or p- tridecylbenzene sulfonic acid).
Dodecyl and tridecyl groups are known as alkyl groups since they are derived
from alkanes (dodecane and tridecane, respectively). For use in the present
invention,
the alkyl groups can be as short as the methyl group CH3- with only one carbon
atom
(derived from methane) or as long as the octadecly group with 18 carbon atoms
(common in fats) or longer (as found in some heavy crudes). Also for use in
the
present invention, the alkyl groups can be in the form of straight chains, or
may
contain any number of side branches of smaller alkyl groups.
As used herein, the terms blending or mixing include methods of combining
ruber, asphalt and AS through simple agitation with a propeller or any other
mixing
apparatus as well as aggressive agitation with high shear and also may include
the
mixing of asphalt rubber and AS by passing the combination through a colloid
or other
mill. Such other methods of blending and mixing are known to those skilled in
the art.
The use of shear and or milling can be used to impart heat to the mixture as
well as
shorten the time for reaction between the asphalt and rubber through the use
of AS.
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PCT/US2003/039570
Although exemplary embodiments of the invention and specific examples have
been described, various changes, modifications and substitutions may be made
by
those having ordinary skill in the art without necessarily departing from the
spirit and
scope of this invention. Specifically, elements or attributes described in
connection
with one embodiment or example may also be used in connection with any another
embodiment or example provided that the inclusion or use of such element or
attribute
would not render the embodiment or example in which it is incorporated
unuseable
or otherwise undesirable for an intended application. Accordingly, all such
changes,
modifications and substitutions to the above-described embodiments and
examples
are to be included within the scope of the following claims.
17
