U.S. patent application number 11/001361 was filed with the patent office on 2006-06-01 for bitumen/rubber compositions crosslinked with polythiomorpholines, polysulfides and/or mercaptobenzimidazole.
This patent application is currently assigned to Fina Technology, Inc.. Invention is credited to Paul J. Buras, James R. Butler, William Lee, Wendy Stanley.
Application Number | 20060116449 11/001361 |
Document ID | / |
Family ID | 36568144 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060116449 |
Kind Code |
A1 |
Buras; Paul J. ; et
al. |
June 1, 2006 |
Bitumen/rubber compositions crosslinked with polythiomorpholines,
polysulfides and/or mercaptobenzimidazole
Abstract
Asphalt and elastomeric polymer compositions crosslinked with
mixed polythiomorpholines or at least one alkyl polysulfide can
give polymer modified asphalts (PMAs) with improved properties
and/or reduced H.sub.2S evolution. When at least one alkyl
polysulfide is used to completely or partially replace conventional
crosslinkers such as S or MBT, mercaptobenzimidazole (MBI) may be
optionally used as a co-crosslinker. The use of mixed
polythiomorpholines as crosslinkers provide PMAs with better low
temperature profiles (BBR m-values). The use of at least one alkyl
polysulfide crosslinker gives PMAs with improved PAV-aged DSR
results, and reduced H.sub.2S evolution. The use of at least one
alkyl polysulfide crosslinker together with MBI may give PMAs with
improved PAV DSR Fail Temperatures.
Inventors: |
Buras; Paul J.; (West
University Place, TX) ; Lee; William; (Humble,
TX) ; Butler; James R.; (Friendswood, TX) ;
Stanley; Wendy; (Webster, TX) |
Correspondence
Address: |
FINA TECHNOLOGY INC
PO BOX 674412
HOUSTON
TX
77267-4412
US
|
Assignee: |
Fina Technology, Inc.
Houston
TX
|
Family ID: |
36568144 |
Appl. No.: |
11/001361 |
Filed: |
December 1, 2004 |
Current U.S.
Class: |
524/68 |
Current CPC
Class: |
C08L 95/00 20130101;
E01C 7/18 20130101; C08L 95/00 20130101; C08L 2666/08 20130101;
C08L 9/06 20130101; C08L 81/04 20130101 |
Class at
Publication: |
524/068 |
International
Class: |
E01C 7/26 20060101
E01C007/26 |
Claims
1. A method for preparing asphalt and polymer compositions
comprising: heating a mixture comprising asphalt, an elastomeric
polymer; and a crosslinker, where the crosslinker comprises at
least one crosslinker that is selected from the group consisting of
mixed polythiomorpholines and at least one alkyl polysulfide, and
curing the mixture to give a polymer modified asphalt (PMA).
2. The method of claim 1 where the crosslinker comprises mixed
polythiomorpholines and sulfur.
3. The method of claim 1 where the crosslinker consists essentially
of mixed polythiomorpholines.
4. The method of claim 3 where the PMA has an improved low
temperature property (BBR m-value) when mixed polythiomorpholines
are employed instead of equivalent amounts of sulfur and/or
mercaptobenzothiazole (MBT).
5. The method of claim 1 where the crosslinker comprises at least
one polythiomorpholine having the structure: ##STR3## where x is
greater than 2.
6. The method of claim 1 where the crosslinker has an absence of
elemental sulfur.
7. The method of claim 1 where the crosslinker has an absence of
MBT.
8. The method of claim 1 where the crosslinker is at least one
alkyl polysulfide, and the crosslinker further comprises
mercaptobenzimidazole (MBI).
9. The method of claim 1 where the crosslinker consists essentially
of at least one alkyl polysulfide.
10. The method of claim 9 where the evolution of H.sub.2S from the
asphalt polymer mixture is reduced compared with an equivalent
mixture in the absence of the alkyl polysulfide, but using the same
amount of sulfur.
11. The method of claim 9 where the PMA has an improved PAV-aged
DSR result as compared with an identical PMA absent the alkyl
polysulfide.
12. The method of claim 9 where the alkyl polysulfide has the
structure R1.sub.3--S--S--R2.sub.3 where R1 and R2 are
independently straight, branched or cyclic alkyl groups or aromatic
groups, where R1 and R2 may be substituted with N, S and/or O, and
the total number of carbon atoms in all R1 groups is 9 or greater
and the total number of carbon atoms in all R2 groups is 9 or
greater.
13. The method of claim 1 where the crosslinker consists
essentially of at least one polysulfide and MBI and the PMA has a
PAV DSR Fail Temperature better than an identical PMA where the
crosslinker is sulfur and/or MBT.
14. The method of claim 1 where the elastomeric polymer comprises
from about 1 to 20 wt % of the asphalt/polymer mixture.
15. The method of claim 1 where the crosslinker is present in an
amount ranging from about 0.01 to about 1 wt %, based on the weight
of the asphalt/polymer mixture.
16. A method for preparing asphalt and polymer compositions
comprising: heating a mixture comprising asphalt, an
styrene-butadiene copolymer, and a crosslinker within a temperature
range from about 300.degree. F. (149.degree. C.) to about
500.degree. F. (260.degree. C.), where the crosslinker comprises at
least one selected from the group consisting of mixed
polythiomorpholines and at least one alkyl polysulfide, where the
crosslinker is present in an amount ranging from about 0.01 to
about 1 wt %, based on the weight of the asphalt/polymer mixture;
and curing the mixture to give a PMA.
17. The method of claim 16 where the crosslinker comprises mixed
polythiomorpholines and sulfur.
18. The method of claim 16 where the crosslinker consists
essentially of mixed polythiomorpholines.
19. The method of claim 18 where the PMA has an improved low
temperature property (BBR m-value) when mixed polythiomorpholines
are employed instead of equivalent amounts of sulfur and/or
mercaptobenzothiazole (MBT).
20. The method of claim 16 where the crosslinker has an absence of
elemental sulfur.
21. The method of claim 16 where the crosslinker has an absence of
mercaptobenzothiazole (MBT).
22. The method of claim 16 where the crosslinker is at least one
alkyl polysulfide, and the crosslinker further comprises
mercaptobenzimidazole (MBI).
23. The method of claim 16 where the crosslinker consists
essentially of at least one alkyl polysulfide.
24. The method of claim 23 where the evolution of H.sub.2S from the
asphalt polymer mixture is reduced compared with an identical
mixture in the absence of the alkyl polysulfide, but using the same
amount of sulfur.
25. The method of claim 23 where the PMA has an improved PAV-aged
DSR result as compared with an identical PMA absent the alkyl
polysulfide.
26. The method of claim 16 where the crosslinker consists
essentially of at least one polysulfide and MBI and the PMA has a
PAV DSR Fail Temperature better than an identical PMA where the
crosslinker is sulfur and/or MBT.
27. The method of claim 16 where the elastomeric polymer comprises
from about 1 to 20 wt % of the asphalt/polymer mixture.
28. A polymer modified asphalt (PMA) composition prepared by the
method comprising: heating a mixture of asphalt, an elastomeric
polymer, and a crosslinker, where the crosslinker comprises at
least one crosslinker selected from the group consisting of mixed
polythiomorpholines and at least one alkyl polysulfide; and curing
the mixture to give the PMA.
29. The PMA of claim 28 where the crosslinker comprises mixed
polythiomorpholines and sulfur.
30. The PMA of claim 28 where the crosslinker consists essentially
of mixed polythiomorpholines.
31. The PMA of claim 28 where the PMA has an improved low
temperature property (BBR m-value) when mixed polythiomorpholines
are employed instead of equivalent amounts of sulfur and/or
mercaptobenzothiazole (MBT).
32. The PMA of claim 28 where the crosslinker comprises at least
one polythiomorpholine having the structure: ##STR4## where x is
greater than 2.
33. The PMA of claim 28 where the crosslinker has an absence of
elemental sulfur.
34. The PMA of claim 28 where the crosslinker has an absence of
mercaptobenzothiazole (MBT).
35. The PMA of claim 28 where the crosslinker is at least one alkyl
polysulfide, and the crosslinker further comprises
mercaptobenzimidazole (MBI).
36. The PMA of claim 28 where the crosslinker consists essentially
of at least one alkyl polysulfide.
37. The PMA of claim 36 where the evolution of H.sub.2S from the
asphalt polymer mixture is reduced compared with an identical
mixture in the absence of the alkyl polysulfide, but using the same
amount of sulfur.
38. The PMA of claim 36 where the PMA has an improved PAV-aged DSR
result as compared with an identical PMA absent the alkyl
polysulfide.
39. The PMA of claim 36 where the alkyl polysulfide has the
structure R1.sub.3--S--S--R2.sub.3 where R1 and R2 are
independently straight, branched or cyclic alkyl groups or aromatic
groups, where R1 and R2 may be substituted with N, S and/or O, and
the total number of carbon atoms in all R1 groups is 9 or greater
and the total number of carbon atoms in all R2 groups is 9 or
greater.
40. The PMA of claim 28 where the crosslinker consists essentially
of at least one polysulfide and MBI and the PMA has a PAV DSR Fail
Temperature better than an identical PMA where the crosslinker is
sulfur and/or MBT.
41. The PMA of claim 28 where the elastomeric polymer comprises
from about 1 to 20 wt % of the asphalt/polymer mixture.
42. The PMA of claim 28 where the crosslinker is present in an
amount ranging from about 0.01 to about 1 wt %, based on the weight
of the asphalt/polymer mixture.
43. A road comprising the PMA of claim 28.
44. A roof sealed with the PMA of claim 28.
45. A method of sealing a roof with PMA comprising heating the PMA
of claim 28 and distributing it over at least a portion of roof
surface.
46. A method of road building comprising combining the PMA of claim
28 with aggregate to form a road paving material, and forming road
pavement with the material.
47. A method of reducing H.sub.2S evolution from a polymer modified
asphalt (PMA) comprising: heating a mixture of asphalt, an
elastomeric polymer; and a crosslinker, where the crosslinker
comprises at least one alkyl polysulfide crosslinker; and curing
the mixture to give the PMA, where the evolution of H.sub.2S from
the PMA is reduced compared with an identical mixture in the
absence of the alkyl polysulfide, but using an equivalent amount of
sulfur.
48. The method of claim 47 where the crosslinker further comprises
MBI.
49. A method of recycling asphalt comprising physically removing
asphalt from a location and in any order reducing the size of the
removed asphalt, heating the removed asphalt, adding a crosslinker
to the mixture, where the crosslinker comprises at least one
selected from the group consisting of mixed polythiomorpholines and
at least one alkyl polysulfide.
50. The method of claim 49 where the crosslinker further comprises
MBI.
51. Recycled asphalt made by the process of claim 49.
52. Aggregate comprising a PMA at least partially coating the
aggregate, where the PMA comprises asphalt, an elastomeric polymer,
and a crosslinker comprising at least one crosslinker selected from
the group consisting of mixed polythiomorpholines and at least one
alkyl polysulfide.
53. The aggregate of claim 52 where the crosslinker further
comprises MBI.
Description
FIELD OF THE INVENTION
[0001] The present invention is related in one non-limiting
embodiment to hydrocarbon-based binders, such as bitumens, asphalts
and tars, modified with elastomers, and including a vulcanized
stage, which are particularly useful as industrial coatings and
road bitumens, or the like. It relates more particularly in another
non-restrictive embodiment to processes for obtaining vulcanized
compositions based on bitumens and on styrene/butadiene copolymers
that are crosslinked with new materials to improve the properties
of the resulting polymer modified asphalts.
BACKGROUND OF THE INVENTION
[0002] The use of bitumen (asphalt) compositions in preparing
aggregate compositions (including, but not just limited to, bitumen
and rock) useful as road paving material is complicated by at least
three factors, each of which imposes a serious challenge to
providing an acceptable product. First, the bitumen compositions
must meet certain performance criteria or specifications in order
to be considered useful for road paving. For example, to ensure
acceptable performance, state and federal agencies issue
specifications for various bitumen applications including
specifications for use as road pavement. Current Federal Highway
Administration specifications require a bitumen (asphalt) product
to meet defined parameters relating to properties such as
viscosity, stiffness, penetration, toughness, tenacity and
ductility. Each of these parameters defines a critical feature of
the bitumen composition, and compositions failing to meet one or
more of these parameters will render that composition unacceptable
for use as road pavement material.
[0003] Conventional bitumen compositions frequently cannot meet all
of the requirements of a particular specification simultaneously
and, if these specifications are not met, damage to the resulting
road may occur, including, but not necessarily limited to,
permanent deformation, thermally induced cracking and flexural
fatigue. This damage greatly reduces the effective life of paved
roads.
[0004] In this regard, it has long been recognized that the
properties of conventional bitumen compositions may be modified by
the addition of other substances, such as polymers. A wide variety
of polymers have been used as additives in bitumen compositions.
For example, copolymers derived from styrene and conjugated dienes,
such as butadiene or isoprene, are particularly useful, since these
copolymers have good solubility in bitumen compositions and the
resulting modified-bitumen compositions have good rheological
properties.
[0005] It is also known that the stability of polymer-bitumen
compositions may be increased by the addition of crosslinking
agents (vulcanizing agents) such as sulfur, frequently in the form
of elemental sulfur. It is believed that the sulfur chemically
couples the polymer and the bitumen through sulfide and/or
polysulfide bonds. The addition of extraneous sulfur is sometimes
required to produce the improved stability, even though bitumens
naturally contain varying amounts of native sulfur.
[0006] Thus, there are known processes for preparing a
bitumen-polymer composition consisting of mixing a bitumen, at
temperatures of about 266-446.degree. F. (130-230.degree. C.), with
2 to 20% by weight of a block or random copolymer, having an
average molecular weight between 30,000 and 300,000. The resulting
mixture is stirred for at least two hours, and then 0.1 to 3% by
weight of sulfur relative to the bitumen is added and the mixture
agitated for at least 20 minutes. The quantity of added sulfur may
be from about 0.1 to 1.5% by weight with respect to the bitumen.
The resulting bitumen-polymer composition is used for road-coating,
industrial coating, or other industrial applications.
[0007] Similarly, there are also known asphalt (bitumen) polymer
compositions obtained by hot-blending asphalt with about 0.1 to
1.5% by weight of elemental sulfur and about 2 to 7% by weight of a
natural or synthetic rubber, which may be a linear
butadiene/styrene copolymer. A process is additionally known for
preparing a rubber-modified bitumen by blending rubber, either
natural or synthetic, such as styrene/butadiene rubber, with
bitumen at 2803-400.degree. F. (138-204.degree. C.), in an amount
up to 10% by weight based on the bitumen, then adjusting the
temperature to 257-320.degree. F. (125-160.degree. C.), and
intimately blending into the mix an amount of sulfur such that the
weight ratio of sulfur to rubber is between 0.01 and 0.9. A
catalytic quantity of a vulcanization-accelerator is then added to
effect vulcanization. A critical nature of the sulfur to rubber
ratio is sometimes reported, for instance that weight ratios of
sulfur to rubber of less than 0.01 gives modified bitumen of
inferior quality.
[0008] A second factor complicating the use of bitumen compositions
concerns the viscosity stability of such compositions under storage
conditions. In this regard, bitumen compositions are frequently
stored for up to 7 days or more before being used and, in some
cases, the viscosity of the composition can increase so much that
the bitumen composition is unusable for its intended purpose. On
the other hand, a storage stable bitumen composition would provide
for only minimal viscosity increases and, accordingly, after
storage it may still be employed for its intended purpose.
[0009] Asphaltic concrete, typically including asphalt and
aggregate, asphalt compositions for resurfacing asphaltic concrete,
and similar asphalt compositions must exhibit a certain number of
specific mechanical properties to enable their use in various
fields of application, especially when the asphalts are used as
binders for superficial coats (road surfacing), as asphalt
emulsions, or in industrial applications. (The term "asphalt" is
used herein interchangeably with "bitumen." Asphaltic concrete is
asphalt used as a binder with appropriate aggregate added,
typically for use in roadways.) The use of asphalt or asphalt
emulsion binders either in maintenance facings as a surface coat or
as a very thin bituminous mix, or as a thicker structural layer of
bituminous mix in asphaltic concrete, is enhanced if these binders
possess the requisite properties such as desirable levels of
elasticity and plasticity.
[0010] As noted, various polymers have been added to asphalts to
improve physical and mechanical performance properties.
Polymer-modified asphalts (PMAs) are routinely used in the road
construction/maintenance and roofing industries. Conventional
asphalts often do not retain sufficient elasticity in use and,
also, exhibit a plasticity range that is too narrow for use in many
modern applications such as road construction. It is known that the
characteristics of road asphalts and the like may be greatly
improved by incorporating into them an elastomeric-type polymer
which may be one such as butyl, polybutadiene, polyisoprene or
polyisobutene rubber, ethylene/vinyl acetate copolymer,
polyacrylate, polymethacrylate, polychloroprene, polynorbornene,
ethylene/propylene/diene (EPDM) terpolymer and advantageously a
random or block copolymer of styrene and a conjugated diene. The
modified asphalts thus obtained commonly are referred to variously
as bitumen/polymer binders or asphalt/polymer mixes or polymer
modified asphalts (PMAs). PMAs and asphalt emulsions typically are
produced utilizing styrene/butadiene based polymers, and typically
have raised softening point, increased viscoelasticity, enhanced
force under strain, enhanced strain recovery, and improved low
temperature strain characteristics as compared with non-modified
asphalts and asphalt emulsions.
[0011] The bituminous binders, even of the PMA type, which are
presently employed in road applications often do not have the
optimum characteristics at low enough polymer concentrations to
consistently meet the increasing structural and workability
requirements imposed on roadway structures and their construction.
In order to achieve a given level of modified asphalt performance,
various polymers are added at some prescribed concentration.
[0012] Current practice is to add the desired level of a single
polymer, sometimes along with a reactant that promotes crosslinking
of the polymer molecules until the desired asphalt properties are
met. This reactant typically is sulfur in a form suitable for
reacting.
[0013] However, the cost of the polymer adds significantly to the
overall cost of the resulting asphalt/polymer mix. Thus, cost
factors weigh in the ability to meet the above criteria for various
asphalt mixes. In addition, at increasing levels of polymer
concentration, the working viscosity of the asphalt mix becomes
excessively great and separation of the asphalt and polymer may
occur.
[0014] It is common in the preparation of polymer-modified asphalts
to include activators and accelerators to make the crosslinking
reaction proceed faster. Zinc oxide (ZnO) is a conventional
activator, and mercaptobenzothiazole (MBT) is a conventional
accelerator. ZnO is also sometimes used to control the tendency of
the polymer to gel. The zinc salt of mercaptobenzothiazole (ZMBT)
combines features of both of these conventional additives.
[0015] In preparing the composition, significant mixing is needed
to insure the uniform addition of both the polymer and any
crosslinking agents, accelerators or activators. The crosslinking
agents and other agents are usually added as a dry powder and mixed
with the asphalt compositions.
[0016] The needed elements for the commercial success of any such
process include keeping the process as simple as possible, reducing
the cost of the ingredients, and utilizing available asphalt cuts
from a refinery without having to blend in more valuable fractions.
In addition, the resulting asphalt composition must meet the
above-mentioned governmental physical properties and environmental
concerns. Thus, it is a goal of the industry to maintain or reduce
the cost of the polymers and crosslinking agents added to the
asphalt without sacrificing any of the other elements and improving
the properties of the asphalt and polymer compositions as much as
possible. In view of the above, bitumen compositions, which
simultaneously meet the performance criteria required for road
paving, and which use an alternative crosslinkers to provide PMAs
with improved properties would be advantageous.
SUMMARY OF THE INVENTION
[0017] There is provided, in one form, a method for preparing
asphalt and polymer compositions that involves heating a mixture of
asphalt, an elastomeric polymer and crosslinker. The crosslinker
includes at least one crosslinker that is mixed polythiomorpholines
or at least one alkyl polysulfide. When at least one alkyl
polysulfide is used, optionally mercaptobenzimidazole (MBI) may
also be used. The mixture is then cured to give a polymer modified
asphalt (PMA).
[0018] In another embodiment, there is provided a polymer modified
asphalt (PMA) composition prepared by the above-noted method.
[0019] In a different non-restrictive embodiment of the invention,
there is provided a road made from the PMA described immediately
above and aggregate.
[0020] In another non-limiting embodiment, there is described a
method of reducing H.sub.2S evolution from a PMA that involves
heating a mixture of asphalt, an elastomeric polymer; and at least
one alkyl polysulfide crosslinker. The mixture is cured to give the
PMA, where the evolution of H.sub.2S from the PMA is reduced
compared with an identical mixture in the absence of the alkyl
polysulfide, but using an equivalent amount of sulfur. MBI may also
be optionally used.
[0021] There is additionally provided in another non-restrictive
form a method of recycling asphalt that involves physically
removing asphalt from a location and in any order reducing the size
of the removed asphalt, heating the removed asphalt, and adding a
crosslinker to the mixture. Suitable crosslinkers include mixed
polythiomorpholines and at least one alkyl polysulfide, where again
MBI may be optionally used along with the alkyl polysulfide.
DETAILED DESCRIPTION OF THE INVENTION
[0022] It has been discovered that improvements in rubber/asphalt
compatibility may be obtained by crosslinking with certain new
crosslinkers. When particular crosslinkers are used to crosslink
mixtures of asphalt and elastomeric polymers improved low
temperature properties may be obtained (BBR m-value) as compared
with identical PMA when mixed polythiomorpholines (MPTM) are used
as at least partial or complete replacements for sulfur and/or
mercaptobenzothiazole (MBT). When alkyl polysulfides are used, the
evolution of hydrogen sulfide (H.sub.2S) may be reduced as compared
with identical PMA mixtures using sulfur as the crosslinker instead
of the alkyl polysulfides. Additionally, improvements after rubber
addition may be obtained when at least one alkyl polysulfide and
mercaptobenzimidazole (MBI) are used instead of MBT and/or sulfur.
This invention may be considered as a potential alternative to the
use of resins or other techniques to reduce separation.
[0023] As used herein, the term "bitumen" (sometimes referred to as
"asphalt") refers to all types of bitumens, including those that
occur in nature and those obtained in petroleum processing. The
choice of bitumen will depend essentially on the particular
application intended for the resulting bitumen composition.
Bitumens that may be used may have an initial viscosity at
140.degree. F. (60.degree. C.) of 600 to 3000 poise (60 to 300
Pa-s) depending on the grade of asphalt desired. The initial
penetration range (ASTM D5) of the base bitumen at 77.degree. F.
(25.degree. C.) is 20 to 320 dmm, and may be 50 to 150 dmm, when
the intended use of the copolymer-bitumen composition is road
paving. Bitumens that do not contain any copolymer, sulfur, etc.,
are sometimes referred to herein as a "base bitumen."
[0024] "Elastomeric Polymers" are natural or synthetic rubbers and
include, but are not necessarily limited to, butyl, polybutadiene,
polyisoprene or polyisobutene rubber, ethylene/vinyl acetate
copolymer, polyacrylate, polymethacrylate, polychloroprene,
polynorbornene, ethylene/propylene/diene (EPDM) terpolymer and
advantageously a random or block copolymer of a vinyl aromatic
compound, e.g. styrene, and conjugated dienes. In one non-limiting
embodiment of the invention, styrene/conjugated diene block
copolymers may be used that are linear, radial, or multi-branched.
Styrene/butadiene and styrene/isoprene copolymers having an average
molecular weight of between 30,000 and 300,000 have been found to
be particularly useful in the present invention.
[0025] "Conjugated dienes" refer to alkene compounds having 2 or
more sites of unsaturation wherein a second site of unsaturation is
conjugated to a first site of unsaturation, i.e., the first carbon
atom of the second site of unsaturation is gamma (at carbon atom 3)
relative to the first carbon atom of the first site of
unsaturation. Conjugated dienes include, by way of non-limiting
example, butadiene, isoprene, 1,3-pentadiene, and the like.
[0026] "Block copolymers of styrene and conjugated-dienes" refer to
copolymers of styrene and conjugated-dienes having a linear or
radial, tri-block structure consisting of styrene-conjugated
diene-styrene block units that are copolymers are represented by
the formula: S.sub.x-D.sub.y-S.sub.z where D is a conjugated-diene,
S is styrene, and x, y and z are integers such that the number
average molecular weight of the copolymer is from about 30,000 to
about 300,000. These copolymers are well known to those skilled in
the art and are either commercially available or may be prepared
from methods known in the art. Such tri-block copolymers may be
derived from styrene and a conjugated-diene, wherein the
conjugated-diene is butadiene or isoprene. Such copolymers may
contain 15 to 50 percent by weight copolymer units derived from
styrene, alternatively may contain 20 to 35 percent derived from
styrene, and then again may contain 28 to 31 percent derived from
styrene, the remainder being derived from the conjugated diene.
These copolymers may have a number average molecular weight range
between about 50,000 and about 200,000, and alternatively have a
number average molecular weight range between about 80,000 and
about 180,000. The copolymer may employ a minimal amount of
hydrocarbon solvent in order to facilitate handling. Examples of
suitable solvents include plasticizer solvent that is a
non-volatile aromatic oil. However, when the hydrocarbon solvent is
a volatile solvent (as defined above), care should be taken to
ensure that the amount of solvent contained in the final bitumen
composition is less than about 3.5 weight percent.
[0027] In one non-limiting embodiment of the invention, the
elastomeric polymer is present in a proportion of from about 1 to
about 20 wt % of the asphalt/-polymer mixture. In another,
non-restrictive form of the invention, the polymer is present in an
amount of from about 1 to about 6 wt % of the mixture.
[0028] The term "sulfur" is defined herein as elemental sulfur in
any of its physical forms, whereas the term "sulfur-containing
derivative" includes any sulfur-donating compound, but not
elemental sulfur. Sulfur-donating compounds are well known in the
art and include various organic compositions or compounds that
generate sulfur under the mixing or preparation conditions of the
present invention. In one non-limiting embodiment, the elemental
sulfur is in powder form known as flowers of sulfur. Other
sulfur-containing derivatives or species that may be used in the
invention include, but are not necessarily limited to
mercaptobenzothiazole, thiurams, dithiocarbamates,
sulfur-containing oxazoles, thiazole derivatives, and the like, and
combinations thereof. "Thiazole derivatives" include, but are not
necessarily limited to, compounds having the necessary functional
group to serve as sulfur donors, such as --N.dbd.C(R)--S--,
including imidazoles and oxazoles. In another non-limiting
embodiment of the invention, the sulfur and/or other crosslinker is
present in an amount ranging from about 0.01 to about 1 wt %,
alternatively when about 0.75 wt % is the upper limit,
alternatively from about 0.06% to about 0.3 wt. % based on the
asphalt, and in another non-limiting embodiment is present in an
amount from about 0.08 to about 0.2 wt. %. As noted earlier, the
zinc salt of mercaptobenzothiazole (ZMBT) combines features of
conventional additives. Other metal salts of MBT may also be
useful.
[0029] Acceptable crosslinkers, in one non-limiting embodiment of
the invention, are thiuram polysulfides. In another non-limiting
embodiment of the invention, the thiuram polysulfides have the
formula: ##STR1## where R.sup.1 and R.sup.2 are the same or
different alkyl substituents having from 1 to 4 carbon atoms, and
wherein M is a metal selected from zinc, barium or copper, and n is
0 or 1. In another non-limiting embodiment of the invention, a
crosslinking temperature range for thiuram polysulfides of formula
(I) is above 180.degree. C. (356.degree. F.), alternatively, the
crosslinking temperature range may be between about 130 and about
205.degree. C. (280-400.degree. F.). Thiuram polysulfides within
the context of this invention include, but are not limited to, zinc
dialkyldithiocarbamates such as dimethyidithiocarbamate.
[0030] In still another non-limiting embodiment of the invention,
the sulfur-containing derivative excludes added elemental sulfur,
per se. Alternatively, the asphalt and elastomeric polymer mixture
may contain added elemental sulfur, but the crosslinking is
conducted at a temperature different from the optimum crosslinking
temperature for elemental sulfur, per se.
[0031] As noted, the inventive crosslinkers herein include
polythiomorpholines and one or more alkyl polysulfide, and in one
non-limiting embodiment mixtures of one or more alkyl polysulfide
with mercaptobenzimidazole (MBI). It has been surprisingly
discovered that these new crosslinkers may replace partially or
entirely the conventional crosslinkers described above, such as
sulfur and/or MBT, to give improved properties. The proportional
amounts of these new crosslinkers are identical to the conventional
crosslinkers, and in another non-restrictive embodiment have
equivalent sulfur proportions, that is, the same sulfur contents as
those of the conventional crosslinkers previously discussed.
[0032] In one non-limiting embodiment the mixed polythiomorpholines
include polythiomorpholine having the structure: ##STR2## where x
is greater than 2. By "mixed" is meant at least two different
polythiomorpholines.
[0033] In another non-restrictive embodiment, the alkyl polysulfide
has the structure R1.sub.3--S--S--R2.sub.3 where R1 and R2 are
independently straight, branched or cyclic alkyl groups or aromatic
groups, where R1 and R2 may be substituted with N, S and/or O, and
the total number of carbon atoms in all R1 groups is 9 or greater
and the total number of carbon atoms in all R2 groups is 9 or
greater.
[0034] The term "desired Rheological Properties" refers primarily
to the SUPERPAVE asphalt binder specification designated by AASHTO
as MP1 as will be described below. Additional asphalt
specifications may include viscosity at 140.degree. F. (60.degree.
C.) of from 1600 to 4000 poise (160-400 Pa-s) before aging; a
toughness of at least 110 inch-pound (127 cm-kilograms) before
aging; a tenacity of at least 75 inch-pound (86.6 cm-kilograms)
before aging; and a ductility of at least 25 cm at 39.2.degree. F.
(4.degree. C.) at 5 cm/min. pull rate after aging.
[0035] Viscosity measurements are made by using ASTM test method
D2171. Ductility measurements are made by using ASTM test method
D113. Toughness and tenacity measurements are made by a Benson
Method of Toughness and Tenacity, run at 20 inches/minute (50.8
cm/minute) pull rate with a 1/8 inch (2.22 cm) diameter ball.
[0036] By "storage stable viscosity" it is meant that the bitumen
composition shows no evidence of skinning, settlement, gelation, or
graininess and that the viscosity of the composition does not
increase by a factor of four or more during storage at
325.+-.0.5.degree. F. (163.+-.2.8.degree. C.) for seven days. In
one non-limiting embodiment of the invention, the viscosity does
not increase by a factor of two or more during storage at
325.degree. F. (163.degree. C.) for seven days. In another
non-limiting embodiment of the invention, the viscosity increases
less than 50% during seven days of storage at 325.degree. F.
(163.degree. C.). A substantial increase in the viscosity of the
bitumen composition during storage is not desirable due to the
resulting difficulties in handling the composition and in meeting
product specifications at the time of sale and use.
[0037] The term "aggregate" refers to rock and similar material
added to the bitumen composition to provide an aggregate
composition suitable for paving roads. Typically, the aggregate
employed is rock indigenous to the area where the bitumen
composition is produced. Suitable aggregate includes granite,
basalt, limestone, and the like.
[0038] As used herein, the term "asphalt cement" refers to any of a
variety of substantially solid or semi-solid materials at room
temperature that gradually liquify when heated. Its predominant
constituents are bitumens, which may be naturally occurring or
obtained as the residue of refining processing. As mentioned, the
asphalt cements are generally characterized by a penetration (PEN,
measured in tenths of a millimeter, dmm) of less than 400 at
25.degree. C., and a typical penetration range between 40 and 300
(ASTM Standard, Method D-5). The viscosity of asphalt cement at
60.degree. C. is more than about 65 poise. Asphalt cements are
alternately defined in terms specified by the American Association
of State Highway Transportation Officials (AASHTO) AR viscosity
system.
[0039] The asphalt terms used herein are well known to those
skilled in the art. For an explanation of these terms, reference is
made to the booklet SUPERPAVE Series No. 1 (SP-1), 1997 printing,
published by the Asphalt Institute (Research Park Drive, P.O. Box
14052, Lexington, Ky. 40512-4052), which is hereinafter referred to
as MP1 (Standard Specification for Performance Graded Asphalt
Binder). For example, Chapter 2 provides an explanation of the test
equipment, terms, and purposes. Rolling Thin Film Oven (RTFO) and
Pressure Aging Vessel (PAV) are used to simulate binder aging
(hardening) characteristics. Dynamic Shear Rheometers (DSR) are
used to measure binder properties at high and intermediate
temperatures. These are used to predict permanent deformation or
rutting and fatigue cracking. Bending Beam Rheometers (BBRs) are
used to measure binder properties at low temperatures. These values
predict thermal or low temperature cracking. The procedures for
these experiments are also described in the above-referenced
SUPERPAVE booklet.
[0040] Asphalt grading is given in accordance with accepted
standards in the industry as discussed in the above-referenced
Asphalt Institute booklet. For example, pages 62-65 of the booklet
include a table entitled Performance Graded Asphalt Binder
Specifications. The asphalt compositions are given performance
grades, for example, PG 64-22. The first number, 64, represents the
average 7-day maximum pavement design temperature in .degree. C.
The second number, -22, represents the minimum pavement design
temperature in .degree. C. Other requirements of each grade are
shown in the table. For example, the maximum value for the PAV-DSR
test (.degree. C.) for PG 64-22 is 25.degree. C.
[0041] One of the methods commonly utilized in the industry to
standardize the measure or degree of compatibility of the rubber
with the asphalt is referred to as the compatibility test.
Compatibility tests provide a measure of the degree of separability
of materials comprising the asphalt. The long-term compatibility
between rubber and the other components of PMA, for example, is an
important consideration when preparing road material. If rubber is
not compatible with the other components of PMA, then the
performance of road materials containing PMA is degraded.
Compatibility is assessed by measuring the softening point of
asphalt after a period of thermally-induced aging (for example
Louisiana DOTD Asphalt Separation of Polymer Test Method TR 326).
The test is performed on a polymer-modified asphalt mixture
comprised of rubber and asphalt with all the applicable additives,
such as the crosslinking agents. The mixture is placed in tubes,
usually made of aluminum or similar material, referred to as cigar
tubes or toothpaste tubes. These tubes are about one inch (2.54 cm)
in diameter and about fifteen centimeters deep. The mixture is
placed in an oven heated to a temperature of about 162.degree. C.
(320.degree. F.). This temperature is representative of the most
commonly used asphalt storage temperature. After the required
period of time, most commonly twenty-four (24) hours, the tubes are
transferred from the oven to a freezer and cooled down to solidify.
The tubes are kept in the vertical position. After cooling down,
the tubes are cut into thirds; three equal sections. The Ring and
Ball softening point of the top one third is compared to the
softening point of the bottom section. This test gives an
indication of the separation or compatibility of the rubber within
the asphalt. The rubber would have the tendency to separate to the
top. The lower the difference in softening point between the top
and bottom sections, the more compatible are the rubber and
asphalt. In today's environment, many states require a difference
of 4.degree. F. (2.degree. C.) or less to consider the
asphalt/rubber composition as compatible. Few standards allow a
higher difference. The twenty-four hour test is used as a common
comparison point. In one non-limiting embodiment of the invention,
this compatibility test value is 20.degree. C. or less.
[0042] In accordance with one non-limiting embodiment of the
present invention, an asphalt composition is prepared by adding the
asphalt or bitumen to a mixing tank that has stirring means. The
asphalt is added and stirred at elevated temperatures. Stirring
temperatures depend on the viscosity of the asphalt and may range
up to 500.degree. F. (260.degree. C.) and alternatively up to about
450.degree. F. (232.degree. C.). In one non-restrictive embodiment,
the lower heating limit is about 300.degree. F. (149.degree. C.),
and alternatively about 325.degree. F. (163.degree. C.). Asphalt
products from refinery operations are well known in the art. For
example, asphalts typically used for this process are obtained from
deep vacuum distillation of crude oil to obtain a bottom product of
the desired viscosity or from a solvent deasphalting process that
yields a demetallized oil, a resin fraction and an asphaltene
fraction. Some refinery units do not have a resin fraction. These
materials or other compatible oils of greater than 450.degree. F.
(232.degree. C.) flash point may be blended to obtain the desired
viscosity asphalt.
[0043] Rubbers, elastomeric polymers, or thermoplastic elastomers
suitable for this application are well known in the art as
described above. For example, FINAPRENE.RTM. SBS rubber products
available from Atofina Elastomers Inc. are suitable for the
applications of the present invention. This example is not limiting
for the inventive technology that may be applied to any similar
elastomeric product particularly those produced from styrene and
butadiene.
[0044] In one non-limiting embodiment of the invention, a metal
oxide activator is also present in the asphalt/polymer mixture of
the invention. As mentioned, zinc oxide is a known, conventional
activator, and may also be used to suppress the evolution of
hydrogen sulfide. Other useful metal oxides include, but are not
necessarily limited to, CaO, MgO and CuO as discussed in U.S.
Patent Application 2004/0030008 A1, incorporated by reference
herein. In one non-restrictive form of the invention, the acid is
present in an equimolar amount of the ZnO present.
[0045] Various other additives suitable for the purposes of this
invention include, but are not necessarily limited to, known and
future accelerators, activators, divalent metal oxides (e.g. zinc
oxide) and the like. A variety of accelerators may be used in
conjunction with this invention, including, but not limited to,
dithiocarbamates and benzothiazoles. Many crosslinking agents and
other additives are normally sold in powder or flake form.
[0046] The methods and compositions of this invention will be
further illustrated with respect to particular Examples that are
only intended to more fully illuminate the invention and not limit
it.
EXAMPLES 1-6
[0047] Without wanting to be limited to any particular explanation
or mechanism, it has been unexpectedly discovered that mixed
polythiomorpholines (MPTM) may serve as crosslinkers, crosslinking
accelerators and/or as sulfur donors for bridge formation.
Formulations were trialed in which the MBT accelerator, elemental
sulfur, or a combination of the MBT/S were replaced by MPTM for
crosslinking activity and resultant PMA SHRP properties.
[0048] The asphalt sample was heated to 350.degree. F. (177.degree.
C.) with low shear mixing. The mixing was changed to high shear and
the polymer added. Mixing continued on high shear for 1 hour at
350.degree. F. (177.degree. C.). The mixing was reduced to low
shear. The crosslinking agents were added and mixing continued on
low shear at 350.degree. F. (177.degree. C.) for 1 hour. The PMA
mixture was aged in the oven at 325.degree. F. (163.degree. C.) for
24 hours. The cured asphalt was tested for 24/48-hour
Compatibility, MP1 graded, and the 135.degree. C. Rotational
Viscosity measured. Observations were noted (e.g. gelling, film
formation, lumps, smoke, etc.).
[0049] The formulation are presented in Table I and the MP1
testing, viscosity, and rubber compatibility results for the
formulations with the indicated amounts of MPTM are presented in
Table II. TABLE-US-00001 TABLE I Formulations of Examples 1-6
Example Formulation 1 100% of a PG67-22 asphalt 2 4.0% FINAPRENE
.RTM. 502 thermoplastic elastomer type linear styrenebutadiene
block copolymer (SBS) in 96.0% of the PG67-22 asphalt of Example 1,
crosslinked with 0.075 ZnO/0.075 MBT/0.15 S 3 4.0% FINAPRENE 502
copolymer (FP502) in 96.0% PG67-22 asphalt of Ex. 1, crosslinked
with 0.075 ZnO/0.075 MBT/0.15 MPTM 4 4.0% FP502 in 96.0% PG67-22
asphalt of Ex. 1, crosslinked with 0.075 ZnO/0.075 MPTM/0.15 S 5
4.0% FP502 in 96.0% PG67-22 asphalt of Ex. 1, crosslinked with
0.075 ZnO/0.0375 MBT/0.075 S/0.1125 MPTM 6 4.0% FP502 in 96.0%
PG67-22 asphalt of Ex. 1, crosslinked with 0.075 ZnO/0.225 MPTM
[0050] TABLE-US-00002 TABLE II MPTM Crosslink Formulation Blends
Units Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 PG67-22 asphalt Wt % 100
96.0 96.0 96.0 96.0 96.0 FP502 copolymer Wt % 4.0 4.0 4.0 4.0 4.0
ZnO Wt % 0.075 0.075 0.075 0.075 0.075 MBT Wt % 0.075 0.075 0.0375
Sulfur Wt % 0.15 0.15 0.075 MPTM Wt % 0.15 0.075 0.1125 0.225
Binder DSR .degree. C. 68.4 85.0 80.5 86.1 83.0 82.8 RTFO DSR
.degree. C. 69.4 79.5 79.8 80.6 81.0 81.1 PAV DSR .degree. C. 26.4
21.9 21.2 23.8 22.8 22.3 m-Value .degree. C. -12.5 -14.6 -13.0
-14.5 -14.6 -13.2 S-Value .degree. C. -13.6 -16.3 -18.8 -16.1 -16.1
-15.7 135.degree. C. Viscosity Pa sec 2.13 1.80 2.17 1.86 1.73
48-hour Compatibility .degree. F. 0.0 0.0 0.7 4.2 2.5 (.degree. C.)
(0.0) (0.0) (0.4) (2.3) (1.4)
[0051] Replacement of sulfur with an equivalent wt % of MPTM
resulted in PMA with similar MP1 properties with the exception of
the ODSR Fail Temperature and the separation between the ODSR/RTFO
DSR Fail Temperatures (see Ex. 3, Table II). There is an
accompanying decrease in the 135.degree. C. Rotational Viscosity
with MPTM-for-sulfur blend, perhaps indicating fewer sulfur bridges
(crosslinks) in the PMA blend of Example 3. The relative extra
crosslinks in the Control Blend (Ex. 2) that may impart a higher
viscosity, as measured by Rotational Viscosity and ODSR Fail
Temperature, are apparently not stable under the moderate oxidation
of RTFO accelerated aging. Not limiting examples would be
inter-polymer (chain) poly-sulfur bridges that could be broken (and
lost) or rearranged to intrapolymer bridges under mild oxidation of
RTFO aging ("Reversion"). Under this hypothesis, the bridging of
the RTFO-aged sample would represent the oxidation and heat stable
crosslinks, while the ODSR Fail Temperature would be considered a
relative measure of all (initial) crosslinks.
[0052] The blend in which the MBT is replaced by MPTM (blend of
Example 5, Table II) has properties very similar to the Control
Blend of Ex. 2, with a repeat of the relatively larger ODSR/RTFO
DSR separation. Replacement of 50% each of the MBT and sulfur (as
in the blend of Ex. 4, Table II) decreases the rubber compatibility
to just outside of the specification maximum of 4.degree. F.
(2.2.degree. C.). However, the ODSR/RTFO DSR Temperature separation
is narrowed, showing improvement.
[0053] Finally, in the blend of Example 6, both the MBT and sulfur
were replaced by an equivalent (total) weight of MPTM. The blend
was rubber compatible and had a narrow ODSR/RTFO DSR Temperature
separation. As with blends of Examples 3 and 5, in which some or
all of the sulfur was replaced by MPTM, the ODSRIRTFO DSR
Temperature separation was narrowed, and the 135.degree. C.
Rotational Viscosity was decreased, relative to the Control Blend
of Example 2.
[0054] From the above Examples, it may be seen that MPTM may be
substituted for MBT in equivalent wt % to produce rubber compatible
PMA. Replacement of sulfur with equivalent MPTM results in PMA with
limiting MP1 properties very similar to the Control PMA (Ex. 2),
crosslinked with traditional ZnO/MBT/S. However, the Rotational
Viscosity and ODSR are significantly lower in the MPTM-for-sulfur
blend.
[0055] In all three blends in which the sulfur is at least
partially replaced (PMA Examples 3, 5 and 6), the Rotational
Viscosity was significantly lower than the Control Blend (Ex. 2),
and the ODSR Temperature was reduced along with the ODSR/RTFO DSR
Temperature separation. In all three blends in which the MBT was at
least partially replaced (Examples 4, 5 and 6), the separation was
improved, relative to the Control Blend (Ex. 2) crosslinked with
ZnO/MBT/S. This is an indication, at least in this asphalt, that
MPTM is a more effective crosslink accelerator.
EXAMPLES 7-10
[0056] Mixed polythiomorpholines (MPTM) are shown in these Examples
to be an effective replacement for MBT, and MBT/S in crosslinking.
These Examples tested MPTM as a replacement for MBT and MBT/S in a
PG64-22 base stock.
[0057] PMAs were crosslinked with traditional ZnO/MBT/S, MPTM
substituted for MBT, and MPTM substituted for MBT/S. Each PMA was
SHRP graded and the Compatibility and 135.degree. C. Viscosity
measured. Formulations tested included those in Table III:
TABLE-US-00003 TABLE III Formulations of Examples 7-10 Example
Formulation 7 100% of a PG64-22 asphalt, MPI graded 8 95.5 wt %
PG64-22 of Ex. 7, 4.5 wt % FP502, crosslinked with 0.06 ZnO/0.06
MBT/0.12 S 9 95.5 wt % PG64-22 of Ex. 7, 4.5 wt % FP502,
crosslinked with 0.06 ZnO/0.06 MPTM/0.12 S 10 95.5 wt % PG64-22 of
Ex. 7, 4.5 wt % FP502, crosslinked with 0.06 ZnO/0.18 MPTM
[0058] The test procedure for Examples 7-10 involved heating the
asphalt sample to 350.degree. F. (177.degree. C.) with low shear
mixing. The mixing was changed to high shear and the polymer added.
Mixing continued on high shear for 1 hour at 350.degree. F.
(177.degree. C.). The mixing was reduced to low shear. The
crosslinking agents were added and mixing continued on low shear at
350.degree. F. (177.degree. C.) for 1 hour. The PMA mixture was
aged in the oven at 325.degree. F. (163.degree. C.) for 24 hours.
The cured asphalt was tested for 48-hour Compatibility, MP1 graded,
and the 135.degree. C. Rotational Viscosity measured. Observations
were noted (e.g. gelling, film formation, lumps, smoke, etc.). The
MP1 grading results of the base asphalt and each of the PMA
formulations are presented in Table IV. TABLE-US-00004 TABLE IV MP1
Properties of PMA Crosslinked with ZnO/MBT/S, ZnO/MPTM/S, and
ZnO/MPTM Units Ex. 7 Ex. 8 Ex. 9 Ex. 10 PG64-22 asphalt Wt % 100
95.5 95.5 95.5 FP502 Wt % 4.5 4.5 4.5 ZnO Wt % 0.06 0.06 MBT Wt %
0.06 Sulfur Wt % 0.12 0.12 MPTM Wt % 0.06 0.18 Binder DSR .degree.
C. 65.4 87.3 85.3 81.1 RTFO DSR .degree. C. 66.4 79.0 79.1 79.0 PAV
DSR .degree. C. 20.5 20.8 15.3 20.1 m-Value .degree. C. -15.4 -17.3
-16.6 -13.8 S-Value .degree. C. -15.4 -18.2 -18.2 -17.6 48-hr
Compatibility .degree. F. 2.5 2.6 1.9 (.degree. C.) (1.4) (1.4)
(1.1) 135.degree. C. Viscosity Pa*s 1.74 1.83 1.52
[0059] All of the PMA blends were rubber compatible and were MP1
graded. The Control Blend (Blend of Example 8, Table IV) had a
large 8.degree. C.+ separation between the ODSR (Binder DSR) Fail
Temperature and the limiting RTFO DSR Fail Temperature. The blend
in which the MBT was replaced by MPTM (Blend of Ex. 9, Table IV),
had an ODSR reduced by 2.degree. C. compared to the Control Blend.
There was significant improvement (lowering) in the PAV DSR Fail
Temperature of the MPTM-for-MBT blend (Ex. 9) compared with the
Control Blend (Ex. 8), although the PAV DSR is not limiting in PMA
from PG67/64-22 base(s). The blend in which all of the MBT/S was
replaced with MPTM (Ex. 10) had an ODSR lowered by 6.degree. C.+
compared to the Control, but there was no change in the limiting
RTFO Fail Temperature. There was a significant loss (increase) of
3.5.degree. C. in the limiting m-Value Fail Temperature vs. the
Control PMA formulation. The significant reduction in the ODSR Fail
Temperatures of the MPTM for MBT/S blend (Ex. 10) may be from a
reduction in crosslink density, as evidenced by a reduction in the
135.degree. C. Viscosity.
[0060] MPTM appears to be suitable as a direct replacement for MBT
in PMA crosslinking. Silica-coated MPTM is generally less expensive
than MBT and thus may be a useful substitute.
EXAMPLES 11-18
[0061] TPS-32 ditertiododecyl polysulfide, available from Atofina,
is a liquid polysulfide discovered to be a substitute for elemental
sulfur in PMA formulations. PMA formulated with TPS-32 at
equivalent additive sulfur rates was rubber compatible and met
target PG76-22 MP1 specifications. The PMA formulated with TPS-32
had properties equivalent to PMA formulated from the same base
stock but crosslinked with the traditional ZnO/MBT/S combination.
There was a reduction in measured H.sub.2S when compared to
traditionally crosslinked PMA.
Experimental Procedure
[0062] A one-half size batch of PG76-22 graded PMA was formulated.
The FINAPRENE 502 rubber concentration was 3.2 wt %, and the
crosslinking agents added at 0.075 wt % ZnO, 0.075 wt % MBT, and
0.48 TPS-32 (0.15 wt % active sulfur).
[0063] The Plant Trial Asphalt Production Procedure was as follows:
[0064] 1) Empty and isolate a PMA production tank for the trial PMA
formulation. [0065] 2) Prepare PMA batch, sized for 2000 bbls
PG67-22 base stock, 33,250 lbs FINAPRENE 502. [0066] 3) Crosslink
with 2200 lbs of modified ZnO/MBT crosslinker (550 lbs ZnO and 550
lbs of MBT in 1100 lbs of SunPave 125T carrier oil available from
Sunoco Inc.) and 2750 lbs of TPS-32 (40% active sulfur). Transfer
from drums into vacuum truck and injection into PMA production
tank. [0067] 4) Pull a 2-gallon sample of the crosslinked PMA
immediately before crosslinker addition. Test can sample using ATX
H.sub.2S Tester and Draeger Tube for H.sub.2S levels; send sample
for testing. (Example 12 material) [0068] 5) Pull a 2-gallon sample
of the crosslinked PMA 5 minutes following crosslinker injection.
Test can sample using ATX H.sub.2S Tester and Draeger Tube for
H.sub.2S levels; send sample for testing. (Example 13 material)
[0069] 6) Pull a 2-gallon sample of the crosslinked PMA 1 hour
after crosslinker addition. Test can sample using ATX H.sub.2S
Tester and Draeger Tube for H.sub.2S levels; send sample for
testing. (Example 14 material) [0070] 7) Pull a 2-gallon sample of
the crosslinked PMA 2 hours after crosslinker addition. Test can
sample using ATX H.sub.2S Tester and Draeger Tube for H.sub.2S
levels; send sample for testing. (Example 15 material) [0071] 8)
Pull a 2-gallon sample of the crosslinked PMA 6 hours after
crosslinker addition. Test can sample using ATX H.sub.2S Tester and
Draeger Tube for H.sub.2S levels; send sample for testing. (Example
16 material) [0072] 9) Pull a 2-gallon sample of the crosslinked
PMA 12 hours after crosslinker addition. Test can sample using ATX
H.sub.2S Tester and Draeger Tube for H.sub.2S levels; send sample
for testing. (Example 17 material) [0073] 10) Pull a 2-gallon
sample of the crosslinked PMA 24 hours after crosslinker addition.
Test can sample using ATX H.sub.2S Tester and Draeger Tube for
H.sub.2S levels; send sample for testing. (Example 18 material)
[0074] Testing involved MP1 grading each of the PMA samples from
the trial, measuring the 135.degree. C. viscosity, testing for
48-hour compatibility, and noting observations. Each of the timed
samples was also tested for H.sub.2S. The MP1 grading of the
asphalt/PMA samples is presented in Table V. TABLE-US-00005 TABLE V
Time-lapsed MP1 Data from TPS-32 Crosslinked PG76-22 PMA Trial
Units Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18
PG67-22 Base Asphalt Wt % 100 Before XL Addition + Rubber Wt % 100
5 mins Post XL Addition Wt % 100 1 hr Post XL Addition Wt % 100 2
hrs Post XL Addition Wt % 100 6 hrs Post XL Addition Wt % 100 12
hrs Post XL Addition Wt % 100 24 hrs Post XL Addition Wt % 100
Binder DSR .degree. C. 68.2 77.9 80.8 82.2 83.6 84.7 84.2 RTFO DSR
.degree. C. 69.8 80.0 80.1 80.8 81.1 80.1 80.6 PAV DSR .degree. C.
24.9 -0.6 13.6 13.8 14.4 12.4 14.6 m-Value .degree. C. -15.0 -16.4
-16.1 -15.8 -17.1 -17.4 -17.4 S-Value .degree. C. -18.5 -22.2 -21.3
-20.9 -21.2 -22.4 -21.4 48 hr Compatibility .degree. F. 69.2 2.2
0.9 1.5 5.4 0.7 0.6 (.degree. C.) (38.4) (1.2) (0.5) (0.8) (9.7)
(0.4) (0.3) 135.degree. C. Viscosity Pa*s 0.55 1.34 1.75 1.97 2.03
1.96 2.04 1.98
[0075] The neat base stock (Ex. 11) met the expected PG67-22
specifications and the test values were consistent with reported
values. The rubberized asphalt (blend from Ex. 12, Table V) was not
compatible with a measured separation of 62.9.degree. F.
(34.9.degree. C.) and was not further tested. The sample collected
5 minutes (blend from Ex. 13, Table V) after crosslinker addition
was compatible. However, the 135.degree. C. Viscosity had not
maximized, compared to the final ODSR Fail Temperature, indicating
that the crosslinking reaction was not complete. In addition, the
Original Binder DSR was still lower than the RTFO DSR, unlike the
finished PMA, another indication that the crosslinking action was
not completed. The PAV DSR Fail Temperature of the same blend was
unexplainably low at 0.6.degree. C. At 1 hr after crosslinker
addition (blend from Ex. 4, Table V), the PMA properties were close
to the final values seen after the complete 24 hrs of heat aging,
although the Original Binder DSR Fail Temperature had still not
stabilized. Final PMA properties were stabilized after at least 6
hrs of heat aging (blend from Ex. 5, Table V). Although the
compatibility of 5.4 for the Example 6 material is
out-of-specification limits, the separation test value is assumed
to be an anomaly, as all other post crosslinker addition
compatibility tests were within specification limits. The MP1
properties (DSR and BBR Fail Temperatures) and the 135.degree. C.
Viscosity did not change significantly after 6 hrs of heat aging.
After 24hrs of heat aging the PMA was moved to finished inventory,
graded, and shipped with normal production.
[0076] For comparison, the MP1 grades from two randomly selected
PG76-22 PMA batches made from the same base stock are presented in
Table VI. It may be seen that the limiting RTFO DSR Fail
Temperatures are statistically equivalent; specifically, the
limiting RTFO DSR Fail Temperature is within the 1.degree. C.
margin of error in the test. There is an increase in the ODSR Fail
Temperature of the TPS-32 crosslinked PMA. There is also
significant improvement (lowering) in the PAV DSR Fail Temperature
in the PMA crosslinked with the TPS-32. The low-temperature MP1
values are essentially the same. TABLE-US-00006 TABLE VI SHRP
Grading of Trial PMA and PG76-22 PMA Batches EX. 19 Ex. 20 Ex. 21
Units TPS-32 Final PG76-22 PG76-22 Binder DSR .degree. C. 84.2 81.1
80.5 RTFO DSR .degree. C. 80.6 80.4 79.6 PAV DSR .degree. C. 14.6
18.1 18.8 m-Value .degree. C. -17.4 -15.8 -18.8 S-Value .degree. C.
-21.4 -21.4 -24.2 48 hr Compatibility .degree. F. 0.6 0.8 0.3
(.degree. C.) (0.3) (0.4) (0.2) 135.degree. C. Viscosity Pa*s 1.98
2.06 1.89
[0077] All PG64/67-22 and PMA base stocks are currently treated
with 0.1 wt % ZnO for H.sub.2S abatement. Currently any PMA base
stock is treated with an additional 0.1 wt % of ZnO immediately
prior to crosslinker addition to eliminate/reduce H.sub.2S
emissions in the final PMA resulting from the sulfur-containing
crosslinker. The second treatment of 0.1 wt % ZnO was not added
prior to TPS-32 XL addition, so that the effects of the sulfur
donor change on H.sub.2S emissions could be determined.
[0078] H.sub.2S measurements were taken during the trial by ATX
Automatic Tester and Draeger Tube Sampler on the air space of
(asphalt) can samples taken from the mix tank during the trial.
There was no measurable H.sub.2S in the Base Asphalt or
asphalt/rubber blend by either the ATX or Draeger Tube Sampler.
After crosslinker addition, the ATX registered 400-450ppm H.sub.2S
consistently over the entire 24 hr cure time; H.sub.2S measured by
the Draeger Tube Sampler was above the 200 ppm detection limit of
the test during the age-curing period. The trial samples were
tested for H.sub.2S by collection of vapors in a caustic trap and
follow-up titration. The results from the testing are presented in
Table VII. The 400-450 ppm levels of H.sub.2S measured during the
trial by the ATX Tester were considerably lower than the 1000+ ppm
readings from earlier testing on PMA following traditional
ZnO/MBT/s crosslinker addition. However, at 400-450 ppm, the
H.sub.2S levels are above the plant action limit of 10 ppm.
TABLE-US-00007 TABLE VII H.sub.2S Measurements from Testing of
Trial Material Example Units 11 PG67-22 Base Asphalt ppm <1 12
Before Crosslinker Addition + Rubber ppm <1 13 5 mins Post
Crosslinker Addition ppm 151 14 1 hr Post Crosslinker Addition ppm
39 15 2 hrs Post Crosslinker Addition ppm 7 16 6 hrs Post
Crosslinker Addition ppm 20 17 12 hrs Post Crosslinker Addition ppm
7 18 24 hrs Post Crosslinker Addition ppm 8
[0079] The finished TPS-32 crosslinked PMA was treated with the
prescribed second doage of 0.1 wt % ZnO after 24 hr aging for
H.sub.2S abatement. After treatment, no H.sub.2S was detected by
either the ATX Automatic Tester or the Draeger Tube Analyzer in the
final PMA and the material was moved to finished inventory.
[0080] TPS-32 was thus found suitable as a replacement crosslinker
for elemental sulfur in crosslinked PMA and was rubber compatible
and met target PG76-22 specifications. There was an increase in the
ODSR Fail Temperature and improvement (lowering) of the PAV DSR
Fail Temperature in the TPS-32 crosslinked PMA. There was a
reduction in the H.sub.2S emissions immediately after TPS-32
crosslinker addition, compared to previous testing on PMA
crosslinked with ZnO/MBT and elemental sulfur. However, the levels
of H.sub.2S, even in the finished/cured PMA (400+ppm by ATX) were
still beyond the action limits of 10 ppm. The final PMA was treated
with 0.1 wt % ZnO and no H.sub.2S was detected in the ZnO-treated
finished product. It should be recognized that this method is not
optimized.
EXAMPLES 19-32
[0081] A wide range of PMA formulations were tested for
relationship of rheological data to rubber compatibility.
Improvements are obtained when MBT is replaced by MBI. The
MBI-crosslinked PMAs were also improved when compared to the
Control blend crosslinked with traditional ZnO/MBT/S. Compatibility
was improved in blends crosslinked with TPS-32. The test procedure
was the same as for Examples 7-10.
[0082] Table VIII contains the test results for the FINAPRENE
502-modified blends, crosslinked with ZnO/MBT/S, and blends in
which the MBT and/or S is replaced by MBI or TPS-32, respectively.
TABLE-US-00008 TABLE VIII FP502 PMA Blends for Compatibility and
Rubber Response Units Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 PG64-22
Base Asphalt Wt % 100 96 96 96 96 FP502 Wt % 4 4 4 4 ZnO Wt % 0.06
0.06 0.06 0.06 MBT Wt % 0.06 0.06 MBI Wt % 0.06 0.06 Sulfur Wt %
0.12 0.12 TPS-32 Polysulfide Wt % 0.40* 0.40* Binder DSR .degree.
C. 66.3 83.4 83.6 82.5 83.0 RTFO DSR .degree. C. 67.8 81.2 82.8
82.0 82.4 PAV DSR .degree. C. 23.0 18.8 N/A 12.6 11.7 m-Value
.degree. C. -14.8 -17.5 -17.1 -17.2 -17.2 S-Value .degree. C. -15.8
-20.4 -19.4 -19.5 -19.6 24 hr Compatibility .degree. F. 4.7 8.6 0.8
2.1 (.degree. C.) (2.6) (4.8) (0.4) (1.2) 135.degree. C. Viscosity
Pa*s 1.88 1.88 1.63 1.71 *0.4 wt % TPS-32 has sulfur equivalent to
0.12 wt % elemental sulfur.
[0083] The Compatibility of FP502 in this asphalt was tested
without crosslinking and found to have a separation of 60.2.degree.
F. (33.4.degree. C.) at 24hrs. The Control PMA (Blend from Ex. 20,
Table VIII) is known to be compatible at the test specification of
48 hrs with a separation of 2.degree. F. (1.degree. C.).
Substitution of MBI for MBT (Blend from Ex. 21, Table VIII)
produced PMA with improved properties. The results from Example 22,
with TPS-32 substituted for sulfur showed improved properties,
relative to the Control blend crosslinked with ZnO/MBT/S,
particularly a dramatic improvement in the 24 hr Compatibility. The
blend crosslinked with ZnO/MBI/TPS-32 showed improved 24 hr
Compatibility, intermediate of the effects seen with just MBI or
TPS-32 substitution into the crosslinker. All of the PMA blends in
Table VII had viscosities within the normal range for PG76-22.
[0084] The trend of dramatic improvement (decrease) in the PAV DSR
Fail Temperature upon crosslinking with MBI and/or TPS-32 has been
seen in Examples 11-18. However, PAV DSR Fail Temperature is never
a limiting factor in PG76-22 production.
[0085] Several FP502 modified blends were formulated and
crosslinked with the ZnO substituted by CaO, Calcium Stearate, or
Zinc Stearate, and in conjunction with MBI/TPS-32. The test results
for these blends are presented in Table IX. TABLE-US-00009 TABLE IX
FP502 PMA blends for Compatibility Units Ex. 19 Ex. 24 Ex. 25 Ex.
26 Ex. 27 PG64-22 Base Asphalt Wt % 100 96 96 96 96 FINAPRENE 502
Wt % 4 4 4 4 CaO Wt % 0.06 Calcium Stearate Wt % 0.12 0.12 Zinc
Stearate Wt % 0.06 MBT Wt % MBI Wt % 0.06 0.06 0.06 0.06 Sulfur Wt
% 0.12 TPS-32 Polysulfide Wt % 0.40 0.40 0.40 Binder DSR .degree.
C. 66.3 81.8 83.5 82.7 82.3 RTFO DSR .degree. C. 67.8 81.8 80.9
81.2 82.6 PAV DSR .degree. C. 23.0 12.9 14.7 12.6 13.2 m-Value
.degree. C. -14.8 -16.7 -17.5 -17.0 -17.1 S-Value .degree. C. -15.8
-19.5 -20.0 -19.6 -19.9 24 hr Compatibility .degree. F. 3.2 1.2 6.4
5.3 (.degree. C.) (1.8) (0.7) (3.6) (2.9) 135.degree. C. Viscosity
Pa*s 1.70 1.85 1.67 1.68
[0086] Substitution of CaO for ZnO in the
ZnO/MBI/TPS-32-crosslinked PMA (Blend of Example 24, Table IX) had
little effect. The Compatibility was within experimental error of
the results for the similar blend crosslinked with ZnO/MBI/TPS-32
(Blend of Ex. 27, Table IX). Substitution of ZnO with an excess of
Calcium Stearate resulted in a slight decrease in the compatibility
properties, compared to the similar blend crosslinked with ZnO.
Finally, the blend crosslinked with Zinc Stearate/MBI/TPS-32 (Ex.
26) had properties similar to the Blend crosslinked with
ZnO/MBI/TPS-32 (Ex. 23); there was no benefit in substitution of
Zinc Stearate for ZnO. All of the blends showed significant
improvement in the PAV DSR Fail Temperature upon crosslinking with
MBI and/or TPS-32.
[0087] Although CaO is cheaper than ZnO, more recent work has shown
that the metal oxide may be eliminated from the crosslinker
formulation, provided that excess ZnO has been added to the base
asphalt for H.sub.2S emission control. CaO has not been shown to
control H.sub.2S emissions. TABLE-US-00010 TABLE X FINAPRENE 401
PMA Blends for Compatibility Units Ex. 19 Ex. 20 Ex. 21 PG64-22
Base Asphalt Wt % 100 96 96 FP401 Wt % 4 4 ZnO Wt % 0.06 0.06 MBT
Wt % 0.06 MBI Wt % 0.06 Sulfur Wt % 0.12 TPS-32 Polysulfide Wt %
0.40* Binder DSR .degree. C. 66.3 82.5 81.7 RTFO DSR .degree. C.
67.8 80.7 79.8 PAV DSR .degree. C. 23.0 13.8 13.4 m-Value .degree.
C. -14.8 -17.3 -17.9 S-Value .degree. C. -15.8 -19.6 -20.5 24 hr
Compatibility .degree. F. 4.0 5.7 (.degree. C.) (2.2) (3.2)
135.degree. C. Viscosity Pa*s 2.77 2.01
[0088] PMA blends made using FINAPRENE 401 copolymer are shown in
Table X. Uncrosslinked PMA modified with FP401 was incompatible
with a separation of 33.8.degree. F. (18.8.degree. C.); the
separation of the uncrosslinked FP401 PMA was significantly better
than the uncrosslinked FP502 PMA with a separation of 60.2.degree.
F. (33.4.degree. C.). The Control FP401 blend (Ex. 19), crosslinked
with ZnO/MBT/S was compatible with a separation of 4.0.degree. F.
(2.2.degree. C.) after 24 hrs. The FP401 PMA had a slightly
increased 24 hr separation of 5.7.degree. F. (3.2.degree. C.). The
MP1 grading results for the two PMA blends are statistically
equivalent, although there is a distinct increase in the
135.degree. C. Viscosity of the FP401 blend crosslinked with
traditional ZnO/MBT/S.
[0089] FP401 modified blends were formulated and crosslinked with
the ZnO substituted for by Calcium Stearate or Zinc Stearate, and
in conjunction with MBI/TPS-32. The test results for these blends
are presented in Table XI. TABLE-US-00011 TABLE XI FINAPRENE 401
PMA blends for Compatibility Units 1 2 3 4 PG64-22 Base Asphalt Wt
% 100 96 96 96 FP401 Wt % 4 4 4 Calcium Stearate Wt % 0.06 0.12
Zinc Stearate Wt % 0.12 MBI Wt % 0.06 0.06 0.06 TPS-32 Polysulfide
Wt % 0.40* 0.40* 0.040* Binder DSR .degree. C. 66.3 81.7 81.1 81.3
RTFO DSR .degree. C. 67.8 80.0 79.9 79.7 PAV DSR .degree. C. 23.0
13.7 10.3 13.1 m-Value .degree. C. -14.8 -17.4 -17.3 -17.2 S-Value
.degree. C. -15.8 -21.2 -20.5 -20.3 24 hr Compatibility .degree. F.
6.7 4.9 4.0 (.degree. C.) (3.7) (2.7) (2.2) 135.degree. C.
Viscosity Pa*s 2.01 1.92 1.96
[0090] All of the blends crosslinked with either Zinc Stearate or
Calcium Stearate and MBI/TPS-32 had Compatibilities in the same
range as the ZnO/MBT/S FP401 Control Blend (Blend from Ex. 28,
Table X). There were no differences in the properties of the FP401
PMA blends crosslinked with Zinc Stearate or Calcium Stearate
compared to the FP401 PMA blend crosslinked with
ZnO/MBI/TPS-32.
[0091] In conclusion, FP502 was found to be compatible with the
base asphalt of Examples 1932 upon crosslinking. Crosslinker
formulations with MBI and/or TPS-32 had improved compatibility. Use
of TPS-32 produced PMA with improved 24 hr Compatibility.
Substitution of CaO for ZnO in CaO/MBI/TPS-32 crosslinker produced
FP502-modified PMA with equivalent properties. The Control FP401
blend, crosslinked with ZnO/MBT/S was compatible with a separation
of 4.0.degree. F. (2.2.degree. C.) after 24 hrs. FP401 modified
PMA, crosslinked with ZnO/MBI/TPS-32 had a 24 hr separation of
5.7.degree. F. (3.2.degree. C.), just outside of the 48 hr
specification maximum of 4.0.degree. F. (2.2.degree. C.). Again, it
will be appreciated that these blends are at the beginning of
development and are not yet optimized. FP401-modified PMAs
crosslinked with Zinc or Calcium Stearate and MBI/TPS-32 had
properties equivalent to the PMA from ZnO/MBI/TPS-32.
[0092] In the foregoing specification, the methods and compositions
herein have been described with reference to specific embodiments
thereof, and have been demonstrated as effective in providing
methods for preparing asphalt and polymer compositions with
improved properties. However, it will be evident that various
modifications and changes may be made to the method without
departing from the broader spirit or scope of the invention as set
forth in the appended claims. Accordingly, the specification is to
be regarded in an illustrative rather than a restrictive sense. For
example, specific combinations or amounts of asphalt, polymer,
crosslinker, acid, activator, accelerator, and other components
falling within the claimed parameters, but not specifically
identified or tried in a particular PMA system, are anticipated and
expected to be within the scope of this invention. Specifically,
the method and discovery of the invention are expected to work with
asphalts, polymers and crosslinkers other than those specifically
exemplified herein.
* * * * *