U.S. patent application number 16/304814 was filed with the patent office on 2020-10-08 for a bitumen composition comprising a wax mixture consisting of a petroleum slack wax and a fischer-tropsch wax, the use of the wax mixture in bitumen compositions, the use of the bitumen composition in asphalt compositions, asphalt compositions comprising the bitumen composition and the method of prod.
The applicant listed for this patent is Sasol Was GmbH. Invention is credited to Thorsten Butz, William Honiball, Carsten Oelkers, Stefan Strydom.
Application Number | 20200317924 16/304814 |
Document ID | / |
Family ID | 1000004943939 |
Filed Date | 2020-10-08 |
United States Patent
Application |
20200317924 |
Kind Code |
A1 |
Butz; Thorsten ; et
al. |
October 8, 2020 |
A Bitumen Composition Comprising a Wax Mixture Consisting of a
Petroleum Slack Wax and a Fischer-Tropsch Wax, the Use of the Wax
Mixture in Bitumen Compositions, the Use of the Bitumen Composition
in Asphalt Compositions, Asphalt Compositions Comprising the
Bitumen Composition and the Method of Producing Asphalt Pavements
Thereof
Abstract
The present invention relates to a bitumen composition
comprising a petroleum slack wax and a Fischer-Tropsch wax, the use
of the waxes in bitumen compositions, the use of the bitumen
composition in asphalt compositions, asphalt compositions
comprising the bitumen composition and a method for producing
asphalt pavements and constructions thereof. The bitumen has proved
to have better processing characteristics.
Inventors: |
Butz; Thorsten; (Buchholz,
DE) ; Oelkers; Carsten; (Seevetal, DE) ;
Strydom; Stefan; (Sasolburg, ZA) ; Honiball;
William; (Sasolburg, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sasol Was GmbH |
Hamburg |
|
DE |
|
|
Family ID: |
1000004943939 |
Appl. No.: |
16/304814 |
Filed: |
May 26, 2017 |
PCT Filed: |
May 26, 2017 |
PCT NO: |
PCT/EP2017/062805 |
371 Date: |
November 27, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 2555/72 20130101;
E01C 9/001 20130101; E01C 19/1009 20130101; C08L 91/08 20130101;
E01C 19/23 20130101; C04B 24/36 20130101; C08L 95/00 20130101; E01C
11/00 20130101; E01C 19/4813 20130101 |
International
Class: |
C08L 91/08 20060101
C08L091/08; C08L 95/00 20060101 C08L095/00; C04B 24/36 20060101
C04B024/36; E01C 11/00 20060101 E01C011/00; E01C 9/00 20060101
E01C009/00; E01C 19/10 20060101 E01C019/10; E01C 19/48 20060101
E01C019/48 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2016 |
EP |
16171822.6 |
Claims
1. A bitumen composition comprising at least one wax mixture
consisting of 20 to 80 wt.-% of a petroleum slack wax (PSW), and 20
to 80 wt.-% of a Fischer-Tropsch wax (FTW), each relative to the
total mass of the at least one wax mixture.
2. The bitumen composition according to claim 1 comprising 0.5 to
2.5 wt. % of the at least one wax mixture.
3. The bitumen composition according to claim 1, wherein the at
least one wax mixtures consists of 30 to 70 wt. % of the PSW, and
the remainder being the FTW.
4. The bitumen composition according to claim 1, wherein the PSW
has one or more of the following features: a congealing point
according to ASTM D 938 below 65.degree. C.; a MEK-oil content
according to ASTM D 7211-06 above 15 wt.-% a kinematic viscosity at
100.degree. C. according to ASTM D 7042-11 between 5 and 10
mm.sup.2/s; a needle penetration at 25.degree. C. according to ASTM
D 1321 above 50 1/10 mm; and a n-alkane content below 40 wt.-%.
5. The bitumen composition according to claim 1, wherein the FTW
has one or more of the following features: a congealing point
according to ASTM D 938 above 70.degree. C.; a MEK-oil content
according to ASTM D 7211-06 below 5 wt. % a kinematic viscosity at
100.degree. C. according to ASTM D 7042-11 between 5 and 10
mm.sup.2/s; a needle penetration at 25.degree. C. according to ASTM
D 1321 below 10 1/10 mm; and a n-alkane content above 80 wt.-%.
6. The bitumen composition according to claim 1, wherein the at
least one wax mixture has one or more of the following features: a
congealing point according to ASTM D 938 between 70 and 85.degree.
C.; a MEK-oil content according to ASTM D 7211-06 below 10 wt.-%; a
needle penetration at 25.degree. C. according to ASTM D 1321
between 15 and 30 1/10 mm; and a n-alkane content above 60
wt.-%.
7. The bitumen composition according to claim 1, wherein the FTW,
the PSW or both are hydrotreated.
8. The bitumen composition according to claim 1, wherein the
bitumen composition further comprises one or more polymers selected
from the group consisting of elastomers and plastomers.
9. The bitumen composition according to claim 1, wherein the
bitumen composition further comprises one or more additives
selected from the group consisting of rubber, resins,
anti-stripping agents, fibers, organosilanes, surfactants and
adhesion promoters.
10. (canceled)
11. (canceled)
12. An asphalt composition comprising the bitumen composition
according to claim 1, stone aggregate and fillers.
13. The asphalt composition according to claim 12, wherein the
asphalt composition comprises greater than 25 wt. % reclaimed
asphalt.
14. A method for the production of asphalt pavements by means of
process A comprising the following steps: mixing the bitumen
composition according to claim 1 with mineral aggregate and fillers
at temperatures between 150 to 190.degree. C.; in case of mastic
asphalt up to 250.degree. C. to obtain an asphalt composition;
filling the asphalt composition in a truck or storage silo;
transporting the asphalt composition to the building site; applying
the asphalt composition to the surface with a paver to obtain an
asphalt surface; and compacting the asphalt surface with a roller,
or by process B comprising the following steps: transporting the
bitumen compositions according to claim 1 to the building site
having temperatures between 150 to 190.degree. C.; spraying the
bitumen composition on the surface; distributing mineral aggregates
over the hot layer of the bitumen composition; and pressing the
mineral aggregates into the layer of the bitumen using a
roller.
15. The method according to claim 14, wherein process A comprises
adding greater 25 wt. % recycled asphalt, without heating it.
16. The method according to claim 14, wherein the applying and/or
compacting of the asphalt composition takes place at temperatures
below 150.degree. C.
Description
[0001] The invention relates to a bitumen composition comprising a
wax mixture consisting of a petroleum slack wax and a
Fischer-Tropsch wax, the use of the wax mixture in bitumen
compositions, the use of the bitumen composition in asphalt
compositions, asphalt compositions comprising the bitumen
composition and a method for producing asphalt pavements and
constructions thereof.
Description of the Prior Art and Object of the Invention
[0002] Bitumen is a natural occurring or from the vacuum
distillation of crude oil obtainable mixture of organic compounds
with elastic-viscose properties. It is sticky, non-volatile,
sealing and almost not-soluble in non-polar solvents.
[0003] Bitumen is used in a plurality of construction applications,
such as coating of buildings, bitumen blanks etc. One of the most
important applications is the use as binder for stone aggregates in
asphalt for the paving of roads.
[0004] Asphalt is produced in large mixing plants with an output of
130 to 350 tons per hour. In this nowadays electronically
controlled process the asphalt components are dosed, mixed and
homogenized. At first the stone aggregate with a defined particle
size and dosage is added to a drum drier. The moisture associated
with the stones is evaporated and the required temperature is
adjusted. Afterwards the aggregate is transferred into a tower,
where the appropriate particle size distribution is produced. Then
the hot bitumen and other additives are sprayed on to aggregate and
thoroughly mixed with it using either a continuous drum mixer or
pug mill batch mixer. At temperatures between 160 and 180.degree.
C. the readily mixed asphalt can then be transported into silos or
trucks to reach the building site, where it is needed and
paved.
[0005] Depending on the layer in the pavement and the traffic load
various types of asphalt mixes are in use that differ in the
gradation of the mineral aggregates sizes and the percentage of
bituminous binder. Important examples of asphalt mix types are
asphalt concrete for base layers, binder layers and wearing
courses, stone mastic asphalt and open graded porous asphalt. A
further asphalt mix type is mastic asphalt or Guss asphalt, which
is produced at very high temperature above 200.degree. C. and is
applied in pourable form. It results in asphalt layers that are
almost free of air voids.
[0006] Alternatively thin asphalt layers can also be produced by
spraying the hot bituminous binder on the surface to be paved,
distributing the mineral aggregates over the hot bituminous binder
and pressing the aggregates into the binder using a roller. This
technique is called spray and chip or chip seal and requires a
specific aggregate gradation.
[0007] Asphalt mixes and pavements are subjected to strict national
and international regulations and standards in order to ensure a
high and satisfying performance of the asphalt.
[0008] Nowadays asphalt may also be recycled if new pavements are
constructed. The recycled pavement is frequently called RAP
(reclaimed asphalt pavement). For that the old asphalt will be
milled from the pavement, crushed to applicable gradation and mixed
with new bituminous binder and stone aggregates to result in a
product of at least the quality as new asphalt. A rejuvenator may
be added during mix production, if the bituminous binder in the
recycled asphalt strongly hardened by ageing during the service
life. Mostly RAP is added into an asphalt mixing plant without
pre-heating it, applying the "cold addition technique". The heat
energy, which is needed for obtaining the final asphalt mix
temperature, has to be introduced by the fresh aggregates and
bitumen heated to the desired temperature. As there are technical
limitations for heating the fresh materials, the percentage of RAP
that can be added by the cold addition technique, is limited to 20
to 30 wt.-% of the resulting asphalt mix. The maximum percentage
depends on the specific asphalt mix type. Only a few asphalt mixing
plants are equipped with a parallel heating drum for preheating
RAP. This "hot addition technique" allows the addition of higher
RAP percentages.
[0009] To improve the properties of the asphalt products in general
different additives or modifiers may be used, selected from the
group of fillers (e.g. hydrated lime, cement, carbon black),
extenders (e.g. sulfur, lignin), rubber, elastomeric polymers,
plastomeric polymers, resins, fibers (e.g. rock wool, cellulose),
anti-oxidants, hydrocarbons, antistripping agents, organosilanes,
surfactants and waste materials.
[0010] From the prior art it is known that waxes are suitable
additives for bitumen to produce high-quality asphalt mixes and
asphalt pavements. Especially hydrocarbon waxes, such as paraffin
waxes and Fischer-Tropsch waxes have been used.
[0011] Waxes in general are mostly defined as chemical
compositions, which have a drop melting point above 40.degree. C.,
are polishable under slight pressure, are knead-able or hard to
brittle and transparent to opaque at 20.degree. C., melt above
40.degree. C. without decomposition, and typically melt between 50
and 90.degree. C. with exceptional cases up to 200.degree. C., form
pastes or gels and are poor conductors of heat and electricity.
[0012] Waxes can be classified according to various criteria such
as e.g. their origin. Here, waxes can be divided into two main
groups: natural and synthetic waxes. Natural waxes can further be
divided into fossil waxes (e.g. petroleum waxes) and non-fossil
waxes (e.g. animal and vegetable waxes). Petroleum waxes are
divided into macrocrystalline waxes (paraffin waxes) and
microcrystalline waxes (microwaxes). Synthetic waxes can be divided
into partially synthetic waxes (e.g. amide waxes) and fully
synthetic waxes (e.g. polyolefin- and Fischer-Tropsch waxes).
[0013] Paraffin waxes originate from petroleum vacuum distillation
cuts. They are clear, odor free and can be refined for food
contact. They contain a range of (primarily) n-alkanes and
iso-alkanes as well as some cyclo-alkanes. Raw or crude paraffin
waxes (slack waxes) have a great number of short-chained and highly
branched alkanes ("oils"), which can be removed when deoiled.
Different distributions and qualities of paraffin waxes can be
obtained therefrom. Further refining may include distillation,
bleaching and hydrotreating.
[0014] Microwaxes originate from deasphalting, dearomatization and
deoiling of petroleum vacuum distillation residues. They are rich
in branched and cyclic alkanes and contain generally less than 50%
n-alkanes.
[0015] Synthetic Fischer-Tropsch waxes or hydrocarbons originate
from the catalyzed Fischer-Tropsch synthesis of syngas (CO and
H.sub.2) to alkanes. There are some major differences between
petroleum based paraffin waxes and Fischer-Tropsch waxes which
result in deviating properties like e.g. crystallization and
rheological behaviour. Another source for the waxes/hydrocarbons
are products obtained from the oligomerization/polymerization of
olefinic monomers, possibly followed by hydrotreating.
[0016] GB 2234512 A discloses a road surfacing composition
comprising aggregate and a binder, which comprises bitumen and a
viscosity modifier comprising a wax. The viscosity is reduced by at
least 25% compared with the original binder. Suitable modifiers
include microcrystalline wax, montan wax or coal tar wax but not
paraffin wax or oil slack wax. The modified binder is mainly
intended for surface dressing (spray and chip) or for hot mix
asphalt. Asphalt recycling is not mentioned. Up to and including
this publication the presence of paraffin waxes for road surface
compositions was held undesirable because it adversely effects the
adsorption of asphaltenes onto marble and therefore increases the
viscosity of the bitumen composition. This is why usually petroleum
vacuum residues that are rich in paraffin waxes by nature are not
used as asphalt binder. GB 2234512 A found that harder waxes with a
lower penetration (e.g. microcrystalline waxes) are suitable as
viscosity reducing agents in bitumen. Instead of completely mixing
with the maltenes phase at all states of the asphalt as paraffin
waxes do, waxes according to this patent are less compatible with
the maltenes and form a dispersed phase at lower temperatures
decreasing the viscosity of it significantly.
[0017] EP 1017760 B1 discloses the use of synthetic Fischer-Tropsch
waxes in asphalt for road pavements to increase the stability
thereof. Fischer-Tropsch waxes have a high content of linear
hydrocarbons (>90 wt.-%) and can have a high congealing point
(up to 105.degree. C.). It was found that 0.5 wt.-% or more
Fischer-Tropsch paraffin wax in the bitumen of the asphalt allow a
higher compaction of the asphalt and at the same time decrease the
viscosity of the bitumen in the liquid state during asphalt
mixing.
[0018] It was found that Fischer-Tropsch waxes allow a lower
temperature of mixing (WMX-warm mix asphalt) but nowadays part of
the asphalt industry discusses an increase in the stiffness and low
temperature brittleness of the bitumen due to the addition of
Fischer-Tropsch waxes.
[0019] Based on the improvements discovered further combinations
with other additives and uses of Fischer-Tropsch waxes in bitumen
have been suggested in the following years.
[0020] WO 02/16499 A1 discloses the use of a wax, preferably a
synthetic Fischer-Tropsch wax, as hydrocarbon resistant, preferably
fuel resistant additive for bitumen. The wax is supposed to render
the bitumen more resistant against fuel by being fuel-resistant
itself and increasing the compaction rate of the asphalt produced
therefrom, thereby decreasing the number of voids in the asphalt
accessible to the fuel.
[0021] WO 2008/101809 A1 discloses an age-resistant bituminous
composition containing at least one paraffin in a concentration of
between 0.5 and 5.0 wt.-%. The age resistance is reflected by a
lower variation of the ring and ball softening temperature of the
bituminous composition after the Rolling Thin Film Oven Test
(RTOFT).
[0022] The paraffins are preferably synthetic paraffins obtained by
the Fischer-Tropsch synthesis.
[0023] U.S. Pat. No. 8,772,381 B2 discloses the use of waxes in a
cross-linked bitumen/polymer composition for improving resistance
to chemical attack.
[0024] U.S. Pat. No. 8,734,581 B2 discloses bituminous paving
mixtures containing lubricating agents or additives which allow
paving and compacting of it at temperatures 10 to 55.degree. C.
lower than the mixing temperature due to improved compacting
properties.
[0025] WO 2009/062925 discloses asphalt modifiers for "warm mix"
application including adhesion promoter.
[0026] US 2010/0227954 A1 discloses asphalt compositions and
products comprising petroleum asphalt, polyolefin and a wax.
[0027] WO 2014/043021 A1 discloses a non-blown roofing grade
bitumen composition comprising a bitumen feedstock, a polyolefin
and optionally one or more additives. The composition is used to
obtain the desired properties of oxidized bitumen without the need
for a blowing process.
[0028] EP 2058056 B1 discloses the use of synthetic paraffin wax as
hardening agent in the recycling of used/reclaimed asphalt together
with softening agents such as oils to reduce the ageing of the
bitumen of the reclaimed asphalt.
[0029] DE 202005003108 U1 discloses bitumen compositions comprising
bitumen, at least one animal and/or vegetable oil and/or fat and at
least one wax. One example is the use of a combination of a
Fischer-Tropsch wax and rapeseed oil to obtain a bitumen with
improved fatigue strength.
[0030] US 2014/0076777 A1 discloses a method for upgrading an
asphalt (i.e. bitumen) by using waxy bitumen and/or adding at least
3% refinery wax and adding a pour point depressant. The wax shall
reduce the viscosity of the bitumen and the pour point depressant
shall improve the low temperature performance of the bitumen.
Asphalt recycling is not mentioned.
[0031] Over time the professional circles realized that each
individual wax has certain properties in bitumen, but a combination
of different waxes or waxes and other additives may show properties
distinct from the properties of the individual components. For
example Fischer-Tropsch waxes alone are able to improve the process
properties of bitumen and asphalt mixes and the stability of the
asphalt obtained therefrom afterwards. On the other hand oils are
able to allow recycling of asphalt by acting as rejuvenator. But no
wax additive or combination is available from the prior art which
improves the processing parameters of bitumen during the asphalt
production without negatively altering at the same time the
physical properties of the bitumen in the final product, in
particular imparting almost no increase of the stiffness and low
temperature brittleness of the bitumen and the asphalt.
[0032] It is thus an aim of the present invention to find a wax
mixture which shows superior properties in bitumen and asphalt mix
processing overcoming the disadvantages of the prior art, but have
no decisive influence on the physical properties of bitumen.
SUMMARY OF THE INVENTION
[0033] It was surprisingly found that a bitumen composition
comprising at least one wax mixture consisting of [0034] 20 to 80
wt.-% of a petroleum slack wax (PSW), and [0035] 20 to 80 wt.-% of
a Fischer-Tropsch wax (FTW), each relative to the total mass of the
at least one wax mixture (=100 wt.-%) shows superior properties in
bitumen processing.
[0036] A further embodiment of the invention is the use of the at
least one wax mixture in bitumen compositions, preferably to
improve the processability and/or elastic recovery thereof.
[0037] Yet another embodiment of the invention is the use of the
bitumen composition for the production of asphalt compositions, in
particular to obtain improved compaction resistance, ageing
resistance and/or low temperature performance of the asphalt
composition. This allows the application in cold climates (below
10.degree. C. or even 0.degree. C.), for long lasting and durable
asphalts as well as for heavy duty and/or heavy traffic asphalt
roads.
[0038] In another embodiment an asphalt composition comprising the
bitumen composition, stone aggregate and fillers is claimed.
[0039] Furthermore the invention includes a method for the
production of asphalt pavements by making use of the bitumen
composition according to the invention.
[0040] While known improvements of Fischer-Tropsch waxes such as
lower viscosity are present, possible disadvantages such as low
temperature brittleness and increased stiffness of the bitumen and
the asphalt produced therefrom can be minimized. That means the
physical properties of the original bitumen are maintained, while
improvements in the processing of the bitumen are achieved.
[0041] Moreover, the bitumen composition according to the invention
allows a further reduction of the asphalt compaction temperature
compared to the sole use of Fischer-Tropsch waxes as the onset of
the crystallization of the wax mixture in the bitumen composition
and in the asphalt mix made therewith was found to be 30.degree. C.
lower.
[0042] Surprisingly it was found that the bitumen composition
according to the invention allows the processing of increased
amounts of recycled asphalts in asphalt compositions using the cold
addition technique compared to the state of the art.
[0043] Furthermore the better processability of the bitumen
composition according to the invention allows the applying and/or
compaction of asphalt compositions at temperatures below
150.degree. C.
DETAILED DESCRIPTION OF THE INVENTION
[0044] In a preferred embodiment the bitumen composition comprises
0.5 to 2.5 wt.-%, more preferably 1.0 to 2.0 wt.-% of the at least
one wax mixture.
[0045] The wax mixture preferably consists of 30 to 70 wt.-% of the
petroleum slack wax; and 30 to 70 wt.-% of the Fischer-Tropsch
wax.
[0046] Furthermore the wax mixture more preferably consists of 50
wt.-%, most preferably 40 wt.-% of the petroleum slack wax (PSW);
and more preferably 50 wt.-%, most preferably 60 wt.-% of the
Fischer-Tropsch wax (FTW).
[0047] Petroleum slack waxes as used in the composition according
to the invention are defined as crude or raw paraffin waxes
originating from petroleum vacuum distillation cuts, which
according to a further embodiment are bleached and/or hydrotreated
(which according to the understanding of this invention are also
defined as slack waxes). They may be further characterized in terms
of viscosity classes according to ASTM D 2161 ranging from 80 to
600 SUS (SUS="Saybolt Universal Seconds"), preferably from 300 to
600 SUS.
[0048] The petroleum slack wax preferably has one or more of the
following features: [0049] a congealing point according to ASTM D
938 below 65.degree. C.; [0050] a MEK-oil content according to ASTM
D 7211-06 above 15 wt.-%; [0051] a kinematic viscosity at
100.degree. C. according to ASTM D 7042-11 between 5 and 10
mm.sup.2/s, preferably 6 to 8 mm.sup.2/s; [0052] a needle
penetration at 25.degree. C. according to ASTM D 1321 above 50 1/10
mm; and [0053] a n-alkane content below 60 wt.-%.
[0054] Fischer-Tropsch waxes as used in the composition according
to the invention are defined as waxes originating from the Cobalt-
or Iron-catalyzed Fischer-Tropsch synthesis of syngas (CO and
H.sub.2) to alkanes. The crude product of this synthesis is
separated into liquid and different solid fractions by
distillation. The waxes contain predominantly n-alkanes, a low
number of iso-alkanes and basically no cyclo-alkanes or impurities
like e.g. sulfur or nitrogen. In return the number of olefins is
higher compared to petroleum based waxes. The Fischer-Tropsch waxes
have a congealing point of 30.degree. C. to 105.degree. C. and a
carbon chain length of 15 to 65 carbon atoms.
[0055] The Fischer-Tropsch wax preferably has one or more of the
following features: [0056] a congealing point according to ASTM D
938 above 70.degree. C., preferably above 75.degree. C., more
preferably between greater 75.degree. C. and 85.degree. C. and most
preferably between greater 75.degree. C. and 82.degree. C.; [0057]
a MEK-oil content according to ASTM D 7211-06 below 5 wt.-%,
preferably below 2 wt.-%; [0058] a kinematic viscosity at
100.degree. C. according to ASTM D 7042-11 between 5 and 10
mm.sup.2/s, preferably 7 to 9 mm.sup.2/s; [0059] a needle
penetration at 25.degree. C. according to ASTM D 1321 below 10 1/10
mm; and [0060] a n-alkane content above 80 wt.-%.
[0061] The wax mixture preferably has one or more of the following
features: [0062] a congealing point according to ASTM D 938 between
70 and 85.degree. C., preferably between 72.degree. C. and
83.degree. C. and more preferably between 75.degree. C. and
82.degree. C.; [0063] a MEK-oil content according to ASTM D 7211-06
below 10 wt.-%; [0064] a needle penetration at 25.degree. C.
according to ASTM D 1321 between 15 and 30 1/10 mm; and [0065] a
n-alkane content above 60 wt.-%.
[0066] The above n-alkane content is determined by gas
chromatography. The standard method 001/03 of the European Wax
Federation may be used for that.
[0067] The Fischer-Tropsch wax or the petroleum slack wax are
preferably hydrotreated, more preferably both are hydrotreated.
Hydrotreatment of the wax components does improve the ageing
resistance of the bitumen composition comprising them.
[0068] Without being bound to this theory this may come from the
lower amount of unsaturated hydrocarbons in the wax components
after hydrotreatment.
[0069] The hydrotreating of the Fischer-Tropsch wax may be
conducted catalytically using any suitable technique known to
persons skilled in the art of wax hydrotreating. Typically, the
Fischer-Tropsch wax is hydrotreated using hydrogen at an absolute
pressure between about 30 and about 70 bar, e.g. about 50 bar and
an elevated temperature between about 150 and about 250.degree. C.,
e.g. about 220.degree. C. in the presence of a Nickel-catalyst,
such as NiSat 310 available from Sued-Chemie SA (Pty) Ltd of 1 Horn
Street, Chloorkop, 1624, South Africa. The hydrotreating of the
Fischer-Tropsch wax is to be understood as a process in which
components such as alcohols or other compounds containing oxygen
and unsaturated hydrocarbons such as olefins are converted to
alkanes by a catalytic reaction with hydrogen. It does not include
cracking reactions such as hydroisomerization or hydrocracking.
[0070] Petroleum slack waxes contain aromatic, sulfur and nitrogen
compounds. The slack waxes can be freed from above other components
by hydrotreating under enhanced conditions such as a hydrogen
pressure of 80 to 150 bar, a temperature of 250 to 350.degree. C.
and preferably at space velocities of 0.3 to 2 h.sup.-1. Preferred
catalysts which are suitable for hydrotreating petroleum slack
waxes are sulfurized Ni, Mo, W catalysts.
[0071] The bitumen composition may also comprise one or more
polymers selected from the group of elastomers, e.g. SBS and
similar block-co-polymers and plastomers, e.g. EVA or polyolefins,
according to one embodiment up to 7 wt. %.
[0072] Further additives may be selected from the group of rubber
(e.g. up to 25 wt. %), resins (e.g. up to 10 wt. %), anti-stripping
agents (e.g. up to 3 wt. %), fibers (e.g. up to 5 wt. %),
organosilanes (e.g. up to 2 wt. %), surfactants and/or adhesion
promoters (e.g. up to 2 wt. %) such as amines, amides or organic
esters of phosphoric acid. It is also possible to add further
hydrocarbons (different from above claimed waxes).
[0073] Such an asphalt composition may be used for road pavements,
airport pavements, fuel station pavements, driveway pavements,
parking lot pavements, bicycle and walking path pavements,
pavements of logistic areas or agricultural pavements.
[0074] Furthermore, the asphalt composition preferably contains
greater 25 wt.-%, preferably greater 30 wt.-%, more preferably
greater 40 wt.-% and most preferably greater 60 wt.-% reclaimed
asphalt.
[0075] In another embodiment of the invention the method for the
production of asphalt pavements (process A) comprising: [0076]
mixing the bitumen composition as described above with mineral
aggregate and fillers at temperatures between 150 to 190.degree.
C., in case of mastic asphalt up to 250.degree. C., to obtain an
asphalt composition; [0077] filling the asphalt composition in a
truck or storage silo; [0078] transporting it to the building site;
[0079] applying the asphalt composition to the surface with a paver
to obtain an asphalt surface; and [0080] compacting the asphalt
surface with a roller is claimed.
[0081] The method may comprise adding greater 25 wt.-%, preferably
greater 30 wt.-%, more preferably greater 40 wt.-% and most
preferably greater 60 wt.-% recycled asphalt without heating
it.
[0082] In another embodiment of the invention the method for the
production of asphalt pavements (process B) comprising: [0083]
transporting the bitumen composition as described above to the
building site; [0084] spraying the bitumen composition on the
surface; [0085] distributing mineral aggregates over the hot layer
of the bitumen composition; and [0086] pressing the mineral
aggregates into the layer of the bitumen composition using a roller
is claimed.
EXAMPLES
Example 1
[0087] Bitumen samples with grade 70/100 (unmodified) according to
DIN EN 12591 were mixed with 1.5 wt.-% of wax mixture A (Sasobit
Redux, see table 1) consisting of 40 wt.-% Sasolwax C80M and 60
wt.-% Prowax 561 or 1.5 wt.-% of a Fischer-Tropsch wax (Sasobit)
relative to bitumen.
TABLE-US-00001 TABLE 1 Properties of wax mixture A, petroleum slack
wax and Fischer-Tropsch wax used in the wax mixture A and Sasobit.
Penetration @ Viscosity @ Congealing 25.degree. C. 100.degree. C.
point [.degree. C.] [1/10 mm] [mm.sup.2/s] n-alkane Oil-content
ASTM D 938 ASTM D 1321 ASTM D 7042-11 content * ASTM D 7211-06 Wax
mixture A (60% PSW1/40% FTW1) = Sasobit Redux 78.0 27 8.2 62.5 7.8
PSW1 (Prowax 561 from ExxonMobil) 63.5 76 8.5 32.6 17.4 FTW1
(Sasolwax C80M) 77.0 9 8.0 86.2 1.3 Sasobit 101.0 1 12.0 @
135.degree. C. 89.9 <1.0 * By gas chromatography according to
the standard method 001/03 of the European Wax Federation
[0088] The congealing point of the wax mixture A is dominated by
the higher-melting Fischer-Tropsch wax component Sasolwax C80M so
that it has the same congealing point as the Fischer-Tropsch wax
within the accuracy of the applicable method (ASTM D 938).
[0089] The properties of the bitumen samples were determined by
measuring needle penetration according to DIN EN 1426, the
softening point (ring & ball) according to DIN EN 1427 and the
complex shear modulus G* as well as the phase angle 6 each
according to DIN EN 14770, the latter by applying a Dynamic Shear
Rheometer. High G* and low .delta. values mean high stiffness of
the bituminous binder (table 2).
TABLE-US-00002 TABLE 2 Bitumen properties. 0% Wax added 1.5% Wax
mixture A 1.5% Sasobit Parameter [unit] (100% bitumen) (98.5%
bitumen) (98.5% bitumen) Penetration at 25.degree. C. [0.1 mm] 72.0
59.0 48.0 Softening point Ring & Ball [.degree. C.] 48.8 50.4
57.4 G* at 40.degree. C. [Pa] 26840 49500 69170 G* at 50.degree. C.
[Pa] 6169 7767 15240 G* at 60.degree. C. [Pa] 1671 1517 3684 Phase
angle .delta. at 40.degree. C. [.degree.] 78.62 74.35 70.94 Phase
angle .delta. at 50.degree. C. [.degree.] 83.35 81.20 75.51 Phase
angle .delta. at 60.degree. C. [.degree.] 86.47 86.30 78.27
[0090] It can be seen that the wax mixture A has much lower impact
on the needle penetration, the softening point, the complex modulus
and the phase angle of the bitumen than the Fischer-Tropsch wax
Sasobit. These results display the reduced impact on the stiffness
of bitumen, when a mixture of petroleum slack wax and
Fischer-Tropsch wax is used.
[0091] To determine the influence of the additive on the processing
of the bitumen comprising the wax mixture according to the
invention dynamic viscosities of the bitumen compositions were
measured using a parallel plate viscometer with plate diameter 25
mm and 1 mm plate distance at different processing temperatures
(see table 3).
TABLE-US-00003 TABLE 3 Viscosities of bitumen compositions at
different processing temperatures. Viscosity at 120.degree. C.,
Viscosity at 135.degree. C., Viscosity at 160.degree. C., at shear
rate 50 Pa at shear rate 30 Pa at shear rate 10 Pa [mPa s] [mPa s]
[mPa s] 70/100 bitumen 1260 550 190 70/100 + 1.5% Sasobit 980 450
160 70/100 + 1.5% wax mixture A 960 455 165
[0092] From the results it can be seen that the bitumen composition
according to the invention can be processed with reasonable
viscosities at much lower temperatures than the standard,
unmodified bitumen. The wax mixture A has nearly the same viscosity
reducing impact on bitumen as the state of the art Sasobit though
it has much lower impact on the stiffness of soft bitumen grades
(see table 2).
Example 2
[0093] A bitumen with grade 50/70 (unmodified) according to DIN EN
12591 was mixed with 1.5 wt.-% of wax mixture A (see table 1).
After laboratory ageing simulation applying RTFOT (Rotating Thin
Film Oven Test, ASTM D2872) and PAV (Pressure Ageing Vessel, DIN EN
14769) the low temperature behavior of the bitumen was
characterized by determining the m- an S-value limits applying the
Bending Beam Rheometer (BBR) according to ASTM D6648 and comparing
it to a bitumen of the same grade without wax (see table 4). RTFOT
is performed in the laboratory for simulating the bitumen ageing
during asphalt mix production and PAV ageing is performed for
simulating the bitumen ageing during the service life of asphalt
pavements. The m- and S-value limits are parameters for the
stiffness that must not be exceeded. According to ASTM D6373/ASTM
D7673 the BBR test was run at different temperatures in order to
determine the temperature at which the stiffness limit is
reached.
TABLE-US-00004 TABLE 4 Low temperature stiffness properties of
bitumen grade 50/70 after RTFOT and PAV ageing. 50/70 + 1.5%
Parameter [unit] 50/70 bitumen wax mixture A BBR m-value limit
-13.8 -13.9 temperature [.degree. C.] BBR S-value limit -17.1 -17.6
temperature [.degree. C.]
[0094] It was found that the wax mixture A according to this
invention does not change the low temperature stiffness of the
bitumen, considering the precision of the test method. Lower
stiffness limit temperatures after ageing are desired for good
performance and durability of asphalt pavements at cold
climates.
Example 3
[0095] The same bitumen grade 50/70 as in example 2 as well as the
bitumen with 1.5 wt.-% of the wax mixture A were used to prepare
asphalt concrete mix AC 11 DS according to TL StB 07/13. Both
asphalt mixes were compacted at 145.degree. C. and the fracture
temperature was examined with the TSRST (Thermal Stress Restrained
Specimen Test) according to DIN EN 12697-46 to obtain information
on the low temperature performance of the asphalt (see table 5).
During TSRST an asphalt specimen is kept at constant length while
cooling it down with 10.degree. C./h until the thermally induced
shrinking forces crack the specimen.
TABLE-US-00005 TABLE 5 TSRST fracture temperature of AC 11 DS.
50/70 + 1.5% Parameter [unit] 50/70 bitumen wax mixture A Fracture
temperature -20.4 -20.9 [.degree. C.]
[0096] The results show that also the low temperature behavior of
asphalt is not influenced by the wax mixture A, considering the
precision of the test method.
Example 4
[0097] A polymer modified bitumen (PmB) grade 25/55-55 was mixed
with 1.5 wt.-% of wax mixture A and the elastic recovery thereof
was measured according to DIN EN 13398 and compared to a PmB
without wax (see table 6). Polymer modified bitumen grades are in
use for asphalt pavements with enhanced performance and durability.
The specifications according to TL Bitumen-StB 07/13 for elastomer
containing polymer modified bitumen grades (PmB A) require minimum
elastic recovery.
TABLE-US-00006 TABLE 6 Elastic recovery test results. PmB 25/55-55
+ 1.5% Parameter [unit] PmB 25/55-55 wax mixture A Elastic recovery
at 72 75 25.degree. C. [%]
[0098] Generally Fischer-Tropsch wax according to the prior art
(Sasobit) reduces the elastic recovery of PmB. It was found that
the wax mixture according to the invention does not reduce the
elastic recovery of the elastomer modified bitumen.
Example 5
[0099] A bitumen with grade 70/100 (unmodified) according to DIN EN
12591 was mixed with 1.5 wt.-% of wax mixture A relative to neat
binder and 30 wt.-% RAP-content to obtain a resulting binder of
50/70 quality and fresh aggregate and filler to produce an asphalt
base layer mix AC 32 T S according to TL Asphalt-StB 07/13. The
amount of wax mixture A in the resulting binder was 1.05 wt.-%. For
comparison the same bitumen and RAP were used to produce the AC 32
T S asphalt mix without adding the wax mixture (reference). The
bituminous binders were extracted from both asphalt mixes according
to DIN EN 12697 and the properties were determined as in example 1
and are displayed in table 7. The physical properties of the
resulting bituminous binder with 1.05 wt.-% of the wax mixture A
were nearly the same as the properties of the bitumen without the
wax, showing that the wax mixture has also no negative impact on
the physical properties of harder bitumen grades.
TABLE-US-00007 TABLE 7 Bitumen properties after extraction from AC
32 T S asphalt mix. Aged bitumen Resulting bitumen without
Resulting bitumen with Parameter [unit] Fresh bitumen 70/100 in RAP
added wax (reference) 1.05% wax mixture A Penetration (25.degree.
C.) [0.1 mm] 91 21 43 42 Softening point Ring & Ball [.degree.
C.] 45.4 68.6 55 57
[0100] Further the compaction resistance of the asphalt mixes
produced with the bitumen composition of table 3 were measured with
the Marshall compaction method according to TP Asphalt-StB Teil 10
B (see table 8).
TABLE-US-00008 TABLE 8 Marshall compaction resistance of asphalts
obtained from bitumen compositions of table 7. 0% 1.5% Parameter
[unit] Additive Wax mixture A Compaction resistance 29.1 25.8
Marshall @ 135.degree. C. [--]
[0101] It was found that the bitumen composition according to the
invention decreases the compaction resistance and therefore
increases the processability of the asphalt made therefrom.
Example 6
[0102] Bitumen samples extracted from various recycled asphalt
pavements having the physical properties as given in table 10 were
modified with 1.5 wt.-% of wax mixtures B consisting of 50 wt.-%
PSW2 and 50 wt.-% FTW2 and wax mixture C consisting of 30 wt.-%
PSW2 and 70 wt.-% FTW2 (see table 9).
TABLE-US-00009 TABLE 9 Properties of wax mixture B, wax mixture C
and petroleum slack wax (PSW) and Fischer Tropsch wax (FTW) used in
these wax mixtures. Penetration @ Viscosity @ Congealing 25.degree.
C. 100.degree. C. point [.degree. C.] [1/10 mm] [mm.sup.2/s]
n-alkane Oil-content ASTM D 938 ASTM D 1321 ASTM D 7042-11 content
* ASTM D 7211-06 Wax mixture B (50% PSW2/50% FTW2) 75.5 27 6.9 Wax
mixture C (30% PSW2/70% FTW2) 79 19 7.9 PSW2 (Prowax 750 from
ExxonMobil) 54.0 78 8.0 FTW2 (Sasolwax C80) 80 6 9.4 81.0 1.0
[0103] The properties of the bitumen samples were determined by
measuring needle penetration according to DIN EN 1426 and the
softening point (ring & ball) according to DIN EN 1427. The
results in table 10 show that wax mixtures B and C in bitumen
compositions according to the invention have no negative impact on
the physical properties of very hard bitumen grades.
TABLE-US-00010 TABLE 10 Bitumen properties. 0% Wax added 1.5% Wax
mixture B 1.5% Wax mixture C 1.5% FTW2 Parameter [unit] (100%
bitumen) (98.5% bitumen) (98.5% bitumen) (98.5% bitumen)
Penetration at 25.degree. C. [0.1 mm] 19.0 19.0 19.0 18 Softening
point Ring & Ball [.degree. C.] 67.6 71.8 72.2 80.4
Example 7
[0104] A bitumen with grade 50/70 according to DIN EN 12591 was
mixed with 1.5 wt.-% of hydrocarbon wax mixture A, aggregate and
filler to produce an asphalt wearing course mix AC 11 D S. This
asphalt mix was compacted using a segmented roller compactor
according to DIN EN 12697-33. During compaction the same method as
in the Marshall compaction (TP Asphalt StB Teil 10 B) was applied
to determine the compaction resistance of the asphalt mix. The
results (see table 11) showed that the hydrocarbon wax mixture A
reduced the compaction resistance.
TABLE-US-00011 TABLE 11 Compaction resistance of asphalt mixes at
different compaction temperatures produced with the bitumen
compositions according to the invention. 0% 1.5% Parameter [unit]
Additive Wax mixture A Compaction resistance at 95.degree. C. 53 Nm
48 Nm Compaction resistance at 145.degree. C. 38.5 Nm 36.5 Nm
Example 8
[0105] As asphalt ages, the stiffness of the bitumen increases. The
complex shear modulus G*, measured with a Dynamic Shear Rheometer
according to DIN EN 14770, is a characteristic value to evaluate
the stiffness of bitumen.
[0106] In order to describe the ageing behavior of the bitumen, G*
had to be determined for different ageing stages. Ageing indices
were then calculated, i.e. G* after ageing divided by G* before
ageing. The smaller the ageing index, the higher the anti-ageing
impact.
[0107] Bitumen from a AC 16 B S binder course asphalt mix according
to TL Asphalt-StB 07/13 with 20 wt.-% RAP was extracted and aged
according to DIN EN 14769 (PAV--Pressure Ageing Vessel). The grade
of the originally used bitumen was a 25/55-55. G* was measured
after extraction and after PAV ageing of the extracted bitumen, and
the ageing indices were calculated. This was done for two
variants--with and without modification with wax mixture A. The
following table 12 shows the results of the ageing indices at
different test temperatures.
TABLE-US-00012 TABLE 12 Ageing indices of bituminous binders
extracted from asphalt mixes AC 16 B S after PAV ageing. Ageing
index G*PAV/G* at 5.degree. C. at 10.degree. C. at 15.degree. C. at
20.degree. C. at 25.degree. C. at 30.degree. C. without wax 1.529
1.549 1.649 1.894 2.098 2.154 with 1.2 wt.-% 1.126 1.150 1.203
1.387 1.529 1.682 wax mixture A
[0108] The results show that the ageing indices for the variant
with the wax mixture A are lower than those for the variant without
the additive. The wax mixture therefore has an anti-ageing impact
on the bitumen.
Example 9
[0109] The onset temperature of the crystallization of the wax
mixture A in bitumen 50/70 was measured applying differential
scanning calorimetry (DSC) technique according to ASTM D4419-90.
Above the crystallization onset temperature the wax mixture reduces
the viscosity of the bitumen composition and thereby improves the
processability and compactibility of asphalt mixes made with the
bitumen composition.
[0110] The results (see table 13) show that the wax mixture A
provides improved asphalt compaction down to 57.degree. C. whereas
the prior art Fischer-Tropsch wax Sasobit provides this effect only
above 90.degree. C.
TABLE-US-00013 TABLE 13 Wax crystallization onset temperatures of
3% wax mixture A and 3% Sasobit in bitumen 50/70 measured by DSC at
2 K/min cooling rate. Bitumen 50/70 + Bitumen 50/70 + Parameter
[unit] 3% wax mixture A 3% Sasobit Wax crystallization 57 90 onset
[.degree. C.]
Example 10
[0111] An asphalt mix was produced using 60% reclaimed asphalt
pavement in the binder course mix ACbin16 and 50% reclaimed asphalt
pavement in the wearing course mix ACsurf 11 according to the Czech
regulations. The fresh part of the mix comprised bitumen grade
50/70 with 2.5 wt.-% wax mixture A. This resulted in 1.25 wt.-% wax
mixture A in the bitumen of the binder course and 1.0 wt.-% wax
mixture A in the bitumen of the binder course of the final asphalt
mixes. The asphalt mixes left the mixing plant at 150.degree. C. As
the ambient temperature was low (November in central Europe), the
asphalt mix had cooled down to 130.degree. C. when paved at the
construction site. Despite this low paving temperature the laying
and roller compaction was possible without problems and the
required minimum degree of compaction was exceeded. The compaction
degree was measured using a Troxler nuclear gauge (table 14).
Nuclear density gauges are a frequently used tool in road paving
for fast and non-destructive measurement of the density of the
asphalt layers at the construction site. A nuclear radiation source
emits a cloud of particles which interact with the asphalt.
Radiation that is scattered back to a detector is counted. The
denser the asphalt, the higher the probability the radiation will
be redirected towards the sensor. A calibration factor is used to
correlate the count to the actual density and compaction
degree.
TABLE-US-00014 TABLE 14 Measured in-place compaction degrees in
paved asphalt. Reclaimed Resulting asphalt content of Average
Specified content wax mixture A compaction compaction Asphalt mix
[%] [%] * degree [%] degree [%] ACsurf11 50 1.25 99.2 >97
ACbin16 60 1.0 99.1 >97 * in relation to total amount of
bitumen
Example 11
[0112] An asphalt concrete wearing course mix AC 11 DS according to
the German regulations TL Asphalt-StB 07/13 was produced. The mix
contained 20% reclaimed asphalt and the fresh part was made with
polymer modified bitumen PmB 25/55-55 according to the German
regulation TL Bitumen-StB 07/13. One part of the asphalt mix
contained 1.5 wt.-% wax mixture A related to the resulting total
amount of bitumen, the other part of the mix did not contain wax
and served as reference for the state of the art asphalt. Both
asphalt mixes were paved at ambient air temperatures of
8-13.degree. C. and at strong wind. The compaction degree was
measured using a Troxler nuclear gauge after the paver and after
each of three roller passes. At the same time the temperature of
the asphalt was measured. The regulations ZTV Asphalt-StB 07/13
require a minimum compaction degree of 98% for the paved asphalt
layer. The measured compaction degrees (table 15) show that the
asphalt which contains wax mixture A was easier to compact and
reached the specified minimum compaction degree of 98% already
after one roller pass. The reference asphalt mix required two
roller passes.
TABLE-US-00015 TABLE 15 Compaction degrees and temperatures during
paving AC 11 DS asphalt mix. AC 11 DS with 1.5% wax mixture A AC 11
DS related to bitumen without wax Degree of compaction [%] Time of
measurement (Asphalt temperature) After paver 88.6 (145.degree. C.)
88.7 (126.degree. C.) After 1 roller pass 98 (122.degree. C.) 96.0
(118.degree. C.) After 2 roller passes 99.1 (90.degree. C.) 98.7
(99.degree. C.) After 3 roller passes 100.0 (87.degree. C.) 99.7
(84.degree. C.)
* * * * *