BITUMINOUS BINDERS WITH AN IMPROVED SOFTENING POINT
Field of the invention
The invention relates to the field of bituminous coatings and more precisely
5 to technologies relating to functional additives added to bitumen to give it
particular physicochemical and mechanical properties. More specifically, the
invention relates to a bituminous binder composition comprising a specific
thermoplastic mixture in order to give it the desired properties.
The invention thus also relates to the use of this combination of particular
10 thermoplastic polymers for a bituminous coating composition and also to this
composition.
Prior art
Bitumen or asphalt is the heaviest portion in the petroleum distillation
15 process. On account of the various origins and processes for distilling such
petroleums, the resulting bitumen may have a wide range of properties and
characteristics. In the present invention, the term "bitumen" denotes not only the
product from petroleum by direct distillation or the distillation of petroleum at
reduced pressures, but also products originating from the extraction of tar and
20 bituminous sands, the products of oxidation and/or fluxing with carbon-based
solvents comprising paraffins and waxes of such bituminous materials, and also
blown or semi-blown bitumens, synthetic bitumens (such as those described, for
example, in FR-A-2 853 647), tars, petroleum resins or indene-coumarone resins
mixed with aromatic and/or paraffinic hydrocarbons and mixtures thereof,
25 mixtures of such bituminous materials with acids, and the like.
The main application for bitumen is in coatings (bituminous coatings), in
which bitumen is mixed with aggregates that may be of various sizes, forms and
chemical nature. These bituminous coatings are used in particular for the
construction, repair and maintenance of sidewalks, roads, highways, car parks or
30 airport runways and service lanes or any other rolling surface. In the present
invention, the aggregates especially, but not exclusively, comprise mineral
aggregates which are produced in quarries, and also aggregates recovered from
preceding coatings (reclaimed asphalt pavement, RAP), produced from the
demolition of roadways, and mixtures thereof, and also organic and inorganic
35 fibers, such as glass, metal or carbon fibers, and also cellulose, cotton,
polypropylene, polyester, poly( vinyl alcohol) and polyamide fibers.
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The use of bitumen in the manufacture of materials for road and industrial
applications has been known for a long time: bitumen is the main hydrocarbonbased
binder (for binding aggregates together) used in the field of road
construction or civil engineering. In order to be able to be used as a binder in these
5 various applications and/or in very varied environments, bitumen must have
certain physicochemical properties.
Thus, the properties of a bituminous binder composition are conventionally
tested using a certain number of well-defined and standardized tools and
experiments.
10 Three of these tests are particularly important and are those that are
considered herein as being the most pertinent for determining the satisfactory
qualities and properties of a bituminous binder composition. They are: the elastic
recovery according to European standard EN 13398 "Bitumens and bituminous
binders - Determination of the elastic recovery of modified bitumens"; the
15 viscosity test according to international standard ISO 2555 " Plastics - Resins in
the liquid state or as emulsions or dispersions - Determination of the apparent
viscosity according to the Brookfield process"; and finally the Ring-and-Ball Point
(RBP) according to European standard EN 1427 (DIN 52011, NF T66-008) or
standard ASTM D36 - IP 58. The ring-and-ball point is a test that is particularly
20 pertinent in the context of determining the working temperature range of a
bituminous binder since it represents the softening point of the modified binder.
Depending on the environment, especially the amplitude of the day-night
and seasonal temperature variations, the degree of humidity or the volume of
traffic on the coating, bituminous binder compositions must have optimum results
25 in these tests presented above. This is why the addition of thermoplastics is
recommended and necessary for giving bituminous binders particularly
advantageous physicochemical-mechanical properties.
Furthermore, it is necessary for the binder thus modified to remain stable
during its storage or its transportation at high temperature for several hours, or
30 even several days. A storage stability test is defined in standard NF EN 13399.
A certain number of thermoplastics have been used as additives for
bituminous binder compositions, but it has been seen that a particular component,
namely an EAD-GMA (ethylene-acrylate derivatives-glycidyl methacrylate)
terpolymer is advantageous for certain properties. EP 0 815 170 and US 5 306 750
35 disclose the use of ethylene-butyl acrylate-glycidyl methacrylate terpolymers.
Conventionally, them1oplastics are incorporated into bitumen during a step
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of supplementation at a temperature of between 120 and 220°C. In the case of
reactive thermoplastics functionalized with epoxy groups, a second maturation step
is necessary to achieve the optimum properties, via slow maturation (24 hours at
about l90°C) or via supplemented maturation in the presence of an acidic
5 adjuvant. Supplemented maturation in the presence of an acidic adjuvant is well
known to those skilled in the art and is more generally used than slow maturation:
EP 0 837 910 especially discloses such a supplemented maturation in the presence
of an acidic adjuvant.
However, such a class of terpolymer also has drawbacks when it is added to
10 bitumen. First, it is not always efficient enough to satisfY strict criteria in the ringand-
ball point test.
Thus, a thermoplastic additive for bitumens is sought, which allows the
bitumen binder to satisfY the three most discriminating tests for this type of
application (cf. tests presented above) and which ensures homogeneity of the
15 bitumen-thermoplastic assembly both at the time of mixing and during storage.
Brief description ofthe invention
Surprisingly, the Applicant has discovered that the combination of a
particular type of terpolymer with a specific copolymer makes it possible to obtain
20 a thermoplastic combination which, with bitumen, satisfies all the desired
properties and is stable on storage. This discovery goes against that which a person
skilled in the art might have expected since each of the two thermoplastics used
alone in bitumen, and irrespective of its amount, does not make it possible to
obtain satisfactory results for all three abovementioned tests and/or for the storage
25 stability test. Thus, the combination of these two thermoplastics does not have the
simple consequence of addition of their respective properties, but rather a
synergistic effect which makes it possible to give the bitumen binder composition
entirely suitable physicochemical-mechanical properties.
What is more, in particular ratios of amounts of the two thermoplastics, the
30 physicochemical-mechanical properties are further improved.
The present invention thus relates to a bituminous binder, comprising:
~from 97% to 99.9%, by weight of the binder, of bitumen,
- the combination of two thermoplastic polymers representing from 0.1% to
3% by weight of the binder, the first polymer consisting of a terpolymer (A) of an
35 alpha-olefin, an unsaturated epoxide and au ethylenic monomer bearing a polar
function with an MFI ofless than 50 g/1 0 min (190°C, 2.16 kg measured according
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to ISO 1133),
characterized in that the second polymer, a copolymer (B), consists of a
copolymer of alpha-olefin and an unsaturated epoxide with an MFI of less than
50 g/10 min (190°C, 2.16 kg measured according to ISO 1133).
5 Other characteristics or embodiments of the invention are presented below:
- preferably, the mass ratio of (B)/[(A) + (B)] is between 0.25 and 0.65,
preferably between 0.45 and 0.55,
- advantageously, the ethylenic monomer bearing a polar function of the
terpolymer (A) consists of an alkyl (meth)acrylate, the alkyl group comprising up
I 0 to 24 carbon atoms,
-preferably, the terpolymer (A) is an ethylene/alkyl (meth)acrylate/glycidyl
(meth)acrylate terpolymer, containing from 0.1% to 65% by weight of alkyl
(meth)acrylate, the alkyl of which comprises from I to I 0 carbons and up to 12%
by weight of glycidyl (meth)acrylate,
15 - preferably, the copolymer (B) is an ethylene/glycidyl (meth)acrylate
copolymer containing up to 12% by weight of glycidyl (meth)acrylate,
- according to a possibility offered by the invention, the binder also
comprises an acidic adjuvant, representing not more than 5% by weight of the
binder, said acidic adjuvant being constituted by one or more compounds chosen
20 from the group formed by phosphoric acids, boric acids, sulfuric acid, anhydrides
of said acids, chlorosulfuric acid, polyphosphoric acids, the phosphonic acids of
formula R-PO(OH)2 and the acids of formula R-(COO)t-S03H with, in said
formulae, t taking the value zero or one and R denoting a monovalent
hydrocarbon-based radical chosen from the group constituted by C1 to C6 acyclic
25 monovalent hydrocarbon-based radicals and cyclic monovalent hydrocarbon-based
radicals containing 4 to 12 ring carbon atoms and optionally substituted with C1 to
C16 acyclic monovalent hydrocarbon-based radicals,
- according to an advantageous embodiment, the binder according to the
invention consists of the abovementioned bitumen and the abovementioned first
30 and second polymers, and also optionally the abovementioned acidic adjuvant,
- the abovementioned first and second polymers have an MFI of less than
25 g/1 0 min (190°C, 2.16 kg measured according to ISO 1133 ), preferably less
than I 0 g/l 0 min.
The invention has the following advantages and thus allows the production
35 of a bituminous binder with an improved ring-and-ball point while at the same
time conserving satisfactory thermomechanical properties.
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The invention thus relates to a bituminous coating composition, comprising
aggregates and the bituminous binder as presented above, the aggregates being
present at between 90% and 99% by weight of the composition and the binder at
between I 0% and I% of said composition.
5 The present invention also relates to the use of a combination of two
thermoplastic polymers for forming a bituminous binder, comprising a terpolymer
(A) of an alpha-olefin, an unsaturated epoxide and an ethylenic monomer bearing a
polar function with an MFI of less than 50 g/10 min (190°C, 2.16 kg measured
according to ISO 1133), characterized in that it also comprises a copolymer (B) of
10 alpha-olefin and an unsaturated epoxide with an MFI of less than 50 g/1 0 min
(190°C, 2.16 kg measured according to ISO 1133); the mass ratio in the mixture
for components (A) and (B) being such that (B)/[(A) + (B)] is between 0.25 and
0.65, preferably between 0.45 and 0.55.
Preferably, the combination of thermoplastic polymers comprises only the
15 abovementioned terpolymer (A) and the abovementioned copolymer (B).
The description that follows is given purely as a nonlimiting illustration.
Detailed description of the invention
As regards the bitumen, this element may consist of any element included
20 in the definition or under the name "bitumen" as a person skilled in the art may
understand it without excessive effort. Such a definition, without being exhaustive,
has been given previously in this description.
As regards the terpolymer (A), it is a terpolymer of an alpha-olefrn, an
unsaturated epoxide and an ethylenic monomer bearing a polar function.
25 The alpha-olefin may be ethylene, propylene, 1-butene, isobutene,
1-pentene, 1-hexene, 1-decene, 4-methyl-1-butene, 4,4-dimethyl-1-pentene,
vinylcyclohexane, styrene, methylstyrene or styrene substituted with alkyls.
Ethylene is advantageously used.
The unsaturated epoxide may be chosen from:
30 - aliphatic glycidyl esters and ethers such as allyl glycidyl ether, vinyl
glycidyl ether, glycidyl maleate and itaconate, glycidyl acrylate and methacrylate,
and
- alicyclic glycidyl esters and ethers such as 2-cyclohexene 1-glycidyl
ether, cyclohexene-4,5-diglycidyl carboxylate, cyclohexene-4-glycidyl
35 carboxylate, 5-norbornene-2-methyl-2-glycidyl carboxylate and endocisbicyclo(
2,2, I)-5-heptene-2,3-diglycidyl dicarboxylate.
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Glycidyl (meth)acrylate is advantageously used.
The ethylenic monomer bearing a polar function consists of an unsaturated
carboxylic acid ester which may be, for example, an alkyl (meth)acrylate, the alkyl
group possibly containing up to 24 carbon atoms, or a carboxylic acid vinyl ester,
5 preferably a vinyl acetate.
Examples of alkyl acrylates (or methacrylates) that may be used are
especially methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and
2-ethylhexyl acrylate.
The unsaturated epoxide is copolymerized with the alpha-olefin and the
10 ethylenic monomer bearing a polar function according to a high-pressure autoclave
or tubular radical polymerization process.
Advantageously, (A) is an ethylene/alkyl (meth)acrylate terpolymer in
which the alkyl contains from 1 to 10 carbons/glycidyl (meth)acrylate containing
up to 65% by weight of (meth)acrylate and up to 12% by weight of epoxide.
15 As regards the copolymer (B), it is a copolymer of an alpha-olefin and an
unsaturated epoxide.
The alpha-olefin and the unsaturated epoxide may be chosen from the same
products already mentioned previously for the copolymer (A).
Advantageously, (B) is an ethylene/glycidyl (meth)acrylate copolymer
20 containing up to 12% by weight of epoxide.
The unsaturated epoxide is copolymerized with the alpha-olefin according
to a high-pressure autoclave or tubular radical polymerization process.
The bituminous binder according to the invention advantageously
comprises an acidic adjuvant. This acidic adjuvant is conventionally that used for
25 performing the supplemented maturation intended to obtain the binder according to
the invention. The acidic adjuvant is preferably one of the acids disclosed in
EP 0 837 910, which describes a supplemented maturation process using these
acids of a particular type.
The Applicant has noted, after extensive experimentation, that this acidic
30 adjuvant improves the properties of the binder, but that it cannot be present beyond
a certain threshold, which depends on the nature of the bitumen, since it results in
substantial stability problems.
This threshold was determined as being about 5% of the (total) weight of
the binder, but it is clearly understood that this percentage depends on the nature of
35 the bitumen under consideration. This conclusion regarding the importance of the
nature of the bitumen also applies, to a certain extent, to the amounts determined
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after experimentation for the polymers (A) and (B) forming the binder according to
the invention.
The preparation of bitumen modified with the mixture of polymers
according to the present invention is performed according to a method that is well
5 known to those skilled in the art. The thermoplastics are incorporated in a first
stage into the bitumen during a supplementation step at a temperature of between
120 and 220°C and more conventionally between 160 and 190°C. In a second step,
maturation is performed to achieve the optimum properties. This maturation may
be slow maturation (24 hours at about 190°C) or supplemented maturation in the
10 presence of an acidic adjuvant, these two routes being well known to those skilled
in the art. Supplemented maturation in the presence of an acidic adjuvant is more
generally used than slow maturation: EP 0 837 910 especially discloses such a
supplemented maturation in the presence of an acidic adjuvant. The preparation of
the bituminous binder is performed via supplemented maturation such as that
15 described in EP 0 837 910, which is the preferred preparation for obtaining the
binder according to the invention, but a preparation by slow maturation or
according to the preparation described in EP 0 815 170 may also be envisaged.
Teachings concerning the preparation of the modified bitumen (binder +
bitumen), and then of the bituminous coating (binder+ bitumen+ aggregates), may
20 be found in the literature, in particular in the publication "Polymer modified
bitumen: properties and characterization" published by Tony McNally, Queen's
University Belfast (September 2011 edition).
Production of the formulations of the compositions tested:
25 The binders were prepared in a temperature-regulated reactor equipped
with a mechanical stirring system. Each preparation allows the production of 1 kg
of bituminous binder. The supplementation step is first performed at a temperature
of 180°C by incorporating the thermoplastics into a non-supplemented bitumen.
The stirring speed is 400 rpm and the mixing time is 2 hours 3 0 minutes. The
30 maturation step is then performed at a temperature of 170°C after adding the acidic
adjuvant (0.2% of the bitumen+ thermoplastics combination). The stirring speed is
400 rpm and the maturation time is 7 5 minutes.
Tests performed:
3 5 Viscosity test
The viscosity measurements are taken using a viscometer of Brookfield
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type. The measunng device used is a Brookfield@ DVIII viscometer. The
measurement principle is based on measuring the torque (proportional to the shear
stress) required to keep constant the angular speed of rotation (proportional to the
shear rate) of a spindle immersed in the modified bitumen, and deducing
5 proportionately therefrom the viscosity of said bitumen.
The measurement is taken using an SC4-21 spindle (standard ISO 2555).
Between 5 to 10 mL (milliliters) of modified bitumen are introduced into the
measuring chamber maintained at 135°C. The values given in the examples below
correspond to a spin speed of the spindle of 20 rpm and are expressed in mPa.s
10 (milliPascal-seconds). The measuring accuracy is± 10% of the indicated value.
Ring-and-ball point test
The softening point (RBP: ring-and-ball point) is the temperature at which
a product (for example a bituminous product) reaches a certain degree of softening
15 under standardized conditions.
To perform the ring-and-ball point method EN 1427 (European standard), a
brass ring (with a collar) of defined dimensions is filled with the bituminous binder
to be tested. This ring thus prepared is placed on its support. A steel ball is placed
on the sample pellet in the middle of the ring.
20 The support frame is then immersed in a thermostatically maintained bath.
The standardized liquid in the beaker is demineralized water for a test from 30 to
80°C, and glycerol or silicone oil for higher temperatures. The bath is heated to
obtain a steady temperature increase of 5°C·min·1 ± 0.5°C. The temperature at the
moment at which the material surrounding the ball that has become detached from
25 the ring touches the lower plate of the support is noted. This temperature is known
as the ring-and-ball softening point or the ring-and-ball point.
Elastic recovery test
The elastic recovery of a modified bitumen is an indicator that makes it
30 possible to characterize the capacity of the binder to regain its original geometrical
properties after a deformation. It is determined by means of a laboratory test using
apparatus similar to that for the ductility test and that for the force-ductility test,
this machine commonly being known as a ductilimeter. The measuring device used
is a Frowag@ 1.723 ductilimeter.
35 The measurement proceeds as described according to standard NF EN
13398: after thermal equilibration of the specimens placed in the machine
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(30 minutes in a bath of water thermostatically maintained at 25°C), they are
drawn at a rate of 50 mm/min (millimeters per minute) to undergo an elongation of
200 mm. Within the I 0 seconds following the end of drawing, the specimens are
then sectioned at the middle and the shrinkage length of the specimen is measured
5 after 30 minutes. The elastic recovery value is the percentage of shrinkage length
of the specimen relative to its total length. A I 00% degree of elastic recovery
would correspond to a binder which entirely regains its original dimensions (before
drawing).
l 0 Storage stability test
This test is defined according to standard NE EN 13399 (European
standard): a cylindrical container is filled with modified binder and then stored
vertically in an oven at !80°C for 72 hours. The stability on storage is checked
visually (absence of formation of a polymer "skin" at the surface of the sample)
15 and quantified by measuring the ring-and-ball point of the top and bottom parts of
the sample. An excessively large difference in ring-and-ball point means that there
is a polymer concentration difference in the sample and thus that the modified
binder is no longer homogeneous. The results table points out the appearance of a
two-phase modified bitumen, when this takes place, which is undoubtedly
20 detrimental to the physicochemical properties of said bitumen.
Starting materials for the test compositions:
Lotader® AX8900: terpolymer of ethylene, methyl acrylate (24% by
weight) and glycidyl methacrylate (8% by weight) produced by Arkema, with an
25 MFI (190°C, 2.16 kg measured according to ISO 1133) of 6 g/l 0 min.
Lotader® AX8840: copolymer of ethylene and glycidyl methacrylate (8%
by weight) produced by Arkema, with an MFI (190°C, 2.16 kg measured
according to ISO 1133) of 5 g/1 0 min.
Lotryl® 24MA02: copolymer of ethylene and methyl acrylate (24% by
30 weight) produced by Arkema, with an MFI (190°C, 2.16 kg measured according to
ISO 1133) of2 g/10 min.
35
Lotader® XR1310: terpolymer of ethylene, methyl acrylate (12% by
weight) and glycidyl methacrylate (8% by weight) produced by Arkema, with an
MFI (190°C, 2.16 kg measured according to ISO 1133) of 6 g/10 min.
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Bitumens:
• Bitumen I = Total Azalt of penetration 50/70 from the Donges
refinery (France)
• Bitumen II = IRPC of penetration 70 from the Rayong refinery
5 (Thailand)
Polyphosphoric acid 1 1 6%: acidic adjuvant produced by F ebex
Hereinbelow, all the tests are performed with specimens comprising the
same content of the mixture or combination of the two polymers, set at 1.8% by
10 weight of the bituminous binder. Nevertheless, the Applicant performed additional
experiments in order to precisely determine the limits of the amounts (in relative
weight) of this combination of polymers in the bituminous binder in order for said
binder to remain efficient according to the criteria set by the present invention.
15 Test results:
The bituminous binder must have certain advantageous properties.
The results relating to a bituminous binder according to the present
invention are reported herein, in a nonexhaustive manner. In this context, three
properties were more particularly targeted, namely:
20 the viscosity at 135°C of the bituminous binder, which must ideally be
less than 3000 mPa.s; and
the elastic recovery (%), which must be greater than 70% and
preferentially greater than 75%; and
the ring-and-ball point, which must be greater than 70°C and
25 preferentially greater than 75°C; and
the ring-and-ball point difference between the top part and the bottom
part of the sample after stability on storage (noted 1'1 RBP), which must be less than
5°C; and finally
the absence of gel (observation with the naked eye) in the bituminous
30 binder.
The table below reports some of the test results obtained by the Proprietor.
Subject to all reserves of interpretation, these results allowed the Proprietor to
define the invention as expressed in all of the attached claims.
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Bitumen Lotader® Lotader00 Lotryl® Lotader® (B)/[(A) Surface Viscosity at Elastic Ring-and- />, RBP after
Composition AX8900 (A) AX8840 (B) 24MA02 XR1310 +(B)] appearance 135°C recovery ball point stability on
content content content content (mPa.s) (%) (°C) storaoe (°C)
I I 1.8% 0 Smooth 2920 83.8 67.1 soc
3 I 1.8% O.S% NA Smooth 3180 82.8 68.6 soc
12 II 1.8% 0 Smooth 1470 82.5 63.4 soc
14 II 0.9% 0.9% 0.5 Smooth 1350 77.6 76.0