WO2008142249A1 - Modified bitumen composition and methods for producing said composition - Google Patents

Abstract

The invention relates to a modified bitumen composition and methods for producing said composition, more particularly to a modified bitumen composition with improved properties for conditions of extreme temperature as found in most parts of the world. Said composition of modified bitumen has a content of adipic acid less than1% by weight off the composition, the adipic acid being introduced by a particular method. The performance of said bitumen is characterised by the gain in the hot softening point called the ring-and-ball temperature (TBA).

Description

 Modified bitumen composition and processes for the preparation thereof

The present invention relates to a modified bitumen composition and manufacturing preparation methods of this composition.

It relates more particularly to a modified bitumen composition having improved properties for extreme temperature conditions encountered in most parts of the world.

[0003] Bitumens are used in many applications, but more particularly for paving pavements or waterproofing roofs. Bitumens are also called asphalts or bituminous binders.

Bitumens can be obtained, in particular, from crude oil, by distillation thereof and / or by de-asphalting the heavy fractions obtained in the various distillations of the oil.

According to the origins, the bitumens consist of various paraffinic or naphthenic oils, aromatic oils, resins and asphaltenes.

Bitumens are viscoelastic materials, that is to say having the characteristics of hardening and becoming brittle at low temperature, and / or of softening and deforming in a non-reversible manner under high temperature stress. Low temperature and high temperature include low temperatures in winter or cold areas of the world, and high temperatures in warmer regions of the world or during the summer season. There are different grades of bitumen, depending on their consistency at room temperature

(penetration index: Penis): soft / semi-hard / hard.

The properties of bitumens are a function of their physico-chemical nature, and can be improved during refining processes. It is thus possible to improve the high-temperature behavior of bitumens by increasing the asphaltenes content: this is the case, for example, with oxidized bitumens. On the other hand, the cold behavior of these hardened bitumens is substantially degraded. To overcome these disadvantages and improve the properties, it has already been proposed to add various additives that will modify the behavior of bitumens, for example by modifying the microstructure (asphaltenes / maltenes) or, for example, by various physico-chemical or mechanical effects of reinforcement (polymers, fibers, etc.).

The performance of use of bitumens are evaluated through the viscoelastic behavior in the field of the use temperature limit (usual range: -15 ° C -> + 60 ⁰ C). The main property sought is a high level of the maximum temperature of use corresponding to the ball-ring temperature (TBA). To obtain the desired values, it is then necessary either to use a viscous (hard) bitumen but fragile at low temperature, or to modify the bitumen by adding additives.

By ball-ring temperature (TBA) is meant the softening temperature determined by the ring-and-ball test. The procedure for determining this critical temperature is carried out according to a hot procedure described in the standard HTPP5-98 or EN1427.

The addition of additives in the bitumens is generally carried out at a sufficiently high temperature at which the bitumen is in the form of a low viscosity liquid, typically around 160 ° - 175 ° C. Temperatures above 200 ^° C. are avoided because of the beginning of aging of the bitumen. This additivation is carried out in stirred reactors. The process can take several hours with some additives that are difficult to disperse. After additivation, the modified bitumen is kept at temperature, generally around 135 ° C., in storage tanks with slow stirring. The bitumen remains hot to be pumpable (T> 120 ⁰ C) during the refining, additivation, transport, storage and use stages.

Various acid compounds are used to modify certain properties of the bitumen. This is for example the case of strong acids (HCl, H 2 SO 4, H 3 PO 4) or their precursors.

Organic acids or their precursors may also be used. Thus, US Pat. No. 5,332,884 describes a process for treating a bitumen with an acidic compound comprising two functional groups capable of grafting onto the bitumen. The proposed acidic precursors are, for example, anhydrides and acid chlorides. This addition makes it possible to improve the properties of the bitumen at high temperature without unduly degrading the properties at low temperature.

It has also been proposed the use of polymers, and in particular elastomers as in US Patents 4,600,635 or US 5,348,994 or more recently WO 97/43342. The added polymers are generally elastomers in different forms. These polymers may be derived from the synthesis or recycling.

Products from the recycling of rubber can be incorporated into the bitumen. Thus, patent WO2004 / 081098 proposes to add to the bituminous binder rubber crumbs. The patent WO2006 / 107179 describes the addition of elastomers in different forms such as particles, leaves, waste.

US3061538 discloses the addition of saturated aliphatic dicarboxylic acid, an acid anhydride or an acid chloride to improve the ductility properties and resistance to deformation at high temperature. This acidic compound is added in a proportion of 0.1 to 10% by weight, preferably between 0.5 and 5% by weight. The acids mentioned in this document are sebacic acid, adipic acid and sebacic acid chloride. In this document, the treatment of bitumen with an acid is carried out at a high temperature (approximately 160 ^° C. for adipic acid).

During the treatment, a large part of these acids vaporizes and sublimates. To obtain a significant and lasting modification of the properties, it is necessary to add a significant amount of acid in the bitumen, typically 1% or more.

The properties of bitumens can also be modified during the oxidation refining process, generally performed by blowing (air, or oxygen) at high temperature (above 200 ⁰ C) for several hours. The asphaltene content of the bitumen is then increased, which leads to a hardening or increase of grade (Péné decrease and ball-ring temperature gain TBA) with most often a cold embrittlement (increase of the glass transition temperature Tg) . Blowing as such is less and less used by refiners, in particular because of the relatively low productivity of this operation. In order to increase the productivity of blowing, various catalysts have been in common use for about thirty years: for example FeCl3, P2O5, etc. The use of catalysts has softened the blowing conditions, which leads to bitumen having good behavior at high temperature (gain of grade: Péné decrease and gain TBA) without adverse effect on their cold behavior . A new type of bitumen thus appeared, commonly called 'multigrade'. However, the problem of the catalysts is their cost and the low kinetics of the reactions developed during blowing.

One of the objects of the present invention is to provide bitumen compositions with modified properties by the addition of small amounts of certain carboxylic acids and more particularly of certain dicarboxylic acids and processes for the preparation of these compositions leading to limited sublimation of the acid.

For this purpose, the invention relates to a modified bitumen composition comprising a low adipic acid content, less than 1% relative to the weight of the composition, the adipic acid being introduced according to a particular method. The performance of the bitumens thus modified are described by the gain of the hot softening point called ball-ring temperature (TBA).

Suitable bitumens for the invention are in particular those obtained from crude oil as described above.

The invention also applies to the bitumen described above comprising a low catalyst content, preferably a concentration by weight of less than 0.7% by weight of bitumen. The preferred catalyst is iron chloride.

The catalyst and adipic acid combination can significantly reduce the blowing conditions such as the air flow rate, the temperature and / or the time of the process.

Significant gains in performance are obtained in the presence of a catalyst and adipic acid combination in the absence of blowing at a much lower temperature than usual temperatures.

According to the invention, the bitumen composition with or without a catalyst modified by addition of adipic acid is characterized in that it comprises at least 0.4% by weight. weight of adipic acid relative to the weight of the composition and an increase in the TBA relative to the non-additive bitumen greater than or equal to 15 ° C.

This composition is capable of being obtained by a process comprising a step of adding the desired amount of adipic acid to the bitumen composition to be modified at a temperature below 130 ^° C., preferably below 120 ^° C. About ^{0 °} C, either at higher temperatures but in a closed chamber to prevent sublimation or evaporation of adipic acid, optionally a step of maintaining the bitumen composition containing adipic acid at a temperature above 130 ⁰ C under confinement conditions preventing the evaporation or sublimation of adipic acid, and a step of homogenizing the adipic acid mixture and bitumen composition by stirring under confinement conditions preventing evaporation or sublimation of adipic acid.

The methods described above allow to add to the bitumen to modify a specific amount of adipic acid necessary and sufficient to obtain a change in properties, without risk of evaporation or sublimation of adipic acid. Accordingly, with the methods of the invention, it is possible to control the amount of adipic acid present in the composition.

According to another characteristic of the invention, the bitumen composition may contain additives such as, for example, thermoplastic resins, elastomers, plasticizers, fillers or the like. Thus, the compositions of the invention may comprise additives selected from the group consisting of: LDPE (low density polyethylene), HDPE (high density polyethylene), EVA (ethylene vinyl acetate), SBR (styrene butadiene elastomer), SBS ( styrene butadiene styrene elastomer), PS (polystyrene), ABS (acrylonitrile butadiene styrene), CMC (carboxymethyl cellulose), PVA (polyvinylacetate), PVC (polyvinylchloride), polybutadiene, HIPS (high resistance polystyrene) .. It may also comprise rubber crumbs as described in the patent application WO2004 / 081098 previously cited advantageously at a concentration by weight of between 5% and 10% by weight of bitumen

In these compositions containing additives, the adipic acid content is expressed by weight of adipic acid relative to the weight of bitumen, without additives. According to one characteristic of the invention, the concentration of adipic acid in the bitumen composition is advantageously between 0.5% and 0.8% by weight. . However, when the bitumen composition comprises an additive such as elastomers, advantageously SBS, or rubber crumb, the adipic acid concentration is advantageously between 0.4% and 0.8% by weight, preferably from 0.4% to 0.6%.

According to the invention, the adipic acid can be added to the bitumen simultaneously with the other additives, before or after the other additives. It is also possible to prepare a premix of adipic acid and one or more additives before the addition in the bitumen. However, this last embodiment is only possible if the adipic acid and the additive do not react with each other.

The invention also relates to methods for manufacturing a modified bitumen composition, as described above. More particularly, these manufacturing processes relate to several modes of addition and mixing of adipic acid with the bitumen to be modified.

In a first embodiment of the process, the adipic acid is brought into contact with the bitumen, for example by adding adipic acid in the bitumen, and then maintaining the bitumen / adipic acid mass at a higher temperature. at about 130 ° C., advantageously between 135 ^° C. and 170 ^° C., under conditions which prevent the sublimation or evaporation of the adipic acid. The addition at a temperature greater than 130 ^° C. makes it possible to obtain, in an extremely rapid manner, a certain reactivity of the adipic acid with respect to the bitumen with generation of chemical, physico-chemical or electronic bonds between the molecules of adipic acid and the compounds forming the bitumen. The reaction is immediate, the duration of the mixture being determined by obtaining a homogeneous mixture.

In one embodiment of the process, the mixtures obtained after maintaining at a temperature above 130 ^° C. are cooled to a temperature of less than about 130 ^° C., preferably less than about 120 ^° C., and then homogenized by stirring. preferably mechanical agitation.

It is also possible to achieve this homogenization before cooling the mixture to a temperature below about 130 ^° C., preferably below 120 ^° C., if this step is carried out in a confined chamber avoiding the sublimation of the acid. adipic. According to another characteristic of the process, the contacting of the bitumen with adipic acid is carried out either by adding adipic acid in the bottom of a reservoir and then pouring the bitumen into said reservoir, or by addition of adipic acid at the heart of the bitumen mass contained in a tank. By addition to the core of the bitumen mass, it should be understood that the point of addition of the adipic acid must be located in the bitumen mass at a distance of at least 1 cm, preferably about 5 cm from the surface top of the bitumen mass.

Thus, when the temperature is maintained at a value greater than 130 ° C., advantageously between 135 ° C. and 170 ^° C., the mass of bitumen situated above the adipic acid forms a buffer preventing sublimation or degradation. Evaporation of adipic acid.

The mixing step is then advantageously carried out at a relatively low temperature, typically below 130 ^° C., preferably below 120 ^° C., a temperature level for which, on the one hand, the bitumen has a sufficient fluidity to be homogenized and on the other hand the phenomenon of sublimation or evaporation of adipic acid no longer exists or is very small or negligible.

This method of adding adipic acid allows to add only the amount of acid necessary to obtain a modification of the properties of the bitumen. According to another embodiment of the process for manufacturing a modified bitumen composition according to the invention, the addition of adipic acid and the mixing or homogenization are carried out in a confined space, such as a tank with closed agitation or a static mixer, for example.

As the space is confined, the sublimation or evaporation of the adipic acid is prevented or limited, the homogenization can be carried out at a temperature above 130 ⁰ C advantageously between 135 ° C and 170 ^° C approximately , the duration of maintenance at this temperature can be much shorter than that required in the absence of agitation.

To minimize the phenomenon of sublimation of adipic acid, it is advantageous that the confined space is filled to at least 90% by the mixture bitumen / adipic acid. In addition, to limit losses of adipic acid, it may be preferable to maintain at a high temperature all internal parts of the equipment used to prevent acid deposition on walls or cold parts of the installation. In the embodiments of the method described above, the bitumen to which the adipic acid is added, may already contain certain additives, or they may be added to the composition after or during the homogenization step of the composition.

The modified bitumen compositions of the invention are especially used for the formation of surface coating and more particularly for the formation of the wearing course of a roadway or road. For this, it can be advantageously mixed with gravel or granules of various kinds.

The modified bitumens of the invention have improved properties at high temperatures. Thus, the bitumens of the invention has an elevation of the TBA of the order of 20 to 30 ^° C., that is to say much higher than that obtained by modifying the bitumens by addition of elastomers or strong acid ( polyphosphoric acid, for example). These bitumens also have a low temperature behavior (embrittlement) at least equivalent to that of unmodified bitumens.

This improvement in properties is obtained for very low concentrations of adipic acid, that is to say with 0.4 or 0.5% of adipic acid. This effect is also observed with bitumens comprising additives such as elastomers such as SBS elastomers or rubber crumb and / or catalysts.

Other advantages, details of the invention will appear more clearly in view of the examples given below only for illustrative and illustrative purposes.

For the realization of the examples, two types of bitumen were considered, in order to take into account the great physicochemical diversity of these products:

-a weakly acidic paraffinic type bitumen (Middle East) from Shell

(Petit Couronne refinery) and

- a much more acidic bitumen type naphthenic (Venezuela) from Nynas (Nynashaam refinery).

The performance of these two bitumens were measured according to the standards in force: -Penetration at room temperature according to the standard (CEN-AFNOR EN1426), this characteristic is expressed in tenth of a millimeter and will be denominated "Péné" in the following of the text and,

softening temperature or ball-ring TBA according to CEN-AFNOR EN1427.

A critical temperature can also be calculated from the DSR rheology results, according to the criteria defined by the Highway Research Program Strategy (SHRP ₁ USA). This temperature, before aging, called Tc is calculated according to the method AASHTO TP5-97. This critical temperature is particularly measured in the case of bitumens modified with polymers, for which the measurement of TBA can sometimes be erroneous because of the absence of shear.

[0051] The characteristics of these bitumens are summarized in the table below:

Table I

These bitumens can be modified by the addition of an elastomer type additive typically dosed at 3% by weight (SBS) or by a strong mineral acid additive dosed at 1, 2% by weight (polyphosphoric acid APP) . The characteristics of these additive bitumens are given as an indication in Table II below:

Table II

Example 1 Addition of adipic acid according to the embodiment in confined space.

Various tests were carried out using a process for adding adipic acid in bitumen contained in a confined (closed) environment. Trials have been made, for example, with a double-walled closed Pyrex reactor equipped with a stirring device. The heating is provided by a circulation of temperature controlled oil. Any other closed system can be used.

An amount of bitumen (100 g) was previously heated in a beaker (250 ml) at 165 ° C. This bitumen is then poured into a container equipped with a lid, and then maintained at 165 ^° C. for 30 min. The temperature is measured by a temperature probe immersed in the bitumen. The container is opened, and the adipic acid is introduced rapidly: for example 0.5 g of acid per 100 g of bitumen. The container is then closed, and the mixture is homogenized by stirring (300 rpm) for 1 h at 165 ° C. The bitumen thus modified is then cooled to a lower temperature, typically 135 ^° C., with slow stirring for about 15 hours. These conditions simulate an industrial process: additivation in a closed reactor, then storage in a closed tank at a lower temperature. The bitumen is then poured directly into various molds in order to carry out the characterization tests on standard test specimens.

In Table III below are collected the properties of different bitumen compositions modified with various concentrations of adipic acid (ADOH).

Table II I

Bitumen + 0, 2% + 0.3% + 0.4% + 0.5% 70/100 ADOH ADOH ADOH ADOH

TBA (° C) 47 46.5 45.5 53 93

The results obtained show that the elevation of TBA appears only for an adipic acid concentration of 0.4%. This elevation of TBA is substantially equivalent to that obtained with 1.2% polyphosphoric acid. For an adipic acid content greater than 0.4%, the performance then becomes extremely high: TBA = 93 ° C. for 0.5% ADOH.

However, such hot performance gains could raise fears of embrittlement of low temperature bitumen. A measurement of the Tg of these compositions by DSC shows that it remains substantially constant and equal to that of the unmodified bitumen and therefore there would be no modification of the bitumen that could lead to a problem of cold embrittlement. In addition, the evolution of the consistency at room temperature (Péné) corresponds to a gain of about one grade on the composition, according to the classification of the viscous products which is illustrated by the evolution of the characteristic of penetrability.

[0058] As the embodiment of the method ^of adding and mixing is conducted in a closed environment, there is no formation of white smoke. Keeping all parts of the installation temperature-free avoids any risk of deposits.

Example 2 Addition of adipic acid according to the embodiment in open space.

A quantity of bitumen (> 100 g) was preheated in a beaker (250 ml) at 165 ^° C. 100 g of this bitumen thus heated is then poured into a beaker containing in its bottom, adipic acid. for example 0.8 g of adipic acid per 100 g of bitumen. The temperature is measured by a temperature probe immersed in the bitumen. The vessel is opened, and the temperature is maintained at 165 ° C for 30 minutes without agitation. The temperature is then lowered to 120 ^° C. and the mixture is homogenized by stirring (300 rpm) for 30 minutes. The bitumen is then poured directly into various molds in order to perform characterization tests on standard test specimens. For an adipic acid content of 0.8%, the measured value of TBA is then extremely high: TBA = 100 ^° C.

Another series of tests was carried out with a lower content namely 0.5% adipic acid. The acid is incorporated as described above: addition in the bottom of the beaker before the addition of the bitumen mass at 165 ° C. without any stirring, in an open medium, then homogenization at a lower temperature (below 130 ^° C. by stirring for 30 min).

The measured TBA value is always extremely high, and this for only 0.5% of adipic acid: TBA = 101 ^° C.

Example 3: Test with 0.4% Adipic Acid in combination with an SBS polymer according to the confined containment mode of addition.

A series of tests was carried out by combination of adipic acid and an SBS polymer. The bitumen has been previously additivated with a polymer according to a procedure specific to this type of product. Shell 70/100 bitumen and Kraton 1184R type SBS polymer were used. The bitumen-polymer mixture SBS was produced in two stages: a dispersion at 175 ° C. in a Silverson-type shearing kneader at 3000 rpm for 1 hour, then

a maturation of the mixture at 165 ^° C. under slow speed kneading (300 rpm) for 2 hours in which the polymer undergoes swelling as a result of the absorption of a portion of the oils of the bitumen.

Different compositions of bitumen modified with a polymer (BmP) have thus been produced: in particular a standard composition containing 3% by weight of SBS, and a composition with a reduced content of typically 2% by weight of SBS.

Adipic acid is incorporated in a confined (closed) in the polymer modified bitumen previously prepared according to the procedure described in Example 1.

The following conditions were retained: incorporation carried out at 165 ° C with stirring (400 rpm) in a closed medium, then maintaining the bitumen at 135 ° C for 15 hours always in a closed environment. These conditions simulate an industrial process: reactor additivation, then tank storage at a lower temperature.

The performance gain observed is extremely high: for 0.4% of adipic acid with only 2% of SBS, the TBA of the polymer modified bitumen thus passes from 51.2 ° C. to 80 ^° C. (ie an elevation of close to 30 ^° C.).

Table IV summarizes the characteristics of various compositions showing the important effect obtained by addition of adipic acid in a bitumen modified by addition of polymer.

Table IV

The Pene penetration value increased from 72 (d / 10 mm) for the unmodified 70/100 bitumen to 38 (d / 10 mm) for the composition at 2% SBS + 0.4% Adipic Acid. Rheology measurements (DSR) carried out on a viscoanalyser (Metravib) allow a finer characterization of the modified bitumens, and in particular the calculation of a critical temperature Tc according to SHRP criteria (Strategy Highway Research Program, USA): the gains of TC observed confirm what is observed at the level of the TBA. [0070] Another test was performed by adding 0.4% of adipic acid in a modified bitumen with 2% of SBS at 165 ° C without stirring and maintaining 30 min, then homogenized at a lower temperature (about 120 ⁰ C) with stirring for 1 h. The measured TBA is then equal to 94 ° C.

Example 4: Test with 0.4% of Adipic acid in combination with rubber crumbs according to the confined containment mode of addition.

The rubber crumb can be used in bitumens as a total or partial substitution of the SBS. A series of tests was carried out, by association of adipic acid and rubber crumb.

A modified bitumen-rubber powder was made according to the specific procedure for this type of product. The bitumen used is a 70/100 bitumen. Two compositions were prepared by adding 5% by weight and 10% by weight of rubber crumb at 175 ^° C.

Adipic acid is added in these compositions according to the embodiment of Example 1. The following conditions were retained, similar to those of an industrial process: incorporation carried out at 165 ° C. with stirring in medium closed for 1 hour, then maintenance of the bitumen at 135 ° C for 15 hours always in a closed environment.

The performance of the bitumen compositions obtained are:

With 10% of rubber crumb, the viscosity of the bitumen begins to be strongly modified, and the elevation of TBA is +9 ⁰ C compared to the unmodified bitumen (TBA = 56 ⁰ C). The performances are therefore slightly higher than those of bitumen modified with 3% of SBS.

For the compositions containing 5% rubber powder without adipic acid, the viscosity is slightly modified but the increase in TBA is only + 4 ° C (TBA = 51 ⁰ C).

The compositions containing 5% by weight of rubber powders and 0.5% by weight of adipic acid, the increase of TBA is + 15.5 ° C. The measured TBA is 66.5 ° C, with a correct viscosity. These properties are summarized in Table V below

Table V

The penetration value (Pene) of the mixture at 0.5% adipic acid + 5% rubber crumb is 35 (in1 / 10 mm). Rheology measurements (DSR) on an viscoanalyzer (Metravib) allow a finer _^ characterization of modified bitumen as well, including the calculation of a critical temperature Tc as SHRP criteria (Strategy Highway Research Program, USA). The presence of 0.5% adipic acid makes it possible to reduce the powdery powder concentration for an equivalent and even higher level of properties.

A production test of a composition containing 5% powder and 0.4% adipic acid was carried out by incorporation at 165 ° C. without stirring adipic acid in the bitumen modified with the crumb and holding for 30 minutes then homogenization by stirring at a temperature of 120 ^° C. for 1 hour. The measured TBA is then 66.5 ° C.

Example 5: Test with Adipic Acid, in the presence of basic filler

In many applications, particularly for the production of asphalt, the bitumen compositions comprise fillers called "filler" having a particle size less than 20 microns. These fillers may be siliceous mineral compounds generally derived from aggregates, or they may come from other basic type fillers such as lime or cements.

In this case, there may be some reactivity between these basic charges and acidic additives such as for example strong acids (polyphosphoric acid, for example). Thus, in the presence of 20% by weight of basic type filler, all the polyphosphoric acid (1%) is neutralized and the performance gain of the bitumen provided by this acid is then completely eliminated. A series of tests was carried out with adipic acid in the presence of a basic filler commonly used cement plant called "Calcia". The results collected in Table VI below show that the effect of adipic acid on the properties of the bitumen is preserved in the presence of basic type of fines.

Example 6: Test with 0.5% Adipic acid in combination with a catalyst.

The catalyst used is ferric chloride FeCl 3, in powder form. This product has a melting point at low temperature.

The bitumen used is a 70/100 bitumen. Various assays were performed using an open addition method (unconfined). Tests were carried out, for example, with a Pyrex beaker placed on a heating plate, the stirring being carried out using a stirrer 3 blades. The temperature is controlled by means of a Pt probe immersed in the bitumen.

An amount of bitumen (100g) was previously heated in a beaker (250 ml) at 165 ° C. This bitumen is then maintained at 165 ^° C. for a fortnight. The catalyst is introduced rapidly, with stirring: for example 1 g of FeCb per 100 g of bitumen. The vessel is stirred (300 rpm) for 1 hour at 165 ° C. The adipic acid is then introduced rapidly, still with stirring: for example 0.5 g of acid per 100 g of catalyzed bitumen. The vessel is then stirred (300 rpm) for 30 minutes at 165 ° C. The bitumen thus obtained is then poured directly into various molds in order to carry out the characterization tests on standard test specimens. ^*

In Table VII below are collected the properties of different bitumen compositions modified with various concentrations of catalyst (FeCb) and adipic acid (ADOH). Table VII

The results obtained show that for mild conditions (much lower than those of the blowing) and without any air blowing, the addition of FeCl ₃ catalyst even in high concentrations (up to 3% by weight) does not no significant modifications of the bitumen. When the FeCI3 catalyst is used in combination with adipic acid ADOH, a significant gain in TBA is observed as well as a strong reduction in Penetration (Péné): TBA of 65 ° C. for 0.5% FeCl ₃ + O, 5% ADOH.

EXAMPLE 7 Comparative Tests

Various tests were carried out for comparison with other carboxylic acids according to the procedure of Example 1.

A first series of tests was carried out with citric acid (non-dicarboxylic acid) and stearic acid at 1%. These acids do not modify the properties of the bitumen. The results obtained are summarized in Table VIII below.

Table VIII

Other carboxylic acids have also been evaluated as succinic acid, glutaric acid. As the melting points of these acids are relatively different: 90 ^° C. for glutaric acid, and 190 ^° C. for succinic acid, the procedures for adding these acids were carried out at different temperatures indicated in the table. IX below which gather the results obtained. Table IX

Claims

claims 1. Composition of bitumen modified by addition of adipic acid, characterized in that it comprises between 0.4% and 1% by weight of adipic acid relative to the weight of the composition and has an elevation of TBA of greater than or equal to 15 ° C relative to the TBA of the composition containing no adipic acid. 2. Composition according to claim 1, characterized in that it comprises a catalyst. 3. Modified bitumen composition comprising adipic acid characterized in that it comprises at least 0.4% by weight of adipic acid relative to the weight of the composition and an elevation of the TBA greater than or equal to 15 ° C, and in that it can be obtained by a process comprising a step of adding adipic acid to the bitumen composition to be modified, a step of maintaining the bitumen composition containing adipic acid at a temperature greater than 130 ^° C. under conditions preventing the evaporation and sublimation of adipic acid and a step of mixing the adipic acid and the bitumen composition by stirring at a temperature of less than 130 ^° C. ⁰ C, in a confined space to prevent sublimation and evaporation of adipic acid. 4. Composition according to claim 3, characterized in that it comprises a catalyst. 5. Composition according to one of claims 1 to 4, characterized in that it comprises additives selected from the group consisting of thermoplastic resins, elastomers, plasticizers, fillers. 6. Composition according to one of claims 1 to 5, characterized in that it comprises at least one additive selected from the group consisting of LDPE (low density polyethylene), HDPE (high density polyethylene), EVA (ethylene vinyl acetate), SBR (styrene butadiene elastomer), SBS (styrene butadiene styrene elastomer), PS (polystyrene), ABS (acrylonitrile butadiene styrene), CMC (carboxymethyl cellulose), PVA (polyvinylacetate), PVC (chloride polyvinyl), polybutadiene, HIPS (high impact polystyrene), rubber crumb. 7. Composition according to one of claims 2, 4 to 6, characterized in that it contains a catalyst at a weight concentration of less than 0.7% by weight of bitumen. 8. Composition according to one of claims 2, or 4 to 7, characterized in that the catalyst is iron chloride. 9. Composition according to one of the preceding claims, characterized in that the adipic acid concentration is between 0.5% and 0.8% by weight. -10. Composition according to Claim 6, characterized in that the weight concentration of adipic acid is between 0.4% and 0.8% relative to the weight of bitumen. 11. Composition according to claims 6 or 10, characterized in that the weight concentration of rubber crumb is between 5% and 10% by weight relative to the weight of bitumen. 12. A method of manufacturing a modified bitumen composition according to one of claims 1 to 11, characterized in that it consists in contacting the adipic acid with the bitumen composition, maintaining the adipic acid and the bitumen composition at a temperature greater than 130 ^° C. under confinement conditions preventing the adipic acid from evaporating or subliming. 13. Process according to claim 12, characterized in that the adipic acid is added and mixed with the bitumen in a static mixer at a temperature above 130 ^° C., preferably between 135 ^° C. and 70 ^° C. 14. Process according to Claim 12, characterized in that the adipic acid is added to the bitumen composition contained, with stirring, in a closed chamber, at a temperature greater than 130 ^° C., preferably between 135 ° C. and 170 ^° C. 15. Process according to claim 12, characterized in that the adipic acid is added to the bitumen composition at a point of injection situated at a distance greater than 1 cm, preferably greater than 5 cm, from the surface of the composition. bitumen, the entire adipic acid / bitumen composition is maintained, in the absence of agitation, at a temperature above 130 ^° C., preferably between 135 ° C. and 170 ^° C., for at least 15 minutes, said assembly then being subjected to stirring after cooling to a temperature below 130 ^° C for a time sufficient to obtain a homogeneous mixture.