Patent Description:
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 hydrocarbon binder used in the field of road construction and civil engineering.

Bituminous compositions are used as bituminous binders, in these different applications, providing they fulfill the required mechanical and elastic characteristics. The mechanical properties of the bituminous compositions are determined by standardized tests of the different mechanical characteristics, such as the softening point, the penetrability and the rheological characteristics in predetermined tension. For improving the elastic properties of the bituminous compositions, it is known in the art to introduce in the bitumen a crosslinkable elastomer, which is crosslinked in situ in the bituminous composition (see for instance <CIT> and prior art mentioned in this document). These kinds of modified bitumen are named bitumen modified by a crosslinked elastomer.

The applicant proposed in its previous <CIT> to incorporate into a bituminous composition, both a hydroxide XOH, with X = Na, Ca, Mg, Li or K, and at least one amine additive selected from amines, diamines, polyamines, alkyl amido amines, amidopolyamines and imidazolines, for improving the stability over time and over external solicitations, with respect to the mechanical properties of said bituminous composition. In its other <CIT>, the applicant also describes the preparation of a master batch composition comprising the hydroxide in a hydrocarbonated component for its introduction in a bituminous composition. In the examples of <CIT>, bitumen without elastomer and bitumen modified by a crosslinked elastomer are prepared accordingly. In these examples, the most usual properties of a bituminous composition are studied (penetrability, measured at <NUM> according to EN <NUM>, ring and ball softening temperature, measured according to EN <NUM>, ageing after solicitations, storage stability). Data on elastic properties are only presented for one modified-bitumen: STYRELF <NUM>/<NUM>-<NUM> comprising <NUM> weight % of LG <NUM> Luprene which is a SBS Polymer comprising <NUM>-<NUM>% by weight of styrene on the basis of the total weight of this polymer. The elastic recovery at <NUM>, which is the only tested elastic property, is strictly identical with or without hydroxide.

Now, the applicant had shown that the addition of a hydroxide XOH like NaOH to a bitumen modified by a specific crosslinked elastomer, has a positive impact on the obtained elastic properties of the obtained bituminous composition.

The invention is relative to the use of a hydroxide XOH with X = Na or K, in a bituminous composition comprising a bitumen modified by a crosslinked elastomer which is a crosslinked vinyl aromatic hydrocarbon and conjugated diene copolymer, having a vinyl aromatic hydrocarbon content representing less than <NUM>% by weight of the weight of the crosslinked elastomer, for improving the effect of the crosslinked elastomer on the elastic properties of the bituminous composition. According to the invention, the improvement is either the improvement of the elastic properties of the bituminous composition, with the use of the same quantity of crosslinked elastomer or the maintaining of at least the same elastic properties of the bituminous composition, but with the use of a lower quantity of crosslinked elastomer in the bituminous composition. For the comparison, the quantity of crosslinked elastomer designates the % by weight of the crosslinked elastomer or of the crosslinkable elastomer leading to the crosslinked elastomer after crosslinking, with respect to the weight of the bitumen modified by a crosslinked elastomer (so without the hydroxide).

According to preferred embodiments, the introduced quantity of hydroxide XOH in the bituminous composition represents at most <NUM> % by weight, preferably from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, of the total weight of said bituminous composition. The said bituminous composition designates the final bituminous composition including the hydroxide XOH.

In particular, the hydroxide XOH is NaOH.

According to the invention, preferentially, the elastic properties of the bituminous composition for which the effect is improved are at least the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard, preferably the elastic properties of the bituminous composition for which the effect is improved are at least the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard and the deformation energy at <NUM> measured according to DIN EN <NUM> standard, and more preferentially the elastic properties of the bituminous composition for which the effect is improved are the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard, the deformation energy at <NUM> measured according to DIN EN <NUM> standard and the phase angle and/or the temperature corresponding to a complex shear modulus of 15kPa measured with a Dynamic Shear Rheometer according to DIN EN <NUM> standard. In particular, the deformation energy at <NUM> measured according to DIN EN <NUM> standard is integrated between <NUM> and <NUM> deformation.

In particular, the crosslinked elastomer is a crosslinked copolymer of vinyl aromatic hydrocarbon and conjugated diene, having a vinyl aromatic hydrocarbon content representing from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>% by weight, of the weight of the crosslinked elastomer.

Advantageously, the crosslinked elastomer is a block copolymer or a random-block copolymer.

Preferentially, the crosslinked elastomer is styrene and butadiene copolymer.

In particular, the crosslinked elastomer is a crosslinked styrene and butadiene block or random-block copolymer.

Particularly suitable crosslinked elastomer are copolymers SB, which are formed either by a block based on monovinylaromatic hydrocarbon monomers, typically styrene, and a butadiene-based block, forming a copolymer of formula S-B, or by a monovinylaromatic hydrocarbon/butadiene, typically styrene and butadiene, random-block copolymer including at least a block based on monovinylaromatic hydrocarbon monomers, typically styrene, followed by at least a butadiene-based block, but also one or several part(s) corresponding to a random copolymer monovinylaromatic hydrocarbon/butadiene, typically styrene/butadiene, said copolymers SB being in their crosslinked form ; preferentially, in these copolymers SB, the vinyl group content of the butadiene units is in the range from <NUM>% to <NUM>% by weight, based on the total weight of condensed polybutadiene sequence(s), preferably from <NUM>% to <NUM>% by weight.

In the previously described crosslinked styrene and butadiene copolymers, the styrene content represents less than <NUM>% by weight of the weight of the crosslinked elastomer, from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>% by weight, of the weight of the crosslinked copolymer.

In particular, the crosslinking of the crosslinked elastomer is achieved within the bituminous composition, by thermal crosslinking or by crosslinking using a sulphured crosslinking agent. The crosslinking is obtained before the incorporation of the hydroxide XOH, within the bituminous composition.

Preferentially, the crosslinked elastomer represents from <NUM> to <NUM> % by weight, more preferentially from <NUM> to <NUM> % by weight, more preferentially from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, of said bituminous composition. Here again, the said bituminous composition designates the final bituminous composition including the hydroxide XOH.

In some embodiments which can be combined to the previous ones, the bituminous composition (here again, the bituminous composition designates the final bituminous composition including the hydroxide XOH) may also include an olefinic polymer, which, in particular, represents from <NUM>% to <NUM>% by weight, preferentially from <NUM>% to <NUM>% by weight, more preferentially still from <NUM>% to <NUM>% by weight, more preferentially still from <NUM>% to <NUM>% by weight, said olefinic polymer being preferentially selected from the group consisting of (a) ethylene/glycidyl (meth)acrylate copolymers; (b) ethylene/monomer A/monomer C terpolymers and (c) the mixtures of these copolymers ; in particular, the olefinic polymer is chosen from the groups (a), (b) and (c) consisting of:.

In some embodiments which can be combined to the previous ones, the bituminous composition may also comprise an adhesive promoter selected from amines, diamines, polyamines, alkyl amido amines, amidopolyamines and imidazolines, which preferably represents at most <NUM> % by weight, preferably from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, of said bituminous composition. Here again, the said bituminous composition designates the final bituminous composition including the hydroxide XOH.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or method step or group of elements or method steps, but not the exclusion of any other element or method step or group of elements or method steps. According to preferred embodiments, the word "comprise", or variations such as "comprises" or "comprising" means "consist exclusively of".

As used in the subject specification, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise. Thus, for example, reference to "a hydroxide XOH" includes a single hydroxide XOH, as well as two hydroxides XOH; reference to "crosslinked elastomer" includes a single crosslinked elastomer, as well as two or more crosslinked elastomer; reference to "the invention" includes single or multiple aspects taught by the present disclosure; and so forth. Aspects taught herein are encompassed by the term "invention". All aspects of the invention are enabled within the width of the claims.

So, in particular, reference to a "hydroxide XOH", "crosslinked elastomer", "olefinic polymer" and "amine additive" includes single entities and combinations/mixtures of two or more of such entities. Nevertheless, according to preferred embodiments, these terms designate a single entity.

The terms "hydroxide" and "hydroxide XOH" are used interchangeably herein and designate a hydroxide XOH, with X = Na or K.

The expression "crosslinked elastomer/bitumen" or "bitumen modified by a crosslinked elastomer" denotes the result from the crosslinking treatment of a mixture comprising at least the bitumen and the crosslinkable elastomer. The elastomer itself is crosslinked and there may also exist crosslinkings between the elastomer and the bitumen.

Unless specified otherwise, the cited European standards are the standards in force on <NUM>st May <NUM>.

A bitumen can be any bitumen, as known in the art. The bituminous composition can comprise one or more bitumen. The bitumen that can be used in the invention includes the bitumen of natural origin, those contained in natural deposits of bitumen, natural asphalt or tar sands and the bitumen obtained from the refining of crude oil. The bitumen used in the bituminous composition is advantageously chosen from the bitumen from the refining of crude oil, particularly from the bitumen containing asphaltenes. The bitumen may be obtained by conventional methods of bitumen manufacturing in a refinery, in particular by direct distillation and/or vacuum distillation of oil.

It is, in particular, standard to carry out the vacuum distillation of the atmospheric residues originating from the atmospheric distillation of crude oil. This manufacturing process consequently corresponds to the sequence of an atmospheric distillation and of a vacuum distillation, the feedstock feeding of the vacuum distillation corresponding to the atmospheric residue. The vacuum residues resulting from the vacuum distillation tower can be used as bitumen. In addition, these residues can optionally be subjected to other treatments in order to modify their mechanical properties, in particular their consistency. The bitumen may be optionally visbroken and/or deasphalted and/or air rectified. The visbreaking corresponds to a conversion process which employs thermal cracking reactions without supplying hydrogen.

The different bitumen obtained by the refining processes can be combined to achieve the best technical compromise in the bituminous composition.

The bitumen may also be a recycled bitumen or an oxidized bitumen.

The bitumen can be selected from bitumen fulfilling one of the following European standards EN <NUM>, EN <NUM>-<NUM> (hard grade) or EN <NUM>-<NUM> (multigrade).

In particular, the bituminous composition contains one or more bitumen chosen among paving grade bitumen as defined by EN <NUM> (<NUM> version). The bitumen can be a bitumen of hard or soft grade. For road application, the bitumen is advantageously chosen from bitumen of grades <NUM>/<NUM> to <NUM>/<NUM>, for instance of grades <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM> and <NUM>/<NUM> and from hard grade bitumen as defined in EN <NUM>-<NUM>.

Advantageously, the bituminous composition corresponding to the use of the invention (meaning including the hydroxide) have a penetrability, measured at <NUM> according to EN <NUM>, between <NUM> and <NUM><NUM>/<NUM>, preferably between <NUM> and <NUM><NUM>/<NUM>, more preferably between <NUM> and <NUM><NUM>/<NUM>.

Advantageously, the bituminous composition corresponding to the use of the invention (meaning including the hydroxide) have a ring and ball softening temperature, measured according to EN <NUM>, preferably less than or equal to <NUM>, and preferably between <NUM> and <NUM>.

In the invention, the bituminous composition includes a bitumen modified by a crosslinked elastomer. Such bitumen modified by a crosslinked elastomer may correspond to a "polymer modified bitumen" fulfilling the European standards EN <NUM>. The use of a crosslinked elastomer in bitumen was previously described, in order to improve the elasticity behaviour of the obtained bituminous composition (see for instance <CIT> and prior art mentioned in this document).

The crosslinking of the elastomer is carried out in situ, after the incorporation of a crosslinkable elastomer in a bitumen, said bitumen can include other additive(s). So, the bitumen modified by a crosslinked elastomer is obtained by the inclusion into the bitumen of a crosslinkable elastomer, in some embodiments with also the inclusion of a crosslinking agent, followed by a crosslinking step of the crosslinkable elastomer leading to the crosslinked elastomer and so to the bitumen modified by a crosslinked elastomer.

Suitable crosslinked elastomers used in the invention are crosslinked vinyl aromatic hydrocarbon (in particular monovinyl aromatic hydrocarbon) and conjugated diene copolymers, in particular crosslinked styrene and butadiene, copolymers, and preferentially block copolymers or random-block copolymers. A particularly suitable crosslinkable elastomer is a copolymer, named copolymer SB, which may be formed either by a block based on monovinyl aromatic hydrocarbon monomers (typically styrene) and a butadiene-based block, forming a copolymer of formula S-B, or by a monovinyl aromatic hydrocarbon/butadiene (typically styrene and butadiene) random-block copolymer including at least a block based on monovinyl aromatic hydrocarbon monomers (typically styrene) followed by at least a butadiene-based block, but also one or several part(s) corresponding to a random copolymer monovinyl aromatic hydrocarbon/butadiene (typically styrene/butadiene). In the specification hereafter, even when the copolymer SB is such a copolymer which is a random-block copolymer, all the monovinyl aromatic hydrocarbon units (typically styrene) are described under S part and all the butadiene units are described under B part.

"Block" has the common meaning in the art and designates, , a polymeric chain comprising several successive monomer units, for instance at least <NUM>, or at least <NUM> successive monomer units, obtained by the polymerisation of one or more monomers of the same chemical nature.

By "random-block copolymer" is meant, within the meaning of the invention, a copolymer which includes both block and random parts. A random part is composed of two or more monomers of different chemical nature with a random sequence of these different monomers.

The monovinylaromatic hydrocarbon monomers of the copolymer SB may be independently any monovinylaromatic hydrocarbon known monomers, such as: styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, <NUM>,<NUM>-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene, vinyltoluene and vinylxylene or mixtures thereof.

The B part (typically the block B) is based on substantially pure butadiene monomers or comprising minor proportions, up to <NUM>% by weight, of structurally related conjugated dienes. Preferably, the B part (typically the B block) is exclusively made up of units derived from butadiene monomers.

The bituminous composition according to the use of the invention comprises at least one crosslinked elastomer resulting from the crosslinking of a copolymer SB. According to a particular embodiment, the bituminous composition according to the invention comprises several crosslinked elastomers, each resulting from the crosslinking of a copolymer SB. Thus, according to this embodiment, the preferred characteristics defined below characterize each of these copolymers SB included in the bituminous composition, before crosslinking.

Preferably, the monovinyl aromatic hydrocarbon monomer of the copolymer SB is styrene, which may be used as a substantially pure monomer or as the major component in mixtures with minor proportions of one or more other structurally related vinyl aromatic monomers, such as o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, <NUM>,<NUM>-dimethylstyrene, alpha-methylstyrene, vinylnaphthalene, vinyltoluene and vinylxylene. Advantageously, styrene is used alone or in a mixture with at most <NUM>% by weight of one or more other vinyl aromatic monomers, based on the total weight of the monomers of the S part of the copolymer SB. The use of substantially pure styrene is particularly preferred.

Advantageously, the copolymer SB has a weight-average molecular weight Mw, measured by conventional detection gel permeation chromatography with polystyrene standard, ranging from <NUM>,<NUM> to <NUM>,<NUM>/mol.

Preferably, the copolymer SB has a weight-average molecular weight Mw, measured by conventional detection gel permeation chromatography with polystyrene standard, of less than or equal to <NUM>,<NUM>/mol, more preferably less than or equal to <NUM>,<NUM>/mol, even more preferably less than or equal to <NUM>,<NUM>/mol and advantageously less than or equal to <NUM>,<NUM>/mol.

Preferably, the copolymer SB has a weight-average molecular weight (Mw), measured by conventional detection gel permeation chromatography with polystyrene standard, greater than or equal to <NUM>,<NUM>/mol, more preferably greater than or equal to <NUM>,<NUM>/mol, still more preferably greater than or equal to <NUM>,<NUM>/mol.

Preferably, the copolymer SB has a weight-average molecular weight (Mw), measured by triple detection gel permeation chromatography, ranging from <NUM>,<NUM> to <NUM>,<NUM>/mol, more preferably from <NUM>,<NUM> to <NUM>,<NUM>/mol, , advantageously from <NUM>,<NUM> to <NUM>,<NUM>/mol.

When the butadiene (<NUM>,<NUM>-butadiene) of the copolymer SB is polymerised via a <NUM>,<NUM>-addition mechanism, the result is a vinyl group pendant from the polymer backbone. The vinyl content of the copolymer SB, determined by coupling 13C NMR (carbon nuclear magnetic resonance) and <NUM> NMR (proton nuclear magnetic resonance) spectroscopy techniques, allows the characterisation of the different elastomers. The vinyl group contents described below refer to the final contents in the copolymer SB and not to the monomers used for their synthesis. Thus, the vinyl group contents defined below do not take into account the vinyl groups that may be present in the precursor monomers but that were reacted during the polymerisation reaction. In particular, they do not take into account the vinyl groups present in the monovinyl aromatic monomers which have reacted to form the S part of the copolymer SB. The vinyl content only characterises the vinyl groups present in the B part (typically the block B) of the copolymer SB due to the polymerisation of <NUM>,<NUM>-butadiene by a <NUM>,<NUM>-addition mechanism.

Preferably, the copolymer SB has a vinyl group content of greater than or equal to <NUM> mol% (% by mole), based on the total number of moles of the copolymer SB, preferably greater than or equal to <NUM> mol%.

Preferably, the copolymer SB has a vinyl group content of less than or equal to <NUM> mol%, based on the total number of moles of copolymer SB, more preferably less than or equal to <NUM> mol%.

Preferably, the B part (typically the block B) of the copolymer SB has a vinyl group content ranging from <NUM>% to <NUM>% by weight, based on the total weight of condensed polybutadiene sequences present in the B part (typically the block B), preferably from <NUM>% to <NUM>% by weight.

The units obtained by the polymerisation of <NUM>,<NUM>-butadiene according to a <NUM>,<NUM>-addition mechanism or according to a <NUM>,<NUM>-addition mechanism have the same molar weight. Thus, the contents of vinyl groups present in the B part (typically the block B) expressed in weight or in moles are equivalent.

Preferably, the B part (typically the block B) of the copolymer SB has a vinyl group content ranging from <NUM> to <NUM> mol%, based on the total amount of condensed polybutadiene sequences present in the B part (typically the block B), preferably from <NUM> to <NUM> mol%.

Advantageously, the B part (typically the block B) of the copolymer SB has a glass transition temperature Tg, determined by differential scanning calorimetry (DSC), of less than or equal to -<NUM>, preferably less than or equal to -<NUM>.

More advantageously, the B part (typically the block B) of the copolymer SB has a glass transition temperature Tg, determined by differential scanning calorimetry (DSC), ranging from -<NUM> to -<NUM>, preferably from -<NUM> to -<NUM>.

According to the invention, the content of monovinyl aromatic hydrocarbon (advantageously styrene) in the copolymer SB is less than <NUM>% by weight, based on the total weight of the copolymer SB. Preferably, the content of monovinyl aromatic hydrocarbon (advantageously styrene) in the copolymer SB, is from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>% by weight, based on the total weight of the copolymer SB. In the invention, the weight content of monovinyl aromatic hydrocarbon (typically styrene) can be determined by as determined by <NUM>C NMR spectroscopy.

Advantageously, the copolymer SB is essentially in a non-hydrogenated form.

The Solprene® <NUM> marketed by Dynasol is an example of such kind of crosslinkable elastomers. The Solprene® <NUM> may be crosslinked by several routes, in particular by thermal crosslinking or crosslinking with a crosslinking agent, typically a sulphured crosslinking agent.

In general, from <NUM> to <NUM>% by weight of a crosslinkable elastomer, and in particular of a copolymer SB, more preferably from <NUM>% to <NUM>% by weight, even more preferably from <NUM>% to <NUM>% by weight, even more preferably from <NUM>% to <NUM>% by weight, is used for forming the bituminous composition. These % by weight are given with respect to the total weight of the bituminous composition, before the crosslinking (so, also, before the addition of the hydroxide).

Preferably, the bituminous composition corresponding to the use of the invention comprises from <NUM> to <NUM>% by weight of a crosslinked elastomer, and in particular of a crosslinked elastomer obtained from the crosslinking of a copolymer SB, more preferably from <NUM>% to <NUM>% by weight, even more preferably from <NUM>% to <NUM>% by weight, even more preferably from <NUM>% to <NUM>% by weight. These % by weight are given with respect to the total weight of the bituminous composition (so including also the hydroxide). The quantity of crosslinked elastomer is substantially identical to the quantity of the crosslinkable elastomer, when no crosslinking agent is used or when the crosslinking agent is used in very low quantity, in particular with a content representing at most <NUM> % of the final bituminous composition (case of sulphur). The crosslinking of the crosslinkable elastomer, and in particular of the monovinyl aromatic hydrocarbon and conjugated diene copolymer, in particular styrene and butadiene copolymer as defined in the specification, may be achieved, in the crosslinked elastomer modified bitumen composition, by different means, known in the art, for instance by using a crosslinking agent or a thermal crosslinking.

In particular, the crosslinking may be achieved thanks to the use of a sulphured crosslinking agent.

Preferably, the crosslinking agent is chosen from sulphur and the hydrocarbyl polysulphides, alone or in a mixture, optionally in the presence of sulphur-donor or non-sulphur-donor vulcanization accelerators, alone or in a mixture. The sulphur is in particular flowers of sulphur or also alpha crystallized sulphur. The hydrocarbyl polysulphides are for example chosen from the dihexyl disulphides, dioctyl disulphides, didodecyl disulphides, ditertiododecyl disulphides, dihexadecyl disulphides, dihexyl trisulphides, dioctyl trisulphides, dinonyl trisulphides, ditertiododecyl trisulphides, dihexadecyl trisulphides, diphenyl trisulphides, dibenzyl trisulphides, dihexyl tetrasulphides, dioctyl tetrasulphides, dinonyl tetrasulphides, ditertiododecyl tetrasulphides, dihexadecyl tetrasulphides, diphenyl tetrasulphides, orthotolyl tetrasulphides, dibenzyl tetrasulphides, dihexyl pentasuiphides, dioctyl pentasulphides, dinonyl pentasulphides, ditertiododecyl pentasulphides, dihexadecyl pentasuiphides, dibenzyl pentasulphides or diallyl pentasulphides.

The sulphur-donor vulcanization accelerators can be chosen from the thiuram polysulphides, such as for example, the tetrabutylthiuram disulphides, tetraethylthiuram disulphides and tetramethylthiuram disulphides, dipentamethylenethiuram disulphides, dipentamethylenethiuram tetrasulphides or dipentamethylenethiuram hexasulphides.

The non-sulphur-donor vulcanization accelerators which can be used according to the invention can be chosen in particular from mercaptobenzothiazole and its derivatives, dithiocarbamates and derivatives, and thiuram monosulphides and derivatives, alone or in a mixture. There may be mentioned as examples of non-sulphur-donor vulcanization accelerators, zinc <NUM>-mercaptobenzothiazole, zinc benzothiazole thiolate, sodium benzothiazole thiolate, benzothiazyl disulphide, copper benzothiazole thiolate, benzothiazyl N,N'-diethyl thiocarbamyl sulphide and benzothiazole suiphenamides such as <NUM>-benzothiazole diethyl sulphenamide, <NUM>-benzothiazole pentamethylene sulphenamide, <NUM>-benzothiazole cyclohexyl sulphenamide, N-oxydiethylene <NUM>-benzothiazole sulphenamide, N-oxydiethylene <NUM>-benzothiazole thiosulphenamide, <NUM>-benzothiazole dicyclohexyl sulphenamide, <NUM>-benzothiazole diisopropyl sulphenamide, <NUM>-benzothiazole tertiobutyl sulphenamide, bismuth dimethyl dithiocarbamate, cadmium diamyl dithiocarbamate, cadmium diethyl dithiocarbamate, copper dimethyl dithiocarbamate, lead diamyl dithiocarbamate, lead dimethyl dithiocarbamate, lead pentamethylene dithiocarbamate, selenium dimethyl dithiocarbamate, tellurium diethyl dithiocarbamate, zinc diamyl dithiocarbamate, zinc dibenzyl dithiocarbamate, zinc diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, zinc dibutyl dithiocarbamate, zinc pentamethylene dithiocarbamate, dipentamethylene thiuram monosulphide, tetrabutyl thiuram monosulphide, tetraethyl thiuram monosulphide and tetramethyl thiuram monosulphide.

The crosslinking agent can also be chosen from the compounds of general formula HS-R-SH where R represents a saturated or unsaturated, linear or branched hydrocarbon group with <NUM> to <NUM> carbon atoms, optionally comprising one or more heteroatoms, such as oxygen. Among the compounds corresponding to this general formula, there can be mentioned for example <NUM>,<NUM> ethanedithiol, <NUM>,<NUM> propanedithiol, <NUM>,<NUM> butanedithiol, <NUM>,<NUM> pentanedithiol, <NUM>,<NUM> hexanedithiol, <NUM>,<NUM> heptanedithiol, <NUM>,<NUM> octanedithiol, bis-(<NUM>-mercaptoethyl)ether, bis-(<NUM>-mercaptoethyl)ether, bis-(<NUM>-mercaptoethyl)ether, (<NUM>-mercaptoethyl) (<NUM>-mercaptobutyl)ether, (<NUM>-mercaptoethyl) (<NUM>-mercaptobutyl)ether, <NUM>,<NUM>-dimercapto-<NUM>,<NUM>-dioxaoctane, benzene-<NUM>,<NUM>-dithiol, benzene-<NUM>,<NUM>-dithiol, benzene-<NUM>,<NUM>-dithiol or toluene-<NUM>,<NUM>-dithiol, biphenyl-<NUM>,<NUM>'-dithiol.

In general, a quantity of crosslinking agent (in particular of sulphured crosslinking agent, such as sulphur) between <NUM>% and <NUM>% by weight, preferably between <NUM>% and <NUM>%, more preferentially between <NUM>% and <NUM>%, even more preferentially between <NUM>% and <NUM>% is used for forming the bituminous composition. These % by weight are given with respect to the total weight of the bituminous composition, before the crosslinking (so before the addition of the hydroxide). Preferably, the quantities of crosslinkable elastomer and cross-linking agent are fixed so as to obtain a crosslinkable elastomer/crosslinking agent (typically copolymer SB/crosslinking agent) ratio comprised between <NUM>:<NUM> and <NUM>:<NUM>, preferably between <NUM>:<NUM> and <NUM>:<NUM>, more preferentially between <NUM>:<NUM> and <NUM>:<NUM>.

The crosslinking may also be achieved thermally, thanks to the use of an monovinyl aromatic hydrocarbon and conjugated diene (typically butadiene), in particular styrene and butadiene, copolymer (typically a copolymer SB, as previously described), having a particular quantity of <NUM>,<NUM> double bond units originating from the conjugated diene (typically butadiene), this quantity of <NUM>,<NUM> double bond units originating from the conjugated diene (typically butadiene), being comprised between <NUM>% and <NUM>% by weight, with respect to the total weight of the conjugated diene, in particular butadiene, units preferably between <NUM>% and <NUM>%, more preferentially between <NUM>% and <NUM>%, even more preferentially between <NUM>% and <NUM>%, even more preferentially between <NUM>% and <NUM>% or between <NUM>% and <NUM>%, or also thanks to the use of said monovinyl aromatic hydrocarbon and conjugated diene (typically butadiene), in particular styrene and butadiene, copolymer (typically a copolymer SB, as previously described), having or not the particular quantity defined above of <NUM>,<NUM> double bond units originating from the conjugated diene (typically butadiene), in combination with a cross-linking agent. In that case, the cross-linking agent may be a sulphured crosslinking agent, as previously described. But, according to specific embodiments, the crosslinking may be essentially thermal. The term "essentially thermal" is understood to mean, within the meaning of the invention, a crosslinking created by heat treatment, in the absence of a chemical crosslinking agent. A crosslinked elastomer/bitumen obtained by such a method thus differs from crosslinked elastomer/bitumen obtained by crosslinking in the presence of crosslinking agents, notably crosslinking agents chosen from sulphur-containing crosslinking agents.

The thermal crosslinking can be obtained by a suitable thermal treatment of the bitumen comprising the crosslinkable elastomer and eventually (an)other additive(s). The crosslinking of the crosslinked elastomer/bitumen can be demonstrated by carrying out on this crosslinked elastomer/bitumen, tensile tests according to the standard NF EN <NUM>. The crosslinked elastomer/bitumen has a higher tensile strength than the elastomer/bitumen. A higher tensile strength results in a high ultimate elongation or maximum elongation (ε max in %), a high rupture stress or maximum elongation stress (σ ε max in MPa), high conventional energy at <NUM>% (E <NUM>% in J/cm<NUM>) and/or high total energy (total E in J). The crosslinked elastomer/bitumen has a maximum elongation, according to the standard NF EN <NUM>, greater than or equal to <NUM>%, preferably greater than or equal to <NUM>%, more preferentially greater than or equal to <NUM>%, even more preferentially greater than or equal to <NUM>%.

The invention uses a hydroxide XOH, with X = Na or K, for adjusting the elastic properties of bituminous compositions including a crosslinked elastomer. It is possible to use one, or more than one hydroxide XOH.

The purpose of the use of the invention is to optimize the elastic properties of bituminous compositions modified by a crosslinked elastomer, in particular as previously described.

According to a particular embodiment, the use of the invention concerns a bituminous composition in which at most <NUM> % by weight, preferably from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM>% by weight, and more preferably from <NUM> to <NUM> % by weight of the hydroxide XOH with X = Na or K, relative to the total weight of the obtained bituminous composition, has been incorporated.

The invention uses NaOH and/or KOH, as hydroxide XOH, and advantageously only NaOH, only KOH or a mixture of NaOH and KOH, as hydroxide XOH. According to a particular embodiment, NaOH is used, as hydroxide XOH, and advantageously only NaOH is used, as hydroxide XOH, in a bituminous composition comprising a bitumen modified by a crosslinked elastomer, for improving the effect of the crosslinked elastomer on the elastic properties of the bituminous composition.

According to the invention, the use of the hydroxide improves the elastic properties of the obtained bituminous composition, when the elastic properties are compared with the same bituminous composition, but without the incorporation of the hydroxide (so, with the use of the same quantity of crosslinked elastomer). According to the invention, it is also possible to maintain at least the same elastic properties of the bituminous composition, but with the use of a lower quantity of crosslinked elastomer within the bituminous composition, which is very advantageous economically. With the use of the invention, it is possible to improve and/or positively influence the elastic behaviour of the obtained bituminous composition. So, the invention is also relative to the use of a hydroxide XOH with X = Na or K, in a bituminous composition comprising a bitumen modified by a crosslinked elastomer which is a crosslinked vinyl aromatic hydrocarbon and conjugated diene copolymer, having a crosslinked vinyl aromatic hydrocarbon content representing less than <NUM>% by weight of the total weight of the crosslinked elastomer, for improving the elastic properties of the bituminous composition, with the use of the same quantity of crosslinked elastomer or for maintaining of at least the same elastic properties of the bituminous composition, but with the use of a lower quantity of crosslinked elastomer in the bituminous composition. All the embodiments described in the specification apply to these uses.

In particular, this elastic behaviour corresponds at least to the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard, preferably to at least the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard and the deformation energy at <NUM> measured according to DIN EN <NUM> standard, and more preferentially to the elastic recovery at <NUM>, measured according to DIN EN <NUM> standard, the deformation energy at <NUM> measured according to DIN EN <NUM> standard and the phase angle and/or the temperature corresponding to a complex shear modulus of 15kPa measured with a Dynamic Shear Rheometer according to DIN EN <NUM> standard. In particular, the deformation energy at <NUM> measured according to DIN EN <NUM> standard is integrated between <NUM> and <NUM> deformation and is designated as the deformation energy at <NUM> (<NUM>-<NUM>) measured according to DIN EN <NUM> standard.

The present invention can be implemented for any types of bituminous compositions, especially bituminous compositions for industrial and road applications. In particular, the bituminous composition in which the hydroxide is used is not a bitumen in water emulsion.

According to a particular embodiment of the invention, one or several additives or adjuvants, other than the hydroxide, are also included and/or present in said bituminous compositions.

Advantageously, and in particular for road applications, the said bituminous composition may contain an amine additive as described in <CIT> which is incorporated by reference. Such an amine additive acts as an adhesive promoter in the bituminous composition. Advantageously, it represents at most <NUM> % by weight, preferably from <NUM> to <NUM> % by weight, and more preferentially from <NUM> to <NUM> % by weight, and more preferably from <NUM> to <NUM> % by weight, of the bituminous composition and so it is introduced in the bituminous composition as described in the invention in such quantities.

In particular, the amine additive is selected from:.

Advantageously, the amine additive is selected from amines, diamines, polyamines, alkyl amido amines and amidopolyamines including a fatty chain. According to a specific embodiment, the amine additive is an amidopolyamine including a fatty chain of formula:.

In particular, the amine additive of the composition is a mixture of amidopolyamines of formula (IV) in which p is an integer from <NUM> to <NUM>, L is -(CH<NUM>)<NUM>-, and R are the hydrocarbon chains of the fatty acids of tall oil.

Wetfix BE (CAS <NUM>-<NUM>-<NUM>) marketed by AkzoNobel is an example of such an amine additive.

According to the invention, the bituminous composition in which the hydroxide is used may contain any conventional additive(s) used by the person skilled in the art in bituminous compositions, in particular an olefinic polymer adjuvant.

Advantageously, the olefinic polymer adjuvant is functionalized by at least one epoxy group. Such kind of olefinic polymer adjuvant may promote to a thermal crosslinking of the crosslinked elastomer polymer, but may be included whatever the chosen crosslinking route.

The olefinic polymer adjuvant functionalized by at least one epoxy group is preferably chosen from the group consisting of (a) ethylene/glycidyl (meth)acrylate copolymers; (b) ethylene/monomer A/monomer C terpolymers and (c) the mixtures of these copolymers.

The monomer A is chosen from vinyl acetate and C1 to C6 alkyl acrylates or methacrylates, preferably chosen from C1 to C6, more preferentially still C1-C3, alkyl acrylates or methacrylates.

Advantageously, the monomer A is chosen from ethyl acrylate and ethyl methacrylate.

More advantageously still, the monomer A is ethyl acrylate.

The monomer C is chosen from glycidyl acrylate and glycidyl methacrylate. Advantageously, the monomer C is glycidyl methacrylate.

The ethylene/monomer A/monomer C terpolymers comprise from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight and more preferentially from <NUM>% to <NUM>% by weight of motifs resulting from the monomer A and from <NUM>% to <NUM>% by weight and preferably from <NUM>% to <NUM>% by weight of motifs resulting from the monomer C, the remainder being formed of motifs resulting from ethylene.

(c) The olefinic polymer adjuvant functionalized by at least one epoxy group can consist of a mixture of two or more copolymers chosen from the categories (a) and (b).

The olefinic polymer adjuvant functionalized by at least one epoxy group is preferably chosen from the ethylene/monomer A/monomer C terpolymers (b) described above and from the mixtures (c) comprising them.

The olefinic polymer adjuvant functionalized by at least one epoxy group is advantageously chosen from the ethylene/monomer A/monomer C terpolymers (b) described above and from the mixtures (c) in which the terpolymers (b) represent at least <NUM>% by weight, with respect to the total weight of the mixture, preferentially at least <NUM>% by weight, even better still at least <NUM>% by weight.

Advantageously, the olefinic polymer adjuvant functionalized by at least one epoxy group is chosen from random terpolymers of ethylene, of a monomer A chosen from Ci to C6 alkyl acrylates or methacrylates and of a monomer C chosen from glycidyl acrylate and glycidyl methacrylate, comprising from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight, more preferentially from <NUM>% to <NUM>% by weight, of motifs resulting from the monomer A and from <NUM>% to <NUM>% by weight, preferably from <NUM>% to <NUM>% by weight, of motifs resulting from the monomer C, the remainder being formed of motifs resulting from ethylene.

Preferably, the number-average molecular weight (Mn) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by gel permeation chromatography with a polystyrene standard, ranges from <NUM> to <NUM><NUM>/mol, more preferentially from <NUM><NUM> to <NUM><NUM>/mol and more preferentially still from <NUM><NUM> to <NUM><NUM>/mol.

Preferably, the weight-average molecular weight (Mw) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by gel permeation chromatography with a polystyrene standard, ranges from <NUM><NUM> to <NUM><NUM>/mol, more preferentially from <NUM><NUM> to <NUM><NUM>/mol and more preferentially still from <NUM><NUM> to <NUM><NUM>/mol.

Advantageously, the number-average molecular weight (Mn) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by triple detection gel permeation chromatography, is greater than or equal to <NUM><NUM>/mol, preferably greater than or equal to <NUM><NUM>/mol, more preferentially still greater than or equal to <NUM><NUM>/mol and advantageously greater than or equal to <NUM><NUM>/mol.

More advantageously, the number-average molecular weight (Mn) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by triple detection gel permeation chromatography, ranges from <NUM><NUM> to <NUM><NUM>/mol, preferably from <NUM><NUM> to <NUM><NUM>/mol, more preferentially still from <NUM><NUM> to <NUM><NUM>/mol and advantageously from <NUM><NUM> to <NUM><NUM>/mol.

Advantageously, the weight-average molecular weight (Mw) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by triple detection gel permeation chromatography, is greater than or equal to <NUM><NUM>/mol, preferably greater than or equal to <NUM><NUM>/mol, more preferentially still greater than or equal to <NUM><NUM>/mol and advantageously greater than or equal to <NUM><NUM>/mol.

More advantageously, the weight-average molecular weight (Mw) of the olefinic polymer adjuvant functionalized by at least one epoxy group, determined by triple detection gel permeation chromatography, ranges from <NUM><NUM> to <NUM><NUM>/mol, preferably from <NUM><NUM> to <NUM><NUM> g/mol, more preferentially still from <NUM><NUM> to <NUM><NUM>/mol and advantageously from <NUM><NUM> to <NUM><NUM>/mol.

Advantageously, the polydispersity index of the olefinic polymer adjuvant functionalized by at least one glycidyl group, determined by triple detection gel permeation chromatography, is less than or equal to <NUM>, preferably less than or equal to <NUM>, more preferentially less than or equal to <NUM> and advantageously less than or equal to <NUM>.

More advantageously, the polydispersity index of the olefinic polymer adjuvant functionalized by at least one glycidyl group, determined by triple detection gel permeation chromatography, ranges from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferentially from <NUM> to <NUM> and advantageously from <NUM> to <NUM>.

The term "monomer unit" is understood to mean, within the meaning of the invention, the largest constituent unit generated by the (co)polymerization of a single molecule of said monomer.

Advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, at least <NUM> ethylene units per macromolecule, preferably at least <NUM> ethylene units, more preferentially at least <NUM> ethylene units, more preferentially still at least <NUM> ethylene units and advantageously at least <NUM> ethylene units.

More advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, from <NUM> to <NUM><NUM> ethylene units per macromolecule, preferably from <NUM> to <NUM> ethylene units, more preferentially from <NUM> to <NUM> ethylene units, more preferentially still from <NUM> to <NUM> ethylene units and advantageously from <NUM> to <NUM> ethylene units.

Advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, at least <NUM> alkyl (meth)acrylate units per macromolecule, preferably at least <NUM> alkyl (meth)acrylate units, more preferentially at least <NUM> alkyl (meth)acrylate units, more preferentially still at least <NUM> alkyl (meth)acrylate units and advantageously at least <NUM> alkyl (meth)acrylate units.

More advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, from <NUM> to <NUM> alkyl (meth)acrylate units per macromolecule, preferably from <NUM> to <NUM> alkyl (meth)acrylate units, more preferentially from <NUM> to <NUM> alkyl (meth)acrylate units, more preferentially still from <NUM> to <NUM> alkyl (meth)acrylate units and advantageously from <NUM> to <NUM> alkyl (meth)acrylate units.

Advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, at least <NUM> glycidyl (meth)acrylate units per macromolecule, preferably at least <NUM> glycidyl (meth)acrylate units.

More advantageously, the olefinic polymer adjuvant functionalized by at least one glycidyl group comprises, on average, from <NUM> to <NUM> glycidyl (meth)acrylate units per macromolecule, preferably from <NUM> to <NUM> glycidyl (meth)acrylate units, more preferentially from <NUM> to <NUM> glycidyl (meth)acrylate units, more preferentially still from <NUM> to <NUM> glycidyl (meth)acrylate units and advantageously from <NUM> to <NUM> glycidyl (meth)acrylate units.

Preferably, the average weight of the ethylene units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group is greater than or equal to <NUM><NUM>, more preferentially greater than or equal to <NUM><NUM>, more preferentially still greater than or equal to <NUM><NUM>, advantageously greater than or equal to <NUM><NUM> and more advantageously greater than or equal to <NUM><NUM>. More preferentially, the average weight of the ethylene units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group ranges from <NUM><NUM> to <NUM><NUM>, more preferentially from <NUM><NUM> to <NUM><NUM>, more preferentially still from <NUM><NUM> to <NUM><NUM>, advantageously from <NUM><NUM> to <NUM><NUM> and more advantageously from <NUM><NUM> to <NUM><NUM>.

Preferably, the average weight of the alkyl (meth)acrylate units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group is greater than or equal to <NUM>, more preferentially greater than or equal to <NUM>, more preferentially still greater than or equal to <NUM> and advantageously greater than or equal to <NUM>.

More preferentially, the average weight of the alkyl (meth)acrylate units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group ranges from <NUM> to <NUM><NUM>, more preferentially from <NUM> to <NUM><NUM>, more preferentially still from <NUM> to <NUM><NUM> and advantageously from <NUM> to <NUM><NUM>. Preferably, the average weight of the glycidyl (meth)acrylate units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group is greater than or equal to <NUM>, more preferentially greater than or equal to <NUM>, more preferentially still greater than or equal to <NUM>, advantageously greater than or equal to <NUM> and more advantageously greater than or equal to <NUM>.

More preferentially, the average weight of the glycidyl (meth)acrylate units present in one mole of olefinic polymer adjuvant functionalized by at least one glycidyl group ranges from <NUM> to <NUM><NUM>, more preferentially from <NUM> to <NUM><NUM>, more preferentially still from <NUM> to <NUM><NUM>, advantageously from <NUM> to <NUM><NUM> and more advantageously from <NUM> to <NUM><NUM>.

The content of olefinic polymer adjuvant functionalized by at least one epoxy group in the bitumen/polymer composition according to the invention is preferably from <NUM>% to <NUM>% by weight, with respect to the total weight of the composition, more preferentially from <NUM>% to <NUM>% by weight, more preferentially still from <NUM>% to <NUM>% by weight, more preferentially still from <NUM>% to <NUM>% by weight, more preferentially still from <NUM>% to <NUM>% by weight.

According to the invention, the bituminous composition can be prepared, by any conventional means, known in the art, in particular by direct incorporation of the hydroxide in the bituminous composition, as described in <CIT> or by the preparation of a master batch composition comprising the hydroxide in a hydrocarbonated component as described in <CIT>. In that last case, the hydrocarbonated component is, in particular, chosen among oils and bitumen, in particular selected among soft bitumen, fluxed bitumen and a cut-back bitumen. Advantageously, the hydroxide is introduced in an intermediary bitumen composition, which already comprised the crosslinked elastomer, so after the crosslinking of the elastomer. The crosslinking of the polymer is previously obtained by conventional means, for instance as described in <CIT> or <CIT>, by the use of a thermal treatment or by the use of a crosslinking agent, in particular a sulphured crosslinking agent, as previously described.

In a preferred embodiment, the different constituents are added subsequently in the bituminous composition.

Preferably, when an olefinic polymer is present in the bituminous composition, it is incorporated into the intermediary bituminous composition, before the hydroxide. Preferably, when an amine additive is present in the bituminous composition, it is incorporated, after the hydroxide.

The different components of the bituminous composition may be introduced, under mixing at a temperature in the range of <NUM> to <NUM>, preferably of <NUM>° to <NUM>. The mixture of the different constituents of the bituminous composition is conventionally obtained under stirring, for instance during a period of time of at least five minutes, preferably from <NUM> minutes to <NUM> hours, more preferably from <NUM> minutes to <NUM> hours, more preferably from <NUM> minutes to <NUM> hours.

According to a preferred embodiment, the manufacture of the bitumen composition includes the preparation of an intermediary bitumen composition (crosslinked elastomer/bitumen, in particular sulphur-crosslinking or heat-crosslinked elastomer/bitumen), in which the hydroxide is introduced. This intermediary bitumen composition may be obtained, for example, by the following successive stages:.

The mixing of stage ii) is preferably carried out for a period of time of at least <NUM> minutes, preferably from <NUM> hour to <NUM> hours, more preferentially from <NUM> hour to <NUM> hours.

Preferably, the stirring at high shear, and notably the stirring carried out by passing through a mill at high shear, makes it possible to facilitate the good dispersion and the good distribution of the crosslinkable elastomer and of the optional olefinic polymer adjuvant.

Advantageously, the hydroxide is introduced in this intermediary bitumen composition (crosslinked elastomer/bitumen), which already comprised the crosslinked elastomer, under mixing at a temperature in the range of <NUM> to <NUM>, preferably of <NUM>° to <NUM> and the mixing is maintained after its introduction. The mixing is conventionally carried out under stirring, advantageously under agitation in the range from <NUM> to <NUM> rpm, preferably in the range from <NUM> to <NUM> rpm, for instance during a period of time of at least five minutes, preferably from <NUM> minutes to <NUM> hours, more preferably from <NUM> minutes to <NUM> hours, more preferably from <NUM> hour to <NUM> hours.

Most of the time, if needed, the intermediary bituminous composition is heated at a temperature where it is in a liquid state, for favouring the regular incorporation of the hydroxide XOH. For instance, a temperature just enough to have the intermediary bituminous composition melting may be used, when the hydroxide is introduced as a powder. When the hydroxide is introduced as a solution in a solvent, for instance, as an aqueous solution, the heating will preferentially be adapted for allowing the spontaneous evaporation of the solvent, simultaneously with its incorporation.

Advantageously, within the composition, the hydroxide XOH forms particles with the maximal size of the particles being equal to <NUM> or less, and preferentially with the maximal size of the particles being equal to <NUM> or less. In particular, the average maximal size of the introduced hydroxide particles is within the range from <NUM> to <NUM>, preferably within the range from <NUM> to <NUM>. The average maximal size of the particles corresponds to the arithmetic average of the maximal sizes of several particles, preferably of <NUM> particles. The maximal sizes can be measured by microscopy. This size may be obtained, in particular, by using the master batch method as described in <CIT> or by direct incorporation of the hydroxide in the bituminous composition, as described in <CIT>. The obtained size of the hydroxide within the composition may be modulated, by the person skilled in the art, by the choice of the conditions of mixing and/or incorporation of the hydroxide XOH within the bituminous composition.

The manufacture of the composition may also include a final maturing stage, carried out by maintaining the composition in an oven at a temperature ranging from <NUM>° C to <NUM>° C, more preferentially ranging from <NUM>° C to <NUM>° C, more preferentially still ranging from <NUM>° C to <NUM>° C, advantageously from <NUM>° C to <NUM>° C and more advantageously still from <NUM>° C to <NUM>° C, preferably for a period of time of at least <NUM>, more preferentially from <NUM> hour to <NUM> hours, more preferentially still from <NUM> hour to <NUM> hours, before it is stored or used.

The bituminous compositions in which the hydroxide is used can be used in the fields of road applications or in the fields of industrial applications. Whatever the field of application, the bituminous composition is used as a bituminous binder and is shaped and/or associated with other components under heat. Conventionally, the heating temperature is in the range <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>.

In road applications, the bituminous composition is, in particular, used for the manufacture of hot bituminous mixes, asphalts or surface coatings. For instance, the bituminous composition may be included in bituminous mixes as materials for the construction and the maintenance of road foundations and their surfacing, and for all road works. Thus, the bituminous composition can be combined with aggregates and/or inorganic and/or synthetic fillers under heat and applying the obtained material to form a part of the road.

The bituminous composition can be employed to prepare a combination with aggregates, advantageously with road aggregates, in particular to form a bituminous mix.

A bituminous mix is understood to mean a mixture of a bituminous composition with aggregates and optionally inorganic and/or synthetic fillers. In general, the aggregates and the inorganic and/or synthetic fillers, when they are present, represent from <NUM> to <NUM> %, preferably from <NUM> to <NUM> % by weight of the bituminous mix and the bituminous composition from <NUM> to <NUM> %, preferably from <NUM> to <NUM> % by weight of the bituminous mix.

The aggregates are inorganic and/or synthetic aggregates, in particular, recycled milled products, with dimensions of greater than <NUM>, preferably of between <NUM> and <NUM>. Inorganic and/or synthetic fillers are preferably chosen from fines, sand, stone chips and recycled milled products.

As regards the road applications, the bituminous composition is also targeted at asphalts as materials for constructing and covering sidewalks. Asphalt is understood to mean a mixture of a bituminous composition with inorganic and/or synthetic fillers. Such an asphalt comprises a bituminous composition and inorganic fillers, such as fines, sand or stone chips, and/or synthetic fillers. The inorganic fillers are composed of fines (particles with dimensions of less than <NUM>), of sand (particles with dimensions of between <NUM> and <NUM>) and optionally of stone chips (particles with dimensions of greater than <NUM>, preferably of between <NUM> and <NUM>).

The asphalts exhibit <NUM>% compactness and are mainly used to construct and cover sidewalks, whereas the mixes have a compactness of less than <NUM>% and are used to construct roads. Unlike the mixes, the asphalts are not compacted with a roller when being put in place.

In industrial applications, the bituminous composition is, in particular, used for the manufacture of internal or external coatings, advantageously for preparing a leaktight coating, a membrane or a seal coat.

As regards the industrial applications of the bituminous compositions, mention may be made of the preparation of leaktight membranes, of noise-reduction membranes, of insulting membranes, of surface coatings, of carpet tiles or of seal coats.

The needle penetrability was measured at <NUM> according to the standard DIN EN <NUM> (Needlepenetration <NUM> in the Table <NUM>).

The ring and ball softening temperature was measured according to the standard DIN EN <NUM> (Softening Point (R+B) in the Table <NUM>).

The elastic recovery was measured at <NUM> according to DIN EN <NUM>.

The deformation energy was measured at <NUM> (<NUM>-<NUM>) according to DIN EN <NUM> standard.

The phase angle (δ) and the temperature (T) corresponding to a complex shear modulus (G*) of 15kPa were measured with a Dynamic Shear Rheometer (DSR) according to DIN EN <NUM> standard.

The storage stability was evaluated according to DIN EN <NUM>: the bitumen was stored in tubes at <NUM> for <NUM> days and the ring and ball softening temperature and the needle penetrability were measured, at the top of the tube and at the bottom. If they match, the bitumen is storage-stable.

RTFOT and RTFOT+PAV at <NUM>: The resistance of the bituminous compositions against hardening and ageing was respectively tested according to the standards DIN EN <NUM>-<NUM> and DIN <NUM>-<NUM> + <NUM>.

The sodium hydroxide (NaOH) was anhydrous and its purity is above <NUM>% and provided in the form of pellets (CARL ROTH GMBH & Co. KG, Article No <NUM>). An aqueous solution containing <NUM>% by weight of this NaOH was prepared with distilled water.

The bitumen AZALT <NUM>/<NUM> had a Needle penetration measured at <NUM> according the standard DIN EN <NUM> of <NUM>/<NUM> and a softening point (R+B) measured according to the standard DIN EN <NUM> of <NUM>.

The crosslinked elastomer was obtained from the crosslinkable elastomer marketed by Dynasol under reference Solprene® <NUM>, which is a linear random-block styrenebutadiene copolymer with a total content of <NUM>% by weight of styrene, <NUM>% by weight are present as a polystyrene block. The content of vinyl groups is <NUM> % based on the total moles of copolymer. The copolymer has a weight molecular weight (Mw), determined by triple detection gel permeation chromatography, of <NUM>,<NUM>/mol.

An intermediary elastomer-modified bitumen AZALT <NUM>/<NUM> was prepared as follows:.

The crosslinking of the elastomer occurred under these conditions. This intermediary elastomer-modified bitumen AZALT <NUM>/<NUM> including <NUM>% of crosslinked elastomer is called STYRELF <NUM>/<NUM>-<NUM>. This STYRELF <NUM>/<NUM>-<NUM> was diluted using AZALT <NUM>/<NUM> bitumen without any elastomer, in order to achieve different elastomer contents starting from <NUM>% to <NUM>% by weight. Afterwards, <NUM>% (by weight of the total weight of the final obtained bituminous composition) caustic soda (as <NUM>% aqueous solution) was added to these intermediary elastomer-modified bitumen compositions, while stirring at <NUM> rpm at <NUM> during <NUM> hours, with a dissolver blade. The final bituminous composition had been conditioned at <NUM> during <NUM> hours in a drying oven before starting the evaluation of their properties.

The obtained results are presented in Table <NUM> hereafter, in comparison with those obtained for STYRELF <NUM>/<NUM>-<NUM> (<NUM>% elastomer-modified bitumen AZALT <NUM>/<NUM>, but without hydroxide).

These results show that the use of the hydroxide according to the invention has a positive impact on the elastic properties of the bituminous composition. It is known that a bitumen modified by the presence of a crosslinked elastomer improves the elastic properties of the obtained bituminous composition. The obtained results with the incorporation of an alkaline hydroxide, like NaOH, show that the use of such an alkaline hydroxide improves again the elastic properties, and so the elastic behaviour of the bituminous composition:.

Claim 1:
- Use of a hydroxide XOH with X = Na or K, in a bituminous composition comprising a bitumen modified by a crosslinked elastomer which is a crosslinked vinyl aromatic hydrocarbon and conjugated diene copolymer, having a vinyl aromatic hydrocarbon content representing less than <NUM>% by weight of the weight of the crosslinked elastomer, for improving the effect of the crosslinked elastomer on the elastic properties of the bituminous composition.