EP2334730A2

EP2334730A2 - Method of crosslinking bitumen/polymer compositions having reduced emissions of hydrogen sulphide

Info

Publication number: EP2334730A2
Application number: EP09738324A
Authority: EP
Inventors: Romuald Botel; Sylvia Dreessen; Pierre Chaverot; Charlotte Godivier
Original assignee: Total Raffinage Marketing SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2008-04-08
Filing date: 2009-04-06
Publication date: 2011-06-22
Also published as: JP2011516678A; US8202922B2; US20110098385A1; WO2009133290A2; FR2929616A1; CN101990557B; RU2501818C2; CA2720491A1; WO2009133290A3; ZA201007007B; CN101990557A; MA32205B1; FR2929616B1; RU2010140701A; KR20110008029A

Abstract

The invention relates to a method of preparing crosslinked bitumen/polymer compositions having reduced emissions of hydrogen sulphide, in which, while operating at temperatures between 100°C and 230°C and with stirring, for a duration of at least ten minutes, at least one bitumen or mixture of bitumens is brought into contact with at least one polymer and at least one crosslinking agent, said crosslinking agent being represented by the general formula HS-R-SH where R represents a saturated or unsaturated, linear or branched, cyclic and/or aromatic hydrocarbon-based group having 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, and that does not comprise a C=O carbonyl function and/or a O-C=O carboxylate function.

Description

PROCESS FOR CROSSLINKING COMPOSITIONS

BITUMEN / POLYMER HAVING REDUCED EMISSIONS

HYDROGEN SULFIDE

TECHNICAL AREA

The present invention belongs to the field of bitumens. More specifically, it relates to a process for preparing crosslinked bitumen / polymer compositions having reduced hydrogen sulfide emissions.

The invention also relates to bitumen / polymer compositions comprising a crosslinking agent making it possible to obtain crosslinked bitumen / polymer compositions with reduced hydrogen sulphide emissions.

The invention also relates to the use of crosslinking agents for crosslinking bitumen / polymer compositions by limiting hydrogen sulphide emissions. TECHNICAL BACKGROUND The use of bitumen in the manufacture of materials for road and industrial applications is known for a long time: bitumen is the main hydrocarbon binder used in the field of road construction or civil engineering.

To be used as a binder in these different applications, the bitumen must have certain physicochemical and mechanical properties. It is well known that the mechanical properties of pure bitumens can be modified by the addition of polymers.

Many polymers have been used in bitumen / polymer compositions, such as styrene and butadiene copolymers, to improve the rheological properties of pure bitumens. It is also well known that the physico-chemical properties of the bitumen / polymer compositions are further improved when the polymers are crosslinked with sulfur, for example.

However, during the preparation of sulfur-crosslinked bitumen / polymer compositions, the crosslinking is accompanied by emissions of hydrogen sulfide (H ₂ S or hydrogen sulfide). Hydrogen sulfide is a colorless and toxic gas with a characteristic odor at very low concentration. Environmental constraints make it necessary to reduce or even eliminate hydrogen sulphide emissions especially in the crosslinking of polymers in the bitumen / polymer compositions. PRIOR ART

To reduce hydrogen sulphide emissions, numerous patents describe the addition of inhibitors during the sulfur crosslinking of bitumen / polymer compositions. In FR2254609, a process for reducing the emission of hydrogen sulfide by hot mixtures containing sulfur and bitumen is claimed. To reduce hydrogen sulphide emissions, a hydrogen sulphide removal agent is added to a bitumen / sulfur mixture. This suppressing agent is chosen from free radical inhibitors and redox catalysts.

For example, tetramethylthiuram disulfide may be mentioned as free radical inhibitor and iron chloride as redox catalyst.

In EP01 21377, a process for preparing a mixture comprising bitumen and elemental sulfur to reduce the evolution of hydrogen sulfide is described. In this process, the agent for decreasing the release of sulfide is a carboxylate or a metal naphthenate. Zinc stearate is one of the preferred compounds.

In the application WO2005059016, sulfur granules comprising a hydrogen sulfide suppressing agent are described. The agent is selected from free radical inhibitors and redox catalysts. The preferred agent is iron chloride. In the application WO2005065177, a process for reducing hydrogen sulphide emissions is described. In this process, a metal salt is added to the bitumen and sulfur. Zinc oxide is one of the preferred compounds.

Patent EP0907687 describes a process for crosslinking bitumen / polymer compositions in which different functionalization agents are used. These functionalizing agents are chosen from carboxylic polythiolesters and / or polythioethers, there being no indication that the functionalising agents described make it possible to reduce hydrogen sulphide emissions. SUMMARY OF THE INVENTION

In these circumstances, the object of the present invention is to propose a new process for the preparation of crosslinked bitumen / polymer compositions having reduced hydrogen sulphide emissions, in particular a reduction of hydrogen sulphide emissions in the first phase of the process, said method being based on the use of new crosslinking agents.

Another object of the invention is to provide a simple process for preparing crosslinked bitumen / polymer compositions without hydrogen sulphide emissions making it possible to obtain compositions having satisfactory rheological characteristics, in particular with regard to elasticity and consistency.

Another objective of the invention is the use of crosslinking agents allowing the crosslinking of bitumen / polymer compositions with emissions. of hydrogen sulfide while obtaining compositions having satisfactory rheological characteristics including elasticity and consistency.

An object of the invention is to provide novel crosslinked bitumen / polymer compositions having rheological characteristics equivalent to sulfur-crosslinked bitumen / polymer compositions, in particular with regard to elasticity and consistency, and having reduced or even zero emissions. of hydrogen sulphide, during their crosslinking.

The invention relates to a process for the preparation of crosslinked bitumen / polymer compositions with reduced emissions of hydrogen sulphide, in which is brought into contact, operating at temperatures between 100 ° C and 230 ° C and with stirring, for a period of time. at least ten minutes, at least one bitumen or mixture of bitumens with at least one polymer and at least one crosslinking agent, said crosslinking agent being represented by the general formula HS-R-SH where R represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, and not comprising a carbonyl function C = O and / or carboxylate function OC = O.

Preferably, the heteroatoms are oxygen atoms. Preferably, the number of oxygen atoms ranges from 0 to 5, preferably from

1 to 4, preferably 2 to 3.

Preferably, the group R represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, preferably 8 to 12 atoms of carbons.

In a first embodiment, the group R represents an exclusively hydrocarbon-based, saturated, linear group of 2 to 40 carbon atoms, preferably 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, preferably from 8 to 12 carbon atoms. In a second embodiment, the R group represents a linear saturated hydrocarbon group comprising one or more heteroatoms.

Preferably, the group R has the general formula - (CH ₂ ) _m -O- (CH ₂ ) _n - with m and n integers varying from 1 to 20, preferably from 2 to 10.

Preferably, the group R has for the general formula - (CH ₂ ) _p -O- (CH ₂ ) _q -O- (CH ₂ ) _r - with p, q and r integers varying from 1 to 10, preferably from 2 to 6.

In a third embodiment, the group R represents an unsaturated group, comprising at least one aromatic ring, preferably at least two aromatic rings. The amount of crosslinking agent of general formula HS-R-SH is between 0.05 and 5% by weight.

The polymer is a copolymer based on conjugated diene units and monovinyl aromatic hydrocarbon units. The conjugated diene unit is chosen from those comprising from 4 to 8 carbon atoms per monomer, for example butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene 1,3-pentadiene and 1,2-hexadiene, chloroprene, carboxylated butadiene, carboxylated isoprene, in particular butadiene and isoprene, and mixtures thereof. The monovinyl aromatic hydrocarbon unit is selected from styrene, p-methyl styrene, p-methyl styrene, p-tert-butyl styrene, 2,3-dimethyl styrene, α-methyl styrene, vinyl naphthalene, vinyl toluene, vinyl xylene, and the like or mixtures thereof, in particular styrene.

The amount of polymer is between 0.5 and 20% by weight, preferably between 1 and 10%, preferably between 2 and 5%.

The bitumen is selected from atmospheric distillation residues, vacuum distillation residues, visbroken residues, blown residues, deasphalted residues, and mixtures thereof.

The bitumen further comprises at least one fluxing agent. The invention also relates to the use of a crosslinking agent of general formula HS-R-SH, as defined above, for reducing hydrogen sulphide emissions during the preparation of crosslinked bitumen / polymer compositions.

The invention also relates to the use of the crosslinked bitumen / polymer compositions obtained by the process, as defined above, for producing a bituminous binder in anhydrous form or in the form of an emulsion.

The invention also relates to the use of the crosslinked bitumen / polymer compositions obtained by the process, as defined above, in admixture with aggregates for producing a surface coating, a hot mix, a cold mix, an asphalt mix. cold cast, a severe emulsion, usable as a base layer, tie layer and / or wearing course.

The invention also relates to the use of the crosslinked bitumen / polymer compositions obtained by the process, as defined above, for producing a sealing coating, a membrane or an impregnating layer.

The invention finally relates to a bitumen / polymer composition comprising at least one bitumen, at least one polymer and at least one crosslinking agent of general formula HS-R-SH where R represents a linear or branched, saturated or unsaturated hydrocarbon-based group, from 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, preferably one or more oxygen atoms, said group R excluding the presence of a carbonyl function C = O and / or carboxylate O-C = O.

Preferably, the number of oxygen atoms ranges from 0 to 5, preferably from 1 to 4, preferably from 2 to 3. Preferably, the group R is as defined above.

Preferably, the amount of crosslinking agent of general formula HS-R-SH is between 0.05 and 5% by weight.

Preferably, the polymer is a copolymer based on conjugated diene units and monovinyl aromatic hydrocarbon units. Preferably, the conjugated diene unit is chosen from those comprising from 4 to

8 carbon atoms per monomer, for example butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,2 hexadiene, chloroprene, carboxylated butadiene, carboxylated isoprene, in particular butadiene and isoprene, and mixtures thereof. Preferably, the monovinyl aromatic hydrocarbon unit is chosen from styrene, o-methyl styrene, p-methyl styrene, p-tert-butylstyrene, 2,3-dimethylstyrene, α-methylstyrene, vinyl naphthalene, vinyl toluene, vinyl xylene, and the like or mixtures thereof, in particular styrene.

Preferably, the amount of polymer is between 0.5 and 20% by weight, preferably between 1 and 10%, preferably between 2 and 5%.

Preferably, the bitumen is selected from atmospheric distillation residues, vacuum distillation residues, visbroken residues, blown residues, deasphalted residues, mixtures thereof and combinations thereof.

Preferably, the bitumen further comprises at least one fluxing agent. DETAILED DESCRIPTION

The crosslinking agent used in the process according to the invention has the general formula HS-R-SH where R represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, such as oxygen and not comprising a carbonyl function C = O and / or carboxylate function OC = O. The crosslinking agent according to the invention has, at each of its ends, a thiol function, making it possible to bind the polymers together, separated by the group R defined above.

The group R is preferably a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, comprising from 4 to 20 carbon atoms, preferably from 6 to 18 carbon atoms, preferably from 8 to 12 atoms. of carbons.

When the R group is substituted by hetero atoms, the oxygen atoms are preferred. When the R group is substituted by oxygen atoms, the number Oxygen atoms can vary from one to five, preferably from one to four, preferably from two to three.

Also preferred are R groups which do not include C carbO carbonyl functions and / or O-C =O carboxylate functions, as can be found, for example, in carboxylic acids or esters. Indeed, the presence of these functions can lead to and / or increase the formation of hydrogen sulphide. The absence of carbonyl functional groups C = O and / or carboxylate functions OC = O makes it possible to obtain crosslinked bitumen / polymer compositions having good elastic properties, in particular in terms of springback and traction, while minimizing the amounts of hydrogen sulfide released during the process for preparing said crosslinked bitumen / polymer compositions.

In a first embodiment, the group R is a saturated hydrocarbon group having no double bond. The R group may be saturated and linear or saturated and branched; saturated and linear R groups are preferred. When the R group is a saturated and linear group, it may or may not include heteroatoms, such as oxygen. When the group R does not contain heteroatoms, the group R is a saturated, exclusively hydrocarbon group.

On the one hand, saturated, linear, exclusively hydrocarbon-based R groups of 2 to 40 carbon atoms, preferably 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, preferably 8 to 18 carbon atoms, are preferred. 12 carbon atoms. When R is a hydrocarbon-only, saturated, linear group, the crosslinking agents according to the invention are, for example, 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1, Hexanedithiol, 1,7 heptanedithiol, 1,8 octanedithiol. The preferred crosslinking agent is 1.8 octanedithiol where R is a saturated, linear hydrocarbon-only group of 8 carbon atoms.

On the other hand, saturated, linear R groups comprising one or more heteroatoms, such as oxygen, are preferred. Preferably, the group R is substituted by one or two oxygen atoms. When the group R is substituted by a single oxygen atom, the crosslinking agent HS-R-SH has the general formula HS- (CH ₂ ) _m -O- (CH ₂ ) _n -SH with R representing the group - (CH ₂ ) _m -O- (CH ₂ ) _n - with n and m integers varying from 1 to 20, preferably from 2 to 10. For example, bis (2-mercaptoethyl) ether, bis - (3-mercaptoethyl) ether, bis- (4-mercaptoethyl) ether with m and n respectively having a value of 2, 3 and 4. Mention may also be made, for example, of (2-mercaptoethyl) (3-mercaptobutyl) ether with m having a value of 2 and min a value of 3; (2-mercaptoethyl) (4-mercaptobutyl) ether with m having a value of 2 and n being a value of 4. When the group R is substituted by two oxygen atoms, the crosslinking agent HS-R-SH has the general formula HS- (CH ₂ ) pO- (CH ₂ ) _q -O- (CH ₂ ) _r -SH with R representing the group - (CH ₂ ) _p -O- (CH ₂ ) _q -O- (CH 2) _r - with p, q and r integers varying from 1 to 10, preferably from 2 to 6. Preferred crosslinking agents are such that p and r are 2 and q are 1, or p, q and r are 2 (as for example in 1,8-dimercapto-3,6-dioxaoctane).

In a second embodiment, the group R is an unsaturated group. The group R can comprise one or more double bonds, along a carbon chain or in rings of 5 to 6 carbon atoms, for example. The R group may also be aromatic, that is to say comprise at least one aromatic ring. The group R comprises at least one aromatic ring, preferably at least two aromatic rings.

When the R group comprises a single aromatic ring, the preferred crosslinking agents are benzene-1,2-dithiol, benzene-1,3-dithiol, benzene-1,4-dithiol or toluene-3,4-dithiol. .

The group R may also comprise at least 2 aromatic rings. The aromatic nuclei of the R group may be condensed or not, they are preferably vicinal. They may be optionally substituted with alkyl or alkoxy groups. When the group R comprises two vicinal aromatic rings, one of the preferred crosslinking agents is biphenyl-4,4'-dithiol.

The amount of crosslinking agent used in the process of the invention is between 0.05 and 5% by weight, preferably between 0.1 and 2%, preferably between 0.2 and 1%, preferably between 0.3 and 0.5% by weight.

It is possible to envisage using the crosslinking agents as defined above, taken alone or as a mixture.

The polymers that can be used in the process according to the invention are the polymers that can be used in the field of bitumens / polymers, such as, for example, polybutadienes, polyisoprenes, butyl rubbers, polyacrylates, polymethacrylates, polychloroprenes, polynorbomenes, polybutenes, polyisobutenes, polyolefins such as polyethylenes or high density polyethylenes, polypropylenes, copolymers of ethylene and vinyl acetate, copolymers of ethylene and methyl acrylate, copolymers of ethylene and butyl acrylate, copolymers of ethylene and maleic anhydride, copolymers of ethylene and glycidyl methacrylate, copolymers of ethylene and glycidyl acrylate, copolymers of ethylene and propene, ethylene terpolymers / propene / diene (EPDM), acrylonitrile / butadiene / styrene terpolymers (ABS), ethylene / acr terpolymers alkyl ylate or methacrylate / acrylate or glycidyl methacrylate and especially ethylene terpolymer / methyl acrylate / glycidyl methacrylate and terpolymers ethylene / alkyl acrylate or methacrylate / maleic anhydride and especially ethylene terpolymer / butyl acrylate / maleic anhydride.

The polymers may also be the polymers described in EPl 572807, EP0837909 and EPl 576058 of the applicant company. Preferred polymers are copolymers based on conjugated diene units and monovinyl aromatic hydrocarbon units. The polymers according to the invention comprise one or more copolymers based on conjugated diene units and monovinyl aromatic hydrocarbon units.

The conjugated diene is chosen from those comprising from 4 to 8 carbon atoms per monomer, for example butadiene, 2-methyl-1,3-butadiene (isoprene),

2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,2-hexadiene, chloroprene, carboxylated butadiene, carboxylated isoprene, especially butadiene and isoprene, and mixtures thereof.

The monovinyl aromatic hydrocarbon is selected from styrene, o-methyl styrene, p-methyl styrene, p-tert-butyl styrene, 2,3-dimethyl styrene, p-methyl styrene, vinyl naphthalene, vinyl toluene, vinyl xylene, and the like or mixtures thereof, in particular styrene.

More particularly, the polymer consists of one or more copolymers chosen from block copolymers of styrene and butadiene, styrene and isoprene, styrene and chloroprene, styrene and carboxylated butadiene or even styrene and isoprene. carboxyl. A preferred polymer is a copolymer based on butadiene units and styrene units such as styrene / butadiene block copolymer SB or styrene / butadiene / styrene block copolymer SBS.

The styrene-conjugated diene copolymer, in particular the styrene-butadiene copolymer, advantageously has a weight content of styrene ranging from 5 to 50%, preferably from 20 to 50%.

The copolymer of styrene and conjugated diene, in particular the styrene-butadiene copolymer, advantageously has a weight content of butadiene (1-2 and 1-4) ranging from 50 to 95%. The copolymer of styrene and conjugated diene, in particular the styrene-butadiene copolymer, advantageously has a weight content of butadiene 1-2 ranging from 5 to 70%. The 1,2-butadiene units are the units which result from the polymerization via the 1-2 addition of the butadiene units.

The average molecular weight of the styrene-conjugated diene copolymer, and in particular that of the styrene-butadiene copolymer, may be, for example, between 10,000 and 500,000, preferably between 50,000 and 200,000, and more preferably between 50,000 to 150,000 daltons. The amount of polymer used in the process of the invention is between 0.5 and 20% by weight, preferably between 1 and 10%, preferably between 2 and 5%.

The bitumens used in the process of the invention are bitumens from different origins. We can first mention bitumen of natural origin, those contained in deposits of natural bitumen, natural asphalt or oil sands.

The bitumens according to the invention are also bitumens derived from the refining of crude oil. Bitumens come from the atmospheric and / or vacuum distillation of oil. These bitumens can be optionally blown, vis-reduced and / or deasphalted. The bitumens may be hard grade or soft grade bitumens. The different bitumens obtained by the refining processes can be combined with one another to obtain the best technical compromise.

The bitumens used may also be fluxed bitumens by addition of volatile solvents, petroleum fluxes, carbochemical fluxes and / or fluxes of vegetable origin.

It is also possible to use synthetic bitumens also called clear, pigmentable or colorable bitumens. These bitumens contain little or no asphaltenes and can therefore be colored. These synthetic bitumens are petroleum resin and / or coumarone-indene resin and lubricating oil as described for example in patent EPl 79510. EXAMPLES bituminous composition T _{j ^} (control)

A control bituminous composition T ₁ is prepared in which the polymer is not crosslinked (physical mixture of bitumen and polymer).

The bituminous control composition Ti is prepared in the following manner:

The mixture is introduced into a hermetic reactor of 2 liters with stirring (300 rpm) and at 195 ° C:

- 95% by weight of a direct distillation bitumen of penetration 50 1/10 mm according to standard NF EN 1426 and

5% by weight of a styrene / butadiene block copolymer, 25% by weight of styrene and 75% by weight of butadiene having a weight-average molecular weight, Mw of 128,000 Dalton.

The mixture is stirred at 300 rpm and heated at 195 ° C for 2 hours. The amounts used are as follows: 1772.2 grams of bitumen and 93.3 grams of styrene / butadiene block copolymer. Bituminous composition T ₂ (control)

A control bituminous composition T ₂ in which the polymer is crosslinked with sulfur (vulcanization) is prepared. The bituminous control composition T ₂ is prepared in the following manner: The mixture is introduced into a hermetic reactor of 2 liters with stirring (300 rpm) and at 195 ° C:

- 94.87% by weight of a direct distillation bitumen of penetration 50 1/10 mm according to standard NF EN 1426 and

The bitumen / polymer mixture is stirred at 300 rpm and heated at 195 ° C for about 2 hours.

0.13% by weight of sulfur (flower sulfur) is then added. The mixture is stirred at 300 rpm and heated at 195 ° C for 2 hours. The amounts used are as follows: 1037.1 grams of bitumen, 54.7 grams of styrene / butadiene block copolymer and 1.42 grams of sulfur. Bituminous composition T ^ (control)

A control bituminous composition T ₃ is prepared in which the polymer is crosslinked with dimercaptosuccinic acid of general formula HS-CH ₂ (COOH) -CH ₂ (COOH) -SH.

The bituminous control composition T ₃ is prepared in the following manner: The following is introduced into a hermetic reactor of 2 liters with stirring (300 rpm) and at 195 ° C:

5% by weight of a styrene / butadiene block copolymer, 25% by weight of styrene and 75% by weight of butadiene having a weight-average molecular weight,

Mw of l28,000 Dalton.

0.13% by weight of dimercaptosuccinic acid is then added. The mixture is stirred at 300 rpm and heated at 195 ° C for 2 hours.

The amounts used were as follows: 1082.4 grams of bitumen, 57.05 grams of styrene / butadiene block copolymer, and 1.47 grams of dimercaptosuccinic acid. Bituminous composition T ₄ (control) a bituminous composition indicator T ₄ is prepared in which the polymer is crosslinked with β-mercaptoproprionate pentaerythrityl of general formula C [CH ₂ OOCCH ₂ CH ₂ SH] _4.

The bituminous control composition T ₄ is prepared as follows: The mixture is introduced into a hermetic reactor of 2 liters with stirring (300 rpm) and at 195 ° C:

94.87% by weight of a direct distillation bitumen with a penetration of 50 1/10 mm according to standard NF EN 1426 and -5% by weight of a styrene / butadiene block copolymer at 25% by weight of styrene and to 75% by weight of butadiene having a weight average molecular weight, M w of 128,000 Dalton.

The bitumen / polymer mixture is stirred at 300 rpm and heated at 195 ° C for about 2 hours. 0.13% by mass β-mercaptoproprionate pentaerythrityl is then added.

The mixture is stirred at 300 rpm and heated at 195 ° C for 2 hours. The amounts used are as follows: 1101.96 grams of bitumen, 58.08 grams of styrene / butadiene block copolymer and 1.51 grams of pentaerythrityl β-mercaptopropionate. Bituminous compositions according to the invention Cj-Cs

Several bituminous compositions according to the invention are prepared using different crosslinking agents (with different R groups) at different concentrations.

The bituminous compositions according to the invention Ci to C ₈ are prepared in the following manner:

the direct distillation bitumen of penetration 50 1/10 mm according to the standard NF EN 1426 and the block copolymer styrene / butadiene, at 25% by weight of styrene and at

75% by weight of butadiene having a weight-average molecular weight, Mw of 128,000 Dalton.

The mixture is stirred at 300 rpm and heated at 195 ° C for about 2 hours. The crosslinking agent HS-R-SH is then added.

The mixture is stirred at 300 rpm and heated at 195 ° C for 2 hours. In Table I below, the chemical natures of the different HS-R-SH crosslinking agents used are indicated: Table I

The crosslinking agent is introduced at different concentrations (from 0.05% to 0.3% by weight). The styrene / butadiene block copolymer is always introduced at a rate of 5% by weight. The bitumen being introduced to arrive at a total of 100% by mass. The amounts in percentages (for the crosslinking agent) and in grams (for the three constituents) used are shown in Table II below:

Table II

Table III below presents the physical characteristics of the crosslinked bitumen / polymer compositions according to the invention Cj to C ₈ and Table IV below shows the physical characteristics of the bitumen / polymer control compositions Ti to T ₄ .

Table III

⁽¹⁾ According to standard NF EN 1426.

^ ²⁾ Ball and Ring temperature, according to NF ENl 427 standard.

⁽³⁾ Elastic return at 25 ° C according to standard NF EN 13398.

⁽⁴⁾ Tensile test at 5 ° C, according to standard NF EN 13587, with a stretching speed of 500 mm / min.

⁽⁵⁾ The gelling test consists in leaving a box of 1 kg of binder at 180 ° C. for 14 days. At each measurement time, a wooden stick is dipped into the box and the way in which the binder flows is examined. A scale of 0 to 4 is used to describe the state of the binder.

- SO: fluid binder, flows drip

- Sl: liquid binder, flows in a thin continuous stream

- S2: viscous binder, flows in a large continuous stream

- S3: very viscous binder, flows into a tablecloth

- S4: solid binder Table IV

⁽¹⁾ to ⁽⁵⁾ See Table III

In view of the results gathered in Tables 1H and IV, we can make the following remarks:

The set of crosslinking agents described according to the invention makes it possible to crosslink the bitumen / polymer compositions. Indeed the values of Ball and Ring Temperature, penetrability, springback, tensile compositions Ci to C ₈ are close to those of the control T ₂ . The crosslinking of the compositions C 1 to C ₈ leads to an increase in the consistency (increase of the ball and ring temperature and decrease of the penetrability).

The crosslinking of the compositions C 1 to C ₈ leads to an improvement of the elasticity characteristics (increase of the tensile elongation and of the stress at the maximum elongation, increase of the elastic return). The crosslinking of compositions T ₃ and T 2 is not optimal, as evidenced by the springback values close to that of composition T 1. Compositions C ₁ to C ₈ are stable and do not gel. When introducing the crosslinking agent into the bitumen / polymer mixture, the crosslinking of the copolymer in the bitumen starts. It is accompanied for the sulfur crosslinking releases of hydrogen sulfide. To evaluate the amount of hydrogen sulphide released during the crosslinking with the HS-R-SH agents according to the invention, the hydrogen sulphide releases are measured in the gas phase using a probe placed in the reaction medium. , during 2 hours. At given times (5 min, 10 min, 20 min, 60 min, 120 min), the decreases in H ₂ S emissions obtained during crosslinking are calculated as a percentage. two bituminous compositions according to the invention (Ci and C ₅ ) relative to the control T ₂ and the decreases in H ₂ S emissions obtained during the crosslinking of the two control bituminous compositions T ₃ and T ₄ relative to the control T ₂ (Table V).

Table V

There is a significant decrease in releases of H ₂ S for compositions C ₁ and C ₅ . Thus for example for Cj and C ₅ to 10 minutes, the reduction of H ₂ S emissions is 97% compared to the control T ₂ . Compositions C _6, C ₇ and C ₈ tested under the same conditions show the same way a sharp decrease in clearance of H ₂ S with respect to the composition T _2.

The releases of H ₂ S are, on the other hand, much more important in the process for preparing the composition T ₃ (there is not a decrease in the amounts of hydrogen sulphide, but an increase with respect to T ₂ ). The clearances of H ₂ S in the process for the preparation of the composition T ₄ are less important than in that of T ₂ from 5 minutes to 20 minutes as for the process according to the invention, but from 60 minutes to 120 minutes, the The process according to the invention makes it possible to reduce the H ₂ S clearances more clearly. Furthermore, it seems that, according to the value of the elastic return of the composition C ₄ , it is not as well cross-linked as the compositions C 1 to C ₈ (value of 57% compared with values of 73% to 85%).

The crosslinking agents of the process implemented according to the invention thus make it possible to obtain crosslinked bitumen / polymer compositions having good properties, in particular with regard to elasticity, without having the disadvantage of the conventional crosslinking agent (sulfur) at the level of the clearances. hydrogen sulfide. In particular, the crosslinking agents of the process implemented according to the invention make it possible to substantially reduce the evolution of hydrogen sulfide during the crosslinking process of the bitumen / polymer compositions while retaining good elastic properties.

Claims

1. Process for the preparation of crosslinked bitumen / polymer compositions with reduced hydrogen sulfide emissions, in which, operating at temperatures of between 100 ^° C. and 230 ° C., and with stirring, is brought into contact for a period of from at least ten minutes, at least one bitumen or mixture of bitumens with at least one polymer and at least one crosslinking agent, said crosslinking agent being represented by the general formula HS-R-SH where R represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 2 to 40 carbon atoms, optionally comprising one or more heteroatoms, and not including a carbonyl function C = O and / or carboxylate function OC = O.

The process of claim 1, wherein the heteroatoms are oxygen atoms.

3. The process according to claim 2, wherein the number of oxygen atoms ranges from 0 to 5, preferably from 1 to 4, preferably from 2 to 3.

4. Method according to one of claims 1 to 3, wherein the R group represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, preferably 8 to 12 carbon atoms.

5. Method according to one of claims 1 to 3, wherein the R group represents a hydrocarbon-based group, saturated, linear, of 2 to 40 carbon atoms, preferably of 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, preferably 8 to 12 carbon atoms.

6. Method according to one of claims 1 to 4, wherein the R group represents a hydrocarbon group, saturated, linear, comprising one or more heteroatoms.

7. The method of claim 6, wherein the R group has the general formula: - (CH ₂₎ _m -O- (CH ₂₎ _n - with n and m integers ranging from 1 to 20, preferably from 2 to 10.

8. The process as claimed in claim 6, in which the group R has the following general formula: - (CH ₂ ) _p -O- (CH ₂ ) _q -O- (CH ₂ ) _r - with p, q and r varying integers from 1 to 10, preferably from 2 to 6.

9. Method according to one of claims 1 to 4, wherein the R group represents an unsaturated group, comprising at least one aromatic ring, preferably at least two aromatic rings.

10. Method according to one of claims 1 to 9, wherein the amount of crosslinking agent of general formula HS-R-SH is between 0.05 and 5% by weight.

11. Method according to one of claims 1 to 10, wherein the polymer is a copolymer based on conjugated diene units and monovinyl aromatic hydrocarbon units.

12. Process according to claim 11, in which the conjugated diene unit is chosen from those comprising from 4 to 8 carbon atoms per monomer, for example butadiene, 2-methyl-1,3-butadiene (isoprene), 2 , 3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,2-hexadiene, chloroprene, carboxylated butadiene, carboxylated isoprene, especially butadiene and isoprene, and mixtures thereof.

The process according to claim 11 or 12, wherein the monovinyl aromatic hydrocarbon unit is selected from styrene, o-methyl styrene, p-methyl styrene, p-tert-butyl styrene, 2,3-dimethyl styrene. , α-methyl styrene, vinyl naphthalene, vinyl toluene, vinyl xylene, and the like or mixtures thereof, in particular styrene.

14. Method according to one of claims 1 to 13, wherein the amount of polymer is between 0.5 and 20% by weight, preferably between 1 and 10%, preferably between 2 and 5%.

15. Process according to one of claims 1 to 14, in which the bitumen is chosen from atmospheric distillation residues, vacuum distillation residues, visbroken residues, blown residues, deasphalted residues, and mixtures thereof.

16. Method according to one of claims 1 to 15, wherein the bitumen further comprises at least one fluxing agent.

17. Use of a crosslinking agent of general formula HS-R-SH as defined in claims 1 to 16, for reducing the hydrogen sulfide emissions during the preparation of crosslinked bitumen / polymer compositions.

18. Use according to claim 17 wherein the crosslinked bitumen / polymer compositions are intended to manufacture a bituminous binder in anhydrous form or in the form of an emulsion.

19. Use according to claim 17 or 18 wherein the crosslinked bitumen / polymer compositions are intended, in admixture with aggregates, to produce a surface coating, a hot mix, a cold mix, a cold mix, a serious emulsion, usable as base layer, tie layer and / or wearing course.

20. Use according to any one of claims 17 to 19 wherein the crosslinked bitumen / polymer compositions are intended to manufacture a sealing coating, a membrane or an impregnating layer.

21. Bitumen / polymer composition comprising at least one bitumen, at least one polymer and at least one crosslinking agent of general formula HS-R-SH where R represents a hydrocarbon group, saturated or unsaturated, linear or branched, from 2 to 40 atoms of carbon, optionally comprising one or more heteroatoms, preferably one or more oxygen atoms, said group R excluding the presence of a carbonyl function C = O and / or carboxylate OC = O.

22. Bitumen / polymer composition according to claim 21 wherein the number of oxygen atoms ranges from 0 to 5, preferably from 1 to 4, preferably from 2 to 3.

23. Bitumen / polymer composition according to claim 21 or 22 wherein the R group is as defined in claims 5 to 10.

24. bitumen / polymer composition according to one of claims 21 to 23 wherein the amount of crosslinking agent of general formula HS-R-SH is between 0.05 and 5% by weight.

25. Bitumen / polymer composition according to one of claims 21 to 24 wherein the polymer is a copolymer based on conjugated diene units and monovinyl aromatic hydrocarbon units.

26. A bitumen / polymer composition according to claim 25 wherein the conjugated diene unit is chosen from those comprising from 4 to 8 carbon atoms per monomer, for example butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and 1,2-hexadiene, chloroprene, carboxylated butadiene, carboxylated isoprene, in particular butadiene and isoprene, and mixtures thereof.

27. bitumen / polymer composition according to claim 25 or 26 wherein the monovinyl aromatic hydrocarbon unit is selected from styrene, o-methyl styrene, p-methyl styrene, p-tert-butylstyrene, 2,3 dimethyl styrene, α-methyl styrene, vinyl naphthalene, vinyl toluene, vinyl xylene, and the like or mixtures thereof, in particular styrene.

28. Bitumen / polymer composition according to one of claims 21 to 27 wherein the amount of polymer is between 0.5 and 20% by weight, preferably between 1 and 10%, preferably between 2 and 5%.

29. bitumen / polymer composition according to one of claims 21 to 28 wherein the bitumen is selected from the atmospheric distillation residues, the vacuum distillation residues, visbroken residues, blown residues, deasphalted residues, mixtures thereof and combinations thereof.

30. bitumen / polymer composition according to one of claims 21 to 29 wherein the bitumen further comprises at least one fluxing agent.