EP2794668A2

EP2794668A2 - Graft polymer, and thermoreversibly cross-linked bitumen/polymer composition containing such a graft polymer

Info

Publication number: EP2794668A2
Application number: EP12818500.6A
Authority: EP
Inventors: Carole RUOT; Ilias Iliopoulos; Ludwik Leibler; Ornella Annabelle Zovi
Original assignee: Centre National de la Recherche Scientifique CNRS; Total Raffinage Marketing SA
Current assignee: Centre National de la Recherche Scientifique CNRS; TotalEnergies Marketing Services SA
Priority date: 2011-12-20
Filing date: 2012-12-20
Publication date: 2014-10-29
Also published as: BR112014014991A2; FR2984329B1; FR2984329A1; US20140329939A1; WO2013092809A3; WO2013092809A2; RU2014129760A; RU2606499C2

Abstract

The invention relates to a thermoreversibly cross-linked graft polymer, to the method for preparing same, and to the use of such a graft polymer in preparing a thermoreversibly cross-linked bitumen/polymer composition. The present invention also relates to a thermoreversibly cross-linked bitumen/polymer composition comprising such a graft polymer, to the method for preparing same, and to bituminous asphalt including such a composition. The polymer comprises: a main polymer chain P consisting of conjugated diene units; at least one side graft G having the following general formula (1): R-(OCH₂CH₂)_m-S---, where R is a straight or branched saturated hydrocarbon chain having at least 18 carbon atoms, and m is an integer varying from 0 to 20, said graft G being connected to the main polymer chain P via the sulfur atom of formula (1); and at least one graft G' having the following general formula (4): ---S-R'-S---, where R' is a straight or branched, saturated or unsaturated hydrocarbon grouping having 2 to 40 carbon atoms, optionally including one or more heteroatoms, said graft G' being connected to the main polymer chain P via each sulfur atom of formula (4).

Description

GRAFTED POLYMER AND COMPOSITION BITUMEN / POLYMER THERMOREVERSIBLE CROSSLINKING CONTAINING SUCH POLYMER

TECHNICAL AREA

The present invention relates to a graft polymer, its method of preparation and the use of such a polymer for the preparation of a thermoreversibly cross-linked bitumen / polymer composition.

The present invention also relates to a thermoreversibly crosslinked bitumen / polymer composition comprising such a graft polymer, its preparation process and a bituminous mix comprising such a composition.

PRIOR ART

Bitumen is a binder that has been used for a long time for various applications, particularly in the field of road construction or civil engineering. It is known that the addition of a thermoplastic polymer in the bitumen improves the rheological properties of the bitumen, in particular, the elastic properties and the cohesiveness thus widening the field of application of the bitumen / polymer compositions. Thermoplastic polymers fluidify and become malleable under the effect of heat, reversibly. In the process of developing the modified binder, the modification of the bitumen is carried out either by simple physical mixing of the bitumen and the polymer or by a chemical crosslinking reaction. In the latter case, the reaction is irreversible. Once the crosslinking has been carried out, it is not possible to return to the initial state existing before the crosslinking reaction. The crosslinked bitumen / polymer compositions thus have good mechanical properties but the viscosity of these is very high. Depending on the intended applications, it is necessary to find the right compromise between the mechanical properties and the fluidity of the crosslinked bitumen / polymer compositions.

Crosslinking according to the prior art is most of the time irreversible crosslinking based on the formation of covalent bonds between the polymer chains. Thus one of the most used crosslinks in the field of bitumen is sulfur crosslinking or vulcanization. By way of examples, mention may in particular be made of the patents FR-A-2376188, EP-A-0799280 and EP-A-0690892.

New polymers with thermoreversible crosslinking have recently been developed. The most of these thermoreversible crosslinks are via thermoreversible covalent bonds. There are also thermoreversible crosslinks that are via coordination bonds or ionic bonds. Thus, JP-A-11106578 describes the modification of a polyolefin with an acid anhydride which reacts in the presence of alcohols to form thermoreversible ester bonds.

EP-A-870793 describes a mixture of a first polymer having at least two acid functional groups and a second polymer having at least two amine functional groups so as to form low temperature stable and dissociable amide groups at high temperature.

FR-A-2558845 describes the reaction between a divinyl ether and a copolymer carrying acid functional groups. The acyl obtained is stable at low temperature and decomposes by raising the temperature.

Other thermoreversibly cross-linked polymers involve polymers comprising carboxylic acid units which are reversibly bonded to metals (JP-A-50139135, JP-A-51019035, JP-A-56014573). Still others involve labile ionic bonds between acid and amine groups (JP-A-52065549, JP-A-57158275).

Recently, the applicant company has developed novel thermoreversibly cross-linked bitumen / polymer compositions from a novel family of graft polymers (WO09 / 030840 and WO09 / 030841). The bitumen / polymer compositions obtained exhibit at the temperatures of use, the properties of conventional crosslinked bitumen / polymer compositions, and at processing temperatures, the properties of the uncrosslinked bitumen / polymer compositions.

OBJECTIVES OF THE INVENTION

The purpose of the present invention is to improve the rheological properties including the mechanical properties, elasticity and cohesiveness of thermoreversibly crosslinked bitumen / polymer compositions described in the applications WO09 / 030840 and WO09 / 030841 of the applicant.

In these circumstances, the present invention aims to obtain polymers that can be thermoreversibly crosslinked in an organic medium, for example in bitumen, these polymers may be used in bitumen / polymer compositions which will themselves be thermoreversibly crosslinked. The present invention aims, in particular, to provide graft polymers which confer on the bitumen / polymer compositions improved rheological properties while maintaining a thermoreversible effect.

Another object of the invention is to provide a graft polymer preparation process, effective, simple to implement and economically viable.

Another object of the invention is to provide bitumen / polymer compositions having, at the temperatures of use, the properties of the bitumen / polymer compositions irreversibly crosslinked, especially at the level of elasticity and / or cohesion, and presenting application temperatures, reduced viscosity.

BRIEF DESCRIPTION In the continuity of its work, the applicant company has developed new thermoreversibly crosslinked bitumen / polymer compositions from a new family of graft polymers. The bitumen / polymer compositions obtained have, at the use temperatures, the properties of the conventional crosslinked bitumen / polymer compositions, and at the processing temperatures, the properties of the uncrosslinked bitumen / polymer compositions.

In addition, the applicant proposes a new process for preparing graft polymers according to the invention. According to the invention, the object of the invention is achieved by a graft polymer with thermoreversible crosslinking comprising:

a polymeric main chain P based on conjugated diene units,

at least one lateral graft G represented by the following general formula (1):

R- (OCH ₂ CH ₂ ) _m -S- (1)

in which R represents a linear or branched saturated hydrocarbon chain of at least 18 carbon atoms and m is an integer ranging from 0 to 20, said graft G being connected to the polymeric main chain P by the sulfur atom of formula (1) and,

at least one graft G 'represented by the following general formula (4): - S-R 'S- (4)

in which 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, said graft G' being connected to the polymeric main chain P by each of the sulfur atoms of formula (4).

According to a particular embodiment, the graft G is represented by the following general formula (2):

wherein n represents an integer ranging from 18 to 110.

According to another particular embodiment, the graft G is represented by the following general formula (3):

C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -S- (3)

wherein n represents an integer ranging from 18 to 10 and m represents an integer ranging from 1 to 20.

According to a preferred embodiment, the graft G 'is represented by the general formula

(5) following:

- SC _n > H _2n > -S- (5)

in which n 'represents an integer ranging from 2 to 40.

According to the invention, the object of the invention is also achieved by a process for preparing a graft polymer according to the invention comprising a grafting reaction of at least one thiol compound and at least one dithiol compound on double bonds. reactive agents of a polymer based on conjugated diene units, said thiol compound being represented by the formula

(6) following:

R- (OCH ₂ CH ₂ ) _m -SH (6)

in which R represents a saturated hydrocarbon chain, linear or branched, of at least 18 carbon atoms and m an integer ranging from 0 to 20,

said dithiol compound being represented by the following general formula (9):

HS-R'-SH (9)

wherein 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.

According to a particular embodiment, the thiol compound is represented by the following general formula (7):

wherein n represents an integer ranging from 18 to 110.

According to another particular embodiment, the thiol compound is represented by the following general formula (8):

C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -SH (8)

wherein n represents an integer ranging from 18 to 10 and m represents an integer varying from 1 to 20. According to another particular embodiment, the dithiol compound is represented by the following general formula (10):

wherein n 'represents an integer ranging from 2 to 40. According to a particular development, the molar ratio noted Rthioi / dithioi between the thiol compound and the dithiol compound is between 10: 1 and 800: 1.

According to another particular development, the reactive double bonds are pendant vinyl double bonds resulting from a 1-2 addition of the conjugated diene units.

Preferably, the polymer based on conjugated diene units has a weight content of pendent vinyl double bond units derived from the addition 1-2 of between 5% and 80% relative to said polymer. Preferably, the molar ratio of R thiol / vinyl between the thiol compound and the pendant vinyl double bond unit from the 1-2 addition is from 1: 10 to 10: 1.

Preferably, the polymer based on conjugated diene units results from the copolymerization of conjugated diene units and monovinyl aromatic hydrocarbon units.

According to a preferred embodiment, the process for preparing a graft polymer according to the invention comprises the following successive stages:

(i) mixing the thiol compound, the dithiol compound and the conjugated diene unit-based polymer at a temperature between 20 ° C and 120 ° C, for a period of 10 minutes to 24 hours, said mixture being free of solvent and radical initiator,

(ii) the mixture is heated at a temperature between 80 ° C and 200 ° C for a period of 10 minutes to 48 hours. The invention relates to the use of a graft polymer according to the invention for preparing a thermoreversibly crosslinked bitumen / polymer composition.

The invention also relates to a thermoreversibly crosslinked bitumen / polymer composition comprising at least one bitumen and at least one graft polymer according to the invention.

According to a particular embodiment, the weight content of graft polymer relative to the bitumen, in the bitumen / polymer composition is between 0.1 to 30%, preferably between 1 to 10%.

The subject of the invention is also a method for preparing a bitumen / polymer composition according to the invention which comprises the mixture of at least one bitumen and at least one graft polymer according to the invention, at a temperature of between 100 ° C. C. and 200 ° C. until the final bitumen / polymer composition with thermoreversible crosslinking is obtained.

Finally, the invention also relates to a bituminous mix comprising aggregates and a bitumen / polymer composition according to the invention.

DETAILED DESCRIPTION

According to one particular embodiment, the graft polymer with heat-reversible crosslinking according to the invention is a graft polymer comprising a polymeric main chain P based on conjugated diene units, at least one lateral graft G and at least one graft G '.

"Polymeric main chain P based on conjugated diene units" means the polymeric backbone obtained by polymerization of several monomers of which at least one of said monomers is a monomer containing a conjugated diene unit so as to form reactive double bonds on which grafted compounds to form grafts G and G '.

The polymeric backbone P is, therefore, post-functionalized mainly via the reactive double bonds so as to form a lateral graft G and a grafting graft G 'according to the following structures:

Structure 1: lateral graft Structure 2: grafting graft

The polymeric main chain P (in bold on the structures 1 and 2) comprises hydrocarbon units (in parentheses on the structures 1 and 2) connected to the lateral graft G and / or graft G '.

The lateral graft G is represented by the following general formula (1):

R- (OCH ₂ CH ₂ ) _m -S- (1)

in which

R represents a saturated hydrocarbon chain, linear or branched, of at least 18 carbon atoms, preferably at least 22 carbon atoms, preferably at least 30 carbon atoms, more preferably at least 40 atoms carbon and,

m is an integer ranging from 0 to 20. The lateral graft G is connected to the polymeric backbone P by the sulfur atom of the formula (1). Thus, the lateral graft G is connected to the polymeric backbone P by a carbon-sulfur bond (dotted bond in formula 1 and structure 1).

The saturated hydrocarbon chain of the graft G is advantageously linear.

The lateral graft G may contain only a saturated hydrocarbon chain. In this case, the lateral graft G is preferably represented by the following general formula (2):

C _n LL _{n + 1} -S- (2)

wherein n represents an integer ranging from 18 to 110, preferably ranging from 18 to 90, preferably from 18 to 70, more preferably from 18 to 40, still more preferably from 26 to 40.

The lateral graft G may alternatively contain an ethoxylated chain. In this case, the lateral graft G is represented by the formula (1) in which m represents an integer varying from 1 to 20, preferably from 1 to 10, more preferably from 2 to 10, even more preferably from 2 to 4.

The lateral graft G is advantageously represented by the following general formula (3): C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -S- (3)

in which

n represents an integer ranging from 18 to 110, preferably ranging from 18 to 90, preferably from 18 to 70, more preferably from 18 to 40, still more preferably from 26 to 40 and,

m represents an integer ranging from 1 to 20, preferably from 1 to 10, more preferably from 2 to 10, even more preferably from 2 to 4.

The average number of grafts G per main polymer chain P is greater than 2, preferably greater than 50, preferably greater than 100, even more preferably greater than 400.

The graft G 'is represented by the following general formula (4): - S-R' S- (4)

in which R 'represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 2 to 40 carbon atoms, preferably of 4 to 20, more preferably of 6 to 18, still more preferably 8 14. The graft G 'is linked to one or two polymeric main chains P by the sulfur atoms of the formula (4). Thus, the graft G 'is connected to one or two polymer main chains P by two carbon-sulfur bonds (dotted bonds on the structure 2 and in the formula 4). The graft G 'may be linked to a polymeric backbone P by the two sulfur atoms of the formula (4) or may be connected to two polymeric main chains P, respectively, by one of the two sulfur atoms of the formula (4). ).

The hydrocarbon group R 'may comprise at least one aromatic ring, preferably at least two aromatic rings. According to a particular preferred embodiment, R 'represents a hydrocarbon group, saturated or unsaturated, linear or branched, of 2 to 40 carbon atoms, preferably of 4 to 20, more preferably of 6 to 18, still more preferably 8 at 14.

The hydrocarbon group R 'is, advantageously, saturated and linear.

In particular, the graft G 'is represented by the following general formula (5):

-SC _n H _2n -S- (5)

in which n 'represents an integer ranging from 2 to 40, preferably from 4 to 20, more preferably from 6 to 18, even more preferably from 8 to 14.

According to a particular embodiment, the graft G 'may optionally comprise one or more heteroatoms. In this case, the graft G 'is preferably devoid of carbonyl function C = O and / or carboxylate function O-C = O. The graft G 'advantageously comprises one or more heteroatoms chosen from oxygen, sulfur and nitrogen. The graft G 'preferably comprises one or more oxygen atoms.

According to a particular embodiment, the graft polymer with thermoreversible crosslinking according to the invention results, advantageously, from a post-functionalization of a polymer based on conjugated diene units containing reactive double bonds. Post-functionalization is understood to mean carrying out a grafting of the polymer after polymerization of the monomers constituting it, to form the grafts G and G 'on the polymeric main chain P.

The graft polymer is thus obtained by polymerization then grafting and not by polymerization of monomers already functionalized by grafts G and G '.

A process for preparing the grafted polymer comprises a grafting reaction of at least one thiol compound (mercaptan) and at least one dithiol compound (di-mercaptan) on reactive double bonds of a polymer based on conjugated diene units .

The term "polymer based on conjugated diene units" means a polymer obtained from at least one conjugated diene unit. Thus, the polymer based on conjugated diene units may result from the homopolymerization only of diene units, preferably of conjugated diene units. The polymer based on conjugated diene units may comprise along the polymer chain several double bonds resulting from the homopolymerization of the diene units, preferably of conjugated diene units. Such polymers are for example polybutadienes, polyisoprenes, polyisobutenes, polychloroprenes, but also butyl rubbers which are obtained by concatenation of isobutene and isoprene copolymers. It is also possible to find copolymers or terpolymers obtained from diene units such as butadiene, isoprene, isobutene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene or chloroprene units. carboxylated butadiene or carboxylated isoprene. The polymer based on conjugated diene units may also result from the copolymerization or terpolymerization of diene units, preferably conjugated diene, and other units containing other reactive functions. These reactive functions will be chosen for example from double bonds, epoxides, acid anhydrides, carboxylic acids, esters, amides, thiols, alcohols and amines, preferably double bonds.

Thus, the polymer based on conjugated diene units can be obtained from diene units, preferably conjugated diene units, and units such as vinyl acetate, methyl acrylate, butyl acrylate, maleic anhydride, glycidyl methacrylate, glycidyl acrylate and norbornene.

The conjugated diene unit-based polymer is, for example, selected from ethylene / propene / diene terpolymers (EPDM) and acrylonitrile / butadiene / styrene terpolymers (ABS).

The polymer based on conjugated diene units may, optionally, have undergone one or more treatments after polymerization, for example a partial hydrogenation.

The preferred polymers based on conjugated diene units are the polymers resulting from the copolymerization of conjugated diene units and monovinyl aromatic hydrocarbon units.

The conjugated diene unit is preferably chosen from diene units containing from 4 to 8 carbon atoms per monomer, such as butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl- 1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene, chloroprene, carboxylated butadiene or carboxylated isoprene. The conjugated diene unit is advantageously the butadiene unit.

The monovinyl aromatic hydrocarbon unit is preferably selected from styrene, o-methyl styrene, p-methyl styrene, p-tert-butyl styrene, 2,3-dimethyl styrene, alpha-methyl styrene vinyl naphthalene, vinyl toluene, vinyl xylene. The monovinyl aromatic hydrocarbon unit is advantageously the styrene unit.

The reactive double bonds of the polymer based on conjugated diene units are of two types depending on the type of addition 1-2 or 1-4 of the conjugated diene units during the polymerization of said polymer.

The double bonds resulting from the 1-2 addition of the conjugated dienes are pendant vinyl double bonds. The reactive double bonds are preferably pendant vinyl double bonds derived from a 1-2 addition of conjugated diene units.

The conjugated diene-based polymer preferably has a weight content of units with pendant double vinyl bonds resulting from an addition 1-2 of between 5% and 80% relative to said polymer.

According to a particular preferred embodiment, the polymer based on conjugated diene units is a block copolymer based on styrene and butadiene. The reactive functions present on said polymer after the polymerization reaction are pendant vinyl double bonds resulting from the 1,2-addition of the butadiene units. Nevertheless, the double bonds resulting from the addition 1-4 of the butadiene units, although less reactive, can also participate in the grafting reaction.

The conjugated diene-based polymer advantageously has a weight content of styrene ranging from 5% to 50% and a weight content of butadiene ranging from 50% to 95% relative to said polymer. The polymer based on conjugated diene units preferably has a weight content of pendent vinyl double bond units derived from the addition of 2-butadiene ranging from 5% to 80% relative to said polymer. The weight average molecular weight of the conjugated diene unit-based polymer may range, for example, from 10,000 to 600,000 daltons, preferably from 30,000 to 400,000 daltons.

The graft polymer is obtained by reaction between the double bonds of the polymer based on conjugated diene units, in particular the pendant vinyl double bonds resulting from the addition of the conjugated dienes 1-2 and the thiol functions of the thiol compound and the dithiol compound of to form carbon-sulfur bonds (dotted bonds on structures 1 and 2).

The thiol compound is represented by the following general formula (6):

R- (OCH ₂ CH ₂ ) _m -SH (6)

in which

m is an integer ranging from 0 to 20.

R is preferably a linear saturated hydrocarbon chain.

The thiol compound may contain only a saturated hydrocarbon chain. In this case, the thiol compound is preferably represented by the following general formula (7):

C _n H _{2n +} i-SH (7) in which n represents an integer ranging from 18 to 110, preferably ranging from 18 to 90, preferably from 18 to 70, more preferably from 18 to 40, even more preferably from 26 to 40. The thiol compound may be chosen from thiols following: C18H ₃₇ -SH, C40H81-SH C70H141-

Alternatively, the thiol compound may contain an ethoxylated chain. In this case, the thiol compound is represented by formula (6) in which m represents an integer ranging from 1 to 20, preferably from 1 to 10, more preferably from 2 to 10, even more preferably from 2 to 4.

The thiol compound is advantageously represented by the following general formula (8):

C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -SH (8)

in which

The dithiol compound is preferably represented by the following general formula (9):

HS-R'-SH (9)

in which R 'represents a hydrocarbon group, saturated or unsaturated, linear or branched, cyclic and / or aromatic, of 2 to 40 carbon atoms, preferably of 4 to 20, more preferably of 6 to 18, still more preferably 8 at 14.

The hydrocarbon group R 'of the dithiol compound may comprise at least one aromatic ring, preferably at least two aromatic rings.

According to a particular preferred embodiment, R 'represents a hydrocarbon group, saturated or unsaturated, linear or branched, neither cyclic nor aromatic, from 2 to 40 carbon atoms, preferably from 4 to 20, more preferably from 6 to 18, even more preferably from 8 to 14.

The hydrocarbon group R 'of the dithiol compound is advantageously saturated and linear. In particular, the dithiol compound is represented by the following general formula (10):

According to a particular embodiment, the dithiol compound may optionally comprise one or more heteroatoms. In this case, the dithiol compound is preferably free of carbonyl function C = O and / or carboxylate function O-C = O. The dithiol compound advantageously comprises one or more heteroatoms chosen from oxygen, sulfur and nitrogen. The dithiol compound preferably comprises one or more oxygen atoms.

The molar ratio, denoted Rthioi / dithioi, between the thiol compound and the dithiol compound is between 10: 1 and 800: 1, preferably between 50: 1 and 500: 1, more preferably between 100: 1 and 400: 1.

The molar ratio, denoted Rthoioi / vinyie, between the thiol compound and the pendant vinyl double bond unit resulting from the addition 1-2 is between 1: 10 and 10: 1, preferably between 1: 5 and 5: 1. more preferably between 1: 2 and 2: 1.

According to a particular preferred embodiment, the process for preparing the graft polymer is carried out in the absence of a solvent and a radical initiator. In particular, the process is characterized by two successive reaction steps. The first step consists of premixing the conjugated diene-based polymer, the thiol compound and the dithiol compound under mild conditions, said polymers, thiol compound and dithiol compound being as described above. The second step consists of the actual grafting reaction, that is to say the reaction between the polymer based on conjugated diene units and the thiol and dithiol compounds, to form the grafts, respectively, G lateral and G 'on the polymeric main chain P of said polymer.

The process for preparing the grafted polymer comprises, in particular, the following successive steps:

(i) mixing the thiol compound, the dithiol compound and the conjugated diene unit-based polymer at a temperature between 20 ° C and 120 ° C, for a period of

10 minutes to 24 hours, said mixture being devoid of solvent and radical initiator,

(ii) the mixture is heated at a temperature between 80 ° C and 200 ° C for a period of 10 minutes to 48 hours.

In step (i), the thiol compound and the dithiol compound may be contacted with the polymer and mixed by any known method, simultaneously or sequentially, in any order. Nevertheless, it will be preferred to put the thiol and dithiol compounds in contact simultaneously with the conjugated diene-based polymer. The temperature of step (i) is preferably between 30 ° C and 110 ° C, preferably 40 ° C and 100 ° C, more preferably between 50 ° C and 90 ° C, even more preferably between 50 ° C and 80 ° C.

It is advantageous to choose thiol and dithiol compounds which melt at the temperature of step (i) to promote the swelling of the conjugated diene-based polymer. The thiol and dithiol compounds, which are liquid at these temperatures, act as solvents for said polymer and make it possible to dispense with the solvent.

According to one variant, step (i) can comprise two distinct substeps, a first substep intended to melt the thiol and dithiol compounds and then a second substep intended to swell the polymer in the thiol and dithiol compounds. melted. The temperature of step (i) may, for example, be applied with a first temperature ramp to a first step set at a temperature between 40 ° C and 60 ° C for a period sufficient to melt the compounds thiol and dithiol, followed by a second temperature ramp to a second plateau set at a temperature between 60 ° C and 110 ° C for a period sufficient to obtain optimal swelling of the polymer. For thiol and dithiol compounds which are not liquid at the temperature of stage (i), solid mixture homogenization means are advantageously used, for example, a kneader or an extruder.

Alternatively, an organic solvent may be added to the polymer to swell the polymer and promote the solubilization of the thiol and dithiol compounds in the polymer provided that the organic solvent is fully evaporated before the second step (ii). free of solvent and radical initiator at the end of step (i). For example, toluene, xylene, chloroform, dichloromethane, alkanes such as dodecane or any other conventional solvent or mixture of solvents will be chosen. The maximum amount of solvent added is 10% by weight relative to the polymer / thiol / dithiol mixture, preferably 5%, more preferably 3%, even more preferably 1%.

The duration of step (i) is preferably between 30 minutes and 12 hours, preferably between 1 hour and 10 hours, more preferably between 2 hours and 8 hours, even more preferably between 4 hours and 6 hours. The durations will be longer when no agitation is planned.

The second step does not require the use of a radical initiator. So the reactions secondary parasitic coupling and chain cleavage due to the presence of the radical initiator are severely limited.

The temperature of step (ii) is preferably between 100 ° C and 160 ° C, more preferably between 100 ° C and 140 ° C.

The duration of step (ii) is advantageously between 30 minutes and 72 hours, preferably between 1 hour and 24 hours, more preferably between 2 hours and 24 hours, even more preferably between 4 hours and 24 hours.

For steps (i) and (ii), an inert atmosphere such as nitrogen or argon may be used, with or without mechanical agitation. Preferably, steps (i) and (ii) are carried out with stirring to improve the yield of the grafting reaction. At the end of the second grafting step (ii), the grafted polymer can advantageously be purified by any known method. The process preferably comprises a subsequent purification step, for example, by precipitation in a suitable solvent or mixture of solvents followed by filtration and drying. The solvent (s) are selected according to well-known solubility principles. For example, methanol will be used for the precipitation.

In addition, an antioxidant, such as 2,6-di-tert-butyl-4-methylphenol, may be added to the graft polymer obtained according to the preparation method described above. In particular, the oxidizing agent may be added to the solvent used for the precipitation step. A graft yield corresponding to the amount of grafted thiol and dithiol compounds relative to the amount of thiol and dithiol compounds employed is defined.

The grafting yields are advantageously between 10 and 99%, preferably between 20 and 90%, more preferably between 30 and 80%, more preferably between 40 and 70%.

According to another particular embodiment, the process for preparing the graft polymer is carried out in the presence of solvent and / or catalyst and / or radical initiator according to any known method.

The process for preparing the graft polymer can comprise the grafting of several thiol compounds and / or several dithiol compounds, thus forming a graft polymer containing several lateral grafts G of different chemical structures and / or several grafts G 'of different chemical structures. It can therefore coexist within the same chain main polymer P, lateral grafts G of different chain length.

The thermoreversible crosslinking of the graft polymer can theoretically result from the assembly of the graft polymers via the lateral grafts G (more specifically via the hydrocarbon chains of the grafts G). This assembly makes it possible to define crystalline zones between the lateral grafts G of the graft polymer. These crystalline zones are stable at low temperature. When the temperature increases, these crystalline zones melt, they recrystallize when the temperature decreases. At low temperature, the interactions of the crystalline zones of the grafts G bring the chains of the grafted polymer which are then crosslinked. When the crystalline zones of the grafts melt, the chains of the grafted polymer move away, they are no longer crosslinked. Therefore, it would appear that the nature of the graft G, in particular, the length of the G side chain, has an effect on the thermoreversible crosslinking of the graft polymer. The graft G 'approximates the main polymer chains P and structures the graft polymer. Surprisingly, the combination of a lateral graft G and graft G 'gives the graft polymer remarkable mechanical properties, including excellent cohesion. The graft polymer described above can advantageously be used to prepare a thermoreversibly crosslinked bitumen / polymer composition. In particular, the graft polymer can be used as additive of a bitumen or bituminous composition. Thus, when an additive bitumen with this graft polymer is obtained, a bitumen / polymer composition is obtained which is crosslinked in a reversible manner and more particularly in a thermoreversible manner and which has improved mechanical properties, especially in terms of penetration and temperature. Ball and Ring (TBA). The grafted polymer confers on the bitumen / polymer composition thermoreversible properties comparable to those of a bitumen / polymer composition grafted only with a graft G. By thermoreversible crosslinking of the bitumen / polymer compositions according to the invention, is meant a crosslinking which results in by the following phenomena:

at low temperature, for example at operating temperatures, the grafts G and G 'of the grafted polymer are associated with each other and form crosslinking points. The polymer network formed gives the bitumen / polymer composition good mechanical properties, especially in terms of elasticity, cohesion, penetrability and ball and ring temperature (TBA).

- When hot, an increase in temperature causes the breaking of the crosslinking points and therefore the dissociation of the polymer chains. The network polymer disappears and the bitumen / polymer composition regains a low viscosity and therefore a good fluidity, which allows handling at lower temperatures.

A decrease in temperature allows the crosslinking points to reform. The phenomenon is thermoreversible.

The bitumen / polymer composition according to the invention comprises at least one bitumen and at least one graft polymer as described above. In addition, the bitumen / polymer composition may comprise at least one fluxing agent.

The weight content of graft polymer relative to the bitumen is between 0.1 to 30%, preferably between 1 to 10%, preferably between 2 and 6%.

The bitumen / polymer composition may contain a bitumen or a mixture of bitumens from different origins.

We can first mention bitumen of natural origin, those contained in deposits of natural bitumen, natural asphalt or oil sands. Bitumens can also be selected from bitumens derived from crude oil refining. Bitumens come from the atmospheric and / or vacuum distillation of oil. These bitumens may optionally be blown, visbroken 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 the addition of volatile solvents, petroleum fuels, carbochemical fluxes and / or fluxes of vegetable origin. The fluxing agents used may comprise C ₆ to C ₂₄ fatty acids in the acid, ester or amide form in combination with a hydrocarbon cut.

The bitumen / polymer compositions may be prepared by any known method.

According to a particular embodiment, a process for the preparation of bitumen / polymer compositions described above comprises mixing at least one bitumen and at least one graft polymer described above, at a temperature of between 90 ° C. and 220 ° C. until the final bitumen / polymer composition with thermoreversible crosslinking is obtained. In particular, the process for preparing these bitumen / polymer compositions comprises the following essential steps:

a) a bitumen is introduced into a container equipped with mixing means, and the bitumen is brought to a temperature between 90 and 220 ° C, preferably between 140 ° C and 180 ° C,

b) introducing from 0.1 to 30% by weight of a graft polymer according to the invention relative to the mass of bitumen, preferably from 0.1 to 10%.

Throughout the process, the composition is heated to a temperature between 90 and 220 ° C, preferably between 140 and 180 ° C, with stirring, until a homogeneous final bitumen / polymer composition is obtained.

Various uses of the bitumen / polymer compositions obtained according to the invention are envisaged, in particular for the manufacture of a bituminous binder, which can in turn be used to prepare an association with aggregates to form asphalt, in particular road. The bituminous binder may be in anhydrous form, in emulsion form or in the form of fluxed bitumen.

Another aspect of the invention is the use of the bitumen / polymer compositions described above in various industrial applications, in particular for producing a waterproofing coating, a membrane or an impregnating layer, anti-noise membranes, insulation membranes, surface coatings, carpet tiles, impregnation layers, etc.

With regard to the road applications of these bituminous / polymer compositions, the invention aims in particular at bituminous mixes as materials for the construction and maintenance of roadway bodies and their pavement, as well as for carrying out all road works. Thus, the invention relates, for example, to surface coatings, hot mixes, cold mixes, cold mixes and emulsions. According to a particular embodiment, a bituminous mix comprises aggregates and a bitumen / polymer composition according to the invention.

The bitumen / polymer compositions may be used to produce base layers, bonding, bonding and rolling layers, anti-renneting layers, draining mixes, or cast asphalts (a mixture of a bituminous binder and granules of the type of sand).

Although the present description only describes applications in the bitumen field, the graft polymer can be used in other applications where its properties mechanical and thermorevitable can be used. EXAMPLES

Preparation of graft polymers

PGi, PG ₂ and PG ₃ graft polymers are prepared from:

randomly-bound styrene / butadiene SB ₀ diblock copolymer having a mass-molecular weight M _w equal to 120,000 g ^/ mol ^-1 , a molar mass in number M _n equal to 115,000 g ^/ mol ^-1 , a mass quantity styrene content of 23% relative to the weight of the copolymer, of which 18% in block form and a mass quantity of butadiene of 77% relative to the weight of copolymer, the quantity by mass of double-bonded units 1-2 (vinyl bonds pendant) from butadiene being 7% relative to the amount by weight of copolymer,

randomly-bound styrene / butadiene SBi diblock copolymer having a mass molecular weight M _w equal to 130 000 g mol ^-1 , a number-average molar mass M _n equal to 125 000 g mol ^-1 , a mass quantity of styrene of 30% relative to the weight of the copolymer, of which 19% in block form and a quantity by weight of butadiene of 70% relative to the weight of copolymer, the quantity by mass of units with double bonds 1-2 butadiene (pendant vinyl bonds) being 15% relative to the amount by weight of copolymer,

a thiol compound of formula C18H37-SH

a dithiol compound of formula HS-C ₁ 0H ₂ O -SH

Preparation of the PG1 polymer (according to the invention)

In a 2L reactor equipped with mechanical stirring, an inlet and a nitrogen outlet, 148.6 g of the thiol compound (0.518 mol), 0.27 g of the dithiol compound (1.295 × 10 ^-3 mol) are introduced. as well as 200 g of SB ₀ copolymer (2,62 mol of butadiene, of which 0.259 mol of pendant vinyl bond), the mixture is stirred at 50 rpm for 2 h at 50 ° C. under an inert atmosphere, the temperature is raised to 110 ° C. The mixture is stirred at 50 rpm for 24 hours under an inert atmosphere, the stirring is stopped and the mixture is cooled to room temperature under an inert atmosphere, followed by a purification step of dissolving the resulting mixture in toluene. The PGi-containing solution is then precipitated from the PGi-containing solution with 8L of methanol, filtered and dried for one hour at room temperature, and the PGi copolymer is then dissolved in toluene. to get a solution to 4% by weight and then introduced an antioxidant, BHT 1/1000 by weight relative to the copolymer. The solution is poured into a teflon mold and the solvent is allowed to evaporate at room temperature. Preparation of the grafted polymer PG2 (according to the invention)

The procedure is the same as for the graft polymer PGi, except that 0.53 g of the dithiol compound (2.59 × 10 ^-3 mol) is used Preparation of the grafted polymer PG (according to the invention)

The procedure is the same as for the graft polymer PGi, except that 158 g of the thiol compound (0.56 mol), 1.15 g of the dithiol compound (5.6 × 10 ^-3 mol) and 200 g are used. of SBi copolymer (2.59 mol of butadiene, of which 0.56 mol of vinyl pendant bond) Preparation of a PGt control graft polymer

The procedure is the same as for the graft polymer PG3 with the exception that no dithiol compound is used. The polymer GP is only _t functionalized with thiol compound. The characteristics of the graft polymers obtained are listed in the following Table I:

Table I

* The molar masses were determined by steric exclusion chromatography SEC or GPC (Gel Permeation Chromatography) at 40 ° C with THF as eluent and using polystyrene for calibration.

** the molar percentage of grafting was determined by ¹ H NMR with a Bruker 400 MHz spectrometer. The molar% of grafting expresses the proportion of a compound with respect to all of the styrene / butadiene repeat units.

*** The grafting yield corresponds to the thiol fraction grafted with respect to the initially introduced thiol. Preparation of bitumen / polymer compositions

Bitumen / polymer compositions are prepared from a class 50/70 bitumen having a penetration of 53 l / 10 mm, the characteristics of which comply with the EN 12591 standard.

Bitumen / polymer compositions according to the invention C_K C ₂ and C

Three bitumen / polymer compositions C ₁ , C ₂ and C ₃ according to the invention are prepared from the graft polymers PG ₁ , PG ₂ and PG ₃ and bitumen described above. A reactor maintained at 180 ° C. and equipped with a mechanical stirring system is charged with 35 g (95% by mass) of bitumen. The bitumen is heated to 185 ° C and stirred for about 60 minutes. 1.85 g (5% by weight) of the graft polymer PGi, PG ₂ or PG ₃ obtained above are then added. The mixture is carried out for a period of 4 hours with stirring. The bitumen / polymer compositions C ₁ , C ₂ and C ₃ obtained respectively from grafted polymers PG ₁ , PG ₂ and PG _{3 are} obtained.

Bitumen / control polymer composition Tn

A sulfur-crosslinked control bitumen / polymer composition is prepared irreversibly (vulcanization).

35.5 g (94.87% by mass) of the above bitumen are introduced into a reactor. The bitumen is heated to 185 ° C and stirred for about 60 minutes at 300 rpm. 1.85 g (5%) by weight of the SB ₀ copolymer is then added. The mixture is stirred and heated at 185 ° C for about 4 hours. 50 mg (0.13% by mass) of sulfur in bloom are then added. The mixture is stirred and heated at 185 ° C for 2h.

Bitumen / control polymer composition

A bitumen / polymer control composition is prepared according to a procedure identical to compositions C 1, C ₂ and C ₃ from the graft polymer PG _t . Table II below shows the physical characteristics of the compositions according to the invention and the control composition.

Table II Ci C ₂ C ₃ T ₀ Ti

Penetration (0.1 mm) ^(l) 46 41 39 36 50

TBA (° C) ⁽²⁾ 57.6 63.4 59.8 64.2 54.4

Viscosity at 80 ° C ⁽ⁱ⁾ (Pa.s) 43.00 41.00 49.00 65.00 27.00

Viscosity at 100 ° C ⁽ⁱ⁾ (Pa.s) 10.68 11.05 12.50 17, 49 9, 15

Viscosity at 120 ° C ⁽⁾ (Pa.s) 2,70 2,73 3,12 4.80 2.30

Viscosity at 140 ° C ⁽ⁱ⁾ (Pa.s) 0.97 0.98 1.05 1.61 0.81 Viscosity at 160 ° C ⁽⁾ (Pa.s) 0.43 0.43 0.46 0.69 0.36

Viscosity at 180 ° C ⁽ⁱ⁾ (Pa.s) 0.23 0.23 0.24 0.34 0.19

Viscosity at 200 ° C ⁽⁾ (Pa.s) 0.14 0.14 0.14 0.20 0.11

Elongation max. at 5 ° C (%) (4)> 700> 700> 700> 700> 700

(1) Penetrability according to standard E N 1426

(2) Ball and Ring Temperature, according to EN 1427

(3) Dynamic viscosity, plane-plan, 25mm to 100s ^-1

(4) Tensile test according to EN 13587

The results of this table show that the viscosities of the bitumen / polymer compositions according to the invention between 80 ° C. and 200 ° C. are always lower than those of the control composition TA from 80 ° C., the bitumen / polymer compositions according to the invention. Thus, the invention is less viscous than a bitumen / sulfur crosslinked polymer composition. At processing temperatures, the bitumen / polymer compositions according to the invention have low viscosities.

Moreover, the values of penetrability, TBA and maximum elongation are very close to those of the control composition T ₀ . Compared to composition T _ls values of TBA and penetrability are better while retaining a low viscosity at temperatures of use of 120 ° to 160 ° C.

The bitumen / polymer compositions according to the invention are remarkable in that they have low viscosities at temperatures lower than those of the prior art while having good rheological properties. The use of graft polymers according to the invention in bitumen / polymer compositions also has the advantage of being free of the stresses associated with the release of hydrogen sulphide (H ₂ S) during manufacture and / or transfer. and / or the loading and / or unloading and / or spreading of the bitumen / polymer compositions of the prior art, crosslinked with sulfur or sulfur derivatives. The use of the bitumen / polymer compositions according to the invention for producing mixes makes it possible to lower the temperature of manufacture of the mixes by about 10 ° C. while maintaining good mechanical properties, in particular the penetrability and the TBA of the mix. .

Claims

A graft polymer comprising:

a polymeric main chain P based on conjugated diene units,

at least one lateral graft G represented by the following general formula (1):

R- (OCH ₂ CH ₂ ) _m -S- (1)

at least one graft G 'represented by the following general formula (4):

- S-R 'S- (4)

2. Polymer according to claim 1, characterized in that the lateral graft G is represented by the following general formula (2):

wherein n represents an integer ranging from 18 to 110.

3. Polymer according to claim 1, characterized in that the lateral graft G is represented by the following general formula (3):

C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -S- (3)

4. Polymer according to any one of claims 1 to 3, characterized in that the graft G 'is represented by the following general formula (5):

-SC _n > H _2n -S- (5)

in which n 'represents an integer ranging from 2 to 40.

5. Process for preparing a graft polymer according to any one of claims 1 to 4, comprising a grafting reaction of at least one thiol compound and at least one dithiol compound on reactive double bonds of a polymer-based of conjugated diene units, said thiol compound being represented by the following formula (6): R- (OCH ₂ CH ₂ ) _m -SH (6)

said dithiol compound being represented by the following general formula (9):

HS-R'-SH (9)

6. Process according to claim 5, characterized in that the thiol compound is represented by the following general formula (7):

wherein n represents an integer ranging from 18 to 110.

7. Process according to claim 5, characterized in that the thiol compound is represented by the following general formula (8):

C "H _{2n + 1} - (OCH ₂ CH ₂ ) _m -SH (8)

8. Process according to any one of claims 5 to 7, characterized in that the dithiol compound is represented by the following general formula (10): HS-C "H _2n > -SH (10)

in which n 'represents an integer ranging from 2 to 40.

9. Process according to any one of claims 5 to 8, characterized in that the molar ratio (Rthioi / dithioi) between the thiol compound and the dithiol compound is between 10: 1 and 800: 1.

10. Process according to any one of claims 5 to 9, characterized in that the reactive double bonds are pendant vinyl double bonds derived from a 1-2 addition of conjugated diene units.

11. Process according to claim 10, characterized in that the polymer based on conjugated diene units has a weight content of pendent vinyl double bond units derived from the addition 1-2 of between 5% and 80% relative to said polymer. .

12. Method according to one of claims 10 and 11, characterized in that the molar ratio (Rthioi / vinyie) between the thiol compound and the pendant vinyl double bond unit from the 1-2-addition is between 1: 10 and 10: 1.

13. Process according to any one of Claims 5 to 12, characterized in that the polymer based on conjugated diene units results from the copolymerization of conjugated diene units and monovinyl aromatic hydrocarbon units.

14. Method according to any one of claims 5 to 13, characterized in that it comprises the following successive steps:

15. Use of a graft polymer according to any one of claims 1 to 4, for preparing a thermoreversible crosslinking bitumen / polymer composition.

16. Bitumen / thermo-reversible crosslinking polymer composition comprising at least one bitumen and at least one graft polymer according to any one of Claims 1 to 4.

17. Bitumen / polymer composition according to claim 16, characterized in that the weight content of graft polymer relative to the bitumen is between 0.1 to 30%, preferably between 1 to 10%.

18. Process for preparing a bitumen / polymer composition according to one of claims 16 and 17, characterized in that it comprises the mixture of at least one bitumen and at least one graft polymer according to any one of the claims. 1 to 4, at a temperature between 90 ° C and 220 ° C until the final bitumen / polymer composition thermoreversibly crosslinked.

19. A bituminous mix comprising aggregates and a bitumen / polymer composition according to one of claims 16 and 17.