EP3810693A1

EP3810693A1 - Elastomer mix comprising plla and pdla

Info

Publication number: EP3810693A1
Application number: EP19745688.2A
Authority: EP
Inventors: Nathalie COSTE; Lise MAISONNEUVE; Gilles MIOCHE; Séverin DRONET; Julien Cayuela; Bertrand DE BACKER; Philippe Ghislain Dubois
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2018-06-19
Filing date: 2019-06-18
Publication date: 2021-04-28
Also published as: US20210253801A1; FR3082519B1; FR3082519A1; WO2019243724A1; US11987671B2

Abstract

An elastomer mix comprising at least: - by way of polymer A), at least one diene/polylactide elastomer copolymer A1, the copolymer A1 comprising: a PLLA or PDLA polylactide block, called first block, where necessary one or more other polylactide block(s), which are all PLLA when the first block is PLLA or which are all PDLA when the first block is PDLA, the mass percentage of the one or more polylactide block(s) in said copolymer A1 being between 0% and 50% by weight, compared to the weight of the copolymer A1; and - by way of polymer B), a diene/polylactide elastomer copolymer B1, the copolymer B1 comprising a polylactide block, called second block, which is PLLA when, in the copolymer A1, the first block is PDLA, or which is PDLA when, in the copolymer A1, the first block is PLLA, where necessary one or more other polylactide block(s), which are all PLLA when said second block is PLLA or which are all PDLA when said second block is PDLA, the mass percentage of the one or more polylactide block(s) in said copolymer B1 being between 10% and 50% by weight, compared to the weight of the copolymer B1; or a polylactide B2, which is PLLA when, in the copolymer A1, the first polylactide block is PDLA or is PDLA when, in the copolymer A1, the first polylactide block is PLLA, or a mixture of said copolymer B1 and of said polylactide B2, the designations PLLA and PDLA designate a chain consisting in units of formula (I) -[CH(CH3)-C(O)-O]- (I), for which at least 70% by weight respectively assume the L and D configuration.

Description

ELASTOMERIC MIXTURE COMPRISING PLLA AND PDLA

The present invention relates to an elastomeric mixture comprising both poly-L-lactide (abbreviated as PLLA) and poly-D-lactide (abbreviated as PDLA), one of both of PLLA and PDLA in the form of a block covalently linked to a diene elastomer and the other in the form of a block covalently linked to another diene elastomer or in the form of a homopolymer. The diene elastomer comprising at least one polylactide block associates an elastomeric skeleton and a rigid block (s) and thus exhibits thermoplastic elastomer properties. The subject of the invention is also a rubber composition which comprises such an elastomeric mixture and a tire of which at least one of its constituent elements comprises such an elastomeric mixture or such a composition.

In order to modify the properties of the synthetic elastomers contained in the rubber compositions for tires, different strategies are possible. Among these, diene elastomers can be reacted with other polymers.

The Applicant is more particularly interested in diene elastomer / polylactide copolymers, associating an elastomeric backbone and pendant or end polylactide blocks. These copolymers thus have thermoplastic elastomer (TPE) properties.

Materials with thermoplastic elastomer properties combine the elastic properties of elastomers with the thermoplastic nature, namely the ability to reversibly melt and harden, under the action of heat, polylactide blocks.

In the context of the invention, for the thermoplastic block, compositions of thermoplastic polymers having a melting point greater than or equal to 150 ° C., advantageously ranging from 150 ° C. to 250 ° C., are sought.

The polylactide has a melting temperature falling within this range.

A mixture comprising PLLA and PDLA has different mechanical and thermal properties than a mixture comprising PLLA alone or PDLA alone. In particular, PDLA and PLLA can together form a stereocomplex having a higher melting temperature than that of PLLA alone or PDLA alone.

Furthermore, in the context of the invention, a material is also sought which can be manufactured by a continuous, flexible and low-cost process, such as, for example, reactive extrusion. Reactive extrusion is a process mainly used for thermoplastics, therefore polymers with high glass transition or melting temperatures. The polylactide comprises units of formula (I):

- [CH (CH ₃ ) -C (0) -0] - (I)

in which the asymmetric carbon can be of configuration L (also designated S) or D (also designated R).

In the present description, the names PLLA and PDLA denote a chain consisting of units of formula (I) of which at least 70% by weight, advantageously at least 90% by weight, are of configuration L and respectively D. It will be understood that the remaining units are units of formula (I) having the opposite configuration.

The polylactide is obtained in particular by polymerization by opening of the lactide cycle. By “lactide” is meant, within the framework of the invention, the cyclic diester of lactic acid, that is to say of 2-hydroxypropionic acid. The lactide corresponds to the following formula (II):

By "L-lactide" or "lactide of configuration L" is meant the (S, S) - lactide stereoisomer.

By "D-lactide" or "lactide of configuration D" is meant the (R, R) - lactide stereoisomer.

By “diene elastomer / polylactide copolymer” is meant, according to the present invention, a copolymer comprising at least one diene elastomer block covalently linked to at least one polylactide block. In particular, the copolymer may comprise a diene elastomer block covalently linked, by its end (s), to one or two polylactide block (s). In another variant, the copolymer may be a comb-type polymer comprising a diene elastomer block, forming the trunk of the comb copolymer, covalently linked to several polylactide blocks distributed along the trunk.

In the present description, by the expression "along the trunk" or "along the chain" with reference to a polylactide block hanging from the copolymer, it is to be understood that the copolymer comprises pendant polylactide groups in several places of the elastomeric chain constituting the trunk. This includes the end (s) of the chain but is not limited to these locations. When a polylactide block is present at at least one chain end, the copolymer advantageously also comprises at least one other polylactide block hanging at another position in the chain. In the present description, by the expression "elastomeric mixture" is meant that the mixture has the properties of an elastomer, namely elasticity properties comparable to those of a rubber.

The molar masses are determined by the methods described in the “measurements and tests used” section, according to the size exclusion chromatography method in polystyrene equivalent (SEC). In the present description, unless otherwise expressly indicated, all the molar masses are number-average molar masses. In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are percentages by weight.

Furthermore, the term "pce" means in the sense of the invention, part by weight per hundred parts of total elastomer, that is to say of an elastomer mixture.

In the present description, any range of values designated by the expression "between a and b" represents the range of values going from more than a to less than b (that is to say limits a and b excluded) while any range of values designated by the expression "from a to b" means the range of values from a to b (that is to say including the strict limits a and b).

By the expression composition "based on" is meant a composition comprising the mixture and / or the reaction product of the various constituents used, some of these base constituents being capable of, or intended to react with each other, less in part, during the various stages of manufacturing the composition, in particular during its crosslinking or vulcanization.

The compounds mentioned in the description and used in the preparation of polymers or rubber compositions can be of fossil origin or bio-based. In the latter case, they can be, partially or totally, from biomass or obtained from renewable raw materials from biomass. Are concerned in particular polymers, plasticizers, fillers ....

PRESENTATION OF THE INVENTION The subject of the invention is an elastomeric mixture comprising at least:

- as polymer A),

• at least one copolymer A1 diene elastomer / polylactide, the copolymer A1 comprising

o a PLLA or PDLA polylactide block, known as the first block o if necessary one or more other polylactide block (s) which are all PLLA when the first block is PLLA or which are all PDLA when the first block is PDLA,

the percentage by mass of the polylactide block (s) in said copolymer A1 being between 10% and 50% by weight, relative to the weight of the copolymer A1, and

- as polymer B),

• a diene elastomer / polylactide copolymer B1, the copolymer B1 comprising

a polylactide block called the second block which is PLLA when in the copolymer A1 the first block is PDLA or which is PDLA when in the copolymer A1 the first block is PLLA,

o where appropriate one or more other polylactide block (s) which are all PLLA when said second block is PLLA or which are all PDLA when said second block is PDLA, o the mass percentage in the block (s) s polylactide in said copolymer B1 being between 10% and 50% by weight, relative to the weight of copolymer B1,

• or a polylactide B2 which is

^■ PLLA when in the copolymer A1 the first polylactide block is PDLA, or

^■ PDLA when in the copolymer A1 the first polylactide block is PLLA,

• or a mixture of said copolymer B1 and of said polylactide B2

the names PLLA and PDLA denote a chain consisting of units of formula (I)

- [CH (CH ₃ ) -C (0) -0] - (I).

of which at least 70% by weight are respectively of configuration L and D.

Advantageously, the names PLLA and PDLA denote a chain consisting of units of formula (I) of which at least 90% by weight are of configuration L and respectively D.

In the elastomeric mixture, the mass content of units of formula (I) is advantageously less than 50% by weight relative to the total weight of the elastomeric mixture. The copolymer A1 and / or B1 advantageously comprises at least one diene elastomer block of molar mass in number, Mn, greater than 25,000 g / mol.

In a variant, the polymer A comprises a mixture of a copolymer A1 and of a polylactide A2, said polylactide A2 being:

• PLLA when in copolymer A1 the first polylactide block is PLLA

• or PDLA when in the copolymer A1 the first polylactide block is PDLA.

The polylactide A2) and / or B2) advantageously has a number-average molar mass, Mn, of less than 150,000 g / mol.

The polymer B) advantageously comprises at least the said copolymer B1.

The copolymer A1 or the copolymer B1 is advantageously chosen from:

- a tri-block, of structure PLLA - diene elastomer - PLLA or of structure PDLA-diene elastomer - PDLA,

- a di-block, of PLLA structure - diene elastomer or of PDLA structure - diene elastomer,

- a comb copolymer, having a diene elastomeric trunk and pendant PLLA or PDLA blocks respectively, distributed along the trunk.

In one embodiment, the copolymer A1 is a tri-block having a number-average molar mass, Mn, ranging from 50,000 g / mol to 300,000 g / mol.

In another embodiment, the copolymer A1 is a comb copolymer of number-average molar mass, Mn, ranging from 100,000 g / mol to 600,000 g / mol.

In another embodiment, the copolymer A1 is a di-block having a number-average molar mass, Mn, ranging from 25,000 g / mol to 200,000 g / mol.

In one embodiment, the copolymer B1 is a tri-block having a number-average molar mass, Mn, ranging from 50,000 g / mol to 300,000 g / mol.

In another embodiment, the copolymer B1 is a comb copolymer of number-average molar mass, Mn, ranging from 100,000 g / mol to 600,000 g / mol.

In another embodiment, the copolymer B1 is a di-block having a number-average molar mass, Mn, ranging from 25,000 g / mol to 200,000 g / mol.

In the copolymer A1 and / or in the copolymer B1, the diene elastomer is advantageously chosen from among polybutadienes (abbreviated "BR"), synthetic polyisoprenes (IR), natural rubber (NR), copolymers of butadiene, isoprene copolymers, ethylene and diene copolymers and mixtures of these polymers.

The polymers A) and B) represent at least 30% by weight of the elastomeric mixture advantageously at least 50% by weight of the elastomeric mixture, even more advantageously at least 90% by weight of the elastomeric mixture.

The invention also relates to a rubber composition which comprises the elastomeric mixture according to the invention and an additive. Advantageously, said elastomeric mixture represents at least 30% by weight of the rubber composition.

The invention also relates to a tire of which one of its constituent elements comprises an elastomeric mixture according to the invention or a rubber composition according to the invention. Advantageously, said constituent element is a tread.

II- DESCRIPTION OF THE FIGURES

FIG. 1 represents a diagram of the elastic conservation module E '(MPa) as a function of the temperature (° C) obtained by characterization DMA (dynamic mechanical analysis) of the tri-block T 1 (in dotted line) and of the composition M1 . (solid line).

III- DETAILED DESCRIPTION OF THE INVENTION

The elastomeric blend according to the invention comprises at least two polymers, polymers A and B, one comprising polylactide of configuration L, PLLA, when the other comprises polylactide of configuration D, PDLA.

In addition, as polymer A), the elastomeric mixture comprises at least one copolymer A1 diene elastomer / polylactide, the copolymer A1 comprising

o a polylactide block PLLA or PDLA called first block, o if necessary one or more other polylactide block (s) which are all PLLA when the first block is PLLA or which are all PDLA when the first block is PDLA,

the percentage by mass of the polylactide block (s) in said copolymer A1 being between 10% and 50% by weight, relative to the weight of the copolymer Ai. Polymer A can also comprise a mixture of a copolymer A1 and of a polylactide A2, said polylactide A2 being:

• PLLA when in copolymer A1 the first polylactide block is PLLA, or

• PDLA when in copolymer A1 the first polylactide block is PDLA.

The elastomeric mixture comprises, as polymer B),

• a diene elastomer / polylactide copolymer B1, the copolymer B1 comprising

o where appropriate one or more other polylactide block (s) which are all PLLA when in said second block is PLLA or which are all PDLA when said second block is PDLA,

the percentage by mass of the polylactide block (s) in said copolymer B1 being between 10% and 50% by weight, relative to the weight of the copolymer B1, and

• or a polylactide B2 which is

^■ PLLA when in the copolymer A1 the first polylactide block is PDLA, or

^■ PDLA when in the copolymer A1 the first polylactide block is PLLA,

• or a mixture of said copolymer B1 and of said polylactide B2.

Thus, the configuration L or D of the polylactide of polymer B is chosen according to the configuration of the polylactide of polymer A.

Advantageously, in the elastomeric mixture, the mass content in units of formula (I) is less than 50% by weight relative to the total weight of the elastomeric mixture. More advantageously, in the elastomeric mixture, the mass content in units of formula (I) is less than 45% by weight, even more advantageously less than 40% by weight, relative to the total weight of the elastomeric mixture.

Advantageously, in the elastomeric mixture, the mass content in units of formula (I) is greater than 10% by weight relative to the total weight of the elastomeric mixture. Advantageously, in the elastomeric mixture all the units of formula (I) are provided by the polymers A and B.

In the elastomeric mixture, the mass ratio of [units of formula (I) of configuration L] / [units of formula (I) of configuration D] is advantageously between 10/90 and 90/10.

Advantageously, in the elastomeric mixture, the mass ratio of polymer A / polymer B is between 10/90 and 90/10. Preferably, the polymer N polymer B mass ratio varies from 75/25 to 25/75.

The elastomeric mixture can also comprise at least one (that is to say one or more) additional diene elastomer.

Advantageously, the elastomeric mixture comprises at least 30% of the polymers A) and B), preferably at least 50%, even more preferably at least 90% by weight of the elastomeric mixture.

The elastomeric mixture according to the invention has the particularity of comprising both PLLA and PDLA, one of the two of PLLA and PDLA in the form of a block in a diene elastomer and the other in the form of a block in another diene elastomer or in the form of a homopolymer. By the expression "in the form of a block in a diene elastomer" is meant a block covalently linked to a diene elastomer.

The melting point of the PLLA and PDLA polylactides of the elastomeric mixture according to the invention, whether they are in the form of a block in a diene elastomer or in the form of a homopolymer, is higher than the melting point d 'a polylactide PDLA alone or PLLA alone, which could be explained by the formation of a stereocomplex between the polylactides PLLA and PDLA. This melting point, also called melting point of the association of polylactides PLLA and PDLA, is advantageously greater than or equal to 150 ° C., more advantageously it varies from 150 ° C. to 250 ° C., even more advantageously from 175 ° C. at 240 ° C.

The elastomeric mixture according to the invention supports large deformations before rupture but can flow at a temperature higher than the melting temperature of the association of polylactides PLLA and PDLA.

In particular, the elastomeric mixture according to the invention has a deformation at break of at least 150%, advantageously at least 200%, more advantageously at least 300%, as measured by the method described before the examples , paragraph "mechanical tests". When the elastomeric mixture according to the invention is studied by dynamic mechanical analysis, the presence of a rubbery plate is observed over a wide temperature range, ranging from 0 ° C. to 175 ° C. for the mixtures exemplified. We will now describe in more detail the structures of the copolymers A1 and B1 then the polylactides A2 and B2 as well as the additional diene elastomer.

111-1. CoDolvmères A1 and B1

In addition to the diene elastomer block, the copolymer A1 comprises:

the percentage by mass of the polylactide block (s) in said copolymer A1 being between 10% and 50% by weight, relative to the weight of the copolymer A1.

In addition to the diene elastomer block, the copolymer B1 comprises

o where appropriate one or more other polylactide block (s) which are all PLLA when said second block is PLLA or which are all PDLA when said second block is PDLA, o the mass percentage in the block (s) s polylactide in said copolymer B1 being between 10% and 50% by weight, relative to the weight of copolymer B1.

Thus, all the blocks of the copolymer A1 have the same configuration: L or D.

All the blocks of copolymer B1 have the same configuration: L when the blocks of copolymer A1 are of configuration D, or D when the blocks of copolymer A1 are of configuration L.

In the copolymer A1 and / or in the copolymer B1, the percentage by mass of the polylactide block (s) is advantageously between 10% and 45% by weight, more advantageously between 10% and 40% by weight, even more advantageously of 15% to 40% by weight, relative to the weight of the copolymer A1 or B1 respectively. The copolymers A1 and B1 have properties of a thermoplastic elastomer, namely elastic properties and an ability to melt and harden, reversibly, under the action of heat, polylactide blocks.

Advantageously, the copolymer A1 and / or B1 comprises at least one diene elastomer block of molar mass in number, Mn, greater than 25,000 g / mol.

The copolymer A1 and / or B1 can in particular be a tri-block, a comb copolymer having a diene elastomeric trunk or a di-block.

In particular, the copolymer A1 and / or the copolymer B1 is chosen from:

a di-block, of structure PLLA - diene elastomer or of structure PDLA - diene elastomer,

111-1, 1 Diene elastomer block in a diene elastomer / polylactide A1 or B1 copolymer

By diene elastomer must be understood according to the invention any elastomer derived at least in part (ie, a homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not). The term “diene elastomer capable of being used in the invention” more particularly means a diene elastomer corresponding to one of the following categories:

(a) any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms;

(b) any copolymer obtained by copolymerization of one or more of the conjugated dienes having from 4 to 12 carbon atoms, such as those mentioned below, with each other or with one or more ethylenically unsaturated monomers;

(c) any homopolymer obtained by polymerization of a non-conjugated diene monomer having from 5 to 12 carbon atoms;

(d) any copolymer obtained by copolymerization of one or more of the non-conjugated dienes having from 5 to 12 carbon atoms, such as those mentioned below, with each other or with one or more ethylenically unsaturated monomers;

(e) natural rubber;

(f) a mixture of several of the elastomers defined in (a) to (f) with one another.

Mention may be made, as conjugated diene monomer suitable for the synthesis of elastomers, of butadiene-1, 3 (hereinafter designated butadiene), 2-methyl-1, 3-butadiene, 2,3-di (alkyl in C1 -C5) - 1, 3-butadienes such as for example 2, 3-dimethyl-1, 3-butadiene, 2,3-diethyl-1, 3-butadiene, 2-methyl-3-ethyl-1 , 3-butadiene, 2-methyl-3-isopropyl-1, 3-butadiene, an aryl-1, 3-butadiene, 1, 3-pentadiene, 2,4-hexadiene.

As nonconjugated diene monomer suitable for the elastomer synthesis, mention may be made of pentadiene-1,4, hexadiene-1,4, ethylidene norbornene, dicyclopentadiene.

As ethylenically unsaturated monomers capable of being involved in the copolymerization with one or more diene monomers, conjugated or not, for synthesizing the elastomers, there may be mentioned:

vinyl aromatic compounds having 8 to 20 carbon atoms, such as, for example, styrene, ortho-, meta-, para-methylstyrene, the commercial mixture vinyl mesitylene, divinylbenzene, vinylnaphthalene;

monoolefins (non-aromatic) such as for example ethylene and alpha-olefins, in particular propylene, isobutene;

(meth) acrylonitrile, (meth) acrylic esters.

Among these, the diene elastomer (s) used in the invention as a block in a diene elastomer / polylactide copolymer are very particularly chosen from the group of diene elastomers constituted by polybutadienes (abbreviated "BR"), polyisoprenes (IR) synthesis, natural rubber (NR), butadiene copolymers, isoprene copolymers, ethylene and diene copolymers and mixtures of these polymers. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene copolymers- butadiene-styrene (SBIR), halogenated or non-halogenated butyl rubbers, and copolymers of ethylene and butadiene (EBR).

The diene elastomer block advantageously has a number-average molar mass, Mn, greater than 25,000 g / mol, advantageously greater than or equal to 30,000 g / mol, even more advantageously greater than or equal to 40,000 g / mol.

In one embodiment, the number-average molar mass, Mn, of the diene elastomer block advantageously varies from 40,000 g / mol to 250,000 g / mol, even more advantageously from 50,000 g / mol to 200,000 g / mol . This embodiment is particularly suitable for the preparation of tri-blocks of structure PLLA - diene elastomer - PLLA or of structure PDLA-diene elastomer - PDLA.

In another embodiment, the number average molar mass, Mn, of the diene elastomer block advantageously ranges from 100,000 g / mol to 500,000 g / mol. This embodiment is particularly suitable for the preparation of comb copolymers, having a diene elastomeric trunk and pendant blocks PLLA, or PDLA respectively, distributed along the trunk.

In another embodiment, the number-average molar mass, Mn, of the diene elastomer block advantageously varies from more than 25,000 g / mol to 150,000 g / mol, advantageously from more than 40,000 g / mol to 150,000 g / mol. This embodiment is particularly suitable for the preparation of di-blocks of structure PLLA - diene elastomer or of structure PDLA-diene elastomer.

111-1 -2 Synthesis of copolvmers A1 and B1

These copolymers A1 and B1 can be prepared by reactive extrusion.

The copolymers are in particular those obtained by the process described below.

In this process, the following are introduced into an extruder:

- L-lactide or D-lactide;

a diene elastomer functionalized by at least one group carrying at least one function capable of initiating polymerization by ring opening of L-lactide or D-lactide; and

a catalytic system. In a first embodiment, the functionalized diene elastomer is a diene elastomer functionalized by two end groups, each group carrying at least one function capable of initiating polymerization by ring opening of L-lactide or D-lactide. The copolymer which will thus be obtained will be a tri-block of structure PLLA-diene elastomer-PLLA or of structure PDLA-diene elastomer-PDLA.

In this embodiment, the number-average molar mass, Mn, of the diene elastomer advantageously varies from 40,000 g / mol to 250,000 g / mol, even more advantageously from 50,000 g / mol to 200,000 g / mol .

In a second embodiment, the functionalized diene elastomer is a diene elastomer functionalized by several pendant groups distributed along the trunk, each group carrying at least one function capable of initiating polymerization by ring opening of L-lactide or D lactide. The copolymer which will thus be obtained will be a comb copolymer having a diene elastomeric trunk and pendant polylactide blocks.

In this embodiment, the number-average molar mass, Mn, of the diene elastomer advantageously varies from 100,000 g / mol to 500,000 g / mol.

In a third advantageous embodiment of the invention, the functionalized diene elastomer is a diene elastomer functionalized with a terminal group, carrying at least one function capable of initiating ring-opening polymerization of L-lactide or D-lactide . The copolymer which will thus be obtained will be a di-block of structure PLLA-diene elastomer or of structure PDLA-diene elastomer.

In this embodiment, the number-average molar mass, Mn, of the diene elastomer advantageously varies from more than 25,000 g / mol to 150,000 g / mol, advantageously from more than 40,000 g / mol to 150,000 g / mol.

Functions capable of initiating polymerization by opening the lactide ring are more particularly alcohol functions -OH or primary amine -NH ₂ .

The diene elastomers functionalized by one or two terminal group (s) (first and third advantageous embodiments of the invention) can be prepared by various methods known to those skilled in the art, in particular by functional priming, by termination reaction with a functionalizing agent or by coupling. A process for the preparation of a diene elastomer functionalized by one or two terminal group (s) amine is for example described in the publication Schulz et al., Journal of Polymer Science, vol. 15, 2401-2410 (1977).

The diene elastomer functionalized by several pendant groups (second advantageous embodiment of the invention) can be prepared by various methods known to those skilled in the art, in particular by grafting. The diene elastomer functionalized by nucleophilic groups along the main chain can be functionalized during a stage of functionalization of the main chain of the elastomer by different techniques, for example by radical reaction, by hydrosilylation, by oxidation of unsaturation followed by 'a hydrogenation. Functionalization makes it possible to obtain a polymer functionalized by nucleophilic groups, advantageously primary amine or alcohol.

In particular, the diene elastomer can be functionalized by radical reaction according to the process described in application WO 2014/095925.

During reactive extrusion, L-lactide or D-lactide reacts with the function (s) carried by the grouping of the functionalized elastomer then the L-lactide or D-lactide polymerizes , by cycle opening, to form one or more PLLA block (s) respectively PDLA.

As described above, the groupings can be pendant along the trunk or terminals. This process thus allows controlled polymerization, by growth of a polylactide chain from each initiator function carried by each group, pendant or terminal, of the diene elastomer. In said grouping, the function capable of initiating polymerization by opening the lactide cycle, also called initiator function, is advantageously terminal.

Advantageously, the functionalized diene elastomer is a diene elastomer functionalized by at least two groups, identical or different, each carrying at least one function capable of initiating polymerization by opening of the lactide cycle, thus leading to tri-block or comb copolymers .

The diene elastomer functionalized by at least two groups can in particular be represented by the following formulas:

(III) ^F - diene elastomer - F

diene elastomer

In these two formulas (III), (IV), the group F is a group carrying at least one function capable of initiating polymerization by opening the lactide cycle. The group F can be different within the same formula.

As explained above, the elastomers of formula (III) will lead to tri-blocks while the elastomers of formula (IV) will lead to comb copolymers.

Advantageously, the method comprises the following successive steps: at. Introduction into an extruder of L-lactide or D-Lactide and of said functionalized diene elastomer, also called functionalized elastomer;

b. Mixture of components introduced in step a); then

vs. Introduction of the catalytic system to the mixture obtained following step b), the introduction of the catalytic system triggering the polymerization; then d. Introduction of a catalyst inhibitor to stop polymerization; e. Recovery of the copolymer at the outlet of the extruder.

Steps a) and b) make it possible to homogenize the mixture and to ensure that the subsequent polymerization proceeds optimally. Advantageously, during step a), all of the functionalized elastomer is introduced.

Since the lactide is sensitive to water and humidity, the functionalized elastomer is advantageously dried beforehand. Advantageously, the residual water content in the diene elastomer is less than 2000 ppm, more advantageously less than 1000 ppm. Advantageously, the residual water content in the lactide is less than 500 ppm, more advantageously less than 300 ppm.

In addition, steps a) and b) are advantageously carried out under anhydrous conditions, for example under the sweeping of an inert gas such as nitrogen, in order to avoid any homopolymerization of the lactide.

In step a), all of the L-lactide or D-lactide or part of the L-lactide or D-lactide can be introduced.

In a first embodiment, during step a), all of the L-lactide or D-lactide is introduced.

In a second embodiment, during step a), part of the L-lactide or of the D-lactide is introduced, advantageously at least 50% by weight, relative to the total amount of the L-lactide or of the D -lactide, more advantageously at least 70% by weight.

The remaining part of L-lactide or D-lactide will be added during step c), previously or simultaneously with the introduction of the catalytic system.

Advantageously, the method comprises the following successive steps:

at. Introduction into an extruder of part of the L-lactide or of the D-lactide and of said functionalized elastomer;

b. Mixture of components introduced in step a); then

vs. Introduction of the remaining part of the L-lactide or of the D-lactide and of the catalytic system to the mixture obtained following step b), the introduction of the catalytic system triggering the polymerization; then d. Introduction of a catalyst inhibitor to stop the polymerization; e. Recovery of the copolymer at the outlet of the extruder.

In the process, whatever the embodiment, is introduced, in one or more times, preferably either L-lactide or D-lactide.

The polymerization of L-lactide or D-lactide begins when the catalytic system is added. It is understood of course that the catalytic system comprises a catalyst allowing the polymerization by opening of the lactide cycle, catalyst which will be described later.

The polymerization is advantageously carried out at a temperature ranging from 80 ° C to 200 ° C, more advantageously ranging from 100 ° C to 200 ° C, even more advantageously ranging from 150 ° C to 200 ° C.

The method is characterized in that the polymerization is carried out in an extruder. Any type of extruder allowing the mixing of components can be used: single-screw extruder, two-stage or co-kneader (in English: co-kneader), twin-screw, planetary gear, rings. Twin screw extruders are particularly suitable. The extruder can allow a continuous or discontinuous process.

For a type of process, continuous or discontinuous, the Long / Dia (length / diameter) ratio of the extruder is adapted as a function of the polymerization time, depending on the flow rate and the residence time. In a continuous process, the Long / Dia ratio can for example be greater than 20, more advantageously greater than 40. It can for example be 56 for a continuous twin-screw extruder and a polymerization time less than 30 minutes. In a batch process, it can for example be 5 or 6 for a micro-extruder and a polymerization time of less than 30 minutes.

In the advantageous embodiment implementing steps a) to e), these steps a) to e) are advantageously carried out in one and the same extruder, mainly for practical reasons. However, one could consider using an extruder for steps a) and b) and another extruder for steps c) to e).

The mixture of stage a) is advantageously carried out under a weaker mixing than the mixture of stage c) of polymerization, in particular so as not to degrade the diene elastomer functionalized during stage a). Those skilled in the art know how to adapt the speed of rotation of the screws of the extruder, its design in the mixing zones as a function of the mixing which it wishes to obtain.

An inhibitor of the catalytic system is introduced during step d), of course after mixing in the previous step for a time sufficient to reach the desired degree of polymerization. During step e), before recovery from the copolymer, the process according to the invention can comprise a step of evaporation of the unreacted volatile components, in particular of the unreacted lactide.

The method according to the invention makes it possible to obtain satisfactory conversions into durations compatible with industrial use. In particular, the polymerization time is advantageously less than 30 minutes, more advantageously it varies from 5 minutes to less than 30 minutes.

In the process according to the invention, it is also possible to introduce, advantageously from step a), an antioxidant agent which makes it possible to avoid degradation of the diene elastomer. This antioxidant agent can also make it possible to avoid depolymerization of the polylactide blocks or of couplings between the chains of diene elastomer / polylactide copolymers formed. The antioxidant agent is described below.

The polymerization is advantageously carried out in bulk, that is to say without adding any additional solvent. The process can be continuous or discontinuous.

In a first embodiment, the process is continuous. Steps a) to e) are therefore simultaneous and take place in different areas of the extruder. For example, step a) is carried out in a feeding zone (located upstream in the extruder), then step b) in a mixing zone. Even further downstream, the extruder includes a catalytic system introduction zone and then a mixing zone. Still further downstream, the extruder includes a zone for introducing the inhibitor of the catalytic system, mixing and then evaporation of the unreacted volatiles with exit and recovery of the copolymer.

It is understood that the upstream is located at the head of the extruder (feeding zone). Relative to a reference point, a downstream area is an area closer to the exit of the extruder.

In a second embodiment, the process is discontinuous. Steps a) to e) are therefore spread out over time and can take place in the same area of the extruder. Steps a) to e) can thus be carried out in cycles, the product leaving the extrusion zone being returned to the supply of the extruder. Step a) corresponds to the start of the first cycle. Then step b) is carried out for a predetermined number of cycles. During step c), the catalytic system is introduced and then the predetermined number of cycles is carried out. During step d), the inhibitor of the catalytic system is introduced and then the predetermined number of cycles is carried out to evaporate the unreacted products before leaving and recovering the copolymer.

To achieve the polylactide, PLLA or PDLA ratios desired in the copolymer, the mass percentage of L-lactide or of D-lactide introduced advantageously varies from 12% to 55% by weight, more advantageously from 12% to 47% by weight, relative to the total weight of functionalized diene elastomer and of L-lactide or of D-lactide introduced.

111-1.2.1. Catalytic system:

The lactide polymerization reaction by ring opening is carried out in the presence of a catalytic system, as is known to those skilled in the art.

A first example of a suitable catalytic system is that described in patent application WO98 / 02480.

This catalytic system comprises at least one catalyst and optionally at least one cocatalyst.

Preferably the catalyst is of formula (V)

(M) (X ¹ , X ² .... X ^m ) _n

(V)

in which

M is a metal selected from the metals of group 2, 4, 8, 9, 10, 12, 13, 14 and 15 of the periodic table of the elements;

X ¹ , X ² ... X ^m is a substituent selected from the alkyl, aryl, oxide, carboxylate, halide, alkoxy, alkyl ester groups;

m is an integer between 1 and 6, and

n is an integer between 1 and 6, the values of m and n depend on the degree of oxidation of the metal ion.

"Alkyl" denotes a linear or branched, saturated, hydrocarbon group of 1 to 20 carbon atoms, in particular from 1 to 16 carbon atoms, in particular from 1 to 12 carbon atoms, in particular from 1 to 10 atoms and more particularly from 1 to 6 carbon atoms. By way of example, are included in this definition radicals such as methyl, ethyl, isopropyl, n-butyl, t-butyl, t-butylmethyl, n-propyl, pentyl, n-hexyl, 2-ethylbutyl, heptyl, octyl , nonyle, or décyle.

"Aryl" denotes an aromatic ring comprising from 1 to 3 aromatic rings, optionally fused, from 6 to 20 carbon atoms, in particular from 6 to 10 carbon atoms. As examples of aryl groups, it is possible to mention phenyl, phenetyl, naphthyl or anthryl.

"Alkoxy" denotes a group of general formula R-O- where R is an alkyl group as defined above. By way of example, mention may be made of methoxy, ethoxy, propoxy, t-butoxy, n-butoxy, isobutoxy, sec-butoxy, n-pentoxy, isopentoxy, sec-pentoxy, t-pentoxy, hexyloxy, isopropoxy groups.

"Halide" means a chloride, fluoride, iodide or bromide. In group 2 the use of Mg and Ca are preferred. In group 4, the use of Ti, Zr and Hf can be mentioned. Within group 8 the use of Fe is preferred. Within group 12 the use of Zn is preferred. Within group 13 the use of Al, Ga, In and Tl can be mentioned. Within group 14 the use of Sn is preferred. Within group 15 the use of Sb and Bi is preferred. In general, the use of metals from Groups 4, 14 and 15 is preferred. It is preferable that M is chosen from Sn, Zr, Hf, Zn, Bi and Ti. The use of an Sn-based catalyst may be particularly preferred.

For halides, tin halides such as SnCI ₂ , SnBr ₂ , SnCI and SnBr ₄ can be mentioned. For the oxides SnO and PbO can be mentioned. In the group of alkyl esters, octoates (for example, 2-ethyl hexanoate), stearates, acetates can be mentioned. In particular, Sn-octanoate, (also known as Sn (II) bis 2-ethylhexanoate or simply as tin octoate), tin stearate, dibutyltin diacetate, butyltin tris (2- ethylhexanoate), tin (2-ethylhexanoate), bismuth (2-ethylhexanoate), tin triacetate, sodium (2-ethyl hexanoate), calcium stearate, magnesium stearate and zinc stearate can be mentioned. Mention may also be made of Ti (OiPr) ₄ , Ti (2-ethylhexanoate) ₄ , Ti (2-ethylhexylate) ₄ , Zr (OiPr) ₄ , Bi (neodecanoate) ₃ or Zn (lactate) ₂ . Other suitable compounds include tetraphenyltin, Sb tris (ethylene glycolate), aluminum alkoxy and zinc alkoxy.

The catalytic system can also comprise a co-catalyst, advantageously of formula (VI)

(Y) (Ri, ¾ ... Rq) p

(VI)

or

Y is an element selected from elements in group 15 and / or 16 of the periodic table,

Ri, R ₂ ... R _q is a substituent selected from the group comprising alkyls, aryls, oxides, halides, alkoxy, aminoalkyls, thioalkyls, phenyloxy, aminoaryls, thioaryls, and compounds containing the elements of group 15 and / or 16 of the periodic table

q is an integer between 1 and 6, and

p is an integer between 1 and 6.

Preferably, the catalytic system comprises the bis (2-ethylhexanoate) of tin as catalyst and the triphenylphosphine PPh ₃ as cocatalyst. The molar ratio between the co-catalyst and the catalyst can be between 1/10 and 10/1, preferably between 1/3 and 3/1. More preferably, the molar ratio between the cocatalyst and the catalyst can be 1/1.

The molar ratio between the lactide and the tin bis (2-ethylhexanoate) catalyst can range from 50/1 to 1000/1, preferably from 100/1 to 900/1, more preferably from 200/1 to 800/1.

When another catalyst is used, a person skilled in the art knows how to adapt the quantities and the temperature thereof to respect the same catalytic activity.

Other catalytic systems can also be used and one can in particular refer to the article Kamber et al. (Organocatalytic ring-opening polymerization, Nahrain E. Kamber et al., Chem. Rev. 2007, 107.5813-5840).

Mention may also be made of organic catalysts of the guanidine family, more particularly of TBD: 1,5,7-triazabicyclo [4.4.0] dec-5-ene (Cyclic guanidine organic catalysts; what is magic about triazabicyclodecene?, Matthew K. Kiesewetter et al., J. Org. Chem., 2009, 74, 6490-9496) or N-heterocyclic olefins (Highly polarized alkenes as organocatalysts for the polymerization of lactones and trimethylene carbonate, stefen naumann et al., ACS Macro Lett., 2016, 5, 134-138). 1.2.2. Antioxidant and polymerization inhibitor:

In the process according to the invention, an antioxidant can be added from step a).

This antioxidant agent is preferably not very nucleophilic so as not to initiate the polymerization by opening of the lactide cycle.

Antioxidant agents of the polylactide are described in particular in US patents 6, 143,863 or EP 912,624.

Organophosphites such as bis (2,4-di-t-butylphenyl) pentraerythritol diphosphite (trade name: Ultranox® 626) are particularly effective.

Hindered phenolic antioxidants such as Irganox® 1070 are also particularly effective.

The polymerization inhibitor (cata-killer) added during step d) of the process can also have an antioxidant effect.

The inhibitors of the catalytic system used in the process of the invention are known to those skilled in the art. We can, for example, refer to US patents 6,1 14,495 or EP 912,624.

Mention may in particular be made of the following commercial products: Irganox® 1425 or Plrganox® 195, which are both phosphonates, doverphos® S680 or doverphos® LP09, which are both phosphites, polyacrylic acid, tartaric acid. Finally, the functionalized elastomer introduced may comprise an antioxidant agent which has been added at the end of the synthesis of the functionalized elastomer.

The antioxidant added at the end of the synthesis of the functionalized elastomer is any antioxidant known to be effective in preventing the aging of elastomers due to the action of oxygen.

Mention may in particular be made of para-phenylene diamine derivatives (abbreviated to "PPD" or "PPDA"), also known in a known manner as substituted para-phenylene diamines, such as for example N-1, 3-dimethylbutyl-N ' -phenyl-p-phenylene diamine (better known under the abbreviated term "6-PPD"), N-isopropyl-N'-phenyl-p-phenylenediamine (abbreviated as "l-PPD"), phenyl-cyclohexyl- p-phenylene diamine, N, N'-di (1,4-dimethyl-pentyl) -p- phenylene diamine, N, N'-diaryl-p-phenylene diamine ("DTPD"), diaryl- p-phenylene diamine ("DAPD"), 2,4,6-tris- (N-1,4-dimethylpentyl-p-phenylenediamino) -1, 3,5-triazine, and mixtures of such diamines.

Mention may also be made of substituted diphenylamines or triphenylamines, as described for example in applications WO 2007/121936, WO 2008/055683 and WO2009 / 138460, in particular 4,4'-bis (isopropylamino) -triphenylamine, 4, 4'-bis (1, 3-dimethylbutylamino) -triphenylamine, 4,4'-bis (1, 4-dimethylpentylamino) -triphenylamine, 4,4 ', 4 "-tris (1,3-dimethylbutylamino) -triphenylamine , 4,4 ', 4 "-tris (1,4-dimethylpentylaminoj-triphenylamine.

Mention may also be made of dialkylthiodipropionates or also phenolic antioxidants, in particular of the family of 2,2'-methylene-bis- [4-alkyl (C '| -Ci o) -6- (Ci -Ci2) alkyl P ^h enols , as described in particular in application WO 99/02590.

Of course, in the present description, the term antioxidant can designate both a single antioxidant compound or a mixture of several antioxidant compounds.

Preferably, the antioxidant is chosen from the group consisting of substituted p-phenylene diamines, substituted diphenylamines, substituted triphenylamines, and mixtures of such compounds; even more preferably, the antioxidant is chosen from the group consisting of substituted p-phenylene diamines and mixtures of such diamines.

III-2. Polylactides A2 and B2

According to certain embodiments, the polymer A and / or the polymer B) can also comprise respectively a polylactide A2 and / or B2.

The polylactide A2 and / or B2 is advantageously a homopolymer with a number-average molar mass, Mn, of less than 150,000 g / mol. Preferably, the number-average molar mass, Mn, of the polylactide A2 and / or B2 is between 2,000 g / mol and 150,000 g / mol, more preferably between 3,000 g / mol and 100,000 g / mol.

Such homopolymers are commercially available.

Advantageously, only one of the two polymers A and B comprises such a polylactide, respectively A2 or B2.

III-3. Additional diene elastomer

The total amount of additional diene elastomer, optional, is included in a range varying from 0 to 70 phr, advantageously 0 to 50 phr, more advantageously 0 to 10 phr. Also very preferably, the elastomeric mixture does not contain an additional diene elastomer.

The additional diene elastomer of the elastomer mixture is preferably chosen from the group of diene elastomers constituted by polybutadienes, synthetic polyisoprenes, natural rubber, butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably chosen from the group consisting of styrene copolymers (SBR, SIR and SBIR), polybutadienes (BR) and natural rubber (NR).

The number average molar mass, Mn, of the additional diene elastomer can vary widely, for example from 20,000 g / mol to 1,000,000 g / mol. 4. Preparation of the elastomeric mixture according to the invention:

The elastomeric mixture according to the invention comprising polymers A) and B) can be prepared in solution or in bulk.

According to one embodiment, the preparation in solution of the elastomeric mixture according to the invention comprises the preparation of a solution of polymer A) and of a solution of polymer B), if necessary of a solution of the diene elastomer additional, then mixing of these solutions.

In particular, the process for preparing the elastomeric mixture according to the invention in solution comprises the following steps:

at. Dissolution of a polymer A) in a solvent;

b. Dissolution of a polymer B) in a solvent;

vs. Mixing of the two solutions obtained in step a) and b);

d. Recovery of the elastomeric mixture after removal of the solvents. Preferably, the solution of polymer A) has a concentration of polymer A) of between 2 and 30% by weight relative to the total weight of the solution.

Preferably, the solution of polymer B) has a concentration of polymer B) of between 2 and 30% by weight relative to the total weight of the solution.

Advantageously, the polymer A), respectively the polymer B), is in solution in a solvent suitable for its dissolution, for example chloroform, tetrahydrofuran, dichloromethane, toluene.

Preferably, step c) of mixing takes place at room temperature, for a few minutes.

Alternatively, the preparation of the elastomeric mixture according to the invention comprises mass mixing of the polymer A), of the polymer B), if necessary of the additional diene elastomer, at a temperature higher than the melting temperature of the combination of PLLA and PDLA.

In particular, the process for the mass preparation of the elastomeric mixture according to the invention comprises the following successive steps:

at. Introduction into polymers A) and B) into an extruder;

b. Molten mixture of the components introduced in step a); then

vs. Recovery of the elastomeric mixture at the outlet of the extruder.

In step b. the mixing takes place at a temperature above the melting temperature of the combination of PLLA and PDLA, preferably at a temperature ranging from 150 ° C to 300 ° C.

Any type of extruder allowing the mixing of components can be used: single-screw extruder, two-stage or co-kneader (in English: co-kneader), twin-screw, planetary gear, rings. Twin screw extruders are particularly suitable. The extruder can allow a continuous or discontinuous process.

In particular, the mixing time varies from 2 minutes to 10 minutes, more advantageously from 3 minutes to 7 minutes.

Advantageously, the mixing speed varies from 50 to 100 revolutions per minute (rpm), more advantageously from 60 to 90 rpm.

Preferably, the elastomeric mixture according to the invention is prepared en masse.

III-4. Composition of rubber and Pneumatics

The invention also relates to a rubber composition comprising the elastomeric mixture according to the invention. Advantageously, the elastomeric mixture according to the invention represents at least 30% by weight of the composition, more advantageously at least 40% by weight, even more advantageously at least 50% by weight. In particular, the polymers A) and B) of the elastomeric mixture can represent the majority polymers by weight of the rubber composition or even the only polymers of the rubber composition. The amount of polymers A) and B) is within a range which advantageously varies from 30 to 100 phr, more advantageously from 50 to 100 phr, even more preferably from 90 to 100 phr. The polymers A) and B) preferably represent the only polymers of the rubber composition, in particular of the tread.

The rubber composition is a rubber composition which can be used in the manufacture of a tire, in particular for the preparation of a tread. The elastomeric mixture according to the invention makes it possible to manufacture a tread making it possible to obtain a very good compromise in performance in grip and in rolling resistance. The rubber composition can comprise, in addition to the elastomeric mixture, one (that is to say one or more) additives, such as a nanometric or reinforcing filler, a plasticizer or other additive, for example conventionally used in a composition for pneumatic.

Nanometric or reinforcing filler

The elastomeric mixture comprising polymers A) and B) is sufficient in itself so that the tread according to the invention can be used.

When a reinforcing filler is used, any type of filler usually used for the manufacture of tires can be used, for example an organic filler such as carbon black, an inorganic filler such as silica, or a blend of these. two types of filler, in particular a blend of carbon black and silica.

Due to the presence of the composition according to the invention in the rubber composition, satisfactory rigidity properties can be obtained even when the content of reinforcing filler is reduced.

To couple the reinforcing inorganic filler to the elastomeric mixture, it is for example possible to use a coupling agent (or bonding agent) at least bifunctional intended to ensure a sufficient connection, of chemical and / or physical nature, between the inorganic filler (surface of its particles) and the elastomeric mixture, in particular organosilanes or bifunctional polyorganosiloxanes. plasticizers

However, according to a preferred embodiment of the invention, the rubber composition can also further comprise a plasticizing agent, such as an oil (or plasticizing oil or extension oil) or a plasticizing resin whose function is to facilitate the implementation of the tread, particularly its integration into the tire by lowering the module and increasing the tackifying power.

- Solid plasticizer:

The solid plasticizer is a plasticizing resin.

In a manner known to those skilled in the art, the name "resin" is reserved in the present application, by definition, to a thermoplastic compound which is a solid at room temperature (23 ° C), in contrast to a liquid plasticizing compound such than an oil.

Resins are polymers well known to those skilled in the art, which can be used in particular as plasticizers or tackifiers in polymeric matrices. They are by nature miscible (i.e., compatible) at the rates used with the polymer compositions for which they are intended, so as to act as true diluents. They have been described for example in the work entitled "Hydrocarbon Resins" by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), chapter 5 of which is devoted to their applications, notably in pneumatic rubber (5.5. "Rubber Tires and Mechanical Goods').

- Liquid plasticizer:

The plasticizer is a liquid plasticizing agent (at 23 ° C) whose function is to soften the matrix by diluting the elastomer and the reinforcing filler; its Tg is preferably less than -20 ° C, more preferably less than -40 ° C.

Any extension oil, whether of an aromatic or non-aromatic nature, any liquid plasticizing agent known for its plasticizing properties with respect to diene elastomers, can be used. At room temperature (23 ° C), these more or less viscous plasticizers or oils are liquids (that is to say, substances having the capacity to take the form of their container in the long term) , as opposed in particular to plasticizing resins which are by nature solid at room temperature. Other additives

The rubber composition may furthermore comprise the various additives usually present in compositions for tires, in particular treads, known to those skilled in the art. One or more additives will be chosen, for example, chosen from protective agents such as antioxidants or antiozonants, anti-UV, various implementing agents or other stabilizers, or alternatively promoters capable of promoting adhesion to the rest of the structure. of the pneumatic object.

In an advantageous variant of the invention, particular mention will be made of antioxidant agents, nucleating agents.

Also and optionally, the rubber composition may contain a crosslinking system known to those skilled in the art.

When in the elastomeric mixture at least one of the copolymers A1 or B1 is a tri-block copolymer or a comb copolymer, the rubber composition may not contain a crosslinking system. Preferably, the rubber composition does not contain a crosslinking system.

When in the elastomeric blend the copolymers A1 or B1 (where appropriate) are di-block copolymers, the rubber composition advantageously contains a crosslinking system.

The crosslinking system may be a vulcanization system, it is preferably based on sulfur or on sulfur donors and the primary vulcanization accelerator (preferably 0.5 to 10.0 phr of primary accelerator). To this vulcanization system are optionally added, various secondary accelerators or known vulcanization activators such as zinc oxide (preferably for 0.5 to 10.0 pce), stearic acid, guanidic derivatives (in particular diphenylguanidine), or others (preferably for 0.5 to 5.0 pce each). Sulfur is used at a preferential rate of between 0.5 and 10 phr, more preferably of between 0.5 and 5.0 phr, for example between 0.5 and 3.0 phr when the invention is applied to a strip. tire bearing.

The rubber composition may contain one or more inert, micrometric fillers such as the lamellar fillers known to those skilled in the art. Preferably, the rubber composition does not contain a micrometric filler.

Advantageously, the rubber composition comprises several additives, in particular antioxidant agents, nucleating agents, fillers; as defined above. The invention also relates to a tire of which one of its constituent elements comprises the elastomeric mixture according to the invention or the rubber composition described above. This constituent element is advantageously the tread.

In particular, one of the constituent elements of the tire comprises the elastomeric mixture according to the invention or the rubber composition described above.

The elastomeric mixture or the rubber composition according to the invention makes it possible to manufacture a tread making it possible to obtain a very good compromise in performance in grip and in rolling resistance.

IV- EXAMPLES OF IMPLEMENTATION OF THE INVENTION

Measurements and tests used

1. Determination of the distribution of molar masses by SEC RI equivalent PS It is determined by size exclusion chromatography (SEC) in polystyrene equivalent. The SEC allows the macromolecules in solution to be separated according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first. Without being an absolute method, the SEC makes it possible to apprehend the distribution of the molar masses of a polymer. From commercial standard products, the various number-average molar masses (Mn) and by weight (Mw) can be determined and the polymolecularity or polydispersity index (Ip = Mw / Mn) calculated via a so-called MOORE calibration.

Polymer preparation: There is no special treatment of the polymer sample before analysis. It is simply dissolved in chloroform, at a concentration of about 2 g / l. The solution is then filtered on a filter with a porosity of 0.45 μm before injection.

SEC analysis: The apparatus used is an “Agilent 1200” chromatograph. The eluting solvent is chloroform. The flow rate is 1 ml / min, the system temperature 30 ° C and the analysis time 30 min. A set of three Agilent columns is used in series preceded by a filter, with the trade names "PLgel 10 pm (precolumn)" and two "PLgel 10 pm mixed B". The injected volume of the polymer sample solution is 100 µl. The detector is an “Agilent 1200” differential refractometer and the software for operating the chromatographic data is the “Chemstation” system. The calculated average molar masses are relative to a calibration curve made from commercial standard polystyrenes "Agilent-KIT PS".

2. Determination of the composition of the copolvmers A1 and B1 by NMR

The determination of the polylactide levels in the copolymers A1 and B1 and the microstructures of the diene elastomers within the copolymer are carried out by an NMR analysis.

The samples (approximately 20 mg) are dissolved in 1 ml of CDCI ₃ and introduced into a 5mm NMR tube. The spectra are recorded on an Avance III HD 500 MHz Bruker spectrometer equipped with a BBFO 1 HX 5mm Z_GRD probe. The spectra are calibrated on the CDCI ₃ signal at 7.20ppm in ¹ hour.

The quantitative ¹ H NMR experiment used is a single pulse sequence with a tilt angle of 30 ° and a recycling time of 5 seconds between each acquisition. 64 accumulations are recorded at room temperature. The spectra are calibrated on the CDCI ₃ signal at 7.20ppm in 1 hour.

When the diene elastomer is an SBR, we observe the signals of the SBR, as well as those of the PLA, which will be used for the quantification:

- CH of the polylactide at d ¹ H = 5.1 ppm and 5 ¹³ C = 68.8 ppm

- CH ₃ of the polylactide at d ¹ H = 1.51 ppm and 6 ¹³ C = 16.5 ppm

The partially soluble samples in CDCI ₃ are analyzed by NMR with rotation at the magic angle HR-MAS (High Resolution - Magic Angle Spinning) in medium swollen in deuterated chloroform. The samples (approximately 10 mg of elastomer) are introduced into a 92 μL rotor containing CDCI ₃ . The spectra are recorded on an Avance III HD 500 MHz BRUKER spectrometer equipped with a dual 1 H / 13C HRMAS Z-GRD 4mm probe.

The quantitative ¹ H NMR experiment used is a single pulse sequence with a tilt angle of 30 ° and a recycling time of 5 seconds between each acquisition. 128 accumulations are recorded at room temperature. The spectra are calibrated on the CDCI ₃ signal at 7.20ppm in 1 hour.

The quantification method is identical to that of soluble samples.

3. DSC (differential scanning calorimetry)

The melting temperatures, enthalpies of melting and glass transition temperatures Tg of the polymers are measured using a differential scanning calorimeter. The copolymers or the mixtures were analyzed by DSC on a DSC Q200 apparatus of the TA instrument brand under the following operating conditions: 1st heating from -40 ° C to 230 ° C (10 ° C / min), cooling 230 ° C to -70 ° C (10 ° C / min), 2nd heating from -70 ° C to 200 ° C (10 ° C / min). The melting temperatures and enthalpies are measured on the ^1st heating.

Method for measuring the degree of crystallinity

ISO 1 1357-3: 2011 is used to determine the temperature and the enthalpy of fusion and crystallization of the polymers used by differential scanning calorimetry (DSC). The reference enthalpy of the polylactide is often given at 93kJ / mol.

Crystallinity = AHf / AHf _PLA

4. Mechanical tests

- Tensile experiences 50 mm / min

The breaking stress (MPa), the breaking strain (%) are measured by tensile tests according to the international standard ASTM D638 (year 2002). All these traction measurements are carried out under normal temperature (23 ± 2 ° C) and hygrometry (50 ± 5% relative humidity) conditions, according to international standard ASTM D638 (year 2002). The measurements are carried out on type V test pieces at a tensile speed of 50 mm / min on a Lloyd LR 10k machine. The deformation is measured by following the displacement of the cross-member.

- Traction experiences 500 mm / min

The breaking stress (MPa), the breaking strain (%) are measured by tensile tests according to French standard NFT 46-002 of September 1988. All these tensile measurements are carried out under normal temperature conditions ( 23 ± 2 ° C or 100 ° C ± 2 ° C) and humidity (50 ± 5% relative humidity), according to French standard NFT 40-101 (December 1979). The measurements are carried out on H2 test pieces at a tensile speed of 500mm / min on a Zwik machine. The deformation is measured by following the displacement of the cross-member.

From the stress and strain measurements, the so-called "nominal" secant modules (or apparent stresses, in MPa) are calculated at 10% strain ("MA10") and 100% strain ("MA100").

- Dynamic mechanical analysis (DMA) in temperature

The linear viscoelastic properties of these materials are measured by sinusoidal elongation of low deformation (0.1%). The measurements are carried out on a dynamic mechanical analyzer (DMA) TA instrument (DMA800) with imposed deformation on test pieces of rectangular shape and dimensions (mm): 25 x 5 x 0.5. The samples are molded at 183 ° C for 5 minutes, then cut with a cookie cutter. The elastic conservation module E ', the viscous module E''and the tanô loss factor are measured during a scanning in film tension mode temperature; deformation = 10 pm, frequency = 1 Hz, -100 ° C -> 170 ° C (3 ° C / min). The following abbreviations are used:

SBR elastomer styrene - butadiene (in English: styrene-butadiene rubber)

LA lactide

LLA L-lactide

DLA D-lactide

PLA polylactide

PLLA poly-L-lactide

PDLA poly-D-lactide

% PB 1, 2 molar ratio of polybutadiene units 1, 2- (vinyl)

% PB 1, 4 molar ratio of polybutadiene units 1, 4

% PS molar rate of styrenic units

Molar molar

Mass mass

DSC differential scanning calorimetry

DMA dynamic mechanical analysis

G * complex modulus in shear G * = (G ' ² + G ” ² ) ^1/2

Sn / P molar ratio Sn (oct) ₂ / P (Ph) ₃

T setpoint Extruder setpoint temperature

Tmixture Temperature of the mixture in the extruder measured

Vvis Rotation speed of the extruder screws

Tf PLA Melting temperature of the polylactide phase in ° C

AHf _PLA Enthalpy of fusion of the polylactide phase in J / g

Example 1: PLLA-SBR-PLLA and PDLA-SBR-PDLA tri-block copolymers obtained by polymerization of L-lactide or D-lactide on a di-functionalized amine SBR in reactive extrusion

Preparation of the di-functionalized SBR:

- Preparation of the initiator solution (Sa):

In a 30L reactor, are successively added: 1 1, 5L of methylcyclohexane (MCH), 1 L of 4-bromo-N, N-bis (trimethylsilyl) aniline (previously bubbled with nitrogen), 5.35L of a solution of s-BuLi at 1.4 mol / L in cyclohexane and 0.35 mol of tetramethylethylenediamine (TMED) previously purified on Al ₂ 0 ₃ . The reaction is left for 24 hours at room temperature. This solution is then stored at 15 ° C - 20 ° C under nitrogen before use. The solution thus obtained is called “solution Sa”.

- Polymerization and coupling:

The following different constituents are added successively to a reactor: 56L of MCH, 350ppm of tetrahydrofuran (THF), 2.7kg of styrene, 5kg of butadiene, 65mL of n-BuLi (0.1mol / L) and 1.07L of Sa solution.

After 50 min at 50 ° C., the conversion is 70%, and 0.48 equivalents (eq) of Me ₂ SiCI ₂ relative to Li ⁺ is added for coupling. The reaction medium is stirred at 50 ° C for 30 min.

Then added 0.4% by weight, relative to the weight of the elastomer, of a lrganox®2246 (2,2 '-Methylenebis (6-t-butyl-4-methylphenol)) / N-1 mixture, 3-dimethylbutyl-N- phenylparaphenylenediamine (80/20 m / m).

- Protection :

The deprotection conditions are as follows: hydrochloric acid is added to the polymer solution at the rate of 2 eq of HCl / amine, the whole is stirred for 48 h at 80 ° C.

The deprotection reaction finished, the reaction medium is washed with water in order to extract the maximum amount of acid and to raise the pH of the aqueous phase to 7. A sodium hydroxide solution can be used to raise the pH above of 7 (0.5 eq soda / HCl).

The polymer solution is then stripped, and the functionalized elastomer is dried in a rotary oven under nitrogen and then in an oven at 60 ° C under vacuum.

Results:

The number-average molar mass of the elastomer is 87300 g / mol (lp = 1.1) and the functional rate is 0.2% mol per chain of elastomer.

The other functionalized SBRs are synthesized using the same protocol.

The microstructures and macrostructures of these SBRs are given in the following table:

Preparation of the PLA-SBR-PLA T1, T2, T3 and T4 tri-blocks:

We use a DSG Xplore micro-extruder with a capacity of 15g according to the following process for TI:

1. Introduction of the functional SBR obtained previously, previously dried for 12 h under vacuum at 60 ° C to a residual water content of less than 300 ppm, (1 1, 2 g) in the micro-extruder (T set = 180 ° C, T mix = 170 ° C, Vvis = 60 rpm), 77% 2.8g of lactide L or D and U626 (antioxidant, ULTRANOX®626, Bis (2,4-di-t-butylphenyl) Pentaerythritol Diphosphite ). Lactide L or D and U626 have been mixed beforehand,

2. Mixing / homogenization of SBR and lactide L or D at Vvis = 60 revolutions / min for 2 min,

3. Introduction of the 23% of lactide L or D remaining in the presence of the catalytic solution Sn (oct) ₂ / P (Ph) ₃ ,

4. Polymerization of the polylactide (T set = 180 ° C, T mix = 170 ° C, V screw = 150 rpm),

5. When the couple has reached a plateau, introduction of the catalyst inhibitor (Irganox® 1425, 28 mg) to stop the polymerization.

The different operating conditions tested are reported in the following table:

Table 2

For each of the tri-block copolymers obtained (T1 to T4), the appearance on the ¹ H NMR spectra of proton signals -Ph-NH- (C = 0) - around 7.88 ppm, characteristic of PLA sequences, is observed. SBR-PLA.

The characteristics of the synthesized tri-block copolymers are given in the following table:

Table 3

¹ Mn of each polylactide block calculated by the following formula:

_{1 M} SBR, SEC eq.PS

l / ibloc P LA _ _ ^M n _. % massPLA ^NMR

⁷¹ 2 1 -% massPLA ^NMR

The SEC chromatograms of the materials obtained are consistent with the structures concerned. The molar masses of the materials obtained are greater than that of the initial functional SBR.

Preparation of the PLLA-SBR-PLLA T5 tri-block:

The tests were carried out in a twin-screw Collins brand extruder, having a length / diameter ratio of 56 and comprising 14 independent heating zones (length / diameter = 4), allowing continuous synthesis. The screw rotation speed is 70 rpm. The setpoint temperatures for the zones (also known as sleeves) are shown in the following table:

Table 4

The SBR-C was synthesized following the protocol given in Example 1.

The microstructures and macrostructures of this SBR are those of the SBR-C given in table 1. This SBR is dried for 12 h at 60 ° C. in air.

The L-lactide is introduced into the sheath # 1, the SBR-C in the sheath 2 and the catalytic system in the sheath # 1 with the L-lactide. The SBR / L-lactide mass ratio is 60/40. The molar ratio [LLA / Sn (oct) ₂ ] is 700 and triphenylphosphine P (Ph) ₃ is added in an amount making it possible to have a molar ratio (Sn / P) of 1/1.

The characteristics of the copolymer obtained are given in the following table:

Table 5

¹ Mn of each poly-L-lactide block calculated by the following formula:

Example 2: SBR-g-PLLA comb copolymer obtained by polymerization of L-lactide on an alcohol functional SBR in reactive extrusion

Comb-type copolymers (SBR-g-PLLA) are synthesized by lactide polymerization, in the presence of a functional SBR (SBD-D) having mercapto 1-butanol groups grafted along the chain.

This functional SBR is prepared by following the following procedure:

Functionalization:

After complete dissolution of 1 10g of SBR in 2.75L of methylcyclohexane, 6.3mL of 4-mercaptobutanol, previously dissolved in 135mL of dichloromethane, are added. Once the temperature of the reaction medium at 80 ° C., 1 g of lauroyl peroxide dissolved in 50 ml of methylcyclohexane are introduced with stirring. The medium is kept at 80 ° C. with stirring overnight.

At 80 ° C., 2 equivalents relative to the lrganox®2246 peroxide are added. After 15 minutes, 2 equivalents relative to the 6-PPD peroxide are added. After cooling, one or two coagulations in methanol are carried out.

The elastomer is then resolubilized, and 0.4% by weight, relative to the weight of the elastomer, of a lrganox®2246 / 6-PPD mixture (80/20) is added. The elastomer is then dried under vacuum at 50 ° C.

Results:

The functionalization obtained is 1.3% mol per elastomer chain, and the mass yield obtained is 82%.

The microstructures and macrostructures of this SBR-D are given in the following table:

Table 6

Conditions of the polymerization: the synthesis is carried out in a micro-extruder in accordance with the experimental protocol described in Example 1.

The different operating conditions tested are reported in the following table:

Table 7

For the comb copolymer obtained (CP1), it is observed on the ¹ H NMR spectra that the signal at 3.64 ppm has disappeared. Consequently all the -S- (CH ₂ ) 4-OH functions initiated the polymerization of the lactide.

The results are reported in the following table:

Table 8

¹ Mn of each block calculated by the following formula:

J .SBR.SEC eq.PS

fyfbloc PLLA _ _ n _% massPLLA ^NMR ⁷¹ Number of OH functions per chain ^' 1% massPLLA ^NMR' Example 3 Elastomeric Blends Comprising a PLLA-SBR-PLLA Tri-Block Copolymer (Polymer A) and a PDLA Polylactide (Polymer B)

Elastomeric mixtures are produced based on the tri-block copolymers T1 and T2 synthesized in Example 1 with PDLA polylactides whose molecular weights are given in the following table.

Table 9

These polylactides are homopolymers. PDLA 1 and PDLA DP400 were synthesized by reactive extrusion following the protocol described in patent application WO98 / 02480A1. The PDLA Corbion D070 was purchased from Corbion Purac and used as is.

The proportion of tri-block copolymers T1 or T2 and of polylactide PDLA in the elastomeric blends M1 to M4 is given in the following table in pce of tri-block copolymer T1 or T2. The compositions are also given in mass proportions of:

- SBR / total polylactide (PLLA in T1 or T2 + PDLA)

- SBR / PLLA blocks of the T1 or T2 copolymer / PDLA homopolymer.

The SBR is the SBR provided by the copolymer T1 or T2.

Table 10

The mixtures are prepared by:

-Dissolution of PDLA in chloroform,

-Dissolution of the tri-block copolymer T1 or T2 in chloroform, -Mixture of the 2 solutions in the mass proportions indicated above,

-Evaporation of the solvent without stirring,

-Recovery of a film (thickness = 0.6 mm),

-Drying at 40 ° C under vacuum.

The characterization by DSC of the mixtures is reported in the following table.

Table 11

Characterization by DSC shows:

for mixtures M1 to M4, the presence of stereocomplexed polylactide phase as evidenced by the melting temperatures of 216 to 219 ° C. of the crystalline phase,

- for mixtures M1 to M4, the absence of melting peaks at lower temperatures, which would have been characteristic of crystalline phases of non-stereocomplexed polylactides,

that the stereocomplex formation is more difficult (decrease in the enthalpy of fusion of the polylactide between M2 and M4) with the increase in the molar mass of PDLA.

In FIG. 1, the DMA characterizations of the tri-block copolymer T1 and of the mixture M1 are reported. A rubbery plateau which extends over a greater temperature range is observed for the mixture M1, this plateau extending up to 175 ° C. Example 4: Elastomeric Blends Comprising a PLLA-SBR-PLLA Tri-Block Copolymer (Polymer A) and a PDLA-SBR-PDLA Tri-Block Copolymer (Polymer B)

50% by weight of tri-block T3 and 50% by weight of tri-block T4 are mixed, the% being expressed relative to the total weight T3 + T4.

These mixtures can be done in solution or in bulk. In the following table are given, for the elastomeric mixtures M5 and M6, the proportion of copolymers in pce and the mass proportions of:

- total SBR / total polylactide (PLLA blocks in T3 + PDLA blocks in T4),

- Total SBR / PLLA blocks in T3 / PDLA blocks in T4.

The total SBR corresponds to the SBR provided by the copolymers T3 and T4.

Table 12

Example 4.1: preparation in solution

Preparation of the M5 elastomer mixture:

-Dissolution in chloroform of the tri-block copolymer T3,

-Dissolution in chloroform of the tri-block copolymer T4,

-Mixing of the 2 solutions according to mass proportions T3 T4 50/50,

-Evaporation of the solvent without stirring,

-Recovery of a film (thickness = 0.6 mm),

-Drying at 40 ° C under vacuum.

The results of the characterization by DSC of M5 and those of T3 and T4 by way of comparison are given in the following table:

Table 13

The DSC characterization of M5 shows the formation of stereocomplexed polylactide phase as evidenced by the melting temperature of 218 ° C of the crystalline phase and the enthalpy of fusion of M5 greatly increased compared to that observed for T3 or T4. EXAMPLE 4.2 Mass Preparation of the M6 Elastomer Mixture

The tri-block copolymers T3 and T4 are mixed in a horizontal micro-extruder

DSM (V = 7.5 cm ³ ) according to the following procedure:

- introduction of the tri-block copolymers T3 and T4 into the micro-extruder and mixing at a speed of 30 rpm for 1 minute at 190 ° C,

- mixing of the two tri-block copolymers T3 and T4 at 190 ° C at a speed of 75 rpm for 4 minutes,

- material recovery,

- pressing at 4 min at 200 ° C then 4 min at 235 ° C to form a plate (thickness:

0.6 mm) used in the following characterization tests.

The elastomeric mixture obtained is called M6.

The results of the DSC are reported in the following table.

Table 14

A stereocomplemented polylactide phase is observed for M6 with a high melting temperature. The tensile properties at 23 ° C and 90 ° C, each time at 50 mm / min, of the mixtures M5 and M6 are given in the following table as well as the properties of T3 for comparison.

Table 15 The deformation and breaking stress properties at 23 ° C are equivalent or better than those observed for T3. On the other hand, at 90 ° C., the breaking properties, in particular the breaking stresses, are improved by a factor of 20 compared to those obtained with T3.

EXAMPLE 5 Elastomeric Blend of SBR-g-PLLA Comb Copolymer (Polymer A) and of PDLA-SBR-PDLA Tri-Block Copolymer (Polymer B)

50% by weight of comb copolymer CP1 and 50% by weight of the tri-block copolymer T4 are mixed.

In the following table are given, for the mixture M7, the proportion in phr of copolymers and the mass proportions of:

- total SBR / total polylactide (PLLA blocks in CP1 + PDLA blocks in T4),

Total SBR / PLLA blocks in CP1 / PDLA blocks in T4.

The total SBR corresponds to the SBR provided by the copolymers CP1 and T4.

Table 16

The elastomeric mixture M7 is prepared from CP1 and T4 by mixing in a horizontal DSM micro-extruder (V = 7.5 cm ³ ) according to the following procedure:

- introduction of the 2 copolymers CP1 and T4 into the micro-extruder and mixing at a speed of 30 rpm for 1 minute at 190 ° C,

- mixing of the 2 copolymers CP1 and T4 at 190 ° C at a speed of 75 rpm for 4 minutes,

- material recovery,

- pressing at 235 ° C to form a plate (thickness: 0.6 mm) used in the following characterization tests.

The elastomeric mixture obtained is called M7.

According to the characterizations by DSC reported in the following table, the melting temperature is 210 ° C.

Table 17

The tensile properties at 23 ° C and 90 ° C, each time at 50 mm / min, of the M7 mixture are given in the following table.

Table 18

The breaking properties at 90 ° C., in particular the breaking stress, are very satisfactory.

EXAMPLE 6 Rubber Compositions Based on a Tri-Block Copolymer PLLA-SBR-PLLA (Polymer A) and Homopolymer PDLA (Polymer B)

The rubber composition CT 1 is a control composition based on a tri-block copolymer T5 as the sole source of polylactide. Thus, the rubber composition CT1 does not comprise an elastomeric mixture according to the invention. Indeed, the rubber composition CT 1 does not include PDLA.

Rubber compositions CM to CI4 based on an elastomeric mixture according to the invention were prepared from a tri-block copolymer T5 and two commercial PDLA polylactides from Corbion Purac D070 and D120 in different proportions reported in the following table.

The polylactide Corbion Purac D070 is as defined in Example 3.

The polylactide Corbion Purac D120 has a molecular weight of 84,900 g / mol and a polymolecularity index of 2.11.

The rubber composition CC1 is a comparative composition prepared from a mixture comprising a tri-block copolymer T5 and a commercial polylactide PDLA from Corbion Purac D070. The mixture comprises more than 50% of rigid polylactide phase and no longer has elastomeric properties. The rubber compositions CT1, CM, CI2, CI4 and CC1 are obtained according to the following procedure:

The mixer used is a Haake Rheomix mixer equipped with an 85cm ³ tank and CAM type rotor. The mixer tank temperature is fixed at 150 ° C, the rotational speed of the rotors at 70rpm and the filling coefficient is fixed at 0.7.

At t = 0s, the tri-block T5 is introduced into the mixer, then after 1 minute the N- (1, 3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (6-PPD) and if necessary the PDLA according to the proportions given in the following table. The whole is kneaded for 5 minutes then the mixture is recovered.

The compositions thus obtained are then shaped in the form of plates (thickness of 2 to 3 mm) for 5 min at 180 ° C. for the composition CT1 and at 230 ° C. for the compositions CM, CI2, CI4 and CC1 in press. (1 Ot) for the measurement of their mechanical properties.

Table 19

The results of the DSC are reported in the following table. According to the compositions, 2 peaks are present on the DSC thermograms: a peak around 165 ° C characteristic of the fusion of homo-crystallites of PLLA or PDLA and a peak around 225 ° C characteristic of the fusion of PLLA stereocomplexes / WLDP.

Table 20

The rubber compositions CM, CI2, and CI4 and CC1 all have a main melting temperature increased by at least 50 ° C compared to the control composition CT1. The enthalpy of fusion and the crystallinity of the polylactide are also greatly increased. On the other hand, the Tg of the central block SBR is not modified following the addition of PDLA and remains at -39 ° C.

Mechanical properties in tension at large deformations at 23 ° C and at 500 mm / min: the results are deviations of properties given in percentage compared to the properties of the reference composition CT 1.

Deviation = (value of Cln- value of CT1) / value of CT1; Cln denoting CM, CI2 or CI4; or Deviation = (value of CC1- value of CT1) / value of CC1.

Table 21

The rubber compositions CM, CI2 and CI4 have improved rigidity (Module at 10% MA10) and breaking stress at 23 ° C.

The composition CC1 does not have elastomeric properties: the test pieces break below 10% deformation. EXAMPLE 7 Crosslinked Rubber Compositions Based on Tri-Block Copolymer PLLA-SBR-PLLA (Polymer A) and PDLA (Polymer B)

The rubber composition CT2 is a control composition based on a tri-block copolymer T5 as the sole source of polylactide. Thus, the rubber composition CT2 does not comprise an elastomeric mixture according to the invention. Indeed, the CT2 rubber composition does not include PDLA.

The CI3 rubber composition is a composition according to the invention based on an elastomeric mixture according to the invention. It is prepared from a tri-block copolymer T5, from commercial PDLA Corbion Purac D070 (as defined in Example 3) and from an elastomer S BR.

The rubber compositions CT2, CI3 are obtained according to the following procedure:

At t = 0s, the tri-block T5 is introduced into the mixer, then after 1 minute the other constituents of the formula with the exception of sulfur and CBS according to the proportions given in the following table. The whole is kneaded for 4 minutes then the sulfur and CBS constituents are introduced. The whole is kneaded for another 1 minute and the mixture is recovered.

The compositions thus obtained are then shaped and cooked in the form of plates (thickness of 2 to 3 mm) for 30 min at 180 ° C for the composition CT2 and at 230 ° C for the composition CI3 in press (1 Ot) for the measurement of their mechanical properties.

In the table which follows are detailed the compositions tested, knowing that:

(1) T5 tri-block copolymer as described above,

(2) non-functional SBR having an Mn of 150,000 g / mol, an Ip = 1.9, and having a percentage of styrene of 26% by mass and of vinyl 1, 2 of 18% by mass,

(3) PDLA homopolymer "Corbion Purac D070",

(4) N-1, 3-dimethylbutyl-N-phenylparaphenylenediamine (6-PPD),

(5) Stearic Acid,

(6) ZnO,

(7) Sulfur,

(8) CBS = N-cyclohexyl-2-benzothiazyl-sulfenamide.

Total SBR = SBR + SBR in T5

total polylactide = PDLA + PLLA in T5

Table 22

The results of the DSC are reported in the following table.

Table 23

The composition CI3 has a main melting temperature raised by at least 50 ° C compared to the control composition CT2 despite the crosslinking of the elastomer phase. The enthalpy of fusion and the crystallinity of the polylactide are also greatly increased.

Mechanical properties in tension at large deformations at 23 ° C and 90 ° C. in both cases at 500 mm / min:

Table 24 The CI3 composition has a rigidity (10% MA10 module) at 23 ° C similar to the CT2 composition comprising the crosslinked T5 tri-block, and improved rupture properties, in particular the rupture deformation.

In addition, the composition CI3 has elastomer properties up to 90 ° C. with rupture deformations beyond 400%, unlike the crosslinked control composition CT2 which breaks at a deformation of less than 10%.

Claims

claims

1. Elastomeric mixture comprising at least:

- as polymer A),

• at least one diene elastomer / polylactide copolymer A1, the copolymer A1 comprising

o a polylactide block PLLA or PDLA called first block o if necessary one or more other polylactide block (s) which are all PLLA when the first block is PLLA or which are all PDLA when the first block is PDLA,

- as polymer B),

• a diene elastomer / polylactide copolymer B1, the copolymer B1 comprising

a polylactide block called the second block, which is PLLA when in the copolymer A1 the first block is PDLA or which is PDLA when in the copolymer A1 the first block is PLLA,

• or a polylactide B2 which is

^■ PLLA when in the copolymer A1 the first polylactide block is PDLA or

^■ PDLA when in the copolymer A1 the first polylactide block is PLLA,

• or a mixture of said copolymer B1 and of said polylactide B2

the names PLLA and PDLA denote a chain consisting of units of formula (I)

- [CH (CH ₃ ) -C (0) -0] - (I)

of which at least 70% by weight are respectively of configuration L and D.

2. Elastomeric mixture according to any one of the preceding claims, in which the mass content of units of formula (I) is less than 50% by weight relative to the total weight of the elastomeric mixture.

3. Elastomeric mixture according to any one of the preceding claims, characterized in that the polylactide B2) has a number-average molar mass, Mn, of less than 150,000 g / mol.

4. Elastomeric mixture according to any one of the preceding claims, characterized in that the polymer B) comprises at least said copolymer B1.

5. Elastomeric mixture according to any one of the preceding claims, characterized in that the copolymer A1 or the copolymer B1 is chosen from: a tri-block, of structure PLLA - diene elastomer - PLLA or of structure PDLA-diene elastomer - PDLA ,

6. Elastomeric blend according to any one of the preceding claims, characterized in that the copolymer A1 is a tri-block having a number-average molar mass, Mn, ranging from 50,000 g / mol to 300,000 g / mol.

7. Elastomeric blend according to any one of claims 1 to 5, characterized in that the copolymer A1 is a comb copolymer of number-average molar mass, Mn, ranging from 100,000 g / mol to 600,000 g / mol.

8. Elastomeric mixture according to any one of claims 1 to 5, characterized in that the copolymer A1 is a di-block having a number-average molar mass, Mn, ranging from 25,000 g / mol to 200,000 g / mol .

9. Elastomeric mixture according to any one of claims 1 to 8, characterized in that the copolymer B1 is a tri-block having a number-average molar mass, Mn, ranging from 50,000 g / mol to 300,000 g / mol .

10. Elastomeric blend according to any one of claims 1 to 8, characterized in that the copolymer B1 is a comb copolymer of number-average molar mass, Mn, ranging from 100,000 g / mol to 600,000 g / mol.

11. Elastomeric mixture according to any one of claims 1 to 8, characterized in that the copolymer B1 is a di-block having a number-average molar mass, Mn, ranging from 25,000 g / mol to 200,000 g / mol .

12. Elastomeric mixture according to any one of the preceding claims, characterized in that in the copolymer A1 and / or in the copolymer B1, the diene elastomer is chosen from among polybutadienes (abbreviated "BR"), polyisoprenes ( Synthetic IR), natural rubber (NR), butadiene copolymers, isoprene copolymers, ethylene and diene copolymers and mixtures of these polymers.

13. Elastomeric mixture according to any one of the preceding claims, characterized in that the polymers A) and B) represent at least 30% by weight of the elastomeric mixture, advantageously at least 50% by weight of the elastomeric mixture, more advantageously still minus 90% by weight of the elastomeric mixture.

14. A rubber composition which comprises the elastomeric mixture according to any one of the preceding claims and an additive.

15. A tire of which one of its constituent elements comprises an elastomeric mixture defined according to any one of claims 1 to 13 or a rubber composition according to claim 14.