WO2018091511A1 - Cross-linked tight inner layer of a pneumatic tyre comprising an elastomer matrix based on a block copolymer comprising an elastomer block with isobutylene and halogenoalkyl styrene units - Google Patents

Abstract

The invention relates to a tight inner layer for a pneumatic tyre based on a rubber composition comprising: an elastomer matrix comprising at least 50 pce of a block copolymer comprising at least one thermoplastic block comprising at least units from at least one styrene monomer and at least one elastomer block in the form of a statistical copolymer comprising at least units from isobutylene and units from at least one halogenoalkyl styrene monomer; and a cross-linking system based on sulphur. The invention also relates to a pneumatic tyre comprising the tight inner layer.

Description

 A tire reticulated sealed inner layer comprising an elastomeric matrix based on a block copolymer comprising an elastomeric block with isobutylene units and

 halogénoalkylstyrène

The invention relates to an airtight inner layer for a tire based on a rubber composition comprising: i) an elastomeric matrix comprising at least 50 phr of a block copolymer comprising at least one thermoplastic block comprising at least units derived from a or a plurality of styrene monomers and at least one elastomeric block in the form of a random copolymer comprising at least units derived from isobutylene and units derived from one or more haloalkylstyrene monomers, ii) a sulfur - based crosslinking system .

 The invention also relates to a tire comprising such a sealed inner layer.

 Tubeless tires have a low air permeability inner surface to prevent deflating of the tire and to protect internal areas sensitive to the tire against oxygen and water inflow, such as groundwater. containing metal cables sensitive to oxidation, this protection to improve the endurance of the tire.

 Today, such protection of the inner surface of tires is generally achieved by sealed inner layers (also sometimes called "inner gums"), consisting of elastomeric compositions based on butyl rubber.

However, the sealed internal layers based on these butyl rubbers have significant hysteretic losses, thus increasing the rolling resistance of the tires. In order to lower this rolling resistance, the applicants have described in WO2008 / 145276 waterproof layers for pneumatic tires comprising, as a majority elastomer, a styrene / isobutylene / styrene blo cs thermoplastic elastomer.

 Nevertheless, it remains advantageous to improve the adhesion of such a watertight layer comprising a thermoplastic elastomer to a blo c, on an adjoining diene layer within the tire such as the carcass ply, as well as the thermal stability of such a layer. waterproof layer.

 In particular, it is advantageous to avoid a significant decrease in the shear modulus G 'with the increase in temperature.

 This reduction in thermal stability is problematic because a rupture within the sealed inner layer can occur during the preparation of the tire and more particularly during its baking. Indeed, when opening the press at 1 80 ° C, the cohesive forces of the sealed inner layer are lower than the adhesion forces thereof to the baking membrane (suction effect) and the tire. Thus, a portion of the sealed inner layer remains on the tire and on the baking membrane.

 Therefore, it is also advantageous to stabilize or even reduce the drop of the module G 'so that the inner sealed layer of tire retains its physical integrity and properties both during cooking and in use at high temperature, while retaining good adhesion of the sealed inner layer of the tire to the carcass ply.

 Therefore, there is a need to develop a pneumatic inner tire layer having good adhesion to the carcass ply and a small decrease in the shear modulus G 'of the high temperature tight inner layer.

It has now been discovered, surprisingly, that a tire-resistant inner layer based on a rubber composition comprising i) an elastomeric matrix comprising at least 50 phr of a block copolymer comprising at least one thermoplastic block comprising at least units derived from one or more styrenic monomers and at least one blo c elastomer under the form of a random copolymer comprising at least units derived from isobutylene and units derived from one or more haloalkylstyrene monomers, and ii) a sulfur-based crosslinking system, made it possible to respond to this technical problem.

 Therefore, the object of the invention is a tire-tight inner layer based on a rubber composition comprising:

 an elastomeric matrix comprising at least 50 phr of a block copolymer comprising at least one thermoplastic block comprising at least units derived from one or more styrenic monomers and at least one elastomer block in the form of a random copolymer comprising at least less units derived from isobutylene and units derived from one or more haloalkylstyrene monomers,

 a sulfur-based crosslinking system.

 This inner tight layer according to the invention has good properties of adhesion to the carcass ply of a tire.

 In addition, it has a smaller decrease in the shear modulus G 'when it is prepared or used at high temperature.

 This sealed inner layer is intended to be integrated with a tire.

 Therefore, another object of the present invention is a tire having the sealed inner layer above.

 The invention as well as its advantages will be readily understood in the light of the description and examples of embodiments which follow.

 In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight.

On the other hand, any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e., terminals 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, including the strict limits a and b).

 In the present application, the term "part per cent elastomer" or "phr" means the part by weight of one component per 100 parts by weight of the elastomer (s), that is to say, the total weight of the elastomers, whether thermoplastic or non-thermoplastic, in the elastomeric composition. Thus, a 60 phr component will mean, for example, 60 g of this component per 100 g of elastomer of the elastomeric composition.

 As is customary in the present application, the terms "elastomer" and "rubber" which are interchangeable are used interchangeably in the text.

 Thus, a first object of the invention is an airtight inner layer for a tire based on a rubber composition comprising:

 an elastomeric matrix comprising at least 50 phr of a block copolymer comprising at least one thermoplastic block comprising at least units derived from one or more styrenic monomers and at least one elastomer block in the form of a random copolymer comprising at least less units derived from isobutylene and units derived from one or more haloalkylstyrene monomers,

 a sulfur-based crosslinking system.

 By styrene monomer is to be understood in the present description any monomer based on styrene, unsubstituted as substituted. In the present application, alkyl is understood to mean a hydrocarbon group, substituted or unsubstituted, comprising from 1 to 10 carbon atoms, preferably from 1 to 5 carbon atoms.

By the term "airtight" inner layer for tire "based on" a rubber composition, it is to be understood that the sealed inner layer comprises a mixture and / or the reaction product of the various constituents used in the rubber composition, some of these basic constituents being capable of or intended to react with each other, at least in part, during the different manufacturing phases of the sealed inner layer, in particular during its crosslinking.

 By "elastomeric matrix" in the sense of the present invention is meant all the elastomers (or rubbers) of the rubber composition. Thus, the elastomeric matrix may in particular consist of a single elastomer but also a blend of two or more elastomers.

 "Block" within the meaning of the present invention means a polymer chain consisting of at least five units, preferably at least ten units.

 By thermoplastic block, it is meant that this blo c comprises at least one sequence of 5 units, preferably at least 10 units derived from one or more styrenic monomers.

 By elastomeric block in the form of a random copolymer, it is meant that this blo c comprises at least one sequence of 5 units, preferably at least 10 units, said sequence consisting of a random distribution of at least 10 units. units derived from isobutylene and units derived from one or more haloalkylstyrene monomers.

 By sulfur-based crosslinking system it is meant that the crosslinking system comprises sulfur and / or a sulfur donor and these basic constituents are capable of, or intended to react with, the other constituents of the rubber composition during the different phases of manufacture of the sealed inner layer, in particular during the cooking of the envelope.

 In the present invention, the thermoplastic block comprises units derived from one or more styrenic monomers.

Preferably, the styrenic monomer or monomers are chosen from styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2,6-dimethylstyrene and 2,4-dimethylstyrene. , alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene, beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4-dimethylstyrene, beta-methyl-2,6- dimethylstyrene, the beta-methyl-2,4-dimethylstyrene, Γο-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chloro styrene, Γ alpha-chloro - m-chloro styrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichloro styrene , alpha-chloro -2,6-dichloro styrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o -, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, styrene derivatives substituted with a silyl group, and mixtures of these monomers.

 Most preferably, the styrenic monomer or monomers are selected from styrene, alpha-methylstyrene, and mixtures of these monomers, and more preferably the styrenic monomer is styrene.

 In the present invention, the elastomeric block is in the form of a random copolymer comprising at least units derived from isobutylene and units derived from one or more haloalkylstyrene monomers.

 Preferably, the haloalkylstyrene monomer or monomers are chosen from the monomers chloroalkylstyrene, bromoalkylstyrene, iodoalkylstyrene, and the mixtures of these monomers, more preferably the haloalkylstyrene monomer or monomers are chosen from bromoalkylstyrene monomers and chloroalkylstyrene monomers, and even more preferentially haloalkylstyrene monomer. is bromomethylstyrene, and in particular the haloalkylstyrene monomer is para-bromomethylstyrene.

 Preferably, the content of the units derived from one or more haloalkylstyrene monomers in the elastomeric block or blocks varies from 0.1 to 10% by mole, preferably from 0.5 to 5% by mole relative to the number of units of the block copolymer.

Advantageously in the present invention, the thermoplastic block or blocks of the block copolymer represent from 5 to 50% by weight. weight, preferably from 1 to 40% by weight, more preferably from 15 to 35% by weight, relative to the total weight of the block copolymer.

 In the present application, when reference is made to the glass transition temperature of the block copolymer comprising at least one thermoplastic block and at least one elastomer block, it is the glass transition temperature relative to the elastomeric blocks. Indeed, in known manner, block copolymers such as that of the invention have two glass transition temperature peaks (Tg, measured according to ASTM D341 8), the lowest temperature being relative to the elastomer portion of the blo copolymer. cs, and the highest temperature being relative to the thermoplastic portion of the block copolymer. Thus, the thermoplastic blocks of the block copolymer are defined by a Tg lower than room temperature (25 ° C), while the elastomeric blocks of the blown copolymer have a Tg greater than 80 ° C. Advantageously, the block copolymer that can be used according to the invention has a glass transition temperature of less than -20 ° C., preferably less than -40 ° C. A value of Tg higher than these minima can reduce the performance of the sealed inner layer when used at very low temperatures. For such use, the Tg of the block copolymer usable according to the invention is preferably less than -50 ° C.

The average molecular weight in number (denoted Mn) of the block copolymer usable according to the invention is preferably from 30,000 to 500,000 g / mol, more preferably from 40,000 to 400,000 g / mol. Below the minimum indicated, the cohesion between the elastomer chains, especially because of their possible dilution by an extension oil or other liquid plasticizer, may be affected. Moreover, a mass Mn that is too high can be detrimental to the flexibility of the internal waterproof layer. Thus, it has been found that a value of from 50,000 to 300,000 g / m 2 is particularly well suited, especially to the use of the sealed inner layer in a tire. The number average molecular weight (Mn) of the block copolymer which can be used according to the present invention is determined in known manner by steric exclusion chromatography (SEC). The sample is previously solubilized in tetrahydrofuran at a concentration of about 1 g / L; then the solution is filtered through a 0.45 μιη porosity filter before injection. The apparatus used is a "WATERS alliance" chromatographic chain. The eluting solvent is tetrahydrofuran, the flow rate is 0.7 mL / min, the system temperature is 35 ° C. and the analysis time is 90 minutes. A series of four WATERS columns in series, with the trade names "STYRAGEL"("HMW7","HMW6E" and two "HT6E") are used. The volume injected from the solution of the polymer sample is 100 μί. The detector is a "WATERS 2410" differential refractometer and its associated software for the exploitation of chromatographic data is the "WATERS MILLENIUM" system. The mean calculated average masses relate to a calibration curve made with polystyrene standards.

 The polydispersity index (Ip = Mw / Mn with M w average molecular weight by weight) of the block copolymer usable according to the invention is preferably less than 3; more preferably, the polydispersity index is less than 2.

 Preferably, the block copolymer that can be used according to the invention is chosen from thermoplastic / elastomeric block copolymers, thermoplastic block triblock copolymers / elastomer block / thermoplastic block and mixtures of these copolymers, and preferably the copolymer copolymer is a thermoplastic triblock copolymer / elastomeric block / thermoplastic block.

The block copolymer useful in the sealed inner layer of the present invention is at least 50 phr, i.e., at least 50% by weight of the total weight of the elastomeric matrix. In a preferred manner in the present invention, the content of block copolymer of the rubber composition varies from 70 to 100 phr, preferably ranges from 90 to 100 phr.

 Particularly preferably in the present invention, the block copolymer usable in the present invention is the only elastomer of the rubber composition.

 Nevertheless, the rubber composition may comprise other elastomers.

 As other elastomers present in the elastomeric matrix in addition to the block copolymer, particular mention may be made of diene elastomers.

 By elastomer or "diene" rubber, should be understood, in known manner, one or more elastomers derived at least in part (ie a homopolymer or a copolymer) of monomers dienes (monomers bearing two carbon-carbon double bonds, conjugated or not).

 These diene elastomers can be classified into two categories: "essentially unsaturated" or "essentially saturated".

 The term "essentially unsaturated" is generally understood to mean a diene elastomer derived at least in part from conjugated diene monomers, having a degree of units of diene origin (conjugated dienes) which is greater than 15% (% by mo). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a dienic units (conjugated dienes) level which is greater than 50%.

 It is thus that diene elastomers such as certain copolymers of dienes and alpha-o-olefins of the EPDM type can be described as "essentially saturated" diene elastomers (level of units of diene origin which is weak or very weak, always lower than at 15%).

As these definitions are given, the term diene elastomer is used more particularly, whatever the category above, capable of being used in the elastomeric matrix of the sealed inner layer according to the invention:

 (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 conjugated dienes with each other or with one or more vinyl aromatic compounds having from 8 to 20 carbon atoms;

 (c) a ternary copolymer obtained by copolymerization of ethylene, an α-o-olefin having 3 to 6 carbon atoms with a non-conjugated diene monomer having from 6 to 12 carbon atoms, for example elastomers obtained from ethylene, propylene with a non-conjugated diene monomer of the aforementioned type, such as, in particular, hexadiene-1,4, ethylidene norbornene, dicyclopentadiene.

 By way of conjugated dienes 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di (C 1 -C 5) alkyl-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, aryl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene. Suitable vinylaromatic compounds are, for example, styrene, ortho-, meta-, para-methylstyrene, the "vinyl-toluene" commercial mixture, para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene, divinylbenzene, vinylnaphthalene.

The aforementioned diene copolymers (category (b)) may contain between 99% and 20% by weight of diene units and between 1% and 80% by weight of vinylaromatic units. The elastomers may have any microstructure which is a function of the polymerization conditions used, in particular the presence or absence of a modifying and / or randomizing agent and the amounts of modifying and / or randomizing agent used. The elastomers may for example be bloated, random, sequenced, microsequenced, and prepared in dispersion or in solution; they can be coupled and / or starred or still functionalized with a coupling agent and / or starring or functionalization.

 Polybutadienes, and in particular those having a content (% molar) in units - 1, 2 of between 4% and 80%, or those having a content (% molar) in cis -1, 4 of greater than 80%, are suitable. polyisoprenes, butadiene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content (% molar) in -1,2 bonds; the butadiene part of between 4% and 65%, a content (% molar) of 1,4-trans-1,4 bonds of between 20% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 80%; % and 90% by weight and a glass transition temperature (Tg, measured according to ASTM D341 8) of -40 ° C to -80 ° C, the isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg between -25 ° C and -50 ° C. In the case of butadiene-styrene-isoprene copolymers are especially suitable those having a styrene content of between 5% and 50% by weight and more particularly of between 10% and 40%, an isoprene content of between 15% and 60%. by weight and more particularly between 20% and 50%, a butadiene content of between 5% and 50% by weight and more particularly between 20% and 40%, a content (% by weight) in units - 1, 2 of the butadiene part of between 4% and 85%, a content (% molar) in trans - 1,4 units of the butadiene part of between 6% and 80%, a content (% molar) in units - 1, 2 plus -3, 4 of the isoprenic portion of between 5% and 70% and a content (% molar) of trans-1,4 units of the isoprenic part of between 10% and 50%, and more generally any butadiene-butadiene copolymer. styrene-isoprene having a Tg between -20 ° C and -70 ° C.

As other elastomers present in the elastomeric matrix in addition to the block copolymer that can be used according to the invention, mention may also be made of isoprenic elastomers. By "isoprene elastomer" is meant in known manner a homopolymer or copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR), synthetic polyisoprenes (IR), different isoprene copolymers and mixtures of these elastomers. Among the isoprene copolymers, mention will be made in particular of the copolymers of isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR). This isoprene elastomer is preferably natural rubber or a synthetic cis-1,4 polyisoprene; Among these synthetic polyisoprenes, polyisoprenes having a content (% molar) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used.

 As described above, the elastomeric composition of the sealed inner layer according to the invention comprises a sulfur-based crosslinking system.

 As previously described, the crosslinking system comprises sulfur and / or a sulfur donor.

 Preferably, the crosslinking system comprises sulfur.

 The sulfur (and / or sulfur donor) is generally from 0.1 to 10 phr, preferably from 0.5 to 5 phr of the elastomeric composition. Preferably, the sulfur-based crosslinking system further comprises one or more vulcanization accelerators.

 In a particularly preferred manner, the sulfur-based crosslinking system comprises sulfur and one or more vulcanization accelerators.

 The vulcanization accelerator (s) are chosen from compounds of the thiuram family, zinc dithiocarbamates, thiazoles, guanidines, thiophosphates, and mixtures of these compounds.

As thiazoles, there may be mentioned 2-mercaptobenzothiazole, 2-mercaptobenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl sulphenamide (CB S), N, N-dicyclohexyl-2-benzothiazyl sulphenamide (DCBS), N-tert-butyl-2-benzothiazyl sulphenamide (TBBS), N -cyclohexyl-2-benzothiazylsulfenimide, N-tert-butyl-2-benzothiazylsulfenimide (TBSI) and mixtures thereof.

 As thiurams, there may be mentioned tetramethyl-thiuram monosulfide, tetraisoisobutyl-thiuram disulfide, tetrabenzyl-thiuram disulfide and mixtures of these compounds.

 Examples of zinc dithio carbamate derivatives that may be mentioned are zinc tetramethyl dithiocarbamate, zinc tetraethyl dithiocarbamate and zinc tetrabenzyl dithiocarbamate.

 The vulcanization accelerator or accelerators that can be used are preferably chosen from compounds of the family of thiazoles, and more preferentially from 2-mercaptobenzothiazyl disulphide (MBTS), N-cyclohexyl-2-benzothiazylsulphenamide (CB S), N, N-dicyclohexyl-2-benzothiazyl sulphenamide (DCBS), N-tert-butyl-2-benzothiazyl sulphenamide (TBB S), N-tert-butyl-2-benzothiazyl sulphenimide (TBSI) and the households of these compounds.

 The vulcanization accelerator or accelerators generally represent from 0.1 to 10 phr, preferably from 2 to 8 phr of the elastomeric composition.

 In a first particularly advantageous embodiment of the invention, the elastomeric composition comprises a metal compound selected from metal oxides, metal sulfides, and a mixture of these compounds.

 This first embodiment makes it possible in particular to further improve the thermal stability of the sealed inner layer of the invention.

Thus, in this first embodiment of the invention, the sealed inner layer has, on the one hand, good adhesion of the sealed inner layer of the tire to the carcass ply, and, on the other hand, a smaller decrease in the modulus G 'of the inner layer sealed at high temperature. Preferably, in this first embodiment of the invention, the metal oxides are chosen from transition metal oxides, that is to say the metals of block d of the periodic table of the elements.

In a very particularly preferred manner, the metal oxides are chosen from ZnO, FeO, HgO, CdO, Ag ₂ O, M02O 5, NiO, CoO, CuO, Cu ₂ O, SnO, Cr ₂ C 3 and MnO, more preferentially oxides. Metals are selected from ZnO, FeO, M02O5 and CuO and in particular the metal oxide is ZnO.

 Preferably, in this first embodiment of the invention, the metal sulphides are also chosen from transition metal sulphides, that is to say the metals of block d of the periodic table of the elements.

Very particularly preferably, the metal sulphides are chosen from ZnS, FeS, FeS ₂ , NiS, Ag ₂ S, CoS, Cr ₂ S 3, CO ₃ S 4, CO ₂ S 3, CuS, Cu ₂ S, SnS, MnS and M02S 5, more preferably the Metal sulfides are selected from ZnS, CuS, FeS and M02S5, and in particular the metal sulfide is ZnS.

 Preferably in this first embodiment of the invention, the content of metal compound of the rubber composition ranges from 0.1 to 10 phr, preferably varies from 1 to 8 phr, more preferably varies from 1 to 7 phr.

 In this first particular embodiment of the invention, the rubber composition of the sealed inner layer according to the invention may further comprise one or more fatty acids.

 The fatty acid is preferably stearic acid.

 Preferably, the fatty acid content of the rubber composition ranges from 0.1 to 10 phr, preferably from 0.5 to 5 phr.

 In a second preferred embodiment of the invention, the rubber composition comprises one or more antioxidants.

This second embodiment makes it possible to increase the delay phase during the preparation of the sealed inner layer of the invention. Thus, the manufacture of the sealed inner layer of the invention is found easier and is more easily industrializable.

 The antioxidant (s) that may be used according to the invention are chosen from all the antioxidants known to be effective in preventing the aging of the rubber compositions attributable to the action of oxygen.

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

 Mention may also be made of quinoline derivatives ("TMQ") such as, for example, 1,2-dihydro-2,2,4-trimethylquinoline and 6-ethoxy-1,2,4-dihydro-2,2,4 trimethyl quinoine.

 Diphenylamines or substituted triphenylamines may also be mentioned, as described for example in applications WO 2007/121936 and WO 2008/055683, in particular 4,4'-bis (isopropylamino) triphenylamine, 4,4'- bis (1,3-dimethylbutylamino) triphenylamine, 4,4'-bis (1,4-dimethylpentylamino) triphenylamine.

 Mention may also be made of dialkylthio dipropionates or else phenolic antioxidants, especially of the family of 2, 2'-methylene-bis-4-alkyl (C 1 -C 10) -6-alkyl (C 1 -C 12) phenols. , as described in particular in the application WO 99/02590.

Preferably, the antioxidant (s) are selected from the group consisting of substituted p-phenylenediamines, substituted diphenylamines, substituted triphenylamines, quinoline derivatives, and mixtures of such compounds; more preferably still, the antioxidant (s) are chosen from group consisting of substituted p-phenylenediamines and mixtures of such diamines.

 When present, the antioxidant (s) represent from 0.1 to 5 phr, preferably from 0.1 to 0.5 phr, and more preferably from 0.1 to 0.3 phr of the rubber composition.

 In this embodiment, the elastomeric composition may further comprise one or more acid scavengers. Preferably, the acid scavenger is present at a level ranging from 0.1 to 5 phr, preferably from 0.5 to 3 phr.

 The two particular embodiments as described above can of course be combined in order to improve both the thermal stability of the sealed inner layer and its manufacture by increasing the lag phase.

 The rubber composition for use in the sealed inner layer of the invention may further comprise one or more fillers.

 The term "filler" according to the invention includes reinforcing fillers, semi-reinforcing fillers and inert fillers.

 For the purposes of the present invention, the term "reinforcing fillers" means any type of filler known for its ability to reinforce a rubber composition that can be used for the manufacture of tires, for example an organic filler such as carbon black or an inorganic filler. reinforcing.

 Thus, in the present invention, the rubber composition that can be used in the tight inner layer according to the invention may comprise from 5 to 50 phr of carbon black.

Carbon blacks are suitable for all carbon blacks, in particular blacks of the HAF, ISAF, SAF type conventionally used in tires (so-called pneumatic grade blacks). Among these, the reinforcing carbon blacks of the 100, 200 or 300 series (ASTI grades), for example the blacks N 1 1 5, N 1 34, N 2 34, N 326, N 3 O 3, N 339, N 347 and N 3 or, depending on the intended applications, blacks of higher series (for example N660, N683, N772), or even N990. Of course, it is possible to use a single carbon black or a blend of several carbon blacks of different ASTM grades.

 In the rubber composition usable in the sealed inner layer according to the invention, the carbon black may constitute the only filler of the composition.

 The rubber composition that can be used in the sealed inner layer according to the invention may also comprise, in addition to the carbon black, one or more additional charges.

 This or these additional charges may be chosen from reinforcing fillers other than carbon black, semi-reinforcing fillers and inert fillers.

 Thus, the rubber composition that can be used in the tight inner layer according to the invention may also comprise one or more reinforcing inorganic fillers.

 By "reinforcing inorganic filler" is meant in this application, by definition, any inorganic or mineral filler (regardless of its color and origin (natural or synthetic), also called "white" filler, "clear" filler or "non-black filler" as opposed to carbon black, capable of reinforcing on its own, with no other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires in other words, able to replace, in its reinforcing function, a conventional carbon black of pneumatic grade, such a charge is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.

The physical state in which the reinforcing inorganic filler is present is indifferent whether in the form of powder, microbeads, granules, beads or any other suitable densified form. Of course, the term "reinforcing inorganic filler" also refers to mixtures of different reinforcing inorganic fillers, in particular highly dispersible siliceous and / or aluminous fillers as described below. Suitable reinforcing inorganic fillers are, in particular, mineral fillers of the siliceous type, in particular of silica (SiO 2), or of the aluminous type, in particular alumina (Al.sub.7O.sub.3). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface both less than 450 m ² / g, preferably from 30 to 400 m ² / g.

 As highly dispersible precipitated silicas (referred to as "HDS"), mention may be made, for example, of the silicas Ultrasil 7000 and Ultrasil 7005 from the company Degussa, the silicas Zeosil 1,165 MP, 1,135MP and 1,15MP from the company Rhodia, silica Hi-Sil EZ 150G from PPG, Zeopol 87, 8745 and 8755 silicas from Huber, silicas with a high specific surface area as described in application WO 03/16837.

 Finally, one skilled in the art will understand that, as equivalent filler of the reinforcing inorganic filler described in this paragraph, it would be possible to use a reinforcing filler of another nature, in particular organic, since this reinforcing filler would be covered with an inorganic layer such as silica, or would comprise on its surface functional sites, especially hydroxyls.

 The presence of an inorganic reinforcing filler or a reinforcing filler of another nature covered with an inorganic layer or having on its surface functional sites in a rubber composition generally requires the use of a coupling agent. to establish the connection between the charge and the elastomer.

 It is recalled here that "coupling agent" means, in a known manner, an agent capable of establishing a sufficient bond, of a chemical and / or physical nature, between the inorganic filler (or of another type as seen above). ) and the elastomer.

Such coupling agents, in particular silica / elastomer, have been described in a very large number of documents, the best known being bifunctional organosilanes bearing alkoxyl functions. (i.e., by definition, "alkoxysilanes") and functions capable of reacting with the elastomer such as, for example, polysulfide functions.

 As seen previously, the additional charge (s) possibly present in the rubber composition that can be used in the tight inner layer according to the invention may be chosen from semi-reinforcing fillers.

 The semi-reinforcing fillers are not capable of reinforcing by themselves a rubber composition intended for the manufacture of tires, in other words they are not able to replace, in its reinforcing function, a conventional carbon black of pneumatic grade, however they allow an increase in tensile modulus of a rubber composition in which they are incorporated, that is why they are called "semi-reinforcing".

 As a semi-reinforcing filler optionally present in the sense of the present invention, there may be mentioned graphite.

 By graphite is generally meant a set of non - compact hexagonal sheets of carbon atoms: graphenes. Graphite, a hexagonal crystalline system, has an ABAB type stack where plane B is translated relative to plane A; it belongs to the crystalline group: space group P63 / mmc.

 Graphite can not be considered as a reinforcing filler unlike carbon black or silica. It simply allows an increase in the tensile modulus of a rubber composition in which it is incorporated but does not make it possible to reinforce this composition.

 As these definitions are given, the term "graphite" that can be used according to the invention is more particularly understood to mean:

(a) any natural graphite associated with rocks affected by metamorphism, after separation of the impurities accompanying the graphite veins and after grinding; (b) any naturally expandable graphite, i. e. wherein a chemical compound in the liquid state, for example an acid, is sandwiched between its graphene planes;

 (c) any expanded natural graphite, the latter being made in two stages: intercalation of a chemical compound in the liquid state, for example an acid, between the graphene planes of a natural graphite by chemical treatment and high expansion temperature ;

 (d) any synthetic graphite obtained by graphitization of petroleum coke.

 The rubber composition that can be used in the sealed inner layer according to the invention can contain a single graphite or a mixture of several graphites, so it is possible to have a blend of natural graphite and / or expanded graphite and / or synthetic graphite.

 Graphite as defined above, can be on a morphological plane in a lamellar form or not.

 Preferably, the graphite that can be used according to the invention is in lamellar form.

 As seen above, the additional charge (s) may be chosen from among the inert charges.

 The inert filler (s) that can be used according to the invention can be chosen from chalk, clay, bentonite, talc, flax kaolin, glass microspheres, glass flakes, and mixture of these compounds.

 In the present invention, the carbon black may advantageously constitute the only reinforcing filler or the majority reinforcing filler.

 More preferably, the carbon black may advantageously be the sole filler of the rubber composition.

 The rubber composition for use in the sealed inner layer may further comprise a plasticizer.

In a manner known to those skilled in the art, a "plasticizing agent" by definition is a liquid or solid compound at room temperature (23 ° C.) and at atmospheric pressure. (1, 013, 10 ^s Pa) compatible, that is to say miscible with the rate used with the rubber composition for which it is intended, so as to act as a true diluent.

 In a preferred manner in the present invention, the plasticizing agent is chosen from plasticizing oils and plasticizing resins.

 By definition, a plasticizing oil (also called liquid plasticizer) is liquid at room temperature and atmospheric pressure.

 This or these plasticizing oils generally have a low glass transition temperature, lower than -20 ° C (Tg, measured according to ASTM D341 8), preferably lower than -40 ° C.

 The glass transition temperatures are measured in a known manner by DSC ("Differential Scanning Calorimetry") according to the ASTM D341 8 standard.

 As a plasticizing oil that can be used in the tight inner layer according to the invention, all the so-called "extension" oils that are of an aromatic or nonaromatic nature known for their plasticizing properties with respect to their properties can be used. elastomers used in the present invention.

 Plasticizing oils chosen from the group consisting of liquid diene polymers, polyolefinic oils, naphthenic oils, paraffinic oils, DAE (Distillate Aromatic Extracts) oils, MES (Medium Extracted Solvates) oils, TDAE oils are particularly suitable. (Treated Distillate Aromatic Extracts), Residual Aromatic Extracts (RAE) oils, Treated Residual Aromatic Extracts (TREE) oils, Safety Residual Aromatic Extracts (SRAE) oils, mineral oils, vegetable oils, plasticizers, ethers, plasticizers esters, plasticizers, phosphates, sulphonate plasticizers and mixtures of these compounds.

Liquid polymers derived from the polymerization of olefins or dienes, for example those selected from the group consisting of polybutenes, polydienes, in particular polybutadienes, polyisoprenes, copolymers of butadiene and isoprene, copolymers of butadiene or isoprene and styrene, and mixtures of these liquid polymers. The average molecular weight in number of such liquid polymers is preferably in a range from 500 g / mol to 50,000 g / mol, more preferably from 1000 g / mol to 10,000 g / mol. By way of example, mention may be made especially of the "Ricon" products of Sartomer.

 Also suitable are functionalized or non-functionalized polyisobutylene oils having a molecular weight of between 200 g / mol and 40,000 g / mol.

 According to another preferred embodiment of the invention, the plasticizing oil or oils are vegetable oils (such as linseed oils, safflower, soybean, corn, cotton, shuttle, castor oil, abrasin, pine, sunflower, palm, o live, coconut, peanut, grape seed, and mixtures of these oils, especially sunflower oil).

 According to another particular embodiment of the invention, the plasticizing oil or oils are an ether such as polyethylene glycols or polypropylene glycols.

 Also suitable are plasticizing oils chosen from the group consisting of ester plasticizers, phosphate plasticizers, sulphonate plasticizers and mixtures of these compounds.

 As a reminder, the plasticizer may also be chosen from plasticizing resins.

In contrast to plasticizing oils, plasticizer resin is understood to mean a compound which is solid at room temperature (23 ° C.) and at atmospheric pressure (1.0 × 10 ⁵ Pa).

 This or these plasticizing resins generally have a glass transition temperature, greater than 20 ° C (Tg, measured according to ASTM D34 18), preferably greater than 30 ° C.

 Preferably, the plasticizing resins used according to the invention are hydrocarbon plasticizing resins.

Hydrocarbon resins are polymers that are well known to those skilled in the art, which are therefore miscible in nature in the compositions elastomer (s) when they are further qualified "plasticizers".

 These hydrocarbon-based polymeric resins generally have a glass transition temperature above 20 ° C and a cooling temperature below 170 ° C.

 Softening point temperatures are measured according to ASTM E-28.

 They have been widely described, for example, in the book entitled Hydrocarbon Resins by R. Mildenberg, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3 -527-28617-9). is devoted to their applications, in particular in pneumatic rubber (5.5 Rubber Tires and Mechanical Goods).

 They may be aliphatic, naphthenic, aromatic or else of the aliphatic / naphthenic / aromatic type, that is to say based on aliphatic and / or naphthenic and / or aromatic monomers. They may be natural or synthetic, whether or not based on petroleum (if so, they are also known as petroleum resins). They are preferably exclusively hydrocarbon-based, that is to say they contain only carbon and hydrogen atoms.

 The content of plasticizer in the rubber composition that can be used in the sealed inner layer according to the invention generally varies from 0 to less than 10 phr.

 The rubber composition that can be used in the tight inner layer according to the invention may also comprise all or part of the usual additives usually used in elastomer compositions intended for the manufacture of tires, such as, for example, protective agents other than the antioxidants already in use. above mentioned such as chemical antiozonants, anti-fatigue agents, acceptors (for example phenolic novolak resin) or methylene donors (for example HMT or H3M).

The rubber composition for use in the sealed inner layer according to the invention can be prepared by any means known to those skilled in the art for the implementation of thermoplastic polymers (TPE). For example, the rubber composition usable in the sealed inner layer according to the invention can be manufactured in suitable mixers.

 The process for preparing such a composition comprises for example the following steps:

 thermomechanically knead (for example in one or more times) the elastomeric matrix with the carbon black and the additional charges if they are present, the plasticizing system if it is present, until a maximum temperature of between 1 and 10 is reached. ° C and 140 ° C (so-called "non-productive" phase);

 - cool all at a temperature below 100 ° C;

- Then incorporate, in a second step (called "productive"), the sulfur-based vulcanization system;

 - mix everything up to a maximum temperature below 1 10 ° C.

 The final composition thus obtained can then be calendered, for example in the form of a sheet, a plate especially for a characterization in the laboratory, or extruded, for example to form a rubber profile used for the manufacture of a waterproof inner layer.

 The sealed inner layer is usable in any type of obj and pneumatic. Examples of such pneumatic objects include pneumatic boats, balloons or balls used for sport or sport.

 Consequently, the invention also relates to a tire comprising a tight inner layer as defined above.

 In general, the tire according to the invention is intended to equip motor vehicles of tourism type, SUV ("Sport Utility Vehicles"), two wheels (including motorcycles), aircraft, as well as industrial vehicles such as vans, heavy goods vehicles and other transport or handling vehicles.

The invention as well as its advantages will be understood in greater depth, in the light of the following exemplary embodiments. Measurement methods

Adhesion test (or peel) Adhesion tests (peel tests) were conducted to test the ability of the sealed inner layer according to the invention to adhere after firing to a diene elastomer layer, more specifically to a conventional rubber composition for tire carcass reinforcement, based on natural rubber (peptized) and carbon black N330 (65 parts by weight per hundred parts of natural rubber), comprising in addition the usual additives (sulfur, accelerator , ZnO, stearic acid, antioxidant).

 The peel test pieces (peel type at 1 80 °) were made by stacking a calendered layer of sealed inner layer (1.5 mm) and a calendered layer of diene elastomer (1.2 mm). A rupture primer is inserted between the two calendered layers.

The test piece after assembly was heated at 150 ° C under pressure for 10 minutes and cooling was carried out under pressure. Strips 30 mm wide were cut with a cutter. Both sides of the fracture primer were then placed in the jaws of an Intron ® brand traction machine. The tests are carried out at ambient temperature and at a tensile speed of 100 mm / min. The tensile forces are recorded and these are normalized by the width of the specimen. A force curve is obtained per unit of width (in N / mm) as a function of the displacement of the moving beam of the traction machine (between 0 and 200 mm). The value of adhesion retained corresponds to the initiation of the rupture within the specimen and therefore to the maximum value of this curve. This measurement was carried out at room temperature as well as at 60 ° C. The results are expressed in peel facies ("cohesive" means that the adhesive interface is stronger than the cohesion of the mixture and is therefore preferred to the "adhesive" facies). The results are also expressed in average peel strength per unit of width of the specimen (N / mm). The performances of the exemptions are standardized (in base 100) with respect to the control, to which, by convention one attributes a performance to 100, for a facilitated comparison of the performances. Thus, the higher the value in base 100, the better the adhesion performance.

Torque measurement (Acouple) and lag phase (tO)

The torque measurement is carried out at 150 ° C. and 170 ° C. with an oscillating chamber rheometer according to DIN 53529 - Part 3 (June 1983). The evolution of the rheometric torque, Acouple, as a function of time describes the evolution of the stiffening of the composition as a result of the vulcanization reaction. The measurements are processed according to DIN 53529 - Part 2 (March 1983). In particular, the maximum torque (Cmax) corresponding to the bearing reached by the torque is measured. The values of Cmax of the examples are normalized (in base 100) with respect to the control, to which, by convention, a performance is attributed to 100, for a facilitated comparison of the values of Cmax. Thus, the higher the value in base 100, the higher the value of C max.

 The delay phase is also measured during the measurement of the torque carried out at 150 ° C. for each example. The delay phase is indicated in minutes.

Measuring the shear modulus G '

The principle consists in measuring the shear modulus G 'of a film of material during a dynamic solicitation. A dynamic mechanical analyzer (DMA Q800) marketed by the company TA Instruments is used. The sample is in the form of two pellets of material 10 mm in diameter and 2 mm in thickness which are shear thinned by means of three metal rolls, the two cylinders at the ends being fixed and the central cylinder with a sinusoidal translation movement at a dynamic strain of 0.5% at a frequency of 10 Hz during a rise in temperature (from ambient to 220 ° C to 4 ° C / min); the shear modulus G 'generated by the material is recorded during this mechanical and thermal stress. The ratio G '(200 ° C) / G' (20 ° C) is then calculated for each sample which reflects the thermal stability of the sample at elevated temperatures.

 The values of G '(200 ° C) / G' (20 ° C) of the examples are standardized (in base 100) with respect to the control, to which, by convention, a performance is attributed to 100, for a facilitated comparison of the values. Thus, the higher the value in base 100, the higher the thermal stability of the sample at high temperatures.

Synthesis of styrene / isobutylene / styrene block copolymer with units derived from a p-bromomethylstyrene monomer

The block copolymer is synthesized as follows:

 A 200-liter container (polymerization vessel) is put under nitrogen, then n-hexane (molecular sieve dried, 23.7 kg) and butyl chloride (molecular sieve dried, 74.3 kg) are added to the mixture. medium of a solvent line. The polymerization vessel is then cooled by a heat-insulated trifluoromethane (HFC-23) shell at -70 ° C. Isobutylene (17.4 kg, 310 mol) is added to the polymerization vessel from an isobutylene reservoir. Then, p-dicumyl chloride (48.8 g, 0.21 mol) dissolved in butyl chloride (molecular sieve dried, 0.31 L), triethylamine (64.1 g, 0.63 mol ), and titanium tetraisopropoxide (600 g, 2.1 mol) are added via additional containers by means of a nitrogen pressure. Then titanium tetrachloride (2.8 kg, 14.8 mol) is added to start the polymerization.

Shortly thereafter, paramethylstyrene (0.10 kg, 8.4 mol) dissolved in n-hexane (molecular sieve dried, 0.24 L) and butyl chloride (molecular sieve dried, 0.57 L ) is added continuously for 30 minutes. The conversions of isobutylene and paramethylstyrene are monitored by gas chromatography (GC). Conversions reach more than 98.5%.

 Styrene (3.8 kg, 36.8 mol) is then added to the polymerization vessel. The conversion of styrene is followed by gas chromatography (GC). When a styrene conversion of 80% is achieved, the polymerization solution and a mixture of solvents consisting of n-hexane and butyl chloride (37.1 kg, 3/7 v / v) are poured into a container of Deactivation containing 48 wt.% NaOH solution (12.3 kg) and deionized water (112.7 kg) at 55 ° C to stop the reaction and this mixture is then stirred for 60 minutes. Then, the polymerization solution is washed with deionized water (3x 125 kg). The solvent and the analogs are evaporated from the washed crude reaction under reduced pressure at 80 ° C for 24 hours to obtain a non-brominated block copolymer.

The non-brominated block copolymer (2.2 kg) was dissolved in butyl chloride (9.5 L) and n-hexane (4.1 L) in a 20 liter flask. Nitrogen is introduced into the stirred polymer solution by means of a stainless steel rod for 1 hour. Then bromine (67.8 ml, 1.37 mol) is added and the whole is irradiated with visible light (LED 4 x 7.3 W). The conversion of the bromination step is followed by an NMR method. When the conversion of the bromination stage reaches 90%, butyl chloride (1.07 kg) and a 10% by weight aqueous solution of Na ₂ SC 3 (1.78 kg) are added and the mixture is The brominated polymer solution is then washed with deionized water (2 x 1.5 kg) and dried with MgSC, the polymer solution is filtered and the mixture is stirred. solvent and the analogs are evaporated from the crude reaction under reduced pressure at 80 ° C for 24 hours to obtain the brominated block copolymer usable according to the invention. Example 1 Study of Crosslinking

The compositions of the comparative leakproof internal layers A1 and A6 and of six sealed inner layers according to the invention A2 to A5, A7 and A8 are shown in Table 1 below. The amounts of products are indicated in phr (parts per hundred parts by weight of elastomer).

Table 1

( 1 ) copolymère à blocs avec 32 unités/moles de copolymère à blo cs issus d'un monomère de p-bromométhylstyrène préparé par le protocole décrit ci-dessus.

(1) Block copolymer with 32 units / mole of block copolymer derived from a p-bromomethylstyrene monomer prepared by the protocol described above.

 (2) DHT4V sold by Kisuma Chemicals

 (3) Irganox l 076 sold by BASF

 (4) N-cyclohexylbenzothiazole-2-sulfenamide

 (5) Zinc oxide (industrial grade - Umicore company)

 (6) Stearin ("Pristerene" from Uniquema Company) The above eight watertight inner layer compositions were heated at two different temperatures (150 ° C and 170 ° C).

 The pair of each of the compositions was measured as a function of time.

 The maximum torque (Cmax) corresponding to the plateau reached by the torque was measured for each of the compositions. The values are collated in Table 2 below.

Table 2 The values of Cmax are given in base 100 (100 for compositions Al and A6 at 150 ° C. and 170 ° C.).

Temperature

 Composition

 150 ° C to 170 ° C

 A l (Comp.) 100 100

 A2 (Inv.) 139,238

 A3 (Inv.) 239 -

A4 (Inv.) 645 1 104

 A5 (Inv.) 435 -

A6 (Comp.) 100 100

A7 (Inv.) 340 - A8 (Inv.) 530

These data show that the compositions A2 to A5 that can be used in the sealed inner layer according to the invention undergo a significant increase in their torque when subjected to a high temperature, unlike the comparative composition A l.

 Thus, the compositions A2 to A5 that can be used in the sealed inner layer according to the invention stiffen more rapidly than the comparative composition A 1.

 In the same way, the compositions A7 and A8 that can be used in the tight inner layer according to the invention undergo a significant increase in their torque when they are subjected to a high temperature, unlike the comparative composition A6. These compositions A7 and A8 used in the inner tight layer according to the invention stiffen more rapidly than the comparative composition A6.

Example 2 Measurement of the Adhesion Properties The adhesion properties of the compositions A3, A5, A7 and A8 as defined in Table 1 were measured at room temperature (23 ° C.) and at 60 ° C. The results are collated in Table 3.

Table 3

The peel forces are indicated in peel facings (cohesive or adhesive) and in base 100. A value of 100 is attributed to the peel strength of a comparative elastomeric composition A0 comprising only a thermoplastic elastomer SIB S (SIBSTAR 1 02T).

This elastomer does not include bromomethylstyrene units in its structure. Peel Strength at Peel Strength at

Composition

 23 ° C to 60 ° C

 100 100

 A0 (Comp.)

 Adhesive Adhesive

 1477 1833

 A3 (Inv.)

 Adhesive Adhesive

 843,875

 A5 (Inv.)

 Adhesive Adhesive

 1230 1620

 A7 (Inv.)

 Adhesive Adhesive

 970 1220

 A8 (Inv.)

 Adhesive Adhesive

These results show that the adhesion of the sealed inner layers according to the invention is much better than the adhesion of the sealed inner layer which does not comprise elastomer comprising bromomethylstyrene units.

Example 3 Measurement of the Thermal Stability at High Temperature The compositions Al, A2, A4, A5, A6, A7 and A8 as defined in Table 1 were subjected to a baking cycle: 40 minutes at 150 ° C.

Their modules G '(T) as a function of the temperature were measured.

 The values of the G '(T) modules at 20 ° C and 200 ° C were extracted and the ratios G' (200 ° C) / G '(20 ° C) are shown in Table 4 below.

Table 4 The ratios G '(200 ° C) / G' (20 ° C) are indicated at base 100 (100 for compositions Al and A6).

It is observed a drop of the lower modulus G 'for the sealed inner layers according to the invention comprising a sulfur-based crosslinking system.

 Thus, this reflects an improvement in the thermal stability of the sealed inner layers according to the invention compared to the comparative inner layer not comprising a sulfur-based crosslinking system.

Example 4: Measurement of the delay phase

The delay phase corresponds to the time interval between the beginning of the heating of the elastomeric composition and the beginning of the increase in the torque of the elastomeric composition.

 The values are summarized in Table 5 below.

Table 5 Delay phase values are given in minutes.

 These data show that the compositions A3, A5, A7 and A8 used in the sealed inner layer according to the invention have a lag phase. Comparative compositions A1 and A6 and compositions A2 and A4 that can be used in the tight inner layer according to the invention do not exhibit a lag phase.

 Thus, the effect of adding an antioxidant to the elastomeric composition that can be used in the tight inner layer according to the invention is well demonstrated.

 Therefore, the manufacture of such a sealed inner layer is facilitated and is more easily industrializable.

Claims

1. A tire sealed inner layer based on a rubber composition comprising:  an elastomeric matrix comprising at least 50 phr of a block copolymer comprising at least one thermoplastic block comprising at least units derived from one or more styrenic monomers and at least one elastomeric block in the form of a random copolymer comprising at least units derived from isobutylene and units derived from one or more haloalkylstyrene monomers,  a sulfur-based crosslinking system. 2. Internal sealed layer according to claim 1, characterized in that the styrenic monomer or monomers are selected from styrene, o-, m- or p-methylstyrene, alpha-methylstyrene, beta-methylstyrene, 2 , 6-dimethylstyrene, 2,4-dimethylstyrene, alpha-methyl-o-methylstyrene, alpha-methyl-m-methylstyrene, alpha-methyl-p-methylstyrene, beta-methyl-o-methylstyrene , beta-methyl-m-methylstyrene, beta-methyl-p-methylstyrene, 2,4,6-trimethylstyrene, alpha-methyl-2,6-dimethylstyrene, alpha-methyl-2,4- dimethylstyrene, beta-methyl-2,6-dimethylstyrene, beta-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, alpha-chloro-o-chloro styrene, alpha-chloro-m-chloro styrene, alpha-chloro-p-chlorostyrene, beta-chloro-o-chlorostyrene, beta-chloro-m-chlorostyrene, beta-chloro-p-chlorostyrene, 2,4,6-trichloro styrene, alpha-chloro-2,6-dichloro styrene, alpha-chloro-2,4-dichlorostyrene, beta-chloro-2,6-dichlorostyrene, beta-chloro-2,4-dichlorostyrene, o-, m- or p-butylstyrene, o-, m- or p-methoxystyrene, o-, m- or p-chloromethylstyrene, o-, m- or p-bromomethylstyrene, styrene derivatives substituted with a silyl group, and the mixtures of these monomers, preferably the styrenic monomer (s) are chosen from styrene, methylstyrene, and the mixtures of these monomers, and more preferably the styrenic monomer is styrene.  3. Internal sealed layer according to claim 1 or 2, characterized in that the halo monomer or genoalkylstyrene are selected from the monomers chloroalkylstyrene, bromoalkylstyrene, iodoalkylstyrene, and mixtures of these monomers, preferably the haloalkylstyrene monomer or monomers are chosen from the bromoalkylstyrene monomers and the chloroalkylstyrene monomers, more preferably the haloalkylstyrene monomer is bromomethylstyrene, and more preferably still the haloalkylstyrene monomer is para-bromomethylstyrene.  4. Inner sealed layer according to any one of the preceding claims, characterized in that the content of the units derived from the haloalkylstyrene monomer (s) in the elastomeric block (s) varies from 0.1 to 10% by weight, preferably from 0 to 5 to 5% by weight relative to the number of units of the block copolymer.  5. Internal sealed layer according to any one of the preceding claims, characterized in that the thermoplastic block or blocks of the block copolymer represent from 5 to 50% by weight, preferably represent from 10 to 40% by weight, more preferably represent from 15 to 35% by weight, based on the total weight of the block copolymer.  6. Inner sealed layer according to any one of the preceding claims, characterized in that the block copolymer has a glass transition temperature of less than -20 ° C, preferably less than -40 ° C.  7. Inner sealed layer according to any one of the preceding claims, characterized in that the block copolymer has a number average molecular weight ranging from 30,000 to 500,000 g / mol, preferably from 40,000 to 400,000 g / mol, more preferably 50,000 to 300,000 g / mol. 8. sealed inner layer according to any one of the preceding claims, characterized in that the blo cs copolymer is selected from diblock copolymers blo cs thermoplastic / elastomeric block, the triblock copolymers blo c thermoplastic / elastomer block / thermoplastic block and blends of these copolymers, and preferably the copolymer copolymer blo cs is a triblo cs blo c thermoplastic / block elastomer / blo c thermoplastic.  9. Inner sealed layer according to any one of the preceding claims, characterized in that the content of block copolymer of the rubber composition varies from 70 to 100 phr, preferably from 90 to 100 phr.  10. Inner sealed layer according to any one of the preceding claims, characterized in that the bloated copolymer is the only elastomer of the rubber composition.  1 1. Inner sealed layer according to one of the preceding claims, characterized in that the sulfur-based crosslinking system comprises sulfur and one or more vulcanization accelerators.  12. Inner sealed layer according to the preceding claim, characterized in that the vulcanization accelerator (s) are chosen from compounds of the thiuram family, zinc dithiocarbamates, thiazoles, guanidines, thiophosphates and mixtures of these compounds. preferably, the vulcanization accelerator or accelerators are chosen from compounds of the thiazole family, and more preferably from 2-mercapto-benzothiazyl disulphide, N-cyclohexyl-2-benzothiazyl sulphenamide, N, N-dicyclohexyl- 2-benzothiazylsulfenamide, N-tert-butyl-2-benzothiazylsulfenamide, N-tert-butyl-2-benzothiazylsulfenimide and the households of these compounds.  13. Inner sealed layer according to any one of the preceding claims, characterized in that the elastomeric composition comprises a metal compound selected from metal oxides, metal sulfides, and a mixture of these compounds. 14. Internal sealed layer according to claim 1 3, characterized in that the metal oxides are chosen from ZnO, FeO, HgO, CdO, Ag ₂ 0, M02O5, NiO, Co O, CuO, Cu ₂ 0, SnO, Cr ₂ 0 ₃ and MnO, preferably the metal oxides are selected from ZnO, FeO, M02O5 and CuO, and preferentially, the metal oxide is ZnO. 15. Internal sealed layer according to claim 13 or 14, characterized in that the metal sulfides are chosen from ZnS, FeS, FeS ₂ , NiS, Ag ₂ S, Co S, Cr ₂ S ₃ , Co ₃ S ₄ , Co ₂ S ₃ , CuS, Cu ₂ S, SnS, MnS and Mo ₂ S ₅ , preferably the metal sulphides are chosen from ZnS, CuS, FeS and Mo ₂ S ₅ , and more preferably the metal sulphide is ZnS.  16. Inner sealed layer according to any one of claims 13 to 15, characterized in that the content of metal compound of the rubber composition varies from 0.1 to 10 phr, preferably ranges from 1 to 8 phr, more preferably varies from 1 to 7 pce.  17. Inner sealed layer according to any one of claims 13 to 16, characterized in that the rubber composition further comprises one or more fatty acids.  8. Inner sealed layer according to claim 17, characterized in that the fatty acid is stearic acid.  19. Inner sealed layer according to claim 18, characterized in that the fatty acid content of the rubber composition ranges from 0.1 to 10 phr, preferably from 0.5 to 5 phr.  20. Inner sealed layer according to any one of the preceding claims, characterized in that the rubber composition comprises one or more antioxidants. 21. Inner sealed liner according to claim 20, characterized in that the antioxidant (s) is (are) selected from the group consisting of substituted p-phenylenediamines, substituted diphenylamines, substituted triphenylamines, quinoline derivatives, and mixtures thereof. preferably, the antioxidant (s) are selected from the group consisting of substituted p-phenylenediamines and mixtures of such diamines. 22. Internal sealed layer according to claim 20 or 21, characterized in that the antioxidant (s) represent from 0.1 to 5 phr, preferably from 0.1 to 0.5 phr, and better still from 0.1 to 0, 3 phr of the rubber composition.  23. A tire comprising a sealed inner layer as defined in any one of the preceding claims.