EP2596061A1 - Rubber composition including glass flakes, in particular for manufacturing tires - Google Patents

Abstract

The invention relates to a rubber composition in particular for manufacturing tires, primarily containing at least one elastomer selected from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, essentially saturated diene elastomers, and mixtures of said elastomers, as well as a reinforcing filler, characterized in that the composition also includes glass flakes and a plasticizer, said plasticizer including a functionalized or non-functionalized polyisobutylene oil, having a molecular weight of between 200 g/mol and 40,000 g/mol, and/or a hydrocarbon plasticizing resin, the glass transition temperature Tg of which is greater than 20°C and the softening temperature of which is lower than 170°C.

Description

 RUBBER COMPOSITION COMPRISING GLASS SCALES ESPECIALLY FOR THE MANUFACTURE OF PNEUMATIC TIRES

The present invention relates to a rubber composition for the manufacture of tires and in particular for the manufacture of an air-impermeable inner layer, commonly called "tire inner liner".

Tubeless tires have a low air permeability inner surface to prevent deflation of the tires and to protect the sensitive internal areas of the latter against oxygen and water inflow, such as groundwater. containing metal cables sensitive to oxidation, this protection to improve the endurance of tires. Today such protection of the inner surface of the tires is achieved by inner gums consisting of elastomeric compositions based on butyl rubber.

But since fuel savings and the need to protect the environment have become priorities, it is desirable to produce watertight or airtight inner layers or "inner liner" hysteresis as low as possible, in order to obtain improved rolling resistance of the tire. But the performance in terms of air impermeability of butyl rubber is related to a minimum significant thickness (of the order of a millimeter) and therefore to a certain weight, which does not allow to respond effectively to these new requirements.

Thus it is necessary to add reinforcing fillers, such as carbon black, to the elastomeric composition of inner liner to improve its impermeability. However, in large quantities, these reinforcing fillers affect certain properties of the composition both raw: difficulty of implementation commonly called "processability", and cooked: degradation of mechanical properties including decreased flexural strength. The introduction of plasticizer of the oil type overcomes these disadvantages of implementation and mechanical properties but strongly penalizes the impermeability. Various solutions have been envisaged to overcome these drawbacks in particular by using other types of charges, often known as inert white filler such as smectites and in particular organophilic smectites. Added to the conventional constituents (reinforcing filler, plasticizer, etc.), these organophilic smectites improve the impermeability properties of the materials if they are well dispersed in the material, that is to say both a homogeneous distribution of these charges within the material and a good accounting with the latter. This dispersion is often difficult to obtain because of the low thermodynamic compatibility existing between the elastomers and such fillers. Also, the applicants have described WO08 / 145314, WO09 / 077541 and WO09 / 077542 rubber compositions for tire inner liner based on at least one butyl rubber, a reinforcing filler, a lamellar inert filler such as graphite or smectite and a plasticizer such as a hydrocarbon plasticizing resin or a polyisobutylene oil. These compositions have good properties of gas impermeability, rolling resistance and endurance without, of course, at the expense of other properties.

 It is therefore known that the use of lamellar fillers makes it possible to reduce the permeability of a material, especially since the exfoliation is extensive. Indeed, the lamellar fillers used are in the form of sheets, and to use them in an optimal way, it is preferable to exfoliate them to benefit at best from their lamellar form. This exfoliation is a costly and delicate step to achieve with conventional lamellar fillers (smectites for example). There is therefore a need for an alternative to conventionally used lamellar fillers, making it possible to limit the various prior treatments and to better control a priori the dispersion of the lamellar particles within the mixture.

Continuing its research, the Applicant has found that the use of flakes (or flakes or flakes) of glass in rubber compositions for pneumatic and especially in those intended to ensure tightness, provides excellent sealing, similar to that described in the prior art, while avoiding the problems associated with the exfoliation of lamellar fillers used until then. Indeed, one of the peculiarities of the glass flakes is that they are in the form of unitary platelets, the exfoliation step is therefore useless.

Thus, the invention relates to a rubber composition based on at least one major elastomer chosen from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, essentially saturated diene elastomers and mixtures of these elastomers, and of a reinforcing filler, this composition also comprises glass flakes and a plasticizer, this plasticizer comprising a functionalized or non-functionalized polyisobutylene oil, having a molecular mass of between 200 g / mol and 40,000 g / mol, and / or a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20 ° C and whose softening temperature is less than 170 ° C. The invention thus makes it possible, in isolation with respect to the solutions known in the prior art, to obtain, without prior exfoliation steps, maximum exploitation of the lamellar form of the glass flakes.

According to a first embodiment, the invention preferably relates to a composition as defined above, in which the majority elastomer is constituted by a butyl rubber; preferentially butyl rubber is a copolymer of isobutene and isoprene; alternatively and preferentially also, the butyl rubber is a brominated polyisobutylene; alternatively and more preferably, the butyl rubber is a chlorinated polyisobutylene.

According to a second embodiment, the invention preferably relates to a composition as defined above, in which the majority elastomer is a diene elastomer, more preferably a substantially unsaturated diene elastomer or a substantially saturated diene elastomer.

According to a variant of these embodiments, the invention relates to a composition as defined above, in which the majority elastomer represents 100% of the elastomers of the composition.

According to another variant, the invention preferably relates to a composition as defined above, which comprises one or more other elastomers chosen from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, essentially saturated diene elastomers and mixtures of these. elastomers.

Preferably, the invention relates to a composition as defined above, in which the reinforcing filler comprises carbon black, the level of carbon black being more preferably greater than or equal to 30 phr; more preferably, the carbon black content ranges from 30 to 120 phr, more preferably from 30 to 70 phr, and more particularly from 35 to 60 phr. Preferentially also the invention relates to a composition as defined above, wherein the reinforcing filler comprises a reinforcing inorganic filler, and preferably silica. Preferably, the invention relates to a composition as defined above, in which the level of glass flakes varies from 2 to 35 phr, preferably from 3 to 25 phr and more particularly from 5 to 20 phr. Equivalently, the invention preferably relates to a composition as defined above, in which the glass scales are without surface treatment, with surface treatment or in which the glass scales comprise a mixture of flakes with and without treatment of surface. Preferably, the invention relates to a composition as defined above, in which the plasticizing system consists of a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20 ° C. and whose softening temperature is less than 170 ° C. Alternatively and preferably also, the invention relates to a composition as defined above, in which the plasticizer system consists of a functionalized or non-functionalized polyisobutylene oil having a molecular mass of between 200 g / mol and 40,000 g / mol. Also, preferably, the invention relates to a composition as defined above, in which the plasticizer system consists of a functionalized or non-functionalized polyisobutylene oil, having a molecular mass of between 200 g / mol and 40,000 g / mol, and a hydrocarbon plasticizing resin whose glass transition temperature, Tg, is greater than 20 ° C and whose softening temperature is less than 170 ° C.

More preferably, the invention, when it comprises a plasticizing resin, relates to a composition as defined above, in which the plasticizing hydrocarbon resin has a Tg greater than + 30 ° C., preferably with a content of between 2 and 35 phr. ; more preferably, the plasticizing hydrocarbon resin is chosen from the group consisting of homopolymer or copolymer resins of cyclopentadiene (abbreviated as CPD) or dicyclopentadiene (abbreviated as DCPD), terpene homopolymer or copolymer resins, homopolymer resins or C5 cutting copolymer, (D) CPD / vinylaromatic copolymer resins, (D) CPD / terpene copolymer resins, (D) CPD / C5 cut copolymer resins, terpene / vinylaromatic copolymer resins, resins of C5 / vinylaromatic cut copolymer, (D) CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D (CPD) copolymer resins, C5 / styrene cut copolymer resins , C5 / C9 cut copolymer resins, and mixtures of these resins. More Preferably, the hydrocarbon resin is alternately a polylimonene resin, a homopolymer resin or C5 cutting copolymer or a C5 cutting copolymer resin and C9 cutting. More preferably, the invention, when it comprises a polyisobutylene oil, relates to a composition as defined above, in which the polyisobutylene oil is present in a proportion of between 2 and 50 phr, more preferably between 5 and 30 phr. Also preferably, the polyisobutylene oil has a molecular weight of between 500 g / mol and 35,000 g / mol; more preferably between 1000 g / mol and 30 000 g / mol.

Preferably, the invention relates to a composition as defined above, which further comprises an inert filler, preferably selected from calcium carbonate, glass beads, graphites, phyllosilicates and mixtures thereof.

The invention also relates to a pneumatic object having a rubber composition as defined above. The invention also relates to a gas-tight tire layer having a composition as defined above; and more preferably the invention relates to such a layer, disposed on the inner wall of the pneumatic object.

In particular, the invention also relates to a tire comprising a composition as defined above.

I. - MEASUREMENTS AND TESTS

The rubber compositions are characterized, before and after firing, as indicated below.

1-1. Plasticity M ooney

An oscillating consistometer is used as described in the French standard NF T 43-005 (1991). The Mooney plasticity measurement is carried out according to the following principle: the composition in the green state (Le., Before baking) is molded in a cylindrical chamber heated to 100 ° C. After one minute of preheating, the rotor rotates within the test tube at 2 revolutions / minute and the useful torque is measured to maintain this movement after 4 minutes of rotation. The Mooney plasticity (ML 1 +4) is expressed in "Mooney unit" (UM, with 1 UM = 0.83 Newton, m being). 1-2. Traction tests

These tests make it possible to determine the elastic stress and the properties at break. Unless otherwise indicated, they are carried out in accordance with the French standard NF T 46-002 of September 1988. The secant modules known as "nominal" (or apparent stresses, in MPa) are measured in second elongation (ie after an accommodation cycle). at 10% elongation (denoted "MA10") and 100% elongation ("MA100"). All these tensile measurements are carried out under normal conditions of temperature (23 ± 2 ° C.) and hygrometry (50 ± 5% relative humidity), according to the French standard NF T 40-101 (December 1979). The breaking stresses (in MPa) and the elongations at break (in%) are also measured at a temperature of 23 ° C.

For more readability the results will be indicated in base 100, the value 100 being attributed to the witness. A result less than 100 indicating a decrease in the value concerned, and vice versa, a result greater than 100, will indicate an increase in the value concerned.

I-3. Permeability The permeability values are measured using a MOCON OXTRAN 2/60 permeability tester at 40 ° C. Samples baked in the form of discs of a certain thickness (approximately 0.8 to 1 mm) are mounted on the apparatus and sealed with vacuum grease. One side of the disc is kept under 10psi of nitrogen while the other side is kept under 10 psi of oxygen. The increase in oxygen concentration is monitored by using a "Coulox" oxygen sensor on the face maintained under nitrogen. The oxygen concentration is noted on the face maintained under nitrogen to reach a constant value, used to determine the permeability to oxygen.

 An arbitrary value of 100 is given for the oxygen permeability of the control, a result of less than 100 indicating a decrease in the permeability to oxygen and therefore a better impermeability.

II. DETAILED DESCRIPTION OF THE INVENTION The rubber composition according to the invention, based on at least one predominant elastomer by weight (that is to say for example for more than 50 phr in a binary mixture) chosen from the group constituted by the butyl rubbers, the essentially unsaturated diene elastomers, the essentially saturated diene elastomers and the mixtures of these elastomers, and a reinforcing filler, also comprises glass flakes, alone or in blending with one or more other fillers inert, and a plasticizer comprising a polyisobutylene oil functionalized or not, having a molecular weight of between 200 g / mol and 40,000 g / mol, and / or a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20. ° C and whose softening temperature is below 170 ° C.

For its use as the inner liner of a tire, the composition comprises, as elastomer, an elastomer chosen from the group consisting of butyl rubbers. However, the good sealing and hysteresis properties of the compositions in accordance with the invention make it possible to also recommend their use at other points of the tire (tread, sidewall, ....) which mainly use diene elastomers essentially unsaturated or not and / or cuts thereof.

 Unless expressly indicated otherwise, the percentages given in this application are percentages by mass.

The levels expressed in "phr" represent parts by weight, per hundred parts of elastomer.

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 term "from a to b" means the range from a to b (i.e., including the strict limits a and b). 11-1. Elastomer or "rubber"

Usually, the terms "elastomer" and "rubber", which are interchangeable, are used interchangeably in the text. The composition according to the invention for a tubeless tire sealing inner liner contains at least one butyl rubber, used alone, in a blend with one or more other butyl rubbers or diene elastomers.

Butyl rubber is understood to mean a linear or branched homopolymer of polyisobutylene or a linear or branched copolymer of polyisobutylene with isoprene (in this case this butyl rubber is part of the diene elastomers), as well as halogenated derivatives, in particular those which are generally brominated. or chlorinated, of these homopolymers of polyisobutylene and copolymers of polyisobutylene and isoprene. Examples of butyl rubber that are particularly suitable for carrying out the invention are: isobutylene rubbers, isobutylene copolymers and isoprene (IIR), chlorobutyl rubbers such as chloroisbutylene-isoprene copolymer (CNR) and bromo-butyl rubbers such as bromoisobutylene-isoprene copolymer (BIIR) and of these, exemplary branched butyls may be mentioned, halogenated star butyls ("halogenated star branched butyl" in English), such as the "Star-branched Bromobutyl 6222" marketed by the company "Exxon".

By extension of the above definition, also referred to as "butyl rubber" copolymers of isobutylene and styrene derivatives such as isobutylene and brominated methylstyrene copolymers (BIMS) including elastomer named " EXXPRO "marketed by the company" Exxon ".

By "elastomer" or "diene" rubber, it is to be understood in a known way (one or more elastomers), 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 level of units or units of diene origin (conjugated dienes) which is greater than 15% (mol%). In the category of "essentially unsaturated" diene elastomers, the term "highly unsaturated" diene elastomer is particularly understood to mean a diene elastomer having a content of units of diene origin (conjugated dienes) which is greater than 50%.

Thus, diene elastomers such as certain butyl rubbers or copolymers of dienes and alpha-olefins of the EPDM type may be described as "essentially saturated" diene elastomers (level of units of diene origin which is weak or very weak, always less than 15%).

Given these definitions, the term "diene elastomer" is used more particularly, whatever the category above, which can be used in the compositions 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 alpha-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 nonconjugated diene monomer of the aforementioned type such as in particular hexadiene-1,4, ethylidene norbornene, dicyclopentadiene;

 (d) - a copolymer of isobutene and isoprene (butyl diene rubber), as well as the halogenated versions, in particular chlorinated or brominated, of this type of copolymer.

Although it applies to any type of diene elastomer, one skilled in the art of the tire will understand that for use as an inner rubber tire, the present invention is preferably implemented with essentially saturated elastomers, in particular of type (d) above.

As 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, are particularly suitable. 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 copolymers 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 can be for example block, statistical, sequenced, microsequenced, and be prepared in dispersion or in solution; they may be coupled and / or starred or functionalized with a coupling agent and / or starring or functionalization. For coupling with carbon black, there may be mentioned for example functional groups comprising a C-Sn bond or amino functional groups such as benzophenone for example; for coupling to a reinforcing inorganic filler such as silica, mention may be made, for example, of silanol or polysiloxane functional groups having a silanol end (as described for example in FR 2 740 778 or US Pat. No. 6,013,718), alkoxysilane groups (such as as described for example in FR 2,765,882 or US 5,977,238), carboxylic groups (as described for example in WO 01/92402 or US 6,815,473, WO 2004/096865 or US 2006/0089445) or groups polyethers (as described for example in EP 1 127 909 or US 6,503,973). As other examples of functionalized elastomers, mention may also be made of elastomers (such as SBR, BR, NR or IR) of the epoxidized type.

Suitable polybutadienes and in particular those having a content (mol%) in units -1, 2 of between 4% and 80% or those having a content (mol%) in cis-1, 4 greater than 80%, polyisoprenes, copolymers of butadiene-styrene and in particular those having a glass transition temperature, Tg, (measured according to ASTM D3418) of between 0 ° C. and -70 ° C. and more particularly between -10 ° C. and -60 ° C., styrene content between 5% and 60% by weight and more particularly between 20% and 50%, a content (mol%) in -1,2 bonds of the butadiene part of between 4% and 75%, a content (% molar) in trans-1,4 bonds between 10% and 80%, butadiene-isoprene copolymers and in particular those having an isoprene content of between 5% and 90% by weight and a Tg of -40 ° C. to -10 ° C. At 80 ° C., the isoprene-styrene copolymers and especially those having a styrene content of between 5% and 50% by weight and a Tg included 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 (mol%) in units -1, 2 of the butadiene part of between 4% and 85%, a content (mol%) in trans-1,4 units of the butadiene part of between 6% and 80%, a content (mol%) in units -1, 2 plus -3 , 4 of the isoprene part of between 5% and 70% and a content (mol%) in trans units -1, 4 of the isoprenic part of between 10% and 50%, and more generally any butadiene-styrene-isoprene copolymer having a Tg between -20 ° C and -70 ° C.

Finally, "isoprene elastomer" is understood to mean, in known manner, a homopolymer or copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR) and synthetic polyisoprenes (IR). the different isoprene copolymers and the mixtures of these elastomers. Among the isoprene copolymers, mention will in particular be made of copolymers of isobutene-isoprene (NR), 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 (mol%) of cis-1,4 bonds greater than 90%, more preferably still greater than 98%, are preferably used. In summary According to one embodiment of the invention: the majority elastomer of the composition according to the invention is a butyl rubber (in particular for applications as inner tire gums), the latter is preferably chosen from the group essentially saturated diene elastomers consisting of isobutene and isoprene copolymers and their halogenated derivatives, this essentially saturated elastomer being able to be used in blending with an elastomer chosen from the group of highly unsaturated diene elastomers constituted by polybutadienes (abbreviated to " BR "), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers, butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR) , isoprene-styrene copolymers (SIR) and isoprene-butadiene-styrene copolymers (SBIR) and blends of these elastomers. According to another embodiment of the invention, the majority elastomer is a substantially unsaturated diene elastomer of the composition according to the invention, the latter is preferably chosen from the group of highly unsaturated diene elastomers constituted by polybutadienes (in particular abbreviated "BR"), synthetic polyisoprenes (IR), natural rubber (NR), butadiene copolymers, isoprene copolymers and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-copolymers. butadiene-styrene (SBIR).

In this embodiment, the diene elastomer is predominantly (Le., For more than 50 phr) an isoprene elastomer or an SBR, whether it is an emulsion prepared SBR ("ESBR") or a solution-prepared SBR ("SSBR"), or a blend (mixture) SBR / BR, SBR / NR (or SBR / IR), BR / NR (or BR / IR), or SBR / BR / NR (or SBR / BR / IR). In the case of an SBR elastomer (ESBR or SSBR), an SBR having an average styrene content, for example between 20% and 35% by weight, or a high styrene content, for example 35 to 35% by weight, is used in particular. 45%, a vinyl ring content of the butadiene part of between 15% and 70%, a content (mol%) of trans-1,4 bonds of between 15% and 75% and a Tg of between -10 ° C. and - 55 ° C; such an SBR can be advantageously used in admixture with a BR preferably having more than 90% (mol%) of cis-1,4 bonds.

This embodiment corresponds in particular to compositions of the invention intended to constitute, in tires, the rubber matrices of certain treads (for example for industrial vehicles), reinforcing plies of at the top (for example of working plies, protective plies or hooping webs), carcass reinforcement plies, flanks, beads, protectors, underlays, rubber blocks and other internal rubbers interface between the aforementioned areas of the tires.

11-2. Reinforcing charge

Any type of reinforcing 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, a reinforcing inorganic filler such as silica, or cutting of these two types of filler, including a cut of carbon black and silica.

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 (ASTM grades), for example blacks N 15, N 134, N 234, N 326, N330, N 339, N 347 or N375, or else, according to the targeted applications, the blacks of higher series (for example N660, N683, N772), or even N990.

 In the case of using carbon blacks with an isoprene elastomer, the carbon blacks could for example already be incorporated into the isoprene elastomer in the form of a masterbatch (see, for example, applications WO 97/36724 or WO 99 / 16600).

As examples of organic fillers other than carbon blacks, mention may be made of the organic functionalized polyvinylaromatic fillers as described in applications WO-A-2006/069792 and WO-A-2006/069793. 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, without any 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 silica (SiO 2), or aluminous type, in particular alumina (Al 2 O 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 1165MP", "1135MP" and "1115MP" of the Rhodia company, the "Hi-Sil EZ150G" silica of the PPG company, the "Zeopol 8715", "8745" and "8755" silicas of the Huber Company, the high surface area silicas as described in the application WO 03 / 16837. In order to couple the reinforcing inorganic filler to the diene elastomer, an at least bifunctional coupling agent (or bonding agent) is used in known manner to ensure a sufficient chemical and / or physical connection between the inorganic filler ( surface of its particles) and the diene elastomer, in particular organosilanes or bifunctional polyorganosiloxanes.

In particular, polysulfide silanes, called "symmetrical" or "asymmetrical" silanes according to their particular structure, are used, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005/016650). In particular, polysulphide silanes known as "symmetrical" silanes having the following general formula (III) are suitable in the following non-limiting definition:

(III) Z - A - S _x - A - Z, wherein: - x is an integer of 2 to 8 (preferably 2 to 5);

- A is a divalent hydrocarbon radical (preferably alkylene groups C1-C18 or arylene groups, C ₆ -C _2, more particularly alkylene C1-C10, including CC _4, in particular propylene);

Z is one of the following formulas: R1 R1 R2

 I i I

 Si- Si- Si-

 R2 R2 in which:

- the radicals, substituted or unsubstituted, identical or different, represent an alkyl group having Ci ₈ cycloalkyl, C ₅ -C ₈ aryl or C ₆ -C ₈

(preferably alkyl groups CC ₆ , cyclohexyl or phenyl, especially alkyl groups CC ₄ , more particularly methyl and / or ethyl).

- the radicals R ^2, substituted or unsubstituted, identical or different, represent an alkoxyl group having Ci ₈ cycloalkoxy or C ₅ -C ₈ (preferably a group selected from alkoxyl DC cycloalkoxyls ₈ and C ₅ - C ₈ , more preferably still a group selected from alkoxy in CC ₄ , in particular methoxyl and ethoxyl).

In the case of a mixture of polysulfurized alkoxysilanes corresponding to the formula (I II) above, in particular common commercially available mixtures, the average value of the "x" is a fractional number preferably between 2 and 5, plus preferentially close to 4. But the invention can also be advantageously implemented for example with disulfide alkoxysilanes (x = 2). By way of examples of polysulphurized silanes, mention may be made more particularly of bis (alkoxyl (CC ₄ ) -alkyl (CrC ₄ ) silyl-alkyl (CrC ₄ ) polysulfides (especially disulfides, trisulphides or tetrasulfides), for example polysulfides of bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl). Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated to TESPT, of formula [(C ₂ H ₅ O) ₃ Si (CH ₂ ) 3 S 2] 2 or bis (triethoxysilylpropyl) disulfide, in abbreviated form, is especially used. TESPD, of formula [(C2H ₅ 0) ₃ Si (CH ₂ ) ₃ S] 2. Also suitable as preferred examples of the bis (mono, trisulfide or tetrasulfide) of bis (monoalkoxyl (CC ₄₎ -dialkyl (CrC ₄₎ silylpropyl), in particular tetrasulfide, bis- monoethoxydimethylsilylpropyl as described in the patent application WO 02/083782 (or US 2004/132880).

As coupling agent other than polysulfurized alkoxysilane, there may be mentioned in particular bifunctional POS (polyorganosiloxanes) or polysulfides of hydroxysilane (R ² = OH in the formula III above) as described in the patent applications. WO 02/30939 (or US 6,774,255) and WO 02/31041 (or US 2004/051210), or silanes or POS bearing functional azo-dicarbonyl groups, as described for example in patent applications WO 2006/125532, WO 2006/125533, WO 2006/125534.

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, in particular hydroxyl sites, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.

Preferably, the total reinforcing filler content (carbon black and / or reinforcing inorganic filler such as silica) is between 20 and 200 phr, more preferably between 30 and 150 phr, the optimum being in a known manner different according to particular applications targeted: the level of reinforcement expected on a bicycle tire, for example, is of course less than that required on a tire capable of running at high speed in a sustained manner, for example a motorcycle tire, a tire for a passenger vehicle or for commercial vehicles such as heavy goods vehicles.

For use of the composition as tire inner liner, carbon black is preferably used as reinforcing filler in a proportion of greater than or equal to 30 phr. Preferably the carbon black content varies from 30 to 120 phr, indeed beyond this rate the penalty in terms of rigidity of the composition is too important for an application as tire inner liner. It is clear that very high ASTM grade carbon blacks, such as N990 carbon black, are less reinforcing than 700 grade carbon blacks, and a fortiori 600, and that it is necessary for identical reinforcing of to use higher levels of carbon black in the case of 900-grade carbon blacks than if they are 600- or 700-grade blacks. More preferentially, the proportion of carbon black varies from 30 to 70 phr, this is particularly the case when using ASTM 600 or 700 grade carbon blacks, and even more preferably this proportion varies from 35 to 60 phr.

Carbon black may advantageously be the only reinforcing filler or the majority reinforcing filler. Of course, it is possible to use a single carbon black or a blend of several carbon blacks of different ASTM grades.

The carbon black may also be used in blending with other reinforcing fillers and in particular reinforcing inorganic fillers as described above, and in particular silica. 11-3 Inert or non-reinforcing fillers

For the implementation of the invention, the glass flakes are used, alone or in combination with other inert fillers, lamellar or not, such as calcium carbonate (or chalk), glass beads, graphite and / or silicon-based lamellar fillers and in particular phyllosilicates such as smectites, kaolin, talc, mica, vermiculite, etc. In total, the inert filler content may vary from 1 to 70 phr. preferably 2 to 60 phr, and it comprises a level of 3 to 50 phr of glass flakes, preferably 5 to 30 phr.

II-3-A Glass Scales

Flakes (or flakes or flakes) of glass (in English "glass flakes") means a synthetic material in the form of platelets predominantly composed of silica (SiO ₂ ), the composition of which may comprise inter alia and in addition: ₂ 0, B ₂ 0 _3, ZnO, Na ₂ 0, MgO, CaO, Al ₂ 0 _3, Ti0 _2. Depending on the applications envisaged, there are glass flakes without surface treatment, or with surface treatment, and in particular with silane-based surface treatments. Their role is to ensure the bond between the silanol (SiOH) mineral function of the glass flake with the organic functions of the elastomer. These silane-based surface treatments are, for example, 3-aminopropyltriethoxysilane, vinyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane or methacryloxypropyltrimethoxysilane. Thus, the glass flakes exist with different characteristics depending on the applications envisaged, for example, for high chemical resistance, or resistance to breakage. The different types of glass flakes are suitable for the realization of the invention, including without surface treatment, despite the presence of free silanols (SiOH), which are positioned on the surface of the glass scales and which could be feared that they react with the vulcanization system, making it unavailable to effect crosslinking of the elastomeric chains.

The glass flakes are in the form of unit sheets, and may for example have a particle thickness ranging from 0.01 to 100 μηι, preferably from 0.1 to 50 μηι and particularly from 1 to 5 μηι. Furthermore, the particle size distribution can be, for example for "GF100M" glass flakes. marketed by Glassflakes Ltd. With or without a surfactant, such that about 10% of the particles have their largest dimension of between 300 and 65 μηι, 65% between 50 and 300 μηι and 25% less than 50 μηι. In the compositions according to the invention, glass flakes of any type may be used, in particular surface-treated glass flakes from those listed above, or glass flakes without surface treatment.

The compositions according to the invention use a glass flake rate ranging from 2 phr to 35 phr, preferably from 3 to 25 phr, and in particular from 5 to 20 phr.

II-3-B Other inert loads

Optionally, the compositions of the invention may comprise in addition to glass flakes, or in blending with them, other inert fillers such as calcium carbonate (or chalk), glass beads, graphite, or silicon-based platy fillers such as smectites, kaolin, talc, mica, montmorillonites and vermiculite, or a mixture thereof. Inert fillers such as graphite, or silicon-based lamellar fillers, or a mixture of these fillers, are indeed also interesting because they also make it possible to improve the impermeability of the compositions in which they are dispersed with a adequate rate. For example, when they are used, the rate of inert fillers other than glass flakes may vary from 2 phr to 35 phr, preferably from 3 to 25 phr, and in particular from 5 to 20 phr, in compliance with the rate total inert loads mentioned above. II-3-Ba Graphite Graphite refers generally to a set of non-compact hexagonal sheets of carbon atoms: graphenes. Graphite, a hexagonal crystalline system, has an ABAB stack where plane B is translated relative to plane A. Graphite can not be considered as a reinforcing filler within the meaning of the definition in paragraph 11-2, however it can be considered as a semi-reinforcing filler in that it allows an increase in the tensile modulus of a rubber composition in which it is incorporated. Given these definitions, the term "graphite" can more particularly be understood as meaning that can be used in the compositions according to the invention:

 - (a) all natural graphite, associated with rocks affected by metamorphism, after separation of the impurities accompanying the graphite veins and after grinding;

 (b) any thermally expandable natural graphite, i.e. in which is interposed one or more chemical compounds in the liquid state, for example an acid, between its graphene planes;

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

 (d) any synthetic graphite obtained by graphitization of petroleum coke. The compositions of the invention may contain a single graphite or a mixture of several graphites, so one can 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.

 It has surprisingly been found that graphites with either of these two types of morphology are suitable in the compositions according to the invention, however graphites having a lamellar form are preferentially suitable, and even more so when they are oriented so as to present their largest face perpendicular to the gas permeation flow. ll-3-B-b Silicon-based lamellar charge

In particular, among the lamellar inorganic fillers based on silicon are suitable phyllosilicates and particularly those included in the group consisting of smectites, kaolin, talc, mica and vermiculite.

Among the phyllosilicates are also suitable for the invention, functionalized phyllosilicates and in particular organomodified. According to a particular embodiment, the organic structure with which the inert filler is associated is a surfactant of formula: -M ⁺ R ¹ R ² R ³ - where M represents a nitrogen, sulfur, phosphorus or pyridine atom and wherein R ¹ , R ² , and R ³ represents a hydrogen atom, an alkyl group, an aryl group or an allyl group, R ¹ , R ² , and R ³ being the same or different. In particular, organomodified montmorillonites are suitable for the invention. Thus, montmorillonites modified with a surfactant such as a dioctadecyldimethyl dihydrogenated quaternary ammonium salt. Such an organomodified montmorillonite is marketed in particular by Southern Clay Products under the trade name: "CLOISITE 6A and 20A".

 Other surfactants based on quaternary ammonium salts may be further used to modify the phyllosilicates as described in the patent application WO06 / 047509. 11-4 Plasticizer

For the implementation of the invention, a plasticizer is used which is chosen from hydrocarbon resins whose Tg, glass transition temperature, is greater than 20 ° C and whose softening point (softening point) is less than 170 ° C, or a polyisobutylene oil of number average molecular weight (Mn) between 200g / mol and 40,000g / mol, or a mixture of the oil and the aforementioned resins.

 In total, the plasticizer content varies from 2 to 50 phr, preferably from 5 to 30 phr. II-4-A Thermoplastic resin

The rubber compositions of the invention may use a hydrocarbon plasticizing resin whose Tg, glass transition temperature, is greater than 20 ° C. and whose softening point temperature is less than 170 ° C. as explained in detail below.

In a manner known to those skilled in the art, the term "plasticizing resin" is reserved in this application, by definition, to a compound which is solid on the one hand at room temperature (23 ° C.) (as opposed to a compound liquid plasticizer such as an oil), on the other hand compatible (that is to say miscible with the rate used, typically greater than 5 phr) with the rubber composition for which it is intended, so as to act as a true diluent.

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

They have been extensively described in the patents or patent applications cited in the introduction to this memo, as well as, for example, in R. Mildenberg's Hydrocarbon Resins, M. Zander and G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9) of which chapter 5 is devoted to their applications, in particular in pneumatic rubber (5.5 "Rubber Tires and Mechanical Goods").

They may be aliphatic (for example C5 or C9 cut), naphthenic, aromatic or aliphatic / naphthenic / aromatic type that is to say based on aliphatic and / or naphthenic monomers and / or aromatic. They may be natural or synthetic, whether or not based on petroleum (if so, also known as petroleum resins). They are preferably exclusively hydrocarbon-based, that is to say they contain only carbon and hydrogen atoms.

In a known manner, C5 (or for example respectively C9) is understood to mean any fraction resulting from a process resulting from petrochemicals or petroleum refining, any distillation cup containing predominantly compounds having 5 (or respectively 9 in the case of a C9) carbon atoms cut.

Preferably, the plasticizing hydrocarbon resin has at least one, more preferably all, of the following characteristics: a number-average molecular weight (Mn) of between 400 and

2000 g / mol;

 a polymolecularity index (Ip) of less than 3 (booster: Ip = Mw / Mn with Mw weight average molecular weight). More preferably, this plasticizing hydrocarbon resin has at least one, still more preferably all, of the following characteristics:

a Tg greater than 30 ° C;

 a mass Mn of between 500 and 1500 g / mol;

 an index Ip less than 2.

The glass transition temperature Tg is measured in a known manner by DSC (Differential Scanning Calorimetry), according to ASTM D3418 (1999), and the softening point ("softening point") is measured according to the ASTM E-28 standard.

The macrostructure (Mw, Mn and Ip) of the hydrocarbon resin is determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35 ° C; concentration 1 g / l; flow rate 1 ml / min; filtered solution on 0.45 μηι porosity filter before injection; Moore calibration with polystyrene standards; set of 3 "WATERS" columns in series ("STYRAGEL" HR4E, HR1 and HR0.5); detection by differential refractometer ("WATERS 2410") and its associated operating software ("WATERS EM POWER"). According to a particularly preferred embodiment, the plasticizing hydrocarbon resin is chosen from the group consisting of homopolymer or copolymer resins of cyclopentadiene (abbreviated as CPD) or dicyclopentadiene (abbreviated as DCPD), terpene homopolymer or copolymer resins, C5 homopolymer or copolymer resins, and mixtures of these resins; and more preferably still, the resin is a homopolymer resin or C5 cutting copolymer or mixture thereof.

Among the above copolymer resins are preferably used those selected from the group consisting of copolymer resins (D) CPD / vinylaromatic, copolymer resins (D) CPD / terpene, copolymer resins (D) CPD / cut C5, terpene / vinylaromatic copolymer resins, C5 / vinylaromatic cut copolymer resins, and mixtures of these resins.

The term "terpene" includes, in a known manner, the alpha-pinene, beta- pinene and limonene monomers; preferably, a limonene monomer is used which is in a known manner in the form of three possible isomers: L-limonene (laevorotatory enantiomer), D-limonene (dextrorotatory enantiomer), or the dipentene, racemic of the dextrorotatory and levorotatory enantiomers. . Examples of suitable vinyl aromatic monomers are styrene, alpha-methylstyrene, ortho-, meta-, para-methylstyrene, vinyl-toluene, para-tertiarybutylstyrene, methoxystyrenes, chlorostyrenes, vinylmesitylene and divinylbenzene. , vinyl naphthalene, any vinylaromatic monomer from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinyl aromatic compound is styrene or a vinylaromatic monomer from a C9 cut (or more generally from a C8 to C10 cut). Preferably, the vinylaromatic compound is the minor monomer, expressed as a mole fraction, in the copolymer under consideration.

According to a more particularly preferred embodiment, the plasticizing hydrocarbon resin is chosen from the group consisting of homopolymer resins (D) CPD, copolymer resins (D) CPD / styrene, polylimonene resins, copolymer resins limonene / styrene, limonene / (D) CPD copolymer resins, C5 / styrene cut copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins. The preferred resins above are well known to those skilled in the art and commercially available, for example sold with regard to:

 polylimonene resins: by the company DRT under the name "Dercolyte L120" (Mn = 625 g / mol, Mw = 1010 g / mol, lp = 1.6, Tg = 72 ° C.) or by the company ARIZONA under the name "Sylvagum TR7125C" (Mn = 630 g / mol, Mw = 950 g / mol, lp = 1.5, Tg = 70 ° C);

C ₅ / vinylaromatic cut copolymer resins, in particular C5 / styrene cut or C5 / C9 cut: by Neville Chemical Company under the names "Super Nevtac 78", "Super Nevtac 85" or "Super Nevtac 99", by Goodyear Chemicals under the name "Wingtack Extra", by Kolon under the names "Hikorez T1095" and "Hikorez T1100", by Exxon under the names "Escorez 2101" and "ECR 373";

 - limonene / styrene copolymer resins: by DRT under the name "Dercolyte TS 105" from the company DRT, by ARIZONA Chemical Company under the names "ZT1 15LT" and "ZT5100".

homopolymer resins or C5 cutting copolymer: aliphatic resin (C5 pure) "Hikorez A-1100" marketed by KOLON, "Wingtack" resins sold by Cray Valley, or resins "QLH-100- 4 "," QLH-100-5 "," QLH-100-6 "marketed by Zibo Qilu Yixi Luhua Chemical Co.

When it is used, the content of hydrocarbon resin is preferably between 2 and 35 phr. Below the minimum indicated, the technical effect may be insufficient, while beyond the maximum stickiness of the compositions in the green state, on the mixing tools, may in some cases become prohibitive point industrial view. The level of hydrocarbon resin is even more preferably between 5 and 25 phr.

II-4-B Polyisobutylene Oil The rubber compositions of the invention can use an extender oil (or plasticizing oil) whose usual function is to facilitate the implementation by lowering the Mooney plasticity and improving endurance by decreasing the lengthening modules cooked. At room temperature (23 ° C), these oils, more or less viscous, are liquids (that is to say, as a reminder, substances having the ability to eventually take the shape of their container), as opposed in particular to resins or rubbers which are inherently solid. In accordance with the invention, polyisobutylene oils having a number-average molecular weight (Mn) of between 200 g / mol and 40,000 g / mol are used. For masses Mn too low, there is a risk of migration of the oil outside the composition, while too large masses can cause excessive stiffening of this composition. The abovementioned low molecular weight polyisobutylene oils have demonstrated a much better compromise of properties compared to other oils tested, especially conventional paraffinic type oils. Preferably for the compositions in accordance with the invention, the polyisobutylene oils have a molecular mass of between 500 g / mol and 35,000 g / mol and more preferably still between 1000 g / mol and 30,000 g / mol.

By way of examples, polyisobutylene oils are sold in particular by the company UNIVAR under the name "Dynapak Poly" (eg "Dynapak Poly 190"), by BASF under the names "Glissopal" (eg "Glissopal 1000") or "Oppanol "(eg" Oppanol B12 "), by Texas Petro Chemical under the name" TPC "(" TPC 1350 "), by Innovene under the name" INDOPOL ". The number average molecular weight (Mn) of the polyisobutylene oil is determined by SEC, the sample being solubilized beforehand in tetrahydrofuran at a concentration of about 1 g / L; then the solution is filtered on 0.45μηι porosity filter before injection. The equipment is the chromatographic chain "WATERS alliance". The elution solvent is tetrahydrofuran, the flow rate is 1 mL / min, the temperature of the system is 35 ° C. and the analysis time is 30 minutes. We use a set of two columns "WATERS" of denomination "STYRAGEL HT6E". The injected volume of the solution of the polymer sample is 100 μί. The detector is a differential refractometer "WATERS 2410" and its associated software for the exploitation of chromatographic data is the "WATERS MILLENIUM" system. The calculated average molar masses relate to a calibration curve made with polystyrene standards.

Polyisobutylene oils of low molecular weight suitable for the invention may be functionalized or not. Thus, by way of non-limiting example, certain functionalizations of polyisobutylene oils such as anhydrous polyisobutylene succinic oils, PI BSA, or polyisobutylene succinimide oils, PIBSI, may be mentioned.

When used, the polyisobutylene oil content is preferably between 2 and 35 phr. Below the minimum indicated, the elastomeric layer or composition may have too much rigidity for certain applications while that beyond the maximum recommended, there is a risk of insufficient cohesion of the composition and loss of tightness may be detrimental to the application in question.

 The polyisobutylene oil content is even more preferably between 5 and 25 phr.

11-5. Various additives

The rubber compositions in accordance with the invention may also comprise all or part of the usual additives normally used in elastomer compositions intended for the manufacture of tires or semi-finished products for tires, for example other plasticizers (other than the plasticizer system of the invention), preferably non-aromatic or very weakly aromatic, for example naphthenic oils, paraffinic oils, MES or TDAE oils, esters (in particular trioleates) of glycerol including natural esters such as vegetable oils of rapeseed or sunflower, pigments, protective agents such as anti-ozonants, anti-oxidants, anti-fatigue agents, a crosslinking system based on either sulfur or sulfur and / or peroxide donors and and / or bismaleimides, and / or vulcanizing resins, and / or metal salts, and / or amines, vulcanization accelerators, activators vulcanization agents, anti-reversion agents.

These compositions may also contain, in addition to the coupling agents, coupling activators, inorganic charge-covering agents or, more generally, processing aids that can be used in a known manner, thanks to an improvement in the dispersion. the charge in the rubber matrix and a lowering of the viscosity of the compositions, to improve their processability in the green state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, amines primary, secondary or tertiary, hydroxylated or hydrolyzable polyorganosiloxanes.

11-6. Manufacture of rubber compositions

The compositions are manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing at high temperature, up to a maximum temperature of between 10 ° C. and 190 ° C, preferably between 1 15 ° C and 150 ° C and even more preferably between 1 15 ° C and 140 ° C (especially when the composition is based on a halogenated butyl elastomer) mechanical up to a more low temperature, typically less than 110 ° C, for example between 40 ° C and finishing phase during which is incorporated the crosslinking system.

The method according to the invention for preparing a rubber composition for an inner tire liner comprises the following steps:

- Incorporating into an elastomer, during a first step, at least one reinforcing filler, glass flakes, and the plasticizer system, thermomechanically kneading the whole, in one or more times, until a maximum temperature is reached. between 110 ° C and 190 ° C;

 - Then incorporate, in a second step, a crosslinking system and knead the whole to a maximum temperature below 1 10 ° C. These two steps can be performed consecutively on the same mixer or be separated by a cooling step at a temperature below 100 ° C, the last step then being performed on a second mixer. By way of example, the first phase is carried out in a single thermomechanical step during which, in a suitable mixer such as a conventional internal mixer, all the necessary basic constituents (elastomer, reinforcing filler) are initially introduced. and coupling agent if necessary, glass flakes, and plasticizer system), then in a second step, for example after one to two minutes of mixing, the other additives, optional additional coating or processing agents, to the exception of the crosslinking system. After cooling the mixture thus obtained, it is then incorporated in an external mixer such as a roll mill, maintained at low temperature (for example between 40 ° C and 100 ° C), the crosslinking system. The whole is then mixed for a few minutes, for example between 2 and 15 min. It will be noted that, in particular when the majority elastomer is chosen from butyl rubbers, the incorporation of the crosslinking system is done on the same mixer as in the first thermomechanical working phase.

The crosslinking system is preferably a vulcanization system based on sulfur and an accelerator. Any compound capable of acting as an accelerator for vulcanizing elastomers in the presence of sulfur, especially those selected from the group consisting of 2-mercaptobenzothiazyl disulfide (abbreviated "MBTS"), N-cyclohexyl-2-benzothiazyl sulfenamide, may be used. (abbreviated "CBS"), N, N-dicyclohexyl-2-benzothiazyl sulfenamide (abbreviated "DCBS"), N-tert-butyl-2-benzothiazyl sulfenamide (abbreviated as "TBBS"), N-tert-butyl- 2-benzothiazyl sulfenimide (abbreviated as "TBSI") and mixtures of these compounds. Preferably, a primary accelerator of the sulfenamide type is used. To this crosslinking system are added, incorporated during the first phase and / or during the second phase, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (in particular diphenylguanidine ), etc.

The final composition thus obtained is then calendered, for example in the form of a sheet or a plate, in particular for a characterization in the laboratory, or else extruded in the form of a rubber profile that can be used as an inner tire liner.

The vulcanization (or crosslinking or baking) is conducted in a known manner at a temperature generally between 130 ° C and 200 ° C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, of the vulcanization system adopted and the kinetics of vulcanization of the composition under consideration.

The invention relates to the rubber compositions described above both in the so-called "raw" state (i.e., before firing) and in the so-called "cooked" or vulcanized state (i.e. after vulcanization).

Thus, the invention also relates to a process for preparing an inner rubber tire composition based on at least one butyl rubber and a reinforcing filler which also comprises glass flakes and a plasticizer comprising a functionalized or non-functionalized polyisobutylene oil. having a molecular weight of between 200 g / mol and 40,000 g / mol, and / or a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20 ° C and whose softening temperature is less than 170 ° C. C, said method comprising the following steps:

- Incorporating into an elastomer, during a first step, at least one reinforcing filler, glass flakes, and the plasticizer system, thermomechanically kneading the whole, in one or more times, until a maximum temperature is reached. between 110 ° C and 190 ° C;

- Then incorporate, in a second step, a crosslinking system; and mix everything up to a maximum temperature below 1 10 ° C.

The invention preferably relates to a process as defined above, in which between the thermomechanical mixing and the incorporation of the crosslinking system, one proceeds to cool the assembly to a temperature of less than or equal to 100 ° C.

III-EXAMPLES OF CARRYING OUT THE INVENTION

The following examples illustrate the invention, the latter can not however be limited to these examples only.

Preparation of rubber compositions

The tests are carried out in the following manner: the reinforcing filler, the glass flakes, the plasticizer system, are successively introduced into an internal mixer, 75% filled and having an initial tank temperature of approximately 60.degree. butyl rubber and various other possible ingredients with the exception of the vulcanization system. One thermomechanical work is then carried out in one step, which lasts in total about 3 to 4 minutes, until a maximum temperature of "fall" of 140 ° C. is reached.

The mixture thus obtained is recovered, cooled and then sulfur and a sulfenamide type accelerator are incorporated on an external mixer (homo-finisher) at 30 ° C., mixing the whole for a suitable time (for example between 5 and 12 minutes). ).

The compositions thus obtained are then extruded either in the form of plates (thickness of 2 to 3 mm) or thin sheets of rubber for the measurement of their physical or mechanical properties, or extruded in the form of inner tires of tire.

Example A, Study of the Compositions Comprising an Inert Filler and of the Resin The control formula (mixture A-1) of the study, the contents of which are expressed in phr, is as follows:

Butyl Elastomer (1) 100

 Carbon black N772 50

 Zinc oxide 1.5

 Stearic acid 1.5

 Sulfur 1.5

 Accelerator (2) 1.2

 (1) Brominated polyisobutylene marketed by the company EXXON CHEMICAL Co.

(2) MBTS: Benzothiazyl disulfide The mixture A-II, according to the invention, is similar to the mixture I, supplemented with 10 phr of glass flakes "GF100M" with surfactant 3-Aminopropyl triethoxysilane marketed by the company "Glassflakes Ltd. And 10 phr aliphatic resin "Hikorez A-1100" sold by the company KOLON.

The mixture A-III, according to the invention, is similar to the mixture I, supplemented with 10 phr of glass flakes "GF100M" without surface agent marketed by the company "Glassflakes Ltd." And 10 phr of aliphatic resin "Hikorez A-1 100" marketed by the company KOLON.

The mixture A-IV, for comparison, is similar to the mixture I supplemented with montmorillonite functionalized methyl tallow bis (2-hydroxyethyl) quaternary ammonium "CLOISITE 30B" sold by the company Southern Clay (14.3 phr corresponding to 10 phr of montmorillonite and 4.3 phr of surfactants) and 10 phr of aliphatic resin "Hikorez A-1100" sold by Kolon.

The A-V mixture, for comparison, is similar to the mixture I supplemented with natural graphite "TIMREX 80 * 150" marketed by TIMCAL and 10 phr aliphatic resin "Hikorez A-1100" marketed by the company KOLON.

The mixture of ingredients is made in a "Banbury" having a capacity of about 4 liters filled to about 75%. The reinforcing filler, the glass flakes, the plasticizer system, the butyl rubber and various other possible ingredients are introduced successively, with the exception of the vulcanization system. Thermomechanical work (non-productive phase) is then carried out in one step, which lasts a total of about 3 to 4 minutes, until a maximum "falling" temperature of 140 ° C is reached. The mixture thus obtained is recovered, cooled and then sulfur and a sulfenamide type accelerator are incorporated on an external mixer (homo-finisher) at 30 ° C., mixing the whole (productive phase) for a suitable time (for example between 5 and 12 minutes). The properties of the compositions are shown in Table 1 below:

Table 1

The compositions A-11 and A-III in accordance with the invention are compared with the control compositions A-1, A-IV and A-V.

In the green state, a significant decrease in Mooney plasticity, indicates a better processability of the compositions A-11 and A-11 relative to the control Al and equivalent processability of the compositions according to the invention compared to the compositions A-IV and AV.

After baking, the modulus values under low and medium strain (MA10, MA100) are close. The breaking stresses are also similar but it may be emphasized a better breaking elongation for the compositions A-11 to A-III relative to the control I, and an equivalent elongation of rupture for the compositions A-11 and A-III in accordance with the invention. invention with respect to compositions A-IV and AV. Finally, the sealing properties are very substantially improved for the compositions A-11 and A-III relative to the control I, as illustrated by a sharp decrease in the permeability value, and a substantially equivalent seal for the compositions A-11. and A-III according to the invention with respect to compositions A-IV and AV.

It will also be noted that the properties before and after firing obtained for compositions A-11 and A-III are equivalent to each other, indicating that the surface treatment of glass flakes has no noticeable effect on the properties of the compositions. . Thus, the compositions according to the invention constitute an alternative solution to the use of known lamellar fillers, having similar properties but without the need for exfoliation treatment of the lamellar filler. Example B, Compositions Comprising Glass Scales and a Plasticizer

The mixture B-1 is similar to the mixture A-III, but instead of using the aliphatic resin, 10 phr of polyisobutylene oil "Oppanol B12" sold by the company BASF.

Mixture B1, is similar to mixture A-III, but uses in substitution of the aliphatic resin, a blend of 5 phr of aliphatic resin (pure C5) "Hikorez A-1 100" marketed by Kolon, and 5 phr of "Oppanol B12" polyisobutylene oil marketed by BASF.

The properties of the compositions are shown in Table 2 below:

Table 2

The compositions B-1 and B-11 according to the invention are compared with the composition A-III, also in accordance with the invention and already discussed in the previous example.

In the green state, the processability of the mixture is equivalent, whether the aliphatic resin or the polyisobutylene oil is used as plasticizer, or a blend of these two plasticizers. In the cooked state, the modulus values obtained at low and medium strain, respectively 10 and 100% deformation, are equivalent to the composition A-III. The air permeability is equivalent that is used as plasticizer aliphatic resin or polyisobutylene oil, or a blend of these two plasticizers. These compositions confirm the diversity of plasticizer possible for the implementation of the invention. Example C, Compositions Comprising an Inert Charge Cutting and Resin

The mixture C-1, is similar to the mixture A-III, but uses in substitution of 10 phr of glass flakes, a cut of 5 phr of glass flakes "GF100M" without surface agent marketed by the company "Glassflakes Ltd." And 5 pce of natural graphite "TIMREX 80 * 150" marketed by the TIMCAL company.

The properties of the compositions are shown in Table 3 below:

Table 3

The composition C-1 according to the invention is compared with the composition A-III, also in accordance with the invention and already discussed in Example A.

In the raw state, the processability of the mixture is equivalent, whether the glass flakes alone, or the graphite alone, or a blend of these fillers are used as filler.

In the fired state, the modulus values obtained for the composition C-1 at low and medium strain, respectively 10 and 100% deformation, are equivalent to the composition A-III. The air permeability is equivalent that is used as plasticizer aliphatic resin or polyisobutylene oil, or a blend of these two plasticizers. In conclusion of these various experimental examples, the glass flakes of the compositions according to the invention, thanks to their lamellar nature and combined with a plasticizer system and possibly other inert fillers, make it possible to reduce the watertightness very substantially. compared to a composition without lamellar charge, without significant increase in low and medium deformation stiffness properties of a butyl matrix.

Moreover, these compositions show properties similar to compositions comprising other lamellar fillers, by limiting the use of exfoliation.

Claims

1) A rubber composition based on at least one major elastomer chosen from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, essentially saturated diene elastomers and mixtures of these elastomers, and a reinforcing filler characterized in that the composition also comprises glass flakes and a plasticizer, this plasticizer comprising a functionalized or non-functionalized polyisobutylene oil, having a molecular mass of between 200 g / mol and 40,000 g / mol, and / or a plasticizing hydrocarbon resin whose glass transition, Tg, is greater than 20 ° C and whose softening temperature is below 170 ° C.

2) Composition according to claim 1, wherein the majority elastomer is constituted by a butyl rubber.

3) Composition according to any one of claims 1 to 2, wherein the butyl rubber is a copolymer of isobutene and isoprene.

4) Composition according to any one of claims 1 to 2, wherein the butyl rubber is a brominated polyisobutylene.

5) Composition according to any one of claims 1 to 2, wherein the butyl rubber is a chlorinated polyisobutylene. 6) Composition according to claim 1, wherein the majority elastomer is a diene elastomer.

The composition of claim 6, wherein the majority elastomer is a substantially unsaturated diene elastomer.

8) Composition according to claim 6, wherein the majority elastomer is a substantially saturated diene elastomer.

9) Composition according to any one of claims 1 to 8, wherein the majority elastomer represents 100% of the elastomers of the composition.

10) Composition according to any one of claims 1 to 8, which comprises one or more other elastomers selected from the group consisting of butyl rubbers, substantially unsaturated diene elastomers, substantially saturated diene elastomers and mixtures of these elastomers. 1 1) Composition according to any one of the preceding claims, wherein the reinforcing filler comprises carbon black. 12) Composition according to claim 1 1, wherein the level of carbon black is greater than or equal to 30 phr.

13) Composition according to any one of claims 11 or 12, wherein the carbon black content varies from 30 to 120 phr.

14. Composition according to any one of the preceding claims, in which the reinforcing filler comprises a reinforcing inorganic filler.

15. Composition according to claim 14, wherein the reinforcing inorganic reinforcing filler is silica.

16) Composition according to any one of the preceding claims, characterized in that it contains a rate of flaking glass ranging from 2 to 35 phr. 17) Composition according to one of the preceding claims, characterized in that the plasticizer system consists of a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20 ° C and whose softening temperature is less than 20 ° C. 170 ° C. 18) Composition according to one of claims 1 to 16, characterized in that the plasticizer system consists of a polyisobutylene oil functionalized or not, having a molecular weight of between 200 g / mol and 40 000 g / mol.

19) Composition according to one of claims 1 to 16, characterized in that the plasticizer system consists of a polyisobutylene oil functionalized or not, having a molecular weight of between 200 g / mol and 40 000 g / mol, and a hydrocarbon plasticizing resin whose glass transition temperature, Tg, is greater than 20 ° C and whose softening temperature is less than 170 ° C. 20) Composition according to any one of claims 17 or 19, wherein the plasticizing hydrocarbon resin has a Tg greater than + 30 ° C.

21) Composition according to any one of claims 17, 19 or 20, wherein the level of plasticizing hydrocarbon resin is between 2 and 35 phr. 22) Composition according to claim 21, wherein the plasticizing hydrocarbon resin is selected from the group consisting of homopolymer or copolymer resins of cyclopentadiene (abbreviated as CPD) or dicyclopentadiene (abbreviated DCPD), homopolymer or copolymer resins terpene, C5 homopolymer or copolymer resins, CPD / vinylaromatic (D) copolymer resins, CPD / terpene (D) copolymer resins, CPD / C5 (D) copolymer resins, terpene / vinylaromatic copolymer, C5 / vinylaromatic cut copolymer resins, (D) CPD / styrene copolymer resins, polylimonene resins, limonene / styrene copolymer resins, limonene / D (CPD) copolymer resins, C5 / styrene cut copolymer resins, C5 / C9 cut copolymer resins, and mixtures of these resins.

23. The composition of claim 22, wherein the hydrocarbon resin is a polylimonene resin.

24. The composition of claim 22, wherein the hydrocarbon resin is a C5 cut homopolymer or copolymer resin. 25. The composition of claim 22, wherein the hydrocarbon resin is a C5 cutting copolymer resin and a C9 cutting resin.

26) Composition according to any one of claims 18 or 19, wherein the polyisobutylene oil is present in a proportion of between 2 and 50 phr.

27) Composition according to claim 26, wherein the polyisobutylene oil content is between 5 and 30 phr.

28) Composition according to any one of claims 18, 19, 26 or 27, wherein the polyisobutylene oil has a molecular mass of between 500 g / mol and

35,000 g / mol.

29. The composition of claim 28, wherein the polyisobutylene oil has a molecular weight of between 1000 g / mol and 30,000 g / mol.

30) Composition according to any one of claims 1 to 29 characterized in that it further comprises an additional inert filler. 31) Composition according to claim 30 characterized in that the additional inert filler is selected from calcium carbonate, glass beads, graphites, phyllosilicates and mixtures thereof. Pneumatic object having a rubber composition according to any one of claims 1 to 31.

33) A gas-tight tire layer having a composition according to any one of claims 1 to 31.

34) Gas-tight layer according to the preceding claim characterized in that it is disposed on the inner wall of the pneumatic object.

Pneumatic tire comprising a composition according to any one of claims 1 to 31.

36) Process for preparing a composition for an inner rubber tire, based on at least one butyl rubber and a reinforcing filler, characterized in that the composition also comprises glass flakes and, a plasticizer comprising a polyisobutylene oil functionalized or not , having a molecular weight of between 200 g / mol and 40 000 g / mol, and / or a plasticizing hydrocarbon resin whose glass transition temperature, Tg, is greater than 20 ° C. and whose softening point is less than 170 ° C. ° C, said process comprising the following steps:

- Incorporating into an elastomer, during a first step, at least one reinforcing filler, glass flakes, and the plasticizer system, thermomechanically kneading the whole, in one or more times, until a maximum temperature is reached. between 110 ° C and 190 ° C;

 - Then incorporate, in a second step, a crosslinking system; and mix everything up to a maximum temperature below 1 10 ° C.

37. The method of claim 36, wherein between the thermomechanical mixing and the incorporation of the crosslinking system, is carried out cooling the assembly at a temperature less than or equal to 100 ° C.