EP2231420A1 - Rubber composition in particular for the manufacture of tyres - Google Patents

Abstract

The invention relates to a rubber composition in particular intended for the manufacture of tyres, based on at least one elastomer that is present in the majority chosen from the group composed of butyl rubbers, predominantly unsaturated diene elastomers, predominantly saturated diene elastomers and blends of these elastomers, and a reinforcing filler, characterized in that the composition also comprises at least one inert filler chosen from lamellar mineral fillers based on silicon, and an unfunctionalized polyisobutylene oil, having a molecular weight between 200 g/mol and 40 000 g/mol, present in a proportion between 2 and 50 phr.

Description

 RUBBER COMPOSITION, IN PARTICULAR FOR MANUFACTURING

PNEUMATIC

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 in fact have a low air permeability inner surface in order to avoid deflation of the tire and to protect the inner sensitive zones of the latter against oxygen and water inflows, such as webs containing metal cables sensitive to oxidation, this protection to improve the endurance of the tire. 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 economy and the need to protect the environment have become a priority, it is desirable to produce interior impregnables that are impervious to air and have as low a weight and hysteresis as possible to achieve 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 of the raw composition, commonly called "processability", cooked: degradation of mechanical properties including decreased resistance to flexion. The introduction of plasticizer type oil overcomes these aspects of implementation and mechanical properties, but highly penalizes the impermeability.

Various solutions have been envisaged to overcome these drawbacks in particular by using other types of charges to be added to the reinforcing fillers, often known as smectites and in particular organophilic smectites. These organophilic smectites improve the impermeability properties of the materials if they are well dispersed in the material, that is to say at the same time 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. Publication WO 2006/047509 of the Applicant describes a composition for an inner rubber tire whose composition based on butyl rubber and comprising carbon black, comprises non-reinforcing fillers consisting of organophilic smectites reducing the permeability to gases, dispersed in the elastomeric matrix and a specific plasticizer consisting of a terpene resin having in particular a glass transition temperature, Tg, greater than or equal to 50 ^° C. This composition actually has mechanical properties and impermeability making it acceptable for use in as a tire inner liner, thanks to the combined effect of these organophilic smectites and this high Tg resin.

The Applicant has pursued this research and has surprisingly discovered that the combination in a tire rubber compound, of a low molecular weight polyisobutylene elastomer with organophilic smectites, in the presence of the elastomer conventionally used such that butyl rubber and a reinforcing filler, not only made it possible to obtain processability and flexural strength properties as good as the compositions of the prior art, but also to obtain improved properties of impermeability to gas, and significantly improve the rolling resistance and endurance properties without, of course, at the expense of other properties.

As mentioned above, oils are known for their ability to improve the processability but it is also known that they can affect the sealing. Here it was surprisingly found, on the one hand, that the combination of lamellar mineral fillers based on silicon and on low-mass polyisobutylene oil made it possible to improve the sealing, including with respect to a conventional control composition, and to on the other hand, that this composition also allowed iso-sealing with respect to the solution smectites organophilic resin above to lower the hysteresis of the mixture and therefore to lower the rolling resistance of a tire whose inner liner would be made to from this composition.

Thus, the subject of the invention is a novel composition, in particular for an inner tire liner, having improved imperviousness properties compared with the aforementioned solutions, as well as improved rolling resistance, without degrading the mechanical properties of processability and flexural strength. .

The invention relates to a rubber composition based on at least one major elastomer selected from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, diene elastomers which are essentially saturated and mixtures of these elastomers, and a reinforcing filler characterized in that the composition also comprises an inert filler selected from silicon-based platy mineral fillers, and a non-functionalized polyisobutylene oil, having a molecular weight of between 200 g / mol and 40 g / mol. OOOg / mol, preferably between 500 g / mol and 35,000 g / mol and even more preferably 1000 g / mol and 30,000 g / mol, present in a proportion of between 2 and 50 phr.

According to an alternative embodiment of the invention, the majority elastomer is constituted by a butyl rubber, and more particularly by a copolymer of isobutene and isoprene or a brominated or chlorinated polyisobutylene.

According to another embodiment of the invention, the majority elastomer is a diene elastomer, and advantageously a substantially unsaturated or essentially saturated diene elastomer.

According to one embodiment of the invention, the majority elastomer represents 100% of the elastomers of the composition.

According to another embodiment of the invention, the composition 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.

Advantageously, the silicon-based lamellar mineral fillers are chosen from phyllo silicates, these phyllosilicates preferably being chosen from the group consisting of smectites, kaolin, talc, mica and vermiculite.

The invention also relates to a pneumatic object having 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 at least one inert filler selected from among the silicon-based platy mineral fillers, and a non-functionalized polyisobutylene oil having a molecular weight of between 200 g / mol and 40,000 g / mol preferably between 500 g / mol and 35 000 g / mol and even more preferably 1000 g / mol and 30 000 g / mol, present in a proportion of between 2 and 50 phr, and also relates to a tire comprising such a rubber composition. . - AT -

The invention finally relates to a process for preparing a 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 at least one inert filler selected from silicon-based platy mineral fillers, and a non-functionalized polyisobutylene oil, said process comprising the following steps:

to incorporate in a diene elastomer, in a mixer: a reinforcing filler,

an inert load,

a polyisobutylene oil, by thermomechanically kneading the whole, in one or more times, until a maximum temperature of between 110 ^° C. and 190 ^° C. is reached; - then incorporate:

a system of crosslinking; mix everything up to a maximum temperature below 110 ⁰ C.

I. - MEASUREMENTS AND TESTS

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

I- 1. Mooney Plasticity

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 uncured state (ie, before firing) is molded in a cylindrical chamber heated to 100 ^° C. After one minute of preheating, the rotor rotates within the 2 rpm test piece 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.meter).

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 humidity (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.

1-3. Dynamic properties:

The dynamic properties ΔG * and tan (δ) max are measured on a viscoanalyzer (Metravib V A4000), according to the ASTM D 5992 - 96 standard. The response of a sample of vulcanized composition (cylindrical test piece 2 mm in diameter) is recorded. thickness and 78.5 mm2 section), subjected to sinusoidal stress in alternating simple shear, at a frequency of 10 Hz, under normal temperature conditions according to ASTM D 1349 - 99. A strain amplitude sweep is carried out peak to peak of 0.1 to 50% (forward cycle), then 50% to 0.1% (return cycle). The results used are the complex dynamic shear modulus (G *) and the loss factor, tan (δ). For the return cycle, the maximum value of tan (δ) observed (tan (δ) max), as well as the complex modulus difference (ΔG *) between the values at 0.15 and 50% of deformation (Payne effect).

1-4. 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 determined 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 10 psi 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 major elastomer (that is to say for more than 50 phr), chosen from the group consisting of butyl rubbers, essentially unsaturated diene elastomers and elastomers. essentially saturated dienes and mixtures of these elastomers, and a reinforcing filler, is characterized in that it also comprises an inert filler selected from silicon-based platy mineral fillers and a non-functionalized polyisobutylene oil, having a molecular weight of between 200 g / mol and 40,000 g / mol, present in a proportion of between 2 and 50 phr.

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 improved sealing and hysteresis properties of the compositions in accordance with the invention make it possible to also recommend their use at other locations 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% by mass.

II- 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 rubber or diene elastomers.

By butyl rubber is meant a homopolymer of poly (iso-butylene) or a copolymer of polyisobutylene with isoprene (in this case this butyl rubber is part of the diene elastomers), as well as halogenated derivatives, in particular generally brominated or chlorinated, of these poly (isobutylene) homopolymers and copolymers of poly (isobutylene) and isoprene.

Examples of butyl rubber that are particularly suitable for carrying out the invention are: copolymers of isobutylene and isoprene (HR), bromo-butyl rubbers such as bromoisobutylene-isoprene copolymer (BIIR), chlorobutyl rubbers such as chloroisbutylene-isoprene copolymer (CIIR) and isobutylene rubbers.

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

By elastomer or "diene" rubber, it is to be understood in a known manner (one or more elastomers) is understood to come from at least a part (ie a homopolymer or a copolymer) of monomers dienes (monomers carrying 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 can be described as "substantially saturated" diene elastomers (level of units of diene origin which are 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 α-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 1,4-hexadiene, 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 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-tertiobutylstyrene, 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, sequence, microsequential, and be prepared in dispersion or in solution; they can be coupled and / or star 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 Pat. No. 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%) of 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., a styrene content of between 5% and 60% by weight and more particularly between 20% and 50%; content (mol%) in -1,2 bonds of the butadiene part between 4% and 75%, a content (mol%) of trans-1,4 bonds of 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 -80 ^° C., the isoprene-styrene copolymers and in particular those having a styrene content of between 5% and 50% by weight and a Tg of 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 between 10% and 40%, an isoprene content 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 isoprenic part of between 5% and 70% and a content (mol%) in trans units -1,4 of the isoprene part of between 10% and 50%, and more generally any butadiene copolymer styrene-isoprene having a Tg of 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 (HR), isoprene-styrene (SIR), isoprene-butadiene (BIR) or isoprene-butadiene-styrene (SBIR) . This isoprene elastomer is preferably natural rubber or synthetic cis-1,4 polyisoprene; of 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 copolymers, styrene (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR) and isoprene-butadiene-styrene copolymers (SBIR) and mixtures 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 (ie, for more than 50 phr) an isoprene elastomer or an SBR, whether it is an emulsion prepared SBR ("ESBR") or a SBR prepared in solution ("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), crown reinforcing plies (for example work webs, protective webs or hoop webs), carcass reinforcement webs, flanks, beads, protectors, underlayments, rubber blocks and other internal gums providing the interface between the zones aforementioned tires.

II-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, can be used. such as silica, or a blend of these two types of filler, including a blend 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 Nl 15, N134, N234, N326, N330, N339, N347 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 even "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 various 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 of the aluminous type, in particular alumina (Al ₂ O ₃ ). The silica used may be any reinforcing silica known to those skilled in the art, especially any precipitated or pyrogenic silica having a BET surface and a CTAB specific surface both less than 450 nf / g, preferably 30 to 400 nf / g. As highly dispersible precipitated silicas (referred to as "HDS"), mention may be made of, for example, the Ultrasil 7000 and Ultrasil 7005 silicas from Degussa, the Zeosil 1165MP, 1135MP and 1115MP silicas from Rhodia, the Hi-SiI silica EZ150G from 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.

When the compositions of the invention are intended for tire treads with a low rolling resistance, the reinforcing inorganic filler used, in particular if it is silica, preferably has a BET surface area of between 45 and 400. m ² / g, more preferably between 60 and 300 m ² / g.

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 or Ci-Cis arylene groups C ₂ -C _6, particularly alkylene C ₁ -C _10, especially C ₁ -C _4, particularly the propylene);

Z is one of the following formulas:

R1 R1 R2

- Si - R1; - Si- R2; - Si- R2,

R2 fc 12 R2

in which: the radicals R ¹ , substituted or unsubstituted, which are identical to or different from one another, represent a C ₁ -C ₁₈ alkyl, C ₅ -C ₁₈ cycloalkyl or C ₆ -C ₁₈ aryl group (preferably C ₁ -C ₈ alkyl groups); ₆ , cyclohexyl or phenyl, especially C1-C4 alkyl groups, more particularly methyl and / or ethyl). the radicals R ² , substituted or unsubstituted, which are identical to or different from one another, represent a C ₁ -C ₁₈ alkoxyl or C ₅ -C ₁₈ cycloalkoxyl group (preferably a group chosen from C ₁ -C ₈ alkoxyls and C ₅ -C 8 cycloalkoxyls); Cs, more preferably still a group selected from C1-C4 alkoxyls, in particular methoxyl and ethoxyl).

In the case of a mixture of polysulfurized alkoxysilanes corresponding to formula (III) above, in particular common commercially available mixtures, the average value of "x" is a fractional number preferably of between 2 and 5, more preferably 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 polysulfides (in particular disulfides, trisulphides or tetrasulfides) of bis (C ₁ -C ₄ alkoxyl) alkyl (C ₁ -C ₄ ) silyl-alkyl (C _1). -C ₄ )), such as 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, is especially used, abbreviated TESPD, of formula [(C ₂ HsO) SSi (CH ₂ ) SS] ₂ . Also preferred are polysulfides (especially disulfides, trisulphides or 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 formula III above) as described in patent applications

WO 02/30939 (or US 6,774,255) and WO 02/31041 (or US 2004/051210), or alternatively silanes or POS bearing azo-dicarbonyl functional 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 have 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 a reinforcing filler in a proportion greater than 30 phr. Preferably the carbon black content is between 30 and 120 phr, indeed beyond this rate the penalty in terms of rigidity of the composition is too important for an application as a 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 use higher levels of carbon black in the case of 900-grade carbon blacks than in the case of 600- or 700-grade blacks.

More preferably, the proportion of carbon black is between 30 and 70 phr, this is particularly the case when using ASTM 600 or 700 grade carbon blacks, and even more preferentially this proportion is between 35 and 60 pce.

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.

II-3 Inert load

Inert fillers are understood to mean non-reinforcing fillers and more particularly here the silicon-based lamellar mineral fillers are suitable. 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 organo-modified. 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 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 identical or different.

In particular, organo-modified 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 2OA.

Other surfactants based on quaternary ammonium salts may be used to modify the phyllosilicates as described in the patent application WO 2206/047509.

The aforementioned inert fillers are indeed particularly interesting because they make it possible to improve the impermeability of the compositions in which they are dispersed with an adequate level.

This inert filler is present in the composition according to the invention in levels ranging from 1 phr to 25 phr, and preferably between 3 and 15 phr.

II-4. - Polyisobutylene oil

The rubber compositions of the invention use an extender oil (or plasticizing oil) whose usual function is to facilitate the implementation, by a lowering of the Mooney plasticity and to improve the endurance by a reduction of the modules. lengthening to 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 high masses can lead to excessive stiffening of this composition. The abovementioned low molecular weight polyisobutylene oils have demonstrated a much better compromise of properties compared to the other oils tested, in particular to conventional oils of the paraffmic type.

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 example, polyisobutylene oils are sold in particular by the company UNIVAR under the name "Dynapak PoIy" (eg "Dynapak PoIy 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 a 0.45μm 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 μL. 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.

The polyisobutylene oil content is preferably between 2 and 50 phr. Below the minimum indicated, the elastomeric layer or composition may have too high rigidity for certain applications while beyond the maximum recommended, there is a risk of insufficient cohesion of the composition and loss of tightness may be harmful depending on the application.

The polyisobutylene oil content is even more preferably between 5 and 30 phr.

II-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, paraffinic, MES or TDAE oils, esters (especially 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 / or or bismaleimides, vulcanization accelerators, vulcanization activators, 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. of 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 alkylalkoxy silanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxylated or hydrolysable polyorganosiloxanes.

It can also be envisaged that the composition comprises other types of filler such as, for example, graphites.

II-6. Manufacture of rubber compositions

The compositions are produced in suitable mixers, using two successive preparation phases well known to those skilled in the art: a first phase of thermomechanical working or mechanical mixing at elevated temperature, until a maximum temperature between 110 ⁰ C and 190 ⁰ C, preferably between 130 ⁰ C and 180 ⁰ C, followed by a second phase of mechanical work to a lower temperature, typically less than 110 ⁰ C, for example between 40 ⁰ C and 100 ⁰ C, 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:

to incorporate in an elastomer, during a first step, at least one reinforcing filler, an inert filler and a polyisobutylene oil by kneading thermomechanically all, in one or more times, until a maximum temperature of between 110 ⁰ C and 190 ⁰ C;

- Then incorporate, in a second step, a crosslinking system;

- mix everything up to a maximum temperature below 110 ⁰ C.

These two steps can be carried out consecutively on the same mixer or be separated by a cooling step at a temperature below 100 ^° C., the last step then being carried out 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, inert filler and polyisobutylene oil), then in a second step, for example after one to two minutes of kneading, the other additives, any additional coating or processing agents, with the exception of 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 ⁰ C and 100 ⁰ 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, particularly when the majority elastomer is chosen from butyl rubbers, the incorporation of the vulcanization 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 vulcanization 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 cooking) is conducted in a known manner at a temperature generally between 130 ⁰ C and 200 ⁰ C, for a sufficient time which may vary for example between 5 and 90 min depending in particular on the cooking temperature, the system of vulcanization 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).

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 as follows: an internal mixer, filled to 75% and whose initial tank temperature is approximately 60 ^° C., is introduced successively into the reinforcing filler, the inert filler and the polyiso-butylene oil. , 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 (homoformer) at 30 ^° C., mixing all 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 This test is intended to show the performance improvement of a composition according to the invention compared to two control compositions of the prior art in terms of rubber properties.

The three compositions A, B, C were prepared in accordance with the method detailed in the preceding paragraph and have the same following basic formulation where the amounts are expressed in phr, parts by weight per hundred parts of elastomer:

Butyl Elastomer (1) 100

Carbon black (N772) 50

Zinc oxide 1.5

Stearic acid 1,5

Accelerator (2) 1,2

Sulfur 1.5

(1): Brominated butyl brominated butyl alcohol "BROMOBUTYL 3220" marketed by EXXON CHEMICAL Co.

(2): 2-mercaptobenzothiazyl disulfide, MBTS.

Compositions A, B and C are defined as follows:

the control composition A is a "conventional" tire interior tire composition that does not include an inert filler,

the control composition B corresponds to the prior art of the patent application WO 2006/047509 which comprises organophilic smectites and a Tg hydrocarbon plasticizing resin conforming to the characteristics of said application,

Composition C according to the present invention comprises an inert filler and a low molecular weight polyisobutylene oil in levels according to the invention.

The differences in wording are presented in Table 1 which follows: Table 1

(3) Functionalized montmorillonite "methyl tallow, bis (2-hydroxyethyl) quaternary amonium": "CLOISITE 3OB" marketed by the company Southern Clay (14.3 phr corresponding to 10 phr of montmorillonite and 4.3 phr of surfactants). active) (4) Polyisobutylene oil "OPPANOL B 12 SFN" marketed by the company

BASF (molecular weight Mn = 25000 g / mol)

(5) aliphatic resin (C5 pure) "Hikorez AI 100", (Tg = 50 ^° C., softening temperature 99 ° C.), marketed by the company KOLON

The rubber properties of these three compositions are measured before firing and after firing at 150 ^° C. for 60 minutes, the results obtained are shown in the table.

2.

Table 2

It is found that composition C according to the invention comprising an inert filler and a non-functionalized polyisobutylene low molecular weight oil has in the green state a much better processability (Mooney lower) than the control composition A and comparable to that of composition B. After firing, it is found that the composition C1 according to the invention has a permeability significantly lower than that of the control composition A and also lower than that of the composition B comprising an organophilic smectite and a high Tg resin, which already has a very high good impermeability. A slight increase is observed when the modules obtained for the compositions B and C compared to the control A, however this increase remains acceptable for the two compositions of the prior art B and according to the invention C. The elongation properties and the tensile stress of the three compositions A, B and C are comparable. Finally, it is noted that the control compositions A and in accordance with the invention C have a similar value of Tan (δ) max, unlike the composition B, which is markedly degraded in terms of hysteresis and therefore in the tire including an inner liner with Composition base B has a lower rolling resistance.

Thus the composition C according to the invention including an inert filler and a low molecular weight polyisobutylene oil allows a strong improvement of the sealing properties compared to a conventional control composition A and also compared to a control composition B already improved in sealing term, without annoying degradation of other properties and without degrading the hysteresis, unlike composition B.

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 at least one inert filler selected from silicon-based platy mineral fillers, and a non-functionalized polyisobutylene oil, having a molecular weight of between 200 g / mol and 40,000 g / mol, present in a proportion of between 2 and 50 pce.

2) The composition of claim 1, wherein the polyisobutylene oil has a molecular weight of between 500 g / mol and 35 000 g / mol;

3) Composition according to claim 1, wherein the polyisobutylene oil has a molecular weight of between 1000 g / mol and 30 000 g / mol.

4) Composition according to any one of claims 1 to 3, wherein the majority elastomer is constituted by a butyl rubber.

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

6) Composition according to any one of claims 1 to 3, wherein the butyl rubber is a brominated polyisobutylene.

7) Composition according to any one of claims 1 to 3, wherein the butyl rubber is a chlorinated polyisobutylene.

8) Composition according to any one of claims 1 to 3, wherein the majority elastomer is a diene elastomer.

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

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

11. Composition according to any one of claims 1 to 10, in which the majority elastomer represents 100% of the elastomers of the composition. 12) A composition according to any one of claims 1 to 10, which comprises one or more other elastomers selected from the group consisting of butyl rubbers, essentially unsaturated diene elastomers, substantially saturated diene elastomers and mixtures of these elastomers.

13) Composition according to any one of the preceding claims, wherein the reinforcing filler comprises carbon black.

14) Composition according to claim 13, wherein the carbon black content is greater than 30 phr.

15) Composition according to any one of claims 13 or 14, wherein the carbon black content is between 30 and 120 phr.

16) Composition according to any one of claims 13 or 14, wherein the carbon black content is between 30 and 70 phr.

17) Composition according to any one of claims 13 or 14, wherein the carbon black content is between 35 and 60 phr.

18) Composition according to any one of the preceding claims, wherein the reinforcing filler comprises a reinforcing inorganic filler.

19. The composition of claim 18, wherein the reinforcing inorganic reinforcing filler is silica.

20) Composition according to any one of claims 1 to 19, wherein the polyiso butylene oil content is between 5 and 30 phr.

21) Composition according to any one of claims 1 to 20, wherein the silicon-based lamellar mineral fillers consist of phyllosilicates.

The composition of claim 21, wherein the phyllosilicates are selected from the group consisting of smectites, kaolin, talc, mica and vermiculite.

23. The composition according to any one of claims 21 or 22, wherein the inert filler is a smectite. 24. The composition of claim 23, wherein the inert filler is a functionalized smectite.

25. The composition according to any one of claims 21 or 22, wherein the inert filler is a kaolin.

26. Composition according to any one of claims 21 or 22, wherein the inert filler is a talc.

27) Composition according to any one of claims 21 or 22, wherein the inert filler is a mica.

28. The composition according to any one of claims 21 or 22, wherein the inert filler is vermiculite.

29) Composition according to any one of the preceding claims, which comprises a plurality of inert fillers chosen from silicon-based lamellar mineral fillers, preferably from phyllosilicates.

30) Composition according to any one of the preceding claims, wherein the rate of inert charges is between 1 and 25 phr.

31) Composition according to any one of the preceding claims, wherein the rate of inert charges is between 3 and 15 phr.

Pneumatic object having a rubber composition according to any one of claims 1 to 31.

33) Tire inner liner having a composition according to any one of claims 1 to 31.

34) A tire comprising a composition according to any one of claims 1 to 31.

35) Process for preparing a rubber composition based on at least one major elastomer selected 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 an inert filler selected from silicon-based lamellar mineral fillers and a non-functionalized polyisobutylene oil, said process comprising the following steps:

to incorporate in a diene elastomer, in a mixer: a reinforcing filler,

an inert load,

a polyisobutylene oil, by thermomechanically kneading the whole, in one or more times, until a maximum temperature of between 110 ^° C. and 190 ^° C. is reached; - then incorporate:

a system of crosslinking; mix everything up to a maximum temperature below 110 ⁰ C.

36) A method according to claim 35, wherein ente the thermomechanical mixing and the incorporation of the crosslinking system, the whole is cooled to a temperature below 100 ⁰ C.