Rubber compound for inner tire rubber containing a rubber powder

Abstract

The present invention relates to a rubber composition comprising a halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system, and a rubber powder consisting of ground inner rubber particles from tires. The rubber composition improves the breaking strength and permeability of the inner rubbers of tires comprising the rubber composition.

Description

Title of the invention: Rubber composition for inner rubber of a tire comprising a rubber powder

[0001] The invention relates to rubber compositions for tires comprising a gum crumb.

[0002] Indeed, it is of interest today for tire manufacturers to find solutions to reduce the costs of rubber compositions without penalizing the performance of tires using these compositions.

[0003] This need is particularly important for the inner rubbers of tubeless tires. Indeed, in order to improve the endurance of the tire by preventing it from deflating and by protecting its sensitive internal areas (the plies containing metal cables sensitive to oxidation, for example) against the ingress of oxygen and water, the inner rubbers are currently made of elastomeric compositions based on butyl rubber, the cost of which is high.

[0004] It is also of interest to manufacturers to promote the recycling of end-of-life tires into new tires with a view to reducing the environmental impact of their activity, for example by incorporating into rubber compositions for tires rubber crumbs resulting from the grinding or micronization of vulcanized rubber compositions. Tires resulting from this type of process are described in the state of the art, for example in document WO2020 / 128255.

[0005] Tire manufacturers have sometimes also incorporated gum powders from the recycling of tires or curing membranes into compositions for tire inner rubber, as described in documents KR100943526, EP1612242 and US6730732.

[0006] However, the incorporation of rubber powders into the inner rubber compositions penalizes the breaking properties of the latter. The Applicant, continuing its research efforts, discovered that the use of rubber compositions containing specific rubber powders resulting from the grinding of inner rubbers of tires made it possible to improve the breaking properties of the inner rubbers of tires.

[0007] Thus, a first subject of the invention is a rubber composition comprising a halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system and a rubber crumb consisting of crushed inner tire rubber particles. Another subject of the invention is an inner rubber of a tire comprising a rubber composition in accordance with the invention. The invention also relates to a tire comprising an inner rubber or a rubber composition in accordance with the invention. A final subject of the invention is a rubber powder consisting of particles of crushed inner tire rubber having a median particle size by volume of between 50 and 500 pm, preferably between 100 and 400 pm. Detailed description

[0008] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from more than a to less than b (i.e., excluding the limits a and b) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict limits a and b).

[0009] The abbreviation "pce" means parts by weight per hundred parts of elastomers present in the elastomer matrix.

[0010] The term “elastomer matrix” means all of the elastomers present in the rubber composition in accordance with the invention.

[0011] The compounds mentioned in the description (typically the polymers, fillers, plasticizers, coupling agents, the vulcanization system, other additives, etc.) may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. In the same way, the compounds mentioned may also come from the recycling of materials already used, that is to say they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0012] The invention described in more detail below has as its object at least one of the objects defined according to any one of the following listed embodiments: 1. A rubber composition comprising a halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system and a rubber crumb consisting of crushed inner tire rubber particles. 2. Rubber composition according to embodiment 1 in which the content of gum powder is greater than or equal to 5 pce. 3. Rubber composition according to any one of the preceding embodiments in which the content of gum powder is strictly less than 40 pce. 4. Rubber composition according to any one of the preceding embodiments in which the gum powder has a median particle size by volume of between 50 and 500 pm, preferably between 100 and 400 pm. 5. Rubber composition according to any one of the preceding embodiments in which the level of halogenated butyl rubber is greater than or equal to 70 pce. 6. Rubber composition according to any one of the preceding embodiments comprising from 0 to 30 pce of a polyisoprene elastomer preferably containing more than 90 mol% of 1,4-cis bond. 7. A rubber composition according to any one of the preceding embodiments wherein the halogenated butyl rubber is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two. 8. Rubber composition according to any one of the preceding embodiments in which the reinforcing filler content ranges from 20 to 80 pce. 9. Rubber composition according to any one of the preceding embodiments in which the carbon black content ranges from 20 to 80 pce. 10. Rubber composition according to any one of the preceding embodiments in which the reinforcing filler is composed solely of carbon black. 11. A rubber composition according to any one of the preceding embodiments wherein the carbon black has a BET specific surface area ranging from 20 to 60 m2 / g. 12. Inner rubber of a tire comprising a rubber composition according to any one of the preceding embodiments. 13. A tire comprising an inner rubber according to embodiment 12 or a rubber composition according to any one of embodiments 1 to 11. 14. Gum powder as defined in embodiments 1 and 4. Elastomer

[0013] Usually, the terms “elastomer” and “rubber” are used interchangeably in the text.

[0014] An essential characteristic of the rubber composition according to the invention is to contain a halogenated butyl rubber. The halogenated butyl rubber can be used alone or in a mixture with one or more diene elastomers.

[0015] By butyl rubber is meant a copolymer of isobutylene and a 1,3-diene, in particular a copolymer of isobutylene and isoprene, as well as halogenated derivatives, in particular generally brominated or chlorinated, of these copolymers.

[0016] Butyl rubbers are well known to those skilled in the art, particularly for their air-impermeability property. Generally, copolymers of isobutylene and a 1,3-diene, particularly isoprene, contain 1 to 5 mol% of diene units, particularly isoprene units, and have a Mooney viscosity (ML 1+8 at 125°C) of 30 to 60. Halogenated copolymers of isobutylene and a 1,3-diene, particularly isoprene, generally have a halogen content of 1 to 4% by mass of the copolymer mass.

[0017] Examples of halogenated butyl rubbers which are particularly suitable for carrying out the invention include bromobutyl rubbers such as brominated isobutylene and isoprene copolymer (BIIR), chlorobutyl rubbers such as chlorinated isobutylene and isoprene copolymer (CIIR) and mixtures of these rubbers.

[0018] According to any one of the embodiments of the invention, the halogenated butyl rubber is preferably a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two.

[0019] By "diene" elastomer, whether natural or synthetic, is meant in a known manner an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers carrying two carbon-carbon double bonds, conjugated or not). As diene elastomers which may be suitable, mention will be made in particular of the diene elastomers usually used in rubber compositions intended for the manufacture of tires, such as polyisoprenes, polybutadienes, isoprene copolymers, butadiene copolymers such as copolymers of butadiene and styrene.

[0020] According to one embodiment of the invention, the rubber composition in accordance with the invention comprises from 0 to 30 pce of a diene elastomer other than a halogenated butyl rubber and chosen from the group consisting of polyisoprenes, polybutadienes, butadiene copolymers, isoprene copolymers and mixtures thereof. Preferably, the diene elastomer is a polyisoprene elastomer. Even more preferably, the polyisoprene elastomer contains more than 90 mol% of 1,4-cis bond. These preferred ranges of elastomer content in the rubber composition according to the invention and of molar percentage of 1,4-cis bond in the polyisoprene elastomer as well as these preferred choices of diene elastomer can be applied to any of the embodiments of the invention.

[0021] According to any one of the embodiments of the invention, the level of halogenated butyl rubber in the rubber composition in accordance with the invention is preferably principally greater than or equal to 70 pce. Preferably, the additional rubber making it possible to reach 100 pce of rubber in the rubber composition in accordance with the invention is natural rubber. Gum powder

[0022] Another essential characteristic of the rubber composition in accordance with the invention is that it contains a gum powder.

[0023] It is recalled that rubber crumbs are generally in the form of granules (or aggregates), possibly formed into a rubber slab. Most often, rubber crumbs are a product of material recycling: they are obtained from grinding, in particular micronization, of cooked rubber compositions already used for a first application, for example as tire curing membranes (as in document US6730732) or as tires that have reached the end of their life (as in document KR100943526). Any method or process that does not degrade the rubber during grinding may be suitable as a method of grinding rubber compositions.For example, a grinding method in the presence of water may be chosen such as those described in documents US4374573, US4714201, US5238194 and US5411215: such a method makes it possible to maintain the temperature of the gum at a sufficiently low level to avoid reversion, i.e. the degradation of the crosslinking network of the gum. A cryogenic grinding method may also be used. Depending on the object size distribution obtained, the gum powder obtained by the processes cited may undergo an additional sieving step so as to control this distribution. The sieving may be carried out by different technologies (vibration, centrifugation, suction) known to those skilled in the art. The gum powders resulting from the grinding process are generally in the form of microparticles.By "microparticles" we mean particles which have a size, namely their diameter in the case of spherical particles or their largest dimension in the case of anisotropic particles, of a few tens or hundreds of microns.

[0024] The gum powder useful for the purposes of the invention is in the form of microparticles preferably having a median size by volume of the particles of the gum powder of between 50 and 500 μm, preferably between 100 and 400 μm. These particle size ranges can be applied to any of the embodiments of the invention.

[0025] An essential characteristic of the gum crumb useful for the purposes of the invention is that it is made up of particles of crushed inner tire rubber. In other words, the constituent elements of the gum crumb are particles of inner tire rubber. The gum crumb useful for the purposes of the invention can then be manufactured by a process which consists of recovering of the inner rubber of the tire, then grinding or micronizing this inner rubber by means of a process as described above.

[0026] The composition of a gum powder useful for the purposes of the invention is typically a vulcanized rubber composition constituting an inner gum.

[0027] In a well-known manner, a rubber composition for the inner rubber of a tire, hereinafter referred to as a rubber composition for the inner rubber, comprises a halogenated butyl elastomer. The halogenated butyl elastomer typically represents from 50% to 75% by mass, preferably from 60% to 75% by mass of the total mass of a rubber composition for the inner rubber. A rubber composition for the inner rubber may also contain natural rubber. The natural rubber then represents less than 30% of the total mass of elastomer in a rubber composition for the inner rubber.

[0028] A rubber composition for interior rubber also contains a reinforcing filler which contains carbon black, the reinforcing filler then typically representing from 10% to 50% by mass of the total mass of a rubber composition for interior rubber.

[0029] A rubber composition for an inner rubber also contains a vulcanization system, i.e. a system based on sulfur (or a sulfur donor) and a primary vulcanization accelerator. In a rubber composition for an inner rubber, sulfur is used at a preferred rate of between 0.5 and 5 parts by weight per 100 parts by weight of the composition for an inner rubber. The primary vulcanization accelerator is used at a preferred rate of between 0.5 and 5 phr. Various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retarders may be added to this basic vulcanization system.As a vulcanization accelerator (primary or secondary) it is possible to cite any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types. The vulcanization system of a rubber composition for interior rubber does not include a curing resin, such as phenolic resins.

[0030] Since the rubber composition of the constituent particles of the gum crumb useful for the purposes of the invention is a rubber composition of an inner gum, it also does not contain any curing resin, such as phenolic resins. Consequently, it should not be confused with a com rubber position for expandable cooking membrane (in English bladdef) which contains as crosslinking agent a cooking resin, in particular phenolic.

[0031] According to one embodiment of the invention, the content of gum powder in the rubber composition in accordance with the invention is greater than or equal to 5 pce. Below this content, the desired technical effect may not be sufficiently strong.

[0032] According to one embodiment of the invention, the content of gum powder in the rubber composition according to the invention is less than 40 pce. For a content equal to or greater than 40 pce, the viscosity of the rubber composition comprising the gum powder becomes too high, which could penalize its industrial implementation process.

[0033] The range of preferred rates of gum powder in the rubber composition according to the invention ranging from 5 pce to less than 40 pce can be applied to any of the embodiments of the invention.

[0034] Advantageously, the rubber composition in accordance with the invention contains less than 1.5 pce of a gum crumb other than the gum crumb useful for the purpose of the invention, more advantageously does not contain any gum crumb other than the gum crumb useful for the purpose of the invention. The advantageous embodiment and in particular the more advantageous embodiment are favorable for the compromise between the breaking properties and the gas-tightness properties. Charge

[0035] The rubber composition in accordance with the invention comprises at least one reinforcing filler. Any type of so-called reinforcing filler, known for its ability to reinforce a rubber composition which can be used in particular for the manufacture of tires, may be used, for example a reinforcing organic filler such as carbon black, a reinforcing inorganic filler such as silica or a mixture of these two types of fillers.

[0036] The reinforcing filler of the rubber composition according to the invention comprises carbon black. Suitable carbon blacks include all carbon blacks, in particular the blacks conventionally used in tires. These carbon blacks can be used in the isolated state, as commercially available, or in any other form, for example as a support for certain of the rubber additives used.

[0037] The carbon black of the rubber composition in accordance with the invention has, according to a preferred embodiment, a BET specific surface area ranging from 20 to 60 m2 / g. This preferred range of BET specific surface area of ​​carbon black can be applied to any of the embodiments of the invention.

[0038] The BET specific surface area is determined by gas adsorption using the Brunauer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, page 309, February 1938), and more precisely according to a method adapted from the NF ISO 5794-1 standard, annex E of June 2010 [multipoint volumetric method (5 points) - gas: nitrogen - vacuum degassing: one hour at 160°C - relative pressure range p / po: 0.05 to 0.2].

[0039] According to one embodiment of the invention, the level of reinforcing filler in the rubber composition according to the invention ranges from 20 to 80 phr. Outside this range, the rubber composition may no longer have a rigidity compatible with use as an inner rubber of a tire.

[0040] According to a preferred embodiment of the invention, the carbon black included in the reinforcing filler of the rubber composition in accordance with the invention is present at a rate ranging from 20 to 80 phr. Obviously, the rate of carbon black in the rubber composition is less than or equal to the rate of reinforcing filler in the rubber composition. Vulcanization system

[0041] An essential characteristic of the rubber composition according to the invention is to comprise a vulcanization system, that is to say a crosslinking system based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. To this basic vulcanization system can be added various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), or even known vulcanization retarders. As a vulcanization accelerator (primary or secondary) we can cite any compound capable of acting as an accelerator for the vulcanization of diene elastomers in the presence of sulfur, in particular accelerators of the thiazole type and their derivatives, accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea and xanthate types.The sulfur is used at a preferred rate of between 0.5 and 12 phr, in particular between 0.5 and 5 phr. The primary vulcanization accelerator is used in the rubber composition according to the invention at a preferred rate of between 0.5 and 10 phr, more preferably between 0.5 and 5.0 phr. These preferred ranges relating to the sulfur and accelerator levels can apply to any of the embodiments. Other additives

[0042] At least one other additive which is known to improve the processing properties, thermal conductivity or, in the case where it is used in an inner rubber of a tire, the impermeability of a rubber composition may be included in the rubber composition according to the invention, such as clay, bentonite, talc, chalk, kaolin or graphite. This additive is then present at a level of 0 to 40 pce in the rubber composition according to the invention.

[0043] The rubber composition in accordance with the invention may also comprise all or part of the usual additives normally used in rubber compositions intended for the manufacture of tires, such as, for example, plasticizers, lubricants, pigments, protective agents such as antiozone waxes, chemical antiozonants, antioxidants, anti-fatigue agents and mixtures of such compounds. Preparation of the compositions

[0044] The rubber composition in accordance with the invention can be manufactured in suitable mixers, generally using two successive preparation phases well known to those skilled in the art: a first phase of working or thermomechanical mixing at high temperature, up to a maximum temperature of between 90°C and 150°C, preferably between 100°C and 130°C, followed by a second phase of mechanical working down to a lower temperature, typically below 110°C, for example between 40°C and 100°C, a phase of finishing and homogenization of the rubber composition.

[0045] The rubber composition in accordance with the invention can be prepared according to a process which comprises the following steps: - thermomechanically kneading the elastomer matrix, the reinforcing filler, the vulcanization system and the other additives of the rubber composition in accordance with the invention until a maximum temperature of between 90°C and 120°C is reached; - cool the assembly to a temperature below 80°C; - knead everything up to a maximum temperature below 90°C to obtain a rubber composition in accordance with the invention.

[0046] After incorporating all the ingredients of the rubber composition according to the invention, the final rubber composition thus obtained is then calendered, for example in the form of a sheet or plate, in particular for laboratory characterization, or extruded, to form for example a rubber profile used as a rubber component or semi-finished product, in particular for making a tire. The rubber composition according to the invention can be used in the form of calendering in a tire. The calendering or the extrudate formed from the rubber composition according to the invention constitutes in whole or in part a semi-finished product, in particular a tire.

[0047] Thus, according to a particular embodiment of the invention, the composition of ca The rubber according to the invention, which may be either in the raw state (before crosslinking or vulcanization), or in the cooked state (after crosslinking or vulcanization), is in a tire, preferably in an inner rubber of the tire.

[0048] The crosslinking (or curing), in this case the vulcanization, is carried out in a known manner at a temperature generally between 130°C and 200°C, for a sufficient time which can vary for example between 5 and 120 min depending in particular on the curing temperature, the crosslinking system adopted and the crosslinking kinetics of the composition considered. Other objects of the invention

[0049] The inner rubber of a tire according to the invention has the essential characteristic of being made up in whole or in part of the rubber composition according to the invention. It can be manufactured according to the process described above which comprises an additional step of calendering or extrusion of the rubber composition. It can be in the raw state (i.e., before curing) as well as in the cured state (i.e., after crosslinking or vulcanization).

[0050] The invention also relates to a tire comprising a rubber composition or an inner rubber according to the invention, which tire is both in the raw state and in the cured state. In the present invention, the term "tire" means a pneumatic or non-pneumatic bandage. A pneumatic bandage usually comprises two beads intended to come into contact with a rim, a crown composed of at least one crown reinforcement and a tread, two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic bandage, for its part, usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement, ensuring the connection with a tread and a deformable structure, such as spokes, ribs or cells, this structure being arranged between the base and the crown.Such non-pneumatic tires do not necessarily include a sidewall. Non-pneumatic tires are described for example in documents WO 03 / 018332 and FR2898077. According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic tire.

[0051] A final object of the invention is a gum powder whose constituents are crushed inner tire rubber particles and whose median particle size in volume is between 50 and 500 μm.

[0052] The above-mentioned characteristics of the present invention, as well as others, will be better understood upon reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes. Examples Measures and tests used

[0053] Determination of the breaking properties of rubber compositions

[0054] Tensile tests are used to determine the properties at break. Unless otherwise indicated, they are carried out in accordance with French standard NF T 46-002 of September 1988.

[0055] The breaking stresses (in MPa) and the elongations at break (in %) are measured at a temperature of 23°C + / - 2°C, and under normal hygrometry conditions (50 + / - 5% relative humidity), according to the French standard NF T 40-101 (December 1979).

[0056] The results are indicated on a base of 100; the arbitrary value 100 being assigned to the control for the breaking stress and for the elongation at break. A result less than 100 for the breaking stress or for the elongation at break indicates a decrease in the value concerned, which corresponds to a decrease in the breaking strength performance and conversely, a result greater than 100 indicates an increase in this value, which corresponds to an improvement in this performance.

[0057] Determination of the permeability of rubber compositions

[0058] The oxygen permeability values ​​are measured at 40°C using an AMETEK / MOCON “OXTRAN 2 / 61” oxygen permeameter. Cured rubber composition samples, hereinafter referred to as “samples”, in the form of discs of a determined thickness (approximately 0.8 to 1.1 mm) are mounted on the apparatus between an upper and a lower chamber, respectively filled with a test gas (15 psi of oxygen), and a carrier gas (15 psi of nitrogen). During the measurement, a quantity of oxygen passes through the membrane formed by the sample to reach the lower chamber. The sealing at the edges of the sample is ensured by applying vacuum grease at the clamping location. The quantification of the oxygen transmitted through the sample is carried out by a “Coulox” coulometric detector and is stabilized during the measurement.The oxygen transmission rate is then measured, which corresponds to the mass of oxygen that passes through a unit area of ​​the sample in twenty-four hours. The value of the oxygen transmission rate is multiplied by the thickness of the sample to calculate the permeability of the material tested to oxygen.

[0059] The results are indicated on a base of 100. An arbitrary value of 100 is given for the oxygen permeability of the control, a result less than 100 indicating a decrease in oxygen permeability and therefore better impermeability.

[0060] Determination of the particle size of gum crumbs

[0061] The volume distribution of the size of the particles of a gum crumb can be measured by laser granulometry, on a mastersizer 3000 type device from the Malvern company. A 1 minute ultrasonic treatment is carried out prior to the measurement in order to guarantee good dispersion. The measurement is carried out in a liquid process: the particles of the gum crumb are dispersed in alcohol. The measurement is carried out in accordance with the ISO-13320-1 standard and allows, from the determination of the diffraction angles of the laser by the particles of the gum crumb, to determine in particular the D10 and the D50, that is to say the diameters below which respectively 10% by volume and 50% by volume of the total population of particles is present. Preparation of rubber compositions

[0062] Four rubber compositions C1, C2, C3 and C4 are prepared. The formulations (in pce) of these compositions are described in Table 1.

[0063] Rubber compositions C2, C3 and C4 are in accordance with the invention; rubber composition C1 is not in accordance with the invention. Rubber compositions C1, C2, C3 and C4 all contain a halogenated butyl rubber (in this case, a brominated butyl rubber), a reinforcing filler comprising carbon black, a vulcanization system and a rubber crumb. In rubber composition C1, not in accordance with the invention, the rubber crumb consists of ground tire tread particles. In rubber compositions C2, C3 and C4, in accordance with the invention, the rubber crumb consists of ground tire inner rubber.

[0064] The tests are carried out as follows: the halogenated butyl rubber is first introduced into an internal mixer, filled to 70% by volume and with an initial tank temperature of approximately 40°C, followed by the reinforcing filler, the rubber crumb, the vulcanization system and the other additives of the rubber composition. A single-stage thermomechanical process is then carried out, lasting a total of approximately 3 to 4 minutes, until a maximum "drop" temperature of 115°C is reached.

[0065] The mixture thus obtained is recovered, cooled on an external mixer (roller tool) to 30°C, mixing everything in order to homogenize the mixture for an appropriate time (for example between 5 and 12 min). The compositions thus obtained are then calendered 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 after vulcanization for 20 min at 150 °C. Properties of rubber compositions

[0066] The properties of rubber compositions C1, C2, C3 and C4 are given on a base of 100 relative to C1 in Table 2.

[0067] The rubber compositions C2, C3 and C4, in accordance with the invention, have a breaking stress and an elongation at break which are much higher than those of Cl, a rubber composition not in accordance with the invention. Indeed, C2, C3 and C4 in particular have increases in breaking stress of 80%, 63% and 66% respectively compared to CL.

[0068] Furthermore, Table 2 shows that the oxygen permeability of rubber composition C1 is significantly higher than that of rubber compositions C2, C3 and C4, which suggests that these last three rubber compositions, if used as the inner rubber of a tire, will ensure better sealing of the tire to the inflation gas.

[0069] The results obtained therefore show that the rubber compositions in accordance with the invention do indeed make it possible to solve the technical problem here, in that they result in improved breaking properties while retaining the impermeability expected for an inner rubber of a tire. [Tables 1] Cl C2 C3 C4 Elastomer (1) 100 100 100 100 Carbon black (2) 40 40 40 40 Kaolin (3) 20 20 20 20 Stearic acid (4) 1.5 1.5 1.5 1.5 Zinc oxide (5) 1.5 1.5 1.5 1.5 Lubricant (6) 2 2 2 2 Accelerator (7) 1.2 1.2 1.2 1.2 Sulphur 1.5 1.5 1.5 1.5 Gum powder 1 (8) 0 10 20 30 Gum powder 2 (9) 20 0 0 0 1. Brominated butyl X-ButylTM BB2030 from ARLANXEO 2. N770 ASTM grade from ORION company 3. Natural kaolin grade Argirec B24 from the company IMERYS 4. Stearic acid from UMICORE 5. Zinc oxide from UMICORE 6. Struktol 40MS from STRUKTOL company 7. Company's 2-Mercaptobenzothiazole Disulfide Accelerator (“MBTS”) Solutia 8. Microparticles of inner rubber from end-of-life heavy goods vehicle tires with a median volume size of 200 μm 9. Microparticles of end-of-life heavy goods vehicle treads with a median volume size of 250 pm marketed by the Lehigh company under the name PolydyneôO [Tables 2] Cl C2 C3 C4 Stress at break 100 180 163 166 Elongation at break 100 168 161 156 O2 permeability 40°C 100 84 88 85

Claims

Claims

1. A rubber composition comprising a halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system and a rubber crumb consisting of crushed tire inner rubber particles.

2. Rubber composition according to claim 1 in which the content of gum powder is greater than or equal to 5 pce.

3. Rubber composition according to any one of the preceding claims in which the content of gum powder is strictly less than 40 pce.

4. Rubber composition according to any one of the preceding claims in which the gum powder has a median particle size by volume of between 50 and 500 pm, preferably between 100 and 400 pm.

5. A rubber composition according to any one of the preceding claims wherein the level of halogenated butyl rubber is greater than or equal to 70 pce.

6. A rubber composition according to any one of the preceding claims comprising from 0 to 30 phr of a polyisoprene elastomer preferably containing more than 90 mol% of 1,4-cis bond.

7. A rubber composition according to any preceding claim wherein the halogenated butyl rubber is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two.

8. A rubber composition according to any preceding claim wherein the reinforcing filler content ranges from 20 to 80 phr.

9. A rubber composition according to any preceding claim wherein the carbon black content is from 20 to 80 phr.

10. A rubber composition according to any preceding claim wherein the reinforcing filler is composed solely of carbon black.

11. A rubber composition according to any preceding claim wherein the carbon black has a BET specific surface area ranging from 20 to 60 m2 / g.

12. A tire inner rubber comprising a rubber composition according to any one of the preceding claims.

13. A tire comprising an inner rubber according to claim 12 or a rubber composition according to any one of claims 1 to 11.

14. Gum powder as defined in claims 1 and 4.