Rubber composition for tire inner containing friculated

Abstract

The present invention relates to a rubber composition comprising halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system and crumb rubber, the crumb rubber comprising halogenated butyl rubber, a reinforcing filler comprising carbon black, a vulcanization system and kaolin. The rubber composition contributes to improving the post-aging tear strength of a tire inner liner comprising the rubber composition.

Description

Technical Field

[0001] This invention relates to a tire rubber composition comprising rubber fragments. Background Technology

[0002] This is because, currently, it is advantageous for tire manufacturers to find solutions that reduce the cost of rubber compositions without compromising the performance quality of tires using these compositions.

[0003] This need is particularly important for the inner liner of tubeless tires. This is because, in order to improve tire durability by preventing tire leakage and protecting its sensitive internal areas (such as the cord layers containing easily oxidized metal cords) from the erosion of oxygen and water, current inner liners consist of elastomeric compositions based on butyl rubber, which is very expensive.

[0004] From the perspective of reducing the environmental impact of manufacturers' activities, it is also beneficial for manufacturers to promote the recycling of end-of-life tires into new tires, for example, by incorporating rubber fragments obtained through grinding or micronizing vulcanized rubber compositions into the rubber compositions used in tires. Tires produced using such processes are described in the prior art, for example in document WO2020 / 128255.

[0005] Tire manufacturers sometimes incorporate rubber fragments recovered from tires or vulcanized bladders into compositions used for tire liners, as described in documents KR100943526, EP 1 612 242 and US 6 730 732.

[0006] However, tire liners must also exhibit good mechanical strength properties, including performance after aging. In fact, the applicant company was quite surprised to find that using a rubber composition containing specific rubber particles (specifically, kaolin) could improve the tear strength properties of tire liners after aging. Summary of the Invention

[0007] Therefore, the first subject of the present invention is a rubber composition comprising a halogenated butyl rubber Bu1, a reinforcing filler R1 comprising carbon black N1, a vulcanization system V1, and a granulated rubber comprising a halogenated butyl rubber Bu2, a reinforcing filler R2 comprising carbon black N2, a vulcanization system V2, and kaolin.

[0008] Another subject of the invention is a tire liner comprising a rubber composition according to the invention.

[0009] Another subject of the invention is a tire comprising a liner or rubber composition according to the invention.

[0010] Detailed description Any numerical interval expressed as “between a and b” represents a range of values ​​from greater than a to less than b (i.e., excluding the endpoints a and b), while any numerical interval expressed as “from a to b” refers to a range of values ​​from a to b (i.e., including the strict endpoints a and b).

[0011] The abbreviation "phr" refers to parts by weight per 100 parts of elastomer present in the elastomer matrix. The term "elastomer matrix" should be understood to mean all elastomers present in the rubber composition according to the invention, but excluding any elastomers present in the granulated rubber, whether referring to granulated rubber used to satisfy the requirements of the invention or other granulated rubber.

[0012] The compounds mentioned in the specification (typically referring to polymers, fillers, plasticizers, coupling agents, vulcanization systems, and other additives) can be fossil-derived or bio-based. In the latter case, they can be partially or wholly produced from biomass, or obtained from renewable raw materials derived from biomass. Similarly, the mentioned compounds can also originate from the recycling of pre-used materials; that is, they can be partially or wholly produced by the recycling process, or obtained from the starting materials themselves generated during the recycling process.

[0013] The invention described in more detail below is subject to at least one of the subject matter defined according to any of the following embodiments: 1- A rubber composition comprising halogenated butyl rubber Bu1, reinforcing filler R1 comprising carbon black N1, vulcanization system V1, and granulated rubber, said granulated rubber comprising halogenated butyl rubber Bu2, reinforcing filler R2 comprising carbon black N2, vulcanization system V2, and kaolin.

[0014] 2- The rubber composition according to embodiment 1, wherein the content of the granulated rubber ranges from 5 phr to less than 40 phr.

[0015] 3- The rubber composition according to any one of the foregoing embodiments, wherein the median particle size of the granulated rubber is between 50 micrometers and 500 micrometers, preferably between 100 micrometers and 400 micrometers.

[0016] 4- The rubber composition according to any one of the foregoing embodiments, wherein the halogenated butyl rubber Bu2 accounts for at least 40% by weight of the total weight of the granulated rubber.

[0017] 5- The rubber composition according to any one of the foregoing embodiments, wherein the granulated rubber comprises 0% to 20% by weight of polyisoprene elastomer, wherein the polyisoprene elastomer preferably comprises more than 90 mol% of cis-1,4- bonds.

[0018] 6- The rubber composition according to any one of the foregoing embodiments, wherein the halogenated butyl rubber Bu2 is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture thereof.

[0019] 7- The rubber composition according to any one of the foregoing embodiments, wherein the reinforcing filler R2 accounts for 10% to 40% by weight, preferably 20% to 30% by weight, of the total weight of the granulated rubber.

[0020] 8- The rubber composition according to any one of the foregoing embodiments, wherein the carbon black N2 accounts for more than 50% by weight of the total weight of the reinforcing filler R2, preferably more than 80% by weight, and even more preferably 100% by weight.

[0021] 9- The rubber composition according to any one of the foregoing embodiments, wherein the kaolin accounts for 3% to 30% by weight of the total weight of the crushed rubber, preferably 5% to 20% by weight.

[0022] 10- The rubber composition according to any one of the foregoing embodiments, wherein the content of the halogenated butyl rubber Bu1 is greater than or equal to 70 phr.

[0023] 11- The rubber composition according to any one of the foregoing embodiments comprises a polyisoprene elastomer of 0 phr to 30 phr, wherein the polyisoprene elastomer preferably comprises more than 90 mol% of cis-1,4- bonds.

[0024] 12- The rubber composition according to any one of the foregoing embodiments, wherein the halogenated butyl rubber Bu1 is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture thereof.

[0025] 13- The rubber composition according to any one of the foregoing embodiments, wherein the content of the reinforcing filler R1 ranges from 20 phr to 80 phr.

[0026] 14- The rubber composition according to any one of the foregoing embodiments, wherein the reinforcing filler R1 consists only of carbon black.

[0027] 15- Tire liner comprising a rubber composition according to any one of the foregoing embodiments.

[0028] 16- A tire comprising the liner according to embodiment 15, or comprising a rubber composition according to any one of embodiments 1-14.

[0029] elastomer Generally, the interchangeable terms "elastomer" and "rubber" are used interchangeably in the text.

[0030] An essential feature of the rubber composition according to the invention is that it contains a halogenated butyl rubber, Bu1. The halogenated butyl rubber can be used alone or in the form of a mixture with one or more other diene elastomers.

[0031] Butyl rubber should be understood to refer to copolymers of isobutylene and 1,3-diene, especially copolymers of isobutylene and isoprene, as well as halogenated derivatives of these copolymers, particularly the usual brominated or chlorinated derivatives.

[0032] Butyl rubber, particularly its air impermeability, is well known to those skilled in the art. Typically, copolymers of isobutylene with 1,3-diene (especially isoprene) contain 1 mol% to 5 mol% diene units (especially isoprene units) and exhibit Mooney viscosity (ML 1+8, at 125°C) of 30 to 60. Halogenated copolymers of isobutylene with 1,3-diene (especially isoprene) typically exhibit a halogen content of 1 wt% to 4 wt% of the copolymer weight.

[0033] As examples particularly suitable for implementing the present invention, reference will be made to brominated butyl rubbers (e.g., brominated copolymers of isobutylene and isoprene (BIIR)), chlorinated butyl rubbers (e.g., chlorinated copolymers of isobutylene and isoprene (CIIR)), and mixtures of these rubbers.

[0034] According to any embodiment of the present invention, the halogenated butyl rubber Bu1 is preferably a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture thereof.

[0035] "Diene elastomers," whether natural or synthetic, should be understood in the known manner as elastomers at least partially (i.e., homopolymers or copolymers) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds). As potentially suitable diene elastomers, particular reference will be made to diene elastomers commonly used in rubber compositions intended for the manufacture of tires, such as polyisoprene, polybutadiene, isoprene copolymers, or butadiene copolymers (e.g., copolymers of butadiene and styrene).

[0036] According to one embodiment of the invention, the rubber composition of the invention comprises a diene elastomer I1 of 0 phr to 30 phr, wherein the diene elastomer I1 is not a halogenated butyl rubber, but is selected from polyisoprene, polybutadiene, butadiene copolymers, isoprene copolymers, and mixtures thereof. Preferably, the diene elastomer I1 is a polyisoprene elastomer; more preferably, the diene elastomer I1 contains greater than 90 mol% of cis-1,4- bonds. These preferred ranges of elastomer content in the rubber composition of the invention, these preferred ranges of the molar percentage of cis-1,4- bonds in the polyisoprene elastomer I1, and these preferred selections of the diene elastomer can all be applied to any embodiment of the invention.

[0037] According to any embodiment of the invention, the content of halogenated butyl rubber Bu1 in the rubber composition according to the invention is preferably greater than or equal to 70 phr. Preferably, the supplementary rubber that enables the rubber content in the rubber composition according to the invention to reach 100 phr is natural rubber.

[0038] filler The rubber composition according to the invention comprises at least one reinforcing filler R1. Any type of "reinforcing" filler known to be capable of reinforcing rubber compositions particularly suitable for manufacturing tires can be used, such as reinforcing organic fillers like carbon black, reinforcing inorganic fillers like silica, or mixtures of both.

[0039] The reinforcing filler R1 of the rubber composition according to the invention comprises carbon black N1. All carbon blacks, especially those commonly used in tires, are suitable for use as carbon black. These carbon blacks can be used alone as commercially available, or in any other form, for example, as a carrier for some of the rubber additives used.

[0040] The carbon black of the rubber composition according to the present invention, according to a preferred embodiment, exhibits a BET specific surface area in the range of 20 m². 2 / g to 60 m 2 / g. This preferred range of BET specific surface area for carbon black can be applied to any embodiment of the present invention.

[0041] BET specific surface area was determined by gas adsorption using the Brueer-Emmett-Teller method described in "The Journal of the American Chemical Society" (Vol. 60, p. 309, February 1938), and more specifically according to the method derived from standard NF ISO 5794-1 (Annex E) of June 2010 [multi-point (5-point) volumetric method - gas: nitrogen - degassed under vacuum: 1 hour at 160°C - relative pressure p / p0 range: 0.05 to 0.2].

[0042] According to one embodiment of the invention, the reinforcing filler R1 is present in a content of 20 phr to 80 phr in the rubber composition according to the invention. Beyond this range, the rubber composition may no longer exhibit the stiffness suitable for use as a tire liner.

[0043] According to a preferred embodiment of the invention, the content of carbon black N1 in the reinforcing filler of the rubber composition according to the invention ranges from 20 phr to 80 phr. Obviously, the amount of carbon black N1 in the rubber composition is less than or equal to the content of reinforcing filler R1 in the rubber composition. In an even more preferred embodiment, when these two contents are equal, the reinforcing filler R1 consists only of carbon black.

[0044] vulcanization system An essential feature of the rubber composition according to the invention is that it comprises a vulcanization system V1, namely a crosslinking system based on sulfur (or a sulfur donor) and a primary vulcanization accelerator. In addition to this basic vulcanization system, various known secondary vulcanization accelerators or vulcanization activators may be present, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or known vulcanization retarder. As a (primary or secondary) vulcanization accelerator, any compound capable of being used as an accelerator for vulcanized diene elastomers in the presence of sulfur can be mentioned, particularly thiazole-type accelerators and their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. The preferred sulfur content is between 0.5 phr and 12 phr, particularly between 0.5 phr and 5 phr. The preferred content of the primary vulcanization accelerator used in the rubber composition according to the invention is between 0.5 phr and 10 phr, more preferably between 0.5 phr and 5.0 phr. These preferred ranges related to the sulfur and accelerator content can be applied to any embodiment.

[0045] Rubber Particles Another essential feature of the rubber composition according to the invention is that it contains granulated rubber.

[0046] It should be remembered that rubber fragments typically exist in the form of particles (or aggregates), optionally formed into rubber sheets. Typically, rubber fragments are a product of material recycling: they are obtained by milling (particularly micronizing) vulcanized rubber compositions that have been used for initial applications, such as tire vulcanizing bladders (as described in US 6 730732) or tires that have reached the end of their service life (as described in KR 100943526). Any method or process that does not degrade the rubber during milling is suitable for milling rubber compositions. For example, methods that can be performed in the presence of water, such as those described in US 4 374 573, US 4 714 201, US 5 238 194, and US 5411 215, can maintain the temperature of the rubber at a sufficiently low level to prevent reversion (i.e., degradation of the rubber's cross-linked network). Cryogenic milling can also be used. Depending on the size distribution of the resulting particles, the rubber fragments obtained by the method can undergo an additional sieving stage to control this distribution. Sieving can be achieved using various techniques known to those skilled in the art (vibration, centrifugation, suction). Rubber fragments obtained by the grinding process are typically in the form of microparticles. The term "microparticle" should be understood to refer to particles exhibiting such a size that, in the case of spherical particles, their diameter, or in the case of non-equiaxed particles, their maximum size is tens or hundreds of micrometers.

[0047] According to one embodiment of the invention, the granulated rubber for satisfying the requirements of the invention exists in the form of microparticles, wherein the microparticles preferably have a median particle size of granulated rubber between 50 micrometers and 500 micrometers, more preferably between 100 micrometers and 400 micrometers. These particle size ranges can be applied to any embodiment of the invention.

[0048] An essential characteristic of the granulated rubber used to satisfy the requirements of this invention is that it contains halogenated butyl rubber Bu2. The halogenated butyl rubber Bu2 can be used alone or in the form of a mixture with one or more other diene elastomers.

[0049] According to any embodiment of the present invention, the halogenated butyl rubber Bu2 is preferably a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture thereof.

[0050] According to one embodiment of the present invention, the granulated rubber for satisfying the requirements of the present invention comprises 0% to 20% by weight of diene elastomer I2, which is not a halogenated butyl rubber, but is selected from polyisoprene, polybutadiene, butadiene copolymers, isoprene copolymers, and mixtures thereof. Preferably, diene elastomer I2 is a polyisoprene elastomer; more preferably, diene elastomer I2 is a polyisoprene elastomer containing more than 90 mol% cis-1,4-bonds. These preferred ranges of the weight percentage of elastomer in the granulated rubber for satisfying the requirements of the present invention, these preferred ranges of the molar percentage of cis-1,4-bonds in the polyisoprene elastomer I2, and these preferred selections of the diene elastomer can all be applied to any embodiment of the present invention.

[0051] According to any embodiment of the invention, the weight percentage of halogenated butyl rubber Bu2 in the granulated rubber used to satisfy the requirements of the invention is preferably greater than or equal to 40%, calculated relative to the total weight of the granulated rubber. Preferably, the only other rubber present in the granulated rubber used to satisfy the requirements of the invention is natural rubber.

[0052] The granulated rubber used to satisfy the requirements of this invention comprises at least one reinforcing filler R2. Any type of "reinforcing" filler known to be able to reinforce rubber compositions that can be particularly used in the manufacture of tires can be used, such as reinforcing organic fillers like carbon black, reinforcing inorganic fillers like silica, or mixtures of both.

[0053] The reinforcing filler R2 in the granulated rubber used to meet the requirements of this invention comprises carbon black N2. All carbon blacks, especially those commonly used in tires, are suitable for use as carbon black. These carbon blacks can be used alone as they are commercially available, or in any other form, such as as a carrier for some of the rubber additives used.

[0054] According to one embodiment of the invention, the weight percentage of reinforcing filler R2 in the granulated rubber used to meet the requirements of the invention ranges from 20% to 30%, which is calculated relative to the total weight of the granulated rubber.

[0055] According to a preferred embodiment of the invention, the carbon black N2 contained in the reinforcing filler R2 of the pellet rubber for satisfying the requirements of the invention accounts for more than 50% by weight, preferably more than 80% by weight, and even more preferably 100% by weight of the reinforcing filler R2 of the pellet rubber for satisfying the requirements of the invention. In this even more preferred embodiment, the reinforcing filler R2 consists only of carbon black, which is the only reinforcing filler present in the rubber composition of the pellet rubber for satisfying the requirements of the invention.

[0056] An essential characteristic of the granulated rubber used to satisfy the requirements of this invention is that it comprises a vulcanization system V2, namely a crosslinking system based on sulfur (or a sulfur donor) and a primary vulcanization accelerator. In addition to this basic vulcanization system, various known secondary vulcanization accelerators or vulcanization activators may be present, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or known vulcanization retarder. As a (primary or secondary) vulcanization accelerator, any compound capable of being used as an accelerator for vulcanized diene elastomers in the presence of sulfur can be mentioned, particularly thiazole-type accelerators and their derivatives, or accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. The preferred sulfur content used in the granulated rubber to satisfy the requirements of this invention is between 0.5% by weight and 12% by weight of the total elastomer weight of the granulated rubber, particularly between 0.5% by weight and 5% by weight of the total elastomer weight of the granulated rubber. The preferred content of the primary vulcanization accelerator in the granulated rubber used to meet the requirements of this invention is between 0.5% by weight and 10% by weight, more preferably between 0.5% by weight and 5.0% by weight, of the total elastomer weight of the granulated rubber. These preferred ranges related to the sulfur and primary accelerator content can be applied to any embodiment.

[0057] The essential characteristic of the granulated rubber used to meet the requirements of this invention is that it contains kaolin. Kaolin (Al2O3·2SiO2·2H2O) is a non-reinforcing plate-shaped mineral filler, belonging to the natural layered silicate class.

[0058] According to a preferred embodiment of the invention, kaolin comprises 3% to 30% by weight, preferably 5% to 20% by weight, of the total weight of the granulated rubber used to meet the requirements of the invention. These weight percentage ranges of kaolin in the granulated rubber used to meet the requirements of the invention can be applied to any embodiment of the invention.

[0059] According to one embodiment of the invention, in the rubber composition according to the invention, the content of broken rubber particles used to satisfy the requirements of the invention ranges from 5 phr to less than 40 phr. When the content of broken rubber particles in the rubber composition is less than 5 phr, the desired effect may not be strong enough. When the content of broken rubber particles in the rubber composition is equal to or greater than 40 phr, it may be disadvantageous for the industrial processing of the rubber composition. This preferred range of broken rubber particle content in the rubber composition according to the invention can be applied to any embodiment.

[0060] Advantageously, the rubber composition according to the invention comprises less than 1.5 phr of other granulated rubber besides the granulated rubber used to satisfy the requirements of the invention; more advantageously, it does not contain any granulated rubber other than the granulated rubber used to satisfy the requirements of the invention. Advantageous embodiments, and particularly more advantageous embodiments, facilitate a trade-off between fracture properties and airtightness properties.

[0061] The granulated rubber used to meet the requirements of this invention can typically be obtained by grinding tire liners. According to embodiments of the invention, the granulated rubber used to meet the requirements of this invention consists of tire liner particles and includes all the common components present in rubber compositions used for tire liners.

[0062] Other additives The rubber composition according to the invention may contain at least one other additive such as clay, bentonite, talc, chalk, kaolin, or graphite, which is known to improve the processability, thermal conductivity, or, in the case of tire lining, impermeability of the rubber composition. The presence level of this additive in the rubber composition according to the invention is from 0 phr to 40 phr.

[0063] The rubber composition according to the invention may also contain all or part of commonly used additives typically used in rubber compositions intended for use in tire manufacturing, such as plasticizers, lubricants, pigments, protective agents (e.g., anti-ozone waxes, chemical anti-ozone agents or antioxidants), anti-fatigue agents, and mixtures of these compounds.

[0064] Preparation of the composition The rubber composition according to the invention can be manufactured in a suitable mixer using two typically consecutive preparation stages known to those skilled in the art: a first stage of thermomechanical processing or kneading at high temperatures (up to a maximum temperature between 90°C and 150°C, preferably between 100°C and 130°C), followed by a second stage of mechanical processing at a lower temperature, typically less than 110°C, for example between 40°C and 100°C, i.e., a stage of refining and homogenizing the rubber composition.

[0065] The rubber composition according to the present invention can be prepared by a method comprising the following stages: - The components of the rubber composition according to the invention are thermomechanically kneaded until a maximum temperature between 90°C and 120°C is reached; - Cool the combined mixture to a temperature below 80°C; - Knead all the materials until the maximum temperature is below 90°C to obtain the rubber composition according to the invention.

[0066] After all the components of the rubber composition according to the invention are introduced, the resulting final rubber composition is subsequently calendered, for example, into sheets or plates for laboratory characterization, or extruded to form, for example, rubber molded parts, which are used as rubber components or semi-finished products, particularly in tire manufacturing. The rubber composition according to the invention can be used in tires as a calendered product. Calendered products or extrusions formed from the rubber composition according to the invention constitute wholly or partially semi-finished products, particularly semi-finished tires.

[0067] Therefore, according to a specific embodiment of the invention, the rubber composition according to the invention (which may be in an unprocessed state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization)) is used in tires, preferably in tire liners.

[0068] Crosslinking (or curing), in this case vulcanization, is carried out in a known manner, typically at a temperature between 130°C and 200°C for a sufficiently long time, which can vary, for example, between 5 minutes and 120 minutes, depending in particular on the curing temperature, the crosslinking system used, and the crosslinking kinetics of the composition under consideration.

[0069] Other topics of the present invention An essential feature of the tire liner according to the invention is that it is composed wholly or partially of the rubber composition according to the invention. It can be manufactured according to the process described above, which includes an additional stage of calendering or extruding the rubber composition. It can be in an unprocessed state (i.e., before curing) or in a cured state (i.e., after crosslinking or vulcanization).

[0070] This invention also relates to a tire comprising a rubber composition or liner according to the invention, which may be in an unprocessed or cured state. In this invention, the term "tire" should be understood to mean either a pneumatic tire or a non-pneumatic tire. A pneumatic tire typically comprises two beads intended to contact a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. A non-pneumatic tire, in terms of its components, typically comprises a base designed for, for example, mounting on a rigid rim, a crown reinforcement ensuring connection to the tread, and deformable structures such as spokes, ribs, or honeycomb units arranged between the base and the crown. Such a non-pneumatic tire does not necessarily include sidewalls. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR 2 898 077. According to any embodiment of the invention, the tire according to the invention is preferably a pneumatic tire.

[0071] The above and other features of the present invention will be better understood by reading the following several embodiments of the invention, which are described by way of example but not limitation. Detailed Implementation

[0072] The measurements and tests used Determination of tear strength properties of rubber compositions On a force-measuring tensile testing machine equipped with a system for measuring and acquiring the force and displacement of a movable crossbeam, a tensile test specimen was subjected to a tensile test at 500 mm / min until the specimen fractured. The tearing force per unit thickness (hereinafter denoted as F) was measured. TB (expressed in N / mm thickness) and elongation at break at tear (hereinafter denoted as E) TB (expressed as a percentage). The tensile test specimen consists of a parallelepiped-shaped rubber sheet with a thickness of 2.5 mm, a length of 145 mm, and a width of 10 mm. Before starting the test, three extremely fine notches, each 3 mm deep, are cut perpendicular to the length of the specimen along one edge using a blade. One notch is located in the middle, and the other two are located on either side of the middle notch, spaced 6 mm apart. F is then determined. TB That is, the force applied to cause the test specimen to break (expressed in N / mm of the test specimen thickness), measured as E. TB F is the elongation (expressed as a percentage) applied to cause the test specimen to break. The test is conducted in air at 100°C. The tear coefficient (expressed in N / mm) is calculated as F. TB With E TB The product of the two. Although crack initiation is observed, the high value reflects the good cohesiveness of the rubber composition.

[0073] In the following embodiments, measurements were performed on “brand new” tensile test specimens (i.e., those that had not undergone any pre-aging treatment) and on test specimens that had undergone 21 days of thermal oxidative aging treatment in air at 77°C prior to the tensile test.

[0074] Results are expressed with a base of 100: the tear coefficient of the control sample is arbitrarily set to 100; a result greater than 100 indicates that the tear strength performance is improved compared with the control sample.

[0075] Determination of the size of rubber fragments The volumetric size distribution of fragmented rubber particles can be measured using laser particle size analysis on a Mastersizer 3000 instrument from Malvern. A one-minute sonication treatment is performed before measurement to ensure good dispersion. The measurement is conducted via a liquid approach: the fragmented rubber particles are dispersed in ethanol. Measurements are performed according to standard ISO-13320-1. By measuring the diffraction angle of the laser on the fragmented rubber particles, the D10 and D50 values ​​can be specifically determined, representing the diameters of particles below which 10% and 50% by volume, respectively, remain in the total particle size distribution.

[0076] Preparation of rubber composition Four rubber compositions, C1, C2, C3 and C4, were prepared. The formulations of these compositions (in phr) are described in Table 1.

[0077] Rubber compositions C3 and C4 conform to the present invention; rubber compositions C1 and C2 do not conform to the present invention.

[0078] All four rubber compositions C1, C2, C3, and C4 comprise a halogenated butyl rubber Bu1 (brominated butyl rubber in this example), a reinforcing filler R1 containing carbon black N1, a vulcanization system V1, and granulated rubber (rubber compositions C1 and C3 are used in amounts of 10 phr, and rubber compositions C2 and C4 are used in amounts of 30 phr), wherein the granulated rubber comprises a halogenated butyl rubber Bu2 (brominated butyl rubber in this example), a reinforcing filler R2 containing carbon black N2, and a vulcanization system V2. In rubber compositions C1 and C2 that do not conform to the present invention, the granulated rubber of composition A (see Table 2) does not contain kaolin; in rubber compositions C3 and C4 that conform to the present invention, the granulated rubber of composition B (see Table 2) contains kaolin.

[0079] On the one hand, the performance of C1 (not in accordance with the present invention) and C3 (in accordance with the present invention) is compared, and on the other hand, the performance of C2 (not in accordance with the present invention) and C4 (in accordance with the present invention) is compared, thereby evaluating the results.

[0080] The test was conducted as follows: First, halogenated butyl rubber, followed by reinforcing fillers, granulated rubber, the vulcanization system, and other additives in the rubber composition were introduced into a closed mixer, filling it to 70% by volume, with an initial container temperature of approximately 40°C. Then, a thermomechanical process was performed in one stage for a total of approximately 3 to 4 minutes until the maximum "discharge" temperature of 115°C was reached.

[0081] The resulting mixture is recovered and cooled at 30°C on an external mixer (open mill) to homogenize the mixture by mixing all the substances for an appropriate time (e.g., between 5 and 12 minutes).

[0082] The resulting compositions are then calendered in the form of rubber sheets (2 to 3 mm thick) or thin rubber sheets to measure their physical or mechanical properties after vulcanization at 150°C for 20 minutes.

[0083] Properties of rubber compositions Table 3 shows the properties of rubber compositions C1, C2, C3 and C4, expressed as a base of 100 relative to C1.

[0084] Rubber composition C3 contains the same amount of broken rubber as rubber composition C1, but the broken rubber in C3 includes kaolin (the broken rubber of composition B), while rubber composition C1 does not contain any such component (the broken rubber of composition A). Therefore, C3 conforms to the present invention and exhibits a tear strength that is 17% higher than that of rubber composition C1, which does not conform to the present invention.

[0085] Similarly, rubber composition C4 and rubber composition C2 contain the same amount of broken rubber, but the broken rubber in C4 includes kaolin (the broken rubber of composition B), while rubber composition C2 does not contain any such component (the broken rubber of composition A). Therefore, C4 conforms to the present invention and exhibits higher tear strength than rubber composition C2, which does not conform to the present invention.

[0086] The results obtained thus demonstrate that the rubber compositions conforming to the present invention can indeed solve the technical problem in this case, because their tear strength after aging is far superior to that of rubber compositions not conforming to the present invention. This result is particularly surprising, because before aging, the rubber compositions conforming to the present invention did not exhibit better tear strength than those not conforming to the present invention.

[0087] Table 1 (1) Bromobutyl, X_Butyl™ BB2030 obtained from Arlanxeo (2) Obtained from Orion ASTM grade N770 (3) Argirec B24 grade natural kaolin obtained from Imerys (4) Stearic acid obtained from Umicore (5) Zinc oxide obtained from Umicore (6) Struktol® 40MS obtained from Struktol (7) Accelerator obtained from Solutia, 2-mercaptobenzothiazolyl disulfide (“MBTS”) (8) The median particle size of the vulcanized liner of composition A is 280 micrometers. (9) The median particle size of the vulcanized liner of composition B is 280 micrometers. Table 2 Table 3

Claims

1. A rubber composition comprising halogenated butyl rubber Bu1, reinforcing filler R1 comprising carbon black N1, vulcanization system V1, and granulated rubber, said granulated rubber comprising halogenated butyl rubber Bu2, reinforcing filler R2 comprising carbon black N2, vulcanization system V2, and kaolin.

2. The rubber composition according to claim 1, wherein, The content of the granulated rubber ranges from 5 phr to less than 40 phr.

3. The rubber composition according to any one of the preceding claims, wherein, The median particle size of the granulated rubber is between 50 micrometers and 500 micrometers, preferably between 100 micrometers and 400 micrometers.

4. The rubber composition according to any one of the preceding claims, wherein, The halogenated butyl rubber Bu2 accounts for at least 40% of the total weight of the granulated rubber.

5. The rubber composition according to any one of the preceding claims, wherein, The granulated rubber comprises 0% to 20% by weight of polyisoprene elastomer, wherein the polyisoprene elastomer preferably comprises more than 90 mol% of cis-1,4- bonds.

6. The rubber composition according to any one of the preceding claims, wherein, The halogenated butyl rubber Bu2 is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two.

7. The rubber composition according to any one of the preceding claims, wherein, The reinforcing filler R2 accounts for 10% to 40% of the total weight of the granulated rubber, preferably 20% to 30% by weight.

8. The rubber composition according to any one of the preceding claims, wherein, The carbon black N2 accounts for more than 50% by weight of the total weight of the reinforcing filler R2, preferably more than 80% by weight, and even more preferably 100% by weight.

9. The rubber composition according to any one of the preceding claims, wherein, The kaolin accounts for 3% to 30% of the total weight of the crushed rubber, preferably 5% to 20% by weight.

10. The rubber composition according to any one of the preceding claims, wherein, The content of the halogenated butyl rubber Bu1 is greater than or equal to 70 phr.

11. The rubber composition according to any one of the preceding claims, comprising a polyisoprene elastomer of 0 phr to 30 phr, wherein the polyisoprene elastomer preferably comprises more than 90 mol% of cis-1,4- bonds.

12. The rubber composition according to any one of the preceding claims, wherein, The halogenated butyl rubber Bu1 is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two.

13. The rubber composition according to any one of the preceding claims, wherein, The content of the reinforcing filler R1 ranges from 20 phr to 80 phr.

14. The rubber composition according to any one of the preceding claims, wherein, The reinforcing filler R1 consists only of carbon black.

15. A tire liner comprising a rubber composition according to any one of the preceding claims.

16. A tire comprising the liner according to claim 15, or comprising a rubber composition according to any one of claims 1 to 14.

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